JPH0643020A - Infrared ray detecting element - Google Patents

Abstract

PURPOSE:To obtain an inexpensive downsized infrared ray detecting element having high sensitivity by arranging a pair of conductive parts oppositely, While spacing apart from each other, on a semiconductor fiber thereby forming a hybrid fiber. CONSTITUTION:A pair of conductive parts 2a, 2b are arranged, while spacing apart from each other, on a semiconductor fiber 1 having electric resistance variable with temperature thus forming a hybrid fiber 3. The conductive parts 2a, 2b are composed of good conductors having resistance close to zero and the resistance R of infrared ray detecting element is determined by the gap (d) between the pair of conductive parts 2a, 2b according to a formula; R = rhod/s. represents resistivity of the fiber 1 and even when the resistivity rho is set high in order to enhance sensitivity of infrared ray detecting element, resistance R can be decreased by decreasing the gap (d). Since the resistance R can be controlled without varying the length and the cross-sectional area (s) of the fiber 1, a fiber 1 having high resistivity can be used with low resistance without imposing negative effect on the thermal characteristics of the fiber 1. Furthermore, number of fibers 1 to be arranged in parallel can be decreased because of low resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting element for converting infrared rays emitted from an object into an electric signal.

[0002]

2. Description of the Related Art Heretofore, as an infrared detecting element, a pyroelectric element utilizing a pyroelectric effect, a thermopile in which thermocouples are integrated, a thermistor bolometer using a metal oxide, and the like are known. However, these infrared detection elements have a difficulty in response speed in applications requiring a high response speed, and also have a limit in use in detecting the position of an infrared source to be detected, and also in terms of price. It was a disadvantage.

The present inventors have previously proposed an infrared detecting element using a semiconductor fiber whose electric resistance is changed by infrared irradiation, as an element capable of solving the above-mentioned drawbacks of the conventional infrared detecting element (Japanese Patent Laid-Open No. Hei 10 (1999) -264242). No. 2-71121), which is shown in FIG. In the figure, 11 is a semiconductor fiber having a length l and a cross-sectional area s, and a conductive paste 15 is provided at both ends thereof.
The electrodes 14a and 14b are adhered via a and 15b. 1
Reference numerals 6a and 16b are lead wires that connect the electrodes 14a and 14b to the infrared detection circuit.

In FIG. 2, when the infrared detecting element is connected to the infrared detecting circuit, when the semiconductor fiber 11 is irradiated with infrared rays, the temperature of the semiconductor fiber 11 rises and the semiconductor fiber 11 rises.
Has an internal resistance that changes with temperature. Therefore, the amount of energy of the emitted infrared rays can be detected by detecting this resistance change with the infrared detection circuit.

By the way, the infrared detection sensitivity of the infrared detection element using the semiconductor fiber 11 depends on the thermistor constant of the semiconductor fiber 11. The thermistor constant is a constant representing the magnitude of resistance change with respect to temperature change, and is determined by the material of the semiconductor fiber 11. The larger the value, the higher the sensitivity.

Further, the thermistor constant has a characteristic that it increases linearly in proportion to the resistivity of the semiconductor fiber 11, and the higher the resistivity of the semiconductor fiber 11, the higher the value (reference:
"Infrared sensor using functional semiconductor fiber and its application to human body detection" IEICE Transactions C-II Vol. J74-
C-II No. 5 PP. 458-466 May 1991).
Therefore, in order to increase the sensitivity of the infrared detection element,
The semiconductor fiber 11 having a large thermistor constant, that is, the semiconductor fiber 11 having a high resistivity may be used.

Here, the resistance value R of the semiconductor fiber 11 is R
= Ρ · l / s, where ρ, 1, and s are the resistivity, length, and cross-sectional area of the semiconductor fiber 11, respectively. Therefore, if the resistivity ρ is increased in order to increase the sensitivity of the infrared detection element, the resistance value R of the infrared detection element also increases, causing problems such as an increase in thermal noise, a reduction in noise resistance, and a complicated signal processing circuit. Occurs. For this reason, the resistance value R needs to be a low resistance of several MΩ or less, and in order to use the semiconductor fiber 11 having a large resistivity ρ with a low resistance in the related art, the length l of the semiconductor fiber 11 is shortened. The cross-sectional area s of the semiconductor fiber 11 is increased. A method of arranging a plurality of semiconductor fibers 11 in parallel has been used.

[0008]

However, when the length l of the semiconductor fiber 11 is shortened, heat radiation to the electrodes 14a and 14b is increased, so that the temperature rise of the semiconductor fiber 11 is suppressed and the detection sensitivity is lowered. I was there. Also, semiconductor fiber 1
When the cross-sectional area s of 1 was increased, the heat capacity of the fiber was increased and the response speed to infrared irradiation was slowed. As described above, according to the above methods and, the semiconductor fiber 11
Since the thermal characteristics of (1) change and the performance as an infrared detection element deteriorates, the resistivity ρ of the semiconductor fiber 11 that can be used is limited, and it is difficult to achieve high sensitivity.

Further, when a plurality of semiconductor fibers 11 are arranged in parallel, the number of fibers must be increased as the resistivity of the fibers is increased, and moreover, the fibers must be arranged without contact with other fibers. However, it is difficult to reduce the size of the infrared detection element, and it takes a lot of time and labor to manufacture the infrared detection element, which makes it difficult to reduce the cost of the infrared detection element.

The present invention has been made to solve the above problems, and has the following features:
An object of the present invention is to obtain a high-sensitivity, small-sized and inexpensive infrared detecting element which can control the resistance value of the infrared detecting element without changing the number thereof and can use the high resistivity semiconductor fiber with low resistance.

[0011]

An infrared detecting element according to the present invention comprises a semiconductor fiber whose electric resistance changes with temperature and a pair of conductors formed on the semiconductor fiber so as to face each other with a space therebetween. At least one hybrid fiber composed of a conductive part and a conductive part connected to both ends of the hybrid fiber so that electricity and heat can be satisfactorily transmitted to both the semiconductor fiber and the conductive part so that the hybrid fiber floats in the air. It is provided with a support electrode for supporting the.

[0012]

According to the present invention, the resistance value of the conductive portion formed on the semiconductor fiber is close to zero, and the resistance value R as the infrared detecting element is determined by the distance d between the pair of conductive portions, and the cross-sectional area of the semiconductor fiber is determined. Let s be R = ρd / s. Therefore, in order to increase the sensitivity of the infrared detecting element, the resistance value R becomes smaller if the distance d between the conductive portions is made smaller even if the resistivity ρ of the semiconductor fiber is made larger.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the basic structure of the infrared detecting element according to this embodiment, and 1 is a semiconductor fiber whose electric resistance changes with temperature, and is composed of SiC fiber, Si-Ti-C-O fiber, carbon fiber or the like. Reference numerals 2a and 2b denote a pair of conductive portions formed on the semiconductor fiber 1 so as to face each other at an arbitrary distance d in the length direction, and include gold, platinum, silver, aluminum,
It is made of a good conductor such as carbon.

3 is a semiconductor fiber 1 and a pair of conductive portions 2a, 2
At least one hybrid fiber 3 is provided. 4a and 4b are gold,
It is a support electrode made of a good conductor such as copper, and is adhered to both ends of the hybrid fiber 3 via conductive pastes 5a and 5b, and electricity and heat are well transferred to the ends of the semiconductor fiber 1 and the pair of conductive portions 2a and 2b. And the supporting electrodes 4a and 4b support the hybrid fiber 3 so as to float in the air. Reference numerals 6a and 6b are lead wires for connecting the support electrodes 4a and 4b to the infrared detection circuit. Also, l, s
Is the length and cross-sectional area of the semiconductor fiber 1.

Next, the operation of the infrared detecting element having the above structure will be described. Since the pair of conductive portions 2a and 2b formed on the semiconductor fiber 1 are formed of a good conductor, the resistance value thereof is close to zero, and the resistance value R of the infrared detecting element depends on the distance d between the pair of conductive portions 2a and 2b. Decided, R = ρd /
s. However, ρ is the resistivity of the semiconductor fiber 1.
Therefore, even if the resistivity ρ of the semiconductor fiber 1 is increased in order to increase the sensitivity of the infrared detection element, the conductive portions 2a, 2
The resistance value R can be reduced by reducing the distance d of b. Therefore, the resistance value R can be controlled without changing the length 1 and the cross-sectional area s of the semiconductor fiber 1, and the semiconductor fiber 1 having a high resistivity can be made to have a low resistance without affecting the thermal characteristics of the semiconductor fiber 1. Can be used in. or,
It is not necessary to arrange a large number of semiconductor fibers 1 in parallel to reduce the resistance, and the number can be reduced.

3 and 4 are a perspective view and a sectional view showing a concrete structure of the infrared detecting element according to this embodiment. The semiconductor fiber 1 has a diameter of about 50 μm, a room temperature resistivity of about 28 Ωcm, and a thermistor constant of about 1200K. The support electrodes 4a and 4b, which are made of carbon-based carbon and are formed on the substrate 7, are bonded via conductive pastes 5a and 5b. Reference numeral 8 indicates an infrared incident direction.

The substrate 7 is an alumina plate, and the semiconductor fiber 1
Has an opening 7a with a width of 5 mm in the major axis direction. The effective fiber length 1 of the semiconductor fiber 1 is the distance between the supporting electrodes 4a and 4b,
That is, the width of the opening 7a is 5 mm. Also, the supporting electrodes 4a, 4
Gold is vapor-deposited on the surface of b, the surfaces of the conductive pastes 5a and 5b, and the non-infrared light receiving surface side of the semiconductor fiber 1 so as to face each other at an arbitrary interval d to form the conductive portions 2a and 2b.

Here, the conductive portions 2a and 2b are connected to the semiconductor fiber 1.
Formed on the non-infrared receiving surface side of the conductive parts 2a, 2b
The gold used for the above is a material that reflects infrared rays well, and this is because the semiconductor fiber 1 absorbs infrared rays well and enhances the detection sensitivity.

With the above structure, the distance between the conductive portions 2a and 2b is 3 m.
An infrared detection element having m and 1 mm was manufactured, and its resistance value R was measured by a tester, and compared with an element (fiber length 1 is 5 mm) before forming the conductive portions 2a and 2b. As a result, at room temperature of 18 ° C., the resistance value is about 740 KΩ before forming the conductive portions 2a and 2b, about 430 KΩ when the distance after forming the conductive portions 2a and 2b is 3 mm, and about 140 KΩ when the distance is 1 mm. Assuming that the resistance value before forming the conductive portions 2a and 2b is 1, the resistance values are about 3/5 and 1/5 when the distance is 3 mm and 1 mm, respectively.

Next, the distance between the conductive portions 2a and 2b is 1 mm, 3
The Wheatstone bridge circuit, which is the infrared detection circuit shown in FIG. 5, was constructed using the mm infrared detection element, and the infrared detection characteristics were measured. In the figure, Rs is an infrared detection element, R ₁ , R ₂ and Rr are fixed resistors, Eb is a direct current power source, and E
out indicates an output terminal. The fixed resistors R ₁ , R ₂ and Rr have the same value as the resistance value of the infrared detection element Rs, and the voltage of the power source Eb is 8V. A black body furnace of 327 ° C. is used as an infrared source, and the infrared detecting element Rs is placed 11 cm away from the black body furnace.
Is installed and the infrared ray is emitted at room temperature of 18 ℃ to output terminal Eou.
The voltage change of t was measured. As a result, the conductive parts 2a, 2b
The output voltage is about 98 when the interval is 1mm or 3mm.
At 0 mV (after 40 dB amplification), the response speed was about 98 ms.
From these results, it has been clarified that the resistance value R of the infrared detecting element can be controlled by changing the distance between the conductive portions 2a and 2b, and the sensitivity and the response speed are not affected at all.

[0021]

As described above, according to the present invention, a pair of conductive portions are arranged on a semiconductor fiber at intervals to form a hybrid fiber. By changing this interval, the infrared detecting element The resistance value can be controlled.
Therefore, a semiconductor fiber having a high resistivity can be used with a low resistance without affecting its thermal characteristics, and an infrared detection element having high sensitivity and good responsiveness can be obtained.
Further, since it is not necessary to increase the number of semiconductor fibers, a small and inexpensive infrared detecting element can be obtained.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an infrared detection element of the present invention.

FIG. 2 is a basic configuration diagram of a conventional infrared detection element.

FIG. 3 is a perspective view showing a specific configuration of an infrared detection element according to the present invention.

FIG. 4 is a sectional view of an infrared detecting element according to the present invention.

FIG. 5 is a circuit diagram of an infrared detection circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor fiber 2a, 2b Electric conduction part 3 Hybrid fiber 4a, 4b Supporting electrode 5a, 5b Conductive paste Rs Infrared detecting element

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Muto Bundle 1-6-6 Moto-Akasaka, Minato-ku, Kyoto Within Sogo Security Guarantee Co., Ltd. 19 (72) Inventor Masaru Miyayama 1048-1-3-609, Nakanoshima, Tama-ku, Kawasaki City, Kanagawa Prefecture

Claims (1)

[Claims] 1. At least one or more composed of a semiconductor fiber whose electric resistance changes with temperature and a conductive portion formed of a pair of conductors formed on the semiconductor fiber so as to face each other with a space therebetween. The hybrid fiber and both ends of the hybrid fiber are connected so that electricity and heat can be well transmitted to both the semiconductor fiber and the conductive portion, and the hybrid fiber is provided with support electrodes for supporting the hybrid fiber so as to float in the air. Infrared detection element.