Importance

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Abstract

A dichroic spiral color wheel (108) having many spiral-shaped color filters (206). The boundary between adjacent color filters follows the spiral of Archimedes, defined as r=a.theta., where r is the radius of the boundary at a given point, a is a constant, and .theta. is the angle between a radial line through the given point and a reference radial. Using the spiral of Archimedes provides a boundary between adjacent color filters that is nearly parallel to the rows or columns of the modulator and moves across the light path at a constant speed. These two features make the spiral color wheel much more efficient than color wheels having pie shaped segments. The use of dichroic filters, which reflect out of band light is crucial to the operation of a sequential color recycling display system. When used in a sequential color recycling display system, small filter segments are used to enable on entire filter segment of each of the primary colors, and a clear segment if used, to be simultaneously imaged on the face of the light valve.

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First Claim