CN110261864A - A kind of pulsed laser ranging system echo signal processing equipment and method - Google Patents

Abstract

The invention discloses a pulse laser ranging system echo signal processing device and method. The device includes a main controller, a drive circuit, a laser, an optical system, a PIN photodetector, a main wave amplifier, a fixed threshold time discrimination circuit, and an APD. Photodetector, preamplifier, main amplifier, autocorrelation detection circuit, double threshold time discrimination circuit, high voltage bias circuit, first peak sampling circuit, first A/D conversion circuit, second peak sampling circuit, second A /D conversion circuit, D/A conversion circuit, LED display and host computer. In the present invention, the first peak sampling circuit, the first A/D conversion circuit, the second peak sampling circuit, the second A/D conversion circuit, and the D/A conversion circuit are combined with a double threshold time discrimination circuit to stabilize the echo signal amplitude and simultaneously The self-correlation detection circuit is adopted to extract the echo signal from the noise, the signal-to-noise ratio of the system is improved, the ranging accuracy is improved, and the measurement range of the system is expanded, and the method can also improve the integration degree of the system at the same time.

Description

A pulsed laser ranging system echo signal processing device and method

technical field

The invention relates to the technical field of laser ranging, and more specifically relates to a high-precision and large-range pulsed laser ranging system echo signal processing device and method based on time-of-flight measurement.

Background technique

Laser is widely used in the field of ranging because of its good directionality, high brightness, and good coherence. Pulse laser ranging has high peak power, long detection distance, high measurement accuracy, low requirements for light source coherence, and no need for cooperative targets. Etc. The basic principle of pulsed laser ranging is that the laser emits laser pulses to the target, and the laser light reaches the target surface and is received by the echo receiving channel after diffuse reflection, and the flight time t of the laser pulse from emission to reception of the echo is measured to calculate the waiting time Distance measurement L=c*t/2, where c is the speed of light, and time measurement accuracy is a key factor determining the distance measurement accuracy.

The traditional pulse laser ranging system includes: laser emission, photoelectric detection, amplification circuit, time identification circuit and timing control circuit. Since the laser pulse will be attenuated to varying degrees due to the influence of the atmosphere and target scattering characteristics during the propagation process, when the distance is relatively short, the energy of the reflected laser pulse signal is strong, resulting in the saturation of the output signal of the photoelectric detection, while when the distance is long , the reflected signal is very weak, even submerged in the noise, resulting in a large change in the amplitude of the laser echo, which causes a large error in the identification of the laser echo time, affects the ranging accuracy, and also restricts the measurement range of the system.

At present, there are three main time identification methods commonly used: fixed threshold time identification method, high-pass resistance-capacitance time identification method and constant ratio timing time identification method. Although the fixed-threshold time discrimination method has a simple circuit structure and can filter out certain noises, it is greatly affected by echo drift errors and has poor precision. Although the high-pass resistance-capacitance method and the constant-ratio timing method are less affected by the amplitude change of the echo signal, neither of them allows the signal to be saturated, which does not meet the requirements of a wide range of applications, and is susceptible to false triggering caused by noise.

Based on the above analysis, stabilizing the echo signal amplitude and improving the system signal-to-noise ratio are the keys to effectively expanding the range of pulsed laser ranging and improving its ranging accuracy.

Therefore, how to provide a novel pulse laser ranging system echo signal processing device and method is an urgent problem to be solved by those skilled in the art.

Contents of the invention

In view of this, the present invention provides a pulse laser ranging system echo signal processing device and method, which can stabilize the echo signal amplitude and improve the system signal-to-noise ratio, improve ranging accuracy, and expand the system measurement range.

In order to achieve the above object, the present invention adopts the following technical solutions:

A pulse laser ranging system echo signal processing device, including: a main controller, a drive circuit, a laser, an optical system, a PIN photodetector, a main wave amplifier, a fixed threshold time discrimination circuit, an APD photodetector, and a preamplifier , a main amplifier, an autocorrelation detection circuit, a double-threshold moment discrimination circuit, a high-voltage bias circuit, a first automatic gain control module, a second automatic gain control module, and a gain adjustment module;

The main controller, the driving circuit and the laser are sequentially connected, the pulsed laser generated by the laser is split by the optical system, and the main wave signal of the pulsed laser enters the PIN photodetector, and the PIN photodetector , the main wave amplifier, the fixed threshold moment discrimination circuit and the main controller are sequentially connected;

The pulsed laser echo signal split by the optical system enters the APD photodetector, the APD photodetector, the preamplifier, the main amplifier, the autocorrelation detection circuit, and the dual threshold The moment discrimination circuit is sequentially connected with the main controller;

The output end of the preamplifier is connected to the input end of the second automatic gain control module, and the output end of the second automatic gain control module is connected to the input end of the main controller;

The output terminal of the autocorrelation detection circuit is connected to the input terminal of the first automatic gain control module, and the output terminal of the first automatic gain control module is connected to the input terminal of the main controller;

The output end of the main controller is respectively connected to the input end of the gain adjustment module and the input end of the high voltage bias circuit, and the output end of the gain adjustment module is connected to the input end of the main amplifier, and the high voltage The output end of the bias circuit is connected to the input end of the APD photodetector.

Further, the optical system includes a beam expander, a beam splitter, a receiving lens and a narrow-band filter, the pulsed laser is divided into two paths of pulsed lasers sequentially through the beam expander and the beam splitter, and the main wave signal of the pulsed laser enters the In the PIN photodetector, pulsed laser echo signals enter the receiving lens and the narrow-band filter sequentially after being diffusely reflected by the measured target.

Further, the first automatic gain control module includes a first peak sampling circuit and a first A/D conversion circuit, the output terminal of the autocorrelation detection circuit is connected to the input terminal of the first peak sampling circuit, and the first The output end of the peak sampling circuit is connected to the input end of the first A/D conversion circuit, and the output end of the first A/D conversion circuit is connected to the input end of the main controller;

The second automatic gain control module includes a second peak sampling circuit and a second A/D conversion circuit, the output of the preamplifier is connected to the input of the second peak sampling circuit, and the second peak sampling circuit The output end of the second A/D conversion circuit is connected to the input end of the second A/D conversion circuit, and the output end of the second A/D conversion circuit is connected to the input end of the main controller;

The gain adjustment module is a D/A conversion circuit, the output end of the main controller is connected to the input end of the D/A conversion circuit, and the output end of the D/A conversion circuit is connected to the input end of the main amplifier .

Further, the main controller is an FPGA main controller.

Further, it also includes an LED display screen and a host computer, and both the LED display screen and the host computer are connected to the main controller.

A pulse laser ranging system echo signal processing method, comprising the following steps:

Step 1: After the system is powered on, the main controller generates a control signal and controls the driving circuit, and the driving circuit drives the laser to emit pulsed laser;

Step 2: After the pulsed laser is split by the optical system, the main wave signal of the pulsed laser enters the PIN photodetector, and the PIN photodetector converts the main wave signal of the pulsed laser into a current signal, and the current signal enters the main wave amplifier to complete the current The voltage is converted and the voltage signal is amplified, and the amplified voltage signal is shaped by a fixed threshold time discrimination circuit to obtain a digital signal at the time of pulse laser emission, and the digital signal enters the main controller as the starting time start of time interval measurement ;

Step 3: The pulsed laser echo signal split by the optical system enters the APD photodetector, and the APD photodetector converts the pulsed laser echo signal into a current signal, and the current signal enters the preamplifier to complete Convert current to voltage and amplify the voltage signal to a voltage signal V that meets the requirements;

The voltage signal V is output in two ways, one way is output to the main amplifier for further amplification to obtain a voltage signal V ₁ meeting the subsequent circuit processing requirements, and the other way is output to the second automatic gain control module;

The digital signal V _p2 is obtained through the second automatic gain control module and stored in the main controller, compared with the threshold value V _th set by the main controller, and the comparison result is fed back to the gain adjustment module or the high-voltage bias circuit middle;

The voltage signal V ₁ enters the autocorrelation detection circuit, and outputs a high signal-to-noise ratio voltage signal V ₂ after autocorrelation processing;

Step 4: The high signal-to-noise ratio voltage signal V ₂ is divided into two outputs, one of which enters the first automatic gain control module to obtain a digital signal V _p1 and stores it in the main controller, and compares it with the two thresholds set by the main controller V _H is compared with V _L , V _H > V _L , and the comparison result is fed back to the gain adjustment module;

The other channel enters the dual threshold time discrimination circuit and sends the two generated echo time discrimination signals to the main controller as stop signals stop1 and stop2 for time interval measurement;

Step 5: The main controller uses the FPGA delay line insertion method to measure the time interval t ₁ between start and stop1 and the time interval t ₂ between start and stop2 respectively, and analyze and process the measurement results to calculate the pulsed laser flight Time Δt, using the pulsed laser flight time Δt to obtain the measured distance S.

Further, the optical system includes a beam expander, a beam splitter, a receiving lens and a narrow-band filter, the pulsed laser is divided into two paths of pulsed lasers sequentially through the beam expander and the beam splitter, and the main wave signal of the pulsed laser enters the PIN photodetector, the pulsed laser echo signal enters the receiving lens and the narrow-band filter sequentially after being diffusely reflected by the measured target, wherein the receiving lens focuses the received pulsed laser main wave signal, so The narrow-band filter filters the main wave signal of the pulsed laser.

Further, the first automatic gain control module includes a first peak sampling circuit and a first A/D conversion circuit, and the first peak sampling circuit collects the peak value of the output signal of the autocorrelation detection circuit and transmits it to the first A/D conversion circuit, the first A/D conversion circuit converts it into a digital signal V _p1 and sends it to the main controller;

The second automatic gain control module includes a second peak sampling circuit and a second A/D conversion circuit, and the second peak sampling circuit collects the output signal peak value of the preamplifier and transmits it to the second A/D conversion circuit , the second A/D conversion circuit converts it into a digital signal V _p2 and sends it to the main controller;

The gain adjustment module is a D/A conversion circuit, and the D/A conversion circuit is used to automatically control the gain of the main amplifier.

Further, the specific steps for the automatic gain control of the D/A conversion circuit are:

A. Compare the digital signal V _p1 with the two thresholds V _H and V _L set by the main controller, V _H >V _L , if V _p1 <V _L , then through the D/A conversion The circuit increases the gain of the main amplifier, and keeps the gain of the main amplifier unchanged if V _L ≤ V _p1 ≤ V _H ;

B. Comparing the digital signal V _p2 with the threshold V _th set by the main controller, if V _p1 >V _H , and V _p2 >V _th , reduce the APD photodetection through the high-voltage bias circuit The bias voltage of the amplifier, if V _p1 >V _H , and V _p2 ≤ V _th , then the gain of the main amplifier is reduced through the D/A conversion circuit.

Further, the main controller is an FPGA main controller, and the calibration curve is used to compensate the error, and the calculation formula of the pulse laser flight time Δt is:

Δt=t ₁ -Δt _err or (1)

Among them, Δt _error represents the time drift error;

Using the pulsed laser flight time Δt to obtain the measured distance S:

S=c·Δt/2(2)

where c is the speed of light in vacuum;

The measured distance S is displayed by an LED display screen, and the data is saved by the host computer.

It can be seen from the above-mentioned technical solutions that, compared with the prior art, the present invention discloses an echo signal processing device and method for a pulsed laser ranging system, which has the following advantages:

(1) The present invention adopts the automatic gain control technology to greatly reduce the amplitude fluctuation of the echo signal, which can effectively reduce the time discrimination error caused by the echo power drift, and simultaneously adopts the double-threshold frontier time discrimination method to compensate the residual drift error, The time identification accuracy is not affected by the echo signal saturation, high-precision time identification is realized, the problem that the echo power drift has a great influence on the ranging accuracy is solved, and the ranging accuracy and measurement range are improved.

(2) The present invention adopts an autocorrelation detection circuit to reduce system noise, and improve system signal-to-noise ratio, distance measurement accuracy and range measurement.

(3) The present invention utilizes the FPGA main controller to realize the measurement of the time interval and the control of the system at the same time, thereby improving the integration degree of the system.

(4) Compared with the prior art, the signal-to-noise ratio of the present invention is improved to more than 10dB, the measurement range is expanded to 2m-3km, and the accuracy is improved to within 0.5m.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings on the premise of not paying creative efforts.

The accompanying drawing in Fig. 1 is a schematic diagram of the pulse laser ranging system echo signal processing device provided by the present invention.

Figure 2 is a schematic diagram of the optical system provided by the present invention.

Figure 3 is a flow chart of the pulse laser ranging system echo signal processing method provided by the present invention.

Figure 4 is a flowchart of the automatic gain control provided by the present invention.

Figure 5 is a schematic diagram of the autocorrelation detection circuit provided by the present invention.

FIG. 6 is a schematic structural diagram of an autocorrelation detection circuit provided by the present invention.

FIG. 7 is a schematic structural diagram of a dual-threshold moment discrimination circuit provided by the present invention.

Fig. 8 is a schematic diagram of the double-threshold moment discrimination circuit provided by the present invention.

Among them, each component represents:

1. Main controller, 2. Driving circuit, 3. Laser, 4. Optical system, 401. Beam expander, 402. Beam splitter, 403. Receiving lens, 404. Narrowband filter, 5. PIN photodetector, 6. Main wave amplifier, 7. Fixed threshold time discrimination circuit, 8. APD photodetector, 9. Preamplifier, 10. Main amplifier, 11. Autocorrelation detection circuit, 12. Double threshold time discrimination circuit, 13. High voltage Bias circuit, 14, first automatic gain control module, 141, first peak sampling circuit, 142, first A/D conversion circuit, 15, second automatic gain control module, 151, second peak sampling circuit, 152, The second A/D conversion circuit, 16, gain adjustment module, 17, LED display screen, 18, upper computer.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the present invention is based on a 1064nm pulsed laser and a light source with a pulse width of 10ns to achieve high-precision, wide-range pulsed laser ranging, and proposes a new echo signal processing device and method. First, an automatic gain control circuit combined with a double-threshold echo signal time identification circuit is designed. , stabilize the echo signal amplitude, and use autocorrelation detection circuit to extract the echo signal from the noise, improve the system signal-to-noise ratio, improve the ranging accuracy, and expand the system measurement range. This method can also improve the system integration.

Specifically, a pulse laser ranging system echo signal processing device includes a main controller 1, a drive circuit 2, a laser 3, an optical system 4, a PIN photodetector 5, a main wave amplifier 6, a fixed threshold time discrimination circuit 7, APD photodetector 8, preamplifier 9, main amplifier 10, autocorrelation detection circuit 11, double threshold time discrimination circuit 12, high voltage bias circuit 13, first automatic gain control module 14, second automatic gain control module 15, Gain adjustment module 16, LED display screen 17 and upper computer 18;

Among them, the laser 3 is used to generate a pulsed laser with a wavelength of 1064nm and a pulse width of 10ns; the optical system 4 is used to converge the pulsed laser signal and split it, and focus, collimate and filter the echo pulse signal; the PIN photodetector 5 is used to Detect the main wave signal and perform photoelectric conversion, APD photodetector 8 is used to detect the echo signal and perform photoelectric conversion; the main wave amplifier 6 and the preamplifier 9 respectively convert the output main wave and echo weak current signals into voltage signals and amplify; the fixed threshold time identification circuit 7 is used to identify the laser pulse main wave signal emission time; the autocorrelation detection circuit 11 is used to reduce noise, improve the system signal-to-noise ratio, and realize the extraction of weak echo signals from noise; Setting circuit 13 is used to provide high-voltage bias voltage to APD photodetector; First automatic gain control module 14, second automatic gain control module 15 and gain adjustment module 16, FPGA master controller outputs voltage according to the detected preamplifier Amplitude and autocorrelation detection circuit output voltage amplitude is compared with the corresponding threshold and calculated, the feedback adjusts the gain of the main amplifier and the bias voltage of the APD photodetector, reduces the fluctuation range of the echo signal amplitude, and then improves the system Signal-to-noise ratio and ranging accuracy; dual-threshold time discrimination circuit 12 is used to accurately identify the arrival time of the echo signal to improve ranging accuracy; the main controller 1 is an FPGA main controller, and the FPGA main controller utilizes an FPGA internal delay unit Realize the high-resolution measurement of the time interval between the main echoes, and at the same time, the FPGA is also used as the system controller to improve the system integration; the LED display 17 is used to display the ranging results calculated and processed by the FPGA main controller; the upper computer 18, It is used for serial communication with the FPGA main controller to save the measurement results.

The connection relationship is as shown in Fig. 1, FPGA main controller, drive circuit 2 and laser 3 are sequentially connected, the pulsed laser light generated by laser 3 is split by optical system 4, and then all the pulsed laser light enters PIN photodetector 5, and PIN photodetector 5 , the main wave amplifier 6, the fixed threshold moment discrimination circuit 7 and the FPGA main controller are connected in sequence;

Another path of pulsed laser light split by the optical system 4 enters the APD photodetector 8, the APD photodetector 8, the preamplifier 9, the main amplifier 10, the autocorrelation detection circuit 11, the double-threshold time discrimination circuit 12 and the main FPGA controller sequential connection;

The first automatic gain control module 14 comprises a first peak sampling circuit 141 and a first A/D conversion circuit 142, the output end of the autocorrelation detection circuit 11 is connected to the input end of the first peak sampling circuit 141, and the output terminal of the first peak sampling circuit 141 The output end is connected to the input end of the A/D conversion circuit, and the output end of the A/D conversion circuit is connected to the input end of the FPGA main controller;

The second automatic gain control module 15 includes a second peak sampling circuit 142 and a second A/D conversion circuit 152, the output of the preamplifier 9 is connected to the input of the second peak sampling circuit 142, and the output of the second peak sampling circuit 142 End connects the input end of the second A/D conversion circuit 152, and the output end of the second A/D conversion circuit 152 connects the input end of the FPGA master controller;

The gain adjustment module 16 is a D/A conversion circuit, the output end of the FPGA main controller is connected to the input end of the D/A conversion circuit, and the output end of the D/A conversion circuit is connected to the input end of the main amplifier 10;

Both the LED display screen 17 and the host computer 18 are connected with the FPGA master controller.

2, the optical system 4 includes a beam expander 401, a beam splitter 402, a receiving lens 403 and a narrow-band filter 404. The pulsed laser is divided into two paths of pulsed lasers through the beam expander 401 and the beam splitter 402 in turn, and the main wave signal of the pulsed laser Entering the PIN photodetector 5 , another pulsed laser light is diffusely reflected by the target to be measured and enters the receiving lens 403 and the narrow-band filter 404 in turn, and the echo signal of the pulsed laser is transmitted to the APD photodetector 8 .

The pulse laser ranging echo signal processing device of the present invention, the system ranging principle adopts the time-of-flight measurement method, that is Where S is the distance to be measured, c is the speed of light in vacuum, and Δt is the flight time of the laser pulse. The key to realizing high-precision and wide-range ranging lies in the precise measurement of time. Therefore, the present invention reduces system noise and stabilizes the signal amplitude through a high-precision echo signal processing circuit, and realizes accurate timing of the echo signal. Discrimination and high-precision time interval measurement.

With reference to Fig. 3, a pulse laser ranging system echo signal processing method includes the following steps:

(1) Turn on the power, the system is powered on, the FPGA main controller controls the drive circuit 2 to drive the laser 3 to emit pulsed laser light with a pulse width of 10 ns. Two-way light with energy ratio of 1:9.

(2) The pulsed laser light that accounts for 10% energy directly enters the PIN photodetector 5, and the PIN photodetector 5 converts the optical signal into a current signal, and this current signal enters the main wave amplifier 6, completes the I/V conversion and amplifies, and outputs The signal is connected to the input terminal of the fixed threshold time discrimination circuit 7, and the digital signal is obtained through shaping, and the digital signal enters the timing module of the FPGA main controller as the starting time start of the time interval measurement.

(3) A pulsed laser signal with 90% energy is diffusely reflected by the measured target, is received by the APD photodetector 8 after being focused by the receiving lens 403 and filtered by the narrow-band filter 404, and is converted into a current signal I output, wherein the APD The photodetector 8 is located at the 2 times focal length of the receiving lens 403, and the receiving lens 403 focuses the received laser light and enlarges the effective receiving area of the APD photodetector 8; the narrowband filter 404 is next to the APD photodetector The 8 photosensitive surfaces of the device can filter out stray light, improve the signal-to-noise ratio and improve the system accuracy at the same time.

The current signal I enters the low-noise preamplifier circuit 9 for I/V conversion and is amplified thousands of times to obtain V, and the voltage signal V enters the main amplifier 10 to further amplify to obtain a voltage signal V1 that meets the level standard required by subsequent circuit processing. All the way into the second automatic gain control module.

Because the laser pulse signal is affected by the atmosphere and the reflection characteristics of the target, there will be different degrees of attenuation and distortion. When the target is far away, the amplitude of the echo signal is small; the background stray light noise, environmental noise and hardware circuit part exist at the same time. The noise makes the echo signal submerged in the noise and it is difficult to extract, which brings a large error to the accurate time identification, and finally affects the ranging accuracy. Therefore, the self-correlation detection circuit 11 is used to suppress noise and improve the signal-to-noise ratio of the system. The output signal V1 of the main amplifying circuit enters the input terminal of the autocorrelation detection circuit 11, and outputs a signal V2 with a high signal-to-noise ratio after autocorrelation processing.

(4) With the change of the target distance, the echo laser power received by the laser range finder will also change. This change is reflected in the voltage amplitude of the echo signal, which will bring great influence to the time identification. Drift error, in addition, signal amplitudes that are too small can be overwhelmed by noise making it impossible to identify the signal. In order to achieve high-precision and wide-range pulse laser ranging, automatic gain control technology is used to stabilize the echo signal amplitude within a small fluctuation range. That is, the output signal V2 of the autocorrelation detection circuit 11 enters the first automatic gain module 14 all the way. Since the peak time of the pulse signal is relatively short, it cannot meet the requirements of the A/D conversion circuit for the input signal, so first the peak value of the echo signal is collected by the first peak detection circuit 141 and kept for a certain time, so that the first A/D conversion The circuit 142 has enough time to convert it into a digital signal V _p1 , so that the main FPGA controller can obtain the amplitude information of the signal. The digital signal V _p1 is stored in the FPGA, and compared with the two thresholds V _H and V _L (V _H >V _L ) set in the main controller of the FPGA, and fed back to the echo receiving circuit D/A conversion circuit 7 , the gain of the main amplifier 10 is adjusted, so that the output voltage of the main amplifier 10 is stabilized in a smaller fluctuation range; the same principle, the second peak sampling signal 151 carries out peak sampling to the output signal of the preamplifier 9, through After the second A/D conversion module, the digital signal V _p2 is obtained, and the digital signal V _p2 is compared with the threshold value V _th set in the FPGA main controller, and the bias voltage of the APD photodetector is adjusted by feedback, so that the output signal V1 of the amplifying circuit The peak value is stable within a small fluctuation range, preventing voltage signal saturation, which is conducive to improving the accuracy of time identification and system ranging accuracy.

The output signal of the autocorrelation detection circuit 11 enters the double-threshold time discrimination circuit 12 in another way, and uses two thresholds V _th1 and V _th2 (V _th1 <V _th2 ) to measure the same laser echo signal, and the two generated echo time discrimination signals Send to the timing module of FPGA main controller as the stop signal stop1 and stop2 of time interval measurement. In the subsequent algorithm processing, the calibrated error compensation relationship is used to compensate the time drift error caused by a single threshold, and the accurate arrival time of the laser echo is obtained.

(5) The output signal of the double-threshold moment discrimination circuit 12 enters the FPGA master controller, and uses the FPGA delay line insertion method to measure the time intervals _t1 and _t2 between start and stop1 and start and stop2 respectively, and analyze the measurement results Processing, calculate the pulse laser flight time Δt, so as to calculate the distance to be measured It is displayed on the LED display screen 17 and transmitted to the host computer 18 through the serial port for data storage.

Wherein, the autocorrelation detection circuit 11 is composed of a multiplier, a delayer and an integrator as shown in FIG. 5 , and a schematic diagram of the circuit structure is shown in FIG. 6 . Since the output signal V1 of the echo main amplifier 10 includes the pulse signal s(t) and the noise signal n(t), in order to show the signal processing flow, an adder is used to represent the inclusion relationship between the signals in FIG. 5 . The signal x(t)=s(t)+n(t) is used as the input signal of the autocorrelation detection circuit.

One way of the input signal x(t) directly enters the multiplier, and the other way enters the multiplier after being delayed by τ by the delay circuit.

The output signal R _x (τ) is obtained after the autocorrelation operation is performed on the signal x(t) through the multiplier and the integrator.

After autocorrelation processing, the noise can be significantly suppressed, the signal can be extracted from the noise, and the signal-to-noise ratio of the system can be improved, thereby improving the ranging accuracy of the system.

Combined with Figure 4, the specific steps of automatic gain control are:

A, the first peak value sampling circuit 141 gathers the voltage signal peak value that self-correlation detection circuit 11 outputs, and this peak value is converted into digital signal V _p1 through the first A/D conversion circuit and stored in the FPGA master controller; the second peak value detection The circuit 151 collects the peak value of the voltage signal output by the preamplifier 9, converts the peak value into a digital signal V _p2 through the second A/D conversion circuit and stores it in the FPGA.

B. Set two thresholds V _H and V _L in the FPGA main controller, V _H > V _L , compare V _p1 with V _H and V _L , if V _p1 > V _H , the signal is likely to be saturated, and in the loop When the output of the APD photodetector 8 or the preamplifier 9 is saturated due to excessive wave power, the bias voltage of the APD photodetector 8 needs to be reduced to obtain a lower multiplication factor, and the peak value data V _p2 of the output signal of the preamplifier 9 and the FPGA main The threshold value V _th stored in the controller is compared, if V _p2 >V _th , adjust and reduce the bias voltage of APD photodetector 8, if V _p2 ≤ V _th , then reduce the main amplifier 10 through D/A conversion circuit feedback control Gain; if V _p1 < V _L , increase the gain of the main amplifier through the D/A conversion circuit; if V _L ≤ V _p1 ≤ V _H , keep the gain of the main amplifier unchanged.

In conjunction with Fig. 7 and Fig. 8, the shaping principle of double-threshold moment discrimination circuit 12 and the specific steps of time interval measurement are:

a. The main factor affecting the time identification is the drift error caused by the change of the echo power. After the automatic gain control module, the drift error is reduced but still exists, so the dual threshold time identification method is used to compensate the residual drift error. By establishing a drift error model, it can be seen that both the size of the drift error and the time interval between the two thresholds are related to the echo signal amplitude, so the time drift error is related to the time interval between the two thresholds.

b. The echo voltage signal V ₂ output by the auto-correlation detection circuit 11 is input to the non-inverting terminal of the first comparator MAX as a voltage signal to be compared. The input voltage of the inverting terminal is the threshold voltage and is set to V _th1 , and V _th1 is set to the minimum value at which noise will not trigger false alarms. Its value is related to the amplified voltage value and the noise voltage after autocorrelation. Environmental adjustment (-5V ~ +5V), generally set to 1/2 of V _th2 . When the voltage at the positive-phase terminal reaches the threshold voltage V _th1 , the comparator outputs a high-level signal.

c. The echo voltage signal V ₂ output by the self-correlation detection circuit 11 enters the non-inverting terminal of the second comparator MAX in another way, and is input as a voltage signal to be compared. The input voltage of the inverting terminal is the threshold voltage set to V _th2 , where V _th1 <V _th2 , V _th2 can be adjusted according to the actual situation through the potentiometer (-5V ~ +5V), generally set to the minimum signal voltage output by the amplifier circuit. When the voltage at the positive-phase terminal reaches the threshold voltage V _th2 , the comparator outputs a high-level signal.

d. The echo signal passes through V _th1 and V _th2 simultaneously to generate two stop timing digital signals, which are sent to the FPGA timing module, and two flight times t ₁ and t ₂ can be measured.

e. The main controller of the FPGA has the relationship between t ₂ -t ₁ and the time drift error Δt _error calibrated in advance through experiments. The time drift error value to be compensated is found by looking up the table, and the pulse flight time is finally calculated as:

Δt=t ₁ -Δt _error

The pulse laser ranging system echo signal processing method provided by the invention expands the system measurement range, can improve the system signal-to-noise ratio and ranging accuracy, and can also improve system integration.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other. As for the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and for the related information, please refer to the description of the method part.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. a kind of pulsed laser ranging system echo signal processing equipment characterized by comprising master controller (1), driving electricity Road (2), laser (3), optical system (4), PIN photoelectric detector (5), main twt amplifier (6), fixed threshold moment identify electricity When road (7), APD photodetector (8), preamplifier (9), main amplifier (10), Autocorrelation Detection circuit (11), dual threshold Carve discriminator circuit (12), HVB high voltage bias circuit (13), the first automatic growth control module (14), the second automatic growth control module (15) and gain adjustment module (16)；

The master controller (1), the driving circuit (2) and the laser (3) are sequentially connected, and the laser (3) generates Pulse laser through the optical system (4) light splitting afterpulse laser main wave signal enter the PIN photoelectric detector (5), institute State PIN photoelectric detector (5), the main twt amplifier (6), the fixed threshold moment discrimination circuit (7) and the main control Device (1) is sequentially connected；

Pulse laser echo-signal after the optical system (4) light splitting enters the APD photodetector (8), the APD It is photodetector (8), the preamplifier (9), the main amplifier (10), the Autocorrelation Detection circuit (11), described Double-threshold moment discriminator circuit (12) and the master controller (1) are sequentially connected；

The output end of the preamplifier (9) connects the input terminal of the second automatic growth control module (15), and described The output end of second automatic growth control module (15) connects the input terminal of the master controller (1)；

The output of the Autocorrelation Detection circuit (11) terminates the input terminal of the first automatic growth control module (14), and institute The output end for stating the first automatic growth control module (14) connects the input terminal of the master controller (1)；

The output end of the master controller (1) be separately connected the gain adjustment module (16) input terminal and the HVB high voltage bias The input terminal of circuit (13), and the output end of the gain adjustment module (16) connects the input terminal of the main amplifier (10), The output end of the HVB high voltage bias circuit (13) connects the input terminal of the APD photodetector (8).

2. a kind of pulsed laser ranging system echo signal processing equipment according to claim 1, which is characterized in that described Optical system (4) includes beam expanding lens (401), spectroscope (402), receiving lens (403) and narrow band filter (404), and pulse swashs Light is successively divided into two-way pulse laser through the beam expanding lens (401) and the spectroscope (402), and the main wave signal of pulse laser enters The PIN photoelectric detector (5), pulse laser echo-signal sequentially enter the receiving lens after measured target diffusing reflection (403) and the narrow band filter (404).

3. a kind of pulsed laser ranging system echo signal processing equipment according to claim 1, which is characterized in that described First automatic growth control module (14) includes the first peak value sample circuit (141) and the first A/D conversion circuit (142), described The output end of Autocorrelation Detection circuit (11) connects the input terminal of the first peak value sample circuit (141), first peak value The output end of sample circuit (141) connects the input terminal of the first A/D conversion circuit (142), the first A/D conversion circuit (142) output end connects the input terminal of the master controller (1)；

The second automatic growth control module (15) includes the second peak value sampling circuit (151) and the 2nd A/D conversion circuit (152), the input terminal of output end connection the second peak value sampling circuit (151) of the preamplifier (9), described second The output end of peak value sampling circuit (151) connects the input terminal of the 2nd A/D conversion circuit (152), the 2nd A/D conversion The output end of circuit (152) connects the input terminal of the master controller (1)；

The gain adjustment module (16) is D/A conversion circuit, and the output end of the master controller (1) connects the D/A conversion The input terminal of circuit, and the output end of the D/A conversion circuit connects the input terminal of the main amplifier (10).

4. a kind of pulsed laser ranging system echo signal processing equipment according to claim 1, which is characterized in that also wrap Include LED display (17) and host computer (18), the LED display (17) and the host computer (18) with the master controller (1) it connects.

5. a kind of pulsed laser ranging system echo signal processing equipment according to claim 1, which is characterized in that described Master controller (1) is FPGA master controller.

6. a kind of pulsed laser ranging system echo signal processing method, which comprises the following steps:

Step 1: after system electrification, master controller (1) generates control signal and controls driving circuit (2), the driving circuit (2) laser (3) emission pulse laser is driven；

Step 2: the pulse laser enters PIN photoelectric detector through optical system (4) light splitting afterpulse laser main wave signal (5), the main wave signal of pulse laser is converted to current signal by the PIN photoelectric detector (5), and the current signal enters main wave Amplifier (6) completes Current Voltage and converts and amplify voltage signal, and amplified voltage signal is through the fixed threshold moment The shaping of discriminator circuit (7) obtains the digital signal at pulse laser emission moment, which enters described-master controller (1) the initial time start in as time interval measurement；

Step 3: the pulse laser echo-signal after the optical system (4) light splitting enters APD photodetector (8), described The road pulse laser echo-signal is converted to current signal by APD photodetector (8), and the current signal enters preceding storing Big device (9) completes Current Voltage and converts and voltage signal is amplified to the voltage signal V met the requirements；

The voltage signal V divides two-way to be exported, exported all the way to main amplifier (10) be further amplified to obtain meet it is subsequent The voltage signal V that processing of circuit requires₁, another output to the second automatic growth control module (15)；

Digital signal V is obtained through the second automatic growth control module (15)_p2And be stored in described-master controller (1), and With the threshold value V of described-master controller (1) setting_thIt is compared, and comparison result is fed back into gain adjustment module (16) or height It presses in biasing circuit (13)；

The voltage signal V₁Into Autocorrelation Detection circuit (11), high s/n ratio voltage signal V is exported after auto-correlation processing₂；

Step 4: the high s/n ratio voltage signal V₂Divide two-way output, enters the first automatic growth control module (14) all the way and obtain To digital signal V_p1And it is stored in the master controller (1), and two threshold value V with the master controller (1) setting_HAnd V_L It is compared, V_H>V_L, and comparison result is fed back into the gain adjustment module (16)；

Another way enters Double-threshold moment discriminator circuit (12) and two echo moment distinguishing signals of generation is sent into main control Stop signal stop1 and stop2 of the device (1) as time interval measurement；

Step 5: the master controller (1) measures the time between start and stop1 using FPGA delay line interpolation method respectively It is spaced t₁, time interval t between start and stop2₂, and measurement result is analyzed and processed, calculate pulse laser flight Time Δ t obtains tested distance S using the pulse laser flight time Δ t.

7. a kind of pulsed laser ranging system echo signal processing method according to claim 6, which is characterized in that described Optical system (4) includes beam expanding lens (401), spectroscope (402), receiving lens (403) and narrow band filter (404), and pulse swashs Light reduces the angle of divergence by the beam expanding lens (401) and is divided into two-way pulse laser, the pulse by the spectroscope (402) Laser main wave signal enter the PIN photoelectric detector (5), pulse laser echo-signal after measured target diffusing reflection successively into Enter the receiving lens (403) and the narrow band filter (404), wherein pulse of the receiving lens (403) to receiving Laser echo signal is focused, and the narrow band filter (404) is filtered pulse laser echo-signal.

8. a kind of pulsed laser ranging system echo signal processing method according to claim 7, which is characterized in that described First automatic growth control module (14) includes the first peak value sample circuit (141) and the first A/D conversion circuit (142), described First peak value sample circuit (141) acquires the output signal peak value of the Autocorrelation Detection circuit (11) and is transferred to described first A/D conversion circuit (142), the first A/D conversion circuit (142) are converted into digital signal V_p1, and it is sent to the master Controller (1)；

The second automatic growth control module (15) includes the second peak value sampling circuit (151) and the 2nd A/D conversion circuit (152), the second peak value sampling circuit (151) acquires the output signal peak value of the preamplifier (9) and is transferred to institute The 2nd A/D conversion circuit (152) is stated, the 2nd A/D conversion circuit (152) is converted into digital signal V_p2, and be sent to The master controller (1)；

The gain adjustment module (16) is D/A conversion circuit, and the D/A conversion circuit is for automatically controlling the main amplifier (10) gain.

9. a kind of pulsed laser ranging system echo signal processing method according to claim 8, which is characterized in that described The specific steps of D/A conversion circuit progress automatic growth control are as follows:

A, by the digital signal V_p1With two threshold value V of the master controller (1) setting_HAnd V_LIt is compared, V_H>V_LIf V_p1 <V_L, then increase the gain of the main amplifier (10) by the D/A conversion circuit, if V_L≤V_p1≤V_H, then the master is kept The gain of amplifier (10) is constant；

B, by digital signal V_p2With the threshold value V of the master controller (1) setting_thIt is compared, if V_p1>V_H, and V_p2>V_th, then lead to Crossing the HVB high voltage bias circuit (13) reduces the bias of the APD photodetector (8), if V_p1>V_H, and V_p2≤V_th, then pass through The D/A conversion circuit reduces the gain of main amplifier (10).

10. a kind of pulsed laser ranging system echo signal processing method according to claim 6, which is characterized in that institute Stating master controller (1) is FPGA master controller, compensates error using calibration curve, calculates pulse laser flight time Δ t:

Δ t=t₁-Δt_error (1)

Wherein, Δ t_errorIndicate time drift error；

Tested distance S is obtained using the pulse laser flight time Δ t:

S=c Δ t/2 (2)

Wherein, c is the light velocity in vacuum；

The tested distance S carries out LED using LED display (17) and shows, and carries out data preservation by host computer (18).