Determination of thickness uniformity of a transparent film based on in-plane ESPI and radial basis function

In-plane electronic speckle pattern interferometry (ESPI) was developed to determine the thickness uniformity of a transparent film. The method is based on the subsequent spatial carrier patterns caused by the change of the rotation angle. Full-field thickness distribution can be obtained according to the relation between the phase difference and optical path difference generated by film rotation. Moreover, radial basis function was applied to improve the image quality of interference patterns. The main principle and experimental procedure of the method were presented. The errors of measurement results were analyzed. It is shown that the thickness uniformity of the thin film can be measured rapidly and accurately. Also, the refractive index can be determined by the developed method simultaneously.