WO2020084867A1

WO2020084867A1 - Concentration sensor

Info

Publication number: WO2020084867A1
Application number: PCT/JP2019/030928
Authority: WO
Inventors: 一成横山; 峻黒田; 長谷川　雅一
Original assignee: 株式会社堀場アドバンスドテクノ
Priority date: 2018-10-25
Filing date: 2019-08-06
Publication date: 2020-04-30
Also published as: JP2022017606A

Abstract

To provide a concentration sensor that makes installation easy and is capable of enhancing concentration measurement accuracy while reducing the chance of contaminating a fluid under measurement, in this invention, a concentration sensor 100 for measuring the concentration of a fluid flowing within a pipe P formed from a transparent material is made to comprise: a light source 2 for emitting measurement light; a collimation lens 3 for collimating the measurement light emitted from the light source 2; a converging lens 8 for converging the measurement light that has passed through the pipe P; a light detection mechanism 9 for detecting the measurement light that has been converged by the converging lens 8; and one or more concave lenses 5, 6 that are each provided between the collimation lens 3 and pipe P or between the pipe P and converging lens 8 and are disposed such that there are gaps between the same and the outside surface of the pipe P.

Description

Concentration sensor

The present invention relates to a concentration sensor used for contactlessly measuring the concentration of a fluid flowing in a light-transmitting pipe.

For example, in the semiconductor manufacturing process, in order to prevent contamination with fluids such as chemicals used, the fluid flowing in a transparent pipe is irradiated with measuring light, and the concentration of the fluid is measured based on its absorbance. In some cases, a non-contact type concentration sensor is used.

Such a concentration sensor is configured so that a casing can be attached later to a resin-made pipe having a light-transmitting property through which a fluid flows as shown in Patent Document 1. In addition, an optical device such as a collimating lens that collimates the light emitted from the light source and a condensing lens that condenses the measurement light that has passed through the fluid in the pipe and guides it to the photodetector is installed in the housing. It is provided.

However, in the above-mentioned concentration sensor, even if the pipe is irradiated with the measuring light collimated by the collimating lens, the pipe itself through which the fluid flows acts as a cylindrical biconvex lens and is diverged. Therefore, there is a problem that the measurement light passing through the fluid detected by the photodetector does not have a sufficient amount of light and the measurement accuracy is inferior to that of the concentration measurement method using electrodes.

Japanese Patent Laid-Open No. 2000-088740

The present invention has been made in view of the above-described problems, and a concentration sensor capable of improving the measurement accuracy of concentration while facilitating installation and reducing the possibility of contaminating a fluid to be measured. The purpose is to provide.

That is, the concentration sensor according to the present invention is a concentration sensor that measures the concentration of a fluid flowing in a pipe formed of a translucent material, and includes a light source that emits measurement light and a light source that emits the measurement light. A collimating lens for collimating the measurement light, a condenser lens for condensing the measurement light passing through the pipe, a light detection mechanism for detecting the measurement light condensed by the condenser lens, One or a plurality of concave lenses provided between the corresponding lens and the pipe or between the pipe and the condenser lens, and the pipe based on the intensity of the measurement light detected by the photodetection mechanism. And a concentration calculator for calculating the concentration of the fluid flowing therein, wherein one or a plurality of the concave lenses are arranged so as to form a gap with respect to the outer surface of the pipe.

With such a configuration, the condensing action of the cylindrical convex lens made of the pipe and the fluid can be canceled by the one or more concave lenses.

Therefore, it is possible to reach the photodetection mechanism with the measurement light that has been conventionally dissipated by the action of the cylindrical convex lens made of the pipe and the fluid, and to increase the amount of detected light to improve the concentration measurement accuracy. it can.

Furthermore, since the concave lens is arranged so as to form a space with respect to the outer surface of the pipe and is not in close contact with each other, for example, a minute gap is generated from the state where the concave lens and the pipe are in close contact with each other. It can be prevented from being formed and causing optical interference. Therefore, it is possible to prevent the optical interference from affecting the concentration measurement. The minute gap in this case refers to a small distance of about several tens mm or less.

If the refractive index of the fluid is smaller than the refractive index of the concave lens, the radius of curvature of the concave surface of the concave lens may be larger than the radius of curvature of the pipe. On the contrary, when the refractive index of the fluid is larger than that of the concave lens, the concave surface of the concave lens may have a radius of curvature smaller than that of the pipe.

In order to make the concave lens cancel the light condensing action only in the radial direction where the light condensing action is exhibited in the cylindrical biconvex lens made of the pipe and the fluid, the collimating lens and the light condensing lens are spherical lenses. It is sufficient that the first concave lens and the second concave lens are cylindrical lenses.

As a specific configuration example suitable for increasing the amount of the measurement light emitted from the light source reaching the photodetection mechanism as much as possible, a plurality of the concave lenses are provided between the collimating lens and the pipe. And a second concave lens provided between the pipe and the condenser lens, and the concave surface of the first concave lens is formed on the measurement light incident side of the pipe. The concave surface of the second concave lens is formed on the incident side of the measurement light facing the outer surface of the pipe.

As another configuration example for improving the density measurement accuracy, a plurality of the concave lenses are a first concave lens provided between the collimating lens and the pipe, the pipe and the condensing lens. And a second concave lens provided between the first concave lens and the second concave lens, the concave surface of the first concave lens is formed on the emission side of the measurement light facing the outer surface of the pipe, and the concave surface of the second concave lens is The one formed on the incident side of the measurement light facing the outer surface of the pipe can be mentioned.

Furthermore, in order to increase the amount of light detected by the light detection mechanism, the first concave lens has a convex surface formed on the measurement light incident side, and the second concave lens is formed on the measurement light emission side. It is sufficient that the convex surface is formed.

In order to sufficiently cancel the light condensing action of the biconvex lens composed of the pipe and the fluid while minimizing the number of lenses required, the concave lens is provided between the collimating lens and the pipe, or It should be provided only on one of the pipe and the condenser lens, and concave surfaces may be formed on both the incident side and the reflection side of the measurement light of the concave lens.

The light source, the collimating lens, the one or more concave lenses, and the light condensing lens are provided so that the pipe can be easily retrofitted to an existing pipe formed of a translucent material. A lens and a housing for holding the photodetection mechanism at a predetermined position are further provided, and the housing is detachable from the pipe, and the first housing is attached to the pipe. It suffices that a gap be formed between the concave lens and the second concave lens and the outer surface of the pipe.

As described above, in the concentration sensor according to the present invention, one or a plurality of the concave lenses provided in the vicinity of the pipe cancels the light condensing function as the cylindrical biconvex lens composed of the pipe and the fluid, and the concentration is detected by the light detection mechanism. It is possible to improve the quantity of the measuring light to be used. Further, since the concave lens is arranged so that a gap is formed with respect to the pipe, it is possible to prevent optical interference from occurring. Further, since the concentration of the fluid can be measured based on the measurement light that passes through the fluid, the concentration sensor itself can be easily installed on the pipe, and the possibility of contamination of the fluid can be reduced.

The schematic block diagram which shows the concentration sensor which concerns on 1st Embodiment of this invention. The typical perspective view which shows the attachment state with respect to the pipe of the 1st concave lens and 2nd concave lens of 1st Embodiment. The schematic optical-path figure of the concentration sensor of 1st Embodiment. FIG. 6 is a schematic optical path diagram of a concentration sensor according to a second embodiment of the present invention. FIG. 6 is a schematic optical path diagram of a concentration sensor according to a third embodiment of the present invention. The schematic optical-path figure of the density sensor which concerns on 4th Embodiment of this invention. The schematic optical-path figure of the density sensor which concerns on 5th Embodiment of this invention.

100 ... Density sensor 1 ... Housing 2 ... Light source 3 ... Collimation lens 5 ... First concave lens 6 ... Second concave lens 8 ... Condensing lens 9 ... Light detection mechanism 10 ... Concentration calculation unit P ... Pipe F ... Fluid

The concentration sensor 100 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3. In FIG. 3, various mirrors shown in FIG. 1 are omitted. For the sake of clarity, the cross section of the pipe P is defined as the XY plane, and the axial direction of the pipe P is defined as the Z axis.

The concentration sensor 100 shown in FIG. 1 is used to measure the concentration of a liquid such as a chemical liquid supplied to a chamber or the like in a semiconductor manufacturing process, for example. The concentration sensor 100 is retrofitted to a pipe P formed of a translucent material through which a fluid F to be measured flows. That is, the concentration sensor 100 is configured to measure the concentration of the fluid F flowing in the pipe P based on the absorbance while using the pipe P as a part of the optical system.

Specifically, the concentration sensor 100 has a plurality of optical devices arranged and housed in a casing 1 attached to the pipe P, and the casing 1 is configured to be attachable to and detachable from the pipe P. There is.

As shown in FIG. 1, the housing 1 has a light source 2, a collimating lens 3, an entrance-side mirror 4, and a plurality of concave lenses, which are formed on the optical path for measurement, which is formed in a substantially U-shape. The concave lens 5, the second concave lens 6, the exit side mirror 7, the condenser lens 8, and the light detection mechanism 9 are arranged. On the optical path for measurement, as shown in FIGS. 1 and 2, a pipe P through which the fluid F to be measured flows is arranged between the first concave lens 5 and the second concave lens 6.

Further, as shown in FIG. 1, the positions of the entrance side mirror 4 and the exit side mirror 7 are between a sample position S where a measurement optical path is formed and a reference position R where a reference optical path is formed. It is configured to be modifiable. When the entrance side mirror 4 and the exit side mirror 7 are arranged at the reference position R, the measurement light emitted from the light source 2 enters the photodetection mechanism 9 through the reference RF instead of the pipe P.

By mounting the casing 1 on the pipe P, the positions of the light source 2, the collimating lens 3, the first concave lens 5, the second concave lens 6, the condensing lens 8 and the light detection mechanism 9 with respect to the pipe P are predetermined. Fixed in place.

Detailed description of each part.

The light source 2 is, for example, an LED, and emits measurement light composed of light in a predetermined wavelength range. Further, the lamp box accommodating the LEDs is fixed to the housing 1.

The collimating lens 3 is a biconvex spherical lens that collimates the light emitted from the light source 2 as shown in FIG.

The first concave lens 5 receives the collimated measurement light emitted from the collimating lens 3 and emits the measurement light to the pipe P. The surface of the first concave lens 5 on the measurement light incident side is formed as a partially cylindrical concave surface, and the surface facing the pipe P on the measurement light emission side is formed as a flat surface. As shown in FIG. 2, the first concave lens 5 is a cylindrical lens having a concave surface on one surface. The concave surface is formed so as to have a curvature in the circumferential direction of the pipe P on the XY plane, and is arranged so as to have an equal cross-sectional shape in the Z-axis direction which is the axial direction of the pipe P. The first concave lens 5 is arranged, for example, so that all the luminous fluxes of the measurement light collimated by the collimating lens 3 enter.

The second concave lens 6 is arranged so as to sandwich the pipe P in the radial direction together with the first concave lens 5. The measurement light emitted from the inside of the pipe P to the outside enters the second concave lens 6. The second concave lens 6 has a partially cylindrical concave surface formed on the surface facing the pipe P that is the measurement light incident side, and the measurement light emission side surface is formed as a flat surface. As shown in FIG. 2, the second concave lens 6 is a cylindrical lens having a concave surface on one surface. The concave surface is formed so as to have a curvature in the circumferential direction of the pipe P on the XY plane, and is arranged so as to have an equal cross-sectional shape in the Z-axis direction which is the axial direction of the pipe P.

As shown in FIGS. 2 and 3, a gap is formed between each of the first concave lens 5 and the second concave lens 6 and the outer surface of the pipe P, and the first concave lens 5 and the second concave lens with respect to the pipe P are formed. 6 is configured not to contact. If the refractive index of the chemical liquid that is the fluid flowing in the pipe P is smaller than the refractive index of the material forming the first concave lens 5 and the second concave lens 6, the concave surfaces of the first concave lens 5 and the second concave lens 6 The radius of curvature is formed larger than the radius of curvature of the outer surface of the pipe P. On the contrary, when the refractive index of the chemical liquid which is the fluid flowing in the pipe P is larger than the refractive index of the material forming the first concave lens 5 and the second concave lens 6, the concave surfaces of the first concave lens 5 and the second concave lens 6 are The radius of curvature is formed smaller than the radius of curvature of the outer surface of the pipe P. Here, the term "void" means a predetermined gap and means that no other substance such as an adhesive agent is present. For example, it is a concept including that only air, gas, or vacuum exists in the void.

The collimated measurement light that enters the first concave lens 5 is slightly diverged to the outside and enters the pipe P. Due to the converging action of the biconvex cylindrical lens composed of the pipe P and the fluid F, the measurement light travels in the pipe P in a substantially parallel state. When the measurement light is emitted from the inside of the pipe P to the outside, the measurement light is slightly condensed to the inside due to the condensing action of the pipe P, but is diverged to the outside again by the second concave lens 6 and becomes substantially parallel. The measured light thus emitted is emitted from the second concave lens 6.

The condenser lens 8 is a biconvex spherical lens, and the collimated measurement light emitted from the second concave lens 6 is incident and condensed on, for example, a slit formed in the photodetection mechanism 9.

The light detection mechanism 9 is provided at a position where a spectroscope (not shown) that disperses the measurement light incident from the slit and a light in the absorption wavelength band of the fluid F to be measured is irradiated from the dispersed measurement light. And a photodetector (not shown). The photodetector outputs a voltage according to the intensity of incident light. The light detection mechanism 9 is also fixed to the housing 1.

A concentration calculation unit 10 that calculates the concentration of the fluid F based on the output of the light detection mechanism 9 is provided outside the housing 1. The function of the density calculator 10 is realized by a so-called computer including input / output devices such as a CPU, a memory, an A / D converter, and a D / A converter. That is, the program stored in the memory is executed, and the various devices cooperate to realize the function as the concentration calculation unit 10. The density value calculated by the density calculation unit 10 is transmitted to and used by another device other than the density sensor 100, such as a density control device.

The concentration calculation unit 10 calculates the absorbance based on the ratio of the intensity of the measurement light that has passed through the optical path for measurement and the intensity of the light that has passed through the optical path for reference RF, and then calculates the logarithm of the absorbance. The concentration of the target fluid F is calculated.

According to the concentration sensor 100 of the first embodiment configured in this way, the pipe P and the fluid F to be measured exert a condensing action as a biconvex cylindrical lens, and are provided in the vicinity of the pipe P. The action can be canceled by the concave lens 5 and the second concave lens 6. Therefore, most of the measurement light emitted from the light source 2 can be detected by the light detection mechanism 9. More specifically, the first concave lens 5 diffuses the light so that the light condensing action on the incident surface of the fluid F is canceled and the light in the fluid F becomes parallel, and the light is emitted to the fluid F, and the fluid F is ejected. The light condensed and emitted from the fluid F by the condensing action on the surface is made parallel by the second concave lens 6.

Therefore, since the intensity of the light detected by the light detection mechanism 9 can be increased, even a slight change in concentration can be detected, and the concentration measurement accuracy can be improved.

Further, since the first concave lens 5 and the second concave lens 6 are not in contact with the pipe P and a gap is formed, light is emitted between the pipe P and each of the first concave lens 5 and the second concave lens 6. It is possible to prevent interference and influence on the concentration measurement.

In addition, the concentration sensor 100 of the first embodiment can be retrofitted to the existing pipe P, and the concentration can be measured in a non-contact manner with respect to the fluid F that is the measurement target. Therefore, the installation is easy, and the possibility of contamination of the fluid F flowing in the pipe P due to the concentration measurement can be eliminated.

Next, the concentration sensor 100 according to the second embodiment of the present invention will be described with reference to FIG. The members corresponding to the members described in the first embodiment are designated by the same reference numerals.

In the density sensor 100 of the second embodiment, the direction of the first concave lens 5 is opposite to that of the first embodiment. That is, in the first concave lens 5, the surface on the side where the measurement light is incident is formed into a flat surface, and the surface on the side where the measurement light is emitted is formed into a concave surface.

Even the concentration sensor 100 of the third embodiment as described above can achieve the same effect as that of the above-described embodiment.

A third embodiment of the present invention will be described with reference to FIG. The members corresponding to the members described in the first embodiment are designated by the same reference numerals.

The density sensor 100 of the third embodiment is different from that of the first embodiment in that the first concave lens 5 and the second concave lens 6 are meniscus concave lenses having not only concave surfaces but also convex surfaces.

Specifically, the first concave lens 5 has a convex surface on the measurement light incident side and a concave surface on the measurement light emission side.

On the other hand, the second concave lens 6 has a concave surface on the measurement light incident side and a convex surface on the measurement light emission side.

According to the concentration sensor 100 of the second embodiment as described above, the refracting action of the measurement light can be generated on the respective surfaces of the first concave lens 5 and the second concave lens 6, and the light condensing that occurs in the pipe P and the fluid F. The effect can be canceled more precisely. Therefore, the light amount of the measurement light detected by the light detection mechanism 9 can be increased, and the density measurement accuracy can be improved.

A fourth embodiment of the present invention will be described with reference to FIG. The members corresponding to the members described in the first embodiment are designated by the same reference numerals.

The density sensor 100 of the fourth embodiment is different from that of the first embodiment in that only the first concave lens 5 is provided between the collimating lens 3 and the pipe P as a concave lens. Further, the first concave lens 5 is formed such that both the surface on the side where the measurement light enters and the surface on the side where the measurement light exits are concave.

According to the concentration sensor 100 of the fourth embodiment as described above, the condensing action of the biconvex cylindrical lens composed of the fluid and the pipe P is canceled and the concentration measurement accuracy is improved while minimizing the number of arranged lenses. It is possible to raise it. More specifically, the light condensing action on the incident surface and the exit surface of the fluid F is canceled, and the light emitted from the fluid F is diffused by the first lens 5 and incident on the fluid F. Let

A fifth embodiment of the present invention will be described with reference to FIG. The members corresponding to the members described in the first embodiment are designated by the same reference numerals.

The density sensor 100 of the fifth embodiment is different from that of the first embodiment in that only the second concave lens 6 is provided between the pipe P and the condenser lens 8 as the concave lens. Further, the surface of the second concave lens 6 on the side where the measurement light enters and the surface on the side where the measurement light exits are formed as concave surfaces.

With the concentration sensor 100 of the fifth embodiment, the same effect as the concentration sensor 100 of the fourth embodiment can be obtained. More specifically, the light condensed and emitted from the fluid F can be made parallel by the second concave lens 6 by the condensing action on the incident surface and the emission surface of the fluid F.

Describe other embodiments.

The arrangement of each optical element is not limited to the one in which the optical path has a substantially U-shape as shown in FIG. 1, and each optical element may be arranged in a straight line, for example. However, as described in each embodiment, the case itself can be made compact and the concentration sensor itself can be made smaller by arranging it in a U-shape.

The surfaces of the first concave lens and the second concave lens on which the concave surface and the convex surface are formed are not limited to those shown in each embodiment. The first concave lens and the second concave lens may be formed as biconcave lenses, or the convex surfaces may be arranged so as to face the pipe.

-The photodetection mechanism is not limited to one equipped with a spectroscope and a photodetector. For example, the photodetection mechanism may include only the photodetector. In this case, it is preferable that the wavelength of the light emitted from the light source substantially includes only the absorption wavelength band of the fluid to be measured.

The pipe to which the concentration sensor is attached is not limited to a straight pipe, but may be a curved pipe.

Other than that, a part of the embodiments may be modified or a part of the embodiments may be combined without departing from the spirit of the present invention.

According to the present invention, the concentration of the fluid can be measured based on the measurement light that passes through the fluid, the concentration sensor itself can be easily installed on the pipe, and the concentration that can eliminate the possibility of contamination of the fluid. A sensor can be provided.

Claims

A concentration sensor for measuring the concentration of a fluid flowing in a pipe formed of a translucent material,
A light source that emits measurement light,
A collimating lens for collimating the measurement light emitted from the light source,
A condenser lens for condensing the measurement light passing through the pipe,
A light detection mechanism for detecting the measurement light condensed by the condenser lens,
One or a plurality of concave lenses provided between the collimating lens and the pipe, or between the pipe and the condenser lens;
A concentration calculation unit that calculates the concentration of the fluid flowing in the pipe based on the intensity of the measurement light detected by the light detection mechanism,
A concentration sensor, wherein one or a plurality of the concave lenses are arranged so as to form a gap with respect to an outer surface of the pipe.
The density sensor according to claim 1, wherein a radius of curvature of the concave surface of the concave lens is larger than a radius of curvature of the pipe.
The collimating lens and the condenser lens are spherical lenses,
The density sensor according to claim 1, wherein the concave lens is a cylindrical lens.
A plurality of the concave lenses,
A first concave lens provided between the collimating lens and the pipe;
A second concave lens provided between the pipe and the condenser lens,
The concave surface of the first concave lens is formed on the measurement light incident side,
The concentration sensor according to claim 1, wherein a concave surface of the second concave lens is formed on an incident side of the measurement light which faces the outer surface of the pipe.
A plurality of the concave lenses,
A first concave lens provided between the collimating lens and the pipe;
A second concave lens provided between the pipe and the condenser lens,
The concave surface of the first concave lens is formed on the measurement light emission side facing the outer surface of the pipe,
The concentration sensor according to claim 1, wherein a concave surface of the second concave lens is formed on an incident side of the measurement light which faces the outer surface of the pipe.
The first concave lens, a convex surface is formed on the incident side of the measurement light,
The density sensor according to claim 5, wherein the second concave lens has a convex surface formed on the measurement light emission side.
The concave lens is provided only between the collimating lens and the pipe, or between the pipe and the condenser lens,
The density sensor according to claim 1, wherein concave surfaces are formed on both the incident side and the reflective side of the measuring light of the concave lens.
Further comprising a housing that holds the light source, the collimating lens, the one or more concave lenses, the condensing lens, and the light detection mechanism at a predetermined position,
The housing is detachable from the pipe, and a gap is formed between the concave lens and the outer surface of the pipe when attached to the pipe. Item 2. The concentration sensor according to item 1.