Phase shifting and phase retrieval with a fully automated laser diode system

A low-cost and fully automated process for phase-shifting interferometry (PSI) by continuously changing the input voltage of a laser diode (LD) under the scheme of an unbalanced Twyman-Green interferometer (TGI) setup is presented. The input signal of a LD is controlled by a data acquisition (NI-DAQ) device that allows it to change its wavelength according to its tunability features. The automation and data analysis will be done using LabVIEW in combination with MATLAB. The phase map is obtained using the Carré algorithm. Measurements of visibility and phase shift to verify the PSI requirements are shown. It is demonstrated with experimental results and statistical analysis that the phase retrieval can be successfully achieved without calibration and using minimal optical devices.