Anorthoscope

An anorthoscope is a device that demonstrates an optical illusion that turns an anamorphic picture on a disc into a normal image by rotating it behind a counter-rotating disk with four radial slits.

[1] During early experiments for his study of physics at the University of Ghent, Plateau looked at two concentric cogwheels rotating in opposite directions, and noted how the fast moving cogs formed the shadowy image of a motionless wheel.

He later read Peter Mark Roget's 1824 article Explanation of an optical deception in the appearance of the spokes of a wheel when seen through vertical apertures that addressed a similar illusion and decided to further investigate the phenomenon.

Some of his findings were published in Correspondance Mathématique et Physique in 1828[2] On 9 June 1829, Plateau presented his (still unnamed) anorthoscope as "une espèce toute nouvelle d'anamorphoses" (a very new sort of anamorphoses]) in his doctoral thesis Sur quelques propriétés des impressions produites par la lumière sur l'organe de la vue (On some properties of the impressions that light produces in the organ of sight),[3] at the University of Liège.

Faraday thought the anorthoscope was a beautiful machine with an exceedingly curious and good effect, and mentioned: "It has wonderfully surprised many to whom I have showed it and they all refuse to believe their own eyes and cannot admit that the forms seen are the things looked at".