Continuous Inspection of Optical Defects in Packaging Films

This work is concerned with the continuous means of counting and sizing optical defects (gels/fisheyes) in clear films using high-speed cameras and image processing electronics. This study clearly shows that the quantitative analysis of defects in clear films is very sensitive to factors such as line speed, film inspection width, instrument threshold settings, and wrinkles. Therefore, these factors must be kept constant and/or reported along with the optical quality (defect count) results. This is essential for consistency in lab-to-lab and sample-to-sample analysis. Consequently, while automatic inspection is a giant step forward from visual inspections, it is evident that such gel counts are qualitative at best. They are by no means an absolute measure of the number of gels in the film. Therefore, extreme caution must be exercised in interpreting such data. In other words, the gel count numbers must only be used as a qualitative indicator of the overall "cleanliness" of a resin lot.