Optical methods in experimental mechanics: Part 49: Measuring phase difference - Part V: Phase calculations

摘要

The method of using the signs that appear in the phase-stepping computation to establish the correct value of the phase angle to modulo 2π and an alternative approach using the atan2 function, was examined. The procedure directly yields a wrapped phase difference map. There are various ways to attend to the modulo π problem, with the choice depending on preference, programming skill, and software available. A direct path to determination of the phase difference to modulo 2π for each set of detector readings involves calculating the phase difference to modulo π/2 by using only the absolute values of the differences in the numerator and denominator of that equation. The result will be an angle between 0 and π/2. An approach for clearing the modulo π ambiguity is to utilize the 'atan2(y,x)' function that is available in commercially available software such as MATLAB?, FORTRAN? and C?.