Optical Simulation of the Influence of Spheres with Local Deviations on the Radius Value

The wavefront reflected by a real sphere was supposed to influence significantly the value of the volume determination. Therefore, optical simulations were performed to investigate the wavefront aberration and the results of simulated and inputted topographies are compared. To evaluate the valid boundary of the raytracing software a synthetic sphere with one local deviation from roundness was simulated. The software was validated with a precision of 0.01 nm for a standard sphere of 50 nm form deviation. In succession the contribution of the wavefront reflection in the uncertainty budget could be reduced for various spheres.