Low-Coherence Shearing Interferometry With Constant Off-Axis Angle

We present a wide-field interferometric imaging module for biomedical and metrological measurements, employing shearing interferometry with constant off-axis angle (SICA) that can work, for the first time, with a low-coherence light source. In the SICA module, the shearing distance between the interfering beams can be fully controlled without a direct relation with the off-axis angle. In contrast to our previous SICA module, here we use a low-coherence illumination source, providing quantitative phase profiles with significantly lower spatial coherent noise. Although a low-coherence source is used, we obtain off-axis interference on the entire camera sensor, where the optical path difference between the two beams is compensated by using a glass window positioned in the confocal plane. This highly stable, common-path, low-coherence, single-shot interferometric module can be used as an add-on unit to a conventional bright-field microscope illuminated by a low-coherence source. We demonstrate the advantages of using the module by quantitative phase imaging of a polymer bead, fluctuations in a human white blood cell, and dynamics of human sperm cells.

Automated summary

This paper introduces a wide-field interferometric imaging module that utilizes shearing interferometry with constant off-axis angle and a low-coherence light source to provide quantitative phase profiles with lower spatial coherent noise. The module allows full control of the shearing distance between interfering beams and can be used as an add-on unit to a conventional bright-field microscope for biomedical and metrological measurements.