29 November 2010

Leti creates IR imaging array with record thermal resolution near 1mK

Leti of Grenoble, France (the Laboratory for Electronics & Information Technology of the French government’s research and technology organization CEA) has announced what is claimed to be the first infrared imaging array in the 8–10µm band capable of returning an image with record minimum temperature difference (thermal resolution) of 1–2mK at ambient temperature and with traditional image cadences of 25–50Hz.

CEA-Leti also created an infrared detection array by linking a CMOS silicon reading circuit to an array of mercury cadmium telluride (HgCdTe) infrared detectors.

Designed for defense and security applications, the HgCdTe array has a 320x256-pixel format and a pitch of 25µm. The array achieved ultimate sensitivity of nearly 1mK at an operating temperature of 77K, representing a 10–20x increase in sensitivity compared with what is normally possible under the same observation conditions with conventional components.

To obtain this high sensitivity, CEA-Leti designed and produced a special silicon reading circuit with a 0.18µm CMOS die, involving analog-to-digital conversion at each elementary detection point with a pitch of 25µm.

The analogue-to-digital conversion is based on the counting of charge packets given off by the detector. An equivalent stored charge of 3 giga-electrons can be obtained. This reading circuit, which is noise-optimized, enables sensitivity never before obtained on a component of this class, it is claimed.

CEA-Leti presented the results earlier this year at April's SPIE Defense, Security and Sensing 2010 conference Orlando, FL, USA, and as part of an invited paper at September's SPIE Defense + Security 2010 conference in Toulouse, France.

The results stem from research performed in a joint Sofradir–CEA (DEFIR) laboratory, with support from CEA, Sofradir, DGA and Onera. Sofradir of Châtenay-Malabry, France produces the HgCdTe infrared detector technology developed by CEA-Leti under an exclusive license from CEA.

Tags: Leti Infrared imaging array HgCdTe

Visit: www.leti.fr

Visit: www.sofradir.com

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