RADIAL AND TANGENTIAL TRACKING
The information on the disc is contained in a spiral that is read from the inside to the outside. For this purpose the ‘read’ objective and other optical elements are mounted on a sledge driven by a small dc motor, and moving radially under the disc. With an average track pitch of 1.6 μm and the disc rotating at 1800 r.p.m. this means an average linear speed of the sledge of 3 mm/m.
The scanning light beam has to remain focused on the track with a radial accuracy of 0.1 μm, a requirement that cannot be met by a purely mechanical guidance system. By varying the speed of the drive motor by incorporating it in a servo control system certain slow corrections are possible. However, to cope with the effects caused by ...
Get Consumer Electronics now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
