JPH0755558A - Infrared detector - Google Patents

Abstract

PURPOSE:To improve an output sensitivity without delaying a responding speed by setting a long axis/short axis of a semiconductor fiber sectional surface for constituting a photoreceiver, a compensator to a specific range. CONSTITUTION:An infrared receiving element 1 has a photoreceiver 2, a compensator 3 made of at least one semiconductor fiber in which its electric resistance is varied upon emitting of an infrared ray. The fibers are connected to electrodes to form a circuit, in which materials, diameters, lengths, number and arrays are necessarily set the same and a long axis/short axis of its section is necessarily set to 2-10. If the ratio is less than 2, a high output sensitivity is not obtained, and when the diameters, the lengths are regulated to raise the output sensitivity, a responding speed is decelerated. If the ratio exceeds 10, high output sensitivity cannot be obtained, and its sectional area is desirably 1500-15000mum<2>.

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,
Specifically, the present invention relates to an infrared detecting element using a semiconductor fiber whose electric resistance changes by irradiation with infrared rays.

[0002]

2. Description of the Related Art Conventionally, as an infrared detecting element, one using a pyroelectric element utilizing a pyroelectric effect or a thermopile in which a thermocouple is integrated is known.

However, these infrared detecting elements have a difficulty in response time in applications where a high response speed is required, and their use in detecting the position of an infrared source to be detected is also limited. Further, the above conventional infrared detecting element is also disadvantageous in terms of price.

The present inventors have previously proposed an infrared detecting element using a semiconductor fiber whose electric resistance is changed by infrared irradiation (Japanese Patent Laid-Open No. 2-71121), and further, a specific silicon carbide fiber as the semiconductor fiber. Infrared detecting element using JP-A-2-310430, infrared detecting element using specific carbon fiber (JP-A-3-96824, JP-A-3-140825), and arrangement of semiconductor fibers Infrared detecting element (Japanese Patent Laid-Open No. 4-337425)
(Japanese Patent Application Laid-Open No. 4) and an infrared detecting element that adjusts the positional relationship between semiconductor fibers and is equipped with a reflection plate and a light-shielding plate (Japanese Patent Application Laid-Open No. Hei 4)
No. 337425) has been proposed.

The infrared detecting element using the above-mentioned semiconductor fiber has a small thermal time constant (τ) and is advantageous in terms of cost, and solves the above-mentioned drawbacks of the infrared detecting element using a pyroelectric element or a thermopile. It was a reward.

However, the above conventional infrared detecting element has a problem that the output sensitivity is not sufficient. The output sensitivity and the thermal time constant are in a proportional relationship, and there is a drawback that if the fiber diameter or the fiber length is increased in order to improve the output sensitivity, the thermal time constant also increases and the response speed becomes slow.

On the other hand, in the infrared detecting element, the viewing angle of the light receiving portion depends on the size of the light collecting port, and it is difficult to freely change the viewing angle.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and improves output sensitivity without delaying the response speed, and further allows the viewing angle of the light receiving portion to be adjusted freely. An object is to provide a changeable infrared detection element.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the major axis / uniaxial ratio in a cross section of a semiconductor fiber constituting a light receiving portion and a compensating portion falls within a specific range. It is achieved by

That is, the infrared detecting element of the present invention comprises a light receiving portion made of at least one semiconductor fiber whose electric resistance is changed by infrared irradiation, and a compensating portion made of at least one semiconductor fiber similar to the above. In addition, the long axis / uniaxial ratio is 2 to 10 in the cross section of the semiconductor fiber of the infrared detecting element and the light receiving section and the compensating section.

The present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing an example of the infrared detection element of the present invention. In the figure, 1 is an infrared detecting element, 2 is a light receiving part, 3 is a compensating part, 4 is a substrate, 5 is a reflecting plate, and d is the width of the light receiving part.

As shown in FIG. 1, the infrared light receiving element 1 of the present invention includes a light receiving portion 2 made of at least one semiconductor fiber whose electric resistance changes by infrared irradiation, and at least one semiconductor similar to the above. And a compensator 3 made of fibers. The semiconductor fibers of the light receiving part and the compensating part are respectively connected to electrodes (not shown) to form a circuit.

The semiconductor fibers here may be those whose electric resistance changes by infrared rays, and the semiconductor fibers of the light receiving part and the compensating part must be made of the same material, diameter, length, number and arrangement.

As the semiconductor fiber, at least one selected from the group consisting of silicon carbide fiber, carbon fiber and precursor fibers thereof is preferable, and the room temperature specific resistance is particularly 10 ² to.
10 ⁶ Ω · cm, thermistor constant B is 1000-300
Those of 0k are preferable. The diameter, length, arrangement method, and number of the semiconductor fibers are not particularly limited, and the diameter is 10 to 100 μm.
m, the length is 0.5 to 4 mm, the number is 1 to 100, and the arrangement method is preferably a method in which the fibers are arranged with a fiber interval of 20 to 1000 μm. Further, the width (d) of the light receiving portion is 1 to 3 m.
A width of about m is desirable.

In the infrared detecting element 1 of the present invention, as shown in FIG. 2, the ratio (a / b) of the major axis (a) and the minor axis (b) of the cross section of the semiconductor fiber is 2 to 10. It is necessary. In FIG. 2, reference numeral 6 indicates the cross-sectional shape of the semiconductor fiber. When a / b is less than 2, high output sensitivity cannot be obtained,
If the output sensitivity is increased by adjusting the fiber diameter and the fiber length, the response speed becomes slow. If a / b exceeds 10, high output sensitivity cannot be obtained. The cross-sectional area of this semiconductor fiber is 1
It is desirable that the thickness is 500 to 15000 μm ² .

Further, in the infrared detecting element 1 of the present invention, as shown in FIG. 1, a reflecting plate is provided on the opposite side of the semiconductor fiber of the light receiving section 2 from the infrared irradiating side and spaced from the semiconductor fiber by a predetermined distance. Arrangement of 5 is desirable. As shown in FIG. 3, this reflection plate preferably has a concave curved surface in the direction of the semiconductor fiber 6, and the radius of curvature (r) of this reflection plate 5 is 2 to 4 of the width (d) of the light receiving portion. It is preferably double. The distance (h) between the bottom surface of the reflector 5 and the semiconductor fiber 6 is preferably 0.5 to 1 times the radius of curvature (r) of the reflector. The thickness of the reflection plate 5 is preferably 200 μm or less, and particularly preferably 50 to 200 μm. This is because if the thickness of the reflection plate 5 is more than 200 μm, the temperatures of the front and back surfaces of the reflection plate do not match at the time of infrared irradiation, and the infrared detection accuracy tends to be adversely affected. Further, the reflector 5 having a thickness of less than 50 μm is generally difficult to handle. As the above-mentioned reflector 5,
A material having a high infrared emissivity and a low emissivity is preferably used, and a gold plate, an aluminum plate, a silver plate, a zinc plate or a plated plate of these metals is particularly preferable.

By using such a reflector,
The output sensitivity is further improved, and the viewing angle of the light receiving section can be freely changed.

In the infrared detecting element 1 of the present invention, the electrodes connected to both ends of the semiconductor fiber of the light receiving portion and the compensating portion are not particularly limited and may be gold plating, copper plating or the like which is commonly used.

In the present invention, it is necessary to dispose the semiconductor fiber of the light receiving portion 2 and the semiconductor fiber of the compensating portion 3 close to each other, and the distance between both semiconductor fibers is preferably 5 mm or less, particularly preferably 0.5. ~ 5 mm. This is because if the distance exceeds 5 mm, it becomes difficult to match the conditions other than infrared irradiation with both semiconductor fibers, and the infrared detection accuracy tends to be adversely affected. Further, it is generally technically difficult to set the interval to less than 0.5 mm and to irradiate only the semiconductor fibers of the light receiving portion with infrared rays.

The infrared detecting element of the present invention may be any one as long as it has the above constitution, and other conditions are not particularly limited.

The detection circuit for detecting infrared rays using the infrared detecting element of the present invention compensates for a change in the electric resistance of the semiconductor fiber of the light receiving section with that of the semiconductor fiber of the compensating section, so that the semiconductor fiber can be electrically irradiated by infrared rays. A Wheatstone bridge circuit is preferable as long as the circuit can detect only the resistance change.

[0022]

In the infrared detecting element of the present invention, since the major axis / uniaxial ratio in the cross section of the semiconductor fiber is controlled within a certain range, the output sensitivity can be improved without delaying the reaction rate. Further, since the irradiated infrared rays are reflected by the reflecting plate having the concave surface and hit the semiconductor fiber again, the output is further increased as compared with the case without the reflecting plate, and the viewing angle of the light receiving portion can be freely changed.

[0023]

The present invention will be described in more detail based on the following examples and comparative examples.

Examples 1 to 3 and Comparative Example 1 The cross-sectional area, major axis, minor axis, major axis / minor axis ratio (a /
An infrared detecting element as shown in FIG. 1 was prepared by using silicon carbide fiber (b) and having a length of 4 mm (normal temperature resistivity: 300 Ω · cm, thermistor constant: 1500 k).

In the infrared detecting element of FIG. 1, the substrate (8
mmL × 5mmW × 0.5mmT) is 6mmL × 3mm
It is an alumina plate having an opening of W, and four electrodes are provided on its upper surface by gold plating. Then, four silicon carbide fibers are arranged in parallel between the pair of electrodes at an interval of 0.5 mm and are connected via a conductive adhesive to form a light receiving portion. Four silicon carbide fibers are similarly connected between the other pair of electrodes to form a compensating portion.

Next, a Wheatstone bridge circuit was constructed using this infrared detecting element. The bridge resistance of this circuit was 2 MΩ, and the applied voltage was a DC voltage of 8V.

The infrared detecting element is replaced by a black body furnace (furnace temperature:
It is placed 11 cm away from 50 ° C.) and irradiated with infrared IR (peak wavelength λmax: 9 μm) at room temperature (21 ° C.) for 100 seconds to measure the voltage output between output terminals and thermal time constant (amplification degree: 40 dB), and the obtained viewing angle was evaluated. The results are shown in Table 1.

[0028]

[Table 1]

As is clear from the results shown in Table 1, the output sensitivity of Examples 1 and 2 is higher than that of Comparative Example 1. On the other hand, in Examples 1 and 2, it is understood that in order to improve the output sensitivity, the thermal time constant increases and the response speed is delayed.

Examples 4 to 15 and Comparative Examples 2 to 5 Example 1 except that a flat reflector and the following three types of curved reflectors were respectively provided on the opposite side of the semiconductor fiber from the infrared irradiation side.
3 and Comparative Example 1, the infrared detection element was prepared.

(1) Curved reflector 1: radius of curvature (r) 2.
2 mm, distance between the bottom surface of the reflector and the semiconductor fiber (h) 1.
4 mm. (2) Curved reflector 2: radius of curvature (r) 2.0 mm, distance (h) 2.0 mm between the bottom surface of the reflector and the semiconductor fiber. (3) Curved reflector 3: radius of curvature (r) 4.0 mm, distance (h) 2.0 mm between bottom of reflector and semiconductor fiber.

Example 1 using these infrared detecting elements
3 to 3 and Comparative Example 1, the Wheatstone bridge circuit is configured to measure the voltage output between the output terminals by infrared irradiation, the obtained viewing angle is evaluated, and the results are shown in Table 2.
Shown in.

[0033]

[Table 2]

As is clear from Table 2, the output sensitivity is further improved by providing the reflection plate. Further, by using the reflection plate having the concave curved surface, the viewing angle of the light receiving portion can be freely changed.

[0035]

As described above, by using the infrared detecting element of the present invention, the output sensitivity can be improved without delaying the response speed. Furthermore, by using a fixed reflector, the output sensitivity can be further improved and the viewing angle of the light receiving part can be freely changed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an infrared detection element of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor fiber used in the infrared detection element of the present invention.

FIG. 3 is a conceptual diagram showing a positional relationship between a semiconductor fiber and a reflector of a light receiving section in the infrared detection element of the present invention.

[Explanation of symbols]

1: infrared detection element, 2: light receiving part, 3: compensating part, 4: substrate, 5: reflector, 6: semiconductor fiber.

Claims (2)

[Claims] 1. An infrared detection element comprising: a light receiving section made of at least one semiconductor fiber whose electric resistance changes by irradiation of infrared rays; and a compensating section made of at least one semiconductor fiber similar to the above. And, in the cross section of the semiconductor fiber of the light receiving part and the compensating part, the major axis / uniaxial ratio is 2-1.
An infrared detection element characterized by being 0. 2. A reflecting plate disposed on the opposite side of the semiconductor fiber of the light receiving portion from the infrared irradiation side, the reflecting plate being arranged at a predetermined distance from the semiconductor fiber, and the reflecting plate with respect to the semiconductor fiber direction. The infrared detection element according to claim 1, which has a concave curved surface.