Lens-in-lens common-path interferometer for quantitative phase imaging

We introduce a common-path interferometer (CPI) based on a two-component confocal scheme where the first component consists of two decentered lenses (lens-in-lens). Compactness, high stability and easy alignment of the proposed scheme allow building precise and robust tools for the analysis of the wave front reflected from the object or transmitted through it. We demonstrate its effectiveness for quantitative phase imaging of microscopic objects. The proposed CPI may be implemented as an attachable module to conventional light microscope to enable digital holographic imaging mode.