JPH0588002A - Infrared optical parts - Google Patents

Abstract

PURPOSE:To provide the IR optical parts having high photosensitive resistance, reliability and transmission performance with materials having relatively low toxicity. CONSTITUTION:An Sb2S3 film 11 is used as a 1st layer on a base body 10 consisting of a metal halide and a CaF2 film 12 is used as a 2nd layer. Consequently, the extremely stable IR optical parts are obtd. Reflection is particularly effectively prevented if particularly the optical film thickness of the Sb2S3 film 11 is specified to lambda/2 with the central wavelength designated as lambda and the optical film thickness of the CaF2 film 12 to lambda/ 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to infrared optical parts used for optical devices and the like.

[0002]

2. Description of the Related Art Currently, optical component materials used in laser-applied equipment or infrared optical devices such as thermal imaging sensors are zinc selenide (ZnSe), gallium arsenide (GaAs), and germanium (Ge). It is formed by an optical polishing method from an infrared transmitting material such as. In this method, a crystal surface manufactured by a CVD method or the like is used to form a mirror surface through a multi-step process from rough polishing to finish polishing using abrasive grains, so that the price is very expensive.

On the other hand, as a cheaper manufacturing method,
A method of forming an infrared optical member made of a metal halide by pressure molding below its melting point is considered promising. (See, for example, Japanese Patent Laid-Open No. 59-212801.) However, as a drawback of this material, for example, when light of a wavelength of 10.6 .mu.m of a CO.sub.2 laser is transmitted, the reflection loss at the substrate interface is about. There is a problem that the transmission efficiency is deteriorated by 11%.

Generally, these materials are often used as optical components such as window materials and lenses, and reflection loss occurs not only on the surface of the optical component but also on the two interfaces of the front surface and the back surface.
Actually, there was a problem that a reflection loss of about 22% occurs and the transmission efficiency deteriorates to about 78%. This is not only a problem of reduction in transmission efficiency, but also reflected light becomes unnecessary light such as flare and ghost, which often causes a serious problem in use.

To solve this problem, JP-A-60-125
As disclosed in Japanese Patent No. 801, an attempt has been made to improve the transmission efficiency by forming an antireflection film having a two-layer structure on a substrate.

For example, an alkali halide film such as KCl or NaCl is formed on a substrate, and silver bromide, silver chloride,
Thallium bromide, thallium iodide, or zinc sulfide, germanium, silicon, cadmium telluride, or gallium arsenide is formed, and the antireflection function is realized by these two-layer films to reduce reflection loss. Came.

Further, this material has a drawback that when it is irradiated with light having a wavelength of about 0.4 micron or less, the material is exposed to light and the optical characteristics at visible and infrared wavelengths are significantly deteriorated. Was there. That is, there is a practically very large problem that the characteristics are deteriorated and the transmittance is reduced to several percent or less by leaving it for a few minutes under sunlight or ultraviolet light.

Therefore, as described in Infrared Engineering (1963, published by Modern Science Co., Ltd., P124), by coating an Sb ₂ S ₃ film on a substrate, a wavelength of about 0.4 μm or less can be obtained. Attempts have been made to improve the resistance to photosensitivity by blocking the light of the above.

[0009]

However, the above-mentioned method has the following problems. That is,
Since an alkali halide film such as KCl or NaCl is extremely weak against moisture, the second thin film is used as a protective film for the alkali halide film, and it is very difficult to manufacture as shown in FIG. Had to film. This not only complicates the mass production process but also increases the cost, which is a serious problem in practical use.

Further, if the second thin film formed on the alkali halide film of the first layer has minute defects such as pinholes, moisture penetrates into the alkali halide film from these defects. However, it also has a problem of attacking the film. In particular, since the alkali halide film itself is tidal, if there is a defect even in one place, moisture will infiltrate more and more through this defect, and eventually the alkali halide film will have a very large problem in practical use. Was.

When a thin film of silver bromide or silver chloride is used as the second layer, the material itself has photosensitivity, and therefore, when exposed to light having a wavelength of about 0.4 micron or less, There is a problem that the second layer thin film itself is exposed to light, and the optical characteristics are significantly deteriorated particularly in the infrared region.

Further, thallium bromide, thallium iodide, zinc sulfide, cadmium telluride, and gallium arsenide have relatively strong toxicity, and therefore have a problem in safety in forming or using a thin film. It was

Further, when silicon or germanium is used as the second layer, the linear expansion coefficient is largely different from that of the substrate, so that there is a problem in adhesion, reliability and the like, especially in a use environment where the temperature greatly changes. It had a big problem in practical use.

When Sb ₂ S ₃ is used, the photosensitivity is improved, but the refractive index is relatively large at about 2.6 to 3.0, so that the optical characteristics shown in FIG. 12, for example, are used. Therefore, there was a big problem in optical performance.

Here, the vertical axis of FIG. 12 represents the transmittance and the horizontal axis represents the wavelength (unit: micron). That is, the transmittance characteristic of only the substrate is 120, but simply coating Sb ₂ S ₃ on the substrate causes the transmittance to be significantly reduced as shown by the transmittance characteristic 121. That is, it shows the same transmittance as that of the substrate only at a certain specific wavelength, and becomes lower than the transmittance of the substrate at other wavelengths. This is due to the interference effect of the thin film and is a problem that cannot be eliminated in principle.

In view of the above problems, it is an object of the present invention to provide an infrared optical component having high photosensitivity, reliability and transmission performance with a material having relatively low toxicity.

[0017]

In order to solve the above problems, an infrared optical component of the present invention comprises at least two thin film layers made of Sb ₂ S ₃ and CaF ₂ on a substrate. It is a thing.

[0018]

According to the present invention, Sb ₂ S ₃ is used to improve the photosensitivity, and a multilayer structure with CaF ₂ is used to exhibit an antireflection effect and improve the transmittance characteristics. Will be done.

[0019]

EXAMPLES Infrared optical components of examples of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the structure of an infrared optical component in an embodiment of the present invention. In FIG. 1, 10 is a substrate, 11 is a Sb ₂ S ₃ film, and 12 is Ca.
It is an F ₂ film. As the substrate 10, for example, a metal halide such as a solid solution of silver chloride / silver bromide or a solid solution of thallium bromide / thallium iodide is used. In this example, a solid solution of silver chloride was used.

Further, here, the films 11 and 12 are formed of the substrate 10.
Although it is shown that it is formed on the plane, it may be a curved surface or a lens shape. In addition, FIG.
Although the structure in which the film is formed only on one surface of 0 is shown, it may be coated on both surfaces.

Here, CaF ₂ is generally a substance having a low refractive index, is transparent in the wavelength range of about 0.15 μm to 8 μm, and is a nontoxic and good substance that is often used for window materials and the like. It is known that there is a large absorption at wavelengths near 10 microns. However, as a result of experimental examination, it was found that the problem of light absorption is almost eliminated when the thin film having a thickness of about several microns is used.

Therefore, forming such a low refractive index, non-toxic thin film on Sb ₂ S ₃ is very useful in terms of antireflection theory or in practice.

Therefore, the Sb ₂ S ₃ film 11 and the CaF ₂ film 12
Is formed by, for example, a vacuum vapor deposition method, and the spectral transmittance is measured. The result is shown by a curve 20 in FIG. Here, the vertical axis represents the transmittance (unit:%), and the horizontal axis represents the wave number and the wavelength. The characteristic curve 21 shows the spectral transmittance characteristic of only the silver chloride substrate. The optical thickness of the Sb ₂ S ₃ film is nd
= 5.6 μm, the optical thickness of the CaF ₂ film is nd
= 2.8 microns.

From this, it can be seen that excellent characteristics in which the transmittance greatly exceeds the transmittance of the substrate can be realized in the wavelength range near 10 microns.

This is not only the Sb ₂ S ₃ film on the substrate,
Since it has a two-layer film structure with a CaF ₂ film, the interference effect of these thin films produces an antireflection effect, and the conventional S
Optical components having significantly improved transmittance characteristics as compared with the b ₂ S ₃ single-layer film have been realized.

FIG. 3 shows the optical characteristics of the present infrared optical component in the visible region. From this, it is understood that the transmittance at a wavelength of about 0.4 micron or less is about 0%, and the light in the wavelength region where the silver chloride material is sensitive can be completely blocked.

As a result of leaving the optical component of this example in the environment of sunlight or artificial ultraviolet light for about 1000 hours, the transmittance characteristics did not change at all. This is because the present optical component was able to completely block the light of the wavelength that the silver chloride material easily sensitized, and it can be seen that an optical component having significantly improved light resistance was realized.

Further, here, the description has been made focusing on an example in which the transmittance is improved in comparison with the substrate transmittance in the wavelength region around 10 microns, but the Sb ₂ S ₃ and CaF ₂ films are 0.7 to 13 microns. Needless to say, since it is transparent in the wavelength range of 1, the useful infrared optical component can be realized in these wavelength ranges only by changing the optical film thickness of each layer.

Further, in the present embodiment, an example in which the thin film is formed on one surface of the substrate has been described, but it may be formed on both surfaces. It goes without saying that the transmittance characteristics are further improved if they are formed on both sides.

Further, Sb ₂ S ₃ and CaF ₂ are not only free from problems such as tidal property, but are relatively less toxic materials, so that they are also very practically useful in this respect.

(Embodiment 2) In this embodiment, the two-layer structure has been described. Next, the second embodiment having the three-layer structure will be described with reference to FIG.

The Sb ₂ S ₃ film 4 as the first layer is formed on the substrate 40.
1, the CaF ₂ film 41 is formed as the _second layer, and the Sb ₂ S ₃ film 43 is formed as the third layer. As the forming method, the vacuum evaporation method is used as in the first embodiment. Further, as the base 40, for example, silver chloride is used as in the first embodiment.

Here, for example, when the optical thickness of each layer is set to a central wavelength λ = 10 μm, the first layer Sb ₂ S ₃ film is λ / 16, and the second layer CaF ₂ film is λ /. 8 shows the spectral transmittance characteristic when the third layer Sb ₂ S ₃ film is set to λ / 16.

The characteristic curve 50 is the spectral transmittance of the substrate 40, and the curve 51 is the spectral transmittance when a thin film having a three-layer structure is formed on the substrate 40. In this way, 3
It can be seen that by forming a thin film having a layer structure, the transmittance in the vicinity of 10 microns is remarkably improved.

In this embodiment, as in the first embodiment having a two-layer structure, an example in which the film is formed on only one side of the substrate has been described, but there is no problem even if the film is formed on both sides. By making both sides, the transmittance can be further improved.

FIG. 6 shows the spectral transmittance characteristics in the ultraviolet-visible region of this example. From this, it can be seen that the light having a wavelength that is easily exposed to light by the silver chloride substrate of 0.4 μm or less is blocked. As with Example 1, the optical component of this example was left in the environment of sunlight or artificial ultraviolet light for about 1000 hours. As a result, the transmittance characteristics did not change at all, and an optical component with significantly improved light resistance was realized. It was confirmed that it was done.

Sb ₂ capable of blocking light of 0.4 micron or less
As a result of examining the film thickness of the S ₃ film, it was found that if the film thickness is about 0.2 μm or more, light in the UV-visible region can be blocked, and there is no problem in the anti-photosensitive property.

Therefore, it can be said that setting the thickness of the Sb ₂ S ₃ film to 0.2 μm or more is extremely useful in terms of anti-photosensitivity.

FIG. 7 shows the transmittance of HeNe laser light and S.
The relationship of the film thickness of the b ₂ S ₃ film is shown. The transmittance decreases remarkably as the film thickness increases, and the transmittance is about 1 μm at the film thickness of about 1.0 μm.
It can be seen that the value drops to about%.

For the inspection of infrared optical parts, the transmittance of HeNe laser is required to be about 1% on one side.
Setting the thickness of the b ₂ S ₃ film to about 1 micron or less
It can be said that it is extremely useful in the inspection process.

Therefore, it can be said that it is very useful to set the film thickness from 0.2 micron to 1.0 micron from the viewpoint of HeNe laser light transmission and photosensitivity.

Next, a result of the anti-reflection study, Optics equal optical thickness of the first layer of Sb ₂ S ₃ film and a third layer of Sb ₂ S ₃ is, and Sb ₂ S ₃ film It has been found that extremely good optical characteristics can be realized when the sum of the optical film thickness and the optical film thickness of the CaF ₂ film satisfies the relationship of about λ / 5.

In this embodiment, as an example, the optical film thickness of the Sb ₂ S ₃ film is λ / 16 and the optical film thickness of the CaF ₂ film is λ / 16.
8 is shown. FIG. 8 shows the case where the optical film thickness of Sb ₂ S ₃ is λ / 40 and the optical film thickness of the CaF ₂ film is λ * 7/40.

Good transmittance characteristics can be realized in the wavelength range around 10 microns. It can be seen that this relational expression is extremely useful, including that of the second embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG.

The first layer is a CaF ₂ film and the second layer is Sb ₂ S
_{The third} film and the third layer are CaF ₂ films. The transmittance characteristics when the center wavelength λ is 10 μm and the optical thickness of each layer is λ / 2 for the first layer, λ / 2 for the second layer, and λ / 4 for the third layer. Shown in 10. Here, the characteristic curve 100 shows the transmittance characteristic of the base body 90 alone, and the curve 101 shows the characteristic when a thin film is formed on the base body 90. As the base body 100, silver chloride is used.

From this, it can be seen that good transmittance characteristics are obtained in the wavelength band around 10 microns.

As with Examples 1 and 2, the optical components of this example were also left in the sunlight or artificial ultraviolet light environment for about 1000 hours. As a result, the transmittance characteristics did not change at all, and the light resistance was remarkably improved. It was found that the optical components described above were realized.

Therefore, by using this structure, it is possible to realize a high-performance infrared optical component having excellent photosensitivity and extremely high transmittance.

[0051]

As described above, according to the present invention, Sb ₂ is formed on the substrate.
By providing a thin film layer made of S ₃ and a thin film layer made of CaF _{2, an} infrared optical component having high light resistance and high transmission performance can be obtained.
It can be provided with a material having relatively low toxicity. It can be said that it is extremely useful in practical use.

[Brief description of drawings]

FIG. 1 is an external view showing a configuration of a first embodiment of an infrared optical component of the present invention.

FIG. 2 is an optical characteristic diagram in the infrared region of the component of the same example.

FIG. 3 is an optical characteristic diagram in the UV-visible region of the component of the same example.

FIG. 4 is an external view showing the configuration of a second embodiment of the infrared optical component of the present invention.

FIG. 5 is an optical characteristic diagram in the infrared region of the component of the same example.

FIG. 6 is an optical characteristic diagram in the UV-visible region of the component of the same example.

FIG. 7 is a diagram showing the relationship between the film thickness and the transmittance of the Sb ₂ S ₃ film.

FIG. 8 is an optical characteristic diagram in the infrared region of the component of the same example.

FIG. 9 is an external view showing the configuration of a third embodiment of the infrared optical component of the present invention.

FIG. 10 is an optical characteristic diagram in the infrared region of the component of the same example.

FIG. 11 is an external view of a conventional optical component.

FIG. 12 is an optical characteristic diagram of the conventional optical component.

[Explanation of symbols]

10, 40, 90, 110, 120 Substrate 11, 41, 43, 92 Sb ₂ S ₃ 12, 42, 91, 93 CaF _{2 20,} 51, 101 Optical properties of the present invention 21, 50, 100 Substrate optical properties 111 KCl 112 CdTe 121 Sb ₂ S ₃ single layer film

Claims (10)

[Claims] 1. A thin film layer made of Sb ₂ S ₃ and C on a substrate.
An infrared optical component having at least two thin film layers made of aF ₂ . 2. An infrared optical component having a thin film layer made of Sb ₂ S ₃ as a first layer and a thin film layer made of CaF ₂ as a second layer on a substrate. 3. The optical film thickness of the thin film layer of Sb ₂ S ₃ of the first layer is about λ / 2, where λ is the central wavelength, and
The optical thickness of the CaF ₂ thin film layer is about λ / 4
The infrared optical component according to claim 2, wherein 4. A thin film layer made of Sb ₂ S ₃ as a first layer and a thin film layer made of CaF ₂ as a _second layer on a substrate,
An infrared optical component including a thin film layer made of Sb ₂ S ₃ as the third layer. 5. The sum of the thickness of the first layer thickness of the thin film layer made of Sb ₂ S ₃ of the third layer thin film composed of Sb ₂ S ₃ of 0.
The infrared optical component according to claim 4, which has a size of 2 to 1 micron. 6. The optical film thickness of the thin film layer made of Sb ₂ S ₃ of the first layer and the optical film thickness of the thin film layer made of Sb ₂ S ₃ of the third layer are equal and Sb ₂ S ₃ The infrared optical component according to claim 4, wherein the sum of the optical film thickness of the thin film layer made of and the optical film thickness of the thin film layer made of CaF ₂ is λ / 5. 7. The optical film thickness of the first thin film layer made of Sb ₂ S ₃ is about λ / 16, where λ is the central wavelength, and the second thin film layer made of CaF ₂ is Optical film thickness is about λ /
8. The infrared optical component according to claim 4, wherein the third thin film layer made of Sb ₂ S _{3 has} an optical film thickness of about λ / 16. 8. A thin film layer made of CaF ₂ as a first layer and a thin film layer made of Sb ₂ S ₃ as a _second layer on a substrate,
An infrared optical component provided with a thin film layer made of CaF ₂ as the third layer. 9. The optical film thickness of the first thin film layer made of CaF ₂ is about λ / 2, where λ is the central wavelength, and
The optical film thickness of the thin film layer of Sb ₂ S ₃ of the _second layer is about λ / 2.
9. The infrared optical component according to claim 8, wherein the third thin film layer made of CaF _{2 has} an optical film thickness of about λ / 4. 10. The infrared optical component according to claim 1, wherein the substrate is a metal halide.