Object Detection by Relative Motion in Freely Flying Flies

摘要

The ability to detect objects and to distinguish them from the background (figure-ground discrimination) is essential if an animal is to navigate successfully in its environment. When an animal moves in the environment, the resulting motion of the retinal image carries powerful cues that can be used to extract information about the three-dimensional structure of the visual surround (e.g.). Small animals that lack the interocular separation or visual acuity necessary for stereopsis can still obtain depth information if they exploit the image motion cues generated by their own motion. As an example, consider the situation of an insect flying over a meadow with flowers raised above the grass. When the insect passes a flower, the image of the flower moves more rapidly across the retina than that of the ground, because the flower is closer to the animal's eye. Thus, relative image motion can be used to distinguish the flower from its immediate background, even if other cues such as differences in colour, brightness or texture are weak or absent.