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What Ever Happened to the Light Pen?

n the mid eighties, the computer mouse was just coming into its own as the user interface of choice. Although invented in 1968, it took computers like the Apple Macintosh and the Commodore Amiga for it to really catch on with consumers. Around the same time, there was another alternative input device available called the light pen. It truly embodied the concept of ‘point and click’, so what happened?

Light pens work on the same principal that video game light guns do. A photocell is contained within the pen, and when you press the button you essentially open the ‘shutter’ (just like a camera) to the photocell. The computer can then track exactly which line (and where on that line) it is redrawing as soon as it passes by the photocell. The software inside the computer can then react appropriately.

The most common use for the light pen is drawing. Essentially like a pen, you can draw on the screen. There are three limitations to this type of environment however. First of all, for long periods of time it is difficult to draw on a screen which is vertical. If you could place the monitor flat on a table, that might make a big difference. This brings us to the next limitation. The technology that is used to detect where you are drawing on the screen is based on a CRT (Cathode Ray Tube) display. That means that those nice flat panel screens (LCD) will not work. Lastly, the typical resolution of the screen is fairly limited so your drawing would end up being fairly low quality.

The Commodore 64 actually had one of the best solutions for a light pen in the eighties. The FlexiDraw pen from Inkwell Systems was not only a decent hardware solution but also had some good software to go along with it. This product was still available to purchase new at the end of the nineties and even worked with the 64’s Graphical User Environment (GEOS). The Macintosh and Lisa computers also had light pens and if you’re ambitious enough with your Amiga there are instructions on how to build your own out there (http://www.programmersheaven.com/zone20/cat268/index.htm). Even the ill-fated gaming system ‘Vectrex’ from Milton Bradley had a light pen available in 1982 and it has since gone on to be one of the most sought after peripherals for game collectors.

In a work environment, the light pen makes a more sensible choice than a touch screen. Light pens let you target very specific pixels (the tiny dots on the screen that make up the display) and they are less expensive than touch screens. The failure rate on these pens is very low and when they do break, you can simply replace then pen and be up and running again. When a touch screen fails, the entire display is gone and must be repaired or replaced.

So what happened? Although you can still buy a light pen today that is more modern and work with USB (one example is Fastpoint, http://www.ftgdata.com/products/lightpennav.html) the interest has definitely faded. The mouse proved to the winner of the user interface wars and as an application for artists, I believe that the advancements in drawing tablets make them a more natural choice. Although the light pen is a better choice in many applications than a touch screen, it seems to be the less popular solution.

The light pen may have limited practical use today but is has helped advanced our interaction with computers to be more natural. If you ever have the opportunity to try one, do so. You might be surprised at just how natural it feels.


Article Copyright ©2005 by Syd Bolton. Original publication date: 8/13/2005.
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