Record carrier body with an optical servo track and optical apparatus for writing and reading information from the carrier

摘要

Disclosed is a system for optically recording information on a disc-shaped record carrier body along an information track, with the write spot being accurately guided in the radial and tangential directions. The record carrier body comprises a servo track formed by a constant and large number of servo areas per revolution of the servo track. In addition to a write spot, the write apparatus also projects a servo spot on the servo track. The tangential speed and the radial position of the servo spot relative to the servo track are determined from the modulated servo beam and used to correct the tangential speed and the radial position of the write spot, which is locked to the servo spot.