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US 4,574,527 AGranted
Toric lens generating
OwnerRobert S. Craxtoninventor
Life of this patent
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OwnerRobert S. Craxtoninventor
Estimating the term…
Elliptical error in the generating of toric lenses is substantially eliminated, thereby reducing the time and cost of the production of such lenses. A cup-shaped cutter wheel is swept to cut the lens in a plurality of cuts, suitably three cuts. During each cut the inclination of the cutter wheel and its displacement from the lens in a direction along the optical axis of the lens are changed. Each subsequent cut reduces the elliptical error left after the preceding cut. A computer controller, including a memory storing a table of values of angular orientations and displacements of the cutter wheel with respect to the lens for each of a series of cross curve powers (D.sub.C) which is desired to accompany each of a series of base curve powers (D.sub.B), is used to control the positioning of the cutter unit mounted on the headstock and the tailstock on which the lens is mounted for cutting so as to cut both convex (plus) and concave (minus) toric lenses with minimal elliptical error in the cross curve thereof.
The method of generating toric surfaces having base and cross curvatures of different radius with the aid of a cutter unit having a cutter wheel which sweeps about an axis perpendicular to the axis of the lens, which comprises the steps of sweeping said cutter wheel about said perpendicular axis a plurality of times to make a plurality of cuts, changing the location of said cutter wheel with respect to said surface being generated prior to each cut after the first of said cuts to reduce the elliptical error in different portions of said cross curve during each of said subsequent cuts whereby to provide a toric surface in which the elliptical error is minimized wherein said location changing step is carried out by changing the angle at which said wheel is inclined to produce cross curves of different powers in a lens desired to have said toric surface, and separating said cutter wheel and said lens on each subsequent cut to prevent increasing the error in the cross curve in any portion thereof which is cut during a preceding one of said plurality of cuts.
In apparatus for generating a toric surface on a lens which apparatus has a cutter wheel which sweeps about an axis perpendicular to the axis of the lens while rotating with respect to said lens, a system for minimizing elliptical error in the cross curve of said lens which comprises means for sweeping said cutter wheel about said perpendicular axis a plurality of times to make a plurality of cuts in said lens, and means for changing the location of said cutter wheel with respect to said lens prior to each cut after the first of said cuts to reduce the elliptical error in different portions of said cross curve during each said subsequent cut whereby to provide a toric surface in which the elliptical error is minimized wherein said means for changing said location comprises means for changing the angle .theta. at which said wheel is inclined to produce cross curves of different powers, and means for separating said cutter wheel and said lens on each said subsequent cut to prevent increasing the error in any portion of the cross curve which is cut during the preceding ones of said plurality of cuts.
Apparatus for controlling a toric lens grinding machine having a cutter wheel unit with a cup-shaped cutter wheel and means for sweeping said unit about an axis perpendicular to the axis of the lens being ground to define the base curve of the lens and means for orienting the axis of said wheel to define the cross curve of said lens, which apparatus comprises memory means for storing a table of values of angles of orientation of said cutter wheel and displacements of said wheel from said lens along the optical axis of said lens for a plurality of different cross curves of a plurality of powers D.sub.C for each of a plurality of base curves of different powers D.sub.B, and computer controller means for controlling said orienting means in accordance with different ones of said values during successive ones of said sweeps across the said lens whereby to simultaneously grind the base and cross curves with minimal elliptical error in said cross curve.
Dependencies are inferred from the claim text.