A Methodology for Measuring the Parameters of Large Concave Aspherical Mirrors by Means of a Wavefront Sensor

Abstract

A methodology has been developed for measuring radius R_v and eccentricity (conic parameter k) of large concave aspherical mirrors using a wavefront sensor. Analytical expressions that directly relate Zernike coefficients a₄ and a₉ to parameters R_v and k of the mirror are obtained. It is shown that the technique does not require accurate mirror alignment before measurements. A computer analysis showed that the developed scheme enables measurements with errors of δR_v < 0.1% and δk < 0.01 for mirrors with radii from 100 to 2000 mm and with errors of δR_v < 0.01% and δk < 0.001 for mirrors with radii of more than 5000 mm.