Light Pen

A light pen is a pointing device that can be used to select an option by simply pointing at it, or to draw figures directly on the screen.

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A light pen has a photo-detector as its tip. This detector can detect changes in brightness of the screen. When the pen is pointed at a particular spot on the screen, it record change in brightness instantly and informs the computer about this. The computer can find out the exact spot with this information. Thus, the computer can identify where you are pointing on the screen.

Light pens are useful for menu-based applications. Instead of moving the mouse around or using a keyboard, the user can select an option by pointing at it.

A light pen is also useful for drawing graphics in programs, such as computer aided design(CAD). An engineer, architect or a fashion designer can draw directly on the screen with the pen. Using a keyboard and a light pen , the designer can select colors and line thickness, reduce or enlarge drawings and edit drawings.