* Departamento de Óptica

Phase detection is an important issue when dealing with optical metrology techniques for which the magnitude to be measured is encoded through the phase of a given fringe pattern. Asynchronous phase detection techniques are employed when the rate of phase change (frequency) it is not known. These techniques always present a variable frequency response, in other words, their ability to recover properly the phase depends strongly on the local frequency. In many experiments, it is possible to have a rough knowledge about the range of frequencies involved. Therefore, it constitutes a great advantage to have a procedure to design an asynchronous demodulation method which is suited to a particular frequency response for a given experiment. In this way, we get a better behaviour against noise which leads to more accurate and reliable phase extraction. In this work we present a technique to design asynchronous demodulation algorithms with a desired frequency response using a Fourier-based technique. The method allows the design of algorithms with a limited algebraic error in the recovered phase which have better properties than standard asynchronous phase detection techniques as it is shown in numeric and real experiments