 The design requires a display that can switch fast enough to avoid image flicker as the images swap each frame.In a standard parallax barrier system, the viewer must position themselves in an appropriate location so that the left and right eye views can be seen by their left and right eyes respectively.In a ‘tracked 3D system’, the viewing freedom can be increased considerably by tracking the position of the user and adjusting the parallax barrier so that the left and right views are always directed to the user's eyes correctly.