Advanced pixel design for infrared 3D LADAR imaging

CEA Leti has demonstrated the good performances of its MWIR HgCdTe avalanche photodiode arrays. Gains above 20 at a moderate bias voltage of 5V have typically been measured with an excess noise factor of only 1.2. The next generation of infrared focal plane arrays will take advantage of these characteristics to address new applications, reduce system complexity and enhance performances. One of the main opportunities offered by avalanche photodiode detectors concerns long range active imaging. This paper reports the development of two novel pixel architectures for 3D active imaging based on flash LADAR technology. Both pixels have been designed in a standard 0.35μm CMOS process and perform time-of-flight measurement in addition to 2D intensity imaging with a single emitted laser pulse. The analog input circuits have been optimized to allow fast pulse detection while providing robustness to process variability. A small readout IC demonstrator has been fabricated and coupled to a 10x10 avalanche photodiode array at 40μm pixel pitch. The first test results in lab conditions show good electro-optical performances with a ranging resolution around 30cm (2ns).