Device for scanning an optical record carrier

摘要

An optical scanning device scans a surface (23) provided with marks with a focused radiation beam (35) along a scan line. The device has a radiation-sensitive detection system (39) comprises a plurality of detectors. An electronic circuit (41) determines the time differences between corresponding parts of the detector signals relating to passage of the radiation beam over one of the marks. The time differences are used to form a signal representing a primary wavefront aberration of the radiation beam.