JPH0216858B2 - - 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 are lead wires connecting the surface electrode 6 and the impedance conversion circuit 11; 21 and 22; is a lead wire that connects 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 5 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 a planar first opposing body fixed to the lower surface of the first infrared transmitting body 24 to face the opening 23 (details will be described later); 26 is the first infrared transmitting body in the storage body 12; 24, which is a second infrared transmitting body disposed close to and opposite to the first infrared transmitting body 24, which is a silicon or germanium plate having a thickness of several hundred μm and having a high transmittance for infrared rays having a wavelength of 2 to 15 μm. It is made up of 27 is a planar second opposing body fixed to the upper surface of the second infrared transmitting body 26 so as to face the opening 23 and further to closely oppose the first opposing body 25 in parallel with the second opposing body 27 (details will be described later). ).

28 is a vibrating body formed by pasting together two piezoelectric plates, that is, a bimorph, and the bimorph has a rectangular parallelepiped shape, and its length, width w, and thickness a are each about approx.
30mm, 5mm, 05mm, crystal, Lotsiel salt,
Ethylene tartrate, diamine, potassium tartrate, potassium monophosphate, ammonium monophosphate, lithium sulfate,
It is made of single crystals such as barium titanate and glycine sulfate, and porcelain materials such as barium titanate-based porcelain, zirconate/lead titanate-based porcelain, and niobate-based porcelain. The bimorph 28 is elongated in the direction perpendicular to the infrared incident direction, that is, in the lateral direction, and its left end 28' is fixed to an insulating stand 29 provided on the header 14. The body 26 is attached. Reference numerals 30 and 31 are third and fourth lead terminals implanted in the header 14 via insulating materials 32 and 33, and 34 and 35 are the bimorph 28 as shown in FIG. The first and second vibrating electrodes are formed on both sides of the left end 28', and the first and second vibrating electrodes are connected to the third and fourth lead terminals 30 and 31, respectively.

When a predetermined AC signal is applied between the first and second vibrating electrodes 34 and 35 via the third and fourth lead terminals 30 and 31, the bimorph 28 flexes in accordance with the frequency of the AC signal. Then, the second infrared transmitting body 26 is periodically vibrated in the arcuate direction A (FIG. 3). In this case, the two opposing bodies 27 vibrate periodically in the arcuate A direction while always being held parallel to the first opposing body 25.

Here, to explain the first and second opposing bodies 25, 27 in detail, in the second opposing body 27, 36, 36...
is made of a material that does not transmit infrared rays, such as aluminum, gold, or silver.
As shown in FIG. b, a plurality of linearly extending second infrared non-transmissive parts 37, 37, . . . are located between the second infrared non-transparent parts 36,
This is a second infrared opaque portion having the same shape and dimensions as 36.... and a second infrared non-transmissive part 3
The dimensions in the vibration direction of each portion of the second infrared transmitting portions 37, 37, . . . are proportional to the vibration width of each portion. Therefore, since the second opposing body 27 vibrates in the arcuate direction A, the second infrared non-transmissive portion 36,
36... and the second infrared transmitting parts 37, 37... are such that the dimension in the vibration direction of the part closest to the bimorph 28 is the minimum width _W1 , and the dimension in the vibration direction of the part farthest from the bimorph 28 is the maximum width _W2 . It is fan-shaped.

Furthermore, in the first opposing body 25, 38,3
8... are made of the same material as the second infrared non-transmissive parts 36, 36..., and are arranged linearly in a direction substantially parallel to the paper surface (FIG. 2) as shown in FIG. 4a. The infrared opaque parts 39, 39... are first infrared transmissive parts located between the first infrared opaque parts, and the first infrared opaque parts 38, 38... 39... is the second opposing body 2
It has the same fan shape and dimensions as the second infrared non-transmissive portions 36, 36, . . . and the second infrared ray transmissive portions 37, 37, .

For example, the first infrared non-transmissive portion 3
8, 38..., the first infrared transmitting parts 39, 39..., the second infrared non-transmitting parts 36, 36, and the second infrared transmitting parts 37, 37... have widths W ₁ and W ₂ of 100 μm, respectively.
120μm, length is 3mm, thickness D is 0.1~
It is 100μm.

Therefore, when the bimorph 28 vibrates, the second infrared non-transmissive portions 36, 3 of the second opposing body 27
6... is the first opposing body 2 as shown in detail in FIG.
It vibrates so as to alternately and completely overlap the first infrared non-transmissive parts 38, 38, . . . and the first infrared ray transmissive parts 39, 39, .

Here, the first infrared non-transmissive portions 38, 39
..., first infrared transmitting sections 39, 39..., second infrared non-transmitting sections 36, 36..., and second infrared transmitting section 3
The widths of 7, 37, . . . are usually constant as shown in FIGS. 6a and 6b. In this case, the second opposing body 27
vibrates in the arc-shaped direction A, so for example, the second infrared non-transmissive portions 36, 36...
It does not completely overlap with the infrared opaque parts 38, 38, . . . Then, even if the infrared rays from the object to be detected outside the infrared detector 4 are periodically interrupted and the infrared rays incident on the infrared detector 5 are changed periodically, that is, the infrared rays are modulated in an alternating current manner, the degree of modulation will be different. Therefore, the SN ratio of the infrared detector 5 decreases.

In this regard, in the infrared detector 4, the second infrared non-transmissive portions 36, 36, . . .
8, 38... and the first infrared transmitting parts 39, 39..., the degree of modulation of the infrared rays incident on the infrared detector 5 is good, and therefore the SN ratio in the infrared detector 5 is significantly improved. do. Note that the output of the infrared detector 5 is based on the temperature difference between the temperature of the object to be detected and the room temperature.

FIG. 8 shows a circuit including the infrared detector 4, and the impedance conversion circuit 11 in the infrared detector 4 has a high input resistance 40 of 10 ¹⁰ to 10 ¹¹ Ω, an FET (field effect transistor) 41, and an output of about 10 KΩ. It is formed of a resistor 42.

The infrared detector 4 is supplied with a DC voltage at a first lead terminal 16, and a second lead terminal 1
7 outputs an AC signal corresponding to the temperature difference between the temperature of the object to be detected and the room temperature. 43 is a diode for measuring room temperature; 44 is an oscillator made of an astable multivibrator that oscillates periodic pulses; and 45 is a drive circuit that outputs an alternating current signal to vibrate (deflect) the bimorph 28 based on the pulses. , 46, 47, and 48 are DC amplifiers, 49 is a filter amplifier, and 50 is a periodic detector, which synchronizes the AC signal from the infrared detector 4 with the pulse from the oscillator 44, and adjusts the temperature of the object to be detected. If 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 if the temperature of the object to be detected is lower than room temperature, a negative DC signal corresponding to the temperature difference is output. 5
1 is the output of the synchronous detector 50 and the diode 43
This circuit outputs a signal corresponding to the temperature of the object to be detected. 52
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 an infrared detector that generates a charge according to the amount of change in incident infrared radiation, a storage body that stores the detector, and an infrared ray from a detected object that is incident on the infrared 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 above-mentioned parallel state, the infrared non-transmitting part of one of the opposing bodies is connected to the infrared transmitting part of the other opposing body. The infrared transmissive part and the infrared non-transmissive part of one opposing body have the same shape and dimensions, and the vibration of each part is The dimension in the direction is proportional to the vibration width of each part, and the shape and dimensions of the infrared transmitting part and the infrared non-transmitting part of the other opposing body are the same as the infrared transmitting part and the infrared non-transmitting part of the one opposing body. Therefore, the conventional tipper and motor are no longer necessary, and the infrared detection section can be made smaller.
Since the infrared rays incident on the infrared detector vary evenly and periodically, infrared rays can be detected with high precision. Furthermore, the degree of modulation when changing infrared rays can be improved, and therefore the SN ratio of the infrared detector can be significantly improved.

Also, JP-A-56-160628 (G01J, 5/62)
The prior art described in 1 uses vibration in the elongation direction (vertical direction) of the piezoelectric vibrator, but the amplitude in the elongation direction is at most about 10 μm even when 100V is applied. On the other hand, in the present invention, since the lateral amplitude of the bimorph oscillator is utilized, 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. There is no need for such a high-precision oscillator; even one is sufficient.

Furthermore, in the technique shown in Japanese Patent Application Laid-Open No. 56-128432 (G01J 1/42), an example is shown in which the dimensions of the light transmitting part on the rotating disk are made proportional to the vibration width. In this conventional example, only one rotary disk is rotated by a motor. Further, Fig. 5 of Japanese Patent Application Laid-Open No. 55-54418 (G01J 5/14) shows an example of intermittent light using a bimorph, but this does not have the structure and effect as described in the present invention. do not have.

[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 FIG. 3 is a view seen from the direction of the arrow in FIG. Figures 4a and b are plan views of the same essential parts, Figure 5 is a diagram of the operating state of the same parts, and Figures 6a and b.
are general plan views of the main parts of the infrared detector corresponding to Figs. 4a and b, respectively, and Fig. 7 is a diagram of the operating state of the same main parts,
FIG. 8 is a circuit diagram including the infrared detector of FIG. 2. 5... Infrared detector, 12... Storage body, 23...
...opening, 25...first opposing body, 38, 38...first infrared non-transmissive section, 39, 39...first infrared transmitting section, 27...second opposing body, 36, 36...second
Infrared non-transmissive part, 37, 37...Second infrared transmissive part, 28...Bimorph.

Claims (1)

[Claims] 1. An infrared detector 5 that generates a charge according to the amount of change in incident infrared rays, and a storage body 12 that stores the detector.
and an opening 2 formed in the housing to allow infrared rays from the object to be detected to enter the infrared detecting object.
3, an infrared transmitting section 39 and an infrared non-transmitting section 38
a pair of planar opposing bodies 25, 2 that are parallel to each other and are arranged to face the opening 23;
7, one of the opposing bodies is attached to the tip of the free open end that can freely vibrate perpendicularly to the longitudinal direction, and while maintaining the parallel state, the one of the opposing bodies is attached so that its infrared non-transmissive part is a bimorph vibrating body 28 that vibrates so as to be periodically and alternately superimposed on the infrared transmitting part and the infrared non-transmitting part of the one opposing body; The shapes and dimensions are the same, the dimensions in the vibration direction of each part are proportional to the vibration amplitude of each part, and the shapes and dimensions of the infrared transmitting part and the infrared non-transmitting part of the other opposing body are the same as that of the one opposing body. An infrared detector consisting of an infrared transmitting part and an infrared non-transmitting part of the body.