JPH04337425A - Infrared radiation detection element - Google Patents

Abstract

PURPOSE:To continuously detect a very small amount of infrared radiation that is emitted from human body at good sensitivity by integrating a light receiving element and a reference device together, and by arranging a reflection plate on a light receiving element side and a shade plate on a reference device side, respectively on a specific condition. CONSTITUTION:A detector element is provided with at least one semiconductor of varying electric resistance and an electrode connected to both ends of the fiber 1. A light receiving element 3 is provided with a reflection plate 2 for reflecting infrared radiation arranged on the reverse side of the irradiation of the fiber 1. An electrode is connected to both ends of a semiconductor fiber 1, and a reference element is provided with a shade plate 4 arranged on the infrared irradiation side of the fiber 1'. An interval (d) between the fiber 1 and the reflection plate 2 and an interval d' between the fiber 1' and the shape plate 4 are the same. The reflection plate 2 and the shade plate 4 are of the same material. The fiber 1 of the light receiving element 3 and the fiber 1' of the reference element 5 are arranged in proximity to one another. By forming such a structure, a very small amount of infrared radiation of the level emitted from human body can thus be continuously detected by a detector element at good sensitivity.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an infrared detection element,
Specifically, the present invention relates to an infrared detection element using semiconductor fibers whose electrical resistance changes upon irradiation with infrared rays.

0002

2. Description of the Related Art Hitherto, as infrared detecting elements, devices using a pyroelectric element utilizing the pyroelectric effect, a thermopile in which thermocouples are integrated, and the like are known.

However, these infrared detection elements have a drawback in terms of response time for applications that require a high response speed, and there are also limits to their use in detecting the position of an infrared source to be detected. Furthermore, the conventional infrared detection element described above is disadvantageous in terms of cost.

The present inventors previously proposed an infrared detection element using a semiconductor fiber whose electrical resistance changes upon irradiation with infrared rays (Japanese Patent Application Laid-Open No. 71121/1999 [Patent Application No. 2225/1989]).
No. 06]), and an infrared detection element using a specific silicon carbide fiber as the semiconductor fiber (Japanese Patent Application Laid-Open No. 2-3104
No. 30 [Japanese Patent Application No. 1-131435]), infrared detection elements using specific carbon fibers (Japanese Patent Application No. 1-232888, Japanese Patent Application No. 1-277050), and infrared rays in which the arrangement of semiconductor fibers is specified. Detection element (Patent application Hei 2-297066
No.) was proposed.

[0005] The infrared detecting element using the above semiconductor fiber has a small thermal time constant (τ) and is advantageous in terms of cost, and eliminates the drawbacks of the infrared detecting element using the above-mentioned pyroelectric element, thermopile, etc. It was something to be gained.

By the way, the above-mentioned conventional infrared detection element using a semiconductor fiber has at least one semiconductor fiber 1 and a conductive adhesive 10 on both ends thereof, as shown in FIG. 7 or 8.
It consisted of an electrode 9 connected through a lead wire 11, and was connected to an infrared detection circuit as shown in FIG. 9 or 10 through a lead wire 11. The infrared detection circuit shown in FIG. This is to detect. Furthermore, the infrared detection circuit shown in FIG.
A Wheatstone bridge circuit is configured by the infrared detection element 13 and resistors 19, 20, and 21, and can detect infrared IR with higher sensitivity.

Furthermore, there is an infrared detection circuit shown in FIG. 11 which is less susceptible to the effects of ambient temperature and self-heating than the above-mentioned infrared detection circuit. This infrared detection circuit is
Two infrared detection elements 13 and 13' are connected in series, and a Wheatstone bridge circuit is formed by them and resistors 22 and 23, so that only one infrared detection element 13 is irradiated with infrared IR. It is.

[0008]

[Problem to be Solved by the Invention] However, all of the above-mentioned conventional infrared detection circuits using infrared detection elements have a problem in that the circuit characteristics tend to change over time during measurement, which is called drift. .

In other words, it is difficult for an infrared detection circuit using one infrared detection element as shown in FIG. 9 or 10 to make corrections in response to temperature changes in semiconductor fibers, and drift occurs due to changes in temperature. occurred, and it was not possible to improve detection accuracy.

In addition, in an infrared detection circuit using two infrared detection elements as shown in FIG. 11, one as a light receiving element and the other as a reference element, although drift due to changes in temperature etc. is considerably reduced, Merely blocking infrared rays to the light-receiving element and the reference element cannot avoid the occurrence of minute differences in temperature conditions between the light-receiving element and the reference element. In particular, when continuously irradiated with infrared rays, drift was likely to occur due to radiant heat from the blocking member of the reference element. Therefore, there is a limit to the improvement of detection accuracy, and in particular, it has been difficult to continuously detect infrared rays of such a small amount as emitted from the human body.

The present invention has been made in view of the problems of the prior art, and provides an infrared detection element capable of sufficiently suppressing the occurrence of drift in an infrared detection circuit and increasing output. The purpose of this technology is to enable the continuous and sensitive detection of small amounts of infrared rays.

0012

[Means for Solving the Problems] As a result of intensive research aimed at achieving the above object, the present inventors have developed a method for connecting the light receiving element and the reference element by bringing the semiconductor fibers on the light receiving element side and the semiconductor fibers on the reference element side close to each other. In addition, a reflector is added on the photodetector side.
The inventors have discovered that the above problem can be solved by arranging a light shielding plate on the reference element side under specific conditions, and have arrived at the present invention.

That is, the infrared detecting element of the present invention includes at least one semiconductor fiber whose electrical resistance changes when irradiated with infrared rays, electrodes connected to both ends of the semiconductor fiber, and a side of the semiconductor fiber opposite to the infrared ray irradiated side. a light-receiving element comprising a reflector disposed at a predetermined distance from the semiconductor fiber, a semiconductor fiber similar to the semiconductor fiber, electrodes connected to both ends of the semiconductor fiber, and an infrared irradiation side of the semiconductor fiber; a reference element comprising a light-shielding plate made of the same material as the reflecting plate and spaced apart from the semiconductor fiber by the same distance as the interval, and the semiconductor fiber of the light-receiving element and the semiconductor fiber of the reference element are provided. It is characterized by being arranged close to each other.

Another infrared detecting element of the present invention includes at least one semiconductor fiber whose electrical resistance changes when irradiated with infrared rays, electrodes connected to both ends of the semiconductor fiber, and an infrared ray irradiated side of the semiconductor fiber. a light-receiving element having a reflection plate arranged at a predetermined distance from the semiconductor fiber on the opposite side; a semiconductor fiber similar to the semiconductor fiber; and electrodes connected to both ends of the semiconductor fiber; The present invention is characterized by comprising a reference element in which fibers are arranged on the opposite side of the reflecting plate and spaced apart from each other by the same distance as the above-mentioned interval.

The present invention will be explained in more detail below with reference to the drawings.

FIGS. 1(a) to 1(e) are schematic cross-sectional views showing an example of the infrared detecting element of the present invention. In the same figure,
1 and 1' are semiconductor fibers, 2 is a reflection plate, 3 is a light receiving element, 4
is a light shielding plate, 5 is a reference element, 6 is a lighting opening, 7 is a heat radiation opening, d
is the distance between the semiconductor fiber 1 and the reflection plate 2, d' is the distance between the semiconductor fiber 1' and the light shielding plate 4, x is the distance between the semiconductor fiber 1 and the semiconductor fiber 1', θ is the viewing angle, and the arrow indicates the infrared rays. (IR)
The irradiation directions are shown respectively. Note that when the same member is used for both the light receiving element and the reference element, a dash is added to the reference element side to distinguish them.

As shown in FIG. 1(a), the infrared detecting element of the present invention comprises a semiconductor fiber 1, electrodes (not shown) connected to both ends of the semiconductor fiber 1, and an infrared ray irradiation side of the semiconductor fiber 1. A light-receiving element 3 comprising a reflector 2 disposed on the opposite side that reflects infrared rays, a semiconductor fiber 1', electrodes (not shown) connected to both ends of the semiconductor fiber 1', and an infrared rays of the semiconductor fiber 1'. The reference element 5 includes a light shielding plate 4 disposed on the irradiation side for blocking infrared rays.

The semiconductor fibers 1 and 1' used in the present invention may be of any type as long as their electrical resistance changes with infrared rays;
It is necessary to make the material, diameter, length, number and arrangement the same.

The semiconductor fibers 1 and 1' are preferably at least one selected from the group consisting of silicon carbide fibers, carbon fibers, and their precursor fibers, particularly those having a specific resistance at room temperature of 102 to 106 Ω·cm and a thermistor constant B of 1000.
~3000k is preferred. In addition, semiconductor fiber 1,
The diameter, length, arrangement method, and number of fibers 1' are not particularly limited.
It is preferable to align them with each other.

In the infrared detecting element of the present invention, it is necessary that the distance d between the semiconductor fiber 1 and the reflecting plate 2 and the distance d' between the semiconductor fiber 1' and the light shielding plate 4 be the same. Reflector 2
This is to match the radiation conditions from the light shielding plate 4 to the semiconductor fiber 1 with the radiation conditions from the light shielding plate 4 to the semiconductor fiber 1'. Also,
The distance d, d' is preferably 0.1 to 1.5 mm, and 0.5
~1.0 mm is particularly preferred. Spacing d, d' is 0.1m
If it is less than 1.5 mm, the amount of radiant energy increases and the infrared detection accuracy tends to be adversely affected.
This is because the viewing angle θ becomes smaller when the angle of view is larger than 1, so that the amount of infrared rays irradiated to the semiconductor fiber 1 becomes smaller, and the output tends to decrease.

Furthermore, in the infrared detecting element of the present invention, the reflecting plate 2 and the light shielding plate 4 need to be made of the same material, and preferably have the same thickness. This is to match the heating conditions of the reflection plate 2 and the light shielding plate 4 by infrared rays. Further, the thickness of the reflecting plate 2 and the light shielding plate 4 is preferably 200 μm or less, particularly preferably 50 to 200 μm. This is because if the thickness of the reflecting plate 2 and the light shielding plate 4 exceeds 200 μm, the temperatures on the front and back sides of each plate will not match when irradiated with infrared rays, which tends to adversely affect the accuracy of infrared detection. Also, the thickness is 50
The reflecting plate 2 and the light shielding plate 4 having a diameter of less than μm are generally difficult to handle. As the reflecting plate 2 and the light shielding plate 4, those having a high infrared reflectance and a low emissivity are preferably employed, and gold plates, aluminum plates, silver plates, zinc plates, or plated plates of these metals are particularly preferable.

[0022] In the infrared detecting element of the present invention, the electrodes connected to both ends of the semiconductor fibers 1, 1' are not particularly limited, and commonly used electrodes such as gold plating or copper plating may be used.

In the present invention, it is necessary to arrange the semiconductor fiber 1 of the light-receiving element 3 and the semiconductor fiber 1' of the reference element 5 close to each other, and the distance x between the semiconductor fiber 1 and the semiconductor fiber 1' is preferably 5 mm or less, particularly preferably 0.5 to 5
It is mm. This is because if the distance x exceeds 5 mm, it becomes difficult to match conditions other than infrared irradiation between semiconductor fibers 1 and semiconductor fibers 1', which tends to adversely affect infrared detection accuracy. Further, it is generally technically difficult to make the distance x less than 0.5 mm and to irradiate only the semiconductor fiber 1 with infrared rays. Furthermore, when arranging the light receiving element 3 and the reference element 5, the reflection plate 2
It is preferable that the light-shielding plate 4 and the light-shielding plate 4 are parallel to each other, and that the light-shielding plate 4 does not block infrared irradiation of the semiconductor fiber 1 of the light-receiving element 3.

The infrared detecting element of the present invention may have the above configuration, and other conditions are not particularly limited.

For example, as shown in FIG. 1(b), the reflection plate 2 and the light shielding plate 4 are integrated, and the reflection plate 2 and the light shielding plate 4 are integrated.
The member between the semiconductor fibers 1 and 1' may pass through the middle of the semiconductor fibers 1 and 1'. Alternatively, as shown in FIG. 1(c), the semiconductor fibers 1 and the semiconductor fibers 1' may be placed in a box that includes a reflection plate 2 and a light shielding plate 4 and has a light opening 6. In this case, in order to dissipate heat near the semiconductor fiber 1', it is preferable to provide a heat dissipation hole 7 on the back side of the semiconductor fiber 1' as shown in FIG. 1(d). The heat sink 7 is particularly preferred.

Furthermore, in the infrared detecting element of the present invention, a semiconductor fiber 1' may be arranged on the back side of the reflecting plate 2 of the light receiving element 3, as shown in FIG. 1(e). This is preferable because the reflection plate 2 also serves as the light shielding plate 4 of the reference element 5, and there is no need to separately provide the light shielding plate 4. In this case as well, the distance d between the semiconductor fiber 1 and the reflector 2 and the distance between the semiconductor fiber 1' and the reflector 2 (shading plate 4)
It is necessary to make the interval d' and the interval d, d' the same.
is preferably 0.1 to 1.5 mm, and 0.5 to 1.0 mm
is particularly preferred.

A detection circuit for detecting infrared rays using the infrared detection element of the present invention includes a detection circuit for detecting infrared rays using the semiconductor fiber 1 of the light receiving element 3.
Any circuit may be used as long as it can detect only the change in the electric resistance of the semiconductor fiber 1 due to infrared irradiation by referring to the change in the electric resistance of the semiconductor fiber 1' of the reference element 5, and a Wheatstone bridge circuit is preferable.

[0028]

[Function] In the infrared detecting element of the present invention, the radiant heat from the reflector to the semiconductor fiber in the light receiving element and the radiant heat from the light shielding plate to the semiconductor fiber in the reference element are made uniform. Therefore, by using the infrared detection element of the present invention, it is possible to detect only the resistance change of the semiconductor fiber due to infrared irradiation without being influenced by other factors.
In other words, an infrared detection circuit in which almost no drift occurs can be obtained.

Furthermore, in the infrared detecting element of the present invention, the irradiated infrared rays are reflected by the reflector and hit the semiconductor fiber again, so the output is increased compared to the case without the reflector.

[0030]

EXAMPLES The present invention will be explained in more detail below based on Examples and Comparative Examples.

Example 1 An infrared detecting element of the present invention shown in FIG. 2 was prepared using silicon carbide fibers (specific resistance at room temperature: 300 Ω·cm, thermistor constant: 1500 k) having a diameter of 50 μm and a length of 4 mm. In the figure, 8 is a substrate, 9, 9' are electrodes, 10, 10' are conductive adhesives, 11, 11' are lead wires, 12 is a spacer, the white arrows indicate the stacking direction, and the other The symbols indicate the same things as in FIG. Note that when the same member is used for both the light receiving element and the reference element, a dash is added to the reference element side to distinguish them.

In the infrared detection element shown in FIG. 2, the substrate 8 (
8mmL x 5mmW x 0.5mmT) is 6mmL x 3m
It is an alumina plate having an opening of mW, and four electrodes 9, 9' are provided on its upper surface by gold plating. Four silicon carbide fibers 1 are arranged in parallel at intervals of 0.5 mm between a pair of electrodes 9 and connected via a conductive adhesive 10. Four silicon carbide fibers 1' were similarly connected between the other pair of electrodes 9', and the distance x between the silicon carbide fibers 1 and 1' was 1 mm. Furthermore, lead wires 11 and 11' are connected to each electrode 9 and 9'.

[0033] The reflector plate 2 has a size of 8 mm L x 5 mm W x 0.1 m.
It is made of mT aluminum foil, and is provided with a heat dissipation port 7 of 3 mm L x 3 mm W. Further, the light shielding plate 4 is also made of aluminum foil similar to the reflecting plate 2, and is provided with a light opening 6 of 3 mm L x 3 mm W. Further, the spacer 12 is an alumina plate having the same shape as the substrate 8.

Next, the above light shielding plate 4, spacer 12,
A Wheatstone bridge circuit shown in FIG. 3 was constructed using an infrared detection element obtained by laminating the substrate 8 and the reflection plate 2. In the figure, 13 is an infrared detection element, 14 and 15 are resistors, 16 is a power source, and 17 is an output terminal, and the other symbols are the same as those in FIG. 2. The bridge resistance of this circuit was 2 MΩ, and the applied voltage was 8 V DC.

The infrared detection element 13 is placed 11 cm away from the black body furnace (furnace temperature: 50°C), and the infrared IR (
Peak wavelength λmax: 9 μm) at room temperature (21°C)
It was irradiated for 0 seconds, and the voltage change between the output terminals 17 was measured (amplification degree: 40 dB).

The results are shown in FIG.

As is clear from FIG. 4, the infrared detection element of Example 1 had a good output voltage of 113 mV, and no drift occurred at all. Therefore, it has been found that by using this infrared detecting element, trace amounts of infrared rays can be detected continuously and with high sensitivity.

Example 2 An infrared detecting element was produced in the same manner as in Example 1 except that a reflector 2 without a heat dissipation port 7 was used, and a Wheatstone bridge circuit was constructed to detect the difference between output terminals 17 by infrared irradiation. The voltage change was measured.

The results are shown in FIG.

As is clear from FIG. 4, although the infrared detecting element of Example 2 slightly drifted compared to the infrared detecting element of Example 1, it did not cause a serious problem in infrared detection. Further, the output voltage was good at about 100 mV. Therefore, it has been found that by using this infrared detection element, it is possible to detect a small amount of infrared rays continuously and with a certain degree of sensitivity.

Example 3 Pitch-based carbon fiber with a diameter of 50 μm and a length of 4 mm (specific resistance at room temperature: 340 Ω·cm, thermistor constant: 1800 k)
Using this method, an infrared detection element of the present invention shown in FIG. 5 was created. The symbols in the figure indicate the same things as in FIG. 2.

In the infrared detecting element shown in FIG. 5, the substrate 8 is an alumina plate with a thickness of 0.5 mm formed into the shape shown in the figure, and four electrodes 9 are plated with gold on the top surface.
, 9' are provided. Three pitch-based carbon fibers 1 are arranged in parallel at intervals of 1 mm between a pair of electrodes 9 and connected via a conductive adhesive 10. Three pitch-based carbon fibers 1' are similarly connected between the other pair of electrodes 9'. In addition, each electrode 9, 9' has a lead wire 11.
, 11' are connected.

[0043] The reflector plate 2 has a size of 5 mm L x 3 mm W x 0.1 m.
mT aluminum foil, pitch-based carbon fiber 1 and 1
’ is inserted between. The reflector 2 in the infrared detection element shown in FIG. 5 also has the function of a light shielding plate 4, and the distance between the pitch-based carbon fiber 1 and the reflector 2 and the distance between the pitch-based carbon fiber 1' and the reflector 2 (light-shielding plate 4) The distance between both is 0.75 mm.

Next, a Wheatstone bridge circuit was constructed using the above infrared detection element in the same manner as in Example 1, and the voltage change between the output terminals 17 due to infrared irradiation was measured.

The results are shown in FIG.

As is clear from FIG. 4, the infrared detection element of Example 1 had a good output voltage of 124 mV, and no drift occurred. Therefore, it has been found that by using this infrared detecting element, trace amounts of infrared rays can be detected continuously and with high sensitivity.

Comparative Example 1 An infrared detection element 13 was prepared in the same manner as in Example 1 except that the reflector 2 was not provided, a Wheatstone bridge circuit was constructed, and the voltage change between the output terminals 17 due to infrared irradiation was measured. .

The results are shown in FIG.

As is clear from FIG. 4, the infrared detection element of Comparative Example 1 had severe drift and low output voltage. Therefore, it has been found that this infrared detection element cannot continuously detect infrared rays with high sensitivity.

Comparative Example 2 Using the same silicon carbide fiber as in Example 1, an infrared detecting element shown in FIG. 6 was produced. The symbols in the figure indicate the same things as in FIG.

A substrate 8 in the infrared detecting element shown in FIG. 6 is obtained by cutting the substrate used in Example 1 in half, and two electrodes 9 are provided on its upper surface by gold plating. Then, between a pair of electrodes 9, four silicon carbide fibers 1 are placed at 0.5
The electrodes 9 are arranged in parallel at mm intervals and connected via a conductive adhesive 10, and a lead wire 11 is connected to each electrode 9. In addition, the reflector plate 2 is 4mmL x 5mmW x 0.1mmT.
aluminum foil.

Next, a Wheatstone bridge circuit shown in FIG. 10 is constructed using the infrared detecting element obtained by laminating the substrate 8 and the reflector 2, and this circuit is used to detect infrared rays in the same manner as in Example 1. The voltage change between the output terminals 17 due to irradiation was measured. The bridge resistance of the above circuit was 2 MΩ, and the applied voltage was 8 V DC voltage.

The results are shown in FIG.

As is clear from FIG. 4, the infrared detecting element of Comparative Example 2 had significant drift. Therefore,
It was found that this infrared detection element cannot continuously detect infrared rays with high sensitivity.

[0055]

As described above, by using the infrared detection element of the present invention, it is possible to obtain an infrared detection circuit in which the occurrence of drift can be sufficiently suppressed and the output can be increased.

Therefore, with the infrared detection element of the present invention, it has become possible to continuously and sensitively detect minute amounts of infrared rays emitted from the human body, which was extremely difficult in the past. It is extremely useful for applications such as security systems.

[Brief explanation of drawings]

FIGS. 1A to 1E are schematic cross-sectional views each showing an example of an infrared detection element of the present invention.

FIG. 2 is an exploded perspective view showing an example of the infrared detection element of the present invention.

FIG. 3 is a circuit diagram showing an example of an infrared detection circuit using the infrared detection element of the present invention.

FIG. 4 is a graph showing infrared measurement results in Examples and Comparative Examples.

FIG. 5 is an exploded perspective view showing another example of the infrared detection element of the present invention.

FIG. 6 is an exploded perspective view showing an example of an infrared detection element other than the present invention.

FIG. 7 is a top view showing an example of a conventional infrared detection element.

FIG. 8 is a top view showing another example of a conventional infrared detection element.

FIG. 9 is a circuit diagram showing an example of a conventional infrared detection circuit.

FIG. 10 is a circuit diagram showing another example of a conventional infrared detection circuit.

FIG. 11 is a circuit diagram showing still another example of a conventional infrared detection circuit.

[Explanation of symbols]

1, 1′ Semiconductor fiber 2 Reflector 3 Photo receiving element 4. Light shielding plate 5 Reference element 6. Lighting opening 7 Heat radiation vent 8 Board 9, 9' electrode 10, 10' Conductive adhesive 11, 11' Lead wire 12 Spacer

Claims (7)

[Claims] 1. At least one semiconductor fiber whose electrical resistance changes when irradiated with infrared rays, electrodes connected to both ends of the semiconductor fiber, and an electrode separated from the semiconductor fiber for a predetermined period on the opposite side of the semiconductor fiber from the infrared irradiated side. a light-receiving element comprising a reflective plate arranged at a distance from the semiconductor fiber; a semiconductor fiber similar to the semiconductor fiber; an electrode connected to both ends of the semiconductor fiber; a reference element having a light-shielding plate made of the same material as the reflecting plate, which is spaced apart from each other; and a semiconductor fiber of the light-receiving element and a semiconductor fiber of the reference element are arranged close to each other. An infrared detection element characterized by: 2. The light receiving element and the reference element are arranged such that the reflecting plate and the light shielding plate are parallel to each other and the light shielding plate does not block infrared irradiation to the semiconductor fiber of the light receiving element. , The infrared detection element according to claim 1. 3. The infrared detecting element according to claim 1, wherein a distance between the semiconductor fiber of the light receiving element and the semiconductor fiber of the reference element is 5 mm or less. 4. The reflecting plate and the light shielding plate are metal plates, aluminum plates, silver plates, zinc plates, or plated plates of these metals, and have a thickness of 200 μm or less and the same thickness. 3. The infrared detection element according to any one of 3 to 3. 5. At least one semiconductor fiber whose electrical resistance changes when irradiated with infrared rays, electrodes connected to both ends of the semiconductor fiber, and an electrode separated from the semiconductor fiber for a predetermined period on the opposite side of the semiconductor fiber from the infrared irradiation side. a light-receiving element equipped with a reflector arranged as above, a semiconductor fiber similar to the semiconductor fiber, and electrodes connected to both ends of the semiconductor fiber,
An infrared detecting element comprising: a reference element in which the semiconductor fibers are arranged on the opposite side of the reflecting plate and spaced apart from each other by the same distance as the spacing. 6. The reflective plate is a metal plate, an aluminum plate,
The infrared detection element according to claim 5, which is a silver plate, a zinc plate, or a plated plate of these metals, and has a thickness of 200 μm or less. 7. The distance between the semiconductor fiber and the reflective plate is 0.
．． The infrared detecting element according to any one of claims 1 to 6, having a diameter of 1 to 1.5 mm.