CHAPTER 8 HOW NEW TECH CHANGES PHOTOGRAPHY^127
In a lens using a vari-
angle prism(VAP) to
correct movements, such as
some of Canon’s video cam-
era lenses and binoculars,
gyrosensors are used to detect
the slightest wiggle. The sen-
sors send electronic informa-
tion to a microprocessor built
in to the lens.The chips’ electrical signals create magnetic fields in the voice coils that, in turn, push or pull a metal plate onto
which the glass walls are mounted. The voice coils widen or narrow different areas of the liquid-filled chamber so
light now strikes the VAP at an angle. The size of the angle is calculated so that rays passing through the VAP are
refracted precisely to put the light beams back on the correct path.3
The microchip sends an electrical signal to voice coil
motors, much smaller versions of the motors used to vibrate
the cones in speakers. The motors sit at 90° angles to each
other on the rim of the vari-prism. The VAP, which is posi-
tioned among the lens elements in the path the light passes, is
made of two plates of glass connected by a flexible resin bel-
lows. The space between the plates contains a clear liquid
with the same refractive characteristics as glass. Ordinarily,
light passes through the VAP without a change in direction.2
1
Vari-Angle Prism
System