Speed considerations for LDPD based time-of-flight CMOS 3D image sensors

Abstract

Recently a 128×96 pixel range imager with a pitch of 40 μm and a fill factor of 38 % was presented for 3D range imaging measurements based on the pulse modulated (PM) time-of-flight (ToF) principle. This sensor employs a high-speed photodetector called lateral drift-field photodiode (LDPD). During the characterization insufficiencies in charge transfer were observed for low-light illumination. Here, characterization and analysis of the former imager is given and a redesign that circumvents the parasitic effects is demonstrated and verified by measurements on chip and on camera level.