Specular-reflection-based flatness tester

摘要

The inspection of plastic film flatness is approached by utilizing the light specular reflection off the film. A grating image formed by the reflection provides the slope information of the film surface. The wedge test shows the specular reflection-based flatness tester can achieve the slope accuracy of 0.01°. The film test shows the capability of the tester on the surface with a variety of slopes resulting in RMS and PV values of the slope. The film appearance in terms of the amount of interference rings is correlated to the RMS value of slope derivative.