Patent ID: 7190650
Filing Date: 2007-03-13
Classification: G11B

Abstract:
1. An optical disc drive for reading and/or writing information from/on multiple types of optical discs, of which information storage layers have mutually different depths as measured from surfaces thereof, the optical disc drive comprising: a light source for emitting light; a lens for converging the light to form a beam spot; a photodetector for detecting the light that has been reflected from an information storage layer and outputting reflected light signals; a spherical aberration generator for generating a minimum spherical aberration when the beam spot is located at a reference depth that is defined by the depths of the information storage layers of the multiple types of optical discs; a focus driver for moving the beam spot perpendicularly to the information storage layer of an loaded optical disc, which has been loaded into the optical disc drive, by controlling position of the lens; a light quantity detector for generating a light quantity signal, representing the quantity of reflected light, on receiving and obtaining the sum of the reflected light signals from the photodetector every time the beam spot is moved; and a type recognizer for recognizing a type of the loaded optical disc by estimating a depth of the information storage layer of the loaded optical disc from a surface thereof according to a degree of symmetry of a waveform of the light quantity signal.