A stereogram composed of two images, each containing black and with dots (sometimes squares). A large proportion of the dots are identical in both, however a subset of dots in one is horizontally offset from the other. Once the separate images are presented to the left and right eye independently, they fuse in the visual system. The disparity of the subset of dots is subsequently "seen" as stereoscopic depth.
RANDOM-DOT STEREOGRAM: "Random-dot stereograms were first developed by U.S. engineer Bela Julesz."