Chip-on-tip fluorescence lifetime imaging micro-camera toward endoscopic applications

We present a chip-on-tip fluorescence lifetime imaging micro-camera on a size scale compatible with endoscopic applications. The micro-camera has an external diameter of 4 mm and comprises a miniaturized 128 × 120 SPAD array detector, integrated imaging optics, and an optical fiber for excitation light delivery. The spatial performance is characterized by imaging a resolution test target showing that the integrated system is able to resolve features of <30<i>μ</i>m. The temporal response is measured at a range of wavelengths, yielding a mean pixel impulse response width of < 1 ns. Benchmarking against a time-correlated single-photon counting system also shows good agreement with the micro-camera. Finally, fluorescence lifetime images of unlabeled <i>ex vivo</i> animal tissue samples are presented as examples.