Laser radar signal receiving method and receiving circuit

Abstract

The invention discloses a laser radar signal receiving method and a receiving circuit, the receiving circuit of a laser radar at least comprises a photoelectric element and a step-down circuit, when a voltage is applied to a first end of the photoelectric element, the photoelectric element generates a light current when receiving an echo signal, and the step-down circuit is connected with the first end of the photoelectric element. When a preset pulse is input to the step-down circuit, the step-down circuit is switched on, so that the first terminal voltage of the photoelectric element is reduced. The method comprises the following steps: when the laser radar emits pulse laser, inputting a preset pulse to the step-down circuit, so that the first end voltage of the photoelectric element is reduced and recovered after a preset time length, and the gain of the photoelectric element is reduced within the preset time length; the preset time length is matched with the delay time length of the echo signal reflected by the interior of the laser radar and received by the photoelectric element relative to the pulse laser. According to the invention, the influence of an echo signal, namely an internal interference signal, reflected by the interior of the laser radar can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of laser radar, and in particular to a laser radar signal receiving method and a receiving circuit. Background Art

[0002] Since the laser radar measurement speed is very fast and the measured target is generally a natural object, the energy of the reflected signal is uncertain and the strength of the echo signal is random and unpredictable, which requires the ranging module to quickly process the echo signal within a large dynamic range. On the other hand, the laser radar measurement is fast and the measurement result is required in a single measurement. Therefore, there is not enough time to adjust the transmission energy or the threshold of the comparator in the receiving channel to ensure the accuracy of the measurement result.

[0003] With the evolution of LiDAR technology, on the one hand, the measurement range is required to be longer and longer, and on the other hand, the minimum distance (i.e., the distance corresponding to the nearest object that LiDAR can detect) is required to be smaller and smaller. Although the measurement range can be improved by increasing the transmission power or increasing the receiving aperture, the size of the receiving aperture is almost limited due to volume limitations, so it can only be improved by increasing the transmission power. However, increasing the transmission power will bring another disadvantage. The greater the transmission power, the greater the driving current required, which will cause electrical and optical co-channel interference to the system. Electrical co-channel interference can be suppressed through module layout, isolation of power supply and ground, and shielding measures, but it can only reduce co-channel interference to a certain extent and cannot be completely eliminated. In terms of optics, the transmission and receiving channels are completely physically isolated through an off-axis optical system, but if LiDAR is used for scanning, the system load that isolates the transmission and receiving channels is relatively heavy, which reduces the stability of the system.

[0004] For systems where the transmitting and receiving channels are coaxial, the transmitting and receiving channels are not isolated. This will cause a certain amount of residual light to be reflected when the transmitting signal reaches a certain optical mirror inside and enter the receiving channel, resulting in a fixed synchronous echo signal with a certain delay from the transmitting signal inside the receiving channel. The existence of this echo signal directly causes the signal reflected from a close-range object to not be well received, and it will be combined with the internal interference signal (i.e. the echo signal generated internally) to form a fusion signal. Figure 1 , Figure 1This is a schematic diagram of the fusion of the internal reflected light and the external reflected light of the laser radar. The internal reflected light corresponds to the echo signal generated by the internal reflection, and the external reflected light corresponds to the echo signal reflected from the outside. There is a certain deviation between the leading edge or pulse width of the fused signal and the signal corresponding to the actual distance of the object. Only when the distance of the object exceeds a certain range can the internal interference signal and the signal reflected from the object be separated on the time axis, thus limiting the ranging range. In addition, because the amplitude of the internal interference signal is basically stable, for close-range weak-reflecting objects, the intensity of the echo signal reflected from the object is relatively weak, resulting in a much larger proportion of the internal interference signal in the fused signal than when the signal is strong, which will result in a relatively large ranging error. Summary of the invention

[0005] The object of the present invention is to provide a laser radar signal receiving method and receiving circuit, which can reduce the influence of internal interference signals.

[0006] To achieve the above object, the present invention provides the following technical solutions: A laser radar signal receiving method, wherein the receiving circuit of the laser radar comprises at least a photoelectric element and a step-down circuit, wherein the photoelectric element is used to generate a photocurrent when a voltage is applied to a first end of the photoelectric element and the photoelectric element receives an echo signal, and the step-down circuit is connected to the first end of the photoelectric element and is used to turn on the step-down circuit when a preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced; The laser radar signal receiving method comprises: When the laser radar emits a pulsed laser, the preset pulse is input into the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period, and the preset time period matches the delay time of the echo signal reflected back from the inside of the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

[0007] Optionally, the step-down circuit includes: A first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the first input end; The first input terminal is used to input the preset pulse from the first input terminal to the first capacitor, so that charge flows on the first capacitor and the voltage at the first terminal of the photoelectric element decreases.

[0008] Optionally, the amplitude of the preset pulse satisfies the following conditional formula: V 1A *M=V rA; Among them, V 1A represents the amplitude of the preset pulse, M represents the gain of the photoelectric element when a voltage is applied to the first end of the photoelectric element, V rA It represents the voltage amplitude corresponding to the photocurrent generated when the photoelectric element receives the echo signal reflected back from the inside of the laser radar when a voltage is applied to the first end of the photoelectric element.

[0009] Optionally, the step-down circuit includes: A first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; A second resistor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the switch device; The switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the first terminal voltage of the photoelectric element is reduced.

[0010] A laser radar receiving circuit, comprising: a photoelectric element, configured to generate a photocurrent when the photoelectric element receives an echo signal when a voltage is applied to a first end of the photoelectric element; A step-down circuit is connected to the first end of the photoelectric element and is used to input a preset pulse to the step-down circuit when the laser radar emits a pulsed laser. The step-down circuit is turned on when the preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period. The preset time period matches the delay time of the echo signal reflected back from the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

[0011] Optionally, the step-down circuit includes: A first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the first input end; The first input terminal is used to input the preset pulse from the first input terminal to the first capacitor, so that charge flows on the first capacitor and the voltage at the first terminal of the photoelectric element decreases.

[0012] Optionally, it also includes: A third resistor, one end of which is connected to the first end of the photoelectric element, is used to generate impedance to the preset pulse after passing through the first capacitor, so that the preset pulse is coupled with the voltage applied to the first end of the photoelectric element.

[0013] Optionally, it further includes a pulse generating circuit, wherein the pulse generating circuit includes a second voltage terminal, a first transistor, a first driver, a second input terminal and a second output terminal; The second voltage terminal is connected to the third electrode of the first transistor, and the second output terminal is led out from the third electrode of the first transistor. The first electrode of the first transistor is grounded, the first driver is connected to the second electrode of the first transistor, and the second input terminal is connected to the input terminal of the first driver. The first driver is used to apply a voltage to the second electrode of the first transistor, so that when a first trigger signal is input from the second input terminal, the voltage applied to the second electrode of the first transistor increases, and when the first transistor is turned on, the preset pulse is output from the second output terminal, and the second output terminal is connected to the first input terminal.

[0014] Optionally, the pulse generating circuit further includes a seventh capacitor, one end of the seventh capacitor is connected to the third electrode of the first transistor, and the other end is grounded, and the second output end is arranged between the third electrode of the first transistor and the seventh capacitor; The pulse width of the preset pulse is obtained according to the following formula: t; in, represents the discharge time of the seventh capacitor when the first transistor is turned on, that is, represents the pulse width of the preset pulse, I represents the current value of the current on the third electrode when the first transistor is turned on, C represents the capacitance value of the seventh capacitor, V represents the voltage value of the second voltage applied from the second voltage terminal, and Q represents the amount of charge stored in the seventh capacitor.

[0015] Optionally, the step-down circuit includes: A first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; A second resistor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the switch device; The switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the first terminal voltage of the photoelectric element is reduced.

[0016] It can be known from the above technical scheme that the laser radar signal receiving method and receiving circuit provided by the present invention, the receiving circuit of the laser radar at least includes a photoelectric element and a step-down circuit, the photoelectric element is used to generate a photocurrent when the photoelectric element receives an echo signal when a voltage is applied to the first end of the photoelectric element, and the step-down circuit is connected to the first end of the photoelectric element, and is used to turn on the step-down circuit when a preset pulse is input to the step-down circuit, so that the voltage of the first end of the photoelectric element is reduced. The laser radar signal receiving method includes: when the laser radar emits a pulse laser, a preset pulse is input to the step-down circuit, so that the voltage of the first end of the photoelectric element is reduced and restored after a preset time length, so that the gain of the photoelectric element is reduced within the preset time length, and the preset time length matches the delay time length of the echo signal reflected back from the laser radar by the photoelectric element relative to the pulse laser, and the gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

[0017] In the present invention, the receiving circuit of the laser radar is provided with a step-down circuit, which is connected to the first end of the photoelectric element. When a preset pulse is input to the step-down circuit, the step-down circuit is turned on, and the voltage of the first end of the photoelectric element can be reduced. When the laser radar emits a pulsed laser, a preset pulse is input to the step-down circuit, so that the voltage of the first end of the photoelectric element is reduced and restored after a preset time, so that the gain of the photoelectric element is reduced within a preset time after the laser radar emits the pulsed laser. The preset time can match the delay time of the echo signal reflected back from the inside of the laser radar relative to the pulsed laser, so that when the photoelectric element receives the echo signal reflected back from the inside of the laser radar, the gain of the photoelectric element is reduced, so that the response of the receiving circuit to the echo signal reflected back from the inside of the laser radar is weakened, thereby reducing the influence of the echo signal reflected back from the inside, that is, the internal interference signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a schematic diagram of the fusion of internal reflected light and external reflected light of the laser radar; Figure 2 Schematic diagram of generating internal interference signals for a system with isolated transmit and receive channels; Figure 3 A curve showing the relationship between the gain of a photoelectric element of a laser radar receiving circuit and the voltage applied to the photoelectric element provided by an embodiment; Figure 4A curve showing the relationship between the gain of a photoelectric element and the voltage at the first end of the photoelectric element after coupling a preset pulse in a laser radar receiving circuit provided by an embodiment; Figure 5 A preset pulse inputted by a laser radar receiving circuit to a step-down circuit and a change in the voltage at the first end of a photoelectric element after the preset pulse is inputted are provided in another embodiment; Figure 6 A schematic diagram of a laser radar receiving circuit provided by an embodiment; Figure 7 A schematic diagram of a pulse generating circuit of a laser radar receiving circuit provided by an embodiment; Figure 8 A waveform diagram of a preset pulse output by a pulse generating circuit of a laser radar receiving circuit provided in an embodiment; Fig. 9 A schematic diagram of a laser radar receiving circuit provided in yet another embodiment; Fig.10 A schematic diagram of a transmitting circuit of a laser radar provided by an embodiment; Fig.11 A waveform diagram of a current passing through a light-emitting element of a transmitting circuit of a laser radar provided by an embodiment; Fig.12 A waveform diagram of a second trigger signal input to a transmitting circuit by a laser radar provided in an embodiment; Fig.13 Three waveform diagrams of a laser radar receiving circuit provided in one embodiment. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0021] For systems where the transmitting and receiving channels are coaxial, the transmitting and receiving channels are not isolated. This will cause a certain amount of residual light to be reflected when the transmitting signal reaches a certain optical mirror inside and enter the receiving channel, resulting in a fixed synchronous echo signal with a certain delay from the transmitting signal inside the receiving channel. The existence of this echo signal directly causes the signal reflected from a close-range object to not be well received, and it will be combined with the internal interference signal (i.e. the echo signal generated internally) to form a fusion signal. Figure 1 , Figure 1This is a schematic diagram of the fusion of the internal reflected light and the external reflected light of the laser radar. The internal reflected light corresponds to the echo signal generated by the internal reflection, and the external reflected light corresponds to the echo signal reflected from the outside. There is a certain deviation between the leading edge or pulse width of the fused signal and the signal corresponding to the actual distance of the object. Only when the distance of the object exceeds a certain range can the internal interference signal and the signal reflected from the object be separated on the time axis, thus limiting the ranging range. In addition, because the amplitude of the internal interference signal is basically stable, for close-range weak-reflecting objects, the intensity of the echo signal reflected from the object is relatively weak, resulting in a much larger proportion of the internal interference signal in the fused signal than when the signal is strong, which will result in a relatively large ranging error.

[0022] For systems with isolated transmitting and receiving channels, i.e., systems with coaxial transmitting and receiving channels, whether it is a 2D or 3D laser radar, the front end is composed of the transmitting, receiving, and scanning optical parts that deflect the laser, as well as the protective cover that needs to be added for dust and water resistance. Figure 2 , Figure 2 Schematic diagram of internal interference signals generated by a system that isolates the transmit and receive channels. Both the scanning optical part and the protective cover will have a certain reflection or scattering effect on the transmitted laser, and these reflected lights may enter the receiving channel and form fixed interference.

[0023] Therefore, for laser radar, due to the influence of internal interference signals, the ranging range will be limited and ranging errors will be generated. In view of this, this embodiment provides a laser radar signal receiving method and receiving circuit, which can reduce the influence of internal interference signals.

[0024] This embodiment provides a laser radar signal receiving method, wherein the laser radar receiving circuit comprises at least a photoelectric element and a step-down circuit, wherein the photoelectric element is used to generate a photocurrent when a voltage is applied to a first end of the photoelectric element and the photoelectric element receives an echo signal, and the step-down circuit is connected to the first end of the photoelectric element and is used to turn on the step-down circuit when a preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced; The laser radar signal receiving method comprises: When the laser radar emits a pulsed laser, the preset pulse is input into the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period, and the preset time period matches the delay time of the echo signal reflected back from the inside of the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

[0025] The photoelectric element is used to receive light and generate photocurrent to detect light. When a voltage is applied to the first end of the photoelectric element, the photoelectric element can generate photocurrent when receiving light. The gain of the photoelectric element is related to the voltage applied to the first end of the photoelectric element. The gain of the photoelectric element can be changed by changing the voltage at the first end of the photoelectric element.

[0026] When a preset pulse is input to the buck circuit, the buck circuit is turned on, which means that charge can flow from the buck circuit, and charge flow occurs on the buck circuit. The buck circuit is connected to the first end of the photoelectric element, and when the buck circuit is turned on, charge flow occurs on the buck circuit, so that the voltage of the first end of the photoelectric element is reduced.

[0027] The laser radar emits a pulsed laser, and the echo signal reflected from inside the laser radar refers to the echo signal generated when the pulsed laser encounters the internal surface of the laser radar and is reflected during the outward emission of the pulsed laser. When the laser radar emits a pulsed laser, a preset pulse is input into the step-down circuit to reduce the voltage at the first end of the photoelectric element and restore it after a preset time, so that the voltage at the first end of the photoelectric element will be reduced within the preset time after the laser radar emits the pulsed laser, so that the gain of the photoelectric element will be reduced within the preset time after the laser radar emits the pulsed laser. The preset time can match the delay time of the echo signal reflected from inside the laser radar relative to the pulsed laser, so that the gain of the photoelectric element can be reduced when the photoelectric element receives the echo signal reflected from inside the laser radar, so that the response of the receiving circuit to the echo signal reflected from inside the laser radar is weakened, thereby reducing the influence of the internally reflected echo signal, i.e., the internal interference signal.

[0028] In some embodiments, the gain of the photoelectric element may be positively correlated with the magnitude of the voltage at the first terminal of the photoelectric element. Figure 3 , Figure 3 A curve showing the relationship between the gain of a photoelectric element of a laser radar receiving circuit and the voltage applied to the photoelectric element is provided in an embodiment, wherein the voltage applied to the photoelectric element is a reverse bias voltage applied to the photoelectric element. It can be seen that the gain of the photoelectric element is positively correlated with the reverse bias voltage applied to the photoelectric element, and the gain of the photoelectric element can be changed by changing the magnitude of the reverse bias voltage applied to the photoelectric element.

[0029] The echo signal reflected back from the inside of the laser radar reaches the photoelectric element, which is delayed relative to the laser radar emitting a pulse laser. In this embodiment, the preset duration is matched with the delay duration of the photoelectric element receiving the echo signal reflected back from the inside of the laser radar relative to the laser radar emitting a pulse laser, so that when the photoelectric element receives the echo signal reflected back from the inside of the laser radar, the voltage at the first end of the photoelectric element decreases and the gain of the photoelectric element decreases, and then the voltage at the first end of the photoelectric element is restored and the gain of the photoelectric element is restored, so as to effectively reduce the influence of internal interference signals and minimize the influence on the photoelectric element's response and detection of echo signals reflected from the outside.

[0030] In practical applications, the laser radar can be tested to obtain the delay time of the echo signal reflected from the laser radar to the photoelectric element relative to the laser radar emitting the pulse laser, and the pulse width of the preset pulse can be set accordingly. For example, in a specific example, the delay time of the echo signal reflected from the laser radar to the photoelectric element relative to the laser radar emitting the pulse laser is in the range of 2nS to 3nS, and the pulse width of the preset pulse can be in the range of 2nS to 3nS.

[0031] In some embodiments, the step-down circuit includes: a first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end is connected to the first input end; the first input end is used to input the preset pulse from the first input end to the first capacitor, so that charge flows on the first capacitor, and the voltage of the first end of the photoelectric element is reduced. The preset pulse is an AC signal. When the preset pulse is input from the first input end to the first capacitor, the preset pulse can cause charge to flow on the first capacitor, so that the preset pulse is coupled with the voltage applied to the first end of the photoelectric element, and the voltage of the first end of the photoelectric element can be reduced. The preset pulse can be opposite to the phase of the voltage applied to the first end of the photoelectric element, so that the voltage of the first end of the photoelectric element can be reduced when the preset pulse is input to the first capacitor. The preset pulse is opposite to the phase of the voltage applied to the first end of the photoelectric element, which means that if a positive voltage is applied to the first end of the photoelectric element, the preset pulse is a negative pulse; if a negative voltage is applied to the first end of the photoelectric element, the preset pulse is a positive pulse. The voltage applied to the first end of the photoelectric element is a DC voltage, and the step-down circuit is in an open circuit state when the preset pulse is not input to the first capacitor.

[0032] In some embodiments, the amplitude of the preset pulse satisfies the following condition: V 1A *M=V rA ; Among them, V 1A represents the amplitude of the preset pulse, M represents the gain of the photoelectric element when a voltage is applied to the first end of the photoelectric element, V rAIt represents the voltage amplitude corresponding to the photocurrent generated when the photoelectric element receives the echo signal reflected back from the inside of the laser radar when a voltage is applied to the first end of the photoelectric element. The amplitude of the preset pulse satisfies this conditional formula, so that the preset pulse can be input to the first capacitor, and the preset pulse is coupled with the voltage applied to the first end of the photoelectric element. When the photoelectric element receives the echo signal reflected back from the inside of the laser radar, the gain of the photoelectric element is reduced, and the photocurrent generated when the photoelectric element receives the echo signal reflected back from the inside of the laser radar is minimized, so that the receiving circuit can achieve the effect of eliminating the internal interference signal as much as possible.

[0033] For example, reference may be made to Figure 4 , Figure 4 A curve of the relationship between the gain of a photoelectric element and the voltage at the first end of the photoelectric element of a laser radar receiving circuit after coupling a preset pulse is provided for one embodiment, wherein the upper figure is a gain curve of the photoelectric element after coupling the preset pulse, and the lower figure is a voltage curve of the first end of the photoelectric element after coupling the preset pulse, and the voltage applied to the photoelectric element is a reverse bias voltage applied to the photoelectric element. As shown in the figure below, after the preset pulse is input, due to the coupling of the preset pulse with the voltage applied to the first end of the photoelectric element, the voltage at the first end of the photoelectric element, i.e., the reverse bias voltage applied to the photoelectric element, decreases for a period of time and then recovers. As shown in the figure above, when the preset pulse is not input, the gain of the photoelectric element reaches M2. After the preset pulse is input, due to the coupling of the preset pulse with the voltage applied to the photoelectric element, the gain of the photoelectric element is reduced to M1, and after a period of time corresponding to the preset pulse, the gain of the photoelectric element recovers and increases.

[0034] In some embodiments, the step-down circuit includes: a first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; a second resistor, one end of which is connected to the first end of the photoelectric element, and the other end is connected to a switch device; the switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the voltage at the first end of the photoelectric element is reduced. When the switch device is not turned on, the second resistor and the switch device are in an open circuit state. When the preset pulse is input to the switch device, the switch device is turned on, the first resistor, the second resistor and the switch device are connected in series and turned on, and the voltage applied from the other end of the first resistor is divided to the first resistor and the second resistor, so that the voltage at the first end of the photoelectric element is reduced. At this time, the voltage at the first end of the photoelectric element is determined by the voltage division of the first resistor, the second resistor and the switch device. In practical applications, the resistance values ​​of the first resistor and the second resistor can be set according to the intensity of the echo signal reflected back from the inside of the laser radar or the amplitude of the photocurrent generated when the photoelectric element receives the echo signal reflected back from the inside of the laser radar.

[0035] In some embodiments, the switching device includes a third transistor, the third electrode of the third transistor is connected to the second resistor, and the second electrode of the third transistor is used to input a preset pulse. When the preset pulse is input to the second electrode of the third transistor, the third electrode and the first electrode of the third transistor are connected, so that charge flow is generated on the first resistor, the second resistor and the third transistor in the step-down circuit, thereby reducing the voltage at the first end of the photoelectric element.

[0036] For example, reference may be made to Figure 5 , Figure 5 A preset pulse input by a laser radar receiving circuit to a step-down circuit and a change in the voltage at the first terminal of a photoelectric element after the preset pulse is input is provided as another embodiment, wherein the upper figure shows the change in the voltage at the first terminal of the photoelectric element after the preset pulse is input, and the lower figure shows the preset pulse input to the step-down circuit. As shown in the figure, after the preset pulse is input, the voltage at the first terminal of the photoelectric element decreases accordingly, and after a period of time corresponding to the preset pulse, the voltage at the first terminal of the photoelectric element recovers. The pulse width of the preset pulse can be set according to the delay time of the echo signal reflected back from the inside of the laser radar reaching the photoelectric element relative to the laser radar emitting the pulsed laser.

[0037] In some embodiments, the start time of inputting a preset pulse into the step-down circuit may be synchronized with the start time of the laser radar emitting a pulsed laser. At the start time of the laser radar emitting a pulsed laser, a preset pulse is synchronously input into the step-down circuit, and the pulse width of the preset pulse can be set so that after the laser radar emits a pulsed laser, when the photoelectric element receives an echo signal reflected from the inside of the laser radar, the gain is reduced, and when the photoelectric element receives an echo signal reflected from the outside, the gain of the photoelectric element is restored, so that the response of the photoelectric element to the echo signal reflected from the inside of the laser radar is weakened, thereby reducing the influence of the echo signal reflected from the inside, i.e., the internal interference signal.

[0038] This embodiment also provides a laser radar receiving circuit, including: a photoelectric element, configured to generate a photocurrent when the photoelectric element receives an echo signal when a voltage is applied to a first end of the photoelectric element; A step-down circuit is connected to the first end of the photoelectric element and is used to input a preset pulse to the step-down circuit when the laser radar emits a pulsed laser. The step-down circuit is turned on when the preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period. The preset time period matches the delay time of the echo signal reflected back from the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

[0039] The photoelectric element is used to receive light and generate photocurrent to detect light. When a voltage is applied to the first end of the photoelectric element, the photoelectric element can generate photocurrent when receiving light. The gain of the photoelectric element is related to the voltage applied to the first end of the photoelectric element. The gain of the photoelectric element can be changed by changing the voltage at the first end of the photoelectric element.

[0040] When a preset pulse is input to the buck circuit, the buck circuit is turned on, which means that charge can flow from the buck circuit, and charge flow occurs on the buck circuit. The buck circuit is connected to the first end of the photoelectric element, and when the buck circuit is turned on, charge flow occurs on the buck circuit, so that the voltage of the first end of the photoelectric element is reduced.

[0041] The laser radar emits a pulsed laser, and the echo signal reflected from inside the laser radar refers to the echo signal generated when the pulsed laser encounters the internal surface of the laser radar and is reflected during the outward emission of the pulsed laser. When the laser radar emits a pulsed laser, a preset pulse is input into the step-down circuit to reduce the voltage at the first end of the photoelectric element and restore it after a preset time, so that the voltage at the first end of the photoelectric element will be reduced within the preset time after the laser radar emits the pulsed laser, so that the gain of the photoelectric element will be reduced within the preset time after the laser radar emits the pulsed laser. The preset time can match the delay time of the echo signal reflected from inside the laser radar relative to the pulsed laser, so that the gain of the photoelectric element can be reduced when the photoelectric element receives the echo signal reflected from inside the laser radar, so that the response of the receiving circuit to the echo signal reflected from inside the laser radar is weakened, thereby reducing the influence of the internally reflected echo signal, i.e., the internal interference signal.

[0042] In some embodiments, the step-down circuit may include: a first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end is connected to the first input end; the first input end is used to input the preset pulse from the first input end to the first capacitor, so that charge flows on the first capacitor, and the voltage at the first end of the photoelectric element is reduced. The preset pulse is an AC signal. When the preset pulse is input from the first input end to the first capacitor, the preset pulse can cause charge to flow on the first capacitor, so that the preset pulse is coupled with the voltage applied to the first end of the photoelectric element, and the voltage at the first end of the photoelectric element can be reduced. The preset pulse may be opposite in phase to the voltage applied to the first end of the photoelectric element, so that the voltage at the first end of the photoelectric element can be reduced when the preset pulse is input to the first capacitor. The preset pulse is opposite in phase to the voltage applied to the first end of the photoelectric element, which means that if a positive voltage is applied to the first end of the photoelectric element, the preset pulse is a negative pulse; if a negative voltage is applied to the first end of the photoelectric element, the preset pulse is a positive pulse. The voltage applied to the first end of the photoelectric element is a DC voltage, and the step-down circuit is in an open circuit state when the preset pulse is not input to the first capacitor. For example, reference may be made to Figure 6 , Figure 6 A schematic diagram of a laser radar receiving circuit is provided for an embodiment. As shown in the figure, one end of the first capacitor C1 is connected to the first end 1 of the photoelectric element D1, the first input end Pulse is connected to the other end of the first capacitor C1, and a preset pulse is input from the first input end Pulse.

[0043] In some embodiments, the laser radar receiving circuit may further include: a third resistor R3, one end of which is connected to the first end 1 of the photoelectric element D1, and is used to generate impedance to the preset pulse after passing through the first capacitor C1, so that the preset pulse is coupled with the voltage applied to the first end 1 of the photoelectric element D1. The preset pulse input from the first input terminal Pulse is coupled with the voltage applied to the first end 1 of the photoelectric element D1 after passing through the first capacitor C1. The third resistor R3 is used to generate a certain impedance to the preset pulse so that the preset pulse can be coupled with the applied voltage. In this way, if there are capacitors in other circuit branches connected to the first end 1 of the photoelectric element D1, setting the third resistor R3 can generate a certain impedance to the preset pulse, avoiding the preset pulse from directly passing through the capacitors on these branches and not being able to couple with the voltage applied to the first end 1 of the photoelectric element D1.

[0044] In some embodiments, the laser radar receiving circuit may also include: a second capacitor C2 and a fourth resistor R4, one end of the third resistor R3 is connected to the first end 1 of the photoelectric element D1, and the other end is connected to one end of the fourth resistor R4, the first voltage is input from the other end of the fourth resistor R4, one end of the second capacitor C2 is connected to one end connected to the fourth resistor R4 and the third resistor R3, and the other end is grounded. The fourth resistor R4 and the second capacitor C2 form an RC low-pass filter circuit, which can filter out the ripple in the first voltage input from one end of the fourth resistor R4. Then, a third resistor R3 is connected between the fourth resistor R4 and the first end 1 of the photoelectric element D1 to prevent the preset pulse from passing through the second capacitor C2 directly to the ground. For example, you can refer to Figure 6 As shown, the fourth resistor R4 and the third resistor R3 are connected in series between the first voltage terminal VDD1 and the first terminal 1 of the photoelectric element D1, one end of the second capacitor C2 is connected to one end connected with the fourth resistor R4 and the third resistor R3, and the other end is grounded, and the first voltage is applied from the first voltage terminal VDD1.

[0045] In some embodiments, the laser radar receiving circuit may further include: a transimpedance amplifier U1, the input end of the transimpedance amplifier U1 is connected to the second end 2 of the photoelectric element D1, so that the photocurrent generated by the photoelectric element D1 is input to the input end of the transimpedance amplifier U1, and the transimpedance amplifier U1 is used to convert the photocurrent generated by the photoelectric element D1 into a voltage signal and output it. In some embodiments, the transimpedance amplifier U1 may include a forward input end and a reverse input end, the reverse input end of the transimpedance amplifier U1 is connected to the second end 2 of the photoelectric element D1, and the forward input end of the transimpedance amplifier U1 is used to input a reference voltage.

[0046] The receiving circuit may further include a fifth resistor R5 connected in series between the second end 2 of the photoelectric element D1 and the reverse input terminal of the transimpedance amplifier U1, and the fifth resistor R5 is used to reduce the parasitic inductance on the wire connected to the reverse input terminal of the transimpedance amplifier U1 to prevent oscillation.

[0047] The receiving circuit may also include a sixth resistor R6 and a seventh resistor R7 connected in series between the third voltage terminal VCC3 and the ground terminal GND. The positive input terminal of the transimpedance amplifier U1 is connected to the connecting terminal between the sixth resistor R6 and the seventh resistor R7. The sixth resistor R6 and the seventh resistor R7 form a voltage divider circuit to provide a reference voltage for the positive input terminal of the transimpedance amplifier U1.

[0048] The receiving circuit may further include a third capacitor C3, one end of the third capacitor C3 is connected to the connection end between the sixth resistor R6 and the seventh resistor R7, and the other end is grounded. The third capacitor C3 is a decoupling capacitor for removing ripple or noise on the reference voltage.

[0049] The receiving circuit may also include an eighth resistor R8 and a fourth capacitor C4, wherein one end of the eighth resistor R8 is connected to the feedback output terminal FB of the transimpedance amplifier U1, and the other end is connected to the second end 2 of the photoelectric element D1, and one end of the fourth capacitor C4 is connected to the feedback output terminal FB of the transimpedance amplifier U2, and the other end is connected to the second end 2 of the photoelectric element D1. The feedback output terminal FB of the transimpedance amplifier U1 is internally connected to the output terminal OUT of the transimpedance amplifier U1, the eighth resistor R8 is the transimpedance gain of the TIA circuit, and the fourth capacitor C4 is a compensation capacitor, which can increase the phase margin of the transimpedance amplifier U1 during operation. At the same time, the eighth resistor R8 and the fourth capacitor C4 also determine the closed-loop bandwidth of the transimpedance amplifier U1. Please refer to Figure 6 As shown, the positive input terminal INP of the transimpedance amplifier U1 is connected to the voltage divider circuit composed of the sixth resistor R6 and the seventh resistor R7, and the negative input terminal INN of the transimpedance amplifier U1 is connected to the second terminal 2 of the photoelectric element D1. The feedback output terminal FB of the transimpedance amplifier U1 is connected to the eighth resistor R8 and the fourth capacitor C4 respectively.

[0050] The output terminal Signal of the transimpedance amplifier U1 is used to output a signal. The output Vout of the transimpedance amplifier U1 = Vinp-I*R8. Vinp represents the reference voltage input to the positive input terminal of the transimpedance amplifier U1, I represents the photocurrent generated by the photoelectric element D1, and R8 represents the resistance value of the eighth resistor R8.

[0051] The transimpedance amplifier U1 may also include a voltage terminal VCC, and the receiving circuit may also include a ninth resistor R9, a fifth capacitor C5, and a sixth capacitor C6. The fifth capacitor C5 and the ninth resistor R9 are connected in series between the fourth voltage terminal VCC4 and the ground terminal GND, and the fifth capacitor C5 and the sixth capacitor C6 are connected in parallel. The voltage terminal VCC of the transimpedance amplifier U1 is connected to the connection terminal between the fifth capacitor C5 and the ninth resistor R9. The ninth resistor R9, the fifth capacitor C5, and the sixth capacitor C6 form a low-pass filter circuit for filtering the ripple on the power supply. The transimpedance amplifier U1 may also include a low-power mode terminal PDN, which is connected to the connection terminal between the fifth capacitor C5 and the ninth resistor R9. When a low level is input to the low-power mode terminal PDN and the VCC terminal, the transimpedance amplifier U1 enters a low-power mode, and when a high level is input, it enters a normal working mode. The ground terminal GND of the transimpedance amplifier U1 is used for grounding.

[0052] The optoelectronic element D1 may be, but is not limited to, an optoelectronic device of the type of an avalanche photodiode (APD), a single photon avalanche photodiode (SPAD), or a SiPM (silicon photomultiplier).

[0053] In a specific example, corresponding to Figure 6In the circuit shown, the third resistor is 1kΩ, the fourth resistor is 100KΩ, the fifth resistor is 10RΩ, the sixth resistor is 10kΩ, the seventh resistor is 20kΩ, the eighth resistor is 10kΩ, and the ninth resistor is 10RΩ. The first capacitor is 100pF / 250V, the second capacitor is 10nF / 250V, the third capacitor is 0.1uF, the fourth capacitor is 0.1pF, the fifth capacitor is 10uF, and the sixth capacitor is 0.1uF. The photoelectric element D1 can be an avalanche photodiode (APD). The transimpedance amplifier U1 can be MS8258D.

[0054] In some embodiments, the laser radar receiving circuit may also include a pulse generating circuit, the pulse generating circuit including a second voltage terminal, a first transistor, a first driver, a second input terminal and a second output terminal; the second voltage terminal is connected to the third pole of the first transistor, the second output terminal is led out by the third pole of the first transistor, the first pole of the first transistor is grounded, the first driver is connected to the second pole of the first transistor, the second input terminal is connected to the input terminal of the first driver, the first driver is used to apply a voltage to the second pole of the first transistor, so that when the first trigger signal is input from the second input terminal, the voltage applied to the second pole of the first transistor rises, when the first transistor is turned on, the preset pulse is output from the second output terminal, and the second output terminal is connected to the first input terminal. Applying a voltage from the second voltage terminal causes a charge to be stored in the circuit connected to the third pole of the first transistor, when the first trigger signal is input from the second input terminal, the voltage applied by the first driver to the second pole of the first transistor rises, when the first transistor is turned on, the charge stored in the circuit connected to the third pole of the first transistor is released, and a preset pulse is output from the second output terminal, which can be input to the first input terminal.

[0055] In some embodiments, the pulse generating circuit further includes a seventh capacitor, one end of the seventh capacitor is connected to the third electrode of the first transistor, the other end is grounded, and the second output terminal is arranged between the third electrode of the first transistor and the seventh capacitor. The seventh capacitor is an energy storage capacitor, and when the second voltage is applied from the second voltage terminal, the seventh capacitor stores charge. When the first transistor is turned on, the charge stored in the seventh capacitor is connected to the ground through the first transistor, and a preset pulse is outputted from the second output terminal accordingly. For example, reference can be made to Figure 7 , Figure 7 A schematic diagram of a pulse generating circuit of a laser radar receiving circuit provided in an embodiment, as shown in the figure, the third electrode 3 of the first transistor Q1 is connected to the second voltage terminal VDD2, one end of the seventh capacitor C7 is connected to the third electrode 3 of the first transistor Q1, and the other end is grounded, and the second output terminal is led out from the third electrode 3 of the first transistor Q1. The first electrode 1 of the first transistor Q1 is grounded, and the first driver U2 is connected to the second electrode 2 of the first transistor Q1.

[0056] Accordingly, the pulse width of the preset pulse can be obtained according to the following formula: ; in, represents the discharge time of the seventh capacitor when the first transistor is turned on, that is, represents the pulse width of the preset pulse, I represents the current value of the current on the third electrode when the first transistor is turned on, C represents the capacitance value of the seventh capacitor, V represents the voltage value of the second voltage applied from the second voltage terminal, and Q represents the amount of charge stored in the seventh capacitor.

[0057] According to the above formula, the pulse width of the preset pulse is related to the capacitance value C of the seventh capacitor C7, the voltage value V of the second voltage applied from the second voltage terminal VDD2, and the current value I of the current on the third pole 3 when the first transistor Q1 is turned on. In practical applications, the pulse width of the echo signal reflected back from the inside of the laser radar can be obtained by testing, and the pulse width of the preset pulse can be determined based on this. Then, the capacitance value C of the seventh capacitor C7 of the pulse generating circuit, the voltage value V of the second voltage applied from the second voltage terminal VDD2, and the current value I of the current on the third pole 3 when the first transistor Q1 is turned on are set, so that the pulse width of the preset pulse generated by the pulse generating circuit meets the requirements.

[0058] In some embodiments, the pulse generating circuit may further include a tenth resistor R10, one end of the tenth resistor R10 is connected to the second voltage terminal VDD2, and the other end is connected to the seventh capacitor C7, the tenth resistor R10 is a current limiting resistor, the seventh capacitor C7 is an energy storage capacitor, and the second voltage input from the second voltage terminal VDD2 is charged to the seventh capacitor C7 through the tenth resistor R10, and the tenth resistor R10 can limit the charging current to prevent the current from being too large, resulting in an overload of the boost circuit of the second voltage terminal VDD2. When the first transistor Q1 is turned on, the current magnitude I of the current on the third pole 3 is related to the resistance value of the tenth resistor R10. Therefore, for the laser radar, the pulse width of the preset pulse generated by the pulse generating circuit can be adjusted by setting the capacitance value C of the seventh capacitor C7 of the pulse generating circuit, the voltage value V of the second voltage applied from the second voltage terminal VDD2, and the resistance value of the tenth resistor R10 to meet the requirements.

[0059] The pulse generating circuit may further include an eighth capacitor C8 and a ninth capacitor C9 connected in parallel to each other, one end of the eighth capacitor C8 and one end of the ninth capacitor C9 are respectively connected to the second voltage terminal VDD2, and the other end of the eighth capacitor C8 and the other end of the ninth capacitor C9 are respectively grounded. The eighth capacitor C8 and the ninth capacitor C9 are decoupling capacitors, which are used to reduce the ripple on the second voltage input by the second voltage terminal VDD2. The pulse generating circuit may further include an eleventh resistor R11, one end of the eleventh resistor R11 is connected to the first electrode 1 of the first transistor Q2, and the other end is grounded.

[0060] The high output terminal OUTH and the low output terminal OUTL of the first driver U2 are both connected to the second electrode 2 of the first transistor Q1. The pulse generating circuit further includes a twelfth resistor R12 and a thirteenth resistor R13, wherein one end of the twelfth resistor R12 is connected to the high output terminal OUTH, and the other end is connected to the second electrode 2 of the first transistor Q1, and one end of the thirteenth resistor R13 is connected to the low output terminal OUTL, and the other end is connected to the second electrode 2 of the first transistor Q1.

[0061] The first driver U2 may include a positive input terminal +IN and a negative input terminal -IN. A first trigger signal may be input to the positive input terminal +IN, and the negative input terminal -IN is grounded. The voltage terminal VDD of the first driver U2 is connected to the power supply, and the ground terminal GND of the first driver U2 is grounded. A first filter capacitor Cs1 is connected between the power supply and the ground terminal GND to prevent the power supply wave from interfering with the operation of the first driver U2. The first transistor Q1 may be EPC2007C. The first driver U2 may be LMG1020. For example, reference may be made to Figure 8 , Figure 8 A waveform diagram of a preset pulse output by a pulse generating circuit of a laser radar receiving circuit provided in one embodiment.

[0062] For the receiving circuit, the starting time of inputting the preset pulse into the first capacitor C1 can be the starting time of the laser radar emitting the pulsed laser. In some embodiments, the first trigger signal can be synchronized with the second trigger signal of the laser radar transmitting circuit, and the second trigger signal is used to control the laser radar transmitting circuit to emit the pulsed laser. The only signal that can be highly correlated with the emission time (i.e., the starting time of the transmitting circuit emitting the pulsed laser) is the second trigger signal of the transmitting circuit.

[0063] In some embodiments, the step-down circuit may include: a first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; a second resistor, one end of which is connected to the first end of the photoelectric element, and the other end is connected to a switch device; the switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the voltage at the first end of the photoelectric element is reduced. When the switch device is not turned on, the second resistor and the switch device are in an open circuit state. When the preset pulse is input to the switch device, the switch device is turned on, the first resistor, the second resistor and the switch device are connected in series and turned on, and the voltage applied from the other end of the first resistor is divided to the first resistor and the second resistor, so that the voltage at the first end of the photoelectric element is reduced. At this time, the voltage at the first end of the photoelectric element is determined by the voltage division of the first resistor, the second resistor and the switch device.

[0064] In some embodiments, the switching device includes a third transistor, the third electrode of the third transistor is connected to the second resistor, and the second electrode of the third transistor is used to input a preset pulse. When the preset pulse is input to the second electrode of the third transistor, the third electrode and the first electrode of the third transistor are connected, so that charge flow is generated on the first resistor, the second resistor and the third transistor in the step-down circuit, thereby reducing the voltage at the first end of the photoelectric element.

[0065] For example, reference may be made to Fig. 9 , Fig. 9 A schematic diagram of a laser radar receiving circuit is provided for another embodiment. As shown in the figure, one end of the first resistor R1 is connected to the first end 1 of the photoelectric element D1, one end of the second resistor R2 is connected to the first end 1 of the photoelectric element D1, and the other end is connected to the third electrode 3 of the third transistor Q3. The first input terminal Pulse is connected to the second electrode 2 of the third transistor Q3, and a preset pulse is input from the first input terminal Pulse to the second electrode 2 of the third transistor Q3.

[0066] When the first input terminal Pulse is at a low level, the third transistor Q3 is turned off, and the first voltage applied from the first voltage terminal VDD1 is directly applied to the first terminal 1 of the photoelectric element D1 after passing through the fourth resistor R4 and the first resistor R1; when the first input terminal Pulse is at a high level, the third transistor Q3 is turned on instantly, and the first voltage applied from the first voltage terminal VDD1 is divided in series by the fourth resistor R4, the first resistor R1 and the second resistor R2. The first terminal voltage of the photoelectric element D1 is VDD1*R2 / (R4+R1+R2), where VDD1 represents the first voltage applied from the first voltage terminal VDD1, R1 represents the resistance value of the first resistor R1, R2 represents the resistance value of the second resistor R2, and R4 represents the resistance value of the fourth resistor R4. The resistance values ​​of the first resistor R1 and the second resistor R2 can be set according to the strength of the echo signal reflected from the inside of the laser radar or the amplitude of the photocurrent generated when the photoelectric element receives the echo signal reflected from the inside of the laser radar. When the first input terminal Pulse returns to a low level, the third transistor Q3 is turned off, and the first voltage applied from the first voltage terminal VDD1 is directly applied to the first terminal 1 of the photoelectric element D1 after passing through the fourth resistor R4 and the first resistor R1.

[0067] In some embodiments, the laser radar includes a transmitting circuit and a receiving circuit, wherein the transmitting circuit is used to emit a pulsed laser; the transmitting circuit includes a third voltage terminal, a light-emitting element, a second transistor, a second driver, and a third input terminal; one end of the light-emitting element is connected to the third voltage terminal, and the other end is connected to the third pole of the second transistor, the first pole of the second transistor is grounded, the second driver is connected to the second pole of the second transistor, the third input terminal is connected to the input terminal of the second driver, and the second driver is used to apply a voltage to the second pole of the second transistor, so that when a second trigger signal is input from the third input terminal, the voltage applied to the second pole of the second transistor increases, and when the second transistor is turned on, the light-emitting element emits a pulsed laser. A voltage is applied from the third voltage terminal so that a charge is stored in the circuit connected to the third pole of the second transistor, and when a second trigger signal is input from the third input terminal, the voltage applied by the second driver to the second pole of the second transistor increases, and when the second transistor is turned on, the charge stored in the circuit connected to the third pole of the second transistor is released, and the charge flows to the ground through the light-emitting element and the second transistor, and a momentary current flows through the light-emitting element, and the light-emitting element is excited to generate a pulsed laser.

[0068] correspond Figure 6 The receiving circuit shown and Figure 7 The pulse generating circuit shown can be a first trigger signal input to the first driver U2 that is synchronized with the second trigger signal. Fig. 9 The receiving circuit shown may be such that a preset pulse input to the first input terminal Pulse is synchronized with the second trigger signal.

[0069] In some embodiments, the transmitting circuit may further include an eleventh capacitor, one end of the eleventh capacitor is connected to the end connected to the light-emitting element and the third voltage end, and the other end is grounded. The eleventh capacitor is an energy storage capacitor. When a voltage is applied from the third voltage end, the eleventh capacitor stores charge. When the second transistor is turned on, the charge stored in the eleventh capacitor flows to the ground through the light-emitting element and the second transistor. When an instantaneous current flows through the light-emitting element, the light-emitting element is excited to generate a pulsed laser. For example, reference may be made to Fig.10 , Fig.10 A schematic diagram of a transmitting circuit of a laser radar provided in an embodiment, as shown in the figure, the second electrode 2 of the light emitting element LD is connected to the third voltage terminal VDD3, the first electrode 1 of the light emitting element LD is connected to the third electrode 3 of the second transistor Q2, one end of the eleventh capacitor C11 is connected to the second electrode 2 of the light emitting element LD, and the other end is grounded. The first electrode 1 of the second transistor Q2 is grounded, and the second driver U3 is connected to the second electrode 2 of the second transistor Q2.

[0070] In some embodiments, the transmitting circuit may also include a fourteenth resistor R14, one end of the fourteenth resistor R14 is connected to the third voltage terminal VDD3, and the other end is connected to the second pole 2 of the light-emitting element LD. The fourteenth resistor R14 is a current limiting resistor, and the eleventh capacitor C11 is a storage capacitor. The third voltage input from the third voltage terminal VDD3 charges the eleventh capacitor C11 through the fourteenth resistor R14. The fourteenth resistor R14 can limit the charging current to prevent excessive current from causing overload of the boost circuit of the third voltage terminal VDD3.

[0071] The transmitting circuit may further include a twelfth capacitor C12 and a thirteenth capacitor C13 connected in parallel, one end of the twelfth capacitor C12 and one end of the thirteenth capacitor C13 are respectively connected to the third voltage terminal VDD3, and the other end of the twelfth capacitor C12 and the other end of the thirteenth capacitor C13 are respectively grounded. The twelfth capacitor C12 and the thirteenth capacitor C13 are decoupling capacitors, which are used to reduce the ripple on the third voltage input by the third voltage terminal VDD3. The transmitting circuit may further include a fifteenth resistor R15, one end of the fifteenth resistor R15 is connected to the first electrode 1 of the second transistor Q2, and the other end is grounded.

[0072] The high output terminal OUTH and the low output terminal OUTL of the second driver U3 are both connected to the second electrode 2 of the second transistor Q2. The transmitting circuit further includes a sixteenth resistor R16 and a seventeenth resistor R17, wherein one end of the sixteenth resistor R16 is connected to the high output terminal OUTH, and the other end is connected to the second electrode 2 of the second transistor Q2, and one end of the seventeenth resistor R17 is connected to the low output terminal OUTL, and the other end is connected to the second electrode 2 of the second transistor Q2.

[0073] The second driver U3 may include a positive input terminal +IN and a negative input terminal -IN, and a second trigger signal may be input to the positive input terminal +IN, and the negative input terminal -IN is grounded. The voltage terminal VDD of the second driver U3 is connected to the power supply, and the ground terminal GND of the second driver U3 is grounded. A second filter capacitor Cs2 is connected between the power supply and the ground terminal GND to prevent the power supply wave from interfering with the operation of the second driver U3. The second transistor Q2 may be EPC2007C. The second driver U3 may be LMG1020. For example, reference may be made to Fig.11 , Fig.11 A waveform diagram of the current passing through the light-emitting element of a transmitting circuit of a laser radar provided in one embodiment.

[0074] For reference Fig.12 , Fig.12 A waveform diagram of a second trigger signal input by a laser radar to a transmitting circuit according to an embodiment, corresponding to Figure 6 The receiving circuit shown and Figure 7 The pulse generating circuit shown in FIG. 1 has the same waveform as the second trigger signal input to the transmitting circuit and is synchronized with the first trigger signal input to the pulse generating circuit. The first trigger signal input to the pulse generating circuit is also the same waveform as the second trigger signal input to the transmitting circuit. Fig.12 The waveform shown.

[0075] In some embodiments, since the transimpedance amplifier U1 can receive ultra-short pulses of at least 1 ns, Figure 7 In the pulse generating circuit shown, the pulse width of the preset pulse mainly depends on the charging time of the circuit composed of the tenth resistor R10 and the seventh capacitor C7 and the discharging time of the first transistor Q1.

[0076] However, for light-emitting elements, such as laser diodes, the emission circuit needs to have a sufficiently large driving current to drive the pulsed laser to reach the rated emission power. The energy stored on the anode of the laser diode, that is, the amount of charge, is related to the driving high voltage and the energy storage capacitor: Q=C*V; Since the driving current of the laser diode is relatively large, the emission high voltage V is generally not too high. Assuming it is set to 40V, in order to achieve the rated driving power, the energy storage capacitor generally needs to reach the nF level, with a typical value of 2~3nF. When Tiger2 inputs a high-level pulse, the second driver U3 outputs a high level, so that the second pole 2 of the second transistor Q2 is pulled high, and the instantaneous current Id between DS can reach tens of amperes. For example, the EPC2007 pulse current can reach 40A. According to the above formula, it can be obtained:

[0077] The pulse width can be calculated as Approximately: 3ns.

[0078] However, the charging time of the capacitor is related to the current limiting resistor and the energy storage capacitor, and satisfies the following formula: .

[0079] Assuming: R = 100 ohms, C = 3nF, the charging time T can be calculated to be about 300nS, which is far from the requirement of 2-3ns for the internal reflection interference waveform. Therefore, this embodiment meets the requirement of adjustable pulse width and amplitude by specially designing a circuit.

[0080] correspond Figure 6 The receiving circuit shown can be referred to Fig.13 , Fig.13 Three waveform diagrams of a laser radar receiving circuit provided in one embodiment, all of which reflect the waveform changes when the laser radar emits a pulsed laser and synchronously inputs a preset pulse to the receiving circuit. Among them, the first waveform is the waveform of the voltage at the first end of the photoelectric element D1. The second waveform is the photocurrent waveform input to the input end of the transimpedance amplifier U1. The lower peak on the left corresponds to the peak of the echo signal reflected back from the inside of the laser radar, and the higher peak on the right corresponds to the peak of the echo signal reflected back from the close-range target. It can be seen that the gain of the photoelectric element D1 is reduced by inputting a preset pulse, so that the amplitude of the photocurrent generated by the photoelectric element for the echo signal reflected back from the inside of the laser radar is reduced. The third waveform is the waveform of the voltage signal output from the output end of the transimpedance amplifier U1, in which the wave with a larger amplitude corresponds to the wave of the echo signal reflected back from the close-range target. It can be seen that the gain of the photoelectric element D1 for the echo signal reflected back from the inside of the laser radar is reduced by inputting a preset pulse, and the internal interference signal in the output waveform of the transimpedance amplifier U1 output end is basically suppressed.

[0081] The above is a detailed introduction to a laser radar signal receiving method and receiving circuit provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A laser radar signal receiving method, characterized in that: The receiving circuit of the laser radar at least includes a photoelectric element and a step-down circuit, wherein the photoelectric element is used to generate a photocurrent when the photoelectric element receives an echo signal when a voltage is applied to the first end of the photoelectric element, and the step-down circuit is connected to the first end of the photoelectric element, and is used to turn on the step-down circuit when a preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced; The laser radar signal receiving method comprises: When the laser radar emits a pulsed laser, the preset pulse is input into the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period, and the preset time period matches the delay time of the echo signal reflected back from the inside of the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

2. The laser radar signal receiving method according to claim 1, characterized in that: The step-down circuit comprises: A first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the first input end; The first input terminal is used to input the preset pulse from the first input terminal to the first capacitor, so that charge flows on the first capacitor and the voltage at the first terminal of the photoelectric element decreases.

3. The laser radar signal receiving method according to claim 2, characterized in that: The amplitude of the preset pulse satisfies the following conditional formula: In 1A *M=V rA ; Among them, V 1A represents the amplitude of the preset pulse, M represents the gain of the photoelectric element when a voltage is applied to the first end of the photoelectric element, V rA It represents the voltage amplitude corresponding to the photocurrent generated when the photoelectric element receives the echo signal reflected back from the inside of the laser radar when a voltage is applied to the first end of the photoelectric element.

4. The laser radar signal receiving method according to claim 1, characterized in that: The step-down circuit comprises: A first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; A second resistor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the switch device; The switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the first terminal voltage of the photoelectric element is reduced.

5. A laser radar receiving circuit, characterized in that: include: a photoelectric element, configured to generate a photocurrent when the photoelectric element receives an echo signal when a voltage is applied to a first end of the photoelectric element; A step-down circuit is connected to the first end of the photoelectric element and is used to input a preset pulse to the step-down circuit when the laser radar emits a pulsed laser. The step-down circuit is turned on when the preset pulse is input to the step-down circuit, so that the voltage at the first end of the photoelectric element is reduced and recovered after a preset time period, so that the gain of the photoelectric element is reduced within the preset time period. The preset time period matches the delay time of the echo signal reflected back from the laser radar received by the photoelectric element relative to the pulsed laser. The gain of the photoelectric element refers to the ratio of the photocurrent generated when a voltage is applied to the first end of the photoelectric element to the photocurrent generated when the photoelectric element is not multiplied.

6. The laser radar receiving circuit according to claim 5, characterized in that: The step-down circuit comprises: A first capacitor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the first input end; The first input terminal is used to input the preset pulse from the first input terminal to the first capacitor, so that charge flows on the first capacitor and the voltage at the first terminal of the photoelectric element decreases.

7. The laser radar receiving circuit according to claim 6, characterized in that: Also includes: A third resistor, one end of which is connected to the first end of the photoelectric element, is used to generate impedance to the preset pulse after passing through the first capacitor, so that the preset pulse is coupled with the voltage applied to the first end of the photoelectric element.

8. The laser radar receiving circuit according to any one of claims 6 to 7, characterized in that: Also included is a pulse generating circuit, the pulse generating circuit including a second voltage terminal, a first transistor, a first driver, a second input terminal and a second output terminal; The second voltage terminal is connected to the third electrode of the first transistor, and the second output terminal is led out from the third electrode of the first transistor. The first electrode of the first transistor is grounded, the first driver is connected to the second electrode of the first transistor, and the second input terminal is connected to the input terminal of the first driver. The first driver is used to apply a voltage to the second electrode of the first transistor, so that when a first trigger signal is input from the second input terminal, the voltage applied to the second electrode of the first transistor increases, and when the first transistor is turned on, the preset pulse is output from the second output terminal, and the second output terminal is connected to the first input terminal.

9. The laser radar receiving circuit according to claim 8, characterized in that: The pulse generating circuit further includes a seventh capacitor, one end of the seventh capacitor is connected to the third electrode of the first transistor, and the other end is grounded, and the second output end is arranged between the third electrode of the first transistor and the seventh capacitor; The pulse width of the preset pulse is obtained according to the following formula: ； in, represents the discharge time of the seventh capacitor when the first transistor is turned on, that is, represents the pulse width of the preset pulse, I represents the current value of the current on the third electrode when the first transistor is turned on, C represents the capacitance value of the seventh capacitor, V represents the voltage value of the second voltage applied from the second voltage terminal, and Q represents the amount of charge stored in the seventh capacitor.

10. The laser radar receiving circuit according to claim 5, characterized in that: The step-down circuit comprises: A first resistor, one end of which is connected to the first end of the photoelectric element, and a voltage is applied from the other end of the first resistor to apply a voltage to the first end of the photoelectric element; A second resistor, one end of which is connected to the first end of the photoelectric element, and the other end of which is connected to the switch device; The switch device is used to turn on the switch device when the preset pulse is input to the switch device, so that charge flow is generated on the first resistor, the second resistor and the switch device, so that the first terminal voltage of the photoelectric element is reduced.

Images