A multifunctional scanning white-light interferometer (SWLI): Construction of 2-D and 3-D measurements

Abstract

It is necessary and important to find the focal plane in order to locate where the interference fringe is, and to determine the vertical-scan range prior to the scanning operation for an SWLI. A novel scheme is proposed in this paper for simultaneously carrying out the auto-focusing and the real-time 2-D measurement. Conventionally in a SWLI, it always happens that the interference fringe appears across the focal plane, and therefore the in-focus image is blurred by the interference fringe, which makes it difficult to carry out the auto-focusing and the 2- D measurement with the in-focus image. A multi-function SWLI has been developed such that the 2-D and 3-D measurements can be done simultaneously. Although the 3-D profile reconstruction is basic to an SWLI, the real-time 2-D measurement is not trivial. The proposed scheme is based on clarifying the out-of-focus images where interference fringes do not exist. The proposed scheme is applied on some preliminary experiments and it shows that the real-time 2-D measurement can be realized, and moreover, the accuracy of the 3-D profile reconstruction can also be improved.