7.4 A 413×240-pixel sub-centimeter resolution Time-of-Flight CMOS image sensor with in-pixel background canceling using lateral-electric-field charge modulators

Time-of-Flight (ToF) range imagers have a wide range of applications, such as 3D mice, gesture-based remote controllers, amusement, robots, security systems, and automobiles. Numerous ToF range imager developments have been reported [1-4]. Recent developments are often based on CMOS image sensor technology with pinned photodiode options [5-7], which are suitable for cost-effective mass production. Reported CMOS ToF range imagers use single-tap or two-tap lock-in pixels; to cancel the influence of background light, two or four sub-frames are used to produce a background-canceled range image. These architectures, however, have difficulty with precise range measurements of moving objects, because background light cancelation is not guaranteed for moving objects. Lock-in pixels without any charge-draining gate suffer from background light during the readout time of the operation. Another important issue with CMOS ToF range imagers for high range resolution is the speed of lock-in pixels, which must be improved to use high-modulation-frequency light or short-duration light pulses.