THERMAL DETECTOR

摘要

A thermal detector comprises a row of thermal detector elements each connected to a common bus line via the gate of a high impedance input preamplifier and a switch. The line output from the bus line is taken across a load resistance providing a common source follower load for the prepamplifiers. The signal across the load is passed through an anti-aliasing low-pass filter to a sample-and-hold. Signals then pass to a high-pass digital filter arranged to substract successive signals from each detector element corresponding to open and closed positions of a radiation modulator. This attenuates 1/f noise. The filters are located outside the row. Bulky filter components may accordingly be employed giving good noise performance without affecting detector element spacing. The preamplifiers and the switches are preferably MOSFETs. The detector may incorporate many rows of detector elements to provide a two-dimensional array.