Laser ranging method and device for single-photon magnitude response

Abstract

The invention discloses a laser ranging method and device based on single-photon magnitude response, and solves the problem that an existing laser ranging system cannot realize single-photon magnitude detection, and the method specifically comprises the following steps: 1, generating a high-frequency narrow pulse signal which excites a measurement laser to an object to be measured, and meanwhile, measuring the measurement laser to the object to be measured; acquiring corresponding reference information when the measurement laser is emitted; 2, detecting the measurement laser reflected by the object to be measured to obtain a measurement pulse signal, and obtaining measurement information corresponding to the measurement laser reflected by the object to be measured through the measurement pulse signal; 3, repeating the step 2 for multiple times to obtain measurement information of a plurality of counting cycles; step 4, performing time domain superposition on the measurement information of the plurality of periods to obtain correct echo light information of the measurement laser; 5, calculating the distance of the object to be measured through the reference information and the correct echo light information, and completing the laser ranging of the object to be measured. According to the method, single-photon-magnitude detection can be realized, and the measurement result is more accurate.

Description

Technical Field

[0001] The invention relates to a laser distance measurement device and method, and in particular to a laser distance measurement method and device with single photon magnitude response. Background Art

[0002] With the continuous development of science and technology, the R&D and production costs of semiconductor lasers and detectors are constantly decreasing, and laser ranging technology has gradually emerged in the fields of civil industrial manufacturing, measuring instruments, smart home appliances, smart driving, assisted driving, etc. The laser ranging used in these fields generally adopts the more mature D-TOF or I-TOF technology, that is, direct measurement of flight time method and indirect measurement of flight time method. When using D-TOF technology, a pulsed laser is emitted, and the receiving detector generally works in avalanche mode. When the returned pulse light enters the receiving target surface of the detector, a photoelectric effect occurs, and the photoelectrons are avalanche-amplified step by step, thereby obtaining a larger photocurrent signal, which is convenient for subsequent circuit amplification to obtain the returned pulse signal. The flight time of the emitted pulse and the returned pulse can be directly measured to calculate the target distance; when using I-TOF technology, a continuous pulse laser or a continuous laser modulated by sinusoidal is emitted, and the receiving detector generally works in non-avalanche mode, so the photocurrent caused by the returned light presents an amplitude characteristic similar to that of the emitted laser. For example, the emitted laser is a micro-modulated sinusoidal signal, and the received signal is also a sinusoidal signal. By measuring the phase difference between the two signals and indirectly measuring the flight time, the target distance can be calculated. Although these two common technologies can meet the needs of most application scenarios, they have great limitations in some special scenarios, especially when the effective reflection area of ​​the target is small or the reflectivity of the target is extremely low, the measurement function will be lost for the following reasons:

[0003] When the irradiation area of ​​the laser on the target is less than or equal to the cross-sectional area of ​​the target, that is, the reflected cross-sectional area of ​​the target is equal to the irradiation area, the detected target is a surface target. At this time, the receiving laser power P of the laser ranging system is R for:

[0004]

[0005] That is, the received echo power is inversely proportional to the square of the distance R between the target and the laser emission; where P T is the laser emission power, D is the aperture of the laser receiving optical antenna, θ is the beam divergence angle of the emitted laser, η T is the transmission coefficient of laser in the atmosphere, η S is the optical transmittance of the receiving optical system, ρ is the target reflectivity, and R is the distance between the target and the laser emitting end.

[0006] When the irradiation area of ​​the laser on the target is much larger than the cross-sectional area of ​​the target, that is, the reflection cross-sectional area of ​​the target is much smaller than the irradiation area, the reflection target is a point target with Lambertian body characteristics. At this time, the receiving laser power P of the laser ranging system is R for:

[0007]

[0008] That is, the received echo power is inversely proportional to the fourth power of the distance R between the target and the laser emission, where σ P is the illuminated point target area.

[0009] It can be seen from the LiDAR equations (1) and (2) that when the target is close, the reflection cross section of the reflecting target is large, and the ranging model with high reflectivity can obtain higher echo power; at the same detection distance, the same reflectivity and the same transmission power, the echo power of the point target is only 1 / R of that of the surface target. 2 For example, at the same detection distance of 100m, the echo power of a point target is only 1 / 10000 of the echo power of a surface target. If the reflectivity of the point target is lower, the echo power obtained will be even lower.

[0010] Therefore, most of the commonly used laser radars at present are surface targets or quasi-surface target models. The SPAD (photoelectric detection avalanche diode) is set in the avalanche mode or linear segment, and has a good response to the return light signal. The use of D-TOF or I-TOF can be widely used in various industries such as smart manufacturing, drone control, warehousing and logistics, smart home products, smart driving, unmanned driving, assisted driving, and big data optimization. The technology has become mature.

[0011] In some point target detection areas, such as airborne lidar detection of overhead cables, air-to-ground small target detection, ground-to-air small aircraft detection and other scenarios, due to the small target and long distance measurement, the echo signal is very weak, reaching the photon level, and there is no mature technology to support it at this stage. Summary of the invention

[0012] In order to solve the technical problem that the existing laser ranging system cannot realize single photon magnitude detection, the present invention provides a laser ranging method and device with single photon magnitude response.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] A laser ranging method for single photon magnitude response, which is special in that it includes the following steps:

[0015] Step 1: Generate a high-frequency narrow pulse signal, which excites the measurement laser to the object to be measured, and at the same time, obtains the reference information corresponding to the emission of the measurement laser;

[0016] Step 2: Detect the measurement laser reflected by the object to be measured to obtain a measurement pulse signal, and obtain measurement information corresponding to the measurement laser reflected by the object to be measured through the measurement pulse signal;

[0017] Step 3, repeat step 2 multiple times to obtain measurement information of multiple counting cycles;

[0018] Step 4: Superimpose the measurement information of multiple cycles in the time domain to obtain the correct echo light information of the measurement laser;

[0019] Step 5: Calculate the distance of the object to be measured by using the reference information and the correct echo light information to complete the laser ranging of the object to be measured.

[0020] Furthermore, step 1 specifically includes:

[0021] 1.1. Set the duration t of each counting cycle, the number of counting cycles N, and the number of uniform time intervals m within each counting cycle; N ≥ 500, t ≤ 10ns, m ≥ 10;

[0022] 1.2. Generate a high-frequency narrow pulse signal, which excites the measuring laser, and the measuring laser is collimated and sent to the object to be measured; at the same time, obtain the reference photocurrent pulse signal corresponding to the emission of the measuring laser, convert the reference photocurrent pulse signal into a reference voltage pulse signal and amplify it, thereby obtaining a reference pulse signal;

[0023] 1.3. In the same counting cycle, the time interval position corresponding to the initial reference pulse in the reference pulse signal is obtained and recorded as the reference time interval position. The reference time interval position is the reference information.

[0024] Furthermore, step 2 is specifically as follows:

[0025] 2.1. Converge and detect the measurement laser reflected by the object to be measured, obtain the measurement photocurrent pulse signal corresponding to the measurement laser, convert the measurement photocurrent pulse signal into a measurement voltage pulse signal and amplify it, so as to obtain the measurement pulse signal;

[0026] 2.2. In the same counting cycle, the time interval position corresponding to each measuring pulse in the measuring pulse signal is obtained, and the time interval position is recorded as the measuring time interval position. All the measuring time interval positions are the measurement information of the counting cycle.

[0027] Furthermore, step 3 is specifically as follows:

[0028] Repeat step 2 N times to obtain measurement information of N counting cycles;

[0029] Step 4 is as follows:

[0030] The measurement information of N counting cycles is superimposed in the time domain to obtain the time interval position that corresponds to the most of all measurement time interval positions. The most corresponding time interval position is the correct echo time interval position, which is the correct echo light information of the measuring laser.

[0031] Furthermore, step 5 specifically includes:

[0032] 5.1. Obtain the time interval difference Δm between the reference time interval position and the correct echo time interval position;

[0033] 5.2. Based on the duration t of the counting cycle, the number of time intervals m, and the time interval number difference Δm, calculate the distance R of the object to be measured:

[0034]

[0035] Where c is the speed of light, Δt = Δm × (t / m);

[0036] Complete the laser ranging of the object to be measured.

[0037] A laser distance measuring device with single photon magnitude response is used to realize the above-mentioned laser distance measuring method with single photon magnitude response, and its special features are: comprising a DSP processing circuit, a DDS circuit, a pulse driving circuit, a semiconductor laser tube, an emission collimation optical system, a gate control circuit, a receiving optical system, a photomultiplier tube detector, a quenching circuit, a detector bias circuit, a low-noise amplification circuit and a counting circuit;

[0038] The DSP processing circuit is connected to the DDS circuit and the counting circuit respectively;

[0039] The output end of the DDS circuit is connected to the input end of the pulse driving circuit;

[0040] The output end of the pulse driving circuit is connected to the input end of the semiconductor laser tube;

[0041] The emission collimation optical system is arranged outside the emission end of the semiconductor laser tube, and its focal plane coincides with the light-emitting surface of the semiconductor laser, and is used to collimate the measurement laser emitted by the semiconductor laser tube and then emit it to the object to be measured;

[0042] The gate control circuit is connected to the reference trigger terminal of the counting circuit, and is used to trigger the counting circuit to work, and generate reference information through the counting circuit;

[0043] The receiving optical system is arranged outside the detection end of the photomultiplier tube detector, and its focal plane covers the receiving target surface of the photomultiplier tube detector, and is used to receive the measuring laser reflected by the object to be measured and send it to the photomultiplier tube detector;

[0044] The output end of the quenching circuit is connected to the input end of the photomultiplier tube detector;

[0045] The output end of the detector bias circuit is connected to the input end of the photomultiplier tube detector;

[0046] The input end of the low-noise amplifier circuit is connected to the output end of the photomultiplier tube detector, and the output end of the low-noise amplifier circuit is connected to the counting end of the counting circuit;

[0047] The counting circuit adopts a gated counting method to count measurement information of multiple cycles;

[0048] The DSP processing circuit is used to initially configure the DDS circuit and the counting circuit, receive and process the reference information and the measurement information of multiple cycles sent by the counting circuit, so as to obtain the distance of the object to be measured.

[0049] Furthermore, it also includes a monostable trigger circuit connected between the DDS circuit and the pulse drive circuit, and a sampling photodiode detector and a sampling signal amplifying circuit connected between the semiconductor laser tube and the gate control circuit;

[0050] The input end of the monostable trigger circuit is connected to the output end of the DDS circuit, and the output end thereof is connected to the input end of the pulse driving circuit;

[0051] The input end of the sampling photodiode detector is connected to the output end of the semiconductor laser tube, and the output end is connected to the input end of the sampling signal amplifying circuit;

[0052] The output end of the sampling signal amplifying circuit is connected to the trigger end of the gate control circuit.

[0053] Furthermore, it also includes a detector temperature control circuit, and a pulse shaping circuit and a time identification circuit arranged between the low-noise amplifier circuit and the counting circuit;

[0054] The detector temperature control circuit is installed on the photomultiplier tube detector;

[0055] The input end of the pulse shaping circuit is connected to the output end of the low noise amplifier circuit, and the output end thereof is connected to the input end of the time identification circuit;

[0056] The output end of the time identification circuit is connected to the counting end of the counting circuit.

[0057] Furthermore, it also includes a first circuit board, a second circuit board and a third circuit board;

[0058] The DSP processing circuit, DDS circuit, monostable trigger circuit, gate control circuit, pulse shaping circuit, time identification circuit and counting circuit are all arranged on the first circuit board;

[0059] The pulse driving circuit, semiconductor laser tube, sampling photodiode detector and sampling signal amplifying circuit are all arranged on the second circuit board; the emission collimating optical system is detachably connected to the second circuit board;

[0060] The photomultiplier tube detector, the detector temperature control circuit, the quenching circuit, the detector bias circuit, and the low-noise amplifier circuit are all arranged on a third circuit board; and the receiving optical system is detachably connected to the third circuit board.

[0061] Furthermore, the pulse driving circuit includes a totem pole Z, a resistor R1, a diode D, a resistor R2 and a MOS tube;

[0062] The input end of the totem pole Z is connected to the output end of the DDS circuit, and the output end thereof is connected to one end of the resistor R1;

[0063] The other end of the resistor R1 is connected to the positive electrode of the diode D;

[0064] The cathode of the diode D is connected to the gate of the MOS tube and one end of the resistor R2 respectively; the diode D is a fast Schottky diode;

[0065] The other end of the resistor R2 is connected to the source of the MOS tube;

[0066] The drain of the MOS tube is connected to the semiconductor laser tube.

[0067] Beneficial effects of the present invention:

[0068] 1. The laser ranging method provided by the present invention obtains measurement information of multiple counting cycles by repeated measurements, and then superimposes the measurement information of multiple cycles in the time domain to obtain the correct echo light information of the measuring laser, and then calculates the distance of the object to be measured by reference information and the correct echo light information. This method can not only realize single-photon level detection, but also the time domain superposition of multiple cycles can more accurately obtain the correct echo light information, thereby making its measurement result more accurate.

[0069] 2. The present invention adopts a multi-cycle pulse time domain accumulation method to reduce the influence of photon noise and dark count noise of the electromultiplier tube detector, and can accurately determine the correct echo light signal.

[0070] 3. The pulse driving circuit provided by the present invention is a dual MOS totem pole structure, which can drive a high-power semiconductor laser tube, realize a narrow pulse signal with a driving capacity of not less than 40A within 3.5ns, and complete shutdown within 2ns.

[0071] 4. The laser measuring device provided by the present invention is provided with a counting circuit using a gated counting method, so that the measurement cycles of the reference information and the measurement information are controllable.

[0072] 5. In the laser measuring device provided by the present invention, the photomultiplier tube detector is equipped with a detector bias circuit and a quenching circuit. The detector bias circuit can provide a bias voltage to the photomultiplier tube detector so that the photomultiplier tube detector can work stably and reliably in the Geiger mode. The quenching circuit can enable the photomultiplier tube detector to detect single photons and quench them in time to reduce tailing.

[0073] 6. The laser measuring device provided by the present invention is provided with a pulse shaping circuit and a time identification circuit, which can shape and identify the time of the measuring voltage pulse signal before counting, thereby reducing the influence of laser jitter and photomultiplier tube detector quenching tailing.

[0074] 7. The laser measurement device provided by the present invention has a high degree of integration and can be expanded to applications such as handheld laser radar, vehicle-mounted laser radar and airborne laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a structural schematic diagram of an embodiment of a laser distance measuring device with single photon magnitude response according to the present invention;

[0076] Figure 2 is a schematic structural diagram of a pulse driving circuit in an embodiment of the present invention;

[0077] Figure 3 This is a schematic diagram of time domain superposition in step 4 of an embodiment of the present invention.

[0078] Figure 4 It is a schematic diagram of obtaining correct echo light information in step 4 of an embodiment of the present invention.

[0079] Figure Number:

[0080] 1-DSP processing circuit, 2-DDS circuit, 3-monostable trigger circuit, 4-pulse driving circuit, 5-semiconductor laser tube, 6-emitting collimating optical system, 7-sampling photodiode detector, 8-sampling signal amplifying circuit, 9-gating circuit, 10-receiving optical system, 11-photomultiplier tube detector, 12-detector temperature control circuit, 13-quenching circuit, 14-detector bias circuit, 15-low noise amplifying circuit, 16-pulse shaping circuit, 17-time identification circuit, 18-counting circuit. DETAILED DESCRIPTION

[0081] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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 are within the scope of protection of the present invention.

[0082] The embodiment of the present invention provides a laser ranging device with single photon magnitude response, such as Figure 1 As shown, it includes a DSP processing circuit 1, a DDS circuit 2, a monostable trigger circuit 3, a pulse drive circuit 4, a semiconductor laser tube 5, an emission collimation optical system 6, a sampling photodiode detector 7, a sampling signal amplification circuit 8, a gate circuit 9, a receiving optical system 10, a photomultiplier tube detector 11 (PMT), a detector temperature control circuit 12, a quenching circuit 13, a detector bias circuit 14, a low noise amplifier circuit 15, a pulse shaping circuit 16, a time identification circuit 17 and a counting circuit 18. The counting circuit 18 adopts a gated counting method. The receiving optical system 10 is coated with a 905nm anti-reflection film and includes a filter to avoid the influence of stray light; the receiving optical system 10 can also be coated with 780nm, 808nm, 850nm, 1064nm, 1550nm and other anti-reflection films. The photomultiplier tube detector 11 can also use a silicon photomultiplier tube (Sipm / MPPC) and other detectors that can be used for single photon detection.

[0083] The connection relationship is as follows:

[0084] The DSP processing circuit 1 is connected to the DDS circuit 2 and the counting circuit 18 respectively; the output end of the DDS circuit 2 is connected to the input end of the monostable trigger circuit 3; the output end of the monostable trigger circuit 3 is connected to the input end of the pulse driving circuit 4; the output end of the pulse driving circuit 4 is connected to the input end of the semiconductor laser tube 5; the output end of the semiconductor laser tube 5 is connected to the input end of the sampling photodiode detector 7; the emission collimation optical system 6 is arranged outside the emission end of the semiconductor laser tube 5, and its focal plane coincides with the light-emitting surface of the semiconductor laser tube 5; the output end of the sampling photodiode detector 7 is connected to the input end of the sampling signal amplifying circuit 8; the output end of the sampling signal amplifying circuit 8 is connected to the trigger end of the gate circuit 9; the gate circuit 9 is connected to the reference trigger end of the counting circuit 18; the receiving optical system 10 is arranged at the detection end of the photomultiplier tube detector 11 The detector temperature control circuit 12 wraps the base of the photomultiplier tube detector 11 and is bonded to the photomultiplier tube detector 11 with thermal conductive silicone; the output end of the quenching circuit 13 is connected to the input end of the photomultiplier tube detector 11; the output end of the detector bias circuit 14 is connected to the input end of the photomultiplier tube detector 11; the input end of the low-noise amplifier circuit 15 is connected to the output end of the photomultiplier tube detector 11, and the output end of the low-noise amplifier circuit 15 is connected to the input end of the pulse shaping circuit 16 through a high-frequency soft coaxial cable; the output end of the pulse shaping circuit 16 is linked to the input end of the moment identification circuit 17; the output end of the moment identification circuit 17 is connected to the counting end of the counting circuit 18; the working mode of the counting circuit 18 is gated, and the counting cycle is set to 500. The low-noise amplifier circuit 15 adopts two-stage amplification. The first stage realizes I / V conversion, converts the weak current pulse signal into a voltage pulse signal, and realizes low-gain amplification; the low voltage signal output by the first stage enters the input end of the second stage amplifier circuit after low-pass filtering, and further amplifies the voltage signal.

[0085] Among them, the pulse driving circuit 4 adopts a dual MOS totem pole structure and has a fast shutdown function, such as Figure 2 As shown, the pulse drive circuit 4 specifically includes a totem pole Z, a resistor R1, a diode D, a resistor R2 and a MOS tube; the input end of the totem pole Z is connected to the output end of the DDS circuit 2, and the output end thereof is connected to one end of the resistor R1; the other end of the resistor R1 is connected to the positive electrode of the diode D; the negative electrode of the diode D is respectively connected to the gate of the MOS tube and one end of the resistor R2; the diode D is a fast Schottky diode; the other end of the resistor R2 is connected to the source of the MOS tube; the drain of the MOS tube is connected to the semiconductor laser tube 5. When the trigger signal disappears, the charge on the equivalent capacitor of the gate of the high-power MOS tube is quickly released, thereby realizing the rapid shutdown of the MOS tube.

[0086] In addition, the DSP processing circuit 1, the DDS circuit 2, the monostable trigger circuit 3, the gate control circuit 9, the pulse shaping circuit 16, the time identification circuit 17 and the counting circuit 18 are all arranged on the first circuit board; the pulse driving circuit 4, the semiconductor laser tube 5, the sampling photodiode detector 7 and the sampling signal amplifying circuit 8 are all arranged on the second circuit board; the photomultiplier tube detector 11, the detector temperature control circuit 12, the quenching circuit 13, the detector bias circuit 14, and the low noise amplifying circuit 15 are all arranged on the third circuit board; the emission collimating optical system 6 is detachably connected to the second circuit board by screws, the receiving optical system 10 is detachably connected to the third circuit board by screws, and other components are connected by wiring on the board accordingly. The sampling photodiode detector 7 and the semiconductor laser tube 5 are packaged in the same metal TO structure.

[0087] The high-frequency narrow pulse signal drives the semiconductor laser 5 to emit the measuring laser through the pulse driving circuit 4. The measuring laser is collimated and emitted to the object to be measured through the emission collimation optical system 6. The signal carried by the measuring laser is sampled, and its triggering time is counted as the reference pulse signal. The photomultiplier tube detector 11 works in the Geiger mode and can respond to the energy of a single photon. The echo light signal reflected by the object to be measured converges on the target surface of the photomultiplier tube detector 11 through the receiving optical system 10, and outputs a photocurrent pulse signal. After low-noise I / V conversion and low-noise amplification circuit, filtering and shaping, the echo pulse signal is obtained, and the photomultiplier tube detector 11 is quenched at the same time. The counting circuit 18 records the reference pulse signal at the triggering time and counts the echo pulse signal. The DSP processing circuit 1 judges and processes the photon counting result to obtain the flight time difference between the reference pulse and the echo pulse, and further calculates the distance of the object to be measured.

[0088] The distance between the object to be measured and the device is used to measure the distance, which specifically includes the following steps:

[0089] Step 1: Generate a high-frequency narrow pulse signal, which excites the measurement laser to the object to be measured, and at the same time, obtains the reference information corresponding to the emission of the measurement laser;

[0090] 1.1. The device is powered on and initialized. The DSP processing circuit 1 performs initial configuration on the DDS circuit 2 and the counting circuit 18, i.e., the duration of each counting cycle t=10ns, the number of counting cycles N=500 (1ms), and the number of uniform time intervals m=80 in each counting cycle are set to the counting circuit 18; the detector bias circuit 14 starts to work, providing a bias voltage to the photomultiplier tube detector 11, and the voltage noise fluctuation is not greater than 0.2mV, so that the photomultiplier tube detector 11 can work stably and reliably in the Geiger mode; the detector temperature control circuit 12 starts to work, so that the substrate temperature of the photomultiplier tube detector 11 is stabilized within 25℃±2℃;

[0091] 1.2. A high-frequency narrow pulse signal with a signal frequency of 1 MHz and a duty cycle of 1% (pulse width of 10 ns) is generated by the DDS circuit 2. The monostable trigger circuit 3 increases the signal amplitude of the high-frequency narrow pulse signal to 12 V, shortens the pulse width to 4.5 ns, and increases the pulse driving capability to 10 A before sending it to the pulse driving circuit 4.

[0092] The pulse driving circuit 4 enables the high-frequency narrow pulse signal to have a driving capacity of not less than 40A within 3.5ns, so as to excite the semiconductor laser tube 5 to emit a measuring laser with a wavelength of 905nm and a peak power greater than 150W to the object to be measured, and the spot is circular, the half-width divergence angle is less than 100μrad, and the output is turned off within 2ns; the emission collimation optical system 6 collimates the measuring laser;

[0093] At the same time, the sampling photodiode detector 7 obtains the reference photocurrent pulse signal corresponding to the emission of the measurement laser, and the sampling signal amplifier circuit 8 converts the reference photocurrent pulse signal into a reference voltage pulse signal and amplifies it (noise is not greater than 2mV at a gain of 100), thereby obtaining a reference pulse signal, which is then sent to the gate control circuit 9;

[0094] 1.3. After being triggered, the gate control circuit 9 outputs a high level to the reference trigger terminal of the counting circuit 18. In the same counting cycle, the counting circuit 18 opens the gate valve to obtain the time interval position corresponding to the initial reference pulse in its reference pulse signal, which is recorded as the reference time interval position. The reference time interval position is the reference information. The gate control circuit 9 maintains a high level before being reset.

[0095] Step 2: Detect the measurement laser reflected by the object to be measured to obtain a measurement pulse signal, and obtain measurement information corresponding to the measurement laser reflected by the object to be measured through the measurement pulse signal;

[0096] 2.1. After being reflected by the object to be measured, the measuring laser enters the receiving optical system 10. The receiving optical system 10 collects the reflected measuring laser and converges it on the receiving target surface of the photomultiplier tube detector 11. The photomultiplier tube detector 11 works in the Geiger mode. When a single photon reaches the detector target surface, the detector avalanches instantly. 5 Under electron multiplication, the measured photocurrent pulse signal is output.

[0097] When the photomultiplier tube detector 11 outputs a photocurrent pulse signal, the quenching circuit 13 instantly reduces the bias voltage of the photomultiplier tube detector 11 to below the Geiger voltage, so that the photomultiplier tube detector 11 loses the photoelectron detection capability and achieves quenching, thereby outputting an extremely narrow measurement photocurrent pulse signal; the time constant of the quenching circuit 13 is no more than 30ns, which can quickly restore the photomultiplier tube detector 11 to the Geiger mode and wait for the next photon trigger;

[0098] The low noise amplifier circuit 15 includes a two-pole amplifier circuit. The low noise amplifier circuit 15 converts the measured photocurrent pulse signal into a measured voltage pulse signal and amplifies it (at 10 6 The noise under gain is not more than 2mV), and then it is sent to the pulse shaping circuit 16, the pulse shaping circuit 16 shapes the amplified measurement voltage pulse signal, and the moment identification circuit 17 performs leading edge identification on the shaped measurement voltage pulse signal to reduce the influence of echo jitter and quenching tail of the photomultiplier tube detector 11, and then obtains the measurement pulse signal and sends it to the counting end of the counting circuit 18.

[0099] 2.2. In the same counting cycle, the counting circuit 18 obtains the time interval position corresponding to each measurement pulse in its measurement pulse signal under the action of the high level output by the gate circuit 9, and records the time interval position as the measurement time interval position. All measurement time interval positions are the measurement information of the counting cycle.

[0100] Step 3: Repeat step 2 500 times to obtain measurement information of 500 counting cycles;

[0101] Step 4: Superimpose the measurement information of multiple cycles in the time domain to obtain the correct echo light information of the measurement laser;

[0102] The counting circuit 18 sends 500 cycles to the DSP processing circuit 1. At the same time, the counting circuit 18 outputs a low level to the reset end of the gate control circuit 9 to reset the gate control circuit 9. After the gate control circuit 9 is reset, it outputs a low level to the reference trigger end of the counting circuit 18. The counting circuit 18 stops counting and resets to zero.

[0103] like Figure 3 and Figure 4 As shown, the measurement information of 500 cycles is superimposed in the time domain by the DSP processing circuit 1 to reduce the influence of photon noise and dark count noise of the electromultiplier tube detector 11. Since the responses of the echo photons are basically within the same counting interval, and the probability of noise falling into the same counting interval is very small, the number of primary photoelectrons detected by a single laser pulse echo signal obeys the Poisson distribution. After time domain superposition, it can be regarded as a Bernoulli experiment, and the result still obeys the Poisson distribution; the expected number of pulses is set as a threshold, and the pulse accumulation window exceeding the threshold is obtained, that is, the time interval position that corresponds to the most of all measurement time interval positions, then the most corresponding time interval position is the correct echo time interval position, and the correct echo time interval position is the correct echo light information of the measuring laser.

[0104] Step 5: Calculate the distance of the object to be measured by using the reference information and the correct echo light information, and complete the laser distance measurement of the object to be measured;

[0105] 5.1. Obtain the time interval difference Δm between the reference time interval position and the correct echo time interval position; thereby determining the number of counting intervals relative to the initial reference pulse, and multiplying the number of intervals by the interval time to obtain the time difference between the echo signal pulse and the reference trigger end pulse of the counting circuit 18 (i.e., the initial reference pulse);

[0106] 5.2. Through the DSP processing circuit 1, based on the duration t of the counting cycle, the number of time intervals m, and the number of time interval differences Δm, the distance R of the object to be measured is calculated:

[0107]

[0108] Where c is the speed of light, and the value of c is 299792458 m / s; Δt = Δm × (t / m);

[0109] Repeat the above steps to achieve continuous measurement.

[0110] The above device and method adopt a gated counting method, which can make the measurement period of the reference pulse and the echo pulse controllable; and the photomultiplier tube detector is set in Geiger mode and equipped with a fast quenching circuit, which can enable the photomultiplier tube detector to detect single photons and quench them in time to reduce tailing. In addition, a shaping and time identification circuit is performed before counting the echo pulse to reduce the influence of the echo laser jitter and the quenching tail of the photomultiplier tube detector, and the measurement result is more accurate.

[0111] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A laser ranging method with single photon magnitude response, characterized in that: The following steps are involved: Step 1: Generate a high-frequency narrow pulse signal, which excites the measurement laser to the object to be measured, and at the same time, obtains the reference information corresponding to the emission of the measurement laser; Step 2: Detect the measurement laser reflected by the object to be measured to obtain a measurement pulse signal, and obtain measurement information corresponding to the measurement laser reflected by the object to be measured through the measurement pulse signal; Step 3, repeat step 2 multiple times to obtain measurement information of multiple counting cycles; Step 4: Superimpose the measurement information of multiple cycles in the time domain to obtain the correct echo light information of the measurement laser; Step 5: Calculate the distance of the object to be measured by using the reference information and the correct echo light information to complete the laser ranging of the object to be measured.

2. The laser ranging method of single photon magnitude response according to claim 1, characterized in that: Step 1 specifically includes: 1.

1. Set the duration t of each counting cycle, the number of counting cycles N, and the number of uniform time intervals m within each counting cycle; N ≥ 500, t ≤ 10ns, m ≥ 10; 1.

2. Generate a high-frequency narrow pulse signal, which excites the measuring laser, and the measuring laser is collimated and sent to the object to be measured; at the same time, obtain the reference photocurrent pulse signal corresponding to the emission of the measuring laser, convert the reference photocurrent pulse signal into a reference voltage pulse signal and amplify it, thereby obtaining a reference pulse signal; 1.

3. In the same counting cycle, the time interval position corresponding to the initial reference pulse in the reference pulse signal is obtained and recorded as the reference time interval position. The reference time interval position is the reference information.

3. The laser ranging method of single photon magnitude response according to claim 2, characterized in that: Step 2 is as follows: 2.

1. Converge and detect the measurement laser reflected by the object to be measured, obtain the measurement photocurrent pulse signal corresponding to the measurement laser, convert the measurement photocurrent pulse signal into a measurement voltage pulse signal and amplify it, so as to obtain the measurement pulse signal; 2.

2. In the same counting cycle, the time interval position corresponding to each measuring pulse in the measuring pulse signal is obtained, and the time interval position is recorded as the measuring time interval position. All the measuring time interval positions are the measurement information of the counting cycle.

4. The laser ranging method of single photon magnitude response according to claim 3, characterized in that: Step 3 is as follows: Repeat step 2 N times to obtain measurement information of N counting cycles; Step 4 is as follows: The measurement information of N counting cycles is superimposed in the time domain to obtain the time interval position that corresponds to the most of all measurement time interval positions. The most corresponding time interval position is the correct echo time interval position, which is the correct echo light information of the measuring laser.

5. The laser ranging method of single photon magnitude response according to claim 4, characterized in that: Step 5 specifically includes: 5.

1. Obtain the time interval difference Δm between the reference time interval position and the correct echo time interval position; 5.

2. Based on the duration t of the counting cycle, the number of time intervals m, and the time interval number difference Δm, calculate the distance R of the object to be measured: Where c is the speed of light, Δt = Δm × (t / m); Complete the laser ranging of the object to be measured.

6. A laser ranging device with single photon magnitude response, used to implement the laser ranging method with single photon magnitude response according to any one of claims 1 to 5, characterized in that: It comprises a DSP processing circuit (1), a DDS circuit (2), a pulse driving circuit (4), a semiconductor laser tube (5), an emission collimation optical system (6), a gate control circuit (9), a receiving optical system (10), a photomultiplier tube detector (11), a quenching circuit (13), a detector bias circuit (14), a low noise amplifier circuit (15) and a counting circuit (18); The DSP processing circuit (1) is connected to the DDS circuit (2) and the counting circuit (18) respectively; The output end of the DDS circuit (2) is connected to the input end of the pulse driving circuit (4); The output end of the pulse driving circuit (4) is connected to the input end of the semiconductor laser tube (5); The emission collimation optical system (6) is arranged outside the emission end of the semiconductor laser tube (5), and its focal plane coincides with the light-emitting surface of the semiconductor laser tube (5), and is used to collimate the measurement laser emitted by the semiconductor laser tube (5) and then emit it to the object to be measured; The gate control circuit (9) is connected to a reference trigger terminal of a counting circuit (18) to trigger the counting circuit (18) to operate and generate reference information through the counting circuit (18); The receiving optical system (10) is arranged outside the detection end of the photomultiplier tube detector (11), and its focal plane covers the receiving target surface of the photomultiplier tube detector (11), and is used to receive the measuring laser reflected by the object to be measured and send it to the photomultiplier tube detector (11); The output end of the quenching circuit (13) is connected to the input end of the photomultiplier tube detector (11); The output end of the detector bias circuit (14) is connected to the input end of the photomultiplier tube detector (11); The input end of the low-noise amplifier circuit (15) is connected to the output end of the photomultiplier tube detector (11), and the output end of the low-noise amplifier circuit (15) is connected to the counting end of the counting circuit (18); The counting circuit (18) adopts a gated counting method to count measurement information of multiple cycles; The DSP processing circuit (1) is used to initially configure the DDS circuit (2) and the counting circuit (18), and to receive and process reference information and multiple cycles of measurement information sent by the counting circuit (18), thereby obtaining the distance of the object to be measured.

7. The laser ranging device with single photon magnitude response according to claim 6, characterized in that: It also includes a monostable trigger circuit (3) connected between the DDS circuit (2) and the pulse drive circuit (4), and a sampling photodiode detector (7) and a sampling signal amplifying circuit (8) connected between the semiconductor laser tube (5) and the gate control circuit (9); The input end of the monostable trigger circuit (3) is connected to the output end of the DDS circuit (2), and the output end thereof is connected to the input end of the pulse drive circuit (4); The input end of the sampling photodiode detector (7) is connected to the output end of the semiconductor laser tube (5), and the output end thereof is connected to the input end of the sampling signal amplifying circuit (8); The output end of the sampling signal amplifying circuit (8) is connected to the trigger end of the gate control circuit (9).

8. The laser ranging device with single photon magnitude response according to claim 7, characterized in that: It also includes a detector temperature control circuit (12), and a pulse shaping circuit (16) and a time identification circuit (17) arranged between a low-noise amplifier circuit (15) and a counting circuit (18); The detector temperature control circuit (12) is installed on the photomultiplier tube detector (11); The input end of the pulse shaping circuit (16) is connected to the output end of the low noise amplifier circuit (15), and the output end thereof is linked to the input end of the time identification circuit (17); The output end of the time identification circuit (17) is connected to the counting end of the counting circuit (18).

9. The laser ranging device with single photon magnitude response according to claim 8, characterized in that: Also includes a first circuit board, a second circuit board and a third circuit board; The DSP processing circuit (1), the DDS circuit (2), the monostable trigger circuit (3), the gate control circuit (9), the pulse shaping circuit (16), the time identification circuit (17) and the counting circuit (18) are all arranged on a first circuit board; The pulse drive circuit (4), semiconductor laser tube (5), sampling photodiode detector (7) and sampling signal amplification circuit (8) are all arranged on the second circuit board; the emission collimation optical system (6) is detachably connected to the second circuit board; The photomultiplier tube detector (11), the detector temperature control circuit (12), the quenching circuit (13), the detector bias circuit (14), and the low-noise amplifier circuit (15) are all arranged on a third circuit board; and the receiving optical system (10) is detachably connected to the third circuit board.

10. The laser ranging device with single photon magnitude response according to any one of claims 6 to 9, characterized in that: The pulse driving circuit (4) comprises a totem pole Z, a resistor R1, a diode D, a resistor R2 and a MOS tube; The input end of the totem pole Z is connected to the output end of the DDS circuit (2), and the output end thereof is connected to one end of the resistor R1; The other end of the resistor R1 is connected to the positive electrode of the diode D; The cathode of the diode D is connected to the gate of the MOS tube and one end of the resistor R2 respectively; the diode D is a fast Schottky diode; The other end of the resistor R2 is connected to the source of the MOS tube; The drain of the MOS tube is connected to the semiconductor laser tube (5).

Images