The capability of monitoring the entire cross section of a tokamak vacuum chamber with an infrared camera can allow both the fulfilling of discharge energy balance to be attained and the existence of impurity generating hot spots to be discovered. In this work an endoscope based on refractive optics has been designed for the wide-angle thermography to be installed on JET. The optical code CODE V was used. Even if reflective optics is presently preferred for ITER relevant diagnostics, nevertheless the present design can be considered a valid back-up solution.