Patent Publication Number: US-11662467-B2

Title: MEMS mirror having spaced actuators

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase entry under 35 U.S.C. § 371 from PCT International Application No. PCT/IB2018/001467, filed Nov. 28, 2018, which claims benefit of priority of U.S. Provisional Patent Application No. 62/591,409, filed Nov. 28, 2017; U.S. Provisional Patent Application No. 62/596,261, filed Dec. 8, 2017; U.S. Provisional Patent Application No. 62/646,490, filed Mar. 22, 2018; U.S. Provisional Patent Application No. 62/747,761, filed Oct. 19, 2018; and U.S. Provisional Patent Application No. 62/754,055, filed Nov. 1, 2018, the contents of each of which are incorporated herein by reference in its entirety 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates generally to surveying technology for scanning a surrounding environment, and, more specifically, to systems and methods that use LIDAR technology to detect objects in the surrounding environment. 
     Background Information 
     With the advent of driver assist systems and autonomous vehicles, automobiles need to be equipped with systems capable of reliably sensing and interpreting their surroundings, including identifying obstacles, hazards, objects, and other physical parameters that might impact navigation of the vehicle. To this end, a number of differing technologies have been suggested including radar, LIDAR, camera-based systems, operating alone or in a redundant manner. 
     One consideration with driver assistance systems and autonomous vehicles is an ability of the system to determine surroundings across different conditions including, rain, fog, darkness, bright light, and snow. A light detection and ranging system, (LIDAR a/k/a LADAR) is an example of technology that can work well in differing conditions, by measuring distances to objects by illuminating objects with light and measuring the reflected pulses with a sensor. A laser is one example of a light source that can be used in a LIDAR system. As with any sensing system, in order for a LIDAR-based sensing system to be fully adopted by the automotive industry, the system should provide reliable data enabling detection of far-away objects. Currently, however, the maximum illumination power of LIDAR systems is limited by the need to make the LIDAR systems eye-safe (i.e., so that they will not damage the human eye which can occur when a projected light emission is absorbed in the eye&#39;s cornea and lens, causing thermal damage to the retina.) 
     The systems and methods of the present disclosure are directed towards improving performance of LIDAR systems while complying with eye safety regulations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate various disclosed embodiments. In the drawings: 
         FIG.  1 A  is a diagram illustrating an exemplary LIDAR system consistent with disclosed embodiments. 
         FIG.  1 B  is an image showing an exemplary output of single scanning cycle of a LIDAR system mounted on a vehicle consistent with disclosed embodiments. 
         FIG.  1 C  is another image showing a representation of a point cloud model determined from output of a LIDAR system consistent with disclosed embodiments. 
         FIGS.  2 A- 2 G  are diagrams illustrating different configurations of projecting units in accordance with some embodiments of the present disclosure. 
         FIGS.  3 A- 3 D  are diagrams illustrating different configurations of scanning units in accordance with some embodiments of the present disclosure. 
         FIGS.  4 A- 4 E  are diagrams illustrating different configurations of sensing units in accordance with some embodiments of the present disclosure. 
         FIG.  5 A  includes four example diagrams illustrating emission patterns in a single frame-time for a single portion of the field of view. 
         FIG.  5 B  includes three example diagrams illustrating emission scheme in a single frame-time for the whole field of view. 
         FIG.  6    is a diagram illustrating the actual light emission projected towards and reflections received during a single frame-time for the whole field of view. 
         FIGS.  7 - 9    are diagrams illustrating a first example implementation consistent with some embodiments of the present disclosure. 
         FIG.  10    is a diagram illustrating a second example implementation consistent with some embodiments of the present disclosure. 
         FIGS.  11 A- 11 F  are illustrations of exemplary MEMS mirror assemblies, consistent with disclosed embodiments. 
         FIGS.  12 A- 12 F  are illustrations of additional exemplary MEMS mirror assemblies, consistent with disclosed embodiments. 
         FIG.  13 A  is another illustration of an exemplary MEMS mirror assembly consistent with disclosed embodiments. 
         FIG.  13 B  is an illustration of L-shaped connectors used to connect the MEMS mirror with one or more actuators consistent with disclosed embodiments. 
         FIG.  14    an illustration of an exemplary MEMS mirror assembly having S-shaped connectors consistent with disclosed embodiments. 
         FIGS.  15 A and  15 B  are illustrations of the attachment locations for attaching connectors with one or more actuating arms consistent with disclosed embodiments. 
         FIG.  16 A  is another illustration of an exemplary MEMS mirror assembly consistent with disclosed embodiments. 
         FIGS.  16 B and  16 C  are additional illustrations of the attachment locations for attaching connectors with one or more actuating arms consistent with disclosed embodiments. 
         FIGS.  17 A- 17 C  are illustrations of exemplary actuator arrangements for various MEMS mirror assemblies, consistent with disclosed embodiments. 
         FIGS.  18 A,  18 B,  19 A,  19 B,  20 A,  20 B,  21 A,  21 B,  22 A,  22 B,  23 A, and  23 B  are illustrations of exemplary MEMS mirror assemblies with different types of interconnects for connecting the actuating arms to the frame consistent with disclosed embodiments. 
         FIG.  24    is an illustration of a one-dimensional MEMS mirror assembly consistent with disclosed embodiments. 
         FIG.  25    is another illustration of a one-dimensional MEMS mirror assembly consistent with disclosed embodiments. 
         FIG.  26    is an illustration of an exemplary MEMS mirror assembly having actuators of varied dimensions, consistent with disclosed embodiments. 
         FIGS.  27  and  28    are additional illustrations of exemplary actuators of varied dimensions, consistent with disclosed embodiments. 
         FIGS.  29 A and  29 B  are additional illustrations of exemplary actuators of varied dimensions, consistent with disclosed embodiments. 
         FIGS.  30 A and  30 B  are illustrations of additional exemplary actuators of varied dimensions and orientations relative to a frame, consistent with disclosed embodiments. 
         FIG.  31    is an illustration of an exemplary MEMS mirror assembly having curved actuators of varied dimensions, consistent with disclosed embodiments. 
         FIG.  32 A  is a side view illustration of an exemplary vehicle system. 
         FIG.  32 B  is a top view illustration of an exemplary vehicle system. 
         FIG.  33    illustrates an example of changes in transmission levels of light in the field of view for a slanted window. 
         FIG.  34 A- 34 D  illustrate exemplary embodiments of a light deflector for a vehicle equipped with a LIDAR system. 
         FIG.  35    illustrates an exemplary LIDAR system calibrated for use with an exemplary optical interface of  FIGS.  34 A- 34 D . 
         FIG.  36    illustrates an exemplary vehicle system including a secondary window affixed to a window of the vehicle. 
         FIGS.  37 A , B, and C illustrate an exemplary vehicle system including a grating affixed to the window or to a secondary window of the vehicle. 
         FIG.  38 A  illustrates an example of a vehicle system including internal and external lenses for collimation/de-collimation of light. 
         FIGS.  38 B- 38 G  illustrate various configurations of structures for addressing laser light reflections into a vehicle. 
         FIG.  39    illustrates an exemplary method of calibration of a LIDAR system in a vehicle system. 
         FIG.  40    illustrates an exemplary method of installing optical interfaces on a window of a vehicle equipped with a LIDAR system. 
         FIG.  41 A  illustrates a micro-electro-mechanical (MEMS) system, in accordance with examples of the presently disclosed subject matter. 
         FIGS.  41 B and  41 C  illustrate two example of optional actuation commands (e.g., voltages, biases, currents) for the different actuation assemblies located at different sides of the active area. 
         FIG.  41 D  illustrates a conceptual diagram in which the actuators are represented as springs, and a diagram of stresses applied to different parts of the actuators during movement of the active area, in accordance with examples of the presently disclosed subject matter. 
         FIG.  42 A  illustrates a MEMS system, in accordance with examples of the presently disclosed subject matter. 
         FIG.  42 B  illustrates two states during operation of a pair of actuators, in accordance with examples of the presently disclosed subject matter. 
         FIG.  43    illustrates a MEMS system, in accordance with examples of the presently disclosed subject matter. 
     
    
    
     SUMMARY 
     In one aspect, a MEMS scanning device may include: a movable MEMS mirror configured to pivot about at least one axis; at least one actuator configured to cause pivoting of the movable MEMS mirror about the at least one axis in a first direction; at least one spring configured to cause pivoting of the movable MEMS mirror about the at least one axis in a second direction different from the first direction. The actuator may include a first actuating arm; a second actuating arm; and a gap between the first actuating arm and the second actuating arm. The first actuating arm and the second actuating arm may lie adjacent each other, at least partially separated from each other by the gap. The first actuating arm and the second actuating arm may be configured to be actuated simultaneously to thereby enable exertion of a combined mechanical force on the at least one spring to pivot the movable MEMS mirror about the at least one axis. 
     In another aspect, a LIDAR system may include: a light source configured to project light for illuminating an object in an environment external to the LIDAR system; a scanning unit configured to deflect light from the light source in order to scan at least part of the environment. The scanning unit may include: a movable MEMS mirror configured to pivot about at least one axis; at least one actuator configured to cause pivoting of the movable MEMS mirror about the at least one axis in a first direction; and at least one spring configured to cause pivoting of the movable MEMS mirror about the at least one axis in a second direction different from the first direction. The actuator may include a first actuating arm; a second actuating arm; and a gap between the first actuating arm and the second actuating arm. The scanning unit may also include at least one sensor within the at least one housing configured to detect reflections of the projected light; and at least one processor configured to: issue an instruction to the at least one actuator causing the actuator to deflect from an initial position; and; and determine a distance between the vehicle and the object based on signals received from the at least one sensor. 
     In one aspect, a MEMS scanning device may include a frame, a movable MEMS mirror configured to be rotated about at least one rotational axis, and at least one connector connected to the movable MEMS mirror. The connector may be configured to facilitate rotation of the movable MEMS mirror about the at least one rotational axis. The MEMS scanning device may also include an elongated actuator configured to apply mechanical force on the at least one connector. The elongated actuator may have a base end connected to the frame and a distal end connected to the at least one connector. A width of the base end of the actuator may be wider than the distal end of the actuator. 
     In one aspect, a light deflector for a LIDAR system located within a vehicle is disclosed. The light deflector may include a windshield optical interface configured for location within a vehicle and along an optical path of the LIDAR system. The optical path may extend through a sloped windshield of the vehicle. An optical angle of the optical path before passing through the sloped windshield may be oriented at a first angle with respect to an adjacent surface of the sloped windshield. The LIDAR system may also include a connector for orienting a LIDAR emitting element to direct light through the windshield optical interface and along the optical path. The optical interface may be configured to alter the optical angle of the optical path from the first angle to a second angle. A ratio of greater than about 0.3 between light refracted through the windshield and light reflected from the windshield may be obtained at the second angle. 
     In another aspect, a LIDAR system is disclosed. The LIDAR system may include a light source configured to project light for illuminating an object in an environment external to the LIDAR system. The LIDAR system may also include a windshield optical interface configured for location within a vehicle and along an optical path of the LIDAR system. The optical path may extend through a sloped windshield of the vehicle. An optical angle of the optical path before passing through the sloped windshield may be oriented at a first angle with respect to an adjacent surface of the sloped windshield. Further, the LIDAR system may include a scanning unit configured to deflect light from the light source in order to scan at least part of the environment. The scanning unit may include a movable MEMS mirror configured to pivot about at least one axis. The scanning unit may also include a connector configured to orient the MEMS mirror to direct light through the windshield optical interface and along the optical path. The LIDAR System may also include at least one sensor configured to detect light received through the windshield optical interface. In addition, the LIDAR system may include at least one processor configured to determine a distance between the vehicle and the object based on signals received from the at least one sensor. 
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several illustrative embodiments are described herein, modifications, adaptations and other implementations are possible. For example, substitutions, additions or modifications may be made to the components illustrated in the drawings, and the illustrative methods described herein may be modified by substituting, reordering, removing, or adding steps to the disclosed methods. Accordingly, the following detailed description is not limited to the disclosed embodiments and examples. Instead, the proper scope is defined by the appended claims. 
     Terms Definitions 
     Disclosed embodiments may involve an optical system. As used herein, the term “optical system” broadly includes any system that is used for the generation, detection and/or manipulation of light. By way of example only, an optical system may include one or more optical components for generating, detecting and/or manipulating light. For example, light sources, lenses, mirrors, prisms, beam splitters, collimators, polarizing optics, optical modulators, optical switches, optical amplifiers, optical detectors, optical sensors, fiber optics, semiconductor optic components, while each not necessarily required, may each be part of an optical system. In addition to the one or more optical components, an optical system may also include other non-optical components such as electrical components, mechanical components, chemical reaction components, and semiconductor components. The non-optical components may cooperate with optical components of the optical system. For example, the optical system may include at least one processor for analyzing detected light. 
     Consistent with the present disclosure, the optical system may be a LIDAR system. As used herein, the term “LIDAR system” broadly includes any system which can determine values of parameters indicative of a distance between a pair of tangible objects based on reflected light. In one embodiment, the LIDAR system may determine a distance between a pair of tangible objects based on reflections of light emitted by the LIDAR system. As used herein, the term “determine distances” broadly includes generating outputs which are indicative of distances between pairs of tangible objects. The determined distance may represent the physical dimension between a pair of tangible objects. By way of example only, the determined distance may include a line of flight distance between the LIDAR system and another tangible object in a field of view of the LIDAR system. In another embodiment, the LIDAR system may determine the relative velocity between a pair of tangible objects based on reflections of light emitted by the LIDAR system. Examples of outputs indicative of the distance between a pair of tangible objects include: a number of standard length units between the tangible objects (e.g. number of meters, number of inches, number of kilometers, number of millimeters), a number of arbitrary length units (e.g. number of LIDAR system lengths), a ratio between the distance to another length (e.g. a ratio to a length of an object detected in a field of view of the LIDAR system), an amount of time (e.g. given as standard unit, arbitrary units or ratio, for example, the time it takes light to travel between the tangible objects), one or more locations (e.g. specified using an agreed coordinate system, specified in relation to a known location), and more. 
     The LIDAR system may determine the distance between a pair of tangible objects based on reflected light. In one embodiment, the LIDAR system may process detection results of a sensor which creates temporal information indicative of a period of time between the emission of a light signal and the time of its detection by the sensor. The period of time is occasionally referred to as “time of flight” of the light signal. In one example, the light signal may be a short pulse, whose rise and/or fall time may be detected in reception. Using known information about the speed of light in the relevant medium (usually air), the information regarding the time of flight of the light signal can be processed to provide the distance the light signal traveled between emission and detection. In another embodiment, the LIDAR system may determine the distance based on frequency phase-shift (or multiple frequency phase-shift). Specifically, the LIDAR system may process information indicative of one or more modulation phase shifts (e.g. by solving some simultaneous equations to give a final measure) of the light signal. For example, the emitted optical signal may be modulated with one or more constant frequencies. The at least one phase shift of the modulation between the emitted signal and the detected reflection may be indicative of the distance the light traveled between emission and detection. The modulation may be applied to a continuous wave light signal, to a quasi-continuous wave light signal, or to another type of emitted light signal. It is noted that additional information may be used by the LIDAR system for determining the distance, e.g. location information (e.g. relative positions) between the projection location, the detection location of the signal (especially if distanced from one another), and more. 
     In some embodiments, the LIDAR system may be used for detecting a plurality of objects in an environment of the LIDAR system. The term “detecting an object in an environment of the LIDAR system” broadly includes generating information which is indicative of an object that reflected light toward a detector associated with the LIDAR system. If more than one object is detected by the LIDAR system, the generated information pertaining to different objects may be interconnected, for example a car is driving on a road, a bird is sitting on the tree, a man touches a bicycle, a van moves towards a building. The dimensions of the environment in which the LIDAR system detects objects may vary with respect to implementation. For example, the LIDAR system may be used for detecting a plurality of objects in an environment of a vehicle on which the LIDAR system is installed, up to a horizontal distance of 100 m (or 200 m, 300 m, etc.), and up to a vertical distance of 10 m (or 25 m, 50 m, etc.). In another example, the LIDAR system may be used for detecting a plurality of objects in an environment of a vehicle or within a predefined horizontal range (e.g., 25°, 50°, 100°, 180°, etc.), and up to a predefined vertical elevation (e.g., ±10°, ±20°, +40°-20°, ±90° or 0°-90°). 
     As used herein, the term “detecting an object” may broadly refer to determining an existence of the object (e.g., an object may exist in a certain direction with respect to the LIDAR system and/or to another reference location, or an object may exist in a certain spatial volume). Additionally or alternatively, the term “detecting an object” may refer to determining a distance between the object and another location (e.g. a location of the LIDAR system, a location on earth, or a location of another object). Additionally or alternatively, the term “detecting an object” may refer to identifying the object (e.g. classifying a type of object such as car, plant, tree, road; recognizing a specific object (e.g., the Washington Monument); determining a license plate number; determining a composition of an object (e.g., solid, liquid, transparent, semitransparent); determining a kinematic parameter of an object (e.g., whether it is moving, its velocity, its movement direction, expansion of the object). Additionally or alternatively, the term “detecting an object” may refer to generating a point cloud map in which every point of one or more points of the point cloud map correspond to a location in the object or a location on a face thereof. In one embodiment, the data resolution associated with the point cloud map representation of the field of view may be associated with 0.1°×0.1° or 0.3°×0.3° of the field of view. 
     Consistent with the present disclosure, the term “object” broadly includes a finite composition of matter that may reflect light from at least a portion thereof. For example, an object may be at least partially solid (e.g. cars, trees); at least partially liquid (e.g. puddles on the road, rain); at least partly gaseous (e.g. fumes, clouds); made from a multitude of distinct particles (e.g. sand storm, fog, spray); and may be of one or more scales of magnitude, such as ˜1 millimeter (mm), ˜5 mm, ˜10 mm, ˜50 mm, ˜100 mm, ˜500 mm, ˜1 meter (m), ˜5 m, ˜10 m, ˜50 m, ˜100 m, and so on. Smaller or larger objects, as well as any size in between those examples, may also be detected. It is noted that for various reasons, the LIDAR system may detect only part of the object. For example, in some cases, light may be reflected from only some sides of the object (e.g., only the side opposing the LIDAR system will be detected); in other cases, light may be projected on only part of the object (e.g. laser beam projected onto a road or a building); in other cases, the object may be partly blocked by another object between the LIDAR system and the detected object; in other cases, the LIDAR&#39;s sensor may only detects light reflected from a portion of the object, e.g., because ambient light or other interferences interfere with detection of some portions of the object. 
     Consistent with the present disclosure, a LIDAR system may be configured to detect objects by scanning the environment of LIDAR system. The term “scanning the environment of LIDAR system” broadly includes illuminating the field of view or a portion of the field of view of the LIDAR system. In one example, scanning the environment of LIDAR system may be achieved by moving or pivoting a light deflector to deflect light in differing directions toward different parts of the field of view. In another example, scanning the environment of LIDAR system may be achieved by changing a positioning (i.e. location and/or orientation) of a sensor with respect to the field of view. In another example, scanning the environment of LIDAR system may be achieved by changing a positioning (i.e. location and/or orientation) of a light source with respect to the field of view. In yet another example, scanning the environment of LIDAR system may be achieved by changing the positions of at least one light source and of at least one sensor to move rigidly respect to the field of view (i.e. the relative distance and orientation of the at least one sensor and of the at least one light source remains). 
     As used herein the term “field of view of the LIDAR system” may broadly include an extent of the observable environment of LIDAR system in which objects may be detected. It is noted that the field of view (FOV) of the LIDAR system may be affected by various conditions such as but not limited to: an orientation of the LIDAR system (e.g. is the direction of an optical axis of the LIDAR system); a position of the LIDAR system with respect to the environment (e.g. distance above ground and adjacent topography and obstacles); operational parameters of the LIDAR system (e.g. emission power, computational settings, defined angles of operation), etc. The field of view of LIDAR system may be defined, for example, by a solid angle (e.g. defined using ϕ, θ angles, in which ϕ and θ are angles defined in perpendicular planes, e.g. with respect to symmetry axes of the LIDAR system and/or its FOV). In one example, the field of view may also be defined within a certain range (e.g. up to 200 m). 
     Similarly, the term “instantaneous field of view” may broadly include an extent of the observable environment in which objects may be detected by the LIDAR system at any given moment. For example, for a scanning LIDAR system, the instantaneous field of view is narrower than the entire FOV of the LIDAR system, and it can be moved within the FOV of the LIDAR system in order to enable detection in other parts of the FOV of the LIDAR system. The movement of the instantaneous field of view within the FOV of the LIDAR system may be achieved by moving a light deflector of the LIDAR system (or external to the LIDAR system), so as to deflect beams of light to and/or from the LIDAR system in differing directions. In one embodiment, LIDAR system may be configured to scan scene in the environment in which the LIDAR system is operating. As used herein the term “scene” may broadly include some or all of the objects within the field of view of the LIDAR system, in their relative positions and in their current states, within an operational duration of the LIDAR system. For example, the scene may include ground elements (e.g. earth, roads, grass, sidewalks, road surface marking), sky, man-made objects (e.g. vehicles, buildings, signs), vegetation, people, animals, light projecting elements (e.g. flashlights, sun, other LIDAR systems), and so on. 
     Disclosed embodiments may involve obtaining information for use in generating reconstructed three-dimensional models. Examples of types of reconstructed three-dimensional models which may be used include point cloud models, and Polygon Mesh (e.g. a triangle mesh). The terms “point cloud” and “point cloud model” are widely known in the art, and should be construed to include a set of data points located spatially in some coordinate system (i.e., having an identifiable location in a space described by a respective coordinate system). The term “point cloud point” refer to a point in space (which may be dimensionless, or a miniature cellular space, e.g. 1 cm3), and whose location may be described by the point cloud model using a set of coordinates (e.g. (X,Y,Z), (r,ϕ,θ)). By way of example only, the point cloud model may store additional information for some or all of its points (e.g. color information for points generated from camera images). Likewise, any other type of reconstructed three-dimensional model may store additional information for some or all of its objects. Similarly, the terms “polygon mesh” and “triangle mesh” are widely known in the art, and are to be construed to include, among other things, a set of vertices, edges and faces that define the shape of one or more 3D objects (such as a polyhedral object). The faces may include one or more of the following: triangles (triangle mesh), quadrilaterals, or other simple convex polygons, since this may simplify rendering. The faces may also include more general concave polygons, or polygons with holes. Polygon meshes may be represented using differing techniques, such as: Vertex-vertex meshes, Face-vertex meshes, Winged-edge meshes and Render dynamic meshes. Different portions of the polygon mesh (e.g., vertex, face, edge) are located spatially in some coordinate system (i.e., having an identifiable location in a space described by the respective coordinate system), either directly and/or relative to one another. The generation of the reconstructed three-dimensional model may be implemented using any standard, dedicated and/or novel photogrammetry technique, many of which are known in the art. It is noted that other types of models of the environment may be generated by the LIDAR system. 
     Consistent with disclosed embodiments, the LIDAR system may include at least one projecting unit with a light source configured to project light. As used herein the term “light source” broadly refers to any device configured to emit light. In one embodiment, the light source may be a laser such as a solid-state laser, laser diode, a high power laser, or an alternative light source such as, a light emitting diode (LED)-based light source. In addition, light source  112  as illustrated throughout the figures, may emit light in differing formats, such as light pulses, continuous wave (CW), quasi-CW, and so on. For example, one type of light source that may be used is a vertical-cavity surface-emitting laser (VCSEL). Another type of light source that may be used is an external cavity diode laser (ECDL). In some examples, the light source may include a laser diode configured to emit light at a wavelength between about 650 nm and 1150 nm. Alternatively, the light source may include a laser diode configured to emit light at a wavelength between about 800 nm and about 1000 nm, between about 850 nm and about 950 nm, or between about 1300 nm and about 1600 nm. Unless indicated otherwise, the term “about” with regards to a numeric value is defined as a variance of up to 5% with respect to the stated value. Additional details on the projecting unit and the at least one light source are described below with reference to  FIGS.  2 A- 2 C . 
     Consistent with disclosed embodiments, the LIDAR system may include at least one scanning unit with at least one light deflector configured to deflect light from the light source in order to scan the field of view. The term “light deflector” broadly includes any mechanism or module which is configured to make light deviate from its original path; for example, a mirror, a prism, controllable lens, a mechanical mirror, mechanical scanning polygons, active diffraction (e.g. controllable LCD), Risley prisms, non-mechanical-electro-optical beam steering (such as made by Vscent), polarization grating (such as offered by Boulder Non-Linear Systems), optical phased array (OPA), and more. In one embodiment, a light deflector may include a plurality of optical components, such as at least one reflecting element (e.g. a mirror), at least one refracting element (e.g. a prism, a lens), and so on. In one example, the light deflector may be movable, to cause light deviate to differing degrees (e.g. discrete degrees, or over a continuous span of degrees). The light deflector may optionally be controllable in different ways (e.g. deflect to a degree a, change deflection angle by Δα, move a component of the light deflector by M millimeters, change speed in which the deflection angle changes). In addition, the light deflector may optionally be operable to change an angle of deflection within a single plane (e.g.,  0  coordinate). The light deflector may optionally be operable to change an angle of deflection within two non-parallel planes (e.g., θ and ϕ coordinates). Alternatively or in addition, the light deflector may optionally be operable to change an angle of deflection between predetermined settings (e.g. along a predefined scanning route) or otherwise. With respect the use of light deflectors in LIDAR systems, it is noted that a light deflector may be used in the outbound direction (also referred to as transmission direction, or TX) to deflect light from the light source to at least a part of the field of view. However, a light deflector may also be used in the inbound direction (also referred to as reception direction, or RX) to deflect light from at least a part of the field of view to one or more light sensors. Additional details on the scanning unit and the at least one light deflector are described below with reference to  FIGS.  3 A- 3 C . 
     Disclosed embodiments may involve pivoting the light deflector in order to scan the field of view. As used herein the term “pivoting” broadly includes rotating of an object (especially a solid object) about one or more axis of rotation, while substantially maintaining a center of rotation fixed. In one embodiment, the pivoting of the light deflector may include rotation of the light deflector about a fixed axis (e.g., a shaft), but this is not necessarily so. For example, in some MEMS mirror implementation, the MEMS mirror may move by actuation of a plurality of benders connected to the mirror, the mirror may experience some spatial translation in addition to rotation. Nevertheless, such a mirror may be designed to rotate about a substantially fixed axis, and therefore consistent with the present disclosure it considered to be pivoted. In other embodiments, some types of light deflectors (e.g. non-mechanical-electro-optical beam steering, OPA) do not require any moving components or internal movements in order to change the deflection angles of deflected light. It is noted that any discussion relating to moving or pivoting a light deflector is also mutatis mutandis applicable to controlling the light deflector such that it changes a deflection behavior of the light deflector. For example, controlling the light deflector may cause a change in a deflection angle of beams of light arriving from at least one direction. 
     Disclosed embodiments may involve receiving reflections associated with a portion of the field of view corresponding to a single instantaneous position of the light deflector. As used herein, the term “instantaneous position of the light deflector” (also referred to as “state of the light deflector”) broadly refers to the location or position in space where at least one controlled component of the light deflector is situated at an instantaneous point in time, or over a short span of time. In one embodiment, the instantaneous position of light deflector may be gauged with respect to a frame of reference. The frame of reference may pertain to at least one fixed point in the LIDAR system. Or, for example, the frame of reference may pertain to at least one fixed point in the scene. In some embodiments, the instantaneous position of the light deflector may include some movement of one or more components of the light deflector (e.g. mirror, prism), usually to a limited degree with respect to the maximal degree of change during a scanning of the field of view. For example, a scanning of the entire the field of view of the LIDAR system may include changing deflection of light over a span of 30°, and the instantaneous position of the at least one light deflector may include angular shifts of the light deflector within 0.05°. In other embodiments, the term “instantaneous position of the light deflector” may refer to the positions of the light deflector during acquisition of light which is processed to provide data for a single point of a point cloud (or another type of 3D model) generated by the LIDAR system. In some embodiments, an instantaneous position of the light deflector may correspond with a fixed position or orientation in which the deflector pauses for a short time during illumination of a particular sub-region of the LIDAR field of view. In other cases, an instantaneous position of the light deflector may correspond with a certain position/orientation along a scanned range of positions/orientations of the light deflector that the light deflector passes through as part of a continuous or semi-continuous scan of the LIDAR field of view. In some embodiments, the light deflector may be moved such that during a scanning cycle of the LIDAR FOV the light deflector is located at a plurality of different instantaneous positions. In other words, during the period of time in which a scanning cycle occurs, the deflector may be moved through a series of different instantaneous positions/orientations, and the deflector may reach each different instantaneous position/orientation at a different time during the scanning cycle. 
     Consistent with disclosed embodiments, the LIDAR system may include at least one sensing unit with at least one sensor configured to detect reflections from objects in the field of view. The term “sensor” broadly includes any device, element, or system capable of measuring properties (e.g., power, frequency, phase, pulse timing, pulse duration) of electromagnetic waves and to generate an output relating to the measured properties. In some embodiments, the at least one sensor may include a plurality of detectors constructed from a plurality of detecting elements. The at least one sensor may include light sensors of one or more types. It is noted that the at least one sensor may include multiple sensors of the same type which may differin other characteristics (e.g., sensitivity, size). Other types of sensors may also be used. Combinations of several types of sensors can be used for different reasons, such as improving detection over a span of ranges (especially in close range); improving the dynamic range of the sensor; improving the temporal response of the sensor; and improving detection in varying environmental conditions (e.g. atmospheric temperature, rain, etc.). 
     In one embodiment, the at least one sensor includes a SiPM (Silicon photomultipliers) which is a solid-state single-photon-sensitive device built from an array of avalanche photodiode (APD), single photon avalanche diode (SPAD), serving as detection elements on a common silicon substrate. In one example, a typical distance between SPADs may be between about 10 μm and about 50 μm, wherein each SPAD may have a recovery time of between about 20 ns and about 100 ns. Similar photomultipliers from other, non-silicon materials may also be used. Although a SiPM device works in digital/switching mode, the SiPM is an analog device because all the microcells may be read in parallel, making it possible to generate signals within a dynamic range from a single photon to hundreds and thousands of photons detected by the different SPADs. It is noted that outputs from different types of sensors (e.g., SPAD, APD, SiPM, PIN diode, Photodetector) may be combined together to a single output which may be processed by a processor of the LIDAR system. Additional details on the sensing unit and the at least one sensor are described below with reference to  FIGS.  4 A- 4 C . 
     Consistent with disclosed embodiments, the LIDAR system may include or communicate with at least one processor configured to execute differing functions. The at least one processor may constitute any physical device having an electric circuit that performs a logic operation on input or inputs. For example, the at least one processor may include one or more integrated circuits (IC), including Application-specific integrated circuit (ASIC), microchips, microcontrollers, microprocessors, all or part of a central processing unit (CPU), graphics processing unit (GPU), digital signal processor (DSP), field-programmable gate array (FPGA), or other circuits suitable for executing instructions or performing logic operations. The instructions executed by at least one processor may, for example, be pre-loaded into a memory integrated with or embedded into the controller or may be stored in a separate memory. The memory may comprise a Random Access Memory (RAM), a Read-Only Memory (ROM), a hard disk, an optical disk, a magnetic medium, a flash memory, other permanent, fixed, or volatile memory, or any other mechanism capable of storing instructions. In some embodiments, the memory is configured to store information representative data about objects in the environment of the LIDAR system. In some embodiments, the at least one processor may include more than one processor. Each processor may have a similar construction or the processors may be of differing constructions that are electrically connected or disconnected from each other. For example, the processors may be separate circuits or integrated in a single circuit. When more than one processor is used, the processors may be configured to operate independently or collaboratively. The processors may be coupled electrically, magnetically, optically, acoustically, mechanically or by other means that permit them to interact. Additional details on the processing unit and the at least one processor are described below with reference to  FIGS.  5 A,  5 B, and  6   . 
     System Overview 
       FIG.  1 A  illustrates a LIDAR system  100  including a projecting unit  102 , a scanning unit  104 , a sensing unit  106 , and a processing unit  108 . LIDAR system  100  may be mountable on a vehicle  110 . Consistent with embodiments of the present disclosure, projecting unit  102  may include at least one light source  112 , scanning unit  104  may include at least one light deflector  114 , sensing unit  106  may include at least one sensor  116 , and processing unit  108  may include at least one processor  118 . In one embodiment, at least one processor  118  may be configured to coordinate operation of the at least one light source  112  with the movement of at least one light deflector  114  in order to scan a field of view  120 . During a scanning cycle, each instantaneous position of at least one light deflector  114  may be associated with a particular portion  122  of field of view  120 . In addition, LIDAR system  100  may include at least one optional optical window  124  for directing light projected towards field of view  120  and/or receiving light reflected from objects in field of view  120 . Optional optical window  124  may serve different purposes, such as collimation of the projected light and focusing of the reflected light. In one embodiment, optional optical window  124  may be an opening, a flat window, a lens, or any other type of optical window. 
     Consistent with the present disclosure, LIDAR system  100  may be used in autonomous or semi-autonomous road-vehicles (for example, cars, buses, vans, trucks and any other terrestrial vehicle). Autonomous road-vehicles with LIDAR system  100  may scan their environment and drive to a destination without human input. Similarly, LIDAR system  100  may also be used in autonomous/semi-autonomous aerial-vehicles (for example, UAV, drones, quadcopters, and any other airborne vehicle or device); or in an autonomous or semi-autonomous water vessel (e.g., boat, ship, submarine, or any other watercraft). Autonomous aerial-vehicles and water craft with LIDAR system  100  may scan their environment and navigate to a destination autonomously or using a remote human operator. According to one embodiment, vehicle  110  (either a road-vehicle, aerial-vehicle, or watercraft) may use LIDAR system  100  to aid in detecting and scanning the environment in which vehicle  110  is operating. 
     It should be noted that LIDAR system  100  or any of its components may be used together with any of the example embodiments and methods disclosed herein. Further, while some aspects of LIDAR system  100  are described relative to an exemplary vehicle-based LIDAR platform, LIDAR system  100 , any of its components, or any of the processes described herein may be applicable to LIDAR systems of other platform types. 
     In some embodiments, LIDAR system  100  may include one or more scanning units  104  to scan the environment around vehicle  110 . LIDAR system  100  may be attached or mounted to any part of vehicle  110 . Sensing unit  106  may receive reflections from the surroundings of vehicle  110 , and transfer reflection signals indicative of light reflected from objects in field of view  120  to processing unit  108 . Consistent with the present disclosure, scanning units  104  may be mounted to or incorporated into a bumper, a fender, a side panel, a spoiler, a roof, a headlight assembly, a taillight assembly, a rear-view mirror assembly, a hood, a trunk or any other suitable part of vehicle  110  capable of housing at least a portion of the LIDAR system. In some cases, LIDAR system  100  may capture a complete surround view of the environment of vehicle  110 . Thus, LIDAR system  100  may have a 360-degree horizontal field of view. In one example, as shown in  FIG.  1 A , LIDAR system  100  may include a single scanning unit  104  mounted on a roof of vehicle  110 . Alternatively, LIDAR system  100  may include multiple scanning units (e.g., two, three, four, or more scanning units  104 ) each with a field of few such that in the aggregate the horizontal field of view is covered by a 360-degree scan around vehicle  110 . One skilled in the art will appreciate that LIDAR system  100  may include any number of scanning units  104  arranged in any manner, each with an 80° to 120° field of view or less, depending on the number of units employed. Moreover, a 360-degree horizontal field of view may be also obtained by mounting a multiple LIDAR systems  100  on vehicle  110 , each with a single scanning unit  104 . It is nevertheless noted, that the one or more LIDAR systems  100  do not have to provide a complete 360° field of view, and that narrower fields of view may be useful in some situations. For example, vehicle  110  may require a first LIDAR system  100  having a field of view of 75° looking ahead of the vehicle, and possibly a second LIDAR system  100  with a similar FOV looking backward (optionally with a lower detection range). It is also noted that different vertical field of view angles may also be implemented. 
       FIG.  1 B  is an image showing an exemplary output from a single scanning cycle of LIDAR system  100  mounted on vehicle  110  consistent with disclosed embodiments. In this example, scanning unit  104  is incorporated into a right headlight assembly of vehicle  110 . Every gray dot in the image corresponds to a location in the environment around vehicle  110  determined from reflections detected by sensing unit  106 . In addition to location, each gray dot may also be associated with different types of information, for example, intensity (e.g., how much light returns back from that location), reflectivity, proximity to other dots, and more. In one embodiment, LIDAR system  100  may generate a plurality of point-cloud data entries from detected reflections of multiple scanning cycles of the field of view to enable, for example, determining a point cloud model of the environment around vehicle  110 . 
       FIG.  1 C  is an image showing a representation of the point cloud model determined from the output of LIDAR system  100 . Consistent with disclosed embodiments, by processing the generated point-cloud data entries of the environment around vehicle  110 , a surround-view image may be produced from the point cloud model. In one embodiment, the point cloud model may be provided to a feature extraction module, which processes the point cloud information to identify a plurality of features. Each feature may include data about different aspects of the point cloud and/or of objects in the environment around vehicle  110  (e.g. cars, trees, people, and roads). Features may have the same resolution of the point cloud model (i.e. having the same number of data points, optionally arranged into similar sized 2D arrays), or may have different resolutions. The features may be stored in any kind of data structure (e.g. raster, vector, 2D array, 1D array). In addition, virtual features, such as a representation of vehicle  110 , border lines, or bounding boxes separating regions or objects in the image (e.g., as depicted in  FIG.  1 B ), and icons representing one or more identified objects, may be overlaid on the representation of the point cloud model to form the final surround-view image. For example, a symbol of vehicle  110  may be overlaid at a center of the surround-view image. 
     The Projecting Unit 
       FIGS.  2 A- 2 G  depict various configurations of projecting unit  102  and its role in LIDAR system  100 . Specifically,  FIG.  2 A  is a diagram illustrating projecting unit  102  with a single light source;  FIG.  2 B  is a diagram illustrating a plurality of projecting units  102  with a plurality of light sources aimed at a common light deflector  114 ;  FIG.  2 C  is a diagram illustrating projecting unit  102  with a primary and a secondary light sources  112 ;  FIG.  2 D  is a diagram illustrating an asymmetrical deflector used in some configurations of projecting unit  102 ;  FIG.  2 E  is a diagram illustrating a first configuration of a non-scanning LIDAR system;  FIG.  2 F  is a diagram illustrating a second configuration of a non-scanning LIDAR system; and  FIG.  2 G  is a diagram illustrating a LIDAR system that scans in the outbound direction and does not scan in the inbound direction. One skilled in the art will appreciate that the depicted configurations of projecting unit  102  may have numerous variations and modifications. 
       FIG.  2 A  illustrates an example of a bi-static configuration of LIDAR system  100  in which projecting unit  102  includes a single light source  112 . The term “bi-static configuration” broadly refers to LIDAR systems configurations in which the projected light exiting the LIDAR system and the reflected light entering the LIDAR system pass through substantially different optical paths. In some embodiments, a bi-static configuration of LIDAR system  100  may include a separation of the optical paths by using completely different optical components, by using parallel but not fully separated optical components, or by using the same optical components for only part of the of the optical paths (optical components may include, for example, windows, lenses, mirrors, beam splitters, etc.). In the example depicted in  FIG.  2 A , the bi-static configuration includes a configuration where the outbound light and the inbound light pass through a single optical window  124  but scanning unit  104  includes two light deflectors, a first light deflector  114 A for outbound light and a second light deflector  114 B for inbound light (the inbound light in LIDAR system includes emitted light reflected from objects in the scene, and may also include ambient light arriving from other sources). In the examples depicted in  FIGS.  2 E and  2 G , the bi-static configuration includes a configuration where the outbound light passes through a first optical window  124 A, and the inbound light passes through a second optical window  124 B. In all the example configurations above, the inbound and outbound optical paths differ from one another. 
     In this embodiment, all the components of LIDAR system  100  may be contained within a single housing  200 , or may be divided among a plurality of housings. As shown, projecting unit  102  is associated with a single light source  112  that includes a laser diode  202 A (or one or more laser diodes coupled together) configured to emit light (projected light  204 ). In one non-limiting example, the light projected by light source  112  may be at a wavelength between about 800 nm and 950 nm, have an average power between about 50 mW and about 500 mW, have a peak power between about 50 W and about 200 W, and a pulse width of between about 2 ns and about 100 ns. In addition, light source  112  may optionally be associated with optical assembly  202 B used for manipulation of the light emitted by laser diode  202 A (e.g. for collimation, focusing, etc.). It is noted that other types of light sources  112  may be used, and that the disclosure is not restricted to laser diodes. In addition, light source  112  may emit its light in different formats, such as light pulses, frequency modulated, continuous wave (CW), quasi-CW, or any other form corresponding to the particular light source employed. The projection format and other parameters may be changed by the light source from time to time based on different factors, such as instructions from processing unit  108 . The projected light is projected towards an outbound deflector  114 A that functions as a steering element for directing the projected light in field of view  120 . In this example, scanning unit  104  also include a pivotable return deflector  114 B that direct photons (reflected light  206 ) reflected back from an object  208  within field of view  120  toward sensor  116 . The reflected light is detected by sensor  116  and information about the object (e.g., the distance to object  212 ) is determined by processing unit  108 . 
     In this figure, LIDAR system  100  is connected to a host  210 . Consistent with the present disclosure, the term “host” refers to any computing environment that may interface with LIDAR system  100 , it may be a vehicle system (e.g., part of vehicle  110 ), a testing system, a security system, a surveillance system, a traffic control system, an urban modelling system, or any system that monitors its surroundings. Such computing environment may include at least one processor and/or may be connected LIDAR system  100  via the cloud. In some embodiments, host  210  may also include interfaces to external devices such as camera and sensors configured to measure different characteristics of host  210  (e.g., acceleration, steering wheel deflection, reverse drive, etc.). Consistent with the present disclosure, LIDAR system  100  may be fixed to a stationary object associated with host  210  (e.g. a building, a tripod) or to a portable system associated with host  210  (e.g., a portable computer, a movie camera). Consistent with the present disclosure, LIDAR system  100  may be connected to host  210 , to provide outputs of LIDAR system  100  (e.g., a 3D model, a reflectivity image) to host  210 . Specifically, host  210  may use LIDAR system  100  to aid in detecting and scanning the environment of host  210  or any other environment. In addition, host  210  may integrate, synchronize or otherwise use together the outputs of LIDAR system  100  with outputs of other sensing systems (e.g. cameras, microphones, radar systems). In one example, LIDAR system  100  may be used by a security system. This embodiment is described in greater detail below with reference to  FIG.  7   . 
     LIDAR system  100  may also include a bus  212  (or other communication mechanisms) that interconnect subsystems and components for transferring information within LIDAR system  100 . Optionally, bus  212  (or another communication mechanism) may be used for interconnecting LIDAR system  100  with host  210 . In the example of  FIG.  2 A , processing unit  108  includes two processors  118  to regulate the operation of projecting unit  102 , scanning unit  104 , and sensing unit  106  in a coordinated manner based, at least partially, on information received from internal feedback of LIDAR system  100 . In other words, processing unit  108  may be configured to dynamically operate LIDAR system  100  in a closed loop. A closed loop system is characterized by having feedback from at least one of the elements and updating one or more parameters based on the received feedback. Moreover, a closed loop system may receive feedback and update its own operation, at least partially, based on that feedback. A dynamic system or element is one that may be updated during operation. 
     According to some embodiments, scanning the environment around LIDAR system  100  may include illuminating field of view  120  with light pulses. The light pulses may have parameters such as: pulse duration, pulse angular dispersion, wavelength, instantaneous power, photon density at different distances from light source  112 , average power, pulse power intensity, pulse width, pulse repetition rate, pulse sequence, pulse duty cycle, wavelength, phase, polarization, and more. Scanning the environment around LIDAR system  100  may also include detecting and characterizing various aspects of the reflected light. Characteristics of the reflected light may include, for example: time-of-flight (i.e., time from emission until detection), instantaneous power (e.g., power signature), average power across entire return pulse, and photon distribution/signal over return pulse period. By comparing characteristics of a light pulse with characteristics of corresponding reflections, a distance and possibly a physical characteristic, such as reflected intensity of object  212  may be estimated. By repeating this process across multiple adjacent portions  122 , in a predefined pattern (e.g., raster, Lissajous or other patterns) an entire scan of field of view  120  may be achieved. As discussed below in greater detail, in some situations LIDAR system  100  may direct light to only some of the portions  122  in field of view  120  at every scanning cycle. These portions may be adjacent to each other, but not necessarily so. 
     In another embodiment, LIDAR system  100  may include network interface  214  for communicating with host  210  (e.g., a vehicle controller). The communication between LIDAR system  100  and host  210  is represented by a dashed arrow. In one embodiment, network interface  214  may include an integrated services digital network (ISDN) card, cable modem, satellite modem, or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, network interface  214  may include a local area network (LAN) card to provide a data communication connection to a compatible LAN. In another embodiment, network interface  214  may include an Ethernet port connected to radio frequency receivers and transmitters and/or optical (e.g., infrared) receivers and transmitters. The specific design and implementation of network interface  214  depends on the communications network(s) over which LIDAR system  100  and host  210  are intended to operate. For example, network interface  214  may be used, for example, to provide outputs of LIDAR system  100  to the external system, such as a 3D model, operational parameters of LIDAR system  100 , and so on. In other embodiment, the communication unit may be used, for example, to receive instructions from the external system, to receive information regarding the inspected environment, to receive information from another sensor, etc. 
       FIG.  2 B  illustrates an example of a monostatic configuration of LIDAR system  100  including a plurality projecting units  102 . The term “monostatic configuration” broadly refers to LIDAR system configurations in which the projected light exiting from the LIDAR system and the reflected light entering the LIDAR system pass through substantially similar optical paths. In one example, the outbound light beam and the inbound light beam may share at least one optical assembly through which both outbound and inbound light beams pass. In another example, the outbound light may pass through an optical window (not shown) and the inbound light radiation may pass through the same optical window. A monostatic configuration may include a configuration where the scanning unit  104  includes a single light deflector  114  that directs the projected light towards field of view  120  and directs the reflected light towards a sensor  116 . As shown, both projected light  204  and reflected light  206  hits an asymmetrical deflector  216 . The term “asymmetrical deflector” refers to any optical device having two sides capable of deflecting a beam of light hitting it from one side in a different direction than it deflects a beam of light hitting it from the second side. In one example, the asymmetrical deflector does not deflect projected light  204  and deflects reflected light  206  towards sensor  116 . One example of an asymmetrical deflector may include a polarization beam splitter. In another example, asymmetrical  216  may include an optical isolator that allows the passage of light in only one direction. A diagrammatic representation of asymmetrical deflector  216  is illustrated in  FIG.  2 D . Consistent with the present disclosure, a monostatic configuration of LIDAR system  100  may include an asymmetrical deflector to prevent reflected light from hitting light source  112 , and to direct all the reflected light toward sensor  116 , thereby increasing detection sensitivity. 
     In the embodiment of  FIG.  2 B , LIDAR system  100  includes three projecting units  102  each with a single of light source  112  aimed at a common light deflector  114 . In one embodiment, the plurality of light sources  112  (including two or more light sources) may project light with substantially the same wavelength and each light source  112  is generally associated with a differing area of the field of view (denoted in the figure as  120 A,  120 B, and  120 C). This enables scanning of a broader field of view than can be achieved with a light source  112 . In another embodiment, the plurality of light sources  102  may project light with differing wavelengths, and all the light sources  112  may be directed to the same portion (or overlapping portions) of field of view  120 . 
       FIG.  2 C  illustrates an example of LIDAR system  100  in which projecting unit  102  includes a primary light source  112 A and a secondary light source  112 B. Primary light source  112 A may project light with a longer wavelength than is sensitive to the human eye in order to optimize SNR and detection range. For example, primary light source  112 A may project light with a wavelength between about 750 nm and 1100 nm. In contrast, secondary light source  112 B may project light with a wavelength visible to the human eye. For example, secondary light source  112 B may project light with a wavelength between about 400 nm and 700 nm. In one embodiment, secondary light source  112 B may project light along substantially the same optical path the as light projected by primary light source  112 A. Both light sources may be time-synchronized and may project light emission together or in interleaved pattern. An interleave pattern means that the light sources are not active at the same time which may mitigate mutual interference. A person who is of skill in the art would readily see that other combinations of wavelength ranges and activation schedules may also be implemented. 
     Consistent with some embodiments, secondary light source  112 B may cause human eyes to blink when it is too close to the LIDAR optical output port. This may ensure an eye safety mechanism not feasible with typical laser sources that utilize the near-infrared light spectrum. In another embodiment, secondary light source  112 B may be used for calibration and reliability at a point of service, in a manner somewhat similar to the calibration of headlights with a special reflector/pattern at a certain height from the ground with respect to vehicle  110 . An operator at a point of service could examine the calibration of the LIDAR by simple visual inspection of the scanned pattern over a featured target such a test pattern board at a designated distance from LIDAR system  100 . In addition, secondary light source  112 B may provide means for operational confidence that the LIDAR is working for the end-user. For example, the system may be configured to permit a human to place a hand in front of light deflector  114  to test its operation. 
     Secondary light source  112 B may also have a non-visible element that can double as a backup system in case primary light source  112 A fails. This feature may be useful for fail-safe devices with elevated functional safety ratings. Given that secondary light source  112 B may be visible and also due to reasons of cost and complexity, secondary light source  112 B may be associated with a smaller power compared to primary light source  112 A. Therefore, in case of a failure of primary light source  112 A, the system functionality will fall back to secondary light source  112 B set of functionalities and capabilities. While the capabilities of secondary light source  112 B may be inferior to the capabilities of primary light source  112 A, LIDAR system  100  system may be designed in such a fashion to enable vehicle  110  to safely arrive its destination. 
       FIG.  2 D  illustrates asymmetrical deflector  216  that may be part of LIDAR system  100 . In the illustrated example, asymmetrical deflector  216  includes a reflective surface  218  (such as a mirror) and a one-way deflector  220 . While not necessarily so, asymmetrical deflector  216  may optionally be a static deflector. Asymmetrical deflector  216  may be used in a monostatic configuration of LIDAR system  100 , in order to allow a common optical path for transmission and for reception of light via the at least one deflector  114 , e.g. as illustrated in  FIGS.  2 B and  2 C . However, typical asymmetrical deflectors such as beam splitters are characterized by energy losses, especially in the reception path, which may be more sensitive to power loses than the transmission path. 
     As depicted in  FIG.  2 D , LIDAR system  100  may include asymmetrical deflector  216  positioned in the transmission path, which includes one-way deflector  220  for separating between the transmitted and received light signals Optionally, one-way deflector  220  may be substantially transparent to the transmission light and substantially reflective to the received light. The transmitted light is generated by projecting unit  102  and may travel through one-way deflector  220  to scanning unit  104  which deflects it towards the optical outlet. The received light arrives through the optical inlet, to the at least one deflecting element  114 , which deflects the reflections signal into a separate path away from the light source and towards sensing unit  106 . Optionally, asymmetrical deflector  216  may be combined with a polarized light source  112  which is linearly polarized with the same polarization axis as one-way deflector  220 . Notably, the cross-section of the outbound light beam is much smaller than that of the reflections signals. Accordingly, LIDAR system  100  may include one or more optical components (e.g. lens, collimator) for focusing or otherwise manipulating the emitted polarized light beam to the dimensions of the asymmetrical deflector  216 . In one embodiment, one-way deflector  220  may be a polarizing beam splitter that is virtually transparent to the polarized light beam. 
     Consistent with some embodiments, LIDAR system  100  may further include optics  222  (e.g., a quarter wave plate retarder) for modifying a polarization of the emitted light. For example, optics  222  may modify a linear polarization of the emitted light beam to circular polarization. Light reflected back to system  100  from the field of view would arrive back through deflector  114  to optics  222 , bearing a circular polarization with a reversed handedness with respect to the transmitted light. Optics  222  would then convert the received reversed handedness polarization light to a linear polarization that is not on the same axis as that of the polarized beam splitter  216 . As noted above, the received light-patch is larger than the transmitted light-patch, due to optical dispersion of the beam traversing through the distance to the target. 
     Some of the received light will impinge on one-way deflector  220  that will reflect the light towards sensor  106  with some power loss. However, another part of the received patch of light will fall on a reflective surface  218  which surrounds one-way deflector  220  (e.g., polarizing beam splitter slit). Reflective surface  218  will reflect the light towards sensing unit  106  with substantially zero power loss. One-way deflector  220  would reflect light that is composed of various polarization axes and directions that will eventually arrive at the detector. Optionally, sensing unit  106  may include sensor  116  that is agnostic to the laser polarization, and is primarily sensitive to the amount of impinging photons at a certain wavelength range. 
     It is noted that the proposed asymmetrical deflector  216  provides far superior performances when compared to a simple mirror with a passage hole in it. In a mirror with a hole, all of the reflected light which reaches the hole is lost to the detector. However, in deflector  216 , one-way deflector  220  deflects a significant portion of that light (e.g., about 50%) toward the respective sensor  116 . In LIDAR systems, the number photons reaching the LIDAR from remote distances is very limited, and therefore the improvement in photon capture rate is important. 
     According to some embodiments, a device for beam splitting and steering is described. A polarized beam may be emitted from a light source having a first polarization. The emitted beam may be directed to pass through a polarized beam splitter assembly. The polarized beam splitter assembly includes on a first side a one-directional slit and on an opposing side a mirror. The one-directional slit enables the polarized emitted beam to travel toward a quarter-wave-plate/wave-retarder which changes the emitted signal from a polarized signal to a linear signal (or vice versa) so that subsequently reflected beams cannot travel through the one-directional slit. 
       FIG.  2 E  shows an example of a bi-static configuration of LIDAR system  100  without scanning unit  104 . In order to illuminate an entire field of view (or substantially the entire field of view) without deflector  114 , projecting unit  102  may optionally include an array of light sources (e.g.,  112 A- 112 F). In one embodiment, the array of light sources may include a linear array of light sources controlled by processor  118 . For example, processor  118  may cause the linear array of light sources to sequentially project collimated laser beams towards first optional optical window  124 A. First optional optical window  124 A may include a diffuser lens for spreading the projected light and sequentially forming wide horizontal and narrow vertical beams. Optionally, some or all of the at least one light source  112  of system  100  may project light concurrently. For example, processor  118  may cause the array of light sources to simultaneously project light beams from a plurality of non-adjacent light sources  112 . In the depicted example, light source  112 A, light source  112 D, and light source  112 F simultaneously project laser beams towards first optional optical window  124 A thereby illuminating the field of view with three narrow vertical beams. The light beam from fourth light source  112 D may reach an object in the field of view. The light reflected from the object may be captured by second optical window  124 B and may be redirected to sensor  116 . The configuration depicted in  FIG.  2 E  is considered to be a bi-static configuration because the optical paths of the projected light and the reflected light are substantially different. It is noted that projecting unit  102  may also include a plurality of light sources  112  arranged in non-linear configurations, such as a two dimensional array, in hexagonal tiling, or in any other way. 
       FIG.  2 F  illustrates an example of a monostatic configuration of LIDAR system  100  without scanning unit  104 . Similar to the example embodiment represented in  FIG.  2 E , in order to illuminate an entire field of view without deflector  114 , projecting unit  102  may include an array of light sources (e.g.,  112 A- 112 F). But, in contrast to  FIG.  2 E , this configuration of LIDAR system  100  may include a single optical window  124  for both the projected light and for the reflected light. Using asymmetrical deflector  216 , the reflected light may be redirected to sensor  116 . The configuration depicted in  FIG.  2 E  is considered to be a monostatic configuration because the optical paths of the projected light and the reflected light are substantially similar to one another. The term “substantially similar” in the context of the optical paths of the projected light and the reflected light means that the overlap between the two optical paths may be more than 80%, more than 85%, more than 90%, or more than 95%. 
       FIG.  2 G  illustrates an example of a bi-static configuration of LIDAR system  100 . The configuration of LIDAR system  100  in this figure is similar to the configuration shown in  FIG.  2 A . For example, both configurations include a scanning unit  104  for directing projected light in the outbound direction toward the field of view. But, in contrast to the embodiment of  FIG.  2 A , in this configuration, scanning unit  104  does not redirect the reflected light in the inbound direction. Instead the reflected light passes through second optical window  124 B and enters sensor  116 . The configuration depicted in  FIG.  2 G  is considered to be a bi-static configuration because the optical paths of the projected light and the reflected light are substantially different from one another. The term “substantially different” in the context of the optical paths of the projected light and the reflected light means that the overlap between the two optical paths may be less than 10%, less than 5%, less than 1%, or less than 0.25%. 
     The Scanning Unit 
       FIGS.  3 A- 3 D  depict various configurations of scanning unit  104  and its role in LIDAR system  100 . Specifically,  FIG.  3 A  is a diagram illustrating scanning unit  104  with a MEMS mirror (e.g., square shaped),  FIG.  3 B  is a diagram illustrating another scanning unit  104  with a MEMS mirror (e.g., round shaped),  FIG.  3 C  is a diagram illustrating scanning unit  104  with an array of reflectors used for monostatic scanning LIDAR system, and  FIG.  3 D  is a diagram illustrating an example LIDAR system  100  that mechanically scans the environment around LIDAR system  100 . One skilled in the art will appreciate that the depicted configurations of scanning unit  104  are exemplary only, and may have numerous variations and modifications within the scope of this disclosure. 
       FIG.  3 A  illustrates an example scanning unit  104  with a single axis square MEMS mirror  300 . In this example MEMS mirror  300  functions as at least one deflector  114 . As shown, scanning unit  104  may include one or more actuators  302  (specifically,  302 A and  302 B). In one embodiment, actuator  302  may be made of semiconductor (e.g., silicon) and includes a piezoelectric layer (e.g. PZT, Lead zirconate titanate, aluminum nitride), which changes its dimension in response to electric signals applied by an actuation controller, a semi conductive layer, and a base layer. In one embodiment, the physical properties of actuator  302  may determine the mechanical stresses that actuator  302  experiences when electrical current passes through it. When the piezoelectric material is activated it exerts force on actuator  302  and causes it to bend. In one embodiment, the resistivity of one or more actuators  302  may be measured in an active state (Ractive) when mirror  300  is deflected at a certain angular position and compared to the resistivity at a resting state (Rrest). Feedback including Ractive may provide information to determine the actual mirror deflection angle compared to an expected angle, and, if needed, mirror  300  deflection may be corrected. The difference between Rrest and Ractive may be correlated by a mirror drive into an angular deflection value that may serve to close the loop. This embodiment may be used for dynamic tracking of the actual mirror position and may optimize response, amplitude, deflection efficiency, and frequency for both linear mode and resonant mode MEMS mirror schemes. This embodiment is described in greater detail below with reference to  FIGS.  32 - 34   . 
     During scanning, current (represented in the figure as the dashed line) may flow from contact  304 A to contact  304 B (through actuator  302 A, spring  306 A, mirror  300 , spring  306 B, and actuator  302 B). Isolation gaps in semiconducting frame  308  such as isolation gap  310  may cause actuator  302 A and  302 B to be two separate islands connected electrically through springs  306  and frame  308 . The current flow, or any associated electrical parameter (voltage, current frequency, capacitance, relative dielectric constant, etc.), may be monitored by an associated position feedback. In case of a mechanical failure—where one of the components is damaged—the current flow through the structure would alter and change from its functional calibrated values. At an extreme situation (for example, when a spring is broken), the current would stop completely due to a circuit break in the electrical chain by means of a faulty element. 
       FIG.  3 B  illustrates another example scanning unit  104  with a dual axis round MEMS mirror  300 . In this example MEMS mirror  300  functions as at least one deflector  114 . In one embodiment, MEMS mirror  300  may have a diameter of between about 1 mm to about 5 mm. As shown, scanning unit  104  may include four actuators  302  ( 302 A,  302 B,  302 C, and  302 D) each may be at a differing length. In the illustrated example, the current (represented in the figure as the dashed line) flows from contact  304 A to contact  304 D, but in other cases current may flow from contact  304 A to contact  304 B, from contact  304 A to contact  304 C, from contact  304 B to contact  304 C, from contact  304 B to contact  304 D, or from contact  304 C to contact  304 D. Consistent with some embodiments, a dual axis MEMS mirror may be configured to deflect light in a horizontal direction and in a vertical direction. For example, the angles of deflection of a dual axis MEMS mirror may be between about 0° to 30° in the vertical direction and between about 0° to 50° in the horizontal direction. One skilled in the art will appreciate that the depicted configuration of mirror  300  may have numerous variations and modifications. In one example, at least of deflector  114  may have a dual axis square-shaped mirror or single axis round-shaped mirror. Examples of round and square mirror are depicted in  FIGS.  3 A and  3 B  as examples only. Any shape may be employed depending on system specifications. In one embodiment, actuators  302  may be incorporated as an integral part of at least of deflector  114 , such that power to move MEMS mirror  300  is applied directly towards it. In addition, MEMS mirror  300  may be connected to frame  308  by one or more rigid supporting elements. In another embodiment, at least of deflector  114  may include an electrostatic or electromagnetic MEMS mirror. 
     As described above, a monostatic scanning LIDAR system utilizes at least a portion of the same optical path for emitting projected light  204  and for receiving reflected light  206 . The light beam in the outbound path may be collimated and focused into a narrow beam while the reflections in the return path spread into a larger patch of light, due to dispersion. In one embodiment, scanning unit  104  may have a large reflection area in the return path and asymmetrical deflector  216  that redirects the reflections (i.e., reflected light  206 ) to sensor  116 . In one embodiment, scanning unit  104  may include a MEMS mirror with a large reflection area and negligible impact on the field of view and the frame rate performance. Additional details about the asymmetrical deflector  216  are provided below with reference to  FIG.  2 D . 
     In some embodiments (e.g. as exemplified in  FIG.  3 C ), scanning unit  104  may include a deflector array (e.g. a reflector array) with small light deflectors (e.g. mirrors). In one embodiment, implementing light deflector  114  as a group of smaller individual light deflectors working in synchronization may allow light deflector  114  to perform at a high scan rate with larger angles of deflection. The deflector array may essentially act as a large light deflector (e.g. a large mirror) in terms of effective area. The deflector array may be operated using a shared steering assembly configuration that allows sensor  116  to collect reflected photons from substantially the same portion of field of view  120  being concurrently illuminated by light source  112 . The term “concurrently” means that the two selected functions occur during coincident or overlapping time periods, either where one begins and ends during the duration of the other, or where a later one starts before the completion of the other. 
       FIG.  3 C  illustrates an example of scanning unit  104  with a reflector array  312  having small mirrors. In this embodiment, reflector array  312  functions as at least one deflector  114 . Reflector array  312  may include a plurality of reflector units  314  configured to pivot (individually or together) and steer light pulses toward field of view  120 . For example, reflector array  312  may be a part of an outbound path of light projected from light source  112 . Specifically, reflector array  312  may direct projected light  204  towards a portion of field of view  120 . Reflector array  312  may also be part of a return path for light reflected from a surface of an object located within an illumined portion of field of view  120 . Specifically, reflector array  312  may direct reflected light  206  towards sensor  116  or towards asymmetrical deflector  216 . In one example, the area of reflector array  312  may be between about 75 to about 150 mm 2 , where each reflector units  314  may have a width of about 10 μm and the supporting structure may be lower than 100 μm. 
     According to some embodiments, reflector array  312  may include one or more sub-groups of steerable deflectors. Each sub-group of electrically steerable deflectors may include one or more deflector units, such as reflector unit  314 . For example, each steerable deflector unit  314  may include at least one of a MEMS mirror, a reflective surface assembly, and an electromechanical actuator. In one embodiment, each reflector unit  314  may be individually controlled by an individual processor (not shown), such that it may tilt towards a specific angle along each of one or two separate axes. Alternatively, reflector array  312  may be associated with a common controller (e.g., processor  118 ) configured to synchronously manage the movement of reflector units  314  such that at least part of them will pivot concurrently and point in approximately the same direction. 
     In addition, at least one processor  118  may select at least one reflector unit  314  for the outbound path (referred to hereinafter as “TX Mirror”) and a group of reflector units  314  for the return path (referred to hereinafter as “RX Mirror”). Consistent with the present disclosure, increasing the number of TX Mirrors may increase a reflected photons beam spread. Additionally, decreasing the number of RX Mirrors may narrow the reception field and compensate for ambient light conditions (such as clouds, rain, fog, extreme heat, and other environmental conditions) and improve the signal to noise ratio. Also, as indicated above, the emitted light beam is typically narrower than the patch of reflected light, and therefore can be fully deflected by a small portion of the deflection array. Moreover, it is possible to block light reflected from the portion of the deflection array used for transmission (e.g. the TX mirror) from reaching sensor  116 , thereby reducing an effect of internal reflections of the LIDAR system  100  on system operation. In addition, at least one processor  118  may pivot one or more reflector units  314  to overcome mechanical impairments and drifts due, for example, to thermal and gain effects. In an example, one or more reflector units  314  may move differently than intended (frequency, rate, speed etc.) and their movement may be compensated for by electrically controlling the deflectors appropriately. 
       FIG.  3 D  illustrates an exemplary LIDAR system  100  that mechanically scans the environment of LIDAR system  100 . In this example, LIDAR system  100  may include a motor or other mechanisms for rotating housing  200  about the axis of the LIDAR system  100 . Alternatively, the motor (or other mechanism) may mechanically rotate a rigid structure of LIDAR system  100  on which one or more light sources  112  and one or more sensors  116  are installed, thereby scanning the environment. As described above, projecting unit  102  may include at least one light source  112  configured to project light emission. The projected light emission may travel along an outbound path towards field of view  120 . Specifically, the projected light emission may be reflected by deflector  114 A through an exit aperture  314  when projected light  204  travel towards optional optical window  124 . The reflected light emission may travel along a return path from object  208  towards sensing unit  106 . For example, the reflected light  206  may be reflected by deflector  114 B when reflected light  206  travels towards sensing unit  106 . A person skilled in the art would appreciate that a LIDAR system with a rotation mechanism for synchronically rotating one or more light sources or one or more sensors, may use this synchronized rotation instead of (or in addition to) steering an internal light deflector. 
     In embodiments in which the scanning of field of view  120  is mechanical, the projected light emission may be directed to exit aperture  314  that is part of a wall  316  separating projecting unit  102  from other parts of LIDAR system  100 . In some examples, wall  316  can be formed from a transparent material (e.g., glass) coated with a reflective material to form deflector  114 B. In this example, exit aperture  314  may correspond to the portion of wall  316  that is not coated by the reflective material. Additionally or alternatively, exit aperture  314  may include a hole or cut-away in the wall  316 . Reflected light  206  may be reflected by deflector  114 B and directed towards an entrance aperture  318  of sensing unit  106 . In some examples, an entrance aperture  318  may include a filtering window configured to allow wavelengths in a certain wavelength range to enter sensing unit  106  and attenuate other wavelengths. The reflections of object  208  from field of view  120  may be reflected by deflector  114 B and hit sensor  116 . By comparing several properties of reflected light  206  with projected light  204 , at least one aspect of object  208  may be determined. For example, by comparing a time when projected light  204  was emitted by light source  112  and a time when sensor  116  received reflected light  206 , a distance between object  208  and LIDAR system  100  may be determined. In some examples, other aspects of object  208 , such as shape, color, material, etc. may also be determined. 
     In some examples, the LIDAR system  100  (or part thereof, including at least one light source  112  and at least one sensor  116 ) may be rotated about at least one axis to determine a three-dimensional map of the surroundings of the LIDAR system  100 . For example, the LIDAR system  100  may be rotated about a substantially vertical axis as illustrated by arrow  320  in order to scan field of  120 . Although  FIG.  3 D  illustrates that the LIDAR system  100  is rotated clock-wise about the axis as illustrated by the arrow  320 , additionally or alternatively, the LIDAR system  100  may be rotated in a counter clockwise direction. In some examples, the LIDAR system  100  may be rotated 360 degrees about the vertical axis. In other examples, the LIDAR system  100  may be rotated back and forth along a sector smaller than 360-degree of the LIDAR system  100 . For example, the LIDAR system  100  may be mounted on a platform that wobbles back and forth about the axis without making a complete rotation. 
     The Sensing Unit 
       FIGS.  4 A- 4 E  depict various configurations of sensing unit  106  and its role in LIDAR system  100 . Specifically,  FIG.  4 A  is a diagram illustrating an example sensing unit  106  with a detector array,  FIG.  4 B  is a diagram illustrating monostatic scanning using a two-dimensional sensor,  FIG.  4 C  is a diagram illustrating an example of a two-dimensional sensor  116 ,  FIG.  4 D  is a diagram illustrating a lens array associated with sensor  116 , and  FIG.  4 E  includes three diagram illustrating the lens structure. One skilled in the art will appreciate that the depicted configurations of sensing unit  106  are exemplary only and may have numerous alternative variations and modifications consistent with the principles of this disclosure. 
       FIG.  4 A  illustrates an example of sensing unit  106  with detector array  400 . In this example, at least one sensor  116  includes detector array  400 . LIDAR system  100  is configured to detect objects (e.g., bicycle  208 A and cloud  208 B) in field of view  120  located at different distances from LIDAR system  100  (could be meters or more). Objects  208  may be a solid object (e.g. a road, a tree, a car, a person), fluid object (e.g. fog, water, atmosphere particles), or object of another type (e.g. dust or a powdery illuminated object). When the photons emitted from light source  112  hit object  208  they either reflect, refract, or get absorbed. Typically, as shown in the figure, only a portion of the photons reflected from object  208 A enters optional optical window  124 . As each ˜15 cm change in distance results in a travel time difference of 1 ns (since the photons travel at the speed of light to and from object  208 ), the time differences between the travel times of different photons hitting the different objects may be detectable by a time-of-flight sensor with sufficiently quick response. 
     Sensor  116  includes a plurality of detection elements  402  for detecting photons of a photonic pulse reflected back from field of view  120 . The detection elements may all be included in detector array  400 , which may have a rectangular arrangement (e.g. as shown) or any other arrangement. Detection elements  402  may operate concurrently or partially concurrently with each other. Specifically, each detection element  402  may issue detection information for every sampling duration (e.g. every 1 nanosecond). In one example, detector array  400  may be a SiPM (Silicon photomultipliers) which is a solid-state single-photon-sensitive device built from an array of single photon avalanche diode (SPAD, serving as detection elements  402 ) on a common silicon substrate. Similar photomultipliers from other, non-silicon materials may also be used. Although a SiPM device works in digital/switching mode, the SiPM is an analog device because all the microcells are read in parallel, making it possible to generate signals within a dynamic range from a single photon to hundreds and thousands of photons detected by the different SPADs. As mentioned above, more than one type of sensor may be implemented (e.g. SiPM and APD). Possibly, sensing unit  106  may include at least one APD integrated into an SiPM array and/or at least one APD detector located next to a SiPM on a separate or common silicon substrate. 
     In one embodiment, detection elements  402  may be grouped into a plurality of regions  404 . The regions are geometrical locations or environments within sensor  116  (e.g. within detector array  400 )—and may be shaped in different shapes (e.g. rectangular as shown, squares, rings, and so on, or in any other shape). While not all of the individual detectors, which are included within the geometrical area of a region  404 , necessarily belong to that region, in most cases they will not belong to other regions  404  covering other areas of the sensor  310 —unless some overlap is desired in the seams between regions. As illustrated in  FIG.  4 A , the regions may be non-overlapping regions  404 , but alternatively, they may overlap. Every region may be associated with a regional output circuitry  406  associated with that region. The regional output circuitry  406  may provide a region output signal of a corresponding group of detection elements  402 . For example, the region of output circuitry  406  may be a summing circuit, but other forms of combined output of the individual detector into a unitary output (whether scalar, vector, or any other format) may be employed. Optionally, each region  404  is a single SiPM, but this is not necessarily so, and a region may be a sub-portion of a single SiPM, a group of several SiPMs, or even a combination of different types of detectors. 
     In the illustrated example, processing unit  108  is located at a separated housing  200 B (within or outside) host  210  (e.g. within vehicle  110 ), and sensing unit  106  may include a dedicated processor  408  for analyzing the reflected light. Alternatively, processing unit  108  may be used for analyzing reflected light  206 . It is noted that LIDAR system  100  may be implemented multiple housings in other ways than the illustrated example. For example, light deflector  114  may be located in a different housing than projecting unit  102  and/or sensing module  106 . In one embodiment, LIDAR system  100  may include multiple housings connected to each other in different ways, such as: electric wire connection, wireless connection (e.g., RF connection), fiber optics cable, and any combination of the above. 
     In one embodiment, analyzing reflected light  206  may include determining a time of flight for reflected light  206 , based on outputs of individual detectors of different regions. Optionally, processor  408  may be configured to determine the time of flight for reflected light  206  based on the plurality of regions of output signals. In addition to the time of flight, processing unit  108  may analyze reflected light  206  to determine the average power across an entire return pulse, and the photon distribution/signal may be determined over the return pulse period (“pulse shape”). In the illustrated example, the outputs of any detection elements  402  may not be transmitted directly to processor  408 , but rather combined (e g summed) with signals of other detectors of the region  404  before being passed to processor  408 . However, this is only an example and the circuitry of sensor  116  may transmit information from a detection element  402  to processor  408  via other routes (not via a region output circuitry  406 ). 
       FIG.  4 B  is a diagram illustrating LIDAR system  100  configured to scan the environment of LIDAR system  100  using a two-dimensional sensor  116 . In the example of  FIG.  4 B , sensor  116  is a matrix of 4×6 detectors  410  (also referred to as “pixels”). In one embodiment, a pixel size may be about 1×1 mm. Sensor  116  is two-dimensional in the sense that it has more than one set (e.g. row, column) of detectors  410  in two non-parallel axes (e.g. orthogonal axes, as exemplified in the illustrated examples). The number of detectors  410  in sensor  116  may vary between differing implementations, e.g. depending on the desired resolution, signal to noise ratio (SNR), desired detection distance, and so on. For example, sensor  116  may have anywhere between 5 and 5,000 pixels. In another example (not shown in the figure) Also, sensor  116  may be a one-dimensional matrix (e.g. 1×8 pixels). 
     It is noted that each detector  410  may include a plurality of detection elements  402 , such as Avalanche Photo Diodes (APD), Single Photon Avalanche Diodes (SPADs), combination of Avalanche Photo Diodes (APD) and Single Photon Avalanche Diodes (SPADs) or detecting elements that measure both the time of flight from a laser pulse transmission event to the reception event and the intensity of the received photons. For example, each detector  410  may include anywhere between 20 and 5,000 SPADs. The outputs of detection elements  402  in each detector  410  may be summed, averaged, or otherwise combined to provide a unified pixel output. 
     In the illustrated example, sensing unit  106  may include a two-dimensional sensor  116  (or a plurality of two-dimensional sensors  116 ), whose field of view is smaller than field of view  120  of LIDAR system  100 . In this discussion, field of view  120  (the overall field of view which can be scanned by LIDAR system  100  without moving, rotating or rolling in any direction) is denoted “first FOV  412 ”, and the smaller FOV of sensor  116  is denoted “second FOV  412 ” (interchangeably “instantaneous FOV”). The coverage area of second FOV  414  relative to the first FOV  412  may differ, depending on the specific use of LIDAR system  100 , and may be, for example, between 0.5% and 50%. In one example, second FOV  412  may be between about 0.05° and 1° elongated in the vertical dimension. Even if LIDAR system  100  includes more than one two-dimensional sensor  116 , the combined field of view of the sensors array may still be smaller than the first FOV  412 , e.g. by a factor of at least 5, by a factor of at least 10, by a factor of at least 20, or by a factor of at least 50, for example. 
     In order to cover first FOV  412 , scanning unit  106  may direct photons arriving from different parts of the environment to sensor  116  at different times. In the illustrated monostatic configuration, together with directing projected light  204  towards field of view  120  and when least one light deflector  114  is located in an instantaneous position, scanning unit  106  may also direct reflected light  206  to sensor  116 . Typically, at every moment during the scanning of first FOV  412 , the light beam emitted by LIDAR system  100  covers part of the environment which is larger than the second FOV  414  (in angular opening) and includes the part of the environment from which light is collected by scanning unit  104  and sensor  116 . 
       FIG.  4 C  is a diagram illustrating an example of a two-dimensional sensor  116 . In this embodiment, sensor  116  is a matrix of 8×5 detectors  410  and each detector  410  includes a plurality of detection elements  402 . In one example, detector  410 A is located in the second row (denoted “R 2 ”) and third column (denoted “C 3 ”) of sensor  116 , which includes a matrix of 4×3 detection elements  402 . In another example, detector  410 B located in the fourth row (denoted “R 4 ”) and sixth column (denoted “C 6 ”) of sensor  116  includes a matrix of 3×3 detection elements  402 . Accordingly, the number of detection elements  402  in each detector  410  may be constant, or may vary, and differing detectors  410  in a common array may have a different number of detection elements  402 . The outputs of all detection elements  402  in each detector  410  may be summed, averaged, or otherwise combined to provide a single pixel-output value. It is noted that while detectors  410  in the example of  FIG.  4 C  are arranged in a rectangular matrix (straight rows and straight columns), other arrangements may also be used, e.g. a circular arrangement or a honeycomb arrangement. 
     According to some embodiments, measurements from each detector  410  may enable determination of the time of flight from a light pulse emission event to the reception event and the intensity of the received photons. The reception event may be the result of the light pulse being reflected from object  208 . The time of flight may be a timestamp value that represents the distance of the reflecting object to optional optical window  124 . Time of flight values may be realized by photon detection and counting methods, such as Time Correlated Single Photon Counters (TCSPC), analog methods for photon detection such as signal integration and qualification (via analog to digital converters or plain comparators) or otherwise. 
     In some embodiments and with reference to  FIG.  4 B , during a scanning cycle, each instantaneous position of at least one light deflector  114  may be associated with a particular portion  122  of field of view  120 . The design of sensor  116  enables an association between the reflected light from a single portion of field of view  120  and multiple detectors  410 . Therefore, the scanning resolution of LIDAR system may be represented by the number of instantaneous positions (per scanning cycle) times the number of detectors  410  in sensor  116 . The information from each detector  410  (i.e., each pixel) represents the basic data element that from which the captured field of view in the three-dimensional space is built. This may include, for example, the basic element of a point cloud representation, with a spatial position and an associated reflected intensity value. In one embodiment, the reflections from a single portion of field of view  120  that are detected by multiple detectors  410  may be returning from different objects located in the single portion of field of view  120 . For example, the single portion of field of view  120  may be greater than 50×50 cm at the far field, which can easily include two, three, or more objects partly covered by each other. 
       FIG.  4 D  is a cross cut diagram of a part of sensor  116 , in accordance with examples of the presently disclosed subject matter. The illustrated part of sensor  116  includes a part of a detector array  400  which includes four detection elements  402  (e.g., four SPADs, four APDs). Detector array  400  may be a photodetector sensor realized in complementary metal-oxide-semiconductor (CMOS). Each of the detection elements  402  has a sensitive area, which is positioned within a substrate surrounding. While not necessarily so, sensor  116  may be used in a monostatic LiDAR system having a narrow field of view (e.g., because scanning unit  104  scans different parts of the field of view at different times). The narrow field of view for the incoming light beam—if implemented—eliminates the problem of out-of-focus imaging. As exemplified in  FIG.  4 D , sensor  116  may include a plurality of lenses  422  (e.g., microlenses), each lens  422  may direct incident light toward a different detection element  402  (e.g., toward an active area of detection element  402 ), which may be usable when out-of-focus imaging is not an issue. Lenses  422  may be used for increasing an optical fill factor and sensitivity of detector array  400 , because most of the light that reaches sensor  116  may be deflected toward the active areas of detection elements  402   
     Detector array  400 , as exemplified in  FIG.  4 D , may include several layers built into the silicon substrate by various methods (e.g., implant) resulting in a sensitive area, contact elements to the metal layers and isolation elements (e.g., shallow trench implant STI, guard rings, optical trenches, etc.). The sensitive area may be a volumetric element in the CMOS detector that enables the optical conversion of incoming photons into a current flow given an adequate voltage bias is applied to the device. In the case of a APD/SPAD, the sensitive area would be a combination of an electrical field that pulls electrons created by photon absorption towards a multiplication area where a photon induced electron is amplified creating a breakdown avalanche of multiplied electrons. 
     A front side illuminated detector (e.g., as illustrated in  FIG.  4 D ) has the input optical port at the same side as the metal layers residing on top of the semiconductor (Silicon). The metal layers are required to realize the electrical connections of each individual photodetector element (e.g., anode and cathode) with various elements such as: bias voltage, quenching/ballast elements, and other photodetectors in a common array. The optical port through which the photons impinge upon the detector sensitive area is comprised of a passage through the metal layer. It is noted that passage of light from some directions through this passage may be blocked by one or more metal layers (e.g., metal layer ML 6 , as illustrated for the leftmost detector elements  402  in  FIG.  4 D ). Such blockage reduces the total optical light absorbing efficiency of the detector. 
       FIG.  4 E  illustrates three detection elements  402 , each with an associated lens  422 , in accordance with examples of the presenting disclosed subject matter. Each of the three detection elements of  FIG.  4 E , denoted  402 ( 1 ),  402 ( 2 ), and  402 ( 3 ), illustrates a lens configuration which may be implemented in associated with one or more of the detecting elements  402  of sensor  116 . It is noted that combinations of these lens configurations may also be implemented. 
     In the lens configuration illustrated with regards to detection element  402 ( 1 ), a focal point of the associated lens  422  may be located above the semiconductor surface. Optionally, openings in different metal layers of the detection element may have different sizes aligned with the cone of focusing light generated by the associated lens  422 . Such a structure may improve the signal-to-noise and resolution of the array  400  as a whole device. Large metal layers may be important for delivery of power and ground shielding. This approach may be useful, e.g., with a monostatic LiDAR design with a narrow field of view where the incoming light beam is comprised of parallel rays and the imaging focus does not have any consequence to the detected signal. 
     In the lens configuration illustrated with regards to detection element  402 ( 2 ), an efficiency of photon detection by the detection elements  402  may be improved by identifying a sweet spot. Specifically, a photodetector implemented in CMOS may have a sweet spot in the sensitive volume area where the probability of a photon creating an avalanche effect is the highest. Therefore, a focal point of lens  422  may be positioned inside the sensitive volume area at the sweet spot location, as demonstrated by detection elements  402 ( 2 ). The lens shape and distance from the focal point may take into account the refractive indices of all the elements the laser beam is passing along the way from the lens to the sensitive sweet spot location buried in the semiconductor material. 
     In the lens configuration illustrated with regards to the detection element on the right of  FIG.  4 E , an efficiency of photon absorption in the semiconductor material may be improved using a diffuser and reflective elements. Specifically, a near IR wavelength requires a significantly long path of silicon material in order to achieve a high probability of absorbing a photon that travels through. In a typical lens configuration, a photon may traverse the sensitive area and may not be absorbed into a detectable electron. A long absorption path that improves the probability for a photon to create an electron renders the size of the sensitive area towards less practical dimensions (tens of um for example) for a CMOS device fabricated with typical foundry processes. The rightmost detector element in  FIG.  4 E  demonstrates a technique for processing incoming photons. The associated lens  422  focuses the incoming light onto a diffuser element  424 . In one embodiment, light sensor  116  may further include a diffuser located in the gap distant from the outer surface of at least some of the detectors. For example, diffuser  424  may steer the light beam sideways (e.g., as perpendicular as possible) towards the sensitive area and the reflective optical trenches  426 . The diffuser is located at the focal point, above the focal point, or below the focal point. In this embodiment, the incoming light may be focused on a specific location where a diffuser element is located. Optionally, detector element  422  is designed to optically avoid the inactive areas where a photon induced electron may get lost and reduce the effective detection efficiency. Reflective optical trenches  426  (or other forms of optically reflective structures) cause the photons to bounce back and forth across the sensitive area, thus increasing the likelihood of detection. Ideally, the photons will get trapped in a cavity consisting of the sensitive area and the reflective trenches indefinitely until the photon is absorbed and creates an electron/hole pair. 
     Consistent with the present disclosure, a long path is created for the impinging photons to be absorbed and contribute to a higher probability of detection. Optical trenches may also be implemented in detecting element  422  for reducing cross talk effects of parasitic photons created during an avalanche that may leak to other detectors and cause false detection events. According to some embodiments, a photo detector array may be optimized so that a higher yield of the received signal is utilized, meaning, that as much of the received signal is received and less of the signal is lost to internal degradation of the signal. The photo detector array may be improved by: (a) moving the focal point at a location above the semiconductor surface, optionally by designing the metal layers above the substrate appropriately; (b) by steering the focal point to the most responsive/sensitive area (or “sweet spot”) of the substrate and (c) adding a diffuser above the substrate to steer the signal toward the “sweet spot” and/or adding reflective material to the trenches so that deflected signals are reflected back to the “sweet spot.” 
     While in some lens configurations, lens  422  may be positioned so that its focal point is above a center of the corresponding detection element  402 , it is noted that this is not necessarily so. In other lens configuration, a position of the focal point of the lens  422  with respect to a center of the corresponding detection element  402  is shifted based on a distance of the respective detection element  402  from a center of the detection array  400 . This may be useful in relatively larger detection arrays  400 , in which detector elements further from the center receive light in angles which are increasingly off-axis. Shifting the location of the focal points (e.g., toward the center of detection array  400 ) allows correcting for the incidence angles. Specifically, shifting the location of the focal points (e.g., toward the center of detection array  400 ) allows correcting for the incidence angles while using substantially identical lenses  422  for all detection elements, which are positioned at the same angle with respect to a surface of the detector. 
     Adding an array of lenses  422  to an array of detection elements  402  may be useful when using a relatively small sensor  116  which covers only a small part of the field of view because in such a case, the reflection signals from the scene reach the detectors array  400  from substantially the same angle, and it is, therefore, easy to focus all the light onto individual detectors. It is also noted, that in one embodiment, lenses  422  may be used in LIDAR system  100  for favoring about increasing the overall probability of detection of the entire array  400  (preventing photons from being “wasted” in the dead area between detectors/sub-detectors) at the expense of spatial distinctiveness. This embodiment is in contrast to prior art implementations such as CMOS RGB camera, which prioritize spatial distinctiveness (i.e., light that propagates in the direction of detection element A is not allowed to be directed by the lens toward detection element B, that is, to “bleed” to another detection element of the array). Optionally, sensor  116  includes an array of lens  422 , each being correlated to a corresponding detection element  402 , while at least one of the lenses  422  deflects light which propagates to a first detection element  402  toward a second detection element  402  (thereby it may increase the overall probability of detection of the entire array). 
     Specifically, consistent with some embodiments of the present disclosure, light sensor  116  may include an array of light detectors (e.g., detector array  400 ), each light detector (e.g., detector  410 ) being configured to cause an electric current to flow when light passes through an outer surface of a respective detector. In addition, light sensor  116  may include at least one micro-lens configured to direct light toward the array of light detectors, the at least one micro-lens having a focal point. Light sensor  116  may further include at least one layer of conductive material interposed between the at least one micro-lens and the array of light detectors and having a gap therein to permit light to pass from the at least one micro-lens to the array, the at least one layer being sized to maintain a space between the at least one micro-lens and the array to cause the focal point (e.g., the focal point may be a plane) to be located in the gap, at a location spaced from the detecting surfaces of the array of light detectors. 
     In related embodiments, each detector may include a plurality of Single Photon Avalanche Diodes (SPADs) or a plurality of Avalanche Photo Diodes (APD). The conductive material may be a multi-layer metal constriction, and the at least one layer of conductive material may be electrically connected to detectors in the array. In one example, the at least one layer of conductive material includes a plurality of layers. In addition, the gap may be shaped to converge from the at least one micro-lens toward the focal point, and to diverge from a region of the focal point toward the array. In other embodiments, light sensor  116  may further include at least one reflector adjacent each photo detector. In one embodiment, a plurality of micro-lenses may be arranged in a lens array and the plurality of detectors may be arranged in a detector array. In another embodiment, the plurality of micro-lenses may include a single lens configured to project light to a plurality of detectors in the array. 
     Referring by way of a nonlimiting example to  FIGS.  2 E,  2 F and  2 G , it is noted that the one or more sensors  116  of system  100  may receive light from a scanning deflector  114  or directly from the FOV without scanning Even if light from the entire FOV arrives to the at least one sensor  116  at the same time, in some implementations the one or more sensors  116  may sample only parts of the FOV for detection output at any given time. For example, if the illumination of projection unit  102  illuminates different parts of the FOV at different times (whether using a deflector  114  and/or by activating different light sources  112  at different times), light may arrive at all of the pixels or sensors  116  of sensing unit  106 , and only pixels/sensors which are expected to detect the LIDAR illumination may be actively collecting data for detection outputs. This way, the rest of the pixels/sensors do not unnecessarily collect ambient noise. Referring to the scanning—in the outbound or in the inbound directions—it is noted that substantially different scales of scanning may be implemented. For example, in some implementations the scanned area may cover 1% or 0.1% of the FOV, while in other implementations the scanned area may cover 10% or 25% of the FOV. All other relative portions of the FOV values may also be implemented, of course. 
     The Processing Unit 
       FIGS.  5 A,  5 B, and  6    depict different functionalities of processing units  108  in accordance with some embodiments of the present disclosure. Specifically,  FIG.  5 A  is a diagram illustrating emission patterns in a single frame-time for a single portion of the field of view,  FIG.  5 B  is a diagram illustrating emission scheme in a single frame-time for the whole field of view, and.  FIG.  6    is a diagram illustrating the actual light emission projected towards field of view during a single scanning cycle. 
       FIG.  5 A  illustrates four examples of emission patterns in a single frame-time for a single portion  122  of field of view  120  associated with an instantaneous position of at least one light deflector  114 . Consistent with embodiments of the present disclosure, processing unit  108  may control at least one light source  112  and light deflector  114  (or coordinate the operation of at least one light source  112  and at least one light deflector  114 ) in a manner enabling light flux to vary over a scan of field of view  120 . Consistent with other embodiments, processing unit  108  may control only at least one light source  112  and light deflector  114  may be moved or pivoted in a fixed predefined pattern. 
     Diagrams A-D in  FIG.  5 A  depict the power of light emitted towards a single portion  122  of field of view  120  over time. In Diagram A, processor  118  may control the operation of light source  112  in a manner such that during scanning of field of view  120  an initial light emission is projected toward portion  122  of field of view  120 . When projecting unit  102  includes a pulsed-light light source, the initial light emission may include one or more initial pulses (also referred to as “pilot pulses”). Processing unit  108  may receive from sensor  116  pilot information about reflections associated with the initial light emission. In one embodiment, the pilot information may be represented as a single signal based on the outputs of one or more detectors (e.g. one or more SPADs, one or more APDs, one or more SiPMs, etc.) or as a plurality of signals based on the outputs of multiple detectors. In one example, the pilot information may include analog and/or digital information. In another example, the pilot information may include a single value and/or a plurality of values (e.g. for different times and/or parts of the segment). 
     Based on information about reflections associated with the initial light emission, processing unit  108  may be configured to determine the type of subsequent light emission to be projected towards portion  122  of field of view  120 . The determined subsequent light emission for the particular portion of field of view  120  may be made during the same scanning cycle (i.e., in the same frame) or in a subsequent scanning cycle (i.e., in a subsequent frame). This embodiment is described in greater detail below with reference to  FIGS.  23 - 25   . 
     In Diagram B, processor  118  may control the operation of light source  112  in a manner such that during scanning of field of view  120  light pulses in different intensities are projected towards a single portion  122  of field of view  120 . In one embodiment, LIDAR system  100  may be operable to generate depth maps of one or more different types, such as any one or more of the following types: point cloud model, polygon mesh, depth image (holding depth information for each pixel of an image or of a 2D array), or any other type of 3D model of a scene. The sequence of depth maps may be a temporal sequence, in which different depth maps are generated at a different time. Each depth map of the sequence associated with a scanning cycle (interchangeably “frame”) may be generated within the duration of a corresponding subsequent frame-time. In one example, a typical frame-time may last less than a second. In some embodiments, LIDAR system  100  may have a fixed frame rate (e.g. 10 frames per second, 25 frames per second, 50 frames per second) or the frame rate may be dynamic. In other embodiments, the frame-times of different frames may not be identical across the sequence. For example, LIDAR system  100  may implement a 10 frames-per-second rate that includes generating a first depth map in 100 milliseconds (the average), a second frame in 92 milliseconds, a third frame at 142 milliseconds, and so on. 
     In Diagram C, processor  118  may control the operation of light source  112  in a manner such that during scanning of field of view  120  light pulses associated with different durations are projected towards a single portion  122  of field of view  120 . In one embodiment, LIDAR system  100  may be operable to generate a different number of pulses in each frame. The number of pulses may vary between 0 to 32 pulses (e.g., 1, 5, 12, 28, or more pulses) and may be based on information derived from previous emissions. The time between light pulses may depend on desired detection range and can be between 500 ns and 5000 ns. In one example, processing unit  108  may receive from sensor  116  information about reflections associated with each light-pulse. Based on the information (or the lack of information), processing unit  108  may determine if additional light pulses are needed. It is noted that the durations of the processing times and the emission times in diagrams A-D are not in-scale. Specifically, the processing time may be substantially longer than the emission time. In diagram D, projecting unit  102  may include a continuous-wave light source. In one embodiment, the initial light emission may include a period of time where light is emitted and the subsequent emission may be a continuation of the initial emission, or there may be a discontinuity. In one embodiment, the intensity of the continuous emission may change over time. 
     Consistent with some embodiments of the present disclosure, the emission pattern may be determined per each portion of field of view  120 . In other words, processor  118  may control the emission of light to allow differentiation in the illumination of different portions of field of view  120 . In one example, processor  118  may determine the emission pattern for a single portion  122  of field of view  120 , based on detection of reflected light from the same scanning cycle (e.g., the initial emission), which makes LIDAR system  100  extremely dynamic. In another example, processor  118  may determine the emission pattern for a single portion  122  of field of view  120 , based on detection of reflected light from a previous scanning cycle. The differences in the patterns of the subsequent emissions may result from determining different values for light-source parameters for the subsequent emission, such as any one of the following. 
     a. Overall energy of the subsequent emission. 
     b. Energy profile of the subsequent emission. 
     c. A number of light-pulse-repetition per frame. 
     d. Light modulation characteristics such as duration, rate, peak, average power, and pulse shape. 
     e. Wave properties of the subsequent emission, such as polarization, wavelength, etc. 
     Consistent with the present disclosure, the differentiation in the subsequent emissions may be put to different uses. In one example, it is possible to limit emitted power levels in one portion of field of view  120  where safety is a consideration, while emitting higher power levels (thus improving signal-to-noise ratio and detection range) for other portions of field of view  120 . This is relevant for eye safety, but may also be relevant for skin safety, safety of optical systems, safety of sensitive materials, and more. In another example, it is possible to direct more energy towards portions of field of view  120  where it will be of greater use (e.g. regions of interest, further distanced targets, low reflection targets, etc.) while limiting the lighting energy to other portions of field of view  120  based on detection results from the same frame or previous frame. It is noted that processing unit  108  may process detected signals from a single instantaneous field of view several times within a single scanning frame time; for example, subsequent emission may be determined upon after every pulse emitted, or after a number of pulses emitted. 
       FIG.  5 B  illustrates three examples of emission schemes in a single frame-time for field of view  120 . Consistent with embodiments of the present disclosure, at least one processing unit  108  may use obtained information to dynamically adjust the operational mode of LIDAR system  100  and/or determine values of parameters of specific components of LIDAR system  100 . The obtained information may be determined from processing data captured in field of view  120 , or received (directly or indirectly) from host  210 . Processing unit  108  may use the obtained information to determine a scanning scheme for scanning the different portions of field of view  120 . The obtained information may include a current light condition, a current weather condition, a current driving environment of the host vehicle, a current location of the host vehicle, a current trajectory of the host vehicle, a current topography of road surrounding the host vehicle, or any other condition or object detectable through light reflection. In some embodiments, the determined scanning scheme may include at least one of the following: (a) a designation of portions within field of view  120  to be actively scanned as part of a scanning cycle, (b) a projecting plan for projecting unit  102  that defines the light emission profile at different portions of field of view  120 ; (c) a deflecting plan for scanning unit  104  that defines, for example, a deflection direction, frequency, and designating idle elements within a reflector array; and (d) a detection plan for sensing unit  106  that defines the detectors sensitivity or responsivity pattern. 
     In addition, processing unit  108  may determine the scanning scheme at least partially by obtaining an identification of at least one region of interest within the field of view  120  and at least one region of non-interest within the field of view  120 . In some embodiments, processing unit  108  may determine the scanning scheme at least partially by obtaining an identification of at least one region of high interest within the field of view  120  and at least one region of lower-interest within the field of view  120 . The identification of the at least one region of interest within the field of view  120  may be determined, for example, from processing data captured in field of view  120 , based on data of another sensor (e.g. camera, GPS), received (directly or indirectly) from host  210 , or any combination of the above. In some embodiments, the identification of at least one region of interest may include identification of portions, areas, sections, pixels, or objects within field of view  120  that are important to monitor. Examples of areas that may be identified as regions of interest may include, crosswalks, moving objects, people, nearby vehicles or any other environmental condition or object that may be helpful in vehicle navigation. Examples of areas that may be identified as regions of non-interest (or lower-interest) may be static (non-moving) far-away buildings, a skyline, an area above the horizon and objects in the field of view. Upon obtaining the identification of at least one region of interest within the field of view  120 , processing unit  108  may determine the scanning scheme or change an existing scanning scheme. Further to determining or changing the light-source parameters (as described above), processing unit  108  may allocate detector resources based on the identification of the at least one region of interest. In one example, to reduce noise, processing unit  108  may activate detectors  410  where a region of interest is expected and disable detectors  410  where regions of non-interest are expected. In another example, processing unit  108  may change the detector sensitivity, e.g., increasing sensor sensitivity for long range detection where the reflected power is low. 
     Diagrams A-C in  FIG.  5 B  depict examples of different scanning schemes for scanning field of view  120 . Each square in field of view  120  represents a different portion  122  associated with an instantaneous position of at least one light deflector  114 . Legend  500  details the level of light flux represented by the filling pattern of the squares. Diagram A depicts a first scanning scheme in which all of the portions have the same importance/priority and a default light flux is allocated to them. The first scanning scheme may be utilized in a start-up phase or periodically interleaved with another scanning scheme to monitor the whole field of view for unexpected/new objects. In one example, the light source parameters in the first scanning scheme may be configured to generate light pulses at constant amplitudes. Diagram B depicts a second scanning scheme in which a portion of field of view  120  is allocated with high light flux while the rest of field of view  120  is allocated with default light flux and low light flux. The portions of field of view  120  that are the least interesting may be allocated with low light flux. Diagram C depicts a third scanning scheme in which a compact vehicle and a bus (see silhouettes) are identified in field of view  120 . In this scanning scheme, the edges of the vehicle and bus may be tracked with high power and the central mass of the vehicle and bus may be allocated with less light flux (or no light flux). Such light flux allocation enables concentration of more of the optical budget on the edges of the identified objects and less on their center which have less importance. 
       FIG.  6    illustrating the emission of light towards field of view  120  during a single scanning cycle. In the depicted example, field of view  120  is represented by an 8×9 matrix, where each of the 72 cells corresponds to a separate portion  122  associated with a different instantaneous position of at least one light deflector  114 . In this exemplary scanning cycle, each portion includes one or more white dots that represent the number of light pulses projected toward that portion, and some portions include black dots that represent reflected light from that portion detected by sensor  116 . As shown, field of view  120  is divided into three sectors: sector I on the right side of field of view  120 , sector II in the middle of field of view  120 , and sector III on the left side of field of view  120 . In this exemplary scanning cycle, sector I was initially allocated with a single light pulse per portion; sector II, previously identified as a region of interest, was initially allocated with three light pulses per portion; and sector III was initially allocated with two light pulses per portion. Also as shown, scanning of field of view  120  reveals four objects  208 : two free-form objects in the near field (e.g., between 5 and 50 meters), a rounded-square object in the mid field (e.g., between 50 and 150 meters), and a triangle object in the far field (e.g., between 150 and 500 meters). While the discussion of  FIG.  6    uses number of pulses as an example of light flux allocation, it is noted that light flux allocation to different parts of the field of view may also be implemented in other ways such as: pulse duration, pulse angular dispersion, wavelength, instantaneous power, photon density at different distances from light source  112 , average power, pulse power intensity, pulse width, pulse repetition rate, pulse sequence, pulse duty cycle, wavelength, phase, polarization, and more. The illustration of the light emission as a single scanning cycle in  FIG.  6    demonstrates different capabilities of LIDAR system  100 . In a first embodiment, processor  118  is configured to use two light pulses to detect a first object (e.g., the rounded-square object) at a first distance, and to use three light pulses to detect a second object (e.g., the triangle object) at a second distance greater than the first distance. This embodiment is described in greater detail below with reference to  FIGS.  11 - 13   . In a second embodiment, processor  118  is configured to allocate more light to portions of the field of view where a region of interest is identified. Specifically, in the present example, sector II was identified as a region of interest and accordingly it was allocated with three light pulses while the rest of field of view  120  was allocated with two or less light pulses. This embodiment is described in greater detail below with reference to  FIGS.  20 - 22   . In a third embodiment, processor  118  is configured to control light source  112  in a manner such that only a single light pulse is projected toward to portions B 1 , B 2 , and C 1  in  FIG.  6   , although they are part of sector III that was initially allocated with two light pulses per portion. This occurs because the processing unit  108  detected an object in the near field based on the first light pulse. This embodiment is described in greater detail below with reference to  FIGS.  23 - 25   . Allocation of less than maximal amount of pulses may also be a result of other considerations. For examples, in at least some regions, detection of object at a first distance (e.g. a near field object) may result in reducing an overall amount of light emitted to this portion of field of view  120 . This embodiment is described in greater detail below with reference to  FIGS.  14 - 16   . Other reasons to for determining power allocation to different portions is discussed below with respect to  FIGS.  29 - 31   , FIGS. 53-55, and FIGS. 50-52. 
     Additional details and examples on different components of LIDAR system  100  and their associated functionalities are included in Applicant&#39;s U.S. patent application Ser. No. 15/391,916 filed Dec. 28, 2016; Applicant&#39;s U.S. patent application Ser. No. 15/393,749 filed Dec. 29, 2016; Applicant&#39;s U.S. patent application Ser. No. 15/393,285 filed Dec. 29, 2016; and Applicant&#39;s U.S. patent application Ser. No. 15/393,593 filed Dec. 29, 2016, which are incorporated herein by reference in their entirety. 
     Example Implementation: Vehicle 
       FIGS.  7 - 9    illustrate the implementation of LIDAR system  100  in a vehicle (e.g., vehicle  110 ). Any of the aspects of LIDAR system  100  described above or below may be incorporated into vehicle  110  to provide a range-sensing vehicle. Specifically, in this example, LIDAR system  100  integrates multiple scanning units  104  and potentially multiple projecting units  102  in a single vehicle. In one embodiment, a vehicle may take advantage of such a LIDAR system to improve power, range and accuracy in the overlap zone and beyond it, as well as redundancy in sensitive parts of the FOV (e.g. the forward movement direction of the vehicle). As shown in  FIG.  7   , vehicle  110  may include a first processor  118 A for controlling the scanning of field of view  120 A, a second processor  118 B for controlling the scanning of field of view  120 B, and a third processor  118 C for controlling synchronization of scanning the two fields of view. In one example, processor  118 C may be the vehicle controller and may have a shared interface between first processor  118 A and second processor  118 B. The shared interface may enable an exchanging of data at intermediate processing levels and a synchronization of scanning of the combined field of view in order to form an overlap in the temporal and/or spatial space. In one embodiment, the data exchanged using the shared interface may be: (a) time of flight of received signals associated with pixels in the overlapped field of view and/or in its vicinity; (b) laser steering position status; (c) detection status of objects in the field of view. 
       FIG.  8    illustrates overlap region  600  between field of view  120 A and field of view  120 B. In the depicted example, the overlap region is associated with 24 portions  122  from field of view  120 A and 24 portions  122  from field of view  120 B. Given that the overlap region is defined and known by processors  118 A and  118 B, each processor may be designed to limit the amount of light emitted in overlap region  600  in order to conform with an eye safety limit that spans multiple source lights, or for other reasons such as maintaining an optical budget. In addition, processors  118 A and  118 B may avoid interferences between the light emitted by the two light sources by loose synchronization between the scanning unit  104 A and scanning unit  104 B, and/or by control of the laser transmission timing, and/or the detection circuit enabling timing. 
       FIG.  9    illustrates how overlap region  600  between field of view  120 A and field of view  120 B may be used to increase the detection distance of vehicle  110 . Consistent with the present disclosure, two or more light sources  112  projecting their nominal light emission into the overlap zone may be leveraged to increase the effective detection range. The term “detection range” may include an approximate distance from vehicle  110  at which LIDAR system  100  can clearly detect an object. In one embodiment, the maximum detection range of LIDAR system  100  is about 300 meters, about 400 meters, or about 500 meters. For example, for a detection range of 200 meters, LIDAR system  100  may detect an object located 200 meters (or less) from vehicle  110  at more than 95%, more than 99%, more than 99.5% of the times. Even when the object&#39;s reflectivity may be less than 50% (e.g., less than 20%, less than 10%, or less than 5%). In addition, LIDAR system  100  may have less than 1% false alarm rate. In one embodiment, light from projected from two light sources that are collocated in the temporal and spatial space can be utilized to improve SNR and therefore increase the range and/or quality of service for an object located in the overlap region. Processor  118 C may extract high-level information from the reflected light in field of view  120 A and  120 B. The term “extracting information” may include any process by which information associated with objects, individuals, locations, events, etc., is identified in the captured image data by any means known to those of ordinary skill in the art. In addition, processors  118 A and  118 B may share the high-level information, such as objects (road delimiters, background, pedestrians, vehicles, etc.), and motion vectors, to enable each processor to become alert to the peripheral regions about to become regions of interest. For example, a moving object in field of view  120 A may be determined to soon be entering field of view  120 B. 
     Example Implementation: Surveillance System 
       FIG.  10    illustrates the implementation of LIDAR system  100  in a surveillance system. As mentioned above, LIDAR system  100  may be fixed to a stationary object  650  that may include a motor or other mechanisms for rotating the housing of the LIDAR system  100  to obtain a wider field of view. Alternatively, the surveillance system may include a plurality of LIDAR units. In the example depicted in  FIG.  10   , the surveillance system may use a single rotatable LIDAR system  100  to obtain 3D data representing field of view  120  and to process the 3D data to detect people  652 , vehicles  654 , changes in the environment, or any other form of security-significant data. 
     Consistent with some embodiment of the present disclosure, the 3D data may be analyzed to monitor retail business processes. In one embodiment, the 3D data may be used in retail business processes involving physical security (e.g., detection of: an intrusion within a retail facility, an act of vandalism within or around a retail facility, unauthorized access to a secure area, and suspicious behavior around cars in a parking lot). In another embodiment, the 3D data may be used in public safety (e.g., detection of: people slipping and falling on store property, a dangerous liquid spill or obstruction on a store floor, an assault or abduction in a store parking lot, an obstruction of a fire exit, and crowding in a store area or outside of the store). In another embodiment, the 3D data may be used for business intelligence data gathering (e.g., tracking of people through store areas to determine, for example, how many people go through, where they dwell, how long they dwell, how their shopping habits compare to their purchasing habits). 
     Consistent with other embodiments of the present disclosure, the 3D data may be analyzed and used for traffic enforcement. Specifically, the 3D data may be used to identify vehicles traveling over the legal speed limit or some other road legal requirement. In one example, LIDAR system  100  may be used to detect vehicles that cross a stop line or designated stopping place while a red traffic light is showing. In another example, LIDAR system  100  may be used to identify vehicles traveling in lanes reserved for public transportation. In yet another example, LIDAR system  100  may be used to identify vehicles turning in intersections where specific turns are prohibited on red. 
     It should be noted that while examples of various disclosed embodiments have been described above and below with respect to a control unit that controls scanning of a deflector, the various features of the disclosed embodiments are not limited to such systems. Rather, the techniques for allocating light to various portions of a LIDAR FOV may be applicable to type of light-based sensing system (LIDAR or otherwise) in which there may be a desire or need to direct different amounts of light to different portions of field of view. In some cases, such light allocation techniques may positively impact detection capabilities, as described herein, but other advantages may also result. 
     It should also be noted that various sections of the disclosure and the claims may refer to various components or portions of components (e.g., light sources, sensors, sensor pixels, field of view portions, field of view pixels, etc.) using such terms as “first,” “second,” “third,” etc. These terms are used only to facilitate the description of the various disclosed embodiments and are not intended to be limiting or to indicate any necessary correlation with similarly named elements or components in other embodiments. For example, characteristics described as associated with a “first sensor” in one described embodiment in one section of the disclosure may or may not be associated with a “first sensor” of a different embodiment described in a different section of the disclosure. 
     It is noted that LIDAR system  100 , or any of its components, may be used together with any of the particular embodiments and methods disclosed below. Nevertheless, the particular embodiments and methods disclosed below are not necessarily limited to LIDAR system  100 , and may possibly be implemented in or by other systems (such as but not limited to other LIDAR systems, other electrooptical systems, other optical systems, etc.—whichever is applicable). Also, while system  100  is described relative to an exemplary vehicle-based LIDAR platform, system  100 , any of its components, and any of the processes described herein may be applicable to LIDAR systems disposed on other platform types. Likewise, the embodiments and processes disclosed below may be implemented on or by LIDAR systems (or other systems such as other electrooptical systems etc.) which are installed on systems disposed on platforms other than vehicles, or even regardless of any specific platform. 
     The present disclosure relates to MEMS scanning devices. While the present disclosure provides examples of MEMS scanning devices that may be part of a scanning LIDAR system, it should be noted that aspects of the disclosure in their broadest sense, are not limited to MEMS scanning devices for a LIDAR system. Rather, it is contemplated that the forgoing principles may be applied to other types of electro-optic systems as well.  FIGS.  3 A- 3 D  depict exemplary MEMS scanning devices  104 . 
     A MEMS scanning device in accordance with the present disclosure may include a movable MEMS mirror configured to pivot about at least one axis. A MEMS scanning device may include a light deflector configured to make light deviate from its original path. In some exemplary embodiments, the light deflector may be in the form of a MEMS mirror that may include any MEMS structure with a rotatable part which rotates with respect to a plane of a wafer (or frame). For example, a scanning MEMS system may include structures such as a rotatable valve, or an acceleration sensor. In some exemplary embodiments, the rotatable part may include a reflective coating or surface to form a MEMS mirror capable of reflecting or deflecting light from a light source. Various exemplary embodiments of MEMS mirror assemblies discussed below may be part of a scanning LIDAR system (such as—but not limited to—system  100 , e.g. MEMS mirror  300 , deflector  114 ), or may be used for any other electro-optic system in which a rotatable MEMS mirror or another rotatable MEMS structure may be of use. While a MEMS mirror has been disclosed as an exemplary embodiment of a light deflector, it should be noted that aspects of the disclosure in their broadest sense, are not limited to MEMS mirror. Thus, for example, the disclosed MEMS mirror in a MEMS scanning device according to this disclosure may instead include prisms, controllable lenses, mechanical mirrors, mechanical scanning polygons, active diffraction (e.g. controllable LCD), Risley prisms, or other types of optical equipment capable of deflecting a path of light. 
     In accordance with the present disclosure, a MEMS mirror assembly may include a frame, which supports the MEMS mirror. As used in this disclosure a frame may include any supporting structure to which the MEMS mirror may be attached such that the MEMS mirror may be capable of rotating relative to the frame. For example, the MEMS mirror may include portions of a wafer used to manufacture the MEMS mirror that may structurally support the MEMS mirror while allowing the MEMS mirror to pivot about one or more axes of rotation relative to the frame. 
       FIG.  11 A  illustrates an exemplary MEMS mirror assembly  1100  consistent with this disclosure. For example, as illustrated in  FIG.  11 A , MEMS mirror assembly  1100  may include MEMS mirror  1102  supported by frame  1104 . MEMS mirror  1102  may be a movable MEMS mirror in that MEMS mirror  1102  may be translatable relative to frame  1104  and/or rotatable about one or more axes relative to frame  1104 . For example, MEMS mirror  1102  may be translatable or rotatable about exemplary axes  1106 ,  1108 , or  1110  (going into the plane of the figure) as illustrated in  FIG.  11 A . In some exemplary embodiments, MEMS mirror  1102  may include a reflective surface and/or reinforcement structures, for example, reinforcing ribs attached to an underside of MEMS mirror  1102  opposite the reflective surface. Although MEMS mirror  1102  has been illustrated as having a circular shape in  FIG.  11 A , it is contemplated that MEMS mirror  1102  may have a square shape, a polygonal shape (e.g. octagonal), an elliptical shape, or any other geometrical shape suitable for use with system  100 . While the present disclosure describes examples of a MEMS mirror and frame, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed examples of the MEMS mirror and/or frame. 
     In accordance with the present disclosure a MEMS scanning device may include at least one actuator configured to cause pivoting of the movable MEMS mirror about the at least one axis in a first direction. An actuator according to the present disclosure may include one or more movable structural members of the MEMS mirror assembly that may be capable of causing translational and/or rotational movement of the MEMS mirror relative to the frame. The disclosed actuator may be an integral part of the MEMS mirror assembly or may be separate and distinct from the MEMS mirror assembly. The disclosed actuator may be directly or indirectly attached to the disclosed MEMS mirror. 
     In some exemplary embodiments, the actuator may be a part of the MEMS mirror assembly and may itself be configured to move relative to the frame and/or relative to the MEMS mirror associated with the MEMS mirror assembly. For example, the disclosed actuator may be connected between the frame and the MEMS mirror and may be configured to be displaced, bent, twisted, and/or distorted to cause movement (i.e. translation or rotation) of the MEMS mirror relative to the frame. It is contemplated that a MEMS mirror assembly according to the present disclosure may include one, two, or any other number of actuators. 
     By way of example,  FIG.  11 A  illustrates exemplary actuators  1112 ,  1114 ,  1116 , and  1118  associated with MEMS mirror assembly  1100  consistent with this disclosure. As illustrated in  FIG.  11 A , actuator  1112  may be connected to frame  1104  adjacent first end  1120  and may be connected to MEMS mirror  1102  adjacent an opposite end  1122  of actuator  1112 . Details regarding the connection between actuator  1112  and MEMS mirror  1102  will be described in more detail below. Actuators  1114 ,  1116 , and  1118  may be connected between frame  1104  and MEMS mirror  1102  in a similar manner Movement of the one or more actuators  1112 ,  1114 ,  1116 , and  1118  may cause translational and/or rotational movement of MEMS mirror  1102  about the one or more axes  1106 ,  1108 , and/or  1110 . While the present disclosure describes examples of actuators associated with a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed actuator examples. 
     The actuators of the MEMS mirror assembly may be actuated in various different ways, such as by contraction of a piezoelectric member on each actuator (e.g. PZT, Lead zirconate titanate, aluminum nitride), electromagnetic actuation, electrostatic actuation, etc. As mentioned above, the actuators may be piezoelectric actuators. It is noted that in the description below, any applicable piezoelectric material may be used wherever the example of PZT is used. Optionally, one or more of the plurality of actuators may include a piezoelectric layer (e.g., a PZT layer), which is configured to bend the respective actuator, thereby rotating the mirror, when subjected to an electrical field. By way of example, the one or more actuators  1112 ,  1114 ,  1116 , and  1118  associated with MEMS mirror assembly  1100  may include one or more PZT layers. Energizing the one or more PZT layers with an electrical field (e.g. by providing a bias voltage or current) may cause the one or more actuators  1112 ,  1114 ,  1116 , and  1118  to expand, contract, bend, twist, or alter their configuration, which in turn may cause MEMS mirror  1102  to be translated or rotated about the one or more axes  1106 ,  1108 , and/or  1110 . While the present disclosure describes examples of axes of rotation of the MEMS mirror, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed examples of the axes of rotation. Thus, for example, the MEMS mirror according to the present disclosure may translate and/or rotate about axes other than the disclosed axes  1106 ,  1108 , and/or  1110 . It is also contemplated that in other implementations, the actuators themselves may move perpendicularly to a plane of the frame, parallel to the plane of the frame and/or in any combination of the two. 
     In accordance with the present disclosure a MEMS scanning device may include at least one spring configured to cause pivoting of the movable MEMS mirror about the at least one axis in a second direction different from the first direction. A spring as used in this disclosure refers to any component or structure configured to provide a restoring force to the MEMS mirror. In some cases, the disclosed spring may limit the motion of the mirror in response to actuation and may restore the mirror to an equilibrium position after actuation (e.g., once an actuating voltage signal has been discontinued). In some embodiments, the at least one second direction may be opposite the at least one first direction. That is, the restoring force provided by the one or more springs may be in a direction opposite to (or substantially opposite to) an actuating force intended to cause at least one displacement (i.e. translation or rotation) of the MEMS mirror. 
     By way of example,  FIG.  3 A  illustrates exemplary springs  302 A and  302 B. Returning to  FIG.  11 A , the silicon in the one or more actuators  1112 ,  1114 ,  1116 , and  1118  may also function as springs and may cause MEMS mirror  1102  to be translated or rotated in a direction opposite to a direction in which the one or more actuators  1112 ,  1114 ,  1116 , and  1118  cause translation and/or rotation of MEMS mirror  1102 . Although the present disclosure describes examples of springs associated with a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed spring examples. 
     According to the present disclosure, the at least one actuator includes a first actuating arm, a second actuating arm, and a gap between the first actuating arm and the second actuating arm. Like an actuator, an actuating arm according to this disclosure may include a structural member that may be capable of causing translational or rotational movement of the MEMS mirror relative to the frame. In some exemplary embodiments, the disclosed actuator may include only one actuating arm. By way of nonlimiting examples,  FIGS.  12 A- 12 F  illustrate actuators having only one actuating arm. In other exemplary embodiments the disclosed actuator may include more than one actuating arm. Each actuating arm may be deemed an actuator that may operate in unison with an actuating arm paired with it. For example, in some embodiments, the disclosed actuator may include two actuating arms separated from each other by a gap. Some or all actuating arms may be equipped with PZT layers, which may cause those actuating arms to expand, contract, bend, twist, or move in some way. Movement of the one or more actuating arms in turn may cause movement of the MEMS mirror associated with the MEMS scanning device. 
     In accordance with the present disclosure, the first actuating arm and the second actuating arm lie adjacent to each other, at least partially separated from each other by the gap. The first and second actuating arms are configured to be actuated simultaneously to thereby enable exertion of a combined mechanical force on the movable MEMS mirror to pivot the movable MEMS mirror about the at least one axis. It is to be understood that when the first and second arms are actuated simultaneously, they may be actuated be totally, substantially, or partly simultaneously. Thus, for example, even when being actuated simultaneously, the two actuating arms may be actuated/de-actuated slightly before or after the other arm. Further, the restoring force due to the spring action of the silicon of the one or more actuating arms may also be applied simultaneously for moving the MEMS mirror in the second direction, for example, by simultaneously not applying voltages on PZT of both actuating arms. It is also contemplated that in some embodiments, other means for applying a restorative force may be used instead of a spring. For example, in some embodiments, the actuating arms may include an additional PZT layer or other electromagnetic actuator that may provide a restorative force. In some exemplary embodiments according to the present disclosure, the actuating arms may be positioned adjacent to each other and may be separated by a gap. As discussed above, in some exemplary embodiments, the one or more actuating arms associated with the disclosed actuator may each include a PZT layer. The PZT layer associated with the discrete actuating arms may be subjected to an electrical field, voltage, etc. at the same time or at different times, which in turn may cause the actuating arms to be displaced simultaneously or at different times. In some embodiments, the first and second actuating arms may be displaced simultaneously to help ensure that the displacement of the two actuating arms applies a combined mechanical force on the MEMS mirror (e.g., via one or more connectors which connect the actuating arms to the MEMS mirror) causing a displacement (e.g. translation and/or rotation) of the MEMS mirror. 
       FIG.  11 A , for example, illustrates first actuator  1112  which includes first actuating arm  1124 , second actuating arm  1126 , and gap  1128  between first actuating arm  1124  and second actuating arm  1126 . As also illustrated in the exemplary embodiment of  FIG.  11 A , first actuating arm  1124  may lie adjacent to second actuating arm  1126 . Each of first and second actuating arms  1124 ,  1126  may include an associated PZT layer. Application of an electrical voltage or current to the PZT layer may cause first and second actuating arms  1124 ,  1126  to deform by, for example, expansion, contraction, bending, twisting etc. Deformation of the first and second actuating arms  1124  and  1126  may in turn cause movement of MEMS mirror  1102 . It is contemplated that in some embodiments, the PZT layers of the first and second actuating arms  1124 ,  1126  may be activated at the same time, which may cause deformation of both first and second actuating arms  1124  and  1126  simultaneously. Such simultaneous deformation in turn may cause a combined mechanical force generated by both first and second actuating arms  1124  and  1126  to be applied on MEMS mirror  1102 . 
     As illustrated in the exemplary embodiment of  FIG.  11 A , first actuating arm  1124  may be an outer actuating arm whereas second actuating arm  1126  may be an inner actuating arm. According to the embodiments of this disclosure, the terms inner and outer may be also understood based on distances relative to a center of the MEMS mirror. For example, as illustrated in  FIG.  11 A , first actuating arm  1124  may be positioned at a distance (e.g. radial distance) from MEMS mirror  1102  that may be greater than a distance (e.g. radial distance) of second actuating arm  1126  from MEMS mirror  1102 . In some exemplary embodiments, first actuating arm  1124  may be an outer actuating arm because it may be positioned nearer to frame  1104  relative to MEMS mirror  1102 , whereas second actuating arm  1126  may be an inner actuating arm because it may be positioned nearer to MEMS mirror  1102  relative to frame  1104 . 
     In accordance with the present disclosure, in the MEMS scanning device the gap may include a slit. Additionally, according to the present disclosure a width of the slit is less than 5% of an average width of the first actuating arm. Thus for example, adjacent actuating arms in exemplary embodiments of MEMS mirror assemblies may be separated by an elongated space or gap in the form of a slit. As illustrated in the exemplary MEMS mirror assembly  1100  of  FIG.  11 A , one or more of gaps  1128 ,  1138 ,  1148 , and  1158  may be in the form of a slit, which may separate one or more of actuators  1112 ,  1114 ,  1116 , and  1118  into their respective actuating arms. A width “W s ” (measured for example in a generally radial direction from MEMS mirror  1102 ) of the slit or gap  1128 ,  1138 ,  1148 , and/or  1158  may be less than about 5%, less than about 10%, or less than about 20%, or less than about 25% of a width “W a ” The width Wa (measured for example in a generally radial direction from MEMS mirror  1102 ) may be the widths of one or more of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and/or  1156 , a width of the wider or the narrower actuating arm, or an average width of adjacent actuating arms 
     In accordance with the present disclosure, in the MEMS scanning device the gap may be filled with stationary non-reflective material. Non-reflective material as used in this disclosure may refer to materials that reduce and/or eliminate reflections of any incident light on the material. Including such non-reflective material may help to reduce or eliminate any unwanted reflections of light from the silicon strips not connected to the MEMS mirror so as to reduce reflection contributions from sources other than the MEMS mirror. By way of example, as illustrated in  FIG.  11 B , one or more of the stationary silicon strips  1125 ,  1135 ,  1145 , and  1155  may be covered with non-reflective material so that light is not reflected by the silicon strips Making the non-reflective material stationary may also help ensure that MEMS mirror  1102  is not subjected to any undesirable movements due to movements of the non-reflective filler material. 
     In accordance with the present disclosure, the at least one actuator of the disclosed MEMS scanning device may include a first actuator and a second actuator. In some exemplary embodiments, the disclosed MEMS scanning device may include more than one actuator. It is contemplated that the MEMS scanning device according to the present disclosure may include two, three, four, or any other number of actuators. One or more of these actuators may be connected to the MEMS mirror associated with the MEMS scanning device to cause a movement (translation and/or rotation) of the MEMS mirror. 
     In accordance with the present disclosure, the first actuator may include the first actuating arm and the second actuating arm, and the second actuator may include a third actuating arm and a fourth actuating arm. As discussed above, in some exemplary embodiments, the first actuator associated with the disclosed MEMS scanning device may include a first actuating arm separated by a first gap from the second actuating arm. It is also contemplated that similar to the first actuator, the second actuator may also include one or more actuating arms. For example, the second actuator may include a third actuating arm and a fourth actuating arm separated from each other by a second gap. The first and second gaps may or may not be equal. Similarly, it is contemplated that in some exemplary embodiments, one or both of the first and second actuators may include one, two, or more actuating arms. 
     By way of example,  FIG.  11 A  illustrates four actuators, including first actuator  1112 , second actuator  1114 , third actuator  1116 , and fourth actuator  1118 . As also discussed above, first actuator  1112  may include first actuating arm  1124  and second actuating arm  1126  separated by gap  1128 , which may be a first gap. Like first actuator  1112 , second actuator  1114  may include third actuating arm  1134  and fourth actuating arm  1136  separated by gap  1138 . It is contemplated that gap  1128  may have dimensions equal to or different from dimensions of gap  1138 . In some exemplary embodiments as illustrated in  FIG.  11 A , third actuating arm  1134  may be an outer actuating arm similar to first actuating arm  1124 , and fourth actuating arm  1136  may be an inner actuating arm similar to second actuating arm  1126 . 
     Third and fourth actuating arms  1134  and  1136  may be similar to first and/or second actuating arms  1124  and  1126 , respectively. To ensure clarity, throughout this disclosure, the discussion of structural and functional characteristics is not repeated when subsequently disclosed elements have structural and functional characteristics similar to those previously discussed in the disclosure. Additionally, unless otherwise stated, throughout this disclosure, similarly numbered elements should be presumed to have similar structural and functional characteristics. Further, similar elements from one structure to the next may also have similar characteristics even if differently numbered. 
     In a MEMS scanning device according to the present disclosure, the at least one axis includes a first axis and a second axis (e.g. axis  1106 , axis  1108 , etc.). The first actuating arm and the second actuating arm may be configured to simultaneously act to pivot the movable MEMS mirror about the first axis. The third actuating arm and the fourth actuating arm being configured to simultaneously act to pivot the MEMS mirror about the second axis. As discussed above, the disclosed MEMS mirror may be translated or rotated (or pivoted) about one or more than one axis. In some exemplary embodiments, the MEMS mirror may be translated relative to or rotated about a first axis and a second axis different from the first axis. The first and second axis may be disposed generally perpendicular to each other or may be inclined relative to each other at an arbitrary angle. According to embodiments of this disclosures, terms such as generally, about, and substantially should be interpreted to encompass typical machining and manufacturing tolerances. Thus, for example, two axes may be deemed to be generally perpendicular if an angle between the two axes lies between 90±0.1°, 90±0.5°, or 90±1°. Likewise two axes or structural elements may be deemed to be generally parallel if an angle between them lies between 0±0.1°, 0±0.5°, or 0±1°. It is also contemplated that the MEMS mirror of the disclosed MEMS scanning device may be rotatable about one, two, or more than two axes of rotation. 
     In some exemplary embodiments, one or more of the actuators (e.g., the first actuator) may be configured to pivot (i.e. rotate) the MEMS mirror about a first axis of rotation, whereas one or more of the actuators (e.g., the second actuator) may be configured to pivot the MEMS mirror about a second axis of rotation. It is contemplated, however, that a single actuator may cause rotation of the MEMS mirror about more than one axis of rotation. For example, the first and second actuating arms associated with the first actuator may be configured to move so that the first and second actuating arms may induce a pivoting motion (or rotation) and/or a translation of the MEMS mirror about the first axis. Likewise, the third and fourth actuating arms associated with the second actuator may be configured to move so that the third and fourth actuating arms may induce a pivoting motion (or rotation) and/or a translation of the MEMS mirror about the second axis. The rotation or pivoting about the first and second axis may occur simultaneously or at different times. Thus for example, the first, second, third, and fourth actuating arms may be configured to move simultaneously or at different times to cause rotation of the MEMS mirror about the first and second axes at the same or different times, respectively. 
     By way of example,  FIG.  11 A  illustrates MEMS mirror assembly  1100  that may have first axis  1106 , second axis  1108 , and third axis  1110 . In the exemplary embodiment of  FIG.  11 A , first, second, and third axes  1106 ,  1108 ,  1110  are disposed generally perpendicular to each other. It is contemplated, however, that in other exemplary embodiments, one or more of first, second, and third axes  1106 ,  1108 ,  1110  may be inclined relative to each other at other angles of inclination. As also illustrated in  FIG.  11 A , first and second actuating arms  1124  and  1126  of first actuator  1112  may be configured to cause MEMS mirror  1102  to pivot, rotate, and/or translate about, for example, first axis  1106 . Similarly, third and fourth actuating arms  1134  and  1136  of second actuator  1114  may be configured to cause MEMS mirror  1102  to pivot, rotate, and/or translate about, for example, second axis  1108  and/or third axis  1110 , different from first axis  1106 . 
     In one exemplary embodiment, first and second actuating arms  1124  and  1126  may be configured to act simultaneously to cause a rotation of MEMS mirror  1102  about axis  1106 . It is contemplated, however, that first and second actuating arms  1124  and  1126  may be configured to act at different times to cause one or more rotations of MEMS mirror  1102  about axis  1106 . Likewise, it is contemplated that third and fourth actuating arms  1134  and  1136  may be configured to act simultaneously or at different times to cause one or more rotations of MEMS mirror  1102  about axis  1108 . In some exemplary embodiments, first, second, third, and fourth actuating arms  1124 ,  1126 ,  1134 , and  1136  may all act simultaneously to cause simultaneous rotations or MEMS mirror  1102  about both first and second axis  1106 ,  1108 . It is also contemplated, however, that one or more of first, second, third, and fourth actuating arms  1124 ,  1126 ,  1134 , and  1136  may act at different times to cause one or more rotations of MEMS mirror  1102  at the same or different times. 
     According to the present disclosure, in the MEMS scanning device, the first actuating arm and the second actuating arm are of differing lengths. In other exemplary embodiments, the first and second actuating arms may be about equal in length. As discussed above, terms such as about encompass typical machining and manufacturing tolerances. Thus, for example, lengths of first and second actuating arms may be deemed to be about equal if they differ by less than ±1 μm, ±1 mm, ±1 mil, etc. It is also contemplated that in some exemplary embodiments, the second actuating arm may be longer than the first actuating arm. 
     In accordance with the present disclosure, one of the actuator arms may be wider than the other actuator arm. For example, in the MEMS scanning device, optionally the first actuating arm and the second actuating arm are of differing widths. In another example, optionally the second actuating arm may be wider than the first actuating arm. The wider arm may be wider by . . . 5%, 10%, 25%, etc. . . . ; wider arm may be for reasons of geometry, required force of the actuator arm, etc. . . . In other exemplary embodiments, the first and second actuating arms may have about equal widths. It is also contemplated that in some exemplary embodiments, the second actuating arm may be wider than the first actuating arm. 
     In accordance with the present disclosure, the disclosed MEMS scanning device may include first and second actuating arms, wherein the first actuating arm is shaped differently than the second actuating arm. In other exemplary embodiments according to the present disclosure, the first actuating arm and the second actuating arm may have the same shape. For example, the first and second actuating arms may have different lengths, widths, areas, geometric shapes, curvatures, etc. 
     By way of example,  FIG.  11 A  illustrates first actuating arm  1124  and second actuating arm  1126 . As illustrated in  FIG.  11 A , first actuating arm  1124  may have a length “L 1 ” and second actuating arm  1126  may have a length “L 2 .” In one exemplary embodiment as illustrated in  FIG.  11 A , length L 1  of first actuating arm  1124  may be greater than length L 2  of second actuating arm  1126 . It is contemplated, however, that length L 1  may be about equal to or smaller than length L 2 . As also illustrated in  FIG.  11 A , first actuating arm  1124  may have a width “W 1 ” and second actuating arm may have a width “W 2 .” In one exemplary embodiment as illustrated in  FIG.  11 A , width W 1  of first actuating arm  1124  may be generally uniform over length L 1 , and width W 2  of second actuating arm  1126  may be generally uniform over length L 2 . It is contemplated, however, that one or more of width W 1  of first actuating arm  1124  and/or width W 2  of second actuating arm  1126  may be nonuniform over lengths L 1  and L 2 , respectively. In some exemplary embodiments, at least one of the pairs of actuating arms in the one or more actuators may include actuators of differing widths. For example, width W 1  of first actuating arm  1124  may be wider than width W 2  of second actuating arm  1126  by about 10%, about 25%, about 50%, about 100%, or by any other percentage value. In other exemplary embodiments the reverse may be true so that width W 2  of second actuating arm  1126  may be wider than width W 1  of first actuating arm  1124  by about 10%, about 25%, about 50%, about 100%, or by any other percentage value or vice-versa. It is also contemplated that length L 1  may be longer than length L 2  by about 10%, about 25%, about 50%, about 100%, or by any other percentage value, or vice-versa. 
     As also illustrated in  FIG.  11 A , first actuating arm  1124  and second actuating arm may have generally similar shapes. For example, as illustrated in  FIG.  11 A , first actuating arm  1124  and second actuating arm  1126  both have generally annular segment shapes. It is contemplated, however, that first and second actuating arms  1124  and  1126  may have the same or different shapes. Although lengths, widths, and shapes have been discussed above with respect to first and second actuating arms  1124  and  1126 , it is to be understood that other actuating arms (e.g. actuating arms  1134  and  1136 ) may have geometries similar to or different from those discussed above for actuating arms  1124  and  1126 . 
     In accordance with the present disclosure, the MEMS scanning device may have first and second actuating arms, wherein the first actuating arm is connected to the MEMS mirror via a first connector and the second actuating arm is connected to the MEMS mirror via a second connector. As used in this disclosure a connector may include a structural element that may electrically and/or mechanically connect other elements of the disclosed MEMS scanning device. For example, a connector may provide electrical and/or mechanical connections between one or more actuating arms, springs associated with the actuating arms, and the MEMS mirror. In some exemplary embodiments, the connector may be directly attached to one or more of actuating arms, to springs, and/or to the MEMS mirror. In other embodiments, the connector may include more than one connector member that may be connected to each other and may be attached to the one or more actuating arms, to springs, and/or to the MEMS mirror. In some embodiments, the connector may be a mechanical connector, which may be configured to allow relative movement between the MEMS mirror and the one or more actuating arms or actuators. In other embodiments, the connector may also be configured to allow electrical current and or signals to pass through the connector during operation of the MEMS scanning device. In some embodiments according to the present disclosure, each actuating arm may be connected to the MEMS mirror by a separate connector. It is contemplated, however, that in other exemplary embodiments, a single connector may connect more than one actuating arm to the MEMS mirror. Such a connector may include more than two ends—for example, one end connected to the mirror, and additional to ends connected to the different actuator arms. 
     By way of example,  FIG.  11 A  illustrates MEMS mirror assembly  1100  that may include first connector  1130  and second connector  1132 . As illustrated in the exemplary embodiment of FIG.  11 A, one end of first connector  1130  may be connected to first actuating arm  1124  whereas an opposite end of first connector  1130  may be connected to MEMS mirror  1102 . Likewise, one end of second connector  1132  may be connected to second actuating arm  1126  and an opposite end of second connector  1132  may be connected to MEMS mirror  1102 . 
     As also illustrated in  FIG.  11 A , second actuator  1114  may be connected to MEMS mirror  1102  via connectors  1140  and  1142 . For example, third actuating arm  1134  of second actuator  1114  may be connected to one end of connector  1140 , whereas an opposite end of connector  1140  may be connected to MEMS mirror  1102 . Similarly, for example, fourth actuating arm  1136  of second actuator  1114  may be connected to one end of connector  1142 , whereas an opposite end of connector  1142  may be connected to MEMS mirror  1102 . As discussed above, one or more springs (not shown) may be disposed between ends of first, second, third, and fourth connectors  1130 ,  1132 ,  1140 , and  1142 , and the first, second, third, and fourth actuating arms  1124 ,  1126 ,  1134 , and  1136 , respectively. 
     Although two actuators (i.e. first actuator  1112  and second actuator  1114 ) have been discussed above, it is contemplated that the MEMS scanning device according to the present disclosure may have more than two actuators. For example, the disclosed MEMS scanning device may include a plurality of actuators operable to rotate the MEMS mirror with respect to a plane of the frame. The MEMS scanning device may also include a plurality of interconnect elements (e.g. springs), each being mechanically connected between one or more of the actuators and the MEMS mirror. The actuation of the actuators in different movement schemes may result in rotation of the MEMS mirror. Additionally or alternatively, actuation of the actuators may also result in translation of the MEMS mirror in one or more directions. It is noted that, optionally, all of the MEMS mirror-assembly components discussed above may be fabricated on a single wafer and may share common layers (e.g., a common silicon layer, a common PZT layer). As also discussed above, different components of the MEMS mirror assembly may include various additional layers, such as an optional PZT layer for the actuators, one or more highly reflective layers for the mirror surface, and so on. The MEMS mirror assembly may also include additional components, such as a controller (e.g. processor or microprocessor, which may be operable to control actuation of the various actuators, mirror location feedback mechanism), optical components, structural elements, casing, etc. Such additional components of the MEMS mirror assembly may be implemented on the same wafer as the MEMS mirror, on another wafer, or be otherwise integrated with the wafer of the movable MEMS mirror. 
     By way of example,  FIG.  11 A  illustrates an exemplary embodiment of MEMS mirror assembly  1100  including actuators  1116  and  1118  in addition to first and second actuators  1112  and  1114 . Similar to the arrangement in actuators  1112  and  1114 , actuator  1116  may include actuating arms  1144  and  1146  separated by gap  1148 . Actuating arm  1144  may be connected to one end of connector  1150  and an opposite end of connector  1150  may be connected to MEMS mirror  1102 . Likewise actuating arm  1146  may be connected to one end of connector  1152  and an opposite end of connector  1152  may be connected to MEMS mirror  1102 . Further, actuator  1118  may include actuating arms  1154  and  1156  separated by gap  1156 . Actuating arm  1154  may be connected to one end of connector  1160  and an opposite end of connector  1160  may be connected to MEMS mirror  1102 . Likewise actuating arm  1156  may be connected to one end of connector  1162  and an opposite end of connector  1162  may be connected to MEMS mirror  1102 . As also illustrated in  FIG.  11 A , actuating arms  1144  and  1154  may be outer actuating arms similar to actuating arms  1124  and  1134 . Likewise, actuating arms  1146  and  1156  may be inner actuating arms similar to actuating arms  1126  and  1136 . 
     In accordance with the present disclosure, the MEMS mirror assembly may include one, two, or more actuators which are spaced apart from the MEMS mirror by one or more corresponding silicon strips (also referred to as silicon bands). The one or more silicon strips may belong to the silicon layer on which the actuator and the mirror are implemented.  FIG.  11 B  illustrates an exemplary embodiment of a MEMS mirror assembly  1101  that may include such a silicon strip or silicon band. Like MEMS mirror assembly  1100  of  FIG.  11 A , the exemplary MEMS mirror assembly  1101  of  FIG.  11 B  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 A,  1114 A,  1116 A, and  1118 A. Unlike actuator  1112  of MEMS mirror assembly  1100  of  FIG.  11 A , however, actuator  1112 A of MEMS mirror assembly  1101  of  FIG.  11 B  may include actuating arm  1124  and silicon strip  1125 . As illustrated in  FIG.  11 B , silicon strip  1125  may be positioned adjacent actuating arm  1124  and may be separated from actuating arm  1124  by gap  1128 . Actuating arm  1124  may be connected to MEMS mirror  1102  via connector  1130  as discussed with respect to MEMS mirror assembly  1100  above. Silicon strip  1125 , however, may not be mechanically or electrically connected to MEMS mirror  1102 . Like second actuating arm  1126  of MEMS mirror assembly  1100 , silicon strip  1125  of MEMS mirror assembly  1101  may be disposed between and spaced apart from actuating arm  1124  and MEMS mirror  1102 . Further, silicon strip  1125  may be similar to second actuating arm  1126  of MEMS mirror assembly  1100  when not connected to MEMS mirror  1102 . 
     Exemplary MEMS mirror assembly  1101  illustrated in  FIG.  11 B  may also include actuators  1114 A,  1116 A, and  1118 A. Like actuator  1112 A, of MEMS mirror  1101 , actuators  1114 A,  1116 A, and  1118 A each may include one actuating arm  1134 ,  1144 , and  1154 , respectively. As also illustrated in  FIG.  11 B , actuators  1114 A,  1116 A, and  1118 A may include silicon strips  1135 ,  1145 , and  1155 , respectively, separated from respective actuating arms  1134 ,  1144 , and  1154  by gaps  1138 ,  1148 , and  1158 , respectively. Additionally, actuating arms  1134 ,  1144 , and  1154  may be connected to MEMS mirror  1102  via connectors  1140 ,  1150 , and  1160 , respectively. Silicon strips  1135 ,  1145 , and  1155  may be similar to actuating arms  1136 ,  1146 , and  1156 , respectively, when actuating arms  1136 ,  1146 , and  1156  are not connected to MEMS mirror  1102 . 
     Unlike prior art MEMS mirrors in which actuators are positioned adjacent to the MEMS mirror (e.g. 10s of micrometers space between the MEMS mirror and its actuator), in the MEMS mirror assemblies of this disclosure (e.g. referenced in  FIGS.  11 A through  11 F, and  12 A , through  12 F), some (or all) of the actuating arms may be spaced apart from the MEMS mirror (e.g. by about 0.5-1 mm, or even more). For example, the widths of gaps  1128 ,  1138 ,  1148 , and  1158 , the width of gaps “W g1 ” (see  FIG.  11 A ) between outer actuating arms (e.g.  1124 ,  1134 ,  1144 , and  1154 ) and frame  1104 , the gaps “W g2 ” (see  FIG.  11 A ) between inner actuating arms (e.g.  1126 ,  1136 ,  1146 , and  1156 ) and MEMS mirror  1102 , and/or the gaps “W g3 ” (see  FIG.  12 A ) between outer actuating arms  1124 ,  1134 ,  1144 , and  1154  in the disclosed embodiments may be of the order of at least about 50 μm, about 75 μm, about 100 μm, about 150 μm, or larger. In some exemplary embodiments, the widths of these gaps may be of more than about ⅕ th, more than about ⅓ rd, more than about ¼ th, or more than about ½ of the actuating arm widths (e.g. W 1  or W 2 ). 
       FIGS.  11 C- 11 F  illustrate exemplary MEMS mirror assemblies  1103 ,  1105 ,  1107 , and  1109  that may be included in the disclosed MEMS scanning device according to the present disclosure. As illustrated in  FIG.  11 C , MEMS mirror assembly  1103  may include MEMS mirror  1102 , frame  1102  and actuators  1112 A,  1114 ,  1116 , and  1118 A. Actuators  1114  and  1116  of MEMS mirror  1103  may be similar to actuators  1114  and  1116 , respectively of MEMS mirror  1100  discussed above with reference to  FIG.  11 A , whereas actuators  1112 A and  1118 A of MEMS mirror assembly  1103  may be similar to actuators  1112 A and  1118 A, respectively, of MEMS mirror assembly  1101  discussed above with reference to  FIG.  11 B . Thus, for example, unlike the configuration of  FIG.  11 A , in actuator  1112 A, only actuating arm  1124  may be connected to MEMS mirror  1102 . Likewise, in actuator  1118 A, only actuating arm  1154  may be connected to MEMS mirror  1102 . 
     As illustrated in  FIG.  11 D , MEMS mirror assembly  1105  may include MEMS mirror  1102 , frame  1102  and actuators  1112 B,  1114 A,  1116 A, and  1118 B. Actuators  1114 A and  1116 A of MEMS mirror  1105  may be similar to actuators  1114 A and  1116 A, respectively of MEMS mirror  1101  discussed above with reference to  FIG.  11 B . Furthermore, actuator  1112 B of MEMS mirror assembly  1105  may include actuating arm  1126 , which may be connected to MEMS mirror  1102  via connector  1132 . Actuating arm  1126  and connector  1132  of MEMS mirror  1105  may be similar to actuating arm  1126  and connector  1132 , respectively, of MEMS mirror assembly  1100  discussed above with reference to  FIG.  11 A . Like actuator  1112 B, actuator  1118 B of MEMS mirror assembly  1105  may include actuating arm  1156 , which may be connected to MEMS mirror  1102  via connector  1162 . Actuating arm  1156  and connector  1162  of MEMS mirror  1105  may be similar to actuating arm  1156  and connector  1162 , respectively, of MEMS mirror assembly  1100  discussed above with reference to  FIG.  11 A . In one exemplary embodiment as illustrated in  FIG.  11 D , actuating arms  1126  and  1156  may be positioned relative to MEMS mirror  1102  at positions similar to actuating arms  1126  and  1156  in MEMS mirror  1100  of  FIG.  11 A , although other positions relative to MEMS mirror  1102  are also contemplated. As also illustrated in  FIG.  11 D , actuator  1112 B of MEMS mirror  1105  may not include outer actuating arm  1124  and actuator  1118 B may not include outer actuating arm  1154 . Instead frame  1104  may extend into the space typically occupied by actuating arms  1124  and  1154 . 
     As illustrated in  FIG.  11 E , MEMS mirror assembly  1107  may include MEMS mirror  1102 , frame  1102  and actuators  1112 B,  1114 ,  1116 , and  1118 B. Actuators  1114  and  1116  of MEMS mirror  1107  may be similar to actuators  1114  and  1116 , respectively of MEMS mirror  1100  discussed above with reference to  FIG.  11 A . Furthermore, actuators  1112 B and  1118 B of MEMS mirror assembly  1107  may be similar to actuators  1112 B and  1118 B, respectively, of MEMS mirror assembly  1105  discussed above with reference to  FIG.  11 D . As also illustrated in  FIG.  11 E , frame  1104  may extend into the space typically occupied by actuating arms  1124  and  1154 . 
     As illustrated in  FIG.  11 F , MEMS mirror assembly  1109  may include MEMS mirror  1102 , frame  1102  and actuators  1112 B,  1114 A,  1116 A, and  1118 B. Actuators  1114 A and  1116 A of MEMS mirror  1109  may be similar to actuators  1114 A and  1116 A, respectively of MEMS mirror  1105  discussed above with reference to  FIG.  11 D . Furthermore, actuators  1112 B and  1118 B of MEMS mirror assembly  1107  may be similar to actuators  1112 B and  1118 B, respectively, of MEMS mirror assembly  1105  discussed above with reference to  FIG.  11 D . As illustrated in  FIG.  11 F , however, connectors  1132  and  1162  may be connected to actuating arms  1126  and  1156  at a location closer to MEMS mirror  1102  as compared to the connector locations for actuating arms  1126  and  1156 , respectively, in MEMS mirror assembly  1105 . As also illustrated in  FIG.  11 F , MEMS mirror  1102  may include radially extending notches  1164  and connectors  1132  and  1162  may be connected to MEMS mirror  1102  at a radially inner location of notches  1164 . Like the embodiments illustrated in  FIGS.  11 D and  11 E , in the embodiment of  FIG.  11 F , frame  1104  may extend into the space typically occupied by actuating arms  1124  and  1154 . While the present disclosure provides numerous examples of MEMS mirror assemblies as illustrated in  FIGS.  11 A- 11 F , it should be noted that aspects of the disclosure, in their broadest sense, are not limited to the illustrated or described MEMS mirror assembly examples. 
     As demonstrated in the examples of  FIGS.  11 A- 11 F , the MEMS mirror assembly may include one, two, or more actuators which are spaced apart from the MEMS mirror by one or more corresponding silicon strips each. These one or more silicon strips may belong to the silicon layer on which the actuator and the mirror are implemented. Such silicon strips, if implemented, may be used as a second actuator arm covering at least partly overlapping part of a perimeter of the MEMS mirror, as a static handle or spacer, or for other uses. If used as a handle or a spacer, the silicon strips may be separated from the respective actuators so respective actuator(s) are not mobilized by movement of the actuators (e.g., as demonstrated in the exemplary embodiments illustrated in  FIGS.  11 B,  11 C,  11 D, and  11 F ). Such static silicon strips are also not directly connected to the MEMS mirror by an interconnect element. Alternatively (or in addition), some or all of the silicon stripes may belong to actuators of the plurality of actuators (e.g., as demonstrated in the exemplary embodiments illustrated in  FIGS.  11 A,  11 C,  11 E, and  11 F ) which are used to translate and/or rotate the MEMS mirror. 
       FIGS.  12 A- 12 F  illustrate additional exemplary MEMS mirror assemblies  1200 ,  1201 ,  1203 ,  1205 ,  1207 , and  1209  that may be included in the disclosed MEMS scanning device according to the present disclosure. For example,  FIG.  12 A  illustrates MEMS mirror assembly  1200  that may include MEMS mirror  1102 , frame  1104 , and actuators  1112 C,  1114 C,  1116 C, and  1118 C. Each of actuators  1112 C,  1114 C,  1116 C, and  1118 C may include one actuating arm connected via a connector to MEMS mirror  1102 . For example, as illustrated in  FIG.  12 A , actuators  1112 C,  1114 C,  1116 C, and  1118 C may include actuating arms  1124 ,  1134 ,  1144 , and  1154 , respectively, connected to MEMS mirror  1102  via connectors  1130 ,  1140 ,  1150 , and  1160 , respectively. In the exemplary embodiment illustrated in  FIG.  12 A , MEMS mirror assembly  1200  may not include any of actuating arms  1126 ,  1136 ,  1146 , and  1156 , or connectors  1132 ,  1142 ,  1152 , and  1162  discussed above with reference to MEMS mirror assembly  1100  of  FIG.  11 A . Instead MEMS mirror  1200  may include an opening or gap “W g3 ” between actuating arms  1124 ,  1134 ,  1144 , and  1154  and MEMS mirror  1102 . 
       FIG.  12 B  illustrates an exemplary MEMS mirror assembly  1201 , which may be included in the disclosed MEMS scanning device according to the present disclosure. MEMS mirror  1201  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 B,  1114 C,  1116 C, and  1118 B. Actuators  1114 C and  1116 C of MEMS mirror assembly  1201  may be similar to actuators  1114 C and  1116 C, respectively, of MEMS mirror assembly  1200  discussed above. Further actuators  1112 B and  1118 B of MEMS mirror assembly  1201  illustrated in  FIG.  12 B  may be similar to actuators  1112 B and  1118 B, respectively, of MEMS mirror assembly  1105  ( FIG.  11 D ) of MEMS mirror assembly  1107  ( FIG.  11 E ) discussed above. Unlike MEMS mirror assemblies  1105  and  1107 , however, in MEMS mirror  1201 , frame  1104  may not extend into the space typically occupied by actuating arms  1124  and  1154 . Instead, as illustrated in  FIG.  12 B , actuating arms  1126  and  1156  of MEMS mirror  1201  may be separated by a gap “W g4 ” from frame  1104 . Gaps W g3  and W g4  may have dimensions similar to those discussed above for gaps W g1  and W g2 . 
       FIG.  12 C  illustrates an exemplary MEMS mirror assembly  1203 , which may be included in the disclosed MEMS scanning device according to the present disclosure. MEMS mirror  1203  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 C,  1114 ,  1116 , and  1118 C. Actuators  1112 C and  1118 C of MEMS mirror assembly  1203  may be similar to actuators  1112 C and  111 C 8 , respectively, of MEMS mirror assembly  1200  discussed above with reference to  FIG.  12 A . Actuators  1114  and  1116  of MEMS mirror assembly  1203  may be similar to actuators  1114  and  1116  of MEMS mirror assembly  1100  discussed above with reference to  FIG.  11 A . 
       FIG.  12 D  illustrates an exemplary MEMS mirror assembly  1205 , which may be included in the disclosed MEMS scanning device according to the present disclosure. MEMS mirror  1205  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 B,  1114 C,  1116 C, and  1118 B. Actuators  1112 B and  1118 B of MEMS mirror assembly  1205  may be similar to actuators  1112 B and  1118 B, respectively, of MEMS mirror assembly  1105  or  1107  discussed above with reference to  FIGS.  11 D and  11 E . Actuators  1114 C and  1116 C of MEMS mirror assembly  1205  may be similar to actuators  1114 C and  1116 C of MEMS mirror assembly  1200  discussed above with reference to  FIG.  12 A . 
       FIG.  12 E  illustrates an exemplary MEMS mirror assembly  1207 , which may be included in the disclosed MEMS scanning device according to the present disclosure. MEMS mirror  1207  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 B,  1114 C,  1116 C, and  1118 B. MEMS mirror  1102  of MEMS mirror  1207  may include radial notches  1164  similar to those discussed above for MEMS mirror  1109  with reference to  FIG.  11 F . Moreover, connectors  1132  and  1162  of MEMS mirror  1207  may be connected to actuating arms  1126  and  1166  at location closer to MEMS mirror  1102  (e.g. locations radially nearer to MEMS mirror  1102 ), similar to the connectors  1132  and  1162 , respectively of MEMS mirror assembly  1107  shown in  FIG.  11 E . 
       FIG.  12 F  illustrates an exemplary MEMS mirror assembly  1209 , which may be included in the disclosed MEMS scanning device according to the present disclosure. MEMS mirror  1209  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 B,  1114 C,  1116 C, and  1118 B. Actuators  1112 B and  1118 B of MEMS mirror assembly  1209  may be similar to actuators  1112 B and  1118 B, respectively, of MEMS mirror assembly  1109  discussed above with reference to  FIG.  11 F . Actuators  1114 C and  1116 C of MEMS mirror assembly  1209  may be similar to actuators  1114 C and  1116 C of MEMS mirror assembly  1200  discussed above with reference to  FIG.  12 A . As illustrated in  FIG.  12 F , portions of frame  1104  may extend closer to actuating arms  1126  and  1156  in MEMS mirror assembly  1209  when compared to MEMS mirror assembly  1207 . While the present disclosure provides numerous examples of MEMS mirror assemblies as illustrated in  FIGS.  12 A- 12 F , it should be noted that aspects of the disclosure, in their broadest sense, are not limited to the illustrated or described MEMS mirror assembly examples. 
     As can be seen, for example, in the exemplary embodiments illustrated in  FIGS.  11 A,  11 C,  11 D, and  12 C , the MEMS mirror assembly may include pairs of actuating arms, each including a first actuating arm (e.g., an “outer” one) and a second actuating arm (e.g., an “inner” one) located between the first actuating arm and the MEMS mirror. The actuating arms of such a pair may be designed (and controlled by a controller) to move in synchronization with each other for rotating the MEMS mirror in cooperation. In some exemplary embodiments, actuators positioned on an opposite side of the MEMS mirror may pull the mirror in the opposite direction. 
     In some exemplary embodiments, the plurality of actuators may further include both paired and unpaired actuating arms distributed around the MEMS mirror (e.g., as exemplified in the embodiments illustrated in  FIGS.  11 C,  11 E, and  12 C . In other exemplary embodiments, the paired and unpaired actuating arms may be arranged in an antisymmetric fashion around the MEMS mirror (e.g., as exemplified in  FIGS.  11 C,  11 E, and  12 C ). Such arrangements may be used, for example, for separating resonance frequencies in different directions of movement of MEMS mirror  1102 . It is contemplated that in some embodiments, more than a pair of arms may be distributed around the MEMS mirror (e.g. as exemplified in the embodiments illustrated in  FIGS.  17 B and  17 C ). 
     According to the present disclosure, the MEMS scanning device includes a connector connecting at least one of the first actuating arm and the second actuating arm to the movable MEMS mirror, the connector having an L shape. For example, some or all of the interconnects may be generally L-shaped, including two elongated parts connected to each other at a substantially right angle. Thus, for example, the two elongated parts may be disposed generally perpendicular to each other. Such a geometric arrangement of the elongated portions of the connector may help reduce the stress induced in the connector portions during movement of the MEMS mirror. 
       FIG.  13 A  illustrates a MEMS mirror assembly  1100  similar to MEMS mirror assembly  1100  of  FIG.  11 A . As illustrated in  FIG.  13 A , MEMS mirror assembly  1100  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 ,  1114 ,  1116 , and  1118 . Further, each actuator  1112 ,  1114 ,  1116 , and  1118  may include a pair of actuating arms as discussed above with reference to  FIG.  11 A . For example, actuator  1114  may include actuating arm  1134  and actuating arm  1136 . Actuating arm  1134  may be connected to one end of connector  1140  and actuating arm  1136  may be connected to one end of connector  1142 . Opposite ends of connectors  1140  and  1142  may be connected to MEMS mirror  1102 . 
       FIG.  13 B  illustrates an exemplary arrangement of actuating arms  1134  and  1136  and their connection with connectors  1140  and  1142 , respectively.  FIG.  13 B  represents a magnified view of actuator  1118  in the section encompassed by the dashed ellipse shown in  FIG.  13 A . As illustrated in  FIG.  13 B , one end of connector  1140  may be connected to outer actuating arm  1134 . Connector  1140  may include elongated parts  1302  and  1304 . Elongated part  1302  may be disposed generally parallel to actuating arm  1134 , whereas elongated part  1304  may be disposed inclined relative to actuating arm  1134 . In one exemplary embodiment as illustrated in  FIG.  13 B , elongated parts  1302  and  1304  may be disposed generally perpendicular to each other, forming a generally L-shaped connector  1140 . Similarly, connector  1142  may include elongated part  1306  and  1308 . Elongated part  1306  may be disposed generally parallel to actuating arm  1136 , whereas elongated part  1308  may be disposed inclined relative to actuating arm  1136 . In one exemplary embodiment as illustrated in  FIG.  13 B , elongated parts  1306  and  1308  may be disposed generally perpendicular to each other, forming a generally L-shaped connector  1142 . Although both connectors  1140  and  1142  have been illustrated in  FIG.  13 B  as being generally L-shaped, it is contemplated that one, both, or none of the connectors  1140  and  1142  may form an L-shape. Furthermore, it is contemplated that the pair of elongated parts  1302 ,  1304 , or the pair of elongated parts  1306 ,  1308  may each be disposed inclined (i.e. at angles different from 90°) relative to each other. Moreover, although connectors  1140  and  1142  have been discussed in connection with actuating arms  1134  and  1136  of actuator  1114 , similar connectors may be implemented with actuators  1112 ,  1116 , and  1118 . 
     In accordance with the present disclosure, the MEMS scanning device may include a connector connecting at least one of the first actuating arm and the second actuating arm to the movable MEMS mirror, the connector having an S shape. For example, some or all of the interconnects may be generally S-shaped. Such a geometric arrangement of the elongated portions of the connector may help reduce the stress induced in the connector portions during movement of the MEMS mirror.  FIG.  14    illustrates an exemplary MEMS mirror assembly  1400 , which may include MEMS mirror  1102 , frame  1104 , and actuators  1112 C,  1114 C,  1116 C, and  1118 C. Actuators  1112 C,  1114 C,  1116 C, and  1118 C may include actuating arms  1124 ,  1134 ,  1144 , and  1154 , respectively, which may be connected to MEMS mirror  1102  via connectors  1130 ,  1140 ,  1150 , and  1160 , respectively. As exemplified in  FIG.  14   , one or more of the flexible connectors  1130 ,  1140 ,  1150 , and  1160  of MEMS mirror assembly  1400  may be an elongated structure which may include at least two turns (e.g.  1402 ) in opposing directions. Each of the turns or bends  1402  may span an angle greater than about 120°. Further, as illustrated in  FIG.  14   , when one turn 1402 is in a clockwise direction, the adjacent turn 1402 is in a counterclockwise direction. In some exemplary embodiments, some or all of the turns of connectors  1130 ,  1140 ,  1150 , and  1160  may be at angles greater than about 150°, of about 180°, or even at reflex angles which are greater than about 180°. The turns 1402 may be continuously curved turns (e.g., as exemplified with respect to the example of interconnect element  1160 ), but may also include one or more angled corners (e.g., as illustrated by interconnect elements  1130 ,  1140 , and/or  1150 ). 
     While the present disclosure provides examples of connector shapes (e.g. L-shaped, S-shaped, etc.), it should be noted that aspects of the disclosure in their broadest sense, are not limited to the disclosed shapes. Furthermore, although the connector shapes have been described above with reference to MEMS mirror  1100 , it should be noted that one or more of the disclosed connector shapes may be implemented to connect one or more actuating in any of the MEMS mirror assemblies, for example,  1101 ,  1103 ,  1105 ,  1107 ,  1109 ,  1200 ,  1201 ,  1203 ,  1205 ,  1207 , and/or  1209  illustrated in  FIGS.  11 A- 11 F  and  FIGS.  12 A- 12 F . 
     In accordance with the present disclosure, the MEMS scanning device includes a first actuating arm and a second actuating arm. In some MEMS scanning devices in accordance with the present disclosure, each of the first actuating arm and the second actuating arm includes an outer side and an opposing inner side closer to the movable MEMS mirror than the outer side, wherein the first connector is connected to the opposing inner side of the first actuating arm and the second connector is connected to the outer side of the second actuating arm. For example, in some exemplary embodiments according to the present disclosure, in at least one pair of actuators, the first actuator may be connected to a respective first interconnect element in an inner part of the first actuator, and the second actuator may be connected to a respective second interconnect element in an outer part of the second actuator. The proposed structure may have at least one of the following structural characteristics: the interconnect of the inner actuator may be relatively long; the interconnect of the inner actuator may be connected in the furthermost distance from the MEMS mirror; the interconnects of both the inner actuator and the outer actuator may be of similar lengths; and the interconnects of both the inner actuator and the outer actuator may be connected to the actuators at proximate points. Various combinations of these features can be used, inter alia, for achieving one or more of the following features: reducing undesirable derivative movements (e.g. movement within the plane of the silicon layer when the intended movement is rotation about an axis parallel thereto), reducing stresses on the interconnects, working in higher frequencies, reaching larger rotation angles, increasing resonance frequencies, working with a thicker mirror, reducing crosstalk between different actuators and/or axes of movement, and so on. In addition to the structure and position of the interconnects, the aforementioned features may also be enhanced by selecting the most suitable structure and combination of actuators, e.g. out of the configuration illustrated in  FIGS.  11 A- 11 F and  12 A- 12 F . 
     It is noted that connecting interconnects at a part of the actuator which is nearest to the MEMS mirror (and not, for example, to a middle, or to the most remote part of the actuator) may be implemented in many MEMS mirror assemblies, and not only in the ones discussed above (e.g., with or without separating silicon strips between the actuators and the mirrors). In accordance with this disclosure, a MEMS mirror assembly is disclosed, including at least: a MEMS mirror; a frame; a plurality of actuators operable to rotate the MEMS mirror with respect to a plane of the frame; and interconnect elements that are mechanically connected between the actuators and the MEMS mirror; wherein for at least two of the interconnect elements are connected to an inner part of a moving end of the respective actuator. Any variations of the MEMS mirror assembly discussed above may also implemented to such a MEMS mirror assembly (if feasible), mutatis mutandis. It is further contemplated that the MEMS scanning device according to the present disclosure, one or both of the first and second connectors may be connected to the outer side or the inner side of the first and second actuating arms respectively. The particular position (outer side or inner side) for connecting the one or more connectors may be determined based on considerations such as limiting the amount of stress induced in the connectors, improving manufacturability of the MEMS scanning device, reducing crosstalk between the different actuators (i.e. reducing the influence of the movement induced by one connector on the movement induced by the other connector), etc. 
       FIGS.  15 A and  15 B  illustrate two exemplary connector arrangements that may be employed to connect one or more of the actuating arms to respective connectors. For example, as illustrated in  FIG.  13 A , actuating arm  1134  of actuator  1118  may be connected to frame  1104  adjacent frame end  1320 . Actuating arm  1134  may extend from adjacent frame end  1320  in a generally circumferential direction towards arm end  1322 . Likewise, actuating arm  1136  of actuator  1118  may be connected to frame  1104  adjacent frame end  1324 . Actuating arm  1136  may extend from adjacent frame end  1324  in a generally circumferential direction towards arm end  1326 .  FIGS.  15 A and  15 B  illustrate magnified views of actuator  1118  (of MEMS mirror assembly  1100 ) in the section encompassed by the dashed ellipse shown in  FIG.  13 A  (i.e. adjacent arm ends  1324  and  1326 ). 
     According to the present disclosure, as illustrated in  FIG.  15 A , MEMS mirror assembly  1100  may include MEMS mirror  1102 , frame  1104 , actuating arm  1134 , actuating arm  1136 , and connectors  1140  and  1142 . As illustrated in  FIG.  15 A , actuating arm  1134  may be positioned at a greater distance from MEMS mirror  1102  as compared to actuating arm  1136 . Actuating arm  1134  may have an outer side  1502  and an inner side  1504 . Outer side  1502  of actuating arm  1134  may be located at a greater distance from MEMS mirror  1102  as compared to inner side  1504 . Thus, outer side  1502  may be positioned nearer to frame  1104  and further from MEMS mirror  1102  as compared to inner side  1504 . Like actuating arm  1134 , actuating arm  1136  may also have an outer side  1506  and an inner side  1508 . Outer side  1506  of actuating arm  1136  may be located at a greater distance from MEMS mirror  1102  as compared to inner side  1508 . Thus, outer side  1506  may be positioned nearer to frame  1104  and further from MEMS mirror  1102  as compared to inner side  1508 . As also illustrated in  FIG.  15 A , outer side  1506  of actuating arm  1336  may be positioned adjacent inner side  1504  of actuating arm  1334 . Outer side  1506  of actuating arm  1336  may be separated (i.e. spaced apart) from inner side  1504  of actuating arm  1334  by gap  1138 . 
     In some exemplary embodiments as illustrated in  FIG.  15 A , connector  1140  may be connected to inner side  1504  of actuating arm  1134 . It is contemplated that connector  1140  may be connected to inner side  1504  at a position between frame end  1320  and arm end  1322 . For example, connector  1140  may be connected to inner side  1504  of actuating arm  1134  at a position relatively nearer to arm end  1322  as compared to frame end  1320 . As also illustrated in  FIG.  15 A , connector  1142  may be connected to outer side  1506  of actuating arm  1136 . For example, connector  1142  may be connected to outer side  1506  of actuating arm  1136  at arm end  1326 . It is contemplated that in other exemplary embodiments, one or both of connectors  1140  and  1142  may be connected to actuating arms  1134  and  1136 , respectively, at or adjacent arm ends  1322  and  1326 , respectively. It is also contemplated that one or both of connectors  1140  and  1142  may be connected either to outer sides  1502  and  1506 , respectively, or inner sides  1504  and  1508 , respectively, of their respective associated actuating arms  1134  and  1136 .  FIG.  15 A  also illustrates PZT layers  1510  and  1512 , which may be disposed on some or all portions of actuating arms  1134  and  1136 , respectively. 
       FIG.  15 B  illustrates a variation of the exemplary arrangement of  FIG.  15 A . As illustrated in  FIG.  15 B , connector  1140  may be connected to arm end  1322  instead of being positioned between frame end  1320  and arm end  1322 . In some exemplary embodiments as illustrated in  FIG.  15 B , actuating arms  1134  and  1136  may include circumferential recesses  1520  and  1522 , respectively. Recess  1520  may extend from arm end  1322  to a predetermined distance in a circumferential direction towards frame end  1320 . Recess  1520  may be disposed nearer inner side  1504 . It is contemplated, however, that recess  1520  may be disposed nearer outer side  1502  or equidistant from outer and inner sides  1502 ,  1504 . Likewise, recess  1522  may extend from arm end  1326  to a predetermined distance in a circumferential direction towards frame end  1324 . Recess  1522  may be disposed nearer outer side  1506 . It is contemplated, however, that recess  1522  may be disposed nearer inner side  1508  or equidistant from outer and inner sides  1506 ,  1508 . The dimensions of recesses  1520  and  1522  may be the same or may be different. Notches  1520  and  1522  may further help minimize the stresses induced in connectors  1140  and  1142  during operation of MEMS mirror assembly  1100 . 
       FIG.  16 A  illustrates a MEMS mirror assembly  1200 , which is similar to MEMS mirror assembly  1200  illustrated in  FIG.  12 A . As illustrated in  FIG.  16 A , MEMS mirror assembly  1200  may include MEMS mirror  1102 , frame  1104 , and actuators  1112 C,  1114 C,  1116 C, and  1118 C. Further, each actuator  1112 C,  1114 C,  1116 C, and  1118 C may include an actuating arm as discussed above with respect to MEMS mirror assembly  1200  with reference to  FIG.  12 A . For example, actuator  1118 C may include actuating arm  1134 , which may be connected to one end of connector  1140 . An opposite end of connectors  1140  may be connected to MEMS mirror  1102 .  FIGS.  16 B and  16 C  illustrate magnified views of actuator  1118 C (of MEMS mirror assembly  1200 ) in the section encompassed by the dashed ellipse shown in  FIG.  16 A  (i.e. adjacent arm end  1322 ). 
     In some exemplary embodiments according to the present disclosure, as illustrated in  FIG.  16 A , actuating arm  1134  may be positioned nearer frame  1104  and may be separated (i.e. spaced apart) from mirror  1102  by a large gap. Actuating arm  1134  may have an outer side  1602  and an inner side  1604 . Outer side  1602  of actuating arm  1134  may be located at a greater distance from MEMS mirror  1102  as compared to inner side  1604 . Thus, outer side  1602  may be positioned nearer to frame  1104  and further from MEMS mirror  1102  as compared to inner side  1604 . 
     In other exemplary embodiments as illustrated in  FIG.  16 B , connector  1140  may be connected to outer side  1602  of actuating arm  1134 . Moreover, connector  1140  may be connected to actuating arm  1134  at arm end  1322 . It is contemplated that in other exemplary embodiments, connector  1140  may be connected to inner side  1604  of actuating arm  1134  either at arm end  1322  or at a position between frame end  1320  and arm end  1322 .  FIG.  16 C  illustrates a variation of the exemplary arrangement of  FIG.  16 B . As illustrated in  FIG.  16 C , actuating arm  1134  may include circumferential recesses  1520  similar to that discussed above with reference to  FIG.  15 A . While the present disclosure provides examples of actuating arm locations for attaching the connectors, it should be noted that aspects of the disclosure in their broadest sense, are not limited to the disclosed attachment configurations. 
     It is noted that first type of interconnect (connected to an inner part of the respective actuator, e.g.  1140  in  FIGS.  15 A and  15 B ) may also be implemented in MEMS mirror assemblies where some or all of the actuators are remote from to the MEMS mirror. Example of such configurations are provided in  FIGS.  11 B,  11 D,  11 F,  12 A,  12 C,  12 D, and  12 F . 
     In accordance with the present disclosure, the MEMS scanning device includes an actuator having a first actuating arm and a second actuating arm, wherein the first actuating arm and the second actuating arm are connected to the MEMS mirror by a single connector. For example, both first and second actuating arms may be connected to the MEMS mirror using the same interconnect (e.g. connector) and/or both first and second actuating arms may be connected to each other at one end by the connecting arm. According to the present disclosure, the first actuating arm and the second actuating arm are connected to each other by a connecting arm, and the connecting arm is connected to the MEMS mirror via a connector. Exemplary MEMS mirror assemblies, in accordance with the present disclosure may include at least: a MEMS mirror; a frame; a plurality of actuators operable to rotate the MEMS mirror with respect to a plane of the frame; and interconnect elements that are mechanically connected between the actuators and the MEMS mirror. Such MEMS mirror assemblies may also include at least one actuator (possibly all of the actuators, possibly some of them) which may have a first end that may be mechanically connected to the frame and a second end that may be opposite to the first end and may be mechanically connected to the respective interconnect element, wherein the at least one actuator comprises two separate bands of silicon (e.g. actuating arms) which may be spaced apart from one another for example, for more than about 50% of the distance between the first end and the second end. Examples or such assemblies are illustrated in  FIGS.  17 A- 17 F , which are discussed below. Optionally, one or more of the actuators may include more than two (e.g., three or four) bands which are spaced apart from one another, for example, for more than about 50% of the distance between the first end and the second end. It is noted that in some exemplary embodiments, the bands may be spaced apart from each other for more than about 60%, more than about 70%, more than about 80%, or more than about 90% of the distance between the first end and the second end. As used in this disclosure the term about should be interpreted to include typical machining or manufacturing tolerances. Thus, the phrase “about 50%” should be interpreted to encompass values ranging between, for example, 50±0.5%, 50±1%, etc. 
     In some exemplary embodiments according to this disclosure, each band may include separate piezoelectric actuation layers. Each band may also include other separate actuation mechanism different from the actuation mechanism for another band. It is contemplated that different bands may concurrently receive the same or different actuation instructions (e.g. different voltages/biases). 
     In other exemplary embodiments according to this disclosure, two (or more) bands may span over different angular sectors having different span angles with respect to a center of the MEMS mirror. Such exemplary configurations are illustrated in  FIGS.  17 A and  17 C . It is noted that the different bands may be of similar length, or of different lengths. It is also noted that the different bands may be of similar width, or of different widths. 
     In some exemplary embodiments according to this disclosure, two bands may be implemented in any one of the aforementioned MEMS mirror assemblies—those which are illustratively represented in the diagrams and others. Such exemplary configurations are illustrated in  FIGS.  17 B and  17 C . When implemented in any one of the previously disclosed MEMS mirror assembly, two bands may be implemented in some or all actuators of the respective MEMS mirror assemblies. It is also contemplated that in some exemplary embodiments, more than one silicon band may not be implemented in all the actuators of any of the MEMS mirror assemblies discussed above. 
     Various implementations of MEMS mirror assemblies whose actuators include more than one spaced apart bands may be used, inter alia, for achieving one or more of the following features: reducing stresses on the interconnects, reducing stress on the actuator (especially in the piezoelectric components, if implemented), working in higher frequencies, reaching larger rotation angles, increasing resonance frequencies, working with a thicker mirror, etc. In addition to the structure and position of the interconnects, the aforementioned features may also be enhanced by selecting the most suitable structure and combination of actuators, e.g. out of the configuration illustrated in  FIGS.  17 A- 17 C , discussed below. 
     By way of example,  FIG.  17 A  illustrates an exemplary MEMS mirror assembly  1700  consistent with this disclosure. For example, as illustrated in  FIG.  17 A , MEMS mirror assembly  1100  may include MEMS mirror  1102  supported by frame  1104 . MEMS mirror assembly  1700  may include exemplary actuators  1112 D,  1114 D,  1116 D, and  1118 D consistent with this disclosure. As illustrated in  FIG.  17 A , actuator  1112 D may be connected adjacent first end  1120  to frame  1104 . Actuator  1112 D may extend circumferentially from adjacent first end  1120  to second end  1122  and may be connected to MEMS mirror  1102  adjacent second end  1122 . 
     As illustrated in the exemplary embodiment of  FIG.  17 A , actuator  1112 D may include first actuating arm  1124 , second actuating arm  1126 , and gap  1128  between first actuating arm  1124  and second actuating arm  1128  similar to the configuration discussed above with respect to MEMS mirror assembly  1100  of  FIG.  11 A . Each of the actuating arms  1124  and  1126  may be a silicon band. Unlike MEMS mirror assembly  1100 , however, in MEMS mirror assembly  1700  of  FIG.  17 A , first actuating arm  1124  may be connected to second actuating arm  1126  by connecting arm  1129 . As also illustrated in  FIG.  17 A , both first and second actuating arms  1124  and  1126  may be connected to one end of connector  1130  and an opposite end of connector  1130  may be connected to MEMS mirror  1102 . In one exemplary embodiment, connector  1130  may be connected to connecting arm  1129  of actuator  1112 D. It is contemplated, however, that in some exemplary embodiments, connector  1130  may be connected to both first and second actuating arms  1124  and  1126 , without the first and second actuating arms  1124  and  1126  being connected to each other. Actuators  1114 D,  1116 D, and  1118 D may have a similar structural arrangement as discussed above for actuator  1112 D. 
     As illustrated in  FIG.  17 A , gap  1128  may extend over nearly an entire length of actuator  1112  from adjacent first end  1120  to adjacent second end  1122 . It is contemplated, however, that gap  1128  may extend only partway over the length between first end  1120  and second end  1122 . Thus, for example, first and second actuating arms  1124  and  1126  may be spaced apart from each other by gap  1128  over only a portion of a length of first and second actuating arms  1124  and  1126 . It is also contemplated that in some embodiments gap  1128  may include a plurality of gaps spaced apart from each other by connections between the actuating arms  1124  and  1126 . In some exemplary embodiments, first and second actuating arms  1124  and  1126  may be spaced apart from each other by gap  1128 , which may be a single gap or a plurality of gaps, over more than about 50%, more than about 50%, more than about 70%, more than about 80%, or more than about 90% of the distance between first end  1120  and second end  1122 . As also illustrated in the exemplary embodiment of  FIG.  17 A , each of first and second actuating arms  1124  and  1126  may include an associated PZT layer, which may be positioned over some portions or over an entire length of the first and second actuating arms  1124  and  1126 . 
     Unlike MEMS mirror assembly  1100 , however, actuating arm  1134  may be connected to actuating arm  1136  by connecting arm  1139 ; actuating arm  1144  may be connected to actuating arm  1146  by connecting arm  1149 ; and actuating arm  1154  may be connected to actuating arm  1156  by connecting arm  1159 . As also illustrated in  FIG.  17 A , connector  1140  may be connected at one end to connecting arm  1139  and connected at the other end to MEMS mirror  1102 ; connector  1150  may be connected at one end to connecting arm  1149  and connected at the other end to MEMS mirror  1102 ; connector  1160  may be connected at one end to connecting arm  1159  and connected at the other end to MEMS mirror  1102 . It is also contemplated that in some exemplary embodiments, connector  1140  may be connected directly to actuating arms  1134 ,  1136 , which may not be connected to each other; connector  1150  may be connected directly to actuating arms  1144 ,  1146 , which may not be connected to each other; and connector  1160  may be connected directly to actuating arms  1154 ,  1156 , which may not be connected to each other. It is further contemplated that like gap  1128 , gaps  1138 ,  1148 , and  1158  may extend over only a portion of a distance between first and second ends  1130  and  1132 ;  1140  and  1142 ; and  1150  and  1152 , respectively. 
       FIG.  17 B  illustrates an exemplary MEMS mirror assembly  1701  consistent with this disclosure. Many of the structural features of MEMS mirror assembly  1701  are similar to that of MEMS mirror assembly  1700 . For example, as illustrated in  FIG.  17 B , MEMS mirror assembly  1701  may include MEMS mirror  1102  supported by frame  1104 . MEMS mirror assembly  1701  may include exemplary actuators  1112 E,  1114 E,  1116 E, and  1118 E, actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , and exemplary connectors  1130 ,  1132 ,  1140 ,  1142 ,  1150 ,  1152 ,  1160 , and  1162  consistent with this disclosure. In the following, only the features of MEMS mirror assembly  1701  that differ from those of MEMS mirror assembly  1700  are discussed. In one exemplary embodiment as illustrated in  FIG.  17 B , first actuating arm  1124  of MEMS mirror assembly  1701  may include actuating arms  1721  and  1723 , spaced apart by gap  1722 . Second actuating arm  1126  of MEMS mirror assembly  1701  may include actuating arms  1725  and  1727 , spaced apart by gap  1726 . Thus, actuating arms  1721 ,  1723 ,  1725 , and  1727  may form a plurality of silicon bands separated from each other by gaps  1722 ,  1128 ,  1723 , etc. Gaps  1722 ,  1726 , and  1128  may have equal or unequal widths. 
     Actuating arm  1134  of actuator  1114 E in MEMS mirror assembly  1701  may include actuating arms  1731  and  1733 , spaced apart by gap  1732 . Actuating arm  1136  of MEMS mirror assembly  1701  may include actuating arms  1735  and  1737 , spaced apart by gap  1736 . Thus, actuating arms  1731 ,  1733 ,  1735 , and  1737  may form a plurality of silicon bands separated from each other by gaps  1732 ,  1138 ,  1736 , etc. Gaps  1732 ,  1736 , and  1138  may have equal or unequal widths. Thus, for example, actuating arms  1731  and  1733  may be spaced apart from each other over a portion of the distance between first end  1130  and second end  1132 , similar to actuating arms  1721  and  1723 . Likewise, actuating arms  1735  and  1737  may be spaced apart from each other over a portion of the distance between first end  1130  and second end  1132 , similar to actuating arms  1721  and  1723 . 
     Actuating arm  1144  of actuator  1116 E in MEMS mirror assembly  1701  may include actuating arms  1741  and  1743 , spaced apart by gap  1742 . Actuating arm  1146  of MEMS mirror assembly  1701  may include actuating arms  1745  and  1747 , spaced apart by gap  1746 . Thus, actuating arms  1741 ,  1743 ,  1745 , and  1747  may form a plurality of silicon bands separated from each other by gaps  1742 ,  1148 ,  1746 , etc. Thus, for example, actuating arms  1741  and  1743  may be spaced apart from each other over a portion of the distance between first end  1140  and second end  1142 , similar to actuating arms  1721  and  1723 . Likewise, actuating arms  1745  and  1747  may be spaced apart from each other over a portion of the distance between first end  1140  and second end  1142 , similar to actuating arms  1721  and  1723 . 
     Actuating arm  1154  of actuator  1118 E in MEMS mirror assembly  1701  may include actuating arms  1751  and  1753 , spaced apart by gap  1752 . Actuating arm  1156  of MEMS mirror assembly  1701  may include actuating arms  1755  and  1757 , spaced apart by gap  1756 . Thus, actuating arms  1751 ,  1753 ,  1755 , and  1757  may form a plurality of silicon bands separated from each other by gaps  1752 ,  1158 ,  1756 , etc. Gaps  1752 ,  1756 , and  1158  may have equal or unequal widths. Thus, for example, actuating arms  1751  and  1753  may be spaced apart from each other over a portion of the distance between first end  1150  and second end  1152 , similar to actuating arms  1721  and  1723 . Likewise, actuating arms  1755  and  1757  may be spaced apart from each other over a portion of the distance between first end  1150  and second end  1152 , similar to actuating arms  1721  and  1723 . While the present disclosure provides examples of actuator arrangements, it should be noted that aspects of the disclosure in their broadest sense, are not limited to the disclosed actuator arrangement examples. 
       FIG.  17 C  illustrates an exemplary MEMS mirror assembly  1703  that includes many of the same features as that of MEMS mirror assembly  1701  discussed above with reference to  FIG.  17 B . Thus for example, MEMS mirror assembly  1703  may include MEMS mirror  1102 , frame  1104 , exemplary actuators  1112 E,  1114 E,  1116 E, and  1118 E, actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , and exemplary connectors  1130 ,  1132 ,  1140 ,  1142 ,  1150 ,  1152 ,  1160 , and  1162  similar to corresponding features of MEMS mirror assembly  1701 . In the following, only the features of MEMS mirror assembly  1703  that differ from those of MEMS mirror assembly  1701  are discussed. 
     In accordance with this disclosure,  FIG.  17 C  illustrates different ways of connecting actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156  to frame  1104 . As one example, MEMS mirror  1703  may include interconnect arrangement  1750 , which may be used to connect actuating arms  1124  and  1126  to frame  1104 . For example, interconnect arrangement  1750  may include a single interconnect  1752 , attached at one end to frame  1104 . Interconnect  1752  may project inwards from frame  1104  towards MEMS mirror  1102 . In some exemplary embodiments, interconnect  1752  may be project in a radially inward direction and may extend over a predetermined angular span. In other exemplary embodiments, interconnect  1752  may be disposed at an angle of inclination relative to the radially inward direction. Interconnect  1752  may have a rectangular, square, trapezoidal, or any other shape. Actuators  1124  and  1126  may be attached to interconnect  1752  adjacent first end  1120 . As also illustrated in  FIG.  17 C , gaps  1128 ,  1724 , and  1726  may extend from adjacent interconnect  1752  to adjacent second end  1122 . Thus, for example, gaps  1128 ,  1724 , and  1726  may not extend into interconnect  1752 . 
     As another example, MEMS mirror  1703  may include interconnect arrangement  1760 , which may be used to connect actuating arms  1134  and  1136  to frame  1104 . For example, interconnect arrangement  1760  may include interconnects  1762  and  1764 , attached at one end to frame  1104 . Interconnect  1762  may project radially inwards from frame  1104  towards MEMS mirror  1102  and may extend over a predetermined angular span. Likewise, interconnect  1764  may project inwards from frame  1104  towards MEMS mirror  1102  and may extend over a predetermined angular span. Interconnect  1762  may be disposed adjacent to interconnect  1764  and may be spaced apart from interconnect  1764  by gap  1138 , which may extend to adjacent frame  1104 . In some exemplary embodiments, interconnects  1762  and  1764  may be positioned parallel to a radially inward direction. In other exemplary embodiments, interconnects  1762  and  1764  may be disposed at an angle of inclination relative to the radially inward direction and/or to each other. Interconnects  1762  and  1764  may have a rectangular, square, trapezoidal, or any other shape. Actuator  1134  may be attached to interconnect  1762  adjacent first end  1130 , and actuator  1136  may be attached to interconnect  1764  adjacent first end  1130 . As also illustrated in  FIG.  17 C , gaps  1734 , and  1736  may extend from adjacent interconnects  1762  and  1764 , respectively, to adjacent second end  1132 . Thus, for example, gaps  1734 , and  1736  may not extend into interconnects  1762  and  1764 , respectively. 
     As yet another example, MEMS mirror  1703  may include interconnect arrangement  1770 , which may be used to connect actuating arms  1144  and  1146  to frame  1104 . For example, interconnect arrangement  1770  may include interconnects  1772  and  1774 , attached at one end to frame  1104 . Interconnects  1772  and  1774  may have structures and functions similar to that of interconnects  1762  and  1764  discussed above. As also illustrated in  FIG.  17 C , gaps  1742  and  1746  may extend from interconnects  1772  and  1774 , respectively, to adjacent second end  1132 . Gaps  1742  and  1746  may include interconnect gap portions  1741  and  1745 , respectively. Gaps  1742  and  1746  may also include actuator gap portions  1743  and  1747 , respectively. Actuator gap portions  1743  and  1747  may extend from interconnects  1772  and  1774  in a generally circumferential direction to adjacent second end  1142 . Interconnect gap portions  1741  and  1745  may extend from actuator gap portions  1743  and  1747 , respectively, partway into interconnects  1772  and  1774 , respectively. 
     As yet another example, MEMS mirror  1703  may include interconnect arrangement  1780 , which may be used to connect actuating arms  1154  and  1156  to frame  1104 . For example, interconnect arrangement  1780  may include interconnects  1782 ,  1884 ,  1786 , and  1788 , attached at one end to frame  1104 . Interconnects  1782 ,  1784 ,  1786 , and  1788  may have structures and functions similar to that of interconnects  1762  and  1764  discussed above. Actuating arms  1751 ,  1753 ,  1755 , and  1757  may be attached to interconnects  1782 ,  1784 ,  1786 , and  1788 , respectively adjacent first end  1150 . As also illustrated in  FIG.  17 C , gaps  1742  and  1746  may extend from adjacent frame  1104  to adjacent second end  1152 . Thus, for example, gap  1752  may be disposed between interconnects  1782  and  1784  and may also extend between actuating arms  1751  and  1753 . Likewise, gap  1756  may be disposed between interconnects  1786  and  1788  and may also extend between actuating arms  1755  and  1757 . Although interconnect arrangements  1750 ,  1760 ,  1770 , and  1780  were discussed with reference to actuators  1112 ,  1114 ,  1116 , and  1118 , respectively, it is contemplated that any of interconnect arrangements  1750 ,  1760 ,  1770 , and  1780  may be implemented with any of actuators  1112 ,  1114 ,  1116 , and/or  1118 . Further, it is contemplated that any of interconnect arrangements  1750 ,  1760 ,  1770 , and  1780  may be implemented on any of MEMS mirror assemblies illustrated in  FIGS.  11 A- 11 F,  12 A- 12 F,  13 A,  15 A,  16 A , and/or  17 A- 17 C. While the present disclosure provides examples of interconnects for connecting the actuators to the frame of the MEMS mirror, it should be noted that aspects of the disclosure in their broadest sense, are not limited to the disclosed interconnect configurations. 
       FIGS.  18 A- 23 B , discussed in detail below, illustrate MEMS mirror assemblies, in accordance with examples of the presently disclosed subject matter. The MEMS mirror assemblies exemplified in the non-exhausting examples of  FIGS.  18 A- 23 B  include at least: a MEMS mirror; a frame; a plurality of actuators operable to rotate the MEMS mirror with respect to a plane of the frame; and interconnect elements that are mechanically connected between the actuators and the MEMS mirror. Optionally, the MEMS mirror assemblies may be manufactured so that the frame (supporting structure) is significantly thicker than the actuators which are designed to bend for rotating the MEMS mirror. As illustrated in  FIGS.  18 A- 23 B , optionally, the connection between the thinner part of an actuator and the thicker part of the frame may be implemented perpendicular to a longitudinal axis of the actuator, or parallel thereto. Optionally, a diagonal version or non-straight connection lines may also be implemented. Optionally, the thinner part of the actuator may include a bend extending at substantially right angle (or somewhat different angle, e.g. between about 70° and about 110°), and the connection to the thicker part of the frame is located “after” the bend, such that the bend is positioned within the thinner part. While the variations where illustrated only for some of the structures exemplified in the previous drawings, any one of these connection structures may be implemented for any one of the suggested structures, or for any MEMS mirror assembly (or other MEMS assembly) in which thinner actuators are supported by a thicker frame for rotating a MEMS mirror (or other MEMS surface) with respect to the frame. 
       FIG.  18 A  illustrates an exemplary MEMS mirror assembly  1801 , many of the features of which are similar to those of MEMS mirror  1100  discussed above with reference to  FIG.  11 A . MEMS mirror assembly  1801  may also include frame  1804 , which may be similar to frame  1104  of MEMS mirror assembly  1100 , except that frame  1804  may be significantly thicker than frame  1104 . As also illustrated in  FIG.  18 A , actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156  may be attached to frame  1804  by interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 , respectively. Interconnects  1822 ,  1832 ,  1842 , and  1852  may be similar to interconnect  1762  discussed above with reference to  FIG.  17 C . Likewise, interconnects  1824 ,  1834 ,  1844 , and  1854  may be similar to interconnect  1764  discussed above with reference to  FIG.  17 C . In some exemplary embodiments as illustrated in  FIG.  18 A , frame  1804  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , and/or any of interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 . 
       FIG.  18 B  illustrates an exemplary MEMS mirror assembly  1803 , many of the features of which are similar to those of MEMS mirror  1801  discussed above with reference to  FIG.  18 A . As illustrated in the exemplary embodiment of  FIG.  18 B , interconnects  1826 ,  1828 ,  1836 ,  1838 ,  1846 ,  1848 ,  1856 , and  1858  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 . The thicknesses of interconnects  1826 ,  1828 ,  1836 ,  1838 ,  1846 ,  1848 ,  1856 , and  1858  may be equal to or different from a thickness of frame  1804 . 
       FIG.  19 A  illustrates an exemplary MEMS mirror assembly  1901 , many of the features of which are similar to those of MEMS mirror assemblies  1101  and  1801  discussed above with reference to  FIGS.  11 B and  18 A , respectively. Like MEMS mirror assembly  1800 , frame  1804  of MEMS mirror assembly  1901  may be significantly thicker than any of actuating arms actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156  or any of interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 . 
       FIG.  19 B  illustrates an exemplary MEMS mirror assembly  1903 , many of the features of which are similar to those of MEMS mirror assembly  1901  discussed above with reference to  FIG.  19 A . As illustrated in  FIG.  19 B , however, unlike the interconnects of MEMS mirror assembly  1901 , MEMS mirror assembly  1903  may include relatively thicker interconnects  1826 ,  1828 ,  1836 ,  1838 ,  1846 ,  1848 ,  1856 , and  1858  similar to those of MEMS mirror assembly  1803 . 
       FIG.  20 A  illustrates an exemplary MEMS mirror assembly  2001 , many of the features of which are similar to those of MEMS mirror assemblies  1103  and  1801  discussed above with reference to  FIGS.  11 C and  18 A , respectively. MEMS mirror assembly  2001  may also include exemplary connectors  1130 ,  1132 ,  1140 ,  1142 ,  1150 ,  1152 ,  1160 , and  1162  (not labeled on the figure for clarity) similar to corresponding features of MEMS mirror assembly  1103 . Like MEMS mirror assembly  1801 , frame  1804  of MEMS mirror assembly  2001  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , or any of interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 . 
       FIG.  20 B  illustrates an exemplary MEMS mirror assembly  2003 , many of the features of which are similar to those of MEMS mirror  2001  discussed above with reference to  FIG.  20 A . As illustrated in  FIG.  20 B , however, unlike the interconnects of MEMS mirror assembly  2001 , MEMS mirror assembly  2003  may include relatively thicker interconnects  1826 ,  1828 ,  1836 ,  1838 ,  1846 ,  1848 ,  1856 , and  1858  similar to those of MEMS mirror assembly  1803 . 
       FIG.  21 A  illustrates an exemplary MEMS mirror assembly  2101 , many of the features of which are similar to those of MEMS mirror  1105  discussed above with reference to  FIG.  11 D . MEMS mirror assembly  2101  may include frame  1804 , which may be similar to frame  1104  of MEMS mirror assembly  1105 , except that frame  1804  may be significantly thicker than frame  1104 . As also illustrated in  FIG.  21 A , actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156  may be attached to frame  1804  by interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 , respectively. Interconnects  1822 ,  1832 ,  1842 , and  1852  may be similar to interconnect  1762  discussed above with reference to  FIG.  17 C . Similarly, interconnects  1824 ,  1834 ,  1844 , and  1854  may be similar to interconnect  1764  discussed above with reference to  FIG.  17 C . In some exemplary embodiments as illustrated in  FIG.  21 A , frame  1804  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , any of interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 . 
       FIG.  21 B  illustrates an exemplary MEMS mirror assembly  2103 , many of the features of which are similar to those of MEMS mirror  2101  discussed above with reference to  FIG.  21 A . As illustrated in  FIG.  21 B , however, unlike the interconnects of MEMS mirror assembly  2101 , MEMS mirror assembly  2103  may include relatively thicker interconnects  1828 ,  1836 ,  1838 ,  1846 ,  1848 , and  1858  similar to corresponding interconnects of MEMS mirror assembly  1803 . 
       FIG.  22 A  illustrates an exemplary MEMS mirror assembly  2201 , many of the features of which are similar to those of MEMS mirror assemblies  1700  discussed above with reference to  FIG.  17 A . MEMS mirror assembly  2201  may also include frame  1804 , which may be similar to frame  1104  of MEMS mirror assembly  1700 , except that frame  1804  may be significantly thicker than frame  1104 . Like MEMS mirror assembly  1800 , frame  1804  of MEMS mirror assembly  1901  may be significantly thicker than any of actuating arms actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156  or any of interconnects  1822 ,  1824 ,  1832 ,  1834 ,  1842 ,  1844 ,  1852 , and  1854 . As also illustrated in  FIG.  22 A , actuating arms  1126 ,  1134 ,  1136 ,  1144 ,  1146 , and  1156  may be attached to frame  1804  by interconnects  1824 ,  1832 ,  1834 ,  1842 ,  1844 , and  1854 , respectively. Interconnects  1832  and  1842  may be similar to interconnect  1762  discussed above with reference to  FIG.  17 C  Similarly, interconnects  1824 ,  1834 ,  1844 , and  1854  may be similar to interconnect  1764  discussed above with reference to  FIG.  17 C . In some exemplary embodiments as illustrated in  FIG.  22 A , frame  1804  may be significantly thicker than any of actuating arms  1126 ,  1134 ,  1136 ,  1144 ,  1146 , and  1156 , any of interconnects  1824 ,  1832 ,  1834 ,  1842 ,  1844 , and  1854 , or connecting arms  1129 ,  1139 ,  1149 , and  1159 . 
       FIG.  22 B  illustrates an exemplary MEMS mirror assembly  2203 , many of the features of which are similar to those of MEMS mirror  2201  discussed above with reference to  FIG.  22 A . As illustrated in  FIG.  22 B , however, unlike the interconnects of MEMS mirror assembly  2201 , MEMS mirror assembly  2203  may include relatively thicker interconnects  1826 ,  1828 ,  1836 ,  1838 ,  1846 ,  1848 ,  1856 , and  1858  similar to corresponding interconnects of MEMS mirror assembly  1803 . 
       FIG.  23 A  illustrates an exemplary MEMS mirror assembly  2301 , many of the features of which are similar to those of MEMS mirror assembly  2201  discussed above with reference to  FIG.  22 A . Features of MEMS mirror assembly  2301  that are similar to those of MEMS mirror assembly  2201  are labeled in  FIG.  23 A  using the same numerical labels as in  FIG.  22 A . As also illustrated in  FIG.  23 A , actuating arms  1124  and  1126  may be connected to interconnect  1872 , actuating arms  1134  and  1136  may be connected to interconnect  1874 , actuating arms  1144  and  1146  may be connected to interconnect  1876 , and actuating arms  1154  and  1156  may be connected to interconnect  1878 . Interconnects  1872 ,  1874 ,  1876 , and  1878  may in turn be connected to frame  1804 . Interconnects  1872 ,  1874 ,  1876 , and  1878  may be similar to interconnect  1752  of MEMS mirror assembly  1703  discussed above with reference to  FIG.  17 C . In some exemplary embodiments as illustrated in  FIG.  23 A , frame  1804  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , any of interconnects  1872 ,  1874 ,  1876 , and  1878 , or connecting arms  1129 ,  1139 ,  1149 , and  1159 . 
       FIG.  23 B  illustrates an exemplary MEMS mirror assembly  2303 , many of the features of which are similar to those of MEMS mirror  2301  discussed above with reference to  FIG.  23 A . As also illustrated in  FIG.  23 B , actuating arms  1124  and  1126  may be connected to interconnect  1882 , actuating arms  1134  and  1136  may be connected to interconnect  1884 , actuating arms  1144  and  1146  may be connected to interconnect  1886 , and actuating arms  1154  and  1156  may be connected to interconnect  1888 . Interconnects  1882 ,  1884 ,  1886 , and  1888  may in turn be connected to frame  1804 . Interconnects  1882 ,  1884 ,  1886 , and  1888  may be significantly thicker than any of actuating arms  1124 ,  1126 ,  1134 ,  1136 ,  1144 ,  1146 ,  1154 , and  1156 , or connecting arms  1129 ,  1139 ,  1149 , and  1159 . Thicknesses of interconnects  1882 ,  1884 ,  1886 , and  1888  may be equal to or different from a thickness of frame  1804 . While the present disclosure provides examples of frames and interconnects of different thicknesses, it should be noted that aspects of the disclosure in their broadest sense, are not limited to the disclosed frame and interconnect examples. 
     Although various exemplary embodiments of the MEMS mirror assemblies discussed with reference to  FIGS.  11 A- 23 B  have been described as being capable of causing movement of MEMS mirror  1102  about more than one axis of rotation, in accordance with various embodiments of this disclosure, the MEMS scanning device may include a MEMS mirror assembly that allows the MEMS mirror to move about only a single axis. Such MEMS mirrors may be referred to as 1D MEMS mirrors. 
       FIG.  24    illustrates an exemplary 1D MEMS mirror assembly  2400  that may be included in the disclosed MEMS scanning device. MEMS mirror assembly  2400  may include MEMS mirror  2402  and frame  2404 . In one exemplary embodiment as illustrated in  FIG.  24   , MEMS mirror  2402  and frame  2402  may each have a generally rectangular shape. It is contemplated, however that MEMS mirror  2402  and frame  2404  may have other shapes. It is also contemplated that the shapes of MEMS mirror  2402  and frame  2404  may be similar or different. Frame  2404  may include recess  2406 , which may have a generally rectangular shape although other shapes are contemplated. Recess  2406  may divide frame  2404  into frame arms  2408 ,  2410 ,  2412 , and  2414 . Frame arms  2408  and  2410  may be disposed generally parallel to and spaced apart from each other, and frame arms  2412  and  2414  may similarly be disposed generally parallel to and spaced apart from each other. In one exemplary embodiment as illustrated in  FIG.  24   , frame arms  2408  and  2410  may be disposed generally perpendicular to frame arms  2412  and  2414 . 
     Actuating arms  2422  and  2426  may extend from frame arm  2408  into recess  2406  towards frame arm  2410 . Actuating arms  2422  and  2426  may be spaced apart from each other by gap  2426 . Actuating arm  2422  may also be spaced apart from frame arm  2412  and actuating arm  2424  may be spaced apart from MEMS mirror  2402 . Actuating arms  2428  and  2430  may extend from frame arm  2410  into recess  2406  towards frame arm  2408 . Actuating arms  2428  and  2430  may be spaced apart from each other by gap  2432 . Actuating arm  2428  may also be spaced apart from frame arm  2412  and actuating arm  2430  may be spaced apart from MEMS mirror  2402 . Actuating arms  2422  and  2424  may also be spaced apart from actuating arms  2428  and  2430  in a direction generally perpendicular to longitudinal axes of actuating arms  2422 ,  2424 ,  2428 , and  2430 . In one exemplary embodiment as illustrate in  FIG.  24   , actuating arms  2422  and  2424  may be disposed generally parallel to each other and to frame arm  2412 . Likewise, actuating arms  2428  and  2430  may be disposed generally parallel to each other and to frame arm  2412 . It is contemplated, however, that one or more of actuating arms  2422 ,  2424 ,  2428 , and  2430  may be inclined relative to each other and/or relative to frame arm  2412 . 
     Actuating arms  2434  and  2436  may extend from frame arm  2408  into recess  2406  towards frame arm  2410 . Actuating arms  2434  and  2436  may be spaced apart from each other by gap  2438 . Actuating arm  2434  may also be spaced apart from frame arm  2414  and actuating arm  2436  may be spaced apart from MEMS mirror  2402 . Actuating arms  2440  and  2442  may extend from frame arm  2410  into recess  2406  towards frame arm  2408 . Actuating arms  2440  and  2442  may be spaced apart from each other by gap  2444 . Actuating arm  2440  may also be spaced apart from frame arm  2414  and actuating arm  2442  may be spaced apart from MEMS mirror  2402 . Actuating arms  2434  and  2436  may also be spaced apart from actuating arms  2440  and  2442  in a direction generally perpendicular to longitudinal axes of actuating arms  2434 ,  2436 ,  2440 , and  2442 . In one exemplary embodiment as illustrate in  FIG.  24   , actuating arms  2434  and  2436  may be disposed generally parallel to each other and to frame arm  2414 . Likewise, actuating arms  2440  and  2442  may be disposed generally parallel to each other and to frame arm  2414 . It is contemplated, however, that one or more of actuating arms  2434 ,  2436 ,  2440 , and  2442  may be inclined relative to each other and/or relative to frame arm  2414 . 
     As also illustrated in  FIG.  24   , first ends of connectors  2450 ,  2452 ,  2454 , and  2456  may be connected to actuating arms  2422 ,  2424 ,  2428 , and  2430 , respectively. Second ends of connectors  2450 ,  2452 ,  2454 , and  2456  may be connected to MEMS mirror  2402 . Similarly, first ends of connectors  2458 ,  2460 ,  2462 , and  2464  may be connected to actuating arms  2434 ,  2436 ,  2440 , and  2442 , respectively. Second ends of connectors  2458 ,  2460 ,  2462 , and  2464  may be connected to MEMS mirror  2402 . Actuating one or more of the actuating arms  2422 ,  2424 ,  2428 ,  2430 ,  2422 ,  2424 ,  2428 , and/or  2430  may cause movement (translation or rotation) of MEMS mirror  2402  about axis  2470 . 
       FIG.  25    illustrates another exemplary 1D MEMS mirror assembly  2500  that may be included in the disclosed MEMS scanning device. MEMS mirror assembly  2500  may include MEMS mirror  2502  and frame  2504 . Frame  2504  may include recess  2506 , which may have a generally circular shape although other shapes are contemplated. MEMS mirror  2502  may be positioned within recess  2506  and spaced apart from frame  2504 . Actuating arms  2512  and  2514  may extend from frame  2504  into recess  2506  and may be disposed on one side of MEMS mirror  2502 . Similarly, actuating arms  2522  and  2524  may extend from frame  2504  into recess  2506  and may be disposed on an opposite side of MEMS mirror  2502 . Actuating arms  2512  and  2514  may be spaced apart by gap  2516 , and actuating arms  2522  and  2524  may likewise be spaced apart by gap  2526 . Actuating arms  2512  and  2522  may each also be spaced apart from frame  2504 , and actuating arms  2514  and  2524  may be spaced apart from MEMS mirror  2502 . In some exemplary embodiments as illustrated in  FIG.  25   , actuating arms  2512  and  2522  may be disposed nearer to frame  2504  than to MEMS mirror  2502  and therefore may constitute outer actuating arms. In contrast, actuating arms  2514  and  2524  may be disposed nearer to MEMS mirror  2502  than to frame  2504  and therefore may constitute inner actuating arms. As illustrated in  FIG.  25   , actuating arms  2512 ,  2514 ,  2522 , and  2524  may have a generally arcuate shape, although other shapes are contemplated. First ends of connectors  2530 ,  2532 ,  2540 , and  2542  may be connected to actuating arms  2512 ,  2514 ,  2522 , and  2524 , respectively. Second ends of connectors  2530 ,  2532 ,  2540 , and  2542  may be connected to MEMS mirror  2502 . Actuating one or more of the actuating arms  2512 ,  2514 ,  2522 , and/or  2524  may cause movement (translation or rotation) of MEMS mirror  2502  about axis  2550 . 
     Consistent with the present disclosure, a LIDAR system may be configured to detect objects by scanning the environment of LIDAR system. A LIDAR system in accordance with the present disclosure may include a light source configured to project light for illuminating an object in an environment external to the LIDAR system. The LIDAR system may also include a scanning unit configured to deflect light from the light source in order to scan at least part of the environment. As discussed above, and by way of example,  FIG.  1 A  illustrates an exemplary scanning unit and  FIGS.  2 A- 2 C  illustrate exemplary embodiments of a LIDAR system, and a light source consistent with embodiments of the present disclosure. 
     In accordance with this disclosure, the scanning unit includes a movable MEMS mirror configured to pivot about at least one axis; at least one actuator configured to cause pivoting of the movable MEMS mirror about the at least one axis in a first direction; at least one spring configured to cause pivoting of the movable MEMS mirror about the at least one axis in a second direction different from the first direction. Further the at least one actuator includes a first actuating arm; a second actuating arm; and a gap between the first actuating arm and the second actuating arm. As discussed in detail above,  FIGS.  11 A- 25    illustrated various exemplary embodiments of MEMS mirror assemblies that include one or more actuators configured to move the MEMS mirror about one or more axes. 
     According to the present disclosure, the LIDAR system includes at least one sensor configured to detect reflections of the projected light. As discussed above, and by way of example,  FIGS.  4 A- 4 C  illustrate exemplary embodiments of the sensor consistent with embodiments of the present disclosure. 
     According to the present disclosure, the LIDAR system includes at least one processor. As discussed above, and by way of example,  FIGS.  2 A and  2 B  illustrate exemplary embodiments of a processor consistent with embodiments of the present disclosure. In accordance with the present disclosure, the processor is configured to issue an instruction to the at least one actuator causing the actuator to deflect from an initial position. As discussed above the one or more actuators or actuating arms associated with the MEMS mirror assemblies may include PZT layers, which may contract or expand when a current is allowed to pass through the PZT layers or when a biasing voltage is applied to the PZT layers. In some exemplary embodiments, issuing an instruction to an actuator may include the processor causing a current to flow through PZT layers associated with one or more actuators. By way of example, processor  118  (see  FIGS.  2 A and  2 B ) may cause current to flow through one or more of PZT layers  1510  and/or  1512  (see  FIGS.  15 A and  15 B ) associated with one or more actuators  1112 ,  1114 ,  1116 , and/or  1118  (see e.g.  FIGS.  11 A- 11 F,  12 A- 12 F,  13 A,  14 ,  16 A,  17 A- 17 C,  18 A- 23 B , etc.). A flow of current through the PZT layers may cause the one or more actuators  1112 ,  1114 ,  1116 , and/or  1118  from their original positions. Movement of these actuators may cause translation or rotation of the one or more connectors  1130 ,  1132 ,  1140 ,  1142 ,  1150 ,  1152 ,  1160 ,  1162  (see e.g.  FIG.  11 A ), which in turn may cause translation or rotation of MEMS mirror  1102 . 
     In accordance with this disclosure, the processor is configured to determine a distance between the vehicle and the object based on signals received from the at least one sensor. As discussed above, and by way of example, as illustrated in  FIG.  2 A , processor  118  may be configured to determine a distance between object  208  and LIDAR system  100  which may be associated with a vehicle. 
     In accordance with this disclosure the processor is configured to issue a single instruction to actuate both the first actuating arm and the second actuating arm. In some embodiments, the controller may issue a single instruction may include applying the same biasing voltage across the PZT layers of more than one actuating arm of an actuator, or causing the same current to flow through the PZT layers of more than one actuating arm. In other embodiments, the controller may issue a single instruction by causing the same amount of current to flow through the PZT layers of more than one actuating arm simultaneously. In both scenarios, the PZT layers will deform on more than one actuating arm at the same time causing a plurality of actuating arms to be moved (i.e. deflected, distorted, bent, twisted, etc.) 
     By way of example, controller  118  may issue an instruction to a power supply unit associated with LIDAR system  100  to cause the same or equal amounts of current to flow through, for example, PZT layers  1510  and  1512  of actuating arms  1134  and  1136  (see  FIG.  15 A or  15 B ). Additionally or alternatively, controller  118  may issue an instruction to a power supply unit associated with LIDAR system  100  to cause the same biasing voltage to be applied across, for example, PZT layers  1510  and  1512  of actuating arms  1134  and  1136 . In response PZT layers  1510  and  1512  may expand or contract causing actuating arms  1134  and  1136  to be displaced, twisted, etc. Movement of actuating arms  1134  and  1136  may also cause MEMS mirror  1102  to be translated or rotated about one or more axes. 
     According to with the present disclosure, the processor is configured to issue a first instruction to the first actuating arm and a second instruction to the second actuating arm. In some embodiments, the controller may issue more than one instruction. Each of these instructions may include applying a biasing voltage across a PZT layer of an actuator or causing a current to flow through the PZT layer of an actuator. In both scenarios, the PZT layers will deform on more than one actuating arm causing a plurality of actuating arms to be moved (i.e. deflected, distorted, bent, twisted, etc.) 
     Thus, for example, controller  118  may issue a first instruction to a power supply unit associated with LIDAR system  100  to apply a biasing voltage across, for example, PZT layers  1510 , or to cause a current to flow through PZT layer  1510  (see e.g.  FIG.  15 A or  15 B ). Controller  118  may also issue a second instruction to the power supply unit to apply a biasing voltage across, for example, PZT layers  1512 , or to cause a current to flow through PZT layer  1512  (see e.g.  FIG.  15 A or  15 B ) In response PZT layers  1510  and  1512  may expand or contract causing actuating arms  1134  and  1136  to be displaced, twisted, etc. Movement of actuating arms  1134  and  1136  may also cause MEMS mirror  1102  to be translated or rotated about one or more axes. 
     In accordance with this disclosure, the processor is configured to issue the first instruction and the second instruction simultaneously. In other embodiments in accordance with this disclosure, the processor is configured to issue the second instruction after the first instruction. As discussed above, the processor may cause the biasing voltage to be applied across the PZT layers of more than one actuator associated with disclosed MEMS mirror assemblies simultaneously or sequentially. Similarly, the processor may cause a current to flow from the power supply unit associated with the LIDAR system to flow through the PZT layers of the more than one actuator simultaneously or sequentially. When the voltage or current is applied to the PZT layers simultaneously, the actuating arms associated with the PZT layers may be caused to be displaced simultaneously. Likewise, when the voltage or current is applied to the PZT layers sequentially the actuating arms may be displaced sequentially. As discussed above, causing the actuating arms to be displaced simultaneously may allow a combined force to be exerted by the actuating arms on the MEMS mirror. Alternatively, causing the actuating arms to be displaced sequentially may help to translate or rotate the MEMS mirror incrementally. Additionally or alternatively, such incremental movements may help to correct the displacement of the MEMS mirror to achieve precise positioning of the MEMS mirror. For example, errors in movement of the MEMS mirror due to actuation of one actuating arm may be corrected by a subsequent actuation of a different actuating arm. 
     By way of example, controller  118  may cause the power supply unit associated with LIDAR system  100  to apply a biasing voltage across, for example, PZT layers  1510 , or to cause a current to flow through PZT layer  1510  (see e.g.  FIG.  15 A or  15 B ). Controller  118  may also cause the power supply unit to apply a biasing voltage across, for example, PZT layers  1512 , or to cause a current to flow through PZT layer  1512  (see e.g.  FIG.  15 A or  15 B ) after first applying the voltage or current to the PZT layer  1510 . In response PZT layer  1510  may be deformed first and PZT layer may be deformed after deformation of PZT layer  1510 , which in turn may cause actuating arm  1134  to be displaced first followed by movement of actuating arm  1136 . 
     Several aspects of the disclosure were discussed above. It is noted that any feasible combination of features, aspects, characteristics, structures, etc. which were discussed above—for example, with respect to any one or more of the drawings—may be implemented as is considered as part of the disclosure. Some of those feasible combinations were not discussed in detail for reasons such as brevity and succinctness of the disclosure, but are nevertheless part of the disclosure, and would present themselves to a person who is of skill in the art in view of the above disclosure. 
     The present disclosure relates to MEMS scanning devices. While the present disclosure provides examples of MEMS scanning devices that may be part of a scanning LIDAR system, it should be noted that aspects of the disclosure in their broadest sense, are not limited to MEMS scanning devices for a LIDAR system. Rather, it is contemplated that the forgoing principles may be applied to other types of electro-optic systems as well.  FIGS.  3 A- 3 D  depict exemplary MEMS scanning devices  104 . 
     A MEMS scanning device in accordance with the present disclosure may include a movable MEMS mirror configured to be rotated about at least one rotational axis. For example, a MEMS scanning device may include a light deflector configured to make light deviate from its original path. In some exemplary embodiments, the light deflector may be in the form of a MEMS mirror that may include any MEMS structure with a rotatable part which rotates with respect to a plane of a wafer (or frame). For example, a MEMS mirror may include structures such as a rotatable valve, or an acceleration sensor. In some exemplary embodiments, the rotatable part may include a reflective coating or surface to form a MEMS mirror capable of reflecting or deflecting light from a light source. Various exemplary embodiments of MEMS mirror assemblies discussed below may be part of a scanning LIDAR system (such as—but not limited to—system  100 , e.g. MEMS mirror  300 , deflector  114 ), or may be used for any other electro-optic system in which a rotatable MEMS mirror or rotatable structure may be of use. While a MEMS mirror has been disclosed as an exemplary embodiment of a light deflector, it should be noted that aspects of the disclosure in their broadest sense, are not limited to MEMS mirror. Thus, for example, the disclosed MEMS mirror in a MEMS scanning device according to this disclosure may instead include prisms, controllable lenses, mechanical mirrors, mechanical scanning polygons, active diffraction (e.g. controllable LCD), Risley prisms, or other types of optical equipment capable of deflecting a path of light. 
     In accordance with the present disclosure, a MEMS scanning device may include a frame, which supports the MEMS mirror. As used in this disclosure a frame may include any supporting structure to which the MEMS mirror may be attached such that the MEMS mirror may be capable of rotating relative to the frame. For example, the MEMS mirror may include portions of a wafer used to manufacture the MEMS mirror that may structurally support the MEMS mirror while allowing the MEMS mirror to pivot about one or more axes of rotation relative to the frame. 
     Referring to the non-limiting example of  FIG.  26   , a MEMS mirror assembly  2600  is disclosed. MEMS mirror assembly  2600  includes at least an active area (e.g. a MEMS mirror  2602 , as illustrated in the example of  FIG.  26   ) and a frame  2604  (also referred to as “support”, e.g. in the above description). Possibly, the active area is completely spaced from the frame (any part of which can move from the plane of the frame) with the exception of a plurality of interconnects. The frame may include a continuous frame or a frame consisting of two or more separate parts. For example, the frame may be made from wafer layers which include one or more silicon layers, the one or more silicon layers possibly including at least one silicon layer which is a part of the movable MEMS mirror. Layers of materials other than silicon may also be used. 
     In accordance with the present disclosure, the MEMS scanning device may include at least one connector connected to the movable MEMS mirror and configured to facilitate rotation of the movable MEMS mirror about the at least one rotational axis. As used in this disclosure a connector may include a structural element that electrically and/or mechanically connect other elements of the disclosed MEMS scanning device. For example, a connector may provide electrical and/or mechanical connections between one or more actuating arms, springs associated with the actuating arms, and the MEMS mirror. In some exemplary embodiments, the connector may be directly attached to one or more of actuating arms, to springs, and/or to the MEMS mirror. In other embodiments, the connector may include more than one connector member that may be connected to each other and may be attached to the one or more actuating arms, to springs, and/or to the MEMS mirror. In some embodiments, the connector may be a mechanical connector, which may be configured to allow relative movement between the MEMS mirror and the one or more actuating arms or actuators. In other embodiments, the connector may also be configured to allow electrical current and or signals to pass through the connector during operation of the MEMS scanning device. 
     In accordance with the present disclosure a MEMS scanning device may include an elongated actuator configured to apply mechanical force on the at least one connector. The elongated actuator may have a base end connected to the frame and a distal end connected to the at least one connector. An elongated actuator according to the present disclosure may include one or more movable structural members of the MEMS mirror assembly that may be capable of causing translational or rotational movement of the MEMS mirror relative to the frame. The actuator may be elongated because it may have a length which may be larger than a width of the actuator. The disclosed actuator may be an integral part of the MEMS mirror assembly or may be separate and distinct from the MEMS mirror assembly. The disclosed actuator may be directly or indirectly attached to the disclosed MEMS mirror. 
     In some exemplary embodiments, the actuator may be a part of the MEMS mirror assembly and may itself be configured to move relative to the frame and/or relative to the MEMS mirror associated with the MEMS mirror assembly. For example, the disclosed actuator may be connected between the frame and the MEMS mirror and may be configured to be displaced, bent, twisted, and/or distorted to cause movement (i.e. translation or rotation) of the MEMS mirror relative to the frame. It is contemplated that a MEMS mirror assembly according to the present disclosure may include one, two, or any number of actuators. 
     According to the present disclosure a width of the base end of the actuator is wider than the distal end of the actuator. It is noted that the geometrical characteristics of the actuators may vary. For example, optionally the width of the actuator may gradually reduce from the first end (or base end) to the second end (or distal end). For example, the width of the piezoelectric element at the first end may be larger than a width of the piezoelectric element at the second end. The first end of the piezoelectric element is the part of the piezoelectric element positioned on the first end of the actuator, and the second end of the piezoelectric element is the part of the piezoelectric element positioned on the second end of the actuator. Optionally, the width of the piezoelectric element may change proportionally with the width of the actuator. 
       FIG.  26    illustrates a plurality of actuators (which may also be referred to as “springs”, “benders”, “cantilever,” etc.), in accordance with examples of the presently disclosed subject matter.  FIG.  26    illustrates an exemplary MEMS mirror assembly  2600  consistent with this disclosure. For example, as illustrated in  FIG.  26   , MEMS mirror assembly  2600  may include MEMS mirror  2602  supported by frame  2604 . MEMS mirror  2602  may be a movable MEMS mirror in that MEMS mirror  2602  may be translatable relative to frame  2604  and/or rotatable about one or more axes relative to frame  2604 . For example, MEMS mirror  2602  may be translatable or rotatable about one, two, or more axes (e.g., exemplary axes  2606 ,  2608 , or  2610 , which is going into the plane of the figure) as illustrated in  FIG.  26   . In some exemplary embodiments, MEMS mirror  2602  may include a reflective surface. Although MEMS mirror  2602  has been illustrated as having a polygonal shape in  FIG.  26   , it is contemplated that MEMS mirror  2602  may have a circular shape, an elliptical shape, a rectangular or square shape, or any other type of geometrical shape suitable for use with system  900  or any other system in which it is installed or for which it is designed. While the present disclosure describes examples of a MEMS mirror and frame, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed examples of the MEMS mirror and/or frame. 
       FIG.  26    illustrates a MEMS system with actuators of varied width, in accordance with examples of the presently disclosed subject matter. Referring to  FIG.  26   , actuators which move the active area of a MEMS system (e.g., the active area being the movable MEMS mirror) may be designed to have varied widths, so that one end of the actuator which is directly connected to the active area (e.g. using a flexible interconnect) is narrower than the other end of the actuator, which is connected to the frame. The width of the actuator is a dimension which is measured in the plane of a layer of the wafer out of which the actuator is made (e.g., a plane of a silicon layer which is also used for the frame), and which is substantially perpendicular to a longitudinal direction of the actuator. Examples of actuators having varied widths are provided, for example, in  FIGS.  26 - 31   . 
     Actuators of differing width as described below with respect to  FIGS.  26 - 31    may be used in different MEMS system. For example, the width of one or more of the first actuators may change between its ends (or between its ends and its middle section) in the manner discussed below with respect to  FIGS.  26 - 31   . It is further noted that actuators of differing width as described below with respect to  FIGS.  26 - 31    may be used with other actuation techniques (i.e. not only piezoelectric actuation, e.g., electrostatic actuation, other actuation techniques mentioned in the present disclosure, etc.), and with differing actuation configurations and piezoelectric material deployments (e.g., both above and under actuators of the LIDAR system). 
     It is noted that utilizing actuators of differing width for controllably moving active areas of MEMS systems may be useful in a system in which the frequency response of the system (e.g., the resonance behavior) is important. For example, most of the vibrations in vehicles are below a frequency of about 1 Kilohertz, and it may therefore be useful to limit the frequency-response of the MEMS systems to such frequencies. 
     As illustrated in the exemplary embodiment of  FIG.  3 A , scanning device  104  may include one or more actuators, each of which may have a first end that is mechanically connected to the frame and a second end that is opposite to the first end and which is mechanically connected to the active area by an interconnect element. While different actuation methods may be used, such as electrostatic or electromagnetic actuation), optionally the actuators may be actuated by piezoelectric actuation. Optionally, the actuator may include an actuator-body (e.g., made of silicon) and a piezoelectric element. The piezoelectric element may be configured to bend the actuator-body and move the active area when subjected to an electrical field. In scanning device  104 , a width of an actuator at the first end may be larger than a width of that actuator at the second end (the difference in widths in not exemplified in  FIG.  3 A ; comparable varying widths of an actuator is exemplified, for example, in  FIG.  26   ). This may be true for one, some, or all of the actuators in scanning device  104 . 
     Referring to MEMS mirror assembly  2600 , optionally a width of one or more of the actuators may gradually reduce from the first end to the second end. Referring to scanning device  104 , optionally a width of the piezoelectric element of one or more of the actuators at the first end may be larger than a width of the piezoelectric element at the second end. Referring to scanning device  104 , optionally a width of the piezoelectric element of one or more of the actuators may change proportionally with the width of the actuator. 
     MEMS scanning device  104  may be used for a LIDAR system, which may further include a processor configured to process detection signals of light reflected by the MEMS mirror. For example, MEMS scanning device  104  may be implemented as the mirror assembly of LIDAR system  100 . The LIDAR system which includes MEMS scanning device  104  may further include a controller configured to modify electrical fields applied to the at least actuator, to move the MEMS mirror to scan a field of view of the LIDAR system. It is noted that the LIDAR system may include a plurality of the MEMS scanning device  104  (e.g., arranged in an array of mirrors), and a controller which is configured to move the plurality of MEMS mirrors (e.g., in a coordinated manner). 
     By way of example,  FIG.  26    illustrates exemplary actuators  2612 ,  2614 ,  2616 , and  2618  associated with MEMS mirror assembly  2600  consistent with this disclosure. As illustrated in  FIG.  26   , actuator  2612  may extend from adjacent base end  2620  to adjacent distal end  2020 . Actuator  2612  may be connected to frame  2604  adjacent base end  2620  and may be connected to MEMS mirror  2602  adjacent distal end  2622 . Actuators  2614 ,  2616 ,  2618  may be connected to frame  2604  and MEMS mirror  2602  in a similar manner Notably, the MEMS mirror assembly may have any number of actuators, e.g., one, two, three, four, or any number larger than that. 
     In accordance with the present disclosure, the MEMS scanning device includes two actuators. Each of the two actuators include a taper decreasing from a base end-side of the actuator toward a distal end-side of the actuator. As used in this disclosure a taper refers to a portion of an actuator that decreases in width along a length of the actuator. It is to be noted that a taper as used in this disclosure may or may not end in a point (i.e. near zero width). By way of example,  FIG.  26    illustrates actuator  2612  that may have a width that decreases in the form of a taper along a length of actuator  2612  from adjacent base end  2620  to adjacent distal end  2622 . One or more of actuators  2614 ,  2616 , and/or  2618  may also have a width that decreases in the form of a taper along a length of the respective actuator from a base end of that actuator to a distal end of that actuator. It is contemplated, however, that one or more of actuators  2612 ,  2614 ,  2616 , and  2618  may have a uniform width or a non-uniform width as illustrated in  FIG.  26   . While the present disclosure describes examples of actuators associated with a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed actuator examples. 
     The actuators of the MEMS mirror assembly may be actuated in various different ways, such as by contraction of a piezoelectric member on each actuator (e.g., PZT, lead zirconate titanate, aluminum nitride), electromagnetic actuation, electrostatic actuation, etc. It is noted that in the description below, any applicable piezoelectric material may be used wherever the example of PZT is used. As mentioned above, the actuators may be piezoelectric actuators. Optionally, one or more of the plurality of actuators may include a piezoelectric layer (e.g., a PZT layer), which is configured to bend the respective actuator, thereby rotating the mirror, when subjected to an electrical field. By way of example, actuators  2612 ,  2614 ,  2616 ,  2618  associated with MEMS mirror assembly  2600  may include one or more PZT layers  2632 ,  2634 ,  2636 , and  2638 , respectively. Energizing the one or more PZT layers with an electrical field (e.g. by providing a bias voltage or current) may cause the one or more actuators  2612 ,  2614 ,  2616 ,  2618  to expand, contract, bend, twist, or alter their configuration, which in turn may cause MEMS mirror  2602  to be translated or rotated relative to the one or more axes  2606 ,  2608 , and/or  2610 . While the present disclosure describes examples of axes of rotation of the MEMS mirror, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed examples of the axes of rotation. Thus, for example, the MEMS mirror according to the present disclosure may translate and/or rotate relative to axes other than the disclosed axes  2606 ,  2608 , and/or  2610 . While the present disclosure describes examples of piezoelectric layers associated with actuators of a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed piezoelectric actuator examples. 
     By way of example,  FIG.  26    illustrates MEMS mirror assembly  2600  that may include one or more connectors connecting (directly or indirectly) the active area and the frame (e.g., connectors  2642 ,  2644 ,  2646 , and  2648 ). As illustrated in the exemplary embodiment of  FIG.  26   , one end of connector  2642  may be connected to actuator  2612  adjacent distal end  2622  whereas an opposite end of connector  2642  may be connected to MEMS mirror  2602 . Connectors  2644 ,  2646 , and  2648  may be similarly connected at their respective first ends to actuators  2614 ,  2616 , and  2618 , respectively. Opposite ends of connectors  2644 ,  2646 , and  2648  may be connected to MEMS mirror  2602 . Movement of the one or more actuators  2612 ,  2614 ,  2616 , and/or  2618  may cause movement of the one or more connectors  2642 ,  2644 ,  2646 , and  2648 , which by virtue of their connection to MEMS mirror  2602  may also cause movement of MEMS mirror  2602 . While the present disclosure describes examples of connectors associated with a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed connector examples. 
     In accordance with the present disclosure, a width of the actuator may taper between the base end and the distal end.  FIG.  27    illustrates a magnified view of an exemplary actuator that may have a width that tapers between the base end and the distal end. For example, as illustrated in  FIG.  27   , actuator  2712  may extend from adjacent base end  2720  to adjacent distal end  2722 . Actuator  2712  may be connected to frame  2704  adjacent base end  2720 . One end of connector  2742  may be connected to actuator  2712  adjacent distal end  2722  and an opposite end of connector  2742  may be connected to MEMS mirror  2702 . A PZT layer  2732  may be disposed on actuator  2712  and may extend from adjacent base end  2720  to adjacent distal end  2722 . MEMS mirror  2702 , frame  2704 , actuator  2712 , and connector  2742  may have structural and functional characteristics similar to those discussed above with respect to MEMS mirror  2602 , frame  2604 , actuators  2612 ,  2614 ,  2616 , or  2618 , and connectors  2642 ,  2644 ,  2646 , or  2648 . 
     As illustrated in the exemplary embodiment of  FIG.  27   , a width of actuator  2722  may taper between base end  2720  and distal end  2722 . For example, actuator  2722  may have a width “W b ” adjacent base end  2720  and a width “W d ” adjacent distal end  2722 . Width W b  adjacent based end  2720  may be larger than width W d  adjacent distal end  2722 . It is to be noted that the widths (W d , W b , etc.) of actuator  2712  refer to a width dimension in the plane of MEMS mirror  2702  and not in a thickness direction, which may be perpendicular to the plane of actuator  2712 . 
     According to the present disclosure, a width of the actuator proximate the base end is between about 1.5 to about 2.5 times larger than a width of the actuator proximate the distal end. In accordance with the present disclosure, a width of the actuator proximate the base end is between about 1.75 to about 2.25 times larger than a width of the actuator proximate the distal end. According to the present disclosure, a width of the actuator proximate base end is at least 2 times larger than a width of the actuator proximate the distal end. A ratio between the widths of the actuator at the base and distal ends of the actuator may be selected, for example, based on a maximum allowable stress in the actuator during operation of the MEMS mirror and the amount of movement of the MEMS mirror desired. In one exemplary embodiment as illustrated in  FIG.  27   , a width of actuator  2712  may decrease uniformly from width W b  adjacent based end  2720  to width W d  adjacent distal end  2722 . For example, width Wb of actuator  2712  may be about 1.2, about 1.5, about 1.75, about 2, about 2.25, about 2.5, or about 4.0 times larger than width Wd. According to embodiments of this disclosures, terms such as generally, about, and substantially should be interpreted to encompass typical machining and manufacturing tolerances. Thus, for example, about 1.5 may encompass ratios of up to 1.5±0.1, 1.5±0.2, etc. 
     It is also contemplated that in some exemplary embodiments in accordance with this disclosure, the width of actuator  2712  may decrease non-uniformly from width W b  adjacent based end  2720  to width W d  adjacent distal end  2722 .  FIG.  28    illustrates a magnified view of an exemplary actuator that may have a width that decreases non-uniformly between the base end and the distal end. MEMS mirror assembly  2700  of  FIG.  28    may include many features similar to those discussed above with respect to MEMS mirror  2700  of  FIG.  27   . These similar features are numbered using the same element numbers as in  FIG.  27   . Unless otherwise stated, throughout this disclosure, similarly numbered elements should be presumed to have similar structural and functional characteristics. Further, similar elements from one structure to the next may also have similar characteristics even if differently numbered. Only the differences between MEMS mirror assemblies  2700  and  2800  are described below. It is noted that different aspects of the invention which are discussed with respect to different drawings for the sake of clarity can be combined. For example, aspects of the invention which are discussed with respect to  FIG.  28    may be implemented in a MEMS mirror assembly having curved actuators, etc. 
     As illustrated in  FIG.  28   , like actuator  2712  of  FIG.  27   , actuator  2812  extends from adjacent base end  2720  to adjacent distal end  2722 . Actuator  2812  may have a length “L 1 ” between base end  2720  and distal end  2722 . Actuator  2812  may have a width W b  adjacent base end  2720  and a width W d  adjacent distal end  2722 . In one exemplary embodiment as illustrated in  FIG.  28   , actuator  2812  may have a width “W m ” between base end  2720  and distal end  2722 . Width W b  may be larger than both widths W m  and W d  and width W m  may be larger than width W d  but smaller than width W b . As also illustrated in  FIG.  28   , a rate of decrease of the width of actuator  2712  from width W b  to W m  along length L 2  may be smaller than a rate of decrease of the width of actuator  2712  from width W m  to W d . It is contemplated that in other exemplary embodiments the rate of decrease of the width in length L 2  may be larger than or about equal to the rate of decrease of the width from width W m  to W d . It is also contemplated that in some exemplary embodiments in accordance with this disclosure, the width of actuator  2712  may overall decrease from width W b  adjacent based end  2720  to width W d  adjacent distal end  2722 , while including some parts which are wider than other parts of the actuator which are closer to the base end. 
     In accordance with the present disclosure, the base end of the actuator is at least 15% more rigid than the distal end of the actuator. The relatively large width at the base end near the frame gives the actuator strength, increases the resonance frequency, allows sufficient area for the piezoelectric element (thus providing sufficient force to move the mirror, which can therefore be larger), and/or provides sufficient rigidity and strength at that part of the actuator and connection to frame (e.g. to match the torques applied on this area by the motion of the active area). Combining the relatively large width at the base end near the frame with the relatively small width at the distal end near the active area reduces the weight of the moving parts, allows twisting of the actuator if needed (e.g., during the rotation of the MEMS mirror), provides rigidity outside the plane of the frame (e.g. to increase resonance frequencies), and/or provides flexibility within the plane of the frame. Thus, the base end of the actuator may be more rigid than the distal end of the actuator. Stated otherwise, the distal end of the actuator may be more flexible than the base end of the actuator. In some exemplary embodiments, the base end of the actuator may be at least about 5%, about 10%, about 15%, or about 20% more rigid than the distal end. As discussed above the term about should be interpreted to encompass typical machining and manufacturing tolerances. Thus, for example, about 15% should be interpreted to encompass 15±0.5%, 15±1%, etc. 
     In accordance with the present disclosure, a first portion of the actuator is tapered and second portion of the actuator is non-tapered. As discussed above, an amount of width reduction of the actuator may be determined based on the allowable stresses generated in the actuator during operation of the MEMS mirror assembly and/or the amount of desired deflection of the actuator adjacent the distal end. It is contemplated that in some exemplary embodiments, the actuator may be tapered over some but not all of a length of the actuator. 
       FIGS.  29 A and  29 B  illustrate exemplary embodiments of actuators that may be tapered over only a part of their length. For example,  FIG.  29 A  illustrates a MEMS mirror assembly  2901  that includes MEMS mirror  2702 , frame  2704 , and connector  2742 . MEMS mirror assembly  2901  includes actuator  2912 , which extends from adjacent base end  2720  to distal end  2722 . Actuator  2912  is connected to frame  2704  adjacent base end  2720  and to connector  2742  adjacent distal end  2722 . As illustrated in  FIG.  29   , actuator  2912  may have a first portion  2950  and a second portion  2952 . First portion  2950  of actuator  2912  may extend from adjacent base end  2720  to location  2954  disposed between base end  2720  and distal end  2722 . A width of first portion  2950  of actuator  2912  may decrease continuously from width W b  adjacent base end  2720  to width W d  at a location  2954 . A width of second portion  2952  of actuator  2912  may generally remain constant between location  2954  and distal end  2722 . Thus, actuator  2912  may have a first portion  2950  that may be tapered and a second portion  2952  that may be non-tapered. 
     In accordance with the present disclosure, the taper extends along a majority of a length of the actuator. In one exemplary embodiment as illustrated in  FIG.  29 A , first portion  2950  of actuator  2912  may have a length L 3 , which may be smaller than a length L 1  of actuator  2912 . In some embodiments, length L 3  of first portion  2950  may be a majority of a length L 1 . Thus, for example, length L 3  may be greater than about 50% of length L 1 . It is contemplated, however, that in some exemplary embodiments, length L 3  may be about equal to or smaller than 50% of length L 1 . 
       FIG.  29 B  illustrates a MEMS mirror assembly  2903  that includes MEMS mirror  2702 , frame  2704 , and connector  2742 , which may have structural and functional characteristics similar to corresponding elements of MEMS mirror  2700  described above with reference to  FIG.  27   . MEMS mirror assembly  2903  may include actuator  2914 , which may extend from adjacent base end  2720  to distal end  2722 . Actuator  2914  may be connected to frame  2704  adjacent base end  2720  and to connector  2742  adjacent distal end  2722 . As illustrated in  FIG.  29 B , actuator  2914  may have a first portion  2960  and a second portion  2962 . First portion  2960  of actuator  2914  may extend from adjacent base end  2720  to location  2964  disposed between base end  2720  and distal end  2722 . A width of first portion  2960  of actuator  2912  may be generally uniform between base end  2720  and location  2764 . A width of second portion  2962  of actuator  2914  may decrease from a width W b  adjacent location  2964  and distal end  2722 . Thus, actuator  2912  may have a first portion  2960  that may be non-tapered and a second portion  2962  that may be tapered. It is contemplated that a length L 4  of first portion  2650  of actuator  2914  may be larger than, about equal to, or smaller than about 50% of length L 1  of actuator  2914 . 
       FIG.  30 A  illustrates a MEMS mirror assembly  3001  that includes MEMS mirror  2702 , frame  2704 , and connector  2742 . MEMS mirror assembly  3001  may include actuator  3012 , which may extend from adjacent base end  2720  to distal end  2722 . Actuator  3012  may be connected to frame  2704  adjacent base end  2720  and to connector  2742  adjacent distal end  2722 . As illustrated in  FIG.  30 A , actuator  3012  may have a width W b  adjacent base end  2720  and a width W d , smaller than width W b , adjacent distal end  2722 . As also illustrated in  FIG.  30 A , the width of actuator  3012  may decrease along its length from width W b  to width W d . The decrease in width from W b  to W d  may be non-uniform such that sides  3013  and  3015  of actuator  3012  may have a generally curved shape. Furthermore, like the actuators illustrated in  FIGS.  27 - 29 B , actuator  3012  may be disposed generally perpendicular to frame  2704 . Thus, for example, a longitudinal axis  3006  of actuator  3012  may be disposed generally perpendicular to frame  2704 . As discussed above, the phrase generally perpendicular should be interpreted to encompass typical manufacturing and machining tolerances, including, for example angles in the range 90±0.1°, 90±0.5°, 90±1°, etc. 
       FIG.  30 B  illustrates a MEMS mirror assembly  3003  that includes MEMS mirror  2702 , frame  2704 , and connector  2742 . MEMS mirror assembly  3003  may include actuator  3014 , which may extend from adjacent base end  2720  to distal end  2722 . Like actuator  3012  of  FIG.  30 A , a width of actuator  3014  may also decrease non-uniformly from a width W b  adjacent base end  2720  to a width W d  adjacent distal end  2722 . Moreover, actuator  3014  may also include sides  3017  and  3019  that may have a generally curved shape. Unlike actuator  3012  of  FIG.  30 A , however, actuator  3014  may not be disposed generally perpendicular to frame  2704 . Instead a longitudinal axis  3008  of actuator  3014  may be disposed generally inclined relative to frame  2704  at an angle □, which may be more than about 0° and less than about 90°. 
     According to the present disclosure, the actuator is substantially straight. Substantially straight in this disclosure refers to a shape of the geometrical longitudinal axis of the actuator. Thus, for example, as illustrated in  FIGS.  30 A and  30 B , actuators  3012  and  3014  both have substantially straight (not curved) longitudinal axes  3006  and  3008 . Similarly actuators  2712 ,  2812 ,  2912 , and  2914  illustrated in  FIGS.  27 - 29 B  are also substantially straight. While the present disclosure describes examples of shapes and width variations of actuators associated with a MEMS scanning device, it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed exemplary shapes and/or width variations. 
     According to the present disclosure the actuator is curved. A shape of the actuators (e.g. straight or curved) may be selected based on, for example, the desired magnitude and direction of deflection of the actuator. By way of example,  FIG.  31    illustrates an exemplary MEMS mirror assembly  3100  that may include one or more curved actuators. For example, MEMS mirror assembly  3100  may include MEMS mirror  3102 , frame  3104 , and actuators  3112 ,  3114 ,  3116 , and  3118 . As illustrated in  FIG.  31   , one or more of actuators  3112 ,  3114 ,  3116 , and  3118  may be curved. For example, actuator  3112  may include arms  3124  and  3126 , separated by gap  3128 . In one exemplary embodiment as illustrated in  FIG.  31   , widths “W 1 ” and “W 2 ” of arms  3124  and  3128 , respectively, may be generally uniform along a length of arms  3124  and  3128  extending from base end  3120  to distal end  3122 . Widths W 1  and W 2  of arms  3124  and  3128 , respectively, may be determined in a plane of MEMS mirror  3102  and frame  3104 , in a generally radial direction relative to a center of MEMS mirror  3102 . As also illustrated in  FIG.  31   , longitudinal axes  3125  and  3127  of actuating arms  3124  and  3128 , respectively, may have a generally curved shape. 
     In accordance with the present disclosure, the actuator includes at least two arms separated by a gap and wherein a width of each arm gradually decreases from the base end of the actuator toward the distal end of the actuator. Like an actuator, an arm according to this disclosure may include a structural member that may be capable of causing translational or rotational movement of the MEMS mirror relative to the frame. In some exemplary embodiments, the disclosed actuator may include only one arm. In other exemplary embodiments the disclosed actuator may include more than one arm. For example, in some embodiments, the disclosed actuator may include two arms separated from each other by a gap. Some or all arms may be equipped with PZT layers, which may cause those arms to expand, contract, bend, twist, or move in some way. Movement of the one or more arms in turn may cause movement of the MEMS mirror associated with the MEMS scanning device. Further as discussed above, widths of the arms may decrease from a base end of the arm to a distal end of the arm. Such a decrease in width may be desirable, for example, to minimize the stresses generated in the arms and/or to obtain a desired amount of deflection or movement of the arms adjacent the distal end. It is noted that any of the different aspects of implementing actuators with more than one arm discussed above (e.g., with respect to  FIGS.  11 A- 25   ) may be implemented for actuators whose distal end width is narrower than their base end width (for one, some or all of the arms of a multi-arm actuator). 
     By way of example,  FIG.  31    illustrates actuator  3114  that may include arm  3134  and  3136 , which may be separated from each other by gap  3138 . Arm  3134  may extend from adjacent base end  3130  to adjacent distal end  3132 . Similarly arm  3136  may extend from adjacent base end  3130  to adjacent distal end  3132 . As illustrated in  FIG.  31   , each of arms  3134  and  3136  may have a generally curved shape. Further, arm  3134  may have a width “W 3 ” adjacent base end  3130  and a width “W 4 ” adjacent distal end  3132 . Similarly, arm  3136  may have a width “W 5 ” adjacent base end  3130  and a width “W 6 ” adjacent distal end  3132 . Widths W 3  and W 5  may be the same or may be different. Likewise, widths W 4  and W 6  may be equal or unequal. In one exemplary embodiment as illustrated in  FIG.  31   , width W 3  may be larger than width W 4  and width W 5  may be larger than width W 6 . Thus, widths of arms  3134  and  3136  may decrease gradually from adjacent base end  3130  to adjacent distal end  3132 . It is contemplated, however, that one or both of arms  3134  and  3136  may have shapes similar to those of one or more of arms  3124  and  3126 . 
     According to the present disclosure, the distal end of the actuator is closer to the movable MEMS mirror than the base end of the actuator. Such a configuration may be implemented, for example, in non-circular mirror in order to free the movement path of the mirror, in order to reduce the amount of light-reflecting parts of the actuators in the immediate vicinity of the mirror, and so on. By way of example,  FIG.  31    illustrates actuator  3118 , which may extend from adjacent base end  3150  to adjacent distal end  3152 . Actuator  3118  may be connected to frame  3104  adjacent base end  3150  and may be connected to MEMS mirror  3102  via connector  3154  adjacent distal end  3152 . In one exemplary embodiment as illustrated in  FIG.  31   , actuator  3118  may be positioned at a distance “D 1 ” from MEMS mirror  3102  adjacent base end  3150 , and at a distance “D 2 ” from MEMS mirror  3102  adjacent distal end  3152 . Distances D 1  and D 2  may be measured in a generally radial direction in a plane of MEMS mirror  3102  and frame  3104 . In one exemplary embodiment, distance D 1  may be larger than distance D 2 . Thus, for example, distal end  3152  of actuator  3118  may be positioned closer to MEMS mirror  3102  as compared to base end  3150 . Although  FIG.  31    illustrates different positions and geometrical characteristics for actuators  3112 ,  3114 ,  3116 , and  3118 , it is contemplated that these positions and geometrical characteristics are interchangeable. That is, any of actuators  3112 ,  3114 ,  3116 , and  3118  may have the characteristics described above corresponding to one or more of the other of actuators  3112 ,  3114 ,  3116 , and  3118 . Although various geometric and other characteristics have been described above for substantially straight actuators with reference to  FIGS.  27 - 30    and for curve actuators with reference to  FIG.  31   , it is contemplated that the characteristics described for the disclosed curved actuators may be implemented on the disclosed substantially straight actuators and vice-versa. 
     In accordance with the present disclosure, an elongated actuator includes a piezoelectric layer having a piezoelectric base-end element and a piezoelectric distal-end element. The piezoelectric layer may be operable to contract when voltage bias is applied between the piezoelectric base-end element and the piezoelectric distal-end element. Further, a width of the piezoelectric base-end element may be wider than the piezoelectric distal-end element. As discussed above, one or more actuators discussed above may include a piezoelectric layer which may be configured to contract when subjected to a voltage bias. Contraction of the piezoelectric layer may further cause the actuator to bend, which in turn may impart movement to the MEMS mirror via one or more connectors. It is contemplated that in some exemplary embodiments, a shape of the piezoelectric layer may be similar to that of the actuator itself. Thus, for example, when the actuator is wider nearer its base end as compared to nearer its distal end, the piezoelectric layer on that actuator may also be wider nearer the base end and narrower nearer the distal end. 
     As illustrated, for example, in  FIG.  27   , actuator  2712  may include a piezoelectric layer  2780 , which may have a piezoelectric-element base-end  2782  and a piezoelectric-element distal-end  2784 . Piezoelectric-element base-end  2782  may extend from adjacent base end  2720  to adjacent position  2786  disposed between base end  2720  and distal end  2722 . Piezoelectric-element distal-end  2784  may extend from adjacent position  2786  to adjacent distal end  2722 . In one exemplary embodiment as illustrated in  FIG.  27   , piezoelectric-element base-end  2782  and a piezoelectric-element distal-end  2784  may be different portions of a single piezoelectric layer. In other embodiments, piezoelectric-element base-end  2782  and a piezoelectric-element distal-end  2784  may be separate and electrically connected by one or more connectors (e.g. wires, interconnects, etc.) As discussed above, applying a biasing voltage between piezoelectric-element base-end  2782  and a piezoelectric-element distal-end  2784  may cause piezoelectric layer  2780  to contract, which in turn may cause bending of actuator  2712 . As also illustrated in  FIG.  27   , for example, piezoelectric-element base-end  2782  may have a width “W b1 ” adjacent base end  2720  and piezoelectric-element distal-end  2782  may have a width “W d1 ” adjacent distal end  2722 . Width W b1  may be larger than width W d1  so that a width of piezoelectric-element base-end  2852  adjacent base end  2720  may be wider than a width of piezoelectric-element distal-end  2854  adjacent distal end  2722 . Having a wider width at the piezoelectric-element base-end provides for larger area of the piezoelectric element (and hence more force to move the mirror) with limited effect on the mass and rigidity of the moving end of the actuator. Although piezoelectric layer  2780  has been described above with reference to actuator  2712  of  FIG.  27   , it is contemplated that similar piezoelectric layers may be present on the actuators illustrated and discussed with reference to one or more of  FIGS.  27 - 31   . Moreover, the piezoelectric layers on the actuators of  FIGS.  27 - 31    may have shapes and width variations similar to those of the respective actuators illustrated in those figures. 
     In accordance with the present disclosure, the elongated actuator includes a flexible passive layer (e.g. silicon) and an active layer operable to apply force for bending the flexible passive layer. The flexible passive layer may have a passive-layer-element base-end and a passive-layer-element distal-end. A width of the passive-layer-element base-end may be wider than the passive-layer-element distal-end. As discussed above, one or more actuators discussed above may include a passive layer (e.g. of silicon) with a piezoelectric layer attached to the passive layer. The piezoelectric layer may be the active layer which may be configured to contract when subjected to a voltage bias. Contraction of the piezoelectric layer may apply a force on the passive layer causing the passive layer to bend, which in turn may impart movement to the MEMS mirror via one or more connectors. 
     As illustrated, for example, in  FIG.  27   , actuator  2712  may include a flexible passive layer  2790  and a piezoelectric layer  2780  (e.g. active layer  2780 ) attached to flexible passive layer  2790 . Flexible passive layer  2790  may have a passive-layer-element base-end  2792  and a passive-layer-element distal-end  2794 . Passive-layer-element base-end  2792  may extend from adjacent base end  2720  to adjacent position  2786  disposed between base end  2720  and distal end  2722 . Passive-layer-element distal-end  2794  may extend from adjacent position  2786  to adjacent distal end  2722 . In one exemplary embodiment as illustrated in  FIG.  27   , passive-layer-element base-end  2792  and a passive-layer-element distal-end  2794  may be different portions of a single passive layer  2790 . As illustrated in  FIG.  27   , for example, passive-layer-element base-end  2782  may have a width W b  adjacent base end  2720 , and passive-layer-element distal-end  2784  may have a width W d  adjacent distal end  2722 . As discussed above Width W b  may be larger than width W d  so that a width of passive-layer-element base-end  2892  adjacent base end  2720  may be wider than a width of passive-layer-element distal-end  2894  adjacent distal end  2722 . Although passive layer  2790  has been described above with reference to actuator  2712  of  FIG.  27   , it is contemplated that similar passive layers may be present on the actuators illustrated and discussed with reference to one or more of  FIGS.  27 - 31   . Moreover, the passive layers on the actuators of  FIGS.  27 - 31    may have shapes and width variations similar to those of the respective actuators illustrated in those figures. 
     In accordance with the present disclosure, the elongated actuator includes a piezoelectric layer having a piezoelectric-element base-end and a piezoelectric-element distal-end, the piezoelectric layer operable to contract when voltage bias is applied between the piezoelectric-element base-end and the piezoelectric-element distal-end, wherein a width of the piezoelectric-element base-end is wider than a width of the piezoelectric-element distal-end. The elongated actuator also includes a flexible passive layer, having a passive-layer-element base-end and a passive-layer-element distal-end, wherein a width of the passive-layer-element base-end is wider than the passive-layer-element distal-end, wherein the piezoelectric layer is operable to apply force for bending the flexible passive layer. As discussed above,  FIG.  27    illustrates and exemplary actuator that includes both the piezoelectric layer  2780  and the flexible passive layer and  2790 . 
     Several aspects of the disclosure were discussed above. It is noted that any feasible combination of features, aspects, characteristics, structures, etc. which were discussed above—for example, with respect to any one or more of the drawings—may be implemented as is considered as part of the disclosure. Some of those feasible combinations were not discussed in detail for reasons such as brevity and succinctness of the disclosure, but are nevertheless part of the disclosure, and would present themselves to a person who is of skill in the art in view of the above disclosure. 
     The present disclosure relates to implementation of LIDAR system  100  (or any other LIDAR system, whether a scanning LIDAR system, a non-scanning LIDAR system, pulsed light system, continuous wave system, or any other type of LIDAR system or device) in a vehicle (e.g., vehicle  110 ). As discussed above, LIDAR system  100  may integrate multiple scanning units  104  and potentially multiple projecting units  102  in a single vehicle. Optionally, a vehicle may take advantage of such a LIDAR system to improve power, range and accuracy in the overlap zone and beyond it, as well as redundancy in sensitive parts of the FOV (e.g. the forward movement direction of the vehicle). As discussed above, a LIDAR system in a vehicle may be used to project light through a window (or windshield) of a vehicle towards an environment in front of the vehicle. Various objects in the environment may reflect a portion of the light projected on them by the LIDAR system. The LIDAR system may determine the positions and/or distances of the various objects in front of the vehicle, for example, by detecting the reflected light received from those objects through the windshield. 
     Reflection of the light off the glass, however, is a significant challenge when attempting to locate a LIDAR system behind a windshield of a vehicle. This is because the reflected light may interfere with light received from objects in the external environment transmitted through the windshield, which in turn may influence determination of the positions and/or distances of the objects in front of the vehicle. At some angles of incidence (mostly in a peripheral area of the FOV) an amount of light reflected back to the vehicle is greater than an amount of light that passes through the windshield.  FIG.  32 A  illustrates a side view illustration of an exemplary vehicle system  3200  in a vehicle having a window (e.g. a windshield of a vehicle in which the LIDAR system is installed). In this disclosure, the terms window and windshield may be used interchangeably because a LIDAR system in a vehicle may be oriented to project and/or receive light through the windshield, the rear window, or any of the other windows of the vehicle. The LIDAR system may be LIDAR system  100 , or any other type of LIDAR system. The window may be, for example, a flat window (e.g., as illustrated) or a curved window.  FIG.  32 B  illustrates a top view illustration of vehicle system  3200 . While the window may be made of glass, other materials may be used in addition or instead of glass, such as clear plastics, polymeric materials, and so on. The window may include at least one layer of one or more transparent or semi-transparent materials, and may also include different types of coatings, stickers, or other transparent or semi-transparent connected to the window. 
     In an exemplary implementation, the LIDAR system may have differing FOV openings in the vertical plane and in the horizontal plane (e.g. ±15° to ±20° vertical opening and ±30° to ±60° horizontal opening). As a result, as illustrated in  FIGS.  32 A and  32 B , light may fall on the window at different angles of incidence, some of which may be relatively wide. It is noted that the range of incidence angles may also depend on the angle between the optical axis of the LIDAR system and that of the window (which may be determined, e.g., in windshields) based on non-optical considerations, such as the aerodynamics of the vehicle. It is to be understood that the optical axis of the LIDAR system may depends on the intended field of view—e.g., toward the road and space in front of the vehicle. It should also be noted that the actual angle of incidence is a combination of the horizontal angle of incidence (denoted OT) and the vertical angle of incidence (denoted Os). 
     As illustrated in  FIG.  32 A , vehicle system  3200  may include, for example, LIDAR system  100  and window (e.g., windshield)  3202  of a vehicle. Window  3202  may be generally flat (as illustrated in  FIG.  32 A ) or it may be curved. Window  3202  may be positioned at a rake angle □ relative to a horizontal plane  3201 , which may be generally parallel to a chassis of the vehicle or to a ground surface. In some embodiments, angle □ may range between about 22° and about 30°. According to this disclosure, terms such as about, generally, and substantially should be interpreted to encompass typical design, manufacturing, and machining tolerances. Thus, for example, an angle of about 22° should be interpreted as encompassing angles in the range of, 22°±0.1°, 22°±0.5°, 22°±1°, etc. 
     LIDAR system  100  may include a light source (e.g. light source  112 ) configured to emit light in a field of view (FOV) defined by, for example, light rays  3204  and  3206 . As illustrated in  FIG.  32 A , some of the light incident on window  3202  may be reflected back into the vehicle by window  3202 , while another portion of the incident light may be transmitted through window  3202  to environment  3216  located in front of window  3202 . As illustrated in  FIG.  32 A , a portion of ray  3204 , for example, may be transmitted through window  3202  as shown by ray  3208 , while another portion of ray  3204  (e.g. ray  3210 ) may be reflected back into the vehicle by window  3202 . Likewise, a portion of ray  3206 , for example, may be transmitted through window  3202  as shown by ray  3212 , while another portion of ray  3206  (e.g. ray  3214 ) may be reflected back into the vehicle by window  3202 . As also illustrated in  FIG.  32 A , a vertical angle of incidence of, for example, of ray  3206  on window  3202  may be represented by an angle □ S . In some embodiments, the angle □ S  may be relatively large, for example, of the order of about 60° to about 75°. In some exemplary embodiments as illustrated in  FIG.  32 A , LIDAR system  100  may be connected to a portion of a vehicle by a connector  3218 , which may include one or more structural elements that may be configured to attach LIDAR system  100  to the vehicle. For example, one end of connector  3218  may be attached to the vehicle while an opposite end may be attached to LIDAR system  100 . It is also contemplated that in some exemplary embodiments, LIDAR system  100  may be oriented in a non-horizontal manner relative to a vehicle chassis or to the ground. For example, as illustrated in  FIG.  34 A , LIDAR system  100  may be positioned at an inclination “□ 3 ” relative to a horizontal plane. 
     To ensure clarity, throughout this disclosure, the discussion of structural and functional characteristics is not repeated when subsequently disclosed elements have structural and functional characteristics similar to those previously discussed in the disclosure. Additionally, unless otherwise stated, throughout this disclosure, similarly numbered elements should be presumed to have similar structural and functional characteristics. Further, similar elements from one structure to the next may also have similar characteristics even if differently numbered. 
     As seen in an exemplary top view illustration of vehicle system  3200 , shown in  FIG.  32 B , the field of view in a horizontal plane may be defined by rays  3234  and  3236 . A portion of ray  3234 , for example, may be transmitted through window  3202  as shown by ray  3238 , while another portion of ray  3234  (e.g. ray  3240 ) may be reflected back into the vehicle by window  3202 . Likewise, a portion of ray  3236 , for example, may be transmitted through window  3202  as shown by ray  3242 , while another portion of ray  3236  (e.g. ray  3244 ) may be reflected back into the vehicle by window  3202 . As also illustrated in  FIG.  32 B , a horizontal angle of incidence of, for example, ray  3236  on window  3202  may be represented by an angle □ T . In some embodiments, the angle □ T  may be relatively large, for example, of the order of about 60° to about 75°. 
     In some exemplary embodiments as illustrated in  FIG.  32 A , LIDAR system  100  may be connected to a portion of a vehicle by a connector  3218 , which may include one or more structural elements that may be configured to attach LIDAR system  100  to the vehicle. For example, one end of connector  3218  may be attached to the vehicle while an opposite end may be attached to LIDAR system  100 . It is also contemplated that in some exemplary embodiments, LIDAR system  100  may be oriented in a non-horizontal manner relative to a vehicle chassis or to the ground. For example, as illustrated in  FIG.  34 A , LIDAR system  100  may be positioned at an inclination “□ 3 ” relative to a horizontal plane. Connector  3218  may be directly connected or otherwise touch window  3202 , but this is not necessarily so. Connector  3218  may be directly connected or otherwise touch LIDAR system  100 , but this is not necessarily so. In some examples, connector  3202  may be indirectly connected to one or more of window  3202  and/or LIDAR system  100 . The connection of connector  3218  may be permanent or detachable, and it may or may not be adjustable (e.g., for direction and/or distance between the LIDAR system  100  and the window  3202 ). 
     Window  3202  (and/or windshield) may be made of different layers of different materials and/or may be covered with one or more types of coatings, which may reduce the level of transmittance even further. It is also noted that the level of transmittance of light through window  3202  may differ between different polarities of light, and that the loss of light due to reflections may occur also in the reception path (of light reflected from the FOV to the LIDAR).  FIG.  33    illustrates an example of changes in transmission levels of the light in the field of view for a slanted window (e.g. windshield  3202  with a rake angle □ of 25°), in accordance with exemplary embodiments of the present disclosure. In  FIG.  33   , the horizontal angle of incidence □ S  is plotted on the x-axis and the vertical angle of incidence □ T  is plotted in the y-axis. The different lines represent the percentage of light transmitted through windshield  3202 . As seen in  FIG.  33   , the amount of light transmitted through window  3202  may vary over a wide range from about 50% to about 90% of the light incident on window  3202 , with the remainder of the light being either reflected from window  3202  or absorbed by the material of window  3202 . 
     In accordance with the present disclosure a light deflector for a LIDAR system located within a vehicle is disclosed. The light deflector includes a windshield optical interface configured for location within a vehicle and along an optical path of the LIDAR system. To overcome the problem of low transmittance of light through vehicle windows, resulting from wide incidence angles, the present disclosure proposes adding (e.g., gluing to the window, vacuuming to the window, suspending from an adjacent fixed location on the vehicle) an optical interface, which may reduce the incidence angles, in at least some parts of the FOV. The optical interface may be located within the vehicle, externally to the vehicle, or it may include parts on both sides of the window. The optical interface may include, for example, prism(s), lens(es), diffraction gratings, grating prisms (also known as grisms), and/or stickers (with any of the optical capabilities described above), etc. The optical interface may be flexible or rigid. The glue used to affix the optical interface to the windshield may be optical glue (transparent to light of the LIDAR), and may be of differing thicknesses (e.g., to allow some tolerance for curvature of different car windshields). The optical interface may also have other optical capabilities, for example, anti-reflective coatings, scratch-resistant coatings, spectral filters, polarization filters, waveplates (retarders), etc. 
     In some embodiments, a window may be manufactured to include an optical interface built into the window. In some cases, such an interface may be raised or depressed relative to a window surface and/or may include a portion that is discontinuous relative to an otherwise continuous plane of the window (whether flat or curved). Such a built-in interface may configured for location in an optical path of the LIDAR FOV and may exhibit optical parameters matching or at least partially matching those of the LIDAR. 
       FIGS.  34 A through  34 D  illustrate exemplary embodiments of light deflector  3400  for a LIDAR system (e.g. LIDAR system  100 ) associated with windshield  3202  of a vehicle. As illustrated in  FIG.  34 A , light deflector  3400  may include optical interface  3402 , which may be in the form of at least one prism  3410 , in accordance with examples of the presently disclosed subject matter. The one or more prisms  3410  may be made from the same material as the window (e.g. glass), a material with similar refractive index as the window, or from any other material. Preferably, the one or more prisms may be transparent. The one or more prisms may be shaped and positioned to reduce the angle of incidence of light in transmission between air and glass (or other material of the window). The LIDAR system may be LIDAR system  100 , or any other type of LIDAR system. 
     In one exemplary embodiment as illustrated in  FIG.  34 A , prism  3410  may be located between a light source of LIDAR system  110  and window  3202 . Prism  3410  may include, for example, internal prism  3412  and external prism  3414 . Internal prism  3412  may be positioned between the light source in LIDAR system  100  and window  3202 . External prism  3412  may be located between window  3202  and an external environment or field of view. 
     The one or more prisms  3410  (including  3412  and  3414 ) may be attached to window  3202  in different ways (e.g. using optical glue, another adhesive, being installed on a rigid frame connected to the window or to the body of the vehicle, etc.) In some exemplary embodiments, window  3202  may include an opening (not shown) and prism  3410  may be received in the opening in window  3202 . In other exemplary embodiments, the internal prism(s)  3412  may be positioned outside of a rigid housing of LIDAR system  100  (e.g. as illustrated in  FIG.  9 A ). In yet other embodiments, the housing of LIDAR system  100  may include the at least one prism  3410  or a part thereof. The housing of LIDAR system  100  may touch (i.e. be in contact with) prism  3410  or may be spaced apart from prism  3412 . 
     In some embodiments, the one or more prisms  3410  may be detachably attachable to the window or to a housing of LIDAR system  100 . Optionally, one or more prisms  3410  may be manufactured as part of window  3202 . For example, the one or more prisms  3410  may be manufactured as part of a windshield of the vehicle. In some embodiments, the one or more prisms  3410  may be manufactured as part of a rear window of the vehicle. In other embodiments, the one or more prisms  3410  may be manufactured as part of a side window of the vehicle. One or more of the system (e.g. window  3202 , prism  3410 , internal prism  3412 , external prism  3414 , etc.) may include a coating and/or another form of filter (e.g., anti-reflective filter/layer, band-pass filter/layer, etc.). 
     In accordance with embodiments of the present disclosure, the optical path of the LIDAR system may extend through a sloped windshield of the vehicle, wherein an optical angle of the optical path before passing through the sloped windshield is oriented at a first angle with respect to an adjacent surface of the sloped windshield. As discussed above, with reference to  FIG.  32   , light from LIDAR system  100  may be incident on window  3202  over a field of view defined by, for example, rays  3204  and  3206  (see  FIG.  32   ). Rays  3204 ,  3206  may pass through window  3202  and may be transmitted to environment  3216  located in front of window  3202  over a range defined by rays  3208  and  3212  (see  FIG.  32   ). Rays  3202  and  3204  may define an optical path for light passing through window  3202 . Returning to  FIG.  34   , ray  3202  may be oriented at first angle □ 1  with respect to an adjacent inner surface  3403  of window  3202 . 
     According to some embodiments of the present disclosure, the light deflector may include a connector for orienting a LIDAR emitting element to direct light through the windshield optical interface and along the optical path. with reference to  FIG.  32 A , LIDAR system  100  may be connected to at least some portion of a vehicle using a connector  3218 , which may also help orient LIDAR system  100  horizontally or inclined relative to a vehicle chassis or a ground surface. 
     In accordance with embodiments of the present disclosure, the optical interface may be configured to alter the optical angle of the optical path from the first angle to a second angle. As discussed above, the optical interface may include one or more of prisms, lenses, diffraction gratings, etc. Each of these optical interfaces may be configured to alter the optical path by reflecting, refracting, and/or diffracting the incident light. Thus, for example, as illustrated in  FIG.  34 A , incident ray  3204  may be refracted by the one or more prisms  3410  (including, for example, internal prism  3412  and external prism  3414 ). The refracted light may exit prism  3410  via, for example, ray  3420 . Similarly, ray  3206  may enter prism  3410  and may exit prism  3410  via, for example, ray  3422 . In one exemplary embodiment as illustrated in  FIG.  34 A , because of the refraction of light at the surface of prism  3410 , ray  3204  may be refracted as ray  3416  within prism  3410 . Ray  3416  may be incident on window  3202  at second angle □ 2 , which may be different from first angle □ 1 . 
     Embodiments of the present disclosure may include an optical interface configured such that at the second angle, there is a ratio of greater than about 0.3 between light refracted through the windshield and light reflected from the windshield. As discussed above with reference to  FIG.  33   , an amount of light transmitted through a windshield depends on an optical angle of incidence of the light on the windshield. Correspondingly, an amount of light refracted through the windshield and an amount of light reflected back by the windshield also depend on the optical angle of incidence. Thus, a change in the angle of incidence from first angle □ 1  to second angle □ 2  may alter an amount of the incident light that may be reflected back from the windshield and an amount of light that may be refracted by the windshield. It is contemplated that a ratio between the amount of light refracted through the windshield and the amount of light reflected from the windshield may be greater than about 0.2, greater than about 0.25, greater than about 0.3, greater than about 0.35, or greater than about 0.4, etc. As also discussed above, the phrase about in this disclosure encompasses typical design, machining, and manufacturing tolerances. Thus, the term about 0.3 should be interpreted as encompassing ratios of 0.3±0.01, 0.3±0.02, 0.3±0.05. 
     According to embodiments of this disclosure, in the light deflector at least a portion of the optical interface protrudes from the windshield. In some exemplary embodiments, the protrusion of the optical interface is inward. In other exemplary embodiments, the protrusion of the optical interface is outward. The optical interface may be used to deflect and/or refract the incident light provided by one or more light sources in LIDAR system  100 . In some exemplary embodiments, the optical interface may be disposed within a thickness of the window or the windshield. In other exemplary embodiments, however, the optical interface may extend out from a surface of the windshield. In one exemplary embodiment as illustrated in  FIG.  34 A , prism  3410  may protrude from window  3202  on both sides, although it is contemplated that prism  3410  may protrude from window  3202  on only one side. Inner prism  3412  of prism  3410  may protrude inward from window  3202  towards LIDAR system  100 . Outer prism  3414  may protrude outward from window  3202  towards environment  3216 . 
     In accordance with embodiments of the present disclosure, the optical interface is located only on an inside of the windshield. Although prism  3410  has been illustrated as including both inner and outer prisms  3412  and  3414 , in the exemplary embodiment of  FIG.  34   , it is contemplated that in some embodiments, prism  3410  may include only one of inner and outer prisms  3412  and  3414 . In embodiments that include only the inner prism  3412 , inner prism  3412  may be located on an inside of window  3202 . 
     In accordance with the present disclosure, the optical interface includes a first portion located on an external surface of the windshield and an internal portion located within the vehicle. In other exemplary embodiments, the internal portion within the vehicle is located on an internal surface of the windshield. In yet other embodiments, the windshield optical interface is affixed to an internal surface of the windshield. As discussed above, prism  3410  may include a first portion (e.g. external prism  3414 ) positioned on external surface  3405  of window or windshield  3202 . As also illustrated in  FIG.  34   , prism  3410  may include a second portion (e.g. internal prism  3412 ) located within the vehicle. Internal prism  3412  may be positioned on internal surface  3403  of window  3202 . Internal and external prisms  3412  and  3414 , respectively, may be affixed to a portion of the vehicle chassis or frame so as to be positioned on internal surface  3403  and external surface  3405 , respectively. In other exemplary embodiments, internal prism  3412  may be affixed to inner surface  3403  of window  3202 . As discussed above, internal prism  3412  may be affixed to window  3202  using an adhesive or glue. It is also contemplated that internal prism  3412  may be positioned in contact with inner surface  3403  by attaching internal prism  3412  to a portion of the vehicle. External prism  3414  may be affixed to outer surface  3405  of window  3202  using techniques similar to those discussed above with respect to internal prism  3412 . 
     Although prism  3410  has been illustrated as having a generally cuboidal shape, it is contemplated that one or more of the prisms may be curved to match the different angles at which light is emitted by the LIDAR system to different parts of the FOV. Some examples are provided in  FIGS.  34 B- 34 D . Although these illustrations show curvature in the vertical direction, it is contemplated that the prisms may additionally or alternatively also be curved in a horizontal direction or in any other direction. 
       FIG.  34 B  illustrates an exemplary embodiment of a curved prism  3430 , which may include internal prism  3432  and external prism  3434 . Internal prism  3432  may protrude inward toward LIDAR system  100  and may have a curved inner surface  3436 , which may face LIDAR system  100 . Internal prism  3432  may be positioned inside the vehicle between LIDAR system  100  and window  3202 , whereas external prism  3434  may be positioned between window  3202  and environment  3216  located in front of window  3202 . Internal and external prisms  3432  and  3434  may be positioned or affixed to window  3202  using techniques similar to those discussed above with respect to prism  3410 , and internal and external prisms  3412  and  3414 . 
     Light from a light source within LIDAR system  100  may be incident on curved inner surface  3436  of internal prism  3432 . External prism  3434  may include curved outer surface  3438 . Light transmitted through internal and external prisms  3432  and  3434  may exit prism  3430  through curved outer surface  3438 . For example, as illustrated in  FIG.  34 B , rays  3204  and  3206  may be incident upon curved inner surface  3436  and may be refracted through internal and external prisms  3432  and  3434  to emerge from curved outer surface  3438  as rays  3440  and  3442 , respectively, which may be transmitted to environment  3216 . 
     In accordance with some embodiments of the present disclosure, the optical interface may include a stepped surface. In accordance with other embodiments of the present disclosure, the optical interface may include a toothed surface. For example, the shape of the one or more prisms may be designed so as to shape the laser spot emitted by the LIDAR system after transmission through the window and the one or more prisms. As demonstrated in the examples of  FIGS.  34 C and  34 D , optionally, one or more of the faces of prism  3410  and/or  3430  may include a discontinuous face, similarly to Fresnel lenses. The face of each of these narrower prisms may be flat or curved. It is noted that each such “Frensel Prism” may be made from a continuous piece of material (e.g. glass), or may be constructed from an array of adjacent prisms. Further, it is noted that while these illustrations show discontinuity of prisms surface in the vertical direction, one or more of the prisms may include discontinuous surfaces in any other direction (e.g. horizontal direction). 
     By way of example,  FIG.  34 C  illustrates optical interface (e.g. prism  3450 ), which may include internal prism  3412  and external prism  3454 . External prism  3454  may project outward from window  3202  towards environment  3216 . External prism  3454  may include a stepped outer surface  3459 , which may include one or more stepped sections  3456 . As illustrated in  FIG.  34 C , each stepped section  3456  may include horizontal surface  3458  and vertical surface  3460 . Horizontal surfaces  3458  may be generally parallel to a chassis of the vehicle or to a ground surface. Vertical surfaces  3460  may be generally perpendicular to horizontal surfaces  3460 . Adjacently located horizontal and vertical surfaces  3458  and  3460  may be connected to each other forming a stepped but continuous outer surface  3459 . It is contemplated that a size and number of stepped sections  3456  may be selected to ensure that light exiting prism  3450  adequately illuminates environment  3216  in front of window  3202 . As also discussed above, the surfaces  3458  and  3460  of stepped sections  3456  may form a prism having characteristics similar to that of a Fresnel lens. It is also contemplated that using stepped sections  3456  may help reduce a thickness of external prism  3452  helping to reduce an amount by which external prism  3452  may protrude from window  3202 . 
     Although surfaces  3458  and  3460  have been illustrated in  FIG.  34 C  as straight (or flat surfaces), it is contemplated that surfaces  3458  and  3460  may instead by curved (in a convex or concave manner) to help direct the light emitted by LIDAR system  100  to the desired field of view in front of window  3202 . Additionally, although only external prism  3454  has been illustrated as having stepped sections  3456 , it is contemplated that in some exemplary embodiments, internal prism  3412  may also include similar stepped sections. A number of stepped sections (e.g.  3456 ) on internal prism  3452  and external prism  3454  may be the same or may be different. In some exemplary embodiments, a plurality of discretely manufactured stepped sections  3456  may be connected to each other (e.g. using glue or transparent adhesive) to form one or more of internal and external prisms  3452  and  3454 . In other embodiments, the sections  3456  may be formed by machining or otherwise generating horizontal and vertical surfaces  3458  and  3460  on a single integral internal or external prism  3412  or  3454 . 
       FIG.  34 D  illustrates another exemplary optical interface (e.g. prism  3470 ), which may include internal prism  3472  and external prism  3474 . External prism  3474  may include a toothed outer surface  3476 , which may include one or more toothed sections  3476 . As illustrated in  FIG.  34 D , each toothed section  3476  may include inclined surfaces  3478  and  3480 . Surfaces  3478  may be generally inclined relative to a horizontal plane defined by, for example, a chassis of the vehicle or a ground surface. Surfaces  3480  may also be generally inclined relative to a vertical plane disposed generally perpendicular to the horizontal plane. Thus, surfaces  3478  and  3480  may form, for example, a toothed shape. Adjacently located surfaces  3478  and  3480  may be connected to each other forming a toothed but continuous outer surface  3469 . It is contemplated that a size and number of toothed sections  3476  may be selected to ensure that light exiting prism  3470  adequately illuminates the field of view in front of window  3202 . It is also contemplated that using toothed sections  3476  may help reduce a thickness of external prism  3472  helping to reduce an amount by which external prism  3472  may protrude from window  3202 . 
     Although surfaces  3478  and  3480  have been illustrated in  FIG.  34 C  as straight (or flat surfaces), it is contemplated that surfaces  3478  and  3480  may instead by curved (in a convex or concave manner) to help direct the light emitted by LIDAR system  100  to the desired field of view in front of window  3202 . In some embodiments, only external prism  3474  may have stepped sections  3476 . In other exemplary embodiments as illustrated in  FIG.  34 D , internal prism  3474  may also include toothed sections similar to sections  3476 . The sizes and number of toothed sections (e.g.  3476 ) on internal prism  3472  and external prism  3474  may be the same or may be different. In some exemplary embodiments, a plurality of discretely manufactured toothed sections  3476  may be connected to each other (e.g. using glue or transparent adhesive) to form one or more of internal and external prisms  3472  and  3474 . In other embodiments, the sections  3476  may be formed by machining or otherwise generating horizontal and vertical surfaces  3458  and  3460  on a single integral internal or external prism  3472  or  3474 . 
     It is contemplated that sizes of the stepped sections  3456  (e.g. dimensions of surfaces  3458  or  3460 ) in the exemplary prism  3450  of  FIG.  34 C , may be selected based on a size of the light beam that is incident on these surfaces from LIDAR system  100 , or based on a size of the light beam that may be incident on these surfaces from environment  3216 . The sizes of toothed sections  3476  (e.g. dimensions of surfaces  3478  or  3480 ) in the exemplary prism  3470  of  FIG.  34 D  may be selected in a similar manner. Moreover, the sizes of surfaces  3458 ,  3460 , or  3478 ,  3480  may be uniform or nonuniform based on a size of the light beam expected to be incident on these surfaces. An orientation of prisms  3450  or  3470 , and or orientations of surfaces  3460  and  3470  may be selected so that light from LIDAR system  100  and/or environment  3216  may be incident on surfaces  3460  and/or  3470  generally perpendicular to, or at a predetermined angle with respect to surfaces  3460  or  3470 . 
     It is noted that in some embodiments the emittance of light by, for example, LIDAR system  100  may require calibration relative to the one or more prisms (e.g.  3410 ,  3430 ,  3450 ,  3470 , etc.), especially if manufactured and/or assembled onto the window separately. For example, the calibration may include matching the scanning pattern of a scanning LIDAR system so that the illumination and/or reception of light would be executed at continuous parts of the prism (e.g. along the rows of the Fresnel prisms exemplified in  FIG.  34 D ) and not at the junction of adjacent toothed or stepped sections (e.g.  3456  or  3476 ).  FIG.  35    illustrates an exemplary LIDAR system  100  that may have been calibrated for use with a prism  3470 . As illustrated in  FIG.  35   , incident light in the form of rays  3502 ,  3504 ,  3506 ,  3508 ,  3510  etc. may fall on internal prism  3474 , which may have one or more stepped sections  3476 , each stepped section having surfaces  3478  and  3480 . As illustrated in  FIG.  35   , LIDAR system  100  may be calibrated so that each of rays  3502 ,  3504 ,  3506 ,  3508 ,  3510  may be incident on respective surfaces  3478  at a predetermined angle of incidence. In one exemplary embodiment as illustrated in  FIG.  35   , the angle of incidence may be about 90° although other angles are also contemplated. The one or more prisms (e.g.  3410 ,  3430 ,  3450 ,  3470 , etc.) discussed above may have any shape, e.g. triangular, hexagonal, or any other regular or irregular shape. It is also noted that although the one or more prisms (e.g.  3410 ,  3430 ,  3450 ,  3470 , etc.) were primarily discussed with respect to LIDAR system, the embodiments of this disclosure are not so limited and may include the use of the disclosed prisms with other types of optical systems such as cameras, projectors, etc. 
     According to various exemplary embodiments of the present disclosure, the optical interface may include a secondary window affixed to the windshield. In some exemplary embodiments, the optical interfaces discussed above may be included in a secondary window (e.g. a smaller pane of glass) which is in turn connected to the window. The secondary window may be detachably or fixedly attached to an existing windshield. Affixing a separate window with the optical interface may avoid having to replace conventional windshields on vehicles and may instead allow the use of a LIDAR system with conventional windshields. 
     By way of example,  FIG.  36    illustrates an exemplary embodiment of a vehicle system  3400 , which may include LIDAR system  100  and windshield  3202 . Windshield  3202  may be a conventional flat or curved windshield or window found on a conventional automobile. In one exemplary embodiment as illustrated in  FIG.  36   , vehicle system  3400  may include secondary window  3610 . Secondary window  3610  may be positioned between LIDAR system  100  and windshield  3202 . 
     Additionally or alternatively secondary window  3610  may be positioned between window  3202  and environment  3216 . It is contemplated that in some embodiments, secondary window  3610  may be positioned in contact with windshield  3202 . It is also contemplated that in some embodiments, secondary window may be affixed to inner surface  3403  and/or to outer surface  3405  of window  3202 . Although not illustrated in  FIG.  36   , in some embodiments, secondary window  3610  may include one or more of prisms  3410 ,  3430 ,  3450 , and/or  3470  discussed above. In other exemplary embodiments as illustrated in  FIG.  36   , secondary window  3610  may include anti-reflective coating  3612  which may be applied on surface  3614  of secondary window  3610 . Anti-reflective coating  3612  and surface  3614  may face LIDAR system  100  so that light emitted by one of more light sources within LIDAR system  100  may be incident on anti-reflective coating  3612 . The anti-reflective coating  3612  may help ensure that more of the light incident on secondary window  3610  may be transmitted through secondary window  3610  and windshield  3202  to environment  3216  instead of being reflected back towards LIDAR system  100 . 
     It is noted that the anti-reflective layer may reduce the amount of light reflected back to the incidence side of the window (e.g., back into the car or into the LIDAR system), and instead may cause more (or all) of the light to be transmitted to the other side of the window (e.g. toward the scene or environment  3216 ). The anti-reflective layer/coating may include more than one layer of material (e.g., in order to improve transmission levels in larger degrees of incidence). In some exemplary embodiments, additional layers, coatings and/or functionalities may be implemented together with anti-reflection (e.g. on the same secondary-window, in interleaving layers, etc.) For example, the other layers, coatings and/or functionalities may include one or more of the following: 
     a. Band-pass filtering; 
     b. Spectral blocking; 
     c. Retardation (and other phase manipulation); 
     d. Polarizers; 
     e. Gratings, etc. 
     The anti-reflective layer (and possibly the optional secondary window as well) may be thin. For example, the anti-reflective layer (and possibly the optional secondary window as well) may be thinner than the window. In some exemplary embodiments, the anti-reflective layer (and possibly the optional secondary window as well) may be at least 10 times thinner than the window. It is noted that anti-reflective layers may be much thinner, and that any type and dimension of anti-reflective layer or coating known in the art may be implemented. 
     In some embodiments, the anti-reflective layer (and possibly the optional secondary window as well) may be included within (or partly within) a rigid housing of the LIDAR system. In other embodiments, the anti-reflective layer (and possibly the optional secondary window as well) may be implemented as a sticker, which includes an adhesive layer which may be used for connecting the respective component to a window. The LIDAR system may be designed such the anti-reflective layer (and possibly the optional secondary window as well) are sufficiently thin so as not to interfere with a cleaning system of the window (e.g., wipers). 
     According to various exemplary embodiments of the present disclosure, the optical interface includes at least one of a grating, prism, or a light deflector. In some embodiments as discussed above, the optical interface may be a prism or may include an anti-reflective coating. In other exemplary embodiments, the optical interface may be a grating. By way of example,  FIG.  37 A  illustrates an exemplary embodiment of a vehicle system  3400 , which may include LIDAR system  100 , windshield  3202 , and secondary window  3610 . Grating  3616  or  3618  may be attached to surface  3614  of secondary window  3610 . In one exemplary embodiment as illustrated in  FIG.  37 B , grating  3616  may be formed by a sheet of material with differing thicknesses. For example grating  3616  may include sections  3620  which may be separated by sections  3622 . As illustrated in  FIG.  37 B , sections  3620  may have a thickness greater than that of sections  3622 . In another exemplary embodiment as illustrated in  FIG.  37 C , grating  3618  may be formed as a sheet of material with differing refraction indexes. For example, grating  3618  may have portions  3626  and  3628  disposed adjacent to each other. Portions  3626  and  3628  of grating  3618  may have different refractive indices. It is further contemplated that in some exemplary embodiments, grating  3616  or  3618  applied to secondary window may be formed using a combination of the grating characteristics illustrated in  FIGS.  37 B and  37 C . It is also contemplated that in some exemplary embodiments, grating  3616 ,  3618 , or a combination of the two may be directly applied to inner surface  3403  of windshield  3202  without requiring a secondary window  3610 . 
     If a secondary window is implemented, the grating layer may preferably be implemented on the side of the secondary window opposing to the window (e.g., the windshield), for example, toward the light source for an inner secondary window, and toward the external environment or FOV for an external secondary window. It is noted that optionally, the LIDAR system may emit polarized light towards the grating layer (e.g.,  1102 ,  1104 ). It is also noted that if the transmission path and the reception path of the LIDAR system are different (e.g. using different LIDAR-system windows, different lenses, mirror, etc.), the optical components discussed above (e.g., prisms, anti-reflective layers, gratings) may be implemented for the transmission path, for the reception path, or both. In such LIDAR systems (e.g. bi-static LIDAR system) where the aforementioned optical components (e.g., prisms, anti-reflective layers, gratings) are used for both transmission and reception, the same or different optical components may be used for the different paths (TX, RX). For example, the LIDAR system may include a first arrangement of one or more prisms, one or more anti-reflective layers, and/or one or more grating layers for transmission path, and a second arrangement of one or more prisms, one or more anti-reflective layers, and/or one or more grating layers for reception path. 
     While the present disclosure describes examples of optical interfaces (e.g.  3410 ,  3430 ,  3450 ,  3470 ), it should be noted that aspects of the disclosure in their broadest sense are not limited to the disclosed examples of optical interfaces. It is also contemplated that the one or more optical interfaces may only be implemented on certain portions of the windshield. For example, the one or more optical interfaces may be implemented only in portions of the windshield having relatively large angles of incidence (e.g. above about 50°, above about 60°, or above about 70°.) In some exemplary embodiments, the one or more optical interfaces may be implemented on some but not all portions of the windshield by manufacturing the optical interfaces separately from the windshield and connecting them to the windshield in the desired regions of the windshield. Further, although anti-reflective coatings and gratings have been discussed above with reference to secondary window  3610 , it is contemplated that anti-reflective coatings and/or gratings may be applied to various surfaces of the one or more prisms  3410 ,  3430 ,  3450 , and/or  3470  discussed above, or may be applied to inner and/or outer surfaces  3403  and  3405  of window  3202 . 
     It is contemplated that the disclosed vehicle systems in accordance with the present disclosure may include a cleaning mechanism (internal and/or external to the car). For example, such cleaning mechanisms may include one or more of wipers, high pressure air vents, water nozzles, etc. It is also contemplated that in some exemplary embodiments, conventional wiper mechanisms already present on the vehicle may be used to clean the optical interfaces and/or windows. To facilitate cleaning of the optical interfaces and/or windows using wipers, the optical interfaces and/or windows may include mechanical transitions outside the field of view to ensure that the wipers can sweep over the optical interfaces and/or windows. For example, such mechanical transitions may include sloping and/or curved edges of the optical interfaces and/or of the secondary windows. In some exemplary embodiments, the wipers of the vehicles may be adapted to sweep over the optical interfaces and/or windows according to this disclosure. For example, the wipers may include one or more flexibly connected parts at a relevant “radius” of the wipers, to ensure that the wipers may “climb over” and sweep the one or more optical interfaces. 
     In accordance with the present disclosure, the disclosed vehicle system may include internal and external lenses in addition to or as an alternative to the one or more optical interfaces discussed above. By way of example,  FIG.  38 A  illustrates an exemplary vehicle system  3400  with both internal and external lenses, in accordance with the present disclosure. As illustrated in  FIG.  38 A , vehicle system  3400  may include LIDAR system  100 , window  3202 , and prism  3410 , although any of prisms  3430 ,  3450 , and/or  3470  may also be used in the configuration of  FIG.  38 A . Vehicle system  3400  may further include one or more internal collimating lenses  3810  and/or one or more external de-collimating lenses  3820 . Internal collimating lens  3810  may be positioned between LIDAR system  100  and internal prism  3412 . External collimating lens  3820  may be positioned between external prism  3414  and environment  3216 . 
     As illustrated in  FIG.  38 A , light from LIDAR system  100  may be incident on internal collimating lens  3810 . For example movement of one or more MEMS mirrors  1102  may produce one or more light beams at different scanning angles. These light beams at different scanning angles may be incident on internal collimating lens  3810 , which may convert the incident light to parallel beams of light. The parallel light beams may pass through prism  3410  (including, for example, internal and external prisms  3412  and  3414 ). Light beams exiting prism  3410  may be incident on external de-collimating lens  3820 . Lens  3820  may recover the angles of the incident light emitted by LIDAR system  100  to recreate a sufficiently wide field of view. It is to be understood that lenses  3810  and  3820  may serve a similar function (e.g. collimating to parallel beams, and reconstructing the angles) for light reflected from one or more objects in environment  3216 , which is received by one or more sensors of LIDAR system  100 . Further, lens  3820  may be used to modify the angular aperture of the LIDAR system to a beam propagation direction which may not be parallel to each other. 
     A LIDAR system in accordance with the present disclosure may include a light source configured to project light for illuminating an object in an environment external to the LIDAR system. The LIDAR system may also include a scanning unit configured to deflect light from the light source in order to scan at least part of the environment. As discussed above, and by way of example,  FIG.  1 A  illustrates an exemplary scanning unit and  FIGS.  2 A- 2 C  illustrate exemplary embodiments of a LIDAR system, and a light source (e.g.  112 ) consistent with embodiments of the present disclosure. 
     In accordance with this disclosure, the scanning unit includes a movable MEMS mirror configured to pivot about at least one axis. As discussed above,  FIGS.  11 A- 25    illustrate various exemplary embodiments of MEMS mirror assemblies that include one or more connectors configured to move the MEMS mirror about one or more axes. The disclosed MEMS mirror (e.g.  1102 ) may direct the light from light source (e.g.  112 ) through the optical interface (e.g.  3410 ,  3430 ,  3450 ,  3470 , etc.) and along the optical path defined by, for example, rays  3204 ,  3206 . 
     According to some exemplary embodiments of this disclosure, the LIDAR system includes a connector configured to connect the LIDAR system to a vehicle with an optical interface configured for location within a vehicle and along an optical path of the LIDAR system. As discussed above,  FIG.  32 A  illustrates an exemplary connector  3218  that may connect LIDAR system  100  to some portion of the vehicle. As discussed above,  FIGS.  32  and  34 - 38    illustrate various exemplary embodiments of optical interfaces associated with windows or windshields and positioned along an optical path (defined by, for example, rays  3204 ,  3206 ,  3420 , and  3422  in  FIG.  32 A ) of an exemplary LIDAR system. 
     In some exemplary embodiments according to this disclosure, when the LIDAR system is connected to the vehicle the optical path extends from the light source through a sloped windshield of the vehicle. An optical angle of the optical path before passing through the sloped windshield is oriented at a first angle with respect to an adjacent surface of the sloped windshield. As discussed above, the light from the light source of LIDAR system  100  may pass through window  3202  (e.g. sloped windshield). As also discussed above, in the disclosed embodiments, the optical angle of the optical path before passing through the windshield may be oriented at a first angle, for example, □ 1 . 
     According to some exemplary embodiments of this disclosure, the LIDAR system includes at least one sensor configured to detect light received through the windshield optical interface, wherein the optical interface is configured to alter the optical angle of the optical path from the first angle to a second angle, such that at the second angle, there is a ratio of greater than about 0.3 between light refracted through the windshield and light reflected from the windshield. As discussed above, and by way of example,  FIGS.  4 A- 4 C  illustrate exemplary embodiments of the sensor (e.g.  116 ) consistent with embodiments of the present disclosure. Sensor  116  may be configured to receive and detect light passing through optical interface (e.g.  3410 ,  3430 , etc.) As also discussed above, it is contemplated that a ratio between the amount of light refracted through the windshield and the amount of light reflected from the windshield may be greater than about 0.2, greater than about 0.25, greater than about 0.3, greater than about 0.35, or greater than about 0.4, etc. 
     According to some exemplary embodiments of this disclosure, the LIDAR system includes at least one processor. As discussed above, and by way of example,  FIGS.  2 A and  2 B  illustrate exemplary embodiments of a processor (e.g.  118 ) consistent with embodiments of the present disclosure. In accordance with the present disclosure, the processor is configured to determine a distance between the vehicle and the object based on signals received from the at least one sensor. As discussed above, and by way of example, as illustrated in  FIG.  2 A , processor  118  may be configured to determine a distance between object  208  and LIDAR system  100  which may be associated with a vehicle based on one or more signals generated by the at least one sensor (e.g.  118 ). 
     According to embodiments of this disclosure, in the LIDAR system at least a portion of the optical interface protrudes from the windshield. In some exemplary embodiments, the protrusion of the optical interface is inward. In other exemplary embodiments, the protrusion of the optical interface is outward. As illustrated above in  FIG.  34 A , prism  3410  may protrude from window  3202  on both sides, although it is contemplated that prism  3410  may protrude from window  3202  on only one side. Inner prism  3412  of prism  3410  may protrude inward from window  3202  towards LIDAR system  100 . Outer prism  3414  may protrude outward from window  3202  towards environment  3216 . 
     In accordance with embodiments of the present disclosure, in the LIDAR system, the optical interface is located only on an inside of the windshield. With reference to  FIG.  34 A , in some exemplary embodiments, prism  3410  may include only one of inner and outer prisms  3412  and  3414 . In embodiments that include only the inner prism  3412 , inner prism  3412  may be located on an inside of window  3202 . 
     In accordance with the present disclosure, the optical interface in the LIDAR system includes a first portion located on an external surface of the windshield and an internal portion located within the vehicle. In other exemplary embodiments, the internal portion within the vehicle is located on an internal surface of the windshield. In yet other embodiments, the windshield optical interface is affixed to an internal surface of the windshield. As discussed in  FIG.  34 A , prism  3410  may include a first portion (e.g. external prism  3414 ) positioned on external surface  3405  of window or windshield  3202 . As also illustrated in  FIG.  34   , in some exemplary embodiments, internal prism  3412  may be affixed to inner surface  3403  of window  3202 . 
     In accordance with some embodiments of the present disclosure, the optical interface in the LIDAR system may include a stepped surface. In accordance with other embodiments of the present disclosure, the optical interface may include a toothed surface. By way of example,  FIG.  34 C  illustrates optical interface (e.g. prism  3450 ), which may include internal prism  3412  and external prism  3454 . As discussed above, external prism  3454  may include a stepped outer surface  3459 , which may include one or more stepped sections  3456 . As also discussed above,  FIG.  34 D  illustrates an external prism  3474  that may include a toothed outer surface  3476 , which may include one or more toothed sections  3476 . 
     According to various exemplary embodiments of the present disclosure, in the LIDAR system, the optical interface may include a secondary window affixed to the windshield. As discussed above,  FIG.  36    illustrates an exemplary embodiment of a vehicle system  3400 , which may include secondary window  3610 . 
     According to various exemplary embodiments of the present disclosure, in the LIDAR system, the optical interface includes at least one of a grating, prism, or a light deflector. As discussed above,  FIG.  37 A  illustrates an exemplary embodiment of grating  3616  or  3618  that may be attached to surface  3614  of secondary window  3610 . 
     Referring to various configurations in which the LIDAR system is installed within the vehicle and its projected light is transferred through a windshield (or another window such as a rear window or side window), it is noted that if the connection between the LIDAR system and the window may leak LIDAR radiation into the interior of the vehicle, such leakage may cause an eye-safety concern, may interfere with other systems within the vehicle, and so on. 
     Reflection from the windshield may be incident to the car interior where it may encounter objects. These objects, in turn, may reflect the light hitting them, and their reflectivity may have Lambertian nature and/or specular nature that is usually uncontrolled. For example, leaked light may be uncontrollably deflected from a car dashboard. This reflected laser light may be harmful for the eyes of the people sitting in the car, and also could potentially be reflected back to the LiDAR creating undesired noise/imaginary targets or other problems. 
     At the typical private car rake angles approach 25 deg angles or less, the reflection at certain angles with very large angle of incidence on the windshield will be relatively strong, which can make the problem more severe. 
     The following LIDAR systems (as well as light control systems for installing with a LIDAR system within a vehicle) may be used in order to block leakage of light, in a way that will not affect the LiDAR functionality. 
     The following systems implement one or both of the following with respect to stray light: 
     1. Reflect the light to areas where the reflection does not interfere or is not absorbed. 
     2. Absorb the light in a “sufficient” manner (depending on the LiDAR specification). 
     Different solutions may be implemented relative to different parts of the scanned LIDAR FOV and/or for different parts of the vehicle interior. 
       FIG.  38 B  is an example of a LIDAR system  3856  and optical components designed and positioned for reflecting the light to areas where the reflection does not interfere or where it may be absorbed, in accordance with examples of the presently disclosed subject matter. Laser beam  3851  is reflected from the windshield  3852  and bounces to an internal casing  3853  that reflects the light  3854  again to a desired location. The desired location could be either another beam trap  3855  ( FIG.  38 B ) or even toward the outside of the vehicle, as seen in  FIG.  38 C . 
     Description of another light reflection strategy is represented in  FIG.  38 D . Laser beam  3851  is reflected from the windshield  3852  and bounces to an internal casing  3853  that absorbs the impacting laser beam.  FIGS.  38 E- 38 G  illustrate three potential structures that may be used in conjunction with internal casing  3853  and/or beam trap  3855  to absorb an impacting laser beam. Any of the examples shown in  FIGS.  38 B- 38 G  may be used in combination with or as partial or full substitutions with any of the structures or system configurations discussed elsewhere in this disclosure. 
     In accordance with embodiments of the present disclosure, a method of calibrating a LIDAR system in a vehicle system is disclosed. The method may include a step of positioning the LIDAR system within an environment of a window associated with a vehicle. By way of example,  FIG.  39    illustrates an exemplary method  3900  for calibration of a LIDAR system, in accordance with the presently disclosed subject matter. It is contemplated that calibration method  3900  may also be used for “Fresnel prisms” or other non-continuous type of prisms discussed above with reference to, for example,  FIGS.  34 - 38   . The order and arrangement of steps in method  3900  is provided for purposes of illustration. As will be appreciated from this disclosure, modifications may be made to process  3900  by, for example, adding, combining, removing, and/or rearranging one or more steps of process  3900 . 
     Method  3900  may include a step  3910  of positioning a LIDAR system (or a part thereof) and/or one or more prisms within the environment of a window (e.g., a windshield  3202  of a car). Positioning of the LIDAR system (e.g. LIDAR system  100 ) may include positioning of the illumination module (e.g. light source  112 ) and/or of the sensor (e.g.  116 ) of the LIDAR system (e.g.  100 ). As discussed above, some parts of the system (e.g. the prisms  3410 ,  3430 ,  3450 ,  3470 , etc.) may be manufactured together with an existing component of the vehicle (e.g. prisms integrated into the window; LIDAR parts integrated with the vehicle systems) etc. 
     According to some embodiments of this disclosure, the method may include a step of illuminating at least one optical interface using a light source associated with the LIDAR system. By way of example,  FIG.  39    illustrates exemplary steps of method  3900  that may be used for calibration of the emission and/or reception of light by the LIDAR system (e.g. LIDAR system  100 ). It is noted that the calibration may include determining a scanning pattern of a scanning module of the LIDAR system (e.g. a mirror, an optical phased array), an illumination pattern of the LIDAR system, positioning of optical components of the LIDAR system, modifying of operational parameters of the LIDAR system (e.g. dynamic range of the sensor), and/or any combination of the above. For example, calibration may include matching the scanning pattern of a scanning LIDAR system so that the illumination and/or reception of light would be executed at continuous parts (e.g. surfaces  3460  or  3480 ) of the prism (e.g. along the rows of the Fresnel prisms exemplified in  FIG.  34 D ). 
     Method  3900  may include step  3920  of illuminating the prisms by using, for example, one or more light sources (e.g.  112 ) of the LIDAR system. In some exemplary embodiments, illuminating in step  3920  may be executed by an external system located adjacent the window (e.g. window  3402 ). It is noted that additionally or alternatively illumination by the LIDAR system may be used also when calibrating the sensor and/or the reception path. The calibration of both directions, for example, outbound illumination (e.g. light travelling from LIDAR system  100  to environment  3216 ) and inbound illumination (e.g. light travelling from the environment  3216  to LIDAR system  100 ) may be performed concurrently. 
     In accordance with exemplary embodiments of this disclosure, the method of calibrating the LIDAR system may include a step of detecting, using at least one sensor, light from the light source after the light has interacted with the at least one optical interface. For example, as illustrated in  FIG.  39   , method  3900  may include step  3930  of detecting the light after it has optically interacted (e.g. been reflected, refracted, diffracted, etc.) with the one or more prisms. Step  3930  may include detection of transmitted light and/or of reflected light. The detection of light in step  3930  may be executed by one or more sensors (e.g.  116 ) of the LIDAR system (e.g.  100 ). In some exemplary embodiments, the detection of light in step  3930  may be executed by an external system located adjacent the window (e.g., when calibrating the illumination pattern and/or the scanning of the transmission path). Additionally or alternatively, sensors (e.g.  116 ) of the LIDAR system may be used with the external system during calibration. The calibration of both directions, for example, outbound illumination (e.g. light travelling from LIDAR system  100  to environment  3216 ) and inbound illumination (e.g. light travelling from environment  3216  to LIDAR system  100 ) may be performed concurrently. 
     According to some exemplary embodiments of this disclosure, the method of calibrating the LIDAR system may include a step of modifying at least one operational parameter of the LIDAR system based on a signal from the at least one sensor. Method  3900  may include step  3940  of modifying an operational parameter of the LIDAR system, based on the results of, for example, the detection of light in step  3930 . Some examples of operational parameters which may be determined and/or modified may include: 
     a. Scanning pattern of a scanning module of the LIDAR system (e.g. a mirror, an optical phased array, etc.); 
     b. An illumination pattern of the LIDAR system; 
     c. Positioning of optical components of the LIDAR system; 
     d. Operational parameters of a sensor of the LIDAR system (e.g. dynamic range, biases). 
     For example, the calibration in method  3900  may include matching the scanning pattern of a scanning LIDAR system so that the illumination and/or reception of light would be executed at continuous parts (e.g. surfaces  3460  or  3480 ) of the prism (e.g. along the rows of the Fresnel prisms exemplified in  FIG.  34 D ). 
       FIG.  40    is a flow chart, illustrating an exemplary method  4000  for installation of a LIDAR system and optical interface on a vehicle. In particular, method  4000  illustrates the steps for installing an optical interface on a vehicle, which is already equipped with a LIDAR system (e.g. LIDAR system  100 ). The order and arrangement of steps in method  4000  is provided for purposes of illustration. As will be appreciated from this disclosure, modifications may be made to process  4000  by, for example, adding, combining, removing, and/or rearranging one or more steps of process  4000   
     Method  4000  may include a step  4010  of projecting light from the one or more light sources (e.g.  112 ) of the LIDAR system installed in the vehicle. Projecting light may include operating one or more MEMS mirror assemblies (e.g.  1100 ) to project one or more light beams towards different portions of a windshield (e.g. window  3402 ) positioned in front of the LIDAR system. For example, one or more controllers (e.g.  118 ) associated with LIDAR system  100  may issue instructions to one or more actuators (e.g.  1112 ) of the one or more MEMS mirror assemblies to adjust the positions of one or more MEMS mirrors (e.g.  1102 ) such that light from a light source within LIDAR system  100  may be projected onto different portions of windshield  3402 . 
     Method  4000  may include a step  4020  of detecting the light at different window locations. In some exemplary embodiments, this may be achieved by placing one or more sensors outside the vehicle, for example in a field of view in front of the windshield. In other exemplary embodiments, the LIDAR system within the vehicle may detect light received from the different locations of the windshield onto which light may be projected, for example, as in step  4010 . 
     Method  4000  may include a step  4030  of determining the position or positions of one or more than one optical interfaces on the windshield based on the detected light. For example, as discussed above, the amount of transmitted light from a windshield is a function of the optical incidence angle of the light. Thus, one or more controllers (e.g.  118 ) associated with LIDAR system (e.g.  100 ) may determine an amount of light transmitted through the various window locations based on signals received by sensors external to the vehicle or based on the light detected by the LIDAR system. The one or more controllers associated with the LIDAR system may determine the positions on the windshield requiring placement of one or more optical interfaces to, for example increase an amount of transmitted light through that portion of the windshield, or, for example, to ensure that a predetermined amount of light projected by the LIDAR system is transmitted through the window. In some exemplary embodiments, the one or more controllers may also determine the optical characteristics of the one or more optical interfaces required to, for example increase the transmittance of light through the optical interfaces. 
     Method  4000  may also include a step  4040  of attaching one or more optical interfaces to the windshield. For example, in step  4040 , one or more optical interfaces (e.g.  3410 ,  3430 ,  3450 ,  3470 , etc.) may be positioned adjacent to or in contact with one or more of inner and/or outer surfaces  3403  or  3405  of window  3402  based on the positions of the optical interfaces determined, for example, in step  4030 . After positioning the optical interfaces, steps  4010 - 4040  of method  4000  may be repeated to optimize the amount of light transmitted through window  3402 . 
     It is contemplated that in some embodiments, the LIDAR system may be installed in a vehicle after installing the optical interfaces on a window of the vehicle. In these situations, it may be possible to adapt the calibration method  3900  discussed above to install the LIDAR system in the vehicle and calibrate the installed LIDAR system based on the already installed optical interfaces on the window of the vehicle. In one exemplary embodiment, steps  3920 - 3940  may be performed to calibrate LIDAR system (e.g. LIDAR system  100 ) after installing it in a vehicle that already includes one or more of optical interfaces  3410 ,  3430 ,  3450 , and/or  3470  associated with a window  3402 . 
     Several aspects of the disclosure were discussed above. It is noted that any feasible combination of features, aspects, characteristics, structures, etc. which were discussed above—for example, with respect to any one or more of the drawings—may be implemented as is considered as part of the disclosure. Some of those feasible combinations were not discussed in detail for reasons such as brevity and succinctness of the disclosure, but are nevertheless part of the disclosure, and would present themselves to a person who is of skill in the art in view of the above disclosure. 
       FIG.  41 A  illustrates micro-electro-mechanical (MEMS) system  4100 , in accordance with examples of the presently disclosed subject matter. MEMS system  4100  includes an active area (e.g. a MEMS mirror, as illustrated in the example of  FIG.  41 A ) and a frame (also referred to as “support”, e.g. in the above description). Possibly, the active area is completely spaced from the frame (any part of which can move from the plane of the frame) with the exception of a plurality of interconnects. The frame may include a continuous frame (e.g. as illustrated in  FIGS.  11 A and  11 B ) or a frame consisting of two or more separate parts (e.g. as optionally suggested by  FIG.  41 A ). 
     MEMS system  4100  includes two type of actuators—at least one first actuator and at least one second actuator. The different types of actuators allows moving of the active area in different directions. This is enabled even if the piezoelectric material in both type of connectors is implemented in the same side of the wafer (e.g. top, as illustrated). Furthermore, the proposed structure allows to move the active area of the MEMS system in opposing directions (e.g. into and out of the surface of the diagram) using piezoelectric elements implemented on the same side of the wafer, while all piezoelectric elements are being used in pulling (contraction) mode, without necessitating any piezoelectric element to work in push (expansion) mode. 
     Each first actuator has a first end that is mechanically connected to the frame and a second end that is opposite to the first end and is mechanically connected to the active area by a first interconnect element. Each first actuator includes a first actuator-body (e.g. a Si layer, could be made from the same layer of Si as the frame), and a first piezoelectric element which is configured to bend the first actuator-body and move the active area at a first direction when subjected to a first electrical field. In the illustrated example, contracting the first piezoelectric element would pull the first actuator-body out of the surface of the diagram (toward the viewer). 
     Each second actuator has a third end, a middle part, and a fourth end that is opposite to the third end. The third end and the fourth end are mechanically connected to the frame. The middle part is mechanically connected to the active area by a second interconnect element. The second actuator includes a second actuator-body and a second piezoelectric element which is configured to bend the second actuator-body and move the active area at a second direction, opposite to the first direction, when subjected to a second electrical field. In the illustrated example, contracting the first piezoelectric element would push the second actuator-body further deeper than the surface of the diagram (away from the viewer). This may be the result of the piezoelectric material becoming shorter than the Si layer on which it is implemented, and therefore the Si is pushed, to allow the piezoelectric element to shrink. 
     It is noted that the different mechanisms of operations may require different rigidity of connections to the frame. For example, a connection to the frame at a first end may be the most rigid, and a connection to the frame at third ends and fourth ends may be more flexible. The interconnect elements themselves may also have different rigidity levels. For example, the second interconnect may be semi-rigid. 
     As aforementioned, all piezoelectric elements may be implemented on the same side of the silicon layer (or any other one or more layers from which the frame is made). For example, the first piezoelectric element may be positioned at a top part of the first actuator-body and the second piezoelectric element may be positioned at a top part of the second actuator-body. 
     As demonstrated in the example of  FIG.  41 A , two or more of the first actuators may be arraigned in pairs, so that the second ends of the first actuators are adjacent to each other. Those first ends may be positioned in proximity to the middle part of a neighboring second actuator. Generally, the first interconnect element and the second interconnect element may be connected to the active area next to each other (e.g. as exemplified in  FIG.  41 A ). 
     Optionally, MEMS system  4100  may include a plurality of actuation assemblies which are connected to the active area at different sides, each actuation assembly including at least one first actuator and at least one second actuator. In the illustrated example there are two actuation assemblies (to the left and to the right of the MEMS mirror), each including a single second actuator and two first actuators. The connection points of all the actuators of an actuation assembly may be proximate to one another, e.g., as illustrated. 
     Optionally, MEMS system  4100  may include a first actuation assembly connected at a first side of the active area (e.g. the left actuation assembly of  FIG.  41 A ) and a second actuation assembly connected at a second side of the active area, opposing the first side (e.g. the right actuation assembly of  FIG.  41 A ). A first actuator of the first actuation assembly (e.g. actuator B 2 ) moves the active area at the first direction concurrent with a second actuator of the second actuation assembly (e.g. actuator A 1 ) moving the active area at the second direction. This may result, of course, in rotation of the active area (e.g. the MEMS mirror) about an axis of the other area (whether an actual axis or an imaginary rotation axis). It is noted that more than one actuator may be used for concurrently moving the active area in a given direction. In other times, different combinations of actuators may be used to move, rotate or translate the active area with respect to the frame. 
       FIGS.  41 B and  41 C  illustrate two example of optional actuation commands (e.g., voltages, biases, currents) for the different actuation assemblies located at different sides of the active area. As can be seen, actuator of different actuation assemblies may receive similar commands at the same time, while actuators of a single actuation assembly may receive opposing commands at the same time (because their actuation results of movement in opposing directions). Referring to the example of  FIG.  41 A , actuators A 1 , A 2  and A 3  are collectively denoted “A” while actuators B 1 , B 2  and B 3  are collectively denoted “B”. 
     It is noted that more than two actuation assemblies may be used, for moving the active area with more than one degree of freedom, possibly in two or more axes. Optionally, the plurality of actuation assemblies may include at least: a first actuation assembly, a second actuation assembly, a third actuation assembly, and a fourth actuation assembly which are collectively configured to move the active area in two dimensional motion. Referring to the example of  FIG.  41 A , the third actuation assembly may be located on a top part of the diagram and the forth actuation assembly may be located at a bottom part of the diagram. 
     Obviously, MEMS system  4100  may be used for a LIDAR system, which further includes and a processor configured to process detection signals of light reflected by the MEMS mirror. For example, MEMS system  4100  may be implemented as the mirror assembly of LIDAR system  100 . The LIDAR system which includes MEMS system  4100  may further include a controller configured to modify electrical fields applied to the at least one first actuator and to the at least one second actuator to move the MEMS mirror to scan a field of view of the LIDAR system. 
       FIG.  41 D  illustrates a conceptual diagram in which the actuators are represented as springs, and a diagram of stresses applied to different parts of the actuators during movement of the active area, in accordance with examples of the presently disclosed subject matter. 
     It is noted that the LIDAR system may include a plurality of the MEMS mirror of system  4100  (e.g., arranged in an array of mirrors), and a controller which is configured to move the plurality of MEMS mirrors (e.g., in a coordinated manner). 
       FIG.  42 A  illustrates MEMS system  4200 , in accordance with examples of the presently disclosed subject matter. MEMS system  4200  includes an active area (e.g. a MEMS mirror, as illustrated in the example of  FIG.  42 A ) and a frame (also referred to as “support”, e.g. in the above description). Possibly, the active area is completely spaced from the frame (any part of which can move from the plane of the frame) with the exception of a plurality of interconnects. The frame may include a continuous frame (e.g. as illustrated in  FIG.  42 A ) or a frame consisting of two or more separate parts. 
     MEMS system  4200  further includes a plurality of actuator pairs, each pair including two paired actuators which are separately connected using separate interconnects to proximate locations of the active area. For example, in the diagram there are four actuator pairs—pair A (including actuators A 1  and A 2 ) positioned on a top part of the diagram; pair B (including actuators B 1  and B 2 ) positioned on a bottom part of the diagram; pair C (including actuators C 1  and C 2 ) positioned on a left part of the diagram; and pair D (including actuators D 1  and D 2 ) positioned on a right part of the diagram. In each pair, the actuator-ends to which the interconnects are connected may be directed toward each other (e.g., as illustrated in the diagram). 
     While different actuation methods may be used, such as electrostatic or electromagnetic actuation), optionally the actuators may be actuated by piezoelectric actuation. Optionally, each actuator may include a body (e.g., made of silicon) and a piezoelectric element. The piezoelectric element is configured to bend the body and move the active area when subjected to an electrical field. In system  4200 , the piezoelectric elements of the paired actuators may be configured to bend the actuators at the same direction and move the active area when subjected to an electrical field. 
     Referring to system  4200  as a whole, the plurality of actuator pairs includes a first actuator pair (e.g. pair A) whose actuators are configured to rotate the active area about a first axis, and a second actuator pair (e.g. pair C) whose actuators are configured to rotate the active area about a second axis. It is noted that MEMS system  4200  may include more than one first actuator pairs configured to rotate the active area about the first axis (e.g. pairs A and B) and/or more than one second actuator pairs configured to rotate the active area about the second axis (e.g. pairs C and D). If more than one pair of actuators can rotate the active area about a given axis, these actuators may operate concurrently, partly concurrently, at alternating times, or according to any other timing scheme. 
       FIG.  42 B  illustrates two states during operation of a pair of actuators of system  4200 , in accordance with examples of the presently disclosed subject matter. When the actuators of each pair move together in a synchronized fashion, movement perpendicular to the plane of the frame is induced by both of the actuators of the pair, while the structure of pairs of actuators causes movements in the plane of the frame to cancel each other out. Also, the structure of the actuators and the interconnects in each pair may provide sufficient resilience from effects of movement about other axes from moving the respective pair of actuators. E.g., the forces applied on the active area by the first pair of actuators may be controlled by the structure of the second pair of actuators, so as to limit the resulting movement of the actuators of the second pair. 
     Optionally, the second axis is substantially perpendicular to the first axis. 
     Optionally, the interconnects may be elongated so as to allow the paired actuators to move away from one another when extending from a plane of the frame. 
     Optionally, the interconnects may be connected to the actuators at a distanced side of the actuators, which is distanced from the active area (e.g., as illustrated in  FIGS.  42 A and  42 B ). 
     Optionally, movement of the first actuators pair substantially rotates the active area only about the first axis and movement of the second actuators pair substantially rotates the active area only about the second axis. 
     Optionally, the first actuators pair may be configured to rotate the active area about the first axis while the second actuators pair rotates the active area about the second axis. 
     Optionally, at least one of the actuators includes piezoelectric element deployed on a top part of the actuator, and at least another one of the actuators includes piezoelectric element deployed on a bottom part of the other actuator. 
     Optionally, the plurality of actuators may be curved opposite to a curvature of the active area (e.g., as illustrated in  FIGS.  42 A and  42 B ). Optionally, the plurality of actuators may be curved so that an end of each actuator which is connected to the frame is more distanced from an edge of the active area than another end of the actuator to which the interconnect is connected. The difference between the distances may be by a factor of at least three, by a factor of at least five, by a factor of at least ten. Such distances are illustrated in  FIG.  42 A  next to actuator B 2 . 
     The optional curving of the actuators in system  4200  may be used for condensing elongated actuators in a relatively small area of the MEMS system. The structure of symmetrically deployed actuators provide sufficient rigidity to the structure (and hence lower response to lower frequencies of vibration), that that the elongation of the actuators would not hamper the frequency-response of the system. The elongated structure of the actuators may be implemented in order to allow large amplitude of movements outside the plane of the frame. It is noted that the angle of the curve is sufficiently obtuse, so that the piezoelectric element of each actuator will not work against itself. 
     Obviously, MEMS system  4200  may be used for a LIDAR system, which further includes and a processor configured to process detection signals of light reflected by the MEMS mirror. For example, MEMS system  4200  may be implemented as the mirror assembly of LIDAR system  100 . The LIDAR system which includes MEMS system  4200  may further include a controller configured to modify electrical fields applied to the at least actuator, to move the MEMS mirror to scan a field of view of the LIDAR system. 
     It is noted that the LIDAR system may include a plurality of the MEMS mirror of system  4200  (e.g., arranged in an array of mirrors), and a controller which is configured to move the plurality of MEMS mirrors (e.g., in a coordinated manner). 
     Actuations by synchronized pairs of actuators as described with respect to  FIGS.  42 A- 42 B  may be used in different MEMS system, such as MEMS systems  4100  and  2600 . 
       FIG.  43    illustrates MEMS system  4300 , in accordance with examples of the presently disclosed subject matter. System  4300  includes a plurality of insulator layers, which are used for improving accuracies of the manufacturing process. The bottom part of MEMS system  4300  includes elements of differing heights. For example, reinforcement substructure (e.g. ribs) may be manufactured on the bottom side of the active area, to provide it with structural strength while keeping its weight relatively low. Such differing heights may be manufactured by etching, but the etching process may suffer from inaccuracies in both shape and depth, in differences between MEMS systems manufactured in the same process. 
     The proposed system includes two etch-stopper layers (e.g., Silicon oxide, other oxide or another insulator layer) which are used in two different etching steps. 
     A method for manufacturing a MEMS system is disclosed, the method including: 
     Obtaining a wafer which includes at least five different layers (e.g. including at least two separate etch-stopping layers such as discussed above) (e.g. including at least two layers of Silicon or other similar material); Etching parts of a first layer (e.g. bottom layer) of the wafer (e.g. using an oxide, or another etching material), wherein a first etch-stopping layer as a stopper for the etching process. For example, etching parts of Si layer  4311  using layer  4321  as a stopper for the etching process; 
     Etching, grinding or otherwise removing parts of the first etch-stopping layer (e.g., using another etching technique); and 
     Etching parts of a second layer (e.g. bottom layer) of the wafer (e.g. using an oxide, or another etching material), wherein a second etch-stopping layer as a stopper for the etching process. For example, etching parts of Si layer  4312  using layer  4322  as a stopper for the etching process. The second etching process may implement a mask, for generating a substructure for the active area (e.g. MEMS mirror) of a MEMS system (e.g. MEMS system  4300 ). 
     The method may include other processing steps known in the art, such as coating (e.g. photo-resist coating), alignment, exposure and developing, dry etching, photo-resist removal, and so on. The method may include connecting (e.g. bonding) a portion of a glass wafer as a protective layer to the aforementioned multi-layered wafer. While not necessarily so, the connecting of the glass portion (or another transparent material) may be performed before the etching steps. The grass wafer may be processed (e.g. etched, grinded) to provide a hollowness in which the active area of the MEMS system may move. 
     Referring to all of the MEMS system discussed above, it is noted that all of the above systems may be implemented to include a plurality of active areas, which are actuated by respective actuators. Some actuators may be connected to more than one active area, but this is not necessarily so. A controller of any MEMS systems discussed above may be configured to actuate active areas (e.g.—mirrors) of such arrays of active areas in synchronized fashion. 
     It is further noted that while different aspects of MEMS systems were discussed above in subtitled portions of the disclosure for sake of simplicity of disclosure, any combination of characteristics of MEMS systems  4100 ,  2600 ,  4200 ,  1100  and  4300  (or of parts thereof, such as actuators, interconnects, active area, etc.) may be implemented, and is considered part of the presently disclosed subject matter. Some nonlimiting examples for such possible combinations were offered above. 
     Notably, in some diagrams the letters “PZT” were used to referred to one or more piezoelectric elements. It is noted that such piezoelectric elements may be made from Lead zirconate titanate (known as “PZT”), or from any other piezoelectric material. 
     The foregoing description has been presented for purposes of illustration. It is not exhaustive and is not limited to the precise forms or embodiments disclosed. Modifications and adaptations will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments. Additionally, although aspects of the disclosed embodiments are described as being stored in memory, one skilled in the art will appreciate that these aspects can also be stored on other types of computer readable media, such as secondary storage devices, for example, hard disks or CD ROM, or other forms of RAM or ROM, USB media, DVD, Blu-ray, or other optical drive media. 
     Moreover, while illustrative embodiments have been described herein, the scope of any and all embodiments having equivalent elements, modifications, omissions, combinations (e.g., of aspects across various embodiments), adaptations and/or alterations as would be appreciated by those skilled in the art based on the present disclosure. The limitations in the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application. The examples are to be construed as non-exclusive. Furthermore, the steps of the disclosed methods may be modified in any manner, including by reordering steps and/or inserting or deleting steps. It is intended, therefore, that the specification and examples be considered as illustrative only, with a true scope and spirit being indicated by the following claims and their full scope of equivalents.