JPS62163947A - State monitor for optical fiber - Google Patents

Abstract

PURPOSE:To simplify the emission construction while assuring the monitoring of the state of an optical fiber, by providing a reflection angle distribution detecting element of a reflected light from the optical fiber at the position where a laser light is focused to be made incident into the optical fiber. CONSTITUTION:As a laser light is reflected at an emission end 9b of an infrared rays fiber 9 and emitted at an incident end 9a again at a slightly greater angle than an incident angle, a reflected light 11 from an infrared ray fiber 9 is made to irradiate a reflection angle distribution detection element 12 arranged outside the incident angle. When the infrared ray fiber 9 is normal, a reflected light distribution parameter shows a fixed value (area I). When the infrared ray fiber is deteriorated, the reflected light distribution parameter decreases significantly (area III) owing to a scattered light at this deteriorated part. Thus, the damaged condition of the infrared ray fiber can be recognized by always comparing the value of the reflected light distribution parameter and a value set as threshold.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is used in a laser processing device that guides a laser beam through an optical fiber to a processed part or a diseased part, and performs welding, cutting, incision, evaporation, etc. of the diseased part. This invention relates to an optical fiber condition monitoring device.

BACKGROUND OF THE INVENTION Laser processing apparatuses or laser scalpels using YAG laser light or C*2 laser light include a mirror joint type and an optical fiber type, which are currently being put into practical use, as light guide paths. The mirror joint method has problems with operability in processing or surgery, and cannot be applied to endoscopes, so it is desired to put optical fiber into practical use as a light guide path. For C*2 laser light, a mixed crystal of thallium iodide and thallium bromide, KR3-5, is listed.

KH2-5 has the disadvantage that it will break if bent beyond a certain curvature, so it must be used carefully with curvature limits.

If the fiber breaks or partially melts due to heat concentration despite the curvature limit, there is a risk that the high-power laser beam will penetrate the jacket and irradiate the patient or operator. there is a possibility.

In addition, the vapor generated when KH2-5 melts may have some effect on the human body, so it is important to prevent the fiber damage mentioned above and constantly monitor the deterioration state of the optical fiber. It was absolutely necessary to do so.

However, although various monitoring methods have been tried in the past, they have various drawbacks and none are perfect.

For example, Fig. 4 (see Japanese Patent Application Laid-open No. 58-103623)
As shown in FIG.
There is a means for monitoring the state of the optical fiber by detecting the light received by the photodetector 5.

Problems to be Solved by the Invention However, since a photodetector is provided on the output side, the configuration on the output side becomes complicated, and with recent miniaturization. It was not possible to use a high-tech handpiece.

Additionally, since there is a photodetector on the output side that becomes part of the electrical circuit, careful attention must be paid to insulation and grounding when designing the handpiece to prevent leakage current from flowing to the surface of the human body. I shouldn't have.

Means for Solving the Problems The present invention provides a laser beam generating means, an optical fiber for transmitting the laser beam generated by the laser beam generating means, and a condenser for condensing the laser beam and making it enter the optical fiber. a lens; a reflection angle distribution detection element disposed at a position surrounding the conical light beam condensed by the condensing lens to receive and detect the reflection angle distribution of the reflected light from the optical fiber; The present invention is an optical fiber condition monitoring device including a control unit that monitors the deterioration condition of the optical fiber from the output.

For production The effect of this technical means is as follows.

That is, by detecting the reflection angle distribution of the reflected light reflected from the optical fiber by a reflection angle distribution detection element provided on the input side and recognizing the state of the optical fiber, the configuration on the output side can be simplified. Monitoring of the condition of the optical fiber becomes reliable.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of an embodiment of an optical fiber condition monitoring device according to the present invention.

The Co2 laser beam 7 emitted from the C2 laser oscillation tube 6 is condensed by a condenser lens 8 made of zinc selenium, which is an infrared transparent material. If the laser beam is focused,
The light is guided through an infrared optical fiber 9 made of hot extrusion molded KH2-5, which is an infrared transmitting material, and is condensed by an output condenser lens 10 on the output side of the infrared optical fiber to incise and incise the affected area. Perform transpiration etc. In general, light that passes through a polycrystalline infrared optical fiber such as KH2-5 is spread out at a greater angle than the angle at which it enters the optical fiber due to scattering at crystal boundaries and the surface condition of the infrared optical fiber. It is emitted.

On the other hand, the laser beam reflected at the input end 9a of the infrared optical fiber 9 is reflected at substantially the same angle as the incident angle θ1 at the input end 9a due to Fresnel reflection.

However, the laser beam reflected at the output end 9b of the infrared optical fiber 9 and emitted again from the input end 9a is emitted with a slightly wider angle than the incident angle. Reflected light 1 from infrared optical fiber 9
1 is irradiated onto a reflection angle distribution detection element 12 arranged outside the incident angle. This output is calculated by the calculation circuit 13 to determine the reflection angle distribution.

FIG. 2 is a configuration diagram of a reflection angle distribution detection element according to the present invention.

Reflected light 1 from the infrared optical fiber 9 is placed on the front side of the donut-shaped substrate 14 made of alumina ceramic and having high thermal conductivity.
There is a light-receiving surface 16 that absorbs light from the sensor 1, and on the back side, three ring-shaped thermosensitive elements 16 are formed by sputtering and firing a thermistor material made of SiC. When the reflected light 11 having an energy distribution P(r) is irradiated onto the light receiving surface, a radial temperature distribution T(r) corresponding to the energy distribution P(r) is generated.

In general, if heat transfer to the air is ignored, the energy distribution P
(r) has the following relationship with temperature distribution T(r).

Here, d is the thickness of the substrate, and d is the thermal conductivity.

In other words, the radius (r, +T
The energy of the laser beam irradiated within i+1)/2 is determined, and the angular distribution P(of the reflected light irradiated onto the light-receiving surface 15) can be derived from this energy.

Next, the operation and principle will be explained using FIG.

The horizontal axis shows the elapsed time, and the vertical axis shows the output energy from the infrared optical fiber and the value P(300Σ-P(40')-) which parameterizes the distribution of the reflected light from the optical fiber.P(30
°).

When the infrared optical fiber is normal, the reflected light distribution parameter shows a constant value of 0.35 (region ■).

Furthermore, even if the incident energy to the infrared light 7-eyeper is increased, the reflected light distribution parameter does not change (region ■).

However, if the infrared optical fiber deteriorates and the output energy of the infrared optical fiber gradually decreases, the reflected light distribution parameter will greatly decrease due to scattered light from the deteriorated part (area ■). .

Furthermore, when the infrared optical fiber is burnt out, the reflected light distribution parameter will be approximately 0.
It decreases to a value of 06 (area ■).

From the above results, the damaged state of the infrared optical fiber can be recognized by constantly comparing the value of the reflected light distribution parameter with the value set as the threshold value, for example, 0.12, which is about half of 0.36. If damage is recognized, processing such as stopping the laser oscillation output can be carried out to ensure the safety of equipment using infrared optical fibers.

Note that although a thermistor was used as the thermal temperature sensing element of the reflection angle distribution detection element, equivalent detection is possible by using a thermocouple.

Furthermore, although boron nitride ceramic is used as the substrate material in the description, a substrate material in which an aluminum substrate is treated with an alumite insulating film may also be used.

Further, although a doughnut-shaped substrate material is used, equivalent detection is possible with a C-shaped substrate material.

Furthermore, even if the infrared optical fiber is coated with an antireflection film or the like, detection is easy.

As described in detail, according to the present invention, reflected light from an optical fiber is constantly received by a reflected light distribution detection element, and the damaged state of the optical fiber can be recognized from the detected reflection distribution. Furthermore, since nothing is placed on the handpiece section, there is no need to consider earthing and insulation, and it is possible to accommodate various types of handpieces.

Furthermore, this detection method has high damage detection sensitivity and can detect damage at an early stage, so it is possible to stop the laser beam incidence before the infrared optical fiber is burned out, allowing safe and reliable light transmission. This is a fiber condition monitoring method.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical fiber condition monitoring device according to an embodiment of the present invention, FIG. 2 is a block diagram of a reflection angle distribution detection element of the same device, and FIG. 3 is a block diagram of an optical fiber condition monitoring device of the present invention. FIG. 4 is a cross-sectional side view of a conventional optical fiber condition monitoring device. 6...CO2 laser oscillation tube, 7...C
○2 Laser beam, 8... Condensing lens, 9...
...Infrared optical fiber, 11...Reflected light, 12
...Reflection angle distribution detection element, 14...
Donut-shaped substrate, 15... River/light receiving surface, 16...
・Heat temperature sensing element group.

Claims (2)

[Claims] (1) A laser beam generating means, an optical fiber that transmits the laser beam generated by the laser beam generating means, a condensing lens that condenses the laser beam and makes it enter the optical fiber, and this condensing lens. A reflection angle distribution detection element is arranged at a position surrounding the condensed conical light beam and receives and detects the reflection angle distribution of the reflected light from the optical fiber, and the deterioration of the optical fiber is detected from the output of this reflection angle distribution detection element. An optical fiber condition monitoring device comprising a control unit that monitors the condition. (2) The reflection angle distribution detection element consists of a thermally conductive donut-shaped substrate, a light-receiving surface that is a light-absorbing surface provided on the surface of this substrate, and a concentric circle located inside the light-receiving surface on the front or back surface of the substrate. 2. The optical fiber condition monitoring device according to claim 1, further comprising a ring-shaped thermal sensing element having two or more N ring-shaped thermal sensing elements arranged in the optical fiber.