Techniques for reducing jitter for taps

• US 9,720,544 B2
• Filed: 03/22/2011
• Issued: 08/01/2017
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Westerman, Wayne Carl
• Primary Examiner(s): Edwards, Carolyn R
• Assistant Examiner(s): NEUPANE, KRISHNA P.
• Application Number:
  US13/069,144
• Publication Number:
  US 20110171998A1
• Time in Patent Office: 2,324 Days
• Field of Search: 345156, 345173-178, 178 18- 20
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

Distinguishing sloppy taps from sliding motions is disclosed using an algorithm that can take into account both a time instability factor Tinst and a touch instability factor Zinst. A limited amount of motion per frame can be subtracted off immediately following the detection of a touch event. Small lateral motions indicative of a sloppy tap can be suppressed, while fast finger motions indicative of a quick, long cursor movement can immediately pass through the filter without being suppressed by a significant amount. A motion pass-through suppression factor can be applied subtractively to motion in particular direction as a function of Zinst and Tinst, wherein Zinst can represent a suppression value given as a finger speed for a particular percentage change in touch instability per frame, and Tinst can represent a suppression value given as finger speed for a particular tpress.

Claims

1. A method for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

measuring a position change per frame of the detected image of touch to obtain a detected position change per frame;

utilizing a change in capacitance detected at a node in the touch sensor panel, computing a suppressed position change per frame for the detected image of touch utilizing a time instability function, representing a varying amount of suppressed position change over time independent of the detected position change per frame; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor pane, the suppressed position change operative to suppress a displayed movement of an object at or near the touch sensor panel.

2. The method of claim 1, wherein the time instability function starts at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapers off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

3. The method of claim 1, wherein the time instability function provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

and

subtracting the first amount of suppressed position change per frame from the detected position change per frame for the detected image of touch to obtain the suppressed position change per frame for the detected image of touch.

4. The method of claim 3, further comprising:

applying a hysteresis filter to the detected position change per frame prior to computing the suppressed position change per frame.

5. A method of claim 3 wherein the time instability function starts at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

6. The method of claim 1, wherein computing the suppressed position change per frame is performed by additionally utilizing a touch instability function, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

7. The method of claim 1, wherein computing the suppressed position change per frame is performed by additionally utilizing a touch instability function, the touch instability function providing a first amount of suppressed position change per frame for a given amount of touch instability per frame, and wherein computing the suppressed position change per frame is performed by subtracting the first amount of suppressed position change per frame from a detected position change per frame value for the detected image of touch to obtain the suppressed position change per frame for the detected image of touch.

8. The method of claim 7, further comprising:

applying a hysteresis filter to a detected position change per frame prior to computing the suppressed position change per frame.

9. The method of claim 1, wherein:

the time instability function starts at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapers off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected; and

wherein computing the suppressed position change per frame is additionally performed by utilizing a touch instability function, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

10. The method of claim 9, wherein computing the suppressed position change per frame comprises:

computing a time instability factor in accordance with the time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

computing a touch instability factor in accordance with the touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame; and

subtracting a larger of the first and second amounts of suppressed position change per frame from the detected position change per frame for the detected image of touch to obtain the suppressed position change per frame for the detected image of touch.

11. The method of claim 1, wherein computing the suppressed position change per frame comprises:

computing a time instability factor in accordance with the time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

computing a touch instability factor in accordance with the touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame; and

subtracting a larger of the first and second amounts of suppressed position change per frame from the detected position change per frame for the detected image of touch to obtain the suppressed position change per frame for the detected image of touch.

12. A non-transitory computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

measuring a position change per frame of the detected image of touch to obtain a detected position change per frame;

utilizing a change in capacitance detected at a node in a touch sensor, computing a suppressed position change per frame for the detected image of touch utilizing a time instability function, representing a varying amount of suppressed position change over time independent of the detected position change per frame; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel, the suppressed position change operative to suppress a displayed movement of an object at or near the touch sensor panel.

13. The non-transitory computer-readable medium of claim 12, wherein the time instability function starts at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapers off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

14. The non-transitory computer-readable medium of claim 12, wherein the time instability function provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

and

subtracting the first amount of suppressed position change per frame from the detected position change per frame for the detected image of touch to obtain the suppressed position change per frame for the detected image of touch.

15. The non-transitory computer-readable medium of claim 14, the program code further for causing performance of a method comprising:

applying a hysteresis filter to the detected position change per frame prior to computing the suppressed position change per frame.

16. The non-transitory computer-readable medium of claim 14 wherein the time instability function starts at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

17. The non-transitory computer-readable medium of claim 12, wherein computing the suppressed position change per frame is performed by additionally utilizing a touch instability function, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

18. The non-transitory computer-readable medium as recited in claim 12, wherein computing the suppressed position change per frame is performed by utilizing,

a time instability factor in accordance with the time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

and

a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting a larger of the first and second amounts of suppressed position change per frame from the detected position change per frame for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

19. The non-transitory computer-readable medium of claim 18, the time instability function starting at a maximum suppressed position change per frame value at a time when the image of touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

20. The non-transitory computer-readable medium of claim 18, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

21. A computing system comprising the non-transitory computer-readable medium of claim 18.

22. A mobile telephone comprising the computing system of claim 21.

23. A digital audio player comprising the computing system of claim 21.

24. A mobile telephone including a non-transitory computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the touch sensor panel having plurality of row traces extending in a first direction and a plurality of column traces extending in a second direction, transverse to the first direction, the intersection of the row and column traces forming capacitive pixels having capacitive sensing nodes, the mobile telephone including:

circuitry for stimulating one of the plurality of row traces or the plurality of column traces with a stimulating voltage; and

circuitry for detecting a change in capacitance of the capacitive pixels at the capacitive sensing nodes of the other of the plurality of row traces or the plurality of column traces;

the program code for causing performance of a method comprising;

measuring a position change per frame of the detected image of touch to obtain a detected position change per frame;

utilizing the change in capacitance, computing a suppressed position change per frame for the detected image of touch utilizing a time instability function, representing a varying amount of suppressed position change over time;

independent of the detected position change per frame and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel, the suppressed position change operative to suppress a displayed movement of an object at or near the touch sensor panel.

25. An apparatus for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the touch sensor panel having plurality of row traces extending in a first direction and a plurality of column traces extending in a second direction, transverse to the first direction, the intersection of the row and column traces forming capacitive pixels having capacitive sensing nodes, comprising:

circuitry for stimulating one of the plurality of row traces or the plurality of column traces with a stimulating voltage;

circuitry for detecting a change in capacitance of the capacitive pixels at the capacitive sensing nodes of the other of the plurality of row traces or the plurality of column traces;

means for measuring a position change per frame of the detected image of touch to obtain a detected position change per frame;

means, utilizing the change in capacitance, for computing a suppressed position change per frame for the detected image of touch utilizing a time instability function, representing a varying amount of suppressed position change over time, independent of the detected position change per frame; and

means for utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel, the suppressed position change operative to suppress a displayed movement of an object at or near the touch sensor panel.