crosstalk, is a problem that is less evident in stereo movies and gaming
due to motion of the scene and lower contrast levels as well as the presence
of color in the images. Medical images viewed in stereo are not forgiving
if the viewing system has even a small level of ghosting. This is because
images are typically grayscale, static, have areas of very high contrast
and also areas in which fine gradations of gray are used to differentiate
structures. The obvious and best solution for the problem is to use
a optical viewing system which has no chance of ghosting.
In using any viewing system where light from the images is physically
superimposed, a small percentage of the image destined for the contralateral
eye does leak through the coding device, whether shutterglasses, polarized
glasses, anaglyph glasses or an autostereoscopic screen. With shutterglasses
the ghosting arises from two components: Firstly, the persistence of
the image on the monitor phosphor persists for a bit longer after it has
been switched off and this time lag allows some of the image to be still
present at high enough levels to be perceptible when the contralateral shutter
opens. Secondly, even with the shutter closed, a small proportion of
light still does leak through from the wrong image.
To eliminate perceptible ghosting, the amount of light leakage to the
contralateral eye should be below 2% of what is being displayed to the that
eye (the Weber fraction).
To make shutterglasses or autostereoscopic screens truly useful for radiology,
the ghosting will have to be eliminated or minimized in future generations
of stereoscopic equipment.