[OPTICAL REVIEW Vol. 5, No. 2 (1998) 93-98]

Electrically-Controllable Liquid Crystal Polarizing Filter for Eliminating Reflected Light

Hideo FUJIKAKE, Kuniharu TAKIZAWA, Tahito AIDA, Hiroshi KIKUCHI, Takanori FUJII and Masahiro KAWAKITA

NHK Science & Technical Research Laboratories, 1-10-1, Kinuta, Setagaya-ku, Tokyo, 157-8510 Japan

(Received December 5, 1997; Accept February 3, 1998)

A high-speed controllable polarizing filter has been developed to eliminate obstructive polarized light reflected from glass and watery surfaces for image pickup in video media program producing and marine dynamic remote sensing. In this device, the polarization plane of incident light is rotated through 0°, 45°, 90° or 135° by an electrically-controllable polarization rotator composed of 45° and 90° twisted nematic liquid crystal cells, and the polarization component of reflected light is absorbed by a fixed polarizing film. It selectively absorbs more than 80% of incident white light linearly polarized in an arbitrary direction. With the drastic reduction of reflected light, the object images hidden by the bright reflected light are clearly captured in real time. Another type of polarizing filter, using a guest-host liquid crystal cell instead of the polarizing film, controls light absorption as well as polarization angle.

Key words : polarizing filter, reflected light elimination, polarization rotator, twisted nematic liquid crystal, guest-host liquid crystal