Patent ID: 6101749
Filing Date: 2000-08-15
Classification: G02B

Abstract:
Viewing apparatus comprising:a viewing surface having a viewing area comprising elemental portions of a given extent;a liquid crystal array comprising an array of controllable liquid crystal light attenuators located behind the viewing surface, each element of the light attenuator array being associated with an elemental portion and including active elements having a controllable opacity;a light source, situated behind the array of light attenuators, illuminating the attenuators with light having a range of angles of incidence with the viewing surface; andlight couplers which couple light which passes through the light attenuators to the viewing surface,wherein the attenuators are switchable between a first condition in which the transmission is a maximum and a second condition in which transmission is a minimum, the ratio of the transmission of light passing through the light attenuator for the two conditions constituting an on-off contrast ratio which varies with the angle of incidence of the illumination of the attenuators andwherein the light couplers couple light which passes through the attenuators at angles having a high on-off contrast ratio with a higher efficiency as compared to light at other angles to the viewing surface and further including:elements situated between the light source and the liquid crystal array which operate on light from said source to provide light of greater intensity at angles at which the on-off contrast ratio is relatively high than at angles at which the on-off contrast ratio is relatively low.