Patent ID: 7304820

Claim:
A method of positioning a disk-shaped medium, comprising the steps of: inserting a cylindrical hub into a center hole of the disk-shaped medium; and covering a hub adaptor, which is eccentrically fixed to a rotary shaft, with the hub so as to position the disk-shaped medium on the rotary shaft; and determining eccentricity between the disk-shaped medium and the rotary shaft such that directions of eccentricity of the disk-shaped medium, the hub and a hub unit are calculated on the basis of a first amount of eccentricity between the disk-shaped medium and the hub, a second amount of eccentricity between the hub and the hub adaptor, and a third amount of eccentricity between the hub adaptor and the rotary shaft, whereby the center of the disk-shaped medium with respect to the rotary shaft is positioned at a prescribed position based on the first, second and third amounts of eccentricity.