Focus tracking control system and method applied to laser processing

Abstract

The invention discloses a focus tracking control system and method applied to laser processing. The system comprises a laser, a focus detection module, a tracking control module and a light path adjusting module. The method comprises the steps that S1, a laser beam is emitted into a light path adjusting module to be split into reference light and sample light, and a focus detection module detects the reference light to obtain focus information before machining and outputs the focus information to a tracking control module; s2, the tracking control module sends a first control signal to an optical path adjusting module; s3, the light path adjusting module adjusts the sample light to enable the sample light to be emitted into the processing object to process the processing object; s4, the tracking control module detects the processing object and sends a second control signal to the light path adjusting module; s5, the light path adjusting module adjusts the reference light and the sample light, and the adjusted sample light continues to be emitted into the processing object to process the processing object; returning to the step S4, and entering the step S6 until the processing of the processing object is completed; and S6, the focus detection module records the obtained focus information in processing. The machining process of the laser beam can be accurately corrected.

Description

Technical Field

[0001] The present invention belongs to the field of focus tracking control, and in particular relates to a focus tracking control system and method applied to laser processing. Background Art

[0002] The Chinese invention patent application with publication number "CN118305425A" discloses a zero focus detection system and correction method for a laser cutting head, which obtains a target zero focus distance between the calibration part of the laser cutting head and the nozzle, and provides a visual camera to set the receiving surface of the visual camera directly opposite the light-emitting surface of the laser cutting head; adjusts the distance between the visual camera and the laser cutting head, and identifies the exit light spot; when the exit light spot meets a preset condition, determines that the exit light spot is a zero focus spot; obtains the actual zero focus distance between the zero focus spot and the calibration part of the laser cutting head, and determines the zero focus correction amount based on the target zero focus distance and the actual zero focus distance; and corrects the position of the focusing system of the laser cutting head based on the zero focus correction amount. However, the patent application is not precise enough in adjusting the laser emitted by the laser cutting head, and is unable to make fine adjustments to the laser, resulting in certain errors in its correction of laser cutting. Summary of the Invention

[0003] The purpose of the present invention is to provide a focus tracking control system and method for laser processing, which makes the optical path of the laser beam adjustable and monitors and corrects the focus position of the laser beam, making the laser processing more accurate and faster.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0005] A focus tracking control system for laser processing, comprising:

[0006] A laser, used for emitting a laser beam to the optical path adjustment module;

[0007] A focus detection module is used to detect the focus of the laser beam after it passes through the optical path adjustment module, obtain the focus information and output it to the tracking control module;

[0008] A tracking control module, configured to send a control signal to the optical path adjustment module based on the focus information;

[0009] The optical path adjustment module is used to adjust the optical path of the laser beam according to the control signal sent by the tracking control module.

[0010] Preferably, the optical path adjustment module includes a collimating submodule, a reflecting submodule, a beam splitting submodule, and a focusing submodule;

[0011] The collimating submodule is used to collimate the laser beam emitted by the laser and then inject it into the reflecting submodule;

[0012] The reflection submodule is used to reflect the collimated laser beam into the beam splitting submodule;

[0013] The beam splitting submodule is used to split the collimated laser beam into reference light and sample light;

[0014] The focusing submodule is used to focus the sample light split by the beam splitting submodule to form a focus;

[0015] The focus detection module is further configured to acquire information of the sample light by detecting the reference light.

[0016] Preferably, the optical path adjustment module further includes a filtering submodule;

[0017] The reflection submodule is further used to reflect the reference light into the filtering submodule;

[0018] The filtering submodule is used to filter the reference light and then inject it into the focus detection module.

[0019] Preferably, the collimating submodule includes a first lens; the focusing submodule includes a second lens; the reflecting submodule includes a first reflector, a second reflector, and a third reflector; the filtering submodule includes a first filter; the beam splitting submodule includes a beam splitter; the laser beam emitted by the laser is collimated by the first lens and then emitted into the first reflector; the first reflector reflects the laser beam collimated by the first lens to the second reflector; the second reflector reflects the laser beam reflected by the first reflector into the beam splitter; the beam splitter splits the laser beam reflected by the second reflector into reference light and sample light; the third reflector reflects the reference light split by the beam splitter into the first filter; the second lens focuses the sample light split by the beam splitter and then emits it.

[0020] Preferably, the focus detection module includes a spectrometer; the first filter filters the reference light reflected by the third reflector and then injects the filtered light into the spectrometer;

[0021] The spectrometer is used to detect the focus of the filtered reference light and obtain focus information.

[0022] Preferably, the focus tracking control system also includes a camera; the filter module also includes a second filter; one side of the second reflector faces the beam splitter; the camera is located on the other side of the second reflector; and the second filter is arranged between the camera and the second reflector.

[0023] Preferably, the optical path adjustment module includes a translation stage; the collimation submodule, the reflection submodule, the beam splitting submodule, and the focusing submodule are all adjustably positioned on the translation stage; the focus tracking control system further includes a processing stage; the processing stage is positioned below the translation stage; an object to be processed by laser processing using the focus tracking control system is placed on the processing stage; the sample light is incident on the object to be processed;

[0024] The optical path adjustment module is further configured to control the translation stage according to a control signal sent by the tracking control module.

[0025] The present invention further provides a focus tracking control method for laser processing, which is applied to the above-mentioned focus tracking control system for laser processing; the focus tracking control method comprises the following steps:

[0026] Step S1. The laser beam enters the optical path adjustment module, which splits the laser beam into a reference beam and a sample beam. The focus detection module detects the reference beam to obtain the focus information before processing and outputs it to the tracking control module.

[0027] Step S2. The tracking control module sends a first control signal to the optical path adjustment module according to the focus information before processing;

[0028] Step S3. The optical path adjustment module adjusts the sample light so that it enters the processing object to process it according to the first control signal sent by the tracking control module;

[0029] Step S4. The tracking control module monitors the processing process of the processing object and obtains processing information of the processing object. The focus detection module obtains the processing focus information of the reference light and sends it to the tracking control module. The tracking control module sends a second control signal to the optical path adjustment module based on the processing information of the processing object and the processing focus information of the reference light.

[0030] Step S5. The optical path adjustment module adjusts the reference light and the sample light according to the second control signal. The adjusted sample light continues to be incident on the processing object to process it. The focus detection module continues to detect the adjusted reference light. The process then returns to step S4 until the processing of the processing object is completed and proceeds to step S6.

[0031] Step S6: The focus detection module records the acquired processing focus information.

[0032] Preferably, step S1 includes: the focus detection module processes the frequency of the reference light to obtain the focus position information and the frequency deviation value; the step S2 includes: the tracking control module generates a first control signal according to the frequency deviation value and sends it to the optical path adjustment module; the step S3 includes: the optical path adjustment module adjusts the collimation submodule, the reflection submodule, the beam splitting submodule, and the focusing submodule through the translation stage.

[0033] Preferably, the processing object includes a layered metal sample; the step S4 includes: the tracking control module monitors the processing process of the layered metal sample and performs ablation detection on the processing object, obtains the processing depth of the layered metal sample according to the result of the ablation detection, determines the focal plane of the sample light, and sends a second control signal to the optical path adjustment module according to the focal plane of the sample light.

[0034] The beneficial effects of the focus tracking control system and method applied to laser processing of the present invention are as follows:

[0035] 1. The present invention relates to a focus tracking control system and method for laser processing. By providing an optical path adjustment module, the optical path of the laser beam is made adjustable. Furthermore, a focus detection module and a tracking control module are used to monitor and correct the focus of the laser beam during the laser processing process, thereby making the laser processing more precise and faster.

[0036] 2. The present invention relates to a focus tracking control system and method for laser processing. Using low-coherence light interferometry, the laser beam emitted by the laser is split into reference light (reference arm) and sample light (sample arm). The optical paths of the reference and sample beams are nearly equal. This allows the spectrometer to acquire information about the reference beam and, in turn, the sample beam used in the processing.

[0037] 3. The present invention provides a focus tracking control system and method for laser processing. Each time a sample is processed, the focus information of the laser beam of the sample during the processing will be recorded. When the same sample is processed next time, the recorded focus information of the laser beam can be used to compensate for the adjustment process of the laser beam during this processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 FIG2 is a mechanical structure diagram of a focus tracking control system applied to laser processing according to an embodiment of the present invention;

[0039] Figure 2 FIG2 is a flowchart of a focus tracking control system for laser processing according to an embodiment of the present invention;

[0040] Figure 3 Shown is a flow chart of a focus tracking control method applied to laser processing according to an embodiment;

[0041] Figure 4 FIG2 is a schematic diagram of a groove at time T0 to T3 during the processing of a layered metal sample by a focus tracking control method applied to laser processing according to an embodiment;

[0042] Figure 5Shown is a comparison diagram of the before and after effects of a focus tracking control method applied to laser processing on focus correction in laser processing according to an embodiment.

[0043] Reference numerals

[0044] 1. Laser; 2. First lens; 3. First reflector; 4. Second reflector; 5. Second filter; 6. Camera; 7. Beam splitter; 8. First filter; 9. Third reflector; 10. Spectrometer; 11. Second lens. DETAILED DESCRIPTION

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0046] The technical solution of the present invention is described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] like Figure 1 and 2 As shown, a focus tracking control system applied to laser processing in this embodiment includes:

[0049] Laser 1, used for emitting a laser beam to the optical path adjustment module;

[0050] A focus detection module is used to detect the focus of the laser beam after it passes through the optical path adjustment module, obtain the focus information and output it to the tracking control module;

[0051] A tracking control module, configured to send a control signal to the optical path adjustment module based on the focus information;

[0052] The optical path adjustment module is used to adjust the optical path of the laser beam according to the control signal sent by the tracking control module.

[0053] Preferably, the optical path adjustment module includes a collimating submodule, a reflecting submodule, a beam splitting submodule, and a focusing submodule;

[0054] The collimating submodule is used to collimate the laser beam emitted by the laser 1 and then inject it into the reflecting submodule;

[0055] The reflection submodule is used to reflect the collimated laser beam into the beam splitting submodule;

[0056] The beam splitting submodule is used to split the collimated laser beam into reference light and sample light;

[0057] The focusing submodule is used to focus the sample light split by the beam splitting submodule to form a focus;

[0058] The focus detection module is further configured to acquire information of the sample light by detecting the reference light.

[0059] Preferably, the optical path adjustment module further includes a filtering submodule;

[0060] The reflection submodule is further used to reflect the reference light into the filtering submodule;

[0061] The filtering submodule is used to filter the reference light and then inject it into the focus detection module.

[0062] Preferably, the collimating submodule includes a first lens 2; the focusing submodule includes a second lens 11; the reflecting submodule includes a first reflector 3, a second reflector 4, and a third reflector 9; the filtering submodule includes a first filter 8; the beam splitting submodule includes a beam splitter 7; the laser beam emitted by the laser 1 is collimated by the first lens 2 and then emitted into the first reflector 3; the first reflector 3 reflects the laser beam collimated by the first lens 2 to the second reflector 4; the second reflector 4 reflects the laser beam reflected by the first reflector 3 into the beam splitter 7; the beam splitter 7 splits the laser beam reflected by the second reflector 4 into reference light and sample light; the third reflector 9 reflects the reference light split by the beam splitter 7 into the first filter 8; the second lens 11 focuses the sample light split by the beam splitter 7 and emits it.

[0063] Preferably, the focus detection module includes a spectrometer 10; the first filter 8 filters the reference light reflected by the third reflector 9 and then injects the filtered light into the spectrometer 10;

[0064] The spectrometer 10 is used to detect the focus of the filtered reference light and obtain focus information.

[0065] Preferably, the focus tracking control system also includes a camera 6; the filter module also includes a second filter 5; one side of the second reflector 4 faces the beam splitter 7; the camera 6 is located on the other side of the second reflector 4; and the second filter 5 is arranged between the camera 6 and the second reflector 4.

[0066] Preferably, the optical path adjustment module includes a translation stage; the collimation submodule, the reflection submodule, the beam splitting submodule, and the focusing submodule are all adjustably positioned on the translation stage; the focus tracking control system further includes a processing stage; the processing stage is positioned below the translation stage; an object to be processed by laser processing using the focus tracking control system is placed on the processing stage; the sample light is incident on the object to be processed;

[0067] The optical path adjustment module is also used to control the translation stage according to the control signal sent by the tracking control module. Specifically, the laser of this embodiment emits a laser beam with a repetition rate of 4kHz to generate 25fs pulses, a central wavelength of 1570nm, a spectral bandwidth (FWHM) of 40nm, and an axial resolution (coherence length) of 9μm. The first filter 8 and the second filter 5 of this embodiment are both variable neutral density filters that can balance the intensity of the reference light and the sample light. The beam splitter 7 of this embodiment is a polarization beam splitter 7, which allows the polarized light pulses to propagate to the spectrometer 10 and the second lens 11 with minimal loss.

[0068] Specifically, the second lens 11 of this embodiment is a 38 mm aperture EFL lens, which is adjusted to have a beam waist w (M=1.6) of 4.7 μm and a confocal parameter of 49.6 μm.

[0069] Specifically, the first lens 2, the second lens 11, the first reflector 3, the second reflector 4, the third reflector 9 and the beam splitter 7 of this embodiment are all mounted on a translation stage, and can be automatically displaced and angle-adjusted by a tracking control module.

[0070] Specifically, the camera 6 of this embodiment is a CCD camera 6, which can collect a portion of the reflected light generated by cutting the processing object during the laser processing process (this portion of the reflected light is first filtered by the second filter 5), realize visual inspection, and visually confirm the focus position and the processing object position.

[0071] This embodiment of a focus tracking control system for laser processing utilizes low-coherence light interferometry to split the laser beam emitted by a laser into a reference arm and a sample arm. The optical path lengths of the reference and sample arms are nearly equal, causing interference on the spectrometer that collects information about the reference arm. This interference allows the system to perform relative optical path length measurements, thereby acquiring information about the sample arm by monitoring the reference arm. The reference light described in this invention is the reference arm in low-coherence light interferometry, and the sample light is the sample arm in low-coherence light interferometry.

[0072] Example 2

[0073] This embodiment also provides a focus tracking control method for laser processing, which is applied to a focus tracking control system for laser processing in the first embodiment; Figure 3 As shown, the focus tracking control method includes the following steps:

[0074] Step S1. The laser beam enters the optical path adjustment module, which splits the laser beam into a reference beam and a sample beam. The focus detection module detects the reference beam to obtain the focus information before processing and outputs it to the tracking control module.

[0075] Step S2. The tracking control module sends a first control signal to the optical path adjustment module according to the focus information before processing;

[0076] Step S3. The optical path adjustment module adjusts the sample light so that it enters the processing object to process it according to the first control signal sent by the tracking control module;

[0077] Step S4. The tracking control module monitors the processing process of the processing object and obtains processing information of the processing object. The focus detection module obtains the processing focus information of the reference light and sends it to the tracking control module. The tracking control module sends a second control signal to the optical path adjustment module based on the processing information of the processing object and the processing focus information of the reference light.

[0078] Step S5. The optical path adjustment module adjusts the reference light and the sample light according to the second control signal. The adjusted sample light continues to be incident on the processing object to process it. The focus detection module continues to detect the adjusted reference light. The process then returns to step S4 until the processing of the processing object is completed and proceeds to step S6.

[0079] Step S6: The focus detection module records the acquired processing focus information.

[0080] Preferably, step S1 includes: the focus detection module processes the frequency of the reference light to obtain the focus position information and the frequency deviation value; the step S2 includes: the tracking control module generates a first control signal according to the frequency deviation value and sends it to the optical path adjustment module; the step S3 includes: the optical path adjustment module adjusts the collimation submodule, the reflection submodule, the beam splitting submodule, and the focusing submodule through the translation stage.

[0081] Preferably, the processing object includes a layered metal sample; the step S4 includes: the tracking control module monitors the processing process of the layered metal sample and performs ablation detection on the processing object, obtains the processing depth of the layered metal sample according to the result of the ablation detection, determines the focal plane of the sample light, and sends a second control signal to the optical path adjustment module according to the focal plane of the sample light.

[0082] Specifically, when detecting the light signal collected by the spectrometer 10, the focus tracking control method of this embodiment processes the frequency signal of the characteristic spectrum in the time domain of the spectrum detection signal through fast Fourier transform, and calculates the frequency deviation value of the focus, so as to determine whether the focus position is correct and adjust the focus position according to the difference before and after the focus.

[0083] Furthermore, through the focus tracking control method of this embodiment, during the laser processing of the processing object, the current focus position and the processing object position are continuously evaluated and the deviation and change trend are taken into consideration to determine the correction scheme of the light path adjustment module.

[0084] In another embodiment, the focus tracking control method is applied to focus detection compensation of continuous light and high-frequency pulsed laser beams.

[0085] In another embodiment, the sample light adopts a grating pattern (0.3 mm / s): consisting of 5 lines with a length of 5 mm, a spacing of 50 μm, a laser pulse energy of (9.05±0.18) μJ, and a fluence equal to 13.5 J / cm.

[0086] In another embodiment, the processing object is a layered metal sample (bronze-plated steel). The sample is placed on the focal plane, and the laser beam is adjusted to a flux of 16.5 J / cm and a femtosecond pulse of (11.72 ± 0.22) μJ and applied to the sample surface. Then, 2500 overlapping laser pulses are started. During this process, the focus tracking control method monitors the changes in the ablation focus of the sample, uses the ablation intensity to map the surface profile, and records the groove profile from time T0 to T3. Figure 4 As shown, the echo characteristic frequency signal spacing of the sample surface at different times can be collected to confirm the processing depth.

[0087] Further, from Figure 4 As can be seen, the focus tracking control method of this embodiment can maintain uniform width and constant depth of grooves created during machining of layered metal samples. Furthermore, all grooves achieve stability, maintaining similar width and depth despite the five machining paths of the sample. Therefore, after the focus detection module in step S6 records the focus information during machining, it can be used as historical data for the next machining of the same sample, compensating for surface profile deviations.

[0088] Furthermore, the quantification process of the groove profile generated when processing the layered metal sample is as follows: establish a spatial coordinate system, obtain the coordinate x of the center of the groove in the spatial coordinate system, obtain the height h(x) of the groove through the tracking control module, and obtain the two relationship equations of the center of gravity u1 and the width u2 of the groove as follows:

[0089]

[0090] Further, Figure 5 Shown is a comparison diagram of the effects of the focus tracking control method of this embodiment on laser focus correction before and after. The area within the two red lines is the focus range required for laser processing, surface tracking point 2 is the focus before correction by this method, and surface tracking point 1 is the focus after correction by this method. The dotted line indicates the degree of correction in each time period.

[0091] Furthermore, the method can effectively improve the removal rate of steel and copper by measuring the change of the profile through low-coherence interferometry and the surface etched away by the ablation process of the sample through optical coherence tomography.

[0092] A focus tracking control method applied to laser processing in this embodiment can use the same laser beam to separate multiple paths to process and monitor the surface of the sample through a low-coherence interferometry measurement setting, while also keeping the sample surface within the focusing range of the laser beam. This allows the width of the groove produced in the sample during laser processing to remain stable and many times larger than the confocal parameter of the laser beam.

[0093] In another embodiment, the scan width uniformity of the beam can be controlled to less than 1 micron.

[0094] In another embodiment, the method can increase the signal strength by adding a laser polarization signal and adding a triggered spectrometer 10 to synchronize the collection with the laser pulse, thereby obtaining better processing results and faster processing speed.

[0095] In another embodiment, the method can process a transparent sample and make the focus below the surface of the transparent sample through an optical path adjustment module, thereby allowing the creation of a waveguide in curved glass for contour detection.

[0096] In another embodiment, the present method can perform tomography to form an image of the surface profile mapped by ablation intensity, and in this case, the setting of the spectrometer 10 is the same as that of an OCT or a white light profilometer.

[0097] The above describes in detail an embodiment of a focus tracking control system and method for laser processing provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only intended to help understand the core concept of the present invention. It should be noted that, for those skilled in the art, without departing from the principles of the present invention, the present invention can be improved and modified in various ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A focus tracking control system for laser processing, characterized in that: include: A laser (1) for emitting a laser beam to the optical path adjustment module; A focus detection module is used to detect the focus of the laser beam after it passes through the optical path adjustment module, obtain the focus information and output it to the tracking control module; A tracking control module, configured to send a control signal to the optical path adjustment module based on the focus information; The optical path adjustment module is used to adjust the optical path of the laser beam according to the control signal sent by the tracking control module.

2. The focus tracking control system according to claim 1, characterized in that: The optical path adjustment module includes a collimating submodule, a reflecting submodule, a beam splitting submodule, and a focusing submodule; The collimating submodule is used to collimate the laser beam emitted by the laser (1) and then inject it into the reflecting submodule; The reflection submodule is used to reflect the collimated laser beam into the beam splitting submodule; The beam splitting submodule is used to split the collimated laser beam into reference light and sample light; The focusing submodule is used to focus the sample light split by the beam splitting submodule to form a focus; The focus detection module is further configured to acquire information of the sample light by detecting the reference light.

3. The focus tracking control system according to claim 2, characterized in that: The optical path adjustment module also includes a filter submodule; The reflection submodule is further used to reflect the reference light into the filtering submodule; The filtering submodule is used to filter the reference light and then inject it into the focus detection module.

4. The focus tracking control system according to claim 3, characterized in that: The collimating submodule includes a first lens (2); the focusing submodule includes a second lens (11); the reflecting submodule includes a first reflecting mirror (3), a second reflecting mirror (4), and a third reflecting mirror (9); the filtering submodule includes a first filter (8); the beam splitting submodule includes a beam splitter (7); the laser beam emitted by the laser (1) is collimated by the first lens (2) and then incident on the first reflecting mirror (3); the first reflecting mirror (3) reflects the laser beam collimated by the first lens (2) to the second reflecting mirror (4); the second reflecting mirror (4) reflects the laser beam reflected by the first reflecting mirror (3) to the beam splitter (7); the beam splitter (7) splits the laser beam reflected by the second reflecting mirror (4) into reference light and sample light; the third reflecting mirror (9) reflects the reference light split by the beam splitter (7) to the first filter (8); the second lens (11) focuses the sample light split by the beam splitter (7) and then emits it.

5. The focus tracking control system according to claim 4, characterized in that: The focus detection module includes a spectrometer (10); the first filter (8) filters the reference light reflected by the third reflector (9) and then injects the filtered light into the spectrometer (10); The spectrometer (10) is used to detect the focus of the filtered reference light and obtain focus information.

6. The focus tracking control system according to claim 4, characterized in that: The focus tracking control system further comprises a camera (6); the filter module further comprises a second filter (5); one side of the second reflector (4) faces the beam splitter (7); the camera (6) is located on the other side of the second reflector (4); and the second filter (5) is arranged between the camera (6) and the second reflector (4).

7. The focus tracking control system according to any one of claims 2 to 6, characterized in that: The optical path adjustment module includes a translation stage; the collimation submodule, reflection submodule, beam splitting submodule, and focusing submodule are all adjustably positioned on the translation stage; the focus tracking control system also includes a processing stage; the processing stage is positioned below the translation stage; an object to be processed by laser processing using the focus tracking control system is placed on the processing stage; the sample light is incident on the object to be processed; The optical path adjustment module is further configured to control the translation stage according to a control signal sent by the tracking control module.

8. A focus tracking control method for laser processing, characterized in that: The focus tracking control system for laser processing according to claim 7 is applied; the focus tracking control method comprises the following steps: Step S1. The laser beam enters the optical path adjustment module, which splits the laser beam into a reference beam and a sample beam. The focus detection module detects the reference beam to obtain the focus information before processing and outputs it to the tracking control module. Step S2. The tracking control module sends a first control signal to the optical path adjustment module according to the focus information before processing; Step S3. The optical path adjustment module adjusts the sample light so that it enters the processing object to process it according to the first control signal sent by the tracking control module; Step S4. The tracking control module monitors the processing process of the processing object and obtains processing information of the processing object. The focus detection module obtains the processing focus information of the reference light and sends it to the tracking control module. The tracking control module sends a second control signal to the optical path adjustment module based on the processing information of the processing object and the processing focus information of the reference light. Step S5. The optical path adjustment module adjusts the reference light and the sample light according to the second control signal. The adjusted sample light continues to be incident on the processing object to process it. The focus detection module continues to detect the adjusted reference light. The process then returns to step S4 until the processing of the processing object is completed and proceeds to step S6. Step S6: The focus detection module records the acquired processing focus information.

9. The focus tracking control method according to claim 8, wherein: The step S1 includes: the focus detection module processes the frequency of the reference light to obtain the focus position information and the frequency deviation value; the step S2 includes: the tracking control module generates a first control signal according to the frequency deviation value and sends it to the optical path adjustment module; the step S3 includes: the optical path adjustment module adjusts the collimation submodule, the reflection submodule, the beam splitting submodule, and the focusing submodule through the translation stage.

10. The focus tracking control method according to claim 8, wherein: The processing object includes a layered metal sample; step S4 includes: the tracking control module monitors the processing process of the layered metal sample and performs ablation detection on the processing object, obtains the processing depth of the layered metal sample according to the result of the ablation detection, determines the focal plane of the sample light, and sends a second control signal to the optical path adjustment module according to the focal plane of the sample light.

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