Imaging of small particles using wide field confocal microscopy

Stephen P. Morgan, N. B E Sawyer, Michael Geoffrey Somekh, C. W. See, B. Y. Shekunov, E. Astrakharchik

Research output: Journal article publicationConference articleAcademic researchpeer-review


Particle measurement is important in many applications such as the manufacture of drugs and paints, and aerosols. In bioimaging there is interest understanding the imaging of nanoparticles and subcellular scatterers. We present in this paper a wide field, phase measuring confocal microscope that can be used for such measurements. The wide field confocal response is obtained by illuminating both sample and reference arms of an interferometric microscope with nominally identical speckle patterns. When the speckle patterns are highly correlated the interference is significant. Contributions from out of focus planes result in uncorrelated speckle patterns and no interference. This provides a wide field confocal response. High speed measurements are enabled by parallel phase stepping using polarisation optics. We have also developed a vector diffraction microscope model, using Mie theory as a scattering function, to validate the images of small particles. Correctly scaling the amplitudes of the unscattered and scattered electric fields enables co-polar transmission imaging to be modelled. Finally it is demonstrated that the phase is a more sensitive measurement of particle size than the amplitude.
Original languageEnglish
Pages (from-to)234-241
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 1 Dec 2002
Externally publishedYes
EventSaratov Fall Meeting 2002 Optical Technologies in Biophysics and Medicine IV - Saratov, Russian Federation
Duration: 1 Oct 20024 Oct 2002


  • Confocal
  • Microscopy
  • Particle sizing
  • Speckle
  • Wide field

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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