Gas analyzer and multiple reflection cell

Abstract

The present invention provides a gas analyzer for measuring the concentration of a target component contained in a sample gas, comprising: an incident window for light to be incident; a central mirror; two or more reflecting mirrors disposed opposite to the central mirror; a reflecting mirror disposed on the side opposite to the incident window relative to the central mirror; and an exit window disposed on the same side as the incident window relative to the central mirror, wherein the reflecting mirror refracts light incident on the incident window back to the exit window.

Description

Technical Field

[0001] This invention relates to gas analyzers and multiple reflection units. Background Technology

[0002] Previously, gas analyzers having multiple reflection units as sample units were known (for example, see Patent Document 1). In addition, gas analyzers using light in the ultraviolet (wavelength range: 200 nm to 400 nm) region were known (for example, see Patent Document 2).

[0003] Patent Document 1: Japanese Patent Application Publication No. 9-49793

[0004] Patent Document 2: Japanese Patent Application Publication No. 11-374106 Summary of the Invention

[0005] The technical problem to be solved by the present invention

[0006] In gas analyzers, miniaturization of the multiple reflection unit is preferred. Summary of the Invention

[0008] To address the aforementioned problems, in a first aspect of the present invention, a gas analyzer is provided for measuring the concentration of a target component contained in a sample gas. The gas analyzer may include an entrance window. The entrance window allows light to enter. The gas analyzer may include a central mirror. The gas analyzer may include two or more reflecting mirrors. The reflecting mirrors may be arranged opposite to the central mirror. The gas analyzer may include a reflecting mirror. The reflecting mirror may be arranged on the side opposite to the entrance window relative to the central mirror. The gas analyzer may include an exit window. The exit window may be arranged on the same side as the entrance window relative to the central mirror. The reflecting mirror can refract light incident on the entrance window back to the exit window.

[0009] The entrance window and the exit window can be shared components.

[0010] The reflecting mirror can be positioned within a range of 85% to 115% of the radius of curvature of the reflecting mirror.

[0011] A reflecting mirror can be configured to be further away from the central mirror than the central mirror.

[0012] Using the center line of the central mirror as a reference and a point symmetrically arranged with the center point of the exit surface of the entrance window as a reference point, and using a line parallel to the center line and passing through the reference point as a reference line, the length of the mirror of the reflecting mirror that is closer to the side opposite to the entrance window than the reference line can be greater than the length of the mirror of the reflecting mirror that is closer to the entrance window than the reference line.

[0013] A reflecting mirror can be a concave mirror.

[0014] The radius of curvature of a catadioptric mirror can be the same as that of a reflecting mirror or a central mirror. Alternatively, the radius of curvature of a catadioptric mirror can be different from that of a reflecting mirror or a central mirror.

[0015] The reflection characteristics of a reflecting mirror can differ from those of a reflecting mirror or a central mirror.

[0016] Gas analyzers may include filters. These filters can be positioned between a reflecting mirror and a folding mirror to alter the reflection characteristics of the folding mirror.

[0017] The reflective properties of a mirror can differ from those of the central mirror.

[0018] A gas analyzer may include optical fibers. The optical fibers can direct light through an entrance window. The entrance window can be configured to have an angle relative to the light emitted from the optical fiber. The entrance window can be configured to have an angle greater than 70° and less than 75° relative to the light emitted from the optical fiber.

[0019] Optical fibers can have an emitting surface for emitting light and a receiving surface for receiving light.

[0020] Optical fibers can have multiple paths for light to pass through. The number of paths that light exiting the fiber and the number of paths that light incident on the fiber can pass through can be controlled according to the concentration of the component being measured.

[0021] The distance between the exit surface of the optical fiber and the reflector can be configured to deviate from a predetermined defocusing distance relative to the radius of curvature of the reflector. The defocusing distance can be less than the width of the light-receiving surface of the optical fiber.

[0022] In a second aspect of the invention, a multiple reflection unit is provided that reflects incident light multiple times and then emits it. The multiple reflection unit may have an entrance window. Light can enter through the entrance window. The multiple reflection unit may have a central mirror. The multiple reflection unit may have two or more mirrors. The mirrors may be arranged opposite to the central mirror. The multiple reflection unit may have a reflecting mirror. The reflecting mirror may be arranged on the side opposite to the entrance window relative to the central mirror. The multiple reflection unit may have an exit window. The exit window may be arranged on the same side as the entrance window relative to the central mirror. The reflecting mirror can reflect light incident on the entrance window back to the exit window.

[0023] Furthermore, the above summary of the invention does not enumerate all the essential features of the invention. In addition, sub-combinations of these feature groups can also constitute an invention. Attached Figure Description

[0024] Figure 1 This is a diagram illustrating an example of a comparative gas analyzer 100.

[0025] Figure 2 This is a diagram showing an example of the multi-reflection unit 13 in the comparative example.

[0026] Figure 3 This is a diagram illustrating the optical relationship that holds true in the multiple reflection unit 13 of the comparative example.

[0027] Figure 4 This is a diagram illustrating an example of a comparative gas analyzer 200.

[0028] Figure 5 This is a diagram illustrating an example of the multiple reflection unit 113 in an embodiment.

[0029] Figure 6 This is a diagram showing the positional relationship between optical fiber 52 and reflector 47.

[0030] Figure 7 This is a diagram showing an example of the configuration of the light-receiving surface 85 and the light-emitting surface 86 in Part 1, 54.

[0031] Figure 8 This is a diagram that details fiber optic cable 52.

[0032] Figure 9 This is a diagram showing an example of the configuration of the light-receiving surface 87 in Part 2, 56.

[0033] Figure 10 This is a diagram showing an example of the configuration of the exit surface 88 in section 3, 58.

[0034] Figure 11 This is a diagram showing the positional relationship between fiber optic cable 52 and window 49.

[0035] Figure 12 This is a diagram showing the positional relationship between the reflecting mirror 42 and the mirror 48.

[0036] Figure 13 This is a diagram illustrating another example of the multiple reflection unit 113 in the embodiment.

[0037] Figure 14 This is a diagram illustrating an example of the reflection characteristics of the reflecting mirror 42.

[0038] Figure 15 This is a diagram illustrating another example of the multiple reflection unit 113 in the embodiment.

[0039] Figure 16 This is another example of the reflection characteristics of the reflecting mirror 42.

[0040] Figure 17 This is a diagram illustrating an example of a gas analyzer 300 according to an embodiment. Detailed Implementation

[0041] The present invention will be described below through embodiments, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, the combinations of features described in the embodiments are not necessarily all necessary for the solutions provided by the invention.

[0042] In this specification, orthogonal coordinate axes of X, Y, and Z are sometimes used to illustrate technical matters. Orthogonal coordinate axes only determine the relative positions of constituent elements, not specific directions. For example, the Z-axis is not necessarily represented as height relative to the ground. Furthermore, the +Z-axis and -Z-axis directions are opposite directions. When the Z-axis direction is not explicitly stated as positive or negative, it indicates a direction parallel to the +Z-axis and -Z-axis.

[0043] Figure 1 This diagram illustrates an example of a comparative gas analyzer 100. The gas analyzer 100 includes a flue 10, a gas intake pipe 11, a gas exhaust pipe 12, a multiple reflection unit 13, a gas filter 14, a preheater 15, a preheating temperature regulator 16, a pump 17, a heater 18, a unit temperature regulator 19, a light source 20, a spectrometer 22, a detection element 26, a processing unit 27, and a communication line 51. The gas analyzer 100 measures the concentration of the target component contained in the sample gas 30. In this example, the gas analyzer 100 measures the concentration of the target component using differential absorbance spectrophotometry (DOAS), which can eliminate variations in the light source 20. By using differential absorbance spectrophotometry, the concentration of the target component can be measured using only minor variations in the absorption spectrum, enabling stable measurements.

[0044] Sample gas 30 is a gaseous sample containing the component to be measured. In this example, sample gas 30 is exhaust gas flowing in flue 10. The component to be measured is the target substance for the gas analyzer 100, such as NO or NO2. The target component can also be SO2, SO3, or SO42-. X NO3, NH3 or NO X .

[0045] The flue 10 is connected to the gas intake pipe 11 and the gas exhaust pipe 12. The multiple reflection unit 13 is also connected to the gas intake pipe 11 and the gas exhaust pipe 12. The gas intake pipe 11 introduces sample gas 30 from the flue 10 into the multiple reflection unit 13. After the concentration of sample gas 30 is measured in the multiple reflection unit 13, the gas exhaust pipe 12 discharges sample gas 30 from the multiple reflection unit 13 back into the flue 10.

[0046] The gas intake pipe 11 can be connected to a gas filter 14, which is used to remove dust from the sample gas 30. The gas intake pipe 11 can also be connected to a preheater 15, which is used to preheat the sample gas 30. The temperature of the preheater 15 can be adjusted by a preheating temperature regulator 16. The gas exhaust pipe 12 can be connected to a pump 17. By connecting the gas exhaust pipe 12 to the pump 17, the sample gas 30 can be introduced into the multi-reflection unit 13 via the gas intake pipe 11, and the sample gas 30 can also be exhausted from the multi-reflection unit 13 to the flue 10.

[0047] The light source 20 emits light 43. In this example, the light source 20 emits light 43 including the absorption wavelength of the component being measured. As an example, the light source 20 is a flash lamp capable of controlling the emission time to an extremely short duration. The light source 20 can be an Xe flash lamp. By using an Xe flash lamp as the light source 20, light 43 can be emitted stably. In this example, the light source 20 preferably emits light with a constant emission period. In this example, the light 43 is light in the ultraviolet (wavelength range: 200 nm to 400 nm) region.

[0048] The multiple reflection unit 13 seals the sample gas 30. When analyzing the concentration of the target component included in the sample gas 30, the sample gas 30 can be introduced into the multiple reflection unit 13 via the gas intake tube 11. After analysis, the sample gas 30 can be discharged from the multiple reflection unit 13 via the gas exhaust tube 12. Light 43 incident on the multiple reflection unit 13 is repeatedly reflected inside the multiple reflection unit 13 and emitted outside the multiple reflection unit 13. The multiple reflection unit 13 performs multiple reflections on the incident light 43 before emitting it. Details of the multiple reflection unit 13 are described later.

[0049] A heater 18 may be provided in the multi-reflection unit 13 to maintain the temperature of the sample gas 30 at a specified temperature. The multi-reflection unit 13 may be in contact with the heater 18. The heater 18 may be controlled by the unit temperature regulator 19.

[0050] Spectrometer 22 disperses ultraviolet light 43 within a specified wavelength range. This specified range is, for example, a wavelength range of 200 nm to 500 nm. However, the wavelength range is not limited to this. The spectrometer 22 directs the dispersed light 43 onto the detection element 26. The spectrometer 22 can divide the light 43 into multiple wavelength bands. In this case, the detection element 26 can acquire the intensity of the light 43 in each wavelength band.

[0051] Detection element 26 acquires the radiation spectrum of light 43 passing through multiple reflection unit 13. Detection element 26 acquires the intensity of the radiation spectrum of light 43 at each wavelength. As an example, detection element 26 is a CMOS (Complementary Metal-Oxide Semiconductor) line sensor. The radiation spectrum of light 43 acquired by detection element 26 is sent as a light receiving signal to computing device 27.

[0052] The processing unit 27 processes the light received signal from the detection element 26. Based on the light received signal from the detection element 26, the processing unit 27 measures the concentration of the target component in the sample gas 30. The processing unit 27 can measure the concentration of the target component by acquiring the change in the intensity of the light 43 at the absorption wavelength of the target component (i.e., the change in the intensity of the light 43 through the multiple reflection unit 13 relative to the intensity of the light 43 emitted from the light source unit 20). In this example, the processing unit 27 is wired to the detection element 26 via the communication line 51, but a wireless connection is also possible.

[0053] Figure 2 This is a diagram illustrating an example of a comparative multiple reflection unit 13. The multiple reflection unit 13 has an entrance window 44, an exit window 45, a central mirror 46, a reflector 47, and a reflector 48. For illustration purposes, in... Figure 2 In this process, the long side direction of the multiple reflection unit 13 is set as the X-axis direction, and the short side direction of the multiple reflection unit 13 is set as the Y-axis direction.

[0054] The entrance window 44 is a window used to guide light 43 into the multiple reflection unit 13. The entrance window 44 can be formed of glass or the like. The entrance window 44 has an entrance surface 71 and an exit surface 72. The light source unit 20 emits light 43 onto the entrance surface 71 of the entrance window 44. The entrance window 44 emits light 43 from the exit surface 72 of the entrance window 44 onto the reflector 47.

[0055] The exit window 45 is used to direct light 43 from the multiple reflection unit 13. The exit window 45 can be made of glass or the like. The exit window 45 has an incident surface 73 and an exit surface 74. The reflector 48 directs light 43 onto the incident surface 73 of the exit window 45. In the exit window 45, light 43 is directed from the exit surface 74 of the exit window 45 to the beam splitter 22.

[0056] The multiple reflection unit 13 includes mirrors for multiple reflections of light 43. Multiple mirrors can be provided in the multiple reflection unit 13. In this example, the multiple reflection unit 13 has a central mirror 46 and multiple reflecting mirrors (reflecting mirror 47, reflecting mirror 48).

[0057] The central mirror 46 is arranged opposite to the reflecting mirrors 47 and 48. "Against arrangement" means that the mirror surface 75 of the central mirror 46 is arranged opposite to the mirror surface of the reflecting mirror. The mirror surface is the surface that reflects light 43. "Against arrangement" also means that at least a portion of the mirror surface 75 of the central mirror 46 is opposite to at least a portion of the mirror surface of the reflecting mirror. Furthermore, the central mirror 46 may have only a portion of its surface as a mirror, or all of its surfaces may be mirrored. The central mirror 46 may not be arranged opposite to the entrance window 44 and the exit window 45. The mirror surface 75 of the central mirror 46 may be configured not to be opposite to the exit surface of the entrance window 44 or the entrance surface of the exit window 45. The central mirror 46 may be arranged between the entrance window 44 and the exit window 45 in the Y-axis direction. The central mirror 46, the entrance window 44, and the exit window 45 may be arranged in a configuration along the Y-axis direction.

[0058] The reflector 47 can be configured opposite to the central mirror 46. The mirror surface 76 of the reflector 47 can be configured to face the mirror surface 75 of the central mirror 46. The reflector 47 can be configured opposite to the entrance window 44. The mirror surface 76 of the reflector 47 can be configured to face the exit surface 72 of the entrance window 44. Furthermore, the reflector 47 may have only a portion of its surface as a mirror, or all of its surface may be mirrored. The reflector 47 can be positioned on the positive side of the central mirror 46 in the X-axis direction.

[0059] The reflector 48 can be configured to face the central mirror 46. The mirror surface 77 of the reflector 48 can be configured to face the mirror surface 75 of the central mirror 46. The reflector 48 can be configured to face the exit window 45. The mirror surface 77 of the reflector 48 can be configured to face the incident surface 73 of the exit window 45. Furthermore, the reflector 48 may have only a portion of its surface as a mirror, or all of its surface may be mirrored. The reflector 48 can be positioned on the positive side of the central mirror 46 in the X-axis direction.

[0060] Central mirror 46, reflecting mirror 47, and reflecting mirror 48 can all be concave mirrors. That is, central mirror 46, reflecting mirror 47, and reflecting mirror 48 each have a radius of curvature. Central mirror 46, reflecting mirror 47, and reflecting mirror 48 can also have the same radius of curvature. The radius of curvature of a mirror can be the radius of curvature of its surface. By having central mirror 46, reflecting mirror 47, and reflecting mirror 48 have the same radius of curvature, multiple reflections of light 43 are possible. That is, the multiple reflection unit 13 can be a white cell. By using a white cell, the optical path length can be increased, enabling highly accurate concentration measurement even of minute amounts of the component being measured.

[0061] The imaging process of light 43 is described in sequence. Reflector 47 directly images the image of the incident window 44 onto the central mirror 46. Next, the central mirror 46 images the image of the incident window 44 formed on reflector 47 onto reflector 48. Then, reflector 48 images the image of the incident window 44 formed on the central mirror 46 back onto the central mirror 46. Next, the central mirror 46 images the image of the incident window 44 formed on reflector 48 onto reflector 47. Next, reflector 47 images the image of the incident window 44 formed on the central mirror 46 back onto the central mirror 46. Repeating the same steps, reflector 48 finally images the image of the incident window 44 formed on the central mirror 46 onto the exit window 45. Figure 2 In the example, the central mirror 46 is configured such that light 43 is reflected 7 times. Additionally, in... Figure 2 In the example, each of mirrors 47 and 48 is configured such that light 43 is reflected 4 times. Examples of the number of reflections are not limited to this.

[0062] Figure 3 This is a diagram illustrating the optical relationships that hold true in the multiple reflection unit 13 of the comparative example. Figure 3 The size is not necessarily the same as Figure 2 The dimensions are consistent. For illustration purposes, in Figure 3 In this design, the long side of the multiple reflection unit 13 is set as the X-axis direction, and the short side of the multiple reflection unit 13 is set as the Y-axis direction. Figure 3 In this context, the radii of curvature of the central mirror 46, the reflecting mirror 47, and the reflecting mirror 48 are set to R.

[0063] Generally, for an object placed near the optical axis of a concave mirror with a radius of curvature R where aberrations are negligible, and its image, the imaging formula of the following mathematical equation (Equation 1) holds true based on the principles of geometric optics. Here, a is the distance from the center of the concave mirror to the object point, b is the distance from the center of the concave mirror to the image point, R is the radius of curvature of the concave mirror, and f is the focal length of the concave mirror. If the distance a from the center of the concave mirror to the object point is equal to the radius of curvature R of the concave mirror, then according to mathematical equation 1, the distance b from the center of the concave mirror to the image point is also R, and the image of the object point is formed at a position symmetrical to the object point relative to the optical axis of the concave mirror.

[0064] (Mathematical Formula 1)

[0065] 1 / a + 1 / b = 2 / R = 1 / f

[0066] In the multiple reflection unit 13, the incident window 44 is positioned at a distance from the mirror surface 76 of the oppositely positioned reflector 47 equal to the radius of curvature R of the reflector 47. Therefore, the image of the incident window 44 is imaged on the mirror surface 75 of the central mirror 46 at a distance equal to the radius of curvature R of the reflector 47. The distance between the mirrors can be, for example, the distance between the centers of the mirror surfaces. Furthermore, the image formed on the mirror surface 75 of the central mirror 46 is re-imaged onto the mirror surface 75 of the central mirror 46 by the reflector 48 at a position determined by the arrangement of the reflector 48. Repeating the same steps, multiple images of the incident window 44 are formed on the mirror surface 75 of the central mirror 46. The multiple images of the incident window 44 formed on the mirror surface 75 of the central mirror 46 are arranged according to the arrangement interval d between the curvature centers C31 and C32 of the reflector 47 and the reflector 48. The curvature center of the central mirror 46 is set to C23. The center of curvature of the reflector is the center of the reflector's circle of curvature. After multiple images of the entrance window 44 are formed on the mirror surface 75 of the central mirror 46, the images of the entrance window 44 exit through the exit window 45 to the outside of the multiple reflection unit 13. At this time, the number of times light 43 passes through is set to n, and the number of reflections by the reflector is set to n-1, and the following mathematical formulas 2 and 3 hold. The number of times light 43 passes through can be, for example, the number of times it crosses the center line O along the X-axis direction of the multiple reflection unit 13. In addition, the required optical path length is set to L, and the distance between the center of the central mirror 46 and the center of the entrance window 44 is set to h.

[0067] (Mathematical Formula 2)

[0068] R≒L / n

[0069] (Mathematical Formula 3)

[0070] h = nd / 4

[0071] Furthermore, on the central mirror 46, the images of the entrance windows 44 are arranged at intervals d, with n / 2-1 points of spacing. The arrangement interval w between the entrance windows 44 and the exit windows 45 is determined by the following mathematical formula 4.

[0072] (Mathematical Expression 4)

[0073] w = nd / 2

[0074] Since the above relationship holds, the number of passes n is set to a multiple of 4, and the exit window 45 can be positioned symmetrically with the central mirror 46 sandwiched in the middle, opposite to the entrance window 44. Figure 2 , Figure 3 In this process, since the number of passes n is set to 16, the light 43 emitted from the entrance window 44 is reflected 15 times, forming 7 images on the central mirror 46. Afterward, the light 43 is emitted through the exit window 45 to the outside of the multiple reflection unit 13.

[0075] As mentioned above, the small volume structure with a small size and minimal dead angle can still ensure the required optical path length, which is an advantage of white units. Therefore, by including a multi-reflection unit 13 in the form of a white unit, the concentration can be measured with high precision even if the component being measured is in trace amounts.

[0076] However, in this example, the components to be measured are NO and NO2, which absorb less light in the ultraviolet region than in the infrared region (wavelength range: 5μm~8μm). Furthermore, low-concentration measurements are required, thus the required optical path length tends to increase. When using infrared light, the typical optical path length is about 1 meter, while using ultraviolet light requires a length of 2 to 5 meters. In the case of designing the multiple reflection unit 13 housed in a casing (19-inch bracket size, internal depth approximately 400mm) identical to that of conventional gas analyzers using infrared light, with an optical path length of 5m, according to mathematical formula 2, n = 5000 / 400, the number of passes is 12 or 16. Since the configuration interval d needs to be at least the width of the entrance window 44, for example, if the diameter of the optical element used in the light source unit 20 is 10mm, then according to mathematical formula 4, the configuration interval w between the entrance window 44 and the exit window 45 is 16 × 10 / 2 = 80mm (as in conventional configuration intervals). Therefore, the size of the multiple reflection unit 13 is approximately 100mm × 400mm. Here, with a height equivalent to conventional gas analyzers using infrared light, the volume is 100mm × 400mm × 25mm = 1000ml (conventional volume), approximately 1L. The gas analyzer's sampling flow rate is 1-2L per minute, and gas sample replacement takes 30 seconds to 1 minute. Considering the effects of signal processing time and internal gas adsorption, the response time for gas analysis in the comparative example may be over 60 seconds. Therefore, to shorten the response time, miniaturization of the multiple reflection unit 13 is preferable.

[0077] Figure 4 This is a diagram illustrating an example of a gas analyzer 200 according to an embodiment. The gas analyzer 200 includes a gas intake pipe 11, a gas exhaust pipe 12, a light source unit 20, a spectrometer 22, a detection element 26, a processing unit 27, a communication line 51, an optical fiber 52, and a multiple reflection unit 113. Figure 4 In Chinese, omission and Figure 1 Explanation of the same symbols. In Figure 4 In this version, a portion of the connection between the gas intake pipe 11 and the gas exhaust pipe 12 is omitted. The gas intake pipe 11 and the gas exhaust pipe 12 can be connected to a flue. The gas analyzer 200 may include a heater and a unit temperature regulator.

[0078] The multiple reflection unit 113 seals the sample gas 30. When analyzing the concentration of the target component included in the sample gas 30, the sample gas 30 can be introduced into the multiple reflection unit 113 via the gas intake tube 11. After analysis, the sample gas 30 can be discharged from the multiple reflection unit 113 via the gas exhaust tube 12. Light 43 incident on the multiple reflection unit 113 is repeatedly reflected and emitted outside the multiple reflection unit 113. In this example, the light 43 incident on the multiple reflection unit 113 is emitted outside the multiple reflection unit 113 via the same exit window as the entrance window.

[0079] Optical fiber 52 is a unit for splitting light. Optical fiber 52 has a receiving surface and an exiting surface. Optical fiber 52 allows light 43-1 to enter through an entrance window. Light 43-1 exiting from the exiting surface of optical fiber 52 enters through the entrance window of the multiple reflection unit 113. Light 43-2 exiting from the exiting window of the multiple reflection unit 113 is received by the receiving surface of optical fiber 52. The received light 43 is split in beam splitter 22. Instead of optical fiber 52, a beam splitter or similar device can be configured.

[0080] Figure 5 This is a diagram illustrating an example of a multi-reflection unit 113 according to an embodiment. The multi-reflection unit 113 includes a reflecting mirror 42, a central mirror 46, a reflecting mirror 47, a reflecting mirror 48, and a window 49. For illustrative purposes, in... Figure 5 In this design, the long side of the multiple reflection unit 113 is set as the X-axis direction, and the short side of the multiple reflection unit 113 is set as the Y-axis direction. Figure 5 In Chinese, omission and Figure 2 , Figure 3 Explanation of the same symbols. In Figure 2 In the diagram, light 43 before reaching the reflecting mirror 42 is designated as light 43-1 and represented by a thick dashed line. Light 43 after reaching the reflecting mirror 42 is designated as light 43-2 and represented by a thick line. In this example, the number of passes for both light 43-1 and light 43-2 is set to 4.

[0081] Window 49 is used to guide light 43 into the multiple reflection unit 113. Window 49 can be formed of glass or the like. Window 49 has a surface 81 and a surface 82. The light source unit 20 (optical fiber 52) emits light 43-1 onto surface 81 of window 49. That is, light is incident on window 49. In window 49, light 43-1 is emitted from surface 82 of window 49 to reflector 47. Window 49 is used to emit light 43 from the multiple reflection unit 113. Reflector 47 emits light 43-2 onto surface 82 of window 49. In window 49, light 43-2 is emitted from surface 81 of window 49 to beam splitter 22 (optical fiber 52). In other words, window 49 serves as both an entrance window and an exit window. In this example, the entrance window and the exit window are shared components. In this example, the exit window is positioned on the same side as the entrance window relative to the central mirror 46.

[0082] The reflecting mirror 42 is configured to face the reflecting mirror 48. The mirror surface 83 of the reflecting mirror 42 can be configured to face the mirror surface 77 of the reflecting mirror 48. Furthermore, the reflecting mirror 42 may have only a portion of its surfaces as mirrors, or all of its surfaces may be mirrors. The reflecting mirror 42 is positioned on the side opposite to the window 49 relative to the central mirror 46. In this example, the reflecting mirror 42 is positioned on the negative Y-axis side relative to the central mirror 46.

[0083] The reflecting mirror 42 reflects light 43-1 incident on the entrance window back to the exit window. In this example, the reflecting mirror 42 reflects light 43-1 incident on window 49 back as light 43-2. ​​In this example, the reflecting mirror 42 reflects light 43-1 incident on mirror 48 back to mirror 48 as light 43-2. ​​The path of light 43-1 incident on the reflecting mirror 42 and the path of light 43-2 exiting the reflecting mirror 42 can be the same. In this example, the reflecting mirror 42 exits light 43-2 such that light 43-2 travels in the opposite direction to the path of light 43-1. Light 43-2 is reflected by mirror 48, central mirror 46, and mirror 47 and reaches window 49. In this example, light 43-1 passes through 4 times, therefore light 43-2 also passes through 4 times. Therefore, light 43-2 exits from window 49 with 8 passes. By setting the reflector 42, the number of times light 43 passes through can be doubled. Therefore, the number of passes in Formula 4 can be halved. If the diameter of the optical element is 10 mm, then by calculating in the same way as Formula 4, the arrangement interval between the reflector 42 and the window 49 is 8 × 10 / 2 = 40 mm, which is a reduction compared to the conventional arrangement interval. At this point, the volume is 60 mm × 400 mm × 25 mm = 600 ml, a reduction compared to existing examples. Therefore, the multiple reflection unit 113 can be miniaturized, further shortening the response time.

[0084] The reflecting mirror 42 is positioned at a distance from at least one reflecting mirror that is more than 85% and less than 115% of the radius of curvature of that reflecting mirror. In this example, the reflecting mirror 42 is positioned at a distance from the reflecting surface of the reflecting mirror 48 that is more than 85% and less than 115% of the radius of curvature of the reflecting mirror 48. Alternatively, the distance between the centers of the mirror surfaces can be used as the distance between the mirrors. By positioning the reflecting mirror 42 at a distance from the reflecting mirror 48 that is more than 85% and less than 115% of the radius of curvature of the reflecting mirror 48, light 43-2 can be effectively returned to the reflecting mirror 48. Regarding the configuration of the reflecting mirror 42 and the reflecting mirror 48, [further details are needed]. Figure 12 Please provide an explanation.

[0085] In this example, the reflecting mirror 42 is configured to be further away from the reflecting mirror 48 than the central mirror 46. That is, the distance between the reflecting mirror 42 and the reflecting mirror 48 is greater than the distance between the central mirror 46 and the reflecting mirror 48. In this example, the reflecting mirror 42 is positioned at a distance from the reflecting mirror 48 that is greater than 100% of the radius of curvature of the reflecting mirror 48 but less than 115% of the radius of curvature of the reflecting mirror 48. Because the reflecting mirror 42 is configured to be further away from the reflecting mirror 48 than the central mirror 46, the optical path length of the light 43 can be extended, and the extended length is twice the difference between the distance between the reflecting mirror 42 and the reflecting mirror 48 and the distance between the central mirror 46 and the reflecting mirror 48.

[0086] The reflecting mirror 42 can be a concave mirror. That is, the reflecting mirror 42 has a radius of curvature. The radius of curvature of the reflecting mirror 42 can be the same as that of the central mirror 46, the reflecting mirror 47, or the reflecting mirror 48. By making the radii of curvature the same, it is easy to manufacture the multiple reflection unit 113. The case referred to as "the same" in this specification can include an error of less than ±10%. The radius of curvature of the reflecting mirror 42 can be different from that of the central mirror 46, the reflecting mirror 47, or the reflecting mirror 48. By making the radii of curvature different, it is possible to adjust so that the light 43-2 is effectively returned to the reflecting mirror 48.

[0087] Figure 6 This diagram shows the positional relationship between the optical fiber 52 and the reflector 47. The portion of the optical fiber 52 with the light-receiving surface 85 and the light-emitting surface 86 is designated as part 1, 54. Figure 6 In this context, the surface of optical fiber 52 with the light-receiving surface 85 and the light-emitting surface 86 is designated as the YZ surface.

[0088] Figure 7 This is a diagram showing an example of the configuration of the light-receiving surface 85 and the light-emitting surface 86 in Part 1, 54. Figure 7 The image shows a view from the positive X-axis side. Figure 6The configuration of the light-receiving surface 85 and the emission surface 86 in Part 1, 54. The light-receiving surface 85 of the optical fiber 52 is located outside the emission surface 86. Furthermore, multiple light-receiving surfaces 85 of the optical fiber 52 are provided. The emission surface 86 of the optical fiber 52 can be located outside the light-receiving surface 85. Multiple emission surfaces 86 of the optical fiber 52 can be provided. The light-receiving range φ can be the range within which the light-receiving surface 85 of the optical fiber 52 is located. Figure 7 As shown, the light-receiving range φ can be the diameter of a circle externally tangent to multiple light-receiving surfaces 85.

[0089] In this example, the distance between the exit surface 86 of the optical fiber 52 and the reflector 47 is configured to deviate from a predetermined defocus distance Df relative to the radius of curvature R of the reflector 47. Figure 6 In this configuration, the distance between the exit surface 86 of the optical fiber 52 and the reflector 47 is configured to differ from the radius of curvature R of the reflector 47 by a predetermined defocusing distance Df. Because the distance is configured to deviate from the predetermined defocusing distance Df relative to the radius of curvature R of the reflector 47, the deviation in light-receiving efficiency can be reduced.

[0090] The defocus distance Df can be below the light-receiving range φ of the optical fiber 52. By setting the defocus distance Df to below the light-receiving range φ of the optical fiber 52, the light-receiving efficiency can be improved while reducing the deviation in light-receiving efficiency. The defocus distance Df can be more than half of the light-receiving range φ of the optical fiber 52. Alternatively, the defocus distance Df can also be less than twice the light-receiving range φ of the optical fiber 52.

[0091] The illumination range of the returned light (light 43-2) on the light-receiving surface 85 is set as 'a'. If the defocus distance is Df, the radius of curvature of the reflector 47 is R, and the effective diameter of the reflector 47 is α, then the diameter of the illumination range 'a' can be expressed by the following mathematical formula 5. The illumination range 'a' is preferably set to the range obtained by adding the deviation amount considered according to manufacturing tolerances and the deviation amount of the illumination range due to temperature to the light-receiving range φ of the optical fiber 52. By setting the illumination range 'a' within such a range, stable measurement can be performed without being affected by temperature. In summary, by setting the defocus distance, the allowable manufacturing tolerance is increased, thus making manufacturing easier. In addition, since the deviations in temperature characteristics and light-receiving efficiency are also improved, it is expected that the temperature characteristics and time-varying changes caused by vibration, etc., of the gas analyzer 200 will also be mitigated, and stable measurement performance over a long period of time can be achieved.

[0092] [Mathematical Expression 5]

[0093]

[0094] Figure 8 This is a diagram detailing optical fiber 52. Optical fiber 52 has section 1 54, section 2 56, and section 3 58. In this example, optical fiber 52 has multiple paths through which light 43 can pass. Figure 8 In this context, the surface of optical fiber 52 with the light-receiving surface 85 and the light-emitting surface 86 is designated as the YZ surface.

[0095] Figure 9 This is a diagram showing an example of the configuration of the light-receiving surface 87 in Part 2, 56. Figure 9 The image shows an observation from the negative X-axis side. Figure 8 The second part 56 has a light-receiving surface 87. The light-receiving surface 87 is provided in the second part 56. The emission surface 86 of the first part 54 and the light-receiving surface 87 of the second part 56 are connected respectively. Therefore, the light 43 emitted from the light source 20 is received by the light-receiving surface 87 of the second part 56 and emitted by the emission surface 86 to the multiple reflection unit 113 (window 49). Figure 9 In this case, the light 43 emitted from optical fiber 52 travels through one path.

[0096] Figure 10 This is a diagram showing an example of the configuration of the exit surface 88 in section 3, 58. Figure 10 The image shows an observation from the negative X-axis side. Figure 8 The configuration of the exit surface 88 in section 3 58. The exit surface 88 is provided in section 3 58. The light-receiving surface 85 of section 1 54 and the exit surface 88 of section 3 58 are connected. Therefore, the light 43 emitted from the multiple reflection unit 113 (window 49) is received by the light-receiving surface 85 of section 1 54 and emitted by the exit surface 88 to the beam splitter 22. Figure 10 In this case, the light 43 incident on the optical fiber 52 travels through 6 paths.

[0097] In this example, the light 43 emitted from fiber 52 travels through one path, while the light 43 incident on fiber 52 travels through six paths. However, both the number of paths for light 43 emitted from and incident on fiber 52 can be controlled. For example, the number of paths for light 43 emitted from and incident on fiber 52 can be controlled based on the concentration of the component being measured. As an example, when the concentration of the component being measured is low, the light 43 emitted from fiber 52 travels through one path, while the light 43 incident on fiber 52 travels through six paths. To increase the light received by fiber 52 when the concentration of the component is low, the number of paths for light 43 incident on fiber 52 can be increased. Conversely, when the concentration of the component being measured is high, the number of paths for light 43 emitted from fiber 52 can be six, while the light 43 incident on fiber 52 can be only one path.

[0098] Figure 11This is a diagram showing the positional relationship between fiber optic cable 52 and window 49. Figure 11 Only part 54 of fiber optic 52 is shown.

[0099] In this example, window 49 is configured to have an angle relative to the light 43-1 emitted from fiber optic cable 52. The term "window 49 configured to have an angle relative to the light 43-1 emitted from fiber optic cable 52" means that the angle θ (or less than 90°) formed between the light 43-1 emitted from fiber optic cable 52 and the surface 81 of window 49 is greater than 0° and less than 90°. In other words, "window 49 configured to have an angle relative to the light 43-1 emitted from fiber optic cable 52" means that the surface 81 of window 49 is neither parallel nor perpendicular to the light 43-1 emitted from fiber optic cable 52. Similarly, "window 49 configured to have an angle relative to the light 43-1 emitted from fiber optic cable 52" means that the angle θ (or less than 90°) formed between the light 43-1 emitted from fiber optic cable 52 and the surface 82 of window 49 is greater than 0° and less than 90°. Because window 49 is configured at an angle relative to the light 43-1 emitted from optical fiber 52, the optical axis of the reflected light obtained after the emitted light 43-1 is reflected by surfaces 81 and 82 is offset from the optical axis of the returning light (light 43-2). Therefore, it is possible to prevent the reflected light obtained after the emitted light 43-1 is reflected by surfaces 81 and 82 from mixing with the returning light.

[0100] In this example, window 49 is configured to have an angle θ of 70° or more and 75° or less relative to the light 43 emitted from fiber 52. If the angle θ is too small, the distance through window 49 will increase, so the angle θ is preferably not too small.

[0101] Figure 12 This diagram illustrates the positional relationship between the reflecting mirror 42 and the reflecting mirror 48. The center of the mirror surface 83 of the reflecting mirror 42 is designated as C41, and the center of the mirror surface 77 of the reflecting mirror 48 is designated as C42. The distance L1 between the reflecting mirror 42 and the reflecting mirror 48 can be the distance between the center C41 of the mirror surface 83 of the reflecting mirror 42 and the center C42 of the mirror surface 77 of the reflecting mirror 48. Therefore, the distance L1 between the reflecting mirror 42 and the reflecting mirror 48 can be greater than 85% and less than 115% of the radius of curvature of the reflecting mirror 48.

[0102] Figure 13 This is a diagram illustrating another example of the multiple reflection unit 113 in the embodiment. Figure 13 In the multiple reflection unit 113, the structure of the folding mirror 42 is similar to... Figure 5 The multiple reflection unit 113 is different. Figure 13 Other structures besides this can be combined with Figure 5 The multiple reflection unit 113 is the same. Figure 13 Light 43 is omitted from the text.

[0103] In this example, the centerline of the mirror surface 75 of the central mirror 46 is D1, and the center point of the surface 82 of the window 49 is C43. Using the centerline D1 as a reference, a point arranged symmetrically to the center point C is designated as reference point C44. A line passing through reference point C44 and parallel to the centerline D1 is designated as reference line D2. In this case, the length L2 of the mirror surface 83 of the reflecting mirror 42 on the opposite side of the window 49 relative to reference line D2 can be greater than the length L3 of the mirror surface 83 of the reflecting mirror 42 on the window 49 side relative to reference line D2. The length of the mirror surface 83 of the reflecting mirror 42 can be the length of the mirror surface 83 in the Y-axis direction. The length of the mirror surface 83 of the reflecting mirror 42 can also be the length along the mirror surface 83. The length L2 of the mirror surface 83 of the reflecting mirror 42 can be more than twice the length L3 of the mirror surface 83 of the reflecting mirror 42. By making the length L2 of the mirror 83 of the folding mirror 42 greater than the length L3 of the mirror 83 of the folding mirror 42, more light 43 from the reflecting mirror 48 can be reflected.

[0104] Figure 14 This is a diagram illustrating an example of the reflection characteristics of the catadioptric mirror 42. Figure 14 The reflectivity of the catenary 42 for each wavelength is shown in the diagram. In this example, the reflectivity of light in the ultraviolet (wavelength range: 200 nm to 400 nm) region is constant in the catenary 42 and does not depend on the wavelength. The mirrors of the central mirror 46, mirror 47, and mirror 48 can also have similar reflectivity. Figure 14 Its reflective properties.

[0105] Figure 15 This is a diagram illustrating another example of the multiple reflection unit 113 in the embodiment. Figure 15 The multiple reflection unit 113 and Figure 5 The difference of the multiple reflection unit 113 is that it includes a filter 60. Figure 15 Other structures besides this can be combined with Figure 5 The multiple reflection unit 113 is the same. Figure 15 Light 43 is omitted from the text.

[0106] Filter 60 is disposed between the retroreflector 42 and the mirror 48. Filter 60 can be positioned in the X-axis direction closer to the retroreflector 42 than the mirror 48. In this example, filter 60 is disposed on the mirror surface 83 of the retroreflector 42.

[0107] The filter 60 alters the reflection characteristics of the retroreflector 42. As an example, the filter 60 is a dielectric multilayer film. By forming a dielectric multilayer film in the retroreflector 42, the reflection characteristics of the retroreflector 42 can be adjusted. By adjusting the film thickness, material, and layer structure of the dielectric multilayer film, the reflectivity other than that at a specific wavelength can be increased, resulting in a relatively low reflectivity at that specific wavelength. The dielectric multilayer film can be locally disposed on the mirror surface 83 of the retroreflector 42.

[0108] Figure 16 This is another example diagram illustrating the reflection characteristics of the catadioptric mirror 42. Figure 16 The image shows the reflectivity of the folding mirror 42 for each wavelength. For example... Figure 16 As shown, in this example, in the reflective mirror 42, the reflectivity at a specific wavelength λ1 is lower than the average reflectivity within a specified wavelength range.

[0109] The reflection characteristics of the catenary 42 may differ from those of the central mirror 46, the reflecting mirror 47, or the reflecting mirror 48. For example, the catenary 42 has... Figure 16 The central mirror 46, mirror 47, and mirror 48 have reflective properties. Figure 14 The reflective properties of the reflective mirror 42 are superior to those of the central mirror 46, the reflecting mirror 47, and the reflecting mirror 48. The light 43 in the reflective mirror 42 is reflected fewer times. Therefore, the reflectivity for a specific wavelength can be easily adjusted.

[0110] The reflection characteristics of mirror 47 or mirror 48 may differ from those of the central mirror 46. For example, mirror 47 and mirror 48 have... Figure 16 The central mirror 46 has reflective properties. Figure 14 The reflectivity of light 43 is significantly improved compared to the central mirror 46. Therefore, the reflectivity of light 43 is reflected less frequently by mirrors 47 and 48. Consequently, the reflectivity for specific wavelengths can be easily adjusted.

[0111] Figure 17 This is a diagram illustrating an example of a gas analyzer 300 according to an embodiment. Figure 17 Gas Analyzer 300 and Figure 4 The gas analyzer 200 differs in that it has a collimation unit 70 instead of an optical fiber 52. Figure 17 Other structures besides this can be combined with Figure 4 The gas analyzer is the same as the 200.

[0112] The collimation unit 70 converts the light 43-1 from the light source 20 into parallel light. The parallel light obtained after conversion by the collimation unit 70 propagates within the multiple reflection unit 113 and is then focused back onto the collimation unit 70. The light 43-2, again focused onto the collimation unit 70, is emitted to the beam splitter 22. The light 43-1 emitted from the light source 20 is diffused light, and... Figure 4 Compared to the case where the gas analyzer 200 emits diffused light into the multiple reflection unit 113, the glare on the walls, mirrors, etc. of the multiple reflection unit 113 can be reduced.

[0113] The collimation unit 70 is preferably a parabolic mirror with minimal aberration. However, the collimation unit 70 is not limited to a parabolic mirror. It can be a lens or the like.

[0114] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Those skilled in the art will understand that various modifications or improvements can be made to the above embodiments. As can be seen from the claims, the various modifications or improvements described above are also included within the technical scope of the present invention.

[0115] Label Explanation

[0116] 10. Flue; 11. Gas intake pipe; 12. Gas exhaust pipe; 13. Multiple reflection unit; 14. Gas filter; 15. Preheater; 16. Preheating temperature regulator; 17. Pump; 18. Heater; 19. Unit temperature regulator; 20. Light source; 22. Spectrometer; 26. Detection element; 27. Calculation device; 30. Sample gas; 42. Reflecting mirror; 43. Light; 44. Entrance window; 45. Exit window; 46. Central mirror; 47. Reflecting mirror; 48. Reflecting mirror; 49. Window; 51. Communication. Line, 52 optical fiber, 54 Part 1, 56 Part 2, 58 Part 3, 60 filter, 70 collimating unit, 71 incident surface, 72 exit surface, 73 incident surface, 74 exit surface, 75 mirror, 76 mirror, 77 mirror, 81 surface, 82 surface, 83 mirror, 85 light-receiving surface, 86 exit surface, 87 light-receiving surface, 88 exit surface, 100 gas analyzer, 113 multiple reflection unit, 200 gas analyzer, 300 gas analyzer.

Claims

1. A gas analyzer for measuring the concentration of a target component contained in a sample gas, characterized in that, include: An entrance window for light to enter; Central mirror; Two or more reflecting mirrors are arranged opposite to the central mirror; A reflecting mirror, which is positioned on the side opposite to the entrance window relative to the central mirror; An exit window, which is positioned on the same side as the entrance window relative to the central mirror; as well as A detection element that detects the light emitted from the exit window. The folding mirror causes light incident on the entrance window to be reflected back to the exit window. Using the center line of the central mirror as a reference, a point symmetrically arranged with respect to the center point of the exit surface of the entrance window is used as a reference point. In the case of using a line parallel to the center line and passing through the reference point as a reference line, The mirror surface of the reflecting mirror located on the side opposite to the entrance window that is closer to the baseline is longer than the mirror surface of the reflecting mirror located on the side closer to the entrance window that is closer to the baseline.

2. The gas analyzer as described in claim 1, characterized in that, The entrance window and the exit window are shared components.

3. The gas analyzer as described in claim 1 or 2, characterized in that, The reflecting mirror is positioned at a distance from the reflecting mirror that is greater than 85% and less than 115% of the radius of curvature of the reflecting mirror.

4. The gas analyzer as described in claim 1 or 2, characterized in that, The reflecting mirror is configured to be further away from the central mirror than the reflecting mirror.

5. The gas analyzer as described in claim 1 or 2, characterized in that, The reflecting mirror is a concave mirror.

6. The gas analyzer as described in claim 5, characterized in that, The radius of curvature of the reflecting mirror is the same as that of the reflecting mirror or the central mirror.

7. The gas analyzer as described in claim 5, characterized in that, The radius of curvature of the reflecting mirror is different from that of the reflecting mirror or the central mirror.

8. The gas analyzer as described in claim 1 or 2, characterized in that, The reflection characteristics of the reflecting mirror are different from those of the reflecting mirror or the central mirror.

9. The gas analyzer as described in claim 8, characterized in that, It includes a filter disposed between the folding mirror and the reflecting mirror to change the reflection characteristics of the folding mirror.

10. The gas analyzer as described in claim 8, characterized in that, The reflection characteristics of the mirror are different from those of the central mirror.

11. The gas analyzer as described in claim 1 or 2, characterized in that, Includes an optical fiber that directs light into the incident window. The entrance window is configured to have an angle relative to the light emitted from the optical fiber.

12. The gas analyzer as described in claim 11, characterized in that, The entrance window is configured to have an angle of 70° or more and 75° or less relative to the light emitted from the optical fiber.

13. A gas analyzer for measuring the concentration of a target component contained in a sample gas, characterized in that, include: An entrance window for light to enter; Central mirror; Two or more reflecting mirrors are arranged opposite to the central mirror; A reflecting mirror, which is positioned on the side opposite to the entrance window relative to the central mirror; An exit window, which is positioned on the same side as the entrance window relative to the central mirror; as well as A detection element that detects the light emitted from the exit window. The folding mirror causes light incident on the entrance window to be reflected back to the exit window. The gas analyzer also includes an optical fiber, which has an exit surface for emitting light and a receiving surface for receiving light. The optical fiber has multiple paths for light to pass through. Based on the concentration of the component to be measured, the number of paths through which light emitted from the optical fiber and the number of paths through which light incident on the optical fiber pass are controlled among the multiple paths.

14. The gas analyzer as described in claim 13, characterized in that, The distance between the exit surface of the optical fiber and the reflector is configured to deviate from a predetermined defocusing distance relative to the radius of curvature of the reflector.

15. The gas analyzer as described in claim 14, characterized in that, The defocus distance is below the width of the light-receiving surface of the optical fiber.

16. A multiple reflection unit that performs multiple reflections on incident light and emits it, characterized in that, include: An entrance window for light to enter; Central mirror; Two or more reflecting mirrors are arranged opposite to the central mirror; A reflecting mirror, which is positioned on the side opposite to the entrance window relative to the central mirror; and An exit window, which is positioned on the same side as the entrance window relative to the central mirror. The folding mirror causes light incident on the entrance window to be reflected back to the exit window. Using the center line of the central mirror as a reference, a point symmetrically arranged with respect to the center point of the exit surface of the entrance window is used as a reference point. In the case of using a line parallel to the center line and passing through the reference point as a reference line, The mirror surface of the reflecting mirror located on the side opposite to the entrance window that is closer to the baseline is longer than the mirror surface of the reflecting mirror located on the side closer to the entrance window that is closer to the baseline.

Images