Phase-edge imaging using q-plate shifts for faster and simpler microscopy.

Abstract

We present a simplified method for isolating the edges of a phase object from the edges of an amplitude object using a 4f system with an off-axis q-plate. Instead of the four off-axis shifts of the q-plate required in previous work, we need only two shifts (along ±x) combined with linear polarizers at 45° and 135°. The number of required mechanical q-plate displacement directions is reduced from four to two. We derive the theoretical basis, showing that the resulting intensity corresponds to the phase gradient squared, with amplitude-object contributions eliminated. Experiments on two phase-amplitude object samples demonstrate amplitude-edge reduction of up to 97.6% and correlation coefficients of up to 0.80 (sample 1) and 0.75 (sample 2). In overlapping regions, the phase edge is partially recovered; full recovery would require additional processing such as inverse filtering. This research is useful for biological imaging applications where fast and simple phase-edge isolation is desired.