LENS FOR VARIABLE SPECTACLES

摘要

PROBLEM TO BE SOLVED: To visually obscure the line of intersection of a free area of an expandable film and a film supporting member by forming the surface of the film supporting member as part of an annular body having an approximaterly circular section and forming the film in such a manner that the outer periphery of its free area comes into contact with the surface of the supporting member. SOLUTION: The expandable film 15 is joined to a holder 23 by applying a stress in a radial direction thereto. The resulted sub-assembly is joined to a front ring 14 and the film supporting member 16 is mounted between the holder 23 and a seal 13. A portion 16' of the top surface on which the film 15 rides is annular regardless of the peripheral shape of the film supporting member 16. The surface in the portion of the film supporting member 16 is preferably curved in a radial direction and the sectional shape is preferably approximate to an arc (of a radius R). Even if the shape is not the arc, the surface shape of the film supporting member 16 in contact with the film is preferably formed to a smooth projecting curve particularly near a contact line 16" in order to visually obscure the shape.