Positioning calibration system and method for femtosecond laser three-dimensional machining system

Abstract

The invention discloses a positioning calibration system and method for a femtosecond laser three-dimensional machining system. The positioning calibration system comprises a focus position calibration assembly, a focus position detection assembly and a three-dimensional scanning assembly. The focus position calibration assembly is located below a laser focusing unit of the femtosecond laser three-dimensional processing system, and laser focuses emitted by the femtosecond laser three-dimensional processing system are converged on a sample in the focus position calibration assembly; the three-dimensional scanning assembly is used for adjusting the laser focus position to enable the laser focus to be located on the sample surface; the focus position detection assembly is used for calibrating a focus detection position as a focus actual position; the actual focus position and the detection value of the focus position detection assembly are corrected through the focus position calibration assembly and the focus position detection assembly, so that the focus position detection value is accurate and is not easily influenced by sample processing depth measurement errors or sample surface stains, and the processing precision is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of laser processing system positioning, and in particular to a positioning and calibration system and method for a femtosecond laser three-dimensional processing system. Background Art

[0002] With the development of laser technology, especially the research and development of high-power lasers, short-pulse lasers, and special wavelength laser technology, laser technology has been applied in many fields and played an important role. For example, the use of femtosecond lasers in industry can achieve fine processing at the micron scale, and has been used in the manufacture of products such as heart stents and microfluidic chips; laser knives are used in medical applications for minimally invasive surgery, ophthalmic corneal refractive surgery, corneal cross-linking surgery, retinal transplantation, and lens capsulectomy, etc., which reduces surgical trauma and reduces postoperative complications.

[0003] Realizing three-dimensional positioning of laser is the basis for the application of laser processing technology, and it is also a necessary function for laser three-dimensional measurement. In order to realize the positioning function of the workpiece, there are two ways: contact measurement and non-contact measurement. The positioning accuracy of the contact measurement method depends on the resolution of the probe. The positioning system has low sensitivity and is easily affected by the thermal expansion of the spindle. In actual operation, the probe is easily damaged or broken due to inaccurate positioning. Common non-contact measurement methods include visual image positioning method, laser confocal positioning, interferometry, coherent optical tomography, etc. Among them, the confocal positioning method is one of the most accurate positioning methods, which is widely used in high-resolution microscopic imaging systems in the field of life sciences. The principle of confocal scanning is that the focus point of the detection laser and the precision small hole in front of the detector are conjugate image points. When the detection light is scanned along the X / Y / Z direction, only the return light at the focus position can pass through the precision small hole to enter the detector. Its resolution depends on the numerical aperture and the small hole diameter of the focusing system. When the numerical aperture is large and the small hole diameter is small, its accuracy can reach the nanometer level. The peak signal of the confocal microscope has a linear relationship between the focus and the position in the z direction, because the confocal signal can easily identify the relative position of the focus. Interferometry and OCT are also very high-resolution positioning methods. They both use the principle of optical coherence and use the phase information of light to determine the relative position of the object.

[0004] In fields such as microscopic imaging, there is no need to locate the absolute position of the sample, and its resolution of the sample only requires the accuracy of the relative position. However, in precision machining systems, the absolute position of the sample needs to be measured and located so that the machining position of the focus is accurate, which requires the absolute position of the confocal system to be calibrated. In an ideal confocal scanning system, the detector and the focus are conjugate image points to each other, so there is a fixed linear correspondence between the two, and in principle, the absolute position can be identified. However, the confocal system is limited by mechanical errors, optical aberrations and other factors during assembly and adjustment, and the conjugate relationship between the confocal signal and the focus is difficult to achieve directly by fixing the mechanical structure. It is usually necessary to fine-tune the pinhole or detector position to determine the position of the confocal system structure. Interferometry and OCT and other methods also require calibration of the focus position before they can be used for precision machining.

[0005] The commonly used calibration method at present is to directly process the sample, measure the depth of the processed sample and compare it with the design value to calibrate the actual focus position and the focus detection position. Another method is to use the threshold characteristics of the ultrafast laser processing sample surface: when the ultrafast laser pulse energy is only slightly higher than the threshold energy, only a very small range of the focus position can cause damage to the sample surface. By continuously reducing the laser pulse energy to the energy threshold, while moving the focus position within the upper and lower ranges, and then finding the damage position through microscopic imaging and other methods, the z-direction focus position can be calibrated. Both methods are easily affected by sample processing depth measurement errors or sample surface stains, and are extremely inefficient. Summary of the invention

[0006] The present invention provides a positioning calibration system and method for a femtosecond laser three-dimensional processing system, which can solve the problem that the existing calibration method is easily affected by sample processing depth measurement errors or sample surface stains.

[0007] A positioning and calibration system for a femtosecond laser three-dimensional processing system, comprising a focus position calibration component, a focus position detection component and a three-dimensional scanning component;

[0008] The focus position calibration component is located below the laser focusing unit of the femtosecond laser three-dimensional processing system, and the laser focus emitted by the femtosecond laser three-dimensional processing system converges on the sample in the focus position calibration component;

[0009] The three-dimensional scanning component is used to adjust the laser focus position so that the laser focus is located on the sample surface;

[0010] The focus position detection component is used to calibrate the focus detection position to the actual focus position.

[0011] Preferably, the focus position calibration assembly includes a sample, a spectrometer, a filter and a detector;

[0012] The first detector is a photoelectric detector, which is used to collect light generated by the nonlinear effect between the sample and the laser emitted by the femtosecond laser three-dimensional processing system.

[0013] Preferably, the focus position detection assembly includes detector 2, lens 2, a pinhole, lens 1 and a reflector. By adjusting the relative position of lens 1 and the pinhole, the conjugate image point of the focus can be located at the center of the pinhole.

[0014] A calibration method for a positioning calibration system comprises the following steps:

[0015] Step 1: Place the focus position calibration component under the focusing component of the femtosecond laser 3D processing system;

[0016] Step 2: adjusting the position of the laser focus of the femtosecond laser 3D processing system through the 3D scanning component so that the laser focus passes through the surface of the sample of the focus position calibration component;

[0017] Step 3: The sample surface exhibits a nonlinear effect on the laser, light generated by the nonlinear effect or light affected by the nonlinear effect is collected, and the laser focus is determined to be on the sample surface;

[0018] Step 4: Fix the three-dimensional scanning component, and let the detection position of the focus position detection component indicate the actual focus position, so as to complete the calibration of the focus time position and the focus detection position.

[0019] Preferably, the nonlinear effect in step three is surface second harmonic, surface third harmonic, nonlinear absorption effect or hyperspectral white light phenomenon.

[0020] Preferably, the method for determining that the laser focus is on the sample surface in step 3 is as follows:

[0021] Light generated by or affected by nonlinear effects is collected by a photodetector. The voltage output by the photodetector increases as the laser focus approaches the sample surface. When the output voltage is at its maximum, the laser focus is located on the sample surface.

[0022] Preferably, the step 4 is specifically as follows:

[0023] When the laser focus is on the sample surface, the spatial position of lens 1 of the focus position detection assembly and the pinhole is adjusted so that the conjugate image point of the laser focus is at the center of the pinhole.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the present application corrects the actual focus position and the detection value of the focus position detection component through a focus position calibration component and a focus position detection component, so that the focus position detection value is accurate and not easily affected by sample processing depth measurement errors or sample surface stains, thereby effectively improving the processing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural block diagram of the positioning and calibration system for femtosecond laser 3D processing system;

[0026] Figure 2 is a structural block diagram of a focus position detection component;

[0027] Figure 3 is a structural block diagram of the focus position calibration component;

[0028] Figure 4 This is a flow chart of the positioning calibration method. DETAILED DESCRIPTION

[0029] A specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation.

[0030] Embodiment 1

[0031] like Figures 1 to 3 As shown, an embodiment of the present invention provides a positioning and calibration system for a femtosecond laser three-dimensional processing system, the positioning and calibration system includes a focus position calibration component, a focus position detection component and a three-dimensional scanning component, the three components are connected by a circuit and can operate synchronously, and the femtosecond laser three-dimensional processing system also includes an ultrafast laser light source, a laser adjustment component and a laser focusing component;

[0032] Among them, the focus position detection component provides position information for the three-dimensional scanning component, so that the three-dimensional scanning component can move the laser focus to the designed position, thereby realizing precision micro-machining, and the focus position calibration component is used to correct the actual focus position and the detection value of the focus position detection component, so that the laser focus position detection value is accurate;

[0033] The focus position calibration component of this embodiment includes a sample, a spectrometer, a filter, and a detector 1, wherein the detector 1 is a photoelectric detector, and the spectrometer and the filter both play a filtering role to reduce the influence of the laser source on the photoelectric detector;

[0034] The focus position detection assembly of this embodiment includes a detector 2, a lens 2, a pinhole, a lens 1 and a reflector. By adjusting the relative position of the lens 1 and the pinhole, the conjugate image point of the focus can be located at the center of the pinhole.

[0035] The focus position calibration component is placed under the laser focusing unit of the femtosecond laser 3D processing system, and the laser focus emitted by the femtosecond laser 3D processing system will converge on the sample in the focus position calibration component;

[0036] The three-dimensional scanning component is used to adjust the laser focus position so that the laser focus is located on the sample surface. The photoelectric detector of the focus position calibration component is used to collect light generated by the nonlinear effect between the sample and the laser emitted by the femtosecond laser three-dimensional processing system, thereby determining that the laser focus is located on the sample surface.

[0037] The focus position detection component can calibrate the focus detection position to the actual focus position, thereby completing the calibration.

[0038] Embodiment 2

[0039] like Figure 1-Figure 4 As shown, this embodiment proposes a calibration method for the positioning calibration system based on the above-mentioned embodiment 1, comprising the following steps:

[0040] Step 1: placing the focus position calibration component under the focusing component of the femtosecond laser 3D processing system, so that the laser focus of the femtosecond laser 3D processing system converges inside the focus position calibration component;

[0041] Step 2: adjusting the position of the laser focus of the femtosecond laser 3D processing system through the 3D scanning component so that the laser focus passes through the surface of the sample of the focus position calibration component;

[0042] The sample surface exhibits nonlinear response characteristics to the laser, that is, as the laser intensity increases, the response curve presents the characteristics of a power function or an exponential function rather than a linear relationship, which makes the focus deviate from the target by a small distance, and the correlation effect will be significantly weakened; therefore, when the laser focus passes through the sample surface, a correlation effect will be generated that changes nonlinearly with the movement of the focus position; specifically, this surface nonlinear effect can be surface second harmonic, surface third harmonic, nonlinear absorption effect, hyperspectral white light phenomenon, etc. This nonlinear effect is strongest only when the laser focal plane is located on the sample surface;

[0043] Thanks to this nonlinear response characteristic, the position of the sample surface can be accurately located by collecting the light generated by the nonlinear effect or the light affected by the nonlinear effect and analyzing its trend as the focal position changes;

[0044] Step 3: The sample surface exhibits a nonlinear effect on the laser, light generated by the nonlinear effect or light affected by the nonlinear effect is collected, and the laser focus is determined to be on the sample surface;

[0045] Specifically, light generated by the nonlinear effect or light affected by the nonlinear effect is collected by a photodetector, and the voltage output by the photodetector increases as the laser focus approaches the sample surface. When the output voltage is at a maximum value, the laser focus is located on the sample surface;

[0046] Step 4: Fix the three-dimensional scanning component, and let the detection position of the focus position detection component indicate the actual focus position, so as to complete the calibration of the focus time position and the focus detection position;

[0047] That is, after positioning on the sample surface, fix the three-dimensional scanning component so that the focus position is on the sample surface, and adjust the focus position detection component so that its detection position indicates the focus position, thereby completing the calibration of the actual focus position and the focus detection position; specifically, after the focus position is fixed on the sample surface, adjust the confocal detection light path to adjust the spatial position of lens 1 and the pinhole of the focus position detection component so that the conjugate image point of the focus is at the center of the pinhole, and at this time, the light power received by the detector of the focus position detection component is the highest; then fix the positions of the lens, pinhole and detector, and at this time, complete the calibration of the absolute position of the detector.

[0048] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit and essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0049] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A positioning and calibration system for a femtosecond laser three-dimensional processing system, characterized in that: It includes a focus position calibration component, a focus position detection component and a three-dimensional scanning component; The focus position calibration component is located below the laser focusing unit of the femtosecond laser three-dimensional processing system, and the laser focus emitted by the femtosecond laser three-dimensional processing system converges on the sample in the focus position calibration component; The three-dimensional scanning component is used to adjust the laser focus position so that the laser focus is located on the sample surface; The focus position detection component is used to calibrate the focus detection position to the actual focus position.

2. According to the positioning and calibration system for a femtosecond laser three-dimensional processing system as described in claim 1, the focus position calibration component includes a sample, a spectrometer, a filter and a detector.

3. The positioning and calibration system for a femtosecond laser three-dimensional processing system according to claim 2, characterized in that: The detector 1 is a photoelectric detector, which is used to collect light generated by the nonlinear effect between the sample and the laser emitted by the femtosecond laser three-dimensional processing system.

4. The positioning and calibration system for a femtosecond laser three-dimensional processing system as described in claim 1, wherein the focus position detection component includes detector 2, lens 2, a pinhole, lens 1 and a reflector, and by adjusting the relative position of lens 1 and the pinhole, the conjugate image point of the focus can be located at the center of the pinhole.

5. A calibration method based on the positioning calibration system according to any one of claims 1 to 4, characterized in that: The steps include: Step 1: Place the focus position calibration component under the focusing component of the femtosecond laser 3D processing system; Step 2: adjusting the position of the laser focus of the femtosecond laser 3D processing system through the 3D scanning component so that the laser focus passes through the surface of the sample of the focus position calibration component; Step 3: The sample surface exhibits a nonlinear effect on the laser, light generated by the nonlinear effect or light affected by the nonlinear effect is collected, and the laser focus is determined to be on the sample surface; Step 4: Fix the three-dimensional scanning component, and let the detection position of the focus position detection component indicate the actual focus position, so as to complete the calibration of the focus time position and the focus detection position.

6. The calibration method of the positioning calibration system according to claim 5, characterized in that: The nonlinear effect in step three is surface second harmonic, surface third harmonic, nonlinear absorption effect or hyperspectral white light phenomenon.

7. The calibration method of the positioning calibration system according to claim 5, characterized in that: The method for determining that the laser focus is on the sample surface in step 3 is as follows: Light generated by or affected by nonlinear effects is collected by a photodetector. The voltage output by the photodetector increases as the laser focus approaches the sample surface. When the output voltage is at its maximum, the laser focus is located on the sample surface.

8. The calibration method of the positioning calibration system according to claim 5, characterized in that: The step 4 is specifically as follows: When the laser focus is on the sample surface, the spatial position of lens 1 of the focus position detection assembly and the pinhole is adjusted so that the conjugate image point of the laser focus is at the center of the pinhole.

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