Abstract: An improved method of converting solar energy into electricity by spreading the solar spectrum and concentrating it onto solar cells that are band-gaped in the corresponding wavelength range. The spectrally separated solar energy can be concentrated into a normal rainbow line or spread out to individual regions. A low cost solar energy conversion collector results because concentration reduces the quantity of photovoltaic cells needed and spectral splitting increases the energy collected by using multiple appropriately band-gaped solar cells in the different wavelengths.

Abstract: A projection system includes a collection lens that minimizes apparent magnification of the light source, so that the resulting system more nearly conforms to a point source idealization. Attendant benefits include improved collimation, a smaller projection lens, and a greater depth of focus. The collection lens is desirably of a "wrap around" configuration to maximize light collection while contributing to reduced source magnification. The opposite side of the collection lens can be provided with a convex lens of Fresnel form. Use of the Fresnel optic moves the principal plane of the collection lens closer to the light source, further minimizing the source's apparent magnification. The projection system additionally includes condensing optics formed with a deliberate asymmetry so as to provide more uniform illumination of a rectangular image plane. The Fresnel surface of the collection lens can be designed to provide this asymmetry.

Abstract: A full color hologram is made by exposing a holographic emulsion to the 514 nm and 458 nm lines of an argon laser and the 413 nm line of a krypton laser. The hologram can be returned to its original thickness and used as a master with the same three wavelengths, or it can be swelled to longer wavelengths to reconstruct with red, green and blue light. The source of the red, green and blue information may be acquired by an electronic video signal displayed on an electronic image modulator.

Abstract: An optical notch filter component in a color LCD display comprises an electronically controllable variable retarder interposed between circularly polarizing elements. Entering light in a particular spectral region is circularly polarized by a first of the circularly polarizing elements, and selectively retarded by zero or a half wavelength by the retarder so as to controllably yield right or left handed circular polarization. The second circular polarizer transmits only one of the circular polarizations of the light. By controlling the circular polarization of the light with the retarder, the light is either transmitted or attenuated. More uniform stopband attenuation is provided when the optical notch filter component comprises oppositely handed circular polarizing elements and a variable retarder which applies zero retardation in one of its states.

Abstract: A multiple-color filter array (94) useful as part of a flat panel display system of either a projection (50) or direct view (70) type is constructed using reflection holography techniques. The filter array includes multiple-color filter elements (110, 114, 116) that reflect wavelengths of light corresponding to colors outside of a color band of interest. Redundant sets of first, second, and third wavelengths selective reflective color filter elements are arranged in stripes to transmit light of the three primary colors red, green, and blue. The three-color filter array is constructed in a single layer (122) of holographic recording material during one sequence of three separate exposures, one for each color filter element. A preferred flat panel display system (200) includes a liquid crystal variable optical retarder of the supertwisted nematic (STN) type.

Abstract: A projector (100) including an liquid crystal display image source (120), a field lens (126), and a projection lens (128) projects a full-color image by projecting and converging images of multiple liquid crystal displays ("LCDs"). The image is properly positioned without keystoning by tilting the field lens and offsetting the center of the LCD image source from the optical axis (142) of the projection lens. Trapezoidal error is eliminated by maintaining the optical center (156) of the field lens on the optical axis of the projection lens. During focusing, a mounting apparatus (164) adjusts the offset (154) between the center of the LCD and the optical axis of the projection lens for proper convergence of the images and maintains the optical center of the field lens on the optical axis of the projection lens.

Abstract: Reflection holograms to be viewed through the front side of a transparent and preferably flexible substrate, and which are insensitive to moisture in liquid and in vapor form, are produced by attaching a layer of holographic recording material to the back side of a transparent substrate, attaching a layer of moisture barrier resin to the back side of the recording material in sufficient thickness to render the hologram insensitive to moisture, and attaching a layer of opaque material to the back side of the moisture barrier layer. Further protection against moisture may be achieved by attaching a solvent deposited layer of transparent moisture barrier resin to the front side of the substrate and/or attaching a layer of moisture barrier sheet to the back side of the opaque layer.

Abstract: A polarization-selective holographic element having first and second holographic layers, each holographic layer including holograms comprising a plurality of fringes. The holographic optical element transmits a first component of light without diffraction and diffracts a second component of the light by a selected angle. The holographic optical element diffracts the second component into only one beam. The holographic optical element can be utilized as a beam splitter which is provided with optical power, for use in an optical head, by storing holograms for cylindrical and other powers and for auto-focusing and tracking capabilities.

Abstract: A polarization-selective holographic element having first and second holographic layers, each holographic layer including holograms comprising a plurality of fringes which are recorded with light having a first wavelength .lambda..sub.1. The holographic optical element transmits a first component of light having a second wavelength .lambda..sub.2 without diffraction and diffracts a second component of the light having the second wavelength by a selected angle. The holograms have a high diffraction efficiency and are recorded with beams making angles .sigma..sub.1 and .sigma..sub.2 with a normal to the surface of the holographic layers, where .vertline..theta..sub.2 -.theta..sub.1 .vertline.=.vertline..sigma..sub.2 -.sigma..sub.1 .vertline.=2.alpha., .lambda..sub.2 /(sin.theta..sub.1 +sin.theta..sub.2)=.lambda..sub.1 /(sin.theta..sub.1 +sin.theta..sub.2), and .theta..sub.1 and .theta..sub.2 are the incident and diffracted angles of the second component of the light having the second wavelength.

Abstract: An erasable optical data storage medium has an embedded servo track and a subsurface recording interface. An erasable recording structure having two dyed polymer layers is separated from the servo track by a compression layer. The servo track is formed in a hard substrate which provides mechanical support for the medium. The medium is adapted to form non-vesicular data bumps projecting into the compression layer when exposed to a write laser beam of predetermined wavelength projected through the substrate and compression layer. The embedded servo track and recording interface are sufficiently close to each to be read simultaneously in the same focal plane.