GB772529A - Improvements relating to the projection of stereoscopic images by means of polarisedlight - Google Patents

Abstract

772,529. Stereoscopic projection apparatus. POLA-LUX GES. FUR BLENDSCHUTZ UND RAUMBILDPROJEKTION. Aug. 15, 1952 [Aug. 21, 1951; April 16, 1952], No. 20616/52. Class 97(1) Apparatus for the projection of stereoscopic images by polarized light comprises an interference polarizer, adapted to split up each of the right and left image forming light beams into a pair of light beams plane polarized at right angles to each other and emerging from said polarizer at different exit surfaces at each of which emerges one right image forming beam and one left image forming beam polarized in perpendicular planes, and to superimpose the right and left image forming beams emerging from the said polarizer at the same exit surface, quarter wave plates, positioned adjacent said exit surfaces, the optical axes of said quarter wave plates being at right angles to one another and at angles of 45 degrees to the polarization planes of said plane polarized beams and optical systems for projecting images on to a common screen by means of the circularly polarized beams thereby produced. In the form shown, diapositives 3a, 3b of a stereoscopic pair are illuminated by a lamp 1 with reflector 1a and condenser 2. The transmitted light beams 10, 11 are divided, into plane polarized components 10a, 10b, 11a, 11b, at the surface 5 in a rhomboid block, further reflections occurring at the surfaces 4, 6 as necessary. The components 10a, 10b and 11a, 11b from the respective diapositives are oppositely polarized, as are the pairs of components 10a, 11a and 10b, 11b emerging from the surfaces 12b, 12a. Quarter wave plates 7, 8 are oriented to convert the beams 10a, 10b into beams circularly polarized in one sense and 11a, 11b into beams circularly polarized in the opposite sense. Images' are projected by objectives 9a, 9b and adjustable prisms 13a, 13b, 14a, 14b permit registration on the screen. In modifications the beam splitting block is arranged to provide an angle of incidence of 55 degrees at the polarizing layer to provide more complete polarization. The block may be shaped so that neither the two exit surfaces nor the two entry surfaces are juxtaposed. It may be provided with quarter wave plates at entry and exit surfaces to provide for reversal of direction of light paths. If desired, one objective may be omitted and the projection effected by the single pair of oppositely circularly polarized beams reaching the other or, if the quarter wave plate is also omitted by a single pair of plane polarized beams.