JPH03273689A - Highly sensitive thermopile - Google Patents

Abstract

PURPOSE:To achieve a sufficient output voltage over a wide temperature range of an object to be measured including normal temperature and obtain a highly sensitive thermopile where influence of fluctuation of room temperature is eliminated by placing a cooling means near one edge of a connection terminal. CONSTITUTION:A thin-film thermocouple pattern 2 according to combination of a first thermoelectric material 2a and a second thermocouple material 2b is located on an insulating substrate 1. A connection terminal at an inside of the thermocouple pattern 2 constitutes a warm contact 21 and the outside connection terminal constitutes a cool contact 22. An insulating layer 3 is coated at a region including a circumferential part of the warm contact 21 and a infrared-ray absorbent layer 4 such as gold black is formed on it. A thin-film Peltier element pattern 5 is located at an outside region of the thin-film thermocouple pattern 2 and at a rear part of the insulating substrate 1. The configuration constitute an absorption junction part 51 and a heat build-up junction part 52 which combines an n-type thermocouple semiconductor 5a and a p-type thermocouple semiconductor 5b and interlocks one inner terminal and the other outer terminal alternately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermopile in which a large number of thermocouples are connected in parallel for use in various types of non-contact temperature detection, human body detection, etc.

[Prior Art] A plan view showing the structure of a conventional thermopile is shown in FIG. 5, and a cross-sectional view is shown in FIG. 6, respectively.

5 and 6, a thin film thermocouple pattern 2 in which thin film thermocouples of a combination of a first thermoelectric material 2a- and a second thermoelectric material 2b" are arranged in series on an insulating substrate 1-
' is formed by means such as vapor deposition or sputtering.

The combinations of the first and second thermoelectric materials 2g- and 2b- are usually B1-3b, B1-B1Sb, B1-Te.
A large combination of thermoelectric powers α such as is selected.

On the inside of each thin film thermocouple pattern 2', hot junctions 21'' are arranged and on the outside, cold junctions 22'' are arranged, alternately connecting the ends of the first and second thermocouple patterns, respectively. Further, the back surface of the cold contact 22'' portion of the board is fixed to a ring-shaped portion of the heat sink 6-. An insulating layer 3 is provided in a region including the outer periphery of the hot junction 21' of the thin film thermocouple pattern 2'.
' is coated, and an infrared absorbing layer 4 of completely black or the like is coated on top of that.
- is formed.

Here, the principle by which a thermopile detects infrared rays will be explained with reference to FIGS. 5 and 6.

The infrared rays generated from the object to be detected are absorbed by the infrared absorbing layer 4-, the temperature of the infrared absorbing layer 4' increases, and the insulating layer 3
- to increase the temperature of the hot junction 21' of the thin film thermocouple pattern 2-. Let that temperature be Th. cold junction 22
' is maintained at approximately the temperature Te of the heat sink 6' (approximately equal to room temperature), so there is a temperature difference ΔT-Th-Te (approximately equal to room temperature) between the hot junction 21' and the cold junction 22'. Unit ℃
) occurs. Output voltage V based on this ΔT. ' is expressed by the following equation (1).

■o −α×ΔT−XN ...(1) (However, ΔT
--Th-Te) Here, a is the thermoelectric power per pair of thin film thermocouple patterns (μ
V/'C), and N is the number of pairs in the thin film thermocouple pattern.

Therefore, the output voltage V in the above equation (1). - occurs between output terminals 81 and 81 in the figure.

[Problems to be Solved by the Invention] The conventional thermopiles shown in FIGS. 5 and 6 have the following problems (a) and (b).

(a) When the temperature of the object to be detected is close to room temperature, the temperature difference ΔT between the thermocouple pattern hot junction and the heat sink is very small, so the output voltage V. Since - is small, it is below the noise level during amplification, and accurate temperature detection cannot be performed.

(b) As the temperature of the heat sink changes as the room temperature changes, the output voltage vO- is subject to changes in the room temperature.

Therefore, the technical problem of the present invention is to improve the conventional drawbacks, and
It is an object of the present invention to provide a highly sensitive thermopile that achieves a sufficient output voltage over a wide temperature range of the object to be measured, including room temperature, and eliminates the influence of room temperature fluctuations.

[Means for Solving the Problems] According to the present invention, an infrared absorbing portion is disposed on an insulating substrate, and one end of a connecting end of a dissimilar metal is disposed at a position away from the absorbing portion,
A highly sensitive thermopile is obtained in which a thermopile is formed with a thermocouple whose other end is disposed in the infrared absorbing portion, and a cooling means is disposed near one end of the connection end.

According to the present invention, there is obtained a high-sensitivity thermopile characterized in that the thermocouple is a thin film thermocouple pattern formed on the insulating substrate by vapor deposition or sputtering.

According to the present invention, there is obtained a high-sensitivity thermopile according to any one of the above-described high-sensitivity thermopiles, characterized in that the cooling means includes a heat-absorbing junction of a Beltier element.

According to the present invention, there is obtained a high-sensitivity thermopile characterized in that in the high-sensitivity thermopile, the Bertier element has a heat-generating joint on a heat sink disposed near the insulating substrate.

According to the present invention, there is obtained a high-sensitivity thermopile characterized in that a thermocouple pattern is provided on the surface of the insulating substrate, and a thin film Peltier element pattern is provided on the back surface opposite to the surface.

According to the present invention, there is obtained a high-sensitivity thermopile characterized in that, in any of the above-described high-sensitivity thermopiles, a thin film temperature detection element pattern is provided near the other end of the connection end of the dissimilar metal on the insulating substrate. It will be done.

[Example code] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a plan view of an embodiment of a thermopile according to the present invention, and FIG. 2 shows a sectional view of FIG. 1.

In FIGS. 1 and 2, an organic film (5 to 10 μm thick) made of polyimide, polyester, or the like is used as the insulating substrate 1, as in the past.

On the insulating substrate 1, a thin film thermocouple pattern 2 consisting of a series connection of thermocouples made of a combination of a first thermoelectric material 2a and a second thermoelectric material 2b is formed by means such as vapor deposition or sputtering. .

The inner connection end of the thermocouple pattern 2 constitutes a hot junction 21, and the outer connection end constitutes a cold junction 22.

An insulating layer 3 is coated on a region including the circumference of the hot junction 21, and an infrared absorbing layer 4 such as goldfish is formed thereon.

In the outer region of the thin film thermocouple pattern 2 and on the back side of the insulating substrate 1, a thin film Peltier element pattern 5 is provided. Its structure is such that an n-type thermoelectric semiconductor 5a and a P-type thermoelectric semiconductor 5b are combined to form a heat-absorbing joint 51 and a heat-generating joint 52, which alternately connect one inner end and the other outer end. By doing so, it is a configuration in which multiple lines are connected in series.

Terminal 13 connected to one end of the Bertier element group in the figure.
14 to flow the current I in the direction of the arrow, the heat-absorbing function is realized in the heat-absorbing joint 51, and the heat-generating function is realized in the heat-generating joint 52, as described above.

The heat-absorbing joints 51 are set to a size that just surrounds each cold junction 22 of the thermocouple pattern 2 from the back side of the insulating substrate 1, while the heat-generating joints 52 are thermally joined to the heat sink 6, and thus , from the heat-absorbing joint 51 to the heat-generating joint 52
Heat is continuously transferred to In addition, thin film thermocouple pattern 2
A thin film temperature sensing element 7 having terminals 15 and 16 is formed near the terminal of the cold junction 22 .

That is, this thin film temperature detection element 7 is formed on the same side as the thin film thermocouple pattern 2 of the insulating substrate 1.

FIG. 3 is a diagram showing current supply control to a Vertier element connected to a high-sensitivity thermopile according to an embodiment of the present invention.

In FIG. 3, the temperature of the cold junction 22 of the thermocouple is detected by a temperature detection element, and an externally provided current supply control circuit 60 controls the current supplied to the Bertier element to cool the thermocouple. Controls the temperature of the contact part to a constant value.

Next, the detection principle of the high-sensitivity thermopile according to the embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

The infrared rays generated from the object to be detected are absorbed by the infrared absorbing layer 4, and the temperature of this infrared absorbing layer 4 rises, causing the insulating layer 3 to rise.
The temperature of the hot junction 21 of the thin film thermocouple pattern 2 is increased through the process. The temperature at this time is defined as TH.

On the other hand, the temperature of the cold junction of the thin film thermocouple pattern 2 is cooled by the endothermic junction 51 of the thin film Peltier element pattern 5 via the insulating substrate 1, and the temperature of the thin film provided near the cold junction 22 is The temperature is controlled to be constant by controlling the current flowing through the Peltier element pattern 5 using the supply current control circuit 60 based on the output of the detection element 7. Its temperature is maintained at a temperature T, which is sufficiently lower than room temperature.

Therefore, the output voltage V from the output terminal 8.8-.

is vO"αXΔTxN (However, ΔT-TH-TL)...
-(2) Here, α is the thermoelectric power (μV/''C) per pair of thin film thermocouple pattern 2, and N is the number of pairs of thin film thermocouple pattern 2.

The high-sensitivity thermopile according to the embodiment of the present invention has the following improvements compared to the conventional example.

(ro) is realized.

(i) The temperature of the cold junction 22 is determined by the thin film Peltier element pattern 5.
Since the heat-absorbing junction 51 is used for cooling, the temperature difference ΔT between the hot junction 21 and the cold junction 22 for the same measured object temperature is
is configured to be larger than before. Therefore,
The output voltage characteristics of the thermopile according to the embodiment of the present invention compared with the conventional one are (ΔT>ΔT', therefore v, >v, -(1).

(see formula (2)).

FIG. 4 is a diagram showing the output voltage characteristics of the thermopile according to the embodiment of the present invention. As shown in FIG. 4, the thermopile according to the embodiment of the present invention draws a curve that is an upward translation of the conventional characteristic curve.

Therefore, the output voltage is higher and the sensitivity is higher than that of the conventional device, and the conventional problem of the output voltage being less than the amplifier noise when the temperature of the object to be measured is near normal temperature is solved.

Note that the shaded area in the figure indicates the noise level of the amplifier.

(b) The temperature TL of the cold junction 22 is maintained at a constant temperature by controlling the temperature at the heat-absorbing junction 51 using a Peltier element, so the output voltage is no longer affected by room temperature, which was a problem in the past. This enables highly accurate non-contact temperature detection.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a highly sensitive thermopile that has a higher output voltage than the conventional thermopile and is not affected by amplifier noise.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the high-sensitivity thermopile according to the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG. 3 is a Peltier element connected to the high-sensitivity thermopile according to the embodiment of the present invention. FIG. 4 is a comparative illustration of the output voltage characteristics of a thermopile according to an embodiment of the present invention and a conventional thermopile. FIG. 5 is a diagram showing an example of a conventional thermopile. The figure is a sectional view of FIG. 5. In the figure, 1.1' is an insulating substrate, 2, 2' are thin film thermocouple patterns, 2a, 2a- are Ml thermoelectric materials, 2b, 2b= are second thermoelectric materials, 21.21- are hot junctions, 22.2';
1'' is a cold junction, 3.3' is an insulating layer, 4.4' is an infrared absorbing layer, 5 is a thin film Peltier element pattern, 5a is an n-type semiconductor, 5b is a P-type thermal semiconductor, 51 is an endothermic junction, 52 is a heat generating junction, 6.6゛ is a heat sink, 60 is a power supply #Im circuit, 7 is a thin film temperature detection element, 8.8-.81゜81- is a thin film thermocouple pattern output terminal. Figure 3 Figure 6゜ Figure 4 □ Measured object temperature ("C) Figure 5 Figure 6ffl

Claims (1)

[Claims] 1. Forming an infrared absorbing section on an insulating substrate, and a thermocouple in which one end of a connection end of a dissimilar metal is disposed at a position away from the absorbing section, and the other end is disposed in the infrared absorbing section. A highly sensitive thermopile characterized in that a cooling means is disposed near one end of the connection end. 2. In the high-sensitivity thermopile according to the first claim,
A highly sensitive thermopile characterized in that the thermocouple is a thin film thermocouple pattern formed on the insulating substrate by vapor deposition or sputtering. 3. The high-sensitivity thermopile according to claim 1 or 2, wherein the cooling means includes a heat-absorbing joint of a Peltier element. 4. In the high-sensitivity thermopile according to the third claim,
The high-sensitivity thermopile is characterized in that the Peltier element has a heat-generating joint on a heat sink disposed near the insulating substrate. 5. In the high-sensitivity thermopile according to the fourth claim,
A highly sensitive thermopile characterized in that a thermocouple pattern is provided on the surface of the insulating substrate, and a thin film Peltier element pattern is provided on the back surface opposite to the surface. 6. The high-sensitivity thermopile according to any one of claims 1 to 5, characterized in that a thin film temperature sensing element pattern is provided near the other end of the connection end of the dissimilar metal on the insulating substrate. Sensitivity thermopile.