Definission: superposition compound eyes where each ommatidium is equipped with a lens cylinder arrangement, producing the equivalent of a pair of lenses, with the first lens producing a small image halfway down the structure and the second lens turning the image back into a parallel beam. In the process the ray direction is reversed. Thus, the emerging beam is on the same side of the axis as the entering beam—the condition for obtaining a superposition image from the whole array.
Definission: A compound eye with no separation between the crystalline-cone layer and the retinula, each rhabdom receiving light only from its own corneal lens.
