Tool and a Method for Polishing Optical Surfaces
The invention relates to a tool for polishing optical surfaces, comprising a rigid body ( 10 ) which is equipped with a polishing face ( 12 ) and an elastic sheet ( 20 ) which is disposed between the polishing face ( 12 ) and the optical surface to be polished. According to the invention, the polishing face ( 12 ) of the rigid body ( 20 ) takes the form of a portion of a geometric surface which is defined by at Least three parameters. In a preferred embodiment of the invention, the aforementioned surface is atoric. The inventive method consists in selecting the above-mentioned tool from a set of available tools, applying an elastic sheet ( 20 ) thereto, polishing at least one optical surface and changing the elastic sheet ( 20 ) before polishing other optical surfaces. The original shape is maintained with greater precision in relation to the entire surface to be polished, but particularly close to the edges and/or at the centre thereof.
1 . A tool for polishing optical surfaces, comprising a rigid body having a polishing face at least as large as an optical surface to be polished, and a resilient pad arranged between said polishing face and the optical surface to be polished, wherein the polishing face of the rigid body is configured as a portion of a geometric surface, said geometric surface being defined by at least three parameters (a,b,R).
2 . A tool as claimed in claim 1 , wherein said geometric surface is an atoric surface.
3 . A tool as claimed in claim 2 , wherein said atoric surface is a surface of revolution.
4 . A tool as claimed in claim 2 , wherein the generatrix of said atoric surface is one or both of an ellipse and substantially elliptical.
5 . A tool as claimed in claim 1 , wherein said resilient pad comprises a first layer of flexible material of a thickness of at least about 3 mm and a second layer of polishing material.
6 . A tool as claimed in claim 5 , wherein said first layer of flexible material has a thickness of between about 3 and about 8 mm.
7 . A tool as claimed in claim 1 , wherein said resilient pad is provided separate from said rigid body and comprises an adhesive film covered with a peelable protection paper.
8 . A tool as claimed in claim 7 , wherein said resilient pad is adapted to be removed from the polishing face after use.
9 . A method for polishing optical surfaces, comprising the following operations:
(A) providing a polishing tool having a rigid body, said body having a polishing face at least as large as an optical surface to be polished and configured as a portion of a geometric surface defined by at least three parameters (a,b,R);
(B) applying a resilient pad to said polishing face;
(C) polishing at least one optical surface with said tool, by placing the tool in contact with an optical surface and causing relative motion between the optical surface and the tool while applying a predetermined pressure, during a predetermined time; and
(D) changing said resilient pad before polishing a further optical surface.
10 . A method as claimed in claim 9 , wherein the operation of providing a polishing tool comprises determining by the least square method the parameters of the atoric surface matching most closely the optical surface to be polished, and selecting from a set of available tools the tool having a polishing surface with parameters substantially close to those determined by the least square method.
11 . A method as claimed in claim 9 , wherein the operation of applying a resilient pad to the polishing face is carried out by means of a tool comprising a support for the rigid body and means to press the resilient pad against the body with a predetermined pressure.
12 . A tool as claimed in claim 5 , wherein said first layer of flexible material has a thickness of between about 3 and about 15 mm.
13 . A method as claimed in claim 11 , wherein said means to press the resilient pad against the rigid body comprise a cylindrical silicone block of medium hardness.
14 . A tool as claimed in claim 1 , wherein the polishing surface of the rigid body is determined by the least square method the parameters of an atoric surface matching most closely the optical surface to be polished.
15 . A tool as claimed in claim 1 , wherein the resilient pad is applied to the polishing face by a tool comprising a support for the rigid body and means to press the resilient pad against the body with a predetermined pressure.
16 . A tool as claimed in claim 15 , wherein said means to press the resilient pad against the rigid body comprises a cylindrical silicone block of medium hardness.
17 . A method as claimed in claim 9 , wherein said geometric surface is an atoric surface.
18 . A method as claimed in claim 9 , wherein said resilient pad comprises a first layer of flexible material of a thickness of at least about 3 mm and a second layer of polishing material.
19 . A method as claimed in claim 18 , wherein said first layer of flexible material has a thickness of between about 3 and about 15 mm.
20 . A method as claimed in claim 9 , wherein said resilient pad is provided separate from said rigid body and comprises an adhesive film covered with a peelable protection paper.