JPH0156367B2 - - Google Patents

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to an infrared detection section.

(b) Prior art and its problems Modern infrared detectors have a built-in infrared detector, for example, a pyroelectric type 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 FIGS. 3 is placed.

However, such a jumper 3 has a large shape and has problems in terms of space.

Therefore, an infrared detector 4 as shown in FIG. 2 has been devised. In the figure, numeral 5 is a pyroelectric infrared detector made of lithium tanchlorate (LiTaO ₃ ) single crystal and generates a charge according to the amount of change in incident infrared rays, and 6 and 7 are the front and back surfaces of the infrared detector, respectively. Front and back electrodes formed with Nikrok vapor deposition film,
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 on which an impedance conversion circuit 11 is arranged to make the infrared detector 4 low resistance since the infrared detector 5 has a high resistance; 12 is a metal cap 13 and a header 1;
4, the header 1 in the storage body is
The support stand 8 and the substrate 10 are fixed on the 4. 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 the impedance conversion circuit 11 and the first and second impedance conversion circuits.
This is a lead wire that connects the 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, and 24 is an infrared transmitting member that closes the opening, which has a high transmittance for infrared rays having a wavelength of 2 to 15 μm. It is made of a silicon or glumanium plate several 100 μm thick.

25 is a shield body made of aluminum or the like and covers the infrared detector 5 and the impedance conversion circuit 11, and 26 is the detector 5 of the shield body.
This is an opening made in the upper part.

27 is a planar first opposing body attached to the opening, and as shown in FIG. A plurality of first infrared non-transmissive portions 28, 28, extending in a fan shape in the direction (FIG. 2)
... and the first infrared transmitting parts 29, 2 located between each of the first infrared non-transmissive parts 28, 28, ...
9,... are formed. The widths W ₁ and W ₂ of the first infrared non-transmissive portions 28, 28, ... are respectively
100 μm, 120 μm, the first infrared transmitting portion 29,
The widths W ₁ ' and W ₂ of 29... are the same dimensions as W ₁ and W ₂ above. 30 is a planar second opposing body arranged parallel to and close to the first opposing body 27;
As shown in FIG. 3b, the second opposing body has the first
A plurality of second infrared non-transparent parts 31, 31, made of the same material as the infrared non-transparent parts 28, 28, .
...and the second infrared transmitting parts 32, 3 located between each of the second infrared non-transmissive parts 31, 31, ...
2,... are formed. Widths W 1 , W 2 of the second infrared non-transmissive portions 31, ₃₁ , _{. .} . and widths W ₁ ′ of the second infrared ray transmissive portions 32, 32, .
W ₂ is the first infrared non-transmissive portion 28, 28,
Widths W ₁ and W ₂ of ... and the first infrared transmitting portions 29 and 2
9,... have the same dimensions as the widths W ₁ and W ₂ '.

33 is a vibrator formed by laminating two piezoelectric plates made of ferroelectric material or a metal plate and a piezoelectric plate made of ferroelectric material, that is, a bimorph, which has a rectangular parallelepiped shape and has a length l and a width. w, thickness a
are approximately 30 mm, 5 mm, and 0.5 mm, respectively. The bimorph 33 is made longer in the direction perpendicular to the infrared incident direction, that is, in the lateral direction, so that the left end 33'
is fixed to an insulating stand 34 provided on the header 14, and the second opposing body 30 is attached to the right end 33''. 35 is a third lead implanted in the header 14 via an insulator 36. The terminals 37 and 38 are located at the left end 33' of the bimorph 33 as shown in FIG.
first and second vibrating electrodes formed on both surfaces of the third lead terminal 35, respectively.
and is connected to the header 14 (earth terminal 15). Reference numeral 39 denotes a support base made of resin such as Teflon, and the free end 3 of the second opposing body 30 is attached to the support base.
A groove 40 is cut to slidably support 0'.

A predetermined alternating current voltage, that is, a periodic pulse, is applied to the first vibrating electrode 37 via the third lead terminal 35, but when no such pulse is applied, the two opposing The second infrared non-transmissive portions 31, 31, . . . of the body 30 are the first opposing body 27.
completely overlap the first infrared transmitting portions 29, 29, . . . (located in the perspective area J in FIG. 3C). When the pulse is applied, the bimorph 33 is bent in the direction A, and the second infrared non-transmissive parts 31, 31, . . .
8, completely overlaps with... (dot area I in Figure 3 C)
). Therefore, by periodically applying pulses to the first vibrating electrode 37, the bimorph 33 is periodically vibrated in the A and B directions, and the infrared detector 5 is exposed to the outside of the infrared detector 4. Infrared rays from the detection object are periodically incident. When such an incident occurs, the amount of infrared rays incident on the infrared detector 5 changes periodically, so that the infrared detector 5
generates a charge according to this amount of change. and,
This charge is caused by the temperature of the object to be detected and the room temperature (second opposing object 3).
0).

FIG. 5 shows a circuit including the infrared detector 4, and the impedance conversion circuit 11 in the infrared detector 4 has a high input resistance 41 of 10 ¹¹ to 10 ¹¹ Ω, an FET (field effect transistor) 42, and an output of about 10 KΩ. It is formed by a resistor 43.

The infrared detector 4 is supplied with a DC voltage through a first lead terminal 16, and when the bimorph 33 vibrates, an amplitude corresponding to the temperature difference between the temperature of the object to be detected and the room temperature is transmitted from the second lead terminal 17. An AC signal e as shown in FIG. 6a is output. 44 is a room temperature diode that measures the room temperature and outputs a DC signal according to the room temperature; 45 is an oscillator consisting of an astable multivibrator that oscillates periodic pulses f as shown in FIG. A drive circuit that outputs periodic pulses to vibrate the bimorph 33, 47, 48, 49 are DC amplifiers, 50 is a filter amplifier, 51 is a synchronous detector, and the detector is a The AC signal e is synchronized with the pulse f from the oscillator 45, and if the temperature of the object to be detected is higher than room temperature, a positive DC signal is output according to the temperature difference,
When the temperature of the object to be detected is lower than room temperature, a negative DC signal corresponding to the temperature difference is output.

That is, as for the output AC signal e of the infrared detector 4, the positive half cycle e+ coincides with the pulse f when the temperature of the detected object is higher than room temperature, and the negative half cycle e when the temperature of the detected object is lower than room temperature. - coincides with pulse f. When the pulse f and the positive half cycle e+ match, the synchronous detector 51 outputs a positive DC signal corresponding to the temperature difference between the detected object and the room temperature, and pulse f and the negative half cycle e+. A negative DC signal corresponding to the temperature difference between the detected object and the room temperature is output, which matches the cycle e-.

Reference numeral 52 denotes a synthesis circuit that adds together the DC signal from the synchronous detector 51 and the DC signal corresponding to the room temperature of the room temperature diode 44, and by such addition, the circuit generates a signal corresponding to the temperature of the object to be detected. Output. 53
is an output terminal for outputting such a temperature signal to a desired circuit.

Here, the vibrational state of the bimorph 33 is the one when the room temperature is 25°C, and when the room temperature rises to, for example, 30°C, the vibrational state of the bimorph 33 changes compared to the above. That is, due to the rise in room temperature, the bimorph 33 is bent by a dimension m in the B direction even when the pulse f is not generated, and the second infrared non-transmissive parts 31, 31, . . . The first infrared transmitting section 29,2 is located at
9, . When the pulse f is generated, the second infrared opaque parts 31, 31, . Infrared rays from the body do not enter the infrared detector 5 sufficiently. Then, the amount of change in the incident infrared rays on the infrared detector 5 decreases significantly, and the output of the infrared detector 4 becomes as shown in Fig. 6a.
The AC signal e' becomes so small that an AC signal e having a desired amplitude cannot be obtained, and therefore the detection accuracy of the infrared detector 4 is significantly reduced.

(C) Embodiments The present invention has been made in view of these points, and embodiments of the present invention will be described in detail below based on the drawings. Incidentally, the same parts as in the conventional example are denoted by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 7, 54 is a fourth lead terminal implanted in the header 14 via an insulating material 55;
is a bimorph diode as a temperature detector placed near the bimorph 33 in the storage body 12 in order to detect the temperature of the bimorph 33 and output a DC voltage based on the detected temperature, and the anode of the diode is It is connected to the fourth lead terminal 54, and its cathode is connected (grounded) to the header 14.

FIG. 8 shows a circuit including such an infrared detector 4',
Reference numeral 57 denotes a differential amplifier, the negative input terminal of which is connected to the anode of the bimorph bimorph 56 via the fourth lead terminal 54, and the positive input terminal connected to a variable resistor 58.

In the variable resistor 58, a desired resistance value is set in advance so that the DC voltage input to the + input terminal of the differential amplifier 57 is equal to the DC voltage input to the - input terminal when the bimorph temperature is 25°C. ing.

59 is an inverter that inverts the output of the differential amplifier 57. The output of the inverter is 0V when the temperature of the bimorph 33 is 25°C,
On the other hand, when the temperature is, for example, 30°C higher than 25°C, a positive DC voltage BS based on the increased temperature of 5°C is output as shown in FIG. 9C. Reference numeral 60 denotes an adder constituting the drive circuit 46, and the adder converts the pulse f from the oscillator 45 into the DC voltage from the inverter 59.
BS is added as shown in FIG. 9d, and the added output is applied to the first vibrating electrode 37.

In this case, the bimorph 33 is connected to the DC voltage
It is in a DC biased state at BS, and with this state as a reference, it vibrates periodically in the A and B directions based on the pulse f. Here, the above bimorph 33
is deflected by a dimension m (Fig. 3 d) in the direction of A under the above DC bias condition, resulting in a rise in temperature of 5°C.
The bimorph 33 no longer bends in this direction. Therefore, in the bimorph 33, as shown in FIG. 3c, the second infrared non-transmissive parts 31, 31, . The infrared detector 4' outputs an alternating current signal e as shown in FIG. 9a (same as the alternating current signal e in FIG. 6a).

In the above embodiment, the room temperature diode 44 and the bimorph diode 56 are provided separately, but the detected temperature of the bimorph diode 56 is the temperature inside the housing 12, and this temperature is the room temperature (second opposite 30), the room temperature diode 44 can be omitted and the bimorph diode 56 can also serve as the room temperature diode 44. In this case, the bimorph diode 56 is placed between the bimorph 33 and the second opposing body 30 as shown by the broken line in FIG. 7 in order to more reliably detect the temperature of the bimorph 33 and the second opposing body 30. good. The anode of the bimorph diode 56 is connected not only to the negative input terminal of the differential amplifier 57 but also to the current amplifier 49.

(d) Effects of the Invention As is clear from the above description, the present invention includes an infrared detector that generates a charge according to the amount of change in incident infrared rays, an infrared transmitting section disposed in the infrared irradiation area to the detector, and A pair of opposing oscillators, both of which have infrared opaque portions, vibrate upon application of an alternating current signal to periodically displace the relative positional relationship between the pair of opposing bodies, and detect the temperature of the oscillators; The sensor is equipped with a temperature sensor that outputs a DC signal for DC biasing the vibrator based on the detected temperature.
The infrared detector can be miniaturized, and the infrared rays incident on the infrared detector can be reliably interrupted without being affected by room temperature (the temperature of the vibrator), and an AC signal with the desired amplitude can be output. The detection accuracy can be significantly improved.

[Brief explanation of drawings]

Figures 1 a and b are a side view and a plan view of a conventional infrared detection mechanism, Figure 2 is a sectional view of an improved conventional infrared detector, and Figures 3 a, b, c, and d are the same. 4 is a view seen from the direction of the arrow in FIG. 2, FIG. 5 is a circuit diagram including the infrared detector in FIG. 2, and FIGS. 6 a and b are main signal waveforms in FIG. 5. 7 is a sectional view of an infrared detector according to an embodiment of the present invention, FIG. 8 is a circuit diagram including the infrared detector of FIG. 7, and FIG. 9 a, b, c, and d are main parts in FIG. 8. It is a signal waveform diagram. 5... Infrared detector, 12... Storage body, 23...
...Opening, 27...First opposing body, 28, 28,...
First infrared non-transmissive part, 29, 29,... First infrared transmissive part, 30... Second opposing body, 31, 31,...
...Second infrared non-transmissive part, 32, 32, ...Second infrared transmissive part, 33...Bimorph, 56...Diode for bimorph.

Claims (1)

[Claims] 1. An infrared detector that generates a charge according to the amount of change in incident infrared rays, a pair of opposing bodies that are placed in the infrared incident area of the detector and have both an infrared transmitting part and an infrared non-transmitting part, which vibrate when an AC signal is applied. and a vibrator that periodically displaces the relative positional relationship between the pair of opposing bodies, detects the temperature of the vibrator, and outputs a DC signal for applying a DC bias to the vibrator based on the detected temperature. An infrared detector characterized by being equipped with a temperature detector.