Angle-insensitive amorphous silicon optical filter for fluorescence contact imaging.

Abstract

We introduce a novel amorphous silicon absorption filter that has high rejection for all angles of incident light for wavelengths below approximately 700nm. This filter is used for microscopic cancer tissue detection in a small intraoperative contact fluorescence imaging system that requires excitation light at oblique angles. Our 15μm thick filter presents over five orders of magnitude rejection at 633nm, making it compatible with several clinically tested fluorophores, including IR700DX. We have demonstrated imaging of fluorescently labeled human epidermal growth factor receptor 2+ breast cancer tissue using the filter, and we can reliably detect microscopic clusters of breast cancer cells with only a 75ms integration time.