Patent Publication Number: US-2022229161-A1

Title: Electro-optical systems for scanning illumination onto a field of view and methods

Description:
BACKGROUND 
     I. 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. 
     II. 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. Although 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 light source may increase the temperature inside an electro optical scanning unit of LIDAR systems. This in turn may influence the operation of a mirror of the electro-optical scanning unit used for reflecting the light the light source. Note that the actuation elements and the steering elements of electro-optical scanning units, as well as the mirror surface (bending) and the sensing element may behave differently under different temperatures. 
     To ensure the desired accuracy of the electro-optical scanning unit and the LIDAR system, respectively, during operation, calibrating of the electro-optical scanning unit at different temperatures may be used during manufacture. Further, calibrating of the electro-optical scanning unit may also be required later, for example at regular maintenance intervals. However, the desired calibrating is a long and costly process. 
     According, there is need for the present invention. 
     SUMMARY 
     Embodiments consistent with the present disclosure provide systems and methods for using LIDAR technology to detect objects in the surrounding environment. 
     Consistent with a disclosed embodiment, an electro-optical system for scanning illumination onto a field of view, includes a light source, a scanning unit including a light deflector arranged at a desired height for deflecting light from the light source, at least one actuator for controlling an orientation of the light deflector, and at least two sensors configured to measure respective measuring values which are correlated with a height of the light deflector in the scanning unit and an orientation of the light deflector, and a control unit connected with the at least two sensors and configured to receive for a given time a respective measuring value from each of the at least two sensors, to determine for the given time a first value indicative of an actual height and a second value indicative of an actual orientation of the light deflector as output of a model of the scanning unit using the measuring values as input of the model of the scanning unit, and to determine an actuation parameter for the at least one actuator using the first value and second value. Typically, the electoral optical system is a LIDAR-system or a part thereof. 
     Consistent with a disclosed embodiment, a method for controlling a pivotable light deflector of a scanning unit of an electro-optical system configured to scan illumination onto a field of view, the method includes measuring for a given time at least two measuring values which are correlated with an actual height of the light deflector in the scanning unit and an actual orientation of the light deflector, determining for the given time a first value indicative of the actual height and a second value indicative of the actual orientation of the light deflector using the at least two measuring values as input of a model of the scanning unit, and controlling the light deflector using the first value and the second value. 
     Other embodiments include (non-volatile) computer-readable storage media or devices, and one or more computer programs recorded on one or more computer-readable storage media or computer storage devices. The one or more computer programs can be configured to perform particular operations or processes by virtue of including instructions that, when executed by one or more processors of a system, in particular electro-optical systems as explained herein, cause the system to perform the operations or processes. 
     Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       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. 1A  is a diagram illustrating an exemplary LIDAR system consistent with disclosed embodiments. 
         FIG. 1B  is an image showing an exemplary output of single scanning cycle of a LIDAR system mounted on a vehicle consistent with disclosed embodiments. 
         FIG. 1C  is another image showing a representation of a point cloud model determined from output of a LIDAR system consistent with disclosed embodiments. 
         FIGS. 2A-2G  are diagrams illustrating different configurations of projecting units in accordance with some embodiments of the present disclosure. 
         FIGS. 3A-3D  are diagrams illustrating different configurations of scanning units in accordance with some embodiments of the present disclosure. 
         FIGS. 4A-4E  are diagrams illustrating different configurations of sensing units in accordance with some embodiments of the present disclosure. 
         FIG. 5A  includes four example diagrams illustrating emission patterns in a single frame-time for a single portion of the field of view. 
         FIG. 5B  includes three example diagrams illustrating emission scheme in a single frame-time for the whole field of view. 
         FIG. 5C  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. 6A-6C  are diagrams illustrating a first example implementation consistent with some embodiments of the present disclosure. 
         FIG. 6D  is a diagram illustrating a second example implementation consistent with some embodiments of the present disclosure. 
         FIGS. 7-37C  are diagrams illustrating various examples of MEMS mirrors and associated components incorporated in scanning units of the LIDAR system in accordance with some embodiments of the present disclosure. 
         FIGS. 38A-41  are diagrams illustrating different configurations of electro-optical system in accordance with some embodiments of the present disclosure. 
         FIG. 42  is a flow chart of a method for controlling a pivotable light deflector of a scanning unit of an electro-optical system configured to scan illumination onto a field of view in accordance with some embodiments of the present disclosure. 
         FIG. 43  is a flow chart of a method for controlling a pivotable light deflector of a scanning unit of an electro-optical system configured to scan illumination onto a field of view in accordance with some embodiments of the present disclosure. 
     
    
    
     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 cm 3 ), 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. 2A-2C . 
     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 α, 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., θ 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. 3A-3C . 
     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 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 differ in 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. 4A-4C . 
     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. 5A-5C . 
     System Overview 
       FIG. 1A  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 vehicle 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 reflections 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. 1A , LIDAR system  100  may include a single scanning unit  104  mounted on a roof 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 an 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. 1B  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. 1C  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. 1B ), 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. 2A-2G  depict various configurations of projecting unit  102  and its role in LIDAR system  100 . Specifically,  FIG. 2A  is a diagram illustrating projecting unit  102  with a single light source;  FIG. 2B  is a diagram illustrating a plurality of projecting units  102  with a plurality of light sources aimed at a common light deflector  114 ;  FIG. 2C  is a diagram illustrating projecting unit  102  with a primary and a secondary light sources  112 ;  FIG. 2D  is a diagram illustrating an asymmetrical deflector used in some configurations of projecting unit  102 ;  FIG. 2E  is a diagram illustrating a first configuration of a non-scanning LIDAR system;  FIG. 2F  is a diagram illustrating a second configuration of a non-scanning LIDAR system; and  FIG. 2G  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. 2A  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. In the example depicted in  FIG. 2A , 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. 2E and 2G , 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. 2A , 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. 2B  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 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. 2D . 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. 2B , 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. 2C  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. 2D  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. 2B and 2C . 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. 2D , 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. 2E  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 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. In another 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. 2E  is considered to be a bi-static configuration because the optical paths of the projected light and the reflected light are substantially different. 
       FIG. 2F  illustrates an example of a monostatic configuration of LIDAR system  100  without scanning unit  104 . Similar to the example embodiment represented in  FIG. 2E , 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. 2E , 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 decipted in  FIG. 2E  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 ovelap between the two optical paths may be more than 80%, more than 85%, more than 90%, or more than 95%. 
       FIG. 2G  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. 2A . 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. 2A , 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. 2G  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 pathes of the projected light and the reflected light means that the ovelap 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. 3A-3D  depict various configurations of scanning unit  104  and its role in LIDAR system  100 . Specifically,  FIG. 3A  is a diagram illustrating scanning unit  104  with a MEMS mirror (e.g., square shaped),  FIG. 3B  is a diagram illustrating another scanning unit  104  with a MEMS mirror (e.g., round shaped),  FIG. 3C  is a diagram illustrating scanning unit  104  with an array of reflectors used for monostatic scanning LIDAR system, and  FIG. 3D  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. 3A  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. 
     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. 3B  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. 3A and 3B  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  maybe 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. 2D . 
     In some embodiments (e.g. as exemplified in  FIG. 3C ), 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. 3C  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, in particular a MEMS tilt 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. 3D  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. 3D  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. 4A-4E  depict various configurations of sensing unit  106  and its role in LIDAR system  100 . Specifically,  FIG. 4A  is a diagram illustrating an example sensing unit  106  with a detector array,  FIG. 4B  is a diagram illustrating monostatic scanning using a two-dimensional sensor,  FIG. 4C  is a diagram illustrating an example of a two-dimensional sensor  116 ,  FIG. 4D  is a diagram illustrating a lens array associated with sensor  116 , and  FIG. 4E  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. 4A  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. 4A , 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. 4B  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. 4B , sensor  116  is a matrix of  4 X 6  detectors  410  (also referred to as “pixels”). In one embodiment, a pixel size may be about lxlmm. 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. 4C  is a diagram illustrating an example of a two-dimensional sensor  116 . In this embodiment, sensor  116  is a matrix of  8 X 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. 4C  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. 4B , 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. 4D  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. 4D , 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. 4D , 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. 4D ) 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. 4D ). Such blockage reduces the total optical light absorbing efficiency of the detector. 
       FIG. 4E  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. 4E , 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. 4E , 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. 4E  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. 
     The Processing Unit 
       FIGS. 5A-5C  depict different functionalities of processing units  108  in accordance with some embodiments of the present disclosure. Specifically,  FIG. 5A  is a diagram illustrating emission patterns in a single frame-time for a single portion of the field of view,  FIG. 5B  is a diagram illustrating emission scheme in a single frame-time for the whole field of view, and.  FIG. 5C  is a diagram illustrating the actual light emission projected towards field of view during a single scanning cycle. 
       FIG. 5A  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. 5A  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. 5B  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 on 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. 5B  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. 5C  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. 5C  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. 5C  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. 
     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. 5C , 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. 6A-6C  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. 6A , 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. 6B  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. 6C  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. 6D  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. 6D , 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 objects 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. 
     Example Implementation: MEMS Mirror and Actuation Techniques 
       FIG. 7  illustrates an example embodiment of a scanning device (e.g., deflector  114  hereinafter “scanning device  8202 ”) and a processing device (e.g., processor  118  hereinafter controller  8204 ). Consistent with the present disclosure, controller  8204  may be local and included within scanning device  8202 . Controller  8204  may include at least one hardware component, one or more integrated circuits, one or more FPGAs, one or more ASICs, one or more hardware accelerators, and the like. A central processor unit (CPU) and an actuation driver are some examples of a controller  8204 . 
     As shown in  FIG. 7 , a mirror configuration may include mirror  8206  which can be moved in two or more axes (θ, φ). Mirror  8206  may be associated with an electrically controllable electromechanical driver such as actuation driver  8208 . Actuation driver  8208  may cause movement or power to be relayed to an actuator/cantilever/bender such as actuator  8210 . Actuator  8210  may be part of a support frame such as frame  8211 . Additional actuators, such as actuators  8212 ,  8214  and  8216 , may each be controlled/driven by additional actuation drivers as shown, and may each have a support frame  8213 ,  8215  and  8217  (appropriately). It is understood that frames  8211 ,  8213 ,  8215  and/or  8217  may comprise a single frame supporting all of the actuators or may be a plurality of interconnected frames. Furthermore, the frames may be electrically separated by isolation elements or sections. Optionally, a flexible interconnect element or connector (interconnect), such as spring  8218 , may be utilized to adjoin actuator  8210  to mirror  8206 , to relay power or movement from actuation driver  8208  to spring  8218 . 
     Actuator  8210  may include two or more electrical contacts such as contacts  8210 A,  8210 B,  8210 C and  8210 D. Optionally, one or more contacts  8210 A,  8210 B,  8210 C and/or  8210 D may be situated on frame  8211  or actuator  8210  provided that they are electronically connected. According to some embodiments, actuator  8210  may be a semiconductor which may be doped so that sections actuator  8210  (except the piezoelectrical layer that is insulative) is generally conductive between contacts  8210 A- 210 D and isolative in isolation  8220  and  8222  to electronically isolate actuator  8210  from actuators  8212  and  8216  (respectively). Optionally, instead of doping the actuator, actuator  8210  may include a conductive element which may be adhered or otherwise mechanically or chemically connected to actuator  8210 , in which case isolation elements may be inherent in the areas of actuator  8210  that do not have a conductive element adhered to them. Actuator  8210  may include a piezoelectric layer so that current flowing through actuator  8210  may cause a reaction in the piezoelectric section which may cause actuator  8210  to controllably bend. 
     According to some embodiments, Controller  8204  may output/relay to mirror driver  8224  a desired angular position described by θ, φ parameters. Mirror driver  8224  may be configured to control movement of mirror  8206  and may cause actuation driver  8224  to push a certain voltage amplitude to contacts  8210 C and  8210 D in order to attempt to achieve specific requested values for θ, φ deflection values of mirror  8206  based on bending of actuators  8210 ,  8212 ,  8214  and  8216 . In addition, position feedback control circuitry may be configured to supply an electrical source (such as voltage or current) to a contact, such as contact  8210 A or  8210 B, and the other contact (such as  8210 B or  8210 A, respectively) may be connected to a sensor within position feedback  8226 , which may be utilized to measure one or more electrical parameters of actuator  8210  to determine a bending of actuator  8210  and appropriately an actual deflection of mirror  8206 . As shown, additional positional feedback similar to position feedback  8226  and an additional actuation driver similar to actuation driver  8208  may be replicated for each of actuators  8212 - 216  and mirror driver  8224  and controller  8204  may control those elements as well so that a mirror deflection is controlled for all directions. 
     The actuation drivers including actuation driver  8208  may push forward a signal that causes an electromechanical reaction in actuators  8210 - 216  which each, in turn is sampled for feedback. The feedback on the actuators&#39; ( 8210 - 8216 ) positions serves as a signal to mirror driver  8224 , enabling it to converge efficiently towards the desired position θ, φ set by the controller  8204 , correcting a requested value based on a detected actual deflection. According to some embodiments, a scanning device or LIDAR may utilize piezoelectric actuator micro electro mechanical (MEMS) mirror devices for deflecting a laser beam scanning a field of view. Mirror  8206  deflection is a result of voltage potential applied to the piezoelectric element that is built up on actuator  8210 . Mirror  8206  deflection is translated into an angular scanning pattern that may not behave in a linear fashion, for a certain voltage level actuator  8210  does not translate to a constant displacement value. A scanning LIDAR system (e.g., LIDAR system  100 ) where the field of view dimensions are deterministic and repeatable across different devices is optimally realized using a closed loop method that provides an angular deflection feedback from position feedback and sensor  8226  to mirror driver  8224  and/or controller  8204 . 
     In some embodiments, position feedback and sensor  8226  may also be utilized as a reliability feedback module. According to some embodiments, a plurality of elements may include semiconductors or conducting elements, or a layer and accordingly, actuators  8201 - 8216  could at least partially include a semiconducting element, springs  8218 ,  8226 ,  8228  and  8230  may each include a semiconductor, and so may mirror  8206 . Electrical Power (current and/or voltage) may be supplied at a first actuator contact via position feedback  8226 , and position feedback  8226  may sense an appropriate signal at actuator  8212 ,  8214  and/or  8216  via contacts  8214 A or  8214 B and/or  8216 A or  8216 B. Some of the following figures illustrate MEMS mirrors, actuators and interconnects. The number of interconnects, the shape of the interconnects, the number of actuators, the shape of the actuators, the shape of the MEMS mirror, and the spatial relationships between any of the MEMS mirror, actuators and interconnects may differ from those illustrated in the following figures. 
     Interconnects 
       FIG. 8  illustrates four L-shaped interconnects  9021 ,  9022 ,  9023  and  9024  that are connected between circular MEMS mirror  9002  and four actuators  9011 ,  9012 ,  9013  and  9014 . Each L-shaped interconnect (for example  9021 ) includes a first segment  90212  and a second segment  90211 . The first and second segments are mechanically connected to each other. In  FIG. 8  the first and second segments are normal to each other. In  FIG. 8  the second segment of each L-shaped interconnect is connected to a circumference or an edge of an actuator and the first segment of each L-shaped interconnect is connected to the circumference or edge of the MEMS mirror. The second segment  90211  is normal to the circumference or edge of first actuator. The first segment is normal to the circumference of the MEMS mirror and/or may be directed towards a center of the MEMS mirror when the MEMS mirror is at an idle position. The MEMS mirror is at an idle position when all of the actuators that are coupled to the MEMS mirror are not subjected to a bending electrical field. 
     In one embodiment, using L-shaped interconnects may provide superior durability and stress relief. Using the L-shaped interconnects facilitates seamless movement about two axes of rotation (see dashed lines denoted AOR near interconnect  9024 ) that are normal to each other. Thereby, the bending and unbending of an actuator does not impose an undue stress on the L-shaped interconnect. Furthermore, the L-shaped interconnects are relatively compact and may have a small volume, which reduces the mechanical load imposed on the actuators, and may assist in increasing the scanning amplitude of the MEMS mirror. It should be noted that the different segments of the interconnect may be oriented in relation to each other (and/or in relation to the MEMS mirror and/or in relation to the actuator) by angles that differ from ninety degrees. These angles may be substantially equal to ninety degrees (substantially may mean a deviation that does not exceed 5, 10, 15 or 20 percent and the like). It should further be noted that the L-shaped interconnects may be replaced by interconnects that include a single segment or more than a pair of segments. An interconnect that has more than a single segment may include segments that are equal to each other and/or segments that differ from each other. Segments may differ by shape, size, cross section, or any other parameter. An interconnect may also include linear segments and/or nonlinear segments. An interconnect may be connected to the MEMS mirror and/or to the actuator in any manner. 
       FIG. 9  illustrates four interconnects  9021 ′,  9022 ′,  9023 ′ and  9024 ′ that are connected between circular MEMS mirror  9002  and four actuators  9011 ,  9012 ,  9013  and  9014 . The first and second segments of each interconnect are connected by joints. For example, interconnect  9021 ′ includes a first segment  90212 , a second segment  90211  and a joint  90213  that is connected to the first and second segments and facilitates relative movement between the first and second interconnects. The joint may be a ball joint or any other type of joint. 
       FIG. 10  illustrates ten non-limiting examples of interconnects. Interconnects  90215 ,  90216 ,  90217 ,  90218  and  90219  do not include joints. Interconnects  90215 ′,  90216 ′,  90217 ′,  90218 ′ and  90219 ′ do include at least one joint. In addition,  FIG. 10  illustrates interconnects that include linear segments, nonlinear segments, one segments, two segments and even nine segments. The interconnects may include any number of segments, have segments of any shape, and may include zero to multiple joints. 
     Response to Mechanical Vibrations 
     A scanning unit (e.g., scanning unit  104 ) may include the MEMS mirror, the actuators, the interconnector and other structural elements of the LIDAR system. Scanning unit  104  may be subjected to mechanical vibrations that propagate along different directions. For example, a LIDAR system that is installed in a vehicle may be subjected to different vibrations (from different directions) when the vehicle moves from one point to another. If all actuators have the same structure and dimensions the response of the unit to some frequencies may be very high (high Q factor). By introducing a certain asymmetry between the actuators, scanning unit  104  may react to more frequencies, however, the reaction may be milder (low Q factor). 
       FIG. 11  illustrates a first pair of actuators  9011  and  9013  that are opposite to each other and are shorter (by DeltaL  9040 ) than actuators of a second pair of actuators  9012  and  9014 . Actuators  9012  and  9014  are opposite to each other and are oriented to actuators  9011  and  9013 .  FIG. 11  also illustrates L-shaped interconnects  9021 ,  9022 ,  9023  and  9024 , and a circular MEMS mirror  9002 . The resonance frequency of the unit may be outside the frequency range of the mechanical vibrations. The resonance frequency of the unit may exceed a maximal frequency of the certain frequency range by a factor of at least two. The resonance frequency of the unit is between four hundred hertz and one Kilohertz. 
       FIG. 12  illustrates a frame  9050  that surrounds the actuators  9011 ,  9012 ,  9013  and  9014 , the interconnects  9021 ,  9022 ,  9023  and  9024 , and the MEMS mirror  9002 . Actuators  9011 ,  9012 ,  9013  and  9014  are connected to the frame  9050  at their bases  9071 ,  9072 ,  9072  and  9074  respectively. In one embodiment, the width of the base may be any fraction (for example below 50%) of the entire length of the actuator. In addition, the base may be positioned at any distance from point of connection of the actuator to the interconnect. For example, the base may be positioned near an end of the actuators that is opposite to the end of the connector that is connected to the interconnect. 
       FIG. 13  illustrates a frame  9050  that surrounds the actuators  9011 ,  9012 ,  9013  and  9014 , the interconnects  9021 ,  9022 ,  9023  and  9024 , and the MEMS mirror  9002 .  FIG. 13  also illustrates a variable capacitor  9061  that is formed between the frame  9050  and actuator  9011 . Variable capacitor  9061  includes multiple plates first plates  90612  that are connected to the actuator and multiple second plates  90611  that are connected to the frame. It may be beneficial to have at least three variable capacitors between at least three actuators and the frame. For simplicity of explanation only a single variable capacitor is shown. The variable capacitor may be located anywhere along the circumference of the actuator, and at any distance from the circumference of the actuator that is connected to the interconnect. In addition, the location of the variable capacitor may be determined based on the shape and size of the plates of the variable capacitor, and the amount of bending that can be experienced by different parts of the actuator. For example, positioning the variable capacitor near the base will result in smaller changed in the overlap area between the first and second plates, while positioning the variable capacitor near the connection point to the interconnect may result in a lack of overlap between the first and second plates. 
       FIG. 13  also illustrates (from left to right) first and second plates ( 90611  and  90612 ) that fully overlap, then (as the actuator starts bending) mostly overlap (overlap area  9068 ), and then only slightly overlap (small overlap area  9068 ) when the actuator continues to bend. The first plates  90612  are coupled in parallel to each other. The second plates  90611  are coupled in parallel to each other. The first and second plates are coupled to a capacitance sensor  9065  that is configured to sense the capacitance of the variable capacitor. A controller of the LIDAR system may estimate the orientation indicated by lines  9069  of the MEMS mirror based on the capacitance of one or variable capacitors. 
       FIG. 14  illustrates a frame  9050  that surrounds the actuators  9011 ,  9012 ,  9013  and  9014 , the interconnects  9021 ,  9022 ,  9023  and  9024 , and the MEMS mirror  9002 .  FIG. 14  also illustrates electrodes  9081 ,  9082 ,  9083  and  9084  that are connected to actuators  9011 ,  9012 ,  9013  and  9014 . The electrodes may be connected to any part of the actuators. An actuator may be connected to multiple electrodes. The electrodes usually spread along significant regions of the actuator. 
     Monitoring the MEMS Mirror Using Dummy Piezoelectric Elements 
     Consistent with the present disclosure, the provided electrode may convey electrical signals for bending the actuator and/or for sensing the bending of the actuator. The bending of the actuators may be monitored by using actuators that include dummy elements. The dummy elements may be dummy electrodes and dummy piezoelectric elements. A dummy piezoelectric element is mechanically coupled to a piezoelectric element that is subjected to a bending electrical field. The piezoelectric element is bent. This bending causes the dummy piezoelectric element to bend. The bending of the dummy piezoelectric element can be measured by electrodes coupled to the dummy piezoelectric element. Therefore, the dummy piezoelectric elements may form or be part of a feedback sensor. Accordingly, the dummy elements and the dummy piezoelectric elements are in the following also referred to as sensing elements and sensing piezoelectric elements, respectively. 
       FIG. 15  illustrates frame  9050  that surrounds the actuators  9011 ,  9012 ,  9013  and  9014 , the interconnects  9021 ,  9022 ,  9023  and  9024 , and the MEMS mirror  9002 .  FIG. 15  also illustrates electrodes  9081 ,  9082 ,  9083  and  9084  that are connected to piezoelectric elements  9111 ,  9112 ,  9113  and  9114  of actuators  9011 ,  9012 ,  9013  and  9014 . Electrodes  9081 ,  9082 ,  9083  and  9084  are used to convey bending control signals.  FIG. 15  also illustrates electrodes  9091 ,  9092 ,  9093  and  9094  that are connected to dummy piezoelectric elements  9011 ′,  9112 ′,  9113 ′ and  9114 ′ of actuators  9011 ,  9012 ,  9013  and  9014 . Electrodes  9091 ,  9092 ,  9093  and  9094  are used to measure the state of dummy piezoelectric elements  9011 ′,  9112 ′,  9113 ′ and  9114 ′. Electrodes  9081 ,  9082 ,  9083 ,  9084 ,  9091 ,  9092 ,  9093  and  9094  usually cover a significant part of the piezoelectric elements. It should be noted that each piezoelectric element is positioned between pairs of electrodes, and that  FIG. 15  illustrates only the external electrodes. Internal electrodes located between a substrate (or a body) of the actuator and the piezoelectric elements are not shown. 
       FIG. 16  is a cross sectional view of an actuator  9011 , a feedback sensor  9142  and a steering source signal  9140 . The actuator  9011  may include substrate (or body) layer  9121 , internal electrode  9081 ′, internal dummy electrode  9091 ′, piezoelectric element  9111 , dummy piezoelectric element  9111 ′, external electrode  9081  and external dummy electrode  9091 . Steering signal sensor  9140  sends steering signals SS 1   9151  and SS 2   9152  to external electrode  9081  and internal electrode  9121  for bending actuator  9011 . Feedback sensor  9142  sensed the bending of the dully piezoelectrical element  9111 ′ be measuring the electrical field between internal dummy electrode  9091 ′ and external dummy electrode  9091 . It should be noted that only one steering signal may be provided. 
       FIG. 17  illustrates that each actuator out of actuators  9011 ,  9012 ,  9013  and  9014  can be formed from four major layers: external electrode layer ( 9124 ,  9134 ,  9144  and  9154 ), a piezoelectric layer ( 9123 ,  9133 ,  9143  and  9153 ), internal electrode layer ( 9122 ,  9132 ,  9142  and  9152 ), and a substrate (or body) layer ( 9121 ,  9131 ,  9141  and  9151 ). 
     Monitoring the MEMS Mirror by Measuring Dielectric Coefficient Changes 
     Consistent with the present disclosure, the bending of the actuator may change the dielectric coefficient of the piezoelectric element. Accordingly, the actuator may be monitored by measuring changes in the dielectric coefficient of the piezoelectric element. The actuator may be fed with electrical field induced by one or more control signals from a control signal source, the one or more control signals are fed to one or more electrodes of LIDAR system  100 , for example, a pair of electrodes that are positioned on opposite sides of the piezoelectric element. One control signal, both control signals and/or a difference between the control signals have an alternating bias component and a steering component. The bending of the body is responsive to the steering component. In some embodiments, the frequency of the alternating bias component may exceed a maximal frequency of the steering component (for example, by a factor of at least ten); and the amplitude of the alternating bias component may be lower than an amplitude of the steering component by any factor, for example, a factor that is not smaller than one hundred. For example, the steering component may be tens of volts while the alternating bias component may range between tens to hundreds of millivolts. Therefore, a sensor of LIDAR system  100  may be configured to sense dielectric coefficient changes of the actuator due to the bending of the actuator. 
       FIG. 18  illustrates an actuator that includes external electrode layer  9124 , piezoelectric layer  9123 , internal electrode layer  9122  and a substrate layer  9121 . Steering signal source  9140  sends control signal SS 1   9151  to external electrode layer  9124  and sends control signal SS 2   9152  to internal electrode layer  9122 . At least one of control signals SS 1   9151  and SS 2   9152  or the difference between the control signals includes the alternating bias component and the steering component. Feedback sensor  9124  is coupled to external electrode layer  9124 , and to internal electrode layer  9122  and may sense (directly or indirectly) changes of the dielectric coefficients of piezoelectric layer  9123 . Feedback sensor  9124  may be, for example, a current amplitude sensor or a combination of a current amplitude sensor and a phase shift sensor. The LIDAR sensor may include a controller that may be configured to receive (from feedback sensor  9142 ) information about the dielectric coefficient changes and to determine an orientation of the MEMS mirror.  FIG. 18  also illustrates the steering signal source  9140  as including an initial signals source  9141  that outputs the steering components ( 9161  and  9164 ) of control signals SS 1   9151  and SS 2   9152 . These steering components are mixed (by mixers  9163  and  9165 ) with the alternating bias components (generated by oscillators  9162  and  9165 ) to generate control signals SS 1   9151  and SS 2   9152 . The actuator may be monitored by sensing the resistance of the actuator. 
       FIG. 19  illustrates two electrodes  9211  and  9212  that are positioned at two opposite ends of actuator  9011 , and are used for measuring the resistance of the actuator. Electrode  9135  is used for bending the actuator. Electrodes  9211 ,  9212  and  9135  are electrically coupled to three conductors  9201 ,  9202  and  9203 . 
       FIG. 20  illustrates stress relief apertures  9220  that are formed in actuator  9011 . The stress relief apertures of  FIG. 20  are curved and are substantially parallel to each other. The number of the stress relief apertures may differ from four, the slots may have any shape or size and may differ from each other. In some of the previous figures the piezoelectric element was positioned above the substrate. It should be noted that the piezoelectric element may be positioned below the substrate. Piezoelectric elements may be positioned below and above the substrate. 
       FIG. 21  illustrates actuator  9012  as including seven major layers: external electrode layer  9124 , piezoelectric layer  9123 , internal electrode layer  9122 , substrate (or body) layer  9121 , additional internal electrode layer  9129 , additional piezoelectric layer  9128 , and additional external electrode layer  9127 . External electrode layer  9124 , piezoelectric layer  9123  and internal electrode layer  9122  are positioned above substrate layer  9121 . Additional internal electrode layer  9129 , additional piezoelectric layer  9128 , and additional external electrode layer  9127  are positioned below substrate layer  9121 . The additional piezoelectric layer  9128  may equal the piezoelectric layer  9123  or may differ from the piezoelectric layer  9123  by at least one out of size, shape and the like. Specifically, any of the electrode layers may be the same or may differ from each other. Additional piezoelectric layer  9128  and piezoelectric layer  9123  may be controlled independently from each other or in a dependent manner. Additional piezoelectric layer  9128  may also be used for bending the actuator downwards while piezoelectric layer  9123  may be used for bending the actuator upwards. The additional piezoelectric layer  9128  may be used as a dummy piezoelectrical sensor (for monitoring the actuator) when the piezoelectric layer  9123  is activated for bending the actuator. In one example, the piezoelectric layer  9122  may be used as a dummy piezoelectrical sensor (for monitoring the actuator) when the piezoelectric layer  9128  is activated for bending the actuator. 
       FIG. 22  illustrates, from top to bottom, (A) an idle state of mirror  9002 , (B) a downward bent actuator that lowers the circumference of MEMS mirror  9002 , and (C) an upward bent actuator that elevates the circumference of MEMS mirror  9002 . MEMS mirror  9002  is coupled to the actuator via interconnect  9300 . The MEMS mirror  9002  may include a thin reflecting surface that is reinforced by reinforcing elements. 
       FIGS. 23 and 24  illustrate frame  9050  and a backside of MEMS mirror  9002 . For simplicity of explanation the actuators are not shown. The reinforcing elements  9003  include concentric rings and radial segment. Any arrangement and shapes of reinforcing elements may be provided. 
     The orientation of the MEMS mirror may be monitored by illuminating the backside of the MEMS mirror  9002 . It may be beneficial to illuminate at least one area of the MEMS mirror and to sense reflected light in at least three locations. The orientation of the MEMS mirror may be monitored by illuminating the backside of the MEMS mirror  9002 . It may be beneficial to illuminate at least one area of the back side of the MEMS mirror and to sense reflected light in at least three locations. It is noted that LIDAR system  100  may include a dedicated light source for illuminating the back side of the MEMS mirror. The dedicated light source (e.g., LED) may be located behind the mirror (i.e., away from its main reflective sensor used for the deflection of light from the at least one light source  112 ). Alternatively, LIDAR system  100  may include optics to direct light onto the back side of the mirror. In some examples, light directed at the back side of the MEMS mirror (e.g. light of the dedicated light source) is confined to a backside area of the mirror, and prevented from reaching the main reflective side of the MEMS mirror. The processing of the signals of the back side sensors may be executed by processor  118 , but may also be processed by a dedicated circuitry integrated into a chip positioned within a casing of the mirror. The processing may include comparing the reflected signals to different back side sensors (e.g.  9231 ,  9232 ,  9233 ), subtracting such signals, normalizing such signals, etc. The processing of such signals may be based on information collected during a calibration phase. 
       FIG. 25  illustrates an illuminated region  9030  and three sensors  9231 ,  9232  and  9233  that are positioned below the MEMS mirror and are arranged to sense light that is reflected (dashed lines) at three different directions thereby allowing to sense the orientation of the MEMS mirror. The illuminated region may be located anywhere at the backside of the MEMS mirror, and may have any shape and size. In embodiment, the MEMS mirror may not be parallel to a window of the Lidar system. The MEMS mirror may receive a light that passes through a window of the Lidar system and deflects the reflected mirror to provide deflected light that may pass through the window and reach other components (such as light sensors) of the Lidar system. A part of the deflected light may be reflected (by the window) backwards—toward the MEMS mirror, the frame or the actuators. However, when the MEMS mirror and the window are parallel to each other the light may be repetitively reflected by the MEMS mirror and the window thereby generating unwanted light artifacts. These light artifacts may be attenuated and even prevented by providing a window that is not parallel to the MEMS mirror or when the optical axis of the MEMS mirror and the optical axis of the window are not parallel to each other. When either one of the MEMS mirror and the window are curved or have multiple sections that are oriented to each other—then it may be beneficial that no part of the MEMS mirror should be parallel to any part of the window. The angle between the window and the MEMS mirror may be set so that the window does not reflect light towards the MEMS mirror, when the MEMS mirror is at an idle position or even when the MEMS mirror is moved by any of the actuators. 
     It is noted that illuminating a backside of the MEMS mirror may be implemented when the back of the mirror is substantially uniformly reflective (e.g. a flat back, without reinforcement ribs). However, this is not necessarily the case, and the back of the mirror may be design to reflect light in a patterned non-uniform way. The patterned reflection behavior of the back side of the mirror may be achieved in various way, such as surface geometry (e.g. protrusions, intrusions), surface textures, differing materials (e.g., Silicon, Silicon Oxide, metal), and so on. Optionally, the MEMS mirror may include a patterned back side, having a reflectivity pattern on at least a part of the back surface of the mirror, which cast a patterned reflection of the back side illumination (e.g. from the aforementioned back side dedicated light source) onto the back side sensors (e.g.  9231 ,  9232 ,  9233 ). The patterned back side may optionally include parts of the optional reinforcing elements  9003  located at the back of the MEMS mirror, but this is not necessarily so. For example, the reinforcing elements  9003  may be used to create shadows onto the sensors  9231  etc. at some angles (or to deflect the light to a different angle), which means that movement of the mirror would change the reflection on the sensor from shadowed to bright. 
     Optionally, the processing of the outputs of the backside sensors ( 9231 ,  9232 ,  9233  etc.) may take into account a reflectivity pattern of the backside (e.g. resulting from the pattern of the reinforcement ribs). Thus, the processing may use the patterning resulting from the backside surface pattern as part of the feedback being processed. Optionally, the backside mirror feedback option discussed herein may utilize a backside reflectivity pattern which can be processed by data from backside sensors which are located in greater proximity to the mirror (comparing to the uniform reflectivity implementation), which reduce the size of the MEMS assembly and improves its packaging. For example, the back side pattern may de designed so that the reflection pattern includes sharp transitions between dark and bright reflections. Those sharp transitions mean that even small changes in the angle/position of the MEMS mirror would cause significant changes in the light reflected to detectors which are positioned in even close distance. In addition, the reflectivity pattern may be associated with a reflectivity gradient, not sharp edges (i.e.—light or shadow). This embodiment, may have linearity from the first option of sharp edges, thus it may ease the post-processing process, and also support a larger angles range and will probably be less sensitive to assembly tolerances. 
     MEMS Mirror that is not Parallel to a Window of the LIDAR System 
     Consistent with the present disclosure, the MEMS mirror may receive a light that passes through a window of the LIDAR system and deflects the reflected mirror to provide deflected light that may pass through the window and reach other components (such as light sensors) of LIDAR system  100 . A part of the deflected light may be reflected (by the window) backwards, toward the MEMS mirror, the frame or the actuators. When the MEMS mirror and the window are parallel to each other, the light may be repetitively reflected by the MEMS mirror and the window thereby generating unwanted light artifacts. These light artifacts may be attenuated and even prevented by providing a window that is not parallel to the MEMS mirror or when the optical axis of the MEMS mirror and the optical axis of the window are not parallel to each other. When either one of the MEMS mirror and the window are curved or have multiple sections that are oriented to each other, then it may be beneficial that no part of the MEMS mirror should be parallel to any part of the window. The angle between the window and the MEMS mirror may be set so that the window does not reflect light towards the MEMS mirror, when the MEMS mirror is at an idle position or even when the MEMS mirror is moved by any of the actuators. 
       FIG. 26  illustrates a housing  9320  that includes window  9322 . The housing encloses the MEMS mirror  9002 . Housing  9320  may be a sealed housing that may be manufactured using wafer level packaging or any other technology. Housing  9320  includes a base  9310 . Base  9310  may be transparent or not transparent. A transparent base may be useful when the backside of MEMS mirror  9002  is monitored by illumination. Light  9601  passes through window  9322  and impinges on MEMS mirror  9002 . MEMS mirror  9002  deflects the light to provide a deflected light  9602 . A part of the deflected light may pass through window  9322 , but another part  9603  is reflected by mirror  9322  towards housing  9320 . Accordingly, part  9603  may not reflected towards MEMS mirror  9002 . 
       FIG. 27  illustrates the housing  9320  as including an upper part. The upper part includes mirror  9320  and two sidewalls  9321  and  9323 . An intermediate part of the housing may be formed from the exterior part (such as but not limited to frame  9050 ) of an integrated circuit that includes various layers (such as  9121  and  9122 ). The integrated circuit may include MEMS mirror  9002  (having an upper reflecting surface  9004 , various intermediate elements of layers  9121  and  9122 , and reinforcing elements  9003 ), interconnects  9022  and  9021 , actuators  9012  and  9014 . A bonding layer  9301  may be positioned between the integrated circuit and base  9310 . 
       FIG. 28  illustrates the housing  9320  that includes a transparent base. For simplicity of explanation this figure illustrates illumination unit  9243 , beam splitter  9263  and a sensor  9253 . Illumination unit  9243  and the light sensor  9253  are positioned outside the housing. 
       FIG. 29  illustrates an anti-reflective layer  9380  that is positioned on top of the actuators, and the interconnects.  FIG. 30  illustrates anti-reflective layer  9380  that is positioned on top of the actuators, frame and the interconnects.  FIG. 31  illustrates anti-reflective layer  9380  that is positioned on top of the frame. Any of the mentioned above anti-reflective layers may be replaced by one or more anti-reflective elements that may differ from a layer. The anti-reflective element may be parallel to the window, oriented in relation to the window, and the like. 
       FIG. 32  illustrates a housing that has a window that is parallel to the MEMS window. The housing includes a transparent base. For simplicity of explanation this figure illustrates illumination unit  9243 , beam splitter  9263  and a sensor  9253 . Illumination unit  9243  and the light sensor  9253  are positioned outside the housing. The MEMS mirror may be of any shape or size. For example, the MEMS mirror may be rectangular. 
       FIGS. 33 and 34  illustrate a rectangular MEMS mirror  9402 , two actuators  9404  and  9407 , two interconnects  9403  and  9406 , electrodes  9410  and  9413 , and a rectangular frame that includes an upper part  9504 , a lower part  9408  and two insulating parts  9411  and  9422  that are connected between the upper and lower parts of the frame. In  FIG. 33 , actuators  9404  and  9407  are parallel to each other opposite, face opposite sides of the MEMS mirror and are connected to opposite parts of the frame. In  FIG. 34 , actuators  9404  and  9407  are parallel to each other opposite, face opposite sides of the MEMS mirror and are connected to the same side of the frame. 
       FIG. 35  illustrates a rectangular MEMS mirror  9402 , four actuators  9404 ,  9407 ,  9424 ,  9427 , four interconnects  9403 ,  9406 ,  9423  and  9436 , four electrodes  9410 ,  9413 ,  9440  and  9443 , and a rectangular frame that includes an upper part  9504 , a lower part  9408  and two insulating parts  9411  and  9422  that are connected between the upper and lower parts of the frame. The four actuators face four facets of MEMS mirrors  9402  and each is connected to a different facet of the frame. Although  FIGS. 30-36  illustrate a single MEMS mirror. LIDAR system  100  may include an array of multiple MEMS mirrors. Any number of MEMS mirrors may be monitored in order to provide feedback that is used to control any of the multiple MEMS mirrors. For example, if there are more N MEMS mirrors than any number between 1 and N, MEMS mirrors may be monitored to provide feedback that may be used for monitoring any number of MEMS mirrors of the N MEMS mirrors. 
     In one embodiment, LIDAR system  100  may include a window for receiving light; a microelectromechanical (MEMS) mirror for deflecting the light to provide a deflected light; a frame; actuators; interconnect elements that may be mechanically connected between the actuators and the MEMS mirror. Each actuator may include a body and a piezoelectric element. The piezoelectric element may be configured to bend the body and move the MEMS mirror when subjected to an electrical field. When the MEMS mirror is positioned at an idle positioned it may be oriented in relation to the window. The light may be reflected light that may be within at least a segment of a field of view of the LIDAR system. The light may be transmitted light from a light source of the LIDAR system. During a first period the light is a transmitted light from a light source of the LIDAR system and during a second period the light is reflected light that is within at least a segment of a field of view of the LIDAR system. 
     In another embodiment, LIDAR system  100  may include at least one anti-reflective element that may be positioned between the window and the frame The anti-reflective element may be oriented in relation to the window. The angle of orientation between the MEMS mirror and the window may range between  20  and  70  degrees. The window may be shaped and positioned to prevent a reflection of any part of the deflected light towards the MEMS mirror. The MEMS mirror may be oriented to the window even when moved by at least one of the actuators. An interconnect element of the interconnect elements may include a first segment that may be connected to the MEMS mirror and a second segment that may be connected to the actuator, wherein the first segment and the second segments may be mechanically coupled to each other. 
     In related embodiments: the first segment may be oriented by substantially ninety degrees to the second segment; the first segment may be connected to a circumference of the MEMS mirror and may be oriented by substantially ninety degrees to circumference of the MEMS mirror; the first segment may be directed towards a center of the MEMS mirror when the MEMS mirror is positioned at an idle position; the second segment connected to a circumference of the actuator and may be oriented by substantially ninety degrees to the circumference of the actuator; a longitudinal axis of the second segment may be substantially parallel to a longitudinal axis of the actuator; the first segment and the second segment may be arranged in an L-shape when the MEMS mirror is positioned at an idle position; the interconnect element may include at least one additional segment that may be mechanically coupled between the first and second segments; the first segment and the second segment may differ from each other by length; the first segment and the second segment may differ from each other by width; the first segment and the second segment may differ from each other by a shape of a cross section; the first segment and the second segment may be positioned at a same plane as the MEMS mirror when the MEMS mirror is positioned at an idle position. The first segment and the second segment may be positioned at a same plane as the actuators. 
     In another embodiment, LIDAR system  100  may include a MEMS mirror that may have an elliptical shape (e.g., the MEMS mirror may be circular), and wherein the actuators may include at least three independently controlled actuators. Each pair of actuator and interconnect elements may be directly connected between the frame and the MEMS mirror. The MEMS mirror may be operable to pivot about two axes of rotation. 
     In related embodiments, the actuators may include at least four independently controlled actuators; a longitudinal axis of the MEMS mirror corresponds to a longitudinal axis of the light beam; a longitudinal axis of MEMS mirror corresponds to a longitudinal axis of a detector array of the LIDAR system; the actuators may include a first pair of actuators that may be opposite to each other along a first direction and a second pair of actuators that may be opposite to each other along a second direction; the first pair of actuators may differ from the second pair of actuators; the window, the MEMS mirror, the frame and the actuators may form a unit; the unit may respond differently to mechanical vibration that propagate along the first direction and to mechanical vibrations that propagate along the second direction; the actuators of the first pair, when idle, may have a length that substantially differs from a length of the actuators of the second pair, when idle; the actuators of the first pair, when idle, may have a shape that substantially differs from a shape of the actuators of the second pair, when idle; during operation, the LIDAR system may be subjected to mechanical vibrations having a certain frequency range; the resonance frequency of a unit may be outside the certain frequency range; the resonance frequency of the unit may exceed a maximal frequency of the certain frequency range by a factor of at least two; the resonance frequency of the unit may be between four hundred hertz and one Kilohertz; an actuator may include a piezoelectric element that may be positioned below the body of the actuator and another actuator may include a piezoelectric element that may be positioned above the body of the other piezoelectric element; the actuator may include a piezoelectric element that may be positioned above the body of the piezoelectric element; the LIDAR system may further include a controller which may be configured to receive from the sensor an indication of the state of the additional piezoelectric element; the controller may be configured to control the actuator based on the indication of the state of the additional piezoelectric element; and the controller may be configured to determine an orientation of the MEMS mirror based on the indication of the state of the additional piezoelectric element. 
     In another embodiment, LIDAR system  100  may include a variable capacitor and a sensor. The capacitance of the variable capacitor represents a spatial relationship between the frame and an actuator of the actuators. the sensor may be configured to sense the capacitance of the variable capacitor. 
     In related embodiments, the variable capacitor may include a first plate that may be connected to the actuator and a second plate that may be connected to the frame. the spatial relationship between the frame and the actuator determines an overlap between the first plate and the second plate; the variable capacitor may include multiple first plates that may be connected to the actuator and multiple second plates that may be connected to the frame; the actuator has 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 interconnect element; a distance between the variable capacitor and the first end exceeds a distance between the variable capacitor and the second end; the actuator has 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 interconnect element; and a distance between the variable capacitor and the first end may be smaller than a distance between the variable capacitor and the second end. 
     In another embodiment, LIDAR system  100  may include a controller which may be configured to receive an indication of a capacitance of the variable capacitor and to determine an orientation of the MEMS mirror based on the capacitance of the variable capacitor. A piezoelectric element may be configured to bend the body and move the MEMS mirror when subjected to an electrical field induced by a control signal from a control signal source, the control signal may be fed to an electrode of the LIDAR system. 
     The control signal has an alternating bias component and a steering component. A bending of the body may be responsive to the steering components, wherein a frequency of the alternating bias component exceeds a maximal frequency of the steering component. The sensor may be configured to sense dielectric coefficient changes of the actuator due to the bending of the actuator. 
     In related embodiments, the sensor may be a current amplitude sensor; the sensor may also be a current amplitude sensor and a phase shift sensor; an amplitude of the alternating bias component may be lower than an amplitude of the steering component by a factor of at least one hundred; the LIDAR system may further include a controller which may be configured to receive information about the dielectric coefficient changes and to determine an orientation of the MEMS mirror; the window may belong to a housing. The housing may be a sealed housing that encloses the MEMS mirror, the frame, and the actuators; the housing may include a transparent region that may be positioned below the MEMS mirror; the LIDAR system may further include at least one optical sensor and at least one light source, the at least one light source may be configured to transmit at least one light beam through the transparent region and towards a backside of the MEMS mirror; the at least one optical sensor may be configured to receive light from the backside of the MEMS mirror; the LIDAR system may include a controller which may be configured to determine an orientation of the MEMS mirror based on information from the at least one optical sensor; different parts of the housing may be formed by wafer level packaging; the frame may belong to an integrated circuit that forms a bottom region of the housing; an interconnect element of the interconnect elements may include multiple segments that may be mechanically coupled to each other by at least one joint; the joint may be a ball joint; and the joint may also be a MEMS joint. 
     MEMS Mirror Assembly Including a Strain Gauge 
       FIG. 36  illustrates a Microelectromechanical system (MEMS) mirror assembly according to embodiments. The MEMS mirror assembly may function as the scanning unit of LIDAR system  100 , of another LIDAR system, of another electro-optic system, or of any other system. The MEMS mirror assembly includes a MEMS mirror (or any other MEMS functional surface such as a piston or a valve), a frame (a supportive structure, possibly sharing wafer layers with the mirrors and/or actuators), and a plurality of actuators operable to rotate the MEMS mirror with respect to a plane of the frame. Each actuator is connected to the mirror by one or more interconnect element. The actuators elements may be actuated by piezoelectric actuation, capacitive actuation, magnetic actuation, thermal actuation, electromagnetic actuation, or any other way known in the art. The MEMS mirror assembly further includes a plurality of strain gauges, each strain gauge is used for measuring a movement of an actuator and includes:
         a. A plurality of interconnected resistors implemented on the MEMS mirror assembly, the plurality of interconnected resistors including: (i) at least one movable resistor implemented on the actuator and (ii) at least one immovable resistor implemented on the frame (or on another immovable part of the MEMS mirror assembly); and   b. Circuitry for processing the response of the plurality of interconnected resistors to applied voltage to determine at least one electrical property of the at least one movable resistor, and to determine a location of the actuator based on the at least one movable resistor.       

     The circuitry (or another processor) may determine a position (e.g., location, tile angle and/or height) of the MEMS mirror based on the determined locations of one or more of the actuators which move the mirror. 
     In the example of  FIG. 7 , strain gauge was illustrated only for one of the actuators (the lower right actuator in the diagram out of the four actuators of the system). In different LIDAR systems, such strain gauges may be implemented for one, some, or all of the actuators of the MEMS mirror. Referring to the examples of  FIGS. 37A, 37B and 37C , it is noted that the example may be implemented for a mirror which is actuated by four actuators denoted “A”, “B”, “C”, and “D” (arranged around the mirror in this order). The strain gauge for each of the actuators is marked using the same reference letter (“A”, “B”, “C”, and “D”, respectively). 
     Referring to the example of  FIG. 36 , it is noted that the power assembly which applies voltages to the different resistor may be implemented on the wafer (as illustrated in the example), but this is not necessarily so. The power assembly may be implemented anywhere in the LIDAR system, and be connected electrically to components on the wafer (especially some or all of the resistors). Referring to the example of  FIG. 36 , it is noted that the comparator or other processor may be implemented on the wafer (as illustrated in the example), but this is not necessarily so. The comparator or other processor may be implemented anywhere in the LIDAR system, and be connected electrically to components on the wafer (especially some or all of the resistors). 
     The one or more movable resistor move as the actuator on which the actuator in which they are implemented moves, and are designed so that their resistivity changes as they move. The resistivity of the movable resistor changes with the movement of the actuator due to strain or other forces (especially—mechanical forces) which are applied onto the movable resistor as a result of the movement. For example, the movement of the actuator may result in stretching of the movable resistor and therefor in increased resistivity. 
     The circuitry which is used to assess the electrical property of the at least one movable resistor based on the response of the plurality of interconnected resistors to applied voltage may include, for example, a bridge circuit which includes the plurality of interconnected resistors. The bridge circuit may be a Wheatstone bridge or any other type of bridge. The circuitry may assess the resistance of the movable actuator directly or indirectly, and may alternatively assess other electromagnetic parameters of the one or more resistors (such as impedance). The strain gauge may include other electric component not discussed above (e.g., capacitors, inductors, comparators, amplifiers). 
     While not necessarily so, the actuator may include at least one actuation electrode implemented on a same layer as the at least one movable resistor. For example, the actuation electrode and the movable resistor may include parts made of platinum/titanium/etc., which are implemented on the same layer (platinum/titanium/etc.) of the wafer. Alternatively, these components may be implemented on any other conductive layer of the wafer. The actuation electrode may belong to a piezoelectric actuation assembly of the actuator, or to any other type of actuation assembly. Optionally, the at least one movable resistor and the at least one immovable resistor are made of titanium. 
     In the example of  FIG. 36  there are four resistors and all of them are implemented on the wafer of the MEMS mirror assembly. Nevertheless, the plurality of interconnected resistors may include one or more resistors that are external to a wafer of the MEMS mirror. Other parts of the strain gauge may also be optionally implemented outside the wafer (e.g.—the aforementioned circuitry). Some or all of the resistors may be implemented as elongated pieces of metal, but other forms of resistors may also be used. 
     While not necessarily so, the movable resistor may be implemented on the actuator in proximity to an immovable resistor which is implemented on the frame (e.g., as exemplified in  FIG. 36 ). The relative proximity means that the resistors (movable and immovable) are subject to similar physical conditions (especially temperature, but also other ambient factors) and therefore both resistors react similarly to changes in conditions (e.g., due to changes in temperature). The circuitry of the strain gauge may be designed so that changes to both resistors happens concurrently and in unison, and the circuitry is designed so that such changes (e.g., due to temperature) do not significantly affect the determination of the position of the actuator. For example, the movable resistor may be located less than 1 mm, 0.5 mm, 0.2 mm, 0.1 mm etc. from one or more of the immovable resistors. 
       FIGS. 37A, 37B, and 37C  are electric charts of the circuitry and the resistors of the MEMS mirror assembly, in accordance with examples of the presently disclosed subject matter.  FIG. 37A  illustrates a simple bridge. As exemplified in  FIG. 37B , the strain gauge may include power assembly for providing a plurality of voltages to the plurality of interconnected resistors at different times. This may be used, for example, in order to improve a dynamic range of the resistors, or to overcome inaccuracies in the manufacturing accuracy of the resistance of the resistors. The Digital to Analog Converter (DAC) circuits may be used to define the dynamic range of output signals which are generated in the possible locations of the respective actuator. 
     Optionally (e.g., as exemplified in  FIG. 37C ), the circuitry may determine the relative position of two actuators with respect to each other, or be otherwise indicative of the positions of more than one actuator. 
     Electrooptical System for Scanning Illumination onto a Field of View 
       FIGS. 38A-41  are diagrams illustrating different configurations of electro-optical systems. The illustrated exemplary electro-optical systems typically represent parts of a scanning unit  104  of a LIDAR-system as explained above. In  FIGS. 38A and 38B , a light source  112  of a projecting unit  102  of the LIDAR-system is additionally shown. 
     The light source  112  is typically a laser, for example an infrared laser. The projecting unit  102  may have more than one light source. However, only one light source  112  is illustrated in  FIGS. 38A, 38B  for sake of clarity. 
     As illustrated in  FIGS. 38A, 38B , the scanning unit  104  has a pivotable light deflector  114  arranged at a desired height h for deflecting light from the (at least one) main light source  112  at a main reflective side  114   m.    
     The desired height h may be a calibration height of the light deflector  114  in the scanning unit  104  and/or a height of the light deflector  114  at rest. 
     Typically, the light deflector  114  is a mirror, in particular a MEMS mirror. 
     Further, the scanning unit  104  has at least one actuator (not shown) for controlling an orientation θ, ϕ of the pivotable light deflector. 
     As indicated by the rotational angles (also referred to as pivot angles) θ, ϕ, the exemplary light deflector  114  is a dual axis light deflector such as dual axis MEMS mirror for deflecting incident light from the light source  112  with two degrees of freedom. 
     For example, the angles θ, ϕ of deflection of a dual axis MEMS mirror may vary within a range of about 30° with respect to the (vertical) direction z and within a range of about 50° with respect to an independent second direction. Note that a dual axis MEMS mirror may be configured to deflect light in a horizontal direction and in a vertical direction. 
     In other embodiments, the light deflector is a single axis light deflector. 
     As illustrated by the full arrows in  FIGS. 38A, 38B , the directions of the reflected light may deviate from the desired directions (dashed arrows) when the height of the light deflector  114  is, at a given time t, changed from a desired height h to a different height h′, even if the rotational angles θ, ϕ remain unchanged as illustrated in  FIG. 38A . In  FIG. 38B  as situation is illustrated in which the rotational angles θ, ϕ are changed in addition to different values θ′, ϕ′. 
     Thus, projected light exiting the system may be changed due to undesired height changes of the light deflector  114 . Geometrically this is due to changing the arrangement of the light source  112  with respect to the light deflector  114 . 
     Likewise, reflected light entering the system may be changed due to undesired height changes of the light deflector(s). This also applies to bi-static configurations, in which the reflected light entering the system pass through a substantially different optical path to a sensor for detecting the reflected light from the FOV. 
     Accordingly, the accuracy and/or reliability of scanning a FOV and detecting objects in the FOV may be reduced if the height of the light deflector  114  within the scanning unit  104  changes in an undesired way. 
     Typically, the height h and the orientation (pivot angles) θ, ϕ of the light deflector  114  are determined with respect to a coordinate system x, y, z which is defined by the scanning unit  104 . 
     The coordinate system x, y, z may be fixed with respect to a frame of the scanning unit  104 , a baseplate of the scanning unit  104 , a main surface of a mounting plate of the scanning unit  104  used for mounting the actuator  302  and the light deflector  114 , respectively. In embodiments referring to MEMS-mirrors as light deflector, the coordinate system x, y, z may be fixed with respect to a wafer of the respective MEMS-mirror, for example a main surface of the wafer. 
     Accordingly, the height of the light deflector may refer to a respective distance of the light deflector from the mounting plate or the wafer. In particular, the height may refer to a direction perpendicular to a main surface of the mounting plate or the wafer. 
     The height may also refer to a direction perpendicular the main reflective side of the light deflector or a central portion thereof 
     Further, the height may refer to a direction of an optical axis of the light deflector (at rest). 
     Even further, the height may refer to a distance of a center of the light deflector from a center of the light deflector at rest and/or in a calibrated position. 
     As the system and method explained herein aim at suppressing or at least reducing undesired height changes, different suitable coordinate systems x,y,z may be used for measuring the heights. However, the coordinate systems x,y,z is typically at least fixed with respect to a non-moving part of the scanning unit  104  even during scanning a FOV. For example, the coordinate systems x,y,z used for measuring the height may be fixed with respect to a frame of the scanning unit  104  or point of the light deflector  114  that does at least substantially not move during scanning operation of the scanning unit  104 , e.g. a center point of the light deflector  114 , a center of mass of the light deflector  114 . The coordinate systems x,y,z may be fixed with respect to a mass center of the scanning unit  104 . 
     Note that the undesired height changes of the light deflector  114  may occur even if the light deflector  114  is mounted at fixed desired height (un-hinged light deflector). 
     Physically, the undesired height changes of the light deflector  114  may be due to a temperature change that may be caused by the light source  112  or other reasons. 
     Note that the properties of actuator(s) for controlling the orientation θ, ϕ of the light deflector  114  and any sensing element as well as a bending of the main reflective side  114   m  (mirror surface) of the light deflector  114  may be temperature dependent. Furthermore, the temperature dependencies of these elements may be different. 
     The exemplary embodiment illustrated in  FIG. 39A  refers to single axis scanning unit  104 . The illustrated scanning unit  104  has an internal light source  113  for illuminating a backside  114   b  of the light deflector  114  and two light sensors  115 A,  115 B which are configured to measure respective measuring values S 1 , S 2  representing a respective portion of light that is received from (scattered and/or reflected at) the backside  114  during illumination with the internal light source  113 . 
     The internal light source  113  may be a dedicated light source, in particular an LED. The dedicated light source (e.g., LED) may, with respect to the light source  112  used for scanning, be located behind the mirror, i.e. behind the main reflective side  114   m.    
     To avoid and/or reduce interferences with light of the main light source  112 , the spectra of the internal light source  113  and the main light source  112  are typically at least substantially disjunct. 
     In other words, the backside  114   b  is typically arranged between the main reflective side  114   m  and at least one of the internal light source  113  and the light sensors  115 A,  115 B. 
     Alternatively, the system may include optics to direct light onto the back side of the light deflector  114 . In some examples, light directed, e.g. via a beam splitter to the back side of the light deflector  114  (e.g. light of the main light source used for scanning the FOV) is confined to a backside area of the light deflector  114 , and prevented from reaching the main reflective side  114   m.    
     Due to the arrangement of the internal light source  113  and the light sensors  115 A,  115 B, the measuring values S 1 , S 2  depend on the height of the light deflector  114  and the orientation of the light deflector  114 . Therefore, the light sensors  115 A,  115 B are in the following also referred as feedback sensors. 
     The measuring values S 1 , S 2  may be determined continuously throughout the scanning path, or discerningly at several points in each scanning cycle. For example, measuring values S 1 , S 2  may be measured with a rate of at least a few times per cycle, at least hundred times per cycle, or even at least 1000 times per cycle. 
     Further, the light sensors  115 A,  115 B may measure a light intensity and/or a polarization of the light received during illuminating the backside  114   b  of the light deflector for determining the values S 1 , S 2 . 
     Based on the measuring values S 1 , S 2 , one or more actuation parameters cs may be determined and send to one or more actuators  302  such that an undesired height change and/or undesired orientation deviation is (expected to be) reduced in the next time step. The controlling of the light deflector is typically performed in a closed-loop manner. 
     Accordingly, the above described undesired height changes (and/or undesired orientation deviations) of the light deflector  114 , in particular undesired height changes which are due to temperature changes may be avoided or at least substantially reduced, in particular kept within a desired height range h 0 +/−Δh from a height h 0 , in particular a height h 0  in which the system was calibrated. 
     For example, the ratio Δh/h 0  may be less than 5%, more typically less than 1% or even 0.5%. 
     Accordingly, time consuming, complicated calibration procedures may be avoided. 
     Surprisingly, this approach is more reliable, more accurate and/or computationally less demanding compared to measuring the temperature inside the scanning unit  104  and taking into account (explicitly) measured temperature value(s) as a basis for calculating the actuation parameter(s). 
     This is mainly due to the fact that the temperature dependencies of the relevant elements of the scanning unit  104  including the actuators  302  and sensors  115 A,  115 B (efficiency, gain) differ and may even change with time. Even further, the elements of the scanning unit  104  may have different response times with respect to temperature changes. Accordingly, it is difficult to take into account all these dependencies explicitly. 
     Depending on the measurement frequency of the measuring values S 1 , S 2 , the measuring values S 1 , S 2  may be averaged prior to further processing. 
     Typically, a model of the scanning unit  104  is used for determining suitable actuation parameter(s) cs for correcting displacements. 
     In particular, the measuring values S 1 , S 2  may be fed as input to the model of the scanning unit  104  that determines a first value indicative of an actual height h(t) and a second value indicative of an actual orientation θ(t) of the light deflector  114  at the measuring time t. 
     The model of the scanning unit  104  may be based on a set of differential equations describing the properties of the scanning unit (at least mechanical properties) or a suitable approximation of the set of differential equations. 
     However, the model of the scanning unit  104  may also be implemented as a so-called neural network, in particular a trained neural network. Once trained, a neural network may be very reliable and/or efficient for determining the values indicative of the actual height and the actual orientation. Accordingly, memory footprint may be reduced and/or performance improved. 
     The term “neural network” (NN) as used in this specification intends to describe an artificial neural network (ANN) or connectionist system including a plurality of connected units or nodes called artificial neurons. The output signal of an artificial neuron is calculated by a (non-linear) activation function of the sum of its inputs signal(s). The connections between the artificial neurons typically have respective weights (gain factors for the transferred output signal(s)) that are adjusted during one or more learning phases. Other parameters of the NN that may or may not be modified during learning may include parameters of the activation function of the artificial neurons such as a threshold. Often, the artificial neurons are organized in layers which are also called modules. The most basic NN architecture, which is known as a “Multi-Layer Perceptron”, is a sequence of so called fully connected layers. A layer consists of multiple distinct units (neurons) each computing a linear combination of the input followed by a nonlinear activation function. Different layers (of neurons) may perform different kinds of transformations on their respective inputs. Neural networks may be implemented in software, firmware, hardware, or any combination thereof. In the learning phase(s), a machine learning method, in particular a supervised, unsupervised or semi-supervised (deep) learning method may be used. For example, a deep learning technique, in particular a gradient descent technique such as backpropagation may be used for training of (feedforward) NNs having a layered architecture. Modern computer hardware, e.g. GPUs makes backpropagation efficient for many-layered neural networks. 
     After determining, the first value and second value may be used to determine actuation parameter(s) cs for the actuator(s)  302  of the light deflector  104 . 
     As indicated in  FIG. 39A  by the capital letter M in the box  109  representing the control unit, the processes of determining the actuation parameter(s) are typically carried out by the control unit  109  receiving the measuring values S 1 , S 2  from the sensors  115 A,  115 B. 
     In other words, the control unit  109  is typically connected with the sensors  115 A,  115 B and configured to receive from each of the sensors  115 A,  115 B a respective measuring value S 1 , S 2  obtained for a given time t, to determine for the given time t values which are indicative of an actual height h(t) and an actual orientation θ(t) of the light deflector as output of a model of the scanning unit  104  using the measuring values S 1 , S 2  as input of the model of the scanning unit  104 , to determine, based on the determined values, one or more actuation parameter cs for the one or more actuators  302 , and to send the one or more actuation parameter cs to the one or more actuators  302 . 
     Typically, a closed-loop control of the height h(t) is performed. 
     Note that the control unit  109  is typically separate from but connected with the processing unit  108  explained above. However, the control unit  109  may also be a part of the processing unit  108 . 
     The exemplary embodiment illustrated in  FIG. 39B  may refer to a single axis or a dual axis scanning unit  104 . 
     However, the control unit  109  in  FIG. 39B  is connected with the internal light source  113  and configured to control the internal light source  113  by sending respective control commands SLS to the light source  113 . 
     For example, the light source  113  may be a switched, and/or a light intensity of the internal light source may be changed or even modulated. 
     In particular, the intensity of the internal light source  113  may be increased if the signal detected by the sensors  115 A to  115 C is too low. 
     Further, the light intensity of the light source  113  may be modulated with a frequency that is at most equal to the scanning frequency of the light deflector  114 . 
     Accordingly, a signal-to-noise ratio of the measured signals at the sensors  115 A to  115 C may be increased. 
     Furthermore, a rate of measurement determined by switching on and off the internal light source  113  may be chosen in dependence of an inaccuracy of previous measurement(s) or another parameter of the system such as the temperature. 
     Even further, determining the actual heights and actual angles of the light deflector  114  may be decoupled by appropriately driving the internal light source  113 . 
     In addition, the scanning unit  104  of  FIG. 39B  has three sensors  115 A to  115 C for measuring respective measuring values S 1  to S 3  which are correlated with the height h(t) and the orientation of the light deflector  114 . 
     Accordingly, there is one additional measuring value at each measuring time t than required for determining the first value indicative of the actual height h(t) and the second value indicative of an actual rotation angle is θ(t). 
     Thus, the control unit  109  in  FIG. 39B  may be configured to additionally determine a third value indicative of a further actual orientation angle (ϕ(t)) in a dual axis setup. 
     In other words, the scanning unit  104  may have N+1 feedback sensors (N=2 in the exemplary embodiment of  FIG. 39B ) configured to measure respective measuring values ({S k }, k=1 . . . N+1) which are correlated with the actual height h(t) and the actual orientation θ, ϕ, and the control unit  104  may be configured to determine for the given time t the first value indicative of the actual height h(t) and N second values which are indicative of the actual orientation θ(t), ϕ(t) of the light deflector  114  as output of a model M using the N+1 measuring values {S k (t)} as input of the model M of the scanning unit. 
     Alternatively, the control unit  109  in  FIG. 39B  may be configured to additionally determine, in a single axis setup, a parameter p of the model M. 
     The parameter p of the model M may be indicative of and/or refer to a temperature of the scanning unit, in particular an effective temperature of the feedback sensors and/or may be indicative of and/or refer to a gain of the scanning unit, in particular a gain of at least one of the sensors, in particular the light sensors. 
     Accordingly, a typically tedious further calibration of the scanning unit  104  may be omitted. 
     The exemplary dual axis scanning unit  104  illustrated in  FIG. 40  is similar to the scanning unit explained above with regard to  FIG. 39B  but the control unit  109  is connected with four feedback sensors  115 A to  115 D for determining respective measuring values S 1  to S 4  which are correlated with a height h of the light deflector  114  and the orientation θ, ϕ, of the light deflector  114 . 
     Accordingly, the control unit  109  may receive for a given time four measuring values S 1  to S 4  and use the four measuring values S 1  to S 4  as inputs of the model M to calculate for the given time three values which are indicative for the actual height h and the two pilot angles θ, ϕ, as well as a value indicative of one parameter p of model M. 
     In a further embodiment, the scanning unit  104  has more than four feedback sensors. Accordingly, more than one parameter p may be determined at a time. 
     According to embodiments, a scanning unit with N degrees of freedom of its light deflector  114  has N+P+1 feedback sensors  115 A- 115 D, and the control unit  109  is configured to use the N+P+1 measuring values ({S k (t)}, k=1 . . . N+P+1) as input of the model M of the scanning unit  104  to determine the first value indicative of the actual height h(t) and N second values which are indicative of the actual orientation θ(t), ϕ(t) as well as at most P values which are indicative for and/or represent P parameters p. 
     As already mentioned above, the light deflector is typically provided by a MEMS-mirror as described herein. 
     Accordingly, the typically used actuators of the MEMS-mirror may also provide feedback signals for the control unit  109  (see figures e.g. 7, 16, 18, 35 for more details). This is also explained in more detail below with regard to  FIG. 41 . 
     Thus, the light sensors  115 A to  115 D may be supplemented with integrated feedback sensors of the MEMS-mirror. 
     Alternatively and/or in addition, at least a part of light sensors  115 A to  115 D may be replaced by the integrated feedback sensors of the MEMS-mirror. 
     As illustrated in  FIG. 40B , even the internal light source may be omitted if (only) measuring values {S k (t)} from N+P+1 integrated feedback sensors of the MEMS-mirror  114  are fed to the control unit  109  and used as input of the model M(p) to calculate as output the first value indicative of the actual height h(t) and N second values which are indicative of the actual orientation θ(t), ϕ(t) as well as at most P values for respective parameters p, with N&gt;=1, and P&gt;=0. Again, the actuation parameter(s) {cs} are calculated based on the output of the model M(p). 
     According to an embodiment, the scanning unit  104  includes a light deflector  114  arranged at a desired height for deflecting light from at least one light source ( 112 ) to a field of view, one or more actuators  302  for controlling an orientation θ, ϕ, of the light deflector  114 , and at least two sensors configured to measure respective measuring values {S k } which are correlated with a height h of the at least one light deflector  114  and an orientation θ, ϕ of the light deflector  114  determined with respect to a coordinate system x, y, z that is fixed with respect to a non-moving, in particular non-oscillating point and/or part of the scanning unit  104 , and a control unit  109  configured to receive for a given time t a respective measuring value {S k (t)} from each of the at least two sensors, determine for the given time t a first value indicative of an actual height h(t) and one or more second value indicative of an actual orientation (θ(t), ϕ(t)) of the light deflector  114  as output of a model M(p) describing the scanning unit  104  using the measuring values {S k (t)} as input of the model M(p), and to calculate actuation parameter(s) {cs 1 }for the one or more actuators  302  using the first value and second value. 
     The at least two sensors may be feedback sensors of a MEMS-mirror. As explained in more detail below with respect to  FIG. 41 , the sensors may, in each measurement, measure L respective measuring values (e.g., 4, if four sensors are used). Based on O measurements the control unit  109  may determine three (x, y, z) O-long vectors of actuation instructions for the next time frame, and a parameter of the model. For example, the three actuation vectors may be translated to (a set of) four instruction if four actuators are used to control the orientation of the MEMS-mirror. 
     The feedback sensors of a MEMS-mirror may include a respective electrode pair, a respective piezoelectric element, a respective resistor, and/or may be implemented as acapacitance sensor, a resistance sensor, a magnetic sensor, an inductance sensor or a strain sensor. 
     However, the feedback sensors may also be implemented as distance sensors, in particular ultra-sound sensors or light sensors as explained above with regard to  FIGS. 39A to 40A . 
     Using distance sensors, in particular light sensors, ultra-sound sensors or magnetic sensors as feedback sensors has the advantage that these sensors are independent of the actuation. 
       FIG. 41  illustrates an example embodiment of a scanning unit  104  that is similar to the scanning device illustrated above with regard to  FIG. 7  and also includes a mirror configuration with a MEMS-mirror  300  which can be moved in two or more axes (θ, φ). The mirror  300  may be associated with four exemplary actuators  302 A to  302 D typically including respective electrically controllable electromechanical drivers (not shown). 
     However, the scanning unit  104  of  FIG. 41  has an internal light source  113  and four optical feedback sensors  115  as explained above with regard to  FIG. 40A  for measuring respective measuring values S 1  to S 4 . 
       FIG. 41  may correspond to a schematic view on a front side of the scanning unit  104 . Therefore, the internal light source  113  and the four optical feedback sensors  115  arranged at/below a backside of the MEMS-mirror  300  are not visible from above and drawn as dashed circles. 
     A main controller  8204  of the scanning unit  104  may output/relay to a mirror driver  8224 B of the control unit  109  a desired angular position/orientation described by θ*, φ* parameters, and optionally a desired height h 0  of the mirror  300 . The desired height ho of the mirror  300  may also be stored in the control unit  109 . 
     Optionally, the mirror driver  8224 B is connected with the internal light source  113  and configured to send control signals SLS to the light source  113 . 
     Further, the main controller  8204  may also be part of the control unit  109 . 
     The mirror driver  8224  may be configured to control movements of mirror  300  by sending respective actuation parameters csl-cs 4  to actuation drivers of the actuators  302 A- 302 D in order to attempt to achieve the specific requested values θ*, φ* and h 0  of the mirror  300 . 
     Due to illuminating the backside of the mirror  300  with light of the internal light source  113 , the light sensors  115  may measure and send respective measuring values S 1  to S 4  to the control unit  109 , in particular to a computational component  8224 A thereof implementing a model M of the control unit  109 . 
     Depending on the sensors, the component  8224 A may include analog-to-digital converters (ADC) for converting analog measuring values of the sensors  115  into digital ones. 
     Further, the component  8224 A of the control unit  109  may include a CPU, a GPU, a DSP and/or is an FPGA for implementing the model M and processing the digital measuring values, respectively. 
     The component  8242 A determines based on the model M actual values of the height h and the orientation θ, φ as (positive) feedback signal to the mirror driver  8224 B. 
     Optionally, a parameter p of model M is additionally determined by the component  8224 A and sent to the mirror driver  8224 B. 
     The mirror driver  8224 B is configured to take into account the received actual height h for determining the actuation parameters cs 1 -cs 4  so that an undesired deviation from the desired height value h* is at least reduced in the next time step. 
     Furthermore, the mirror driver  8224 B typically also takes into account the values of the actual orientation θ, φ of the mirror  300  and optionally the parameter p for determining the actuation parameters cs 1 -cs 4 . 
     Alternatively or in addition, respective signals of a position feedback control circuitry of the mirror  300  which may be integrated into the MEMS device may be fed to the component  8242 A and used as input for the model M. 
     For example, the position feedback control circuitry as explained above with regard to  FIG. 7  may be used for this purpose. 
     Likewise, feedback sensor as explained above with regard to  FIGS. 16, 18 and 35  may be used to provide respective measuring values for the component  8242 A and the model M, respectively. 
     Typically, the control unit  104  performs a closed loop control of the height, more typically a close loop control of the height and the orientation θ, φ of the mirror  300 . 
     The control unit  104  may be a control unit of a LIDAR system. 
     Further, the control unit  104  is typically configured to perform the method explained in the following with regard to  FIG. 42  and  FIG. 43 . 
       FIG. 42  is a flow chart of a method  1000  for controlling a pivotable light deflector of a scanning unit of an electro-optical system configured to scan illumination onto a field of view, in particular a scanning unit of the LIDAR system. 
     In a first block  1100 , N+1 measuring values {S k (t)} each of which is typically correlated with an actual height h(t) of the light deflector and an actual orientation θ(t), ϕ(τ) of the light deflector with respect to the scanning unit are measured for a given time t. The integer number N typically corresponds is to the number of rotational degrees of freedom of the light deflector (N&gt;1). 
     In a subsequent block  1200 , a first value indicative of the actual height h(t) and N second values indicative of the actual orientation θ(t), ϕ(t) of the light deflector are determined as outputs of a model using the N measuring values {S k (t)} as input of the model. 
     Note that the first value may correspond to and/or represent the actual height or a function of the actual height. 
     Likewise, the N second values may correspond to and/or represent a respective actual pivot angle(s) θ(t), ϕ(t) or a respective function thereof 
     Thereafter, the first value and the N second values may be used for controlling the light deflector in a block  1300 . 
     Typically, actuation parameter(s) {cs} for actuators of the light deflector are determined in block  1300 . 
     Furthermore, determining the actuation parameter(s) {cs} is typically done so that deviation of a desired height ho of the light deflector is at least reduced in the next time step. 
     The desired height ho of the light deflector may be used as a setpoint for controlling the height h(t) of the light deflector. 
     Accordingly, the light deflector may be kept at or at least close to the desired height h 0 , i.e. within a predefined range. 
     Typically, none of the measuring values {S k (t)} is only correlated with the actual height of the light deflector. 
     More typically, each of the measuring values is {S k (t)} is correlated with the actual height of the light deflector and the actual orientation of the light deflector. 
     In particular in embodiments referring to non-hinged mounted light deflectors such as un-hinged mirrors, in particular unhinged MEMS-mirrors, the desired height ho is typically a calibration height of the light deflector in the scanning unit. 
     As indicated by the dashed dotted arrow in  FIG. 42 , method  1000  is typically implemented as a closed-loop control. 
     In particular, the height h of the light deflector may be closed-loop controlled. 
     However, the orientation θ(t), ϕ(t) of the light deflector may also be closed-loop controlled. 
       FIG. 43  is a flow chart of a method  1001  for controlling a pivotable light deflector of a scanning unit of an electro-optical system configured to scan illumination onto a field of view in accordance with some embodiments of the present disclosure. Method  1001  is similar to method  1000  explained above with regard to  FIG. 42 . 
     However, N+P+1 measuring values {S k (t)} with P&gt;0 are determined in block  1100  and used as inputs of a model in block  1201  to determine in addition to the first and second values a further value which is indicative for a parameter p(t) of the model. 
     Typically, the desired orientation θ*, ϕ* of methods  1000 ,  1001  illustrated in  FIGS. 42, 43  is changed in accordance with the requirements of scanning for detecting objects using a LIDAR system. 
     During operation of LIDAR system in a manner consistent with the presently disclosed embodiments, beside setting the desired orientation θ*, ϕ* for controlling at least one light deflector  114  to deflect light from at least one (main) light source ( 112 ) in order to scan the field of view, the at least one main light source  112  may be controlled in a manner enabling light flux to vary over a scan of a field of view using light from the at least one light source  112 . 
     In some embodiments, the methods  1000 ,  1001  may include scanning of a field of view over a plurality of scanning cycles, wherein a single scanning cycle includes moving the at least one light deflector across a plurality of instantaneous positions. While the at least one light deflector is located at a particular position, the methods may include deflecting a light beam from the at least one light source toward an object in the field of view, and deflecting received reflections from the object toward at least one sensor  116  of a sensing unit  106  as explained above. 
     According to an embodiment of a LIDAR system, the LIDAR system includes a light source for illuminating a field of view, and a scanning unit comprising a mirror arranged at a desired height for deflecting light from the light source to the field of view, at least one actuator for controlling an orientation of the mirror, and at least two sensors configured to measure respective measuring values which are correlated with an actual height of the mirror in the scanning unit and an actual orientation of the mirror. The LIDAR system further includes a control unit connected with the at least two sensors and configured to use the measuring values for determining a first value indicative of an actual height and at least one second value indicative of an actual orientation of the light deflector, and to use the desired height, the first value and the at least one second value for determining a respective actuation parameter for the at least one actuator. 
     Typically, the control unit implements a model of the control unit for determining the first value and the at least one second value using the measurement values as inputs. 
     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. 
     Computer programs based on the written description and disclosed methods are within the skill of an experienced developer. The various programs or program modules can be created using any of the techniques known to one skilled in the art or can be designed in connection with existing software. For example, program sections or program modules can be designed in or by means of .Net Framework, .Net Compact Framework (and related languages, such as Visual Basic, C, etc.), Java, C++, Objective-C, HTML, HTML/AJAX combinations, XML, or HTML with included Java applets. 
     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.