Pulse time discrimination digital system based on pulse laser echo differential signal and laser ranging method

Abstract

The invention belongs to the technical field of pulse laser ranging, and provides a pulse time discrimination digital system based on pulse laser echo differential signals, which comprises a laser, a photoelectric conversion module, a controller and a differential comparison circuit, the laser sends a pulse laser signal to a target; the photoelectric conversion module is used for receiving the echo signal and converting the echo signal into a differential alternating current signal; the differential comparison circuit compares the differential voltage of the differential alternating current signal with the threshold voltage of the differential comparison circuit in the laser ranging process and outputs an echo monitoring signal; before laser ranging is started, the controller is configured to adjust the threshold voltage of the differential comparison circuit according to the collected noise signal; in the laser ranging process, the controller is configured to determine the echo time of the target according to the time when the echo monitoring signal is collected; the invention further discloses a laser ranging method. The threshold voltage of the differential comparison circuit is adaptively adjusted to be optimal according to ambient light noise, false alarms and false alarms are reduced, and the ranging accuracy is improved.

Description

Technical Field

[0001] This invention relates to the field of pulsed laser ranging technology, and in particular to a pulse timing identification digital system and laser ranging method based on pulsed laser echo differential signals. Background Technology

[0002] The principle of pulsed laser ranging is that the laser actively emits a laser pulse signal towards the target. The photoelectric conversion module (such as a photodetector) detects the laser pulse echo signal reflected back from the target and converts it into a differential AC signal. The differential AC signal is input to the pulse timing discrimination circuit. The differential comparison circuit in the pulse timing discrimination circuit compares the differential voltage of the differential AC signal with the threshold voltage of the differential comparison circuit. When the differential voltage is greater than the threshold voltage, the echo monitoring signal (such as a high-level pulse signal) is output. The round-trip time of the pulsed laser signal is calculated based on the acquisition time of the acquired echo monitoring signal, that is, the echo time of the target is obtained. The distance between the target and the laser is obtained based on the echo time of the target and the speed of light.

[0003] In existing pulse timing discrimination circuits, the threshold voltage of the differential comparison circuit is a fixed value. For example... Figure 3 In the dual-threshold voltage pulsed laser ranging scheme demonstrated, two high-speed differential comparator circuits (U2 and U3) are used. By reasonably setting the resistance values ​​of R8, R9, R10 and R11, as well as the resistance values ​​of R15, R16, R17 and R18, the voltage of VCC is divided to obtain two different fixed threshold voltages. Figure 4 Another dual-threshold voltage pulsed laser ranging scheme demonstrated uses only one high-speed differential comparator circuit. By controlling the high and low levels of the CTRL pin through software, the VCC voltage is divided in different proportions, thereby achieving two different fixed threshold voltage levels in terms of timing.

[0004] A fixed threshold voltage cannot be adaptively adjusted according to ambient light noise during ranging, so the threshold voltage can only be set when the ambient light noise is at its maximum. If it is not set in this way, false alarms may occur in actual testing, resulting in false alarms. However, if the threshold voltage is set when the ambient light noise is at its maximum, and ranging is performed when the ambient light noise is weak, the signal-to-noise ratio will be low, resulting in a short distance that cannot be measured. Summary of the Invention

[0005] This application aims to at least solve the technical problems existing in the prior art and provide a pulse timing identification digital system and laser ranging method based on pulsed laser echo differential signals.

[0006] In a first aspect, this application provides a pulse timing identification digital system based on pulsed laser echo differential signals. The system includes a laser, a photoelectric conversion module, a controller, and a differential comparison circuit. The controller controls the laser to send pulsed laser signals to a target. The photoelectric conversion module receives the echo signal reflected back from the target and converts the echo signal into a differential AC signal. The differential comparison circuit is configured to compare the differential voltage of the differential AC signal with a threshold voltage of the differential comparison circuit during laser ranging, and outputs an echo monitoring signal when the differential voltage is greater than the threshold voltage. Before laser ranging begins, the controller is configured to acquire the noise signal output by the differential comparison circuit and adjust the threshold voltage of the differential comparison circuit according to the acquired noise signal. During laser ranging, the controller is configured to acquire the echo monitoring signal output by the differential comparison circuit and determine the echo time of the target based on the time when the echo monitoring signal is acquired.

[0007] In a second aspect, this application provides a laser ranging method based on the pulse timing discrimination digital system based on pulsed laser echo differential signal as described in the first aspect of this application. The method includes: before the laser ranging begins, the controller acquires the noise signal output by the differential comparison circuit and adjusts the threshold voltage of the differential comparison circuit according to the acquired noise signal. During laser ranging, the following steps are performed: The controller controls the laser to emit pulsed laser signals toward the target, records the time of the emitted pulsed laser signal, and uses the recorded time as the start time; when the pulsed laser signal reaches the target, the target reflects back an echo signal; the echo signal enters the photoelectric conversion module and is converted into a differential AC signal; the differential AC signal is input to the differential comparator circuit; when the controller acquires the echo monitoring signal output by the differential comparator circuit, it records the time and uses the recorded time as the end time; the end time is subtracted from the start time to obtain the echo time of the target, and the distance between the target and the laser is calculated based on the echo time.

[0008] Thirdly, this application provides a laser ranging method based on the pulse timing discrimination digital system based on pulsed laser echo differential signals as described in the first aspect of this application. The method includes: before laser ranging begins, a controller acquires a noise signal output by a differential comparator circuit, and adjusts the threshold voltage of the differential comparator circuit according to the acquired noise signal, recording the adjusted threshold voltage as a first threshold voltage; during laser ranging, the following steps are performed: the controller controls the laser to emit a first pulsed laser signal towards the target; after the first pulsed laser signal reaches the target, the target reflects back a first echo signal; the first echo signal enters a photoelectric conversion module and is converted into a first differential AC signal; the first differential AC signal is input to the differential comparator circuit; when the controller acquires the first pulsed laser signal output by the differential comparator circuit... When the first echo monitoring signal is received, the first interval time from the emission of the first pulse laser signal to the acquisition of the first echo monitoring signal is recorded; the controller controls the laser to emit a second pulse laser signal towards the target, and synchronously adjusts the threshold voltage of the differential comparator circuit to a second threshold voltage; after the second pulse laser signal reaches the target, the target reflects back the second echo signal; the second echo signal enters the photoelectric conversion module and is converted into a second differential AC signal; the second differential AC signal is input to the differential comparator circuit; when the controller acquires the second echo monitoring signal output by the differential comparator circuit, the second interval time from the emission of the second pulse laser signal to the acquisition of the second echo monitoring signal is recorded; the echo time of the target is obtained according to the first interval time and the second interval time, and the distance between the target and the laser is calculated according to the echo time.

[0009] The beneficial technical effects of this application are as follows: Before laser ranging begins, the signal output by the differential comparison circuit is a noise signal, which reflects the current ambient light noise situation. The controller collects the noise signal output by the differential comparison circuit and adjusts the threshold voltage of the differential comparison circuit according to the collected noise signal. This achieves the optimal adaptive adjustment of the threshold voltage of the differential comparison circuit according to the ambient light noise, reduces false alarms, improves ranging accuracy, and can measure a longer distance even when the ambient light noise is weak. This improves the environmental adaptability of laser ranging and can save circuit components that set a fixed threshold voltage in related technologies, thus reducing the circuit size. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a pulse timing identification digital system according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the pulse timing identification digital system in another preferred embodiment of the present invention; Figure 3 It is the first dual-threshold voltage pulsed laser ranging scheme in related technologies; Figure 4 This is the second dual-threshold voltage pulsed laser ranging scheme in related technologies; Figure 5 This is a schematic diagram illustrating the calculation principle of the echo time of the target in a preferred embodiment of the present invention. Detailed Implementation

[0011] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0012] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0013] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0014] This invention provides a pulse timing discrimination digital system based on pulsed laser echo differential signals. In a preferred embodiment, such as... Figure 1 As shown, the system includes a laser, a photoelectric conversion module, a controller, and a differential comparator circuit; The controller is used to control the laser to send pulsed laser signals to the target; The photoelectric conversion module is used to receive the echo signal reflected back from the target and convert the echo signal into a differential AC signal; The differential comparator circuit is configured to compare the differential voltage of the differential AC signal with the threshold voltage of the differential comparator circuit during laser ranging. When the differential voltage is greater than the threshold voltage, an echo monitoring signal is output. The echo monitoring signal is a high-level pulse.

[0015] Before laser ranging begins, the controller is configured to acquire the noise signal output by the differential comparator circuit and adjust the threshold voltage of the differential comparator circuit based on the acquired noise signal. During laser ranging, the controller is configured to acquire the echo monitoring signal output by the differential comparator circuit and determine the target's echo time based on the time when the echo monitoring signal is acquired.

[0016] In this embodiment, the laser outputs a pulsed laser signal, which is not limited to a Q-switched laser, such as an Nd:YAG Q-switched laser, a Nd:YAG-doped Q-switched laser, and a ruby ​​Q-switched laser. The controller is preferably an MCU (microcontroller), but is not limited to a single-chip microcomputer or an ARM processor. The controller can control the output of a pulsed laser signal or not by controlling the electronic switch in the laser's power-on circuit to turn it on or off through an I / O pin.

[0017] In this embodiment, preferably, the controller controls the laser's operation via a laser driver IC. The laser driver IC is not limited to an LM317, MAX1968, or LT3748 driver chip. The controller outputs a pulse signal through an I / O pin to drive the laser driver IC, which then provides a drive power signal to the laser under the control of the pulse signal.

[0018] In this embodiment, the photoelectric conversion module includes a photoelectric conversion unit and a preamplifier circuit connected in sequence. The photoelectric conversion unit is preferably, but not limited to, a photodiode or a phototransistor, which converts the echo signal into a photocurrent signal. The preamplifier circuit includes a transimpedance amplifier circuit and a fully differential amplifier circuit. The transimpedance amplifier circuit converts the photocurrent signal into a voltage signal, and the voltage signal is input to the fully differential amplifier circuit to be converted into a differential AC signal.

[0019] In this embodiment, please see Figure 1 and Figure 2 The differential comparator circuit includes a differential comparator (U4) and its peripheral power supply circuit. The differential comparator is not limited to LM358, LM324, or OP07. Preferably, a high-speed differential comparator, such as LMH7322 or ADCMP600, is selected to speed up the response and improve ranging accuracy. The positive input terminal of the differential comparator circuit is the positive input terminal of the differential comparator, and the negative input terminal is the negative input terminal of the differential comparator. For example... Figure 1 and Figure 2 As shown, the positive terminal signal S_P of the differential AC signal output by the photoelectric conversion module is connected to the positive input terminal C_P of the differential comparator, and the negative terminal signal S_N of the differential AC signal is connected to the negative input terminal C_N of the differential comparator.

[0020] In this embodiment, to facilitate the filtering of DC common-mode noise signals in the differential AC signal, improve the anti-interference capability of the echo signal, and increase the signal-to-noise ratio of the echo signal, preferably, as follows: Figure 1 and Figure 2As shown, an AC coupling unit is connected in series in the connection path between the photoelectric conversion module and the differential comparator circuit. The AC coupling unit includes a ninth capacitor C9 connected in series between the positive output terminal S_P of the differential AC signal of the photoelectric conversion module and the positive input terminal C_P of the differential comparator, and a tenth capacitor C10 connected in series between the negative output terminal S_N of the differential AC signal of the photoelectric conversion module and the negative input terminal C_N of the differential comparator circuit.

[0021] In this embodiment, the voltage difference between the positive and negative input terminals of the differential comparator circuit is the threshold voltage of the differential comparator circuit. To simplify control and enable continuous adjustment of the threshold voltage, preferably, the first voltage output terminal of the controller is connected to the positive input terminal of the differential comparator circuit, and the second voltage output terminal of the controller is connected to the negative input terminal of the differential comparator circuit. The first and second voltage output terminals of the controller are not limited to the two voltage output pins DAC_P and DAC_N of the internal digital-to-analog converter (D / A) module of the controller. The threshold voltage is adjusted by regulating the voltage values ​​of DAC_P and DAC_N.

[0022] In this embodiment, the signal input terminal of the controller is connected to the output terminal of the differential comparator circuit (i.e., the output terminal S_OUT of the differential comparator). Preferably, the signal input terminal of the controller is the input pin of the internal timer. This timer input pin is used to capture interrupts. The interrupt triggering method of this pin is not limited to high-level triggering or rising-edge triggering. When the timer input pin is triggered, the interrupt time is recorded. Therefore, the controller can record the number of interrupts based on multiple interrupt times. To reduce pin usage, the controller uses the same timer input pin to collect the number of noise signal pulses before laser ranging begins and to collect the return time of the echo monitoring signal during laser ranging.

[0023] In this embodiment, before laser ranging begins, the controller is configured to acquire the noise signal output by the differential comparator circuit and record the noise quantity per unit time. At this time, no echo signal is input to the photoelectric conversion module. The ambient stray light within the wavelength range of the photoelectric conversion module is converted into a stray photovoltage signal by the photoelectric conversion module. The stray photovoltage signal is input to the voltage comparator circuit, which compares the differential voltage of the photovoltage signal with the current threshold voltage. Based on the comparison result, the voltage comparator outputs a stray pulse signal (mainly a non-periodic pulse signal, with the high level of each pulse determined based on the power supply voltage of the differential comparator). This stray pulse signal is used as the noise signal.

[0024] In a preferred embodiment, before laser ranging begins, the controller is configured to acquire a noise signal output by the differential comparator circuit and adjust the threshold voltage of the differential comparator circuit based on the acquired noise signal, including: Step 1: Obtain the noise quantity per unit time of the noise signal; The input pin of the timer inside the controller is triggered by a pulse in the noise signal, causing an interrupt. The controller records the interrupt time of each interrupt. One interrupt time corresponds to one pulse in the noise signal. Thus, by recording the number of interrupts triggered by the input pin of the timer within a unit time (such as 1 second or 1 minute), the noise quantity per unit time of the noise signal is obtained. Step 2: If the noise quantity per unit time is within the preset range, the threshold voltage of the differential comparator circuit is not adjusted, indicating that the threshold voltage set at this time is reasonable. If the noise quantity per unit time is not within the preset range, it indicates that the threshold voltage may be set too high, resulting in a small noise quantity, which may prevent the acquisition of echo signals reflected from distant targets. Alternatively, the threshold voltage may be set too low, resulting in an excessive noise quantity, which may introduce false alarms and misjudgments. Therefore, the threshold voltage of the differential comparator circuit needs to be adjusted until the noise quantity per unit time in the noise signal output by the differential comparator circuit is within the preset range.

[0025] In this embodiment, the preset quantity range can be set based on experience or multiple experiments. Utilizing the magnitude of the noise quantity per unit time of the noise signal can more accurately assess the noise level of the detection environment, avoiding errors caused by component background drift. The threshold voltage is increased with the goal of keeping the noise quantity per unit time within the preset quantity range, ensuring that it can measure targets at greater distances while avoiding false alarms caused by noise.

[0026] In this embodiment, more preferably, if the noise quantity per unit time exceeds the upper limit of the preset quantity range, the threshold voltage of the differential comparator circuit is increased until the noise quantity per unit time is within the preset noise quantity range; if the noise quantity per unit time is lower than the lower limit of the preset quantity range, the threshold voltage of the differential comparator circuit is decreased until the noise quantity per unit time is within the preset noise quantity range.

[0027] In this embodiment, in order to achieve rapid and accurate adjustment of the threshold voltage of the differential comparator circuit and ensure that the noise quantity per unit time is within the preset noise quantity range, a PID control algorithm is used to adjust the threshold voltage.

[0028] In a preferred embodiment, to improve the impedance matching performance between the controller and the differential comparator circuit and enhance system stability, such as... Figure 2 As shown, a positive pull-down resistor R13 is connected between the positive input terminal of the differential comparator circuit and ground; and / or, a negative pull-down resistor R19 is connected between the negative input terminal of the differential comparator circuit and ground.

[0029] In this embodiment, preferably, to further improve the system's operational stability, a positive pull-up resistor R12 is connected between the positive input terminal of the differential comparator circuit and the first voltage output terminal of the controller; and / or, a negative pull-up resistor R14 is connected between the negative input terminal of the differential comparator circuit and the second voltage output terminal of the controller.

[0030] This invention also discloses a laser ranging method based on the above-mentioned pulse timing discrimination digital system based on pulsed laser echo differential signal, the method comprising: Step A1: Before laser ranging begins, the controller acquires the noise signal output by the differential comparator circuit and adjusts the threshold voltage of the differential comparator circuit according to the acquired noise signal. Step A2, during laser ranging, perform the following steps: Step A21: The controller controls the laser to emit pulsed laser signals toward the target, records the time of the emitted pulsed laser signals, and uses the recorded time as the start time. ; Step A22: After the pulsed laser signal reaches the target, the target reflects back the echo signal; Step A23: The echo signal enters the photoelectric conversion module and is converted into a differential AC signal; The differential AC signal is input to the differential comparator circuit; Step A24: When the controller acquires the echo monitoring signal output by the differential comparator circuit, record the time and use the recorded time as the end time. ; Step A25: Subtract the start time from the end time to obtain the target's echo time. The distance between the target and the laser is calculated based on the echo time. .

[0031] In this embodiment, . ,in, The distance is the speed of light. This implementation method uses a single-pulse method to test the distance between the target and the laser. The calculation process is simple and fast, but the ranging accuracy is generally low.

[0032] In the aforementioned single-pulse laser ranging method, if the laser emits laser pulse signals at two target objects at the same distance with the same emission angle, the amplitude and shape of the laser pulse echoes will differ due to differences in the surface reflectivity and irregularities of the two target objects. Comparing these echoes with the same fixed threshold voltage will result in different arrival times, which is the time drift error, affecting the accuracy of pulse ranging. To solve the time drift error and achieve accurate ranging, this invention also provides a dual-pulse laser ranging method. This method is based on the aforementioned pulse timing discrimination digital system based on pulse laser echo differential signals. The method includes: Step B1: Before laser ranging begins, the controller acquires the noise signal output by the differential comparison circuit and adjusts the threshold voltage of the differential comparison circuit according to the acquired noise signal. The adjusted threshold voltage is recorded as the first threshold voltage Vth1.

[0033] Step B2, during laser ranging, perform the following steps: Step B21: The controller controls the laser to emit the first pulse laser signal toward the target.

[0034] Step B22: After the first pulse laser signal reaches the target, the target reflects back the first echo signal.

[0035] Step B23: The first echo signal enters the photoelectric conversion module and is converted into a first differential AC signal; the first differential AC signal is input to the differential comparator circuit; the differential comparator circuit compares the differential voltage of the first differential AC signal with the first threshold voltage Vth1. If the differential voltage is greater than the first threshold voltage Vth1, the differential comparator circuit outputs a high level to form a high-level pulse, which is used as the first echo monitoring signal. Figure 5 As shown, the output terminal S_OUT of the differential comparator circuit outputs a high level, that is, it outputs the first echo monitoring signal. If the differential voltage is not greater than the first threshold voltage Vth1, the differential comparator circuit outputs a low level, that is, it does not output the first echo monitoring signal.

[0036] Step B24: When the controller acquires the first echo monitoring signal output by the differential comparator circuit, record the first interval time from the emission of the first pulse laser signal to the acquisition of the first echo monitoring signal. .

[0037] Step B25: The controller controls the laser to emit a second pulse laser signal towards the target, and simultaneously adjusts the threshold voltage of the differential comparator circuit to the second threshold voltage Vth2. Vth1 = *Vth2, , , This indicates that when the differential comparator circuit has a ratio coefficient and satisfies the condition that the threshold voltage of the differential comparator circuit is the second threshold voltage Vth2 before the laser ranging starts, the noise quantity per unit time is within the preset noise quantity range.

[0038] Step B26: After the second pulse laser signal reaches the target, the target reflects back the second echo signal.

[0039] In step B27, the second echo signal enters the photoelectric conversion module and is converted into a second differential AC signal; the second differential AC signal is input to the differential comparator circuit. The differential comparator circuit compares the differential voltage of the second differential AC signal with the second threshold voltage Vth2. If the differential voltage is greater than the second threshold voltage Vth2, the differential comparator circuit outputs a high level to form a high-level pulse, which is used as the second echo monitoring signal. Figure 5 As shown, at time t2, the output terminal S_OUT of the differential comparator circuit outputs a high level, that is, it outputs the second echo monitoring signal. If the differential voltage is not greater than the second threshold voltage Vth2, the differential comparator circuit outputs a low level, that is, it does not output the second echo monitoring signal.

[0040] Step B28: When the controller acquires the second echo monitoring signal output by the differential comparator circuit, record the second interval time from the emission of the second pulse laser signal to the acquisition of the second echo monitoring signal. .

[0041] Step B29: Obtain the target's echo time based on the first interval time and the second interval time. echo time This is approximately the time from when the laser pulses the signal towards the target to when the echo signal reaches the photoelectric conversion module. Based on the echo time... Calculate the distance between the target and the laser .

[0042] In this embodiment, preferably, the second threshold voltage Vth2 is less than the first threshold voltage Vth1.

[0043] In this embodiment, it can be seen that time-division dual-pulse ranging is used, and the value at time t0 is independent of the shape of the echo pulse, eliminating the influence of time drift error and improving the accuracy of time discrimination. It is worth noting that during the control logic algorithm processing, t1 and t2 must be obtained sequentially. If only one is obtained, the data set should be discarded. In addition, if the difference between t1 and t2 significantly exceeds the maximum duration of the rising edge of the signal, the data set should also be discarded.

[0044] In the description of this specification, the references to terms such as "an embodiment," "some embodiments," "example," "specific example," "a implementation," "a preferred implementation," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A digital system for pulse timing discrimination based on pulsed laser echo differential signals, characterized in that, The system includes a laser, a photoelectric conversion module, a controller, and a differential comparator circuit; The controller is used to control the laser to send pulsed laser signals to the target; The photoelectric conversion module is used to receive the echo signal reflected back from the target and convert the echo signal into a differential AC signal; The differential comparator circuit is configured to compare the differential voltage of the differential AC signal with the threshold voltage of the differential comparator circuit during laser ranging, and output an echo monitoring signal when the differential voltage is greater than the threshold voltage. Before laser ranging begins, the controller is configured to acquire the noise signal output by the differential comparator circuit and adjust the threshold voltage of the differential comparator circuit according to the acquired noise signal. During laser ranging, the controller is configured to acquire the echo monitoring signal output by the differential comparator circuit and determine the echo time of the target based on the time when the echo monitoring signal is acquired.

2. The pulse timing discrimination digital system based on pulsed laser echo differential signal as described in claim 1, characterized in that, Before laser ranging begins, the controller is configured to acquire the noise signal output by the differential comparator circuit and adjust the threshold voltage of the differential comparator circuit based on the acquired noise signal, including: Obtain the amount of noise per unit time in the noise signal; If the amount of noise per unit time is within the preset range, the threshold voltage of the differential comparator circuit will not be adjusted. If the amount of noise per unit time is not within the preset range, adjust the threshold voltage of the differential comparator circuit until the amount of noise per unit time in the noise signal output by the differential comparator circuit is within the preset range.

3. The pulse timing discrimination digital system based on pulsed laser echo differential signal as described in claim 2, characterized in that, If the amount of noise per unit time exceeds the upper limit of the preset range, the threshold voltage of the differential comparator circuit is increased; if the amount of noise per unit time is lower than the lower limit of the preset range, the threshold voltage of the differential comparator circuit is decreased.

4. The pulse timing discrimination digital system based on pulsed laser echo differential signal as described in any one of claims 1-3, characterized in that, The controller's first voltage output terminal is connected to the positive input terminal of the differential comparator circuit, and the controller's second voltage output terminal is connected to the negative input terminal of the differential comparator circuit.

5. The pulse timing discrimination digital system based on pulsed laser echo differential signal as described in claim 4, characterized in that, A positive pull-down resistor is connected between the positive input terminal of the differential comparator circuit and ground; And / or, a negative pull-down resistor is connected between the negative input of the differential comparator circuit and ground.

6. The pulse timing discrimination digital system based on pulsed laser echo differential signal as described in claim 5, characterized in that, A positive pull-up resistor is connected between the positive input terminal of the differential comparator circuit and the first voltage output terminal of the controller; And / or, a negative pull-up resistor is connected between the negative input terminal of the differential comparator circuit and the second voltage output terminal of the controller.

7. The pulse timing discrimination digital system based on pulsed laser echo differential signals as described in any one of claims 1-3, 5, and 6, characterized in that, An AC coupling unit is connected in series in the connection path between the photoelectric conversion module and the differential comparator circuit.

8. A laser ranging method based on a pulse timing discrimination digital system based on pulsed laser echo differential signals according to any one of claims 1-7, characterized in that, The method includes: Before laser ranging begins, the controller acquires the noise signal output by the differential comparator circuit and adjusts the threshold voltage of the differential comparator circuit based on the acquired noise signal. During laser ranging, the following steps are performed: The controller controls the laser to emit pulsed laser signals toward the target, records the time of the emitted pulsed laser signals, and uses the recorded time as the start time. When the pulsed laser signal reaches the target, the target reflects back the echo signal; The echo signal enters the photoelectric conversion module and is converted into a differential AC signal; The differential AC signal is input to the differential comparator circuit; When the controller acquires the echo monitoring signal output by the differential comparator circuit, it records the time and uses the recorded time as the end time. Subtract the start time from the end time to obtain the target's echo time, and calculate the distance between the target and the laser based on the echo time.

9. A laser ranging method based on a pulse timing discrimination digital system based on pulsed laser echo differential signals according to any one of claims 1-7, characterized in that, The method includes: Before laser ranging begins, the controller acquires the noise signal output by the differential comparator circuit and adjusts the threshold voltage of the differential comparator circuit according to the acquired noise signal. The adjusted threshold voltage is recorded as the first threshold voltage. During laser ranging, the following steps are performed: The controller directs the laser to emit the first pulse laser signal toward the target; After the first pulse laser signal reaches the target, the target reflects back the first echo signal; The first echo signal enters the photoelectric conversion module and is converted into a first differential AC signal; The first differential AC signal is input to the differential comparator circuit; When the controller acquires the first echo monitoring signal output by the differential comparator circuit, it records the first interval time from the emission of the first pulse laser signal to the acquisition of the first echo monitoring signal. The controller controls the laser to emit a second pulse laser signal toward the target, and simultaneously adjusts the threshold voltage of the differential comparator circuit to the second threshold voltage. After the second pulse laser signal reaches the target, the target reflects back the second echo signal; The second echo signal enters the photoelectric conversion module and is converted into a second differential AC signal; The second differential AC signal is input to the differential comparator circuit; When the controller acquires the second echo monitoring signal output by the differential comparator circuit, it records the second interval time from the emission of the second pulse laser signal to the acquisition of the second echo monitoring signal. The echo time of the target is obtained based on the first interval time and the second interval time, and the distance between the target and the laser is calculated based on the echo time.

10. The laser ranging method as described in claim 9, characterized in that, The second threshold voltage is less than the first threshold voltage.

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