Method for automated in-line determination of center thickness of an ophthalmic lens

Method for an automated in-line determination of the center thickness (55) of an ophthalmic lens (5) in an automated manufacturing line for ophthalmic lenses, the method comprising the steps of:

• providing an inspection cuvette (2) comprising an optically transparent bottom (21) having a concave inner surface (210) and containing the ophthalmic lens (5) immersed in a liquid, and positioning the inspection cuvette (2) at a first inspection location (800) of an inspection module (1) of the automated manufacturing line;
• providing an interferometer (3) comprising a light source and a focusing probe (30), the focusing probe focusing light coming from the light source to a set position (310) of the ophthalmic lens at the center of the concave inner surface of the optically transparent bottom of the inspection cuvette, and the focusing probe (30) further directing light reflected at the boundary (510) between the back surface (51) of the ophthalmic lens and the liquid as well as light reflected at the boundary (500) between the front surface (50) of the ophthalmic lens and the liquid or light reflected at the boundary (502) between the front surface (50) of the ophthalmic lens (5) and the concave inner surface (210) of the optically transparent bottom (21) of the inspection cuvette (2) to a detector of the interferometer (3);
• determining the center thickness (55) of the ophthalmic lens (5) from the signals generated at the detector by the light reflected at the respective boundary (510;
• 500,502) at the back surface (51) and at the front surface (50) of the ophthalmic lens (5), and
• wherein the step of determining the center thickness (55) of the ophthalmic lens (5) comprises
• counting the number of signals generated by the light reflected at the respective boundary (510;
• 500,502), and
• for a counted number of two signals, selecting the two signals for determining the center thickness (55) of the ophthalmic lens (5),
• for a counted number of three signals, ignoring the signal corresponding to the light reflected at the boundary (200) between the concave inner surface (210) of the optically transparent bottom (21) of the inspection cuvette (2) and the liquid, and selecting the remaining two signals for determining the center thickness (55) of the ophthalmic lens (5).