Hardware Implementation of Sensor Architecture with Multiple Power States

Abstract

In one specific implementation, an event sensor includes a plurality of pixels and an event compiler. The plurality of pixels are positioned to receive light from a scene disposed within a field of view of the event sensor. Each pixel is configured to have an operating state modified by a control signal generated by a corresponding state circuit. The event compiler is configured to output a stream of pixel events. Each corresponding pixel event corresponds to a breach of a comparator threshold associated with incident illumination intensity. Each control signal is generated based on feedback information received from an image pipeline configured to consume image data derived from the stream of pixel events.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is related to international application PCT / US2020 / 023750, entitled “SENSOR SYSTEM ARCHITECTURE WITH FEEDBACK LOOP AND MULTIPLE POWER STATES”, filed on March 20, 2020, the entire text of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to the field of image processing, and in particular, to techniques for implementing a sensor having a hardware architecture configured to support enabled, standby, and non-enabled operating states. Background Art

[0004] An event camera may include an image sensor known as a dynamic vision sensor ("DVS"), a silicon retina, an event-based sensor, or a frameless sensor. Thus, an event camera generates (and transmits) data regarding changes in light intensity at each pixel sensor, whereas a frame-based camera outputs data regarding the absolute light intensity at each pixel. In other words, while the illumination level of a scene disposed within the field of view remains stable, a frame-based camera will continue to generate (and transmit) data regarding the absolute light intensity at each pixel, whereas an event camera will refrain from generating or transmitting data until a change in illumination level is detected.

[0005] Some image processing operations utilize incomplete image data sets derived from pixel events output by event-driven sensors. Such image processing operations can improve computational efficiency by cropping image data, and processing the cropped image data to save power, etc. However, pixels of the event-driven sensor corresponding to image data outside the cropped image data continue to operate and, therefore, continue to consume power. Therefore, it is desirable to address this inefficiency problem that occurs when image processing operations utilize incomplete image data sets derived from pixel events output by event-driven sensors. Summary of the invention

[0006] Various specific implementations disclosed herein relate to a technology for implementing an event-driven sensor having a hardware architecture that is configured to support enabled, standby, and non-enabled operating states. A plurality of pixels are positioned to receive light from a scene disposed within a field of view of an event sensor. Each pixel is configured to have an operating state modified by a control signal generated by a corresponding state circuit. An event compiler is configured to output a stream of pixel events. Each corresponding pixel event corresponds to a breakthrough of a comparator threshold associated with incident illumination intensity. Each control signal is generated based on feedback information received from an image pipeline that is configured to consume image data derived from the stream of pixel events.

[0007] In another specific implementation, a pixel includes a photodetector circuit, an event circuit, and a state circuit. The photodetector circuit is configured to generate pixel data indicating incident illumination intensity. The event circuit is configured to generate the event data when the pixel data indicates that the photodetector circuit has detected a change in light intensity that exceeds a comparator threshold. The state circuit is configured to transition the pixel between an enabled state and a standby state based on feedback information generated by an image pipeline that consumes image data derived using the event data.

[0008] In another specific implementation, a pixel includes a photodetector circuit, an event circuit, and a state circuit. The photodetector circuit is configured to generate pixel data indicating incident illumination intensity. The event circuit is configured to generate the event data when the pixel data indicates that the photodetector circuit has detected a change in light intensity that has breached a comparator threshold. The state circuit is configured to generate a control signal that modifies an operational state of the pixel based on feedback information generated by an image pipeline that consumes image data derived using the event data. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the present disclosure may be understood by those of ordinary skill in the art, a more detailed description may be obtained with reference to aspects of some exemplary implementations, some of which are illustrated in the accompanying drawings.

[0010] Figure 1 A functional block diagram of an event sensor according to some implementations is shown.

[0011] Figure 2 is a block diagram of an exemplary system for implementing an event-driven sensor with a hardware architecture configured to support enabled, standby, and non-enabled operating states.

[0012] Figure 3 An example of a complete image data set derived by an image pipeline from pixel events output by an event sensor is shown.

[0013] Figure 4An example of cropped image data derived by an image pipeline from pixel events output by an event sensor is shown.

[0014] Figure 5 An example of different pixels within a pixel array of an event sensor having different operating states based on feedback information received from an image pipeline is shown.

[0015] Figure 6 An example of a pixel array having different pixels having different operating states is shown, with the operating states of some pixels being modified as feedback information received from an image pipeline is updated between a first time and a second time.

[0016] Figure 7 Shows Figure 6 A subset of pixels within a pixel array is configured to transition from one operating state to another operating state as feedback information received from an image pipeline is updated between a first time and a second time.

[0017] Figure 8 is a circuit diagram of an exemplary pixel having a hardware architecture configured to support enabled and standby operating states.

[0018] Fig. 9 is a circuit diagram of an exemplary pixel having a hardware architecture configured to support enabled, standby, and non-enabled operating states.

[0019] As is common practice, the various features shown in the drawings may not be drawn to scale. Therefore, the sizes of the various features may be arbitrarily expanded or reduced for clarity. In addition, some drawings may not depict all components of a given system, method, or device. Finally, throughout the specification and drawings, similar reference numerals may be used to represent similar features. DETAILED DESCRIPTION

[0020] Many details are described in order to provide a thorough understanding of the example implementations shown in the accompanying drawings. However, the accompanying drawings only illustrate some example aspects of the present disclosure and should not be considered limiting. One of ordinary skill in the art will appreciate that other effective aspects or variations do not include all of the specific details described herein. In addition, well-known systems, methods, components, devices, and circuits are not described in detail in order to avoid obscuring more relevant aspects of the exemplary implementations described herein.

[0021] A functional block diagram of an exemplary event sensor 100 is shown by Figure 1 The event sensor 100 includes a plurality of pixels 105 positioned to receive light from a scene disposed within a field of view of the event sensor 100. Figure 1In the embodiment of the present invention, the plurality of pixels 105 are arranged in a matrix 107 of rows and columns, and thus, each pixel of the plurality of pixels 105 is associated with a row value and a column value. Each pixel of the plurality of pixels 105 includes a photodetector circuit 110 and an event circuit 180.

[0022] The photodetector circuit 110 is configured to generate a signal indicative of the intensity of light ("incident illumination") incident on the corresponding pixel 105. To this end, the photodetector circuit 110 includes a photodiode 112 configured to generate a photocurrent proportional to the intensity of the incident illumination. The photocurrent generated by the photodiode 112 flows into a logarithmic amplifier 120 formed by transistors 121, 123, 125 and 127. The logarithmic amplifier 120 is configured to convert the photocurrent into a voltage at node A, the value of which is the logarithm of the photocurrent value. The voltage at node A is then amplified by a buffer amplifier 130 formed by transistors 131 and 133 before being applied to the input side of the differential circuit 140 of the event circuit 180.

[0023] The pixel 105 also includes an event circuit 180, which includes a differential circuit 140, a comparator 160, and a controller 170. The differential circuit 140 is composed of an alternating current ("AC") coupling capacitor 145 and a switched capacitor amplifier 150. The differential circuit 140 is configured to remove a direct current ("DC") voltage component from the voltage at node A to produce pixel data at a sampling node B. By removing the DC voltage component from the voltage at node A, the pixel data at the sampling node B provides a differential value of the incident illumination intensity detected by the photodiode 112. The gain provided by the amplifier 151 corresponds to a ratio defined by the respective capacitance values ​​of the AC coupling capacitor 145 and the capacitor 153. When a reset signal is received from the controller 170, the reset switch 155 is activated (i.e., transitioned from an open state to a closed state). By activating the reset switch 155, the operating point of the amplifier 151 is reset to a reference voltage associated with the threshold of the comparator 160.

[0024] Comparator 160 is configured to provide pixel-level processing of pixel data received from sample node B. To this end, when the pixel data received from sample node B indicates that photodiode 112 detects a change in incident illumination intensity that breaks through a threshold, comparator 160 outputs an electrical response (e.g., a voltage). Alternatively, when the pixel data received from sample node B indicates that photodiode 112 does not detect a change in incident illumination intensity that breaks through a threshold, comparator 160 refrains from outputting the electrical response.

[0025] In one implementation, comparator 160 is implemented using a plurality of comparators including a first comparator configured to output an electrical response indicative of a positive event (e.g., an event having a positive polarity) and a second comparator configured to output an electrical response indicative of a negative event (e.g., an event having a negative polarity). In one implementation, the first comparator outputs an electrical response when the pixel data received from sample node B indicates that photodiode 112 detects a change in incident illumination intensity that breaks through a positive threshold. In one implementation, the second comparator outputs an electrical response when the pixel data received from sample node B indicates that photodiode 112 detects a change in incident illumination intensity that breaks through a negative threshold.

[0026] The controller 170 is configured to cooperate with other components of the event sensor 100 (e.g., controllers within other pixels) to transmit an event signal (e.g., a sample of event data) to the event compiler 190 for each electrical response output by the comparator 160. In one specific implementation, the reset switch 155 receives a reset signal from the controller 170 each time the comparator 160 obtains pixel data that exceeds the threshold at the sampling node B.

[0027] The event compiler 190 receives an event signal (e.g., a sample of event data) from each pixel in the plurality of pixels 105 that each indicates that a change in incident illumination intensity has broken through a threshold. In response to receiving a sample of event data from a particular pixel in the plurality of pixels 105, the event compiler 190 generates a pixel event. In addition, the event compiler 190 populates the pixel event with information indicating an electrical response included in the event signal (e.g., a value and / or polarity of the electrical response). In one specific implementation, the event compiler 190 also populates the pixel event with one or more of: timestamp information corresponding to a point in time when the pixel event was generated and an address identifier corresponding to a particular pixel that sent an event signal that triggered the pixel event. The pixel event stream including each pixel event generated by the event compiler 190 can then be transmitted to an image pipeline (e.g., an image or video processing circuit) (not shown) associated with the event sensor 100 for further processing.

[0028] By way of example, the pixel event streams generated by the event compiler 190 may be accumulated or otherwise combined to produce image data. In some implementations, the pixel event streams are combined to provide an intensity reconstruction image. In this implementation, an intensity reconstruction image generator (not shown) may accumulate pixel events over time to reconstruct / estimate absolute intensity values. As additional pixel events accumulate, the intensity reconstruction image generator changes the corresponding values ​​in the reconstructed image. In this way, it generates and maintains an updated image of values ​​for all pixels of the image, even though only some pixels may have recently received events.

[0029] In various implementations, event-driven sensors are implemented using a hardware architecture configured to support enabled, standby, and operational states. Generally, this involves the event sensor 210 outputting pixel events to the image pipeline 220 and, in response, receiving feedback information from the image pipeline 220, such as Figure 2 The image pipeline 220 is configured to consume image data derived from pixel events output by the event sensor 210. To this end, the image pipeline 220 includes one or more components, such as those described above with reference to Figure 1 The intensity reconstruction image generator discussed above is used to derive image data from pixel events. One or more components of the image pipeline 220 may be implemented using various combinations of hardware components (e.g., application specific integrated circuits, digital signal processors, etc.) and software components (e.g., noise reduction processes, image scaling processes, color space conversion processes, etc.).

[0030] In various implementations, the image pipeline 220 implements some functionality that utilizes an incomplete image data set derived from pixel events output by the event sensor 210. By way of example, the image pipeline 220 may also include a feature tracker configured to detect features depicted in image data derived from pixel events (e.g., using techniques such as SIFT, KAZE, etc.) and track the features over time (e.g., using techniques such as Kanade-Lucas-Tomasi tracker, Shi-Tomasi tracker, etc.). In this example, the feature tracker of the image pipeline 220 may implement eye tracking functionality by detecting and tracking gaze characteristics (e.g., pupil center, pupil outline, glint position, gaze direction, etc.) using image data depicting the user's eyes derived from pixel events output by the event sensor 210.

[0031] Figure 3 An example of a full image dataset 300 is shown depicting an eye of a user that the image pipeline 220 may derive from pixel events output by the event sensor 210. To implement the eye tracking functionality, a feature tracker of the image pipeline 220 has used a subset of the image data 300 that resides in the region of interest 320 to estimate the location of the pupil center (“estimated pupil center”) 310 within the eye. Processing the full image dataset 300 to implement the eye tracking functionality may be computationally intensive for the feature tracker of the image pipeline 220 and consume excessive power and computing resources. To improve computational efficiency and reduce power consumption, the feature tracker of the image pipeline 220 may process a subset of the image data that resides in the region of interest 320. The image data that resides outside the region of interest 320 may be cropped to form cropped image data 400, as shown. Figure 4 shown.

[0032] One technique for cropping image data residing outside of the region of interest 320 may be implemented using the image pipeline 220. According to the technique, the image pipeline 220 may receive pixel events corresponding to the field of view of the event sensor 210. To form the cropped image data 400, the image pipeline 220 may ignore pixel events corresponding to image data residing outside of the region of interest 320, or crop image data residing outside of the region of interest 320 after the full image data set 300 is derived. However, in either case, the event sensor 210 includes a subset of pixels that generate pixel events corresponding to image data residing outside of the region of interest 320, which continue to consume power. In addition, the pixel events corresponding to image data residing outside of the region of interest 320 continue to consume bandwidth of the communication path between the event sensor 210 and the image pipeline 220. Therefore, implementing a technique for cropping image data residing outside of the region of interest 320 involving the event sensor 210 may further reduce power and bandwidth consumption.

[0033] To this end, the image pipeline 220 transmits feedback information to the event sensor 210, such as Figure 2 As shown. In various embodiments, such feedback information represents a feedback loop between an event sensor (e.g., event sensor 210) and an image pipeline (e.g., image pipeline 220). As discussed in more detail below, the image pipeline consumes image data derived from pixel events output by the event sensor. Based on the image data, the image pipeline generates feedback information corresponding to a subset of the image data (e.g., a region of interest), which feedback information may be more useful for a particular image processing operation than for other portions of the image data. That is, the feedback information corresponds to a subset of the image data on which processing is performed for a particular image processing operation. In response to the feedback information, the operating state of each pixel within the pixel array of the event sensor can be modified accordingly. Specifically, different pixels within the pixel array of the event sensor can have different operating states based on the feedback information received from the image pipeline.

[0034] Figure 5 An example of a pixel array 500 of an event sensor is shown, wherein the pixels are configured to support different operating states. The pixel array 500 includes a plurality of pixels positioned to receive light from a scene disposed within a field of view of the event sensor. Thus, when the operating state of each of the plurality of pixels is an enabled state, image data derived from pixel events output by the event sensor typically depicts the field of view of the event sensor. As used herein, an "enabled state" refers to an operating state of a pixel in which the photodetector circuit and event circuit of the pixel are each activated (or fully functional).

[0035] When the event sensor receives feedback information from the image pipeline that an incomplete image data set is being processed by a specific image processing operation, some pixels of the event sensor can be transitioned from an enabled state to another operating state. For example, some pixels of the event sensor can be transitioned to a non-enabled state. As used herein, a "non-enabled state" refers to an operating state of a pixel in which the pixel is not fully functional. In one specific implementation, the photodetector circuit and the event circuit of the pixel in the non-enabled state are each deactivated (or non-functional).

[0036] In some cases, pixels of an event sensor may not be able to immediately transition from a non-enabled state to an enabled state. To mitigate such delay issues, some pixels of the event sensor may transition from an enabled state to a standby state. As used herein, a "standby state" refers to an operating state of a pixel in which the pixel is not fully functional but is more functional than a pixel in a non-enabled state. In one specific implementation, the event circuit of a pixel is deactivated (or non-functional) when the pixel transitions to the standby state, while the photodetector circuit of the pixel is activated (or fully functional).

[0037] By way of example, an image pipeline can be based on Figure 3 In response to the feedback information, a first subset of pixels in region 520 of pixel array 500 is in an enabled state, a second subset of pixels in region 510 is in a standby state, and a third subset of pixels outside regions 510 and 520 is in a non-enabled state. In this example, the first subset of pixels in region 520 may be in a state corresponding to the image data 300. Figure 3 and Figure 4 The pixel events of the region of interest 320 are associated.

[0038] In one specific implementation, the feedback information includes parameters defining the location of one or more regions within pixel array 500. For example, the parameters defining the location of region 510 may include an offset value specified relative to a boundary of pixel array 500, such as x-offset 512, y-offset 514, or a combination thereof. For another example, the parameters defining the location of region 520 may include an offset value specified relative to a boundary of pixel array 500, such as some combination of x-offset 512, x-offset 522, y-offset 514, and y-offset 524.

[0039] In one implementation, one or more regions of pixel array 500 have predefined dimensions. For example, region 510 may have predefined dimensions specified as width 516 and height 518. As another example, region 520 may have predefined dimensions specified as width 526 and height 528. In one implementation, the feedback information includes parameters defining the dimensions of one or more regions within pixel array 500. For example, the parameters of the feedback information may define one or more of width 516, width 526, height 518, and height 528.

[0040] In one implementation, the feedback information may include a bit mask encoding the target operating state for each individual pixel. For example, the bit mask may represent a circular region of pixels in an enabled state, while pixels outside the circular region (e.g., including the remaining pixels of the event sensor) are in a ready or non-enabled state. It will be appreciated by those skilled in the art that the bit mask mask may represent any arbitrarily shaped region or group of regions in the event sensor that is in one of the disclosed operating states, where the smallest size of such region is any individual pixel.

[0041] Figure 6 An example of a pixel array 600 of an event sensor having different pixels having different operating states, where the operating states of some of the pixels are modified as feedback information received from an image pipeline is updated between a first time and a second time. At the first time, the image pipeline may generate feedback information based on image data derived from pixel events output by the event sensor. In response to receiving the feedback information generated by the image pipeline at the first time, a first subset of pixels within a region 620A of the pixel array 600 is in an enabled state, a second subset of pixels within a region 610A is in a standby state, and a third subset of pixels outside of regions 610A and 620A is in a non-enabled state.

[0042] After the first time, the image pipeline may receive additional pixel events from the event sensor that change the image data being processed by the image pipeline. For example, a feature of interest (e.g., Figure 3 The position of the pupil center 310 of the pixel array 600 within the image data may change as the image data is updated by the additional pixel event. At a second time, the image pipeline may generate feedback information that describes the change in the image data caused by the additional pixel event. In response to receiving the feedback information generated by the image pipeline at the second time, a first subset of pixels within region 620B of the pixel array 600 is in an enabled state, a second subset of pixels within region 610B is in a standby state, and a third subset of pixels outside of regions 610B and 620B is in a non-enabled state.

[0043] Between the first time and the second time, some pixels within pixel array 600 transition from one operating state to another operating state in response to feedback information received from the image pipeline. Figure 7 As shown, the pixels in the sub-region 710 that were in the standby state at the first time will be changed to the non-enabled state at the second time. The pixels in the sub-region 720 of the pixel array 600 that were in the enabled state at the first time will be changed to the standby state at the second time. Similarly, the pixels in the sub-region 730 that were in the standby state at the first time will be changed to the enabled state at the second time, and the pixels in the sub-region 740 that were in the non-enabled state at the first time will be changed to the standby state at the second time.

[0044] Figure 8 is a circuit diagram of an exemplary pixel 805 having a hardware architecture configured to support enabled and standby operating states. Figure 1 105, pixel 805 includes a photodetector circuit 110 configured to generate pixel data indicating incident illumination intensity and an event circuit 820 configured to generate event data when the pixel data indicates that the photodetector circuit 110 detects a change in light intensity that exceeds a comparator threshold of the comparator 160. Unlike pixel 105, pixel 805 also includes a state circuit 810 configured to generate a control signal that modifies the operating state of pixel 805 based on feedback information generated by the image pipeline.

[0045] Among the control signals, the state circuit 810 generates a first control signal ("LP"). In one implementation, the state circuit 810 generates the first control signal by performing a logical "OR" operation 812 on a signal received from an associated row controller ("LP_row") or a signal received from an associated column controller ("LP_col"). In one implementation, the state circuit 810 generates the first control signal based on one or more signals received from: an associated row controller, an associated column controller, or a combination thereof.

[0046] In operation, the first control signal is activated when the operating state of the pixel 805 is changed to the standby state. Activating the first control signal minimizes the bias current of the amplifier 151 within the switched capacitor amplifier 150. In one embodiment, minimizing the bias current of the amplifier 151 maintains the virtual ground for the AC coupling capacitor 145 within a target error tolerance (e.g., + / -5%). In one embodiment, the bias current of the amplifier 151 is returned to a "normal" value (e.g., a value corresponding to the bias current of the amplifier 151 when the operating state of the pixel 805 is the enabled state) before the pixel 805 completes the transition from the standby state to the enabled state. In one embodiment, the bias current is returned to the normal value before deactivating the first control signal. By returning the bias current of the amplifier 151 before completing the transition from the standby state to the enabled state, the virtual ground for the AC coupling capacitor can recover the error accumulated when the pixel 805 is in the standby state. Returning the bias current of the amplifier 151 before completing the transition can also prevent false triggering of the comparator 160.

[0047] Another control signal generated by the state circuit 810 is a second control signal ("PD1"). In one implementation, the state circuit 810 generates the second control signal by performing a logical "OR" operation 814 on a signal received from an associated row controller ("PD1_row") or a signal received from an associated column controller ("PD1_col"). In one implementation, the state circuit 810 generates the second control signal based on one or more signals received from: an associated row controller, an associated column controller, or a combination thereof.

[0048] In operation, the second control signal is activated when the operating state of the pixel 805 is changed to the standby state. Activating the second control signal deactivates the comparator 160, the controller 170, or a combination thereof within the event circuit 820. In one specific implementation, deactivating the controller 170 also bypasses the capacitor 153 of the switched capacitor amplifier 150. In one specific implementation, the second control signal of the deactivating controller 170 is also passed to the first input 832 of the logical "OR" operation 830. When the second control signal is passed to the first input 832 of the logical "OR" operation 830, the reset switch 155 receives the reset signal from the logical "OR" operation 830. In bypassing the capacitor 153 when the controller 170 is deactivated, the AC coupling capacitor 145 can continue to track changes in the incident illumination intensity detected by the photodetector circuit 110 when the pixel 805 is in the standby state. In other words, the AC coupling capacitor 145 is configured to track background changes in light intensity when the second control signal activates the reset switch 155.

[0049] In one implementation, when the operational state of the pixel 805 is the enabled state, the second input terminal 831 of the logical OR operation 830 receives a signal from the controller 170. In one implementation, the controller 170 is configured to output a signal to the second input terminal 831 of the logical OR operation 830 when the comparator 160 receives pixel data from the sample node B indicating that the photodiode 112 detected that the incident illumination intensity change exceeded the threshold when the pixel 805 was in the enabled state.

[0050] Fig. 9 is a circuit diagram of an exemplary pixel 905 having a hardware architecture configured to support enabled, standby, and non-enabled operating states. Similar to pixel 805, pixel 905 includes a state circuit 910 configured to generate a control signal that modifies the operating state of pixel 905 based on feedback information generated by the image pipeline. Similar to state circuit 810 of pixel 805, state circuit 910 also generates a first control signal (“LP”) and a second control signal (“PD1”).

[0051] In one implementation, generating the first control signal by the state circuit 910 includes performing a logical OR operation 918 on a signal received from an associated row controller (“LP_row”) or a signal received from an associated column controller (“LP_col”). In one implementation, activating the first control signal minimizes a bias current of amplifier 151 within switched capacitor amplifier 150. In one implementation, the state circuit 910 generates the first control signal based on one or more signals received from: an associated row controller, an associated column controller, or a combination thereof.

[0052] In one implementation, generating the second control signal by the state circuit 910 includes performing a logic OR operation 912 on a signal received from an associated row controller ("PD1_row") or a signal received from an associated column controller ("PD1_col"). In one implementation, generating the second control signal by the state circuit 910 includes performing a logic OR operation 916 on an output signal received from the logic OR operation 912 or an output signal received from the logic OR operation 914. In one implementation, the state circuit 910 generates the second control signal based on one or more signals received from: an associated row controller, an associated column controller, or a combination thereof.

[0053] In pixel 905, controller 170 is deactivated when the second control signal is activated. In one implementation, as in pixel 805, deactivating controller 170 in pixel 905 also bypasses capacitor 153 of switched capacitor amplifier 150. When the second control signal deactivating controller 170 is also passed to first input 942 of logical OR operation 940, capacitor 153 is bypassed in pixel 905. When the second control signal is passed to first input 942 of logical OR operation 940, reset switch 155 receives a reset signal from logical OR operation 940.

[0054] In one implementation, when the operational state of the pixel 905 is the enabled state, the second input terminal 941 of the logic “OR” operation 940 receives a signal from the controller 170. In one implementation, the controller 170 is configured to output a signal to the second input terminal 941 of the logic “OR” operation 940 when the comparator 160 receives pixel data from the sample node B indicating that the photodiode 112 detected a change in incident illumination intensity that broke through a threshold when the pixel 905 was in the enabled state.

[0055] Another control signal generated by the state circuit 910 is a third control signal ("PD2"). In one implementation, the state circuit 910 generates the third control signal by performing a logical "OR" operation 914 on a signal received from an associated row controller ("PD2_row") or a signal received from an associated column controller ("PD2_col"). In one implementation, the state circuit 910 generates the third control signal based on one or more signals received from: an associated row controller, an associated column controller, or a combination thereof.

[0056] In operation, the third control signal is activated when the operating state of the pixel 905 is changed to the non-enabled state. Activating the third control signal causes at least a subset of the photodetector circuit 920 to be deactivated by deactivating the logarithmic amplifier 120 by activating the first power-down switch 922 and deactivating one or more of the buffer amplifiers 130 by activating the second power-down switch 924. In one specific implementation, activating the third control signal deactivates the switched capacitor amplifier 150 by minimizing the bias current of the amplifier 151.

[0057] The use of "suitable for" or "configured to" herein is meant to be open and inclusive language that does not exclude devices that are suitable for or configured to perform additional tasks or steps. In addition, the use of "based on" is meant to be open and inclusive, as a process, step, calculation, or other action "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated. The headings, lists, and numbers included herein are for ease of explanation only and are not intended to be limiting.

[0058] It will also be understood that, although the terms "first", "second", etc. may be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first node may be referred to as a second node, and similarly, a second node may be referred to as a first node, which changes the meaning of the description, as long as all occurrences of the "first node" are consistently renamed and all occurrences of the "second node" are consistently renamed. Both the first node and the second node are nodes, but they are not the same node.

[0059] The terms used herein are only for describing specific implementations and are not intended to limit the claims. As used in the description of this specific implementation and the appended claims, the singular forms of "a" and "the" are intended to also cover the plural forms, unless the context clearly indicates otherwise. It will also be understood that the term "or" used herein refers to and covers any and all possible combinations of one or more items in the associated listed items. It will also be understood that the term "comprising" when used in this specification specifies the presence of stated features, integers, steps, operations, elements or parts, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts or their groupings.

[0060] As used herein, the term “if” may be interpreted to mean “when the antecedent is true” or “when the antecedent is true” or “in response to determining” or “upon determining” or “in response to detecting” that the antecedent is true, depending on the context. Similarly, the phrase “if it is determined that [the antecedent is true]” or “if [the antecedent is true]” or “when [the antecedent is true]” is interpreted to mean “upon determining that the antecedent is true” or “in response to determining” or “upon determining” that the antecedent is true or “when detecting that the antecedent is true” or “in response to detecting” that the antecedent is true, depending on the context.

[0061] The foregoing description and summary of the present invention should be understood to be illustrative and exemplary in every aspect, rather than restrictive, and the scope of the present invention disclosed herein is determined not only by the detailed description of the exemplary specific implementations, but by the full breadth allowed by the patent law. It should be understood that the specific implementations shown and described herein are only illustrative of the principles of the present invention, and that various modifications can be implemented by those skilled in the art without departing from the scope and essence of the present invention.

Claims

1. An event sensor, comprising: a plurality of pixels positioned to receive light from a scene disposed within a field of view of the event sensor, each pixel being configured to have an operational state modified by a control signal generated by a corresponding state circuit to be an enabled state, a standby state, or a non-enabled state, wherein, in the enabled state, both the photodetector circuit and the event circuit of the pixel are activated, In the standby state, one of the photodetector circuit and the event circuit is deactivated, and the other of the photodetector circuit and the event circuit is activated, In the non-enabled state, both the photodetector circuit and the event circuit are deactivated, and wherein, based on the control signal, pixels of the plurality of pixels in a first area are in the enabled state, and pixels of the plurality of pixels in a second area around the first area are in the standby state, and wherein the operating state is capable of transitioning from the standby state to the enabled state and the non-enabled state; and an event compiler configured to output a stream of pixel events, each respective pixel event corresponding to a breach of a comparator threshold associated with incident illumination intensity, Each control signal is generated based on feedback information received from an image pipeline configured to consume image data derived from the pixel event stream. 2 . The event sensor according to claim 1 , wherein each pixel includes the event circuit, and the event circuit is deactivated when the operation state is changed to the standby state or the non-enabled state. 3 . The event sensor of claim 1 , wherein the event circuit comprises a differential circuit, a comparator, a controller, or a combination thereof. 4 . The event sensor of claim 1 , wherein each pixel includes the photodetector circuit, the photodetector circuit being deactivated when the operating state transitions to the non-enabled state. 5 . The event sensor of claim 1 , wherein the photodetector circuit comprises a photodiode, a logarithmic amplifier, a buffer amplifier, or a combination thereof.

6. The event sensor of claim 1, wherein each state circuit generates the control signal based on a signal received from: an associated column controller, an associated row controller, or a combination thereof.

7. The event sensor of claim 1, wherein the feedback information corresponds to a region of interest tracked by a processing unit within the image data. 8 . The event sensor of claim 1 , wherein the control signal comprises a first control signal configured to deactivate a corresponding controller coupling a particular pixel to the event compiler.

9. The event sensor of claim 1, wherein the control signal comprises a second control signal configured to deactivate a corresponding photodetector circuit and a switched capacitor amplifier within a particular pixel. 10 . The event sensor of claim 1 , wherein the feedback information corresponds to a bit mask that encodes a target operating state for each pixel in the plurality of pixels.

11. A pixel comprising: a photodetector circuit configured to generate pixel data indicative of incident illumination intensity; an event circuit configured to generate event data when the pixel data indicates that the photodetector circuit detected a change in light intensity that exceeded a comparator threshold; and a state circuit configured to transition the pixel between an enabled state, a non-enabled state, and a standby state based on feedback information generated by an image pipeline that consumes image data derived using the event data, wherein, in the enabled state, both the photodetector circuit and the event circuit are activated, In the standby state, one of the photodetector circuit and the event circuit is deactivated, and the other of the photodetector circuit and the event circuit is activated, In the non-enabled state, both the photodetector circuit and the event circuit are deactivated, and wherein the pixel is one of a plurality of pixels of an event sensor, each of the plurality of pixels being configured to have an operating state modified by a control signal, wherein, based on the control signal, pixels of the plurality of pixels in a first area are in the enabled state, and pixels of the plurality of pixels in a second area surrounding the first area are in the standby state, and wherein the operating state is capable of transitioning from the standby state to the enabled state and the non-enabled state.

12. The pixel of claim 11, wherein the event circuit is deactivated while the photodetector circuit remains operational when the pixel transitions from the enabled state to the standby state.

13. The pixel of claim 11, wherein the event circuit comprises a differential circuit having a switched capacitor amplifier, and wherein a bias current of the switched capacitor amplifier is minimized when the pixel transitions from the enabled state to the standby state.

14. The pixel of claim 13, wherein a virtual ground for a capacitor interposed between the photodetector circuit and the switched capacitor amplifier is maintained within a target error tolerance when the bias current is minimized.

15. The pixel of claim 13, wherein the bias current is returned to a nominal value before the pixel completes a transition between the standby state and the enabled state.

16. The pixel of claim 13, wherein a controller that deactivates the event circuit also bypasses a feedback capacitor of the switched capacitor amplifier when the pixel transitions from the enabled state to the standby state.

17. A pixel comprising: a photodetector circuit configured to generate pixel data indicative of incident illumination intensity; an event circuit configured to generate event data when the pixel data indicates that the photodetector circuit detected a change in light intensity that breached a comparator threshold; and a state circuit configured to generate a control signal that modifies an operational state of the pixel based on feedback information generated by an image pipeline that consumes image data derived using the event data, wherein the control signal transitions the operational state of the pixel to an enabled state, a standby state, or a non-enabled state, wherein, in the enabled state, both the photodetector circuit and the event circuit are activated; In the standby state, one of the photodetector circuit and the event circuit is deactivated, and the other of the photodetector circuit and the event circuit is activated; In the non-enabled state, both the photodetector circuit and the event circuit are deactivated, and wherein the pixel is one of a plurality of pixels of an event sensor, each of the plurality of pixels being configured to have an operating state modified by a control signal, wherein, based on the control signal, pixels of the plurality of pixels in a first area are in the enabled state, and pixels of the plurality of pixels in a second area surrounding the first area are in the standby state, and wherein the operating state is capable of transitioning from the standby state to the enabled state and the non-enabled state. 18 . The pixel according to claim 17 , wherein the control signal comprises a first control signal that changes the operation state of the pixel to the standby state.

19. The pixel of claim 18, wherein the event circuit comprises a coupling capacitor configured to track background changes in light intensity when the first control signal activates a switch of a switched capacitor amplifier within the event circuit.

20. The pixel of claim 17, wherein the control signal comprises a second control signal that transitions the operational state of the pixel to the non-enabled state.

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