Front-light Structure for a Lensless Fluorescence Imaging Device with a Hybrid Emission Filter

Lensless optical imaging is extensively used for deep brain imaging. In this study, we propose and demonstrate a front-light structure to improve the fluorescence observation performance of a lensless fluorescence imaging device. A thin front-light structure is inserted between the object to be observed and the emission filter. This enables the irradiation of excitation light from the same side as the lensless imaging device. We fabricated a front-light structure by patterning diffraction gratings on a thin glass and combined it with a high-performance emission filter to obtain a fluorescence imaging device, which facilitates fluorescence observation as well.