AN IMPROVED METHOD OF PREPARING A LENS BLANK FOR AN OPERATION OF SURFACING THEREOF

A method of preparing a lens blank for a further operation of surfacing to transform the lens blank into a surfaced lens for further transformation into a lens having a lens shape, the operation of surfacing including processing the lens blank so that the surfaced lens exhibits a crib diameter, the method being implemented using a processing module and comprising: - based on input data (ID) which define the lens shape, defining a temporary crib diameter (D temp ) so that said temporary crib diameter satisfies a set of constraints which includes at least: - a first constraint whereby the temporary crib diameter (D temp ) is large enough for the surfaced lens having said temporary crib diameter to be suitable to be processed into said lens, - a second constraint whereby the temporary crib diameter is large enough for the surfaced lens having said temporary crib diameter to include a plurality of reference points defined on the lens blank and which together identify an optical center of the lens, - choosing the crib diameter as a function of the temporary crib diameter (D temp ), said choosing the crib diameter being configured so that, when a step cribbing configuration is destined to be applied to the operation of surfacing, said crib diameter is chosen among at least one predetermined discrete value (Val 1 ).