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Abstract
Microscopy is of high interest for biology since it allows imaging features that are too small to
be seen with naked eyes. However, cells are mostly transparent to visible and infrared light
which makes it difficult to see with a traditional microscope. To do so, phase imaging was
invented by F. Zernike, who received the Nobel prize in 1953 for this invention. It provides
intensity contrast to visualize transparent samples such as those found in biology without
any staining. Among the different implementations of phase imaging, digital holographic
microscopy (DHM) is a well-known phase method which provides a quantitative value of the
phase generated by the sample under test.
Implementations of DHMs without the help of any lens element (so called lensless) offer the
added advantage to provide large field of views (severalmm2 compared to several hundred
¹m2) and more compact setups than traditional DHMs which have high quality microscope
objectives. The lateral resolution is limited by the pixel size of the camera. However, several
techniques have been developed to obtain subpixel resolution with lensless setups, hence
giving a resolution smaller than the pixel size.
In this thesis, two lensless transmission DHMs are presented using a side illumination technique
in order to further reduce the device size and keep a visual access to the sample. The
first one operates in an in-line configuration: the most compact but using time-consuming
image post-processing. The second one is also lensless and uses an off-axis configuration
allowing quasi-real time imaging but less compact. Their practical use is described and images
of transparent (phase only) samples are shown. Super-resolution (subpixel) using several subpixel
shifted holograms was then investigated for the in-line configuration and demonstrated
on absorptive samples.
Since those microscopes are compact and made out of off-the-shelf low priced elements, they
could be broadly spread in schools for educational purposes. They could also be implemented
in cells incubators, allowing visualization inside processes at low cost and multiplication of
the number of measurements made at the same time.