Viewing Direction (Bias Angle)
Viewing direction (or bias angle) is
the direction from which the display will look the best. It is set during
the manufacturing process, and cannot be changed later by rotating the
polarizers. Viewing direction is specified as positions of a clock face. A
twelve o'clock viewing direction means that the optimum direction is above
the normal to the display, while a part with a six o'clock viewing direction
is best viewed from below the normal.
When specifying the viewing direction,
one needs to think about how the device is going to be used. For example, a
calculator is usually sitting on a desktop or held in the palm of your hand
and viewed from the six o'clock direction . Some instrumentation, like a
wall thermostat, may be mounted below the viewer and needs to be viewed from
the twelve o'clock direction. Other viewing directions are possible but not
common. A car clock display, which is usually to the drivers right, may have
a nine o'clock viewing direction, or possibly a ten-thirty one if the clock
is low on the dashboard.
In a direct drive display, viewing direction is not critical
because the display will look good from almost any direction. It becomes
critical when the display is multiplexed. The higher the multiplex rate, the
greater the problem becomes. In displays with extremely high multiplex
rates, great care must be taken when designing the drive circuitry. Special
films can also be applied to the front of the display glass to enhance the
overall viewability. However they tend to be expensive. |
