Fully Integrated Time-Gated 3D Fluorescence Imager for Deep Neural Imaging

This paper reports an implantable 3D imager for time-gated fluorescence imaging in the deep brain. Fluorescence excitation is provided by dual ns-pulsed blue micro-light-emitting diodes (μLED), and fluorescence emission is collected by an 8-by64 single-photon avalanche diode (SPAD) array, together packaged to a width of 420 μm to allow deep insertion through a cannula. Each SPAD is masked by a repeating pattern of Talbot gratings that give each pixel a different angular sensitivity, allowing three-dimensional image reconstruction to a resolution of ~20 μm. The integrated imager is able to monitor fluorescent targets across a field of view of 1000 μm by 600 μm by 500 μm at arbitrary tissue depths.