1. Apparatus for inspecting an image of one or more objects having identical significant features (object), said apparatus including means for producing an image of (an object) said one or more objects in an image plane, means comprising a plurality of detectors placed in (different) identical positions (of like geometry) with respect to said significant features (image), and means coupled to detectors situated alike with respect to different identical features in pairs and responsive to outputs therefrom for producing a signal only when said outputs are different.