Abstract:
Systems and methods are provided for analyzing vehicle signal lights in order to operate an autonomous vehicle. A method includes receiving an image from a camera regarding a vehicle proximate to the autonomous vehicle. Data from a lidar sensor regarding the proximate vehicle is used to determine object information for identifying a subsection within the camera image. The identified subsection corresponds to an area of the proximate vehicle containing one or more vehicle signals. One or more vehicle signal lights of the proximate vehicle is located by using the identified camera image subsection as an area of focus.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure generally relates to autonomous vehicles, and more particularly relates to systems and methods for vehicle signal light detection in an autonomous vehicle. 
       INTRODUCTION 
       [0002]    An autonomous vehicle is a vehicle that is capable of sensing its environment and navigating with little or no user input. An autonomous vehicle senses its environment using sensing devices such as radar, lidar, image sensors, and the like. The autonomous vehicle system further uses information from global positioning systems (GPS) technology, navigation systems, vehicle-to-vehicle communication, vehicle-to-infrastructure technology, and/or drive-by-wire systems to navigate the vehicle. 
         [0003]    Vehicle automation has been categorized into numerical levels ranging from Zero, corresponding to no automation with full human control, to Five, corresponding to full automation with no human control. Various automated driver-assistance systems, such as cruise control, adaptive cruise control, and parking assistance systems correspond to lower automation levels, while true “driverless” vehicles correspond to higher automation levels. 
         [0004]    Some autonomous vehicles can include systems that detect signal lights of vehicles within the driving environment. In these systems, an entire image obtained from a camera is typically searched for vehicle signals that need to be detected. This approach to vehicle signal detection is computationally intensive and expensive, which makes it slow and very time consuming. 
         [0005]    Accordingly, it is desirable to provide systems and methods that can speed up the process of vehicle signal detection. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
       SUMMARY 
       [0006]    Systems and methods are provided for analyzing vehicle signal lights in order to operate an autonomous vehicle. In one embodiment, a system and method includes receiving, by one or more data processors, an image from a camera regarding a vehicle proximate to the autonomous vehicle. Data from a lidar sensor regarding the proximate vehicle is used to determine object information for identifying a subsection within the camera image. The identified subsection corresponds to an area of the proximate vehicle containing one or more vehicle signals. One or more vehicle signal lights of the proximate vehicle is located by using the identified camera image subsection as an area of focus. 
         [0007]    In other embodiments, a system and method includes receiving, by one or more data processors, an image from a camera regarding a vehicle proximate to the autonomous vehicle. Data from a lidar sensor regarding the proximate vehicle is used, by the one or more processors, to determine object geometry and position information for identifying a subsection within the camera image. The identified subsection corresponds to an area of the proximate vehicle containing one or more vehicle signals. One or more vehicle signal lights of the proximate vehicle is located, by the one or more processors, by using the identified camera image subsection as an area of focus. Tracking of the proximate vehicle is based upon the located one or more vehicle signal lights of the proximate vehicle. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0008]    The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
           [0009]      FIG. 1  is a functional block diagram illustrating an autonomous vehicle, in accordance with various embodiments; 
           [0010]      FIG. 2  is a functional block diagram illustrating a transportation system having one or more autonomous vehicles as shown in  FIG. 1 , in accordance with various embodiments; 
           [0011]      FIG. 3  is functional block diagram illustrating an autonomous driving system (ADS) associated with an autonomous vehicle, in accordance with various embodiments; 
           [0012]      FIGS. 4 and 5  are functional block diagrams depicting a vehicle signal processing system, in accordance with various embodiments; 
           [0013]      FIG. 6  depicts an exemplary vehicle that includes a plurality of radar devices, cameras, and lidar devices that are distributed about the vehicle in accordance with various embodiments of the present disclosure; 
           [0014]      FIG. 7  is a flowchart depicting an operational scenario involving vehicle signal detection; and 
           [0015]      FIG. 8  is a functional block diagram depicting a vehicle signal processing system using fixed exposure cameras, in accordance with various embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. As used herein, the term “module” refers to any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), a field-programmable gate-array (FPGA), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0017]    Embodiments of the present disclosure may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of the present disclosure may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any number of systems, and that the systems described herein is merely exemplary embodiments of the present disclosure. 
         [0018]    For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, machine learning, image analysis, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure. 
         [0019]    With reference to  FIG. 1 , a system for performing an autonomous vehicle control shown generally as  100  is associated with a vehicle  10  in accordance with various embodiments. In general, the system  100  provides for low level processing of three-dimensional images of surroundings of the vehicle  10 , in the form of point clouds, to determine velocity of surrounding objects for use in controlling the vehicle  10 . 
         [0020]    As depicted in  FIG. 1 , the vehicle  10  generally includes a chassis  12 , a body  14 , front wheels  16 , and rear wheels  18 . The body  14  is arranged on the chassis  12  and substantially encloses components of the vehicle  10 . The body  14  and the chassis  12  may jointly form a frame. The wheels  16 - 18  are each rotationally coupled to the chassis  12  near a respective corner of the body  14 . 
         [0021]    In various embodiments, the vehicle  10  is an autonomous vehicle and the system  100 , and/or components thereof, are incorporated into the autonomous vehicle  10  (hereinafter referred to as the autonomous vehicle  10 ). The autonomous vehicle  10  is, for example, a vehicle that is automatically controlled to carry passengers from one location to another. The vehicle  10  is depicted in the illustrated embodiment as a passenger car, but it should be appreciated that any other vehicle, including motorcycles, trucks, sport utility vehicles (SUVs), recreational vehicles (RVs), marine vessels, aircraft, and the like, can also be used. 
         [0022]    In an exemplary embodiment, the autonomous vehicle  10  corresponds to a level four or level five automation system under the Society of Automotive Engineers (SAE) “J3016” standard taxonomy of automated driving levels. Using this terminology, a level four system indicates “high automation,” referring to a driving mode in which the automated driving system performs all aspects of the dynamic driving task, even if a human driver does not respond appropriately to a request to intervene. A level five system, on the other hand, indicates “full automation,” referring to a driving mode in which the automated driving system performs all aspects of the dynamic driving task under all roadway and environmental conditions that can be managed by a human driver. It will be appreciated, however, the embodiments in accordance with the present subject matter are not limited to any particular taxonomy or rubric of automation categories. Furthermore, systems in accordance with the present embodiment may be used in conjunction with any autonomous or other vehicle that utilizes a navigation system and/or other systems to provide route guidance and/or implementation. 
         [0023]    As shown, the autonomous vehicle  10  generally includes a propulsion system  20 , a transmission system  22 , a steering system  24 , a brake system  26 , a sensor system  28 , an actuator system  30 , at least one data storage device  32 , at least one controller  34 , and a communication system  36 . The propulsion system  20  may, in various embodiments, include an internal combustion engine, an electric machine such as a traction motor, and/or a fuel cell propulsion system. The transmission system  22  is configured to transmit power from the propulsion system  20  to the vehicle wheels  16  and  18  according to selectable speed ratios. According to various embodiments, the transmission system  22  may include a step-ratio automatic transmission, a continuously-variable transmission, or other appropriate transmission. 
         [0024]    The brake system  26  is configured to provide braking torque to the vehicle wheels  16  and  18 . Brake system  26  may, in various embodiments, include friction brakes, brake by wire, a regenerative braking system such as an electric machine, and/or other appropriate braking systems. 
         [0025]    The steering system  24  influences a position of the vehicle wheels  16  and/or  18 . While depicted as including a steering wheel  25  for illustrative purposes, in some embodiments contemplated within the scope of the present disclosure, the steering system  24  may not include a steering wheel. 
         [0026]    The sensor system  28  includes one or more sensing devices  40   a - 40   n  that sense observable conditions of the exterior environment and/or the interior environment of the autonomous vehicle  10 . The sensing devices  40   a - 40   n  might include, but are not limited to, radars, lidars, global positioning systems, optical cameras, thermal cameras, ultrasonic sensors, and/or other sensors. The actuator system  30  includes one or more actuator devices  42   a - 42   n  that control one or more vehicle features such as, but not limited to, the propulsion system  20 , the transmission system  22 , the steering system  24 , and the brake system  26 . In various embodiments, autonomous vehicle  10  may also include interior and/or exterior vehicle features not illustrated in  FIG. 1 , such as various doors, a trunk, and cabin features such as air, music, lighting, touch-screen display components (such as those used in connection with navigation systems), and the like. 
         [0027]    The data storage device  32  stores data for use in automatically controlling the autonomous vehicle  10 . In various embodiments, the data storage device  32  stores defined maps of the navigable environment. In various embodiments, the defined maps may be predefined by and obtained from a remote system (described in further detail with regard to  FIG. 2 ). For example, the defined maps may be assembled by the remote system and communicated to the autonomous vehicle  10  (wirelessly and/or in a wired manner) and stored in the data storage device  32 . Route information may also be stored within data device  32 —i.e., a set of road segments (associated geographically with one or more of the defined maps) that together define a route that the user may take to travel from a start location (e.g., the user&#39;s current location) to a target location. Also in various embodiments, the data storage device  32  stores processing algorithms and data for processing three-dimensional point clouds to determine velocity of objects in the surroundings on a frame by frame basis. As will be appreciated, the data storage device  32  may be part of the controller  34 , separate from the controller  34 , or part of the controller  34  and part of a separate system. 
         [0028]    The controller  34  includes at least one processor  44  and a computer-readable storage device or media  46 . The processor  44  may be any custom-made or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among several processors associated with the controller  34 , a semiconductor-based microprocessor (in the form of a microchip or chip set), any combination thereof, or generally any device for executing instructions. The computer readable storage device or media  46  may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the processor  44  is powered down. The computer-readable storage device or media  46  may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by the controller  34  in controlling the autonomous vehicle  10 . 
         [0029]    The instructions may include one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. The instructions, when executed by the processor  44 , receive and process signals from the sensor system  28 , perform logic, calculations, methods and/or algorithms for automatically controlling the components of the autonomous vehicle  10 , and generate control signals that are transmitted to the actuator system  30  to automatically control the components of the autonomous vehicle  10  based on the logic, calculations, methods, and/or algorithms. Although only one controller  34  is shown in  FIG. 1 , embodiments of the autonomous vehicle  10  may include any number of controllers  34  that communicate over any suitable communication medium or a combination of communication mediums and that cooperate to process the sensor signals, perform logic, calculations, methods, and/or algorithms, and generate control signals to automatically control features of the autonomous vehicle  10 . In one embodiment, as discussed in detail below, controller  34  is configured for use in processing three-dimensional imaging data of surroundings of the vehicle  10  in the form of point clouds to determine velocity on a frame by frame basis for use in autonomous control of the vehicle. 
         [0030]    The communication system  36  is configured to wirelessly communicate information to and from other entities  48 , such as but not limited to, other vehicles (“V2V” communication), infrastructure (“V2I” communication), remote transportation systems, and/or user devices (described in more detail with regard to  FIG. 2 ). In an exemplary embodiment, the communication system  36  is a wireless communication system configured to communicate via a wireless local area network (WLAN) using IEEE 802.11 standards or by using cellular data communication. However, additional or alternate communication methods, such as a dedicated short-range communications (DSRC) channel, are also considered within the scope of the present disclosure. DSRC channels refer to one-way or two-way short-range to medium-range wireless communication channels specifically designed for automotive use and a corresponding set of protocols and standards. 
         [0031]    With reference now to  FIG. 2 , in various embodiments, the autonomous vehicle  10  described with regard to  FIG. 1  may be suitable for use in the context of a taxi or shuttle system in a certain geographical area (e.g., a city, a school or business campus, a shopping center, an amusement park, an event center, or the like) or may simply be managed by a remote system. For example, the autonomous vehicle  10  may be associated with an autonomous vehicle based remote transportation system.  FIG. 2  illustrates an exemplary embodiment of an operating environment shown generally at  50  that includes an autonomous vehicle based remote transportation system (or simply “remote transportation system”)  52  that is associated with one or more autonomous vehicles  10   a - 10   n  as described with regard to  FIG. 1 . In various embodiments, the operating environment  50  (all or a part of which may correspond to entities  48  shown in  FIG. 1 ) further includes one or more user devices  54  that communicate with the autonomous vehicle  10  and/or the remote transportation system  52  via a communication network  56 . 
         [0032]    The communication network  56  supports communication as needed between devices, systems, and components supported by the operating environment  50  (e.g., via tangible communication links and/or wireless communication links). For example, the communication network  56  may include a wireless carrier system  60  such as a cellular telephone system that includes a plurality of cell towers (not shown), one or more mobile switching centers (MSCs) (not shown), as well as any other networking components required to connect the wireless carrier system  60  with a land communications system. Each cell tower includes sending and receiving antennas and a base station, with the base stations from different cell towers being connected to the MSC either directly or via intermediary equipment such as a base station controller. The wireless carrier system  60  can implement any suitable communications technology, including for example, digital technologies such as CDMA (e.g., CDMA2000), LTE (e.g., 4G LTE or 5G LTE), GSM/GPRS, or other current or emerging wireless technologies. Other cell tower/base station/MSC arrangements are possible and could be used with the wireless carrier system  60 . For example, the base station and cell tower could be co-located at the same site or they could be remotely located from one another, each base station could be responsible for a single cell tower or a single base station could service various cell towers, or various base stations could be coupled to a single MSC, to name but a few of the possible arrangements. 
         [0033]    Apart from including the wireless carrier system  60 , a second wireless carrier system in the form of a satellite communication system  64  can be included to provide uni-directional or bi-directional communication with the autonomous vehicles  10   a - 10   n . This can be done using one or more communication satellites (not shown) and an uplink transmitting station (not shown). Uni-directional communication can include, for example, satellite radio services, wherein programming content (news, music, and the like) is received by the transmitting station, packaged for upload, and then sent to the satellite, which broadcasts the programming to subscribers. Bi-directional communication can include, for example, satellite telephony services using the satellite to relay telephone communications between the vehicle  10  and the station. The satellite telephony can be utilized either in addition to or in lieu of the wireless carrier system  60 . 
         [0034]    A land communication system  62  may further be included that is a conventional land-based telecommunications network connected to one or more landline telephones and connects the wireless carrier system  60  to the remote transportation system  52 . For example, the land communication system  62  may include a public switched telephone network (PSTN) such as that used to provide hardwired telephony, packet-switched data communications, and the Internet infrastructure. One or more segments of the land communication system  62  can be implemented through the use of a standard wired network, a fiber or other optical network, a cable network, power lines, other wireless networks such as wireless local area networks (WLANs), or networks providing broadband wireless access (BWA), or any combination thereof. Furthermore, the remote transportation system  52  need not be connected via the land communication system  62 , but can include wireless telephony equipment so that it can communicate directly with a wireless network, such as the wireless carrier system  60 . 
         [0035]    Although only one user device  54  is shown in  FIG. 2 , embodiments of the operating environment  50  can support any number of user devices  54 , including multiple user devices  54  owned, operated, or otherwise used by one person. Each user device  54  supported by the operating environment  50  may be implemented using any suitable hardware platform. In this regard, the user device  54  can be realized in any common form factor including, but not limited to: a desktop computer; a mobile computer (e.g., a tablet computer, a laptop computer, or a netbook computer); a smartphone; a video game device; a digital media player; a component of a home entertainment equipment; a digital camera or video camera; a wearable computing device (e.g., smart watch, smart glasses, smart clothing); or the like. Each user device  54  supported by the operating environment  50  is realized as a computer-implemented or computer-based device having the hardware, software, firmware, and/or processing logic needed to carry out the various techniques and methodologies described herein. For example, the user device  54  includes a microprocessor in the form of a programmable device that includes one or more instructions stored in an internal memory structure and applied to receive binary input to create binary output. In some embodiments, the user device  54  includes a GPS module capable of receiving GPS satellite signals and generating GPS coordinates based on those signals. In other embodiments, the user device  54  includes cellular communications functionality such that the device carries out voice and/or data communications over the communication network  56  using one or more cellular communications protocols, as are discussed herein. In various embodiments, the user device  54  includes a visual display, such as a touch-screen graphical display, or other display. 
         [0036]    The remote transportation system  52  includes one or more backend server systems, not shown), which may be cloud-based, network-based, or resident at the particular campus or geographical location serviced by the remote transportation system  52 . The remote transportation system  52  can be manned by a live advisor, an automated advisor, an artificial intelligence system, or a combination thereof. The remote transportation system  52  can communicate with the user devices  54  and the autonomous vehicles  10   a - 10   n  to schedule rides, dispatch autonomous vehicles  10   a - 10   n , and the like. In various embodiments, the remote transportation system  52  stores store account information such as subscriber authentication information, vehicle identifiers, profile records, biometric data, behavioral patterns, and other pertinent subscriber information. In one embodiment, as described in further detail below, remote transportation system  52  includes a route database  53  that stores information relating to navigational system routes, including lane markings for roadways along the various routes, and whether and to what extent particular route segments are impacted by construction zones or other possible hazards or impediments that have been detected by one or more of autonomous vehicles  10   a - 10   n.    
         [0037]    In accordance with a typical use case workflow, a registered user of the remote transportation system  52  can create a ride request via the user device  54 . The ride request will typically indicate the passenger&#39;s desired pickup location (or current GPS location), the desired destination location (which may identify a predefined vehicle stop and/or a user-specified passenger destination), and a pickup time. The remote transportation system  52  receives the ride request, processes the request, and dispatches a selected one of the autonomous vehicles  10   a - 10   n  (when and if one is available) to pick up the passenger at the designated pickup location and at the appropriate time. The transportation system  52  can also generate and send a suitably configured confirmation message or notification to the user device  54 , to let the passenger know that a vehicle is on the way. 
         [0038]    As can be appreciated, the subject matter disclosed herein provides certain enhanced features and functionality to what may be considered as a standard or baseline autonomous vehicle  10  and/or an autonomous vehicle based remote transportation system  52 . To this end, an autonomous vehicle and autonomous vehicle based remote transportation system can be modified, enhanced, or otherwise supplemented to provide the additional features described in more detail below. 
         [0039]    In accordance with various embodiments, controller  34  implements an autonomous driving system (ADS)  70  as shown in  FIG. 3 . That is, suitable software and/or hardware components of controller  34  (e.g., processor  44  and computer-readable storage device  46 ) are utilized to provide an autonomous driving system  70  that is used in conjunction with vehicle  10 . 
         [0040]    In various embodiments, the instructions of the autonomous driving system  70  may be organized by function or system. For example, as shown in  FIG. 3 , the autonomous driving system  70  can include a sensor fusion system  74 , a positioning system  76 , a guidance system  78 , and a vehicle control system  80 . As can be appreciated, in various embodiments, the instructions may be organized into any number of systems (e.g., combined, further partitioned, etc.) as the disclosure is not limited to the present examples. 
         [0041]    In various embodiments, the sensor fusion system  74  synthesizes and processes sensor data and predicts the presence, location, classification, and/or path of objects and features of the environment of the vehicle  10 . In various embodiments, the sensor fusion system  74  can incorporate information from multiple sensors, including but not limited to cameras, lidars, radars, and/or any number of other types of sensors. 
         [0042]    The positioning system  76  processes sensor data along with other data to determine a position (e.g., a local position relative to a map, an exact position relative to lane of a road, vehicle heading, velocity, etc.) of the vehicle  10  relative to the environment. The guidance system  78  processes sensor data along with other data to determine a path for the vehicle  10  to follow. The vehicle control system  80  generates control signals for controlling the vehicle  10  according to the determined path. 
         [0043]    In various embodiments, the controller  34  implements machine learning techniques to assist the functionality of the controller  34 , such as feature detection/classification, obstruction mitigation, route traversal, mapping, sensor integration, ground-truth determination, and the like. 
         [0044]    For example, as shown at  100  in more detail with regard to  FIG. 4  and with continued reference to  FIG. 3 , system  102  uses the sensor system  28  of an autonomous vehicle  104  to detect signals of other vehicles  106 . The system  102  can also analyze characteristics of the detected signals, such as whether the signals are brake lights, turn signals, etc. 
         [0045]    The system  102  uses lidar  108  to obtain fine details of object geometry and position in images from camera(s)  110 . With this information, the system  102  knows where the back, sides, and top of the car are. This provides a more efficient and less computationally intensive approach to finding the taillights and filtering out false positives more easily. The output of system  102  can be used for the autonomous vehicle  104  for many purposes including autonomous vehicle tracking control operations  112 . As an illustration, the system  102  can determine signal state such as whether the other vehicles are braking, have hazards on, have turn signals on, etc. This signal behavior improves tracking of the other vehicles that are in proximity to the autonomous vehicle  104 . 
         [0046]      FIG. 5  depicts a tracking system  200  assisting the system  102  with the detection analysis of the other vehicles&#39; signals. Tracking by system  200  results in identification of where other vehicles should be relative to the autonomous vehicle. Tracking information can include object data, such as geometry and position information  202  of the other vehicles relative to the autonomous vehicle. 
         [0047]    System  102  uses the tracking information to analyze regions within a camera image for vehicle light sources. The analysis produces vehicle image subsections  204  of the camera image that the system  102  can further process to detect vehicle signal lights. Such further processing can include delineating light sources within the image frame to narrow regions for analysis. 
         [0048]    The system  102  uses a combination of sensors within the sensor system  28  to obtain information for vehicle signal detection and analysis. Many different types of sensor configurations can be used as shown, for example, in  FIG. 6 . 
         [0049]      FIG. 6  depicts an exemplary autonomous vehicle  104  that includes a plurality of radar devices  240   a  distributed about the vehicle  104 , a plurality of cameras  240   b  distributed about the vehicle  104  and a plurality of lidar devices  240   c  distributed about the vehicle  104 . 
         [0050]    The radar devices  240   a  are disposed at different locations of the vehicle  104 , and in one embodiment, are disposed symmetrically about the longitudinal axis of the vehicle  104  to achieve parallax. Each of the radar devices  240   a  may include or incorporate components suitably configured to horizontally and rotatably scan the environment to generate radar data that is consumed by other systems. 
         [0051]    The cameras  240   b  are also disposed at different locations and oriented to provide different field of views that capture different portions of the surrounding environment in the vicinity of the vehicle  104 . For example, a first camera  240   b  is positioned at the front left (or driver) side of the vehicle  104  and has its field of view oriented 45° counterclockwise relative to the longitudinal axis of the vehicle  104  in the forward direction, and another camera  240   b  may be positioned at the front right (or passenger) side of the vehicle  104  and has its field of view oriented 45° clockwise relative to the longitudinal axis of the vehicle  104 . Additional cameras  240   b  are positioned at the rear left and right sides of the vehicle  104  and similarly oriented away from the longitudinal axis at 45° relative to the vehicle longitudinal axis, along with cameras  240   b  positioned on the left and right sides of the vehicle  104  and oriented away from the longitudinal axis perpendicular to the vehicle longitudinal axis. The illustrated embodiment also includes a pair of cameras  240   b  positioned at or near the vehicle longitudinal axis and oriented to capture a forward looking field of view along a line of sight substantially parallel to the vehicle longitudinal axis. 
         [0052]    In exemplary embodiments, the cameras  240   b  have angle of views, focal lengths, and other attributes that are different from those of one or more other cameras  240   b . For example, the cameras  240   b  on the right and left sides of the vehicle may have an angle of view that is greater than the angle of view associated with the cameras  240   b  positioned at the front left, front right, rear left, or rear right of the vehicle. In some embodiments, the angle of view of the cameras  240   b  are chosen so that the field of view of different cameras  240   b  overlap, at least in part, to ensure camera coverage at particular locations or orientations relative to the vehicle  104 . 
         [0053]    The lidar devices  240   c  are also disposed at different locations of the vehicle  104 , and in one embodiment, are disposed symmetrically about the longitudinal axis of the vehicle  104  to achieve parallax. Each of the lidar devices  240   c  may include or incorporate one or more lasers, scanning components, optical arrangements, photodetectors, and other components suitably configured to horizontally and rotatably scan the environment in the vicinity of the vehicle  104  with a particular angular frequency or rotational velocity. For example, in one embodiment, each lidar device  240   c  is configured to horizontally rotate and scan 360° at a frequency of 10 Hertz (Hz). As used herein, a lidar scan should be understood as referring to a single revolution of a lidar device  240   c.    
         [0054]    In exemplary embodiments described herein, the frequency or rate at which the cameras  240   b  capture images is greater than the angular frequency of the lidar devices  240   c . For example, in one embodiment, the cameras  240   b  capture new image data corresponding to their respective field of view at a rate of 30 Hz. Thus, each camera  240   b  may capture multiple images per lidar scan, and capture the images at different times independent of the orientation of the lidar device  240   c  or the angular position within the scan. Accordingly, the subject matter described herein selects or otherwise identifies an image from each respective camera  240   b  that is temporally associated with the lidar point cloud data from a particular lidar scan based on the timestamps of the images captured by that respective camera  240   b  relative to a sampling time at which the angular position of the lidar scan corresponds to the line of sight of a lidar device  240   c  being aligned substantially parallel to the bisector (or line of sight) of the angle of view of the respective camera  240   b.    
         [0055]    The tracking system of the autonomous vehicle uses the information from these different types of sensors to track the three-dimensional location and geometry of objects in the vicinity of the vehicle. In one exemplary embodiment, the tracking system can generate or use such tracking for as three-dimensional locations of objects, distance/depth of the object from the vehicle, dimensions and shapes of the objects, velocity of the objects, etc. 
         [0056]      FIG. 7  illustrates an operational scenario where information from the tracking system is used for detecting and analyzing other vehicles&#39; signal lights. Process block  300  obtains camera image and lidar information. This information is used by process block  302  for determining object data and other types of tracking information. 
         [0057]    In this operational scenario, process block  304  uses the output of the tracking process to focus on specific spots within the image that have the highest probability of containing vehicle lights. Process block  304  identifies the highest probability locations within the image by knowing the sizes of lights the system is expecting to see within the image. 
         [0058]    Additional analysis can further refine the focus area within the image. Process block  306  obtains additional vehicle environmental information  308  to facilitate the focused analysis. The additional information  308  from this process can include lane information, vehicle velocity, etc. For example, lane information can determine vehicle orientation (e.g., whether a proximate car is facing away or towards the autonomous vehicle). This in turn provides a filter for determining which lights of the other proximate vehicles are actually vehicle rear lights (versus a vehicle&#39;s headlights) as well as resolving false positives such as images on truck or reflections in surfaces. In this operational scenario, it is noted that proximate indicates that the other vehicle is within the driving environment of the autonomous vehicle and is in front of the autonomous vehicle, to the side, or at another orientation where vehicle signals are entirely or partially visible to the autonomous vehicle. The additional information  308  can be obtained such as from vehicle localization operations. Vehicle localization operations can include estimating position and orientation of the vehicle in both typical and challenging driving scenarios. These challenging driving scenarios include, but are not limited to, dynamic environments with many cars (e.g., dense traffic), environments with large scale obstructions (e.g., roadwork or construction sites), hills, multi-lane roads, single lane roads, a variety of road markings and buildings or lack thereof (e.g., residential vs. business districts), and bridges and overpasses (both above and below a current road segment of the vehicle). Localization can also incorporate new data collected as a result of expanded map areas obtained via onboard mapping functions performed by the vehicle during operation and mapping data “pushed” to the vehicle via the wireless carrier system  60 . 
         [0059]    The focused areas within the camera images allow for easier and more efficient identification of signal lights and process block  310 . The focused area(s) within the camera images allow for easier and more efficient identification of signal lights by process block  310 . Process block  310  can perform identification of the vehicle signal lights within the focused areas in many different ways. For example, a neural network, such as a convolutional neural network, can be trained to identify the state of the vehicle signal lights. The convolutional neural network, can be trained to perform the identification based upon the colors appearing within the focused areas as well as such other factors as position of the objects (e.g., “blobs”) of color within the focused areas as well as distinguish between circles and arrows associated with the signal lights. 
         [0060]    Additionally, the neural network can assess symmetry of the objects of color. For example, the neural network can be trained to detect that vehicle brake lights have been activated based upon red colors appearing at the left side and right side of the vehicle along a horizontal plane. Other positional information can be used, such as assessing whether a red brake light is also activated within the rear window of the vehicle. 
         [0061]    The increase in efficiency is realized, among other reasons, by the processing overcoming the difficulty of performing vehicle signal detection by merely looking for a light within the image as this can lead to many responses. The processing in  FIG. 7  overcomes this by avoiding the analysis of non-relevant portions of the image, thereby resulting in a reduction of image processing cycles. 
         [0062]      FIG. 8  depicts the use of fixed exposure cameras  340  on the autonomous vehicle for vehicle signal detection and analysis. An example of a fixed exposure camera includes the aperture of the camera&#39;s lens being fixed as well as the sensor exposure time and sensor gain being fixed. In this way, the intensity of light sources is the same and becomes more stable. This allows a more effective use of thresholds on brightness. More specifically, because a fixed exposure camera allows lights to appear with the same intensity, a fixed exposure camera allows light sources to be delineated within the image frame to narrow regions for analysis by the vehicle signal detection and analysis system  102 . 
         [0063]    While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.