JPS62116901A - Antireflection film - Google Patents

Abstract

PURPOSE:To decrease reflectivity in a specific wavelength band to about 0.05% by using a high refractive index material for the 1st and 3rd layers an a low refractive index material for the 2nd and 4th layers with a film consisting of 4 layers and standardizing and specifying the film thicknesses thereof at 1/4 the design wavelength. CONSTITUTION:Four layers of optical films are formed on a transparent substrate 5 consisting of glass, etc. The high refractive index material (for example, TiO2, 2.3 refractive index) is used for the 1st layer 1 and 3rd layer 3 counted from the substrate side and the low refractive index material (for example, SiO2, 1.46 refractive index) is used for the 2nd layer 2 and 4th layer 4. The respective layers are formed to the following film thickness with the thickness of 1/4 the design wavelength as 1: The 1st layer 1 is formed to 0.205-0.215, the 2nd layer 2 to 0.336-0.346, the 3rd layer 3 to 1.788-1.798 and the 4th layer 4 to 0.828-0.848. Then the transmission loss is 0.002dB at about 850nm and 1,100nm wavelength if the design wavelength is 1,250nm and the reflectivity is made about 0.05%.

Description

[Detailed Description of the Invention] [Summary] The anti-reflection film is composed of four layers, with the first and third layers made of a high refractive index material and the second and fourth layers made of a low layer index material. The thickness is standardized by the design wavelength of 2, and the first layer is 0.205.
~0.215, second layer 0.336~0.346, third layer
The layer is 1.788-1.798, the fourth layer is 0.828-0
．． 848 makes it possible to reduce the reflectance to about 0.05% in a specific wavelength band.

[Industrial application field]

The present invention relates to an antireflection film that has particularly reduced reflectance in a specific wavelength band.

[Conventional technology]

An anti-reflection film is a film mainly used to reduce reflection on the surface of glass or other transparent materials and increase transmittance, and conventionally, optical single-layer films or multi-layer films have been used.

[Problem that the invention seeks to solve]

Conventional antireflection films usually have a transmittance of 99.5%, that is, a reflectance of about 0.5%, and there is a problem in that the reflectance is too high for special uses.

The present invention was created in view of these points, and an object of the present invention is to provide an antireflection film with a low reflectance of about 0.05%.

Means for Solving Problem C] Therefore, in the present invention, the first to fourth layers 1 to 4 counting from the substrate side are formed on the glass substrate 5, and the first and third layers are formed on the glass substrate 5. 1.3 is made of a material with a high refractive index,
The second and fourth layers 2 and 4 are formed of a material with a low refractive index, and the film thickness of each layer is standardized by the design wavelength A of the antireflection film, and the thickness of the first layer 1 is 0.205 to 0. .215, second layer 2 is 0.336-0.346, third layer 3 is 1.788
~1.79B, and the fourth layer 4 is characterized by having a value of 0.828 to 0.848.

[For production]

With the above configuration, when the design wavelength is 1250nm, the reflectance is reduced to 0.05 around 850nm and 1l100n.
% (transmission loss 0.002 dB).

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention.

In this embodiment, four layers of optical films are formed on a transparent substrate 5 such as glass, and the first to fourth layers are counted from the substrate side, and the first layer 1 and the third layer 3 are A material with a high refractive index (for example, TiO2, refractive index 2.3) is used for the second layer 2 and the fourth layer
Layer 4 is made of a material with a low refractive index (e.g. SiO□, refractive index 1.4).
6), and the film thickness of each layer is 0.210±o,oos for the first layer 1, and 0.210±o,oos for the first layer 1, with the design wavelength A being 1.
Layer 2 is 0.341±0.005, third layer 3 is 1.793
±0.005, and 0.838±0.01 for the fourth layer 4.

In this embodiment configured in this way, the design wavelength is set to 1250.
In the case of nr@, the transmission loss characteristics are as shown in FIG. Transmission loss is 0 at wavelength 850nm and around 1l100n
．． 002 dB, and the reflected light is about 30 dB compared to the incident light.
dB attenuation (ie, the reflectance is approximately 0.05%). This is 10 dB greater than the attenuation of a normal anti-reflection film.
Reflection can be reduced accordingly.

The antireflection film of the present invention can be used, for example, in detecting an optical fiber break point. FIG. 3 shows a method of detecting a break point in an optical fiber using a fault locator.

To explain with a diagram, the light sent out from the laser light source built into the fault locator 10 is reflected at the break point of the optical fiber 11 (indicated by an x mark) and returns to the receiver inside the fault locator 10, and the delay time is The fracture position is detected by counting.

The reflection at the break point is Fresnel reflection due to the difference in refractive index between the optical fiber and air, and the reflectance is (n-1/n+1)'', where n is the refractive index of the optical fiber.

This reflection condition is the same at the optical fiber input end face, so there is reflection here as well, and since it is the input end, it returns to the locator body without being attenuated, and if it continues as it is, it will not adversely affect the detection of the break point. By applying the antireflection film of the present invention to the input end face, reflection at the input end face can be prevented and the optical fiber break point can be easily detected.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce the reflectance with an extremely simple configuration, and it is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing transmission loss characteristics of an embodiment of the present invention, and Fig. 3 is a diagram illustrating a method for detecting a break point in an optical fiber using a fault locator. It is. In FIG. 1, 1 is a first layer 2, a second layer 3, a third layer 4, and a fourth layer 5, which are substrates. Figure 1 shows an embodiment of the present invention.1...First layer 2...Second layer 3...Third layer 4...Fourth layer 5...Substrate wavelength (nm) This invention Fig. 2 shows the transmission loss characteristics of the embodiment of Fig. 2. Fig. 3 for explaining the method of detecting the break point of an optical fiber using a fault locator.

Claims (1)

[Scope of Claims] 1. The first to fourth layers (1 to 4) counting from the substrate side are sequentially formed on a glass substrate (5), and the first and third layers (1, 3 ) is formed of a material with a high refractive index, the second and fourth layers (2, 4) are formed of a material with a low refractive index, and the film thickness of each layer is 1/1 of the design wavelength of the antireflection film. 4
Normalized by 4) is an anti-reflection film characterized in that it has an anti-reflection coating of 0.828 to 0.848.