Receiving device for direct time-of-flight ranging

Abstract

The invention provides a receiving device for direct time-of-flight distance measurement, and the device is characterized in that the device comprises a photosensitive array which comprises at least two photosensitive units, and the at least two photosensitive units comprise a first photosensitive unit and a second photosensitive unit; the reading circuit comprises a first time-to-digital converter TDC and a second TDC, the signal output end of the first photosensitive unit is connected to the input end of the first TDC, and the signal output end of the second photosensitive unit is connected to the input end of the second TDC.

Description

Technical Field

[0001] The present disclosure relates to the technical field of ranging, and more specifically, to a receiving device, method and system for direct time-of-flight ranging. Background Art

[0002] Direct-Time of Flight (DToF) ranging is a ranging technology in the field of 3D image sensing. The DToF ranging device mainly includes a transmitter Tx and a receiver Rx. Generally, the DToF ranging process is as follows: the transmitter sends a laser pulse to the object to be measured, and the photons reflected back to the receiving end by the object to be measured generate electrical signals after the response of the SPAD (Single Photon Avalanche Diode) photosensitive unit, and then converted into the arrival time of the photon by the TDC (Time Digital Converter), thereby completing the record of an avalanche event. After repeated pulse emission, a histogram of the number of avalanche events at different times within the pulse cycle can be drawn, and then the distance of the object to be measured can be calculated. However, the current DToF technology has a peak forward tilt phenomenon (also called pile-up phenomenon), especially when the distance to the object to be measured is too close or the reflectivity is too high, the reflected light energy is too strong, the peak forward tilt phenomenon is serious, and even the peak saturation problem occurs, which seriously affects the ranging accuracy.

[0003] Therefore, there is a need for a method, system and device that can effectively increase the dynamic range of DToF ranging and improve the ranging accuracy. Summary of the invention

[0004] An embodiment of the present disclosure provides a receiving device for direct time-of-flight ranging, characterized in that the receiving device includes: a photosensitive array, including at least two photosensitive units, the at least two photosensitive units include a first photosensitive unit and a second photosensitive unit; a readout circuit, including a first time-to-digital converter TDC and a second TDC, wherein a signal output end of the first photosensitive unit is connected to an input end of the first TDC, and a signal output end of the second photosensitive unit is connected to an input end of the second TDC.

[0005] According to an embodiment of the present disclosure, the signal output end of the second photosensitive unit is individually connected to the input end of the second TDC, and the signal output ends of all photosensitive units in the photosensitive array except the second photosensitive unit are commonly connected to the input end of the first TDC through an OR gate.

[0006] According to an embodiment of the present disclosure, the photosensitive array includes N 2 photosensitive units, the N 2The photosensitive units are arranged in an NxN array, wherein N is an integer greater than 1, wherein the second photosensitive unit is the N 2 Any one of the photosensitive units.

[0007] According to an embodiment of the present disclosure, the photosensitive array includes two photosensitive units, wherein the photon detection efficiency PDE of the first photosensitive unit is greater than the PDE of the second photosensitive unit.

[0008] According to an embodiment of the present disclosure, the signal output ends of all photosensitive units in the photosensitive array are commonly connected to the input end of the first TDC through an OR gate; and the signal output ends of all photosensitive units in the photosensitive array are commonly connected to the input end of the second TDC through an AND gate.

[0009] According to an embodiment of the present disclosure, the photosensitive unit is a single photon avalanche diode SPAD photosensitive unit.

[0010] According to an embodiment of the present disclosure, the receiving device further includes a control circuit, which is connected to the photosensitive array and configured to control the operation of the photosensitive array.

[0011] According to an embodiment of the present disclosure, the receiving device also includes: a first counting circuit, which is connected to the output end of the first TDC and is configured to perform statistical counting on the output signal of the first TDC at a predetermined time interval to generate a first histogram; and a second counting circuit, which is connected to the output end of the second TDC and is configured to perform statistical counting on the output signal of the second TDC at the predetermined time interval to generate a second histogram.

[0012] According to an embodiment of the present disclosure, the receiving device also includes: a selection circuit, which is connected to the first counting circuit and the second counting circuit and is configured to select one from the first histogram and the second histogram as an output histogram based on a preset rule.

[0013] According to an embodiment of the present disclosure, the preset rules include at least one of the following: when the peak values ​​of the first histogram and the second histogram are at different temporal positions, one of the first histogram and the second histogram whose peak value is later in time is selected as the output histogram; when the difference between the total number of samples of the first histogram and the total number of samples of the second histogram is greater than a preset threshold, one of the first histogram and the second histogram whose total number of samples is larger is selected as the output histogram; and one of the first histogram and the second histogram whose peak sample number is closer to the expected peak sample number is selected as the output histogram, wherein the expected peak sample number is determined based on the total number of pulses transmitted by the transmitting end.

[0014] The embodiments of the present disclosure can provide a method, system and device that can effectively increase the dynamic range of DToF ranging and improve ranging accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0016] Figure 1a A schematic structural diagram of a receiving device 100 for DToF ranging according to an embodiment of the present disclosure is shown;

[0017] Figure 1b 1 shows a circuit connection between the SPAD photosensitive array 102 and the TDC in the SPAD readout circuit 104 according to an embodiment of the present disclosure;

[0018] Figure 1c A schematic diagram of a receiving device 150 for direct time-of-flight ranging according to an embodiment of the present disclosure is shown;

[0019] Figure 2a shows a histogram of TDC1 under strong reflected light according to an embodiment of the present disclosure;

[0020] Figure 2b shows a histogram of TDC2 under strong reflected light according to an embodiment of the present disclosure;

[0021] Figure 3a shows a histogram of TDC1 under weak reflected light according to an embodiment of the present disclosure;

[0022] Figure 3b shows a histogram of TDC2 under weak reflected light according to an embodiment of the present disclosure;

[0023] Figure 4a A schematic structural diagram of a receiving device for DToF ranging according to an embodiment of the present disclosure is shown;

[0024] Figure 4b The circuit connection between the SPAD photosensitive array and the TDC in the SPAD readout circuit according to an embodiment of the present disclosure is shown;

[0025] Figure 5a shows a histogram of TDC1 under strong reflected light according to an embodiment of the present disclosure;

[0026] Figure 5b shows a histogram of TDC2 under strong reflected light according to an embodiment of the present disclosure;

[0027] Figure 6ashows a histogram of TDC1 under weak reflected light according to an embodiment of the present disclosure;

[0028] Figure 6b shows a histogram of TDC2 under weak reflected light according to an embodiment of the present disclosure;

[0029] Figure 7a A schematic structural diagram of a receiving device for DToF ranging according to an embodiment of the present disclosure is shown;

[0030] Figure 7b The circuit connection between the SPAD photosensitive array and the TDC in the SPAD readout circuit according to an embodiment of the present disclosure is shown;

[0031] Figure 8a shows a histogram of TDC1 under strong reflected light according to an embodiment of the present disclosure;

[0032] Figure 8b shows a histogram of TDC2 under strong reflected light according to an embodiment of the present disclosure;

[0033] Figure 9a shows a histogram of TDC1 under weak reflected light according to an embodiment of the present disclosure; and

[0034] Figure 9b A histogram of TDC2 under weak reflected light according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0035] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The terms "coupling", "connection" and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are in physical contact with each other. The terms "transmission", "reception" and "communication" and their derivatives cover direct and indirect communication. The terms "include" and "comprise" and their derivatives refer to including but not limited to. The term "or" is inclusive, meaning and / or. The phrases "associated with...", "corresponding to..." and their derivatives refer to including, including within, interconnecting, including, including within, connecting or connecting with, coupling or coupling with, communicating with, cooperating, interweaving, parallel, close to, binding or binding with, having, having attributes, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware, or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of", when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0036] Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior and future uses of such defined words and phrases.

[0037] In this patent document, the application combination of modules and the division level of submodules are only used for illustration. Without departing from the scope of the present disclosure, the application combination of modules and the division level of submodules can have different modes. The embodiments of the present disclosure can be implemented in different forms and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure thorough and complete, and to fully convey exemplary implementation methods to those skilled in the art. The embodiments of the present disclosure can be combined to form additional embodiments.

[0038] The present disclosure will be described in detail below with reference to exemplary embodiments of the present disclosure. However, the present disclosure is not limited to the embodiments described herein, and it can be implemented in many different forms. The described embodiments are only used to make the present disclosure thorough and complete, and to fully convey the concept of the present disclosure to those skilled in the art. The features of the various embodiments described can be combined or replaced with each other, unless explicitly excluded or should be excluded according to the context.

[0039] Generally, the DToF ranging process is as follows: the transmitter sends a laser pulse to the object to be measured, and the photons reflected by the object to be measured back to the receiving end generate electrical signals after the response of the SPAD (Single Photon Avalanche Diode) photosensitive unit, and then converted into the arrival time of the photon by the TDC (Time Digital Converter), thereby completing the record of an avalanche event. After repeated pulse transmission, a histogram of the number of avalanche events at different times within the pulse cycle can be drawn, and the distance of the object to be measured can be calculated.

[0040] When the SPAD responds to a photon and triggers the avalanche effect, the time required to return from the avalanche state to the initial state is called the dead time. In some cases, due to the inability to respond to arriving photons during the dead time, the measured histogram waveform is compared with the original laser pulse waveform, resulting in a peak forward tilt phenomenon (also called pile-up phenomenon). When the distance to the measured object is too close or the reflectivity is too high, the reflected light energy is too strong, the peak forward tilt phenomenon is serious, and even peak saturation problems occur, which seriously affects the ranging accuracy. In this article, the peak forward tilt phenomenon can refer to the phenomenon that the peak of the measured histogram waveform is earlier in time than the peak of the original laser pulse waveform or the actual pulse waveform peak.

[0041] In addition, in some cases, the flight time of light reflected from close objects is shorter and will be received in the first half of the exposure at the receiving end, while the reflected light from distant objects will be received in the second half. Therefore, the entire detection cycle can be divided into n sub-cycles, and different exposure times are set for different sub-cycles, so that the total exposure time of distant objects is longer than that of close objects, ensuring the accuracy of long-distance measurement while preventing overexposure at close range, thereby improving the dynamic range of DToF ranging.

[0042] However, the current methods do not consider the influence of the pile-up phenomenon under different reflected light intensities, and the measurement error is large when the distance to the measured object is too close or the reflectivity is too high. In addition, some current methods to ensure the measurement accuracy of close-range and highly reflective objects may result in insufficient number of photons returned by distant or low-reflective objects, which in turn leads to a decrease in histogram signal-to-noise ratio and ranging accuracy. In addition, by dividing the measurement cycle to take into account the reflected light intensity of the same object at long and short distances, it cannot solve the problem of different reflected light intensities of high and low reflectivity objects at the same measurement distance.

[0043] The embodiments of the present disclosure provide a DToF ranging system receiving-end design scheme that takes into account both long and short distances and high and low reflective objects. By designing the selection and arrangement of SPAD photosensitive units and the signal acquisition circuit, etc., the measurement accuracy of objects of different distances and materials in the same field of view can be guaranteed, further improving the ranging dynamic range.

[0044] According to the embodiment of the present disclosure, the DToF ranging system based on the SPAD sensor may include a controller, a light source transmitting end and a receiving end. In some embodiments, the receiving end (or referred to as a receiving circuit or a receiving device) may mainly include a SPAD photosensitive array, a SPAD control circuit, and one or more of a SPAD readout circuit. Among them, SPAD (Single Photon Avalanche Diode) is a photoelectric device that receives a single photon to form an avalanche amplification to generate a signal count, obtains the flight time of the photon through repeated counting, and then obtains the distance result. In the present disclosure, a SPAD array is formed by using at least two SPAD units as the receiving end of the DToF ranging system.

[0045] Specifically, Figure 1c A schematic diagram of a receiving device 150 for direct time-of-flight ranging according to an embodiment of the present disclosure is shown.

[0046] like Figure 1c As shown, a receiving device 150 for direct time-of-flight ranging according to an embodiment of the present disclosure may include: a photosensitive array 151 and a readout circuit 152. The photosensitive array 151 may include at least two photosensitive units, wherein the at least two photosensitive units may include, for example, a first photosensitive unit SPAD1 and a second photosensitive unit SPAD2. The readout circuit 152 may include a first time-to-digital converter TDC (e.g., TDC1) and a second TDC (e.g., TDC2). In some embodiments, the signal output end of the first photosensitive unit SPAD1 may be connected to the input end of TDC1, and the signal output end of the second photosensitive unit SPAD2 may be connected to the input end of TDC2.

[0047] In some embodiments, the receiving device 150 may further include a control circuit. The control circuit may be connected to the photosensitive array 151 and may be configured to control the operation of the photosensitive array 151, for example, to control the operations required for the normal operation of the photosensitive array 151 and any one or more photosensitive units included in the photosensitive array 151 according to any existing and future methods, which are not limited herein. In the following description, the control circuit is schematically described as a part of the receiving device according to the embodiment of the present disclosure. However, it should be understood that the receiving device according to the embodiment of the present disclosure may not include the control circuit.

[0048] In some embodiments, the signal output end of the second photosensitive unit SPAD2 can be individually connected to the input end of TDC2, and the signal output ends of all photosensitive units (including SPAD1) in the photosensitive array except the second photosensitive unit SPAD2 can be commonly connected to the input end of TDC1 through an OR gate.

[0049] In some embodiments, the photosensitive array 151 may further include N 2 photosensitive units, and the N 2 The photosensitive units may be arranged in an NxN array, where N is an integer greater than 1. In some embodiments, the second photosensitive unit SPAD2 may be N 2 In some embodiments, the second photosensitive unit SPAD2 may be a photosensitive unit located at the center of the NxN array.

[0050] More specifically, Figure 1a A schematic structural diagram of a receiving device 100 for DToF ranging according to an embodiment of the present disclosure is shown.

[0051] like Figure 1a As shown, the receiving device 100 of the DToF ranging system may include a SPAD photosensitive array 102, a SPAD control circuit 101, and a SPAD readout circuit 104. The SPAD photosensitive array 102 may operate under the control of the SPAD control circuit 101. When the SPAD receives an optical signal and generates an avalanche current, the SPAD readout circuit 104 may process the electrical signal and calculate the flight time, thereby calculating the distance of the target object.

[0052] like Figure 1a As shown, the SPAD photosensitive array 102 may include 9 small-sized SPAD photosensitive units 103 (e.g., SPAD1 to SPAD9, arranged in a 3x3 array). The SPAD readout circuit 104 may include two time-to-digital converters (TDCs), for example, TDC1 and TDC2. It should be understood that the number of 9 photosensitive units or the 3x3 array in this embodiment is only an example, and the receiving device 100 according to the embodiment of the present disclosure may also include any other number or any other arrangement (e.g., MxN, etc.) of photosensitive units.

[0053] Figure 1b FIG. 2 shows a circuit connection between the SPAD photosensitive array 102 and the TDC in the SPAD readout circuit 104 according to an embodiment of the present disclosure. Figure 1bAs shown, SPAD5 (in other examples, it can also be any other photosensing unit not in the center of the array) can be connected to TDC2 alone, and the output signals (i.e., signal output terminals) of the remaining 8 SPADs can be connected together and connected to TDC1 after being processed by an OR operation. The logic of the OR operation is: if any one of the 8 SPADs is triggered to generate an avalanche current, an avalanche event will be recorded, which is equivalent to the photosensing area of ​​the SPAD connected to TDC1 being 8 times that of TDC2.

[0054] When the target object is close or made of a high-reflectivity material, the reflected light energy is strong. Since the SPAD connected to TDC1 has a large photosensitive area, the accumulated histogram will have a peak forward tilt phenomenon, resulting in a large ranging error. Figure 2a As shown in the figure. Since TDC2 is only connected to a small-sized SPAD photosensitive unit with low sensitivity, the accumulated histogram can still restore the light pulse waveform well, as shown in the figure. Figure 2b At this time, the histogram of TDC2 can be selected for distance calculation.

[0055] When the target object is far away or made of low-reflectivity material, the reflected light energy is weak. Since the number of photons received by a single SPAD is insufficient, the signal-to-noise ratio of the histogram accumulated by TDC2 is low and the optical signal waveform cannot be fully restored. Figure 3b However, a larger photosensitive area can increase the number of received photons, so the TDC1 accumulated histogram better restores the reflected light pulse waveform, as shown in Figure 3a At this time, the histogram of TDC1 can be selected for distance calculation.

[0056] At this point, this receiver design can simultaneously measure target objects at long and short distances and with high and low reflectivity materials, effectively solving the peak forward tilt problem under strong reflected light and the low signal-to-noise ratio problem under weak reflected light.

[0057] In some embodiments, the photosensitive array may include two photosensitive units, a first photosensitive unit SPAD1 and a second photosensitive unit SPAD2 , wherein the photon detection efficiency PDE of the first photosensitive unit SPAD1 may be greater than the PDE of the second photosensitive unit SPAD2 .

[0058] More specifically, Figure 4a A schematic structural diagram of a receiving device 400 for DToF ranging according to an embodiment of the present disclosure is shown.

[0059] like Figure 4aAs shown, the receiving device 400 of the DToF ranging system may include a SPAD photosensitive array 402, a SPAD control circuit 401, and a SPAD readout circuit 405. The SPAD photosensitive array 402 may operate under the control of the SPAD control circuit 401. When the SPAD receives an optical signal and generates an avalanche current, the SPAD readout circuit 405 may process the electrical signal and calculate the flight time, thereby calculating the distance of the target object.

[0060] like Figure 4a As shown, the SPAD photosensitive array 402 may include two SPAD photosensitive units SPAD1 and SPAD2 with different photon detection efficiencies (PDE). In one example, the PDE of SPAD1 403 may be greater than the PDE of SPAD2 404, that is, under the same light intensity, SPAD1 403 is more likely to experience avalanche effect. The SPAD readout circuit 405 may include two time-to-digital converters (TDCs), for example, TDC1 and TDC2.

[0061] Figure 4b FIG. 4 shows a circuit connection between the SPAD photosensitive array 402 and the TDC in the SPAD readout circuit 405 according to an embodiment of the present disclosure. Figure 4b As shown, SPAD1 can be connected to TDC1, and SPAD2 can be connected to TDC2.

[0062] When the target object is close or made of a high-reflectivity material, the reflected light energy is strong. Due to the high photon detection efficiency of SPAD1403, the accumulated histogram will have a peak forward tilt phenomenon, resulting in a large ranging error. Figure 5a As shown in the figure. However, the sensitivity of the SPAD2 404 photosensitive unit is low, and the accumulated histogram can better restore the light pulse waveform, as shown in the figure. Figure 5b At this time, the histogram of TDC2 can be selected for distance calculation.

[0063] When the target object is far away or made of low reflectivity material, the reflected light energy is weak. At this time, SPAD2404 can no longer accurately detect a small number of photons, so the histogram accumulated by TDC2 cannot record the light pulse waveform. Figure 6b However, due to its strong photon detection efficiency, SPAD1 403 can still respond to a small amount of photons, so the histogram accumulated by TDC1 can record the waveform of the reflected light pulse, as shown in Figure 6a At this time, the histogram of TDC1 can be selected for distance calculation.

[0064] At this point, this receiver design can simultaneously measure target objects at long and short distances and with high and low reflectivity materials, effectively solving the peak forward tilt problem under strong reflected light and the low signal-to-noise ratio problem under weak reflected light.

[0065] In some embodiments, the signal output ends of all photosensitive units in the photosensitive array 151 can be connected to the input end of TDC1 through an or gate; and the signal output ends of all photosensitive units in the photosensitive array 151 can be connected to the input end of TDC2 through an and gate.

[0066] More specifically, Figure 7a A schematic structural diagram of a receiving device 700 for DToF ranging according to an embodiment of the present disclosure is shown.

[0067] like Figure 7a As shown, the receiving device 700 of the DToF ranging system may include a SPAD photosensitive array 702, a SPAD control circuit 701, and a SPAD readout circuit 704. The SPAD photosensitive array 702 may operate under the control of the SPAD control circuit 701. When the SPAD receives a light signal and generates an avalanche current, the SPAD readout circuit 704 may process the electrical signal and calculate the flight time, thereby calculating the distance of the target object.

[0068] like Figure 7a As shown, the SPAD photosensitive array 702 may include three SPAD photosensitive units 703 of the same size (e.g., SPAD1, SPAD2, and SPAD3), and the SPAD readout circuit 704 may include two time-to-digital converters (TDCs), e.g., TDC1 and TDC2. It should be understood that the number of photosensitive units 3 in this embodiment is only an example, and the receiving device 700 according to the embodiment of the present disclosure may also include any other number of photosensitive units.

[0069] Figure 7b FIG. 2 shows a circuit connection between the SPAD photosensitive array 702 and the TDC in the SPAD readout circuit 704 according to an embodiment of the present disclosure. Figure 7b As shown, the output signals (i.e., signal output terminals) of SPAD1, SPAD2, and SPAD3 can be connected together and divided into two paths for subsequent operations. For example, one path can be connected to TDC1 through an OR operation (or), and the other path can be connected to TDC2 through an AND operation (and). The logic of the OR operation (or) is: if any one of the three SPADs is triggered to generate an avalanche current, an avalanche event will be recorded. The logic of the AND operation (and) is: if and only if the three SPADs are triggered at the same time, an avalanche event will be recorded.

[0070] When the target object is close or made of a high-reflectivity material, the reflected light energy is strong. Since any one of the SPADs connected to TDC1 will output an event when triggered, the accumulated histogram is more likely to have a peak forward tilt phenomenon, resulting in a large ranging error. Figure 8a As shown. TDC2 needs the three connected SPADs to be triggered at the same time to output a count, which is equivalent to reducing the trigger probability. Therefore, the accumulated histogram of TDC2 can better restore the light pulse waveform, as shown in Figure 8b At this time, the histogram of TDC2 can be selected for distance calculation.

[0071] When the target object is far away or made of low-reflectivity material, the reflected light energy is weak. At this time, the probability of a single SPAD triggering is low, and the probability of three SPADs triggering at the same time is even lower. Therefore, the histogram accumulated by TDC2 cannot completely restore the optical signal waveform. Figure 9b However, if any one of the three SPADs is triggered, the count is equivalent to three times the trigger probability, so the histogram accumulated by TDC1 can better restore the reflected light pulse waveform, as shown in Figure 9a At this time, the histogram of TDC1 can be selected for distance calculation.

[0072] At this point, this receiver design can simultaneously measure target objects at long and short distances and with high and low reflectivity materials, effectively solving the peak forward tilt problem under strong reflected light and the low signal-to-noise ratio problem under weak reflected light.

[0073] In some embodiments, the photosensitive units included in the photosensitive array according to the embodiments of the present disclosure as described above may be SPAD photosensitive units.

[0074] In some embodiments, one or more of the receiving device 150, the receiving device 100, the receiving device 400, and the receiving device 700 according to the embodiments of the present disclosure may further include a first counting circuit and a first counting circuit. The first counting circuit may be connected to the output terminal of the first TDC, and may be configured to perform statistical counting on the output signal of the first TDC at a predetermined time interval to generate a first histogram (for example, Figure 2a , Figure 3a , Figure 5a , Figure 6a , Figure 8a and Figure 9a The second counting circuit may be connected to the output terminal of the second TDC, and may be configured to perform statistical counting on the output signal of the second TDC at a predetermined time interval to generate a second histogram (for example, Figure 2b , Figure 3b , Figure 5b , Figure 6b , Figure 8b and Figure 9b The predetermined time interval may be each statistical interval of the preset histogram as shown in the figure.

[0075] In some embodiments, one or more of the receiving device 150, the receiving device 100, the receiving device 400, and the receiving device 700 according to the embodiments of the present disclosure may further include a selection circuit. The selection circuit may be connected to the first counting circuit and the second counting circuit, and may be configured to select one from the first histogram generated according to the first counting circuit and the second histogram generated according to the second counting circuit based on a preset rule as a final output histogram.

[0076] In some embodiments, the preset rules described above may include at least one of the following:

[0077] When the peak values ​​of the first histogram and the second histogram are at different positions in time, the one with the later peak value in time is selected as the output histogram. Figure 2a and Figure 2b As shown, in the first histogram (eg, Figure 2a ) is earlier in time than the peak of the second histogram generated according to the second counting circuit (for example, Figure 2b ) peak, it can be considered that the first histogram (for example, Figure 2a ) has a peak forward tilt phenomenon, and the ranging error is large, so a second histogram with a peak later in time can be selected (for example, Figure 2b ) as the final output histogram to calculate the distance of the object to be measured;

[0078] When the difference between the total number of samples in the first histogram and the total number of samples in the second histogram is greater than a preset threshold, the one with the larger total number of samples in the first histogram and the second histogram is selected as the output histogram. Figure 3a and Figure 3b As shown, in the first histogram (eg, Figure 3a ) is greater than the total number of samples included in the second histogram generated by the second counting circuit (for example, Figure 3b ) when the total number of samples included in the second histogram (for example, Figure 3b ) has insufficient number of received photons and the accumulated histogram signal-to-noise ratio is low, so the first histogram with a larger total number of samples can be selected (for example, Figure 3a ) as the final output histogram to calculate the distance of the object to be measured. The preset threshold number (for example, any integer greater than or equal to 0) described here can be set by experience, or based on any existing or future mathematical method depending on the actual application scenario, and this article does not limit it.

[0079] In some embodiments, the preset rules described above may include: selecting one of the first histogram and the second histogram whose peak value is closer to the expected peak value as the output histogram. For example, one of the first histogram and the second histogram whose number of samples in the peak interval (i.e., the number of peak samples) is closer to the expected number of peak samples may be selected as the output histogram. In this article, the peak interval of the histogram may refer to the statistical interval with the largest number of samples in the histogram. In some embodiments, the expected peak value may be determined based on the total number of pulses transmitted by the transmitting end. For example, when the total number of pulses transmitted by the transmitting end is N, the expected peak value may be determined as N / 5, and so on. The value N / 5 here is only an example, and the present application may also determine the expected peak value based on any other specific value, or based on the ratio of the number of peak samples to the total number of transmitted pulses determined by experience.

[0080] It should be understood that one or more of the receiving devices 150, 100, 400, and 700 described above are merely illustrative, and the receiving device according to the embodiment of the present disclosure may also include one or more other devices other than those included in one or more of the receiving devices 150, 100, 400, and 700, or omit or replace any one or more of the receiving devices 150, 100, 400, and 700, which is not limited herein. In addition, the embodiment of the present disclosure may also include any implementation method or operation method of one or more of the receiving devices 150, 100, 400, and 700 described above (and a computer storage medium recording instructions for implementing these methods), and any circuit system including one or more of the receiving devices 150, 100, 400, and 700, for example, including a receiving device, a controller, and a DToF ranging system of an optical transmitter according to an embodiment of the present disclosure.

[0081] The hardware computing device described in the present disclosure may be implemented in its entirety or in parts thereof through various suitable hardware means, including but not limited to FPGA, ASIC, SoC, discrete gate or transistor logic, discrete hardware components, or any combination thereof.

[0082] The block diagrams of circuits, devices, apparatuses, equipment, and systems involved in the present disclosure are only illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these circuits, devices, apparatuses, equipment, and systems may be connected, arranged, or configured in any manner as long as the desired purpose can be achieved.

[0083] Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

[0084] Any description in this disclosure should not be construed as implying that any particular element, step, or function is an essential element that must be included in the claims scope. The scope of the patented subject matter is limited solely by the claims.

[0085] Exemplary embodiments according to the present disclosure have been disclosed herein, and although specific terms are employed, they are used and interpreted only in a general and descriptive sense and not for limiting purposes. In some cases, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise stated. Therefore, it will be understood by those skilled in the art that various changes in form and detail may be made to the present disclosure without departing from the spirit and scope of the claims.

Claims

1. A receiving device for direct time-of-flight ranging, characterized in that: The receiving device comprises: A photosensitive array, comprising at least two photosensitive units, wherein the at least two photosensitive units include a first photosensitive unit and a second photosensitive unit; The readout circuit comprises a first time digitizer TDC and a second TDC, The signal output terminal of the first photosensitive unit is connected to the input terminal of the first TDC, and the signal output terminal of the second photosensitive unit is connected to the input terminal of the second TDC.

2. The receiving device according to claim 1, characterized in that The signal output terminal of the second photosensitive unit is connected to the input terminal of the second TDC separately, and The signal output ends of all the photosensitive units in the photosensitive array except the second photosensitive unit are commonly connected to the input end of the first TDC through an OR gate.

3. The receiving device according to claim 2, characterized in that The photosensitive array includes N 2 photosensitive units, the N 2 The photosensitive units are arranged in an NxN array, where N is an integer greater than 1. Wherein, the second photosensitive unit is the N 2 Any one of the photosensitive units.

4. The receiving device according to claim 1, characterized in that The photosensitive array includes two photosensitive units, wherein: The photon detection efficiency PDE of the first photosensitive unit is greater than the PDE of the second photosensitive unit.

5. The receiving device according to claim 1, characterized in that The signal output terminals of all the photosensitive units in the photosensitive array are connected to the input terminal of the first TDC through an OR gate; and The signal output terminals of all the photosensitive units in the photosensitive array are commonly connected to the input terminal of the second TDC through an AND gate.

6. The receiving device according to claim 1, characterized in that The photosensitive unit is a single photon avalanche diode SPAD photosensitive unit.

7. The receiving device according to claim 1, characterized in that The receiving device also includes a control circuit, which is connected to the photosensitive array and is configured to control the operation of the photosensitive array.

8. The receiving device according to claim 1, characterized in that The receiving device also includes: a first counting circuit connected to the output terminal of the first TDC and configured to perform statistical counting on the output signal of the first TDC at a predetermined time interval to generate a first histogram; and The second counting circuit is connected to the output terminal of the second TDC and is configured to perform statistical counting on the output signal of the second TDC according to the predetermined time interval to generate a second histogram.

9. The receiving device according to claim 8, characterized in that The receiving device also includes: A selection circuit is connected to the first counting circuit and the second counting circuit and is configured to select one of the first histogram and the second histogram as an output histogram based on a preset rule.

10. The receiving device according to claim 9, characterized in that The preset rules include at least one of the following: When the peak values ​​of the first histogram and the second histogram are at different positions in time, selecting the one with the later peak value in time from the first histogram and the second histogram as the output histogram; When the difference between the total number of samples of the first histogram and the total number of samples of the second histogram is greater than a preset threshold, selecting the one with the larger total number of samples from the first histogram and the second histogram as the output histogram; The one of the first histogram and the second histogram whose peak sample number is closer to the expected peak sample number is selected as the output histogram, wherein the expected peak sample number is determined based on the total number of pulses transmitted by the transmitting end.

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