Definition: the method used by some animals (e.g. bats, dolphins and some whales) to determine the location of something by measuring the time it takes for an echo to return from it. These animals emit sound waves and listen for the echo, calculating the distance to the object from the time lapse between sound emission and the echo returning.
Definition: 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.
Definition: A light sensing organ composed of multiple ommatidia, visual units consisting of a limited number of rhabdomeric photoreceptor cells, cornea-secreting epithelial cells, interommatidial pigment cells, and sometimes crystalline cone cells
Definition: 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.
Definition: A light sensing organ composed of multiple ommatidia, visual units consisting of a limited number of rhabdomeric photoreceptor cells, cornea-secreting epithelial cells, interommatidial pigment cells, and sometimes crystalline cone cells
Definition: Eye-spots which may be set into a pit to reduce the angles of light that enters, to allow the organism to deduce the angle of incoming light. Lens-like structures may be present, but stemmata, unlike lens eyes, cannot form an image, either for lack of refractive power or retinal resolution.
Definition: A light sensing organ composed of multiple ommatidia, visual units consisting of a limited number of rhabdomeric photoreceptor cells, cornea-secreting epithelial cells, interommatidial pigment cells, and sometimes crystalline cone cells
