A review of MI3 produced Active Pixel Sensors

Despite the continuing success of the charge couple device (CCD), the last 2 decades have seen APS devices become increasingly popular in their use as portable, low cost imagers. Despite suering from higher readout noise than the CCD, APS have a number of advantages. These include lower power consumption, lower cost, random access and selective readout. The possibility to incorporate on-chip functionality such as analogue-to-digital conversion (ADC), timing logic for thresholding and gain adjustment is driving an increased interest in these devices from the scientic community. In 2004, A UK consortium (MI3) was formed under an RC-UK Basic Technology Programme to develop CMOS active pixel sensors for a broad range of scientic applications including space science, particle physics and medical imaging. During the programme 6 APS' were designed, fabricated and tested. Highlights from the project include: the LAS (Large Area Sensor), a novel stitched sensor designed for use in medical imaging; eLeNA (Low Noise), a test structure which develops a range of low noise pixels and OPIC (On Pixel Intelligent CMOS), a test structure designed for in-pixel intelligence including sparse read-out, ADC and storage in each pixel and thresholding. This paper reports on the results and conclusion from highlight of some of the 6 active pixel sensors produced by the MI3 consortium.