Patent GB-541752-A (GB)
Title: Improvements in or relating to the photography and projection of pictures with stereoscopic effect
IPC: G03B35/24
Filed: 1940-05-03
Abstract: 541,752. Producing relief effects in projected images. GABOR, D. May 3, 1940, No. 7982. [Classes 97 (i) and 98 (ii)] Film stock used in taking and projecting images exhibiting relief effects has lenticulations which are horizontal or are acutely inclined to the horizontal, and the lens aperture is a slit or the equivalent acutely inclined to the lenticulations ; the angles between the lenticulations and slit may be variable in accordance with the position of the principal object plane during taking, and to vary the apparent depth during projection. The Specification demonstrates that, during taking, each point in the principal object plane 4, Fig. 13, is imaged by the lens 2 and lenticulations 21 as a line perpendicular to the lenticulations, and that a point Q out of the plane 4 is imaged as a continuous line q or as a divided line having its parts parallel to q but displaced through a distance equal to the pitch of the lenticles. The line q, or its parts, is inclined to the perpendicular in the same sense as the lens slit, or in the opposite sense, according to whether the point is behind or before the plane 4, the total geometrical projection of the line in the direction of the lenticular axes depending on the distance from the plane, and the geometrical projection perpendicular thereto upon the length of the corresponding projection hc of the lens slit in a diaphragm 19. The projection hc is determined by a rectangular aperture in a frame 20 and is selected so that the emulsion surface is fully utilized. The inclination of the slit is chosen in accordance with the distance of the plane 4, and the diaphragm 19 may be mechanically connected to the focusing movement for the lens 2 so that adjustment occurs automatically. If the camera film is developed as a positive and used for projection, the inclination of the lenticular axes may be such that the projector slit or its equivalent may be horizontal, and a cylindrical lens having its axis parallel to the lenticular axis may be provided in front of the film ; projection is effected so that the projection screen corresponds to the plane 4 and so that points at infinity appear to be at infinity. If the positive film is produced by projection printing, a printer having a standard focal length may be used, so that all positive films, even if made from negatives from varying cameras, may be used in a projector having a standard distance between an illuminated slit and the projection lens, an image of the slit being produced in the projection lens by a lens substantially coincident with the film. The taking film may be of larger size than that used for projection. The projector may comprise a spherical lens 30 in front of the film 29, Figs. 16 and 16A, and a spherical condenser 32 behind the film, the aplanatic point of the lens 30 and the centre of curvature of the lens 32 being in the film. An illuminated slit in a curved sheet 34 is imaged by the lenses 30, 32 in the projection lens 31. Figs. 18 and 18A show an alternative projection system wherein a linear source 42 is imaged by a toroidal lens 44 in a slit 45, and the beam is reflected by mirrors 46, 47 on to the film 48. Projection is effected by a spherical mirror 50 in conjunction with a correcting plate 51. Taking may be effected with the aid of shutters covering halves of the lens slit alternately in exposures on consecutive frames, and moving colour filters may be associated with the shutters to produce colourrecord films. The projector may have similar shutters or printing may be effected by a projection printer having a shutter alternately covering upper and lower halves of the lens, successive negative images being printed on the same positive frame to render shutters in the projector unnecessary. Arrangements of such shutters and colour filters are described, together with the use of dyed multi-coated positive film stock which is printed so as to render separate projector filters unnecessary. Specifications 410,515, 541,751 and 541,753 are referred to.