title: Harmonics rejection in pixelated interferograms using spatio-temporal demodulation.
abstract: Pixelated phase-mask interferograms have become an industry standard in spatial phase-shifting interferometry. These pixelated interferograms allow full wavefront encoding using a single interferogram. This allows the study of fast dynamic events in hostile mechanical environments. Recently an error-free demodulation method for ideal pixelated interferograms was proposed. However, non-ideal conditions in interferometry may arise due to non-linear response of the CCD camera, multiple light paths in the interferometer, etc. These conditions generate non-sinusoidal fringes containing harmonics which degrade the phase estimation. Here we show that two-dimensional Fourier demodulation of pixelated interferograms rejects most harmonics except the complex ones at {-3(rd), +5(th), -7(th), +9(th), -11(th),…}. We propose temporal phase-shifting to remove these remaining harmonics. In particular, a 2-step phase-shifting algorithm is used to eliminate the -3(rd) and +5(th) complex harmonics, while a 3-step one is used to remove the -3(rd), +5<(th), -7(th) and +9(th) complex harmonics.
authors: Centro de Investigaciones en Óptica A. C. Loma del Bosque 115, Lomas del Campestre C.P.37150. León, Guanajuato, México.
authors: J M
authors: JM
authors: Padilla
authors: M
authors: M
authors: Servin
authors: J C
authors: JC
authors: Estrada
mesh_terms: D000465:Algorithms; D007368:Interferometry / Q000379:methods*; D008027:Light; D008962:Models, Theoretical; D055096:Optical Devices; D012031:Refractometry / Q000379:methods*; D015203:Reproducibility of Results