CN115533347A - On-line monitoring method for femtosecond laser extreme micropore machining - Google Patents
On-line monitoring method for femtosecond laser extreme micropore machining Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 41
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- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
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- 229910052700 potassium Inorganic materials 0.000 claims description 2
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Abstract
The invention discloses an online monitoring method for femtosecond laser extreme micropore processing, which comprises a femtosecond laser processing optical path module and an online monitoring device for femtosecond laser extreme micropore processing, wherein the online monitoring device for femtosecond laser extreme micropore processing is an online frequency-sweeping OCT (optical coherence tomography) monitoring module, and can realize ultrahigh-precision online real-time monitoring in the femtosecond laser processing process, and realize the following real-time online measurement precision and measurement precision by utilizing an optical coherence imaging (OCT): 2.5 μm; measurement range (maximum measurement length): 6mm; the measurement mode is as follows: online real-time measurement; center wavelength: 1310nm; frequency sweeping speed: 20kHz.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of femtosecond laser micropore processing, and particularly relates to an on-line monitoring method for femtosecond laser extreme micropore processing.
[ background of the invention ]
The femtosecond laser processing integrates an ultrafast laser technology, an ultrahigh precision positioning technology and a microscopic technology, is a novel CMC-SiC material processing mode, and has the following main advantages compared with the common processing mode: 1. the processing damage is small: the femtosecond ultrashort pulse laser has short pulse duration, the energy finishes the interaction with the substance in a very small time and space, the heat cannot be diffused in time from the beginning to the end of the processing, the energy is only accumulated in a thin layer of a material micro area, and after the processing is finished, the material around the damaged area is still in a cold state, so that a plurality of negative effects brought by the thermal effect in the traditional processing are greatly reduced; 2. the processing precision is high: the femtosecond laser energy is distributed in a Gaussian or quasi-Gaussian form in space and time, so that the intensity of only the central part of a focusing light spot can reach the processing threshold of a material, the energy absorption and action range in processing is limited in a small volume at the central part of a focus, the processing scale is far smaller than the size of the light spot, and the processing scale reaches submicron or even nanoscale.
There are related studies at present, for example, chinese patent application No. CN202110490885.8 is a femtosecond laser rotary type dual-spot beam micropore processing method, which uses a spatial light modulator to load 0-pi phase to perform phase shaping on incident femtosecond laser with gaussian intensity distribution, because different phases are applied to the left and right parts of an incident gaussian light field, in the middle area where the two parts are overlapped, a light field intensity dark area is formed due to phase distortion, so that the original gaussian beam is shaped into a dual-spot beam; in the micropore machining process, the light field dark area at the center of the double-light-spot light beam is beneficial to the generated plasma to be sprayed from the position, so that the influence on subsequent laser pulse is reduced, the energy deposition efficiency is improved, and the micropore machining depth is increased.
The femtosecond laser micromachining technology is a new special processing technology, has the advantages of high processing precision, small heat affected zone, thin recasting layer, no burr, strong material applicability and the like, and is a new method for realizing the processing of the gas film hole of the ultra-precise aeroengine blade. In the femtosecond laser precision machining process of making holes (in micrometer scale), in order to obtain the required machining depth and aperture size, the machining parameters of the femtosecond laser need to be explored and optimized according to the characteristics of a target material, however, because a theoretical framework of a system is lacked as guidance, the exploration of the parameters of the femtosecond laser machining usually carries out repeated iteration on multiple groups of parameters, and the process is complicated and complex. At present, the scanning electron microscope and the atomic force microscope are generally adopted to represent the depth and aperture size results of laser processing, and the two methods can only obtain static images and cannot provide dynamic data in the processing process.
[ summary of the invention ]
The invention provides an on-line monitoring method for femtosecond laser extreme micropore processing, which can realize ultrahigh precision on-line real-time monitoring in the femtosecond laser processing process and aims to overcome the defects that in the prior art, search for parameters of femtosecond laser processing usually repeatedly iterates a plurality of groups of parameters, the process is complicated, and the scanning electron microscope and the atomic force microscope which are usually adopted at present represent the results of the depth and the aperture size of laser processing, and the two methods can only obtain static images and cannot provide dynamic data in the processing process.
The purpose of the invention is realized by the following technical scheme:
optical Coherence imaging (OCT) is divided into Time Domain signal Optical Coherence imaging (Time Domain Optical Coherence Tomography, TD-OCT) and frequency Domain signal Fourier Optical Coherence imaging (FD-OCT), and FD-OCT is divided into a spectrometer-based spectral Domain OCT system (SD-OCT) and a frequency sweep-based OCT system (SS-OCT) according to the type of light Source and the way of interference signal acquisition, where SS-OCT is the latest generation of SD imaging, and does not require a reference arm mechanical scan, and depth information is extracted by Fourier transform, which has characteristics of TD-point detection and advantages of fast imaging.
And (3) calculating:
the SS-OCT is to image the measured object by utilizing the backscattering of light, and the light generates the effects of absorption, refraction, scattering and the like after being emitted into tissues, wherein the single scattering, multiple scattering and the backscattering comprise the internal information of the tissues, and the single scattering, the multiple scattering and the backscattering are main detection targets; if only one path of light signal is measured, because the intensity is very weak, imaging cannot be carried out, therefore, the OCT adopts the Michelson interferometer on the light path structure, generates interference signals with the reflected light of the plane mirror, carries out tissue imaging by detecting the interference signals, has the mathematical principle similar to optical frequency domain ranging, and a light source sends out one path of light signals which respectively enter after being divided in a certain proportionA reference arm and a sample arm; because the two paths of light are generated from the same light source, the two paths of light meet the light wave coherence condition (same frequency, same vibration direction and constant phase difference), and are different from the low coherence light source of the time domain OCT, the swept frequency light source only outputs very narrow light beams each time according to the time sequence in a swept frequency period, and therefore the coherence length of the swept frequency light source is very long. Suppose the return light amplitude of the reference arm is E r (λ) sample arm return light amplitude E s (λ), assuming the reference arm is totally reflected and noting the reference arm position depth as L without loss of generality r ，L s The sample arm depth position, a(s) is the depth L s The reference arm and sample arm return amplitudes can be expressed as:
the optical signals returned by the two arms are acquired by a balanced detector, and in a sweep period, the interference signal I (k) received by the detector for a specific wavelength is as follows:
wherein
Z n ，Z m Respectively is a reaction of 2 In (2), s is replaced by n, m is the depth information extracted by analyzing the interference signal, and the Fourier transform of the formula (2) is as follows:
known from the Vena-Sinkinson theorem: under the condition of a wide stationary random process, the power spectral density of the light source is Fourier transform of an autocorrelation function of the light source, and gamma (z) is a coherent function of the light source; similarly, it can be seen from equation (3) that after fourier transform, the depth information is resolved, the direct-current term corresponding to equation (2) is the self-phase term of the reference arm, which is usually displayed as a straight line at the zero optical path position during imaging and is the noise affecting the imaging effect to be removed, the second term is a coherent signal term which includes positive and negative parts corresponding to the depth information and its mirror image at both sides of the zero optical path, and the third term AC [ a(s) ] represents the different-depth cross-correlation noise of the sample, which is much lower than the interference signal and is usually removed as the background noise;
an SS-OCT online monitoring device composed of optical fibers is used for measuring the precision of a processing structure in laser processing, light beams from a Sweep Light Source (SLS) with the center wavelength of 1.3 mu m, the spectral width of 80nm and the repetition frequency of 20kHz in frequency scanning pass through a target arm and reference arm optical fiber (SMF) coupler (Thorlabs, TW1300R2A 1) and the coupling ratio of 9:1, and the light source adopts an electro-optic crystal of potassium tantalate-niobate (KTa 1-xNbxO3, KTN) as a driver of scanning output wavelength, so that the light source has no mechanical moving part and can be stably used in industrial application needing quantitative analysis; a target beam is radiated coaxially with the femtosecond laser beam onto the processed sample through a dichroic mirror (galvanometer DM) via an SMF circulator (Thorlabs, CIR 1310-APC) having a core diameter of 8.2 μm; a Polarization Controller (PC) (Thorlabs, CPC 900) for adjusting the polarization of the light beam; the optical interference signal between the reflecting object and the reference beam is detected by a Balanced Detector (BD) (Hamamatsu, C12668-02) with an SMF coupler (Thorlabs, TW1300R5 A1), with a coupling ratio of 5:5; the interference signal is collected by a high-flux electronic lens data acquisition system (DAQ) (Pico Technology, pico scope 3205A)) and converted into an industrial personal computer, the signal collection trigger is controlled by a Scanning Light Source (SLS), and the depth of the processed structure is quantitatively evaluated by performing inverse Fourier transform on the interference signal; the time required for capturing the optical interference signal and for calculating the fourier spectrum (a-scan curve) was 3 and 10 milliseconds, respectively, as a sample, and the workpiece to be machined was mounted on a three-axis translation motor stage (Thorlabs, ZFS 13B).
The invention provides an on-line monitoring method for femtosecond laser extreme micropore machining, which particularly adopts an on-line monitoring device for femtosecond laser extreme micropore machining and a femtosecond laser machining light path module to accurately monitor the machining precision in the precise machining process of a femtosecond laser machining workpiece;
the femtosecond laser extreme micropore processing online monitoring device is an online frequency sweep OCT monitoring module;
the femtosecond laser processing light path module is used for carrying out precision processing on a processed workpiece;
the femtosecond laser processing optical path system comprises a cooperative control module, a laser control module, a light beam deflection control module, a light beam translation control module and a scanning distribution, speed, laser power and taper parameter control module;
on the output light path of the femtosecond laser, a convex lens and a concave lens of a beam expanding module, a total reflection prism, an upper deflection optical wedge and a lower deflection optical wedge of a deflection optical wedge group, an upper flat plate of a parallel flat plate group, a lower flat plate of the parallel flat plate group and a focusing lens are sequentially arranged, and finally, a light beam reaches a processed workpiece, wherein the beam expanding module consists of the concave lens and the convex lens; the laser control module controls a femtosecond laser, the light beam deflection control module controls an upper deflection light wedge and a lower deflection light wedge of a deflection light wedge group, and the light beam translation control module controls an upper flat plate of a parallel flat plate group and a lower flat plate of the parallel flat plate group; the laser control module, the light beam deflection control module and the light beam translation control module are connected with the cooperative control module through data lines, and the cooperative control module is connected with the industrial personal computer through the data lines; controlling the incident femtosecond laser beam to sequentially pass through the laser control module, the beam deflection control module, the beam translation control module and the focusing mirror and then carrying out micropore machining on the machined workpiece;
the on-line frequency-sweeping OCT monitoring module is used for accurately monitoring the processing precision in the precise processing process of a femtosecond laser processing workpiece and comprises a frequency-sweeping light source, an optical fiber coupler I, a circulator I, a polarization controller I, a collimating mirror II, a collimating mirror III, a polarization controller II, a circulator II, a collimating mirror I, a convex lens, a total reflecting mirror, an optical fiber coupler II, a balance detector and an industrial personal computer.
Furthermore, the laser control module comprises a beam expander and a total reflection prism which are sequentially arranged along the direction of an optical path, the beam expander is arranged on the emergent surface of the femtosecond laser, and the total reflection prism is arranged on the emergent surface of the beam expander; and the light beam deflection control module, the light beam translation control module and the focusing mirror are sequentially and vertically distributed below the total reflection prism. Furthermore, the light beam emitted by the laser firstly passes through the beam expander to carry out beam expansion collimation on the light beam, then passes through the deflection light wedge group to form an included angle of +/-5 degrees with the optical axis, then passes through the parallel plate group to generate translation of +/-6 mm, and then is focused on a focal plane which deviates from the optical axis by +/-6 cm distance through the focusing lens, when the deflection light wedge group and the parallel plate group synchronously rotate at high speed, a circular track can be formed on the focal plane, and the processing of the micropore with large depth-diameter ratio and controllable taper is realized by changing the relative deflection angle of the light wedge and the relative rotation angle of the parallel plate in real time; furthermore, the wedge angle of the upper deflection optical wedge and the lower deflection optical wedge is less than or equal to +/-5 degrees, an air gap is formed between the upper deflection optical wedge and the lower deflection optical wedge, the upper deflection optical wedge and the lower deflection optical wedge rotate around the optical axis relatively, an included angle is formed between a light beam and the optical axis after passing through the optical wedges, and the included angle is equal to the combined angle of the two deflection optical wedges; when the wedge angle directions of the two deflection optical wedges are opposite, the generated deflection angle is 0 degrees, the double optical wedges have the function of being equivalent to a parallel flat plate, and light rays only generate tiny offset at the upper position and the lower position; when the wedge angle directions of the two deflection optical wedges are the same, namely the relative rotation of the two deflection optical wedges is 180 degrees, the maximum deflection angle generated at the moment is 2 times of that generated by a single optical wedge; if the relative rotation angle of the two wedges is 360 °, a maximum reverse deflection angle is generated. Furthermore, the rotating shafts and the optical axes of the upper deflection optical wedge and the lower deflection optical wedge are mutually vertical in pairs. Furthermore, the upper flat plate of the parallel flat plate group and the lower flat plate of the parallel flat plate group are parallel flat plates with equal thickness. Further, the upper flat plate of the parallel flat plate group and the lower flat plate of the parallel flat plate group are arranged in parallel, and the angle range of the upper flat plate of the parallel flat plate group and the lower flat plate of the parallel flat plate group inclined relative to the horizontal direction is 0-90 degrees.
Further, the beam expander comprises a beam expander lens and a collimating lens.
Further, the laser beam emitted by the femtosecond laser horizontally passes through the total reflection prism.
Further, the online frequency sweep OCT monitoring module, which is used to measure the accuracy of the processing structure in laser processing, is characterized in that the light beam from the Sweep Light Source (SLS) with a center wavelength of 1.3 μm, a spectral width of 80nm, and a repetition frequency of 20kHz in frequency sweep passes through the target arm and reference arm fiber optic (SMF) coupler (Thorlabs, TW1300R2 A1) with a coupling ratio of 90; a target beam is radiated coaxially with the femtosecond laser beam onto the workpiece to be processed through a dichroic mirror (galvanometer DM) via an SMF circulator (Thorlabs, CIR 1310-APC) having a core diameter of 8.2 μm; a Polarization Controller (PC) (Thorlabs, CPC 900) for adjusting the polarization of the light beam; the optical interference signal between the reflecting object and the reference beam is detected by a Balanced Detector (BD) (Hamamatsu, C12668-02) with an SMF coupler (Thorlabs, TW1300R5 A1) with a coupling ratio of 50; the interference signal is collected by a high-flux electronic lens data acquisition system (DAQ) (Pico Technology, pico scope 3205A)) and converted into an industrial personal computer, the signal collection trigger is controlled by a Scanning Light Source (SLS), and the depth of the processed structure is quantitatively evaluated by performing inverse Fourier transform on the interference signal; the time required for capturing the optical interference signal and for calculating the fourier spectrum (a-scan curve) was 3 and 10 milliseconds, respectively, as a sample, and the workpiece to be machined was mounted on a three-axis translation motor stage (Thorlabs, ZFS 13B).
Compared with the prior art, the invention has the following advantages:
the invention relates to an on-line monitoring method for femtosecond laser extreme micropore processing, which adopts an on-line monitoring device for femtosecond laser extreme micropore processing, the on-line monitoring device for femtosecond laser can realize ultrahigh precision on-line real-time monitoring in the femtosecond laser processing process, and the measurement precision is as follows: 2.5 μm; measurement range (maximum measurement length): 6mm; the measurement mode is as follows: online real-time measurement; center wavelength: 1310nm; frequency sweeping speed: 20kHz.
[ description of the drawings ]
FIG. 1 is a schematic structural diagram of an on-line monitoring device for femtosecond laser extreme micro-hole processing according to an embodiment of the present invention;
fig. 2 is a schematic diagram of the final measurement in the embodiment of the present invention.
Wherein, labeled in the figures:
1. a total reflection prism; 2. a convex lens; 3. a concave lens; 4. a femtosecond laser; 5. an industrial personal computer; 6. a polarization controller I; 7. a circulator I; 8. 90, a fiber coupler of; 9. sweeping a light source; 10. a polarization controller II; 11. a circulator II; 12. a collimating lens I; 13. a convex lens; 14. a total reflection mirror; 15. a balance detector; 16. 50; 17. a workpiece to be processed; 18. a focusing lens; 19. a collimating mirror II; 20. a dichroic mirror; 21. a collimating mirror III; 22. a lower plate of the parallel plate group; 23. the parallel flat plate group is provided with an upper flat plate; 24. a lower deflection optical wedge; 25. an upper deflection optical wedge; 26. and a parameter control module.
[ detailed description ] embodiments
The following examples are provided to further illustrate the embodiments of the present invention.
Example (b):
an on-line monitoring method for femtosecond laser extreme micropore processing specifically adopts a femtosecond laser extreme micropore processing on-line monitoring device and a femtosecond laser processing light path module to accurately monitor the processing precision in the precision processing process of a femtosecond laser processing workpiece;
the femtosecond laser extreme micropore processing online monitoring device is an online frequency sweep OCT monitoring module;
the femtosecond laser processing light path module is used for precisely processing a processed workpiece 17;
the femtosecond laser processing optical path system comprises a cooperative control module, a laser control module, a light beam deflection control module, a light beam translation control module and a scanning distribution, speed, laser power and taper parameter control module 26;
on the output light path of the femtosecond laser, a convex lens 2 and a concave lens 3 of a beam expanding module, a total reflection prism (1), an upper deflection optical wedge 25 and a lower deflection optical wedge 24 of a deflection optical wedge group, an upper flat plate 23 of a parallel flat plate group, a lower flat plate 22 of the parallel flat plate group and a focusing lens 18 are sequentially arranged, and finally, a light beam reaches a processed workpiece 17, wherein the beam expanding module consists of the concave lens 3 and the convex lens 2; the laser control module controls the femtosecond laser 4, the beam deflection control module controls an upper deflection optical wedge 25 and a lower deflection optical wedge 24 of a deflection optical wedge group, and the beam translation control module controls an upper flat plate 23 and a lower flat plate 22 of a parallel flat plate group; the laser control module, the light beam deflection control module and the light beam translation control module are connected with the cooperative control module through data lines, and the cooperative control module is connected with the industrial personal computer 5 through the data lines; controlling the incident femtosecond laser beam to sequentially pass through the laser control module, the beam deflection control module, the beam translation control module and the focusing mirror and then carrying out micropore machining on the machined workpiece 17;
the on-line frequency-sweeping OCT monitoring module is used for accurately monitoring the processing precision in the precise processing process of a femtosecond laser processing workpiece and comprises a frequency-sweeping light source 9, an optical fiber coupler I8, a circulator I7, a polarization controller I6, a collimating mirror II 19, a collimating mirror III 21, a polarization controller II 10, a circulator II 11, a collimating mirror I12, a convex lens 13, a total reflector 14, an optical fiber coupler II 16, a balance detector 15 and an industrial personal computer 5, wherein near infrared light output by the frequency-sweeping light source 9 is divided into a monitoring light path and a reference light path after passing through the optical fiber coupler I8, the circulator I7, the polarization controller I6, the collimating mirror II 19 and the collimating mirror III 21 are sequentially arranged on the monitoring light path, the monitoring light path can be irradiated to the processed workpiece 17 through a dichroic mirror 20 and a focusing lens 18 on the processing light path sequentially, the polarization controller II 10, the circulator II 11, the collimating mirror I12, the convex lens 13 and the total reflector 14 are sequentially arranged on the reference light path, the optical fiber coupler II 16, the balance detector 15 and the industrial personal computer 5 are sequentially connected, and the optical fiber coupler II 16 is connected with the circulator I7 and the circulator II 11.
Furthermore, the laser control module comprises a beam expander and a total reflection prism which are sequentially arranged along the direction of an optical path, the beam expander is arranged on the emergent surface of the femtosecond laser, and the total reflection prism is arranged on the emergent surface of the beam expander; the light beam deflection control module, the light beam translation control module and the focusing mirror are sequentially and vertically distributed below the total reflection prism;
the beam emitted by the laser is subjected to beam expanding collimation through a beam expander, then passes through a deflection light wedge group and forms an included angle of +/-5 degrees with an optical axis, then passes through a parallel plate group to generate translation of +/-6 mm, and then is focused on a focal plane which deviates from the optical axis by +/-6 cm through a focusing lens, when the deflection light wedge group and the parallel plate group synchronously rotate at high speed, a circular track can be formed on the focal plane, and the processing of micropores with large depth-diameter ratio and controllable taper is realized by changing the relative deflection angle of an optical wedge and the relative rotation angle of the parallel plate in real time;
the wedge angle of the upper deflection optical wedge 25 and the lower deflection optical wedge 24 is less than or equal to +/-5 degrees, an air gap is formed between the upper deflection optical wedge 25 and the lower deflection optical wedge 24, the upper deflection optical wedge 25 and the lower deflection optical wedge 24 rotate around the optical axis relatively, a light beam passes through the optical wedges and then forms an included angle with the optical axis, and the included angle is equal to the combined angle of the two deflection optical wedges; when the wedge angle directions of the two deflection optical wedges are opposite, the generated deflection angle is 0 degrees, the double optical wedges have the function of being equivalent to a parallel flat plate, and light rays only generate tiny offset at the upper position and the lower position; when the wedge angle directions of the two deflection optical wedges are the same, namely the relative rotation of the two deflection optical wedges is 180 degrees, the maximum deflection angle generated at the moment is 2 times of that generated by a single optical wedge; if the relative rotation angle of the two optical wedges is 360 degrees, a reverse maximum deflection angle is generated;
the rotating shafts and the optical axes of the upper deflection optical wedge 25 and the lower deflection optical wedge 24 are mutually vertical in pairs;
the parallel flat plate group upper flat plate 23 and the parallel flat plate group lower flat plate 22 are parallel flat plates with equal thickness;
the parallel flat plate group upper flat plate 23 and the parallel flat plate group lower flat plate 22 are arranged in parallel, and the inclined angle range of the parallel flat plate group upper flat plate 23 and the parallel flat plate group lower flat plate 22 relative to the horizontal direction is 0-90 degrees;
the beam expander comprises a beam expander lens and a collimating lens;
the laser beam emitted by the femtosecond laser horizontally passes through the total reflection prism;
the online frequency sweep OCT monitoring module is used for measuring the precision of a processing structure in laser processing, light beams from a frequency Sweep Light Source (SLS) 9 with the center wavelength of 1.3 mu m, the spectral width of 80nm and the repetition frequency of 20kHz in frequency sweep pass through a target arm and reference arm optical fiber (SMF) coupler (Thorlabs, TW1300R2A 1) 8, the coupling ratio is 90; the target beam is radiated onto the workpiece 17 to be processed coaxially with the femtosecond laser beam via an SMF circulator (Thorlabs, CIR 1310-APC) 7 having a core diameter of 8.2 μm by a dichroic mirror (galvanometer DM) 20; a Polarization Controller (PC) (Thorlabs, CPC 900) 6 for adjusting the polarization of the light beam; the optical interference signal between the reflecting object and the reference beam is detected by a Balanced Detector (BD) (Hamamatsu, C12668-02) 15 with an SMF coupler (Thorlabs, TW1300R5 A1) 16, with a coupling ratio of 50; the interference signal is collected by a high-flux electronic lens data acquisition system (DAQ) (Pico Technology, pico scope 3205A) and converted into an industrial personal computer 5, the signal collection trigger is controlled by a Scanning Light Source (SLS) 9, and the depth of the processed structure is quantitatively evaluated by performing inverse Fourier transform on the interference signal; the time required for capturing the optical interference signal and calculating the fourier spectrum (a-scan curve) was 3 and 10 milliseconds, respectively, as a sample, and the workpiece 17 to be processed was mounted on a three-axis translation motor stage (Thorlabs, ZFS 13B).
Fig. 1 is a schematic structural diagram of the femtosecond laser extreme micro-hole processing online monitoring device in this embodiment.
Fig. 2 is a diagram illustrating a final measurement in an embodiment of the present invention.
Comparative example:
the existing on-line monitoring method for femtosecond laser extreme micro-hole processing adopts template positioning, non-real-time positioning monitoring, and specifically adopts a paraxial camera to capture the outline of a workpiece, and establishes a positioning template, and when batch sample processing is carried out, automatic compensation is carried out according to the set template. After the paraxial camera is adopted to complete positioning, the accurate positioning of the processing focal plane needs to be carried out under the distance measuring sensor. The method is to position and determine the template before processing the workpieces in batch, as shown in fig. 2. If the workpiece moves and the workpiece deviation exceeds the standard in the machining process, the machining position is inaccurate.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the inventive concept of the present invention, which falls into the protection scope of the present invention.
Claims (10)
1. An on-line monitoring method for femtosecond laser extreme micropore processing is characterized in that: the femtosecond laser extreme micropore machining online monitoring device and the femtosecond laser machining light path module are adopted to accurately monitor the machining precision in the precise machining process of the femtosecond laser machining workpiece;
the femtosecond laser extreme micropore processing online monitoring device is an online frequency sweep OCT monitoring module;
the femtosecond laser processing light path module is used for carrying out precision processing on a processed workpiece (17);
the femtosecond laser processing optical path system comprises a cooperative control module, a laser control module, a light beam deflection control module, a light beam translation control module and a scanning distribution, speed, laser power and taper parameter control module (26);
on the output light path of the femtosecond laser, a convex lens (2) and a concave lens (3) of a beam expanding module, a total reflection prism (1), an upper deflection optical wedge (25) and a lower deflection optical wedge (24) of a deflection optical wedge group, an upper flat plate (23) of a parallel flat plate group, a lower flat plate (22) of the parallel flat plate group and a focusing lens (18) are sequentially arranged, and finally, a light beam reaches a processed workpiece (17), wherein the beam expanding module is composed of the concave lens (3) and the convex lens (2); the laser control module controls a femtosecond laser (4), the beam deflection control module controls an upper deflection optical wedge (25) and a lower deflection optical wedge (24) of a deflection optical wedge group in the beam deflection control module, and the beam translation control module controls an upper flat plate (23) and a lower flat plate (22) of a parallel flat plate group; the laser control module, the light beam deflection control module and the light beam translation control module are connected with the cooperative control module through data lines, and the cooperative control module is connected with an industrial personal computer (5) through the data lines; controlling the incident femtosecond laser beam to sequentially pass through the laser control module, the beam deflection control module, the beam translation control module and the focusing mirror and then carrying out micropore machining on a machined workpiece (17);
the on-line frequency-sweep OCT monitoring module is used for accurately monitoring the processing precision in the precision processing process of a femtosecond laser processing workpiece and comprises a frequency-sweep light source (9), an optical fiber coupler I (8), a circulator I (7), a polarization controller I (6), a collimating mirror II (19), a collimating mirror III (21), a polarization controller II (10), a circulator II (11), a collimating mirror I (12), a convex lens (13), a total reflection mirror (14), an optical fiber coupler II (16), a balance detector (15) and an industrial personal computer (5), wherein near infrared light output by the frequency-sweep light source (9) is divided into a monitoring light path and a reference light path after passing through the optical fiber coupler I (8), the circulator I (7), the polarization controller I (6), the collimating mirror II (19) and the collimating mirror III (21) are sequentially arranged on the monitoring light path, and the monitoring light path can irradiate on a processed workpiece (17) through a dichroic mirror (20) and a focusing lens (18) on the processing light path in sequence, a polarization controller II (10), a circulator II (11), a collimating mirror I (12), a convex lens (13) and a total reflection mirror (14) are arranged on a reference light path in sequence, an optical fiber coupler II (16), a balance detector (15) and an industrial personal computer (5) are connected in sequence, and the optical fiber coupler II (16) connects the circulator I (7) and the circulator II (11).
2. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the laser control module comprises a beam expander and a total reflection prism which are sequentially arranged along the direction of a light path, the beam expander is arranged on the emergent surface of the femtosecond laser, and the total reflection prism is arranged on the emergent surface of the beam expander; and the light beam deflection control module, the light beam translation control module and the focusing mirror are sequentially and vertically distributed below the total reflection prism.
3. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the beam emitted by the laser is subjected to beam expanding and collimating through the beam expander, then passes through the deflection light wedge group and forms an included angle of +/-5 degrees with an optical axis, then passes through the parallel plate group to generate translation of +/-6 mm, and then is focused on a focal plane deviated from the optical axis by a distance of +/-6 cm through the focusing lens, when the deflection light wedge group and the parallel plate group synchronously rotate at high speed, a circular track can be formed on the focal plane, and the processing of the micropore with large depth-diameter ratio and controllable taper is realized by changing the relative deflection angle of the light wedge and the relative rotation angle of the parallel plate in real time.
4. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the wedge angle of the upper deflection optical wedge (25) and the lower deflection optical wedge (24) is less than or equal to +/-5 degrees, an air gap is formed between the upper deflection optical wedge (25) and the lower deflection optical wedge (24), the upper deflection optical wedge (25) and the lower deflection optical wedge (24) rotate around the optical axis relatively, an included angle is formed between a light beam and the optical axis after the light beam passes through the optical wedges, and the included angle is equal to the combined angle of the two deflection optical wedges; when the wedge angle directions of the two deflection optical wedges are opposite, the generated deflection angle is 0 degrees, the double optical wedges have the function of being equivalent to a parallel flat plate, and light rays only generate tiny offset at the upper position and the lower position; when the wedge angle directions of the two deflection optical wedges are the same, namely the relative rotation of the two deflection optical wedges is 180 degrees, the maximum deflection angle generated at the moment is 2 times of that generated by a single optical wedge; if the relative rotation angle of the two wedges is 360 °, a maximum reverse deflection angle is generated.
5. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the rotating shafts and the optical axes of the upper deflection optical wedge (25) and the lower deflection optical wedge (24) are mutually vertical in pairs.
6. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the upper parallel flat plate group flat plate (23) and the lower parallel flat plate group flat plate (22) are parallel flat plates with equal thickness; the parallel flat plate group upper flat plate (23) and the parallel flat plate group lower flat plate (22) are arranged in parallel, and the angle range of the parallel flat plate group upper flat plate (23) and the parallel flat plate group lower flat plate (22) inclining relative to the horizontal direction is 0-90 degrees.
7. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the center wavelength of the sweep light source (9) is 1.3 mu m, the spectral width is 80nm, and the repetition frequency in frequency scanning is 20kHz.
8. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the sweep frequency light source (9) adopts an electro-optic crystal of potassium tantalate-niobate as a driver for scanning output wavelength.
9. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the processed workpiece (17) is converged on a three-axis moving motor table through a dichroic mirror (20) and a circulator I (7) with a core diameter of 8.2 mu m together with a processing light path.
10. The on-line monitoring method for femtosecond laser extreme micro-hole machining according to claim 1, characterized in that: the fiber coupler (16) is a coupler with SMF.
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