COLOR PROJECTION SCREEN Russian patent published in 1997 - IPC

FIELD: design of large-screen projection TV home appliances, in particular, projection of TV or computer picture on large-size reflection or transparent screen. SUBSTANCE: device has screen 1 and projection lens which has cubic prism 3 which is made from four glued rectangular prisms so that two diagonal surfaces with extended diachronic mirrors are shaped. In addition device has two mirrors 3 which are located at output faces of cubic prism, and three cathode-ray tubes 9. Lens has three members, first of which is shared by all cathode-ray tubes 9, is located before input face of cubic prism 3. Its axis is perpendicular to plane of screen 1. Said first member has positive and negative mobile and stationary lenses which are spaced by two gaps. Focal length of first member 2 is greater than focal length of projection lens more than twice. Intersection line of diagonal surfaces of cubic prism 3 is perpendicular to axis of first member 2. Second member is made from three pairs of positive lenses 4 which are located at three output faces of cubic prism 3. Their refraction index is less than 1.6. Their non-spherical surfaces face each other. Mirrors 5 are located at angle of 40-50 degrees to axis of first member 2 at upper and lower faces of cubic prism 3 between second and third members. Edges of mirrors 5 that are closest to cubic prism are closer to screen 1. Third member is made from three negative menisci 6 which are spaced from lenses of second member by air spaces. Said menisci are directed to screen 1 with their concave surface. In addition third member has three protection flat-parallel plates 7 and transparent liquid which is located between plates 7 and negative menisci 8. Said plates serve as protection for cathode-ray tubes 9. Another claim of invention describes device design in which additional third mirror 11 is located before third input face of cubic prism 3 as other ones but position of these members differ; in particular, intersection line of diagonal surfaces of cubic prism 3 coincides with optical axis of first member 2; mirrors 5, 11 are located at angle of 40-50 degrees with respect to corresponding output face of cubic prism 3 so that lower edge of each mirror 5, 11 is closer to lenses of second member 2. Yet another claim of invention describes device design which is identical to second claim but yet another mirror 12 is inserted between screen and lens. Said mirror alters direction of optical axis by right angle in horizontal plane. In addition position of members is different; in particular, axis of first member 2 is parallel to plane of screen 1; intersection line of diagonal surfaces of cubic prism 3 is perpendicular to plane of screen 1; three mirrors 5, 11, 12 which are located at three output faces of cubic prism 3 are positioned so that their edges that are closer to cubic prism 3 are located at minimal space from output face of cubic prism 3 which is parallel to input face. Mirrors 5, 11, 12 are located at angle of 40-50 degrees with respect to input face. EFFECT: increased quality of picture, decreased warm-up time. 3 cl, 5 dwg