In this paper we are going to review two interferometric techniques to demodulate a single fringe pattern containing closed fringes. It is well known that analyzing a single interferogram with spatial carrier is relatively easy . That is, whenever the modulating phase of the interferogram contains a linear component large enough to guarantee that the total modulating phase would remain an increasing function in a given direction of the two dimensional space. Why it is interesting to demodulate a single or a series of interferograms in which there is no spatial or temporal carrier ?, knowing that this is a substantially more difficult task ?. The answer is that although one always tries to obtain a single or a series of interferograms with spatial and/or temporal carrier , sometimes the very nature of the experimental set-up do not permit to obtain them. One reason could be that one is studying fast transient phenomena where there is no time to introduce a carrier. In these cases one still wants to demodulate the interferograms to evaluate quantitatively the physical variable under study.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.