JP2000155050A - Infrared ray sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase sensitiveness and responsiveness of an infrared sensor so as to improve a signal-to-noise(SN) ratio by arranging a pyroelectric element constructed of a polymer dielectric film with a thermal capacity of a specific value or less and an electrode on a base board with a heat conductivity of a specific value or less. SOLUTION: In this infrared ray sensor, pyroelectric elements 3, 4 are arranged on a base board 6 arranged on a support 8 made of silicon or the like. The pyroelectric elements 3, 4 are constructed of a common electrode 5 and split electrodes 1, 2 arranged on both surfaces of a polymer dielectric film 7, and the pyroelectric elements 3, 4 are polarized from each other substantially. A heat conductivity of the base board 6 is 0.3 W/(m. deg.C) or less, while the polymer dielectric film 7 with thermal capacity of 5×10-4 J/K or less is arranged in the pyroelectric elements 3, 4. The base board 6 is formed of resin selected from polyester resins, polyamide resins, polyimide resins, fluorine resins and olefinic resins. In addition, copolymer of vinylidene fluoride and ethylene trifluoride or the like is used for the polymer dielectric film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared sensor using a pyroelectric element capable of detecting a small temperature change without contact. More specifically, the present invention relates to a pyroelectric infrared sensor having stable performance with improved sensitivity, responsiveness, and SN ratio.

[0002]

2. Description of the Related Art In general, infrared sensors are roughly classified into a thermal type having no wavelength dependence and a quantum type which is advantageous for detection of a relatively short wavelength from the detection principle. Elements used for the thermal sensor include, for example, a thermopile, a thermistor, and a pyroelectric element, and the quantum type includes a photovoltaic element and a photoconductive element.
A pyroelectric infrared sensor, which is a type of thermal sensor, is a PbT
Inorganic materials such as TiO ₃ , BaTiO ₃ and TGS and ceramics are mainly used, and have been widely used for intruder alarm devices, automatic water supply devices and the like.

In order to increase the sensitivity of this pyroelectric infrared sensor, it is required to devise a technique that does not allow the heat absorbed by the pyroelectric element to escape to the surroundings. Therefore, in the pyroelectric element using the above-mentioned inorganic material, a technique of utilizing the rigidity thereof and supporting the element at a point to provide an air layer around the element to obtain heat insulation properties is used. In addition, there is also known a method in which an element is arranged on a substrate having low thermal conductivity, a hole is provided in a portion in contact with the element, and heat insulation is ensured (see Japanese Patent Publication No.
No. 82073).

However, these are all effective methods for using inorganic materials. For example, when a flexible polymer material is used, point support becomes difficult due to insufficient strength of the element, and the performance is poor. Had the problem of becoming unstable. Further, even when the technique disclosed in the above publication is applied to a polymer material, the sensor output becomes insufficient, and improvement has been demanded.

On the other hand, in order to improve the response of the sensor, it is effective to reduce the heat capacity of the element. However, in the example using the above inorganic material, the film thickness is about 100 μm, and the heat capacity is as large as 1 × 10 ^{−2 to} 5 × 10 ⁻³ J / K.
The response was such that a moving object of about 10 Hz could be detected. In addition, if the heat capacity is large, the temperature change of the element becomes small, so that the output signal becomes small.

In order to improve the S / N ratio of the sensor, it is important to reduce the noise as well as to increase the output signal. However, in a pyroelectric sensor, since the pyroelectric element has Noise is easily generated by vibration and noise. In particular, when a method of attaching a separately manufactured pyroelectric element to a substrate later is used, there have been problems such as an increase in factors that cause an increase in noise.

[0007] Under the circumstances described above, there has been reported an example in which an inorganic material is thinned by sputtering or the like to improve sensitivity and responsiveness (for example, J. App.
l. Phys., 61, 411 (1987)), all of which require large-scale facilities because of inorganic materials, and have a problem of increasing the manufacturing cost.

As described above, in the pyroelectric infrared sensor, among the sensors using an organic polymer material for the pyroelectric element, a sensor having high sensitivity, responsiveness and SN ratio and having stable performance can be obtained. I didn't.

[0009]

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a pyroelectric infrared sensor, particularly a pyroelectric infrared sensor using an organic polymer material, in which sensitivity and responsiveness are reduced. An object of the present invention is to provide a pyroelectric infrared sensor that is high and has an improved SN ratio.

[0010]

The present invention for achieving the above object includes a substrate having a thermal conductivity of 0.3 W / (m · ° C.) or less, and a pyroelectric element provided on the substrate. The pyroelectric element has a polymer dielectric film having a heat capacity of 5 × 10 ⁻⁴ J / K or less, and electrodes provided on both surfaces of the polymer dielectric film, and the electrode on one of the surfaces is provided. Is characterized by an infrared sensor arranged so as to be on the substrate.

Here, it is also preferable that at least one electrode is divided and two pyroelectric elements are formed in cooperation with the other electrode.

It is also preferable that the substrate is formed of a resin selected from a polyester resin, a polyamide resin, a polyimide resin, a fluorine resin and an olefin resin.

Further, the polymer dielectric film is made of a copolymer of vinylidene fluoride and ethylene trifluoride and / or a copolymer of vinylidene fluoride and ethylene tetrafluoride. It is also preferable that the vinylidene fluoride component in the polymer is in the range of 60 to 90 mol% in molar ratio.

It is also preferable that the substrate and the polymer dielectric film are made of the same material, and that the ten-point average roughness (Rz) of the surface of the substrate on which the pyroelectric element is arranged is 2 μm or less.

Further, it is preferable that the substrate is provided on a support.

Further, an infrared sensor unit in which the above-mentioned infrared sensor is housed in a housing including an infrared transmission window is also preferable.

Further, using the above-mentioned infrared sensor, 2
It is also preferable that an infrared ray is incident on only one of the pyroelectric elements and a method of measuring infrared rays is to extract a difference signal between a signal obtained from the pyroelectric element and a signal obtained from the other pyroelectric element.

It is also preferable to use a yarn inspection device provided with means for measuring the calorific value of the yarn using the infrared sensor.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An infrared sensor according to one embodiment of the present invention has a substrate 6 disposed on a support 8 made of silicon or the like as shown in FIG.
4 are provided. The pyroelectric elements 3 and 4 are composed of a common electrode 5 and split electrodes 1 and 2 provided on both surfaces of a polymer dielectric film 7, and the portions indicated by arrows in the figure are polarized in the same direction, and Are formed with two pyroelectric elements.

FIG. 2 shows an example of an infrared sensor unit incorporating the infrared sensor of FIG. The infrared sensor is accommodated in a housing 13 provided with a transmission window 11 having transparency to the infrared ray, since the infrared ray enters only one pyroelectric element. Then, lead wires 14 and 15 for extracting output signals are connected to the split electrodes 1 and 2 via the electronic circuit 12.
Is connected to

In the present invention, the thermal conductivity of the substrate is 0.3 W / (m · ° C.) or less. By setting the thermal conductivity to the above value, the heat (infrared rays) received by the pyroelectric element becomes difficult to escape to the surroundings, and even if the amount of received heat is small, a signal output can be obtained in proportion to the heat, The sensitivity of the infrared sensor can be improved. This is particularly effective when the incident frequency of infrared rays is 10 to 100 Hz.

The heat capacity of the polymer dielectric film is 5 × 10 ⁻⁴ J /
K or less. The heat capacity here means the heat capacity of the polymer dielectric film in the pyroelectric element formed by the opposing electrodes. This heat capacity is set to the above value, more preferably 2 ×
By setting it to 10 ⁻⁴ J / K, a signal proportional to the heat received by the pyroelectric element is output, and then heat transfer is quickly performed, so that the responsiveness of the infrared sensor can be improved.
In particular, in the present invention, by setting the thermal conductivity of the substrate to 0.3 W / (m · ° C.) or less in total, 1
At an infrared incidence frequency of 0 to 100 Hz, an appropriate heat holding time can be obtained, and good responsiveness can be obtained.

The above heat capacity depends on the volume of the pyroelectric element if the polymer dielectric films are of the same material. That is,
Since it depends on the thickness of the polymer dielectric film and the area of the facing electrode, it is preferable to appropriately adjust them. For example, the area of the electrode is usually
It is preferably 4 to ²⁰ mm ² . Further, the preferred film thickness is in the range of 0.01 μm to 7 μm, more preferably in the range of 1 to 4 μm. When the film thickness is less than 0.01 μm, the production becomes difficult, and the characteristics become difficult to stabilize. On the other hand, if it exceeds 7 μm, the heat capacity tends to be large, and the sensitivity and responsiveness to infrared rays tend to be insufficient.

The electrodes are provided on both sides so as to face each other with the polymer dielectric film interposed therebetween, and one of the electrodes is disposed on the substrate. As a result of the polarization treatment, the pyroelectric film of the pyroelectric element is formed only between the electrodes facing each other across the polymer dielectric film.

Although the pyroelectric element may constitute an infrared sensor alone, it is preferable that one of the electrodes is divided into two parts.
A plurality of pyroelectric elements are formed to form an infrared sensor. In this case, the electrode that is not divided becomes a common electrode, and can cancel out signal outputs due to various noises to extract only a difference signal, so that an infrared sensor having a high SN ratio is obtained.
It is preferable that the divided electrodes (divided electrodes) have the same size and the same area. This is to make the characteristics of the respective pyroelectric elements coincide with each other and to effectively perform the above-described signal cancellation. Further, if the opposing electrode areas of the pyroelectric elements are the same, the area of the common electrode may be smaller than the area of the divided electrodes. Further, the pyroelectric element may be formed on a common polymer dielectric film, or the pyroelectric element may be formed on each individual polymer dielectric film and one electrode may be connected.

It is preferable to use a material having a high absorptivity of infrared rays, such as nichrome, for the electrode on the side where the infrared rays are incident, and to use a material having a high reflectivity for the infrared rays, such as aluminum, on the electrode opposite to the side on which the infrared rays are incident. It is preferable to use a high material. It is also preferable to color the above-mentioned incident-side electrode by coating it with a black film in order to further increase the absorptivity of infrared rays.

As a material for the substrate, it is preferable to use a material having a generally low thermal conductivity such as a resin. For example, polyester resins such as polyethylene terephthalate (PET), polyamide resins such as nylon, polyimide resins, fluorine resins such as Teflon, and olefin resins can be used. Further, a copolymer containing these resin components in the structural unit may be used. In this case, a copolymer of vinylidene fluoride and ethylene trifluoride can be used. These resins are preferably used in the form of a thin film or a film. In this case, a plurality of film-shaped substrates may be stacked and an electrode or a polymer dielectric film may be formed on the outermost surface.

Further, as the material of the substrate, it is preferable to use the same material as a polymer ferroelectric film described later in order to prevent deformation due to heat and peeling due to a difference in strain. By using the same material, the durability of the infrared sensor can be increased.

Examples of the material for the polymer dielectric film include vinylidene fluoride, a copolymer of vinylidene fluoride and ethylene trifluoride, a copolymer of vinylidene fluoride and tetrafluoroethylene, and cyanide. Polymer dielectrics such as vinylidene-based copolymers, urea-based polymers, and odd-numbered nylons can be used. By using such a polymer dielectric, compared to the case of using inorganic materials and ceramics,
A thin film of about several μm can be easily formed. In particular, if a copolymer of vinylidene fluoride and ethylene trifluoride and the constituent molar ratio of the vinylidene fluoride component is 60 to 90 mol%, spontaneous processing is not performed without stretching. Polarized crystals can be obtained, and thin films can be easily obtained.

The ten-point average roughness (Rz) of the surface of the substrate on which the pyroelectric elements are arranged is preferably 2 μm or less. Rz
Exceeds 2 μm, it tends to be difficult to reduce the thickness of the pyroelectric element. In addition, it is preferable that the surface of the substrate be free from irregularities and scratches that hinder the formation of the pyroelectric element.

The substrate is preferably provided on a support such as silicon. By providing the infrared sensor on the support, the substrate and the pyroelectric element can be fixed stably, and an infrared sensor which is hardly affected by external vibration or noise can be obtained. When a semiconductor such as silicon is used as the support, electronic circuit components and the like can be provided over the support at the same time, which is preferable.

Next, a method of manufacturing the infrared sensor will be described with reference to FIG.

First, the substrate 6 is placed on a support 8 such as silicon.
Is provided. Depending on the substrate material, adhesion by an adhesive, thermal welding, ultrasonic welding, or the like can be used. In particular,
In order to obtain an infrared sensor with good performance uniformity and good noise resistance, directly coat the molten substrate material,
It is preferable to use a method of coating the solution in which the substrate material is dissolved, and then rotating the support to obtain a desired film thickness while evaporating the solution.

Next, the common electrode 5 is provided on the substrate. The electrode can be formed by a method such as vapor deposition, adhesion, printing, or coating of a conductive substance; however, vapor deposition is preferably used in order to increase the degree of adhesion and extract a stable signal with little noise or the like.

The polymer dielectric film 7 is formed on the common electrode 5.
Is provided. For this, the same arrangement method as that of the substrate 6 can be used. Here, in order to promote crystallization, it is preferable to perform heat treatment at a temperature between the melting point of the polymer dielectric and the ferroelectric-paraelectric transition point.

Next, the split electrodes 1 and 2 on the side where infrared rays are incident are provided. Also for this, the same forming method as that of the common electrode 5 can be used.

Finally, polarization is performed between the split electrodes 1, 2 and 5 to form a pyroelectric element. The polarization is preferably performed with an electric field equal to or higher than the coercive electric field at which the polarization of the film is reversed. further,
By performing the above-described polarization processing a plurality of times while changing the polarity of the electric field, the polarization directions can be made more consistent. Polarization is preferably performed using an electric field of usually 45 MV / m or more.

The above-described infrared sensor is preferably housed in a housing including an infrared transmission window and used as an infrared sensor unit. In particular, in the case of an infrared sensor having two pyroelectric elements, it is preferable to configure the infrared sensor unit using a housing having a transmission window through which infrared light enters only one of the pyroelectric elements. In this case, by electrically connecting one of the electrodes of the two pyroelectric elements, noise signals due to fluctuations in atmospheric pressure, noise, vibration, temperature changes, etc. are canceled, and only signals derived from infrared rays are extracted. It can be used as a method for measuring infrared rays having a high SN ratio.

The infrared sensor is used as a means for measuring the calorific value of the yarn and can be suitably used in a yarn inspection device. For example, when the yarn is traversed by a winder and the yarn is wound on a drum, an infrared sensor is installed downstream of the traverse guide, and the yarn crossing the front surface of the sensor by the traverse is used as a chopper. Thereby, the calorific value of the yarn can be measured. This allows
The yarn can be inspected by detecting abnormality of the oil agent attached to the yarn. Further, it can also be used for detecting a single yarn movement or a single yarn break of the yarn at the same time, and further indirectly detecting a process abnormality such as a melting temperature, a chimney air volume, a chimney temperature, and a hot roller temperature during spinning.

[0040]

In the following Examples and Comparative Examples, a copolymer of vinylidene fluoride and ethylene trifluoride was used as a polymer dielectric film (pyroelectric film) (the substrate was also used in Example 1). Wherein a copolymer having a constituent molar ratio of vinylidene fluoride component of 75 mol% was used (hereinafter referred to as P (D
VDF-TrFE)).

A silicon plate having a thickness of about 1 mm and a surface Rz of 0.3 μm was used as a support.

As for the electrodes, the electrodes provided on the substrate were formed by vapor deposition using aluminum to have a thickness of 0.1 μm. An electrode provided so as to face the aluminum electrode (common electrode) was formed by vapor deposition using Nichrome so as to have a thickness of 0.1 μm. Two nichrome electrodes (divided electrodes) having the same shape and the same area were provided. The size is 4 mm × 4 mm, and the electrode area of the portion facing the aluminum electrode is 16 mm.
It was mm ^2. Further, a terminal portion for connecting a lead wire for extracting a signal output was provided with a width of 2 mm.

The pyroelectric element was formed by applying an electric field of 90 MV / m between the nichrome electrode and the aluminum electrode. The polarization treatment was performed by repeating the reversal of the polarity seven times. Finally, a DC voltage was applied to make the polarities uniform, thereby obtaining a pyroelectric element.

(Example 1) On the above silicon support,
A dimethylformamide solution containing 20% by weight of the above copolymer was added dropwise. Next, the solvent was removed at 13 Pa using a reduced-pressure drier, and further, heat treatment was performed at 160 ° C. for 10 minutes to increase the adhesion between the film and the silicon support to form a 160 μm-thick substrate. An aluminum electrode was formed on the substrate.

Then, a dimethylformamide solution containing 10% by weight of the copolymer was dropped on the substrate including the electrodes, and the rotation speed of the spin coater was set to 800 rpm, and the solution was cooled to 30 rpm.
The substrate was rotated for seconds. Then, using a vacuum dryer, 1
After removing the solvent at 3 Pa and further heat-treating at 100 ° C. for 120 minutes, annealing was performed at 140 ° C. for 70 minutes to promote crystallization of the copolymer, and a film thickness of 1.5
A polymer dielectric film of μm was formed.

Next, a nichrome electrode was provided and polarization treatment was performed to obtain an infrared sensor. Table 1 shows the evaluation results.

The noise resistance of the obtained infrared sensor was measured. Without incident infrared rays, noise as 10
When only 0.2 G vibration was applied at Hz, the signal output became 2.8 mV. Also, as noise, 9 kHz at 1 kHz
When a noise of 5 dB was similarly applied, the signal output was 0.8 mV. In each case, the signal output was sufficiently smaller than the signal output by infrared rays.

(Example 2) A substrate having a thickness of 0.25 mm
An infrared sensor was obtained in the same manner as in Example 1, except that the ET resin film was provided on the support by adhesion and the thickness of the polymer dielectric film was 3.8 μm. Table 1 shows the evaluation results.

[0049]

Comparative Example 1 Comparative Example 1
An infrared sensor was obtained in the same manner as in Example 2 except that the thickness was 2 μm and the heat capacity was 12.4 × 10 ⁻⁴ J / K. Table 1 shows the evaluation results.

Comparative Example 2 A thermal conductivity of 230 W / (m ·
° C), an infrared sensor having a thickness of 0.5 mm was provided on the support by bonding, and the thickness of the polymer dielectric film was 2.2 μm, except that the infrared sensor was the same as in Example 1. I got Table 1 shows the evaluation results.

(Comparative Example 3) The thermal conductivity was 0.72 W / (m
.Degree. C.), a glass substrate having a thickness of 2.0 mm is provided on the support by bonding, and the thickness of the polymer dielectric film is changed to 2.8 .mu.m. I got a sensor. Table 1 shows the evaluation results.

(Comparative Example 4) A thermal conductivity of 84 W / (m ·
° C), and an infrared sensor was obtained in the same manner as in Comparative Example 3 except that a silicon substrate having a thickness of 1.1 mm was provided on a support by adhesion. Table 1 shows the evaluation results.

(Comparative Example 5) The thermal conductivity was 0.42 W / (m
(° C.), a glass epoxy resin substrate having a thickness of 1.6 mm was provided on the support by bonding, and the thickness of the polymer dielectric film was changed to 10.0 μm. To obtain an infrared sensor. Table 1 shows the evaluation results.

(Evaluation Method) (1) Signal Output (mV) A laser diode (hereinafter referred to as LD) having a wavelength of 1.55 μm was made to emit light at 50 Hz, and was vertically incident on the pyroelectric element. Then, the signal output from the pyroelectric element was captured for 128 seconds and averaged to obtain a signal output. Note that the output value is an effective value.

(2) Responsivity (msec) An LD having a wavelength of 1.55 μm was emitted at 1 Hz and a duty of 50%, and was vertically incident on the pyroelectric element. The signal output from the pyroelectric element was captured for a very short time, and the time required for the output value to recover from 0 to 90% of the maximum value was defined as the responsiveness. (3) D ^* (cm · Hz ^1/2 · W ⁻¹ ) An LD having a wavelength of 1.55 μm was emitted at 50 Hz, and was vertically incident on the pyroelectric element. D ^* was calculated by the following equation. Note that D ^* is standardized so that the characteristics of different elements can be easily compared with each other. The larger the value, the higher the detection sensitivity.

D ^* = {(S / N) · Δf ^1/2 } / (P · A ^1/2 ) where, S: signal output value (V) N: noise output value (measured at 1 Hz bandwidth) (V) (measured at 1 Hz bandwidth) Δf: noise bandwidth (= 100) (Hz) P: incident energy (= 1.27 × 10 ⁻³ ) (W · cm ⁻² ) A: light receiving area (= 7) 6.0 × 10 ^-2 ) (cm ² )

[Table 1]

[0057]

According to the present invention, the thermal conductivity is 0.3 W /
(M · ° C.) and a pyroelectric element provided on the substrate, wherein the pyroelectric element has a heat capacity of 5 × 10 ⁻⁴ J / K.
Since it has the following polymer dielectric film and electrodes provided on both surfaces of the polymer high dielectric film, and one of the electrodes is arranged so as to be on the substrate, the The heat generated by the infrared rays can be held appropriately, and an infrared sensor excellent in sensitivity and responsiveness can be obtained.

Further, at least one of the electrodes is divided,
When two pyroelectric elements are formed in cooperation with the other electrode, infrared rays are incident only on one of the pyroelectric elements,
Since a difference signal between the signal obtained from the pyroelectric element and the signal obtained from the other pyroelectric element can be extracted,
An infrared sensor having a high SN ratio can be provided.

Further, when the substrate is formed of a resin selected from a polyester resin, a polyamide resin, a polyimide resin, a fluorine resin and an olefin resin, the thermal conductivity can be reduced, so that more sensitivity can be obtained. Infrared sensor can be obtained.

Further, the polymer dielectric film is made of a copolymer of vinylidene fluoride and ethylene trifluoride, and / or
When it is composed of a copolymer of vinylidene fluoride and ethylene tetrafluoride, and the constituent molar ratio of the vinylidene fluoride component in the copolymer is 60 to 90 mol%,
Since a thin film can be easily obtained, an infrared sensor having excellent responsiveness can be provided.

Further, when the substrate and the polymer dielectric film are made of the same material, peeling due to differences in thermal deformation and strain hardly occurs, so that an infrared sensor having stable performance for a long period of time can be obtained. .

In addition, when the ten-point average roughness (Rz) of the surface of the substrate on which the pyroelectric element is arranged is 2 μm or less, the polymer dielectric can be made thinner, and the response is excellent. Infrared sensor can be obtained.

Further, when the substrate is disposed on a support, the substrate is less susceptible to noise such as vibration, so that an infrared sensor having more stable performance can be provided.

Further, by measuring the calorific value of the yarn using the infrared sensor of the present invention, it is possible to obtain a yarn inspection device excellent in responsiveness and sensitivity.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an infrared sensor according to an embodiment of the present invention.

FIG. 2 is a schematic side view of an infrared sensor unit incorporating the infrared sensor of FIG. 1;

FIG. 3 is a schematic exploded perspective view of the infrared sensor according to one embodiment of the present invention.

[Explanation of symbols]

 1: split electrode 2: split electrode 3: pyroelectric element 4: pyroelectric element 5: common electrode 6: substrate 7: polymer dielectric film 8: support body 9: signal extraction line 10: signal extraction line 11: transmission window 12: Electronic circuit 13: Housing 14: Lead wire (signal extraction line) 15: Lead wire (signal extraction line)

Claims (10)

[Claims] 1. A pyroelectric element comprising a substrate having a thermal conductivity of 0.3 W / (m · ° C.) or less, and a pyroelectric element provided on the substrate, wherein the pyroelectric element has a heat capacity of 5 × 10 ⁻⁴ J. / K or less, and electrodes provided on both surfaces of the polymer dielectric film, and any one of the electrodes is disposed on the substrate. Features infrared sensor. 2. The infrared sensor according to claim 1, wherein at least one electrode is divided and two pyroelectric elements are formed in cooperation with the other electrode. 3. The infrared sensor according to claim 1, wherein the substrate is formed of a resin selected from a polyester resin, a polyamide resin, a polyimide resin, a fluorine resin, and an olefin resin. 4. A polymer dielectric film comprising vinylidene fluoride and 3
It consists of a copolymer of ethylene fluoride and / or a copolymer of vinylidene fluoride and tetrafluoroethylene,
And the vinylidene fluoride component in the said copolymer is in the range of 60-90 mol% in molar ratio.
The infrared sensor according to any one of the above. 5. The infrared sensor according to claim 1, wherein the substrate and the polymer dielectric film are made of the same material. 6. The infrared sensor according to claim 1, wherein the ten-point average roughness (Rz) of the surface of the substrate on which the pyroelectric element is arranged is 2 μm or less. 7. The infrared sensor according to claim 1, wherein said substrate is provided on a support. 8. A housing including an infrared transmission window.
An infrared sensor unit comprising the infrared sensor according to any one of the above. 9. An infrared ray is incident on only one of the two pyroelectric elements, and a difference signal between a signal obtained from the pyroelectric element and a signal obtained from the other pyroelectric element is extracted. Item 8. An infrared measuring method using the infrared sensor according to any one of Items 2 to 7. 10. A yarn inspection device comprising means for measuring the calorific value of a yarn using the infrared sensor according to any one of claims 1 to 7.