Inspection method, inspection apparatus, and inspection program for disk-shaped graduation plate

A defect inspection apparatus for a disk-shaped graduation plate, the defect inspection apparatus comprising:

• an image-data acquiring unit configured to acquire data about an image of the disk-shaped graduation plate as disk-shaped graduation-plate image data;
• a polar-coordinate transforming unit configured to transform the disk-shaped graduation-plate image data into polar coordinates using a center of the disk-shaped graduation plate as a reference to generate polar-coordinate graduation image data;
• and
• a defect detecting unit configured to detect a defect in the disk-shaped graduation plate by comparing a pitch of graduations in the polar-coordinate graduation image data with a predetermined reference value.

A computer-readable recording medium storing an inspection program for a disk-shaped graduation plate, the program causing a computer to execute:

• an image-data acquisition step of acquiring data about an image of the disk-shaped graduation plate as disk-shaped graduation-plate image data;
• a polar-coordinate transformation step of transforming the disk-shaped graduation-plate image data into polar coordinates using a center of the disk-shaped graduation plate as a reference to generate polar-coordinate graduation image data;
• and
• a defect detection step of detecting a defect in the disk-shaped graduation plate by comparing a pitch of graduations in the polar-coordinate graduation image data with a predetermined reference value.