Quantitative phase imaging by wide-field interferometry with variable shearing distance uncoupled from the off-axis...

Area of Science:

• Optics and Photonics
• Biomedical Imaging
• Microscopy

Background:

• Traditional shearing interferometers couple off-axis angle and shearing distance, limiting imaging flexibility.
• Overlapping wavefronts in the spatial frequency domain can lead to loss of spatial frequency content.
• Quantitative phase imaging (QPI) is crucial for label-free biological sample analysis.

Purpose of the Study:

• To introduce a new shearing interferometry module for digital holographic microscopy.
• To decouple the off-axis angle from the shearing distance for enhanced imaging control.
• To enable flexible quantitative phase imaging of diverse biological samples.

Main Methods:

• Development of a module using a 4f imaging unit and a diffraction grating.
• Generation of holograms from two mutually coherent, partially overlapping sample beams.
• Integration of the module as an add-on to an inverted microscope for QPI.

Main Results:

• Achieved independent control of shearing distance and off-axis angle.
• Demonstrated high temporal (2.5 nm) and spatial (3.4 nm) stability without vibration isolation.
• Successfully performed QPI experiments on silica beads, red blood cells, and cancer cells.

Conclusions:

• The new module offers simple alignment, common-path geometry, and versatility for QPI.
• Decoupling shearing distance and off-axis angle overcomes limitations of conventional shearing interferometers.
• The system is suitable for various imaging scenarios, including dynamic biological processes.