  Structured illumination microscopy (SIM) is a very important super-resolution
microscopy technique, which provides high speed super-resolution with about
two-fold spatial resolution enhancement. Several attempts aimed at improving
the performance of SIM reconstruction algorithm have been reported. However,
most of these highlight only one specific aspect of the SIM reconstruction --
such as the determination of the illumination pattern phase shift accurately --
whereas other key elements -- such as determination of modulation factor,
estimation of object power spectrum, Wiener filtering frequency components with
inclusion of object power spectrum information, translocating and the merging
of the overlapping frequency components -- are usually glossed over
superficially. In addition, most of the work reported lie scattered throughout
the literature and a comprehensive review of the theoretical background is
found lacking. The purpose of the present work is two-fold: 1) to collect the
essential theoretical details of SIM algorithm at one place, thereby making
them readily accessible to readers for the first time; and 2) to provide an
open source SIM reconstruction code (named OpenSIM), which enables users to
interactively vary the code parameters and study it's effect on reconstructed
SIM image.
