Determination of the best phase step of the Carre algorithm in phase shifting interferometry

The Carre algorithm is a widely used phase shifting algorithm in optical in terferometry because its phase step is arbitrary. It is important to determ ine the best phase step in order to minimize the phase measurement errors. A detailed error analysis is carried out to reveal the relationships betwee n the phase measurement errors and the phase step, according to which a sui table phase step can be selected. A good and recommendable phase step is 11 0 degrees, but it is only valid for minimizing the influence of the random intensity noises. For a better choice the behavior of the experimental syst em should be considered.