JPH0262810B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an infrared detector.

In recent infrared detectors, for example, a pyroelectric infrared detector is built into the infrared detector.

Such an infrared detector has a characteristic of generating electric charge based on the amount of change in the amount of incident infrared rays, and the detection accuracy of the infrared detector improves as the amount of incident infrared rays changes more periodically. It is necessary to periodically interrupt the infrared rays incident on the detection object, and for this purpose, as shown in FIG. Chiyotsupa 3 is placed.

However, such a chopper 3 has a large shape and there is a space problem, and the motor 2 has uneven rotation and does not necessarily rotate the chopper 3 periodically, resulting in a decrease in detection accuracy.

The present invention has been made in view of these points, and embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an infrared detector 4, in which 5 is a pyroelectric infrared detector made of lithium tantalate (LiTaO ₃ ) single crystal and generates a charge according to the amount of change in incident infrared rays, and 6 and 7 are infrared ray detectors, respectively. Front and back electrodes are formed on the front and back surfaces of the detection object using nichrome vapor deposited films, and reference numeral 8 is a metal support made of copper, phosphor bronze, etc. On the support, the back electrode 7 is mounted on a support 8.
The infrared detecting body 5 is arranged so as to face the upper surface.
is fixed with a conductive adhesive 9 such as silver paste.

10 is an alumina substrate on which an impedance conversion circuit 11 is arranged to convert the high resistance of the infrared detector 5 to a low resistance because the infrared detector 5 has a high resistance;
Reference numeral 12 denotes a storage body consisting of a metal cap 13 and a header 14, and the support stand 8 and the substrate 10 are fixed on the header 14 inside the storage body.
Reference numeral 15 denotes a ground terminal directly implanted in the header 14, and the terminal is electrically connected to the back electrode 7 via the support base 8 and adhesive 9. 16 and 17 are first and second lead terminals implanted in the header 14 via insulating materials 18 and 19, respectively; 20 is a lead wire connecting the surface electrode 6 and the impedance conversion circuit 11; 21 and 22; is a lead wire connecting the impedance conversion circuit 11 and the first and second lead terminals 16 and 17.

23 is an opening formed in the cap 13 to allow infrared rays to enter the infrared detector 5 from the surface electrode 6 side; 24 is a first infrared transmitting member that closes the opening; the transmitting member has a wavelength of 2 to 15 μm; It is made of a silicon or germanium plate several 100 μm thick that has high transmittance to infrared rays. 25 is the first infrared transmitting body 24 facing the opening 23;
3. In the first opposing body, 26, 26, . As shown in a, a plurality of first infrared opaque portions 27, 27, . . . extend linearly as shown in FIG.
is a first infrared transmitting portion located between each of the first infrared non-transmitting portions 26, 26, . and,
The width W of the first infrared non-transmissive portions 26, 26... is
1 μm to 2 μm, the thickness D is 0.1 to 100 μm, and the first
The width t of the infrared transmitting portions 27, 27, . . . is the same as the width W described above. Reference numeral 28 denotes a second infrared transmitting body disposed in the storage body 12 so as to be close to and opposite to the first infrared transmitting body 24, and the transmitting body is
Like the infrared transmitting body 24, it is made of a silicon or germanium plate with a thickness of several 100 μm and has a high transmittance for infrared light having a wavelength of 2 to 15 μm. In more detail, 29 is the first opening 29 facing the opening 23.
The second
A planar second opposing body fixed to the upper surface of the infrared transmitting body 28, in which 30, 30
... are a plurality of second infrared non-transparent parts 31, made of the same material as the first infrared non-transparent parts 26, 26, and extending linearly in a direction parallel to the plane of the paper as shown in FIG. 3b. 31... is such a second infrared non-transmissive part 3
The second infrared transmitting portion is located between 0, 30, and so on. The infrared non-transmissive portions 30, 3
The width W' and the thickness D' of 0... and the width t' of the second infrared transmitting parts 31, 31... are the width W, the thickness D and the first infrared rays of the first infrared non-transmitting parts 26, 26, respectively. It has the same dimension as the width t of the transparent parts 27, 27....

32 is a piezoelectric vibrating body formed by pasting two piezoelectric plates together, that is, a bimorph, and the bimorph has a rectangular parallelepiped shape, and its length l, width w, and thickness a are approximately 30 mm, 5 mm, and 0.5 mm, respectively. , single crystals such as crystal, Rothsiel salt, ethylene tartrate, diamine, potassium tartrate, potassium monophosphate, ammonium monophosphate, lithium sulfate, barium titanate, glycine sulfate, barium titanate porcelain, zirconate, etc. It is made of porcelain materials such as lead titanate-based porcelain and niobate-based porcelain. The bimorph 32 is elongated in the direction perpendicular to the infrared incident direction, that is, in the lateral direction, so that the left end 32' is attached to the header 1.
It is fixed to the insulating stand 33 provided at the right end 3.
The second infrared transmitting body 28 is attached to the header 14.
The third and fourth lead terminals 38 and 39, which are implanted through the terminals 6 and 37, are connected to the first and fourth lead terminals formed on both sides of the left end 32' of the bimorph 32, as shown in FIG.
The first and second vibrating electrodes of the second vibrating electrode are connected to the third and fourth lead terminals 34 and 35, respectively.

When a predetermined AC signal is applied between the first and second vibrating electrodes 38 and 39 via the third and fourth lead terminals 34 and 35, the bimorph 32 flexes in accordance with the frequency of the AC signal. The second infrared transmitting body 28 is then periodically vibrated in the direction A perpendicular to the plane of the paper. In this case, since the bimorph 32 has the long length l as described above, the right end 32'' of the bimorph 32 vibrates greatly, and the second opposing body 29 vibrates as shown in detail in FIG. The second infrared non-transmissive portions 30, 30... are the first opposing body 25
The portion (broken line I) that overlaps with the first infrared transmitting portions 27, 27... and the first infrared non-transmitting portions 26, 26...
It vibrates greatly so as to be periodically located in the overlapped part (solid line J). In this state, the second opposing body 29 always maintains a parallel state with respect to the first opposing body 25.

Here, if the bimorph 32 is arranged so as to be elongated in the infrared incident direction as shown by the broken line in FIG. If the dimension of the installation space of the detector in the infrared incident direction is small, it is difficult to install the infrared detector. and,
In such a case, the second opposing body 29 vibrates to a position that is not parallel to the first opposing body 25, as shown in FIG.

However, in the infrared detector 4, the bimorph 32 is arranged to be long in the lateral direction and to vibrate in the A direction so as to vibrate the second opposing body 29 while keeping it parallel to the first opposing body 25. Therefore, the dimensions in the infrared incident direction can be reduced.

Note that when the above-mentioned vibration is performed, infrared rays from an object to be detected outside the infrared detector 4 are periodically incident on the infrared detecting body 5, that is, the infrared rays that are incident on the infrared detecting body 5 are periodically changed. Therefore, the infrared detector 5 generates a charge corresponding to the amount of change.
This charge is based on the temperature difference between the temperature of the object to be detected and the room temperature.

FIG. 7 shows an infrared detector 4' according to another embodiment of the present invention. In the figure, the same parts as those in the above embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted.

40 is a shield body made of aluminum or the like and has a height e of approximately 5 mm and covers the infrared detector 5 and the impedance conversion circuit 11; 41 is an opening formed in a portion of the shield body located above the detector 5; The first opposing body 25 is attached to the opening. The shield body 40 prevents noise from being induced into the infrared detector 5 and the impedance conversion circuit 11 due to the vibration of the bimorph 32. Furthermore, the right end 3 of the bimorph 32
2'' is directly attached to the second opposing body 29. Reference numeral 42 is a support made of resin such as Teflon, and the free end 29' of the second opposing body 29 is attached to the support. A groove 43 is formed to slidably support the.

FIG. 8 shows a circuit including the infrared detectors 4, 4', and the impedance conversion circuit 11 in the infrared detectors 4 or 4' has a high input resistance 4 of ^{10 10} to 10 ¹¹ Ω.
4. FET (field effect transistor) 45 and approx.
It is formed by an output resistor 46 of 10KΩ.

The infrared detector 4 or 4' is supplied with a DC voltage through a first lead terminal 16, and an AC signal corresponding to the temperature difference between the temperature of the object to be detected and the room temperature is output from a second lead terminal 17. . 47 is a diode for measuring room temperature; 48 is an oscillator consisting of an astable multivibrator that oscillates periodic pulses;
49 is the bimorph 32 based on the pulse.
50, 51, 52 are DC amplifiers, 53 is a filter amplifier, 54 is a synchronous detector, which outputs an AC signal to vibrate (deflect) the AC signal from the infrared detector 4 or 4'. is synchronized with the pulse from the oscillator 48,
When the temperature of the object to be detected is higher than room temperature, a positive DC signal corresponding to the temperature difference is output, and when the temperature of the object to be detected is lower than room temperature, a negative DC signal is output according to the temperature difference. Reference numeral 55 denotes a combining circuit that combines (adds) the output of the synchronous detector 54 and the output of the diode 47, and this circuit outputs a signal corresponding to the temperature of the object to be detected. 56 is an output terminal for outputting the temperature to a desired circuit.

As is clear from the above description, according to the present invention, there is provided an infrared detector that generates a charge according to the amount of change in incident infrared rays, a storage body that stores the detector, and an infrared ray from an object to be detected that is incident on the detector. a pair of planar opposing bodies having both an infrared transmitting part and an infrared non-transmitting part and disposed parallel to each other to face the opening, with respect to the longitudinal direction; One of the opposing bodies is attached to the tip of the free open end that can freely vibrate vertically, and while maintaining the parallel state, the infrared non-transmitting part of one of the opposing bodies is replaced by the infrared transmitting part of the other opposing body. and a piezoelectric vibrating body that vibrates in a manner that periodically overlaps the infrared opaque portion, and the piezoelectric vibrating body is arranged to vibrate the one opposing body while maintaining the parallel state, so that infrared ray detection is possible. This eliminates the need for a tipper or motor to change the infrared rays incident on the body, making it possible to downsize the infrared detector itself.The infrared rays incident on the infrared detection body change evenly and periodically, making it possible to achieve high accuracy. Infrared detection can be performed. Furthermore, the size of the infrared detector in the infrared incident direction can be reduced, and therefore, when the infrared detector is installed in a space with small dimensions in the infrared incident direction, the infrared detector can be easily installed. Furthermore, in the conventional technology described in JP-A No. 56-160628 (GO1J5/62), vibration in the elongation direction (vertical direction) of a piezoelectric vibrator is used, but the amplitude in the elongation direction is small even when an application of several 100 V is applied. It is about 10 μm at most.
On the other hand, since the present invention utilizes the amplitude in the lateral direction of the bimorph vibrating body, it is possible to obtain a large amplitude of several tens of μm even when applying several tens of V, that is, an amplitude approximately ten times as large as that of the former. possible and extremely efficient. In addition, in this conventional example, two oscillators are required, and since the infrared rays are stepped at a frequency that is the difference between the oscillation frequencies of both oscillators, it is necessary to precisely control the frequency. A high-precision oscillator is not required; one is sufficient.

[Brief explanation of drawings]

1A and 1B are a side view and a plan view of a conventional infrared detection mechanism, FIG. 2 is a sectional view of an infrared detector according to an embodiment of the present invention, and FIGS. Figure 4 is a view seen from the arrow direction in Figure 2, Figure 5 is a sectional view taken along the - line in Figure 2,
FIG. 6 is a sectional view of an infrared detector for comparison corresponding to FIG. 5, FIG. 7 is a sectional view of an infrared detector according to another embodiment of the present invention, and FIG. FIG. 2 is a circuit diagram including an infrared detector. 5... Infrared detecting body, 12... Storage body, 23... Opening, 25... First opposing body, 26, 26... First infrared non-transmitting part, 27, 27... First infrared transmitting part, 29
...Second opposing body, 30, 30... Second infrared non-transmissive part, 31, 31... Second infrared transmissive part, 32... Bimorph.

Claims (1)

[Scope of Claims] 1. An infrared detector 5 that generates an electric charge in accordance with the amount of change in incident infrared rays; A storage body 12 that houses the detector 5; and an infrared detector 5 that allows infrared rays from a detected body to enter the detector 5. An opening 23 formed in the storage body 12 as shown in FIG.
and infrared transmitting parts 27, 31 and infrared non-transmitting part 2
6 and 30, parallel to each other, and the opening 2
A pair of planar opposing bodies 25 and 29 are arranged to face each other, and one of the opposing bodies 29 is attached to the tip of a free open end that can freely vibrate perpendicularly to the longitudinal direction, and While maintaining the parallel state, the infrared non-transmissive portion 30 of the one opposing body 29 is connected to the infrared transparent portion 27 and the infrared non-transparent portion 26 of the other opposing body 25.
An infrared detector comprising: a bimorph vibrating body 32 that vibrates so as to be periodically and alternately superimposed on each other;