H. Fujikake et al., Automatic color-temperature compensator with guest-host liquid-crystal filter for video image sensing, APPL OPTICS, 40(14), 2001, pp. 2275-2281
A color-temperature compensating system with an electrically controllable l
iquid-crystal filter and a color sensor mounted on a video camera has been
developed for color image sensing. The filter contains two guest-host liqui
d-crystal devices with dichroic dyes that have strong light absorption for
shorter-wavelength light; two devices are necessary because of the spectral
difference between the sun and an incandescent lamp as light sources. The
filter's absorption is continuously controlled by the voltage applied to th
e filter. Because the filter is driven according to spectral information ab
out the illumination detected by the color sensor, the color balance of the
video image to be sensed can be compensated automatically and rapidly. Thi
s is especially useful for video image shooting in which a video camera exp
eriences changes in illumination color temperatures. (C) 2001 Optical Socie
ty of America.