JP6626281B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor.

A light emitting element is used for many purposes, for example, a gas sensor that combines a light emitting element and a light receiving element and detects an object in a space where the light emitting element and the light receiving element are arranged.
For example, in the infrared gas analyzer described in Patent Document 1, light generated from an infrared light source passes through a cell into which a gas to be measured is introduced, and then light that has passed through a filter having a different optical characteristic is used for infrared detection. When light enters the sensor, the presence or absence and concentration of the gas to be measured are detected according to the output signal of the infrared detection sensor.
In the infrared gas analyzer described in Patent Document 2, infrared light emitted from a light source is reflected by a concave reflecting mirror arranged so as to face the light source, and is incident on a light receiver. At this time, the degree of absorption of infrared light by the gas is measured by the light receiver by flowing the gas to be measured into the space between the light source and the light receiver and the concave reflecting mirror. An optical filter for transmitting infrared light in a gas absorption band is provided on the front surface of the light receiver.

JP 08-75642 A JP 09-184803 A

By the way, as described in Patent Document 1, there is an infrared gas analyzer that detects the presence or absence and concentration of a gas to be measured by detecting light passing through filters having different optical characteristics with an infrared detection sensor. Since it is necessary to ensure a sufficient optical path length for the gas to be measured to absorb infrared light, a light-emitting portion such as an infrared light source and a light-receiving portion such as an infrared detection sensor are arranged sufficiently apart from each other. I have. For this reason, there is a problem that the device becomes large.
Further, in an infrared gas analyzer described in Patent Document 2 in which a non-measurement gas is caused to flow into a space between a light source and a light receiving device and a concave reflecting mirror, the light emitted from the light source is used. A reflecting mirror for reflecting infrared light and an optical filter for allowing the light receiver to receive only infrared light in a specific wavelength band are required. For this reason, there is a problem that the number of parts increases.
Therefore, the present invention has been made in view of such circumstances, and has as its object to provide a gas sensor that can be reduced in size and that can reduce the number of parts.

A gas sensor according to one embodiment of the present invention has a light-emitting portion on a first main surface, and light emitted from the light-emitting portion is emitted from a second main surface on a side opposite to the first main surface. And, having a sensor portion on the first main surface, the second substrate for detecting light incident on the second main surface opposite to the first main surface by the sensor portion, the first substrate and the On the second main surface side of each of the second substrates, a first light reflecting portion disposed apart from each of the second main surfaces, and disposed between the first substrate and the second substrate in a top view. The second light reflection portion, and while supplying a current to the light emitting portion, a signal processing portion for processing the output signal from the sensor portion, the first substrate and the second substrate and the second The one light reflecting portion and the second light reflecting portion are light emitted by the light emitting portion and emitted from the second main surface of the first substrate, at least. After passing through an optical path reflected in the order of the first light reflecting portion, the second light reflecting portion and the first light reflecting portion, the first light reflecting portion is arranged to be incident on the sensor portion through the second substrate, and the The two-light reflecting section includes a first wavelength band in which the reflectance of the second light reflecting section is 30% or more in a wavelength band in which the sensitivity of the sensor section is 10% or more, and a first wavelength band adjacent to the first wavelength band. And the second wavelength band in which the reflectance is less than 30% on each of the long wavelength side and the short wavelength side, and the wavelength at which the sensitivity of the sensor unit is maximum is included in the first wavelength band. The second light reflection unit and the signal processing unit are integrally formed .

  According to one embodiment of the present invention, the size of the gas sensor can be reduced, and the number of components can be further reduced.

1 is an example of a configuration diagram for explaining a basic structure of a gas sensor according to a first embodiment of the present invention. FIG. 1 is an example of a configuration diagram illustrating a specific configuration of a gas sensor according to a first embodiment of the present invention. FIG. 4 is a characteristic diagram illustrating optical characteristics of a light reflecting section. It is a lineblock diagram showing an example of a gas sensor concerning a 2nd embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning a 3rd embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning a 4th embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning a 5th embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning a 6th embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning a 7th embodiment of the present invention. It is a lineblock diagram showing an example of a gas sensor concerning an 8th embodiment of the present invention. It is a lineblock diagram showing another example of a gas sensor concerning an 8th embodiment of the present invention.

Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as the present embodiment) will be described with reference to the drawings.
It is noted that in the following detailed description, numerous specific specific configurations are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, that other embodiments may be practiced without limitation to such specific specific configurations. Further, the following embodiments do not limit the invention according to the claims. In addition, not all combinations of the features described in the embodiments are necessarily indispensable to the solution of the invention.

<First aspect>
[Gas sensor]
The gas sensor according to the first aspect has a light emitting portion on the first main surface, light emitted by the light emitting portion is emitted from a second main surface opposite to the first main surface, a first substrate, A second substrate that has a sensor portion on the first main surface and detects light incident on the second main surface opposite to the first main surface by the sensor portion, and each of the first substrate and the second substrate On the second main surface side, a light reflecting portion disposed apart from each of the second main surfaces, and the first substrate, the second substrate and the light reflecting portion are illuminated by the light emitting portion and the first substrate The light emitted from the two main surfaces is reflected by the light reflecting portion, and the light reflected by the light reflecting portion is arranged to be incident on the sensor portion through the second substrate. The light reflecting portion has a sensitivity of the sensor portion of 10%. In the above wavelength band, the first wavelength band in which the reflectance of the light reflecting portion is 30% or more, and the long wavelength side and the short wavelength side adjacent to the first wavelength band. It has the property of including a second wavelength band reflectance Le is less than 30%, the sensitivity of the sensor portion is the wavelength of maximum included in the first wavelength band.

Then, by introducing the gas to be detected into the space between the first substrate and the second substrate and the light reflecting portion, the light affected by the gas to be detected is incident on the sensor portion. The presence of the gas to be detected can be detected by detecting the light affected by the detection gas by the sensor unit.
With such a configuration, the size of the gas sensor can be reduced, and the number of components can be reduced.
Here, the sensitivity (%) of the sensor unit means “{(sensitivity of the sensor unit at a certain wavelength) / (maximum value of the sensitivity of the sensor unit)} × 100”.

[First substrate]
The first substrate has a light emitting portion formed on the first main surface.
The material of the first substrate is not particularly limited. Examples of the material of the first substrate include silicon Si, gallium arsenide GaAs, sapphire, indium phosphide InP, indium arsenide InAs, and germanium Ge.
As a first substrate, a semi-insulating substrate can be used, and a GaAs substrate can be used as an embodiment from the viewpoint of increasing the diameter. Further, from the viewpoint of improving the measurement sensitivity, as the material of the first substrate, a material having high transmittance of light output from the light emitting unit can be applied as one embodiment. In addition, from the viewpoint of compensating output fluctuations of the light emitting unit with high accuracy, as the material of the first substrate, as one embodiment, a material that reflects a part of light output from the light emitting unit on the second main surface is applied. Can be.

  Further, the first substrate may further include, on the first main surface, the same sensor unit as the sensor unit provided on the second substrate. The sensor unit formed on the first main surface of the first substrate can receive light reflected by the second main surface of the first substrate among light emitted from the light emitting unit of the first substrate. Therefore, the sensor portion formed on the first substrate can be used as a reference sensor of the gas sensor, and the accuracy of measuring the gas concentration can be improved.

[Light emitting unit]
The light emitting section is formed on the first main surface of the first substrate. The light emitting unit is not particularly limited as long as it emits light including a wavelength absorbed by the gas to be detected.
The light emitting section can be applied to any light source as long as it can be formed on the first main surface of the first substrate. Specific examples of the light emitting unit include MEMS and LED. Among them, from the viewpoint of reducing noise due to light absorption of components other than the gas to be detected, as an embodiment, a light emitting unit that outputs only light in a wavelength band where absorption of the gas to be detected is large can be used. Specifically, from the viewpoint that the emission wavelength band can be controlled by the band gap of the active layer (commonly called an active layer), a light emitting portion having an LED structure can be used as one embodiment.

  In one embodiment, the light emitting unit includes a laminated structure of a PN junction or a PIN junction formed by using a film forming method such as MBE (Molecular Beam Epitaxy) or CVD (Chemical Vapor Deposition). By supplying power to the laminated structure, the laminated structure operates as an LED (Light Emitting Diode), and can emit light having a wavelength corresponding to the band gap of the material of the I layer serving as the active layer.

  As one embodiment, the laminated structure portion includes a diode structure including at least two types of layers, a P-type semiconductor and an N-type semiconductor, and the active layer includes any material of indium In or antimony Sb. When the active layer contains In or Sb, light in the infrared region (that is, infrared light) can be emitted. Specifically, by using indium antimonide InSb, InAlSb, or InAsSb for the active layer, a wavelength of 1 μm or more and 10 μm or less can be output.

  When the gas to be detected is carbon dioxide, the carbon dioxide gas exhibits strong absorption near a wavelength of 4.3 μm, and therefore, as an embodiment, InAlSb can be used for the active layer. Here, a gas sensor with high sensitivity and high resolution can be realized by tuning the Al content so that the light emission peak of the light emitting portion (LED) becomes 4.3 μm. Further, it is preferable to use InAsSb for the active layer in the case of a gas having a CO bond that absorbs in the vicinity of several μm or more and 10 μm or less (for example, a vaporized alcohol that absorbs in the vicinity of 10 μm).

  Further, when the sensor section is formed together with the light emitting section on the first main surface of the first substrate as described later, a light emitting section similar to the light emitting section provided on the first substrate is further provided on the first main face of the second substrate. It may be formed on a surface. Thus, even when a defect occurs in the light emitting portion formed on the first main surface of the first substrate, the light emitting portion formed on the first main surface of the second substrate is used as a light source instead. It becomes possible. In addition, by alternately driving the light emitting units formed on each substrate at regular time intervals, the life of the light emitting units can be extended. Also, one light emitting unit can be used as a main light source, and the other light emitting unit can be used as a light source for calibration. This makes it possible to monitor the degree of deterioration of one of the light sources from the amount of light emitted from the other light source or the like, and to correct the deterioration of the light emitting unit.

[Second substrate]
The second substrate is not particularly limited as long as it has a sensor section on the first main surface. Light incident from the second main surface passes through the inside of the second substrate and is incident on the sensor unit.
The material of the second substrate is not particularly limited. Examples of the material of the second substrate include, but are not limited to, Si, GaAs, and sapphire. In one embodiment, from the viewpoint of improving the measurement sensitivity, a material having high transparency to light incident from the second main surface side can be used as the material of the second substrate. In addition, from the viewpoint of mass productivity and production yield, the first substrate and the second substrate can use the same material as one embodiment.

In addition, from the viewpoint of miniaturization, as one embodiment, the second substrate is disposed adjacent to the first substrate with the side surfaces facing each other, and the light blocking unit is disposed between the first substrate and the second substrate. It is also possible to make it. The light blocking portion has a characteristic of absorbing incident light.
The first substrate and the light blocking portion may be arranged so that they are in contact with each other, or may be arranged with an interval. Similarly, the light blocking portion and the second substrate may be arranged so that they are in contact with each other, or may be arranged with an interval. By having a light blocking portion between the first substrate and the second substrate, light output from the light emitting portion is transmitted to a sealing portion such as a mold resin interposed between the first substrate and the second substrate. The light output from the light emitting unit is transmitted to the sensor unit through the light emitting unit, the first substrate, the sealing material, the second substrate, and the sensor unit, and passes through the gas space to the sensor unit. It is possible to prevent incidence. As a result, detection sensitivity (a change in signal due to a change in gas concentration) can be improved.

  When a sensor section is also formed on the first main surface of the first substrate as described later, the second substrate uses a light emitting section similar to the light emitting section provided on the first substrate to the first main board of the second substrate. It may be formed on a surface. Thus, even when a defect occurs in the light emitting portion formed on the first main surface of the first substrate, the light emitting portion formed on the first main surface of the second substrate is used as a light source instead. It is possible to do. In addition, by alternately driving the light emitting units formed on each substrate at regular time intervals, the life of the light emitting units can be extended. Also, one light emitting unit can be used as a main light source, and the other light emitting unit can be used as a light source for calibration. This makes it possible to monitor the degree of deterioration of one light source from the amount of light emitted by the other light source and the like, and to correct the deterioration of the light receiving unit.

[Sensor part]
The sensor section is formed on the first main surface of the second substrate. In one embodiment, as described later, the sensor unit has sensitivity to light in the first wavelength band that is selectively reflected by the light reflection unit.
The position of the sensor unit is not particularly limited as long as the light reflected from the light reflecting unit is incident on the light output from the light emitting unit provided on the first substrate.
From the viewpoint of the response speed of signal processing, the sensor unit has a diode structure of a PN junction or a PIN junction, and may include any material of indium or antimony. Further, the sensor unit may include a mixed crystal material further including at least one material selected from the group consisting of Ga, Al, and As according to the absorption wavelength of the gas to be detected.

In one embodiment, the sensor section includes a wavelength band in which the sensitivity of the sensor is 10% or more in a range of 1 μm or more and 12 μm or less. Since the sensor unit has sensitivity to the light absorption band of the environmental gas such as carbon dioxide gas, the output of the sensor unit can be used for measuring the concentration of the environmental gas.
In one embodiment, from the viewpoint of mass productivity, the material and the laminated structure of the light receiving element of the sensor unit can be the same as the material and the laminated structure of the light emitting unit.

From the viewpoint of the S / N ratio when the sensor unit is connected to a circuit (amplifier), the internal resistance of the entire light receiving unit can be increased by providing a large number of light receiving elements. An S / N ratio can be realized. Therefore, as an embodiment, the sensor section may have a form in which a plurality of light receiving elements are connected in series.
Further, the sensor unit as described above may be further formed on the first main surface of the first substrate. The sensor section formed on the first main surface of the first substrate can receive the light reflected by the second main surface of the first substrate out of the light emitted from the light emitting section. This sensor section can be used as a reference sensor of the gas sensor, and by using the output of the reference sensor, the gas concentration can be reduced as compared with the case where the light receiving section is formed only on the second substrate. Measurement accuracy can be improved.

[Light reflection section]
The light reflecting portion is disposed on the second main surface side of the first substrate and the second substrate at a position apart from each of the first substrate and the second substrate, and is located in a wavelength band where the sensitivity of the sensor portion is 10% or more. A characteristic including a first wavelength band having a reflectance of 30% or more, and a second wavelength band having a reflectance of less than 30% in both the long wavelength side and the short wavelength side adjacent to the first wavelength band. And the wavelength at which the sensitivity of the sensor unit is maximized is included in the first wavelength band.
Here, the reflectance means the ratio of the intensity of light of a specific wavelength substantially perpendicularly reflected from the light reflecting portion to the intensity of light of a specific wavelength incident substantially perpendicularly on the light reflecting portion.

In addition, from the viewpoint of reducing noise when the sensor unit is used as a reference sensor of a gas sensor, the light reflection unit has a half width of 0. It can be 5λ or less. Depending on the application, a half width of 0.2λ or less or a half width of 0.1λ or less may be preferable from the viewpoint of improving sensitivity to a change in the concentration of the detected gas (signal change / signal ratio of gas concentration change). . For example, as one embodiment, in the case of CO ₂ detection, sensitivity can be improved by setting the half width at 0.3 μm or less around a wavelength of 4.3 μm. By designing the wavelength λ at which the reflectance at the light reflection section becomes the maximum in combination with the wavelength band where absorption by the gas to be measured is strong, noise entering the sensor section is reduced, and the accuracy of gas concentration measurement is improved. Becomes possible.

  Generally, the reflection characteristics differ depending on the incident angle, and the maximum value (peak) differs depending on the optical path design. At other angles of incidence, the peak of the reflection characteristic shifts to the shorter wavelength side with respect to the normal angle of incidence, so the designer must detect the incident / reflection angle of the main light path determined by the optical path structure. It may be adjusted to the absorption wavelength of the gas. Then, a change in the signal becomes large in response to a slight change in the gas concentration, so that a highly sensitive and highly accurate gas sensor can be realized, which is preferable in some cases.

  FIG. 3 shows the relationship between the wavelength and the transmission characteristic when an optical filter having a multilayer structure laminated on a Si substrate is applied as an example of the light reflecting portion. The first wavelength band has a higher reflectance at the optical filter than other wavelength bands. The higher the reflectivity of the optical filter, the better the S / N ratio of the gas sensor. Therefore, in one embodiment, the reflectivity of the peak of the first wavelength band of the optical filter can be set to 50%. In an embodiment, it can be 60% or more, and in still another embodiment, it can be 80% or more.

In the case of a light reflecting portion included in a gas sensor used for a CO ₂ gas detecting device or a concentration measuring device, 4.3 μm having strong absorption characteristics of the CO ₂ gas is set at 4.3 μm as the center of the first wavelength band and several tens nm or more from the center. Light of 500 nm or less may be reflected. In order to realize high sensitivity of the system, the reflection characteristics of the light reflecting portion may be appropriately changed according to the optical design of the gas sensor. For example, it may be designed to reflect light only at a specific incident angle.

  The light reflector may transmit or absorb light other than the first wavelength band among the light emitted from the second main surface of the first substrate. Here, a band other than the first wavelength band is referred to as a second wavelength band. The second wavelength band refers to a wavelength band which is detected by the sensor unit among wavelengths emitted by the light emitting unit but is unnecessary for detection of a substance to be measured. The light reflecting section may transmit or absorb light in the second wavelength band. Since it is conceivable that the light reflecting portion emits light due to absorption of light and enters the sensor portion as disturbance, as an embodiment, it is possible to suppress the disturbance by adopting a configuration in which light in the second wavelength band is transmitted. It is possible. For example, when the light emitting unit emits light of 2 μm or more and 8 μm or less, and the light receiving unit has the ability to detect the same wavelength band, and the absorption wavelength band of the substance to be detected is in the vicinity of 4.2 μm or more and 4.4 μm or less. The second wavelength band may be in the range of 2 μm to 4.2 μm and in the vicinity of 4.4 μm to 8 μm. In this case, as one embodiment, the transmittance or absorptance of the light reflecting portion in the second wavelength band may be set to 50% or more.

The light reflection section may be an interference filter composed of a multilayer film in which materials having different refractive indexes are stacked. As a specific example of the light reflecting portion, an interference structure in which materials having different refractive indexes (for example, Ge, ZnSe, ZnS, SiO ₂ , and the like) are alternately stacked on a transparent substrate can be used. Depending on the wavelength, the incident light may be strengthened or weakened by the interference phenomenon, and only specific light may be strongly reflected. These laminated structures may be formed on both sides of the substrate of the light reflecting portion, or may be formed on one side. Specific examples of the substrate include GaAs, Si, and sapphire.

As a specific example of the interference filter, there is an interference filter in which thin films of Ge and ZnS are alternately stacked on several sides of a Si substrate having a high transmittance in several cycles or more and several tens cycles or less. By using such a structure, it is possible to realize an interference filter having a high reflectance (for example, 80% or more) at only some wavelengths, and a structure that transmits other wavelengths.
Further, the light reflecting portion may be provided on the back surface (surface opposite to the circuit surface) of a substrate (for example, a Si substrate) used for a signal processing portion described later. In this case, it may be preferable from the viewpoint of further downsizing the system.
[Signal processing unit]
The gas sensor according to the first aspect may further include a signal processing unit that supplies an electric current to the light emitting unit and processes an output signal from the sensor unit.

<Second aspect>
Next, a second embodiment will be described. The description of the same parts as those in the first embodiment will be omitted.
[Gas sensor]
The gas sensor according to the second aspect has a light emitting portion on the first main surface, light emitted by the light emitting portion is emitted from a second main surface opposite to the first main surface, a first substrate, A second substrate that has a sensor portion on the first main surface and detects light incident on the second main surface opposite to the first main surface by the sensor portion, and each of the first substrate and the second substrate On the second principal surface side, a first light reflection portion disposed apart from each of the second principal surfaces, and a second light reflection portion disposed between the first substrate and the second substrate in top view. Having a first substrate, a second substrate, a first light reflecting portion, and a second light reflecting portion, light emitted from the light emitting portion and emitted from the second main surface of the first substrate has at least a first light reflection. Part, the second light reflecting part, and the first light reflecting part. The light reflecting part is arranged so as to be incident on the sensor part through the second substrate after passing through the optical path. Is 10% or more in the wavelength band where the reflectance of the second light reflecting portion is 30% or more, and the reflectances are respectively on the long wavelength side and the short wavelength side adjacent to the first wavelength band. The first wavelength band has a characteristic including a second wavelength band that is less than 30%, and the wavelength at which the sensitivity of the sensor unit is maximum is included.

Then, by introducing the gas to be detected into the space between the first substrate, the second substrate and the first light reflecting portion, and the second light reflecting portion, the light affected by the detected gas becomes the sensor portion. Then, the presence of the gas to be detected can be detected by detecting the light affected by the gas to be detected by the sensor unit.
With such a configuration, the size of the gas sensor can be reduced, and the number of components can be reduced. As a result, it is possible to secure a sufficient optical path length while being small, and to provide a highly accurate gas sensor.

[First light reflector]
The first light reflecting portion is disposed on the second main surface side of the first substrate and the second substrate, at a position apart from the first substrate and the second substrate, and is emitted from the second main surface of the first substrate. Reflects light. Also, the first light reflecting portion is configured such that a part of light emitted from the second main surface of the first substrate is reflected by the first light reflecting portion and the second light reflecting portion, and at least once, the second light reflecting portion After being reflected by the first light reflection unit, the light is reflected by the first light reflection unit and is incident on the sensor unit.
The first light reflecting portion may be a reflecting mirror having a reflecting surface parallel to the reflecting surface of the second light reflecting portion, or a concave mirror that condenses and reflects at least a part of incident light. Is also good.

[Second light reflector]
The second light reflecting portion is provided between the first substrate and the second substrate when viewed from above, and selectively reflects light in the first wavelength band among the light reflected by the first light reflecting portion. Further, the second light reflecting portion is configured such that part of the light emitted from the second main surface of the first substrate is reflected by the first light reflecting portion and the second light reflecting portion, and at least once by the second light reflecting portion. After being reflected, it is arranged so as to be reflected by the first light reflecting portion and to enter the sensor portion.
The second light reflecting portion has a first wavelength band in which the reflectance of the second light reflecting portion is 30% or more in a wavelength band in which the sensitivity of the sensor portion is 10% or more, and a long wavelength adjacent to the first wavelength band. A wavelength band on the wavelength side and a short wavelength side, and a second wavelength band in which the reflectivity of the second light reflecting portion is less than 30%. It is included in one wavelength band. Here, the reflectance means the ratio of the intensity of light of a specific wavelength substantially perpendicularly reflected from the light reflecting portion to the intensity of light of a specific wavelength incident substantially perpendicularly on the light reflecting portion.

In addition, the second light reflecting portion, from the viewpoint of reducing noise when the sensor portion is used as a reference sensor of the gas sensor, as one embodiment, the wavelength at which the reflectance of the second light reflecting portion is maximum is λ. Sometimes, the half width can be set to 0.5λ or less. Depending on the application, a half width of 0.2λ or less or a half width of 0.1λ or less may be preferable from the viewpoint of improving sensitivity to a change in the concentration of the detected gas (signal change / signal ratio of gas concentration change). . For example, in the case of CO ₂ detection, the sensitivity can be improved by setting the half width at 0.3 μm or less near the wavelength of 4.3 μm. By designing the wavelength λ at which the reflectivity at the second light reflection part becomes the maximum in combination with the band where the absorption by the gas to be measured is strong, the noise incident on the sensor part is reduced, and the accuracy of the gas concentration measurement is improved. It becomes possible.
The second light reflector may transmit or absorb light in a wavelength band other than the first wavelength band among the lights reflected by the first light reflector.
The second light reflection section may be an interference filter formed of a multilayer film in which materials having different refractive indexes are stacked.
[Sealing part]
The first substrate, the second substrate, the first light reflecting portion, and the second light reflecting portion may be sealed by a sealing portion.

<Embodiment>
Next, a specific example of the present embodiment will be described with reference to the drawings. In the drawings described below, parts having the same configuration are denoted by the same reference numerals, and a repeated description thereof will be omitted.
[First Embodiment]
FIG. 1 is a conceptual diagram showing a configuration example of a gas sensor 100 according to a first embodiment of the present invention, and shows a basic structure.
The gas to be measured is introduced into a space between the first substrate 11 and the second substrate 21 and the light reflection unit 15.
Light emitted from the light emitting portion 13 formed on the first main surface 12 of the first substrate 11 is transmitted from the second main surface 14 of the first substrate 11 opposite to the first main surface 12 to the first substrate 11. It is emitted to the outside of 11.
Part of the light emitted from the first substrate 11 reaches the light reflecting portion 15. The light reflecting portion 15 is adjacent to the first wavelength band in which the reflectance of the light reflecting portion 15 is 30% or more in a wavelength band in which the sensitivity of the sensor portion 24 described later is 10% or more. The second wavelength band in which the reflectance of the light reflecting portion 15 is less than 30% on both the long wavelength side and the short wavelength side. Further, the wavelength at which the sensitivity of the sensor unit 24 is maximum is included in the first wavelength band.

Therefore, the light of the first wavelength band, which has reached the light reflecting portion 15 and is emitted from the first substrate 11, is selectively reflected.
The light of the first wavelength band reflected by the light reflecting portion 15 is incident on the second main surface 22 of the second substrate 21, passes through the second substrate 21, and is provided on the first main surface 23 of the second substrate 21. Incident on the sensor unit 24.
Then, the first substrate 11, the light emitting unit 13, the second substrate 21, and the sensor unit 24 are sealed by a sealing unit 31 made of a mold resin or the like.
As shown in FIG. 1, the first substrate 11 and the second substrate 21 are arranged such that light emitted from the light emitting unit 13 is reflected by the light reflecting unit 15 and the reflected light enters the sensor unit 24. Have been. Further, since the light in the first wavelength band received by the sensor unit 24 is affected by absorption by the gas to be measured, the gas concentration can be calculated from the intensity.

  As described above, the gas sensor 100 of the first embodiment reflects the light emitted from the light emitting unit 13 by the light reflecting unit 15 and receives the reflected light by the sensor unit 24 as a light receiving unit. Thus, a distance equivalent to the sum of the distance between the light emitting unit 13 and the light reflecting unit 15 and the distance between the light reflecting unit 15 and the sensor unit 24 can be obtained. Therefore, an optical path length longer than the distance between the light emitting unit 13 and the sensor unit 24 and the light reflecting unit 15 can be obtained. In other words, by providing the light reflecting portion 15, a longer optical path length can be obtained while maintaining the distance between the light emitting portion 13 and the sensor portion 24 and the light reflecting portion 15, that is, the light reflecting portion 15 is provided. Thus, without increasing the distance between the light emitting unit 13 and the sensor unit 24 and the light reflecting unit 15, an optical path length longer than the distance between the light emitting unit 13 and the sensor unit 24 and the light reflecting unit 15 can be obtained. Can be secured. Therefore, the size of the gas sensor can be reduced. In addition, since the light reflecting portion 15 has an optical characteristic of reflecting light in the first wavelength band including the wavelength at which the sensitivity of the sensor portion 24 is maximized, there is no need to separately provide an optical filter, and a conventional light filter is provided. Since both a reflecting mirror and an optical filter are not required, the number of parts can be reduced.

FIG. 2 shows the configuration of the gas sensor 100 according to the first embodiment in more detail.
As shown in FIG. 2, the light reflecting section 15 is held by the holding section 32. The holding portion 32 is formed in a concave shape, and the light reflecting portion 15 is arranged at a position corresponding to the bottom of the concave portion. Are provided, and the second main surface 22 of the second substrate 21 provided with the sensor portion 24 is included. The second main surfaces 14 and 22 and the light reflecting portion are provided. 15 and are fixed by a sealing portion 31 such as a mold resin. As a result, a space formed by the concave portion of the holding portion 32 is formed between the second main surfaces 14 and 22 of the first substrate 11 and the second substrate 21 and the light reflecting portion 15. The concentration measurement is performed by introducing the gas to be measured from.
The holding unit 32 is designed to reflect the light emitted from the first substrate 11 and hold the light reflecting unit 15 at an appropriate position where the light can be efficiently incident on the second substrate 21.
Further, it is preferable that the holding unit 32 has a structure that absorbs light reaching the holding unit 32 from the viewpoint of reducing disturbance incident on the sensor unit 24.

FIG. 3 is a diagram illustrating optical characteristics of the light reflection unit 15 of the gas sensor 100 according to the first embodiment.
In FIG. 3, the horizontal axis is a wavelength, and the vertical axis is a characteristic diagram showing the transmittance and the reflectance of the light reflection unit 15.
As shown in FIG. 3, the light reflecting portion 15 has a reflection characteristic in which the reflectance is 30% or more in the first wavelength band. Each of the long wavelength side band and the short wavelength side band adjacent to the first wavelength band has a second wavelength band in which the reflectance is less than 30%. That is, the light reflecting portion 15 has a reflection characteristic in the first wavelength band, and has a transmission characteristic in the second wavelength bands on both sides of the first wavelength band. Further, the wavelength at which the sensitivity of the sensor unit 24 is maximum is included in the first wavelength band. In other words, since the light in the first wavelength band including the wavelength at which the sensitivity of the sensor unit 24 is maximized is selectively reflected by the light reflecting unit 15 and is incident on the sensor unit 24, the light emitted from the light emitting unit 13 Among them, the light included in the first wavelength band in which the sensitivity of the sensor unit 24 is maximum can be efficiently incident on the sensor unit 24. Further, since the light reflecting portion 15 selectively reflects the light of the first wavelength band and the light is incident on the sensor portion 24, it is not necessary to provide an optical filter as in the related art.

  In the first embodiment, the light reflecting portion 15 does not need to be arranged in parallel with the second main surface 14 of the first substrate 11 and the second main surface 22 of the second substrate 21, The light emitted and emitted from the second main surface 14 of the first substrate 11 is reflected by the light reflecting portion 15 and is incident on the second main surface 22 of the second substrate 21, and is transmitted through the second substrate 21 to the sensor portion 24. May be arranged in any positional relationship as long as it can be incident on the surface.

[Second embodiment]
Next, a second embodiment of the present invention will be described.
The same portions as those of the gas sensor according to the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 4 is a configuration diagram illustrating an example of the gas sensor 200 according to the second embodiment of the present invention.
The first light reflection unit 41 of the gas sensor 200 according to the second embodiment is configured by, for example, a reflection mirror having a mirror surface parallel to the second light reflection unit 42. The first light reflector 41 has a larger area than the light reflector 15 in the gas sensor 100 according to the first embodiment shown in FIG. 2, and is located between the first light reflector 41 and the second light reflector 42. The light emitting portion 13 is formed to have a size capable of reflecting the light emitted from the light emitting portion 13 from the first substrate 11 a plurality of times.

  The first light reflecting portion 41 is held by the holding portion 32 having a concave shape, similarly to the gas sensor 100 according to the first embodiment shown in FIG. 2, and the first light reflecting portion 41 and the second light reflecting portion 42 are parallel. And fixed by the sealing portion 31. Then, between a surface including the second main surfaces 14 and 22 of the first substrate 11 and the second substrate 21 and the second light reflecting portion 42 and a region surrounded by the holding portion 32 including the first light reflecting portion 41. A space is formed, and the concentration measurement is performed by introducing a gas to be measured from an inlet (not shown).

  In the gas sensor 200, as shown in FIG. 4, the first substrate 11, the second substrate 21, the first light reflecting portion 41, and the second light reflecting portion 42 were emitted from the second main surface 14 of the first substrate 11. A part of the light emitted by the light emitting unit 13 is reflected at least once by the second light reflecting unit 42, then by the first light reflecting unit 41, and from the second main surface 22 of the second substrate 21. It is arranged so as to be incident on the sensor part 24 provided on the first main surface 23. That is, at least the light path in which the light emitted from the light emitting unit 13 and emitted from the second main surface 14 is reflected in the order of at least the first light reflecting unit 41, the second light reflecting unit 42, and the first light reflecting unit 41. After that, the light is incident on the second main surface 22 of the second substrate 21 and is incident on the sensor unit 24.

Then, the gas to be measured is introduced into the space between the first substrate 11, the second substrate 21, the second light reflection part 42, and the first light reflection part 41 via an introduction port (not shown).
As described above, the light emitted from the light emitting unit 13 is multiple-reflected by the first light reflecting unit 41 and the second light reflecting unit 42, so that a long optical path length can be realized. The affected light enters the sensor unit 24. Therefore, the accuracy of the gas sensor 200 can be improved. That is, if the optical path length in the space where the gas to be measured of the light incident on the sensor unit 24 is introduced is long, the influence of absorption by the gas to be measured increases, so that the S / N ratio increases and the accuracy of the gas sensor increases. Is improved. Further, the wavelength selectivity at the second light reflection unit 42 can be improved by reflecting the light a plurality of times. That is, it is possible to increase both the detection accuracy and sensitivity of a substance (such as a gas).

[Third embodiment]
FIG. 5 is a configuration diagram illustrating an example of a gas sensor 200a according to the third embodiment of the present invention. The gas sensor 200a according to the third embodiment differs from the gas sensor 200 according to the second embodiment in that a signal processing unit 33 is further provided. It is provided.
The signal processing unit 33 supplies a current to the light emitting unit 13 and processes an output signal from the sensor unit 24.
The signal processing unit 33 is composed of, for example, an IC created by using an LSI technology of Si, and calculates a concentration of a gas to be measured based on an output signal of a driving circuit for driving the light emitting unit 13 and a sensor unit 24. , An amplification circuit for amplifying the output signal of the sensor unit 24, input of a measurement request signal from an external circuit such as a higher-level device (not shown), and input / output for transmitting a concentration calculation result to the external circuit. A control unit, and the like.

The light emitting unit 13 and the sensor unit 24 are connected to the signal processing unit 33 using, for example, a wire bonding technique, and the connection between the signal processing unit 33 and an external circuit (not shown) is performed by connecting terminals of the lead frame. Do through.
With such a configuration, a highly accurate and small gas sensor can be realized, and a small area of the installation location including the signal processing unit 33 (for example, the total thickness of 5 mm or less in the direction perpendicular to the substrate surface, or 2 mm or less, and further 1 mm or less).

In the gas sensor 100 according to the first embodiment shown in FIG. 2, the signal processing unit 33 can be provided in the same manner.
Further, unlike the gas sensors 100 and 200 according to the first and second embodiments, the signal processing unit 33 configured by an IC or the like is not incorporated in the gas sensors 100 and 200 together with the light emitting unit 13 and the sensor unit 24 and the like. In this case, various circuits included in the signal processing unit 33 such as the drive circuit and the density calculation unit may be externally connected and connected to these externally connected circuits using a wire bonding technique or the like.

  In the second and third embodiments, the first light reflecting portion 41 and the second light reflecting portion 42 do not necessarily need to be arranged in parallel. The light emitted from the main surface 14 passes through an optical path that reflects the first light reflecting portion 41, the second light reflecting portion 42, and the first light reflecting portion 41 in this order, and then enters the second main surface 22 of the second substrate 21. However, as long as the light can enter the sensor unit 24 through the second substrate 21, they may be arranged in any positional relationship.

[Fourth embodiment]
Next, a fourth embodiment of the present invention will be described.
The same portions as those of the gas sensor 200 according to the second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 6 is a configuration diagram illustrating an example of the gas sensor 300 according to the fourth embodiment of the present invention.
The gas sensor 300 according to the fourth embodiment differs from the gas sensor 200 according to the second embodiment in that the first light reflecting portion 41 is replaced with a first light reflecting portion 41a formed of a concave mirror. The first light reflecting portion 41a formed of a concave mirror collects and reflects at least a part of the incident light. In the gas sensor 300 according to the fourth embodiment, the amount of light incident on the sensor unit 24 can be maximized, and the light emitted by the light emitting unit 13 can be efficiently guided to the sensor unit 24 without waste. As a result, the S / N ratio of the sensor unit 24 increases, and the measurement accuracy of the gas sensor 300 improves.

  The first light reflecting portion 41a is held by the holding portion 32, and the first substrate 11 and the second substrate 21 are provided in the opening of the first light reflecting portion 41a corresponding to the edge of the concave portion of the first light reflecting portion 41a. Positioning is performed so that the two main surfaces 14 and 22 and the second light reflecting portion 42 are included, and the first light reflecting portion 41a and the holding portion 32 side, and the second main surfaces of the first substrate 11 and the second substrate 21 are provided. 14 and 22 and the side including the second light reflecting portion 42 are fixed by a sealing portion 31 such as a mold resin, and the second main surfaces 14 and 22 of the first substrate 11 and the second substrate 21 and the second light The concentration measurement is performed by introducing a gas to be measured from a not-shown inlet into a space formed between the surface including the reflecting portion 42 and the first light reflecting portion 41a.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described.
The same portions as those of the gas sensor 300 according to the fourth embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 7 is a configuration diagram illustrating an example of a gas sensor 300a according to the fifth embodiment.
The gas sensor 300a according to the fifth embodiment includes a light emitting unit 13 and a sensor unit 13a on the first main surface 12 of the first substrate 11. The sensor unit 13a has the same functional configuration as the sensor unit 24 provided on the second substrate 21. Further, the gas sensor 300a includes a sensor unit 24 and a light emitting unit 24a on the first main surface 23 of the second substrate 21. The light emitting unit 24a has the same functional configuration as the light emitting unit 13 provided on the first substrate 11.

  Further, the gas sensor 300a includes a signal processing unit 33a that supplies current to the light emitting units 13 and 24a and processes an output signal from the sensor units 13a and 24. Like the signal processing unit 33 described in the third embodiment, the signal processing unit 33a includes, for example, an IC created by using Si LSI technology, and includes a driving circuit that drives the light emitting units 13 and 24a. A concentration calculation unit for calculating the concentration of the gas to be measured based on the output signals of the sensor units 13a and 24, an amplification circuit for amplifying the output signals of the sensor units 13a and 24, and measurement from an external circuit such as a higher-level device (not shown). An input / output control unit for inputting a request signal, transmitting a concentration calculation result to an external circuit, and the like. Further, the light emitting units 13 and 24a formed on each substrate are alternately driven at regular time intervals, and By using one light-emitting part as the main light source and using the other light-emitting part as a calibration light source, the degree of deterioration of one light source can be determined based on the amount of light emitted from the other light source. Monitor Control section for deterioration correction and the like of the light-emitting portion by graying, and a like.

The light emitting units 13 and 24a and the sensor units 13a and 24 are connected to the signal processing unit 33 using, for example, a wire bonding technique, and the connection between the signal processing unit 33 and an external circuit (not shown) is connected to a lead. This is performed through the terminal of the frame.
With such a configuration, it is possible to realize a highly accurate and small gas sensor in which the signal processing unit 33a is incorporated, and furthermore, it is possible to suppress a temperature difference between the sensor units on both sides due to heat generation of the light emitting unit. Therefore, a highly accurate gas sensor can be realized.

[Sixth embodiment]
FIG. 8 is a configuration diagram illustrating an example of a gas sensor 300b according to the sixth embodiment of the present invention.
The gas sensor 300b according to the sixth embodiment differs from the gas sensor 300 according to the fourth embodiment shown in FIG. 6 in that a signal processing unit 33 having the same functional configuration as the signal processing unit 33 in the third embodiment is provided. A terminal for extracting the output of the unit 33 is provided in an element of the gas sensor 300b. As shown in FIG. 8, the element of the gas sensor 300b includes terminal portions 35 and 36 formed in a lead frame shape.
The terminals 35 and 36 are used for connection between the external circuit 38 and the signal processing unit 33. The connection between the terminal units 35 and 36 and the signal processing unit 33 and the connection between the signal processing unit 33 and the light emitting unit 13 and the sensor unit 24 are performed by wire bonding using wires 37.

[Seventh embodiment]
FIG. 9 is a configuration diagram illustrating an example of a gas sensor 300c according to the seventh embodiment of the present invention.
A gas sensor 300c according to the seventh embodiment is obtained by integrally forming the signal processing unit 33a and the second light reflection unit 42 in the gas sensor 300a according to the fifth embodiment shown in FIG. The signal processing unit 33a includes a substrate a1 and a circuit unit a2 formed on one surface of the substrate a1. The second light reflecting portion 42 is provided on a surface of the substrate a1 opposite to the surface on which the circuit portion a2 is formed. With such a configuration, a highly accurate and small gas sensor in which the signal processing unit 33a and the second light reflecting unit 42 are integrally formed can be realized.

[Eighth Embodiment]
FIGS. 10 and 11 are configuration diagrams illustrating an example of the gas sensor according to the eighth embodiment of the present invention.
The gas sensor according to the eighth embodiment has a light blocking portion provided between the first substrate 11 and the second substrate 21, and the light blocking portion has a characteristic of absorbing incident light. FIG. 10 shows a gas sensor 100 according to the first embodiment shown in FIGS. 1 and 2 in which a light blocking section 51 is further provided between the first substrate 11 and the second substrate 21.
Even if the light output from the light emitting unit 13 is transmitted from the first substrate 11 to the sealing unit 31, the light output from the light emitting unit 13 is absorbed by the light blocking unit 51. The transmission to the sensor unit 24 via the substrate 11, the sealing unit 31, and the second substrate 21 can be avoided. Therefore, it is possible to prevent the light output from the light emitting unit 13 from being incident on the sensor unit without passing through the gas space, and as a result, it is possible to improve the detection sensitivity.

  FIG. 11 shows a gas sensor 300b according to the sixth embodiment shown in FIG. 8, in which a light blocking portion 52 is provided between the first substrate 11 and the second light reflecting portion 42, and the second light reflecting portion 42 A light blocking section 53 is provided between the light shielding section 53 and the substrate 21. For example, a part of the plurality of lead frame-shaped terminals provided as the terminals 35 and 36 may be used as the light blocking parts 52 and 53 as the light blocking parts, or may be newly provided.

Even if the light output from the light emitting unit 13 is transmitted from the first substrate 11 to the sealing unit 31, the light output from the light emitting unit 13 is absorbed by the light blocking unit 52, 11. Transmission to the second light reflection section 42 via the sealing section 31 can be avoided. Similarly, even if the light incident on the second light reflecting portion 42 is transmitted from the second light reflecting portion 42 to the sealing portion 31, the light is absorbed by the light blocking portion 53, so that the second light reflecting portion It is possible to prevent the light incident on the part 42 from being transmitted to the second substrate 21 via the second light reflection part 42 and the sealing part 31.
Therefore, it is possible to prevent the light output from the light emitting unit 13 from being incident on the sensor unit without sufficiently passing through the gas space, and as a result, it is possible to improve the detection sensitivity.
Although the gas sensor according to the first embodiment and the sixth embodiment further includes a light blocking unit, the light blocking unit may be provided in other embodiments in the same manner. In this case, the same operation and effect can be obtained.

<Others>
The gas sensor according to the present invention is not limited to an infrared gas sensor, and may be, for example, an ultraviolet gas sensor.
Note that the present invention is not limited to the embodiment described above. Within the scope of the technical idea, a design change or the like may be added to the embodiment based on the knowledge of those skilled in the art, and the first to sixth embodiments may be arbitrarily combined, and such a change may be made. Are also included in the scope of the present invention.
Also, the scope of the present invention is not limited to the combination of features of the invention defined by the claims, but may be defined by any desired combination of specific features among all the disclosed features. .

DESCRIPTION OF SYMBOLS 11 1st board | substrate 12 1st main surface 13 light emitting part 13a sensor part 14 2nd main surface 15 light reflection part 21 2nd board 22 2nd main surface 23 1st main surface 24 sensor part 24a light emitting part 31 sealing part 32 holding | maintenance Unit 33 signal processing unit 35, 36 terminal unit 41, 41a first light reflecting unit 42 second light reflecting unit 51 to 53 light blocking unit 100 gas sensor 200, 200a gas sensor 300, 300a, 300b, 300c gas sensor

Claims (10)

A first substrate having a light-emitting portion on the first main surface, light emitted by the light-emitting portion is emitted from a second main surface opposite to the first main surface,
A second substrate that has a sensor portion on the first main surface and detects light incident on the second main surface opposite to the first main surface by the sensor portion,
On the second main surface side of each of the first substrate and the second substrate, a first light reflecting portion disposed apart from the second main surface,
A second light reflection portion disposed between the first substrate and the second substrate in a top view,
A signal processing unit that supplies an electric current to the light emitting unit and processes an output signal from the sensor unit,
The first substrate, the second substrate, the first light reflecting portion, and the second light reflecting portion are light emitted by the light emitting portion and emitted from the second main surface of the first substrate, at least. After passing through the optical path reflected in the order of the first light reflecting portion, the second light reflecting portion and the first light reflecting portion, it is arranged to be incident on the sensor portion through the second substrate,
The second light reflecting portion includes a first wavelength band in which the reflectance of the second light reflecting portion is 30% or more, in a wavelength band in which the sensitivity of the sensor portion is 10% or more; Has a characteristic including a second wavelength band in which the reflectance is less than 30% on each of a long wavelength side and a short wavelength side adjacent to the first wavelength band. Included
A gas sensor in which the second light reflection unit and the signal processing unit are integrally formed.   2. The gas sensor according to claim 1, wherein the second light reflection portion has a half-value width of 0.5λ or less, where λ is a wavelength at which the reflectance is maximum. 3.   The gas sensor according to claim 1, wherein a wavelength band in which the sensitivity of the sensor unit is 10% or more is 1 μm or more and 12 μm or less.   The gas sensor according to any one of claims 1 to 3, wherein the second light reflection unit is an interference filter including a multilayer film in which materials having different refractive indexes are stacked.   The gas sensor according to any one of claims 1 to 4, wherein the first light reflection unit is a concave mirror that collects and reflects at least a part of incident light.   The gas sensor according to any one of claims 1 to 5, wherein the first substrate, the second substrate, and the second light reflection unit are sealed by a sealing unit.   The gas sensor according to any one of claims 1 to 6, wherein the sensor unit and the light emitting unit are each made of the same material and have the same laminated structure.   The gas sensor according to claim 7, wherein the stacked structure is a diode structure including at least two types of layers, a P-type semiconductor and an N-type semiconductor, and includes one of indium and antimony.   The gas sensor according to any one of claims 1 to 8, wherein the first substrate and the second substrate are made of the same material. The signal processing unit includes a substrate and a circuit unit formed on one surface of the substrate,
The gas sensor according to any one of claims 1 to 9, wherein the second light reflection unit is provided on a surface of the substrate for the signal processing unit opposite to a surface on which the circuit unit is formed. .

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