Superresolution microscopy using common-path phase-shifting interferometry

In this contribution, we present a new approach aimed to achieve superresolution in digital holographic microscopy that overcomes the limitations imposed by the Abbe's diffraction limit. Based on time multiplexing and off-axis illumination, a common-path interferometric architecture allows the synthesis of an enlarged aperture that expands the cutoff frequency of the conventional imaging system. Complex object amplitude distribution is recovered using an extremely simple phase-shifting configuration instead of image plane off-axis holographic recording. As a consequence, the setup becomes easy-to-configure (less requirements and lower number of optical elements) and it is useful for practical implementation in microscopes while only simple modifications are required (no higher magnifications are needed to resolve the interference pattern at the CCD plane). Experimental results validating the capabilities of the presented approach when a low numerical aperture commercial microscope objective is used as imaging lens are included using both a synthetic object (high resolution USAF test target) and a biosample (red blood cells) as objects under test.