JP3302208B2 - Infrared analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared analyzer for analyzing a sample using an optical filter that reflects light such as an interference filter or a cut-on filter, and more particularly to an infrared analyzer that reflects not only light transmitted through a filter but also reflected light. The present invention relates to an infrared spectrometer capable of analyzing a plurality of samples by utilizing the same.

[0002]

2. Description of the Related Art As an example of a conventional infrared analyzer for analyzing a gas sample having an absorption band in an infrared region, the one shown in FIG. 11 is known. That is, two measurement cells 21
a and 21b are arranged so that the reference gas R and the sample gas S are alternately introduced by the flow path switching device 22, and one of the measuring cells is provided with the infrared ray generating devices 24a and 24b and the light sources 23a and 23b on the other. Are arranged such that detectors (for example, microphone condensers) 25a and 25b are arranged, signals obtained by these detectors are amplified and displayed on an indicator 26. In this case, two measurement cells 21a, 2
The reason why the reference gas R and the sample gas S are alternately introduced using 1b is to cancel errors based on the characteristics of each component (luminance of light source, contamination state of measurement cell, temperature difference) and perform accurate measurement. is there.

When an infrared spectrometer projects infrared light onto a measurement cell, a filter that transmits infrared light having a wavelength in a specific infrared region and cuts off others is often used according to the sample. In this case, the interference filter is important. The interference filter is formed of a multilayer film that transmits a desired wavelength band and reflects the other wavelength region by utilizing the interference effect of light, and includes Si, Ge, SiO ₂ , and Al. _A plurality of thin films of Ge, SiO, ZnS, etc. are coated on both surfaces of a filter substrate such as ₂ O ₃ . This filter has the same configuration on both sides, for example, when a bandpass filter surface is provided on both sides, and when different films are formed on each surface, for example, a bandpass surface and an SLC (short long cut) surface. In some cases.

[0004]

The interference filter usually uses only the desired seven transmitted lights, and the reflected light is rarely used effectively as a cut-off area. Further, in an optical system using reflection, the surface on the reflection side is not distinguished, and a bandpass surface may be used and an SLC surface may be used in some cases. However, the interference filter can selectively operate the transmission and reflection of infrared light in a specific wavelength range, so if any wavelength range can be used effectively, the analyzer can be simplified and multiple samples can be measured simultaneously. Becomes The present invention has been made in view of such a problem, and an object of the present invention is to provide an infrared spectrometer capable of simultaneously analyzing a plurality of samples by effectively using not only transmitted light but also reflected light. I do.

[0005]

According to the present invention, there is provided an infrared analyzer for analyzing a plurality of samples having a light source, one or more measuring cells, and a plurality of detectors. Wherein an optical filter is inclined between the light source and the measurement cell and / or between the measurement cell and the detector, and the optical filter has a thin-film configuration in which both surfaces of a filter substrate are different. The film configuration on the side surface has a film configuration that more selectively transmits the infrared wavelength region corresponding to the sample to which the detector is sensitive in the direction in which the transmitted infrared light passes, than the film configuration on the other surface. Yes,
Infrared light having a wavelength range absorbed by one sample is incident on one sample analysis detector in a direction in which the infrared light transmitted through the optical filter passes, and infrared light having a wavelength range absorbed by another sample is emitted. The infrared ray reflected on the surface of the optical filter is incident on another sample analysis detector in a direction in which the infrared ray passes.

[0006]

If an infrared analyzer is used as the above means, part of the infrared light projected from the infrared light source passes through the measuring cell and then passes through the filter to enter the detector, and the rest reflects and enters the detector. Alternatively, part of the infrared light projected from the infrared light source passes through the filter, passes through the measuring cell, and enters the detector,
The rest reflects and passes through the measuring cell or directly into the detector. In this case, the infrared ray transmitted through the filter has a wavelength range where it is absorbed by the sample to be analyzed, and the infrared ray reflected on the filter surface has a wavelength range where it is absorbed by another sample to be analyzed. If the filter is designed as described above, it is possible to measure a plurality of samples simultaneously with one infrared light source.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the state of reflection and transmission of light (infrared light) when the interference filter 1 used in the infrared analyzer of the present invention is inclined. In this example, a filter having a band pass surface and an SLC (short long cut) surface will be described. This is a short cut that reflects the shorter wavelength side than the specific wavelength and reflects the longer wavelength side than the specific wavelength to prevent the infrared radiation of the cyber band from being generated in the bandpass filter that reflects the infrared wavelength other than the specific wavelength. This is a filter that can be greatly reduced by a combination with a long cut. Although the bandpass surface 1a is used as a reflection surface, when the film configurations of both surfaces are different as described above, it is theoretically possible to compare the reflectances when the bandpass surface 1a is used as the reflection surface and when the SLC surface 1b is used as the reflection surface. Although there is no difference in the reflectance depending on the placement, a considerable difference is actually observed.

FIG. 2 is a reflectance spectrum of a NO bandpass filter when measuring nitrogen oxides (NO).
In this figure, looking at the reflectance of 5.8 microns, a high reflectance is obtained when measured from the bandpass surface 1a having a high reflectance, whereas a low reflectance is obtained when measured from the SLC surface 1b having a low reflectance. Has been obtained. The reason for this is
This is because in the actual optical system, only a part of the sequentially reflected light rays is collected, and there is a difference in light dissipation due to scattering or the like between the bandpass surface 1a and the SLC surface 1b. Also, SLC surface 1
In the case of reflection by b, the waveform is missing even in the entire reflection spectrum. Therefore, when using the reflected light, it is clear that using the bandpass surface 1a as the reflecting surface leads to improvement in sensitivity and accuracy and stability.

Next, an embodiment of an infrared spectrometer using transmitted light and reflected light of infrared light using an interference filter will be described. FIG. 3 shows an embodiment of an infrared spectrometer for measuring nitrogen oxides (NO) and sulfur dioxide (SO ₂ ) using the interference filter 1. The sample gas in which NO and SO ₂ are mixed is introduced from an inlet 2a provided in the measurement cell 2, and discharged from an outlet 2b after measurement. One of the measurement cells 2 is provided with an infrared light source 3 and the other is provided with a filter chamber 4.
Is arranged. The filter chamber 4 has an interference filter 1
Is installed at an angle, and a nitrogen oxide (NO) detector 5 is disposed in a direction in which the infrared light transmitted through the interference filter 1 in the filter chamber 4 passes, and the infrared light reflected on the surface of the interference filter 1 is Sulfur dioxide (SO
₂ ) The detector 6 is arranged. Further, a cut-on filter 7 for SO ₂ is provided on the front surface of the SO ₂ detector 6.

In the infrared spectrometer having the above configuration, a part of the wavelength of the infrared light emitted from the infrared light source 3 is absorbed by nitrogen oxide (NO) and sulfur dioxide (SO ₂ ) in the measuring cell 2. You. And the infrared light that has passed through the measurement cell 2 is partially the interference filter 1 enters the NO detector 5 passes through, the remainder enters the SO ₂ detector 6 passes through the cut-on filter 7 for SO ₂ is reflected. In this case, the infrared light transmitted through the interference filter 1 has a wavelength region where it is absorbed by NO, and the infrared light reflected on the surface of the interference filter 1 has a wavelength region where it is absorbed by SO _2. If the filter 1 is designed, it is possible to measure two gas samples simultaneously with one infrared light source 3.

FIG. 4 shows an example in which nitrogen oxide (NO), sulfur dioxide (SO ₂ ) and carbon dioxide (C
It is an example of an infrared analyzer for measuring O ₂ ). In this embodiment, an interference filter (4.6) is provided before the infrared light source 3.
A filter chamber 9 in which a μ cut-on filter 8 is installed in an oblique direction is arranged, and a measurement cell 2 ′ is arranged in a direction in which the infrared light transmitted through the 4.6 μ cut-on filter 8 in the filter chamber 9 passes. .6μ cut-on filter 8 surface reflected infrared to the passage direction measurement cell 2 "and carbon dioxide were (CO ₂₎ detector 10 is arranged. Moreover, the front of the carbon dioxide gas (CO ₂₎ detector 10 Is provided with a CO ₂ band-pass filter 11. The measurement cell 2 '
And the measurement cell 2 ″ are connected to each other by the pipe line 12 and the sample gas (N
O, SO ₂ , CO _2, etc.) are discharged from a discharge port 2′b provided in another measurement cell 2 ′.
Further, a filter chamber 4 in which the interference filter 1 is installed in an oblique direction is arranged in the measuring cell 2 ′ which is arranged in the transmission direction of the infrared light of the 4.6 μ cut-on filter 8. A nitrogen oxide (NO) detector 5 is disposed in the direction in which the infrared rays reflected from the surface of the interference filter 1 pass.
₂ ) The detector 6 is arranged. Further, a cut-on filter 7 for SO ₂ is installed on the front surface of the SO ₂ detector 6.

In the infrared analyzer having the above-described configuration, a part of the infrared light emitted from the infrared light source 3 passes through the 4.6 μ cut-on filter 8 and the measurement cell 2 ′.
And the rest is reflected on the surface of the 4.6 μ cut-on filter 8 and projected to the measurement cell 2 ″, and a part is absorbed by the CO ₂ gas and transmitted through the CO ₂ band-pass filter 11, and the carbon dioxide gas (CO 2 ₂ ) Entering the detector 10. A part of the infrared light that passes through the 4.6 μ cut-on filter 8 and passes through the measuring cell 2 ′ is part of nitrogen oxide (NO) and sulfur dioxide (SO ₂ ) in the measuring cell 2 ′. Further, a part of the infrared light that has passed through the measuring cell 2 ′ passes through the interference filter 1 and enters the NO detector 5, and the rest reflects and passes through the SO ₂ cut-on filter 7. Enter the SO ₂ detector 6.
In this embodiment, the wavelength range in which the infrared light transmitted through the 4.6 μ cut-on filter 8 is absorbed by NO and SO ₂ , and the infrared light reflected on the surface of the 4.6 μ cut-on filter 8 is absorbed by CO ₂ So that the infrared light transmitted through the interference filter 1 has a wavelength range where it is absorbed by NO, and the infrared light reflected on the surface (bandpass surface) of the interference filter 1 has a wavelength range where it is absorbed by SO _2. If the 4.6 μ cut-on filter 8 and the interference filter 1 are designed, three types of gas samples can be measured simultaneously by one infrared light source 3.

Next, in the embodiment shown in FIG.
FIGS. 5 to 10 show data of actually measured values of the relationship (wavelength characteristic) between the wavelength of the infrared ray transmitted or reflected by the cut-on filter 8 and the interference filter 1 and the transmittance, respectively. However, in this case, the relationship between the wavelength band of the transmitted or reflected infrared ray and the transmittance is shown without considering the absorption of the infrared ray by NO, SO ₂ , CO ₂ or the like. (1) FIG. 5 shows the transmittance of infrared light having a wavelength transmitted through the 4.6 μ cut-on filter 8. According to this figure 4.6
Infrared rays having a wavelength of μ or less are cut off, and 90% or more of infrared rays having a wavelength of 4.6 μ or more are transmitted. (2) FIG. 6 shows the relationship between the wavelength and the transmittance of the infrared light transmitted through the 4.6 μ cut-on filter 8 and further transmitted through the interference filter 1. According to this figure, most of the infrared rays between 5 μ and 6 μ transmitted through the 4.6 μ cut-on filter 8 are transmitted. (3) FIG. 7 shows the relationship between the wavelength of the infrared light transmitted through the 4.6 μ cut-on filter 8 and further reflected by the interference filter 1 and the transmittance. This figure has a front and back relationship with FIG. 6, and infrared rays other than wavelengths between 5 μm and 6 μm are reflected by the interference filter 1. (4) FIG. 8 shows the transmittance of infrared light having a wavelength transmitted through the cut-on filter for SO ₂ (6 μ cut-on filter) 8. Therefore, according to this figure, even the infrared rays reflected by the interference filter 1 are cut off the infrared rays having a wavelength of 6 μm or less. (5) FIG. 9 shows the relationship between the wavelength of infrared light reflected on the surface of the 4.6 μ cut-on filter 8 and the transmittance. According to this figure, infrared rays having a wavelength of 4.6 μ or less are almost reflected. (6) FIG. 10 shows the bandpass filter 11 for CO ₂ among the infrared rays reflected on the surface of the 4.6 μ cut-on filter 8.
Shows the relationship between the infrared ray having a wavelength that transmits light and the transmittance. This figure shows that most of the infrared light having a wavelength of 4.2 μm to 4.3 μm is transmitted.

In the above embodiment of the present invention, the interference filter is installed at an angle, and the interference filter is provided with a half mirror.
That is, an apparatus for measuring a plurality of samples using a single light source using a bandpass surface as a reflection surface has been described. However, the present invention is not limited to an interference filter, but a cut surface of a cut-on filter and an anti-reflection coating surface ( Anti Refrection,
The same measurement can be performed using the cut-on surface as the reflection surface.

[0015]

As described above in detail, according to the infrared spectrometer of the present invention, it is possible to analyze a plurality of samples by one light source using not only the transmitted light of the interference filter but also the reflected light. Becomes In addition, by using the band pass surface of the interference filter as the reflection surface, the sensitivity and accuracy of the waveform without omission are improved, and the indicated value at the time of measurement can be stabilized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of reflection and transmission of light (infrared rays) when an interference filter used in an infrared spectrometer of the present invention is inclined.

FIG. 2 is a diagram showing a reflectance spectrum of a NO bandpass filter when measuring nitrogen oxides (NO).

FIG. 3 shows nitrogen oxides (NO) using an interference filter;
It illustrates an embodiment of an infrared analyzer for measuring sulfur dioxide (SO _2).

FIG. 4 is a diagram showing an embodiment of an infrared analyzer for measuring nitrogen oxide (NO), sulfur dioxide (SO ₂ ), and carbon dioxide (CO ₂ ) using an interference filter.

FIG. 5 is a diagram showing the transmittance of infrared light having a wavelength transmitted through a 4.6 μ cut-on filter.

FIG. 6 is a diagram showing the relationship between the wavelength and the transmittance of infrared light transmitted through a 4.6 μ cut-on filter and further transmitted through an interference filter.

FIG. 7 is a diagram showing a relationship between a wavelength of infrared rays transmitted through a 4.6 μ cut-on filter and further reflected by an interference filter and transmittance.

FIG. 8 is a diagram showing the transmittance of infrared light having a wavelength transmitted through a cut-on filter for SO ₂ (6 μ cut-on filter).

FIG. 9 is a diagram showing the relationship between the wavelength of infrared light reflected on the surface of the 4.6 μ cut-on filter and the transmittance.

FIG. 10 is a diagram showing a relationship between infrared rays having a wavelength that passes through a CO ₂ band-pass filter among infrared rays reflected on the surface of a 4.6 μ cut-on filter and transmittance.

FIG. 11 is a schematic diagram of a configuration of a conventional infrared analyzer.

[Explanation of symbols]

1 interference filter 1a bandpass surface 1b SLC surfaces 2,2 ', 2 "measuring cell 3 cut-on filter for the light source 5 NO detectors 6 SO ₂ detector 7 SO ₂ (6 [mu cut-on filter) 8 4.6μ cut-on filter 10 CO ₂ detector 11 Band pass filter for CO ₂

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Fujiwara 2 Higashi-cho, Kichijoin-gu, Minami-ku, Kyoto, Kyoto Prefecture (56) Reference: JP-A-5-122710 (JP, A) 2-284045 (JP, A) JP-A-2-240546 (JP, A) JP-A-53-140044 (JP, A) JP-A-53-122469 (JP, A) JP-A-4-78544 (JP, A) U) JP-A 3-48705 (JP, U) JP-A 5-79502 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/00-21/61 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (1)

(57) [Claims] 1. An infrared analyzer for analyzing a plurality of samples having a light source, one or more measurement cells, and a plurality of detectors, wherein the infrared light is between the light source and the measurement cells and / or the measurement cells and the detection. The optical filter is installed between the chambers at an angle, and the optical filter has a thin film configuration in which both surfaces of the filter substrate are different, and the film configuration on the light source side is more infrared light transmitting than the film configuration on the other surface. Is a film configuration that more selectively transmits an infrared wavelength region corresponding to a sample to which a detector in the direction in which the light passes passes, and infrared light having a wavelength region that is absorbed by one sample passes through the optical filter. The infrared light having a wavelength range that is incident on one sample analysis detector in the direction in which the transmitted infrared light passes and is absorbed by another sample is reflected in the direction in which the infrared light reflected on the surface of the optical filter passes. Infrared analyzer, characterized in that entering the other sample analysis detector.