ATLAS: a large array, on-chip compute SPAD camera for multispeckle diffuse correlation spectroscopy
Alistair Gorman, Neil Finlayson, Ahmet T. Erdogan, Lars Fisher, Yining Wang, Francescopaolo Mattioli Della Rocca, Hanning Mai, Edbert J. Sie, Francesco Marsili, Robert Henderson
Abstract
We present ATLAS, a 512 × 512 single-photon avalanche diode (SPAD) array with embedded autocorrelation computation, implemented in 3D-stacked CMOS technology, suitable for single-photon correlation spectroscopy applications, including diffuse correlation spectroscopy (DCS). The shared per-macropixel SRAM architecture provides a 128 × 128 macropixel resolution, with parallel autocorrelation computation, with a minimum autocorrelation lag-time of 1 µs. We demonstrate the direct, on-chip computation of the autocorrelation function of the sensor, and its capability to resolve changes in decorrelation times typical of body tissue in real time, at long source-detector separations similar to those achieved by the current leading optical modalities for cerebral blood flow monitoring. Finally, we demonstrate the suitability for in-vivo measurements through cuff-occlusion and forehead cardiac signal measurements.