Lens surface cutting apparatus and lens surface cutting method for spectacle lens, and spectacle lens

摘要

A lens surface cutting method for a spectacle lens includes the steps of calculating the mean curvature of a lens surface (5) to be machined, calculating a helical machining path (4) that matches the mean curvature, and cutting the lens surface (5) to be machined by a cutting means. The helical machining path (4) calculated by the helical machining path calculating step is a path in which helix spacings P (=P₁, P₂, . . . P_n) on the lens surface (5) to be machined are equidistant and a helix spacing d (=d₁, d₂, . . . d_n) on an X-Y projection plane 100 increases continuously from a lens outer periphery toward a center. The cutting means cuts the lens surface (5) to be machined from the outer periphery toward the center along the helical machining path (4). Thus, a spectacle lens having a lens surface with a surface accuracy that is almost uniform throughout an entire surface can be obtained.