JPH0240172B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to an infrared sensor for detecting the temperature of an object to be detected using infrared rays, for example. (b) Prior Art In FIGS. 1a and 1b, a recent infrared sensor 1 has a built-in infrared detector, for example, of a pyroelectric type. 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 change the infrared rays incident on the object to be detected, and for this purpose, a metal chopper 3 that is driven to rotate periodically by a synchronous motor 2 is arranged in front of the infrared sensor 1. Therefore, when the infrared rays from the object to be detected and the infrared rays from the chopper 3 are alternately and periodically incident on the infrared detecting body due to the rotation of the chopper 3, the amount of incident infrared rays is periodically incident on the infrared detecting body. and generates an electric charge. Such charges are used to measure the temperature of the object to be detected. However, in the above configuration, the motor 2 and the chopper 3 have a considerably large shape, and there are problems in terms of space. Therefore, an infrared sensor 4 as shown in FIGS. 2 and 3 has been devised. Such an infrared sensor 4
The length, width, and height of the external dimensions are approximately
It has a small rectangular parallelepiped shape with dimensions of 60, 20, and 15 mm, and has a built-in novel chopper mechanism, thus eliminating the need for the motor 2 and chopper 3 as described above, and solving the space problem. The specific structure of the infrared sensor 4 will be explained below. Inside a sensor case 8 consisting of a metal header 5 and a cap 7 having an infrared transmitting section 6,
a pyroelectric infrared detector 10 that is surrounded by a shield body 9 and generates an electric charge based on the amount of change in incident infrared rays;
A chopper mechanism is provided to change the infrared rays incident on the detection object. The tippa mechanism is
A pair of voltage vibrating bodies 11, 12 and a pair of opposing bodies 13, 14 fixed to the free ends of each of the vibrating bodies
It is made up of A plurality of slits 15, 15, . . . of the same shape and size are formed in the opposing bodies 13, 14, respectively, to allow infrared rays to pass therethrough. The vibrating bodies 11 and 12 periodically vibrate in directions opposite to each other (direction A or B), and as a result, the relative positional relationship of the opposing bodies 13 and 14 changes periodically. A state in which the slits 15, 15, . . . of each of the slits 13, 14 are overlapped and open, and a state in which the slits 15, 15, . . . are not overlapped and are closed, are periodically repeated. Then, in the superimposed state, the infrared rays from the object to be detected are transmitted to the infrared transmitting part 6 of the case 8 and both opposing bodies 13 and 1.
On the other hand, in the non-overlapping state, only the infrared rays from the opposing bodies 13 and 14 enter the infrared detector 10 through the slits 15, 15, . . .
0, the amount of incident infrared rays changes periodically and generates a charge for measuring the temperature of the object to be detected, for example. Now, in the case of the sensor 4, an insulating substrate IS having a plurality of electrodes patterned on its upper surface is further arranged, and the infrared detector 10, piezoelectric vibrators 11, 12, etc. are arranged on the substrate to make the sensor 4 as much as possible. It is arranged in a hybrid manner to make it compact. The charge signal from the infrared detector 10 is led out to the outside of the sensor 4 through a predetermined electrode on the substrate IS for measuring the temperature of the object to be detected. Thus, the piezoelectric vibrators 11 and 12 are connected to other predetermined electrodes on the substrate IS and conductive lead wires l ₁ ,
By applying an alternating current drive signal through l _{1 .} . . , it vibrates periodically in the A or B direction as described above. Here, since the drive signal voltage transmitted through the other predetermined electrodes and conductive lead wires l ₁ , l ₁ . The noise is generated from the lines l ₁ , l _{1 .} . . and enters the shield body 9 and rides on the signal output from the infrared detector 10, resulting in a decrease in the SN ratio of the sensor 4. There is. (c) Description of the invention An object of the present invention is to obtain a highly reliable infrared sensor that is not affected by noise based on an AC drive signal applied to a vibrating body and does not cause a decrease in the S/N ratio. be. (d) Structure of the Invention In order to achieve the above object, the infrared sensor of the present invention includes a sensor case, an insulating substrate arranged in the case and patterned with a plurality of electrodes, and a signal that outputs a signal according to the amount of change in incident infrared rays. an infrared detector whose signal is generated and guided to a predetermined electrode on the substrate; and a pair of opposing bodies having a plurality of infrared passing parts and infrared non-passing parts and located in an infrared incidence area of the infrared detector. , a vibrating body that vibrates to periodically change the opening/closing degree of the infrared passing portions of the pair of opposing bodies and another predetermined electrode of the substrate and the vibrating body are electrically connected, and an electric current is applied to the other predetermined electrode. a conductive part for guiding an AC driving signal of the vibrating body to the vibrating body, and the driving signal is applied to the predetermined electrode on the substrate to which the signal from the infrared detecting body is guided. A ground electrode is interposed between the above-described other predetermined electrode, and a ground body connected to the ground electrode is disposed in a space above the ground electrode. (E) Embodiment FIGS. 4 to 11 show an infrared sensor 16 according to an embodiment of the present invention. The external dimensions of the sensor are length,
The width and height are 24, 16, and 15 mm, respectively, and the sensor 16
has been sufficiently miniaturized. First, the sensor case 17 is made of metal cap 1.
8 and a header 19. The cap 18 is closed with an infrared-transmissive silicon plate 20 and is formed with an external infrared ray entrance opening 21 having a diameter of 3.5 mm for guiding external infrared rays emitted by the object to be detected into the case 17. In addition, first to fifth terminals 22a to 22e are implanted in the header 19 via an insulator, and a third grounding terminal 22f is connected to the header 19.
are directly planted. Furthermore, seventh and eighth terminals 22g and 22h are implanted as dummies. Therefore, the header 19 is installed inside the case 17.
An alumina insulating main substrate 23 is bonded thereon with an epoxy-based insulating adhesive 24. In this case, the main board 23 has the first to eighth terminal holes 25a to
25h, and these terminal holes 25a to 25
The first to eighth terminals 22a to 22h are fitted into the terminals h, respectively. Further, on the upper surface of the main substrate 23, a first
- The seventh electrodes 26a to 26g are patterned by screen printing and sintering silver palladium. These first to sixth electrodes 26a to 26
The first to sixth terminals 22a to 22f are soldered to f, respectively. The seventh and eighth terminals 22g and 22h are further soldered connected to the sixth electrode 26f. Then, the main board 23 is placed inside the case 17.
On the top, there is an infrared detector 27 and a chopper mechanism part 28.
etc. are configured in a hybrid manner, making it more compact. First, to explain the infrared detection section 27, it has front and back electrodes 29, 30, and is made of lithium tantalate (LiTaO ₃ ) single crystal, which generates electric charge based on the amount of change in incident infrared rays. A pyroelectric infrared detector 31 is provided, and the detector is adhesively fixed onto a metal support 32 made of phosphor bronze with a conductive adhesive 33 such as silver paste. The support base 32 is also attached to the wide part 2 of the sixth electrode 26f using a conductive adhesive 34 such as silver paste.
6f', and thereby the back electrode 30 is fixed to the adhesive 33, 34, the support base 32, and the sixth electrode 26.
f, and is electrically connected to the sixth terminal 22f, while the surface electrode 29 is connected to the seventh electrode 22f.
It is electrically connected to 6g. In addition to the infrared detector 31, a resistor chip 35 and a FET 36 are also provided. Such a resistor chip 35 is particularly constructed as shown in FIG. 10, in which an alumina piece 37 is used, and by screen printing silver palladium on both ends of one side of the piece and sintering it, a pair of resistor electrodes 38a, 38b is formed, and a resistance layer 39 of 10 ¹⁰ to 10 ¹¹ Ω is formed by screen printing so as to span between the electrodes. The resistance chip 35 has both resistance electrodes 38a,
38b with cream solder to the sixth and seventh electrodes 2.
By adhering to 6f and 26g, the main board 2
It is fixed on 3. Furthermore, the source S, drain D, and gate G of the FET 36 are connected to the first, second, and seventh electrodes 26 using the same cream solder.
It is fixed on the main board 23 by adhering to the parts a, 26b, and 26g. The infrared detector 31, resistor chip 35, and FET 36 are covered with a metal shield 40 made of phosphor bronze or tin and whose inner surface is coated with black matte paint. The shield body has a triangular roof shape, and the length l ₁ , lower width w ₁ , upper width w ₂ , and height h are, for example, 10, 11, 2, and 9 mm, respectively. 40a, 40a and claw 40
b, 40b. Thus, the lower pieces 40a, 40a of the shield body 40 are connected to the main board 23.
The claws 40b, 4 engage with the long sides 23a, 23a of the
0b is a notch 23b formed in the main board 23
The shield body 40 is soldered to the sixth electrode 26f while being engaged with the engagement hole 23c, thereby fixing the shield body 40 on the main board 23. An infrared passing hole 41 with a diameter of about 1.8 mm is formed on the upper surface of the shield body 40, just above the infrared detecting body 31. Next, to explain the chopper mechanism section 28, an alumina insulating fixing plate 42 is provided. The fixing plate has engaging pieces 43a, 43 at both ends of the lower part.
b is a notch 44 formed at a corner of the main board 23;
a, 44b so as to engage with the main board 23.
It is adhesively fixed perpendicularly to the epoxy-based insulating adhesive 45. Further, on the upper part of the fixing plate 42, there are a pair of notches 46a, for example, 4 mm in length and 0.5 mm in width.
46b are formed at an interval of 5 mm from each other, and the main board 23 is formed on one side of the fixing plate 42.
Similarly, two electrodes 47a and 47b are patterned by screen printing and sintering silver palladium. This electrode 47b has a pattern surrounding the cuts 46a and 46b,
Further, the electrode 47a has a pattern located between the notches 46a and 46b, and both electrodes 4
7a and 47b are soldered to third and fourth electrodes 26c and 26d on the main board 23, respectively. A pair of vibrating bodies 48, 49 having lengths, heights, and thicknesses of, for example, 18, 4, and 0.5 mm, respectively, are arranged in the notches 46a, 46b so as to be perpendicular to the fixing plate 42. The vibrating bodies 48 and 49 are fixed with an epoxy-based insulating adhesive. In the vibrating bodies 48 and 49, as shown in detail in FIG. 6, a central electrode 50 made of phosphor bronze, etc.
a, 50b, and piezoelectric bodies 51a, 51b and 52a, 52b are provided on each side of the central electrode, and these piezoelectric bodies 51a, 51b and 52a,
A surface electrode 5 made of silver or the like is provided on the outer surface of 52b.
3a, 53b and 54a, 54b are formed. The piezoelectric bodies 51a, 51b and 52a, 52
b is polarized in the same direction for each of the vibrating bodies 48 and 49 and in opposite directions between the vibrating bodies 48 and 49 (polarization direction P in FIG. 6). The surface electrodes 53a, 53b and 54a, 54b are all connected to the electrode 47b of the fixing plate 42 with cream solder, and the center electrodes 50a, 50b are branch pieces extending from the ends of the vibrating bodies 48, 49. 55a, 55
It has b. The branch piece is bent toward the electrode 47a side of the fixing plate 42 and connected to the electrode 47a with cream solder. A pair of opposing bodies 56, 57 are provided on the free end sides of the vibrating bodies 48, 49, facing the external infrared ray entrance 21 closely with an interval of about 1.1 mm, so that they are parallel to each other. Sumikit SG210M
(trade name of Sumitomo Chemical Co., Ltd.) and other acrylic insulating adhesives. In this case, recesses 58a and 58b having a length of 2.7 mm and a depth of 0.17 mm, for example, are formed in the bonded portions of the center electrodes 50a and 50b, and the acrylic insulating adhesive accumulates in these portions, and the opposing body 56, 57 and the vibrating body 48,
A large amount of adhesive 56', 57' is interposed between the opposing bodies 56, 57, and the adhesive fixing strength of the opposed bodies 56, 57 is therefore sufficient. Next, the opposing bodies 56 and 57 are made of an infrared opaque material such as aluminum, and are shown in FIG.
As shown in detail in FIG. 1B, infrared passing portions 59 and 60 are formed as a plurality of fan-shaped linearly extending slits, and infrared non-passing portions 61 and 62 are located between each of the passing portions. ing. These passage parts 5
9, 60 and non-passing portions 61, 62 both have the same size and shape. On the main board 23 in the case 17, the infrared detection section 27 and the chopper mechanism section 2 are provided.
In addition to 8, a temperature measuring diode 65 for measuring the temperature inside the sensor case 17, which is equal to the temperature of the opposing bodies 56 and 57, is incorporated. The diode 65 is placed in an upright state so that its anode and cathode are connected to the fifth and sixth electrodes 2 on the main substrate 23, respectively.
It is soldered connected to 6e and 26f. Next, the specific operation of the sensor 16 will be explained. The vibrating bodies 48 and 49 vibrate based on the voltages applied to the third and fourth terminals 22c and 22d. That is, a DC constant voltage of about +5 volts is applied to the fourth terminal 22d, while the third terminal 22d
Voltages of approximately +35 and -25 volts are applied alternately and periodically (frequency 3 to 5 Hz) to c. Then, the fixing plate 4 is attached to the third and fourth terminals 22c and 22d.
Center electrodes 50a, 50b of the vibrating bodies 48, 49 connected via electrodes 47a, 47b on 2
and surface electrodes 53a, 53b and 54a, 54b
Regarding the state in which the center electrodes 50a, 50b are 30 volts higher than the surface electrodes 53a, 53b and 54a, 54b (hereinafter referred to as the H state), 30
The state in which the voltage is lowered by the volt (hereinafter referred to as the L state) is alternately repeated at a frequency of 3 to 5 Hz as shown in FIG. 13a. In the case of the above-mentioned H state, the piezoelectric bodies 51a and 52b of the vibrating bodies 48 and 49 contract and the piezoelectric bodies 51b and 52b expand, and both the vibrating bodies 48 and 49 move in the S and S' directions (Fig. 6). ).
On the other hand, in the case of the L state, both vibrators 48 and 49 bend in the S' and S directions, respectively, contrary to the above. As a result, the vibrating bodies 48 and 49 periodically vibrate in opposite directions. Based on such vibration, the opposing body 5
6 and 57 are displaced in relative position, and both opposing bodies 5
A state in which the infrared passing portions 59 and 60 of 6 and 57 are almost overlapped and open (corresponding to the above H state)
, and a state in which they are occluded with almost no overlap (corresponding to the L state) are periodically repeated. In this case, the opposing bodies 56 and 57 are the infrared detectors 3
The infrared detector 31 is located in the infrared incident area of No. 1, so that the infrared detecting body 31 detects the infrared rays from the object to be detected that pass through the infrared incident port 21 and enters the sensor case 17, and the infrared rays from the opposing bodies 56 and 57. Based on this, the amount of incident infrared rays changes periodically, and thus 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 56 and 57 is output. . FIG. 12 shows a circuit including such a sensor 16.
The constant voltage of about +5 volts is applied to the fourth terminal 22d from the constant voltage circuit 66, and the third terminal 22d
2c, the output from the oscillator 67 is amplified via the amplifier circuit 68, and the above-mentioned voltages of about +35 and -25 volts are alternately and periodically applied. As a result, the vibrating bodies 48 and 49 vibrate as described above, and when vibrating, the vibrations are transmitted to the first terminal 2 via the first electrode 26a.
A signal corresponding to the temperature difference between the object to be detected and the opposing bodies 56 and 57 is output from 2a. Such a signal actually forms an alternating current e as shown in FIG. 13b, and its amplitude corresponds to the above-mentioned temperature difference. The signal from the first terminal 22a is input to the synchronous detector 70 via the filter amplifier 69. In addition, a resistor 7 of about 10KΩ is connected to the input side of the filter amplifier 69.
1 is connected. The resistor 71 constitutes an impedance conversion circuit 72 together with the resistor 39 of the sensor 16 and the FET 36. The detector 70 synchronizes the alternating current signal e with the output of the oscillator 67, and when the temperature of the object to be detected is higher than the temperature of the opposing bodies 56 and 57, the detector 70 generates a signal corresponding to the temperature difference. Detects and outputs the DC signal of
When the temperature of the object to be detected is lower than the temperature of the opposing bodies 56 and 57, 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 56, 57, the positive half cycle e+ coincides with the above H state, and the temperature of the object to be detected is higher than the temperature of the opposing bodies 56, 57. When the temperature is lower than that, the negative half cycle e- coincides with the above-mentioned H state. When the former matches, the detector 70 outputs a positive DC signal corresponding to the temperature difference between the object to be detected and the opposing bodies 56 and 57, and when the latter matches, it outputs a positive DC signal corresponding to the temperature difference. A negative DC signal is output. The output from the detector 70 is input to a combining circuit 74 via a DC amplifier 73. The output from the temperature measuring diode 65, that is, a signal corresponding to the temperature of the opposing bodies 56 and 57 is further input to the synthesis circuit via a DC amplifier 75. Then, the synthesis circuit 75 adds these two inputs and outputs a signal corresponding to the actual temperature of the object to be detected. This output is led via a DC amplifier 76 to an output terminal 77 for output to a desired circuit. Now, the AC drive signals (+35 volts and -25 volts) for periodically driving the vibrating bodies 48 and 49 are sent from the third terminal 22c to the third electrode 26c of the main board 23 and fixed as a conductive part. The vibrating bodies 48, 49 are passed through the electrode 47a of the plate 42.
is transmitted to the center electrodes 50a, 50b of the center electrodes 50a, 50b. Here, when the AC drive signal is applied to the third electrode 26c and the electrode 47a, noise based on the AC component is generated from the electrodes 26c and 47a. However, in this case, the first electrode 26a receives a signal based on the output of the infrared detector 31, that is, a signal corresponding to the temperature difference between the object to be detected and the opposing bodies 56 and 57;
The third electrode 26 to which the AC drive signal is guided
A cross section 26f'' of the sixth electrode 26f, which is grounded via the sixth terminal 22f, is interposed between the temperature measuring section 26f'' and the temperature measuring body connected to the cross section 26f''. The cathode lead wire 65' of the diode 65 is located in the space above the crossing section 26f''.With this configuration, together with the presence of the shield body 40, the first electrode 26a, etc. The electrostatic coupling with the third electrode 26c and the electrode 47a is significantly weakened, thereby significantly preventing the noise from being transmitted to the first electrode 26a, etc., and reducing the SN of the sensor 16. The center electrode 50a of the vibrating bodies 48, 49,
Of course, noise is also generated from 50b due to the application of an AC drive signal. However, in this case, the central electrodes 50a, 50b are sandwiched between the surface electrodes 53a, 53b and 54a, 54b, respectively;
Noise from the surface electrodes 53a, 53a, 50b
b and 54a, 54b are significantly shielded,
Therefore, such noise hardly causes a decrease in the SN ratio of the sensor 16. Here, a comprehensive numerical comparison of the infrared sensor 16 and the conventional infrared sensor 4 is as shown in the table below.

【table】

[Table] (F) Effects of the Invention The infrared sensor of the present invention includes a sensor case, an insulating substrate disposed inside the case and patterned with a plurality of electrodes, and a sensor that generates a signal according to the amount of change in incident infrared rays, and an infrared detector whose signal is guided to a predetermined electrode on the substrate; a pair of opposing bodies having a plurality of infrared passing parts and infrared non-passing parts and located in an infrared incidence area of the infrared detector; A vibrating body that vibrates to periodically change the opening/closing degree of the infrared passing portion of the opposing body, and the vibrating body that connects another predetermined electrode of the substrate with the vibrating body, and applies an electric current to the other predetermined electrode. a conductive part for guiding an AC drive signal to the vibrating body, the predetermined electrode on the substrate to which a signal from the infrared detector is guided, and the other predetermined electrode to which the drive signal is applied. Since a ground electrode is interposed between the ground electrode and the ground body connected to the ground electrode is placed in the space above the ground electrode, the influence of noise based on the AC drive signal applied to the vibrating body can be reduced. Therefore, the signal-to-noise ratio is improved, and a highly reliable infrared sensor can be obtained.

[Brief explanation of drawings]

FIGS. 1a and 1b are a side view and a plan view of a conventional infrared detection mechanism, FIGS. 2 and 3 are a sectional view and a plan view of essential parts of an improved conventional infrared sensor, respectively, and FIGS. 11 shows the structure of an infrared sensor according to an embodiment of the present invention, FIG. 4 is an exploded perspective view, FIG. 5 is a cross-sectional view seen from the side, FIG. 6 is a cross-sectional view taken along the - line in FIG. 5, and FIG. In Figure 5 -
8 is a sectional view taken along the - line in FIG. 5, FIG. 9 is a plan view of the main board, FIG. 10 is a bottom view of the resistor chip, and FIGS. 11a and 11b are plan views of the opposing body, respectively. 12 are circuit diagrams including the infrared sensor of the above embodiment, and FIGS. 13a and 13b are main signal waveform diagrams in FIG. 12. 17...Sensor case, 23...Main board, 26a~
26g...first to seventh electrodes, 26f''...crossing section, 31
...Infrared detector, 42...Fixing plate, 47a, 47b
... Electrode of fixed plate, 48, 49 ... Vibrating body, 56, 5
7... Opposing body, 59, 60... Infrared passing section, 61,
62... Infrared ray non-passing part, 65'... Cathode lead wire.

Claims (1)

[Claims] 1. A sensor case, an insulating substrate placed inside the case and patterned with a plurality of electrodes, and an infrared detector that generates a signal according to the amount of change in incident infrared rays, and the signal is guided to a predetermined electrode on the substrate. and a pair of opposing bodies having a plurality of infrared passing parts and infrared non-passing parts and located in the infrared incident area of the infrared detecting body, and periodically changing the opening/closing degree of the infrared passing parts of the pair of opposing bodies. conduction between a vibrating body that vibrates to increase the vibration, another predetermined electrode of the substrate, and the vibrating body, and conducting an alternating current driving signal of the vibrating body applied to the other predetermined electrode to the vibrating body; a ground electrode is interposed between the predetermined electrode on the substrate to which the signal from the infrared detector is guided and the other predetermined electrode to which the drive signal is applied; An infrared sensor characterized in that a grounding body connected to an electrode is arranged in a space above the grounding electrode.