Simultaneously grinding and polishing preforms for optical lenses

A machine for grinding and simultaneously polishing an optical surface on a glass blank for an optical lens comprising:

• an air bearing work spindle for rotating said glass blank;
• a cutting ring;
• an air bearing tool spindle for rotating said cutting ring, the axis of said tool spindle being positioned at an angle with respect to the axis of said work spindle, and the active cutting diameter of said cutting ring being substantially centered on the axis of rotation of said blank;
• a work table;
• said work spindle and said tool spindle being mounted on said work table;
• means for moving one of said spindles linearly with respect to the other for moving said cutting ring into feeding engagement with said blank;
• said means for linearly moving one of said spindles includes means for biasing said one spindle under a constant load into feeding relationship with respect to the other, and motor means mounted remotely from said work table to isolate said spindles from the vibration of said motor means, and for allowing said one spindle biased under said constant load to move at a desired feed rate with respect to said other spindle for grinding a precisely shaped, polished optical surface thereon.

A method of generating an optical quality polished surface which comprises:

• providing a resilient grinding tool having diamond grit impregnated in resin about an annulus;
• rotating said grinding tool about a first axis by means of a first air bearing spindle;
• rotating a glass work piece about a second axis by means of a second air bearing spindle;
• setting said first and second axes at an angle with respect to each other such that said grinding annulus passes substantially centrally of said rotating work piece;
• urging said grinding tool and said work piece into relative contact with each other under a constant force;
• moving said work piece into contact with said grinding tool at a desired feed rate by means of an air slide and a remotely mounted drive motor means for controlling the feed rate without inducing vibration to said spindles;
• and
• maintaining said work piece in contact with said grinding tool by means of said constant force for generating an optical quality polished surface on said work piece.