Importance

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Abstract

A switchable color filter employs chiral liquid crystal circular polarizers to minimize the attenuation of light passing through a system in which it is incorporated. One preferred embodiment (12) of the switchable color filter includes a light modulator (32) positioned between the light polarizing assembly (20) and first and second chiral liquid crystal cells (36 and 38). The light polarizing assembly receives unpolarized light and transmits circularly polarized light of colors included within first and second narrow color bands. The first chiral cell reflects incident light within the first color band and in a first polarization state, and the second chiral cell reflects incident light within the second color band and in a second polarization state. The light modulator cooperates with a switching circuit (34) to selectively provide first and second polarization switching states. The first switching state causes light within the first color band to exit the color filter and blocks light within the second color band from exiting the color filter, and the second switching state causes light within the second color band to exit the color filter and block light within the first color band from exiting the color filter. Another preferred embodiment (100) of the switchable color filter is capable of receiving light within three color bands and selectively providing a light output of one of three colors. Either embodiment of the switchable color filter can be advantageously implemented in systems (10 and 100) that are insensitive to a restricted viewing angle, which stems from the use of chiral liquid crystal circular polarizers.

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First Claim