JPS61267019A - Light transmitting device - Google Patents

Abstract

PURPOSE:To reduce heat lens operation due to the temperature rise of a transmission part until it is ignored by providing >=1 light transmission body, a means which insulates thermally the outer peripheral part including the peripheral flank of the light transmission body, and a means which cools one transmission surface of the transmission body. CONSTITUTION:The light transmission body 20 is a plane circular transmission body composed of an output mirror, etc., constituting one resonator of a solid laser device or gas laser device and the outer peripheral part including the peripheral flank is held by an annular heat insulator 21 which has specific thickness. A nonmetallic material having small heat conductivity such as ethylene tetrafluororesin and ceramic is used suitably for the heat insulator. The light transmission body 20 is provided with a cooling means, which blows cooling gas 22 to one transmission surface of the light transmission body 20 at a high speed. The outer peripheral part of the light transmission body 20 is insulated thermally, so no heat flows in a radial direction (r) and the heat distribution 24 in the radial directions (r) is uniform and linear. Consequently, heat lens operation is removed from the light transmission body 20.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a light transmission device.

[Technical background of the invention and its problems]

FIG. 7 schematically shows a conventional high-output gas laser device and how the laser beam generated therein propagates. In the figure, (1) is a laser medium sealed at a predetermined pressure in a container (not shown); for example, in the case of a carbon dioxide laser, it is a mixed gas of helium, nitrogen, and carbon dioxide. A high reflection mirror (2) and an output mirror (3) arranged coaxially and facing each other with the laser medium (1) in between form a resonator, and a laser beam with sharp directionality is emitted from the laser medium in an excited state. It has the function of generating light. A portion of the generated laser light is transmitted through the output mirror (3) and taken out of the resonator. The substrate of the output mirror (3) is made of a material that is transparent to the laser beam, for example, a wavelength of 10.6.
For micrometer (μm) carbon dioxide laser light, zinc selenide (Zn8e), gallium arsenide (GaAs)
) is made of materials such as This is because these materials have the property of absorbing a small amount of laser light.

An output mirror (
A cooling device (4) such as cooling water, cooling gas, or a heat sink is in contact with the outer peripheral surface of the cooling device (4).

In the above configuration, the operation when the cooling medium (4) is not added will be explained. When the output of the laser beam is small and the temperature rise of the output mirror (3) is also small, the beam becomes a parallel beam (6) with small wavefront distortion, as shown in the figure. However, as the output increases, the output mirror (3) expands as shown by the broken line (5), and the above materials have the property of increasing their refractive index as the temperature rises, and these factors work together. It begins to exhibit convex lens action. The lens effect based on a change in refractive index is also called the thermal lens effect, and the lens effect is 4 orders of magnitude larger than the lens effect due to thermal expansion.Also, the aberration becomes large, so it is not suitable for outputting as described above. A beam that is difficult to focus (7)
) There was a problem called K. to solve this problem,
Although a cooling device (4) is added.

The heat distribution of the output mirror (3) having such a configuration is considered as follows. That is, as shown in FIG.
), a part of the transmitted laser light is absorbed inside the output mirror (3) and uniformly generates heat, and the increased heat is removed by the cooling medium (4). It will be done. At this time, as shown in FIG. 9, the temperature distribution α1 in the thickness (Z) direction becomes linear.

However, since heat is transmitted radially from the center of the output mirror (3) toward the periphery, the temperature distribution αυ in the radial (r) direction becomes like the curve (parabola) in FIG. 10. Therefore, even if the cooling medium (4) was added, the above problem remained unsolved. In addition, apart from the above configuration,
A similar technique has also been proposed in Publication No. 664, but even with this technique, although the transmission surface is forcibly cooled, the periphery of the output mirror is cooled, and the above-mentioned problem still remains.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light transmitting device in which the thermal lens effect due to temperature rise in the transmitting portion is reduced to a negligible extent.

[Summary of the invention]

In order to achieve the above object, at least four or more light transmitting bodies, a means for thermally insulating the outer circumference including the peripheral side of the light transmitting bodies, and cooling at least one transmitting surface of the light transmitting bodies are provided. The device is configured to include means.

[Embodiments of the invention]

are given the same reference numerals.

In FIG. 1, the frame is a planar, circular light-transmitting body made of, for example, a solid-state laser device or an output mirror 2-, which constitutes one of the resonators of a gas laser device.

The outer periphery including the peripheral side surface is held by an annular heat insulator (2) having a predetermined thickness. As the thermal insulator 3υ, a non-metallic material with low thermal conductivity such as tetrafluoroethylene resin or ceramics is suitable. The light transmitting body (21) is provided with a cooling means.This cooling stage is provided with a cooling gas t22 on one transmitting surface of the light transmitting body (a), for example, the transmitting surface on the light output side.
1 is configured to spray at high speed.

The operation of the above configuration will be explained. For example, if we consider the case where a laser beam (9) with a uniform intensity distribution is incident on and transmitted through the light transmitting body (to), when a part of the laser beam (9) passes through the light transmitting body (HK), Absorbed.

Here, since the cooling gas (2) cools only the light emitting surface opposite to the laser beam (9), the temperature distribution (c) in the thickness (Z) direction is as shown in Figure 2. The distribution becomes sloping. On the other hand, the diameter (r) is uniformly surface cooled.

In addition, since the outer periphery of the light transmitting body (a) is thermally insulated, the phenomenon of heat flow in the radial (r) direction does not occur. Distribution 04) shows a uniform linear distribution as shown in FIG.

Due to this, no thermal lens effect occurs in the light transmitting body.

The same effect as in the above embodiment is achieved! Figures 4 to 6 show other embodiments of the invention, and the one shown in Figure 4 includes an output mirror (C) and an output window (A) held by a thermal insulator ■υ. They are arranged close to each other coaxially and are configured to allow cooling gas to flow at high speed through a small gap @1 formed by facing each other. FIG. 5 shows a configuration in which one of the output mirrors in the configuration of FIG. 4 is replaced with a convex lens. Also, the 6th
The figure shows an example in which both lenses are replaced with a pair of lenses (c) and (to) and used as components of a compound lens, which has the advantage of reducing spherical aberration compared to a single lens.

Although each of the above embodiments describes one or two optical components, it is clear that the present invention is not limited to one type of optical component, and that three or more optical components of a single type or different types of optical components may be used in various combinations. It is. By the way, in a gas laser that operates with the laser medium at a pressure of several atmospheres or more, the output mirror or output window must withstand the force due to the differential pressure between the operating gas pressure and atmospheric pressure. Combining three or more optical members like this.

By changing the pressure of the cooling gas and reducing the differential pressure applied to each sheet, a higher output gas laser device can be realized.

〔Effect of the invention〕

in the radial direction of the optical component, i.e. on the beam cross section.

The temperature gradient is so small that it can be ignored.
Lens effect has been eliminated. This makes it possible to obtain a beam with high directivity, that is, a beam with high convergence.1 For example, in laser processing, the cutting width can be minute. In addition to being able to stably perform good cutting with less burrs,
It was possible to achieve practical effects such as making other welding processes such as 4-hole drilling much better.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, FIGS. 2 and 3 are heat distribution diagrams of the light transmitting body in the above embodiment, and FIG.
6 to 6 are sectional views showing other embodiments of the present invention, and FIG.
The figure is a schematic diagram for explaining the conventional example, FIG. 8 is a sectional view showing the transmission state of laser light in the conventional example, and FIGS. 9 and 10 are heat distribution diagrams of the output mirror in the conventional example.・(A)...Light transmitting body t2η...Thermal insulator (C)...Cooling gas agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Fig. 5E Fig. 6 Fig. 8 Fig. 9 Fig. 1O Fig.

Claims (1)

[Claims] It is characterized by comprising at least one or more light transmitting bodies, means for thermally insulating the outer peripheral portion including the circumferential side of the light transmitting bodies, and means for cooling at least one transmitting surface of the light transmitting bodies. Light transmission device.