Abstract

Structured surfaces with three dimensional (3D) features such as v-groove [1], pyramid [2, 3] and sinusoid [4] are commonly found in advanced technologies since they have many advantageous specific functions. The dimensional information of the features is incontestably important since they affect the overall optical path. Due to the geometrical complexity of the structured surfaces, it is difficult to evaluate the conformance of this kind of surfaces by most of the optical measurement instruments. This is particularly true when the surfaces are measured and presented in three dimensional data sets. One of the methods attempts to separate the features per direction and the 3D features are evaluated directionally. Curvelet is the technology firstly developed in image processing [5] which is found to be able to separate directional features including tool marks and scratches [6]. However, the performance is still only limited in a visualization manner. This paper presents a directional feature evaluation method using curvelet. First, the basic and the detail of the method are provided. Second, experiments are presented for realizing the technical feasibility of the method. The performance of the evaluation method is evaluated quantitatively. Discussion and conclusion with some suggestions for further work are provided at the end. The convictive result provides some ideas for the evaluation of the complex surface especially for those with strong directional features.