Patent ID: 7349298
Filing Date: 2008-03-25
Classification: G11B

Abstract:
1. An optical disc drive for reading data from an optical disc and/or writing data on an optical disc having an information storage layer, comprising: a light source; a collector optics for focusing light from the light source; a light-receiving section for receiving a peripheral part of the light reflected by the information storage layer to generate a first detection signal and for receiving a non-peripheral part of the light to generate a second detection signal; a first focus signal generating section for generating a first focus signal based on the first detection signal according to a focusing state of the light in the peripheral part; a second focus signal generating section for generating a second focus signal based on the second detection signal according to a focusing state of the light in the non-peripheral part; a first light quantity generating section for generating a first light quantity signal based on the first detection signal according to a total light quantity of the peripheral part; a second light quantity generating section for generating a second light quantity signal based on the second detection signal according to a total light quantity of the non-peripheral part; a first normalizing section for generating a first normalized signal by normalizing the first focus signal based on the first light quantity signal; a second normalizing section for generating a second normalized signal by normalizing the second focus signal based on the second light quantity signal; and a detecting section for generating a spherical aberration signal based on the first normalized signal and the second normalized signal according to a quantity of spherical aberration produced at a focusing position of the light, wherein the detecting section calculates a difference between the first normalized signal and the second normalized signal to generate the spherical aberration signal.