Single-shot phase-shifting digital holography (PSDH) implementations are attractive for quantitative phase imaging of dynamic objects, such as living cells; however, they require precise alignment of the optical elements. This study presents a novel single-shot PSDH configuration where the diffraction grating is placed on the focal plane of the object light path. The grating has a checkerboard pattern that provides spatially periodic phase shifts of 0 and π. The object light is diffracted by the grating such that the ±1st order diffractions form four wavefront copies. Since the spatial positions of these copies are determined using only the grating period, it is not necessary to precisely align the grating with the image sensor. The conventional PSDH involves phase shifts of the reference beam, whereas the proposed method allows advance phase shifts to occur between the object light copies. Therefore, phase-shifting interferograms can be obtained simultaneously by irradiating all copies with a uniform reference light. Since the phase-shift amounts between the copies depend on the lateral positions of the grating, it is necessary to estimate the degree of displacement of the grating to calculate the quantitative phase values. We therefore present a solution that adds two markers to the object light and estimates the grating displacements from the interference intensities between the markers and reference light. We also conducted numerical simulations to confirm that the proposed method obtains quantitative phase values from a single image.
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