JP2022071816A - Gas detector - Google Patents

Abstract

To provide a compact and high accuracy gas detector using an elliptical mirror.SOLUTION: The gas detector comprises a light emission part 10, a light reception part 20, and a light guide part 30. The shape of at least a portion of inner surface of the light guide part is composed of entire or partial diagram of n ellipsoids, and when it is assumed, using n ellipsoids E1 to En, an ellipse Eci having a maximum area in the cross section of an ellipsoid Ei, and an ellipsoid Esi passing through two focal points Fai, Fbi of the ellipse Eci and having a minimum area in an expansion/contraction relationship with the ellipsoid Ei, not being rotated, that the region inside of the ellipsoid Ei and not including the ellipsoid Esi is a region Ri, that the ellipsoid Ei including the light source region of the light emission part is an ellipsoid Es, that the ellipsoid Ei including the light reception region of the light reception part is an ellipsoid Ed, that the region Ri of the ellipsoid Es is a region Rin, and that the region Ri of the ellipsoid Ed is a region Rout, 60% or more of the light source region exists in the region Rin, and 60% or more of the light reception region exists in the region Rout.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a gas detector.

Gas detectors that detect gas are used in various fields. For example, Patent Document 1 provides a light source that radiates infrared rays and a detector that detects infrared rays of a specific wavelength in a case having an inner surface of an ellipsoid (ellipsoidal mirror), and a gas to be detected is introduced into the case. The device configured to be such is disclosed.

US Patent Application Publication No. 2018/0348121

1 and 2 are examples of light ray tracing in an optical path design in which a light emitting portion and a light receiving portion are arranged at the focal position of an ellipsoidal mirror as in Patent Document 1. When the ellipsoidal mirror is sufficiently large with respect to the size of the light emitting part as shown in FIG. 1, the light rays emitted from the light emitting part placed at the focal position are collected by the light receiving part placed at the other focal point. Can be done. That is, since the light emitting portion can be approximately regarded as a point light source, the light rays emitted from one focal position are concentrated at the other focal position according to the general property of the ellipsoid.

On the other hand, when the ellipsoidal mirror is not sufficiently large with respect to the size of the light emitting portion as shown in FIG. 2, the light rays emitted from the light emitting portion are scattered over the entire ellipsoidal mirror and collected at the light receiving portion of the light receiving element. I can't. This is because the physical image in which the light emitting portion behaves approximately as a point light source is broken, and the aberration of the ellipsoidal mirror due to the size of the light emitting portion is strongly affected.

With the trend of miniaturization of gas detectors in recent years, the size ratio of the light emitting part to the size of the ellipsoidal mirror has become smaller.

An object of the present disclosure made in view of such a point is to provide a small and highly accurate gas detection device using an ellipsoidal mirror.

The gas detection device according to one embodiment is
It is equipped with a light emitting unit, a light receiving unit, and a light guide unit that guides the light from the light emitting unit to the light receiving unit.
The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) ellipsoids.
Let the n ellipsoids be ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En.
The ellipsoid having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n) is defined as the ellipse Ec _i , and passes through the two focal points F _ai and F _bi of the ellipsoid E c _i without being rotated. When the ellipsoid with the smallest volume that has a scaling relationship with the ellipsoid _{Ei is the ellipsoid Esi ,}
The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i .
The ellipsoid E _i including the light source region of the light emitting portion is defined as an ellipsoid E _s .
The _ellipsoid E _i including the light receiving region of the light receiving portion is referred to as an ellipsoid Ed.
The region R _i of the ellipsoid _Es is defined as a region R _in .
When the region R _i of the ellipsoid _Ed is defined as the region R _out ,
More than 60% of the light source region is present in the region R _in , and 60% or more of the light receiving region is present in the region R _out .

The gas detection device according to one embodiment is
It is equipped with a light emitting unit, a light receiving unit, and a light guide unit that guides the light from the light emitting unit to the light receiving unit.
The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) ellipsoids.
Let the n ellipsoids be ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En.
The ellipsoid having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n) is defined as the ellipse Ec _i , and passes through the two focal points F _ai and F _bi of the ellipsoid E c _i without being rotated. When the ellipsoid with the smallest volume that has a scaling relationship with the ellipsoid _{Ei is the ellipsoid Esi ,}
The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i .
The ellipsoid E _i including the light source region of the light emitting portion is defined as an ellipsoid E _s .
The _ellipsoid E _i including the light receiving region of the light receiving portion is referred to as an ellipsoid Ed.
The region R _i of the ellipsoid _Es is defined as a region R _in .
When the region R _i of the ellipsoid _Ed is defined as the region R _out ,
The center of gravity of the light source region or the peak point of luminance is defined as a point G _in , and the center of gravity of the light receiving region is defined as a point G _out .
The point G _in exists in the region R _in , and the point G _out exists in the region R _out .

According to the embodiment of the present disclosure, it becomes possible to provide a small and highly accurate gas detection device using an ellipsoidal mirror.

FIG. 1 is a diagram showing an example of ray tracing in an ellipsoidal mirror. FIG. 2 is a diagram showing another example of ray tracing in an ellipsoidal mirror. FIG. 3 is a perspective view showing a part of the gas detection device according to the embodiment. FIG. 4 is a diagram showing a ray tracing simulation result in a mirror of a spheroid. FIG. 5 is a diagram for explaining the region _Ri . FIG. 6 is a diagram showing a configuration example of the gas detection device according to the present embodiment. FIG. 7 is a diagram showing a modified example of the gas detection device according to the present embodiment. FIG. 8 is a diagram showing a ray simulation result of a general ellipsoid. FIG. 9 is a diagram showing a configuration example of a light emitting unit including a passive element and a light receiving unit including an indirect element. FIG. 10 is a diagram showing another configuration example of a light emitting unit including a passive element and a light receiving unit including an indirect element.

<Gas detection device of this embodiment>
The gas detection device of the present embodiment includes a light emitting unit, a light receiving unit, and a light guide unit that guides light from the light emitting unit to the light receiving unit.

The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) spheroids.

N spheroids are defined as ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En. It passes through the two focal points F _ai and F _bi of the ellipsoid E _i (a natural number satisfying i: 1 ≤ i ≤ n), has the same axis of rotational symmetry as the axis of rotational symmetry of the ellipsoid E _i , and has the same axis of rotational symmetry as the ellipsoid E _i . An ellipsoid having a similarity reduction relationship is defined as an ellipsoid E _si . The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i . The ellipsoid E _i including the light source region of the light emitting portion is defined as the ellipsoid E _s . The ellipsoid E _i including the light receiving region of the light receiving portion is defined as an ellipsoid Ed (when there is one ellipsoid, that is, when _n = 1, E _s = _Ed ). The region _Ri of the ellipsoid _Es is defined as the region R _in . The region R _i of the _ellipsoid Ed is defined as the region R _out .

In the gas detection device of the present embodiment, 60% or more of the area of the light source region is present in the region R _in , and 60% or more of the area of the light receiving region is present in the region R _out .

Although the detailed principle will be described later, by providing this configuration, it becomes possible to provide a compact and highly accurate gas detection device using an ellipsoidal mirror.

<Example of specific configuration of the gas detection device of this embodiment>
FIG. 3 is a perspective view showing a part of the gas detection device according to the embodiment of the present disclosure. As an example, the gas detection device is a small device having a length × width × height of 7 mm × 5 mm × 3 mm, and is also referred to as a gas sensor.

In the present embodiment, the gas detection device is an NDIR (Non Dispersive InfraRed) type device that measures the concentration of the detected gas based on the infrared rays transmitted through the introduced gas.

The detected gas is, for example, carbon dioxide, water vapor, carbon monoxide, nitrogen monoxide, ammonia, sulfur dioxide or alcohol, a hydrocarbon gas such as formaldehyde, methane, or propane.

<Architecture (mutual relationship of components)>
The gas detection device includes a light emitting unit, a light receiving unit, and a light guide unit. The gas detector may further include a retainer. Further, the gas detection device may additionally include a control unit. The gas detection device according to the embodiment of the present disclosure shown in FIG. 3 includes a light receiving unit 20 held by a holding unit 40, a light emitting unit 10, and a light guide unit 30 held by the holding unit 40. Although not shown, the holding unit 40 may include a control unit that controls at least one of the light emitting unit 10 and the light receiving unit 20.

The surfaces of the light emitting unit 10 and the light receiving unit 20 are in contact with the space (detection space) between the inner wall of the light guide unit 30 and the upper surface of the holding unit 40. Further, the light guide unit 30 is provided with a gas port 31 capable of introducing and deriving gas into the detection space.

The light radiated from the light emitting unit 10 is reflected at least once on the inner surface of the light guide unit 30 and reaches the light receiving unit 20.

Next, the constituent members of the gas detection device of the present embodiment will be described in detail.

<Light emitting part>
The light emitting unit 10 is a component that emits light used for detecting the gas to be detected. The light emitting unit 10 is not particularly limited as long as it outputs light including a wavelength absorbed by the detected gas. In the present embodiment, the light emitted by the light emitting unit 10 is infrared rays, but the light is not limited thereto.

The light emitting unit 10 has a light emitting element 10A. In the present embodiment, the light emitting element 10A is an LED (light emitting diode), but as another example, a lamp, a laser (Light Amplification by Standardized Emission of Radiation), an organic light emitting element, or a MEMS (MicroElectromechanical System). ) It can be a heater or the like. Further, the light emitting unit 10 may include not only the light emitting element 10A but also a passive element that passively emits light by receiving the light emitted by the light emitting element 10A. Specifically, the passive element is a mirror, an optical filter, a phosphor, an optical image, an optical fiber, an optical waveguide, a lens, or a diffraction grating.

In this embodiment, since the light emitting unit 10 has only the light emitting element 10A, the light emitting unit 10 and the light emitting element 10A have the same meaning.

The light emitting unit 10 has a light source region. The light source region is a region in which photons of the light emitting element 10A are generated when the light is directly guided from the light emitting element 10A to the light guide unit 30 without passing through the passive element as in the present embodiment. Specifically, if it is a quantum type light emitting element 10A, it is an active region, and if it is a thermal light source, it is a high temperature region. For example, in the case of a lamp, it is a filament.

Further, when the light emitting unit 10 includes a passive element and the light emitted by the light emitting element 10A is guided to the light guide unit 30 via the passive element, the light source region is an aggregate of the emission ends of the light rays of the passive element. be. Specifically, when the passive element is a mirror, the light source region is a region that reflects light rays.

Further, when the passive element is an optical filter having a wavelength selection function, a region in which a light ray passes on a surface in contact with the space of the optical filter may be regarded as a light source region. Further, when the passive element is an optical fiber, an optical waveguide, or a lens, the emission surface through which the light beam passes on the surface in contact with the space may be regarded as the light source region.

Further, when an optical image is formed as the light emitting portion 10 by a lens, a mirror, or the like, the formed image may be regarded as a light source region.

Here, the light emitting element 10A is preferably a planar surface light source such as an LED, a MEMS heater, or a VCSEL (Vertical Cavity Surface Emitting Laser).

<Light receiving part>
The light receiving unit 20 is a component that receives light transmitted through the introduced gas. The light receiving unit 20 is not particularly limited as long as it has sensitivity in the band of light including the wavelength absorbed by the detected gas. In the present embodiment, the light received by the light receiving unit 20 is infrared rays, but the light is not limited thereto.

The light receiving unit 20 has a light receiving element 20A. In the present embodiment, the light receiving element 20A is a photodiode, but another example may be a phototransistor, a thermopile, a charcoal sensor, a bolometer, a photoacoustic detector, or the like. Further, the light receiving unit 20 may include not only the light receiving element 20A but also an indirect element that guides light to the light receiving element 20A. Specifically, the indirect element is a mirror, an optical filter, a phosphor, a lens, a diffraction grating, an optical fiber, and an optical waveguide.

In this embodiment, since the light receiving unit 20 has only the light receiving element 20A, the light receiving unit 20 and the light receiving element 20A have the same meaning.

The light receiving unit 20 has a light receiving region. The light receiving region is a region having a function of converting the received light into a signal in the light receiving element 20A when the light receiving element 20A directly receives light without interposing the indirect element as in the present embodiment. Specifically, when the light receiving element 20A is a photodiode, the light receiving region is an active layer, and in the case of a thermopile, it is a thermoelectric conversion unit.

Further, when the light receiving unit 20 receives light from the light receiving element 20A via the indirect element, the light receiving region has an optical function in guiding the received light from the indirect element to the light receiving element 20A, and is a region through which the light beam passes. be. Specifically, when the indirect element is an optical filter having a wavelength selection function, the region in which the light beam passes on the surface of the optical filter in contact with the space may be regarded as the light receiving region. Further, when the indirect element is an optical fiber, an optical waveguide, or a lens, the incident surface on which the light ray passes on the surface in contact with the space may be regarded as the light receiving region. When the indirect element is a mirror, the light receiving region is a region that reflects light rays.

<Light guide unit>
The light guide unit 30 is a member that guides the light emitted by the light emitting unit 10 to the light receiving unit 20, and is an optical system of a gas detection device. The light emitted from the light emitting unit 10 is reflected by the light guide unit 30 and reaches the light receiving unit 20. In other words, the light guide unit 30 optically connects the light emitting unit 10 and the light receiving unit 20.

In the present embodiment, the inner surface of the light guide unit 30 is a mirror (reflection surface). The shape of at least a part of the inner surface is a figure of all or a part of a spheroid. The light guide unit 30 may further include a planar mirror, a concave mirror or a convex mirror, a lens, and a diffraction grating as an auxiliary.

The material constituting the mirror may be, for example, metal, glass, ceramics, stainless steel, etc., but is not limited to this.

From the viewpoint of improving the detection sensitivity, it is preferable that the material constituting these mirrors is made of a material having a small light absorption coefficient and a high reflectance. Specifically, a resin housing coated with aluminum, an alloy containing gold, silver, a dielectric, or a laminate thereof is preferable. Examples of the material of the resin housing include LCP (liquid crystal polymer), PP (polyetherketone), PEEK (polyetheretherketone), PA (polyetherketone), PPE (polyphenylene ether), PC (polycarbonate), or PPS (polyphenylensuulfide). ), PMMA (polymethylmethacrylate resin), PAR (polyallylate resin), etc., and a hard resin obtained by mixing two or more of these. Further, from the viewpoint of reliability and aging, a resin housing coated with gold or an alloy layer containing gold is preferable. Further, it is preferable to form a dielectric laminated film on the surface of the metal layer in order to increase the reflectance. When the inner surface of the light guide portion 30 is formed on the resin housing by thin film deposition or plating, it is possible to improve productivity and weight reduction as compared with the case where the inner surface is formed of a metal material. Further, the difference in the coefficient of thermal expansion from the holding portion 40 is reduced, thermal deformation is suppressed, and the sensitivity is less likely to fluctuate.

Further, the light guide portion 30 may be formed by cutting, and is more preferably formed by injection molding from the viewpoint of productivity.

<Holding part>
The holding unit 40 is a member that holds the light receiving unit 20, the light emitting unit 10, and the light guide unit 30. Holding means trying to maintain the relative positional relationship of each member with respect to an external force. The form of holding is not particularly limited, but mechanical holding is preferable. The form of retention may be electromagnetic or chemical retention.

When the gas detection device of the present embodiment has a control unit, the control unit may be held by the holding unit 40.

The holding unit 40 is not particularly limited as long as it can hold the light receiving unit 20, the light emitting unit 10, and the light guide unit 30. In the present embodiment, the holding portion 40 is a resin package, but as another example, it may be a printed circuit board or a ceramic package. Alternatively, the semiconductor substrate may be used as the holding portion 40, and the light receiving portion 20 and the light emitting portion 10 may be formed on the same semiconductor substrate. When the holding unit 40 is a resin package, a lead frame may be built in, and the lead frame, the light emitting unit 10, the light receiving unit 20, and the control unit may be electrically connected by a wire or the like. When the holding portion 40 is a printed circuit board, the printed circuit board, the light receiving portion 20, and the light emitting portion 10 may be electrically and mechanically bonded by solder. Further, the holding portion 40 and the light guide portion 30 are mechanically held by an adhesive, screws, claws, fittings, grommets, welding and the like. Further, the holding portion 40 may have a connection terminal for making an electrical connection with the outside.

<Control unit>
The control unit is a member that controls at least one of the light emitting unit 10 and the light receiving unit 20. The control unit may have an analog-to-digital conversion circuit that converts an analog electric signal output from the light receiving unit 20 into a digital electric signal. Further, the control unit may have a calculation unit that executes a gas concentration calculation based on the converted digital electric signal.

The control unit may have at least one of a general-purpose processor that executes a function according to a program to be read and a dedicated processor specialized in a specific process. The dedicated processor may include an application specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD).

<Size of gas detector>
1 (a) and 1 (b) show that when the ellipsoidal mirror is sufficiently large with respect to the size of the light emitting unit 10, the light rays emitted from the light emitting unit 10 can be collected by the light receiving unit 20. rice field. Here, as the size of the light guide unit 30, a part of the shape of the light guide unit 30 is configured as an ellipsoid, of which the maximum length of the ellipsoid including the light emitting unit 10 is Lms and the maximum length of the light source region is set. Defined as Ls. Here, when the condition of Ls <Lms / 50 is satisfied, the size of the light emitting unit 10 is sufficiently small with respect to the ellipsoidal mirror, and it can be approximately regarded as a point light source. Therefore, the light rays emitted from one focal position are focused on the other focal position. On the other hand, when the ellipsoidal mirror is not sufficiently large with respect to the size of the light emitting unit 10 as shown in FIGS. 2 (a) and 2 (b) (Ls ≧ Lms / 50), the light emitting unit 10 exits. The light rays are scattered over the entire ellipsoidal mirror and cannot be collected by the light receiving unit 20.

Although not particularly limited, the gas detection device of the present embodiment exerts a particularly remarkable effect when Ls ≧ Lms / 50.

Although not particularly limited, similarly, in the gas detection device of the present embodiment, when the maximum length of the ellipsoid including the light receiving unit 20 is Lmd and the maximum length of the light receiving unit 20 is Ld, Ld ≧ Lmd / 50. In the case of, it has a particularly remarkable effect.

Next, the principle of the gas detection device of the present embodiment will be described in detail with reference to the drawings.

<Explanation of the principle>
FIG. 4 is a diagram for explaining the basic principle in the present embodiment, and is a result of a ray tracing simulation in a plane passing through the axis of rotation of a spheroidal mirror. As described above, the gas detector may be configured with a plurality of spheroids, but one spheroid will be used in the explanation of the basic principle. When n (n: 1 or more natural numbers) spheroids constituting the gas detection device are ellipsoids E ₁ , ..., E _i , ..., En (natural numbers satisfying i: _1≤i≤n ) In addition, the spheroids of FIGS. 4 (a), 4 (b) and 5 correspond to one ellipsoid Ei ( _i = n = 1).

FIG. 4A shows a simulation result of a light ray when the light ray is emitted from the point of the region _Ri , which is a region outside the focal points F _ai and F _bi of the spheroid. At this time, the light rays repeatedly reflect on the mirror surface. However, the light beam does not penetrate into the region R _INTER , which is the region connecting the focal point and the focal point near the center of the ellipsoid.

Further, FIG. 4B is a simulation result of a light ray when the light ray is emitted from the point of the region R _INTER . No light rays enter the region R _EDGE , which is the region at both ends outside the focal points F _ai and F _bi of the spheroid.

The separation phenomenon of the intrusion region of the light ray in the region _{Ri and the region R INTER (} hereinafter referred to as the region separation phenomenon) includes the trajectory of the light ray and the trajectory of a rigid sphere that repeatedly elastically collides with the wall having the same shape as the mirror surface. Is explained by equating. General angular momentum J = _which is the inner product of the angular momentum L _Fai centered on the focal point F _ai and the angular momentum L F _bi centered on the focal point F bi with respect to the motion of the rigid sphere in the free space elastically reflected by the elliptical wall. L _Fai and L _Fbi are saved. At this time, since the orbit of the rigid sphere emitted from the point of the region _Ri is rotationally moving in the same direction when viewed from each focal point, the angular momentums L _Fai and L _{F bi} are in the same direction, and the general angular momentum J is positive. (J> 0). On the other hand, in the case of an orbit passing through the region R _INTER , the general angular momentum J is negative because the rotation direction seen from each focal point is opposite (J <0).

That is, according to the conservation law of the general angular momentum J, the trajectory (ray) of the rigid sphere first emitted from the region _Ri has a positive value for the general angular momentum J, and no matter how many times it is reflected by the wall on the mirror, The general angular momentum J does not become the orbit (ray) of a rigid sphere passing through the region R _INTER with a negative value. On the contrary, the trajectory (light ray) of the rigid sphere emitted from the region R _INTER where the general angular momentum J is a negative value has a positive value regardless of how many times it is reflected by the wall on the mirror. It does not become the orbit (ray) of a rigid sphere passing through the region R _i . In this way, the region separation phenomenon occurs. Here, when the general angular momentum J = 0, it corresponds to the orbit emitted from the focal point and reaching the other focal point, whereby the phase space of the motion of the rigid sphere is separated.

Here, when the ellipsoid having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n) is the ellipsoid Ec _i , the focal point is uniquely determined if it is a spheroid. The largest area is the cross section through the two focal points. Further, when the ellipsoid having the smallest volume having a scaling relationship with the ellipsoid E _i without being rotated through the two focal points F _ai and F _bi of the ellipsoid E c _i is the ellipsoid E _si , it is rotated. If it is an ellipsoid, the focus is uniquely determined. Therefore, in the above principle, in general, the ellipse having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1≤i≤n) is defined as the ellipse Ec _i , and the two focal points F of the ellipsoid Ec _i . This is true when the ellipsoid E _si , which passes through _ai and F _bi and has the smallest volume in the relationship of enlargement / reduction with the ellipsoid E _i without being rotated, is defined as the ellipsoid E si. "

Next, the configuration of the gas detection device of the present embodiment based on the above-mentioned separation phenomenon of the light beam intrusion region will be described.

FIG. 5 is a diagram illustrating the present embodiment in which the region separation phenomenon is applied to the inner surface of the light guide unit 30 including one spheroidal shape. By arranging at least a part of the light source region in the region _Ri due to the region separation phenomenon, the light rays emitted from the light source at this position always exist in the region _Ri even if the mirror repeatedly reflects them. At this time, by similarly arranging the light receiving region in the region _{Ri, the light rays stay in the region Ri without being scattered in the region R INTER , so} that the light can be efficiently collected with respect to the light receiving region.

This makes it possible to improve the gas sensitivity of the detector. Even when the light source region and the light receiving region partially exist in the region _Ri , the effect of the present embodiment is exhibited in the partial region. Therefore, the effect is realized when 60% or more of the light source region exists in the region _Ri . Further, although the expressions are complementary and the same, the effect is realized when less than 40% of the light source region and the light receiving region are present in the region R _INTER . From the viewpoint of improving gas sensitivity, it is preferable that 70% or more of the light source region is present in the region R _i , more preferably 80% or more of the light source region is present in the region R _i , and the entire light source region is present in the region R _i . It is preferable to be present in. Similarly, from the viewpoint of improving gas sensitivity, it is preferable that 70% or more of the light receiving region is present in the region _Ri , more preferably 80% or more of the light receiving region is present in the region _Ri , and all of the light receiving region is present. It is preferably present in the region _Ri .

That is, the shape of at least a part of the inner surface of the light guide portion 30 passes through the two focal points F _ai and F _bi of the ellipsoid E _i , has the same axis of rotational symmetry as the axis of rotational symmetry of the ellipsoid E _i , and is an ellipsoid. When the ellipsoid that has a similar reduction relationship with E _i is defined as the ellipsoid E _si , the area inside the ellipsoid E _i that does not include the ellipsoid E _si is defined as the area R _i , and the area is the light source region of the light emitting unit 10. Since 60% or more of the area of the light receiving region of the light receiving unit 20 exists in the region _Ri , a compact and highly accurate gas detection device using an ellipsoidal mirror is realized. This effect is noticeable when the two focal points of the spheroid are sufficiently far apart and the region R _INTER is formed. Specifically, this effect is remarkably exhibited when the ratio "a / b" of the short radius b and the long radius a of the spheroid is 1.2 or more.

Here, it is assumed that 60% or more of the light source region exists in the region R _in and 60% or more of the light receiving region exists in the region R _out . However, when focusing on the center of gravity or the peak point of the luminance, the following holds. That is, the center of gravity of the light source region or the peak point of luminance is defined as a point G _in , and the center of gravity of the light receiving region is defined as a point G _out . At this time, the point G _in exists in the region R _in , and the point G _out exists in the region R _out .

<Arrangement in multiple ellipsoids>
In the above, the embodiment in the case of one spheroidal mirror (in the case of i = 1) has been described, but the gas detection device of the present embodiment includes a light guide unit 30 having a plurality of spheroidal mirrors. The same effect is exhibited with respect to.

FIG. 6 is a diagram illustrating a gas detection device according to the present embodiment when three light guide portions 30 having an inner surface (reflection surface) having a spheroidal shape are used. FIG. 6A is a schematic diagram. FIG. 6B is a ray tracing simulation result.

In FIG. 6A, the region R ₁ with respect to the ellipsoid E ₁ including the light source region among the spheroids is defined as the region R _in . Adjacent ellipsoids E ₂ include region R ₂ . When the light source region is in the region R _in , the light rays are carried without being scattered in the region R _in on the other end side of the ellipsoid _Es1 . By considering the region where this light is carried as the light source of the ellipsoid E2 again, the light rays can move without being _scattered in the region _R2 . In order to efficiently realize this, an auxiliary reflection unit 50 as shown in FIGS. 6 (a) and 6 (b) is provided as a light guide unit 30 to the adjacent spheroid for folding back the light beam. It is preferable to have more. The form of the auxiliary reflection unit 50 is not particularly limited, and examples thereof include a flat mirror, a concave mirror, and a convex mirror. The auxiliary reflection unit 50 may be formed of a figure different from that of the spheroid. From the viewpoint of simplicity and efficiency, the auxiliary reflection unit 50 is preferably a flat mirror. Further, the auxiliary reflection unit 50 may have a wavelength selection function. The auxiliary reflection unit 50 is preferably arranged in the region _Ri of the spheroid.

By repeating this sequentially, as shown in the ray tracing simulation result of FIG. 6B _, the ray can move without being scattered _, but finally the light receiving region is set in the region R3 of the ellipsoid E3. By arranging it in a certain region R _out , light can be efficiently collected as in the case of one spheroidal mirror.

That is, an ellipsoidal mirror was used because 60% or more of the area of the light source region of the light emitting unit 10 is present in the region R _in and 60% or more of the area of the light receiving region of the light receiving unit 20 is present in the region R _out . A compact and highly accurate gas detection device can be realized. It is possible to design an optical path length longer than in the case of one spheroidal mirror, which may be preferable from the viewpoint of detection accuracy.

FIG. 7 is a modified example when there are two spheroids. The light guide unit 30 is composed of a mirror in which two spheroids are combined and one plane mirror, and the long axes of the two spheroids intersect at right angles. At this time, by providing the auxiliary reflection unit 50 in the region _Ri , a compact and highly accurate gas detection device using an ellipsoidal mirror can be realized as in the case of FIG.

Although the light guide unit 30 has been described above as a spheroid, it may be a general ellipsoid, that is, one having no rotational symmetry and having three different diameters. This is because the system of rigid spheres that elastically reflect in the ellipsoidal wall (so-called billiard problem) is also an integrable system, so there is a conserved quantity similar to the general angular momentum J, and the same region separation phenomenon follows. FIG. 8 shows a simulation result of a light ray when the light ray is emitted from the point of the region _Ri , which is a region outside the focal points F _ai and F _bi of a general ellipsoid. The focal points F _ai and F _bi shown in FIG. 8 are the focal points in a plane ellipsoid that has the maximum area when the ellipsoid is cut by a plane, and the light rays emitted from the region R _i outside the focal point reflect reflection. Even if it is repeated, it remains in the area _Ri . This is also understood from the fact that when the smallest diameter of an ellipse becomes 0 in the limit, it becomes the same as the region separation phenomenon due to the focal point when a light beam is emitted in a plane ellipse, and a general ellipse is a general ellipse. , The case is positioned between the case of the spheroid described so far and the case of this plane ellipse.

Although the embodiments have been described above based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and modifications based on the present disclosure. It should therefore be noted that these modifications and modifications are within the scope of this disclosure. For example, the functions included in each member, each means, and the like can be rearranged so as not to be logically inconsistent, and a plurality of means and the like can be combined or divided into one.

9 and 10 are diagrams showing a configuration example of a light emitting unit 10 including a passive element and a light receiving unit 20 including an indirect element in another embodiment. In the example of FIG. 9, the light emitting unit 10 includes a light emitting element 10A and a passive element which is a 45 ° mirror. Further, in the example of FIG. 9, the light receiving unit 20 includes a light receiving element 20A and an indirect element which is a 45 ° mirror. In the example of FIG. 10, the light emitting unit 10 includes a light emitting element 10A and a passive element which is a lens. Further, in the example of FIG. 10, the light receiving unit 20 includes a light receiving element 20A and an indirect element which is a concave mirror.

(Additional note)
The gas detection device according to one embodiment is
It is equipped with a light emitting unit, a light receiving unit, and a light guide unit that guides the light from the light emitting unit to the light receiving unit.
The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) spheroids.
Let the n spheroids be ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En.
It passes through the two focal points F _ai and F _bi of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n), has the same axis of rotational symmetry as the axis of rotational symmetry of the ellipsoid E _i , and has the same axis of rotational symmetry as the ellipsoid E _i . When the ellipsoid that has a similar reduction relationship with is the ellipsoid E _si ,
The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i .
The ellipsoid E _i including the light emitting surface of the light emitting portion is defined as an ellipsoid E _s .
The _ellipsoid E _i including the light receiving surface of the light receiving portion is referred to as an ellipsoid Ed.
The region R _i of the ellipsoid _Es is defined as a region R _in .
When the region R _i of the ellipsoid _Ed is defined as the region R _out ,
60% or more of the area of the light emitting surface may be present in the region R _in , and 60% or more of the area of the light receiving surface may be present in the region R _out .

10 Light emitting part 20 Light receiving part 30 Light guide part 31 Gas port 40 Holding part 50 Auxiliary reflecting part

Claims (12)

It is equipped with a light emitting unit, a light receiving unit, and a light guide unit that guides the light from the light emitting unit to the light receiving unit.
The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) ellipsoids.
Let the n ellipsoids be ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En.
The ellipsoid having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n) is defined as the ellipse Ec _i , and passes through the two focal points F _ai and F _bi of the ellipsoid E c _i without being rotated. When the ellipsoid with the smallest volume that has a scaling relationship with the ellipsoid _{Ei is the ellipsoid Esi ,}
The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i .
The ellipsoid E _i including the light source region of the light emitting portion is defined as an ellipsoid E _s .
The _ellipsoid E _i including the light receiving region of the light receiving portion is referred to as an ellipsoid Ed.
The region R _i of the ellipsoid _Es is defined as a region R _in .
When the region R _i of the ellipsoid _Ed is defined as the region R _out ,
A gas detection device in which 60% or more of the light source region is present in the region R _in and 60% or more of the light receiving region is present in the region R _out . The gas detection device according to claim 1, wherein the ratio a / b of the semi-major axis a and the semi-minor axis _b of the ellipsoid _Es and the ellipsoid Ed is 1.2 or more. The gas detection device according to claim 1 or 2, wherein Ls ≧ Lms / 50 when the maximum length of the light source region is Ls and the maximum length of the ellipsoid Es is _Lms . The gas detection device according to any one of claims 1 to 3, wherein Ld ≧ Lmd / 50 when the maximum length of the light receiving portion is Ld and the maximum length of the ellipsoid Ed is _Lmd . The gas detection device according to any one of claims 1 to 4, wherein the same holding unit holds the light emitting unit and the light receiving unit. The gas detection device according to claim 5, wherein the same holding unit further holds a control unit. The gas detection device according to any one of claims 1 to 6, wherein at least one of the light receiving unit and the light emitting unit includes an optical filter. The gas detection device according to any one of claims 1 to 7, further comprising an auxiliary reflection unit having a figure different from the n ellipsoids. The gas detection device according to claim 8, wherein the auxiliary reflection unit exists in the region _Ri . The gas detection device according to any one of claims 1 to 9, wherein the light emitting unit is a surface light source. The gas detection device according to any one of claims 1 to 10, wherein the n ellipsoids are spheroids. It is equipped with a light emitting unit, a light receiving unit, and a light guide unit that guides the light from the light emitting unit to the light receiving unit.
The shape of at least a part of the inner surface of the light guide portion is composed of all or a part of n (n: 1 or more natural numbers) ellipsoids.
Let the n ellipsoids be ellipsoids E ₁ , E ₂ , ..., E _{(n-1) ,} En.
The ellipsoid having the largest area in the cross section of the ellipsoid E _i (a natural number satisfying i: 1 ≦ i ≦ n) is defined as the ellipse Ec _i , and passes through the two focal points F _ai and F _bi of the ellipsoid E c _i without being rotated. When the ellipsoid with the smallest volume that has a scaling relationship with the ellipsoid _{Ei is the ellipsoid Esi ,}
The region inside the ellipsoid E _i and not including the ellipsoid E _si is defined as the region R _i .
The ellipsoid E _i including the light source region of the light emitting portion is defined as an ellipsoid E _s .
The _ellipsoid E _i including the light receiving region of the light receiving portion is referred to as an ellipsoid Ed.
The region R _i of the ellipsoid _Es is defined as a region R _in .
When the region R _i of the ellipsoid _Ed is defined as the region R _out ,
The center of gravity of the light source region or the peak point of luminance is defined as a point G _in , and the center of gravity of the light receiving region is defined as a point G _out .
A gas detector in which a point G _in is present in the region R _in and a point G _out is present in the region R _out .

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