|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
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.
The Lissajous Lab provides you with a virtual oscilloscope which
you can use to generate these patterns. (You
will control the horizontal. You will
control the vertical.) The applet also allows you to apply a signal
to modulate the hue of the trace, so you can create colorful designs.
Select the Preset buttons at the left to
see sample patterns. To generate your own patterns, use the digital
readouts at the right. Adjust the readouts by clicking on the
digits: clicking near the top of a digit increases its value;
clicking near the bottom decreases its value.
(More about the readout values)