Apparatus and method for generating tracking error signal and optical recording/reproducing system using same

An optical recording/reproducing system, comprising:

• a pickup which emits a laser beam toward an optical medium and detects a reflected laser beam reflected from a disc;
• a tracking error signal generating unit that generates a tracking error signal by calculating a difference between an MPP signal obtained by calculating a deviation of beam powers detected by main photodetecting units which are arranged in right and left directions with respect to a track and an SPP signal obtained by calculating a deviation of beam powers detected by photodetecting units which are one of main photodetecting units diagonally arranged with respect to the track and signals output by side photodetecting units disposed on opposing sides of the main photodetectors;
• a servo controller which generates a tracking driving signal which is used to move an optical system of the pickup in a radial direction so as to direct the laser beam at a center of the track, using the tracking error signal;
• and
• a tracking servo driving unit which drives a tracking actuator included in the pickup in response to the tracking driving signal.

A tracking error signal generator comprising:

• a main push pull (MPP) signal generator which generates an MPP signal based on a difference between a first sum signal representing the sum of signals output from main photodetecting portions disposed on a side of a track and a second sum signal representing the sum of signals output by the main photodetecting portions disposed on an opposing side of the track;
• a side push pull (SPP) signal generator which generates an SPP signal based on a difference between one of a third sum signal representing the sum of signals output from the main photodetecting portions which are diagonally disposed with respect to the track in a first direction and a fourth sum signal representing the sum of signals output by the main photodetecting portions diagonally disposed with respect to the track in a second direction normal to the first and a fifth signal output by a first side photodetector and a sixth signal output by a second side photodetector;
• a filter which removes one or more AC components from the SPP signal;
• and
• a subtractor which generates a tracking error signal based on a difference between the MPP signal and a filtered SPP signal.

A method of generating a tracking error signal, comprising:

• generating a main push pull (MPP) signal based on a difference between a first sum signal representing the sum of signals output from main photodetecting portions disposed on a side of a track and a second sum signal representing the sum of signals output by the main photodetecting portions disposed on an opposing side of the track;
• generating a side push pull (SPP) signal based on a difference between one of a third sum signal representing the sum of signals output from the main photodetecting portions which are diagonally disposed with respect to the track in a first direction and a fourth sum signal representing the sum of signals output by the main photodetecting portions diagonally disposed with respect to the track in a second direction normal to the first and a firth sum signal output by a first side photodetector and a sixth sum signal output by a second side photodetector;
• removing one or more AC components from the SPP signal;
• and
• generating a tracking error signal based on a difference between the MPP signal and a filtered SPP signal.

A computer readable medium encoded with processing instructions for implementing a method of generating a tracking error signal, the method comprising:

• generating a main push pull (MPP) signal based on a difference between a first sum signal representing the sum of signals output from main photodetecting portions disposed on a side of a track and a second sum signal representing the sum of signals output by the main photodetecting portions disposed on an opposing side of the track;
• generating a side push pull (SPP) based on a difference between one of a third sum signal representing the sum of signals output from the main photodetecting portions which are diagonally disposed with respect to the track in a first direction and a fourth sum signal representing the sum of signals output by the main photodetecting portions diagonally disposed with respect to the track in a second direction normal to the first and a firth sum signal output by a first side photodetector and a sixth sum signal output by a second side photodetector;
• removing one or more AC components from the SPP signal;
• and
• generating a tracking error signal based on a difference between the MPP signal and a filtered SPP signal.

An optical recording/reproducing system, comprising:

• a pickup having a light beam generator which generates a light beam, an optical system which focuses the light beam onto an optical medium, a focus/tracking actuator which moves the optical system in a radial direction with respect to the optical medium in response to a tracking driving signal so as to direct the light beam at a specific track on the optical medium, and a photodetector section including main photodetecting portions which receive the light beam after the light beam is reflected from the optical medium and output respective signals in response thereto;
• a tracking error signal generator which generates a tracking error signal representing a difference between a main push pull (MPP) signal and a side push pull (SPP) generator;
• a servo controller which generates the tracking driving signal based on the tracking error signal,
• wherein the MPP signal is generated based on a difference between a first sum signal representing the sum of signals output from the main photodetecting portions disposed on a side of a track and a second sum signal representing the sum of signals output by the main photodetecting portions disposed on an opposing side of the track, and
• wherein the SPP signal is generated based on a difference between one of a third sum signal representing the sum of signals output from the main photodetecting portions which are diagonally disposed with respect to the track in a first direction and a fourth sum signal representing the sum of signals output by the main photodetecting portions diagonally disposed with respect to the track in a second direction normal to the first and a fifth signal output by a first side photodetector and a sixth signal output by a second side photodetector.