Patent Publication Number: US-2023161012-A1

Title: Lidar systems and methods with beam steering and wide angle signal detection

Description:
This application claims the benefit of U.S. Provisional Application No. 62/790,842, filed Jan. 10, 2019, the disclosure of which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates generally to light detection and ranging (LiDAR) systems and methods and, more particularly, to systems and methods for steering consecutive light pulses using micro electro-mechanical system (MEMS) to illuminate objects in a field of view. 
     BACKGROUND 
     LiDAR system can be used to measure the distance between an object and the system. Specifically, the system can transmit a signal (e.g., using a light source), record a returned signal (e.g., using light detectors), and determine the distance by calculating the delay between the returned signal and the transmitted signal. 
     BRIEF SUMMARY 
     The following presents a simplified summary of one or more examples in order to provide a basic understanding of the disclosure. This summary is not an extensive overview of all contemplated examples, and is not intended to either identify key or critical elements of all examples or delineate the scope of any or all examples. Its purpose is to present some concepts of one or more examples in a simplified form as a prelude to the more detailed description that is presented below. 
     Embodiments discussed herein refer to using LiDAR systems for steering consecutive light pulses using micro electro-mechanical system (MEMS) or other beam steering systems to illuminate objects in a field of view. Returned light pulses can be detected using different receiver systems. One such receiver system may use a relatively large optic in combination with a detector array. Another receiver system may use multiple optics in combination with multiple detectors. 
     In one embodiment, a LiDAR system can include a beam steering system, a laser system operative to emit light pulses that are steered by the beam steering system such that each emitted light pulse is steered along an optical path within a field of view (FOV), and receiver system operative to receive return pulses from the FOV. The beam steering system can include a micro-electrical mechanical system (MEMS) structure and a mirror. The receiver system can include an optical lens and a detector array comprising a plurality of detector segments. The LiDAR system can include control circuitry operative to activate a subset of the detector segments based on the optical path; deactivate the detector segments not included within the subset; and process a return pulse detected by the activated subset of detector segments. 
     In one embodiment, the MEMS structure is a MEMS polygon. 
     In one embodiment, the MEMS structure is a liquid crystal. 
     In one embodiment, the MEMS structure includes at least one micro mirror. 
     In one embodiment, the optical lens is a wide angle lens. 
     In one embodiment, the detector array is positioned at or near a focal plane of the optical lens. 
     In one embodiment, the control circuitry is operative to register the optical path with the selective activation of the subset of detector segments such that only the subset of detector segments is active to receive the return pulse. 
     In one embodiment, a deactivated detector segment is powered off and wherein an activated detector segment is powered on. 
     In one embodiment, the beam steering system does not direct the return pulse to the detector array. 
     In one embodiment, the controller is operative to control a repetition rate of the light pulses based on the optical path. 
     In one embodiment, the controller is operative to adjust the movement speed of the mirror based on the optical path. 
     In one embodiment, the controller is operative to coordinate at least one of movement speed of the mirror and a repetition rate of the light pulses based on the optical path. 
     In one embodiment, a method for using a LiDAR scanning system is provided that includes controlling, via a beam steering system, transmission of a light pulse along an optical path within a field of view (FOV), the beam steering system comprising a micro-electrical mechanical system (MEMS) structure; activating a subset of detector segments of a detector array comprising a plurality of detector segments based on the optical path; deactivating the detector segments not included in the activated subset; monitoring the activated subset of detector segments for a return pulse; and processing the monitored return pulse. 
     In one embodiment, the beam steering system comprises a mirror. 
     In one embodiment, the method further includes receiving a return pulse from the FOV, wherein the return pulse is collected by an optical lens that directs the return pulse to the activated subset of detector segments. 
     In one embodiment, the optical lens is a wide angle lens. 
     In one embodiment, the detector array is positioned at or near a focal plane of the optical lens. 
     In one embodiment, the MEMS structure is a MEMS polygon. 
     In one embodiment, the MEMS structure is a liquid crystal. 
     In one embodiment, the MEMS structure comprises at least one micro mirror. 
     In one embodiment, the method further includes registering the optical path with the selective activation of the subset of detector segments such that only the subset of detector segments is active to receive the return pulse. 
     In one embodiment, a deactivated detector segment is powered off and wherein an activated detector segment is powered on. 
     In one embodiment, the beam steering system does not direct the return pulse to the detector array. 
     In one embodiment, the method further includes controlling a repetition rate of the light pulses based on the optical path. 
     In one embodiment, the method further includes adjusting movement speed of a mirror included in the beam steering system based on the optical path. 
     In one embodiment, the method further includes coordinating at least one of movement speed of a mirror included in the beam steering system and a repetition rate of the light pulses based on the optical path. 
     In one embodiment, a LiDAR system is provided that includes a beam steering system, a laser system operative to emit light pulses that are steered by the beam steering system such that each emitted light pulse is steered along an optical path within a field of view (FOV), a receiver system operative to receive return pulses from the FOV, and control circuitry. The beam stearing system can include a micro-electrical mechanical system (MEMS) structure and a mirror. The receiver system can include a multi-lens array comprising a plurality of lenses each associated with a window within the FOV, wherein at least two windows overlap each other such that the lenses associated with the overlapping windows receive the same return pulse; and a plurality of detectors, each one of the plurality of detectors corresponding to one of the plurality of lenses. The control circuitry is operative to process signals received from each of the plurality of detectors, and discriminate among the processed signals by filtering out received return pulses that are not captured by the at least two overlapping windows to produce a filtered signal. 
     In one embodiment, the MEMS structure is a MEMS polygon. 
     In one embodiment, the MEMS structure is a liquid crystal. 
     In one embodiment, the MEMS structure comprises at least one micro mirror. 
     In one embodiment, the at least two windows overlap each other at a minimum distance within the FOV. 
     In one embodiment, a LiDAR system is provided that includes a beam steering system; a laser system operative to emit light pulses that are steered by the beam steering system such that each emitted light pulse is steered along an optical path within a field of view (FOV); and a receiver system operative to receive return pulses from the FOV. The receiver system can include a multi-lens array comprising a plurality of lenses each associated with a window within the FOV, wherein at least two windows overlap each other such that the lenses associated with the overlapping windows receive the same return pulse; and a plurality of detectors, each one of the plurality of detectors corresponding to one of the plurality of lenses. The LiDAR system can include control circuitry operative to process signals received from each of the plurality of detectors; and discriminate among the processed signals by filtering out received return pulses that are not captured by the at least two overlapping windows to produce a filtered signal. 
     In one embodiment, a method for a LiDAR system is provided that includes controlling, via a beam steering system, transmission of a light pulse along an optical path within a field of view (FOV); receiving returned light pulses from the FOV via a multi-lens array comprising a plurality of lenses each associated with a window within the FOV, wherein at least two windows overlap each other such that the lenses associated with the overlapping windows receive the same returned light pulse, and wherein each of the plurality of lenses directs any returned light pulse to a detector corresponding to that particular one of the plurality of lenses; processing signals received from each detector corresponding to the plurality of lenses; and discriminating among the processed signals by filtering out received return pulses that are not captured by the at least two overlapping windows to produce a filtered signal. 
     In one embodiment, a LiDAR system is provided that includes a laser transmission and steering system operative to transmit light pulses along transmission paths within a field of view (FOV); and a receiver system operative to receive return pulses from the FOV, wherein at least one of the return pulses is received along a reception path that is not the same as any of the transmission paths. The receiver system includes a plurality of optical lens and detector combinations (ODC), each ODC associated with a reception path, and wherein at least two ODCs process a return pulse from the same object within the FOV. The LiDAR system can include control circuitry operative to filter out received return pulses that do not correspond to the same object being processed by the at least two ODCs. 
     In one embodiment, all of the return pulses are received along reception paths that are not the same as any of the transmission paths. 
     In one embodiment, each ODC comprises an optical lens and a detector. 
     In one embodiment, a LiDAR system further includes a vehicle, wherein the light pulses are transmitted from a first location on the vehicle, wherein each of the plurality of ODCs are located at respective different locations on the vehicle other than the first location. 
     A further understanding of the nature and advantages of the embodiments discussed herein may be realized by reference to the remaining portions of the specification and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 - 3    illustrate an exemplary LiDAR system using pulse signal to measure distances to points in the outside environment. 
         FIG.  4    depicts a logical block diagram of the exemplary LiDAR system. 
         FIG.  5    depicts a light source of the exemplary LiDAR system. 
         FIG.  6    depicts a light detector of the exemplary LiDAR system. 
         FIG.  7    shows an illustrative MEMS based LiDAR system according to an embodiment. 
         FIGS.  8 ,  8 A, and  8 B  illustrate exemplary multi-segmented detectors according to various embodiments. 
         FIGS.  9 A,  9 B, and  9 C  show illustrative examples of selective activation and deactivation of detector segments based on a position of a beam steering system. 
         FIG.  10    shows an illustrative process according to an embodiment. 
         FIGS.  11 A and  11 B  show simplified diagrams of different LiDAR systems, according to various embodiments 
         FIGS.  12 A and  12 B  show illustrative fields of view of a LiDAR system according to various embodiments. 
         FIG.  12 C  shows illustrative field of view of a LiDAR system according to an embodiment. 
         FIG.  13    shows an illustrative block diagram of LiDAR system according to an embodiment. 
         FIG.  14    shows an illustrative fiber tip arrangement according to an embodiment. 
         FIGS.  15 A and  15 B  show multiple mirror alignment arrangement that may be used for various embodiments. 
         FIG.  15 C  shows an illustrative multiple collimator arrangement that may be used for various embodiments. 
         FIG.  15 D  shows an illustrative collimator and lens arrangement according to an embodiment. 
         FIG.  16    shows illustrative scanning resolution using multiple fiber tips, a multiple mirror alignment arrangement, or multiple collimator arrangement according to an embodiment. 
         FIG.  17 A  shows another illustrative diagram of vertical resolution using multiple fiber tips or a multiple mirror alignment arrangement, according to an embodiment. 
         FIG.  17 B  shows an illustrative close-up view of a sparse region within  FIG.  17 A  and  FIG.  17 C  shows an illustrative close-up view of the dense region within  FIG.  17 A , according to various embodiments. 
         FIG.  18    shows illustrative FOV with variable sized laser pulses according to an embodiment. 
         FIG.  19    shows an illustrative multi-lens array based LiDAR system according to an embodiment. 
         FIG.  20    shows an illustrative diagram of multi-lens array according to an embodiment. 
         FIGS.  21 A,  21 B,  21 C,  21 D,  21 E, and  21 F  show different window arrangements that are derived from a corresponding multi-lens array according to various embodiments. 
         FIG.  22    shows an illustrative process according to an embodiment. 
         FIG.  23    shows an illustrative LiDAR system according to an embodiment. 
         FIG.  24    shows an illustrative schematic of two optic/detector combinations having overlapping windows that capture returned light pulses from the same object within a FOV of a LiDAR system. 
         FIG.  25    shows an illustrative vehicle  2501  with an integrated LiDAR system according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments are now described more fully hereinafter with reference to the accompanying drawings, in which representative examples are shown. Indeed, the disclosed 
     LiDAR systems and methods may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the various embodiments. Those of ordinary skill in the art will realize that these various embodiments are illustrative only and are not intended to be limiting in any way. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     In addition, for clarity purposes, not all of the routine features of the embodiments described herein are shown or described. One of ordinary skill in the art would readily appreciate that in the development of any such actual embodiment, numerous embodiment-specific decisions may be required to achieve specific design objectives. These design objectives will vary from one embodiment to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine engineering undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     Some light detection and ranging (LiDAR) systems use a single light source to produce one or more light signals of a single wavelength that scan the surrounding environment. The signals are scanned using steering systems that direct the pulses in one or two dimensions to cover an area of the surrounding environment (the scan area). Many different types of steering systems can be used to direct light pulses within the FOV. For example, the steering system can include MEMS, a mechanical phase array, an optical phase array, or other suitable system. 
     For example, some embodiments of the present technology use one or more light sources that produce light signals of different wavelengths and/or along different optical paths. These light sources provide the signals to a signal steering system at different angles so that the scan areas for the light signals are different (e.g., if two light sources are used to create two light signals, the scan area associated with each light source is different). This allows for tuning the signals to appropriate transmit powers and the possibility of having overlapping scan areas that cover scans of different distances. Longer ranges can be scanned with signals having higher power and/or slower repetition rate (e.g., when using pulsed light signals). Shorter ranges can be scanned with signals having lower power and/or high repetition rate (e.g., when using pulse light signals) to increase point density. 
     As another example, some embodiments of the present technology use signal steering systems with one or more dispersion elements (e.g., gratings, optical combs, prisms, etc.) to direct pulse signals based on the wavelength of the pulse. A dispersion element can make fine adjustments to a pulse&#39;s optical path, which may be difficult or impossible with mechanical systems. Additionally, using one or more dispersion elements allows the signal steering system to use fewer mechanical components to achieve the desired scanning capabilities. This results in a simpler, more efficient (e.g., lower power) design that is potentially more reliable (due to fewer moving components). 
     Some LiDAR systems use the time-of-flight of light signals (e.g., light pulses) to determine the distance to objects in the path of the light. For example, with respect to  FIG.  1   , an exemplary LiDAR system  100  includes a laser light source (e.g., a fiber laser), a steering system (e.g., a system of one or more moving mirrors), and a light detector (e.g., a photon detector with one or more optics). LiDAR system  100  transmits light pulse  102  along path  104  as determined by the steering system of LiDAR system  100 . In the depicted example, light pulse  102 , which is generated by the laser light source, is a short pulse of laser light. Further, the signal steering system of the LiDAR system  100  is a pulse signal steering system. However, it should be appreciated that LiDAR systems can operate by generating, transmitting, and detecting light signals that are not pulsed can be used to derive ranges to object in the surrounding environment using techniques other than time-of-flight. For example, some LiDAR systems use frequency modulated continuous waves (i.e., “FMCW”). It should be further appreciated that any of the techniques described herein with respect to time-of-flight based systems that use pulses also may be applicable to LiDAR systems that do not use one or both of these techniques. 
     Referring back to  FIG.  1    (a time-of-flight LiDAR system that uses light pulses) when light pulse  102  reaches object  106 , light pulse  102  scatters and returned light pulse  108  will be reflected back to system  100  along path  110 . The time from when transmitted light pulse  102  leaves LiDAR system  100  to when returned light pulse  108  arrives back at LiDAR system  100  can be measured (e.g., by a processor or other electronics within the LiDAR system). This time-of-flight combined with the knowledge of the speed of light can be used to determine the range/distance from LiDAR system  100  to the point on object  106  where light pulse  102  scattered. 
     By directing many light pulses, as depicted in  FIG.  2   , LiDAR system  100  scans the external environment (e.g., by directing light pulses  102 ,  202 ,  206 ,  210  along paths  104 ,  204 ,  208 ,  212 , respectively). As depicted in  FIG.  3   , LiDAR system  100  receives returned light pulses  108 ,  302 ,  306  (which correspond to transmitted light pulses  102 ,  202 ,  210 , respectively) back after objects  106  and  214  scatter the transmitted light pulses and reflect pulses back along paths  110 ,  304 ,  308 , respectively. Based on the direction of the transmitted light pulses (as determined by LiDAR system  100 ) as well as the calculated range from LiDAR system  100  to the points on objects that scatter the light pulses (e.g., the points on objects  106  and  214 ), the surroundings within the detection range (e.g., the field of view between path  104  and  212 , inclusively) can be precisely plotted (e.g., a point cloud or image can be created). 
     If a corresponding light pulse is not received for a particular transmitted light pulse, then it can be determined that there are no objects that can scatter sufficient amount of signal for the LiDAR light pulse within a certain range of LiDAR system  100  (e.g., the max scanning distance of LiDAR system  100 ). For example, in  FIG.  2   , light pulse  206  will not have a corresponding returned light pulse (as depicted in  FIG.  3   ) because it did not produce a scattering event along its transmission path  208  within the predetermined detection range. LiDAR system  100  (or an external system communication with LiDAR system  100 ) can interpret this as no object being along path  208  within the detection range of LiDAR system  100 . 
     In  FIG.  2   , transmitted light pulses  102 ,  202 ,  206 ,  210  can be transmitted in any order, serially, in parallel, or based on other timings with respect to each other. Additionally, while 
       FIG.  2    depicts a 1-dimensional array of transmitted light pulses, LiDAR system  100  optionally also directs similar arrays of transmitted light pulses along other planes so that a 2-dimensional array of light pulses is transmitted. This 2-dimentional array can be transmitted point-by-point, line-by-line, all at once, or in some other manner. The point cloud or image from a 1-dimensional array (e.g., a single horizontal line) will produce 2-dimensional information (e.g., (1) the horizontal transmission direction and (2) the range to objects). The point cloud or image from a 2-dimensional array will have 3-dimensional information (e.g., (1) the horizontal transmission direction, (2) the vertical transmission direction, and (3) the range to objects). 
     The density of points in point cloud or image from a LiDAR system  100  is equal to the number of pulses divided by the field of view. Given that the field of view is fixed, to increase the density of points generated by one set of transmission-receiving optics, the LiDAR system should fire a pulse more frequently, in other words, a light source with a higher repetition rate is needed. However, by sending pulses more frequently the farthest distance that the LiDAR system can detect may be more limited. For example, if a returned signal from a far object is received after the system transmits the next pulse, the return signals may be detected in a different order than the order in which the corresponding signals are transmitted and get mixed up if the system cannot correctly correlate the returned signals with the transmitted signals. To illustrate, consider an exemplary LiDAR system that can transmit laser pulses with a repetition rate between 500 kHz and 1 MHz. Based on the time it takes for a pulse to return to the LiDAR system and to avoid mix-up of returned pulses from consecutive pulses in conventional LiDAR design, the farthest distance the LiDAR system can detect may be 300 meters and 150 meters for 500 kHz and 1 Mhz, respectively. The density of points of a LiDAR system with 500 kHz repetition rate is half of that with 1 MHz. Thus, this example demonstrates that, if the system cannot correctly correlate returned signals that arrive out of order, increasing the repetition rate from 500 kHz to 1 Mhz (and thus improving the density of points of the system) would significantly reduce the detection range of the system. 
       FIG.  4    depicts a logical block diagram of LiDAR system  100 , which includes light source  402 , signal steering system  404 , pulse detector  406 , and controller  408 . These components are coupled together using communications paths  410 ,  412 ,  414 ,  416 , and  418 . These communications paths represent communication (bidirectional or unidirectional) among the various LiDAR system components but need not be physical components themselves. While the communications paths can be implemented by one or more electrical wires, busses, or optical fibers, the communication paths can also be wireless channels or open-air optical paths so that no physical communication medium is present. For example, in one exemplary LiDAR system, communication path  410  is one or more optical fibers, communication path  412  represents an optical path, and communication paths  414 ,  416 ,  418 , and  420  are all one or more electrical wires that carry electrical signals. The communications paths can also include more than one of the above types of communication mediums (e.g., they can include an optical fiber and an optical path or one or more optical fibers and one or more electrical wires). 
     LiDAR system  100  can also include other components not depicted in  FIG.  4   , such as power buses, power supplies, LED indicators, switches, etc. Additionally, other connections among components may be present, such as a direct connection between light source  402  and light detector  406  so that light detector  406  can accurately measure the time from when light source  402  transmits a light pulse until light detector  406  detects a returned light pulse. 
       FIG.  5    depicts a logical block diagram of one example of light source  402  that is based on a fiber laser, although any number of light sources with varying architecture could be used as part of the LiDAR system. Light source  402  uses seed  502  to generate initial light pulses of one or more wavelengths (e.g., 1550 nm), which are provided to wavelength-division multiplexor (WDM)  504  via fiber  503 . Pump  506  also provides laser power (of a different wavelength, such as 980 nm) to WDM  504  via fiber  505 . The output of WDM  504  is provided to pre-amplifiers  508  (which includes one or more amplifiers) which provides its output to combiner  510  via fiber  509 . Combiner  510  also takes laser power from pump  512  via fiber  511  and provides pulses via fiber  513  to booster amplifier  514 , which produces output light pulses on fiber  410 . The outputted light pulses are then fed to steering system  404 . In some variations, light source  402  can produce pulses of different amplitudes based on the fiber gain profile of the fiber used in the source. Communication path  416  couples light source  402  to controller  408  ( FIG.  4   ) so that components of light source  402  can be controlled by or otherwise communicate with controller  408 . Alternatively, light source  402  may include its own controller. Instead of controller  408  communicating directly with components of light source  402 , a dedicated light source controller communicates with controller  408  and controls and/or communicates with the components of light source  402 . Light source  402  also includes other components not shown, such as one or more power connectors, power supplies, and/or power lines. 
     Some other light sources include one or more laser diodes, short-cavity fiber lasers, solid-state lasers, and/or tunable external cavity diode lasers, configured to generate one or more light signals at various wavelengths. In some examples, light sources use amplifiers (e.g., pre-amps or booster amps) include a doped optical fiber amplifier, a solid-state bulk amplifier, and/or a semiconductor optical amplifier, configured to receive and amplify light signals. 
     Returning to  FIG.  4   , signal steering system  404  includes any number of components for steering light signals generated by light source  402 . In some examples, signal steering system  404  may include one or more optical redirection elements (e.g., mirrors or lens) that steer light pulses (e.g., by rotating, vibrating, or directing) along a transmit path to scan the external environment. For example, these optical redirection elements may include MEMS mirrors, rotating polyhedron mirrors, or stationary mirrors to steer the transmitted pulse signals to different directions. Signal steering system  404  optionally also includes other optical components, such as dispersion optics (e.g., diffuser lenses, prisms, or gratings) to further expand the coverage of the transmitted signal in order to increase the LiDAR system  100 &#39;s transmission area (i.e., field of view). An example signal steering system is described in U.S. Patent Application Publication No. 2018/0188355, entitled “2D Scanning High Precision LiDAR Using Combination of Rotating Concave Mirror and Beam Steering Devices,” the content of which is incorporated by reference in its entirety herein for all purposes. In some examples, signal steering system  404  does not contain any active optical components (e.g., it does not contain any amplifiers). In some other examples, one or more of the components from light source  402 , such as a booster amplifier, may be included in signal steering system  404 . In some instances, signal steering system  404  can be considered a LiDAR head or LiDAR scanner. 
     Some implementations of signal steering systems include one or more optical redirection elements (e.g., mirrors or lens) that steers returned light signals (e.g., by rotating, vibrating, or directing) along a receive path to direct the returned light signals to the light detector. The optical redirection elements that direct light signals along the transmit and receive paths may be the same components (e.g., shared), separate components (e.g., dedicated), and/or a combination of shared and separate components. This means that in some cases the transmit and receive paths are different although they may partially overlap (or in some cases, substantially overlap). 
       FIG.  6    depicts a logical block diagram of one possible arrangement of components in light detector  404  of LiDAR system  100  ( FIG.  4   ). Light detector  404  includes optics  602  (e.g., a system of one or more optical lenses) and detector array  604  (e.g., one or more charge coupled devices (CCD), photodiodes, avalanche photodiodes, a photomultiplier vacuum tube, an image sensor, etc.) that is connected to controller  408  ( FIG.  4   ) via communication path  418 . The optics  602  may include one or more photo lenses to receive, focus, and direct the returned signals. Light detector  404  can include filters to selectively pass light of certain wavelengths. Light detector  404  can also include a timing circuit that measures the time from when a pulse is transmitted to when a corresponding returned pulse is detected. This data can then be transmitted to controller  408  ( FIG.  4   ) or to other devices via communication line  418 . Light detector  404  can also receive information about when light source  402  transmitted a light pulse via communication line  418  or other communications lines that are not shown (e.g., an optical fiber from light source  402  that samples transmitted light pulses). Alternatively, light detector  404  can provide signals via communication line  418  that indicate when returned light pulses are detected. Other pulse data, such as power, pulse shape, and/or wavelength, can also be communicated. 
     Returning to  FIG.  4   , controller  408  contains components for the control of LiDAR system  100  and communication with external devices that use the system. For example, controller  408  optionally includes one or more processors, memories, communication interfaces, sensors, storage devices, clocks, ASICs, FPGAs, and/or other devices that control light source  402 , signal steering system  404 , and/or light detector  406 . In some examples, controller  408  controls the power, rate, timing, and/or other properties of light signals generated by light source  402 ; controls the speed, transmit direction, and/or other parameters of light steering system  404 ; and/or controls the sensitivity and/or other parameters of light detector  406 . 
     Controller  408  optionally is also configured to process data received from these components. In some examples, controller determines the time it takes from transmitting a light pulse until a corresponding returned light pulse is received; determines when a returned light pulse is not received for a transmitted light pulse; determines the transmitted direction (e.g., horizontal and/or vertical information) for a transmitted/returned light pulse; determines the estimated range in a particular direction; and/or determines any other type of data relevant to LiDAR system  100 . 
       FIG.  7    shows an illustrative MEMS based LiDAR system  700  according to an embodiment. System  700  can include laser source  710 , beam steering system  720 , which may include galvo system  722  and MEMS steering unit  724 , receiver system  730 , which include receiving optic  732  and detector array  734 , and control circuitry  750 . In operation, light pulses from laser source  710  are directed to MEMS  724 , which redirects the light pulses to galvo system  722 , which then redirects the lights pulses to the FOV. If desired one or more light beams originate from laser source  710 . For example, an originating laser beam may be split to provide two or more beams (shown here as the solid line and the dashed line). Returned pulses (not shown) are collected by optic  732  and directed to detector array  734 . Detector array  734  senses the returned light pulse and provides a signal corresponding to the returned signal to control circuitry  750 . Laser source  710  can be similar to laser  402 , discussed above. Beam steering system  720  is able to direct light pulses provided by laser source  710  to a location within a field of view (FOV) of system  700 . MEM steering unit  742  may be responsible for a first axis sweep (e.g., vertical axis) within the FOV and galvo  723  may be responsible for controlling a second axis sweep (e.g., horizontal axis) within the FOV and galvo  722  may be a mirror. In some embodiments, galvo  722  may be single plane mirror such as that shown in  FIG.  11 A  or a dual plane mirror such as that shown in  FIG.  11 B . 
     MEMS steering system  724  may be a liquid crystal, a miniaturized rotating polygon, or any other suitable MEMS based component that can control direction of the light beam. In some embodiments, MEMS steering system  724  can include a MEMS device that uses micro-mirrors. The MEMS mirror can steer the laser generated by the laser source in two or three dimensions to illuminate objects in a field of view. It is appreciated that MEMS beam steering system  724  can also include other MEMS components such as optical switches, optical cross-connects, lens, etc. 
     Use of a MEMS steering system is desirable in that such solutions reduce the size of the LiDAR system, which can translate to less power consumption, smaller packaging, and less cost. In some embodiment, a MEMS steering system can have an optical aperture cross-section that it is on the order of a few millimeters or less (e.g., less than 5 mm). The relatively small optical cross-section is suitable for broadcasting light beams to the FOV, but is not suitable for redirecting return pulses to receiver system  730 . That is, in contrast with system that has a relatively large optical aperture cross-section, a MEMS steering system may not be large enough to “collect” and redirect returned pulses to a receiver system. To compensate for the relatively small size of MEMS steering system  724 , optic  732  may be sized relatively large to collect returned pulses and focus them to detector array  734 . For example, in one embodiment, optic  732  may be a fisheye lens or other optic with a relatively wide acceptance angle. A fisheye lens can be a wide-angle lens that produces visual distortion intended to create a wide panoramic or hemispherical image. Thus, the fisheye lens can collect scattered light within a wide-angle, thereby enhancing or increasing the visibility of the LiDAR system. A fisheye lens can be, for example, a circular fisheye lens or a full-frame fisheye lens. In some embodiments, the fisheye lens&#39;s field of view can be selected or configured to match the field of view of the MEMS beam steering range. The fisheye wide angle receiving lens can be coupled to MEMS beam steering system  724 , for example, side by side. 
     Detector array  734  may include a 1×N array of detector segments or an N×M array of detector segments, where N and M are integers. The detector segments can be implemented using an InGaAs-based detector or a SiGe-based detector. Detector array  734  includes several detector segments, as opposed to a single detector arrangement, because the optical cross-section of MEMS steering system  724  requires that multiple detector segments be used in combination with optic  732  in order to detect returned light signals. However, use of detector array  734  (as opposed to single discrete detector) will increase detection of noise (e.g., background light), thus potentially hampering returned light pulse detection. More particularly, because a relatively large light collecting optic is being used in conjunction with detector array  734 , the overall size of detector array  734  may be relatively large compared to the size of the returning light pulse. For example, the returning light pulse may be on the order micrometers, whereas the cross-sectional area of detector array  734  may be on the order of millimeters. As such, the return beam size is considerably smaller than the area of the entire detector array  734 . This may significantly increase detector noise and reduce signal-to-noise ratio because any portion of detector array  734  that is not processing a returned light beam is generating noise by picking background light and radiation. Moreover, detector array  734  uses a multi-segmented array of detectors, as opposed to a single large detector. Use of a relatively large area detector (e.g., a big non-segmented detector such as detector  734 ) may also introduce a large junction capacitance, which is proportional to the area of the detector. A large junction capacitance is undesired as it may slow down operation of components (e.g., an amplifier) and contributes to excess noise gain. 
       FIG.  8    illustrates an exemplary multi-segmented detector  800  according to an embodiment. Multi-segmented detector  800  shows multiple small segments  802  arranged in a 2×4 array. Also shown is a returned light signal (e.g., shown as a spot) to illustrate the relatively small size of the returned light signal compared to the overall size of multi-segmented detector  800 . By segmenting detector  800  into multiple segments, the smaller junction capacitance can be made smaller compared to that of an equivalently sized single detector. 
       FIG.  8 A  illustrates another exemplary multi-segmented detector  820  according to an embodiment. Detector  820  is arranged in a 9×9 grid composed of nine 3×3 subgrids. As shown, each subgrid includes nine (9) segments 1-9. Each segment is rectangular in shape, and the entirety of multi-segmented detector  820  can be rectangular. Similarly numbered segments may all be interconnected with each other. For example, all segments labeled one (1) are connected, and all segments labeled two (2) are connected, and so on. The multi-segmented detector array can be a silicon based detector, or InGaAs based detector, or a SiGe based detector. 
       FIG.  8 B  illustrates yet another exemplary multi-segmented detector  840  according to an embodiment. Detector  840  is composed of several six-sided polygon segments arranged in a honeycomb-like pattern. Similarly numbered segments are interconnected with each other. 
     Referring now back to  FIG.  7   , detector array  734  is shown to be segmented into segments  734   a - 734   i.  The number of segments and arrangement thereof is merely illustrative. During operation of LiDAR system  700 , when a return light signal is received, a subset of segments  734   a - 734   i  (e.g., just one of the segments) may detect that returned signal. Each returned light signal corresponds to its beam steering angle or position as directed by MEMS beam steering system  724 . Since the beam steering angle is known, the return angle of the return light pulse is also known. With this knowledge, the system knows which subset of segments  734   a - 734   i  should receive the returned light signal. Control circuitry  750  can selectively activate the subset of segments  734   a - 734   i  based on a registration with MEMS steering system  724  and/or galvo  722 . This way, only the necessary segments are active for monitoring for a returned signal and the other segment are deactivated (to conserve power and reduce noise). Control circuitry  750  has knowledge of galvo  722  position and MEMS steering system  724  position, and thus is able to selectively activate and deactivate segments  734   a - 734   i  based on the positioning of galvo  722  and MEMS steering system  724 . By selectively activating a subset of detectors and deactivating other detectors, junction capacitance of a detector can be significantly reduced and in turn, the signal-to-noise ratio can be improved. In addition, selective activation and deactivation of segments saves power and improves thermal management of the system. Moreover, since only the necessary subset of segments is active, noise is reduced, thereby reducing computational burden that would otherwise be required to process returned signals. 
       FIG.  9 A- 9 C  show illustrative examples of selective activation and deactivation of detector segments based on a position of a beam steering system. Each of  FIGS.  9 A- 9 C  show beam steering system  910  and detector array  920 , which has detector segments  920   a - 920   k . Referring to  FIG.  9 A , beam steering system  910  is directing a light pulse to FOV1 location. Based on this particular FOV1 location, detector segments  920   c  and  920   d  are ON, whereas all other detector segments are OFF. In  FIG.  9 B , beam steering system  910  is directing a light pulse to FOVN location. Based on this particular FOVN location, detector segments  920   i  and  920   j  are ON, whereas all other detector segments are OFF. In  FIG.  9 C , beam steering system  910  is directing two light pulses to FOV1(A) and FOV2(B) locations. Based on these light pulse FOV angles, detector segment  920   c  is ON to detect the return angle corresponding to FOV1(A) and detector segment  920   e  is ON to detect the return angle corresponding to FOV2(B). All other detector segments are turned OFF. 
     In some embodiments, an exemplary LiDAR system can further include a second detector array configured to provide auto-balancing. For example, the second detector array can have the same type or configuration as detector array  734 . The second detector array, however, can be configured to receive only background light or noise and provide the noise signal to the controller. The controller can thus correlate the signals provided by the first and second detector arrays by, for example, subtracting the background noise signals provided by the second detector array from the signal provided by the first detector array (which includes both the scattered light generated by an object and the background noise). The auto-balancing can enhance the performance of the LiDAR system under certain conditions where the background noise may not be readily distinguished from the scattered light of an object. For example, during night time, many ambient lights are illuminating and thus background noise may include light at the laser wavelength used by the LiDAR system. As a result, absent of auto-balancing, the scattered light from an object may not be readily distinguished from ambient lights. 
       FIG.  10    shows illustrative process  1000  according to an embodiment. Process  1000  may be implemented in a LiDAR system such as LiDAR system  700 . Process  1000  may start at step  1010 , where transmission of a light pulse is controlled, via a beam steering system, to be directed along an optical path within a field of view (FOV), wherein each transmitted light pulse corresponds to an unique optical path. For example, beam steering system  720  may control where each light pulse is directed within a FOV of the LiDAR system, and control circuitry  750  has knowledge of the optical path. At step  1020 , a subset of detector segments of a detector array comprising a plurality of detector segments is activated based on the optical path. For example, control circuitry  750  may turn one or more detectors segments  734   a - 734   i  of detector array  734  based on the optical path of the light being transmitted by the beam steering system. 
     At step  1030 , detector segments not included in the activated subset are deactivated. The activated subset of detector segments monitor for a return pulse, at step  1040 . If a return pulse is detected in the activated subset of detector segments (at step  1050 ), the detected return pulse is processed (at step  1060 ). That is, the detected return pulse is used to populate a frame of the FOV. If the determination at step  1050  is NO, process  1000  can return to step  1010 . 
     It should be appreciated that the steps shown in  FIG.  10    are merely illustrative and that additional steps may be added. 
       FIGS.  11 A and  11 B  show simplified diagrams of LiDAR system  1100  and  1150 , respectively. LiDAR systems  1100  and  1150  can include many of the same components as LiDAR system  700 , and can include laser source  1110  and  1160 , Galvo controller  1120  and  1170 , galvo  1125  and  1175 , repetition rate controller  1130  and  1180 , and MEMS steering system  1140  and  1190 , respectively. Galvo  1120  and  1170  may differ between system  1100  and  1150 . Galvo  1120  may be a single plane mirror, whereas galvo  1170  may be a dual plane mirror. Both galvos  1120  and  1170  oscillate to redirect laser pulses to their respective MEMS steering system and to control a first axis of the LiDAR system&#39;s FOV. The operation of galvos  1100  and  1150  can produce different scanning patterns (assuming all things are equal such as a constant repetition rate). If desired, the position of galvos  1125  and  1175  may be switched with MEMS steering systems  1140  and  1175 , respectively, such that 
     During oscillation of galvo  1120 , galvo  1120  will slow down at the transition points (e.g., the point at which the single plane reverses direction). As a result, the scanning density can be higher at the transition points than other points of the oscillation cycle. For example,  FIG.  12 A  shows an illustrative scanning density produced by galvo  1120  (when the repetition rate is held constant). As shown in  FIG.  12 A , the density is higher near the transition points than the other points. The higher density near the transition points may not be as desired because light transmissions at those regions within the FOV may not be as useful as other angles within the FOV. One way to control the density of light transitions throughout the oscillation cycle of galvo  1120  is to control the repetition rate of the light pulses being emitted by laser source  1110 . Repetition rate controller  1130  can control the repetition rate. For example, the time interval between successive light pulses may be increased (e.g., to decrease frequency) at and/or near the transition points for galvo  1120 . This way, when galvo  1120  is at or approaching its transition points, the repetition rate can be decreased to reduce the density of light pulses transmitted at or near the transition point. If desired, the repetition rate can be increased for one or more regions of interest within the FOV. For example, the repetition rate may be increased when galvo  1120  is positioned to transmit light pulses at angles ranging between −2 degrees to 3 degrees of the LiDAR system&#39;s FOV.  FIG.  12 B  shows an illustrative scanning density produced by galvo  1120  when the repetition rate is controlled. As shown, density if greater in the middle portion of the FOV and less dense at the transition points. 
     The dual plane mirror of galvo  1170  can be driven using a direct drive or a resonant drive. Direct drive is typically used for relatively slow scanning rates (e.g., up to around 3 Hertz) and a resonant drive is typically used for relatively faster scanning rates (e.g., greater than 5 Hertz). Direct drives may be limited in their ability to operate at faster scanning rates because the power required support the scanning rate is the cube of the frequency. This may be because a strong anti-current is needed to reverse direction. Thus, while a faster scan rate may be desirable, it may not be practical in implementation. For example, if a system such as system  1100  uses a direct drive, increased scanning rates may be realized with the cost of a significant power penalty. This may be because significant energy must be expended to reverse direction of the single plane mirror&#39;s movement. In addition, because a single plane mirror is being used in a direct drive mode, the scanning density is relatively higher at the top and low ends of the vertical field of view, and the center region of the field of view has a relatively low scanning density, as shown in  FIG.  12 A . 
     In a system such as system  1150 , which uses a dual plane mirror, increased scanning rates can be achieved using a resonant drive mode. The resonant drive mode can leverage a “spring” or potential energy to operate at relatively higher frequencies without an exponential (e.g., cube of the frequency) power penalty. Using a dual plane mirror in resonance mode can result in a scanning density that is relatively higher in the middle portion of the field of view as compared to the top and bottom portions. See, for example,  FIG.  12 B , which shows scanning density of a system using a dual plane mirror in a resonance mode. Note that although  FIG.  12 B  is also being used in context with system  1100 , the same scanning pattern can be reproduced by both systems  1100  and  1150 . 
       FIG.  12 C  shows illustrative field of view (FOV)  1200  of a LiDAR system according to an embodiment. As shown, FOV  1200  is a two-dimensional space bounded by X and Y dimensions. Although the LiDAR system can collect data points from the entirety of FOV  1200 , certain regions of interest (ROI) may have higher precedence over other regions within FOV  1200  (e.g., such as undesired regions that occupy all space within FOV  1200  that is not a ROI).  FIG.  12    shows five different illustrative ROIs  1210 - 1214  to illustrate different regions within FOV  1200  that require additional data points than other regions within FOV  1200 . For example, ROI  1210  occupies an entire band of a fixed y-axis height across the x-axis of FOV  1200 . ROIs  1211  and  1212  show localized ROIs below ROI  1210 , and ROIs  1213  and  1214  show localized ROIs above ROI  1210 . It should be understood that any number of ROIs may exist and that the ROIs can occupy any portion of FOV  1200 . Embodiments discussed herein enable additional data points to be collected in the ROIs in a manner that does not disrupt the operation of the LiDAR system. 
       FIG.  13    shows an illustrative block diagram of LiDAR system  1300  according to an embodiment. LiDAR system  1300  can include laser subsystem  1310 , receiver system  1320 , laser controller  1330 , region of interest controller  1340 , MEMS structure  1350 , MEMS controller  1355 , mirror  1360 , and mirror controller  1365 . LiDAR system  1300  may be contained within one or more housings. In multiple housing embodiments, at least one of the housings may be a temperature controlled environment in which selection portions of LiDAR system  1300  (e.g., laser controller  1330 , laser source  1312 , controller  1340 ) are contained therein. MEMS structure  1350 , MEMS controller  1355 , mirror  1360 , and mirror controller  1365  may collectively be represented by beam steering system  1369 . 
     Laser subsystem  1310  may be operative to direct light energy towards mirror  1360 , which redirects the light energy to MEMS structure  1350 . Mirror  1360  may be moved under the control of mirror controller  1365 , which can control the speed and direction of mirror movement. As mirror  1360  moves, it causes light being transmitted by laser subsystem  1310  to interface with MEMS structure  1350 . MEMS structure  1350  can be a MEMS mirror or a liquid crystal. MEMS structure  1350  is controlled by MEMS controller  1355  and is operative to direct the light energy received from mirror  1360  in accordance with the field of view parameters of LiDAR system  1300 . That is, if LiDAR system  1300  has a field of view with range of z, a lateral angle of x, and vertical angle of y, the range z can be controlled by the power of laser source  1312 , the vertical angle y can be controlled by MEMS structure  1350 , and the lateral angle x can be controlled by the movement of mirror  1360 . Light energy that is reflected back from objects in the field of view and returns to polygon structure  1350  where it is directed back to mirror  1360 , which redirects it back to receiver system  1320 . 
     Receiver system  1320  can include receiving optics  1322 , detector array  1324 , and detector array controller  1326 . Receiving optics  1322  may be operative to collect returned light pulses and direct the returned pulses to detector array  1324 . Detector array  1324  may include a several detector segments that are selectively turned ON and OFF under the direction of detector array controller  1326 . Detector array controller  1326  may selectively turn detector segments ON and OFF based on registration signals provided by mirror controller  1365  and/or MEMS controller  1355 . This way, two different degrees of angle control can be used to register selective activation and deactivation of detector segments. 
     As defined herein, a frame rate may refer to the time it takes for scanning system  1302  to complete one full scan of the FOV. For each frame, scanning system  1302  can obtain data points from each row (or column) of a plurality of rows (or columns) that are defined by the FOV. Each row may correspond to a vertical angle within the vertical range of the FOV. The vertical angle is controlled by mirror  1360 . As mirror  1360  moves, the vertical angle changes, thereby enabling scanning system  1302  to obtain data points from multiple rows within the FOV. Vertical angle resolution refers spacing between adjacent rows of data points. An increase in vertical angular resolution corresponds to denser spacing between adjacent rows, and such an increase can be achieved by decreasing the delta of the vertical angles between adjacent vertical angles. The delta between adjacent vertical angels can be decreased by slowing down the movement of mirror  1360 . That is, as mirror movement speed slows down, the change in the vertical angle delta decreases. A decrease in vertical angular resolution corresponds to sparser spacing between adjacent rows, and such a decrease can be achieved by increasing the vertical angle delta. The delta between adjacent vertical angels can be increased by speeding up the movement of mirror  1360 . That is, as mirror movement speed speeds up, the change in the vertical angle delta increases. 
     The plurality of data points obtained within any row may depend on a horizontal angle within the horizontal range of the FOV. The horizontal range may be controlled by polygon  1350 , and the horizontal angle resolution may be controlled by a time interval of successive laser pulses. The time interval is sometimes related to the repetition rate. A smaller time interval can result in increased horizontal angular resolution, and a larger time interval can result in decreased horizontal angular resolution. 
     The above reference to vertical and horizontal angles and vertical and horizontal angular resolution was made in reference to a system in which mirror  1360  controls the horizontal angle. It should be understood that mirror  1360  can be repurposed to control the vertical angle and used in a system different than that shown in  FIG.  13   . 
     Laser subsystem  1310  can include laser source  1312  and fiber tips  1314 - 1316 . Any number of fiber tips may be used as indicated the “n” designation of fiber tip  1316 . As shown, each of fiber tips  1314 - 1316  may be associated with laser source  1312 . Laser source  1312  may be a fiber laser or diode laser. Fiber tips  1314 - 1316  may be aligned in a fixed orientation so that the light exiting each tip strikes mirror  1360  at a particular location. The actual orientation may depend on several factors, including, for example, frame rate, mirror movement and speed, polygon speed, ROIs, repetition rate, etc. Additional discussion of fiber tips and their characteristics in obtaining additional data points within ROIs is discussed in more detail below. 
     Laser controller  1330  may be operative to control laser source  1312 . In particular, laser controller  1330  can control power of laser source  1312 , can control a repetition rate or time interval of light pulses emitted by laser source  1312  (via time interval adjustment module  1332 ), and can control pulse duration of laser source  1312 . Time interval adjustment module  1332  may be operative to control and/or adjust the repetition rate/time interval of the transmitter pulse of laser  1310 . Time interval adjustment circuitry  1332  can vary the repetition rate/time interval for different regions within the FOV. For example, the repetition rate may be increased for ROIs but may be decreased for areas of FOV that are not of interest. As another example, the time interval can be decreased for ROIs and increased for areas of FOV that are not of interest. 
     Region of Interest controller  1340  may be operative to control LiDAR system  1300  to obtain additional data points for the ROIs. That is, when LiDAR system  1300  is scanning a ROI, ROI controller  1340  may cause system  1300  to operate differently than when system  1300  is not scanning a ROI. ROI controller  1340  may control operation of laser controller  1330 , polygon controller  1355 , and mirror controller  1365  to alter the quantity of data being obtained by system  1300 . ROI controller  1340  may receive several inputs that dictate how it should control the scanning subsystem  1302 . The inputs can include, for example, frame rate  1342 , sparse regions  1343 , dense regions  1344 , distance range, or any other suitable input. Frame rate  1342  may specify the frequency at which scanning subsystem  1302  completes a FOV scan. Sparse and dense regions  1343  and  1344  may provide specific locations of ROIs. For example, dense regions  1344  may correspond to ROIs and sparse regions  1343  may correspond to regions within the FOV that are not ROIs. Fiber tip angles  1345  may be used as a design constraint within which scanning sub-system  1302  operates in order to optimally perform scanning. 
     Mirror  1360  may be a single plane or multi-plane mirror that oscillates back and forth to redirect light energy emitted by laser source  1312  to MEMS structure  1350 . The single plane mirror may provide higher resolutions at the top and bottom portions of the vertical field of view than the middle portion, whereas the multi-plane mirror may provide higher resolution at a middle portion of the vertical field of view than the top and bottom portions. Mirror  1360  may be a galvanometer. Varying the oscillation speed within an oscillation cycle can enable scanning subsystem  1302  to acquire sparse or dense data points within the FOV. For example, if dense data points are required (for a particular ROI), the movement speed may be reduced, and if sparse data points are required (for non-ROIs), the movement speed may be increased. 
       FIG.  14    shows illustrative fiber tip arrangement according to an embodiment. Four fiber tips  1401 - 1404  are shown to be oriented with respect to each other such that the same angle a exists between adjacent fiber tips. Multiple fiber tips (as opposed to just one fiber tip) may be used so that high data collection is achieved. When an ROI is being scanned, the mirror movement speed is adjusted to a ROI speed (e.g., a speed that is slower than a sparse or non-ROI speed), the combination of additional fiber tips and reduced relative mirror movement speed yields denser data capture. Moreover, when a non-ROI is being scanned, the mirror movement speed operates at a non-ROI speed (e.g., a speed that is faster than the ROI speed), the presence of multiple fiber tips ensures that sufficient data collection is achieved. The angle a may be selected based on properties of the light energy being emitted by each fiber tip (e.g., size), speed and movement characteristics of a mirror (e.g., mirror  1360 ) for both ROIs and non-ROIs, and speed of the polygon (e.g., polygon structure  1350 ). The angles between each of tips may be the same or they can be different. 
     In some embodiments, all four fiber tips may be associated with the same laser source. Thus, if the laser source is turned OFF, none of the fiber tips will emit light energy. In another embodiment, each fiber tip may be associated with its own respective laser source. This embodiment provides a high degree of ON/OFF control of each fiber tip. In yet another embodiment, a subset of the fiber tips may be associated with the same laser source. For example, fiber tips FT1 and FT3 may share a first common laser source, and fiber tips FT2 and FT4may share a second common laser source. This embodiment provides a balance between all or none and individual ON/OFF control. 
       FIG.  15 A  shows a multiple mirror alignment arrangement (MMAA)  1500  that may be used for ROI and non-ROI embodiments. MMAA  1500  is an alternative to using multiple fiber tips such as that shown in  FIG.  14   . As shown, MMAA  1500  shows collimator  1510 , partial reflective mirrors  1521 - 1523 , and reflective mirror  1524 . Light energy originating from a laser source (not shown) is routed to collimator  1510 , which directs light energy to partial reflective mirror  1521 . Partial reflective mirror  1521  permits a portion of the light energy to pass through (shown as exit path  1531 ) and the remaining light energy is redirected to partial reflective mirror  1522 . Partial reflective mirror  1522  allows a portion of the light energy to pass through to partial reflective mirror  1523 . Partial reflective mirror  1522  redirects light energy along exit path  1532 . Partial reflective mirror allows a portion of the light energy to pass through to partial reflective mirror  1524 . Partial reflective mirror  1523  redirects light energy along exit path  1533 . Reflective mirror  1524  may redirect all or at least a portion of all the remaining light energy along exit path  1534 . 
     The angles between adjacent exit paths may be selected to achieve the desired resolution for ROIs and non-ROIs. For example, angles between adjacent exit paths may be similar to the a angles shown in  FIG.  14   . In some embodiments, the angle between adjacent exit paths may be fixed. In other embodiments, the angle between adjacent exit paths may be variable. Variable angle adjustment may be used to provide different resolutions on demand. For example, if the LiDAR system is being used in a vehicle, the angles may be set to a first configuration when the vehicle operating in a first mode (e.g., driving at highway speeds or vehicle is driven by a first driver) and may be set to a second configuration when the vehicle is operating in a second mode (e.g., driving at city speeds or vehicle is driven by a second driver). 
       FIG.  15 B  shows another multiple mirror alignment arrangement (MMAA)  1501  that may be used for ROI and non-ROI embodiments. MMAA  1501  is an alternative to MMAA  1500 . As shown, MMAA  1501  shows collimator  1512 , partial reflective mirrors  1525 - 1527 , reflective mirror  1528 , and exit paths  1535 - 1538 . MMAA  1501  is similar to MMAA  1500  with exception of the positioning of collimator  1512 . As shown, collimator  1512  is positioned above mirror  1525 . If desired, collimator  1512  can be positioned below mirror  1528 . As a further alternative, collimator  1512  can be aimed at a different mirror such as mirror  1526  or mirror  1527 , and such mirrors can redirect the light energy as necessary to achieve the desired results. 
       FIG.  15 C  shows an illustrative multiple collimator arrangement  1550  that may be used for ROI and non-ROI embodiments. Arrangement  1550  can include collimators  1561 - 1563 . Each of collimators  1561 - 1563  may be associated with its own laser source. Associating each collimator with its own laser source enables selective turning ON and OFF of light energy emanating from each collimator. For sparse regions, one or more of the laser sources may be turned OFF (to save power) and for dense regions, all laser sources may be turned ON to maximize resolution. Each of collimators  1561 - 1563  may be fixed in a particular orientation to achieve the desired a angle between each collimator. If desired, each of collimators  1561 - 1563  may be movable to dynamically adjust the a angle between each collimator. 
       FIG.  15 D  shows an illustrative collimator and lens arrangement  1570  that may be used to control divergence of the light beam existing collimator  1571  according to an embodiment. Lens  1572  may be moved towards and away from collimator  1571  to adjust divergence of the light beam. Arrangement  1570  may be used to adjust the size of the light beam as it is projected by the scanning system. For ROI regions, it may be desirable to have a relatively narrow beam. To produce a relatively narrow beam, lens  1572  may positioned at a narrow beam distance away from the collimator  1571 . For non-ROI regions, it may be desirable to have a relatively wide beam. To produce a relatively wide beam, lens  1572  may positioned at a wide beam distance away from the collimator  1571 . 
       FIG.  16    shows illustrative scanning resolution using multiple fiber tips, a multiple mirror alignment arrangement, or multiple collimator arrangement according to an embodiment. The illustrative vertical resolution lines from fiber tips (FT1-FT4) are shown. The resolution lines are grouped according to sparse resolution and dense resolution as shown. In sparse regions, the scanning system is moving the mirror at a relatively faster speed than when in the dense region, and in dense regions, the scanning system is moving the mirror at a relatively slower speed than when in the sparse region. The spacing between the adjacent scanning lines (as shown by the repeated pattern of FT 1 -FT 4 ) is substantially equidistant. This equidistant spacing may be made possible by coordinating the alignment of the fiber tips with the frame rate, mirror speed, polygon speed, and any other suitable factors. In contrast, if alignment of fiber tips is not properly coordinated, the equidistant spacing may not be possible, thereby yielding an undesirable scanning pattern. In the dense region, each fiber tip may provide multiple lines of resolution. For example, as shown, FT1 provides four lines of resolution before FT2 provides its four lines of resolution. Thus, each fiber tip provides four lines of resolution before transitioning to the next fiber tip. It should be understood that the number of lines of resolution provided by each fiber tip depends on a number of factors, including, for example, mirror speed, polygon speed, and angle between fiber tips. The lines of resolution among fiber tips may interlace at the transition between the sparse and dense regions. For example, at least one line of resolution from one or more of fiber tips FT2-FT4 may be interlaced among the four lines of resolution pertaining to FT1 (as shown in  FIG.  17 A ). 
     The angle between the fiber tips (e.g., the a) may be selected based on the mirror speeds, polygon speed, desired angular resolution of the ROI, and a requirement for the spacing between the resolution lines in the sparse region(s) to be substantially equidistant to each other. At least two different mirror speeds are used to provide the dense and sparse resolutions, and it is the variance in mirror speeds that can cause the resolution lines to be non-equidistant if the angles between fiber tips are not properly aligned. For example, assume that the angle of the dense region is θ. θ can represent the total degrees within the FOV that are part of the ROI and require dense resolution. If the mirror speed is constant throughout the entire frame, the angle between fiber tips, α, can be approximately θ/n, where n is the number of fiber tips. This α cs , referred to as angle with constant speed may represent a target angle for the fiber tips, but additional calculations are required to take into account that the mirror operates at different speeds, and as a result α, cannot be set to exactly θ/n. The sparse regions must be taken into account. In the sparse region, assume that the desired angle between adjacent lines of resolution is ϕ. For the example, ϕ may exist between FT1 and FT2, between FT2 and FT3, between FT3 and FT4, between FT4 and FT1 in the sparse region. In order to achieve ϕ between different fiber tips, the angle between fiber tips can be calculated by the following equation: 
       α=α vs   =ϕ*n* 2−ϕ
 
     where α vs  is the angle with a variable speed mirror, ϕ is the angle between adjacent lines of resolution within the sparse region, n is the number of fiber tips, and the number 2 is a scaling factor to take into account overlapping lines of resolution. The variables of ϕ, n, mirror speed, and polygon speed are selected such that α vs  is the same as or approximately the same as α cs . Selecting the variables such that α vs  is the same as or approximately the same as α cs , enables the scanning system to achieve the desired scanning densities for both ROI and non-ROI regions within the FOV each frame. 
       FIG.  17 A  shows another illustrative diagram of vertical resolution using multiple fiber tips or a multiple mirror alignment arrangement, according to an embodiment. Sparse regions and a dense region are shown. Four fiber tips FT1-4 are used. In the sparse region, the resolution lines for each fiber tip are evenly spaced. In the dense region, the vertical lines of resolution are substantially more dense than the vertical lines of resolution in the sparse regions. Within the dense region, the vertical lines of resolution are grouped predominantly for each fiber tip, however, interlacing resolution lines from other fiber tips may exist within a particular group. 
       FIG.  17 B  shows an illustrative close-up view of a sparse region within  FIG.  17 A  and  FIG.  17 C  shows an illustrative close-up view of the dense region within  FIG.  17 A , according to various embodiments. Note that the scaling factor in  FIG.  17 B  is less zoomed in than it is in  FIG.  17 C . As a result,  FIG.  17 B  shows lines of resolution for multiple fiber tips, and where  FIG.  17 C  shows multiple lines of resolution for only one fiber tip. 
     The dynamic resolution discussed above has been in the context of dynamic vertical resolution. If desired, the laser subsystem (e.g., the fiber tips, multiple mirror alignment arrangement, or multiple collimator arrangement) can be oriented in a horizontal direction (as opposed to the above-described vertical direction) to provide dynamic horizontal resolution. 
     Assuming speed changes to mirror movement are used to control the vertical resolution, the repetition rate or time interval can be changed to dynamically control the horizontal resolution. This provides dual axis dynamic resolution control that can be synchronized by a controller (e.g., ROI controller  1340 ) to provide increased resolution for ROIs and decreased resolution for non-ROIs for both vertical and horizontal orientations. For example, when the scan cycle comes across an ROI, the mirror movement speed is decreased and the time interval between successive light pulses is decreased (thereby increasing repetition rate). When the scan cycle comes across a non-ROI, the mirror movement speed is increased and the time interval between successive light pulses is increased (thereby decreasing repetition rate). 
     In some embodiments, the laser source(s) can be selectively turned ON and OFF to provide vertical dynamic range (assuming the laser subsystem is oriented as such). This can eliminate the need to adjust the mirror speed to achieve dynamic vertical resolution. If desired, however, the laser source(s) can be selectively turned ON and OFF in conjunction with variations in mirror movement speed. 
       FIG.  18    shows illustrative FOV  1800  with variable sized laser pulses according to an embodiment. FOV  1800  includes two sparse regions and one dense region as shown. Both the sparse and dense regions show illustrative light pulses that take the form of different sized circles. The sparse sized circles are larger than the dense sized circles. When the scanning system is projecting light to the sparse region, the mirror speed may be moving at a sparse speed and the repetition rate may be set to a sparse region repetition rate. Conversely, when the scanning system is projecting light to the dense region, the mirror speed may be moving at the dense speed and the repetition rate may be set to a dense region repetition rate. The sparse speed is faster than the dense speed and the sparse region repetition rate is slower than the dense region repetition rate. As a result, there are fewer light pulses being sent into the sparse region than in the dense region. If the circle size of the light pulses projected into the sparse region were the same size as the circles in the dense region, underfilling could exist. Underfill may occur when too much space exists between adjacent light pulse circles. Thus, in order to minimize underfill, it is desirable to project an appropriately sized light pulse for both the sparse and dense regions. 
     Although LiDAR system  1300  and  FIGS.  14 - 18    are described in the context of a system using a single large optic and a detector array similar principles may be applied to a receiver system using a multiple optics and a multiple detectors, such as that described below. 
     A multiple optic/multiple detector system according to embodiments discussed herein can be used in a LiDAR system in which the light transmission path is not necessarily the same as the light reception path. Decoupling the transmission and reception paths provides design flexibility in the placement of each optic/detector combination. Each optic/detector combination may include an optic designed to capture returned light pulses in a window existing within the 
     FOV and those returned light pulses are processed by a detector that corresponds to that optic. Each window can capture a subset of the FOV or the entirety of the FOV. The optics/detectors can be independently positioned out of the transmission path of the light so long as any object in the FOV is captured by at least two overlapping windows. Capturing return pulses, via at least two overlapping windows, from an object can enable the receiver system to filter out errant light or background noise. 
       FIG.  23    shows an illustrative LiDAR system  2300  according to an embodiment. LiDAR system  2300  can include laser transmission and steering system  2310  and light receiver system  2320 . Other components may be included, but are omitted to avoid overcrowding the drawing. Light pulses are transmitted along illustrative paths  2311 - 2313  towards objects  2330  in the FOV. Light pulses returned from objects  2330  are shown returning along illustrative paths  2321 - 2323 . Return path  2321  may be the same as transmission path  2313  and would require transmission system  2310  to redirect the returned light pulse to receiver system  2320  (e.g., similar to the way light is redirected in  FIG.  1   ). Light returning on paths  2322  and  2323  do not coincide with any transmission path and are returned directly to light receiver system  2320 . In some embodiments, first optic/detector combination  2325  may detect light returned along path  2322  and second optic/detector combination  2326  may detect light returned along path  2323 . 
     Both optic/detector combinations  2325  and  2326  may have overlapping windows that capture returned light from the same object. 
       FIG.  24    shows an illustrative schematic of two optic/detector combinations having overlapping windows that capture returned light pulses from the same object within a FOV of a LiDAR system. Detector/lens combination  2410  has associated window, W1, and detector/lens combination  2420  has associated window, W2. Windows, W1 and W2, overlap as illustrated. 
       FIG.  19    shows an illustrative multi-lens array based LiDAR system  1900  according to an embodiment. System  1900  can include laser source(s)  1910 , beam steering system  1920 , receiver system  1930 , which can include receiving lens array  1940  and detector circuitry  1950 , and control circuitry  1960 . In some embodiments, LiDAR system  1900  is similar to LiDAR system  700 , but the components of receiver system  1930  are different. The general operating principles are similar. If desired one or more light beams originate from laser source  1910 . Returned pulses (not shown) are collected by receiving lens array  1940  and directed to detector circuitry  1950 . Detector circuitry  1950  processes returned light pulse and provides a signal corresponding to the returned signal to control circuitry  1960 . 
     Receiving lens array  1940  can include several lenses, shown as lenses  1 -N. The combination of all lenses  1 -N can detect returned light pulses within the FOV of LiDAR system  1900 . The lenses can be arranged to detect all returned light pulses anywhere within the FOV or the lenses can be arranged to emphasize detection of returned light pulses within regions of interest of the FOV (e.g., −10 to +10 degrees in the vertical FOV) and to deemphasize detection of returned light pulses outside of the regions of interest. Each lens can be designed to detect light returned by an object within a window of the FOV. The window represents an area within the FOV. The lenses  1 -N can be arranged such that the window corresponding to any given lens overlaps with at least one other window corresponding to at least one other lens. This window overlap can enable two or more lenses corresponding to the overlapping windows to receive the same returned light pulse. For example,  FIG.  19    shows that lens  1  and lens  2  have windows that overlap, as shown by WOL 1 - 2 , and the windows of lenses  2  and  3  overlap, as shown by WOL 2 - 3 . The overlapping windows, in combination with the discreet detectors  1 -N of detector circuitry  1950 , can be effective in filtering out noise existing in the FOV. 
     Detector circuitry  1950  can include several discreet detectors  1 -N. Detectors  1 -N can be discrete and not an array of detectors as shown in  FIG.  7   . Each one of detectors  1 -N is associated with one of lenses  1 -N. Thus, any returned light pulses received by lens  1 , for example, is only detected by detector  1 , and any returned light pulses received by lens  2  is only detected by detector  2 , and so on. This provides a one to one correspondence between lens and detector. This can be advantageous because discrete detectors are cheaper and easier to implement than array based detectors such as detector array  734 . 
       FIG.  20    shows an illustrative diagram of receiver system  1930  of  FIG.  19    according to an embodiment. As shown, receiver system  1930  can include receiver processing circuitry  1960 , which may be the same as or separate from control circuitry  1960 . System  1930  can include detectors  1951 - 1954  (only four of N possible detectors are shown) and can include lenses  1941 - 1944  (only four of N possible lenses are shown). Receiver processing circuitry  1960  is connected to each of detectors  1951 - 1954 , and each of detectors  1951 - 1954  is associated with lenses  1941 - 1944 , respectively. Each of lenses  1941 - 1944  has associated window  1941   a - 1944   a,  as shown. As also shown, two or more of windows  1941   a - 1944   a  overlap each other. 
     The multi-lens array and use of several discrete detectors can provide enhanced flexibility in the design and shape (e.g., the industrial design) of the LiDAR system. For example, LiDAR systems may be used on vehicles such as automobiles or drones and it may be desirable for the LiDAR system to be integrated within or attached to the vehicle in a way that is visually pleasing and unobtrusive, yet is not compromised with respect to its performance. 
     Thus, the multi-lens array can be arranged to have any desired number and configuration of windows that capture returned light from objects in the FOV.  FIGS.  21 A- 21 F  show different window arrangements that are derived from a corresponding multi-lens array according to various embodiments.  FIG.  21 A  shows a M×N array of windows  2102   a - 2102   f  arranged with a horizontal bias. Windows  2102   a - f  may each be approximately the same size as each other. Each window may overlap three other windows. For example, windows  2102   a  may overlap windows  2102   b,    2102   d,  and  2102   e.  The window overlap shown in  FIG.  21 A  is merely illustrative. If desired, the windows of  FIG.  21 A  can be arranged so that only two windows overlap each other.  FIG.  21 B  shows a N×M array of windows  2112   a - 2112   f  arranged with a vertical bias. In some embodiments, the array of  FIG.  21 B  is the same as the array of  FIG.  21 A , but turned ninety degrees. 
       FIG.  21 C  shows a single row or column of windows  2122   a - 2122   e.  Windows  2122   a  and  2122   e  may be sized the same, and windows  2122   b  and  2122   d  may be sized the same, and window  2122   c  may be sized different from the other windows. As shown, window  2122   a  may only overlap with window  2122   b,  and window  2122   b  may overlap with both windows  2122   a  and  2122   c,  window  2122   c  may overlap with windows  2122   b  and  2122   d,  window  2122   d  may overlap with windows  2122   c  and  2122   e,  and window  2122   e  may only overlap with window  2122   d.    
       FIG.  21 D  shows a combination of different sized windows  2132   a  and  2132   b  as shown.  FIG.  21 E  shows a combination of similarly sized windows  2142   a  that overlap each other in a snake like configuration.  FIG.  21 F  shows a combination of similarly sized windows overlapping each other form a triangular shape. 
       FIG.  22    shows an illustrative process  2200  according to an embodiment. Starting at step  2210 , transmission of a light pulse controlling, via a beam steering system, is transmitted along an optical path within a field of view (FOV). At step  2220 , returned light pulses can be received from the FOV via a multi-lens array comprising a plurality of lenses each associated with a window within the FOV, wherein at least two windows overlap each other such that the lenses associated with the overlapping windows receive the same returned light pulse, and wherein each of the plurality of lenses directs any returned light pulse to a detector corresponding to that particular one of the plurality of lenses. The multi-lens array can be for example, the multi-lens array of  FIGS.  18 - 20    and  FIGS.  21 A- 21 F . At step  2230 , signals received from each detector corresponding to the plurality of lenses can be processed. At step  2240 , the processed signals can be discriminated by filtering out received return pulses that are not captured by the at least two overlapping windows to produce a filtered signal. That is, if the detectors associated with the overlapping windows do not detect a return light pulse, then that returned light pulse is rejected. 
     It should be appreciated that the steps shown in  FIG.  22    are merely illustrative and that additional steps may be added. 
       FIG.  25    shows an illustrative vehicle  2501  with an integrated LiDAR system according to an embodiment. Laser transmission and steering system  2510  can be integrated into rear view mirror assembly  2502 . If desired, system  2510  can be placed elsewhere on vehicle  2501 . Moreover, multiple instances of system  2510  can be placed on vehicle  2501 . Multiple instances of optic/detector combinations (ODC) can be placed at various locations on vehicle. For example, ODCs  2520  and  2521  may be located near or at the front of vehicle (e.g., near the grill assembly or the bumper assembly). ODCs  2522  and  2523  may be co-located near the headlight assemblies. ODC  2524  may be co-located with a side mirror assembly as shown. ODCs  2525  and  2526  may be located near the roofline adjacent to the windshield. If desired, an ODC may be integrated with steering system  2510 . It should be appreciated that by decoupling the ODC from the light transmission paths, design flexibility in placing ODCs anywhere on vehicle  2501  can be realized. 
     It is believed that the disclosure set forth herein encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Each example defines an embodiment disclosed in the foregoing disclosure, but any one example does not necessarily encompass all features or combinations that may be eventually claimed. Where the description recites “a” or “a first” element or the equivalent thereof, such description includes one or more such elements, neither requiring nor excluding two or more such elements. Further, ordinal indicators, such as first, second or third, for identified elements are used to distinguish between the elements, and do not indicate a required or limited number of such elements, and do not indicate a particular position or order of such elements unless otherwise specifically stated. 
     Moreover, any processes described with respect to  FIGS.  1 - 25   , as well as any other aspects of the invention, may each be implemented by software, but may also be implemented in hardware, firmware, or any combination of software, hardware, and firmware. They each may also be embodied as machine- or computer-readable code recorded on a machine- or computer-readable medium. The computer-readable medium may be any data storage device that can store data or instructions which can thereafter be read by a computer system. Examples of the computer-readable medium may include, but are not limited to, read-only memory, random-access memory, flash memory, CD-ROMs, DVDs, magnetic tape, and optical data storage devices. The computer-readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. For example, the computer-readable medium may be communicated from one electronic subsystem or device to another electronic subsystem or device using any suitable communications protocol. The computer-readable medium may embody computer-readable code, instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave or other transport mechanism, and may include any information delivery media. A modulated data signal may be a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. 
     It is to be understood that any or each module or state machine discussed herein may be provided as a software construct, firmware construct, one or more hardware components, or a combination thereof. For example, any one or more of the state machines or modules may be described in the general context of computer-executable instructions, such as program modules, that may be executed by one or more computers or other devices. Generally, a program module may include one or more routines, programs, objects, components, and/or data structures that may perform one or more particular tasks or that may implement one or more particular abstract data types. It is also to be understood that the number, configuration, functionality, and interconnection of the modules or state machines are merely illustrative, and that the number, configuration, functionality, and interconnection of existing modules may be modified or omitted, additional modules may be added, and the interconnection of certain modules may be altered. 
     Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. Therefore, reference to the details of the preferred embodiments is not intended to limit their scope.