JPH0651237A - Laser beam transmission device - Google Patents

Abstract

PURPOSE:To greatly enhance the machining performance of a laser beam transmission device, as in cutting, etc. CONSTITUTION:An input coupling portion 7 is provided with a first lens 10 for converging a laser beam from a carbon dioxide laser oscillator 5, a second lens 11 for converting the converged beam into parallel rays, a third lens 12 for converging the paralell rays and causing them to impinge on a hollow wave- guide line 6, with an aperture 13 mounted between the first and second lenses 10, 11, and an output converging portion 9 is provided with a fourth lens 14 for converging the beam output from the wave-guide line into parallel rays, a fifth lens 15 for converging the parallel rays, a sixth lens 16 for reconverting the converged beam into parallel rays, and a seventh lens 17 for converging the parallel rays, with an aperture 18 mounted between the fifth and sixth lenses 15, 16. The beam from which higher mode components are removed can thus be used for machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser light transmission device.

[0002]

2. Description of the Related Art Laser light is expected to be used in various industrial fields because it has good directivity and light converging property and high power density. In particular, carbon dioxide laser light is highly efficient and highly effective. Since the output can be obtained, it is already used in the fields of processing and medical care in the industrial field.

Conventionally, as a laser light transmission device for guiding a carbon dioxide laser beam to an object to be irradiated, there is one that sets a path of the laser light from the laser oscillator to the object to be irradiated by a combination of optical parts such as a mirror and a lens. Are known. However, in this type of device, it is necessary to precisely adjust the positional relationship between the optical components used in order to prevent inconveniences such as displacement of the optical axes between the optical components. There has been a problem that the optical axis control mechanism for correcting the deviation is complicated, or it is difficult to make the emitting end of the laser light movable so that the degree of freedom of processing by the laser light is hindered.

Therefore, in order to simplify the above-mentioned optical axis control mechanism and increase the degree of freedom of processing by laser light, a flexible laser light transmission path such as an optical fiber or a hollow waveguide is used to emit light from a laser oscillator. A laser light transmission device that guides a laser light to an object to be irradiated has been studied. Among these laser light transmission lines, the metal hollow waveguide with a built-in dielectric can transmit carbon dioxide laser light with low loss, and because it has a hollow structure, there is no end face reflection at the incident end and easy cooling. Therefore, it is suitable as a transmission line for high power transmission. Currently, as such a dielectric-containing metal hollow waveguide, a hollow waveguide containing a germanium and silver thin film is commercialized.

FIG. 2 shows the structure of a germanium-containing silver hollow waveguide. As shown in the figure, a germanium layer 2 and a silver layer 3 are provided on the inner surface of a pipe-shaped nickel layer 1, and a hollow region 4 for transmitting carbon dioxide laser light is defined by the germanium layer 2. . Up to now, this germanium-containing silver hollow waveguide has realized transmission of 3 kW carbon dioxide laser light with a length of 2 m. By using such a dielectric-containing metal hollow waveguide, it is possible to configure a laser light transmission device that can flexibly transmit laser light.

[0006]

The dielectric hollow metal waveguide of the prior art described above is a multimode transmission line in which the diameter of the hollow portion which is the propagation region of laser light is large and the number of propagation modes is large. . Therefore, when the laser light incident on the waveguide contains many higher-order mode components, the waveguide exit beam becomes a multimode including many higher-order modes.

Further, if the inner surface of the waveguide is rough or the waveguide is bent, a higher-order mode is generated. The higher-order mode has a large divergence angle when radiated from the exit end of the waveguide, and therefore the condensing diameter when converging with a lens becomes large, and the higher-order mode makes the intensity distribution of the waveguide exit beam asymmetric. It is easy to use and adversely affects the use of the waveguide for processing. For example, when the waveguide is applied to the cutting process, (1) the cutting width becomes large. (2) Dross is likely to occur. (3) The cut surface becomes rough. Such disadvantages occur. As described above, the fact that the hollow waveguide is a multimode transmission path hinders its practical application in the processing field.

That is, when a hollow waveguide is used as the laser light transmission path, the number of modes to propagate is large because the inner diameter of the waveguide is sufficiently larger than the wavelength of the laser light. Therefore, the laser light emitted from the waveguide becomes a multimode including a higher-order mode component. In general, multi-mode light including higher-order modes tends to have an asymmetric beam intensity distribution, and has a large beam diameter when condensed. When cutting is performed with such multi-mode light, the cutting width becomes large and dross easily occurs. Also, the roughness of the cut surface becomes large.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a laser light transmission device capable of greatly improving processing performance such as cutting.

[0010]

The above object is to provide a first lens for focusing a laser beam from a laser oscillator at an input coupling section,
Three lenses are provided: a second lens that makes the focused light parallel and a third lens that focuses the parallel light and makes it enter the optical waveguide.
Further, an aperture is attached between the first lens and the second lens to form an output condensing unit, a fourth lens for collimating the waveguide output beam into parallel light, a fifth lens for converging parallel light, and converging light. A sixth lens for returning to parallel light and a seventh lens for focusing parallel light, that is, four lenses, are provided, and the fifth lens and the sixth lens are provided.
It is achieved by mounting an aperture between the lens and the lens.

[0011]

Since the above-mentioned means is provided, processing can be performed with a beam from which higher order mode components have been removed.

[0012]

EXAMPLES Next, the present invention will be specifically described by way of examples.

[Embodiment 1] FIG. 1 shows an embodiment of the present invention. Since the same parts as those of the prior art are designated by the same reference numerals, the description thereof will be omitted. An input coupling section 7 for coupling laser light to a hollow waveguide 6 for guiding the laser light emitted from a carbon dioxide gas laser oscillator 5 to an irradiation section, and a laser light emitted from the hollow waveguide 6 are focused on a workpiece 8. In this embodiment, in the laser light transmission device including the output condensing unit 9 for irradiating, the input coupling unit 7 in the present embodiment is the first lens 10 for converging the laser light from the laser oscillator 5, and the second lens 11 for collimating the converging light. And three lenses 10, 11, 12 of a third lens 12 for focusing parallel light and making it enter the hollow waveguide 6,
In addition, the aperture 13 was attached between the first lens 10 and the second lens 11 to form it. Then, the output condensing unit 9 has a fourth lens 14 for converting the waveguide outgoing beam into parallel light, a fifth lens 15 for focusing the parallel light, and a sixth lens for returning the focused light into the parallel light.
4 of the lens 16 and the seventh lens 17 for focusing the parallel light
The lenses 14, 15, 16 and 17 are provided and the aperture 18 is mounted between the fifth lens 15 and the sixth lens 16. By doing so, it becomes possible to process with a beam from which higher-order mode components have been removed, the cutting width can be reduced during cutting, and cutting with a small cut surface roughness can be performed, and processing performance such as cutting can be improved. It is possible to obtain a laser light transmission device capable of being greatly improved.

That is, FIG. 1A shows the input coupling section 7 of the laser light transmission device. The laser beam emitted from the carbon dioxide gas laser oscillator 5 generally contains higher-order mode components, and does not have a perfect Gaussian intensity distribution. This laser beam is condensed by the first lens 10, and the aperture 13 is installed at the condensing position. Since the higher-order mode component of the laser beam is removed by this aperture 13, the intensity distribution 19a of the oscillator output light including the higher-order mode is converted into a Gaussian intensity distribution 19b.
Since this Gaussian beam spreads greatly after passing through the aperture 13, the second lens 11 is placed at an appropriate position to collimate the laser beam. The collimated laser beam is condensed by the third lens 12 and coupled to the hollow waveguide 6. As described above, the number of modes excited in the waveguide 6 can be reduced by coupling the laser beam excluding the higher-order mode components to the waveguide 6.

However, it is conceivable that the laser light propagating through the waveguide 6 will have higher-order modes due to the surface roughness of the inner wall of the waveguide, the bending of the waveguide 6, and the like. When the inner surface of the waveguide is rough or when the waveguide 6 is severely bent, a higher-order mode is generated during propagation in the waveguide, so it is necessary to reduce the higher-order mode at the exit end of the waveguide. Becomes

FIG. 1B shows the output condensing unit 9 of the laser light transmission device. Since the laser beam emitted from the waveguide 6 has a large divergence angle, it is collimated by the fourth lens 14. The laser beam that has become parallel light is condensed by the fifth lens 15, and the aperture 18 is installed at the condensing position. Since the higher-order mode component of the laser beam is removed by this aperture 18, the intensity distribution 19c of the waveguide output light including the higher-order mode is the Gaussian intensity distribution 1
Converted to 9d. Since this Gaussian beam spreads greatly after passing through the aperture 18, the sixth lens 16 is placed at an appropriate position to collimate the laser beam. The laser beam that has become parallel light is condensed by the seventh lens 17 and applied to the workpiece 8. When the cutting process is performed by removing the higher-order mode component in the laser beam in this manner, the cutting width can be reduced and the cutting surface roughness can be reduced. Also, dross is less likely to occur.

As described above, according to the present embodiment, the laser light transmission device with greatly improved processing performance is obtained by removing the higher-order mode component of the waveguide exit beam and processing it as a Gaussian beam. be able to. For example, in the cutting process, it is possible to reduce the cutting width, improve the cut surface roughness, and suppress dross generation.

In the present invention, it is more effective to implement both the input coupling section and the output condensing section at the same time, but it is effective to implement only one of them. Further, in the present embodiment, the cutting process is described, but the performance improvement can be expected in other applications such as welding.

[0019]

As described above, according to the present invention, the input coupling portion has the first lens for focusing the laser light from the laser oscillator, the second lens for collimating the focused light, and the parallel light for being incident on the optical waveguide. A fourth lens formed by providing three lenses of a third lens and mounting an aperture between the first lens and the second lens, and making the output condensing unit to make the waveguide output beam parallel light; A fifth lens for focusing the parallel light, a sixth lens for returning the focused light to the parallel light and a seventh lens for focusing the parallel light are provided, and an aperture is provided between the fifth lens and the sixth lens. Since it is mounted and formed, it becomes possible to process with a beam from which higher-order mode components have been removed, making it possible to reduce the cutting width when cutting and also to cut with a small cut surface roughness. To significantly improve It can be obtained capable and the laser light transmission device.

[Brief description of drawings]

1A and 1B show an embodiment of a laser light transmission device of the present invention, FIG. 1A is an explanatory diagram of an input coupling portion, and FIG.

FIG. 2 is a perspective view of a hollow waveguide of a conventional laser light transmission device.

[Explanation of symbols]

 5 Carbon dioxide laser oscillator 6 Hollow waveguide 7 Input coupling part 8 Workpiece 9 Output condensing part 10 First lens 11 Second lens 12 Third lens 13 Aperture 14 Fourth lens 15 Fifth lens 16 Sixth lens 17 Seventh Lens 18 aperture

Claims (2)

[Claims] 1. An input coupling section for coupling laser light to an optical waveguide that guides laser light emitted from a laser oscillator to an irradiation section, and a laser beam emitted from the optical waveguide is focused and applied to a workpiece. In a laser light transmission device including an output condensing unit, the input coupling unit focuses the laser light from the laser oscillator, a first lens, a second lens for collimating the focused light, and a parallel light for focusing the parallel light. A laser light transmission device comprising three lenses of a third lens that enter a waveguide, and an aperture is mounted between the first lens and the second lens. 2. The output condensing unit has a fourth lens for collimating the waveguide output beam into parallel light, and a fifth lens for converging parallel light.
There are provided four lenses, a sixth lens for returning the focused light to parallel light and a seventh lens for focusing the parallel light, and the fifth lens.
The laser light transmission device according to claim 1, wherein an aperture is mounted between the lens and the sixth lens.