In this paper we consider risk sensitive filtering for Poisson process obse
rvations. Risk sensitive filtering is a type of robust filtering which offe
rs performance benefits in the presence of uncertainties. We derive a risk
sensitive filter for a stochastic system where the signal variable has dyna
mics described by a diffusion equation and determines the rate function for
an observation process. The filtering equations are stochastic integral eq
uations. Computer simulations are presented to demonstrate the performance
gain for the risk sensitive filter compared with the risk neutral filter.