JPH08184558A - Infrared analyzer - Google Patents

Abstract

PURPOSE: To obtain an infrared analyzer in which a plurality of samples can be analyzed simultaneously by utilizing the reflected light, as well as the transmitted light, effectively. CONSTITUTION: An optical filter 1 transmitting a part of infrared rays projected from an infrared light source 3 and reflecting the remainder is set while inclining. A measuring cells 2 and a detector 5 or 6 are arranged, respectively, in the transmitting direction of infrared rays passing through the optical filter 1 and reflected infrared rays. The optical filter 1 has a thin film constitution in which a filter substrate has different thin films on the both sides thereof. The film is constituted so that the face on the light source side selectively transmits the infrared wavelength region corresponding to the measured components of passing infrared rays to which the detector is sensitive as compared with the other side.

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 by using a light-reflecting optical filter such as an interference filter or a cut-on filter, and more particularly to not only a light transmitted through a filter but also a reflected light. The present invention relates to an infrared analyzer capable of analyzing a plurality of samples.

[0002]

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

In the case of projecting infrared rays on a measuring cell in an infrared analyzer, a filter which transmits infrared rays having a wavelength in a specific infrared region and cuts off others is often used depending on the sample. Interference filters have become important. The interference filter is composed of a multilayer film that transmits a desired wavelength band and reflects other wavelength regions by utilizing the interference effect of light. Si, Ge, SiO ₂ , Al _A plurality of thin films of Ge, SiO, ZnS, etc. on both surfaces of a filter substrate of ₂ O ₃ etc. are coated. When the filter has the same structure on both sides, for example, when both sides are provided with bandpass filter surfaces, and when different membranes are formed on each surface,
For example, band pass surface and SLC (short long cut)
The surface may be provided.

[0004]

The interference filter normally uses only the desired transmitted light, and the reflected light has not been effectively used as a blocking region. 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, since the interference filter can selectively operate infrared transmission and reflection in a specific wavelength range, if any wavelength range can be used effectively, the analyzer can be simplified and simultaneous measurement of multiple samples is possible. Becomes The present invention has been made in view of such problems, and an object thereof is to provide an infrared analyzer capable of simultaneously analyzing a plurality of samples by effectively utilizing not only transmitted light but also reflected light. .

[0005]

That is, in order to solve the above-mentioned problems, the present invention installs an optical filter inclined so that a part of infrared rays projected from an infrared light source is transmitted and the other is reflected, In an infrared analyzer in which a measuring cell or / and a detector are arranged in the respective passing directions of infrared rays that pass through the filter and infrared rays that reflect, the optical filter is a thin film structure in which both sides of the filter substrate are different, It is characterized in that it has a film structure that allows the infrared wavelength region corresponding to the measurement component to which the detector for the infrared rays transmitted through the surface is sensitive to be transmitted more selectively than the other surface.

[0006]

When the infrared analyzer is used as the above means, the infrared light projected from the infrared light source passes through the measuring cell, then a part of the infrared light passes through the filter and enters the detector, and the rest reflects and enters the detector. Alternatively, a part of the infrared rays 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 passing through the filter has a wavelength range absorbed by the sample to be analyzed, and the infrared ray reflected by the filter surface has a wavelength range absorbed by another sample to be analyzed. If the filter is designed so as to be provided, it becomes possible to measure a plurality of samples at the same time with one infrared light source.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific 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 rays) when the interference filter 1 used in the infrared analyzer of the present invention is tilted. In this example, a filter having a bandpass surface and an SLC surface will be described. This is a short cut that reflects the short wavelength side of the specific wavelength and a long wavelength side that reflects the short wavelength side of the cyber band that is generated in the bandpass filter that tries to reflect the infrared ray of a wavelength other than the specific wavelength. It is a filter that can be significantly reduced by combining it with a long cut. Band pass side 1
Although a is used as a reflecting surface, when the film configurations on both surfaces are different as described above, theoretically comparing the reflectances when the bandpass surface 1a is used as the reflecting surface and when the SLC surface 1b is used as the reflecting surface, it is theoretically possible. Although there is no difference in reflectance depending on the placement, a considerable difference is actually seen.

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

Next, an infrared analyzer that utilizes infrared transmitted light and reflected light using an interference filter will be described.
FIG. 3 shows that the interference filter 1 is used for nitrogen oxide (NO).
And an example of an infrared analyzer for measuring sulfur dioxide (SO ₂ ). The sample gas in which NO and SO ₂ are mixed is introduced from the inlet 2a provided in the measurement cell 2 and is discharged from the outlet 2b after the measurement. An infrared light source 3 is arranged on one side of the measuring cell 2 and a filter chamber 4 is arranged on the other side. The interference filter 1 is installed in a tilted manner in the filter chamber 4, and a nitrogen oxide (NO) detector 5 is arranged in the filter chamber 4 in a direction in which infrared rays passing through the interference filter 1 pass. A sulfur dioxide (SO ₂ ) detector 6 is provided in the direction in which infrared rays reflected by the surface of the filter 1 pass.
Is arranged. In addition, the front surface of the SO ₂ detector 6 is SO
A cut-on filter 7 for ₂ is installed.

In the infrared analyzer having the above-mentioned structure, a part of the wavelength of infrared rays projected from the infrared light source 3 is absorbed by nitrogen oxide (NO) and sulfur dioxide (SO ₂ ) in the measuring cell 2. It The infrared light passing through the measurement cell 2 partially 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 and enters the SO ₂ detector 6. In this case, the infrared rays passing through the interference filter 1 have a wavelength range in which NO is absorbed, and the infrared rays reflected on the surface of the interference filter 1 have a wavelength range in which SO ₂ is absorbed. If the filter 1 is designed, it becomes possible to measure two gas samples simultaneously with one infrared light source 3.

In FIG. 4, the interference filter 1 is used for nitrogen oxide (NO), sulfur dioxide (SO ₂ ) and carbon dioxide (CO).
It is an example of an infrared analyzer for measuring ₂ ). In this embodiment, an interference filter (4.6 μm) is provided in front of the infrared light source 3.
A filter chamber 9 in which a cut-on filter 8 is installed in an oblique direction is arranged, and a measuring cell 2 ′ is arranged in the passing direction of infrared rays transmitted through the 4.6 μ cut-on filter 8 of the filter chamber 9.
There is disposed, said 4.6μ cut-on filter 8 surface reflected infrared to the passage direction measurement cell 2 "and carbon dioxide were (CO ₂₎ detector 10 is disposed. Further, carbon dioxide gas (CO ₂ ) A CO ₂ bandpass filter 11 is installed on the front surface of the detector 10. The measuring cell 2'and the measuring cell 2 "are connected by a conduit 12 and an inlet 2 is provided on the measuring cell 2" side. Sample gas from “a” (NO, SO
₂ and CO _{2 and the} like) are discharged from a discharge port 2'b provided in another measuring cell 2 '. Further, a filter chamber 4 in which the interference filter 1 is installed in an oblique direction is arranged in the measurement cell 2 ′ arranged in the infrared ray transmitting direction of the 4.6 μ cut-on filter 8 so that the infrared ray transmitted through the interference filter 1 passes through. A nitrogen oxide (NO) detector 5 is arranged in the direction in which the infrared rays are reflected, and a sulfur dioxide (SO ₂ ) detector 6 is arranged in the direction in which the infrared rays reflected by the surface of the interference filter 1 pass. In addition, S is placed on the front surface of the SO ₂ detector 6.
A cut-on filter 7 for O ₂ is installed.

In the infrared analyzer having the above structure, a part of the infrared rays projected from the infrared light source 3 passes through the 4.6 μ cut-on filter 8 and the measuring cell 2 '
And the rest is reflected by the surface of the 4.6 μ cut-on filter 8 and projected onto the measuring cell 2 ″, and a part is absorbed by CO ₂ gas and transmitted through the CO ₂ bandpass filter 11 and carbon dioxide gas (CO 2 ₂ ) Enter the detector 10. A part of the infrared rays passing through the 4.6 μ cut-on filter 8 and passing through the measuring cell 2 ′ is a part of nitrogen oxide (NO) and sulfur dioxide (SO ₂ ) in the measuring cell 2 ′. In addition, a part of the infrared ray 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, there is a wavelength range in which infrared rays passing through the 4.6 μ cut-on filter 8 are absorbed by NO and SO ₂ , and infrared rays reflected by the surface of the 4.6 μ cut-on filter 8 are absorbed by CO _2. In addition, the infrared ray passing through the interference filter 1 has a wavelength range in which NO is absorbed, and the infrared ray reflected by the surface (bandpass surface) of the interference filter 1 has a wavelength range in which SO ₂ is absorbed. If the 4.6 μ cut-on filter 8 and the interference filter 1 are designed, one infrared light source 3 can simultaneously measure three types of gas samples.

Next, in the embodiment shown in FIG. 4, 4.6 μ
FIGS. 5 to 10 show data of measured values of the relationship (wavelength characteristic) between the wavelength and the transmittance of infrared rays that pass through or are reflected by the cut-on filter 8 and the interference filter 1, respectively. However, in this case, absorption of infrared rays by NO, SO ₂ , CO _2, etc. is not considered, and the relationship between the wavelength band of infrared rays that are transmitted or reflected and the transmittance is shown. (1) FIG. 5 shows the transmittance of infrared rays having a wavelength transmitted through the 4.6 μ cut-on filter 8. According to this figure 4.6
Infrared light having a wavelength of μ or less is cut, and 90% or more of infrared light having a wavelength of 4.6 μ or more is transmitted. (2) FIG. 6 shows the relationship between the wavelength of infrared rays transmitted through the 4.6 μ cut-on filter 8 and further transmitted through the interference filter 1 and the transmittance. According to this figure, most of the infrared rays between 5μ and 6μ transmitted through the 4.6μ cut-on filter 8 are transmitted. (3) FIG. 7 shows the relationship between the wavelength and the transmittance of infrared rays that have passed through the 4.6 μ cut-on filter 8 and are further reflected by the interference filter 1. This figure has a front and back relationship with FIG. 6, and infrared rays other than the wavelengths between 5 μm and 6 μm are reflected by the interference filter 1. (4) FIG. 8 shows the transmittance of infrared rays having a wavelength transmitted through the SO ₂ cut-on filter (6 μ cut-on filter) 8. Therefore, according to this figure, even the infrared light reflected by the interference filter 1 has a wavelength of 6 μm or less. (5) FIG. 9 shows the relationship between the wavelength of infrared rays reflected on the surface of the 4.6 μ cut-on filter 8 and the transmittance. According to this figure, almost all infrared rays having a wavelength of 4.6 μ or less are reflected. (6) FIG. 10 shows the CO ₂ band pass filter 11 out of the infrared rays reflected on the surface of the 4.6 μ cut-on filter 8.
The relationship between the infrared ray having a wavelength that transmits the light and the transmittance is shown. According to this figure, most of the infrared rays having a wavelength of 4.2μ to 4.3μ are transmitted.

In the above-described embodiment of the present invention, the interference filter is installed so as to be inclined, and the interference filter is provided with the half mirror.
That is, the device for measuring a plurality of samples by using one light source with the bandpass surface as the reflecting surface has been described, but not limited to the interference filter, the cut surface of the cut-on filter and the antireflection coating surface ( Anti Refrection,
The same is true for the normal AR surface), and the same measurement can be performed using the cut-on surface as a reflective surface.

[0015]

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

[Brief description of drawings]

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

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

FIG. 3 shows nitrogen oxide (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 example 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 rays having a wavelength that has passed through a 4.6 μ cut-on filter.

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

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

FIG. 8 is a diagram showing the transmittance of infrared rays having a wavelength that has passed through a SO ₂ cut-on filter (6 μ cut-on filter).

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

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

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

[Explanation of symbols]

1 Interference Filter 1a Bandpass Surface 1b SLC Surface 2, 2 ', 2 "Measuring Cell 3 Light Source 5 NO Detector 6 SO ₂ Detector 7 SO ₂ Cut-on Filter (6μ Cut-on Filter) 8 4.6μ Cut-on Filter 10 CO ₂ detector 11 CO ₂ band pass filter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Fujiwara 2 Higashimachi, Kichijoin Miya, Minami-ku, Kyoto-shi, Kyoto Inside Horiba Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. An optical filter that transmits a part of infrared rays projected from an infrared light source and reflects the other, is installed so as to be inclined, and a measuring cell is provided in each of the passing directions of the infrared rays that pass through the filter and the infrared rays that reflect. Or / and in an infrared analyzer in which a detector is arranged, the optical filter has a thin film structure in which both surfaces of the filter substrate are different, and an infrared ray corresponding to the measurement component to which the detector is sensitive for the infrared ray transmitted through the surface on the light source side An infrared analyzer having a film structure that allows a wavelength region to be transmitted more selectively than other surfaces.