Digital visibility measurements by fourier analysis

A phase-measuring Fizeau interference microscopy with a visible laser-diode (LD) source has been studied that is based on a phase-shifting method using the wavelengths varied stepwise by changing the current in LD. The influence of Fizeau fringes with multiple-beam interference on phase-extraction algorithms has been theoretically and numerically investigated. The phase error can be minimized, when two sets of measurements corresponding to initial phase difference of n/4 are averaged. Experimental results are presented.