Touchpad providing screen cursor/pointer movement control

A touchpad providing an output signal that is indicative of a desired direction of movement of a cursor across a generally flat display screen, comprising:

• a generally flat dielectric sensing surface having a plurality of surface-portions, the sensing surface being adapted to be physically touched by a fingertip,
• a plurality R×C of sensor-cells associated with the surface-portions, the sensor-cells being arranged in a cell array having R rows and C columns, wherein R and C are integers, the rows and columns forming R×C intersections with one of the sensor cells being located at each of the intersections and at a corresponding surface portion of the sensing surface,
• each of the sensor-cells having an amplifier with an amplifier input and an amplifier output,
• each of the sensor cells having a first and a second physically spaced capacitor plate associated with but isolated from the corresponding surface portion,
• each of the sensor cells having circuit means connecting the first capacitor plate to the amplifier input and the second capacitor plate to the amplifier output to provide a negative input to output amplifier feedback signal as a function of a fingerprint pattern on a portion of the fingertip touching the corresponding surface-portion;
• a plurality R×C of resistor nodes arranged in a resistor array having R rows and C columns, the rows and columns forming R×C intersections with one of the resistor nodes being located at each of the intersections;
• a plurality R×C of circuit means, each circuit means connecting one of the amplifier outputs to one resistor node;
• first computation means connected to the resistor array and operable to compute a centroid output signal as a function of surface portions touched by a fingertip;
• and
• output means connected to the first computation means and providing a cursor-movement signal as a function of the centroid output signal.

A capacitance touchpad first useful to determine user-authorization of a device having a display screen, and thereafter useful for providing an electrical output signal that is operable to selectively control movement of a cursor across the display screen, comprising:

• a dielectric sensing surface adapted to be physically engaged by a user's 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 to provide amplifier feedback;
• user-authorization means connected to the first array, operable to cause the sensing cell amplifiers to operate in a low-gain mode, operable to generate a user fingerprint pattern for comparison to stored authorized user fingerprint patterns, and operable upon a match being detected to cause the sensing cell amplifiers to operate in a high-gain mode and to enable operation of the touchpad thereafter for use to control movement of the cursor as a function of a contact area of a user fingertip on the sensing surface;
• a plurality N of 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 correpsonding 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 a user's fingertip on the sensing surface, and
• first output means connected to the first computation means and providing a cursor movement control signal as a function of the centroid output signal.