Optical gas sensor device

Abstract

This optical gas sensor device based on a reference beam method achieves low cost, size reduction, and high accuracy.　The optical gas sensor device is provided with a light source, optical filters 31, 32, light-receiving units 41, 42, and one ceramic substrate 400. The light source emits infrared rays to a detection target gas. The optical filter 31 allows transmission of infrared rays at the absorption wavelength of the detection target gas, among the infrared rays that are emitted from the light source and have passed through the detection target gas. The light-receiving unit 41 detects the infrared rays incident through the optical filter 31 and generates a detection signal. The optical filter 32 allows transmission of infrared rays at wavelengths other than the absorption wavelength of the detection target gas, among the infrared rays that are emitted from the light source and have passed through the detection target gas. The light-receiving unit 42 detects the infrared rays incident through the optical filter 31 and generates a detection signal. The ceramic substrate 400 accommodates thereon the light-receiving units 41, 42.

Description

Optical gas sensor device

[0001] The present invention relates to an optical gas sensor device.

[0002] Traditionally, continuous monitoring of gas concentrations has been conducted in homes, factories, and businesses from the perspective of managing chemical substances and ensuring worker safety. ２ Non-dispersive infrared absorption (NDIR) gas sensors are known for detecting the concentration of gases such as [list of gases]. NDIR gas sensors utilize the property that many gases absorb specific infrared wavelengths. When infrared light is emitted to the target gas, the sensor detects which wavelengths are absorbed and to what extent, thereby measuring the concentration of the target gas. For example, a gas sensor equipped with an infrared light source and a light receiver detects the concentration of the target gas in the optical path of the light source and light receiver.

[0003] For example, a gas sensor is known that includes an infrared light source as a light source, an optical filter, and one infrared detector as a light receiving unit (see Patent Document 1).

[0004] Furthermore, optical gas sensor devices known as the reference light method or two-wavelength method are also known. The reference light method optical gas sensor device comprises a light source and two sets of optical filters and light receiving units. One set of optical filters and light receiving units detects infrared light transmitted at the absorption wavelength of the gas to be detected. The other set of optical filters uses an optical filter with transmission characteristics that do not match the absorption wavelength of the gas to be detected. This other set of optical filters and light receiving unit detects infrared light as reference light transmitted through the optical filter. The reference light method optical gas sensor device achieves improved detection accuracy by using the difference between the detection signal of the gas to be detected and the detection signal of the reference light.

[0005] Japanese Patent Publication No. 2010-139298

[0006] However, the conventional optical gas sensor devices using the reference light method described above require low cost, compact size, and high accuracy.

[0007] The objective of the present invention is to achieve low cost, compact size, and high accuracy in an optical gas sensor device using a reference light method.

[0008] To solve the above problems, the optical gas sensor device of the present invention comprises: a light source that emits infrared rays to a gas to be detected; a first optical filter that transmits or attenuates the absorption wavelength of the gas to be detected from the infrared rays emitted from the light source and transmitted through the gas to be detected; a first light receiving unit that detects the infrared rays incident through the first optical filter and generates a detection signal; a second optical filter that transmits or attenuates wavelengths of infrared rays emitted from the light source and transmitted through the gas to be detected that do not match the absorption wavelength of the gas to be detected; a second light receiving unit that detects the infrared rays incident through the second optical filter and generates a detection signal; and a container unit that houses the first light receiving unit and the second light receiving unit.

[0009] According to the present invention, an optical gas sensor device using a reference light method can be made inexpensive, compact, and highly accurate.

[0010] This is a schematic diagram of an optical gas sensor device according to an embodiment of the present invention. This is a perspective view of the optical gas sensor device. This is a partially transmitted perspective view of the optical gas sensor device. This is a perspective view of the sealing device. This is a perspective view of the light source. This is a top view of the light receiving unit. This is an equivalent circuit diagram of the light receiving unit. This is a top view of the sealing device of the first embodiment. This is a cross-sectional view of the sealing device of the first embodiment. This is a cross-sectional view of the sealing device of the first embodiment. This is a top view of the sealing device of the second embodiment. This is a cross-sectional view of the sealing device of the second embodiment. This is a top view of the sealing device of the third embodiment. This is a cross-sectional

[0011] Embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the scope of the invention is not limited to the illustrated examples.

[0012] Embodiments of the present invention will be described with reference to Figures 1 to 16. First, the schematic configuration of the optical gas sensor device 100 of this embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram of the optical gas sensor device 100 of this embodiment.

[0013] As shown in Figure 1, the optical gas sensor device 100 of this embodiment is a reference light type NDIR gas sensor. The optical gas sensor device 100 comprises an optical cover 1, a light source 2, an optical filter 31 as a first optical filter, an optical filter 32 as a second optical filter, a light receiving unit 41 as a first light receiving unit, a light receiving unit 42 as a second light receiving unit, a signal processing unit 5, and a switch 81. In the optical gas sensor device 100, the light source 2 emits (emits, emits) infrared light. The emitted infrared light is emitted through an optical path (path) inside the optical cover 1 to the gas G of the object to be detected (measured object) inside the optical cover 1.

[0014] The amount of light reaching the light-receiving unit 41 decreases as molecules of the target gas G present in the optical path absorb infrared radiation. The optical gas sensor device 100 detects the infrared radiation partially absorbed by the target gas G via the optical filter 31 to the light-receiving unit 41. The optical filter 31 is a bandpass filter. The bandpass filter transmits light in the wavelength band that includes the absorption wavelength of the gas G. With this configuration, the light-receiving unit 41 does not receive unfiltered infrared radiation emitted from sources other than the light source 2, improving the signal-to-noise ratio (SNR) of the sensor.

[0015] The optical filter 32 is a bandpass filter with transmission characteristics at a wavelength that does not match the absorption wavelength of the gas G to be detected, and preferably does not match the absorption wavelength of any gas species. The optical gas sensor device 100 detects infrared light at a wavelength that does not match the absorption wavelength of the gas G to be detected, using the optical filter 32 as reference light, via the light receiving unit 42.

[0016] The optical gas sensor device 100 processes the detection signals of the target gas G detected by the light receiving units 41 and 42 and the detection signals of the reference light using the signal processing unit 5 to detect (measure) the concentration of the target gas G and output it. Switch 81 is a switch that turns the light emission of the light source 2 on and off, and is included in the circuit element unit 8 which will be described later. When gas detection is performed, the signal processing unit 5 turns the light source 2 on and off via switch 81.

[0017] The optical cover 1 has a gas introduction port 11, which serves as a gas inlet and outlet for the gas G to be detected. A contamination filter 12 is attached to the gas introduction port 11. The contamination filter 12 is, for example, a metal mesh filter or a porous resin film, and prevents foreign matter from entering from the outside.

[0018] In this manner, the optical gas sensor device 100 filters the infrared light emitted from the light source 2 to the gas G to be detected by optical filters 31 and 32 and receives it with light receiving units 41 and 42. Optical filter 31 is located near the light receiving unit 41 on the optical path upstream of the light receiving unit 41. Optical filter 32 is located near the light receiving unit 42 on the optical path upstream of the light receiving unit 42.

[0019] In this embodiment, the optical path is designed so that the infrared light received by the light-receiving units 41 and 42 arrives after reflecting off the inner surface of the optical cover 1 from the light source 2. It is desirable for the inner surface of the optical cover 1 to have a high reflectivity to improve the efficiency of light (infrared light) utilization. The optical path of the infrared light received by the light-receiving units 41 and 42 may include not only the optical path that arrives after reflecting off the inner surface of the optical cover 1, but also an optical path that arrives directly from the light source 2.

[0020] Furthermore, in this embodiment, the light source 2 and the optical filter 30 (described later) are packaged as a single component, the sealing device 20 (described later). The optical filters 31, 32 and the light receiving units 41, 42 are packaged as a single component, the sealing device 40 (described later).

[0021] The optical gas sensor device 100 is designed to detect alternative fluorocarbon refrigerants, which are used as refrigerants in air conditioners, as the target gas G. Alternative fluorocarbons are synthetic compound (gas) refrigerants used industrially as substitutes for specific chlorofluorocarbons (CFCs). Because CFC refrigerants have a high ozone depletion potential and contribute to the depletion of the Earth's ozone layer, replacement with hydrochlorofluorocarbon (HCFC) refrigerants, which have a lower ozone depletion potential, has begun. Furthermore, in developed countries, there is a shift from HCFC refrigerants to HFC refrigerants (R410A), which have an ozone depletion potential of 0.

[0022] CFC refrigerants, HCFC refrigerants, and HFC refrigerants are known to have high global warming potentials and to be greenhouse gases that cause global warming. For this reason, the replacement of HFC refrigerants (R410A) with HFC refrigerants (R32) with lower global warming potentials is being considered. In this embodiment, for example, R32 as a fluorocarbon refrigerant is detected as the gas G to be detected.

[0023] However, the gas G to be detected is not limited to R32. Other fluorocarbon refrigerants may also be detected, such as R-454C, which has an extremely low Global Warming Potential (GWP). Examples of other fluorocarbon refrigerants include R143a, R152a, R1132, R142b, R1234yf, R1234ze(E), R-444A, R-444B, R-445A, R-446A, R-447A, R-447B, R-451A, R-451B, R-452B, R-454A, R-454B, R-454C, R-455A, R-457A, R-459A, R-459B, R-462A, and R-465A. Furthermore, the gas G to be detected is not limited to fluorocarbon refrigerants, but may also include carbon dioxide, carbon monoxide, propane, methane, butane, ammonia, oxygen disulfide, nitrogen dioxide, nitric oxide, ozone, sulfur hexafluoride, difluoromethane, hydrochlorofluorocarbons (HCFCs), other hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), ethylene, and the like.

[0024] The optical gas sensor device 100 outputs various status signals based on the gas concentration of the detected gas G to an information processing unit of a device that performs processing based on the status of the optical gas sensor device 100. The information processing unit is, for example, an MCU (Micro Controller Unit). The status signals are, for example, fault signals, alarm signals, and monitoring signals (normal signals). A fault signal indicates a fault in the optical gas sensor device 100. An alarm signal indicates an abnormal state (alarm state) where the concentration of the detected gas G exceeds a threshold concentration that indicates a gas leak. A monitoring signal indicates that the concentration of the detected gas G is in a normal state. If the device is an alarm, it will issue various alarms (for example, an alarm for a fault in the optical gas sensor device 100 based on a fault signal, or an alarm for an abnormal concentration of the detected gas G based on an alarm signal) in response to the various signals received from the optical gas sensor device 100. The device may be a device including an optical gas sensor device 100 and an MCU, or it may be a separate device (an external device including an MCU) from the optical gas sensor device 100. Examples of such devices include room air conditioners, air conditioners for shops and offices, and multi-split air conditioners for buildings.

[0025] Next, the specific configuration of the optical gas sensor device 100 will be described with reference to Figures 2 to 7. Figure 2 is a perspective view of the optical gas sensor device 100. Figure 3 is a partially transmitted perspective view of the optical gas sensor device 100. Figure 4 is a perspective view of the sealing device 20. Figure 5 is a perspective view of the light source 2. Figure 6 is a top view of the light receiving unit 41. Figure 7 is an equivalent circuit diagram of the light receiving unit 41.

[0026] As shown in Figures 2 and 3, the optical gas sensor device 100 comprises an optical cover 1, sealants 20 and 40, a signal processing unit 5, a substrate 6, a connector 7, and a circuit element unit 8. The sealant 20 has a light source 2 and an optical filter 30. The sealant 40 has optical filters 31 and 32 and light receiving units 41 and 42. In Figure 2, the x, y, and z axes are shown. These three axes are the same in the other figures. Note that the contamination filter 12 is not shown in Figures 2 and 3.

[0027] The optical cover 1 is mounted on the surface of the substrate 6 in the +z direction and is a cover that covers (encompasses) the sealants 20 and 40. The optical cover 1 has a cavity (space) inside that can accommodate the gas G to be detected, and the gas G to be detected is introduced into and out of the cavity via the gas introduction port 11. The base material of the optical cover 1 is, for example, made of resin.

[0028] As shown in Figure 2, the optical cover 1 has cover portions 110A and 110B. Cover portion 110A is the upper (+z direction) part and is integrated with cover portion 110B by methods such as bonding or heat crimping. Cover portion 110B is the lower (-z direction) part and is integrated with cover portion 110A by methods such as bonding or heat crimping.

[0029] Furthermore, as shown in Figure 3, the optical cover 1 has a light guide section 13, which is a cavity into which the gas G to be detected is introduced. The light guide section 13 is a pipe-shaped optical path, with a circular cross-section perpendicular to the axial direction. Cover section 110A has a half-pipe section. Cover section 110B also has a half-pipe section. The light guide section 13 is formed by the joining of the half-pipe sections of cover sections 110A and 110B. Thus, the optical cover 1 has cover sections 110A and 110B, which are divided by the axial cross-section of the light guide section 13. As shown in Figure 3, the light guide section 13 has a roughly U-shape in three dimensions when viewed from the +z direction (in an xy-plane view).

[0030] The inner surface of the light guide section 13 is covered with an infrared reflective film. In this embodiment, gold is used as the infrared reflective film, but it is not limited to this. Silver or aluminum may also be used as the infrared reflective film. Furthermore, if necessary, a protective film such as silicon oxide or silicon nitride may be formed on the infrared reflective film to prevent corrosion of the metal film of the infrared reflective film. Methods for forming the infrared reflective film and protective film include plating, sputtering, and vacuum deposition. For example, the optical cover 1 may be integrally fabricated from a metal such as aluminum using a metal 3D printer. In any case, it is preferable to have a mirror finish on the inner surface of the light guide section 13 in order to efficiently reflect infrared rays.

[0031] The light guide unit 13 reflects the infrared light emitted from the light source 2 of the sealing device 20 and incident via the optical filter 30 with the infrared reflective film on its inner surface. The light guide unit 13 then emits the reflected infrared light to the light receiving units 41 and 42 via the optical filters 31 and 32 of the sealing device 40. In this way, the optical cover 1 plays the role of efficiently guiding the infrared light from the light source 2 to the light receiving units 41 and 42 as an optical path, by reflecting the infrared light emitted from the light source 2 with the infrared reflective film, so that at least a portion of the reflected light reaches the light receiving units 41 and 42 via the optical filters 31 and 32.

[0032] In this embodiment, the optical path inside the optical cover 1 is made of a light guide section 13 with a circular pipe shape and a cross-section perpendicular to the axial direction. This keeps the infrared reflection angle constant in all three dimensions (x-axis, y-axis, z-axis) regardless of the diameter of the cross-section of the light guide section 13, allowing the infrared light emitted from the light source 2 to be reflected inside the light guide section 13 and efficiently enter the light receiving sections 41 and 42. The cross-section of the light guide section 13 of the optical cover 1 perpendicular to the axial direction of the optical path may be elliptical or a shape that combines curves and straight lines.

[0033] Furthermore, the length of the infrared light path from the light source 2 to the light receiving units 41 and 42 can be changed relatively easily by changing the diameter of the cross-section of the light guide unit 13.

[0034] Furthermore, the cross-sectional area of ​​the light guide section 13 perpendicular to the axial direction is constant in the axial direction for the main part (parts other than the inlet section 131 and outlet section 132, which will be described later). Because the cross-sectional area is constant, the gas concentration per unit volume is easily homogenized for the gas G to be detected that enters the light guide section 13, and because the infrared rays do not pass through a specific path but randomly, it is highly responsive to changes in the gas concentration of the gas G. Figure 3 shows the optical path propagation state, with multiple infrared light lines within the light guide section 13 represented by solid arrows. In this way, the infrared light lines are random within the light guide section 13.

[0035] Further, infrared light emitted from the light source 2 of the sealing member 20 is incident on the light guide portion 13 on the -x direction side via the optical filter 30. The light guide portion 13 on the -x direction side has an axial direction extending from the -z direction side to the +z direction side, then bends in an R-shape, and extends linearly from the -y direction side to the +y direction side. The end portion of the light guide portion 13 on the infrared incident side is defined as an inlet portion 131. The light guide portion 13 extending toward the +y direction side bends in an R-shape, has an axial direction extending from the -x direction side to the +x direction side, and bends in an R-shape again.

[0036] Then, the light guide portion 13 on the +x direction side has an axial direction extending linearly from the +y direction side to the -y direction side, then bends in an R-shape, and extends toward the -z direction side. The infrared light passing through the light guide portion 13 is emitted to the light receiving portions 41 and 42 via the optical filter 32 of the sealing member 40. The end portion of the light guide portion 13 on the infrared emission side is defined as an outlet portion 132.

[0037] The outlet portion 132 has a tapered shape in which the cross-sectional area becomes smaller as the axial direction of the light guide portion 13 goes from the +z direction side to the -z direction side. Similarly, the inlet portion 131 has a tapered shape in which the cross-sectional area becomes smaller as the axial direction of the light guide portion 13 goes from the +z direction side to the -z direction side. For this reason, the condensing degree of the infrared light radiated to the light receiving portions 41 and 42 through the light guide portion 13 can be increased.

[0038] Further, the cover portions 110A and 110B have hollow portions (not shown) as spaces for lightening (material reduction). Weight reduction of the optical cover 1 (the optical gas sensor device 100) can be achieved by these hollow portions.

[0039] Further, the cover portion 110B has fixing pins 121 and 122. The fixing pins 121 and 122 are convex portions extending in the +z direction, and are abutted against concave portions (female holes) (not shown) of the cover portion 110A and integrated by a method such as adhesion or thermal caulking. By the integration achieved by a method such as adhesion or thermal caulking in which the fixing pins are abutted against the concave portions of the cover portion 110A, the cover portions 110A and 110B are positioned, fixed, and formed into an integrated component.

[0040] Furthermore, as shown in Figure 2, the cover portion 110A has gas inlet ports 111 and 112 as gas introduction ports 11. The gas inlet ports 111 and 112 are holes drilled in the -z direction from the upper surface of the cover portion 110A. The space around the sealing device 20 is electrically connected to the light guide portion 13. The space around the sealing device 40 is electrically connected to the light guide portion 13.

[0041] The gas inlets 111 and 112 are connected to the light guide section 13 via the gas inlets 133 and 134. The gas taken in from the gas inlets 111 and 112 enters the inner space of the optical cover 1 and is then introduced into the light guide section 13 through the gas inlets 133 and 134. Here, the gas inlets 133 and 134 are positioned such that, when viewed from above, the line connecting the centers of the gas inlets 111 and 112 and the centers of the gas inlets 133 and 134 forms a 45-degree angle with respect to the x-axis. Note that the shape, size, and position of the gas introduction port 11 (gas inlets 111 and 112) of the optical cover 1 in Figure 2 are examples only and are not limited thereto.

[0042] As shown in Figure 4, the sealing device 20 is mounted on the substrate 6 and seals the light source 2 inside the sealing device 20. The sealing device 20 protects the light source 2 from external environmental factors such as humidity and environmentally harmful gases inside and outside the sealing device 20, i.e., the space enclosed by the cover portions 110A and 110B. Inside the sealing device 20, the light source 2 is mounted by bonding it to the bottom (bottom surface 213) of the space enclosed by the protective cover, for example, the ceramic substrate 21 in this embodiment, using an adhesive portion (not shown), and the optical filter 30 is bonded and sealed to the upper surface of the ceramic substrate 21 with adhesive 33.

[0043] The ceramic substrate 21 is made of, for example, aluminum oxide (alumina) and protects the light source 2 from the sides and bottom. The ceramic substrate 21 is mounted on the bottom of the seal 20 or directly on the substrate 6. The ceramic substrate 21 also has no ventilation holes and the optical filter 30 is mounted on it.

[0044] The ceramic substrate 21 has recesses 211 and 212. Recess 211 is a recess located on the upper surface (+z direction) side, and the planar shape of its opening is approximately rectangular. Recess 212 is a recess located on the lower surface (-z direction) side of recess 211, and the planar shape of its opening is approximately rectangular and smaller than that of recess 211. Recess 212 has a bottom surface 213, and the light source 2 is bonded and mounted on the bottom surface 213. The ceramic substrate 21 electrically connects the terminals of the light source 2 and wire-bonded terminals to the terminals of the substrate 6, for example, by through holes.

[0045] The optical filter 30 is an AR (Anti-Reflection) filter or another type of optical filter. An AR filter is a filter that prevents the reflection of infrared rays and allows them to pass through. The optical filter 30 is placed over the entire surface of the upper surface of the ceramic substrate 21 so as to cover the opening on the upper surface, and is attached to the ceramic substrate 21 with adhesive 33. The adhesive 33 is an epoxy resin or silicone resin for hermetically sealing the light source 2. The adhesive 33 may be a glass frit material for sealing the light source 2, or a preform or paste of a metallic material such as AuSn or solder. In the case of a metallic material, it is desirable to apply metallization such as Cr / Pt / Au, Cr / Ni / Au, or Ti / Ni / Au to the bonding area between the ceramic substrate 21 and the optical filter 30 to ensure adhesion.

[0046] As shown in Figure 5, the light source 2 is a MEMS (Micro Electro Mechanical Systems) type light source mounted on the upper surface (the surface in the +z direction) of the bottom surface 213. The light source 2 has a membrane structure M formed on a Si support layer 201. The membrane M is formed such that a planar heater layer 202 covers the membrane M.

[0047] The light source 2, when viewed from the +z direction (in an xy-plane view), has a light source region 230 and electrode pads P1 and P2. The light source region 230 is a region that functions as a light source in a substantially rectangular shape and has electrodes 231 and 232. Electrode 231 extends in the y-axis direction and is located on the +x direction side of the light source region 230. Electrode 231 is electrically connected to electrode pad P1 via wiring. Electrode 232 extends in the y-axis direction and is located at the -x direction end of the light source region 230. Electrode 232 is electrically connected to electrode pad P2 via wiring.

[0048] The light source 2 has a cross-sectional configuration in which, for example, a Si support layer 201, a heater layer support layer, a heater layer 202, electrodes 231, 232, an electrode support layer, and a protective layer (those without a sign are not shown) are stacked in order from the -z direction to the +z direction. The heater layer support layer, electrode support layer, and protective layer are insulating layers that sandwich the heater layer 202 above and below in the z-axis direction.

[0049] The Si support layer 201 is a substrate made of Si and serves as a support layer for the membrane M of the light source 2. The Si support layer 201 has a circular space (cylindrical shape) when viewed from the -z direction. The space is surrounded on all four sides by the outer frame of the Si support layer 201. Therefore, the light source 2 has a circular membrane M on the xy plane perpendicular to the film thickness direction (z-axis direction). The membrane M covers the space from the upper surface (+z direction side) of the outer frame.

[0050] The heater layer support layer has, for example, a silicon oxide film, a silicon nitride film, and a silicon oxide film from the -z direction to the +z direction. The silicon oxide film is silicon dioxide (SiO₂) as an insulator (dielectric). ２ It is a thin film made of ). Alternatively, the membrane M may have no silicon oxide film on the -z direction side. The silicon nitride film is silicon nitride (Si) as an insulator (dielectric). ３ N ４ It is a thin film made of SiO. ２It is a thin film formed of. The heater layer 202 is a thin film heater serving as a light source (metal) layer, which generates heat when energized and heats the membrane M. The heated membrane M emits infrared radiation having intensity and wavelength dependency that depend on the surface temperature and surface emissivity. The heater layer 202 is made of, for example, molybdenum disilicide (MoSi ２ ). However, the heater layer 202 is not limited to this, it may be formed of molybdenum (Mo), MoSi composed of Mo and Si ２ which is a compound with a different composition ratio, tungsten (W), tungsten disilicide (WSi ２ ), WSi composed of W and Si ２ which is a compound with a different composition ratio, platinum (Pt), titanium (Ti), gold (Au), silver (Ag), nickel chromium (NiCr), nickel (Ni), aluminum (Al), copper (Cu), titanium nitride (TiN), polycrystalline silicon (PolySilicon), or other materials. The heater layer 202 is formed in a rectangular shape wider than the outer shape of the circular space on the xy plane, so as to equalize the tensile stress in the membrane M region.

[0051] The electrodes 231 and 232 are made of a metal such as aluminum-silicon alloy (Al-Si), and are arranged to be electrically connected to the heater layer 202. The electrode support layer is made of SiO ２ and supports the electrodes 231 and 232. The protective layer is made of Si ３ N ４ and protects the lower layer including the electrode support layer from external disturbances. The electrodes 231 and 232 are exposed on the +z direction side from the upper surface of the protective layer.

[0052] The membrane M is a film-shaped portion on the xy plane, formed of each layer except the Si support layer 201 among the plurality of layers of the light source 2. That is, the membrane M has, in order from the -z direction side to the +z direction side, for example, a silicon oxide film, a silicon nitride film, a silicon oxide film, the heater layer 202, the electrode support layer, and the protective layer.

[0053] The heater layer 202 is electrically connected to electrodes 231 and 232. Electrode pads P1 and P2 are electrode pads for wire bonding, with electrode pad P1 electrically connected to electrode 231 and electrode pad P2 electrically connected to electrode 232. Electrode pads P1 and P2 are wire-bonded to the terminals of the wiring pattern on the substrate 6, and the heater layer 202 is energized by the application of voltage.

[0054] Light source 2, as a MEMS-type light source, is small and low-profile, enabling miniaturization of the sensor module. Furthermore, light source 2, as a MEMS-type light source, has features such as long lifespan, low power consumption, and short response time, contributing to low overall power consumption of the sensor module. The short response time of the MEMS-type light source allows for reduced standby time after power-on when performing intermittent operation, thereby lowering average power consumption.

[0055] Furthermore, since light source 2, as a MEMS-type light source, can directly utilize synchrotron radiation from the high-temperature surface, it can also be applied to the detection of gases with absorption bands at high wavelengths. In addition, the infrared radiation-emitting region of light source 2 is precisely patterned as a membrane M on the plane of the Si support layer 201, resulting in very small individual variations in the radiation direction. Therefore, variations in the amount of light received when light source 2 is used to construct a sensor module are reduced, contributing to improved product yield. Moreover, since light source 2 is mass-producible because it is produced in bulk using MEMS technology based on a silicon wafer, it offers excellent mass-production capabilities.

[0056] Furthermore, because the membrane M of the light source 2 is circular in shape on the xy plane and located within the region of the heater layer 202, the thermal stress generated during heating becomes uniform, improving mechanical strength. As a result, damage to the membrane M due to thermal stress during operation is suppressed in the light source 2, contributing to an extended product life.

[0057] The light source 2 is mounted on the bottom surface 213 of the sealant 20 and wire-bonded. The electrode pads P1 and P2 are electrically connected to the terminals of the recesses 211 of the sealant 20 via wires.

[0058] The optical filter 31 is a bandpass filter acting as a λ-selective filter, provided to cover the light-receiving surface of the light-receiving unit 41, and transmits light (infrared) of wavelength λ corresponding to the absorption wavelength unique to the gas G to be detected. In this way, the transmission wavelength of the optical filter 31 is designed to match the unique absorption wavelength of the gas G to be detected. As a result, changes in light intensity caused by gases other than the gas G to be detected are suppressed, and the signal-to-noise ratio of the detection signal of the light-receiving unit 41 is improved.

[0059] The optical filter 31 includes, for example, a silicon substrate as a base material and a dielectric multilayer film, or a multilayer film made of an infrared-transmitting material such as Si, Ge, sulfide, and fluoride. The silicon substrate is a planar silicon substrate. However, the material of the substrate is not limited to silicon, but can also be germanium (Ge), quartz (SiO ２ ), alumina (Al ２ O ３ ), barium fluoride (BaF ２ ), calcium fluoride (CaF ２ ) and the like can be used. A multilayer film is a plurality of layered films provided on both sides of a silicon substrate.

[0060] The optical filter 32 is a bandpass filter provided to cover the light-receiving surface of the light-receiving unit 42, and has transmission characteristics at wavelengths that do not match the absorption wavelength of the gas G to be detected, and preferably do not match the absorption wavelength of any gas species. The optical filter 32, for example, similar to the optical filter 31, has a silicon substrate as a base material and a multilayer film.

[0061] The sealing device 40, like the sealing device 20, is mounted on the substrate 6 and includes a ceramic substrate 400 as a container portion similar to the ceramic substrate 21, and optical filters 31, 32 and light receiving units 41, 42 mounted on the ceramic substrate 400.

[0062] The light-receiving units 41 and 42 are surface-mount components mounted on the +z side of the bottom surface 403 of the ceramic substrate 400 (described later) of the sealing device 40. They detect the amount of incident infrared light and output a detection signal as an analog electrical signal. The light-receiving units 41 and 42 are, for example, MEMS elements of a thermopile-type optical sensor (infrared sensor) having multiple thermocouples. However, the light-receiving units 41 and 42 are not limited to thermopile-type infrared sensors, but may also be quantum-type (cooled) phototubes, photoconductive-type, or photovoltaic-type infrared sensors, or thermal-type (uncooled) pyroelectric-type, thermocouple-type, or bolometer-type infrared sensors.

[0063] Here, the configurations of the light-receiving units 41 and 42 will be described with reference to Figures 6 and 7. Since the light-receiving unit 42 has the same configuration as the light-receiving unit 41, the light-receiving unit 42 will be described as a representative example. The light-receiving unit 41 has a structure in which a membrane M1 is formed on a Si support layer 410, similar to the light source 2. The membrane M1 is rectangular in plan view. Also, similar to the membrane M1 of the light-receiving unit 41, the light-receiving unit 42 has a membrane M2.

[0064] As shown in Figure 6, the light-receiving unit 41, in plan view, has electrode pads P11, P12, and P13, and thermopiles 411, 412 and contact portions 413, 414, and 415 on the membrane M1. Electrode pad P11 is an electrode pad at an intermediate potential. Electrode pad P12 is an electrode pad on the high potential side. Electrode pad P13 is an electrode pad on the low potential side. Thermopile 411 is a plurality of wires of a predetermined type of conductor. Thermopile 412 is a plurality of wires of a different type of conductor than thermopile 411. A pair of thermopiles 411 and 412 constitutes a thermocouple. Thermopiles 411 and 412 each generate an electromotive force when irradiated with infrared light. Contact portion 413 is the terminal portion on the high potential side of thermopile 411.

[0065] As shown in Figure 7, the light receiving unit 41 is equivalent to a circuit consisting of electrode pads P11, P12, P13, resistor elements 501, 502, and electromotive force units 503, 504. Resistor element 501 is the resistance of the thermopile 411. Resistor element 502 is the resistance of the thermopile 412. Electromotive force unit 503 generates the electromotive force of the thermopile 411 (which varies depending on the conditions). Electrode pad P11 is connected to electrode pad P13 via the electromotive force unit 503 and resistor element 501 in that order. Electrode pad P11 is connected to electrode pad P12 via the electromotive force unit 504 and resistor element 502 in that order. In the subsequent circuit (not shown), by differential amplification of the voltage between electrode pads P11 and P13 and the voltage between electrode pads P11 and P12, common-mode noise is canceled out and the signal-to-noise ratio can be improved.

[0066] The signal processing unit 5 is mounted on a planar area of ​​the substrate 6 other than the optical cover 1 on the +z side surface, and is an AFE (Analog Front End)-IC (Integrated Circuit) that performs signal processing related to the detection signals of the light receiving units 41 and 42. The signal processing unit 5 amplifies the analog detection signals of the light receiving units 41 and 42 and performs AD (Analog to Digital) conversion, and when the light source 2 is driven intermittently, it generates a difference value between the detection value when the light source 2 is ON and the detection value when the light source 2 is OFF. The signal processing unit 5 corrects the difference value of the detection values ​​for temperature and individual variations of the optical gas sensor device 100, and generates various status signals from the digital difference value of the detection values. The signal processing unit 5 outputs the digital difference value of the detection values ​​and the status signals.

[0067] The substrate 6 is an FR-4 (Flame Retardant type-4) PCB (Printed Circuit Board) with conductive wiring printed on a board made of glass epoxy resin or the like. The optical cover 1, sealants 20 and 40, signal processing unit 5, and circuit element unit 8 are mounted on the +z side of the substrate 6. The +z side of the substrate 6 and the light-emitting surface of the light source 2, and the light-receiving surfaces of the optical filters 30, 31, and 32 and light-receiving units 41 and 42 are approximately parallel. Thus, the sealant 20 (light source 2) and the sealant 40 (light-receiving units 41 and 42) may be on the same plane. By placing the sealants 20 and 40 on the same plane, the shape of the optical cover 1 can be simplified, and manufacturing costs can be reduced.

[0068] Furthermore, a connector (not shown) may be mounted on the circuit board 6. The connector is mounted on a planar area on the +z side surface of the circuit board 6, excluding the optical cover 1 and the signal processing unit 5, and is used to output various digital signals output from the signal processing unit 5 to the information processing unit of a subsequent device. The connector is connected to the information processing unit of the device via a cable with a plug.

[0069] The circuit element section 8 is mounted on the planar area of ​​the substrate 6 on the +z side surface other than the optical cover 1, and consists of circuit elements such as switches 81, amplifiers, chip resistors, and chip capacitors.

[0070] Here, with reference to Figures 8 to 16, the sealants 40, 40a, and 40b will be described as specific first to third embodiments of the sealant 40 of the embodiment. Figure 8 is a top view of the sealant 40 of the first embodiment. Figure 9 is a cross-sectional view of the sealant 40 of the first embodiment. Figure 10 is a cross-sectional view of the sealant 40 of the first embodiment. Figure 11 is a top view of the sealant 40a of the second embodiment. Figure 12 is a cross-sectional view of the sealant 40a of the second embodiment. Figure 13 is a cross-sectional view of the sealant 40a of the second embodiment. Figure 14 is a top view of the sealant 40b of the third embodiment. Figure 15 is a cross-sectional view of the sealant 40b of the third embodiment. Figure 16 is a cross-sectional view of the sealant 40b of the third embodiment.

[0071] (First Embodiment) The first embodiment of the sealant 40 will be described with reference to Figures 8 to 10. Figure 9 is a cross-sectional view of the sealant 40 in Figure 8 along the line IX-IX. Figure 10 is a cross-sectional view of the sealant 40 in Figure 8 along the line XX. As shown in Figures 8 to 10, the ceramic substrate 400 of the sealant 40 has recesses 401, recesses 402, and a bottom surface 403 as openings, similar to the recesses 211, 212 and bottom surface 213 of the ceramic substrate 21, and has terminals 404 and wires 405. Terminals 404 are metal terminals for light-receiving parts 41 and 42 formed on the bottom surface portion of recess 401, and are electrically connected to terminals of the substrate 6 via through holes or the like. Wires 405 are formed by wire bonding and are metal wires that electrically connect the electrode pads P11, P12, P13 of the light-receiving parts 41 and 42 to terminals 404.

[0072] The light-receiving units 41 and 42 may be mounted adjacent to each other within cavities formed by recesses 401 and 402 on a single ceramic substrate 400, and mounted on the same plane on the bottom surface 403 using adhesive 407. By placing the light-receiving unit 41 as the first light-receiving unit and the light-receiving unit 42 as the second light-receiving unit on the same plane, the difference in distance from the light source 2 can be eliminated, improving measurement accuracy, and the same applies to the second and third embodiments. The light-receiving units 41 and 42 are arranged such that the direction of the wires 405 extending from the electrode pads P11, P12, and P13 to the terminal 404 is opposite to each other on the y-axis. Therefore, the electrode pads P11, P12, and P13 of the light-receiving units 41 and 42 and the terminal 404 of the ceramic substrate 400 can be electrically connected with the wires 405 without them touching each other and with the wires 405 being short. In this way, the electrode pads P11, P12, and P13 and the terminal 404 can be connected accurately and reliably.

[0073] The optical filters 31 and 32 are attached (placed) to the frame portion 406, which is the uppermost surface (the surface closest to the +z direction) of the ceramic substrate 400, using an adhesive. The adhesive is made of the same material as adhesive 33, for example. Optical filter 31 is positioned in a shape (rectangular) that covers approximately half of the recess 401, including the light-receiving surface (membrane M1) of the light-receiving unit 41, on the +x direction side. Optical filter 32 is positioned in a shape (rectangular) that covers approximately half of the recess 401, including the light-receiving surface (membrane M2) of the light-receiving unit 42, on the -x direction side. In other words, optical filters 31 and 32 are two optical filters with different characteristics, and each is positioned over the entire upper surface of the light-receiving units 41 and 42. As a result, a gap is formed between the optical filters 31 and 32, and the light-receiving units 41 and 42 are substantially sealed.

[0074] The optical filters 31 and 32 may be a single optical filter, with optical filter sections having different characteristics formed by dividing the region. In this configuration, the optical filters 31 and 32 are formed without gaps, and the light-receiving sections 41 and 42 are completely sealed.

[0075] (Second Embodiment) The sealing device 40a of the second embodiment will be described with reference to Figures 11 to 13. Figure 12 is a cross-sectional view of the sealing device 40a of Figure 11 along the line XII-XII. Figure 13 is a cross-sectional view of the sealing device 40a of Figure 11 along the line XIII-XIII.

[0076] As shown in Figures 11 to 13, the sealing device 40a comprises a ceramic substrate 400, light-receiving sections 41 and 42, and optical filters 31a and 32a. Optical filter 31a is attached to the upper surface (the +z direction side) of the light-receiving section 41 with adhesive (not shown). Optical filter 31a is a bandpass filter having the same transmission characteristics as optical filter 31, and is positioned in a shape (rectangular) that covers at least the membrane M1 which serves as the light-receiving surface of the light-receiving section 41. Optical filter 32a is attached to the upper surface of the light-receiving section 41 with adhesive. Optical filter 32a is a bandpass filter having the same transmission characteristics as optical filter 32, and is positioned in a shape (rectangular) that covers at least the membrane M2 of the light-receiving section 42.

[0077] Therefore, the optical filters 31a and 32a can obtain the same transmission characteristics as the optical filters 31 and 32, but with a smaller area than the optical filters 31 and 32, thereby further reducing manufacturing costs. In addition, the sealant 40a can be made lower in profile than the sealant 40.

[0078] Furthermore, when mounting the sealant 40a, a flat lid may be mounted on the frame portion 406 of the ceramic substrate 400, and the sealant 40a with the lid mounted may be mounted on the substrate 6. This protects the wire 405 and allows for substrate mounting using a surface mount collet.

[0079] (Third Embodiment) The sealing device 40b of the third embodiment will be described with reference to Figures 14 to 16. Figure 15 is a cross-sectional view of the sealing device 40b of Figure 14 along the line XV-XV. Figure 16 is a cross-sectional view of the sealing device 40b of Figure 14 along the line XVI-XVI.

[0080] As shown in Figures 14 to 16, the sealing device 40b comprises a ceramic substrate 400, light-receiving sections 41 and 42, and optical filters 31b and 32b. In Figures 14 to 16, the thickness of the optical filters 31b and 32b is shown to be thicker than the actual thickness for easier identification in the drawings. Similarly, the thickness of the optical filters 31 and 32 in Figures 8 to 10, and the thickness of the optical filters 31a and 32a in Figures 11 to 13 are also shown to be thicker than the actual thickness. The optical filter 31b is formed on the membrane M1, which serves as the light-receiving surface (upper surface on the +z direction side) of the light-receiving section 41. The optical filter 31b is formed, for example, by masking the parts of the membrane M1 other than those where film deposition is required, and then performing the film deposition process. The optical filter 31b is a bandpass filter having the same transmission characteristics as the optical filter 31. The optical filter 31b is positioned in a shape (rectangular) and location that covers at least the central part of the membrane M1. The optical filter 32b is formed on the membrane M2, which serves as the light-receiving surface of the light-receiving section 41. Like the optical filter 31b, the optical filter 32b is formed by, for example, masking the parts of the membrane M2 other than those where film deposition is required, and then performing the film deposition process. The optical filter 32b is a bandpass filter having the same transmission characteristics as the optical filter 32. The optical filter 32b is positioned in a shape (rectangular) and location that covers at least the central part of the membrane M2.

[0081] As shown in Figure 6, in the light-receiving section 41, the thermopiles 411, 412 and contact portion 414, which are the detection components of the thermocouple, are concentrated in the center of the membrane M. Therefore, the optical filter 31b is formed to cover the center of the membrane M1 of the light-receiving section 41. The optical filter 32b is formed to cover the center of the membrane M2 of the light-receiving section 42. Thus, the optical filters 31b and 32b can obtain the same transmission characteristics as the optical filters 31 and 32, while also being able to reduce their area even further than the optical filters 31a and 32a, thereby further reducing manufacturing costs. In addition, the sealant 40b can be made lower in height than the sealant 40.

[0082] The optical filter 31b may also be a notch filter that attenuates light (infrared) corresponding to the absorption wavelength of the gas G to be detected. A notch filter generates heat when it attenuates (absorbs) light. Since the optical filter 31b is formed on the membrane M1 of the light receiving unit 41, the light receiving unit 41 can detect the generated heat and generate a detection signal, which is output as a detection signal for the gas G to be detected. Therefore, the optical filter 31b of the notch filter only needs to cover the central part of the membrane M1 where the detection components are concentrated, and like the optical filter 31b of the bandpass filter, its area can be made even smaller, further reducing manufacturing costs.

[0083] In this case, the optical filter 32b may be a notch filter that attenuates (absorbs) wavelengths that do not match the absorption wavelength of the gas G to be detected and preferably do not match the absorption wavelength of any gas species. Since the optical filter 32b is formed on the membrane M2 of the light-receiving unit 42, the light-receiving unit 42 can detect the generated heat and generate a detection signal, which is output as a detection signal for the reference light. Therefore, the optical filter 32b of the notch filter only needs to cover the central part of the membrane M2 where the detection components are concentrated, and its area can be made even smaller, similar to the optical filter 32b of the bandpass filter, and manufacturing costs can be further reduced.

[0084] Furthermore, similar to the sealing device 40a, when mounting the sealing device 40b, a flat lid may be mounted on the frame portion 406 of the ceramic substrate 400, and the sealing device 40b with the lid mounted may be mounted on the substrate 6.

[0085] Table I summarizes the features and effects of the sealing devices 40 to 40b of the first to third embodiments.

[0086] As described above, according to this embodiment, the optical gas sensor device 100 comprises a light source 2, optical filters 31 and 32, light receiving units 41 and 42, and one ceramic substrate 400. The light source 2 emits infrared light to the gas G to be detected. The optical filter 31 transmits the absorption wavelength of the gas G among the infrared light emitted from the light source 2 and transmitted through the gas G to be detected. The light receiving unit 41 detects the infrared light incident through the optical filter 31 and generates a detection signal. The optical filter 32 transmits wavelengths that do not match the absorption wavelength of the gas G among the infrared light emitted from the light source 2 and transmitted through the gas G to be detected. The light receiving unit 42 detects the infrared light incident through the optical filter 31 and generates a detection signal. The ceramic substrate 400 houses the light receiving units 41 and 42. Compared to a configuration in which the light receiving units 41 and 42 are each mounted on different ceramic substrates, the optical gas sensor device 100 can use fewer ceramic substrates (one).

[0087] Therefore, in the reference light type optical gas sensor device 100, the optical filters 31 and 32 can be made smaller, reducing costs and making the optical gas sensor device 100 inexpensive. In addition, the area of ​​the encapsulant 40, which is a package including the two light-receiving units 41 and 42, can be reduced. Furthermore, by placing the two light-receiving units 41 and 42 in close proximity and mounting them on a ceramic substrate 400 with good thermal conductivity, the temperature difference between the light-receiving units 41 and 42 is reduced, improving the stability of the measurement. Moreover, surface mount technology can be applied to mounting the chips (light-receiving units 41 and 42) onto the ceramic substrate 400 and to mounting the encapsulant 40 as a chip-mounted package onto the substrate, allowing the optical gas sensor device 100 to be mass-produced at a lower cost.

[0088] Furthermore, according to the first embodiment, optical filter 31 transmits the absorption wavelength of the gas G to be detected. Optical filter 32 transmits wavelengths that do not match the absorption wavelength of the gas G to be detected. Optical filters 31 and 32 are placed on a frame portion 406 that surrounds a recess 401 which serves as an opening in the ceramic substrate 400, and cover the recess 401. Optical filters 31 and 32 are two optical filters that are separated from each other. Therefore, the cost of optical filters can be reduced.

[0089] Furthermore, according to the first embodiment, the optical filters 31 and 32 may be composed of a single optical filter. This makes it easier to perform tasks such as mounting the optical filters 31 and 32, and also allows for better sealing of the light-receiving sections 41 and 42 within the ceramic substrate 400.

[0090] Furthermore, according to the second embodiment, the optical filter 31a transmits the absorption wavelength of the gas G to be detected. The optical filter 32a transmits wavelengths that do not match the absorption wavelength of the gas G to be detected. The optical filter 31a is placed on the membrane M1 which serves as the light-receiving surface of the light-receiving unit 41 and covers the membrane M1. The optical filter 32a is placed on the membrane M2 which serves as the light-receiving surface of the light-receiving unit 42 and covers the membrane M2. Therefore, the optical filters 31a and 32a can obtain the same transmission characteristics as the optical filters 31 and 32, while having a smaller area than the optical filters 31 and 32, thereby reducing costs.

[0091] Furthermore, according to the third embodiment, the optical filter 31b transmits or attenuates the absorption wavelength of the gas G to be detected. The optical filter 32b transmits or attenuates wavelengths that do not match the absorption wavelength of the gas G to be detected. The optical filter 31b is formed on the membrane M1, which serves as the light-receiving surface of the light-receiving unit 41, and covers the central part of the membrane M1. The optical filter 32b is formed on the membrane M2, which serves as the light-receiving surface of the light-receiving unit 42, and covers the central part of the membrane M2. Therefore, the optical filters 31b and 32b only need to cover at least the central parts of the membranes M1 and M2, allowing for an even smaller area than the optical filters 31a and 32a, and further reducing costs.

[0092] Furthermore, the optical gas sensor device 100 includes an optical cover 1. The optical cover 1 covers the light source 2, optical filters 31, 32, light receiving units 41, 42 and ceramic substrate 400, and forms an infrared light path from the light source 2 to the light receiving units 41, 42. As a result, infrared light can be efficiently guided along the light path of the optical cover 1. In particular, the area of ​​the seal 40 including the light receiving units 41, 42 can be reduced, so the optical cover 1 can be made smaller. Also, because the seal 40 is smaller, the diameter of the light path of the optical cover 1 can be reduced. This makes it possible to increase the intensity of light (infrared) reaching the light receiving units 41, 42.

[0093] The above description of the embodiment is merely an example of an optical gas sensor device according to the present invention, and is not limited thereto.

[0094] For example, in the above embodiment, the light source 2 is sealed with a sealing device 20, but the configuration is not limited to this. The light source 2 may also be surface mounted (COB (Chip On Board) mounted) to the substrate 6 via a plurality of adhesive parts.

[0095] Alternatively, the light source 2 may be sealed with a sealant 20, and the light receiving units 41 and 42 may be sealed with sealants 40, 40a, or 40b, and surface-mounted onto a small substrate acting as a child substrate via multiple adhesive parts. The small substrate with the sealant 20 mounted and the small substrate with the sealant 40, 40a, or 40b mounted are mounted onto the substrate 6 acting as a parent substrate.

[0096] Furthermore, the detailed configuration and operation of the optical gas sensor device 100 in the above embodiment can also be modified as appropriate without departing from the spirit of the present invention.

[0097] As described above, the optical gas sensor device according to the present invention is suitable for detecting gases such as refrigerants.

[0098] 100 Optical Gas Sensor Device G Gas 1 Optical Cover 110A, 110B Cover Section 11 Gas Inlet Port 111, 112 Gas Inlet 12 Contamination Filter 13 Light Guide Section 131 Inlet Section 132 Outlet Section 133, 134 Gas Inlet 20, 40, 40a, 40b Sealing Device M, M1, M2 Membrane P1, P2, P11, P12, P13 Electrode Pad 21, 400 Ceramic Substrate 211, 212, 401, 402 Recess 213, 403 Bottom Surface 2 Light Source 201 Si Support Layer 202 Heater Layer 230 Light Source Area 231, 232 Electrodes 30, 31, 32, 31a, 32a, 31b, 32b Optical Filter 33 Adhesive 41, 42 Light receiving part 404 Terminal 405 Wire 406 Frame part 407 Adhesive 410 Si support layer 411, 412 Thermopile 413, 414, 415 Contact part 501, 502 Resistor element 503, 504 Electromotive force part 5 Signal processing part 6 Substrate 8 Circuit element part 81 Switch

Claims

1. An optical gas sensor device comprising: a light source that emits infrared radiation to a gas to be detected; a first optical filter that transmits or attenuates the absorption wavelength of the gas among the infrared radiation emitted from the light source and transmitted through the gas to be detected; a first light receiving unit that detects the infrared radiation incident through the first optical filter and generates a detection signal; a second optical filter that transmits or attenuates wavelengths of infrared radiation emitted from the light source and transmitted through the gas to be detected that do not match the absorption wavelength of the gas to be detected; a second light receiving unit that detects the infrared radiation incident through the second optical filter and generates a detection signal; and a container unit that houses the first light receiving unit and the second light receiving unit.

2. The optical gas sensor device according to claim 1, wherein the first optical filter transmits the absorption wavelength of the gas to be detected, the second optical filter transmits wavelengths that do not match the absorption wavelength of the gas to be detected, and the first optical filter and the second optical filter are placed on a frame surrounding the opening of the container and cover the opening.

3. The optical gas sensor device according to claim 2, wherein the first optical filter and the second optical filter are two optical filters separated from each other.

4. The optical gas sensor device according to claim 2, wherein the first optical filter and the second optical filter are a single optical filter.

5. The optical gas sensor device according to claim 1, wherein the first optical filter transmits the absorption wavelength of the gas to be detected, the second optical filter transmits wavelengths that do not match the absorption wavelength of the gas to be detected, the first optical filter is placed on the light-receiving surface of the first light-receiving unit and covers the light-receiving surface of the first light-receiving unit, and the second optical filter is placed on the light-receiving surface of the second light-receiving unit and covers the light-receiving surface of the second light-receiving unit.

6. The optical gas sensor device according to claim 1, wherein the first optical filter is formed on the light-receiving surface of the first light-receiving unit and covers the central part of the light-receiving surface of the first light-receiving unit, and the second optical filter is formed on the light-receiving surface of the second light-receiving unit and covers the central part of the light-receiving surface of the second light-receiving unit.

7. An optical gas sensor device according to any one of claims 1 to 6, comprising an optical cover that covers the light source, the first optical filter, the second optical filter, the first light receiving unit, the second light receiving unit, and the container unit, and forms the optical path of the infrared light from the light source to the first light receiving unit and the second light receiving unit.

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