Abstract: An overhead projector including a Fresnel lens, a single element meniscus projection lens having a concave side and a convex side, and a folding mirror placed in an optical path between the Fresnel lens and the projection lens. The projection lens is oriented to have the concave side optically facing the Fresnel lens. The optical design of the overhead projector follows the following equation, FFres=(FLens(MLens+1)/MLens−SLD)/(MFres+1), where the Fresnel lens has a focal length FFres, and a magnification MFres, the projection lens has a focal length FLens and a magnification MLens, and SLD is the distance from the stop position and the projection lens.

Abstract: A front projection screen and associated system and method are disclosed that utilize a back structured layer and a front diffusing layer to provide improved viewable image quality. The structured layer is formed with a plurality of grooves and can operate to direct light into a defined audience view region. The diffusing layer is coupled to the structured layer and is formed from a matte polyester film to provide dry erase capability on a front surface of the diffusing layer. For example, the matte polyester film can be TEKRA Marnot XL matte Melinex polyester film. Further, the structured layer can be formed as an acrylate linear prismatic structure having a gloss white coating. The acrylate linear prismatic structure and the matte polyester film can be coupled, for example, by lamination or can be coupled by being extruded as a unitary construction.

Abstract: An overhead projector including a Fresnel lens, a single element meniscus projection lens having a concave side and a convex side, and a folding mirror placed in an optical path between the Fresnel lens and the projection lens. The projection lens is oriented to have the concave side optically facing the Fresnel lens. The optical design of the overhead projector follows the following equation, FFres=(FLens(MLens+1)/MLens−SLD)/(MFres+1), where the Fresnel lens has a focal length FFres, and a magnification MFres, the projection lens has a focal length FLens and a magnification MLens, and SLD is the distance from the stop position and the projection lens.

Abstract: A front projection display system that integrates an optical engine, having control and power supply electronics, and a dedicated projection screen to provide a compact video display device. The projection engine is coupled to a high gain projection screen, having an optimized reflection pattern to give optimum optical performance in ambient H& and viewing angle sensitive environments. Components of the projection engine are modularly placed in a retractable arm pivotally connected to the screen. The arm offers precise registration to the screen apparatus and thus repeatably precisely aligns optically and mechanically to the screen. The projection wall system has an open projection position and a closed storage position. Use of a radically offset projection head having matching keystone correction features allows the arm to protrude above the head of the presenter and offer a sharp and unobtrusive projection zone.

Abstract: A front projection screen and associated system and method are disclosed that utilize a back structured layer and a front diffusing layer to provide improved viewable image quality. The structured layer is formed with a plurality of grooves and can operate to direct light into a defined audience view region. The diffusing layer is coupled to the structured layer and is formed from a matte polyester film to provide dry erase capability on a front surface of the diffusing layer. For example, the matte polyester film can be TEKRA Marnot XL matte Melinex polyester film. Further, the structured layer can be formed as an acrylate linear prismatic structure having a gloss white coating. The acrylate linear prismatic structure and the matte polyester film can be coupled, for example, by lamination or can be coupled by being extruded as a unitary construction.

Abstract: A front projection display system that integrates an optical engine, having control and power supply electronics, and a dedicated projection screen to provide a compact video display device. The projection engine is coupled to a high gain projection screen, having an optimized reflection pattern to give optimum optical performance in ambient light and viewing angle sensitive environments. Components of the projection engine are modularly placed in a retractable arm, pivotally connected to the screen. The arm offers precise registration to the screen apparatus and thus repeatably precisely aligns optically and mechanically to the screen. The projection wall system has an open projection position and a closed storage position. Use of a radically offset projection head having matching keystone correction features allows the arm to protrude above the head of the presenter and offer a sharp and unobtrusive projection zone.

Abstract: A device for homogenizing light rays from a light source. The device includes a first multi-prismatic surface, a second multi-prismatic surface, and a reflective housing connecting the first multi-prismatic surface with the second multi-prismatic surface. The device may be employed in a liquid crystal display projection system. The system includes, in addition to the device, a parabolic reflective collimator, a lamp centered in the parabolic reflective collimator, the lamp emitting light rays reflected by the parabolic reflective collimator, and a liquid crystal display positioned to receive light rays passing through the first multi-prismatic surface, the reflective housing, and the second multi-prismatic surface.

Abstract: An illumination system is described that efficiently produces linear polarized light for use in LCD projection. A polarizing beam splitter and half-wave retarder plate produce two adjacent collimated beams of light having a common polarization direction. These adjacent beams are spatially integrated into a single collimated polarized beam whose aspect ratio is subsequently converted to match that of the LCD format.

Abstract: A liquid crystal display projector including a light source, a collimator lens, a planar polarization converter, a liquid crystal display panel, and projection lenses. The collimator lens is optically aligned to receive a beam of light from the light source and to produce a collimated light beam. The planar polarization converter is optically aligned in front of the collimator lens to receive the collimated beam of light. The polarization converter includes a prismatic film having a first prismatic surface, a reflective polarization film, and a quarter wave retarder film positioned between the prismatic film and the polarization film sheet. The prismatic surface has alternating transmissive prismatic facets and reflective prismatic facets positioned at supplementary base angles, the reflective prismatic facets positioned at a second base angle .beta. and the transmissive prismatic facets positioned at a first base angle generally equal to 180.degree.-.beta..

Abstract: A low-profile transmissive overhead projector employs a folded optical path and an off-axis Fresnel lens condensing system which includes a catadioptric lens element. This lens provides a fast condensing system which allows collimation, dispersion, or concentration of light striking the lens at a high angle of incidence, with efficient transmission to the far edge of the lens. This also enables additional reduction in the OHP base height by allowing the single mirror to be mounted at a flatter angle, with the light source still maintained at a position below (and adjacent) the stage. A novel catadioptric lens design further imparts achromaticity to the element, so that it may be constructed of any material, regardless of its index of refraction. The condensing system may have a single or doublet catadioptric lens.

Abstract: A projection system is described which efficiently combines the output from multiple lamps, images of which are focused to a common point. The projected screen brightness is multiplied over that of a conventional single lamp of equivalent wattage. The screen brightness can be increased or diminished by switching individual lamps on or off, adjusting the light level for conventional overhead transparencies, or low transmission liquid crystal display projection panels.

Abstract: A low-profile, transmissive overhead projector (OHP) employs a novel condensing lens system having a catadioptric Fresnel lens and a dioptric Fresnel lens. Each of the lenses exhibits chromatic aberration, but the dispersion of one lens is selected to cancel out the dispersion of the other, e.g., if the catadioptric lens has negative dispersion then the dioptric lens is selected to have positive dispersion. The mutual cancellation of the dispersion of each lens practically eliminates longitudinal chromatic aberration through the lens system. The lens system provides a fast condensing system which allows collimation, dispersion or concentration of light striking the lens at a high angle of incidence. This characteristic is particularly suited for a low-profile OHP as it allows the light source to be placed directly under, but very close to, the stage area.

Abstract: A low-profile transmissive overhead projector employs a folded optical path and an off-axis Fresnel lens condensing system which includes a catadioptric lens element. This lens provides a fast condensing system which allows collimation, dispersion, or concentration of light striking the lens at a high angle of incidence, with efficient transmission to the far edge of the lens. This also enables additional reduction in the OHP base height by allowing the single mirror to be mounted at a flatter angle, with the light source still maintained at a position below (and adjacent) the stage. A novel catadioptric lens design further imparts achromaticity to the element, so that it may be constructed of any material, regardless of its index of refraction. The condensing system may have a single or doublet catadioptric lens.

Abstract: A low-profile, transmissive overhead projector (OHP) employs a novel condensing lens system having a catadioptric Fresnel lens and a dioptric Fresnel lens. Each of the lenses exhibits chromatic aberration, but the dispersion of one lens is selected to cancel out the dispersion of the other, e.g., if the catadioptric lens has negative dispersion then the dioptric lens is selected to have positive dispersion. The mutual cancellation of the dispersion of each lens practically eliminates longitudinal chromatic aberration through the lens system. The lens system provides a fast condensing system which allows collimation, dispersion or concentration of light striking the lens at a high angle of incidence. This characteristic is particularly suited for a low-profile OHP as it allows the light source to be placed directly under, but very close to, the stage area.

Abstract: A low-profile transmissive overhead projector employs a folded optical path and an off-axis Fresnel lens condensing system which includes a catadioptric lens element. This lens provides a fast condensing system which allows collimation, dispersion, or concentration of light striking the lens at a high angle of incidence, with efficient transmission to the far edge of the lens. This also enables additional reduction in the OHP base height by allowing the single mirror to be mounted at a flatter angle, with the light source still maintained at a position below (and adjacent) the stage. A novel catadioptric lens design further imparts achromaticity to the element, so that it may be constructed of any material, regardless of its index of refraction. The condensing system may have a single or doublet catadioptric lens.

Abstract: This invention consists of a wide-angle, multi-element condenser system for an overhead projector that provides uniform illumination at the plane of the projection transparency, and a well-formed lamp image at the entrance pupil of the projection lens. This is accomplished by using a combination of a glass spherical meniscus lens, a glass plano-convex spherical lens and a plastic aspheric Fresnel lens system.

Abstract: A reflective stage overhead projector has a light source, a projection lens and mirror assembly for focusing and reflecting an illuminated image onto a screen, and a stage area for supporting an image to be illuminated and projected. One reflective surface of the stage area is defined by a noncentral portion of a Fresnel lens.

Abstract: This invention consists of a Fresnel lens having focusing grooves on both sides of a single element. The relative frequencies of the grooved surfaces are controlled such that Moire fringe patterns between the two grooved surfaces are reduced. Specifically, the frequency of the Fresnel elements on one surface of the element is at least four times that of the Fresnel elements on the other surface and not a integral multiple thereof.

Abstract: A four-element inverted telephoto projection lens assembly for use in conventional overhead projectors is disclosed. The lens assembly features a reduced projection distance from the lens assembly to the projection screen while retaining the same back focus as conventional two-element projection lenses for overhead projectors.

Abstract: A solar concentrator with wide effective aperture is disclosed, which comprises at least one linear echelon reflector element which is inclined with respect to the direction of incident solar radiation to direct incident solar radiation to a line focus.