Semi-finished lens to be machined for forming an ophthalmic lens to be mounted in a spectacle frame, set and a method involving the same

A method for manufacturing an ophthalmic lens having a first optical face, a second optical face, and a final outline for the ophthalmic lens to be mounted in a spectacle frame, the method comprising:

• providing:
• a semi-finished lens including
• a blank formed in a first material having a first hardness, the blank having
• an outline,
• a first face, and
• a second face configured to be surfaced to constitute a first optical face of the ophthalmic lens, and
• a top layer formed in a second material having a second hardness that is greater than the first hardness, the top layer having
• an outline,
• a first face, and
• a second face of the top layer arranged on the first face of the blank,
• the outline of the top layer being equal to or included in the outline of the blank,
• the outline of the top layer satisfying a predetermined dimensional selection criterion involving the final outline of the ophthalmic lens,
• a first data support containing data representative of said final outline of said ophthalmic lens to be mounted in said spectacle frame, and
• a second data support containing additional data representative of a range of predetermined outlines;
• retrieving the data representative of said final outline from the first data support;
• and
• using the retrieved data representative of said final outline, surfacing the second face of the blank of the semi-finished lens to form the first optical face of the ophthalmic lens,
• wherein the additional data is used so that the outline of the top layer of the semi-finished lens is the outline in said range for which the difference between the area of the surface delimited by the outline of the top layer and the area of the surface delimited by the final outline of the ophthalmic lens is minimized, said predetermined dimensional selection criterion of the outline of the top layer being the minimization of said difference.