A CMOS imager with on-chip temporal filtering for motion pre-processing

Robust motion detection algorithms such as the motion energy model require temporal filtering at the pixel level. We have designed and tested a CMOS imager with integrated, pixel-level temporal filtering necessary for motion detection. This temporal filtering enhances transients and provides a delayed and non-delayed channel for each pixel in the array. By varying bias currents on the chip, we are able to control the time constant of continuous-time low-pass filters that set the delay. By varying a reset switching frequency, we can control the high-pass filter time constant which determines the time course of transient enhancement. Operation primarily in weak inversion results in a low-power sensor well suited for integration into a motion processing system. We have constructed a 16×16 temporal processing array in a 0.5 μm CMOS process.