Common-path phase-shifting digital holographic microscopy: A way to quantitative phase imaging and superresolution

We present an experimental setup useful for complex amplitude evaluation and phase image quantification of three-dimensional (3-D) samples in digital holographic microscopy (DHM). It is based on a common-path interferometric configuration performed by dividing the input plane in two contiguous regions and by placing a translation grating near to the Fourier plane. Then, complex amplitude distribution of the sample under test is recovered with phase-shifting standard method obtained by moving the grating using a linear motion stage. Some experimental results of an USAF resolution test are presented for different numerical aperture (NA) microscope lenses. In a second part, the proposed setup is tested under superresolution purposes. Based on the object's spectrum shift produced by off-axis illumination, we use time multiplexing to generate a synthetic aperture enlargement that improves the final image resolution. Experimental results for the case of a biosample (human red blood cells) and a commercial low NA microscope lens validates the suggested superresolution approach.