Band-shifted liquid crystal structure for projection of images without spectral distortion

An optical system, comprising:

• at least one reflective liquid crystal lightvalve for modulating the polarization of incident light within a specified band of wavelengths into on and off states, the lightvalve comprising:
• (i) a pixelated reflective backplane;
• (ii) a first liquid crystal layer, positioned proximate the pixelated reflective backplane, the first liquid crystal layer being tuned in the off state to switch incident light at the center of the specified band of wavelengths into a state that is not fully off;
• and (ii) a second liquid crystal layer, positioned proximate the first liquid crystal layer wherein the first liquid crystal layer is positioned between the second liquid crystal layer and the pixelated reflective backplane, the second liquid crystal layer having a birefringence which, at a given depth within its thickness, is substantially equal and opposite to a birefringence of a layer within the first liquid crystal layer that is located at a matching distance from a midplane separating the first and second liquid crystal layers;
• and
• an optics subsystem, positioned proximate the at least one lightvalve, for receiving an input light signal, directing at least a portion of the input light signal towards the lightvalve such that the lightvalve modulates the portion of the input light signal and projects an output light signal in response thereto, the optics subsystem directing the output light signal through an exit surface associated therewith.

A liquid crystal structure for use in an optical lightvalve, the structure comprising:

• a first twisted nematic liquid crystal layer;
• a second twisted nematic liquid crystal layer, positioned proximate the first layer;
• and
• a quarterwave retarder, positioned proximate the first and second layers, each twisted nematic layer being set to a thickness that provides, from the individual layer, an optimum projected black state at shorter wavelengths than a wavelength band of interest.