JP2007007683A - Beam superposition device, and laser machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more enlarge superposed parts in a beam superposition optical device where a plurality of laser beams are partially superposed. <P>SOLUTION: A plurality of laser beams in which central beams are mutually parallel are made incident on a broadening angle expansion optical system. The broadening angle expansion optical system widens the beam broadening angle of each incident laser beam, and emits them, and parallelly holds the central beams of the emitted laser beams each other, and makes the spacing between the central beams of the emitted laser beams narrower than the spacing between the central beams of the incident laser beams, thus the laser beams are partially superposed each other. The laser beams partially superposed by the broadening angle expansion optical system are made incident on a broadening angle reduction optical system. The broadening angle reduction optical system narrows the beam broadening angle of each incident laser beam, and emits them, and also, in a state where the emitted laser beams are partially superposed, parallelly holds their central beams each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a beam superimposing apparatus and a laser processing method, and more particularly to a beam superimposing apparatus that superimposes a plurality of laser beams to obtain a laser beam having substantially high power, and a laser processing method using the apparatus.

  A laser beam superimposing apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2002-176006 will be described.

  Two linearly polarized laser beams can be combined into one laser beam using a polarizing beam splitter. Four laser oscillators and two polarization beam splitters are used to obtain two laser beams that are translated close to each other. The two laser beams are incident on a concave lens to diverge, and the two are partially overlapped. Then, it returns to a parallel light beam with a convex lens.

JP 2002-176006 A

  When two translated laser beams are incident on one concave lens, the central rays of the two laser beams after passing through the concave lens are gradually separated as they travel. If the incident laser beams are ideal parallel beam bundles, divergent beam bundles after passing through the concave lens do not overlap. When the incident laser beam has a certain beam divergence angle, the concave lens increases the beam divergence angle. However, since the distance between the central rays of the two laser beams gradually increases, the area where they overlap is very small.

  An object of the present invention is to make the overlapping portion larger in a beam superimposing optical device that partially overlaps a plurality of laser beams. Another object of the present invention is to provide a laser processing method using this beam superposing optical device.

  According to one aspect of the present invention, a plurality of laser beams whose central rays are parallel to each other are incident, emitted with an increased beam divergence angle of each of the incident laser beams, and the central rays of the emitted laser beams are mutually reflected. A divergence angle expanding optical system that partially superimposes the laser beams by keeping the interval between the central rays of the emitted laser beam smaller than the interval between the central rays of the incident laser beams, In a state where a laser beam partially overlapped by the divergence angle expanding optical system is incident, emitted with a small beam divergence angle of each of the incident laser beams, and the emitted laser beams are partially overlapped, There is provided a beam superposing optical device having a diverging angle reducing optical system for keeping these central rays parallel to each other.

  According to another aspect of the present invention, a plurality of optical fibers arranged such that emission ends are arranged along a plane, and central rays of laser beams emitted from the emission ends are parallel to each other, and the optical fiber A plurality of laser light sources that respectively make laser beams incident on the incident end of the optical fiber, and a pre-converging lens that is incident from a laser beam that is emitted from the emission end of the optical fiber and propagates with a certain beam divergence angle. And a post-stage converging lens having a focal length longer than that of the front-stage converging lens and having a rear focal point as the front focal point. An alignment optical device is provided.

  According to another aspect of the present invention, there is provided a method for performing laser processing using an apparatus in which a homogenizing optical system is combined with the beam superimposing optical apparatus described above.

  By increasing the beam divergence angle of each laser beam while keeping the central rays of the plurality of laser beam beams parallel to each other, the plurality of laser beams can be efficiently superimposed. As a result, the light intensity distribution in the cross section of the combined beam can be made to have a shape substantially similar to the light intensity distribution in the cross section of one laser beam.

  When a plurality of optical fibers are arranged close to each other, laser beams emitted from these optical fibers can be efficiently superimposed.

  By superimposing a plurality of laser beams and homogenizing them with a homogenizing optical system, a high-power homogenized laser beam can be obtained.

  FIG. 1 shows a schematic diagram of a beam superimposing optical apparatus according to the first embodiment. The laser light source 1 emits a plurality of laser beams, for example, five laser beams. The central rays of the five laser beams are parallel to each other. An xyz orthogonal coordinate system is defined in which the traveling direction of the laser beam is the z axis. The central rays of the five laser beams are arranged at equal intervals in the x-axis direction.

  Five laser beams emitted from the laser light source 1 enter the superposition optical system 2. The superposition optical system 2 emits five laser beams in which part of the beam cross sections of the laser beams overlap each other. The central rays of these five laser beams are also parallel to each other.

  A laser beam emitted from the superposing optical system enters the homogenizing optical system 3. The homogenizing optical system 3 divides the incident laser beam into a plurality of small beams in the beam cross section, and superimposes the divided small beams on the homogenization surface 50. As a result, the light intensity distribution on the homogenized surface becomes closer to uniform.

  The stage 4 holds the workpiece 5 so that the surface thereof coincides with the homogenized surface 50. Thereby, it is possible to perform processing with a laser beam having a uniform light intensity distribution on the surface of the workpiece 5.

  FIG. 2 shows a schematic diagram of the laser light source 1. The laser beam emitted from the laser oscillator 30 is reflected by the folding mirror 34 and enters the polarization beam splitter 33. The laser beam emitted from the other laser oscillator 31 enters the polarization beam splitter 33 from the opposite surface. The laser beams emitted from the laser oscillators 30 and 31 are linearly polarized so as to be S-polarized light and P-polarized light with respect to the polarization beam splitter 33, respectively. In order to obtain a desired linearly polarized light, for example, a half-wave plate (not shown) can be used. The S-polarized laser beam is reflected by the polarization beam splitter 33, and the P-polarized laser beam is transmitted through the polarization beam splitter 33, so that two laser beams are combined into one laser beam.

  A total of five sets of light sources having the same configuration as that of the laser oscillators 30 and 31, the polarization beam splitter 33, and the folding mirror 34 are prepared. The five laser beams emitted from the five sets of light sources are reflected by a plurality of folding mirrors 35 to obtain five laser beams L1 to L5 that are translated close to each other. The central beams of the laser beams L1 to L5 are parallel to the z axis and are arranged at equal intervals in the x axis direction. It should be noted that the distance between these central rays is not necessarily equal. However, it is preferable to arrange them at equal intervals for efficiency.

  FIG. 3 shows a schematic diagram of the superposition optical system 2. The superposition optical system 2 includes a divergence angle expansion optical system 2A and a divergence angle reduction optical system 2B disposed on the rear side thereof. The diverging angle enlarging optical system 2A includes a first converging lens 11 and a second converging lens 12, and the diverging angle reducing optical system 2B includes a third converging lens 15 and a fourth converging lens 16. These four converging lenses 11, 12, 15, 16 are arranged so that their optical axes coincide. This common optical axis is parallel to the z-axis. Each of the converging lenses 11, 12, 15, 16 may be composed of a single convex lens or a compound lens in which a plurality of lenses are combined.

  The second convergent lens 12 is disposed behind the first convergent lens 11 and has a shorter focal length than the first convergent lens 11. The position of the front focal point of the second converging lens 12 coincides with the position of the rear focal point of the first converging lens 11. The fourth convergent lens 16 is disposed on the rear side of the third convergent lens 15 and has a longer focal length than the third convergent lens 15. The position of the front focal point of the fourth converging lens 16 matches the position of the rear focal point of the third converging lens 15. As an example, the focal lengths of the first converging lens 11, the second converging lens 12, the third converging lens 15, and the fourth converging lens 16 are 500 mm, 100 mm, 200 mm, and 500 mm, respectively.

  Five laser beams L <b> 1 to L <b> 5 emitted from the laser light source 1 (FIG. 2) enter the first converging lens 11. The central rays of the laser beams L1 to L5 are all parallel to the z axis and are arranged at equal intervals in the x axis direction, for example, at an interval of 10 mm.

  4A, 5A, and 6A, a plane (hereinafter referred to as “focal plane”) 10 that includes the front focal point of the first converging lens 11 and is perpendicular to the optical axis. The light intensity distribution of the position is shown. 4 (A) and FIGS. 4 (B) to 4 (D), which will be described later, are diagrams showing light intensity in shades, and FIG. 5 (A) and FIGS. 5 (B) to 5 (D) to be described later. FIG. 6A is a graph showing the light intensity distribution in the x-axis direction, and FIG. 6A and FIGS. 6B to 6D described later are graphs showing the light intensity distribution in the y-axis direction.

Each of the beam cross sections 20 of the laser beams L1 to L5 has an elliptical shape that is long in the y-axis direction. The major axis (dimension in the y-axis direction) of each beam section 20 is about 50 mm, and the minor axis (dimension in the x-axis direction) is slightly shorter than the distance 10 mm between the centers of the beam sections 20, for example, 9 mm. Here, the “beam cross section” means a region surrounded by a line connecting points where the light intensity becomes 1 / e ² of the maximum value. Here, e is the base of the natural logarithm. The beam divergence angle θd in the xz plane of the laser beams L1 to L5 is about 2.5 mrad. In this specification, “beam divergence angle” refers to a half angle of beam divergence.

  The central rays of the five laser beams L1 to L5 that have passed through the second convergent lens 12 are parallel to the z axis.

  4B, 5B, and 6B show the light intensity distribution at the position of the rear focal plane 13 of the second convergent lens 12. FIG. The front focal plane 10 of the first convergent lens 11 and the rear focal plane 13 of the second convergent lens 12 are in a conjugate relationship. Therefore, the image of the position of the front focal plane 10 of the first converging lens 11 is transferred to the position of the rear focal plane 13 of the second converging lens 12, and the magnification is 1/5. For this reason, the dimension of each of the beam cross sections 23 in the y-axis direction is about 10 mm, the dimension in the x-axis direction is about 1.8 mm, and the distance between the central rays is 2 mm. Since the beam divergence angle is almost inversely proportional to the magnification, the beam divergence angle θd in the xz plane of each laser beam that has passed through the second converging lens 12 is 12.5 mrad.

  In this way, the divergence angle widening optical system 2A makes the beam divergence angle of each of the emitted laser beams larger than the beam divergence angle of the incident laser beam, and sets the interval between the central rays of the emitted laser beams to be incident. The distance between the center beams of the laser beam is narrower. For this reason, the laser beam paths tend to overlap each other.

  The third convergent lens 15 is arranged on the rear side by 800 mm from the second convergent lens 12. That is, the front focal plane 14 of the third convergent lens 15 is located 500 mm behind the rear focal plane 13 of the second convergent lens 12. Since the beam divergence angle of the laser beam that has passed through the second converging lens 12 is 12.5 mrad, the dimension in the x-axis direction of each beam cross section 24 at the position of the front focal plane 14 of the third converging lens 15 is about 14. .3mm. The beam divergence angle in the y-axis direction is a negligible magnitude when the traveling distance is about 500 mm between the rear focal plane 13 and the front focal plane 14. For this reason, the dimension of the beam cross section 24 in the y-axis direction remains approximately 10 mm.

  4C, FIG. 5C, and FIG. 6C show the light intensity distribution at the position of the front focal plane 14 of the third converging lens 15. FIG. Since the dimension of the beam cross section 24 of each of the laser beams L1 to L5 in the x-axis direction is 14.3 mm and the distance between the centers of the beam cross sections 24 is 2 mm, the five beam cross sections 24 partially overlap. As shown in FIGS. 4C and 5C, individual beam cross sections cannot be identified, and a light intensity distribution substantially equivalent to the beam cross section of one laser beam appears.

  The central rays of the five laser beams L1 to L5 that have passed through the fourth convergent lens 16 are parallel to the z axis.

  The rear focal plane 17 of the fourth convergent lens 16 and the front focal plane 14 of the third convergent lens 15 have a conjugate relationship. Therefore, the image of the position of the front focal plane 14 of the third converging lens 15 is transferred to the position of the rear focal plane 17 of the fourth converging lens 16, and the magnification is 2.5 times. For this reason, the dimension in the x-axis direction of each beam cross section 27 of the laser beams L1 to L5 at the position of the rear focal plane 17 is about 35.75 mm, and the dimension in the y-axis direction is about 25 mm. The distance between the central rays of the laser beam is 5 mm. The beam divergence angle θd in the xz plane is 5 mrad.

  In this way, the divergence angle reduction optical system 2B is configured such that each beam divergence angle of the emitted laser beam is smaller than the beam divergence angle of the incident laser beam and the emitted laser beam is partially overlapped. , Make these central rays parallel to each other.

  4 (D), 5 (D), and 6 (D) show the light intensity distribution at the position of the rear focal plane 17. FIG. The beam cross sections of the five laser beams L1 to L5 partially overlap each other, so that individual beam cross sections cannot be identified. As described above, the light intensity distribution in the combined beam section of the laser beam group 47 obtained by combining the beam sections of the five laser beams L1 to L5 that have passed through the divergence angle reduction optical system 2B is substantially one Gaussian beam. It can be considered that the light intensity distribution is almost the same. The dimension in the x-axis direction of the combined beam cross section is 55.75 mm.

  FIG. 7 shows a cross-sectional view of the homogenizing optical system 3. FIG. 7A shows a cross-sectional view parallel to the yz plane, and FIG. 7B shows a cross-sectional view parallel to the xz plane.

  As shown in FIG. 7A, seven equivalent cylindrical lenses are arranged in a cylinder array along a virtual plane parallel to the xy plane, with each generatrix direction parallel to the x-axis and arranged in the y-axis direction. 45A and 45B are configured. The optical axis surfaces of the cylindrical lenses of the cylinder arrays 45A and 45B are parallel to the xz plane. Here, the optical axis plane means the plane of symmetry of the imaging system that is plane-symmetric with the cylindrical lens (the plane of symmetry of the imaging system that includes the center line of curvature of the columnar surface of the cylindrical lens). The cylinder array 45A is arranged on the light incident side (left side in the figure), and the cylinder array 45B is arranged on the emission side (right side in the figure).

  As shown in FIG. 7B, seven equivalent cylindrical lenses have their respective generatrix directions parallel to the y axis and arranged in the x axis direction, and cylinder arrays 46A along a virtual plane parallel to the xy plane. And 46B are configured. The optical axis surfaces of the cylindrical lenses of the cylinder arrays 46A and 46B are parallel to the yz plane. The cylinder array 46A is disposed in front of the cylinder array 45A (left side in the figure), and the cylinder array 46B is disposed between the cylinder arrays 45A and 45B. The optical axis surfaces of the corresponding cylindrical lenses of the cylinder arrays 45A and 45B coincide, and the optical axis surfaces of the corresponding cylindrical lenses of the cylinder arrays 46A and 46B also coincide.

  A condenser lens 49 is disposed behind the cylinder array 45B. The optical axis of the condenser lens 49 is parallel to the z axis.

  With reference to FIG. 7A, a state of propagation of the light beam in the yz plane will be described. In the yz plane, the cylinder arrays 46A and 46B are simply flat plates, and thus do not affect the focusing and divergence of the light beam.

  Five laser beams having an optical axis parallel to the z-axis are incident from the left side of the cylinder array 46A. As shown in FIG. 6D, the five laser beams can be considered to have approximately the same light intensity distribution as that of one Gaussian beam in the y-axis direction. The incident laser beam 47 has a light intensity distribution that is strong in the central portion and weak in the peripheral portion, as shown by a curve 51y, for example.

  The laser beam 47 passes through the cylinder array 46A and enters the cylinder array 45A. The incident beam bundle is divided into seven focused beam bundles corresponding to the respective cylindrical lenses by the cylinder array 45A. In FIG. 7A, only the light beam at the center and both ends is shown as a representative. The seven focused beam bundles have light intensity distributions indicated by curves 51ya to 51yg, respectively. The light beam focused by the cylinder array 45A is again focused by the cylinder array 45B.

  The seven focused light bundles 48 focused by the cylinder array 45B are imaged in front of the focusing lens 49, respectively. This imaging position is closer to the lens than the incident side focal point of the condenser lens 49. For this reason, the seven light fluxes transmitted through the condenser lens 49 become divergent light fluxes, which overlap on the homogenizing surface 50. The light intensity distribution in the y-axis direction of the seven light bundles that irradiate the homogenized surface 50 is equal to a distribution obtained by extending the light intensity distributions 51ya to 51yg in the y-axis direction, respectively. Since the light intensity distributions 51ya and 51yg, 51yb and 51yf, and 51yc and 51ye have inverted relations with respect to the y-axis direction, the light intensity distribution obtained by superimposing these light bundles is uniform as shown by the solid line 52y. Approach the distribution.

  With reference to FIG. 7B, the state of propagation of the light beam in the xz plane will be described. In the xz plane, the cylinder arrays 45A and 45B are simply flat plates, and thus do not affect the convergence and divergence of the light flux. Five ray beams 47 are incident on the cylinder array 46A. As shown in FIG. 5D, the five laser beams 47 can be considered to have approximately the same light intensity distribution as that of one Gaussian beam in the x-axis direction. The laser beam 47 has a light intensity distribution that is strong in the central portion and weak in the peripheral portion, for example, as shown by a curve 51x.

  The laser beam 47 is divided into seven focused beam bundles corresponding to the respective cylindrical lenses by the cylinder array 46A. In FIG. 7B, only the light beams at the center and both ends are shown as representatives. The seven focused beam bundles have light intensity distributions indicated by curves 51xa to 51xg, respectively.

  Each light flux forms an image in front of the cylinder array 46B and enters the cylinder array 46B as a divergent light flux. Each light beam incident on the cylinder array 46B is emitted with a certain emission angle and is incident on the condenser lens 49.

  The seven light fluxes that have passed through the condenser lens 49 become focused light fluxes that overlap on the homogenizing surface 50. The light intensity distribution in the x-axis direction of the seven light bundles that irradiate the homogenized surface 50 approaches a uniform distribution as shown by the solid line 52x as in the case of FIG.

  The light irradiation region on the homogenized surface 50 has a linear shape that is long in the y-axis direction and short in the x-axis direction. By disposing the surface of the object to be irradiated at the position of the homogenized surface 50, a linear region that is long in the y-axis direction in the surface can be irradiated almost uniformly.

  In the first embodiment, the laser beams emitted from the ten laser oscillators 30 and 31 shown in FIG. 2 are superimposed on the surface of the workpiece 5. For this reason, it becomes possible to perform laser processing equivalent to the case of using one laser oscillator having 10 times the output.

  In the first embodiment, the diverging angle enlarging optical system 2A and the diverging angle reducing optical system 2B are configured by Kepler type beam expanders, but may be configured by Galileo type beam expanders. When the divergence angle widening optical system 2A is of the Galileo type, a diverging lens is used instead of the second converging lens 12. At this time, the diverging lens is arranged so that the rear focal point of the diverging lens coincides with the rear focal point of the first converging lens. When the divergence angle reduction optical system 2B is a Galileo type, a diverging lens is used instead of the third converging lens 15. At this time, the diverging lens is arranged so that the front focal point of the diverging lens coincides with the front focal point of the fourth converging lens 16.

  FIG. 8 shows a schematic diagram of a beam superposition optical system according to the second embodiment. Hereinafter, the description will be made focusing on differences from the beam superposition optical system according to the first embodiment shown in FIG.

  In the beam superimposing optical system according to the second embodiment, a cylindrical optical device 6 is disposed between the divergence angle expanding optical system 2A and the divergence angle reducing optical system 2B. Other configurations are the same as those of the first embodiment.

  The cylindrical optical device 6 has a cylindrical shape with both ends opened, and its inner surface is a reflecting surface that reflects the laser beam. The inner surface is constituted by a column surface parallel to the z axis, for example. As the cylindrical optical device 6, a kaleidoscope can be used. The laser beam that has passed through the diverging angle enlarging optical system 2A enters the cylindrical optical device 6 from one opening. The incident laser beam is emitted through the opening on the emission side of the cylindrical optical device 6.

  The exit-side opening is disposed at the position of the front focal plane 14 of the third converging lens 15. The spread 24 a of the light intensity distribution at the position of the front focal plane 14 is limited by the opening on the exit side of the cylindrical optical device 6. The opening on the exit side of the cylindrical optical device 6 is transferred to the position of the rear focal plane 17 of the fourth converging lens 16.

  For this reason, compared with the case of the 1st Example, the synthetic beam cross section of the laser beam group radiate | emitted from the divergence angle reduction optical system 2B can be narrowed.

  FIG. 9 shows a schematic diagram of a beam superimposing optical apparatus according to the third embodiment. The laser oscillator 60, the condenser lens 61, and the optical fiber 62 constitute one light source, and a plurality of these light sources are prepared. The laser beam emitted from the laser oscillator 60 is collected by the corresponding condenser lens 61 and enters the incident end face of the corresponding optical fiber 62. The emission end faces of the plurality of optical fibers 62 are arranged in a matrix along the virtual plane 69. Each optical fiber 62 is arranged so that the central ray of the laser beam emitted from the emission end face thereof is perpendicular to the virtual plane 69. An xyz orthogonal coordinate system in which a plane parallel to the virtual plane 69 is defined as an xy plane is defined.

  The laser beam emitted from the end face of the optical fiber 62 has a beam divergence angle of 100 mrad, for example.

  A pre-converging lens 63 is disposed at a position where the laser beam emitted from the optical fiber 62 is incident. A rear stage converging lens 64 is disposed on the rear side. Both optical axes coincide and are parallel to the z-axis. The focal length of the front stage convergence lens 63 is, for example, 50 mm, and the focal length of the rear stage convergence lens 64 is longer than the focal length of the front stage convergence lens 63, for example, 500 mm. The position of the rear focal point of the front stage converging lens 63 coincides with the position of the front side focal point of the rear stage converging lens 64. The homogenizing optical system 3 and the stage 4 shown in FIG. 1 are disposed behind the rear stage converging lens 64.

  The beam cross-sections 67 of the laser beams emitted from the plurality of optical fibers 62 partially overlap each other at the position of the front focal plane 65 of the front-stage converging lens 63. The relationship between the front-stage converging lens 63 and the plurality of laser beams incident thereon is the same as that between the third converging lens 15 shown in FIG. 3 and the plurality of laser beams incident thereon.

  The beam divergence angle of each laser beam that has passed through the post-converging lens 64 is 10 mrad. The state of the beam cross section 67 at the position of the front focal plane 65 of the front stage converging lens 63 is transferred to the position of the rear side focal plane 66 of the rear stage converging lens 64 at a magnification of 10 times. Since the plurality of beam sections 67 partially overlap at the position of the front focal plane 65, the beam sections 68 also partially overlap at the position of the rear focal plane 66. For this reason, as in the first embodiment, a light intensity distribution substantially the same as the light intensity distribution in the beam cross section of one laser beam can be obtained.

  By using the beam superimposing optical apparatus according to the first to third embodiments, it is possible to perform processing using a high-power laser beam that is difficult to realize with one laser oscillator. In addition, when the power density on the surface of the workpiece 5 is made the same as when one laser oscillator is used, the incident area of the laser beam can be expanded. When processing using a long beam having a long beam cross section in one direction, the beam cross section can be made longer.

  In the first and second embodiments, ten laser oscillators are used, but more laser oscillators can be used.

  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.

1 is a schematic view of a beam superposing optical device according to a first embodiment. It is the schematic of a laser light source. It is a schematic diagram of a superposition optical system. It is a figure which shows the light intensity distribution in the various positions of a superposition | stacking optical system by shading. It is a figure which shows the light intensity distribution of the x-axis direction in the various positions of a superposition | stacking optical system. It is a figure which shows the light intensity distribution of the y-axis direction in the various positions of a superimposition optical system. It is the schematic of a uniformization optical system. It is the schematic of the superimposition optical system of the beam superimposition optical apparatus by a 2nd Example. It is the schematic of the beam superimposition optical apparatus by a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 2 Superimposition optical system 2A Spreading angle expansion optical system 2B Spreading angle reduction optical system 3 Uniformation optical system 4 Stage 5 Processing object 30, 31, 60 Laser oscillator 33 Polarization beam splitter 34 Folding mirror 10 First convergence Front focal plane 11 of lens First convergent lens 12 Second convergent lens 13 Rear focal plane 14 of second convergent lens Front focal plane 15 of third convergent lens Third convergent lens 16 Fourth convergent lens 17 Rear focal plane of the fourth convergent lens 20, 23, 24, 27 Beam cross section 24a, 27a Composite beam cross section 46 Cylinder array 47 Laser beam group 49 Condenser lens 50 Homogenizing surface 61 Condensing lens 62 Optical fiber 63 Pre-stage converging lens 64 Rear-stage convergent lens 65 Front-side focal plane of front-stage convergent lens 66 Rear-side focal plane of rear-stage convergent lens 7,68 beam section 69 virtual plane

Claims (11)

Multiple laser beams whose central rays are parallel to each other are incident and emitted by increasing the beam divergence angle of each of the incident laser beams, and the central rays of the emitted laser beams are kept parallel to each other and emitted. A divergence angle expanding optical system that partially overlaps the laser beams by narrowing the interval between the central rays of the beams to be smaller than the interval between the central rays of the incident laser beams;
In a state where a laser beam partially overlapped by the divergence angle expanding optical system is incident, emitted with a reduced beam divergence angle of each of the incident laser beams, and the emitted laser beams are partially overlapped A beam superposition optical device having a diverging angle reduction optical system that keeps these central rays parallel to each other. The divergence angle magnifying optical system is:
A first converging lens on which the laser beam is incident;
A second converging lens disposed behind the first converging lens, having a focal length shorter than that of the first converging lens, and having a rear focal point of the first converging lens as a front focal point; The beam superimposing optical apparatus according to claim 1, comprising: The divergence angle magnifying optical system is:
A first converging lens on which the laser beam is incident;
A second diverging lens disposed behind the first converging lens, having a focal length shorter than that of the first converging lens, and having a rear focal point at the rear focal point of the first converging lens; The beam superimposing optical apparatus according to claim 1. The divergence angle reduction optical system is:
A third converging lens on which the laser beam that has passed through the divergence angle expanding optical system is incident;
A fourth converging lens disposed on the rear side of the third converging lens, having a focal length longer than that of the third converging lens, and having the position of the rear focal point of the third converging lens as a front focal point; The beam superposition optical apparatus according to any one of claims 1 to 3. The divergence angle reduction optical system is:
A third converging lens on which the laser beam that has passed through the divergence angle expanding optical system is incident;
A fourth diverging lens disposed behind the third converging lens, having a focal length longer than that of the third converging lens, and having a back focal point located at the rear focal point of the third converging lens; The beam superposition optical apparatus according to any one of claims 1 to 3.   Furthermore, it is a cylindrical optical device that is disposed between the divergence angle expansion optical system and the divergence angle reduction optical system, has an inner surface as a reflection surface that reflects the laser beam, and has both ends opened. 6. A cylindrical optical device according to claim 1, further comprising: a cylindrical optical device that allows a laser beam that has passed through the system to enter from one opening, emits the incident laser beam from the other opening, and enters the diverging angle reducing optical system. A beam superposition optical device according to claim 1.   The beam superimposing optical apparatus according to claim 6, wherein an inner surface of the cylindrical optical device is a column surface parallel to a central ray of each incident laser beam.   Further, the laser beam that has passed through the diverging angle reduction optical system is incident, the incident laser beam is divided into a plurality of small beams in the beam cross section, and the divided small beams are superimposed on the homogenized surface. The beam superimposing optical apparatus according to claim 1, further comprising a homogenizing optical system that makes the light intensity distribution on the homogenizing surface closer to uniform. A plurality of optical fibers arranged such that the emission ends are arranged along a plane and the central rays of the laser beams emitted from the emission ends are parallel to each other;
A plurality of laser light sources that respectively make laser beams incident on the incident end of the optical fiber;
A pre-stage converging lens that is incident from a laser beam that is emitted from the emission end of the optical fiber and propagates with a certain beam divergence angle partially overlapping;
Beam superposition optics having a rear stage converging lens on which the laser beam that has passed through the front stage converging lens is incident, has a focal length longer than that of the front stage converging lens, and has the rear focal point of the front stage converging lens as the front focal point apparatus.   Further, the laser beam that has passed through the latter lens is incident, the incident laser beam is divided into a plurality of small beams with respect to the cross section of the beam, and the divided small beams are superimposed on the homogenized surface, thereby producing a homogenized surface. The beam superimposing optical apparatus according to claim 9, further comprising a homogenizing optical system that makes the light intensity distribution on the top approach uniform. Disposing a processing object at a position of the homogenized surface of the beam superimposing apparatus according to claim 8 or 10;
A laser processing method including performing a laser processing by causing a laser beam having a uniform light intensity distribution to enter the processing object.