A real time 3D video CMOS sensor with time gated photon counting

The real time acquisition of a 3D scene has been recently democratized by video game consoles. The most popular approaches such as the structure-light and the stereo vision are appropriate for short distances but they are not well suited for long time measurements in the range of a hundred meters up to a few kilometers or a scattering environment. In this case, the time of flight method is more convenient but is limited by the heavy and expensive hardware requirement for military applications. Indeed, a strong laser illumination and a time gated intensified camera is generally used to carry out this kind of measurement. The signal reflected at a long distance is so weak that very few photons reach the camera, thus using an image intensifier is mandatory. Moreover, the acquisition time and processing is quite long as several laser pulse are required for distance measurement and several frame of distance measurement are required to build a 3D scene. As a consequence, real time measurement cannot be achieved at this time. The paper describes a novel CMOS imager based on time gated single photon avalanche diode in order to detect the reflected light and accomplish distance memorization. The processing is fully parallelized and embedded within the pixel. The pixel includes 46 transistors, operates independently and has a size of 36×43 µm2. As a result, the readout of the sensor generates the 3D images immediately in real time.