Servo Branch of Optical Disc Drive Comprising a Switchable Diaphragm and a Device for Beam Deflection, and Methods for Measuring Beam Lanking and Spherical Aberration

摘要

A switchable diaphragm ( 9 ) and a device for beam deflection ( 10 ) are placed in the servo branch of an optical drive, in a path of light beams of different diffraction orders. This permits redirection of light beam orders towards a detection means ( 8 ) on an individual basis and selection of light orders at a detection means ( 8 ) depending on requirements. The number of detectors in the device detection means ( 8 ) can thus be reduced, thereby also reducing additional components associated with those detectors and saving on cost and complexity. With such device functionality, new methods for measuring beam landing and spherical aberration are developed.