WO2012140482A1

WO2012140482A1 - Gas component detection device

Info

Publication number: WO2012140482A1
Application number: PCT/IB2012/000685
Authority: WO
Inventors: 古久保　英一; 俊輔松島
Original assignee: パナソニック株式会社
Priority date: 2011-04-11
Filing date: 2012-04-05
Publication date: 2012-10-18
Also published as: JP2012220353A; TW201243313A

Abstract

In order to simplify and reduce the dimensions of wiring, a light-emitting section (3) and a light receiving section (4) are each formed from a semi-conductor bare chip (a light-emitting diode chip and a photo-diode chip), and the optical path of the infrared light from the light-emitting section (3) to the light-receiving section (4) is altered so as to be a polygonal line rather than a straight line. Therefore, in comparison to conventional examples (see patent documents 1 and 2) in which package-type light-emitting diodes and photo-diodes are used, this embodiment has the benefit of simplifying the wiring. Additionally, in this embodiment the optical path of the infrared light (see the dashed line in fig. 1) is altered by a first reflecting mirror (80) and a second reflecting mirror (81) so as to be approximately a 'C' shape, and thus the dimensions of the vertical height of the optical path can be reduced (given a low profile) without reducing the length of the optical path, in contrast to the conventional example disclosed in document 2 in which the optical path is approximately a 'V' shape.

Description

Gas component detector

The present invention relates to a gas component detection device that detects the concentration of a gas component using infrared absorption characteristics.

As a conventional gas component detection device, there are an infrared gas detector described in Patent Document 1, an infrared gas analyzer described in Patent Document 2, and the like.
The conventional example described in Cited Document 1 includes a housing in which a gas to be detected (for example, carbon monoxide) is introduced, a light source that irradiates infrared rays in the housing, and an infrared detector that detects infrared rays in the housing. With. The light source consists of a light emitting diode chip (bare element), a stem on which the bare element is mounted, a package type light emitting diode composed of a sealing material for sealing the bare element, and the like from a lead terminal protruding from the stem. Power is emitted to emit light. The infrared detector is composed of a photodiode chip (bare element), a stem on which the bare element is mounted, a package-type photodiode composed of a sealing material for sealing the bare element, and is projected from the stem. A detection signal is taken out from the lead terminal. In this conventional example, an ellipsoidal space is formed inside the housing, and the light emitting diode chip and the photodiode chip are located at two focal points of the ellipsoid. On the other hand, the conventional example described in the cited document 2 includes a box-shaped metal case, an elliptical reflecting mirror disposed in the metal case, a light source and a light receiver disposed to face the reflecting surface of the elliptical reflecting mirror, and the like. The metal case is provided with a vent hole, and a mixed gas containing a gas to be detected (for example, carbon dioxide) is introduced into the metal case through the vent hole. And the detection target which exists in a housing or a metal case according to the quantity (level) of the infrared rays received by the infrared detector or the light receiver without being absorbed in the detection target gas among the infrared rays irradiated from the light source The concentration of the gas can be detected.
JP 2006-275980 A JP-A-9-184803

By the way, in the conventional example described in the cited document 1, since both the light source and the infrared detector are configured by package-type components and are arranged so that their optical axes coincide with each other, the leads of the light source and the infrared detector are arranged. There was a problem that wiring to the terminals became difficult. Further, in the conventional example described in the cited document 2, since it is necessary to increase the distance between the light source and the light receiver and the elliptical reflecting mirror to some extent in order to improve the detection sensitivity, it is necessary to reduce the height dimension of the metal case (low There was a problem that it was difficult.
The present invention has been made in view of the above problems, and an object thereof is to simplify and reduce the height of wiring.

A gas component detection device according to an embodiment of the present invention includes one or more light-emitting units composed of semiconductor chips that emit infrared rays, and one or more light-receiving units composed of semiconductor chips that receive infrared rays and convert them into electrical signals. , A holder that holds the light emitting unit and the light receiving unit, a first optical path changing unit that changes an optical path of infrared rays emitted from the light emitting unit in a longitudinal direction of the holding unit, and a change in the first optical path changing unit And a second optical path changing unit that changes the optical path in a direction crossing the light receiving surface of the light receiving unit.
Preferably, the gas component detection device further includes one or more wavelength filters including a predetermined wavelength band in a pass band, and the light receiving unit receives infrared light that passes through the wavelength filter.
In this gas component detection device, it is preferable that the wavelength filter is held by the holding body together with the light receiving unit.
In this gas component detection device, it is preferable that the wavelength filter is disposed on the optical path between the first optical path changing unit and the second optical path changing unit.
In this gas component detection device, the wavelength filter is preferably attached to the light receiving unit.
In this gas component detection device, at least one of the wavelength filters includes a first wavelength filter that includes a wavelength band that is absorbed by the gas to be detected in a pass band, and the pass band of the first wavelength filter. And a second wavelength filter that includes a wavelength band in the vicinity of the passband in the passband, wherein at least one of the light receivers receives the infrared light that passes through the first wavelength filter. And a second light receiving portion that receives infrared light that passes through the second wavelength filter.
The gas component detection device includes a signal processing circuit unit that processes an electrical signal output from the light receiving unit, and the signal processing circuit unit is sandwiched between the light emitting unit and the light receiving unit and changes the first optical path. It is preferable that the optical path is arranged at a position that does not overlap the optical path that is changed by the unit.
In this gas component detection device, it is preferable that a reflecting mirror is disposed between the signal processing circuit unit and the optical path.
In this gas component detection device, the reflecting mirror is formed in a flat plate shape having one surface as a reflecting surface, and is held by the holding body so that the reflecting surface is flush with the light emitting surface of the light emitting unit. preferable.
In this gas component detection device, it is preferable that a wall that shields infrared rays emitted from the light emitting unit is provided between the light emitting unit and the signal processing circuit unit.
In this gas component detection device, the wall is preferably formed integrally with the holding body.
In this gas component detection device, it is preferable that a condensing lens is disposed on an optical path between the light emitting unit and the first optical path changing unit.
In this gas component detection device, the holding body is preferably a three-dimensional wiring board in which wirings to the light emitting unit and the light receiving unit are integrally formed.
The gas component detection device includes a cover that holds the first optical path changing unit and the second optical path changing unit and is coupled to the holding body, and includes one or a plurality of covers on a coupling surface of the cover with the holding body. It is preferable that a protrusion is provided, a fitting hole for fitting with the protrusion is provided on the coupling surface of the holding body, and a hole having a smaller diameter than the fitting hole is provided on the bottom surface of the fitting hole.

The invention's effect

The gas component detection device of the present invention has an effect that the wiring can be simplified and reduced in height.

The objects and features of the present invention will become apparent from the following drawings and description of preferred embodiments.
1 is a schematic cross-sectional view of a first embodiment. It is a schematic exploded perspective view same as the above. It is a schematic perspective view of the circuit block same as the above. It is a rough principal part sectional drawing same as the above. FIG. 6 is a schematic cross-sectional view showing another configuration of the same, partially omitted. The other structure of a light-receiving part and a wavelength filter in the same as above is shown, (a) is a schematic sectional view, (b) is a schematic exploded perspective view, and (c) is a schematic sectional view of still another configuration. is there. 6 is a schematic exploded perspective view of Embodiment 2. FIG. It is a schematic perspective view of the circuit block which shows another structure same as the above.

Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, which form a part of this specification. The same or similar parts throughout the drawings are denoted by the same reference numerals, and the description thereof is omitted.
(Embodiment 1)
A gas component detection apparatus (hereinafter referred to as a gas sensor) of the present embodiment includes a circuit block 1 and an optical block 2 as shown in FIG. In the following description, up, down, left, and right front and back are defined in FIG.
The circuit block 1 is configured by housing a light emitting unit 3, a light receiving unit 4, a wavelength filter 5, a wiring board 11 on which a signal processing circuit unit 6 is mounted in a body 10 made of a synthetic resin molding. The light emitting unit 3 includes a semiconductor bare chip that emits infrared light (for example, a light source in which a resistance element using a MEMS technology is formed on a light emitting diode chip or a semiconductor substrate). However, the wavelength of infrared rays radiated from the light emitting unit 3 is a wavelength that is easily absorbed by a gas to be detected (for example, carbon monoxide, carbon dioxide, methane, nitrogen oxide, etc.). The light receiving unit 4 includes a semiconductor bare chip (for example, a photodiode chip or a pyroelectric element) that receives infrared rays and converts the infrared rays into an electrical signal. The wavelength filter 5 is composed of a bandpass filter that includes a predetermined wavelength band, for example, a wavelength band that is absorbed by the gas to be detected in the infrared wavelength emitted from the light emitting unit 3 in the passband. This type of band-pass filter is also called an interference filter and mainly has a multilayer structure of dielectric films. The signal processing circuit unit 6 drives the light emitting unit 3 to irradiate infrared rays, or amplifies and shapes the waveform of the signal output from the light receiving unit 4, sampling, A / D conversion, arithmetic processing, correction processing, abnormality It consists of an integrated circuit (IC) that performs signal processing such as density determination processing.
As shown in FIG. 3, the wiring board 11 has a rectangular main part 11A and an extension part 11B which is smaller than the main part 11A and protrudes to the left from the left rear end of the main part 11A. Is formed. The signal processing circuit unit 6 is mounted substantially at the center of the main part 11A, and printed wiring (not shown) is formed on the upper surface of the main part 11A and the upper surface of the extension part 11B.
The body 10 is formed in a flat rectangular parallelepiped shape and is provided with a recess 100 that opens to the upper surface side, and the wiring board 11 is accommodated in the recess 100. Moreover, the recessed part 101 is formed in the left end part in the upper surface side of the body 10, and the light emission part 3 is mounted in the bottom face (lower surface) of this recessed part 101 (refer FIG. 1). That is, in this embodiment, the body 10 corresponds to a holding body. In addition, the light emission part 3 is electrically connected with the printed wiring of the extension part 11B by appropriate methods, such as wire bonding. Here, the right end of the recess 101 is provided with a wall 102 that is substantially the same height as the upper surface of the body 10. In other words, the wall 102 is provided between the light emitting unit 3 and the signal processing circuit unit 4, and the infrared rays emitted from the light emitted from the light emitting unit 3 are shielded by the walls 102, thereby causing a signal caused by the irradiation of the infrared rays. The malfunction of the processing circuit unit 6 can be suppressed. In addition, since the wall 102 is formed integrally with the body 10, there is an advantage that the cost and size can be reduced as compared with the case where the wall is formed separately from the body 10.
On the other hand, at the right end portion on the upper surface side of the body 10, the upper concave portion 103 whose vertical depth is substantially equal to the thickness of the wavelength filter 5 (height in the vertical direction) and the center of the upper concave portion 103 in the front-rear direction are located. A lower recess 104 is formed. And the light-receiving part 4 is mounted in the bottom face (lower surface) of the lower side recessed part 104, and the wavelength filter 5 is arrange | positioned in the center of the upper side recessed part 103 so that the upper part of the light-receiving part 4 may be covered (refer FIG. 1). Therefore, the infrared rays traveling toward the light receiving unit 4 pass through the wavelength filter 5 and are received by the light receiving unit 4. The light receiving portion 4 is electrically connected to the printed wiring of the main portion 11A by an appropriate method such as wire bonding. Here, since the wavelength filter 5 is held in the body 10 together with the light receiving unit 4 in the present embodiment, there is an advantage that the cost can be reduced and the size can be reduced because it is not necessary to store the wavelength filter 5 in the package.
As shown in FIGS. 2 and 3, a plurality of (four in the illustrated example) terminals 12 protrude side by side in the left-right direction on both front and rear side surfaces of the body 10. These terminals 12 are made of a metal plate and are insert-molded in the body 10. In addition, prismatic base portions 105 are formed in the front and rear in the recess 100 (rear only shown), and the ends of the four terminals 12 protruding from the front side surface are exposed on the upper surface of the front base portion 105. In addition, the end portions 12A of the four terminals 12 protruding from the rear side surface are exposed on the upper surface of the rear base portion 105. Then, the end 12A of each terminal 12 exposed on the upper surface of the base 105 is electrically connected to the printed wiring of the wiring board 11 by an appropriate method such as wire bonding.
The optical block 2 is configured by housing a light guide 8 inside a cover 20 made of a synthetic resin molding. (See FIG. 1) The cover 20 is formed in a rectangular parallelepiped shape in which the length dimensions of the front, rear, left and right are equal to the body 10, and is provided with a recess 200 that opens to the lower surface side. The light guide 8 is placed in the recess 200. It is joined to the upper surface side of the body 10 in the housed state. In addition, a rectangular vent hole 201 penetrating the cover 20 in the vertical direction is provided in the center of the upper portion of the cover 20, and outside air (a plurality of types of mixed gas including a gas to be detected; the same applies hereinafter) through the vent hole 201. Is introduced into the recess 200 (light guide 8). The shape of the vent hole 201 is not limited to a rectangle, and may be other shapes such as a circle, and may be plural. However, the opening of the vent hole 201 on the upper surface of the cover 20 is covered with the dustproof filter 7 in order to prevent foreign matters other than outside air such as dust from entering the vent hole 201 (see FIG. 1).
As shown in FIG. 1, the light guide 8 includes a first reflecting mirror (first optical path changing unit) 80, a second reflecting mirror (second optical path changing unit) 81, a third reflecting mirror 82, and a fourth reflecting mirror. And a mirror 83. The first reflecting mirror 80 has, for example, a parabolic reflecting surface, and the optical path (optical axis) of infrared rays emitted from the light emitting unit 3 (see the broken line in FIG. 1) is the upper surface (holding surface) of the body 10. It is reflected (changed) in a direction (horizontal direction) along. The second reflecting mirror 81 has, for example, a flat reflecting surface, and a direction (vertical direction) in which the optical path (optical axis) changed by the first reflecting mirror 80 intersects the light receiving surface (upper surface) of the light receiving unit 4. To reflect (change). The third reflecting mirror 82 is formed in a semi-cylindrical shape in which the first reflecting mirror 80 and the second reflecting mirror 81 are arranged at both ends. However, a hole (not shown) connected to the vent hole 201 of the cover 20 is opened at the center of the third reflecting mirror 82. These three reflecting mirrors 80 to 82 may be formed of a metal material and insert-molded on the cover 20, or may be formed by depositing or plating a metal such as aluminum on the inner surface of the recess 200. May be. In particular, when the reflecting mirrors 80 to 82 are formed by vapor deposition or plating, the cost can be reduced and the dimensional accuracy can be improved as compared with the case where the reflecting mirrors 80 to 82 are formed of a metal material.
As shown in FIG. 2, the fourth reflecting mirror 83 is formed in a flat plate shape by using a metal material such as aluminum, or formed in a flat plate shape by depositing or plating a metal such as aluminum on the molded product. Is done. Steps 106 substantially equal to the thickness (vertical thickness) of the fourth reflecting mirror 83 are formed at the opening edges on the front and rear sides of the recess 100 of the body 10, and the fourth reflection is performed with the reflecting surface facing upward. Ends on both the front and rear sides of the mirror 83 are placed on the step 106. That is, as shown in FIG. 1, the opening of the recess 100 is closed by the fourth reflecting mirror 83 in the range from the wall 102 of the body 10 to the upper recess 103. That is, the fourth reflecting mirror 83 is disposed between the signal processing unit 6 and the optical path. At this time, if the reflecting surface (upper surface) of the fourth reflecting mirror 83 is lower than the light emitting surface (upper surface) of the light emitting unit 3, the depth of the recess 100 in which the signal processing circuit unit 6, the wiring board 11 and the like are accommodated is increased. This has to increase the thickness (height) of the body 10. On the other hand, if the reflecting surface of the fourth reflecting mirror 83 is higher than the light emitting surface of the light emitting unit 3, infrared rays are reflected at the end of the fourth reflecting mirror 83 and the loss increases. It becomes necessary to increase the size, which makes it difficult to reduce the size. On the other hand, in the present embodiment, the fourth reflecting mirror 83 is placed on the step 106 that is substantially equal to the thickness dimension thereof, so that the reflecting surface of the fourth reflecting mirror 83 becomes the light emitting surface (upper surface) of the light emitting unit 3. Since they are flush with each other, inconveniences as described above can be avoided.
In the gas sensor configured as described above, the outside air is introduced into the light guide 8 through the vent hole 201, and the infrared light emitted from the light emitting unit 3 is absorbed by the detection target gas contained in the outside air, thereby receiving the light receiving unit. 4, the amount of received infrared light decreases. Therefore, the signal processing circuit unit 6 processes the output signal of the light receiving unit 4 according to the amount of received infrared light, thereby detecting the concentration of the gas (gas component) to be detected contained in the outside air in the light guide 8. it can. However, the specific contents of the signal processing performed in the signal processing circuit unit 6 for detecting the gas concentration are well known in the art and will not be described in detail.
Thus, in the present embodiment, the light emitting unit 3 and the light receiving unit 4 are each formed of a semiconductor bare chip (light emitting diode chip and photodiode chip), and the infrared light path from the light emitting unit 3 to the light receiving unit 4 is linear. Instead, it has been changed to a polygonal line. Therefore, this embodiment has an advantage that the wiring can be simplified as compared with the conventional examples (see Patent Documents 1 and 2) in which package type light emitting diodes and photodiodes are used. Further, in the present embodiment, since the optical path of infrared rays (see the broken line in FIG. 1) is changed to a substantially U shape by the first reflecting mirror 80 and the second reflecting mirror 81, it is described in Patent Document 2 in which the optical path is substantially V-shaped. Compared with the conventional example, the height dimension in the vertical direction can be reduced (lower profile) without shortening the optical path length. In addition, since the distance from the vent hole 201 to the optical path is shortened as compared with the conventional example described in Patent Document 2 due to the low profile, the detection responsiveness to the change in the ratio of the detection target gas in the outside air can be improved. There are also advantages.
In the present embodiment, the signal processing circuit unit 6 is located at a position that is sandwiched between the light emitting unit 3 and the light receiving unit 4 and does not overlap with the optical path changed by the first reflecting mirror 80, that is, inside the body 10 (inside the recess 100). Thus, the body 10 and the cover 20 are reduced in size by effectively using the dead space.
By the way, substantially cylindrical projections 202 project downward from the lower surface of the cover 20 near the center in the left-right direction and at both ends in the front-rear direction (see FIG. 4). Further, circular fitting holes 107 for fitting with the protrusions 202 of the cover 20 are provided in the vicinity of the center in the left-right direction and both ends in the front-rear direction on the upper surface of the body 10 (see FIGS. 2 and 3). In other words, the protrusion 202 and the fitting hole 107 are fitted to each other to enable positioning when the body 10 and the cover 20 are joined, and the light emitting unit 3 and the first reflecting mirror 80 are aligned, and the light receiving unit 4 and the second reflecting member. Positioning with the mirror 81 is facilitated. In particular, in the present embodiment, the reflecting surface of the first reflecting mirror 80 is formed in a parabolic shape, and the light emitting unit is positioned at the focal point of the reflecting surface (parabolic surface) by positioning the body 10 and the cover 20. 3 can be easily arranged.
Here, when the present embodiment is assembled by the automatic assembly machine, the light emitting unit 3 and the light receiving unit 4 are used by using a well-known image processing technique (for example, edge detection) from the image of the body 10 captured by the camera from above. Positioning of the mounting position is performed. In this embodiment, as shown in FIG. 4, a hole 108 having a smaller diameter than the fitting hole 107 is provided on the bottom surface of the fitting hole 107 in the body 10, and the fitting hole 107 is formed by an opening edge (edge) of the hole 108. The positions of the light emitting unit 3 and the light receiving unit 4 are positioned with reference to the position of the fitting hole 107. When the position of the fitting hole 107 is detected by the opening edge of the fitting hole 107 using a known image processing technique, the position in the depth direction of the surface of the light emitting unit 3 or the light receiving unit 4 and the depth of the fitting hole 107 are detected. Since the position in the vertical direction is different, a position detection error occurs due to the difference in the image formation (focus) position in the captured image. In order to reduce this position detection error, a small-diameter hole 108 is provided, and the position of the opening edge in the depth direction is the same as or substantially the same as the position in the depth direction of the surface of the light emitting unit 3 or the light receiving unit 4. That is, in the present embodiment, the positioning of the circuit block 1 and the optical block 2 and the positioning of the mounting positions of the light emitting unit 3 and the light receiving unit 4 with respect to the body 10 are performed using the same fitting hole 107 as a reference. As a result, the accuracy of alignment of the light emitting unit 3 and the light receiving unit 4 with the light guide 8 (the first reflecting mirror 80 and the second reflecting mirror 81) is compared with the case where the positions of both are different from each other. Has the advantage of improving. One such projection 202 and one fitting hole 107 may be provided.
By the way, since the light emitting unit 3 is not small enough to be regarded as a point light source with respect to the size of the first reflecting mirror 80, only a part of infrared rays radiated from the light emitting unit 3 is reflected on the reflecting surface (parabolic) of the first reflecting mirror 80. Will not pass through the focal point). Therefore, as shown in FIG. 5, a condensing lens 21 is disposed on the optical path between the light emitting unit 3 and the first reflecting mirror 80 so that the condensing point of the lens 21 and the focus of the first reflecting mirror 80 coincide. It is preferable. In this way, most of the infrared light emitted from the light emitting unit 3 passes through the focal point of the first reflecting mirror 80, so that the infrared light can be efficiently received by the light receiving unit 4.
Although the wavelength filter 5 is attached to the body 10 in this embodiment, the wavelength filter 5 may be attached to the light receiving unit 4 (semiconductor bare chip) as shown in FIG. For example, the rectangular flat wavelength filter 5 is bonded to the upper surface of the light receiving unit 4 so as to cover the light receiving surface 40 of the light receiving unit 4. However, a frame portion 50 is provided on the periphery of the lower surface of the wavelength filter 5, and a gap is formed between the light receiving surface 40 of the light receiving portion 4 and the lower surface of the wavelength filter 5 by the frame portion 50. Note that the wavelength filter 5 having a flat bottom surface may be bonded with a bonding material 51 such as a low melting glass, a low melting metal, or a polymer (see FIG. 6C). If the wavelength filter 5 is configured integrally with the light receiving unit 4 in this way, the upper concave portion 103 for attaching the wavelength filter 5 becomes unnecessary, and the gap between the wavelength filter 5 and the light receiving surface is reduced. There is an advantage that the thickness of the body 10 can be reduced to reduce the size (lower profile). Further, a large number of light receiving units 4 and wavelength filters 5 can be manufactured at once using a manufacturing process of a semiconductor wafer, and manufacturing costs can be reduced. Alternatively, the wavelength filter 5 may be provided between the first reflecting mirror 80 and the second reflecting mirror 81.
Here, the first reflecting mirror 80 is not limited to a reflecting surface having a parabolic shape, and may have a reflecting surface having a spherical shape or a polygonal shape, for example. Similarly, the second reflecting mirror 81 is not limited to a flat reflecting surface, and may have a curved reflecting surface.
(Embodiment 2)
The gas sensor of this embodiment is shown in FIG. The present embodiment is characterized in that two sets of the light receiving unit 4 and the wavelength filter 5 are provided, and other configurations are the same as those in the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and illustration and description thereof are omitted as appropriate.
As shown in FIG. 7, at the right end portion on the upper surface side of the body 10, two lower

concave portions

104A and 104B are formed side by side in the front-rear direction. The first light receiving unit 4A and the second light receiving unit 4B are mounted on the bottom surfaces of the

lower recesses

104A and 104B, respectively, and the first wavelength filter 5A and the second wavelength filter 5A are covered so as to cover the top of the

light receiving units

4A and 4B. The wavelength filter 4B is disposed on the bottom surface of the upper recess 103.
Here, the first wavelength filter 5A includes the infrared wavelength range absorbed by the detection target gas in the pass band, but the second wavelength filter 5B uses the infrared wavelength range absorbed by the detection target gas as the pass band. For example, the passband includes a wavelength range near the wavelength range. That is, among the infrared rays radiated from the light emitting unit 3, the amount of infrared rays passing through the first wavelength filter 5A and received by the first light receiving unit 4A decreases according to the concentration of the gas to be detected. The amount of infrared light that passes through the two-wavelength filter 5B and is received by the second light receiving unit 4B does not decrease according to the concentration of the gas to be detected. Then, the signal processing circuit unit 6 calculates the difference between the output signal levels of the first light receiving unit 4A and the second light receiving unit 4B, and calculates the concentration of the detection target gas based on this difference.
That is, when the signal processing circuit unit 6 calculates the gas concentration based on the output signal level of the light receiving unit 4 as in the first embodiment, the gas concentration is changed when the output signal level of the light receiving unit 4 fluctuates due to some disturbance factor. There is a possibility that the detection accuracy is lowered. On the other hand, if the signal processing circuit unit 6 calculates the concentration of the gas to be detected based on the difference between the output signal levels of the first light receiving unit 4A and the second light receiving unit 4B as described above, the output of each light receiving unit 4 It is possible to cancel the decrease in gas concentration detection accuracy by offsetting the signal level fluctuation.
In the first and second embodiments, the gas sensor that detects the concentration of one kind of gas contained in the outside air is illustrated, but a plurality of sets of the light emitting unit 3, the light receiving unit 4, the wavelength filter 5, and the light guide 8 are provided. Then, the gas sensor which detects the density | concentration of a different kind of gas for each group is realizable. Even in such a case, the first light receiving unit 4A, the second light receiving unit 4B, the first wavelength filter 5A, and the second wavelength filter 4B are provided for each set, and the first light receiving unit 4A and the second light receiving unit 4B are provided. The concentration of each gas may be detected from the difference between the output signal levels. The first set may include the first light receiving unit 4A, the second light receiving unit 4B, the first wavelength filter 5A, and the second wavelength filter 4B, and the second set may include the light receiving unit 4 and the wavelength filter 5. In this case, the first set detects the concentration of each gas from the difference between the output signal levels of the first light receiving part 4A and the second light receiving part 4B, and the second set is the light receiving part 4 and the second light receiving part of the first set. It is also possible to detect the concentration of each gas from the difference in the output signal level of 4B.
By the way, if the body 10 is a three-dimensional wiring board (so-called MID board) capable of integrally forming the wiring to the light emitting part and the light receiving part as shown in FIG. 8, the signal processing circuit part 6 does not go through the wiring board 11 but the body. Therefore, the body 10 can be further miniaturized.
All the above-mentioned embodiments, the explanation examples and the modification examples in the embodiments can be combined with each other. The preferred embodiments of the present invention have been described above, but the present invention is not limited to these specific embodiments, and various modifications and variations that do not depart from the scope of the claims are possible. It belongs to the category of the present invention.

Claims

One to a plurality of light emitting units made of semiconductor chips that emit infrared rays;
One or a plurality of light receiving parts made of semiconductor chips that receive infrared rays and convert them into electrical signals;
A holding body for holding the light emitting unit and the light receiving unit;
A first optical path changing unit that changes an optical path of infrared rays emitted from the light emitting unit in a direction along a holding surface of the holding body;
A gas component detection device comprising: a second optical path changing unit that changes the optical path changed by the first optical path changing unit in a direction intersecting with a light receiving surface of the light receiving unit.
Further comprising one or more wavelength filters including a predetermined wavelength band in the passband;
The gas component detection device according to claim 1, wherein the light receiving unit receives infrared rays that pass through the wavelength filter.
The gas component detection device according to claim 2, wherein the wavelength filter is held by the holding body together with the light receiving unit.
The gas component detection device according to claim 2, wherein the wavelength filter is disposed on the optical path between the first optical path changing unit and the second optical path changing unit.
The gas component detection device according to claim 2, wherein the wavelength filter is attached to the light receiving unit.
At least one of the wavelength filters includes a first wavelength filter that includes a wavelength band that is absorbed by a gas that is a detection target in a pass band, and does not include the pass band of the first wavelength filter and is in the vicinity of the pass band. A second wavelength filter including the wavelength band of
At least one light receiving unit in the light receiving unit includes a first light receiving unit that receives infrared light that passes through the first wavelength filter, and a second light receiving unit that receives infrared light that passes through the second wavelength filter. 6. The gas component detection device according to claim 2, wherein the gas component detection device is a gas component detection device.
A signal processing circuit unit for processing an electrical signal output from the light receiving unit;
7. The signal processing circuit unit according to claim 1, wherein the signal processing circuit unit is disposed at a position sandwiched between the light emitting unit and the light receiving unit and not overlapping an optical path changed by the first optical path changing unit. The gas component detection device according to Item 1.
The gas component detection device according to claim 7, wherein a reflecting mirror is disposed between the signal processing circuit unit and the optical path.
The reflecting mirror is formed in a flat plate shape having one surface as a reflecting surface,
The gas component detection device according to claim 8, wherein the reflecting surface is held by the holding body so as to be flush with the light emitting surface of the light emitting unit.
The gas component detection according to any one of claims 7 to 9, wherein a wall that shields infrared rays emitted from the light emitting unit is provided between the light emitting unit and the signal processing circuit unit. apparatus.
The gas component detection device according to claim 10, wherein the wall is formed integrally with the holding body.
The gas component detection device according to any one of claims 1 to 11, wherein a condensing lens is disposed on an optical path between the light emitting unit and the first optical path changing unit.
The gas component detection device according to any one of claims 1 to 12, wherein the holding body is a three-dimensional wiring board in which wirings to the light emitting unit and the light receiving unit are integrally formed.
A cover that holds the first optical path changing unit and the second optical path changing unit and is coupled to the holding body;
One or more protrusions are provided on the surface of the cover that is coupled to the holding body,
A fitting hole for fitting with the protrusion is provided in the coupling surface of the holding body,
14. The gas component detection device according to claim 1, wherein a hole having a smaller diameter than the fitting hole is provided on a bottom surface of the fitting hole.