| abstract |
PCT No. PCT/GB98/01203 Sec. 371 Date Oct. 25, 1999 Sec. 102(e) Date Oct. 25, 1999 PCT Filed Apr. 24, 1998 PCT Pub. No. WO98/49585 PCT Pub. Date Nov. 5, 1998A collimator is formed of a stack of layers (11) of different thicknesses in a way analogous to a low-pass interference filter. When illuminated by narrow-band light of a predetermined wavelength just within the pass band of the filter, the collimator preferentially transmits light incident within a predetermined angular range, usually near-normal. The collimator is especially useful with photoluminescent liquid-crystal display, having phosphor emitters (17), because the collimator layers can simply be deposited on one face of the liquid-crystal modulator (1). |