Column-Parallel Dynamic TDC Reallocation in SPAD Sensor Module Fabricated in 180nm CMOS for Near Infrared Optical Tomography

A major problem for optical biomedical imaging methods, e.g. near-infrared optical tomography (NIROT), using time resolved SPAD sensors is a slow acquisition time, resulting in motion artefacts and decreased patient comfort. We present a new SPAD sensor module optimised for the NIROT application. Dynamic TDC reallocation is employed to reduce the die area occupied by timing circuitry whilst also minimising the probability of photon pileup. High pixel PDE is achieved with a wide spectral range SPAD and cascoded passive quenching circuit. The sensor is fabricated in a 180nm CMOS process, enabling an image acquisition time in the NIROT application of 3.8 seconds per source and wavelength pair.