Patent Publication Number: US-2023152429-A1

Title: Auto-Exposure Occlusion Camera

Description:
BACKGROUND 
     Optical systems such as lidar devices and/or cameras may be used to sense a surrounding environment. For example, a lidar device may be used to generate a point cloud associated with an environment surrounding an autonomous vehicle, and that point cloud may be used by the autonomous vehicle for object detection and avoidance. Such lidar devices and/or cameras may include one or more optical components with which incident light may interact. For example, a lidar device and/or a camera may include an optical window, a mirror, a lens, etc. 
     In conventional optical systems, imperfections in the one or more optical components may affect the performance of the optical system. For example, in a lidar context, an occlusion or a scratch in an optical component of the lidar may adversely affect ranging and localization of objects in an environment. In such scenarios, fouled or degraded optical components may render the lidar system ineffective and/or cause the lidar system to provide incorrect or inaccurate information about the environment. 
     Conventional approaches may include a defect camera configured to capture images of the optical components in an effort to detect potential imperfections. However, such conventional approaches may be ineffective in scenes with very bright or very dim illumination. For example, the defect camera may capture high quality images under normal illumination conditions. However, under very bright conditions, the images from the defect camera may appear overexposed or “blown out” and under very low conditions, the images from the defect camera may appear dark and/or underexposed. Accordingly, improved systems and methods that may help more effectively identify and mitigate optical imperfections in optical systems, under various environmental background conditions, are desired. 
     SUMMARY 
     The present disclosure relates to optical systems, lidars, and methods of their use that may be configured to determine imperfections associated with one or more optical components under background scenarios having wide variations in illumination light. In some examples, embodiments may include detection and characterization of optical imperfections in systems and lidars configured to be utilized with self-driving vehicles. 
     In a first aspect, an optical system is provided. The optical system includes one or more optical components and a light detector configured to receive light from a field of view of an environment by way of the one or more optical components. The optical system also includes an occlusion-detection camera configured to capture images of the one or more optical components. Yet further, the optical system includes a controller having at least one processor and a memory. The at least one processor executes instructions stored in the memory so as to perform operations. The operations include receiving information indicative of a light intensity of the field of view and adjusting, based on the received information, at least one operating parameter of the occlusion-detection camera. The operations also include causing the occlusion-detection camera to capture at least one image of the one or more optical components according to the at least one adjusted operating parameter. 
     In a second aspect, an optical system is provided. The optical system includes one or more optical components and a light emitter device configured to emit emission light toward a field of view of an environment by way of the one or more optical components. The optical system also includes a light detector configured to receive light from a field of view of the environment by way of the one or more optical components. At least a portion of the received light includes reflected light. The reflected light includes at least a portion of the emission light that has reflected back toward the optical system after interaction with the environment. The optical system also includes an occlusion-detection camera configured to capture images of the one or more optical components. The optical system further includes a controller having at least one processor and a memory. The at least one processor executes instructions stored in the memory so as to perform operations. The operations include receiving information indicative of a light intensity of the field of view and adjusting, based on the received information, at least one operating parameter of the occlusion-detection camera. The operations also include causing the occlusion-detection camera to capture at least one image of the one or more optical components according to the at least one adjusted operating parameter. The operations yet further include determining, based on the reflected light, one or more objects in the environment. 
     In a third aspect, a method is provided. The method includes receiving, from a light detector, information indicative of a light intensity of a field of view of an optical system. The optical system includes one or more optical components and a light detector configured to receive light from a field of view of an environment by way of the one or more optical components. The optical system also includes an occlusion-detection camera configured to capture images of the one or more optical components. The method also includes adjusting, based on the received information, at least one operating parameter of the occlusion-detection camera. The method also includes causing the occlusion-detection camera to capture at least one image of the one or more optical components according to the at least one adjusted operating parameter. 
     Other aspects, embodiments, and implementations will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    illustrates an optical system, according to an example embodiment. 
         FIG.  2    illustrates a swimlane diagram, according to an example embodiment. 
         FIG.  3    illustrates a lidar, according to an example embodiment. 
         FIG.  4    illustrates a lidar, according to an example embodiment. 
         FIG.  5 A  illustrates a vehicle, according to an example embodiment. 
         FIG.  5 B  illustrates a vehicle, according to an example embodiment. 
         FIG.  5 C  illustrates a vehicle, according to an example embodiment. 
         FIG.  5 D  illustrates a vehicle, according to an example embodiment. 
         FIG.  5 E  illustrates a vehicle, according to an example embodiment. 
         FIG.  6    illustrates a method, according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Example methods, devices, and systems are described herein. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. Other embodiments can be utilized, and other changes can be made, without departing from the scope of the subject matter presented herein. 
     Thus, the example embodiments described herein are not meant to be limiting. Aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are contemplated herein. 
     Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall embodiments, with the understanding that not all illustrated features are necessary for each embodiment. 
     In various scenarios, as a result of one or more imperfections of optical components within a camera or a lidar device, aberrations within captured images/generated point clouds can result. For example, a scratch, a crack, a smudge, a deformation, debris, an air bubble, an impurity, a degradation, a discoloration, an opacity, a warp, or condensation, etc. may cause light from a scene to be directed to unintended/improper regions of an image sensor/light detector, may prevent light from a scene from ever reaching an image sensor/light detector, or may otherwise modify light from a scene (e.g., modify polarization or wavelength) prior to the light reaching an image sensor/light detector. Such issues can result in improper object identification/distance detection. In autonomous vehicle applications, improper object identification/distance detection can adversely affect the operation of the vehicle. 
     In some embodiments, imperfections could include debris such as dust, soil, mud, insects, or other types of organic or inorganic matter that may collect along an optical surface of the lidar system. Additionally or alternatively, the imperfections could include water droplets and/or condensation. 
     To detect such imperfections (and possibly thereafter take a remedial action), the devices disclosed herein may include an additional camera (an “occlusion-detection camera”) used to capture images of one or more of the optical components of the lidar device/camera being used to sense the surrounding environment. In some examples, the occlusion-detection camera could include a digital image sensor configured to detect incoming light intensity. In an example embodiment, such an image sensor could include a charge-coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, and/or a back-side illuminated CMOS (BSI-CMOS) sensor. It will be understood that other types of photodetectors are possible and contemplated. 
     Images captured by the occlusion-detection camera may be analyzed to determine whether one or more imperfections are present on a given optical component, the location of one or more imperfections on a given optical component, the size of one or more imperfections on a given optical component, and/or the type of one or more imperfections on a given optical component. Further, the occlusion-detection camera may be positioned adjacent to one or more detectors associated with the lidar device/camera that is being used to collect data about the surrounding environment. 
     However, images captured by the occlusion-detection camera may be susceptible to and/or adversely affected by background light (e.g., glare). For example, if the sun is present in an image captured by the occlusion-detection camera, it may be difficult to use that image to detect imperfections associated with an optical component. This is especially true when the occlusion-detection camera has a low dynamic range (e.g., low relative to the dynamic range of intensities present in the surrounding scene). 
     Embodiments described herein attempt to mitigate the effect of background light on the images captured by the occlusion-detection camera by adjusting exposure settings of the occlusion-detection camera based on data collected by the associated lidar device/camera. For example, the associated lidar device (e.g., which may have a higher dynamic range than the occlusion-detection camera) may collect intensity information from the surrounding scene. Other types of image sensors or photodetectors could be used to determine the intensity information from the scene. As an example, the other image sensors or photodetectors could be mounted internal or external from the camera or lidar device. The determined intensity information may indicate the brightness of the surrounding scene (e.g., the brightness of the solar background in the surrounding scene). Then, one or more of the exposure settings (e.g., exposure time, aperture size, and/or a gain setting of the image sensor) of the occlusion-detection camera may be modified (e.g., by an associated computing device) based on the brightness of the surrounding scene. By modifying the exposure settings, the effects of bright objects in the surrounding scene (e.g., the sun) may be minimized. Using the intensity information collected by the lidar device/camera may include generating a brightness map based on a field of view of the lidar device/camera and then transforming the brightness map based on the associated field of view of the occlusion-detection camera, as the fields of view of the lidar device/camera and the occlusion-detection camera are unlikely to be the same fields of view (e.g., as the occlusion-detection camera may only capture images of optical components of the lidar device/camera rather than an entire surrounding scene). The brightness map could include a two- or three-dimensional representation of received light intensity from the scene. The brightness map could include information indicative of, for example, bright objects (e.g., retroreflectors) in the scene. Transforming the brightness map based on the field of view of the occlusion-detection camera could include applying an affine transformation or another type of image transformation technique to reconcile the different fields of view of the occlusion-detection camera and the lidar device/camera. 
       FIG.  1    illustrates an optical system  100 , according to an example embodiment. Some or all elements of optical system  100  could be physically coupled together. Additionally or alternatively, some elements of optical system  100  could be located remote from one another. Some or all elements of optical system  100  could be communicatively coupled via a communication interface  155 . The communication interface  155  could include a wired and/or wireless communication link. 
     The optical system  100  includes one or more optical components  110 . In some examples, the one or more optical components  110  could include at least one of: an optical window, a mirror, a lens, or a waveguide. As an example, the optical components  110  could include optical elements that may interact with (e.g., transmit, guide, block, focus, defocus, reflect, attenuate, etc.) incident light. 
     The optical system  100  also includes one or more light detectors  120  configured to receive light from a field of view  12  of an environment  10  of the optical system  100  by way of the one or more optical components  110 . In some scenarios, at least some of the incident light could include a portion of solar background and/or glare light  16 . Additionally or alternatively, some of the incident light may be indicative of various objects  14  (e.g., pedestrians, vehicles, signs, buildings, roads, etc.) in the environment  10 . The environment  10  is further described elsewhere herein (e.g., paragraph [0053] and paragraph [0055]). 
     The optical system  100  additionally includes an occlusion-detection camera  130  configured to capture images of the one or more optical components  110 . In various embodiments, the occlusion-detection camera  130  could include a charge-coupled device (CCD) image sensor. Additionally or alternatively, the occlusion-detection camera  130  could include an active-pixel sensor (e.g., a complementary metal-oxide semiconductor (CMOS) sensor). The occlusion-detection camera  130  could include one or more amplifiers configured to modify a gain characteristic of the image sensor. Overall, the total amount of incident light to the system could be determined to have a light intensity  18 . In such scenarios, various operating characteristics of the occlusion-detection camera  130  could be adjusted based on the light intensity  18 . 
     The optical system  100  also includes a controller  150 . In an example embodiment, the controller  150  includes at least one processor  152  and a memory  154 . In some embodiments, the controller  150  could include an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a microprocessor, or a graphics processing unit (GPU). Other types of circuits and computing devices are possible and contemplated. The at least one processor  152  executes instructions stored in the memory  154  so as to perform operations. The operations include receiving information indicative of a light intensity  18  of the field of view  12 . As an example, receiving information indicative of the light intensity  18  could include a signal from the detector(s)  120  that is based on (e.g., proportional to) the light intensity  18 . 
     The operations additionally include adjusting, based on the received information, at least one operating parameter  132  of the occlusion-detection camera  130 . Adjustable operating parameters  132  could include, for example, a camera exposure value (EV), a shutter speed, an f-number (e.g., ratio of the optical system&#39;s focal length to the diameter of the clear aperture), image sensor gain, image sensor exposure index (EI) and/or image sensor ISO. It will be understood that adjusting other types of operating parameters in an effort to controllably and dynamically change the exposure of the occlusion-detection camera  130  is possible and contemplated. 
     The operations further include causing the occlusion-detection camera  130  to capture at least one image  134  of the one or more optical components  110  according to the at least one adjusted operating parameter  132 . 
     In some examples, the operations may further include determining, based on the at least one image  134 , a presence of at least one imperfection  112  associated with the one or more optical components  110 . 
     In various example embodiments, the operations could further include determining, based on the at least one image  134 , a location of at least one imperfection  112  associated with the one or more optical components  110 . Additionally or alternatively, the operations may further include determining, based on the at least one image  134 , a size of at least one imperfection  112  associated with the one or more optical components  110 . In some examples, the operations could include determining, based on the at least one image  134 , a type of at least one imperfection  112  associated with the one or more optical components  110 . 
     In various examples, the type of the at least one imperfection  112  could include at least one of: a scratch, a crack, a smudge, a deformation, an occlusion, debris, an air bubble, an impurity, a degradation, a discoloration, an imperfect transparency, a warp, or condensation. It will be understood that other types of optical imperfections are possible and contemplated. 
     In example embodiments, the occlusion-detection camera  130  could have a low-dynamic range relative to a range of light intensities  18  present in the field of view  12  (e.g., ½, 1/10, 1/100, 1/1000, 1/10000, or less dynamic range compared to the dynamic range of light present in the scene). 
     In some embodiments, adjusting, based on the received information, at least one operating parameter  132  of the occlusion-detection camera  130  includes adjusting at least one exposure setting of the occlusion-detection camera  130 . In such scenarios, the at least one exposure setting could include an exposure time, an aperture size, a gain setting, or a sensitivity. 
     Various examples may include that the operations also include determining, based on the received information, a brightness map  156  associated with the field of view  12 . In such scenarios, the operations may also include transforming the brightness map  156  based on a camera field of view  136  of the occlusion-detection camera  130  to provide a transformed brightness map  158 . Furthermore, the operations could include that adjusting the at least one operating parameter  132  of the occlusion-detection camera  130  could be further based on the transformed brightness map  158 . 
       FIG.  2    illustrates a swimlane diagram  200 , according to an example embodiment. The swimlane diagram  200  illustrates various blocks or steps that could be carried out by elements of optical system  100 . For example, the swimlane diagram  200  includes blocks or steps that could be caused and/or carried out by the occlusion-detection camera  130 , the detector(s)  120 , and/or the controller  150 . 
     In various examples, block  202  could include detector(s) (e.g., detector(s)  120 ) detect a light intensity (e.g., light intensity  18 ) of a field of view (e.g., field of view  12 ) via optical components (e.g., optical components  110 ). The detectors could include an image sensor of a camera and/or a detector of a lidar receiver module. It will understood that other types of detectors are possible and contemplated. 
     Block  204  includes receiving, at the controller  150 , information indicative of the light intensity of the field of view. In such a scenario, the controller  150  could receive the information from the detectors via a wired or wireless communication link (e.g., communication interface  155 ). 
     Block  206  could include the controller  150  determining operating parameter instructions. In such a scenario, the controller  150  could calculate and/or utilize a look-up table to select a set of operating parameter instructions. The selected set of operating parameter instructions could be selected based on the detected light intensity so as to adjust the occlusion-detection camera  130  for proper imaging/exposure of the optical components  110 . 
     Once the operating parameter instructions are determined, block  208  could include transmitting the instructions to the occlusion-detection camera  130 . As an example, the instructions could be transmitted to the occlusion-detection camera  130  via the communication interface  155 . 
     Block  210  includes the occlusion-detection camera  130  receiving the operating parameter instructions. 
     Block  212  includes the occlusion-detection camera  130  changing its operating parameters. In an example embodiment, the occlusion-detection camera  130  could adjust its aperture size, shutter time/exposure time, zoom setting, focus setting, detector gain, and/or ISO setting. Other adjustable parameters are possible and could be adjusted. 
     Block  214  includes the controller  150  causing the occlusion-detection camera  130  to capture images  134  of the optical components  110 . In an example embodiment, the controller  150  could transmit instructions to the occlusion-detection camera  130  by way of the communication interface  155 . In some examples, block  210  and  214  could be combined in a single instruction set from the controller  150 . In other words, the operating parameters and imaging instructions could be transmitted by the controller  150  in the same message and/or message set. Other combinations of instructions are possible and contemplated within the scope of the present disclosure. 
     Block  216  includes the occlusion-detection camera  130  capturing one or more images  134  of the optical component(s)  110 . As an example, the occlusion-detection camera  130  may capture a digital photograph of the optical component(s)  110 . In some embodiments, the digital photographs may include light intensity information that could be encoded in the RGB color space and/or as raw data. In examples, the images  134  could be captured in various resolutions, including 1600 pixels×1200 pixels (1.92 megapixels), 2048 pixels×1536 pixels (3.1 megapixels), 3840 pixels×2160 pixels (4K UHDTV), or another digital image resolution. 
     It will be understood that the aspect ratio of the images  134  may be based, at least in part, on the physical format of the image sensor. For example, the occlusion-detection camera  130  could include an image sensor in an APS-C format, Micro Four Thirds format, Nikon CX format, ¼″ format, among other possibilities. 
     Block  218  includes the controller  150  determining, based on the images  134 , a presence, location, size, or type of at least one imperfection  112  associated with the optical component(s)  110 . In some examples, the controller  150  could utilize various computer vision algorithms and/or processes in order to determine the various characteristics of the imperfection(s)  112 . In some examples, the controller  150  could utilize artificial intelligence (e.g., a convolutional neural network) to perform various object recognition, identification, and/or detection tasks. It will be understood that other types of object recognition techniques could be implemented within the context of the present disclosure to determine information about the imperfection(s)  112 . 
     In various embodiments, the controller  150  could compare a prior image (e.g., a reference image) with a current image  134 . In such scenarios, the controller  150  could determine the presence, location, size, and/or type of the imperfection(s)  112  based on the comparison between the reference image and the current image  134 . 
     Embodiments described herein may relate to a lidar system. An example lidar system may include a plurality of light-emitter devices configured to emit pulses of laser light into an environment. As an example, an environment could include an interior or exterior environment, such as inside a building or outside of the building. Additionally or alternatively, the environment could include a vicinity around and/or on a roadway. Furthermore, the environment could include objects such as other vehicles, traffic signs, pedestrians, roadway surfaces, buildings, terrain, etc. Additionally light pulses could be emitted into a local environment of the lidar system itself. For example, the light pulses could interact with a housing of the lidar system and/or surfaces or structures coupled to the lidar system. In some cases, the lidar system could be mounted to a vehicle. In such scenarios, the lidar system could be configured to emit light pulses that interact with objects within a vicinity of the vehicle. 
     The lidar system may additionally include a firing circuit configured to selectively control the plurality of light-emitter devices to emit the light pulses in accordance with one or more adjustable light-emission parameters. The lidar system also includes a plurality of detectors configured to receive return light generated by interactions between the emitted laser light pulses and the environment. 
     In specific embodiments, the lidar system could provide lidar functionality for a semi- or fully-autonomous vehicle. Such a vehicle can include motor vehicles (cars, trucks, buses, motorcycles, all-terrain vehicles, recreational vehicle, any specialized farming or construction vehicles, etc.), aircraft (planes, helicopters, drones, etc.), naval vehicles (ships, boats, yachts, submarines, etc.), or any other self-propelled vehicles (e.g., robots, factory or warehouse robotic vehicles, sidewalk delivery robotic vehicles, etc.) capable of being operated in a self-driving mode (without a human input or with a reduced human input) to navigate its environment. As described herein, the environment could include an interior or exterior environment, such as inside a building or outside of the building. Additionally or alternatively, the environment could include a vicinity around and/or on a roadway. Furthermore, the environment could include objects such as other vehicles, traffic signs, pedestrians, roadway surfaces, buildings, terrain, etc. Additionally or alternatively, the environment could include the interior of the semi- or fully-autonomous vehicle. In some embodiments, the lidar system could be configured to obtain point cloud information that could include information indicative of a plurality of points in specific locations in three-dimensional space. As an example, the point cloud information could indicate the location of objects in the environment. 
       FIG.  3    illustrates a lidar  300 , according to an example embodiment. Lidar  300  could include some or all of the elements of optical system  100 . For example, lidar  300  may include optical components  110 , detectors  120 , an occlusion-detection camera  130  and a controller  150 . Lidar  300  may additionally include one or more light-emitter devices  310 , which may be configured to emit light pulses  312  into the environment  10  of the lidar  300 . The light-emitter devices  310  could include one or more laser diodes (e.g., semiconductor laser bars), light-emitting diodes (LEDs), vertical-external-cavity surface-emitting-lasers (VECSELs), vertical-cavity surface-emitting lasers (VCSELs), or other types of devices configured to emit light in discrete light pulses. In an example embodiment, the light pulses could be emitted in an adjustable and/or controllable manner. However, other types of light-emitter devices are possible and contemplated. In some embodiments, the light-emitter devices  310  could be configured to emit light with wavelength around 905 nm. It will be understood that other emission wavelengths are possible and contemplated. 
     At least some of the light pulses  312  emitted by the light-emitter devices  310  may interact with objects  14  in the field of view  12  and some portion of those light pulses  312  may be reflected back toward the lidar  300  in the form of reflected emission light  322 , which could be incident upon the optical components  110 . Additionally, environmental light  324  from the environment  10  could be incident upon the optical components  110 . 
     In such scenarios, the detectors  120  could be configured to receive the reflected emission light  322  and the environmental light  324 . As described with respect to optical system  100 , the detectors  120  could be configured to provide controller  150  with information indicative of the light intensity  18  of the environment  10 . In response, the controller  150  could determine, based on the received information, various operating parameters  132  for the occlusion-detection camera  130 . In such scenarios, the operating parameters  132  of the occlusion-detection camera  130  could be adjusted so as to provide a well-exposed image of the optical components  110  under the given solar background/glare conditions  16 . 
       FIG.  4    illustrates a cross-sectional view of a lidar  400 , according to an example embodiment.  FIG.  4    could include elements that are similar or identical to those of optical system  100  and lidar  300  illustrated and described in reference to  FIGS.  1  and  3   . 
     For example, in some embodiments, the lidar  400  could include a first substrate  410  having a mounting surface  412 . In some embodiments, the first substrate  410  could be a printed circuit board (PCB). In some other embodiments, the first substrate  410  could include a semiconductor substrate material such as silicon, gallium arsenide, or the like. In some embodiments, the first substrate  410  could include a silicon-on-insulator (SOI) material. Alternatively, the first substrate  410  could be formed from a variety of other solid and/or flexible materials, each of which is contemplated in the present disclosure. The lidar  400  could include a spacer structure  420  having a first surface  422  and a second surface  424 . The spacer structure  420  could include one or more cavities  426   a - 426   d . The spacer structure  420  could include a semiconductor material and/or a polymeric material. Subsequently, using one or more techniques, at least one cavity (e.g., cavities  426   a - 426   d ) could be formed in the spacer structure  420 . That is, a first surface  422  of the spacer structure  420  could have an opening forming part of the at least one cavity and a second surface  424  of the spacer structure  420  could have an opening forming part of the at least one cavity. In some embodiments, the cavities  426   a - 426   d  could be formed by removing at least a portion of the spacer structure  420  using semiconductor manufacturing methods such as dry or wet etching processes. Other ways to form the cavities in the spacer structure  420  are contemplated. 
     One or more light-emitter devices  430  could be coupled to the second surface  424  of the spacer structure  420 . The light-emitter devices  430  could each include one or more light-emitting regions  431 . The second surface  424  could include an upper surface  424   a  and a lower surface  424   b . For example, the upper surface  424   a  could define a first plane and the lower surface  424   b  could define a second plane. That is, in some embodiments, the second surface  424  could include an upper surface  424   a  that “steps down” to a lower surface  424   b.    
     In some embodiments, detector devices  440   a - 440   d  could be disposed within the one or more cavities  426   a - 426   d . For example, as illustrated, each cavity could include one detector device. Alternatively, multiple detector devices and/or detector arrays could be disposed in a single cavity. The detector devices  440   a - 440   d  could be configured to detect the light emitted by the one or more light-emitter devices  430  after interaction with the external environment. In examples, the at least one detector devices  440   a - 440   d  could include a silicon photomultiplier (SiPM), an avalanche photodiode (APD), or another type of photodetector. 
     As additionally illustrated in  FIG.  4   , an intermediate lid  450  could be coupled to the second surface  424  (e.g., the lower surface  424   b ) of the spacer structure  420 . In embodiments, the intermediate lid  450  could include a plurality of apertures  452   a - 452   d , which could be disposed adjacent to the cavities  426   a - 426   d . In some embodiments, the apertures  452   a - 452   d  could have a diameter of 150 microns. However, other aperture diameters are possible and contemplated. 
     In some embodiments, the plurality of apertures  452   a - 452   d  could include holes drilled or lithographically etched through a material that is substantially opaque to light emitted by the light-emitter devices  430 . In other embodiments, the plurality of apertures  452   a - 452   d  could include optical windows that are substantially transparent to light emitted by the light-emitter devices  430 . 
     While  FIG.  4    illustrates the intermediate lid  450  as including the plurality of apertures  452   a - 452   d , it will be understood that in some embodiments, the plurality of apertures  452   a - 452   d  could be formed in the spacer structure  420 . For example, the spacer structure  420  could include one or more holes forming the plurality of apertures  452   a - 452   d . In one example embodiment, plurality of apertures  452   a - 452   d  could be formed between the upper surface  424   a  and the lower surface  424   b  of the spacer structure  420 . 
       FIG.  4    also illustrates a second substrate  460  that includes a mounting surface  462 . In some embodiments, the second substrate  460  could be substantially transparent to light emitted by light-emitter device  430 . At least one lens  464  could be coupled to the mounting surface  462  of the second substrate  460 . The second substrate  460  could be formed from a transparent material, such as glass, plastic, fused silica, or another transparent low-refractive index material. A top surface of the second substrate  460  could include an antireflective coating. Optionally, an antireflective coating could be applied to the mounting surface  462  of the second substrate  460 . Furthermore, at least one waveguide  466  is coupled to the mounting surface  462  of the second substrate  460 . In embodiments, the at least one waveguide  166  could include reflective surfaces  467   a - 467   d  (e.g., mirrored facets). 
     For example, the at least one waveguide  466  could be configured to efficiently guide light along a propagation direction. For example, the at least one waveguide  466  may be configured to couple light emitted from the at least one light-emitter device  430 . At least a portion of such light may be guided within at least a portion of the at least one waveguide  466  via total internal reflection and/or evanescent optical coupling. 
     In some embodiments, the at least one waveguide  466  includes at least one reflective surface. In such scenarios, at least a portion of the optically-coupled light could interact with the at least one reflective surface so as to be directed toward an external environment. For example, the at least one waveguide  466  may include one or more reflective surfaces (e.g., mirrored facets) configured to direct light normal to the propagation direction. In such a scenario, at least a portion of the light may be coupled out of the at least one waveguide  166  via a mirrored facet. 
     In examples, a shim  470  could be disposed between a second surface  424  of the spacer structure  420  and the mounting surface  462  of the second substrate  460 . The shim  470  could be configured to prevent light from leaking through the edge of the lidar  400 . In some embodiments, the shim  470  could include a polymer material that cures or molds around the second substrate  460 . In such a scenario, the shim  470  could hold the second substrate  460  at a fixed height and/or location relative to the spacer structure  420  and other elements of the lidar  400 . The spacer structure  120  could include a semiconductor material and/or a polymeric material. In some embodiments, the shim  470  could be selected such that a light-emitting region  431  is disposed at a predetermined or desired position with respect to the at least one lens  464  and/or the at least one waveguide  466 . For example, the shim  470  could be selected so that light emitted from the light-emitting region  431  is efficiently collected by the at least one lens  464  and efficiently optically-coupled into the at least one waveguide  466 . 
     While  FIG.  4    illustrates shim  470  as being located near the sides of the lidar  400 , it will be understood that the shim  470  could be located elsewhere. For example, shim  470  could be disposed between the intermediate lid  450  and the mounting surface  462  of the second substrate  460 . Additionally or alternatively, shim  470  could be present in other regions of the lidar  400 , for example, to provide a baffle (e.g., to prevent stray light). 
     The lidar  400  could additionally include a circuit board  490  that could be physically coupled to the first substrate  410  by way of controlled-collapse solder balls  480 . Other ways to physically and/or electrically connect the first substrate  410  to the circuit board  490  are possible and contemplated, such as, without limitation, conventional solder balls, ball-grid arrays (BGA), land-grid arrays (LGA), conductive paste, and other types of physical and electrical sockets. It will be understood that while  FIGS.  3  and  4    illustrate specific lidar embodiments, other types and arrangements of lidars and/or cameras are possible and contemplated. 
       FIGS.  5 A,  5 B,  5 C,  5 D, and  5 E  illustrate a vehicle  500 , according to an example embodiment. In some embodiments, the vehicle  500  could be a semi- or fully-autonomous vehicle. While  FIGS.  5 A,  5 B,  5 C,  5 D, and  5 E  illustrates vehicle  500  as being an automobile (e.g., a passenger van), it will be understood that vehicle  500  could include another type of semi- or fully-autonomous vehicle that is capable of being operated in a self-driving mode (without a human input or with a reduced human input) to navigate within its environment using sensors and other information about its environment. 
     In some examples, the vehicle  500  may include one or more sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and  512 . In some embodiments, sensor systems  502 ,  504 ,  506 ,  508 ,  510  and/or  512  could represent one or more optical systems  100  as illustrated and described in relation to  FIG.  1    and/or one or more lidars  300  as illustrated and described in relation to  FIG.  3   . In other words, optical systems and lidar systems described elsewhere herein could be coupled to the vehicle  500  and/or could be utilized in conjunction with various operations of the vehicle  500 . As an example, the lidar system  300  could be utilized in self-driving or other types of navigation, planning, perception, and/or mapping operations of the vehicle  500 . 
     In some examples, the one or more optical systems and/or lidars could be disposed in various locations on the vehicle  500  and could have fields of view that correspond to an environment that is internal and/or external to the vehicle  500 . 
     While the one or more sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and  512  are illustrated on certain locations on vehicle  500 , it will be understood that more or fewer sensor systems could be utilized with vehicle  500 . Furthermore, the locations of such sensor systems could be adjusted, modified, or otherwise changed as compared to the locations of the sensor systems illustrated in  FIGS.  5 A,  5 B,  5 C,  5 D, and  5 E . 
     The one or more sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  could include other lidar sensors. For example, the other lidar sensors could include a plurality of light-emitter devices arranged over a range of angles with respect to a given plane (e.g., the x-y plane). For example, one or more of the sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  may be configured to rotate or pivot about an axis (e.g., the z-axis) perpendicular to the given plane so as to illuminate an environment around the vehicle  500  with light pulses. Based on detecting various aspects of reflected light pulses (e.g., the elapsed time of flight, polarization, intensity, etc.), information about the environment of the vehicle  500  may be determined. 
     In an example embodiment, sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  may be configured to provide respective point cloud information that may relate to physical objects within the environment of the vehicle  500 . While vehicle  500  and sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and  512  are illustrated as including certain features, it will be understood that other types of sensor systems are contemplated within the scope of the present disclosure. 
     While lidar systems with multiple light-emitter devices (e.g., a light-emitter device with multiple laser bars on a single laser die) are described and illustrated herein, lidar systems with single light-emitter devices are also contemplated. For example, light pulses emitted by one or more laser diodes may be controllably directed about an environment of the system. The angle of emission of the light pulses may be adjusted by a scanning device such as, for instance, a mechanical scanning mirror and/or a rotational motor. For example, the scanning devices could rotate in a reciprocating motion about a given axis and/or rotate about a vertical axis. In another embodiment, the light-emitter device may emit light pulses towards a spinning prism mirror, which may cause the light pulses to be emitted into the environment based on an angle of the prism mirror angle when interacting with each light pulse. Additionally or alternatively, scanning optics and/or other types of electro-opto-mechanical devices are possible to scan the light pulses about the environment. While  FIGS.  5 A- 5 E  illustrate various lidar sensors attached to the vehicle  500 , it will be understood that the vehicle  500  could incorporate other types of sensors. 
     The lidar system of vehicle  500  further includes a plurality of detectors (e.g., detectors  120 ). 
     The lidar system of vehicle  500  additionally includes a controller (e.g., controller  150 ) having at least one processor (e.g., processor(s)  152 ) and a memory (e.g., memory  154 ). The at least one processor executes instructions stored in the memory so as to perform operations. The operations may include any of the method steps or blocks described with regard to method  600 . 
     In some embodiments, the one or more sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  could include image sensors. For example, vehicle  500  could include a camera that includes an image sensor configured to provide images of a field of view. In various examples, the image sensor may include a plurality of detector elements. 
     In such scenarios, the camera could be disposed within sensor system  502 ,  504 ,  506 ,  508 ,  510  and/or  512 . The camera can be a photosensitive instrument, such as a still camera, a video camera, a thermal imaging camera, a stereo camera, a night vision camera, etc., that is configured to capture a plurality of images of the environment of the vehicle  500 . To this end, the camera can be configured to detect visible light, and can additionally or alternatively be configured to detect light from other portions of the spectrum, such as infrared or ultraviolet light. The camera can be a two-dimensional detector, and can optionally have a three-dimensional spatial range of sensitivity. In some embodiments, the camera can include, for example, a range detector configured to generate a two-dimensional image indicating distance from the camera to a number of points in the environment of the vehicle  500 . To this end, the camera may use one or more range detecting techniques. For example, the camera can provide range information by using a structured light technique in which the vehicle  500  illuminates an object in the environment of the vehicle  500  with a predetermined light pattern, such as a grid or checkerboard pattern and uses the camera to detect a reflection of the predetermined light pattern from environmental surroundings. Based on distortions in the reflected light pattern, the vehicle  500  can determine the distance to the points on the object. The predetermined light pattern may comprise infrared light, or radiation at other suitable wavelengths for such measurements. In some examples, the camera can be mounted inside a front windshield of the vehicle  200 . Specifically, the camera can be situated to capture images from a forward-looking view with respect to the orientation of the vehicle  500 . Other mounting locations and viewing angles of the camera can also be used, either inside or outside the vehicle  500 . Further, the camera can have associated optics operable to provide an adjustable field of view. Still further, the camera can be mounted to vehicle  500  with a movable mount to vary a pointing angle of the camera, such as via a pan/tilt mechanism. 
     Additionally or alternatively, the vehicle  500  and/or sensor system  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  could include one or more radar systems. The radar system(s) could be configured to emit radio waves to determine the range, angle, and/or relative velocity of objects within the environment of the vehicle  500 . As an example, the radar system could include a transmitter configured to emit radio waves or micro waves and a receiver configured to receive information about how those radio waves or micro waves interact with the environment of the vehicle  500 . In various embodiments, the radar system could be configured to operate in pulsed and/or continuous mode. 
     In some embodiments, the vehicle  500  and/or sensor systems  502 ,  504 ,  506 ,  508 ,  510 , and/or  512  could include other types of sensors such as one or more range finders, one or more inertial sensors, one or more humidity sensors, one or more acoustic sensors (e.g., microphones, sonar devices, etc.), and/or one or more other sensors configured to sense information about the environment of the vehicle  500 . Any sensor system described elsewhere herein could be coupled to the vehicle  500  and/or could be utilized in conjunction with various operations of the vehicle  500 . As an example, a lidar system could be utilized in self-driving or other types of navigation, planning, perception, and/or mapping operations of the vehicle  500 . Yet further, one or more sensor types could be utilized in combination with one another (e.g., lidar and radar, lidar and camera, camera and radar, etc.). 
     Although not shown in  FIGS.  5 A- 5 E , the vehicle  500  can include a wireless communication system. The wireless communication system may include wireless transmitters and receivers that could be configured to communicate with devices external or internal to the vehicle  500 . Specifically, the wireless communication system could include transceivers configured to communicate with other vehicles and/or computing devices, for instance, in a vehicular communication system or a roadway station. Examples of such vehicular communication systems include DSRC, radio frequency identification (RFID), and other proposed communication standards directed towards intelligent transport systems. 
       FIG.  6    illustrates a method, according to an example embodiment. While method  600  illustrates several blocks of a method, it will be understood that fewer or more blocks or steps could be included. In such scenarios, at least some of the various blocks or steps may be carried out in a different order than of that presented herein. Furthermore, blocks or steps may be added, subtracted, transposed, and/or repeated. Some or all of the blocks or steps of method  600  may be carried out so as to operate the optical system  100 , lidar  300 , and/or vehicle  500 , as illustrated and described in reference to  FIG.  1   ,  FIG.  3   , and  FIG.  5   , respectively. 
     Block  602  includes receiving, from a light detector (e.g., light detector  120 ), information indicative of a light intensity (e.g., light intensity  18 ) of a field of view (e.g., field of view  12 ) of an optical system (e.g., optical system  100 ). In such scenarios, the optical system includes one or more optical components (e.g., optical component(s)  110 ) and a light detector (e.g., light detector  120 ) configured to receive light from a field of view of an environment (e.g., environment  10 ) of the optical system by way of the one or more optical components. The optical system also includes an occlusion-detection camera (e.g., occlusion-detection camera  130 ) configured to capture images of the one or more optical components. 
     Block  604  includes adjusting, based on the received information, at least one operating parameter (e.g., operating parameter  132 ) of the occlusion-detection camera. 
     Block  606  includes causing the occlusion-detection camera to capture at least one image (e.g., images  134 ) of the one or more optical components according to the at least one adjusted operating parameter. 
     In some examples, method  600  may include determining, based on the at least one image, at least one of: a presence, a location, a size, or a type of at least one imperfection (e.g., imperfection  112 ) associated with the one or more optical components. In such scenarios, the type of the at least one imperfection comprises at least one of: a scratch, a crack, a smudge, a deformation, an occlusion, debris, an air bubble, an impurity, a degradation, a discoloration, an opacity, a warp, or condensation. It will be understood that other types of optical imperfections and/or optical characteristics are possible and contemplated within the scope of the present disclosure. 
     In some embodiments, adjusting, based on the received information, at least one operating parameter of the occlusion-detection camera could include adjusting at least one exposure setting of the occlusion-detection camera. As an example, the at least one exposure setting could include an exposure time, an aperture size, a gain setting, or a sensitivity. 
     In various embodiments, the method  600  may also include determining, based on the received information, a brightness map (e.g., brightness map  156 ) associated with the field of view. 
     In such scenarios, the method  600  may additionally include transforming the brightness map based on a field of view of the occlusion-detection camera to provide a transformed brightness map. Furthermore, the method  600  may include that adjusting the at least one operating parameter of the occlusion-detection camera is further based on the transformed brightness map. 
     The particular arrangements shown in the Figures should not be viewed as limiting. It should be understood that other embodiments may include more or less of each element shown in a given Figure. Further, some of the illustrated elements may be combined or omitted. Yet further, an illustrative embodiment may include elements that are not illustrated in the Figures. 
     A step or block that represents a processing of information can correspond to circuitry that can be configured to perform the specific logical functions of a herein-described method or technique. Alternatively or additionally, a step or block that represents a processing of information can correspond to a module, a segment, or a portion of program code (including related data). The program code can include one or more instructions executable by a processor for implementing specific logical functions or actions in the method or technique. The program code and/or related data can be stored on any type of computer readable medium such as a storage device including a disk, hard drive, or other storage medium. 
     The computer readable medium can also include non-transitory computer readable media such as computer-readable media that store data for short periods of time like register memory, processor cache, and random access memory (RAM). The computer readable media can also include non-transitory computer readable media that store program code and/or data for longer periods of time. Thus, the computer readable media may include secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media can also be any other volatile or non-volatile storage systems. A computer readable medium can be considered a computer readable storage medium, for example, or a tangible storage device. 
     While various examples and embodiments have been disclosed, other examples and embodiments will be apparent to those skilled in the art. The various disclosed examples and embodiments are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.