White Light Spectral Interferometry for Real-time Surface Profile Measurement

This paper presents a high speed surface profile optical measurement technique based on white light spectral interferometry and parallel signal processing using a general purpose graphic processing unit (GPGPU). A white light source is used to acquire the surface profile of the sample instantly in real time through a cylindrical Michelson interferometer. The interference signals are resolved by a diffraction grating and recorded by a high speed CCD camera. The spectrum of the interference signal contains the phase information in just one shot of the CCD camera frame image. By analysing the spectrum of the interference signal, the system can measure a surface profile as the measured surface in a moving state. As the measured surface laterally passes through the measurement arm of the interferometer, a surface map can be constructed by combining each of the measured profiles. Structured surface samples were measured and the results are discussed. This measurement system can be applied for roll-to-roll processed film surface inspection.