Broad-Band Light-Wave Correlation Topography Using Wavelet Transform

Abstract

The absolute longitudinal distance between two points can be deterinined by the corresponding correlation peaks of two light-waves from a broad-band light source. Using this technique, the height of three-dimensional objects can be measured without 2lz: phase ambiguity. We can also detect the absolute position of scattering seeds in sub-surface or bulk materials such as defects, dislocations or impurities of high purity materials. The wavelet analysis is used to determine the correlation peaks. This technique can be applied to measurement of thickness of a few hundred microns.

Recent trends in white-light interferometry

“…of SPIE Vol. 6382 638201-4 However, those traditional methods require visual determination of peak positions 11,12 or use a complex calculation algorithm, 14,15 and no automatic measuring device for practical use was available in the market until our development of such a device in 2002. 16 We have developed an algorithm, named KF (thicK Film), which can automatically detect the positions of two contrast peaks in an interferogram generated by VSI.…”

Investigation of a dual-layer structure using vertical scanning interferometry

“…In this paper, we propose a wholefield method based on white light VSI to simultaneously obtain the thickness of each layer and the three-dimensional (3D) profile of the interfaces in a dual-layer structure. Wavelet transform has been used in white light interferogram analysis using cross-sectional distribution of the transformed spectrum [12]. However, in this paper, continuous wavelet transform (CWT) is used to obtain subscanning-increment resolution and improve its accuracy using the phases of a transformed interferogram.…”