OPTICAL EXPOSURE HEAD FOR A PHOTOPLOTTING MACHINE

摘要

1431866 Photoplotting apparatus HOLLANDSE SIGNAALAPPARATEN BV 6 April 1973 [10 April 1972] 16648/73 Heading G2A In an optical exposure head for a photoplotting machine the image of a selected one of a number of indicia 23a -n carried on a plate 20 mounted in a cylindrical box 14 and rotatable about a spindle 22, is projected on to a photo-sensitive surface placed on a table 44, the orientation of the image in the plane of the surface being adjustable by rotating the cylindrical box 14, via a worm drive 16, 17, about the main optical axis of the exposure head. The main axis is formed by light source 2, thermal filter 11, condenser 7a, 7b, objective lens 9 and zoom lens 36, one component of which is mounted in an air cushioned element 45. This element is maintained at a desired distance from the photo-sensitive surface by pumping air through a line 47 to outlets 46 to form an air cushion and resiliently mounting the element on a block 48 by spring-steel leaves 54. The selected indicium 23a is positioned in the optical axis of the exposure head by rotating disc 20 by a stepping motor 24 and locking the disc in position by a lever 28 engaging recesses in a ring 27 mounted on the disc holder 19.