O'Reilly logo

Consumer Electronics by S. P. Bali

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

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 ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required