JP2004122233A - Laser marking device, marking method, and marked optical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a marking device capable of enhancing visibility of a mark without reducing a processing speed. <P>SOLUTION: A hologram board 16 is arranged in the optical path of a laser beam 3 emitted from a laser beam source 11. A scanning optical system 13 straddles each optical axis of the beam diffracted by the hologram board. A converging optical system 14 converges the diffracted beams whose optical axis is straddled by the scanning optical system. A workpiece 1 is held at the place where the diffracted beams are converged by the converging optical system. The beam 3 diffracted by the hologram board 16 forms inside the workpiece 1 a unit diffraction pattern for diffracting visible light. By straddling the optical axes of the diffracted beams by the scanning optical system, a plurality of unit diffraction patterns can be formed inside the workpiece. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser marking device, a marking method, and a marked optical member, and more particularly to a laser marking device, a marking method, and a marked optical member that can improve the visibility of the mark.
[0002]
[Prior art]
When a laser beam is focused in a transparent material such as glass to cause multiphoton absorption, the refractive index of that portion changes. A mark can be formed by distributing the points where the refractive index has changed to desired positions.
[0003]
[Problems to be solved by the invention]
Since the region where the refractive index changes by condensing the laser beam is very small, it is difficult to visually recognize a mark composed of a set of points where the refractive index has changed. The visibility of the mark can be improved by increasing each of the plurality of points constituting the mark. However, in order to enlarge each point, a large machining energy is required, and the mark periphery of the workpiece is damaged.
[0004]
An object of the present invention is to provide a marking device and a marking method that can reduce damage to a workpiece and increase the visibility of the mark.
[0005]
[Means for Solving the Problems]
According to one aspect of the present invention, a laser light source that emits a laser beam, a hologram plate disposed in an optical path of the laser beam emitted from the laser light source, and an optical axis of each of the diffracted beams diffracted by the hologram plate A scanning optical system, a condensing optical system for converging the diffracted beam whose optical axis is swung by the scanning optical system, and a workpiece to be held at a position where the diffracted beam is condensed by the condensing optical system A diffracted beam diffracted by the hologram plate forms a unit diffraction pattern for diffracting visible light in the workpiece, and the optical axis of the diffracted beam is shaken by the scanning optical system. There is provided a laser marking device capable of forming a plurality of the unit diffraction patterns in the workpiece.
[0006]
Using a plurality of diffracted beams, it is possible to cause a change in refractive index at a plurality of locations simultaneously. Since each point where the refractive index change occurs is very small, it is possible to reduce damage to be embedded by the object to be processed. In addition, since the refractive index can be changed at a plurality of locations at the same time, the marking time can be shortened. Further, since the unit element itself is composed of a set of a plurality of points, diffraction can be generated with only one unit element. For this reason, the visibility of a mark can be improved.
[0007]
According to another aspect of the present invention, there is provided an optical member in which marks are formed by distributing unit elements each having a pattern that diffracts visible light on a surface.
[0008]
According to another aspect of the present invention, a step of condensing a plurality of diffracted beams diffracted by a hologram plate on a surface of a workpiece and forming a unit element comprising a pattern for diffracting visible light, and the unit There is provided a marking method including a step of forming another unit element having the same pattern as the element at another position on the surface of the workpiece and forming a mark composed of a plurality of unit elements.
[0009]
Since diffraction can be generated with only one unit element, the visibility of the mark can be improved. In addition, since the individual points constituting the unit element are very small, damage to the member can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic perspective view of a laser marking device 10 according to an embodiment of the present invention. The marking device 10 includes a laser light source 11, a beam shaper 12, a hologram plate 16, a galvano scanner 13, an fθ lens 14, and a stage 15. On the stage 15, the transparent glass substrate 1 which is a processing target is placed.
[0011]
As the laser light source 11, for example, a mode-locked Ti: sapphire laser oscillator is used. This Ti: sapphire laser oscillator outputs a pulsed laser beam having, for example, a pulse width of 130 fs, a wavelength of 800 nm, an average output of 1 W, and a repetition frequency of 1 kHz. The light in this wavelength region is transmitted through the transparent glass substrate 1 that is the object to be processed. As the laser light source 11, in addition to the Ti: sapphire laser, a laser diode (LD) excitation type solid laser oscillator such as a YAG laser or a YLF laser can also be used. Various laser light sources that generate harmonics of the fundamental wave output from these laser oscillators can also be used.
[0012]
The beam shaper 12 shapes the cross-sectional shape of the laser beam emitted from the laser light source 11. The shaped laser beam enters the hologram plate 16. The hologram plate 16 is a quartz substrate with irregularities corresponding to a predetermined phase distribution. The hologram plate 16 diffracts the laser beam according to the phase distribution corresponding to the unevenness applied to the surface.
[0013]
The galvano scanner 13 swings each optical axis of the diffracted beam diffracted by the hologram plate 16. The fθ lens 14 condenses the diffracted beam whose optical axis is shaken at a desired depth position of the transparent glass substrate 1. By shaking each optical axis of the diffracted beam with the galvano scanner 13, the condensing position of the diffracted beam formed inside the transparent glass substrate 1 can be moved to a desired position. The stage 15 can move the transparent glass substrate 1 in a two-dimensional direction parallel to the surface.
[0014]
The galvano scanner 13 includes a mirror drive device that rotationally drives a pair of galvanometer mirrors 13a and a highly sensitive position detection device. The galvano scanner 13 is controlled by the computer 20 via the drive unit 13b. The computer 20 synchronizes the driving of the galvano scanner 13 with the pulse oscillation of the laser light source 11.
[0015]
The fθ lens 14 not only condenses the diffracted beam 3 inside the transparent glass substrate 1 but also keeps the converging position of the diffracted beam 3 at a certain depth during scanning by the galvano scanner 13.
[0016]
At each condensing position of the diffracted beam 3 formed by the fθ lens 14, an altered portion where a refractive index change has occurred due to multiphoton absorption is formed. Since the laser light source 11 generates an extremely short pulse on the order of femtoseconds, multiphoton absorption occurs efficiently at the condensing position. If such multi-photon absorption is used, energy can be injected by infrared laser light that does not inherently absorb. Thereby, it is possible to cause a change in optical characteristics such as a relatively large refractive index, limited to the condensing position. Such a characteristic change is an optical non-linear phenomenon formed due to a density change or a bonding state change of the transparent glass substrate 1, and the altered part remains in the glass permanently.
[0017]
The transparent glass substrate 1 is not particularly limited as long as it transmits the laser beam from the laser light source 11 and allows efficient multiphoton absorption with respect to the laser beam. However, in order to visually recognize the mark formed in the inside, it is also necessary to substantially transmit visible light. For example, GeO ₂ —SiO ₂ glass or the like can be used. It has also been confirmed that marks can be formed on various materials such as soda lime glass and quartz glass.
[0018]
The distribution of the plurality of altered portions formed at the condensing position of the diffracted beam 3 depends on the phase distribution of the hologram plate 16. The method for obtaining the phase distribution of the hologram plate is described in, for example, M.H. A. Appl. Opt, 26, pp 2788-2798 (1987).
[0019]
FIG. 2A shows an example of the distribution of the altered portion formed inside the transparent glass substrate 1. The altered portions 30 are distributed so as to form a 5 × 5 matrix. The pitch a in the row direction and the column direction is, for example, 4 μm. Each altered portion 30 has a rod-like shape along the optical axis of the diffracted beam, and has a length of about 20 to 30 μm and a thickness of about 1 μm. A group of altered portions 30 constituting the 5-by-5 matrix is called a unit element.
[0020]
Next, a method for performing marking using the laser marking apparatus of FIG. 1 will be described. First, the transparent glass substrate 1 is placed on the stage 15 and the part to be marked is moved directly below the fθ lens 14. Next, the laser light source 11 is oscillated and the galvano scanner 13 is operated to scan the condensing position of the diffracted beam. A plurality of unit elements are formed inside the transparent glass substrate 1 along the scanning trajectory of the galvano scanner 13.
[0021]
FIG. 2B shows an example of a mark composed of a plurality of unit elements. The alphabet “H” is drawn in 11 unit areas. The minimum pitch b for moving the unit elements in the row direction and the column direction is 6 times the pitch a.
[0022]
Next, the laser beam scanning is temporarily interrupted, the stage 15 is operated, and the transparent glass substrate 1 is moved. As a result, the position where the mark is to be formed next moves directly below the fθ lens 14.
[0023]
The galvano scanner 13 and the laser light source 11 are operated so as to be synchronized with each other to scan the condensing point of the laser beam. By repeating the above steps, desired marks can be sequentially formed at desired positions.
[0024]
A mark formed by distributing a plurality of unit elements diffracts visible light. Thereby, the mark is visually recognized. If the pitch b shown in FIG. 2B is an integral multiple of the pitch a, the diffracted lights from the neighboring unit elements will be strengthened, and the visibility of the mark will be improved.
[0025]
In the above embodiment, the unit elements are constituted by 25 points arranged in a matrix of 5 rows and 5 columns, but other configurations may be adopted. By redesigning the phase distribution of the hologram plate, the arrangement of points in the unit element can be variously changed. Further, the unit element can be constituted by a plurality of straight lines instead of a plurality of points. For example, the unit element may be a grating that functions as a diffraction grating.
[0026]
The stage 15 can also finely move the transparent glass substrate 1 in the Z direction. Thereby, the depth of the mark formed inside the transparent glass substrate 1 can be adjusted. For example, if a first mark is formed at a first depth position on the transparent glass substrate 1 and a second mark is formed at a second depth position, a multilayer structure mark can be formed. . Furthermore, a mark having a three-dimensional shape can be formed by moving the stage 15 three-dimensionally while forming the unit element.
[0027]
In the above embodiment, the mark is formed by distributing unit elements in which small points are gathered. For this reason, a mark with high visibility can be obtained without enlarging individual points.
[0028]
In the above embodiment, the unit elements constituting one mark are all congruent patterns. However, the unit elements may be similar to each other by changing the pitch of each point in the unit element. . In this case, each unit element will be recognized as a different color.
[0029]
In the above-described embodiment, a plurality of points having a changed refractive index can be formed by one pulse laser irradiation. For this reason, it is possible to shorten the marking time. Further, in the case where one point is formed by one pulse laser irradiation, when the energy per pulse is larger than a suitable value, it is necessary to attenuate the laser beam by an attenuator or the like. In the case of the above embodiment, when the energy per pulse of a plurality of diffracted beams obtained from one beam is within a preferable range, the energy of the laser beam can be effectively used without inserting an attenuator. Can do.
[0030]
In the above-described embodiment, the case where the refractive index change is generated inside the workpiece is described. However, a unit element formed of a diffraction grating pattern may be formed on the surface of the workpiece. For example, the surface of a semiconductor substrate such as silicon may be irradiated with a laser beam and locally melted to form unevenness. When processing silicon, an ArF laser that does not transmit silicon can be used. Alternatively, the surface of the metal member may be discolored by being irradiated with a laser beam and locally oxidized. In the case of melting or oxidizing, the irradiated laser beam does not need to be pulsed, and a continuously oscillating laser beam can be used.
[0031]
Even when a diffraction grating pattern is formed on the surface, since the concave portions and discolored regions are very small, damage to the workpiece can be reduced as compared with the case where marking is performed by dispersing simple points. . If the processing time is not limited, the unit element may be formed by scanning one laser beam without using the hologram plate.
[0032]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0033]
【The invention's effect】
As described above, according to the present invention, since a plurality of points can be formed by one pulse laser irradiation, the marking time can be shortened.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a marking device according to an embodiment of the present invention.
FIG. 2A is a plan view illustrating an example of a unit element when marking is performed, and FIG. 2B is a plan view illustrating an example of a mark configured with the unit element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent glass substrate 3 Laser beam 10 Marking apparatus 11 Laser light source 12 Beam shaper 13 Galvano scanner 14 f (theta) lens 15 Stage 16 Hologram board 20 Computer

Claims (4)

A laser light source for emitting a laser beam;
A hologram plate disposed in an optical path of a laser beam emitted from the laser light source;
A scanning optical system that swings the optical axis of each of the diffracted beams diffracted by the hologram plate;
A condensing optical system for converging the diffracted beam whose optical axis is swung by the scanning optical system, and a stage for holding a workpiece at a position where the diffracted beam is condensed by the condensing optical system,
The diffracted beam diffracted by the hologram plate forms a unit diffraction pattern for diffracting visible light in the object to be processed,
A laser marking apparatus capable of forming a plurality of unit diffraction patterns in the object to be processed by oscillating an optical axis of a diffraction beam by the scanning optical system. The laser marking device according to claim 1, wherein the unit diffraction pattern formed in the object to be processed by the hologram plate includes a plurality of points arranged in a matrix. An optical member in which a mark is formed by distributing unit elements composed of a pattern for diffracting visible light on a surface. A step of condensing a plurality of diffracted beams diffracted by the hologram plate on the surface of the object to be processed, and forming a unit element consisting of a pattern for diffracting visible light;
Forming another unit element having the same pattern as the unit element at another position on the surface of the workpiece, and forming a mark composed of a plurality of unit elements.

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