An improved system for measuring absolute angular deviation through transparencies, such as aircraft windscreens, uses an incoherent light source and a target configuration in the form of an opaque slide with a transparent "L"-shaped pattern. The positions of images of the legs of the "L" passed through the transparency are detected by CCD arrays for measurement of the azimuth and elevation components of angular deviation for each tested point on the transparency, uncontaminated by lateral displacement errors.