NONCONTACT SPHERICITY MEASUREMENT BY MEANS OF PHASE-SHIFT INTERFEROMETRY

This paper presents an accurate optical technique for sphericity measu rement of a ball by means of phase shift interferometry. The ball is p laced in a fixture on a numerically control rotary stage to achieve a 360 degrees inspection. A CCD camera is used to capture the images of interference fringes, and the generated interferograms are used to cal culate the phase values which can then be used to quantify the spheric ity error. With the calculated phase values, the eccentricity of the r otary stage's spindle can be estimated and compensated. The Zernike po lynomials is employed in the process of calibration to gracefully remo ve defocus and tilts. The experimental procedure, the sphericity measu rement results and their statistical data analysis are presented.