TWI727592B - Laser cutting method and device for filter - Google Patents

Abstract

The invention discloses a laser cutting method and device for a filter. The device includes: an ultra-fast laser, a beam shaping module, a focusing objective lens, a visual inspection device, and a motion platform; the visual inspection device is located on the upper part of the focusing objective lens and moves The platform is located at the bottom of the focusing objective lens for carrying the filter, the focusing objective lens is the imaging objective lens of the visual inspection device; the ultra-fast laser emits an ultra-short pulse laser beam and enters the beam shaping module, which is shaped into a uniform energy through the beam shaping module The distributed linear non-diffracted light beam enters the focusing objective lens and is focused by the focusing objective lens to form a high-energy density non-diffracted light beam of the cutting filter. The cross-sections and upper and lower surfaces of each element obtained after cutting of the present invention are well formed, with good straightness, and no obvious damage to the surface film. The thickness and position of the modified layer formed during the cutting process can be selected according to the thickness of the substrate or actual requirements to meet Processing requirements of different specifications.

Description

Laser cutting method and device for filter

The invention relates to the technical field of laser processing, in particular to a method and device for laser cutting of a filter.

As an optical element that can pass or cut off a specific wavelength, the filter is a key functional component in the fields of aerospace precision remote sensing, optical communications, high-performance cameras, etc. With it, it can achieve higher precision and sensitivity detection and high-quality information. transmission. For example, in order to achieve multi-band detection in the aerospace field and suppress the background radiation of infrared light, a plurality of infrared light filter sets with specific wavelength ranges will be installed in the multi-band infrared light visual detection device used; in the transceiver of optical communication components In the module, the communication quality can be significantly improved by selecting the signal of the required wavelength, and the noise interference during the transmission process can be suppressed; the special filter in front of the lens of the high-performance camera can improve the image quality. Basically, in all applications, it is necessary to cut the large filter into smaller individual components according to the required size requirements for assembly and use.

With the development of integration and miniaturization of visual inspection devices, the size of the filters that need to be processed is getting smaller and smaller, and the requirements for processing quality continue to increase. At present, the traditional methods of cutting the filter are mainly two kinds of wire drawing cutting and mechanical wheel cutting. Among them, the wire drawing cutting of the wire wheel is arranged by multiple sets of wire wheels opposite to each other, and then the cutting wire is threaded on the wire wheel, and the cutting of filters of different sizes can be realized by controlling the distance between the wire wheels. This method can cut multiple filters with little damage to the filters, but due to the limitation of the wire drawing structure of the wire wheel, the size of the filters processed by this method cannot be smaller than the wire The diameter of the wheel. The mechanical wheel cutting is to directly process the filter substrate with a blade. The blade used in this method will cause great damage to the surface film of the filter, and the cooling liquid used in the cutting process will affect the surface film. Produce pollution.

In summary, the traditional filter processing method can no longer meet the forming and cutting requirements of its application. The development of laser technology provides a good solution for the processing of optical filters. Especially after the continuous accumulation and development of continuous laser and long pulse laser processing technology, ultra-fast laser (pulse width less than 10-12 seconds) is considered to be the better method for processing related materials. The ultra-fast laser can internally modify the material by virtue of its extremely high peak power and the nonlinear absorption effect in the process of interacting with its transparent material. This modification process does not directly remove the material, in order to achieve efficient and high-quality cutting processing Provide the possibility. However, the modified area obtained by the internal modification cutting with the Gaussian beam directly output by the laser has only a small width, which leads to more cracks after cutting thicker materials (as shown in Figure 5(a)) .

Related research results show that the improvement of the cutting section is the key to improving the cutting quality, and increasing the thickness of the modified layer to a certain extent can improve the cutting quality. The non-diffraction linear focused spot has attracted much attention in the processing field of related materials because it can obtain a wider modified layer, but the directly generated non-diffracted beam energy is unevenly distributed along its propagation direction (as shown in Figure 6(a)) , Which means that although the section can be cut without cracks with the directly generated non-diffracted beam, the uneven beam energy distribution will cause the morphology of the modified layer after cutting to be uneven (as shown in Figure 5(b)).

Therefore, the conventional technology needs to be improved and developed.

In view of the shortcomings of the above-mentioned conventional technology, the purpose of the present invention is to provide a laser cutting method and device for a filter, so as to overcome the problem of poor cutting quality using the conventional filter cutting method.

The technical solution of the present invention is as follows: The present invention provides a laser cutting device for a filter, which includes: an ultrafast laser, a beam shaping module, a focusing objective, a visual inspection device, and a motion platform; the visual inspection device is located at The upper part of the focusing objective lens, the moving platform is located at the lower part of the focusing objective lens for carrying the filter, the focusing objective lens is the imaging objective lens of the visual inspection device; the ultra-fast laser emits an ultra-short pulse laser beam which enters the beam shaping module through the beam shaping module After being assembled to form a linear non-diffracted light beam with uniform energy distribution, it enters the focusing objective lens and is focused by the focusing objective lens to form a high-energy density non-diffracted light beam of the cutting filter.

In the above-mentioned laser cutting device for optical filters, the beam shaping module includes: a non-diffracted beam generating module to generate an initial non-diffracted beam output from the incident ultrashort pulse laser beam; and an energy homogenization and shaping module to make The initial non-diffracted beam output by the non-diffracted beam generating module is transformed into a linear non-diffracted beam with uniform energy distribution.

In the above-mentioned laser cutting device for the optical filter, the energy homogenization and shaping module includes: an attenuation plate whose energy attenuation of the light beam in the middle area is greater than that of the surrounding area.

In the above-mentioned laser cutting device for the optical filter, the attenuator is rotatably arranged in the output direction of the non-diffracted light beam.

In the above-mentioned laser cutting device for optical filters, the non-diffracting beam generating module includes an axicon.

In the above-mentioned laser cutting device for the filter, the pulse width of the ultra-short pulse laser beam generated by the ultra-fast laser is less than 100 picoseconds (ps).

In the above-mentioned laser cutting device for optical filters, the laser cutting device further includes a control system for controlling the ultrafast laser, the beam shaping module, the focusing objective lens, the visual inspection device, and the motion platform.

The present invention also provides a laser cutting method for a filter, which includes the steps of: providing any one of the above-mentioned laser cutting devices; after placing the filter on a moving platform, adjusting the visual inspection device and the moving platform to find To the processing surface and the cutting position; turn on the ultra-fast laser to emit an ultra-short pulse laser beam, which is shaped into a linear non-diffraction beam with uniform energy distribution through the beam shaping module, and then enters the focusing objective lens; adjust the moving platform and the focusing objective lens for precision Focusing, the high energy density non-diffracted beam formed by focusing by the focusing objective lens acts on the selected area of the filter to complete the laser cutting of the filter.

In the above-mentioned laser cutting method for a filter, in the laser cutting of the filter, the thickness of the modified layer is adjusted and controlled by the beam shaping module, and the modified layer is realized by adjusting the focus position of the focusing objective lens and the moving platform Position adjustment.

In the above-mentioned laser cutting method for the filter, the dot pitch during the laser cutting of the filter is 4-20 microns, and the energy density of the high-energy-density non-diffracted beam is greater than 1J/cm ² .

The beneficial effects of the present invention are: the present invention uses the beam shaping module to form a linear non-diffracted light beam with uniform energy distribution to cut the filter, and the cross-sections and upper and lower surfaces of each element obtained after cutting are well shaped and have good straightness. There is no obvious damage to the surface film, and the thickness and position of the modified layer formed during the cutting process can be selected according to the thickness of the substrate or actual requirements to meet the processing requirements of different specifications.

1: Upper surface film system

2: Lower surface film

3: substrate

100: Laser cutting device

110: Ultrafast laser

120: beam shaping module

121: Non-diffraction beam generation module

122: Energy homogenization and shaping module

123: Energy Redistribution Element

130: focus objective

140: The first laser transmission element

150: The second laser transmission element

200: Visual inspection device

210: Motion Platform

300: filter

400: control system

S100, S200, S300, S400: steps

Figure 1 is a schematic diagram of the filter structure.

FIG. 2 is a schematic structural diagram of a laser cutting device for a filter according to an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a beam shaping module according to an embodiment of the present invention.

FIG. 4 is a flowchart of the laser cutting method of the filter according to the embodiment of the present invention.

Figure 5 shows the cutting effect of traditional Gaussian beam and non-diffraction beam before shaping.

Figure 6 is a comparison of the initial energy distribution of the non-diffracted beam and the energy distribution along its propagation direction after the energy homogenization process; where the abscissa represents the position (Position (μm)), and the ordinate represents the energy intensity (Intensity (au) ), (a) is the non-diffracted beam with uneven energy distribution along its propagation direction before shaping, and (b) is the non-diffracted beam with uniform energy distribution along the propagation direction after shaping.

Figure 7 shows the cross-section and cutting effect of the filter after adjusting the shape of different modified layers. Among them, (a) and (b) are beam shaping modules adjusted to achieve different modified layer widths and point spacing cutting, (c) ) Is the straightness of the crack before separation after laser cutting, (d) is the cutting effect of the front side of the filter after separation by mechanical split.

The present invention provides a laser cutting method and device for a filter. In order to make the objectives, technical solutions and effects of the present invention clearer and clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not used to limit the present invention.

Referring to Fig. 2, an embodiment of the present invention provides a filter laser cutting device 100, which includes: an ultrafast laser 110, a beam shaping module 120, a focusing objective 130, a vision inspection device 200, And a moving platform 210; wherein the vision detection device 200 is located on the upper part of the focusing objective lens 130, and the moving platform 210 is located on the lower part of the focusing objective lens 130 for carrying the filter 300, and the focusing objective lens 130 is the viewing lens The imaging objective of the visual inspection device 200; the focusing objective 130, the visual inspection device 200, and the motion platform 210 constitute a focus positioning system during processing, which can realize the cutting positioning and precise focusing during the processing of different types of filters; ultra-fast laser 110 The ultra-short pulse laser beam is emitted into the beam shaping module 120, which is shaped into a linear non-diffracted beam with uniform energy distribution through the beam shaping module 120, and then enters the focusing objective 130, and is focused by the focusing objective 130 to form a high-profile cutting filter 300. Energy density non-diffracted beam.

The present invention uses the beam shaping module to form a linear non-diffracted light beam with uniform energy distribution for filter cutting. After cutting, the cross-sections and upper and lower surfaces of each element obtained after cutting are formed in a regular shape, with good straightness, and no obvious damage to the surface film. And the thickness and position of the modified layer formed in the cutting process can be selected according to the thickness of the substrate or actual requirements to meet the processing requirements of different specifications.

Further, referring to FIG. 3, in this embodiment, the beam shaping module 120 includes at least: a non-diffracting beam generating module 121 and an energy uniformizing and shaping module 122; wherein, the non-diffracting beam generating module 121 is used for Make the incident ultrashort pulse laser beam generate the initial non-diffracted beam output; the energy homogenization shaping module 122 is used to make the energy distribution of the initial non-diffracted beam output by the non-diffracted beam generating module along its propagation direction uniform in energy For the distributed linear non-diffracted light beam, the energy attenuation of the light beam in the middle area of the energy homogenization and shaping module 122 is greater than that of the surrounding area in order to achieve a uniformly distributed non-diffracted light beam.

Preferably, referring to FIG. 3, in this embodiment, the beam shaping module 120 further includes an energy redistribution element 123 located in front of the energy homogenization and shaping module 122, and the energy output from the energy homogenization and shaping module 122 is uniform. The distributed linear non-diffracted beam enters the energy redistribution element 123 and then converges the beam, and then enters the focusing objective 130. In specific implementation, the energy redistribution element 123 may be a lens that plays a converging function. The energy homogenization and shaping module includes: the attenuation of the energy of the light beam in the middle area is greater than that of the surrounding area, and the attenuation piece is an attenuation device with ring characteristics with stronger attenuation in the middle and outer ring areas. Preferably, the attenuator is arranged to rotate in the output direction of the non-diffracted beam, and the uniformity of the energy distribution can be further enhanced by rotation, and a more uniform energy distribution can be obtained to shape the spot.

The key element of the non-diffraction beam energy homogenization processing device used in the embodiment of the present invention is an attenuation sheet in which the energy attenuation of the beam in the middle area is greater than that in the surrounding area. The fundamental reason for the uneven energy distribution of the directly formed non-diffraction beam is that the energy in the middle area of the beam is more concentrated, and a specific energy attenuation device can make the energy distribution uniform. And the essence of the non-diffracted beam is the interference of the wavefront, so the attenuation characteristics of the element (different area attenuation ratio) can be adjusted to be located in different areas (such as the dotted line) in front of the non-diffracted beam generating element. In this embodiment, the middle and The attenuation device with ring characteristics with stronger attenuation in the outer ring area is roughly placed at the position of the solid line in Figure 3 to obtain a non-diffracted beam with the best energy distribution as shown in Figure 6(b). This is the best position It is half of the initial beam length.

Further, in this embodiment, the non-diffracting beam generating module includes an axicon or other elements or systems that can achieve the same effect. The pulse width of the ultrashort pulse laser beam produced by the ultrafast laser is less than 100ps. The laser cutting device also includes a control system 400 (controller) for controlling the ultrafast laser 110, the beam shaping module 120, the focusing lens 130, the visual inspection device 200, and the motion platform 210. The control system 400 can Realize the automatic control of the cutting positioning and focusing process, so that the reshaped non-diffraction beam is focused for filter cutting.

Further, the vision detection device in this embodiment is a CCD camera, the CCD camera is located directly above the focusing objective lens, and the objective lens serves as both a laser focusing objective lens and an imaging objective lens of the CCD camera. Specifically, the objective lens selected in this embodiment The numerical aperture value is 0.5, the magnification is 50 times, and the CCD camera has 400,000 pixels.

For specific implementation, referring to Figure 2, the laser cutting device 100 includes an ultrafast laser 110, a beam shaping module 120, a processing objective 130, a first laser transmission element 140 and a second laser transmission element 150, The first laser transmission element 140 is a mirror, and the second laser transmission element 150 is a half mirror, which can realize coaxial imaging observation. The ultrafast laser is used to generate an ultrashort pulse laser beam that meets the corresponding characteristics. The generated laser beam is preliminarily formed into a linear non-diffracted beam with a high concentration of energy through the beam shaping module 120. The non-diffracted beam selected in this embodiment The diffracted beam generating element is an axicon, the output of the laser generating device A Gaussian beam with a wavelength of 532 nm and a pulse width of 15 picoseconds. The generated Gaussian beam is incident on an approximately flat axicon, and then the diffracted light is interfered by the wavefront to produce a non-diffracted beam. The generation method of this non-diffracted beam determines that more than 90% of its energy is distributed in the linear spot. The energy distribution of the laser beam decreases sharply outside the area slightly away from the linear spot. Furthermore, the selected energy homogenization and shaping module can respectively shape the non-uniform initial energy of the beam along the propagation direction into a substantially uniformly distributed non-diffracted beam. Under the condition that the energy distribution shape does not change after the processed objective lens is focused, a high energy density non-diffracted beam can be formed for material processing.

Referring to Figure 4, an embodiment of the present invention also provides a laser cutting method for a filter, which includes: step S100, providing a laser cutting device; step S200, after placing the filter on the moving platform, adjusting the vision The detection device and the moving platform find the processing surface and the cutting position; step S300, turn on the ultra-fast laser to emit an ultra-short pulse laser beam, which is shaped into a linear non-diffracted beam with uniform energy distribution through the beam shaping module, and then enters and focuses Objective lens: Step S400, adjust the moving platform and the focusing objective lens for precise focusing, so that the high-energy density non-diffraction beam formed by focusing by the focusing objective lens acts on the selected area of the filter to complete the laser cutting of the filter.

The present invention proposes to cut the filter based on a linear focused non-diffracted beam with uniform energy distribution. The quality of the modified layer after cutting is greatly improved compared with the Gaussian beam and the non-diffracted beam before shaping, which can further improve the laser technology Advantages in related material processing applications.

The above method is based on a non-diffracted beam with uniform energy distribution along the propagation direction of the linear light spot, and the filter is cut. The cross-section and upper and lower surfaces of each element obtained after cutting are well-shaped, with good straightness, no obvious damage to the surface film, and cutting The thickness and position of the modified layer formed in the process can be selected according to the thickness of the substrate or actual requirements to meet the processing requirements of different specifications.

Furthermore, in this embodiment, when the filter is laser cut, the thickness of the modified layer is adjusted by the beam shaping module, and the position of the modified layer is adjusted by adjusting the focus position of the focusing objective lens and the moving platform. The generated energy uniformly distributed non-diffracted beam is focused inside the filter for cutting, and the thickness and position of the formed modified layer are adjustable. The thickness of the modified layer can be adjusted and controlled by the shaping module, and the position of the modified layer can be achieved by motion control and the adjustment of the focus position of the vision system. It can be selected according to actual needs when ensuring the processing effect.

Further, in this embodiment, when the step S400 is specifically implemented, the filter and the objective lens are moved relative to the set distance so that the processing beam is focused on the selected area of the filter, and the material is cut under the set process parameters . The dot pitch during laser cutting of the filter is 4-20 microns, and the energy density of the high-energy-density non-diffracted beam is greater than 1J/cm ² . The initial laser pulse width generated by the ultrafast laser is less than 100 picoseconds, the wavelength is not limited to 532 nm, and it can be focused on the inside of the filter for modification processing.

Further, in this embodiment, referring to Figure 1, the structure of the filter can be that the surface (upper and lower surface or only one surface) has an optical film, the substrate 3 is transparent optical glass or colored glass, and other corresponding Functional materials, the optical film can be one layer or multiple layers. In this embodiment, both the upper and lower surfaces of the filter have optical films, which are the upper surface film system 1 and the lower surface film system 2 respectively. The filter is penetrated by the used 532nm wavelength laser (the transmittance is greater than 80%). According to the spectral characteristics, it can be a bandpass filter, a cut-off filter, a spectroscopic filter, etc. that meet this characteristic. , Can also be distinguished by spectral bands: ultraviolet light filter, visible light filter and infrared filter that meet the characteristic requirements. After processing with a uniformly distributed non-diffracting beam, a single straight crack can be observed on the surface of the filter and subsequent separation can be carried out. The two cracks formed after the actual vertical cross cutting are maintained and perpendicular to each other. The modified layer of the filter after cutting under the optimized processing parameters is well formed and no cracks appear except for the modified area. With an optical film, the optical performance and strength of the components outside the cutting area can be guaranteed, and There is no obvious damage to the film near the cutting area. This method can be used for higher cutting requirements under optimized processing parameters. It is necessary to process filters with more complex structures, so this method can also be directly used for cutting transparent materials such as sapphire and ordinary glass.

The upper surface of the cut sample is found by the CCD and related detection devices, and the found position is used as the focus reference point of the cutting movement, and the cutting parameters and the set relative movement distance are adjusted. After optimizing the processing process, the figure 7 can be obtained respectively. As shown in the cutting section, all sections have a uniform cutting modified layer, and there are no cracks in other areas except the modified layer. The processing material selected in this embodiment is a glass substrate filter with a thickness of 0.2 mm and only one surface with a film layer (infrared light band cut-off). In particular, it is worth mentioning that the device and method of the present invention can adjust the shape of the modified layer by adjusting the parameters of the shaping module. After adjustment as shown in the figure, it can achieve different modified layer widths and point spacing cutting (only By replacing the correlation of the attenuator). Observe the crack straightness before separation (Figure 7(c)) and the front side of the filter after separation (Figure 7(d)), the final single element edge is basically free of chipping, and the surface film layer is well protection of. The above experimental results all show that this method can significantly improve the cutting quality of the filter, and also provides a complete solution for the cutting of filters of different specifications.

In summary, the present invention is based on the continuously increasing demand for filter processing, the advantages of laser cutting technology, and the improvement space of current ultrafast laser processing. The present invention provides an ultrafast laser cutting device and method for filters . The invented device is based on specific optical elements or devices that directly generate the initial non-diffracted beam with uneven energy distribution for energy homogenization; the above method is based on the non-diffracted beam after the shaping treatment, and its processing quality is higher and the formation The width of the modified layer can be adjusted according to the thickness of the substrate or the actual processing requirements to meet the needs of different practical applications.

It should be understood that the application of the present invention is not limited to the above examples. For those with ordinary knowledge in the technical field, they can make improvements or changes based on the above descriptions. All these improvements and changes shall fall within the scope of the attached patent application of the present invention. protected range.

100: Laser cutting device

110: Ultrafast laser

120: beam shaping module

130: focus objective

140: The first laser transmission element

150: The second laser transmission element

200: Visual inspection device

210: Motion Platform

300: filter

400: control system

Claims (8)

A laser cutting device for a filter, comprising: an ultrafast laser, a beam shaping module, a focusing objective lens, a visual inspection device, and a moving platform. The beam shaping module includes a non-diffracting beam Generating module and an energy homogenization and shaping module, the energy homogenization and shaping module includes an attenuation sheet whose energy attenuation of the light beam in the middle area is greater than that of the surrounding area; the visual detection device is located on the upper part of the focusing objective lens, and the movement platform is located on the The lower part of the focusing objective lens is used to carry a filter to be cut. The focusing objective lens is an imaging objective lens of the visual inspection device; the ultrafast laser emits an ultrashort pulse laser beam to enter the non-diffraction beam generating module, Make the incident ultrashort pulse laser beam generate an initial non-diffracted beam output, and then enter the energy homogenization shaping module, so that the initial non-diffracted beam output from the non-diffracted beam generating module is shaped into a line of uniform energy distribution The non-diffracted light beam enters the focusing objective lens, and is focused by the focusing objective lens to form a high-energy density non-diffracted light beam of the cutting filter. The laser cutting device for the optical filter according to claim 1, wherein the attenuator is rotatably arranged in the output direction of the initial undiffracted light beam. The laser cutting device for a filter according to claim 1, wherein the undiffracted beam generating module includes an axicon. The laser cutting device for a filter according to claim 1, wherein the pulse width of the ultrashort pulse laser beam generated by the ultrafast laser is less than 100 picoseconds. The laser cutting device for a filter according to claim 1, wherein the laser cutting device further includes the ultrafast laser, the beam shaping module, the focusing objective lens, the visual inspection device, and The motion platform controls a control system System. A laser cutting method for a filter, which includes the steps of: providing the laser cutting device according to any one of claims 1 to 5; after placing the filter on the moving platform, adjusting the visual inspection device and The moving platform finds the processing surface and the cutting position; turns on the ultrafast laser to emit the ultrashort pulse laser beam, which is shaped into the linear non-diffracted beam with uniform energy distribution through the beam shaping module, and then enters the focus Objective lens; adjusting the moving platform and the focusing objective lens for precise focusing, so that the high-energy density non-diffracting beam formed by focusing the focusing objective lens acts on the selected area of the filter to complete the laser cutting of the filter. The laser cutting method for a filter according to claim 6, wherein when the filter is laser cut, the thickness of a modified layer is adjusted and controlled by the beam shaping module, and the focusing objective lens and the moving platform are used to adjust and control the thickness of a modified layer The adjustment of the focus position realizes the adjustment of the position of the modified layer. The laser cutting method for a filter according to claim 6, wherein the dot pitch during laser cutting of the filter is 4-20 microns, and the energy density of the high-energy-density non-diffracted beam is greater than 1J/cm ² .

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