Optical Lens Member Comprising A Sub-Surface Referencing Element

1 . An optical lens member comprising first and second faces connected by an external periphery surface, the optical lens member further comprises a reference system identified by at least one sub-surface referencing element located between the first and second optical faces wherein the first face comprises a first optical surface having a surface design associated with the reference system.

2 . The optical lens member according to claim 1 , wherein when an optical lens is manufactured from said optical lens member, said sub-surface referencing element remains at least partially on the optical lens as non-discernable.

3 . The optical lens member according to claim 1 , wherein the sub-surface referencing element is located in the periphery of the optical lens member so as to be removed when the optical lens is edged so as to be fit in a spectacle frame.

4 . The optical lens member according to claim 1 , wherein the sub-surface referencing element comprises a plurality of sub-surface markings, the sub-surface markings defining a plan.

5 . The optical lens member according to claim 1 , wherein the referencing element comprises sets of coplanar sub-surface markings each set of markings defining a different plan.

6 . The optical lens member according to claim 1 , wherein the surface design of the first optical face of the optical lens member is oriented and positioned with respect to the reference system identified by the referencing element.

7 . The optical lens member according to claim 1 , wherein the sub-surface referencing element comprises local modifications of the refractive index of the optical lens member.

8 . The optical member according to claim 1 , wherein the sub-surface referencing element comprises sub-surface markings.

9 . The optical lens member according to claim 8 , wherein the sub-surface markings are realized by using a pulsed laser source with pulse duration within femto-second range, wherein the light emitted by the pulsed laser source is focused within the optical lens member.

10 . The optical lens according to claim 1 , wherein the second face comprises a second optical surface having a surface design associated with the reference system.

11 . A method of blocking an optical lens member, the method comprising:

an optical lens member providing step during which an optical lens member according to claim 1 is provided;

a taping step during which an adhesive tape is provided on the first face of the lens member;

a blocker providing step, during which a blocker with a blocker reference system is provided;

an optical lens member positioning step during which the first face of the optical lens member is placed on the blocker and positioned in a blocking position with respect to the blocker reference system using the sub-surface referencing element; and

a blocking step during which the optical lens member is blocked on the blocker in the blocking position.

12 . The method according to claim 11 , wherein the method further comprises a blocking position determining step during which the blocking position of the optical lens member is determined with respect to the blocker reference system using the sub-surface referencing element,

13 . The method according to claim 11 , wherein the position and/or orientation of the referencing element is measured by lighting the optical lens member through the external periphery surface and capturing an image of the lighted sub-surface referencing element.

14 . The method according to claim 13 , wherein the referencing element is visualized through the second face of the lens member and wherein the refractive properties of the lens member are taken into account when determining the position and/or orientation of the referencing element.

15 . A method of manufacturing an optical lens, the method comprising:

the steps of the method according to claim 11 ;

a surface data providing step during which surface data corresponding to the second optical surface to be manufactured on the second face of the optical lens member are provided and

a manufacturing step during which the second optical surface of the optical lens member is manufactured according to the surface data.

16 . A method of manufacturing an optical lens, the method comprising:

a first optical surface manufacturing step during which the second optical face of the optical lens member is manufactured according to claim 15 , from a first optical lens blank;

a second optical surface manufacturing step during which the first optical face of said optical lens member is manufactured according to claim 15 ,

wherein during the first and second optical surface manufacturing steps, the same reference system identified by the sub-surface referencing element is used.