Infrared light source device and fourier transform infrared spectroscope

An infrared light source device includes: a heater portion which emits infrared light by being heated; and a cover member arranged to cover an entire circumference of the heater portion without contacting the heater portion, and having a hole formed therein for emitting the infrared light from the heater portion to outside. A material for the cover member is a pure aluminum (an aluminum alloy with a purity of 99% or more), which has a high heat reflectivity and is less likely to be denatured by heat dissipation from the heater portion.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to an infrared light source device, and a Fourier transform infrared spectroscope including the infrared light source device.

Description of the Background Art

A Fourier transform infrared spectroscope (FTIR) splits infrared light from an infrared light source device into two by a beam splitter, emits one split infrared light to a fixed mirror and the other split infrared light to a moving mirror. Then, their reflection light beams are guided into the same optical path to generate interference light. This interference light is emitted to a sample to be measured, transmitted light therethrough or reflected light therefrom is detected by a detector, and a detection signal by the detector is sent to a data processing device. The data processing device Fourier-transforms the detection signal to produce a spectrum, and performs qualitative analysis or quantitative analysis of the sample based on peak wavelength, peak intensity, and the like of this spectrum (see, for example, WO 2016/166872).

SUMMARY OF THE INVENTION

An infrared light source device of an FTIR generally includes a ceramic heater which serves as an infrared light source by being heated to about 1000° C. and emitting infrared light, a heat insulating material (such as porous ceramic) with a low heat conductivity arranged to cover the circumference of the heater (infrared light source), and a metal cover which covers the circumference of the heat insulating material. By covering the heater with the two layers, that is, the heat insulating material and the metal cover, as described above, the temperature of the heater can be maintained at a target temperature or more, while suppressing power consumption of the heater.

In order to maintain the temperature of the heater (infrared light source) at the target temperature or more in the infrared light source device having a structure as described above, it is necessary to set the thickness of the heat insulating material to a certain value or more, which may lead to an increase in size of the infrared light source device. Accordingly, in order to downsize the infrared light source device, options other than the heat insulating material (such as porous ceramic) are required as a member for maintaining the temperature of the light source at the target temperature or more.

The present disclosure has been made to solve the aforementioned problem, and an object of the present disclosure is to downsize an infrared light source device while maintaining the temperature of an infrared light source at a target temperature or more.

An infrared light source device in accordance with the present disclosure includes: a heater which emits infrared light by being heated; and a cover member arranged to cover an entire circumference of the heater without contacting the heater, and having a hole formed therein for emitting the infrared light from the heater to outside. A material for an inner wall of the cover member is aluminum or gold.

A Fourier transform infrared spectroscope in accordance with the present disclosure includes the infrared light source device described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. It should be noted that identical or corresponding parts in the drawings will be designated by the same reference numerals, and the description thereof will not be repeated.

FIG.1is a view schematically showing an example of a configuration of an FTIR (Fourier transform infrared spectroscope) including an infrared light source device1in accordance with the present embodiment.

This FTIR includes an interferometer chamber400, a paraboloidal mirror432, a sample chamber470, an ellipsoidal mirror433, and an infrared light detector480. Interferometer chamber400accommodates a main interferometer including infrared light source device1, a converging mirror431a, a collimator mirror431b, a beam splitter440, a moving mirror450, and a fixed mirror460. Sample chamber470accommodates a sample S to be measured.

In the main interferometer within interferometer chamber400, infrared light source device1emits infrared light. The infrared light emitted from infrared light source device1impinges on converging mirror431aand collimator mirror431band is split into two by beam splitter440. Of the infrared light split into two by beam splitter440, one split infrared light is reflected by fixed mirror460and the other split infrared light is reflected by moving mirror450, and they are merged again into an identical light path and becomes infrared interference light.

The infrared interference light is emitted from interferometer chamber400toward paraboloidal mirror432, is converged by paraboloidal mirror432, and then enters into sample chamber470. When the infrared interference light is emitted to sample S, it is subject to absorption at a wavelength specific to sample S. The infrared interference light which has been subject to absorption impinges on ellipsoidal mirror433, is detected by infrared light detector480, and is Fourier-transformed to produce a spectrum.

In such an FTIR, it is possible to obtain a spectrum with high accuracy by keeping the moving speed of moving mirror450constant. To measure the moving speed of moving mirror450, a control interferometer is used, which includes a laser light source420, first and second laser light reflecting mirrors421and422, beam splitter440, moving mirror450, and fixed mirror460. In the control interferometer, laser light emitted from laser light source420is introduced onto the same light path as that of the infrared light by first laser light reflecting mirror421, passes through the same interference system (beam splitter440, moving mirror450, fixed mirror460) as that of the infrared light, and thereby laser interference light is generated. The laser interference light is taken out of the light path of the infrared interference light by second laser light reflecting mirror422, and is detected by a laser light detector490. The moving speed of moving mirror450is calculated based on the detected laser interference light.

FIG.2is a cross sectional view of infrared light source device1. Infrared light source device1includes a ceramic heater10, a cylindrical cover member20, a cylindrical support member30, and a cylindrical case40.

Ceramic heater10includes a heater portion11made of ceramic such as silicon nitride SiN, a power line12for supplying power to heater portion11, and a base portion13which supports heater portion11and power line12. Ceramic heater10is fixed to support member30by fitting base portion13of ceramic heater10into an inner wall on a root side of support member30.

Cover member20has the shape of a cylinder whose end portion on a tip side is closed and whose end portion on the root side is opened. Cover member20includes a main body portion21and a fitted portion22arranged closer to the root side than main body portion21. The thickness of fitted portion22is formed to be thinner than the thickness of main body portion21. Cover member20is fixed to support member30by fitting fitted portion22of cover member20into the inner wall on the tip side of support member30.

In a state where ceramic heater10and cover member20are fitted into support member30, cover member20is arranged to cover the entire circumference of heater portion11without contacting heater portion11of ceramic heater10.

A region on the tip side of heater portion11is provided with a heat generating portion HA which generates heat using the power supplied from power line12. By heating this heat generating portion HA to about 1000° C., heater portion11serves as an infrared light source which emits infrared light.

Case40is formed to cover cover member20. Case40is fixed to support member30by fitting an inner wall on the root side of case40onto an outer wall of support member30. The infrared light emitted from heat generating portion HA of ceramic heater10passes through a hole21ain cover member20and is emitted to the outside.

FIG.3is a plan view of ceramic heater10. As shown inFIG.3, heater portion11is formed in the shape of a rectangular plate.FIG.3shows a state where ceramic heater10is viewed from a direction along a normal to a main surface11aof heater portion11. It should be noted thatFIG.2described above shows a state where infrared light source device1is viewed from a direction along main surface11aof heater portion11.

A dimension L1in a longitudinal direction of heater portion11, a dimension L2in a short direction of heater portion11, and the thickness of heater portion11can be set, for example, to about 50 mm, about 5 mm, and about 1.5 mm, respectively.

FIG.4is a plan view of cover member20.FIG.5is a cross sectional view of cover member20inFIG.4taken along a line V-V. As described above, cover member20has the shape of a cylinder whose end portion on the tip side is closed and whose end portion on the root side is opened.

A diameter din of an inner wall of cover member20is set to a value (for example, about 8 mm) which is slightly larger than dimension L2(for example, about 5 mm) in the short direction of heater portion11of ceramic heater10.

Main body portion21of cover member20has hole21aformed therein for emitting the infrared light from heat generating portion HA of ceramic heater10to the outside. The diameter of hole21acan be set to about 8 mm, for example. In addition, a thickness T of main body portion21of cover member20can be set to about 1.5 mm, for example.

In the present embodiment, a pure aluminum (aluminum with a purity of 99% or more), which has a high heat reflectivity and is less likely to be denatured by heat dissipation from heater portion11, is employed as a material for cover member20. For example, an aluminum alloy of JIS (Japanese Industrial Standards) A1000 series, more specifically, A1070 with an aluminum purity of 99.7% or more, or A1050 with an aluminum purity of 99.5% or more, is employed as the material for cover member20.

In infrared light source device1in accordance with the present embodiment, cover member20made of the pure aluminum having a high heat reflectivity as described above is arranged to cover the entire circumference of heater portion11. Thereby, instead of trapping the heat of heater portion11using a heat insulating material, heat radiation released from heater portion11can be efficiently reflected to heater portion11to heat heater portion11. Thus, when compared with a case where the circumference of heater portion11is covered with a heat insulating material such as porous ceramic (a case corresponding to a conventional structure), infrared light source device1can be downsized by reducing the thickness of cover member20, while maintaining the temperature of heater portion11at a target temperature (for example, about 1000° C.) or more. In addition, infrared light source device1can also be manufactured at a lower cost, because the pure aluminum is less expensive than the heat insulating material such as porous ceramic.

Further, in the present embodiment, the pure aluminum, which has a high heat reflectivity and is also less likely to be denatured by heat (on which an oxide film is less likely to be formed), is employed as the material for cover member20. This can suppress deterioration over time of the heat reflectivity of cover member20as much as possible.

The inventors of the present application set power consumption of ceramic heater10to be constant, covered the heater with a cover made of a variety of materials, and conducted experiments to confirm how much infrared light the heater emitted (that is, how much high temperature the heater itself had) using an infrared light detector.

When the material for the cover was ceramic (alumina), the heater had a low temperature, because alumina originally has a high emissivity.

When the material for the cover was stainless steel (SUS), at the beginning of an experiment, the heater had a high temperature, because stainless steel has a high reflectivity (that is, a low emissivity). However, as time passed, an oxide film was gradually formed on a cover surface, the cover surface turned black, and thereby the reflectivity of stainless steel decreased and the temperature of the heater gradually decreased.

Also when the material for the cover was stainless steel (SUS) and the inner wall of the cover was plated with gold, at the beginning of an experiment, the heater had a high temperature, because gold plating has a very high reflectivity. However, due to change over time, the cover surface turned black and the temperature of the heater decreased.

When the material for the cover was stainless steel (SUS) and the inner wall of the cover was plated with chromium, the heater had a low temperature, because the reflectivity of chromium is lower than that of gold or aluminum.

When the material for the cover was A6061 (an aluminum alloy with an aluminum purity of less than 99%), at the beginning of an experiment, the heater had a high temperature due to a high reflectivity. However, the temperature of the heater gradually decreased due to an oxide film of an alloy content added to aluminum.

When the material for the cover was A1050 (an aluminum alloy with an aluminum purity of 99.5% or more), the temperature of the heater was maintained at a high value due to a high reflectivity, and there was almost no influence of an oxide film and there was no temperature decrease over time. From the results of these experiments, it can be understood that the most excellent result can be obtained by employing a pure aluminum (aluminum with a purity of 99% or more) as the material for cover member20as in the present embodiment.

Further, in infrared light source device1in accordance with the present embodiment, by employing the structure of fitting ceramic heater10and cover member20into support member30, cover member20can be easily and appropriately suppressed from contacting heater portion11. That is, even if heater portion11is inclined with respect to cover member20when heater portion11is inserted into cover member20, cover member20can be fixed without contacting heater portion11as ceramic heater10and cover member20are eventually fitted into support member30. Thereby, even in a case where the temperature of heater portion11reaches or exceeds 1000° C., which is higher than the melting point of aluminum (660° C.), the temperature of cover member20can be maintained at a temperature lower than the melting point of aluminum (660° C.). As a result, cover member20can be appropriately suppressed from melting and deforming due to the heat from heater portion11.

It should be noted that, in order to fix a heat insulating material such as porous ceramic, which is difficult to be finely machined, without contacting heater portion11, it may be necessary to take measures such as additionally providing a metal cover for fixation around the heat insulating material. In contrast, in infrared light source device1in accordance with the present embodiment, the material for cover member20is aluminum, which can be finely machined easily. Thus, there is no need to additionally provide a metal cover for fixation, and infrared light source device1can have a simple structure.

As described above, in the present embodiment, infrared light source device1can be downsized and manufactured at a lower cost, while maintaining the temperature of heater portion11(infrared light source) at the target temperature or more.

The above embodiment has described the case where the material for cover member20is a pure aluminum. However, the material for cover member20is not necessarily limited to a pure aluminum. For example, the material for cover member20may be gold.

Further, as long as the material for the inner wall of cover member20is a pure aluminum or gold, the material for cover member20itself may not necessarily be a pure aluminum or gold. For example, a pure aluminum or gold may be deposited on the inner wall of cover member20made of a material other than a pure aluminum and gold.

Further, the material for cover member20may be an aluminum alloy with a purity of less than 99%. However, in order to suppress deterioration due to an oxide film as described above, it is preferable to set the purity of the aluminum alloy to a value which is close to 99% as much as possible.

As will be appreciated by those skilled in the art, the embodiment and variations thereof described above are specific examples of the following aspects.

An infrared light source device in accordance with one aspect includes: a heater which emits infrared light by being heated; and a cover member arranged to cover an entire circumference of the heater without contacting the heater, and having a hole formed therein for emitting the infrared light from the heater to outside. A material for an inner wall of the cover member is aluminum or gold.

According to the infrared light source device according to the first item, the cover member having the inner wall made of aluminum or gold with a high heat reflectivity is arranged to cover the entire circumference of the heater. Thereby, heat radiation from the heater can be efficiently reflected by the inner wall of the cover member to the heater to heat the heater. Thereby, when compared with a case where a heat insulating material is used, the thickness of the cover member can be reduced, while maintaining the heater at a high temperature. As a result, the infrared light source device can be downsized, while maintaining the temperature of the heater at a target temperature or more.

In the infrared light source device according to the first item, a material for the cover member is aluminum with a purity of 99% or more.

According to the infrared light source device according to the second item, since the material for the cover member is aluminum with a purity of 99% or more, heat radiation from the heater can be efficiently reflected to the heater to heat the heater. Further, when compared with a case where the material for the cover member is ceramic (alumina), stainless steel (SUS), or aluminum with a purity of less than 99%, for example, an oxide layer can be less likely to be formed on the surface of the cover member. Thus, deterioration over time of the heat reflectivity of the cover member can be easily suppressed.

The infrared light source device according to the first or second item further includes a support member into which the heater and the cover member are fitted. In a state where the heater and the cover member are fitted into the support member, the cover member is arranged to cover the entire circumference of the heater without contacting the heater.

According to the infrared light source device according to the third item, by employing the structure of fitting the heater and the cover member into the support member, the cover member can be easily and appropriately suppressed from contacting the heater.

A Fourier transform infrared spectroscope in accordance with one aspect includes the infrared light source device according to any one of the first to third items.

According to the Fourier transform infrared spectroscope, it is possible to achieve a Fourier transform infrared spectroscope including an infrared light source device which is downsized while maintaining the temperature of a heater at a target temperature or more.

Although the embodiment of the present invention has been described, it should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the scope of the claims, and is intended to include any modifications within the scope and meaning equivalent to the scope of the claims.