Detection of decorative phase defects on a polymeric non-planar object

• Published in: Polymer testing 2022-05, Vol.109, p.107558, Article 107558
• Main Authors: Šmíd, Petr, Pavlíček, Pavel, Kmec, Jakub
• Format: Article
• Language: English
• Subjects: Defect detection; Diffraction; Image processing; Non-planar object; Phase defect; Polymer
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2022.107558

This paper presents an optical noncontact method making the phase defects of transparent polymeric or glass objects visible, and image processing techniques detecting these defects. Phase defects affect the phase of the light passing through them, not its amplitude. Therefore, the presented method is based on Fresnel diffraction of a spatially coherent and temporally incoherent light. The method is suitable for both non-planar and planar objects. It is verified on polymeric non-planar objects with different phase defects. The tested objects are made from transparent polycarbonate with a special surface coating showing the orange peel effect. The image processing techniques allow to detect defects in a diffraction image with uneven brightness and nonuniform variance caused by the orange peel of the surface coating. •Phase defects are located in the transparent part of a polymeric or glass object.•An optical noncontact method using diffraction of light makes phase defects visible.•Image processing methods allow the detection of defects in the diffraction image.