California Institute of Technology

Xerox Corporation

Other

Eric B Hochberg

Michael Costen

Norman Alan Page

Edmund C Baroth

A lightweight solar concentrator of the reflecting parabolic or trough type is realized via a thin reflecting film, an inflatable structural housing and tensioned fibers. The reflector element itself is a thin, flexible, specularly-reflecting sheet or film. The film is maintained in the parabolic trough shape by means of a plurality of identical tensioned fibers arranged to be parallel to the longitudinal axis of the parabola. Fiber ends are terminated in two identical spaced anchorplates, each containing a plurality of holes which lie on the desired parabolic contour. In a preferred embodiment, these fibers are arrayed in pairs with one fiber contacting the front side of the reflecting film and the other contacting the back side of the reflecting film. The reflective surface is thereby slidably captured between arrays of fibers which control the shape and position of the reflective film. Gas pressure in the inflatable housing generates fiber tension to achieve a truer parabolic shape.

Lightweight, low-cost solar energy collector

An novel interferometric apparatus and method for measuring the topography of aspheric surfaces, without requiring any form of scanning or phase shifting. The apparatus and method of the present invention utilize a white-light interferometer, such as a white-light Twyman-Green interferometer, combined with a means for dispersing a polychromatic interference pattern, using a fiber-optic bundle and a disperser such as a prism for determining the monochromatic spectral intensities of the polychromatic interference pattern which intensities uniquely define the optical path differences or OPD between the surface under test and a reference surface such as a reference sphere. Consequently, the present invention comprises a 'snapshot' approach to measuring aspheric surface topographies such as the human cornea, thereby obviating vibration sensitive scanning which would otherwise reduce the accuracy of the measurement. The invention utilizes a polychromatic interference pattern in the pupil image plane, which is dispersed on a point-wise basis, by using a special area-to-line fiber-optic manifold, onto a CCD or other type detector comprising a plurality of columns of pixels. Each such column is dedicated to a single point of the fringe pattern for enabling determination of the spectral content of the pattern. The auto-correlation of the dispersed spectrum of the fringe pattern is uniquely characteristic of a particular optical path difference between the surface under test and a reference surface.

Method and apparatus for white-light dispersed-fringe interferometric

A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

Wavelength independent interferometer

A process for extracting long-equivalent wavelength interferometric information from a two-wavelength polychromatic or achromatic interferometer. The process comprises the steps of simultaneously recording a non-linear sum of two different frequency visible light interferograms on a high resolution film and then placing the developed film in an optical train for Fourier transformation, low pass spatial filtering and inverse transformation of the film image to produce low spatial frequency fringes corresponding to a long-equivalent wavelength interferogram. The recorded non-linear sum irradiance derived from the two-wavelength interferometer is obtained by controlling the exposure so that the average interferogram irradiance is set at either the noise level threshold or the saturation level threshold of the film.

Method for extracting long-equivalent wavelength interferometric

Method and apparatus for full-color reproduction of a continuous tone color picture or scene using multiple diffraction gratings and masking techniques. A properly photosensitized media, containing regular arrays of multiple diffraction gratings (70), is first created using computer-generated masks and an interferometric recording technique. This plate is referred to as the 'white grating canvas' master or WGC master. Reflective and/or transmissive replicas of the WGC master are then created. For the reproduction of each unique scene, one of these WGC replicas is selectively masked in order to leave only certain gratings or portions thereof active. Photographic or xerographic means are two possible ways in which the masking might be accomplished. The selective masking of the WGC itself, or an intermediate material which is then laminated in registration with the WGC, is done in such a way as to reproduce the primary color components in the original scene when properly illuminated and viewed.

Full color images using multiple diffraction gratings and masking

Method and apparatus for full-color reproduction of a continuous tone color picture or scene using multiple diffraction gratings. The reproduction consists of a plurality of small diffraction gratings (70). A plurality of color separation masks (60) are created for each unique scene. Those picture elements in the original scene containing a given primary color are captured in these transmission-type masks. In certain zones dictated by the separation masks, a plurality of interference patterns are recorded in the properly photosensitized media (70). The spatial freqency of said interference patterns correlates to the primary color to be reproduced. These interference patterns become multiple diffraction gratings when properly developed. The properly photosensitized media may be used as a master for replication purposes. When either master or replica (78) are properly illuminated in white light (76) and properly viewed, the multiple diffraction gratings act to reproduce the colors in the original scene.

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Altadena, CA, United States of America

Eric B Hochberg