Laser lines at 635 nm or longer (ideally 647 nm) are preferred for red,
giving energy-efficient, bright, rapid-motion images with rich, full
film-comparable colors. Green and blue lines are used too--and cyan
retained for best color mixing, an extra light-power boost, and aid in
speckle suppression. Speckle is suppressed through beam-path
displacement--by deflecting the beam during projection, thereby avoiding
both absorption and diffusion of the beam while preserving
pseudocollimation (noncrossing rays). The latter in turn is important to
infinite sharpness. Path displacement is achieved by scanning the beam on
the liquid-crystal valves (LCLVs), which also provides several
enhancements--in energy efficiency, brightness, contrast, beam uniformity
(by suppressing both laser-mode ripple and artifacts), and convenient
beam-turning to transfer the beam between apparatus tiers. Preferably
deflection is performed by a mirror mounted on a galvanometer or motor
for rotary oscillation; images are written incrementally on successive
portions of the LCLV control stage (either optical or electronic) while
the laser "reading beam" is synchronized on the output stage. The beam is
shaped, with very little energy loss to masking, into a shallow
cross-section which is shifted on the viewing screen as well as the
LCLVs. Beam-splitter/analyzer cubes are preferred over polarizing sheets.
Spatial modulation provided by an LCLV and maintained by
pseudocollimation enables imaging on irregular projection media with
portions at distinctly differing distances from the projector--including
domes, sculptures, monuments, buildings; waterfalls, sprays, fog, clouds,
ice; scrims and other stage structures; trees and other foliage; land and
rock surfaces; and even assemblages of living creatures including people.