Disclosed is a machining method by turning at least one surface of an ophthalmic lens, using a turning machine having at least one geometrical defect. The method includes a step (101-104) of determining a turning configuration for machining by turning the at least one surface of the ophthalmic lens, the turning configuration including turning parameters and machine defects parameters associated to the turning parameters.

A position control apparatus includes an inversion detector which detects an inversion of a position command and generates an inversion detection signal, a deflection characteristic storage unit which stores a deflection characteristic representing an amount of deflection with respect to a torque command, and an inversion correction calculator which calculates an inversion correction amount. The inversion correction calculator stores a torque command immediately before the inversion, and calculates the inversion correction amount from a difference between an amount of deflection immediately before inversion in which the stored torque command is checked with the deflection characteristic, and an amount of deflection after the inversion in which a value obtained by inverting a sign of the stored torque command is checked with the deflection characteristic. A value obtained by adding the inversion correction amount to the position command value is used for position error calculation.

Disclosed is a machining method by turning at least one surface of an ophthalmic lens, using a turning machine having at least one geometrical defect. The method includes a step (101-104) of determining a turning configuration for machining by turning the at least one surface of the ophthalmic lens, the turning configuration including turning parameters and machine defects parameters associated to the turning parameters.

A position control apparatus includes an inversion detector which detects an inversion of a position command and generates an inversion detection signal, a deflection characteristic storage unit which stores a deflection characteristic representing an amount of deflection with respect to a torque command, and an inversion correction calculator which calculates an inversion correction amount. The inversion correction calculator stores a torque command immediately before the inversion, and calculates the inversion correction amount from a difference between an amount of deflection immediately before inversion in which the stored torque command is checked with the deflection characteristic, and an amount of deflection after the inversion in which a value obtained by inverting a sign of the stored torque command is checked with the deflection characteristic. A value obtained by adding the inversion correction amount to the position command value is used for position error calculation.