Biomedical Engineering Reference
In-Depth Information
CHAPTER 9
Synthetic Aperture Lensless Digital
Holographic Microscopy (SALDHM)
for Superresolved Biological Imaging
Vicente Mic´
1
, Zeev Zalevsky
2
, Luis Granero
3
, Javier Garc´a
1
Departamento de
´
ptica, Universitat de Valencia, Burjassot, Spain
2
School of Engineering, Bar-Ilan
University, Ramat-Gan, Israel
3
AIDO: Instituto Tecnol´gico de
´
ptica, Color e Imagen,
Parc Tecnol`gic, Paterna, Spain
1
Editor: Natan T. Shaked
9.1 Introduction
Holography was invented by Dennis Gabor in 1948 when proposing a scheme to improve
image quality in electron microscopy by avoiding lenses in the experimental setup since, at
that time, resolution in electron microscopes were generally limited by spherical aberration
of magnetic electron lenses
[1
3]
. In a few words, Gabor's concept implies the addition, in
a given plane, of an imaging wave caused by diffraction at the sample plane and a reference
wave incoming from the nondiffracted light passing through the sample. The resulting light
distribution contains information about the interference of both waves and it is recorded on
a photographic film. The reconstruction is obtained by illuminating the film with a
reconstruction wave which is identical to the reference wave that was used in the recording
process. The diffracted electron field of the sample is reconstructed without spherical
aberrations by a suitable arrangement of lenses. This two-step holographic electron
microscopy method is unique but suffered from three major drawbacks: the
reconstructed image is affected by coherent noise, the twin image problem also affects the
final image quality, and a restricted sample range due to the weak diffraction assumption
(samples must be essentially transparent) is needed for preserving the holographic behavior
of the method (otherwise, the sample excessively blocks the reference beam and diffraction
rules the recording process, preventing the accurate recovery of the sample's complex wave
front).
Search WWH ::
Custom Search