  Quantitative phase microscopy (QPM) has found significant applications in the
field of biomedical imaging which works on the principle of interferometry. The
theory behind achieving interference in QPM with conventional light sources
such as white light and lasers is very well developed. Recently, the use of
dynamic speckle illumination (DSI) in QPM has attracted attention due to its
advantages over conventional light sources such as high spatial phase
sensitivity, single shot, scalable field of view (FOV) and resolution. However,
the understanding behind obtaining interference fringes in QPM with DSI has not
been convincingly covered previously. This imposes a constraint on obtaining
interference fringes in QPM using DSI and limits its widespread penetration in
the field of biomedical imaging. The present article provides the basic
understanding of DSI through both simulation and experiments that is essential
to build interference optical microscopy systems such as QPM, digital
holographic microscopy and optical coherence tomography. Using the developed
theory of DSI we demonstrate its capabilities of using non-identical objective
lenses in both arms of the interference microscopy without degrading the
interference fringe contrast and providing the flexibility to use user-defined
microscope objective lens. It is also demonstrated that the interference
fringes are not washed out over a large range of optical path difference (OPD)
between the object and the reference arm providing competitive edge over low
temporal coherence light sources. The theory and explanation developed here
would enable wider penetration of DSI based QPM for applications in biology and
material sciences.
