High-speed measurement of three-dimensional surface profiles up to 10 μm using two-wavelength phase-shifting interferometry utilizing an injection locking technique

High-speed two-wavelength phase-shifting interferometry is presented. The technique is aimed at high-speed in-line inspection of spacers in liquid crystal display panels or wafer bumps where the measuring range is well determined and high-speed measurements are essential. With our test setup, the measuring range is extended to 10 μm by using two injection locked frequency scanning lasers that offer fast and equidistant phase shifting of interference fringes. A technique to determine the unwrapped phase map in a frequency scanning phase-shifting interferometry without the ordinary phase-unwrapping process is proposed.