Wide-field anti-aliased quantitative differential phase contrast microscopy

Area of Science:

• Optical Microscopy
• Phase Contrast Imaging
• Quantitative Phase Imaging

Background:

• Differential Phase Contrast (DPC) microscopy recovers quantitative phase information from transparent samples using multi-axis illumination.
• Conventional DPC requires small pixel-size sensors to avoid spatial aliasing and undersampling, limiting the field of view or necessitating magnification adapters.
• Large pixel sizes in standard microscope cameras prevent adequate sampling of optical intensity information.

Purpose of the Study:

• To introduce Anti-aliased DPC (AADPC), a novel quantitative DPC approach to overcome sensor undersampling limitations.
• To enable wide-field, aliasing-free phase imaging by utilizing multiple aliased intensity images.
• To improve phase transfer characteristics and imaging resolution beyond conventional DPC.

Main Methods:

• AADPC employs an iterative de-multiplexing algorithm to refine an initial phase estimate obtained from DPC-like deconvolution.
• It analyzes phase transfer functions under various illumination patterns to optimize illumination schemes.
• The method uses several aliased intensity images under asymmetric illumination to reconstruct wide-field, aliasing-free phase images.

Main Results:

• AADPC mitigates spatial undersampling using an iterative algorithm with only 4 images, achieving a nearly 4-fold increase in space-bandwidth product (SBP).
• Experimental verification demonstrated a half-pitch imaging resolution of 345 nm (1.88x the Nyquist-Shannon limit imposed by sensor pixel size).
• High-speed imaging of HeLa cells achieved a full-pitch lateral resolution of 665 nm across a 1.77 mm² field of view at 25 fps.

Conclusions:

• AADPC effectively overcomes the tradeoff between field of view and sampling resolution in quantitative phase imaging.
• The developed method provides high-speed, high-throughput quantitative phase imaging with enhanced resolution and wide field of view.
• AADPC represents a significant advancement for imaging delicate biological samples like live cells.