Patent ID: 7251580

Claim:
A method for measuring a curved surface of a workpiece, comprising: a theoretical expression input step for obtaining a theoretical expression of the workpiece, the curved surface of which is measured with a measuring probe having a stylus; a measuring area determination step for determining a measuring area on the curved surface which is a range of measuring; a representative point computation step for defining a representative point in the measuring area and computing coordinate values and a normal vector of the representative point based on the theoretical expression; an axis angle determination step for determining an axis angle of the stylus within the measuring area based on the normal vector; an area measuring step for measuring the measuring area with the stylus while keeping the axis angle constant; and displaying the measured data of the curved surface; wherein the axis angle determination step computes a tangent vector in a flank direction in the measuring area of the curved surface of the workpiece based on the normal vector, and determines a flank direction axis angle of the stylus based on the tanaent vector; wherein the representative point computation step, in which the representative point includes a first end-point located at one end of the measuring area and a second end-point located at another end of the measuring area, computes first end-point coordinate values, a first end-point normal vector, second end-point coordinate values, and a second end-point normal vector based on the theoretical expression, and wherein the axis angle determination step determines the flank direction axis angle based on the tangent vector computed from the first end-point normal vector and the second end-point normal vector.