Patent GB-556578-A (GB)
Title: Improvements in or relating to stereoscopic and other colour images in polarizing material
IPC: G03B33/00
Filed: 1941-05-29
Abstract: 556,578. Stereoscopic multi-coloured kinematography; polarizing apparatus. INTERNATIONAL POLAROID CORPORATION. May 29, 1941, No. 6912. Convention date, June 7, 1940. [Class 97 (i)] The molecules in the image areas of an imagebearing sheet of polyvinyl alcohol or other transparent, hydrophilic, linear, polymeric plastic material are oriented into substantial parallelism and are dyed with a dye which not only renders the areas dichroic but also capable of use as a member of a subtractive multi-coloured image assembly; multi-coloured image assemblies may be produced by assembling three, or two, such sheets in superposition, the image areas in the sheets being appropriately dyed, or by applying different coloured dyes to one such sheet, and two such assemblies respectively containing left and right images of a stereoscopic pair may be superposed, the directions of orientation being different in the two assemblies. Means for projecting such stereoscopic assemblies, and, for viewing the projected images, with or without the aid of means for circularly polarizing the image beams, is also described. Fig. 1 shows a multicoloured stereoscopic kinematograph film comprising layers 12, 14, 16 of polyvinyl alcohol having their molecules oriented in the direction of the arrows 24, and respectively containing images of minus red, minus blue, and minus green colour, produced by dichroic dyes, and together forming one multi-coloured component of a stereoscopic pair. Similar layers 18, 20, 22, with molecules oriented in the direction of the arrows 26, the directions of the arrows 24, 26 being preferably at right angles, and at 45 degrees to the length of the film, contain similarly multicoloured images forming the other component of the pair. The layers are secured together by adhesive, and may be superposed in any desired order. Each set of three layers may be replaced by two layers containing images coloured appropriately to a two-colour system. Alternatively, each set of three layers may be replaced by one layer containing the three, or two, dye images. The dyes may be applied by imbibition from a gelatin relief or other carrier, by the use of resists, by a diazotype process, or by a discharge printing process as used in the textile industry &c. ; they may be direct cotton dyes, and various known cotton and other dyes are set out as examples for three-colour and two-colour systems. Multi-coloured stereoscopic prints forming single pictures may be similarly produced and may be used as transparencies, or be backed by a non- depolarizing reflecting material such as paper coated with aluminium flake in a plastic material, or by the direct application of an aluminium paint &c. A waterproofing coating may be applied to the outer layer of the assembly, and may be a coating of the adhesive if a hard adhesive is used. Projection may be effected by a standard projector on to a non-depolarizing screen, viewing being effected through polarizing spectacles of which the windows respectively have polarizing axes parallel to the transmission axes of the right and left images. Alternatively, the projector may be provided with a fixed quarter-wave plate 118, Fig. 5, having its transmission axis in a position bisecting the right angle between the axes 24, 26 on the film, the light of the projection beam being thus circularly polarized in opposite directions for the two component images. The viewing spectacles comprise polarizers having axes 126, 130, preferably parallel to the axes of the film, and quarter-wave plates 124, 128 with parallel axes bisecting the angle between the axes 126, 130. The projector and viewer shown in Fig. 5 may also be used for black-and-white projection. Specifications 547,554, 549,668, 549,698 and 562,877 are referred to.