JPS6336254Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pyroelectric infrared detector, and particularly to an improvement of an infrared detector having a dual type structure and connected in parallel with opposite polarities.

An infrared detector having a dual type structure and connected in series with opposite polarities is disclosed in US Pat. No. 3,839,640. This detector has excellent characteristics such as being able to compensate for various noises caused by external disturbances due to its reverse polarity, and since the lead wire can be taken out from the electrode on one side of the pyroelectric material, the lead wire can be taken out with a single working method. It also has structural and manufacturing advantages.

On the other hand, there is currently a detector with a dual type structure and a method of connecting parallel and opposite polarities, as shown in FIG. However, this detector
Each electrode 2a, 2b, 3a, 3 provided on both the front and back sides of
A total of four lead wires have to be taken out from b, so the disadvantage is that the large number of lead wires and the fact that lead wires have to be taken out from both the front and back sides combine to make the workability very poor. . Therefore,
In order to improve the workability of a detector that uses a parallel reverse polarity wiring method, it is necessary to devise a way to take out the lead wire from one side of the pyroelectric material, just as with a detector that uses a series reverse polarity wire connection method. be. in this case,
Cut the pyroelectric material 1 shown in Fig. 1 at the center A and 2.
A technique has been considered to reduce the number of lead wires by separating the cut pieces into pieces, then turning one of the cut pieces inside out and gluing them together so that the lead wires can be taken out one by one from both the front and back sides. The drawback of not being able to do this in a single operation because the lead wires have to be taken out cannot be solved. Not only that, but this technology is equivalent to a structure in which two single-type detectors are glued together in different directions, and therefore two pyroelectric materials are used.
It also has the disadvantage of having poor balance of characteristics. Therefore, it is required to provide all electrodes on a single pyroelectric material to achieve a good balance of properties.

In view of the above-mentioned drawbacks, the present invention has an essentially dual-type structure in which two pairs of infrared sensing electrodes are provided on a single pyroelectric material, but two lead wires are taken out from one side. Therefore, it is an object of the present invention to provide a pyroelectric infrared detector which can realize a connection method of parallel and opposite polarity, and which also has excellent infrared detection characteristics.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 2A shows a plan view of a pyroelectric infrared detector as an embodiment of the present invention, FIG. 2B shows a bottom view, and FIG. , 10 is a single pyroelectric material, for example
PZT, LiTaO ₃ , PbTiO ₃ , PVF ₂ , etc. are used. 11a, b, 12a, b, 13a, b, 14
a and b are vapor deposited on both the front and back sides of the pyroelectric material 10,
It is an electrode provided by sputtering or etching, for example, Au, Ni, NiCr, Ta,
Cr, Ti, Al, etc. are used. The electrode 11a on the front side and the electrode 11b on the back side of the pyroelectric material 10 have the same shape and are provided at corresponding positions with the pyroelectric material sandwiched therebetween. The remaining electrodes 12a and 1
2b, 13a and 13b, and 14a and 14b are also provided at corresponding positions with the pyroelectric material 10 in between, and the corresponding parts have the same shape. Moreover, the electrodes 12a and 13a, 11a and 14
As is clear from FIGS. 2A and 2B, a, 12b and 13b, 11b, 14b are in a line-symmetrical relationship with each other. Then, the pyroelectric material 10 and each pair of electrodes 11a and 11b, 12a and 1 corresponding to each other on both the front and back surfaces thereof.
Four elements 11, 12, 13, and 14 are constituted by 2b, 13a and 13b, and 14a and 14b. The light-receiving side electrodes 12a and 13a of elements 12 and 13, for example, the surface side, are made of an infrared absorbing material such as gold black (not shown), Ni,
It is made of an infrared transmitting material such as NiCr, Au, InSb, etc., and the elements 12 and 13 are elements that sense infrared rays. On the other hand, the electrode 11 on the surface side which is the light receiving side of the remaining elements 11 and 14
a, 14a are entirely covered with aluminum foil Al of about 30 microns, and elements 11, 14
is used as an auxiliary element that does not sense infrared rays.

Here, one element 1 that senses infrared rays
The explanation will be continued by referring to 2 as a first infrared sensing element, the other element 13 as a second infrared sensing element, one element 11 that does not sense infrared rays as a first auxiliary element, and the other element 14 as a second auxiliary element. and the pyroelectric material 1
On the surface side of 0, the electrode 12a of the first infrared sensing element 12 and the first auxiliary element 11,
11a, and the electrodes 13a of the second infrared sensing element 13 and the second auxiliary element 14,
14a are electrically connected to each other by a member indicated by 15 in the figure.

On the other hand, on the back side of the pyroelectric material 10, the first
The electrodes 12b and 14b of the infrared sensing element 12 and the second auxiliary element 14 are connected to each other, and the electrodes 13b and 11b of the second infrared sensing element 13 and the first auxiliary element 11 are connected to each other by members indicated by 16 in the figure. electrically connected.
The members 15 and 16 are electrodes 11a, b, 12a,
b, 13a, b, 14a, b can be provided on the pyroelectric material 10 at the same time using the same material as the electrode constituent material and using the same method (evaporation, sputtering or etching) as for providing the electrodes. In the figure, 17 and 18 are electrode extraction parts. This extraction part 1
Similarly to the members 15 and 16, the members 7 and 18 can be made of the same material as the electrodes and provided at the same time. Lead wires are connected to these take-out portions 17 and 18. The extraction parts 17 and 18 are provided only on the front side of the pyroelectric material 10, and are not provided on the back side. 19 is a detector mounting material; 21 is a detector case; and the first and second infrared sensing elements 12, 13.
A light receiving window 22 is provided at a location corresponding to the surface side electrodes 12a, 13a.

Next, the configuration and operation of the detector will be considered based on the equivalent circuit with the above configuration shown in FIG.

In Fig. 4, 20, 20' are elements 12, 1
Each pyroelectric current that occurs when 3 senses infrared rays, etc.
io and C _S is between the electrodes 12a and 12b and 13
Each capacitance between a and 13b, R _S is each resistance between electrodes 12a and 12b and between 13a and 13b, C _L is each capacitance between the electrodes 11a and 11b and between 14a and 14b, and R _L is each capacitance between electrodes 11a and 11b and between 14a and 14b. These are resistances between electrodes 11a and 11b and between electrodes 14a and 14b. These pyrocurrents
io, capacitance C _S , C _L resistance R _S , R _L between two elements 12, 13 and auxiliary elements 11, 14
The use of a single pyroelectric material 10 and the elements 12,
This is because the electrodes of the thirteen electrode auxiliary elements 11 and 14 are arranged in a line-symmetrical relationship as described above.

(1) Features of the configuration of the above pyroelectric infrared detector.

The detector consists of four elements 1 as shown.
In the two elements 11 and 14, the surfaces of the electrodes 11a and 14a on the light receiving side are covered with aluminum foil Al to prevent infrared rays from being sensed. In terms of functionality, it can be said that it is essentially a dual-type detector. In addition, the elements 12 and 13 that sense infrared rays are the auxiliary element 11,
14, but the auxiliary elements 11,1
4 does not sense infrared rays, so this can be ignored, and when viewed from the extraction sections 17 and 18, they are connected in parallel and with opposite polarities.

Therefore, although the detector has an essentially dual-type structure and uses a parallel and reverse polarity connection method, the structure and lead wire extraction work are such that only two lead wires need to be taken out from the surface of a single pyroelectric material 10. It has the above characteristics.

And the two auxiliary elements 11, 14
In order to prevent the electrodes from sensing infrared rays, it has been thought to apply a mixture of silicone adhesive and powdered Al ₂ O ₃ to the electrodes 11a and 14a, and an actual experiment has shown that the amount of application Due to variations in the adhesive and changes in the viscosity of the adhesive during application, the application state becomes unbalanced between the two electrodes 11a and 14a, and the auxiliary element 1
Not only was it not possible to make the outputs of No. 1 and No. 14 zero, but there was also a large variation in the sensitivity difference, and it was found that there was room for improvement in terms of characteristics.

Therefore, as mentioned above, the electrode 11 on the light receiving side
By covering the surfaces of auxiliary elements 11 and 14a with aluminum foil Al, the output of auxiliary elements 11 and 14 can be made extremely small or zero, and the sensitivity difference can also be made extremely small with no variation, dramatically improving the detection characteristics. can be improved.

(2) Operational characteristics (a) As mentioned in (1) above, since it has a dual-type structure and uses a parallel and opposite polarity connection method, the elements cannot be exposed to sunlight, light from lighting equipment, etc. (in-phase disturbance). Even if it is incident, this can be canceled out.

(b) For the same reason, even if vibration is transmitted through the lead wire, the effects of this vibration will be canceled out.

(c) When heat is transmitted through the lead wire or the mounting material 19, the lead wire is
The mount material 19 is connected to the auxiliary elements 11, 14 via the lead wires 11, 14, and the mount material 19 is in contact with the electrodes 11b, 14b of the auxiliary elements 11, 14, so that when heat is transferred through the lead wire or the mount material, the Since the heat is diffused by the auxiliary element, the pyroelectric material quickly becomes subject to a uniform temperature distribution. Generally, if a pyroelectric material exhibits an uneven temperature distribution, the operation becomes unstable, but if the temperature distribution is uniform as described above, the operation is stable. Therefore, it can be said that the pyroelectric infrared detector having the above configuration is resistant to heat.

(d) The upper detector has a higher resistance value than other dual-type detectors by the resistance R _L of the auxiliary element. It is generally known that the SN ratio of a detector is inversely proportional to the resistance value. However, as shown, the auxiliary elements 11, 14
If the area of the electrodes is made sufficiently larger than the area of the electrodes of elements 12 and 13, the resistance value will decrease accordingly, so the S/N ratio of the above detector will be practically the same as that of other dual-type detectors. The value can be improved.

However, the present invention is not limited to the auxiliary elements 11, 1.
It is not a constituent requirement to reduce the resistance value of elements 11 to 14, and in view of this point, for example, as shown in another embodiment in FIG. Its size and shape can be changed in various ways.

In FIG. 5, the same reference numerals are given to the same constituent members as in the structure of the embodiment, and the explanation thereof is omitted.

(e) For the reasons stated in (a) to (d) above, the detector with the above configuration is functionally equivalent to other dual-type detectors, and the safety of operation against heat is also taken into consideration. Then we can conclude that it is even better than that.

In the above embodiment, the lead wire extraction portion is provided only on the front side of the pyroelectric material 10, but it may also be provided only on the back side.

As described above, the pyroelectric infrared detector according to the present invention has four pairs of electrodes arranged in corresponding positions on the front and back surfaces of a single pyroelectric material, and two pairs of electrodes for sensing infrared rays are provided. element and two pairs of auxiliary elements, and on one surface of the pyroelectric material, the electrode of the first infrared sensing element and the electrode of the first auxiliary element are connected to the electrode of the second infrared sensing element. The electrodes are electrically connected to the electrodes of the second auxiliary element, and the electrodes of the first infrared sensing element and the second
The electrode of the auxiliary element is electrically connected to the electrode of the second auxiliary element, and the electrode of the second infrared sensing element is electrically connected to the electrode of the first auxiliary element. It is characterized by being covered with aluminum foil so as not to detect infrared rays, and as described in detail in the embodiment, for example, the electrode of the first auxiliary element and the second auxiliary element on one side are covered with aluminum foil. By taking out the lead wires from the electrodes of the element, even though the detector has an essentially dual-type structure and uses parallel and opposite polarity wiring, it is possible to remove just two lead wires from only one side of the pyroelectric material. Therefore, the intended purpose of being able to easily complete the lead wire removal work in a single work format was achieved.

Furthermore, by covering the surface of the light-receiving electrode of the auxiliary element with aluminum foil, the infrared detection characteristics can be dramatically improved compared to, for example, applying a mixture of aluminum oxide powder and adhesive. This led to this.

In particular, if the structure is as in the embodiment, as mentioned in the discussion above, there is an effect that it is possible to obtain a detector that is superior to other dual-type structure detectors not only in terms of structure but also in terms of operation.

[Brief explanation of the drawing]

Figure 1 shows a conventional pyroelectric infrared detector with a dual-type structure and a parallel and opposite polarity connection method, and Figures 2 to 4 show pyroelectric infrared detectors as an embodiment of the present invention. Figure 2A is a top view, Figure B is a bottom view, and Figure 3 is Figure 2A.
FIG. 4 is an equivalent circuit diagram.
FIG. 5 is a schematic plan view of a detector according to another embodiment of the present invention. 10...Pyroelectric material, 11...First auxiliary element, 12...First infrared sensing element, 13
...Second infrared sensing element, 14...Second
Auxiliary elements, 11a, 11b, 12a, 12
b, 13a, 13b, 14a, 14b... electrode,
Al...aluminum foil.

Claims (1)

[Scope of utility model registration request] Four pairs of electrodes are provided in corresponding positions on the front and back surfaces of a single pyroelectric material to constitute two pairs of infrared sensing elements and two pairs of auxiliary elements, and one of the pyroelectric materials is The electrode of the first infrared sensing element and the electrode of the first auxiliary element are electrically connected to each other on the surface, and the electrode of the second infrared sensing element and the electrode of the second auxiliary element are electrically connected to each other; , the electrodes of the first infrared sensing element and the electrodes of the second auxiliary element are electrically connected, and the electrodes of the second infrared sensing element and the electrodes of the first auxiliary element are electrically connected, respectively; A pyroelectric infrared detector characterized in that the surface of the electrode on the light-receiving side of the second auxiliary element is covered with aluminum foil so as not to detect infrared rays.