Patent GB-684799-A (GB)
Title: Improvements in or relating to changeable picture apparatus
IPC: G09F11/02
Filed: 1950-11-09
Abstract: 684,799. Composite photographs; zoetropes. KODAK, Ltd. Nov. 9, 1950 [Nov. 9, 1949], No. 27448/50. Classes 97 (i) and 98 (ii). [Also in Group XVIII] A picture-bearing member for use with a grid 17 having a plurality of parallel spaced slots 18 comprises a plurality of picture elements extending lengthwise of the member and each representative of a transverse element of a different picture, the picture elements being substantially equal in width to one another and each being substantially equal in width to the grid slot. The picture-bearing member may consist of a substantially rectangular photographic transparency each picture element on which is a transverse element of a different picture and each element of which consequently varies in density and which forms part of a changing sign when it is wrapped round a tubular electric lamp; it may consist of a tubular electric lamp, the picture elements being formed on its periphery by suitably exposing and developing a coating of photographic emulsion on its surface or it may consist of a tubular electric lamp, the surface of which has been made opaque with paint or tape and with clear light-transmitting slots left where desired. A changeable sign is made with a plurality of picture-bearing lamps 10, Fig. 2, as above, mounted between vertical supports 11 in parallel side-by-side arrangement. Each lamp is seen through a separate slot 18 of the slotted opaque grid 17, each slot exposing a single picture element at a time, the elements of the several lamps combining to form a picture, symbol or the like when seen from a reasonable distance at which the gaps between the slots 18 are unobtrusive. The lamps are rotated in synchronism either intermittently or continuously by a motor M through reduction gearing.. They may all turn in the same direction or adjacent lamps may be arranged to turn in opposite directions. Current is fed to the lamps through brushes 16 and slip-rings 14. Two grids 17 may be used positioned on opposite sides of the lamps, different pictures being seen on each side. Both pictures are seen upright in relation to the top of the device since although the elements on one side are upside down as compared to the others, their width is made sufficiently small so that no perceptible variation in tone occurs across the width. When photographic transparencies are used they may be prepared by wrapping light-sensitive film around each lamp while it is dark, and indexing its position on the lamp, then with the lamp in position behind the grid a picture is projected on to the grid exposing the emulsion behind each slot. The lamps are then moved synchronously to move an unexposed area of emulsion behind the grid openings and a different picture projected. The process is repeated until all the emulsion is exposed. The films are then removed and treated to form black-and-white or coloured transparencies by normal photographic means and replaced on the lamps. Duplicates of each film may be produced by normal photographic means, if required. A similar method of exposing the emulsion may be used when the lamps are directly coated.