  X-ray Talbot-Lau interferometer has been used widely to conduct phase
contrast imaging with a conventional low-brilliance x-ray source. Typically, in
this technique, background correction has to be performed in order to obtain
the pure signal of the sample under inspection. In this study, we reported on a
research on the background correction strategies within this technique,
especially we introduced a new phase unwrapping solution for one conventional
background correction method, the key point of this new solution is changing
the initial phase of each pixel by a cyclic shift operation on the raw images
collected in phase stepping scan. Experimental result and numerical analysis
showed that the new phase unwrapping algorithm could successfully subtract
contribution of the system's background without error. Moreover, a potential
advantage of this phase unwrapping strategy is that its effective phase
measuring range could be tuned flexibly in some degree for example to be
(-pi+3, pi+3], thus it would find usage in certain case because measuring range
of the currently widely used background correction method is fixed to be (-pi,
pi].
