Temperature measurement method and temperature measurement device for gas

Abstract

In order to measure the temperature of a gas, a light source (11) capable of emitting light (A) having a wavelength [lambda] A absorbed by the gas so as to change the light intensity and a light sensor (16) capable of measuring the light reception intensity of the light (A) are provided, and the light source and the light sensor are arranged on an optical path between the light source and the light sensor so that the gas is interposed therebetween. The light intensity of the light sensor is measured by changing the light intensity of the light source, so that the light intensity Imin of the light source when the shake amplitude of the light intensity in space or / and time is minimum is obtained, and the equivalent temperature TS of the light source LA corresponding to the light intensity Imin when the light emission spectrum of the light source is approximately processed according to ideal blackbody radiation is calculated. And taking TS as the temperature of the gas.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a gas temperature measurement method and a gas temperature measurement device. BACKGROUND

[0002] With increasing environmental concerns, the demand for detection and measurement techniques for various gas leaks is increasing. Exhaust gas from exhaust pipes or chimneys that emit gas into the atmosphere is generally monitored by various sensors and the emission of harmful gas is suppressed. On the other hand, gas leaks from pipes in natural gas plants or petrochemical plants are detected by remote monitoring systems, inspections by monitoring personnel, and on-site measures. In particular, with regard to leaks of flammable hydrocarbon gases (VOCs) such as methane, which have the risk of explosion or poisoning, various techniques have been developed to date to detect and measure them.

[0003] Carbon dioxide (CO2) has been a concern for global warming, and thus the recovery and reuse of carbon dioxide is likely to become more prevalent. It is therefore expected that carbon dioxide leaked from pipes will also become an object of detection and measurement. In addition, ammonia (NH3), which is expected to be used for power generation, nitrogen oxides (NOx) from exhaust gas, and the like are also likely to become objects of monitoring in the future. Thus, the need to detect various gases is increasing. x

[0004] To detect gas leaks from pipes, a portable gas sensor is generally used to inspect the connection portions of the pipes and the like. However, with this method, it is difficult to comprehensively inspect the entire pipes over a long distance. In addition, inspection of high places or places that are difficult to access requires a large cost and is dangerous for the monitoring personnel. To solve such problems, the following practical method has been mainly adopted for VOCs: using the absorption phenomenon of infrared rays by gas to visualize the gas with an infrared camera, thereby monitoring from a distance.

[0005] For example, Patent Literature 1 discloses a method (gas visualization technology) of detecting leaked hydrocarbon gas with an infrared camera that can only observe the absorption wavelength of the gas, and further quantitatively evaluating the concentration and the amount of emission.

[0006] The gas visualization technology, although a convenient method that can detect gas leaks from a distance if the conditions are met, has a problem that quantitative measurement is difficult. This is because the visual effect of the gas is affected not only by the concentration but also by the temperature. Even if the detection intensity of the gas is simply measured, the concentration cannot be calculated if the gas temperature is not known.

[0007] ​Fortunately, in terms of VOCs that have been observed so far, the temperature of the leaked gas can generally be regarded as room temperature. In Patent Literature 1, the concentration is measured on the premise that the gas temperature can generally be regarded as the same as the ambient air temperature. Alternatively, in necessary cases, the gas temperature is obtained using a separate temperature sensor.

[0008] However, in terms of gas species that will become important in the future, particularly CO2, the gas temperature cannot generally be regarded as room temperature. CO2 is a gas discharged after combustion of a raw gas such as VOC. Therefore, the temperature of CO2 to be measured is often higher than room temperature. CO2 is also contained in human exhaled breath, in which case it is discharged at a temperature close to the body temperature of a human being. Furthermore, from the viewpoint of recovery and reuse of CO2 and underground disposal, quantitative measurement of leakage from a pipe through which high-concentration CO2 is sent in the future will also be required. In this case, since the leaked CO2 expands rapidly outside the pipe and causes a decrease in the temperature of CO2, measurement of CO2 at a temperature lower than room temperature is required.

[0009] As described above, the temperature of a gas to be measured differs depending on the gas species. Unlike VOC, which can be regarded as room temperature, quantitative measurement of gases at various temperatures will be required in the future. For this reason, a method of obtaining the gas temperature is important.

[0010] In the past, a temperature sensor such as a thermocouple has been inserted into a gas flow to measure the gas temperature. However, for a gas that leaks into a large space and diffuses with a gas flow, it is difficult to correctly align the temperature sensor to obtain reliable temperature information. In addition, it is also unrealistic to bring a temperature sensor with a limited heat capacity into thermal equilibrium with a small amount of leaked gas.

[0011] Here, if the feature that the infrared information of a gas is also affected by the temperature can be successfully utilized, the gas temperature can also be obtained using infrared light in a remote manner. For example, Patent Literature 2 focuses on a plurality of absorption wavelengths that differ in dependence on the gas temperature, and proposes a method of optically obtaining the gas temperature using a laser. However, such a method in which a large and expensive laser system is used only for measuring the temperature can hardly be said to be a practical method.

[0012] (Prior Art Documents) (Patent Literature) Patent Literature 1: U.S. Patent No. 9225915 Patent Literature 2: Japanese Patent Application Laid-Open No. 2017-515117 Patent Literature 3: Japanese Patent Application Laid-Open No. 2022-171533 (Non-Patent Literature) Non-patent literature 1: Kiyohiro Koda, Takayuki Takahashi, Spectrometric Measurement of Flame and Its Application, Flame Spectroscopy, Japan Spectroscopic Society Measurement Series 20, Society Publishing Center, pp. 30-32 (June 20, 1990) SUMMARY (PROBLEMS TO BE SOLVED BY THE INVENTION) An object of the present disclosure is to provide a temperature measuring device and a temperature measuring method capable of simply measuring the temperature of a gaseous substance present at a remote place with a portable, small, and simple device.

[0013] (Technical means for solving the problems) The temperature measuring method of the present disclosure is a method of measuring the temperature of a gaseous substance that absorbs light A of wavelength λ A , and includes: providing a light source L A capable of emitting light A in a manner to change the intensity of the light, and a light sensor S A capable of receiving the light A and measuring the intensity of the received light; arranging the light source L A and the light sensor S A in a manner that the gaseous substance is interposed therebetween, on the light path of the light A emitted from the light source L A and received by the light sensor S A ; measuring the light receiving intensity of the light sensor S A when the light source L A emits the light A in a manner to change the intensity of the light; obtaining the intensity I min of the light source L A at which the light receiving intensity is the smallest in terms of spatial or / and temporal fluctuation, from the measurement of the light receiving intensity; calculating the equivalent temperature T S of the light source L A corresponding to the intensity I min , in the case where the emission spectrum of the light source L A is approximated by ideal black body radiation; using the equivalent temperature T S as the temperature of the gaseous substance.

[0014] The temperature measuring device of the present disclosure is a device of measuring the temperature of a gaseous substance that absorbs light A of wavelength λ AAn apparatus for measuring the temperature of a gaseous substance absorbed by light A, comprising: a camera having an image sensor, an imaging optical system, and a bandpass filter, wherein the image sensor is equipped with multiple light sensors capable of receiving light A and measuring the intensity of the received light; a light source emitting light in a wavelength band including light A; a light intensity variable device capable of changing the light intensity of the light source; an image processing device; and an integrated control device that controls both the light intensity variable device and the image processing device together. The image processing device has the following function: based on the signal output from the camera, it calculates the light intensity I of the light source when the measured light intensity fluctuates extremely little in space and / or time. min The emission spectrum of the light source is approximated based on ideal blackbody radiation to calculate the light intensity I of the light source. min Correspondingly, the equivalent temperature T of the light source S .

[0015] The temperature measuring device for gaseous substances disclosed herein is used to measure the wavelength λ. A An apparatus for measuring the temperature of a gaseous substance by means of light absorption A, comprising: The light-receiving device includes a detection element, an imaging optical system, and a bandpass filter. The detection element includes a light sensor capable of receiving light A and measuring the intensity of the received light. A light source emits light in a wavelength band including light A. A light intensity variable device is capable of changing the light intensity of the light source. A signal processing device performs signal processing for the light-receiving device. Finally, a comprehensive control device controls both the light intensity variable device and the signal processing device. The signal processing device has the following function: to calculate the light intensity I of the light source when the measured light intensity fluctuates over time to an extremely small extent. min (t); The emission spectrum of the light source is approximated according to ideal blackbody radiation to calculate the light intensity I of the light source. min (t) Corresponding to the equivalent temperature T of the light source S .

[0016] (Invention effect) According to this disclosure, a temperature measuring device is provided that can easily measure the temperature of a gaseous substance existing in a remote location using a portable, small, and convenient device, as well as its usage method and temperature measuring method. Attached Figure Description

[0017] Figure 1 This is an explanatory diagram illustrating the structural outline of the apparatus (measuring apparatus system) disclosed herein.

[0018] Figure 2 This is a characteristic diagram of the optical density spectrum of a gas.

[0019] Figure 3 is a plot of the characteristic of an ideal blackbody radiation spectrum at a typical temperature.

[0020] Figure 4 is a plot of the relationship between optical density and detected light intensity for the case where the light source equivalent temperature is higher than the gas temperature.

[0021] Figure 5 is a plot of the detected light intensity spectrum for the case where the light source equivalent temperature is higher than the gas temperature.

[0022] Figure 6 is a plot of the relationship between optical density and detected light intensity for the case where the light source equivalent temperature is lower than the gas temperature.

[0023] Figure 7 is a plot of the detected light intensity spectrum for the case where the light source equivalent temperature is lower than the gas temperature.

[0024] Figure 8 is a plot of the relationship between optical density and detected light intensity for the case where the light source equivalent temperature is equal to the gas temperature.

[0025] Figure 9 is a plot of the detected light intensity spectrum for the case where the light source equivalent temperature is equal to the gas temperature.

[0026] Figure 10 is a plot of the relationship between the signal intensity difference of light that has passed through the gas-like substance compared to light that has not passed through the gas-like substance and the light source equivalent temperature.

[0027] Figure 11 is a flowchart of the temperature measurement method of the present disclosure.

[0028] Figure 12 is a typical gas visualization image during a rise in the light source equivalent temperature.

[0029] Figure 13 is a typical gas visualization image during a fall in the light source equivalent temperature.

[0030] Figure 14 is a plot of the relationship between the average luminance of the gas visualization images during a rise (a) and a fall (b) in the light source equivalent temperature and the light source equivalent temperature.

[0031] Figure 15 is a typical gas visualization center difference image during a rise in the light source equivalent temperature.

[0032] Figure 16 is a typical gas visualization center difference image during a fall in the light source equivalent temperature.

[0033] Figure 17 is a characteristic diagram of the relationship between the variance of the visualized image of the gas during the rise (a) and the fall (b) of the light source equivalent temperature and the light source equivalent temperature.

[0034] Figure 18 is a block diagram of a measurement system for gas thermometry using a light source with variable intensity and an infrared detector.

[0035] Figure 19 is a characteristic diagram of the time variation of the detected intensity of the gas irradiated area and the detected intensity when there is no gas.

[0036] Figure 20 is a characteristic diagram of the time variation of the time axis differential signal of the detected light intensity of the gas irradiated area.

[0037] Figure 21 is a characteristic diagram of the time variation of the time axis differential signal of the detected light intensity of the gas irradiated area. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Here, the description mode "A to B" appearing in the text means A or more and B or less.

[0039] <Configuration of the device> As shown in FIG. 1, a temperature measurement device (temperature measurement system) 101 has a light source 11, a light source intensity variable device (intensity variable device) 12, a comprehensive control device 13, a light receiving device 14 including a video camera 15, and an image processing device 19. Alternatively, as shown in FIG. 2, the temperature measurement device 101 has a light receiving device 14 including a light sensor 16, a lens 17, and a band pass filter 18, and a signal processing device 20, in place of the video camera 15. Here, the lens 17 functions as an imaging optical system for imaging an image of a gaseous substance 21 on a light receiving portion of the light sensor 16. Figure 1 Figure 18 The light source 11 and the light sensor 16 as a part of the light receiving device 14 are configured so that the light emitted from the light source 11 reaches the light sensor 16 via the gaseous substance (gas) 21 as a measured object. The gaseous substance 21 is placed on the light path (light route) from the light source 11. Therefore, a mirror can also be used in the middle of the light route, and the position of the gaseous substance 21 is deviated from the straight line between the light source 11 and the light sensor 16. In addition, an optical fiber can also be used to transmit the light and emit the light from the optical fiber on the front side of the gaseous substance.

[0040] The light source 11 and the light sensor 16 as a part of the light receiving device 14 are configured so that the light emitted from the light source 11 reaches the light sensor 16 via the gaseous substance (gas) 21 as a measured object. The gaseous substance 21 is placed on the light path (light route) from the light source 11. Therefore, a mirror can also be used in the middle of the light route, and the position of the gaseous substance 21 is deviated from the straight line between the light source 11 and the light sensor 16. In addition, an optical fiber can also be used to transmit the light and emit the light from the optical fiber on the front side of the gaseous substance.

[0041] ​The light source 11 can be a planar light source covering a large-sized area of the entire gas, or a small-area light source that illuminates a part of the gas. However, regardless of whether it is a large-area light source or a small-area light source, the blackbody radiation equivalent temperature (hereinafter sometimes referred to as "equivalent temperature") of the light emitted by the light source 11 needs to have a range that covers from an equivalent temperature higher than the gas temperature to an equivalent temperature lower than the gas temperature.

[0042] The gas 21 is not particularly limited as long as it is a gas that absorbs light in a specific wavelength range. For example, one gas selected from the group consisting of methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), sulfur trioxide (SO3), water vapor (H2O), ammonia (NH3), sulfur hexafluoride (SF6), and freon can be given. These gases are particularly highly demanded as measurement targets. The gas 21 can be a gas that absorbs ultraviolet light, visible light, and terahertz light.

[0043] The light source 11 emits light in a wavelength range that includes the light absorption band of the gas of the gas 21, and is a light source whose light intensity is changed by the light intensity variable device 12. Specifically, as the light source 11, a thermal radiation light source, a cavity blackbody furnace, a light-emitting diode (LED), and a laser light source can be given. From the viewpoint of performing ideal blackbody radiation approximation processing in image analysis or signal analysis, a thermal radiation light source coated with a blackbody can be particularly preferably used.

[0044] The light intensity variable device 12 is, for example, a device that changes the intensity of the light emitted from the light source 11 in the following (1) to (5).

[0045] (1) Control of power supply to the light source 11; (2) Transmission rate variable filter processing using two linearly polarized filters; (3) Filter processing using light reduction filters having different transmission rates; (4) Continuous variable light reduction filter; (5) Variable aperture.

[0046] In order to perform measurement with high contrast, it is preferable to limit the wavelength range of the light reaching the light sensor from the light source to the vicinity of the light absorption band of the gas. Here, the "vicinity of the light absorption band" means a wavelength range that includes the wavelength λAof the light A absorbed by the gas 21 and is of the same order as the bandwidth of the gas absorption band spectrum of the gas. Here, the bandwidth of the gas absorption band spectrum includes the wavelength λAof the light A and corresponds to 1 / 10 of the peak width of the gas absorption coefficient. The wavelength range in the vicinity of the light absorption band is more preferably 0.25 times or more and 4 times or less of the bandwidth of the gas absorption band spectrum of the gas. A A ​​

[0047] As a means of limiting wavelength, one can use: (1) a bandpass filter that efficiently turns on only for a certain wavelength range; or (2) a device that combines a beam splitter with a built-in diffraction grating or prism with a slit to efficiently turn on only for a specific wavelength range. Alternatively, if the light source itself or the photosensor itself is a narrowband element, they can also be used as a means of limiting wavelength.

[0048] The light-receiving device 14 is a device that receives light from the light source 11 and outputs a light-receiving signal. Examples of light-receiving devices 14 include... Figure 1 The (2D) imaging system shown and Figure 18 The single-pixel detection system shown is an example. Figure 1 As shown, the light-receiving device 14 of the (2D) image system can be composed of a camera 15 including an imaging element (light sensor) 16, a lens 17, and a bandpass filter 18. Figure 18 As shown, the light-receiving device 14 of the single-pixel detection system can be composed of a photodetector (photosensor) 16, a lens 17, and a bandpass filter 18.

[0049] Here, the absorption band of the gas being measured can be any one of infrared, visible, ultraviolet, and terahertz light. Depending on the absorption band of the gas, for example, an ultraviolet imaging element, an ultraviolet lens, and an ultraviolet bandpass filter can be used in the case of ultraviolet light.

[0050] CO2, NO x Most gaseous substances 21, such as CO and NH3, which are in high demand for measurement, have absorption bands for infrared light. Therefore, the following explanation focuses on the infrared band. In this case, for the light receiving device 14, a (2D) imaging system can be cited as an example. Figure 1 ) and single-pixel detection system ( Figure 18 (2D) Image System Light Receiving Device 14 Figure 1 The infrared camera 15 comprises an infrared imaging element (light sensor) 16, an infrared lens 17, and a bandpass filter 18. The light-receiving device 14 of the single-pixel detection system... Figure 18 It consists of an infrared detector (optical sensor) 16, an infrared lens 17, and a bandpass filter 18.

[0051] Furthermore, as shown in the embodiments, the (2D) imaging system for measuring spatial tremor can easily achieve high measurement accuracy. On the other hand, the single-pixel detection system is characterized by its simplicity and ease of cost reduction.

[0052] <2D Graphics System> The infrared lens 17 is not particularly limited as long as it has sufficient imaging performance as a camera. As its optical system, for example, (1) a lens imaging system based on an optical lens using Ge, Si, ZnSe, ZnS, sapphire, (2) a reflective optical system using a mirror, and (3) a composite optical system using a mirror and a lens can be used. The optical lens can be a short focal length lens or a zoom lens. The magnification, F value, allowable aberration, and the like of the optical lens are not particularly limited, and can be appropriately selected in view of cost, convenience of use, weight, resolution, field of view, and the like.

[0053] The infrared imaging element (light sensor) 16 is a pixel type infrared sensor having a plurality of light receiving pixels, and is not particularly limited as long as it is a light receiving element having sensitivity to the above-described wavelength band. That is, the light receiving element is a light receiving element that detects light having a wavelength identical to the absorption wavelength of the gas to be measured. As the infrared imaging element (light sensor) 16, for example, a photoelectric conversion element such as InSb, HgCdTe, InAs / GaSb superlattice, InGaAs / InAlAs quantum well, or GaAs / AlGaAs quantum well can be used. In addition, as the infrared imaging element 16, a bolometer, a thermopile, or a thermal type infrared light sensing element using a pyroelectric element can be used. Here, in order to easily perform image analysis, the pixels of the infrared imaging element 16 are preferably arranged in a matrix shape.

[0054] The pixel size and the number of pixels of the infrared imaging element 16 are not particularly limited. If the pixel size is reduced, the size of the infrared imaging element 16 is also reduced, and thus the infrared lens 17 is also easily downsized. In the case of a large pixel size, the sensitivity and S / N are easily improved, and thus the resolution is also easily improved. As the pixel size, for example, 10 x 10 to 30 x 30 μm 2 may be used. The number of pixels is not particularly limited, and can be appropriately set in accordance with the size of the device, the required resolution, and the like. As the number of pixels, for example, 64 x 64 to 1920 x 1536 can be given.

[0055] The band pass filter 18 is not particularly limited as long as it selectively transmits light of the above-described wavelength band. As the band pass filter 18, for example, a multilayer film composed of SiO, ZnS, and Ge, or the like formed on a sapphire or a germanium substrate can be used.

[0056] The position where the band pass filter is provided can be in front of the infrared lens 17 as viewed from the infrared imaging element 16, or can be behind the infrared lens 17. In the case where the band pass filter is provided in front of the infrared lens 17, there is an advantage that the band pass filter is easy to replace and attach and detach. In the case where the band pass filter is provided behind the infrared lens 17, there is an advantage that the band pass filter is small, and there is an advantage that the infrared imaging element 16 can be cooled together in the case where cooling is performed later.

[0057] The infrared imaging element 16 and the band pass filter 18 are preferably cooled. By cooling, noise caused by thermal radiation from the outside environment or components and the like can be reduced. In the case where the band pass filter 18 is at room temperature, thermal radiation from the band pass filter 18 is superimposed on the signal of the infrared imaging element 16 as a larger baseline. As a result, the contrast of the resulting image is significantly reduced. As a cooling method, a Stirling cooler, a Peltier element, liquid nitrogen cooling, and the like can be given. The Stirling cooler and the Peltier element can be preferably employed because they are easy to operate. In particular, the Stirling cooler can be particularly preferably employed because it can be cooled to 80 K or less even in a size that is hand-held, and can be operated with a battery.

[0058] The cooling temperature is preferably 50 K or more and 250 K or less. By making the temperature 250 K or less, the noise level can be improved by one order of magnitude or more. The lower the temperature, the lower the noise level. If the temperature is 50 K, the noise level is reduced by 20 orders of magnitude or more compared to the case of using at room temperature, and thus noise caused by voltage fluctuations and other factors becomes dominant. However, if an extremely low temperature is used, simplicity and ease of operation can be reduced, and thus it is preferable to make the temperature 50 K or more.

[0059] Here, the light sensor 16, the lens 17, and the band pass filter 18 (hereinafter referred to as "light sensor 16 and the like") are described taking them as typical infrared devices. However, the light sensor 16 and the like preferably have a wavelength band that coincides with the light absorption wavelength of the gas to be measured. Therefore, depending on the type of gas, a light sensor 16 and the like suitable for at least one of infrared light, visible light, ultraviolet light, and terahertz light is used.

[0060] The image processing device 19 is a device that performs the following processes (1) to (3).

[0061] (1) The signal captured by the infrared imaging element 16 receiving light is processed to find the wobble (wobble of the image) of the spatial distribution of light intensity.

[0062] (2) The light intensity I of the light source 11 is found for which the amplitude of the wobble of the spatial distribution is extremely small. min .

[0063] (3) approximating the emission spectrum of the light source 11 in accordance with ideal black body radiation to calculate the equivalent temperature T min of the light source 11 corresponding to the light intensity I s .

[0064] As a specific hardware of the image processing device 19, a computer such as a portable PC can be given. The portable PC is small and light, and can be easily carried to work, and is easy to operate.

[0065] <Single-pixel system> The infrared lens 17 and the band pass filter 18 of the single-pixel system are the same as those in the 2D imaging system.

[0066] As the infrared detector (light sensor) 16 of the single-pixel system, a photoelectric conversion element such as InSb, HgCdTe, InAs / GaSb superlattice, InGaAs / InAlAs quantum well, GaAs / AlGaAs quantum well, and the like can be used without particular limitation as long as it has sensitivity to the above-described wavelength band. In addition, as the infrared detector 16, a bolometer, a thermopile, a thermal type infrared sensing element using a pyroelectric element can be used. Since it is a single pixel, the pixel size of the infrared detector 16 can be designed to be large, and it is possible to try to improve the S / N ratio. Here, the light sensor 16 and the like are described taking an infrared device as a typical example. However, the light sensor 16 and the like preferably have a wavelength band coinciding with the light absorption wavelength of the gas to be measured. Therefore, depending on the kind of the gas, a light sensor 16 and the like suitable for at least one of infrared light, visible light, ultraviolet light, and terahertz light is used.

[0067] The signal processing device 20 is a device that performs the following processes (1) to (3).

[0068] (1) The light receiving signal of the infrared detector 16 is processed to find the fluctuation of the light intensity over time.

[0069] (2) The light intensity I min (t) of the light source 11 for which the amplitude of the fluctuation over time is extremely small is found.

[0070] (3) The emission spectrum of the light source 11 is approximated in accordance with ideal black body radiation to calculate the equivalent temperature T min of the light source 11 corresponding to the light intensity I s .

[0071] As a specific hardware of the signal processing device 20, a computer such as a portable PC can be given. The portable PC is small and light, and can be easily carried to work, and is easy to operate.

[0072] The integrated control device 13 is a device that performs measurements by controlling the light intensity variable device 12, the image processing device 19, or the signal processing device 20. The integrated control device 13 is used in this measurement in relation to the light intensity I... min Or light intensity I min It serves as a bridge between the calculation of (t). As a specific hardware component of the integrated control device 13, a computer such as a portable PC can be cited as an example. The computer can be a standalone unit equipped with the integrated control device 13 and the image processing device 19 or the signal processing device 20, which is small and easy to use.

[0073] <Measurement Principle> like Figure 1 As shown, when infrared light emitted from light source 11 passes through the gas, a portion of it is absorbed or amplified, and then passes through a bandpass filter with a transmission band located near the absorption wavelength of the gas before being incident on the infrared imaging element and detected.

[0074] In most cases, infrared light is absorbed and its intensity decreases when it passes through a gas. However, even infrared light of the same wavelength can sometimes appear to increase in intensity (enhance) when it passes through other gases (gases in other states). This is because the gas's own luminescence is superimposed on the infrared light.

[0075] The following is a detailed explanation. The intensity of infrared light passing through the gaseous object 21 varies significantly depending on the relationship between the blackbody radiation equivalent temperature (hereinafter referred to as the equivalent temperature) of the infrared light emitted by the light source 11 and the temperature of the gaseous object 21. That is, if the temperature of the gaseous object 21 is lower than the equivalent temperature of the infrared light, the infrared light is absorbed by the gaseous object 21, thus reducing the intensity of the infrared light passing through it. On the other hand, if the temperature of the gaseous object 21 is higher than the equivalent temperature of the infrared light, the infrared light is enhanced due to the emission of light from the gaseous object 21 itself. Thus, the intensity of infrared light passing through the gaseous object 21 varies significantly, with the equilibrium point where the equivalent temperature of the infrared light equals the temperature of the gaseous object 21 as the boundary. Therefore, when the equivalent temperature of the infrared light is changed to cause a significant change in the intensity of the infrared light passing through the gaseous object 21, the temperature of the gaseous object 21 can be determined based on this equivalent temperature.

[0076] In this disclosure, the temperature of the gaseous substance 21 is determined based on the change in infrared light intensity corresponding to the equivalent temperature of the infrared light. Furthermore, to improve temperature accuracy, the moment when the infrared light intensity changes is determined more precisely, taking into account fluctuations in the infrared light intensity variation. Details will be described later.

[0077] It can approximate the emission spectrum of a light source as a function of temperature T. s Ideal blackbody radiation I b (λ,T s The temperature T at this time.s This is called the equivalent temperature of the light source. Here, the change in light source intensity corresponds to the equivalent temperature T of the light source. s The change in λ, where λ is the wavelength.

[0078] Luminous intensity I b (λ,T s When light passes through a gas of concentration c and thickness L, the gas absorbs the light according to its own absorption spectrum. At the same time, the gas itself also absorbs the light as its temperature T increases. g And it emits light. At this time, the light intensity I detected by the gas... dg (λ,T s T g ,c,L) are represented by the following formulas (1) and (2).

[0079] [Mathematical Expression 1]

[0080] Here, the first term on the right-hand side of equation (1) represents the intensity I of the gas incident from the light source. b (λ,T s The light is absorbed by the gas and decays exponentially.

[0081] τ g (λ,T g , c, L) is the optical density of the gas, as shown in equation (3) below.

[0082] [Mathematical Expression 2]

[0083] Here, α(λ, T) g α(λ, T) is the absorbance coefficient of the gas relative to its unit concentration. g The absorption coefficient varies significantly with λ, and increases as λ approaches the absorption wavelength of the gas. Furthermore, the absorption coefficient α(λ, T) varies with λ. g It also varies with the gas temperature T g And it changes. Furthermore, the higher the gas concentration c and the greater the gas thickness L, the higher the absorption coefficient α(λ, T). g The larger it gets.

[0084] The second term on the right-hand side of equation (1) represents the light intensity emitted by the gas, indicating that the higher the optical density of the gas, the more the light intensity increases exponentially towards a given intensity I. b (λ,T g Gradual. Light intensity I b (λ,T g ) is temperature T g The radiation intensity of an ideal blackbody at that time.

[0085] Equation (2) represents the sum of the two terms mentioned above in Equation (1). As shown in Equation (2), the greater the optical density of the gas, the greater the light intensity. s ) Radiates Ig(λ, T) onto an ideal blackbody of gas g (Gradual)

[0086] The intensity I of light emitted from a light source but not passing through the gas d0 (λ,T s ) is represented by the following formula (4).

[0087] [Mathematical Expression 3]

[0088] The intensity I of the light d0 (λ,T s Yes, when Figure 1 The detection intensity of light in the background area where the light source can be directly seen is given when (1) a background area where the light source can be directly seen and (2) a gas-illuminated area where the light source can be seen through the gas in the field of view of the infrared camera shown.

[0089] Here, the intensity difference between light that has passed through the gas and light that has not passed through the gas is represented by the following equation (5).

[0090] [Mathematical Expression 4]

[0091] The first term of equation (5) is determined solely by the equivalent temperature T of the light source. s and gas temperature T g The second term of equation (5) is determined solely by the type of gas. It is close to 0 when the light absorption of the gas is low, and increases towards 1 as the optical density increases.

[0092] Next, we will explain the specific actions based on equations (2) and (5). Imagine a gas that exhibits an absorption peak at a wavelength of 4.25 μm. Figure 2 The absorption coefficient α(λ, T) of the gas is shown. g And the optical density τ, which is determined by the concentration c and the thickness L. g (λ,T g (c, L). In light of the following explanation, the wavelength λ that results in greater gas absorption is... A Medium wavelength λ b Smaller wavelength λ c These three typical value points (wavelengths) are considered.

[0093] Figure 3 The ideal blackbody radiation spectrum I at typical temperatures is shown.b (λ, T). It can be seen that the higher the temperature, the greater the light intensity. Equations (2) and (5) can be used to describe the above absorption coefficient α(λ, T). g ) and spectral I b Combinations of (λ, T).

[0094] [1] When the equivalent temperature of the light source is higher than the gas temperature (T) s >T g ) If the equivalent temperature of the light source is higher than the gas temperature, then "I" b (λ,T s )-I b (λ,T g ")>0", therefore "ΔI" d (λ,T s T g (c, L) < 0. That is, the light intensity of the gas-illuminated area is lower than that of the background area.

[0095] Figure 4 The diagram schematically illustrates the case of equation (2) at a certain wavelength λ. When the gas absorbs no light, the detected light intensity I... dg The light intensity I of the light source b (λ,T s And optical density τ g The larger the value, the higher the detected light intensity I. dg The smaller the value, the more it radiates towards the ideal blackbody corresponding to the gas temperature. b (λ,T g (Gradual) Figure 4 The symbol ○ (hollow circle) is used to schematically represent this. Figure 2 The corresponding positions are for three typical values ​​of different optical densities.

[0096] Figure 5 Equation (2) is shown in the form of a spectrum in "T". s =45℃, T g The situation at 25℃. It can be seen that at wavelengths that do not cause light absorption, the detected light intensity I is directly the light intensity of the light source. b (λ,T s However, the greater the light absorption, the smaller the detected light intensity becomes.

[0097] [2] When the equivalent temperature of the light source is lower than the gas temperature (T) s <T g ) If the equivalent temperature of the light source is lower than the gas temperature, then "I" b (λ,T s )-I b (λ,T g )<0], therefore "ΔId (λ,T s T g "c, L)>0". That is, the light intensity of the gas-illuminated area is greater than that of the background area.

[0098] Figure 6 The diagram schematically illustrates the case of equation (2) at a certain wavelength λ. When the gas absorbs no light, the detected light intensity I... dg The intensity I of the light source b (λ,T s And optical density τ g The larger the value, the greater the light intensity I. dg The more it increases, the more it radiates towards the ideal blackbody corresponding to the gas temperature. b (λ,T g (Gradual) Figure 6 The symbol ○ (hollow circle) is used to schematically represent this. Figure 2 The corresponding positions are for three typical values ​​of different optical densities.

[0099] Figure 7 Equation (2) is shown in the form of a spectrum in "T". s =5℃, T g The situation at 25℃. At a wavelength that does not cause light absorption, the light intensity I of the light source is directly detected. b (λ,T s As we can see, the greater the light absorption, the greater the detected light intensity. The fact that the greater the light absorption of a gas, the greater the detected light intensity may seem strange, but it's a result of Kirchhoff's laws. An object's ability to absorb light (absorbency) is equal to its ability to emit heat (emissivity); this is Kirchhoff's law. Whether an object absorbs or radiates light depends on its relative thermal equilibrium with its surroundings. Figure 7 In the example, the gas is relatively hot compared to the equivalent temperature of the incident light source, so the gas preferentially radiates.

[0100] [3] When the equivalent temperature of the light source is equal to the gas temperature (T) s =T g ) What's particularly interesting is the boundary between the two temperatures mentioned above, namely [T]. s =T g In this case, "I" b (λ,T s )-I b (λ,T g ")=0", therefore "ΔI" d (λ,T s T g"c, L)=0". That is, in this case, there is no detectable intensity difference between the background area and the gas irradiated area, and the boundary between the background area and the gas irradiated area cannot be detected.

[0101] Figure 8 The diagram schematically illustrates the case of equation (2) at a certain wavelength λ. Figure 9 In the figure, equation (2) is shown in the form of a spectrum in “T”. s =25℃, T g The situation at 25℃. Regardless of optical density τ. g In any case, the difference in detection intensity caused by the presence or absence of gas will not occur.

[0102] The specific measurement is explained below. The actual signal obtained from the infrared camera is obtained by integrating the light intensity shown in equations (2) and (5) according to the band [λ1, λ2] defined by the bandpass filter.

[0103] The difference in signal intensity between light that has passed through the gas and light that has not passed through the gas is expressed by the following formula.

[0104] [Mathematical Expression 5]

[0105] Here, regarding τ g (λ,T g ,c,L), which determines the meaning of its function α(λ,T) g It has a strong dependence on λ. In contrast, regarding I... b (λ,T s ) or I b (λ,T g In cases where a narrow band is of concern, as disclosed herein, it can be considered as α(λ, T). g It has a relatively low dependence on λ.

[0106] When it is possible to determine I based on the value at the center wavelength λ0 of the band. b (λ,T s ), I b (λ,T g When approximating, the following equation (6) holds true.

[0107] [Mathematical Expression 6]

[0108] The greater the optical density of the gas, the greater the value of the second term in equation (6). Figure 10 In the example, three typical examples of gases with optical densities ranging from high to low are shown, illustrating "T". gThe relationship between signal strength difference (Equation (6)) and equivalent temperature of light source under the condition of =25℃. The higher the concentration c, the thicker the gas thickness L, and the greater the overlap between the wavelength band [λ1, λ2] and the absorption peak, the greater the light absorption of the gas.

[0109] exist Figure 10 In the equation (6), the solid line corresponds to the case where the optical density of the gas is relatively high, the dashed line corresponds to the case where the optical density is relatively low, and the dashed line corresponds to the case where the optical density is in the middle. Specifically, the solid line, dashed line, and dashed line represent the cases where the value of the second term in equation (6) is 0.16 μm, 0.09 μm, and 0.02 μm, respectively. Here, the second term in equation (6) is given by the following formula.

[0110] [Mathematical Expression 7]

[0111] Equivalent temperature T of the light source s At lower temperatures, the light intensity in the gas-illuminated area is higher than that in the background area. As the equivalent temperature of the light source increases, the light intensity in the gas-illuminated area decreases. At a certain stage, the sign of the detection intensity (signal strength difference) reverses, and thereafter, the light intensity in the gas-illuminated area decreases further. Furthermore, at a certain equivalent temperature T of the light source... s Under constant conditions, the greater the light absorption of the gas, the greater the change in the detectable light intensity in the gas-illuminated area compared to the background area.

[0112] However, regardless of the gas's absorbance, in all typical cases, when "T" s =25℃, that is, when "T s =T g At this time, the area of ​​gas being illuminated is indistinguishable from the background area. In this way, by making the equivalent temperature T of the light source... s The change in light intensity caused by the gas is minimized (when the illuminated area and the background area become indistinguishable), which is the equivalent temperature T of the light source. s As the gas temperature T g Let's find out.

[0113] The intersection point (the point where the signal strength difference reverses from positive to negative) itself does not depend on the gas's absorbance. However, the greater the absorbance, the greater the signal change, and the more clearly the intersection point can be identified. The gas concentration c and thickness L are properties of the measured object. However, by selecting the bandpass filter [λ1, λ2], it is possible to determine the relative absorbance coefficient α(λ, T) of the gas. gThis increases the integral value of the second term in equation (6). Therefore, the band [λ1, λ2] is preferably limited to a narrow region near the absorption peak, but if it is too narrow, the signal-to-noise ratio (SN) will decrease due to the reduction in signal quantity itself. Therefore, the appropriate band [λ1, λ2] needs to be determined based on a comprehensive consideration of these factors.

[0114] After studying various cases, it was determined that the optimal absorption spectral bandwidth [λ1, λ2] relative to the gas absorption band is [λ]. g1 , λ g2 The range is 0.25 times or more and 4 times or less. Within this range, the gas can be visualized with high contrast. Here, the measured band corresponds to the half-width at half-maximum (WHM) of the transmittance of a bandpass filter, etc. The bandwidth of the reference gas absorption band corresponds to 1 / 10 of the peak width of the gas absorption coefficient.

[0115] The method disclosed herein differs from the prior art in that it independently measures temperature using only a gas visualization device with an added variable-intensity light source. Therefore, even for gases whose temperature is not necessarily room temperature, the gas concentration can be measured with high precision based on the visualized image and temperature information, thereby enabling a quantitative assessment of gas leakage.

[0116] Furthermore, in this disclosure, based on the light tremors received by the light sensor (infrared detector), the value of T when the detection (signal) intensity difference between the background area and the gas-illuminated area disappears is calculated. g With T s The points of convergence between them.

[0117] Regarding gaseous substances, their density often fluctuates spatially and / or temporally. Therefore, it is assumed that the intensity of the received light signal will also fluctuate, leading to difficulties in calculating T. g With T s The error at the point of agreement between them also increases.

[0118] However, the lower the signal strength, the smaller the jitter. This is a general property of noise. From a simulation perspective, for example, light intensity jitter, or shot noise, is proportional to the half power of the light intensity. Intuitively, the weaker the light, the greater the jitter, and the signal seems to be buried in noise. But statistically, the stronger the light, the more photons there are, and the greater the jitter in both intensity and photon count. In the case of this disclosure, the smaller the detection intensity difference between the background area and the gas-irradiated area, the smaller the jitter.

[0119] Therefore, if the equivalent temperature T of the light source is made s By statistically measuring the spatial and / or temporal fluctuations of the signal during the change process, it can be known that as T... s Approaching T gThe light intensity difference decreases, therefore the tremor also decreases. When "T" s =T g "When no gas is present, the shaking is minimal; thereafter, with T..." s Gradually with T g As the difference in light intensity widens, so does the oscillation. Therefore, by focusing solely on spatial and / or temporal oscillation as an objective statistical and mathematical indicator, T can be calculated with high precision. s With T g The point of convergence between them is used as the minimum point of tremor.

[0120] Since this method seeks the value at a minimum point, it is a null method. The null method is ideal for high-precision measurements. In this method, as long as the equivalent temperature of the light source is appropriately corrected to ensure a range covering an equivalent temperature higher than the temperature of the gas to be measured to an equivalent temperature lower than the temperature of the gas, the measurement results are less susceptible to influence from other factors. For example, even if a similar gas (e.g., CO2) is present in the atmosphere between the gas to be measured and the light sensor, the overall measurement signal light will only be weakened due to light absorption by the gas, while the brightness relationship of the detected intensity remains unchanged, thus having no impact on the measurement.

[0121] On the other hand, the zero-position method requires a reference value (in this case, the light source temperature T). s The traditional scanning process is time-consuming. However, when using LEDs as the light source, high-speed scanning of light intensity can be achieved through voltage scanning. Furthermore, when using a thermal radiation light source, the size of the light source does not need to cover the entire gaseous surface; it can be a small-area light source illuminating only a portion of it. Therefore, the heat capacity of the thermal radiation light source can be reduced, and high-speed temperature scanning can be performed using a large-capacity heater or a large-capacity Peltier element, thus achieving high-speed measurement. In this way, the temperature of the gaseous substance can be measured with high reliability and high reproducibility without inserting the temperature measuring instrument into the gas, simply by observing it optically from a distance.

[0122] <Determination Method> The temperature measurement method disclosed herein is a method for measuring the temperature of a gaseous substance, wherein the gaseous substance emits wavelength λ. A Light A is absorbed. Combined Figure 11 The process flow diagram is used to illustrate this method.

[0123] First, the infrared imaging element, i.e., an infrared detector with multiple pixels arrayed, is used as a light sensor S. A The plan will be explained at that time.

[0124] The first step is to provide a light source L that can emit light A by changing the light intensity.A And a light sensor S capable of receiving light A and measuring the intensity of the received light. A (Step S11). Here, the light sensor S... A It is an infrared camera element.

[0125] Next, from the light source L A Emitted and received by the light sensor S A Along the ray path of the received light A, the light source L... A and light sensor S A They are configured such that the gaseous substance is present between them (step S12).

[0126] Then, the measurement was performed at the source L. A The light sensor S emits light A by changing the light intensity. A The light-receiving image and its light intensity on the surface (step S13).

[0127] Then, by measuring the received light image and the received light intensity, the light source L is determined to be at its minimum amplitude of spatial and / or temporal fluctuation in the received light intensity. A Light intensity I min (Step S14).

[0128] Here, the spatial jitter of the received light intensity can be calculated using the variance of the differential image of the signal output by the infrared camera element. On the other hand, the temporal jitter can be calculated using the AC component extracted by time-axis differentiation of the received light signal output by the infrared camera element. The differential image (e.g., the center differential image I described later) m A jitter image is a difference image obtained by taking images at time intervals, so it also reflects temporal jitter. Therefore, strictly speaking, the jitter calculated from the variance of the difference images is a "spatial and temporal jitter" that reflects not only spatial jitter but also temporal jitter.

[0129] Here, if the gas concentration of the gaseous substance being measured is subject to common spatial fluctuations, then spatial fluctuations are generally used, as this makes it easier to achieve high measurement accuracy. If both spatial and temporal fluctuations are used to determine the light intensity I,... min This allows for more accurate measurement of the temperature of gaseous substances.

[0130] Then, the radiation of the light source L is calculated according to the ideal blackbody radiation. A The emission spectrum was approximated, and the light intensity I was compared with that of the light intensity I. min Correspondingly, light source L A Equivalent temperature T S (Step S15).

[0131] Finally, the equivalent temperature T S The temperature of the gaseous substance is determined (step S16), and the temperature measurement of the gaseous substance is terminated (S02).

[0132] Next, the single-pixel infrared detector was used as a light sensor S. A The plan will be explained at that time.

[0133] When using this infrared detector, the light sensor S A The light intensity measured in step S13 is the light intensity received. Additionally, the light intensity I calculated in step S14... min The light source L is the light intensity that fluctuates over time at its minimum. A The light intensity. Except as described above, the temperature of the gaseous substance is measured using the same procedures as when using an infrared imaging element.

[0134] By following the steps above, when it is necessary to measure the temperature of a gaseous substance, it is possible to easily measure the temperature of a gaseous substance located at a remote location using a portable, small, and convenient device.

[0135] Furthermore, the ability to optically measure gas temperature from a distance without inserting the measuring instrument into the gas also enables reliable and highly reproducible measurements.

[0136] Furthermore, in the gaseous temperature measurement disclosed herein, not only can the equivalent temperature be changed by electronically scanning the intensity of the light source, but the gas temperature can also be measured in a short time even when the equivalent temperature is changed by altering the temperature of the thermal radiation source. By reducing the heat capacity of the blackbody plate emitting thermal radiation and using a large-capacity heater or Peltier element for high-speed temperature scanning, the gas temperature can be changed in a short time.

[0137] Furthermore, the gaseous temperature measurement disclosed herein has the following characteristics: even if the gas to be measured, such as CO2 or H2O, is present in the atmosphere between the detector and the detector, only the measurement signal light will weaken, while the brightness relationship of the detection intensity will not change, thus not affecting the measurement.

[0138] <Extended to concentration measurement and discharge measurement> The primary motivation for measuring the temperature of gaseous substances in this disclosure is to utilize the inherent infrared absorption characteristics of gases to visualize specific gases using an infrared camera, thereby enabling quantitative gas measurement. Gas visualization technology is a convenient method for detecting gas leaks from a distance and is an important technology in advancing solutions to environmental problems. However, the visual effectiveness of gases is affected not only by concentration but also by temperature, thus posing a problem that concentration cannot be quantitatively measured without knowing the gas temperature. This disclosure, by measuring the temperature of gaseous substances, has the potential to be extended to gas concentration measurement and emission measurement within gas visualization technology.

[0139] A key feature of this disclosure is the ability to measure gas temperature using virtually the same optical system when quantitatively evaluating gas concentration and emission rates. Specifically, predictive measurement is possible; that is, the temperature of the gas is pre-measured by placing a variable-intensity light source behind the gas and scanning its intensity. This allows for direct measurement of concentration and emission rates. For high-precision concentration measurements, infrared light sources or similar sources are sometimes placed behind the gas. In this case, the equivalent temperature of the light source is scanned using the same optical system to measure the gas temperature, and then the concentration and emission rates are measured while maintaining the temperature suitable for concentration measurement.

[0140] In cases where the simplicity of temperature measurement is desired, only a reflector, scatterer, or fiber optic outlet needs to be placed in front of the gas, rather than the light source itself. In this case, since the reflector, scatterer, and fiber optic are lightweight components, their tubes only need to be positioned in front of the gas when the temperature is to be measured.

[0141] After determining the temperature of the gaseous substance, the concentration and discharge volume can be measured in the following manner.

[0142] Here, equation (6) also plays an important role. First, ΔI(T) serves as the luminance signal for the gas visualization camera. s T g (c, L) are already known. Among them, the gas temperature T g The equivalent temperature T of the light source, calculated according to this disclosure, when the tremor amplitude is extremely small. s In formal measurements, a different background is typically used, and the temperature of this background can be measured by using an infrared camera for thermal imaging.

[0143] The bandwidth of the infrared camera used here has been limited for gas visualization. Here, the light intensity of the background region is determined by correction at a specific emissivity and temperature, and the temperature T of the background region of the gas being observed is then calculated from the image of the gas at the moment of deformation.s Therefore, the column density “c×L” can be calculated according to equations (6) and (3).

[0144] To determine the concentration (c) of a gas, information about its thickness (L) is needed. This can be determined by observing the same gas from another direction.

[0145] When calculating the discharge volume (flow rate), there's no need to break down the column density "c×L" into individual elements; the column density itself is the useful information. It represents the integral amount of gas along the line of sight (z-direction). By integrating it along the camera's field of view (xy-direction), the total amount of gas reflected in the image can be calculated.

[0146] Furthermore, by applying gas dynamic vector image measurement methods such as optical flow to visualized images, it is possible to determine the velocity vectors of various localities within the gas. Gas visualization processing using vector image measurement methods is disclosed, for example, in Patent Document 3.

[0147] By applying Gauss's theorem, the integral value on a measuring line can be calculated based on the column density and the velocity component perpendicular to that measuring line, which can then be used as the volumetric flow rate (discharge) along that measuring line. Thus, according to this disclosure, if the temperature of a gas can be measured, it can be directly extended to the quantitative determination of the gas concentration, flow rate, and discharge.

[0148] <Example> (Example 1) A variable-temperature thermal radiation source with a surface coated with a blackbody of emissivity of 0.96 and a luminous surface size of 130 mm square was used as the light source. In front of this light source, a fan-shaped nozzle with a rectangular opening of 12.6 mm on the long side and 1.5 mm on the short side ejected CO2 gas at a concentration of 9% (diluted with nitrogen). The nozzle was oriented with its long side parallel to the surface of the light source, and its short side representing the thickness L of the gas. Using a separately prepared radiation thermometer, the temperature of the central portion of the light source was measured from an angle unaffected by the gas.

[0149] The temperature represented by setting the emissivity to 1.00 is the equivalent temperature T. s The precise surface temperature of the light source should be obtained by correcting for an emissivity of 0.96, and thus should be a value higher than the apparent measured value T. s A slightly higher temperature. However, since this disclosure requires the intensity I of the actual radiated infrared light. b (λ,T s Therefore, T will be used here. s The temperature of the light source is directly considered as the actual physical temperature.

[0150] The situation was observed using an infrared camera capable of visualizing CO2. The camera used was a FLIR A6796 model, a 640×512 pixel camera with an InSb infrared imaging element, which incorporates a bandpass filter in the band [4.12μm, 4.33μm]. This bandpass filter was cooled to below 80K. The infrared lens had a focal length of 50mm and an f / 2.5 aperture, and the shooting conditions were an exposure time of 40ms and a frame rate of 25fps. On the other hand, the absorption spectrum of CO2 has a bandwidth of [4.21μm, 4.33μm], and the bandpass filter's bandwidth (0.21μm) is 1.8 times wider than the bandwidth of the gas absorption spectrum (0.12μm).

[0151] Figure 12 Typical images are shown when the temperature of the light source is increased. Figure 13 A typical image is shown when the temperature of the light source is cooled.

[0152] The image during heating specifically refers to the image of rapidly heated CO2 gas as the light source temperature is initially set to 10°C until the set temperature is changed to 40°C. The image during cooling specifically refers to the image of rapidly cooled CO2 gas as the light source temperature is initially set to 40°C until the set temperature is changed to 10°C. Here, in Figure 12 , 13 In the image, the brightness of the center area has been adjusted to match the brightness of the background area. The brightness range in both images is set to a fixed value.

[0153] exist Figure 12 In the process, CO2, which initially appears bright as it heats up, gradually changes to appear darker, with imperceptible moments in between. Figure 13 In the image, CO2, initially appearing dimmer during cooling, gradually changes to appear brighter, with imperceptible moments occurring in between. These imperceptible moments are determined by visually inspecting the image's brightness range with appropriate magnification. The light source's temperature relative to its equivalent temperature at this point... Figure 12 The middle is T s =23.5℃, at Figure 13 The middle is T s =23.7℃. Regardless of whether the temperature rises or falls, at T... s At 23.6 ± 0.1℃, CO2 is just barely visible. That is, this is precisely the calculated gas temperature T. g .

[0154] Next, to provide a more quantitative analysis, T was calculated based on information measured from the image sensor. g . Figure 14 (a) and (b) are based on the equivalent temperature T of the light source. sThe forms of the functions are shown respectively. Figure 12 The average luminance in (a) varies along the time axis during heating and cooling. This average luminance is Figure 12 (a) shows the average luminance within a rectangular window (40 pixels wide and 32 pixels high) that is always used to observe the gas. However, Figure 14 The average luminance refers to the difference in luminance between the illuminated area of ​​the gas and a typical location in the background area, which is equivalent to equation (6). Figure 10 In reality, due to the violent shaking of the gas, the average luminance (luminance difference) is calculated using a moving average over a period of 1.0 seconds.

[0155] CO2 initially appears bright as it heats up, but when T... s At 23.46℃, the luminance difference reverses from positive to negative, after which CO2 appears dimmer. The reversal of the luminance difference occurs at temperature T during cooling. s =23.20℃. As with visual observation, the gas temperature is calculated as T. g =23.33±0.13℃ (in the figure below, characteristic points representing gas temperature are depicted by ○ (circles)).

[0156] The average luminance always fluctuates by the same degree. Furthermore, there are sometimes instances where gas deformation causes the illuminated area to deviate from the set measurement window. For example, in... Figure 14 At the start of the measurement in (a) (left end), the observed image has a smaller brightness difference because the area of ​​gas illumination is slightly off-center from the rectangular window.

[0157] To address this, a more robust statistical metric was designed. Specifically, it focuses on the portion of the image without changes, thus obtaining a difference image along the temporal axis as part of the preprocessing. Figure 15 , 16 They respectively showed the targets for Figure 12 , Figure 13 The center difference image is obtained from the images of the previous and next frames of the image of interest.

[0158] Central difference image I m () is to compare the preceding and following frames I of the image of interest I0. -1 I +1 The brightness (luminance) of the image is averaged over each pixel and is calculated using the following formula. Hereinafter, the center difference image is sometimes referred to as the "difference image".

[0159] I m =(I -1 +I +1 ) / 2 I -1The brightness (luminance) of the pixels in the previous frame of the image I0 of interest. I +1 The brightness (luminance) of the pixels in the next frame of the image of interest, I0. exist Figure 15 , 16 In China, targeting not only including Figure 13 (a) shows a rectangular area (534 pixels horizontally × 448 pixels vertically) that includes the gas-illuminated area and the background area. The variance of the fluctuating value (luminance) was calculated as a statistical indicator of image complexity.

[0160] Figure 17 (a) and (b) are based on the equivalent temperature T of the light source. s The variance of the difference images (center difference images) during heating and cooling is shown as a function over time. This variance is calculated using a moving average over 1.0 s. It can be seen that, regardless of whether heating or cooling occurs, the initially drastically fluctuating images gradually become more homogenized, but then become complex again from a certain point. The moment of minimum variance represents the instant when the background region and the illuminated gas region become indistinguishable. The temperature at this point is T for heating. s =23.53℃, which becomes T under cooling conditions. s =23.12℃. Therefore, the gas temperature calculated from the variance of the image is T. g =23.33±0.21℃, which is the same as the average value obtained when using average luminance.

[0161] (Example 2) In Example 2, a method that does not require a special camera, different from that in Example 1, will be described.

[0162] The light source used, the method for measuring the light source temperature, the CO2 gas supply conditions, the nozzle used, and the temperature setting of the light source are the same as in Example 1. However, as Figure 18 As shown, a single-pixel InSb detector with a side length of 120 μm was used as the infrared detector. A bandpass filter with a wavelength range of [4.12 μm, 4.33 μm] was placed in front of the detector. A specific point in the gas-irradiated area was imaged onto the detector using an infrared lens with a focal length of 50 mm and an F-value of 2.5.

[0163] Figure 19 (a) and (b) show the temporal changes in the detection intensity of the gas-irradiated area during heating and cooling, respectively. However, the detection intensity is calculated using a moving average over 1.0 s. The equivalent temperature T of the light source was determined separately. sAnd the detection intensity obtained through the same optical system in the absence of gas. Here, in Figure 19 In the diagram, dashed lines depict the instantaneous detection intensity in the absence of gas. At the intersection of the detection intensity in the presence of gas (the gas-illuminated area) and the detection intensity in the absence of gas (the background area), T... g =T s Regarding the temperature at this intersection point, it is T under the condition of increasing temperature. g =23.51℃, which becomes T under cooling conditions. g =23.19℃. Thus, even with a single-pixel detector, the gas temperature T was successfully determined by reversing the detection intensity based on the presence or absence of gas. g =23.35±0.16℃.

[0164] In this example, the temperature of the same gas appears to have been calculated with high precision. However, according to... Figure 19 It can be seen that the motion curves in the absence of gas (background area) and the presence of gas (gas-illuminated area) are not significantly different, and the intersection angle is small, therefore the accuracy is not very high. Therefore, regarding... Figure 17 The same statistical indicators were also studied. Due to airflow tremors, the signal intensity in the illuminated area of ​​the gas fluctuates dramatically. However, the signal intensity difference itself decreases precisely at the moment of brightness reversal, so the signal intensity variation is also relatively small.

[0165] Figure 20 (a) and (b) illustrate the temporal changes of the AC component extracted by time-axis differentiation of the signal during heating and cooling, respectively. Regardless of heating or cooling, the AC component becomes very small at a certain point, indicating that the brightness of the background region and the illuminated gas region is reversed at this point.

[0166] To quantitatively evaluate this situation, for Figure 20 The variance of the differential signal was calculated for each point within a 1.0s interval. Figure 21 (a) and (b) plot the variances during heating and cooling, respectively. These plotted curves are... Figure 17 The indices with similar variances in the images shown correspond to noise densities. For example... Figure 21 As shown, the noise density is minimal at a certain instant, and the noise density at this instant is T under the condition of temperature rise. g =22.24℃, which becomes T under cooling conditions. g =23.34℃.

[0167] Thus, even when using a single-pixel detector, the gas temperature T was successfully determined based on the minimum limit of the change in detection intensity over time. g =22.79±0.55℃. (Based on...)Figure 19 The calculated results show a difference of 0.56°C between the two methods. Compared to the first embodiment, the second embodiment has lower determination accuracy, and the results obtained by the signal processing method exhibit a larger deviation. This demonstrates the usefulness of using an image sensor as a detector.

[0168] Here, we adopt Figure 18 The optical system, and according to such Figure 19 The method of determining gas temperature by reversing the detection intensity of the gas absorption spectrum relative to the background light from the light source is a previously known method for determining flame temperature (spectral reversal method). This spectral reversal method is described, for example, in Non-Patent Document 1. This method mainly involves mixing elements such as sodium (Na) as markers into the flame and observing the glow line wavelength in the visible light region caused by the marker element's flame color reaction. The spectral reversal method sometimes also observes the infrared emission spectra of CO2 and H2O contained in the flame, which is equivalent to... Figure 19 The situation shown is incorrect. However, the spectral inversion method does not take into account the situation described above. Figure 20 The method for determining temperature is based on the inversion point of statistically processed values ​​of intensity changes as shown.

[0169] Here, although examples of raising or lowering the equivalent temperature of the light source are shown in the embodiments described above, the gas temperature can be determined with greater accuracy by repeatedly measuring the equivalent temperature of the light source by changing it periodically.

[0170] Furthermore, although the above describes a scheme for detecting one gas, by using an array of bandpass filters with different center wavelengths, it is also possible to determine the concentration and temperature of multiple gases using the same optical system.

[0171] Furthermore, while most gases absorb light in the infrared domain, some also exhibit absorption in the ultraviolet, visible, and terahertz domains. In such cases, this disclosure can be directly applied as long as a light source or optical sensor with an absorption wavelength consistent with that of the gas of interest is used.

[0172] 〔Summarize〕 The method for measuring the temperature of gaseous substances involved in aspect 1 of this disclosure is based on the wavelength λ. A Methods for determining the temperature of a gaseous substance by means of light A absorption include: Provides a light source L capable of emitting light A by varying the light intensity. A And a light sensor S capable of receiving light A and measuring the intensity of the received light. A ; From the light source L A Emitted and received by the light sensor S A Along the ray path of the received light A, the light source L...A and the light sensor S A They are configured such that the gaseous substance is interposed between them; Measurement at the source L A The light sensor S emits light A in a manner that causes a change in light intensity. A The intensity of light received; By measuring the light intensity, the light source L is determined to be the one whose spatial and / or temporal fluctuation amplitude of the light intensity is minimized. A Light intensity I min ; The calculation is based on the ideal blackbody radiation for the light source L. A The emission spectrum was approximated, and the light intensity I was compared with that of the light intensity I. min Correspondingly, the light source L A Equivalent temperature T S ; The equivalent temperature T S The temperature of the gaseous substance.

[0173] In the method for measuring the temperature of gaseous substances disclosed herein based on aspect 2 of aspect 1, The optical sensor S A It is a pixel-type sensor with multiple light-receiving pixels.

[0174] In the method for measuring the temperature of gaseous substances disclosed herein based on aspect 3 of aspect 2, The plurality of light-receiving pixels are configured in a matrix.

[0175] In the method for measuring the temperature of gaseous substances disclosed herein, based on aspect 4 of any one of aspects 1 to 3, The imaging optical system displays the image of the gaseous substance on the light sensor S. A The light-receiving part is configured in a way that allows for imaging.

[0176] In the method for measuring the temperature of gaseous substances disclosed herein based on any one of aspects 1 to 4, aspect 5, According to the optical sensor S A The variance of the differential signal obtained by time-axis differentiation of the received light signal is used to calculate the tremor amplitude.

[0177] In the method for measuring the temperature of gaseous substances disclosed herein, based on any one of aspects 1 to 5, aspect 6, By selecting the light source L A The optical sensor S A and one or more of the bandpass filters, to draw from the light source L A Reaching the light sensor SA The wavelength range of light is limited to the vicinity of the wavelength range of light A. The bandwidth of the band is more than 0.25 times and less than 4 times the bandwidth of the gas absorption band spectrum of the gaseous substance.

[0178] In the method for measuring the temperature of gaseous substances disclosed herein, based on any one of aspects 1 to 6, aspect 7, The reflector is positioned on the light path.

[0179] In the method for measuring the temperature of gaseous substances disclosed herein, which is based on any one of aspects 1 to 7, The light source L A It is an infrared light source.

[0180] In the method for measuring the temperature of gaseous substances disclosed herein, based on any one of aspects 1 to 8, aspect 9, The gaseous substance includes one gas selected from methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), sulfur trioxide (SO3), water vapor (H2O), ammonia (NH3), sulfur hexafluoride (SF6), and Freon.

[0181] In the method for measuring the temperature of gaseous substances disclosed herein, based on any one of aspects 1 to 8, The light source L A It emits light that encompasses the absorption bandwidth of various gaseous substances. An array of bandpass filters, comprising multiple bandpass filters with different center wavelengths, is configured in the optical sensor S. A The front side of the light-receiving surface.

[0182] The temperature measuring device for gaseous substances disclosed in aspect 11 of this document is for measuring the temperature of a substance with wavelength λ. A An apparatus for measuring the temperature of a gaseous substance by means of light absorption A, comprising: A camera includes an image sensor, an imaging optical system, and a bandpass filter, wherein the image sensor includes multiple light sensors capable of receiving light A and measuring the intensity of the received light; A light source that emits light containing the wavelength λ A Light in the wavelength band; A variable light intensity device that can change the light intensity of the light source; Image processing apparatus; and The integrated control device controls both the variable light intensity device and the image processing device. The image processing device performs: Based on the signal output from the camera, the light intensity I of the light source is calculated when the measured light intensity exhibits minimal spatial and / or temporal fluctuation. min ; The emission spectrum of the light source is approximated based on ideal blackbody radiation to calculate the light intensity I of the light source. min Correspondingly, the equivalent temperature T of the light source S .

[0183] In the temperature measuring device for gaseous substances disclosed in aspect 12 of aspect 11, The signal output by the camera includes information representing the temporal variation in the intensity distribution of light passing through the gaseous object. The amplitude of the spatial tremor is calculated by the variance of a difference image (e.g., a center difference image), wherein the difference image is the difference between a plurality of images having a time difference.

[0184] The temperature measuring device for gaseous substances disclosed in aspect 13 of this document is for measuring the temperature of gaseous substances with wavelength λ. A An apparatus for measuring the temperature of a gaseous substance by means of light absorption A, comprising: A light-receiving device comprising a detection element, an imaging optical system, and a bandpass filter, wherein the detection element is equipped with a light sensor capable of receiving light A and measuring the intensity of the received light. A light source that emits light in the wavelength range including light A; A variable light intensity device that can change the light intensity of the light source; A signal processing device that performs signal processing on the light-receiving device; and The integrated control device controls both the variable light intensity device and the signal processing device. The signal processing device performs: Calculate the light intensity I of the light source when the measured light intensity fluctuates over time to an extremely small extent. min (t); The emission spectrum of the light source is approximated based on ideal blackbody radiation to calculate the light intensity I of the light source. min (t) Corresponding to the equivalent temperature T of the light source S .

[0185] In the temperature measuring device for gaseous substances disclosed in aspect 14 of aspect 13, The AC component extracted by time-axis differentiation of the light-receiving signal output by the light-receiving device is used as the temporal jitter amplitude.

[0186] <Industry availability> This disclosure enables the convenient measurement of the temperature of gaseous substances located at a distance. Furthermore, the gaseous temperature measurement method disclosed herein not only allows for point-to-point measurement but also features a small and easily portable device, making it convenient to set up and use in various locations. In addition, it allows for real-time measurement.

[0187] The measurement of gaseous substances is in high demand in various aspects, including environmental protection such as mitigating urban heat islands, combustion gas management, factory exhaust gas management, and gas hazard management, whether for civilian or industrial use. Therefore, this disclosure is believed to have a significant driving force on society and a substantial impact on industry.

[0188] <Explanation of Figure Markers> 11: Light source 12: Variable light intensity device 13: Integrated Control Device 14: Light receiving device 15: Camera (Infrared Camera) 16: Light sensor (infrared imaging element, infrared detector) 17: Lens (Infrared Lens) 18: Bandpass filter 19: Image processing device 20: Signal processing device 21: Gas (gas-like substance) 101: Temperature Measurement System 102: Temperature Measurement System

Claims

1. A method for measuring the temperature of a gaseous substance, wherein the wavelength λ is... A Methods for determining the temperature of a gaseous substance by means of light A absorption include: Provides a light source L capable of emitting light A by varying the light intensity. A And a light sensor S capable of receiving light A and measuring the intensity of the received light. A ; From the light source L A Emitted and received by the light sensor S A Along the ray path of the received light A, the light source L... A and the light sensor S A They are configured such that the gaseous substance is interposed between them; Measurement at the source L A The light sensor S emits light A in a manner that causes a change in light intensity. A The intensity of light received; By measuring the light intensity, the light source L is determined to be the one whose spatial and / or temporal fluctuation amplitude of the light intensity is minimized. A Light intensity I min ; The calculation is based on the ideal blackbody radiation for the light source L. A The emission spectrum was approximated, and the light intensity I was compared with that of the light intensity I. min Correspondingly, the light source L A Equivalent temperature T S ; The equivalent temperature T S The temperature of the gaseous substance.

2. The method for measuring the temperature of a gaseous substance according to claim 1, wherein, The optical sensor S A It is a pixel-type sensor with multiple light-receiving pixels.

3. The method for measuring the temperature of a gaseous substance according to claim 2, wherein, The plurality of light-receiving pixels are configured in a matrix.

4. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 3, wherein, The imaging optical system displays the image of the gaseous substance on the light sensor S. A The light-receiving part is configured in a way that allows for imaging.

5. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 4, wherein, According to the optical sensor S A The variance of the differential signal obtained by time-axis differentiation of the received light signal is used to calculate the tremor amplitude.

6. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 5, wherein, By selecting the light source L A The optical sensor S A and one or more of the bandpass filters, to draw from the light source L A Reaching the light sensor S A The wavelength range of light is limited to the vicinity of the wavelength range of light A. The bandwidth of the band is more than 0.25 times and less than 4 times the bandwidth of the gas absorption band spectrum of the gaseous substance.

7. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 6, wherein, The reflector is positioned on the light path.

8. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 7, wherein, The light source L A It is an infrared light source.

9. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 8, wherein, The gaseous substance includes one gas selected from methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), sulfur trioxide (SO3), water vapor (H2O), ammonia (NH3), sulfur hexafluoride (SF6), and Freon.

10. The method for measuring the temperature of a gaseous substance according to any one of claims 1 to 8, wherein, The light source L A It emits light that encompasses the absorption bandwidth of various gaseous substances. An array of bandpass filters, comprising multiple bandpass filters with different center wavelengths, is configured in the optical sensor S. A The front side of the light-receiving surface.

11. A temperature measuring device for a gaseous substance, which measures the temperature of a substance with a wavelength λ. A An apparatus for measuring the temperature of a gaseous substance by means of light absorption A, comprising: A camera includes an image sensor, an imaging optical system, and a bandpass filter, wherein the image sensor includes multiple light sensors capable of receiving light A and measuring the intensity of the received light; A light source that emits light containing the wavelength λ A Light in the wavelength band; A variable light intensity device that can change the light intensity of the light source; Image processing device; as well as The integrated control device controls both the variable light intensity device and the image processing device. The image processing device performs: Based on the signal output from the camera, the light intensity I of the light source is calculated when the measured light intensity exhibits minimal spatial and / or temporal fluctuation. min ; The emission spectrum of the light source is approximated based on ideal blackbody radiation to calculate the light intensity I of the light source. min Correspondingly, the equivalent temperature T of the light source S .

12. The temperature measuring device for a gaseous substance according to claim 11, wherein, The signal output by the camera includes information representing the temporal variation in the intensity distribution of light passing through the gaseous object. The amplitude of the spatial tremor is calculated by the variance of a difference image, wherein the difference image is the difference between multiple images having a time difference.

13. A temperature measuring device for a gaseous substance, which measures the temperature of a substance with a wavelength λ. A An apparatus for measuring the temperature of a gaseous substance by means of light absorption A, comprising: A light-receiving device comprising a detection element, an imaging optical system, and a bandpass filter, wherein the detection element is equipped with a light sensor capable of receiving light A and measuring the intensity of the received light. A light source that emits light in the wavelength range including light A; A variable light intensity device that can change the light intensity of the light source; A signal processing device that performs signal processing on the light receiving device; as well as The integrated control device controls both the variable light intensity device and the signal processing device. The signal processing device performs: Calculate the light intensity I of the light source when the measured light intensity fluctuates over time to an extremely small extent. min (t); The emission spectrum of the light source is approximated based on ideal blackbody radiation to calculate the light intensity I of the light source. min (t) Corresponding to the equivalent temperature T of the light source S .

14. The temperature measuring device for a gaseous substance according to claim 13, wherein, The AC component extracted by time-axis differentiation of the light-receiving signal output by the light-receiving device is used as the temporal jitter amplitude.

Images