Optical gas sensor device

Abstract

The purpose of the present invention is to improve detection accuracy of a gas to be detected using infrared rays passing through an optical path accompanying reflection. This gas sensor device is provided with: a light source (2) that emits infrared rays toward a gas to be detected; an optical filter (3) that is a long-pass filter having an initial wavelength smaller than the center wavelength of the absorption wavelength band of the gas to be detected and a transmission wavelength including the center wavelength, and that transmits infrared rays that have passed through the gas to be detected; a light receiving unit (4) that detects the infrared rays incident through the optical filter (3) and generates a detection signal; and an optical cover (1) that covers the light source, the optical filter, and the light receiving unit (4). The optical cover (1) is provided with a light guide part (13) which guides infrared rays incident from a light source (2) to a light receiving part (4) through an optical filter (3) by reflection of the inner surface, and the light guide part (13) is in a tube shape and has a circular or elliptical cross section perpendicular to the axial direction.

Description

Technical Field

[0001] This invention relates to an optical gas sensor device. Background Technology

[0002] Previously, gas sensors based on non-dispersive infrared (NDIR) absorption were known. NDIR gas sensors utilize the property that a large number of gases absorb inherent infrared wavelengths separately. When infrared light is emitted towards the gas to be detected, the sensor detects which wavelength is absorbed and how much, thereby measuring the concentration of the gas. For example, a gas sensor may have an infrared emitting part and a light-receiving part, and detect the concentration of the gas to be detected along the optical path located in the emitting and receiving parts.

[0003] Furthermore, in air conditioners that use refrigerant, a refrigerant leak detection device is known that uses an infrared sensor to detect the refrigerant concentration and detect refrigerant leaks (see Patent Document 1). This infrared sensor includes: a light-emitting part, a light-receiving part disposed opposite the light-emitting part, and an optical filter disposed between the light-emitting part and the light-receiving part. The optical filter allows infrared light to pass through a specific wavelength that is absorbed by the refrigerant.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-28392 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Regarding the refrigerant leak detection device in Patent Document 1, the light-emitting part and the light-receiving part are arranged opposite each other, so the incident angle of infrared light onto the optical filter and the light-receiving part is approximately 0°. Furthermore, in order to extend the optical path length for the reaction between infrared light and gas and to miniaturize the gas sensor, a structure is considered that accompanies the reflection of the infrared light along the optical path from the light-emitting part to the light-receiving part. In this reflected path structure, the proportion of infrared light with an incident angle other than 0° that reaches the light-receiving part is increased.

[0009] Conventional optical filters for gas sensors use bandpass filters that allow infrared light, representing the wavelength of maximum absorption in the absorption spectrum of the gas being detected, to pass through. However, as the incident angle of infrared light incident on the light-receiving section via the bandpass filter moves away from 0°, the center wavelength of the infrared absorption band shifts towards shorter wavelengths. Consequently, the absorption band of the infrared light deviates from the transmission band of the bandpass filter, resulting in a decrease in the amount of light received by the light-receiving section and potentially reducing the detection accuracy of the gas being detected.

[0010] The objective of this invention is to improve the detection accuracy of gases in a target object by using infrared light that travels through a path of reflected light.

[0011] Methods for solving problems

[0012] To address the aforementioned issues, the optical gas sensor device of the present invention comprises:

[0013] A light source that emits infrared rays toward the gas being detected;

[0014] An optical filter is a long-pass filter having a starting wavelength smaller than the center wavelength of the absorption wavelength band of the gas being detected and a transmission wavelength containing the center wavelength, and allowing infrared radiation passing through the gas being detected to pass through.

[0015] The light-receiving part detects infrared light incident through the optical filter and generates a detection signal;

[0016] An optical cover that covers the light source, the optical filter, and the light-receiving part.

[0017] The optical cover has a light guide portion that guides infrared rays incident from the light source to the light receiving portion via the optical filter through reflection from its inner surface. The light guide portion is tubular in shape and has a circular or elliptical cross section perpendicular to the axial direction.

[0018] Furthermore, the optical gas sensor device of the present invention includes:

[0019] A light source that emits infrared rays toward the gas being detected;

[0020] An optical filter is a bandpass filter that shifts the center wavelength of transmittance at perpendicular incidence (θ = 0°) by a predetermined offset from the wavelength representing maximum absorption in the absorption spectrum of the gas being detected to a higher wavelength side, and allows infrared radiation passing through the gas being detected to pass through.

[0021] The light-receiving part generates a detection signal by detecting infrared light incident through the optical filter;

[0022] An optical cover that covers the light source, the optical filter, and the light-receiving part.

[0023] The optical cover has a light guide portion that guides infrared rays incident from the light source to the light receiving portion via the optical filter through reflection from its inner surface. The light guide portion is tubular in shape and has a circular or elliptical cross section perpendicular to the axial direction.

[0024] Invention Effects

[0025] According to the present invention, the detection accuracy of the gas of the target object can be improved by using infrared light that passes through the light path accompanied by reflection. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an optical gas sensor device according to the first embodiment of the present invention.

[0027] Figure 2 This is a three-dimensional view of an optical gas sensor device.

[0028] Figure 3 It is a three-dimensional view of the optical cover, light source, optical filter, and light-receiving part.

[0029] Figure 4 It is a three-dimensional diagram of the light source.

[0030] Figure 5 This is a top view of an optical gas sensor device.

[0031] Figure 6A This is a cross-sectional view of the optical gas sensor device according to the first embodiment.

[0032] Figure 6B This is a cross-sectional view of a modified optical gas sensor device.

[0033] Figure 7 It is a diagram showing the distribution of the incident angle of light rays towards the light-receiving part.

[0034] Figure 8 This is a graph representing the transmission characteristics of a long-pass filter.

[0035] Figure 9 This is a graph showing the angle dependence of the transmittance of a long-pass filter.

[0036] Figure 10 This is a graph showing the transmission characteristics of a conventional bandpass filter.

[0037] Figure 11 This is a graph showing the angle dependence of transmittance of conventional bandpass filters.

[0038] Figure 12 It is a graph showing the absorption wavelengths of various gases.

[0039] Figure 13 This is a diagram showing the transmission characteristics of the optical filter in the first embodiment.

[0040] Figure 14 This is a graph showing the transmission characteristics of the optical filter of the first comparative example.

[0041] Figure 15This is a graph showing the transmission characteristics of the optical filter of the first embodiment and the absorption spectra of R32 and R1234yf.

[0042] Figure 16 This is a graph showing the transmission characteristics of a conventional bandpass filter.

[0043] Figure 17 This is a graph showing the transmission characteristics of the bandpass filter according to the second embodiment.

[0044] Figure 18 This is a graph showing the transmission characteristics and center wavelength of a bandpass filter in an example. Detailed Implementation

[0045] Hereinafter, the first embodiment, the example, and the second embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the invention is not limited to the examples shown in the drawings.

[0046] (First Implementation)

[0047] Reference Figures 1-15 The first embodiment of the present invention will now be described. First, referring to... Figure 1 The general structure of the optical gas sensor device 100 of this embodiment will be described. Figure 1 This is a schematic diagram of the optical gas sensor device 100 according to this embodiment.

[0048] like Figure 1 As shown, the optical gas sensor device 100 of this embodiment includes: an optical cover 1, a light source 2, an optical filter 3, a light-receiving unit 4, a signal processing unit 5, and a switch 81. The optical gas sensor device 100 is an NDIR-type gas sensor as follows: infrared rays are emitted from the light source 2, and transmitted through the optical path within the optical cover 1 to the gas G of the target gas (measurement target) within the optical cover 1. The molecules of the gas G in the target gas, present in the optical path, absorb the infrared rays, thereby reducing the amount of light reaching the light-receiving unit 4. The infrared rays partially absorbed by the gas G of the target gas are detected by the light-receiving unit 4 via the optical filter 3. The signal processing unit 5 processes the detection signal, detects (measures), and outputs the concentration of the gas G of the target gas. The switch 81 is a switch for turning the light source 2 on / off and is included in the circuit element unit 8 described later. When gas detection is performed, the signal processing unit 5 turns on the light source 2 via the switch 81; when gas detection is completed, the signal processing unit 5 turns off the light source 2 via the switch 81. The optical cover 1 has a gas inlet port 11, which is the outlet for the gas G to be detected. In order to prevent foreign objects from entering, a contamination filter 12 (e.g., a metal mesh filter, a porous resin membrane, etc.) is attached to the gas inlet port 11.

[0049] In particular, the optical gas sensor device 100 uses an optical filter 3 to filter infrared light emitted from the light source 2 towards the gas G to be detected, and the infrared light is received by the light-receiving unit 4. The optical filter 3 is disposed near the light-receiving unit 4 in the optical path upstream of the light-receiving unit 4. Compared with the structure that uses an optical filter to filter infrared light emitted from the light source 2 before emitting it towards the gas G to be detected, this structure only requires filtering using the light-receiving surface of the light-receiving unit 4, thus reducing the area of ​​the optical filter 3 and lowering the cost. Furthermore, it does not receive unfiltered infrared light emitted from sources other than the light source 2, thereby improving the signal-to-noise ratio (SNR) of the sensor. However, the optical gas sensor device 100 can also be configured to use an optical filter 3 to filter infrared light emitted from the light source 2 and emit it towards the gas G to be detected. In this embodiment, the infrared light received by the light-receiving unit 4 via the optical filter 3 is not the light path that directly reaches from the light source 2, but is designed to arrive by reflection from the inner surface of the optical cover 1. Preferably, the higher the reflectivity of the inner surface of the optical cover 1, the higher the utilization efficiency of light (infrared rays).

[0050] An optical gas sensor device 100 detects the gas G, specifically the refrigerant (or alternative Freon) in an air conditioner. Alternative Freons are synthetic compounds (gases) used industrially as replacements for specific Freons (chlorofluorocarbons, CFCs). CFC refrigerants have high ozone depletion potential, contributing to the destruction of the Earth's ozone layer; therefore, replacement with hydrochlorofluorocarbons (HCFCs), which have a low ozone depletion potential, is underway. Furthermore, developed countries are transitioning from HCFC refrigerants to HFC refrigerants (R410A), which have a zero ozone depletion potential.

[0051] CFC, HCFC, and HFC refrigerants are known to have high global warming coefficients, thus contributing to global warming as greenhouse gases. Therefore, research is underway to replace HFC refrigerant (R410A) with HFC refrigerant (R32), which has a lower global warming coefficient.

[0052] The gas G, which is the test object in this embodiment, is a substitute Freon refrigerant. Here, Table I below shows the product groups of air conditioners (types of each product), the main refrigerants that were previously used, the refrigerants that were switched as substitutes, and the refrigerants that were studied as substitutes.

[0053] [Table 1]

[0054] Table I

[0055]

[0056] Furthermore, specific examples of the gas G that is the target of detection in this embodiment are listed in Table II below.

[0057] [Table 2]

[0058] Table II

[0059]

[0060] Table II's flammability classification indicates toxicity and flammability. "A" indicates low toxicity, "2L" indicates slightly flammable, "2" indicates flammable, and "3" indicates highly flammable. Refrigerants with an "0" to the left of their name are the gas G being tested. The refrigerant G being tested is either a single molecule containing at least one F (fluorine) atom, or a mixture of multiple such molecules with different structures, and its flammability classification is "A2L" or higher.

[0061] The substituted Freon exhibits maximum absorption around 9 μm. For example, R32 shows maximum absorption at 9.1 μm, which is the center wavelength of the absorption band. This absorption band originates from the CF bond, a bond unique to Freon, and by using this absorption band, interference caused by the absorption of other gases can be suppressed. Therefore, it is necessary that the gas G to be detected is a refrigerant consisting of a single molecule of a substituted Freon containing at least one F (fluorine) atom or a mixture of multiple molecules with different structures.

[0062] Furthermore, in Table II, for gases with low lower flammability limits but high combustibility, detection is particularly important to prevent accidents such as combustion during gas leaks. Therefore, it is a necessary condition that the refrigerant flammability classification of the gas G being tested is "A2L" or higher.

[0063] Preferably, the optical gas sensor device 100 detects the absorption of infrared light at the wavelength with the highest absorption among multiple absorption wavelengths of the gas G to be detected. For example, when detecting gas G to be detected where R32 is the concentration, the absorption of infrared light at the center wavelength of the absorption wavelength band with the highest absorption among multiple absorption wavelength bands is detected.

[0064] The signal processing unit 5 outputs various status signals based on the detected gas concentration of gas G (e.g., a fault signal indicating a fault state of the optical gas sensor device 100, an alarm signal indicating an abnormal state (alarm state) where the detected gas concentration of gas G requires an alarm, and a monitoring signal (normal signal) indicating that the detected gas concentration of gas G is in a normal state) and the gas concentration (output voltage) or a value corresponding to the concentration as a detection signal of the light receiving unit 4 to the processing unit of the air conditioner and other equipment.

[0065] Next, refer to Figures 2-6B The specific structure of the optical gas sensor device 100 will be described. Figure 2 This is a perspective view of the optical gas sensor device 100. Figure 3 It is a perspective stereoscopic view of the optical cover 1, the light source 2, the optical filter 3, and the light receiving part 4. Figure 4 This is a 3D view of light source 2. Figure 5 This is a top view of the optical gas sensor device 100. Figure 6A This is a cross-sectional view of the optical gas sensor device 100. Figure 6B This is a cross-sectional view of a modified optical gas sensor device 100.

[0066] like Figure 2 , Figure 3 As shown, the optical gas sensor device 100 includes, for example, an optical cover 1, a light source 2, an optical filter 3, a light-receiving unit 4, a signal processing unit 5, a substrate 6, a connector 7, and a circuit element unit 8. Furthermore, in Figure 2 , Figure 3 In the diagram, the x-axis, y-axis, and z-axis of three-dimensional space are used for illustration. These three axes are... Figures 4-6B The same diagram is shown in the middle. Furthermore, in... Figure 2 , Figure 3 , Figures 5-6B The illustration of the contamination filter 12 is omitted in the text.

[0067] The optical cover 1 is a cover that is mounted on the +z side of the substrate 6, covering (including) the light source 2, the optical filter 3, and the light receiving part 4, and forming a cavity (space) inside to accommodate the gas G of the object being detected. The gas G of the object being detected is introduced and discharged relative to the cavity through the gas inlet port 11. The substrate of the optical cover 1 is, for example, made of resin.

[0068] like Figure 2 As shown, the optical cover 1 has cover portions 110A and 110B. Cover portion 110A is the upper (+z direction side) component, which is integrated with cover portion 110B by bonding, thermal riveting, or other methods. Cover portion 110B is the lower (-z direction side) component, which is integrated with cover portion 110A by bonding, thermal riveting, or other methods.

[0069] In addition, such as Figure 3 As shown, the optical cover 1 has a light guide section 13, which serves as a cavity, guiding the gas G of the object to be detected into its interior. The light guide section 13 is a tubular optical path with a circular cross-section perpendicular to the axial direction. Cover section 110A has a semi-tubular section. Cover section 110B has a semi-tubular section. The light guide section 13 is formed by aligning the semi-tubular sections of cover sections 110A and 110B. Thus, the optical cover 1 has cover sections 110A and 110B divided by the axial cross-section of the light guide section 13. Figure 3 As shown, the light guide 13 has a roughly three-dimensional U-shaped appearance when viewed from its upper surface (the surface in the +z direction).

[0070] An infrared reflective film is applied to the inner surface of the light guide portion 13. In this embodiment, gold is used as the infrared reflective film, but it is not limited to this. Silver, aluminum, dielectric multilayer films, or multilayer films formed from infrared-transmitting materials such as Si, Ge, sulfides, and fluorides can be used as the infrared reflective film. Furthermore, if necessary, a protective film such as silicon oxide or silicon nitride can be formed on the infrared reflective film to prevent corrosion of the metal film. The infrared reflective film and protective film can be formed using methods such as plating, sputtering, and vacuum evaporation. Alternatively, for example, a structure can be designed using a metal 3D printer, where the optical cover 1 is integrally molded from a metal such as aluminum.

[0071] The light guide 13 reflects the infrared light incident from the light source 2 through the infrared reflective film on its inner surface, and then emits it to the light receiving part 4 via the optical filter 3. In this way, the optical cover 1, by using the infrared reflective film to reflect the infrared light emitted from the light source 2, and by ensuring that at least a portion of the reflected light reaches the light receiving part 4 via the optical filter 3, serves as an optical path to efficiently guide the infrared light from the light source 2 to the light receiving part 4.

[0072] In this embodiment, by setting the light path inside the optical cover 1 as a tube-shaped light guide 13 with a circular cross-section, the reflection angle of infrared rays can be kept constant in any direction in three dimensions (x-axis, y-axis, z-axis) regardless of the diameter or path of the cross-section of the light guide 13. Infrared rays emitted from the light source 2 are reflected inside the light guide 13 and efficiently incident on the light receiving part 4.

[0073] Furthermore, by changing the diameter of the cross-section of the light guide 13, the length of the infrared light path from the light source 2 to the light receiving part 4 can be changed relatively easily.

[0074] In addition, such as Figure 2 , Figure 3As shown, the optical cover 1 is designed and formed in three dimensions on the substrate 6, which is located below (in the -z direction) a portion of the light guide portion 13 in the x-axis direction. At least a portion of the signal processing portion 5 and the circuit element portion 8 are disposed in the spatial portion S1 and mounted on the substrate 6.

[0075] Furthermore, regarding the cross-sectional area of ​​the light guide section 13 perpendicular to the axial direction, the main part (excluding the inlet section 131 and the outlet section 132, described later) is constant in the axial direction. Since the cross-sectional area is constant, the gas concentration per unit volume relative to the gas G of the detection object entering the light guide section 13 is easily homogenized, and the infrared rays pass randomly without following a specific path, thus easily responding to changes in the gas concentration of gas G. Figure 3 The solid lines represent the optical path propagation state of multiple infrared optical paths within the light guide section 13. Thus, the infrared optical paths are random within the light guide section 13.

[0076] Furthermore, light emitted from the light source 2 is incident on the light guide section 13 on the -x direction side. The light guide section 13 on the -x direction side extends axially 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 infrared incident end of the light guide section 13 is designated as the entrance section 131. The light guide section 13 extending towards the +y direction side bends in an R-shape, and extends axially from the -x direction side to the +x direction side, again bending in an R-shape.

[0077] Furthermore, the light guide section 13 on the +x direction side extends linearly from the +y direction side to the -y direction side in the axial direction, then bends in an R-shape and extends towards the -z direction side. Infrared rays passing through the light guide section 13 are emitted to the optical filter 3 and the light receiving section 4. The end of the light guide section 13 on the infrared emitting side is designated as the outlet section 132.

[0078] In addition, the covers 110A and 110B have hollow portions (not shown) as spaces for weight reduction (thinning). Through these hollow portions, the optical cover 1 (optical gas sensor device 100) can be made lighter.

[0079] Additionally, cover 110B has a retaining pin (not shown). The retaining pin is a protrusion extending in the +z direction, which mates with the recess (hole) (not shown) of cover 110A and is integrated by methods such as bonding or thermal riveting. By mates the retaining pin with the recess of cover 110A and integrates them by methods such as bonding or thermal riveting, cover 110A and 110B are positioned and fixed, becoming a single component.

[0080] In addition, such as Figure 2As shown, cover 110A has gas inlets 111 and 112 as gas inlet ports 11. Cover 110B has gas inlets (gas inlet holes) 113 and 114 as gas inlet ports 11. Gas inlets 111 and 112 are holes that open from the upper surface of cover 110A in the -z direction and extend to the light guide 13. Gas inlet 113 is a hole that opens from the -y side of cover 110B in the -y direction to the +y side and extends to the space surrounding (beside) the light source 2. The space surrounding the light source 2 is connected to the light guide 13. Gas inlet 114 is a hole that opens from the -y side of cover 110B in the -y direction to the +y side and extends to the space surrounding (beside) the optical filter 3 and the light receiving part 4. The space surrounding the optical filter 3 and the light receiving part 4 is connected to the light guide 13.

[0081] Gas inlets 111 and 112 are directly connected to the light guide section 13, which removes a portion of the inner surface of the light guide section 13, thus reducing the utilization efficiency of infrared light. In contrast, gas inlet 113 is indirectly connected to the light guide section 13 via the space surrounding the light source 2, thus avoiding damage (removal) of a portion of the inner surface of the light guide section 13 and increasing the utilization efficiency of infrared light. Similarly, gas inlet 114 is indirectly connected to the light guide section 13 via the space surrounding the optical filter 3 and the light receiving section 4, thus avoiding damage to a portion of the inner surface of the light guide section 13 and increasing the utilization efficiency of infrared light.

[0082] also, Figure 2 The shape, size, and position of the gas inlet ports 11 (gas inlets 111, 112, 113, 114) of the optical cover 1 are examples and are not limited thereto.

[0083] like Figure 4 As shown, the light source 2 is a MEMS (Micro ElectroMechanical Systems) type light source mounted on the upper surface (+z side) of the substrate 6, such as a diaphragm M with a diaphragm structure. The light source 2 has an electrode 231 and a pad P1 disposed on the +x direction side, and an electrode 232 and a pad P2 disposed on the -x direction side.

[0084] The light source 2, acting as a film M disposed on a Si substrate, has a structure in which, from the -z direction side to the +z direction side, layers such as a light source layer support layer, a light source layer 21, an electrode support layer, and a protective layer (all omitted from the diagram) are stacked. The light source layer support layer, from the -z direction side to the +z direction side, has, for example, a silicon oxide film, a silicon nitride film, or an HLD (High Temperature Low Pressure Dielectric Layer) layer. The light source layer 21 is a thin-film heater serving as a light source (metal) layer (light-emitting layer) that emits infrared radiation, and is, for example, made of MoSi2. The light source layer heats the film M by applying an electric current, emitting infrared radiation with intensity and wavelength dependence dependent on surface temperature and surface emissivity. The electrode support layer, from the -z direction side to the +z direction side, has, for example, two insulating layers that support the electrodes. The protective layer is a protective layer on the upper surface made of an insulator.

[0085] The light source layer 21 is electrically connected to electrodes 231 and 232. Pad P1 is a wire bonding pad and is electrically connected to electrode 231. Pad P2 is a wire bonding pad and is electrically connected to electrode 232. Pads P1 and P2 are bonded to the terminal leads of the wiring pattern on the substrate 6. By applying voltage, the light source layer 21 is energized and emits infrared rays.

[0086] Light source 2, as a MEMS-type light source, is small and thin, enabling miniaturization as a sensor module. Furthermore, light source 2, as a MEMS-type light source, features long lifespan, low power consumption, and short response time, contributing to low power consumption as part of the overall sensor module. The short response time of the MEMS-type light source shortens standby time after power-on and reduces average power consumption during intermittent driving.

[0087] Furthermore, as a MEMS-type light source, light source 2 can directly utilize emitted light from the surface of the high-temperature section, thus enabling applications such as the detection of gases with absorption bands at high wavelengths. Additionally, the region of light source 2 that emits infrared light is precisely patterned on the plane of the Si substrate of diaphragm M, resulting in very small individual deviations in the emission direction. Therefore, the deviation in the amount of light received when light source 2 is used to construct a sensor module is reduced, contributing to improved product yield. Moreover, light source 2 is manufactured on a silicon wafer using MEMS technology, thus offering excellent mass production capabilities.

[0088] The light source 2 is set as a surface mount component, but it is not limited to this. It can also be set as a DIP (Dual Inline Package) component (CAN package, etc.).

[0089] The optical filter 3 is configured to cover the light-receiving surface of the light-receiving section 4, allowing light (infrared radiation) in the band corresponding to the inherent absorption wavelength of the gas G being detected to pass through. In this way, the transmission wavelength of the optical filter 3 is designed to match the inherent absorption wavelength of the gas G being detected, thereby suppressing changes in light intensity caused by gases other than the gas G being detected, and improving the signal-to-noise ratio (SN ratio) of the detection signal from the light-receiving section 4.

[0090] The optical filter 3 may have, for example, a silicon substrate as a substrate and a dielectric multilayer film, or a multilayer film formed from infrared-transmitting materials such as Si, Ge, sulfides, and fluorides. The silicon substrate is a planar silicon substrate. The substrate material is not limited to silicon; Ge (germanium), quartz, alumina, BaF2 (barium fluoride), CaF2 (calcium fluoride), etc., can be used. The multilayer film is a multilayer film disposed on both sides of the silicon substrate. Furthermore, the planar shape of the optical filter 3 is rectangular, but not limited to this; other shapes such as circles can also be used.

[0091] In this embodiment, as described later, the optical filter 3 is not only a bandpass filter that allows wavelengths of a specific frequency band to pass through, but also a longpass filter that cuts off light on the shorter wavelength side relative to any wavelength and allows light on the longer wavelength side to pass through.

[0092] The light-receiving part 4 is mounted on the +z side of the substrate 6 and is a thermopile-type light sensor (infrared sensor) with multiple thermocouples. It detects the amount of incident infrared light and outputs a detection signal as an analog electrical signal. However, the light-receiving part 4 is not limited to a thermopile-type infrared sensor, but can also be an infrared sensor of various types shown in Table III below.

[0093] [Table 3]

[0094] Table III

[0095]

[0096] Furthermore, the light-receiving part 4 is a surface-mount component, but it is not limited to this structure and can also be a DIP component (CAN package, etc.). In addition, the light guide part 13 can efficiently obtain light regardless of the orientation of the surface-mount component, DIP component, or other components, for both the light source 2 and the light-receiving part 4.

[0097] Figure 5 The planar structure of the optical gas sensor device 100 and the cut-off line VIA-VIA parallel to the y-axis direction of the optical cover 1 are shown. Figure 6A This is a side view showing the cross-sectional structure of the optical cover 1 cut by the cutting line VIA-VIA. The optical filter 3 can be mounted in the light guide section 13, which serves as the light path from the light source 2 to the light receiving section 4.

[0098] like Figure 6A As shown, the infrared emission end of the light guide 13 is designated as the outlet 132. The optical filter 3 is positioned directly below (and near) the outlet 132, with its plane parallel to the xy-plane (parallel to the surface of the light-receiving part 4). In this configuration, the optical filter 3 is, for example, engaged with the lower surface of the outlet 132. The optical filter 3a has an area covering at least the axial section of the outlet 132.

[0099] However, optical filter 3 is not limited to Figure 6A The location. For example, such as Figure 6B As shown, an optical filter 3a, replacing the optical filter 3, can also be configured to be positioned below the outlet portion 132 near the surface (light-receiving surface) of the light-receiving portion 4, with its plane parallel to the xy plane. In this configuration, the optical filter 3a is, for example, bonded to the upper surface of the light-receiving portion 4. The optical filter 3a has an area that at least covers the area of ​​the light-receiving surface of the upper surface of the light-receiving portion 4. That is, the area of ​​the plane of the optical filter 3a is smaller than the area of ​​the plane of the optical filter 3.

[0100] Furthermore, the outlet portion 132 has a conical shape in which the cross-sectional area decreases as the axial direction of the light guide portion 13 moves from the +z direction side to the -z direction side. Similarly, the inlet portion 131 has a conical shape in which the cross-sectional area decreases as the axial direction of the light guide portion 13 moves from the +z direction side to the -z direction side. Therefore, the concentration of infrared rays emitted to the light receiving portion 4 through the light guide portion 13 can be improved.

[0101] The signal processing unit 5 is mounted on a planar area on the +z direction side of the substrate 6. It is an AFE (Analog Front End)-IC (Integrated Circuit) that performs signal processing related to the detection signal from the light-receiving unit 4. The signal processing unit 5 amplifies and performs AD conversion on the analog detection signal from the light-receiving unit 4, corrects individual deviations of the optical gas sensor device 100, etc., and uses the amplified digital detection signal to perform signal processing (calculation of gas concentration or values ​​corresponding to gas concentration, calculation of the state of the optical gas sensor device 100, and generation of various signals), generating and outputting various digital signals.

[0102] The substrate 6 is a PCB (Printed Circuit Board) on a glass epoxy resin or similar substrate with conductor wiring printed on it. On the upper surface (+z side) of the substrate 6, an optical cover 1, a light source 2, a light receiving part 4, a signal processing part 5, a connector 7, and a circuit element part 8 are mounted.

[0103] Connector 7 is mounted on the planar area of ​​the surface of the substrate 6 on the +z direction side, excluding the optical cover 1 and the signal processing unit 5. It is used to output various digital signals from the signal processing unit 5 to the information processing unit of a subsequent device (such as an alarm). Connector 7 is a socket connector that connects to a cable with a plug. Connector 7 is connected to the information processing unit of the aforementioned device via this cable.

[0104] The circuit element section 8 is a planar area on the +z direction side of the substrate 6, containing circuit elements such as switches 81, chip resistors, and chip capacitors.

[0105] Next, refer to Figures 7-12 The characteristics of the optical filter 3 and the optical gas sensor device 100 will be explained. Figure 7 This is a diagram showing the distribution of the incident angle of light rays toward the light-receiving part 4. Figure 8 This is a graph representing the transmission characteristics of a long-pass filter. Figure 9 This is a graph showing the angle dependence of the transmittance of a long-pass filter. Figure 10 This is a graph showing the transmission characteristics of a conventional bandpass filter. Figure 11 This is a graph showing the angle dependence of transmittance of conventional bandpass filters. Figure 12 It is a graph showing the absorption wavelengths of various gases.

[0106] like Figure 3 As shown, in the light guide section 13, the infrared light rays, indicated by the solid lines, do not travel parallel to the inner wall surface of the light path, but rather travel while being repeatedly reflected at an angle. Therefore, the light rays incident on the light receiving section 4 are not perpendicular, but are mainly composed of angled rays. Figure 7 In the figure, the incident angle distribution of infrared rays toward the light-receiving part 4, obtained by ray tracing simulation, represents the contribution rate [%] of the light amount relative to the incident angle θ [°] toward the light-receiving part 4 (light-receiving element).

[0107] Figure 6A The incident angle θ is shown. The incident angle θ is the angle of incidence of the light ray relative to the perpendicular line to the light-receiving surface of the light-receiving part 4. According to... Figure 7 As a result, the proportion of the vertical incident component of light (≈0°) is small relative to the total light quantity, and the component at angles above the peak of 30~35° accounts for half.

[0108] Here, we consider the case where the gas G being detected is refrigerant R32. In this embodiment, the optical filter 3 uses... Figure 8 and Figure 9 The characteristics of the long-pass filter are shown. Figure 8In this context, the transmittance characteristic of a long-pass filter is expressed as the transmittance (%) of the long-pass filter at incident angles of 0, 30, 45, and 60° relative to the wavelength of light (μm). Figure 9 In this context, the angle dependence of the transmittance of the long-pass filter is expressed as the transmittance [%] of the long-pass filter relative to the incident angle of light [°].

[0109] As a comparative example, optical filter 3 is used Figure 10 and Figure 11 The structure of a conventional bandpass filter with the characteristics shown will be explained. Figure 10 In the above, the transmittance characteristics of a conventional bandpass filter are shown, with respect to the wavelength of light [μm] and the transmittance [%] at incident angles of 0, 30, 45, and 60 [°]. Figure 11 In the figure, the transmittance of the bandpass filter as a conventional bandpass filter is shown as an angle dependence relative to the incident angle of light [°].

[0110] The conventional bandpass filter used in the comparative example is a bandpass filter designed to allow the absorption wavelength of R32, which is 9.1 μm, to pass through when incident perpendicularly (incident angle θ = 0°). For example... Figure 10 As shown, as the incident angle θ moves away from 0°, the center wavelength of R32 shifts towards the shorter wavelength side, and the transmittance at 9.1 μm decreases. Therefore, if this conventional bandpass filter's optical filter 3 is combined with the light guide 13, the actual amount of infrared light received is lower than the design value. Figure 11 As shown, the transmittance of the conventional bandpass filter in the comparative example drops sharply as the incident angle θ is greater than 40°.

[0111] In contrast, such as Figure 8 As shown, regarding the long-pass filter of this embodiment, the transmittance [%] of R32 at the absorption wavelength of 9.1 [μm] has low dependence on the incident angle. Therefore, even when combining the optical filter 3 and the light guide 13 of this long-pass filter, it is possible to receive light from all angles reaching the light receiving part 4, thereby improving the output signal of gas detection (accurately detecting the concentration of gas G of the target object). Figure 9 As shown, compared with the conventional bandpass filter of the comparative example, the long-pass filter of this embodiment will delay the decrease in transmittance (%) even if the incident angle θ is greater than 40°.

[0112] Furthermore, when the refrigerant in Table II is used as the gas G to be detected, the transmission characteristics of the long-pass filter in this embodiment at an incident angle θ = 0° require an initial wavelength λo = 5~8 μm and a transmission wavelength λpass = 7~12 μm. However, it is necessary to set λo < λpass. Here, the initial wavelength λo is the wavelength with a transmittance of 5%, and the transmission wavelength λpass is defined as the wavelength region with a transmittance of 70% or more. The lower limit of the initial wavelength λo of the long-pass filter is set to a wavelength longer than the main absorption wavelength of carbon dioxide, i.e., 4 μm, i.e., 5 μm, and the upper limit needs to be the main absorption wavelength of R1234yf, i.e., 8.5 μm or less. The lower limit of the transmission wavelength λpass needs to be the absorption wavelength of water vapor, i.e., 6 μm or more, and the upper limit needs to be the absorption wavelength of carbon dioxide, i.e., 12 μm or less. Preferably, the initial wavelength λo of the long-pass filter is 7~8 μm and the transmission wavelength λpass is 8~11 μm.

[0113] However, by using the optical filter 3 with a long-pass filter, the bandwidth is widened, and components other than the gas G of the target object may affect the detection signal (the gas detection signal contains components of gas other than the gas G of the target object). Figure 12 This indicates the absorption wavelength [μm] for various gases. For example... Figure 12 As shown, in the wavelength region above 7.5 [μm], the types of gases that may be contained in the living space are few, and the absorption effect of such gases is also low, so it will not be a problem in practice.

[0114] The long-pass filter with the transmittance characteristics of this embodiment can also be applied to non-contact temperature sensors and human body sensors. By manufacturing the long-pass filter simultaneously for applications of temperature sensors, human body sensors, and optical filter 3, the film deposition cost (manufacturing cost) can also be reduced.

[0115] According to this embodiment, the optical gas sensor device 100 includes: a light source 2 that emits infrared light to the gas G to be detected; an optical filter 3 that is a long-pass filter having a starting wavelength smaller than the center wavelength of the absorption wavelength band of the gas G to be detected and a transmission wavelength including the center wavelength, allowing infrared light passing through the gas G to pass through; a light-receiving part 4 that detects the infrared light incident through the optical filter 3 and generates a detection signal; and an optical cover 1 that covers the light source 2, the optical filter 3, and the light-receiving part 4. The optical cover 1 includes: a light guide part 13 that guides the infrared light incident from the light source 2 through the optical filter 3 to the light-receiving part 4 by reflection from its inner surface. The light guide part 13 is tubular in shape and has a circular cross-section perpendicular to the axial direction.

[0116] Therefore, when the gas G to be detected is detected using infrared light from the light guide 13 which is a light path accompanied by reflection, the optical filter 3 can reduce the influence of the angle dependence of the incident angle θ on the transmittance of the gas G to be detected, thereby increasing the output voltage of the light receiving unit 4 and improving the detection accuracy of the gas G to be detected.

[0117] Furthermore, the gas G to be detected is either a refrigerant consisting of a single molecule containing at least one fluorine atom, or a refrigerant consisting of a mixture of multiple molecules containing at least one fluorine atom and having different structures. Therefore, as the gas G to be detected, the detection accuracy of alternative Freon refrigerants with a center wavelength of absorption around 9 [μm] can be improved.

[0118] Furthermore, regarding optical filter 3, the starting wavelength is 5~8 [μm], and the transmission wavelength is 7~12 [μm], with the starting wavelength being shorter than the transmission wavelength. Therefore, optical filter 3 has appropriate filtering characteristics for refrigerants that replace Freon, and can improve the detection accuracy of refrigerants that replace Freon in the gas G being detected.

[0119] Furthermore, the optical gas sensor device 100 includes a substrate 6 on which the light source 2, the light-receiving part 4, and the optical cover 1 are mounted. Therefore, the light source 2, the light-receiving part 4, and the optical cover 1 can be accurately and reliably configured and fixed, further improving the detection accuracy of the gas G to be detected.

[0120] Furthermore, the light guide section 13 has an entrance section 131 for infrared rays emitted from the light source 2 to enter. The entrance section 131 has a conical shape whose cross-sectional area decreases along the axial direction as it approaches the light source 2. Therefore, the concentration of infrared rays toward the light receiving section 4 can be improved.

[0121] Furthermore, the light guide section 13 has an exit section 132 that directs the guided infrared light through the optical filter 3 to the light receiving section 4. The exit section 132 has a conical shape whose cross-sectional area decreases along the axial direction as it approaches the light receiving section 4. Therefore, the concentration of infrared light toward the light receiving section 4 can be improved.

[0122] (Example)

[0123] Reference Figures 13-15 Specific embodiments and comparative examples (designated as Embodiment 1 and Comparative Example 1) of the above-described implementation methods will be described. Figure 13 This is a graph showing the transmission characteristics of the optical filter 3 of Embodiment 1. Figure 14 This is a graph showing the transmission characteristics of the optical filter in Comparative Example 1. Figure 15 This is a graph showing the transmission characteristics of the optical filter 3 of Example 1 and the absorption spectra of R32 and R1234yf.

[0124] Used in Figure 6A An optical gas sensor device 100 with an optical filter 3 is positioned as shown. The chip size of the light source 2 is set to 2.5 × 0.4 mm, and the size of the diaphragm M is set to φ1.6 (diameter = 1.6 mm). Furthermore, after die bonding of the light source 2 chip on the substrate 6, wire bonding is performed on pads P1 and P2 in a predetermined connection manner. The resistance of the light source 2 at room temperature is 16 Ω, and the applied voltage is set to 3.3 V.

[0125] The light-receiving unit 4 is a MEMS thermopile with a chip size of 1.3 × 0.7 mm, a height of 0.4 mm, and a diaphragm size of 0.71 mm. The resistance of the light-receiving unit 4 is 44 kΩ. The output signal from the light-receiving unit 4 is amplified 70 times by an external amplifier circuit and a signal processing unit 5. Furthermore, the output signal from the light-receiving unit 4 is obtained as a digital value from the optical gas sensor device 100 via an I2C interface. More specifically, the analog voltage output from the light-receiving unit 4 is converted into a digital value by an AD converter inside the signal processing unit 5. This digital value is calculated based on the full-scale voltage and resolution of the AD converter, and considering the aforementioned 70-fold gain, it is converted into a direct output voltage from the light-receiving unit 4 and obtained as a digital value.

[0126] The optical filter 3 in Example 1 is a long-pass filter. Figure 13 In this document, the transmittance characteristics of the optical filter 3 of Example 1 are expressed as the transmittance [%] of the optical filter 3 of Example 1 relative to the wavelength [μm]. The optical filter 3 of Example 1, as a long-pass filter, has the following characteristics: starting wavelength: 7.5 [μm], maximum transmittance: 90 [%). The substrate of the optical filter 3 of Example 1 is silicon with a thickness of 0.32 [mm]. After the filter film (constituting materials of Ge and ZnS) is deposited on this substrate, it is cut into 3mm square pieces.

[0127] The optical filter in Comparative Example 1 is a bandpass filter. Figure 14In this section, the transmittance characteristics of the optical filter used as a comparative example are represented by the transmittance [%] of the optical filter of Comparative Example 1 relative to the wavelength [μm]. The optical filter of Comparative Example 1, as a bandpass filter, has the following characteristics: center wavelength: 9.1 [μm], maximum transmittance: 89 [%], FWHM (Full Width at Half Maximum): 1 [μm], and blocking: 2~12 [μm]. FWHM is used to represent the width of the spectrum and is the interval between two wavelengths corresponding to 50% of the peak transmittance. The substrate of the optical filter of Comparative Example 1 is silicon with a thickness of 0.34 [mm]. After the filter film (constituting materials Ge and ZnS) is deposited on this substrate, it is cut into 3 mm square pieces.

[0128] Table IV below shows the output voltage [mV] of the optical gas sensor device 100 using the optical filter 3 of Example 1 or the optical filter of Comparative Example 1 at multiple R32 concentrations. The multiple R32 concentrations were 5000, 15000, and 30000 [ppm].

[0129] [Table 4]

[0130] Table IV

[0131]

[0132] Compared to the optical filter of Comparative Example 1, the optical filter 3 of Example 1 produces a higher output voltage at any R32 concentration. The output voltage of the optical filter 3 of Example 1 is approximately 1.3 times higher than that of the optical filter of Comparative Example 1.

[0133] Furthermore, the transmission band of the optical filter 3 in Example 1 extends to the longer wavelength side, thereby enabling the detection of various types of refrigerants and their mixtures, not limited to a specific refrigerant. Figure 15 In the diagram, the transmittance characteristics of the optical filter 3 of Example 1 are shown, with respect to wavelength [μm], representing the transmittance [%]. Similarly, Figure 15 In the diagram, the absorption spectra of R32 and R1234yf are shown, with respect to wavelength [μm], and the absorption cross-sections [cm²] of R32 and R1234yf are displayed. 2 / molecular].

[0134] R32 and R1234yf are refrigerants that constitute R454B, a representative example of a mixed refrigerant, and are mixed in a ratio of 68.9:31.1 by mass, respectively. Both R32 and R1234yf have the strongest absorption in the transmission band of a long-pass filter, enabling highly sensitive measurement.

[0135] According to the optical filter 3 of Embodiment 1, when the gas G to be detected is detected using infrared light passing through the light guide 13 as a path of accompanying reflection, the detection accuracy of R32, R1234yf and R454B of the gas G to be detected can be improved by the optical filter 3.

[0136] (Second Implementation)

[0137] Reference Figures 16-18 The second embodiment of the present invention will now be described. Figure 16 This is a graph showing the transmission characteristics of a conventional bandpass filter. Figure 17 This is a graph showing the transmission characteristics of the bandpass filter in this embodiment. Figure 18 This is a graph showing the transmission characteristics and center wavelength of a bandpass filter in an example.

[0138] In the first embodiment described above, the optical filter 3 or 3a is a long-pass filter. In this embodiment, the optical filter 3 or 3a is a band-pass filter.

[0139] The device structure in this embodiment is the same as that in the first embodiment described above, using an optical gas sensor device 100. Therefore, the description of structural parts that are the same as those in the first embodiment is omitted, and the description will focus on different parts such as the optical filter 3.

[0140] In conventional NDIR-based optical gas sensor devices, the bandpass filter used in the optical filter corresponds to the wavelength of infrared transmission that represents maximum absorption in the absorption spectrum of the gas being detected. For example, ... Figure 12 As shown, the wavelength representing maximum absorption in the methane absorption spectrum is 3.3 [μm]. Conventional bandpass filters used for methane detection are designed with a transmission wavelength of 3.3 [μm]. Similarly, as... Figure 12 As shown, the wavelength representing maximum absorption in the absorption spectrum of carbon dioxide is 4.26 [μm]. Conventional bandpass filters used for carbon dioxide detection were designed with a transmission wavelength of 4.26 [μm].

[0141] Here, we will explain the bandpass filter when the gas G being detected is R32. Figure 16 It is a reduction relative to Figure 10 The characteristics of infrared wavelength [μm] and transmittance [%] of conventional bandpass filters are easily observed in a graph over a wavelength range. (See figure). Figure 16As shown, conventional bandpass filters are designed to allow the wavelength representing maximum absorption, 9.1 μm (thick line), in the absorption spectrum of R32, the gas being detected, to pass through when infrared light is incident perpendicularly to the receiving part (incident angle θ = 0°). More specifically, conventional bandpass filters ensure that the center wavelength of transmittance in the perpendicular incidence characteristic (incident angle θ = 0°) coincides with the center wavelength of the absorption spectrum of R32, i.e., 9.1 μm.

[0142] Here, refer to Figure 18 This section explains the "center wavelength of transmittance" for bandpass filters. Figure 18 In the characteristic of transmittance [%] of a bandpass filter with an infrared wavelength [μm] at perpendicular incidence (incident angle θ = 0°), the wavelengths λ1 and λ2 representing the maximum transmittance and 50% of the maximum transmittance are represented. The center wavelength of the transmittance of this bandpass filter is defined by the center wavelength of wavelengths λ1 and λ2 (=(sum of wavelengths λ1 and λ2) / 2).

[0143] like Figure 16 As shown, for conventional bandpass filters, as the incident angle of infrared light increases, the transmittance [%] at the wavelength of maximum absorption, i.e., 9.1 [μm], in the absorption spectrum of R32 further decreases.

[0144] In the optical filter 3 or 3a using the conventional bandpass filter described above, in the optical gas sensor device 100, the center wavelength of transmittance deviates from the wavelength representing maximum absorption in the absorption spectrum of R32 relative to infrared light emitted from the tubular optical path, i.e., the light guide 13. Therefore, the change in light quantity caused by gas absorption of R32 is reduced.

[0145] In contrast, Figure 17 This describes the transmittance [%] of the bandpass filter of this embodiment used for optical filter 3 or 3a, relative to the wavelength [μm] of infrared light. The bandpass filter of this embodiment... Figure 16 Compared to conventional bandpass filters, this one is designed to shift the center wavelength of the transmittance at vertical incidence by a predetermined offset from the wavelength representing maximum absorption (9.1 [μm]) in the absorption spectrum of R32 towards a higher wavelength. Thus, during the design and manufacturing monitoring of the bandpass filter of this embodiment used for optical filter 3, by setting the center wavelength of the transmittance at vertical incidence to a wavelength higher than 9.1 [μm], the change in light intensity caused by gas absorption of R32 can be increased. Figure 17 As shown, with respect to the bandpass filter of this embodiment, as the incident angle of infrared light increases, the transmittance [%] at the wavelength of maximum absorption, i.e., 9.1 [μm], in the absorption spectrum of R32 does not decrease.

[0146] Figure 17 In this embodiment, the specified offset of the center wavelength of the transmittance of the bandpass filter at perpendicular incidence (θ = 0°) relative to the wavelength representing maximum absorption in the absorption spectrum of R32 is +0.2 [μm]. An appropriate offset of the center wavelength of the transmittance of the bandpass filter relative to the wavelength representing maximum absorption in the absorption spectrum of the gas G being detected is +0.05 to +1 [μm], preferably +0.1 to +0.4 [μm].

[0147] According to this embodiment, the optical gas sensor device 100 includes: a light source 2 that emits infrared light to the gas G to be detected; an optical filter 3 or 3a, which is a bandpass filter that shifts the center wavelength of the transmittance at perpendicular incidence (θ = 0°) by a predetermined offset from the wavelength representing maximum absorption in the absorption spectrum of the gas G to a higher wavelength side, allowing infrared light passing through the gas G to pass through; a light-receiving section 4 that detects the infrared light incident through the optical filter 3 or 3a and generates a detection signal; and an optical cover 1 that covers the light source 2, the optical filter 3 or 3a, and the light-receiving section 4. The optical cover 1 includes: a light guide section 13 that guides the infrared light incident from the light source 2 through the optical filter 3 or 3a to the light-receiving section 4 by reflection from its inner surface. The light guide section 13 is tubular in shape and has a circular cross-section perpendicular to the axial direction.

[0148] Therefore, by using infrared light through the accompanying reflection light path, the detection accuracy of the target gas G can be improved, and the light intensity variation and output of the light receiving unit 4 when the target gas G is present can be increased. Thus, the influence of light intensity fluctuations caused by interference can be suppressed, and the detection performance can be stabilized. Furthermore, the power input to the light source 2 can be reduced. Additionally, the optical path length can be shortened, thus enabling miniaturization of the optical gas sensor device 100.

[0149] Furthermore, the offset is specified to be +0.05 to +1 μm relative to the wavelength representing the maximum absorption in the absorption spectrum of the gas G being detected. Therefore, it is possible to further increase the change in light intensity when the gas G being detected is present and the output of the light receiving unit 4, further suppress the influence of light intensity fluctuations caused by interference, further stabilize the detection performance, and further reduce the power supply to the light source 2.

[0150] Furthermore, the description in the above embodiments is an example of the optical gas sensor device of the present invention, and is not limited thereto.

[0151] Furthermore, in the above embodiment, the light guide portion 13 of the optical cover 1 is configured as a tube with a circular cross-section perpendicular to the axial direction, but it is not limited to this. For example, the light guide portion 13 may also be configured as a tube with an elliptical cross-section perpendicular to the axial direction. The elliptical cross-section structure of the light guide portion 13, like the circular cross-section structure, can reduce the deviation of the infrared reflection angle in the optical path. Even if there is a misalignment in the installation of the light source 2 and the light receiving portion 4, the loss of infrared light can be reduced, thus resisting the misalignment and improving the detection accuracy of the gas G of the object to be detected.

[0152] Furthermore, in the above embodiment, the optical gas sensor device 100 is configured to have a set of light sources 2, optical filters 3, light-receiving parts 4, and light guide parts 13, but it is not limited to this. The optical gas sensor device may also be configured to have multiple sets of light sources 2, optical filters 3, light-receiving parts 4, and light guide parts 13.

[0153] Furthermore, the detailed structure and operation of the optical gas sensor device 100 in the above embodiments can be appropriately modified without departing from the spirit of the present invention.

[0154] Industrial applicability

[0155] As described above, the optical gas sensor device of the present invention is suitable for detecting gases such as refrigerants.

[0156] Explanation of reference numerals in the attached figures

[0157] 100 Optical Gas Sensor Device

[0158] G gas

[0159] 1 Optical cover

[0160] 110A and 110B cover

[0161] 11 Gas inlet port

[0162] Gas inlets / outlets 111, 112, 113, 114

[0163] 13 Light guide section

[0164] 12 Contamination Filters

[0165] S1 Space Division

[0166] 2. Light source

[0167] 21. Light Source Layer

[0168] Electrodes 231 and 232

[0169] P1, P2 pads

[0170] M membrane

[0171] 3.3a ​​Optical Filter

[0172] 4 Light-receiving part

[0173] 5. Signal Processing Department

[0174] 6 substrate

[0175] 7 Connectors

[0176] 8. Circuit Components Section

[0177] 81 Switch.

Claims

1. An optical gas sensor device, characterized in that, have: A light source that emits infrared rays toward the gas being detected; An optical filter is a long-pass filter having a starting wavelength smaller than the center wavelength of the absorption wavelength band of the gas being detected and a transmission wavelength containing the center wavelength, and allowing infrared radiation passing through the gas being detected to pass through. The light-receiving part generates a detection signal by detecting infrared light incident through the optical filter; An optical cover that covers the light source, the optical filter, and the light-receiving part. The optical cover has a light guide portion that guides infrared rays incident from the light source to the light receiving portion via the optical filter through reflection from its inner surface. The light guide portion is tubular in shape and has a circular or elliptical cross section perpendicular to the axial direction.

2. The optical gas sensor device according to claim 1, characterized in that, The gas to be detected is a refrigerant consisting of a single molecule containing at least one fluorine atom, or a mixture of multiple molecules containing at least one fluorine atom and having different structures.

3. The optical gas sensor device according to claim 1, characterized in that, Regarding the optical filter, the starting wavelength is 5~8 [μm], and the transmission wavelength is 7~12 [μm], with the starting wavelength being shorter than the transmission wavelength.

4. An optical gas sensor device, characterized in that, have: A light source that emits infrared rays toward the gas being detected; An optical filter is a bandpass filter that shifts the center wavelength of transmittance at perpendicular incidence (θ = 0°) by a predetermined offset from the wavelength representing maximum absorption in the absorption spectrum of the gas being detected to a higher wavelength side, and allows infrared radiation passing through the gas being detected to pass through. The light-receiving part generates a detection signal by detecting infrared light incident through the optical filter; An optical cover that covers the light source, the optical filter, and the light-receiving part. The optical cover has a light guide portion that guides infrared rays incident from the light source to the light receiving portion via the optical filter through reflection from its inner surface. The light guide portion is tubular in shape and has a circular or elliptical cross section perpendicular to the axial direction.

5. The optical gas sensor device according to claim 4, characterized in that, The specified offset is relative to the wavelength of maximum absorption in the absorption spectrum of the gas of the object being detected, which is +0.05 to +1 [μm].

6. The optical gas sensor device according to any one of claims 1 to 5, characterized in that, The optical gas sensor device includes: a substrate on which the light source, the light-receiving part, and the optical cover are mounted.

7. The optical gas sensor device according to any one of claims 1 to 5, characterized in that, The light guide portion has an entrance portion for infrared light emitted from the light source to enter. The inlet has a conical shape with a smaller cross-sectional area along the axial direction and as it approaches the light source side.

8. The optical gas sensor device according to any one of claims 1 to 5, characterized in that, The light guide portion has an outlet portion that emits the guided infrared light through the optical filter toward the light receiving portion. The outlet portion has a conical shape with a smaller cross-sectional area along the axial direction and as it approaches the light-receiving portion.

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