Data carrier e.g. DVD, tracks scanning arrangement, has two light detectors to detect null signal during photometric balance, where information about depth position of carrier is determined based on sign and magnitude of detected signal

摘要

The arrangement has a diffraction zone lens (421) to execute a chromatic depth splitting while imaging a focal point formed by focusing light on a data carrier by a polychromatic light source (1). Two light detectors (31, 32) detect a null signal during photometric balance. Information about the depth position of the carrier is determined based on the sign and magnitude of the detected signal. An independent claim is also included for a method for confocal scanning of data tracks of a data carrier.