JP3644431B2 - Laser equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser device, and more particularly to a laser device having a beam shaping function for making the intensity distribution of a laser beam uniform.
[0002]
[Prior art]
FIG. 6 is a diagram showing a conventional laser apparatus shown in, for example, Sato et al., “CO ₂ Laser Processing Technology”, Nikkan Kogyo Shimbun (1992). In the figure, 11 is a laser oscillator, 12 is a laser beam emitted from the laser oscillator 11, and 16 is an integration mirror that performs beam shaping.
[0003]
The conventional laser apparatus is configured as described above, and the laser beam 12 emitted from the laser oscillator 11 is often a Laguerre or Hermitian Gaussian mode generated by a stable resonator. In the case of a high output, a ring-shaped beam using an unstable resonator may be used. In surface hardening and drilling, a flat beam having a flat intensity distribution is often required instead of such a beam shape. For such applications, the integration mirror 16 is used as an optical system for performing beam forming. In addition to the integration mirror 16, a beam integrator such as a fly-eye lens or a kaleidoscope may be used. The laser beam incident on the integration mirror 16 is once divided into a large number and superimposed at a predetermined position to be shaped into a beam having a uniform intensity distribution.
[0004]
[Problems to be solved by the invention]
In the conventional laser apparatus as described above, in order to superimpose laser beams with high spatial coherency, the shaped beam is macroscopically homogenized, but microscopically, ripples are generated due to interference effects. However, there is a problem of causing a processing defect. In addition, the beam quality after passing through the integrator is greatly deteriorated, the divergence angle is increased, a beam transmission system with a large aperture is required, and the focal depth is shallow.
[0005]
The present invention has been made to solve the above-described problems, and generates a high-quality beam having a uniform intensity distribution, a small divergence angle and no ripples, and a degree of freedom in using the beam. An object of the present invention is to provide a laser device capable of obtaining a large value.
[0006]
[Means for Solving the Problems]
[0007]
In the laser apparatus according to the first configuration of the present invention, at least one aspheric lens having an aspheric shape is provided on the optical path of the laser beam, and the aspheric lens has a smooth curved surface. The curvature is the sum of a converging spherical curvature component and a local divergent curvature component that exist uniformly over the entire surface, and the local divergent curvature component is the beam of the laser beam on the aspheric lens. The beam transmission optical system that is proportional to the intensity distribution and that guides the laser beam from the aspherical lens to the processing point has a focal position corresponding to the convergent spherical curvature component of the aspherical lens. This is a beam transmission optical system for transferring to a point.
[0008]
In the laser apparatus according to the second configuration of the present invention, the beam transmission optical system is a zoom optical system for expanding and reducing the laser beam.
[0009]
In the laser device according to the third configuration of the present invention, the laser beam is a laser beam generated from a laser resonator including one partial reflecting mirror, and the laser beam of the partial reflecting mirror constituting the laser resonator is used. The outer surface has an aspherical shape, and the partial reflecting mirror of the resonator and the aspherical lens are integrated.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[0011]
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a laser apparatus according to Embodiment 1 of the present invention. In the figure, 11 is a laser oscillator, 12 is a laser beam emitted from the laser oscillator 11, and 13 is an aspheric lens. And a smooth curved surface having a curvature that is a sum of a converging spherical curvature component that exists uniformly over the entire surface and a local divergent curvature component that is proportional to the beam intensity distribution at the installation position.
[0012]
In the laser device configured as described above, the curvature of the aspherical lens 13 is a local divergence proportional to the convergent spherical curvature component that exists uniformly over the entire surface and the beam intensity distribution on the aspherical lens 13. Since it is the sum of the sexual curvature components, the beam at each local point is expanded according to the divergent curvature component proportional to the beam intensity distribution. As a result, at the focal position corresponding to the converging spherical curvature component, the beams originating from the local points are aligned with the same power density. Here, since the aspherical lens 13 has a smooth curved surface, the beams originating from local points are arranged so as to contact 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, and has a very small divergence angle.
[0013]
FIG. 2 explains the principle of uniformizing the laser beam intensity by the aspherical lens 13. The convergence power of uniform convergence spherical curvature component of the aspherical lens P _+, the power of local diverging curvature component proportional to the beam intensity distribution P _- (r), the beam intensity distribution of the aspheric lens position If D 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), then f ₊ = 1 / P ₊ , f (r) = 1 / (P ₊ −P ₋ (r)), f ′ (r) = M (r) · f (r)
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)
Can be expressed as
M (r) = f ′ (r) / f (r) = (f (r) −f ₊ )) / f (r) = P ₋ (r) / P ₊ (3)
From the relationship
_{D 2 (r) = D 1} (r) / M (r) = (P - (r) / K) / (P - (r) / P +) = P + / K = const of r ...... (4 )
Is established. That is, the local divergence power P _- (r) is long in proportion to the beam intensity distribution D ₁ (r) of the aspherical lens position, the beam intensity distribution D ₂ at the position of the f ₊ aspherical lens (r) Becomes uniform. This relationship holds for an arbitrary K. When the value of K is changed, the beam cross-sectional diameter at the position (f ₊ ) where a uniform beam is obtained changes.
[0014]
Embodiment 2. FIG.
FIG. 3 is a diagram showing the configuration of the laser apparatus according to the second embodiment of the present invention. In FIG. 3, reference numeral 21 denotes a total reflection mirror that constitutes a laser resonator, 22 denotes a partial reflection mirror that also constitutes a laser resonator, Reference numeral 23 denotes an aperture for limiting the beam.
[0015]
In the first embodiment, the aspherical lens for homogenization is installed at a position away from the laser resonator. However, as shown in FIG. 3, the outer surface of the partial reflection mirror 22 may have an aspherical shape for beam homogenization. Good. By integrating the partially transmitting mirror of the resonator and the aspherical lens that performs beam equalization, 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.
[0016]
Reference Example 1
FIG. 4 is a diagram showing a configuration of a laser apparatus which is Reference Example 1 related to the present invention. In the figure, reference numeral 1 denotes a total reflection mirror constituting a laser resonator, 2 denotes a partial reflection mirror which also constitutes a laser resonator, and 3 denotes an aperture for controlling the beam.
[0017]
In the laser apparatus configured as described above, the total reflection mirror 1 and the partial reflection mirror 2 are concave spherical mirrors, and the curvature and installation interval constitute a confocal negative branch unstable resonator, and the enlargement ratio is 1. It is set to a value close to. In a confocal negative branch unstable resonator, if the aperture 3 is installed at a recursive conjugate point where the light emitted from one point converges to one point again after going around the resonator, the laser limited by the aperture 3 is used. The beam recursively forms an enlarged image of the beam inside the aperture 3 at the position of the aperture 3 by circling the resonator. At this time, the magnifying action is repeated, and the light at the center of the opening 3 spreads over the entire opening 3, thereby forming a beam having a uniform intensity distribution at the position of the opening 3. This beam is a single mode in which the phases are aligned, there is no ripple due to beam superposition, and the diffraction limited quality. It is possible to use a beam having a uniform intensity distribution by taking out this laser beam from the partial reflection mirror 2 and transferring the image of the aperture 3 onto the work using an optical system such as a lens provided outside. Become. Further, as apparent from the above, it is possible to use a beam having an arbitrary shape such as a quadrangle by selecting the shape of the opening.
[0018]
Embodiment 3 FIG.
FIG. 5 is a diagram showing a configuration of a laser apparatus according to Embodiment 3 of the present invention. In the figure, 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 workpiece to be irradiated with a laser beam.
[0019]
In general, a laser beam having a uniform intensity distribution is realized only at one point on the optical axis and loses its shape with spatial propagation. For this reason, there is a limitation in setting the irradiation point to a free position. Here, by using the imaging optical system to transfer the point 15 having a uniform beam intensity distribution onto the work 18, the irradiation point can be set at a free position, and irradiation is performed by enlargement or reduction transfer. The size of the beam and the irradiation power density can be adjusted, and the degree of freedom in processing can be increased. Here, an example in which an aspheric lens is used to obtain a uniform beam is shown, but the same applies to the case where a negative branch unstable resonator is used.
[0020]
Embodiment 4 FIG.
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, the manufacturing margin is about 20 times that of a visible laser, and sufficient accuracy can be obtained by general machining without relying on optical polishing. Further, since the beam diameter in the resonator can be increased, in the configuration using the negative branch unstable resonator, the density of the beam that irradiates the opening in the resonator can be reduced.
[0021]
【The invention's effect】
According to the laser device of the first configuration of the present invention, at least one aspheric lens having an aspheric shape is provided on the optical path of the laser beam, and the aspheric lens has a smooth curved surface. In addition, the curvature is the sum of the converging spherical curvature component and the local divergent curvature component that exist uniformly over the entire surface, and the local divergent curvature component is the sum of the laser beam on the aspheric lens. A beam transmission optical system provided so as to be proportional to the beam intensity distribution and to guide the laser beam from the aspheric lens to the processing point, the focal position corresponding to the convergent spherical curvature component of the aspheric lens is processed. Since the beam transmission optical system is transferred to a point, a laser beam having a uniform intensity distribution and no ripples at the processing point can be obtained with a small number of parts. Results can be obtained.
[0022]
According to the laser apparatus of the second configuration of the present invention, the beam transmission optical system is a zoom optical system that expands and contracts the laser beam, so that the intensity distribution is uniform, the divergence angle is small, and ripples are not included. In addition to obtaining a laser beam, the position at which the laser beam has a uniform intensity distribution can be freely set, and the effect that the size of the beam cross section can be freely changed can be obtained.
[0023]
According to the laser device of the third configuration of the present invention, the laser beam is a laser beam generated from a laser resonator including one partial reflecting mirror, and the partial reflecting mirror constituting the laser resonator. The aspherical outer surface of the resonator and the above-mentioned partial reflection mirror of the resonator and the aspherical lens are integrated, so that a laser beam with a uniform intensity distribution, a small divergence angle and no ripples can be obtained, and alignment is simplified. As a result, the number of parts can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a laser apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining the principle of uniformizing a laser beam intensity by an aspheric lens.
FIG. 3 is a diagram showing a configuration of a laser apparatus according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a laser apparatus that is a first reference example related to the present invention.
FIG. 5 is a diagram showing a configuration of a laser apparatus 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, 13 aspherical lens, 16 integration mirror, 17 zoom lens, 18 workpiece.

Claims (3)

A single aspherical lens having at least one aspherical shape is provided on the optical path of the laser beam, and this aspherical lens has a smooth curved surface and its curvature is uniform over the entire surface. A sum of a spherical curvature component and a local divergent curvature component, the local divergent curvature component being proportional to the beam intensity distribution of the laser beam on the aspheric lens, and from the aspheric lens The beam transmission optical system provided to guide the laser beam to the processing point is a beam transmission optical system that transfers the focal position corresponding to the convergent spherical curvature component of the aspheric lens to the processing point. Laser device to do. 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. The outer surface of the partially reflecting mirror constituting the laser resonator is aspherical. This aspherical shape has a smooth curved surface, and its curvature is uniform with the convergent spherical curvature component that exists uniformly over the entire surface. A laser apparatus, wherein the local divergent curvature component is proportional to the beam intensity distribution of the laser beam on the partial reflector in the laser resonator.

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