Patent GB-623444-A (GB)
Title: Improvements in or relating to the manufacture of stereoscopic pictures
IPC: G03B35/24
Filed: 1945-10-02
Abstract: 623,444. Stereoscopic pictures. SPERRY GYROSCOPE CO., Inc. Oct. 2, 1945, No. 25580. Convention date, Oct. 2, 1944. [Classes 97 (i) and 98 (ii)] [Also in Group XXXV] A stereoscopic picture which may be viewed directly comprises a transparent sheet which is lenticulated on its front surface and has printed in ink on its back surface the two views of a stereoscopic pair, the views being disposed in narrow alternating strips so that they are respectively visible through the lenses to the particular eye corresponding thereto. In the production of stock upon which such pictures are to be printed, a transparent sheet 2, Fig. 1, as of celluloid is formed with cylindrical lenses 4 and with a light-sensitive coating 6 as of bichromated gelatine. This coating is exposed to light from a source which may be moved slowly between the extreme positions A, B of the right eye of an observer (or which may be an elongated light source of length AB), to divide the coating into exposed and unexposed strips 5, 7 respectively. The bichromate may then be washed out of the unexposed strips or these strips may be removed by washing in warm water. The pictures are then printed on the stock so formed. Methods described are (1) the stock from which the bichromate has been leached is wetted to make the desensitized strips 7 oil repellent; the right eye view is printed with an oil base ink which is retained only by the strips 5; the left eye view is then printed in a water ink and is retained only by the strips 7; a paper backing is applied. (2) The left eye view is printed with a soft roll or transfer blanket on the back of stock from which the unexposed strips 7 have been removed; the top surfaces of strips 5 are wiped clean so that the left eye view only remains in the spaces therebetween; a hand roll or plate is then used to print the right eye view on the strips 5 and a paper or other backing is applied. (3) Stock from which the strips 7 have been removed is wetted with water to render strips 5 oil-repellent, whereupon the left eye view is printed with oil ink on a soft roll, the ink taking only in the spaces between strips 5; the right eye view is then printed with water ink on a hard roll and a backing applied. (4) Stock from which the strips 7 have been removed is printed with the right eye view using a hard roll; an opaque light-reflecting coating is applied to the printed strips 5; the left eye view is then printed over the entire back of the stock with a soft roll and is then backed by a light-reflective coating. (5) Stock from which the strips 7 have been removed is etched to form grooves between the exposed strips; the exposed strips, which act as a resist, are then removed; left eye view is then printed over the back of the stock with a soft roll; the strips from which the exposed gelatine has been removed are wiped clean and a light-reflecting opaque coating applied to the back of the stock and subsequently wiped away from said strips; a paper backing carrying a " reversed " print of the right eye view is then applied to the back of the sheet. The stock may be produced by another method. Thus, strips of gelatine (corresponding to the strips 5 of Fig. 1) are applied to the back of a lenticulated sheet and are aligned with the lenses corresponding thereto by means, such as an electric motor. controlled by the difference in outputs of two photo-electric cells on to which light passing through one of the lenses impinges and arranged to produce transverse movement of the sheet 62 relative to the printing roll if the light does not play equally on the two photo-electric cells, i.e. if the strips 65 are not correctly aligned with the corresponding lenses. Stereoscopic pictures may be printed on to such stock by printing the left eye view over the back of the stock; coating the back with an opaque reflecting material (e.g. white pigment) which will not adhere to the gelatine strips 65; dissolving the strips 65 in warm water and then using a soft roll to print the right eye view; a paper backing is then applied. Light-sensitive materials, other than bichromated gelatine, which may be used, comprise polyvinyl alcohol and partial polymers of monomers, such as methyl methacrylate, which polymerize on exposure to light. The printing processes may be performed by lithograph, offset or collotype processes; cameo and intaglio engraved plates, electrotypes and stereotypes may be used provided line plates are employed with the lines transverse to the strips on the back of the stock. When it is necessary to remove the print from the strips 5, the sheet may be wetted with a liquid which is not an ink solvent and then abraded by a ground glass surface. Otherwise the stock may be passed between rollers as of rubber, one of the rollers dipping into an ink solvent, such as naphtha, a doctor blade being provided to remove the solvent and ink from this roller. Fig. 5 illustrates an apparatus whereby the stock may be formed. The lenticulated sheet is unreeled from a roll 30 in a light-tight casing 48 and is exposed. at 50 to light from an elongated source 52 (the length of which or of a reflector provided therewith is equal to the distance AB, Fig. 1). Thus, the exposed and unexposed strips 5, 7, Fig. 1, are formed in the bichromated gelatine coating 6. The stock may then be washed in warm water in a tank 38 to remove the unexposed strips 7 (or in cold water to remove the bichromate from such strips) and then wound on roll 46 after being dried by radiant heat at 56.