Non-destructive inspection of film-winding conditions via three-dimensional visualization of in-roll structures using optical coherence tomography (A feasibility study)

Abstract

In the production line of film rolls, defects such as cracks, wrinkles, and contaminations in the film may occur and lead to a large manufacturing loss. To prevent manufacturing loss due to defects, various methods to inspect films have been developed and employed. However, they are mostly surface inspection methods and thus are not applicable to the film-winding process where defects not visible from the surface may occur inside the film roll. In this study, we proposed a non-destructive inspection of film-winding conditions using optical coherence tomography (OCT). OCT is a three-dimensional structural imaging technique with a microscale spatial resolution based on low coherence light interferometry and will be applicable to the inspection at the film-winding process via three-dimensional visualization of in-roll structures. In order to test the feasibility of the proposed method, we applied OCT to film roll samples made of commonly used films, a polyethylene terephthalate film, a polypropylene film, and a polyethylene film, and visualized their in-roll structures. The experimental results demonstrated that OCT can clearly visualize in-roll structures to inspect the presence and types of defects and can detect air gap sizes inside film rolls quantitatively, suggesting the potential utility of OCT applied to the inspection at the film-winding process in the production line of film rolls. tomography (OCT), Three-dimensional (3D) imaging