APD bias voltage rapid adjusting circuit and range finder

Abstract

The invention provides an APD bias voltage rapid adjusting circuit and a range finder, and the APD bias voltage rapid adjusting circuit comprises a control signal collection circuit, a control signal widening circuit, an APD divider resistor, and a coupler. The control signal acquisition circuit, the control signal broadening circuit and the coupler are electrically connected in sequence, the APD divider resistor is connected with a controlled APD in series and then is connected with critical bias voltage, and the coupler is connected to the two ends of the APD divider resistor in parallel; the control signal acquisition circuit converts an optical signal of the laser into an electric signal at the light emitting moment of the laser and transmits the electric signal to the control signal broadening circuit, and the control signal broadening circuit broadens the electric signal and outputs a broadened signal to the coupler; the coupler enables the APD divider resistor not to be short-circuited within a set time period after the laser is emitted according to the broadening signal, and the APD divider resistor is short-circuited after the set time period; when the APD divider resistor is not short-circuited, the APD bias voltage is lower than the critical bias voltage. According to the invention, the APD depth saturation phenomenon caused by back scattering light is effectively improved, and the measuring range of the laser is expanded.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a rapid APD bias voltage adjustment circuit and a rangefinder. Background Art

[0002] In the field of laser rangefinding, pulsed laser rangefinders in the 1064 nm wavelength band are widely used, and the optoelectronic detectors matched with them are generally silicon-based avalanche photodiodes (APDs). The peak power of a single laser pulse of a long-range laser rangefinder is on the order of dozens of megawatts. When the atmospheric visibility is poor, aerosols in the atmosphere will cause obvious backscattering to the laser pulses emitted by the laser rangefinder. For a laser rangefinder with a coaxial transceiver, the backscattered optical signal is very likely to enter the receiving optical system, resulting in deep saturation of the APD. Moreover, the stronger the scattered optical signal, the longer the saturation time of the APD. During the APD saturation time interval, the laser rangefinder cannot perform rangefinding. This phenomenon directly limits the minimum ranging distance of the laser rangefinder. Summary of the Invention

[0003] The purpose of the present invention is to provide a rapid APD bias voltage adjustment circuit and a rangefinder to reduce the APD saturation time length and extend the ranging distance of the laser rangefinder.

[0004] To solve the above technical problems, the present invention provides a rapid APD bias voltage adjustment circuit, including a control signal acquisition circuit, a control signal broadening circuit, an APD voltage dividing resistor, and a coupler; the control signal acquisition circuit, the control signal broadening circuit, and the coupler are electrically connected in sequence. The APD voltage dividing resistor is connected in series with the controlled APD and then connected to the critical bias voltage, and the coupler is connected in parallel across the two ends of the APD voltage dividing resistor. The control signal acquisition circuit converts the optical signal of the laser into an electrical signal at the moment when the laser emits light, and transmits the electrical signal to the control signal broadening circuit. The control signal broadening circuit broadens the electrical signal and outputs a broadened signal to the coupler. The coupler makes the APD voltage dividing resistor not be short-circuited within a set time period after the laser emits light according to the broadened signal, and be short-circuited after the set time period; when the APD voltage dividing resistor is not short-circuited, the APD bias voltage is lower than the critical bias voltage.

[0005] According to the above solution, the control signal acquisition circuit includes a current limiting resistor R1, a photoelectric element D1, a voltage dividing resistor R2, a voltage dividing resistor R3, and a coupling capacitor C1. One end of the current limiting resistor R1 and one end of the voltage dividing resistor R2 are both connected to the positive power supply; the other end of the current limiting resistor R1 is respectively connected to one end of the photoelectric element D1 and one end of the coupling capacitor C1; the other end of the coupling capacitor C1 is respectively connected to one end of the voltage dividing resistor R3 and the other end of the voltage dividing resistor R2, and serves as the output node of the electrical signal; the other end of the photoelectric element D1 and the other end of the voltage dividing resistor R3 are both connected to the power supply ground.

[0006] According to the above solution, the control signal broadening circuit includes a first NAND gate, a second NAND gate, a time constant configuration capacitor C4, and a time constant configuration resistor R4; The first input interface of the first NAND gate is connected to an electrical signal, the VCC interface of the first NAND gate is connected to the positive power supply, the second input interface of the first NAND gate is connected to the output interface of the second NAND gate, and the output interface of the first NAND gate outputs a broadened signal; The first input interface of the second NAND gate is connected to the output interface of the first NAND gate after passing through the time constant configuration capacitor C4. The second input interface of the second NAND gate is connected to the first input interface of the second NAND gate and is grounded through the time constant configuration resistor R4, and the GND interface of the second NAND gate is grounded.

[0007] According to the above solution, one end of the coupler is connected to the broadened signal after passing through a resistor R6, and the other end of the coupler is grounded.

[0008] According to the above solution, it includes a first filtering circuit; the first filtering circuit includes an inductor L1, capacitors C2 and C3; one end of the inductor L1 is connected to the positive power supply, the other end is connected to one ends of the capacitors C2 and C3, and the VCC interface of the first NAND gate, and the other ends of the capacitors C2 and C3 are both grounded.

[0009] According to the above solution, the APD voltage dividing resistor and the controlled APD are connected in series and then connected to the critical bias voltage through a second filtering circuit; the second filtering circuit includes capacitors C5 and C6, inductors L2 and L3; one end of the inductor L2 is connected to the positive pole of the critical bias voltage and one end of the capacitor C5, the other end of the inductor L2 is connected to one end of the capacitor C6 and the APD voltage dividing resistor, one end of the inductor L3 is connected to the ground of the critical bias voltage and the other end of the capacitor C5, and the other end of the inductor L3 is connected to the other end of the capacitor C6 and the APD.

[0010] According to the above solution, the optoelectronic element D1 is a PIN photodiode.

[0011] According to the above solution, the coupler is an optoelectronic coupler.

[0012] The present invention also provides a laser rangefinder, including the APD bias voltage rapid adjustment circuit described above.

[0013] The present invention also provides a laser ranging method, which realizes ranging by using the laser rangefinder described above.

[0014] Beneficial effects The present invention performs photoelectric conversion and signal broadening through the provided control signal acquisition circuit and control signal broadening circuit, generating a control signal with a certain time width at the moment of laser emission, such that the APD voltage-dividing resistor is not short-circuited within a set time period after the laser emits, and is short-circuited after the set time period. Furthermore, the voltage across both ends of the APD is lower than the critical bias voltage within the set time period, thus achieving: enabling the APD to be in a low bias state within the optical signal scattering time zone, and enabling the APD to be in a critical bias state outside the optical signal scattering time zone. This not only reduces the saturation time length of the APD, shortening the time when the laser rangefinder cannot measure distance due to APD saturation, but also does not affect the ranging ability of the laser rangefinder.

[0015] Furthermore, through the provided first filter circuit and second filter circuit, the influence of power supply noise on the control signal and ranging accuracy is reduced, the reliability of the overall circuit is improved, and the laser ranging ability is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the APD bias voltage control schematic diagram of Embodiment 1 of the present invention; Figure 2 is the APD bias voltage control circuit schematic diagram of Embodiment 1 of the present invention; Figure 3 is the APD bias voltage time sequence diagram of Embodiment 1 of the present invention; Figure 4 is the saturation region test diagram of the APD when it is at the critical bias voltage in Embodiment 1 of the present invention; Figure 5 is the saturation region test diagram of the APD when its bias voltage is controlled in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the described embodiments of the present disclosure fall within the scope of protection of the present disclosure.

[0018] Embodiment 1: When the atmospheric visibility is poor, the aerosol in the atmosphere will cause obvious backscattering to the high-energy laser pulse emitted by the laser rangefinder. For a laser rangefinder with a coaxial transceiver, the backscattered optical signal is very likely to enter the receiving optical system, resulting in deep saturation of the APD. Moreover, the stronger the scattered optical signal, the longer the APD saturation time. Within the APD saturation time interval, the laser rangefinder cannot measure distance. This phenomenon directly limits the minimum ranging distance of the laser rangefinder.

[0019] Since the APD gain is positively correlated with the APD bias voltage, as the APD bias voltage increases, the multiplication factor of the APD increases rapidly. Therefore, the APD gain can be reduced by lowering the bias voltage across the APD, and the APD saturation time can be reduced when strong light is incident. However, if the time interval for reducing the APD bias voltage is not restricted, the APD will always operate at a low bias voltage state with a low gain, and the ranging ability of the laser rangefinder will be affected.

[0020] Based on the above situation, this embodiment provides a fast APD bias voltage adjustment circuit. Refer to Figure 1 、 Figure 2 , including a control signal acquisition circuit, a control signal broadening circuit, an APD voltage dividing resistor, and a coupler; the control signal acquisition circuit, the control signal broadening circuit, and the coupler are electrically connected in sequence, and the APD voltage dividing resistor is connected in series with the controlled APD and then connected to the critical bias voltage, and the coupler is connected in parallel across the APD voltage dividing resistor; The control signal acquisition circuit converts the optical signal of the laser into an electrical signal at the moment when the laser emits light, and transmits the electrical signal to the control signal broadening circuit. The control signal broadening circuit broadens the electrical signal and outputs a broadened signal to the coupler. The coupler makes the APD voltage dividing resistor not be short-circuited within a set time period after the laser emits light according to the broadened signal, and be short-circuited after the set time period; when the APD voltage dividing resistor is not short-circuited, the APD bias voltage is lower than the critical bias voltage.

[0021] Further, the control signal acquisition circuit includes a current limiting resistor R1, a photoelectric element D1, a voltage dividing resistor R2, a voltage dividing resistor R3, and a coupling capacitor C1; One end of the current limiting resistor R1 and one end of the voltage dividing resistor R2 are both connected to the positive power supply; the other end of the current limiting resistor R1 is respectively connected to one end of the photoelectric element D1 and one end of the coupling capacitor C1; the other end of the coupling capacitor C1 is respectively connected to one end of the voltage dividing resistor R3 and the other end of the voltage dividing resistor R2, and serves as the output node of the electrical signal; the other end of the photoelectric element D1 and the other end of the voltage dividing resistor R3 are both connected to the power supply ground; When the laser emits light, the photocurrent of the PIN photodiode D1 flows through R1 to generate a potential difference, and a pulse signal is coupled and output through the coupling capacitor C1. The signal amplitude is ensured to be adapted to the subsequent circuit by voltage division of the voltage dividing resistors R2 and R3.

[0022] Further, the control signal broadening circuit includes a first NAND gate, a second NAND gate, a time constant configuration capacitor C4, and a time constant configuration resistor R4; The first input interface of the first NAND gate accesses the electrical signal, the VCC interface of the first NAND gate is connected to the positive power supply, the second input interface of the first NAND gate is connected to the output interface of the second NAND gate, and the output interface of the first NAND gate outputs the broadened signal; The first input interface of the second NAND gate is connected to the output interface of the first NAND gate after passing through the time constant configuration capacitor C4. The second input interface of the second NAND gate is connected to the first input interface of the second NAND gate, and is connected to the power ground after passing through the time constant configuration resistor R4. The GND interface of the second NAND gate is connected to the power ground. The control signal broadening circuit is used to broaden the input electrical signal into a bias control signal with a specific time width (i.e., the broadening signal, and the time width of the broadening signal corresponds to the set time period). The time width of the broadening signal is jointly determined by the time constant configuration capacitor C4 and the time constant configuration resistor R4.

[0023] Further, one end of the coupler is connected to the broadening signal after passing through the resistor R6, and the other end of the coupler is connected to the power ground.

[0024] Further, it includes a first filtering circuit. The first filtering circuit includes an inductor L1, capacitors C2 and C3. One end of the inductor L1 is connected to the positive power supply, the other end is connected to one ends of the capacitors C2 and C3, and the VCC interface of the first NAND gate. The other ends of the capacitors C2 and C3 are both connected to the power ground.

[0025] Further, the APD voltage-dividing resistor is connected in series with the controlled APD and then connected to the critical bias voltage through a second filtering circuit. The second filtering circuit includes capacitors C5, C6, inductors L2 and L3. One end of the inductor L2 is connected to the positive pole of the critical bias voltage and one end of the capacitor C5. The other end of the inductor L2 is connected to one end of the capacitor C6 and the APD voltage-dividing resistor. One end of the inductor L3 is connected to the ground of the critical bias voltage and the other end of the capacitor C5. The other end of the inductor L3 is connected to the other end of the capacitor C6 and the APD.

[0026] Further, the optoelectronic element D1 is a PIN-type photodiode.

[0027] Further, the coupler is an optoelectronic coupler. When the control signal is a TTL high level, the optoelectronic coupler is turned on, and the APD voltage-dividing resistor R5 is short-circuited, and the APD bias voltage input to the bias voltage adjustment circuit is completely applied across the APD. When the control signal is a TTL low level, the optoelectronic coupler is turned off. At this time, the voltage across the APD is obtained by dividing the critical bias voltage by the APD internal resistance and the APD voltage-dividing resistor R5 (when the APD voltage-dividing resistor R5 is equal to the APD internal resistance, the bias voltage across the APD is only half of the critical bias voltage).

[0028] In this embodiment, the time width of the broadening signal is configured to be 400 μs, and the corresponding distance capacity of the laser rangefinder is 60 km. Figure 3It is a timing diagram of the bias voltage at both ends of the APD driven by a control signal. The blue signal is the APD bias voltage, and the yellow signal is used to record the moment when the laser emits light. It can be seen that the initial value of the bias voltage at both ends of the APD is about 100V. When the laser rangefinder emits laser, the APD bias voltage quickly rises to 270V.

[0029] Figure 4 、 Figure 5 It is a test comparison diagram of the detector saturation region. The atmospheric visibility on the test day is 5km. Among them Figure 4 is the test diagram of the saturation region measured when the APD is in the critical bias voltage state. It can be seen that the time length of the saturation region is about 4us, and the saturation region overlaps with the signal reflected by the target. At this time, the laser rangefinder cannot obtain the distance information of the target; Figure 5 is the test diagram of the saturation region after applying the APD bias voltage rapid adjustment circuit of the present invention. It can be seen that the time length of the APD saturation region has dropped to 2.8us, and there is no overlap with the target reflection signal. At this time, the laser rangefinder can normally extract the target distance information. Through the comparison test, the beneficial effects of the present invention are manifested.

[0030] The present invention provides an APD bias voltage rapid adjustment circuit. In the silent state of the laser rangefinder, the APD bias voltage is significantly lower than the critical bias voltage by using the APD voltage dividing resistor in series with the APD. When the laser rangefinder emits laser, a bias voltage control signal is generated by using the control signal acquisition circuit and the control signal broadening circuit to control the conduction of the optocoupler (the conduction time of the optocoupler is about 5us). During the conduction process of the optocoupler, since the APD bias voltage is lower than the critical bias voltage, the APD gain is small at this time, and the scattered optical signal will not cause the APD to enter the deep saturation state; after the optocoupler is completely conducted, the voltage dividing resistor is short-circuited, and at this time the APD bias voltage is equal to the critical bias voltage, and the signal-to-noise ratio reaches the best state. And at this time, the APD is no longer in the scattering region, and there is no need to worry about the influence of the scattered optical signal. This circuit solves the problem that the APD in the laser rangefinder is saturated due to laser backscattering through the segmented control of the APD bias voltage, and does not affect the ranging ability of the laser rangefinder (for the laser rangefinder, the peak power of the optical signal reflected by the target within 10us is large, and even if the APD is in a low gain state, it does not affect the detection of the target. After 10us, the APD is in the critical bias voltage state, and its ranging ability is not affected).

[0031] Embodiment 2: The principle of this embodiment is basically the same as that of Embodiment 1. On the basis of Embodiment 1, this embodiment provides a laser rangefinder, which includes the APD bias voltage rapid adjustment circuit described in Embodiment 1.

[0032] It should be understood that when the APD bias voltage rapid adjustment circuit is set in the laser rangefinder, the control signal acquisition circuit in the APD bias voltage rapid adjustment circuit should be able to collect the emitted laser of the laser rangefinder (for example, the optoelectronic element in the control signal acquisition circuit is set at the laser emission port of the laser rangefinder).

[0033] Embodiment 3: Based on Embodiment 2, this embodiment provides a laser ranging method, which uses the laser rangefinder described in Embodiment 2 to achieve ranging, including the following steps: S1. Turn on the laser rangefinder to emit laser for detection; S2. Collect the emitted laser and convert the optical signal of the emitted laser into an electrical signal; S3. Broaden the electrical signal to form a broadened signal; S4. Based on the broadened signal, make the APD voltage-dividing resistor not be short-circuited within a set period, and be short-circuited after the set period; when the APD voltage-dividing resistor is not short-circuited, make the APD bias voltage lower than the critical bias voltage; S5. Receive the returned laser through the laser rangefinder and obtain ranging information according to the returned laser.

[0034] It should be noted that according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0035] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An APD bias voltage rapid adjustment circuit, characterized in that It includes a control signal acquisition circuit, a control signal broadening circuit, an APD voltage-dividing resistor, and a coupler; the control signal acquisition circuit, the control signal broadening circuit, and the coupler are electrically connected in sequence, and the APD voltage-dividing resistor is connected in series with the controlled APD and then connected to the critical bias voltage, and the coupler is connected in parallel across the two ends of the APD voltage-dividing resistor; The control signal acquisition circuit converts the optical signal of the laser into an electrical signal at the moment when the laser emits light, and transmits the electrical signal to the control signal broadening circuit. The control signal broadening circuit broadens the electrical signal and outputs a broadened signal to the coupler. The coupler makes the APD voltage-dividing resistor not be short-circuited within a set time period after the laser emits light according to the broadened signal, and be short-circuited after the set time period; when the APD voltage-dividing resistor is not short-circuited, the APD bias voltage is lower than the critical bias voltage.

2. The APD bias voltage fast adjustment circuit according to claim 1, wherein The control signal acquisition circuit includes a current-limiting resistor R1, a photoelectric element D1, a voltage-dividing resistor R2, a voltage-dividing resistor R3, and a coupling capacitor C1; One end of the current-limiting resistor R1 and one end of the voltage-dividing resistor R2 are both connected to the positive power supply; the other end of the current-limiting resistor R1 is respectively connected to one end of the photoelectric element D1 and one end of the coupling capacitor C1; the other end of the coupling capacitor C1 is respectively connected to one end of the voltage-dividing resistor R3 and the other end of the voltage-dividing resistor R2, and serves as the output node of the electrical signal; the other end of the photoelectric element D1 and the other end of the voltage-dividing resistor R3 are both connected to the power supply ground.

3. The APD bias voltage fast adjustment circuit according to claim 1, wherein, The control signal broadening circuit includes a first NAND gate, a second NAND gate, a time constant configuration capacitor C4, and a time constant configuration resistor R4; The first input interface of the first NAND gate receives the electrical signal, the VCC interface of the first NAND gate is connected to the positive power supply, the second input interface of the first NAND gate is connected to the output interface of the second NAND gate, and the output interface of the first NAND gate outputs a broadened signal; The first input interface of the second NAND gate is connected to the output interface of the first NAND gate after passing through the time constant configuration capacitor C4, the second input interface of the second NAND gate is connected to the first input interface of the second NAND gate, and is connected to the power supply ground after passing through the time constant configuration resistor R4, and the GND interface of the second NAND gate is connected to the power supply ground.

4. The APD bias voltage rapid adjustment circuit according to claim 1, characterized in that One end of the coupler is connected to the broadened signal after passing through a resistor R6, and the other end of the coupler is connected to the power supply ground.

5. The APD bias voltage rapid adjustment circuit according to claim 3, characterized in that It includes a first filtering circuit; the first filtering circuit includes an inductor L1, a capacitor C2, and a capacitor C3; one end of the inductor L1 is connected to the positive power supply, and the other end is connected to one end of the capacitor C2 and the capacitor C3, and the VCC interface of the first NAND gate, and the other ends of the capacitor C2 and the capacitor C3 are both connected to the power supply ground.

6. The APD bias voltage rapid adjustment circuit according to claim 1, wherein The APD voltage-dividing resistor is connected in series with the controlled APD and then connected to the critical bias voltage through a second filtering circuit; the second filtering circuit includes a capacitor C5, a capacitor C6, an inductor L2, and an inductor L3; one end of the inductor L2 is connected to the positive pole of the critical bias voltage and one end of the capacitor C5, the other end of the inductor L2 is connected to one end of the capacitor C6 and the APD voltage-dividing resistor, one end of the inductor L3 is connected to the ground of the critical bias voltage and the other end of the capacitor C5, and the other end of the inductor L3 is connected to the other end of the capacitor C6 and the APD.

7. The APD bias voltage rapid adjustment circuit according to claim 2, characterized in that The photoelectric element D1 is a PIN-type photodiode.

8. The APD bias voltage fast adjustment circuit according to claim 1, characterized in that The coupler is an optocoupler.

9. A laser rangefinder, characterized in that, It includes the APD bias voltage rapid adjustment circuit according to any one of claims 1 to 8.

10. A laser ranging method, characterized in that, Perform ranging using the laser rangefinder described in claim 9.

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