JPS6064304A - Non-polarizing beam splitter - Google Patents

Abstract

PURPOSE:To decrease the rate of change in the polarizing component with respect to a change in incident angle by providing a three-layered structure coated with semitransparent films on the surface of a thin silver film to a transparent base material thereby constituting a non-polarizing beam splitter. CONSTITUTION:The semitransparent film 3, then thin silver film 4 and further semitransparent film 5 formed on the reflecting surface of a rectangular prism 1 of a beam splitter A using two rectangular prisms 1, 2 are required to be controlled in order to be made non-polarizing. The films 1, 3 can be easily controlled by selecting conditions for vapor deposition of, for example, titanium dioxide, silicon monoxide, etc. Titanium dioxide is superior in the visible region and particularly silicon monoxide is superior in the near IR region. The refractive index of the silicon monoxide changes with the speed of vapor deposition, etc. and therefore the refractive index is controllable as desired within an about 1.5-2.0 range.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a non-polarized beam spooler to be used, and the object is to make the P-polarized light and the S-polarized light of transmitted light and reflected light equal or close to this.

Conventional non-polarized beam splitters have often had a multilayer thin film structure, but these multilayer thin film structures have a complex structure, require many processing steps, are difficult in terms of accuracy, and have problems with reproducibility. In addition, other beam splitters made by laminating a metal thin film or a metal thin film and a semi-transparent film on a transparent substrate such as a plane mirror, a-rhythm, etc. also have relatively improved polarization characteristics. This is still not sufficient to satisfy the objectives of a non-polarized beam sinter: transmitted P-polarized light (Tp) = transmitted S-polarized light (Tg) and reflected P-polarized light (Rp) = reflected S-polarized light (Rs).

The present invention relates to the improvement of a non-polarizing beam sinter by combining the metal film and the semi-transparent film, and consists of a total of three layers, seven layers of the metal film and one layer of the semi-transparent film on the transparent base material. It is something.

Next, embodiments of the present invention shown in the drawings will be described in detail.

The example shows an optical system for signal (tracking, focus) detection, consisting of one right-angle prism 1.2
In beam striper A using
In order to make the light non-polarized, it is necessary to control the thickness of the semi-transparent film 3.5 and the refractive index to appropriate values. This is because the semitransparent film 1.3 is made of titanium dioxide (T), for example.
It can be easily controlled by vapor deposition conditions such as IO*) or silicon monoxide (810).

However, in the visible region (TiOl) is particularly important in the near-infrared region (
The refractive index of (Sin) is superior, but the refractive index of (Sho) changes depending on the deposition speed, etc., so the refractive index can be controlled within the range of 13 to 2.0.

In the present invention, the division ratio between transmittance and reflectance is roughly controlled by the thickness of the silver thin film 4, and Tp=Ts and R
Setting p=Rs is controlled by the thickness and refractive index of the semitransparent film 3.5.

However, the beam splitter of the present invention has a substantially uniform reflectance and a transmittance in the wavelength range 7AO-1 of the semiconductor laser.
Good characteristics were obtained up to gA;Om. (See Figure 1) Furthermore, with the conventional multilayer film described above, there is a drawback that the polarization component is highly dependent on the angle of incidence, but in the present invention, even if the angle of incidence changes by 100 degrees, the polarization component does not change. The amount of change is extremely small.

As described above, the results of the experiment confirmed the superiority of the present invention.

[Brief explanation of the drawing]

The figures show an embodiment of the non-polarizing beam slitter of the present invention. FIG. 1 is a front view, and FIG. 2 is a graph. Symbols A are beam slitters 11 and 2 are right-angle grisms, 3.5 is a translucent film, and 4 is a thin silver film. Procedural amendment 58.10.24 Showa year, month, day 1, case description 1988 Patent Application No. 172813 2
, Title of the invention Non-polarizing beam splinter 3, Relationship to the amended person case Applicant 4, Agent 5, ? i! The date of the official order is self-initiated, so amend it to ``.

Claims (1)

[Claims] A non-polarizing beam striper with a three-layer structure film on a transparent surface plate material, consisting of a thin silver film and semi-transparent films on both sides.