Vibrating Pinscreen Portrait
Mosaiced into the pinfield is a photographic portrait of the Exploratorium’s founder Frank Oppenheimer. The pins comprising the
portrait are one inch in length and are surrounded by pins five eighths
of an inch in length that predominate the thirty square inch field.
Being of greater mass the one-inch pins lag behind their shorter
neighbors when excited at any given frequency. The light reflected off
the longer pins’ polished heads lags in reaching the viewer, thus
revealing the pertinent information. A second condition that makes the
revelation possible is that the longer pins comprising the portrait are
arranged in specifically calibrated clusters that correspond to
relative amounts of light and shade in the photo portrait. This
directly translates to there being one more long pin per cluster for
each of the ascending steps in the eight step greyscale, where, for
example, eight long pins congregate around the center of a gride
square, corresponding to the lightest value possible in the portrait.
The above is a description of a masking technique which allows the
introduction of photographic imagery into the excitable medium of the
pinscreen. The description delineates an extended use of what is
inventor, Bob Miller, refers to as a pinhole portrait. Bob’s original
intended use of the device was for masking sun rays and producing
calibrated photonic impressions. He freely made its use available to
me for this experiment. Many thanks and fond remembrance.
The field of pins is 30” square. Each pin hangs by its
head in a hold through a thin steel plate. The hole is over-sized,
allowing the pin to freely swing and rotate. The entire pinfield is
being driven by a powerful variable speed, variable force vibrator.
The emergent patterns resemble those produced by the simple rules
governing wave propagation in cellular automata. Devised in the 1960s
by mathematicians John von Neumann and Stanislaw Vlam who were
interested in modeling self-reproducing entities, each pin can exist in
one of three states: receptive (meaning that it is liable to become
excited); excited and refractory (which means that it is recovering
from a period of excitation). When in an excited state, the pins
deliver a stimulus to those around it. If any receptive cell receives
a sufficiently large stimulus from its neighbors it too becomes
excited. But, once excited, a cell eventually enters the refractory
state, during which time it remains unresponsive to stimuli regardless
of what its neighbors are doing. Thus the vibrated pinfield, being an
excitable medium, its complicated behavior as a whole depends on the
simple interactions between neighboring pins giving rise to the
traveling spiral and target patterns occurring when excitations are
initiated at a few points – the wavefronts annihilating each other in
just the same way as they do in the models of cellular automata. I am
astonished that from these few basic rules such complex and gorgeous
phenomena arise. Does life in all its bewildering complexity arise
from such simple rules? If so, what a deep implication!
