Description of a Mouse Mechanism............

This variant of the mouse resembled an inverted trackball and became the predominant form used with personal computers throughout the 1980s and 1990s.

Operating an opto-mechanical mouse..............

1. moving the mouse turns the ball.
2. X and Y rollers grip the ball and transfer movement
3. Optical encoding disks include light holes.
4. Infrared LEDs shine through the disks.
5. Sensors gather light pulses to convert to X and Y vectors