Patent ID: 8138468
Filing Date: 2012-03-20
Classification: G03G,G11B

Abstract:
1. An eccentricity measurement method of measuring eccentricity between a center of a radial scale of a rotary disk formed around a peripheral portion of the rotary disk and a center of a connection portion of the rotary disk for connecting the rotary disk to a rotary shaft of a measured object, the eccentricity measurement method comprising: forming, on the rotary disk, at least one first straight-line pattern group in different radial directions, the first straight-line pattern group including a plurality of straight-line patterns equally spaced radially and extending in a normal line direction from a base point a predetermined distance away from the center of the radial scale; forming, on a table comprising a projection that engages the connection portion of the rotary disk, at least one second straight-line pattern group, the second straight-line pattern group including the same number of the plurality of straight-line patterns as the straight-line patterns of the first straight-line pattern group in the same radial direction as that of the first straight-line pattern group from a base point the predetermined distance away from the center of an outer diameter of the projection at a pitch different from the pitch of the first straight-line pattern group; placing the rotary disk on the table such that the first straight-line pattern group and the second straight-line pattern group on the table are parallel to each other; and measuring an amount and direction of the eccentricity of the rotary disk using the position of the straight-line pattern of the first straight-line pattern group that coincides with the position of the straight line pattern of the second straight-line pattern group in the radial direction, wherein a central portion of the rotary disk includes the connection portion.