Patent ID: 6088941
Filing Date: 2000-07-18
Classification: G02B

Abstract:
Viewing apparatus comprising:a viewing surface having a viewing area comprising a plurality of elemental portions of a given extent;an array of controllable liquid crystal light attenuators located behind the viewing surface, each light attenuator of the array being associated with a particular elemental portion of said plurality of elemental portions and including active elements having a controllable opacity over an area different from the given extent of the elemental portion with which it is associated;a light source behind the array of light attenuators which illuminates the light attenuators; anda plurality of light couplers, each associated with an elemental portion and located between the elemental portion and a corresponding element of the array, which provide controlled and substantially uniform back-illumination of the elemental portion of the viewing surface,wherein the attenuators have a maximum transmission condition and a minimum transmission condition, the ratio of the transmission of light for the two conditions defining an on-off contrast ratio which varies with an angle of incidence of illumination of the attenuators and wherein the light attenuators are illuminated more strongly at angles of incidence for which the on-off contrast ratio is relatively higher than at angles for which the on-off contrast ratio is relatively lower.