Optical device for a timepiece

Abstract

A timepiece glass, in particular a watch glass, wherein it comprises an optical device comprising at least one lens intended to enlarge an indication supplied by a timepiece, said lens comprising at least one aspherical face comprising at least one section passing through a vertical plane comprising an optical axis of vertical direction z, of which at least one outline can be defined by the following equation: z ⁡ ( r ) = r 2 R ⁡ ( 1 + 1 - ( 1 - κ ) ⁢ ⁢ r 2 R 2 ) + α 4 ⁢ r 4 + α 6 ⁢ r 6 + … in which R is the nominal radius of curvature, k is the constant of conicity, and α(4,6, . . . ) is or are coefficient(s) of asphericity, and in which at least the constant of conicity k and/or at least one coefficient of asphericity is different from zero.

Dependencies are inferred from the claim text.