| 摘要 |
PURPOSE:To improve directivity, to occupy less space and to permit easy cleaning by forming a diagonally vapor deposited film to be sandwiched between two polarizing elements on the surface of one polarizing element at a prescribed vapor deposition angle in such a manner that the intersection line with the surface of the polarizing element attains about 45 deg. angle. CONSTITUTION:The polarizing plates 11, 12 are made of a resin and are so disposed that the optical axes thereof intersect orthogonally with each other. The diagonally vapor deposited film 13 is formed by vapor deposition of tungsten oxide on the surface of the polarizing plate 11 at the azimuth of 45 deg. angle with the optical axis of the plate 11 and at 70 deg. vapor deposition angle. As a result, this filter acts effectively as the directional optical filter which makes use of the polarizing effect of the polarizing plates and the double refraction effect of the diagonally vapor deposited film; in addition, the color of the transmitted light can be controlled by selecting a light source and since a louver is not used, the filter occupies less space and is easy to clean.
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