Quantitative phase microscopy of biological samples using a portable interferometer.

Area of Science:

• Biophysics
• Optical Microscopy
• Biomedical Engineering

Background:

• Interferometric microscopy typically requires highly stable environments and coherent light sources.
• Existing setups are often complex, expensive, and difficult to operate with biological samples.
• There is a need for accessible and robust interferometric techniques for micro-scale biological imaging.

Purpose of the Study:

• To introduce the τ interferometer, a portable and cost-effective device for spatial interferometry of microscopic biological samples.
• To demonstrate its operation with low-coherence illumination and conventional microscopy.
• To enable quantitative measurement of sample optical properties.

Main Methods:

• The τ interferometer utilizes off-the-shelf optical elements and integrates with a standard inverted microscope.
• It operates with low-coherence illumination, reducing stringent stability requirements.
• Interferograms are processed to yield quantitative amplitude and phase profiles, from which optical-path-delay is derived.

Main Results:

• The τ interferometer achieves high temporal (0.18 nm) and spatial (0.42 nm) stability in optical-path-delay measurements.
• It successfully obtains spatial interferograms of microscopic biological samples.
• Quantitative thickness profiles of live red blood cells were imaged.

Conclusions:

• The τ interferometer offers a practical and affordable solution for advanced interferometric microscopy of biological samples.
• Its ability to work with low-coherence light and standard microscopes broadens accessibility.
• This technique facilitates quantitative analysis of micro-scale biological structures, such as cell thickness.