Laser ranging system and method based on sine frequency modulation

Abstract

The invention provides a laser ranging system and method based on sine frequency modulation, and the system comprises the steps: a function signal generator generates a first sine wave and a second sine wave, and a laser receives the first sine wave, controls the laser to generate a modulation laser signal, and transmits the modulation laser signal to a first coupler; the first coupler performs light splitting on the modulated laser signal to generate a first laser signal and a second laser signal, and transmits the first laser signal to the integrated optical lens module; the integrated optical lens module outputs the first laser signal to a target object and receives an echo signal returned after the first laser signal detects the target object; the beat frequency signal generator receives the echo signal and the second laser signal and processes the echo signal and the second laser signal to obtain a beat frequency signal; and the data acquisition card performs signal acquisition on the beat frequency signal and the second sine wave, and the signal processor performs resampling and Fourier transform on the beat frequency signal based on the second sine wave to obtain the distance to be measured between the integrated optical lens module and the target object.

Description

Technical Field

[0001] The present invention relates to the technical field of laser distance measurement, and in particular to a laser distance measurement system and method based on sinusoidal frequency modulation. Background Art

[0002] Laser ranging is an active detection technology that has its own transmitting and receiving systems and can be used all-weather. It is widely used in aerospace, autonomous driving, terrain mapping and other fields. It transmits lasers of a specific wavelength and receives the light signal reflected by the target, and calculates the distance based on the flight time of the light. It has the characteristics of fast measurement speed, high accuracy and strong anti-interference ability.

[0003] In traditional laser ranging systems, pulse laser ranging is usually used, that is, the distance is determined by measuring the time difference between the emission of a laser pulse and the receipt of the echo. However, this method may be limited when measuring long-distance targets or working in high-dynamic environments because it relies on the precise time measurement of very short light pulses. Summary of the invention

[0004] The present invention provides a laser ranging system and method based on sinusoidal frequency modulation, which are used to solve the defect that the traditional laser ranging system may be limited when measuring long-distance targets or working in a high dynamic environment, and realize laser ranging by using a frequency modulated continuous wave method.

[0005] The present invention provides a laser ranging system based on sinusoidal frequency modulation, comprising: A function signal generator generates a first sine wave and a second sine wave, outputs the first sine wave to a laser and outputs the second sine wave to a data acquisition card, wherein the first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes; A laser, wherein the laser receives the first sine wave, uses the first sine wave as a modulation signal to control the laser to generate a modulated laser signal and sends the modulated laser signal to a first coupler; A first coupler, which receives the modulated laser signal and performs light splitting to generate a first laser signal and a second laser signal, transmits the first laser signal to an integrated optical lens module, and outputs the second laser signal as an intrinsic reference signal to a beat frequency signal generator; an integrated optical lens module, wherein the integrated optical lens module outputs the first laser signal to a target object, receives an echo signal returned after the first laser signal detects the target object, and sends the echo signal to a beat frequency signal generator; a beat signal generator, wherein the beat signal generator receives the echo signal and the second laser signal for processing to obtain a beat signal; A data acquisition card, wherein the data acquisition card acquires signals of the beat frequency signal and the second sine wave and sends the signals to a signal processor; A signal processor is provided, wherein the signal processor resamples the beat frequency signal based on the second sine wave to obtain a resampled beat frequency signal, and performs Fourier transform on the resampled beat frequency signal to obtain a distance to be measured between the integrated optical lens module and the target object.

[0006] According to the laser ranging system based on sinusoidal frequency modulation provided by the present invention, the function signal generator includes a first channel and a second channel, the first channel is connected to the laser, and is used to output the first sinusoidal wave to the laser; the second channel is connected to the data acquisition card, and is used to output the second sinusoidal wave to the data acquisition card.

[0007] According to the laser ranging system based on sinusoidal frequency modulation provided by the present invention, the first coupler splits the modulated laser signal in a ratio of 95:5, generates a first laser signal from 95% of the modulated laser signal, and generates a second laser signal from 5% of the modulated laser signal.

[0008] According to the laser ranging system based on sinusoidal frequency modulation provided by the present invention, the beat frequency signal generator includes: a second coupler, the second coupler receiving the echo signal and the second laser signal, coupling the echo signal with the second laser signal, and outputting a generated coupling signal to a photodetector; A photoelectric detector is connected to the second coupler and processes the received coupling signal to obtain the beat frequency signal.

[0009] According to the laser ranging system based on sinusoidal frequency modulation provided by the present invention, the signal processor samples the second sinusoidal wave at equal intervals to obtain multiple index points; the signal processor extracts the signals corresponding to the multiple index points in the beat frequency signal to obtain a single-frequency sinusoidal signal carrying ranging information as a resampled beat frequency signal.

[0010] According to the laser ranging system based on sinusoidal frequency modulation provided by the present invention, the integrated optical lens module comprises: an optical circulator and a lens; The optical circulator receives the first laser signal and transmits it to the lens; the lens outputs the first laser signal to the target object, receives the echo signal returned after the first laser signal detects the target object, and sends the echo signal to the optical circulator; the optical circulator sends the echo signal to the beat frequency signal generator.

[0011] The present invention also provides a laser ranging method based on sinusoidal frequency modulation, which is used in the laser ranging system as described above, and the method comprises: Generate a first sine wave and a second sine wave by a function signal generator, output the first sine wave to a laser and output the second sine wave to a data acquisition card; wherein the first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes; receiving the first sine wave through the laser, and using the first sine wave as a modulation signal to control the laser to generate a modulated laser signal and send the modulated laser signal to the first coupler; The modulated laser signal is received by the first coupler for light splitting to generate a first laser signal and a second laser signal, the first laser signal is transmitted to an integrated optical lens module, and the second laser signal is output as an intrinsic reference signal to a beat frequency signal generator; Outputting the first laser signal to the target object through the integrated optical lens module, receiving an echo signal returned after the first laser signal detects the target object, and sending the echo signal to a beat frequency signal generator; The beat signal generator receives the echo signal and the second laser signal for processing to obtain a beat signal; The beat frequency signal and the second sine wave are collected by the data acquisition card and sent to a signal processor; The beat frequency signal is resampled based on the second sine wave through a signal processor to obtain a resampled beat frequency signal, and the resampled beat frequency signal is Fourier transformed to obtain a distance to be measured between the integrated optical lens module and the target object.

[0012] According to the laser ranging method based on sinusoidal frequency modulation provided by the present invention, the modulated laser signal is received by the first coupler for splitting to generate a first laser signal and a second laser signal, which specifically includes: The modulated laser signal is split by the first coupler in a ratio of 95:5, 95% of the modulated laser signal is generated into a first laser signal, and 5% of the modulated laser signal is generated into a second laser signal.

[0013] According to the laser ranging method based on sinusoidal frequency modulation provided by the present invention, the beat frequency signal generator includes: a second coupler and a photodetector; The beat frequency signal is received by the beat frequency signal generator for processing to obtain the beat frequency signal, specifically including: receiving the echo signal and the second laser signal by the second coupler, coupling the echo signal with the second laser signal, and outputting the generated coupled signal to the photodetector; and processing the received coupled signal by the photodetector to obtain the beat frequency signal.

[0014] According to the laser ranging method based on sinusoidal frequency modulation provided by the present invention, the beat frequency signal is resampled based on the second sinusoidal wave by a signal processor to obtain a resampled beat frequency signal, which specifically includes: sampling the second sinusoidal wave at equal intervals by the signal processor to obtain multiple index points; extracting signals corresponding to the multiple index points in the beat frequency signal by the signal processor to obtain a single-frequency sinusoidal signal carrying ranging information as the resampled beat frequency signal.

[0015] The laser ranging system and method based on sinusoidal frequency modulation provided by the present invention, frequency modulates the first sine wave by a laser, then splits the modulated laser signal through a first coupler, and the generated first laser signal is emitted through an integrated optical lens module, and the echo signal reflected by the measured target is received; the echo signal is mixed and interfered with the second laser signal by a beat signal generator to obtain a beat signal, and then the beat signal and the second sine wave are collected by a data acquisition card, and sent to a signal processor, and the beat signal is resampled based on the second sine wave by the signal processor to obtain a resampled beat signal, and the resampled beat signal is Fourier transformed, and according to the corresponding relationship between frequency and distance, the measurement of the distance to be measured can be converted into the measurement of the beat signal frequency, so as to accurately obtain the distance to be measured between the integrated optical lens module and the target object. This method not only improves the accuracy of measurement, but also broadens the application scope of laser ranging technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are 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.

[0017] Figure 1 It is a structural schematic diagram of a laser ranging system based on sinusoidal frequency modulation provided by the present invention.

[0018] Figure 2 This is a 25kHz sinusoidal frequency modulation 20m optical fiber beat frequency spectrum provided by the present invention.

[0019] Figure 3 It is a schematic diagram of generating a resampled beat frequency signal provided by the present invention.

[0020] Figure 4 It is a schematic diagram of the triangular wave frequency modulation result provided by the present invention using a driving voltage of 20Vpp and a modulation frequency of 25KHz.

[0021] Figure 5 It is a schematic diagram of the sine wave frequency modulation result provided by the present invention using a driving voltage of 20Vpp and a modulation frequency of 25kHz.

[0022] Figure 6 It is a structural schematic diagram of the experimental stage of the laser ranging system based on sinusoidal frequency modulation provided by the present invention.

[0023] Figure 7 This is a result diagram of the distance to be measured obtained by the signal processing algorithm of the laser distance measurement system provided by the present invention.

[0024] Figure 8 It is a flow chart of the laser ranging method based on sinusoidal frequency modulation provided by the present invention.

[0025] Reference numerals: 101, 601: function signal generator; 102, 602: laser; 103: a first coupler; 104: an integrated optical lens module; 105: beat frequency signal generator; 106, 604: data acquisition card; 107, 605: signal processor; 141: optical circulator; 142: lens

[0026] 151: second coupler; 152, 603: Photodetector. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0028] First, the terms in the embodiments of the present invention are explained.

[0029] Function signal generator: an electronic device that can generate an electrical signal with a specific waveform (such as a sine wave, square wave, triangle wave, etc.) and frequency. In the laser ranging system, the function signal generator is usually used to generate modulation signals, which are used to control the laser to emit lasers of a specific frequency. In the system of the present invention, it generates two sine waves with the same frequency, the same initial phase but different amplitudes, one for modulating the laser and the other as a reference signal for the data acquisition card.

[0030] Laser: A device that can produce a coherent beam of light. In a laser ranging system, the laser usually receives a modulated signal from a function signal generator and adjusts the frequency or phase of the emitted laser according to this signal to generate a modulated laser signal. These modulated laser signals are used to illuminate the target object and are used to measure the distance after being reflected back.

[0031] Coupler: An optical or radio frequency device used to distribute or combine light or radio signals to different paths. In laser ranging systems, couplers (such as fiber couplers) are usually used to split the modulated laser signal emitted by the laser into two parts according to a certain ratio (such as 95:5): one part is sent to the target object, and the other part is used as an intrinsic reference signal.

[0032] Photodetector (PD): A sensor that converts light signals into electrical signals, usually used to detect and measure light intensity. In laser ranging systems, photodetectors are used to receive reflected laser signals and convert them into electrical signals of beat frequency signals for further processing.

[0033] Data Acquisition Card (DAQ): A hardware device used to collect analog or digital signals from various sensors or signal sources and convert them into digital data that can be processed by a computer. In the laser ranging system, the data acquisition card is used to collect the beat signal generated by the beat signal generator and the second sine wave generated by the function signal generator.

[0034] Signal processor (Digital Signal Processor, DSP): A microprocessor specifically used to quickly implement digital signal processing algorithms. In the laser ranging system, the signal processor DSP is used to receive the beat signal and the second sine wave, and resample the beat signal based on the second sine wave to obtain the resampled beat signal, and execute signal processing algorithms such as fast Fourier transform (FFT) to calculate the distance between the laser and the target object.

[0035] Optical circulator (CIR): A non-reciprocal optical device that allows light to pass through multiple ports in one direction while blocking light from traveling in the opposite direction.

[0036] In an embodiment of the present invention, by improving the frequency modulated continuous wave (FMCW) laser ranging technology, the frequency modulation of the sine wave is realized, and then the modulated laser signal is emitted, and the echo signal reflected by the measured target is received; the echo signal and the modulated laser signal are processed to obtain a beat frequency signal; and then the beat frequency signal is resampled based on the synchronous sine wave, and the resampled beat frequency signal is Fourier transformed to obtain the distance to be measured between the integrated optical lens module and the target object.

[0037] Combine the following Figure 1-Figure 8 The laser ranging system and method based on sinusoidal frequency modulation according to the embodiments of the present invention are described.

[0038] The embodiment of the present invention discloses a laser ranging system based on sinusoidal frequency modulation, see Figure 1 ,include: The function signal generator 101 generates a first sine wave and a second sine wave, outputs the first sine wave to the laser 102 and outputs the second sine wave to the data acquisition card 106, and the first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes.

[0039] Among them, the function signal generator 101 is one of the key components of the laser ranging system. Its main function is to generate two sine wave signals with specific characteristics, which are used to modulate the laser and as reference signals for the data acquisition card 106. The amplitude of the first sine wave is designed to meet the modulation requirements of the laser 102 to ensure effective laser modulation. The amplitude of the second sine wave is adjusted according to the input range of the data acquisition card 106 to ensure that the signal is not distorted during the acquisition process.

[0040] Specifically, the function signal generator 101 includes a first channel and a second channel. The first channel is connected to the laser 102 for outputting a first sine wave to the laser 102 ; the second channel is connected to the data acquisition card 106 for outputting a second sine wave to the data acquisition card 106 .

[0041] In addition, the function signal generator 101 also sends a trigger signal Tri to the data acquisition card 106 to ensure that the modulation signal emitted by the laser is synchronized with the data acquisition card 106 .

[0042] The laser 102 receives the first sine wave, uses the first sine wave as a modulation signal to control the laser 102 to generate a modulated laser signal and sends the modulated laser signal to the first coupler 103 .

[0043] Among them, laser 102 uses a stress-tuned laser based on the photoelastic effect, and the tuning rate can be improved by driving the external cavity with the photoelastic effect. This hybrid integrated external cavity self-injection laser can realize a frequency-tunable continuous wave laser light source with a lower spectral linewidth, and the light source has a wide tuning range. Due to the low transmission loss of the silicon-based silicon nitride integrated external cavity, a high-Q value micro-ring external cavity is realized, which provides narrow-band optical feedback for the system, significantly prolongs the photon lifetime, and thus compresses the spectral linewidth. By bonding PZT above the waveguide, the stress generated by the inverse piezoelectric effect is used to act on the waveguide, and the change in the waveguide refractive index caused by the photoelastic effect causes the tuning of the micro-ring resonant wavelength, thereby improving the tuning bandwidth and tuning rate.

[0044] If sinusoidal wave modulation is used for ranging, the frequency expression of the modulated laser signal output by the laser is as follows:

[0045] in, is the initial frequency of the modulated laser signal, is the repetition frequency of the modulation waveform of the modulated laser signal, and B is the bandwidth of the modulated laser signal output by the laser. Then the phase expression of the modulated laser signal output by the laser is formula (2):

[0046] The modulated laser signal expression can be obtained as formula (3):

[0047] in, is the initial phase.

[0048] The first coupler 103 receives the modulated laser signal for splitting to generate a first laser signal and a second laser signal, transmits the first laser signal to the integrated optical lens module 104, and outputs the second laser signal as an intrinsic reference signal to the beat frequency signal generator 105.

[0049] The first coupler 103 may be an optical coupler, such as a fiber coupler or a free space coupler, for splitting the modulated laser signal emitted by the laser 102 into two channels.

[0050] The first coupler 103 can achieve a specific power distribution ratio, for example, splitting the modulated laser signal at a ratio of 95:5, generating a first laser signal from 95% of the modulated laser signal and sending it to the integrated optical lens module 104, and generating a second laser signal from 5% of the modulated laser signal as an intrinsic reference signal and sending it to the beat frequency signal generator 105.

[0051] The integrated optical lens module 104 outputs the first laser signal to the target object, receives the echo signal returned after the first laser signal detects the target object, and sends the echo signal to the beat frequency signal generator 105.

[0052] In this embodiment, the integrated optical lens module 104 includes: an optical circulator 141 and a lens 142; The optical circulator 141 receives the first laser signal and transmits it to the lens 142; the lens 142 outputs the first laser signal to the target object, receives the echo signal returned after the first laser signal detects the target object, and sends the echo signal to the optical circulator 141; the optical circulator 141 sends the echo signal to the beat frequency signal generator 105.

[0053] The lens 142 is a collimating lens, which is used to convert the light beam emitted by the laser into a parallel light beam, or to focus the received parallel light beam to a point.

[0054] The optical circulator 141 is a non-reciprocal optical device that allows light to pass through multiple ports in one direction without being transmitted in the opposite direction. In the laser ranging system, the optical circulator 141 can separate the emitted laser signal and the reflected signal to ensure that they do not interfere with each other. This is crucial to improving the performance and stability of the system.

[0055] Specifically, through formula (3), the expression of the echo signal is obtained (4):

[0056] in, is the delay caused by the first laser signal passing through the distance to be measured.

[0057] For the meaning of other letters, please refer to the explanation in the above formula.

[0058] The beat signal generator 105 receives the echo signal and the second laser signal for processing to obtain a beat signal.

[0059] Alternatively, see Figure 1 The beat frequency signal generator 105 includes: a second coupler 151 and a photodetector 152; the second coupler 151 receives the echo signal and the second laser signal, couples the echo signal with the second laser signal, and outputs the generated coupled signal to the photodetector 152; the photodetector 152 processes the received coupled signal to obtain the beat frequency signal.

[0060] The coupled signal detected by the photodetector 152 contains the interference result of two light waves with similar frequencies. The frequency of this signal is the difference between the two original signal frequencies, that is, the beat frequency. The frequency of the beat signal is directly related to the distance of the target object. Therefore, the distance can be calculated by measuring the frequency of the beat signal.

[0061] Specifically, the expression of the beat frequency signal is as follows:

[0062] The frequency expression of the beat frequency signal is as follows:

[0063] It can be seen that the beat frequency is a sine form. If the beat frequency is directly Fourier transformed, the spectrum will be from 0 to a certain frequency band, such as Figure 2 The 25kHz sine frequency modulated 20m optical fiber beat frequency spectrum shown in the figure makes it difficult to accurately evaluate the ranging results.

[0064] Therefore, in this embodiment, it is also necessary to resample the beat frequency signal based on the second sine wave, and the obtained signal processing result can be an independent target frequency peak, and the result can be evaluated.

[0065] The data acquisition card 106 collects the beat frequency signal and the second sine wave and sends them to the signal processor.

[0066] The signal processor 107 receives the resampled beat frequency signal and performs Fourier transform to obtain the distance to be measured between the integrated optical lens module 104 and the target object.

[0067] Specifically, the distance to be measured between the integrated optical lens module 104 and the target object is the distance to be measured between the lens 142 and the target object.

[0068] Specifically, see Figure 3 , the signal processor 107 samples the second sine wave at equal intervals to obtain multiple index points; the signal processor 107 extracts the signals corresponding to the multiple index points in the beat frequency signal to obtain a single-frequency sine signal carrying ranging information as a resampled beat frequency signal.

[0069] For example, if sampling is done at a rate of 1 MHz over a period of 1 second, then the time interval between each index point is is 1 microsecond, then according to the sampling index point of the second sine wave, the corresponding signal point is extracted from the beat frequency signal.

[0070] The collected second channel data is sampled at equal intervals in each upward or downward scan, with an interval of , record the index points corresponding to the equally spaced sampling; retain the data corresponding to the index points in the beat signal to form a resampled beat signal. Perform a direct Fourier transform on the newly obtained data to obtain the distance. greater than the delay caused by the first laser signal passing through the distance to be measured twice as much.

[0071] The first sine wave expression of the first channel output of the function signal generator is shown in equation (7):

[0072] in, 25kHz, is 10, the second sine wave expression of the second channel output of the function signal generator is shown in formula (8):

[0073] If the distance to be measured is less than 100m, then ,but

[0074] Then the beat frequency signal expression (5) can be approximately simplified to equation (11):

[0075] In formula (11), The second sine wave has the same form as the second sine wave output by the second channel of the function signal generator. , , formula (11) can be further rewritten as formula (12):

[0076] in , oscilloscope shape Performing equal-interval sampling means performing equal-phase interval sampling on the beat frequency signal collected by the first channel. Setting the equal-phase sampling interval to

[0077] in, To construct the auxiliary path delay, B is the bandwidth of the laser modulation waveform. To satisfy the Nyquist sampling theorem, the value is Requires twice the measurement path , and perform equal-interval sampling to obtain the following formula (14):

[0078] Complete the resampling signal processing algorithm, the processed beat frequency signal Expression (15):

[0079] Since the phase difference between the cosine wave and the sine wave is only 90 degrees, expression (15) presents a single-frequency sine wave form, so the distance can be directly obtained through Fourier transform.

[0080] Specifically, the signal processor 107 performs a fast Fourier transform on the resampled beat frequency signal to convert the time domain signal into a frequency domain signal. Fast Fourier transform analysis reveals the frequency components of the signal, where the most significant frequency peak corresponds to the frequency f of the beat frequency signal. beat .

[0081] The signal processor 107 analyzes the FFT results and identifies the main frequency peak, which is directly related to the distance of the target object.

[0082]

[0083] Wherein, L is the distance to be measured between the integrated optical lens module and the target object; c is the speed of light, which is approximately 3×10 8 m / s; k is an integer, usually related to the position of the sampling point in the modulation period; It is a constructed auxiliary path delay used to simulate or compensate for the delay of signal propagation in signal processing; N usually represents the number of sampling points used for signal processing.

[0084] This formula may be derived under a specific modulation and sampling scheme, where and N are related to the modulation characteristics and processing methods of the signal. In this case, It represents a delay of a specific integer multiple within the modulation period, and N is related to the sampling point in the FFT analysis.

[0085] In addition, the peaks and troughs of channel 2 data can be sampled or the channel 2 data can be used as the clock input of the acquisition card to obtain a single-frequency sinusoidal signal expression.

[0086] The laser ranging system based on sine frequency modulation provided by the embodiment of the present invention performs frequency modulation on the first sine wave through a laser, and then the modulated laser signal is split through the first coupler, and the generated first laser signal is emitted through the integrated optical lens module, and the echo signal reflected by the measured target is received; the echo signal is mixed and interfered with the second laser signal through the beat signal generator to obtain the beat signal, and then the beat signal and the second sine wave are collected by the data acquisition card and sent to the signal processor, and the beat signal is resampled based on the second sine wave by the signal processor to obtain the resampled beat signal, and the resampled beat signal is Fourier transformed, and according to the corresponding relationship between frequency and distance, the measurement of the distance to be measured can be converted into the measurement of the beat signal frequency, so as to accurately obtain the distance to be measured between the integrated optical lens module and the target object. This method not only improves the accuracy of measurement, but also broadens the application scope of laser ranging technology.

[0087] In order to verify the effect of the embodiment of the present invention, the embodiment of the present invention also conducted relevant experiments. In the experiment, the driving voltage of 20Vpp and the modulation frequency of 25kHz were used, and the results of triangular wave frequency modulation were as follows: Figure 4 As shown, Figure 4 a and Figure 4 b are the output frequency of the laser and the distance measurement result respectively. At this time, due to the large frequency modulation, the linearity of the frequency modulation decreases, and the linearity order of magnitude is 10 -2 , and resonance occurs during frequency modulation. From the perspective of the frequency domain, the driving signal is a triangular wave signal, which contains harmonics of multiple frequencies, and resonant components of other frequencies are mixed in during the modulation process. Piezoelectric ceramics have an intrinsic resonant frequency. After coupling with the silicon photonic chip load, the resonant frequency moves to a low frequency. When the modulation frequency increases, the harmonic components of the triangular wave signal excite the mechanical resonance point, introducing additional frequencies, resulting in nonlinearity of the frequency modulation, which leads to severe band broadening during the ranging process and the inability to accurately extract the frequency points.

[0088] Since the harmonic component of the triangular wave excites the ultimate resonance point of the piezoelectric ceramic, if a sine wave is used as the driving signal, the influence of this factor can be greatly reduced. Figure 5 The figure shows the result of sine wave frequency modulation with a driving voltage of 20Vpp and a modulation frequency of 25kHz. Figure 5 a and Figure 5 c are the single-cycle and four-cycle output frequencies of the laser, Figure 5 b and Figure 5 d are the frequency domain results of single-cycle and four-cycle output frequency isolation with DC, respectively.

[0089] It can be seen that its frequency harmonic components are reduced, the 25kHz component is more than other components, and it is not easy to excite the mechanical harmonic points of piezoelectric ceramics. It can be approximately considered that the output frequency of the laser is a standard sine wave, and the frequency modulation effect is better than that of a triangle wave.

[0090] See also Figure 6 , PZT laser is selected for 20m optical fiber ranging test, the first channel CH1 of function signal generator 601 outputs a sine wave driving modulation signal with a modulation frequency of 25kHz and a driving voltage of 20Vpp to laser 402, and the modulation waveform bandwidth B is 800MHz, the second channel CH2 of function signal generator 601 is frequency phase coupled with the first channel to output the same synchronous sine signal wave with a modulation frequency of 25kHz and a driving voltage of Vpp, and the data acquisition card sampling rate is 250MS / s.

[0091] It should be noted that during the experimental stage, the integrated optical lens module and the target object were replaced by the optical fiber to be tested.

[0092] The laser 602 is modulated and divided into two paths of light, one path is used as intrinsic light, and the other path passes through the optical fiber 606 to be tested as measurement light. A beat frequency signal is formed in the photoelectric detector 603 and collected by the first channel CH1 of the data acquisition card 604. The second channel CH2 of the data acquisition card 604 receives the synchronous sinusoidal signal output by the second channel CH2 of the function signal generator 601. The trigger signal Tri is simultaneously connected to the trigger channel of the data acquisition card 604, and the synchronous sinusoidal signal and the beat frequency signal are input into the signal processor 605. The beat frequency signal is resampled by the signal processor 605 using the synchronous sinusoidal signal to obtain the resampled beat frequency signal, and then the resampled beat frequency signal is fast Fourier transformed to obtain the optical fiber distance.

[0093] Figure 7 The figure shows the distance to be measured obtained by the signal processing algorithm of the laser distance measurement system of this embodiment. The final distance to be measured is 20.86m. Figure 7 a is the time domain diagram after the resampling signal processing algorithm, Figure 7 b is a schematic diagram of the distance to be measured after signal processing.

[0094] The following is a description of a laser ranging method based on sinusoidal frequency modulation provided in an embodiment of the present invention. The laser ranging method based on sinusoidal frequency modulation described below and the laser ranging system based on sinusoidal frequency modulation described above can refer to each other.

[0095] The embodiment of the present invention provides a laser ranging method based on sinusoidal frequency modulation, see Figure 8 ,include: 801. Generate a first sine wave and a second sine wave by using a function signal generator, output the first sine wave to a laser, and output the second sine wave to a data acquisition card.

[0096] The first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes.

[0097] 802. Receive the first sine wave through the laser, use the first sine wave as a modulation signal to control the laser to generate a modulated laser signal, and send the modulated laser signal to the first coupler.

[0098] 803. Receive the modulated laser signal through the first coupler to perform splitting to generate a first laser signal and a second laser signal, transmit the first laser signal to the integrated optical lens module, and output the second laser signal as an intrinsic reference signal to the beat frequency signal generator.

[0099] 804. Output the first laser signal to the target object through the integrated optical lens module, receive an echo signal returned after the first laser signal detects the target object, and send the echo signal to a beat frequency signal generator.

[0100] 805. Receive the echo signal and the second laser signal through the beat frequency signal generator to process and obtain a beat frequency signal.

[0101] 806. Collect the beat frequency signal and the second sine wave through the data acquisition card, and send them to a signal processor.

[0102] 807. Resample the beat frequency signal based on the second sine wave through a signal processor to obtain a resampled beat frequency signal, and perform Fourier transform on the resampled beat frequency signal to obtain a distance to be measured between the integrated optical lens module and the target object.

[0103] Optionally, in step 803, the modulated laser signal is received by the first coupler and split to generate a first laser signal and a second laser signal, which specifically includes: splitting the modulated laser signal by the first coupler in a ratio of 95:5, generating a first laser signal from 95% of the modulated laser signal, and generating a second laser signal from 5% of the modulated laser signal.

[0104] Optionally, the beat frequency signal generator includes: a second coupler and a photodetector; step 805 specifically includes: receiving the echo signal and the second laser signal through the second coupler, coupling the echo signal with the second laser signal, and outputting the generated coupled signal to the photodetector; and processing the received coupled signal through the photodetector to obtain the beat frequency signal.

[0105] Optionally, step 806 specifically includes: sampling the second sine wave at equal intervals through a signal processor to obtain multiple index points; extracting signals corresponding to the multiple index points in the beat frequency signal through a signal processor to obtain a single-frequency sine signal carrying ranging information as a resampled beat frequency signal.

[0106] Optionally, step 804 specifically includes: receiving a first laser signal through an optical circulator and transmitting it to a lens; outputting the first laser signal to a target object through the lens, receiving an echo signal returned after the first laser signal detects the target object, and sending the echo signal to the optical circulator; sending the echo signal to a beat frequency signal generator through the optical circulator.

[0107] The laser ranging method based on sinusoidal frequency modulation provided by the embodiment of the present invention performs frequency modulation on the first sine wave through a laser, and then the modulated laser signal is split through the first coupler, and the generated first laser signal is emitted through the integrated optical lens module, and the echo signal reflected by the measured target is received; the echo signal is mixed and interfered with the second laser signal through the beat signal generator to obtain the beat signal, and then the beat signal and the second sine wave are collected by the data acquisition card and sent to the signal processor, and the beat signal is resampled based on the second sine wave by the signal processor to obtain the resampled beat signal, and the resampled beat signal is Fourier transformed, and according to the corresponding relationship between frequency and distance, the measurement of the distance to be measured can be converted into the measurement of the beat signal frequency, so as to accurately obtain the distance to be measured between the integrated optical lens module and the target object. This method not only improves the accuracy of measurement, but also broadens the application scope of laser ranging technology.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser ranging system based on sinusoidal frequency modulation, characterized in that: include: A function signal generator generates a first sine wave and a second sine wave, outputs the first sine wave to a laser and outputs the second sine wave to a data acquisition card, wherein the first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes; A laser, wherein the laser receives the first sine wave, uses the first sine wave as a modulation signal to control the laser to generate a modulated laser signal and sends the modulated laser signal to a first coupler; A first coupler, which receives the modulated laser signal and performs light splitting to generate a first laser signal and a second laser signal, transmits the first laser signal to an integrated optical lens module, and outputs the second laser signal as an intrinsic reference signal to a beat frequency signal generator; an integrated optical lens module, wherein the integrated optical lens module outputs the first laser signal to a target object, receives an echo signal returned after the first laser signal detects the target object, and sends the echo signal to a beat frequency signal generator; a beat signal generator, wherein the beat signal generator receives the echo signal and the second laser signal for processing to obtain a beat signal; A data acquisition card, wherein the data acquisition card acquires signals of the beat frequency signal and the second sine wave and sends the signals to a signal processor; A signal processor is provided, wherein the signal processor resamples the beat frequency signal based on the second sine wave to obtain a resampled beat frequency signal, and performs Fourier transform on the resampled beat frequency signal to obtain a distance to be measured between the integrated optical lens module and the target object.

2. The laser ranging system based on sinusoidal frequency modulation according to claim 1, characterized in that: The function signal generator includes a first channel and a second channel, wherein the first channel is connected to the laser and is used to output the first sine wave to the laser; and the second channel is connected to the data acquisition card and is used to output the second sine wave to the data acquisition card.

3. The laser ranging system based on sinusoidal frequency modulation according to claim 1, characterized in that: The first coupler splits the modulated laser signal in a ratio of 95:5, generates a first laser signal from 95% of the modulated laser signal, and generates a second laser signal from 5% of the modulated laser signal.

4. The laser ranging system based on sinusoidal frequency modulation according to claim 1, characterized in that: The beat frequency signal generator comprises: a second coupler, the second coupler receiving the echo signal and the second laser signal, coupling the echo signal with the second laser signal, and outputting a generated coupling signal to a photodetector; A photoelectric detector is connected to the second coupler and processes the received coupling signal to obtain the beat frequency signal.

5. The laser ranging system based on sinusoidal frequency modulation according to claim 1, characterized in that: The signal processor samples the second sine wave at equal intervals to obtain a plurality of index points; The signal processor extracts signals corresponding to multiple index points in the beat frequency signal, and obtains a single-frequency sinusoidal signal carrying ranging information as a resampled beat frequency signal.

6. The laser ranging system based on sinusoidal frequency modulation according to claim 1, characterized in that: The integrated optical lens module comprises: an optical circulator and a lens; The optical circulator receives the first laser signal and transmits it to the lens; The lens outputs the first laser signal to the target object, receives an echo signal returned after the first laser signal detects the target object, and sends the echo signal to the optical circulator; The optical circulator sends the echo signal to the beat frequency signal generator.

7. A laser ranging method based on sinusoidal frequency modulation, characterized in that: For use in a laser ranging system as claimed in any one of claims 1 to 6, the method comprising: Generate a first sine wave and a second sine wave by a function signal generator, output the first sine wave to a laser and output the second sine wave to a data acquisition card; wherein the first sine wave and the second sine wave are sine waves with the same frequency and the same initial phase but different amplitudes; receiving the first sine wave through the laser, and using the first sine wave as a modulation signal to control the laser to generate a modulated laser signal and send the modulated laser signal to the first coupler; The modulated laser signal is received by the first coupler for light splitting to generate a first laser signal and a second laser signal, the first laser signal is transmitted to an integrated optical lens module, and the second laser signal is output as an intrinsic reference signal to a beat frequency signal generator; Outputting the first laser signal to the target object through the integrated optical lens module, receiving an echo signal returned after the first laser signal detects the target object, and sending the echo signal to a beat frequency signal generator; The beat signal generator receives the echo signal and the second laser signal for processing to obtain a beat signal; The beat frequency signal and the second sine wave are collected by the data acquisition card and sent to a signal processor; The beat frequency signal is resampled based on the second sine wave through a signal processor to obtain a resampled beat frequency signal, and the resampled beat frequency signal is Fourier transformed to obtain a distance to be measured between the integrated optical lens module and the target object.

8. The laser ranging method based on sinusoidal frequency modulation according to claim 7, characterized in that: The method further comprises: receiving the modulated laser signal through the first coupler to split the light to generate a first laser signal and a second laser signal. The modulated laser signal is split by the first coupler in a ratio of 95:5, 95% of the modulated laser signal is generated into a first laser signal, and 5% of the modulated laser signal is generated into a second laser signal.

9. The laser ranging method based on sinusoidal frequency modulation according to claim 7, characterized in that: The beat frequency signal generator comprises: a second coupler and a photodetector; The beat signal generator receives the echo signal and the second laser signal for processing to obtain a beat signal, specifically comprising: receiving the echo signal and the second laser signal through the second coupler, coupling the echo signal with the second laser signal, and outputting the generated coupling signal to a photodetector; The photoelectric detector processes the received coupling signal to obtain the beat frequency signal.

10. The laser ranging method based on sinusoidal frequency modulation according to claim 7, characterized in that: Resampling the beat frequency signal based on the second sine wave by a signal processor to obtain a resampled beat frequency signal specifically includes: Sampling the second sine wave at equal intervals by the signal processor to obtain a plurality of index points; The signal processor extracts signals corresponding to a plurality of index points from the beat frequency signal, and obtains a single-frequency sinusoidal signal carrying ranging information as a resampled beat frequency signal.

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