Patent ID: 7680003

Claim:
An optical disk drive having the ability to read data from a given optical disk that includes at least one information storage layer, the drive comprising: a motor for spinning the given optical disk; at least one optical system including at least one light source for radiating a light beam and a lens for converging the light beam onto the optical disk; a spherical aberration correcting section that is able to change the spherical aberration states of the light beam; and a control section for controlling the operations of the motor, the optical system and the spherical aberration correcting section, wherein the control section includes disk type recognizing means that makes the optical system irradiate the optical disk with the light beam, thereby determining whether or not the given optical disk is compatible with the optical system, and wherein the disk type recognizing means recognizes the type of the given optical disk by reference to first and second signal waveforms that have been generated based on the light beams reflected from the optical disk when the spherical aberration correcting section sets the spherical aberration states of the light beams to a first state and a second state, respectively, the second state being different from the first state.