Method of positioning disk-shaped medium

1. 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.

2. 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,

characterized in that directions of eccentricity of the disk-shaped medium, the hub and a hub unit are defined on the basis of amount of eccentricity between the disk-shaped medium and the hub, that between the hub and the hub adaptor and that 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,

wherein the amount and the direction of eccentricity of the disk-shaped medium with respect to the rotary shaft are defined by biasing the disk-shaped medium toward the hub and making an inner face of the center hole of the disk-shaped medium contact with an outer face of the hub,

the amount and the direction of eccentricity of the hub with respect to the hub adaptor are defined by biasing the hub toward the hub adaptor and making an inner face of the hub contact with an outer face of the hub adaptor, and

the directions of eccentricity of the disk-shaped medium, the hub and the hub unit are defined by rotating the hub adaptor, without fixing the hub to the hub adaptor, in a prescribed angle with respect to the rotary shaft.

3. The method according to claim 2 ,

wherein the rotary shaft is rotated by a motor, and

rotational angle of the rotary shaft is controlled by a motor driver so as to rotate the hub adaptor in the prescribed angle.

4. The method according to claim 3 ,

wherein amount of correcting the eccentric directions of the disk-shaped medium, the hub and the hub adaptor are calculated on the basis of dimensions of the disk-shaped medium, dimensions of parts of the hub and the hub adaptor, and the amount of the eccentricity of the hub adaptor with respect to the rotary shaft, and

the amount of correcting the eccentric directions are inputted to the motor driver so as to correctly position the disk-shaped medium.

5. The method according to claim 2 ,

wherein a plurality of the disk-shaped media are biased toward the hub from the same direction so as to simultaneously position the disk-shaped media.

6. The method according to claim 2 ,

wherein the center of the disk-shaped medium is positioned with respect to the rotary shaft by adjusting two of the amount of eccentricity between the disk-shaped medium and the hub, that between the hub and the hub adaptor, and that between the hub adaptor and the rotary shaft.