JP3103338B2 - Radiation thermometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation thermometer for measuring the temperature of a measuring object by detecting the radiant energy emitted from the measuring object with an infrared sensor. It concerns a radiation thermometer of the formula.

[0002]

2. Description of the Related Art Even if it is difficult to measure a temperature with a liquid expansion type thermometer or a thermocouple, an infrared sensor is used as a thermometer capable of remotely measuring the temperature of a measurement target. There is a radiation thermometer that detects the temperature of a measurement target by detecting the temperature.

There are a lens type, a mirror type, a light guide type, a fiber type and the like as a light condensing method of the radiation thermometer, but it is convenient for measuring the inside of an object having a flexible and complicated shape. Therefore, a fiber-type radiation thermometer using an optical fiber has been frequently used.

Conventionally, quartz fibers, chalcogenide fibers, fluoride fibers, thallium halide fibers and the like have been used as optical fibers. Infrared sensors that detect radiant energy guided by optical fibers include thermal infrared detectors such as thermistor bolometers that use the thermal conductivity effect, pyroelectric infrared detectors that use the pyroelectric effect such as TGS, and sulfides. A quantum infrared detecting element using a photoconductive effect such as lead or a photovoltaic effect such as cadmium mercury telluride or InSb is used.

[0005]

However, as shown in FIG. 5, a quartz fiber or a fluoride fiber has a transmission wavelength range of about 5 μm or less, and a chalcogenide fiber has a low transmittance in a wavelength range of 8 μm or more. Large loss.

Therefore, when these optical fibers are used for a radiation thermometer, as shown in FIG. 6, it is possible to accurately measure the temperature at 450 ° C. or higher for a quartz fiber and 150 ° C. or higher for a fluoride fiber. Lower temperatures cannot be measured accurately.

With a chalcogenide fiber, the temperature can be accurately measured above 80 ° C., but a temperature lower than 80 ° C. cannot be measured accurately. In particular, high-sensitivity measurement cannot be performed at 100 ° C. or lower unless a quantum infrared detecting element such as cadmium mercury telluride is used.

Here, FIG. 6 shows Infrared ray detecting elements as In.
This is an experimental value using Sb. According to the Vienna's displacement law, the peak wavelength of radiant energy emitted from the measurement target at 100 ° C. is 7.8 μm, and the peak wavelength becomes longer when the measurement target is lower temperature.

In addition, as shown in FIG. 7, in a wavelength range of 8 μm or less, there is absorption of moisture, oxygen, carbon dioxide and the like in the measurement atmosphere, so that it is easily affected by the measurement atmosphere (FIG.
Indicates the transmittance of radiant energy on the sea surface in the atmosphere with an optical path length of 300 m).

[0010] In order to accurately measure the temperature range from room temperature to the middle temperature range around 100 ° C, the transmittance must be high and the loss must be small in the wavelength range of 8 µm or more. Although thallium halide fibers can be measured at a low temperature, they are not preferred because they have toxicity.

The thermistor bolometer also requires a power supply and changes over time. The pyroelectric infrared detector requires an optical chopper, and the quantum infrared detector requires cooling. And expensive.

Therefore, there has been a demand for the development of an inexpensive radiation thermometer capable of measuring accurately from room temperature to a medium temperature range around 100 ° C. Furthermore, when measuring radiation temperature using lenses in a microwave heating furnace, the lens, its supporting parts, or components of the input device are heated slightly by microwaves and the temperature is increased. Since the secondary radiation was sent to the infrared sensor in duplicate and affected the measured value, it was not possible to measure the radiation temperature accurately.

The present invention solves the above-mentioned problems in a fiber-type radiation thermometer, and provides an inexpensive radiation thermometer that can measure accurately from a normal temperature to a medium temperature range and has a simple structure. The purpose is to do.

When the radiation temperature is measured in a microwave heating furnace, the components of the input device are heated by the microwave, and the secondary radiation therefrom is duplicated and sent to the infrared sensor to obtain the measured value. It is an object of the present invention to provide a radiation thermometer capable of preventing the influence thereof and accurately measuring the radiation temperature.

[0015]

SUMMARY OF THE INVENTION The present invention relates to a radiation thermometer for measuring the temperature of a measuring object by detecting radiant energy emitted from the measuring object with an infrared sensor. Provided with an inner tube for a lens having an infrared transmitting lens and a bandpass filter, and a metal film for microwave protection sandwiched between an inner wall surface and an outer wall surface of the lens holder. , and the said infrared transmission lens and bandpass filter and an optical fiber for guiding the infrared radiant energy only wavelength range of 8μm~14μm transmitted to the infrared sensor a is silver Hara id based fibers, wherein the infrared sensor is a thermopile Is a radiation thermometer.

In the radiation thermometer of the present invention, since the silver halide fiber is used as the optical fiber, the infrared ray has a high transmittance and a small loss even in a wavelength region of 8 μm or more. Therefore, using infrared rays in the wavelength range of 8 μm to 14 μm,
Accurately measures from room temperature to medium temperature around 100 ℃,
It is not affected by the absorption of moisture, oxygen, carbon dioxide, etc. in the measurement atmosphere. This radiation thermometer is inexpensive because it uses a thermopile, which does not require a power source and has a simple structure, as an infrared sensor.

Further, by providing a lens holder having an infrared transmitting lens and a stop at the end of the optical fiber, it is possible to reduce a change in output due to a change in the distance between the object to be measured and the lens holder.

Further, when a metal film for microwave protection is provided on the lens holder, when measuring the radiation temperature in a microwave heating furnace, the infrared transmitting lens and the lens holder are heated by the microwave, and the lens is heated therefrom. Can be prevented from being duplicated and sent to the infrared sensor to affect the measured value.

[0019]

FIG. 1 is a structural view of a radiation thermometer according to an embodiment of the present invention, and FIG. 2 is a structural view of a lens holder of the radiation thermometer.

This radiation thermometer is a fiber radiation thermometer that guides radiant energy emitted from an object 1 to be measured to an infrared sensor 3 through an optical fiber 2. The optical fiber 2 is a silver halide fiber. The lens holder 4 is provided at the front end, and the infrared sensor 3 is provided at the rear end.

The infrared sensor 3 is a thermopile for converting radiant energy into electric energy. A voltmeter 5 for measuring the output voltage of the infrared sensor 3 is connected to the infrared sensor 3, and the voltmeter 5 is measured by a voltmeter. A display device 6 that converts a voltage into a temperature and displays the measured temperature is connected.

The lens holder 4 is provided with a fiber holder 7 at the rear end and an inner tube 8 for the lens at the center.
The optical fiber 2 is fixed by a fiber holder 7, and the infrared transmitting lens 9 and the bandpass filter 11 are held by a lens inner cylinder 8 at a position separated by a predetermined distance forward from the tip of the optical fiber 2. Here, a polyethylene Fresnel lens having a focal length of 10 mm is used as the infrared transmitting lens 9. Infrared transmission lens 9 and optical fiber 2
Is slightly smaller than the focal length. The position of the bandpass filter 11 may be anywhere in the lens holder 4 (before or after the infrared transmitting lens 9). It may be provided between the optical fiber 2 and the infrared sensor 3. Further, a front end diaphragm 10 is provided at the front end of the lens holder 4.

At the time of temperature measurement, radiant energy emitted from the measurement object 1 enters the lens holder 4 through the tip diaphragm 10 and passes through the infrared transmitting lens 9 and the bandpass filter 11 to a wavelength of 8 μm to 14 μm. Infrared light in the wavelength range is guided to the infrared sensor 3 by the optical fiber 2 and converted into electric energy. The output voltage of the infrared sensor 3 is measured by the voltmeter 5, and the voltage is converted into a temperature and displayed on the display device 6.

FIG. 3 shows the relationship between the measured temperature and the output voltage when the surface temperature is changed from room temperature to 120 ° C. with the reference hot plate as the object 1 to be measured. Here, since a silver halide fiber is used for the optical fiber 2, as shown in FIG. 5, the transmittance of infrared rays is high and the loss is small in the wavelength region of 8 μm or more. Therefore, as the infrared sensor 3, a thermopile having a lower sensitivity than a pyroelectric infrared detecting element or a quantum infrared detecting element but having sensitivity over a wide range of infrared light can be used.
The measurement can be performed accurately from normal temperature to a medium temperature range around 100 ° C. using infrared rays in the above wavelength range.

In this wavelength range, as shown in FIG.
It is not affected by the absorption of moisture, oxygen, carbon dioxide, etc. in the measurement atmosphere. This radiation thermometer is inexpensive because the infrared sensor 3 uses a thermopile that does not require a power source and has a simple structure.

FIG. 4 shows the relationship between the output voltage and the object distance when the distance between the object 1 and the tip of the lens holder 4 (object distance) is measured with the reference hot plate as the object 1 to be measured. Show.

In the lens holder 4, the viewing angle is fixed by the tip stop 10, and the radiant energy collected by the infrared transmitting lens 9 is held at a position covering the entire front end face of the optical fiber 2. The output fluctuation is small in the range of up to 80 mm.

FIG. 8 is a configuration diagram of a lens holder of a radiation thermometer provided with a metal film for microwave protection. The lens holder 40 is provided with a fiber holder 7 at the rear end and a lens inner cylinder 8 at the center in the same manner as the lens holder 4 of FIG. 2, and fixes the optical fiber 2 with the fiber holder 7 and transmits infrared rays. The lens 9 and the bandpass filter 11 are held by the lens inner cylinder 8 at a position separated from the tip of the optical fiber 2 by a predetermined distance forward. At the tip of the lens holder 40, a tip stop 10 is provided.

Further, the lens holder 40 is provided with a metal film 41 for microwave protection. The metal film 41 is formed as a film or a vapor-deposited film. The metal film 41 is formed on the lens holder 40 so that a discharge phenomenon does not occur with an external metal and the microwave does not enter the inner wall surface 42 of the lens holder 40. It is sandwiched between the inner wall surface 42 and the outer wall surface 43. The inner wall surface 42 is covered with Teflon or the like to prevent reflection.

When the lens holder 40 is used in a microwave heating furnace, the metal film 41 reflects the microwaves to prevent intrusion into the inside, and the infrared ray transmitting lens 9 and the inner wall surface 41 of the lens holder 40 are formed. Secondary radiation due to temperature rise can be eliminated. Therefore, when the radiation temperature is measured in a microwave heating furnace, the radiation temperature can be measured more accurately.

[0031]

As described above, the radiation thermometer according to the present invention can measure accurately from a normal temperature to a medium temperature range, and has a simple structure and is inexpensive.

By providing a lens holder provided with an infrared transmitting lens and a tip stop at the tip of the optical fiber, it is possible to reduce a change in output due to a change in the distance between the object to be measured and the lens holder.

Further, when a metal film for microwave protection is provided on the lens holder, when measuring the radiation temperature in a microwave heating furnace, the infrared transmitting lens and the lens holder are heated by the microwave and are then heated. Of secondary radiation is not transmitted to the infrared sensor in duplicate, which affects the measured value, thereby enabling accurate measurement of the radiation temperature.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a radiation thermometer according to an embodiment of the invention.

FIG. 2 is a configuration diagram of a lens holder of the radiation thermometer.

FIG. 3 is a graph showing a relationship between a measured temperature of a radiation thermometer and an output voltage.

FIG. 4 is a graph showing a relationship between an objective distance and an output voltage of the radiation thermometer.

FIG. 5 is a graph showing the relationship between wavelength and transmission loss of quartz fiber, fluoride fiber, chalcogenide fiber, and silver halide fiber.

FIG. 6 is a graph showing a relationship between a measured temperature and an output voltage when a quartz fiber, a fluoride fiber, and a chalcogenide fiber are used in a radiation thermometer.

FIG. 7: Optical path length 300 of radiant energy on the sea surface
7 is a graph showing the transmittance of m in the atmosphere.

FIG. 8 is a configuration diagram of a radiation thermometer provided with a metal film for microwave protection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measurement object 2 Optical fiber 3 Infrared sensor 4 Lens holder 5 Voltmeter 6 Display device 7 Fiber holder 8 Lens inner cylinder 9 Infrared transmission lens 10 Tip stop 11 Band filter 40 Lens boulder 41 Metal film 42 Inner wall surface 43 Outer wall surface

──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshiyuki Nagao, Inventor Yoshitoshi Yasuda 3-13-10, Nishigaoka, Kita-ku, Tokyo Inside the Tokyo Metropolitan Industrial Technology Research Institute (72) 1-9-16-1 Kamijujo, Kita-ku, Tokyo Inside Fuji Tok Co., Ltd. (72) Inventor Kazuo Tsuto 1-9-16-1 Kamijujo, Kita-ku, Tokyo Inside Fuji Tok Co., Ltd. Furukawa Machinery & Metal Co., Ltd. Iwaki Plant (72) Inventor Tetsuhiro Iwata 20th Kamiyoshima Kodate, Yoshima-cho, Iwaki-shi, Fukushima Prefecture Furukawa Machinery & Metals Co., Ltd. JP-A-2-122225 (JP, A) JP-A-62-203071 (JP, A) JP-A-3-264829 (JP, A) JP-A-63-61884 (JP, A) JP U) JitsuHiraku flat 4-122336 (JP, U) JitsuHiraku flat 4-121696 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) G01J 5/02 - 5/10 G01J 1 / 02 G01K 11/12

Claims (1)

(57) [Claims] 1. A radiation thermometer for measuring the temperature of a measurement target by detecting radiant energy emitted from the measurement target with an infrared sensor, wherein a lens holder has a tip stop at the tip and an infrared transmission lens and a bandpass filter at the center. The lens holder has a lens inner cylinder, and the lens holder has a metal film for microwave protection sandwiched between an inner wall surface and an outer wall surface. the infrared radiant energy in a wavelength range only 8μm~14μm transmitted through the bandpass filter is an optical fiber silver Hara id based fiber for guiding the infrared sensor, a radiation thermometer, wherein the infrared sensor is a thermopile.