Light Pen

Overview

The light pen was a pointing device that detected the electron beam of a CRT display, allowing users to draw or select items directly on the screen. Popular in the 1980s home computer era for art programs, light pens offered an intuitive drawing experience years before graphics tablets became affordable.

Like light guns, light pens only worked with CRT displays and faded as technology moved on.

Fast Facts

First use: 1952 (MIT Whirlwind computer)
Home computer era: 1980s
Technology: Photodiode detects CRT beam timing
Primary use: Drawing, menu selection
Limitation: CRT-only, arm fatigue

How They Worked

Light pens detected screen position:

Photodiode in pen tip detects phosphor glow
Timing of detection compared to beam position
Computer calculates screen coordinates
Pen position tracked in real-time

Unlike light guns, light pens needed to touch or nearly touch the screen.

Home Computer Light Pens

Various manufacturers offered light pens:

Product	Platform	Use
Gibson Light Pen	C64	Art software
Tech 2	BBC Micro	Drawing
Koala Pad + Pen	Various	Could use pen input
Various generic	Multi-platform	Budget options

Light Pen Software

Drawing programs supported light pens:

Koala Painter - C64 art program
Art Studio - Various platforms
Technical drawing - BBC Micro
Educational software - Selection interfaces

Why They Faded

Light pens had significant problems:

Arm fatigue - Holding at screen level
Precision - Difficult to draw finely
CRT-only - Technology limitation
Competition - Mice and tablets were better
Cost - Decent pens weren’t cheap

By the late 1980s, mice and joysticks dominated.

The Graphics Tablet Succession

What light pens couldn’t do, tablets could:

Draw comfortably on desk
Work with any display
Pressure sensitivity (eventually)
Better precision

Wacom tablets became the artist’s choice.

Draw on your screen