A non-contact optically based apparatus for measuring the motion of a diffusely reflecting surface. The motion measurements and signals derived therefrom are used to provide input control signals to a computer or other electronic control systems requiring a human tactile or other control. The apparatus includes a unique optical sensor which senses both the magnitude and direction of the motion of a surface, relative to the apparatus, by measuring the motion of the pattern generated by illuminating the diffusely reflecting surface with a light source.