Patent ID: 9151601
Filing Date: 2015-10-06
Classification: G01B

Abstract:
1. An aspheric face form measuring method comprising: calculating, in a phase calculating process via a computing apparatus, phase information of interference light from light intensity of a fringe pattern image obtained by detecting interference light that is formed by measurement light reflected off a subject aspheric face being overlaid and reference light, wherein the measurement light and the reference light were formed by light being divided after being emitted from a light source; changing, in a scanning process via the computing apparatus and in an aspheric axis direction, a relative distance between an optical system, which forms measurement light and reference light, and the subject aspheric face, and transitioning, in the scanning process via the computing apparatus and in a diameter direction, a null region position of a null region where a fringe pattern on the fringe pattern image is a single color stripe; performing, in a first form calculating process via the computing apparatus, calculation of form data for a perpendicular incident region of null regions, where measurement light is vertically incident to the subject aspheric face, using phase information of the perpendicular incident region found in the phase calculating process and a scanning amount which is a change amount of the relative distance between the optical system and the subject aspheric face; performing, in a second form calculating process via the computing apparatus, calculations of form data, of the null regions, a non-perpendicular incident region that is outside of the perpendicular incident region, serving as a relative form as to a perpendicular incident region form; and compositing, in a form compositing process via the computing apparatus, a plurality of partial form data of the subject aspheric face calculated with the first and second form calculating process, using each of a plurality of the phase information and scanning amounts, obtained by alternately repeating the phase calculating process and scanning process, wherein the first form calculating process further includes finding horizontal coordinates of the perpendicular incident region while finding phase difference between a phase of the perpendicular incident region and a phase of an axis of symmetry of the aspheric surface, and calculating the form of the perpendicular incident region from the found phase difference and the scanning amount, and wherein the second form calculating process further includes finding differences between the perpendicular incident region and the non-perpendicular incident region in the phase difference between the horizontal coordinates and the phase of the aspheric face axis portion, as relative values, and calculating, using the relative values of the phase differences and horizontal coordinates, a form measurement of the non-perpendicular incident region as the relative form of the perpendicular incident region.