One of the early attempts at developing a
small mechanical scanner was the
Vibratory scanner. In this device, a small
mirror, "rocked" in the "horizontal"
direction and simultaneously, in a
"vertical" direction, perpendicular to the
first. The mirror, usually about 1/4"
square, was controlled by a pair of
electromagnets driven by appropriate
sweep signal frequencies. Because of the
added weight of the rocking frame, it was
always driven by the framing sweep
signal because it was the lower frequency
of the two. Therefore, the rocking mirror
was always driven by the line sweep
To improve the efficiency of the scanner, the mirror mounting and the rocking frame were made resonant to the
two sweep frequencies. A light source, modulated by the picture signal was reflected by the vibrating mirror onto
Pictures as large as 3 feet square and with up to 240 lines were claimed with this system.
The main failing of the Vibratory scanner was that it produced a sine wave scanning action, not compatible with
signals from cameras equipped with the usual Nipkow disk or electronic pickup tubes such as the Image Dissector
or Iconoscope. In addition, sine wave scanning produces undesirable shading of the image. Similar scanners
were attempted using Piezo-Electric crystals or Electrostatic drivers instead of electromagnets. They suffered
from the same problems.