All-optical difference engine for in-process defect inspection for roll-to-roll printed electronics

The increasing capabilities of roll-to-roll (R2R) printing processes present challenges for quality control, requiring inprocess inspection of large substrates with high resolution at high speed. In this paper, an all-optical difference engine (AODE) sensor has been developed for in-process defect inspection for R2R printed electronics. The AODE sensor achieves high-speed inspection by utilising the principle of coherent optical subtraction to minimise data processing. The capability of the developed sensor is demonstrated using industrial printed electrical circuity samples and the sensor is capable of inspecting areas of 4 mm width with a resolution of the order of several micrometres.