Development of confocal optical holographic microscopy
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Date
2006-09-06T22:37:44Z
Authors
McLeod, Robert A.
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Abstract
Optical Confocal Holography is a combination of two well known concepts: confocal
microscopy and optical (laser) holography. Confocal microscopy places an aperture at a
conjugate focus to the specimen focus. This filters any rays that are not on the focus
plane, allowing a 3-dimensional image of the specimen to be built up over a set of planes.
Holography is the measurement of both the amplitude and phase characteristics of light.
Typically most methods only measure the amplitude of the image. The phenomenon of
interference allows the determination of the phase shift for a coherent source as well. The
phase information is directly related to the index of refraction of a material, which in turn
is a function of the temperature and composition. As a technique, confocal holography
holds promise to better characterize many physical processes in materials science, such as
combustion and convection. It also may contribute to the biological sciences by imaging
low-contrast, weak-phase objects. Thanks to the ongoing, continued improvement in
computer processing speed, it has recently become practical to interpret data from
confocal holography microscopy with a computer. The objective of the microscope is to
non-invasively measure the three-dimensional, internal temperatures and compositions
(e.g. solute/solvent gradient) of a specimen.
My contributions over the course of two years to the project were: generation and
optimization of an optical design with a software package known as Zemax; sourcing and
purchasing all components; formation of a CAD model of the microscope; experiments to
characterize building vibrations and air currents; and the development of software in
Visual Basic to simulate holograms and execute reconstruction algorithms for the specific
application of confocal holography.
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Keywords
phase imaging, convergent beam holography, digital fourier reconstruction, holographic interferometry, three-dimensional imaging, confocal microscopy, holography