GB869237A - Improvements in or relating to reducing cameras - Google Patents

Abstract

869,237. Reducing cameras. FARRERBROWN, L. Sept. 22, 1959 [Oct. 24, 1958], No. 34191/58. Class 98(1) A reducing camera comprises means for supporting the original film, means for supporting a length of unexposed film, an optical system for projecting an image of reduced size on the unexposed film and driving means adapted to move the original film and the unexposed film, the latter at a speed of 1n/<SP>th</SP> of that of the former where n is the reduction factor; the first supporting means are movable transversely of the direction of projection between a number of predetermined settings selected by means of an adjustable stepped cam. In the camera shown in Fig. 1, light from a lamp 10 and condenser 11 passes through a horizontal slit in a plate 12 and a record film 14 and forms a reduced image of said film on an unexposed film 21 by means of a microscope objective 20. The two films are driven simultaneously in opposite directions by a motor operating through a belt, gearing, a rod 26 and worm gearings 25, 28 and 27, 17. The initial focusing is performed with the aid of an air jet passed through the microscope head 32. The unexposed film 21 is formed as a continuous loop and when it has been passed once over the supporting plate 22 in front of the objective 20 it is moved transversely in the following way. A thicker region is formed on a dead part of the loop and is detected by an air jet 48 which then closes an air switch which operates through a time switch an electromagnet 44 which in turn rotates a stepped cam 40 so that a bed 34 on which the unexposed film supporting means is mounted moves transversely over the base 13 of the camera, by action of a spring 39 until a cam follower on the bed engages the next step in the cam. The film 21 is thus moved sideways step by step until, after six steps, the bed 34 operates a switch 46 to switch the whole camera off. The air switch 31 also acts in conjunction with a microswitch to disengage a clutch 47 by means of a lever 55 and push rod 56 so that the record film is not driven during the time the dead space is in the image plane. When the thickened part of the dead space passes in front of a second jet 49 the clutch is closed and exposure of the next row on film 21 takes place.