No tags yet.
This article is referenced from http://optica.machorro.net/Optica/SciAm/Harmograms/1965-05-body.html
THE ORNAMENTAL FIGURES AMONG the illustrations accompanying this article can be variously interpreted as frozen music, the flow of electrons in a radio receiver or merely pleasing patterns. All such phenomena arise from the interplay of two or more harmonic motions, such as those that are found in the swing of a pendulum. For this reason the figures are known as harmonograms. They first attracted general interest in 1857 when the French physicist Jules Antoine Lissajous demonstrated his harmonograph, an apparatus for creating harmonograms.
Figure 1: A harmonograph of the crank type
Lissajous's apparatus used light to trace the patterns. To a pair of tuning forks he attached small mirrors that vibrated at different frequencies in separate planes. A beam of light reflected by the mirrors fell on a nearby screen, where the vibrations generated a slowly changing pattern of interlacing curves. The demonstration so fascinated audiences that the design and operation of harmonographs mushroomed into a widespread pastime.
The pastime still has devotees. Last year, for instance, Katherine 0. Reed of Concord, Mass., joined with her father, Thomas B. Reed, a chemist at the Lincoln Laboratory of the Massachusetts Institute of Technology, to construct a harmonograph as a project for her high school science fair. By the time the fair had ended the senior member of the team found himself deeply immersed in the century-old avocation. As a result the Reeds have since turned out a succession of harmonographs for creating ever prettier doodles, and they are still at it. Their latest machine is a complicated affair that weighs more than 50 pounds.
The Reeds write as follows: "Harmonograms can be generated by a number of devices, all of which have certain elements in common. A 'writing' apparatus of some kind is essential; it can be pen and paper, a beam of light that writes on photographic paper, a feather that traces marks on soot-coated glass, an electric spark that darkens conductive paper or a beam of electrons that writes on the phosphor of an oscilloscope. The 'pen,' whatever form it takes, must be moved across the paper by an oscillating mechanism.