System and method for pixel on-off switching in a focal plane array

Abstract

Systems and methods for optical processing are described. In some aspects, an optical processing device may include a pixelated photodiode array (PDA), where each pixel of the PDA includes a radiation detector. The device may also include a readout integrated circuit (ROIC) that includes logic circuitry and a plurality of switch elements. The plurality of switch elements are switchable between an armed state that transmits signals received from a corresponding radiation detector to the ROIC and a disarmed state that disarms the corresponding detector and blocks transmission of the signals, and in the armed state, the PDA is configured to detect incoming optical signals, and in the disarmed state, the PDA is configured to ignore incoming optical signals. Further, the logic circuitry controls the switch state of selectable switch elements associated with the radiation detectors.

Description

Technical Field

[0001] The present disclosure generally relates to the operation of Focal Plane Arrays (FPAs). More specifically, the present disclosure relates to implementing systems and methods for improving the performance of FPAs using non-functional units that can have a significant impact on overall performance and production yield.

Background Art

[0002] Modern vehicles can be configured to operate in an autonomous driving mode in which the vehicle explores in an environment with little or no input. Such an autonomous vehicle may include one or more sensors that detect information about the environment in which the vehicle operates. An autonomous vehicle (AV) and a computer-implemented controller associated therewith use the sensed information to navigate the environment. For example, if the controller senses that the AV is approaching an obstacle as determined by the computer-implemented controller, the controller adjusts the direction control of the AV so that the AV bypasses the obstacle. Thus, autonomous driving is highly dependent on vehicle sensors to accurately sense and map the environmental conditions encountered by the AV. One such sensor is a LiDAR (Light Detection And Ranging) device. The LiDAR device actively estimates the distance to environmental features while scanning a scene and assembles a cloud of point positions that indicates the three-dimensional shape of the environmental scene. Individual points are measured by generating a laser pulse, sensing the pulse (if any) reflected back from an environmental object, and determining the distance to the reflecting object based on the time delay between the emitted pulse and the reception of the reflected pulse. Other sensors may include infrared (IR) sensors and still other imaging sensors (e.g., Focal Plane Arrays (FPAs)).

[0003] The FPA is an image sensor composed of an array of light sensing elements (e.g., pixels) located in the focal plane of the lens. The FPA can be used not only for imaging purposes (e.g., taking photos or video images), but also for the same non-imaging purposes as spectroscopy, wavefront sensing, LiDAR, and other sensor applications.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Manufacturing limitations of semiconductor devices (e.g., III-V semiconductor devices such as FPAs) often result in devices with poor performance in the manufactured wafers. When the device is composed of several identical units (e.g., pixels within an FPA), the units with poor performance can have a significant impact on the yield of a given wafer and the overall performance of the sensor. For example, a typical FPA may be composed of a PhotoDiode Array (PDA) and a readout integrated circuit (ROIC). In one aspect, the ROIC controls the arming and disarming of the PDA. In current FPA designs, the ROIC arm bias is applied to all pixels of the FPA, including pixels with noise that can have poor performance and degrade the performance of other neighboring pixels. Therefore, improving the performance of an FPA with non-functional units (e.g., non-functional pixels) is essential for the operation of the FPA, and through this, the sensing function of the sensor and the autonomous driving of AVs can be improved. The systems and methods of the present disclosure address the problems described above.

Means for Solving the Problems

[0005] In this specification, a system and method for selectively controlling an arm and a disarm in a pixelated Photo Diode Arrays (PDA) by a side surface are disclosed. According to some aspects, an apparatus (e.g., an optical processing apparatus) is disclosed, the apparatus includes a PDA, and each pixel in the PDA includes a radiation detector. According to some aspects, the apparatus further includes a readout integrated circuit (ROIC), and the ROIC includes a plurality of switch elements respectively connected to individual radiation detectors of each pixel - each switch element of the plurality of switch elements is switchable between an armed state for arming a corresponding radiation detector and receiving an output signal from the corresponding radiation detector and a disarmed state for disarming the corresponding radiation detector and blocking the output signal, in the armed state, the PDA is configured to detect the incoming optical signal, and in the disarmed state, the PDA is configured to ignore the incoming optical signal. The ROIC also includes a logic circuit configured to control the switch state of each switch element of the plurality of switch elements.

[0006] Further, the logic circuit is additionally configured to arm the PDA and place a first switch of a plurality of switch elements associated with a first radiation detector in a disarmed state for detecting a malfunction of the radiation detector.

[0007] Also, the PDA includes one or more Geiger-mode avalanche photodiodes (GMAPDs).

[0008] Also, the logic circuit is additionally configured to place the first switch element of the plurality of switch elements associated with the first radiation detector in a disarmed state by applying the forward and reverse voltage values under the detected breakdown voltage of one or more GmAPDs.

[0009] Also, the logic circuit is additionally configured to place the second switch element of the plurality of switch elements associated with the second radiation detector in an armed state by increasing the reverse voltage value above the detected breakdown voltage of one or more GmAPDs to a bias level, and the first and second switches are different from each other.

[0010] Also, the logic circuit is additionally configured to determine the operating state of each individual radiation detector, and the determined operating state corresponds to the stored selection / deselect mapping for each individual radiation detector.

[0011] Also, the operating state corresponds to the observed dark current value above a predetermined dark current threshold.

[0012] Also, the operating state corresponds to the observed noise level above a predetermined noise threshold.

[0013] Also, the operating state corresponds to the observed leakage current level above a predetermined leakage current threshold.

[0014] Also, the apparatus further includes a circuit fuse configured to be electrically disengaged from each individual radiation detector.

[0015] Also, the circuit fuse is configured to be electrically disengaged from each individual radiation detector for the operation of the radiation detector associated with the observed leakage current above a predetermined leakage current threshold.

[0016] Also, the circuit fuse is integrated within the ROIC.

[0017] In addition, the circuit fuse includes a pair of transistors configured to control the voltage across the circuit fuse, and the logic circuit is additionally configured to apply a predetermined voltage to the pair of transistors, and the predetermined voltage burns the fuse to create a permanent open circuit between the PDA and the ROIC.

[0018] In addition, the logic circuit is configured to apply a predetermined voltage when the observed leakage current exceeds a predetermined leakage current threshold.

[0019] According to some aspects, a method includes receiving an optical signal with a pixelated photodiode array (PDA); arming a radiation detector of a pixel of the PDA by controlling a selectable switch element of a readout integrated circuit (ROIC) with a logic circuit; and disarming the radiation detector of the pixel of the PDA by controlling a selectable switch element to separate the radiation detector from a power source and block the radiation detector from an output signal with the logic circuit.

[0020] The method may further include disarming the radiation detector by applying a forward and reverse voltage value under a detected breakdown voltage of the radiation detector.

[0021] The method further includes arming the radiation detector by increasing a reverse voltage value at a bias level above the breakdown voltage of the radiation detector.

[0022] The method further includes using a circuit fuse to permanently disengage a detected radiation detector associated with an operation.

[0023] In addition, in the method, the detected operation may be a malfunction of the radiation detector.

[0024] On one side, in a readout integrated circuit (ROIC), a plurality of switch elements connected to individual radiation detectors of a pixelated photodiode array (PDA) - each switch element of the plurality of switch elements is switchable between an armed state for arming a corresponding radiation detector to receive an output signal from the corresponding radiation detector and a disarmed state for disarming the corresponding radiation detector to block the output signal, and in the armed state, the PDA is configured to detect incoming optical signals, and in the disarmed state, the PDA is configured to ignore the incoming optical signals - ; and a readout integrated circuit (ROIC) including a logic circuit configured to control the switch state of each switch element of the plurality of switch elements is disclosed. The apparatus includes a readout integrated circuit (ROIC).

Brief Description of the Drawings

[0025] The attached drawings are hereby incorporated and form a part of the specification.

Figure 1

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[0026] In the figures, like reference numerals generally refer to the same or similar elements. Also, generally, the left - most digit of a reference numeral identifies the figure in which the reference numeral is first shown. DETAILED DESCRIPTION

[0027] The development and mass production of autonomous vehicles (AVs) have the potential to revolutionize transportation mobility and safety. AVs combine a variety of sensors such as radar, LiDAR, sonar, GPS, odometers, and inertial measurement units to recognize the surrounding environment. In one aspect, an advanced control system can interpret sensory information to identify an appropriate navigation route and sense signage related to obstacles.

[0028] One of the core sensors that AVs rely on is LiDAR, which depends on a system and method that targets objects with a laser and measures the time it takes for the reflected light to return to a receiver to determine range. According to some aspects, LiDAR may be used to create a digital 3D representation of a perception area (e.g., the area around the AV). In the 3D representation (also referred to as a LiDAR grid), a LiDAR computing system or an on - board computing device (such as computing device 220 discussed below in this specification) can sense objects moving within the perception area, generate one or more possible object trajectories relative to the AV for the sensed objects, and analyze the possible object trajectories to evaluate the likelihood of a collision between the object and the AV. The performance and accuracy of the sensor system including LiDAR enable the AV to successfully explore a route regardless of obstacles. For this reason, the hardware components that make up sensors such as LiDAR must operate with optimal performance.

[0029] Manufacturing sensors, such as lidar, may involve acceptable tolerances for non-performance components. For example, the limitations of manufacturing semiconductor devices (e.g., III-V semiconductor devices such as FPAs) often lead to some non-performance devices being derived from the manufactured wafers. That is, the manufactured FPA may contain various non-performance pixels that can affect the overall performance of the FPA, and thus may affect the overall performance of the sensor (e.g., lidar) and autonomous driving operation.

[0030] When manufacturing an FPA, a manufacturer may discover that a large number of FPAs have a high level of non-performance elements (e.g., noise, leakage, or non-functional pixels) that can degrade the performance of the FPA. Generally, such a discovery leads the manufacturer to discard such FPAs (thus resulting in a significant decrease in production yield), or to deploy the FPAs in the field (thus resulting in a decrease in sensing accuracy and a drop in sensor performance below optimal). To address such problems, the present disclosure provides systems and methods for selectively turning non-performance elements on and off. It can be understood that such systems can be deployed during the manufacturing process (e.g., during testing) and in the field (e.g., during operation).

[0031] According to aspects of the present disclosure, a system and method for improving object perception are provided by selectively managing arm and disarm at the pixel level of an FPA. Through this, the system can temporarily or permanently deactivate non-performing pixels that can negatively affect the performance of other nearby pixels and degrade performance. The advantages provided in the embodiments discussed herein can reduce processing time and bandwidth, allowing the on-board computing device 220 to generate faster object trajectories. This is particularly important for AVs operating in the field, as faster and more accurate perception and decision-making capabilities (due to reduced time and bandwidth) can help generate and execute faster navigation base decisions, improving the operation of the AV. Also, as mentioned herein, the reduction in processing time and bandwidth also improves power consumption, for example increasing the overall range of battery-operated AVs.

[0032] The techniques described herein are found to provide various advantages over existing systems. For example, existing systems provide global biasing of all PDA pixels in the same armed state. In this case, non-performing pixels (e.g., noisy pixels) can generate spurious electrical noise that can degrade the performance of nearby pixels that are operating properly. As described in the present disclosure, the ability to selectively deactivate noisy pixels provides a higher performance FPA and also yields a higher FPA module yield for the manufacturer. In one aspect, the selective deactivation of noisy pixels can be performed during module assembly or at the in-field test stage. As further described herein, the present disclosure also provides a fuse circuit that can selectively isolate noisy pixels from direct current (DC) biasing. For example, if the FPA is placed in an AV and a performance degradation is sensed, the noisy pixels can be selectively and permanently isolated from the DC bias so as not to provide any leakage current and / or noise signal. Such performance improvements provide advantages to both the manufacturer and the system integrator. For example, the manufacturer can utilize the selective biasing techniques described herein to produce a higher yield of FPA models (instead of discarding the FPA). Also, a system integrator (e.g., a lidar system or other sensor) that integrates the FPA in the field can utilize the selective biasing techniques to extract higher performance from each FPA placed in order to suppress spurious information generated by the noisy pixels. That is, in turn, improve the sensing function of the sensor (e.g., lidar) to improve autonomous driving in relation to speed, accuracy, and safety.

[0033] Next is an exemplary description of a solution (autonomous vehicle and related sensors) that integrates the systems and methodologies described herein. One of ordinary skill in the art can understand that such an exemplification is not restrictive and that other sensors and other applications within the solution can also be placed.

[0034] According to one aspect, the term "vehicle" refers to any mobile conveyance capable of transporting one or more passengers and / or cargo and driven by any form of energy. The term "vehicle" includes, but is not limited to, automobiles, trucks, vans, trains, self-driving vehicles, airplanes, aerial drones, etc. A "self-driving vehicle (or AV)" is a vehicle having a processor, programming instructions, and components of a drive train that can be controlled by the processor without a human driver. A self-driving vehicle may be fully autonomous in that a human driver is not required for most or all driving conditions and functions, or may be semi-autonomous in that a human driver may be required for certain conditions or certain operations, or in that a human driver can override the vehicle's self-driving system to control the vehicle.

[0035] In particular, the present solution is described herein in the context of self-driving vehicles. However, the present solution is not limited to applications of self-driving vehicles. The present solution may be used in other applications such as robotic applications, radar system applications, metric applications, and / or system performance applications. The embodiments used herein can be understood to illustrate one aspect of the present solution. It can be understood that all embodiments are exemplary and can be combined with other embodiments.

[0036] FIG. 1 is a drawing illustrating an exemplary self-driving vehicle system 100 according to an aspect of the present disclosure. System 100 includes a vehicle 102a that travels along a road in a semi-autonomous or autonomous driving mode. Vehicle 102a is also sometimes referred to herein as a self-driving vehicle (AV) 102a. AV 102a may include, but is not limited to, a land vehicle (as shown in FIG. 1), an airplane, or a water vehicle.

[0037] AV102a is generally configured to detect objects (102b, 114, 116) in its vicinity. The objects may include, but are not limited to, vehicle 102b, bicycle rider 114 (e.g., a bicycle rider, an electric scooter, a motorcycle, or a similar operator) and / or pedestrian 116. When such detection is made, AV102a generates one or more possible object trajectories for the detected object and analyzes one or more of the generated possible object trajectories to perform an operation of determining whether the likelihood of a collision occurring between the AV and the object within a critical time (e.g., one minute) is at an unacceptable level. This is hereinafter referred to as collision probability assessment. Then, if the given vehicle trajectory is tracked by AV102a and any one of a plurality of dynamically generated emergency activations is performed within a predefined time period (e.g., N milliseconds), AV102a performs an operation to determine whether a collision can be avoided. If a collision can be avoided, then AV102a either takes no action or, alternatively, performs a cautious activation (e.g., slightly decelerates). On the contrary, if a collision cannot be avoided, then AV102a immediately performs an emergency activation (e.g., braking and / or changing the direction of movement). Other approaches to collision sensing and avoidance by AV102a are contemplated by this disclosure as would be understood by one of ordinary skill in the relevant art.

[0038] As will be described in further detail in connection with FIG. 3, AV102a may be configured with a lidar system 300. The lidar system 300 may include a light emitter system (transmitter) 304 that transmits light pulses 104 to detect objects located within the distance or distance range of AV102a. The light pulses 104 may impinge on one or more objects (e.g., 102b) and be reflected back to the lidar system 300. The reflected light pulses 106 that impinge on the photodetector 308 may be processed by the lidar system 300 to determine the distance between the object and AV102a. The photodetector 308 may, in some embodiments, include an array of photodetectors or a photodetector arranged and configured to receive the light reflected back within the system. For example, the photodetector 308 may include a focal plane array including a photodiode array (PDA) and a readout integrated circuit (ROIC). According to some aspects, each pixel of the PDA may be electrically coupled to a dedicated channel of the ROIC for the ROIC to control the arming and disarming of individual PDA pixels via an ON / OFF switch, as will be further described herein. According to some aspects, the PDA may include a Geiger-mode avalanche photodiode (GmAPD) capable of detecting single photon levels.

[0039] On one side, a silicon photodiode can convert light into an electrical signal. Such conversion occurs when photons with more energy than the bandgap of the detector material are absorbed, exciting electrons from the valence band to the conduction band of the semiconductor and reading them as a signal. GmAPD uses the same process but generates internal gain using an avalanche region. The avalanche region is generated within the APD, creating a region of very high electric field strength. If an electron generated optically (or thermally) in the conduction band moves into the avalanche region, the electric field strength is sufficient to cause "impact ionization" and accelerate the electron to a point where it can release other electrons. These two electrons can both be accelerated to generate avalanche amplification. This process generates the detector gain. The typical gain of an APD ranges from 10 to several hundred.

[0040] Geiger mode operation can increase the moderate gain of an APD to a much higher level. The gain of the APD increases with a stronger internal electric field but is maintained finite up to a critical breakdown electric field Eb set by the corresponding breakdown voltage Vb applied externally. For an applied voltage lower than Vb, the output photocurrent of the APD is proportional to the input optical intensity, and the device operation below the breakdown voltage is called "linear mode". On the contrary, an applied voltage greater than Vb leads to a finite probability of triggering a self-sustaining avalanche characterized by a divergent (i.e., infinite) gain for a single carrier injected into the avalanche region. Such a rapid generation of an avalanche current easily measurable by a single optically excited carrier allows for efficient detection of a single photon. In actual operation, the self-sustaining Geiger mode avalanche disappears once detected. In this case, it refers to the effective gain given by the number of charges flowing as a response to injecting only a single electron into the avalanche region (generally >> 10 5 )

[0041] On one side, the quenching and reset of the GmAPD can be achieved passively by placing a sufficiently large resistor in series with the detector. A fixed bias voltage is applied to the combination of the GmAPD and the resistor in series. When no current is flowing, the overall bias drops across the GmAPD, which is in the "armed" state. If the junction breaks, a large current flows through the resistor, and the resulting voltage drop across the resistor reduces the voltage across the GmAPD, causing the avalanche process to passively disappear in the "disarmed" state. In other cases, if an avalanche breakdown is sensed, the bias voltage is actively reduced below the breakdown voltage, and the GmAPD avalanche actively disappears. For all two types of disappearance in the "disarmed" state, the bias voltage across the GmAPD is reset to a value higher than the breakdown voltage and is armed again for subsequent sensing. The discharge reset cycle is known as the Geiger operating mode. Such operation can be further described here with reference to FIGS. 4 to 6.

[0042] As discussed further in connection with FIG. 4, aspects of the present disclosure are directed to enabling the FPA to continue to perform the necessary functions during operation even if not all pixels are operating, with the goal of selectively extinguishing pixels within the FPA. In the case of an APD using a GmAPD, the PDA may be armed and disarmed by operating the forward and reverse voltages applied in relation to the GmAPD breakdown voltage. For example, the PDA may be armed when the applied forward and reverse voltage is higher than the breakdown voltage of the GmAPD. Similarly, the PDA may be disarmed when the applied forward and reverse voltage is lower than the GmAPD breakdown voltage. It can be understood that by increasing the reverse voltage to a bias above the breakdown voltage, the PDA is considered to be armed. According to some aspects, the overall voltage of the PDA is a fixed negative DC bias voltage (V DC)and may be the sum of additional arm biases to which ROIC is applied. For example, if the arm bias is such that the arm transistor switches between +5V and 0V (ground), the (negative) sum (e.g., V DC +5V) places the PDA in a disarmed state. In other words, instead of arming the entire PDA, the present disclosure enables selective disarming of non-performing pixels such that these operations (when biased above the breakdown voltage) do not interfere with the performance of adjacent pixels. Such selective disarming may be accomplished via switches, as shown in FIG. 4. In some exemplifications, even during testing or in the field (e.g., within an active sensor such as a lidar sensor), the disarmed pixels may generate sufficient leakage current to still degrade the performance of surrounding pixels. In such exemplifications, fuses may be activated to permanently disarm non-functional pixels. The implementation of fuses is described in FIGS. 5 and 6, respectively.

[0043] Referring again to FIG. 1, lidar information, such as sensed object information, is communicated from the lidar system 300 to the on-board computing device 220 (FIG. 2). The AV 102a can also communicate via the communication network 108 to a remote computing device 110 (e.g., a cloud processing system). The remote computing device 110 may be composed of one or more servers for processing one or more processes of the techniques described herein. The remote computing device 110 may also be configured to communicate data / instructions to / from the AV 102a, to / from the server and / or database 112 via the network 108.

[0044] Network 108 may include one or more wired or wireless networks. For example, network 108 may include a cellular network (e.g., LTE (Long-Term Evolution) network, CDMA (Code Division Multiple Access) network, 3G network, 4G network, 5G network, other types of next-generation networks, etc.). The network may also include a public land mobile network (PLMN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), a telephone network (e.g., PSTN (Public Switched Telephone Network)), a private network, an ad-hoc network, an intranet, the Internet, a fiber optic backbone network, a cloud computing network, and / or a similar network to this, and / or a combination of such networks or other types of networks.

[0045] AV102a can search, receive, display, and edit information generated by a local application or transmitted via network 108 in database 112. Database 112 may be configured to store and supply raw data, indexed data, structured data, map data, program instruction words, or other known configurations.

[0046] Figure 2 shows an exemplary system architecture 200 for a vehicle according to one aspect of the present disclosure. The vehicle 102a and / or 102b of FIG. 1 may have the same or a similar system architecture as that shown in FIG. 2. Therefore, the following discussion of the system architecture 200 is sufficient to understand the vehicles 102a, 102b of FIG. 1. However, other types of vehicles are considered to be within the scope of the technology described herein and may include more or fewer elements as described in connection with FIG. 2. As a non-limiting example, an aerial vehicle may exclude a brake or a gear controller but may include altitude sensors. As yet another non-limiting example, a water vehicle may include depth sensors. A person of ordinary skill will understand that other propulsion systems, sensors, and controllers may be included depending on the vehicle type, as is well known.

[0047] As shown in FIG. 2, the system architecture 200 includes an engine or motor 202 and various sensors 204-218 for measuring various vehicle parameters. In a gas-powered or hybrid car with a fuel-driven engine, the sensors may include, for example, an engine temperature sensor 204, a battery voltage sensor 206, an engine RPM sensor 208, and a throttle position sensor 210. If the vehicle is an electric or hybrid car, the vehicle may have an electric motor, and thus may include sensors such as a battery monitoring system 212 (measuring battery current, voltage, and / or temperature), a motor current 214 and voltage 216 sensor, and a motor position sensor 218 such as a resolver and an encoder.

[0048] Actuation parameter sensors common to both types of vehicles include, for example, position sensors 236 such as an accelerometer, a gyroscope, and / or an inertial measurement unit; a speed sensor 238; and an odometer sensor 240. The vehicle may also have a clock 242 used to determine vehicle time while the system is operating. The clock 242 may be encoded in the vehicle on-board computing device, a separate device, or various clocks may be used.

[0049] The vehicle also includes various sensors that operate to collect information about the environment in which the vehicle is traveling. Such sensors may include, for example, a position sensor 260 (e.g., a GPS device); an object detection sensor such as one or more cameras 262; a lidar system 264; and / or a radar and / or ultrasonic system 266. The object detection sensor may also include an environmental sensor 268 such as a precipitation sensor and / or a peripheral temperature sensor. The object detection sensor enables the vehicle to detect objects within a given distance range from all directions of the vehicle 200, while the environmental sensor collects data on the environmental conditions within the vehicle's driving area.

[0050] During operation, information is communicated from the sensors to the vehicle on-board computing device 220. The vehicle on-board computing device 220 analyzes the data collected by the sensors and selectively controls the operation of the vehicle in response to the analysis results. For example, the vehicle on-board computing device 220 can control braking (brakes) via a brake controller 222; direction via a steering controller 224; speed and acceleration via a throttle controller 226 (in the case of a gasoline-powered vehicle) or a motor speed controller 228 (e.g., a current level controller for an electric vehicle); a differential gear controller 230 (in the case of a vehicle with a transmission); and / or other controllers. The auxiliary device controller 254 may be configured to control one or more auxiliary devices such as a test system, auxiliary sensors, mobile devices carried by the vehicle, and the like.

[0051] Geographic location information may be communicated from the position sensor 260 to the on-board computing device 220. The on-board computing device 220 can access a map of the environment corresponding to the location information and determine known fixed features of the environment such as distances, buildings, stop signs, and / or stop / go signals. Object detection information captured by sensors such as the camera 262 and / or the lidar system 264 is communicated from the sensor to the on-board computing device 220. The object detection information and / or the captured image are processed by the on-board computing device 220 to detect objects near the vehicle 200. Known or to-be-known techniques for detecting objects based on sensor data and / or the captured image may be used in aspects disclosed in this document.

[0052] Lidar information, for example, is communicated from the lidar system 264 to the on-board computing device 220 captured by the detector 308. Also, the captured image is communicated from the camera 262 to the vehicle on-board computing device 220. The lidar information and / or the captured image are processed by the vehicle on-board computing device 220 to detect objects near the vehicle 200. The manner in which object detection is performed by the vehicle on-board computing device 220 includes such functions as detailed in this specification.

[0053] If the detection capabilities of the lidar system 264, and more specifically the detector 308, are improved so that the ordinary person skilled in the art can understand the normal state of the technical field, the on-board computing device 220 can receive more accurate detections and generate more accurate object tracking and trajectories for the detected objects. This leads to improved autonomous driving because at least one sensor of the vehicle sensor suite is improved to provide more accurate detection information. Such improvements provide many downstream benefits. For example, by processing more accurate information, the on-board computing device 220 can perform analysis at a faster speed to provide solutions, because less computing bandwidth can be used to check sensor accuracy data.

[0054] FIG. 3 shows an exemplary architecture for a lidar system 300 according to one aspect of the present disclosure. In some aspects, the lidar system 264 of FIG. 2 may be the same as or substantially similar to the lidar system 300. Accordingly, the discussion of the lidar system 300 is sufficient to understand the lidar system 264 of FIG. 2.

[0055] As shown in FIG. 3, the lidar system 300 includes a housing 306 that can rotate 360 degrees about a central axis such as the hub of the motor 316 or the axle 315. The housing may include an emitter / receiver aperture 312 made of a light-transmissive material. Although a single aperture is shown in FIG. 3, the present solution is not limited in this regard. In other scenarios, multiple apertures for emitting and / or receiving light may be provided. In any scenario, the lidar system 300 can emit light through one or more apertures 312 and receive light reflected toward the one or more apertures 312 as the housing 306 rotates around the internal components. In an alternative scenario, the outer shell of the housing 306 may be a fixed dome made of a material that is at least partially light-transmissive, with rotatable components inside the housing 306.

[0056] Inside the rotating shell or the fixed dome, there is an optical emitter system 304 configured and arranged to generate and emit optical pulses through one or more laser emitter chips or other light-emitting devices, either through the aperture 312 or through the transparent dome of the housing 306. The optical emitter system 304 may include any number of individual emitters (e.g., 8 emitters, 64 emitters, or 128 emitters). The emitters can emit light of substantially the same intensity or of varying intensities. The lidar system also includes a photodetector 308, which is an array of photodetectors (e.g., a focal plane array (FPA) including a photodiode array (PDA) and / or a Geiger-mode PDA) arranged and configured to receive the light reflected by the system. In one example, the optical emitter system 304 and the photodetector 308 will rotate with the rotating shell or rotate inside the fixed dome of the housing 306. It should be understood that the mechanical lidar system described here is only an exemplary lidar system that depends on the aspects of the current solution and can also be embodied in examples of other lidar systems such as solid-state lidar systems.

[0057] In one aspect, one or more optical element structures 310 are located in front of the optical emitter system 304 and / or the photodetector 308 and can serve as one or more lenses or waveplates that focus the light passing through the optical element structure 310.

[0058] One or more optical element structures 310 may be arranged in front of a mirror (not shown) (e.g., like a focal plane array) to focus the light passing through the optical element structure 310. As shown below, the system includes an optical element structure 310 that is arranged in front of a mirror and connected to the rotating element of the system so that the optical element structure 310 rotates with the mirror. As an alternative or in addition to this, the optical element structure 310 may include various such structures (e.g., lenses and / or waveplates). Optionally, the various optical element structures 310 may be arranged in an array on or integrally with the shell portion of the housing 306.

[0059] According to one aspect, the lidar system 300 includes a power unit 318 that supplies power to the light emission unit 304, a motor 316, and electronic components. The lidar system 300 also includes an analyzer 314 having components such as a processor 322 and a non-transitory computer-readable memory 320, where the system receives data collected by the light detector device, analyzes it to measure the characteristics of the received light, and the connected system is configured with programming instructions that can generate information used to make decisions regarding operation in the environment where the data was collected. Optionally, the analyzer 314 may be integrated with the lidar system 300 as shown, be partially or entirely external to the lidar system, and be communicatively coupled to the lidar system via a wired or wireless communication network or link.

[0060] According to one aspect, the lidar system 300 can generate and provide an output to a vehicle on-board computing system (e.g., the on-board computing device 220). Such output may include a three-dimensional (3-D) mapping of the perception area (the area illuminated by the lidar 264 or lidar 300). The three-dimensional mapping according to one aspect may be referred to as a lidar grid, where the grid cells can each provide a proportional representation of the perception area. When an object is detected within the lidar grid, the on-board computing device 220 can attempt to generate a point cloud mapping (e.g., the lidar grid) including the perceived object and generate collision threat assessments and potential navigation instructions for other AV systems. Thus, systems and methods for improving the detection function and performance of the FPA are described herein in connection with FIGS. 4 through 7 below.

[0061] FIG. 4 shows an exemplary schematic switch architecture 400 of a pixel ON / OFF switch according to some embodiments. The switch architecture 400 may include a photodiode 402, a high voltage source 404, an arm / disarm control circuit 406, a disarm voltage source 408, an arm voltage source 410, and a counter stop 412. According to some aspects, the high voltage source 404 may be connected to the cathode of the photodiode 402. The photodiode 402 may be a GmAPD photodiode. According to some aspects, the arm / disarm control circuit 406 may be configured to dynamically increase a bias voltage (e.g., a high voltage supply) above the breakdown voltage of the photodiode 402. In one example, if an avalanche event occurs (e.g., when light is received), the disarm circuit turns off (i.e., stops), and the counter stop mechanism is triggered. Although not shown, the arm / disarm control circuit 406 may include a microprocessor, a central processing unit (CPU), and / or logic circuitry configured to process instructions enabling the arm / disarm operation of the switch. In some aspects, the arm / disarm control circuit 406 may not assert an arm control signal to prevent the photodiode from being armed above its breakdown voltage. Although not shown in the drawings, the switch architecture 400 may be able to connect the output of the photodiode 402 to the ROIC. According to some aspects, the circuit elements connected to the anode of the photodiode 402 may be part of the ROIC (e.g., elements 406, 408, 410, and 412).

[0062] It can be appreciated that the PDA can be a pixelated photodiode array where each pixel of the PDA includes a radiation detector such as photodiode 402. Further, while FIG. 4 shows a single switch architecture, it can be appreciated that the PDA interfaces to a plurality of switches each coupled to an individual radiation detector (e.g., photodiode 402) to selectively arm and disarm the individual photodiodes 402. As mentioned herein, selectively arming and disarming can vary depending on the observed performance of each photodiode 402 of the PDA, so non-performing photodiodes may be selectively disarmed in accordance with aspects of the disclosure. Selectively arming and disarming can vary according to scenarios where the user (e.g., tester or operator) does not want to arm a particular detector because they have no interest in the data for that region of the scene being imaged.

[0063] As described herein, aspects of the present disclosure provide an addressable pixel-level switch (such as switch assembly 400) that selectively prevents noise pixels from being armed during operation of the FPA to deactivate non-performing pixels (e.g., noise pixels / noise photodiodes). In this regard, the arm / disarm circuit 406 may maintain the arm transistor associated with the noise pixel at the +5V rail and may not allow the transistor to be pulled to ground. This operation forces the associated PDA pixel to maintain a disarmed state. That is, the arm / disarm circuit 406 prevents the arm transistor from switching from +5V to 0V (ground) and maintains the noise pixel at V DC biased at +5V in a disarmed state. In this case, the noise pixel is always at V DCThe disarm bias remains. Thus, by applying a forward-reverse voltage value lower than the breakdown voltage of the GmAPD, the switch assembly 400 prevents noisy pixels from being armed during the operation of the APD. To place a pixel in the armed state, the switch assembly 400 can apply a forward-reverse voltage value higher than the breakdown voltage of the photodiode 402.

[0064] The determination that a given pixel is non-performing may be made during the test phase, and it can be understood that the state of the non-performing pixel can be stored as part of the deselection map. In some aspects, the deselection map can indicate the state of each pixel of the PDA and the type of error (if any) that may be associated with each pixel. For example, the deselection map can include the state associated with the photodiode 402 and indicate that the photodiode is non-performing. Further, the deselection map can also indicate that the non-performing photodiode 402 is a noisy pixel. It can be understood that other non-performing states, including but not limited to, observed dark current values above a predetermined dark current threshold and / or observed leakage current levels above a predetermined leakage current threshold, can be stored in the deselection map. Additionally, the deselection map can list user settings for disarming a particular detector, as described herein.

[0065] According to some aspects, the switch architecture (e.g., the switch architecture 400 may include fuse elements, as described in the present disclosure with reference to FIGS. 5 and 6. According to some aspects, the fuse elements may be integrated as additional elements within the switch architecture described in FIG. 4. In some cases, even in the disarmed state, V DCIt can be understood that a leakage current can be generated that reduces the performance of nearby pixels with a +5V bias. In other words, even if a noise pixel is disabled, a leakage current can be generated that reduces the performance of pixels near the bias voltage. In this case, the fuse circuit can be integrated into the PDA or ROIC to selectively isolate the noise pixel from the DC bias. According to some aspects, the combination of the switch and the fuse element provides certain advantages. For example, by using the switch element, the operator can have a higher level of freedom when initially selecting and deselecting pixels / detectors. This provides a more robust testing practice and increases the adaptability of the sensor and switch architecture. If a disabled pixel can still affect the performance of other nearby pixels, the fuse element can be used to permanently remove such an effect.

[0066] According to some aspects, the fuse element described herein may be integrated as an alternative to the switch element. According to some aspects, using only the fuse element can reduce the complexity of the switch assembly and the associated processing bandwidth.

[0067] Regardless of whether the fuse element is implemented alone or in conjunction with a switch element, the operation of the fuse element will be described below. According to some aspects, the fuse element may blow, and selectable pixels can be permanently separated. According to some aspects, the blowing of the fuse may be programmed at a specific processing stage after an initial test of the FPA to identify leaky pixels. According to some aspects, the blowing of the fuse may be programmed at a specific stage that is executed when leaky pixels are identified in the field. This may occur when pixel performance degrades over time, and the pixel becomes a noisy pixel or the leakage current of a disabled pixel is observed in the field over time. In order not to alternate the entire sensor assembly of the operating AV, the fuse circuit blows and the associated PDA pixels can be permanently / electrically separated from the ROIC channel and the DC bias circuit.

[0068] FIG. 5 shows a fuse assembly 500 according to some aspects. The fuse assembly 500 may include a fuse 502 disposed between an APD 504 and an ROIC input 506. The fuse assembly 500 may also include a pair of transistors 508 and 510 configured to control a voltage 512 through the fuse. As mentioned herein, the placement of the fuse allows noisy pixels that generate leakage current even in the disabled state to be permanently separated from the ROIC channel and the biasing circuit. According to some aspects, if the voltage 512 is asserted to ground through the fuse 502, the fuse 502 blows and a permanent open circuit is generated between the APD 502 and the ROIC input 504, and the associated pixels are permanently deactivated. It can be understood that the fuse 502 can be an integrated component of the ROIC or PDA.

[0069] FIG. 6 shows a fuse assembly 600 according to an aspect of the present disclosure. The fuse assembly 600 may include a fuse 602 that may be disposed inside the PDA (e.g., the PDA die). In such a manner, there may be a complete electrical method of deactivating pixels during wafer level probing. According to some aspects, the fuse 602 may be provided at the cathode or anode of an APD 608 (shown as the cathode here). In some aspects, pixels identified as leaks will draw enough current to cut the fuse when biased in the forward direction. In some aspects, the fuse may be in line with the APD circuit or accessed by a separate pad such as pad 604. Similar to the fuse assembly 500, when the pixels generate leakage current as they are biased in the forward direction, enough current is drawn through the high voltage 606 to cut the fuse 602, thereby creating an open circuit. According to some aspects, the open circuit created by the blown fuse separates the APD from the DC bias and effectively isolates the pixel generating the leakage current. The function of the resistor 610 can be understood to serve as a quenching resistor as described herein. Manual quenching reduces the amplitude of the total avalanche current in the fuse assembly 600 and can be utilized to protect the photodiode element from high current overload in the presence of a very large optical input signal. It can be understood that the activation of the fuse 602 (e.g., blowing of the fuse) can be automatically triggered via the forward bias operation of the attached pixels and / or the operation of the control circuit (e.g., circuit 400). It can be understood that the control circuit may assert the transistors 508, 510 such that a sufficiently large current from the voltage source may blow the fuse 502.

[0070] FIG. 7 shows an exemplary process 700 for performing the switching operations described in this disclosure. According to some aspects, process 700 may include receiving an optical signal with a pixelated photodiode array (PDA) as shown at step 702. According to some aspects, this optical signal may be reflected light reflected from a surrounding surface. According to some aspects, process 700 may further include controlling a selectable switch element of a ROIC coupled to the PDA to arm the radiation detectors of the PDA's pixels as shown at step 704. The arming may be performed by the logic circuitry of the ROIC, and it can be understood that the selectable switch can transmit the received output signal of the radiation detector. According to some aspects, process 700 may also further include controlling the selectable switching element of the ROIC to disarm the radiation detectors of the PDA's pixels by the logic circuitry, and the selectable switch element is configured to block such that the radiation detector cannot output a signal as shown at step 704. It can be understood that the arming and disarming operations using the switch follow the operations described herein in connection with FIG. 4.

[0071] According to one example, when embodied within a sensor assembly (FPA and / or lidar sensor), the ROIC may be configured to sense the occurrence of an avalanche event, stop a pixel-level counter, and record the time stamp of the counter with an indication that the pixel had an avalanche. The ROIC may also be configured to provide the exact time when the pixel had an avalanche, which corresponds to the time-of-flight (TOF) of the reflected pulse returned to the pixel. The time stamps recorded at all pixels (including pixels that record a “terminal count” if no avalanche occurs) are read into an external electronic device and used to generate a lidar point cloud using appropriate digital signal processing (DSP) firmware using this “time stamp” information.

[0072] According to one aspect, this process may also include detecting the breakdown voltage of the GmAPD and increasing the reverse voltage value to a bias level higher than the breakdown voltage of the GmAPD to activate other selectable switch elements associated with the operating radiation element. According to one aspect, this process may also include storing a de-selection mapping indicating a malfunction of the radiation detector and detecting a malfunction of the radiation detector based on the de-selection mapping. According to one aspect, a malfunction of the radiation detector is associated with an observed dark current value higher than a predetermined dark current threshold. A malfunction of the radiation detector may also be associated with an observed noise level higher than a predetermined noise threshold. It can be understood that the de-selection mapping can store detector data beyond the malfunction. As would be understood by one of ordinary skill in the art, the de-selection mapping can store de-selection metrics associated with other physical attributes of the radiation detector and / or user settings. Such user settings can be set for various reasons including, but not limited to, test and integration purposes.

[0073] According to one aspect, a malfunction of the radiation detector may also be associated with an observed leakage current level equal to or higher than a predetermined leakage current threshold. In connection with this, the process may also include using a circuit fuse to isolate the radiation detector associated with a detected malfunction corresponding to the observed leakage current exceeding a predetermined leakage current threshold. The process may also include applying a predetermined voltage to a pair of transistors in the circuit fuse to cause the fuse to blow. It can be understood that the transistors are asserted by allowing a sufficiently large current from a voltage source (e.g., high voltage 606 or voltage source 512) to blow the fuse. The blown fuse creates a permanent open circuit between the PDA and the ROIC (i.e., permanently disconnects them) corresponding to the observed leakage current exceeding a predetermined leakage current threshold.

[0074] It is understood that the detailed description section is intended to be used to interpret claims that are not in other sections. Since the other sections can present one or more that are not all the exemplary aspects contemplated by the inventor, there is no intention to limit this disclosure or the appended claims in any way.

[0075] According to some aspects of the present disclosure, an apparatus including a pixelated photodiode array (PDA) may be disclosed, where each pixel of the PDA includes a radiation detector; and a readout integrated circuit (ROIC). According to some aspects, the ROIC may include a plurality of switch elements respectively connected to the individual radiation detectors of each pixel, and each switch element of the plurality of switch elements can be switched between an armed state for arming the corresponding radiation detector and receiving an output signal from the corresponding detector and a disarmed state for disarming the corresponding radiation detector and blocking the output signal. In the armed state, the PDA is configured to detect incoming optical signals, and in the disarmed state, the PDA is configured to ignore incoming optical signals. The ROIC includes a logic circuit configured to control the switch state of each switch element of the plurality of switch elements.

[0076] According to some aspects, the logic circuit may be additionally configured to arm the PDA and place a first switch of a plurality of switch elements associated with a first radiation detector in the disarmed state in response to detecting a malfunction of the radiation detector.

[0077] According to some aspects, the PDA includes one or more Geiger-mode avalanche photodiodes (GMAPDs). According to some aspects, the logic circuit is additionally configured to place the first switch element of the plurality of switch elements associated with the first radiation detector in a disarmed state by applying a forward-reverse voltage value under the detected breakdown voltage of one or more GmAPDs. Further, the logic circuit is additionally configured to place the second switch element of the plurality of switch elements associated with the second radiation detector in the armed state by increasing the reverse voltage value above the detected breakdown voltage of one or more GmAPDs to a bias level, and the first and second switch elements are different.

[0078] According to some aspects, the logic circuit is additionally configured to determine the operating state of each individual radiation detector, and the determined operating state corresponds to the stored selection / deselect mapping for each individual radiation detector. According to some aspects, the operating state corresponds to the observed dark current value above a predetermined dark current threshold. According to some aspects, the operating state corresponds to the observed noise level above a predetermined noise threshold. According to some aspects, the operating state corresponds to the observed leakage current level above a predetermined leakage current threshold.

[0079] According to some aspects, the apparatus may further include a circuit fuse configured to not electrically engage with each individual radiation detector. According to some aspects, the circuit fuse is configured to not electrically couple the individual radiation detectors in response to the operation of the radiation detector being associated with an observed leakage current that is greater than a predetermined leakage current threshold. According to some aspects, the circuit fuse is integrated within the ROIC. The circuit fuse may include a pair of transistors configured to control the voltage across the circuit fuse, and the logic circuit is additionally configured to apply a predetermined voltage to the pair of transistors, where the predetermined voltage causes the fuse to blow and create a permanent open circuit between the PDA and the ROIC. According to some aspects, the logic circuit is additionally configured to apply the predetermined voltage in response to the observed leakage current exceeding the predetermined leakage current threshold.

[0080] This disclosure describes representative aspects with respect to representative fields and application areas, but it should be understood that the disclosure is not limited thereto. Other aspects and modifications thereto are possible and are within the scope and spirit of the present disclosure. For example, without limiting the generality of this paragraph, one aspect is not limited to the software, hardware, firmware, and / or entities shown in the drawings or described herein. Also, one aspect (whether explicitly described in the present disclosure or not) has considerable utility in the fields and application areas beyond the examples described herein.

[0081] Aspects have been described herein with the aid of functional components for illustrating specific functions and relationships. The boundaries of such functional components have been arbitrarily defined for the convenience of the description. Alternative boundaries can be defined as long as the specified functions and relationships (or equivalents thereof) are properly performed. Also, alternative aspects can perform functional blocks, steps, operations, methods, etc. using a different order than that described herein.

[0082] As used herein, references to "one aspect", "an aspect", "exemplary aspect" or similar phrases are to be understood that while the described aspect may include a particular function, structure or characteristic, not all aspects necessarily can include the particular function, structure or characteristic. Moreover, such phrases do not necessarily refer to the same aspect. Further, when a particular function, structure or characteristic is described in relation to an aspect, one of ordinary skill in the relevant art would be within the scope of knowledge to incorporate such function, structure or characteristic, whether or not explicitly recited or described herein, into other aspects. Also, some aspects may be described using the terms "coupled" and "connected" and derivatives thereof. Such terms are not necessarily intended as synonyms for each other. For example, some aspects may be described using the terms "connected" and / or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "coupled" can also mean that two or more elements are not in direct contact with each other but still cooperate or interact with each other.

[0083] The breadth and scope of this disclosure should not be limited by the exemplary aspects described above, but rather should be defined in accordance with the following claims and equivalents thereof.

[0084] It should be understood that the detailed description section is intended, not other sections, to be used in interpreting the claims. Other sections may present one or more embodiments that are not all of the embodiments conceived by the inventor, and are not intended to limit this disclosure or the appended claims in any way.

[0085] This disclosure describes representative embodiments for representative fields and applications, but it should be understood that the disclosure is not limited thereto. Other embodiments and modifications thereto are possible and are within the scope and spirit of the present disclosure. For example, without limiting the generality of this paragraph, embodiments are not limited to the software, hardware, firmware, and / or entities illustrated in the drawings or described herein. Also, embodiments (whether or not explicitly described herein) have considerable utility in fields and applications beyond the examples described herein.

[0086] Embodiments are described herein with the aid of functional components that illustrate the implementation of particular functions and their relationships. The boundaries of such functional components are arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined as long as the particular functions and relationships (or their equivalents) are properly performed. Also, alternative embodiments can perform functional blocks, steps, operations, methods, etc. using a different order than that described herein.

[0087] Here, references to "one embodiment", "an embodiment", "exemplary embodiments", or similar phrases indicate that the described embodiments can include certain features, structures, or characteristics, but not all embodiments necessarily can include the specific features, structures, or characteristics. Moreover, such phrases do not necessarily refer to the same embodiment. Also, when a particular feature, structure, or characteristic is described in connection with an embodiment, whether explicitly recited here or not, one of ordinary skill in the art would be within the scope of knowledge to incorporate such feature, structure, or characteristic into other embodiments. Further, in some embodiments, the terms "coupled" and "connected" and their derivatives can be used in the description. Such terms are not necessarily intended as synonyms for each other. For example, in some embodiments, the terms "connected" and / or "coupled" can be used to describe that two or more elements are in direct physical or electrical contact with each other. However, the term "coupled" can also mean that two or more elements do not directly contact each other but still cooperate or interact with each other.

[0088] The breadth and scope of the present disclosure should not be limited by the exemplary embodiments described above, but should be defined in accordance with the following claims and equivalents thereof.

Claims

Claim 1 In an apparatus,[[]] A pixelated photodiode array (PDA) - each pixel within the PDA includes a radiation detector; and As a read out integrated circuit (ROIC), A plurality of switch elements respectively connected to individual radiation detectors of each pixel - each switch element of the plurality of switch elements arms a corresponding radiation detector and is switchable between an armed state for receiving an output signal from the corresponding radiation detector and a disarmed state for disarming the corresponding radiation detector and blocking the output signal, in the armed state, the PDA is configured to detect incoming optical signals, and in the disarmed state, the PDA is configured to ignore the incoming optical signals; and A read out integrated circuit (ROIC) including a logic circuit configured to control the switch state of each switch element of the plurality of switch elements,[[]] An apparatus comprising the above.[[]] Claim 2 The apparatus according to claim 1, wherein the logic circuit is additionally configured to arm the PDA and place a first switch of the plurality of switch elements associated with a first radiation detector in the disarmed state to detect malfunction of the radiation detector.[[]] Claim 3 The apparatus according to claim 1, wherein the PDA includes one or more Geiger-mode avalanche photodiodes (GMAPDs).[[]] Claim 4 The apparatus according to claim 3, wherein the logic circuit is additionally configured to place a first switch element of the plurality of switch elements associated with a first radiation detector in the disarmed state by applying a forward and reverse voltage value under the detected breakdown voltage of the one or more GMAPDs.[[]] Claim 5 The logic circuit is additionally configured to place the second switch element of the plurality of switch elements associated with the second radiation detector in the armed state by increasing the reverse voltage value on the detected breakdown voltage of the one or more GmAPDs to a bias level. The apparatus according to claim 4, wherein the first and second switch elements are different. **Claim 6** The logic circuit is additionally configured to determine the operating state of each individual radiation detector. The apparatus according to claim 1, wherein the determined operating state corresponds to a stored selection / deselect mapping for each individual radiation detector. **Claim 7** The apparatus according to claim 6, wherein the operating state corresponds to an observed dark current value above a predetermined dark current threshold. **Claim 8** The apparatus according to claim 6, wherein the operating state corresponds to an observed noise level above a predetermined noise threshold. **Claim 9** The apparatus according to claim 6, wherein the operating state corresponds to an observed leakage current level above a predetermined leakage current threshold. **Claim 10** The apparatus according to claim 1, further comprising a circuit fuse configured to be electrically disengaged from each individual radiation detector.

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