Reflectance Transformation Imaging as a Tool for Computer-Aided Visual Inspection

Abstract

This work investigates the use of Reflectance Transformation Imaging (RTI) rendering for visual inspection. This imaging technique is being used more and more often for the inspection of the visual quality of manufactured surfaces. It allows reconstructing a dynamic virtual rendering of a surface from the acquisition of a sequence of images where only the illumination direction varies. We investigate, through psychometric experimentation, the influence of different essential parameters in the RTI approach, including modeling methods, the number of lighting positions and the measurement scale. In addition, to include the dynamic aspect of perception mechanisms in the methodology, the psychometric experiments are based on a design of experiments approach and conducted on reconstructed visual rendering videos. The proposed methodology is applied to different industrial surfaces. The results show that the RTI approach can be a relevant tool for computer-aided visual inspection. The proposed methodology makes it possible to objectively quantify the influence of RTI acquisition and processing factors on the perception of visual properties, and the results obtained show that their impact in terms of visual perception can be significant.

Reflectance Transformation Imaging Visual Saliency: Local and Global Approaches for Visual Inspection of Engineered Surfaces

“…This approach induces many issues and scientific challenges, in particular, the choice of measurement technology, the choice of the scale for both measurement and analysis tasks, and the choice of filtering and post-treatment methods. In this context, the RTI imaging method is currently experiencing significant growth [4,6,7] and is positioned as a complement to conventional techniques in industry, which are often based on 3D microscopy for the measurement of surface roughness.…”

“…Thus, we can observe the response of a point on the surface despite it being geometrically of a smaller size than the resolution of the sensor. RTI acquisition and characterization makes it possible to more directly measure and describe aspect function, i.e., the effect that is not geometry intrinsic and is instead created by the geometry of the surface [7,31].…”

Can Surface Topography Give Us Best Light Positions for Reflectance Transformation Imaging?

“…Recently, RTI has found a lot of applications in the industry. The prime use of RTI is in quality control [10]. RTI helps quality control inspectors to find defects that otherwise are challenging to find [11].…”