Laser scanning system and non-linear correction method

Abstract

The embodiment of the application discloses a kind of laser scanning system and nonlinear correction method, the system includes laser emission and control module, scanning device, receiving device and signal processing module, can by obtaining initial first beat signal, and remove direct current signal and high frequency signal in first beat signal, obtain second beat signal after removing direct current signal and high frequency signal, according to the input voltage corresponding to first beat signal, and the target voltage of the instantaneous frequency of second beat signal is calculated to second beat signal, based on target voltage output new beat signal, obtain target beat signal with preset target frequency of frequency;Wherein, target frequency and time are linear relationship.The frequency of beat signal is controlled by controlling input voltage, and the frequency of output beat signal and time are linear relationship.

Description

Technical Field

[0001] This invention relates to the field of laser signal processing technology, and in particular to a laser scanning system and a nonlinear correction method. Background Technology

[0002] Distance measurement can generally be performed using a laser. Specifically, the difference between the emitted light (emission signal) and the reflected light (echo signal) of the laser on the target object is calculated to obtain the beat signal. The distance to the target object can be calculated based on the frequency of the beat signal.

[0003] Ideally, the frequency of the beat signal output by a laser is linearly related to time. However, external factors (such as temperature) can cause this relationship to become non-linear, leading to decreased ranging accuracy. Current technology can adjust the beat signal frequency through current tuning, but theoretical analysis shows a linear relationship between the injected current and the output wavelength. Since laser wavelength is inversely proportional to frequency, even injecting a linear current cannot produce a linearly frequency-modulated laser. Furthermore, temperature changes during current tuning also affect 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 linearly related to time. Summary of the Invention

[0005] The main objective of this invention is to provide a laser scanning system, a nonlinear correction method, a computer device, and a storage medium that can solve the problem of frequency and time nonlinearity of beat signals in the prior art.

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

[0007] The laser emission and control module is used to acquire 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 the 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 light signals to the target object to form emitted light;

[0009] The receiving device is connected to the scanning device and is used to receive the echo signal, calculate the difference between the transmitted 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 acquire the spectrum of the first beat signal. Based on the spectrum, the DC current signal and high-frequency signal in the first beat signal are removed to obtain a second beat signal after removing the DC current signal and high-frequency signal. The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are acquired. Based on the instantaneous frequency and the input voltage, the target voltage of the second beat signal is calculated.

[0011] The signal processing device is connected to the laser emission and control module and is used to output the 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 preset target frequency, and the target frequency is linearly related to time.

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

[0014] The FPGA is equipped with a phase accumulator. The FPGA is used to store preset waveform data and establish a correspondence 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 conjunction with the first aspect, in one possible implementation, the laser emitting and control module 101 further includes a laser; the waveform generator further includes a digital-to-analog converter, a filter, and a subsequent amplifier.

[0016] The digital-to-analog converter is connected to the FPGA. The FPGA is used to output the target waveform data as an initial waveform signal to the digital-to-analog converter. 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, perform smoothing filtering on the analog signal to obtain the smoothed target analog signal, and output the target analog signal.

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

[0019] The laser is connected to the subsequent amplifier to receive the target signal and output an optical signal.

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

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

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

[0023] The FPGA is used to control the horizontal X-axis scanning device to deflect the first fixed angle multiple times; the scanning device is used to emit light signals based on the current angle after each horizontal X-axis scanning device deflects the first fixed angle, forming emitted light, so as to horizontally scan the target object.

[0024] The FPGA is also used to control the longitudinal Y-axis scanning device to deflect a second fixed angle after the scanning device has finished scanning the target object laterally, and return to execute the step of controlling the transverse X-axis scanning device to deflect a first fixed angle multiple times, so as to control the scanning device to emit light signals based on the current angle after the transverse X-axis scanning device deflects the first fixed angle each time, so as to form emitted light, until the target object has been scanned laterally.

[0025] If the target object is not completely scanned, the FPGA is also used to return to the step of controlling the longitudinal Y-axis scanning device to deflect a second fixed angle after the scanning device has finished scanning the target object laterally, until the target object is completely scanned.

[0026] In conjunction with the first aspect, in one 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 the preset target frequency. If the instantaneous frequency of the second beat signal does not reach the preset target frequency, an initial voltage is calculated based on the instantaneous frequency and the input voltage, and a third beat signal is obtained after using the initial voltage as the input voltage of the laser emission and control module. Based on the spectrum of the third beat signal, the DC current signal and high-frequency signal in the third beat signal are removed to obtain a fourth beat signal after removing the DC current signal and 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. The process then returns to the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency.

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

[0028] Obtain the initial first beat signal and obtain the spectrum of the first beat signal. Based on the spectrum, remove the DC current signal and high-frequency signal from the first beat signal to obtain the second beat signal after removing the DC current signal and high-frequency signal.

[0029] The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are obtained. It is determined 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 the preset target frequency. If the frequency of the second beat signal does not reach the preset target frequency, a target voltage is calculated based on the instantaneous frequency and the input voltage. A new beat signal is output based on the target voltage to obtain a target beat signal with the preset target frequency. The target frequency is linearly related to time.

[0030] In conjunction with the second aspect, in one possible implementation, the above-mentioned calculation of the target voltage based on the instantaneous frequency and the input voltage, and the output of a beat signal based on the target voltage to obtain a target beat signal with a preset target frequency, includes:

[0031] The initial voltage is calculated based on the instantaneous frequency and the input voltage. The third beat signal is obtained after using the initial voltage as the input voltage of the laser emission and control module. The DC current signal and high-frequency signal in the third beat signal are removed based on the spectrum of the third beat signal to obtain the fourth beat signal after removing the DC current signal and 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. The process then returns to the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency.

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

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

[0035] In conjunction with the second aspect, in one possible implementation, the calculation formula for calculating the initial voltage based on the instantaneous frequency and the input voltage is as follows:

[0036]

[0037] Where 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 objectives, a third aspect of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the following steps:

[0039] Obtain the initial first beat signal and obtain the spectrum of the first beat signal. Based on the spectrum, remove the DC current signal and high-frequency signal from the first beat signal to obtain the second beat signal after removing the DC current signal and high-frequency signal.

[0040] The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are obtained. It is determined 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 the preset target frequency. If the frequency of the second beat signal does not reach the preset target frequency, a target voltage is calculated based on the instantaneous frequency and the input voltage. A new beat signal is output based on the target voltage to obtain a target beat signal with the preset target frequency. The target frequency is linearly related to time.

[0041] To achieve the above objectives, a fourth aspect of the present invention provides a computer device, 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 causes the processor to perform the following steps:

[0042] Obtain the initial first beat signal and obtain the spectrum of the first beat signal. Based on the spectrum, remove the DC current signal and high-frequency signal from the first beat signal to obtain the second beat signal after removing the DC current signal and high-frequency signal.

[0043] The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are obtained. It is determined 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 the preset target frequency. If the frequency of the second beat signal does not reach the preset target frequency, a target voltage is calculated based on the instantaneous frequency and the input voltage. A new beat signal is output based on the target voltage to obtain a target beat signal with the preset target frequency. The target frequency is linearly related to time.

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

[0045] This invention provides a laser scanning system. It acquires an initial first beat signal and its spectrum. Based on the spectrum, it removes the DC current signal and high-frequency signals from the first beat signal to obtain a second beat signal. It then acquires the input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal. Based on the instantaneous frequency and the input voltage, it calculates a target voltage for the second beat signal and outputs a new beat signal based on the target voltage, resulting in a target beat signal with a preset target frequency. The target frequency is linearly related to time. By controlling the input voltage, the frequency of the beat signal is controlled, achieving a linear relationship between the frequency of the output beat signal and time. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] in:

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

[0049] Figure 2 This is a schematic diagram of a receiving device according to an embodiment of the present invention;

[0050] Figure 3 This is a flowchart illustrating a nonlinear correction method in an embodiment of the present invention;

[0051] Figure 4 This is a flowchart of a beat signal processing embodiment of the present invention;

[0052] Figure 5 This is a structural block diagram of a computer device in an embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] This invention provides a laser scanning system, referring to... Figure 1 , Figure 1 A structural block diagram of a laser scanning system provided in an embodiment of the present invention is shown below. 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 incident and emission, and the receiving device 103 is used to preprocess the laser echo signal. The preprocessing may include sampling, circuit amplification, filtering, analog-to-digital conversion, etc. The difference between the preprocessed echo signal and the transmitted signal is calculated to obtain the 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 acquires the beat signal, adjusts the input voltage of the beat signal, and outputs the beat signal with the target frequency to achieve a linear relationship in the time-frequency curve of the beat signal. The time-frequency curve is the relationship curve between the frequency of the beat signal 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 acquire target waveform data and output the target waveform signal corresponding to the target waveform data as an optical signal. The target waveform data is the waveform data corresponding to a preset input voltage. Specifically, the laser emission and control module 101 is used to establish a correspondence between waveform data and corresponding read addresses to obtain a lookup table. The waveform data represents the amplitude value of the waveform, and is the waveform data corresponding to the input voltage of the laser emission and control module 101, which is equivalent to establishing a correspondence between the preset input voltage and the corresponding read address. Based on the lookup table, the corresponding waveform data is acquired 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] FPGA 201 contains a phase accumulator 23. FPGA 201 stores preset waveform data and establishes a correspondence between the waveform data and the corresponding read address to obtain a lookup table. Based on the read address output by the phase accumulator, the waveform data corresponding to the read address is retrieved 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 based on the frequency and waveform of the periodic signal, and uses a frequency control word to cyclically look up the table in the memory within FPGA 201 to output the corresponding waveform data to the DAC circuit. Specifically, the preset waveform data is first generated using the host computer MATLAB and stored in the random access memory (RAM). The preset waveform data can be any desired waveform data. The core of the DDS waveform generator is the phase accumulator. The phase accumulator accumulates data according to the frequency control word (FCW) in each clock cycle, thereby changing the read address of the waveform data. Since there is a correspondence between the waveform data and the read address, a lookup table can be obtained by establishing a correspondence between the waveform data and the corresponding read address. The frequency can be adjusted by changing the value of FCW to control the reading speed of waveform data. According to the reading address output by the phase accumulator, the corresponding waveform data is read from the lookup table. This waveform data is digital and represents 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] Filter 203 is connected to digital-to-analog converter 202, and is used to receive the analog signal output by digital-to-analog converter 202, and to smooth and filter the analog signal to obtain the smoothed and filtered target analog signal, which is then output. Amplifier 204 is connected to filter 203, and is used to receive the target analog signal output by filter 203, and to amplify 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 spurious components, which need to be smoothed and filtered by the filter. The filtered analog signal is then amplified by the amplifier circuit, and the voltage amplitude is adjusted to obtain the final output waveform signal.

[0061] The power amplifier 204 is connected to the laser 22. The waveform generator 21 outputs the target signal to the laser 22 to drive the laser 22 to output an optical signal. The waveform generator 21 inputs the final output waveform signal to the laser so that the laser outputs an optical signal to the scanning device 102.

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

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

[0064] The laser emission and control module 101 is connected to the scanning device 102. Specifically, the horizontal X-axis scanning device and the vertical Y-axis scanning device are respectively connected to the FPGA. The FPGA is used to control the horizontal X-axis scanning device to deflect a first fixed angle multiple times. The scanning device is used to emit light signals based on the current angle after each horizontal X-axis scanning device deflects the first fixed angle, forming emitted light, so as to horizontally scan the target object. In one possible implementation, during the initial scan, the FPGA outputs a first fixed voltage to the horizontal X-axis scanning device to control the horizontal X-axis scanning device to deflect the first fixed angle. The scanning device emits light signals based on the current angle after the horizontal X-axis scanning device deflects the first fixed angle, forming emitted light. Then, the FPGA outputs a first fixed voltage to the horizontal X-axis scanning device again to control the horizontal X-axis scanning device to deflect the first fixed angle again. The scanning device emits light signals again based on the current angle after the horizontal X-axis scanning device deflects the first fixed angle, forming emitted light, and so on, until the target object is horizontally scanned once.

[0065] The FPGA is also used to control the vertical Y-axis scanning device to deflect a second fixed angle after the scanning device has completed a horizontal scan of the target object, and then return to execute the step of controlling the horizontal X-axis scanning device to deflect a first fixed angle multiple times. This controls the scanning device to emit light signals based on the current angle after each deflection of the vertical Y-axis scanning device to the first fixed angle, forming emitted light, until the target object has been scanned horizontally. After the scanning device completes a horizontal scan of the target object, the FPGA outputs a second fixed voltage to the vertical Y-axis scanning device to control it to deflect a second fixed angle. Based on the deflection of the vertical Y-axis scanning device to the second fixed angle, the FPGA then outputs a first fixed voltage to the horizontal X-axis scanning device multiple times to control it to deflect a first fixed angle. The scanning device emits light signals based on the current angle after each deflection of the horizontal X-axis scanning device to the first fixed angle, forming emitted light, until another horizontal scan of the target object is completed.

[0066] If the target object has not been scanned yet, the FPGA is used to return to the step of controlling the longitudinal Y-axis scanning device to deflect a second fixed angle after the scanning device has finished scanning the target object laterally, until the target object is scanned.

[0067] For example, if the target object is scanned sequentially from top to bottom, at the beginning, the horizontal X-axis scanning device first scans sequentially from the leftmost end to the rightmost end of the target object. After one horizontal scan is completed, before the bottom end of the target object is scanned (i.e., before the entire target object is scanned), the vertical Y-axis scanning device deflects downwards by a second fixed angle, and then the horizontal X-axis scanning device scans sequentially from the rightmost end to the leftmost end of the target object. This process continues until the entire target object is scanned.

[0068] The scanning device 102 is connected to the receiving device 103, and the receiving device is connected to the scanning device. It is used to receive the echo signal, calculate the difference between the transmitted 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 transmitted light, to receive the echo signal corresponding to the transmitted signal, and to preprocess the echo signal, calculate the difference between the preprocessed echo signal and the transmitted signal, and obtain the beat signal. (Referring to...) Figure 2 , Figure 2This is a 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 and is used to transmit the echo signal. The coupler is used to receive the echo signal and the corresponding transmitted signal, and output the echo signal and the corresponding transmitted 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 transmitted signal, and obtain the beat signal.

[0069] In addition, the system also includes a data acquisition card (ADC), which is connected to both the FPGA and the receiving device 103. When the FPGA outputs a preset fixed voltage to the horizontal X-axis scanning device, the FPGA sends a trigger signal to the ADC, causing the ADC to acquire the beat signal received by the receiving device 103. This allows for precise determination of the deflection angle corresponding to each acquired data point, thereby achieving synchronization of laser distance and angle.

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

[0071] The signal processing device 104 is further configured to acquire the spectrum of the first beat signal, and remove the DC current signal and high-frequency signal from the first beat signal based on the spectrum to obtain the second beat signal after removing the DC current signal and high-frequency signal. Specifically, this can be achieved by performing a Fourier transform on the first beat signal to obtain its spectrum, identifying the DC current signal reaching a first frequency and the high-frequency signal reaching a second frequency in the first beat signal based on the spectrum, and then using a bandpass filter to filter out the DC current signal at the first frequency and the high-frequency signal at the second frequency.

[0072] The signal processing device 104 is also used to acquire the input voltage corresponding to the first beat signal and acquire the instantaneous frequency of the second beat signal, calculate the target voltage of the second beat signal based on 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 based on the instantaneous frequency and the input voltage, and the initial voltage is output to the laser emission and control module as the 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 the third beat signal obtained after using the initial voltage as the input voltage of the laser emission and control module. Based on the spectrum diagram of the third beat signal, the DC current signal and high-frequency signal in the third beat signal are removed to obtain the fourth beat signal after removing the DC current signal and high-frequency signal. The new fourth beat signal is judged, 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. Then, the step of judging whether the instantaneous frequency of the second beat signal reaches the preset target frequency is returned.

[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 the process is iterated continuously. It can be seen that the target voltage is the input voltage that enables the instantaneous frequency of the output second beat signal to reach the preset target frequency.

[0074] The formula for calculating the initial voltage based on the instantaneous frequency and the input voltage can be:

[0075]

[0076] Where 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. Specifically, the signal processing device can be connected to an FPGA. First, after calculating the initial voltage corresponding to the second beat signal, the signal processing device outputs the initial voltage to the FPGA of the laser emission and control module. The laser emission and control module also outputs an optical signal based on the initial voltage. Similarly, the signal processing device again acquires the beat signal preprocessed by the receiving device 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, the initial voltage is recalculated, and the process returns to outputting the initial voltage to the FPGA of the laser emission and control module. This process continues until the frequency of the beat signal output based on the initial voltage reaches the preset target frequency, at which point the target beat signal is output, and the corresponding initial voltage is the target voltage. The target beat signal is a beat signal with a 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 Newton's secant method and MATLAB, iteratively inputting the input voltage to bring the frequency of the output beat signal close to a certain fixed value. First, the frequency spectrum of the beat signal is determined by Fourier transform. Then, a bandpass filter is used to remove the DC bias and high-frequency signals from the beat signal. Next, a Hilbert transform is performed on the beat signal to solve for the instantaneous frequency. Then, a smoothing filter is used to remove noise, obtaining a smoothed instantaneous frequency. Finally, an iterative algorithm formula is used to solve for the iterative input voltage. Simultaneously, the iterative input voltage can be downsampled to meet the storage requirements of the 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. This corrects the nonlinearity of the time-frequency curve and ensures that the output time-frequency curve is linear. The system achieves the purpose of correcting the nonlinearity of the output beat signal while simultaneously controlling the deflection and scanning of the scanning device.

[0080] Based on the above system, embodiments of the present invention also provide a nonlinear correction method, referring to... Figure 2 , Figure 3 This is a flowchart illustrating a nonlinear correction method provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the specific steps of this method are as follows:

[0081] Step S101: Obtain the initial first beat signal and obtain the spectrum of the first beat signal. Based on the spectrum, remove the DC current signal and high-frequency signal from the first beat signal to obtain the second beat signal after removing the DC current signal and high-frequency signal.

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

[0083] Among them, the target frequency has a linear relationship with time.

[0084] Reference Figure 4 , Figure 4 A flowchart of beat signal processing provided in an embodiment of the present invention is shown below. Figure 4 As shown.

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

[0086] Based on the spectrum analysis, the DC current signal and high-frequency signal in the first beat signal are removed to obtain the second beat signal after removing the DC current signal and high-frequency signal. Specifically, based on the spectrum analysis, the DC current signal reaching a preset first frequency and the high-frequency signal reaching a preset second frequency in the first beat signal are found, and a bandpass filter is used to filter out the DC current signal at the first frequency and the high-frequency signal at the second frequency.

[0087] Obtain the input voltage corresponding to the first beat signal, perform Hilbert transform on the second beat signal, solve for the instantaneous frequency of the second beat signal, and then perform smoothing filtering on the instantaneous frequency to remove noise and obtain a smooth instantaneous frequency.

[0088] The target voltage is calculated based on the instantaneous frequency and the input voltage. A new beat signal is output based on the target voltage, resulting in a target beat signal with a preset target frequency. Specifically, this can be seen in steps S201-S202:

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

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

[0091] The formula for calculating the initial voltage based on the instantaneous frequency and the input voltage can be:

[0092]

[0093] Where 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] The third beat signal is obtained after using the initial voltage as the input voltage of the laser emission and control module. Based on the spectrum of the third beat signal, the DC current signal and high-frequency signal in the third beat signal are removed to obtain the fourth beat signal after removing the DC current signal and high-frequency signal. 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 based on 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. The step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency is returned to execute. 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 one possible implementation, the input voltage can be downsampled before being 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 linearly related to time.

[0097] Figure 5 An internal structural diagram of a computer device in one embodiment is shown. This computer device can specifically be a terminal or a server. Figure 5As shown, the computer device includes a processor, memory, and network interface connected via a system bus. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and may also store a computer program. When executed by the processor, this computer program causes the processor to perform all the steps of the above-described method. The internal memory may also store a computer program, which, when executed by the processor, causes the processor to perform all the steps of the above-described method. Those skilled in the art will understand that... Figure 5 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0098] In one embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program that, when executed by the processor, causes the processor to perform the steps of the aforementioned method.

[0099] In one embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, causes the processor to perform the steps of the aforementioned method.

[0100] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0101] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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 embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended 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 acquire 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 the 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 light signals to the target object to form emitted light; The receiving device is connected to the scanning device and is used to receive the echo signal, calculate the difference between the transmitted 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 acquire the spectrum of the first beat signal. Based on the spectrum, the DC current signal and high-frequency signal in the first beat signal are removed to obtain a second beat signal after removing the DC current signal and high-frequency signal. The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are acquired. Based on the instantaneous frequency and the input voltage, the target voltage of the second beat signal is calculated. The signal processing device is connected to the laser emission and control module and is used to output the 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 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; The FPGA is equipped with a phase accumulator. The FPGA is used to store preset waveform data and establish a correspondence 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-amplifier. The digital-to-analog converter is connected to the FPGA. The FPGA is used to output the target waveform data as an initial waveform signal to the digital-to-analog converter. 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, perform smoothing filtering on the analog signal to obtain the smoothed target analog signal, and output the target analog signal. The post-amplifier is connected to the filter and is used to receive the target analog signal output by the filter, perform voltage amplification on the target analog signal to obtain the final target signal, and output the target signal. The laser is connected to the subsequent amplifier to receive the target signal and output 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, which emits the light signal at the current angle after deflection to the target object to form emitted light.

5. The system according to claim 4, characterized in that, The scanning device includes a horizontal X-axis scanning device and a vertical Y-axis scanning device; The horizontal X-axis scanning device and the vertical Y-axis scanning device are respectively connected to the FPGA; The FPGA is used to control the horizontal X-axis scanning device to deflect the first fixed angle multiple times; the scanning device is used to emit light signals based on the current angle after each horizontal X-axis scanning device deflects the first fixed angle, forming emitted light, so as to horizontally scan the target object. The FPGA is also used to control the longitudinal Y-axis scanning device to deflect a second fixed angle after the scanning device has finished scanning the target object laterally, and return to execute the step of controlling the transverse X-axis scanning device to deflect a first fixed angle multiple times, so as to control the scanning device to emit light signals based on the current angle after the transverse X-axis scanning device deflects the first fixed angle each time, so as to form emitted light, until the target object has been scanned laterally. If the target object is not completely scanned, the FPGA is also used to return to the step of controlling the longitudinal Y-axis scanning device to deflect a second fixed angle after the scanning device has finished scanning the target object laterally, until the target object is completely scanned.

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 the 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 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 based on the instantaneous frequency and the input voltage, and a third beat signal is obtained after using the initial voltage as the input voltage of the laser emission and control module. Based on the spectrum of the third beat signal, the DC current signal and high-frequency signal in the third beat signal are removed to obtain a fourth beat signal after removing the DC current signal and 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. The process returns to the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency.

7. A nonlinear correction method, characterized in that, The method is applied to the system of claim 1, and the method includes: Obtain the initial first beat signal and obtain the spectrum of the first beat signal. Based on the spectrum, remove the DC current signal and high-frequency signal from the first beat signal to obtain the second beat signal after removing the DC current signal and high-frequency signal. The input voltage corresponding to the first beat signal and the instantaneous frequency of the second beat signal are obtained. It is determined 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 the preset target frequency. If the frequency of the second beat signal does not reach the preset target frequency, a target voltage is calculated based on the instantaneous frequency and the input voltage. A new beat signal is output based on the target voltage to obtain a target beat signal with the preset target frequency. 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 based on the instantaneous frequency and the input voltage, and outputting a new beat signal based on the target voltage to obtain a target beat signal with a preset target frequency includes: The initial voltage is calculated based on the instantaneous frequency and the input voltage. The third beat signal is obtained after using the initial voltage as the input voltage of the laser emission and control module. The DC current signal and high-frequency signal in the third beat signal are removed based on the spectrum of the third beat signal to obtain the fourth beat signal after removing the DC current signal and 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. The process then returns to the step of determining whether the instantaneous frequency of the second beat signal reaches the preset target frequency.

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

10. The method according to claim 8, characterized in that, The formula for calculating the initial voltage based on the instantaneous frequency and the input voltage is as follows: Where 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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