Three-dimensional CMOS image sensor with 4x64 pixel array

A 3D CMOS imager based on time-of-flight (TOF) has been developed and successfully tested. It uses an active pulsed class 1 laser operating at 905nm to illuminate a 3D scene. The scene depth is determined by measurement of the travel time of reflected pulses by employing a fast on-chip synchronous shutter. A so-called "Multiple Double Short Time Integration" (MDSI) enables suppression of the background illumination and correction for reflectivity variations in the scene objects. The sensor chip contains 2 pixel lines with each pixel containing twin photodiodes, thus the chip contains 4x64 sensors. The chip allows two operating modes; the first is the binning mode (mode0 and mode1 are activated), where the twin pixels are short-circuited (tow lines on the die) and the average signal is measured. The second mode is the high-resolution mode (either mode0 or mode1 is activated). In this mode the pixels operate separately (four lines on the die). The chip has been realized in 0.5 mum n-well standard CMOS process. The pixel pitch is 130 mum. To get a good fill factor, the readout circuitry is located at the sides of the chip.