Patent ID: 7517092

Claim:
An optical system for use in a display device, the optical system comprising: an illumination source, including a color wheel, wherein the illumination source produces light of a plurality of colors; a digital micromirror device wherein the digital micromirror device modulates the light of the plurality of colors to generate modulated light in correspondence with an image being displayed; one or more optical elements for directing the light of the plurality of colors and the modulated light so as to display the image; and a position selectable filter spaced apart from the color wheel and operable separately from the color wheel, wherein the filter attenuates a substantially constant percentage of one of (i) the light of the plurality of colors and (ii) the modulated light across the image being displayed, the percentage of attenuation being dependent on a selected position of the filter, wherein the position selectable filter includes an optical coating applied in an angularly gradient fashion where each adjacent section results in a different amount of light attenuation.