1. An optical inspection system for analyzing the object content of a field of view comprising: an optical system adapted to produce either from the said object content or an image thereof, a diffraction pattern; a light level detection means on which the diffraction pattern is focussed for producing electrical signals corresponding to the light intensity at different points within the pattern; electrical circuit means response to said electrical signals comprising means for storing a plurality of different reference signal patterns and comparison means for comparing the electrical signals from the light level detection means produced from a subsequent field of view with each of the stored reference signal patterns to facilitate the identification of the subsequent signal pattern.