JPS587104A - Optical transmission device - Google Patents

Abstract

PURPOSE:To eliminate various dangers due to the leakage of the laser light from a clad, by making it difficult that the laser light propagated in a core is transmitted through the clad in a bending part. CONSTITUTION:A core 4 is coated throughout its length with the first clad 5 except the incidence end part, and this incident end part of the core 4 is coated with the second clad 11 which has a refractive index lower than that of the core and higher than that of the first clad. Consequently, the critical angle of the part coated with the first clad 5 in the core 4 is larger than that of the part coated with the second clad 11, and a laser light L incident to the core has beams, which have a wide spread angle, eliminated in the incident end part in accordance with a critical angle determined by refractive indexes of the core and the second clad; and therefore, even if the part coated with the first clad 5 in the core 4 is bent and used, the danger of the transmission of the laser light through the first clad is almost eliminated by the margin of the critical angle generated in the first clad part by the difference between refractive indexes of both clads.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission device for fully transmitting laser light for medical purposes, processing, and the like.

Generally, in order to transmit laser light for the above purpose, an optical transmission device is provided with a cladding made of a material that is also transparent around a core made of a material that is transparent to the laser beam, and the periphery of this cladding is covered with a resin cover. It is formed as follows. In such an optical transmission device, the cladding is made of a material with a smaller Fi3 refractive index than the core, and the laser beam incident into the core is totally reflected at the boundary between the core and the cladding, so that the laser beam rises. b [1 It is made so that it does not pass through the cladding.

However, in optical transmission devices for medical and processing purposes, the above device is often fully bent in order to guide the laser beam to all target areas, so at the boundary of the bent portion, the laser beam propagating through the core is The angle of incidence becomes large and it may pass through the boundary surface. If the energy of the laser beam is high, the laser beam that has completely passed through the cladding may heat up the cladding and leak to the outside, causing a fire or medical treatment. When used for commercial purposes, there were problems such as the risk of causing burns to the human body.

This invention was made based on the following two circumstances, and its purpose is to allow the laser light propagating through the core to pass through the cladding at the bent portion, thereby causing various problems caused by leakage of the laser light from the cladding. An object of the present invention is to provide a laser beam transmission device that eliminates the danger of

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a laser oscillator. Laser light output from this laser oscillator 1 is focused by a first lens 2 and is made to enter a core 4 of an optical transmission device 3. The outer peripheral surface of this core 4 has almost the entire length, excluding the input end, of 8r! 1
The outer peripheral surface of the first clad 5 is covered with a resin cover 6.

A metal light shield 7 is attached to the entrance end of the core 4. That is, the light shielding body 2 is formed by coaxially forming a first cylindrical portion 8 fitted onto the resin cover 6 and a second surface portion 9 from which the incident end of the core 4 protrudes. The outer peripheral surface of the cylindrical portion 9 is formed with a rough scratched surface 10 and has a weight of 748 g2.
A cladding 11 is loosely provided on the outer peripheral surface of the core 4. The ascending core 4, the first cladding 5, and the second cladding 1 are made of a material transparent to laser light such as quartz glass or gaseous glass, and the refractive index kn+ of the core 4 and the first cladding 1 are 5, and the refractive index of the second cladding 11 is ns, then nl)ns
) nz.

Further, a holder 13 in which a second lens J2 is held is attached to the output end of the optical transmission device 3, and the laser beam Li emitted from the core 4 is connected to the second lens 12.
The beam is focused E7 and irradiated onto the object 14.

In the optical transmission device 43 configured in this way, the core 4
The laser light incident on the laser beam does not have a trench, and at this incident end, the refractive index n1 of the core 4 and the refractive index n of the second cladding 11 are
A light beam incident at an angle greater than or equal to the first critical angle 01 is transmitted through the second cladding 11, is scattered by the diffusely reflecting surface 10 of this outer peripheral surface, is absorbed by the light shielding body 7, and is absorbed by the light shielding body 7.
The laser light of the light beam within the critical plane θ1 will propagate to the core 4. The laser beam propagating through the core 4 has a refractive index nl of the core 4 and a refractive index nl of the first cladding 5.
Since the second critical angle θ2 determined by ns)>nz is larger than the first critical angle θl, the core 4
It is totally reflected at the interface of the first clan 1 and 5 and propagated.

By the way, the optical transmission device f3 emits a laser beam from its emission end face, ``/(I L k, an object 1 at an arbitrary distance ml.
4, it is often bent as shown in the drawing. Then, in this bent portion 3a, the core 4
The angle of incidence of the laser beam propagating on the interface between the core 4 and the cladding 5 of the IL is the second boundary angle θ of this part.
There is a possibility that it will exceed 2. However, the laser beam is transmitted from the second cladding 11 at a portion where the laser beam is formed at the first critical angle θl, which is smaller than the second critical angle θ2, at the incident end to the core 4. Therefore, even if the incident angle of the laser beam with respect to the boundary surface at the bent portion 3a becomes somewhat large, the critical angle is 02-θ in the curved section 3a.
Since there is a margin of 1, the laser light is transmitted to the first cladding 55.
- Rarely total penetration. Therefore, it is possible to eliminate the risk that the laser light will cause heat damage to the resin cover 6 and be emitted in the evening, irradiating unnecessary parts.

In the above embodiment, the terminal 3 is located at the input end of the laser beam from the laser oscillator. i! However, if it is also provided at the output end of the laser beam, the optical transmission device can be protected from the reflected light from the object.

As described above, this invention has the advantage that the entrance end of the core is completely removed.
The entire length of the upper cladding is covered by the first cladding, and the first cladding has a refractive index smaller than that of the entire core.
The second cladding has a higher refractive index than the second cladding. Therefore, the part of the core covered by the first cladding has a larger critical angle than the part covered by the second cladding, and the laser beam incident on the core crosses the core and the second cladding at its incident end. Since light beams with a large divergence angle are removed according to the critical angle determined by the refractive index of Due to the critical angle margin created in the second cladding part due to the difference in refractive index between the first cladding and the second cladding, there is almost no risk that the Rede light will completely pass through the first cladding.

[Brief explanation of the drawing]

The drawing is a configuration diagram showing an embodiment of the present invention. 4...Core, 5...First cladding, 7...f
i-light K, 11...second cladding, L...laser light. U-related sole agent Patent attorney Takeshi Nawae μ-7-: 壣く--17

Claims (2)

[Claims] (1) A core, a first cladding that covers almost the entire length of the core except for the entrance end; An optical transmission device characterized by comprising a large second cladding. (2) The optical transmission device according to claim 1, characterized in that the second cladding is surrounded by an optical material.