Anamorphoscopes: a visual aid for circle inversion

Extract

The use of reflecting surfaces to unscramble distorted pictures has been apparent over the past three centuries, at least, in an art form known as anamorphic (ana = back again, morphe = form) art. Of course, working in the opposite sense, the mirrors in fun parlours give distorted images from an undistorted (!) object. A famous portrait of “Bonnie Prince Charlie” in the West Highland Museum, Fort William, Scotland, appears as a series of incomplete concentric circular streaks of colour, but when a cylindrical reflecting surface (the anamorphoscope) is placed at the centre of the painting a recognisable image is seen on looking into it. Niceron and DuBreuil both wrote treatises in the seventeenth century on the techniques of producing anamorphograms, and Gardner has given a recent discussion of the general topic. DuBreuil described a method for generating a distorted object (drawing) that will be transformed into an undistorted image by the use of a conical reflecting surface whose base sits on the plane of the object. The drawings are very easily done by following simple rules of geometry.