The Cat's Eye: Slit Pupils, Thin-Film Mirrors, and 135-Fold Dynamic Range
A cat’s eye contains two distinct optical technologies that human engineers have copied — one consciously, one not. The slit pupil achieves a dynamic range of 135:1 in light transmission, nearly ten times that of the human circular pupil. The tapetum lucidum is a multilayer thin-film reflector of crystalline rodlets, producing constructive interference at the peak of scotopic sensitivity and sending light through the retina twice. Banks et al. (Science Advances, 2015) showed why the slit geometry specifically evolved in ambush predators; Percy Shaw’s 1934 Catseye road reflector borrowed the principle directly.