3m Innovative Properties Company

R Edward English, Jr

Simon Magarill

Todd S Rutherford

Charles L Bruzzone

Jiaying Ma

Stephen K Eckhardt

Sean M Donnelly

E Gregory Fulkerson

Boris Ardashnikov

Arlie R Conner

Arlie Richard Connor

An illumination system, such as might be used for illuminating a projection system, includes at least a first source of incoherent light capable of generating light in a first wavelength range. The system also includes a body containing a fluorescent material that emits light in a second wavelength range, different from the first wavelength range, when illuminated by light in the first wavelength range. The body has an extraction area and at least some of the light at the second wavelength is internally reflected within the body to the extraction area.

Fluorescent volume light source

High pressure mercury arc lamps are commonly used as the illumination source in many projection systems. Such lamps may be deficient in either output power or spectrum, and so it is desirable to combine the light from the lamp with light from a second light generator. The second light generator may be another mercury lamp or a solid state source, such as one or more light emitting diodes. Different ways of combining light from two light generators are described. The second light source may be an arrangement of a number of red LEDs that supplements the red light produced by the mercury light. A tunnel integrator may be used to homogenize the combined light beam and to reduce the angular separation between the light beams from the two light generators.

Combined light source for projection display

A projection display system employs one or more color modifying aperture stops, such as apodizing aperture stops, to provide high contrast, balanced color and high throughput. One projection system includes a reflective liquid crystal-on-silicon light valve positioned with a polarizing beam splitter, such as a wire grid polarizing beam splitter, for each of the primary color component light paths to separately impart image information into each of the primary color components of light. A color combiner receives and combines the primary color components of light with imparted image information to provide light representing a polychromatic display image. At least one aperture stop is positioned along at least one of the primary color component light paths to balance relative intensities of the primary color components of light.

Color component aperture stops in projection display system

A compound polarization beam splitter () for use with a reflective, polarization-modulating, imaging device (), e.g., a LCoS device, is provided. The compound PBS has: (a) an input prism (); (b) an output prism (), and (c) a polarizer (), which is located between the two prisms () and which may be a wire grid polarizer () or a multi-layer reflective polarizer (). Polarized illumination light () enters the input prism () through a first surface () and undergoes total internal reflection at a second surface () before being reflected from the polarizer () and polarization-modulated at the imaging device (). The polarizer's tilt angle (&#x3b2;) is less than 45&#xb0;, which reduces astigmatism and the required back working distance of the system's projection lens ().

Compound polarization beam splitters

A compound polarization beam splitter ( ) for use with a reflective, polarization-modulating, imaging device ( ), e.g., a LCoS device, is provided. The compound PBS has: (a) an input prism ( ); (b) an output prism ( ), and (c) a polarizer ( ), which is located between the two prisms ( ) and which may be a wire grid polarizer ( ) or a multi-layer reflective polarizer ( ). Polarized illumination light ( ) enters the input prism ( ) through a first surface ( ) and undergoes total internal reflection at a second surface ( ) before being reflected from the polarizer ( ) and polarization-modulated at the imaging device ( ). The polarizer's tilt angle (&bgr;) is less than 45&deg;, which reduces astigmatism and the required back working distance of the system's projection lens ( ).

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Cincinnati, OH, United States of America

R Edward English, Jr