US 6,549,338 B1 · Bandpass filter to reduce thermal impact of dichroic light shift

Abstract

A color splitting prism assembly (100) comprised of three prisms. Each a dichroic filter at an interface (112) between a first and second of the three prisms reflects a first primary color component of a white light beam passing through the prism assembly. The first primary color component is directed to a first modulator (118). The remaining portions of the white light beam enter a second prism (108) and strike a second dichroic filter at the interface between (124) the second and third prisms. The second dichroic filter separates a second primary color component from the white light beam leaving a third primary color component to travel through the third prism (110) to a third modulator. The second primary color component of the white light beam is directed to a second modulator (128). Light modulated by the first and third modulators travels through the prisms at a slightly different angle than the unmodulated light and therefore reacts differently upon striking the first dichroic filter for the second time. Portions of the light modulated by the first and third modulator travel toward the second modulator (128). An additional filter on or near the exit face (126) of the second prism (108) prevents light in the first and third primary color components from reaching the second modulator (128) and heating the second modulator (128). The light rejected by the additional filter is dispersed by ground glass surfaces of the color splitting prism assembly.

Claims18

Dependent claims

A method of creating a full color image, the method comprising the steps of:

providing a white light beam to a first prism, said white light beam entering a first face of said first prism and traveling to a second face of said first prism;
reflecting a first primary color portion of said white light beam and passing a first remainder portion through said second face of said first prism and a first face of a second prism, said reflected first primary color portion exiting said first prism through an exit face;
modulating said first primary color portion to reflect a modulated first primary color portion to said second face of said first prism;
reflecting a second primary color portion of said first remainder portion at a second face of said second prism to exit an exit face of said second prism;
passing a third primary color portion through a third prism to exit an exit face of said third prism;
modulating said second and third primary color portions to reflect modulated second and third primary color portions to said second face of said second prism;
focusing said first, second, and third modulated primary color portions onto an image plane;
and
further filtering at one said exit face to block light modulated at another exit face.

6 more elements

Dependencies are inferred from the claim text.

Bandpass filter to reduce thermal impact of dichroic light shift

Life of this patent

Bandpass filter to reduce thermal impact of dichroic light shift

Life of this patent

Abstract

Claims18