Surface profile measurement technique via common input/output polarizing interferometer

• Profilometry by common input/output polarizing interferometer with polarizing phase-shifter placed at the input. • The method avoids environmental vibration noise by not working on the OPD once the interferometer is aligned near the ZPD. • The design is more robust, using rotation increments of tens of degrees instead of translation displacements of nanometers. • The technique uses broadband illumination to avoid interferogram filtering and ensure low-cost availability. A profilometry approach using phase-shifting interferometry is proposed, in which phase steps are introduced through polarization control within a common input/output polarizing interferometer. The method involves rotating a half-wave plate in increments of 22.5°, while an equivalent optical path difference is defined to account for the measured profiles. Additionally, several broadband illumination sources and the two-wavelength phase-shifting interferometry method are incorporated. The use of achromatic waveplates and broadband optical components results in achromatic phase-shifts, with the same amount of rotation applied regardless of wavelength. This approach improves upon existing methods by offering more robust and precise phase shifts that are independent of wavelength, thereby enhancing the accuracy of measurements. The procedure is described theoretically and validated by measuring profiles on a 2.38 mm × 1.78 mm area on each of two standard objects. For comparison, Atomic Force Microscopy profiles of the two samples are also shown.