JPS6255529A - Radiation thermometer - Google Patents

Abstract

PURPOSE:To enable the measurement of the temperature of a fine object to be measured, by providing apertures each with a mirror face on the side of the object at an opening arranged in the object side front center of an infrared detection element to remove infrared rays resulting from a disturbance by things other than the object being measured. CONSTITUTION:A first filter 2 is inserted into a tip opening of a detection head 1 and a lens 3 is fitted into the inside thereof. Then, a box body 8 in which an aperture 80 is fitted into the front opening thereof while a case 4 provided inside through a heat insulating material 9 is projected at the rear end of the detection head 1, apertures 41 and 42 and a second filter 5 are arranged at the opening thereof while the front faces of the apertures 41 and 42 are formed as mirror surface. Infrared rays resulting from a disturbance by things other than a fine object to be measured are removed gradually with the apertures 80, 41 and 42 and hence, the temperature of the apertures 41 and 42 will not rise when infrared rays only from the object being measured reach a thermal type infrared rays detection element 6. This prevents a possible temperature difference between the second filter 5 and the detection element 6, thereby enabling accurate measurement of the temperature of the fine object being measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation thermometer that non-contactly measures the temperature of an object by measuring the amount of energy of infrared rays emitted from the object. The present invention relates to a radiation thermometer for low temperature measurement that uses an aspiration infrared detection element as an element and is capable of measuring temperatures near room temperature.

[Conventional technology]

There are two types of infrared detection elements that measure the amount of energy of infrared rays emitted from an object: quantum infrared detection elements and aspirational infrared detection elements. Quantum infrared detection elements that can measure temperatures near room temperature are themselves expensive;
It is necessary to constantly cool it using liquid nitrogen or the like. Therefore, the disadvantage is that the device becomes larger and the cost increases. Therefore, an aspirational infrared detection element is generally used to measure temperatures near room temperature.

By the way, as is well known, the amount of energy of infrared rays emitted from an object is proportional to the fourth power of the absolute temperature according to the Stefan-Poltzmann law (see below).

W=εσT4 In this second, W: Amount of infrared energy emitted per unit time from unit area of the object (WCm-2) σ: Stefan-Boltzmann constant (5,67xlo-12Wcm-"K-') ε: Radiation Rate T: Absolute temperature Therefore, the lower the temperature, the smaller the amount of infrared energy emitted.Therefore, it is more susceptible to influences from objects other than the measurement target, and radiation thermometers for low temperature measurement Accurate temperature measurements in the In order to do this, it was necessary to use optical components made of special materials.

In general, a reflecting mirror system and a lens system have been commonly used as optical systems for low-temperature radiation thermometers for measuring temperatures near room temperature.

Cassegrain II is the most common reflecting mirror method. The advantage of this method is that temperature can be measured without using optical parts made of special materials to transmit far infrared rays. However, on the other hand, there is a problem when an aspirational infrared detection element is used as the infrared detection element. It is extremely difficult to keep the infrared detection element and the components inside the radiation thermometer at the same temperature without increasing the size of the device. The problem is that they are easily affected by infrared energy.

Then, as mentioned above, in radiation thermometers for low temperature measurement, the energy of infrared rays emitted from the object to be measured is affl, so even a small amount of infrared energy from sources other than the object to be measured will not have a large effect. This causes errors and makes accurate temperature measurement impossible. In order to eliminate this drawback, various proposals have been made to provide a chopper linked to a motor in front of the infrared detection element. However, with this method, the radiation thermometer itself becomes larger,
In addition, the mechanical complexity increased, and there were problems in terms of reliability of measured values and mechanical life.

In comparison, the lens method does not have the problems that the reflective mirror method has when downsizing. However, lenses have the property of emitting infrared rays in a wavelength range that cannot be transmitted.
The infrared radiation emitted from the lens itself reaches the infrared detection element, generating an erroneous temperature signal. Therefore, there is a drawback that accurate temperature measurement is impossible. In order to eliminate this drawback, germanium lenses could be used, but germanium itself is expensive and
An anti-reflective coating must be applied to the surface to suppress reflections, making it extremely expensive.

In order to solve this problem, the present applicant filed a patent application filed in 1986-
No. 34734 has been filed. The invention related to this application will be simply explained below.

As shown in FIG. 2, a first filter 2 that transmits infrared rays in a desired wavelength range is fitted into the opening at the tip of the detection head 1 of the radiation thermometer. A lens 3 is fitted inside the first filter 2. This lens 3 has wavelength transmission characteristics that are equal to or wide than those of the first filter 2.

Therefore, after the first filter 2 transmits infrared rays in a desired wavelength range, the remaining infrared rays are concentrated by the lens 3.

This is because the energy of infrared rays radiated from an object near normal temperature is extremely small ffl, so even the slightest omission of infrared rays is unacceptable for accurate temperature measurement.

A case 4 with good thermal conductivity is provided protruding from the terminal end of the detection head 1 inside the lens 3. A second film 5 having wavelength transmission characteristics equal to or narrower than that of the first filter 2 is fitted into the opening at the tip of the case 4 . An aspirational infrared detection element 6 is provided inside the second filter 5 . The aspiration infrared detection element 6 is connected by a connection cord 7 to an external device (not disclosed) that processes its own temperature signal. Of the infrared rays condensed by the lens 3, only infrared rays in a desired wavelength range are selected and transmitted by the second filter 5. Therefore, the infrared rays that have reached the eager infrared detection element 6 are from the object to be measured and the second filter 5.

However, the second filter 5 is housed in the same case 4 as the Aspiration infrared detection element 6, and since this case 4 has good thermal conductivity, a temperature difference occurs between the second filter 5 and the Aspiration infrared detection element 6. do not have. The eager infrared detection element 6 outputs a temperature signal only when measuring an object whose temperature is different from its own temperature.

Therefore, the temperature signal output by the aspirational infrared detection element 6 is the one that is output after receiving only the infrared rays from the object to be measured.

[Problem that the invention seeks to solve]

With this application, the applicant has dramatically improved the accuracy of a lens-type radiation thermometer for low temperature measurement using an inexpensive lens. However, the following problems remained. First, if the object to be measured is small and low temperature, and there is a high temperature object around or behind it, the infrared rays from this high temperature object will also be focused, and the detection head 1 (see Figure 2) There was a problem in that the inner circumference of the sensor caused a temperature rise, resulting in erroneous measurements. Another problem is that when measuring the temperature of a high-temperature object, the inner circumference of the detection head 1 receives infrared energy from the object, causing a rise in temperature, as described above. However, if the temperature of the low-temperature object to be measured is measured immediately after this, the infrared rays emitted from the inner peripheral portion of the detection head 1 will reach the eager infrared detection element 6, resulting in an erroneous measurement.

An object of the present invention is to be able to accurately measure the temperature of an object to be measured even if it is minute, and to be able to measure the temperature of a low-temperature object immediately after measuring the temperature of a high-temperature object. Another object of the present invention is to provide a lens-type radiation thermometer for low temperature measurement that does not cause erroneous measurements.

[Means for solving problems]

This invention was made in view of the above problem, and a specific means for solving this problem is to measure the amount of energy of infrared rays emitted from an object using an infrared detection element. In a radiation thermometer for measuring temperature, a diaphragm having an opening in the center and having a mirror surface on the object side is disposed in front of the infrared detecting element on the object side.

[For production]

Since this invention employs the above-mentioned means, even if the object to be measured is minute, infrared rays caused by background disturbances can be removed by the aperture. Even if you measure the temperature of the object,
Infrared rays caused by this effect can be removed, and since the surface of this diaphragm on the side of the object to be measured is mirror-finished, the infrared rays can be reflected.
The temperature of the aperture itself does not rise. Therefore, it is completely unaffected by infrared rays emitted from the aperture.

〔Example〕

This invention will be explained in detail below based on one embodiment.

Note that the same parts as those in the prior art are given the same numbers to simplify the explanation.

As shown in FIG. 1, a first
A filter 2 is fitted therein, and a lens 3 is fitted inside this first filter 2. A housing 8 having a front opening fitted with a diaphragm 80 is protruded from the terminal end of the detection head 1, and a case 4 with good thermal conductivity is installed inside the housing 8 with a heat insulating material 9 interposed therebetween. There is. This case 4 has an opening at the front, and a diaphragm 41, 42 and a second filter 5 are arranged in this opening in order from the front. Apertures 41 and 4
2 has a mirror surface on the front. An aspiration infrared detection element 6 is fixedly installed at the end of the opening, and a temperature signal processing section 10 that processes the temperature signal from the aspiration infrared detection element 6,
It is connected to the inside of the housing 8 at the rear of the case 4 with a heat insulating material 9 interposed therebetween. A connection cord 7 for transmitting the processed signal to an external device (not shown) is connected to the temperature signal processing unit 10 by penetrating the housing 8 and the detection head 1 .

The operation of the present invention constructed as described above will now be described. First, the case of a minute object to be measured will be described.

Of the infrared rays caused by the object to be measured and disturbances behind the object that are transmitted through the first filter 2 and focused by the lens 3, some infrared rays caused by the disturbance are first removed by the diaphragm 80. Next, it is further removed by the aperture 41,
Finally, it is almost completely removed by the aperture 42. Therefore, the infrared rays that have passed through the aperture 42 and reached the calorific infrared detection element 6 are only from the object to be measured.

At this time, since the front surfaces of the apertures 41 and 42 are formed of mirror surfaces, the infrared rays caused by the removed disturbance are reflected by the apertures 41 and 42 and absorbed by the case 4. Therefore, the temperature of the apertures 41 and 42 itself does not increase, and maintains the same temperature as the case 4.

The part of the opening of the case 4 into which the aperture 4L42 is inserted absorbs the infrared rays and the temperature rises, but because of its good thermal conductivity, it immediately diffuses and the temperature rises between the infrared ray detection element 6 and the second filter 5. There is no temperature difference. Therefore, the infrared rays from the object to be measured and the second filter 5 reach the calorific infrared detecting element 6, but since there is no temperature difference between the second filter 5 and the calorific infrared detecting element 6, the generated temperature signal is The temperature signal is output by receiving infrared rays from only the object to be measured.

Next, a description will be given of the operation when the temperature of a high-temperature measurement object is measured and immediately after that the temperature of a low-temperature measurement object is measured.

In this case, the inner peripheral portion of the detection head 1.

The housing 8, the diaphragm 80, etc. receive infrared rays from the object to be measured, causing a temperature rise. At this time, when the temperature of the low-temperature object to be measured is measured, the infrared rays from this object to be measured first reach the calorimetric infrared detection element 6, as described above. Next, the infrared rays emitted from the inner peripheral portion of the detection radar 1, etc., which were causing the temperature rise, are blocked by the apertures 41 and 42 and do not reach the heat quantity infrared detection element 6. The light is then reflected by mirror surfaces formed on the front surfaces of the apertures 41 and 42.

Then, as in the above case, the infrared energy is quickly diffused by case 4, and the aperture 41.42
Since its own temperature does not rise, there is no temperature difference between the second filter 5 and the thermal infrared detection element 6, and the calorific infrared detection element 6 receives only the infrared rays emitted from the low-temperature measurement object. Generates a temperature signal.

In this embodiment, both front surfaces of the diaphragm 41 and 42 are formed with mirror surfaces, but substantially the same effect can be obtained by simply forming only the front surface of the diaphragm 42 with a mirror surface. Further, not only the front surface but also the rear surface may be formed with a mirror surface. Furthermore, the front or rear surface of the diaphragm 80 may be formed with a mirror surface.

Further, in this embodiment, the aperture 42 is arranged in front of the second filter 5, but the same effect can be obtained even if it is arranged behind the second filter 5.

Further, in this embodiment, two apertures 41 and 42 are provided, but substantially the same effect can be obtained with only the aperture 41. Alternatively, three or more apertures may be provided.

〔Effect of the invention〕

As is clear from the above description, the present invention provides a radiation thermometer that measures the temperature of an object by measuring the amount of energy of infrared rays emitted from the object using an infrared detection element. A diaphragm with an opening in the center in front of the object side and a mirror surface on the object side is provided, so that the diaphragm can remove infrared rays from disturbances other than the object to be measured. It is possible to measure the temperature of even the object to be measured. Furthermore, even if the temperature of a high-temperature measurement object is measured and then the temperature of a low-temperature measurement object is measured immediately after that, the influence of infrared rays from the high-temperature measurement object can be removed by the aperture. Furthermore, since the infrared rays are reflected by the aperture, the temperature of the aperture itself does not rise, and the infrared detection element is not affected by the infrared rays emitted from the aperture. Therefore, accurate temperature measurement is always possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a radiation thermometer according to the present invention, and FIG. 2 is a sectional view of a conventional radiation thermometer.

Claims (3)

[Claims] (1) A radiation thermometer that measures the temperature of an object by measuring the amount of energy of infrared rays emitted from the object using an infrared detection element, which has an opening in the center in front of the object side of the infrared detection element. A radiation thermometer, further comprising an aperture whose object-side surface is a mirror surface. (2) The radiation thermometer according to claim 1, wherein a filter that transmits infrared light in a desired wavelength range is disposed between the infrared detection element and the aperture. (3) The radiation thermometer according to claim 1 or 2, wherein the infrared detection element and the aperture are housed in the same case with good thermal conductivity.