A digital holographic technique is implemented in a microscope for
three-dimensional imaging reconstruction. The setup is a
Mach–Zehnder interferometer that uses an incoherent light source to
remove the coherent noise that is inherent in the laser sources. A
phase-stepping technique determines the optical phase in the image
plane of the microscope. Out-of-focus planes are refocused by
digital holographic computations, thus considerably enlarging the depth
of investigation without the need to change the optical focus
mechanically. The technique can be implemented in transmission for
various magnification ratios and can cover a wide range of
applications. Performances and limitations of the microscope are
theoretically evaluated. Experimental results for a test target are
given, and examples of two applications in particle localization and
investigation of biological sample are provided.
© 1999 Optical Society of America
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