JPS63236936A - Optical temperature measuring instrument - Google Patents

Abstract

PURPOSE:To perform stable temperature measurement with high sensitivity by using an interference film filter as a temperature sensing part and an image sensor for a photodetection part and measuring temperature from variation in the quantity of photodetection. CONSTITUTION:Light from a light source 1 is projected by an optical fiber 21 on the interference film filter 3 as the temperature sending part which varies in transmissivity or reflection factor with temperature and light from an optical fiber 22 is diffracted spectrally by a spectral means 4 such as a diffraction grating and photodetected by the image sensor 5 such as a CCD. The interference film filter 3 shifts in transmission wavelength characteristics to the long- wavelength side as the temperature rises, so the peak value wavelength and temperature are found previously. Further, picture elements of the sensor 5 and wavelength are made to correspond to each other and then the temperature is measured stably with high accuracy from the picture element position of the peak value or bottom value among respective picture element outputs without being affected by variation in the light quantity and the optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical concentration measuring device using an optical fiber.

[Prior art] Conventionally, a semiconductor or the like whose transmittance changes depending on temperature is used as a temperature sensing part, light is emitted to and received by a fiber, and the temperature is measured from the change in the amount of light received by a detector. .

[Problems to be solved by this invention] However,
With these methods, stable measurement is difficult due to changes in the intensity of the light source, changes in light amount due to bending of the optical fiber, changes in ambient temperature, and other environmental changes. In addition, it has been difficult to change measurement conditions and ensure compatibility due to changes in optical loss depending on the length of the optical fiber and variations in splicing loss of optical connectors.

In view of the above points, an object of the present invention is to provide an optical measuring device that uses an interference film filter as a humidity sensing section and is capable of highly sensitive temperature measurement.

Means for Solving Problem E] This invention projects and receives light from a light source via an optical fiber to an interference film filter as a temperature-sensitive part whose transmittance or reflectance changes depending on temperature, and from the optical fiber. This is an optical temperature measuring device in which the light is separated by a spectroscopic means and detected by an image sensor, and the temperature is measured by a measuring means from the pixel position of the peak value or bottom value of each pixel output of this image sensor. .

[Embodiment] FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention.

In the figure, light from a light source 1 such as an incandescent bulb, a halogen lamp, or an LED is projected through an optical fiber 21 to a multilayer interference film filter 3 as a temperature sensing section, and the interference filter 3, such as a band-pass filter with a narrow half-width, is transmitted through an optical fiber 21. The light transmitted through the membrane filter 3 is extracted by an optical fiber 22. The light from this optical fiber 22 is separated by a spectroscopic means 4 such as a diffraction grating or a prism, and is received by each pixel of an image sensor 5 such as a COD, and the temperature is measured by a measuring means 6 from the output of this image sensor 5. be exposed.

In other words, when the temperature T rises, the interference film filter 3
If the transmission wavelength characteristic shifts to the long wavelength side as shown from A to A' in the diagram, and the relationship between the wavelength λ of the peak value and the temperature T is determined in advance by experiment, measurement W, etc., the peak value can be measured by the measuring means 6. Temperature T can be found from the wavelength.

On the other hand, since the image sensor 5 receives the light separated by the spectrometer 4, if the horizontal axis in FIG. 2 is the pixel position (number) of the image sensor 5, the output of the image sensor 5 is similar to that in FIG. output wavelength is obtained. Therefore, if the correspondence between the pixels of the image sensor 5 and the wavelength is established in advance, tm 11 T can be determined from the pixel position of the output waveform.

In this way, in this invention, only the position of the peak value is required, and as long as there is the amount of light necessary to detect the peak position,
Changes in the amount of light have no essential effect on the measured values. Therefore, stable measurement is possible without being affected by the drift 1 of the light source, changes in bending or length of the optical fiber, changes in optical loss due to optical connectors, etc. Furthermore, since the output is based on the pixel position of the image sensor 5, it is easy to digitize it.

The interference film filter 3 is made of Si or Ge for the high refractive index film, SiO, etc. for the low refractive index film, and is formed into a multi-m film by vapor deposition or the like, and has the desired transmission wavelength characteristics according to the temperature range and sensitivity. A filter with

In this way, by changing the number of layers and film configuration of the multilayer interference film filter, one filter with the required bandpass characteristics can be obtained, and the temperature coefficient of the refractive index of 3i and Qe is approximately 1.5X10-'//'C is large enough to be used as a temperature sensing part.

FIG. 3 is a configuration explanatory diagram showing another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate equivalent components.

In the figure, light from a light source 1 is transmitted via a half mirror 7 to an optical fiber 2 through an interference film filter 3 as a temperature sensing section.
is illuminated. The light reflected by an interference film filter 3 such as a bandpass filter with a narrow half-width provided at the tip of the optical fiber 2 by vapor deposition or other means is extracted again through the optical fiber 2 and reflected by a half mirror 7. The light reflected by the half mirror 7 is separated by the spectroscopic means 4 and received by the image sensor 5, and the temperature is measured by the measuring means 6 from the output of the image sensor 5.

In other words, when the temperature T of the interference film filter 3 rises, the reflection wavelength characteristic shifts to the long wavelength side from Δ to A- in FIG. 4. Therefore, the temperature T can be determined from the bottom value pixel position of the image sensor 5 using the same principle as in FIG.

Furthermore, as shown in FIG. 5, by forming an interference film filter 3 on the end face of the optical fiber 20 by vapor deposition or the like (for example, by forming interference film filters on the end faces of many optical fibers at the same time), uniform The S wet part can be produced inexpensively and easily, has compatibility, and can be deposited on the optical fiber 2 using the optical connector 20a, making it easy to handle,
Maintenance, etc. becomes easier. In other words, even if such an optical connector 20a is used, variations in the amount of light do not cause a disturbance, so even if the optical connector 20a is replaced, it will not be affected by variations in coupling loss.

[Effects of the Invention] As described above, the present invention uses an interference film filter as the temperature sensing section, makes light from the spectroscopic means enter the image sensor using an optical fiber, and measures the temperature from each pixel position. Therefore, it is not affected by changes in the sales floor, it is not affected by the optical path, etc., and it is possible to maintain a stable temperature with high accuracy.

[Brief explanation of drawings]

FIGS. 1, 3, and 5 are configuration explanatory diagrams showing one embodiment of the present invention, and FIGS. 2 and 4 are wavelength characteristic diagrams. DESCRIPTION OF SYMBOLS 1...Light source, 2.20.21.22...Optical fiber, 3...Interference film filter, 4...Spectroscopy means, 5...
・Image sensor, 6... Measuring means, 7... Half mirror 120a... Optical connector

Claims (1)

[Claims] 1. Two interference film filters as temperature-sensitive parts whose transmittance or reflectance changes depending on temperature, and a light that projects light from a light source onto these interference film filters and extracts the light that is transmitted or reflected by the interference film filters. A fiber, a spectroscopic means for separating the light from the optical fiber, an image sensor for receiving the light separated by the spectroscopic means, and a temperature is measured from the peak value or bottom value of each pixel output of the image sensor. An optical temperature measuring device characterized by comprising: a measuring means.