Demonstration of enhanced lateral resolution in Fizeau interferometry using a tilted binary pseudo-random array test sample

The instrument transfer function (ITF) quantifies the lateral spatial resolution of Fizeau interferometers, interferometric microscopes, and other optical and non-optical surface and wavefront metrology instruments. The inherently uniform spatial frequency content of binary pseudo-random array (BPRA) surface structures makes them especially useful for calibrating the ITF. Recently, we used BPRA artifacts to experimentally demonstrate that the ITF calibration of Fizeau interferometers is strongly affected by the instrument data acquisition and processing procedures, as well as by the shape of the optic under test and its alignment (tip and tilt) with respect to the interferometer. This paper presents the results of preliminary theoretical modeling of the effect and compares them with the previously observed dependence of ITF on sample tilt. Our results include an analysis of potential error sources and demonstrate an increase of the spatial resolution with object tilt attributable to capturing of higher diffraction orders scattered by the object.