The Light Pen: A Precursor Legacy

Andrew Linscott

The Light Pen A Precursor Legacy Legacy

ITGM705 | Prof. David Meyers | Fall 2017

“If I have seen further, it is by standing on the shoulders of Giants.�

- Sir Isaac Newton

When these words were first issued in a letter to a colleague he was referring to scientific findings and techniques, but this statement applies to any discipline, in truth, that’s current state and stage of development is directly influenced by the work of other both now and throughout the past. In few places is this relationship between the current state of things and what came before more apparent than the world of digital interface

Mighty is the Pen

tools. With every iteration, with each step forward in their evolution, the innovators behind such tools draw insight and wisdom from the preceding generations of digital interface devices in order to optimize the performance of the tool for whatever problem or task it is being designed to accomplish.

One such digital interface device in which we can see the beginnings of a chain that continues to the present day is the light pen. As opposed to the mouse, which translates the user’s movements along a lateral plane, independent from that which they are mapped to, to the computer screen in the form of a pointer or cursor that lives there, a light pen allows the user to directly interface with the screen itself. This is done by sensing the light of pixels on a cathode ray tube (CRT) monitor and their change in intensity as the electron beam of the CRT scans across the screen. The mechanism by which this system projects information to the screen is quite structured,

scanning each pixel location individually, moving from top to bottom in a straight line and working its way accross the display in the blink of an eye. Thusly, when the light of the electron beam is detected by the pen tool, the timing of this scanning action can be mapped in such a way that

the computer is able to accurately determine the location of pen in regards to the area of the screen.

It could be used both as a pointer, hovering just off the screen itself being tracked by a marker on the display to indicate the user’s position, and as a direct input by, typically, tapping the pen’s tip to the display or with a click of a button on the pen’s side in later iterations.

Let There Be Light The very first noted light pen was developed in the early 1950s at the Massachusetts Institute of Technology for use with the Whirlwind project by the engineer Robert R. Everett. Its intention was principally for diagnostic purposes with the CRT display. It presence in academia continued through the 1960s, becoming more and more prominent of a tool for text and graphic manipulation. Graphic terminals, such as the IBM 2250, which utilized light pens as the main interface device became somewhat common in the computer labs of universities such as Brown and Columbia. The pen’s capacities in controlling vectors made the tool an intuitive

interface device for engineering and design applications. As opposed to running yards and yards of punch tape through a computer for it to interpret the structure of a shape or font, the same could now be accomplished with a brief, albeit methodical, set of taps on a screen. And while some circles used the light pen for more academic purposes – researches and the like at Columbia noted the light pens with their IBM 2250 were predominantly used for character manipulation – others saw the tool as an intuitive solution to early Graphical User Interface(GUI) systems. Three years before the groundbreaking introduction of the Xerox Alto, in 1970, the IDIIOM(Information Dislays, Inc. Input-Output Ma-

chine) computer aided design platform utilized a light pen to interface with a GUI chess game it ran.

Funnily enough, another chess application, J. Biit, which utilized a GUI with light pen tool was developed at Columbia University for the IBM 2250 terminal.

Usability In terms of how intuitive or affective of a tool the light pen actually is, there is some room for debate.

As with most interface devices, those of today included, prolonged use in suboptimal ergonomic positions could eventually lead to repetitive strain injuries. In the case of early light pens, most displays the user would interact with would be positioned in a quite vertical manner with users working at a station for long periods of time, potentially resulting in “Gorilla Arm�. But this was fairly easy corrected by taking breaks to rest the arm and/or resting the display on an incline, as is common with similar modern technologies.

A study published in the magazine

Human Factors in the fall of 2004 found, not too surprisingly as it is currently the predominant method by which user interact with GUI systems, that the mouse is more efficient and preferred over the light pen by the majority of users. That being said, the natural movements of the pen tool do offer certain advantages in some regards to the typical mouse interface. Chiefly, the lack of having to translate the one’s movements from one plane to another makes the device versatile in it’s application. That same study published in 2004 demonstrated that the light pen was a more efficient means of interfacing in novel ways, such as using one’s non-dominant hand, as well as more accessible for users of all ages and levels of experience

with a computer. Particularly, tasks that required precise pointing and selection were performed more efficiently with the use of a light pen. Here, the light pen’s role in graphic manipulation, most noteably in regards to design, begins to become clearer.

Legacy For nearly four decades, light pens were arguably the most efficient and effective interface tool of their kind in their niche. Several technologies during that time even emulated the input process of determining the user’s position by detecting the scanning of the electron beam of CRT displays. One such was the light gun, which

was popularized with the use of home console games (i.e. the Nintendo Zapper and Atari XG-1).

But with the dawning of a new millennia, CRT display systems would become more and more outmoded by LCD and LED flat screens for the sake of picture quality and special economy. This would be an insurmountable obstacle for interface devices such as light pens that relied on CRT technology, as they are incompatible with anything but. Today, capacative and pressure sensitive touch tools carry on the legacy of light pens. The same innate advantages of working directly on one’s display screen are seen in the modern pen devices of today as they continue to be an integral part of digital art and design.

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