JPH09196756A - Infrared sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an infrared sensor by which infrared rays can be fast detected with high sensitivity by a method wherein one pair of heat sensing elements are installed side by side so as to arrange their polarities in order, the polarities at one element are connected electrically and heat information at the other element is converted into an electric signal so as to be processed. SOLUTION: One pair of Al electrodes 91a, 92b are formed on a silicon or magnesia substrate by a sputtering operation, a vapor deposition operation or the like, a ferroelectric thin film 93 is formed on them by a coating and drying operation or the like, and NiCr electrodes 91a, 92a whose shape and area are identical to those of the electrodes 91b, 92b are formed so as to be situated directly on the electrodes. The electrodes 91a, 91b and thin film 93 as well as the electrodes 92a, 92b and the thin film 93 form respective pyroelectric elements, and an infrared shielding film is formed on the latter pyroelectric element so as not to be irradiated with infrared rays. As a result, infrared rays are absorbed by the former pyroelectric element with good efficiency, and a signal corresponding to the intensity of the infrared rays is output. Since the influence of the temperature change of an atmosphere appears in the same manner at both pyroelectric elements, the influence can be reduced when identical polarities of both pyroelectric elements are connected to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared sensor using a ferroelectric thin film capable of emitting a signal to a minute temperature change. More specifically, an improved manufacturing method capable of manufacturing an infrared sensor with high sensitivity, a high response speed, a high ratio of noise such as vibration to an output signal (hereinafter referred to as S / N ratio), and capable of withstanding repeated thermal history with high accuracy. Regarding

[0002]

2. Description of the Related Art Conventional infrared sensors are roughly classified into thermal type and quantum type according to their detection principle. Generally, comparing the features of the thermal infrared sensor and the quantum sensor, the thermal sensor has an advantage that it has no wavelength dependence, but it tends to have low sensitivity and low response. The detector using the pyroelectric material of the present invention is one of the thermal infrared sensors, and has been widely used in recent years for intruder alarm devices, automatic water supply devices, etc. because it is relatively inexpensive.

A pyroelectric material is an element in which the amount of spontaneous polarization changes and electric charges are induced when the temperature changes. In an infrared sensor using this element, the pyroelectric material absorbs infrared rays incident from the outside and The presence or absence of incident light and the intensity of the incident light are detected by taking out the induced signal by utilizing the change of. As a pyroelectric element, many inorganic materials, organic materials, or composites thereof are known, and as an application, they are used in an infrared sensor and put on the market.

[0004]

However, an infrared sensor in which a pyroelectric element is formed of a ferroelectric substance is actually a D ^* (ratio detection ability) that represents the S / N ratio, and the specific heat of the material of the ferroelectric substance. ,
The capacity determined by thickness and area, that is, determined by impedance) is 2 × 10 ⁸ cm · Hz ^1/2 / W, which is 6 × 10 ⁸ cm · Hz ^1/2 / of thermocouples and thermopiles.
W, or PbSe which is a quantum type detection element used at room temperature
1 × 10 ⁹ cm · Hz ^1/2 / W, which is not so high, it is difficult to separate minute infrared intensity changes.

Further, in addition to the fact that it can be used at room temperature and has no wavelength dependence, the rise time is 1 to 1 of the quantum type detector.
There is a problem in that there are many functional disadvantages such as being 3 to 5 orders of magnitude slower than 0 μs.

That is, thermal type sensors such as pyroelectric sensors and thermocouples have the problems that D ^* is lower and the response speed is slower than quantum type infrared sensors, but quantum type infrared sensors also have wavelength dependence. However, there is a problem that those used at room temperature are generally effective only for short wavelengths.

Further, when the pyroelectric infrared sensor is used to detect the infrared rays of the running yarn in the spinning process, for example,
When used for a long period of time, oil and dust adhere to the light receiving window to lower the sensitivity, so that there is a problem that a separate cleaning means or the like must be added.

[0008]

SUMMARY OF THE INVENTION Therefore, a first object of the present invention is to form a pyroelectric element with a ferroelectric thin film, to improve electrical characteristics, to have high sensitivity, fast response speed, and extremely high S / N ratio, It is to provide a highly reliable infrared sensor. It is intended to provide an infrared sensor suitable for detecting infrared intensity of a substance that emits a weak infrared ray and vibrates at a high speed or emits an infrared pulse at a high frequency.

A second object of the present invention is that the oil agent and the dust are less likely to adhere to the light receiving portion and can be used at room temperature, the sensitivity and the S / N ratio.
It is intended to provide a highly reliable infrared sensor having a high ratio, a high response speed, a high environmental resistance to oil agents and dust, and a stable sensitivity for a long period of time.

[0010]

An infrared sensor according to claim 1 is an infrared sensor for detecting heat information from the outside by means of a heat sensitive element, and two heat sensitive elements (191) (19).
2) are installed side by side so that the polarities of the respective elements are the same, one of the same polarities is electrically connected, and the thermal information of the element from at least one of the other same polarities is electrically supplied. It is characterized in that it is converted into a signal, processed by a subsequent electronic circuit, and then taken out.

An infrared sensor according to a second aspect is an infrared sensor in which thermal information from the outside is detected by a heat sensitive element, and electrodes (191a) (19) provided on one surface of the heat sensitive element material.
2a) and the electrode (196) provided on the other surface form a substantially equivalent thermosensitive element, which is connected in series through the respective electrodes (191a) and (192a), It is characterized in that thermal information is converted into an electric signal, processed by a subsequent electronic circuit, and then the signal is taken out.

The infrared sensor according to claim 3 is characterized in that the thermosensitive element material is a ferroelectric thin film (93).

An infrared sensor according to a fourth aspect of the present invention includes a ferroelectric thin film, an electrode provided on one surface of the ferroelectric thin film, and two substantially equivalent electrodes provided on the other surface. Is provided and two pyroelectric elements are formed.

In the infrared sensor of the present invention, the electrode provided on the one surface is individually provided at a portion corresponding to two substantially equivalent electrodes provided on the other surface. is there.

In the infrared sensor according to a sixth aspect of the present invention, the ferroelectric thin film is divided into two or more portions including an electrode-containing portion and an electrode-containing portion, and the respective polarization directions are the same.

In the infrared sensor according to a seventh aspect of the present invention, the electrodes having the same polarization on either of the same surfaces are connected to each other, and the outputs of the pyroelectric elements connected in series are obtained through the electrodes on the opposite surfaces. It is a thing.

The infrared sensor of claim 8 connects the electrodes of different polarization polarities on the surfaces opposite to each other, and obtains the output of the pyroelectric elements connected in parallel through the respective connected electrodes. is there.

In an infrared sensor according to a ninth aspect, the ferroelectric thin film is divided into two or more portions including a portion including an electrode and a portion including an electrode.

In the infrared sensor of the tenth aspect, the polarization directions of the pyroelectric element and the pyroelectric element are different from each other, electrodes on the same plane are connected to each other, and the pyroelectric elements connected in parallel are connected through the respective connected electrodes. To get the output.

According to another aspect of the infrared sensor of the present invention, the output of the pyroelectric element is sent to two impedance converters provided with one resistance serving as a load of the pyroelectric element provided in the signal processing circuit, and the two outputs thereof are output. Is provided with a signal processing circuit having a balanced amplifier circuit that is connected to the input ends of the differential amplifiers of the signal processing circuit.

An infrared sensor according to a twelfth aspect includes a signal processing circuit having a constant voltage circuit.

A method for manufacturing an infrared sensor according to claim 13 is
Two types of substantially equivalent electrodes are formed on an insulating substrate, a ferroelectric thin film is formed on the two types of electrodes, and a portion of the ferroelectric thin film corresponding to the two types of electrodes is formed. It is characterized in that an electrode is formed on the substrate to form two pyroelectric elements.

A method for manufacturing an infrared sensor according to claim 14 is
A ferroelectric thin film is formed on a substrate having a conductive portion on its surface, and two types of substantially equivalent electrodes are formed on a portion of the ferroelectric thin film corresponding to the conductive portion. It is characterized in that individual pyroelectric elements are formed.

In the infrared sensor of the fifteenth aspect, the electrodes formed on the ferroelectric thin film and the subsequent electric processing circuit are provided with conductive portions on a substantially flat surface of the electronic circuit board, and the ferroelectric thin film is provided at substantially the same position. Is formed, and one of the electrodes is connected to the electrode directly formed on the ferroelectric thin film as a conductive portion.

According to a sixteenth aspect of the present invention, there is provided an infrared sensor, which comprises two electrodes substantially equivalent to each other on a substantially flat surface opposite to the incident direction of an infrared-transmissive entrance window material, and forms a ferroelectric thin film. In this embodiment, two pyroelectric elements that are equivalent to each other are formed.

The infrared sensor according to claim 17 is characterized in that a polymer pyroelectric material is used as the ferroelectric thin film.

In the infrared sensor according to claim 18, as the polymer pyroelectric material, a vinylidene fluoride / 3-fluorinated ethylene copolymer or a vinylidene fluoride / 4-fluorinated ethylene copolymer is used and the vinylidene fluoride is from 60 mol% to 90 mol. % Is used for the polymer pyroelectric material.

In the infrared sensor of the nineteenth aspect, the thickness of the polymer ferroelectric thin film is set to 100 μm or less.

The infrared sensor according to claim 20 is the infrared sensor according to claim 16.
The infrared sensor as described above, wherein the window material is the same material as the ferroelectric thin film.

The infrared sensor according to claim 21 is the infrared sensor according to claim 20.
Infrared sensor, characterized in that the window material and the ferroelectric thin film are the same material, wherein the ferroelectric thin film is vinylidene fluoride / 3-fluorinated ethylene copolymer or vinylidene fluoride / 4-fluorinated ethylene. It is characterized by being a copolymer.

In the infrared sensor of the twenty-second aspect, the electrode (91a) and the electrode (92a) are formed of a nickel chromium alloy.

In the infrared sensor of the twenty-third aspect, the electrode and the electrode are made of aluminum.

In the infrared sensor of the twenty-fourth aspect, the ferroelectric thin film is formed of an inorganic ferroelectric.

In the infrared sensor of the twenty-fifth aspect, the thickness of the inorganic ferroelectric thin film is set to 100 μm or less.

In the infrared sensor according to the twenty-sixth aspect, a thin tube having a closed tip is connected to one inlet hole of the pressure sensor having two inlet holes for introducing the pressure of the fluid, and the infrared inert gas is sealed therein. It is characterized by.

In the infrared sensor of the twenty-seventh aspect, the infrared inert gas is any one of nitrogen, helium, argon and xenon gas.

In the infrared sensor of the twenty-eighth aspect, the pressure is adjusted between one inlet hole of the pressure sensor provided with two inlet holes for introducing the pressure of the fluid and a thin tube having a closed tip connected to the inlet holes. It has a valve installed.

In the infrared sensor according to claim 29, electrode layers are provided on both sides of the piezoelectric body of the pressure sensor, and two piezoelectric elements formed in a planar and deformable manner are respectively sandwiched from two sides by two pairs of holders. Equipped with a pressure detector that is held and arranged 2
The piezoelectric elements are arranged so as to face in the same direction and have the same polarization planes in the same direction, and the pressure detecting portion is provided with two inlet holes for introducing the pressure of fluid, and one inlet is provided. The hole communicates with the second surface of the other piezoelectric element having a different polarization polarity from the first surface of the one piezoelectric element via the first fluid pressure introduction path, and the other inlet hole has the second fluid pressure. The two piezoelectric elements are communicated with the second surface of the one piezoelectric element through an introduction path and with the first surface of the other piezoelectric element through a third fluid pressure introduction path. Is sent to the amplification circuit section of the signal processing circuit, and a constant voltage circuit is provided inside the signal processing circuit.

An infrared sensor according to claim 30 is the infrared sensor according to claim 26.
One of the two piezoelectric elements of the pressure sensor is connected to the electrodes on the same surface, and the output of the piezoelectric element becomes the load of the piezoelectric element provided in the signal processing circuit through the electrode on the other surface. A balanced amplifier circuit is provided, which sends the resistors to two impedance converters each including one resistor, and sends the two outputs to a differential amplifier in the amplifier circuit section of the signal processing circuit. It also has a constant voltage circuit.

In the infrared sensor of the thirty-first aspect, the two piezoelectric elements of the pressure sensor are formed of a polymer ferroelectric.

In the infrared sensor of the thirty-second aspect, the polymer ferroelectric thin film of the pressure sensor is made of a copolymer of vinylidene fluoride and ethylene trifluoride.

[0042]

In the infrared sensor according to any one of claims 1 to 3, the infrared ray is guided to one of the heat sensitive elements, and the infrared ray is used as a signal, and the other heat sensitive element is used as a correction (dummy) to obtain a heat sensitive element. In-phase noise caused by common temperature fluctuations, pressure fluctuations, vibrations, etc. can be offset and reduced by the two heat sensitive elements. Therefore, it is possible to simultaneously achieve the improvement of the S / N ratio accompanying the cancellation reduction of the in-phase noise.

According to the infrared sensor of claim 4, two kinds of electrodes having the same area are provided on one surface of the ferroelectric thin film, and the other surface has the same position, shape and area as the electrodes on the one surface. Since the electrodes are formed and the pyroelectric element is formed, by guiding infrared rays to one of the pyroelectric elements and using this as a signal, the other pyroelectric element is used for correction (dummy). ,
In-phase noise caused by temperature fluctuations, pressure fluctuations, vibrations and the like common to the pyroelectric elements can be offset and reduced by the two pyroelectric elements. Therefore, it is possible to simultaneously achieve an increase in the response speed due to the use of the ferroelectric thin film and an improvement in the S / N ratio due to the cancellation reduction of in-phase noise.

According to the infrared sensor of claims 5 to 10,
An electrode provided on the one surface is individually provided at a portion corresponding to two substantially equivalent electrodes provided on the other surface, and the two pyroelectric elements are connected by the electrode. The infrared sensor described in 4 can be used.

According to the infrared sensor of the eleventh aspect, the output of the pyroelectric element is sent to each of the two impedance converters having one resistance serving as a load of the pyroelectric element, and the two outputs are output as signals. Outputs of the same value with opposite polarities, and in-phase noise that could not be canceled out inside the pyroelectric element can be obtained as outputs of the same value with the same polarity, and a balanced amplifier equipped with a differential amplifier that processes these outputs. The circuit can also accurately remove noise caused by fluctuations in the electronic circuit itself and the power supply.

According to the twelfth aspect of the infrared sensor, since the signal processing circuit is provided with the constant voltage circuit, the power supply of the elements in the circuit is stabilized, and the detection result which is not affected by the power supply fluctuation can be obtained.

According to the method of manufacturing an infrared sensor of claim 13, two kinds of substantially equivalent electrodes are formed on an insulating substrate, and a ferroelectric thin film is formed on the two kinds of electrodes. Since the electrodes are formed on the portions of the ferroelectric thin film corresponding to the two types of electrodes to form the two pyroelectric elements, it is possible to obtain an infrared sensor having the same effect as that of the fourth aspect.

According to the infrared sensor of claim 14, a ferroelectric thin film is formed on a substrate having a conductive portion on its surface,
Since two types of substantially equivalent electrodes are formed on a portion of the ferroelectric thin film corresponding to the conductive portion to form two pyroelectric elements, the same operation as that of claim 4 is performed. It is possible to obtain an infrared sensor that plays.

With the infrared sensor according to any one of claims 15 to 25, the same operation as that of claim 4 can be achieved.

In the infrared sensor according to the twenty-sixth aspect, a thin tube having a closed tip is connected to one inlet hole of the pressure sensor having two inlet holes for introducing the pressure of the fluid, and the infrared inert gas is sealed therein. Therefore, a thin tube is placed at a right angle or in parallel with the infrared ray generating substance to absorb the infrared ray, and the infrared ray absorbed expands the infrared inert gas to cause a pressure change. It can be detected by a sensor. Here, since the pressure change is proportional to the amount of infrared absorption, the infrared intensity is detected.

With the infrared sensor according to claim 27 or 28, the same action as that of claim 26 can be achieved.

In the infrared sensor of claim 29, electrode layers are provided on both sides of the piezoelectric body of the pressure sensor, and two piezoelectric elements which are flat and deformable are formed on both sides by a pair of holders. And a pressure detecting section sandwiched between the two piezoelectric elements are arranged so that the two piezoelectric elements are oriented in the same direction and the surfaces in the same direction have the same polarization polarity. There are two inlet holes to introduce,
One inlet hole is communicated with the first surface of the one piezoelectric element via a first fluid pressure introduction path, and the first surface of the one piezoelectric element is also connected with a fourth fluid pressure introduction path. Is communicated with the second surface of the other piezoelectric element having a different polarization polarity, the other inlet hole is communicated with the second surface of the one piezoelectric element through the second fluid pressure introduction path, and Three
Of the other piezoelectric element via the fluid pressure introduction path of
Since it is communicated with the surface of, the noise caused by the vibration is detected as a signal of the same phase of the two piezoelectric elements, and by connecting the electrodes on the same surface of either one of the two piezoelectric elements, This can be offset and reduced inside the piezoelectric element.

According to the infrared sensor of the thirtieth aspect, the electrodes on the same surface of one of the two piezoelectric elements of the pressure sensor of the twenty-sixth aspect are connected, and the piezoelectric element is connected through the electrodes on the other side. The output of is sent to two impedance converters, each of which has one resistance as a load of the piezoelectric element provided in the signal processing circuit. Therefore, the signals can be obtained as outputs having the same value but opposite polarities. , In-phase noise components that cannot be canceled out inside the piezoelectric element can be obtained as outputs with the same polarity and same value, and due to the balanced circuit and constant voltage circuit equipped with a differential amplifier that processes these outputs, the electronic circuit itself and power supply fluctuations The noise that occurs can also be accurately removed at the same time.

With the infrared sensors of claims 31 and 32, the same operation as that of claim 29 or 30 can be achieved.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic plan view showing an embodiment of the infrared sensor of the present invention, and FIG. 2 is a schematic vertical sectional view.

This infrared sensor is made of, for example, silicon,
A pair of electrodes 91b and 92b made of Al are formed on a substrate 94 made of magnesia or the like.
The ferroelectric thin film 93 is formed on 2b, and the ferroelectric thin film 93 is formed.
The electrodes 91a and 92a made of NiCr having the same shape and the same area and located directly above the electrodes 91b and 92b are formed thereon. Here, the electrodes 91a and 91b and the electrode 92a,
The areas of 92b are set equal to each other. In this case, the electrode 91a, the ferroelectric thin film 93 and the electrode 91b
The first pyroelectric element 91 is composed of the electrodes 92a,
A second pyroelectric element 92 is composed of the ferroelectric thin film 93 and the electrode 92b. Then, for example, an infrared shielding film (not shown) is provided so that infrared rays are not emitted only to the second pyroelectric element 92. Also, Ni
Cr has an infrared absorption coefficient of about 0.7, and Al has an infrared reflectance of about 0.9. The electrode irradiated with infrared rays may be coated with a material having a higher infrared absorption coefficient.

However, this infrared sensor is not limited to the above structure, and each of the electrodes 92a and 92b is divided into two as shown in FIGS.
The electrodes a and 91b may be arranged at the target position with respect to the center, and as shown in FIGS. 5 and 6, the electrodes 92a and 92b are ring-shaped and the electrodes 91a and 91b are circular and the electrodes 92a and 92b are The electrodes 91a and 91b may be arranged inside the 92b, respectively, and lead-out leads for the electrodes 91a and 91b may be formed through the notches of the ring-shaped electrodes 92a and 92b. Further, NiC is used as the electrodes 91a and 92a.
It is preferable to use a material having an infrared absorption coefficient larger than that of r and a good electric conductor, which is suitable for vapor deposition and sputtering. On the other hand, as the electrodes 91b and 92b, it is preferable to use those having a higher infrared reflectance than Al, a good electric conductor, suitable for vapor deposition and sputtering, and having a small heat capacity. Further, the relative relationship between the pyroelectric element 91 and the pyroelectric element 92 may be reversed. Further, the areas do not necessarily have to be the same, and any area may be used as long as it can generate an equivalent signal. The electrodes on one surface of the ferroelectric thin film 93 are shown in FIG.
They may be integrated as shown in FIG. In this case, two electrodes on the other surface may be formed so as to generate substantially equivalent signals. At this time, one of the two separated electrodes is irradiated with infrared light.

Further, as a method of manufacturing the ferroelectric thin film,
For example, the electrodes 91b and 92 are formed by sputtering, vapor deposition, or the like.
The substrate 94 on which b is formed or the window material on which the electrodes 91a and 92a are formed is set on a spinner, and for example, a solution obtained by dissolving a copolymer of vinylidene fluoride and ethylene trifluoride in a solvent is added to the substrate 94. Alternatively, it is placed at the center of the window material, the spinner is rotated, and a predetermined thickness (for example, a thickness of 100 μm or less) is set by centrifugal force. However, instead of using a spinner, a predetermined thickness may be set using a bar or a slit die coater that moves while maintaining a constant distance from the bottom plate. Then, the solution having a predetermined thickness is dried to form the electrodes 91a and 92a, or the electrodes are brought into contact with the ferroelectric thin film, and a voltage equal to or higher than the rf electric field that causes polarization is applied to the pyroelectric sensor. Can be made. Note that this voltage application may be alternately performed a plurality of times. Further, instead of the ferroelectric thin film, a ferroelectric thin film made of lead titanate PbLiO ₃ may be adopted. In this case, the ferroelectric thin film may be formed by sputtering or the like.

FIG. 8 shows an example of an electric circuit for obtaining an infrared detection signal by using the infrared sensor having the above structure. The polarization directions of the first pyroelectric element 91 and the second pyroelectric element 92 are shown. Are set to be opposite to each other, both pyroelectric elements 91, 92
Are connected in parallel. However, as shown in FIG.
The pyroelectric elements 91 and 92 may be connected in series while the polarization directions of the pyroelectric element 91 and the second pyroelectric element 92 are set to be opposite to each other. The output signals from these pyroelectric elements may be supplied to the non-inverting input terminal of the operational amplifier 103 having the output terminal and the inverting input terminal connected as shown in FIG. 10, but shown in FIG. As described above, the output terminal and the inverting input terminal may be supplied to the inverting input terminal of the operational amplifier 103 formed by connecting the resistor and the capacitor through a parallel circuit.

The impedance of the pyroelectric element using the ferroelectric thin film and the piezoelectric element (pressure sensitive element) described later is
200 to 3 depending on the area, thickness and frequency used
It may reach about 00 GΩ. In this case, FIG.
A resistor such as 104a in FIGS. 11 and 12 may be a discrete component such as a diode or transistor as shown in FIG. 23, or a component molded on a substrate. The capacitor also uses discrete parts or parts molded on the substrate.

[0062] Figure 10, Figure 11 when amplifying Since the basic circuit is mainly operational amplifier becomes 93 Jo Tokoro amplification factor by a combination of resistance class between the output terminal and the inverting input terminal of the arrangement.

The operation of the infrared sensor having the above structure and the embodiment of the manufacturing method will be described.

Since infrared rays can be guided (irradiated with infrared rays) to one heat sensitive element 191 and infrared rays cannot be guided to the other heat sensitive element 192, the infrared rays can be used for one heat sensitive element 191. Output a signal corresponding to the infrared intensity efficiently. However, in practice,
One of the heat sensitive elements 191 has an ambient temperature fluctuation, a pressure fluctuation,
It also outputs signals corresponding to vibration fluctuations.

However, the influence of the ambient temperature and the like also appears in the other thermosensitive element 192 in the same manner and outputs the same signal, so that the thermosensitive element 1 as shown in FIG.
91 and 192 are electrically connected in series with the surfaces of the same polarity,
By connecting so that signals are output from the electrodes on the opposite sides, signals (common-mode noise) that correspond to atmospheric temperature fluctuations, pressure fluctuations, vibration fluctuations, etc. can be offset and reduced, and signals that correspond only to infrared intensity can be reduced. Is output.

Here, the same effect can be obtained by using the pyroelectric element made of the ferroelectric material 93 as the heat sensitive element, and the same effect can be obtained even if the pyroelectric elements 91 and 92 are made of the polymer piezoelectric film. is there.

That is, infrared rays can be guided (irradiated with infrared rays) to the first pyroelectric element 91, and
Since the infrared rays cannot be guided to the second pyroelectric element 92, the infrared rays are efficiently absorbed by the electrode 91a of the first pyroelectric element 91, and the infrared intensity can be coped with from the first pyroelectric element 91. To output the signal. However, in reality, the first
The pyroelectric element 91 also outputs signals corresponding to ambient temperature fluctuations, pressure fluctuations, vibrations, and the like.

However, the influence of the ambient temperature and the like also appears in the second pyroelectric element 92 in the same manner, and the same signal is output, so that both pyroelectric elements 91 as shown in FIG. 8 or FIG. , 92, it is possible to offset and reduce signals (in-phase noise) corresponding to ambient temperature fluctuations, pressure fluctuations, vibrations, etc., and a signal corresponding only to the infrared intensity is output.

Then, as shown in FIG. 12, this output is
It is supplied to two impedance converters 104 having one resistance 104a which is a load of the pyroelectric element, and the two outputs are obtained as outputs of the same value with opposite polarities, which cancel each other out inside the pyroelectric element. The common-mode noise that cannot be reduced can be obtained as outputs having the same value and the same polarity. By supplying these outputs to the balanced amplifier circuit 106 including the differential amplifier, the common-mode noise can be further reduced and the electronic circuit can be reduced. At the same time, it is possible to accurately remove noise caused by itself and power fluctuations. As a result, infrared detection accuracy can be improved.

If a signal processing circuit having a constant voltage circuit is adopted, the voltage in the circuit is stabilized and the impedance from the pyroelectric element to the amplifier is balanced, so that the two pyroelectric elements cancel each other. In-phase noise that cannot be completely suppressed, noise due to impedance imbalance, noise of the circuit itself, and noise generated due to power supply fluctuation can be accurately removed, and an extremely high S / N ratio can be obtained.

In order to obtain the above infrared sensor element structure, one embodiment of the manufacturing method shown in FIG. 30 will be described.
When the lead plane electrodes 97a and 97b are formed in advance on the electric circuit board 5 for processing the obtained signal and the elements are directly formed, output take-out pins and soldering are not required, and the circuit board 5 is electrically connected. Can be done reliably. Further, since there is no influence of the heat capacity of the solder or the conductive material, it is possible to achieve high speed and high sensitivity of the sensor. Further, by adding an electronic circuit process as shown in FIG. 12, it is possible to improve the infrared detection accuracy. Further, the infrared-transmissive window material 110 is installed in the outer case. As shown in FIG. 32, in the configuration in which the ferroelectric material is formed on the back surface of the window material to obtain the pyroelectric element, infrared rays from the outside are incident. There is no heat transfer or loss in the subsequent space, and the sensitivity of the sensor can be improved. In addition, since the element and the outer case have the same temperature because they can be integrated with the outer case 114, there is no malfunction caused by a change in the temperature of the outer case. Furthermore, it is not necessary to support the elements in the case by supporting columns and arrange them in a space for heat separation, and the number of parts can be reduced.

On the other hand, when infrared rays are incident on one of the pyroelectric elements, the electrodes on the surface of the element mainly absorb heat, and as a result, the temperature of the element rises and thermal expansion occurs. On the contrary, when the incidence of infrared rays is blocked, the temperature of the element also decreases and the element contracts. For example, if the linear expansion coefficient of the window material and the thermal expansion coefficient of the pyroelectric element are different, thermal strain occurs at the interface between the two, and the element peels due to the strain. If the window member and the element are the same member, of course, the linear expansion coefficient is the same, so no strain occurs, and the element is not damaged even if infrared rays are repeatedly incident on the sensor, so durability is improved. Can be improved.

Further, by reducing the thickness of the ferroelectric thin film 93, the infrared detection sensitivity can be improved.

This is because the present invention makes it possible to make the pyroelectric material described below into a thin film at a high speed and a specific detectability D showing an S / N ratio.
^The fact that ^* is improved can be found by theoretical calculation and experiments, and in actual sensor manufacturing, the sensitivity can be improved 5 to 10 times with respect to the sensor noise similar to the conventional one.

For example, in the case of an inorganic material, PbTi of the embodiment of the present invention is used.
O ₃ , lithium niobate LiNbO ₃ , zinc oxide ZnO, barium titanate BaTiO ₃ , lithium titanate LiTiO ₃ , sodium barium niobate Ba
₂ NaNb ₅ O ₁₅ , organically, vinylidene fluoride copolymer P (VDF-TrFE), P shown in the embodiment of the present invention
(VDF-TeFE) and vinylidene fluoride PV
DF, vinylidene cyanide-based copolymer P (VACN-V
ac), urea-based polymers; aromatic polyureas, aliphatic polyureas, odd-numbered nylons; aromatic nylons, urethane-based polymers, amino acid polymers, etc., and combinations thereof are limitless. To further explain, it can be applied to all infrared sensors that can be made into a thin film by some method and can be composed of a ferroelectric material that is not thermally deformed in the operating temperature range.

Specifically, the thickness of the ferroelectric thin film made of a copolymer of vinylidene fluoride and ethylene trifluoride is set to 2 μm.
m, area set to 2 mm ² , electrode 9 made of NiCr
The thickness of the electrodes 1a and 92a is set to 0.1 mm or less, the thickness of the electrodes 91b and 92b made of Al is set to 0.1 mm or less, and the thickness of the window material made of silicon is set to 0.4 mm. When manufactured, D ^* is 10 ⁹ cm
・ Hz ^1/2 / W or more, rise time is 15μs
ec. This D ^* is 5 times or more compared to the conventional infrared sensor, and the rising time is 5000 times compared to the rising time of 100 msec of the conventional infrared sensor.
It was shorter than one-third.

Regarding the film thickness of the pyroelectric element, the ferroelectric polymer thin film disclosed in JP-A-61-48983 has a range of thickness less than 1000 angstrom and a graph of high speed pyroelectric property. Since the coercive electric field for changing the memory is improved to improve the memory characteristic and the memory reading is performed by using the infrared detection characteristic, the output 1, 0 (+,
-) Is for judging the polarization polarity and is not suitable as an infrared sensor for the following reasons.

(1) Impedance becomes too small and sensitivity is lowered.

(2) Uniformity of thickness cannot be maintained.

(3) It is difficult to set conditions for production such that the film is deformed or the front and back surfaces of the electrodes are electrically connected to each other due to heat generated by sputtering or vapor deposition when applying the electrodes.

By using the infrared sensor having the above-mentioned structure, it is possible to detect the infrared intensity of a substance that emits a weak infrared ray and vibrates at a high speed or that emits an infrared pulse at a high frequency. Specifically, the pyroelectric infrared sensor has not been able to cope with the temperature of the yarn running while vibrating in the spinning process, the infrared intensity measurement of an infrared gas analyzer such as high-speed CO ₂ and optical communication. It is useful as a substitute for other infrared sensors, which are expensive even if applicable in the field, and have large peripheral devices, at room temperature.

FIG. 13 is a schematic view showing another embodiment of the infrared sensor of the invention. 1 shows an example of an embodiment of an infrared sensor of a type in which an infrared inert gas in a certain volume is expanded by irradiation of infrared rays and a generated pressure difference is detected.

In this infrared sensor, one of the pair of inlet holes 39, 40 of the pressure sensor 1 having a pair of piezoelectric elements is opened, and the other is communicated with a thin tube 81 whose tip is closed. .

This thin tube 81 is, for example, shown in FIG.
As shown in Fig. 5, a cylindrical body having a tip end of the conduit 81a made of ceramic, plastic, etc., closed by fitting, bonding, screwing, etc., and having an outer diameter substantially equal to the outer diameter of the conduit 81a. 81b is mounted, and as the cylindrical body 81b, a cylinder 81b made of glass, metal or the like, preferably provided with a thin film of chrome, nichrome, unichrome or the like by plating, vapor deposition or the like is adopted. Then, an infrared inert gas such as nitrogen, helium, argon, or xenon gas, or air is sealed inside the pipe 81a and the cylindrical body 81b. However, instead of the cylindrical body 81b, as shown in FIG. 14B, a cylindrical body 81c having an outer diameter substantially equal to the inner diameter of the conduit 81a may be adopted. Further, instead of the cylindrical body 81c, as shown in FIG. 14C, a spherical body 81d having a communication conduit may be adopted. Furthermore, the cylindrical body 81
Instead of b, as shown in FIG. 14D, a cylindrical body 81e whose tip is not closed may be adopted, and a cap 81f which closes the tip end of this cylindrical body 81e may be adopted. Here, as the cap 81f, one made of ceramic, plastic, rubber or the like can be adopted, but it is preferable to use a cap made of rubber, and the amount of infrared inert gas can be increased by penetrating an unillustrated injection needle. That is, the internal pressure can be adjusted. Of course, the closed state can be secured after the injection needle is pulled out.

Further, as shown in FIG. 15, a pressure control valve 81g may be provided in the middle of the thin tube 81.

FIG. 16 is a schematic vertical sectional view showing a main part of the pressure sensor.

In FIG. 16, reference numeral 1 denotes the entire pressure sensor. The pressure sensor 1 includes a pressure detecting portion 4 having two piezoelectric elements 2 and 3, and an electric signal processing circuit 5 described later.
(See FIG. 26).

Two piezoelectric elements 2 and 3 which are formed in a planar shape and are deformable, for example, formed into spherical surfaces, have a pair of two holders 12, 13 and 14, 15 whose peripheral portions are sandwiched from both sides. Has been done. The piezoelectric elements 2 and 3 are, as shown in an enlarged view in FIG. 17, film-shaped piezoelectric bodies 6 and 7 made of a piezoelectric material.
The chromium / gold electrode layers 8, 9 and 10, 11 having good corrosion resistance are formed by vapor deposition on both surfaces of. However, the kind and composition of the metal and the forming method are not limited thereto, and other conventionally known metals and forming methods can be adopted.

The shape of the sandwiching surface of the pair of holders 12, 13 and 14, 15 for sandwiching the piezoelectric elements 2 and 3 is shown in the figure according to the shape of the two piezoelectric elements 2 and 3. As shown in FIG. 19, curved surfaces 12 a, 1 having an arbitrary curvature ρ
3a and 14a, 15a.

As the curvature in this embodiment, 51 mm was adopted in consideration of the shape-maintainability in the calculation result of sensitivity-curvature, and the experimental result. The pressure receiving area was 9 mm and the film diameter was 1 mm.
It is 0.5 to 11.3 mm.

A holder having a holding surface formed as an inclined surface can also be used within the range of the embodiment. In this case, as the shape of the sandwiching surface, as shown in FIG.
Are formed on the inclined surfaces 12b, 13b and 14b, 15b.

As the tilt angle θ in this case, an angle of 5 ° was adopted in consideration of the shape maintainability in the calculation result of the sensitivity-tilt angle and the test result.

The planar shape of the two piezoelectric elements 2 and 3 is
In the present embodiment, the shape is circular, but the shape is not limited to this, and any planar shape can be adopted. As materials for the piezoelectric bodies 6 and 7, vinylidene fluoride copolymer, urea-based polymer, odd-numbered nylon, lead titanate (Pb) is used as a ferroelectric polymer.
Various piezoelectric materials such as TiO3) are applicable, but in the present embodiment, a polymeric piezoelectric material made of a copolymer of vinylidene fluoride and ethylene trifluoride is used. The thickness of the polymeric piezoelectric film is determined in consideration of sensitivity, strength, moldability, and shape retention, and is 17 μm in this embodiment.

The peripheral portions of the piezoelectric elements 2 and 3 are held from both sides via the electrode layers 8, 9 and 10, 11 to the holders 12, 13 respectively.
And 14 and 15 are sandwiched. The piezoelectric elements 2 and 3 held by the respective holders are arranged in parallel so that both surfaces thereof face in the same direction, and the surfaces in the same direction have the same polarization polarity.

In this embodiment, the holders 12, 13, 14,
Since 15 requires substantially the same coefficient of thermal expansion and electrical conductivity as the piezoelectric element, it is molded with engineering plastic filler-containing PBT (polybutylene terephthalate), and like the piezoelectric element electrode layers 8, 9 and 10, 11, It is configured to have conductivity over the entire surface by depositing chromium / gold having good corrosion resistance, but the material, metal, and molding method of the holder are not limited to this.

The holders 12, 13, 14, 15 are electrically connected to the electrode layers 8, 9, 10, 11 respectively and function as output terminals of the piezoelectric elements. Holders 12 and 13,
The piezoelectric elements 6 and 7 insulate between 14 and 15.

This pair of two holders 12, 13 and 1
At 4 and 15, the piezoelectric elements 2 and 3 are sandwiched as shown in FIGS. That is, it is held by the holder at its peripheral edge.

FIG. 18 is a vertical sectional view showing the assembly of these components.
Is shown in an exploded perspective view of FIG.

The piezoelectric elements 2 and 3 are sandwiched by the holders 12, 13 and 14 and 15 from the both sides in the middle case 17, and the lower holders 12 and 1 below the piezoelectric elements 2 and 3 are sandwiched.
4 is supported by the inner bottom plate 16 and is plated with nickel in the shape of a strip at the center of its surface to electrically connect these two holders.

Further, in order to adjust the pressure fluctuations with respect to the piezoelectric elements 2 and 3, the diameters of 3 to 3 are respectively provided at the centers of the portions in contact with the holder.
It may have a 7 mm hole. This is to make the resistance to pressure fluctuation stronger, and is not necessary if the specification for resistance to pressure fluctuation is low.

Middle bottom plate 16, middle case 17 and middle lid 33
Is made of engineering plastic PBT having the same coefficient of thermal expansion as the piezoelectric element.
It is fixed to an outer case 41 made of aluminum at 8 and 29.

The circuit board 35 includes the middle bottom plate 16 and the middle case 17.
And the outer case 4 with one long screw 30 together with the inner lid 33.
Fixed to 1. This is to prevent the circuit board 35 from being distorted when the circuit board 35 is fixed with some screws.

The electric signal processing circuit 5 is incorporated in the circuit board 35.

The upper holders 13 and 15 include the electrode plates 23 and
It is pressed by springs 21 and 22 via 24. That is, by the springs 21 and 22, the piezoelectric element 2,
3 is pressed and sandwiched between the holders 12, 13 and 14, 15.

The inner lid 33 and the circuit board 35 are connected to the circuit board 35 in order to prevent gas from leaking from the pressure detecting portion 4.
From the input terminals of the piezoelectric elements 2 and 3,
The square nuts 25 and 26 set under the electrode plate 23 are connected by tightening the screws 31 and 32 via the O-rings 48 and 49 between the inner lid 33 and the circuit board 35.
I try to hold down.

In FIG. 16, the power input terminals 36, 3 of the circuit 5 are
7. The input / output terminals of the output terminal 38 are inside the connector 47, and the connection pins 36a, 37a, 38a are input / output of the outer lid 46 via the chips 36b, 37b, 38b molded of engineering plastic PBT, respectively. The terminals 50a, 59b and 56 are configured.

The above description is for the case where the piezoelectric elements 2 and 3 are connected in series. When the piezoelectric elements 2 and 3 are connected in parallel, it is necessary to change the electrode forming of the inner bottom plate 16 and the circuit formation on the circuit board 35 for this purpose. The electric circuit configuration is as shown in FIGS. 26 shows the case where the piezoelectric elements 2 and 3 are connected in series, and FIG. 27 shows the case where the piezoelectric elements 2 and 3 are connected in parallel. The details of these electric circuits will be described later.

The outer case has two respective fluid pressure introduction paths from the two inlet holes 39 and 40 to the inner bottom plate 16,
A deformed O-ring groove is formed to separate the fluid pressure introduction path and keep the airtightness, and the O-ring 18 is sandwiched between the O-ring 18 and the inner bottom plate 16.

The first fluid pressure introducing path 4 is provided on the inner bottom plate 16.
The second and fourth fluid pressure introduction paths 45, the first fluid pressure introduction path 43, the third fluid pressure introduction path 44, and the deformed O-ring groove for separating these fluid pressure introduction paths and keeping confidentiality are provided. It is formed and holds the O-ring 19 between it and the middle case 17.

In the middle case 17, two holes for accommodating the piezoelectric elements 2 and 3 and the holders 12, 13 and 14, 15 for holding them, the second fluid pressure introducing path 43 and the fourth fluid pressure introducing. Path 45, square nuts 25, 26 and electrode plates 23, 2
The groove for deforming O-ring for separating the two grooves for accommodating 4 and these fluid pressure introduction paths and for keeping the airtightness is formed, and holds the O-ring 20 between the inner lid 33 and the groove.

In order to keep the inner lid 33 airtight, O-rings 48 and 49 are sandwiched between the piezoelectric elements 2 and 3 of the circuit board 35 and the input terminal portions (upper and lower through hole processed portions). An O-ring groove, a protrusion for positioning the circuit board 35, and a stand for the connector 47 of the circuit board 35 are formed.

One inlet hole 39 is formed on the first surface of one piezoelectric element 2 via the first fluid pressure introducing passage 42 after the fluid pressure introducing passage of the outer case 41 is branched by the inner bottom plate 16. While communicating with each other, the fourth of the inner case 17 and the inner lid 33
Of the other piezoelectric element 3 via the fluid pressure introduction path 45 of
It communicates with a surface (second surface) having a polarization polarity different from that of the first surface.

The other inlet hole 40 is formed on the first surface of the other piezoelectric element 3 via the third fluid pressure introducing passage 44 after the fluid pressure introducing passage of the outer case 41 is branched by the inner bottom plate 16. While communicating with each other, the second case of the middle case 17 and the middle lid 33
Of the one piezoelectric element 2 via the fluid pressure introduction path 43 of
It communicates with a surface (second surface) having a polarization polarity different from that of the first surface.

As described above, in this embodiment, the inlet holes 39, 40 and the fluid pressure introducing paths 42, 44 and the fluid pressure introducing paths 43, 45 are arranged with respect to the two piezoelectric elements 2, 3. The internal structure of the pressure detection unit 4 is configured to have substantially the same shape and symmetry.

The pressure detector 4 and the signal processing circuit 5 are
They are housed in an outer case 41 which also serves as a shield made of metal, which is a good electrical conductor, so as not to receive electromagnetic induction noise from a commercial power source or the like. The minus electrode (0 V) of the power source that can be placed in the circuit and the outer case 41 are connected via one long screw 30.

Next, the electrical signal processing circuit 5 incorporated on the circuit board 35 will be described with reference to FIGS. 26 and 27.

The piezoelectric elements 2 and 3 can be connected in series or in parallel, as shown in FIGS. 26 and 27, respectively. Since the difference in this circuit configuration is only the difference in the connection method of the piezoelectric elements 2 and 3, the description will be given only with respect to FIG.

The battery power source 52 is a 3V lithium battery,
The + pole side is connected to the VDD terminal 50a, and the-pole side is connected to the VSS terminal 50b. The + side of the battery power supply 52 is VDD
From the terminal 50a through the power supply protection circuit 54 to the constant voltage circuit 51
Connected to. Then, the amplifier circuit section 53 and the voltage comparator 5
5, the output of the constant voltage circuit 51 is supplied as the + power source of the midpoint power source I57 and the midpoint power source II58. On the other hand, the + power supply of the level converter 59 supplies the output of the power supply protection circuit 54 and is approximately the same voltage as the voltage supplied from the outside. The output of the midpoint power source I57 is used as the intermediate potential pole of the amplifier circuit section 53, and the output of the midpoint power source II58 is used as the intermediate potential pole of the voltage comparator 55.

A circuit in which the piezoelectric elements 2 and 3 and the amplifier circuit section 53 of the signal processing circuit 5 are configured as a balanced amplifier circuit is shown in FIGS.

The amplifier itself of the amplifier circuit section 53 has a low power supply voltage characteristic and malfunctions due to a small fluctuation thereof. This signal processing method is adopted and a constant voltage circuit which cuts (absorbs) the fluctuation of the power supply voltage fluctuation. The circuit including 51 is used together to prevent malfunction due to small fluctuations in the power supply voltage.

The balanced amplifier circuit of FIG. 21, which is composed of the piezoelectric elements 2 and 3 and the amplifier circuit section 53 of the signal processing circuit 5, has a difference between the output sections of the two piezoelectric elements 2 and 3 as shown in FIG. Since the pressure signal (the signal corresponding to the infrared intensity) has almost the same potential with different polarities, the signal of the differential pressure component is obtained as the same output as before, but it is canceled in the piezoelectric element due to vibration or pressure fluctuation. In addition to the remaining common-mode noise components, noise due to the electronic circuit itself and power supply fluctuations can be obtained at potentials of approximately the same value with the same polarity, so this noise component is accurately canceled and removed by the differential amplifier after that, and extremely S / N
A signal with a high ratio is obtained.

In the present embodiment, the input section of the amplifier circuit section 53 has a diode characteristic of a transistor (included in the resistors 75 in FIG. 21, not shown) as shown in FIG. 23 as a substitute for the resistor. Since the two terminals are used, the output from the piezoelectric element has a compression effect in a region where the signal is large, and is not compressed in a region where the signal is small.

In the pressure sensor 1 of this embodiment, the output from the amplification circuit section 53 is sent to the voltage comparator 55 having hysteresis and processed into a pulse signal, which is output from the output terminal 56 through the level converter 59. Is output.

The voltage comparator 55 has an input / output waveform as shown in FIG. 24 and has a hysteresis characteristic as shown in FIG. 24, and this width is the sensitivity of the pressure sensor.

Since there are threshold levels SH1 and SH2, noise components below the level can be completely removed. Also, the input is one threshold level SH1.
When the level reaches the threshold level of the other S
Since it changes to H2, the amount of overdrive instantaneously increases. As a result, the output rises faster.

Therefore, a stable pulse can be obtained accurately even if some noise is superimposed.

As a result, the pulse signal can be taken out more accurately. Furthermore, since the pulse is converted into a pulse having a large slew rate and almost the same amplitude as the supply voltage through a level converter, when connecting to a MOS type digital IC for signal processing, the rise time is fast and power consumption is low. It also has the advantage of being completed.

The fluctuations in the power supply that occur when the level converter 59 is driven at high speed are the same as those in the constant voltage circuit 51 shown in FIG.
It is removed by the balanced amplifier circuit of and does not become noise.

The hysteresis width (difference between threshold levels) is determined by the element (resistance value) used in the voltage comparator 55 and the output amplitude, which corresponds to the power supply voltage. Therefore, by using the constant voltage circuit 51 as in the present embodiment, when the supplied power supply voltage is kept constant, this hysteresis width also becomes constant, and the sensitivity of the entire signal processing circuit 5 becomes constant and stable. , Reliability is further improved.

In this embodiment, the potential of one battery power source 52 is divided, and the intermediate potential is used for signal processing from the piezoelectric element. In this embodiment, two circuits are provided in order to enhance the isolation between the amplifier circuit section 53 and the voltage comparator 55. The midpoint power source I57 is an amplifier circuit unit 5.
3, the midpoint power supply I58 is used for the voltage comparator 55. By doing so, only one battery is required as the power source and the space for accommodating the power source may be small, so that the infrared sensor as a whole can be downsized.

Further, in the present embodiment, the two piezoelectric elements 2 and 3 and the amplification circuit section 53 of the signal processing circuit 5 are shown in FIG.
With the configuration of the balanced amplifier circuit of No. 1, in-phase noise that could not be canceled out in the two piezoelectric elements 2 and 3 due to vibration and pressure fluctuation can be reduced, and further fluctuation of supply power voltage and level converter. Noise caused by the fluctuation of the power supply 52 inside the signal processing circuit 5 caused by driving 59 can be further reduced, and a high S / N ratio can be obtained. Further, in the present embodiment, in order to further enhance the noise removal effect, the arrangement of the inlet holes 39, 40 and the fluid pressure introduction paths 42, 43, 44, 45 for the two piezoelectric elements 2, 3 is made. The structure of the pressure detection unit 1 is configured to have substantially the same shape and symmetry.

Further, since the output from the piezoelectric element is connected to the input portion of the amplifier circuit portion 53 used as a substitute for the resistor 75, the two terminals having the diode characteristic of the transistor are compressed in the area where the signal is large. Has an effect,
The structure is such that it is not compressed in a small signal area.

In the present embodiment, the final output is a pulse, but by adding a necessary processing circuit to the electric circuit of the present embodiment, the final output of the pressure sensor 1 is a voltage or voltage proportional to the infrared intensity. You may make it output a current. It is also possible to add a processing circuit for displaying the output as a numerical value or converting the intensity of radio waves, light or sound, blinking of light, or pitch of sound.

A battery may be provided in the pressure sensor 1 in order to cope with the case where it is necessary that the pressure sensor 1 is not affected by the quality of the power supply or the power supply is difficult. As in this embodiment, the constant voltage circuit 51 is internally provided.
By including the above, it is possible to provide an infrared sensor with high accuracy even with respect to a power supply of poor quality such that the measurement sensitivity becomes constant as described above and the power supply voltage fluctuates. Further, in the above embodiment, since the power consumption is 10 μA or less,
It can be used for a long time without changing batteries.

Examples of the infrared sensor using the pyroelectric element of the present invention will be described below.

[0136]

【Example】

[0137]

Example 1 A vinylidene fluoride composition of vinylidene fluoride and trifluoroethylene copolymer as a ferroelectric thin film 75
1 shows an embodiment in which a pyroelectric element made of a ferroelectric thin film is formed using mol% of a polymer.

The polymer was melted in an N, N-dimethylformamide solvent with stirring for 20 hours to prepare a solution having a weight concentration of 15%. The film formation method was spin coating, and after dropping the polymer solution on the glass substrate, the rotation substrate was rotated for 30 seconds at a rotation speed of 450 times / minute to remove unnecessary solvent to obtain a predetermined film thickness.

When vacuum-dried in a vacuum dryer at 13 Pa for 5 hours, the solvent could be removed almost completely. In addition, 100 ° C
Then, the solvent was removed by drying for 2 hours. After that, in order to enhance crystallization of the ferroelectric thin film, heat treatment is performed at 140 ° C. for 1 hour,
Slowly cooled slowly. When the film was removed from the glass plate and the film thickness was measured, it was 9.5 μm.

Nichrome and aluminum were formed as an electrode on this film by vacuum vapor deposition. Both materials were vaporized by resistance heating at a vacuum degree of 10 ⁻³ Pa to form electrodes uniformly on the ferroelectric thin film.

In this electrode formation, as shown in the embodiment of FIG. 29, the electrodes 91a and 92a on one surface were formed in a comb shape by masking aluminum. The width of the comb electrode is 4
mm and the spacing is 4 mm. On the other hand, the electrode 96 on the other surface was formed of nichrome on the entire surface. The electrode-formed film was polarized by applying a high voltage from the outside at room temperature.
The voltage is a coercive electric field that reverses the polarization direction of the pyroelectric material: 45 MV /
At a voltage of m or more, 90 MV / m was actually used. By repeating the polarity reversal and finally applying a DC voltage, the polarities were perfectly aligned. Here, an electric field is applied only to the portions where the aluminum electrode and the nichrome electrode are opposite to each other on the opposite sides, the polarization directions can be aligned, and a pyroelectric body can be obtained. On the other hand, in the part where the electrode is on only one side, the polarization directions are not aligned, and it is not a pyroelectric body.

When the performance of the obtained pyroelectric film was measured, it was 3.5 × 10 ⁵ C / m ² / K.

Using a sharp die-cutting device, two 4 × 4 mm square pyroelectric elements (91, 92) having electrodes on both sides and a nichrome surface on one side sandwiched between the two elements are formed. × 4
An element having a total size of 4 mm × 12 mm was punched out.

On the other hand, the circuit board 5 to be subjected to the electric treatment is a board made of glass epoxy resin, and after mounting predetermined components, the lead electrode portions 97a, 97b made of gold having an area of 3 mmφ and having no unevenness are formed on the back surface. Element consisting of a punched ferroelectric thin film on a substrate on a substantially flat surface: 4 × 1
Fix 2 mm with a very small amount of conductive adhesive. For the fixing, a weight of 1 kg was placed from the top, the adhesive layer was made very thin, and care was taken to prevent wrinkles on the element.

In this embodiment, the rectangular shape of 4 × 12 mm is used, but the shape of the element is not limited to this, and the conductive portion sandwiched between two elements may be narrowed, for example.

According to this embodiment, the two elements are electrically connected to each other by the nichrome electrode provided on the film in advance, and the electric charge is taken out to the electric circuit on the opposite surface by the gold lead plane electrode provided on the back surface of the substrate. Since it is sent in parts, soldering of lead wires and bonding of electrodes are unnecessary.

To confirm the performance of the obtained infrared sensor,
The signal detection sensitivity was investigated using a 400K blackbody furnace. It is installed so that the infrared ray can be vertically incident on one of the pyroelectric elements, and mechanically 20H for the infrared ray to be intermittently incident.
The test was performed by chopping z. The result is shown in Figure 3.
As shown in FIG. 4, it was confirmed that it has a good signal detection capability. The figure shows that a temperature change occurs in one of the elements due to the incident infrared rays and a signal is obtained, but the signal of the sensor also follows as the infrared rays turn on and off.

Further, as the noise resistance, the output value was 1 mV or less even under the noise of 95 phons, and an infrared sensor having an excellent S / N ratio could be manufactured. In this embodiment, the result at the frequency of 20 Hz is shown, but the excellent response is obtained even at 100 Hz.

[0149]

[Embodiment 2] In this embodiment, a ferroelectric thin film is directly formed on the back surface of a circuit board for electrical processing, and an electronic circuit board 5 made of glass epoxy resin on which predetermined parts are mounted is mounted.
An embodiment in which a flat electrode portion (hereinafter abbreviated as a lead flat electrode) made of gold having a certain area is formed on the back surface of the infrared ray incident surface side and a pyroelectric thin film made of a ferroelectric substance is formed will be described. To do.

Vinylidene fluoride composition 7 comprising vinylidene fluoride and trifluoroethylene copolymer, which are ferroelectric thin films.
0 mol% was melted in N, N dimethylformamide with stirring to prepare a solution having a weight concentration of 20%.

In advance, two lead flat electrodes provided on the back surface of the circuit board were formed with a shape of 4 × 4 mm and an interval of 4 mm. The polymer solution was dropped directly onto the substrate, and spin coating was performed at a rotation speed of 1200 times / minute for 30 seconds.

Immediately after film formation, put in a vacuum dryer,
It was dried in a for 8 hours to completely remove the solvent. After that, in order to enhance crystallization, heat treatment at 135 ° C. for 1 hour,
Slowly cooled slowly. The thickness of the ferroelectric thin film thus obtained was 5 μm.

A 90 nm nichrome electrode was formed by vapor deposition on the opposite surface (on the infrared ray incident surface side) where the lead flat electrodes 97a and 97b were formed. At this time, the shape of the nichrome electrode was masked to a predetermined shape. The shape was such that the two lead plane electrode portions formed on the substrate were covered, and one surface of the two pyroelectric elements on the ferroelectric thin film could be electrically connected.

A high electric field was applied between the lead flat electrode and the nichrome electrode formed on the back surface of the substrate in the same manner as in Example 1 to align the polarization directions of the pyroelectric film and form a pyroelectric body.

In the present embodiment, the pyroelectric element made of the ferroelectric thin film is formed on the back surface of the electronic circuit board, but it is not limited to the electronic circuit board as long as the lead electrode is formed. The same effect can be obtained by forming an element on another plate member provided with a lead electrode and connecting it to an electric circuit.

When infrared rays were incident on one of the elements of the obtained ferroelectric thin film and the signal detection power was confirmed, as shown in FIG. 35, it was possible to detect repetitive input at a frequency of 40 Hz and noise resistance. It was confirmed to be excellent and a good infrared sensor.

[0157]

[Embodiment 3] In the present embodiment, a window member 1 capable of entering infrared rays
An embodiment of an infrared sensor in which a pyroelectric element made of a ferroelectric material is directly formed on the back surface of 10 will be described.

An electrode was formed on the opposite side of the infrared ray incident surface of a silicon plate having infrared ray transparency as a window material. The electrode is a Nichrome electrode formed by vacuum vapor deposition as shown in FIG.
b, 92a). The divided electrodes 91a and 91b were connected by a lead line 99 and combined to be substantially equivalent to the electrode 92a.

Polymer containing vinylidene fluoride / trifluoroethylene with a vinylidene fluoride composition of 82% and vinylidene fluoride / tetrafluoroethylene with a vinylidene fluoride composition of 80%
15% of the solution was prepared by mixing 9: 1 of the above polymer. By rotating the spinner at 1500 times / min for 30 seconds, the ferroelectric thin film 93 was made to have a predetermined thickness on the entire surface of the window material. The solvent was removed in vacuum and a uniform 4 μm film was provided on the silicon plate. Then, heat treatment was performed at 135 ° C. for 30 minutes to enhance crystallization.

The aluminum electrode 96 was formed so as to cover the portions 91a, 91b and 92a while paying attention to thermal melting of the formed ferroelectric thin film. 91a, 91b, 92a
Other parts were masked to form no electrodes, and then the ferroelectric thin film was peeled off to expose the lead line of the nichrome electrode on the lower surface.

A polarization process was performed by applying a high electric field of 80 MV / m using the lead lines of the nichrome electrode and the aluminum electrode. The pyroelectric coefficient of the obtained pyroelectric film was 4 × 10 ⁵ C / m ²
/ K.

In this embodiment, the electrodes (91a, 91b,
Although 92a) is formed on the surface of the infrared transmitting window material, the electrode 96 may be formed directly on the window material. However, at this time, the electrode material is provided so as to form nichrome in the infrared incident direction.

This window material was incorporated into a commercially available TO-5 can so that infrared rays could enter only one element (only the electrode 92a in FIG. 32 was previously formed in the infrared ray incident part). The connection with the electric circuit was performed by pressing the connection pin against the back surface of the window material. The connection positions were two points 111 and 112 on the nichrome electrode, and signals were taken out and led to an electrical processing circuit. When the responsiveness of this infrared sensor was evaluated, it was good at 2 msec or less.

[0164]

Example 4 An embodiment of an infrared sensor in which the infrared transmitting window material silicon of Example 3 is changed to an infrared incident window material made of the same material (a separately manufactured vinylidene fluoride / trifluoroethylene 66 μm film). I will give you.

First, in the production of a window material made of the same material, a 10% solution of vinylidene fluoride / trifluoroethylene with a vinylidene fluoride composition ratio of 70 mol% was made into a 10% solution, which was cast on a glass substrate in a predetermined amount to form a cast film. To a uniform thickness by vacuum drying (8 hours) and then heat drying (2 hours) to remove the solvent to form a film. The film thickness obtained is 66.
μm.

This polymer film was cut into a size of 15φ,
Similarly to Example 3, a nichrome electrode was first formed on one surface, and then a pyroelectric film of 5 μm was formed thereon. Furthermore, after forming an aluminum electrode by a predetermined method, polarization treatment was performed to form a pyroelectric element made of the same member on vinylidene fluoride / 3-fluoroethylene.

In this element, infrared rays other than the infrared absorption band of vinylidene fluoride / 3-fluorinated ethylene are incident on the element,
The energy absorbed by the nichrome electrode having a good infrared absorption changes the temperature of the pyroelectric material to obtain an output.

Since this sensor has the same thermal expansion as that of the substrate upon incidence of infrared rays, it has no distortion and has good durability (repetition characteristic of 10,000 times or more).

[0169]

According to the present invention, the infrared rays are guided to one of the thermosensitive elements, and the infrared rays are used for signals, and the other thermosensitive element is used for correction (dummy). Common-mode noise caused by temperature fluctuations, pressure fluctuations, vibrations, etc., can be offset and reduced by two heat-sensitive elements, and as a result, the response speed can be increased and the common-mode noise can be canceled by using the heat-sensitive element. The improvement of the S / N ratio accompanying the reduction can be achieved at the same time.

The invention of claim 4 is common to pyroelectric elements by guiding infrared rays to one of the pyroelectric elements and using the infrared rays for signals and using the other pyroelectric element for correction (dummy). In-phase noise caused by temperature fluctuations, pressure fluctuations, vibrations, etc. can be canceled and reduced by the two pyroelectric elements, and as a result, the response speed can be increased with the use of the ferroelectric thin film, There is a unique effect that the improvement of the S / N ratio accompanying the cancellation reduction of the in-phase noise can be achieved at the same time.

The inventions of claims 5 to 10 have the same effects as those of claim 4.

According to the eleventh aspect of the present invention, the output of the pyroelectric element is sent to two impedance converters each having one resistance as a load of the pyroelectric element, and the two outputs have opposite polarities. Can be obtained as an output of the same value, and in-phase noise that could not be canceled out inside the pyroelectric element can be obtained as an output of the same value having the same polarity. It also has a unique effect that noise due to fluctuations in the circuit itself and power supply can be accurately removed at the same time.

According to the twelfth aspect of the invention, the power source of the elements in the circuit is stabilized, and a specific result that a detection result which is not influenced by the power source fluctuation can be obtained.

According to the thirteenth to fifteenth aspects of the present invention, it is possible to omit the work steps which were conventionally conducted by soldering the lead wire or using a conductive adhesive in the connection to the electric circuit, and surely conduct the conduction by a simple method. Can be done. There is an effect that the work efficiency is improved, and the disconnection and the damage of the element can be surely suppressed, so that the yield is increased.

According to the sixteenth aspect of the present invention, if the pyroelectric element made of a ferroelectric material is formed by utilizing the back surface of the window material on which infrared rays are incident, the sensitivity of the sensor is further improved. Further, since the space can be saved as a whole, miniaturization of the sensor can be achieved.

According to the invention of claims 17 to 19, the same effect as that of claim 4 can be obtained. P (VDF-
When the vinylidene composition ratio of TrFE is 60 to 90 mol%, an element having good pyroelectric performance can be easily obtained, and therefore, the sensitivity of the infrared sensor is improved.

According to the twentieth and twenty-first aspects, not only the same effect as that of the sixteenth aspect can be obtained, but also the effect of suppressing the thermal contraction difference and the expansion difference generated between the plate material and the infrared rays is suppressed. Yes, the thermal durability of the sensor can be improved.

The inventions of claims 22 to 25 have the same effects as those of claim 4.

According to the twenty-sixth aspect of the present invention, a thin tube is arranged at a right angle or in parallel with an infrared ray generating substance to absorb the infrared ray, and the infrared ray absorbed expands the infrared inert gas to cause a pressure change. This pressure change can be detected by the pressure sensor, and since this pressure change is proportional to the amount of absorption of infrared rays, there is a unique effect that the intensity of infrared rays can be detected. Since this infrared sensor directly senses the amount of heat without passing through the light receiving window, it has an effect of improving environmental resistance to oil agents and dust due to long-term use.

The invention of claim 27 or claim 28 is
An effect similar to that of (26) is achieved.

According to a twenty-ninth aspect of the invention, noise caused by vibration or the like is detected as an in-phase signal of two piezoelectric elements, and
By connecting the electrodes on the same surface of either one of the individual piezoelectric elements, it is possible to reduce the offset inside the piezoelectric element, which in turn has the unique effect of increasing the infrared detection sensitivity and accuracy.

According to the thirtieth aspect of the invention, signals can be obtained as outputs having the same value but opposite polarities, and in-phase noise components that cannot be canceled inside the piezoelectric element can be obtained as outputs having the same polarity and the same value. With a balanced amplifier circuit equipped with a differential amplifier for processing noise, it is possible to accurately remove noise caused by fluctuations in the electronic circuit itself and the power supply at the same time, and it is possible to further improve infrared detection sensitivity and accuracy. .

The invention of claim 31 or claim 32 is
The same effect as in claim 29 or claim 30 is achieved.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of an infrared sensor of the present invention.

FIG. 2 is a schematic vertical sectional view of the above.

FIG. 3 is a schematic plan view showing another embodiment of the infrared sensor of the present invention.

FIG. 4 is a schematic vertical sectional view of the above.

FIG. 5 is a schematic plan view showing still another embodiment of the infrared sensor of the present invention.

FIG. 6 is a schematic vertical sectional view of the above.

FIG. 7 is a schematic vertical sectional view showing still another embodiment of the infrared sensor of the present invention.

8 is a diagram showing an example of an electric circuit for obtaining an infrared detection signal using the infrared sensor of FIG. 1, FIG. 3 or FIG.

9 is a diagram showing another example of an electric circuit for obtaining an infrared detection signal using the infrared sensor of FIG. 1, FIG. 3 or FIG.

FIG. 10 is a diagram showing an example of an amplifier circuit.

FIG. 11 is a diagram showing another example of the amplifier circuit.

FIG. 12 is a diagram showing a main part of a circuit for supplying an output of an infrared sensor to a balanced amplifier circuit through an impedance converter.

FIG. 13 is a schematic view showing another embodiment of the infrared sensor of the present invention.

FIG. 14 is a schematic diagram showing a configuration example of a thin tube.

FIG. 15 is a schematic view showing a configuration example in which a pressure control valve is provided in the middle of a thin tube.

FIG. 16 is a sectional view of a pressure sensor according to an embodiment of the present invention.

17 is an enlarged partial sectional view of a piezoelectric element portion of the pressure sensor of FIG.

FIG. 18 is an exploded perspective view of a piezoelectric element holding portion in the pressure sensor of FIG.

FIG. 19 is an enlarged partial exploded cross-sectional view of a piezoelectric element in the pressure sensor of FIG.

20 is an enlarged partial exploded cross-sectional view of another piezoelectric element in the pressure sensor of FIG.

FIG. 21 is a configuration diagram of a balanced amplifier circuit.

22 is an output example of the impedance converter of the balanced amplifier circuit of FIG. 20. FIG.

FIG. 23 is a relationship diagram between voltage and current of a transistor.

FIG. 24 is an input / output characteristic diagram of a voltage comparator that outputs a pulse.

FIG. 25 is a characteristic diagram showing hysteresis in the voltage comparator.

FIG. 26 is an electrical signal processing circuit diagram in the infrared sensor according to the embodiment of the present invention.

FIG. 27 is an electrical signal processing circuit diagram in an infrared sensor according to another embodiment of the present invention.

FIG. 28 is a schematic view of a thermosensitive element according to an embodiment of the present invention.

FIG. 29 is a schematic diagram of a polarization treatment method for a pyroelectric film having comb-shaped electrodes on one surface and electrodes formed on the other surface.

FIG. 30 is a schematic cross-sectional view when a lead plane electrode is provided on the electrically processed circuit board and a pyroelectric film is directly formed in the embodiment of the present invention.

FIG. 31 is a schematic plan view when a lead flat electrode is provided on the electrically processed circuit board and a pyroelectric film is directly formed in the embodiment of the present invention.

FIG. 32 is an exploded schematic diagram when a ferroelectric thin film is directly formed on an infrared transmitting window material in an embodiment of the present invention.

FIG. 33 is a schematic assembly diagram of an infrared sensor according to an embodiment of the present invention.

FIG. 34 is a signal waveform at the time of infrared detection at 20 Hz in one embodiment of the present invention.

FIG. 35 is a signal waveform during infrared detection at 40 Hz in one embodiment of the present invention.

[Explanation of symbols]

2, 3 Piezoelectric element 4 Pressure detection unit 5 Electrical signal processing circuit 6,7 Piezoelectric body 8, 9, 10, 11 Electrode layer 39, 40 Inlet hole 42 First fluid pressure introduction path 43 Second fluid pressure introduction path 44 Third fluid pressure introduction path 45 Fourth fluid pressure introduction path 51 Constant voltage circuit 53 Amplification circuit section 75 Resistor 81 Capillary tube 81g Pressure control valve 91, 92 Pyroelectric element 91a, 91b, 92a, 92b Electrode 93 Ferroelectric Body thin film 104 Impedance converter 104a 97a, 98a Lead plane electrode 99 on electric circuit board 99 Lead line 110 Infrared ray incident part 111, 112 Charge extraction connection pin 113 Pyroelectric element detection part 114 Outer case 115 Signal output line 191, 192 Thermal Element 191a, 192
a, 196 electrodes

Claims (32)

[Claims] 1. In an infrared sensor for detecting heat information from the outside by means of a heat sensitive element, two heat sensitive elements (19
1) (192) is installed side by side so that the polarities of the respective elements are the same, and one of the same polarities is electrically connected to each other, and heat of the element from at least one of the other same polarities. An infrared sensor that converts information into an electrical signal, processes it in a subsequent electronic circuit, and then takes it out. 2. An infrared sensor for detecting heat information from the outside by a heat sensitive element, wherein electrodes (191a) (192a) provided on one surface of the heat sensitive element and an electrode (196) provided on the other surface. To form a substantially equivalent heat sensitive element, and the electrodes (192a) (19)
An infrared sensor characterized by being connected in series through 2a), converting thermal information from the heat-sensitive element into an electric signal, processing it by a subsequent electronic circuit, and then taking out the signal to the outside. 3. The thermosensitive element material is a ferroelectric thin film (93).
The infrared sensor according to claim 2, wherein 4. A ferroelectric thin film (93) and electrodes (96) (91) provided on one surface of the ferroelectric thin film (93).
b) (92b) and two substantially equivalent electrodes (91a) (92a) provided on the other surface, and two pyroelectric elements (91) (92) are formed. Infrared sensor characterized in that. 5. An electrode (91) provided on the one surface.
The infrared sensor according to claim 4, wherein b) and (92b) are individually provided at portions corresponding to two substantially equivalent electrodes (91a) and (92a) provided on the other surface. . 6. The ferroelectric thin film (93) is an electrode (91).
The infrared sensor according to claim 4, wherein the infrared sensor is divided into two or more portions including a portion including a) and a portion including an electrode (92a), and the respective polarization directions are the same. 7. An output of a pyroelectric element connected in series is obtained by connecting electrodes having the same polarization polarity on either of the same surfaces and connecting the electrodes on the opposite surfaces to each other.
Infrared sensor described in. 8. Connecting electrodes of different polarization polarities on opposite surfaces of each other, and through each connected electrode,
The infrared sensor according to claim 4, wherein an output of a pyroelectric element connected in parallel is obtained. 9. The ferroelectric thin film (93) is an electrode (91).
The infrared sensor according to claim 4, wherein the infrared sensor is divided into two or more portions including a portion including a) and a portion including an electrode (92a). 10. A pyroelectric element (91) and a pyroelectric element (92).
5. The infrared sensor according to claim 4, wherein electrodes having different polarization directions are connected to each other on the same surface, and the output of the pyroelectric elements connected in parallel is obtained through the respective connected electrodes. 11. The output of the pyroelectric element is sent to two impedance converters (104) each having one resistance (104a) as a load of the pyroelectric element provided in the signal processing circuit, and the two outputs thereof are provided. The infrared sensor according to claim 4, further comprising a signal processing circuit having a balanced amplifier circuit that connects the output of the signal processing circuit to the input terminals of the differential amplifier. 12. The infrared sensor according to claim 4, further comprising a signal processing circuit having a constant voltage circuit. 13. A substantially equivalent two kinds of electrodes (91b) (92b) are formed on an insulating substrate (94), and a ferroelectric thin film ((b) is formed on the two kinds of electrodes (91b) (92b). 93), and electrodes (91a) (92a) are formed on portions of the ferroelectric thin film (93) corresponding to the two kinds of electrodes to form two pyroelectric elements (91) (92). A method for manufacturing an infrared sensor, comprising: 14. A ferroelectric thin film (93) is formed on a substrate (94) having a conductive part (96) on its surface, and the conductive part (96) is formed on the ferroelectric thin film (93). Two kinds of electrodes (91a) (9
2a) is formed to form two pyroelectric elements (91) and (92). 15. An electrical connection between an electrode formed on a ferroelectric thin film and a subsequent electric processing circuit, wherein a conductive portion is provided on a substantially flat surface of an electronic circuit board, and the conductive portion of the ferroelectric thin film is provided at substantially the same position. The electrode (97a) (97b) is formed, and when connecting one electrode to another, the electrode directly formed on the ferroelectric thin film is used as a conductive portion. A method for manufacturing the infrared sensor described above. 16. A ferroelectric thin film is formed on a substantially flat surface opposite to the incident direction of an infrared transmitting entrance window material (110) to form a ferroelectric thin film and is substantially equivalent. 9. The method for manufacturing an infrared sensor according to claim 1, wherein two pyroelectric elements (91, 92) are formed. 17. The infrared sensor according to claim 4, wherein a polymer pyroelectric material is used as the ferroelectric thin film. 18. A vinylidene fluoride / 3-fluorinated ethylene copolymer or a vinylidene fluoride / 4-fluorinated ethylene copolymer as the polymer pyroelectric material.
The infrared sensor according to claim 17, wherein a polymer pyroelectric material composed of mol% to 90 mol% is used. 19. The infrared sensor according to claim 18, wherein the polymer ferroelectric thin film (93) has a thickness of 100 μm or less. 20. The infrared sensor according to claim 16, wherein the window material is the same material as the ferroelectric thin film. 21. An infrared sensor, wherein the window material and the ferroelectric thin film of claim 20 are the same material, wherein the ferroelectric thin film is a vinylidene fluoride / trifluoroethylene copolymer or An infrared sensor characterized by being a vinylidene fluoride / tetrafluoroethylene copolymer. 22. The electrode (91a) and the electrode (92)
The infrared sensor according to claim 4, wherein a) is formed of a nickel chromium alloy. 23. The electrode (91b) and the electrode (92)
The infrared sensor according to claim 4, wherein b) is made of aluminum. 24. The infrared sensor according to claim 4, wherein the ferroelectric thin film (93) is made of an inorganic ferroelectric material. 25. The infrared sensor according to claim 24, wherein the thickness of the inorganic ferroelectric thin film (93) is set to 100 μm or less. 26. An infrared ray is obtained by connecting a thin tube (81) with a closed tip to one inlet hole of a pressure sensor (1) provided with two inlet holes (39) (40) for introducing the pressure of a fluid. An infrared sensor characterized by containing an inert gas. 27. The infrared sensor according to claim 26, wherein the infrared inert gas is nitrogen, helium, argon or xenon gas. 28. One inlet hole of a pressure sensor (1) provided with two inlet holes (39) (40) for introducing the pressure of a fluid, and a thin tube (81) having a closed tip connected to the inlet holes.
3. A pressure control valve (81g) is installed between and.
6. The infrared sensor according to item 6. 29. Piezoelectric body (6) of the pressure sensor (1)
Electrode layers (8), (9), (10), and (11) are provided on both surfaces of (7), and two piezoelectric elements (2) and (3), which are molded in a planar shape and can be deformed, are paired in pairs. (12)
(13) A pressure detecting portion sandwiched from both surfaces of (14) and (15) is provided, and the two piezoelectric elements (2) and (3) face the same direction, and the surfaces of the same direction have the same polarization polarity. And two inlet holes (39) (40) for introducing the pressure of the fluid are provided in the pressure detecting portion, and one inlet hole (39) is connected to the first fluid pressure introducing path ( 42) and the first surface of the one piezoelectric element (2), and also communicates with the first surface of the one piezoelectric element (2) through the fourth fluid pressure introduction path (45). And is communicated with the second surface of the other piezoelectric element (3) having a polarization polarity different from that of the first surface of the one piezoelectric element (2) via the fourth fluid pressure introduction path (45). , The other inlet hole (40) is connected to the first piezoelectric element (2) through the second fluid pressure introducing path (43). From the two piezoelectric elements (2) and (3) through the third fluid pressure introducing path (44) and the first surface of the other piezoelectric element (3). Of the output of the signal processing circuit (5) to the amplification circuit section (53) of the signal processing circuit (5) and
The infrared sensor according to claim 26, further comprising a constant voltage circuit (51) provided therein. 30. The two piezoelectric elements (2) (3) of the pressure sensor (1) according to claim 26, wherein electrodes on the same surface of either one of them are connected to each other, and electrodes on the other surface of each are connected,
The output of the piezoelectric element is sent to each of two impedance converters (104) provided with one resistance (104a) serving as a load of the piezoelectric element provided in the signal processing circuit, and the two outputs are sent to the signal processing circuit ( An infrared sensor comprising a balanced amplifier circuit for sending to a differential amplifier in the amplifier circuit section (53) of 5), and also comprising a constant voltage circuit. 31. The infrared sensor according to claim 29 or 30, wherein the two piezoelectric elements (2) (3) of the pressure sensor (1) are made of a polymer ferroelectric. 32. The infrared sensor according to claim 29 or 30, wherein the polymer ferroelectric thin film of the pressure sensor is made of a copolymer of vinylidene fluoride and ethylene trifluoride.