Eric H Pollmann, Yatin Gilhotra, Heyu Yin, Kenneth L Shepard, Fully Implantable 192× 256 SPAD Sensor with Global-Shutter and Micro-LEDs for Bidirectional Subdural Optical Brain-Computer Interfaces, ESSCIRC 2022-IEEE 48th European Solid State Circuits Conference (ESSCIRC), pp. 205-208
We demonstrate a fully implantable optoelectronic neural interface device featuring an array of single-photon avalanche photodiode (SPAD) detectors with a global shutter and monolithically integrated with an array of flip-chip bonded microLEDs (µLED) for fluorescence excitation and optogenetic stimulation. The device is integrated with optical filters and a lensless computation mask to create a 200-μm-thick implantable device. To enable the global shutter, an area-efficient 10b roll-over counter is used in-pixel. With a phase unwrapping algorithm, these counters can be used in a “modulo” fashion providing high dynamic range extension. Our SPAD sensor architecture achieves a better noise ∙ power figure-of-merit (FoM) than comparable photodiode image sensors.
Keywords—optoelectronic implants, single photon avalanche diodes, optogenetics, heterogeneous co-integration, brain computer interfaces.