JP7244900B2 - Front and back identification method of reflective member - Google Patents

Description

The present invention relates to a method for identifying front and back surfaces of a reflecting member, and more particularly to a method for identifying front and back surfaces of a reflecting member formed of a translucent plate having a reflective layer formed on one side, which is used in a reflection-type density measuring apparatus.

Conventionally, it is incorporated in a gas supply line that supplies a raw material gas formed from a liquid material such as an organic metal (MO) or a solid material to a semiconductor manufacturing apparatus, and is configured to measure the concentration of the gas flowing through the gas supply line. densitometers (so-called in-line densitometers) are known.

In this type of concentration measuring apparatus, light of a predetermined wavelength is made incident from a light source through a light entrance window into a measuring cell in which a fluid to be measured flows, and the transmitted light that has passed through the measuring cell is received by a light-receiving element to determine the absorbance. to measure. Also, from the measured absorbance, the concentration of the fluid to be measured can be obtained according to the Beer-Lambert law (for example, Patent Documents 1 and 2).

In this specification, various transmitted light detection structures used for detecting the concentration of the fluid to be measured introduced therein are broadly referred to as measurement cells. The measurement cell includes not only a cell structure branched from the gas supply line, but also an in-line transmitted light detection structure provided in the middle of the gas supply line as shown in Patent Documents 1 and 2. .

Patent Literature 2 discloses a reflection-type concentration measuring device in which a reflective member is provided at the end of a measuring cell, and the concentration of a fluid to be measured flowing through the measuring cell is detected based on the absorbance of light traveling back and forth within the measuring cell. It is By using a reflecting member, it is possible to increase the optical path length of the light passing through the measurement cell and improve the measurement accuracy while realizing the miniaturization of the device.

JP 2014-219294 A WO2018/021311 JP 2018-25499 A

In a reflection-type concentration measuring apparatus, for example, a translucent plate (for example, a sapphire plate or a quartz plate) having an aluminum film or a dielectric multilayer film as a reflection layer provided on one side thereof is used as the reflection member. A reflective layer formed of an aluminum film or a dielectric multilayer film can reflect ultraviolet light, which is suitably used for measuring the concentration of an organometallic gas, with a high reflectance.

However, when arranging a reflective member in the measuring cell of an in-line concentration measuring device, if the reflective layer formed of an aluminum film or a dielectric multilayer film is placed in contact with the flow path of the measuring cell, the gas will be contaminated. There is a risk. For this reason, when using a reflective member, it is required that the reflective layer is attached to the measurement cell without confusing the front and back so that the reflective layer is not arranged on the flow path side of the measurement cell.

On the other hand, Japanese Patent Laid-Open No. 2002-200003 describes a technique of providing a reflection member with a front/back identification structure by providing a convex portion or a concave portion on the surface or by providing a flat portion on the side surface. By providing such a front/back identification structure, it is possible to prevent the reflection member from being attached upside down.

However, in order to provide the front/back identification structure as described above, it is necessary to mechanically process the reflecting member, and it is also necessary to provide a corresponding structure in the concave portion of the measurement cell that supports the reflecting member. Therefore, there is a problem that it requires time and effort and cost. Therefore, it would be advantageous to have a way to identify the front and back of the reflector member and to attach it to the measuring cell without making additional mechanical modifications to the reflector member.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its main object is to provide a method for identifying the front and back of a reflecting member in a density measuring apparatus without requiring additional mechanical processing.

A method for identifying the front and back surfaces of a reflecting member according to an embodiment of the present invention includes a measuring cell having a flow path through which a fluid to be measured flows, a light source emitting light incident on the measuring cell, and a reflector reflecting the light incident on the measuring cell. a member, a photodetector that detects light reflected by the reflecting member and emitted from the measurement cell, and a computing unit that computes the concentration of the fluid to be measured based on the output of the photodetector, wherein the computation A method for identifying the front and back surfaces of a reflecting member performed in a concentration measuring device, wherein the unit is configured to obtain the fluid concentration based on the Beer-Lambert law based on the detection signal of the photodetector, wherein the reflecting member has a translucent plate having a first surface and a second surface parallel to each other, and a reflective layer formed only on the first surface of the translucent plate, the first A step of measuring the reflectance when light of the same wavelength is applied to each of the surface and the second surface, wherein the light of the same wavelength is measured to each of the first surface and the second surface. A step of measuring the reflectance when irradiating light, wherein the reflectance when the first surface is irradiated and the reflectance when the second surface is irradiated are different wavelengths a step of measuring the reflectance by irradiating the first surface and the second surface with light of a first wavelength, and applying the specified light of the first wavelength to the reflecting member and identifying the front and back of the reflecting member by irradiating with and measuring the reflectance.

In one embodiment, the above-described front/back identification method includes measuring the reflectance by irradiating the first surface and the second surface with light of the same wavelength while changing the wavelength until the first wavelength can be specified. including the step of

In one embodiment, the reflecting member is formed by providing a dielectric multilayer film as the reflecting layer on a sapphire plate as the translucent plate, and the first wavelength is 300 nm or less.

In one embodiment, the first wavelength is 280 nm or less.

In one embodiment, the step of measuring the reflectance includes the step of irradiating light by varying the wavelength of the irradiating light within a range of at least 280 nm to 320 nm in order to specify the first wavelength.

Alternatively, a method for identifying front and back surfaces of a reflecting member according to another embodiment of the present invention comprises a measurement cell having a flow channel through which a fluid to be measured flows, a light source emitting light incident on the measurement cell, and light incident on the measurement cell. , a photodetector for detecting the light reflected by the reflecting member and emitted from the measurement cell, and a calculation unit for calculating the concentration of the fluid to be measured based on the output of the photodetector. A method for identifying the front and back surfaces of a reflecting member performed in a concentration measuring device, wherein the calculation unit is configured to obtain the fluid concentration based on the Beer-Lambert law based on the detection signal of the photodetector, , the reflecting member has a translucent plate having a first surface and a second surface parallel to each other, and a reflective layer formed only on the first surface of the translucent plate, The reflectance when the first surface is irradiated with light of the first wavelength is different from the reflectance when the second surface is irradiated with the light of the first wavelength, By irradiating the light of the first wavelength and measuring the reflectance, the front and back of the reflecting member are identified.

According to the embodiment of the present invention, in a reflection-type density measuring device, it is possible to distinguish between the front and back of a reflection member having a reflection layer formed on one side thereof, and to prevent the device from being used in a state in which the front and back are attached by mistake. be able to.

1 is a schematic diagram showing the overall configuration of a concentration measuring device used in an embodiment of the present invention; FIG. 2 is a cross-sectional view showing the detailed configuration of a measurement cell included in the concentration measuring device shown in FIG. 1; FIG. FIG. 4 is a diagram showing incident light and reflected light in a reflecting member having a reflective layer formed on one side of a sapphire plate; (c) and (d) show views in which the aluminum film as the reflective layer is placed on the side opposite to the incident light and on the incident light side. FIG. 4 is a table showing reflectance when light with wavelengths of 265 nm and 365 nm is irradiated for each example shown in FIGS. 3(a) to 3(d). FIG. 2 is a graph showing the relationship between the wavelength of incident light and the reflectance of a reflecting member, where (a) is a graph when the dielectric multilayer film is arranged on the incident light side, and (b) is a graph when the dielectric multilayer film is disposed on the incident light side; It is a graph when it is arranged on the opposite side of the incident light. FIG. 2 is a schematic diagram showing a two-core reflection-type density measuring device;

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

FIG. 1 is a schematic diagram showing the overall configuration of a concentration measuring device 100 used in an embodiment of the present invention. The concentration measuring apparatus 100 includes a hot gas unit 50 having a measuring cell 4 incorporated in a gas supply line, and an electric unit 52 spaced apart from the hot gas unit 50 and including a light source 1 and a computing unit 8. . The hot gas unit 50 and the electric unit 52 are connected by an optical fiber 10a and a sensor cable 10b.

The high-temperature gas unit 50 may be heated to, for example, about 100° C. to 150° C. depending on the type of fluid to be measured. It is Examples of fluids to be measured include process gases containing organometallic materials such as trimethylgallium (TMGa) and trimethylaluminum (TMAl). Although it is referred to as a "high temperature gas unit" here, it does not always reach a high temperature, and when using a gas at normal temperature (room temperature) or below normal temperature, it may be used in a state where it does not reach a high temperature (is not heated).

In the illustrated embodiment, the electric unit 52 is also connected to an external control device 54 via device net communication or the like. The external control device 54 can send operation control signals to the concentration measuring device 100 and receive measured concentration signals from the concentration measuring device 100 .

The high-temperature gas unit 50 has an inflow port 4a, an outflow port 4b, and a flow path 4c extending in the longitudinal direction for the fluid to be measured, and is provided with a translucent window (translucent plate) 3 in contact with the flow path 4c. A measuring cell 4 is provided. Further, the measuring cell 4 is provided with a reflecting member 5 for reflecting incident light. As used herein, light includes not only visible light but also at least infrared rays and ultraviolet rays, and may include electromagnetic waves of any wavelength. The translucency means that the internal transmittance of the light incident on the measuring cell 4 is sufficiently high enough to measure the density.

The window portion 3 of the measurement cell 4 is fixed to the cell body 40 by a window pressing member 30, and the window pressing member 30 is attached with the collimator 6 to which the optical fiber 10a is connected. The collimator 6 has a collimator lens 6 a and can make the light from the light source 1 enter the measurement cell 4 as parallel light, and the collimator 6 can receive the reflected light from the reflecting member 5 . can. The collimator 6 is designed so that even when the gas to be measured flowing through the measuring cell 4 is at a high temperature, the concentration can be measured with high accuracy without damage.

Further, in this embodiment, the high-temperature gas unit 50 is provided with a pressure sensor 20 for detecting the pressure of the fluid to be measured flowing through the measurement cell 4 . Although the pressure sensor 20 is arranged downstream of the outlet 4b of the measurement cell 4 in this embodiment, it may be arranged upstream of the measurement cell 4, or may be arranged upstream of the flow path 4c of the measurement cell 4. It may be provided in the middle. The pressure sensor 20 may have any form as long as it can measure the pressure of the fluid existing in the flow path 4c in the measurement cell 4, and various known pressure sensors can be used. The measurement cell 4 is also provided with a temperature sensor 11 (a temperature sensor, a thermistor, a thermocouple, etc.) for measuring the temperature of the fluid to be measured. The outputs of pressure sensor 20 and temperature sensor 11 are input to electric unit 52 via sensor cable 10b. Although the temperature sensor 11 is arranged near the outflow port 4b in this embodiment, it is sufficient if the temperature of the fluid existing in the flow path 4c can be measured. It may be installed in the section 3.

The electrical unit 52 includes a light source 1 for generating light incident on the measuring cell 4 , a measuring light detector 7 for receiving light emitted from the measuring cell 4 , and a light source output from the measuring light detector 7 . A calculation unit 8 configured to calculate the concentration of the fluid to be measured based on a detection signal corresponding to the intensity of light, and a reference light detector 9 receiving reference light from the light source 1 are provided.

In this embodiment, the measurement light detector 7 and the reference light detector 9 are arranged to face each other with the beam splitter 12 interposed therebetween. The beam splitter 12 causes part of the light from the light source 1 to enter the reference photodetector 9 and the detected light from the measurement cell 4 to enter the measurement photodetector 7 . Photodiodes and phototransistors are preferably used as the light receiving elements that constitute the measurement light detector 7 and the reference light detector 9 .

The calculation unit 8 is configured by, for example, a processor and memory provided on the circuit board PCB, includes a computer program that executes a predetermined calculation based on an input signal, and can be realized by a combination of hardware and software. .

In this embodiment, the light source 1 is configured using two light emitting elements 13A and 13B, and the light emitting elements 13A and 13B are LEDs that emit ultraviolet light of different wavelengths. Drive currents of different frequencies are supplied to the light emitting elements 13A and 13B using an oscillation circuit, and frequency analysis (for example, fast Fourier transform or wavelet transform) is performed to obtain the detection signal detected by the measurement photodetector 7. , the intensity of light corresponding to each wavelength component can be measured. The lights emitted by the light emitting elements 13A and 13B are combined by a WDM (Wavelength Division Multiplexing) multiplexer 14 and enter the measurement cell 4 . The wavelength of light from the light emitting element 13A is, for example, 300 nm, and the wavelength of light from the light emitting element 13B is, for example, 365 nm.

As the light emitting elements 13A and 13B, light emitting elements other than LEDs, such as LDs (laser diodes), can be used. Also, instead of using a light source with multiple different wavelengths, a light source with a single wavelength can be used. In this case, the multiplexer and the frequency analysis circuit can be omitted. Three or more light emitting elements may be provided, or only selected arbitrary light emitting elements may be used to generate incident light. Further, the multiplexer 14 may be attached with a resistance temperature detector 14a as shown in the figure. Furthermore, the light emitted by the light emitting element is not limited to ultraviolet light, and may be visible light or infrared light.

In the concentration measuring apparatus 100, the light source 1 and the measuring cell 4 are connected by an optical fiber 10a as a light guide member. Light from the light source 1 is guided to the window portion 3 of the measurement cell 4 by the optical fiber 10a. The optical fiber 10 a also has the function of guiding the light reflected by the reflecting member 5 to the measurement light detector 7 . The optical fiber 10a may include an optical fiber for incident light and an optical fiber for detection light, or may be provided in the form of an optical fiber bundle. In another aspect, the optical fiber for guiding the incident light to the measurement cell 4 and the optical fiber for guiding the light emitted from the measurement cell 4 may be separately provided ( See Figure 6).

FIG. 2 is a cross-sectional view showing a more detailed configuration of the measurement cell 4. As shown in FIG. The measurement cell 4 is formed in a cell body (cell block) 40 made of stainless steel, and a post-stage block 45 is connected to the cell body 40 via a gasket or the like. A pressure sensor 20 is attached to the channel of the rear block 45 .

The inlet 4a and the outlet 4b of the measurement cell 4 are arranged on both sides of the flow path 4c (on the right and left sides of the flow path 4c in the drawing). While the gas is configured to flow horizontally, the flow path 4c extends in a direction orthogonal to the overall flow direction in the gas supply line. Such a configuration is referred to herein as a vertical measuring cell 4 . The use of the vertical measuring cell 4 has the advantages of being able to save space when incorporated in the gas supply line and of facilitating maintenance. In the illustrated measurement cell 4, the inlet 4a is arranged near the reflecting member 5, and the outlet 4b is arranged near the window 3. In another embodiment, the inlet 4a is arranged near the window 3 , and the outlet 4b may be arranged near the reflecting member 5, and the flow path 4c does not necessarily have to extend in a direction perpendicular to the overall flow direction.

As the window part 3, sapphire, which has resistance to detection light used for concentration measurement such as ultraviolet light and high transmittance, and is mechanically and chemically stable, is preferably used. For example, quartz glass can also be used. The cell body 40 (flow path forming portion) of the measurement cell 4 may be made of, for example, SUS316L. Also good. In this embodiment, the window portion 3 is fixed to the concave portion of the cell body 40 by the window pressing member 30 via the gasket 15 .

The reflecting member 5 arranged at the opposite end of the window 3 of the measurement cell is fixed to the supporting surface of the mounting recess provided on the lower surface of the cell body 40 by the pressing member 32 via the gasket 16. It is The reflecting surface of the reflecting member 5 is provided so as to be perpendicular to the traveling direction of the incident light or the central axis 4x of the flow path, and the reflected light passes through substantially the same optical path as the incident light and reaches the window portion 3. reflected to

In this embodiment, as the reflecting member 5, a sapphire plate having a dielectric multilayer film as a reflecting layer formed on one side thereof is used. By using a dielectric multilayer film, it is possible to selectively reflect light in a specific wavelength range (for example, near-ultraviolet rays). A dielectric multilayer film is composed of a laminate of a plurality of optical films with different refractive indices (for example, a laminate of a high refractive index thin film and a low refractive index thin film), and the thickness and refractive index of each layer are appropriately adjusted. By selection, specific wavelengths of light can be reflected or transmitted.

Moreover, the dielectric multilayer film can reflect light at an arbitrary ratio. Therefore, instead of reflecting 100% of the incident light, a part (for example, 10%) of the incident light is transmitted, and a photodetector installed below the reflecting member 5 or an optical device connected to the photodetector It can also receive transmitted light. The light transmitted through the reflecting member 5 can be used as reference light, and the above photodetector can be used as a substitute for the reference light detector 9 shown in FIG.

The reflecting member 5 is made of sapphire and has dimensions of, for example, a diameter of 10 to 20 mm (more specifically, a diameter of about 16 mm) and a thickness of 1.0 to 2.0 mm (more specifically, a thickness of about 1.8 mm). It is produced by forming a dielectric multilayer film on one side of a circular plate. The dielectric multilayer film is made of, for example, oxides or fluorides such as _TiO2 , _Ta2O5 , _Al2O3 , _{SiO2 , MgF2} , and has _a refractive index and thickness corresponding to the reflection wavelength. It is formed by alternately laminating a high refractive index thin film and a low refractive index thin film by vapor deposition or the like. The thickness of the dielectric multilayer film is, for example, 300 nm to 5 μm, depending on the number of layers (for example, several to several tens of layers).

In the measuring cell 4 described above, the optical path length of light propagating back and forth in the measuring cell 4 can be defined by twice the distance between the surface of the window portion 3 and the surface of the reflecting member 5 . In the concentration measuring apparatus 100, the light incident on the measuring cell 4 and then reflected by the reflecting member 5 is absorbed by the gas present in the flow path 4c in the measuring cell 4 to an extent that depends on the concentration of the gas. be. Then, the calculation unit 8 (see FIG. 1) can measure the absorbance Aλ at the absorption wavelength λ by frequency-analyzing the detection signal from the measurement photodetector 7, and further, the following formula (1 ), the gas concentration C can be calculated from the absorbance Aλ based on the Beer-Lambert law shown in FIG.
Aλ=−log ₁₀ (I/I ₀ )=αLC (1)

In the above formula (1), I ₀ is the intensity of incident light entering the measurement cell, I is the intensity of light that has passed through the gas in the measurement cell, α is the molar extinction coefficient (m ² /mol), and L is The optical path length of the measuring cell (m), C is the concentration (mol/m ³ ). The molar extinction coefficient α is a coefficient determined by substances.

Regarding the incident light intensity I ₀ in the above formula, when there is no light-absorbing gas in the measurement cell 4 (for example, when it is filled with a purge gas that does not absorb ultraviolet light, or when it is evacuated) ), the intensity of the light detected by the measuring photodetector 7 may be regarded as the incident light intensity I ₀ .

Since the optical path length L of the measuring cell 4 can be defined as twice the distance between the window portion 3 and the reflecting member 5 as described above, the light entrance window and the light exit window are placed at both ends of the measuring cell. A double optical path length can be obtained as compared with the conventional densitometer provided. Thereby, the measurement accuracy can be improved in spite of the miniaturization. Further, in the concentration measuring apparatus 100, light is incident and received using only one optical device through one window 3 provided on one side of the measuring cell 4, so the number of parts can be reduced.

Furthermore, the concentration measuring device 100 is provided with a pressure sensor 20 that can measure the pressure of the gas within the measuring cell 4 . Therefore, based on the output from the pressure sensor 20, the absorbance measured by the output of the photodetector can be corrected to the absorbance at a predetermined pressure (for example, 1 atm). Then, based on the corrected absorbance, the concentration of the fluid to be measured can be calculated from the Beer-Lambert law in the same manner as the concentration measuring device described in Patent Document 3. In this manner, since the calculation unit 8 calculates the concentration of the fluid to be measured using the measurement light detector 7 and the pressure sensor 20, the concentration can be measured with higher accuracy. Since a temperature sensor 11 (see FIG. 1) for measuring the temperature of the gas flowing through the measurement cell 4 is provided, it is also possible to perform concentration detection by further performing temperature correction.

A method for identifying the front and back of the reflecting member 5 having a dielectric multilayer film on one side thereof, which is used in the density measuring apparatus 100, will be described below.

FIGS. 3(a) and 3(b) show a reflective member having a dielectric multilayer film formed on one side of a sapphire plate (translucent plate). FIG. 3A shows a case where a film 5b1 is formed and a case where a dielectric multilayer film 5b2 is formed on the incident light side surface of a sapphire plate 5a2 (FIG. 3B). be.

As shown in FIG. 3A, when the dielectric multilayer film 5b1 is provided on the opposite surface, incident light transmitted through the sapphire plate 5a1 is reflected by the dielectric multilayer film 5b1. On the other hand, when the dielectric multilayer film 5b2 is provided on the light incident surface as shown in FIG. reflected to

FIGS. 3(c) and 3(d) show the case where an aluminum film 5c1 is formed on the surface of the sapphire plate 5a1 opposite to the incident light side in the reflecting member having the aluminum film formed on one surface of the sapphire plate. 3(c)) and a case where an aluminum film 5c2 is formed on the incident light side surface of the sapphire plate 5a2 (FIG. 3(d)).

FIG. 4 is a table showing the reflectance (%) when the incident light wavelength is 265 nm or 365 nm in each of the cases shown in FIGS. 3(a) to 3(d). The reflectance (%) is, for example, measured light detection when ultraviolet light of 265 nm or 365 nm is incident from the light source 1 in a state where no light absorbing gas exists inside the measurement cell 4 in the concentration measurement device 100. It can be obtained from the output of the detector 7 and the output of the reference photodetector 9 .

As can be seen from FIG. 4, in the case (a) in which the dielectric multilayer film 5b1 is provided on the surface of the sapphire plate 5a1 opposite to the incident light side, the reflectance of light at 265 nm is relatively small at 18%. Therefore, the reflectance for light of 365 nm is relatively high at 89%.

On the other hand, when the dielectric multilayer film 5b2 is provided on the incident light side surface of the sapphire plate 5a2 (b), the reflectance for light at 265 nm and the reflectance for light at 365 nm are both 100%. It can be seen that the incident light is completely reflected even at the wavelength of .

In addition, when the aluminum film 5c1 is provided on the surface of the sapphire plate 5a1 opposite to the incident light side (c) and when the aluminum film 5c2 is provided on the surface of the sapphire plate 5a2 on the incident light side (d), 265 nm The reflectance of light at 365 nm is relatively high at 90% and 91%, and the reflectance at 365 nm is also relatively high at 84% and 89%.

From the above results, when the dielectric multilayer films 5b1 and 5b2 are provided on one side of the sapphire plates 5a1 and 5a2, the front and back of the reflective member can be identified by irradiating ultraviolet light with a wavelength of 265 nm and measuring the reflectance. know that you can. In addition, when the dielectric multilayer films 5b1 and 5b2 are provided and the reflectance is measured by irradiating light with a wavelength of 365 nm, it is found that it is not easy to identify the front and back of the reflecting member. Furthermore, when the aluminum films 5c1 and 5c2 are provided as the reflective layers, it is difficult to distinguish between the front and back sides based on the reflectance regardless of whether the light having a wavelength of 265 nm or 365 nm is irradiated. .

FIGS. 5A and 5B show the case where the dielectric multilayer film 5b1 is formed on the surface of the sapphire plate 5a1 opposite to the incident light side (sometimes referred to as the back surface) (corresponding to FIG. 3A). ) and the case where the dielectric multilayer film 5b2 is formed on the surface (sometimes referred to as the surface) of the sapphire plate 5a2 on the incident light side (corresponding to FIG. 3(b)). It is a graph which shows the relationship with a rate.

From FIGS. 5A and 5B, when light in a wavelength range of 300 nm or less, for example, is incident, the reflectance varies depending on whether the dielectric multilayer films 5b1 and 5b2 exist on the front side or the back side. It turns out that they are very different. Above all, it can be seen that at wavelengths of 290 nm or less, particularly 280 nm or less, the difference in reflectance is extremely large. On the other hand, it can be seen that the difference in reflectance is small when light of 320 nm to 450 nm is incident. Therefore, in order to identify the front and back of the reflecting member by measuring the reflectance, it is necessary to let light in a specific wavelength range (for example, 230 nm or more and 300 nm or less) be incident. The reflecting member for which the results of the graphs of FIGS. 5(a) and (b) were obtained is different from the reflecting member for which the results of the table of FIG. 4 were obtained. The height is slightly different.

In order to specify wavelengths with different reflectances on the front and back, in the present embodiment, a dielectric multilayer film is formed only on one surface (sometimes referred to as the first surface) of the translucent plate. In this case, the reflectance is measured when light of the same wavelength is applied to each of the one surface and the other surface (sometimes referred to as a second surface). The measurement of the reflectance continues until the wavelength at which the reflectance when one surface is irradiated with light and the reflectance when the other surface is irradiated with light is different. I am trying to change it. In this step, for example, as shown in FIG. 5A, the wavelength is changed continuously or discretely in the range of 230 nm to 450 nm and at least in the range of 280 nm to 320 nm. This may be done by illuminating each of the surfaces and the second surface and taking reflectance measurements.

Then, when the wavelength causing a significant difference in reflectance can be specified, the reflecting member on which the dielectric multilayer film is formed on which side is unknown is irradiated with light of the specified wavelength. By measuring the reflectance, the front and back of the reflecting member can be identified.

As described above, by measuring the reflectance when the light of a specific wavelength is irradiated, it is possible to determine on which surface of the translucent plate the dielectric multilayer film is formed. Even after the reflecting member 5 is incorporated into the density measuring apparatus 100 shown in FIGS. 1 and 2, the front and back surfaces can be identified by irradiating light and measuring the reflected light. Therefore, it is possible to prevent the dielectric multilayer film from being used with the dielectric multilayer film arranged on the flow path side as a result of attaching the front and back in a wrong way, and it is possible to prevent contamination of the gas flowing through the measurement cell.

Further, when the wavelength or wavelength band of the light at which the reflectance when irradiated on the first surface and the reflectance when irradiated on the second surface are different is known in advance, simply By irradiating light and measuring the reflectance, the front and back of the reflecting member can be identified. A light source that emits light used for front/back identification may be included in the light source for density measurement in the density measurement device, or may be provided separately.

Although the concentration measuring device according to the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention.

For example, as shown in FIG. 1, a mode using a device that guides incident light and outgoing light with a single optical fiber 10a has been described above, but a two-core concentration measuring device can also be used. preferred. Such a two-core concentration measuring device is described, for example, in Patent Document 3 (FIG. 8, etc.).

As shown in FIG. 6, in the two-core concentration measuring apparatus, the measuring cell 4 and an electric unit 52 are connected by an incident optical fiber 10c and an exiting optical fiber 10d (here, the measuring cell 4 The provided temperature sensor and the sensor cable connected thereto are omitted). The light from the light emitting elements 13A and 13B is guided by the incident fiber 10c and enters the measuring cell 4 through the window 3. As shown in FIG. Further, the measuring light reflected by the reflecting member 5 and emitted from the measuring cell 4 is guided by the emitting optical fiber 10 d and received by the measuring light detector 7 . The influence of stray light can be reduced by guiding the incident light and the emitted light through different paths in this way. Further, as shown in FIG. 6, by arranging the normal direction of the window surface of the window portion 3 at an angle of, for example, about 1 to 5 degrees from the optical axis direction of the collimator, the generation of stray light can be reduced. Also, the gas inlet and the gas outlet of the measuring cell 4 may be provided on the same side of the measuring cell 4, unlike the embodiment shown in FIG.

The front/back identification method according to the embodiment of the present invention is suitably used, for example, for identifying the front/back of a reflecting member incorporated in a reflection-type density measuring apparatus.

REFERENCE SIGNS LIST 1 light source 3 window 4 measurement cell 4a inlet 4b outlet 4c channel 5 reflective member 5a1, 5a2 sapphire plate 5b1, 5b2 dielectric multilayer film 5c1, 5c2 aluminum film 6 collimator 7 measurement light detector 8 calculator 9 reference light Detector 10a Optical fiber 10b Sensor cable 11 Temperature sensor 100 Concentration measuring device

Claims (5)

A measuring cell having a flow path through which a fluid to be measured flows, a light source emitting light incident on the measuring cell, a reflecting member reflecting the light incident on the measuring cell, and being reflected by the reflecting member and emitted from the measuring cell. a photodetector for detecting the emitted light; and a computing unit for computing the concentration of the fluid to be measured based on the output of the photodetector, wherein the computing unit, based on the detection signal of the photodetector, A method for identifying the front and back surfaces of a reflecting member in a concentration measuring device configured to determine the concentration of a fluid according to Beer-Lambert's law, comprising:
The reflective member has a translucent plate having a first surface and a second surface parallel to each other, and a reflective layer formed only on the first surface of the translucent plate,
A step of measuring the reflectance when light of the same wavelength is applied to each of the first surface and the second surface, wherein the reflectance when the first surface is irradiated and the and measuring the reflectance by irradiating the first surface and the second surface with light having a first wavelength, which is a wavelength different from the reflectance when the second surface is irradiated. and,
identifying the front and back of the reflecting member by irradiating the reflecting member with light of the first wavelength and measuring the reflectance ,
The reflecting member is formed by providing a dielectric multilayer film as the reflecting layer on a sapphire plate as the translucent plate, and the light of the first wavelength is ultraviolet light. Front and back identification method. 2. The method for identifying front and back surfaces of a reflecting member according to claim 1, wherein said first wavelength is 300 nm or less. 3. The method for identifying front and back sides of a reflecting member according to claim 2, wherein said first wavelength is 280 nm or less. 4. The step of measuring the reflectance includes the step of irradiating light by changing the wavelength of the light to be irradiated in a range of at least 280 nm to 320 nm in order to specify the first wavelength. 2. The front/back identification method of the reflecting member according to 1. A measuring cell having a flow path through which a fluid to be measured flows, a light source emitting light incident on the measuring cell, a reflecting member reflecting the light incident on the measuring cell, and being reflected by the reflecting member and emitted from the measuring cell. a photodetector for detecting the emitted light; and a computing unit for computing the concentration of the fluid to be measured based on the output of the photodetector, wherein the computing unit, based on the detection signal of the photodetector, A method for identifying the front and back surfaces of a reflecting member in a concentration measuring device configured to determine the concentration of a fluid according to Beer-Lambert's law, comprising:
The reflective member has a translucent plate having a first surface and a second surface parallel to each other, and a reflective layer formed only on the first surface of the translucent plate,
The reflectance when the first surface is irradiated with light of the first wavelength is different from the reflectance when the second surface is irradiated with the light of the first wavelength,
A step of identifying the front and back of the reflecting member by irradiating the light of the first wavelength and measuring the reflectance,
The reflecting member is formed by providing a dielectric multilayer film as the reflecting layer on a sapphire plate as the translucent plate, and the light of the first wavelength is ultraviolet light. Front and back identification method.

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