JP2004177502A - Laser scanning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a galvanometer scanning device in which an object is scanned with a laser beam at a high accuracy. <P>SOLUTION: The object is two-dimensionally scanned with a machining laser beam superimposed with a guiding laser beam by using a galvanometer. Thereafter, the guiding laser beam is separated with a beam splitter or the like and made incident to a two-dimensional position sensor to detect the position of the laser beam. The deterioration of the stability of the position sensor and a detection circuit due to heat generation in the galvanometer is prevented by using the position sensor provided outside the galvanometer, and a position correction including the influence of the vibration of the scanning mirror, the twisting or the like is possible by detecting the position of the scanning laser beam itself. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser device, and more particularly to a laser scanning device capable of positioning and scanning a laser beam at an arbitrary position on a workpiece with high accuracy.
[0002]
2. Description of the Related Art Conventionally, a beam scanning method using a galvanometer (or galvanometer scanner) has been widely used as a laser beam scanning method. In this method, a reflecting mirror is attached to the tip of the output shaft of a galvano motor controlled to rotate within a certain angle range, and the reflection direction of the laser beam incident on it is scanned in any direction by changing the rotation angle of the galvano motor Control.
[0003]
For example, JP-A-09-103893 and JP-A-11-149635 describe such a laser scanning device. In these methods, after a laser beam is reflected twice by two galvanometers having different directions, the laser beam is condensed on the surface of an object to be processed by a condenser lens and processed. Two galvanometers are used to process an arbitrary position on the workpiece with the laser beam, and these are controlled so that the focal point of the laser beam is scanned at an arbitrary position on the surface of the workpiece. Has become.
[0004]
In the galvanometer used for the above-mentioned purpose, a position sensor is built in the galvanometer itself to accurately position the reflection mirror, thereby detecting and controlling the rotation angle of the galvanometer. However, the method of providing the position sensor on the galvanometer itself has some unavoidable problems.
[0005]
The first problem concerns the resolution and accuracy of the position sensor. Usually, a capacitance sensor or an optical sensor is often used as a position sensor built in the galvanometer, and each of these sensors detects a change in the relative angle between the rotor and the stator of the galvanometer. For example, if the galvanometer is designed to scan the laser beam by 25 mm at its focal position when the galvanometer is rotated at an angle of 20 degrees, to position the laser beam with an accuracy of 1 μm, a simple proportional calculation is performed to calculate the laser beam at 20 degrees × An angle accuracy and resolution of 0.001 mm / 25 mm = 0.0008 degrees are required, and the position sensor needs to detect this angle with high accuracy. However, the galvanometer generates heat when energized at the time of driving, causing the sensitivity characteristics of the built-in position sensor, the gain drift of the amplifier circuit, the origin drift, etc., so it was practically impossible to maintain the above detection accuracy. .
[0006]
The second problem is related to the method and is a fundamental problem. In a system in which a position sensor is built in the galvanometer and the rotational position of the galvanometer alone is detected, there is a limit to high-precision laser beam scanning. For example, a reflection mirror for scanning a laser beam is attached to the tip of the output shaft of the galvanometer and rotates. However, the acceleration and deceleration driving at this time is accompanied by small vibrations such as torsion and bending. Since the laser beam is scanned while being enlarged twice as much as the angle of the displacement of the reflection surface due to the vibration of the reflection mirror or the like, the vibration of the reflection mirror adversely affects the scanning accuracy of the laser beam. Although the position sensor built in the galvanometer can detect the rotation angle of the rotor of the galvanometer, it cannot detect an error due to the vibration of the reflection mirror itself.
[0007]
JP-A-2001-042247 describes a method of detecting and controlling the position of a galvanometer to avoid such a problem. In this method, another guide laser for position reference is reflected from the outside to the back surface of a scanning mirror provided at the tip of the galvanometer, and the position of the scanning mirror in the rotation direction is detected by an optical sensor provided outside the galvanometer.
[0008]
In this method, a position sensor provided separately from the galvanometer is used, so that detection accuracy does not decrease due to heat generation, and error detection including vibration of the reflection mirror can be performed to detect displacement of the reflection mirror itself.
[0009]
However, in this method, since the guide laser is reflected by the back surface of the reflecting mirror, it is inconvenient when performing two-dimensional scanning. In order to perform two-dimensional scanning, it is necessary to reflect the laser beam twice in two directions perpendicular to each other with two galvanometers as described in the above two embodiments. The guide laser must be reflected on the back of the reflecting mirror of each of the two galvanometers.
[0010]
For this reason, it is necessary to prepare a light source for the guide laser and a position sensor for each galvanometer, and to make the detection sensitivity and electrical characteristics uniform, which complicates the configuration of the apparatus.
[0011]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a laser scanning device capable of scanning a laser beam with high accuracy.
[0012]
[Means for Solving the Problems]
To achieve the above object, a processing laser oscillator and a guide laser oscillator, and a processing laser beam emitted from the processing laser oscillator and a guide laser beam emitted from the guide laser beam. Laser coupling means for combining to generate a mixed laser beam, laser scanning means for spatially scanning the mixed laser beam, and a processing laser beam before combining the scanned mixed laser beam again A laser beam splitting means for separating the laser beam into a guide laser beam, and a laser beam detecting means for receiving a guide laser beam obtained by the separation and detecting a change in the position of the guide laser beam. A position detection signal of the guide laser beam detected by the laser beam detection means. And feeds back variation is obtained to perform the scan operation control of the laser scanning unit.
[0013]
[Action]
Hereinafter, the operation of the present invention will be described.
[0014]
Even when performing two-dimensional scanning, the position of the laser beam itself to be scanned is detected by another optical sensor provided outside the galvanometer, and the position of the laser beam is directly controlled by feeding it back to each galvanometer. can do.
[0015]
In addition, the laser beam to be scanned is superimposed with a guide laser beam of another wavelength or another polarization, and this is scanned with a galvanometer, and then only the guide laser is separated and another optical sensor provided outside the galvanometer is used. There is also a method of detecting the position.
[0016]
In general, the purpose of scanning a laser beam is to process an object to be processed by a laser beam or to perform welding. In such a case, the laser beam for processing has a pulsed output, Repeat stop. For this reason, it is often inconvenient to use it for position detection. Therefore, in the present invention, the latter method will be mainly described.
[0017]
In order to superpose the guide laser beam on the processing laser beam, a 45-degree two-wavelength mirror may be used. A processing laser beam is incident on the first surface of the mirror at an incident angle of 45 degrees, and is coated so as to be totally reflected and a guide laser beam of another wavelength is completely transmitted. On the other hand, the second surface of the mirror is coated so as to completely transmit the guide laser beam having an incident angle of 45 degrees.
[0018]
A laser beam for processing is incident on the first surface of such a mirror at an incident angle of 45 degrees, and a laser beam for guiding is incident on the first surface through the second surface so as to overlap the optical axis after reflection. In this way, the processing laser beam and the guide laser beam can be superimposed on one optical axis. When the mixed laser beam superimposed from the first surface side is incident at an incident angle of 45 degrees using the same mirror, the laser beam can be separated into laser beams of the original two wavelengths.
[0019]
The laser beams overlapped as described above are scanned in two directions by two galvanometers. At this time, the reflection mirror attached to the galvanometer is coated so as to reflect both the processing laser beam and the guide laser beam.
[0020]
After scanning the superimposed laser beam, it is again separated into two laser beams by the same mirror as when the previous laser beam was superimposed, and a two-dimensional light position where only a guide laser beam is separately provided By incident on the sensor, the position of the laser beam itself including the error of the galvanometer and the reflection mirror can be detected. The position detection signal may be fed back to control each galvanometer.
[0021]
【Example】
An embodiment of the present invention will be described below with reference to FIG.
[0022]
A processing laser beam 2 is emitted from the processing laser oscillator 1. This is an ultraviolet pulse laser having a wavelength of 266 nm. Further, the guide laser oscillator 3 emits the guide laser beam 4 in a direction orthogonal to the processing laser beam 2. The guide laser beam 4 is a continuous red laser beam having a wavelength of 670 nm.
[0023]
The first folding mirror 5 is arranged such that these two laser beams are incident at an angle of 45 degrees. The first surface S1 of the first folding mirror 5 is coated with a dielectric multilayer so that the laser beam having a wavelength of 266 nm is completely reflected and the laser beam having a wavelength of 670 nm is completely transmitted. S2 is coated so as to completely transmit only a laser beam having a wavelength of 670 nm.
[0024]
The processing laser beam 2 reflected by the first folding mirror 5 at an angle of 90 degrees is superimposed on the guide laser beam 4 which has also passed through the first folding mirror 5 so that the optical axis exactly coincides therewith and mixed. The laser beam becomes 2 + 4.
[0025]
The mixed laser beam 2 + 4 is incident on the condenser lens 10 after being reflected twice by the first scanning mirror 6 and the second scanning mirror 8. The first and second scanning mirrors 6 and 8 are both coated so as to reflect the two laser beams having wavelengths of 266 nm and 670 nm almost completely. Further, each is attached to the tip of the output shaft of the first galvanometer 7 and the second galvanometer 9 and is driven to rotate so as to scan the mixed laser beam 2 + 4 two-dimensionally.
[0026]
The condenser lens 10 is an Fθ lens designed to focus while moving the emission position of the laser beam by a distance corresponding to the scanning angle of the incident laser beam. The shape and arrangement of the condenser lens 10 are 266 nm in wavelength. Is focused on the surface of the object 14 to be processed. The mixed laser beam 2 + 4 that has exited the condenser lens 10 is reflected at an angle of 90 degrees by the second folding mirror 11 and is incident on the third folding mirror 12.
[0027]
The third folding mirror 12 is the same as the first folding mirror 5, and is formed by coating the first surface S1 and the second surface S2, respectively. Since the first surface S1 is coated so as to reflect only the processing laser beam 2 having a wavelength of 266 nm, the processing laser beam 2 is separated here and reflected at 90 degrees, and focuses on the surface of the processing object 14. Tie.
[0028]
On the other hand, the guide laser beam 4 passes through the first surface S1 and the second surface S2 of the third folding mirror 12, is condensed by the convex lens 13, and then enters the two-dimensional position sensor 15. The convex lens 13 is provided to condense the guide laser beam 4 scanned two-dimensionally by the first and second galvanometers 7 and 9 to narrow the scanning range. Accordingly, the first and second galvanometers 7 and 9 scan the mixed laser beam 2 + 4 and scan the processing range X and Y of the processing laser beam 2 on the two-dimensional position sensor 15 of the guide laser beam 4. Can be adjusted so that the scanning ranges x and y become narrower, and the small-sized two-dimensional position sensor 15 can detect the position of the laser beam over the entire scanning range.
[0029]
The movements x and y of the guide laser beam 4 on the two-dimensional position sensor 15 correspond one-to-one with the movements X and Y of the processing laser beam 2 on the surface of the processing object 14, and thereby the first In addition, the position of the processing laser beam 2 including the influence of torsion and bending of the first and second scanning mirrors 6 and 8 driven to rotate by the second and second galvanometers 7 and 9 can be detected. Further, by feeding back the position detection signals from the two-dimensional position sensor 15 to the corresponding control circuits of the first and second galvanometers, the processing laser beam 2 can be scanned and positioned with high accuracy.
[0030]
【The invention's effect】
In the present invention, the scanning position of the laser beam itself is detected using a position detection sensor provided separately from the galvanometer. Therefore, the stability of the position sensor does not decrease due to the heat generated by the galvanometer, and the displacement of the laser beam caused by the deformation or vibration of the reflection mirror scanned by the galvanometer can be detected and corrected together. Therefore, a laser scanning device with high stability can be realized.
[Brief description of the drawings]
FIG. 1 is an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Processing laser oscillator 2 Processing laser beam 3 Guide laser oscillator 4 Guide laser beam 2 + 4 Mixed laser beam 5 First folding mirror 6 First scanning mirror 7 First galvanometer 8 Second scanning mirror 9 Second Galvanometer 10 Condensing lens 11 Second folding mirror 12 Third folding mirror 13 Convex lens 14 Workpiece 15 Two-dimensional position sensor S1 First surface S2 Second surface X, Y Scanning range x of processing laser beam , Y Guide laser beam scanning range

Claims (1)

A processing laser oscillator and a guide laser oscillator, and a combined laser beam generated by combining a processing laser beam emitted from the processing laser oscillator and a guide laser beam emitted from the guide laser beam Laser coupling means for spatially scanning the mixed laser beam, and separating the scanned mixed laser beam into a processing laser beam and a guide laser beam before being combined again. And a laser beam detecting means for receiving the separated guiding laser beam and detecting a change in the position of the guiding laser beam. Feedback of the change in the position detection signal of the guide laser beam detected in The laser scanning apparatus characterized by performing a scanning operation control of the laser scanning unit Te.

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