JPH03202733A - Infrared-ray thermometer - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate measurement even if environmental temperature is suddenly changed by providing a structure wherein a lens, an infrared-ray detecting element, a sensor holder, stop parts and the like are contained in a case which is provided in a heat insulating structure part. CONSTITUTION:An infrared-ray detecting element 52 and a lens 50 are held in a hollow sensor holder (formed of a material having high heat conductivity) 54. An infrared-ray inlet diaphragm 54a is formed at a part in front of the lens. An outlet diaphragm 54b is formed at the rear part of the lens 50. The inner surface of the holder 54 functions as a lens barrel for the lens 50. The entire holder 54 acts as a heat sink for the lens 50 and the element 52. A temperature sensor 56 is attached to the element 52. A preamplifier 58 is provided at the rear position of the element 52. The constituent members described above are contained in a case 60 as a unitary body. A heat insulating structure part 60a is provided in the case 60, and the effect of environmental temperature on the holder 54 is decreased. Thus the temperature differences in the diaphragms 54a and 54b and the element 52 are decreased, and the temperature of the element 52 can be accurately measured with the sensor 56.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an infrared thermometer that is capable of measuring temperature with high accuracy without being affected by environmental temperature.

[Prior Art] Various thermometers have been known in the past, and an infrared thermometer is one that can measure the temperature of an object in a non-contact manner. This infrared thermometer measures the temperature of an object by detecting the amount of infrared rays emitted from the object.

Here, as shown in FIG. 6, for example, a conventional infrared thermometer includes a lens 10 that collects incident infrared rays, and an infrared ray that detects the infrared rays collected by this lens 10 and outputs an electrical signal. The infrared detection element 12 has a detection element 12, and the signal output from the infrared detection element 12 is the output regarding the temperature of the object to be measured.

The lens 10 and the infrared detection element 12 are held by a holder 14. This sensor holder 14
consists of a front holder 14a, a rear holder 14b, and an intermediate holder 14c, and the lens 1o is held by the rear end of the front holder 14a, and is fitted and held by the infrared detection element 12 at the front end of the rear holder 14b. ing.

Further, the front end of the front holder 14a is formed into an entrance diaphragm 16 that regulates incoming infrared rays, and an exit diaphragm 18 that regulates infrared rays collected by the lens 10 is provided between the lens 10 and the infrared detection element 12. It is located. In addition,
This injection aperture 18 is fixed to the intermediate holder 14c.

In such a conventional infrared thermometer, among the infrared rays emitted from the object to be measured, the infrared rays that pass through the entrance aperture 16, the lens 10, and the exit aperture 18 and are focused are incident on the infrared detection element 12.

Then, the infrared detection element 12 outputs an electric signal corresponding to the amount of human infrared rays.

Here, the amount of infrared rays emitted from a constant object depends on its temperature. Therefore, the infrared detection element 12
The temperature of the object to be measured can be calculated from the output. In this way, the temperature of the object to be measured can be measured without contact with the infrared thermometer.

However, with such infrared thermometers, measurement errors may occur due to infrared rays emitted from objects other than the object being measured, or due to changes in the temperature of the thermometer itself in response to changes in the environmental temperature. Put it away.

Therefore, conventional infrared thermometers and infrared radiometers (which can also be used as infrared thermometers) have been proposed that take into account the effects of environmental temperature fluctuations.

Japanese Utility Model Publication No. 55-145329 discloses that in a small electronic thermometer that measures human body temperature, when a person holds it in their hands or when it is exposed to direct sunlight, a temperature difference occurs between the internal devices and the measurement is interrupted. A configuration is shown that reduces the occurrence of errors. That is, in this conventional example, a pyroelectric element is used as the infrared detection element, and a heat insulating material is provided near the infrared detection element to reduce the influence of environmental temperature and suppress measurement errors.

On the other hand, JP-A-1-110225 discloses an infrared radiometer that can also be used as a thermometer, and by monitoring the temperature of the optical system, temperature drift in optical systems such as lenses can be detected. A quantum version is shown that corrects for the effects.

That is, in this infrared radiation meter, the field of view is limited by a cold shield so that the quantum-type infrared detection element looks only into the lens in the optical system.

The lens barrel that holds the lens is made of a material with high thermal conductivity, and the temperature of this lens barrel is measured to correct the amount of infrared rays emitted from the optical system.

[Problems to be Solved by the Invention] As described above, in the thermometer disclosed in Japanese Utility Model Application Publication No. 55-145329, a heat insulating material is provided to suppress the generation of temperature differences inside the thermometer. That is, when a pyroelectric type is used as an infrared detection element, a chopper is provided in front of the element for cutting and cutting incident light. Therefore, by providing a heat insulating material, it is possible to reduce the temperature difference between the chopper and the pyroelectric detection element, and the error caused by this can be reduced.

However, this thermometer does not take into account the influence of infrared rays emitted from the inner surface of the lens barrel.

Therefore, if the environmental sensitivity around the thermometer changes significantly, a temperature difference will occur between the lens barrel of the optical system and the infrared detection element, and the infrared rays emitted from the inner surface of the lens barrel will greatly affect temperature measurement.

Figure 7 shows the thermometer output when a conventional infrared thermometer, which does not take into account the effects of infrared rays emitted from the lens barrel, is used under conditions where the environmental temperature changes significantly. shows the thermometer output when the environmental temperature changes from 60°C to 25°C, with the blackbody furnace temperature being measured being constant at 35°C.

As is clear from the figure, when the environmental temperature changes, the temperature of the optical system, particularly the entrance aperture of the lens barrel, changes before the detection element, and the detection element senses the infrared rays emitted from the lens barrel. Therefore, the thermometer output will be lower than the blackbody furnace temperature.

Next, when the detection element temperature changes and approaches the lens barrel temperature,
The error caused by the temperature difference between the two will be reduced, and the correct output will return when the two temperatures become equal.

As described above, when the environmental temperature changes significantly, measurement errors occur due to infrared rays emitted from the lens barrel. When the temperature of the object to be measured is around room temperature, this measurement error is so large that it cannot be used as a thermometer.

On the other hand, in the infrared radiometer disclosed in Japanese Patent Application Laid-Open No. 1-11022, if the environmental temperature changes greatly and rapidly, the temperature of the cold shield itself changes, and the gap between the detection element and the cold shield changes. A temperature difference will occur. Therefore, the detection element senses the infrared rays emitted from the cold shield, and the above-mentioned Utility Model Application No. 55-1
Similar to the thermometer disclosed in Japanese Patent No. 45329, there is a problem in that accurate temperature measurement cannot be performed when the environmental temperature changes significantly and temperature measurement is performed near normal temperature.

Therefore, the inventors of the present invention, regarding the conventional infrared thermometer,
After conducting various experiments, we discovered that the reason why conventional infrared thermometers do not improve their measurement accuracy (particularly, they are virtually impossible to measure near room temperature) is as follows.

(A) When the environmental temperature changes suddenly, the temperature of the detection element itself changes suddenly, which may cause the thermal balance inside the thermal infrared detection element to collapse, or the temperature of the detection element package itself to become uneven, causing the temperature to change accordingly. The output value of the meter fluctuates. Errors caused by temperature differences in such detection elements cannot be dealt with by normal temperature compensation, since it is meaningless to detect the temperature around the detection element.

(B) Due to a sudden change in environmental temperature, a temperature difference occurs between the lens barrel and the detection element that make up the optical system, and the detection element senses infrared rays emitted from the lens barrel itself.

Therefore, if these points can be resolved, it is thought that even when the environmental temperature changes suddenly, it will be possible to accurately measure the temperature of the measurement target near normal temperature.

The present invention was made in view of the above problems, and provides an infrared thermometer that can accurately measure the temperature of a measurement target near room temperature even under conditions where the environmental temperature changes greatly and rapidly, and is easy to handle. The purpose is to provide.

[Means for Solving the Problems] An infrared thermometer according to the present invention includes a lens that collects incident infrared rays, an aperture that further narrows down the infrared light that has been focused by the lens, and a thermometer that has passed through the lens and the aperture. an infrared detection element that detects infrared rays and outputs an electrical signal;
A sensor holder that includes a lens barrel provided with the aperture, holds an infrared detection element and a lens, and thermally couples the lens barrel and the infrared detection element; and a sensor holder provided near the infrared detection element. a temperature sensor that detects the temperature of the infrared detection element; an infrared detection element having a heat insulating structure inside and housing the senna holder and the infrared detection element;
The present invention is characterized by comprising a case that reduces the temperature difference between the sensor holders and also reduces these temperature changes.

In this way, in the present invention, the lens barrel and the infrared detection element constituting the optical system are thermally coupled by a sensor holder made of a material with high thermal conductivity.

Therefore, the temperature difference between the infrared detection element and the sensor holder can be reduced, and the temperature of the detection element can be accurately measured by the temperature sensor. Furthermore, by housing the entire sensor holder in a case with heat insulating material,
The optical system and detection element are kept at the same temperature, and the interior is not affected by sudden changes in environmental temperature.

(Principle of Measurement) First, a discussion of the principle of temperature measurement when an infrared detection element is used by the inventors of the present invention will be described.

In the case of an infrared detection element in a heat chamber, an infrared detection element in a heat chamber converts a change in element temperature due to radiant heat transfer between the object and the detection element into an electrical signal, and detects the amount of incident infrared rays. As shown in FIGS. 8(A) and 8(B), the infrared detecting element of such a heat chamber, for example, a thermomobile, has an all-black 30 which is an infrared sensing part (hot junction) and a substrate which is a cold junction. 32 are connected by a plurality of thermocouples 34, and a plurality of thermocouples 34 are connected in series. Then, by detecting the potential difference generated in the thermocouple, an electrical signal regarding the incident infrared rays is obtained by the thermoelectromotive force of the thermocouple generated due to the temperature difference between the full black 30 and the substrate 32.

In addition, by making the entire infrared detection element a membrane structure,
The heat capacity of the all-black 30 which is the hot junction part is reduced, and the all-black 3
The responsiveness and sensitivity of the detection element is improved by reducing heat conduction loss from 0 to the substrate 32. Note that the entire detection element is packaged, and the infrared transmitting window 3
The infrared rays incident from 6 are irradiated onto all black 30.

In such an infrared detection element in a heat chamber, the relationship between the amount of incident infrared rays and the output of the detection element can be expressed as shown in equation (1) from an energy balance that takes radiant heat transfer into consideration.

(Tf-TS) -kV...(1)
Here, Q: Incident infrared energy σ: Stefan-Boltzmann constant ε: #J constant Emissivity of the object ε: Emissivity inside the element package ε: Emissivity on the inner surface of the lens barrel εR: Emissivity of the lens: Object to be measured The product of the view factor ν between the entire black area and the area of the gold black area is: The product of the view factor and the area of the gold black area between the inside of the element package and the entire black area is the product of the view coefficient ν between the inner surface of the lens barrel and the entire black area and the area of the gold black area. Product: Product of the view factor between the lens and the total black area and the total black area area T: Absolute temperature of the measurement target T: Absolute temperature of the element package T,: Absolute temperature of the inner surface of the lens barrel TR: Absolute temperature of the lens T: of the substrate Absolute temperature T, : Absolute temperature of the total black part α : Thermoelectromotive force constant determined by the thermoelectric material : Constant representing the output and detection sensitivity of the infrared detection element■ And, the infrared absorption rate (-emissivity) of the lens material
If an infrared transmitting material with a low infrared transmittance is used, it can be considered as R20. Therefore, the fourth term on the right side regarding radiation heat transfer with the lens in equation (1) can be treated as "0", and the influence of radiation from the lens can be ignored compared to other radiation heat transfer.

Therefore, equation (1) is expressed as equation (2).

4 Q=σε to (T-Tf)+σεpv v
v 4 4 4 (T - Tr ) + σε k (Tkp T ) - α (Tr - T8) mlIkv ... (2
) Also, when the environmental temperature is stable and the detection element temperature can be considered to be the same as the environmental temperature, T, -TR-T h -T
If S holds true and the object to be measured is near room temperature, the change in the temperature of the entire black area 30 due to the incident infrared rays is very small, so it can be safely assumed that T - T, O.

Therefore, equation (2) is expressed as equation (3).

tc (T'-T')-kV-
=C3) w v S Therefore, the temperature of the object to be measured is expressed by equation (4), and the object temperature T can be determined by compensating the sensing element temperature T with the output V of the sensing element.

Tw = ((kV/cyεtc) 10T'l
114v v S... (4) However, when the environmental temperature suddenly changes, the temperature of the lens barrel and element changes in the structure of the conventional infrared thermometer, and the heat conduction speed of each is different, resulting in a temperature difference, Tp= IFTk~T,
Therefore, the temperature of the object to be measured cannot be determined by equation (4), but must be determined from the relationship of equation (2). Further, the solid angle at which the detection element looks into the inner surface of the lens barrel and the element package is larger than the solid angle with respect to the measurement object narrowed by the lens.

Therefore, the view factor becomes large (to 1(to k(to )
Even if the temperature difference is small, the detection element will be affected by infrared rays from the element package and the inner surface of the lens barrel, and the output will contain errors.

Therefore, it is necessary to compensate for the detection element package temperature T and the lens barrel temperature T. However, in the conventional structure, when the temperature changes unsteadily, a temperature distribution exists on the inner surface of the lens barrel and is not uniform. In addition, when determining the experimental constants ε, and k for ε, it is virtually impossible to individually raise the lens barrel or element package to a different temperature than the element, so it is impossible to determine the experimental constants. , accurate temperature compensation is very difficult.

In addition, because the element has a membrane structure, the thermal resistance between the substrate and the hot junction is large, and if the element temperature changes suddenly due to a sudden change in the environmental temperature, the thermal balance will collapse and the temperature between the substrate and the hot junction will increase. A response difference ΔT occurs.

Since the temperature change of the total black area due to incident infrared rays from the measurement target near room temperature is very small, this temperature response difference is of the same order as the total black area temperature change due to infrared rays, and the detection element output includes this response error. α(Tr
'r, +AT) -kV, so the measurement results will include an extremely large error.

In the present invention, the structure is such that the temperatures of the lens barrel, package, and element change in the same way, and the rate of change changes slowly so as not to upset the thermal balance between the element substrate and the entire black. Therefore, even if the environmental temperature suddenly changes, the temperature to be measured can be determined with high accuracy using the above equation (4).

Case of Pyroelectric Detection Element Next, a case will be described in which a non-electroelectric infrared detection element is used as the detection element. A pyroelectric element detects the amount of incident infrared rays by the spontaneous polarization effect that occurs when the element temperature changes due to the incident infrared rays. Therefore, it is necessary to intermittent the incident infrared rays using an intermittent means such as a chopper (if the infrared rays are continuously irradiated, the element temperature will not change and the output will be saturated).

Then, when the incident infrared rays are interrupted by the chopper, the time when the incident infrared rays are irradiated and the time when the infrared rays from the measurement target are blocked by the chopper are repeated, and the detection element output is the amount of incident infrared rays to the detection element in these two states. The value is proportional to the difference.

Then, as in the case of the thermopile, the detection element output is determined from the energy balance and is expressed as in equation (5).

4 kV ■ σε to (T − Tr) − σε.

v v v 4 4 (5) σε (T − Tf ) RRR where ε : Emissivity of chopper : Product of view factor between chopper and element sensing part and element sensing part T : Chopper Absolute temperature V: Output k of the infrared detection element: Constant representing detection sensitivity Other values are the same as in equation (1) Therefore, when the environmental temperature is stable and the detection element, chopper, and lens barrel temperatures are the same as the environmental temperature, ,T, -T
R” T k−T holds true, and in addition, a film made of a material with high infrared reflectivity (gold, aluminum, etc.) is applied to the chopper surface.
Since Tc2Tr2T holds true if Tc2Tr2T is coated, Equation (5) is expressed by Equation (6).

4 kV = σε = (T - Tf) - σε.

v v v to (T-T')2σε to (T4 c c f vv
wT')...
・(6) Therefore, in this case as well, the temperature to be measured T is calculated using the formula (4
). However, when the environmental temperature changes significantly, as in the case of a thermopile, if there is a temperature difference between the lens barrel, chopper, and detection element, the object temperature cannot be determined by equation (4), and the element package temperature T or mirror Cylinder temperature Tk
It is necessary to compensate by the chopper temperature T0. Furthermore, if the rate of change in element temperature is fast, spontaneous polarization will occur due to element temperature change, and this error will be included in addition to the output due to temperature change due to incident infrared rays.

According to the present invention, as in the case of a thermopile, the temperatures of the lens barrel, package, chopper, and detection element change in the same way, and the rate of change is slow, so there is no effect of spontaneous polarization due to changes in element temperature.

Therefore, even if the environmental temperature changes, the temperature to be measured can be determined with high accuracy using the above equation (4).

[Operations and Effects of the Invention] As explained above, according to the present invention, the element and the sensor holder are thermally coupled, and it is possible to make the temperature of both the aperture part in the sensor holder and the detection element equal. Can, T,
-T R"" T k"' T S holds true, so it is possible to obtain an infrared thermometer that is simple, inexpensive, and capable of highly accurate temperature measurement without the need for advanced temperature compensation of the lens barrel. .

According to the present invention, a heat insulating structure is provided inside the case so as to reduce the temperature difference between the lens, the infrared detecting element, the sensor holder, and the aperture part, and to slow down the temperature change of the element temperature. Because of this structure, the temperature changes slowly so as not to upset the thermal balance of the infrared detection element even if the environmental temperature changes suddenly. Therefore, it is possible to reduce the output error due to the collapse of the thermal balance of the element due to a sudden change in the element temperature, and it is possible to perform highly accurate measurement even when the environmental temperature changes suddenly.

[Example] First Example Below, the structure and effects of the infrared thermometer according to the first example of the present invention will be described in detail.

FIG. 1 shows a cross-sectional view of the infrared thermometer of the first embodiment, and infrared rays emitted from the object to be measured enter a lens 50 that transmits infrared rays. Then, the infrared transmission lens focuses the incident infrared rays onto the infrared detection element 52. Therefore, the infrared detection element 52 detects the infrared light focused by the infrared transmission lens 50 and outputs an electrical signal. In this embodiment, a thermopile, which is an element of a heat chamber, is used as an infrared detection element.

This infrared detection element 52 and lens 50 are held inside a hollow sensor holder 54. An infrared incidence diaphragm 54a is formed in the front part of the sensor holder 54 to narrow down the field of view for measurement, and a lens 50 is provided.
An infrared ray exit diaphragm 54b is formed at the rear of the lens 50.

Here, the inner surface of the sensor holder 54 functions as a lens barrel of the lens 50, and the entire sensor holder 54 functions as a lens barrel for the lens 50.
0 and the detection element 52. Also,
Since the sensor holder 54 is made of a material with high thermal conductivity, the lens 50 and the detection element 5 are thermally coupled.

Further, a temperature sensor is attached to this infrared detection element 52, and the output of this temperature sensor 56 is used for temperature compensation of the output of the detection element 52.

On the other hand, a preamplifier 58 that amplifies the output from the detection element 52 is located behind the detection element 52 of the sensor holder 54.
is provided.

The components including the sensor holder 54 and the preamplifier 58 are housed integrally within a case 60. Also,
This case 60 has a heat insulating structure 60a inside thereof, which reduces the influence of environmental temperature on the sensor holder 54. Note that a transmission window 62 is provided at the front end of the lens 50 of the case 60.

External to the case 60 is a calculation unit that calculates the temperature of the object to be measured from the output of the infrared detection element 52 amplified by the preamplifier 58 and the output of the temperature sensor 56, and outputs a temperature display and an analog output corresponding to the temperature to the outside. A processing circuit 64 is provided.

Here, the material of the infrared condenser lens 50 is determined by the temperature range of the object to be measured, that is, the wavelength band of the infrared rays emitted from the object to be measured. In the first embodiment, the temperature to be measured is set in the measurement range of -10 to 150 degrees Celsius, near room temperature, and B a which easily passes infrared rays of 7 to 12 μm is set.
F2, CaF2.

SI, Ge materials, etc. are used.

When using Si or Ge materials, the lens surface is coated with an antireflection film to reduce reflection loss on the lens surface. Furthermore, when using the thermometer outdoors, it is necessary to prevent the thermometer from sensing diffused reflection of sunlight hitting the object to be measured. Therefore, the infrared condensing lens 50
, either the transmission window provided on the front surface of the detection element 52 or the transmission window 62 provided at the tip of the case 60 has a thickness of 6 μm.
It is preferable to use a long-wavelength transmission filter (long-pass filter) that passes only the above-mentioned long-wavelength infrared rays to prevent reflected sunlight from reaching the inside of the detection element 52.

Next, the sensor holder 54 is made of a material with high thermal conductivity, such as aluminum metal and copper metal.

The inner surface of the sensor holder 54, which serves as the entrance diaphragm 54a and the injection diaphragm 54b, is coated with a high emissivity paint. In general, materials with high thermal conductivity have a high reflectance of infrared rays (the emissivity of Nialuminum, which has a low surface emissivity, is 0.0
4 to 0.08), therefore, if left as is, infrared rays arriving from outside the measurement range will be reflected on the inner surface of the sensor holder, and this reflected infrared rays will enter the infrared detecting element 52. When the infrared detection element 52 senses this reflected infrared rays, the measurement field of view cannot be narrowed down effectively, and the entrance diaphragm 54g and the exit diaphragm 54b
will not function as an aperture.

Therefore, by coating the entrance diaphragm 54a and the exit diaphragm 54b on the inner surface of the sensor holder with a paint having a high emissivity, infrared rays arriving from outside the measurement range are absorbed, and together with the lens 50, the measurement field of view is limited.

In this way, the lens 50 and the aperture 54a.

The infrared rays focused with a limited field of view by the infrared rays 54b are detected by the infrared detection element 52 and converted into electrical signals.

Further, in the first embodiment, the package of the detection element 52 held in the sensor holder 54 has a structure in which all surfaces of the element, except for the infrared transmitting window on the entire surface of the element, are in close contact with the sensor holder 54.

Therefore, the detection element 52 and the sensor holder are thermally coupled sufficiently tightly. Furthermore, since the sensor holder 54 is made of a material with high thermal conductivity, the temperature difference between the detection element 52 and the sensor holder 54 is reduced, and the temperature difference between the detection element 52 and the sensor holder 54 is reduced.
2 can be accurately measured by the temperature sensor 56.

Therefore, when the environmental temperature changes, the entrance diaphragm 54a and the exit diaphragm 54b on the inner surface of the sensor holder 54 and the detection element 52
The temperature difference between the sensor holder 54 and the infrared rays emitted from the inner surface of the sensor holder 54 can be reduced. Therefore, the measurement accuracy of the infrared thermometer can be improved without highly accurately compensating the temperature of the inner surface of the sensor holder 54 (inner surface of the lens barrel).

A transmission window 62 provided at the tip of the case 60 prevents outside air from directly entering the entrance aperture portion 54a of the sensor holder 54. Therefore, it is possible to prevent the sensor holder 54 from being locally cooled or heated and causing temperature distribution.

The sensor holder 54 and the preamplifier circuit 58 are integrally housed in a case 60 that includes a heat insulating structure 60a inside.

The case 60 is made of a material with low thermal conductivity (in this first embodiment, a polyacetal resin with excellent workability and low thermal conductivity [thermal conductivity rate λ-0,2kca
l/mh'c]), an air layer is provided inside as a double cylindrical structure, and this insulating air layer 60b
It has a sealed structure. Therefore, the case 60 has excellent heat insulation properties, and even if the environmental temperature suddenly changes and a large thermal load is applied, the temperature changes in the sensor holder 54 and the preamplifier 58 can be made small and gentle. Therefore, it is possible to reduce the temperature difference between the detection element 52 and the sensor holder 54, and to reduce measurement errors caused by the imbalance of heat inside the detection element 52. Further, temperature drift that occurs when the temperature of the preamplifier 58 suddenly changes can also be suppressed to a small level.

As described above, according to the thermometer of the first embodiment, the function of the sensor holder 54 and the heat insulating case 60 allows the sensor holder 5 to
4, the temperature difference between the inner apertures 54a and 54b and the detection element 52 is reduced, and the temperature sensor 56 detects the detection element 52.
temperature can be measured accurately. Therefore, even in environments where the environmental temperature changes rapidly, the effects of temperature changes can be minimized, making it possible to measure temperature with high accuracy.

Figure 2 shows the environmental temperature measured by the infrared thermometer of Example 1 at 6.
These are the results of simultaneously measuring the thermometer output and the surface temperature of the object to be measured using a thermocouple when the temperature changed from 0°C to 20°C in 25 minutes. In this example, the temperature of the object to be measured is controlled to be constant at 35°C.

It is thus understood that the output of the thermometer of Example 1 is sufficiently stable despite sudden changes in the environmental temperature, and that highly accurate measurement is possible even when the environmental temperature changes significantly. .

FIG. 3 shows an example in which the infrared thermometer of the first embodiment is installed in the passenger compartment of an automobile.

In this way, by attaching the infrared thermometer to the needle base or ceiling in the vehicle interior, it is possible to detect the facial skin temperature of a passenger such as the driver. Therefore, if the vehicle air conditioner is controlled by taking this information about the occupant's facial skin temperature into account, the vehicle interior temperature can be controlled more appropriately to the occupant's condition.

In the above example, the entrance diaphragm 54a is provided in front of the lens 50, but this may be omitted and the lens 50 may be directly exposed to the outside. With such a configuration, the infrared thermometer can be shortened.

Second Embodiment The second embodiment concerns an infrared thermometer in which a pyroelectric detection element is used as a thermal infrared detection element.

When a pyroelectric detection element is used, in addition to the structure of the first embodiment, a chopper for cutting off incident infrared rays is required. Therefore, in this second embodiment, as shown in FIG.
A chopper 72 is built in between the detection element 70 and the lens 50 in the sensor holder 54.

Note that the chopper 72 of this second embodiment has a piezoelectric element 72
The piezoelectric element 72a is oscillated by the electric power from the chopper drive circuit 72c, and the shielding plate 72b interrupts the incidence of infrared rays on the detection element.

That is, the chopper drive circuit 72c applies a drive pulse of ±90V to the piezoelectric element 72a at a cycle of 10Hz or less.

This pulsed power supply causes the piezoelectric element 72a to bend and its free end to vibrate.

Therefore, a shielding plate 72b attached to this free end moves up and down in front of the detection element 52, and periodically cuts off the incident infrared rays.

Then, the arithmetic processing circuit 64 calculates the temperature of the object to be measured in synchronization with the output of the infrared detection element 52 based on the pulse voltage cycle applied to the piezoelectric element 72a from the chopper drive circuit 72c. Note that, similarly to the first embodiment, temperature compensation is performed based on the output of the temperature sensor 56.

In this example, a chopper 72 is also built inside the sensor holder 54. Therefore, even if the environmental temperature changes, the temperatures of the sensor holder 54, which functions as a lens barrel, the chopper 72, the detection element 52, and the temperature sensor 56 can be made equal. Further, as in the first embodiment, the case 60 can reduce the rate of temperature change of these components.

Therefore, in this example as well, T , −T R−T k
-T -T holds true, there is no need to perform sophisticated temperature compensation for the lens barrel and the temperature bar, and the temperature of the object to be measured can be determined with high accuracy using the above equation (4).

Third Embodiment The third embodiment is characterized in that a heater 80 is provided outside the sensor holder 3 of the first and second embodiments, as shown in FIG. Then, this heater 80 causes the sensor holder 5 to
4. Control the temperature at a constant level.

That is, using the temperature sensor 56 output of the detection element 52,
The temperature control circuit 82 feedback-controls the power supply to the heater 80 so that this temperature becomes a predetermined value.

Thereby, the temperature of the sensor holder 54 etc. is always kept constant. Note that since the heater 80 cannot normally be cooled, the temperature of the sensor holder 54 is controlled to be constant at a temperature higher than the ambient temperature (for example, 70 to 90° C.).

By controlling the temperature of the sensor holder 54 to always be constant in this way, even when the environmental temperature changes greatly, the detection element 52 housed inside the sensor holder 54, the inner surface of the sensor holder 54 that functions as a lens barrel, and the chopper 72 temperatures can be made isothermal. Therefore, T, -TR-Tk-Ts (-
The relationship T, ) holds true even if the environmental temperature suddenly changes, and the temperature of the object to be measured can be determined with high accuracy using equation (4) without performing advanced temperature compensation for the lens barrel, chopper, etc.

Note that if a Peltier element is used in the heater 80 described above, cooling and heating can be performed depending on the direction of the current.
The degree of freedom regarding the temperature setting can be expanded.

Furthermore, in each of the embodiments described above, the arithmetic processing circuit, chopper drive circuit, and temperature control circuit can be built into the case.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the configuration of an infrared thermometer according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the measurement results of the same embodiment, and Fig. 3 is an example of the same embodiment installed in a vehicle. 4 is a sectional view showing the configuration of the second embodiment, and FIG. 5 is a sectional view showing the configuration of the third embodiment.
FIG. 6 is a cross-sectional view showing the structure of the embodiment, FIG. 6 is a cross-sectional view showing the structure of the conventional example, and FIG. 7 is a characteristic diagram showing the measurement results of the conventional example. FIGS. 8(A) and 8(B) are a plan view and a front view showing the configuration of a heat chamber infrared detection element. 50... Lens 52... Infrared detection element 54... Sensor holder 54a... Incoming aperture 54b... Exit aperture 56... Temperature sensor 60... Case

Claims (1)

[Claims] A lens that condenses incident infrared rays, an aperture that further narrows down the infrared light condensed by the lens, and an electrical signal that detects the infrared rays that have passed through the lens and the aperture. a sensor holder that includes an infrared detection element and a lens barrel provided with the aperture, holds the infrared detection element and the lens, and thermally couples the lens barrel and the infrared detection element; and the infrared detection element has a temperature sensor installed near the infrared detecting element to detect the temperature of the infrared detecting element, and a heat insulating structure inside to house the sensor holder and the infrared detecting element to reduce the temperature difference between the infrared detecting element and the sensor holder. An infrared thermometer characterized by comprising: a case that reduces these temperature changes at the same time as increasing temperature changes;