A SPAD Relative Address Coding for Lateral Resolution Improvement in Coincidence Detection

In the readout integrated circuit (ROIC) with coincidence detection, a macro-pixel internal single photon avalanche diode (SPAD) relative address coding scheme is proposed for lateral resolution improvement. Conventional coincidence detection scheme suffers from lateral resolution deterioration due to combining multiple SPADs as one pixel. By distinguishing the triggered SPAD from others, the proposed SPAD relative address coding scheme can obtain independent address of SPADs within macro-pixel. A prototype ROIC with macro-pixels containing 2×2 SPADs was designed by TSMC 180-nm CMOS process with improved lateral resolution of 4 times.