Patent ID: 7301592

Claim:
A method of adjusting display brightness comprising operating a liquid crystal comprising in order (a) a backlight unit for providing illumination; (b) a rear absorptive polarizer disposed proximate the backlight unit for receiving the incident illumination and transmitting substantially polarized illumination; (c) a liquid crystal spatial light modulator for forming a modulated beam by selective, pixel-wise modulation of the polarization of the substantially polarized illumination; (d) an absorptive color filter array for transmitting selected wavelengths of the modulated beam from the LC spatial light modulator; (e) a front absorptive polarizer having a transmission axis for transmitting the portion of the modulated beam having a polarization in alignment with the transmission axis; and, (f) a reflective polarizing element disposed between the liquid crystal spatial light modulator (c) and the front absorptive polarizer (e), the reflective polarizing element reflecting a portion of dark state light back toward the backlight unit, wherein the backlight unit comprises at least one light source for which the light output can be controlled as a function of the number of dark pixels in the displayed image.