JP3113903U - Infrared spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a deliquescent optical element used in an infrared spectrophotometer from deliquescent by moisture in the air.
[Solution]
When a deformable expansion part is provided in a part of the sealed space containing the optical system, when the gas in the sealed space expands due to a temperature change, the volume in the sealed space increases and contracts. Since the volume is reduced, the pressure in the sealed space does not change. Thereby, intrusion of outside air into the sealed space can be prevented, and deliquescent elements installed in the sealed space can be prevented.

[Selection] Figure 2

Description

 The present invention relates to an infrared spectrophotometer which performs qualitative and quantitative analysis of a substance by measuring an infrared absorption spectrum of a sample.

An infrared spectrophotometer irradiates a sample with infrared light, measures the spectrum of light transmitted through the sample to be measured, and examines the wavelength of the light absorbed by the sample or the wavelength of the transmitted light. Analyze. Using such an infrared spectrophotometer, it is possible to measure infrared light absorption spectra of a wide variety of samples such as gases, liquids, and solids.

A Fourier transform type infrared spectrophotometer (FTIR) is equipped with an interferometer for producing infrared interference light, and there is potassium bromide (KBr) as an optical element such as a beam splitter. An optical material having deliquescent properties (a property of absorbing and dissolving moisture in the air) is used. When this optical material is deliquescent, satisfactory measurement cannot be performed. Therefore, various methods for preventing deliquescation such as an interferometer in an airtight space blocked from the outside air have been studied. Yes.

In order to prevent the deliquescence of the element, it is only necessary to house the element with deliquescence in an airtight space with low humidity and completely shut off the outside air to prevent the entry and exit of water vapor. It is difficult to form an airtight space that can maintain an airtight state for a long period of time, which is very expensive. In general, an interferometer including an optical element is accommodated in a sealed chamber. In order to keep the humidity in the sealed chamber low, a desiccant such as silica gel that purges dry air and removes water vapor is used. Methods such as incorporating a dehumidifier that discharges moisture out of the system are used.

For example, in a sealed chamber containing an interferometer that uses a deliquescent optical material and an infrared light source heater, a box containing a desiccant is placed in the vicinity of the infrared light source heater. Has been proposed that includes a first opening that communicates with the atmosphere side and a second opening that communicates with the sealed chamber and includes an interlocking valve that opens only one of the two openings (patent) Reference 1).

JP-A-10-253454

A light source used in FTIR is a light source that generates light in the infrared region, and generates heat. Therefore, in general, the FTIR apparatus is warmed by the light source when the power is turned on and becomes higher than room temperature, and returns to room temperature when the power is turned off. It is considered that the gas inside the sealed interferometer is repeatedly expanded and contracted due to the temperature difference at this time.

Therefore, the pressure in the sealed chamber is changed, and it is considered that a part of the gas in the sealed chamber leaks to the outside when the temperature rises and the pressure in the sealed chamber increases. After that, when the temperature returns to room temperature, the pressure in the sealed chamber decreases, and external air enters the sealed chamber, and at the same time, water vapor is introduced, leading to an increase in humidity. At this time, in addition to water vapor, the outside air may contain an organic solvent that interferes with infrared spectroscopic measurement, and contamination by external air may occur.

In addition, it is conceivable that the dehumidifier always discharges the water vapor in the sealed room out of the system and keeps it at a low humidity, but in general, the dehumidifier is expensive, and the power for operating the dehumidifier is also low. is necessary.

In addition, it may be possible to prevent the expansion and contraction of the gas in the sealed chamber by always energizing the power source and keeping the temperature of the device constant. There are drawbacks such as shortening the life of parts, and it is desirable to energize only when necessary.

An infrared spectrophotometer according to the present invention is an idea related to an infrared spectrophotometer having a sealed chamber provided with an optical element having deliquescence and an infrared light source inside, the sealed chamber being A part is provided with an inflating part.

In the FTIR of the present invention, the sealed space containing the element composed of a material having deliquescence has an expansion part in a part thereof, and the internal part is free by deformation of the expansion part. Can be changed. When the gas in the sealed space expands due to a temperature change, the expansion portion is deformed and the volume in the space increases. Conversely, when the gas inside contracts, the expanding portion is deformed and the volume in the space is reduced. At this time, since the volume in the space changes while the pressure is kept substantially the same between the sealed chamber and the outside air, it is possible to prevent the outside air from entering the sealed space.

Therefore, water vapor does not enter the sealed chamber, the inside of the sealed space is kept at a low humidity, and the device can be prevented from deliquescent. At the same time, the gas that causes contamination contained in the outside air does not enter.

As a result, a normal desiccant or a dehumidifier can be omitted, and even when used in combination with a desiccant, it is possible to reduce the frequency of replacement of the desiccant. Moreover, it is not necessary to energize constantly.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an FTIR according to an embodiment of the present invention, and FIG. 2 is a sectional view of an interferometer portion thereof.

In FIG. 1, the interferometer includes an infrared light source 11, a condensing mirror 12, a collimator mirror 13, a beam splitter 14, a fixed mirror 15, a moving mirror 16, and the like, and generates interfering infrared light for spectrum measurement. To do. That is, the infrared light emitted from the infrared light source 11 is applied to the beam splitter 14 through the condensing mirror 12 and the collimator mirror 13, and is divided into two directions, a fixed mirror 15 and a moving mirror 16. The lights reflected by the fixed mirror 15 and the movable mirror 16 are combined again by the beam splitter 14 and sent to the optical path toward the parabolic mirror 21. At this time, since the movable mirror 16 reciprocates back and forth (in the direction of the arrow M in FIG. 1), the combined light becomes interference light (interferogram) whose amplitude varies with time. The light collected by the parabolic mirror 21 is irradiated into the sample chamber 22, and the light that has passed through the sample 23 disposed in the sample chamber 22 is condensed by the ellipsoidal mirror 24 onto the infrared light detector 25. The

The interferometer includes a laser light source 17, a laser mirror 18, a beam splitter 14, a fixed mirror 15, and a movable mirror 16, and generates laser interference light for obtaining an interference fringe signal. That is, the light emitted from the laser light source 17 is applied to the beam splitter 14 via the laser mirror 18 and is transmitted to the parabolic mirror 21 as interference light in the same manner as the infrared light. Since this laser interference light travels as a light beam having a very small diameter, it is reflected by the laser mirror 19 inserted in the optical path and introduced into the laser detector 20.

The light reception signal of the laser detector 20, that is, the laser light interference fringe signal is used as a pulse signal for sampling the light reception signal with respect to the infrared interference light. This laser beam interference fringe signal is also used to perform stable sliding control of the movable mirror. The received light signal obtained by the infrared light detector 25 is sent to the data processing unit 30 to create a spectrum.

The light source 11 and the beam splitter 14 constituting the interferometer are arranged in the sealed chamber 1 and are blocked from the outside air. This is mainly because the humidity in the airtight chamber needs to be kept low because the beam splitter 14 is configured using KBr having deliquescence. Furthermore, it is preferable to provide a desiccant inside the sealed chamber 1.

FIG. 2 is a cross-sectional view of an FTIR according to an embodiment of the present invention. The sealed chamber 1 is a sealed chamber that houses the interferometer, and is disposed in the lower housing portion 7 and the upper housing portion 6. In the sealed chamber 1, as shown in FIG. 1, an infrared light source 11, a movable mirror 16, a beam splitter 14 and the like are installed. The sealed chamber 1 includes a bag 3 at the lower portion thereof, and the inside constitutes a sealed space that is shielded from the outside air. The sealed chamber 1 is configured by a cover 5 installed on a metal base 4 and a bag 3 communicating with each other through a hole 2 provided in the base 4. The connecting portion between the base 4 and the cover 5 is sealed with resin packing or the like. The bag 3 is not particularly limited, but is preferably composed of a material that minimizes the force required for deformation, for example, a film in which a highly impervious nylon resin is laminated. There is no particular limitation on the size and shape, and any shape that can be easily expanded / contracted and that can change the internal volume without applying a large force can be used. It may be structured such that the position of the cylinder changes due to expansion and contraction.

When the apparatus is not used (the power is not turned on), the bag 3 is crushed because there is no gas inside as shown in FIG. When the power is turned on during use, the infrared light source 11 generates heat, so that the gas in the sealed chamber 1 is warmed and begins to expand. At this time, since the bag portion 3 is formed of a soft material that can be deformed, the gas in the sealed chamber whose volume has increased due to the expansion flows into the bag 3 through the hole portion 2, and FIG. ), The bag 3 is inflated. At this time, it is considered that there is almost no pressure difference between the inside of the sealed chamber and the outside air, and the gas inside the sealed chamber does not flow out to the outside air even if it is not completely airtight.

Since the light source does not generate heat when the power is turned off, the gas in the sealed chamber is cooled by the ambient temperature of the apparatus and begins to contract. When the volume of the gas is reduced by the contraction, as shown in FIG. 2C, the gas in the bag 3 flows into the case, and as a result, the bag 3 is crushed again. At this time, it is considered that there is almost no pressure difference between the inside of the sealed chamber and the outside air, and no external gas flows into the inside of the sealed chamber.

At this time, since the bag 3 is made of a soft material, it easily deforms even when the gas in the sealed chamber expands and contracts, and there is no pressure difference between the inside of the sealed chamber and the outside air. Does not happen. Therefore, air (water vapor) outside the sealed chamber is not introduced into the sealed chamber.

The schematic block diagram of FTIR by one Example of this invention. 1 is a cross-sectional view of an FTIR according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sealed chamber 2 ... Hole part 3 ... Bag part 4 ... Base 5 ... Cover 6 ... Case upper part 7 ... Case lower part 11 ... Light source 12 ... · Condensing mirror 13 ··· Collimator mirror 14 ··· Beam splitter 15 · · · Fixed mirror 16 · · · Moving mirror 17 · · · Laser light source 18 · · · Laser mirror 19 · · · Laser mirror 20 · · · ..Laser detector 21 ... parabolic mirror 22 ... sample chamber 23 ... sample 24 ... ellipsoidal mirror 25 ... infrared light detector 30 ... data processing unit

Claims (1)

An infrared spectrophotometer having a sealed chamber provided with an optical element having deliquescence and an infrared light source inside, wherein the sealed chamber has an expansion / contraction part in a part thereof Infrared spectrophotometer.

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