Evaluation of spherical particle sizes with an asymmetric illumination microscope

Jessica C. Ramella-Roman, Paulo R. Bargo, Scott A. Prahl, Steven L. Jacques

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


A polarized microscope system is used to perform goniometric measurements of light scattered by small particles. The light incident angle on a sample of monodispersed latex microspheres is increased sequentially and a microscope objective lens collects scattered light from the samples. Light is only collected at angles greater than the objective lens numerical aperture (NA) so that only light scattered by the spheres is collected. The experimental results were modeled with a Mie theory-based algorithm. Experiments conducted with microspheres of diameter 1.03, 2.03, and 6.4 μm show that, by decreasing the objective lens NA from NA = 0.55 to NA = 0.0548, a more distinguishable scattering pattern is detectable. From these highly shaped curves, we found that the size of a sphere of nominal diameter 2.03 μm was 2.11 ±0.06 μm and a 6.4 μm sphere was 6.34 ±0.07 μm.

Original languageEnglish (US)
Pages (from-to)301-306
Number of pages6
JournalIEEE Journal on Selected Topics in Quantum Electronics
Issue number2
StatePublished - Mar 2003


  • Asymmetric illumination
  • Goniometry
  • Mie theory
  • Oblique microscopy
  • Polarized light microscopy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


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