Reference STATE OF THE ART Stan Augarten

ISBN 0-89919-195-9
Index
Scanned

1980
Photo of
The Optical Mouse
A Chip that Detects Motion

XEROX


First, some definitions. A mouse is a plastic box about the size of a cigarette pack that's used in some computer systems to move a cursor around on a video display terminal. (A cursor is an electronically generated pointer, usually in the shape of an arrow or rectangle, that indicates the position of the next item to be written or erased. It can also be used to give the computer instructions.) By pushing the mouse around on a flat surface next to the terminal, the computer operator can direct the cursor to any spot on the screen.

  Until a few years ago, mice were strictly electromechanical devices with ball bearings or wheels, whose movements were translated into electrical pulses that shifted the cursor around. Mice were relatively expensive to make and were somewhat unreliable, because the mechanical parts tended to get dirty and malfunction. Then a Xerox engineer by the name of Richard Lyon came up with a better mouse, a solid-state device that does away with moving parts by using the light-sensitive silicon chip depicted on the right.

  This IC behaves like the rods and cones in the human eye, although it can't distinguish colors. To work, it needs a little lamp and a board or other flat surface patterned with tiny black dots. As the operator slides the mouse across the board, the chip detects the passing dots and issues digital signals to the computer, which moves the cursor on the screen. Despite the need for a lamp and a patterned surface, it is cheaper to make and easier to use than electromechanical versions.

This chip detects motion using sixteen optical cells (the large red and white grids). The square features along the perimeter are connectors, used to link the chip electrically to the outside world. The name of the chip's designer, Lyon, has been etched in the corner. Actual size: 0.140 x 0.180 inches. Photo of

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STATE OF THE ART
©Copyright Stan Augarten
This book is provided for general reference. The National Museum of American History and the Smithsonian Institution make no claims as to the accuracy or completeness of this work.

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