Process for holding an optical lens on a holder of a lens machining equipment

Abstract

A process is provided for rapidly holding an optical article having a convex surface on a holder of a lens machining equipment, the holder being equipped with a suction chuck comprising a cavity with a side wall and sealing means on a front end of the side wall, comprising the following steps: / a / providing a flexible curved wafer with a concave surface arranged to close the cavity at the front end of the side wall; / b / a fixing step in which the wafer is fixed onto the holder by providing vacuum between the concave surface of the wafer and the suction chuck; and / c / a pressing step in which the concave surface of the optical article is pressed onto the concave surface of the wafer, an adhesive material being arranged between the wafer and the optical article The assembly is tight enough for sustaining machining forces, and the lens can be released rapidly.

Description

FIELD OF THE INVENTION[0001]The invention relates to a process for holding an optical article, for example a lens, on a holder of a lens machining equipment. In particular, it is useful when manufacturing an ophthalmic lens.BACKGROUND OF THE INVENTION[0002]When producing an optical lens, and especially an ophthalmic lens, it is necessary to fix the lens on the holder of a machining equipment for machining the lens. For example, the machining corresponds to the lens surface generating step, the fining step, the polishing step or the edging step in the lens production process. For an ophthalmic lens, such production steps are carried out in a prescription lab where a semi-finished lens is machined so as to obtain a spectacle lens which corresponds to the ametropy of a lens carrier.[0003]Usually, a wax or an alloy is used for fixing firmly the semi-finished optical lens on the equipment holder. The wax or alloy connects the convex surface of the semi-finished lens to an end part of the...

AI Technical Summary

Benefits of technology

[0014]Using a flexible wafer between the optical element and the suction chuck ensures that all stresses produced by the vacuum implementation are accommodated by the wafer. This also results from the chronological order between steps / b / and / c / . The stress level produced in the lens in then significantly reduced, so that no change occurs in the lens shape. Therefore, an accurate lens machining can be achieved, because the positioning of the optical element with respect to the holder is accurately defined, and because the optical element shape is not altered after machining for recovering the optical element.

[0015]Using a flexible wafer also ensures that the wafer is blocked firmly to the vacuum chuck. An important optical element holding strength can be obtained, because the flexible wafer together with the sealing means provides a tight vacuum sealing. Then lens machining can performed, even if it involves important forces transmitted from the optical element to the holder.

[0018]Using a pressure sensitive adhesive for sticking the optical element to the wafer enables easy removal of the optical element from the holder of the machining equipment. This can be achieved in a two-step process. First, the vacuum in the cavity of the suction chuck is suppressed, so that the optical element together with the wafer is removed from the suction chuck. Then, the wafer is removed from the convex surface of the optical element.

[0020]Another advantage results from the fact that neither heating step nor cooling step is involved. Then, the optical element is free of thermal stresses. In addition, all steps can be implemented rapidly, so that a process according to the invention allows high production rate in a prescription lab for manufacturing ophthalmic lenses.

[0022]According to an improvement of the invention, the suction chuck may further comprise a rigid support arranged within the cavity. It is arranged so that a rear surface of the flexible curved wafer is in contact with the rigid support on a side opposite to the wafer concave surface, once said wafer has been fixed to the holder in step / b / . Such support helps to further avoid deformation of a lens being machined, by providing a back contact to the wafer for supporting the machining forces. This may be useful when the lens thickness is small, especially for negative lenses.

Problems solved by technology

Then, such lens deformation prevents from achieving accurate machining, and may also alter the lens material.

Furthermore, such method with heating steps is time-consuming and costly.

Such method involves in general toxic alloys, generates waste, in particular contamined wax and alloys.

For example, U.S. Pat. No. 3,994,101 discloses using a suction chuck, but this method may create lens deformation, especially when the lens is rather thin.

Furthermore, the vacuum sealing produces scratches on the convex lens surface.

U.S. Pat. No. 5,567,198 describes a compression sleeve chuck suitable for holding a lens, but such holding system is rather complex for easy fitting to conventional machining equipment.

Such device is also rather complex and requires a back-supporting system for supporting the buffer on a side opposite to the resilient membrane.

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