Video projector technologies are commonly limited in the brightness
or resolution of the image. Although laser image projectors have
frequently been tried, and are used in theme parks for vector-displays,
there is a difficulty in producing an information-dense raster-scanned
display. If mirror scanners are used, impractically high mirror
speeds are necessary to fulfill the line-rate requirements of typically
16kHz. If acousto-optic scanning is used, rather low scan angles
are feasible and efficiency can be badly compromised.
The system developed made use of a combination of technologies which
enabled a compact, high efficiency, high brightness and high resolution
In this system, a copper vapour laser produces a pulsed beam of
light. The pulsing rate is synchronised with the video line
rate. The beam is optically configured to illuminate the aperture
of a Tellurium Dioxide modulator, operating in slow shear mode.
This is critical, since a slow-shear modulator of this type has both an anomalously
low propagation speed for the sound wave, and a very high diffraction
efficiency. In this way, a complete video line can be pre-loaded
into the modulator between laser pulses. The laser acts like a
sophisticated flashlight, taking a snapshot of the information in the
Downstream optics produces a line focus of the light onto the screen,
and the line is scanned vertically using a galvanometer mirror scanner
operating at either 50Hz or 60Hz, synchronised to the video frame rate.
This system has been adopted for use in the BAe Microdome training
simulator, where a single laser is used to generate four independent
images on the inner surface of a dome. Many of these systems are
now in use worldwide.
This system was developed when Dr Sawyers worked with PA Technology
and Scientific Generics.