Lidar system, and method and sensor used therefor

Abstract

To cause an avalanche breakdown in a detector with a single photon while an avalanche detector and a silicon photoelectron multiplier apply an effectively high gain to photon detection.SOLUTION: The present invention relates to a method of performing light detection and ranging (LIDAR), and the method comprises: illuminating a scene along a first direction with first interrogating infrared, the illuminating results in first reflected infrared, the first reflected infrared reflected from a first object disposed within the scene; activating a plurality of pixels such that each pixel of the plurality of pixels is sensitive to the first reflected infrared during respective first activation periods; creating, by each pixel, a first signal that is proportional to a number of photons of the reflected infrared absorbed by each pixel, the creating results in a plurality of first signals; and estimating a distance to the first object based on an amplitude of at least one of the plurality of first signals.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] Various examples relate to light detection and ranging (LIDAR), and more particularly to LIDAR systems, related LIDAR sensors, and related methods. [Background technology]

[0002] Many systems use light detection and ranging (LIDAR) to perform vision-like control, including weapons systems, mobile autonomous robots, safety systems for automobiles, and semi-autonomous and autonomous driving systems.

[0003] Lidar systems are time-of-flight systems. Light, such as near-infrared light, is guided into a scene of interest. The light propagates outward and reflects off objects in the scene. The reflected light travels back to the detection system, and based on the round-trip flight time of the light, the distance to objects in the scene can be determined.

[0004] Therefore, related art LIDAR systems are primarily concerned with the timing of the arrival of reflected light, not necessarily the number of photons of reflected light received. For that reason, related art LIDAR systems use photodetectors configured for avalanche breakdown. That is, related art LIDAR systems use single photon avalanche detectors (SPADs) or silicon photomultiplier (SiPM) systems to detect the arrival of reflected light. Avalanche detectors and silicon photomultipliers effectively apply high gain to photon detection, and in some cases, a single photon can cause avalanche breakdown in the detector. Summary of the Invention

[0005] One example is a method of performing light detection and ranging (LIDAR), the method including: illuminating a scene along a first direction with a first interrogating infrared light, the illuminating producing a first reflected infrared light, the first reflected infrared light reflected from a first object disposed within the scene; activating a plurality of pixels such that each pixel of the plurality of pixels is sensitive to the first reflected infrared light during a respective first activation period; generating, by each pixel, a first signal proportional to a number of photons of the reflected infrared light absorbed by each pixel, the generating producing a plurality of first signals; and estimating a distance to the first object based on an amplitude of at least one of the plurality of first signals.

[0006] The exemplary method may further include deactivating each pixel of the plurality of pixels outside of each pixel's respective first activation period such that each pixel is insensitive to the first reflected infrared radiation.

[0007] In an exemplary method, actuating the plurality of pixels may include sequentially actuating each pixel of the plurality of pixels.

[0008] In an exemplary method, actuating the plurality of pixels may include actuating each pixel to generate electrons in accordance with a number of photons of the first reflected infrared radiation absorbed by the pixel during a respective first actuation period, and deactivating each pixel of the plurality of pixels outside each respective first actuation period so that the pixel is insensitive to the first reflected infrared radiation.

[0009] The exemplary method may further include illuminating the scene along a first direction with a second interrogation infrared ray and actuating each pixel of the plurality of pixels to supplement its respective first signal in proportion to the second reflected infrared ray arriving at the pixel within a respective second actuation period. The exemplary method may further include transferring each first signal to a respective memory capacitor after illuminating the scene with the second interrogation infrared ray and actuating each pixel of the plurality of pixels to supplement its respective first signal.

[0010] An exemplary method may further include illuminating the scene along a second direction with a second interrogation infrared light, where the illuminating produces second reflected infrared light, the second reflected infrared light reflected from a first object disposed within the scene; actuating a plurality of pixels such that each pixel is sensitive to the second reflected infrared light during a respective second actuation period; generating, by each pixel, a second signal proportional to a number of photons of the second reflected infrared light absorbed by each pixel, where the generating produces a plurality of second signals; and estimating a distance to the first object based on amplitudes of at least one of the plurality of first signals and at least one of the plurality of second signals.

[0011] In an exemplary method, actuating the plurality of pixels may include at least one selected from the group including: each pixel being actuated for a trigger period that does not overlap with other pixels; and each pixel being actuated for a trigger period that overlaps with the trigger periods of adjacent pixels of the plurality of pixels.

[0012] In an exemplary method, illuminating the scene may include at least one selected from the group including illuminating the scene with a laser dot aligned with a first direction, illuminating the scene with a laser line aligned with a first direction, illuminating the scene with a vertically oriented laser line, and illuminating the scene with a horizontally oriented laser line.

[0013] Yet another example may be a light detection and ranging (LIDAR) sensor comprising: a first plurality of pixels including one or more shutter transistors, one or more photodetectors, one or more transfer transistors, one or more floating diffusions, and one or more memory capacitors; a row controller coupled to the first plurality of pixels, the row controller configured to position the first plurality of pixels for readout; a column controller coupled to the first plurality of pixels, the column controller configured to read out a signal from each pixel of the first plurality of pixels; and a gating controller coupled to the first plurality of pixels, the gating controller configured to gate each pixel of the first plurality of pixels so that each pixel is sensitive to reflected infrared radiation during a respective activation period and insensitive to reflected infrared radiation outside of a respective activation period.

[0014] In an exemplary LIDAR sensor, a gating controller may define a timing signal input, and the gating controller may be configured to extract a sample period from the timing signal applied to the gating controller and gate each pixel within the sample period.

[0015] In an exemplary LIDAR sensor, when the gating controller gates each pixel, the gating controller may be configured, for each pixel, to place the corresponding shutter transistor in a conductive state outside of the actuation period, making the pixel insensitive to reflected infrared light, and to place the corresponding shutter transistor in a non-conductive state and the corresponding transfer transistor in a conductive state during the actuation period, causing electrons generated by the photodetector in response to the reflected infrared light to modify the voltage on the floating diffusion. The row controller may be further configured, for each pixel of the plurality of pixels and after the gating controller has gated each pixel within the sample period, to drive a voltage to a corresponding memory capacitor proportional to the voltage on the floating diffusion.

[0016] In an exemplary LIDAR sensor, when the gating controller gates each pixel, the gating controller may be configured to gate each pixel such that the activation periods are mutually exclusive.

[0017] In an exemplary LIDAR sensor, when the gating controller gates each pixel, the gating controller may be configured to gate each pixel such that actuation periods between two pixels of the plurality of pixels at least partially overlap.

[0018] The exemplary LIDAR sensor may further include a row controller coupled to the second plurality of pixels, the second plurality of pixels including one or more second shutter transistors, one or more second photodetectors, one or more second transfer transistors, one or more second floating diffusions, and one or more second memory capacitors; a row controller configured to arrange the second plurality of pixels for readout; a column controller coupled to the second plurality of pixels and configured to readout a signal generated by the photodetector of each pixel of the second plurality of pixels; and a gating controller coupled to each pixel of the second plurality of pixels, the gating controller configured to gate each pixel of the second plurality of pixels so that each pixel of the second plurality of pixels is sensitive to reflected infrared radiation during a respective activation period and is insensitive to reflected infrared radiation outside of a respective activation period.

[0019] Yet another example is a LIDAR system including a LIDAR controller, a LIDAR source coupled to the LIDAR controller and configured to transmit interrogation light into a scene in response to commands from the LIDAR controller, and a LIDAR sensor coupled to the LIDAR controller. The LIDAR sensor may include a first plurality of pixels, a row controller coupled to the first plurality of pixels and configured to arrange the first plurality of pixels for readout, a column controller coupled to the first plurality of pixels and configured to read out a sample signal from each pixel of the first plurality of pixels, and a gating controller coupled to each pixel of the first plurality of pixels and configured to gate the first plurality of pixels so that each pixel is sensitive to reflected infrared radiation during a respective activation period and insensitive to reflected infrared radiation outside of the respective activation period. The LIDAR controller may be configured to obtain a histogram of the sample signals from the LIDAR sensor and estimate a distance to a reflecting object based on the amplitude of the sample signals in the histogram.

[0020] In an exemplary LIDAR system, when the gating controller gates each pixel, the gating controller may be configured, for each pixel, to render the pixel's shutter transistor conductive outside of the actuation period, making the pixel insensitive to reflected infrared light, and to render the corresponding shutter transistor nonconductive and the pixel's transfer transistor conductive during the actuation period, causing electrons generated by the photodetector in response to the reflected infrared light to modify the voltage on the floating diffusion. The row controller may be further configured, for each pixel of the plurality of pixels and after the gating controller has gated each pixel within the sample period, to transfer a representation of the voltage on the pixel's floating diffusion to the pixel's memory capacitor.

[0021] In an exemplary LIDAR system, when the gating controller gates each pixel of the plurality of pixels, the gating controller may be configured to gate each pixel such that the activation periods are mutually exclusive.

[0022] In an exemplary LIDAR system, when the gating controller gates each pixel of the plurality of pixels, the gating controller is configured to gate each pixel such that actuation periods between two pixels of the plurality of pixels at least partially overlap.

[0023] The exemplary LIDAR system may further include a second plurality of pixels, a row controller coupled to the second plurality of pixels, the row controller configured to arrange the second plurality of pixels for readout, a column controller coupled to the second plurality of pixels, the column controller configured to readout signals generated by the photodetectors of each pixel of the second plurality of pixels, and a gating controller coupled to each pixel of the second plurality of pixels. The gating controller may be configured to gate each pixel of the second plurality of pixels such that each pixel of the second plurality of pixels is sensitive to reflected infrared radiation during a respective activation period and is insensitive to reflected infrared radiation outside of a respective activation period. [Brief explanation of the drawings]

[0024] Exemplary embodiments will now be described in detail with reference to the accompanying drawings. [Figure 1] FIG. 1 illustrates a block diagram of a LIDAR system, according to at least some embodiments. [Figure 2] 1 illustrates an exemplary LIDAR system in the form of a vehicle, according to at least some embodiments. [Figure 3] FIG. 1 illustrates a block diagram of a LIDAR sensor, according to at least some embodiments. [Figure 4] 1 shows an electrical schematic diagram of a pixel according to at least some embodiments. [Figure 5] 1 illustrates a timing diagram according to at least some embodiments. [Figure 6] 1 illustrates a histogram according to at least some embodiments. [Figure 7] 1 illustrates a method according to at least some embodiments.

[0025] definition Various terms are used to refer to particular system components. Different companies may refer to a component by different names, and this specification does not intend to distinguish between components that differ in name but not function. In the following description and claims, the terms "including" and "comprising" are used in an open-ended manner and, therefore, should be interpreted to mean "including, but not limited to." Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. Thus, when a first device couples to a second device, the connection may be by a direct connection or by an indirect connection via other devices and connections.

[0026] As used herein, "a," "an," and "the" refer to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a processor" programmed to perform various functions refers to one processor programmed to perform each and every function, or to more than one processor collectively programmed to perform each of the various functions. For clarity, an initial reference to "a referent" and then a subsequent reference, for purposes of precedence, to "the referent" does not preclude the stated referent from being plural.

[0027] "About" in reference to a stated parameter shall mean plus or minus ten percent (+ / -10%) of the stated parameter.

[0028] "Assert" shall mean producing or maintaining a first predetermined state of a Boolean signal. At the discretion of the circuit designer, a Boolean signal may be asserted high or at a higher voltage, and a Boolean signal may be asserted low or at a lower voltage. Similarly, "deassert" shall mean producing or maintaining a second predetermined state of a Boolean signal, opposite the asserted state.

[0029] In reference to an electrical device, whether stand-alone or part of an integrated circuit, the terms "input" and "output" refer to an electrical connection to the electrical device and should not be understood as a verb requiring an action. For example, a comparator, such as an operational amplifier, may have a first input and a second input. These "inputs" define an electrical connection to the comparator and are not necessarily read as requiring a signal to be input to the comparator.

[0030] "Controller" shall mean, alone or in combination, a discrete circuit component, an application specific integrated circuit (ASIC), a microcontroller with control software, a reduced-instruction-set computer (RISC) with control software, a digital signal processor (DSP), a processor with control software, a programmable logic device (PLD), a field programmable gate array (FPGA), or a programmable system-on-a-chip (PSOC) configured to read inputs and drive outputs in response to the inputs. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following description relates to various embodiments of the present invention. While one or more of these embodiments may be preferred, the disclosed embodiments should not be construed or otherwise used as limiting the scope of the present disclosure, including the claims. In addition, those skilled in the art will understand that the following description has broad applicability, and the description of any embodiment is intended to be merely an example of that embodiment and is not intended to imply that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0032] Various examples relate to methods and systems for light detection and ranging (LIDAR). More specifically, various examples relate to LIDAR systems in which the sensor does not use single-photon avalanche detectors (SPADs) or silicon photomultipliers (SiPMs) for detection because SPAD / SIPM devices obscure information about the number of received photons. Even more specifically, various examples relate to operating a sensor such that time-of-flight information is encoded in the identity of the pixel receiving the reflected light, rather than necessarily the direct timing of the arrival of the reflected light at the sensor in general. Thus, spatial information, that is the identity of the pixel receiving the reflected light during each activation period, can then be correlated with the time-of-flight of the reflected light and, therefore, the distance to the reflecting object. Even more specifically, various examples generate a gating signal that is applied to pixels in a row of the sensor. During periods in which a pixel's gate signal is asserted, each pixel is activated and capable of generating a detection signal. When a pixel's gate signal is deasserted, the photon arrival information is discarded. The distance to the object can then be inferred directly from the pixel or groups of pixels whose detection signal exhibits reflected light arrival greater than a predetermined threshold.We turn here to an exemplary system to orient the reader.

[0033] FIG. 1 illustrates, in block diagram form, an exemplary LIDAR system 100. Specifically, the exemplary LIDAR system 100 includes a LIDAR source 102, a LIDAR sensor 104, and a LIDAR controller 106. The exemplary LIDAR source 102 is designed and constructed to direct interrogation light into a scene in front of the LIDAR source 102. The LIDAR source 102 can be any suitable light source for use in a LIDAR system. In one example, the LIDAR source 102 includes an array of laser diodes, such as an array of vertical-cavity surface-emitting laser (VCSEL) diodes. In some cases, the light generated by the LIDAR source 102 is within the visible spectrum, while in other cases, the light generated is outside the visible spectrum, such as infrared or near-infrared. In one example, the interrogation light used to illuminate the scene can be infrared having a wavelength of 905 nanometers (nm) or 1550 nm. For convenience in the following description, the light produced by the LIDAR source 102 will be referred to below as infrared or interrogating infrared, although it will be understood that any suitable interrogating light may be used. Reference is now made to the LIDAR sensor 104.

[0034] An exemplary LIDAR sensor 104 may include multiple pixels. As described in more detail below, the pixels of the LIDAR sensor 104 may be organized into rows and columns. When properly configured, each pixel is sensitive to the arrival of interrogating infrared radiation that reflects off objects in the scene. The interrogating infrared radiation that reflects off objects in the scene is hereinafter referred to as reflected infrared radiation. Reference is now made to the LIDAR controller 106.

[0035] An exemplary LIDAR controller 106 is coupled to the LIDAR source 102 to control the timing of the generation and emission of interrogating infrared radiation. The LIDAR controller 106 is further coupled to the LIDAR sensor 104 such that the LIDAR controller 106 reads one or more histograms from the LIDAR sensor 104. Based on analysis of the one or more histograms, the LIDAR controller 106 determines a combined time-of-flight of the emitted interrogating infrared radiation and the returning reflected infrared radiation.

[0036] The exemplary LIDAR source 102 illuminates a scene with interrogation infrared radiation. However, for LIDAR systems, the interrogation infrared radiation does not simultaneously illuminate the entire scene. Rather, in the exemplary LIDAR system 100, the LIDAR source 102 selectively illuminates the scene in specific directions and repeatedly illuminates the scene along incrementally varying directions until the entire scene is illuminated in a piecewise manner. Steering of the interrogation infrared radiation may take any suitable form, such as a solid-state LIDAR source 102 that steers the interrogation infrared radiation through selective operation of a phased array source, or a mechanical system in which the interrogation infrared radiation is steered or guided by movable lenses and / or mirrors.

[0037] In one example, the LIDAR source 102 may illuminate a scene using a series of laser “dots” emitted from the LIDAR source 102. For example, the LIDAR source 102 may be designed and constructed to generate a first interrogation infrared ray in the form of a dot 108. That is, the interrogation infrared ray is transmitted in the form of a tight beam of infrared light that intersects with an exemplary object in the scene, shown here as a sphere 110. The interrogation infrared dot 108 reflects back to the LIDAR sensor 104 and is used to determine the distance to the exemplary sphere 110 at the location of the dot 108. A second interrogation infrared ray may be transmitted in the form of a second dot 112, which again reflects back to the LIDAR sensor 104. By sequentially illuminating the scene with the interrogation infrared dots, the location and distance to objects in the scene, such as the exemplary sphere 110, may be determined. Illuminating a scene with interrogation infrared dots may be used when the LIDAR sensor 104 is a single “row” of pixels.

[0038] In other cases, the LIDAR source 102 may illuminate the scene with an interrogation infrared line. For example, the LIDAR source 102 may be designed and constructed to generate a first interrogation infrared light in the form of an infrared line 114. That is, the interrogation infrared light is transmitted in the form of an infrared line that intersects the exemplary sphere 110 at several locations. While the exemplary infrared line 114 is shown as a vertical line, in other cases the line 114 may be a horizontal line, or the line 114 may sweep the exemplary sphere 110 at any suitable angle. The interrogation infrared line 114 reflects back to the LIDAR sensor 104 and is used to determine the distance to objects in the scene at various locations intersected by the line 114. Further interrogation infrared light may then be transmitted in the form of additional lines at locations offset from the line 114. By sequentially illuminating the scene with interrogation infrared lines, the location and distance to the exemplary sphere 110 may be determined. Illuminating the scene with an interrogating infrared line can be used when the LIDAR sensor 104 has multiple rows of pixels.

[0039] FIG. 2 illustrates another example of a LIDAR system 100. The LIDAR system 100 illustrated in FIG. 2 includes an automobile or vehicle 200. While the vehicle 200 is illustratively shown as a passenger car, the LIDAR system 100 may be other types of vehicles, including commercial vehicles, on-road vehicles, and off-road vehicles. Commercial vehicles may include buses and tractor-trailers. Off-road vehicles may include tractors and crop harvesting equipment. In the example of FIG. 2, the vehicle 200 includes a forward-looking LIDAR 202 configured to capture images of a scene in front of the vehicle 200. Such a forward-looking LIDAR 202 may be used for any suitable purpose, such as a collision warning system, a distance-keeping cruise control system, an autonomous driving system, and proximity detection. The vehicle 200 further includes a rear-looking LIDAR 204 configured to capture images of a scene behind the vehicle 200. Such a rear-looking LIDAR 204 may be used for any suitable purpose, such as a collision warning system, an autonomous driving system, proximity detection, monitoring the position of an overtaking vehicle, and reversing. Vehicle 200 further comprises a side-looking camera module 206 configured to capture images of the scene beside vehicle 200. Such a side-looking camera module may be used for any suitable purpose, such as blind spot monitoring, collision warning systems, autonomous driving systems, monitoring the location of overtaking vehicles, lane change detection, and proximity detection. In situations where LIDAR system 100 is a vehicle, LIDAR controller 106 may be the controller of vehicle 200. LIDAR sensor 104 will now be described in more detail.

[0040] FIG. 3 illustrates an exemplary LIDAR sensor 104. Specifically, FIG. 3 illustrates that the LIDAR sensor 104 may include a substrate 300 of a semiconductor material, such as silicon, that is encapsulated in packaging to create a packaged semiconductor device or product. Bond pads or other connection points on the substrate 300 are coupled to terminals of the LIDAR sensor 104. The connections may include a serial communication channel 302 coupled to terminal(s) 304, a capture input 306 coupled to terminal 308, and a phase lock input 310 coupled to terminal 312. Additional terminals, such as ground, common, or power, may be present, but have been omitted to avoid overcomplicating the diagram. While a single instance of the substrate 300 is illustrated, in other cases, multiple substrates may be combined to form the LIDAR sensor 104 in the form of a multi-chip module, produced before or after singulation.

[0041] The exemplary LIDAR sensor 104 includes a pixel array 320 including a plurality of pixels, such as pixels 322 arranged in rows and columns. The pixel array 320 may include, for example, hundreds or thousands of rows and columns of pixels 322. Control and readout of the pixel array 320 may be performed by an image sensor controller 324 coupled to a row controller 326 and a column controller 328. The row controller 326 may receive row addresses from the image sensor controller 324 and provide corresponding row control signals, such as reset, row select, charge transfer, and readout control signals, to the pixels 322. The row control signals may be communicated via one or more conductors, such as row control paths 330.

[0042] The column controller 328 may be coupled to the pixel array 320 by one or more conductors, such as column lines 332. The column controller may be referred to as a column control circuit, a readout circuit, or a column decoder. The column lines 332 may be used to read out a histogram from the pixels 322 and to supply bias currents and / or bias voltages to the pixels 322. If desired, during a readout operation, a row of pixels in the pixel array 320 may be selected using the row controller 326, and a histogram generated by the pixels 322 in that row may be read out along the column lines 332. The column controller 328 may include sample-and-hold circuits for sampling and temporarily storing signals read out from the pixel array 320, amplifier circuits, analog-to-digital conversion (ADC) circuits, bias circuits, column memory, latch circuits for selectively enabling or disabling column circuits, or other circuits coupled to one or more columns of pixels in the pixel array 320 to operate the pixels 322 and read out a histogram from the pixel array 320. An ADC circuit within the column controller 328 may convert analog values ​​received from the pixel array 320 into corresponding digital data. The column controller 328 may provide the histogram data to the image sensor controller 324. The image sensor controller 324 may determine the distance to the reflected object from the histogram data, or the image sensor controller 324 may provide the histogram data over the serial communication channel 302 to the LIDAR controller 106 of FIG. 1 for such determination.

[0043] 3, the exemplary LIDAR sensor 104 includes a gating controller 340. Although the gating controller 340 is shown in FIG. 3 as separate and distinct from the column controller 328, in other cases the functionality of the gating controller 340 may be incorporated within the column controller 328. The exemplary gating controller 340 is coupled to the pixel array 320 and is designed and constructed to gate each pixel 322 of the pixel array 320 so that each pixel 322 is sensitive to reflected infrared light during its respective activation period. Specifically, the gating controller 340 defines a phase lock input 310, and the gating controller 340 is coupled to the pixel array 320 through a gating path 342. Through the phase lock input 310, the gating controller 340 receives a sample signal or timing signal 344 that defines a sample period. The timing signal 344 may take any suitable form, such as a square wave, which defines a sample period as the period of the square wave, or a sinusoid, which defines a sample period as the period of the sinusoid. Through selective placement of the gating signal and in response to the timing signal 344, the gating controller 340 activates the pixels 322 of the pixel array 320 so that each pixel 322 is sensitive to reflected infrared radiation during each activation period. Furthermore, outside of each pixel's respective activation period, the gating controller 340 is designed and constructed to deactivate each pixel so that each pixel is insensitive to reflected infrared radiation. Aspects of gating within each activation period are further described below after an overview of exemplary pixels.

[0044] FIG. 4 shows an electrical schematic of a representative pixel 322. The pixel 322 is merely an example; in practice, a pixel may have fewer components, additional components, or different components in a different configuration than those shown in FIG. 4. Specifically, the exemplary pixel 322 includes a photodetector 400, a shutter transistor 402, a floating diffusion 404, a first memory capacitor 406, and a second memory capacitor 408. The photodetector 400 defines an anode coupled to ground or common and a cathode coupled to the source of the shutter transistor 402. A positive supply voltage (Vdd) is coupled to the drain of the shutter transistor 402. When the gate of the shutter transistor 402 is asserted and the shutter transistor 402 is conductive, the positive supply voltage Vdd is applied to the cathode of the photodetector 400, reverse-biasing the photodetector 400. During the period when the shutter transistor 402 is conductive, the photodetector 400 is effectively insensitive to the arrival of reflected light. More specifically, during the period when the shutter transistor 402 is conductive, any reflected infrared light that strikes the photodetector 400 will generate electrons in the photodetector 400, but the electrons will be immediately drawn out into the positive supply voltage Vdd.

[0045] The exemplary pixel includes a transfer transistor 412. The transfer transistor 412 defines a drain coupled to the floating diffusion 404, a source coupled to the cathode of the photodetector 400, and a gate. During periods when the exemplary pixel 322 is actuated, the shutter transistor 402 is non-conductive and the transfer transistor 412 is conductive, coupling the photodetector 400 to the floating diffusion 404.

[0046] The exemplary pixel 322 includes a reset transistor 414. The reset transistor 414 defines a drain coupled to the positive supply voltage Vdd, a source coupled to the floating diffusion, and a gate. During the period when the exemplary reset transistor 414 is conductive, the voltage on the floating diffusion is reset by pulling up the voltage to the magnitude of the positive supply voltage Vdd. Stated another way, in the exemplary system, the "reset" voltage for the floating diffusion 404 is approximately Vdd.

[0047] To transfer the voltage signal held on the floating diffusion 404, the floating diffusion 404 is coupled to a source follower amplifier in the form of a source follower transistor 416. Specifically, the gate of the source follower transistor 416 is coupled to the floating diffusion 404, the drain is coupled to the positive supply voltage Vdd, and the source is selectively coupled to downstream components via a memory select transistor 418. The drain of the memory select transistor 418 is coupled to the source of the source follower transistor 416, and the source of the memory select transistor 418 defines a memory node 420. Therefore, the signal generated by the photodetector 400 and stored on the floating diffusion 404 can be transferred to the memory node 420 via the source follower transistor 416, the memory select transistor 418, and a precharge transistor 426, which provides a load for the source follower transistor 416. Memory node 420 allows memory capacitors 406 and 408 to sample and hold the voltage driven onto memory node 420 .

[0048] The memory capacitor 406 is selectively coupled to a memory node 420 via a select transistor 422 (selF1 in the figure). Similarly, the memory capacitor 408 is selectively coupled to the memory node 420 via a select transistor 424 (selF2 in the figure). The exemplary pixel 322 further includes a precharge transistor 426. The precharge transistor 426 defines a drain coupled to the memory node 420, a source coupled to ground or common, and a gate. To reset or prepare the memory capacitors 406 and 408 for a sampling operation, the precharge transistor 426 is rendered conductive along with the select transistors 422 and 424. Therefore, the memory capacitors 406 and 408 can be reset to 0 volts or any adjustable voltage.

[0049] 4. To read out the voltages from the memory capacitors 406 and 408, the exemplary pixel 322 further includes another source-follower amplifier in the form of a source-follower transistor 428. The source-follower transistor 428 defines a gate coupled to the memory node 420, a drain coupled to the positive supply voltage Vdd, and a source. The source of the source-follower transistor 428 is coupled to a row select transistor 430 (row_sel in the figure). When the row select transistor 430 is conductive, the column controller 328 can read out the voltages stored on the memory capacitors 406 and 408 individually. That is, the column controller 328 can read out the voltage stored on the memory capacitor 406 by making the select transistor 422 conductive, the select transistor 424 non-conductive, and the row select transistor 424 conductive. Similarly, the column controller 328 can read the voltage stored on the memory capacitor 408 by making the select transistor 422 non-conductive, the select transistor 424 conductive, and the row select transistor 424 conductive.

[0050] Prior to using the pixel array 320 to generate a histogram of reflected infrared radiation arrival, each pixel 322 may be reset. Specifically, resetting a pixel may be accomplished by placing the shutter transistor 402 in a conductive state and the transfer transistor 412 in a non-conductive state. The configuration of the shutter transistor 402 and transfer transistor 412 therefore applies a positive supply voltage Vdd to the cathode of the photodetector 400, and as described above, this configuration makes the pixel 322 insensitive to reflected infrared radiation. That is, by coupling the positive supply voltage Vdd to the cathode of the photodetector 400, electrons generated by infrared radiation incident on the photodetector are swept into the positive supply voltage Vdd. Still considering the reset action, as part of resetting the pixel 322, the reset transistor 414 is temporarily placed in a conductive state, which pulls up the voltage on the floating diffusion 404 to substantially match the voltage of the positive supply voltage Vdd. On the memory capacitor side of the circuit, the memory capacitors 406 and 408 can be reset to 0 or some other adjustable voltage by placing the respective select transistors 422 and 424 in a conductive state and simultaneously placing the precharge transistor 426 in a fully or partially conductive state, which drains the charge stored on the memory capacitors 406 and 408. All of the above reset actions can be performed by any suitable portion of the LIDAR sensor 104, such as the row controller 326.

[0051] In various examples, each pixel 322 is actuated by operation of the gating controller 340 of FIG. 3. Specifically, the gating controller 340 is coupled to the gate of the shutter transistor 402 and the gate of the transfer transistor 412, and the gating controller 340 asserts the gates of the shutter transistor 402 and the transfer transistor 412 in a mutually exclusive manner. When the pixel 322 is in an inactive state, the shutter transistor 402 is in a conductive state and the transfer transistor 412 is in a non-conductive state. However, during a gating period for the pixel 322, the gating controller 340 causes the shutter transistor 402 to be in a non-conductive state and the transfer transistor 412 to be in a conductive state. Therefore, any reflected infrared light that strikes the photodetector 400 during the gating period generates electrons in the photodetector 400. The electrons generated in the photodetector 400 reduce the voltage across the floating diffusion 404. Therefore, a higher voltage at the floating diffusion 404 after the gating period indicates that less reflected infrared light reached the photodetector 400, and a lower voltage at the floating diffusion 404 after the gating period indicates that more reflected infrared light reached the photodetector 400.

[0052] In some cases, a single gating period generates sufficient charge accumulation on the floating diffusion 404. In such cases, the voltage on the floating diffusion 404 can be transferred to one of the memory capacitors 406 or 408, and the floating diffusion 404 can then be reset by temporarily placing the reset transistor 414 in a conductive state. However, in other cases, illumination of a scene with interrogating infrared light along a particular direction can be repeated multiple times, such as 100 times or 1000 times. Each time illumination is repeated along a particular direction, the LIDAR sensor 104 is designed and constructed to actuate the pixel 322 such that the voltage on the floating diffusion 404 is compensated for through second and subsequent actuations. After a predetermined number of iterations, the resultant voltage on the floating diffusion can be transferred to one of the memory capacitors 406 or 408.

[0053] 4, the exemplary pixel 322 with two memory capacitors 406 and 408 allows the LIDAR system 100 to take multiple readings before reading out the voltage. As will become more apparent based on further teachings below, having multiple storage elements within the pixel 322 allows for the use of multiple different gating periods before reading out the result.

[0054] Before proceeding, let's consider a few points. An exemplary LIDAR system 100, including pixels 322 as part of a LIDAR sensor 104, is directed to illuminate a scene with interrogating infrared radiation and receive reflected infrared radiation. The reflected infrared radiation generates an analog value on the floating diffusion 404, and the magnitude of the voltage on the floating diffusion is proportional to the number of photons received during activation. More specifically, the magnitude of the voltage on the floating diffusion 404, which is pulled lower as more photons arrive, is inversely proportional to the number of photons arriving at the photodetector 400 during each activation. Other LIDAR systems may use SPADs or SiPMs for detection in the infrared. SPAD and SiPM detectors are configured for avalanche operation; that is, the photodetector is biased so that it is on the verge of avalanche breakdown in the absence of incident infrared radiation. The bias voltages used to bring the SPADs and SiPMs to the brink of avalanche breakdown are considered high for complementary metal oxide semiconductor (CMOS) devices, with bias voltages of approximately 20 V or greater. Detecting the arrival of reflected infrared light in an avalanche system is achieved by detecting the voltage associated with the avalanche current; therefore, the SPAD photodetector is actively biased during the detection phase. In other words, during detection operations, the SPADs and SiPMs are coupled to a positive supply voltage, Vdd.

[0055] In contrast, in the exemplary pixel 322, during periods when the pixel 322 is in an inactive state, the shutter transistor 402 is conductive and the photodetector 400 is negatively biased by the positive supply voltage Vdd. However, the bias provided by the positive supply voltage Vdd is relatively low, such as 5 V or less, and in some cases 3 V or less. The bias provided by the positive supply voltage Vdd is insufficient for the photodetector 400 to experience avalanche breakdown in the presence of reflected infrared radiation incident on the photodetector 400. Furthermore, during periods when the pixel 322 is activated, the active bias is removed through the non-conducting state of the shutter transistor 402. Any negative bias experienced by the photodetector 400 when the pixel 322 is in an activated state is a bias voltage maintained by the intrinsic capacitance of the photodetector itself. Furthermore, the bias is reduced as reflected infrared radiation impinges on the photodetector 400, thereby generating electrons. In other words, determining the arrival time of the reflected infrared light is based in part on the fact that the amplitude of the voltage on the floating diffusion 404 is proportional to the number of photons incident on the photodetector 400. However, the SPAD / SIPM drowns out the amplitude because even a single photon can cause avalanche breakdown. In other words, the response of the SPAD / SIPM can be the same for a single photon of reflected infrared light and 10,000 photons of reflected infrared light.

[0056] FIG. 5 illustrates an exemplary timing diagram. Specifically, FIG. 5 plots a gating signal 500 used to gate pixels 322 of pixel array 320, a timing signal 344 used to generate gating signal 500, and an analog signal representing reflected infrared radiation 502 incident on pixel array 320. The exemplary timing diagram assumes that each row of pixel array 320 has 12 columns, hence the numbers 1 through 12 on the vertical axis. However, having 12 columns is merely an example for ease of explanation. In reality, each row of pixel array 320 may have many hundreds or thousands of columns.

[0057] For purposes of explanation, consider a timing signal 344 generated by the LIDAR controller 106 and provided to the gating controller 340. An exemplary timing signal 344 is asserted at time T1, deasserted at time T3, and asserted again at time T4. Here, the timing signal is shown as a square wave; however, any timing signal may be used as long as the timing signal defines a period that is the inverse of the frequency. A period of the timing signal 344 is defined as the duration between corresponding features of the timing signal 344. In FIG. 3, the corresponding features may be transitions to an asserted state at times T1 and T4, although any corresponding features may be used, such as transitions to a deasserted state at times T3 and T5.

[0058] Further, although not specifically shown or plotted, consider that the interrogation infrared light is emitted along a particular direction at time T1, again at time T4, and again at time T6. Each burst of interrogation infrared light propagates into the scene, and the interrogation infrared light is reflected by objects within the scene. The reflected infrared light propagates back toward the pixel array 320 of the LIDAR sensor 104. First, consider an interrogation infrared light emitted at time T1. This results in reflected infrared light photons impinging on the pixel array 320 with a first set of peak photon arrivals at time T2. Similarly, a second interrogation infrared light is emitted at time T4, which results in reflected infrared light photons arriving at the pixel array 320 with a second set of peak photon arrivals at time T5. Finally, a third interrogation infrared light is emitted at time T6, which results in reflected infrared light photons arriving at the pixel array 320 with a third set of peak photon arrivals at time T7.

[0059] The arrival of the reflected infrared radiation at times T3, T5, and T7 is merely exemplary. The arrival time of the reflected infrared radiation is directly dependent on the distance between the reflecting object and the LIDAR sensor 104. If the reflecting object is closer to the LIDAR sensor 104, the arrival time will be shifted earlier in time. If the reflecting object is farther away from the LIDAR sensor 104, the arrival time will be shifted later. Therefore, there is no causal relationship between the arrival of the reflected infrared radiation and the transition of the exemplary timing signal 344 to the de-asserted state at times T3, T5, and T7.

[0060] 5, gating signal 500 is generated by gating controller 340 based on timing signal 344. Specifically, gating controller 340 is provided with at least one full period of timing signal 344 prior to time T1. Gating controller 340 extracts a setpoint period from at least one prior period of timing signal 344, and then gating controller 340 generates gating signal 500 based on the setpoint period and state transitions of timing signal 344 during the current period. Gating controller 340 may use any suitable system for extracting the setpoint period and generating gating signal 500, such as a delay-locked loop (DLL) as described in commonly assigned U.S. patent application Ser. No. 18 / 062,920, filed Dec. 7, 2022.

[0061] Reference is made specifically to the gating signal associated with column 1, which is gating signal 504. Specifically, gating controller 340 generates gating signal 504, which is asserted at time T1. While gating signal 504 is shown as being asserted high, any assertion state, such as asserted low, may be used. Gating controller 340 is designed and constructed to deassert gating signal 504 and then assert gating signal 506 associated with column 2. Gating controller 340 is designed and constructed to deassert gating signal 506 and then assert gating signal 508 associated with column 3. The process is repeated for each column within a set value period, culminating with gating controller 340 asserting gating signal 510 associated with column 12. Thus, in the exemplary system, gating signals 500 are asserted sequentially, starting with column 1. However, the starting column does not have to be column 1, and gating can begin at any column, such as the highest numbered column.

[0062] Furthermore, the exemplary gating signals 500 are asserted such that their trigger times or trigger periods do not overlap. Stated another way, in the example of FIG. 5 , the gating signals 500 are asserted mutually exclusively. For example, the asserted time or asserted duration of gating signal 504 does not overlap the asserted time of gating signal 506. In yet a further example, the trigger times of the gating signals may overlap. For example, gating signal 504 may be deasserted after gating signal 506 is asserted. Gating signal 506 may be deasserted after gating signal 508 is asserted, and so on. Having overlapping gating signals has the advantage of smoothing the histogram and using a larger pixel area to gather information. As explained further below, because the goal is to extract peaks from a histogram, peaks can still be extracted from a smoothed histogram. One advantage of overlapping gating signals is that less time is required to collect the signals. In other words, when there is overlap in the gating signals, the information used to determine the peak comes from more than one pixel.

[0063] Therefore, the asserted state of the gating signal 500 represents a respective period during which each pixel is sensitive to the arrival of reflected infrared photons. Conversely, the deasserted state represents a respective period during which each pixel is insensitive to the arrival of reflected infrared photons. That is, while the photodetector within each pixel may occasionally generate electrons in response to reflected infrared photons, when the photodetector's cathode is coupled to the positive supply voltage Vdd, the generated electrons are swept to the positive supply voltage Vdd, and the entire pixel is therefore insensitive to reflected infrared. As described with respect to FIG. 4, configuring a pixel to be sensitive to the arrival of reflected infrared photons requires that the shutter transistor 402 be non-conductive and the transfer transistor 412 be conductive. Therefore, for each pixel 322, there may be additional circuitry to oppositely drive the gates of the shutter transistor 402 and the transfer transistor 412 in response to the pixel's gating signal.

[0064] Further, consider that the timing diagram of Figure 5 represents the transmission of multiple pulses of interrogation infrared light along a single, specific direction. That is, during a first period between times T1 and T4, a first interrogation infrared light is transmitted in a specific direction, and an object in the scene produces a first reflected infrared light centered at time T2. During a second period beginning at time T4, a second interrogation infrared light is transmitted again in a specific direction, and an object in the scene produces a second reflected infrared light centered at time T5. During an Nth period beginning at time T6, an Nth interrogation infrared light is transmitted in a specific direction, and an object in the scene produces an Nth reflected infrared light centered at time T7. The variable N can be any non-zero positive integer, such as 100 or 1000.

[0065] In various examples, the round-trip travel time of the infrared light is not directly timed. Instead, the magnitude of the signal generated by each pixel indicates the arrival of the reflected infrared light, and the identity of pixels having non-trivial signal magnitudes indicates the distance to the reflecting object. For example, the signals generated by pixels in columns 1 through 5 would indicate a relatively small number of photon arrivals during their respective activation periods. In contrast, the signals generated by pixels in columns 6 and 7 would indicate a significantly larger number of photon arrivals during their respective activation periods. The signals generated by pixels in columns 8 through 12 would indicate a small number of photon arrivals during their respective activation periods. Therefore, the distance to the reflecting object may be determined based on the identity of the pixels, such as the column number of each pixel whose signal indicates the arrival of photons with a reflected energy greater than the threshold. In other words, the distance to the reflecting object may be estimated based on the amplitude of the signal of at least one of pixels 322. Therefore, the determination of the arrival time need not be directly timed.

[0066] Many variations exist in the construction of the pixel array 320 and the related operational aspects of generating and reading out histograms. This specification now turns to exemplary operational techniques for various configurations. First, consider a pixel array having only a single “row” of pixels, which defines multiple “columns.” For purposes of explanation, the columns of the single row are assumed to be adjacent and define a “horizontal” row. However, in the case of a LIDAR sensor 104 having only a single row of pixels, the “column” may not define a horizontal row. For example, the “columns” may be arranged in a circle or spiral. Therefore, the terms “row” and “column” should not necessarily be read as defining a physical orientation of the pixels 322 within the pixel array 320.

[0067] Using a pixel array 320 including a single row of pixels 322 can limit the amount of information that can be gleaned from the reflected infrared light. That is, the LIDAR sensor 104 responds to reflected infrared light from anywhere in the scene. Therefore, when using a pixel array 320 including a single row, the interrogation infrared light is a series of laser “dots” emitted from the LIDAR source 102. Thus, when using interrogation infrared light in the form of dots, the reflected infrared light comes only from the locations in the scene illuminated by the dots. To illuminate the entire scene, multiple laser dots can be emitted in different directions to cover the entire scene over time. For example, N dots can be emitted along a first particular direction, then N dots can be emitted along a second direction that is incrementally different from the first direction, and so on, until the entire scene is illuminated with interrogation infrared light.

[0068] Next, consider N dots of interrogation energy being sent in a first particular direction. Each time the interrogation infrared energy is sent in the form of a dot, each pixel 322 is activated for a respective activation period. Reflected infrared light from the illumination location, if present, will be incident on the respective photodetector. Thus, the first pixel in the column will change the voltage on its floating diffusion during each of its activation periods. The second pixel in the column will change the voltage on its floating diffusion during each of its activation periods. In the example of 12 columns, the 12th pixel in the column will change the voltage on its floating diffusion during each of its activation periods. After N dots of interrogation infrared light have been sent along a particular direction, the example LIDAR sensor 104 may transfer the voltage on the floating diffusion 404 of the first pixel to a memory capacitor, such as the memory capacitor 406 in the first pixel, the example LIDAR sensor 104 may transfer the voltage on the floating diffusion of the second pixel to the memory capacitor 406 of the second pixel, and so on, including the example LIDAR sensor 104 may transfer the voltage on the floating diffusion of the twelfth pixel to the memory capacitor 406 of the twelfth pixel.

[0069] After transmitting the N dots of interrogating infrared light and transferring their respective voltages on the floating diffusions to their respective memory capacitors, the voltages stored on the memory capacitors as a group can be thought of as a histogram of photon arrival information. By the column controller 328 reading the voltages stored on the memory capacitors, the column controller 328 and / or the LIDAR controller 106 reads a histogram of arrival data from which the distance to a reflecting object can be determined.

[0070] According to at least some examples, before gradually increasing the direction in which the interrogation energy is emitted, the LIDAR system 100 may repeatedly transmit N dots of interrogation energy along a first direction, but this time with a different setpoint duration defined by the timing signal 344. That is, the LIDAR system 100 does not necessarily know the location of reflective objects in the scene. Some reflective objects may be very close to the LIDAR sensor 104, while others may be far away. Therefore, repeating N dots of interrogation energy with different setpoint durations may therefore "focus" the data for a particular distance. For example, the first N dots may be transmitted with a setpoint duration selected to capture reflected infrared light for any object out to a first predetermined distance. The second, subsequent N dots may be transmitted with a setpoint duration selected to capture reflected infrared light for objects within a second predetermined distance that is closer than the first predetermined distance. The reflected infrared light associated with the second subsequent N dots modifies the respective floating diffusions, and the voltages on the respective floating diffusions can then be transferred to second respective memory capacitors, such as memory capacitor 408. Thus, column controller 328 can now read out multiple histograms for later readout.

[0071] Another reason for repeating the N dots sent along a particular direction is multiple reflections: the interrogating IR beam propagates outward and the reflected IR beam propagates toward the LIDAR sensor 104. However, the reflected IR beam may itself reflect back into the scene, be reflected again by objects in the scene, and then re-enter the pixel array 320. Therefore, having multiple different sample periods used to generate the histogram can be useful to identify and discard multiple reflections, or simply multiples, of the reflected IR beam.

[0072] The transmission of N dots of interrogation infrared light can then be repeated for multiple, incrementally different directions, with each successive series of N dots having its own sample period. The column controller 328 can read out the histogram at any convenient time. If each pixel 322 has two memory capacitors, two sets of N dots can be transmitted, and then the histogram can be read out before transmitting an additional set of N dots along the same or a different particular direction. However, pixels 322 can have any number of memory capacitors, such as three or five, and therefore more than two sets of N dots of interrogation infrared light can be transmitted before being read out.

[0073] We now describe the operation of a pixel array 320 having multiple "rows" and aligned or substantially aligned columns, such as the layout implied in Figure 3. For purposes of explanation, the pixels in each row are assumed to be adjacent and linear, and each column of pixels is assumed to be adjacent and linear. However, neither the rows nor the columns need to be linear or adjacent.

[0074] Using a pixel array 320 with multiple rows and columns increases the amount of information that can be gleaned from the arrival of reflected infrared light compared to a single-row implementation. Thus, when using a pixel array 320 with multiple rows and columns, the interrogating infrared light can be a series of laser “lines” emitted from the LIDAR source 102. Thus, when using interrogating infrared light in the form of laser lines, reflected infrared light will only come from locations within the scene illuminated by the lines. Multiple laser lines can be emitted to illuminate the entire scene. For example, N laser lines can be emitted along a first particular direction, then N laser lines can be emitted along a second direction that is incrementally different from the first direction, and so on, until the entire scene is illuminated with interrogating infrared light.

[0075] Next, consider that N laser lines of interrogation energy are transmitted in a first particular direction. Each time the interrogation infrared light is transmitted in the form of a laser line, the pixels in each column are activated for a respective activation period. For example, all pixels in column 1 may be activated for a first activation period, then all pixels in column 2 may be activated for a second activation period, and so on. Reflected infrared light, if present, from the location of the laser line will be incident on a respective photodetector. Thus, during the first activation period, each pixel in column 1 changes the voltage on its floating diffusion. During the second activation period, each pixel in column 2 changes the voltage on its floating diffusion. In the example of 12 columns, during the twelfth activation period, all pixels in column 12 change the voltage on their floating diffusion. After the N laser lines of interrogation infrared light have been transmitted along a particular direction, the exemplary LIDAR sensor 104 may transfer the respective voltages on the respective floating diffusions to respective memory capacitors, such as memory capacitor 406, in each pixel.

[0076] Therefore, after transmitting N laser lines of interrogating infrared light and transferring the respective voltages on the floating diffusions for each pixel in the column to respective memory capacitors, the voltages stored by the memory capacitors can be thought of as a histogram of photon arrival information. By the column controller 328 reading the voltages stored on the memory capacitors, the column controller 328 and / or the LIDAR controller 106 reads a histogram of arrival data from which the distance to a reflecting object can be determined.

[0077] According to at least some examples, before gradually increasing the direction in which the interrogation energy is emitted, LIDAR system 100 may repeatedly transmit N laser lines of interrogation energy along a first direction, but this time with different setpoint durations defined by timing signal 344. Repeating N laser lines of interrogation infrared light with different setpoint durations may therefore “focus” data for a particular distance. For example, the first N laser lines may be transmitted with a setpoint duration selected to capture reflected infrared light for any object outside up to a first predetermined distance. The second, subsequent N laser lines may be transmitted with a setpoint duration selected to capture reflected infrared light for objects within a second, predetermined distance that is closer than the first predetermined distance. The reflected infrared light associated with the second, subsequent N laser lines modifies the respective floating diffusions, and the voltages of the respective floating diffusions may then be transferred to second respective memory capacitors, such as memory capacitor 408. Therefore, multiple histograms can now be read out by the column controller 328 for later readout.

[0078] The transmission of N laser lines of interrogation infrared light can then be repeated for a number of incrementally different directions, with each series of N laser lines having its own sample period. The column controller 328 can read out the histogram at any convenient time. If each pixel 322 has two memory capacitors, two sets of N laser lines can be transmitted, and then the histogram can be read out before transmitting an additional set of N laser lines along the same or a different particular direction. However, the pixel 322 can have any number of memory capacitors, such as three or five, and therefore more than two sets of N laser lines of interrogation infrared light can be transmitted before being read out.

[0079] FIG. 6 illustrates an exemplary histogram. Specifically, FIG. 6 illustrates a histogram 600 of memory capacitor signal levels (vertical axis) plotted against column number (horizontal axis). Consistent with FIG. 5, the exemplary histogram has 12 columns, but again, in practice, pixel array 320 may have hundreds or thousands of columns. Each column represents a bar graph indicating photon arrivals during the respective activation periods associated with the column. In practice, after reset, the floating diffusion voltage starts at a high voltage, such as the positive supply voltage Vdd. As photons arrive during the activation period(s), electrons generated in response to the photons reduce the voltage at the floating diffusion. Furthermore, the voltage on the floating diffusion is transferred to the memory capacitor without inversion. Thus, in practice, a lower voltage on the floating diffusion and / or memory capacitor indicates a higher number of photons arriving during the respective activation period, and vice versa. However, for ease of understanding, FIG. 6 inverts the levels so that the higher the level within each column, the greater the number of photons that arrived during the activation period of that column.

[0080] Therefore, determining the arrival time of the reflected infrared light is a two-step process. The signal level associated with each column is analyzed. If the signal level indicates a peak, indicating a photon arrival greater than the threshold, then the column identifier indicates the distance to the reflecting object. In this example, the signal levels associated with columns 6 and 7 indicate a photon arrival greater than the threshold. Note that the determination regarding the signal level can be made using a relatively simple analog-to-digital converter (ADC), such as a 2- or 3-bit ADC, or even a comparator. In other words, assuming each sample period is known, identifying the column having a signal level indicating a photon arrival greater than the threshold directly indicates the distance to the reflecting object. In this way, the pixels in each column are effectively depth-sensing pixels.

[0081] 7 shows an exemplary method. Specifically, the method starts (block 700) and includes illuminating a scene along a first direction with a first interrogation infrared ray, where the illuminating produces a first reflected infrared ray, the first reflected infrared ray reflected from a first object disposed in the scene (block 702); activating a plurality of pixels during respective first activation periods such that each pixel of the plurality of pixels is sensitive to the reflected infrared ray (block 704); generating, by each pixel, a first signal proportional to a number of photons of the reflected infrared ray absorbed by the pixel, where the generating produces a plurality of first signals (block 706); and estimating a distance to the object based on the amplitude of at least one of the plurality of first signals (block 708). The method then ends (block 710) and may be restarted for another series of illuminations along an overlapping path or for another series of illuminations along a second path.

[0082] Although many of the electrical connections in the drawings are shown as direct couplings with no intervening devices, and are not explicitly stated as such in the description above, this paragraph shall nevertheless serve as the basis for precedent in the claims to refer to any electrical connection as a "direct coupling" with respect to the electrical connection shown in the drawings without any intervening device(s).

[0083] The foregoing is intended as an exemplification of the principles and various embodiments of this invention. Numerous variations and modifications will be apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.

Claims

1. 1. A light detection and ranging (LIDAR) sensor, comprising: a first plurality of pixels including one or more shutter transistors, one or more photodetectors, one or more transfer transistors, one or more floating diffusions, and one or more memory capacitors; a row controller coupled to the first plurality of pixels, the row controller configured to position the first plurality of pixels for readout; a column controller coupled to the first plurality of pixels, the column controller configured to read out a signal from each pixel of the first plurality of pixels; a gating controller coupled to the first plurality of pixels, the gating controller configured to gate each pixel of the first plurality of pixels such that each pixel is sensitive to reflected infrared light during a respective activation period and is insensitive to reflected infrared light outside of the respective activation period; A LIDAR sensor comprising:

2. 10. The LIDAR sensor of claim 1, wherein the gating controller defines a timing signal input, the gating controller configured to derive a sample period from the timing signal applied to the gating controller and gate each pixel within the sample period.

3. When the gating controller gates each pixel, the gating controller performs the following for each pixel: outside said activation period, causing the corresponding shutter transistor to be conductive, which makes said pixel insensitive to reflected infrared light; During the activation period, a corresponding shutter transistor is made non-conductive and a corresponding transfer transistor is made conductive, thereby allowing electrons generated by the photodetector in response to reflected infrared light to modify the voltage on the floating diffusion.

10. The LIDAR sensor of claim 1, wherein the LIDAR sensor is configured as follows:

4. 4. The LIDAR sensor of claim 3, wherein the row controller is further configured to drive, for each pixel of the plurality of pixels and after the gating controller gates each pixel within a sample period, a voltage onto a corresponding memory capacitor that is proportional to the voltage on the floating diffusion.

5. 2. The LIDAR sensor of claim 1, wherein when the gating controller gates each pixel, the gating controller is configured to gate each pixel such that the actuation periods are mutually exclusive.

6. 2. The LIDAR sensor of claim 1, wherein when the gating controller gates each pixel, the gating controller is configured to gate each pixel such that the actuation periods between two pixels of the plurality of pixels at least partially overlap.

7. a second plurality of pixels including one or more second shutter transistors, one or more second photodetectors, one or more second transfer transistors, one or more second floating diffusions, and one or more second memory capacitors; the row controller is coupled to the second plurality of pixels, the row controller configured to configure the second plurality of pixels for readout; the column controller is coupled to the second plurality of pixels, the column controller being configured to read out a signal generated by the photodetector of each pixel of the second plurality of pixels; 10. The LIDAR sensor of claim 1, further comprising: the gating controller coupled to each pixel of the second plurality of pixels, the gating controller configured to gate each pixel of the second plurality of pixels such that each pixel of the second plurality of pixels is sensitive to reflected infrared radiation during a respective activation period and is insensitive to reflected infrared radiation outside of the respective activation period.

8. a LIDAR controller; and a LIDAR source coupled to the LIDAR controller, the LIDAR source configured to transmit an interrogation light into a scene in response to commands from the LIDAR controller; A LIDAR sensor according to any one of claims 1 to 7; 1. A light detection and ranging (LIDAR) system comprising:

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