Patent ID: 8690324

Claim:
A method for modifying spectacle frame shape data, comprising the steps of: generating spectacle frame data by measuring the shape of a rim of a spectacle frame with a spectacle frame shape measuring apparatus; determining the principal axes of inertia of the measured shape of the rim of the spectacle frame using the rim spectacle frame data; rotating the X and Y axes of the principal axes of inertia around the Z axis of an angle θ, Z being the axis perpendicular to the average plane of the measured shape of the spectacle frame and Arc ⁢ tg ⁡ ( X y X x ) - 1 ≤ θ ≤ Arc ⁢ tg ⁡ ( X y X x ) + 1 with X x being the projection of the axis X of the principal axis of inertia on the x axis of the axis of the measuring apparatus, and X y being the projection of the axis X of the principal axis of inertia on the y axis of the axis of the measuring apparatus; and calculating new spectacle rim frame data expressed in the principal axes of inertia of the measured shape of the rim of the spectacle frame.