The project aim is to develop a new lateral shearing achromatic interferometry method utilizing the Fresnel diffraction field properties of diffraction gratings. These elements used as beam splitters/recombiners enable operation in a wide spectral range. Main project goals are as follows:
- Development of theoretical background and experimental verification of achromatic grating interferometry free of contrast modulations introduced by the self-imaging phenomenon;
- Development of the moirégram imaging model for Fresnel double-diffraction systems;
- Development of the automatic fringe pattern analysis algorithms.
Quantitative phase imaging (QPI) plays an important role in life sciences and micro technology. In general, the most suited techniques for quantitative and accurate phase distribution determination are based on interferometry, and especially on digital holographic microscopy (DHM). The main objective of the project is to introduce new, fast measurement techniques for DHM and digital holographic tomographic microscopy (DHTM) utilizing dynamic modulation of illumination wavefront, which are capable of imaging with extended depth of focus and measurement of 3D/4D topography, objects thickness and 4D (3D + time) refractive index distribution with improved accuracy, resolution and enlarged unambiguous measurement range. The theoretical ground of MO will be based on new theoretical developments: 1) construction of an artificial partially spatially coherent hologram based on coherent mode decomposition for its propagation, 2) new methods of 3D/4D objects information recovery, which are coded in sets of holograms with different modulation of an illuminating wavefront, 3) new optical tomographic solutions allowing for dynamic 3D refractive index distribution reconstruction with sparse 3D frequency spectrum coverage. The first two approaches are related to QPI while 3) to quantitative 3D imaging. We would like to stress that the approaches 1) and 2) are completely different, in 1) the information about the object is recovered from an artificially created partially coherent 3D object wavefront, while in 2) from the interdependence between series of 3D complex object wavefronts. The theoretical grounds of MO will allow overcoming several severe limitations of DHM and tomographic microscopy by introducing:
- new methods for measurement of topographies with large steps of height;
- new methods for construction, numerical propagation, reconstruction and objects information recovery from an artificial partially coherent hologram;
- new automatic focusing methods with improved accuracy and extended focusing range basing on three different principles incl.: frequency support extension, phase interdependence, artificial partially coherent hologram construction;
- new non-paraxial shape and thickness measurement methods without the need for a reference measurement plane;
- new methods for simulating 3D scattering in the micro-optics domain;
- novel tomographic solutions (tomographic algorithms, systems) using dynamic modulation of illumination for static and dynamic 3D reconstruction of refractive index distribution, incl.: various schemes of illumination modulation: spherical illumination, set of illuminating plane waves,
- new non-iterative and iterative tomographic reconstruction algorithms tackling two major challenging aspects of 1) minimization of number captured holograms and 2) experimental system simplification.