Laser scanning system and nonlinear correction method

Abstract

The embodiment of the invention discloses a laser scanning system and a nonlinear correction method, the system comprises a laser emission and control module, a scanning device, a receiving device and a signal processing module, an initial first beat signal is obtained, and a direct current signal and a high-frequency signal in the first beat signal are removed, so that the nonlinear correction of the laser scanning system is realized. A second beat signal with the direct current signal and the high-frequency signal removed is obtained, the target voltage of the second beat signal is calculated according to the input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal, a new beat signal is output based on the target voltage, and the target beat signal with the frequency being the preset target frequency is obtained; wherein the target frequency and the time form a linear relation. And the frequency of the beat signal is controlled by controlling the input voltage, so that the frequency of the output beat signal and the time form a linear relation.

Description

Technical Field

[0001] The present invention relates to the technical field of laser signal processing, and in particular to a laser scanning system and a nonlinear correction method. Background Art

[0002] Generally, the distance can be measured by laser. Specifically, the difference between the laser's emitted light (emission signal) and reflected light (echo signal) on the target object is calculated to obtain a beat signal. The distance of the target object can be calculated based on the frequency of the beat signal.

[0003] Ideally, the frequency and time of the beat signal output by the laser are in a linear relationship. However, due to the influence of external factors (such as temperature), the frequency and time of the beat signal will be in a nonlinear relationship, which will reduce the accuracy of ranging. In the prior art, the frequency of the beat signal can be adjusted by current tuning, but theoretical analysis shows that the relationship between the injected current and the output wavelength is a linear relationship, while the laser wavelength is inversely proportional to the frequency. Therefore, even if a linear current is injected, a linear frequency modulated laser cannot be obtained. On the other hand, the temperature changes during the current tuning process, which affects the output frequency.

[0004] Therefore, a method is needed to correct the frequency of the beat signal so that the frequency of the output beat signal is in a linear relationship with time. Summary of the invention

[0005] The main purpose of the present invention is to provide a laser scanning system, a nonlinear correction method, a computer device and a storage medium, which can solve the frequency and time nonlinearity problems of the beat signal in the prior art.

[0006] To achieve the above-mentioned object, the first aspect of the present invention provides a laser scanning system, the system comprising a laser emission and control module, a scanning device, a receiving device and a signal processing module;

[0007] The laser emission and control module is used to obtain target waveform data and output a target waveform signal corresponding to the target waveform data as an optical signal; wherein the target waveform data is waveform data corresponding to a preset input voltage;

[0008] The scanning device is connected to the laser emission and control module, and the scanning device is used to emit a light signal to a target irradiation object to form an emission light;

[0009] The receiving device is connected to the scanning device and is used to receive the echo signal, calculate the difference between the transmission signal and the echo signal, and obtain the beat signal;

[0010] The signal processing device is connected to the receiving device, and is used to receive the beat signal, obtain an initial first beat signal, and obtain a frequency spectrum of the first beat signal, and remove a DC current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the DC current signal and the high-frequency signal are removed; obtain an input voltage corresponding to the first beat signal, and obtain an instantaneous frequency of the second beat signal, and calculate a target voltage of the second beat signal according to the instantaneous frequency and the input voltage;

[0011] The signal processing device is connected to the laser emission and control module, and is used to output a target voltage to the laser emission and control module; the laser emission and control module is also used to output an optical signal based on the target voltage;

[0012] The signal processing device is used to output a target beat signal based on the target voltage to obtain a linear time-frequency curve; wherein the target beat signal is a beat signal with a frequency of a preset target frequency, and the target frequency is linearly related to time.

[0013] In combination with the first aspect, in a possible implementation, the laser emission and control module includes a waveform generator; the waveform generator includes an FPGA;

[0014] A phase accumulator is provided in the FPGA, and the FPGA is used to store preset waveform data and establish a corresponding relationship between the waveform data and the corresponding read address to obtain a lookup table; according to the read address output by the phase accumulator, the waveform data corresponding to the read address is obtained from the lookup table to obtain the target waveform data.

[0015] In combination with the first aspect, in a possible implementation, the laser emission and control module 101 further includes a laser; the waveform generator further includes a digital-to-analog converter, a filter, and a post-stage amplifier;

[0016] The digital-to-analog converter is connected to the FPGA, the FPGA is used to output the target waveform data to the digital-to-analog converter as an initial waveform signal, and the digital-to-analog converter is used to receive the initial waveform signal output by the FPGA, convert the initial waveform signal into an analog signal, and output the analog signal;

[0017] The filter is connected to the digital-to-analog converter, and is used to receive the analog signal output by the digital-to-analog converter, and perform smoothing and filtering on the analog signal to obtain a target analog signal after the smoothing and filtering, and output the target analog signal;

[0018] The post-stage amplifier is connected to the filter, and is used to receive the target analog signal output by the filter, perform voltage amplification processing on the target analog signal, obtain a final target signal, and output the target signal;

[0019] The laser is connected to the post-stage amplifier and is used for receiving a target signal and outputting an optical signal.

[0020] In combination with the first aspect, in a possible implementation, the laser emission and control module is also used to control the deflection of a scanning device, and the scanning device is used to emit the light signal at a current angle after deflection to the target object to form emitted light.

[0021] In combination with the first aspect, in a possible implementation manner, the scanning device includes a transverse X-axis scanning device and a longitudinal Y-axis scanning device;

[0022] The transverse X-axis scanning device and the longitudinal Y-axis scanning device are respectively connected to the FPGA;

[0023] The FPGA is used to control the transverse X-axis scanning device to deflect the first fixed angle multiple times; the scanning device is used to transmit the optical signal based on the current angle after each deflection of the transverse X-axis scanning device by the first fixed angle, to form the emission light, so as to complete the transverse scanning of the target irradiation object;

[0024] The FPGA is also used to control the longitudinal Y-axis scanning device to deflect by a second fixed angle after the scanning device has completed transverse scanning of the target irradiated object, and return to execute the step of controlling the transverse X-axis scanning device to deflect by the first fixed angle multiple times, so as to control the scanning device to emit light signals based on the current angle after each transverse X-axis scanning device deflects by the first fixed angle after the longitudinal Y-axis scanning device has deflected by the second fixed angle, to form emission light, until the transverse scanning of the target irradiated object is completed;

[0025] If the target object has not been scanned completely, the FPGA is further used to return to execute the step of controlling the longitudinal Y-axis scanning device to deflect by a second fixed angle after the scanning device has completed the transverse scanning of the target object, until the target object has been scanned completely.

[0026] In combination with the first aspect, in a possible implementation, the signal processing module is used to determine whether the instantaneous frequency of the second beat signal reaches a preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, the second beat signal is output to obtain a target beat signal with a frequency of the preset target frequency; if the instantaneous frequency of the second beat signal does not reach the preset target frequency, the initial voltage is calculated according to the instantaneous frequency and the input voltage, and a third beat signal is obtained after the initial voltage is used as the input voltage of the laser emission and control module, and the DC current signal and the high-frequency signal in the third beat signal are removed based on the frequency spectrum of the third beat signal to obtain a fourth beat signal after the DC current signal and the high-frequency signal are removed; the third beat signal is used as the first beat signal and the fourth beat signal is used as the second beat signal, and the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency is returned.

[0027] To achieve the above object, the second aspect of the present invention provides a nonlinear correction method, the method comprising:

[0028] Acquire an initial first beat signal, and acquire a frequency spectrum of the first beat signal, and remove a direct current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the direct current signal and the high-frequency signal are removed;

[0029] Obtain the input voltage corresponding to the first beat signal, and obtain the instantaneous frequency of the second beat signal, and determine whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, output the second beat signal to obtain a target beat signal with a frequency of the preset target frequency; if the frequency of the second beat signal does not reach the preset target frequency, calculate the target voltage according to the instantaneous frequency and the input voltage, output a new beat signal based on the target voltage, and obtain a target beat signal with a frequency of the preset target frequency; wherein the target frequency is linearly related to time.

[0030] In combination with the second aspect, in a possible implementation manner, the target voltage is calculated according to the instantaneous frequency and the input voltage, and a beat signal is output based on the target voltage to obtain a target beat signal having a frequency that is a preset target frequency, including:

[0031] Calculating an initial voltage according to the instantaneous frequency and the input voltage, obtaining a third beat signal obtained by taking the initial voltage as the input voltage of the laser emission and control module, and removing a DC current signal and a high-frequency signal from the third beat signal based on a frequency spectrum of the third beat signal to obtain a fourth beat signal after removing the DC current signal and the high-frequency signal;

[0032] The third beat signal is used as the first beat signal and the fourth beat signal is used as the second beat signal, and the step of returning to determine whether the instantaneous frequency of the second beat signal reaches a preset target frequency is executed.

[0033] In conjunction with the second aspect, in a possible implementation manner, the removing of the DC current signal and the high-frequency signal in the first beat signal based on the spectrum diagram includes:

[0034] Based on the spectrum diagram, a direct current signal reaching a first frequency and a high-frequency signal reaching a second frequency in the first beat signal are searched, and a bandpass filter is used to filter out the direct current signal with the first frequency and the high-frequency signal with the second frequency.

[0035] In conjunction with the second aspect, in a possible implementation manner, the calculation formula for calculating the initial voltage according to the instantaneous frequency and the input voltage is:

[0036]

[0037] Among them, U2 represents the initial voltage, a represents the frequency modulation rate, r represents the transmission delay, f represents the instantaneous frequency of the second beat signal, and U1 represents the input voltage.

[0038] To achieve the above object, the third aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor performs the following steps:

[0039] Acquire an initial first beat signal, and acquire a frequency spectrum of the first beat signal, and remove a direct current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the direct current signal and the high-frequency signal are removed;

[0040] Obtain the input voltage corresponding to the first beat signal, and obtain the instantaneous frequency of the second beat signal, and determine whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, output the second beat signal to obtain a target beat signal with a frequency of the preset target frequency; if the frequency of the second beat signal does not reach the preset target frequency, calculate the target voltage according to the instantaneous frequency and the input voltage, output a new beat signal based on the target voltage, and obtain a target beat signal with a frequency of the preset target frequency; wherein the target frequency is linearly related to time.

[0041] To achieve the above object, a fourth aspect of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0042] Acquire an initial first beat signal, and acquire a frequency spectrum of the first beat signal, and remove a direct current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the direct current signal and the high-frequency signal are removed;

[0043] Obtain the input voltage corresponding to the first beat signal, and obtain the instantaneous frequency of the second beat signal, and determine whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, output the second beat signal to obtain a target beat signal with a frequency of the preset target frequency; if the frequency of the second beat signal does not reach the preset target frequency, calculate the target voltage according to the instantaneous frequency and the input voltage, output a new beat signal based on the target voltage, and obtain a target beat signal with a frequency of the preset target frequency; wherein the target frequency is linearly related to time.

[0044] The embodiments of the present invention have the following beneficial effects:

[0045] The present invention provides a laser scanning system, which obtains an initial first beat signal and a spectrum diagram of the first beat signal, removes a DC current signal and a high-frequency signal from the first beat signal based on the spectrum diagram, obtains a second beat signal after the DC current signal and the high-frequency signal are removed, obtains an input voltage corresponding to the first beat signal, and obtains an instantaneous frequency of the second beat signal, calculates a target voltage of the second beat signal according to the instantaneous frequency and the input voltage, outputs a new beat signal based on the target voltage, and obtains a target beat signal with a frequency of a preset target frequency; wherein the target frequency is linearly related to time. The frequency of the beat signal is controlled by controlling the input voltage, so that the frequency of the output beat signal is linearly related to time. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] in:

[0048] Figure 1 is a structural block diagram of a laser scanning system in an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of a receiving device in an embodiment of the present invention;

[0050] Figure 3 Schematic diagram of a flow chart of a nonlinear correction method in an embodiment of the present invention;

[0051] Figure 4 A beat signal processing flow chart according to an embodiment of the present invention;

[0052] Figure 5 4 is a structural block diagram of a computer device in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] The embodiment of the present invention provides a laser scanning system, referring to Figure 1 , Figure 1 A structural block diagram of a laser scanning system provided by an embodiment of the present invention, such as Figure 1As shown, the system 10 includes a laser emission and control module 101, a scanning device 102, a receiving device 103 and a signal processing module 104. The laser emission and control module 101 is used to control laser emission, the scanning device 102 is used to control the direction of laser incidence and emission, and the receiving device 103 is used to preprocess the laser echo signal, wherein the preprocessing may include sampling, circuit amplification, filtering, analog-to-digital conversion, etc., and the difference between the preprocessed echo signal and the emission signal is calculated to obtain a beat signal. The signal processing device 104 is used to analyze the beat signal to achieve nonlinear correction of the beat signal frequency. Specifically, the signal processing device 104 obtains the beat signal, adjusts the input voltage of the beat signal, and outputs the beat signal with a target frequency, so as to achieve a linear relationship between the time-frequency curve of the beat signal, wherein the time-frequency curve is a curve of the relationship between the beat signal frequency and time.

[0055] Specifically, the laser emission and control module 101 is connected to the scanning device 102 , the scanning device 102 is connected to the receiving device 103 , the receiving device 103 is connected to the signal processing module 104 , and the signal processing module 104 is connected to the laser emission and control module 101 .

[0056] The laser emission and control module 101 is used to obtain target waveform data, and output the target waveform signal corresponding to the target waveform data as an optical signal, wherein the target waveform data is waveform data corresponding to a preset input voltage. Specifically, the laser emission and control module 101 is used to establish a corresponding relationship between the waveform data and the corresponding read address, and obtain a lookup table; wherein the waveform data represents the amplitude value of the waveform, and the waveform data is the waveform data corresponding to the input voltage of the laser emission and control module 101, which is equivalent to establishing a corresponding relationship between the preset input voltage and the corresponding read address; based on the lookup table, the corresponding waveform data is obtained according to the read address to obtain the target waveform data, and the target waveform signal corresponding to the target waveform data is output as an optical signal to the scanning device 102.

[0057] The laser emission and control module 101 includes a waveform generator 21 and a laser 22. The waveform generator 21 includes an FPGA 201, a digital-to-analog converter 202 (DAC), a filter 203, and a post-amplifier 204. The waveform generator outputs a specific waveform to drive the laser and control the scanning device 102. The waveform generator can be a DDS waveform generator.

[0058] A phase accumulator 23 is provided in FPGA 201. FPGA 201 is used to store preset waveform data, and establish a corresponding relationship between the waveform data and the corresponding read address to obtain a lookup table. According to the read address output by the phase accumulator, the waveform data corresponding to the read address is obtained from the lookup table to obtain the target waveform data. Specifically, the waveform data can be a triangular wave. FPGA 201 executes a direct digital frequency synthesis algorithm according to the frequency and waveform of the periodic signal, and reads the memory in FPGA 201 in a loop table with a frequency control word to output the corresponding waveform data to the DAC circuit. Specifically, firstly, the preset waveform data is generated by the host computer matlab and stored in the random access memory ram, wherein the preset waveform data can be the required waveform data, and the core of the DDS waveform generator is the phase accumulator, which is accumulated according to the frequency control word (Frequency ControlWord, FCW) in each clock cycle, thereby changing the read address of the waveform data, and the waveform data has a corresponding relationship with the read address, therefore, the waveform data can be established with the corresponding read address to obtain a lookup table. Among them, the reading speed of waveform data can be controlled by changing the value of FCW, thereby realizing frequency adjustment. According to the reading address output by the phase accumulator, the corresponding waveform data is read from the lookup table. These waveform data are digital and represent the amplitude value of the waveform at a certain moment.

[0059] The digital-to-analog converter 202 is connected to the FPGA 201. The FPGA 201 is used to output the target waveform data as an initial waveform signal to the digital-to-analog converter 202. The digital-to-analog converter 202 is used to receive the initial waveform signal output by the FPGA, convert the initial waveform signal into an analog signal, and output the analog signal.

[0060] The filter 203 is connected to the digital-to-analog converter 202, and is used to receive the analog signal output by the digital-to-analog converter 202, and performs smoothing and filtering on the analog signal to obtain the target analog signal after smoothing and filtering, and output the target analog signal. The post-stage amplifier 204 is connected to the filter 203, and is used to receive the target analog signal output by the filter 203, and performs voltage amplification processing on the target analog signal to obtain the final target signal. The analog signal converted by the digital-to-analog converter may contain high-frequency noise and stray components, and needs to be smoothed and filtered by the filter. The analog signal after filtering is amplified by the post-stage amplifier circuit, and the voltage amplitude is adjusted to obtain the final output waveform signal.

[0061] The post-amplifier 204 is connected to the laser 22 , and the waveform generator 21 outputs the target signal to the laser 22 to drive the laser 22 to output the optical signal. The waveform generator 21 inputs the waveform signal finally output to the laser to make the laser output the optical signal to the scanning device 102 .

[0062] The scanning device is connected to the laser emission and control module, and the scanning device is used to emit the light signal to the target object to form the emission light. Specifically, the laser emission and control module controls the deflection of the scanning device, and the scanning device emits the light signal to the target object at the current angle after deflection to form the emission light.

[0063] The scanning device 102 includes a transverse X-axis scanning device 31 and a longitudinal Y-axis scanning device 32, wherein the X-axis scanning device is responsible for scanning in the horizontal direction, and the longitudinal Y-axis scanning device is responsible for scanning in the vertical direction. The scanning device can be a combination of a rotating polygonal mirror (for X-axis scanning) and a Y-axis galvanometer, or a combination of an X-axis galvanometer and a rotating polygonal mirror (for Y-axis scanning), or a combination of two galvanometers (X-axis galvanometer and Y-axis galvanometer). The rotating polygonal mirror and the galvanometer can be driven by a motor, which can be used as a driving motor to drive the rotating polygonal mirror and the galvanometer for high-speed scanning. The driving motor can be implemented by a control algorithm.

[0064] The laser emission and control module 101 is connected to the scanning device 102. Specifically, the transverse X-axis scanning device and the longitudinal Y-axis scanning device are respectively connected to the FPGA. The FPGA is used to control the transverse X-axis scanning device to deflect the first fixed angle multiple times. The scanning device is used to emit a light signal based on the current angle after each deflection of the transverse X-axis scanning device by the first fixed angle to form an emission light, so as to complete the transverse scanning of the target object. In a possible implementation, during the initial scanning, the FPGA outputs a first fixed voltage to the transverse X-axis scanning device to control the transverse X-axis scanning device to deflect the first fixed angle. The scanning device emits a light signal based on the current angle after the transverse X-axis scanning device deflects the first fixed angle to form an emission light. Then, the FPGA outputs a first fixed voltage to the transverse X-axis scanning device to control the transverse X-axis scanning device to deflect the first fixed angle again. The scanning device again emits a light signal based on the current angle after the transverse X-axis scanning device deflects the first fixed angle to form an emission light, and so on, until a transverse scanning of the target object is completed.

[0065] The FPGA is also used to control the longitudinal Y-axis scanning device to deflect the second fixed angle after the scanning device has completed the transverse scanning of the target irradiated object, and return to execute the step of controlling the transverse X-axis scanning device to deflect the first fixed angle multiple times, so as to control the scanning device to emit the light signal based on the current angle after each transverse X-axis scanning device deflects the first fixed angle after the longitudinal Y-axis scanning device deflects the second fixed angle, to form the emission light, until the transverse scanning of the target irradiated object is completed. When the scanning device completes the transverse scanning of the target irradiated object once, the FPGA outputs the second fixed voltage to the longitudinal Y-axis scanning device to control the longitudinal Y-axis scanning device to deflect the second fixed angle, and based on the longitudinal Y-axis scanning device deflecting the second fixed angle, the FPGA outputs the first fixed voltage to the transverse X-axis scanning device multiple times to control the transverse X-axis scanning device to deflect the first fixed angle, and the scanning device emits the light signal based on the current angle after each transverse X-axis scanning device deflects the first fixed angle, to form the emission light, until the transverse scanning of the target irradiated object is completed again.

[0066] If the target object has not been scanned completely at this time, the FPGA is also used to return to execute the step of controlling the longitudinal Y-axis scanning device to deflect by a second fixed angle after the scanning device has completed the horizontal scanning of the target object, until the target object is scanned completely.

[0067] For example, when the target object is scanned from top to bottom, at the beginning, the horizontal X-axis scanning device first scans horizontally from the leftmost end of the target object to the rightmost end. After one horizontal scan is completed, when the lowermost end of the target object has not been scanned (that is, the entire target object has not been scanned), the vertical Y-axis scanning device deflects downward by a second fixed angle, and the horizontal X-axis scanning device scans horizontally from the rightmost end of the target object to the leftmost end, and so on, to scan the entire target object.

[0068] The scanning device 102 is connected to the receiving device 103, and the receiving device is connected to the scanning device, and is used to receive the echo signal, calculate the difference between the transmission signal and the echo signal, and obtain the beat signal. Specifically, the receiving device 103 is used to receive the reflected light corresponding to the transmission light, to receive the echo signal corresponding to the transmission signal, and to pre-process the echo signal, calculate the difference between the pre-processed echo signal and the transmission signal, and obtain the beat signal. Figure 2 , Figure 2A schematic diagram of a receiving device provided in an embodiment of the present invention, the receiving device 103 may include a Mach Zehnder interferometer and a balanced detector, one end of the Mach Zehnder interferometer is connected to the scanning device 102, and the other end of the Mach Zehnder interferometer is connected to the balanced detector, the Mach Zehnder interferometer includes an optical fiber and a coupler, the optical fiber is connected to the coupler, the optical fiber is used to transmit an echo signal, the coupler is used to receive the echo signal and a transmission signal corresponding to the echo signal, and output the echo signal and the transmission signal corresponding to the echo signal to the balanced detector, the balanced detector is used to preprocess the echo signal, calculate the difference between the preprocessed echo signal and the transmission signal, and obtain a beat signal.

[0069] In addition, the system also includes a data acquisition card ADC, which is connected to the FPGA and the receiving device 103 respectively. When the FPGA outputs a preset fixed voltage to the horizontal X-axis scanning device, the FPGA sends a trigger signal to the ADC to enable the ADC to collect the beat signal received by the receiving device 103. In this way, the deflection angle corresponding to each collected data can be accurately known to achieve synchronization of laser distance and angle.

[0070] The signal processing device 104 is connected to a data acquisition card (ADC) to obtain the beat signal collected in the ADC to obtain an initial first beat signal. In a possible design, the system further includes a photodetector 105, and the receiving device 103 is also connected to the photodetector 105. The receiving device 103 outputs the beat signal to the photodetector 105, and the photodetector converts the beat signal from an optical signal to an electrical signal. The photodetector 105 is connected to the ADC, and the photodetector 105 outputs the beat signal, which is an electrical signal, to the ADC. The signal processing device 104 can be a computer (PC).

[0071] The signal processing device 104 is also used to obtain a spectrum diagram of the first beat signal, and remove the DC current signal and the high-frequency signal in the first beat signal based on the spectrum diagram to obtain a second beat signal after the DC current signal and the high-frequency signal are removed. Specifically, the spectrum diagram of the first beat signal can be obtained by performing Fourier transform on the first beat signal, and the DC current signal reaching the first frequency and the high-frequency signal reaching the second frequency in the first beat signal can be searched based on the spectrum diagram, and the DC current signal with the first frequency and the high-frequency signal with the second frequency can be filtered out using a bandpass filter.

[0072] The signal processing device 104 is also used to obtain the input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal, calculate the target voltage of the second beat signal according to the instantaneous frequency and the input voltage, output the target beat signal based on the target voltage, and obtain a linear time-frequency curve. Specifically, it is determined whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, the second beat signal is output, and the target beat signal with the preset target frequency can be directly obtained. If the instantaneous frequency of the second beat signal does not reach the preset target frequency, the initial voltage is calculated according to the instantaneous frequency and the input voltage, and the initial voltage is output to the laser emission and control module as a new input voltage of the laser emission and control module. The laser emission and control module outputs an optical signal based on the initial voltage, so that the signal processing device can obtain a third beat signal obtained after taking the initial voltage as the input voltage of the laser emission and control module, remove the DC current signal and the high-frequency signal in the third beat signal based on the frequency spectrum of the third beat signal, and obtain a fourth beat signal after removing the DC current signal and the high-frequency signal, and judge the obtained new fourth beat signal, that is, take the third beat signal as the first beat signal and the fourth beat signal as the second beat signal, and return to execute the step of judging whether the instantaneous frequency of the second beat signal reaches the preset target frequency.

[0073] If the frequency of the second beat signal output based on the initial voltage does not reach the preset target frequency, the initial voltage is used as the new input voltage and iterated continuously. It can be seen that the target voltage is the input voltage that can make the instantaneous frequency of the output second beat signal reach the preset target frequency.

[0074] The calculation formula for calculating the initial voltage according to the instantaneous frequency and the input voltage may be:

[0075]

[0076] Among them, U2 represents the initial voltage, a represents the frequency modulation rate, r represents the transmission delay, f represents the instantaneous frequency of the second beat signal, and U1 represents the input voltage.

[0077] Specifically, the signal processing device is connected to the laser emission and control module, wherein the signal processing device can be specifically connected to the FPGA. First, after the signal processing device calculates the initial voltage corresponding to the second beat signal, the initial voltage is output to the FPGA of the laser emission and control module. The laser emission and control module is also used to output the optical signal based on the initial voltage. Similarly, the signal processing device collects the beat signal preprocessed by the receiving device again, and determines whether the frequency of the beat signal output based on the initial voltage reaches the preset target frequency. If the frequency of the beat signal output based on the initial voltage does not reach the preset target frequency, the initial voltage is used as the input voltage corresponding to the first beat signal, and the initial voltage is calculated again. Return to the step of outputting the initial voltage to the FPGA of the laser emission and control module until the frequency of the beat signal output based on the initial voltage reaches the preset target frequency, and the target beat signal is output, and the corresponding initial voltage at this time is the target voltage. Wherein, the target beat signal is a beat signal with a frequency of the preset target frequency, and the target frequency is linearly related to time.

[0078] The signal processing device 104 receives the beat signal as an electrical signal, and processes the obtained beat signal data using the Newton secant method and matlab, and continuously iterates the input voltage to make the frequency of the output beat signal close to a certain fixed value. First, the spectrum of the beat signal is determined by Fourier transform, and then the DC bias and high-frequency signal of the beat signal are filtered out by bandpass filtering, and then the beat signal is Hilbert transformed to solve the instantaneous frequency of the beat signal, and then the noise is removed by smoothing filtering to obtain a smooth instantaneous frequency, and then the iterative algorithm formula is used to solve the iterative input voltage. At the same time, the iterative input voltage can also be downsampled to meet the storage size of the memory RAM.

[0079] Based on the above system, the frequency of the beat signal is controlled by controlling the input voltage, so that the frequency of the output beat signal is a target frequency that is linearly related to time, so as to correct the nonlinearity of the time-frequency curve and ensure that the output time-frequency curve is a linear relationship. The system achieves the purpose of correcting the nonlinearity of the output beat signal and controls the deflection scanning of the scanning device at the same time.

[0080] Based on the above system, the embodiment of the present invention further provides a nonlinear correction method, referring to Figure 2 , Figure 3 A flow chart of a nonlinear correction method provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, the specific steps of this method are as follows:

[0081] Step S101, obtaining an initial first beat signal, and obtaining a frequency spectrum of the first beat signal, and removing a DC current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after removing the DC current signal and the high-frequency signal.

[0082] Step S102, obtain the input voltage corresponding to the first beat signal, and obtain the instantaneous frequency of the second beat signal, and determine whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, output the second beat signal to obtain a target beat signal with a frequency of the preset target frequency; if the frequency of the second beat signal does not reach the preset target frequency, calculate the target voltage according to the instantaneous frequency and the input voltage, output a new beat signal based on the target voltage, and obtain a target beat signal with a frequency of the preset target frequency.

[0083] Among them, the target frequency is linearly related to time.

[0084] Reference Figure 4 , Figure 4 A beat signal processing flow chart provided by an embodiment of the present invention, such as Figure 4 shown.

[0085] First, an initial first beat signal M is obtained, and a frequency spectrum diagram of the first beat signal M is obtained. Specifically, the frequency spectrum diagram of the first beat signal M is obtained by performing Fourier transform on the first beat signal M.

[0086] Based on the spectrum diagram, the DC current signal and the high-frequency signal in the first beat signal are removed to obtain the second beat signal after the DC current signal and the high-frequency signal are removed. Specifically, based on the spectrum diagram, the DC current signal reaching the preset first frequency and the high-frequency signal reaching the preset second frequency in the first beat signal are searched, and the DC current signal with the first frequency and the high-frequency signal with the second frequency are filtered out by a bandpass filter.

[0087] The input voltage corresponding to the first beat signal is obtained, and the second beat signal is subjected to Hilbert transform to solve the instantaneous frequency of the second beat signal, and then the instantaneous frequency is subjected to smoothing filtering to remove noise and obtain a smooth instantaneous frequency.

[0088] The target voltage is calculated according to the instantaneous frequency and the input voltage, and a new beat signal is output based on the target voltage to obtain a target beat signal with a frequency of a preset target frequency. Specifically, as shown in step S201-step S202:

[0089] Step S201, calculate the initial voltage according to the instantaneous frequency and the input voltage, obtain the third beat signal after taking the initial voltage as the input voltage of the laser emission and control module, remove the DC current signal and the high-frequency signal in the third beat signal based on the spectrum diagram of the third beat signal, and obtain the fourth beat signal after removing the DC current signal and the high-frequency signal.

[0090] Step S202: use the third beat signal as the first beat signal and the fourth beat signal as the second beat signal, and return to the step of determining whether the instantaneous frequency of the second beat signal reaches a preset target frequency.

[0091] The calculation formula for calculating the initial voltage according to the instantaneous frequency and the input voltage can be:

[0092]

[0093] Among them, U2 represents the initial voltage, a represents the frequency modulation rate, r represents the transmission delay, f represents the instantaneous frequency of the second beat signal, and U1 represents the input voltage.

[0094] A third beat signal is obtained after taking the initial voltage as the input voltage of the laser emission and control module, and the DC current signal and the high-frequency signal in the third beat signal are removed based on the spectrum diagram of the third beat signal to obtain a fourth beat signal after removing the DC current signal and the high-frequency signal, and the instantaneous frequency of the fourth beat signal is obtained, and it is determined whether the instantaneous frequency of the fourth beat signal reaches the preset target frequency. If the instantaneous frequency of the fourth beat signal output based on the initial voltage does not reach the preset target frequency, a new initial voltage is recalculated according to the instantaneous frequency of the fourth beat signal and the input voltage corresponding to the third beat signal, that is, the third beat signal is used as the first beat signal and the fourth beat signal is used as the second beat signal, and the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency is returned to execute, and the input voltage is iteratively calculated so that the initial voltage at which the frequency of the output beat signal reaches the preset target frequency is the target voltage.

[0095] In a possible implementation, the input voltage may be downsampled before the initial voltage is used as the new input voltage.

[0096] Based on the above method, the frequency of the beat signal can be controlled by controlling the input voltage, so that the frequency of the output beat signal is in a linear relationship with time.

[0097] Figure 5 FIG. 1 shows an internal structure diagram of a computer device in an embodiment. The computer device may be a terminal or a server. Figure 5As shown, the computer device includes a processor, a memory and a network interface connected via a system bus. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor can implement all the steps of the above method. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement all the steps of the above method. Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0098] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes each step of the aforementioned method.

[0099] In one embodiment, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, the processor executes each step of the aforementioned method.

[0100] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0101] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A laser scanning system, characterized in that: The system includes a laser emission and control module, a scanning device, a receiving device and a signal processing module; The laser emission and control module is used to obtain target waveform data and output a target waveform signal corresponding to the target waveform data as an optical signal; wherein the target waveform data is waveform data corresponding to a preset input voltage; The scanning device is connected to the laser emission and control module, and the scanning device is used to emit a light signal to a target irradiation object to form an emission light; The receiving device is connected to the scanning device and is used to receive the echo signal, calculate the difference between the transmission signal and the echo signal, and obtain the beat signal; The signal processing device is connected to the receiving device, and is used to receive the beat signal, obtain an initial first beat signal, and obtain a frequency spectrum of the first beat signal, and remove a DC current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the DC current signal and the high-frequency signal are removed; obtain an input voltage corresponding to the first beat signal, and obtain an instantaneous frequency of the second beat signal, and calculate a target voltage of the second beat signal according to the instantaneous frequency and the input voltage; The signal processing device is connected to the laser emission and control module, and is used to output a target voltage to the laser emission and control module; the laser emission and control module is also used to output an optical signal based on the target voltage; The signal processing device is used to output a target beat signal based on the target voltage to obtain a linear time-frequency curve; wherein the target beat signal is a beat signal with a frequency of a preset target frequency, and the target frequency is linearly related to time.

2. The system according to claim 1, characterized in that The laser emission and control module includes a waveform generator; the waveform generator includes an FPGA; A phase accumulator is provided in the FPGA, and the FPGA is used to store preset waveform data and establish a corresponding relationship between the waveform data and the corresponding read address to obtain a lookup table; according to the read address output by the phase accumulator, the waveform data corresponding to the read address is obtained from the lookup table to obtain the target waveform data.

3. The system according to claim 1, characterized in that The laser emission and control module 101 also includes a laser; the waveform generator also includes a digital-to-analog converter, a filter and a post-stage amplifier; The digital-to-analog converter is connected to the FPGA, the FPGA is used to output the target waveform data to the digital-to-analog converter as an initial waveform signal, and the digital-to-analog converter is used to receive the initial waveform signal output by the FPGA, convert the initial waveform signal into an analog signal, and output the analog signal; The filter is connected to the digital-to-analog converter, and is used to receive the analog signal output by the digital-to-analog converter, and perform smoothing and filtering on the analog signal to obtain a target analog signal after the smoothing and filtering, and output the target analog signal; The post-stage amplifier is connected to the filter, and is used to receive the target analog signal output by the filter, perform voltage amplification processing on the target analog signal, obtain a final target signal, and output the target signal; The laser is connected to the post-stage amplifier and is used for receiving a target signal and outputting an optical signal.

4. The system according to claim 2, characterized in that The laser emission and control module is also used to control the deflection of the scanning device, and the scanning device is used to emit the light signal at the current angle after deflection to the target irradiation object to form emitted light.

5. The system according to claim 4, characterized in that The scanning device includes a transverse X-axis scanning device and a longitudinal Y-axis scanning device; The transverse X-axis scanning device and the longitudinal Y-axis scanning device are respectively connected to the FPGA; The FPGA is used to control the transverse X-axis scanning device to deflect the first fixed angle multiple times; the scanning device is used to transmit the optical signal based on the current angle after each deflection of the transverse X-axis scanning device by the first fixed angle, to form the emission light, so as to complete the transverse scanning of the target irradiation object; The FPGA is also used to control the longitudinal Y-axis scanning device to deflect by a second fixed angle after the scanning device has completed transverse scanning of the target irradiated object, and return to execute the step of controlling the transverse X-axis scanning device to deflect by the first fixed angle multiple times, so as to control the scanning device to emit light signals based on the current angle after each transverse X-axis scanning device deflects by the first fixed angle after the longitudinal Y-axis scanning device has deflected by the second fixed angle, to form emission light, until the transverse scanning of the target irradiated object is completed; If the target object has not been scanned completely, the FPGA is further used to return to execute the step of controlling the longitudinal Y-axis scanning device to deflect by a second fixed angle after the scanning device has completed the transverse scanning of the target object, until the target object has been scanned completely.

6. The system according to claim 1, characterized in that The signal processing module is used to determine whether the instantaneous frequency of the second beat signal reaches a preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, the second beat signal is output to obtain a target beat signal with a frequency of the preset target frequency; if the instantaneous frequency of the second beat signal does not reach the preset target frequency, the initial voltage is calculated according to the instantaneous frequency and the input voltage, and a third beat signal is obtained after the initial voltage is used as the input voltage of the laser emission and control module. Based on the frequency spectrum of the third beat signal, the DC current signal and the high-frequency signal in the third beat signal are removed to obtain a fourth beat signal after the DC current signal and the high-frequency signal are removed; the third beat signal is used as the first beat signal and the fourth beat signal is used as the second beat signal, and the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency is returned.

7. A nonlinear correction method, characterized in that: The method is applied to the system according to claim 1, and the method comprises: Acquire an initial first beat signal, and acquire a frequency spectrum of the first beat signal, and remove a direct current signal and a high-frequency signal from the first beat signal based on the frequency spectrum to obtain a second beat signal after the direct current signal and the high-frequency signal are removed; Obtain the input voltage corresponding to the first beat signal, and obtain the instantaneous frequency of the second beat signal, and determine whether the instantaneous frequency of the second beat signal reaches the preset target frequency. If the instantaneous frequency of the second beat signal reaches the preset target frequency, output the second beat signal to obtain a target beat signal with a frequency of the preset target frequency; if the frequency of the second beat signal does not reach the preset target frequency, calculate the target voltage according to the instantaneous frequency and the input voltage, output a new beat signal based on the target voltage, and obtain a target beat signal with a frequency of the preset target frequency; wherein the target frequency is linearly related to time.

8. The method according to claim 7, characterized in that The step of calculating the target voltage according to the instantaneous frequency and the input voltage, outputting a new beat signal based on the target voltage, and obtaining a target beat signal having a frequency of a preset target frequency includes: Calculating an initial voltage according to the instantaneous frequency and the input voltage, obtaining a third beat signal obtained by taking the initial voltage as the input voltage of the laser emission and control module, and removing a DC current signal and a high-frequency signal from the third beat signal based on a frequency spectrum of the third beat signal to obtain a fourth beat signal after removing the DC current signal and the high-frequency signal; The third beat signal is used as the first beat signal and the fourth beat signal is used as the second beat signal, and the step of returning to determine whether the instantaneous frequency of the second beat signal reaches a preset target frequency is executed.

9. The method according to claim 7, characterized in that: The removing of the direct current signal and the high-frequency signal in the first beat signal based on the frequency spectrum includes: Based on the spectrum diagram, a direct current signal reaching a first frequency and a high-frequency signal reaching a second frequency in the first beat signal are searched, and a bandpass filter is used to filter out the direct current signal with the first frequency and the high-frequency signal with the second frequency.

10. The method according to claim 8, characterized in that The calculation formula for calculating the initial voltage according to the instantaneous frequency and the input voltage is: Among them, U2 represents the initial voltage, a represents the frequency modulation rate, r represents the transmission delay, f represents the instantaneous frequency of the second beat signal, and U1 represents the input voltage.

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