Monday, March 29, 2010


My son recently installed a screensaver on his computer and this leads me to reminisce about the screensavers I have seen over the years. In the distant past, computer screens were all built using cathode ray tube (CRT) technology, where a beam of electrons is accelerated to hit a screen of phosphor causing a release of photons lighting up the screen. One drawback of such screens is that in heavily used areas of the screen the phosphor will lose its ability to release photons after a while. If one continues to display the exact same image on the screen for an extended period of time, this would cause the image to be burned-in at the display. Common places where you see this phenomenon is in ATMs and Airport terminals.

To prevent burn-in of personal computer displays, screensavers were created, which are programs that are activated after several minutes of inactivity to constantly change the images displayed on the screen, in order to wear down the phosphor more evenly. One of the earliest screensavers for PCs is the flying toaster screensaver, where toasters are flying across the screen. Since then the screensaver has become much more sophisticated (e.g. displaying fractals and other beautiful patterns based on mathematical equations) and has been used for a myriad of tasks, including advertising, display of news (e.g. PointCast), photo slideshows (e.g. Picasa) and collaborative computing (e.g. World Community Grid) to help solve various important problems in the world today. Since most computer screens today are based on LCD technology, the problem of screen burn-in is less of a problem (but could still exist). However screensavers are still popular since they create a useful diversion to mundane computing tasks.

Back to the screensaver that was installed on my son's computer. This screensaver is associated with a popular video game, and when the screensaver starts, the logo of the game is displayed at a fixed location at the center of the screen with a scrolling star field in the background. This is exactly the kind of burn-in prone images the screensaver is trying to prevent. So it seems we have reached full circle!