JP5853873B2 - Concentration detector - Google Patents

Description

  The present invention detects an inspection light that passes through an infrared light source that irradiates inspection light, a housing in which a detection target is disposed, and inspection light that has passed through the detection target, and the optical path length of the detected inspection light and the inspection light And a calculation unit for calculating the concentration of the detection target based on the above.

  Conventionally, for example, as shown in Patent Document 1, an optical path body, a measurement cell in which the optical path body and the sample gas are disposed in a hollow, a light source that irradiates light in the measurement cell, and the optical path body and the sample gas are transmitted. An infrared gas analyzer including an infrared detector that detects the detected light has been proposed. The optical path body has a plurality of longitudinal members having different lengths, and the plurality of longitudinal members are connected in a manner intersecting on the same plane. And a rotating shaft is connected to the site | part which the some longitudinal member in the optical path body crossed, and this rotating shaft can be rotated with a motor.

  When the optical path member is rotated by the motor, a state occurs in which the longitudinal direction of a certain longitudinal member coincides with the direction connecting the light source and the infrared detector. In this state, the light emitted from the light source passes through the sample gas between the light source and the longitudinal member, the longitudinal member, and the sample gas between the longitudinal member and the infrared detector to detect infrared rays. Incident light. In this case, the total length between the light source and the longitudinal member and between the longitudinal member and the infrared detector corresponds to the optical path length of the light passing through the sample gas, which is the length of the longitudinal member. It is prescribed by As described above, since the length of each longitudinal member is different, the optical path length defined by each longitudinal member is different. Therefore, the optical path length is changed intermittently (discontinuously) by rotating the optical path body.

JP-A-62-19736

  As described above, the infrared gas analyzer disclosed in Patent Document 1 has a configuration in which the optical path length is changed by rotating the optical path body. According to this, although it is possible to change the optical path length, an optical path body having a plurality of longitudinal members having different lengths, and a rotating shaft and a motor for rotating the optical path body are required. The physique of the cell increases. As a result, there has been a problem that the size of the infrared gas analyzer increases.

  In view of the above problems, an object of the present invention is to provide a concentration detection device in which an increase in physique is suppressed.

In order to achieve the above-described object, the present invention is formed of an infrared light source (10) that irradiates inspection light including infrared light, and a material that transmits infrared light included in the inspection light, and an object to be detected is disposed therein. And the inspection light transmitted through the casing and the detection target in the casing, and based on the detected inspection light and the optical path length through which the inspection light has transmitted through the detection target, A concentration detection device having a calculation unit (50) for calculating a concentration of a detection target, wherein the housing includes an incident wall portion (33) on which inspection light emitted from an infrared light source is incident, and an interior of the housing An exit wall (36) from which the inspection light transmitted through the object to be detected is emitted, and the distance between the entrance wall and the exit wall corresponds to the optical path length, and a part of the housing is by deforming, control unit for controlling the optical path length (70) possess, the control unit is continuously deformed is a part of the housing Thus, the optical path length is continuously controlled, and the calculation unit obtains the inspection light transmitted through the casing and the detection target in the casing when the optical path length is continuously changed by the control unit. The concentration of the detected object is calculated based on the detected intensity of the inspection light, the differential value with respect to the optical path length of the detected inspection light, and the extinction coefficient of the detected object. A plurality of inspection lights with respect to the optical path length are detected, and a differential value with respect to the detected inspection light is calculated using a least square method .

  Thus, according to the present invention, the optical path length is controlled by deforming a part of the housing (30). According to this, it is not necessary to ensure the space for rotating compared with the structure which rotates the optical path body which has several longitudinal members from which length differs. Therefore, an increase in the physique of the concentration detection device (100) is suppressed.

In a further the invention, the control unit (70), by continuously deforming a portion of the housing (30), continuously control the optical path length. According to this, as compared with the configuration in which the optical path length is controlled discontinuously, it is possible to select the optimal optical path length for measuring the detection target. In addition, as a structure which controls optical path length continuously, the structure which rotates the optical path body which has several longitudinal member whose length was changed continuously can also be considered. However, in the case of this configuration, it is necessary to have many longitudinal members, and there is a concern about an increase in the size of the optical path body. Therefore, in the concentration detection apparatus (100) according to the present invention, an increase in physique is suppressed as compared with the above-described comparison configuration.

It is sectional drawing which shows schematic structure of the density | concentration detection apparatus which concerns on 1st Embodiment. It is an expanded sectional view of the housing | casing shown in FIG. It is sectional drawing for demonstrating a preparatory process. It is sectional drawing for demonstrating a groove | channel formation process. It is sectional drawing for demonstrating a moth eye structure formation process. It is sectional drawing for demonstrating a 1st mask patterning process. It is sectional drawing for demonstrating a 1st etching process. It is sectional drawing for demonstrating a 2nd mask patterning process. It is sectional drawing for demonstrating a 2nd etching process. It is sectional drawing for demonstrating a preparatory process. It is sectional drawing for demonstrating a piezoelectric element formation process. It is sectional drawing for demonstrating a thin part formation process. It is sectional drawing for demonstrating a moth eye structure formation process. It is a graph which shows the sensor output with respect to the optical path length for demonstrating the detectable range of each component which comprises a to-be-detected object. It is a graph which shows the sensor output with respect to optical path length for demonstrating the relationship between the density | concentration of the to-be-detected object with respect to a fixed value, and optical path length. It is a graph which shows the sensor output with respect to optical path length for demonstrating the detection of a density | concentration. It is sectional drawing which shows the modification of a housing | casing. It is sectional drawing for demonstrating metal wiring. It is sectional drawing for demonstrating the area | region to which the impurity was added.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The concentration detection apparatus according to this embodiment will be described with reference to FIGS. The detection target according to the present embodiment is a liquid. More specifically, the detection target is a mixed liquid containing at least one of ethanol, gasoline, and water. It is expected that the concentration of ethanol contained in the detection target is 0 to 100%, the concentration of gasoline is 0 to 100%, and the concentration of water is about 0 to 7%.

  As shown in FIG. 1, the concentration detection apparatus 100 includes an infrared light source 10, a housing 30, a calculation unit 50, and a control unit 70 as main parts. The inspection light emitted from the infrared light source 10 is incident on the calculation unit 50 via the housing 30 and the detection target disposed in the housing 30. The calculation unit 50 calculates the concentration of the detection target based on the incident inspection light and the optical path length corresponding to the length of the inspection light transmitted through the detection target. The control unit 70 controls the optical path length by deforming a part of the housing 30, and this control of the optical path length is a characteristic point of the concentration detection apparatus 100 according to the present embodiment. In the following, the irradiation direction of the inspection light indicated by the broken-line arrow in FIG. 1 (the direction from the infrared light source 10 toward the housing 30) is simply referred to as the irradiation direction.

  In addition, the density | concentration detection apparatus 100 which concerns on this embodiment has the optical path length detection part 90 and the housing 91 other than the said components 10-70. An output signal of the optical path length detection unit 90 is input to the calculation unit 50 and the control unit 70, and the infrared light source 10, the housing 30, a part of the calculation unit 50, and a part of the control unit 70 are included in the housing 91. Is provided. Hereinafter, each component will be described.

  The infrared light source 10 emits inspection light including infrared rays.

  The casing 30 is formed of a material that transmits infrared rays contained in the inspection light, and a detection target is disposed inside the casing 30. Specifically, the housing 30 is formed of a semiconductor (for example, silicon) that transmits infrared rays included in the inspection light. As shown in FIG. 2, the housing 30 is formed by bonding two semiconductor substrates 31 and 32, and a cavity is formed between opposing surfaces (inner surfaces) of the two semiconductor substrates 31 and 32. An object to be detected is supplied (arranged) in the cavity, and the cavity is filled with the object to be detected. Accordingly, when the shape of the cavity changes, the shape of the detection target arranged in the cavity also changes accordingly.

  The first semiconductor substrate 31 is a first facing wall portion whose outer surface faces the infrared light source 10, and the incident wall portion 33 on which the inspection light irradiated from the infrared light source 10 is incidentally thin. The thin-walled portion 34 and the first connecting wall portion 35 for connecting to the second semiconductor substrate 32 are formed. The periphery of the incident wall portion 33 is surrounded by the thin portion 34, and the periphery of the thin portion 34 is surrounded by the first connecting wall portion 35. And the unevenness | corrugation (moth eye structure) for absorbing the incident light of a specific wavelength is formed in the outer surface and inner surface of the incident wall part 33, respectively.

  The second semiconductor substrate 32 is a second opposing wall portion whose outer surface faces the calculation unit 50, and includes an emission wall portion 36 from which inspection light transmitted through the detection target is emitted, a thin portion 34, and a predetermined space. And a second connecting wall portion 38 for connecting to the first semiconductor substrate 31. The periphery of the emission wall portion 36 is surrounded by a wall portion 37, and the periphery of the wall portion 37 is surrounded by a second connection wall portion 38. And the unevenness | corrugation (moth eye structure) for absorbing the incident light of a specific wavelength is formed in the outer surface and the inner surface of the output wall part 36, respectively.

  A predetermined space is formed between the entrance wall 33 and the exit wall 36, and the detection target is arranged in this space. Accordingly, the light transmitted through the incident wall portion 33 is emitted to the outside of the housing 30 through the detection target and the emission wall portion 36 disposed between the incident wall portion 33 and the emission wall portion 36. . The inspection light transmitted through the detection target is absorbed by each component included in the detection target, and the intensity thereof is reduced.

  As described above, the cavity of the housing 30 is filled with the detection target. Therefore, when the distance between the incident wall portion 33 and the exit wall portion 36 changes, the length of the detection target arranged between the entrance wall portion 33 and the exit wall portion 36 also changes accordingly. The distance between the entrance wall 33 and the exit wall 36 corresponds to the optical path length of the inspection light that passes through the detection target, and is controlled by the control unit 70. As described above, when the light passes through the detection target, the intensity of the inspection light is reduced, but the reduction amount of the intensity is proportional to the optical path length of the detection target. Therefore, the longer the optical path length, the lower the intensity of the detection target. Of course, the reduction amount of the intensity of the inspection light is also proportional to the density of the detection target.

  The calculation unit 50 detects the inspection light transmitted through the housing 30 and the detection target in the housing 30, and calculates the concentration of the detection target based on the detected inspection light and the optical path length of the inspection light. Is. The calculation unit 50 splits the incident inspection light, the spectroscope 51, the detector 52 that detects the intensity of the inspection light split by the spectroscope 51 (converts it into an electrical signal), and the output signal of the detector 52. An amplification circuit 53 that amplifies, and an operation unit 54 that performs an operation for calculating the concentration of the detection target based on the output signal of the amplification circuit 53 and the optical path length. As shown in FIG. 1, the output signal of the amplifier circuit 53 is output not only to the arithmetic unit 54 but also to a supply unit 72 described later. And the calculating part 54 fulfill | performs not only the above-mentioned function but the function which controls the wavelength area | region which the spectrometer 51 carries out the spectroscopy. As described above, the calculation of the density is performed by the calculation unit 54, which will be described later.

  The controller 70 controls the optical path length by deforming a part of the housing 30. The control unit 70 according to the present embodiment continuously controls the optical path length by applying stress to the housing 30 and continuously deforming a part of the housing 30. The control unit 70 includes a piezoelectric element 71 that generates pressure by supplying current and a supply unit 72 that supplies current to the piezoelectric element 71. The piezoelectric element 71 is formed on the outer surface of the thin portion 34, and when a current is applied from the supply unit 72, a pressure corresponding to the strength of the current and the flow direction is generated. Specifically, the piezoelectric element 71 generates pressure in the irradiation direction or in the direction opposite to the irradiation direction. The shape of the thin wall portion 34 is changed by the pressure generated by the piezoelectric element 71, and the incident wall portion 33 is displaced in the irradiation direction or in the opposite direction. As a result, the distance (optical path length) between the entrance wall portion 33 and the exit wall portion 36 increases or decreases.

  The piezoelectric element 71 according to this embodiment has a light shielding property, and an opening 71 a is formed in the piezoelectric element 71. The inspection light emitted from the infrared light source enters the incident wall 33 through the opening 71a. In the present embodiment, the piezoelectric element 71 is formed not only on the outer surface of the thin portion 34 but also on the outer surface of the first connecting wall portion 35. This is not for applying pressure to the first connecting wall portion 35 but for preventing inspection light from entering other than the incident wall portion 33 of the first semiconductor substrate 31.

  The supply unit 72 according to this embodiment supplies currents based on the output signals of the amplification circuit 53 and the optical path length detection unit 90 to the piezoelectric element 71. The supply unit 72 determines whether the intensity of the detected inspection light is suitable for measurement based on the output signal of the amplifier circuit 53 (hereinafter referred to as sensor output), and the output of the optical path length detection unit 90 Based on the signal, it is determined whether the optical path length can be controlled as intended.

  Further, the supply unit 72 according to the present embodiment continuously changes the optical path length by causing a current to flow gradually when detecting the concentration. By doing so, a graph of sensor output (intensity of detected inspection light) with respect to the optical path length shown in FIG. 15 is obtained.

  The optical path length detection unit 90 includes a strain gauge 92 and an optical path length detection circuit 93. As shown in FIG. 2, the strain gauge 92 is formed in the thin portion 34, and the strain of the thin portion 34 generated by the piezoelectric element 71 is converted into an electric signal by the strain gauge 92. The displacement amount (change amount of the optical path length) of the incident wall portion 33 is proportional to the strain amount of the thin portion 34, and the output signal of the strain gauge 92 is also proportional to the strain amount of the thin portion 34. Thereby, the optical path length detection circuit 93 detects the change amount of the optical path length based on the change amount of the output signal of the strain gauge 92. The detected signals are supplied to the calculation unit 54 and the supply unit 72, respectively.

  Next, a method for manufacturing the housing 30 of the concentration detection apparatus 100 according to the present embodiment will be described with reference to FIGS. First, after describing the manufacturing method of the second semiconductor substrate 32 based on FIGS. 3 to 9, the manufacturing method of the first semiconductor substrate 31 and the piezoelectric element 71 will be described based on FIGS. 10 to 13. And finally, the manufacturing method of the housing | casing 30 is shown. In the following, in order to distinguish between before processing and after processing, the first semiconductor substrate 31 before processing is referred to as a semiconductor substrate 31a, and the second semiconductor substrate 32 before processing is referred to as a semiconductor substrate 32a.

  First, as shown in FIG. 3, a semiconductor substrate 32a is prepared. The above is the preparation process.

  After the preparation step, as shown in FIG. 4, a groove for defining the initial optical path length is formed in the semiconductor substrate 32a. As a result, the semiconductor substrate 32 a is roughly divided into an emission wall portion 36, a wall portion 37, and a second connection wall portion 38. The above is the groove forming step.

  After the groove forming step, as shown in FIG. 5, irregularities (moth eye structure) for absorbing incident light of a specific wavelength are formed on the outer surface and the inner surface of the emission wall 36. The above is the moth-eye structure forming step. The second semiconductor substrate 32 is manufactured through the above steps.

  This moth-eye structure forming step includes the steps shown in FIGS. In other words, the moth-eye structure forming process includes a first mask patterning process, a first etching process, a second mask patterning process, and a second etching process.

  In the first mask patterning step, as shown in FIG. 6, a first mask 40 for forming irregularities (moth eye structure) is formed on the outer surface of the semiconductor substrate 32a. Thereafter, as shown in FIG. 7, in the first etching process, the outer surface of the semiconductor substrate 32 a exposed from the first mask 40 is etched to remove the first mask 40. By doing so, irregularities (moth eye structure) are formed on the outer surface of the semiconductor substrate 32a. Thereafter, as shown in FIG. 8, in the second mask patterning step, a second mask 41 for forming irregularities (moth eye structure) is formed on the inner surface of the semiconductor substrate 32a. Finally, as shown in FIG. 9, in the second etching step, the inner surface of the semiconductor substrate 32 a exposed from the second mask 41 is etched to remove the second mask 41. By doing so, irregularities (moth eye structure) are formed on the inner surface of the semiconductor substrate 32a.

  Next, a method for manufacturing the first semiconductor substrate 31 and the piezoelectric element 71 will be described. First, as shown in FIG. 10, a semiconductor substrate 31a is prepared. The above is the preparation process.

  After the preparation step, as shown in FIG. 11, a piezoelectric element 71 is formed on the outer surface of the semiconductor substrate 31a. The above is the piezoelectric element forming step.

  After the piezoelectric element forming step, as shown in FIG. 12, etching is performed from the inner surface of the semiconductor substrate 31a to locally form a thin portion. Thus, the semiconductor substrate 31 a is partitioned into the incident wall portion 33, the thin wall portion 34, and the first connection wall portion 35. The above is a thin part formation process.

  After the thin-walled portion forming step, as shown in FIG. 13, irregularities (moth eye structure) for absorbing incident light having a specific wavelength are formed on the outer surface and the inner surface of the emission wall portion 36, respectively. The above is the moth-eye structure forming step. Through the above steps, the first semiconductor substrate 31 and the piezoelectric element 71 are manufactured. The moth-eye structure forming step shown in FIG. 13 is the same as the steps shown in FIGS. Further, the formation of the strain gauge 92 is not particularly mentioned, but may be performed anytime after the thin portion forming step.

  Finally, a method for manufacturing the housing 30 will be described. First, each of the semiconductor substrates 31 and 32 manufactured through the above-described steps is placed in a vacuum atmosphere, and the surface layer on the inner surface of each of the connecting wall portions 35 and 38 is removed to expose the bond. Then, the inner surfaces of the connecting wall portions 35 and 38 are brought into contact with each other to join the bonding hands, thereby directly joining the semiconductor substrates 31 and 32. The above is the direct bonding process. Thereby, the housing | casing 30 shown in FIG. 2 is manufactured.

  Next, the detection principle of the concentration detection apparatus 100 according to the present embodiment will be described with reference to FIGS. The horizontal axis of each of FIGS. 14 and 15 indicates the optical path length, and the vertical axis indicates the sensor output (the intensity of the detected inspection light). The vertical axis normalizes the sensor output as 1.0 when the inspection light does not pass through the detection target, that is, when the specific wavelength component included in the inspection light is not absorbed by the detection target. Therefore, the unit of the vertical axis is an arbitrary unit. In the horizontal axis, the optical path length is 0.0 when the optical path length is not changed, that is, when the thin portion 34 is not deformed by the control unit 70. The unit of the horizontal axis is m.

  As described above, the inspection light emitted from the infrared light source 10 is incident on the calculation unit 50 via the casing 30 and the detection target disposed in the casing 30. The inspection light transmitted through the detection target is absorbed by the component included in the detection target, and the intensity thereof is reduced. This amount of intensity reduction is proportional to the concentration of the detection target and the optical path length. Therefore, when the concentration of the detection target is low, it is necessary to increase the optical path length so that the change in the intensity of the detected inspection light (the amount of change in the sensor output) is larger than the resolution of the calculation unit 50. On the other hand, when the concentration of the detection target is high, the optical path is set so that the intensity of the detected inspection light (sensor output) does not become smaller than the resolution of the calculation unit 50 as a result of the intensity change of the detection target being too large. It is necessary to shorten the length.

  When the object to be detected is composed of a plurality of components and the concentrations of the components are different, the optical path length suitable for measuring each component (the change amount of the sensor output is larger than the resolution of the calculation unit 50 and the sensor output It is necessary to select an optical path length that does not become smaller than the resolution of the calculation unit 50. However, an optical path length suitable for one component is not necessarily an optical path length suitable for another component.

As described above, the detection target according to the present embodiment is a mixed liquid containing at least one of ethanol, gasoline, and water, the ethanol concentration is 0 to 100%, and the gasoline concentration is 0 to 100%. The concentration of water is expected to be about 0-7%. In FIG. 14, the dependency of the sensor output on the optical path length detected when the three components are at the maximum density is indicated by a solid line, and the dependency on the optical path length of the sensor output detected at the minimum density is indicated by a broken line. It shows with. As indicated by the alternate long and short dash line in FIG. 14, the resolution of the calculation unit 50 is 1.0 × 10 ⁻³ , but when the change amount of the sensor output and the sensor output are higher than this resolution, Each component can be detected. As shown by the two-dotted line and the solid line arrow in FIG. 14, in the case of ethanol, detection is possible when the optical path length is about 1.0 × 10 ^{−6 to} 5.0 × 10 ⁻⁴ m, and in the case of gasoline, Detection is possible when the optical path length is about 0.8 × 10 ^{−5 to} 1.0 × 10 ⁻⁴ m, and in the case of water, the optical path length is about 3.0 × 10 ^{−4 to} 1.0 × 10 ⁻ Detection is possible in the case of ³ m. Thus, since the detectable ranges of ethanol, gasoline, and water are different, it is necessary to detect with an optical path length suitable for each.

  In contrast, in the present embodiment, the optical path length is continuously changed by gradually passing a current through the piezoelectric element 71, and the inspection light when the optical path length is continuously changed is detected. The data obtained by this is shown in FIG. The solid line shown in FIG. 15 indicates the sensor output with respect to the optical path length of one component included in the detection target, and the density of each line is different. Thus, when the concentration is different, the sensor output with respect to the optical path length changes, and the optical path length suitable for measuring this component also changes. However, as shown in FIG. 15, by detecting the optical path length when the detected inspection light intensity (sensor output) is a constant value, the component is measured no matter how the concentration of the component changes. It is possible to detect the sensor output at the optical path length suitable for the above.

In the above description, although one component has been described, the above-described operation is performed for each component in the present embodiment. This makes it possible to select an optical path length suitable for measuring each component even when the concentration of each component is different. The constant value shown in FIG. 15 is 8.0 × 10 ⁻¹ , which is a value indicating that the sensor output has changed by 2.0 × 10 ⁻¹ depending on the detection target. The change value of the sensor output is a value that can be detected by the calculation unit 50 and is sufficiently higher than the thermal noise generated in the detector 52. That is, the value is within the inspectable range and has a high S / N ratio. Incidentally, as the constant value, not only the S / N ratio is high, but also a value in which the slope of the sensor output with respect to the optical path length is in a linear region is adopted.

The calculation unit 54 performs a calculation for calculating the concentration of the detection target based on the sensor output and the optical path length obtained by the above method. More specifically, if the sensor output is I, the sensor output when the change in optical path length is zero, I ₀ , the absorption coefficient is α, the concentration is n, and the optical path length is l, then n = − {log ((I ₀ − The density is calculated by performing an operation of I) / I ₀ )} / (αl). This equation is easily obtained from Lambert-Beer law. Incidentally, the sensor output I ₀ and the extinction coefficient α when the change in the optical path length is zero are stored in advance in the calculation unit 50 (calculation unit 54).

  Next, the function and effect of the concentration detection apparatus 100 according to this embodiment will be described. As described above, the optical path length is controlled by deforming a part of the housing 30 (the thin portion 34). According to this, it is not necessary to ensure the space for rotating compared with the structure which rotates the optical path body which has several longitudinal members from which length differs. Therefore, an increase in the physique of the concentration detection device 100 is suppressed.

  The control unit 70 continuously controls the optical path length by continuously deforming a part (thin wall portion 34) of the housing 30. According to this, as compared with the configuration in which the optical path length is controlled discontinuously, it is possible to select the optimal optical path length for measuring the detection target. In addition, as a structure which controls optical path length continuously, the structure which rotates the optical path body which has several longitudinal member whose length was changed continuously can also be considered. However, in the case of this configuration, it is necessary to have many longitudinal members, and there is a concern about an increase in the size of the optical path body. Therefore, in the concentration detection apparatus 100 according to the present embodiment, an increase in the physique is suppressed as compared with the above-described comparison configuration.

  A light-shielding piezoelectric element 71 is formed on the outer surface of each of the thin portion 34 and the first connecting wall portion 35, and an opening 71 a is formed in the piezoelectric element 71. According to this, the opening 71a functions as an aperture, and the inspection light only through the incident wall portion 33 enters the housing 30. Therefore, the inspection light incident through the wall portions (thin wall portion 34, first connection wall portion 35) excluding the incident wall portion 33 in the first semiconductor substrate 31 is suppressed from entering the calculation portion 50. Thereby, an increase in noise is suppressed.

  The detection target is a liquid. According to this, since the concentration of the detection target is higher than when the detection target is a gas, the inspection light can be effectively reduced by changing the optical path length slightly. Therefore, it is not necessary to increase the size of the housing 30 in order to greatly change the optical path length, and a semiconductor substrate can be adopted as a material for forming the housing 30. Thereby, the increase in the physique of the housing | casing 30 is suppressed and the increase in the physique of the density | concentration detection apparatus 100 is suppressed.

  The optical path length is continuously changed, and the inspection light at the time of the continuous change is detected. Then, the optical path length when the sensor output is a constant value is detected. This is done for each component. By doing so, it is possible to select an optical path length suitable for measuring each component even when the concentration of each component is different.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the present embodiment, the optical path length when the sensor output is a constant value is detected, and the concentration of the detection target is calculated based on the detected optical path length and the sensor output. However, the concentration of the detection target can be calculated by a method different from this.

According to Lambert-Beer's law, I = I ₀ exp (−αnl) holds. When this is differentiated with respect to l, dI / dl = −αnI ₀ exp (−αnl) is obtained. From these two formulas, n = (dI / dl) / (− αI). Therefore, in order to detect the concentration, it is only necessary to know the sensor output and the differential value (change amount) with respect to the optical path length of the sensor output. This eliminates the need to previously detect the sensor output I ₀ when the change in the optical path length is zero. Therefore, after detecting the intensity I ₀ , for example, it is suppressed that the detected intensity I ₀ fluctuates due to contamination on the optical path and the density detection accuracy is reduced. .

  In order to obtain a sensor output and a differential value (amount of change) with respect to the optical path length of the sensor output, as shown in FIG. 16, the optical path length is continuously changed by the control unit 70, and continuously. A plurality of sensor outputs are detected when changed. In FIG. 16, five inspections are performed to obtain one differential value, and the differential value (change amount) with respect to the sensor output is detected using the least square method. By doing so, the influence of disturbance is suppressed, and a decrease in density detection accuracy is also suppressed. Incidentally, the optical path length l represented by the above equation is the optical path length corresponding to the middle (third point) sensor output among the sensor outputs detected at five points.

  In the present embodiment, an example in which the optical path length is controlled by changing the shape of the thin portion 34 of the first semiconductor substrate 31 by the pressure generated in the piezoelectric element 71 has been described. However, as shown in FIG. 17, the wall portion 37 of the second semiconductor substrate 32 is locally thinned in the same manner as the thin portion 34, and the piezoelectric element 71 is formed on the wall portion 37. It can also be adopted. According to this, the optical path length can be controlled by changing the shape of each of the thin portion 34 and the wall portion 37. Although not shown, it is possible to adopt a configuration in which the optical path length is controlled by changing only the shape of the wall portion 37.

  In the present embodiment, an example in which the piezoelectric element 71 is formed in the thin portion 34 is shown. However, the configuration for controlling the optical path length by changing the shape of the thin portion 34 is not limited to the above example. For example, as shown in FIG. 18, a configuration in which a metal wiring 73 having a linear expansion coefficient different from that of the first semiconductor substrate 31 is provided in the thin portion 34 may be employed. The shape of the thin portion 34 may be changed by a thermal stress caused by a difference in linear expansion coefficient between the metal wiring 73 and the thin portion 34 by causing a current to flow through the metal wiring 73. Alternatively, as shown in FIG. 19, by adding an impurity to each of the thin portion 34 and the wall portion 37 and applying a voltage to the region to which the impurity is added to generate an electrostatic force, The shape may be changed. 18 and 19, a light shielding film 74 is formed on the outer surface of the first semiconductor substrate 31. Therefore, the inspection light emitted from the infrared light source is incident on the incident wall 33 through the opening 74 a of the light shielding film 74.

  In the present embodiment, the optical path length detection unit 90 includes a strain gauge 92 and an optical path length detection circuit 93, and the optical path length detection circuit 93 is based on the output signal of the strain gauge 92 and changes in the optical path length. An example of detecting is shown. However, although not shown, the optical path length detection unit 90 has electrodes formed on the thin wall portion 34 and the wall portion 37 instead of the strain gauge 92, and the optical path length detection circuit 93 includes an electrostatic capacitance between these electrodes. The amount of change in the optical path length may be detected based on the change in capacitance. Alternatively, the optical path length detection unit 90 has a piezoelectric thin film formed in the thin portion 34 instead of the strain gauge 92, and the optical path length detection circuit 93 changes the optical path length based on the output signal of the piezoelectric thin film. May be detected.

  In the present embodiment, the formation materials of the semiconductor substrates 31 and 32 are not particularly mentioned, but a silicon substrate or an SOI substrate can be adopted as the formation material.

  In the present embodiment, an example in which the semiconductor substrates 31 and 32 are directly bonded is shown. However, the bonding of the semiconductor substrates 31 and 32 is not limited to the above example. As a joining method, any method can be used as long as it is highly durable and does not leak the detection target (liquid) from the inside of the housing 30. For example, bonding with a low-melting glass can be employed.

  In the present embodiment, the example in which the detection target is a mixed liquid containing at least one of ethanol, gasoline, and water is shown. However, the detection target is not limited to the above example. The object to be detected is not limited to liquid but may be gas.

DESCRIPTION OF SYMBOLS 10 ... Infrared light source 30 ... Case 33 ... Incident wall part 36 ... Output wall part 50 ... Calculation part 70 ... Control part 100 ... Concentration detection apparatus

Claims (6)

An infrared light source (10) for irradiating inspection light including infrared;
A housing (30) formed of a material that transmits infrared rays contained in the inspection light and in which a detection target is arranged;
The inspection light transmitted through the casing and the detection target in the casing is detected, and the concentration of the detection target is determined based on the detected inspection light and the optical path length through which the inspection light has transmitted through the detection target. A concentration detector having a calculation unit (50) for calculating,
The housing includes an incident wall portion (33) on which inspection light emitted from the infrared light source is incident, and an exit wall portion (36) from which inspection light transmitted through the detection target in the housing is emitted, Have
The distance between the incident wall and the exit wall corresponds to the optical path length,
Said By deforming a portion of the housing, have a control unit for controlling the optical path length (70),
The control unit continuously controls the optical path length by continuously deforming a part of the housing,
The calculation unit detects the inspection light transmitted through the casing and the detection target in the casing when the optical path length is continuously changed by the control unit, and the intensity of the detected inspection light The concentration of the detection target is calculated based on the differential value of the detected inspection light with respect to the optical path length and the extinction coefficient of the detection target.
The concentration detection apparatus is characterized in that the calculation unit detects a plurality of inspection lights for a plurality of optical path lengths and calculates a differential value for the detected inspection light using a least square method . A part of the casing is a thin part (34) having a locally thin thickness,
At least one of the incident wall portion and the emission wall portion is connected to the thin portion,
The concentration detection apparatus according to claim 1, wherein the control unit controls the optical path length by deforming the thin portion . The facing wall portion (31) facing the infrared light source in the housing includes the incident wall portion,
A light-shielding film (71, 74) is formed on the outer surface of the opposing wall;
Openings (71a, 74a) are formed in the light shielding film,
The concentration detection apparatus according to claim 2 , wherein the inspection light emitted from the infrared light source enters the incident wall portion through an opening formed in the light shielding film . The object to be detected, the concentration detection apparatus according to any one of claims 1 to 3, wherein the liquid der Rukoto. Wherein the housing, the concentration detection apparatus according to claim 4, characterized that you have been formed by a semiconductor (31, 32) that transmits infrared radiation included in the inspection light. The calculation unit detects the inspection light transmitted through the casing and the detection target in the casing when the optical path length is continuously changed by the control unit, and the intensity of the detected inspection light There detecting light path length in the case of a constant value, based on the detected optical path length and a predetermined value, said any one of claims 1 to 5, wherein that you calculate the concentration of the object to be detected Concentration detector.

Images