Vibration-desensitized fiber-diffraction interferometer for industrial surface measurements

We describe an industrial interferometer designed to conduct high-precision surface measurements in the presence of severe vibration. The principle of common-path interferometry is realized by devising a single-mode fiber waveguide that generates the reference wave directly from the measurement wave, enabling removal of the temporal wavefront fluctuation caused by vibration. In addition, a continuous-scanning phase-measuring method is adopted to isolate spurious vibration residuals in interferometric fringes captured using a high-speed digital camera. Experimental tests prove that the proposed interferometer is suited for in-line measurements of large mirrors, silicon wafers, and flat display panels with no excessive ground isolation for anti-vibration.