Low-cost, open-access quantitative phase imaging of algal cells using the transport of intensity equation

Stephen D. Grant, Kyle Richford, Heidi L. Burdett, David McKee, Brian R. Patton

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Phase microscopy allows stain-free imaging of transparent biological samples. One technique, using the transport of intensity equation (TIE), can be performed without dedicated hardware by simply processing pairs of images taken at known spacings within the sample. The resulting TIE images are quantitative phase maps of unstained biological samples. Therefore, spatially resolved optical path length (OPL) information can also be determined. Using low-cost, opensource hardware, we applied the TIE to living algal cells to measure their effect on OPL. We obtained OPL values that were repeatable within species and differed by distinct amounts depending on the species being measured. We suggest TIE imaging as a method of discrimination between different algal species and, potentially, non-biological materials, based on refractive index/OPL. Potential applications in biogeochemical modelling and climate sciences are suggested.
Original languageEnglish
Article number191921
Number of pages12
JournalRoyal Society Open Science
Issue number1
Publication statusPublished - 29 Jan 2020



  • algeu
  • phase-microscopy
  • three-dimensional printing
  • 3D printing
  • open access
  • ecosystems

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