JPH0812281B2 - Light attenuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Since the dielectric multilayer can change the wavelength dependence by design considerably, by combining this with an optical attenuating film, an optical attenuating plate having a desired attenuating wavelength characteristic can be obtained. It will be possible to create.

[Industrial applications]

The present invention relates to an optical attenuating plate, and more particularly to an optical attenuating plate having a large degree of freedom in selecting wavelength characteristics.

[Conventional technology]

The light attenuating plate is used for attenuating light in an optical measuring device or other optical system to adjust it to a desired light amount, and usually,
A metal film is vapor-deposited on the surface of a substrate such as glass and the thickness thereof is adjusted to obtain a desired light attenuation amount.

[Problems to be solved by the invention]

The characteristics of the light attenuating plate as described above depend on the characteristics of the metal film. There is no problem if the wavelength band of the light used is narrow, but when it is necessary to attenuate the light over a wide wavelength band, the attenuation characteristics of the metal film are not always constant with respect to the wavelength. Light of varying quantity is obtained, which is problematic for some applications.

[Means for solving problems]

The present invention solves the above problems, and its basic configuration is shown in FIG. Dielectric multilayer films 3, 4, 5 and 6 are formed on the back surface or the same surface of the substrate 1 on which the light attenuation film 2 is applied. The figure shows a case where a dielectric multilayer film is formed on the back surface of the light attenuation film 2.

Thus, according to the present invention, the dielectric multi-layered film (3, 4, 5, 4) is formed on the same surface or the back surface of the light attenuating plate composed of the substrate (1, 11) on which the light attenuating film (2, 12) is adhered. 6; 13,14,15,16,17,18) to eliminate or reduce the attenuation-wavelength dependence of the optical attenuating plate.

[Work]

Since the dielectric multilayer film is used as an antireflection film and others, its characteristics have already been evaluated and clarified, and the wavelength characteristics can be set quite freely by appropriately selecting the type of dielectric, film thickness, and film structure. It is known that it can be designed. Therefore, it is possible to cancel the wavelength dependence of the light attenuation characteristic (light transmittance characteristic) of the conventional light attenuating plate by selecting an appropriate dielectric multilayer film.

〔Example〕

FIG. 1 shows a 10 dB optical attenuating plate which constitutes an embodiment of the present invention.
In the figure, 1 is a glass substrate, 2 is a titanium film, and 3 and 5 are TiO _2.
The films 4, 4 and 6 are SiO ₂ films. Titanium film 2 is about 50n
m, and the dielectric multilayer film is λ / 4 with the design center wavelength λ = 800 nm
= 1.00, the TiO ₂ film is 0.216 and the SiO ₂ film 4 is
0.331, TiO ₂ film 5 is 1.848, and SiO ₂ film 6 is 0.864. The glass substrate 1 has a thickness of about 0.5 to 1 mm.

The glass substrate (BK
-7) After polishing and cleaning both surfaces of 1, a titanium film 2 was deposited on one surface of the glass substrate 1 to form a 10 dB optical attenuation film by using an electron beam evaporation apparatus, and then on the surface opposite to the optical attenuation film.
The TiO ₂ film 3, the SiO ₂ film 4, the TiO ₂ film 5, and the SiO ₂ film 6 are sequentially deposited to form a dielectric multilayer film. This dielectric multilayer film may be formed on the light attenuating film, or conversely, the light attenuating film may be formed on the dielectric multilayer film.

In order to evaluate the attenuation characteristics of such a light attenuating film, it is necessary to compare the received light intensity with and without passing the light of a specific wavelength through the light attenuating plate and to change the wavelength continuously. it can.

FIG. 2 shows the results of examining the attenuation-wavelength dependence characteristics of a conventional optical attenuating plate in which a titanium film is formed on a glass substrate similarly to FIG. 1, but a dielectric multilayer film is not subsequently formed. As shown in Fig. 2, the loss decreases as the wavelength increases, and at the wavelength of 1300 nm, it decreases by 0.5 dB at around the design wavelength of 800 to 850 nm. Such wavelength dependence of loss cannot be ignored depending on the purpose of use.

As shown in FIG. 2, the wavelength dependence of the attenuation (loss) of the titanium film is slightly wavy in the wavelength region of 800 nm to 1300 nm, but it is decreasing almost monotonically. FIG. 3 shows the attenuation characteristics of the dielectric multilayer film described with reference to FIG. 1, but the attenuation amount (loss) increases almost monotonically with wavelengths of 800 nm to 1300 nm. Therefore, if this dielectric multilayer film is used in combination with the above titanium film,
It is considered that the attenuation characteristic at m to 1300 nm can be made almost constant without depending on the wavelength.

Fig. 4 shows the first diagram, which was created based on this idea.
It is the attenuation-wavelength dependence characteristic of the optical attenuating plate shown in the figure. From the figure, it can be seen that almost constant attenuation characteristics are achieved in the wavelength range of 700 nm to 1300 nm.

FIG. 5 shows a 20 dB optical attenuating plate which is another embodiment of the present invention. In the figure, 11 is a glass substrate, 12 is a titanium film, 13-18 are dielectric multilayer films consisting of 6 layers, 13, 15, 17 are TiO ₂ films,
14, 16 and 18 are SiO ₂ films. The thickness of titanium film 12 is about 100n
m, and the dielectric multilayer film has a design center wavelength λ = 850 nm λ / 4
= 1.00, the TiO ₂ film 13 is 0.20 and the SiO ₂ film 14 is
Is 0.33, the TiO ₂ film 15 is 1.80, the SiO ₂ film 16 is 1.85, and the TiO ₂ film 17 is 1.4.
0, the SiO ₂ film 18 is 0.85. Glass substrate 11 has a thickness of 0.5-1 mm
It is a degree.

This light attenuating plate can be manufactured by the same method as the light attenuating plate of FIG.

The results of evaluating the attenuation characteristics of this light attenuating film by the same method as in the case of the light attenuating plate of FIG. 1 are shown in FIGS. 6 to 8.

6 and 8 indicate the wavelength dependence of the optical attenuation characteristic of the conventional 20 dB optical attenuating plate to which the dielectric multilayer film is not applied. Although this optical attenuator has a design center wavelength of 850 nm, the attenuation (loss) decreases with increasing wavelength from 700 nm, and at 1400 nm, a decrease of 4.5 dB is observed with respect to 700 nm. FIG. 7 shows the attenuation characteristics of the dielectric multilayer film composed of 6 layers shown in FIG.
At 0 nm, the attenuation tends to increase almost monotonically. The circles in FIG. 8 indicate the final attenuation characteristics when the dielectric multilayer film having the attenuation characteristics in FIG. 7 is applied to the 20 dB optical attenuating plate having the attenuation characteristics in FIG. 6, that is, the light in FIG. It is the damping characteristic of the damping plate. By applying the dielectric multi-layer film in this way, the attenuation is 4.5 at wavelengths of 700 nm to 1400 nm.
It can be seen that it has decreased from dB to 1.5 dB.

〔The invention's effect〕

According to the present invention, it is possible to create a light attenuating plate in which the wavelength dependence of the attenuation of the light attenuating plate is corrected. Thus, the light attenuating plate of the present invention can be used in an optical system using a wide wavelength range and is very useful.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a 10 dB optical attenuating plate of the embodiment, FIG. 2 is a graph showing the attenuation characteristics of a conventional 10 dB optical attenuating plate, and FIG.
The figure is a graph showing the attenuation characteristics of the correction dielectric multilayer film.
FIG. 4 is a graph showing the attenuation characteristic of the 10 dB optical attenuating plate of the embodiment, FIG. 5 is a schematic sectional view of the 20 dB optical attenuating plate of another embodiment, and FIG. 6 is the attenuation characteristic of the conventional 20 dB optical attenuating plate. FIG. 7 is a graph showing the attenuation characteristics of the correction dielectric multilayer film, and FIG. 8 is the graph of the embodiment of FIG.
It is a graph showing the attenuation characteristic of the dB optical attenuating plate. 1 …… glass substrate, 11 …… glass plate, 2 …… titanium film, 12 …… 3,5 …… TiO ₂ film, 13,15,17 …… TiO ₂ film, 4,6 …… SiO ₂ film, 14,16,18 …… SiO ₂ film.

Claims (1)

[Claims] 1. A substrate (1,11) coated with an optical attenuation film (2,12).
A dielectric multi-layered film (3,4,5,6; 13,14,15,16,17,18) is formed on the same surface or the back surface of the light attenuating plate made of Attenuation-wavelength dependence is eliminated or reduced.