JP2573938Y2 - Fourier transform infrared spectrometer - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fourier transform infrared spectrometer.

[0002]

2. Description of the Related Art An FTIR (Fourier transform red) for quantitatively analyzing a specific component contained in a measurement gas based on the absorbance at a designated wave number point of an absorption spectrum obtained by irradiating a measurement gas in a cell with infrared light. External spectrometers) are known.

[0003] When measuring low-concentration gases with such an infrared spectrometer, a long cell of, for example, several tens of meters may be required to obtain high sensitivity. In such a case, a configuration in which the length of the cell can be variably adjusted may be employed. However, when measuring a high-concentration gas, a relatively short cell of, for example, about several cm can sufficiently measure.

[0004]

As described above, even when the cell length can be variably adjusted, it is necessary to fix the cell length before starting the measurement. Therefore, there is a limit on the concentration range that can be measured, and a single infrared spectrometer may not be able to cope with the measurement of the concentration of multiple components in which the concentration is distributed over a relatively wide range.

When the cell length is large, a multi-reflection type long optical path cell is often used. In this case, infrared light is focused on the long optical path cell and incident on the long optical path cell. A condensing mirror and a reflecting mirror for focusing the light, and a reflecting mirror and a condensing mirror for focusing the infrared light emitted from the long optical path cell on the detector are required, and a relatively complicated optical system is configured. You. Therefore, especially when setting a wide measurement range from low concentration to high concentration, it is desirable that the calibration of the optical system can be performed easily and accurately so that high measurement accuracy can always be maintained.

The present invention has been made in view of such circumstances.
It is an object of the present invention to provide a Fourier-transform infrared spectrometer that can measure in a wide range from a low concentration to a high concentration and can easily and accurately calibrate an optical system.

[0007]

According to the present invention, the means for solving the above-mentioned problems are constituted as follows. That is, an infrared light source that generates infrared light, an interferometer disposed in the optical path of the infrared light emitted from the infrared light source, and a first collection that reflects the infrared light modulated by the interferometer. An optical mirror, a second condensing mirror provided apart from the first condensing mirror and condensing infrared light to a detector, and an optical path between the first and second condensing mirrors A short optical path cell and a multiple reflection type long optical path cell, and a first reflecting mirror that reflects infrared light transmitted through the short optical path cell and enters the long optical path cell, and transmits through the long optical path cell. By reflecting infrared light, the second
A second reflecting mirror for condensing light on the detector via the converging mirror is provided integrally with a detachable reflecting mirror unit.

[0008]

When measuring a gas having a low concentration, a measuring gas is introduced into the long optical path cell, while a zero gas such as N ₂ gas is introduced into the short optical path cell, and infrared light is irradiated from an infrared light source. After the infrared light modulated by the interferometer is reflected by the first focusing mirror and transmitted through the short optical path cell, it is reflected by the first reflecting mirror and is incident on the long optical path cell, and transmits through the long optical path cell. After the reflected infrared light is reflected by the second reflecting mirror, it is focused on the detector by the second focusing mirror. Thus, the data processing unit connected to the detector can measure the interferogram of the measurement gas, perform the Fourier transform, and perform the analysis.

On the other hand, when measuring a high concentration gas,
Conversely, a zero gas is introduced into the long optical path cell, and a measurement gas is introduced into the short optical path cell, and the analysis can be performed in the same manner.

In other words, a long optical path cell capable of obtaining high sensitivity for a low concentration measurement gas and a short optical path cell for a high concentration measurement gas can appropriately cope with each other.
Highly accurate analysis is possible over a wide concentration range from low concentration to high concentration.

When the optical system is calibrated, two systems can be checked by attaching and detaching a reflector unit in which the first reflector and the second reflector are integrally mounted. Perform accurate troubleshooting. That is, when the reflecting mirror unit is set, the entire system combining the short optical path system and the long optical path system can be checked, and when the reflecting mirror unit is removed, only the short optical path system can be checked.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the Fourier transform infrared spectrometer of the present invention will be described below in detail with reference to the drawings. 1 is an overall configuration diagram of a Fourier transform infrared spectrometer, FIG. 2 is a gas supply circuit diagram thereof, and in FIG.
An interferometer chamber defined by a partition plate 5 in 10 is an infrared light source that generates parallel infrared light, 3 is an interferometer that is arranged in the infrared light path and modulates infrared light, Although not shown, it is composed of a beam splitter, a fixed mirror, a movable mirror, etc., and the infrared light modulated by the interferometer 3 is reflected by a first condenser mirror 4 composed of a concave mirror, and opened on a partition plate 5 of a main body 10. After passing through the short optical path cell 6 fitted in the cell storage hole, the light enters the reflecting mirror unit 8 which is detachably provided in the gas cell chamber 7 defined in the main body 10 by the partition plate 5.

The reflecting mirror unit 8 reflects the infrared light transmitted through the short optical path cell 6 and makes it incident on the entrance window 9a of the long optical path cell 9 provided in the gas cell chamber 7.
And a second reflecting mirror for reflecting infrared light emitted from the emission window 9b of the long optical path cell 9 to a second focusing mirror 13 formed of a concave mirror.
12 are integrally assembled to a frame (not shown), and are detachably attached to the main body 10 by attaching bolts or the like.

When the reflecting mirror unit 8 is removed, the second focusing mirror 13 provided in the gas cell chamber 7 reflects the infrared light reflected by the first focusing mirror 4 in the interferometer chamber 1. Thus, a short optical path system for condensing the light on the detector 15 is formed, and in a state where the reflecting mirror unit 8 is attached to the main body 10, the infrared light emitted from the long optical path cell 9 is reflected as described above. A long optical path system for focusing light on the detector 15 is also configured. Therefore, by attaching and detaching the reflecting mirror unit 8 to and from the main body 10 with this configuration, the calibration of the two optical systems can be separated and performed independently, as described later. The effect is significantly improved, and calibration can be performed easily and accurately.

The above-described short optical path cell 6 is sealed on both sides by an entrance window 6a provided in the interferometer chamber 1 and an emission window 6b provided in the gas cell chamber 7, and is formed outward on the partition plate 5. Zero gas or measurement gas can be introduced from the gas inlet 6c and discharged from the gas outlet 6d.
N ₂ gas is sealed in the interferometer chamber 1.

On the other hand, the long optical path cell 9 provided in the gas cell chamber 7 is provided with a plurality of condensing mirrors 9c, 9d, 9e therein, and performs multiple refraction of infrared light incident from the entrance window 9a. It is configured to emit light through the injection window 9b, and a zero gas or a measurement gas can be introduced from the gas inlet 9f opened in the main body 10 and discharged from the gas outlet 9g.

The detector 15 provided in the gas cell chamber 7
Is composed of a semiconductor infrared detecting element, etc., is connected to a data processing unit (not shown), and irradiates the measurement gas in each cell 6, 9 with infrared light modulated by an interferometer to obtain an interferogram. The data processing unit performs a Fourier transform to perform the analysis.

The short optical path cell 6 and the long optical path cell 9 are both connected to the gas supply path shown in FIG. 2 and individually select and introduce a zero gas or a measurement gas.
It can be discharged. That is, the short optical path cell 6
The gas inlet 6c is connected to the N through an electromagnetic three-way valve 21 with a flow meter.
The gas inlet of the long optical path cell 9 is connected to the first gas line 22 and the second gas line 23 for supplying zero gas such as ₂
9f is the first gas line via an electromagnetic three-way valve 24 with a flow meter
The gas outlet 6d of the short optical path cell 6 is connected to a first exhaust gas line 27 provided with a manual opening / closing valve 25 and a pump 26, and the gas exhaust port 6d of the long optical path cell 9 is connected to the second gas line 23. The outlet 9g is connected to a second exhaust gas line 30 provided with a manual on-off valve 28 and a pump 29, respectively.

In the infrared spectrometer configured as described above,
When measuring low concentration gas, the electromagnetic three-way valve 24 is operated to connect the gas inlet 9g to the second gas line 23, and the measurement gas is introduced into the long optical path cell 9 while the electromagnetic three-way valve 21 is operated. When the gas inlet 6c is connected to the first gas line 22 to introduce a zero gas such as N ₂ gas into the short optical path cell 6 and irradiate infrared light from the infrared light source 2, modulation is performed by the interferometer 3. After the reflected infrared light is reflected by the first condenser mirror 4 and transmitted through the short optical path cell 6, it is reflected by the first reflecting mirror 11 and is incident on the long optical path cell 9 and transmitted through the long optical path cell 9. Infrared light is the second reflecting mirror
After being reflected by 12, it is condensed on the detector 15 by the second condensing mirror 13. As a result, the interferogram of the gas is measured by the data processing unit connected to the detector 15 and Fourier-transformed to perform the concentration analysis. On the other hand, when measuring a gas having a high concentration, a zero gas is introduced into the long optical path cell 9 and a measurement gas is introduced into the short optical path cell 6, and the analysis can be performed in the same manner.

That is, by operating the electromagnetic three-way valves 21 and 24, the long optical path cell 9 can obtain high sensitivity for a low concentration measurement gas, and the short optical path cell 6 for a high concentration measurement gas. Thus, appropriate measures can be taken for each, and highly accurate analysis can be performed over a wide concentration range from low concentration to high concentration.

Then, by attaching and detaching the reflecting mirror unit 8 in which the first reflecting mirror 11 and the second reflecting mirror 12 are integrally assembled to the main body 10, the optical system is divided into two systems and the optical path and the like are divided. Was able to be checked, which enabled accurate troubleshooting. That is, when the reflecting mirror unit 8 is set, the entire system combining the short optical path system and the long optical path system can be checked, and when the reflecting mirror unit 8 is removed, only the short optical path system can be checked. It is. Further, the attachment and detachment of the reflecting mirror unit 8 can be easily performed by operating the mounting bolt, and there is an advantage that the usability is extremely high.

[0022]

As described above, according to the Fourier transform infrared spectrometer of the present invention, the first condenser mirror for reflecting the infrared light modulated by the interferometer and the first condenser mirror A second focusing mirror, which is provided at a distance, and focuses infrared light on the detector; a short optical path cell disposed in an optical path between the first focusing mirror and the second focusing mirror; A first reflecting mirror that reflects infrared light transmitted through the short path cell and makes it incident on the long path cell, and reflects the infrared light transmitted through the long path cell to reflect the second light. Since a second reflecting mirror for condensing light on a detector via an optical mirror is provided integrally with a detachable reflecting mirror unit, high sensitivity can be obtained for a low-concentration measurement gas. With the long-path cell, high-concentration measurement gas can be properly dealt with with the short-path cell, respectively.
By performing high-precision analysis over a wide concentration range from low concentration to high concentration, and by attaching and detaching a reflecting mirror unit in which the first reflecting mirror and the second reflecting mirror are integrally assembled. The optical system can be divided into two systems and checked without the need for a separate member. This makes it possible to more reliably and easily calibrate the optical system, and to maintain and manage the measurement accuracy with good operability and accuracy. Now you can do it.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a Fourier transform infrared spectrometer of the present invention.

FIG. 2 is a gas supply circuit diagram.

[Explanation of symbols]

Reference numeral 2: infrared light source, 3: interferometer, 4: first converging mirror, 6: short optical path cell, 8: reflecting mirror unit, 9: long optical path cell, 11: first reflecting mirror, 12: second reflecting mirror , 13 ... second focusing mirror, 15 ... detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/00-21/61 G01J 3/00-3/52

Claims (1)

(57) [Scope of request for utility model registration] 1. An infrared light source for generating infrared light, an interferometer disposed in an optical path of infrared light emitted from the infrared light source, and reflecting the infrared light modulated by the interferometer. A first condenser mirror, a second condenser mirror that is provided apart from the first condenser mirror and condenses infrared light to a detector, and a first condenser mirror and a second condenser mirror. A short optical path cell and a multi-reflection long optical path cell disposed in an optical path between the first optical path cell and a first optical element that reflects infrared light transmitted through the short optical path cell and makes the infrared light incident on the long optical path cell;
A reflecting mirror unit that is integrally assembled with a reflecting mirror and a second reflecting mirror that reflects the infrared light transmitted through the long optical path cell and collects the infrared light on the detector via the second collecting mirror; And a Fourier transform infrared spectrometer.