Multiple magnification mode copying apparatus

A document reproduction apparatus including a document support surface, a full rate scanning system and a half rate scanning system arranged to travel along a path parallel to, and below, said support surface, and a lens for projecting an image of the scanned document onto a photosensitive surface, the apparatus further including an arrangement for detecting a start-of-scan and end-of-scan position and for causing image to copy sheet registration, the arrangement comprising:

• a pulley/cable/gear system connected to a main drive shaft for moving said full rate and half rate scanning carriages at speeds required for the particular magnification, an optical notched timing disc operatively connected to said main drive shaft so as to complete one full rotation during one scan excursion of said full rate carriage;
• said timing disc having formed on its periphery, a plurality of notches, said notches proportionally distributed on said periphery to conform to various positions of said full rate carriage;
• and
• a light source and photosensor positioned on opposing sides of said disc and adapted to sense the movement therebetween of one of said notches and to generate signals representing at least start-of-scan and end-of-scan positions of said full rate scanning systems.