  The Collins function belongs to the class of the so-called time-reversal odd
fragmentation functions. Being chiral-odd as well, it can serve as an important
tool to observe the nucleon's transversity distribution in semi-inclusive DIS.
Due to the possible presence of final state interactions, this function can be
non-zero, though this has never been demonstrated in an explicit model
calculation. We use a simple pseudoscalar coupling between pions and quarks to
model the fragmentation process and we show that the inclusion of one-loop
corrections generates a non-vanishing Collins function, therefore giving
support to its existence from the theoretical point of view.
