Tool for smoothing or polishing optical surfaces

Abstract

There is disclosed a tool for smoothing or polishing an optical surface. The tool comprises: a body part which is rotatable about an axis of rotation; and a plurality of pads arranged in an array to bear against said optical surface for movement across the surface as the tool is rotated about said axis of rotation, wherein said pads are each mounted: i) for substantially linear movement relative to said body part in a direction substantially normal to said surface in the region where the pad contacts the surface; and ii) universal pivotal movement relative to said body part. The pads are biased towards said optical surface. In a preferred arrangement, a plurality of pistons are mounted for individual reciprocating movement relative to the body part along respective longitudinal axes, each of said pistons having a distal end to which a respective said pad is universally articulated, wherein said pistons are each biased towards said optical surface.

1 . A tool for smoothing or polishing an optical surface, the tool comprising: a body part which is rotatable about an axis of rotation; a plurality of pistons mounted for individual reciprocating movement relative to the body part along respective longitudinal axes, each of said pistons having a distal end to which a respective pad is universally articulated, said pads being arranged in an array to bear against said optical surface for movement across the surface as the tool is rotated about said axis of rotation, wherein said pistons are each biased towards said optical surface along their respective longitudinal axes. 
     
     
         2 . A tool according to  claim 1 , wherein each said piston is spring-biased towards said optical surface. 
     
     
         3 . A tool according to  claim 2 , wherein each said piston is biased towards said optical surface by a respective spring. 
     
     
         4 . A tool according to  claim 3 , wherein each said spring is a compression spring. 
     
     
         5 . A tool according to  claim 3 , wherein the spring constant of each spring is determined in dependence on the radial distance of the respective piston from the axis of rotation of the tool. 
     
     
         6 . A tool according to  claim 5 , wherein the spring constants of the individual springs are inversely proportional to the radial distance of the respective pistons from the axis of rotation of the tool. 
     
     
         7 . A tool according to  claim 1 , wherein each said piston is mounted for sliding movement within a respective bore, and comprises at least one internal flow conduit in fluid communication with an outlet port provided in the piston to direct lubricating fluid between the piston and the bore. 
     
     
         8 . A tool according to  claim 7 , wherein the internal flow conduits are all provided in fluid communication with a plenum chamber within the body part. 
     
     
         9 . A tool according to  claim 8 , wherein the plenum chamber is supplied with lubricating fluid via a flow channel which is substantially coaxial with the axis of rotation of the body part. 
     
     
         10 . A tool according to  claim 7 , wherein said lubricating fluid is compressed air. 
     
     
         11 . A tool according to  claim 1 , wherein each pad is mounted to the distal end of the respective piston via a ball joint. 
     
     
         12 . A tool according to  claim 11 , wherein each ball joint comprises flexible adhesive to secure the pad to the piston. 
     
     
         13 . A tool according to  claim 1 , wherein each pad is mounted to the distal end of the respective piston via a spherical bearing. 
     
     
         14 . A tool according to  claim 1 , wherein said pads are arranged in a substantially planar array. 
     
     
         15 . A tool according to  claim 1 , wherein said pads are arranged in a substantially convex array. 
     
     
         16 . A tool according to  claim 1 , wherein said pads are arranged in a substantially concave array. 
     
     
         17 . A tool according to  claim 1 , wherein each pad is substantially circular in shape. 
     
     
         18 . Use of a tool according to  claim 17  for smoothing or polishing an optical surface having a predefined surface profile to remove or reduce surface waves, wherein each pad is configured so as to have a diameter which is greater than the wavelength of the surface waves.