From 1830 onward, Plateau studies the combination of two moving curves to one stationary image In his doctoral thesis he describes this as "une espèce toute nouvelle d'anamorphoses". In 1836 he uses the name "anorthoscope" for the first time in the "Notice sur l'anorthoscope" in which Plateau presents his new instrument to the members of the Academy. The instrument (in brass) contains two wheels, different in diameter, on one axis, and driven by gears. The wheels are interchangeable, so that it is possible to have different relative speeds.

Between 1830 and 1836 several short papers are published in relation to visual perception. In 1849 all this results in three very elaborate review papers "Deuxième (troisième en quatrième) note sur de nouvelles applications curieuses de la persistance des impressions de la rétine" in which Plateau goes further into the matter of the angular velocities of the revolving anorthoscopic discs and the discs with slits.

Anorthoscopes designed by Joseph Plateau
Collection J.Plateau, Ghent

Brass anorthoscope with adjustable relative angular velocities.
Wooden anorthoscope built by the Ghent instrument maker J. Van Hese.



Anorthoscopic discs
Collection J.Plateau, Ghent

Anorthoscopic discs can be made in two versions: a drawing on a white background, or a drawing on a black background. The drawings on white background must revolve behind a (revolving) slit in a black disc. The normal figure then is a black drawing on a light background. To view the drawings on a black background, a luminous slit must revolve behind the (revolving) disc with translucent drawing. The normal image then is white on a black background. The discs for use in transparency are made in different densities (oil lamps are very weak light sources!). The discs are made translucent by impregnating them on the back with oil and then applying a layer of varnish on both sides. This is a tedious process, and not really suited for mass production. Hand-coloured discs are also made.