Patent ID: 7983130

Claim:
An optical disk device comprising: a unit which rotationally drives a loaded optical disk with a relatively low torque and then rotationally drives the loaded optical disk with a relatively high torque; a unit which measures a first reaching time until a first target rotational speed is reached when the optical disk is rotationally driven with the low torque; a first judging unit which judges a type of the optical disk by comparing the first reaching time with a threshold time for low torque; a unit which measures a second reaching time until a second target rotational speed is reached when the optical disk is rotationally driven with the high torque; a second judging unit which judges a type of the optical disk by comparing the second reaching time with a threshold time for high torque; and a detecting unit which detects that a number of loaded optical disks is a plurality based on a judgment result by the first judging unit and a judgment result by the second judging unit.