Essilor International

Pierre Devie

Francoise Ahsbahs

Gilles Le Saux

Francis Bell

A method for measuring the geometrical structure of an optical component () in transmission, comprises illuminating the optical component by means of a first incident beam (), the wavefront of which is known. After the first beam is transmitted by the optical component, its wavefront is measured by deflectometry (). The optical component is then illuminated by a second incident beam (), the wavefront of which is known. After the second beam is transmitted by the optical component, its wavefront is measured by deflectometry (). The geometrical structure of the optical component is then calculated from the measured wavefronts. Measuring light transmitted in two distinct optical configurations allows a calculation by optimizing the two surfaces of the component, without prior knowledge of one of the surfaces. The first and second beams may be different and may illuminate the same surface of the component; thus it is possible to use identical beams and to illuminate each surface of the component in succession.

Method and apparatus for measuring the geometrical structure of an optical component in transmission

A progressive multifocal ophthalmic lens having a far vision region, an intermediate vision region and a near vision region, a main meridian of progression passing through said three regions, and a power addition equal to a difference in mean sphere between a near vision region control point and a far vision region control point is provided. The lens has a progression length less than 12 mm, defined as the vertical distance between a mounting center and a point on the meridian where mean sphere is greater than mean sphere at the far vision control point by 85% of the power addition value. To ensure good visual characteristics not only around the meridian, but also in regions of extra-foveal vision, the ratio between the integral of the product of cylinder times the norm of sphere gradient, on a 40 mm diameter circle centered on the center of the lens, and the product of the area of this circle, power addition and a maximum value of the norm of sphere gradient over that part of the meridian comprised within this circle is less than 0.14.

Progressive multifocal ophthalmic lens with rapid power variation

A progressive multifocal ophthalmic lens having a far vision region, an intermediate vision region and a near vision region, a main meridian of progression passing through said three regions, and a power addition equal to a difference in mean sphere between a near vision region control point and a far vision region control point is provided. The lens has a progression length less than 12 mm, defined as the vertical distance between a mounting center and a point on the meridian where mean sphere is greater than mean sphere at the far vision control point by 85% of the power addition value. To ensure excellent optical performance of the lens despite this short length of progression, the ratio between the product of cylinder times the norm of sphere gradient, and the square of power addition is less than 0.08 mm at every point within a 40 mm diameter disc centered on the center of the lens. Additionally, cylinder within that part of the disc situated above the mounting center is less than 0.5 times power addition.

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Chevilly-Larue, France

Pierre Devie