CMOS Monolithic Active Pixel Sensors (MAPS): New ‘eyes’ for science

Re-invented in the early 1990s on both sides of the Atlantic, Monolithic Active Pixel Sensors (MAPS) in a CMOS technology have slowly invaded the world of consumer imaging and are now on the edge of becoming the first technology in this field, previously dominated by Charge-Coupled Devices (CCD). Thanks to the advantages brought by the use of standard CMOS technology, MAPS have great potential in many areas including function integration, leading to the concept of a camera-on-a-chip, pixel size, random access to selected region-of-interest, low power, higher speed and radiation resistance. In many ways, MAPS have introduced a new way of doing imaging. Despite their success in the consumer arena, MAPS are still to make a definitive impact in the world of scientific imaging. This paper first briefly reviews the way radiation is detected by a CMOS sensor, before analysing the main noise source and its relationship with the full well capacity and the dynamic range. This paper will also show first examples of scientific results, obtained in the detection of low-energy electrons.