Computational refocusing in phase-resolved confocal microscopy

We demonstrate numerical refocusing in monochromatic, phase-resolved confocal microscopy. The refocusing method is based on the pseudoinverse of the forward operator of the confocal imaging system and a subsequent re-imaging of the object to a new focal plane. The application of the model requires the acquisition of amplitude- and phase-resolved confocal data. To this end, we implement synthetic optical holography, a recently introduced holographic modality for quantitative phase imaging in scanning optical microscopy, in a homebuilt confocal setup. Using a resolution test target, we demonstrate that numerical refocusing restores a spatial resolution near the theoretical diffraction limit for situations where the object is located up to 60 microns away from the system's focal plane. Our method brings numerical refocusing to monochromatic confocal microscopy, allowing for refocusing out-of-focus images after image acquisition.