JP2014142236A - Infrared receiving unit and infrared gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared receiving unit capable of increasing the reliability and the sensibility and an infrared gas sensor using the same.SOLUTION: An infrared receiving unit 2 includes: an infrared detection element 20; a first optical filter 31 and a second optical filter 32; a base 43; and a package 29. A first light receiving element 2a and a second light receiving element 2b have a first electrode 2h and a second electrode 2i connected to a first output terminal 2j and a second output terminal 2k respectively at the front side and the rear side of a pyroelectric substrate 2g. The first output terminal 2j and the second output terminal 2k are not overlapped with each other in a thickness direction the pyroelectric substrate 2g and are connected to a first lead terminal 43j and a second lead terminal 43k of the base 43 at a first joint 7j and a second joint 7k formed of a conductive adhesive respectively. An insulation base 43 protrudes in a thickness direction from outside of area to be mounted with the infrared detection element 20 between the first lead terminal 43j and the second lead terminal 43k and a projection 43c for positioning the infrared detection element 20 is formed.

Description

  The present invention relates to an infrared light receiving unit and an infrared gas sensor using the same.

  As an infrared light receiving unit, for example, an infrared light receiving device 91 configured as shown in FIG. 23 is known (Patent Document 1). The infrared light receiving device 91 includes a first light receiving element 92 and a second light receiving element 93, and a ceramic substrate 94 on which rectangular windows 94a and 94b for housing the first light receiving element 92 and the second light receiving element 93 are formed. Yes. The infrared light receiving device 91 includes a base 95 and four lead wires 106 to 109 (see FIG. 24) fixed to the base 95. Each of the lead wires 106 to 109, the first light receiving element 92, and the second light receiving element. Necessary wiring is made between the terminals 93 and 93.

  In the infrared light receiving device 91, the first infrared filter piece 101 covering the light receiving surface of the first light receiving element 92 is fixed to the upper surface 94 c of the ceramic substrate 94 with an adhesive, and the first light receiving surface of the second light receiving element 93 is covered. Two infrared filter pieces 102 are fixed by an adhesive.

  In the infrared light receiving device 91, a case 103 that houses the first light receiving element 92, the second light receiving element 93, the first infrared filter piece 101, and the second infrared filter piece 102 is fixed to the base 95.

  The light receiving window 103b of the case 103 is provided with a window filter 104 that is a broadband infrared filter.

  Patent Document 1 describes that the first light receiving element 92 and the second light receiving element 93 are not limited to the thermopile type light receiving elements, but can be pyroelectric light receiving elements.

Japanese Utility Model Publication No. 5-81667

  By the way, in the infrared light receiving unit, it is conceivable to use, as a light receiving element, a pyroelectric element in which a first electrode and a second electrode are formed on the front side and the back side of the pyroelectric substrate from the viewpoint of increasing sensitivity. In this case, the light receiving element includes a first output terminal connected to the first electrode on the front side of the pyroelectric substrate, and a second output terminal connected to the second electrode on the back side of the pyroelectric substrate. It is conceivable to fix the ceramic substrate 94 by using a conductive adhesive.

  However, since the infrared light receiving device 91 has a configuration in which the first light receiving element 92 and the second light receiving element 93 are accommodated in the rectangular windows 94a and 94b of the ceramic substrate 94, the first light receiving element 92 and the second light receiving element 93 respectively include the first light receiving element 92 and the second light receiving element 93. There is a concern that the electrode and the second electrode are short-circuited. Further, in the infrared light receiving device 91, there is a concern that noise due to floating charges due to leakage between the first electrode and the second electrode may occur.

  The present invention has been made in view of the above reasons, and an object thereof is to provide an infrared light receiving unit capable of improving reliability and achieving high sensitivity, and an infrared gas sensor using the same. It is in.

An infrared receiving unit of the present invention includes an infrared detecting element having a first light receiving element and a second light receiving element, a first optical filter disposed in front of the light receiving surfaces of the first light receiving element and the second light receiving element, and A second optical filter; a substrate on which the infrared detection element is mounted; and a package in which the infrared detection element, the first optical filter, the second optical filter, and the substrate are housed.
The package has a window hole on a light incident surface side of the first optical filter and the second optical filter, and a window material that closes the window hole and transmits infrared rays.
Each of the first light receiving element and the second light receiving element is formed on each of the front side and the back side of the pyroelectric substrate and is opposed to each other in the first electrode, the second electrode, and the pyroelectric substrate. A light receiving portion having a portion sandwiched between second electrodes; a first output terminal connected to the first electrode on the front side of the pyroelectric substrate; and the second on the back side of the pyroelectric substrate. A second output terminal connected to the electrode, the first output terminal and the second output terminal are arranged so as not to overlap in the thickness direction of the pyroelectric substrate,
The substrate is provided with an insulating base material having electrical insulation, and the insulating base material, and the first output terminal and the second output terminal are made of a conductive adhesive. A first lead terminal and a second lead terminal electrically connected to each other through two joint portions;
The insulating substrate protrudes in a direction along the thickness direction of the infrared detection element from the outside of the region where the infrared detection element is to be mounted between the first lead terminal and the second lead terminal. It is characterized in that a positioning projection for restricting the movement in the in-plane direction is formed.

  In the infrared light receiving unit, it is preferable that a protrusion dimension of the protrusion is larger than a height dimension of the first joint portion.

  In this infrared light receiving unit, it is preferable that a positioning portion that projects in a direction along the thickness direction of the infrared detection element and positions the first optical filter and the second optical filter is formed.

  In the infrared light receiving unit, the positioning unit defines positions of the first optical filter and the second optical filter in a direction orthogonal to a direction in which the first optical filter and the second optical filter are arranged in plan view. It is preferable to include a wall portion and a support portion on which the first optical filter and the second optical filter are installed.

  In this infrared light receiving unit, the projecting dimension of the support portion is larger than the thickness dimension of the infrared detection element, and the first optical filter, the second optical filter, and the infrared detection element in the thickness direction of the infrared detection element, It is preferable that there is a gap between them.

  In this infrared light receiving unit, it is preferable that the support portion has a recess formed on a surface facing the side surface of the infrared detection element.

  In the infrared light receiving unit, the wall portion is formed with a recessed portion in which a front end surface and a surface facing the first optical filter and the second optical filter are opened, and the first optical filter and the second optical filter are formed. It is preferable that the optical filter is fixed to the wall portion by an adhesive portion made of an adhesive in the recess portion.

  In the infrared light receiving unit, the first lead terminal is provided outside the planned mounting area of the infrared detection element, and the second lead terminal is provided between the planned mounting area and the planned mounting area of the infrared detection element. Preferably, the first joint is provided on the front side of the infrared detection element, and the second joint is provided on the back side of the infrared detection element.

  In the infrared light receiving unit, each of the first light receiving element and the second light receiving element is disposed on the back side of the pyroelectric substrate and along the side surface of the pyroelectric substrate out of the outer peripheral surface of the second output terminal. It is preferable that an electrical insulation layer is provided except for one surface, and the electrical insulation layer is made of a material having lower wettability to the conductive adhesive than the pyroelectric substrate.

  In this infrared light receiving unit, it is preferable that the insulating base material is provided with a hole for thermal insulation in a projection region of each light receiving unit.

  In the infrared light receiving unit, it is preferable that the infrared detection element has a surface of the first electrode covered with an infrared absorption layer having a higher emissivity than the first electrode.

  The infrared light receiving unit includes a first amplifier circuit and a second amplifier circuit that individually amplify output signals of the first light receiving element and the second light receiving element, respectively, and the substrate includes the infrared light on one surface side in the thickness direction. Preferably, a detection element is disposed, and the first amplifier circuit and the second amplifier circuit are disposed on the other surface side in the thickness direction.

  An infrared gas sensor according to the present invention includes a light source, a photodetector, a sample cell disposed between the light source and the photodetector, and a signal processing unit, and the photodetector detects the infrared light. A first transmission wavelength range is set so that the first optical filter transmits infrared light having an absorption wavelength of a gas to be detected, and the second optical filter has infrared light having a reference wavelength that is not absorbed by the gas. And a second transmission wavelength range that does not overlap the first transmission wavelength range is set, and the signal processing unit sets the difference or ratio between the output signal of the first light receiving element and the output signal of the second light receiving element. Based on this, the concentration of the gas is obtained.

  In this infrared type gas sensor, the sample cell has a cylindrical shape, and an inner surface thereof is a reflecting surface that reflects infrared rays radiated from the light source, and the reflecting surface has a length defined on a central axis of the sample cell. Each of both ends in the major axis direction of the spheroid having the axis as a rotation axis is cut by two planes orthogonal to the major axis, and the light source is one of the spheroids on the central axis. It is preferable that the infrared light receiving unit is disposed in the vicinity of the focal point, and the infrared light receiving unit is disposed closer to the light source than the other focal point of the spheroid on the central axis.

  In this infrared gas sensor, the infrared light receiving unit has a shape obtained by combining the planar shape of the first electrode of the first light receiving element and the planar shape of the first electrode of the second light receiving element. The shape is preferably along a line of intersection between the front surface of the substrate and the spheroid.

  The infrared light receiving unit of the present invention can improve reliability and increase sensitivity.

  The infrared gas sensor of the present invention can improve reliability and increase sensitivity.

FIG. 2 is a schematic exploded perspective view of the infrared light receiving unit according to the first embodiment. FIG. 2 is a schematic perspective view of the infrared light receiving unit according to the first embodiment. (A) is a schematic sectional drawing of the infrared receiving unit of Embodiment 1, (b) is another schematic sectional drawing of the infrared receiving unit of Embodiment 1. 2 is a schematic perspective view of a main part of the infrared light receiving unit according to Embodiment 1. FIG. (A) is a schematic top view of the principal part in the infrared rays light reception unit of Embodiment 1, (b) is AA 'schematic sectional drawing of (a), (c) is BB' schematic sectional drawing of (a). It is. It is the schematic perspective view seen from the back surface side of the circuit block in the infrared rays light reception unit of Embodiment 1. (A) is a schematic plan view of the infrared light receiving element in the infrared light receiving unit of Embodiment 1, (b) is a schematic cross-sectional view of XX ′ of (a), and (c) is an infrared light receiving in the infrared light receiving unit of Embodiment 1. It is a schematic bottom view of an element. (A) is a schematic sectional drawing of the 1st optical filter in the infrared receiving unit of Embodiment 1, (b) is a schematic sectional view of the 2nd optical filter in the infrared receiving unit of Embodiment 1. (A) is a schematic plan view of a first modification of the infrared light receiving element in the infrared light receiving unit of Embodiment 1, (b) is a schematic cross-sectional view of XX ′ of (a), and (c) is the infrared light of Embodiment 1. It is a schematic bottom view of the 1st modification of the infrared rays light receiving element in a light reception unit. (A) is a schematic top view of the 2nd modification of the infrared light receiving element in the infrared light receiving unit of Embodiment 1, (b) is XX 'schematic sectional drawing of (a), (c) is the infrared rays of Embodiment 1. It is a schematic bottom view of the 2nd modification of the infrared rays light receiving element in a light reception unit. 6 is a schematic cross-sectional view of another configuration example of the first optical filter and the second optical filter in the infrared light receiving unit of Embodiment 1. FIG. It is a schematic perspective view of the principal part in the infrared rays light reception unit of a comparative example. (A) is a schematic top view of the 3rd modification of the principal part in the infrared rays light reception unit of Embodiment 1, (b) is AA 'schematic sectional drawing of (a), (c) is B- of (a). It is B 'schematic sectional drawing. It is a schematic perspective view of the 4th modification of the principal part in the infrared rays light reception unit of Embodiment 1. It is a schematic block diagram of the infrared type gas sensor using the infrared rays light reception unit of Embodiment 1. FIG. It is a principal part schematic exploded perspective view of the infrared type gas sensor using the infrared light receiving unit of Embodiment 1. FIG. (A) is a principal part schematic perspective view of the infrared type gas sensor using the infrared light receiving unit of Embodiment 1, (b) is the perspective view which fractured | ruptured partially the infrared type gas sensor using the infrared light receiving unit of Embodiment 1. . (A) is a schematic plan view of the infrared radiation element in the infrared type gas sensor using the infrared light receiving unit of Embodiment 1, and (b) is a schematic cross-sectional view along X-X ′ of (a). It is explanatory drawing of the filter characteristic of each of the 1st optical filter and the 2nd optical filter in the infrared rays light reception unit of Embodiment 1. It is principal part explanatory drawing of the infrared type gas sensor using the infrared rays light reception unit 2 of Embodiment 1. FIG. It is a schematic perspective view of the modification 4 of the principal part in the infrared light receiving unit of Embodiment 1. It is a schematic exploded perspective view of the human body detection sensor of Embodiment 2. It is a schematic sectional drawing of the infrared rays light receiving device of a prior art example. It is a principal part top view in the infrared rays receiver of a prior art example.

(Embodiment 1)
Below, the infrared rays light reception unit 2 of this embodiment is demonstrated based on FIGS.

  The infrared light receiving unit 2 includes an infrared detection element 20, a first optical filter 31 and a second optical filter 32, a substrate 43, and a package 29.

  The infrared detection element 20 includes a first light receiving element 2a and a second light receiving element 2b. The 1st optical filter 31 and the 2nd optical filter 32 are arrange | positioned ahead of the light-receiving surface (upper surface in Fig.3 (a)) of each of the 1st light receiving element 2a and the 2nd light receiving element 2b. The substrate 43 is mounted with the infrared detection element 20. The package 29 houses the infrared detection element 20, the first optical filter 31, the second optical filter 32, and the substrate 43.

  The package 29 has a window hole 29c on the light incident surface (the upper surface in FIG. 3A and FIG. 8) side of the first optical filter 31 and the second optical filter 32, and a window that closes the window hole 29c and transmits infrared rays. Material 29w. As a result, the infrared light receiving unit 2 can suppress the first optical filter 31 and the second optical filter 32 from being stored in the package 29 and exposed to the outside air, and suppress the change in filter characteristics over time. Is possible.

  Each of the first light receiving element 2a and the second light receiving element 2b includes, for example, as shown in FIG. 7, one light receiving unit 2r, a first output terminal 2j electrically connected to the light receiving unit 2r, and a second output. A pyroelectric element having a terminal 2k can be used. The light receiving unit 2r is formed on the front side and the back side of the pyroelectric substrate 2g and is opposed to each other, and the first electrode 2h and the second electrode 2i in the pyroelectric substrate 2g. It is comprised by the part 2gg pinched | interposed. The first output terminal 2j is formed on the front side of the pyroelectric substrate 2g and is electrically connected to the first electrode 2h. The second output terminal 2k is formed on the back side of the pyroelectric substrate 2g and is electrically connected to the second electrode 2i. Each of the first light receiving element 2a and the second light receiving element 2b is arranged such that the first output terminal 2j and the second output terminal 2k do not overlap in the thickness direction of the pyroelectric substrate 2g.

  The substrate 43 of the circuit block 44 includes an insulating base material 43a having electrical insulation, two first lead terminals 43j, and two second lead terminals 43k. Each first lead terminal 43j and each second lead terminal 43k are provided integrally with the insulating base material 43a. Each first lead terminal 43j is electrically connected to the first output terminal 2j of each of the first light receiving element 2a and the second light receiving element 2b via a first joint 7j (see FIG. 5) made of a conductive adhesive. Connected to. Each second lead terminal 43k is electrically connected to the second output terminal 2k of each of the first light receiving element 2a and the second light receiving element 2b via a second joint 7k (see FIG. 5) made of a conductive adhesive. Connected to.

  The insulating base material 43a protrudes in the direction along the thickness direction of the infrared detection element 20 from the outside of the planned mounting area of the infrared detection element 20 between the first lead terminal 43j and the second lead terminal 43k. A protrusion 43c for positioning is formed.

  As a result, the infrared light receiving unit 2 can position the infrared detection element 20 by the protrusion 43c, and the position accuracy of the infrared detection element 20 can be increased. Therefore, a redundant design due to the position accuracy of the infrared detection element 20 is unnecessary. Thus, it is possible to reduce the size and improve the sensitivity. Further, the infrared light receiving unit 2 suppresses the occurrence of a short circuit between the first electrode 2h and the second electrode 2i by the protrusion 43c being positioned between the first joint 7j and the second joint 7k. It becomes possible to improve the reliability. In addition, the infrared light receiving unit 2 can suppress the generation of noise due to floating charges caused by the leak between the first electrode 2h and the second electrode 2i, thereby improving the S / N ratio and increasing the sensitivity. It becomes possible.

  By the way, in the infrared light receiving device 91 having the configuration shown in FIG. 23, it is considered that it is necessary to pick up the first light receiving element 92 and the second light receiving element 93 one by one with the pick-up tool and put them into the rectangular windows 94a and 94b. It is done. For this reason, in the infrared light receiving device 91, it is necessary to make the size of the rectangular windows 94a and 94b relatively larger than the plane sizes of the first light receiving element 92 and the second light receiving element 93, respectively. The planar size of the 2nd infrared filter piece 102 will become large. Therefore, in the infrared light receiving device 91, the cost of the first infrared filter piece 101 and the second infrared filter piece 102 is increased.

  In the infrared light receiving device 91, there is a concern that the distance between the first light receiving element 92 and the first infrared filter piece 101 may vary, and there is a concern that the distance between the second light receiving element 93 and the second infrared filter piece 102 may vary. is there. Further, Patent Document 1 does not specifically describe the wiring structure between each of the lead wires 106 to 109 and the first light receiving element 92 and the second light receiving element 93.

  On the other hand, the infrared light receiving unit 2 is formed with a positioning portion 43 d that projects in the direction along the thickness direction of the infrared detection element 20 and positions the first optical filter 31 and the second optical filter 32. Accordingly, the infrared light receiving unit 2 can position the first optical filter 31 and the second optical filter 32 on the substrate 43. Therefore, the infrared light receiving unit 2 can increase the relative positional accuracy between the first optical filter 31 and the second optical filter 32 and the first light receiving element 2a and the second light receiving element 2b. In addition, the second optical filter 32 can be reduced in size. The infrared light receiving unit 2 can be reduced in cost by downsizing the first optical filter 31 and the second optical filter 32.

  23, the output signals of the first light receiving element 92 and the second light receiving element 93 are taken out through the wiring of the ceramic substrate 94 and the lead wires 106-109. However, since the output signals of the first light receiving element 92 and the second light receiving element 93 are weak in the infrared light receiving device 91, they are easily affected by noise, and there is a concern that the S / N ratio and sensitivity are lowered.

  On the other hand, in the infrared light receiving unit 2, the first amplification circuit 41 and the second amplification circuit 42 (see FIGS. 3 and 6) that amplify the output signals of the first light receiving element 2 a and the second light receiving element 2 b separately are provided on the substrate 43. Is provided. Thereby, the infrared light receiving unit 2 can shorten the wiring length between the first light receiving element 2a and the second light receiving element 2b and the first amplifier circuit 41 and the second amplifier circuit 42, and the S / N ratio. It is possible to suppress a decrease in sensitivity.

  In the infrared light receiving unit 2, a circuit block 44 is constituted by the substrate 43, the first amplifier circuit 41, the second amplifier circuit 42, and the like. Therefore, in the infrared light receiving unit 2, the circuit block 44 is accommodated in the package 29.

  Hereinafter, each component of the infrared light receiving unit 2 will be described in more detail.

  For example, as shown in FIG. 7, the infrared detection element 20 may include a first light receiving element 2 a and a second light receiving element 2 b formed on one pyroelectric substrate 2 g. Thereby, the infrared detecting element 20 can easily make the characteristics of the first light receiving element 2a and the characteristics of the second light receiving element 2b substantially the same. The infrared detection element 20 may be one in which the first light receiving element 2a and the second light receiving element 2b are formed on separate pyroelectric substrate 2g. In this case, it is preferable to use the first light receiving element 2a and the second light receiving element 2b which are formed on the same pyroelectric wafer at the time of manufacture and are cut out from the pyroelectric wafer. The infrared detection element 20 preferably has a configuration in which one side surfaces of the first light receiving element 2a and the second light receiving element 2b are bonded to each other with an adhesive.

  In the infrared detection element 20, it is preferable that the first light receiving element 2a and the second light receiving element 2b are arranged side by side. The infrared detection element 20 is preferably arranged so as to be symmetric with respect to the center point in the direction in which the first light receiving element 2a and the second light receiving element 2b are arranged. Thereby, the infrared detecting element 20 can make the stress received by the light receiving portion 2r of the first light receiving element 2a from the substrate 43 substantially equal to the stress received by the light receiving portion 2r of the second light receiving element 2b from the substrate 43. The sensitivity of the first light receiving element 2a and the sensitivity of the second light receiving element 2b can be made substantially equal.

  In the infrared detection element 20, it is preferable that the first output terminal 2j and the second output terminal 2k are arranged on the opposite side of the first light receiving element 2a from the second light receiving element 2b side. The infrared detection element 20 includes a first wiring 2m that connects the first electrode 2h and the first output terminal 2j in the first light receiving element 2a, and a second wiring that connects the second electrode 2i and the second output terminal 2k. 2n is also preferably arranged on the side opposite to the second light receiving element 2b side in the first light receiving element 2a. Similarly, in the infrared detection element 20, it is preferable that the first output terminal 2j and the second output terminal 2k are arranged on the opposite side of the second light receiving element 2b from the first light receiving element 2a side. The infrared detection element 20 includes a first wiring 2m that connects the first electrode 2h and the first output terminal 2j in the second light receiving element 2b, and a second wiring that connects the second electrode 2i and the second output terminal 2k. 2n is also preferably arranged on the opposite side of the second light receiving element 2b from the first light receiving element 2a side.

  The infrared detection element 20 preferably has a hole 2s that surrounds each light receiving part 2r except for a part of each light receiving part 2r in plan view and penetrates in the thickness direction. The hole 2s is preferably formed so as to surround the light receiving part 2r while avoiding the first wiring 2m and its peripheral part, the second wiring 2n and its peripheral part as a part of the light receiving part 2r. As a result, the infrared detection element 20 can thermally insulate the light receiving parts 2r and can reduce popcorn noise, which is sudden noise.

  Each of the first light receiving element 2a and the second light receiving element 2b is arranged such that the first output terminal 2j and the second output terminal 2k do not overlap in the thickness direction of the pyroelectric substrate 2g. As a result, the infrared light receiving element 20 can prevent the occurrence of parasitic capacitance between the first output terminal 2j and the second output terminal 2k in each of the first light receiving element 2a and the second light receiving element 2b. In addition, it is possible to suppress a short circuit between the first output terminal 2j and the second output terminal 2k.

As the pyroelectric substrate 2g, for example, a single crystal LiTaO ₃ substrate can be adopted. The material of the pyroelectric substrate 2g is LiTaO ₃ , but is not limited to this. For example, LiNbO ₃ , PbTiO ₃ , PZT (: Pb (Zr, Ti) O ₃ ), PZT-PMN (: Pb (Zr, Ti) O ₃ —Pb (Mn, Nb) O ₃ ) or the like may be employed.

  The direction of spontaneous polarization of the pyroelectric substrate 2g is one direction along the thickness direction of the pyroelectric substrate 2g, and is the upward direction of FIG.

  The thickness of the pyroelectric substrate 2g is set to 50 μm, but is not limited to this value. The thickness of the pyroelectric substrate 2g is preferably thinner, for example, from the viewpoint of improving the sensitivity of the infrared detecting element 20. For this reason, it is preferable to set the thickness of the pyroelectric substrate 2g within a range of about 30 μm to 150 μm. If the thickness of the pyroelectric substrate 2g is less than 30 μm, there is a concern of breakage due to fragility, and if the thickness is more than 150 μm, there is a concern that the sensitivity is lowered.

  The 1st electrode 2h and the 2nd electrode 2i are comprised by the electrically conductive film which has electroconductivity and can absorb the infrared rays of a detection target. This conductive film is made of a NiCr film. The conductive film is not limited to the NiCr film, and may be, for example, a Ni film or a gold black film. The first output terminal 2j can be formed of a conductive film having the same material and thickness as the conductive film of the first electrode 2h. The second output terminal 2k can be formed of a conductive film having the same material and thickness as the conductive film of the second electrode 2i.

  The infrared detection element 20 may employ a configuration in which the surface of the first electrode 2h is covered with an infrared absorption layer 26 having a higher emissivity than the first electrode 2h, as in the first modification shown in FIG. it can. Thereby, the infrared light receiving unit 2 can improve the infrared absorption rate of each of the first light receiving element 2a and the second light receiving element 2b, and can increase the sensitivity of each of the first light receiving element 2a and the second light receiving element 2b. It becomes. The infrared radiation rate and infrared absorption rate are the same value.

  The infrared absorption layer 26 is made of, for example, a resin layer in which at least one conductive fine powder selected from the group of carbon fine powder, metal fine powder, and metal oxide fine powder is dispersed in a resin. . The conductive fine powder is a fine powder having conductivity. The volume concentration of the conductive fine powder in the infrared absorbing layer 26 is set to 17%, but this value is an example and is not particularly limited. The volume concentration of the conductive fine powder can be set within a range of about 1 to 30%, for example. Thereby, although the infrared absorption layer 26 has conductivity, the specific resistance is larger than that of the first electrode 2h.

  The infrared absorption layer 26 is cured by printing a paste (printing ink) obtained by dispersing conductive fine powder in a resin and mixing an organic solvent by, for example, a screen printing method or a gravure printing method, and then baking the paste. Can be formed. In forming the infrared absorption layer 26, for example, if the composition of the conductive fine powder in the paste is 8.5%, the volume concentration of the conductive fine powder in the infrared absorption layer 26 can be about 17%. is there.

  The infrared absorbing layer 26 is desirably chemically and physically stable over a wider temperature range. For this reason, as the resin of the infrared absorption layer 26, a thermosetting resin is desirable.

  Examples of the thermosetting resin include phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane resin, thermosetting polyimide resin, and the like. And it is preferable that the infrared detection element 20 employ | adopts a thermosetting resin with a higher infrared absorption factor of the detection target of the infrared detection element 20 among these thermosetting resins. Thereby, the infrared detection element 20 can reduce the thickness of the infrared absorption layer 26, and can further increase sensitivity. The resin capable of absorbing the infrared rays to be detected preferably has an absorptivity of the infrared rays to be detected of 30% or more, and more preferably 50% or more.

  As the carbon fine powder, a fine powder that is a solid carbon material and has a high infrared absorption rate and can be dispersed in a resin is suitable. Examples of this type of carbon-based fine powder include carbon black, carbon fiber, graphite and the like classified as amorphous (microcrystalline) carbon, and fullerene, nanotube, graphene and the like classified as nanocarbon. It is done. In particular, carbon black is preferable because it has a small particle size and is chemically stable.

  Regarding the metal fine powder, the metal fine powder having a particle size of about 0.1 μm or less has a property of absorbing infrared rays and has a feature of high absorptance in a wide infrared wavelength region. This feature does not depend on the type of metal. For this reason, as the material of the metal-based fine powder, chemically stable noble metals such as Au, Pt, and Ag, refractory metals such as W, Mo having high heat resistance, Zn, Mg, Examples thereof include Cd, Al, Cu, Fe, Cr, Ni, Co, Sn, and alloys of two or more thereof.

  The metal oxide fine powder efficiently absorbs far infrared rays and is chemically stable, so that it is preferably used when the infrared detection element 20 is applied to uses such as human body detection. Can do. Examples of the material for the metal oxide fine powder include ITO (Indium Tin Oxide), AZO (Al-doped ZnO), and GZO (Ga-doped ZnO).

  The infrared absorption layer 26 is not limited to the above-described example, and may be constituted by, for example, a carbon black layer.

  As in the second modified example shown in FIG. 10, the infrared detection element 20 is configured such that each of the first light receiving element 2a and the second light receiving element 2b is on the back side of the pyroelectric substrate 2g and the outer peripheral surface of the second output terminal 2k. Among them, an electrical insulating layer 2p may be provided that surrounds the pyroelectric substrate 2g except for one surface along the side surface. The electrical insulating layer 2p is made of a material (for example, epoxy resin, acrylic resin, etc.) that has lower wettability with respect to the conductive adhesive than the pyroelectric substrate 2g. As a result, the infrared light receiving unit 2 can further suppress the occurrence of defective products in which the first output terminal 2j and the second output terminal 2k are short-circuited by the conductive adhesive at the time of manufacturing, and the manufacturing cost is low. Can be achieved. In addition, the infrared light receiving unit 2 can further improve the electrical insulation between the first output terminal 2j and the second output terminal 2k.

  The substrate 43 can be configured by, for example, an MID (Molded Interconnect Devices) substrate, a component built-in substrate, a ceramic substrate, a printed substrate, or the like. In the MID substrate, the first lead terminal 43j, the second lead terminal 43k, and other wirings may be appropriately formed on the surface of the insulating base material 43a made of a resin molded product.

  In the infrared light receiving unit 2, the infrared detection element 20 is mounted on the substrate 43. In the infrared light receiving unit 2, the first output terminal 2j and the first lead terminal 43j of each of the first light receiving element 2a and the second light receiving element 2b are electrically connected to each other through a first joint portion 7j made of a conductive adhesive. Connected. Further, in the infrared light receiving unit 2, each second lead terminal 43k and each second output terminal 2k of each of the first light receiving element 2a and the second light receiving element 2b has a second joint portion 7k made of a conductive adhesive. Electrically connected. The conductive adhesive is, for example, an epoxy resin or polyimide resin adhesive containing Ag or Au powder. A conductive paste can be used as the conductive adhesive. The conductive paste is, for example, a silver paste, a gold paste, a copper paste, or the like.

  As the conductive adhesive, it is preferable to employ an organic resin-based conductive adhesive. Thereby, the infrared light receiving unit 2 can suppress heat conduction from the substrate 43 to the infrared detection element 20.

  The circuit block 44 includes a first amplifier circuit 41 that amplifies and outputs the output signal of the first light receiving element 2a, and a second amplifier circuit 42 that amplifies and outputs the output signal of the second light receiving element 2b. .

  The infrared light receiving unit 2 may be provided in the package 29 by integrating the first amplifier circuit 41 and the second amplifier circuit 42 into a one-chip IC element. Each of the first amplifier circuit 41 and the second amplifier circuit 42 may be configured by appropriately connecting a plurality of discrete components.

  In the infrared light receiving unit 2, the infrared detection element 20 is disposed on one surface side in the thickness direction of the substrate 43, and the first amplifier circuit 41 and the second amplifier circuit 42 are disposed on the other surface side in the thickness direction of the substrate 43. Is preferred. As a result, the infrared light receiving unit 2 can be reduced in size as compared with the case where the first amplifier circuit 41 and the second amplifier circuit 42 are disposed on the side of the infrared detection element 20 on one side of the thickness direction of the substrate 43. It becomes possible to plan. Further, the infrared light receiving unit 2 can further suppress the heat generated in each of the first amplification circuit 41 and the second amplification circuit 42 from being transferred to the infrared detection element 20.

  Each of the first amplifier circuit 41 and the second amplifier circuit 42 is formed of a bare chip IC element, and an epoxy resin or the like is formed on the inner bottom surface of the recess 43y (see FIG. 3) provided on the other surface side of the substrate 43. It is fixed with a die-bonding material. Further, as shown in FIG. 6, the substrate 43 includes a conductive portion 46 to which the first amplifier circuit 41 and the second amplifier circuit 42 are electrically connected via a conductive metal wire (wire) 45. Yes. As a material of the metal thin wire 45, for example, gold, aluminum, copper or the like can be adopted. As the conductive portion 46, a conductive portion 46s electrically connected to the lead pin 29d for feeding power to the first amplifier circuit 41 and the second amplifier circuit 42, and a conductive portion electrically connected to the lead pin 29d for ground. There is 46g. The conductive portion 46 includes a conductive portion 46a electrically connected to the first output lead pin 29d for extracting the output signal of the first amplifier circuit 41, and a second output for extracting the output signal of the second amplifier circuit 42. And a conductive portion 46b electrically connected to the lead pin 29d.

  It is preferable that the first amplifier circuit 41, the second amplifier circuit 42, and the thin metal wires 45 are covered with a sealing portion (not shown) made of a sealing material (for example, epoxy resin, silicone resin, etc.). As a result, the infrared light receiving unit 2 can prevent disconnection of each metal thin wire 45 and contact between each metal thin wire 45 and the package 29. Further, the infrared light receiving unit 2 has an advantage that the heat generated in each of the first amplifier circuit 41 and the second amplifier circuit 42 is not easily transferred to the infrared detection element 20 side by providing the sealing portion. .

  The first optical filter 31 and the second optical filter 32 may be designed with filter characteristics so as to have optical characteristics required for the application of the infrared light receiving unit 2.

  For example, as shown in FIG. 8, the first optical filter 31 includes a substrate 31s, a first filter part 31a, and a second filter part 31b. Further, the second optical filter 32 can employ a configuration including a substrate 32s, a third filter portion 32a, and a fourth filter portion 32b. The substrates 31s and 32s can transmit infrared rays. As the substrates 31s and 32s, for example, a silicon substrate, a germanium substrate, a sapphire substrate, a magnesium oxide substrate, or the like can be employed. In the infrared light receiving unit 2, the second filter part 31b and the fourth filter part 32b can have the same configuration. Thereby, the infrared light receiving unit 2 can make the spectral characteristic of the second filter unit 31b and the spectral characteristic of the fourth filter unit 32b substantially the same.

The first filter unit 31a can be a band-pass filter including, for example, a λ / 4 multilayer film 34, a wavelength selection layer 35, and a λ / 4 multilayer film 36. The λ / 4 multilayer film 34 is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 31aa and 31ab) having different refractive indexes and the same optical film thickness are stacked. The λ / 4 multilayer film 36 is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 31aa and 31ab) are stacked. The wavelength selection layer 35 is interposed between the λ / 4 multilayer film 34 and the λ / 4 multilayer film 36. The wavelength selection layer 35 has an optical film thickness different from the optical film thickness of each of the thin films 31aa and 31ab according to the selected wavelength. The λ / 4 multilayer film 34 and the λ / 4 multilayer film 36 may have a refractive index periodic structure and may be a laminate of three or more kinds of thin films. As the material of the thin film, for example, Ge, Si, MgF ₂ , Al ₂ O ₃ , SiO _x , Ta ₂ O ₅ , SiN _x or the like can be employed.

The third filter unit 32a can be a band-pass filter including, for example, a λ / 4 multilayer film 37, a wavelength selection layer 38, and a λ / 4 multilayer film 39. The λ / 4 multilayer film 37 is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 32aa and 32ab) having different refractive indexes and the same optical film thickness are stacked. The λ / 4 multilayer film 39 is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 32aa and 32ab) are stacked. The wavelength selection layer 38 is interposed between the λ / 4 multilayer film 37 and the λ / 4 multilayer film 39. The wavelength selection layer 38 has an optical film thickness different from the optical film thickness of each of the thin films 32aa and 32ab according to the selected wavelength. The λ / 4 multilayer film 37 and the λ / 4 multilayer film 39 need only have a refractive index periodic structure, and may be a laminate of three or more types of thin films. As the material of the thin film, for example, Ge, Si, MgF ₂ , Al ₂ O ₃ , SiO _x , Ta ₂ O ₅ , SiN _x or the like can be employed.

  The same material can be used for the thin films 31aa and 31ab of the first filter part 31a and the thin films 32aa and 32ab of the third filter part 32a.

  The first filter unit 31a and the third filter unit 32a are provided with wavelength selective layers 35 and 38 having different optical film thicknesses in the refractive index periodic structure to introduce local disturbance in the refractive index periodic structure. A transmission band having a narrower spectral width than the reflection bandwidth can be localized in the band. The first filter unit 31a and the third filter unit 32a can change the transmission peak wavelength in the transmission wavelength region by appropriately changing the optical film thickness of the wavelength selection layers 35 and 38.

Selected wavelength of the first filter portion 31a is a center wavelength lambda ₁ of the transmission wavelength range of the first filter portion 31a. Moreover, the selected wavelength of the third filter portion 32a is a center wavelength lambda ₂ of the transmission wavelength range of the third filter portion 32a.

The second filter portion 31b is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 31ba and 31bb) having different refractive indexes and the same optical film thickness are stacked. The second filter portion 31b can employ, for example, Ge, Si, etc., as a thin film material having a relatively high refractive index, and, for example, MgF ₂ , Al, etc., as a thin film material, having a relatively low refractive index. ₂ O ₃ , SiO _x , Ta ₂ O ₅ , SiN _{x and the} like can be employed. SiO _x is SiO or SiO ₂ . SiN _{x and the} like are SiN, Si ₃ N _{4 and the} like.

The fourth filter portion 32b is a multilayer film in which a plurality of types of thin films (in the illustrated example, two types of thin films 32ba and 32bb) having different refractive indexes and the same optical film thickness are stacked. The fourth filter portion 32b can employ, for example, Ge, Si, or the like as a thin film material having a relatively high refractive index, and examples of the thin film material having a relatively low refractive index include, for example, MgF ₂ , Al ₂ O ₃ , SiO _x , Ta ₂ O ₅ , SiN _{x and the} like can be employed.

  The first optical filter 31 and the second optical filter 32 may be integrated into one chip as in another configuration example shown in FIG.

  For example, a can package can be adopted as the package 29 of the infrared light receiving unit 2. The can package includes a pedestal (stem) 29a and a cap 29b fixed to the pedestal 29a, and one window hole 29c is formed in front of the first light receiving element 2a and the second light receiving element 2b in the cap 29b. It can be.

  The pedestal 29a is made of metal. The pedestal 29a is formed in a disk shape. The cap 29b is made of metal. The cap 29b is formed in a can shape.

  The pedestal 29a is provided with four lead pins 29d penetrating in the thickness direction. The pedestal 29a holds these four lead pins 29d. Each lead pin 29 d is coupled to the circuit block 44. The four lead pins 29d are used one by one for power supply, for ground, for extracting the output signal of the first amplifier circuit 41, and for extracting the output signal of the second amplifier circuit 42, respectively. The ground lead pin 29d is fixed to the base 29a with a conductive sealing material, and is electrically connected to the base 29a. The other lead pins 29d are fixed to the pedestal 29a with an electrically insulating sealing material (glass), and are electrically insulated from the pedestal 29a. In the infrared light receiving unit 2, a shield plate or a shield layer to which the ground lead pin 29 d is electrically connected may be provided in the circuit block 44.

  The pedestal 29a has a circular shape in plan view, but is not limited thereto, and may be a polygonal shape, for example. Moreover, what is necessary is just to change the shape of the cap 29b suitably according to the shape of the base 29a. For example, when the planar view shape of the pedestal 29a is rectangular, the planar view shape of the cap 29b may be circular or rectangular.

  The window hole 29c has an opening size that is slightly larger than the combined size of the first light receiving element 2a and the second light receiving element 2b. The opening shape of the window hole 29c is a rectangular shape, but is not limited thereto, and may be, for example, a circular shape or a polygonal shape other than a rectangular shape.

  The window material 29w that closes the window hole 29c has a function of transmitting infrared rays. The window material 29w is constituted by a flat silicon substrate. The window material 29w is formed in a rectangular plate shape that is slightly larger than the opening size of the window hole 29c. The window material 29w is preferably fixed to the cap 29b with a conductive material (for example, solder, conductive adhesive, etc.). Thereby, the infrared light receiving unit 2 can make the window material 29w substantially the same potential as the cap 29b, and has an advantage that it is less susceptible to external electromagnetic noise. The window material 29w is not limited to a silicon substrate, but may be, for example, a germanium substrate or a zinc sulfide substrate. However, using a silicon substrate is advantageous in terms of cost reduction. In addition, a lens may be employed as the window material 29w. The lens can be composed of a semiconductor lens (for example, a silicon lens).

  In manufacturing the semiconductor lens, for example, a semiconductor substrate (for example, a silicon substrate) is prepared. After that, an anode whose contact pattern with the semiconductor substrate is designed according to the desired lens shape is formed on one surface side of the semiconductor substrate so that the contact with the semiconductor substrate becomes ohmic contact. Thereafter, a porous portion serving as a removal site is formed by anodizing the other surface side of the semiconductor substrate in an electrolytic solution composed of a solution for removing oxides of constituent elements of the semiconductor substrate by etching. Thereafter, a semiconductor lens is formed by removing the porous portion. As a method for manufacturing a semiconductor lens using this type of anodization technology, for example, a method for manufacturing a semiconductor lens disclosed in Japanese Patent No. 3897055 and Japanese Patent No. 3897056 can be applied. In addition, what is necessary is just to isolate | separate the lens which consists of the above-mentioned semiconductor lens into each lens by dicing etc., after forming many lenses, using a semiconductor wafer (for example, silicon wafer) as a semiconductor substrate, for example.

  The lens is preferably a semiconductor lens in which a lens part and a flange part surrounding the lens part are formed continuously and integrally. As a result, the infrared light receiving unit 2 includes flange portions whose thickness is substantially constant and both surfaces in the thickness direction are flat, thereby increasing the accuracy of the distance between the lens and the infrared light receiving element 20 in the optical axis direction of the lens. It becomes possible to raise.

  The insulating base material 43a of the substrate 43 is preferably provided with a hole 43b for thermal insulation in the projection region of each light receiving portion 2r. Thereby, the infrared light receiving unit 2 can improve the thermal insulation between the light receiving portion 2r and the insulating base material 43a, and the sensitivity of each of the first light receiving element 2a and the second light receiving element 2b is improved. It becomes possible. One heat insulating hole 43b may be provided for each light receiving part 2r, but it is preferable that the hole 43b is provided across the two light receiving parts 2r in a projected view.

  The region where the infrared detection element 20 is scheduled to be mounted on the insulating substrate 43a is a region where the infrared detection element 20 overlaps in plan view. The protrusion 43c for positioning the infrared detection element 20 is an infrared ray from a portion outside the planned mounting area of the infrared detection element 20 between the adjacent first lead terminal 43j and the second lead terminal 43k in the insulating base 43a. The detection element 20 protrudes in the direction along the thickness direction (upward in FIG. 3). Therefore, one protrusion 43c is formed on each side of the insulating base material 43a on both sides in the direction in which the two light receiving portions 2r are arranged. Accordingly, the infrared light receiving unit 2 can position the infrared detection element 20 by the two protrusions 43c, and can improve the positional accuracy of the infrared detection element 20 in the direction in which the two light receiving portions 2r are arranged. The redundant design resulting from the position accuracy of 20 is not required, and it is possible to reduce the size and improve the sensitivity. Further, the infrared light receiving unit 2 includes the first electrode compared to the case where the protrusion 43c is not provided or the protrusions 43p are positioned in the vicinity of the four corners of the infrared light receiving element 20 as in the comparative example illustrated in FIG. The occurrence of a short circuit between 2h and the second electrode 2i can be suppressed, and the reliability can be improved. In addition, the infrared light receiving unit 2 can suppress the generation of noise due to floating charges caused by the leak between the first electrode 2h and the second electrode 2i, thereby improving the S / N ratio and increasing the sensitivity. It becomes possible.

  In the infrared light receiving unit 2, the protrusion dimension of the protrusion 43c is preferably larger than the height dimension of the first joint 7j. Thereby, the infrared light receiving unit 2 can more reliably suppress the first output terminal 2j and the second output terminal 2k from being short-circuited via the first joint portion 7j. In the infrared light receiving unit 2, the protrusion dimension of the protrusion 43 c may be larger than the height dimension from the back surface of the infrared detection element 20 to the first optical filter 31 and the second optical filter 32. As a result, the infrared light receiving unit 2 has a dimension in which the first optical filter 31 and the second optical filter 32 in the direction in which the first optical filter 31 and the second optical filter 32 are arranged is the first in the infrared detection element 20. When the dimensions of the light receiving element 2a and the second light receiving element 2b are approximately equal to each other, not only the infrared detecting element 20 but also the first optical filter 31 and the second optical filter 32 can be positioned by the projection 43c.

  In the substrate 43, the first lead terminal 43j is provided outside the region where the infrared detection element 20 is to be mounted, and the second lead terminal 43k extends over the region where the infrared detection element 20 is to be mounted and the outside of the region where the infrared detection element 20 is to be mounted. Is provided. The first joint portion 7j is provided on the front side of the infrared detection element 20. On the other hand, the second joint portion 7k is provided on the back side of the infrared detection element 20.

  Thereby, as in the third modification shown in FIG. 13, the infrared light receiving unit 2 includes the first lead terminal 43 j and the second lead terminal 43 k so that the infrared detection element 20 is to be mounted on the outside of the planned mounting area. Compared to the case where the first output terminal 2j and the second output terminal 2k are short-circuited, it is possible to more reliably suppress the short circuit between the first output terminal 2j and the second output terminal 2k.

  In the infrared light receiving unit 2, the positioning unit 43d defines the positions of the first optical filter 31 and the second optical filter 32 in a direction orthogonal to the direction in which the first optical filter 31 and the second optical filter 32 are arranged in plan view. It is preferable to include a wall portion 43e that supports and a support portion 43f on which the first optical filter 31 and the second optical filter 32 are installed. The wall 43e and the support 43f are formed on both sides in a direction orthogonal to the direction in which the first optical filter 31 and the second optical filter 32 are arranged in plan view. Thereby, the infrared light receiving unit 2 can increase the relative positional accuracy of the first optical filter 31 and the second optical filter 32 and the infrared detection element 20. Therefore, the infrared light receiving unit 2 can be reduced in size and sensitivity. In addition, the height dimension of the wall part 43e from the support part 43f is not specifically limited, You may be smaller than the thickness dimension of the 1st optical filter 31 and the 2nd optical filter 32. FIG.

  For example, the first optical filter 31 and the second optical filter 32 are preferably fixed to the wall 43e with an adhesive. As a result, the infrared light receiving unit 2 includes the infrared detection element 20, the first optical filter 31, and the second optical filter as compared with the case where the first optical filter 31 and the second optical filter 32 are fixed to the support portion 43f with an adhesive. It becomes possible to improve the accuracy of the distance to the optical filter 32. In the infrared light receiving unit 2, the protrusion dimension of the support portion 43 f is larger than the thickness dimension of the infrared detection element 20, and the first optical filter 31, the second optical filter 32, and the infrared detection element 20 are arranged in the thickness direction of the infrared detection element 20. It is preferable that there is a gap between them. As a result, the infrared light receiving unit 2 can thermally insulate the infrared detection element 20 from the first optical filter 31 and the second optical filter 32, and can increase the sensitivity of the infrared detection element 20. .

  In the infrared light receiving unit 2, the wall portion 43 e is formed with a recess 43 g in which the front end surface and the opposed surfaces of the first optical filter 31 and the second optical filter 32 are opened. It is preferable that the optical filter 32 is fixed to the wall portion 43e by an adhesive portion 9 made of an adhesive in the recess portion 43g. Thereby, the infrared light receiving unit 2 can stabilize the application amount of the adhesive at the time of manufacture, and can improve productivity. The inner side surface of the recess 43g may be a smoothly continuous surface or a combination of a plurality of planes. The inner side surface of the recessed portion 43g can have the same shape as the R chamfered portion or the C chamfered portion. For example, an epoxy resin, an acrylic resin, or the like can be used as the adhesive of the bonding portion 9. The adhesive may be a thermosetting adhesive, but more preferably an ultraviolet curable adhesive.

  For example, as in the fourth modification shown in FIG. 14, the infrared light receiving unit 2 is preferably formed with a recess 43 h on the surface of the support portion 43 f that faces the side surface of the infrared detection element 20. As a result, the infrared light receiving unit 2 can further suppress heat conduction from the first optical filter 31 and the second optical filter 32 to the infrared detection element 20, and further increase the sensitivity of the infrared detection element 20. It becomes possible to plan.

  The infrared light receiving unit 2 may be applied by appropriately combining the first to fourth modified examples and other configuration examples with respect to the configuration described with reference to FIGS.

  Below, the infrared type gas sensor 100 is demonstrated based on FIG. 15 as an example of the infrared application apparatus provided with the infrared light reception unit 2. FIG.

  The infrared gas sensor 100 includes a light source 1, an infrared light receiving unit 2 that is a light detector, a sample cell 6 disposed between the light source 1 and the infrared light receiving unit 2, and a signal processing unit 4. In addition, the line with the arrow in FIG. 15 schematically shows the traveling path of the infrared rays emitted from the light source 1.

  The first optical filter 31 has a first transmission wavelength region set so as to transmit infrared rays having an absorption wavelength of the gas to be detected. The second optical filter 32 is set with a second transmission wavelength region that transmits infrared light having a reference wavelength that is not absorbed by the gas to be detected and does not overlap the first transmission wavelength region. The signal processing unit 4 obtains the concentration of the gas to be detected based on the difference or ratio between the output signal of the first light receiving element 2a and the output signal of the second light receiving element 2b. Since the infrared gas sensor 100 uses the infrared light receiving unit 2 as a light detector, it is possible to improve the reliability and increase the sensitivity.

  The signal processing unit 4 includes a signal processing circuit 45 that generates an output based on a difference or ratio between the output signal amplified by the first amplifier circuit 41 and the output signal amplified by the second amplifier circuit 42. ing. When the infrared application apparatus A is an infrared gas sensor, the signal processing circuit 45 is based on the difference or ratio between the output signal amplified by the first amplification circuit 41 and the output signal amplified by the second amplification circuit 42. Then, the concentration of the gas to be detected is obtained and an output corresponding to this concentration is generated.

  The light source 1 is an infrared light source that emits infrared rays by thermal radiation. The first optical filter 31 constitutes a first optical system 3a disposed between the light source 1 and the first light receiving element 2a, and the second optical filter 32 is disposed between the light source 1 and the second light receiving element 2b. The 2nd optical system 3b arrange | positioned is comprised. The first optical system 3a and the second optical system 3b have different transmission wavelength ranges (transmission bands). The first optical filter 31 in FIG. 8A has a substrate 31s, a first filter part 31a that defines the transmission wavelength range of the first optical system 3a, and a longer wavelength side than the transmission wavelength range of the first filter part 31a. And a second filter portion 31b that lowers the transmittance of infrared rays in the predetermined wavelength region. Further, the second optical filter 32 in FIG. 8B is longer than the substrate 32s, the third filter part 32a that defines the transmission wavelength range of the second optical system 3b, and the transmission wavelength range of the third filter part 32a. And a fourth filter portion 32b that lowers the transmittance of infrared rays in a predetermined wavelength region on the wavelength side. The 2nd filter part 31b in Fig.8 (a) is a filter interrupted | blocked by absorbing the infrared rays of a predetermined wavelength range. The 4th filter part 32b in FIG.8 (b) is a filter interrupted | blocked by absorbing the infrared rays of a predetermined wavelength range.

FIG. 19 is a schematic explanatory diagram of transmission spectra of the first optical filter 31 and the second optical filter 32. Here, FIG. 19C shows a first optical filter including the first filter unit 31a having the transmission spectrum of FIG. 19A and the second filter unit 31b having the transmission spectrum of FIG. 19B. 31 shows the transmission spectrum. FIG. 19F shows a second optical filter 32 including the third filter unit 32a having the transmission spectrum of FIG. 19D and the fourth filter unit 32b having the transmission spectrum of FIG. The transmission spectrum of is shown. Λ _{1 in} FIGS. 19A to 19F indicates the center wavelength of the transmission wavelength region of the first filter unit 31a. Also, λ ₂ in FIGS. 19A to 19F indicates the center wavelength of the transmission wavelength region of the third filter portion 32a.

  As can be seen from FIG. 19, in the infrared gas sensor 100, the first optical filter 31 includes a first filter part 31a and a third filter part 31b, and the second optical filter 32 includes a second filter part 32a and a fourth filter part. By including the filter unit 32b, it is possible to reduce the transmittance of infrared rays in a predetermined wavelength region, and to improve the S / N ratio of the output signals of the first light receiving element 2a and the second light receiving element 2b. Is possible. In the infrared gas sensor 100, the second filter portion 31b and the fourth filter portion 32b are filters that reduce the transmittance by absorbing infrared rays in a predetermined wavelength region. It is possible to suppress the reflection of infrared rays at each filter 32.

The sample cell 6 is a cell into which a gas containing a detection target gas or a detection target gas is introduced. In the infrared type gas sensor 100, since the infrared absorption wavelength differs depending on the type of gas to be detected, it becomes possible to improve the gas discrimination. The absorption wavelengths are, for example, 3.3 μm for CH ₄ (methane), 4.3 μm for CO ₂ (carbon dioxide), 4.7 μm for CO (carbon monoxide), and 5.3 μm for NO (nitrogen monoxide). . Therefore, the infrared light receiving unit 2, when applied to the infrared gas sensor 100, for example, a center wavelength lambda ₁ of the first filter portion 31a is set to the absorption wavelength of the gas detection target, the central wavelength of the third filter portion 32a λ ₂ may be set to a wavelength that does not absorb in the gas to be detected and other gases (H ₂ O, CH ₄ , CO, NO, etc.). As the 1st filter part 31a and the 3rd filter part 32a, the band pass filter with a narrow full width at half maximum of a transmission spectrum is preferable. The infrared gas sensor 100, it the difference between the central wavelength lambda ₂ having the central wavelength lambda ₁ and the second filter portion 32a of the first filter portion 31a is preferably small. Thus, the infrared gas sensor 100 can reduce the difference between the amount of infrared light transmitted through the first filter portion 31a and the amount of infrared light transmitted through the third filter portion 32a when there is no gas to be detected. It becomes. When the gas to be detected is, for example, carbon dioxide, the infrared gas sensor 100 sets the center wavelength λ ₁ of the first filter part 31 a to 4.3 μm and sets the center wavelength λ ₂ of the third filter part 32 a to, for example, 3.9 μm. Can be set to

  The infrared gas sensor 100 includes a drive circuit 5 that drives the light source 1. The infrared gas sensor 100 modulates the intensity of infrared rays emitted from the light source 1 by the drive circuit 5. The drive circuit 5 drives the light source 1 so that the intensity of light emitted from the light source 1 periodically changes at a constant period, but may be driven so that the intensity of light changes continuously. You may make it drive so that the intensity | strength of may change intermittently.

Since the light source 1 emits infrared rays by thermal radiation, it can emit infrared rays having a wider wavelength range than infrared light emitting diodes. The light source 1 can emit broadband infrared light including the center wavelength λ ₁ of the first filter portion 31 a and the center wavelength λ ₂ of the third filter portion 32 a. In short, the light source 1 can emit infrared rays in a wavelength range including the transmission wavelength range of the first optical filter 31 and the transmission wavelength range of the second optical filter 32.

  As the light source 1, for example, a light source including an infrared radiation element 10 that emits infrared light and a package 19 that houses the infrared radiation element 10 can be used. As the package 19, for example, a package having a window hole 19 r in front of the infrared radiation element 10 and closed by the window material 19 w can be used. As the infrared radiation element 10, for example, the one having the configuration shown in FIG. 18 can be used. The infrared radiation element 10 having the configuration shown in FIG. 18 can be manufactured by using a manufacturing technology of MEMS (micro electro mechanical systems). The infrared radiating element 10 includes a substrate 11, a thin film portion 12 provided on one surface side of the substrate 11, a hole 11 a penetrating in the thickness direction of the substrate 11, and a side opposite to the substrate 11 side in the thin film portion 12. And an infrared radiation layer 13 provided. The infrared radiation element 10 includes a protective layer 14 that covers the infrared radiation layer 13 on the opposite side of the thin film portion 12 from the substrate 11 side, and a plurality of pads 16 that are electrically connected to the infrared radiation layer 13. Yes. The protective layer 14 is formed of a material that can transmit infrared rays emitted from the infrared radiation layer 13. The infrared radiation layer 13 and each pad 16 are electrically connected via the wiring 15.

  In the infrared radiation element 10, the infrared radiation layer 13 generates heat when the infrared radiation layer 13 is energized, and infrared rays are emitted from the infrared radiation layer 13 by thermal radiation.

  As the substrate 11, for example, a single crystal silicon substrate, a polycrystalline silicon substrate, or the like can be adopted.

  The thin film portion 12 can be constituted by, for example, a laminated film of a silicon oxide film 12a on the substrate 11 side and a silicon nitride film 12b laminated on the opposite side of the silicon oxide film 12a to the substrate 11 side. The thin film portion 12 may have a single layer structure of a silicon oxide film or a silicon nitride film, for example.

  The material of the infrared radiation layer 13 is, for example, tantalum nitride, titanium nitride, nickel chromium, tungsten, titanium, thorium, platinum, zirconium, chromium, vanadium, rhodium, hafnium, ruthenium, boron, iridium, niobium, molybdenum, tantalum, osmium. Rhenium, nickel, holmium, cobalt, erbium, yttrium, iron, scandium, thulium, palladium, lutetium, conductive polysilicon, or the like may be employed.

  The infrared radiation element 10 can change the Joule heat generated in the infrared radiation layer 13 by adjusting the input power applied between the pair of pads 16 from the drive circuit 5, for example, and the temperature of the infrared radiation layer 13 can be changed. Can be changed. Therefore, the infrared radiation element 10 can change the peak wavelength of the infrared radiation emitted from the infrared radiation layer 13 by changing the temperature of the infrared radiation layer 13.

  For example, a can package can be adopted as the package 19. The can package includes a pedestal (stem) 19a on which the infrared radiating element 10 is mounted and a cap 19b fixed to the pedestal 19a so as to cover the infrared radiating element 10, and a window is provided in front of the infrared radiating element 10 in the cap 19b. It can be set as the structure in which the hole 19r was formed. The pedestal 19a is provided with a plurality of pins 19d for feeding power to the infrared radiation element 10 penetrating in the thickness direction. The package 19 is not limited to a can package, and for example, a ceramic package or the like may be employed.

  The window material 19w has a function of transmitting infrared rays. The window material 19w is composed of a flat silicon substrate. The window material 19w is not limited to a silicon substrate, and may be, for example, a germanium substrate or a zinc sulfide substrate. However, using a silicon substrate is advantageous in terms of cost reduction. Moreover, a lens can also be employ | adopted as the window material 19w. The lens can be composed of a semiconductor lens (for example, a silicon lens).

  The lens is preferably a semiconductor lens in which a lens part and a flange part surrounding the lens part are formed continuously and integrally. Thereby, the light source 1 includes a flange portion whose thickness is substantially constant and each of both surfaces in the thickness direction is planar, thereby increasing the accuracy of the distance between the lens and the infrared radiation element 10 in the optical axis direction of the lens. Is possible.

  In the infrared gas sensor 100, an optical filter that reflects infrared rays in a predetermined wavelength region may be disposed instead of the window material 19 w of the light source 1. The optical filter in the light source 1 is a non-reflective coating filter in which a substrate is coated with an antireflection film that reduces infrared reflectance in the transmission wavelength region of each of the first optical filter 31 and the second optical filter 32. Those optically designed to reflect infrared rays are preferred. As the substrate, for example, a silicon substrate, a germanium substrate, a sapphire substrate, or the like can be employed. In such a case, the optical filter constitutes a part of each of the first optical system 3a and the second optical system 3b.

  The light source 1 is not limited to the configuration including the infrared radiation element 10 and the package 19, and for example, a halogen lamp can be employed.

The first optical filter 31, preferably a central wavelength lambda ₁ of the first filter portion 31a is set to the absorption wavelength of the gas detection target. Thereby, the 1st optical filter 31 can permeate | transmit the infrared rays of the absorption wavelength of gas to be detected with a higher transmittance. The first filter portion 31a is the transmittance for the central wavelength lambda ₁ in the infrared is not less than 50%, preferably, more preferably 70% or more, still more preferably 90% or more. The second optical filter 32, the center wavelength lambda ₂ and is not absorbed by the gas and other gas detection target wavelength of the third filter portion 32a (hereinafter, also referred to as "reference wavelength".) The is set to preferably. It is preferable that the transmission wavelength region of the third filter part 32a does not overlap with the transmission wavelength region of the first filter part 31a. The third filter unit 32a, the transmittance with respect to the central wavelength lambda ₂ of the infrared is not less than 50%, preferably, more preferably 70% or more, still more preferably 90% or more. Transmittance with respect to the central wavelength lambda ₂ of the infrared third filter portion 32a is more difference between the transmittance with respect to the central wavelength lambda ₁ of the infrared of the first filter portion 31a is preferably small.

  The infrared gas sensor 100 has a difference or ratio between the output signal of the first light receiving element 2a and the output signal of the second light receiving element 2b, which is a value corresponding to the concentration of the gas to be detected (for example, carbon dioxide). In the processing unit 4, the concentration of the gas to be detected can be obtained with high accuracy. From the viewpoint of widening the dynamic range, the infrared gas sensor 100 preferably obtains the gas concentration based on the difference between the output signal of the first light receiving element 2a and the output signal of the second light receiving element 2b. On the other hand, the infrared gas sensor 100 preferably obtains the gas concentration based on the ratio of the output signal of the first light receiving element 2a and the output signal of the second light receiving element 2b from the viewpoint of suppressing the temporal variation.

  Next, the sample cell 6 of the infrared gas sensor 100 will be described with reference to FIGS. 16, 17, and 20.

  The sample cell 6 is formed in a cylindrical shape. The sample cell 6 is preferably formed with a plurality of air holes 69 that communicate between the internal space and the outside in a direction perpendicular to the axial direction of the sample cell 6. When the sample cell 6 is formed in a cylindrical shape, the vent hole 69 is preferably formed so as to penetrate in the radial direction of the sample cell 6. In the sample cell 6, gas from the outside is introduced through the vent hole 69, or air in the internal space is led out.

  In the infrared gas sensor 100, the light source 1 is arranged on one end side in the axial direction of the sample cell 6, and the infrared light receiving unit 2 is arranged on the other end side in the axial direction of the sample cell 6. In the infrared gas sensor 100, for example, a gas to be detected from the outside or a gas containing a gas to be detected is introduced into the internal space of the sample cell 6 through the vent hole 69. For this reason, in the infrared gas sensor 100, when the concentration of the gas to be detected in the internal space of the sample cell 6 increases, the amount of infrared light incident on the infrared light receiving unit 2 decreases, and the detection in the internal space of the sample cell 6 occurs. When the concentration of the target gas decreases, the amount of infrared light incident on the infrared light receiving unit 2 increases.

  The sample cell 6 is formed by joining a pair of halves 64 and 65 (see FIG. 16) divided by a plane including the central axis OX (see FIG. 20) of the sample cell 6. The half body 64 and the half body 65 can be coupled by a technique selected from fitting, ultrasonic welding, adhesion, and the like.

  It is preferable that the sample cell 6 also serves as an optical element that reflects the infrared light emitted from the light source 1 toward the infrared light receiving unit 2. Here, when the sample cell 6 is formed of, for example, a synthetic resin, it is preferable that the sample cell 6 includes a reflection layer that reflects infrared rays inside.

  The material of the sample cell 6 is not limited to a synthetic resin, and may be a metal, for example. When the sample cell 6 is formed of a metal having a relatively high reflectance with respect to infrared rays having a specific wavelength, the sample cell 6 may or may not include a reflective layer separately.

  In short, it is preferable that the sample cell 6 has a cylindrical shape, and the inner surface thereof is a reflecting surface 66 that reflects infrared rays emitted from the light source 1. When the above-described reflective layer is provided, the surface of this reflective layer can constitute the reflective surface 66. In addition, the line with the arrow in FIG. 20 schematically shows the traveling path of the infrared rays emitted from the light source 1.

  The infrared gas sensor 100 includes a holding member 70 that holds the light source 1, and the holding member 70 is attached to the sample cell 6. The infrared gas sensor 100 includes a holding member 80 that holds the infrared light receiving unit 2, and the holding member 80 is attached to the sample cell 6.

  The holding member 70 includes a cap portion 71 and a pressing plate 72. The cap part 71 is disc-shaped, and a recess 71a into which one end of the sample cell 6 is inserted is provided on the end surface on the sample cell 6 side, and the light source 1 is inserted into the center of the bottom of the recess 71a. A hole 71b is provided. The holding plate 72 is for holding the light source 1 against the cap portion 71.

  The holding member 70 is screwed into the screw portions 64d and 65d at one end of the sample cell 6 by attaching mounting screws (not shown) passed through the holding plate 72 and the holes 72b and 71d of the cap portion 71, whereby the sample cell 6 Is attached.

  The holding member 80 includes a cap portion 81 and a pressing plate 82. The cap portion 81 has a disc shape, and is provided with a recess 81a into which the other end of the sample cell 6 is inserted on the end surface on the sample cell 6 side, and the infrared light receiving unit 2 is inserted in the center of the bottom of the recess 81a. A through hole 81b is provided. The pressing plate 82 is for pressing the infrared light receiving unit 2 against the cap portion 81.

  The holding member 80 is attached to the sample cell 6 by attaching a mounting screw (not shown) passed through the holes 82 b and 81 c of the holding plate 82 and the cap portion 81 into the screw portion at the other end of the sample cell 6. It has been.

  Note that the structure of each of the holding members 70 and 80 is not particularly limited. Further, the attachment structure of the holding members 70 and 80 to the sample cell 6 is not particularly limited.

  By the way, the reflecting surface 66 of the sample cell 6 has two planes VP1 that are perpendicular to the major axis at both ends in the major axis direction of the spheroid whose major axis is defined on the central axis OX of the sample cell 6. , And a shape cut by VP2 (see FIG. 20). Therefore, the sample cell 6 has an internal space corresponding to a part of the spheroid (ellipsoid).

  In the infrared type gas sensor 100, the light source 1 is disposed on one focal point P1 of the spheroid on the center axis OX of the sample cell 6, and the infrared light receiving unit 2 is disposed on the center axis OX of the sample cell 6. It is preferable to arrange the spheroid on the side closer to the light source 1 than the other focal point P2.

  In the infrared gas sensor 100, the light source 1 is arranged in the vicinity of one focal point P1 of the spheroid. The vicinity is a subset including all points whose distance between the focal point P1 and the light source 1 is smaller than a predetermined value, and includes the point of the focal point P1. The predetermined value varies depending on the distance between the focal point P1 and the focal point P2 of the spheroid. In short, the light source 1 does not need to be disposed at the focal point P1 in a strict sense, and may be at a position that can be regarded as being substantially disposed at the focal point P1. The infrared rays emitted from the light source 1 in the oblique direction are reflected by the reflecting surface 66 and guided so as to be condensed at the other focal point P2. However, in the infrared gas sensor of the comparative example in which the infrared light receiving unit 2 is disposed at the other focal point P2, the light is reflected by the reflecting surface 66 at the other end of the sample cell 6 and is incident on the first optical filter 31 and the second optical filter 32. Incidence angle of infrared rays to be increased. In the first optical filter 31 and the second optical filter 32, as the incident angle increases, the transmission spectrum (transmittance-wavelength characteristics) shifts to the short wavelength side, and infrared rays in a specific wavelength region including a selected wavelength. The transmittance of the will be reduced. Therefore, in the infrared type gas sensor of the comparative example, there is a concern that the S / N ratio is lowered. On the other hand, in the infrared gas sensor of the comparative example, as the distance between the sample cell 6 and the infrared light receiving unit 2 in the direction along the center axis OX of the sample cell 6 becomes longer, the loss of infrared rays increases.

  On the other hand, in the infrared type gas sensor 100 of the present embodiment, the infrared light receiving unit 2 is disposed on the side closer to the light source 1 than the other focal point P2 of the reflecting surface on the central axis OX of the sample cell 6. . That is, the infrared light receiving unit 2 includes the first optical filter 31, the second optical filter 32, the first light receiving element 2 a, and the second light receiving element 2 b in the direction along the center axis OX of the sample cell 6. And closer to the light source 1 than between the sample cell 6 and the other focal point P2. Thereby, in the infrared type gas sensor 100 of the present embodiment, when the distance between the sample cell 6 and the infrared light receiving unit 2 in the direction along the central axis OX of the sample cell 6 is the same as that of the comparative example, compared to the comparative example. It is possible to reduce the incident angle of infrared rays that are reflected by the reflecting surface 66 at the other end of the sample cell 6 and enter the first optical filter 31 and the second optical filter 32. Therefore, the infrared gas sensor 100 according to the present embodiment transmits infrared light in a specific wavelength range (designed transmission wavelength ranges of the first optical filter 31 and the second optical filter 32) as compared with the infrared gas sensor of the comparative example. It is possible to suppress a decrease in the rate, and it is possible to improve the S / N ratio. Further, the infrared light transmitted through the first optical filter 31 and the second optical filter 32 is a second light other than the first light receiving element 2 a and the second light receiving element 2 b facing the first optical filter 31 and the second optical filter 32. The occurrence of crosstalk incident on the light receiving element 2b and the first light receiving element 2a can be suppressed, and the measurement accuracy can be improved. The distance between the sample cell 6 and the infrared light receiving unit 2 in the direction along the central axis OX of the sample cell 6 is preferably short, and more preferably zero.

  The infrared gas sensor 100 does not particularly limit the shape, number, arrangement, or the like of a member (sample cell 6 or the like) disposed between the light source 1 and the infrared light receiving unit 2.

  In the above-described infrared gas sensor 100, for the infrared light receiving unit 2, as shown in FIG. 21, for example, the planar shape of the first electrode 2h of the first light receiving element 2a and the planar shape of the first electrode 2h of the second light receiving element 2b. Can be made to be a shape along the intersection of the table of pyroelectric substrate 2g and the above-mentioned spheroid. As a result, the infrared gas sensor 100 can reduce a region of the light receiving unit 2r that does not contribute to infrared light reception, can reduce the heat capacity of the light receiving unit 2r, and achieve high sensitivity. It becomes possible.

(Embodiment 2)
Below, the human body detection sensor B provided with the structure shown in FIG. 22 is illustrated as an infrared application apparatus using the infrared light reception unit 2 demonstrated in Embodiment 1. FIG. The human body detection sensor B detects the movement of a person, which is an object that emits infrared rays, and outputs a detection signal. The human body detection sensor B can be used in combination with, for example, a control circuit for turning on and off a switch element (switching element, relay, etc.) provided between the illumination load and the power source. Further, the human body detection sensor B may output a detection signal related to the movement direction of a person, for example.

  The human body detection sensor B includes an infrared light receiving unit 2, an IC element 213, a circuit board 211, and a cover 212.

  When the infrared light receiving unit 2 is applied to a human body detection sensor, the first amplifying circuit 41 and the second amplifying circuit 42 amplify, for example, a voltage signal having a frequency component close to human movement (a component centered on 1 Hz). It is preferable to use a band pass amplifier.

  In the human body detection sensor B, the wavelength of infrared rays to be detected is about 8 to 13 μm, and the center wavelength is about 10 μm. For this reason, it is preferable that the filter characteristics of the first optical filter 31 and the second optical filter 32 are set so as to cut electromagnetic waves with a wavelength shorter than a predetermined wavelength (for example, 5 μm) shorter than 8 μm.

  The IC element 213 is formed with a signal processing circuit that processes the output signal of the infrared light receiving unit 2 and outputs a detection signal.

  The infrared light receiving unit 2 and the IC element 213 are mounted on the circuit board 211. The circuit board 211 can be composed of, for example, a printed wiring board.

  The cover 212 is preferably attached to the circuit board 211 so as to cover the package 29 of the infrared light receiving unit 2. In this case, the infrared light receiving unit 2 is preferably mounted on the circuit board 211 so that a gap is formed between the pedestal 29a and the circuit board 211. Accordingly, the human body detection sensor B suppresses heat conduction from the circuit board 211 to the pedestal 29a because the space surrounded by the cover 212, the package 29, and the circuit board 211 constitutes a gas layer composed of an air layer. Therefore, it is possible to suppress the occurrence of erroneous detection due to the fluctuation of the heat around the human body detection sensor B. The cover 212 may be attached to the infrared light receiving unit 2.

  The cover 212 is preferably made of polyethylene so that infrared rays can be transmitted. The shape of the cover 212 can be, for example, a dome shape. The cover 212 is a lens in which the infrared ray incident from the side opposite to the window material 29w side of the package 29 can collect the infrared ray incident from the opposite side to the infrared detection element 20 (for example, see FIG. 1). It is preferable that it is formed in a shape. This lens shape may be an array lens in which a plurality of lens portions are combined and the focal positions of the lens portions are the same, or may be a single lens.

  For example, the signal processing circuit may include a detection circuit and an output circuit. For example, the detection circuit compares each output signal amplified by the first amplification circuit 41 and the second amplification circuit 42 with a suitably set threshold value, and outputs a detection signal when each output signal exceeds the threshold value. Such a detection circuit can be constituted by a comparison circuit using a comparator or the like, for example. The output circuit outputs the detection signal of the detection circuit as a predetermined human body detection signal.

  The detection circuit obtains a difference or ratio between the output signal amplified by the first amplification circuit 41 and the output signal amplified by the second amplification circuit 42, compares the value with a threshold value set as appropriate, and exceeds the threshold value. In this case, a detection signal may be output. In this case, for example, the filter characteristic of the first optical filter 31 is set so as to transmit infrared rays to be detected, and the filter characteristic of the second optical filter 32 is set so as not to transmit infrared rays of the detection target. Good.

  The detection circuit determines the moving direction of the person based on the timing when the output signal amplified by the first amplifier circuit 41 exceeds the threshold and the timing when the output signal amplified by the second amplifier circuit 42 exceeds the threshold. It may be. In this case, the detection circuit can be realized, for example, by installing an appropriate program in the microcomputer. In this case, the filter characteristics of the first optical filter 31 and the filter characteristics of the second optical filter 32 are preferably set to be the same.

The infrared application device is not limited to the infrared gas sensor 100 or the human body detection sensor B. The infrared application device may be any device that uses infrared rays. For example, a non-dispersive gas analyzer, resonance radiation of carbon dioxide (CO ₂ gas) in a flame in a fire (also called “CO ₂ resonance radiation”). Infrared flame detectors that detect flames by detecting infrared rays having a specific wavelength (4.3 μm to 4.4 μm) generated by the

1 Light source 2 Infrared light receiving unit (photodetector)
2a First light receiving element 2b Second light receiving element 2g Pyroelectric substrate 2p Electrical insulation layer 2r Light receiving part 2h First electrode 2i Second electrode 2j First output terminal 2k Second output terminal 4 Signal processing part 6 Sample cell 7j First Bonding part 7k Second bonding part 9 Adhesion part 20 Infrared detection element 26 Infrared absorption layer 29 Package 31 First optical filter 32 Second optical filter 41 First amplification circuit 42 Second amplification circuit 43 Substrate 43a Insulating base material 43b Hole 43c Projection 43d Positioning portion 43e Wall portion 43f Support portion 43j First lead terminal 43k Second lead terminal 43g Depression portion 43h Recess 44 Circuit block 45 Signal processing circuit 100 Infrared gas sensor OX Central axis P1 focus P2 focus VP1 plane VP2 plane

Claims (15)

An infrared detecting element having a first light receiving element and a second light receiving element; a first optical filter and a second optical filter disposed in front of light receiving surfaces of the first light receiving element and the second light receiving element; and the infrared light A substrate on which a detection element is mounted; and a package in which the infrared detection element, the first optical filter, the second optical filter, and the substrate are housed,
The package has a window hole on a light incident surface side of the first optical filter and the second optical filter, and a window material that closes the window hole and transmits infrared rays.
Each of the first light receiving element and the second light receiving element is formed on each of the front side and the back side of the pyroelectric substrate and is opposed to each other in the first electrode, the second electrode, and the pyroelectric substrate. A light receiving portion having a portion sandwiched between second electrodes; a first output terminal connected to the first electrode on the front side of the pyroelectric substrate; and the second on the back side of the pyroelectric substrate. A second output terminal connected to the electrode, the first output terminal and the second output terminal are arranged so as not to overlap in the thickness direction of the pyroelectric substrate,
The substrate is provided with an insulating base material having electrical insulation, and the insulating base material, and the first output terminal and the second output terminal are made of a conductive adhesive. A first lead terminal and a second lead terminal electrically connected to each other through two joint portions;
The insulating base material is formed with a protrusion between the first lead terminal and the second lead terminal that protrudes in the thickness direction from the outside of the region where the infrared detection element is to be mounted and positions the infrared detection element. An infrared receiving unit characterized by that.   The infrared light receiving unit according to claim 1, wherein a protrusion dimension of the protrusion is larger than a height dimension of the first joint portion.   3. The infrared light receiving unit according to claim 1, wherein a positioning portion that projects in a direction along the thickness direction of the infrared detection element and positions the first optical filter and the second optical filter is formed. 4. .   The positioning portion includes a wall portion that defines positions of the first optical filter and the second optical filter in a direction orthogonal to a direction in which the first optical filter and the second optical filter are arranged in a plan view. The infrared light receiving unit according to claim 3, further comprising: a first optical filter and a support portion on which the second optical filter is installed.   The projecting dimension of the support portion is larger than the thickness dimension of the infrared detection element, and there is a gap between the first optical filter, the second optical filter, and the infrared detection element in the thickness direction of the infrared detection element. The infrared light receiving unit according to claim 4.   6. The infrared light receiving unit according to claim 4, wherein the support part is formed with a concave portion on a surface facing the side surface of the infrared detection element.   The wall portion is formed with a recessed portion in which a front end surface and a surface facing the first optical filter and the second optical filter are opened, and the first optical filter and the second optical filter are formed in the recessed portion. The infrared light receiving unit according to any one of claims 4 to 6, wherein the infrared light receiving unit is fixed to the wall portion by an adhesive portion made of an adhesive in the portion.   The first lead terminal is provided outside the planned mounting area of the infrared detecting element, and the second lead terminal is provided across the planned mounting area of the infrared detecting element and the outside of the planned mounting area. The first joint portion is provided on the front side of the infrared detection element, and the second joint portion is provided on the back side of the infrared detection element. The infrared light receiving unit according to item.   Each of the first light receiving element and the second light receiving element surrounds the back side of the pyroelectric substrate except for one surface along the side surface of the pyroelectric substrate of the outer peripheral surface of the second output terminal. The electrical insulating layer is provided, and the electrical insulating layer is made of a material having lower wettability with respect to the conductive adhesive than the pyroelectric substrate. Infrared light receiving unit.   The infrared light receiving unit according to claim 1, wherein the insulating base is provided with a hole for thermal insulation in a projection region of each light receiving unit.   11. The infrared ray according to claim 1, wherein a surface of the first electrode of the infrared detection element is covered with an infrared absorption layer having a higher emissivity than the first electrode. Light receiving unit.   A first amplifying circuit and a second amplifying circuit for individually amplifying output signals of the first light receiving element and the second light receiving element, respectively, and the infrared detecting element is disposed on one surface of the substrate in the thickness direction; The infrared light receiving unit according to claim 1, wherein the first amplifier circuit and the second amplifier circuit are arranged on the other surface side in the thickness direction.   A light source, a light detector, a sample cell disposed between the light source and the light detector, and a signal processing unit, the light detector according to any one of claims 1 to 12. The first optical filter has a first transmission wavelength region set so as to transmit infrared light having an absorption wavelength of a gas to be detected, and the second optical filter is not absorbed by the gas. A second transmission wavelength range that transmits infrared light of a reference wavelength and does not overlap with the first transmission wavelength range is set, and the signal processing unit outputs an output signal of the first light receiving element and an output signal of the second light receiving element. An infrared gas sensor, wherein the concentration of the gas is obtained based on a difference or a ratio.   The sample cell has a cylindrical shape, and an inner surface thereof is a reflecting surface that reflects infrared rays emitted from the light source, and the reflecting surface has a major axis defined on the central axis of the sample cell as a rotation axis. Each of the two ends of the spheroid in the major axis direction is cut by two planes orthogonal to the major axis, and the light source is disposed near one focal point of the spheroid on the central axis, The infrared gas sensor according to claim 13, wherein the infrared light receiving unit is disposed closer to the light source than the other focal point of the spheroid on the central axis.   The infrared light receiving unit has a shape obtained by combining the planar shape of the first electrode of the first light receiving element and the planar shape of the first electrode of the second light receiving element with the front surface of the pyroelectric substrate and the surface of the pyroelectric substrate. The infrared gas sensor according to claim 14, wherein the infrared gas sensor has a shape along a line of intersection with the spheroid.

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