Microfilm index display mechanism - is used for finding particular microfilm frames quickly and operates by displaying addresses during film winding

摘要

A mechanism for winding a microfilm through a projector simultaneously displays frame addresses in a readable form. The microfilm (10) is wound from one spool (12) on to another (14) through a projector unit (16) which contains a light source (30) mirror (26) lens unit (32) and screen (40). At one edge of the film are a series of marks (46) one for each frame, whilst at the opposite edge a series of address codes (44) are printed. The marks (46) are used as a clocking track, detected by means of a light source (56) sensor (48) and pulse shaping network which drives a discharge lamp (28) in such a way that an image of the current address word is thrown on to the screen (40).