To provide an optical filter element which is formed of an interference film having a small number of layers, exhibits nearly the same optical characteristics as a multi-layered film filter having many layers, and is reducible in insertion loss polarization dependency.
A dielectric multi-layered film filter is formed as a film on a 1/4-wavelength plate. On the reverse surface of the 1/4-wavelength plate, a reflecting film 3 is formed. The dielectric multi-layered film filter 1 is designed so as to have a desired characteristic as light passes through it twice. Light made incident on the dielectric multi-layered film filter 1 has its plane of polarization rotated by 90° when reflected by a total reflecting film 3 to impinge the dielectric multi-layered film filter 1 again as compared with that when it is incident on the dielectric multi-layered film filter 1 for the 1st time. Consequently, the light passes through the dielectric multi-layered film filter 1 twice to have the plane of polarization changed and the insertion loss polarization dependency is eliminated.
NOGUCHI YOSHIKIYO
HOSOYA HIDEYUKI
Tadashi Takahashi
Takashi Watanabe
Masakazu Aoyama
Next Patent: ELECTROPHOTOGRAPHIC IMAGE RECEIVING SHEET AND ITS MANUFACTURING METHOD