The paper focuses on illumination angle self-calibration for Fourier ptychographic microscopy (FPM). However, there appears to be errors in FPM due to shifts or rotations of the LED array, source instabilities, nonplanar illuminator arrangements, or sample-induced aberrations. The paper proposes a two-pronged-angle self-calibration method that uses both preprocessing (brightfield calibration) and iterative joint estimation (spectral correlation calibration) that is quicker and more robust to system changes than state- of-the-art calibration methods.
For the Brightfield calibration, the following algorithm is used to perform the task.
For Spectral Correlation Calibration, we can see from the figure below that cost function is lower when both BC and SC are implemented.
The paper have presented a novel two-part calibration method for recovering the illumination angles of a computational illumi- nation system for Fourier ptychography. We have demon- strated how this self-calibrating method makes Fourier ptychographic microscopes more robust to system changes and sample-induced aberrations. The method also makes it possible to use high-angle illuminators, such as the quasi-dome, and nonrigid illuminators, such as laser-based systems, to their full potential.
References:
R. Eckert, Z.F. Phillips,L.Waller.”Efficient illumination angle self-calibration in Fourier ptychography”, 2018 Optical Society of America