Screens that allow viewers to see 3D images without them wearing special 3D glasses are referred to as being autostereoscopic. This provides so called ‘glasses-free’ 3D viewing. Typically the displays make use of a lenticular filter on the front of the screen – rather like those sometimes used on the post cards you can find in tourist shops. The filter is designed so that our left eye sees the left image on the screen, and the same with the right. With this type of system there are sweet spots, typically called ‘zones’ or ‘views’, where you can appreciate the 3D, but sadly, outside those areas 3D is not seen. So you have to pick your spot and stay there. A way to improve matters is to offer more sweet spots. Today six or eight is common, and some screens offer more. Philips and Dolby have been working together; their autostereoscopic screen provides 14 views. Some say this is so many that you can always see the 3D. Another solution is to add a camera to the screen so it can see where its viewers are and so adjust the left and right images so each can see the 3D. This can work for several viewers.