Laser receiving circuit and laser radar

Abstract

The invention provides a laser receiving circuit and a laser radar, the laser receiving circuit comprises an SIPM detector, a bias voltage generation circuit and an impedance switching circuit, when a laser emission circuit emits a laser pulse, the laser receiving circuit is triggered by a corresponding first level signal to generate a first equivalent resistor and performs voltage division to generate a second bias voltage; the second bias voltage is smaller than a preset bias voltage when the SIPM detector works, the SIPM detector does not output an effective electric signal, the influence of stray light at the light emitting moment is eliminated, a second equivalent resistor is generated by a corresponding second level signal after stray light is finished, a third bias voltage is generated through voltage division, photoelectric conversion is achieved through the SIPM detector, and an effective electric signal is output. According to the laser radar system, laser pulse transmitting and receiving conversion and distance measurement are achieved, a bias voltage generation circuit and an impedance switching circuit are adopted in the laser receiving circuit, the system structure of the laser radar of the laser receiving circuit is simplified, and the design cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lidar, and particularly relates to a laser receiving circuit and a lidar. Background Art

[0002] Lidar uses light as a medium and is widely used because of its many advantages such as long detection distance, high resolution, and strong anti-interference ability. Generally, a lidar system includes a laser emission system and a detection and reception system. The laser emission system emits a light beam and collimates it in the optical path and emits it outward. After the detection and reception system receives the reflected light of the measurement target, it performs photoelectric conversion, processes the electrical signal and sends it to the controller, and finally calculates the detection distance through the ToF principle.

[0003] However, in fact, there is a stray light transmission path in the optical path. After the light generated by the laser emission system enters the optical path, a very small part of the light will enter the receiving system through this path, causing a weak electrical signal in the SIPM, thus affecting the measurement error.

[0004] The suppression of stray light generally reduces the photon detection rate by reducing the bias voltage applied across the SIPM. When the bias voltage is reduced, fewer SPAD cells of the stray light on the SIPM are excited, reducing the conversion of the electrical signal.

[0005] The bias voltage circuit of the existing laser receiving circuit usually consists of two bias voltage generating circuits and a switching circuit. The two bias voltage generating circuits generate different magnitudes of bias voltages respectively. Before the stray light arrives, a small bias voltage is used to eliminate the influence of the stray light. Before the effective optical signal arrives, a large bias voltage is used for the SIPM detector to perform photoelectric conversion.

[0006] The traditional laser receiving circuit uses two bias voltage generating circuits, and the structures of the two bias voltage generating circuits are different, increasing the design complexity and cost. Summary of the Invention

[0007] An object of the present invention is to provide a laser receiving circuit, aiming to solve the problems of complex structure and high cost of the bias voltage circuit in the traditional laser receiving circuit.

[0008] A first aspect of an embodiment of the present invention provides a laser receiving circuit, including:

[0009] A SIPM detector, which is triggered to work by a preset bias voltage and converts the laser pulse output by the laser emission circuit into an electrical signal;

[0010] A bias voltage generating circuit, which is used to output a first bias voltage;

[0011] An impedance switching circuit is connected between the bias voltage generating circuit and the SIPM detector. The impedance switching circuit is configured to generate a first equivalent resistance upon being triggered by a first level signal, divide the first bias voltage, and output a second bias voltage. It is also configured to generate a second equivalent resistance upon being triggered by a second level signal, divide the first bias voltage, and output a third bias voltage. The second bias voltage is less than the preset bias voltage, and the third bias voltage is greater than or equal to the preset bias voltage. The first level signal and the second level signal are opposite level signals.

[0012] Optionally, the laser emission circuit includes a laser driving circuit and a laser. The laser driving circuit is configured to output a driving signal to drive the laser to emit laser pulses.

[0013] The laser receiving circuit further includes:

[0014] A signal conversion circuit, which is connected to the output end of the laser driving circuit and the control end of the impedance switching circuit, and is configured to convert the driving signal into the first level signal and output it to the impedance switching circuit.

[0015] An inverting delay circuit, which is connected to the output end of the signal conversion circuit and the control end of the impedance switching circuit, and is configured to invert and convert the first level signal into the second level signal and output it to the impedance switching circuit after delaying for a preset duration.

[0016] Optionally, the inverting delay circuit includes an odd number of inverters connected in series.

[0017] Optionally, the impedance switching circuit includes a first resistor, a second resistor, and a switching transistor.

[0018] The first end of the first resistor forms the input end of the impedance switching circuit. The second end of the first resistor and the first end of the second resistor are commonly connected to form the output end of the impedance switching circuit. The second end of the second resistor is connected to the second end of the switching transistor, and the control end of the switching transistor forms the control end of the impedance switching circuit.

[0019] Optionally, the laser receiving circuit further includes:

[0020] A first filtering circuit, which is connected to the output end of the bias voltage generating circuit and the input end of the impedance switching circuit, and is configured to filter the first bias voltage.

[0021] A second filtering circuit, which is connected to the output end of the impedance switching circuit, and is configured to filter the second bias voltage or the third bias voltage output by the impedance switching circuit.

[0022] Optionally, the first filtering circuit includes a first capacitor;

[0023] A first end of the first capacitor is connected to an output end of the bias voltage generation circuit and an input end of the impedance switching circuit, and a second end of the first capacitor is grounded;

[0024] The second filtering circuit includes a second capacitor;

[0025] A first end of the second capacitor is connected to an output end of the impedance switching circuit, and a second end of the second capacitor is grounded.

[0026] Optionally, the bias voltage generation circuit includes:

[0027] A power supply circuit configured to output a fourth bias voltage;

[0028] A boost circuit connected to the power supply circuit and configured to boost the fourth bias voltage to the first bias voltage.

[0029] Optionally, the bias voltage generation circuit further includes:

[0030] A feedback circuit connected to an output end of the boost circuit and a control end of the power supply circuit. The feedback circuit is configured to sample an output voltage of the boost circuit and generate a voltage regulation signal to the power supply circuit so that the power supply circuit outputs the fourth bias voltage with a constant voltage.

[0031] Optionally, the bias voltage generation circuit further includes:

[0032] An adjustment circuit connected to the power supply circuit. The adjustment circuit is configured to obtain an external voltage regulation instruction and generate a voltage regulation signal to the power supply circuit so that the power supply circuit adjusts the voltage to output the fourth bias voltage with a corresponding voltage magnitude.

[0033] A second aspect of the embodiments of the present invention provides a lidar, including a laser emission circuit and the laser reception circuit as described above.

[0034] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows: The above laser receiving circuit is composed of a SIPM detector, a bias voltage generating circuit, and an impedance switching circuit. When the laser emitting circuit emits laser pulses, it can be triggered by a corresponding first level signal to generate a first equivalent resistance and divide the voltage to generate a second bias voltage. The second bias voltage is less than the preset bias voltage when the SIPM detector operates, and the SIPM detector does not output an effective electrical signal, eliminating the influence of stray light at the moment of light emission. And after the stray light ends, it can be triggered by a corresponding second level signal to generate a second equivalent resistance and divide the voltage to generate a third bias voltage. The SIPM detector realizes photoelectric conversion and outputs an effective electrical signal, realizing the emission and reception conversion of laser pulses and ranging. The laser receiving circuit adopts a bias voltage generating circuit and an impedance switching circuit, simplifying the system structure of the lidar of the laser receiving circuit and reducing the design cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 is a schematic structural diagram of a traditional bias voltage circuit;

[0037] Figure 2 is a first schematic structural diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0038] Figure 3 is a schematic waveform structural diagram of each signal in the laser receiving circuit provided by the embodiment of the present invention;

[0039] Figure 4 is a second schematic structural diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0040] Figure 5 is a schematic structural diagram of the inverting delay circuit provided by the embodiment of the present invention;

[0041] Figure 6 is a third schematic structural diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0042] Figure 7 is a circuit schematic diagram of the impedance switching circuit and the filtering circuit provided by the embodiment of the present invention;

[0043] Figure 8 is a fourth schematic structural diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0044] Figure 9 The fifth structural schematic diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0045] Figure 10 The sixth structural schematic diagram of the laser receiving circuit provided by the embodiment of the present invention;

[0046] Figure 11 The structural schematic diagram of the lidar provided by the embodiment of the present invention. Specific embodiments

[0047] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0049] In the first aspect of the embodiment of the present invention, a laser receiving circuit 200 is proposed. The laser receiving circuit 200 is correspondingly arranged with the laser transmitting circuit 100. The laser transmitting circuit 100 can select the corresponding laser 120 and laser driving circuit 110. The laser 120 is used to receive electricity and emit laser signals. The laser driving circuit 110 is connected to the laser 120 and is used to output a driving signal to the laser 120. The laser 120 can select the corresponding type of laser 120. The laser driving circuit 110 can select the corresponding structure of the charge-discharge circuit. The charge-discharge circuit charges and discharges according to the received driving signal and controls the laser 120 to emit laser pulses at a corresponding angle according to a corresponding timing sequence.

[0050] The laser receiving circuit 200 is used to receive the laser pulses emitted by the laser transmitting circuit 100 and convert them into echo pulse signals. The echo pulse signals are output to the main control circuit 300. The main control circuit 300 determines the distance information and reflectivity of the object to be measured 1 according to the pulse echo signals.

[0051] Among them, as Figure 2 shown, in order to balance simplifying the system structure and eliminating stray light, in this embodiment, the laser receiving circuit 200 includes:

[0052] The SIPM detector 10, the SIPM detector 10 is triggered to work by a preset bias voltage and converts the laser pulses output by the laser transmitting circuit 100 into electrical signals;

[0053] A bias voltage generation circuit 20 for outputting a first bias voltage;

[0054] An impedance switching circuit 30 is connected between the bias voltage generation circuit 20 and the SiPM detector 10. The impedance switching circuit 30 is configured to generate a first equivalent resistance when triggered by a first level signal and divide the first bias voltage to output a second bias voltage, and generate a second equivalent resistance when triggered by a second level signal and divide the first bias voltage to output a third bias voltage. The second bias voltage is less than a preset bias voltage, and the third bias voltage is greater than or equal to the preset bias voltage. The first level signal and the second level signal are opposite level signals.

[0055] In this embodiment, according to the working principle of the SiPM detector 10, in order to convert and generate an effective electrical signal, when a laser pulse is received, the bias voltage needs to be set to reach the preset value. The magnitude of the preset bias voltage can be specifically set according to different types of SiPM detectors 10. Generally, the preset bias voltage is about 50V. When the bias voltage applied to the SiPM detector is less than the preset bias voltage, the SiPM detector 10 cannot convert to form an effective electrical signal when receiving a laser pulse. Only when the bias voltage reaches the preset bias voltage, the SiPM detector 10 realizes effective photoelectric conversion and generates an electrical signal of corresponding magnitude.

[0056] Among them, in order to realize laser ranging, as Figure 2 shown, the laser receiving circuit 200 further includes a signal processing circuit 40. The signal processing circuit 40 may include a DC blocking capacitor, a transimpedance amplifier, a detection circuit, etc. The corresponding echo pulse signal is obtained through the signal processing circuit 40, and the echo pulse signal is output to the main control circuit 300. The main control circuit 300 determines the distance information and reflectivity of the object 1 to be measured according to the pulse echo signal.

[0057] As Figure 3 shown, when the laser receiving circuit 200 works, at time t0, when the laser transmitting circuit 100 emits a laser pulse, the impedance switching circuit 30 synchronously receives the first level signal, and the impedance switching circuit 30 switches to generate a first equivalent resistance. The first equivalent resistance divides the first bias voltage of the bias voltage generation circuit 20 to generate a second bias voltage. The second bias voltage is less than the preset bias voltage when the SiPM detector 10 works normally. At this time, the SiPM detector 10 does not generate an effective electrical signal, and the extremely small electrical signal formed by the SiPM detector 10 receiving is not enough to affect the system judgment, eliminating the influence of stray light at the light emitting moment.

[0058] After the reception of the stray light echo signal ends, at time t1, the effective laser pulse reflected by the detection optical path is emitted to the laser receiving circuit 200. At this time, the corresponding second-level signal is output to the impedance switching circuit 30. The impedance switching circuit 30 switches to generate a second equivalent resistance to the bias voltage terminal of the bias voltage generation circuit 20 to the SIPM detector 10, and divides the first bias voltage output by the bias voltage generation circuit 20 to generate a third bias voltage. The third bias voltage reaches the preset bias voltage when the SIPM detector 10 operates normally. At this time, the SIPM detector 10 receives the effective laser pulse returned from the detection optical path and converts it into an effective electrical signal. The electrical signal is output to the main control circuit 300 or output to the main control circuit 300 after being processed by the signal processing circuit 40, and the main control circuit 300 determines the distance information and reflectivity according to the transmission and reception time of the laser pulse and the magnitude of the echo pulse signal.

[0059] The laser receiving circuit 200 realizes the switching output of the bias voltage by using a bias voltage generation circuit 20 and an impedance switching circuit 30, which simplifies the system structure of the lidar of the laser receiving circuit 200 and reduces the design cost.

[0060] Among them, the first-level signal and the second-level signal can be a high-level signal and a low-level signal respectively, which are set according to the specific structure of the impedance switching circuit 30. At the same time, the first-level signal and the second-level signal can be adjusted and output by the main control circuit 300 according to the timing correspondence of the stray light and the effective echo pulse, or the signal conversion circuit 50 is connected to the laser transmitting circuit 100 to convert and output the corresponding first-level signal and second-level signal according to the emission time of the laser pulse.

[0061] Among them, in order to simplify the design logic and realize hardware control, as Figure 4 shown, in an optional embodiment, the laser transmitting circuit 100 includes a laser driving circuit 110 and a laser 120. The laser driving circuit 110 is configured to output a driving signal to drive the laser 120 to emit a laser pulse;

[0062] The laser receiving circuit 200 further includes:

[0063] A signal conversion circuit 50, which is connected to the output terminal of the laser driving circuit 110 and the control terminal of the impedance switching circuit 30, and is configured to convert the driving signal into a first-level signal and output it to the impedance switching circuit 30;

[0064] An inverting delay circuit 60, which is connected to the output terminal of the signal conversion circuit 50 and the control terminal of the impedance switching circuit 30, and is configured to invert and convert the first-level signal into a second-level signal and output it to the impedance switching circuit 30 after delaying a preset time.

[0065] In this embodiment, with reference to Figure 2 As shown, when the laser driving circuit 110 outputs a driving signal, the laser 120 is powered to emit laser pulses. At this time, the signal conversion circuit 50 converts the driving signal into a first-level signal and outputs it to the impedance switching circuit 30 and the inverting delay circuit 60. The impedance switching circuit 30 switches to generate a first equivalent resistance, and the first equivalent resistance divides the first bias voltage of the bias voltage generation circuit 20 to generate a second bias voltage. The second bias voltage is less than the preset bias voltage when the SIPM detector 10 operates normally. At this time, no effective electrical signal is generated by the SIPM detector 10, and the extremely small electrical signal formed by the SIPM detector 10 is not sufficient to affect the system judgment, eliminating the influence of stray light at the emission moment.

[0066] The first-level signal is inverted in the inverting delay circuit 60 to be converted into a second-level signal and output after a delay. After the receiving time of the stray light echo signal ends, at time t1, the effective laser pulse reflected by the detection optical path is emitted to the laser receiving circuit 200. At this time, the inverting delay circuit 60 outputs the second-level signal to the impedance switching circuit 30. The impedance switching circuit 30 switches to generate a second equivalent resistance to the bias voltage terminal of the bias voltage generation circuit 20 to the SIPM detector 10, and divides the first bias voltage output by the bias voltage generation circuit 20 to generate a third bias voltage. The third bias voltage reaches the preset bias voltage when the SIPM detector 10 operates normally. At this time, the SIPM detector 10 receives the effective laser pulse returning from the detection optical path and converts it into an effective electrical signal. The electrical signal is output to the main control circuit 300 or is output to the main control circuit 300 after being processed by the signal processing circuit 40, and the main control circuit 300 determines the distance information and reflectivity according to the transmission and reception time of the laser pulse and the magnitude of the echo pulse signal.

[0067] Among them, the signal conversion circuit 50 can be a signal comparison circuit, an inverting circuit, etc., such as a comparator, an inverter U1, etc., and is set according to the type of the driving signal output by the laser driving circuit 110. For example, when the driving signal is a voltage signal, when driving the laser 120 to emit laser pulses, the signal conversion circuit 50 compares the voltage signal with a preset voltage to generate a first-level signal and stops outputting after the stray light ends.

[0068] The inverting delay circuit 60 can adopt a delay chip, an inverter U1, etc. In an alternative embodiment, as Figure 5 shown, the inverting delay circuit 60 includes 2n - 1 serially connected inverters U1, where n is a positive integer.

[0069] Among them, the inverter U1 performs an inversion operation on the one hand and plays a role in delaying the output on the other hand. After the first-level signal is input, an odd number of inverters U1 invert and delay for a preset period to output a second-level signal. Among them, the number of inverters U1 is specifically set according to the time when the stray light reaches the SIPM detector 10 and the time when the effective optical signal reaches the SIPM detector 10. The more the number of inverters U1, the longer the delay duration.

[0070] The impedance switching circuit 30 can adopt a resistor array or a structure of multiple voltage-dividing resistors. The first equivalent resistance is greater than the second equivalent resistance, and the resistance value of the second equivalent resistance can be zero resistance or a corresponding resistance value.

[0071] In an alternative embodiment, as Figure 7 shown, the impedance switching circuit 30 includes a first resistor R1, a second resistor R2, and a switching transistor Q1;

[0072] The first end of the first resistor R1 constitutes the input end of the impedance switching circuit 30. The second end of the first resistor R1 and the first end of the second resistor R2 are commonly connected to form the output end of the impedance switching circuit 30. The second end of the second resistor R2 is connected to the second end of the switching transistor Q1, and the control end of the switching transistor Q1 constitutes the control end of the impedance switching circuit 30.

[0073] In this embodiment, when the impedance switching circuit 30 receives the first-level signal, the switching transistor Q1 is turned on. The first resistor R1 and the second resistor R2 divide the first bias voltage of the bias voltage generation circuit 20 to generate a second bias voltage. The second resistor R2 is the first equivalent resistance, and the terminal voltage of the second resistor R2 is the second bias voltage. The second bias voltage is less than the preset bias voltage when the SIPM detector 10 operates normally. At this time, no effective electrical signal is generated by the SIPM detector 10, and the extremely small electrical signal formed by the reception of the SIPM detector 10 is not sufficient to affect the system judgment, eliminating the influence of stray light at the emission moment.

[0074] And after the reception moment of the stray light echo signal ends, at time t1, the effective laser pulse reflected back through the detection optical path is emitted to the laser receiving circuit 200. At this time, the corresponding second-level signal is output to the impedance switching circuit 30, and the switching transistor Q1 is turned off. At this time, the resistance value of the second equivalent resistance is close to zero, and the voltage magnitude of the third bias voltage is close to the first bias voltage. The third bias voltage reaches the preset bias voltage when the SIPM detector 10 operates normally. At this time, the SIPM detector 10 receives the effective laser pulse returned from the detection optical path and converts it into an effective electrical signal. The electrical signal is output to the main control circuit 300 or is output to the main control circuit 300 after being processed by the signal processing circuit 40, and the main control circuit 300 determines the distance information and the reflectivity according to the transmission and reception time of the laser pulse and the magnitude of the echo pulse signal.

[0075] Among them, adjusting the first resistor R1 can change the rising time of the edge of the bias voltage from the second bias voltage to the third bias voltage, which is beneficial to improving the minimum measurement distance.

[0076] Specifically, referring to Figure 3 As shown, the minimum measurement distance D = C * (t1 - t0), where C is the propagation speed of the laser pulse. The time point t1 is affected by the rise time Tr. If the bias voltage rise time is further shortened, Tr decreases, the time point t1 will be advanced, and the minimum measurement distance will be improved.

[0077] Among them, the switching transistor Q1 can be a triode, a MOS transistor, etc. In an alternative embodiment, the switching transistor Q1 is an NMOS transistor. Correspondingly, the first level signal is a high level, and the second level signal is a low level.

[0078] Furthermore, in order to reduce clutter interference, in an alternative embodiment, as Figure 6 shown, the laser receiving circuit 200 further includes:

[0079] A first filtering circuit 70, which is connected to the output end of the bias voltage generating circuit 20 and the input end of the impedance switching circuit 30, and is configured to filter the first bias voltage;

[0080] A second filtering circuit 80, which is connected to the output end of the impedance switching circuit 30, and is configured to filter the second bias voltage or the third bias voltage output by the impedance switching circuit 30.

[0081] By setting the filtering circuit, the input and output bias voltages can be filtered, clutter interference can be reduced, the mis-triggering of the SIPM detector 10 can be avoided, and the ranging accuracy can be improved.

[0082] Among them, the filtering circuit can adopt corresponding capacitors, optocouplers, etc. In an alternative embodiment, as Figure 7 shown, the first filtering circuit 70 includes a first capacitor C1;

[0083] The first end of the first capacitor C1 is connected to the output end of the bias voltage generating circuit 20 and the input end of the impedance switching circuit 30, and the second end of the first capacitor C1 is grounded;

[0084] The second filtering circuit 80 includes a second capacitor C2;

[0085] The first end of the second capacitor C2 is connected to the output end of the impedance switching circuit 30, and the second end of the second capacitor C2 is grounded.

[0086] The bias voltage generating circuit 20 can be composed of a voltage source and a power conversion circuit. In an alternative embodiment, as Figure 8 shown, the bias voltage generating circuit 20 includes:

[0087] A power supply circuit 21, configured to output a fourth bias voltage;

[0088] A boost circuit 22, connected to the power supply circuit 21, configured to boost the fourth bias voltage to a first bias voltage.

[0089] In this embodiment, the power supply circuit 21 may adopt an input rectifier circuit, an inverter circuit, an output rectifier circuit, etc., and may also adopt a switching power supply. By converting the input AC signal or DC signal and outputting the corresponding fourth bias voltage. At the same time, in order to meet the bias voltage level of the SIPM detector 10, the fourth bias voltage is also boosted by the boost circuit 22 and output.

[0090] In order to achieve constant voltage output, in an alternative embodiment, as Figure 9 shown, the bias voltage generation circuit 20 further includes:

[0091] A feedback circuit 23, the feedback circuit 23 is connected to the output end of the boost circuit 22 and the control end of the power supply circuit 21. The feedback circuit 23 is configured to sample the output voltage of the boost circuit 22 and generate a voltage regulation signal to the power supply circuit 21, so that the power supply circuit 21 outputs a constant voltage fourth bias voltage.

[0092] In this embodiment, the feedback circuit 23 may be a voltage sampling circuit. For example, it includes two voltage dividing resistors. The voltage dividing resistors are connected to the output end of the boost circuit 22 and obtain the output voltage of the boost circuit 22. After dividing the output voltage, it is used as the sampling voltage and output to the power supply circuit 21. The power supply circuit 21 performs feedback regulation according to the magnitude of the sampling voltage and the preset reference voltage, so as to achieve constant voltage output.

[0093] Further, in order to adapt to the working requirements of different SIPM detectors 10, the output voltage of the power supply circuit 21 can also be adjusted by an adjustment signal, so that it outputs fourth bias voltages of different voltage levels. As Figure 10 shown, in an alternative embodiment, the bias voltage generation circuit 20 further includes:

[0094] An adjustment circuit 24, the adjustment circuit 24 is connected to the power supply circuit 21. The adjustment circuit 24 is configured to obtain an external voltage regulation instruction and generate a voltage regulation signal to the power supply circuit 21, so that the power supply circuit 21 adjusts the voltage and outputs a fourth bias voltage corresponding to the voltage magnitude.

[0095] In this embodiment, the adjustment circuit 24 performs voltage conversion or internal conversion on the input external voltage regulation instruction. The adjustment circuit 24 may include multiple sampling resistors, and sampling resistors with different resistance values are output according to the external voltage regulation instruction. The power supply circuit 21 outputs a fourth bias voltage with different voltage levels according to the sampling resistors with different resistance values. The specific structure of the adjustment circuit 24 can be specifically set according to the structure and conversion method of the power supply circuit 21.

[0096] The beneficial effects of the embodiment of the present invention compared with the prior art are as follows: The above-mentioned laser receiving circuit 200 is composed of a SIPM detector 10, a bias voltage generation circuit 20, and an impedance switching circuit 30. When the laser transmitting circuit 100 emits a laser pulse, it can be triggered by a corresponding first-level signal to generate a first equivalent resistance and divide the voltage to generate a second bias voltage. The second bias voltage is less than the preset bias voltage when the SIPM detector 10 works, and the SIPM detector 10 does not output an effective electrical signal, eliminating the influence of stray light at the moment of light emission. And after the stray light ends, it can be triggered by a corresponding second-level signal to generate a second equivalent resistance and divide the voltage to generate a third bias voltage. The SIPM detector 10 realizes photoelectric conversion and outputs an effective electrical signal, realizing the emission and reception conversion of laser pulses and ranging. The laser receiving circuit 200 adopts a bias voltage generation circuit 20 and an impedance switching circuit 30, which simplifies the system structure of the lidar of the laser receiving circuit 200 and reduces the design cost.

[0097] As Figure 11 shown, the present invention also proposes a lidar, which includes a laser transmitting circuit 100 and a laser receiving circuit 200. The specific structure of the laser receiving circuit 200 refers to the above embodiment. Since this lidar adopts all the technical solutions of the above all embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0098] The laser receiving circuit 200 is correspondingly arranged with the laser transmitting circuit 100. The laser transmitting circuit 100 can select corresponding lasers 120 and laser driving circuits 110. The laser 120 is used to emit a laser signal when powered. The laser driving circuit 110 is connected to the laser 120 and is used to output a driving signal to the laser 120. The laser 120 can select a corresponding type of laser 120. The laser driving circuit 110 can select a corresponding structure of charge and discharge circuit. The charge and discharge circuit charges and discharges according to the received driving signal and controls the laser 120 to emit laser pulses at a corresponding angle according to a corresponding timing sequence.

[0099] The laser receiving circuit 200 is used to receive the laser pulses emitted by the laser transmitting circuit 100 and convert them into pulse echo signals. The pulse echo signals are output to the main control circuit 300, and the main control circuit 300 determines the distance information and reflectivity of the object to be measured 1 according to the pulse echo signals.

[0100] The lidar may further include a main control circuit 300, which is configured to drive the laser emission circuit 100 to emit laser pulses, and at the same time receive the echo pulse signal output by the laser receiving circuit 200, and determine the flight time of the echo signal, as well as the distance information and reflectivity according to the echo pulse width and the arrival time of the pulse of the echo pulse signal.

[0101] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A laser receiving circuit, characterized in that, it includes: a SIPM detector, which is triggered to work by a preset bias voltage and converts the laser pulse output by the laser emitting circuit into an electrical signal; a bias voltage generating circuit, which is used to output a first bias voltage; an impedance switching circuit, connected between the bias voltage generating circuit and the SIPM detector, the impedance switching circuit is configured to generate a first equivalent resistance when triggered by a first level signal and divide the first bias voltage to output a second bias voltage, and generate a second equivalent resistance when triggered by a second level signal and divide the first bias voltage to output a third bias voltage, the second bias voltage is less than the preset bias voltage, the third bias voltage is greater than or equal to the preset bias voltage, and the first level signal and the second level signal are opposite level signals.

2. The laser receiving circuit according to claim 1, characterized in that, the laser emitting circuit includes a laser driving circuit and a laser, and the laser driving circuit is configured to output a driving signal to drive the laser to emit a laser pulse; the laser receiving circuit further includes: a signal conversion circuit, which is connected to the output end of the laser driving circuit and the control end of the impedance switching circuit, and is configured to convert the driving signal into the first level signal and output it to the impedance switching circuit; an inverting delay circuit, connected to the output end of the signal conversion circuit and the control end of the impedance switching circuit, and is configured to invert the first level signal into the second level signal and output it to the impedance switching circuit after delaying a preset time.

3. The laser receiving circuit according to claim 2, characterized in that, the inverting delay circuit includes 2n - 1 inverters connected in series, where n is a positive integer.

4. The laser receiving circuit according to claim 1, characterized in that, the impedance switching circuit includes a first resistor, a second resistor and a switching tube; the first end of the first resistor constitutes the input end of the impedance switching circuit, the second end of the first resistor and the first end of the second resistor are commonly connected to constitute the output end of the impedance switching circuit, the second end of the second resistor is connected to the second end of the switching tube, and the control end of the switching tube constitutes the control end of the impedance switching circuit.

5. The laser receiving circuit according to claim 1, characterized in that, the laser receiving circuit further includes: a first filtering circuit, which is connected to the output end of the bias voltage generating circuit and the input end of the impedance switching circuit, and is configured to filter the first bias voltage; a second filtering circuit, which is connected to the output end of the impedance switching circuit, and is configured to filter the second bias voltage or the third bias voltage output by the impedance switching circuit.

6. The laser receiving circuit according to claim 5, characterized in that, the first filtering circuit includes a first capacitor; The first end of the first capacitor is connected to the output end of the bias voltage generation circuit and the input end of the impedance switching circuit, and the second end of the first capacitor is grounded; The second filtering circuit includes a second capacitor; The first end of the second capacitor is connected to the output end of the impedance switching circuit, and the second end of the second capacitor is grounded.

7. The laser receiving circuit according to claim 1, wherein, The bias voltage generation circuit includes: A power supply circuit configured to output a fourth bias voltage; A boost circuit connected to the power supply circuit and configured to boost the fourth bias voltage to the first bias voltage.

8. The laser receiving circuit according to claim 7, wherein, The bias voltage generation circuit further includes: A feedback circuit connected to the output end of the boost circuit and the control end of the power supply circuit. The feedback circuit is configured to sample the output voltage of the boost circuit and generate a voltage regulation signal to the power supply circuit so that the power supply circuit outputs a constant voltage of the fourth bias voltage.

9. The laser receiving circuit according to claim 7, wherein, The bias voltage generation circuit further includes: An adjustment circuit connected to the power supply circuit. The adjustment circuit is configured to obtain an external voltage regulation instruction and generate a voltage regulation signal to the power supply circuit so that the power supply circuit adjusts the voltage to output the fourth bias voltage corresponding to the voltage magnitude.

10. A lidar, wherein, It includes a laser emission circuit and the laser receiving circuit according to any one of claims 1 to 9.

Images