CEA-Leti has developed an infrared imaging array in the 8-10µm band capable of returning an image with a minimum temperature difference, or thermal resolution, of 1 to 2mK, at ambient temperature and with traditional image cadences of 25-50 Hertz.
The HgCdTe array, with a format of 320x256 and a pitch of 25µm, achieved ultimate sensitivity of close to one-thousandth of a degree Kelvin at an operating temperature of 77K.
To obtain such sensitivity, CEA-Leti said it has designed and produced a special silicon reading circuit with a 0.18µm CMOS die, involving an analog-to-digital conversion at each elementary detection point with a pitch of 25µm.
The analog-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 to achieve the 10-20x increase in sensitivity compared with what is normally possible under the same observation conditions with conventional components.
CEA-Leti has teamed with Sofradir-CEA (DEFIR) laboratory, with support from CEA, Sofradir, DGA and Onera.
Sofradir is producing the HgCdTe infrared detector technology developed by CEA-Leti under exclusive license from CEA.