Photoelectric detection module for laser radar, laser radar and ambient light detection method

Abstract

The present application discloses a photoelectric detection module for laser radar, laser radar and ambient light detection method. The photoelectric detection module for laser radar includes a photoelectric detection unit, a signal conditioning unit and a data processing unit; the output end of the photoelectric detection unit is connected to the input end of the signal conditioning unit, and the output end of the signal conditioning unit is connected to the input end of the data processing unit; the photoelectric detection unit is used to sense the light signal incident thereon and convert the sensed light signal into an electrical signal; the signal conditioning unit includes an ambient light detection subunit, and the ambient light detection subunit is used to detect the DC signal in the electrical signal and quantize the DC signal; the data processing unit is used to analyze and process the received quantized DC signal. The brightness of the ambient light in which the laser radar is located can be inferred by the size of the detected DC signal, so as to adjust the corresponding parameters of the laser radar.

Description

Technical Field

[0001] The present application relates to the field of laser detection, and in particular to a photoelectric detection module for laser radar, a laser radar and an ambient light detection method. Background Art

[0002] LiDAR is usually used to detect information about external obstacles, such as the distance of the obstacle from the LiDAR, the shape of the obstacle, etc.

[0003] The laser radar includes a transmitting module and a receiving module, and the receiving module includes a photoelectric detection module. The photoelectric detection module usually receives the echo laser signal after the detection laser emitted by the transmitting module hits an obstacle.

[0004] As far as the inventors know, it is difficult for existing solutions to accurately detect weak DC signals flowing out of photoelectric detection units such as APD, SPAD and SiPM under voltage changes. Therefore, the problems that need to be solved urgently are how to detect weak DC signals and how to compensate for current detection errors caused by voltage changes. Summary of the invention

[0005] This application content section is provided to introduce the concepts in a brief form, which will be described in detail in the detailed implementation section below. This application content section is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to be used to limit the scope of the technical solution claimed for protection.

[0006] In the first aspect, the present application provides a photoelectric detection module for a laser radar, comprising: a photoelectric detection unit, a signal conditioning unit and a data processing unit; the output end of the photoelectric detection unit is connected to the input end of the signal conditioning unit, and the output end of the signal conditioning unit is connected to the input end of the data processing unit; the photoelectric detection unit is used to sense the light signal incident thereon, and convert the sensed light signal into an electrical signal, wherein the light signal incident thereon comprises an ambient light signal and an echo laser signal generated by reflection after the laser beam is irradiated onto the object to be measured; the signal conditioning unit comprises an ambient light detection subunit, and the ambient light detection subunit is used to detect a DC signal in the electrical signal and quantize the DC signal; wherein the DC signal comprises a DC signal generated by the photoelectric detection unit sensing the ambient light signal; the data processing unit is used to analyze and process the received quantized AC signal and the quantized DC signal, and adjust the photoelectric detector unit according to the result of the ambient light detection.

[0007] In a second aspect, an embodiment of the present application provides a laser radar, which includes the photoelectric detection module for the laser radar described in the first aspect.

[0008] In a third aspect, an embodiment of the present application provides an ambient light detection method, which is used for the photoelectric detection module for laser radar described in the first aspect; the method comprises: obtaining a reference voltage signal that rises monotonically under the control of the same clock signal and a counting signal that counts monotonically; comparing the reference voltage signal with the measured voltage signal output by the current-voltage conversion module; wherein the current-voltage conversion module is used to convert the DC current signal generated by the photoelectric detection module from the detected ambient light into a measured voltage signal; when the reference voltage signal rises to the same moment as the measured voltage signal, the count value corresponding to the counting signal at that moment is determined as the target count value; and the intensity of the ambient light of the laser radar is determined according to the target count value.

[0009] The photoelectric detection module, laser radar and ambient light detection method for laser radar provided in the embodiment of the present application detect the intensity of the DC signal caused by ambient light by setting an ambient light detection subunit in the photoelectric detection module. Thus, the brightness of the ambient light in which the laser radar is located can be inferred by detecting the magnitude of the DC signal, which is conducive to adjusting the corresponding parameters of the laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0011] Figure 1 A schematic structural diagram of a photoelectric detection module for a laser radar provided in an embodiment of the present application;

[0012] Figure 2 A schematic circuit structure diagram of an embodiment of a photoelectric detection module for a laser radar provided in an embodiment of the present application;

[0013] Figure 3 A schematic circuit structure diagram of another embodiment of a photoelectric detection module for a laser radar provided in an embodiment of the present application;

[0014] Figure 4 A timing diagram of an ambient light detection scheme for a multi-channel photoelectric detection module for a lidar;

[0015] Figure 5 for Figure 1 to Figure 3 A schematic diagram of a circuit structure of a photoelectric detection module for a laser radar is shown;

[0016] Figure 6 A schematic flow chart of an embodiment of an ambient light detection method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] In the laser radar receiving system, ambient light will affect the detection of the receiving system. The specific manifestation is that the ambient light forms a current proportional to the light intensity on the photodetector. This current value varies with the external light intensity. For example, it may range from 0.9uA to 17uA (avalanche photodetector, APD). The echo of APD is a pulse current, and the current peak value varies greatly, ranging from a few uA to 1A. The DC in the photodetector will increase the shot noise (shot noise of the photocurrent), that is, the external ambient light will affect the signal-to-noise ratio of the detector.

[0018] There is a lack of methods for detecting the impact of ambient light on detection current in existing laser radars in real time. Taking the existing multi-line laser radars that use APD as detectors as an example, each channel shares a high voltage, which is controlled based on temperature feedback to reduce the drift of APD gain with temperature. However, this solution cannot measure the DC current of the detector, and therefore cannot quantitatively evaluate the noise impact of external ambient light on the detection of the laser radar.

[0019] Some existing technologies detect and quantify DC current into digital signals, which requires the circuit to have two functions: one is the conversion from current to voltage, and the other is the quantization of the voltage signal. For DC detection of intermediate current-voltage conversion, the commonly used technology in the circuit is to connect a detection resistor in series with the current input branch, and complete the current value detection by measuring the voltage difference across the series resistor. When considering that the DC voltage of the photoelectric detection unit (APD) changes with temperature and process, some existing technologies use a common-mode voltage differential amplifier to perform current detection under wide common-mode voltage conditions.

[0020] The above circuit completes the conversion from current to voltage, and has the following two disadvantages. First, the conversion resistor cannot take a larger resistance value. If it is too large, the common-mode suppression of the current will deteriorate, resulting in an increase in output deviation. For detecting microampere-level current, the transimpedance gain cannot be too small, because it is equivalent to the voltage noise level, and a too small voltage cannot be effectively quantized. Therefore, in order to ensure effective quantization, further amplification is required. Further amplification will cause the mismatch of the differential amplifier to be further amplified. Taking the minimum effective quantization value as an example, at least two additional amplifiers are required. Therefore, this circuit is used for small current detection, which increases the complexity of the entire detection circuit; second, in order to meet better detection accuracy, the op amp is required to have a good input offset voltage and the DC of the measured current will not be shunted inside the detection circuit. If it is not shunted, it is necessary to ensure that the equivalent resistance of the positive and negative terminals of the op amp is completely consistent, the proportional error is small, and the op amp input is small enough. It is necessary to improve the resistance matching accuracy and the op amp input to tube matching accuracy, which will greatly increase the circuit area and increase the cost.

[0021] The DC detection of APD is performed through the scheme in the present application. A preset ramp voltage generating circuit related to ambient light is provided in the synchronous logic circuit. The ramp voltage generating circuit generates a voltage signal Vramp that changes linearly from a preset minimum voltage value (for example, 0V) to a preset maximum voltage value in each time period of ambient light detection. The current-voltage converter outputs the measured voltage value output by the photoelectric detection module according to the measured intensity of the ambient light. The measured voltage value is compared with Vramp, and the actual voltage value corresponding to the obtained ambient light is determined by the comparison result. Thus, the DC current corresponding to the ambient light is determined, and then the ambient light intensity is determined. Then, the relevant parameters of the photodetector are adjusted according to the ambient light intensity. Thus, the power consumption of the laser radar can be adjusted according to the ambient light. On the premise of ensuring that the laser radar can obtain accurate signals of the detected object, the power consumption and system complexity can be reduced, and the detection accuracy can be improved.

[0022] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] Please refer to Figure 1 , Figure 1 A schematic structural diagram of a photoelectric detection module for a laser radar provided in an embodiment of the present application is shown.

[0025] like Figure 1 As shown, the photoelectric detection module for laser radar includes: a photoelectric detection unit 11, a signal conditioning unit 12 and a data processing unit 13. The output end of the photoelectric detection unit 11 is connected to the input end of the signal conditioning unit 12. The output end of the signal conditioning unit 12 is connected to the input end of the data processing unit 13.

[0026] The photoelectric detection unit 11 is used to sense the light signal incident thereon and convert the sensed light signal into an electrical signal, wherein the light signal incident thereon includes an ambient light signal and an echo laser signal generated by reflection after the laser beam is irradiated onto the object to be measured. In addition to the ambient light and the echo signal, the electrical signal may also include dark current.

[0027] The signal conditioning unit 12 includes an ambient light detection subunit 121 and an AC detection subunit 122. The ambient light detection subunit 121 is used to detect the DC signal in the electrical signal and quantify the DC signal, and the quantization result reflects the intensity of the ambient light. The AC detection subunit 122 is used to amplify and quantize the AC signal in the electrical signal; wherein the AC signal includes the AC signal generated by the photoelectric detection unit 11 sensing the echo signal, and the DC signal includes the DC signal generated by the photoelectric detection unit 11 sensing the ambient light signal.

[0028] The data processing unit 13 is used to analyze and process the received quantized AC signal and quantized DC signal. For example, the data processing unit converts the quantized DC voltage signal into a corresponding DC voltage amplitude.

[0029] In this embodiment, an ambient light detection subunit is provided in the photoelectric detection module to detect the intensity of the DC signal caused by the ambient light. Thus, the brightness of the ambient light in which the laser radar is located can be inferred by detecting the magnitude of the DC signal, which is conducive to adjusting the corresponding parameters of the laser radar.

[0030] In some optional implementations of this embodiment, the signal conditioning unit 12 further includes a bias regulating subunit 123. The output end of the bias regulating subunit 123 is electrically connected to the anode of the photodetection unit 11; wherein the bias regulating subunit 123 is used to adjust the bias of the photodetection unit 11 to calibrate the working current drift of the photodetection unit 11 caused by temperature and process deviation. Figure 1 and Figure 5 , the bias adjustment subunit 123 (DAC, digital-to-analog converter) outputs a voltage VB connected to the anode of the photodetection unit, and the cathode of the photodetection unit is connected to HV, so the voltage difference of the photodetection unit is HV-VB, and the target quantity of the photodetection unit is current. For the photodetection unit, the physical relationship related to the current I can be expressed as I=f(HV-VB,T,P). Since the temperature T and process P will cause different diodes to have different I values, it is necessary to adjust HV-VB to make the I value the same, while HV remains unchanged, so VB must be adjusted. That is, the output voltage of the bias adjustment subunit 123 is used to adjust the current of the photodetection unit.

[0031] Please combine Figure 2 , which shows a schematic circuit structure diagram of an embodiment of a photoelectric detection module for a laser radar provided in an embodiment of the present application.

[0032] like Figure 2As shown, the photoelectric detection module may include a photoelectric detection unit 11, a signal conditioning unit 12 and a data processing unit 13. The photoelectric detection unit 11 may be an APD, Spad(s) or SiPM.

[0033] In this embodiment, the signal conditioning unit 12 includes: Figure 1 The ambient light detection subunit 121 and the AC signal detection subunit 122 are shown.

[0034] In addition, the photoelectric detection module for laser radar can also include Figure 1 The bias regulation subunit 123 and the AC detection subunit 122 are shown.

[0035] The AC detection subunit 122 may include a capacitor 1221, an AC current signal amplifier 1222, and an analog-to-digital converter (ADC) 1223. The capacitor is used to block the DC signal.

[0036] The ambient light detection subunit 121 includes a current-voltage conversion module. The input end of the current-voltage conversion module is electrically connected to the anode of the photodetection unit. The output end of the current-voltage conversion module is connected to the input end of the data processing unit. The current-voltage conversion module includes: a synchronous logic circuit 1211, a ramp voltage generator 1212, a counter 1213, a current-voltage converter 1214, a voltage comparator 1215 and a latch 1216; wherein the output end of the photodetection unit 11 is connected to the input end of the current-voltage converter 1214. The signal output end of the synchronous logic circuit can output the same clock signal. The signal output end of the synchronous logic circuit 1211 is respectively connected to the input end of the ramp voltage generator 1212 and the input end of the counter 1213. The clock signal output by the synchronous logic circuit 1211 controls the ramp voltage generator 1212 and the counter 1213 to work simultaneously. Under the control of the clock signal output by the counter 1211, the ramp voltage generator 1212 generates a monotonically rising voltage signal that changes with time. The counter 1213 is controlled by the clock signal output by the synchronous logic circuit 1211 to generate a count value that increases monotonically over time.

[0037] The inverting input terminal of the voltage comparator 1215 is connected to the output terminal of the current-voltage converter 1214; the non-inverting input terminal of the voltage comparator 1215 is connected to the output terminal of the ramp voltage generator 1212; the control terminal of the latch 1216 is connected to the output terminal of the voltage comparator 1215, and the signal input terminal of the latch 1216 is connected to the output terminal of the counter 1213. The output terminal of the latch is connected to the data processing unit 13 as the output terminal of the current-voltage conversion module.

[0038] Under the control of the signal output by the synchronous logic circuit 1211, the ramp voltage generator 1212 generates a ramp voltage signal (Vramp). In each ambient light signal detection time period, the ramp voltage generator 1212 generates a linearly changing voltage signal from a preset minimum voltage value to a preset maximum voltage value. The counter 1213 counts according to a preset counting frequency (Cout). When the ramp voltage signal (Vramp) input to the in-phase input terminal of the voltage comparator 1215 is greater than the voltage signal Vout output by the current-voltage converter, the voltage comparator outputs a control signal for controlling the operation of the latch; the control terminal of the latch inputs the control signal, the latch latches the count value input by the signal input terminal at this time, and outputs the latched count value Lout. Lout is a digital code value that does not change with time. The above digital code value latched by the latch is controlled by the high level output by the voltage comparator 1215. The voltage comparator 1215 outputs a high level signal when the voltage Vramp output by the ramp voltage generator rises linearly from a preset minimum value to a preset maximum value, and when the value of Vramp at a certain moment is just greater than (or can be regarded as equal to) the voltage Vout output by the current-voltage converter. In the case where the APD ambient light remains unchanged for a short time, the original APD DC value can be inferred from the code value of Lout. Therefore, the data processing unit determines the DC voltage value corresponding to the ambient light signal according to the count value.

[0039] The ramp voltage generator generates a ramp voltage signal rising from a preset minimum voltage value to a preset maximum voltage value within a preset sampling time period; the counter counts from a preset minimum value to a preset maximum value according to a preset counting frequency within the preset sampling time period. The preset maximum voltage value is related to the expected ambient light level. The stronger the expected ambient light, the greater the maximum voltage value. In a specific implementation, the maximum voltage value may be slightly higher than or equal to the expected ambient light level.

[0040] The photoelectric detector used for laser radar can include multiple sampling time periods when it is working. In each sampling time period, the synchronization signal generated by the synchronous logic circuit controls the ramp voltage generator and the counter to work simultaneously. In this sampling time period, the ramp voltage generator generates a ramp voltage signal from a preset minimum voltage to a preset maximum voltage. At the same time, in this sampling time period, the counter changes from 000...0 to 111...1 (the number of bits counted depends on the expected quantization accuracy, such as n=8bit), so that the voltage value Vramp output by the ramp voltage generator and the count value Cout of the counter increase proportionally with time.

[0041] The current-voltage converter can be any existing converter that converts a DC current into a DC voltage. The current-voltage converter can input an analog DC current signal produced by the photodetection unit by sensing ambient light, and convert the above analog DC current signal into an analog DC voltage signal Vout. The voltage signal Vout output by the current-voltage converter is input to the inverting input terminal of the voltage comparator. The voltage signal Vramp output by the ramp voltage generator is input to the non-inverting input terminal of the voltage comparator. When the voltage signal Vout is greater than the voltage signal Vramp, the voltage comparator outputs a low level. When the voltage signal Vout is less than the voltage signal Vramp, the voltage comparator outputs a high level.

[0042] When the voltage comparator 1215 outputs a low level, that is, the control terminal of the latch inputs a low level, the latch does not work, and the count value input to the latch 1216 is not latched by the latch. The latch has no output. When the voltage comparator 1215 outputs a high level, the control terminal of the latch inputs a high level, the latch starts to work, and the count value input to the latch 1216 is latched by the latch. The latch can output the count value input therein, and the output value is Lout.

[0043] Lout may be a binary number. The data processing unit may convert the binary number into a corresponding DC voltage value, or into a DC current value related to the ambient light and the dark current, and then determine information such as the size or intensity of the ambient light.

[0044] In a single-channel circuit, the DC voltage Vout is compared with Vramp. When the Vramp voltage exceeds the Vout voltage value, the comparator output voltage Vcmp flips, and Vcmp triggers the Latch circuit to latch the current count value of the Counter and output it as Lout (digital code value). At this time, the corresponding relationship between Vout and Lout is:

[0045]

[0046] Wherein, n is the preset number of count bits of the counter, and VFS is the preset maximum voltage value that the ramp voltage generator can generate.

[0047] Assuming that the transimpedance gain of the current-to-voltage converter is Rt, the corresponding relationship between the count value of the input DC current latch output is

[0048]

[0049] Among them I in(DC) is the direct current generated by the photodetector; Vout is the direct voltage value output by the current-to-voltage converter; Rt is the transimpedance gain of the current-to-voltage converter; VFS is the maximum preset voltage that the ramp voltage generator can generate; Lout is the count value output by the latch; n is the preset number of count bits of the above counter.

[0050] In this embodiment, the comparator and latch are used to implement DC quantization. This solution does not require high performance and power consumption, has a simple circuit structure, and is only triggered once when Vramp is greater than Vout. The ramp voltage generator, counter and latch are reset before the next measurement begins. The number of flips is small, so the power consumption is low and the system complexity is low.

[0051] Please refer to Figure 3 , which shows a schematic circuit structure diagram of another embodiment of a photoelectric detection module for a laser radar provided in an embodiment of the present application.

[0052] and Figure 2 compared to, Figure 3 The circuit structure diagram of the photoelectric detection module for laser radar shown in the figure includes a plurality of photoelectric detection units 111, 112, ..., 11N. Each photoelectric detection unit corresponds to a channel. Each channel includes a photoelectric detection unit and a signal conditioning unit. Figure 3 As shown, the photoelectric detection module for laser radar includes signal conditioning units 101, 102, ..., 10N. N is the number of channels, which is an integer greater than 2.

[0053] Each signal conditioning unit may include an ambient light detection subunit, a bias adjustment subunit, and an AC detection subunit. The ambient light detection subunit includes a current-voltage conversion module. The current-voltage conversion module includes a current-voltage converter 1214, a voltage comparator 1215, and a latch 1216; the AC detection subunit may include a capacitor 1221, an amplifier 1222, and an analog-to-digital converter 1223.

[0054] In this embodiment, the current-to-voltage conversion modules of the ambient light detection subunits 101, 102, ... 10N of multiple channels can share a synchronous logic circuit, a ramp voltage generator, and a counter. The multi-channel ambient light detection subunits share a synchronous logic circuit, a ramp voltage generator, and a counter, which can save chip area and reduce overall system complexity and power consumption.

[0055] That is to say, in this embodiment, the in-phase input terminal of the voltage comparator of the ambient light detection subunit of each channel in the multiple channels 101, 102, ... 10N is input with the ramp voltage signal output by the same ramp voltage generator; the signal input terminal of the latch is input with the count value output by the same counter.

[0056] Please refer to Figure 4 , which shows a timing diagram of an ambient light detection scheme for a multi-channel photoelectric detection module for a lidar. Figure 4 Taking the quantization of three channels as an example, the timing relationship of Cout, Vramp, Vcmp, and Lout is shown. At t1, the ramp voltage generator and the counter are started, and the voltage Vramp generated by the ramp voltage generator starts to climb upward at a constant slope from 0V. The counter count value (Cout) starts from 0 and changes once at the rising edge of the clock (not shown, each X indicates a clock change) to increase the digital code value by 1. At t2, Vramp exceeds the Vout1 voltage of channel 101, the comparator output Vcmp1 flips, and the latch latches the counter count value 3 at this moment in Lout1. At t3, Vramp exceeds the Vout2 voltage of channel 102, the comparator output Vcmp2 flips, and the latch latches the counter count value 80 at this moment in Lout2. At t4, Vramp exceeds the Vout3 voltage of channel 103, the comparator output Vcmp3 flips, and the latch latches the counter count value 253 at this moment in Lout3. At time t5, the counter stops counting, and the ramp voltage generator stops rising, waiting for the next quantization command to arrive. Before the next quantization command arrives, each channel latch is reset, and the counter and the ramp voltage generator repeat the actions of t1 to t5. It should be noted that time t1 can be the moment after receiving the laser detection echo, or it can be the moment before receiving the laser detection echo. In practice, in order to avoid the interference of the circuit action of the ambient light detection subunit on the received laser detection echo (causing ranging errors or reduced accuracy), the ambient light detection subunit can detect the ambient light signal intensity after receiving the laser detection echo.

[0057] In the present application, times t1, t2, t3, and t4 are all within the time window for measuring the APD DC once, t1 indicates the start time of measurement for all channels, t5 indicates the end time of measurement for all channels, t2, t3, and t4 indicate the end values ​​of the measurement times corresponding to different channels (channel 1, channel 2, channel 3), and the difference between the end value of the measurement time and t1 (for example: t2-t1) is proportional to the DC current value on the photoelectric detection unit being detected (the current amplitude is quantified by the length of time).

[0058] In this embodiment, a ramp voltage generating circuit that is preset and related to ambient light is provided in the synchronous logic circuit, and the ramp voltage generating circuit generates a voltage signal Vramp that changes linearly from a preset minimum voltage value (for example, 0V) to a preset maximum voltage value in each time period of ambient light detection. The current-voltage converter outputs the measured voltage value output by the photoelectric detection module according to the measured intensity of the ambient light. The measured voltage value is compared with Vramp, and the actual voltage value corresponding to the obtained ambient light is determined by the comparison result. Thus, the DC current corresponding to the ambient light is determined, and then the ambient light intensity is determined. Then, the relevant parameters of the photodetector are adjusted according to the ambient light intensity. Thus, the power consumption of the laser radar can be adjusted according to the ambient light, and the power consumption of the laser radar can be reduced under the premise of ensuring that the laser radar can obtain accurate signals of the detected object.

[0059] Compared with the digital quantization unit using multi-channel analog-to-digital conversion, the solution proposed in this application is to use a ramp voltage generator and counter shared between channels, and a single channel through a comparator and a latch to reduce the overall system complexity and power consumption. The comparator and latch used do not require high performance and power consumption, the circuit structure is simple, and it is only triggered once when Vramp is greater than Vout. The ramp voltage generator, counter and latch are reset before the next measurement begins, and the number of flips is small, so the power consumption is low and the system complexity is low.

[0060] Please continue to refer to Figure 5 , which shows Figure 1 to Figure 3 The figure shows a schematic diagram of a circuit structure for implementing a photoelectric detection module for a laser radar.

[0061] exist Figure 5 In a circuit structure of a photodetector for a laser radar, the photodetector is connected to the amplifier AMP of the AC signal detection subunit through a DC blocking capacitor to ensure that the DC signal does not flow into the AC signal detection subunit. In addition, the current-voltage converter of the bias adjustment subunit (DAC) and the ambient light detection subunit are integrated into the circuit.

[0062] like Figure 5As shown, the bias regulation subunit DAC includes a low voltage regulation subunit LVDAC and a medium voltage amplification subunit (medium voltage amplifier); the medium voltage amplification subunit includes: a DC current source I0, a first transistor M1, a first operational amplifier A1, a first input resistor R1 and a first feedback resistor R2; wherein, one end of the first input resistor R1 is connected to the ground line, and the other end is connected to one end of the first feedback resistor R2; the other end of the first feedback resistor R2 is respectively electrically connected to the anode of the photoelectric detection unit APD1, the output end of the DC current source and the drain of the first transistor; the photo The cathode of the electrical detection unit APD1 is electrically connected to the first high potential HV, and the anode of the photodetection unit APD1 is also electrically connected to the output end of the DC current source I0; the source of the first transistor M1 is connected to the ground wire, and the drain of the first transistor M1 is connected to the output end of the DC current and the anode of the photodetection unit; the gate of the first transistor M1 is connected to the output end of the first operational amplifier A1; the non-inverting input end of the first operational amplifier is connected to the other end of the first input resistor, and the inverting input end of the first operational amplifier is connected to the output end of the low-voltage regulation subunit.

[0063] The current-voltage comparison module includes a second triode M2, a third triode M3, a fourth triode M4, a third resistor R4, a voltage comparator CMP and a latch circuit latch; wherein the gate of the second triode M2 ​​is connected to the gate of the first triode M1, the source of the second triode M2 ​​is connected to the ground line, and the drain of the second triode M2 ​​is connected to the drain of the third triode M3;

[0064] The gate of the third transistor M3 is connected to the gate of the fourth transistor M4; the source of the third transistor M3 is connected to the second high potential LV1, and the gate of the third transistor M3 is connected to the drain of the third transistor M3;

[0065] The source of the fourth transistor M4 is connected to the third high potential LV2; the drain of the fourth transistor M4 is connected to one end of the third resistor R4 and to the inverting input end of the voltage comparator CMP;

[0066] The non-inverting input terminal of the voltage comparator CMP is connected to the output terminal of the ramp voltage generator, and the output terminal of the voltage comparator CMP is connected to the control terminal of the latch Latch;

[0067] The signal input end of the latch is connected to the output end of the counter, and the output end of the latch is connected to the data processing unit, and the data processing unit determines the DC voltage corresponding to the DC current according to the output end of the latch;

[0068] The other end of the third resistor R4 is connected to the ground line.

[0069] In addition, the ambient light detection subunit of the photoelectric detection module for the laser radar also includes a current compensation module; wherein the current compensation module is electrically connected to the bias adjustment subunit and the current-voltage conversion module respectively.

[0070] The current compensation module includes a second operational amplifier A2, a fifth transistor M5, a sixth transistor M6, a seventh transistor M7, an eighth transistor M8 and a ninth transistor M9; wherein,

[0071] The non-inverting input terminal of the second operational amplifier A2 is connected to the inverting input terminal of the first operational amplifier A1; the inverting input terminal of the second operational amplifier A2 is electrically connected to the source of the fifth transistor and one end of the fourth resistor R3; the output terminal of the second operational amplifier A2 is connected to the gate of the fifth transistor M5;

[0072] The other end of the fourth resistor R3 is connected to the ground line;

[0073] The drain of the fifth transistor M5 is electrically connected to the gate and drain of the sixth transistor M6 and the gate of the seventh transistor M7;

[0074] The source of the sixth transistor M6 is electrically connected to the fourth high potential LV3; the gate of the sixth transistor M6 is connected to the gate of the seventh transistor M7;

[0075] The source of the seventh transistor M7 is electrically connected to the fifth high potential LV4; the drain of the seventh transistor M7 is electrically connected to the drain of the eighth transistor M8;

[0076] The source of the eighth transistor M8 is connected to the ground line, and the gate is electrically connected to the gate of the ninth transistor M9; the drain of the eighth transistor M8 is electrically connected to the gate of the eighth transistor M8;

[0077] The source of the ninth transistor M9 is connected to the ground line, and the drain is electrically connected to the drain of the fourth transistor M4.

[0078] The DAC output voltage range is 0~M(V), M>0. The voltage output by the DAC is used to adjust the bias voltage of the photodetector. The DAC consists of two circuits, one is the LVDAC (low voltage DAC), and the other is the MV amplifier (medium voltage amplifier). The MV amplifier includes A1, R1, R2, I0 and M1. A1 is an operational amplifier. R1 and R2 are the input resistor and feedback resistor respectively. I0 is a DC current source. M1 is an output NMOS. The gain of the MV amplifier is (1+R2 / R1). The open-loop impedance of the MV amplifier is the resistance ro of the M1 tube in parallel with the output impedance of the current source I0, which is approximately ro. If the ro value is selected as a high impedance, the output of the MV amplifier is equivalent to a low-pass network, and the AC signal will not flow into the output of the MV DAC. The I-VConverter circuit, also known as the current-voltage converter, consists of two parts. One is the resistor load current mirror circuit composed of M2, M3, M4 and R4. Second, there is a current compensation circuit (Current Compensation) composed of A2, R3, M5, M6, M7, M8, and M9. Assume that the DC current generated by the photodetector is I in (DC), then the DC current flowing through M1 is I0+I in (DC), and the gates of M1 and M2 are connected, forming a current mirror circuit. At the same time, M3 and M4 also form a current mirror, continuing to mirror the current of M2 to M4. Assuming that the working current ratio of M1 and M2 is p1, and the working current ratio of M3 and M4 is p2, the current I4 of M4 is

[0079] I4=p2×I3=p2×p1×I1=p2×p1×(I0+ I in (DC)) (3);

[0080] Among them, I4 is the working current of M4, I3 is the working current of M3; I1 is the working current of M1; I in (DC) is the direct current generated by the photodetector; I0 is the current generated by the direct current source.

[0081] The current of M4 forms a voltage on R4. When the current compensation circuit is not considered, the output voltage Vout of the current-voltage converter (I-V Converter) is

[0082] Vout=I4×R4=p2×p1×(I0+I in (DC))×R4 (4);

[0083] Here, R4 represents the resistance value of the resistor R4.

[0084] That is, Vout and I in (DC) and has a DC voltage term related to I0.

[0085] In order to increase the DAC output voltage range (close to 0 ~ MV, where M is a preset value, M is greater than zero), a single-tube PMOS is used to implement the current source of I0. Therefore, the I0 characteristic is not an ideal current source. The I0 current will be affected by the DAC output voltage Vdac. The approximate expression of the I0 current is:

[0086] I0=I0'(1+λ×Vdac) (5);

[0087] Wherein, Vdac is the output voltage of the voltage regulating unit; I0' represents a DC component that is independent of the Vdac voltage, and λ is a pre-determined proportionality coefficient.

[0088] When considering the current compensation circuit, the output voltage Vout of the IV Converter is expressed as

[0089] Vout=(I4-I9)×R4= (p2×p1×(I0+ I in (DC)-I9)×R4 (6);

[0090] Wherein, I9 is ​​the working current of the ninth transistor M9; R4 represents the resistance value of the resistor R4;

[0091] I9 is ​​generated by the current compensation circuit. Assuming that the current mirror ratio formed by M6 and M7 is p3, and the current mirror ratio formed by M8 and M9 is p4, then

[0092]

[0093] Wherein, Vlvdac is the output voltage of the low voltage DAC (LVDAC); R3 represents the resistance value of the resistor R3.

[0094] The relationship between LVDAC output voltage and DAC output voltage is:

[0095]

[0096] Then there is

[0097]

[0098] The output voltage expression of IV Converter is:

[0099]

[0100]

[0101] When a suitable proportionality factor is selected,

[0102]

[0103] Then the Vout output is approximately independent of the Vdac voltage.

[0104] In the Vout expression, I in The equivalent transresistance Rt of the relationship between (DC) and output voltage is:

[0105] Rt= Vout / I in (DC) = p2 × p1 × R4 (13);

[0106] Since the expression of transresistance only contains a single resistor, the requirements for the resistor ratio are not high. For the current mirror ratios p1 and p2, a smaller ratio can be selected to ensure a smaller mirror error, and a larger R4 resistance value can be selected to ensure sufficient transresistance gain. For example, if p1=p2=3 and R4=50kΩ are selected, then Rt=450kΩ. For a 0.2uA signal, when the transresistance is Rt=450kΩ, the output voltage increase is 0.2uA*450kΩ=90mV, which can meet the effective quantization range of general digital circuits.

[0107] The implementation circuit of the photoelectric detection module for laser radar provided in this embodiment adopts a current mirroring method to convert the DC current converted by the photoelectric detection unit from ambient light into a DC voltage, and adopts the current mirroring method to indirectly detect the DC current obtained by the photoelectric detection unit from converting ambient light without changing the DC working state of the photoelectric detection unit.

[0108] In addition, in this embodiment, a current compensation module is used to compensate for the nonlinearity of the current mirror caused by the output voltage of the bias regulation subunit, thereby improving the DC detection accuracy of the photoelectric detection unit.

[0109] The present application also provides a laser radar, the laser radar includes: Figure 1 to Figure 3 One of the embodiments shown provides a photoelectric detection module for a laser radar.

[0110] Further references Figure 6 , which shows an ambient light detection method for Figure 1 to Figure 4 One of the embodiments shown provides a photoelectric detection module for a laser radar.

[0111] like Figure 6 As shown, the ambient light detection method includes the following steps:

[0112] Step 601 , obtaining a monotonically rising reference voltage signal and a monotonically increasing counting signal under the control of the same clock signal, wherein the reference voltage signal monotonically rises between a preset minimum voltage value and a preset maximum voltage value.

[0113] Step 602, compare the reference voltage signal with the measured voltage signal output by the current-voltage conversion module; wherein the current-voltage conversion module is used to convert the DC current signal generated by the photoelectric detection module based on the detected ambient light into the measured voltage signal.

[0114] Step 603: When the reference voltage signal rises to the same level as the measured voltage signal, the count value corresponding to the count signal at this moment is determined as the target count value.

[0115] Step 604, determining the intensity of the ambient light of the laser radar according to the target count value.

[0116] The data processing unit can determine the magnitude of the direct current corresponding to the ambient light through the above counting value, and further determine the magnitude of the ambient light.

[0117] In each sampling period, the ramp voltage generator and the counter are controlled to work synchronously using the same synchronous clock signal output by the synchronous logic unit, for example.

[0118] In practice, the analog voltage signal output by the current-voltage conversion module can be input to the inverting input terminal of the voltage comparator; the ramp voltage signal output by the output terminal of the ramp voltage generator can be input to the non-inverting input terminal of the comparator. The analog voltage signal has a preset relationship with the current signal generated by the photoelectric detection module sensing the ambient light. When the ramp voltage signal rises to the analog voltage signal, the voltage comparator outputs a control signal to control the latch to work, and the latch latches the count value currently corresponding to the counter input by the input terminal, and outputs the latched count value to the data processing unit. The data processing unit determines the DC current signal corresponding to the ambient light according to the physical relationship between the predetermined DC current signal caused by the ambient light and the preset maximum count value and the target count value and the transimpedance gain of the current-voltage conversion module (please refer to formula (2)), thereby determining the ambient light intensity of the laser radar.

[0119] The detailed description of steps 601 to 604 can be found in Figure 2 and Figure 3 The description of the illustrated embodiment will not be repeated here.

[0120] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0121] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. A photoelectric detection module for laser radar, characterized in that: include: A photoelectric detection unit, a signal conditioning unit and a data processing unit; the output end of the photoelectric detection unit is connected to the input end of the signal conditioning unit, and the output end of the signal conditioning unit is connected to the input end of the data processing unit; The photoelectric detection unit is used to sense the light signal incident thereon and convert the sensed light signal into an electrical signal, wherein the light signal incident thereon includes an ambient light signal and an echo laser signal generated by the laser beam being reflected after irradiating the object to be measured; The signal conditioning unit includes an ambient light detection subunit, and the ambient light detection subunit is used to detect a DC signal in the electrical signal and quantify the DC signal, wherein the DC signal includes a DC signal generated by a photoelectric detection unit sensing an ambient light signal, and the DC signal includes a DC current signal; The ambient light detection subunit is used to quantize the DC signal, including: converting the DC current signal into a DC voltage signal by a current mirror method, and determining a quantization result of the DC signal according to the DC voltage signal and a preset reference voltage signal, wherein the ambient light detection subunit includes a first current mirror circuit and a second current mirror circuit, the reference current side of the first current mirror circuit is used to receive the DC signal, the replica current side of the first current mirror circuit is at least partially included in the reference current side of the second current mirror circuit, and the DC voltage signal is obtained from the replica current side of the second current mirror circuit; The data processing unit is used to analyze and process the received quantized AC signal and quantized DC signal, and adjust the photoelectric detector unit according to the result of the ambient light detection.

2. The photoelectric detection module for laser radar according to claim 1, characterized in that: The ambient light detection subunit comprises a current-voltage conversion module, the input end of the current-voltage conversion module is electrically connected to the anode of the photoelectric detection unit; in The current-voltage conversion module includes: a synchronous logic circuit, a ramp voltage generator, a counter, a current-voltage converter, a voltage comparator, and a latch; in The output end of the photoelectric detection unit is connected to the input end of the current-voltage converter; The signal output by the synchronous logic circuit controls the ramp voltage generator and the counter to work simultaneously; The inverting input terminal of the voltage comparator is connected to the output terminal of the current-voltage converter; the non-inverting input terminal of the voltage comparator is connected to the output terminal of the ramp voltage generator; The control end of the latch is connected to the output end of the voltage comparator, and the signal input end of the latch is connected to the output end of the counter.

3. The photoelectric detection module for laser radar according to claim 2, characterized in that: The photoelectric detection module includes a plurality of channels, and each of the plurality of channels includes the photoelectric detection unit and the signal conditioning unit; Wherein, the signal conditioning unit of each channel includes a current-voltage conversion module, and the current-voltage conversion module of each channel includes a current-voltage converter, a voltage comparator and a latch; and The current-to-voltage conversion modules of the multiple channels share the same synchronous logic circuit, ramp voltage generator, and counter.

4. The photoelectric detection module for laser radar according to claim 2 or 3, characterized in that: Under the control of the signal output by the synchronous logic circuit, the ramp voltage generator generates a ramp voltage signal and the counter counts according to a preset counting frequency; When the ramp voltage signal input to the non-inverting input terminal of the voltage comparator is greater than the voltage signal output by the current-voltage converter, the voltage comparator outputs a control signal for controlling the operation of the latch; The control signal is input to the control terminal of the latch, the latch latches the count value input by the signal input terminal at this time, and outputs the count value; The data processing unit determines a DC voltage value corresponding to the ambient light signal according to the count value.

5. The photoelectric detection module for laser radar according to claim 4, characterized in that: The ramp voltage generator generates a ramp voltage signal rising from a preset minimum voltage value to a maximum voltage value within a preset sampling time period; the counter counts from a preset minimum value to a preset maximum value according to a preset counting frequency within the preset sampling time period.

6. The photoelectric detection module for laser radar according to claim 2 or 3, characterized in that: The signal conditioning unit further comprises a bias voltage regulating subunit; The output end of the bias voltage regulating subunit is electrically connected to the anode of the photoelectric detection unit; in The bias voltage regulating subunit is used to regulate the bias voltage of the photodetection unit to calibrate the working current drift of the photodetection unit caused by temperature and process deviation.

7. The photoelectric detection module for laser radar according to claim 6, characterized in that: The ambient light detection subunit also includes a current compensation module; wherein The current compensation module is electrically connected to the bias voltage adjustment subunit and the current-voltage conversion module respectively.

8. The photoelectric detection module for laser radar according to claim 7, characterized in that: The bias voltage regulating subunit includes a low voltage regulating subunit and a medium voltage amplifying subunit; The medium voltage amplification subunit includes: a direct current source, a first triode, a first operational amplifier, a first input resistor and a first feedback resistor; in One end of the first input resistor is connected to the ground wire, and the other end is connected to one end of the first feedback resistor; The other end of the first feedback resistor is electrically connected to the anode of the photodetection unit, the output end of the DC current source and the drain of the first transistor respectively; The cathode of the photoelectric detection unit is electrically connected to the first high potential, and the anode of the photoelectric detection unit is also electrically connected to the output end of the direct current source; The source of the first transistor is connected to the ground wire, the drain of the first transistor is connected to the output end of the DC current and the anode of the photodetection unit; the gate of the first transistor is connected to the output end of the first operational amplifier; the in-phase input end of the first operational amplifier is connected to the other end of the first input resistor, and the inverting input end of the first operational amplifier is connected to the output end of the low-voltage regulation subunit.

9. The photoelectric detection module for laser radar according to claim 8, characterized in that: The current-voltage conversion module includes a second triode, a third triode, a fourth triode, a third resistor, a voltage comparator and a latch circuit; wherein The gate of the second triode is connected to the gate of the first triode, the source of the second triode is connected to the ground line, and the drain of the second triode is connected to the drain of the third triode; The gate of the third triode is connected to the gate of the fourth triode; the source of the third triode is connected to the second high potential, and the gate of the third triode is connected to the drain of the third triode; The source of the fourth transistor is connected to the third high potential; the drain of the fourth transistor is connected to one end of the third resistor and the inverting input end of the voltage comparator; The non-inverting input terminal of the voltage comparator is connected to the output terminal of the ramp voltage generator, and the output terminal of the voltage comparator is connected to the control terminal of the latch; The signal input end of the latch is connected to the output end of the counter, and the output end of the latch is connected to the data processing unit, and the data processing unit determines the DC voltage corresponding to the DC current according to the output end of the latch; The other end of the third resistor is connected to the ground line.

10. The photoelectric detection module for laser radar according to claim 9, characterized in that: The current compensation module includes a second operational amplifier, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor and a ninth transistor, and the current-voltage conversion module also includes a fourth resistor; wherein The non-inverting input terminal of the second operational amplifier is connected to the inverting input terminal of the first operational amplifier; the inverting input terminal of the second operational amplifier is electrically connected to the source of the fifth transistor and one end of the fourth resistor; the output terminal of the second operational amplifier is connected to the gate of the fifth transistor; The other end of the fourth resistor is connected to the ground line; The drain of the fifth triode is electrically connected to the gate and drain of the sixth triode and the gate of the seventh triode; The source of the sixth triode is electrically connected to the fourth high potential; the gate of the sixth triode is connected to the gate of the seventh triode; The source of the seventh transistor is electrically connected to the fifth high potential; the drain of the seventh transistor is electrically connected to the drain of the eighth transistor; The source of the eighth triode is connected to the ground line, and the gate is electrically connected to the gate of the ninth triode; the drain of the eighth triode is electrically connected to the gate of the eighth triode; The source of the ninth transistor is connected to the ground line, and the drain is electrically connected to the drain of the fourth transistor.

11. The photoelectric detection module for laser radar according to claim 1, characterized in that: The signal conditioning unit further includes an AC detection subunit, which is used to amplify and quantify the AC signal in the electrical signal; wherein the AC signal includes the AC signal generated by the photoelectric detection unit sensing the echo laser signal.

12. A laser radar, characterized in that: The laser radar comprises a photoelectric detection module for a laser radar according to any one of claims 1-11.

13. An ambient light detection method, used in the photoelectric detection module for laser radar according to any one of claims 1 to 11; the method comprising: Acquire a reference voltage signal that rises monotonically under the control of a synchronous clock signal and a counting signal that counts monotonically; Compare the reference voltage signal with the measured voltage signal output by the current-voltage conversion module; wherein the current-voltage conversion module is used to convert the DC current signal generated by the photoelectric detection module from the detected ambient light into the measured voltage signal; When the reference voltage signal rises to the same level as the measured voltage signal, the count value corresponding to the count signal at this moment is determined as the target count value; The intensity of the ambient light of the laser radar is determined according to the target count value.

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