JPH0453371B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to infrared measurement, and uses infrared rays to measure temperature, earth resource observation, weather observation, pollution observation, crime prevention/disaster prevention monitoring, transportation, and thermal management. This invention relates to a pyroelectric infrared detection element that monitors and measures processes.

BACKGROUND ART A thermistor infrared detector with an immersion lens is an infrared detector that improves infrared detection performance by directly attaching an infrared detection element to a condensing lens to increase condensing efficiency and improve infrared detection performance. (Electronic Technology Research Institute Investigation Report No. 177
No. PP65-66) An example is shown in Figure 4. Figure a is a side view, and figure b is a bottom view. A thermistor element 11 is in close contact with an immersion type germanium lens 12. 1
3 and 14 are electrodes for signal extraction. 1
5 and 16 are lead wires for taking out signals, respectively.

A conventional thermistor-type infrared detection element detects infrared heat absorption by a change in resistance due to temperature, and generally has a structure in which lead wires 15 and 16 are taken out from the side ends of the thermistor element 11.

The infrared light incident on the immersion type germanium lens 12 is condensed by the lens 12 and is incident on the thermistor element 11. The temperature of the thermistor element 11 increases due to the incident infrared light, and its resistance value decreases, so that the current flowing through the lead wires 15 and 16 increases. The amount of change in resistance is used to quantitatively detect incident infrared light and perform various measurements.

Problems to be Solved by the Invention This thermistor type infrared detection element is inferior in sensitivity compared to a pyroelectric type infrared detection element. On the other hand, if you try to combine a pyroelectric infrared detection element with an immersion lens, since the pyroelectric infrared detection element uses the polarization of the pyroelectric material, the electrodes cannot be taken out from the side like a thermistor type. The problem is that the sensitivity cannot be fully demonstrated. To increase the sensitivity sufficiently,
It is necessary to form electrodes on the infrared incident surface, that is, the surface in close contact with the infrared condensing lens, and on the surface opposite thereto, that is, the back surface of the infrared incident surface. However, it is not easy to form a signal extraction electrode on the infrared incident surface in terms of manufacturing. In particular, since it is required to form an electrode that is transparent to infrared rays and does not reflect, no pyroelectric infrared detection element that is in close contact with a condenser lens has been developed. The present invention solves all of these problems and realizes a highly sensitive pyroelectric infrared detection element with a condenser lens.

Means for Solving the Problems In order to solve the above problems, the present invention comprises an immersion lens made of a material that is transparent to infrared rays and has electrical conductivity, and a pyroelectric element is closely attached to the bottom surface of the immersion lens. The immersion lens also serves as one electrode of the pyroelectric element, and a signal extraction electrode is formed on the other side of the pyroelectric element.

Function In the above configuration, the immersion lens collects incident infrared light and makes it enter the pyroelectric element. On the other hand, a highly sensitive pyroelectric infrared detection element can be obtained by using the condensing lens itself as the ground electrode of the pyroelectric element and extracting the signal from the signal extraction electrode on the other side of the pyroelectric element.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 show the structure of a pyroelectric infrared detection element with a condenser lens according to the present invention, with FIG. 1 being a side view and FIG. 2 being a bottom view. Reference numeral 2 denotes an infrared focusing lens made of a material having electrical conductivity and transparent to infrared rays, such as germanium or silicon. In this example, germanium was used. Germanium has a high resistivity of 50Ω-cm,
It is sufficiently transparent to infrared rays even with a resistance of about 10 Ω-cm. The radius of curvature of germanium lens 2 is 1.5 mm, and the diameter is 3
mm hemispherical lens. An antireflection coating is required on the curved surface on the infrared incident side. As the antireflection film, a vapor-deposited film of zinc sulfide was used. The wavelength center was set at 10 μm. A pyroelectric element 1 was formed as a thin film on the bottom surface of the germanium lens 2 by sputter deposition. The film thickness was 3 μm, the material was lead titanate, and after vapor deposition, a gold-black signal extraction electrode 3 and infrared absorbing layer was formed on the back side. Gold-black absorbs most of the infrared rays. As shown in Figure 2, the lead wire extraction part is made of aluminum at the part that protrudes slightly from the effective light receiving surface.
A vapor deposited film was formed, and lead wires 4 were taken out using an ultrasonic bonder.

The germanium lens itself is used as the ground electrode of the pyroelectric element 1. The pyroelectric element 1 is made of a material with very high resistance, so even if there is some resistance as an electrode, it will not affect its function or performance.As mentioned above, the specific resistance of the germanium lens is at most 50Ω.
cm, so there is no problem in using it as the electrode of the pyroelectric element 1.

The lead wire from the germanium lens 2 should be taken out a little away from the pyroelectric element 1 and as close to the pyroelectric element 1 as possible, as shown in Fig. 2.
An Al vapor deposition film is formed, and the lead wire 5 is fixed and taken out from there using an ultrasonic bonder.

The dimensions of the pyroelectric element 1 were 0.3 mmφ. After connecting the lead wires, the pyroelectric element 1 is polarized. This polarization treatment was carried out using a general method, and was carried out at 200° C. by applying an electric field of 60 KV/cm for about 20 minutes.

The incident infrared rays are condensed by a condensing lens 2 and incident on the pyroelectric element 1. The pyroelectric element generates pyroelectricity in response to incident infrared rays, and the generated pyroelectricity is extracted from the signal extraction electrode 3.

This configuration makes it possible to create an electrode that is transparent to infrared rays and has almost no reflection, making it possible to combine it with a lens with high light collection efficiency while maintaining the high sensitivity of the pyroelectric element. Become.

FIG. 3 shows another embodiment of the invention. This embodiment is an example in which a pyroelectric infrared detection element having the structure shown in FIG. 1 is provided with a field-of-view limiting plate 6, and the aperture of the field-of-view limiting plate 6 is 0.9 mmφ. This embodiment can improve the SN ratio by reducing sensitivity to unnecessary light outside the field of view.

Effects of the Invention As described above, the present invention provides a pyroelectric infrared detection element in which a pyroelectric element is closely attached to one surface of an infrared lens having electrical conductivity, and this infrared lens is also used as an electrode of the pyroelectric element. Since the electrodes are provided in the thickness direction of the pyroelectric element and the condenser lens is in close contact with the pyroelectric element, it is possible to obtain a pyroelectric infrared detection element with very high sensitivity. For example, due to the focusing characteristics of the focusing lens,
The infrared radiation incident on the 0.3mmφ pyroelectric element is approximately 9 times greater, and even after subtracting the 20% infrared reflection loss and infrared absorption loss, it is 7 times greater, and the sensitivity as an infrared detection element has been improved by 7 times. .

Additionally, by installing a field-of-view limiter of 0.9 mmφ in front of the condenser lens, we were able to suppress sensitivity outside the field of view while maintaining the sensitivity improvement rate.

[Brief explanation of the drawing]

1 and 2 show the structure of a pyroelectric infrared detection element with a condenser lens according to the present invention, with FIG. 1 being a side view and FIG. 2 being a bottom view. FIG. 3 is a cross-sectional side view of a pyroelectric infrared detection element showing another embodiment of the present invention, and FIGS. 4a and 4b show the structure of a conventional thermistor infrared detection element with an infrared condensing lens. They are a side view and a bottom view. 1...Pyroelectric element, 2...Infrared condensing lens, 3...
...Signal extraction electrode, 4, 5...Lead wire, 6...
...Visual field restriction plate.

Claims (1)

[Claims] 1. A pyroelectric element is brought into close contact with one surface of an infrared condensing lens, the infrared condensing lens is used as one electrode of the pyroelectric element, and the other electrode is placed on the other surface of the pyroelectric element. A pyroelectric infrared detection element characterized in that: 2. A pyroelectric infrared detection element according to claim 1, in which the infrared condensing lens is used as a ground electrode. 3. The pyroelectric infrared detection element according to claim 1, wherein the infrared condenser lens is made of an infrared transparent body having electrical conductivity. 4. The pyroelectric infrared detection element according to claim 3, wherein the infrared transparent material having electrical conductivity is germanium or silicon. 5. The pyroelectric infrared detection element according to claim 1, wherein a field limiting plate is provided on the infrared incident side of the condenser lens.