XpanD

XpanD is a 3-D film system. With Dolby 3D and RealD Cinema it's one of the three concurring technologies available on the market. While others use passive glasses XpanD uses LCD shutter glasses.
The DCI Stereoscopic Digital Cinema Addendum, published on July 11, 2007 has defined the 3D parameters of Digital 3D Cinema. The specs calls for Single Inventory of Stereoscopic Digital Cinema Packages, forbidding the usage of special copies that require a unique color or density timing. This applies especially to RealD that had to be supplied with a special version of each movie due to RealD’s ghosting problem. The specs also define that Stereoscopic presentations shall interleave the left and right eye frames alternating at a 48 frames per second rate.
XpanD became the dominant player in 3D digital cinema in the Europe ad Asia. XpanD is running a single digital projector at 144FPS. To separate the images, they place infrared transmitter in the booth, facing the screens. The transmitter uses plug & play infrastructure and it is very easy to move it from theater to theater, a fact that exhibitors find very effective as they can move the 3D system from big screens to small screens. XpanD are using active glasses, which act as high-speed shutters synchronized with the frame being projected. XpanD works with regular white screen. The disadvantage of XpanD is that the glasses are expensive and need to be cleaned and recycled. XpanD have almost 1200 screens of which over 80% are in Europe and Asia.
There are several methods used to produce a 3d image in digital cinema. All rely in reproducing the stereoscopic disparity between the images seen by the left and right eyes.
One method is to alter the spectral quality of the left and right eye images, and display them simultaneously.
A special pair of spectral filtering glasses then separates out the two images. This is the method used by Dolby and is the principle behind the crude red/blue glasses of anaglyph.
Another method is to circularly polarize the left and right eye images and use a pair of polarizing glasses to separate the images, which are shown sequentially. This is the method used by Real-D.
The third method is to leave the left and right eye images unfiltered and change which one is seen by which eye. This is done by presenting the images sequentially, along with coordinating an infrared signal. The infrared signal bounces from the screen and triggers a pair of special LCD shutter glasses, causing the appropriate eye's LCD shutter to close (go black). This is the method used by XpanD.
Another major advantage is the mobility of the XpanD system, allowing it to be moved from theater to theater within few minutes.

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