Method of lens positioning for tilt compensation, method and apparatus for reading and recording data onto an optical disc

Abstract

A method of controlling the positioning of an objective lens of a lens system for controlling an optical beam used in reading and / or recording information from / onto a track of an optical disc, the method comprising steps of detecting modulated optical signals corresponding to the intensity of a reflected optical beam, the reflected optical beam being modulated by the periodic structures of the track of the optical disc, deriving a radial tilt error signal from the modulated optical signals indicative of a radial tilt, wherein the radial tilt refers to the tilt of the objective lens with respect to the optical disc in a radial direction; using the radial tilt error signal for adjusting the position of the objective lens with respect to the optical disc in a radial direction, the method characterized by using the radial tilt error signal for adjusting the position of the objective lens by means of a feedback loop. The radial tilt error signal may be proportional to a cross correlation signal between a Radial Push Pull (RPP) signal and a Central Aperture (CA) signal or a cross correlation signal between a Radial Push Pull (RPP) and a Diagonal Push Pull (DPP) signal.

Description

technical field [0001] The present invention generally relates to a method of controlling the positioning of an objective lens of a lens system in order to control a light beam for reading and / or recording information from / to a track of an optical disc. The present application also relates to a method of reading and / or recording data from / onto an optical disc and a device for reading and / or recording data from / to a track of an optical disc. Background technique [0002] Optical disc technology relies on focusing electromagnetic beams into small spots on the information layer beneath the disc's protective cover layer in order to read and / or record information. The density of information recorded in the information layer of an optical disc is continuously increasing. For example, the track pitch of a CD-type optical disk is 1.6 μm, and the track pitch of a DVD-type optical disk is only 0.74 μm but its information density is increased to 7 times. [0003] Future high-density ...

AI Technical Summary

Problems solved by technology

This method is slow as it relies on maximizing the generated signal using a parabolic fit as a function of the tilt angle, which is varied in fixed steps

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