JPS61212736A - Reflection type temperature sensor - Google Patents

Abstract

PURPOSE:To enable temperature measurement with a high sensitivity and a high accuracy, by inserting the tip of an optical fiber into a through hole of a holder with a reflector arranged at a hollow part thereof while a position compensating member is provided on the back side of the reflector. CONSTITUTION:An optical fiber 11 and a reflector 12 are fixed through a holder 13 and light incident through the optical fiber 11 reaches the reflector 12 without being reflected uselessly. Hence, this reflection type temperature sensor can obtained an intense reflected light from the reflector 12 and receive no noise from any unnecessary boundary, proving high sensitivity. Moreover, the difference in the expansion between the optical fiber 11 and the holder 13 as caused by changes in the atmospheric temperature is eased by a position compensating member 16. Thus, the reflector 13 arranged in a hollow part 15 of the holder 13 is held at the proper position from the tip face of the optical fiber 11 thereby enabling temperature measurement with a high sensitivity and a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a reflective temperature sensor that is provided at the tip of a reflective plate or fiber whose reflection spectrum changes depending on the temperature.

"Prior Art" FIG. 3 shows a conventional reflective temperature sensor, in which reference numeral 1 is a reflective fiber and reference numeral 2 is a reflective plate. Reflector 2
The reflection spectrum changes depending on the temperature, and for example, the reflector plate 2 made of GaAs has a layer made of GaAs.As the temperature rises, the fundamental absorption edge wavelength (λ /2) shifts to the longer wavelength side and the reflection spectrum changes, so the temperature can be determined from this. The optical fiber 1 is an organic coated optical fiber coated with a synthetic resin coating, and is used to guide the nine to the reflector plate 2 and to derive the obtained reflection coefficient.

In the conventional reflective optical fiber, the reflective plate 2 is attached to the tip of the optical fiber 1 with an adhesive 3 such as glass resin.
In addition, this part was protected by a cover 4.

"Problem" In a reflective temperature sensor having such a structure, there is a distance K between the tip surface of the optical fiber 1 and the reflecting plate 2 during manufacturing.

The adhesive 3 used to fix them has permeated, and this permeated adhesive 3 forms an unnecessary boundary between the nine fibers 1 and the reflector 2 that reflects the original. This boundary reflects much of the light that is irradiated onto the reflector 2 via the light 7 eyeper 1 during measurement. For this reason, in the conventional reflective temperature sensor, the reflected light that reaches the reflector plate 2 is small (), the reflected light obtained is weak, and the reflected light from the above boundary becomes noise. Therefore, there were complaints that the sensitivity of the sensor was arbitrary (and it was not possible to perform highly accurate measurements).

In addition, in this type of reflective temperature sensor, the reflective plate 2
It is necessary to attach the fiber 1 perpendicularly to the reflective plate 2, but since this is done using adhesive 3 in conventional reflective temperature sensors, it is difficult to install the reflective plate 2 and the fiber 1 perpendicularly. There were complaints that it required a lot of technology and had a poor production yield.

"Means for Solving the Problems" Next, means for solving the above problems will be described with reference to the embodiment shown in Figure 1.

Reflection temperature sensor of the present invention (hereinafter abbreviated as sensor)
consists of a base 7-eyeper 11, a reflector 12, and a holder 13 that holds these.The holder 13 has a through hole 14 into which the tip 11a of the 9-fiber 11 is fitted along its length. , a through hole 1 is provided in front of this through hole 14.
A hollow part 15 is formed along the axial direction of the holder 13, and the reflecting plate 12 is arranged so that the surface thereof faces toward the optical fiber II. A position compensation member 16 is provided on the back side.

"Example" Hereinafter, the senna of the present invention will be described in detail in accordance with the example.
FIG. 1 shows an embodiment of the sensor of the present invention.

The optical fiber 11 used in the Senna of this example is a metal-coated optical fiber coated with a metal such as aluminum or nickel. The tip 11a of this optical fiber 11
The coating on the leading edge of the optical fiber llb is removed to expose a bare optical fiber llb made of quartz or the like.

The reflection plate 12 has a reflection spectrum that changes depending on the temperature, and materials with such properties include GaAa,
CdTe, etc., and this reflective plate 12 is made of Aj? A three-layer structure of N-GaAs-E1102 is preferably used. This AlN-GaAs-8i
The reflector plate 12 consisting of AIN/l power 1000AX
It is formed by forming a GaAs layer with a thickness of about 200μm%Sin and a layer of about 200OA.It is created by optically polishing both sides of a GaAs plate and then forming an AlN layer, an 810 layer, and a layer by sputtering. be done.

The holder 13 is provided with a through hole 14 and a hollow portion 15, and in this example, is composed of two members: a seven-hole 17 and an outer cylinder 18. In order to increase the sensitivity of the senna, it is desirable that the holder be made of a material with high thermal conductivity, and is usually made of a metal material such as copper or iron.

e) The 7/L/17 of the v tick 3 is cylindrical and has a through hole 14 and a hollow portion 15 along its central axis. The through hole 14 is located at the tip end 11 of the optical fiber 11.
a is fitted along its length, and consists of a holding part 14a and a guide part 14b. Hold part 1
4a is formed approximately at the center of Fell/L/17. This holding portion 14a is formed to have a diameter that allows the bare wire llb of the optical fiber 11 to fit loosely.The portion from this holding portion 14a to one end of 7/1/17 is connected to the guide portion 14. This guide part 14
b is formed to have a slightly larger diameter than the outer diameter of the outer fiber 11, and loosely holds the tip 11a of the outer fiber 11.

In front of this through hole 14 (on the right side in the figure), the hollow part 1
5 is formed along the axial direction of the through hole 14.

This hollow portion 15 is a portion in which the reflecting plate 12 is placed with its surface facing toward the tip of the optical fiber 11 fitted into the through hole 14 . The cross section of this hollow part 15 is set so that the reflection plate 12 is arranged without loosening and can maintain a predetermined angle with respect to the optical fiber 11.
It is formed in a substantially W shape with the ff1 plane. Further, the length of this hollow portion 15 is formed to be larger than the thickness dimension of the reflecting plate 12.

The outer cylinder 18 has a cylindrical shape, and the seven errules 17 are fitted together along the central axis direction without loosening. These wires 7t, -, a, 17 and the outer cylinder 18 are integrally fixed with high temperature solder 19 or the like. Also, due to this high temperature No. 19.

The original 7-eyeper 11 is also fixed to the open end of the through hole 14. The hollow part 15 of the above-mentioned 7D #, zl 7 is the outer cylinder "l
It is closed by the bottom part 18a.

A position compensating member 16 is provided in the hollow portion 15 of the holder 13 so as to be located on the good side of the reflecting plate 120.

When the holder 13 expands due to a temperature change, the position compensating member 16 compensates for the distal end surface of the optical fiber 11 and the reflecting plate 1.
This prevents the gap between the two parts from expanding. The position compensation member 16 may be an expansible member exhibiting an amount of thermal expansion approximately equal to the amount of thermal expansion of the holder 13, or a biasing member of a coil spring shade that biases the reflector 12 toward the optical 7 eyeper 11. It consists of things like In the senna of this example, a cylindrical expandable member made of a material having a larger coefficient of thermal expansion (β) than the material of the holder 16 is used as the position compensating member 16.

"Function" In the reflection type temperature sensor having such a configuration, the optical fiber 11 and the reflection plate 12 are fixed via the holder 13, and an adhesive is applied between the optical fiber 11 and the reflection plate 12. ,
Since there is no substance forming an unnecessary boundary that reflects light, the light incident through the optical fiber 11 reaches the reflecting plate 12 without being unnecessarily reflected. Therefore, in the reflective temperature sensor of the present invention, strong reflected light can be obtained from the reflecting plate 12.

There is no unnecessary noise from the border, making it a highly sensitive book.

Further, in the senna of the present invention, the optical fiber 11 is connected to the hollow portion 15 of the holder 13 through the through hole 14 of the holder 13.
Since the reflecting plate 12 is held by the holder 13, the optical fiber 11 and the reflecting plate 12 are always fixed at a predetermined angle by the holder 13.

Therefore, the assembly of the present invention is easy to manufacture without requiring a skilled technique to fix the optical fiber 11 and the reflecting plate 12 at a predetermined angle.

Furthermore, in the sensor of the present invention, the bare optical fiber i
Even if the holder 15 is made of a material with a larger coefficient of thermal expansion than the quartz (coefficient of thermal expansion β = 5.5 x 10K) that forms the ib, the expansion of the optical fiber 11 and holder 16 that occurs due to changes in ambient temperature. The difference in amount is alleviated by the position compensating member 16. Therefore, the reflector 12 disposed in the hollow part 15 of the holder 13
It is maintained at an appropriate position from the tip surface of 1 under any temperature.

That is, when the holder 13 is made of iron or copper, copper β=
0. l75xlOK ) is a bare optical fiber &! 11
Since the coefficient of thermal expansion is larger than that of quartz (β=5.5×10K), the holder 13 expands significantly compared to the Hikari 7 Eyepa 11 when the ambient temperature rises. And reflector 1
However, in this example, the senna is made of a material with a larger coefficient of thermal expansion than the holder 13 (for example, aluminum β = 0).
．． A position compensating member 16 consisting of 257 Since this is offset by the expansion, the expansion of the gap between the reflecting plate 12 and the optical fiber 110 is reduced, and the above-mentioned disadvantage is eliminated.

Note that the senna of the present invention is not limited to the above embodiment.
was closed by the bottom 18& of the outer cylinder 18, and the position compensation member 16 was disposed therein.
If the structure is such that the ends are screwed together, there is no need to provide the outer cylinder 18. In this case as well, the same effects as in the above embodiment are expected.

"Prototype Example" Create the senna shown in No. 119 with the following specifications,
I was able to test its performance. (In addition, each numerical value is a value at room temperature.5) (1) Optical 7fi/<11...Gold stripe coated quartz glass single mode fiber, (thermal expansion coefficient β = 5.5X10K) Core diameter 100μ7 Cladding diameter: 125/+m Outer diameter: 175μm Length a from the metal to be coated, nickel fiber fixing point A to the tip of the optical fiber = 1.3 l1l (2) Reflector plate 12-AJN-GaAs-Sin,
Shape thickness: 2oo μm (3) Holder 13--Made of copper (β=Q, 175xl
OK) Length b from the fiber fixing point A to the tip of the through hole 14 = 1.2 Depth Q from the fiber fixing point A to the bottom 18 = 4.5fl (4) Position compensation member... Made of aluminum (β ;0.2
The gap between the reflective plate 12 of the sensor and the tip of the optical fiber 11 with a length cl = 3 NM was 0.1 mm at room temperature.

When this sensor is placed in an atmosphere of 300°C, each dimension is 'a = = 1.3002 mm, C = 4,523 mm, and d = 3.023 m, so the reflector 12 / optical fiber The change in the 110 gap was almost eliminated, and it was expected that this senna would exhibit good sensitivity even at high temperatures.

Next, the sensor whose performance was tested was set in a thermostat, and a light pulse (λ=Q, 87 μm) was applied from the input end of the optical fiber 110. By measuring the intensity of the resulting reflected pulse while gradually increasing the temperature of the thermostat, it was confirmed that there was almost logarithmic linearity between temperature and pulse intensity in the range of 0 to 600°C. .

As a result of this test, it was confirmed that this senna can measure a wide temperature range with high accuracy.

"Effects of the Invention" As explained above, in the reflective temperature sensor of the present invention, the tip of the optical fiber is fitted into the through hole of the holder, the reflective plate is arranged in the hollow part, and the back surface of the reflective plate is Since the optical fiber is provided with a position compensation member, the light sent through the optical fiber directly reaches the reflective plate without any adhesive or the like intervening between the optical fiber and the reflective plate. Therefore, with these four sensors, it is possible to obtain strong reflected light by irradiating the reflector with sufficient light, and noise that interferes with measurement is also reduced. Therefore, the sensor of the present invention:
It has high sensitivity and can measure temperature with high accuracy.

Further, in the sensor of the present invention, since the angle between the optical fiber and the reflector is set by the holder, the optical fiber and the reflector can be accurately fixed without using a skilled technique. Therefore, the senna of the present invention is easy to manufacture and can be produced with high quality and high yield.

Furthermore, in the sensor of the present invention, even if the temperature changes, the gap between the optical fiber and the reflector is maintained within a predetermined range by the position compensation member, so that the light irradiated onto the reflector via the optical fiber is The strength is not affected by temperature changes. Therefore, the reflected light obtained from the reflector plate exhibits good response to temperature changes, and the sensor of the present invention is capable of measuring a wide temperature range with high accuracy.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the reflective temperature sensor of the present invention, Fig. 2 is a sectional view showing the sensor of the same embodiment under high temperature conditions, and Fig. 3 is a part showing a conventional sensor. FIG. 2 is a cross-sectional plan view. 11... Optical fiber, lla... Tip part, 12...
-Reflector, 15...Holder, 14...Through hole, 15
...Hollow part, 16...Position compensation member.

Claims (1)

[Scope of Claims] An optical fiber that guides light, a reflector that emits a different spectrum depending on the temperature of the light irradiated through the optical fiber, and a holder that holds these optical fibers and the reflector. The holder includes a through hole into which the tip of the optical fiber is fitted along its length, and a reflecting plate formed in front of the through hole along the axial direction of the through hole, and the reflecting plate facing toward the optical fiber. 1. A reflective temperature sensor comprising: a hollow portion arranged with the front surface facing the holder; and a position compensating member provided on the back side of the reflective plate in the hollow portion of the holder.