Surface profile measurement is an important technique in the semiconductor industry and the manufacturing of the optical components. Due to its noncontact nature, full-field, high accuracy and resolution, phase-shifting interferometry (PSI) has been quite evolved in surface profile measurement of high-tech products. However, movement of the phase shifter, the vibration and air disturbance, and longer image-grabbing time make the PSI measurement inaccurate, and not suitable for on-line measurement. In this context, a measurement system that is capable to grab the phase-shifted interferometric images instantaneously (or simultaneously) for surface profile measurement is introduced. Using the polarization phase-shifting interferometry principles and through a four-image combining device, the system allows the four phase-shifted images to be grabbed by one CCD simultaneously. Then the grey-level values of the four images can be adjusted, digitally aligned to calculate the phase. The surface profile is obtained after phase unwrapping. Test of the system on a flat mirror and a silicon wafer demonstrates its usefulness. The accuracy and stability of the measurement is discussed. The development of such system will reduce the effect due to environmental vibration, and thus applicable for practical use.
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