Method for deciding a bevel curve, method for determining the locus of a bevel, method for processing a lens and apparatus for processing a lens

A method for determining a locus of a bevel in a high power minus lens comprising the steps of:

• calculating a value of a bevel curve based on a value of the curve of a convex face of the high power minus lens;
• determining a location of a first reference position, which is decided to be on a peripheral edge of the high power minus lens in a first portion having a minimum thickness of the high power minus lens, wherein this first portion having the minimum thickness is on a side of the lens that is closest to a wearer's nose, wherein the location of the first reference position is based on a thickness of this first portion having the minimum thickness;
• calculating a location of a second reference position on a peripheral edge of the high power minus lens in a second portion having a maximum thickness of the high power minus lens, wherein this second portion having the maximum thickness is on the side of the lens that is closest to a wearer's nose, wherein the calculation of the second reference position is based on a ratio of a thickness of the second portion having a maximum thickness to the thickness of the first portion having a minimum thickness;
• calculating an angle of inclination relative to the direction of an initial reference axis of the high power minus lens, wherein the angle of inclination calculation is based on data describing a shape of the high power minus lens to be obtained by processing;
• and,
• determining the locus of the bevel based on the value of the bevel curve, the first reference position and the second reference position.

A method for determining a locus of a bevel in a high power minus lens comprising the steps of:

• calculating a value of a bevel curve based on a value of the curve of a convex face of the high power minus lens;
• determining an orientation of an initial reference axis of a bevel curve to be in the same direction as a direction of the curvature of the convex face of the high power minus lens;
• determining a location of a first reference position of the bevel on a peripheral edge of the high power minus lens in a first portion having a minimum thickness of the high power minus lens, wherein the first portion having the minimum thickness is on a side of the lens that is closest to a wearer's nose, wherein the location of the first reference position is based on a thickness of the first portion having the minimum thickness;
• calculating a correction value for the initial reference axis of the bevel curve, wherein the correction value calculation is based on a ratio of a thickness of a second portion having a maximum thickness of the high power minus lens to the thickness of the first portion having the minimum thickness, wherein the second portion having the maximum thickness is on the side of the lens that is closest to a wearer's nose;
• calculating an angle of inclination of a reference axis of the bevel curve from a direction of the initial reference axis of the bevel curve, wherein the angle of inclination calculation is based on the correction value for the initial reference axis of the bevel curve and data describing a shape of the high power minus lens to be obtained by processing;
• and,
• determining the locus of the bevel based on the value of the bevel curve, the reference position of the bevel and the angle of inclination of the reference axis.