Drift error and background light rejection circuit and method for spad lidar

Abstract

This invention relates to a circuit and method for suppressing drift error and background light in a SPAD lidar. The SPAD array and readout circuit unit acquire optical signals; a target recognition algorithm unit measures the distance to targets within the effective field of view based on the optical signals to obtain distance measurement information; a laser power adjustment drive unit dynamically adjusts the output power of the laser emitting unit based on the distance measurement information; a nonlinearly modulated gated high-voltage drive circuit unit adjusts the drive voltage of the SPAD array and readout circuit unit based on the distance measurement information; and the laser emitting unit, acting as a pulsed laser source, emits laser light from its output end to an optical lens, which then illuminates the surface of the target within the effective field of view. This invention effectively suppresses SPAD drift error and improves the dynamic range, measurement accuracy, and background light suppression capability of the SPAD lidar.

Description

Technical Field

[0001] This invention belongs to the field of lidar system design, specifically relating to the drift error and background light suppression circuit and method of SPAD lidar. Background Technology

[0002] SPAD (Special Active Distance) lidar, as an active remote sensing technology, enables precise 3D imaging of targets. It is currently widely used in civilian fields such as handheld smart devices, industrial ranging, and autonomous driving, as well as military fields such as spacecraft landing, precision guidance, and field topographic mapping. Compared to traditional millimeter-wave radar, infrared imaging, image sensors and optical cameras, and linear APD lidar, SPAD lidar offers longer measurement distances, higher accuracy, larger fields of view, and higher frame rates. SPAD lidar eliminates the need for heterogeneous integration, allowing for full integration of the laser drive circuit, detector, and processing circuitry. This gives SPAD lidar significant advantages in terms of integration, size, power consumption, pixel resolution, circuit consistency, and cost. Furthermore, SPAD's high sensitivity enables the detection of low-light signals, making it ideal for long-distance measurements and representing the mainstream development direction for lidar in the future.

[0003] Currently, due to the limited dynamic range of SPAD measurements, to meet the practical application needs of industry, the peak emission power of the laser is often increased to achieve long-range measurements with SPAD lidar. However, increasing the peak emission power of the laser places stringent requirements on the performance of the laser and the driving circuit. Furthermore, increasing the peak emission power of the laser can lead to a decrease in the measurement accuracy of the SPAD lidar when the target reflectivity increases or the measurement distance decreases, due to the stacking effect of the single-photon detector.

[0004] At this point, using a gated high-voltage drive circuit can effectively improve the background light suppression capability of SPAD LiDAR. However, the background light suppression algorithm based on the gated high-voltage drive circuit requires the system to dynamically adjust the enabling time of the gate signal according to the target distance. The traditional method of dynamically adjusting the gate enabling signal based on the successive approximation method will reduce the system's measurement frame rate, thus limiting the application scenarios of SPAD LiDAR. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a circuit and method for suppressing drift error and background light in SPAD lidar. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] This invention provides a drift error and background light suppression circuit for a SPAD lidar, comprising a nonlinear modulation gated high voltage drive circuit unit, a SPAD array and readout circuit unit, a target recognition algorithm unit, a laser power adjustment drive unit, and a laser emission unit;

[0007] The input terminal of the nonlinear modulation gated high-voltage drive circuit unit is connected to the first output terminal of the target object recognition algorithm unit; the output terminal of the nonlinear modulation gated high-voltage drive circuit unit is connected to the input terminal of the SPAD array and readout circuit unit; the output terminal of the SPAD array and readout circuit unit is connected to the input terminal of the target object recognition algorithm unit; the second output terminal of the target object recognition algorithm unit is connected to the input terminal of the laser power adjustment drive unit; the output terminal of the laser power adjustment drive unit is connected to the input terminal of the laser emitting unit; the laser emitting unit serves as a pulsed laser source, and its output terminal emits laser light to an optical lens, which then uses the optical lens to irradiate the surface of the target object within the effective field of view.

[0008] The SPAD array and readout circuit unit are used to acquire optical signals; the target object recognition algorithm unit is used to measure the distance of the target object within the effective field of view based on the optical signals to obtain distance measurement information; the laser power adjustment drive unit is used to dynamically adjust the output power of the laser emitting unit based on the distance measurement information; the nonlinear modulation gated high voltage drive circuit unit is used to adjust the drive voltage of the SPAD array and readout circuit unit based on the distance measurement information.

[0009] In one embodiment of the present invention, the nonlinearly modulated gated high-voltage drive circuit unit includes a switching circuit, a charging circuit, a high-voltage DC voltage source, and a SPAD high-voltage selection unit.

[0010] The input terminal of the switching circuit is connected to the first output terminal of the target object recognition algorithm unit; the output terminal of the switching circuit is connected to the input terminal of the charging circuit; the output terminal of the charging circuit is connected to the first input terminal of the SPAD high-voltage selection unit; the second input terminal of the SPAD high-voltage selection unit is connected to the high-voltage DC voltage source; the third input terminal of the SPAD high-voltage selection unit receives an external control signal; and the output terminal of the SPAD high-voltage selection unit is connected to the input terminal of the SPAD array and readout circuit unit.

[0011] The switching circuit dynamically opens and closes based on the distance measurement information to provide the charging voltage for the charging circuit; the charging circuit charges and discharges based on the charging voltage to generate a nonlinear modulation voltage; the SPAD high-voltage selection unit is used to select the nonlinear modulation voltage or the output voltage of the high-voltage DC voltage source as the input voltage for the SPAD array and readout circuit unit based on the external control signal.

[0012] In one embodiment of the present invention, the switching circuit includes a gating generation circuit unit, a low-voltage DC voltage source, a MOS switching unit, and a voltage divider network unit, wherein the input terminal of the gating generation circuit unit is connected to the first output terminal of the target object recognition algorithm unit; the gate of the MOS switching unit is connected to the charging circuit; the output terminal of the low-voltage DC voltage source is connected to the drain of the MOS switching unit; and the output terminal of the voltage divider network unit is connected to the source of the MOS switching unit.

[0013] The gating generation circuit unit is used to dynamically adjust the enabling time of the gating signal according to the distance measurement information; the MOS switch unit is used to open and close according to the enabling time of the gating signal; the low-voltage DC voltage source is used to control the maximum voltage output by the MOS switch unit; the voltage divider network unit is used to adjust the opening voltage and closing voltage of the MOS switch unit.

[0014] In one embodiment of the present invention, the charging circuit includes a current buffer unit, a coupling unit, and a charging unit;

[0015] The input terminal of the current buffer unit is connected to the output terminal of the switching circuit; the output terminal of the current buffer unit is connected to the first input terminal of the coupling unit, the second input terminal of the coupling unit is connected to the output terminal of the high voltage DC voltage source, the output terminal of the coupling unit is connected to the input terminal of the charging unit; the output terminal of the charging unit is connected to the first input terminal of the SPAD high voltage selection unit.

[0016] The current buffer unit is used to adjust the charging time of the charging unit; the coupling unit is used to connect the output voltage of the switching circuit and the output voltage of the high voltage DC voltage source in series to obtain the charging voltage; the charging unit charges and discharges according to the charging voltage to generate a nonlinear modulation voltage to adjust the gain of the SPAD array and the readout circuit unit.

[0017] In one embodiment of the present invention, the target object recognition algorithm unit includes a light intensity measurement unit, a target object comparison and classification unit, a pixel fusion unit, a histogram statistics unit, and a peak detection unit;

[0018] The output terminals of the SPAD array and readout circuit unit are respectively connected to the input terminal of the light intensity measurement unit and the second input terminal of the pixel fusion unit; the output terminal of the light intensity measurement unit is connected to the input terminal of the target object comparison and classification unit; the output terminal of the target object comparison and classification unit is connected to the first input terminal of the pixel fusion unit; the output terminal of the pixel fusion unit is connected to the input terminal of the histogram statistics unit; the output terminal of the histogram statistics unit is connected to the input terminal of the peak detection unit; the first output terminal of the peak detection unit is connected to the nonlinear modulation gated high voltage drive circuit unit, and the second output terminal is connected to the laser power adjustment drive unit.

[0019] The light intensity measurement unit is used to measure the light intensity of the light signal; the target object comparison and classification unit is used to compare and classify the light intensity measurement results, and classify the target objects according to reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance; the pixel fusion unit is used to fuse the pixels of each category of target objects to obtain the pixel fusion result of each category; the histogram statistics unit is used to perform statistics on the pixel fusion results to obtain statistical results; the peak detection unit detects the statistical results to obtain the maximum value of the statistical results, and obtains the distance measurement information of the target object based on the maximum value of the statistical results.

[0020] This invention provides a method for suppressing drift error and background light in SPAD lidar, applicable to the drift error and background light suppression circuit of SPAD lidar described in any of the above embodiments, comprising:

[0021] The optical signal acquisition unit acquires the optical signal based on the applied driving voltage;

[0022] Based on the optical signal, distance measurement information is obtained by measuring the distance to the target object within the effective field of view.

[0023] Based on the distance measurement information, the output power of the laser and the driving voltage of the optical signal acquisition unit are dynamically adjusted.

[0024] In one embodiment of the present invention, dynamically adjusting the driving voltage of the optical signal acquisition unit based on the distance measurement information includes:

[0025] A nonlinear modulation voltage is generated based on the distance measurement information;

[0026] The nonlinear modulation voltage or DC voltage is selected as the driving voltage for the optical signal acquisition unit based on the external control signal.

[0027] In one embodiment of the present invention, the optical signal acquisition unit acquires an optical signal based on the applied driving voltage, including:

[0028] According to the external control signal, a DC voltage is applied to the optical signal acquisition unit as the driving voltage to acquire the optical signals of target objects with different reflectivities.

[0029] Based on the external control signal, a nonlinear modulation voltage is applied to the optical signal acquisition unit as the driving voltage to acquire optical signals from targets at different distances.

[0030] In one embodiment of the present invention, distance measurement information is obtained by measuring the distance to a target within the effective field of view based on the optical signal, including:

[0031] The light intensity of the light signal is measured, the light intensity measurement results are compared and classified, and the target objects are classified according to reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance.

[0032] The pixels of each category of target objects are fused to obtain the pixel fusion result for each category;

[0033] The pixel fusion results were statistically analyzed to obtain the statistical results.

[0034] The statistical results are detected to obtain the maximum value of the statistical results, and the distance measurement information of the target object is obtained based on the maximum value of the statistical results.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The drift error and background light suppression circuit and method of the SPAD lidar of the present invention employs a nonlinearly modulated gated high-voltage drive circuit unit, which can effectively improve the background light suppression capability of the SPAD lidar. Furthermore, by dynamically adjusting the enable timing of the gate signal through the output of the target object recognition algorithm unit, the measurement frame rate and dynamic range of the SPAD lidar are improved while ensuring the output power of the laser emitting unit meets human eye safety requirements. Through feedback from the target object recognition algorithm unit, the modulated drive voltage causes the gain of the SPAD lidar to increase with the measurement distance, thereby effectively suppressing the drift error of the SPAD and improving the measurement dynamic range, measurement accuracy, and background light suppression capability of the SPAD lidar.

[0037] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0038] Figure 1This is a schematic diagram of the structure of a SPAD lidar drift error and background light suppression circuit provided in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the circuit structure of the nonlinear modulation gated high voltage drive unit provided in an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the circuit structure of the target object recognition algorithm unit provided in an embodiment of the present invention;

[0041] Figure 4 This is a flowchart of the method for suppressing drift error and background light of SPAD lidar provided in the embodiments of the present invention.

[0042] Icons: 100 - Nonlinear modulation gated high-voltage drive circuit unit; 110 - Gated generation circuit unit; 120 - Low-voltage DC voltage source; 130 - MOS switching unit; 140 - Voltage divider network unit; 150 - Current buffer unit; 160 - Coupling unit; 170 - High-voltage DC voltage source; 180 - Charging unit; 190 - SPAD high-voltage selection unit; 200 - SPAD array and readout circuit unit; 300 - Target object recognition algorithm unit; 310 - Light intensity measurement unit; 320 - Target object comparison and classification unit; 330 - Pixel fusion unit; 340 - Histogram statistics unit; 350 - Peak detection unit; 400 - Laser power adjustment drive unit; 500 - Laser emission unit. Detailed Implementation

[0043] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail, with reference to the accompanying drawings and specific embodiments, a drift error and light suppression circuit suitable for SPAD lidar proposed according to the present invention.

[0044] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0045] Example 1

[0046] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a SPAD lidar drift error and background light suppression circuit provided in an embodiment of the present invention.

[0047] As shown in the figure, this embodiment of the invention provides a drift error and background light suppression circuit for a SPAD lidar, characterized in that it includes a nonlinearly modulated gated high-voltage drive circuit unit 100, a SPAD array and readout circuit unit 200, a target object recognition algorithm unit 300, a laser power adjustment drive unit 400, and a laser emission unit 500.

[0048] In this embodiment, the input terminal of the nonlinear modulation gated high voltage drive circuit unit 100 is connected to the first output terminal of the target object recognition algorithm unit 300, and the output terminal of the nonlinear modulation gated high voltage drive circuit unit 100 is connected to the input terminal of the SPAD array and readout circuit unit 200.

[0049] In this embodiment, the output terminal of the SPAD array and readout circuit unit 200 is connected to the input terminal of the target object recognition algorithm unit 300; the second output terminal of the target object recognition algorithm unit 300 is connected to the input terminal of the laser power adjustment drive unit 400; and the output terminal of the laser power adjustment drive unit 400 is connected to the input terminal of the laser emission unit 500.

[0050] Optionally, the main functions of the SPAD array and readout circuit unit 200 are implemented using SPAD (Single Photon Avalanche Diode).

[0051] In this embodiment, the laser emitting unit 500 serves as a pulsed laser source, emitting laser light from its output end to an optical lens, which then illuminates the surface of a target object within the effective field of view. The SPAD array and readout circuit unit 200 acquires the optical signal; the target object recognition algorithm unit 300 measures the distance to the target object within the effective field of view based on the optical signal to obtain distance measurement information; the laser power adjustment drive unit 400 dynamically adjusts the output power of the laser emitting unit 500 based on the distance measurement information; and the nonlinearly modulated gated high-voltage drive circuit unit 100 adjusts the drive voltage of the SPAD array and readout circuit unit 200 based on the distance measurement information.

[0052] Please see Figure 2 , Figure 2 This is a schematic diagram of the circuit structure of the nonlinear modulation gated high voltage drive unit provided in an embodiment of the present invention.

[0053] In an optional implementation, the nonlinearly modulated gated high-voltage drive circuit unit 100 includes a switching circuit, a charging circuit, a high-voltage DC voltage source 170, and a SPAD high-voltage selection unit 190.

[0054] The input terminal of the switching circuit is connected to the first output terminal of the target object recognition algorithm unit 300; the output terminal of the switching circuit is connected to the input terminal of the charging circuit; the output terminal of the charging circuit is connected to the first input terminal of the SPAD high voltage selection unit 190; the second input terminal of the SPAD high voltage selection unit 190 is connected to the high voltage DC voltage source 170; the third input terminal of the SPAD high voltage selection unit 190 receives an external control signal, which is provided by an external main control system (not shown in the figure); and the output terminal of the SPAD high voltage selection unit 190 is connected to the input terminal of the SPAD array and readout circuit unit 200.

[0055] In this embodiment, the switching circuit dynamically opens and closes based on distance measurement information to provide the charging voltage for the charging circuit. The charging circuit charges and discharges according to the charging voltage to generate a nonlinear modulation voltage. The SPAD high voltage selection unit 190 is used to select the nonlinear modulation voltage or the output voltage of the high voltage DC voltage source 170 as the input voltage of the SPAD array and readout circuit unit 200 according to the external control signal.

[0056] It should be noted that in different workflows, the external master control system selects whether the driving voltage connected to the SPAD array and readout circuit unit 200 is the nonlinear modulation voltage output by the charging circuit or the high-voltage DC voltage output by the high-voltage DC voltage source 170 through external control signals.

[0057] Optionally, the high-voltage DC voltage output by the high-voltage DC voltage source 170 can be configured to 28.5V or 30V, depending on the selection of the external control signal.

[0058] In one alternative implementation, the switching circuit includes a gate generation circuit unit 110, a low-voltage DC voltage source 120, a MOS switching unit 130, and a voltage divider network unit 140.

[0059] Optionally, the low-voltage DC voltage source 120 is a DC voltage source with an output voltage of 6V.

[0060] The input terminal of the gate generation circuit unit 110 is connected to the first output terminal of the target object recognition algorithm unit 300; the gate of the MOS switch unit 130 is connected to the charging circuit; the output terminal of the low-voltage DC voltage source 120 is connected to the drain of the MOS switch unit 130; and the output terminal of the voltage divider network unit 140 is connected to the source of the MOS switch unit 130.

[0061] In this embodiment, the gate generation circuit unit 110 is used to dynamically adjust the enable time of the gate signal according to the distance measurement information, and the MOS switch unit 130 realizes opening and closing according to the enable time of the gate signal.

[0062] It should be noted that the gating signal activation time is positively correlated with the distance between the target object in the effective field of view and the SPAD lidar. By activating the gating signal before the arrival of the effective echo signal, the light suppression capability of the SPAD lidar can be effectively improved.

[0063] In this embodiment, the low-voltage DC voltage source 120 is used to control the maximum voltage output by the MOS switching unit 130; the voltage divider network unit 140 adjusts the turn-on voltage and turn-off voltage of the MOS switching unit 130 through the voltage divider network.

[0064] It should be noted that by adjusting the turn-on voltage and turn-off voltage of the MOS switch unit 130 through the voltage divider network unit 140, it can be ensured that the drive voltage of the SPAD is lower than the breakdown voltage of the SPAD before the gating signal is enabled; at the same time, when the gating signal is enabled, it is ensured that the maximum drive voltage applied to the SPAD drive terminal is less than the highest voltage that the SPAD can withstand.

[0065] In one alternative implementation, the charging circuit includes a current buffer unit 150, a coupling unit 160, and a charging unit 180.

[0066] The input terminal of the current buffer unit 150 is connected to the output terminal of the switching circuit; the output terminal of the current buffer unit 150 is connected to the first input terminal of the coupling unit 160; the second input terminal of the coupling unit 160 is connected to the output terminal of the high voltage DC voltage source 170; the output terminal of the coupling unit 160 is connected to the input terminal of the charging unit 180; and the output terminal of the charging unit 180 is connected to the first input terminal of the SPAD high voltage selection unit 190.

[0067] In this embodiment, the current buffer unit 150 is used to adjust the charging time of the charging unit 180; the coupling unit 160 is used to connect the output voltage of the switching circuit in series with the output voltage of the high voltage DC voltage source 170 to obtain the charging voltage.

[0068] It is worth noting that in order to improve the measurement accuracy and dynamic range of the SPAD lidar, the effective measurement range of the SPAD lidar needs to be divided into different measurement sub-intervals. By setting the output current of the current buffer unit 150 in different sub-intervals, it is ensured that the gain change curve of the SPAD is basically consistent in different measurement sub-intervals, thus achieving relatively stable measurement accuracy and dynamic range.

[0069] In this embodiment, the charging unit 180 charges and discharges according to the charging voltage to generate a nonlinear modulation voltage, thereby adjusting the gain of the SPAD array and the readout circuit unit 200.

[0070] It should be noted that by adjusting the resistor and capacitor of the charging unit 180, the rate at which the gain of the SPAD array and the readout circuit unit 200 changes with the measurement distance can be adjusted, so that the driving voltage of the SPAD increases with the increase of the measurement distance. This compensates for the attenuation of the echo signal strength received by the SPAD as the measurement distance increases, ensuring that the number of triggers of the SPAD remains basically unchanged within the sub-measurement interval of the defined effective measurement range, thereby improving the measurement accuracy of the SPAD lidar.

[0071] Please see Figure 3 , Figure 3 This is a schematic diagram of the circuit structure of the target object recognition algorithm unit provided in an embodiment of the present invention.

[0072] In this embodiment, the target object recognition algorithm unit 300 includes a light intensity measurement unit 310, a target object comparison and classification unit 320, a pixel fusion unit 330, a histogram statistics unit 340, and a peak detection unit 350.

[0073] The output of the SPAD array and readout circuit unit 200 is connected to the input of the light intensity measurement unit 310 and the second input of the pixel fusion unit 330, respectively. The output of the light intensity measurement unit 310 is connected to the input of the target object comparison and classification unit 320. The output of the target object comparison and classification unit 320 is connected to the first input of the pixel fusion unit 330. The output of the pixel fusion unit 330 is connected to the input of the histogram statistics unit 340. The output of the histogram statistics unit 340 is connected to the input of the peak detection unit 350. The first output of the peak detection unit 350 is connected to the nonlinear modulation gated high voltage drive circuit unit 100, and the second output is connected to the laser power adjustment drive unit 400.

[0074] In this embodiment, the light intensity measurement unit 310 is used to measure the light intensity of the light signal; the target object comparison and classification unit 320 is used to compare and classify the light intensity measurement results, and classify the target objects according to the reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance.

[0075] When the SPAD driving voltage is a DC power supply and a nonlinear modulation voltage, the intensity of the optical signal received by the SPAD satisfies a uniform distribution in the time domain within a certain measurement time range. According to the SPAD response model, the number of times the SPAD is triggered is positively correlated with the intensity of the optical signal received by the SPAD. Therefore, the intensity of the optical signal received by the SPAD can be obtained based on the number of times the SPAD is triggered per unit time.

[0076] In an optional implementation, when the SPAD driving voltage is a DC power supply and a nonlinear modulation voltage, the target object comparison and classification unit 320 compares the intensity of the light signal received by the same pixel of the SPAD. When the SPAD driving voltage is a DC voltage source, since the intensity of the light signal received by the SPAD is related to the target reflectivity but not to the distance of the target object, the SPAD cannot distinguish multiple target objects with the same reflectivity but different target distances. At this time, based on the reflectivity of the target object, the target objects within the effective field of view can be distinguished as A1, A2, A3, etc. When the SPAD driving voltage is set to a nonlinear modulation high voltage, the gain of the SPAD also changes when the target object measurement distance changes. Therefore, for two target objects with the same reflectivity but different distances, the driving voltage of the nonlinear modulation high voltage can be used to distinguish target objects with different reflectivities and different distances.

[0077] In this embodiment, the pixel fusion unit 330 is used to fuse the pixels of each category of target objects to obtain the pixel fusion result of each category; the histogram statistics unit 340 is used to perform statistics on the pixel fusion results to obtain the statistical results.

[0078] In an optional implementation, the pixel fusion unit 330 sums all pixel outputs of each category of target objects through a data selector and connects to the same module in the histogram statistics unit via time-division multiplexing.

[0079] In this embodiment, the peak detection unit 350 detects the statistical results, obtains the maximum value of the statistical results, and obtains the distance measurement information of the target object based on the maximum value of the statistical results.

[0080] Example 2

[0081] This embodiment provides a method for suppressing drift error and background light in a SPAD lidar, applicable to the drift error and background light suppression circuit of the SPAD lidar in Embodiment 1. Please refer to [link / reference]. Figure 4 , Figure 4 This is a flowchart of the method for suppressing drift error and background light of SPAD lidar provided in the embodiments of the present invention.

[0082] like Figure 4 As shown, the drift error and background light suppression method of the SPAD lidar in this embodiment includes:

[0083] The optical signal acquisition unit acquires the optical signal based on the applied driving voltage;

[0084] Based on the optical signal, distance measurement information is obtained by measuring the distance to the target object within the effective field of view.

[0085] Based on distance measurement information, the output power of the laser and the driving voltage of the optical signal acquisition unit are dynamically adjusted.

[0086] In one optional implementation, dynamically adjusting the driving voltage of the optical signal acquisition unit based on distance measurement information includes:

[0087] A nonlinear modulation voltage is generated based on distance measurement information; the nonlinear modulation voltage or DC voltage is selected as the driving voltage for the optical signal acquisition unit based on an external control signal.

[0088] In one optional implementation, the optical signal acquisition unit acquires the optical signal based on the applied driving voltage, including:

[0089] According to the external control signal, a DC voltage is applied to the optical signal acquisition unit as the driving voltage to acquire the optical signals of target objects with different reflectivities.

[0090] Based on the external control signal, a nonlinear modulation voltage is applied to the optical signal acquisition unit as the driving voltage to acquire optical signals from targets at different distances.

[0091] In an optional implementation, distance measurement information is obtained by measuring the distance to a target within the effective field of view based on the optical signal, including:

[0092] The light intensity of the light signal is measured, the light intensity measurement results are compared and classified, and the target objects are classified according to reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance.

[0093] The pixels of each category of target objects are fused to obtain the pixel fusion result for each category;

[0094] The pixel fusion results were statistically analyzed to obtain the statistical results.

[0095] The statistical results are tested to obtain the maximum value, and the distance measurement information of the target object is obtained based on the maximum value.

[0096] The drift error and background light suppression circuit and method of the SPAD lidar in this invention employs a nonlinearly modulated gated high-voltage drive circuit unit, which can effectively improve the background light suppression capability of the SPAD lidar. Furthermore, by dynamically adjusting the enable timing of the gate signal through the output of the target object recognition algorithm unit, the measurement frame rate and dynamic range of the SPAD lidar are improved while ensuring the output power of the laser emitting unit meets human eye safety requirements. Through feedback from the target object recognition algorithm unit, the modulated drive voltage causes the gain of the SPAD lidar to increase with the measurement distance, thereby effectively suppressing the drift error of the SPAD and improving the measurement dynamic range, measurement accuracy, and background light suppression capability of the SPAD lidar.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0098] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A drift error and background light suppression circuit for a SPAD lidar, characterized in that, It includes a nonlinear modulation gated high voltage drive circuit unit (100), a SPAD array and readout circuit unit (200), a target object recognition algorithm unit (300), a laser power adjustment drive unit (400), and a laser emission unit (500). The input terminal of the nonlinear modulation gated high voltage drive circuit unit (100) is connected to the first output terminal of the target object recognition algorithm unit (300), and the output terminal of the nonlinear modulation gated high voltage drive circuit unit (100) is connected to the input terminal of the SPAD array and readout circuit unit (200). The output terminal of the SPAD array and readout circuit unit (200) is connected to the input terminal of the target object recognition algorithm unit (300); the second output terminal of the target object recognition algorithm unit (300) is connected to the input terminal of the laser power adjustment drive unit (400); the output terminal of the laser power adjustment drive unit (400) is connected to the input terminal of the laser emitting unit (500). The laser emitting unit (500) serves as a pulsed laser source, and its output end emits laser light to the optical lens, which then uses the optical lens to irradiate the surface of the target object within the effective field of view. The SPAD array and readout circuit unit (200) are used to acquire optical signals; The target object recognition algorithm unit (300) is used to perform distance measurement on the target object within the effective field of view based on the light signal to obtain distance measurement information; The laser power adjustment drive unit (400) is used to dynamically adjust the output power of the laser emitting unit (500) according to the distance measurement information; The nonlinear modulation gated high-voltage drive circuit unit (100) is used to adjust the drive voltage of the SPAD array and readout circuit unit (200) according to the distance measurement information; the nonlinear modulation gated high-voltage drive circuit unit (100) includes a switching circuit, a charging circuit, a high-voltage DC voltage source (170), and a SPAD high-voltage selection unit (190); wherein, the input terminal of the switching circuit is connected to the first output terminal of the target object recognition algorithm unit (300); the output terminal of the switching circuit is connected to the input terminal of the charging circuit; the output terminal of the charging circuit is connected to the first input terminal of the SPAD high-voltage selection unit (190); the second input terminal of the SPAD high-voltage selection unit (190) is connected to... The high-voltage DC voltage source (170) receives an external control signal at its third input terminal; the output terminal of the SPAD high-voltage selection unit (190) is connected to the input terminal of the SPAD array and readout circuit unit (200); the switching circuit dynamically opens and closes according to the distance measurement information to provide the charging voltage for the charging circuit; the charging circuit charges and discharges according to the charging voltage to generate a nonlinear modulation voltage; the SPAD high-voltage selection unit (190) is used to select either the nonlinear modulation voltage or the output voltage of the high-voltage DC voltage source (170) as the input voltage for the SPAD array and readout circuit unit (200) according to the external control signal. The switching circuit includes a gate generation circuit unit (110), a low-voltage DC voltage source (120), a MOS switching unit (130), and a voltage divider network unit (140). The input terminal of the gate generation circuit unit (110) is connected to the first output terminal of the target object recognition algorithm unit (300). The gate of the MOS switching unit (130) is connected to the charging circuit. The output terminal of the low-voltage DC voltage source (120) is connected to the drain of the MOS switching unit (130). The voltage divider network unit (140)... The output terminal of the MOS switch unit (130) is connected to the source of the MOS switch unit (130); the gate generation circuit unit (110) is used to dynamically adjust the enable time of the gate signal according to the distance measurement information; the MOS switch unit (130) is turned on and closed according to the enable time of the gate signal; the low voltage DC voltage source (120) is used to control the maximum voltage output of the MOS switch unit (130); the voltage divider network unit (140) is used to adjust the turn-on voltage and the turn-off voltage of the MOS switch unit (130).

2. The drift error and background light suppression circuit of the SPAD lidar according to claim 1, characterized in that, The charging circuit includes a current buffer unit (150), a coupling unit (160), and a charging unit (180). The input terminal of the current buffer unit (150) is connected to the output terminal of the switching circuit; The output terminal of the current buffer unit (150) is connected to the first input terminal of the coupling unit (160), the second input terminal of the coupling unit (160) is connected to the output terminal of the high voltage DC voltage source (170), and the output terminal of the coupling unit (160) is connected to the input terminal of the charging unit (180). The output terminal of the charging unit (180) is connected to the first input terminal of the SPAD high voltage selection unit (190); The current buffer unit (150) is used to adjust the charging time of the charging unit (180); the coupling unit (160) is used to connect the output voltage of the switching circuit in series with the output voltage of the high voltage DC voltage source (170) to obtain the charging voltage. The charging unit (180) charges and discharges according to the charging voltage to generate a nonlinear modulation voltage to adjust the gain of the SPAD array and readout circuit unit (200).

3. The drift error and background light suppression circuit of the SPAD lidar according to claim 1, characterized in that, The target object recognition algorithm unit (300) includes a light intensity measurement unit (310), a target object comparison and classification unit (320), a pixel fusion unit (330), a histogram statistics unit (340), and a peak detection unit (350). The output terminal of the SPAD array and readout circuit unit (200) is connected to the input terminal of the light intensity measurement unit (310) and the second input terminal of the pixel fusion unit (330), respectively. The output of the light intensity measurement unit (310) is connected to the input of the target object comparison and classification unit (320); The output of the target object comparison and classification unit (320) is connected to the first input of the pixel fusion unit (330); the output of the pixel fusion unit (330) is connected to the input of the histogram statistics unit (340); the output of the histogram statistics unit (340) is connected to the input of the peak detection unit (350). The first output terminal of the peak detection unit (350) is connected to the nonlinear modulation gated high voltage drive circuit unit (100), and the second output terminal is connected to the laser power adjustment drive unit (400). The light intensity measurement unit (310) is used to measure the light intensity of the light signal; The target object comparison and classification unit (320) is used to compare and classify the light intensity measurement results, and classify the target objects according to reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance. The pixel fusion unit (330) is used to fuse the pixels of each category of target objects to obtain the pixel fusion result of each category; The histogram statistics unit (340) is used to perform statistics on the pixel fusion results to obtain statistical results; The peak detection unit (350) detects the statistical results and obtains the maximum value of the statistical results. Based on the maximum value of the statistical results, the distance measurement information of the target object is obtained.

4. A method for suppressing drift error and background light in a SPAD lidar, used in the drift error and background light suppression circuit of the lidar as described in any one of claims 1-3, characterized in that, include: The optical signal acquisition unit acquires the optical signal based on the applied driving voltage; Based on the optical signal, distance measurement information is obtained by measuring the distance to the target object within the effective field of view. Based on the distance measurement information, the output power of the laser and the driving voltage of the optical signal acquisition unit are dynamically adjusted.

5. The method for suppressing drift error and background light in SPAD lidar according to claim 4, characterized in that, Based on the distance measurement information, dynamically adjust the driving voltage of the optical signal acquisition unit, including: A nonlinear modulation voltage is generated based on the distance measurement information; The nonlinear modulation voltage or DC voltage is selected as the driving voltage for the optical signal acquisition unit based on the external control signal.

6. The method for suppressing drift error and background light in SPAD lidar according to claim 4, characterized in that, The optical signal acquisition unit acquires the optical signal based on the applied driving voltage, including: According to the external control signal, a DC voltage is applied to the optical signal acquisition unit as the driving voltage to acquire the optical signals of target objects with different reflectivities. Based on the external control signal, a nonlinear modulation voltage is applied to the optical signal acquisition unit as the driving voltage to acquire optical signals from targets at different distances.

7. The method for suppressing drift error and background light in SPAD lidar according to claim 4, characterized in that, Based on the optical signal, distance measurement information is obtained by measuring the distance to the target object within the effective field of view, including: The light intensity of the light signal is measured, the light intensity measurement results are compared and classified, and the target objects are classified according to reflectivity and distance based on the comparison results. Target objects of the same category have the same reflectivity and the same distance. The pixels of each category of target objects are fused to obtain the pixel fusion result for each category; The pixel fusion results were statistically analyzed to obtain the statistical results. The statistical results are detected to obtain the maximum value of the statistical results, and the distance measurement information of the target object is obtained based on the maximum value of the statistical results.

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