Touchpad providing screen cursor/pointer movement control

• US 6,392,636 B1
• Filed: 01/22/1998
• Issued: 05/21/2002
• Est. Priority Date: 01/22/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Tartagni, Marco, Ferrari, Alberto
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): LESPERANCE, JEAN E
• Application Number:
  US09/012,065
• Time in Patent Office: 1,580 Days
• Field of Search: 345/157, 345/161, 345/173, 345/174, 345/178, 382/115, 382/116, 382/124, 356/71, 340/5.53, 340/5.83, 902/3, 902/6, 707/6, 434/155
• US Class Current: 345/173
• CPC Class Codes: G06F 21/32 using biometric data, e.g. fingerprints, iris scans or voiceprints
• CPC Class Codes: G06F 21/83 input devices, e.g. keyboards, mice or controllers thereof
• CPC Class Codes: G06F 2203/0338 Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A plurality N of capacitance sensing cells are arranged in a row/column array top to cooperate with a fingertip and produce an output signal that controls the movement of a cursor/pointer across a display screen. The output of each individual sensing cell is connected to the corresponding individual node of a resistor array that has N nodes arranged in a similar row/column array. A centroid output of the resistor nodes in row configuration provides an output signal for control of cursor movement in a row direction. A centroid output of the resistor nodes in column configuration provides an output signal for control of cursor movement in an orthogonal column direction. A mass signal output of the row/column resistor mode array provides a switch on/off signal.

Claims

1. 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.

2. The capacitance touchpad of claim 1, including:

second computation means connected to the second array for computing a mass output signal as a function of the contact area occupied by the user fingertip on the sensing surface; and

second output means connected to the second computation means and providing a switch on/off signal as a function of the mass output signal.

3. 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.

4. The touchpad of claim 3, including:

second computation means connected to the resistor array for computing a mass output signal as a function of a surface portion area touched by a fingertip; and

second output means connected to the second computation means and providing a switch open/closed signal as a function of the mass output signal.

5. 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.

6. The capacitance touchpad of claim 5, including:

second computation means connected to the second array for computing a mass output signal as a function of the contact area occupied by a user fingertip on the sensing surface; and

second output means connected to the second computation means and providing a switch on/off signal as a function of the mass output signal.

7. The capacitance touchpad of claim 5 wherein the plurality N of capacitance sensing cells and the plurality N of resistance nodes are integrated into a solid state unit.

8. A secure cursor control device, comprising:

a two dimensional array of individual capacitive sensing cells each including at least one capacitive electrode proximate to a sensing surface on which a human fingertip is placed for finger-print acquisition and each generating an output signal;

a plurality of individual resistors connected to form a two dimensional network of nodes each corresponding to a sensing cell within the array of sensing cells, each node receiving the output signal from the corresponding sensing cell, the network of nodes generating an output representing a location of a centroid for a contact area between the human fingertip and the sensing surface;

a processor receiving the output signals generated by the sensing cells and the output generated by the network of nodes, the processor employing the outputs of the capacitive sensing cells to verify a fingerprint on the human fingertip and employing the output of the network of nodes to control movement of a cursor in response to movement of the centroid.

9. The secure cursor control device of claim 8, wherein the processor compares the fingerprint on the human fingertip contacting the sensing surface to a fingerprint image for an authorized user of the secure cursor control device.

10. The secure cursor control device of claim 8, wherein the centroid of the contact area between the human fingertip and the sensing surfaces moves in response to rolling or pitching of the human fingertip on the sensing surface without requiring lateral movement of the human fingertip across the sensing surface.

11. The secure cursor control device of claim 8, wherein each sensing cell further comprises:

an amplifier connected between two sensing electrodes within the sensing cell, wherein the amplifier is shorted during finger-print acquisition to equalize an input voltage and an output voltage within the cell and wherein the amplifier, after the shorting of the amplifier is terminated, generates the output signal based a distance between a skin surface on the human fingertip and each of the two sensing electrodes, wherein the amplifier operates in a low-gain mode during fingerprint acquisition and switches to a high-gain mode following a match of the acquired fingerprint to a fingerprint pattern for an authorized user.

12. The secure cursor control device of claim 8, wherein the network of nodes further comprises:

a current buffer at each corner of the network of nodes, each current buffer connected to a first series of resistors across an end of each column of nodes within the network and a second series of resistors across an end of each row of nodes within the network.

13. A sensor structure for secure fingertip control of a cursor, comprising:

an X-Y array of capacitive electrodes proximate to a sensing surface on which a human fingertip is placed, wherein the capacitive electrodes are utilized for fingerprint acquisition when the human fingertip is first placed on the sensing surface and are utilized for contact area detection after user authorization is determined; and

an X-Y array of nodes within a network of individual interconnected resistors, each node within the array receiving an output signal from a corresponding set of one or more capacitive electrodes, wherein the array of nodes is employed for contact area detection after user authorization is determined.

14. The sensor structure of claim 13, further comprising:

current buffers at each corner of the array of nodes, each current buffer connected across the array row end or the array column end of the array of nodes, each pair of current buffers at opposite ends of one side of the array of nodes generating an output signal;

an X-displacement network receiving the output signal from the current buffer pairs on opposite horizontal ends of the array of nodes and generating an X displacement signal for a centroid of a contact area between the human fingertip and the sensing surface; and

an Y-displacement network receiving the output signal from the current buffer pairs on opposite vertical ends of the array of nodes and generating an Y displacement signal for the centroid of the contact area.

15. The sensor structure of claim 14, wherein the X-displacement network and the Y-displacement network generate a mass signal for the contact area, wherein the mass signal corresponds to pressure of the human fingertip on the sensing surface.

16. The sensor structure of claim 14, wherein the X-displacement network and the Y-displacement network calculate a zero moment value and first moment coordinates for the contact area to generate the mass signal and the X and Y displacement signals.