Single-shot two-channel Fresnel bimirror interferometric microscopy for quantitative phase imaging of biological cell

A simple slight-off-axis, single-shot, and two-channel interferometric microscopy is demonstrated for the quantitative phase imaging of a biological sample, only using a cube beamsplitter and a Fresnel bimirror interferometer. The incident beam is replicated into two parallel beams using a tilted cube beamsplitter, while the transmission beam is the replica and the reflection beam is the mirror-reverted replica. The two replicas encounter different mirrors of the Fresnel bimirror interferometer, and are reflected and brought to interfere with each other at the image plane of a digital camera. Subsequently, two interference channels with a relative π (rad) phase shift in one interferogram are acquired simultaneously using only one digital camera. The proposed method is capable of obtaining two-channel, slight-off-axis interference in a single shot. The use of small amount of ready-made and low-cost optical components renders the system compact, stable, and easy to implement. In addition, two identical mirrors of the Fresnel bimirror interferometer are symmetrically arranged with a very small angle. Their reflected beams vary in direction over a wide space range with the rotation of the Fresnel bimirror interferometer and the interference always occurs. Based on this characteristic, we are able to capture the interferograms over a large space range and obtain the quantitative phase information. This is a suitable method for the quantitative phase imaging of biological samples.