| Summary: | Gratings are fundamental and important elements in optical metrology. Our
particular interest involves two applications of gratings which are optical
spectrometer and three-dimensional (3D) profilometer. An one-layer thin film
thickness measurement system is established based on spectrometer, in which the
deflection is produced by diffraction in a diffraction grating. A calculation method
derived from thin film interference principle is applied to postprocessing. As the
second important application of grating, 3D profilometer combines the grating theory
with illumination technique, and is used for surface measurement. In other part of this
project, a 3D profilometer is designed using Digital Light Processing (DLP) fringe
projector and CCD camera. Moreover, a few attempts to measure the different types
of specimens have already been made with this 3D profilometer to identify what
effects would be induced by diffusive and shiny surface, dark and bright
environment, black and white color of objects, and polarizer.
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