Abstract
A CMOS image sensor with stacked photodiodes has been developed to observe fluorescence in lensless digital ELISA (enzyme-linked immunosorbent assay) system. The sensor has been fabricated by using 0.18μm mixed signal CMOS process. Sensitivities of the both stacked photodiodes indicate that they can distinguish the fluorescence from excitation light which cannot be completely eliminated by an on-chip fluorescent filter.