Question

What are two methods for detecting motion in a computer mouse?

Answer 1

2 methods for detecting motion:

Mechanical :

        - Ball on underside of mouse turns as mouse is moved

        - Rotates orthogonal potentiometers

        - Can be used on almost any flat surface

Optical:

        - Light emitting diode on underside of mouse

        - may use special grid-like pad or just on desk

        - Less susceptible to dust and dirt

        - detects fluctuating alterations in reflected light intensity to calculate relative motion in (x,z) plane.

Comments

When you write a question, make sure it does makes sense. I have added "computer mouse" to the title