Read-out electronics for IR microbolometers array with Smart features.

摘要

In this work are presented read-out electronic modules for IR microbolometers array, having the task of extracting useful informations from IR scenarios, for Smart applications as pattern recognition, position and motion detection. This read-out electronics, comlying with the constraint due to the microbolometer features, introduces from the lower level of interface, elements of distributed analog processing, giving to the whole array Smart like features. The nature of the single microbolometer detector fixes important constraint respect to the classical read-out of resistive elements. In fact, because the microbolometer detects the IR signal through the change of its temperature and so through the change of its electrical resistance, it isn't advisable the DC biasing, because is this case the biasing power, heating the detector, could destroy the useful information. So it is better to bias the microbolometer in pulsed mode, for a suitable time window. Furthermore the bolometric detector isn't intrinsically differential, so the use of a reference element is needed for the background fluctuations removal. For these considerations we propose a read-out electronic modules realising: - the pulsed and differential read-out of the detector and its reference (blind element) by switched current bias based on crossed current mirrors; - the local computation of spatial mean and gradient between adjacent pixels (distributed analog Smart like processing), by the use of a second level switches and circuit configurations accomplishing the sum and the difference between currents; - the management of the internal timing of the various switches levels, by a suitable finite state machine; - the I-V conversion, the A-D conversion, the data presentation by a high level processing circuits.