1. A method for controlling the movement of a cursor on a video screen using a pointer and a separate track pad having a sensing area which is smaller than the area of the video screen which includes the steps of: transmitting two directional orthogonally oriented light curtains substantially parallel to and simultaneously across the entirety of said sensing area to create a sharply defined shadow of at least one edge of a pointer in two orthogonal directions x and y of pointer movement when said pointer is contacted by said light curtains, optically sensing only the velocities and direction of movement of said pointer in a first direction x and a second orthogonal direction y by detecting movement of the edges of said shadows when a pointer is moved in contact with said light curtains over the touch pad regardless of the actual position of the pointer within the sensing area of the touch pad; generating a velocity control signal as a function of the velocity of movement of the pointer in each of the x and y directions; and using the velocity control signal to cause movement of the cursor on the video screen in the x and y directions at a velocity which is a function of the sensed velocities of the pointer.