 |
 |
 |
|
4.2 temporal Techniques
for increasing temporal resolution are exactly analogous to those that
can be used for increasing spatial resolution. For example, consider presenting
a stimulus to an observer by turning it full-on on one frame of the display,
leaving at the desired luminance for 10 frames and then turning it off
again. If the display is operating with a 100Hz frame-rate this corresponds
to viewing the stimulus through a 100ms square time window. As usual, the
word square should be a warning that bandwidth limiting is not operating
and that the frequency components of the underlying stimulus are liable
to be modified when viewed in this way. The preferred technique in this
case is to utilise available luminance resolution by viewing through something
like a raised cosine or Gaussian window whereby the stimulus intensity
is slowly increased from zero over several frames before reaching a plateau
and then being ramped off again. The desired stimulus waveform should be
seen as coming from a continuous function or a least a very long list of
numbers which is subsequently sampled by the display process once per frame.
In this way, the temporal resolution of the system is determined only by
the available luminance resolution and the accuracy with which the function
can be calculated and not by the display's frame-rate.
|
Previous |
Next |
|
^ Back to top
|