JPH0553372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an infrared detection device for detecting, for example, the temperature of a detected part based on infrared rays.

(b) Prior Art FIG. 11 shows an infrared detector 100 of a conventional infrared detection device. In such a detector 100, inside an outer case 104 consisting of a metal header 101 and a cap 103 having an infrared transmitting section 102, there is a pyroelectric infrared detector 105 that generates an electric charge based on the amount of change in incident infrared rays. and a chopper mechanism that changes the infrared rays incident on the detection object. The chopper mechanism, also shown in FIG. 12, consists of a pair of piezoelectric vibrators 106, 107 and a pair of opposing bodies 108, 109 fixed to each end of the vibrator. Such an opposing body 10
8, 109 are formed with a plurality of slits 110, 110, .

The vibrating bodies 106 and 107 periodically vibrate in opposite directions (direction A or B) based on the applied predetermined AC drive signal, thereby causing the opposing bodies 108 and 109 to change their relative positions. The relationship changes periodically, and the slits 110, 110 of each of the opposing bodies 108, 109 overlap and open, and the slit 1 of one opposing body 108 overlaps and opens.
10, 110... overlap with parts other than the slits 110, 110... of the other opposing body 109, and the slits 110, 11 of each opposing body 108, 109
The state in which 0... is blocked is repeated. Then,
In the open state, the infrared rays from the detected part pass through the infrared transmitting part 102 of the case 104 and the slits 110, 110 of the opposing bodies 108, 109, and enter the infrared detecting body 105, while in the closed state, the infrared rays enter the infrared detecting body 105. Only the infrared rays from the bodies 108 and 109 are incident on the infrared detecting body 105, so that the infrared detecting body 105 periodically changes the amount of incident infrared rays and generates a charge for measuring the temperature of the detected part, for example.

Now, in the infrared detector 100, the vibrating bodies 106 and 107 are affected by the ambient temperature,
Based on changes in ambient temperature, deflection in the A or B direction occurs, and the amplitude values of vibrations etc. vary.
If the deflection occurs as in the former case, the relative positional relationship between the opposing bodies 108 and 109 changes from the desired state when not vibrating, and the slit 11 changes when vibrating.
The desired open/closed state of 0,110... cannot be obtained. In addition, when the amplitude value fluctuates as in the latter case, the slits 110 and 11 also change during vibration.
The desired open/closed state of 0... cannot be obtained. When the desired open/closed state is no longer obtained, the amount of change in the infrared rays incident on the infrared detector 105 changes, and the amount of charge generated from the infrared detector 105 changes based on the change in ambient temperature. The amount will fluctuate, making accurate temperature measurements impossible.

The former deflection that occurs in response to changes in ambient temperature is caused by the deflection of both vibrators 106 and 1 in response to changes in ambient temperature, as seen in Japanese Patent Application Laid-Open No. 59-46826.
By applying a DC bias signal to 07, its occurrence is suppressed in advance, thus eliminating inaccuracies in temperature measurements due to such deflections.

However, a solution to the latter problem, in which the amplitude value fluctuates in response to changes in ambient temperature, resulting in inaccurate temperature measurement, has not yet been proposed.

(c) Problems to be Solved by the Invention The object of the present invention is to provide an infrared detection device that can prevent the amplitude value of a vibrating body from changing due to changes in ambient temperature and can perform accurate temperature measurements.

(d) Means for Solving the Problems The present invention includes an infrared detecting body that generates an electric charge according to the amount of change in incident infrared light, and an infrared passing part and an infrared non-passing part arranged in an infrared incident area to the detecting body. a pair of opposing bodies that both have a In the infrared detection device, the infrared detection device includes a pair of vibrating bodies that periodically change the relative positional relationship of The present invention is characterized in that it includes an adjusting means for adjusting the magnitude of the drive signal so as to suppress the fluctuation thereof accordingly.

(E) Effect When the ambient temperature changes, the magnitude of the drive signal applied to the vibrating body is adjusted accordingly, and the amplitude value of the vibrating body is suppressed from fluctuating in accordance with the change in the ambient temperature.

(F) Embodiment FIGS. 1 and 2 show an infrared detector 1 in an infrared detection apparatus according to an embodiment of the present invention. In such a detector 1, an infrared detection section 7 and a chopper mechanism section 8 are contained inside an outer case 6 consisting of a metal header 2 and a cap 5 having an infrared entrance port 4 closed with an infrared transmission filter 3. and are arranged.

The infrared detecting section 7 is provided with a pyroelectric infrared detecting body 11 made of lithium tantalate (LiTaO ₃ ) single crystal, which has front and back electrodes 9 and 10 and generates an electric charge according to the amount of change in incident infrared rays. ,
The object to be detected is a metal support 12 made of phosphor bronze or the like.
It is adhesively fixed on the top with a conductive adhesive 13.
The infrared detector 11 has an infrared incidence opening 1.
It is shielded from external noise by a shield body 15 having a diameter of 4. Furthermore, the surface electrode 9
An impedance conversion circuit (described later) is connected to the signal terminal 16 installed in the header 2 via an insulating material.
The back electrode 10 is electrically connected to the ground terminal 17 via the adhesive 13, the support base 12, and the header 2.

Next, in the chopper mechanism section 8, the infrared rays are incident on the detection body 11, that is, the detection body 1
A pair of planar first and second opposing bodies 18 and 19 are located between the opening 4 and the opening 4 in parallel to each other. As shown in FIGS. 3a and 3b, the first and second opposing bodies are made of a material that does not pass infrared rays, such as aluminum, and have infrared rays passing parts 20 and 21 in the form of a plurality of slits extending in a fan shape. Infrared passing portions 22 and 23 are located between each of the passing portions. Above passage section 2
0, 21 and non-passing parts 22, 23 have the same dimensions,
The widths W ₁ and W ₂ are 100 μm and 200 μm, respectively.

The first and second opposing bodies 18 and 19 are fixed to the right ends of the first and second vibrating bodies 24 and 25, respectively. The structures of the first and second vibrating bodies are shown in detail in FIG. That is, there are central electrodes 26 and 27 made of phosphor bronze or the like, and on both sides of each central electrode there are piezoelectric electrodes made of barium titanate, lead zirconate titanate, etc. and polarized in a single direction (arrow p). The piezoelectric bodies 28, 29 are provided so that their polarization directions are the same, and surface electrodes 30, 31 made of silver or the like are formed on the outer surfaces of the piezoelectric bodies 28, 29.

The first and second vibrating bodies 24 and 25 are clamped and fixed by first and second metal fixing bases 33 and 34 fixed on the header 2 with an insulating layer 32 interposed therebetween. In this case, the first and second fixing bases 33, 34
Surface electrodes 30 and 31 are in electrical contact with the electrodes. The center electrode 26 of the first vibrating body 24 and the second fixing base 34 are connected to a first vibrating terminal 35 implanted in the header 2 via an insulating material, and the second vibrating body 25 is The center electrode 27 and the first fixing base 33 are connected to a second vibration terminal 36 which is similarly implanted in the header 2 via an insulating material.

Therefore, a potential difference +V volt (first
The signals of -V volts (the voltage at the vibrating terminal 35 is higher than the second vibrating terminal 36) and -V volts (the voltage at the second vibrating terminal 36 is higher than the first vibrating terminal 35) are alternated periodically (frequency 3 Hz). is applied repeatedly. In the case of the latter potential difference, in the first vibrating body 24, the lower piezoelectric body 28 (FIG. 4) contracts while the upper piezoelectric body 28 expands, so that the first vibrating body 24 bends in the direction of arrow A. . Further, in the second vibrating body 25, the lower piezoelectric body 29 extends and the upper piezoelectric body 29 contracts, so that the second vibrating body 25 is bent in the B direction. On the other hand, in the case of the former potential difference, the first and second vibrating bodies 24 and 25 bend in directions B and A, respectively, contrary to the above description.

As a result, the first and second vibrating bodies 24, 25
vibrate periodically in opposite directions, and based on such vibrations, the relative positional relationship of the first and second opposing bodies 18, 19 is displaced, and the infrared passing portions 20, 21 of both opposing bodies 18, 19 are displaced. The infrared passing portion 20 of the first opposing body 18 overlaps with the infrared non-passing portion 23 of the second opposing body 19 and is closed (the infrared passing portion 20 of the first opposing body 18 overlaps and is open).
2 overlaps with the infrared passing portion 21 of the second opposing body 19 and is occluded) is repeated periodically. Then, the infrared detecting body 11 changes the amount of incident infrared rays based on the infrared rays from the object to be detected that pass through the filter 3 and enter the outer case 6, and the infrared rays from the opposing bodies 18 and 19. Therefore, a charge corresponding to the temperature of the object to be detected, more specifically, a signal corresponding to the temperature difference between the object to be detected and the opposing bodies 18 and 19 is output.

The outer case 6 further includes a built-in temperature measuring diode 37 for detecting the temperature of the opposing bodies 18 and 19. The anode of the diode is connected to a diode terminal 38 implanted in the header 2 via an insulating material, and the cathode is grounded.

FIG. 5 shows the structure of an infrared detection device including the infrared detector 1, which is fixed to a printed circuit board 39 via its terminals. The printed circuit board 39 includes a temperature circuit 40 that processes the temperature signal from the infrared detector 1;
A drive circuit 41 is provided which outputs signals of periodic potential differences of +V volts and -V volts as drive signals for the vibrating bodies 24 and 25. The printed circuit board 39 to which the infrared detector 1 is fixed is disposed within the box body 42.

FIG. 6 shows a circuit of an infrared detecting device including the infrared detector 1 described above. The surface electrode 9 of the infrared detector 11 is connected to the shield body 15 together with the infrared detector 11.
It is connected to an impedance conversion circuit 43 located inside. The conversion circuit consists of a high input resistance 44 of 10 ¹⁰ to 10 ¹¹ Ω, a FET 45, and an output resistance 46 of about 10 KΩ, the source of the FET 45 is connected to the signal terminal 16, and the drain is connected to the DC voltage application terminal 47. It is connected to the.

Thus, between the first and second vibration terminals 35 and 36, a drive signal is sent from the drive circuit 41.
Potential difference signals (FIG. 7C) of ±V volts are applied alternately.

That is, in the drive circuit 41, the oscillator 4
8 outputs a low level (-7 volts) pulse P at a frequency of 3 Hz (FIG. 7b). On the other hand, a stabilized power supply circuit 53 consisting of a Zener diode 49, a diode 50, transistors 51, 52, etc. receives a voltage of -V _DD (approximately -40 volts) through a switch 54, so that the stabilized power supply circuit 53 receives a voltage of -V _C volts. A voltage is generated (Figure 7a). At this time, when the pulse P is output, the transistor 55 is turned on, and the next transistor 56 is also turned on, so that O volts are applied to the first vibration terminal 35 and the second vibration terminal 3
-V _C volts are applied to 6. In short, first,
A potential difference signal of +V volts is applied between the second vibration terminals 35 and 36. Further, while the pulse P is not output, the transistor 55 is turned off, and the next transistor 56 is also turned off, so that -V _C volts and 0 volts are applied to the first and second vibration terminals 35 and 36, respectively. In short, a potential difference signal of -V volts is applied between the first and second vibration terminals 35 and 36.

In this way, the first and second vibration terminals 3
When a potential difference signal of ±V volts is applied alternately between the objects 5 and 36, the first and second vibrating bodies 24 and 25 vibrate as described above, and at the time of such vibration, the object to be detected and the opposing body 18, A signal corresponding to the temperature difference with respect to the detector 19 is led out from the signal terminal 16 through the impedance conversion circuit 43 to the outside of the detector 1. Such a signal actually forms an alternating current e as shown in FIG. 7d, and its amplitude corresponds to the temperature difference. The signal derived in this way then reaches the temperature circuit 40, passes through the filter amplifier 57, and is then sent to the synchronous detector 5.
8 is input.

The detector 58 synchronizes the AC signal e with the output of the oscillator 48, and when the temperature of the object to be detected is higher than the temperature of the opposing bodies 18 and 19, a positive DC signal corresponding to the temperature difference is generated. If the temperature of the object to be detected is lower than the temperature of the opposing bodies 18 and 19, a negative DC signal corresponding to the temperature difference is detected and output. That is, as for the AC signal e, when the temperature of the object to be detected is higher than the temperature of the opposing bodies 18 and 19, the positive half cycle e+ coincides with the portion corresponding to the potential difference +V volts of the output of the oscillator 48, and the temperature of the object to be detected is When the temperature is lower than that of the opposing bodies 18 and 19, the negative half cycle e- coincides with the portion corresponding to the potential difference +V volts of the oscillator 48 output. Then, the detector 58 detects the detected object and the opposing object 1 when the former matches.
A positive DC signal corresponding to the temperature difference between 8 and 19 is output, and when the latter match, a negative DC signal corresponding to the temperature difference is output.

The output from the detector 58 is inputted to a combining circuit 60 via a DC amplifier 59. Further, the output from the temperature measuring diode 37, that is, a signal corresponding to the temperature of the opposing bodies 18 and 19 is input to the synthesis circuit via a DC amplifier 61. Then, the synthesis circuit 60 adds these two inputs and outputs a signal corresponding to the actual temperature of the object to be detected. The output is output from the output terminal 63 to the outside of the box 42 via the DC amplifier 62, and is input to a control circuit 64 including a microcomputer.

The control circuit 64 performs various controls based on the temperature signal thus input. For example, in a microwave oven, heating is controlled based on the temperature signal. Further, when inputting this temperature signal, the control circuit 64 causes the oscillator 48 to start oscillating in advance and turns on the switch 54.

Now, the first and second vibrating bodies 24 and 25 are composed of piezoelectric bodies 28 and 29, etc., and have a characteristic that the amplitude value of the periodic vibration changes according to changes in the ambient temperature, as shown in FIG. Specifically, there is a positive temperature characteristic in which the amplitude value increases as the ambient temperature rises. When the amplitude value fluctuates in this way, as shown in FIG. Potential difference signal ±
(corresponding to V volts)
The temperature signal output from the sensor fluctuates in response to changes in ambient temperature. Specifically, when the absolute value of the output voltage -Ve volts is Vp (-30 volts), when the ambient temperature changes to 5°C, 25°C, and 60°C, the temperature signals become RT ₅ , RT ₂₅ , RT varies to ₆₀ .
Therefore, the ambient temperature changes, and the first and second vibrating bodies 3
If the amplitude values of 5 and 36 vary, the temperature measurement will be inaccurate.

Here, in the embodiment of the present invention, the emitter-base of the diode 50 and transistor 52 constituting the stabilized power supply circuit 53 of the drive circuit 41 have negative temperature characteristics, so that the output voltage -Ve The absolute value of volts has a negative temperature characteristic as shown in FIG. In this case, the stabilized power supply circuit 53 constitutes the drive circuit 41 and is disposed on the printed circuit board 39,
It exists in the same box body 42 together with the infrared detector 1 including the first and second vibrating bodies 24 and 25, and therefore the negative of the absolute value of the output voltage -Ve volts in the stabilized power supply circuit 53. The temperature characteristics correspond to the ambient temperature that is substantially the same as that of the first and second vibrating bodies 24 and 25.

Therefore, when the ambient temperature changes to 5℃, 25℃, and 60℃, the absolute value of the output voltage −Ve volts becomes V _P ′,
V _P , V _P ″. And, in comparison with Fig. 9, as the ambient temperature changes, the output voltage −Ve
Even if the absolute value of volt changes to V _P ′, V _P , V _P ″,
The temperature signal output from the output terminal 63 is
It becomes constant at RT ₂₅ , and the first and second vibrating bodies 24, 2
This indicates that fluctuations in the amplitude value of 5 are suppressed in advance. Therefore, the temperature measurement will not be inaccurate.

Here, the stabilized power supply circuit 5 of the drive circuit 41
A diode 50 and a transistor 52 in the drive circuit 3 adjust the drive signal from the drive circuit 41 so as to suppress fluctuations in the amplitude values of the first and second vibrating bodies 24 and 25 in response to changes in ambient temperature. It's hot,
This corresponds to the adjustment means of the present invention.

In this embodiment, if the amplitude values of the first and second vibrating bodies 24 and 25 vary greatly with respect to the ambient temperature, for example, the Zener diode 49 in the stabilized power supply circuit 53 also has a negative temperature characteristic. Conversely, if the temperature is small, for example, the diode 50 may not have negative temperature characteristics, or the Zener diode 49 may have positive temperature characteristics.

(G) Effects of the Invention According to the present invention, the amplitude value of the vibrating body does not change even if the ambient temperature changes, and therefore accurate temperature measurement etc. can be performed.

[Brief explanation of the drawing]

1 to 10 show embodiments of the present invention,
Figure 1 is an exploded perspective view of the infrared detector, Figure 2 is a sectional view of the same, Figures 3a and b are plan views of the first and second opposing bodies, respectively, and Figure 4 is the main part of the infrared detector. Plan view,
Fig. 5 is a perspective view of the infrared detection device, Fig. 6 is its circuit diagram, Fig. 7 is a signal waveform diagram, Fig. 8 is a characteristic diagram of amplitude value with respect to ambient temperature, and Fig. 9 is a voltage value |-V _C
FIG. 10 is a characteristic diagram of the voltage value |−V _C | with respect to the ambient temperature, and FIGS. 11 and 12 show conventional examples, and FIG.
FIG. 1 is a sectional view of the infrared detector, and FIG. 12 is a plan view of the main part thereof. 11... Infrared detector, 18, 19... 1st,
Second opposing body, 20, 21...Infrared passing section, 2
2, 23... Infrared non-passing section, 24, 25... First and second vibrating bodies, 41... Drive circuit.

Claims (1)

[Claims] 1. An infrared detecting body that generates a charge according to the amount of change in incident infrared rays; a pair of opposing bodies that are disposed in an infrared incident region to the detecting body and have both an infrared passing section and an infrared non-passing section; a pair of vibrating bodies that are fixed to each body and have a characteristic that the amplitude value of vibration caused by application of a drive signal varies according to changes in ambient temperature, and that periodically changes the relative positional relationship between the pair of opposing bodies; and a drive circuit that outputs the drive signal, the drive circuit configured to control the drive circuit so as to suppress fluctuations in the amplitude value of the vibrating body in accordance with changes in the ambient temperature. An infrared detection device characterized by having an adjustment means for adjusting the magnitude of a signal.