1. A detection system comprising: a first array of detector pixels having a first field of view; a second array of detector pixels having the first field of view; a subtractor connectable to each pixel pair of the first and second arrays; and a comparator connected to the subtractor; and wherein: the first sensing array has a sensitivity to light in a lower portion of a reflective infrared spectrum; the second sensing array has a sensitivity to light in an upper portion of a reflective infrared spectrum; a pixel pair includes a first pixel at a location of the first array of detector pixels of the first array which a one-to-one correlation with a second pixel of the pixel pair at a corresponding location of the second array of detector pixels; the subtractor may detect the differences of magnitudes of output signals from the first and second pixels of each pixel pair and output a magnitude difference signal for each pixel pair; and a comparator may compare the magnitude difference signals to a certain threshold value and select the pixel pairs having magnitude difference values on one side of the threshold value.