Active Stereo

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Currently, the only way to produce high quality stereo on a large screen is to use a projection system. Active systems (e.g. the Infocus DepthQ and Christie's Mirage range) work by switching between the left and right images very quickly. This is also known as page-flipping, time-sequential or quad-buffered stereo. The projection system is synchronised via a control box with an infra-red link to electronics in a pair of LCD shutter-glasses which alternately blank each eye so that only the correct image gets through.

This same technique is also used on CRT monitors. The two main manufacturers of shutter glasses are NuVision and StereoGraphics, follow the links to see their respective products.

Starlight Express road show featuring digital 3D-projection by Inition

Active versus Passive Stereo

Active systems using shutter glasses have been around for a long time and were once the only option for digital stereoscopic projection. They require either CRT or DLP projectors because of the high refresh rate required (~120Hz) to switch quickly between both eyes without noticable flicker. Passive systems are usually based on a pair of LCD projectors.

	Passive Projection System				Active Projection System
	Relatively inexpensive				Relatively expensive
	Large choice of projectors and lenses				Limited choice
	Card or plastic 3d glasses are lightweight and inexpensive and can be branded				Glasses are bulky, fragile and expensive
	Alignment required during installation/setup				No alignment required as only single projector
	Head must remain fairly level for 3D filters to work*				Can be viewed with head tilted to one side
	Must use a special non-depolarising screen				Can use standard screen materials

* This can be worked around by using circular polarising filters, instead of linear.

If you have any questions about stereoscopic displays then please call +44 (0)20 7613 5004 or email inition@inition.co.uk. We have a wide range of 3d screens available to view in our central London demo suite. Please contact us to arrange an appointment.

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