Patent GB-1229691-A (GB)
IPC: H04N1/393
Filed: 1969-01-14
Abstract: 1,229,691. Facsimile system. PRINTING DEVELOPMENTS INTERNATIONAL S.A. 14 Jan., 1969 [16 Jan., 1968], No. 2115/69. Heading H4F. In a colour facsimile system, the colour transparency original 105, Fig. 4, is shaped by and held against the curved face 100 of a cylinder section 75, reciprocating about an axis 70 and scanned by a light beam 94 produced by source 90 and a reproducing photographic film 17 is mounted on a rotating drum 17 and illuminated by modulated light source 26. The angular extent a of the film 17 around the drum 17 is much greater than that # of the original 105 around the axis 70-the invention thus provides for the adjustment of the ratio between the scanning speeds of the original and the reproducing film whereby both scannings take the same time and real time reproduction can be used. The rotation speed # of shaft 12 carrying drum 16 is divided by two in reduction gear and the reduced speed #/2 is used to rotate a cam 47. Follower 49 bearing against the cam causes arm 50, radius R to move outwards through an angle of # for one revolution of drum 16 and to move back through said angle during the next revolution of the drum. A slotted arm 55 is fixed to arm 50 and carries push-rod end 57 at a variable radius r. Push-rod 60 is thus reciprocated through distances r# and causes corresponding rotations of arm 63, to which its other end is attached, through an angle #= (r#/p), where p is the radius of arm 63. The duration of this rotation or swing is one revolution of drum 16 or 1/#. The original is thus scanned in a period T 1  = (1/#) - (#/#) = (##)/(#.r.#). The film 17 is scanned in time T 2  = (α/2#). (1/#). Radius r is thus adjusted until T 1 =T 2  or r = (#/α) . (2#/#) . p. For the axial scans of the original and film, light source 26 is mounted on a carriage 25 moving on rails 24 and the original is fixed by edge 119, Fig. 3, to a second cylinder sector 121, connected to the first sector 75 by slidable bar 82, whereby the two sectors are caused to reciprocate about axis 70 together but sector 121 is free to move axially with respect to sector 75, thereby drawing the original past the scanning beam 94. Sector 121 is thus mounted on chassis 130 axially movable on rails 131 and 132. Carriage 25 is caused to move through a step of one line after every other revolution of drum 16 by means of drive 31 and motor 11 and this motion is transferred to chassis 130 by linkage 141. The reduction in the produced motion of chassis 130, in the ratio of the angular scans of the original and the film, is caused by linkage 141 being connected with the remote end of lever 142 with linkage 146, connected to chassis 130, being connected to the lever 142 at a point situated nearer the lever axis. The video output of detector 95 receiving the beam 94 after passage through the original is blocked from the light source 26 on each downward movement of sector 75, i.e. for every other revolution of drum 16. This gating off is controlled by cam 48 and micro-switch 150. The video signals representing red, green and blue components are fed to a processing unit 41 in which masking, background colour removal &c. takes place, and yellow, magenta, cyan and luminous signals are produced on outputs 37 to 40 respectively, for connection to respective modulated light sources 26 to 30 and reproducing films 17 to 20 respectively (Fig. 6, not shown).