Quantitative Phase Imaging of Live Roots by Gradient Retardance Optical Microscopy
Authors:
Jinming Zhang1* ([email protected]), Maria J. Harrison2, Andreas E. Vasdekis1 (PI)
Institutions:
1University of Idaho; 2Boyce Thompson Institute
Abstract
Quantitative phase imaging (QPI) has recently emerged as a widespread optical imaging method for measuring the dry mass and density of individual cells, two key metabolic parameters in biological systems. Despite its potential, applying QPI techniques to specimens that are thicker than 500 wavelengths faces significant challenges. In such cases, optical scattering from thick specimens compromises image quality by increasing background noise and reducing contrast. To overcome these challenges, various strategies have been explored, including laser-based tomographic methods and asymmetric illumination/detection interferometry that uses incoherent light to avoid speckle-driven image degradation. However, these methods require expensive optical elements, such as spatial light modulators or polarization-sensitive cameras, that additionally are known to reduce imaging efficiency due to energy losses.
To address these shortcomings, this research team developed Gradient Retardance Optical Microscopy (GROM), a QPI technique that is compatible with 3D imaging and requires no computational image reconstruction. GROM operates by transforming asymmetrically illuminated intensity images into phase gradient images and enables fully automated 3D acquisition of interferometric images using custom-made routines in open access platforms. Further, GROM can transform any standard microscope into a QPI platform by placing only a liquid crystal retarder between the illumination condenser and the sample. Through this method, the group has successfully reconstructed a variety of imaging targets, including conducting 3D volume viewing of individual bacteria and fungi, as well as a 500 micrometer–diameter plant roots tissue of the model system Medicago truncatula, showcasing the depth and versatility of GROM’s capabilities.
References
Zhang, J., et al. In review. “Quantitative Phase Imaging by Gradient Retardance Optical Microscopy (GROM).”
Funding Information
The research team gratefully acknowledges funding from the U.S. DOE, project number DE-SC0022282.