JPH0695047B2 - General-purpose integrating sphere - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an integrating sphere used for measuring luminous flux, for example, an integrating sphere used as a photometric instrument in an analyzer such as a spectrophotometer, a colorimeter, and a turbidimeter. It depends on the sphere, specifically, the inner wall of the integrating sphere.

<Prior Art> Since the inner wall of the integrating sphere needs to have a uniform high reflectance in the measurement wavelength range, the conventional inner wall is filled with white powder 9 such as magnesium oxide, barium sulfate, or aluminum oxide. It has been applied.

For coating the white powder with such a conventional integrating sphere, a binder that changes the optical characteristics of the powder is not used in order to maintain the high reflectance as described above. And
The white powder was adhered to the inner wall of the integrating sphere by the solidification due to the adhesive force and the cohesive force of the powder itself.

<Problems to be Solved by the Invention> However, the adhesive strength is extremely weak only by relying on the adhesive force and cohesive force of the powder itself as described above, and there are the following drawbacks.

Since the adhesive strength of the powder was weak, it was easily peeled off by a slight impact, the reflectance of the inner wall surface was changed, and the dropped powder adhered to the photometric window and the measurement sample, thus lowering the measurement accuracy.

Also, when measuring a soft measurement sample such as cloth, the sample contacts the inner wall edge of the sample opening of the integrating sphere,
There is a problem that the white powder itself spills out and the powder contaminates the sample. In order to prevent such contamination, a method is used in which powder is not applied to the light incident hole and the peripheral portion of the sample opening as shown in FIG. 2 (A). The metal surface exposed in the part impairs the light diffusivity of the inner wall, and there is a drawback that an accurate measured value cannot be obtained.

Furthermore, in the powder state, the optical characteristics change with time due to water adsorption and contamination, so that it is difficult to stably maintain the optical characteristics for a long period of time, and there is a drawback that the durability is poor. .

Further, as shown in FIG. 3, there is a problem that a rapid change in reflectance occurs in the near infrared region and accurate measurement cannot be performed.

To solve these drawbacks, sintered products such as ceramics, which have stable optical characteristics and little change over time, are conceivable. However, the manufacturing cost and the difficulty of processing after forming and sintering, etc. From what, industrial substitute value is poor.

On the other hand, as a low-priced product, a product in which a white resin paint is simply applied to the inner surface of the sphere has been used, but as shown in FIG. 4, when a resin such as acrylic or enamel is used, the wavelength is
For light of 450 nm or less, there is a problem that the reflectance becomes extremely low and measurement becomes impossible, and it cannot be used as an integrating sphere in a wide wavelength range.

<Means for Solving the Problems> The present invention for solving the above problems includes an integrating sphere 1
It is characterized in that the inner wall is coated with a thermal spray coating 8 having diffuse reflectivity in the wavelength range of use with respect to light entering therein.

<Operation> The thermal spray coating 8 coated on the inner wall of the integrating sphere 1 diffusely reflects the light incident on the integrating sphere 1. The thermal spray coating 8 formed by thermal spraying has high adhesive strength to the inner wall of the integrating sphere 1, is not easily peeled off by shock or vibration during handling, and has little change in optical characteristics over time.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. The drawing shows an integrating sphere 1 when applied to a colorimeter. Fig. 1 is a sectional view of the integrating sphere 1, and Fig. 5 is a gun for plasma spraying showing a method for forming a sprayed coating 8 on the inner wall of the integrating sphere 1. 12 is a cross-sectional view of 12 and a radius 1a of the integrating sphere 1. FIG.

The integrating sphere 1 is provided with a light entrance hole 2, a light exit hole 3 and a sample opening 4 on the same great circle. The light entrance hole 2 and the sample opening 4 are formed on the same axis of the integrating sphere 1, and the light exit hole 3 is formed at a position perpendicular to the axis.

The measurement sample 5 is applied to the sample opening 4 from the outside, and the light entering from the light incident hole 2 first strikes the measurement sample 5 and is reflected. At this time, the peripheral end faces of the light entrance hole 2, the light exit hole 3 and the sample opening 4 are covered with the thermal spray coating 8 as shown in FIG. However, there is no error in the measured value due to reflection on the peripheral surface of the hole which is not covered with white powder.

A photodetector 6 is attached to the outside of the light emitting hole 3. The light reflected from the measurement sample 5 repeats diffuse reflection in the integrating sphere 1 and then reaches the photodetector 6 attached to the light emitting hole 3.

The integrating sphere 1 has two hemispheres with the center line shown in FIG. 1 as a boundary.
It is composed by combining 1a. The base material 7 of each hemisphere 1a is aluminum in the integrating sphere of the present embodiment, and aluminum oxide powder is sprayed on the inner surface to form a sprayed coating 8.

The method of manufacturing the integrating sphere 1 will be described below. The inside of the aluminum base material is cut out into a hemispherical shape and mechanically formed, and the inner surface is mirror-finished to some extent. Since the base material 7 is made of aluminum, it has the advantages of good workability, inexpensiveness, and rust resistance.

Next, a treatment such as shot blasting is applied to the inner surface to form fine irregularities. This improves the adhesiveness of the thermal spray coating 8 and promotes the diffusivity when reflecting light.

Thermal spraying is performed on the inner surface of the base material 7 which has been subjected to the base treatment as described above.

FIG. 5 shows a sprayed state by the plasma spray gun 12. The electrode 4 is housed inside the nozzle body 13, and a DC voltage is applied to the nozzle body 13 and the electrode 14 from a power supply 15. A jet hole 17 through which a plasma flame 16 is jetted is provided at the tip of the nozzle body 13, and a gas introduction port 18 is provided at the base end.
Has been drilled. A required amount of gas is supplied from the gas inlet 18. A spray material supply port 19 is provided on the jet side of the jet hole 17,
They are provided close to each other in a direction intersecting with the ejected plasma flame 16.

At a position of about 100 mm from the ejection hole 17 of the gun 12 for plasma spraying, a hemispherical base material 7a is arranged with the inner surfaces facing each other, and the spraying material is jetted and melted from the spraying material supply port 19 into the plasma flame 16. ,
A thermal spray material is attached as a thermal spray coating 8 to the inner wall of the base material 7a.

Here, the particle size of the thermal spray material, the material of the thermal spray material, the type of gas to be injected, and the supply amount thereof vary depending on the condition of the base treatment, the wavelength range to be used, and the like. For example, in the integrating sphere 1 of this embodiment, The particle size of the material is 10 to 20 μm, the material of the thermal spray material is aluminum oxide, the gas to be injected is argon hydrogen gas, and the supply rate is 35 [/ min].

Further, as the material of the thermal spray material, a material exhibiting diffuse reflectance in the wavelength range of the light to be measured is used. As described above, aluminum oxide is used in the integrating sphere of this embodiment, but spinel, mullite, and the like may be used as the thermal spray material that can be used in the visible and near infrared wavelength regions. In addition, the composition is not limited as long as it exhibits diffuse reflectance in the used wavelength range, including diffuse reflectance of light outside the visible and near infrared wavelength ranges. Other than the above, examples of the gas used include argon nitrogen (inert) gas.

As described above, the hemisphere 1a is formed, and the pair of hemispheres 1a is combined to form the integrating sphere 1. Integrating sphere 1 by thermal spraying
Since the coating is formed on the inner wall, the thermal spray coating 8 is formed not only on the inner wall but also on the peripheral portions of the respective light entrance holes 2, light exit holes 3, and sample opening 4.
Can be formed, and since the adhesive strength is strong, the thermal spray coating 8 does not easily peel off. Further, it can be used regardless of the use atmosphere, for example, it can be used in water.

FIG. 3 shows the conventional powder-adhered reflection surface and spray coating 8 for each wavelength.
3 is a graph showing the diffuse reflectance of the reflective surface of FIG. Thermal spray coating 8
In this case, the measurement range is widened from the visible light range to the near infrared range, and the reflectance is rather improved particularly in the wavelength range of 1800 nm or more. Therefore, the measurement of light in the near infrared region, which has a problem in measurement accuracy with the conventional integrating sphere, can be made accurate.

FIG. 4 is a graph showing the ratio of the reflectance to the reflectance of barium sulfate for each wavelength, but the thermal spray coating 8 was high and stable even in the vicinity of 400 nm where the reflectance of the inner wall coated with white paint drops. The reflectance is shown.

Therefore, the sprayed coating 8 enables measurement in a wide range from a short wavelength range of about 400 nm to a near infrared wavelength range in visible light.

Although the integrating sphere of the embodiment has been described above, the integrating sphere of other formats and systems can be similarly implemented.

<Effects of the Invention> According to the general-purpose integrating sphere of the present invention configured as described above, the coating formed by thermal spraying has high adhesive strength, and the thermal sprayed coating does not peel off even if it receives some impact, and also has optical characteristics. Since there is little change with time, problems such as deterioration of measurement accuracy are solved, and an optically stable integrating sphere can be obtained for a long period of time. Moreover, unlike the case of applying the conventional white powder, the trouble that the white powder that has peeled off contaminates the sample is eliminated, and it is not necessary to particularly unpaint the peripheral wall of the hole such as the sample opening. It is possible to prevent a defect such as a decrease in light diffusive reflectivity of a coated portion.

Furthermore, improved impact resistance makes handling of the equipment extremely easy, and it can be installed not only in test and research equipment, but also in a wide range of other industrial products, such as for portable use or as an optical element holder. Can be easily sprayed regardless of the shape of the sprayed surface and can be produced at a low cost, which has the advantage of increasing versatility.

Further, by changing the thermal spray material, a high reflectance can be maintained in a wide wavelength range, so that there is an effect that it can be used in an extremely wider wavelength range than in the past.

In addition to the high reflectivity, the film formed on the inner surface of the integrating sphere is formed by the thermal spraying by depositing melted droplet-shaped particles on the sprayed surface by collision. It has an effect of being particularly excellent in diffuse reflectance.

[Brief description of drawings]

FIG. 1 is a front sectional view of an integrating sphere, FIGS. 2A and 2B are enlarged sectional views of a conventional integrating sphere and a sample opening of the integrating sphere of the present invention, and FIG. FIG. 4 is a graph showing the diffuse reflectance of the powder-attached reflecting surface and the reflecting surface of the thermal spray coating on the integrating sphere of the present invention. FIG. 4 shows the reflectance of the white paint and the thermal spray coating when the reflectance of barium sulfate is 100. FIG. 5 is a graph showing each wavelength, and FIG. 5 is a cross-sectional view of a plasma spray gun and a hemisphere of an integrating sphere showing a method for forming a sprayed coating on the inner wall of the integrating sphere. 1: Integrating sphere, 2: Base material 8: Thermal spray coating, 12: Plasma spray gun

Claims (1)

[Claims] 1. A thermal spray coating (8) having diffuse reflectivity in a wavelength range used for light incident on an integrating sphere (1).
A general-purpose integrating sphere whose inner wall is covered with.