Laser radar outgoing laser frequency calibration device and method based on hollow cathode lamp

Abstract

The application provides a kind of laser radar exit laser frequency calibration device and method based on hollow cathode lamp, it is related to the technical field of laser radar, device includes: laser generation device, including first seed source and second seed source, the output frequency of one continuous light of first seed source is locked after frequency and the other continuous light is combined after frequency beating, compare output frequency with target frequency, generate the approximate value of lock frequency deviation;The continuous light output by second seed source is amplified after frequency calibration and output;Light source module is used to produce as incident light;Energy regulation module is used to adjust the light intensity of incident light;Absorption signal detection module includes hollow cathode lamp and reflector, for obtaining target saturated absorption spectrum, based on lamb dip method, the continuous light output by second seed source is calibrated according to target saturated absorption spectrum and the approximate value of lock frequency deviation.The frequency locking precision can be improved to 1MHz, which helps high-resolution detection of vertical velocity.

Description

Technical Field

[0001] This application relates to the technical field of lidar, and in particular to a lidar output laser frequency calibration device and method based on a hollow cathode lamp. Background Technology

[0002] Resonance fluorescence lidar uses metal atoms (such as sodium, potassium, iron, etc.) at a range of 80km-100km as tracers. It excites the metal atoms to resonate with fluorescence by emitting narrow-linewidth, frequency-stable lasers, and analyzes the Doppler broadening and frequency shift of the resonance fluorescence signal to retrieve atmospheric temperature and wind field.

[0003] Laser technology is the biggest obstacle to the development of iron resonance fluorescence lidar, with the generation of 372nm wavelength laser pulses and precise laser frequency locking being the most significant technical challenges. Because narrow-band, frequency-stable pulsed light is required during measurement, laser frequency locking is essential, and the locking accuracy greatly affects the wind measurement accuracy of the iron resonance fluorescence lidar. Achieving high-precision laser frequency locking is a crucial research topic in overcoming these technical challenges.

[0004] Chinese patent application number CN202311739528.6, published on June 17, 2025, discloses an iron resonance fluorescence Doppler lidar and a laser generation device and method, including a first seed source, a first laser processor, a second seed source, and a second laser processor. The first seed source is used to output continuous seed lasers. The first laser processor is used to amplify the power of the continuous seed lasers, perform frequency doubling and stabilization processing, and mix the lasers after power amplification and frequency doubling and stabilization processing to obtain a difference frequency signal, and adjust the center wavelength of the continuous seed lasers according to the difference frequency signal. The second seed source is used to output continuous seed lasers. The second laser processor is used to combine the continuous seed lasers adjusted by the first seed source and the continuous seed lasers emitted by the second seed source to achieve frequency matching, and lock the phase of the difference frequency signal onto an externally provided radio frequency signal, wherein the signal loaded on the radio frequency signal includes a fixed carrier frequency difference w, the center frequency required for temperature and wind measurement, and the frequency hopping amount between the two wing frequencies. Controlling radio frequency signals in w- w and w+ The light source cycles through the two sources, locks in, and then amplifies and outputs the continuous light emitted by the second seed source.

[0005] The above method is a frequency-locking method based on the saturated absorption spectral line of iodine molecules. To address the lack of suitable atomic / molecular spectral lines at the 1116nm wavelength, a two-step frequency-locking scheme is proposed (iodine molecule frequency locking and heterodyne beat frequency shifting), as illustrated in the diagram below. Figure 1 As shown. The first step utilizes the characteristic absorption lines of iodine molecules combined with saturated absorption modulation transfer spectroscopy to achieve frequency locking of the first seed source. However, there is a frequency locking deviation between the frequency of the first seed source and the desired frequency. The second step involves frequency shifting and locking the second seed source using heterodyne beat frequency (the shift amount corresponds to the frequency locking deviation, which is...). ), making the output frequency match the iron atom 5 D4→ 5 The F5 transition spectral lines were precisely matched. Continuous light from the second seed source was injected into the Nd:YAG resonant cavity, and after multi-stage amplification and nonlinear frequency conversion, a 372 nm pulsed laser was generated.

[0006] The above method has a problem with spectral line selection. Iodine molecules have dense characteristic absorption lines near the 558nm wavelength, with only about 10MHz intervals between them. When locking the frequency, it is easy to mistakenly select adjacent spectral lines, leading to… Offset. For example... Figure 2 As shown in the simulation, A 10MHz offset will introduce system errors (temperature 0.4K, wind speed 4m / s). Meanwhile, currently... When the preset frequency is 1.2 GHz, there is a problem of insufficient accuracy in evaluating frequency locking deviation, which limits the detection accuracy. Summary of the Invention

[0007] Therefore, it is necessary to provide a laser frequency calibration device and method for lidar based on a hollow cathode lamp to address the above-mentioned technical problems. By identifying the characteristic spectral lines of iodine molecules, an approximate value of the frequency locking deviation is obtained. Then, an iron atom saturated absorption spectrum is generated by the hollow cathode lamp. Based on the Lamb dip method, the precise value of the frequency locking deviation is obtained according to the iron atom saturated absorption spectrum and the approximate value of the frequency locking deviation, thus completing the precise locking of the laser frequency of the iron resonance fluorescence lidar.

[0008] In a first aspect, this application provides a laser radar output laser frequency calibration device based on a hollow cathode lamp, comprising: The laser generating device includes a first seed source and a second seed source. The first seed source outputs two continuous beams of light. One of the continuous beams is frequency-locked using a frequency-locking module and then combined with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. The continuous light output from the second seed source is amplified and output after frequency calibration. The light source module is used to generate target laser light as incident light based on the output continuous light; The energy regulation module is used to adjust the intensity of the incident light. The absorption signal detection module includes a hollow cathode lamp and a reflector. Incident light penetrates the hollow cathode lamp, is reflected by the reflector, and then penetrates it again. The target saturated absorption spectrum is obtained based on the two-way laser light passing through the hollow cathode lamp. The detection is then performed using the Lamb's concave method and an approximation of the target saturated absorption spectrum and the frequency locking deviation. Frequency calibration is performed on the continuous light output from the second seed source.

[0009] In one embodiment, the laser generating apparatus includes an 1116nm seed laser.

[0010] In one embodiment, the light source module includes a 372nm power laser for generating 372nm narrow linewidth frequency-stabilized pulsed laser.

[0011] In one embodiment, the energy control module includes a laser energy meter, a beam splitter, and a λ / 2 waveplate. The beam splitter splits the incident light and transmits it to the laser energy meter and the λ / 2 waveplate respectively. The laser energy meter monitors the intensity of the incident light and adjusts the intensity of the incident light in conjunction with the λ / 2 waveplate.

[0012] In one embodiment, the absorption signal detection module further includes a λ / 4 waveplate disposed between the hollow cathode lamp and the reflector, for controlling the light intensity of the two-way laser.

[0013] Secondly, this application also provides a method for calibrating the emitted laser frequency of a lidar based on a hollow cathode lamp, comprising: The laser generator outputs two continuous beams from its first seed source. One beam's frequency is locked to the target signal's frequency lock point, and then it is combined with the other beam for frequency matching, thus correcting the first seed source's output frequency. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The incident light penetrates the hollow cathode lamp and then penetrates the hollow cathode lamp in the opposite direction. The target saturation absorption spectrum is obtained based on the two-way laser passing through the hollow cathode lamp. The incident light is generated based on the continuous light output from the second seed source of the laser generating device. Based on the Lamb dip method, the target saturated absorption spectrum is used as the reference spectrum, and the approximate value of the frequency locking deviation is used. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; precise value As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

[0014] In one embodiment, obtaining the target saturated absorption spectrum based on the Lamb's dip method using two-way laser light penetrating a hollow cathode lamp includes: The incident light penetrates the hollow cathode lamp as pump light, and then penetrates the hollow cathode lamp in the opposite direction as probe light; The target saturated absorption spectrum is obtained by using differential detection based on the pump light and probe light.

[0015] Thirdly, this application also provides a lidar output laser frequency calibration system based on a hollow cathode lamp, comprising: The frequency locking deviation generation module is used to output two continuous beams of light from the first seed source of the laser generator. After locking the frequency of one of the continuous beams to the frequency locking point of the target signal, it performs frequency matching with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The saturated absorption spectrum generation module is used to pass incident light through a hollow cathode lamp and obtain the target saturated absorption spectrum based on the two-way laser passing through the hollow cathode lamp; the incident light is generated based on the continuous light output from the second seed source of the laser generation device. The module for generating precise values ​​of frequency-locking bias is used to generate approximate values ​​of frequency-locking bias based on the Lamb's dip method, using the target saturated absorption spectrum as the reference spectrum. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; Frequency calibration module, used to accurately measure values As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

[0016] Fourthly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the following steps: The laser generator outputs two continuous beams from its first seed source. One beam's frequency is locked to the target signal's frequency lock point, and then it is combined with the other beam for frequency matching, thus correcting the first seed source's output frequency. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The incident light passes through the hollow cathode lamp and then passes through the hollow cathode lamp in the opposite direction. The target saturation absorption spectrum is obtained based on the two-way laser passing through the hollow cathode lamp using the Lamb dip method. Using the target saturated absorption spectrum as the reference spectrum, and an approximate value of the frequency locking deviation... As the center frequency, the output frequency of the second seed source of the laser generator. f2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; precise value As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

[0017] Fifthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, performs the following steps: The laser generator outputs two continuous beams from its first seed source. One beam's frequency is locked to the target signal's frequency lock point, and then it is combined with the other beam for frequency matching, thus correcting the first seed source's output frequency. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The incident light passes through the hollow cathode lamp and then passes through the hollow cathode lamp in the opposite direction. The target saturation absorption spectrum is obtained based on the two-way laser passing through the hollow cathode lamp using the Lamb dip method. Using the target saturated absorption spectrum as the reference spectrum, and an approximate value of the frequency locking deviation... As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; precise value As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

[0018] The laser radar output laser frequency calibration device and method based on hollow cathode lamps described above have the following advantages: 1. Using saturated absorption modulation transfer spectroscopy with characteristic absorption lines of iodine molecules around 558 nm, a 1116 nm seed laser is initially frequency-locked with an accuracy on the order of hundreds of kHz. Using the Doppler-free saturated absorption spectrum generated by hollow cathode lamp excitation as a frequency reference, the frequency-locking deviation between the seed laser and the required frequency is precisely calibrated, which can improve the frequency locking accuracy to 1 MHz, thus facilitating high-resolution detection of vertical velocity. 2. Hollow cathode lamps can produce a relatively high concentration of stable iron vapor, and the overall device structure is simple; at the same time, hollow cathode lamps are a mature off-the-shelf product. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the laser generation device in an iron resonance fluorescence lidar embodiment; Figure 2 In one embodiment A schematic diagram of the simulation results of the offset; where, Figure 2 (a) in the figure represents the change of temperature sensitivity function with atmospheric temperature under different laser frequency deviations and radial wind speed of 0 m / s. Figure 2 In (b), the wind speed sensitivity function varies with radial wind speed at different laser frequency deviations when the temperature is 180K. Figure 3 This is a schematic diagram of the structure of a lidar output laser frequency calibration device based on a hollow cathode lamp in one embodiment; Figure 4 This is a schematic diagram of the laser generation device in an improved iron resonant fluorescence lidar in one embodiment. Figure 5 This is a schematic diagram of the scanning results of the characteristic absorption lines of iodine molecules in one embodiment; Figure 6 This is a schematic diagram of the output result of the laser generating device after frequency locking of the first seed source in one embodiment. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0021] The Lamb depression bandwidth is close to the natural linewidth and can be used as a reference for frequency calibration. Iron atoms from the ground state... 5 D4 to excited state 5 The F5 transition is a simple two-level system. Pump light (intensity) I p ) and detection light (intensity) I d Backpropagation saturates the pump light to the atomic transitions of a specific velocity group, suppressing the absorption of the probe light by atoms of the same velocity group, thus determining the absorption coefficient of the probe light. Represented as:

[0022] in, Natural line width; k For wave vectors; The velocity of iron atoms; f The frequency of an iron atom; f 0 represents the central frequency of atomic transitions; The saturation light intensity; Let be the Maxwell velocity distribution function.

[0023] When the pump light is much greater than At that time, it resonates with iron atoms with a velocity of 0 (i.e., When atoms are excited to higher energy levels, population inversion occurs. At this point, the above equation can be approximated as:

[0024] Iron atoms in the same velocity group tend to saturate in their absorption of the probe light, causing the probe light to absorb at the center frequency. f Absorption at 0 decreases, forming a Lamb depression. The depression depth is determined by the pump light intensity, while the depression width is dominated by Γ, but it is affected by the broadening effect of atomic collisions, so the iron atom density needs to be controlled.

[0025] Firstly, based on the above principles, this application provides a laser radar output laser frequency calibration device based on a hollow cathode lamp, which utilizes the Lamb depression to achieve precise calibration of the laser frequency, ensuring alignment with iron atoms. 5 D4→ 5 Precise matching of the F5 transition spectral lines.

[0026] like Figure 3 and Figure 4 This application provides a laser radar output laser frequency calibration device based on a hollow cathode lamp, comprising: a laser generating device, a light source module, and an energy control module. The laser generating device includes a first seed source and a second seed source. The first seed source outputs two continuous beams of light. One of the continuous beams is frequency-locked using a frequency-locking module and then combined with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. The continuous light output from the second seed source is amplified and output after frequency calibration; the light source module is used to generate target laser light as incident light based on the output continuous light; the energy control module is used to adjust the light intensity of the incident light; the energy control module includes a hollow cathode lamp and a reflector. The incident light penetrates the hollow cathode lamp, is reflected by the reflector, and then penetrates the hollow cathode lamp in the opposite direction. The target saturated absorption spectrum is obtained based on the two-way laser light penetrating the hollow cathode lamp. Based on the Lamb's concave method, the target saturated absorption spectrum and the approximate value of the frequency locking deviation are used. Frequency calibration is performed on the continuous light output from the second seed source.

[0027] This application utilizes the characteristic absorption lines of iodine molecules combined with saturated absorption modulation transfer spectroscopy to achieve frequency locking of the first seed source. Because the absorption lines of iodine molecules are relatively dense near the 558 nm wavelength, it is easy to select the wrong locking spectral line during detection experiments. Therefore, an approximate value of the frequency difference is determined through experimental research. Previously, it was necessary to identify the selected characteristic absorption lines.

[0028] like Figure 4As shown, by connecting the output signal of the iodine frequency lock module to a high-speed oscilloscope and performing a triangular wave scan (1 GHz range), the following results are obtained: Figure 5 The 10 iodine molecule absorption lines are shown. Figure 5 There is cross-interference between spectral lines 1 to 3, while spectral lines 4 to 10 are independent of each other and their full width at half maximum (FWHM) and full width at half maximum (FWHM) are relatively close, indicating potential for equivalent frequency locking. Considering the three-peak structure on the left side of spectral line 4 (with an interval of approximately 80 MHz), which facilitates rapid identification, this application intends to select spectral line 4 as the characteristic absorption line.

[0029] In one embodiment, the laser generating apparatus includes an 1116nm seed laser. For example... Figure 4 As shown, the 1116 nm wavelength seed laser is improved by adding an optical fiber output, i.e., the output frequency is increased. f 1. Frequency locking of the continuous light output from the first seed source is achieved by modulating the transfer spectrum of iodine molecules using saturated absorption. This continuous light beam is then combined with unlocked continuous light for beat frequency adjustment. The error signal generated by the beat frequency adjustment is used for feedback regulation to correct the output frequency of the first seed source. f 1. Make f 1. Absolutely locked onto the characteristic absorption line of the iodine molecule. Measured using a laser wavelength meter. f The specific value of 1, and its correlation with the wavelength of 1116.29778 nm (i.e., the wavelength of iron atoms). 5 D4→ 5 By comparing the frequency corresponding to three times the F5 transition spectrum (with a wavelength of 372.09926 nm in vacuum), an approximate value of the frequency locking deviation can be obtained. .

[0030] In one embodiment, such as Figure 3 As shown, the light source module includes a 372nm power laser for generating 372nm narrow-linewidth frequency-stabilized pulsed laser; the energy control module includes a laser energy meter, a beam splitter, and a λ / 2 waveplate. The beam splitter splits the incident light and transmits it to the laser energy meter and the λ / 2 waveplate respectively. The laser energy meter monitors the intensity of the incident light and adjusts the intensity of the incident light in conjunction with the λ / 2 waveplate; the absorption signal detection module also includes a polarizing beam splitter and a λ / 4 waveplate. The polarizing beam splitter is placed after the λ / 2 waveplate. The incident light, after its intensity is adjusted, passes through the hollow cathode lamp through the polarizing beam splitter, is reflected by the mirror, and then passes back through the hollow cathode lamp. It is then transmitted to the photodetector for detection by the polarizing beam splitter. The λ / 4 waveplate is placed between the hollow cathode lamp and the mirror to control the intensity of the two-way laser.

[0031] In this application, the hollow cathode lamp is an iron hollow cathode lamp.

[0032] The frequency calibration device provided in this application adopts a two-way orthogonal optical path structure, with its core consisting of a light source module, an energy control unit, an absorption signal detection system, and an industrial computer integrated control system. The system uses a 372nm narrow-linewidth frequency-stabilized pulsed laser as the light source (scanning range 5GHz), and achieves incident light intensity modulation through a laser energy meter combined with a λ / 2 waveplate. The laser, through the two-way orthogonal optical path design, first penetrates the hollow cathode lamp body as pump light, and then penetrates in the opposite direction as probe light. The intensity of the two-way light is controlled by a λ / 4 waveplate, and the saturated absorption spectrum of iron atoms is obtained using the differential detection method. The photoelectric converted signal is digitally processed by a high-speed acquisition card, and finally, the industrial computer performs integrated operation of frequency scanning control and data storage analysis.

[0033] In one embodiment, an optical isolator is provided between the 372nm power laser and the beam splitter.

[0034] After constructing and debugging the optical path of the aforementioned frequency calibration device, the incident light parameters need to be optimized. To optimize the signal-to-noise ratio of the Doppler-free saturated absorption spectrum of iron atoms, the effect of laser pulse energy (50-500 μJ) on the saturated absorption depression depth was systematically studied under the conditions of fixed hollow cathode lamp current (5 mA) and argon buffer pressure (3 Torr). The incident light intensity was precisely adjusted by using a λ / 2 waveplate, and the pump-probe intensity ratio was monitored synchronously by combining a two-way orthogonal optical path design. The signal amplitude of the photodetector was captured in real time using a high-speed oscilloscope, and the optimal energy threshold was determined based on the stability of the depression depth (avoiding atomic vapor thermal disturbance and self-absorption effects). The experimental environment was triple-protected by TEC temperature control (±0.1℃), an optically isolated platform, and an electromagnetically shielded chamber.

[0035] After optimizing the incident light parameters, the parameters of the hollow cathode lamp were optimized. Under the optimal laser parameter conditions, the operating current of the hollow cathode lamp (1mA to 10mA) and the filling gas pressure (2Torr to 5Torr) were changed sequentially. The optimal operating parameters were determined by comprehensively considering the signal-to-noise ratio (the ratio of the peak signal to the root mean square noise), the signal amplitude (the depth of the saturation absorption depression), and the background noise level (the noise intensity in the non-resonant region). The sensitivity relationship between the operating parameters and the above physical quantities was also clarified.

[0036] In addition, in order to reduce To mitigate measurement errors, the frequency scanning range should be reduced to avoid nonlinear effects that may occur during the scanning process in PZT. The stability of laser energy during the scanning process should be better than 2%, and the statistical error of the obtained extreme point position of spectral intensity should be controlled within 0.1MHz through repeated experiments.

[0037] After completing the above parameter optimization, the frequency locking deviation is approximated. As the center frequency, the output frequency of the second seed source f2. Perform a scan with a scan step size of 1MHz to obtain high resolution. 5 D4→ 5 The iron atom undergoing the F5 state transition exhibits a Doppler-free saturated absorption spectrum, generating a precise value for the frequency-locking bias. The frequency corresponding to the Lamb dip in the spectrum is an approximation. With precise value The deviation between the frequency and the target frequency is determined by using the characteristic absorption line of iodine molecules near 558 nm for frequency locking and calibrating the frequency locking deviation between the frequency locking point of the iodine molecules and the desired frequency (the calibration process obtains the precise value of the frequency locking deviation). After the process, the precise value will be... As a frequency shifter, heterodyne beat frequency technology can achieve precise frequency locking. The final 372nm pulsed light frequency, after frequency doubling, will be precisely locked to the iron atom. 5 D4→ 5 Peak position of the F5 transition line.

[0038] Secondly, this application also provides a method for calibrating the output laser frequency of a lidar based on a hollow cathode lamp, comprising: using a first seed source of a laser generating device to output two continuous beams of light; locking the frequency of one of the continuous beams to the frequency lock point of the target signal; and then combining it with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. The incident light is passed through a hollow cathode lamp, and then back through the hollow cathode lamp. The target saturated absorption spectrum is obtained based on the two-way laser passing through the hollow cathode lamp using the Lamb's dimple method. The incident light is generated from the continuous light output from the second seed source of the laser generator. Based on the Lamb's dimple method, the target saturated absorption spectrum is used as the reference spectrum, and an approximate value of the frequency locking deviation is used. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; to the precise value As a frequency shift, heterodyne beat frequency technology is used to achieve frequency... f 2. Precise locking.

[0039] In one embodiment, the target saturated absorption spectrum is obtained based on the Lamb dip method using a two-way laser penetrating a hollow cathode lamp, comprising: the incident light penetrating the hollow cathode lamp as pump light, and then penetrating the hollow cathode lamp in the opposite direction as probe light; and the target saturated absorption spectrum is obtained using a differential detection method based on the pump light and the probe light.

[0040] In practical applications, such as Figure 6As shown, the distribution of characteristic absorption lines near the 558nm wavelength has been obtained through scanning, and frequency locking was performed using spectral line 4. The frequency locking results were obtained through a beat frequency experiment using two seed lasers. During the test period of over 27 hours, the peak-to-peak frequency of the 1116nm continuous light was less than 200kHz, and the root mean square frequency was better than 21kHz, indicating that frequency locking using the characteristic absorption lines of iodine molecules near 558nm achieved excellent results.

[0041] To ensure the stability of the spectrum from external environmental influences, the laser source was placed in a semiconductor constant temperature chamber with a temperature control accuracy of 0.1℃, and vibration isolation and electromagnetic interference prevention measures were implemented.

[0042] Furthermore, hollow cathode lamps can produce a relatively high concentration and stable iron vapor, and the overall device structure is simple. At the same time, hollow cathode lamps are a mature, off-the-shelf product.

[0043] Thirdly, this application also provides a lidar output laser frequency calibration system based on a hollow cathode lamp, comprising: The frequency locking deviation generation module is used to output two continuous beams of light from the first seed source of the laser generator. After locking the frequency of one of the continuous beams to the frequency locking point of the target signal, it performs frequency matching with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The saturated absorption spectrum generation module is used to pass incident light through a hollow cathode lamp and obtain the target saturated absorption spectrum based on the two-way laser passing through the hollow cathode lamp; the incident light is generated based on the continuous light output from the second seed source of the laser generation device. The module for generating precise values ​​of frequency-locking bias is used to generate approximate values ​​of frequency-locking bias based on the Lamb's dip method, using the target saturated absorption spectrum as the reference spectrum. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; Frequency calibration module, used to accurately measure values As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

[0044] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0045] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0046] 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.

[0047] 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 application should be determined by the appended claims.

Claims

1. A laser radar output laser frequency calibration device based on a hollow cathode lamp, characterized in that, include: The laser generating device includes a first seed source and a second seed source. The first seed source outputs two continuous beams of light. One of the continuous beams is frequency-locked using a frequency-locking module and then combined with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The continuous light output from the second seed source is amplified and output after frequency calibration; The light source module is used to generate target laser light as incident light based on the output continuous light; The energy regulation module is used to adjust the intensity of the incident light. The absorption signal detection module includes a hollow cathode lamp and a reflector. Incident light penetrates the hollow cathode lamp, is reflected by the reflector, and then penetrates it again. The target saturated absorption spectrum is obtained based on the two-way laser light passing through the hollow cathode lamp. The detection is then performed using the Lamb's concave method and an approximation of the target saturated absorption spectrum and frequency locking deviation. Frequency calibration is performed on the continuous light output from the second seed source.

2. The frequency calibration device according to claim 1, characterized in that, The laser generating device includes an 1116nm seed laser.

3. The frequency calibration device according to claim 1, characterized in that, The light source module includes a 372nm power laser for generating 372nm narrow linewidth frequency-stabilized pulsed laser.

4. The frequency calibration device according to claim 1, characterized in that, The energy control module includes a laser energy meter, a beam splitter, and a λ / 2 waveplate. The beam splitter splits the incident light and transmits it to the laser energy meter and the λ / 2 waveplate respectively. The laser energy meter monitors the intensity of the incident light and adjusts the intensity of the incident light in conjunction with the λ / 2 waveplate.

5. The frequency calibration device according to claim 1, characterized in that, The absorption signal detection module also includes a λ / 4 waveplate, which is placed between the hollow cathode lamp and the reflector to control the intensity of the two-way laser.

6. A method for calibrating the emitted laser frequency of a lidar based on a hollow cathode lamp, characterized in that, include: The laser generator outputs two continuous beams from its first seed source. One beam's frequency is locked to the target signal's frequency lock point, and then it is combined with the other beam for frequency matching, thus correcting the first seed source's output frequency. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The incident light passes through the hollow cathode lamp and then passes through the hollow cathode lamp in the opposite direction. The target saturation absorption spectrum is obtained based on the two-way laser passing through the hollow cathode lamp. The incident light is generated based on the continuous light output from the second seed source of the laser generating device; Based on the Lamb dip method, the target saturated absorption spectrum is used as the reference spectrum, and the approximate value of the frequency locking deviation is used. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; precise value As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

7. The method according to claim 6, characterized in that, Based on the Lamb's dip method, the target saturation absorption spectrum is obtained from the two-way laser passing through the hollow cathode lamp, including: The incident light penetrates the hollow cathode lamp as pump light, and then penetrates the hollow cathode lamp in the opposite direction as probe light; The target saturated absorption spectrum is obtained by using differential detection based on the pump light and probe light.

8. A lidar output laser frequency calibration system based on a hollow cathode lamp, characterized in that, include: The frequency locking deviation generation module is used to output two continuous beams of light from the first seed source of the laser generator. After locking the frequency of one of the continuous beams to the frequency locking point of the target signal, it performs frequency matching with the other continuous beam to correct the output frequency of the first seed source. f 1. Output frequency f 1. Compare with the target frequency to generate an approximate value for the frequency locking deviation. ; The saturated absorption spectrum generation module is used to pass incident light through a hollow cathode lamp and obtain the target saturated absorption spectrum based on the two-way laser passing through the hollow cathode lamp; the incident light is generated based on the continuous light output from the second seed source of the laser generation device. The module for generating precise values ​​of frequency-locking bias is used to generate approximate values ​​of frequency-locking bias based on the Lamb's dip method, using the target saturated absorption spectrum as the reference spectrum. As the center frequency, the output frequency of the second seed source of the laser generator. f 2. Perform a scan to obtain the target's Doppler-free saturated absorption spectrum and generate a precise value for the frequency-locking bias. ; Frequency calibration module, used to accurately measure values As a frequency shift, the heterodyne beat frequency technique is used to measure the frequency. f 2. Lock it.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 6 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 6 to 7.

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