Method of calculating a setpoint for beveling or grooving an ophthalmic lens

A method of calculating a shape of a longitudinal profile of an engagement ridge or groove (28) for machining on the edge face (23) of an ophthalmic lens (20), the method comprising:

• an operation of acquiring with an outline-reader appliance (100) a shape of an initial longitudinal profile (29);
• an operation of prepositioning said initial longitudinal profile (29) in a coordinate system tied to the ophthalmic lens (20);
• an operation of searching for two remarkable points (Pr1, Pr2) of said initial longitudinal profile (29), which points are distinct from each other, said operation comprising:
• a) acquiring a plurality of characteristics relating to the ophthalmic lens (20) or to the initial longitudinal profile (29);
• b) determining whether any of said acquired characteristics satisfies a decision criterion, by comparing the value of said acquired characteristic with a predetermined threshold value;
• c) selecting the first remarkable point (Pr1) from a first list of points of said initial longitudinal profile (29) as being the point at which one of said acquired characteristics satisfies a first positioning criterion, said first positioning criterion being selected as a function of the result of step b);
• and
• d) selecting the second remarkable point (Pr2) from a second list of points of said initial longitudinal profile (29), as being the point at which one of said acquired characteristics satisfies a second positioning criterion, said second list being deduced from the result of step c);
• an operation of correcting the position of each remarkable point (Pr1, Pr2) along an axial direction (Z1) substantially perpendicular to a mean plane of the ophthalmic lens (20);
• and
• an operation of calculating with a control unit (400) the three-dimensional shape of a final longitudinal profile (29′) in the coordinate system of the ophthalmic lens (20), resulting from a geometrical transformation of the initial longitudinal profile (29) that is such as to cause the final longitudinal profile (29′) to pass via the first and second remarkable points (Pr1, Pr2) as modified during the preceding operation,
• wherein each positioning criterion includes selecting from the points of the first or second list of points, the point at which the value of the acquired characteristic is at a maximum or a minimum.

A method of calculating a shape of a longitudinal profile of an engagement ridge or groove (28) for machining on the edge face (23) of an ophthalmic lens (20), the method comprising:

• an operation of acquiring with an outline-reader appliance (100) a shape of an initial longitudinal profile (29);
• an operation of prepositioning said initial longitudinal profile (29) in a coordinate system tied to the ophthalmic lens (20);
• an operation of searching for two remarkable points (Pr1, Pr2) of said initial longitudinal profile (29), which points are distinct from each other, said operation comprising:
• a) acquiring a plurality of characteristics relating to the ophthalmic lens (20) or to the initial longitudinal profile (29);
• b) determining whether any of said acquired characteristics satisfies a decision criterion, by comparing the value of said acquired characteristic with a predetermined threshold value;
• c) selecting the first remarkable point (Pr1) from a first list of points of said initial longitudinal profile (29) as being the point at which one of said acquired characteristics satisfies a first positioning criterion, said first positioning criterion being selected as a function of the result of step b);
• and
• d) selecting the second remarkable point (Pr2) from a second list of points of said initial longitudinal profile (29), as being the point at which one of said acquired characteristics satisfies a second positioning criterion, said second list being deduced from the result of step c);
• an operation of correcting the position of each remarkable point (Pr1, Pr2) along an axial direction (Z1) substantially perpendicular to a mean plane of the ophthalmic lens (20);
• and
• an operation of calculating with a control unit (400) the three-dimensional shape of a final longitudinal profile (29′) in the coordinate system of the ophthalmic lens (20), resulting from a geometrical transformation of the initial longitudinal profile (29) that is such as to cause the final longitudinal profile (29′) to pass via the first and second remarkable points (Pr1, Pr2) as modified during the preceding operation,
• wherein, in step b), if the decision criterion is not satisfied, provision is made for determining whether one of the characteristics acquired in step a) satisfies another decision criterion, and in step c), the first positioning criterion is selected also as a function of the result obtained with said other decision criterion.