Sensing control device and method for direct time-of-flight (DTOF) sensor

Abstract

This invention provides a sensing control device and method for a direct time-of-flight (DTOF) sensor, comprising: a SPAD array including N different SPAD pixel groups with varying photosensitivity for detecting photon information and generating pulse signals; a switching device configured to connect between the SPAD array and a readout circuit for controlling the selection or deactivation of the SPAD pixel groups; a readout circuit including a time-of-destruction (TDC) for recording breakdown time information of the SPAD pixel groups and an storage RAM for storing a photon information histogram; and a control circuit configured to select pixel groups based on the photon information histogram and process their data.

Description

Technical Field

[0001] This invention relates to the field of 3D depth sensing, and more specifically, to a sensing control apparatus and method for a Direct Time of Flight (DTOF) sensor. Background Technology

[0002] With the development of lidar technology, time-of-flight (TOF) ranging has received increasing attention. The principle of TOF is to continuously emit light pulses to the object being measured, and then use a sensor to receive the light reflected from the object. The distance to the object is obtained by detecting the flight time of the light pulses.

[0003] DTOF ranging is a ranging method developed based on TOF, and it has received increasing attention due to its advantages in use. The core device for implementing DTOF ranging is a photon-triggered counting detector of the single-photon avalanche diode (SPAD) type.

[0004] A DTOF sensor is an active optical sensor that consists of at least two main parts: a transmitter and a receiver. The transmitter emits short-pulse laser light, which illuminates the object being measured. Part of the laser light is reflected and received by the receiver. Because the transmitter and receiver have a synchronization signal, the control circuit can record the time t it takes for the laser to travel back and forth in the air. Given the speed of light C, the distance d to the object being measured can be calculated as 1 / 2 * C * t.

[0005] When measuring distances at close range, the DTOF sensor may experience signal saturation due to strong reflected light, making it unable to measure distances, or it may produce a stacking effect, causing distortion of the recorded signal (in histogram form) and a decrease in ranging accuracy.

[0006] To address the aforementioned technical issues, there is an urgent need for devices and methods to enhance the light intensity sensing range of TOF 3D sensing systems, thereby enabling accurate ranging in close-range, high-intensity light measurement scenarios. Summary of the Invention

[0007] Technical problems to be solved

[0008] When measuring distances at close range, the DTOF sensor may experience signal saturation due to strong reflected light, making it unable to measure distances, or it may produce a stacking effect, causing distortion of the recorded signal (in histogram form) and a decrease in ranging accuracy.

[0009] Technical Solution

[0010] To address the aforementioned problems, this invention provides a sensing control device and method for a DTOF sensor.

[0011] This invention provides a sensing control device for a DTOF sensor, comprising: a SPAD array, the SPAD array including N different SPAD pixel groups with varying photosensitivity, where N is a natural number greater than or equal to 2; a switching device configured to connect between the SPAD array and a readout circuit for controlling the selection or deactivation of the SPAD pixel groups; a readout circuit including a time-discharge converter (TDC) and a storage RAM (SRAM), wherein the TDC is used to record breakdown time information of the SPAD pixel groups, and the SRAM is used to store a photon information histogram; and a control circuit configured to select pixel groups based on the photon information histogram and process their data.

[0012] The present invention provides a sensing control device for a DTOF sensor, wherein the SPAD pixel group includes a SPAD pixel group with high sensitivity and a SPAD pixel group with low sensitivity.

[0013] The present invention provides a sensing control device for a DTOF sensor, wherein the low sensitivity is 1 / 10 of the high sensitivity.

[0014] The present invention provides a sensing control device for a DTOF sensor, wherein the SPAD pixel group includes one or more SPAD pixels with the same photosensitivity connected in parallel.

[0015] The present invention provides a sensing control device for a DTOF sensor, wherein the switching device is configured to select a first group of SPAD pixel groups and turn off other SPAD pixel groups except for the first group of SPAD pixel groups during a first time period; select a second group of SPAD pixel groups and turn off other SPAD pixel groups except for the second group of SPAD pixel groups during a second time period; and select an Nth group of SPAD pixel groups and turn off other SPAD pixel groups except for the Nth group of SPAD pixel groups during an Nth time period.

[0016] The present invention provides a sensing control device for a DTOF sensor, wherein the TDC is configured to read the signal of a first group of SPAD pixel groups in a first time period, read the signal of a second group of SPAD pixel groups in a second time period, and read the signal of an Nth group of SPAD pixel groups in an Nth time period.

[0017] The present invention provides a sensing control device for a DTOF sensor, wherein the SRAM stores a photon information histogram about the SPAD breakdown time.

[0018] This invention provides a sensing control device for a DTOF sensor, wherein the control circuit includes a controller; the controller is configured to: read the photon information histogram of a first group of SPAD pixel groups in a first time period, read the photon information histogram of a second group of SPAD pixel groups in a second time period, and read the photon information histogram of an Nth group of SPAD pixel groups in an Nth time period; compare the signal intensity related to the acquired first to Nth groups of photon information histograms, select a SPAD pixel group based on the comparison result, and perform signal processing on its data.

[0019] The present invention also provides a method for controlling a sensing control device for a DTOF sensor. The sensing control device for the DTOF sensor includes a SPAD array, a switching device, a readout circuit, and a control circuit. The method includes: selecting and deselecting SPAD pixel groups in the SPAD array through the switching device; recording the breakdown time information of the selected SPAD pixel groups and storing a photon information histogram through the readout circuit; comparing the signal intensity related to the photon information histogram through the control circuit, selecting SPAD pixel groups according to the comparison result, and performing signal processing on their data.

[0020] The present invention also provides a method for controlling a sensing control device for a DTOF sensor, wherein selecting and deselecting SPAD pixel groups in a SPAD array via a switching device includes: selecting a first group of SPAD pixel groups in the SPAD array and deselecting other SPAD pixel groups except for the first group of SPAD pixel groups via a switching device in a first time period; selecting a second group of SPAD pixel groups in the SPAD array and deselecting other SPAD pixel groups except for the second group of SPAD pixel groups in a second time period; and selecting an Nth group of SPAD pixel groups in the SPAD array and deselecting other SPAD pixel groups except for the Nth group of SPAD pixel groups in an Nth time period.

[0021] The present invention also provides a method for controlling a sensing control device for a DTOF sensor, wherein recording the breakdown time information of the SPAD pixel group and storing the photon information histogram by the readout circuit includes: reading the signal of the first group of SPAD pixel groups and generating the photon information histogram of the first group of SPAD pixel groups in a first time period, reading the signal of the second group of SPAD pixel groups and generating the photon information histogram of the second group of SPAD pixel groups in a second time period, and reading the signal of the Nth group of SPAD pixel groups and generating the photon information histogram of the Nth group of SPAD pixel groups in an Nth time period.

[0022] The present invention also provides a method for controlling a sensing control device for a DTOF sensor, wherein comparing signal strengths related to photon information histograms via a controller includes: comparing signal strengths related to photon information histograms of a first group of SPAD pixel groups, a second group of SPAD pixel groups, and an Nth group of SPAD pixel groups via a controller.

[0023] The present invention also provides a method for controlling a sensing control device for a DTOF sensor, wherein the SPAD pixel group includes a SPAD pixel group with high sensitivity and a SPAD pixel group with low sensitivity.

[0024] The present invention also provides a method for controlling a sensing control device for a DTOF sensor, wherein the low sensitivity is 1 / 10 of the high sensitivity.

[0025] Beneficial effects

[0026] Compared with the prior art, the present invention provides a sensing control device and method for a DTOF sensor, which has the following beneficial effects: (1) The presence of low-sensitivity SPAD pixels avoids signal saturation and accumulation effects caused by excessive reflected light during close-range ranging, effectively improving the ranging accuracy at close range; (2) Time-division multiplexing of the supporting TDC and SRAM resources makes the TDC and SRAM resources most economical, the chip area most economical, and the cost low; (3) The DTOF sensor can adapt to a wide range of strong and weak light signals. Attached Figure Description

[0027] Figure 1 This is a schematic diagram showing the connection and relationship of various key components of the sensing control device for a DTOF sensor according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of a histogram according to an embodiment of the present invention; and

[0029] Figure 3 This is a schematic diagram of the operating timing of a SPAD array according to an embodiment of the present invention; Detailed Implementation

[0030] Before proceeding with the detailed description below, it may be advantageous to define certain words and phrases used throughout this patent document. The terms “coupled,” “connected,” and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are physically in contact with each other. The terms “transmit,” “receive,” and “communicate,” and their derivatives cover both direct and indirect communication. The terms “comprise,” “include,” and their derivatives refer to, but are not limited to, those including, those including, those including, those including. The term “or” is inclusive, meaning and / or. The phrase “associated with,” and its derivatives refer to, including, being contained within, interconnected, containing, being included in, being connected or connected to, coupled or coupled to, communicating with, cooperating, intertwining, juxtaposed, proximate, bound or bound to, having, having attributes, having a relationship or being related to, etc. The term “controller” refers to any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware, or a combination of hardware and software and / or firmware. The functionality associated with any particular controller may be centralized or distributed, local or remote. The phrase "at least one" when used with a list of items means that different combinations of one or more of the listed items may be used, and that only one item from the list may be required. For example, "at least one of A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0031] Definitions of other specific words and phrases are provided throughout this patent document. Those skilled in the art will understand that, in many, if not most, cases, such definitions apply to the prior and future use of the words and phrases thus defined.

[0032] In this patent document, the application combination of modules and the hierarchical division of sub-modules are for illustrative purposes only. Without departing from the scope of this disclosure, the application combination of modules and the hierarchical division of sub-modules can be in different ways.

[0033] Figure 1 This is a schematic diagram showing the connection and relationship of various key components of the sensing control device for a DTOF sensor according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a histogram according to an embodiment of the present invention, where the horizontal axis represents time and the vertical axis represents the count.

[0035] Figure 3 This is a schematic diagram of the operating timing of a SPAD array according to an embodiment of the present invention.

[0036] The sensing and control device of a DTOF sensor includes a SPAD array, a switching device, a readout circuit, and a control circuit.

[0037] A SPAD array consists of N groups of SPAD pixels with different photosensitive sensitivities, where N is a natural number greater than or equal to 2. The SPAD array is used to detect photon information and generate pulse signals.

[0038] The SPAD pixel group includes a SPAD pixel group with high sensitivity and a SPAD pixel group with low sensitivity. According to an embodiment of the present invention, the SPAD pixel group with high sensitivity includes pixels with a sensitivity greater than a first sensitivity threshold, and the SPAD pixel group with low sensitivity includes pixels with a sensitivity lower than a second sensitivity threshold. The low sensitivity can be 1 / 8, 1 / 10, or 1 / 100 of the high sensitivity, preferably 1 / 10. This specific value is exemplary and does not limit the invention to the above-described embodiments.

[0039] A SPAD pixel group consists of one or more SPAD pixels of the same sensitivity connected in parallel.

[0040] A switching device is configured to connect between the SPAD array and the readout circuit for controlling the selection or deactivation of SPAD pixel groups. Specifically, the switching device is configured to select a first group of SPAD pixel groups and deactivate other SPAD pixel groups except for the first group during a first time period; select a second group of SPAD pixel groups and deactivate other SPAD pixel groups except for the second group during a second time period; and select an Nth group of SPAD pixel groups and deactivate other SPAD pixel groups except for the Nth group during an Nth time period.

[0041] The readout circuitry includes a time-to-digital converter (TDC) 110 and a static random-access memory (SRAM) 120.

[0042] The TDC 110 is a high-precision clock used to record SPAD breakdown time information, that is, the moment when the SPAD array breaks down and generates a pulse signal. The TDC 110 is configured to read the signal of the first group of SPAD pixels in a first time period, the signal of the second group of SPAD pixels in a second time period, and the signal of the Nth group of SPAD pixels in the Nth time period.

[0043] SRAM 120 stores SPAD breakdown time information in the form of a histogram, specifically a histogram of photon information, that is, a histogram storing photon information about the SPAD breakdown time. The histogram can be in the following format: Figure 2 The histogram shown is in the form of a diagram. TDC 110 is connected to SRAM 120.

[0044] The control circuit is configured to retrieve and process data based on the photon information histogram. The control circuit includes a controller 130 configured to retrieve and process data from the photon information histogram of SPAD breakdown time information stored in SRAM 120. The controller 130 reads the photon information histogram of a first group of SPAD pixels in a first time period, reads the photon information histogram of a second group of SPAD pixels in a second time period, and reads the photon information histogram of an Nth group of SPAD pixels in an Nth time period. The signal strengths associated with the acquired first to Nth groups of photon information histograms are compared, and a SPAD pixel group is selected based on the comparison result, and its data is processed. SRAM 120 is connected to the controller 130.

[0045] According to the aforementioned sensing control device for the DTOF sensor, a method for controlling the sensing control device of the DTOF sensor includes:

[0046] The SPAD pixel groups in the SPAD array are selected and deselected via a switching device; the breakdown time information of the selected SPAD pixel groups and the photon information histogram are recorded by a readout circuit; the signal intensity related to the photon information histogram is compared by a control circuit, and a SPAD pixel group is selected based on the comparison result, and its data is processed. The SPAD pixel groups include SPAD pixel groups with high sensitivity and SPAD pixel groups with low sensitivity, wherein the low sensitivity is 1 / 8, 1 / 10, or 1 / 100 of the high sensitivity, preferably 1 / 10. This specific value is exemplary and does not limit the invention to any particular embodiment.

[0047] Specifically, the switching device selects the first group of SPAD pixels in the SPAD array during a first time period and turns off all other SPAD pixel groups except the first group; selects the second group of SPAD pixels in the SPAD array during a second time period and turns off all other SPAD pixel groups except the second group; and selects the Nth group of SPAD pixels in the SPAD array during the Nth time period and turns off all other SPAD pixel groups except the Nth group.

[0048] TDC 110 and SRAM 120 read the signal of the first group of SPAD pixels in the first time period and generate a photon information histogram of the first group of SPAD pixels, storing it in SRAM 120; read the signal of the second group of SPAD pixels in the second time period and generate a photon information histogram of the second group of SPAD pixels, storing it in SRAM 120; and read the signal of the Nth group of SPAD pixels in the Nth time period and generate a photon information histogram of the Nth group of SPAD pixels, storing it in SRAM 120.

[0049] The controller 130 reads the photon information histograms of the first group of SPAD pixel groups, the second group of SPAD pixel groups, and the Nth group of SPAD pixel groups from the SRAM 120; compares the signal strengths related to the photon information histograms of the first group of SPAD pixel groups, the second group of SPAD pixel groups, and the Nth group of SPAD pixel groups; selects the SPAD pixel group with a suitable signal strength based on the comparison results, and performs signal processing on its data; after one frame of ranging is completed, the above process is repeated for continuous operation.

[0050] like Figure 1 , Figure 2 As shown, the sensing control device of a DTOF sensor according to an embodiment of the present disclosure when N=2 includes a SPAD array, a switching device, a readout circuit, and a control circuit.

[0051] like Figure 1 As shown, the SPAD array may include SPAD pixel groups with varying photosensitivity, such as SPAD 1 and SPAD 2. The SPAD array is used to detect photon information and generate pulse signals. SPAD 1 has higher photosensitivity, and SPAD 2 has lower photosensitivity. The photosensitivity of SPAD 2 is 1 / 10 of the photosensitivity of SPAD 1. This specific value is exemplary and does not limit the invention to any particular embodiment.

[0052] A SPAD 1 pixel group includes one or more SPAD 1 pixels connected in parallel. A SPAD 2 pixel group includes one or more SPAD 2 pixels connected in parallel.

[0053] A switching device is configured to connect between the SPAD array and the readout circuitry for controlling the selection or deactivation of SPAD 1 pixel group and SPAD 2 pixel group. Specifically, the switching device is configured to select SPAD 1 pixel group and deactivate other SPAD pixel groups during time period T1; and to select SPAD 2 pixel group and deactivate other SPAD pixel groups during time period T2.

[0054] The readout circuitry includes a TDC 110 and an SRAM 120.

[0055] The TDC 110 is a high-precision clock used to record the SPAD breakdown time information, that is, the moment when the SPAD array breaks down and generates a pulse signal. The TDC 110 is configured to read the signal of SPAD 1 pixel group in time period T1 and the signal of SPAD 2 pixel group in time period T2.

[0056] SRAM 120 stores SPAD breakdown time information in the form of a histogram, specifically a histogram of photon information, that is, a histogram storing photon information about the SPAD breakdown time. The histogram can be in the following format: Figure 2 The histogram shown is in the form of a diagram. TDC 110 is connected to SRAM 120.

[0057] The control circuit is configured to retrieve and process data based on the photon information histogram. The control circuit includes a controller 130 configured to retrieve and process data from the photon information histogram of SPAD breakdown time information stored in SRAM 120. The controller 130 reads the photon information histogram of SPAD pixel group 1 during time period T1 and reads the photon information histogram of SPAD pixel group 2 during time period T2. The signal strengths of the acquired photon information histograms of SPAD pixel group 1 and SPAD pixel group 2 are compared, and based on the comparison result, a SPAD pixel group is selected, and its data is processed. SRAM 120 is connected to the controller 130.

[0058] like Figure 3 As shown, a sensing control method for a DTOF sensor according to an embodiment of the present disclosure when N=2 includes:

[0059] The SPAD 1 pixel group and SPAD 2 pixel group in the SPAD array are selected and deselected by a switching device; the breakdown time information of the selected SPAD pixel group and the photon information histogram are recorded by a readout circuit; the signal intensity related to the photon information histogram is compared by a control circuit, the SPAD pixel group is selected according to the comparison result, and its data is processed. The SPAD pixel group includes a high-sensitivity SPAD 1 pixel group and a low-sensitivity SPAD 2 pixel group, wherein the sensitivity of SPAD 2 is 1 / 10 of the sensitivity of SPAD 1. This specific value is exemplary and does not limit the invention to any particular embodiment.

[0060] Specifically, the switching device selects SPAD 1 pixel group and closes SPAD 2 pixel group during time period T1; and selects SPAD 2 pixel group and closes SPAD 1 pixel group during time period T2.

[0061] The TDC 110 and SRAM 120 read the signal from the SPAD 1 pixel group during the T1 time period and generate the photon information histogram of the SPAD 1 pixel group. Figure 1 The signal is stored in SRAM 120; the signal of the SPAD 2 pixel group is read during time period T2 and the photon information histogram of the SPAD 2 pixel group is generated. Figure 2 It is stored in SRAM 120.

[0062] Controller 130 reads the photon information histogram from SRAM 120 Figure 1 and photon information histogram Figure 2 Compare the histogram of photon information Figure 1 and photon information histogram Figure 2 The signal strength is measured; based on the comparison results, a SPAD pixel group with a suitable signal strength is selected, and its data is processed; once a frame of ranging is completed, the above process is repeated to continue working.

[0063] Although this disclosure has been described with reference to exemplary embodiments, various changes and modifications may be suggested to those skilled in the art. This disclosure is intended to cover such changes and modifications that fall within the scope of the appended claims.

[0064] Any description in this invention should not be construed as implying that any particular element, step, or function is essential and must be included within the scope of the claims. The scope of the patent subject matter is defined only by the claims.

Claims

1. A sensing and control device for a direct time-of-flight (DTOF) sensor, comprising: SPAD array, the SPAD array comprising N different groups of SPAD pixels with different photosensitive sensitivities, where N is a natural number greater than or equal to 2; A switching device configured to be connected between the SPAD array and the readout circuit for controlling the SPAD pixel group to be selected or turned off; The readout circuit includes a TDC and an SRAM, wherein the TDC is used to record the breakdown time information of the SPAD pixel group, and the SRAM is used to store a photon information histogram. A control circuit configured to select SPAD pixel groups based on a photon information histogram and perform signal processing on their data. The SPAD pixel group includes a SPAD pixel group with high sensitivity and a SPAD pixel group with low sensitivity. The SPAD pixel group includes one or more SPAD pixels with the same photosensitivity connected in parallel. The control circuit includes a controller; the controller is configured to: The photon information histogram of the first group of SPAD pixels is read in the first time period, the photon information histogram of the second group of SPAD pixels is read in the second time period, and the photon information histogram of the Nth group of SPAD pixels is read in the Nth time period. The signal intensity is compared with the acquired first to Nth group photon information histograms. Based on the comparison results, the SPAD pixel group is selected and its data is processed.

2. The sensing control device for the DTOF sensor according to claim 1, wherein, The low sensitivity is 1 / 10 of the high sensitivity.

3. The sensing control device for the DTOF sensor according to claim 1, wherein, The switching device is configured to select the first group of SPAD pixel groups in a first time period and turn off other SPAD pixel groups except the first group of SPAD pixel groups; and to select the second group of SPAD pixel groups in a second time period and turn off other SPAD pixel groups except the second group of SPAD pixel groups. In the Nth time period, select the Nth SPAD pixel group and disable all other SPAD pixel groups except the Nth SPAD pixel group.

4. The sensing control device for the DTOF sensor according to claim 1, wherein, The TDC is configured to read the signal of the first group of SPAD pixels in a first time period, read the signal of the second group of SPAD pixels in a second time period, and read the signal of the Nth group of SPAD pixels in the Nth time period.

5. The sensing control device for the DTOF sensor according to claim 1, wherein, The SRAM stores a histogram of photonic information about the SPAD breakdown time.

6. A method for controlling a sensing control device for a DTOF sensor, the sensing control device for the DTOF sensor comprising a SPAD array, a switching device, a readout circuit, and a control circuit, the method comprising: By using a switching device to select and deselect SPAD pixel groups with different photosensitivity in the SPAD array; The breakdown time information of the selected SPAD pixel group and the stored photon information histogram are recorded by the readout circuit. The control circuit compares the signal intensity related to the photon information histogram, selects SPAD pixel groups based on the comparison results, and performs signal processing on their data. The SPAD pixel group includes a SPAD pixel group with high sensitivity and a SPAD pixel group with low sensitivity. The SPAD pixel group includes one or more SPAD pixels with the same photosensitivity connected in parallel. The comparison of signal strengths related to the photon information histograms via the control circuit includes: comparing the signal strengths related to the photon information histograms of the first group of SPAD pixel groups, the second group of SPAD pixel groups, and the Nth group of SPAD pixel groups via the control circuit.

7. The method according to claim 6, wherein, Selecting and deselecting SPAD pixel groups in the SPAD array via a switching device includes: The switching device selects the first group of SPAD pixels in the SPAD array during the first time period and turns off all other SPAD pixel groups except the first group; selects the second group of SPAD pixels in the SPAD array during the second time period and turns off all other SPAD pixel groups except the second group; selects the Nth group of SPAD pixels in the SPAD array during the Nth time period and turns off all other SPAD pixel groups except the Nth group.

8. The method according to claim 6, wherein, The breakdown time information of the SPAD pixel group and the stored photon information histogram are recorded by the readout circuit, including: In the first time period, the signal of the first group of SPAD pixels is read and the photon information histogram of the first group of SPAD pixels is generated. In the second time period, the signal of the second group of SPAD pixels is read and the photon information histogram of the second group of SPAD pixels is generated. In the Nth time period, the signal of the Nth group of SPAD pixels is read and the photon information histogram of the Nth group of SPAD pixels is generated.

9. The method according to claim 6, wherein, The low sensitivity is 1 / 10 of the high sensitivity.

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