  Fourier ptychographic microscopy (FPM) can achieve quantitative phase imaging
with a large space-bandwidth product by synthesizing a set of low-resolution
intensity images captured under angularly varying illuminations. Determining
accurate illumination angles is critical because the consistency between actual
systematic parameters and those used in the recovery algorithm is essential for
high-quality imaging. This paper presents a full-pose-parameter and
physics-based method for calibrating illumination angles. Using a physics-based
model constructed with general knowledge of the employed microscope and the
brightfield-to-darkfield boundaries inside captured images, we can solve for
the full-pose parameters of misplaced LED array, which consist of the distance
between the sample and the LED array, two orthogonal lateral shifts, one
in-plane rotation angle, and two tilt angles, to correct illumination angles
precisely. The feasibility and effectiveness of the proposed method for
recovering random or remarkable pose parameters have been demonstrated by both
qualitative and quantitative experiments. Due to the completeness of the pose
parameters, the clarity of the physical model, and the high robustness for
arbitrary misalignments, our method can significantly facilitate the design,
implementation, and application of concise and robust FPM platforms.
