North American Philips Corporation

U.S. Philips Corporation

Jill F Goldenberg

Thomas S McKechnie

William F Guerinot

Ralph H Bradley, Jr

Joshua D Eskin

Jeffrey Arthur Shimizu

Roland Winston

Arne L Duwaer

Wilhelmus A Timmers

Leendert Vriens

T Stewart McKechnie

A video color image projector which includes a block of crossed dichroic mirrors for combining the light rays from image rasters on respective monochrome image display devices and a projection lens for projecting the composite color rays so as to form an enlarged color image on a display screen. Each display device has a faceplace which is convex on the interior surface thereof and having thereon an interference filter in the form of an internal angularly reflecting coating (IARC). Each faceplate is liquid - coupled to a negative power lens element, so that the faceplate, coupling liquid (or gel) and such lens element effectively constitute a single negative power field flattener lens at each entrance side of the dichroic block. The composite color rays at the exit side of the dichroic block are projected on the display screen by an assembly of lens elements which includes at least one optically positive lens element. The focal length of the complete projection lens formed by such assembly and each of the negative field flattener lenses may be from 0.5 to 0.9 times the diagonal D of the image raster on each display device, so that the projector is sufficiently compact to be included in a cabinet suitable for consumer television receivers.

Short focal length video color projector employing dichroic mirror block

A light valve projection system includes an illumination system having a light collector in the form of a non-imaging reflector with a rectangular input aperture and a rectangular output aperture. A two dimensional light source at the input aperture illuminates the output aperture substantially uniformly.

Light valve projection system with improved illumination

The present invention is directed to illumination structures useful in display systems for projection video and television devices performing with high efficiency and good color rendition. Such illumination sources include a light source having an inner and outer envelope with plane mirrors within the outer envelope to direct reflected light, a light source providing randomly polarized light with polarizing structure for passing a desired polarization of the polarized light, and an arc lamp having at least two arcs for supplying uniform illumination in two dimensions. These illuminating structures enable significantly improved illumination in the appropriate projection video and television systems.

Illumination system for LCD projection television

In a liquid crystal projection t.v. system the color gradient over the projected image, which is due to angular sensitivity of the dichroic mirrors, is minimized by introducing a field lens (61,62,63) next to the light values or LC-panels (21, 22, 23) in the light paths of the blue (b.sub.B), green (b.sub.G) and red (b.sub.R) beams. By chosing different length light paths before and after the light valves and LC-panels a difference in angular sensitivity of the separation mirror (41,42) and the recombination mirrors (52,53) can be compensated for.

Modulation system for projection display

A first concave mirror collects the light emitted by a light source in a first half space and forms a first image of the light source at a point proximate thereto. A second larger concave mirror opposite the first mirror forms second and third images from the respective source and first image. The second and third images are formed at the input aperture of a non-imaging reflector, which in turn emits the light uniformly through the output aperture thereof.

Illumination system for non-imaging reflective collector

An illumination system for an LCD projection display system to increase the brightness of the system. The system includes a polarizing beam splitter which splits a beam of light from a light source into two orthogonally polarized beams. The beam of the desired polarization direction is directed through a first face of a prism so that it reflects off of a second face of the prism and exists through a third face. The other beam of the non-desired polarization direction is passed through a device for rotating its polarization 90.degree. and towards the underside of the second face of the prism at an angle such that it is refracted into the prism. Both beams then exit the prism through its third face, have the same polarization direction, and are only slightly divergent. The recombined beam may be thereafter directed towards the light modulation system. The illumination system minimizes the number of air-glass interfaces and the number of reflecting surfaces.

Illumination system for an LCD display system

Display system includes an illumination system which utilizes a light collector in the form of a non-imaging reflector having a rectangular output aperture, a modulating device in the path of light emitted by the illumination system, and a projection lens. Three such collectors having spectrally tuned lamps therein and using rectangular LCD's as modulating devices can be used in a television projection system.

Light valve projection system with non imaging optics for illumination

Display systems useful for projection video and television systems are provided to perform with high efficiency and good color rendition. In these systems, color may be provided, as one example, by various light valves, such as liquid crystal displays. Each of the liquid crystal displays are positioned at equal path distances from an illuminating subsystem, and have equal path distances from the light valves to a projection subsystem. This enables optimum illumination of each of the light valves. Various embodiments of arranging the light valves, as well as providing illumination are described.

Display system with equal path lengths

a Fresnel lens for use in rear projection screens wherein said lens has a plurality of facets facing away from the light source and each of said facets has an optimal riser angle, said riser angle varying from the center to the outer edge of said lens as a function of the focal length the refractive index, the angular subtense of the exit pupil and the radial distance from the center of the lens, thereby improving the efficiency of the Fresnel lens.

Optimum riser angle for fresnel lenses in projection screens

A one-piece projection screen with improved overall efficiency and contrast, the elimination of corner illumination deficiencies and undesirable image artifacts. The optical power of the screen is divided between two or more surfaces acting as Fresnel lenses, and the region or medium separating the surfaces has a different index of refraction than that of the mediums upstream or downstream of the surfaces. The preferred embodiment of the projection screen includes a diffuser and a lenticular array downstream of the surfaces.

One-piece projection screen

A screen consists of a clear mechanically stable substrate and a bulk diffuser portion which is as close to the front lenticules as possible. The diffuser may be dispersed within the lenticules or in a separate area immediately adjacent to them. The screen may be a two element screen, either the front or the rear element having the clear substrate. Surface diffusion may be used as an alternative, or in addition to, the bulk diffuser.

Projection screen having high resolution and good mechanical stability

A bulk diffuser for rear projection television screens which exhibits a Gaussian intensity profile. By appropriately selecting the indices of refraction of the substrate and the spheres therein and the range of diameters of the spheres, the intensity half-angle is made equal to the energy half-angle.

Growing community of inventors

Pelham Manor, NY, United States of America

Jill F Goldenberg