Newnes Audio and Hi-Fi Engineer's Pocket Book, 3rd Edition

106

laser beam to wander over 60 adjacent tracks! The optically

correct centre (the centre of the circular tracks, not necessarily

of the disc perimeter) is found and the hole punched by laser

beam. In one plant, if an accurate centre cannot be found after

three attempts by the laser, the disc is scrapped.

Finishing A special offset printing press prints the

programme details on the lacquered side of the disc, which is

then carefully examined under polarised light and packed.

Rejects There are some 60 points during the manufacture at

which losses can occur. Total rejection from all causes runs at

around 15%. As polycarbonate cannot be re-cycled ...