Patent ID: 7149169

Claim:
A method for distinguishing the type of optical disc in an optical disc apparatus, the optical disc apparatus comprising a laser, a focusing lens, and a sensor for generating a signal corresponding to laser emitted light reflected from the optical disc, the method comprising: emitting light from the laser to the optical disc; moving the focusing lens such that a focal point of the focused light emitted from the laser moves through the optical disc at substantially constant velocity; while the lens is moving, measuring a first duration that the generated signal exceeds a first predefined threshold, the first predefined threshold indicating that the focal point of the focused emitted light is within a first layer of the optical disc; while the lens is moving, measuring a second duration between a first predetermined location in the generated signal during the first duration and a second predetermined location in the generated signal when the generated signal exceeds a second predefined threshold, the second predefined threshold indicating that the focal point of the focused emitted light is within a second layer of the optical disc; distinguishing the type of optical disc according to the first duration and the second duration.