Measuring equipment

Abstract

To provide a measuring device which is suitable for increasing or decreasing the temperature in an optical resonator to a desired temperature and conducting measurement.SOLUTION: A gas measuring device 100 comprises: an optical resonator 3 for resonating light; a light generator 1 for generating light with which the optical resonator 3 is irradiated; and an optical detector 6 for detecting light taken out of the optical resonator 3. The optical resonator 3 includes a plurality of mirrors 31, 32, holding members 33, 34, a cylindrical member 36, a cylindrical member 37, and a temperature adjuster 38. The coefficient of thermal expansion of the holding members 33, 34 is lower than the cylindrical member 36. The cylindrical member 36 includes a portion whose thermal conductivity is higher than the holding members 33, 34 and bellows 36a, 36b whose flexibility is higher than a first portion. The cylindrical member 37 has equivalent or higher thermal conductivity than the cylindrical member 36, and is disposed through to the positions of the plurality of mirrors 31, 32 including the inside of the bellows 36a, 36b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device that includes an optical resonator. [Background technology]

[0002] Gas measurement devices that use measurement principles such as gas absorption spectroscopy are widely used to measure environmental pollutants in the air. These gas measurement devices irradiate the gas to be measured with light and quantify the substance contained in the gas based on the intensity of light absorbed at the same frequency as the resonant frequency of the substance.

[0003] For example, when measuring volatile organic compounds (VOCs) or trace amounts of gas (carbon monoxide, carbon dioxide isotopes, etc.) contained in a gas to be measured, the gas measurement device needs to measure the gas to be measured using an optical resonator to increase detection sensitivity. A gas measurement device using an optical resonator is disclosed in, for example, Non-Patent Document 1. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] "Development of a low-temperature cavity Ring-Down Spectrometer for the detection of CarBon-14", McCartt, Stanford University, July 2014 Summary of the Invention [Problem to be solved by the invention]

[0005] By reflecting light between two or more highly reflective mirrors, an optical resonator can extend the effective optical path length available for gas measurement to the order of kilometers. Therefore, if the optical resonator is significantly deformed by heat, it will have a significant impact on the detection sensitivity of the gas measurement device. Therefore, it is considered to construct the optical resonator from a material with a low thermal expansion coefficient (e.g., Invar alloy or ultra-low expansion glass).

[0006] However, if an optical resonator is made of a material with a low thermal expansion coefficient, the thermal conductivity of the material is low, so it takes a long time to heat or cool the temperature inside the optical resonator to the target temperature. Furthermore, if an optical resonator is made of a material with a low thermal conductivity, the temperature distribution inside the optical resonator is likely to be uneven, and this uneven temperature distribution can cause detection errors when measuring gas in a gas measurement device. Furthermore, materials with a low thermal expansion coefficient are difficult to process and are expensive.

[0007] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a measurement device that is suitable for performing measurements by heating or cooling the temperature inside an optical resonator to a target temperature. [Means for solving the problem]

[0008] A measurement device according to an embodiment of the present disclosure includes an optical resonator that resonates light, a light generator that generates light to irradiate the optical resonator, and a photodetector that detects the light extracted from the optical resonator. The optical resonator includes multiple mirrors, a holder that holds the multiple mirrors, a first cylindrical portion having both ends that contact the holder and form a space containing the multiple mirrors, a second cylindrical portion that is provided inside the first cylindrical portion along the first cylindrical portion, and a temperature adjustment portion that adjusts the temperature inside the first cylindrical portion. The holder is made of a material with a lower thermal expansion coefficient than the first cylindrical portion, and the first cylindrical portion has a first portion made of a material with a higher thermal conductivity than the holder, and a second portion that is more elastic than the first portion. The second cylindrical portion is made of a material with a thermal conductivity equal to or higher than that of the first portion and is provided up to the position of the multiple mirrors, including the inside of the second portion. [Effects of the Invention]

[0009] According to the present disclosure, the optical resonator holds multiple mirrors with a holding section made of a material with a lower thermal expansion coefficient than the first cylindrical section, and a second cylindrical section with a thermal conductivity equal to or greater than that of the first section is provided up to the position of the multiple mirrors, including the inside of the second section.This allows for heating or cooling to a target temperature while ensuring optical stability and suppressing any imbalance in temperature distribution that occurs inside. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the overall configuration of a gas measurement device according to an embodiment. [Figure 2] 1 is a schematic diagram illustrating a configuration of an optical resonator according to an embodiment. [Figure 3] FIG. 10 is a schematic diagram showing the configuration of a comparative optical resonator. [Figure 4] FIG. 10 is a block diagram showing the overall configuration of a gas measurement device according to a modified example. [Figure 5] FIG. 10 is a block diagram showing the overall configuration of a gas measurement device according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0012] [Embodiment Mode] <Configuration of measurement device> Fig. 1 is a block diagram showing the overall configuration of gas measurement apparatus 100 according to an embodiment. Gas measurement apparatus 100 shown in Fig. 1 measures the optical absorption of a target component contained in a gas to be measured (sample gas) using an optical resonator 3. Gas measurement apparatus 100 includes a light generator 1 which is a laser light source, the optical resonator 3, a photodetector 6, and a controller 10.

[0013] The light generator 1 emits laser light to be irradiated onto the optical resonator 3. The light generator 1 can vary the oscillation frequency of the laser light in accordance with commands from the controller 10. For example, the light generator 1 is a quantum cascade laser (QCL) laser light source, and emits mid-infrared laser light (wavelength of about 5 μm). The controller 10 can change the oscillation frequency of the laser light by changing the drive current of the light generator 1.

[0014] Optical resonator 3 is a container capable of enclosing a sample gas to be measured, and has, for example, a cylindrical shape. Optical resonator 3 is provided with an inlet pipe 41 for introducing the sample gas before the start of measurement, a solenoid valve 42 provided on inlet pipe 41, an outlet pipe 43 for discharging the sample gas after the measurement is completed, and a solenoid valve 44 provided on outlet pipe 43 (see FIG. 2). Gas measurement device 100 opens solenoid valves 42 and 44 every time a measurement is performed to introduce the sample gas to be measured from inlet pipe 41 into optical resonator 3, and after the measurement, opens solenoid valves 42 and 44 to discharge the sample gas for which measurement has been completed from optical resonator 3 through outlet pipe 43.

[0015] The optical resonator 3 is provided between the light generator 1 and the photodetector 6. The optical resonator 3 includes a pair of mirrors 31 and 32. The mirrors 31 and 32 are arranged facing each other so that light is reflected between them inside the optical resonator 3. It is preferable to use mirrors 31 and 32 with high reflectivity (for example, about 99.98%) so that the light leaking out of the optical resonator 3 is extremely weak.

[0016] In this embodiment, the resonator length L1 of the optical resonator 3 is the distance between the mirrors 31 and 32 in the direction (optical axis direction) connecting the mirrors 31 and 32. The resonator length L1 is, for example, several tens of centimeters (approximately 30 cm in this example).

[0017] In the example shown in Fig. 1, both mirrors 31 and 32 are concave mirrors. However, it is not essential that both mirrors 31 and 32 are concave mirrors. It is sufficient that at least one of mirrors 31 and 32 is a concave mirror. For example, one of mirrors 31 and 32 may be a concave mirror and the other a plane mirror.

[0018] The photodetector 6 is a detector such as a photodiode or an image sensor. The photodetector 6 detects the weak transmitted light extracted from the mirror 32, and outputs a signal (detection signal) indicating the detection result to the controller 10.

[0019] Controller 10 includes processor 101 such as a CPU (Central Processing Unit) or FPGA (Field-Programmable Gate Array), memory 102 such as ROM (Read Only Memory) and RAM (Random Access Memory), and an input / output port (not shown). Controller 10 controls the various devices that make up gas measurement device 100. More specifically, controller 10 outputs commands to light generator 1 for scanning the oscillation frequency of laser light and receives detection signals from photodetector 6. Controller 10 also A / D converts the detection signals from photodetector 6, and then performs various data processing operations to analyze information such as the concentration (absolute concentration) of a target component contained in the sample gas based on the A / D converted data.

[0020] The controller 10 may be configured by dividing it into two or more units for each function. For example, the controller 10 may be divided into a unit that controls each device and a unit that executes various data processing.

[0021] <Measurement principle> The measurement principle of absorption spectroscopy using an optical resonator 3 will be briefly explained. Generally, an optical resonator 3 has a resonance condition where resonance occurs when the frequency of light irradiated onto the optical resonator 3 is a specific frequency. Hereinafter, the frequency of the laser light irradiated onto the optical resonator 3 will be referred to as the "laser frequency." The frequency of light that can cause resonance by the optical resonator 3 will be referred to as the "mode frequency."

[0022] When the laser frequency matches one of the mode frequencies, the power of the laser light is stored in the optical resonator 3. After the power of the laser light has sufficiently accumulated in the optical resonator 3, the laser light irradiated to the optical resonator 3 is blocked. The light stored in the optical resonator 3 before blocking travels back and forth between the mirrors 31 and 32 many times (usually thousands to tens of thousands of times). As this light travels back and forth between the mirrors 31 and 32, it gradually attenuates due to absorption by the target component in the sample gas. During this process, the attenuation of the transmitted light leaking from the mirror 32 is detected by the photodetector 6. In absorption spectroscopy using the optical resonator 3, by using the optical resonator 3 to lengthen the distance the light travels through the sample gas (effective optical path length), it is possible to detect even very slight light absorption by the target component.

[0023] The controller 10 determines the time constant of the optical attenuation based on the detection signal from the photodetector 6. From this time constant, the absorption coefficient of the target component at the laser frequency at that time can be calculated. By scanning the laser frequency and repeating similar measurements, it is also possible to create an absorption spectrum of the target component. Furthermore, the concentration of the target component can be calculated from the absorption coefficient.

[0024] <Optical resonator> In gas measurement device 100, in order to measure volatile organic compounds or trace amounts of gas contained in the gas to be measured, it is necessary to keep the temperature inside optical resonator 3 low. For this reason, optical resonator 3 is provided with a temperature regulator that adjusts the internal temperature. Fig. 2 is a schematic diagram showing the configuration of optical resonator 3 according to the embodiment. Meanwhile, Fig. 3 is a schematic diagram showing the configuration of optical resonator 3a for comparison.

[0025] 3, the optical resonator 3a for comparison has a structure in which a holding member 33 that holds a mirror 31 and a holding member 34 that holds a mirror 32 are connected to both ends of a cylindrical member 39. In the optical resonator 3a, the holding members 33 and 34 and the cylindrical member 39 are made of a material with a low thermal expansion coefficient so that the distance between the mirrors 31 and 32 (resonator length L1) does not change.

[0026] Furthermore, in order to keep the internal temperature of the optical resonator 3a low, a temperature regulator 38 is provided on the side surface of the cylindrical member 39 to regulate the temperature inside the optical resonator 3a. However, the cylindrical member 39 on which the temperature regulator 38 is provided is made of a material with a low thermal expansion coefficient, which results in low thermal conductivity, and it takes a long time to cool the temperature inside the optical resonator 3a to the target temperature. Furthermore, if the optical resonator 3a is made of a material with low thermal conductivity, the temperature distribution inside the optical resonator 3a is likely to become uneven, and this uneven temperature distribution becomes a cause of detection errors when measuring gas in a gas measurement device.

[0027] 2, the optical resonator 3 according to this embodiment employs a structure in which a holding member 33 (first holding part) that holds the mirror 31 (first mirror) and a holding member 34 (second holding part) that holds the mirror 32 (second mirror) are fixed by a plurality of rods 35 so that the distance (resonator length L1) between them is constant. Furthermore, the optical resonator 3 is provided with a cylindrical member 36 (first cylindrical part) that forms a space that includes the mirrors 31 and 32, and each end of the cylindrical member 36 is in contact with the holding members 33 and 34. A temperature regulator 38 that adjusts the temperature inside the optical resonator 3 is provided on the side surface of the cylindrical member 36.

[0028] The optical resonator 3 has a structure in which flange-shaped holding members 33 and 34 provided on both ends of a cylindrical member 36 are fixed by three or more rods 35. The holding members 33 and 34 and the rods 35 are made of a material (e.g., Invar alloy or ultra-low expansion glass) with a lower thermal expansion coefficient than the cylindrical member 36, making it difficult for the distance between the mirrors 31 and 32 (resonator length L1) to change even when temperature changes occur. On the other hand, the cylindrical member 36 is made of a material (e.g., aluminum, copper, etc.) with a higher thermal conductivity than the holding members 33 and 34 and the rods 35 so that the inside of the optical resonator 3 can be easily heated or cooled.

[0029] However, if the cylindrical member 36 were composed only of a portion (first portion) with higher thermal conductivity than the holding members 33 and 34 and the rod 35, deformation of the cylindrical member 36 caused by temperature changes in the temperature regulator 38 would apply force to the holding members 33 and 34 and the rod 35, potentially affecting the distance (resonator length L1) between the mirror 31 and the mirror 32. Therefore, as shown in FIG. 2 , the cylindrical member 36 is provided with bellows 36a and 36b at both ends. The bellows 36a and 36b are portions (second portions) that are more elastic than the other portions (first portion) of the cylindrical member 36. Here, elasticity refers to the amount of deformation that occurs in the extension direction of the cylindrical member 36 when a tensile stress or a compressive stress is applied in the extension direction, and can be defined by an elastic compliance constant. Therefore, deformation of the portion (first portion) with higher thermal conductivity caused by temperature changes in the temperature regulator 38 is offset or reduced by the expansion and contraction of the bellows 36a and 36b (second portion). This allows the optical resonator 3 to easily adjust the temperature by the temperature regulator 38, while reducing the effect on the distance between the mirrors 31 and 32 held by the holding members 33 and 34 and the rod 35. Note that deformation of the cylindrical member 36 may also be caused by thermal fluctuations in the portion that contains the gas, in addition to temperature changes in the temperature regulator 38.

[0030] Although bellows 36a, 36b are provided at both ends of cylindrical member 36, only one of bellows 36a, 36b may be provided on cylindrical member 36 as long as deformation occurring in the portion with high thermal conductivity can be offset or reduced. Furthermore, the location of the bellows is not limited to the end of cylindrical member 36, and they may be provided at other locations, such as the center. Furthermore, cylindrical member 36 may be configured by combining the portion with high thermal conductivity (first portion) and the portion of bellows 36a, 36b (second portion) made from separate members, or by processing a portion of a single member into the shape of a bellows to form the first portion and the second portion into an integrated structure.

[0031] Here, the temperature regulator 38 is a temperature adjusting unit that adjusts the temperature inside the cylindrical members 36, 39, and includes, for example, a heater, a Peltier element, etc. The controller 10 controls the temperature regulator 38 so that the temperature inside the cylindrical members 36, 39 becomes a target temperature.

[0032] As described above, the cylindrical member 36 is not composed only of a portion (first portion) with high thermal conductivity, but also has bellows 36a and 36b (second portion). Therefore, the bellows 36a and 36b may function as thermal resistance and may hinder the transfer of heat from the temperature regulator 38 into the cylindrical member 36. In other words, providing the bellows 36a and 36b in the cylindrical member 36 makes it easier for the temperature distribution inside the cylindrical member 36 to become uneven.

[0033] 2, the optical resonator 3 according to this embodiment further includes a cylindrical member 37 (second cylindrical portion) provided inside the cylindrical member 36. The cylindrical member 37 is made of a material (e.g., aluminum, copper, etc.) with thermal conductivity equal to or higher than that of the cylindrical member 36, and is provided up to the positions of the mirrors 31 and 32, including the insides of the bellows 36a and 36b. Therefore, the cylindrical member 37, which has no thermal resistance, can propagate heat from the temperature regulator 38 throughout the entire interior of the cylindrical member 36, including the insides of the bellows 36a and 36b. In other words, providing the cylindrical member 37 can prevent uneven temperature distribution within the cylindrical member 36.

[0034] Since the sample gas needs to be sealed inside the cylindrical member 36, it is necessary to connect it to the holding members 33, 34 while ensuring airtightness. On the other hand, since the sample gas does not need to be sealed inside the cylindrical member 37, it is sufficient that it is provided up to the vicinity of the holding members 33, 34 that hold the mirrors 31, 32, and it is not necessary to connect it to the holding members 33, 34. Therefore, unlike the cylindrical member 36, the cylindrical member 37 does not need to be provided with a bellows that would create thermal resistance.

[0035] As described above, gas measurement apparatus 100 according to the present embodiment includes optical resonator 3 for resonating light, light generator 1 for generating light to irradiate optical resonator 3, and photodetector 6 for detecting light extracted from optical resonator 3. Optical resonator 3 includes multiple mirrors 31 and 32, holding members 33 and 34 for holding the multiple mirrors 31 and 32, a cylindrical member 36 having opposite ends that contact holding members 33 and 34, respectively, and forming a space containing the multiple mirrors 31 and 32, a cylindrical member 37 provided inside cylindrical member 36 along the cylindrical member 36, and a temperature regulator 38 for adjusting the temperature inside cylindrical member 36. Holding members 33 and 34 are made of a material with a lower thermal expansion coefficient than cylindrical member 36. Cylindrical member 36 includes a first portion made of a material with a higher thermal conductivity than holding members 33 and 34, and bellows 36a and 36b (second portion) that are more elastic than the first portion. The cylindrical member 37 is made of a material having thermal conductivity equal to or greater than that of the cylindrical member 36, and is provided up to the position of the multiple mirrors 31, 32, including the inside of the bellows 36a, 36b. As a result, the optical resonator 3 according to this embodiment can fix the positions of the mirrors 31, 32 with the holding members 33, 34 to ensure optical stability, while the cylindrical member 37 can suppress uneven temperature distribution inside the optical resonator 3, thereby heating or cooling to a target temperature.

[0036] The bellows 36a, 36b are provided at at least one end of the cylindrical member 36, and the relative positions of the flange-shaped holding members 33, 34 that hold the mirrors 31, 32, respectively, are fixed by three or more rods 35 (fixing parts), so that the distance between the mirrors 31 and 32 (resonator length L1) can be kept constant.

[0037] [Variations] (1) Fig. 4 is a block diagram showing the overall configuration of gas measurement apparatus 200 according to a modified example. Gas measurement apparatus 200 shown in Fig. 4 differs from gas measurement apparatus 100 according to the embodiment (see Fig. 1) in that an optical switch 2 is provided between light generator 1 and optical resonator 3, and that a piezoelectric element 4 for displacing mirror 32 is provided on holding member 34. In other words, gas measurement apparatus 200 can change resonator length L1 by displacing mirror 32.

[0038] The optical switch 2 switches between irradiating and blocking the laser light from the light generator 1 to the optical resonator 3 in accordance with commands from the controller 10. An acousto-optic modulator (AOM), for example, can be used as the optical switch 2. The optical switch 2 blocks the laser light irradiated to the optical resonator 3 after the power of the laser light from the light generator 1 has been sufficiently accumulated in the optical resonator 3.

[0039] The piezoelectric element 4 has a doughnut-shaped hole for passing light, and displaces the mirror 32 in the optical axis direction. The controller 10 controls the piezoelectric element 4 to displace the mirror 32, thereby changing the resonator length L1. The controller 10 scans the mirror 32 so that the resonator length L1 changes by a predetermined amount. The piezoelectric element may be provided on a holding member 33 on the mirror 31 side, and the mirror 31 may be displaced in the optical axis direction. The configuration for displacing the mirror 32 is not limited to the piezoelectric element 4, and any actuator that can displace the mirror 32 in the optical axis direction may be used.

[0040] As described above, in gas measurement apparatus 200 according to the modified example, holding member 34 has piezoelectric element 4 that displaces mirror 32 that it holds. This enables gas measurement apparatus 200 to perform measurements by changing resonator length L1 by a predetermined amount.

[0041] (2) Fig. 5 is a block diagram showing the overall configuration of gas measurement apparatus 300 according to another modification. Gas measurement apparatus 300 shown in Fig. 5 differs from gas measurement apparatus 100 according to the embodiment (see Fig. 1) in that it employs a ring-type optical resonator including three mirrors instead of a Fabry-Perot-type optical resonator including two mirrors.

[0042] Optical resonator 8 includes three mirrors 81 to 83 arranged inside. Laser light irradiated onto optical resonator 8 is repeatedly reflected in the order mirror 81-mirror 82-mirror 83-mirror 81-mirror 82-mirror 83, and so on. Mirrors 81 and 82 are plane mirrors. Mirror 83 is a concave mirror. The distance between mirror 81 and mirror 82 is equal to the distance between mirror 83 and mirror 82. This distance is referred to as the "resonator length L2."

[0043] The mirror 83 is provided with a piezoelectric element 9. The piezoelectric element 9 displaces the mirror 83 in accordance with a command from the controller 10. This makes it possible to change the resonator length L2. If there is no need to displace the mirror 83, the mirror 83 does not need to be provided with the piezoelectric element 9.

[0044] Although not shown, the holding members that hold the mirrors 81-83 and the rods that fix the positions of the holding members are made of a material with a low thermal expansion coefficient (for example, an Invar alloy or ultra-low expansion glass). Also, the cylindrical member (first cylindrical portion) that forms the space that contains the mirrors 81-83 is made of a material with high thermal conductivity (for example, aluminum, copper, etc.). The cylindrical member (first cylindrical portion) has a bellows, and is further provided with a cylindrical member (second cylindrical portion) inside that has the same or higher thermal conductivity.

[0045] (3) In the above embodiment, a Fabry-Perot type optical resonator has been described. However, the optical resonator may be a Herriott cell (multi-reflection cell) made up of two or more mirrors.

[0046] (4) In the above-described embodiment, the cylindrical members 36 and 37 are used in the optical resonator 3. However, the optical resonator is not limited to the cylindrical members 36 and 37, which are cylindrical, and a cylindrical member having a prismatic shape such as a triangular prism or a square prism may be used as long as it is cylindrical.

[0047] (5) In the above-described embodiment, it has been described that bellows 36a and 36b are provided to offset or reduce deformation of cylindrical member 36. However, optical resonator 3 is not limited to a configuration in which bellows are provided on cylindrical member 36, and a highly elastic material (for example, resin, rubber, etc.) may be used instead of the bellows. Furthermore, in the above-described embodiment, it has been described that rod 35 is used as a fixing portion that fixes the positions of holding members 33 and 34. However, the fixing portion is not limited to rod 35, and may be a plate member, a part of another device, or the like, as long as it can fix the positions of holding members 33 and 34. In addition, if holding members 33 and 34 are fixed to the gas measurement device itself, a fixing portion itself need not be provided. [Aspect] It will be understood by those skilled in the art that the above-described embodiments are examples of the following aspects.

[0048] (Section 1) A measuring device according to one embodiment comprises an optical resonator that resonates light, a light generator that generates light to be irradiated onto the optical resonator, and a photodetector that detects light extracted from the optical resonator. The optical resonator comprises a plurality of mirrors, a holding portion that holds the plurality of mirrors, a first cylindrical portion having both ends that contact the holding portion and that forms a space containing the plurality of mirrors, a second cylindrical portion that is provided inside the first cylindrical portion along the first cylindrical portion, and a temperature adjustment portion that adjusts the temperature inside the first cylindrical portion. The holding portion is made of a material that has a lower thermal expansion coefficient than the first cylindrical portion. The first cylindrical portion has a first portion made of a material that has a higher thermal conductivity than the holding portion and a second portion that is more elastic than the first portion. The second cylindrical portion is made of a material that has a thermal conductivity equal to or higher than that of the first portion and is provided up to the position of the plurality of mirrors, including the inside of the second portion.

[0049] According to the measurement device described in paragraph 1, the multiple mirrors are held by a holder having a thermal expansion coefficient lower than that of the first cylindrical portion, and the second cylindrical portion having a thermal conductivity equal to or higher than that of the first portion is provided up to the position of the multiple mirrors, including the inside of the second portion, so that it is possible to heat or cool to a target temperature while ensuring optical stability and suppressing bias in temperature distribution that occurs inside. Furthermore, according to the measurement device described in paragraph 1, it is possible to control the temperature inside the optical resonator and obtain high detection sensitivity.

[0050] (Section 2) In the measuring device described in paragraph 2, the second portion is provided at at least one end of the first cylindrical portion. According to the measuring device described in paragraph 2, deformation occurring in the first portion having high thermal conductivity can be offset or reduced.

[0051] (Section 3) In the measuring device according to claim 3, the second part is a bellows. According to the measuring device according to claim 3, it is possible to cancel or reduce deformation occurring in the first part having high thermal conductivity.

[0052] (Section 4) In the measurement device described in paragraph 4, the holder has a plurality of holding members that respectively hold a plurality of mirrors, and further includes a fixing unit that fixes the relative positions of each holding unit. According to the measurement device described in paragraph 4, by fixing the relative positions of the holding units with the fixing unit, the distance between the mirrors can be kept constant.

[0053] (Section 5) A measuring device as described in paragraph 5, wherein the plurality of mirrors include a first mirror and a second mirror, the holding portion includes at least a first holding portion that holds the first mirror and a second holding portion that holds the second mirror, and the fixing portion maintains a constant distance between the first holding portion and the second holding portion.

[0054] According to the measuring device described in paragraph 5, even when the temperature is adjusted by the temperature adjustment unit, the distance between the first mirror and the second mirror can be kept constant.

[0055] (Section 6) In the measuring device described in paragraph 6, the fixing portion is three or more rods that fix the flange-shaped first holding portion and second holding portion, and the rods are made of a material with a lower thermal expansion coefficient than the first cylindrical portion.

[0056] According to the measuring device described in item 6, it is possible to reduce manufacturing costs and keep the distance between the first mirror and the second mirror constant.

[0057] (Section 7) In the measurement device described in paragraph 7, the holder has a piezoelectric element that displaces the mirror that it holds. According to the measurement device described in paragraph 7, the resonator length can be changed by displacing the mirror.

[0058] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0059] 1 light generator, 2 optical switch, 3, 3a, 8 optical resonator, 4, 9 piezoelectric element, 6 light detector, 10 controller, 31, 32, 81, 82, 83 mirror, 33, 34 holding member, 35 rod, 36, 37, 39 cylindrical member, 36a, 36b bellows, 38 temperature regulator, 100, 200, 300 gas measurement device, 101 processor, 102 memory.

Claims

1. A measurement device comprising: an optical resonator that resonates light; a light generator that generates light to be irradiated onto the optical resonator; and a photodetector that detects the light extracted from the optical resonator, The optical resonator comprises: A plurality of mirrors; a holder for holding the plurality of mirrors; a first cylindrical portion having two ends respectively contacting the holding portion and forming a space containing the plurality of mirrors; a second cylindrical portion provided along the first cylindrical portion and inside the first cylindrical portion; a temperature adjusting unit that adjusts the temperature inside the first cylindrical portion, the holding portion is made of a material having a lower thermal expansion coefficient than the first cylindrical portion, The first cylindrical portion is a first portion made of a material having a higher thermal conductivity than the holding portion; a second portion having a higher elasticity than the first portion, The second cylindrical portion is A measurement device made of a material having a thermal conductivity equal to or greater than that of the first portion, and provided up to the position of the plurality of mirrors including the inside of the second portion.

2. The measuring device according to claim 1 , wherein the second portion is provided at least at one end of the first cylindrical portion.

3. 3. The measuring device of claim 1, wherein the second part is a bellows.

4. the holding unit has a plurality of holding members that respectively hold the plurality of mirrors, 4. The measuring device according to claim 1, further comprising a fixing part that fixes the relative positions of the holding parts.

5. the plurality of mirrors includes a first mirror and a second mirror; the holding unit has at least a first holding unit that holds the first mirror and a second holding unit that holds the second mirror, The measuring device according to claim 4 , wherein the fixing portion maintains a constant distance between the first holding portion and the second holding portion.

6. 6. The measuring device according to claim 5, wherein the fixing portion is three or more rods that fix the flange-shaped first holding portion and the second holding portion, and the rods are made of a material having a lower thermal expansion coefficient than the first cylindrical portion.

7. 7. The measuring device according to claim 1, wherein the holding unit has a piezoelectric element that displaces the mirror that it holds.

Images