JP3182703B2 - Infrared detector - Google Patents

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 radiation emitted from an object into an electric signal.

[0002]

2. Description of the Related Art Conventionally, as an infrared detecting element, there have been known a pyroelectric element utilizing a pyroelectric effect, a thermopile integrated with a thermocouple, a thermistor bolometer using a metal oxide, and the like. However, these infrared detecting elements have drawbacks in terms of response speed in applications requiring a high response speed, and there is a limit in the use of the detected infrared source for position detection, and also in terms of price. Was disadvantageous.

The present inventors have previously proposed an infrared detecting element using a semiconductor fiber whose electric resistance changes upon irradiation with infrared rays, as an element capable of solving the above-mentioned drawbacks of the conventional infrared detecting element (Japanese Patent Laid-Open Publication No. HEI 9 (1994)]. This is illustrated in FIG. In the figure, reference numeral 11 denotes a semiconductor fiber having a length 1 and a sectional area s, and a conductive paste 15 is provided at both ends thereof.
The electrodes 14a and 14b are bonded via the electrodes a and 15b. 1
Reference numerals 6a and 16b are lead wires for connecting the electrodes 14a and 14b to the infrared detection circuit.

In FIG. 2, when the semiconductor fiber 11 is irradiated with infrared rays with the infrared detecting element connected to the infrared detecting circuit, the temperature of the semiconductor fiber 11 rises,
Changes the internal resistance according to the temperature. Therefore, by detecting this resistance change by the infrared detecting circuit, the energy amount of the irradiated infrared light can be detected.

[0005] The infrared detection sensitivity of the infrared detecting 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 the resistance change with respect to the temperature change, and is determined by the material of the semiconductor fiber 11, and the higher 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.
"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 detecting 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, l, 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 detecting element, the resistance value R of the infrared detecting element also increases, causing problems such as an increase in thermal noise, a decrease in noise resistance, and a complicated signal processing circuit. Occurs. For this reason, it is necessary that the resistance value R be low resistance of several MΩ or less, and conventionally, the length l of the semiconductor fiber 11 is shortened in order to use the semiconductor fiber 11 having a large resistivity ρ at a low resistance. The 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 increases, so that the temperature rise of the semiconductor fiber 11 is suppressed and the detection sensitivity is lowered. Was. 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 reduced. Thus, in the above-mentioned method and the method described above, the semiconductor fiber 11
Since the thermal characteristics of the semiconductor fiber 11 are changed and the performance as an infrared detecting element is deteriorated, the resistivity ρ of the semiconductor fiber 11 that can be used is limited, and it is difficult to increase the sensitivity.

When a plurality of semiconductor fibers 11 are arranged in parallel, the number of fibers must be increased as the resistivity of the fibers increases, and the fibers must be arranged without contacting other fibers. In addition, there is a problem that it is difficult to reduce the size of the infrared detection element, and it takes a lot of time and effort to manufacture the infrared detection element, and the infrared detection element cannot be made inexpensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a length, a cross-sectional area, and a length of a semiconductor fiber.
It is an object of the present invention to obtain a high-sensitivity, small-sized, and inexpensive infrared detecting element that can control the resistance value of the infrared detecting element without changing the number thereof and can use a high-resistivity semiconductor fiber with low resistance.

[0011]

The 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 at intervals. At least one or more hybrid fibers composed of a conductive portion, and both ends of the hybrid fiber are connected so that electricity and heat are well transmitted to both the semiconductor fiber and the conductive portion, so that the hybrid fiber floats in the air. Is provided with a supporting electrode for supporting.

[0012]

According to the present invention, the resistance value of the conductive portion formed on the semiconductor fiber is close to zero, 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. Is s, and R = ρd / s. Therefore, in order to increase the sensitivity of the infrared detecting element, if the spacing d between the conductive portions is reduced even if the resistivity ρ of the semiconductor fiber is increased, the resistance value R decreases.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of an infrared detecting element according to this embodiment, and 1 is a semiconductor fiber whose electric resistance changes with temperature, and is made of SiC fiber, Si-Ti-CO 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 oppose each other at an arbitrary interval d in the length direction, and include gold, platinum, silver, aluminum, and the like.
It is formed of a good conductor such as carbon.

Reference numeral 3 denotes a semiconductor fiber 1 and a pair of conductive portions 2a, 2
b, and at least one or more hybrid fibers 3 are provided. 4a and 4b are gold,
A support electrode made of a good conductor such as copper, which is adhered to both ends of the hybrid fiber 3 via conductive pastes 5a and 5b, so that electricity and heat are well transmitted to the semiconductor fiber 1 and the ends of the pair of conductive portions 2a and 2b. And the support electrodes 4a and 4b support the hybrid fibers 3 so as to float in the air. 6a and 6b are lead wires for connecting the support electrodes 4a and 4b to an 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 configuration 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 is close to zero, and the resistance value R of the infrared detecting element is determined by the distance d between the pair of conductive portions 2a and 2b. Determined, R = ρd /
s. Here, ρ is the resistivity of the semiconductor fiber 1.
Therefore, even when the resistivity ρ of the semiconductor fiber 1 is increased in order to increase the sensitivity of the infrared detecting element, the conductive portions 2a, 2
By reducing the distance d between b, the resistance value R can be reduced. For this reason, 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 high-resistance semiconductor fiber 1 can be reduced in resistance without affecting the thermal characteristics of the semiconductor fiber 1. Can be used with or,
It is not necessary to arrange a large number of semiconductor fibers 1 in parallel to reduce the resistance, and the number thereof can be reduced.

FIGS. 3 and 4 are a perspective view and a sectional view, respectively, showing the specific structure of the infrared detecting element according to this embodiment. The semiconductor fiber 1 has a diameter of about 50 μm, a normal temperature resistivity of about 28 Ωcm, and a thermistor constant of about 1200 K. It is made of a base carbon fiber and is adhered to the support electrodes 4a and 4b formed on the substrate 7 via conductive pastes 5a and 5b. Reference numeral 8 denotes the direction of incidence of infrared rays.

The substrate 7 is an alumina plate.
Has an opening 7a having 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 support electrodes 4a and 4b,
That is, the width of the opening 7a is 5 mm. Also, the support electrodes 4a, 4
Gold is deposited on the surface 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 oppose each other at an arbitrary interval d to form the conductive portions 2a and 2b.

Here, the conductive portions 2a and 2b are
Are formed on the non-infrared light receiving surface side of the conductive portions 2a, 2b
Is a material that reflects infrared light well, and the semiconductor fiber 1 absorbs infrared light well to increase detection sensitivity.

In the above structure, the distance between the conductive parts 2a and 2b is 3 m.
An infrared detection element having m and 1 mm was manufactured, and its resistance R was measured with a tester, and compared with the element before forming the conductive portions 2a and 2b (fiber length 1 was 5 mm). As a result, at a room temperature of 18 ° C., the resistance value is about 740 KΩ before forming the conductive parts 2a and 2b, about 430 KΩ when the gap after forming the conductive parts 2a and 2b is 3 mm, and about 140 KΩ when the gap is 1 mm. Assuming that the resistance value before forming the conductive portions 2a and 2b is 1, the resistance values are approximately 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,
A Wheatstone bridge circuit, which is an infrared detection circuit shown in FIG. 5, was configured using an infrared detection element having a diameter of mm, and infrared detection characteristics were measured. In the figure, Rs is an infrared detecting element, R ₁ , R ₂ , and Rr are fixed resistors, Eb is a DC power supply, and E
out indicates an output terminal. The fixed resistances R ₁ , R ₂ and Rr were set to the same value as the resistance value of the infrared detecting element Rs, and the voltage of the power supply Eb was set to 8V. Further, a black body furnace at 327 ° C. was used as an infrared ray source, and the infrared detecting element Rs was separated from the black body furnace by 11 cm.
And irradiate infrared rays at room temperature 18 ° C 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 in both cases of 1mm and 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 interval between the conductive portions 2a and 2b, and that the sensitivity and the response speed are not affected at all.

[0021]

As described above, according to the present invention, a hybrid fiber is formed by arranging a pair of conductive portions on a semiconductor fiber at an interval, and by changing the interval, a hybrid fiber is obtained. The resistance value can be controlled.
Therefore, a semiconductor fiber having a high resistivity can be used at a low resistance without affecting its thermal characteristics, and an infrared detecting element having high sensitivity and good responsiveness can be obtained.
Further, since there is no need to increase the number of semiconductor fibers, a small and inexpensive infrared detecting element can be obtained.

[Brief description of the drawings]

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

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

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

FIG. 4 is a sectional view of the 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 Conductive part 3 Hybrid fiber 4a, 4b Supporting electrode 5a, 5b Conductive paste Rs Infrared detecting element

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Muto 1-6-6 Moto-Akasaka, Minato-ku, Kyoto Sogo Security Services Co., Ltd. (72) Inventor Hiroaki Yanagita 1-3-19 Sasucho, Chofu-shi, Tokyo (72) Inventor Masaru Miyayama 1048-1-3-609 Nakanoshima, Tama-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-2-310430 (JP, A) JP-A-4-92656 (JP, U) ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 1/02 G01J 5/02 H01L 37/00 H01L 31/00-31/09

Claims (1)

(57) [Claims] At least one or more semiconductor fibers each comprising 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 at intervals. A hybrid fiber, and a support electrode that is connected to both ends of the hybrid fiber so that electricity and heat are well transmitted to both the semiconductor fiber and the conductive portion, and that supports the hybrid fiber so as to float in the air. Infrared detecting element.