This is a 3-D photography technique presented in 1908 by M. G. Lippmann. A microlens array or other such means is used to control the direction of light rays to record and reproduce the light rays as if the photographed object were actually present. The principle on which this method works is that when a microlens array is placed in front of photographic film for exposure to a point light source, many points of light are recorded on the film in correspondence to each lens. After the image is taken, the film is illuminated from behind so that the light passes through the film and the microlens array, making the point light source visible in 3-D as though it were actually there.
