GB1272631A - Optical apparatus and methods for projecting images - Google Patents

Abstract

1,272,631. Spatial filtering. TECHNICAL OPERATIONS Inc. April 29, 1969, No.21884/69. Heading G2J. Preferential images of a predetermined order of diffraction are selected from a multi-record carrier 46 by selective illumination of the carrier 46 with one or more of a plurality of coherent light sources 49 , forming a Fourier transform of desired records and placing a spatial filter in the transform plane to pass only the required orders of diffraction. Each record on the carrier has a direction vector transverse to the optical axis of the system and alignable with each such vector is one of the light sources 49. The vectors have a predetermined angular separation from one to the other. Azimuthal alignment transverse to the optic axis is effected for each light source with its corresponding vector, and each beam of each light-source is angled with respect to the axis to locate the predetermined diffracted orders of each image on the axis. A carrier 46 formed to have records related to the colours red, blue, green and yellow is located in an optical system with respect to a transform lens 42 such that a Fourier transform of the records is formed. Six light sources 49 connected diagonally in pairs illuminate the carrier, each pair being angularly oriented with respect to another pair so that it is aligned with the direction vector appropriate to the red, green or blue colour of the records. The desired image or images is set up by illuminating the appropriate pairs of light sources, there being a spectral filter 54 with three pairs of filters 1 and 4, 2 and 5, 3 and 6. The distances 1-4, 2-5, 3-6 are set according to the wavelength of light to be transmitted to give the correct diffraction angle. A spatial filter 48 located in the transform plane only permits transmission of the selected orders of diffraction. In an alternative embodiment, Fig.2, the light sources 85 are located in a plate containing a plurality of light guides 78 each light guide being fed from an arc lamp 76 and having associated with each guide a determined spectral filter and a continuously varying neutral density filter 87. The filters may be individually adjusted by D.C. stepping-type motors via manual controls 96, 98, 100. The selected image received from the transform plane as passed by the spatial filter 112 is seen through binoculars 74. Preferably the angular geometry of the direction vectors is a 0-45-135 degrees configuration.