New Structured Illumination Technique for the Inspection of High-Reflective Surfaces: Application for the Detection of Structural Defects without any Calibration Procedures

Yannick Caulier,Klaus Spinnler,Salah Bourennane,Thomas Wittenberg

doi:10.1155/2008/237459

Abstract

We present a novel solution for automatic surface inspection of metallic tubes by applying a structured illumination. The strength of the proposed approach is that both structural and textural surface defects can be visually enhanced, detected, and well separated from acceptable surfaces. We propose a machine vision approach and we demonstrate that this technique is applicable in an industrial setting. We show that recording artefacts drastically increases the complexity of the inspection task. The algorithm implemented in the industrial application and which permits the segmentation and classification of surface defects is briefly described. The suggested method uses perturbations from the stripe illumination to detect, segment, and classify any defects. We emphasize the robustness of the algorithm against recording artefacts. Furthermore, this method is applied in 24 h/7 day real-time industrial surface inspection system.

Highlights

One essential part of nondestructive surface inspection techniques working in the visible light domain is the choice of the appropriate illumination
The most common way is the projection of certain pattern of a structured light in such a way that the knowledge of the projected pattern combined with the observed deformation of the structure on the object surface permits the retrieval of accurate depth information of the scene [2]
We show that the proposed method is robust against recording artefacts and that a good discrimination between nondefective surfaces, textural defects, and structural defects is possible

Summary

Introduction

One essential part of nondestructive surface inspection techniques working in the visible light domain is the choice of the appropriate illumination. The most common way is the projection of certain pattern of a structured light in such a way that the knowledge of the projected pattern combined with the observed deformation of the structure on the object surface permits the retrieval of accurate depth information of the scene [2]. This method can be improved by using more complex patterns, such as encoded light [3], color-coded light [4], or Moire projection [5]. In contrast to these solutions, Winkelbach and Wahl [6] proposed a reconstruction method of shapes in the scene with only one stripe pattern and one camera by computing the normal surface

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Conclusion