A simple defect detection technique for high speed roll-to-roll manufacturing

A prototype industrial defect inspection system, which can operate at speeds of up to 1 ms-1 and over web widths of 500 mm, is being developed at the National Physical Laboratory for roll-to-roll manufacturing of highly-transparent materials. The prototype is designed to detect defects with lateral dimensions larger than 10 μm. The findings of a feasibility study for a sensor based on dark-field imaging principles are presented. The design of the sensor is introduced and the results of a preliminary characterisation are discussed. Off-the-shelf equipment was used including a monochromatic CMOS sensor paired with a telecentric lens. The illumination was supplied from a high-power LED and a range of illumination wavelengths was used. The characterisation was performed on custom-made transparent polymer artefacts and the results are presented