Gas sensor
By using wavelength confinement elements and optical filters in gas sensors, the difficulties in optical path design and optical loss caused by filter miniaturization are solved, enabling miniaturization and high-precision measurement of gas sensors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ASAHI KASEI MICRODEVICES CORP
- Filing Date
- 2024-09-25
- Publication Date
- 2026-07-10
Smart Images
Figure CN224480404U_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to gas sensors. Background Technology
[0002] Light sources are used for many purposes, such as indoor or building lighting and optical devices. Optical devices use light sources that emit light of specific wavelengths, such as sterilization devices using ultraviolet light and rangefinders using reflected light. Additionally, there are known light-emitting devices that combine a light source and a light-receiving unit (sensor) to detect the spatial state between the light source and the light-receiving unit. For example, a gas sensor using infrared light detects the concentration of a target gas in a gas introduced into the space, thus detecting the spatial state. Further improvements in accuracy are sought in gas sensors. For example, Patent Document 1 discloses a gas concentration detection device configured using NDIR (Non-Dispersive Infrared) technology, which is corrected for variations in output characteristics.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: International Publication No. 2016 / 021495 Utility Model Content
[0006] The problem to be solved by the utility model
[0007] Here, the gas concentration detection device (gas sensor) in Patent Document 1 includes a first bandpass filter and a second bandpass filter used for calibration. In recent years, there has been a pursuit of further miniaturization in gas sensors. In the technology of Patent Document 1, if only the filters are miniaturized, the optical distance changes, thus making optical path design potentially difficult. Furthermore, problems arise with filter interference and light loss.
[0008] The purpose of this disclosure, made in view of the above circumstances, is to provide a gas sensor that can reduce the size of the filter and also allows for easy optical path design.
[0009] Methods for solving problems
[0010] (1) One embodiment of the gas sensor disclosed herein includes:
[0011] The light source has an active layer;
[0012] The first sensor unit is configured to receive light emitted from the light source to detect the state of the space.
[0013] The second sensor unit is configured to allow light emitted from the light source to be incident on it, and is used to compensate for temperature changes or aging changes of the first sensor unit.
[0014] A first wavelength confinement body restricts the wavelength of light emanating from the active layer and reaching the first and second sensor portions, and is connected to the light source without being separated by the space; and
[0015] The second wavelength confinement body restricts the wavelength of light that exits from the active layer and reaches the second sensor unit, and is connected to the second sensor unit without being separated by the space.
[0016] (2) As one embodiment of this disclosure, in (1),
[0017] The gas sensor includes a third wavelength confinement element that restricts the wavelength of light that exits from the active layer and reaches the first sensor unit, and is connected to the first sensor unit without being separated by the space.
[0018] (3) As one embodiment of this disclosure, in (1),
[0019] The first wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the light source or the substrate on which the light source is disposed.
[0020] (4) As one embodiment of this disclosure, in (1),
[0021] The second wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the second sensor unit or the substrate on which the second sensor unit is disposed.
[0022] (5) As one embodiment of this disclosure, in (2),
[0023] The third wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the first sensor portion or the substrate on which the first sensor portion is disposed.
[0024] (6) As one embodiment of this disclosure, in (2), (4) or (5),
[0025] The light source has a light intensity that reaches its maximum peak wavelength λp.
[0026] The first wavelength confinement has a maximum transmittance of less than 5% in the wavelength range of (λp×0.6)nm to (λp×0.8)nm.
[0027] (7) As one embodiment of this disclosure, in (1),
[0028] The first wavelength confinement body prevents a portion of light wavelengths from passing through and is part of the light source or the substrate on which the light source is disposed.
[0029] (8) As one embodiment of this disclosure, in (1),
[0030] The second wavelength limiter prevents a portion of light wavelengths from passing through and is part of the second sensor unit or the substrate on which the second sensor unit is disposed.
[0031] (9) As one embodiment of this disclosure, in (2),
[0032] The third wavelength confinement body prevents light of a certain wavelength from passing through and is part of the first sensor unit or the substrate on which the first sensor unit is disposed.
[0033] (10) As one embodiment of this disclosure, in any of (1) to (5),
[0034] The first wavelength limiter is disposed in the optical path from the active layer to the second sensor section until the light reaches the substrate on which the light source is disposed.
[0035] (11) As one embodiment of this disclosure, in any of (1) to (5),
[0036] The second wavelength confinement body is disposed on the light path from the active layer to the second sensor portion until the light reaches the substrate on which the second sensor portion is disposed and is incident on the second sensor portion.
[0037] (12) As one embodiment of this disclosure, in (10),
[0038] The wavelength limiter has a reflective structure that reflects light of a specific wavelength.
[0039] (13) As one embodiment of this disclosure, in (1),
[0040] The gas sensor includes a fourth wavelength confinement element that restricts the wavelength of light that emerges from the active layer and reaches the first sensor portion, and is connected to the front side of the substrate on which the light source is disposed without any gap in the space.
[0041] (14) As one embodiment of this disclosure, in (13),
[0042] The light source has a light intensity that reaches its maximum peak wavelength λp.
[0043] The fourth wavelength confinement has a maximum transmittance of less than 5% in the wavelength range of (λp×0.6)nm to (λp×0.8)nm.
[0044] (15) As one embodiment of this disclosure, in (1),
[0045] The gas sensor includes an optical filter disposed in the optical path of the light that exits from the active layer and reaches the first sensor unit.
[0046] (16) As one embodiment of this disclosure, in any of (1) to (5),
[0047] The first sensor unit has the same structure as the light source.
[0048] (17) As one embodiment of this disclosure, in any of (1) to (5),
[0049] When the distance between the first sensor unit and the light source is set as d and the thickness of the substrate on which the light source is installed is set as T, d / T is in the range of 0.70 to 6.00.
[0050] Utility Model Effect
[0051] According to this disclosure, a gas sensor that can reduce the size of the filter and facilitate optical path design can be provided. Attached Figure Description
[0052] Figure 1 This is a diagram illustrating a structural example of a gas sensor according to an embodiment of the present disclosure.
[0053] Figure 2 This is a diagram showing a structural example of a wavelength confinement body.
[0054] Figure 3A This is a diagram showing a structural example of a wavelength confinement body.
[0055] Figure 3B This is a diagram showing a structural example of a wavelength confinement body.
[0056] Figure 3C This is a diagram showing a structural example of a wavelength confinement body.
[0057] Figure 4A This is a diagram showing a structural example of a wavelength confinement body.
[0058] Figure 4B This is a diagram showing a structural example of a wavelength confinement body.
[0059] Explanation of reference numerals in the attached figures
[0060] 16 optical filters
[0061] 20 light sources
[0062] 31 Second Sensor Section
[0063] 32 First Sensor Section
[0064] 41 First substrate
[0065] 42 Second substrate
[0066] 51 First Floor
[0067] 52 Second layer
[0068] 53 active layer
[0069] 54 specific wavelength reflective layers
[0070] 55 opening
[0071] 56 filters
[0072] 57 semi-reflective mirror
[0073] 58 Absorption Layer
[0074] 104 Computing Department Detailed Implementation
[0075] Hereinafter, a gas sensor according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same reference numerals. In the description of this embodiment, the description of the same or equivalent parts will be appropriately omitted or simplified.
[0076] (Gas sensor)
[0077] Figure 1 This diagram illustrates the structure of the gas sensor according to this embodiment. The gas sensor measures the presence or concentration of the detected gas in a gas. Figure 1 In the example, the gas sensor has a gas chamber depicted as a semicircle. Here, the gas sensor is not limited to... Figure 1 The structure allows for the use of air chambers with shapes other than semicircles. Additionally, in... Figure 1 In the example, the inner surface of the gas chamber is a reflective surface, but a gas chamber with a non-reflective inner surface can also be used. The gas sensor introduces gas into the interior space of the gas chamber and measures the presence or concentration of the target gas in the introduced gas. The gas sensor involved in this embodiment is an NDIR type gas sensor. The gas sensor involved in this embodiment can be applied to various devices. For example, it can be used for environmental measurement in buildings, as a portable, small measuring device for integration into portable communication devices such as smartphones, and for detecting indoor gas concentrations in mobile structures such as automobiles, trains, or airplanes.
[0078] Furthermore, based on the structure of the gas sensor according to this embodiment, it can be used as a light-emitting device for purposes other than a gas sensor. That is, the disclosure derived by changing the term "gas sensor" described above to "light-emitting device," "optical device," "optical concentration measuring device," "optical physical quantity measuring device," etc., is included within the scope of this disclosure. For example, it can detect the state of the optical path space outside the substrate (for example, the presence or concentration of a specific component of a fluid, other than a gas). For example, it can be used as a component detection device or component concentration measuring device for substances (e.g., water or bodily fluids) existing in the optical path space between the light source 20 and the first sensor unit 32. For example, if the substance existing in the optical path space is blood, the component detection device or component concentration measuring device can be used for measuring the glucose concentration in the blood.
[0079] A component detection device or component concentration measuring device can measure the glucose concentration in blood glucose by measuring the absorption of light with wavelengths of 1 to 10 μm. In measuring glucose concentration in blood glucose, it is preferable to measure the absorption of light at wavelengths of 1.6 μm, 2.0–2.3 μm, and 9.6 μm. This enables the development of a small, highly accurate, and highly reliable non-invasive glucose concentration meter. With such a glucose concentration meter, for example, diabetic patients can accurately check their blood glucose levels themselves without causing damage to the skin as is done in invasive methods. Furthermore, more accurate medication management (e.g., insulin) can be achieved based on the measured blood glucose levels.
[0080] The gas sensor includes a light source 20, a second sensor unit 31, and a wavelength limiter. Alternatively, the gas sensor may include a first substrate 41, a second substrate 42, and a first sensor unit 32. The wavelength limiter is a functional part that limits the wavelength of light reaching the second sensor unit 31, and as described later, it may be, for example, part of the light source 20 or the substrate (first substrate 41) on which the light source 20 is disposed. Figure 1 This is a cross-sectional view showing a gas sensor containing these components. Details about the components of the gas sensor will be described later.
[0081] Here, as Figure 1 Therefore, the gas sensor may also include an optical filter 16. Additionally, the gas sensor may also include a processing unit 104. The optical filter 16 is disposed in the optical path of the light emanating from the light source 20 and reaching the first sensor unit 32, limiting the transmission wavelength of the light. The optical filter 16 may be, for example, a bandpass filter with a known structure. The processing unit 104 may be configured, for example, a processor, and calculates the concentration of the detected gas using the output signals from the second sensor unit 31 and the first sensor unit 32. The calculation of the concentration of the detected gas can use known methods.
[0082] The gas sensor described in this embodiment has the following structural outline. In the gas sensor, a second sensor unit 31 and a first sensor unit 32 are respectively arranged so that light emitted from the light source 20 can be incident upon it. The inner surface (the surface on the internal space side) of the gas chamber reflects light. Figure 1 In the diagram, the light path of the light emitted from the light source 20, reflected on the inner surface of the gas chamber, and incident on the first sensor unit 32 is indicated by an arrow. Additionally, the light path of a portion of the light emitted from the light source 20, reflected from one side of the first substrate 41 (inside the second main surface described later), and incident on the second sensor unit 31 is also indicated by an arrow. The gas sensor includes a first substrate 41, which has a first main surface and a second main surface opposite to the first main surface. The light source 20 and the second sensor unit 31 are disposed on the first main surface. Here, the light source 20 and the second sensor unit 31 may not be disposed on the same substrate. Furthermore, the gas sensor includes a second substrate 42, which has a first main surface and a second main surface opposite to the first main surface. The first sensor unit 32 is disposed on the first main surface. A portion of the light emitted from the light source 20 and incident on the first sensor unit 32 is incident on the second sensor unit 31. Therefore, even if the light-emitting characteristics of the light source 20 change due to variations in the operating environment or aging, the detection signal from the second sensor unit 31 can still accurately detect the spatial state by the first sensor unit 32. In other words, the second sensor unit 31 compensates for temperature or aging changes in the first sensor unit 32 used for spatial state detection. Furthermore, in Figure 1 In the example, the light is emitted from the back side of the first substrate 41 (the side without the light source 20, etc.) and incident from the back side of the second substrate 42, but it can also be a structure in which the light is emitted from the front and incident from the front.
[0083] Here, in the gas sensor, based on the relationship between the emission efficiency and reflection of the light source, the first substrate 41 can be designed such that the angle of light incident on the second sensor unit 31 is 20° to 70°. More preferably, the first substrate 41 can be designed such that the angle of light incident on the second sensor unit 31 is 30° to 60°. In other words, when the distance between the second sensor unit 31 and the light source 20 is set as d and the thickness of the substrate (first substrate 41) on which the light source 20 is disposed is set as T, d / T is, for example, in the range of 0.70 to 6.00. Here, d / T can be in the range of 0.72 to 5.50 corresponding to the aforementioned angle of light. More preferably, d / T can be in the range of 1.15 to 3.50.
[0084] Furthermore, in the gas sensor, the second sensor section 31 and the first sensor section 32 preferably have the same temperature characteristics. The same temperature characteristics do not need to be strictly identical; they can be approximately the same. Additionally, to achieve a high signal-to-noise ratio (S / N) for the overall gas sensor, the areas of the second sensor section 31 and the first sensor section 32 can be different. Furthermore, the second sensor section 31 and the first sensor section 32 can be formed from a plurality of light-receiving elements.
[0085] Here, as described above, the detection signal of the second sensor unit 31 can be used to compensate for temperature or aging changes in the first sensor unit 32. However, especially when the gas sensor is configured to include the optical filter 16, higher precision compensation is sometimes required relative to changes in the light emission characteristics of the light source 20. For example, if the second sensor unit 31 receives approximately all wavelengths of light from the light source 20, the change in the amount of light received (cumulative intensity) of the second sensor unit 31 before and after a wavelength shift (change in wavelength distribution) occurs in the light source 20 is small. In contrast, in the first sensor unit 32, which receives only light of a specific wavelength through the optical filter 16, the change in the amount of light received (cumulative intensity) before and after a wavelength shift (change in wavelength distribution) occurs in the light source 20 is large. In such cases, the relationship between the amount of light received by the second sensor unit 31 and the amount of light received by the first sensor unit 32 deviates from the true value, and the compensation becomes insufficient, sometimes failing to provide a high-precision gas sensor. To address this problem, the following solution exists: A filter component identical to the optical filter 16 is also provided in the second sensor unit 31, forming a structure where both the second sensor unit 31 and the first sensor unit 32 only receive light of a specific wavelength. However, there is a pursuit of further miniaturization in gas sensors. Therefore, if the same filter as the optical filter 16 is arranged in the optical path of the light incident on the second sensor unit 31, the size of the gas sensor increases. Furthermore, miniaturizing the filter leads to problems of filter interference and light loss, making optical path design difficult. The gas sensor according to this embodiment, by incorporating the wavelength limiting element described later, can reduce the size of the filter and facilitate optical path design.
[0086] (light source)
[0087] The following describes the details of the components of the gas sensor. The light source 20 emits light containing wavelengths absorbed by the gas being detected. For example, a lamp, an LED (Light Emitting Diode), a MEMS (Micro Electro Mechanical Systems) emitter, or a laser (Light Amplification by Stimulated Emission of Radiation) can be used as the light source 20. In this embodiment, the light source 20 is an LED and has an active layer 53 (see reference 53). Figure 2 Here, the active layer 53 is the layer that performs photoelectric conversion; in an LED, it is the light-emitting layer, and in a sensor, it is the light-receiving layer.
[0088] The light source 20 preferably has a stacked structure of PN or PIN junctions formed using a film deposition method such as MBE (Molecular Beam Epitaxy) or CVD (Chemical Vapor Deposition). By supplying power to this stacked structure, it can operate as an LED, emitting light with a wavelength corresponding to the band gap of the material of the stacked structure. By including In or Sb in the active layer 53, infrared radiation can be emitted. Specifically, by using InSb, InAlSb, or InAsSb in the active layer 53, light with a wavelength of 1 to 12 μm can be output.
[0089] (Second Sensor Section)
[0090] The second sensor unit 31 receives light (infrared radiation) and outputs a signal corresponding to the amount of light received. For example, a photodiode, photoconductor, thermopile, or pyroelectric sensor can be used as the second sensor unit 31. From the viewpoint of signal processing response speed, the second sensor unit 31 can be a diode structure with a PN junction or PIN junction, containing indium or antimony as the material. The second sensor unit 31 may also contain a mixed-crystal material, which includes at least one material selected from the group consisting of Ga, Al, and As. Furthermore, from the viewpoint of ensuring consistent temperature or wavelength characteristics, the material and stacked structure of the second sensor unit 31 are preferably the same as those of the light source 20. In this embodiment, the second sensor unit 31 is a photodiode with an active layer 53 having the same structure as the light source 20.
[0091] (First substrate)
[0092] The first substrate 41 has a light source 20 and a second sensor section 31 on its first main surface. The material of the first substrate 41 is not particularly limited. For example, the material of the first substrate 41 can be Si, GaAs, sapphire, InP, InAs, Ge, etc., but is not limited to these; it can be selected according to the wavelength band used. From the viewpoint of easily electrically isolating the second sensor section 31 and the light source 20, a semi-insulating substrate is preferred for the material of the first substrate 41. From the viewpoint of enabling large aperture, a GaAs substrate is particularly preferred for the material of the first substrate 41. From the viewpoint of improving measurement sensitivity, a material with high transmittance of light emitted from the light source 20 is preferred for the material of the first substrate 41. Furthermore, from the viewpoint of accurately compensating for output variations of the light source 20, a material that efficiently reflects light emitted from the light source 20 at the second main surface is preferred for the material of the first substrate 41. The first substrate 41 can suppress the transmission of light on the shorter wavelength side than the peak wavelength where the intensity of light emitted from the light source 20 is greatest. This allows for efficient measurement while maintaining a small size.
[0093] (First Sensor Division)
[0094] The first sensor unit 32 receives light (infrared radiation) and outputs a signal corresponding to the amount of light received. For example, a photodiode, photoconductor, thermopile, or pyroelectric sensor can be used as the first sensor unit 32. From the viewpoint of signal processing response speed, the first sensor unit 32 can be a diode structure with a PN junction or PIN junction, containing indium or antimony as the material. The first sensor unit 32 may also contain a mixed-crystal material, which includes at least one material selected from the group consisting of Ga, Al, and As. Preferably, the material and stacked structure of the first sensor unit 32 are the same as those of the light source 20.
[0095] In this embodiment, from the viewpoint of improving measurement sensitivity, an optical filter 16 is provided in the optical path that allows only a specific wavelength band to pass through until the light radiated from the second main surface of the first substrate 41 enters the first sensor unit 32. However, the provision of the optical filter 16 is not necessary and is arbitrary.
[0096] (Second substrate)
[0097] The second substrate 42 has a first sensor portion 32 on its first main surface. Light incident from the second main surface passes through the interior of the second substrate 42 and enters the first sensor portion 32. The material of the second substrate 42 is not particularly limited. The material of the second substrate 42 can be, for example, Si, GaAs, sapphire, InP, InAs, Ge, etc., but is not limited thereto; it can be selected according to the wavelength band used. From the viewpoint of improving measurement sensitivity, the material of the second substrate 42 is preferably a material with high transmittance relative to light incident from the second main surface.
[0098] (wavelength limiter)
[0099] The wavelength limiter restricts the wavelength of light emanating from the active layer 53 of the light source 20 and reaching the second sensor unit 31, and is configured to be connected to the light source 20 without any spatial separation. The connection between the wavelength limiter and the light source 20 can be any connection without spatial separation, including both direct and indirect connections, and also includes the wavelength limiter being located within the light source 20. Here, "without spatial separation" can mean without separation from a space containing the object to be measured (e.g., a gas space); there can be a space between the wavelength limiter and the light source 20 without the object to be measured. The wavelength limiter has the same filtering function as the optical filter 16, ensuring that both the second sensor unit 31 and the first sensor unit 32 receive only light of a specific wavelength. The wavelength limiter is not limited to a specific structure and can be implemented using any of the structures described below.
[0100] like Figure 2 As shown, the wavelength confinement body can be constructed by stacking materials with different refractive indices and is part of the light source 20. The light source 20 has a structure comprising a first layer 51, a second layer 52, and an active layer 53, at least the first layer 51 corresponds to the wavelength confinement body. That is to say, in Figure 2In this example, the wavelength confinement element is provided in the optical path until the light from the active layer 53 reaches the second sensor unit 31 and then the first substrate 41. The first layer 51 is a layer on the first main surface of the first substrate 41, which, like the optical filter 16, allows only light of a specific wavelength to pass through, for example, through a resonant structure (DBR: Distributed Bragg Reflector). Therefore, the second sensor unit 31 can only receive light of a specific wavelength. Here, the second layer 52 can be, for example, a resonant structure (DBR) formed by stacking layers with different refractive indices. Alternatively, the second layer 52 can be a layer of metal that reflects light. In this case, the wavelength confinement element is a combination of the first layer 51 of the resonant structure and the second layer 52 of the metal layer, forming a reflective structure that reflects light of a specific wavelength. When the wavelength confinement element is part of the light source 20, the second sensor unit 31 can also be configured to include a wavelength confinement element in the same way. Furthermore, since the same wavelength of light can be used, it is preferable to include the same wavelength confinement element in both the first layer 51 and the active layer 53. Furthermore, the wavelength band confined by the optical filter 16 is not particularly limited, but since the influence can be reduced even when the wavelength distribution of light deviates significantly, it is preferable that the wavelength distribution of light passing through the optical filter 16 is narrower than that of light passing through the wavelength confining body. The gas sensor can have multiple wavelength confining bodies. These multiple wavelength confining bodies with different structures are sometimes referred to as, for example, a first wavelength confining body, a second wavelength confining body, a third wavelength confining body, or a fourth wavelength confining body for distinction. For example, the first wavelength confining body can be disposed between the light source 20 and the first substrate 41. For example, the second wavelength confining body can be disposed between the second sensor section 31 and the first substrate 41. For example, the third wavelength confining body can be disposed between the first sensor section 32 and the second substrate 42. For example, the fourth wavelength confining body can be disposed between the space and the first substrate 41 (or the second substrate 42). That is, the fourth wavelength confining body can be a structure connected to the front side of the substrate. Additionally, for example, the maximum transmittance of the first and fourth wavelength confining bodies in the wavelength range of (λp×0.6) nm to (λp×0.8) nm can be 5% or less. The light source 20 has a light intensity that reaches its maximum peak wavelength, which is λp.
[0101] like Figures 3A-3C As shown, the wavelength limiter can be part of the substrate, allowing only light of a specific wavelength to be reflected towards the second sensor section 31. Figure 3A and Figure 3B In this example, the specific wavelength reflective layer 54 corresponds to the wavelength confinement body. The specific wavelength reflective layer 54 has the same characteristics as... Figure 2The example uses the same resonant structure. The specific wavelength reflective layer 54 can suppress the transmission of light whose intensity peaks at wavelengths shorter than the light emitted from the light source 20. Here, Figure 3A In the example, the specific wavelength reflective layer 54 has the properties of a semi-reflective mirror 57, allowing a portion of the light to pass through the first sensor unit 32 and a portion of the light to be reflected towards the second sensor unit 31. Figure 3B In this example, the specific wavelength reflective layer 54 has an opening 55, through which light passes to the first sensor unit 32. Light reflected by the specific wavelength reflective layer 54 goes to the second sensor unit 31. Figure 3C In this example, the wavelength limiter is composed of a layer of semi-reflective mirror 57 and filter 56. Only light of a specific wavelength passes through the filter 56, while the semi-reflective mirror 57 allows a portion of the light to pass through the first sensor unit 32 and reflects a portion of the light towards the second sensor unit 31. Alternatively, the wavelength limiter may be configured to include a dichroic mirror.
[0102] like Figure 4A and Figure 4B As shown, the wavelength confinement body can be composed of an absorption layer 58. The absorption layer 58 absorbs a portion of light wavelengths (light wavelengths other than the aforementioned "specific wavelengths") in a manner that prevents them from passing through. The material of the absorption layer 58 is selected based on the wavelength to be absorbed. For example, when it is desired to absorb light with wavelengths of 1 μm or less or 2 μm or less, Si, GaAs, GaInAsP, etc., can be used as the material of the absorption layer 58. From the viewpoint of ease of film formation, GaAs is preferred. In addition, from the viewpoint of insulation, the absorption layer 58 can be a structure containing an oxide layer. For example, when it is desired to absorb light with wavelengths of 6 μm or more, AlInAsSb can be used as the material of the absorption layer 58, and InSb is more preferred. From the viewpoint of increasing the amount of absorption, the absorption layer 58 preferably contains dopants such as Si or Sn. From the viewpoint of increasing light intensity, a portion of the absorption layer 58 can be voids. The voids can be used to change the direction of light propagation, and after reflecting several times in a direction parallel to the surface of the substrate inside the absorption layer, the light is emitted into space. Furthermore, the materials listed as materials for the absorption layer 58 can be used in appropriate combinations. The absorption layer 58 may be part of the light source 20 or the first substrate 41. As a specific example, such as Figure 4A In this way, the absorption layer 58 can be disposed close to the active layer 53 inside the light source 20. Additionally, as... Figure 4B In this way, the absorption layer 58 can be disposed inside the light source 20 at a position in contact with the first substrate 41. Preferably, the intensity of the wavelength of light emitted from the light source 20 that is not absorbed by the wavelength limiter is greater than the intensity of the wavelength of light that is absorbed by the wavelength limiter.
[0103] As described above, the gas sensor according to this embodiment, through the structure described above, can utilize a wavelength limiting body to filter the light incident on the second sensor unit 31, thereby reducing its size. Furthermore, in the gas sensor according to this embodiment, the filter for the light incident on the second sensor unit 31 can be configured as part of the light source 20 or the substrate (first substrate 41), thus facilitating easy optical path design.
[0104] (Methods for determining refractive index)
[0105] The refractive indices of the first and second layers can be determined using an ellipsometer in accordance with "JIS K7142".
[0106] (Methods for measuring the transmittance of optical filters)
[0107] The transmittance of optical filters can be measured using a micro-FT-IR apparatus (Bruker, Hyperion 3000 + TENSOR 27).
[0108] The embodiments described herein have been based on the accompanying drawings and examples. However, it should be noted that those skilled in the art can easily make various modifications or alterations based on this disclosure. Therefore, please be aware that such modifications or alterations are included within the scope of this disclosure.
[0109] Furthermore, the structures of the aforementioned wavelength confinement elements can be combined as long as they are not mutually exclusive. For example, a gas sensor could be configured to include... Figure 2 The first layer 51 of that light source 20 Figure 3A The specific wavelength reflective layer 54, the first layer 51 and the specific wavelength reflective layer 54 function as wavelength confinement bodies.
Claims
1. A gas sensor, comprising: The light source has an active layer; The first sensor unit is configured to receive light emitted from the light source to detect the state of the space. The second sensor unit is configured to allow light emitted from the light source to be incident on it, and is used to compensate for temperature changes or aging changes of the first sensor unit. A first wavelength confinement body restricts the wavelength of light emanating from the active layer and reaching the first and second sensor portions, and is connected to the light source without being separated by the space; and The second wavelength confinement body restricts the wavelength of light that exits from the active layer and reaches the second sensor unit, and is connected to the second sensor unit without being separated by the space.
2. The gas sensor according to claim 1, wherein, The gas sensor includes a third wavelength confinement element that restricts the wavelength of light that exits from the active layer and reaches the first sensor unit, and is connected to the first sensor unit without being separated by the space.
3. The gas sensor according to claim 1, wherein, The first wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the light source or the substrate on which the light source is disposed.
4. The gas sensor according to claim 1, wherein, The second wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the second sensor unit or the substrate on which the second sensor unit is disposed.
5. The gas sensor according to claim 2, wherein, The third wavelength confinement body is constructed by stacking materials with different refractive indices and is part of the first sensor portion or the substrate on which the first sensor portion is disposed.
6. The gas sensor according to claim 2, 4 or 5, wherein, The light source has a light intensity that reaches its maximum peak wavelength λp. The first wavelength confinement has a maximum transmittance of less than 5% in the wavelength range of (λp×0.6) nm to (λp×0.8) nm.
7. The gas sensor according to claim 1, wherein, The first wavelength confinement body prevents a portion of light wavelengths from passing through and is part of the light source or the substrate on which the light source is disposed.
8. The gas sensor according to claim 1, wherein, The second wavelength limiter prevents a portion of light wavelengths from passing through and is part of the second sensor unit or the substrate on which the second sensor unit is disposed.
9. The gas sensor according to claim 2, wherein, The third wavelength confinement body prevents light of a certain wavelength from passing through and is part of the first sensor unit or the substrate on which the first sensor unit is disposed.
10. The gas sensor according to any one of claims 1 to 5, wherein, The first wavelength limiter is disposed in the optical path from the active layer to the second sensor section until the light reaches the substrate on which the light source is disposed.
11. The gas sensor according to any one of claims 1 to 5, wherein, The second wavelength confinement body is disposed on the light path from the active layer to the second sensor portion until the light reaches the substrate on which the second sensor portion is disposed and is incident on the second sensor portion.
12. The gas sensor according to claim 10, wherein, The wavelength limiter has a reflective structure that reflects light of a specific wavelength.
13. The gas sensor according to claim 1, wherein, The gas sensor includes a fourth wavelength confinement element that restricts the wavelength of light that emerges from the active layer and reaches the first sensor portion, and is connected to the front side of the substrate on which the light source is disposed without any gap in the space.
14. The gas sensor according to claim 13, wherein, The light source has a light intensity that reaches its maximum peak wavelength λp. The fourth wavelength confinement has a maximum transmittance of less than 5% in the wavelength range of (λp×0.6)nm to (λp×0.8)nm.
15. The gas sensor according to claim 1, wherein, The gas sensor includes an optical filter disposed in the optical path of the light that exits from the active layer and reaches the first sensor unit.
16. The gas sensor according to any one of claims 1 to 5, wherein, The first sensor unit has the same structure as the light source.
17. The gas sensor according to any one of claims 1 to 5, wherein, When the distance between the first sensor unit and the light source is set as d and the thickness of the substrate on which the light source is mounted is set as T, d / T is in the range of 0.70 to 6.00.