Patent Publication Number: US-2022229164-A1

Title: Systems and methods for time-of-flight optical sensing

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 62/857,793, filed Jun. 5, 2019, and U.S. Provisional Patent Application No. 63/027,021, filed May 19, 2020. Each of the above-referenced applications is incorporated herein by reference in their entirety. 
    
    
     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. Currently, however, the maximum illumination power of LIDAR systems is limited by the need to make the LIDAR systems eye-safe (i.e., so that they will not damage the human eye which can occur when a projected light emission is absorbed in the eye&#39;s cornea and lens, causing thermal damage to the retina.) 
     The systems and methods of the present disclosure are directed towards improving performance of LIDAR systems while complying with eye safety regulations. 
     SUMMARY 
     In an embodiment, a time-of-flight (TOF) optical sensor may include a controller, a sensing array, and a readout unit. The sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The number of the plurality of readout TOF modules may be less than the number of the plurality of sensing cells. The controller may be configured to trigger a connection of a first sensing cell of the plurality of sensing cells to a first readout TOF module of the plurality of readout TOF modules at a first time during a sampling period, thereby enabling the first readout TOF module to provide a first measurement of a change in output of the first sensing cell. 
     In an embodiment, a method for controlling a time-of-flight (TOF) optical sensor is provided. The TOF optical sensor may include a sensing array and a readout unit. The sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The number of the plurality of readout TOF modules may be less than the number of the plurality of sensing cells. The method may include triggering a connection of a first sensing cell of the plurality of sensing cells to a first readout TOF module of the plurality of readout TOF modules at a first time during a sampling period, thereby enabling the first readout TOF module to provide a first measurement of a change in output of the first sensing cell. 
     In an embodiment, a time-of-flight (TOF) optical sensor may include a controller, a sensing array, and a readout unit. The sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The number of the plurality of readout TOF modules may be less than the number of the plurality of sensing cells. The controller may be configured to, for each sensing cell of a first subset of the plurality of sensing cells, trigger a connection of the each sensing cell of the first subset of the plurality of sensing cells to one of the plurality of readout TOF modules at a first time, thereby enabling the one of the plurality of readout TOF modules to provide a first measurement of a change in output of one or more sensing cells of the first subset that are connected to the one of the plurality of readout TOF modules. The controller may also be configured to based on the measurements, determine an offset of an expected area of the sensing array in which a reflection signal appears. 
     In an embodiment, a time-of-flight (TOF) optical sensor may include a two-dimensional sensing array, a readout unit, and a controller. The two-dimensional sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The number of the plurality of readout TOF modules may be less than the number of the plurality of sensing cells. The controller may be configured to trigger a connection of a first subset of the plurality of sensing cells to the plurality of readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the plurality of sensing cells by the plurality of readout TOF modules during a first sampling period. The controller may also be configured to determine a second subset of the plurality of sensing cells to be connected to the plurality of readout TOF modules based on the first measurements. The controller may further be configured to trigger a connection of the second subset of the plurality of sensing cells to the plurality of readout TOF modules at a second time for providing a plurality of second measurements of changes in output of the second subset of the plurality of sensing cells by the plurality of readout TOF modules during a second sampling period. 
     In an embodiment, a method for controlling a time-of-flight (TOF) optical sensor may include triggering a connection of a first subset of a plurality of sensing cells of the TOF optical sensor to a plurality of readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the plurality of sensing cells by the plurality of readout TOF modules during a first sampling period. The number of the plurality of readout TOF modules may be less than the number of the plurality of sensing cells. The method may also include determining a second subset of the plurality of sensing cells to be connected to the plurality of readout TOF modules based on the first measurements. The method may further include triggering a connection of the second subset of the plurality of sensing cells to the plurality of readout TOF modules at a second time for providing a plurality of second measurements of changes in output of the second subset of the plurality of sensing cells by the plurality of readout TOF modules during a second sampling period. 
     The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims. 
    
    
     
       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, 2B, 2C, 2D, 2E, 2F, and 2G  are diagrams illustrating different configurations of projecting units in accordance with some embodiments of the present disclosure. 
         FIGS. 3A, 3B, 3C, and 3D  are diagrams illustrating different configurations of scanning units in accordance with some embodiments of the present disclosure. 
         FIGS. 4A, 4B, 4C, 4D, and 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, 6B, and 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. 
         FIG. 7  is a diagram illustrating an exemplary time-of-flight optical sensor consistent with some embodiments of the present disclosure. 
         FIG. 8  is a diagram illustrating an exemplary time-of-flight optical sensor consistent with some embodiments of the present disclosure. 
         FIGS. 9A and 9B  are diagrams illustrating an exemplary sensor array consistent with some embodiments of the present disclosure. 
         FIGS. 10A, 10B, and 10C  are diagrams illustrating exemplary fields of view of a LIDAR system consistent with some embodiments of the present disclosure. 
         FIG. 11  is a flowchart illustrating an exemplary process for controlling a time-of-flight optical sensor consistent with some embodiments of the present disclosure. 
         FIG. 12  is a diagram illustrating an exemplary time-of-flight sensing array consistent with some embodiments of the present disclosure. 
         FIG. 13  is a flowchart illustrating an exemplary process for controlling a time-of-flight optical sensor consistent with some embodiments of the present disclosure. 
         FIGS. 14A and 14B  are diagrams illustrating an exemplary sensor array consistent with some embodiments of the present disclosure. 
         FIG. 15  is a flowchart illustrating an exemplary process for controlling a time-of-flight optical sensor consistent with some embodiments of the present disclosure. 
         FIG. 16  is a diagram illustrating an exemplary sensor array consistent 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 oembodiment, 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°x0.1° or 0.3°x0.3° 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 its size 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 facing 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,  74   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. 11A  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 reflection signals indicative of light reflected from objects in field of view  120  to processing unit  108 . Consistent with the present disclosure, scanning units  104  may be mounted to or incorporated into a bumper, a fender, a side panel, a spoiler, a roof, a headlight assembly, a taillight assembly, a rear-view mirror assembly, a hood, a trunk or any other suitable part of vehicle  110  capable of housing at least a portion of the LIDAR system. In some cases, LIDAR system  100  may capture a complete surround view of the environment of vehicle  110 . Thus, LIDAR system  100  may have a  360 -degree horizontal field of view. In one example, as shown in  FIG. 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 (optical components may include, for example, windows, lenses, mirrors, beam splitters, etc.). 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. 
     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 service 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 outbound and inbound light beams pass. In another example, the outbound light may pass through an optical window (not shown) and the inbound light radiation may pass through the same optical window. A monostatic configuration may include a configuration where the scanning unit  104  includes a single light deflector  114  that directs the projected light towards field of view  120  and directs the reflected light towards a sensor  116 . As shown, both projected light  204  and reflected light  206  hits an asymmetrical deflector  216 . The term “asymmetrical deflector” refers to any optical device having two sides capable of deflecting a beam of light hitting it from one side in a different direction than it deflects a beam of light hitting it from the second side. In one example, the asymmetrical deflector does not deflect projected light  204  and deflects reflected light  206  towards sensor  116 . One example of an asymmetrical deflector may include a polarization beam splitter. In another example, asymmetrical  216  may include an optical isolator that allows the passage of light in only one direction. A diagrammatic representation of asymmetrical deflector  216  is illustrated in  FIG. 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  112  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 reflection 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 reflection 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 sensing unit  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 optionally include an array of light sources (e.g.,  112 A- 112 F). In one embodiment, the array of light sources may include a linear array of light sources controlled by processor  118 . For example, processor  118  may cause the linear array of light sources to sequentially project collimated laser beams towards first optional optical window  124 A. First optional optical window  124 A may include a diffuser lens for spreading the projected light and sequentially forming wide horizontal and narrow vertical beams. Optionally, some or all of the at least one light source  112  of system  100  may project light concurrently. For example, processor  118  may cause the array of light sources to simultaneously project light beams from a plurality of non-adjacent light sources  112 . In the depicted example, light source  112 A, light source  112 D, and light source  112 F simultaneously project laser beams towards first optional optical window  124 A thereby illuminating the field of view with three narrow vertical beams. The light beam from fourth light source  112 D may reach an object in the field of view. The light reflected from the object may be captured by second optical window  124 B and may be redirected to sensor  116 . The configuration depicted in  FIG. 2E  is considered to be a bi-static configuration because the optical paths of the projected light and the reflected light are substantially different. It is noted that projecting unit  102  may also include a plurality of light sources  112  arranged in non-linear configurations, such as a two dimensional array, in hexagonal tiling, or in any other way. 
       FIG. 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 depicted 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 overlap 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 paths of the projected light and the reflected light means that the overlap between the two optical paths may be less than 10%, less than 5%, less than 1%, or less than 0.25%. 
     The Scanning Unit 
       FIGS. 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. This embodiment is described in greater detail below with reference to  FIGS. 32-34 . 
     During scanning, current (represented in the figure as the dashed line) may flow from contact  304 A to contact  304 B (through actuator  302 A, spring  306 A, mirror  300 , spring  306 B, and actuator  302 B). Isolation gaps in semiconducting frame  308  such as isolation gap  310  may cause actuator  302 A and  302 B to be two separate islands connected electrically through springs  306  and frame  308 . The current flow, or any associated electrical parameter (voltage, current frequency, capacitance, relative dielectric constant, etc.), may be monitored by an associated position feedback. In case of a mechanical failure—where one of the components is damaged- the current flow through the structure would alter and change from its functional calibrated values. At an extreme situation (for example, when a spring is broken), the current would stop completely due to a circuit break in the electrical chain by means of a faulty element. 
       FIG. 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  FIG. 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  may be connected to frame  308  by one or more rigid supporting elements. In another embodiment, at least of deflector  114  may include an electrostatic or electromagnetic MEMS mirror. 
     As described above, a monostatic scanning LIDAR system utilizes at least a portion of the same optical path for emitting projected light  204  and for receiving reflected light  206 . The light beam in the outbound path may be collimated and focused into a narrow beam while the reflections in the return path spread into a larger patch of light, due to dispersion. In one embodiment, scanning unit  104  may have a large reflection area in the return path and asymmetrical deflector  216  that redirects the reflections (i.e., reflected light  206 ) to sensor  116 . In one embodiment, scanning unit  104  may include a MEMS mirror with a large reflection area and negligible impact on the field of view and the frame rate performance. Additional details about the asymmetrical deflector  216  are provided below with reference to  FIG. 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, 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 ) 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 diodes (SPADs, 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 4×6 detectors  410  (also referred to as “pixels”). In one embodiment, a pixel size may be about 1×1 mm. Sensor  116  is two-dimensional in the sense that it has more than one set (e.g. row, column) of detectors  410  in two non-parallel axes (e.g. orthogonal axes, as exemplified in the illustrated examples). The number of detectors  410  in sensor  116  may vary between differing implementations, e.g. depending on the desired resolution, signal to noise ratio (SNR), desired detection distance, and so on. For example, sensor  116  may have anywhere between 5 and 5,000 pixels. In another example (not shown in the figure) Also, sensor  116  may be a one-dimensional matrix (e.g. 1×8 pixels). 
     It is noted that each detector  410  may include a plurality of detection elements  402 , such as Avalanche Photo Diodes (APD), Single Photon Avalanche Diodes (SPADs), combination of Avalanche Photo Diodes (APD) and Single Photon Avalanche Diodes (SPADs)or detecting elements that measure both the time of flight from a laser pulse transmission event to the reception event and the intensity of the received photons. For example, each detector  410  may include anywhere between 20 and 5,000 SPADs. The outputs of detection elements  402  in each detector  410  may be summed, averaged, or otherwise combined to provide a unified pixel output. 
     In the illustrated example, sensing unit  106  may include a two-dimensional sensor  116  (or a plurality of two-dimensional sensors  116 ), whose field of view is smaller than field of view  120  of LIDAR system  100 . In this discussion, field of view  120  (the overall field of view which can be scanned by LIDAR system  100  without moving, rotating or rolling in any direction) is denoted “first FOV  412 ”, and the smaller FOV of sensor  116  is denoted “second FOV  412 ” (interchangeably “instantaneous FOV”). The coverage area of second FOV  414  relative to the first FOV  412  may differ, depending on the specific use of LIDAR system  100 , and may be, for example, between 0.5% and 50%. In one example, second FOV  412  may be between about 0.05° and 1° elongated in the vertical dimension. Even if LIDAR system  100  includes more than one two-dimensional sensor  116 , the combined field of view of the sensors array may still be smaller than the first FOV  412 , e.g. by a factor of at least 5, by a factor of at least 10, by a factor of at least 20, or by a factor of at least 50, for example. 
     In order to cover first FOV  412 , scanning unit  106  may direct photons arriving from different parts of the environment to sensor  116  at different times. In the illustrated monostatic configuration, together with directing projected light  204  towards field of view  120  and when least one light deflector  114  is located in an instantaneous position, scanning unit  106  may also direct reflected light  206  to sensor  116 . Typically, at every moment during the scanning of first FOV  412 , the light beam emitted by LIDAR system  100  covers part of the environment which is larger than the second FOV  414  (in angular opening) and includes the part of the environment from which light is collected by scanning unit  104  and sensor  116 . 
       FIG. 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 X 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 X 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 ML6, 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. 
     Referring by way of a nonlimiting example to  FIGS. 2E, 2F and 2G , it is noted that the one or more sensors  116  of system  100  may receive light from a scanning deflector  114  or directly from the FOV without scanning. Even if light from the entire FOV arrives to the at least one sensor  116  at the same time, in some implementations the one or more sensors  116  may sample only parts of the FOV for detection output at any given time. For example, if the illumination of projection unit  102  illuminates different parts of the FOV at different times (whether using a deflector  114  and/or by activating different light sources  112  at different times), light may arrive at all of the pixels or sensors  116  of sensing unit  106 , and only pixels/sensors which are expected to detect the LIDAR illumination may be actively collecting data for detection outputs. This way, the rest of the pixels/sensors do not unnecessarily collect ambient noise. Referring to the scanning—in the outbound or in the inbound directions—it is noted that substantially different scales of scanning may be implemented. For example, in some implementations the scanned area may cover 1% or 0.1% of the FOV, while in other implementations the scanned area may cover 10% or 25% of the FOV. All other relative portions of the FOV values may also be implemented, of course. 
     The Processing Unit 
       FIGS. 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). 
     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. 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. 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 . 
     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  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 . 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 , 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  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  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 mechanism 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. Two-Dimensional Time-of-Flight Optical Sensor 
     Unlike complementary metal-oxide-semiconductor (CMOS) based sensors, which obtain a single readout of an accumulated signal of its sensing units, a Time-of-Flight (TOF) sensor includes a plurality of sensing cells electrically connected in a temporary fashion to a readout TOF module, which can read the changes in the voltage (or other electric parameters) during a sampling period (or a scanning period). Additionally, unlike existing CMOS sensors in which the pixels collect data from the field of view even when not read, in the disclosed TOF sensors, since information is being read in real time, the sensing cells of a TOF sensor that are not connected to readout TOF module at a given moment may not collect data at that time. 
     The readout circuitry of a TOF sensor may be relatively large in comparison for the size of each pixel of the TOF sensor due to the need to record a large number of samples (outputs of the pixels) over a duration of time. This disclosure provides TOF sensors that use fewer TOF readout modules than the number of the pixels (or sensing cells), while enabling the data from each sensing cell to be read. The disclosed TOF sensors may be used in LIDAR systems (e.g., LIDAR system  100  or any other LIDAR system), or in other types of electrooptical systems which may require TOF detection of light (whether reflected light and/or ambient light). 
     A TOF sensor may include a sensing array, which may include a plurality of sensing cells (or sensing units) configured to receive reflections from the surroundings (e.g., a surrounding of a vehicle). For example, the sensing array may include 120,000 sensing cells arranged in 200 rows and 600 columns, which may form a 200×600 rectangular lattice array. The TOF optical sensor may also include a readout unit, which may include a plurality of readout TOF modules. A readout TOF module may be configured to provide a measurement of the change in output of one or more sensing cells that are connected to the readout TOF module during a period of time (e.g., a sampling period or a scanning period). The number of readout TOF modules may be less than the number sensing cells of the sensing array. For example, the number of the sensing cells of the sensing array may be 120,000, and the number of the readout TOF modules may be 300. The TOF sensor may also include a controller configured to trigger a connection of a first subset of the sensing cells with the readout TOF modules at a first time for providing a first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. For example, the TOF sensor may be configured to determine a first subset of the sensing cells that correspond to a first part of the field of view of a LIDAR system, and trigger the connection of the first subset of the sensing cells to the readout TOF modules. The readout TOF modules may be configured to provide first measurements of changes in output of the first subset of the sensing cells during a first sampling period. The TOF sensor may also be configured to determine a second subset of the sensing cells to be connected to the readout TOF modules at a second time based on the first measurements. For example, the first measurements may indicate that no objects are detected in the first part of the field of view corresponding to the first subset of the sensing cells. The controller may determine a second subset of the sensing cells that correspond to a second part of the field of view. The controller may also trigger the connections of the second subset of the sensing cells to the readout TOF modules at a second time. The readout TOF modules may provide second measurements of changes in output of the second subset of the sensing cells during a second sampling period. In some embodiments, the LIDAR system may further include a processor configured to process the first and/or second measurements. For example, the processor may be configured to process the first measurements to detect one or more objects in the first part of the field of view. 
     Implementing a relatively low number of readout TOF modules and possibly placing them outside the sensing array may make it possible to have large sensing cells, fast electronics (thus, for example, faster readout of the sensing cells, low noise, a large bandwidth, and/or continuous data capturing (e.g., obtaining many readings from the same region in the field of view, then moving to another region). Additionally, placing the electronics of the readout TOF modules away from the sensing cells (on the same chip or a different chip) may help to design and configure more complicated circuitry that may not be achievable in a design in which readout TOF modules are placed mixed with or adjacent to the respective sensing cells. 
     The sensing cells may be implemented using any of the types of sensing technologies discussed elsewhere in this application or other types of TOF sensing technologies, such as SPADs, SiPM, PIN diodes, other photodiodes, amplified photodiodes, time-to-digital convertors (TDC)). In some embodiments, the sensing cells of the TOF optical sensor may include same type of sensing cells (e.g., SiPMs having substantially the same characteristics or properties. Alternatively, at least two of the sensing cells may be of different types. For example, the sensing array may include a group of feedback cells used for determining feedback on a direction (and/or size, intensity distribution, etc.) of the LIDAR scanning and a group of “main cells” used for the TOF sensing. A feedback cell may be smaller than a main cell. Alternatively or additionally, a feedback cell may have a lower quality and/or a slower response time than a main cell. In some embodiments, feedback cells may optionally be detection cells which may not be suitable for TOF detection (at least not in the full frequency used for LIDAR detection, e.g., 1-nanosecond temporal-resolution), mutatis mutandis. For example, such non-TOF sensing cells may include a capacitor, and suitable readout modules may be used for reading of the charge collected by the one or more temporarily connected feedback cell. Alternatively, feedback cells may be TOF sensing cells (e.g., SiPMs, PIN diodes, etc.) in, for example, bi-static LIDAR systems, where a LIDAR detection angle may depend on distance. In some embodiments, separate readout circuitry (e.g., decoders, muxes, lines) may be used for different types of sensing cells, but this is not necessarily so. Optionally, the feedback cells may implement pseudo-TOF by reading out the charge by the connected readout module multiple times during the sampling period (or a scanning period), but in lesser sampling frequency (e.g., 10 Hz, 100 Hz, 1 Khz, 10 Khz, etc.). In some embodiments, the sensing cells may include at least one light sensitive cell operable to output an electric signal whose magnitude is correlated to amount of impinging light on the cell. 
     The sensing cells may be implemented using any of the types of sensing technologies discussed above, or other types of TOF sensing technologies, many of which are known in the art (e.g., SPADs, SiPM, PIN diodes, other photodiodes, amplified photodiodes, time-to-digital convertors (TDC)). In some embodiments, at least some of the sensing cells may be sensitive for detecting light at about 905 nanometer wavelengths. Alternatively or additionally, some of the sensing cells may be sensitive for detecting light at about 1550 nanometer wavelengths. 
     The TOF optical sensor may include a two-dimensional optical sensing array, which may include sensing cells in a planar arrangement. In some embodiments, at least portion of the sensing cells may be substantially arranged along a straight line. For example, the sensing cells may be arranged in a lattice (e.g., a rectangular lattice, a rhombic lattice, a hexagonal lattice, an oblique lattice, or the like, or a combination thereof). Other arrangements may also be possible (e.g., a periodic arrangement of sensing cells over one axis but not over the other axis, or non-periodic 2D arrangements). 
     In some embodiments, all of the sensing cells may be implemented in a continuous array. Alternatively, the sensing cells may be arranged in two or more separated areas (on a same chip or different chip). 
     In some embodiments, the sensing array may include at least one sensing cell having at least one high-gain transistor and at least one low-gain transistor. For example, the sensing cell may be divided into one part with high gain and one part with low gain. The controller may be configured to determine which part of the sensing cells was connected to the readout TOF modules, based on the measurement of a previous scanning cycle (e.g., a sampling period or a scanning period). 
     Each of the readout TOF modules may be operable to detect modifications in an output of at least one connected sensing cell during a light sampling period (or a scanning period), by, for example, measuring values such as voltage or current, changes in these values over time, or other information indicative of modification of the amount of light detected by the respective sensing cells. A readout TOF module may include one or more different types of electronics, such as amplifiers, analog-to-digital converters (ADCs), filters, analog-and-time-digital converters (TDCs), or the like, or a combination thereof. 
     In some embodiments, the number of the readout TOF modules may be less than the number of the sensing cells by at least one order of magnitude, at least two orders of magnitude, at least three orders of magnitude, or at least four orders of magnitude. For example, For example, in the example of 120,000 sensing cells arranged as 200×600 rectangular lattice array, there may be 40, 200, or 600 readout TOF modules to be connected to one or more (e.g., two, four, or more) of the sensing cells at a time. 
     The readout TOF modules of the TOF optical sensor may include one type of readout TOF modules. Alternatively, at least two readout TOF modules may be different types of readout TOF modules (e.g., as discussed elsewhere in this disclosure with respect to measuring different types of parameters such as voltage, current frequency, capacitance, relative dielectric constant, etc.). 
     In some embodiments, a readout TOF module may be configured to provide a measurement of the output of one or more sensing cells that are connected to the readout TOF module during a sampling period (or a scanning period). Alternatively, a readout TOF module may be configured to provide multiple measurements of the output of the connected one or more sensing cells during a sampling period. For example, for a sampling at 1 GHz, a readout TOF module may be configured to provide 1,000 consecutive measurements of the output of the connected one or more sensing cells during a sampling period of 1 microsecond, a measurement may occur every 1 nanosecond. 
     In some embodiments, a readout TOF module may be connected to two or more sensing cells and configured to provide a readout indicative of a change in an amount of light detected by the two or more sensing cells during a sampling period (or a scanning period). For example, while triggering a connection of a subset of the sensing cells to a plurality of the readout modules, the controller may trigger a connection of multiple sensing cells to a single readout module, so that the readout module may provide a single readout (one measurement or a plurality of consecutive measurements) indicative of modifications in the overall amount of light detected by the multiple sensing cells concurrently and temporarily connected to that readout module. 
     The TOF sensor may include a controller configured to control the connections of one or more sensing cells to one or more readout TOF modules. For example, the controller may determine a first subset of the sensing cells that correspond to a part of the field of view of the LIDAR system. The controller may also trigger a connection of the first subset of the sensing cells with a plurality of readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. The controller may also determine a second subset of the sensing cells that correspond to another part of the field of view based on the first measurements. The controller may also trigger the connections of the second subset of the sensing cells to the readout TOF modules at a second time for providing second measurements of changes in output of the second subset of the sensing cells during the second sampling period. 
     In some embodiments, the controller may include one or more decoders associated with the sensing array to connect to two or more sensing cells (e.g., by opening the switches associated with the two or more sensing cells). This may be used for hardware binning, for example, e.g., to increase detection sensitivity (to low reflectivity targets) in order to increase detection range, or for any other reason. In some embodiments, one or more decoders may be configured to determine the first subset of the sensing cells and the readout TOF modules and/or determine the second subset of the sensing cells and the readout TOF modules. 
     In some embodiments, the TOF sensor may also include one or more processors configured to process the measurement data (e.g., the first and/or second measurements) received from the readout TOF modules. For example, the processor(s) may be configured to receive from the first (and/or second) subset of the readout TOF modules the first (and/or second) measurements and detect one or more objects in the corresponding part of the field of view based on the first (and/or second) measurements by, for example, detecting the timings of peaks in the signal from each readout TOF module, or by other techniques of signal processing applied to the measurements provided to the processor(s). In some embodiments, a processor may be an on-board (or on-chip) of the TOF sensor. Alternatively (or additionally), a processor may be implemented separately from the TOF sensor (e.g., a component of a LIDAR system separated from the TOF sensor). 
     In some embodiments, the processor may be configured to synchronize measurements with a light source of a LIDAR system in which the TOF optical sensor is installed. Alternatively or additionally, the processor may be configured to synchronize measurements with a scanning module (or one or more components thereof, such as a light source, a light deflector (e.g., a mirror), etc.) of a LIDAR system in which the TOF optical sensor is installed. In some embodiments, the processor may be configured to synchronize measurements with a scanning module and a light source of a LIDAR system in which the TOF optical sensor is installed. In some embodiments, the controller and the processor may be integrated into one signal component and configured to perform the functions of a controller and/or a processor disclosed herein. 
     The TOF optical sensor may be implemented on a single chip (e.g., silicon, InGaAs, etc.), or on two or more chips (e.g., silicon and InGaAs). In some embodiments, the sensing cells may be implemented on a single chip, or on two or more chips (e.g., for readout in different spectral ranges). In some embodiments, the sensing cells and the readout TOF modules may be implemented on a single chip. Alternatively, the sensing cells and the readout TOF modules may be implemented on different chips. For example, at least one sensing cell may be implemented on a chip different from the chip(s) on which the readout TOF modules are implemented. Alternatively or additionally, at least one readout TOF module may be implemented on a chip different from the chip(s) on which the sensing cells are implemented. 
       FIG. 7  is a diagram illustrating an exemplary time-of-flight optical sensor consistent with some embodiments of the present disclosure. As illustrated in  FIG. 7 , TOF sensor  700  may include a sensing array  710 , a readout unit  720 , a controller  730 , and a processor  740 . Sensing array  710  may include a plurality of sensing cells  711  configured to receive reflection signals indicative of reflections of flash light emissions from one or more objects. Readout unit  720  may include a plurality of readout TOF modules  721 , and each of the readout TOF modules may be configured to provide measurements of changes in output of one or more connected sensing cells during a sampling period (or a scanning period). 
     Controller  730  may be configured to control the connections of the sensing cells with the readout TOF modules. For example, controller  730  may be configured to trigger connections of a first subset of the sensing cells to the readout TOF modules at a first time, which may provide first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. 
     Processor  740  may be configured to process measurements provided by one or more readout TOF modules. For example, processor  740  may receive the first measurements from the readout TOF modules and detect one or more objects based on the first measurements. 
     Controller  730  (and/or processor  740 ) may also be configured to determine a second subset of the sensing cells to be connected to the readout TOF modules based on the first measurements. Controller  730  may further be configured to trigger the connections of the second subset of the sensing cells to the readout TOF modules at a second time, which may provide second measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a second sampling period. Processor  740  may also be configured to process the second measurements (e.g., detecting one or more objects based on the second measurements. In some embodiments, controller  730  and processor  740  may be integrated into one signal component and configured to perform the functions of a controller and/or a processor disclosed herein. 
       FIG. 8  is a diagram illustrating another exemplary time-of-flight optical sensor consistent with some embodiments of the present disclosure. As illustrated in  FIG. 8 , TOF sensor  800  may include a sensing array  810 , a first readout unit  820 , a second readout unit  830 , a controller  840 , and a processor  850 . 
     Sensing array  810  may include a plurality of sensing cells  811 . In some embodiments, sensing cells  811  may be similar to sensing cells  711  illustrated in  FIG. 7  and described above. 
     Readout unit  820  may include a plurality of readout TOF modules  821 , and readout unit  830  may include a plurality of readout TOF modules  831 . Readout unit  820  may be configurable to be connected to some of sensing cells  811  (e.g., the left half portion of sensing cells  811 ), but not to other sensing cells  811  (e.g., the right half portion of sensing cells  811 ). Similarly, readout unit  830  may be configurable to be connected to some of sensing cells  811  (e.g., the right half portion of sensing cells  811 ), but not to other sensing cells  811  (e.g., the left half portion of sensing cells  811 ). In some embodiments, readout TOF modules  821  and  831  may be similar to readout TOF modules  721  illustrated in  FIG. 7  and described above. 
     Controller  840  may be configured to control the connections of sensing cells  811  with readout TOF modules  821  and/or  831 . For example, controller  840  may be configured to trigger connections of a first subset of the sensing cells (e.g., a subset of the sensing cells in the left half portion of sensing cells  811 ) to readout TOF modules (e.g., a subset of readout TOF modules  821 ) at a first time, which may provide first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. Controller  840  may also be configured to determine a second subset of the sensing cells (e.g., a subset of the sensing cells in the right half portion of sensing cells  811 ) to the readout TOF modules (e.g., a subset of readout TOF modules  831 ). Controller  840  may further be configured to trigger connections of the second subset of the sensing cells to the readout TOF modules, which may provide second measurements of changes in output of the second subset of the sensing cells by the readout TOF modules during a second sampling period. In some embodiments, controller  840  may be similar to controller  730  illustrated in  FIG. 7  and described above. 
     Processor  850  may be configured to process measurements provided by one or more readout TOF modules. In some embodiments, processor  850  may be similar to processor  740  illustrated in  FIG. 7  and described above. In some embodiments, controller  840  and processor  850  may be integrated into one signal component and configured to perform the functions of a controller and/or a processor disclosed herein. 
     The ability to dynamically connect different subsets of sensing cells to the readout TOF modules may be used to read out real-time TOF from holey areas of the array (i.e., having unread sensing cells, which are not connected to a readout TOF module for TOF readout, being surrounded by read sensing cells, which are connected to and being actively read by one or more readout TOF modules). For example, the controller may connect for readout every other pixel of an area of the sensor array for one sampling period, and every other pixel of a second area of the sensor array for another sampling period. Such a “diluted” sampling may be used for a faster scanning, energy reduction, or other potential advantages. 
     In some embodiments, a subset (a first subset or a second subset) of the sensing cells to be connected to a subset (a first subset or a second subset) of the readout TOF modules may be up to a certain percentage of all sensing cells (e.g., in a range of up to 1% to 90%, such as up to 10%, 20%, 33%, 50%, or 70%). 
     In some embodiments, the controller of a TOF sensor may be configured to select a subset of the sensing cells (e.g., a first subset of the sensing cells) to be connected to one or more readout TOF modules. For example, the controller may randomly select a first subset of the sensing cells to be connected to readout TOF modules at a first time. Alternatively, the controller may select the first subset of the sensing cells based on one or more factors. For example, the first subset of the sensing cells may be selected based on the light emitted by a light source of the LIDAR system. Alternatively or additionally, the first subset of the sensing cells may be selected based on a particular part of the field of view that the scanning module of the LIDAR system scans. Alternatively or additionally, the first subset of the sensing cells may be selected based on an area on the sensing array that reflections may be expected to be detected. 
     In some embodiments, the shape of the light emitted by a light source of the LIDAR system may affect the area on the sensing array that receives the reflection signal. For example, if the laser emitted to the field of view is a line, the received reflection signal may appear as a line shape over a number of sensing cells. As illustrated in  FIG. 9A , an exemplary sensor array  900  may include a plurality of sensing cells  901 . A laser having a beam that is line-shaped may be emitted to the field of view of the LIDAR system, and a reflection signal may appear as a line  911  on a certain area of sensing array  900 , covering a group of sensing cells  912 . The controller of the TOF sensor may be configured to divide sensing cells  901  into a plurality of groups of sensing cells, and each of the groups may include  8  sensing cells in the vertical axis. In some embodiments, each of the groups may also include one or more adjacent sensing cells in the horizontal axis and/or one or more adjacent sensing cells in the vertical axis. For example, each of the groups may include 16 sensing cells (by, for example, including one adjacent sensing cell on the left or the right), 24 sensing cells (by, for example, including one adjacent sensing cell on the left and one adjacent sensing cell on the right), or 32 sensing cells, or other suitable numbers of sensing cells. The controller may also be configured to select one of the groups as the first subset of the sensing cells. In some embodiments, the controller may further be configured to randomly select one of the groups as the first subset of the sensing cells. Alternatively or additionally, the controller may be configured to rotate the groups and select one of the groups to be connected to one or more readout TOF modules, and may not select the same group unless other groups have been selected in a rotation. 
     In some embodiments, alternatively or additionally, the controller may be configured to select the first subset of the sensing cells based on an area on the sensing array that reflections may be expected to be detected. For example, the controller may expect the reflection signal based on the laser emitted to the field of view of the LIDAR system to appear in an area on the sensing array (e.g., an area at least partially overlapping sensing cells  912 ). The controller may be configured to select sensing cells  912  as the first subset of the sensing cells. 
     In some embodiments, if the laser beam is split into a plurality of beam spots, the reflection signal of a spot may appear on the sensing array as a dot (compared to the shape of the reflection signal appearing on the sensing array if the laser has a line shape described above). For example, as illustrated in  FIG. 9B , the reflection signal of a spot may appear to be a dot  921  on sensing array  900 . The controller may divide sensing cells  901  into a plurality of groups of sensing cells, each of which may include two sensing cells, four sensing cells, eight sensing cells, or other suitable numbers of sensing cells. The controller may also be configured to select one of the groups as the first subset of the sensing cells. In some embodiments, the controller may further be configured to randomly select one of the groups as the first subset of the sensing cells. Alternatively or additionally, the controller may be configured to rotate the groups and select one of the groups to be connected to one or more readout TOF modules, and may not select the same group unless other groups have been selected in a rotation. In some embodiments, the controller may be configured to select a sensing cell  901  that covers dot  921  as the first subset of the sensing cells to be connected to a readout TOF module. Alternatively, the controller may be configured to include one or more sensing cells into the first subset of the sensing cells in addition to the sensing cells covering dot  921 . For example, the controller may select a group of sensing cells  922  by including three adjacent sensing cells into the first subset of the sensing cells. 
     In some embodiments, as discussed above, the controller may be configured to select the first subset of the sensing cells based on a part of the field of view that the scanning module of the LIDAR system scans. For example, the first subset of the plurality of sensing cells may be configured to receive reflection signals indicative of reflections of flash light emissions from one or more objects in a first segment of a field of view of a LIDAR system, and the second subset of the plurality of sensing may be configured to receive reflection signals indicative of reflections of flash light emissions from one or more objects in a second segment of the field of view of the LIDAR system. In some embodiments, the first segment of the field of view may be positioned closer to the LIDAR system (or a component thereof) than the second segment of the field of view.  FIGS. 10A, 10B, and 10C  are diagrams illustrating various exemplary fields of view of a LIDAR system consistent with some embodiments of the present disclosure. As illustrated  FIG. 10A , field of view  1010  may be divided into three portions, namely, part  1011 , part  1012 , and part  1013 . While exemplary field of view  1010  is divided into three parts, one skilled in the art would understand that the field of view may be divided into more than three parts (e.g., in a range of 4 to 100 parts, etc.). Each of part  1011 , part  1012 , and part  1013  may correspond to a particular group of one or more sensing cells on the sensing array. Part  1011  of the field of view is the closest to the LIDAR system (or a component thereof), and part  1012  is farther than part  1011  but is closer than part  1013 , which is the most distant from the LIDAR system. The scanning module may be configured to scan an area in the field of view (e.g., scanning part  1011  or a sub-area thereof) by emitting light emissions into the area. The controller may be configured to determine one or more sensing cells that correspond to part  1011  (or the sub-area thereof) as the first subset of the sensing cells to be connected to the readout TOF modules. The first subset of the plurality of sensing cells may be configured to receive reflection signals indicative of reflections of flash light emissions from one or more objects in part  1011 . The controller may also be configured to trigger a connection of the first subset of the sensing cells with the readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period (as described elsewhere in this disclosure). The controller may also be configured to detect one or more objects in part  1011  based on the first measurements. For example, the controller may detect the presence of a human being in part  1011  based on the first measurements. To avoid damage to the eyes of the human subject detected in part  1011 , the controller (or another component of the LIDAR system) may determine to scan part  1012  in the next sampling period and determine one or more sensing cells that correspond to part  1012  as a second subset of the sensing cells to be connected to the readout TOF modules. The second subset of the sensing cells may be configured to receive reflection signals indicative of reflections of flash light emissions from one or more objects in part  1012 . The controller may also be configured to trigger a connection of the first subset of the sensing cells with the readout TOF modules at a second time for providing a plurality of second measurements of changes in output of the second subset of the sensing cells by the readout TOF modules during a second sampling period (as described elsewhere in this disclosure). 
     As another example, as illustrated in  FIG. 10B , field of view  1020  may be divided into three slices  1021 ,  1022 , and  1023 . While exemplary field of view  1020  is divided into three slices, one skilled in the art would understand that the field of view may be divided into more than three slices (e.g., in a range of 4 to 180 slices, etc.). Each of part  1011 , part  1012 , and part  1013  may correspond to a particular group of one or more sensing cells on the sensing array. The scanning module may be configured to scan an area in the field of view (e.g., scanning slice  1023  or a sub-area thereof) by emitting light emissions into the area. The controller may be configured to determine one or more sensing cells that correspond to slice  1023  (or the sub-area thereof) as the first subset of the sensing cells to be connected to the readout TOF modules. The controller may also be configured to trigger a connection of the first subset of the sensing cells with the readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period, as described elsewhere in this disclosure. 
     As yet another example, as illustrated in  FIG. 10C , field of view  1030  may be divided into parts  1031 ,  1032 ,  1033 ,  1034 ,  1035 ,  1036 ,  1037 ,  1038 , and  1039 . While exemplary field of view  1030  is divided into 9 parts, one skilled in the art would understand that the field of view may be divided into more than 9 parts (e.g., in a range of 10 to 360 parts, etc.). Each of the parts of the field of view may correspond to a particular group of one or more sensing cells on the sensing array. The scanning module may be configured to scan an area in the field of view (e.g., scanning part  1035  or a sub-area thereof) by emitting light emissions into the area. The controller may be configured to determine one or more sensing cells that correspond to part  1035  (or the sub-area thereof) as the first subset of the sensing cells to be connected to the readout TOF modules. The controller may also be configured to trigger a connection of the first subset of the sensing cells with the readout TOF modules at a first time for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period, as described elsewhere in this disclosure. 
       FIG. 11  is a flowchart illustrating an exemplary process  1100  for controlling a time-of-flight sensor consistent with some embodiments of the present disclosure. The TOF sensor may be a TOF sensor described elsewhere in this disclosure. For example, the TOF sensor may include a sensing array, a readout unit, and a controller. The sensing array may include a plurality of sensing cells configured to receive reflections from the surroundings (e.g., a surrounding of a vehicle). The readout unit may include a plurality of readout TOF modules. A readout TOF module may be configured to provide a measurement of changes in output of one or more sensing cells that are connected to the readout TOF module during a period of time (e.g., a sampling period). The number of readout TOF modules may be less than the number sensing cells of the sensing array. 
     At step  1101 , the controller of the TOF sensor may be configured to trigger a connection of a first subset of the plurality of sensing cells to a plurality of readout TOF modules at a first time. For example, the controller may open the switches associated with the first subset of the sensing cells to trigger a connection of the first subset of the sensing cells to the readout TOF modules. 
     In some embodiments, the controller may select the first subset of sensing cells as described elsewhere in this disclosure. For example, the controller may select the first subset of the sensing cells based on an area on the sensing array that a reflection signal is expected to appear (by, for example, selecting the sensing cells covering the area as the first subset of the sensing cells). 
     At step  1103 , the readout TOF modules may be configured to provide a plurality of first measurements of changes in output of the first subset of the sensing cells during a first sampling period. For example, each of the readout TOF modules may be operable to detect modifications in an output of one or more connected sensing cells during the first sampling period, by, for example, measuring values such as voltage or current, changes in these values over time, or other information indicative of modification of the amount of light detected by the respective sensing cells. 
     In some embodiments, at least one of the readout TOF modules may be connected to two or more sensing cells of the first subset of the sensing cells. The at least one of the readout TOF modules may be configured to provide a readout indicative of a change in an amount of light detected by the two or more sensing cells of the first subset of the sensing cells. 
     In some embodiments, the first (and/or second) measurements measure a trace of light intensity impinging on each of the first (and/or second) subset of sensing cells along a time of flight corresponding to at least  10  meters from the LIDAR system (or a component thereof). 
     In some embodiments, the controller (or a processor) may also receive the plurality of first measurements and detect a first object based on the plurality of first measurements. 
     In some embodiments, the controller (or a processor) may modify at least one parameter of the scanning module of the LIDAR system based on the first measurements. For example, the controller may detect the presence of a human being in an area of the field of view based on the first measurements. The controller may also decrease the intensity of the light emitted to that area to minimize or prevent the impact by the light on the human being. As another example, the controller may determine an offset of an actual area on the sensing array that a reflection signal appear compared to the expected area of the reflection signal on the sensing array, based on the first measurements. The controller may also adjust the light deflector (e.g., a mirror) to deflect the light emission to an updated area in the field of view based on the offset so that the expected area of the reflection signal on the sensing array may match the actual area on the sensing array in the next sampling period. 
     At step  1105 , the controller (or the processor) may be configured to determine a second subset of the sensing cells to be connected to the readout TOF modules based on the first measurements. For example, the controller may be configured to determine a second subset of the sensing cells that correspond to a part of the field of view that is different from the part of the field of view associated with the first measurements. 
     In some embodiments, in determining the second subset of the sensing cells, the controller may consider one or more other factors in addition to the first measurements. For example, the second subset of the sensing cells may be selected further based on the light emitted by a light source of the LIDAR system (as described elsewhere in this disclosure). Alternatively or additionally, the second subset of the sensing cells may be selected further based on a part of the field of view that the scanning module of the LIDAR system scans (as described elsewhere in this disclosure). Alternatively or additionally, the second subset of the sensing cells may be selected further based on an area on the sensing array that reflections may be expected to be detected (as described elsewhere in this disclosure). 
     In some embodiments, the first subset and the second subset of sensing cells may be the same. Alternatively, the first subset and the second subset of sensing cells may have at least one common sensing cell. In other embodiments, the first subset and the second subset of sensing cells may have no common sensing cells. In some embodiments, the first subset and the second subset of sensing cells may be different. For example, at least one of the second subset of the plurality of sensing cells is not connected to a readout TOF module at the first time. Alternatively or additionally, at least one of the first subset of the plurality of sensing cells is not connected to a readout TOF module at the second time. 
     At step  1107 , the controller may trigger a connection of the second subset of the plurality of sensing cells to a plurality of readout TOF modules at a second time. For example, the controller may open the switches associated with the second subset of the sensing cells to trigger a connection of the second subset of the sensing cells to the readout TOF modules. 
     At step  1109 , the readout TOF modules may be configured to provide a plurality of second measurements of changes in output of the second subset of the sensing cells during a second sampling period. For example, each of the readout TOF modules may be operable to detect modifications in an output of one or more connected sensing cells during the second sampling period, by, for example, measuring values such as voltage or current, changes in these values over time, or other information indicative of modification of the amount of light detected by the respective sensing cells. 
     In some embodiments, the first subset and the second subset of readout TOF modules may be the same. Alternatively, the first subset and the second subset of readout TOF modules may have at least one common readout TOF module. Alternatively, the first subset and the second subset of sensing cells may have no common readout TOF modules. 
     In some embodiments, the controller (or a processor) may be configured to receive the plurality of second measurements and detect one or more objects based on the plurality of second measurements. 
     In some embodiments, the controller may be configured to synchronize measurements with a light source of a LIDAR system in which the TOF optical sensor is installed. Alternatively or additionally, the controller may be configured to synchronize measurements with a scanning module (or one or more components thereof, such as a light source, a light deflector (e.g., a mirror), etc.) of a LIDAR system in which the TOF optical sensor is installed. In some embodiments, the controller may be configured to synchronize measurements with a scanning module and a light source of a LIDAR system in which the TOF optical sensor is installed. For example, the controller may be configured to trigger a connection of a first subset of the sensing cells to the readout TOF modules for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. The controller may also trigger an analog measurement (not a TOF measurement) of one or more sensing cells (or referred to the surrounding sensing cells) adjacent to the first subset of the sensing cells to determine the presence of a reflection signal (and/or the intensity thereof) based on the analogy measurement. 
       FIG. 12  is a diagram illustrating an exemplary sensing array  1200  consistent with some embodiments of the present disclosure. As illustrated in  FIG. 12 , sensing array  1200  may include a plurality of sensing cells  1201 . An expected position of a reflection signal may be determined to be in an area  1211  on sensing array  1200 . The controller may be configured to determine the sensing cells covering area  1211  as a first subset (or a second subset) of the sensing cells to be connected to a first subset (or a second subset) of the readout TOF modules. The controller may also be configured to switch four adjacent sensing cells  1221 ,  1222 ,  1223 , and  1234  to analogy measurements (which are not TOF measurements) and determine the presence of a reflection signal and/or the intensity thereof based on the analogy measurements. If the presence of a reflection signal is detected based on the analogy measurements (e.g., the actual reflection signal shifts to the left of expected area  1211  and partially overlaps with sensing cells  1222 ), the controller may determine the offset between the actual position of the reflection signal and the expected position of the reflection signal based on the analogy measurements and the first measurements (i.e., TOF measurements provided by the first or second subset of readout TOF modules). 
     The controller may also cause adjustment of at least one aspect of the scanning module. For example, the controller (or a processor) may adjust the position (and/or orientation) of the mirror and/or the position (and/or orientation) of the light source to realign an actual position of a reflection signal with the sensing cells that are selected to receive the reflection signal in the next sampling period. By way of example, if the actual reflection signal shifts to the left of expected area  1211  and partially overlaps with sensing cells  1222 , the controller may cause adjust the position (and/or orientation) of the mirror and/or the position (and/or orientation) of the light source to realign an actual position of a reflection signal with sensing cells in area  1211  (so that sensing cell  1222  may not detect part of the reflection signal). Alternatively, instead of adjusting the scanning module, the controller may add one or more of sensing cells  1221 ,  1222 ,  1223 , and  1234  to the first subset of the sensing cells as the second subset of the sensing cells to be connected to the readout TOF modules for the next sampling period. The controller may also trigger a connection of the second subset of the sensing cells to the readout TOF modules at a second time, and the readout TOF modules may provide second measurements of changes in output of the second subset of the sensing cells during the next sampling period, as described elsewhere in this disclosure. 
       FIG. 13  is a flowchart illustrating an exemplary process  1300  for controlling a time-of-flight optical sensor consistent with some embodiments of the present disclosure. Process  1300  may be used for controlling any one of exemplary TOF optical sensors described elsewhere in this disclosure. For example, a TOF optical sensor may include a two-dimensional sensing array and a readout unit. The sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The TOF optical sensor may also include a controller (and/or a processor) configured to perform one or more steps of process  1300 . In some embodiments, the controller may also be configured to perform other functions of a controller (and/or a processor) as described elsewhere in this disclosure (e.g., one or more steps of process  1100  illustrated in  FIG. 11  and/or processor  1500  illustrated in  FIG. 15 ). 
     In some embodiments, the sensing array may include sensing cells in a planar arrangement. In some embodiments, at least portion of the sensing cells may be substantially arranged along a straight line. For example, the sensing cells may be arranged in a lattice (e.g., a rectangular lattice, a rhombic lattice, a hexagonal lattice, an oblique lattice, or the like, or a combination thereof). Other arrangements may also be possible (e.g., a periodic arrangement of sensing cells over one axis but not over the other axis, or non-periodic 2D arrangements). 
     The TOF optical sensor may be implemented on a single chip (e.g., silicon, InGaAs, etc.), or on two or more chips (e.g., silicon and InGaAs). In some embodiments, the sensing cells may be implemented on a single chip, or on two or more chips (e.g., for readout in different spectral ranges). In some embodiments, the sensing cells and the readout TOF modules may be implemented on a single chip. 
     Alternatively, the sensing cells and the readout TOF modules may be implemented on different chips. For example, at least one sensing cell may be implemented on a chip different from the chip(s) on which the readout TOF modules are implemented. Alternatively or additionally, at least one readout TOF module may be implemented on a chip different from the chip(s) on which the sensing cells are implemented. 
     In some embodiments, the number of the readout TOF modules may be less than the number of the sensing cells by at least one order of magnitude, at least two orders of magnitude, at least three orders of magnitude, or at least four orders of magnitude. For example, For example, in the example of 120,000 sensing cells arranged as 200×600 rectangular lattice array, there may be 40, 200, or 600 readout TOF modules to be connected to one or more (e.g., two, four, or more) of the sensing cells at a time. 
     In some embodiments, the controller may include one or more decoders associated with the sensing array to connect to two or more sensing cells (e.g., by opening the switches associated with the two or more sensing cells). This may be used for hardware binning, for example, e.g., to increase detection sensitivity (to low reflectivity targets) in order to increase detection range, or for any other reason. For example, one or more decoders may be configured to determine the first sensing cell of the plurality of sensing cells to be connected to a readout TOF module. 
     In some embodiments, the controller may be configured to synchronize measurements with a light source of a LIDAR system in which the TOF optical sensor is installed. Alternatively or additionally, the controller may be configured to synchronize measurements with a scanning module (or one or more components thereof, such as a light source, a light deflector (e.g., a mirror), etc.) of a LIDAR system in which the TOF optical sensor is installed. In some embodiments, the controller may be configured to synchronize measurements with a scanning module and a light source of a LIDAR system in which the TOF optical sensor is installed. For example, the controller may be configured to trigger a connection of a first subset of the sensing cells to the readout TOF modules for providing a plurality of first measurements of changes in output of the first subset of the sensing cells by the readout TOF modules during a first sampling period. The controller may also trigger an analog measurement (not a TOF measurement) of one or more sensing cells (or referred to the surrounding sensing cells) adjacent to the first subset of the sensing cells to determine the presence of a reflection signal (and/or the intensity thereof) based on the analogy measurement. 
     At step  1301 , the controller may be configured to trigger a connection of a first sensing cell of the plurality of sensing cells to a first readout TOF module of the plurality of readout TOF modules at a first time during a sampling period. For example, the controller may select one of the sensing cells of the sensing array and trigger a connection of the selected sensing cells to one of the readout TOF modules at a time point during a sampling period. In some embodiments, the first sensing cell of the plurality of sensing cells may be randomly selected to be connected to the plurality of the readout TOF modules at the first time. 
     At step  1303 , the first readout TOF module may be configured to provide a first measurement of a change in output of the first sensing cell. The first readout TOF module may provide a first measurement of a change in output of the first sensing cell as described elsewhere in this disclosure. For example, the first readout TOF module may be configured to detect modifications in an output of the first sensing cell by, for example, measuring values such as voltage or current, changes in these values over time, or other information indicative of modification of the amount of light detected by the first sensing cell. 
     In some embodiments, the first readout TOF module (or any readout TOF module) may be connected to two or more sensing cells, which may include the first sensing cell. The first readout TOF module may be configured to provide a readout indicative of a change in an amount of light detected by the two or more sensing cells. 
     In some embodiments, the TOF optical sensor may include a processor configured to receive the first measurement and detect one or more objects based on the first measurement. Alternatively, the controller may be configured to receive the first measurement and detect one or more objects based on the first measurement. 
     At step  1305 , the controller may be configured to trigger a connection of a second sensing cell of the plurality of sensing cells to the first readout TOF module at a second time during the sampling period. The second sensing cell may be different from the first sensing cell. In some embodiments, the second time may be after the first time. For example, the controller may select a sensing cell adjacent to the first sensing cell as the second sensing cell. Alternatively, the controller may randomly select a sensing cell (other than the first sensing cell) among the sensing cells as the second sensing cell. The controller may also be configured to trigger a connection of the second sensing cell to the first readout TOF module at the second time. 
     At step  1307 , the first readout TOF module may be configured to provide a second measurement of a change in output of the second sensing cell. The first readout TOF module may provide a second measurement of a change in output of the second sensing cell as described elsewhere in this disclosure. For example, the first readout TOF module may be configured to detect modifications in an output of the second sensing cell by, for example, measuring values such as voltage or current, changes in these values over time, or other information indicative of modification of the amount of light detected by the second sensing cell. 
     In some embodiments, the first sensing cell may be not connected to any readout TOF modules at the second time. Alternatively or additionally, the second sensing cell is not connected to any readout TOF modules at the first time. In some embodiments, at least one of the plurality of sensing cells is not connected to any readout TOF modules at the first time. Alternatively or additionally, at least one of the plurality of sensing cells is not connected to any readout TOF modules at the second time. 
     In some embodiments, during a sampling period, the controller may trigger a connection of each of all the sensing cells (or a subset of the sensing cells) to one readout TOF module at least once. By way of example, the sensing array may include 16 sensing cells, and the readout unit may include 2 readout TOF modules. The controller may trigger a connection of sensing cell  1  to a first readout TOF module and a connection of sensing cell  2  to a second readout TOF module at a first time. The controller may also trigger a connection of sensing cell  3  to the first readout TOF module and a connection of sensing cell  4  to the second readout TOF module at a second time. The controller may further trigger a connection of sensing cell  5  to the first readout TOF module and a connection of sensing cell  6  to the second readout TOF module at a third time. The controller may also trigger a connection of one of the rest of the sensing cells to one of the readout TOF modules at a different time until all sensing cells have been connected to a readout TOF module at least once. A readout TOF module may be configured to provide a measurement of a change in output of the connected sensing cell as described elsewhere in this disclosure. 
     In some embodiments, the controller may receive one or more measurements of the sensing cells during the sampling period (also referred herein as sampling measurements) and determine a group of the sensing cells to be connected to one or more readout TOF modules in a next sampling period or a scanning period. For example, the controller may receive a first measurement of a first sensing cell and determine a subset of the plurality of sensing cells to be connected to one or more of the plurality of readout TOF modules during a scanning period after the sampling period based on the received measurement. In some embodiments, the subset may include the first sensing cell. Alternatively, the first sensing cell may not be included in the subset. The controller may also trigger a connection of each sensing cell of the subset to one of the plurality of readout TOF modules during the scanning period. Each of the plurality of the readout TOF module may be configured to provide a scanning measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF module during the scanning period. In some embodiments, the controller (or a processor) may further be configured to receive the scanning measurements and detect one or more objects based on the scanning measurements. As another example, the controller may receive the sampling measurements of all sensing cells obtained during a sampling period. The controller may determine a subset of the plurality of sensing cells to be connected to one or more of the readout TOF modules during a scanning period after the sampling period based, at least in part, on the sampling measurements. 
     In some embodiments, the duration of the sampling period may be equal to, less than, or greater than the duration of the scanning period. 
     In some embodiments, the controller may be configured to trigger a connection of an analog sensor to an adjacent sensing cell that is adjacent to the first sensing cell at the first time. The adjacent sensing cell may not be connected to a readout TOF module at the first time. The analogy sensor may provide a second measurement of a change in output of the adjacent sensing cell. In some embodiments, the controller may also be configured to determine a subset of the plurality of sensing cells to be connected to one or more readout TOF modules during a scanning period after the sampling period, based, at least in part, on the second measurement and/or the first measurement (i.e., the measurement by the first readout TOF module connected to the first sensing cell). For example, the second measurement may indicate the presence of a reflection signal (or a portion thereof) in the adjacent cell. The controller may be configured to include the adjacent cell in a subset of the plurality of sensing cells to be connected to one of the readout TOF modules in the next scanning period. 
     In some embodiments, the controller (or a processor) may be configured to adjust (or cause an adjustment of) a scanning module to modify at least one light emission directed to a field of view of a LIDAR system, based on one or more sampling measurements obtained during the sampling period. For example, the controller may be configured to adjust the position (and/or orientation) of the mirror and/or the position (and/or orientation) of the light source to realign an actual position of a reflection signal with the sensing cells that are selected to receive the reflection signal in a scanning period, based, at least in part on the first measurement (i.e., the measurement by the first readout TOF module connected to the first sensing cell). 
     In some embodiments, the first measurement measures a trace of light intensity impinging on the first sensing cell along a time of flight corresponding to at least  10  meters. 
     In some embodiments, the controller may be configured to select a subset of the sensing cells of the sensing array to be connected to one or more readout TOF modules. The subset may include the first sensing cell. For each sensing cell of a subset of the plurality of sensing cells, the controller may be configured to trigger a connection of the each of the subset of sensing cells to one of the plurality of readout TOF modules at a first time during a sampling period. Each of the readout TOF modules may be configured to provide a measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF modules. In some embodiments, the subset of the plurality of sensing cells may include less than 75%, 50%, 33%, 20%, 10%, or 5% of the plurality of sensing cells. 
     In some embodiments, the controller may be configured to select the subset of the sensing cells based on a shape of a light emission directed to a field of view of a LIDAR system. As discussed above, the shape of the light emitted by a light source of the LIDAR system may affect the area on the sensing array that receives the reflection signal. For example, if the laser emitted to the field of view is a line, the received reflection signal may appear as a line shape over a number of sensing cells. As illustrated in  FIG. 14A , an exemplary sensor array  1400  may include a plurality of sensing cells  1401 . A laser having a beam that is line-shaped may be emitted to the field of view of the LIDAR system, and a reflection signal may appear as a line (e.g., similar to line  911  on certain area of sensing array  900  illustrated in  FIG. 9A , covering a group of sensing cells  912 ). The controller may be configured to divide sensing cells  1401  into a plurality of subsets of sensing cells, and each of the groups may include  8  sensing cells in the vertical axis. In some embodiments, each of the groups may also include one or more adjacent sensing cells in the horizontal axis and/or one or more adjacent sensing cells in the vertical axis. For example, as illustrated in  FIG. 14A , the controller may divide sensing cells  1401  ( 128  sensing cells in total) into  8  subsets (e.g., first subset  1411 , second subset  1412 , third subset  1413 , and so on), each of which includes  16  sensing cells (by, for example, including one adjacent sensing cell on the left or the right). The controller may also be configured to select a first subset (e.g., first subset  1411 ) to be connected to one or more readout TOF modules. For each sensing cells of first subset  1411 , the controller may be configured to trigger a connection of the each of the subset of sensing cells to one of the plurality of readout TOF modules at a first time during a sampling period. Each of the readout TOF modules may be configured to provide a first measurement of a change in output of one or more sensing cells in first subset  1411  that are connected to the each of the plurality of the readout TOF module. 
     In some embodiments, the controller may be configured to select a second subset of the sensing cells of the sensing array to be connected to one or more readout TOF modules. For example, the controller may select a subset adjacent to the first subset (e.g., first subset  1411  in the example above). By way of example, the controller may select second subset  1412  or third subset  1413  as the second subset to be connected to one or more readout TOF modules. For each sensing cell of the second subset of the plurality of sensing cells, the controller may be configured to trigger a connection of the each of the second subset of sensing cells to one of the plurality of readout TOF modules at a second time (after the first time) during a sampling period. Each of the readout TOF modules may be configured to provide a measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF module. 
     In some embodiments, as described elsewhere in this disclosure, if the laser beam is split into a plurality of beam spots, the reflection signal of a spot may appear on the sensing array as a dot (compared to the shape of the reflection signal appearing on the sensing array if the laser has a line shape described above). As illustrated in  FIG. 14B , sensor array  1400  may include a plurality of sensing cells  1401 . A laser having a beam that have beam spots may be emitted to the field of view of the LIDAR system, and a reflection signal may appear as a plurality of spots (e.g., similar to dot  921  on sensing array  900  illustrated in  FIG. 9B ). The controller may be configured to divide sensing cells  1401  into a plurality of subsets of sensing cells, and each of the groups may include a certain number of sensing cells. For example, the controller may be configured to include one or more sensing cells into a subset of the sensing cells in addition to a sensing cell covering the dot (e.g., dot  921  illustrated in  FIG. 9B ). By way of example, as illustrated in  FIG. 14B , the controller may divide all sensing cells  1401  ( 128  sensing cells in total) into  32  subsets (e.g., first subset  1421 , second subset  1422 , third subset  1423 , and so on), each of which includes  4  sensing cells. The controller may also be configured to select a first subset (e.g., first subset  1421 ) to be connected to one or more readout TOF modules. For each sensing cells of first subset  1421 , the controller may be configured to trigger a connection of the each of the subset of sensing cells to one of the plurality of readout TOF modules at a first time during a sampling period. Each of the readout TOF modules may be configured to provide a first measurement of a change in output of one or more sensing cells in first subset  1421  that are connected to the each of the plurality of the readout TOF module. In some embodiments, the controller may be configured to select a second subset of the sensing cells of the sensing array to be connected to one or more readout TOF modules. For example, the controller may select a subset adjacent to the first subset (e.g., first subset  1421  in the example above). By way of example, the controller may select second subset  1422  or third subset  1423  as the second subset to be connected to one or more readout TOF modules. For each sensing cell of the second subset of the plurality of sensing cells, the controller may be configured to trigger a connection of the each of the second subset of sensing cells to one of the plurality of readout TOF modules at a second time (after the first time) during a sampling period. Each of the readout TOF modules may be configured to provide a measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF module. 
     In some embodiments, during a sampling period, the controller may trigger a connection of each of all the sensing cells (with other sensing cells in a same subset) to one readout TOF module at least once. By way of example, as illustrated in  FIG. 14A , sensing array  1400  may be divided into  8  subsets (e.g., first subset  1411 , second subset  1412 , third subset  1413 , and so on), each of which includes  16  sensing cells. The controller may trigger a connection of each sensing cell of a first subset (e.g., first subset  1411 ) to one of the readout TOF modules at a first time during a sampling period, thereby enabling the one of the plurality of readout TOF modules to provide a first measurement of a change in output of one or more sensing cells of the first subset that are connected to the one of the plurality of readout TOF modules. The controller may also trigger a connection of each sensing cell of a second subset (e.g., second subset  1412 ) to one of the readout TOF modules at a second time during the sampling period, thereby enabling the one of the plurality of readout TOF modules to provide a second measurement of a change in output of one or more sensing cells of the first subset that are connected to the one of the plurality of readout TOF modules. The controller may further trigger a connection of each sensing cell of a third (or fourth, . . . , or eighth) subset to one of the readout TOF modules at a third (or fourth, . . . , or eighth) time during the sampling period, thereby enabling the one of the plurality of readout TOF modules to provide a third (or fourth, . . . , or eighth) measurement of a change in output of one or more sensing cells of the third (or fourth, . . . , or eighth) subset that are connected to the one of the plurality of readout TOF modules. 
     In some embodiments, the controller (or a processor) may be configured to receive the measurements of one or more subsets and detect one or more objects based on the received measurements. 
     In some embodiments, not all subsets are connected to a readout TOF module at a given time. For example, the sensing cells of the second subset may not be connected to any readout TOF modules at the first time. Alternatively or additionally, the sensing cells of the first subset may not be connected to any readout TOF modules at the second time. 
     In some embodiments, the controller may receive the measurements of one or more subsets during the sampling period (also referred herein as sampling measurements of a subsets) and determine a group of the sensing cells to be connected to one or more readout TOF modules in a next sampling period or a scanning period based on the received measurements. For example, the controller may receive the sampling measurement of all subsets obtained during a sampling period. The controller may also determine a subset of the plurality of sensing cells to be connected to one or more of the plurality of readout TOF modules in a next scanning period based on the received sampling measurements). In some embodiments, the determined subset may include one or more of the “old” subsets that were connected to one or more readout TOF modules during the sampling period. For example, the controller may determine that may indicate the presence of an object in certain part of the field of view based on the sampling measurements of an “old” subset obtained during the sampling period. The controller may also include this “old” subset in a “new” subset of sensing cells to be connected to at least one of the readout TOF modules in the next scanning cycle. The controller may also trigger a connection of each sensing cell of the “new” subset to one of the plurality of readout TOF modules during the scanning period. Each of the plurality of the readout TOF module may be configured to provide a scanning measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF module during the scanning period. In some embodiments, the controller (or a processor) may further be configured to receive the scanning measurements and detect one or more objects based on the scanning measurements. 
     In some embodiments, the controller may be configured to trigger a connection of an analog sensor to one or more adjacent sensing cells that are adjacent to a subset at the time when the subset is connected to one or more readout TOF modules. The adjacent sensing cell(s) may not be connected to a readout TOF module at that time. For example, the controller may be configured to trigger a connection of each sensing cell of a subset (e.g., a subset including the sensing cells covering area  1211  illustrated in  FIG. 12 ) to one of the readout TOF modules at a first time. The controller may also be configured to trigger a connection of an analog sensor to one or more of sensing cells  1221 ,  1222 ,  1223 , and  1224  at the same time (i.e., the first time). The analogy sensor may provide an analog measurement of a change in output of the connected adjacent sensing cell(s). In some embodiments, the controller may also be configured to determine a “new” subset of the plurality of sensing cells to be connected to one or more readout TOF modules during a scanning period after the sampling period, based, at least in part, on the analog measurement and/or the TOF measurements (i.e., the measurement by the readout TOF modules connected to the sensing cells of the “old” subset). For example, the analog measurement may indicate the presence of a reflection signal (or a portion thereof) in the adjacent cell(s). The controller may be configured to include the adjacent cell(s) in a “new” subset of the plurality of sensing cells to be connected to one of the readout TOF modules in the next scanning period. 
     In some embodiments, the controller (or a processor) may be configured to adjust a scanning module to modify at least one light emission directed to a field of view of a LIDAR system, based on sampling measurements of one or more subsets obtained during the sampling period. For example, the controller may be configured to may adjust the position (and/or orientation) of the mirror and/or the position (and/or orientation) of the light source to realign an actual position of a reflection signal with the sensing cells that are selected to receive the reflection signal in a scanning period, based, at least in part on the first measurements (i.e., the measurement by the readout TOF modules connected to the sensing cell of the first subset). 
       FIG. 15  is a flowchart illustrating an exemplary process  1500  for controlling a time-of-flight optical sensor consistent with some embodiments of the present disclosure. Process  1500  may be use for controlling any one of exemplary TOF optical sensors described elsewhere in this disclosure. For example, a TOF optical sensor may include a two-dimensional sensing array and a readout unit. The sensing array may include a plurality of sensing cells. The readout unit may include a plurality of readout TOF modules. The TOF optical sensor may also include a controller (and/or a processor) configured to perform one or more steps of process  1500 . In some embodiments, the controller may also be configured to perform other functions of a controller (and/or a processor) as described elsewhere in this disclosure (e.g., one or more steps of process  1100  illustrated in  FIG. 11  and/or processor  1500  illustrated in  FIG. 1500 ). 
     At step  1501 , the controller may be configured to, for each sensing cell of a first subset of a plurality of sensing cells, trigger a connection of the each sensing cell of the first subset of the plurality of sensing cells to one of a plurality of readout TOF modules at a first time. Each of the readout TOF modules may be configured to provide a measurement of a change in output of one or more sensing cells that are connected to the each of the plurality of the readout TOF module. In some embodiments, the subset of the plurality of sensing cells may include less than 75%, 50%, 33%, 20%, 10%, or 5% of the plurality of sensing cells. 
     At step  1503 , the controller may be configured to receive the measurements of the sensing cells of the first subset and determine an offset of an expected area of the sensing array in which a reflection signal appears, based on the received measurements. For example, as illustrated in  FIG. 16 , sensing array  1600  may include a plurality of sensing cells  1601 . The controller (or a processor) may be configured to determine an expected area  1611  of the sensing array in which a reflection signal appears. By way of example, the LIDAR system on which the TOF optical sensor is implemented may direct a light emission to an area in the field of view of the LIDAR. The controller may determine that a reflection signal of the light emission may appear in a corresponding area (or an expected area  1611 ) of the sensing array. However, a reflection signal may actually appear in area  1612  on the sensing array. The controller may be configured to, for each sensing cell of subset  1631 , trigger a connection of the each sensing cell of subset  1631  of the plurality of sensing cells to one of a plurality of readout TOF modules at the first time, thereby enabling the one of the plurality of readout TOF modules to provide a measurement of a change in output of one or more sensing cells of subset  1631  that are connected to the one of the plurality of readout TOF modules. The controller may also be configured to receive the measurements and determine a position of the reflection signal appearing on the sensing array (e.g., an area at least partially overlapping with subset  1621 ) based on the received measurements. The controller may further be configured to determine an offset (e.g., offset  1631 ) between the expected area and the determined (or measured) area by, for example, comparing the sensing cells covering the expected area and the sensing cells covering the measured area. In some embodiments, the offset may be expressed with an offset of the pixel(s) in the vertical axis and/or an offset of the pixel(s) in the horizontal axis. For example, assuming sensing cell  1641 , which is the left, top sensing cell, has a coordinate (0, 0), offset  1631  may be expressed as (−3, +1) from the expected area. 
     At step  1505 , the controller may be configured to determine a second subset of the plurality of sensing cells, each sensing cells of which is to be connected to one of the plurality of readout TOF modules at a second time, based on the determined offset. For example, the controller may determine a second subset of the sensing cells, which may include subset  1631 , to be connected to at least one of the readout TOF modules at a second time (e.g., during a next scanning period). As another example, the controller may be configured to adjust (or cause an adjustment of) a scanning module of the LIDAR system to modify at least one light emission directed to the field of view of a LIDAR system in the next scanning cycle, based on the determined offset. For example, the controller may be configured to adjust the position (and/or orientation) of the mirror and/or the position (and/or orientation) of the light source to realign an actual position of a reflection signal to expected area  1611 . The controller may also be configured to determine one or more sensing cells that at least partially overlapping with expected area  1611  as the second subset. 
     In some embodiments, for each sensing cell of the second subset of the plurality of sensing cells, the controller may be configured to trigger a connection of the each sensing cell of the second subset of the plurality of sensing cells to one of the plurality of readout TOF modules at the second time, thereby enabling the one of the plurality of readout TOF modules to provide a second measurement of a change in output of one or more sensing cells of the second subset that are connected to the one of the plurality of readout TOF modules during a scanning period. In some embodiments, the controller may also be configured to receive the second measurements and detect one or more objects based on the second measurements. 
     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.