StereoImaging Corporation Display FAQ
How do I display 3-D?
When the DentiMag3D™ puts out the video containing spatial separation, the basic problem is how to display each eye's information separately.
Displays fall into four basic separation methods: Spatial, Time, Polarization, and Frequency.
Spatial:
A separate display (or part of a display) is used for each eye and the
corresponding image, left or right, goes there. One of the
best examples of this is the head mounted display (HMD). The user puts on
a visor, with each eye looking at its own separate micro-display. e-Magin
is a maker of this type of display. Another type of spatially separated
display is the auto-stereoscopic display. There are a variety of ways in
which these work, but the basic idea is that the display is spilt into
sections, usually vertical stripes, where the left and right information is
alternated. Just sit in front with no special glasses or goggles, and you see images with depth.
Makers of this type of unit include Dimension Technologies (DTI)
and See Real Technologies.
Time:
In a time-based display, the left and right images are alternated on a single
screen and a shutter is synchronized so that the left eye is blocked when the
right image is displayed and the right eye is blocked when the left image is
displayed. As long as this happens fast enough, usually 100Hz or over,
the brain interprets the image stereoscopically without flicker. The usual method of
blocking each eye is LCD shuttered glasses. The glasses contain an LCD panel per eye. Each eye panel is
essentially one giant pixel, made to either shut off light or allow it to pass through, in synchronization with the
frame being displayed in the monitor. In effect, you are being shown an image in one eye, while the
other eye is shuttered or blanked out. The glasses can be made in
wired or wireless versions. The display used is usually a CRT since the
speed needed is beyond the capability of most LCD screens. One
maker of shutter glasses is MacNaughton NuVision.
Polarization:
This method uses the polarization property of light to separate the left and
right channels. This allows the user to wear polarized glasses,
which are similar to sunglasses, just not as dark. The different
polarization of each lens allows the eye to see the correct image and blocks
the other eye's image. These glasses are much lighter and cheaper
than shutter glasses, since there are no electronics, just passive
lenses. There are several types of polarization, for example
linear, circular, or elliptical, depending upon the type of display
used. You may have worn polarized glasses if you've seen an IMAX 3D
movie or gone to a theme park 3D ride. Popular displays using
polarization include projection setups, polarizing shutter
panels to be placed in front of CRTs, and special LCD based stereo
displays.
Frequency (Anaglyphs):
This method uses color to separate the two images. Each image is
reduced to mostly one color and the user wears glasses with different colored
lenses. The most popular colors are red/blue or red/cyan. The original way
that many of us probably saw this anaglyph 3-D was at some horror movie, comic
book, or via Sports Illustrated. The color matching is critical for good
stereo, so it's difficult to do this method well on uncalibrated
monitors. This is the reason the great examples of anaglyphs are on film and
in print, where color matching is both a science and religion.
What is the best display?
The best display is the one that works well for your situation. For
groups, projection is usually best. For a single user sitting in one
position, an auto-stereoscopic display can work. Some users might like
the head mounted display visors. We think that for use with the
DentiMag3D™ in a dental suite, a polarized monitor (CRT or special LCD) is
the best.
What about flicker?
As you probably know, television (and films) create motion by displaying
still images in rapid succession. As long as these images are displayed fast
enough, you will not notice jerkiness or flicker in the motion. Standard
analog television runs at 60 fields per second in the US and 50 fields per
second in Europe. When displaying stereo on a single monitor, these
rates may have to be doubled, depending on the technology. The
DentiMag3D™ uses either 100Hz or 60Hz, depending on the display type.
This is fast enough to avoid the perception of flicker for all but the most
sensitive people.
Can I use the display that I already have in my office for the
DentiMag3D™?
Unless you already have a special 3D display, the answer is usually
no. A shutter panel can be added to a CRT to make a great 3D display,
but the CRT must be able to go fast enough and be a "super bright"
display to be an effective 3D monitor. All LCD panels that are currently
made are not fast enough to do single monitor stereo. However, there a
couple of new special LCD panels on the market specifically for stereo.
We have tested the NuVision version of this type of LCD and it works well.
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