Capacitive semiconductor user input device

• US 6,408,087 B1
• Filed: 01/13/1998
• Issued: 06/18/2002
• Est. Priority Date: 01/13/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Kramer, Alan
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): CHAWAN, SHEELA C
• Application Number:
  US09/006,691
• Time in Patent Office: 1,617 Days
• Field of Search: 382/125, 382/126, 382/312, 345/326, 345/334, 345/156, 345/157, 345/158, 345/159, 345/163, 345/173, 345/174, 345/183, 345/202
• US Class Current: 382/124
• 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 3/04166 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

Abstract

A method of and system for providing user input to a computer, or the like, having a display by detecting a change in fingerprint pattern of a user. The system controls the position of a pointer on a display by detecting motion of ridges and pores of a fingerprint of a user and moving the pointer on the display according to detected motion of the ridges and pores of the fingerprint. The system captures successive images of the fingerprint ridges and pores and detects motion of the ridges and pores based upon the captured successive images.

Claims

1. A method of moving a pointer on a screen of a computer, comprising:

placing a user'"'"'s finger on a sensing element with a portion of the fingerprint of a pad of the finger in contact with a flat detector surface of the sensing element, wherein the area of the detector surface is substantially smaller than the fingerprint pad of the finger;

capacitively sensing a pattern of ridges of the fingerprint to create a first image of the fingerprint pattern at a first time;

moving the finger to cause the fingerprint to move in a plane parallel to the flat detector surface;

capacitively sensing a pattern of ridges of the fingerprint to create a second image of the fingerpint to create a second image of the fingerprint pattern at a second time;

detecting a change in position on the flat detector surface of ridges of the fingerprint pattern from the first image to the second image;

computing a displacement and direction of displacement of the fingerprint pattern from the first image to the second image; and

moving the pointer on the computer screen a distance that is proportional to the computed displacement and in a direction corresponding to the computed direction.

2. The method of claim 1 wherein successive images of the fingerprint pattern are captured at predetermined time intervals to detect the speed and direction of movement of the fingerprint pattern parallel to the flat detector surface from image to image, and wherein the pointer is moved on the computer screen at a corresponding speed and in a corresponding direction during each predetermined time interval.

3. The method of claim 2 further comprising:

capacitively detecting changes in pressure of the fingerprint on the flat detector surface to identify a mouse click command by the user; and

sending a mouse click signal to the computer upon the occurrence of the identification of the mouse click command.

4. A method of providing user input to a computer system including a display, comprising:

providing a detector surface adapted to have a fingerprint of a user'"'"'s finger pressed against it;

providing an array of capacitive sensors beneath the detector surface;

detecting variations in capacitance indicative of variations in a user'"'"'s fingerprint pattern of ridges and valleys when the user'"'"'s fingerprint is pressed against the detector surface;

capturing successive images of the user'"'"'s fingerprint pattern;

detecting motion of the user'"'"'s fingerprint in a plane parallel to the detector surface by comparing successive images;

determining the direction and speed of the detected motion;

moving a pointer on the display according to the determined direction and speed of motion;

detecting an increase in pressure of the user'"'"'s finger on the detector surface by comparing the width of fingerprint ridges in successive images of the user'"'"'s fingerprint; and

outputting a mouse click signal to the display whenever a predetermined increase in pressure is detected.

5. The method of claim 4 further comprising:

detecting the lifting and return of the user'"'"'s fingerprint on the detector surface; and

outputting a mouse click signal to the display whenever the lifting and return is detected as having occurred within a predetermined time period.

6. The method of claim 4 further comprising:

scanning the array of capacitive sensors horizontally and vertically according to a predetermined scanning pattern; and

amplifying the detected variations in capacitance using amplifiers, each of which corresponds to and is located proximate to a sensor of the array.

7. The method of claim 4 wherein the motion detecting step is carried out by determining displacement of fingerprint ridges and valleys in X and Y orthogonal directions in the plane parallel to the detector surface.

8. A user input device for moving a cursor on a display screen of a computer in response to movement of a user'"'"'s finger that has a pad portion corresponding to a complete fingerprint, comprising:

a flat detector surface adapted to receive contact by a fingerprint portion of a user'"'"'s finger, the flat detector surface having an area that is substantially smaller than the fingerprint pad portion of the user'"'"'s fingerprint;

means for capacitively sensing a pattern of the fingerprint in contact with the detector surface;

means for capturing successive images of the pattern as the fingerprint moves parallel to the detector surface;

means for determining the speed and direction of movement of the fingerprint by comparing successive images; and

means for controlling movements of the cursor at a speed and direction on the display screen in response to the speed and direction of movement of the fingerprint parallel to the detector surface.

9. The user input device of claim 8 further comprising:

means for detecting a predetermined change in pressure of the fingerprint against the detector surface; and

means for transmitting a mouse click signal to the computer upon detection thereof.

10. The user input device of claim 8 wherein the capacitively sensing means includes:

an array of capacitor plates disposed beneath the flat detector surface; and

semiconductor integrated circuitry disposed beneath the array for amplifying and transmitting signals to the capturing means that correspond to changes in capacitance at locations within the array sensed at predetermined time intervals.

11. A system for controlling the position of a pointer on a display screen, comprising:

a user input device for detecting motion of a fingerprint pattern of a user, the user input device including;

(a) a sensing element having a flat detector surface and a two-dimensional array of cells disposed beneath the detector surface, each cell including a capacitive sensor and an amplifier, the capacitive sensor detecting variations in the fingerprint pattern of ridges and valleys of the user'"'"'s fingerprint when pressed against detector surface, the amplifier producing an output corresponding to the variation in the fingerprint pattern detected by the capacitive sensor;

(b) control circuitry for controlling operation of the sensing element to produce the outputs from the amplifiers; and

(c) logic circuitry responsive to the outputs for capturing successive images of the fingerprint pattern at a predetermined frame rate, comparing successive images to detect movement of the fingerprint in X and Y directions parallel to a plane defined by the flat detector surface, and computing X and Y displacement signals corresponding to the movement of the fingerprint between successive images; and

a pointer controller in communication with the user input device for receiving the X and Y displacement signals and producing outputs to control the position of the pointer on the display screen;

wherein the logic circuitry includes means for comparing the width of fingerprint ridges in successive images to determine the change in pressure of the user'"'"'s finger on the detector surface, and for outputting a Z displacement signal to the pointer controller whenever a widening of the fingerprint ridges has been detected, the widening indicating an increase in pressure of the user'"'"'s finger on the detector surface.

12. The system of claim 11 wherein the logic circuitry includes means for comparing successive images to detect a lifting of the user'"'"'s finger from the detector surface and a return of touching of the user'"'"'s finger to the detector surface within a predetermined time period, and for outputting a Z displacement signal to the pointer controller whenever a lifting and return of the user'"'"'s finger has been detected to have occurred within the predetermined time period.

13. The system of claim 11 wherein each amplifier of each cell is a high gain inverting amplifier having an input and an output, and wherein each capacitive sensor includes a first plate and a second plate, the first plate being connected to the respective amplifier input and the second plate being connected to the respective amplifier output.

14. The system of claim 13 wherein each cell further includes a reset switch for shorting the input and output of each inverting amplifier during a selected phase to cause each inverting amplifier to settle at its logical threshold.

15. The system of claim 11 wherein the control circuitry includes horizontal and vertical scanning stages for enabling one cell at a time to provide an output to the logic circuitry, the scanning stages operating according to a predetermined scanning pattern.