Patent ID: 7170833
Filing Date: 2007-01-30
Classification: G11B

Abstract:
1. Apparatus for reading from or writing to optical recording media, comprising: a tracking device, a four-quadrant detector, two summation points, a phase detector for tracking in accordance with a differential phase detection method, said phase detector comprising converters and a phase comparator, and variable delay elements that can be set by a control device, wherein at least one of said variable delay elements is a digital delay element for delaying only edges in an input signal which assumes just two states and at least one of said variable delay elements is an analog delay element for preserving both phase and amplitude information of its input signal, wherein at least one of said variable delay elements is arranged between one of said converters and said phase comparator and at least one of said variable delay elements is arranged between said four-quadrant detector and one of said summation points and, wherein none of the variable delay elements being a digital delay element is arranged between said four-quadrant detector and one of said converters.