3D Television Technology

Active Shutter 3D Technology

While passive polarization 3DTV is great for a cinema, where hundreds can watch one projected image with relatively cheap glasses, it is significantly less practical for home viewing. The projectors cost thousands of dollars, much more than most would be able to pay for the feature. A method using glasses that mechanically block the view of one eye is actually much more affordable for the home. This method is often known as active shutter 3D

A pair of CrystalEyes 3D glasses used in an active shutter system.[1]

Active shutter 3D takes advantage of stereopsis the same way as other methods of 3D display: by displaying two images and allowing each to reach only one eye. The active shutter takes a much more direct approach however. Instead of using polarization or colour schemes, the active shutter simply alternates which image is shown on the screen very quickly and alternates which eye it blocks at the same rate. Each eye then sees a different image, giving a false impression of depth.

The TV sends out two kinds of images, one for the right eye (represented as blue) and one for the left eye (represented as red). The shutters on the glasses are timed with the TV so that when the right-eye (blue) image is shown, the right shutter opens and when the left-eye (red) image is shown, the left lens opens. Each eye then sees only the image intended for it.

While the theory is very straightforward, making it work in real life is not. A television display of the proper framerate (how many frames it can display per second) can be made compatible, but it is more difficult to synchronize the image and the glasses such that the shutters open and close at the same rate as the image changes. In order to avoid a noticeable "flicker" in the image, the rate of switching must be very fast. Lightweight glasses that can handle the rate of switching accurately are unsurprisingly very expensive, upwards of $100 each. When a family of four wants to sit down and watch a 3D movie, the cost starts rising even more. However, active shutter is still significantly cheaper at this point than installing a polarized projector.