JP2002283085A - Laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality laser beam in which the intensity distribution is uniform and a ripple or the like is not included at a working point. SOLUTION: An aspherical lens is provided at the outside of a resonator of a laser oscillator, the curvature element of the aspherical lens is a sum of a convergent curvature element which is uniform on the whole plane and a divergent curvature element which is proportional to the distribution of the beam intensity at the lens position, and a beam transmitting optical system, which is provided for guiding the laser beam transmitted from the aspherical lens to the machining point, copies the focal point position corresponding to the covergent spherical curvature element of the aspherical lens onto the machining point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser device,
In particular, the present invention relates to a laser device having a beam shaping function for making the intensity distribution of a laser beam uniform.

[0002]

BACKGROUND ART FIG. 6, for example Sato others, "CO ₂ laser processing technology", is a diagram showing a conventional laser device shown in Nikkan Kogyo Shimbun (1992). In the figure, reference numeral 11 denotes a laser oscillator, 12 denotes a laser beam emitted from the laser oscillator 11, and 16 denotes an integration mirror for performing beam shaping.

A conventional laser device is configured as described above, and a laser beam 12 emitted from a laser oscillator 11 is often in a Laguerre or Hermite Gaussian mode generated by a stable resonator. In the case of a large output, a ring-shaped beam using an unstable resonator may be used. In surface quenching and drilling, a flat beam having a flat intensity distribution is often required instead of such a beam shape.
For such an application, an integration mirror 16 is used as an optical system for forming a beam.
In addition to the integration mirror 16, a beam integrator such as a fly-eye lens or a kaleidoscope may be used. Integration mirror 16
Is once divided into a large number and superimposed at a predetermined position to form a beam having a uniform intensity distribution.

[0004]

In such a conventional laser apparatus as described above, the formed beam is macroscopically homogenized in order to superimpose the laser beam having high spatial coherency, but the microscopic beam is formed. In general, there is a problem that a ripple occurs due to an interference effect and causes a processing defect. Further, the beam quality after passing through the integrator is greatly deteriorated, the divergence angle is increased, a beam transmission system having a large aperture is required, and the depth of focus is small.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to generate a high-quality beam having a uniform intensity distribution, a small divergence angle, and free from ripples and the like. It is an object of the present invention to provide a laser device capable of increasing a degree of freedom.

[0006]

[Means for Solving the Problems]

In the laser device according to the first aspect of the present invention, a single aspheric lens having at least one aspheric surface is provided on the optical path of the laser beam, and the aspheric lens has a smooth curved surface. And the curvature is the sum of a convergent spherical curvature component and a local divergent curvature component that exist uniformly over the entire surface, and the local divergent curvature component is the laser on the aspheric lens. The beam position is proportional to the beam intensity distribution of the beam, and a beam transmission optical system provided to guide the laser beam from the aspheric lens to a processing point has a focal position corresponding to the convergent spherical curvature component of the aspheric lens. Is a beam transmission optical system for transferring the light beam to the processing point.

In the laser apparatus according to the second configuration of the present invention, the beam transmission optical system is a zoom optical system that expands and contracts a laser beam.

In a laser device having a third configuration according to the present invention, the laser beam is a laser beam generated by a laser resonator including one piece of partial reflecting mirror, and the laser beam forming the laser resonator. The outer surface of the reflecting mirror has an aspherical shape, and the partial reflecting mirror of the resonator and the aspherical lens are integrated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a diagram showing a configuration of a laser device according to a first embodiment of the present invention. In the drawing, 11 is a laser oscillator, 12 is a laser beam emitted from the laser oscillator 11, and 13 is an aspheric lens. Has a smooth curved surface whose curvature is a sum of a convergent spherical curvature component existing uniformly over the entire surface and a local divergent curvature component proportional to the beam intensity distribution at the installation position.

In the laser device configured as described above, the curvature of the aspherical lens 13 is locally proportional to the convergent spherical curvature component existing uniformly over the entire surface and the beam intensity distribution on the aspherical lens 13. The beam at each local point is expanded according to the divergent curvature component that is proportional to the beam intensity distribution. As a result, at the focal position corresponding to the convergent spherical curvature component, the beams originating from the local points are made to have the same power density. Here, since the aspheric lens 13 has a smooth curved surface, beams originating from local points are arranged so as to be in contact with each other without overlapping. As a result, a beam having a uniform intensity distribution at the focal position corresponding to the convergent spherical curvature component is obtained. This beam has no ripple due to beam superposition,
The divergence angle is also very small.

FIG. 2 illustrates the principle of making the laser beam intensity uniform by the aspheric lens 13. The convergence power of the uniform convergent spherical curvature component of the aspherical lens is P ₊ , and the power of the local divergent curvature component proportional to the beam intensity distribution is P
_- (r), the beam intensity distribution at the position of the aspherical lens is D
Assuming that ₁ (r), the beam intensity distribution at the focal position corresponding to the convergent spherical curvature component is D ₂ (r), and the distance from the focal position to the beam convergence position is f ′ (r), f ₊ = 1 / P
_{+, F (r) = 1} / (P + -P - (r)), f '(r) = M
As (r) · f (r), from the configuration of the aspherical lens, P ₋ (r) = KD ₁ (r) (K is a proportional constant) (1) From the geometric relationship of the beam intensity ratio, D ₂ (r) = D ₁ (r) / M (r) (2) where M (r) = f ′ (r) / f (r) = (f (r) − _{f +)) / f (r} ) = P - (r) / P + ...... ( from the relationship of _{3), D 2 (r)} = D 1 (r) / M (r) = (P - (r) _{/ K) / (P - (} r) / P +) = P + / K = const of r ...... (4) is true. That is, the local divergence power P _- if (r) is long in proportion to the beam intensity distribution D ₁ (r) of the aspherical lens position, the beam intensity distribution at the position of f ₊ aspherical lens D
₂ (r) becomes uniform. This relationship holds for an arbitrary K, and when the value of K is changed, a position (f
₊ ) The beam cross section diameter changes.

Embodiment 2 FIG. FIG. 3 is a diagram showing a configuration of a laser device according to a second embodiment of the present invention. In the figure, reference numeral 21 denotes a total reflection mirror that forms a laser resonator; Reference numeral 23 denotes an aperture for limiting a beam.

In the first embodiment, the aspherical lens for homogenizing is installed at a position distant from the laser resonator. However, as shown in FIG. It may be shaped. By integrating the partial transmission mirror of the resonator and the aspherical lens for uniformizing the beam, alignment of the aspherical lens and the laser beam axis becomes unnecessary, and stable beam shaping can be obtained. Further, the apparatus can be simplified by reducing the number of parts.

Reference Example 1 FIG. 4 is a diagram showing a configuration of a laser device that is a first embodiment related to the present invention. In the figure, 1 is a total reflection mirror constituting a laser resonator, 2 is a partial reflection mirror also constituting a laser resonator, and 3 is an aperture for controlling a beam.

In the laser device configured as described above, the total reflection mirror 1 and the partial reflection mirror 2 are concave spherical mirrors, and the curvature and the installation interval constitute a confocal negative branch unstable resonator and are enlarged. The rate is set to a value close to one.
In a confocal negative branch unstable type resonator, if the aperture 3 is set at a recursive conjugate point where light emitted from one point converges again to one point when the light goes around the resonator, the laser limited by the aperture 3 The beam recursively forms an enlarged image of the beam inside the aperture 3 at the position of the aperture 3 by orbiting the resonator. At this time, the expanding action is repeated, and the light existing at the center of the opening 3 spreads over the entire opening 3, so that a beam having a uniform intensity distribution at the position of the opening 3 is established. This beam is a single mode with a uniform phase, has no ripple due to superposition of beams, and has a diffraction-limited quality. By taking out this laser beam from the partial reflecting mirror 2 and transferring the image of the aperture 3 onto the work using an optical system such as a lens provided outside, a beam having a uniform intensity distribution can be used. Become. Also,
As is clear from the above, by choosing the shape of the opening,
For example, a beam having an arbitrary shape such as a square can be used.

Embodiment 3 FIG. 5 is a diagram showing a configuration of a laser device according to a third embodiment of the present invention. In the drawing, 11 is a laser oscillator, 12 is a laser beam emitted from the laser oscillator 11, and 17 is a zoom transfer optical system. A lens group 18 is a work to be irradiated with a laser beam.

In general, a laser beam having a uniform intensity distribution is realized only at one point on the optical axis, and its shape collapses with spatial propagation. For this reason, there is a limitation in setting the irradiation point to a free position. Here, using the imaging optical system, a point 15 having a uniform beam intensity distribution
8, the irradiation point can be set at a free position, and the size or irradiation power density of the irradiation beam can be adjusted by enlargement or reduction transfer, thereby increasing the degree of freedom of processing. Can be taken. Here, an example in which a uniform beam is obtained using an aspherical lens has been described, but the same applies to the case where a negative branch unstable resonator is used.

Embodiment 4 When configuring the laser device structure of the a CO ₂ laser, CO ₂ laser is relatively oscillation wavelength is long, without requiring high precision in the fabrication of the laser resonator, in particular using an aspherical lens to perform beam homogenization In the configuration, there is an advantage that the manufacturing accuracy of the aspherical lens is not required. For example, there is a manufacturing margin about 20 times that of a visible laser, and sufficient precision can be obtained by general machining without using optical polishing. Further, since the beam diameter in the resonator can be increased, in the configuration using the negative branch unstable type resonator, the density of the beam irradiating the opening in the resonator can be reduced.

[0021]

According to the laser apparatus of the first configuration of the present invention, one aspheric lens having at least one aspheric surface is provided on the optical path of the laser beam. While having a smooth curved surface, its curvature is the sum of a convergent spherical curvature component and a local divergent curvature component that are uniformly present over the entire surface, and the local divergent curvature component is a component on the aspherical lens. The beam transmission optical system provided so as to be proportional to the beam intensity distribution of the laser beam in the above, and to guide the laser beam from the aspheric lens to a processing point corresponds to the convergent spherical curvature component of the aspheric lens. Since the beam transmission optical system transfers the focal position to the processing point, the laser beam with a uniform intensity distribution at the processing point and free of ripples etc. It says the effect obtained is obtained.

According to the laser device of the second aspect of the present invention, since the beam transmission optical system is a zoom optical system for expanding and contracting the laser beam, the intensity distribution is uniform, the divergence angle is small, the ripple and the like are reduced. Is obtained, the position where the laser beam has a uniform intensity distribution can be freely set, and the size of the beam cross section can be freely changed.

According to the laser device of the third aspect of the present invention, the laser beam is a laser beam generated by a laser resonator including a single partial reflecting mirror, and the laser beam forming the laser resonator. Since the outer surface of the partial reflector is made aspherical and the above-mentioned partial reflector and the aspheric lens of the resonator are integrated, a laser beam having a uniform intensity distribution, a small divergence angle, and free from ripples, etc. can be obtained and alignment Is simplified and the number of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a laser device according to a first embodiment of the present invention;

FIG. 2 is a diagram for explaining the principle of making the laser beam intensity uniform by an aspherical lens.

FIG. 3 is a diagram illustrating a configuration of a laser device according to a second embodiment of the present invention;

FIG. 4 is a diagram illustrating a configuration of a laser device that is a first embodiment related to the present invention.

FIG. 5 is a diagram showing a configuration of a laser device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a conventional laser device.

[Explanation of symbols]

1,21 Total reflection mirror, 2,22 Partial reflection mirror, 3,23
Aperture, 11 laser oscillator, 12 laser beam, 1
3 aspherical lens, 16 integration mirror,
17 zoom lens, 18 work.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/10 H01S 3/10 Z

Claims (3)

[Claims] 1. An aspherical lens having at least one aspherical surface on an optical path of a laser beam. The aspherical lens has a smooth curved surface and the curvature is uniform over the entire surface. Is the sum of the convergent spherical curvature component and the local divergent curvature component present in the local divergent curvature component is proportional to the beam intensity distribution of the laser beam on the aspheric lens, A beam transmission optical system provided to guide a laser beam from the aspheric lens to a processing point is a beam transmission optical system that transfers a focal position corresponding to a convergent spherical curvature component of the aspheric lens to the processing point. A laser device, comprising: 2. The laser apparatus according to claim 1, wherein the beam transmission optical system is a zoom optical system that expands and contracts a laser beam. 3. The partial reflecting mirror constituting the laser resonator has an aspheric outer surface. The aspheric surface has a smooth curved surface, and its curvature is uniform over the entire surface. Component and a local divergent curvature component, wherein the local divergent curvature component is proportional to a beam intensity distribution of the laser beam on the partial reflector in the laser resonator. Laser device.