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Publications [#280508] of David J. Brady

Papers Published

  1. Balberg, M; Barbastathis, G; Brady, DJ, Imaging through turbulence with the volume-holographic confocal microscope, Smart Structures and Materials 2005: Active Materials: Behavior and Mechanics, vol. 4087 (December, 2004), pp. 1089-1090, SPIE, Quebec City, Que., Canada [doi]
    (last updated on 2019/11/21)

    Abstract:
    The confocal microscope with volume-holographic collector utilizes Bragg selectivity in order to achieve depth sectioning. The volume hologram is recorded by the interference of two beams, one of which originates as a point source at a reference depth. When a reconstructing (probe) source is at the reference depth, it is Bragg-matched and causes a strong diffracted signal; sources at different depths are rejected because of Bragg mismatch. Therefore, the use of a pinhole in front of the detector (as in traditional confocal microscopes) is not required. The arguments for use of a volume hologram instead of a pinhole to achieve depth sectioning are: (1) the depth resolution of the microscope is independent of its photon-collection performance; (2) the hologram phase conjugates aberrations and other systematic phase distortions, and hence acts as an ideal matched filter to the reference source (unlike the ad hoc filtering function performed by the pinhole). We focus on the depth-resolving properties of volume diffraction when a turbulent (scattering) medium, emulating a biological tissue, is present in the path of the light entering the microscope. In particular, we compare the depth resolution of a microscope recorded with and without precompensation for the presence of the scatterer. Precompensation extends the matched filtering principle by use of a priori information (the thickness of the turbulent medium) during the recording phase of the hologram. Our experimental results demonstrate that precompensation increases the scatterer thickness over which confocal imaging is possible

    Keywords:
    holography;light diffraction;optical microscopy;turbulence;