Patent ID: 8014250

Claim:
A method for inspecting an optical information storage medium, the method comprising the steps of: irradiating the optical information storage medium with a laser beam and rotating the storage medium by a constant linear velocity control technique by reference to the radial location at which the laser beam forms a spot on the storage medium; changing the rotational velocities according to the radial location on the storage medium between at least two linear velocities that include a first linear velocity Lv 1 and a second linear velocity Lv 2 , which is higher than the first linear velocity Lv 1 ; generating a focus error signal and/or a tracking error signal based on the light reflected from the storage medium; performing a focus control and/or a tracking control on the laser beam that irradiates the storage medium based on the focus error signal and/or the tracking error signal; and passing branched outputs of the focus error signal and/or the tracking error signal through predetermined types of frequency band-elimination filters for the focus and/or tracking error signal(s) to obtain residual errors of the focus and/or tracking error signal(s) and comparing the residual errors to predetermined reference values, wherein a gain crossover frequency of the focus control remains the same, no matter whether the optical information storage medium, being subjected to the focus control to make a comparison to the predetermined reference value, is rotated at the first linear velocity or the second linear velocity, and wherein a gain crossover frequency of the tracking control also remains the same, no matter whether the optical information storage medium, being subjected to the tracking control to make a comparison to the predetermined reference value, is rotated at the first linear velocity or the second linear velocity.