JPH09257582A - Optical measuring method and optical measuring aid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring the light in the condition that S/N ratio is high and that the influence of the heat to a light detecting unit is small. SOLUTION: In this method for measuring the light, the light to be detected, which is generated from a subject 2 to be checked in the high temperature condition side of a combustion chamber and which has a specified detecting wave length, is led to a light detecting unit 3 for measurement through a wave lenght selecting unit 10 for selectively transmitting the light. In this case, a selective reflecting mirror 7 for reflecting the light to be detected, which is generated from the subject 2 to be checked, to as wave length selecting unit side is deranged on an optical path extended from the subject 2 to be checked to the wave length selecting unit 10, and the light to be detected is led to the light detecting unit 3 for measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which light to be detected having a specific detection wavelength, which is generated from an object in a combustion chamber at a high temperature, is transmitted through a wavelength selector which selectively transmits the light to be detected. The present invention relates to an optical measurement method that guides to a detector to perform measurement, and relates to an optical measurement auxiliary tool that can be used in such an optical measurement method.

[0002]

2. Description of the Related Art A conventional technique of such a measuring method will be described below by taking a flame observation in a high temperature furnace as an example. When light with a specific wavelength (this wavelength is called a specific detection wavelength) is selectively detected from inside the high-temperature furnace, the radiation emitted from the high-temperature body inside the furnace causes the noise for this detection target light. . Therefore, conventionally, a selective transmission filter or the like as a wavelength selector is arranged in front of the photodetector to perform optical measurement. There are various types of light measurement, such as those that try to measure the specific wavelength component of spontaneous emission from the flame, those that measure the fluorescence emitted from the flame by irradiating the flame with laser light. Are known. Here, when trying to capture spontaneous emission, radiant light in the ultraviolet, visible, and infrared regions becomes a noise component, and when trying to capture scattered light accompanying laser light irradiation, The natural light emission of becomes noise. Therefore, when measuring
It is necessary to satisfactorily remove such noise.

[0003]

However, in the selective transmission filter or the like which has been adopted in the conventional method, the shielding property against the noise component is often not perfect, so that spontaneous emission as noise, high temperature red heat is generated. If the influence of radiation from the furnace in the state is large, S
There has been a problem that (signal intensity of light to be detected) / N (signal intensity of components other than the light to be detected) is lowered, and detection sensitivity is lowered. Further, when the photodetector is not heat-resistant, there is a problem that the detector is susceptible to radiant heat from the high temperature body in the furnace and is likely to fail.

Therefore, an object of the present invention is to obtain an optical measurement method capable of performing optical measurement in a state where the S / N ratio is high and the influence of heat on the photodetector is small, and it is possible to use it in such a method. To get a light measurement auxiliary tool.

[Means for Solving the Problems]

[Structure] Detection target light of a specific detection wavelength generated from a subject in a high temperature state in the combustion chamber according to the present invention for achieving the above object, a wavelength selector that selectively transmits the detection target light. The characteristic means of the light measurement method of guiding the light to the photodetector via the light detector is as follows. That is, a selective reflection mirror that reflects the detection target light from the subject to the wavelength selector side is arranged on the optical path from the subject to the wavelength selector, and the detection target light is guided to the photodetector to perform measurement. Of. [Operation] In this configuration, the light generated from the subject is sent to the selective reflection mirror, and the detection target light of the specific detection wavelength is reflected to the wavelength selector side by this mirror. on the other hand,
Light other than the specific detection wavelength, which is a noise component, passes through the selective reflection mirror and does not go to the wavelength selector side. And in the wavelength selector, due to its wavelength selection characteristics,
The detection target light required for measurement is selected and sent to the photodetector. Therefore, the optical measurement can be performed in a state in which the S / N ratio is remarkably improved as compared with the conventional configuration including the transmission type wavelength selector. Furthermore, the radiation that causes heating in the photodetector (for example, the radiation from the furnace wall that constitutes the combustion chamber in the red heat state) can be sent as a noise component to the transmission lower side of the selective reflection mirror. Also, the inconvenience such as the photodetector being heated and causing a failure does not occur. Now, in contrast to such a configuration, it is possible to provide a plurality of wavelength selectors instead of the combination of the selective reflection mirror and the wavelength selector, but in this case, the attenuation of the detection target light is large. Too much. For example, in the selective reflection mirror, the light to be detected is reflected up to about 99% and can be sent to the wavelength selector without being attenuated, but in the case of the wavelength selector, this attenuation degree is relatively large. Therefore, the configuration of the present application is significantly superior. [Structure] In the above method, it is preferable that the subject is a flame formed in a high temperature furnace. [Operation] In a high-temperature furnace, the inner wall of the furnace is generally in a high-temperature, red-hot state, and a large amount of radiation is naturally generated from this wall. However, there is a great demand to satisfactorily understand the flame condition in the furnace. In such a case, for example, if the detection target light near the wavelength of 308 nm is captured separately from the radiant light, the state of the flame in the furnace can be captured well. When the characteristic means of the present application described above is adopted for the measurement, the flame state in the furnace can be measured with a high S / N ratio without applying a large heating load to the photodetector. it can. [Configuration] Furthermore, in the above method, it is preferable that the detection target light of the specific detection wavelength is light emitted from the subject by irradiating the subject with laser light. [Function] Irradiating a subject such as a flame with a laser beam and detecting the induced fluorescence generated from the subject to see the distribution of a specific component in the flame and estimate the temperature distribution. In this case, increasing the S / N ratio is an essential requirement, but depending on the flame, the surrounding environment of the flame, etc., it has been difficult to realize in the past. However, in the present application, a very useful laser measurement method can be made more convenient by a simple operation of inserting the selective reflection mirror into the measurement system. [Structure] The characteristic structure of the optical measurement auxiliary tool for achieving the above object is as follows. That is, this is provided with a light entrance portion into which light is introduced and a light exit portion from which detection target light of a specific detection wavelength is led out, and on the detection target light optical path between the light entrance portion and the light exit portion. In the, from the light incident portion side, a selective reflection mirror that reflects the detection target light from the light incident portion to the light output portion side, and a wavelength selector that selectively transmits the detection target light, comprising in order of description. Is configured. [Operation] This optical measurement auxiliary tool is configured to include, from the light entrance side, a light entrance part, a selective reflection mirror, a wavelength selector, and a light exit part in the optical path of the light to be detected. In use, the light exit portion is opposed to the detection light introduction portion of the photodetector, and the light entrance portion is opposed to the light-emitting detection object, and is used. The light incident from the light incident part is separated into detection target light and other light (noise component) by the selective reflection mirror, and the detection target light is guided to the wavelength selector and the light output part and introduced to the photodetector. And is used for optical measurement. Therefore, the same action and effect as described in the description of the above method can be exhibited. Furthermore, in this optical measurement auxiliary tool, since it is integrally configured,
It is possible to maintain good optical performance and to use it in a convenient state.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description, an example will be described in which the state of the flame 2 formed in the heating furnace 1 which is the subject is observed by the spectrum analyzer 3 which is a photodetector, and the flame spectrum in the furnace is measured. in this case,
The space inside the heating furnace corresponds to the space inside the combustion chamber. FIG.
Shows a device configuration in a state in which observation is performed using the optical measurement method of the present application, and FIG. 5 shows a conventional device configuration with which this can be compared. In the heating furnace 1 equipped with the burner 4, the flame 2 is formed by the burner 4. In the figure, the flame 2 is schematically shown by a broken line, but actually, in the heating furnace 1 in a high temperature state, the flame 2 is visually observed due to the relationship with the red heat and the like on the inner wall surface 5. It is almost impossible to (identify). Now, the heating furnace 1 is provided with an observation window 6 for observation, and light is emitted from this window 6. Then, when the method of the present application is adopted, the selective reflection mirror 7 is arranged in such a manner that it intersects the observation window 6 at an angle of about 45 degrees. That is, the selective reflection mirror 7 is arranged so as to be oblique to the light 8 traveling straight from the observation window 6 to the left side in FIG.
1 is orthogonal to the path of the light 8 in FIG.
It is supposed to face up and down. On the other hand, this mirror 7
The light passing through passes through the mirror 7 and goes straight. That is, the optical path of transmitted light is different from the optical path of reflected light, and the optical path of incident light and the optical path of reflected light to the selective reflection mirror 7 are also different. On the lower side of the reflection path 9, a selective transmission filter 1 as a wavelength selector is provided.
0 and the spectrum analyzer 3 are provided in the order described. Therefore, the detection target light of the specific detection wavelength, which is the detection target and is reflected by the selective reflection mirror 7, is introduced into the photodetector.

The characteristics of each of the concretely used devices will be described below. The selective reflection mirror 7 has a center wavelength of 308 nm, a half width of 20 nm, and a reflectance of 99%. The selective transmission filter 10 has a center wavelength of 308 nm and a half width of 10 nm. The flame spectrum was determined. Therefore, this case corresponds mainly to the case where it is desired to obtain spectral information near the wavelength of 308 nm, and the information near this wavelength avoids radiation from the furnace wall, sunlight, fluorescence of indoor fluorescent tubes, and the like. Become a thing,
It can well represent information about flames. The results are shown in FIG. In FIG. 2, the horizontal axis represents wavelength and the vertical axis represents optical signal intensity at each wavelength. As a result, center wavelength 30
It can be seen that only the signal in the vicinity of 8 nm is satisfactorily detected.

The above is the result of the optical measurement using the method of the present invention. For comparison with the above result, the optical measurement was also performed in the conventional method. The apparatus system in this example is shown in FIG. 5, and the obtained signal spectrum is shown in FIG. Corresponding devices are shown in FIG. 5 by the same drawing numbers as in FIG. In this case, of course, in the direction orthogonal to the observation window 6,
A selective transmission filter 10 and a spectrum analyzer 3 are provided. In comparison with FIG. 2, the result of FIG. 6 shows that the conventional method satisfactorily captures the signal in the vicinity of 308 nm to be detected, but contains a relatively large amount of signal components of 350 nm or more. There is. Therefore, comparing the result of FIG. 2 with the result of FIG. 6, the former is remarkably superior.

The above is the embodiment of the present application, but in the case of performing the optical measurement in such a form, it is preferable to use the optical measurement auxiliary tool 50 as shown in FIG. The light measurement assisting tool 50 includes a light entering section 5 into which light is introduced.
1 and the light output part 5 from which the detection target light of the specific detection wavelength is derived.
2 and a selective reflection mirror for reflecting the detection target light from the light incident portion 51 to the light emission portion side on the detection target light optical path 53 between the light incident portion 51 and the light emission portion 52. 55 and a wavelength selector 56 that selectively transmits light to be detected are provided in the order described. Therefore, it is possible to easily use the light incident section 51 toward the observation window 6 and the light emitting section 52 toward the photodetector. Also in this case, the optical path of the incident light to the selective reflection mirror 55 is different from the optical path of the light transmitted through the mirror 55 and the optical path of the detection target light reflected by the mirror 55.

Another Embodiment Another embodiment of the present application will be described below. (A) In the above embodiment, an example in which a spectrum analyzer is used as the photodetector has been shown, but this may be any as long as it detects light as a detection target.
Other than the above, a CCD camera, a semiconductor photosensor, a photoelectric tube, or the like may be used. (B) In the above embodiment, the case where the flame in the furnace is targeted was shown, but the subject is a flame in a closed space such as a boiler, a turbine combustor, or an engine. May be. That is, the method of the present application can be suitably applied to the case where the flame formed in the combustion chamber, which is a so-called closed space covered by the wall surface or the like, is measured by the optical measurement method. (C) In the above-described embodiment, the flame in the furnace was observed as it was as the subject, but it does not matter how the detection target light is generated. Therefore, in addition to observation of spontaneous emission,
Even when optical measurement is performed using F, CARS, Raman scattering, Rayleigh scattering, PIV method, or the like, the method of the present application can be preferably adopted. (D) In the above embodiment, the selective reflection mirror 7
However, as shown in FIG. 4, it is also preferable to provide a plurality of them on the optical path of the detection target light to apply the present invention. In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a flame spectrum is measured using the optical measurement method of the present application.

FIG. 2 is a diagram showing a flame spectrum obtained by the method of the present application.

FIG. 3 is a diagram showing a configuration of an optical measurement auxiliary tool of the present application.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram showing a state in which a flame spectrum is measured using a conventional optical measurement method.

FIG. 6 is a diagram showing a flame spectrum obtained by a conventional method.

[Explanation of symbols]

 2 subject 3 photodetector 7 selective reflection mirror 10 wavelength selector 51 light input part 52 light output part 55 selective reflection mirror 56 wavelength selector

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hideki Okamoto Osaka Gas Co., Ltd. 4-1-2, Hirano-cho, Chuo-ku, Osaka

Claims (4)

[Claims] 1. A subject (2) in a combustion chamber in a high temperature state
An optical measurement method of guiding the detection target light of a specific detection wavelength generated from the photodetector (3) through a wavelength selector (10) that selectively transmits the detection target light, and measuring the light.
A selective reflection mirror (7) that reflects the detection target light from the subject (2) to the wavelength selector side is arranged on the optical path from the subject (2) to the wavelength selector (10). Then, the optical measurement method of guiding the detection target light to the photodetector (3) and measuring the same. 2. The optical measurement method according to claim 1, wherein the subject is a flame formed in a furnace. 3. The optical measurement according to claim 1, wherein the detection target light of the specific detection wavelength is light emitted from the subject (2) by irradiating the subject (2) with a laser beam. Method. 4. A light entrance part (51) into which light is introduced and a light exit part (52) from which detection target light of a specific detection wavelength is led out, and the light entrance part (51) and the light exit part (52). 52) and a selective reflection mirror (55) that reflects the detection target light from the light incident part (51) from the light incident part side to the light output part side on the detection target light optical path between the light reflection part and the light reflection part. An optical measurement assisting tool, comprising: a wavelength selector (56) that selectively transmits light to be detected.