Patent ID: 6392636
Filing Date: 2002-05-21
Classification: G06F,G06K

Abstract:
A capacitance touchpad for determining user-authorization of a device having a display screen, followed by providing an electrical output signal for selectively controlling movement of a cursor across the display screen, comprising:a sensing surface adapted to receive a user fingertip; a plurality N of capacitance sensing cells associated with the sensing surface and arranged in a first row/column array having N row/column intersections, the first array having one sensing cell located at each row/column intersection; each of the sensing cells having an amplifier with an amplifier input and an amplifier output, a first and a second physically spaced capacitor plate associated with the sensing surface, and circuit means connecting the first capacitor plate to the amplifier input and the second capacitor plate to the amplifier output; user-authorization means connected to the first array and operable to generate a user fingerprint pattern for comparison to authorized user fingerprint patterns, and to enable operation of the touchpad to thereafter control movement of the cursor as a function of a contact area of a user fingertip on the sensing surface; a plurality N of individual resistance nodes arranged in a second row/column array, the second array having N row/column intersections in a configuration that corresponds to the N row/column intersections of the first array; circuit means connecting each of the amplifier outputs within the first array to a corresponding resistance node of the second array; first computation means connected to the second array for computing a centroid output signal as a function of the contact area of the user fingertip on the sensing surface; and first output means connected to the first computation means and providing a pointer movement control signal as a function of the centroid output signal.