JPS5816205A - Optical waveguide for infrared ray - Google Patents

Abstract

PURPOSE:To transmit infrared rays efficiently by working the intermal surface of the hollowd part of each optical waveguide unit made of a cylindrical hollow body into a specular surface, and successively araying plural optical waveguide units in the axial line direction of the optical waveguide units and thus obtaining flexibility. CONSTITUTION:The hollow part 2 of each optical waveguide 1 for infrared rays has specular surface 3 as its internal surface. A number of optical waveguide units are arrayed successively in the direction of the axial line 4, and this array is covered entirely with a sheath 5 made of a flexible material to constitute an optical waveguide. Further, optical waveguide units 31 and 31 which have similar sectional optical transmission hollow parts at right angles to the optical waveguide unit axial line 4 are manufactured and then arrayed so that the sectional area of the hollow part increases gradually toward a waveguide light emission part B, thus improving the optical transmission efficiency of the whole of the optical waveguide

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared light guide path that is flexible and has little light transmission loss.

Silica-based optical fibers and plastic-based optical fibers, which have traditionally been used as flexible light guides, have excellent light transmission in the visible and near-infrared light ranges, but they absorb in the infrared light range. The oscillation wavelength of the C02 laser beam (10.6 μm)
It cannot be used in the infrared light range including .

However, in recent years, CO2 lasers have become increasingly useful as high-power continuous wave oscillation lasers in fields such as processing and medicine (laser scalpels), and it has become possible to efficiently transmit infrared rays such as CO2 laser light. The development of flexible light guides is desired.

As one method of transmitting infrared rays, a multi-joint method using mirrors has been proposed. According to this method (2), a large number of rigid metal pipes of appropriate length are connected by rotatable joints, and can be bent freely at the joints.
By arranging a mirror inside each joint, the light traveling straight through the pipe can be reflected in the bending direction of the pipe at the bent joint. However, this multi-joint method has problems such as difficulty in adjusting the optical axis, misalignment of the optical axis due to thermal expansion and vibration, and poor operability, and is not necessarily satisfactory.

SUMMARY OF THE INVENTION Therefore, the present invention has been made with the object of providing a light guide path that can efficiently transmit infrared rays, has excellent flexibility, and is easy to handle.

That is, in the present invention, the inner surface of the hollow part of a light guide unit made of a cylindrical hollow body is mirror-finished, a plurality of light guide units are continuously arranged in the axial direction of this light guide unit, and the entire light guide unit arrangement is made flexible. This is an infrared light guide path characterized by being covered with an outer cover.

(3) The present invention will be further described below with reference to embodiments shown in the drawings.

1 to 3 show a basic embodiment of the present invention, and FIG. 1 shows one light guide unit 1 made of a hollow cylindrical pipe. A mirror surface 3 is formed on the inner surface of the hollow portion 2 of this light guide unit. As the material of the light guide unit 1, metals such as copper, aluminum, silver, gold, iron, or alloys thereof can be used. The method of forming the mirror surface 3 on the inner surface of the hollow part of the light guide unit (I) is to polish the inner surface of a metal hollow cylindrical pipe to make it a mirror surface, or to polish the inner surface of the metal hollow cylindrical pipe and then to the polished surface. A method of forming a metal reflective surface by vapor deposition, plating, etc. can be adopted. When forming a metal reflective surface, the material of the hollow cylindrical pipe and the material of the reflective surface can be made of different metals.

FIG. 2 shows the light guide unit 1 shown in FIG. 1 along its axis 4.
The light guide of the present invention is shown assembled by arranging a large number of light guides in a continuous manner in the direction and continuously covering the entire array (4) with an outer sheath 5 made of a flexible material.

゛ As the flexible material for the outer cover 6, polymeric substances such as polyethylene, polypropylene, butadiene, isoprene rubber, silicone rubber, polytetrafluoride, metal cloth, etc. can be used. As shown in FIG. 2, each light guiding unit is rigid, but a large number of light guiding units 1, 1 are connected to each other inside the flexible outer cover 6 with their longitudinal end faces facing each other and in contact with each other. By arranging the light guides in such a structure, a series of flexible light guide paths that can be bent as a whole is formed.

FIG. 3 shows a cross section of the light guide units 1 arranged linearly in the series of light guide paths shown in FIG. 2. Light entering the light transmission hollow part 2 from the light incidence part A of the light guide is transmitted to the output part B while being repeatedly reflected by the mirror surface 3 on the inner surface of the hollow part, and is emitted from there to the outside of the light guide.

FIG. 4 shows a state in which the light guide shown in FIG. 3 is bent. Even in this state, the light incident from the entrance part A is repeatedly reflected by the mirror surface 3 and transmitted to the exit part B. be done. However, as long as the light guide unit 1 is a hollow cylindrical pipe as shown in FIG.
(Figure) is unavoidable, and there is also a possibility that the axes of adjacent light guide units may deviate, both of which cause light transmission loss in the light guide path.

Therefore, as shown in FIG. 5, the end face on the light incidence part side and the end face on the light output part side of the light guide unit 11 are made into a concave tapered surface 12 and a convex tapered surface 13, respectively, and such light guide units 11 are successively connected. By doing so, it is possible to minimize the gap between the opposing end surfaces of adjacent light guide units in the bent portion of the light guide path, and furthermore, it is possible to prevent the axes of adjacent light guide units from being misaligned.

In this case, the apex angle of the tapered surface 12.13 is
It is desirable to make the exit part side 1 angle more acute than the exit part side 1 angle than the exit part side 1 angle, and thereby, as shown in FIG. By sequentially fitting into the concave taper 12 on the incident side side, it is possible to arrange them so as to be rotatable and bendable.

The light transmission hollow part 2 of the light guiding unit shown in FIGS. Can be polygonal. For example, when the cross-sectional shape of the light transmission hollow part 22 is a flat rectangle like the light guide unit 21 shown in FIG. 7, linearly polarized light can be transmitted.

Furthermore, as shown in FIG. 8, a light guide unit (31, 31) having a similar shape of the light transmission hollow section in the cross section perpendicular to the light guide unit axis 4 is manufactured, and a light guide unit (31, 31) is manufactured near the light guide exit part B. By arranging the light guide units so that the cross-sectional area of the hollow portion becomes large, it is possible to improve the light transmission efficiency of the light guide as a whole.

In any of the embodiments described above, when performing optical transmission using a light guide path, the optical transmission hollow section is usually filled with N2.
An inert gas such as Ar is introduced from the light incidence part to cool the inner surface of the light transmission hollow part and prevent dust from adhering to it.

The results of an optical transmission experiment conducted using the light guide of the present invention will be described below. Outer diameter 5mm, inner diameter 3mm, length JOm
An aluminum hollow cylindrical pipe having a shape as shown in FIG. 1 was used as a light guiding unit. The inner surface of the hollow part was polished with carborundum and cerium oxide to give a mirror surface, and 100 light guiding units were inserted and arranged in a polyethylene tube having an inner diameter of 5 am to produce a series of light guiding paths as shown in FIG. A CO laser beam (wavelength 10.6 μm, continuous wave) is input into this light guide with an input power of 30 W.
The results of measuring the output output when the light guide path was straight and when the light guide path was curved by 900 degrees were as follows.

Straight line 23W 77%90
°Curved 20W 67%*Transmission efficiency: As can be seen from the experimental results described in section 2, even when curved at 9o0, the transmission efficiency decreases by only about 10% compared to when it is straight, making it suitable for flexible infrared rays. Data that should be sufficiently evaluated as a light guide path was obtained.

As explained above, the present invention has a simple configuration in which cylindrical hollow light guiding units whose hollow inner surfaces are mirror-finished are continuously arranged in a flexible jacket along the axial direction of the units.
A light guide having excellent flexibility and capable of efficiently transmitting infrared rays can be provided, and in particular C.
It is useful as a flexible light guide for an O2 laser.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of a light guide unit that constitutes the light guide path of the present invention; FIG. 2 is a perspective view showing a light guide path configured from the light guide unit of FIG. 1; Fig. 2 is a longitudinal sectional view; Fig. 4 is a sectional view showing the light guide path in Fig. 3 bent; Fig. 5 is a perspective view showing another embodiment of the light guide unit; Fig. 6 is a sectional view showing a bent state of the light guide path; A sectional view showing a light guide path constructed from the light guide unit shown in FIG. 5; FIG. 7 a perspective view showing yet another embodiment of the light guide unit; and FIG. 8 a further embodiment of the light guide path of the present invention. FIG. 1,, 11.21.3.1...Light guide unit, 2゜22
...Hollow part, 3...Mirror surface, 4...Light guide unit axis, 5...Flexible outer cover, 12...Concave taper one end surface,
13... Convex taper one end surface. .

Claims (1)

[Claims] 1. The inner surface of the hollow part of a light guide unit made of a cylindrical hollow body is made into a mirror surface, and a plurality of light guide units are continuously arranged in the axial direction of this light guide unit, and the entire light guide unit arrangement is An infrared light guide path characterized by being covered with a flexible outer covering. 2. The light guide path according to claim 1, wherein the shape of the hollow portion in a cross section perpendicular to the axis of the light guide unit is circular or polygonal. 3. The light-incidence side end face and the light-output side end face of the light guide unit are concave and convex tapered surfaces, respectively, and one convex taper end face of one light guide unit is sequentially connected to one concave taper end face of another light guide unit. The light guide path according to claim 1 or 2, wherein the light guide path is fitted and arranged so as to be rotatable and bendable. 4. The light guide path according to claim 3, wherein the apex angle of one end surface of the convex taper on the light output side is made more acute than the apex angle of the one end surface of the concave taper on the light distribution input side.