|
Digital In-line Holographic Microscopy (DIHM) is a two-steps microscopy technique that allows for accessing to
complex wave information of the optical field scattered by a sample. Initially, the sample is illuminated by a spherical
wavefront such that the amplitude superposition of the portions of the spherical wavefront scattered and not by sample,
is recorded on a digital camera; the recorded intensity is often referred as in-line hologram. On the second step, a
numerical diffraction scheme is used to emulate the diffraction of a spherical wavefront by the in-line hologram
therefore producing a reconstruction in amplitude and phase of the original object. Due to its evident experimental
simplicity, DIHM is a widely used technique for in-situ applications and more recently on real time measurements. This
widespread employment of the technique introduces the necessity of establishing the practical limits achievable with this
imaging technique. Particularly, for the practical study of mono-disperse colloids, the critical concentration is a relevant
factor to identify, in order to establish the optimal conditions up to which DIHM can successfully work. The
reconstruction step produces a set of intensity images, at different axial distances, containing the information of all the
recorded particles; in large study volumes and high concentrations the number of particles overcome the easiness of
manual processing and therefore evidences the need of implementing more automatic tracking algorithms. In this way
the limits of applicability of DIHM rely on both the experimental configuration and the digital processing. With the use
of a modeling tool for DIHM and a semi-automatic tracking algorithm, a numerical estimation of the concentration limit
for which DIHM can work is proposed, following the analysis for its dependence with the experimental configuration of
the recording process.
|
