Demodulation pixels in CCD and CMOS technologies for time-of-flight ranging

A new generation of smart pixels, so-caned demodulation or lock-in pixels is introduced in this paper. These devices are capable of measuring phase, amplitude and offset of modulated light up to some tens of MHz, making them ideally suited to be used as receivers in 3D time-of-flight (TOF) distance measurement systems. Different architectures of such devices are presented and their specific advantages and disadvantages are discussed. Furthermore, a simple model is introduced giving the shot noise limited range resolution of a range camera working with these demodulation pixels. Finally, a complete TOF range camera based on an array of one of the new lock-in pixels will be described. This TOF-camera uses only standard components and does not need any mechanically scanning parts. With this camera non-cooperative targets can be measured with a few centimeters resolution over a distance of up to 20 meters.