1. A passive infrared (PIR) security sensor comprising: a focal plane array (FPA) including a plurality of imaging pixels, each of said pixels including a mosaic of sub-pixels that are electrically interconnected within the focal plane to form a resistor network, the mosaic of sub-pixels being arranged to form a mosaic pixel focal plane array (MP-FPA) and each said sub-pixel being a resistance microbolometer infrared detector; a signal readout means; an infra red transmitting lens; a signal processing means; and a display means.