How computer mice are made

An optical mouse is a tiny camera that photographs the desk surface over and over and tracks how the picture shifts.

stations: 5
things upstream: 79
raw sources: 24
steps from the ground: 9

The short version

A computer mouse is a molded plastic shell around a small circuit board. An LED or laser lights the surface, and an optical sensor on the board takes successive pictures of it. A chip compares them to work out movement. Buttons, a scroll wheel and a cable or wireless radio finish it.

Mold the shell

Top and bottom shells are injection molded in plastic, along with the button covers.

Goes in
ABS plastic
Assemble the sensor board

An LED or laser diode and an imaging sensor go onto a small board with a processor. The sensor is essentially a low-resolution video camera.

Goes in
Printed circuit board Microchip LED
Fit buttons and wheel

Micro switches under each button and an encoder under the scroll wheel are soldered or snapped in.
Connect cable or radio

A cord is attached, or a wireless chip and battery are fitted. Battery-powered optical mice flash their LED intermittently to save power and glow steadily only while moving.

Goes in
Copper wire
Close and test

The shell is screwed shut, and each mouse is moved across a test surface to confirm tracking and clicks.

End of the lineComputer mouse

Worth repeating

The Xerox 8010 Star of 1981 was the third marketed computer to ship with an integrated mouse.
Richard F. Lyon demonstrated a low-resolution imager with in-pixel amplification for an optical mouse in 1981.
Most optical mice cannot track on polished stone because it is too smooth and shiny to reveal texture.