Patent ID: 6796659
Filing Date: 2004-09-28
Classification: G02B,H04N

Abstract:
A projection display device comprising:an illumination system having a light source and an optical system for providing an illumination beam, an image display system for modulating the illumination beam with image information and projecting an image on a screen, filter means for transmitting a first portion of the radiation from the light source having a first wavelength range in the visible area to the optical system, and for absorbing a second portion of the radiation from the light source, the second portion having a second wavelength range outside the visible area and between 250 and 425 nm; and cooling means comprising a liquid for cooling the filter means, characterized in that the filter means comprises the liquid which contains a radiation-absorbent additive for absorbing the second wavelength range, wherein the liquid comprises water and the radiation-absorbent additive is a substance which is soluble in water and is selected from the group consisting of benzophenonephosphates and benzotriazolephosphates.