Our team was published in SPIE and that can be found here.
We describe a technique for measuring the instrument transfer function (ITF) of an interferometric microscope, allowing both characterization and data processing to increase the fidelity and effective resolution of the tool. The technique, based on test samples structured as two-dimensional (2D) binary pseudo-random arrays
(BPRAs), employs the unique properties of the BPRA patterns in the spatial frequency domain. The inherent 2D power spectral density of the pattern has a deterministic white-noise-like character that allows direct determination of the ITF with uniform sensitivity over the entire spatial frequency range and field-of-view of an instrument. As such, the BPRA samples satisfy the characteristics of a test standard: functionality, ease of specification and fabrication, reproducibility, and low sensitivity to manufacturing error. We discuss the results of the development and application of highly randomized (HR) BPRA test samples with elementary feature sizes in the range from 80 nm and up to 2.5 μm, optimized for the ITF characterization of interferometric microscopes broadly used for 2D optical surface profiling. The data acquisition and analysis procedures for different applications of the ITF calibration technique developed are also discussed.