Method for tumble grinding optical lens edge

Claim 1

A process for providing rounded edges on a molded plastic lens, said lens having first and second optical surfaces spaced axially apart and a circumferential edge, each of said lens surfaces having a central optical zone and a peripheral transition zone spaced radially outwardly of said central optical zone, the steps of said process comprising: placing a first lens holder having an exterior surface and a lens-protecting surface with said lens-protecting surface in confronting relationship to a first optical surface of said lens; placing a second lens holder having an exterior surface and a lens-protecting surface with its lens-protecting surface placed in confronting relationship to a second optical surface of said lens so that said central optical zone is protected by said lens holders and said circumferential edge extends beyond the periphery of said lens holders; holding said lens holders together; placing said lens and said lens holders together in an abrasive medium; tumbling said lens and said lens holders together in said abrasive medium until said circumferential edge of said lens is sufficiently rounded, without changing the geometry of the central optical zone of the lens.