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Abstract

A color switch is provided for selectively switching between color bands for use, for example, in projection optics and direct view optics. The color switch has fewer and thinner layers than in the prior art, but exhibits equal or better color purity and light efficiency. The color switch or filter includes a first filter section for selectively blocking green light and including a cholesteric filter, a quarter wave plate and a liquid crystal switch. The color filter has a second filter section for selectively blocking blue and/or red light including a stack of retarder elements and liquid crystal switches, preferably Deformed Helical Ferroelectric (DHF) switches. The parameters of the filter are determined by an optimization process including minimizing a cost function (G) with respect to the parameters of the second filter section. A polarizing element may be positioned in front of the stack and may be of a type which does not absorb radiation.

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First Claim