JP2002321081A - Laser irradiation apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser irradiation apparatus and method capable of irradiating uniformly a work even with a coherence-rich laser light source. SOLUTION: The linearly polarized laser beam 24 half of which is rotated by 90 degrees relative to the electric field direction with the λ/2 polarization plate 25 does not interfere with the other half of the laser beam. With respect to the two kinds of laser beam not interfering with each other, by making them pass through light path compensation lenses 28, 29 comprising transparent glass plates 28a-28d having a length longer than the coherent length, the coherence effect is eliminated, thereby the interference between the laser beams is canceled. The linear beam having a uniform spectral density can be obtained by making such laser beams not having interference with each other pass through a homogenizer 32 and the series of lenses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a laser irradiation apparatus and a laser irradiation method.

[0002]

2. Description of the Related Art FIG. 6A is a plan view of a laser irradiation apparatus to which a conventional laser irradiation method is applied, and FIG. 6B shows a laser beam emitted from the laser irradiation apparatus shown in FIG. It is sectional drawing of light.

The laser irradiation apparatus 1 includes a laser light source 3 for emitting a laser beam 2 having a circular cross section, an expander 4 for expanding the width of the laser beam 2, and a plurality of cylindrical lenses. A homogenizer 6 for dividing and mixing the laser beam 5, a condenser lens 8 for condensing the laser beam 7 transmitted through the homogenizer 6, and a superposition lens system for expanding the width of the laser beam 9 condensed by the condenser lens 8. Group 10,
A superposition lens system rear group 12 for converting the laser beam 11 widened by the superposition lens system front group 10 into a linear shape, and a short axis direction condensing lens 14 for condensing a linear laser beam 13 in a short axis direction. It is composed of

When the laser irradiation device 1 is operated, a laser beam 2 having a circular cross section emitted from a laser light source 3 is emitted.
A linear laser beam (FIG. 6B) is applied to an irradiation target (not shown).

[0005]

However, FIG.
In the conventional laser irradiation apparatus 1 shown in (a), when a light source having high coherence such as a YAG laser is used as the laser light source 3, an interference action occurs after the laser beam passes through the homogenizer 4, and the irradiation target is irradiated. There was a problem that irradiation could not be performed uniformly.

An object of the present invention is to solve the above-mentioned problems and to provide a laser irradiation apparatus and a laser irradiation method capable of uniformly irradiating an irradiation object even using a laser light source having high coherence.

[0007]

In order to achieve the above-mentioned object, a laser irradiation apparatus according to the present invention uses a homogenizer comprising a plurality of cylindrical lenses and a lens system for emitting a laser beam having a circular cross section emitted from a laser light source. A laser light source that emits a linearly polarized laser beam with a circular cross section and a λ / 2 polarized light that is arranged to substantially cross the laser beam in a laser irradiation apparatus that irradiates an irradiation target with a linear cross section being deformed. And a plurality of transparent glass plates which are arranged in parallel on the optical path of the laser beam transmitted through the λ / 2 polarizer plate and the remaining laser beam and which are sequentially elongated by a length longer than the coherent length of the laser beam. And two sets of optical path correction lenses.

In addition to the above configuration, the width of the transparent glass plate forming the optical path correction lens of the laser irradiation apparatus of the present invention is made equal to the width of the cylindrical lens forming the homogenizer.

In addition to the above configuration, the laser irradiation apparatus of the present invention may be arranged in a pyramid shape such that the transparent glass plates of both optical path correction lenses become shorter from the center to the end of the laser beam when viewed from above.

In addition to the above configuration, the laser irradiation apparatus of the present invention is arranged such that the length of the transparent glass plate of one of the optical path correction lenses becomes shorter from the center of the laser beam to the end thereof.
The transparent glass plate of the other optical path correction lens may be arranged such that the length thereof increases from the center of the laser beam toward the end.

According to the laser irradiation method of the present invention, a laser beam having a circular cross-sectional shape emitted from a laser light source is deformed into a linear cross-sectional shape by using a homogenizer composed of a plurality of cylindrical lenses and a lens system to irradiate an irradiation target. In the laser irradiation method, a linearly polarized laser beam having a circular cross-sectional shape is emitted from a laser light source, half of the laser beam is transmitted through a λ / 2 polarizer plate, rotated by 90 degrees in the direction of an electric field, and the other half is irradiated. The laser beam is transmitted through two sets of optical path correction lenses composed of a plurality of transparent glass plates sequentially longer by a length longer than the coherent length of the laser beam, and is incident on the homogenizer.

According to the present invention, half of the linearly polarized laser beam is rotated by 90 degrees in the direction of the electric field by the λ / 2 polarizer plate so that it does not interfere with the original laser beam, that is, the remaining laser beam. These do not interfere with each other 2
When the types of beams are a P-polarized beam and an S-polarized beam,
The light enters the independent optical path correction lenses, and becomes a P-polarized beam group and an S-polarized beam group composed of a plurality of transparent glass plates. In each of the beam groups, interference is eliminated by the effect of the optical path correction lens, and interference does not occur between the P-polarized beam group and the S-polarized beam group because the polarization components differ by 90 degrees. The laser beam has no interference.

By transmitting such a laser beam having no interference between laser beams through the homogenizer and the lens system, a linear beam having a uniform light intensity can be obtained. In order to completely eliminate the interference, the width of the transparent glass plate forming the optical path correction lens must be equal to the width of the cylindrical lens forming the homogenizer.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1A is a plan view showing an embodiment of a laser irradiation apparatus to which the laser irradiation method of the present invention is applied, and FIG. 1B is a plan view showing the laser irradiation apparatus shown in FIG. FIG. 3 is a cross-sectional view of a laser beam emitted from a laser beam.

The laser irradiation device 20 includes a laser light source (for example, a YAG second harmonic laser) 22 for emitting a linearly polarized laser beam 21 having a circular cross section, an expander 23 for expanding the width of the laser beam 21, and an expander 23. A λ / 2 polarizer plate 25 and a λ / 2 polarizer plate 2 arranged so as to cross substantially half the laser beam 24 widened by the panda 23.
5 and the remaining laser beam 2
7, two sets of optical path correction lenses 28 and 29 arranged in parallel on the optical path, laser beams 30 and 31 transmitted through the optical path correction lenses 28 and 29 are divided and mixed, and a homogenizer 32 is transmitted through the homogenizer 32. Laser beam 33
A condenser lens 34 for condensing the laser beam, a superposition lens system front group 36 for expanding the width of the laser beam 35 condensed by the condenser lens 34, and a superposition lens system front group 36.
And a short axis direction condensing lens 40 for condensing the linear laser beam 39 in the short axis direction.

FIG. 2 is a plan view around the optical path correction lens used in the laser irradiation apparatus shown in FIG.

The λ / 2 polarizer plate 25 is an optical component for rotating the polarization (electric field direction) of the incident laser beam by 90 degrees. For example, when the laser beam from the YAG laser is P-polarized, it is emitted as S-polarized light. Things. The width Wp of the λ / 2 polarizer plate 25 may be larger than the width of the optical path correction lens 28. Although the λ / 2 polarizer plate 25 is disposed on the incident side of the optical path correction lens 28 in the drawing, it may be disposed on the incident side of the optical path correction lens 29.

The optical path correction lens 28 is an optical component for transmitting P-polarized light, and the optical path correction lens 29 is an optical component for transmitting S-polarized light. The optical path correction lens 28 includes a plurality of transparent glass plates 28a, 28b, 28c, and 2 that are sequentially elongated by a length longer than the coherent length of the laser beam.
8d are optical components joined in parallel. Similarly, the optical path correction lens 29 includes a plurality of transparent glass plates 29a and 29 sequentially elongated by a length longer than the coherent length of the laser beam.
b, 29c are optical components joined in parallel.

These optical path correction lenses 28 and 29 are arranged in the optical path of the laser beam in parallel with the optical path.
Each of the transparent glass plates 28a to 28d and 29a to 29c is divided into n laser beams and transmitted therethrough. The transparent glass plates 28a to 28d and 29a to 29c constituting each of the optical path correction lenses 28 and 29 are arranged in a pyramid shape so as to become shorter from the center toward the ends. Transparent glass plate 28a constituting optical path correction lenses 28 and 29
To 28d and 29a to 29c are equal to the width Wc of the cylindrical lens constituting the homogenizer 31.

X indicates an optical path difference (transparent glass length).

Since the laser beam 21 from the YAG laser 22 shown in FIG. 1A is emitted in the horizontal direction, when irradiating the upper surface of the irradiation object, the linearly deformed laser beam is reflected by a reflecting mirror. And may be bent downward to irradiate the irradiation target.

When the laser irradiation device 20 operates, Y
A P-polarized laser beam 21 is emitted from the AG laser 22. The laser beam 21 having a small outer diameter (for example, several mm) is expanded by the expander 23 to the width of the homogenizer 32 (for example, several tens mm). Half of the widened linearly polarized laser beam 24 enters the λ / 2 polarizer plate 25. The laser beam transmitted through the λ / polarizer plate 25 is rotated by 90 degrees in polarization (electric field direction) to become an S-polarized laser beam 26. The S-polarized laser beam 26 does not interfere with the original laser beam 24, that is, the remaining laser beam 27, because the polarization is different by 90 degrees. These two types of laser beams 26 and 27 that do not interfere with each other are incident on an optical path correction lens 28 for P polarization and an optical path correction lens 29 for S polarization, respectively. The beam 26 transmitted through the optical path correction lens 28 becomes a beam bundle 30 composed of the number of glass beams in the optical path correction lens 28, and is incident on the homogenizer 32. At this time, the optical path becomes longer by the length of the glass, and an optical path difference is generated between the respective beams at a distance longer than the coherent length.

Similarly, the beam 27 transmitted through the optical path correction lens 29 becomes a beam bundle 31 consisting of the number of glasses in the optical path correction lens 29, and a homogenizer 32
Incident on. Since the laser beams 26 and 27 do not interfere with each other, the beam bundles 30 and 31 also do not interfere with each other.

The laser beams 30, 31 having no interference between the laser beams are transmitted through the homogenizer 32, and the condenser lens 7, the superimposing lens system front group 9,
Superposition lens system rear group 11, short axis direction condensing lens 13
A linear beam having a uniform light intensity can be obtained by transmitting through a lens system consisting of

Here, the two sets of optical path correction lenses 28 and 29 used in the laser irradiation apparatus 20 have a pyramid shape as a whole, but the present invention is not limited to this. The arrangement of the transparent glass plates 28a to 28d and 29a to 29c may be replaced in each of the optical path correction lenses 28 and 29.

FIG. 3 is a plan view showing a modification around the optical path correction lens used in the laser irradiation apparatus of the present invention.

The difference from the optical path correction lens shown in FIG. 2 is that the transparent glass plates 28a to 28d and 29a to 29c are arranged in a sawtooth shape.

That is, this optical path correction lens is composed of an optical path correction lens 28 for S-polarized light and transparent glass plates 29a-29.
c is joined to an optical path correction lens 290 for P-polarization, which is arranged so as to be longer from the center to the end of the laser beam.

The same effect as the optical path correction lens shown in FIG. 2 can be obtained by using such optical path correction lenses 28 and 290.

FIG. 4 is a plan view showing another modification around the optical path correction lens used in the laser irradiation apparatus of the present invention.

The difference from the optical path correction lens shown in FIG. 2 is that the transparent glass plates 28a to 28d and 29a to 29c are arranged in a parallelogram.

That is, this optical path correction lens is composed of an optical path correction lens 28 for S-polarized light and transparent glass plates 29a-29.
The optical path correction lens 291 for P-polarized light, which is arranged so that c becomes longer from the end of the laser beam toward the center, is joined.

The same effects as those of the optical path correction lens shown in FIG. 2 can be obtained by using such optical path correction lenses 28 and 291.

In this embodiment, the λ / 2 polarizer plate 25 is the longest transparent glass plate 28 of the optical path correcting lens 28.
However, the present invention is not limited to this, and the side surface 25a of the λ / 2 polarizer plate 25 is indicated by a broken line L, that is, the longest transparent glass. What is necessary is just to be on the entrance end face of the plate 28d. In addition, the number of all transparent glass plates 28a to 28d and 29a to 29c is seven, but the present invention is not limited to this, and the number of transparent glass plates may be eight or more.
It may be less than this.

The present invention uses the λ / 2 polarizer plate 25 and two sets of optical path correction lenses 28 and 29 to prevent interference between laser beams. A plurality of transparent glass plates 41a to 41g sequentially extended by a length longer than the coherent length of the laser beam without using
It is conceivable to use only the optical path correction lens 41 provided with 41g to prevent interference between laser beams (see FIG. 5).

However, when it is intended to prevent interference between laser beams only by such an optical path correction lens 41, the length X × n of the optical path correction lens 41 is set to the length of the optical path correction lenses 28 and 29 shown in FIG. It is about twice as large as X × n / 2. On the other hand, the laser irradiation apparatus of the present invention has a special effect that the length of the optical path correction lens 41 shown in FIG.

FIG. 5 is a plan view of an optical path correction lens used in the laser irradiation apparatus on which the present invention is based.

As described above, according to the present invention, by using a λ / 2 polarizer plate and two sets of optical path correction lenses, it is possible to uniformly irradiate an irradiation target even with a laser light source having high coherence. it can.

When the laser beam emitted from the laser light source is not linearly polarized light (for example, circularly polarized light), TFP (Thin Film Polari) is provided on the emission side of the laser light source.
zer: a thin-film polarizing element, an element that reflects one of polarized light of vertical polarized light and horizontal polarized light and transmits the other polarized light)
What is necessary is just to arrange | position a board | plate and to make it emit only a linearly polarized laser beam.

[0041]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide a laser irradiation apparatus and a laser irradiation method that can uniformly irradiate an irradiation target even when a laser light source having high coherence is used.

[Brief description of the drawings]

FIG. 1A is a plan view showing an embodiment of a laser irradiation apparatus to which a laser irradiation method of the present invention is applied,
FIG. 2B is a cross-sectional view of a laser beam emitted from the laser irradiation device shown in FIG.

FIG. 2 is a plan view around an optical path correction lens used in the laser irradiation apparatus shown in FIG.

FIG. 3 is a plan view showing a modification around an optical path correction lens used in the laser irradiation apparatus of the present invention.

FIG. 4 is a plan view showing another modified example of the vicinity of the optical path correction lens used in the laser irradiation apparatus of the present invention.

FIG. 5 is a plan view of an optical path correction lens used in a laser irradiation device on which the present invention is based.

6A is a plan view of a laser irradiation apparatus to which a conventional laser irradiation method is applied, and FIG. 6B is a cross-sectional view of laser light emitted from the laser irradiation apparatus shown in FIG.

[Explanation of symbols]

 1,20 Laser irradiation device 2,5,7,9,12,13 Laser beam 3,22 Laser light source 4,23 Expander 6,32 Homogenizer 8,34 Condenser lens 10,36 Superposition lens system front group 12,38 Superposition lens system rear group 14, 40 Short axis direction condensing lens 25 λ / 2 polarizer plate 28, 29 Optical path correction lens

Continued on the front page (72) Inventor Kino Kawaguchi 3-1-1, Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center (72) Inventor Miyuki 3-1-1, Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center (72) Inventor Atsushi Yoshinouchi 3-1-1, Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries, Ltd. Tokyo Engineering Center F-term (reference) 2H099 AA17 BA09 CA08 CA11 4E068 CB10 CD05 CD08 CD13

Claims (5)

[Claims] 1. A laser irradiation apparatus for irradiating a laser beam having a circular cross section emitted from a laser light source into a linear cross section using a homogenizer composed of a plurality of cylindrical lenses and a lens system, and irradiating an irradiation target with the laser beam. A laser light source that emits a linearly polarized laser beam having a circular cross-sectional shape, a λ / 2 polarizer plate disposed so as to substantially cross the laser beam, a laser beam transmitted through the λ / 2 polarizer plate, and the rest And two sets of optical path correction lenses comprising a plurality of transparent glass plates which are arranged in parallel on the optical path with the laser beam and are sequentially elongated by a length longer than the coherent length of the laser beam. Laser irradiation device. 2. The laser irradiation apparatus according to claim 1, wherein a width of the transparent glass plate forming the optical path correction lens is equal to a width of a cylindrical lens forming the homogenizer. 3. The laser irradiation apparatus according to claim 1, wherein the transparent glass plates of both optical path correction lenses are arranged in a pyramid shape so as to be shorter from the center of the laser beam toward the end. 4. The transparent glass plate of one of the optical path correction lenses is arranged so that the length of the transparent glass plate becomes shorter from the center of the laser beam to the end, and the length of the transparent glass plate of the other optical path correction lens is set to be shorter than that of the laser beam. The laser irradiation device according to claim 1, wherein the laser irradiation device is arranged so as to be longer from a center to an end. 5. A laser irradiation method for deforming a laser beam having a circular cross section emitted from a laser light source into a linear cross section using a homogenizer including a plurality of cylindrical lenses and a lens system and irradiating an irradiation target with the laser beam. A laser beam of linearly polarized light having a circular cross section is emitted from a laser light source, half of the laser beam is transmitted through a λ / 2 polarizer plate, rotated by 90 degrees in the direction of the electric field, and the laser beam is emitted together with the other half of the laser beam. A laser irradiation method characterized by transmitting through two sets of optical path correction lenses composed of a plurality of transparent glass plates sequentially longer by a length longer than the coherent length of the above and entering the homogenizer.