Patent ID: 7471398
Filing Date: 2008-12-30
Classification: G01B

Abstract:
1. A controlled material adding or removing method for shaping a contour of an object, comprising the steps of, during material addition or removal: irradiating a measuring area of the object that changes under the influence of the material addition or removal, with a light beam, while reflection or transmission of the beam occurs; splitting the transmitted or reflected beam; varying the phase of the split beams relative to each other, such that the differential phase is kept within the range of 2 pi; combining the split beams with each other and observing a fringe pattern which represents a differential phase between the split beams; calculating an optical path length difference from the differential phase; and relating the optical path length difference to the contour variation of the object, wherein the phase is varied by placing, in only one of said split beams, an optical phase filter for generating a predetermined phase plane.