GB1316210A - Process for the preparation and the checking of a photographic negative intended to be mounted on a sensitised printing cylinder and means for the application of this process - Google Patents

Abstract

1316210 Optical alignment device R J J BASSEREAU 19 April 1971 [30 April 1970] 27290/71 Heading G2J The invention relates to checking the parallelism of the mating edges of a photographic negative used in a photogravure process. A substantially rectangular negative ABCD is located on a vertical plate glass sheet 3 in a frame 17, Fig. 3. A pair of projection lenses 8, 10 are fixed to supports 24, 25 connected to slides 21, 22 movable along the horizontal upper and lower parallel member 17", 17' of frame 17. The slides 21, 22 are also vertically adjustable and also carrying pivotal plates on which are mounted, on the opposite side of the glass sheet 3, light sources for the lenses 8, 10. The slides are moved with lens 8 in operation to establish upper side AB of the negative as being substantially parallel to member 17". With the slides then adjacent one end, e.g. BC of the negative both projectors are operated and corresponding points at the edges AB, CD are imaged on a screen. Movement of the light source brings the image into coincidence. The slides are then moved along their respective members 17", 17'. If the negative edges AB, CD are not parallel their image points will not coincide. The negative edges may then be touched up. As a further check marks 13, 14, Fig. 2, are made in the extension of edges AB, DC which if the edges are parallel should also be coincident. The proposed edges may be delineated by marks 11, 12.