METHOD OF CALCULATING A SETPOINT FOR BEVELING OR GROOVING AN OPHTHALMIC LENS

• US 20120133886A1
• Filed: 07/08/2011
• Published: 05/31/2012
• Est. Priority Date: 07/20/2010
• Status: Active Grant

• Current Assignee: Essilor International SA (EssilorLuxottica SA)
• Original Assignee: Essilor International SA (EssilorLuxottica SA)
• Inventors: FRESON, David, BELLONI, Eric, BITON, Jérémie, ALLOUIS, Thierry, HOLVOET VERMAUT, Benoit
• Granted Patent: US 8,523,353 B2
• Time in Patent Office: Days
• US Class Current: 351/159.74
• CPC Class Codes: B24B 49/00 Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation B24B33/06, B24B37/005 take precedence; if applicable to other machine tools, B23Q15/00 - B23Q17/00 take precedence
• CPC Class Codes: B24B 9/148 electrically, e.g. numerically, controlled

Abstract

A method of calculating a shaping setpoint for an ophthalmic lens along a longitudinal profile includes:

• • an operation of acquiring an initial longitudinal profile;
  • an operation of centering the initial longitudinal profile on the lens;
  • an operation of searching for two remarkable points of the initial longitudinal profile as a function of determined criteria;
  • an operation of calculating a modified axial coordinate for each remarkable point in order to ensure proper mounting and esthetic appearance of the lens in its eyeglass frame; and
  • an operation of calculating a final longitudinal profile resulting from a transformation of the initial longitudinal profile that is such that the final longitudinal profile passes through the two remarkable points.

Claims

1. A method of calculating the 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 the 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 (Ep, Dav, Dar) 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 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.

2. A calculation method according to claim 1, wherein each positioning criterion consists in 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.

3. A calculation method according to claim 1, wherein each characteristic acquired in step a) relates to the shape of the ophthalmic lens (20) or to the axial position of the initial longitudinal profile (29) relative to one of the optical faces (21, 22) of the ophthalmic lens (20).

4. A calculation method according to claim 1, wherein, in step b), said decision criterion relates to the thickness (Ep) of the ophthalmic lens (20) at least one point of the initial longitudinal profile (29).

5. A calculation method according to claim 4, wherein said decision criterion consists in determining whether the minimum thickness (Ep) of the ophthalmic lens (20) along the initial longitudinal profile (29) is less than a thickness threshold (S_Ep).

6. A calculation method according to claim 4, wherein said decision criterion consists in determining whether the axial distance (Dar) between the rear face (21) of the ophthalmic lens (20) and the initial longitudinal profile (29) is, at least one point situated in a nose zone of said initial longitudinal profile (29), less than an interference threshold (S_coll).

7. A calculation method according to claim 1, 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.

8. A calculation method according to claim 1, wherein, in step c), the first positioning criterion relates to the minimum thickness (Ep) of the ophthalmic lens (20) along the initial longitudinal profile (29), and the first remarkable point (Pr1) corresponds to the point of the initial longitudinal profile (29) at which the thickness of the ophthalmic lens (20) is at a minimum.

9. A calculation method according to claim 1, wherein, in step c), the first positioning criterion relates to the ratio (Re) of the axial distance (Dar) between the initial longitudinal profile (29) and one of the optical faces (21, 22) of the ophthalmic lens (20) divided by the thickness (Ep) of the ophthalmic lens (20).

10. A calculation method according to claim 9, wherein, for said optical face being the rear face (21) of the ophthalmic lens (20), the first remarkable point (Pr1) corresponds to the point in the first list that presents the maximum ratio (Re).

11. A calculation method according to claim 9, wherein the first list of points comprises exactly four points (Ph, Pb, Pn, Pt) respectively situated at less than ten millimeters in curvilinear abscissa from the four points of intersection between the initial longitudinal profile (29) and the two axes of symmetry of the boxing rectangle (B1) of said initial longitudinal profile (29).

12. A method according to claim 9, wherein the first list of points comprises exactly four points (Ph, Pb, Pn, Pt) respectively situated at the intersections of the initial longitudinal profile (29) and the boxing rectangle (B1) of said initial longitudinal profile (29).

13. A calculation method according to claim 12, wherein the second list comprises two points (Ph, Pb, Pn, Pt) situated at less than ten millimeters in curvilinear abscissa from the two points of intersection between the initial longitudinal profile (29) and one of the two axes of symmetry of the boxing rectangle (B1) of said initial longitudinal profile (29), said axis of symmetry being the axis of symmetry that is the furthest away from the first remarkable point (Pr1).

14. A calculation method according to claim 1, wherein the second positioning criterion relates to the ratio (Re) of the axial distance (Dar) between the initial longitudinal profile (29) and one of the optical faces (21) of the ophthalmic lens (20) divided by the thickness (Ep) of the ophthalmic lens (20).

15. A calculation method according to claim 1, wherein, in step d), the second remarkable point (Pr2) is selected in such a manner that it lies at least thirty millimeters in curvilinear abscissa from the first remarkable point (Pr1).