Multiple Aperture Shear Interferometry (MArS) and the influence of spatial light modulator and light sources on measurement errors

Within the framework of the joint DFG project „Optical surface metrology with spatially and temporally partially coherent light wave fields“ (OPaL, project No. 460789164) of BIAS and PTB an optical form measurement system based on Multiple Aperture Shear Interferometry (MArS) is developed. In a MArS measurement, a spatial light modulator (SLM) is used to shear the wavefront in order to determine the wavefield. Various error input quantities are currently being investigated to calculate the uncertainty of the form measurement. In particular, the following two error influences must be taken into account: 1) The MArS setup uses LEDs as light sources which have variances in the light wavelength of several nanometers. 2) The SLM itself is not homogeneous and has variations in phase response. These influences lead to measurement errors, which will be discussed qualitatively and quantitatively in our contribution. In addition, we present the current setup of the MArS system, including a new flexible multi-light source.