Pyroelectric elements, infrared detectors and gas analyzers

Abstract

Provided is a pyroelectric element in which the infrared light detection sensitivity has been improved by making thermal conduction from light-receiving electrodes to compensating electrodes difficult. Also provided are an infrared ray detector and a gas analyzer.　The pyroelectric element comprises: a plate-like pyroelectric body; a plurality of light-receiving electrodes that are provided to one surface of the pyroelectric body and used for receiving infrared light; and a plurality of compensating electrodes that are provided to said one surface, the number of the plurality of compensating electrodes being the same as the number of the plurality of light-receiving electrodes. Each of the plurality of light-receiving electrodes forms a pair with one of the plurality of compensating electrodes. The light-receiving electrode and the compensating electrode included in each pair are adjacent to each other, and a slit that runs through the pyroelectric body is provided between the light-receiving electrode and the compensating electrode included in each pair, the position of said slit including the center position between the light-receiving electrode and the compensating electrode included in each pair.

Description

[Technical field]

[0001] The present invention relates to a pyroelectric element, an infrared detector, and a gas analyzer. [Background technology]

[0002] Conventionally, non-dispersive infrared absorption methods are used to analyze gas components. In general, multiple gas components absorb different wavelengths of infrared light. The infrared light that has passed through the gas is passed through a specific optical filter that transmits infrared light of a wavelength absorbed by the specific gas component, and the intensity of the infrared light that has passed through the specific optical filter is detected. Also, the intensity of reference infrared light that has passed through an optical filter that transmits infrared light of a wavelength different from that absorbed by the specific gas component is detected. When a specific gas component is present, the intensity of the infrared light that has passed through the specific optical filter is different from the intensity of the reference infrared light. The concentration of the specific gas component is obtained from the difference in the infrared light intensity. For example, non-dispersive infrared absorption methods are used to analyze gas components contained in automobile exhaust gas.

[0003] A pyroelectric element may be used as a detection element provided in an infrared detector. A pyroelectric element is configured by providing a light receiving electrode on the surface of a plate-shaped pyroelectric material and a back electrode on the back side. In a pyroelectric material, the charge on the surface changes according to a change in temperature. When the light receiving electrode receives infrared light, the temperature of the part of the pyroelectric element where the light receiving electrode is provided rises, and the potential difference between the light receiving electrode and the back electrode changes. The intensity of the infrared light is detected according to the change in the potential difference. The surface charge of the pyroelectric element varies not only due to the incident infrared light, but also due to sudden changes in the temperature of the environment or vibration. For this reason, the output from the light receiving electrode contains a variable component unrelated to the infrared light. Therefore, the pyroelectric element has a compensation electrode that does not receive infrared light and a back electrode on the back side of the compensation electrode, and the output from the compensation electrode is used to offset the variable component contained in the output from the light receiving electrode. Patent Document 1 discloses an example of a pyroelectric element having a compensation electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-18816 Summary of the Invention [Problem to be solved by the invention]

[0005] In a pyroelectric element having a light-receiving electrode and a compensating electrode, heat generated by infrared light is conducted from the light-receiving electrode to the compensating electrode. This thermal conduction causes the output from the compensating electrode to contain a component originating from infrared light. As a result of using the output from the compensating electrode to offset the fluctuation component contained in the output from the light-receiving electrode, the output of the pyroelectric element is reduced compared to the output originating from the original infrared light. This reduces the detection sensitivity of infrared light.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a pyroelectric element, an infrared detector, and a gas analyzer in which the detection sensitivity of infrared light is improved by making it difficult for heat to be conducted from the light-receiving electrode to the compensating electrode. [Means for solving the problem]

[0007] The pyroelectric element of the present invention comprises a plate-shaped pyroelectric body, a plurality of light-receiving electrodes provided on one side of the pyroelectric body for receiving infrared light, and a plurality of compensating electrodes provided on the one side and in the same number as the plurality of light-receiving electrodes, wherein each of the plurality of light-receiving electrodes is paired with one of the plurality of compensating electrodes, the light-receiving electrodes and the compensating electrodes included in each pair are adjacent to each other, a slit is provided between the light-receiving electrodes and the compensating electrodes included in each pair, and the position of the slit includes a central position between the light-receiving electrodes and the compensating electrodes included in each pair.

[0008] In one embodiment of the present invention, the pyroelectric element includes a plurality of pairs of light-receiving electrodes and compensation electrodes provided on the surface of a plate-shaped pyroelectric body, and a slit penetrating the pyroelectric body is provided between each pair of the light-receiving electrodes and the compensation electrodes. The presence of the slits makes it difficult for heat to be conducted from the light-receiving electrodes that receive infrared light to the compensation electrodes. Therefore, the output from the compensation electrodes contains almost no components derived from infrared light. The output from the light-receiving electrodes does not decrease below the output derived from the original infrared light.

[0009] The pyroelectric element according to the present invention is characterized in that each of the plurality of light-receiving electrodes has a rectangular shape, and each of the plurality of compensation electrodes has a shape surrounding a portion of the light-receiving electrode included in the same set.

[0010] In one embodiment of the present invention, the compensation electrode has a rectangular shape and surrounds a part of the light-receiving electrode. By surrounding a part of the light-receiving electrode with the compensation electrode, a necessary area for the compensation electrode can be secured near the light-receiving electrode. Also, a necessary area for the slit can be secured between the light-receiving electrode and the compensation electrode.

[0011] The pyroelectric element of the present invention is characterized in that each of the multiple compensation electrodes has an L-shape that follows a side of the light-receiving electrode included in the same group, is positioned between the light-receiving electrode and the center of the one surface, and the slit has an L-shape that follows each compensation electrode.

[0012] In one embodiment of the present invention, the compensation electrode has an L-shape and is disposed at a position between the light receiving electrode and the center of the surface of the pyroelectric body. The compensation electrode is L-shaped, so that it can surround a part of the light receiving electrode. Since the light receiving electrode is away from the center of the surface of the pyroelectric body, infrared light that should be received by another light receiving electrode is unlikely to be mistakenly received by that light receiving electrode. In addition, the slit has an L-shape. This allows the slit to be disposed over a long distance between the light receiving electrode and the compensation electrode.

[0013] The pyroelectric element according to the present invention is characterized in that the slits are processed so that the interior angles of the slits that are less than 180° are rounded.

[0014] In one embodiment of the present invention, the slits are processed so that the interior angles of the slits that are less than 180° are rounded, thereby preventing cracks from occurring in the pyroelectric body starting from the interior angles of the slits that are less than 180°.

[0015] The pyroelectric element according to the present invention is characterized in that the light-receiving electrode and the compensation electrode included in each pair are connected in parallel or in series inverse to each other.

[0016] In one embodiment of the present invention, the light receiving electrode and the compensation electrode are connected in parallel or in series inverse to each other. More specifically, an element including a light receiving electrode and an element including a compensation electrode are connected in parallel or in series inverse to each other. The fluctuation components included in the potential difference of the elements are cancelled out, and the components derived from the received infrared light are output.

[0017] The infrared detector of the present invention comprises a plurality of optical filters, each of which selectively transmits infrared light of a predetermined wavelength, and a pyroelectric element of the present invention, and is characterized in that the plurality of light receiving electrodes of the pyroelectric element correspond one-to-one to the plurality of optical filters, and infrared light that has passed through the corresponding optical filter is incident on each of the plurality of light receiving electrodes, while infrared light is not incident on the plurality of compensation electrodes of the pyroelectric element.

[0018] The gas analyzer of the present invention is a gas analyzer for analyzing the concentration of a specific gas component contained in a gas to be analyzed, and is characterized in that it comprises an infrared detector of the present invention, a light source that emits infrared light, and a cell through which the gas to be analyzed flows, and the infrared light from the light source passes through the gas to be analyzed flowing through the cell, and the infrared light that has passed through the gas to be analyzed is incident on the infrared detector.

[0019] In one aspect of the present invention, an infrared detector includes a pyroelectric element according to the present invention, which makes it difficult for heat to be conducted from the light-receiving electrode that receives infrared light to the compensation electrode, thereby improving detection sensitivity. The improved detection sensitivity of the infrared detector to infrared light enables the gas analyzer to accurately calculate the concentration of gas components contained in the gas to be analyzed. Effect of the Invention

[0020] The present invention provides excellent effects such as improved sensitivity of the infrared detector to detect infrared light. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a perspective view illustrating an infrared detector. [Diagram 2] 1 is a cross-sectional view illustrating a schematic internal configuration of an infrared detector according to Embodiment 1. FIG. [Diagram 3] FIG. 1 is an exploded perspective view showing a schematic internal configuration of an infrared detector according to a first embodiment. [Figure 4] FIG. 2 is a schematic plan view of a light collecting block. [Figure 5A] 1 is a schematic diagram showing a pyroelectric element according to embodiment 1. FIG. [Figure 5B] 1 is a schematic diagram showing a pyroelectric element according to embodiment 1. FIG. [Figure 6] FIG. 2 is a plan view of a slit according to the first embodiment. [Figure 7] 1 is a circuit diagram showing a part of an equivalent circuit of an infrared detector according to Embodiment 1. FIG. [Figure 8] FIG. 1 is a schematic diagram showing an example of a gas analyzer using an infrared detector. [Figure 9] FIG. 1 is a block diagram showing a configuration of a gas analysis device using a gas analyzer. [Figure 10A] 10 is a schematic diagram showing a first example of a pyroelectric element according to embodiment 2. FIG. [Figure 10B] 10 is a schematic diagram showing a first example of a pyroelectric element according to embodiment 2. FIG. [Figure 11]FIG. 11 is a circuit diagram showing a part of an equivalent circuit of an infrared detector according to a second embodiment. [Figure 12A] 11 is a schematic diagram showing a second example of the pyroelectric element according to the second embodiment. FIG. [Figure 12B] 11 is a schematic diagram showing a second example of the pyroelectric element according to the second embodiment. FIG. [Figure 13A] 11 is a schematic diagram showing a first example of a pyroelectric element according to embodiment 3. FIG. [Figure 13B] 11 is a schematic diagram showing a first example of a pyroelectric element according to embodiment 3. FIG. [Figure 14] FIG. 11 is a circuit diagram showing a part of an equivalent circuit of an infrared detector according to a second embodiment. [Figure 15A] 13 is a schematic diagram showing a second example of a pyroelectric element according to embodiment 3. FIG. [Figure 15B] 13 is a schematic diagram showing a second example of a pyroelectric element according to embodiment 3. FIG. [Figure 16A] 13 is a schematic diagram showing a third example of the pyroelectric element according to the third embodiment. FIG. [Figure 16B] 13 is a schematic diagram showing a third example of the pyroelectric element according to the third embodiment. FIG. [Figure 17A] 13 is a schematic diagram showing a fourth example of the pyroelectric element according to the third embodiment. FIG. [Figure 17B] 13 is a schematic diagram showing a fourth example of the pyroelectric element according to the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present invention will now be described in detail with reference to the drawings showing embodiments thereof. <Embodiment 1> FIG. 1 is a perspective view showing an infrared detector 1. The infrared detector 1 is a detector that detects infrared light using a pyroelectric element, and detects infrared light of a wavelength absorbed by multiple types of gas components. In this embodiment, infrared light and infrared light are used interchangeably. The infrared detector 1 is used to analyze the concentration of multiple types of gas components. In the first embodiment, the infrared detector 1 detects infrared light of a wavelength absorbed by each of three types of gas components and reference infrared light unrelated to any of the gas components. For example, the three types of gas components are carbon dioxide, carbon monoxide, and hydrocarbons.

[0023] FIG. 2 is a cross-sectional view showing a schematic internal configuration of the infrared detector 1 according to the first embodiment. The cross section shown in FIG. 2 is a cross section of the infrared detector 1 cut along the line II-II in FIG. 1. FIG. 3 is an exploded perspective view showing a schematic internal configuration of the infrared detector 1 according to the first embodiment. The infrared detector 1 includes a cylindrical package 21, an infrared transmission window 22, and a stem 24. The package 21 is made of a material that does not transmit infrared light, and both ends are open. The infrared transmission window 22 is made of a material that transmits infrared light, and closes the opening at one end of the package 21. The package 21 covers the stem 24, and the other end of the package 21 is joined to the stem 24. More specifically, the other end of the package 21 is welded to the stem 24. Since the other end of the package 21 is joined to the stem 24, the other end of the package 21 is closed, and the inside of the package 21 is sealed.

[0024] Further, inside the package 21, a filter section 3, a light collecting block 4, a pyroelectric element 5, and a circuit board 23 are arranged. The filter section 3 is a combination of a plurality of optical filters 31, 32, 33, and 34 having wavelength selectivity for transmitting infrared light of a predetermined wavelength. The light collecting block 4 is a combination of a plurality of light collecting sections 41, 42, 43, and 44 for collecting infrared light transmitted through the optical filters 31, 32, 33, and 34. The pyroelectric element 5 is flat and is formed of a pyroelectric material such as PZT (lead zirconate titanate) or LiTaO3 (lithium tantalate). On the surface of the pyroelectric element 5, light receiving electrodes 511, 521, 531, and 541 for receiving the infrared light collected by the light collecting sections 41, 42, 43, and 44, and compensation electrodes 512, 522, 532, and 542 are provided. Furthermore, the pyroelectric element 5 has slits 515, 525, 535 and 545 formed therein.

[0025] The pyroelectric element 5 is fixed to a circuit board 23. The circuit board 23 is provided with a circuit that connects to the pyroelectric element 5. The circuit board 23 is supported by a stem 24. A plurality of lead terminals 241 are inserted through the stem 24. The lead terminals 241 are connected to the circuit of the circuit board 23. Power is supplied to and signals are output from the outside of the infrared detector 1 via the lead terminals 241.

[0026] The optical filters 31, 32, 33, and 34 constituting the filter unit 3 transmit infrared light of different wavelengths. For example, the optical filters 31, 32, 33, and 34 are bandpass filters and multilayer interference filters. The optical filter 31 transmits infrared light of a wavelength absorbed by a first gas component, the optical filter 32 transmits infrared light of a wavelength absorbed by a second gas component, and the optical filter 33 transmits infrared light of a wavelength absorbed by a third gas component. The optical filter 34 transmits infrared light of a wavelength different from that of any of the optical filters 31, 32, and 33. The infrared light transmitted by the optical filter 34 is infrared light for reference. The optical filters 31, 32, 33, and 34 all have a rectangular flat plate shape.

[0027] The light-collecting block 4 is formed by a combination of light-collecting sections 41, 42, 43, and 44, and has a rectangular parallelepiped shape. The light-collecting section 41 collects infrared light transmitted through the optical filter 31, the light-collecting section 42 collects infrared light transmitted through the optical filter 32, the light-collecting section 43 collects infrared light transmitted through the optical filter 33, and the light-collecting section 44 collects infrared light transmitted through the optical filter 34. The light-receiving electrode 511 receives the infrared light collected by the light-collecting section 41, the light-receiving electrode 521 receives the infrared light collected by the light-collecting section 42, the light-receiving electrode 531 receives the infrared light collected by the light-collecting section 43, and the light-receiving electrode 541 receives the infrared light collected by the light-collecting section 44. The optical filter 31, the light collecting portion 41 and the light receiving electrode 511 correspond to each other, the optical filter 32, the light collecting portion 42 and the light receiving electrode 521 correspond to each other, the optical filter 33, the light collecting portion 43 and the light receiving electrode 531 correspond to each other, and the optical filter 34, the light collecting portion 44 and the light receiving electrode 541 correspond to each other.

[0028] 4 is a schematic plan view of the light collecting block 4. The light collecting sections 41, 42, 43, and 44 are arranged in a matrix in a plan view and are formed integrally with one another. The light collecting sections 41, 42, 43, and 44 each have a shape of a rectangular block with a through hole formed therein. One end of the through hole is an entrance port through which infrared light enters, and the other end of the through hole is an exit port through which the infrared light exits. The entrance port and the exit port are rectangular in shape. The inner surface of the through hole is a reflective surface that reflects infrared light. The light-collecting section 41 has an entrance 411, an exit 412, and a reflecting surface 413, the light-collecting section 42 has an entrance 421, an exit 422, and a reflecting surface 423, the light-collecting section 43 has an entrance 431, an exit 432, and a reflecting surface 433, and the light-collecting section 44 has an entrance 441, an exit 442, and a reflecting surface 443.

[0029] The entrances 411, 421, 431, and 441 face the infrared-transmitting window 22. The optical filters 31, 32, 33, and 34 are disposed between the infrared-transmitting window 22 and the entrances 411, 421, 431, and 441. The optical filter 31 is disposed at a position to block the entrance 411, the optical filter 32 is disposed at a position to block the entrance 421, the optical filter 33 is disposed at a position to block the entrance 431, and the optical filter 34 is disposed at a position to block the entrance 441.

[0030] The light-emitting openings 412, 422, 432, and 442 face the surface of the pyroelectric element 5. The light-receiving electrode 511 is disposed at a position facing the light-emitting opening 412, the light-receiving electrode 521 is disposed at a position facing the light-emitting opening 422, the light-receiving electrode 531 is disposed at a position facing the light-emitting opening 432, and the light-receiving electrode 541 is disposed at a position facing the light-receiving opening 442. Since the light-receiving electrodes face the light-emitting openings of the corresponding light-collecting parts, it is difficult for the infrared light collected by the other light-collecting parts to be mistakenly received by the light-receiving electrodes. In FIG. 4, the positions of the optical filters 31, 32, 33, and 34 and the positions of the light-receiving electrodes 511, 521, 531, and 541 are indicated by dashed lines.

[0031] The areas of the exit ports 412, 422, 432, and 442 are smaller than the areas of the entrance ports 411, 421, 431, and 441. The areas of the exit ports 412, 422, 432, and 442 are substantially the same. The reflecting surfaces 413, 423, 433, and 443 are formed by coating the inner surfaces of the through holes of the light collecting units 41, 42, 43, and 44 with a material having a good reflectance of infrared light. For example, the light collecting block 4 is made of resin, and the reflecting surfaces 413, 423, 433, and 443 are formed by coating the inner surfaces of the through holes with a metal such as gold. The diameters of the through holes of the light collecting units 41, 42, 43, and 44 are continuously reduced from the entrance ports 411, 421, 431, and 441 to the exit ports 412, 422, 432, and 442. Therefore, the reflecting surfaces 413, 423, 433, and 443 form a funnel-shaped curved surface tapering from the entrances 411, 421, 431, and 441 to the exits 412, 422, 432, and 442. The reflecting surfaces 413, 423, 433, and 443 are inclined with respect to a plane including the entrances 411, 421, 431, and 441. The light-collecting block 4 may be made of a metal such as aluminum. The reflecting surfaces 413, 423, 433, and 443 may be made of a metal finished to a mirror surface, or may be made of a metal coated with another metal such as gold that has a good reflectance of infrared light.

[0032] The infrared light incident on the entrances 411, 421, 431, and 441 is reflected by the reflecting surfaces 413, 423, 433, and 443, and is collected at the exits 412, 422, 432, and 442. The infrared light is collected by collecting the infrared light at the exits 412, 422, 432, and 442, which have smaller areas than the entrances 411, 421, 431, and 441. The collected infrared light is emitted from the exits 412, 422, 432, and 442, and is received by the light receiving electrodes 511, 521, 531, and 541. The infrared light is collected by the light collecting sections 41, 42, 43, and 44, and the amount of light increases, and the detected intensity is amplified.

[0033] Infrared light from outside the infrared detector 1 passes through the infrared-transmitting window 22 and then passes through one of the optical filters 31, 32, 33, and 34. The infrared light that passes through each optical filter enters the corresponding light-collecting section, is collected, and is received by the corresponding light-receiving electrode. Light paths other than the light paths between the corresponding optical filters and light-receiving electrodes are blocked by the light-collecting block 4. For this reason, infrared light that passes through an optical filter that does not correspond to the light-receiving electrode is prevented from being received by the light-receiving electrode, and infrared light is prevented from being received by parts other than the light-receiving electrode.

[0034] 5A and 5B are schematic diagrams showing a pyroelectric element 5 according to the first embodiment. FIG. 5A shows a schematic plan view of the pyroelectric element 5 according to the first embodiment. FIG. 5B shows the arrangement of electrodes provided on the back surface of the pyroelectric body 50 according to the first embodiment, seen through from the front surface side. The pyroelectric element 5 includes a plate-shaped pyroelectric body 50. The pyroelectric body 50 is made of a pyroelectric material such as PZT or LiTaO3, and is rectangular in plan view. A plurality of light receiving electrodes and a plurality of compensation electrodes are provided on the surface of the pyroelectric body 50. The compensation electrodes are electrodes provided at positions on the surface of the pyroelectric body 50 that do not receive infrared light. The number of light receiving electrodes and compensation electrodes is the same. Each of the plurality of light receiving electrodes is paired with one of the plurality of compensation electrodes. In the first embodiment, four pairs of light-receiving electrodes and compensation electrodes are provided, including a pair including a light-receiving electrode 511 and a compensation electrode 512, a pair including a light-receiving electrode 521 and a compensation electrode 522, a pair including a light-receiving electrode 531 and a compensation electrode 532, and a pair including a light-receiving electrode 541 and a compensation electrode 542. The light-receiving electrodes and compensation electrodes included in each pair are disposed close to each other on the surface of the pyroelectric body 50 and spaced apart from the other pairs. In Figs. 5A and 5B, two opposing sides of the pyroelectric body 50 and a bisector 55 that bisects the area of ​​the pyroelectric body 50, and a bisector 56 perpendicular to the bisector 55 are shown by dashed dotted lines. The light-receiving electrodes and compensation electrodes of each pair are disposed in the four equal parts divided by the bisectors 55 and 56 on the surface of the pyroelectric body 50. Note that the bisectors 55 and 56 are imaginary lines that do not actually exist on the surface of the pyroelectric body 50. The bisectors described below are also imaginary lines.

[0035] The light-receiving electrode 511 has a rectangular shape. The compensation electrode 512 has an L-shape along two sides of the light-receiving electrode 511. The compensation electrode 512 has an L-shape, and thus has a shape that surrounds a part of the light-receiving electrode 511. The light-receiving electrode 511 and the compensation electrode 512 have different shapes, but have the same area. The compensation electrode 512 is disposed at a position between the light-receiving electrode 511 and the center of the surface of the pyroelectric body 50. The center of the surface of the pyroelectric body 50 is the intersection of the bisectors 55 and 56. That is, the distance from the center of the surface of the pyroelectric body 50 to the light-receiving electrode 511 is longer than the distance from the center of the surface of the pyroelectric body 50 to the compensation electrode 512. Since the light-receiving electrode 511 is away from the center of the surface of the pyroelectric body 50, infrared light that should be received by another light-receiving electrode is less likely to be mistakenly received by the light-receiving electrode 511.

[0036] A lead wire 511a for connecting to a circuit provided on the circuit board 23 is connected to the light receiving electrode 511. The lead wire 511a extends to one side of the pyroelectric body 50. A lead wire 512a for connecting to the circuit is connected to the compensation electrode 512. The lead wire 512a extends to the other side of the pyroelectric body 50.

[0037] A slit 515 is provided between the light-receiving electrode 511 and the compensation electrode 512. The slit 515 penetrates from the front surface to the back surface of the pyroelectric body 50. For example, the slit 515 is formed by excavating a part of the pyroelectric body 50 using a laser beam. The slit 515 has an L-shape along the compensation electrode 512. The position of the slit 515 includes a central position between the light-receiving electrode 511 and the compensation electrode 512. The compensation electrode 512 surrounds a part of the light-receiving electrode 511, so that an area required for the compensation electrode 512 in the vicinity of the light-receiving electrode 511 can be secured. Also, an area required for the slit 515 can be secured between the light-receiving electrode 511 and the compensation electrode 512.

[0038] FIG. 6 is a plan view of the slit 515 according to the first embodiment. 515a shown in the figure is an interior angle of less than 180°. 515b shown in the figure is an interior angle of 270°, which is an interior angle of 180° or more. The interior angle is an angle formed inside the slit 515. An interior angle of less than 180° may be the starting point of a crack that occurs in the pyroelectric body 50. The slit 515 is processed to round the interior angle of less than 180°. In FIG. 6, a virtual interior angle of less than 180° that is not rounded is shown by a dashed line. By rounding the interior angle of less than 180°, it is possible to prevent a crack from occurring in the pyroelectric body 50 starting from the interior angle, and the pyroelectric element 5 is less likely to be damaged. In addition, the slit 515 is not processed to round the interior angle of 180° or more. Since interior angles of 180° or more do not become the starting point of cracks, damage to pyroelectric element 5 is prevented even if the interior angles are not rounded. By eliminating the process of rounding interior angles of 180° or more, the number of steps in manufacturing pyroelectric element 5 is reduced.

[0039] A slit 525 is provided between the light-receiving electrode 521 and the compensation electrode 522, and a lead wire 521a connected to the light-receiving electrode 521 and a lead wire 522a connected to the compensation electrode 522 are provided. The positions and shapes of the light-receiving electrode 521, the compensation electrode 522, the slit 525, and the lead wires 521a and 522a are point-symmetric with respect to the center of the surface of the pyroelectric body 50, as well as the light-receiving electrode 511, the compensation electrode 512, the slit 515, and the lead wires 511a and 512a.

[0040] A slit 535 is provided between the light-receiving electrode 531 and the compensation electrode 532, and a lead line 531a connected to the light-receiving electrode 531 and a lead line 532a connected to the compensation electrode 532 are provided. The positions and shapes of the light-receiving electrode 531, the compensation electrode 532, the slit 535, and the lead lines 531a and 532a are symmetrical with respect to the bisector 55 with respect to the light-receiving electrode 511, the compensation electrode 512, the slit 515, and the lead lines 511a and 512a.

[0041] A slit 545 is provided between the light-receiving electrode 541 and the compensation electrode 542, and a lead line 541a connected to the light-receiving electrode 541 and a lead line 542a connected to the compensation electrode 542 are provided. The positions and shapes of the light-receiving electrode 541, the compensation electrode 542, the slit 545, and the lead lines 541a and 542a are symmetrical with those of the light-receiving electrode 511, the compensation electrode 512, the slit 515, and the lead lines 511a and 512a with respect to the bisector 56. The slits 525, 535, and 545 are formed, for example, by using laser light, similarly to the slit 515.

[0042] An electrode is also provided on the back surface of the pyroelectric body 50. As shown in Fig. 5B, a back surface electrode 513 is provided on the back surface of the pyroelectric body 50 at a position corresponding to the back side of the light-receiving electrode 511. The back surface electrode 513 has a shape that overlaps with the light-receiving electrode 511 from the front and back. A back surface electrode 514 is provided at a position corresponding to the back side of the compensation electrode 512. The back surface electrode 514 has a shape that overlaps with the compensation electrode 512 from the front and back.

[0043] Lead wires 513a and 513b for connection to a circuit are connected to the back electrode 513. The lead wire 513a extends to one side of the pyroelectric body 50, and the lead wire 513b extends to the other side of the pyroelectric body 50. The lead wire 514a for connection to a circuit is connected to the back electrode 514. The lead wire 514a extends to the other side of the pyroelectric body 50. The lead wire 513a is provided with a contact 513c connected to the circuit, and the lead wire 513b is provided with a contact 513d. The lead wire 514a is provided with a contact 514b. In FIG. 5A, the lead wires 513a, 513b, and 514a are shown by dashed lines. The lead wire 511a is connected to the lead wire 514a via the side surface of the pyroelectric body 50. Therefore, the light receiving electrode 511 is connected to the back electrode 514. The lead wire 512a is connected to the lead wire 513b via the side surface of the pyroelectric body 50. Therefore, the compensation electrode 512 is connected to the back electrode 513. The positions and shapes of the lead wires 511a and 512a and the lead wires 513a, 513b and 514a are designed so that they do not overlap on the front and back except in the vicinity of the connection portions.

[0044] The back surface of the pyroelectric body 50 is provided with back electrodes 523 and 524, lead lines 523a, 523b, and 524a, and contacts 523c, 523d, and 524b. The positions and shapes of the back electrodes 523 and 524, lead lines 523a, 523b, and 524a, and contacts 523c, 523d, and 524b are point-symmetric with the back electrodes 513 and 514, lead lines 513a, 513b, and 514a, and contacts 513c, 513d, and 514b with respect to the center of the back surface of the pyroelectric body 50. The lead line 521a is connected to the lead line 524a via the side surface of the pyroelectric body 50. The lead line 522a is connected to the lead line 523b via the side surface of the pyroelectric body 50.

[0045] The back surface of the pyroelectric body 50 is provided with back electrodes 533 and 534, lead lines 533a, 533b, and 534a, and contacts 533c, 533d, and 534b. The positions and shapes of the back electrodes 533 and 534, lead lines 533a, 533b, and 534a, and contacts 533c, 533d, and 534b are symmetrical with the back electrodes 513 and 514, lead lines 513a, 513b, and 514a, and contacts 513c, 513d, and 514b with respect to the bisector 55. The lead line 531a is connected to the lead line 534a through the side surface of the pyroelectric body 50. The lead line 532a is connected to the lead line 533b through the side surface of the pyroelectric body 50.

[0046] The back surface of the pyroelectric body 50 is provided with back electrodes 543 and 544, lead lines 543a, 543b, and 544a, and contacts 543c, 543d, and 544b. The positions and shapes of the back electrodes 543 and 544, lead lines 543a, 543b, and 544a, and contacts 543c, 543d, and 544b are symmetrical with respect to the bisector 56 with the back electrodes 513 and 514, lead lines 513a, 513b, and 514a, and contacts 513c, 513d, and 514b. The lead line 541a is connected to the lead line 544a through the side surface of the pyroelectric body 50. The lead line 542a is connected to the lead line 543b through the side surface of the pyroelectric body 50. The light-receiving electrode, compensation electrode, back electrode and lead wire are each formed on the front, back and side surfaces of the pyroelectric body 50 by, for example, vapor deposition or sputtering using a metal material.

[0047] FIG. 7 is a circuit diagram showing a part of the equivalent circuit of the infrared detector 1 according to the first embodiment. The light receiving electrode 511 and the back electrode 513 constitute an element with the pyroelectric body 50 as a dielectric. The compensation electrode 512 and the back electrode 514 constitute an element with the pyroelectric body 50 as a dielectric. Here, the element is an electric element formed by sandwiching a part of the pyroelectric body 50 between the light receiving electrode or the compensation electrode and the back electrode. The electrode arranged on the front surface of the pyroelectric body 50 becomes the negative (or positive) side electrode, and the electrode arranged on the back surface of the pyroelectric body 50 becomes the positive (or negative) side electrode. The element including the light receiving electrode 511 and the back electrode 513 and the element including the compensation electrode 512 and the back electrode 514 are connected in parallel and inversely connected. The two elements are connected in parallel to a resistor 517. The electric charge generated by the two elements flows through the resistor 517 to generate a current, and a potential difference is generated in the resistor 517. The generated potential difference is impedance converted by a FET (Field effect transistor) 516, and an output voltage Vout1 is obtained.

[0048] The light-receiving electrode 511 receives the infrared light that has passed through the optical filter 31 and been collected by the light-collecting unit 41. Since the infrared light is blocked by the light-collecting block 4, the compensation electrode 512 does not receive the infrared light. When the light-receiving electrode 511 receives the infrared light, the temperature of the portion of the pyroelectric element where the light-receiving electrode 511 is provided rises, and the potential difference between the light-receiving electrode 511 and the back electrode 513 changes. Since the compensation electrode 512 does not receive the infrared light, the potential difference between the compensation electrode 512 and the back electrode 514 does not change. The potential difference between the light-receiving electrode 511 and the back electrode 513 includes a fluctuation component that fluctuates due to a sudden change in temperature or vibration in the environment. The same fluctuation component is also included in the potential difference between the compensation electrode 512 and the back electrode 514. Since the element including the light-receiving electrode 511 and the rear electrode 513 and the element including the compensation electrode 512 and the rear electrode 514 are connected in reverse in parallel, the fluctuation components contained in the potential difference are cancelled out. The components resulting from the reception of infrared light contained in the potential difference generated by the two elements and the resistor 517 are not cancelled out, and are subjected to impedance conversion by the FET 516, resulting in an output voltage Vout1 corresponding to the reception of infrared light. The output voltage Vout1 is a detection signal corresponding to the intensity of the infrared light received by the light-receiving electrode 511.

[0049] When heat generated by infrared light is conducted from the light-receiving electrode 511 to the compensation electrode 512, the component derived from the infrared light is offset. In this embodiment, since the slit 515 is provided between the light-receiving electrode 511 and the compensation electrode 512, heat is unlikely to be conducted from the light-receiving electrode 511 to the compensation electrode 512. Since the slit 515 is L-shaped, the slit 515 can be arranged over a long distance between the light-receiving electrode 511 and the compensation electrode 512. Therefore, heat conduction is effectively prevented. Since heat is unlikely to be conducted from the light-receiving electrode 511 to the compensation electrode 512, the potential difference between the compensation electrode 512 and the back electrode 514 contains almost no component derived from infrared light. Therefore, the component derived from the reception of infrared light contained in the potential difference between the light-receiving electrode 511 and the back electrode 513 is not offset. The output voltage Vout1 does not decrease below the output derived from the original infrared light. Therefore, the detection sensitivity of infrared light using the light-receiving electrode 511 is improved.

[0050] The light-receiving electrode 521 and the rear electrode 523 are connected in the same manner as the compensation electrode 522 and the rear electrode 524. A resistor 527 is connected in parallel to the element including the light-receiving electrode 521 and the rear electrode 523 and the element including the compensation electrode 522 and the rear electrode 524. The fluctuation component included in the potential difference between the light-receiving electrode 521 and the rear electrode 523 is offset by the potential difference between the compensation electrode 522 and the rear electrode 524. The component originating from the infrared light received by the light-receiving electrode 521, included in the potential difference generated by the two elements and the resistor 527, is impedance-converted by the FET 526, and an output voltage Vout2 according to the reception of the infrared light is obtained. The light-receiving electrode 531 and the rear electrode 533 are connected in the same manner as the compensation electrode 532 and the rear electrode 534. A resistor 537 is connected in parallel to the element including the light-receiving electrode 531 and the rear electrode 533 and the element including the compensation electrode 532 and the rear electrode 534. The component originating from the received infrared light and included in the potential difference generated by the two elements and resistor 537 is impedance converted by FET 536, and an output voltage Vout3 corresponding to the reception of infrared light is obtained. The light-receiving electrode 541 and rear surface electrode 543 are similarly connected to the compensation electrode 542 and rear surface electrode 544. The resistor 537 is connected in parallel to the element including the light-receiving electrode 541 and rear surface electrode 543 and the element including the compensation electrode 542 and rear surface electrode 544. The component originating from the received infrared light and included in the potential difference generated by the two elements and resistor 547 is impedance converted by FET 546, and an output voltage Vout4 corresponding to the reception of infrared light is obtained.

[0051] Due to the presence of the slits 525, 535, and 545, the components resulting from the reception of infrared light contained in the potential difference are not cancelled out, and the output voltages Vout2, Vout3, and Vout4 do not decrease below the outputs resulting from the original infrared light. Therefore, similar to the case of the light-receiving electrode 511, the detection sensitivity of infrared light using the light-receiving electrodes 521, 531, and 541 is improved. The ratio of the total area of ​​the slits 515, 525, 535, and 545 to the surface size of the pyroelectric body 50 is about 9 / 350. With the slits having such a size, heat conduction is effectively prevented, and the detection sensitivity of infrared light is effectively improved.

[0052] The output voltages Vout1, Vout2, Vout3, and Vout4 are detection signals corresponding to the intensity of infrared light received by the light-receiving electrodes 511, 521, 531, and 541, respectively. The light-receiving electrodes 511, 521, 531, and 541 receive infrared light transmitted through the optical filters 31, 32, 33, and 34, respectively. The output voltages Vout1, Vout2, and Vout3 are detection signals corresponding to the intensity of infrared light of wavelengths absorbed by the first, second, and third gas components, respectively. The output voltage Vout4 is a detection signal corresponding to the intensity of reference infrared light.

[0053] The infrared detector 1 is used to analyze the concentration of three types of gas components contained in a gas such as exhaust gas. FIG. 8 is a schematic diagram showing an example of a gas analyzer 6 using the infrared detector 1. The gas analyzer 6 includes a light source 61 that emits infrared light, a cell 62 through which a gas to be analyzed flows, and the infrared detector 1. The gas to be analyzed is, for example, automobile exhaust gas. The flow of gas flowing through the cell 62 is indicated by dashed arrows. Infrared light from the light source 61 is incident on the cell 62 while gas is flowing through the cell 62. The infrared light passes through the gas in the cell 62 and is incident on the infrared detector 1. The infrared light is indicated by solid arrows. Each gas component contained in the gas absorbs the infrared light, and then the infrared detector 1 detects the infrared light. The infrared detector 1 outputs a detection signal according to the intensity of the infrared light of the wavelength absorbed by each of the three types of gas components and the intensity of the reference infrared light.

[0054] FIG. 9 is a block diagram showing the configuration of a gas analyzer 64 using a gas analyzer 6. The gas analyzer 64 includes a gas analyzer 6 including a light source 61, a cell 62, and an infrared detector 1, and a concentration calculation unit 63. The concentration calculation unit 63 includes a control unit 631 using a processor, a memory 632, a display unit 634 using a display, and an amplifier unit 635. The amplifier unit 635 is connected to the infrared detector 1, and receives and amplifies the detection signal output by the infrared detector 1. The memory 632 stores necessary data. The control unit 631 calculates the concentration of the gas component contained in the gas to be analyzed based on the amplified detection signal. The display unit 634 displays the calculated concentration value. The detection signal received by the amplifier unit 635 has a value corresponding to the intensity of the infrared light detected by the infrared detector 1. The intensity of the infrared light detected by the infrared detector 1 changes depending on the concentrations of the three types of gas components contained in the gas to be analyzed. The control unit 631 calculates the concentration of each gas component contained in the gas based on a comparison between the detected intensity of the infrared light having a wavelength absorbed by each gas component and the detected intensity of the reference infrared light. The amplification unit 635 may be provided outside the concentration calculation unit 63 and connected to the infrared detector 1 and the concentration calculation unit 63.

[0055] As described above in detail, in the first embodiment, the infrared detector 1 uses a pyroelectric element 5 having a slit between the light-receiving electrode and the compensation electrode, making it difficult for heat to be conducted from the light-receiving electrode to the compensation electrode. By making it difficult for heat to be conducted to the compensation electrode, the output derived from the infrared light received by the light-receiving electrode is not offset, and the detection signal corresponding to the intensity of the infrared light is not reduced. Therefore, the infrared detector 1 has improved infrared light detection sensitivity. By improving the infrared light detection sensitivity of the infrared detector 1, the gas analyzer 6 and the gas analyzer 64 can accurately calculate the concentrations of the three types of gas components contained in the gas to be analyzed.

[0056] In addition, the position of the slit includes the center position between the light-receiving electrode and the compensation electrode. If the slit is too close to the light-receiving electrode, the insulation between the light-receiving electrode and the back electrode may be broken through the space of the slit. Similarly, if the slit is too close to the compensation electrode, the insulation between the compensation electrode and the back electrode may be broken through the space of the slit. By arranging the slit at a position including the center position between the light-receiving electrode and the compensation electrode, the slit is kept at a certain distance from both the light-receiving electrode and the compensation electrode. Therefore, the insulation between the light-receiving electrode and the back electrode, and the insulation between the compensation electrode and the back electrode are both less likely to be broken, and the function of the pyroelectric element 5 is more likely to be maintained.

[0057] <Embodiment 2> 10A and 10B are schematic diagrams showing a first example of a pyroelectric element 5 according to the second embodiment. FIG. 10A shows a schematic plan view of the first example of the pyroelectric element 5 according to the second embodiment. FIG. 10B shows the arrangement of electrodes provided on the back surface of the first example of the pyroelectric body 50 according to the second embodiment, seen through from the front surface side. The light-receiving electrode 511 has a rectangular shape. The compensation electrode 512 has a band shape along one side of the light-receiving electrode 511. The light-receiving electrode 511 and the compensation electrode 512 have the same area. The compensation electrode 512 is disposed at a position between the light-receiving electrode 511 and the center of the front surface of the pyroelectric body 50. The light-receiving electrode 511 and the compensation electrode 512 are connected by a connection line 511b.

[0058] A slit 515a is provided between the light-receiving electrode 511 and the compensation electrode 512. The slit 515a has a band-like shape along the compensation electrode 512. The position of the slit 515a includes the center position between the light-receiving electrode 511 and the compensation electrode 512. In addition, an L-shaped slit 515b is provided along one side of the light-receiving electrode 511, the connection line 511b, and the compensation electrode 512. The slits 515a and 515b penetrate the pyroelectric body 50 from the front surface to the back surface.

[0059] A slit 525a is provided between the light-receiving electrode 521 and the compensation electrode 522, and a slit 525b is also provided. The light-receiving electrode 521 and the compensation electrode 522 are connected by a connection line 521b. The positions and shapes of the light-receiving electrode 521, the compensation electrode 522, the connection line 521b, and the slits 525a and 525b are point-symmetric with the light-receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slits 515a and 515b with respect to the center of the surface of the pyroelectric body 50. A slit 535a is provided between the light-receiving electrode 531 and the compensation electrode 532, and a slit 535b is also provided. The light-receiving electrode 531 and the compensation electrode 532 are connected by a connection line 531b. The positions and shapes of the light receiving electrode 531, the compensation electrode 532, the connection line 531b, and the slits 535a and 535b are linearly symmetrical with respect to the bisector 55 with respect to the light receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slits 515a and 515b. A slit 545a is provided between the light receiving electrode 541 and the compensation electrode 542, and a slit 545b is further provided. The light receiving electrode 541 and the compensation electrode 542 are connected by a connection line 541b. The positions and shapes of the light receiving electrode 541, the compensation electrode 542, the connection line 541b, and the slits 545a and 545b are linearly symmetrical with respect to the bisector 56 with respect to the light receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slits 515a and 515b.

[0060] 10B, a back surface electrode 513 is provided on the back surface of the pyroelectric body 50 at a position corresponding to the back side of the light-receiving electrode 511. The back surface electrode 513 has a shape that overlaps with the light-receiving electrode 511 from the front and back. A back surface electrode 514 is provided at a position corresponding to the back side of the compensation electrode 512. The back surface electrode 514 has a shape that overlaps with the compensation electrode 512 from the front and back.

[0061] A lead wire 513a for connection to a circuit is connected to the rear electrode 513. A lead wire 514a for connection to a circuit is connected to the rear electrode 514. A contact point 513c for connection to the circuit is provided on the lead wire 513a, and a contact point 514b is provided on the lead wire 514a. In Fig. 10A, the lead wires 513a and 514a are shown by dashed lines.

[0062] On the back surface of the pyroelectric body 50, back electrodes 523 and 524, lead lines 523a and 524a, and contacts 523c and 524b are provided. The positions and shapes of the back electrodes 523 and 524, lead lines 523a and 524a, and contacts 523c and 524b are point-symmetric with the back electrodes 513 and 514, lead lines 513a and 514a, and contacts 513c and 514b with respect to the center of the back surface of the pyroelectric body 50. On the back surface of the pyroelectric body 50, back electrodes 533 and 534, lead lines 533a and 534a, and contacts 533c and 534b are provided. The positions and shapes of the rear electrodes 533 and 534, the leads 533a and 534a, and the contacts 533c and 534b are symmetrical with respect to the bisector 55 with respect to the rear electrodes 513 and 514, the leads 513a and 514a, and the contacts 513c and 514b.

[0063] Back electrodes 543 and 544, lead lines 543a and 544a, and contacts 543c and 544b are provided on the back surface of the pyroelectric body 50. The positions and shapes of the back electrodes 543 and 544, lead lines 543a and 544a, and contacts 543c and 544b are symmetrical with respect to the bisector 56 with respect to the back electrodes 513 and 514, lead lines 513a and 514a, and contacts 513c and 514b.

[0064] FIG. 11 is a circuit diagram showing a part of an equivalent circuit of the infrared detector 1 according to the second embodiment. The light receiving electrode 511 and the back electrode 513 constitute an element, and the compensation electrode 512 and the back electrode 514 constitute an element. The electrode arranged on the front surface of the pyroelectric body 50 becomes the negative (or positive) side electrode, and the electrode arranged on the back surface of the pyroelectric body 50 becomes the positive (or negative) side electrode. The element including the light receiving electrode 511 and the back electrode 513 and the element including the compensation electrode 512 and the back electrode 514 are connected in series inversely. A resistor 517 is connected in parallel to the two elements. A current corresponding to the difference in charges generated in the two elements flows through the resistor 517, and a potential difference is generated in the resistor 517. The generated potential difference corresponds to the difference between the potential differences generated in the two elements. The generated potential difference is impedance converted by the FET 516, and an output voltage Vout1 is obtained.

[0065] When the light-receiving electrode 511 receives infrared light, the potential difference between the light-receiving electrode 511 and the back electrode 513 changes. The fluctuation component included in the potential difference between the light-receiving electrode 511 and the back electrode 513 is also included in the potential difference between the compensation electrode 512 and the back electrode 514. A potential difference corresponding to the difference between the potential differences generated in the element including the light-receiving electrode 511 and the back electrode 513 and the element including the compensation electrode 512 and the back electrode 514 is generated in the resistor 517, so that the fluctuation component included in the potential difference is offset. The component derived from the reception of infrared light included in the potential difference is not offset, and is impedance converted by the FET 516, so that an output voltage Vout1 corresponding to the reception of infrared light is obtained. The output voltage Vout1 is a detection signal corresponding to the intensity of the infrared light received by the light-receiving electrode 511.

[0066] The light receiving electrode 521 and the back electrode 523, the compensation electrode 522 and the back electrode 524, and the resistor 527 are also connected in the same manner. The component originating from the received infrared light included in the potential difference generated in the resistor 527 is impedance converted by the FET 526, and an output voltage Vout2 corresponding to the reception of the infrared light is obtained. The light receiving electrode 531 and the back electrode 533, the compensation electrode 532 and the back electrode 534, and the resistor 537 are also connected in the same manner. The component originating from the received infrared light included in the potential difference generated in the resistor 537 is impedance converted by the FET 536, and an output voltage Vout3 corresponding to the reception of the infrared light is obtained. The light receiving electrode 541 and the back electrode 543, the compensation electrode 542 and the back electrode 544, and the resistor 547 are also connected in the same manner. The component originating from the received infrared light included in the potential difference generated in the resistor 547 is impedance converted by the FET 546, and an output voltage Vout4 corresponding to the reception of the infrared light is obtained.

[0067] The provision of the slits 515a, 515b, 525a, 525b, 535a, 535b, 545a, and 545b makes it difficult for heat to be conducted from the light-receiving electrodes to the compensation electrodes. Therefore, similarly to the first embodiment, the output voltages Vout1, Vout2, Vout3, and Vout4 do not decrease below the outputs derived from the original infrared light, and the detection sensitivity of the infrared light using the light-receiving electrodes 511, 521, 531, and 541 is improved.

[0068] 12A and 12B are schematic diagrams showing a second example of the pyroelectric element 5 according to the second embodiment. FIG. 12A shows a schematic plan view of the second example of the pyroelectric element 5 according to the second embodiment. FIG. 12B shows the arrangement of electrodes provided on the back surface of the second example of the pyroelectric body 50 according to the second embodiment, seen through from the front surface side. The light-receiving electrode 511 has a rectangular shape. The compensation electrode 512 has a band shape along one side of the light-receiving electrode 511. The light-receiving electrode 511 and the compensation electrode 512 have the same area. The compensation electrode 512 is disposed at a position between the light-receiving electrode 511 and the center of the front surface of the pyroelectric body 50. The light-receiving electrode 511 and the compensation electrode 512 are connected by a connection line 511b.

[0069] A slit 515 is provided between the light-receiving electrode 511 and the compensation electrode 512. The slit 515 penetrates from the front surface to the back surface of the pyroelectric body 50. The slit 515 has a T-shape. A part of the slit 515 runs along one side of the light-receiving electrode 511, and another part of the slit 515 runs along the other side of the light-receiving electrode 511 and the compensation electrode 512. The position of the slit 515 includes a central position between the light-receiving electrode 511 and the compensation electrode 512.

[0070] The positions and shapes of the light-receiving electrode 521, the compensation electrode 522, the connection line 521b, and the slit 525 are point-symmetric with the light-receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slit 515 with respect to the center of the surface of the pyroelectric body 50. The positions and shapes of the light-receiving electrode 531, the compensation electrode 532, the connection line 531b, and the slit 535 are line-symmetric with the light-receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slit 515 with respect to the bisector 55. The positions and shapes of the light-receiving electrode 541, the compensation electrode 542, the connection line 541b, and the slit 545 are line-symmetric with the light-receiving electrode 511, the compensation electrode 512, the connection line 511b, and the slit 515 with respect to the bisector 56.

[0071] 12B, a back electrode 513 is provided at a position corresponding to the back side of the light-receiving electrode 511. The back electrode 513 has a shape overlapping the light-receiving electrode 511 from the front and back. A back electrode 514 is provided at a position corresponding to the back side of the compensation electrode 512. The back electrode 514 has a shape overlapping the compensation electrode 512 from the front and back. A lead line 513a is connected to the back electrode 513, and a contact point 513c is provided on the lead line 513a. A lead line 514a is connected to the back electrode 514, and a contact point 514b is provided on the lead line 514a.

[0072] The positions and shapes of the rear electrodes 523 and 524, the lead lines 523a and 524a, and the contact points 523c and 524b are point-symmetric with the rear electrodes 513 and 514, the lead lines 513a and 514a, and the contact points 513c and 514b with respect to the center of the rear surface of the pyroelectric body 50. The positions and shapes of the rear electrodes 533 and 534, the lead lines 533a and 534a, and the contact points 533c and 534b are line-symmetric with the rear electrodes 513 and 514, the lead lines 513a and 514a, and the contact points 513c and 514b with respect to the bisector 55. The positions and shapes of the rear electrodes 543 and 544, the leads 543a and 544a, and the contacts 543c and 544b are symmetrical with respect to the bisector 56 with respect to the rear electrodes 513 and 514, the leads 513a and 514a, and the contacts 513c and 514b.

[0073] The connection mode of the pyroelectric element 5 to the circuit of the second example is similar to that of the first example shown in Fig. 11. As in the first example, output voltages Vout1, Vout2, Vout3, and Vout4 corresponding to the reception of infrared light are obtained in response to the reception of infrared light by the light-receiving electrodes 511, 521, 531, and 541. By providing the slits 515, 525, 535, and 545, the detection sensitivity of the infrared light using the light-receiving electrodes 511, 521, 531, and 541 is improved.

[0074] The configuration of the infrared detector 1 according to the second embodiment is the same as that of the first embodiment, except for the pyroelectric element 5 described with reference to Figures 10A, 10B, 12A and 12B, and part of the circuit described with reference to Figure 11. The configurations of the gas analyzer 6 and the gas analyzer 64 using the infrared detector 1 are the same as those of the first embodiment.

[0075] In the infrared detector 1 of the second embodiment, by using a pyroelectric element 5 having a slit between the light-receiving electrode and the compensating electrode, the detection signal corresponding to the intensity of infrared light is not reduced, and the detection sensitivity of infrared light is improved. The gas analyzer 6 and the gas analyzer 64 can accurately calculate the concentrations of three types of gas components contained in the gas to be analyzed. As in the first embodiment, the position of the slit includes the center position between the light-receiving electrode and the compensating electrode, so that the insulation between the light-receiving electrode and the back electrode, and the insulation between the compensating electrode and the back electrode are less likely to be broken, and the function of the pyroelectric element 5 is easily maintained.

[0076] In the first and second embodiments, the infrared light transmitted through the optical filter is incident on the light collecting section, but the infrared detector 1 may be configured so that the infrared light collected by the light collecting section is transmitted through the optical filter. In the present embodiment, the optical filter, the entrance, the exit, and the light receiving section are rectangular, but the infrared detector 1 may be configured so that the optical filter, the entrance, the exit, or the light receiving section have a shape other than a rectangle. For example, the optical filter, the entrance, the exit, or the light receiving section may be circular. The package 21, the infrared transmission window 22, the light collecting block 4, the pyroelectric element 5, the circuit board 23, and the stem 24 may also have a shape other than a rectangle in a plan view. The areas of the optical filters 31, 32, 33, and 34 and the entrances 411, 421, 431, and 441 may be unequal. In addition, the infrared detector 1 may use a light shielding part other than the light collecting block 4 to block the infrared light so that it does not enter the compensation electrode.

[0077] <Embodiment 3> In the first and second embodiments, four types of infrared light having different wavelengths are detected, whereas in the third embodiment, two types of infrared light having different wavelengths are detected. FIGS. 13A and 13B are schematic diagrams showing a first example of a pyroelectric element 5 according to the third embodiment. FIG. 13A shows a schematic plan view of the first example of a pyroelectric element 5 according to the third embodiment. FIG. 13B shows the arrangement of electrodes provided on the back surface of the first example of a pyroelectric body 50 according to the third embodiment, as seen through from the front surface. The pyroelectric element 5 includes a disk-shaped pyroelectric body 50. Two pairs of light receiving electrodes and compensation electrodes are provided on the front surface of the pyroelectric body 50, one pair including a light receiving electrode 511 and a compensation electrode 512, and the other pair including a light receiving electrode 521 and a compensation electrode 522. In FIGS. 13A and 13B, a bisector 55 that bisects the area of ​​the pyroelectric body 50 and a bisector 56 that is perpendicular to the bisector 55 are shown by dashed lines. The light-receiving electrodes 511 and 521 and the compensation electrodes 512 and 522 are disposed on the surface of the pyroelectric body 50 in four equal parts divided by the bisectors 55 and 56, respectively.

[0078] The light-receiving electrode 511 and the compensation electrode 512 have the same area. The position and shape of the compensation electrode 512 are linearly symmetrical to the light-receiving electrode 511 with respect to the bisector 55. A lead wire 511a for connection to a circuit is connected to the light-receiving electrode 511. The lead wire 511a extends to an end of the pyroelectric body 50. A lead wire 512a for connection to a circuit is connected to the compensation electrode 512. The lead wire 512a extends to an end of the pyroelectric body 50. The positions and shapes of the light-receiving electrode 521 and the lead wire 521a are point-symmetrical to the light-receiving electrode 511 and the lead wire 511a with respect to the center of the surface of the pyroelectric body 50. The positions and shapes of the compensation electrode 522 and the lead wire 522a are point-symmetrical to the compensation electrode 512 and the lead wire 512a with respect to the center of the surface of the pyroelectric body 50.

[0079] The pyroelectric element 5 is provided with a cross-shaped slit 57 centered on the center of the surface of the pyroelectric body 50. The slit 57 penetrates from the front surface to the back surface of the pyroelectric body 50. The position of the slit 57 includes the central position between the light-receiving electrode 511 and the compensation electrode 512, and the central position between the light-receiving electrode 521 and the compensation electrode 522. In addition, a part of the slit 57 is between the light-receiving electrode 511 and the compensation electrode 522, and another part is between the compensation electrode 512 and the light-receiving electrode 521.

[0080] 13B, a back surface electrode 513 is provided on the back surface of the pyroelectric body 50 at a position corresponding to the back side of the light-receiving electrode 511. The back surface electrode 513 has a shape that overlaps with the light-receiving electrode 511 from the front and back. A back surface electrode 514 is provided at a position corresponding to the back side of the compensation electrode 512. The back surface electrode 514 has a shape that overlaps with the compensation electrode 512 from the front and back.

[0081] A lead wire 513a for connection to a circuit is connected to the back electrode 513. The back electrode 513 is connected to the circuit via the lead wire 513a. A connection portion 513e for connection to a circuit is provided on the back surface of the pyroelectric body 50. The lead wire 511a is connected to the connection portion 513e via the side surface of the pyroelectric body 50. The light receiving electrode 511 is connected to the circuit via the lead wire 511a and the connection portion 513e. A lead wire 514a for connection to a circuit is connected to the back electrode 514. The back electrode 514 is connected to the circuit via the lead wire 514a. A connection portion 514c for connection to a circuit is provided on the back surface of the pyroelectric body 50. The lead wire 512a is connected to the connection portion 514c via the side surface of the pyroelectric body 50. The compensation electrode 512 is connected to the circuit via the lead wire 512a and the connection portion 514c.

[0082] A back electrode 523, a lead wire 523a, and a connection portion 523e are provided on the back surface of the pyroelectric body 50. The positions and shapes of the back electrode 523, the lead wire 523a, and the connection portion 523e are point-symmetrical with the back electrode 513, the lead wire 513a, and the connection portion 513e with respect to the center of the back surface of the pyroelectric body 50. The lead wire 521a is connected to the connection portion 523e via the side surface of the pyroelectric body 50. A back electrode 524, a lead wire 524a, and a connection portion 524c are provided on the back surface of the pyroelectric body 50. The positions and shapes of the back electrode 524, the lead wire 524a, and the connection portion 524c are point-symmetrical with the back electrode 514, the lead wire 514a, and the connection portion 514c with respect to the center of the back surface of the pyroelectric body 50. The lead wire 522a is connected to the connection portion 524c via the side surface of the pyroelectric body 50.

[0083] 14 is a circuit diagram showing a part of an equivalent circuit of the infrared detector 1 according to the second embodiment. The light receiving electrode 511 and the back electrode 513 constitute an element, and the compensation electrode 512 and the back electrode 514 constitute an element. The electrode arranged on the front surface of the pyroelectric body 50 becomes the negative (or positive) side electrode, and the electrode arranged on the back surface of the pyroelectric body 50 becomes the positive (or negative) side electrode. The element including the light receiving electrode 511 and the back electrode 513 and the element including the compensation electrode 512 and the back electrode 514 are connected in parallel and inversely connected. A resistor 517 is connected in parallel to the two elements. Charges generated by the two elements flow through the resistor 517 to generate a current, and a potential difference is generated in the resistor 517. The generated potential difference is impedance converted by the FET 516, and an output voltage Vout1 is obtained.

[0084] When the light-receiving electrode 511 receives infrared light, the potential difference between the light-receiving electrode 511 and the back electrode 513 changes. The fluctuation component included in the potential difference between the light-receiving electrode 511 and the back electrode 513 is also included in the potential difference between the compensation electrode 512 and the back electrode 514. Since the element including the light-receiving electrode 511 and the back electrode 513 and the element including the compensation electrode 512 and the back electrode 514 are connected in reverse in parallel, the fluctuation component included in the potential difference is offset. The component originating from the reception of infrared light included in the potential difference generated by the two elements and the resistor 517 is not offset, and is impedance converted by the FET 516, so that an output voltage Vout1 according to the reception of infrared light is obtained. The output voltage Vout1 is a detection signal according to the intensity of the infrared light received by the light-receiving electrode 511.

[0085] The light-receiving electrode 521 and the rear electrode 523 are similarly connected to the compensation electrode 522 and the rear electrode 524, and to the resistor 527. The component originating from the received infrared light contained in the potential difference generated in the resistor 527 is subjected to impedance conversion by the FET 526, and an output voltage Vout2 corresponding to the received infrared light is obtained.

[0086] The provision of the slits 57 makes it difficult for heat to be conducted from the light-receiving electrode 511 to the compensating electrode 512 and from the light-receiving electrode 521 to the compensating electrode 522. Also, it makes it difficult for heat to be conducted from the light-receiving electrode 511 to the compensating electrode 522 and from the light-receiving electrode 521 to the compensating electrode 512. Therefore, the output voltages Vout1 and Vout2 do not decrease below the output derived from the original infrared light, and the detection sensitivity of the infrared light using the light-receiving electrodes 511 and 521 is improved. Since it becomes difficult for heat to be conducted between the light-receiving electrodes and the compensating electrodes included in the same set, and also difficult for heat to be conducted between the light-receiving electrodes and the compensating electrodes of different sets, heat conduction to the compensating electrodes is reliably prevented, and the detection sensitivity of the infrared light is reliably improved.

[0087] 15A and 15B are schematic diagrams showing a second example of a pyroelectric element 5 according to embodiment 3. Fig. 15A shows a schematic plan view of the second example of a pyroelectric element 5 according to embodiment 2. Fig. 15B shows a see-through view from the front surface side of the arrangement of electrodes provided on the back surface of the second example of a pyroelectric body 50 according to embodiment 2. The positions and shapes of the light-receiving electrode 511, the lead wire 511a, the compensation electrode 512, the lead wire 512a, the light-receiving electrode 521, the lead wire 521a, the compensation electrode 522, and the lead wire 522a are the same as those of the first example. In addition, the positions and shapes of the back electrode 513, the lead line 513a, the connection portion 513e, the back electrode 514, the lead line 514a, the connection portion 514c, the back electrode 523, the lead line 523a, the connection portion 523e, the back electrode 524, the lead line 524a and the connection portion 524c are the same as in the first example.

[0088] A slit 571 is provided between the light-receiving electrode 511 and the compensation electrode 512, and a slit 572 is provided between the light-receiving electrode 521 and the compensation electrode 522. A slit 573 is provided between the light-receiving electrode 511 and the compensation electrode 522, and a slit 574 is provided between the light-receiving electrode 521 and the compensation electrode 512. The slits 571, 572, 573, and 574 penetrate the pyroelectric body 50 from the front surface to the back surface. The slits 571, 572, 573, and 574 have a band-like shape in a plan view, and are spaced apart from one another.

[0089] The connection mode of the pyroelectric element 5 to the circuit of the second example is similar to that of the first example shown in Fig. 14. As in the first example, output voltages Vout1 and Vout2 corresponding to the reception of infrared light are obtained in response to the reception of infrared light by the light-receiving electrodes 511 and 521. The provision of the slits 571, 572, 573, and 574 makes it difficult for heat to be conducted from the light-receiving electrodes to the compensation electrodes, improving the detection sensitivity of infrared light using the light-receiving electrodes 511 and 521. The separation of the slits 571, 572, 573, and 574 improves the strength of the pyroelectric body 50 and the durability of the pyroelectric element 5 compared to the first example.

[0090] 16A and 16B are schematic diagrams showing a third example of a pyroelectric element 5 according to embodiment 3. Fig. 16A shows a schematic plan view of the third example of the pyroelectric element 5 according to embodiment 2. Fig. 16B shows a see-through view from the front surface side of the arrangement of electrodes provided on the back surface of the third example of the pyroelectric body 50 according to embodiment 2. The positions and shapes of the light receiving electrode 511, the lead wire 511a, the compensation electrode 512, the lead wire 512a, the light receiving electrode 521, the lead wire 521a, the compensation electrode 522, and the lead wire 522a are the same as those of the first example. In addition, the positions and shapes of the back electrode 513, the lead line 513a, the connection portion 513e, the back electrode 514, the lead line 514a, the connection portion 514c, the back electrode 523, the lead line 523a, the connection portion 523e, the back electrode 524, the lead line 524a and the connection portion 524c are the same as in the first example.

[0091] Slits 575 are provided at positions between the light-receiving electrode 511 and the compensation electrode 512 and between the light-receiving electrode 521 and the compensation electrode 522. The slits 575 penetrate from the front surface to the back surface of the pyroelectric body 50. The slits 575 have a strip shape along the bisector 55.

[0092] The connection mode of the pyroelectric element 5 to the circuit of the third example is similar to that of the first example shown in Fig. 14. As in the first example, output voltages Vout1 and Vout2 corresponding to the reception of infrared light are obtained in response to the light-receiving electrodes 511 and 521 receiving infrared light. The provision of the slit 575 makes it difficult for heat to be conducted from the light-receiving electrode 511 to the compensation electrode 512 and from the light-receiving electrode 521 to the compensation electrode 522, improving the detection sensitivity of infrared light using the light-receiving electrodes 511 and 521. The provision of the strip-shaped slit 575 alone improves the strength of the pyroelectric body 50 and improves the durability of the pyroelectric element 5, compared to the first example in which the cross-shaped slit 57 is provided.

[0093] 17A and 17B are schematic diagrams showing a fourth example of a pyroelectric element 5 according to embodiment 3. Fig. 17A shows a schematic plan view of the fourth example of a pyroelectric element 5 according to embodiment 2. Fig. 17B shows a perspective view from the front side of the arrangement of electrodes provided on the back surface of the fourth example of a pyroelectric body 50 according to embodiment 2. The positions and shapes of the light receiving electrode 511, the lead wire 511a, the compensation electrode 512, the lead wire 512a, the light receiving electrode 521, the lead wire 521a, the compensation electrode 522, and the lead wire 522a are the same as those of the first example. In addition, the positions and shapes of the back electrode 513, the lead line 513a, the connection portion 513e, the back electrode 514, the lead line 514a, the connection portion 514c, the back electrode 523, the lead line 523a, the connection portion 523e, the back electrode 524, the lead line 524a and the connection portion 524c are the same as in the first example.

[0094] A slit 571 is provided between the light-receiving electrode 511 and the compensation electrode 512, and a slit 572 is provided between the light-receiving electrode 521 and the compensation electrode 522. The slits 571 and 572 penetrate from the front surface to the back surface of the pyroelectric body 50. The slits 571 and 572 have a band-like shape in a plan view and are spaced apart from each other.

[0095] The connection mode of the pyroelectric element 5 to the circuit of the fourth example is similar to that of the first example shown in Fig. 14. As in the first example, output voltages Vout1 and Vout2 corresponding to the reception of infrared light are obtained in response to the light-receiving electrodes 511 and 521 receiving infrared light. The provision of the slits 571 and 572 makes it difficult for heat to be conducted from the light-receiving electrode 511 to the compensation electrode 512 and from the light-receiving electrode 521 to the compensation electrode 522, improving the detection sensitivity of infrared light using the light-receiving electrodes 511 and 521. The slits 571 and 572 are spaced apart, improving the strength of the pyroelectric body 50 and the durability of the pyroelectric element 5 compared to the first and third examples.

[0096] The infrared detector 1 according to the third embodiment is configured so that infrared light is incident on the light receiving electrodes 511 and 521 and infrared light is not incident on the compensation electrodes 512 and 522, as in the first and second embodiments. For example, the infrared detector 1 includes a light collecting block 4 having the entrances 411 and 421 open and the entrances 431 and 441 closed. The infrared detector 1 is also configured so that infrared light of different wavelengths is incident on the light receiving electrodes 511 and 521. For example, the infrared detector 1 includes two optical filters that transmit infrared light of different wavelengths. One optical filter transmits infrared light of a wavelength absorbed by one gas component, and the other optical filter transmits reference infrared light of a different wavelength. The infrared light that has transmitted through one optical filter is incident on the light receiving electrode 511, and the infrared light that has transmitted through the other optical filter is incident on the light receiving electrode 521. In this manner, the infrared detector 1 detects infrared light of two different wavelengths.

[0097] The configurations of the gas analyzer 6 and the gas analyzer 64 using the infrared detector 1 are the same as those of the first and second embodiments. The infrared detector 1 according to the third embodiment is used to analyze the concentration of a specific gas component contained in a gas such as exhaust gas. The infrared detector 1 outputs a detection signal according to the intensity of infrared light having a wavelength absorbed by the specific gas component and the intensity of reference infrared light. The concentration calculation unit 63 calculates the concentration of the specific gas component contained in the gas according to a comparison between the detected intensity of infrared light having a wavelength absorbed by the specific gas component and the detected intensity of the reference infrared light, and displays the concentration on the display unit 634.

[0098] In the infrared detector 1 of the third embodiment, by using a pyroelectric element 5 having a slit between the light-receiving electrode and the compensating electrode, the detection signal corresponding to the intensity of infrared light is not reduced, and the detection sensitivity of infrared light is improved. The gas analyzer 6 and the gas analyzer 64 can accurately calculate the concentration of a specific gas component contained in the gas to be analyzed. In addition, the position of the slit includes the center position between the light-receiving electrode and the compensating electrode, so that the insulation between the light-receiving electrode and the back electrode and the insulation between the compensating electrode and the back electrode are not easily broken, and the function of the pyroelectric element 5 is easily maintained.

[0099] The present invention is not limited to the contents of the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention. [Explanation of symbols]

[0100] 1. Infrared detector 21 Packages 22 Infrared transparent window 23 Circuit Board 24 Stem 3. Filter section 31, 32, 33, 34 Optical filters 4. Focusing block 41, 42, 43, 44 Light collecting section 411, 421, 431, 441 Inlet 412, 422, 432, 442 Exit 413, 423, 433, 443 reflective surface 5 Pyroelectric element 50 Pyroelectric 511, 521, 531, 541 Light receiving electrode 512, 522, 532, 542 compensation electrode 513, 514, 523, 524, 533, 534, 543, 544 Back electrode 515, 525, 535, 545, 515a, 515b, 525a, 525b, 535a, 535b, 545a, 545b, 57, 571, 572, 573, 574, 575 Slit 511a, 512a, 513a, 513b, 514a, 521a, 522a, 523a, 523b, 524a, 531a, 532a, 533a, 533b, 534a, 541a, 542a, 543a, 543b, 544a Leader line 513c, 513d, 514b, 523c, 523d, 524b, 533c, 533d, 534b, 543c, 543d, 544b contacts 511b, 521b, 531b, 541b connecting lines 513e, 514c, 523e, 524c Connections 6 Gas analyzers 61 Light source 62 cells

Claims

1. A pyroelectric element including a plate-shaped pyroelectric body, a plurality of light-receiving electrodes provided on one surface of the pyroelectric body for receiving infrared light, and a plurality of compensation electrodes provided on the one surface, the same number as the plurality of light-receiving electrodes, Each of the plurality of light receiving electrodes is paired with one of the plurality of compensation electrodes, the light-receiving electrode and the compensation electrode included in each set are adjacent to each other, and the compensation electrode included in each set is disposed at a position surrounding one corner of the light-receiving electrode included in the same set; a slit penetrating the pyroelectric body between the light-receiving electrode and the compensation electrode included in each pair for preventing thermal conduction from the light-receiving electrode to the compensation electrode is provided along two sides forming one corner of the light-receiving electrode; The position of the slit includes a central position between the light receiving electrode and the compensation electrode included in each pair. A pyroelectric element characterized by:

2. Each of the plurality of light receiving electrodes has a rectangular shape, Each of the plurality of compensation electrodes has a shape surrounding a part of the light receiving electrode included in the same set. The pyroelectric element according to claim 1 .

3. each of the plurality of compensation electrodes has an L-shape along a side of a light-receiving electrode included in the same set, and is disposed at a position between the light-receiving electrode and a center of the one surface; The slits have an L-shape along the respective compensation electrodes. The pyroelectric element according to claim 2 .

4. The slit has an inner angle of less than 180° rounded off.

4. The pyroelectric element according to claim 1, wherein

5. The light receiving electrodes and the compensation electrodes included in each set are connected in parallel or in series inverse to each other.

5. The pyroelectric element according to claim 1,

6. a plurality of optical filters each of which selectively transmits infrared light of a predetermined wavelength; The pyroelectric element according to any one of claims 1 to 5, the plurality of light receiving electrodes of the pyroelectric element correspond one-to-one to the plurality of optical filters; Infrared light transmitted through a corresponding optical filter is incident on each of the plurality of light receiving electrodes, and infrared light is not incident on a plurality of compensation electrodes of the pyroelectric element. An infrared detector comprising:

7. A gas analyzer for analyzing the concentration of a specific gas component contained in a target gas, An infrared detector according to claim 6; A light source that emits infrared light; a cell through which the gas to be analyzed flows; Infrared light from the light source passes through the gas to be analyzed flowing through the cell, and the infrared light having passed through the gas to be analyzed is incident on the infrared detector. A gas analyzer characterized by:

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