JPH0526162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer interference film filter used in an optical measuring device that optically measures the properties of an object to be measured.

[Prior art] When measuring the properties of an object to be measured, such as thickness, moisture, color tone, etc., comparison wavelengths are provided near both sides of the measurement wavelength, and comparison calculations are performed to determine the properties of the object to be measured using three colors. There are measurement methods that can be used.

Conventionally, when performing spectroscopy of three wavelengths, a method has been used in which three filters are provided in a multi-rotation selector and rotated by a motor to perform spectroscopy.

[Problems to be Solved by the Invention] However, when three filters are used in this way, there are problems such as the device becoming larger and the motor generating heat.

Therefore, the measurement system can be simplified and highly accurate by realizing spectroscopy of two comparison wavelengths with a single filter using a multilayer interference film filter having a double peak.

In view of the above points, an object of the present invention is to provide a multilayer interference film filter having two peaks near both sides of a reference wavelength.

[Means for Solving the Problems] This invention consists of a high refractive index film with an optical thickness of λ/4, a low refractive index film with an optical thickness of λ/4, and a high refractive index film from the substrate side. At least one set of alternating layers, a low refractive index film with an optical thickness of λ/2, a high refractive index film with an optical thickness of λ/4, a low refractive index film with an optical thickness of λ/2, an optical film. A multilayer film consisting of at least one set of alternating layers of a high refractive index film and a low refractive index film with a thickness of λ/4, and a stack of high refractive index films with an optical thickness of λ/4, near both sides of the reference wavelength λ. to 2
This is a multilayer interference film filter with two peaks.

[Embodiment] FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention.

Generally, interference film filters are made by laminating high refractive index films and low refractive index films alternately by vapor deposition, sputtering, etc. The materials for the high refractive index films include Ge,
Si, TiO ₂ , ZrO ₂ , ZnS, etc. are used, and as the material of the low refractive index film, SiO, SiO ₂ , MgF ₂ etc. are used.

Next, the structure of a filter using such a high refractive index film and a low refractive index film will be explained with reference to FIG.

In the figure, S is a substrate such as glass, the reference wavelength is λ, and the optical film thickness λ/
At least one set of alternating layers of a high refractive index film 1 with an optical thickness of λ/4, a low refractive index film 2 with an optical thickness of λ/4, and a high refractive index film 3 with an optical thickness of λ/4; /2 low refractive index film 4, optical thickness λ/4 high refractive index film 5, optical film thickness λ/2 low refractive index film 6, optical film thickness λ/4 high refractive index film 7 and a low refractive index film 8 with an optical thickness of λ/4.
The high refractive index film 9 has an optical thickness of λ/4 and is laminated with at least one set of alternating layers, and the outermost layer is in contact with an external medium.

For example, TiO ₂ is used for high refractive index films, and TiO 2 is used for low refractive index films.
SiO ₂ is used, the number of alternating layers is 3, and the reference wavelength λ
= 1.0 μm, a multilayer interference film filter (double peak filter) having two peaks near both sides of the reference wavelength λ is obtained as shown in FIG.

Note that the number of alternate layers is suitably 1 to 3.

FIG. 3 shows another embodiment of the invention;
In the embodiment shown in the figure, a low refractive index film 1 having an optical thickness of λ/4 is placed between the substrate S and the high refractive index film 1 of the multilayer film.
0, a low refractive index film 11 having an optical thickness of λ/4 is provided on the high refractive index film 9 as the outermost layer of the multilayer film. In this case as well, a similar multilayer interference film filter having two peaks near both sides of the reference wavelength λ as shown in FIG. 2 can be obtained.

In this case, if we look only at the number of alternating layers, it is 2 to 4.
It becomes the rank.

[Effect of the invention] By stacking the high refractive index film and the low refractive index film as described above, two
A multilayer interference film filter (double peak filter) with two peaks is obtained and can be used for various optical measurements.

[Brief explanation of the drawing]

1 and 3 are configuration explanatory diagrams showing one embodiment of the present invention, and FIG. 2 is a transmittance characteristic diagram of the filter of the present invention. S...Substrate, 1,3,5,7,9...High refractive index film, 2,4,6,8,10,11...Low refractive index film.

Claims (1)

[Claims] 1. At least one set of alternating layers of a high refractive index film with an optical thickness of λ/4, a low refractive index film with an optical thickness of λ/4, and a high refractive index film from the substrate side. , optical thickness is λ/2
A low refractive index film with an optical thickness of λ/4, a high refractive index film with an optical thickness of λ/4,
Low refractive index film with optical thickness λ/2, optical thickness λ/2
A multilayer film consisting of at least one set of alternating layers of high refractive index films and low refractive index films (4) and high refractive index films with an optical thickness of λ/4, which have low transmittance at the reference wavelength λ, and have low transmittance at the reference wavelength λ. A multilayer interference film filter characterized by having two peaks of high transmittance at nearby wavelengths. 2. The multilayer interference film filter according to claim 1, characterized in that a low refractive index film with an optical thickness of λ/4 is provided between the substrate and the multilayer film and on the outermost layer of the multilayer film. . 3. The multilayer interference film filter according to claim 1 or 2, characterized in that the number of said alternating layers is 1 to 3.