Patent ID: 8348423

Claim:
A disc intended to be attached to a curved concave surface (S 0 ) of an optical component in order to modify an optical power of said component, the disc comprising a Fresnel lens formed of a series of Fresnel zones nested inside one another parallel to a smooth face of said disc (S 2 ) and having height differences between two successive zones, said height differences being measured along a direction (z) perpendicular to the smooth face at an optical center of the disc (O), wherein the disc possesses: a generally spherical shape in addition to the height differences between successive Fresnel zones, said generally spherical shape having a mean radius of curvature of between 135 mm and 53 mm, and wherein the height differences between successive Fresnel zones are situated on a concave face (S 1 ) of the disc, said height differences between successive Fresnel zones having: constant amplitudes within a radius circle (C) surrounding the optical center of the disc (O) and of a dimension defined as a function of the power of the disc, and variable amplitudes which increase in a peripheral part of the disc, when traveling away from the optical center (O) and outside said circle (C), said radius circle (C) having a value of between 5 mm and 25 mm for a power of between 1 diopter and 10 diopters, and a first central height difference amplitude greater than or equal to 5 μm, and wherein the height differences between successive Fresnel zones within the circle (C) have amplitudes of between 5 μm and 25 μm, and the height differences between successive Fresnel zones outside the circle (C) and out to a peripheral part of the disc have variable amplitudes of between 5 μm and 250 μm.