Optical disk apparatus and method of controlling optical disk apparatus

An optical disc apparatus for applying a light beam to a surface of an optical disc and detecting a return light beam from the surface of the optical disc, comprising:

• a first light detector and a second light detector for detecting the return light beam, said first light detector and said second light detector being disposed along a light path of said return light beam;
• said first light detector having a first divided area and a second divided area which are divided from each other at the center of the return light beam in a direction perpendicular to a track on the surface of the optical disc, and a third divided area and a fourth divided area which are positioned respectively outwardly of said first divided area and said second divided area in the direction perpendicular to the track, said first divided area and said second divided area being positioned so as not to overlap an area where zeroth-order light and first-order light contained in the return light beam overlap each other;
• and
• said second light detector having a fifth divided area disposed at the center of the return light beam in the direction perpendicular to the track, and a sixth divided area and a seventh divided area which are positioned outwardly of said fifth divided area in the direction perpendicular to the track.

A method of controlling an optical disc apparatus for applying a light beam to a surface of an optical disc and detecting a return light beam from the surface of the optical disc with a first light detector and a second light detector, said first light detector and said second light detector being disposed along a light path of said return light beam, each of said first light detector and said second light detector having a first divided area and a second divided area which are divided from each other at the center of the return light beam in a direction perpendicular to a track on the surface of the optical disc, and a third divided area and a fourth divided area which are positioned respectively outwardly of said first divided area and said second divided area in the direction perpendicular to the track, said first divided area and said second divided area being positioned so as not to overlap an area where zeroth-order light and first-order light contained in the return light beam overlap each other, said method comprising the steps of:

• canceling a direct current component of a tracking error with the difference between an output signal from said first divided area and an output signal from said second divided area of said first light detector or said second light detector;
• performing tracking control on said optical disc apparatus with a signal whose direct current component is canceled;
• detecting a focus error from a combination of output signals from said first light detector and said second light detector;
• and
• performing focus control on the light beam applied to the surface of the optical disc based on said focus error.

A method of controlling an optical disc apparatus for applying a light beam to a surface of an optical disc and detecting a return light beam from the surface of the optical disc with a first light detector and a second light detector, said first light detector and said second light detector being disposed along a light path of said return light beam, said first light detector having a first divided area and a second divided area which are divided from each other at the center of the return light beam in a direction perpendicular to a track on the surface of the optical disc, and a third divided area and a fourth divided area which are positioned respectively outwardly of said first divided area and said second divided area in the direction perpendicular to the track, said first divided area and said second divided area being positioned so as not to overlap an area where zeroth-order light and first-order light contained in the return light beam overlap each other, and said second light detector having a fifth divided area disposed at the center of the return light beam in the direction perpendicular to the track, and a sixth divided area and a seventh divided area which are positioned outwardly of said fifth divided area in the direction perpendicular to the track, said method comprising the steps of:

• canceling a direct current component of a tracking error with the difference between an output signal from said first divided area and an output signal from said second divided area of said first light detector;
• performing tracking control on said optical disc apparatus with a signal whose direct current component is canceled;
• detecting a focus error from a combination of output signals from said first light detector and said second light detector;
• and
• performing focus control on the light beam applied to the surface of the optical disc based on said focus error.

A method of controlling an optical disc apparatus for applying a light beam to a surface of an optical disc and detecting a return light beam from the surface of the optical disc with a first light detector and a second light detector, said first light detector and said second light detector being disposed along a light path of said return light beam, said first light detector light detector having at least first and second pairs of divided areas which are symmetrical with respect to the center of the return light beam in a direction perpendicular to a track on the surface of the optical disc, said first pair of divided areas being positioned so as not to overlap an area where zeroth-order light and first-order light contained in the return light beam overlap each other, and being positioned in an area where only the zeroth-order light is applied, and said second pair of divided areas being disposed in an area where the first-order light is applied, and said second light detector having a pair of divided areas which are symmetrical with respect to the center of the return light beam in the direction perpendicular to the track, and a central undivided area aligned with said first pair of divided areas of said first light detector, said method comprising the steps of:

• obtaining a direct current component of a tracking error quantity from the difference between output signals from said first pair of divided areas of said first light detector;
• performing tracking control on said optical disc apparatus with an output signal which is produced by subtracting said direct current component from a tracking error quantity generated from the difference between output signals from said second pair of divided areas of said first light detector;
• and
• performing focus control on the light beam applied to the surface of the optical disc based on a focus servo error quantity which is produced from the difference between the sum of the output signals from said second pair of divided areas of said first light detector and the sum of the output signals from said pair of divided areas of said second light detector.