JPS622246B2 - - 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. Such a configuration is also shown in Japanese Patent Publication No. 10467-1983.

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 formed with nichrome vapor deposited film on the front and back sides of the detection object,
Reference numeral 8 denotes a metal support made of copper, phosphor bronze, etc., on which the back electrode 7 faces the upper surface of the support 8, and the infrared detector 5 is made of conductive material such as silver paste. It is fixed with adhesive 9.

10 is an alumina substrate; 11 is an impedance conversion circuit disposed on the substrate; since the infrared detector 5 has a high resistance, an impedance conversion circuit is used to convert the high resistance into a low resistance; 12 is a metal cap 13; The storage body includes a header 14, and on the header 14 inside the storage body, a support base 8 on which the detection body 5 is fixed and a substrate 10 on which the impedance conversion circuit 11 is arranged are fixed. Reference numeral 15 denotes a ground terminal that is directly implanted in the header 14, and this 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 21 and 22 connecting the surface electrode 6 and the impedance conversion circuit 11; This is a lead wire that connects the impedance conversion circuit 11 and the first and second lead terminals 16 and 17.

Reference numeral 23 denotes an opening formed in the cap 13 to allow infrared rays to enter the infrared detector 5 from the surface electrode 6 side, and the opening is circular with a diameter of 8 mm.
It has a square or rectangular shape. 24 is a first infrared transmitting material having the same shape as the opening 23 and closing the opening 23, and the dielectric material has a wavelength of 2 to 5 μm.
Thickness of several 100 μm with high transmittance to infrared rays
It is made of silicon or germanium plate.
Note that the first infrared transmitting body 24 and the infrared detecting body 5
The distance T is 500 μm to 3 cm. 25
are a plurality of linear first infrared ray transmissive bodies made of a material that does not pass infrared rays such as aluminum, gold, or silver, and extend in a direction perpendicular to the plane of the paper on the lower surface of the first infrared transmissive body 24; Body width W is 1 μm to 2
mm, and the thickness D is 0.1 to 100 μm. Further, the first infrared ray blocking bodies 25 are spaced apart from each other by a predetermined dimension t, and the dimension t is the same as the width W. The portions corresponding to the dimension t serve as a plurality of first infrared passing portions. 2
6 is the distance d (=0.1μ) in the storage body 12.
a second infrared transmitting body that closely opposes the first infrared transmitting body 24 and having a diameter of 1 cm to 1 cm), the transmitting body has the same shape as the opening 23 like the first infrared transmitting body 24, and It is made of a silicon or germanium plate several hundred micrometers thick that has high transmittance to infrared rays with a wavelength of 2 to 15 micrometers. Reference numeral 27 denotes a plurality of linear second infrared non-transmissive bodies extending in the same direction as the first infrared non-transmissive body 25 (direction perpendicular to the plane of the paper) on the upper surface of the second infrared transparent body 26; The passing body is made of an infrared ray blocking material such as aluminum, gold, silver, etc., like the first infrared ray blocking body 25, and the width W' of the second infrared ray blocking body 27 is 1 μm to 1 μm.
2 mm, and the thickness D' is 0.1 to 100 μm. Furthermore, the second infrared ray blocking bodies 27 are spaced apart from each other by a predetermined dimension t', and the dimension t' is equal to the width.
It is the same as the dimension of W′. The portions corresponding to the dimension t' serve as a plurality of second infrared passing portions.

Reference numeral 28 denotes a vibrating body, ie, a bimorph, formed by pasting together two piezoelectric plates.The bimorph is fixed at its lower end to an insulating stand 29 provided on the header 14, and at its upper end is the second infrared transmitting body 26. is attached. The shape of the bimorph 28 is a rectangular parallelepiped, the height h is 1 to 3 mm, and the thickness a is 50 μm.
m~5mm, width (dimension perpendicular to the page) 0.5~
It is 15mm. The bimorph 28 includes crystal, Rothsiel salt, ethylene tartrate, diamine,
Single crystals such as potassium tartrate, potassium monophosphate, ammonium monophosphate, lithium sulfate, barium titanate, glycine sulfate, barium titanate porcelain,
It is made of porcelain materials such as zirconate/lead titanate porcelain and niobate porcelain. Reference numerals 30 and 31 denote third and fourth lead terminals which are respectively implanted in the header 14 via insulating materials 32 and 33, and these lead terminals are connected to electrode pads 34 and 35 formed on both sides of the bimorph 28, respectively. is connected to.

Therefore, between the electrode pads 34 and 35, a third
When an AC drive signal with a predetermined amplitude and a predetermined frequency is applied via the fourth lead terminals 30 and 31, the bimorph 28 is bent in accordance with the frequency of the AC drive signal, and the second infrared transmitting body 26 is periodically moved in the direction of arrow A. vibrate, thereby causing the first and second infrared ray non-passing bodies 25 and 27 to overlap each other and the first and second infrared passing parts to overlap each other (the state shown in FIG. 2).
and a first infrared passing section and a first infrared non-passing body 2
5, the state in which the second infrared ray non-passing body 27 and the second infrared ray passing section overlap are periodically repeated. At this time, the infrared rays from the object to be detected outside the infrared detector 4 are periodically incident on the infrared detector 5, that is, the infrared rays that are incident on the infrared detector 5 are periodically changed. The body 5 generates an electric charge corresponding to the amount of change. More specifically, the output of the detection object 5 is an AC signal having an amplitude based on the temperature difference between the temperature of the object to be detected and the room temperature and having the same frequency as the AC drive signal applied to the bimorph 28. It's a signal.

FIG. 3 shows an infrared detector 4s of another embodiment, in which the second infrared transmitting body 26s is located outside the storage body 12 and the first infrared transmitting body 26s is located outside the housing 12.
are closely facing. In this figure, the same parts as those in FIG. 1 are given the same numbers, and the same parts as in FIG. 1 are given the same numbers with a suffix s.

FIG. 4 shows a circuit including the infrared detector 4 or 4s, and the impedance conversion circuit 11 in the infrared detector 4 or 4s has a high input resistance 36 of 10 ¹⁰ to 10 ¹¹ Ω, and a FET (field effect transistor) 37.
and an output resistor 38 of about 10KΩ.

The infrared detector 4 or 4s is supplied with a DC voltage through a first lead terminal 16, and has an amplitude corresponding to the temperature difference between the temperature of the object to be detected and the room temperature from a second lead terminal 17, and has an amplitude corresponding to the temperature difference between the temperature of the object to be detected and the room temperature. An AC signal having the same frequency as the drive signal applied to 28 is output. 39 is a diode for measuring the room temperature; 40 is an oscillator made of an astable multivibrator that oscillates periodic pulses; 41 is the AC signal (described above) for vibrating (deflecting) the bimorph 28 or 28s based on the pulse; a drive circuit that outputs the same frequency as the pulse), 4
2, 43, 44 are DC amplifiers, 45 is a filter amplifier, 46 is a synchronous detector, 47 is a synthesis circuit, 48
is the output terminal.

Therefore, these DC amplifiers 42, 43, 44,
Although the operations of the filter amplifier 45, synchronous detector 46, and combining circuit 47 are similar to those of the circuit shown in Japanese Patent Publication No. 10467/1982, the operations of the synchronous detector 46 and combining circuit 47 will be described in detail. The synchronous detector 46 operates to synchronously detect the alternating current signal from the detection object 5 that has passed through the filter amplifier 45 based on the pulses from the oscillator 40. That is, in this case, in the synchronous detector 46, the pulse from the oscillator 40 coincides with the positive or negative half cycle of the AC signal from the detection object 5. When the temperature of the object to be detected is higher than the room temperature, the above pulse corresponds to the positive half cycle of the AC signal from the object to be detected 5, and when the room temperature is higher than the temperature of the object to be detected, the above pulse is detected. It is designed to coincide with the negative half cycle of the AC signal from the body 5. In the former case, the synchronous detector 46 detects a positive DC signal corresponding to the amplitude value of the AC signal (the signal represents the difference between the temperature of the object to be detected and the room temperature and the amplitude value of the object to be detected). (which indicates that the temperature is higher) is output,
In the latter case, a negative DC signal corresponding to the amplitude value of the AC signal (this signal represents a similar temperature difference and represents that the temperature of the detected object is lower)
Output.

Next, the combining circuit 47 connects the diode 39
DC signal from (the signal represents room temperature)
Based on this, the output of the synchronous detector 46 is operated to correct the room temperature. That is, when the temperature of the object to be detected is higher than the room temperature, a positive DC signal from the synchronous detector 46 corresponding to the difference between the temperature of the object to be detected and the room temperature,
A DC signal from the diode 39 corresponding to the room temperature is added, and thereby the synthesis circuit 47 outputs a DC signal corresponding to the actual temperature of the object to be detected.
Also, if the temperature of the object to be detected is lower than room temperature,
Similarly, the diode 3 is connected to the negative DC signal from the synchronous detector 46 according to the difference between the temperature of the detected object and the room temperature.
In other words, the DC signal representing the temperature difference is subtracted from the DC signal representing the room temperature, so that the combining circuit 47 generates a DC signal corresponding to the actual temperature of the object to be detected. Output. Then, a DC signal corresponding to the actual temperature outputted from the combining circuit 47 is led out from an output terminal 48 to a desired circuit.

Incidentally, each of the above embodiments may be slightly modified to provide infrared detectors 49 and 50 as shown in FIGS. 5 and 6. That is, in the infrared detector 49 in FIG.
It is provided in the infrared transmitting body 24. In the infrared detector 50 in FIG.
6 is fixed to another fixing base (not shown) provided in the storage body 12, and the bimorph 28
The frame body 51 is attached to the frame body 51 .

As is clear from the above description, the infrared detector of the present invention includes an infrared detecting body that generates a charge according to the amount of change in incident infrared light, a storage body that houses the detecting body, a plurality of infrared passing parts, and an infrared non-passing part. a pair of opposing bodies located in a region through which infrared rays from the object to be detected pass in order to be incident on the object to be detected, a state in which the infrared passing parts of the pair of opposing bodies and the infrared passing parts substantially overlap each other; and a state in which the infrared passing portion and the infrared non-passing portion of one opposing body substantially overlap with the infrared passing portion and infrared passing portion of the other opposing body, respectively, which vibrate to periodically repeat. , there is no need for a chopper or motor to change the infrared rays incident on the infrared detector, which allows the infrared detector itself to be made smaller, and the infrared rays incident on the infrared detector are uniform and periodic. Infrared detection can be carried out with high precision because of the change in temperature.

[Brief explanation of the drawing]

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 sectional view of an infrared detector according to another embodiment of the present invention. 4 are circuit diagrams including the infrared detectors of FIGS. 2 and 3, and FIGS. 5 and 6 are sectional views of infrared detectors according to still other embodiments of the present invention, respectively. 5... Infrared detecting body, 12... Storage body, 23... Opening, 24... First infrared transmitting body, 25, 25s... First infrared non-passing body, 26, 26s... Second infrared transmitting body, 27, 27s... Second Infrared non-transmissive body, 28
and 28s...bimorph.

Claims (1)

[Claims] 1. It has an infrared detection body that generates a charge according to the amount of change in incident infrared rays, a storage body that houses the detection body, a plurality of infrared passing parts and infrared non-passing parts, and the infrared rays from the object to be detected reach the said detection body. A pair of opposing bodies located in a region through which the incident light should pass, a state in which the infrared passing portions and infrared non-passing portions of the pair of opposing bodies substantially overlap each other, and an infrared passing portion and an infrared non-passing portion of one of the opposing bodies. An infrared detector comprising: a vibrating body that vibrates to periodically repeat a state in which the non-infrared passing portion and the infrared passing portion of the other opposing body substantially overlap, respectively.