COL49 Lissajous figures (p. 31)

[jbor]

Lissajous Figures 

http://members.aol.com/edhobbs/applets/lissajous/index.html

Lissajous (pronounced LEE-suh-zhoo) figures were discovered by the French
physicist Jules Antoine Lissajous. He would use sounds of different
frequencies to vibrate a mirror. A beam of light reflected from the mirror
would trace patterns which depended on the frequencies of the sounds.
Lissajous' setup was similar to the apparatus which is used today to project
laser light shows. 

Before the days of digital frequency meters and phase-locked loops,
Lissajous figures were used to determine the frequencies of sounds or radio
signals. A signal of known frequency was applied to the horizontal axis of
an oscilloscope, and the signal to be measured was applied to the vertical
axis. The resulting pattern was a function of the ratio of the two
frequencies. 

Lissajous figures often appeared as props in science fiction movies made
during the 1950's. One of the best examples can be found in the opening
sequence of The Outer Limits TV series. ("Do not attempt to adjust your
picture--we are controlling the transmission.") The pattern of criss-cross
lines is actually a Lissajous figure.

http://www.alphaomega.se/english/lissajousfig.html

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