Flexible devices such as perovskite solar cells have attracted increasing attention in recent years, leading to the widespread use of thin and flexible webs in their manufacturing. Roll-to-Roll (R2R) processing is commonly employed for the continuous production of such webs. However, defects such as troughs and wrinkles frequently occur during web transport in R2R systems, which can affect device performance. This study aims to establish a technique for measuring trough height using a line scan camera during R2R transport. Trough images were captured in real time using a line scan camera, and image processing techniques were applied to reduce noise and correct for uneven illumination. Based on the corrected grayscale images, the relative height of the troughs was evaluated. To validate this method, Stereo Digital Image Correlation (Stereo-DIC) was used to obtain three-dimensional measurements of the trough shape and displacement. The results from Stereo-DIC were then compared with those obtained from the line scan camera to assess the measurement accuracy. The comparison showed that the trough profiles captured by the line scan camera were in good agreement with those obtained by Stereo-DIC, confirming the reliability of the proposed method. Troughs tended to appear near the center of the web width but did not occur at consistent positions. This irregular occurrence is likely caused by variations in web thickness, which lead to uneven cross-sectional areas and stress concentrations. These stress concentrations in thinner regions may result in localized deformation and the formation of irregular troughs during transport.
NAKADA et al. (Wed,) studied this question.