JPS60187829A - Infrared radiation thermometer - Google Patents

Abstract

PURPOSE:To reduce influence exerting upon the output of an infrared detector of a shutter temp., by intermittently interrupting infrared rays by a shutter constituted of a material with infrared emissivity epsilon of 0.2 or less. CONSTITUTION:A shutter 2b is constituted of a material with infrared emissivity epsilon of 0.2 or less such as an iron plate, an SUS polished plate or an aluminum plate and driven by a motor 3 and intermittently interrupts infrared ray input R from an object to a pyroelectric type infrared detector 1. A thermistor 5 is provided in the vicinity of the infrared detector 1 and used as an atmospheric temp. detector.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an infrared radiation thermometer used as a non-contact thermometer.

Configuration of conventional example and its problems A conventional infrared radiation thermometer will be explained with reference to Fig. 1. 1 is a pyroelectric infrared detector, and 2a is an infrared ray detector that intermittently transmits infrared rays R from a target object. A shutter, 3 a motor for driving the shutter, and 4 a diode for measuring the temperature of the shutter.

To explain the operation of the above configuration, the infrared detector 1 receives intermittently human infrared power R from the shutter 2.
Outputs an electrical signal proportional to the temperature difference between the target object and the shutter. In order to accurately detect the temperature of the target object, it is necessary to accurately detect the temperature of the shutter 2.

A shutter generally has a small heat capacity, and its temperature is largely influenced by changes in ambient temperature. Furthermore, in order to measure the shutter temperature, it is necessary to measure the temperature without contact. Therefore, it was necessary to provide an expensive diode 4 with a small heat capacity and a fast response speed close to the shutter 2a.

However, in the above configuration, it is necessary to reduce the heat capacity of the shutter 2a so that the shutter 2a can sufficiently follow changes in the ambient temperature, or the shutter 2a must have a small heat capacity.
In order to accurately measure the temperature of the shutter 2a, a coating treatment is applied to bring the infrared emissivity ε of the shutter 2a close to 1.0.
The shutter 2a required careful attention, and there were limitations on the materials used.

Further, since the diode 4 is used to measure the temperature of the shutter 2a, the signal to be taken out is small, and a constant current or constant voltage circuit must be constructed, resulting in complicated signal processing.

Furthermore, if the temperatures of the infrared detector 1 and the shutter 2a are different, the temperature of the target object cannot be detected accurately.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and is less susceptible to fluctuations in shutter temperature, simplifies signal processing of ambient temperature, and can detect the temperature of a target object with high precision. The purpose is to provide an infrared radiation thermometer.

Structure of the Invention The present invention includes a shutter that intermittently blocks infrared rays and is made of a material with an infrared emissivity ε of 0.2 or less, and an infrared detector that receives infrared rays that are intermittently blocked by the shutter. This infrared radiation thermometer is equipped with an ambient temperature detector that detects the temperature of this infrared detector.

This configuration reduces the influence of the shutter temperature on the output of the infrared detector, and accurately detects the temperature of the target object regardless of fluctuations in the shutter temperature.

Description of examples A first embodiment of the present invention will be described with reference to FIG.

Components common to the conventional example are given the same numbers as in FIG.

5 indicates a commercially available thermistor element used as an ambient temperature detector provided near the infrared detector 1.

The shutter 2b was constructed using an iron plate, a 5Us5F polished plate, a 7luminium plate, etc., and the plate thickness was 0.1 mm.

The infrared detector 1 was a To-5 package type pyroelectric detector. The shutter 2b and the infrared detector 1 were placed approximately 5 mm apart.

Table 1 shows the measurement results of this example and the conventional example. Measurement conditions: The output ratio of the infrared detector 1 is shown when the room temperature is 25°C, the target object is 100°C, and the shutter temperatures are 25°C and 45°C. The infrared emissivity of each shutter is also listed in Table 1.

Table 1 Measurement Results of Examples and Conventional Examples In Table 1, ■ indicates a conventional example, in which the shutter is made of an aluminum plate, a coating is formed with lacquer, and the infrared emissivity ε is 0.85. , ■, ■, and @ indicate examples of the present invention.

The output ratio in Table 1 shows the ratio of the output voltage V25 of the infrared detector 1 when the shutter temperature is 25°C and the output voltage V45 when the shutter temperature is 45°C.

Figure 3 shows changes in the output voltage of the infrared detector.

In the figure, the horizontal axis shows time and the vertical axis shows output voltage. S
indicates the time the shutter was opened. H indicates the output voltage.

From Table 1, it can be seen that in the conventional infrared radiation thermometer, the output decreases by as much as 40% when the shutter temperature fluctuates. On the other hand, in the embodiment of the present invention, the change is small, and the output reduction is very small, 2 to 10%.

As described above, by constructing the shutter with a material with an infrared emissivity ε of 0.2 or less, an infrared radiation thermometer that is less affected by the shutter temperature can be realized, and a highly accurate infrared radiation temperature can provide a meter.

As explained above, according to the embodiment of the present invention, the output signal of the infrared detector 1 is less affected by the temperature of the shutter, so there is no need to accurately measure the temperature of the shutter, and Therefore, there is no need to provide an expensive diode with a small heat capacity and a fast response speed.

As shown in Table 1, the output of the infrared detector becomes less dependent on the shutter temperature by setting the infrared emissivity ε of the shutter constituent material to 0.2 or less. In this case, the output of the infrared detector is proportional to the temperature difference between the target object and the infrared detector.

Therefore, as an ambient temperature detector, it is sufficient to install a commercially available inexpensive thermistor element near the infrared detector without selecting it based on heat capacity, response speed, etc., and one with the same heat capacity as the infrared detector is sufficient. be. Therefore, compared to the diode, it is possible to obtain a larger output signal,
In addition, normal thermistor usage is sufficient, and signal processing becomes extremely simple. Furthermore, there are no restrictions on the installation location, such as proximity to the shutter.

Next, a second embodiment of the present invention will be described using FIG. 4.5.

In the figure, the difference from the above embodiment is that the infrared detector 1' is replaced by a surface acoustic wave detector instead of a pyroelectric detector, and the thermistor element 5 for measuring the ambient temperature is eliminated. It is.

The surface acoustic wave infrared detector 1' includes a surface acoustic wave element 6 (
(hereinafter referred to as an element) and an amplifier 7 form an oscillator, and its oscillation frequency is detected from an output terminal 8. At this time, element 6 acts as a delay line. When the element 6 is irradiated with infrared rays, a temperature change occurs in the element 6, the delay characteristic along the elastic surface of the element 6 changes, and the oscillation frequency changes.

For example, if the surface acoustic wave element 6 of the detector 1' is made of a piezoelectric material such as LiNbO3 and an oscillator with an oscillation frequency of about 174 MHz is purchased, the change in the oscillation frequency will be caused by the change in the ambient temperature of the detector 1'. Approximately 15 KHz per 1℃
It is. Further, the change in oscillation frequency due to infrared rays from the target object shown in the measurement conditions is several tens of Hz.

FIG. 6 shows changes in the oscillation frequency according to opening and closing of the shank in this second embodiment. The horizontal axis shows time and the vertical axis shows oscillation frequency. 9.1o indicates the open time and closed time of shi and s, respectively. 5 The oscillation frequency shown in FIG. 6 changes depending on the absolute temperature of the surface acoustic wave element 6, so by detecting the oscillation frequency immediately before the shank opening time 9, the oscillation frequency of the surface acoustic wave element 6 itself can be determined. The temperature, that is, the temperature of the infrared detector 1' can be known.

Further, the temperature difference between the target object and the detector can be detected based on the change in the oscillation frequency due to opening and closing of the shank, and Δf shown in FIG. 6.

According to the second embodiment, the shank is made of a material with low infrared emissivity so that the output signal of the infrared detector is not influenced by the temperature of the shank, and the infrared detector is made of a surface acoustic wave type material. By purchasing the infrared radiation thermometer, there is no need for a thermistor to measure the temperature of the infrared detector, and a highly accurate infrared radiation thermometer can be realized.

Effects of the Invention In the infrared radiation thermometer of the present invention, the output signal of the infrared detector is not influenced by the shank temperature by using a material with low infrared emissivity as the shutter component.

In addition, since it is only necessary to measure the temperature of the infrared detector itself,
There is no need to use a high-speed response diode with a small heat capacity, and a commercially available thermistor can be used, which simplifies signal processing.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional infrared radiation thermometer, Fig. 2 is a cross-sectional view of an infrared radiation thermometer according to the first embodiment of the present invention, and Fig. 3 shows the output J signal of an infrared detector. FIG. 4 is a cross-sectional view of an infrared radiation thermometer according to a second embodiment of the present invention.
FIG. 5 is a diagram showing the principle of a surface acoustic wave type infrared detector, and FIG. 6 is a diagram showing an output example of the surface acoustic wave type infrared detector. 1.1'... Infrared detector, 2b ・Shank, 5
...Temperature thermistor, 6...Surface acoustic wave element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Ash 1 Figure 3 Figure 4 Figure 5 Figure 1' Figure 6

Claims (1)

[Claims] (1) A shutter that intermittently blocks infrared rays and is made of a material with an infrared emissivity ε of 0.2 or less, and an infrared detector that receives infrared rays that are intermittently blocked by the shutter;
An infrared radiation thermometer comprising an atmosphere temperature detector that detects the temperature of this infrared detector. 2. The infrared radiation thermometer according to claim 1, wherein the shutter is made of an iron plate, a polished stainless steel plate, or an aluminum plate. Ω The infrared radiation thermometer according to claim 1, wherein the ambient temperature detector comprises a thermistor element. (2) The infrared radiation thermometer according to claim 1, wherein the infrared detector is a surface acoustic wave infrared detector.