Toric lenses, method and apparatus for making same

Abstract

A unique lens (10) having a peripheral carrier surface (13), a central optical zone (18) providing the toricity required to achieve a given spherical and cyclinder correction that is oriented to a selected axis angle (.psi.) and an intermediate, annular, transitional surface (15) between the optical and carrier surfaces (16 and 13). The method and apparatus for providing such a toric lens (10) employs a generator (50) that produces a sinusoidal signal in response to rotaton of the lathe spindle (26), and a signal that is selectively phased at a predetermined angularity with respect to the circumference of the rotatable spindle (26). The aforesaid signal is applied to a tool post oscillator (90) in order to oscillate the tool (36) in synchronization with rotation of the spindle (26) thereby cutting both curves of the toric surface (16) in one pass. The signal is also modulated (140) in response to the rotational swing of the quadrant (3) on which the cutting tool is supported progressively to null the signal as the cutting tool (36) approaches the apex (22) of the optical zone (18), thus permitting the two curves of the toric, optical surface to merge smoothly at the apex (22). Finally, a switch/ramp control (170) is employed to provide no oscillations of the cutting tool as the carrier surface (13) is lathe-cut and thereafter gradually to increase the signal to the tool oscillator (90) in order to cut an annular transitional surface (15) between the carrier and optical surfaces (13 and 16).