Design Of Wide Angle Projection Lenses For LCOS Rear-Projection TV Sets With A Large Screen And Compact Structure

The current development of rear-projection TV's tends higher resolution, larger screen size, compact construction and brighter colour. The projection lens is the core part of a rear-projection TV. As its imaging unit, the lens should form a high definition and free-distortion image with high magnification between a short conjugate distance.In this paper, based on the design experience and knowledge of objectives, the choice about the form of projection optical system is analyzed. The relationship among the structure parameters of a telecentric retrofocus lens is deduced and discussed. And the method to determinate its first-order parameters is given and discussed. Then according to the development tendency of rear-projection TV,a set of expected design index of its projection lens is prescribed. Two objectives that are both suitable for high-level projection television sets are obtained with help of an optical design software. Their optimal results and performance evaluations are given in detail. They have the advantages of compactness and high imaging performance, but include fewer aspheric surfaces and make of domestic normal glasses. The aspheric lenses make of PMMA so that they fit for mass production. Finally, the tolerance of one designed lens is analysed and assigned. It is shown that the designed projection objectives can be manufactured with current art.Moreover, a new type of tilt projection lens to actualize large screen and ultra-thin rear-projection structure is introduced. Its basic principle is expounded. As an example an initially designed tilt projection lens is given.