Determining touch locations and forces thereto on a touch and force sensing surface

• US 9,430,107 B2
• Filed: 04/16/2014
• Issued: 08/30/2016
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Microchip Technology Incorporated
• Inventors: Hanauer, Jerry, Lamont, Lance, Curtis, Keith E.
• Primary Examiner(s): Ghebretinsae, Temesgh
• Assistant Examiner(s): Ketema, Benyam
• Application Number:
  US14/254,098
• Publication Number:
  US 20140210791A1
• Time in Patent Office: 867 Days
• Field of Search: 345/174
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• 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 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A projected capacitive touch and force sensor capable of detecting multiple touches thereto and forces thereof is coupled with a digital device having multi-touch and force decoding capabilities. Once a touch has been established, a force thereof may be assigned to the touch based upon the magnitude of change of capacitance values determined during scans of the projected capacitive touch and force sensor. The touch forces applied to the touch sensor from the associated tracked touch points may be utilized in further determining three dimensional gesturing, e.g., X, Y and Z positions and forces, respectively.

Claims

1. A method for decoding multiple touches and forces thereof on a touch sensing surface, said method comprising the steps of:

scanning a plurality of channels aligned on an axis for determining self-capacitance values of each of the plurality of channels;

comparing the self-capacitance values to determine which one of the channels has a local maximum self-capacitance value, wherein left and right slope values are determined for the at least one self-value, wherein;

the left slope value is equal to the at least one self-value minus a self-value of a channel to the left of the at least one channel, and

the right slope value is equal to the at least one self-value minus a self-value of a channel to the right of the at least one channel;

wherein when the left slope value is greater than zero (0) and the right slope value is less than zero (0), then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when no then continue to next step;

wherein when a ratio between a positive left slope value and a positive right slope value is greater than a predefined threshold, then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when not then continue to the next step;

wherein when a ratio between a negative left slope value and a negative right slope value is less than a predefined threshold, then determine a local maximum self-capacitance value and return to the step of scanning the plurality of nodes of the at least one channel, and when not then continue to the next step;

wherein when there is another self-value, then return to the step of determining left and right slope values;

scanning a plurality of nodes of at least one channel having local maximum self-capacitance value for determining mutual values of the nodes;

comparing the mutual values to determine which one of the nodes has the largest mutual capacitance value, wherein the node having the largest mutual capacitance value on the local maximum self-capacitance value channel is a potential touch location; and

determining a force at the potential touch location from a change in the mutual capacitance values of the node at the potential touch location during no touch and during a touch thereto.

2. The method according to claim 1, further comprising the steps of:

determining the left and right slope value only when the at least one self-value is greater than a self-touch threshold.

3. The method according to claim 2, further comprising the steps of:

determining if at least one of the mutual values is greater than a mutual touch threshold, wherein

if yes then continue to the step of scanning a plurality of nodes of the at least one channel having the largest self value, and

if no then end the touch detection frame as completed.

4. The method according to claim 3, further comprising the steps of:

determining a next slope value, wherein the next slope value is equal to a current mutual value minus a next mutual value of a next node; and

determining a previous slope value, wherein the previous slope value is equal to the current mutual value minus a previous mutual value of a previous node.

5. The method according to claim 4, further comprising the steps of:

determining if the next slope value is less than zero (0) and the previous slope value is greater than zero (0), wherein

when yes then begin the step of validating the node, and

when no then continue to next step;

determining if the next slope value is greater than zero (0) and less than a percentage of the previous slope value, wherein

when yes then begin the step of validating the node, and

when no then continue to next step;

determining if the next slope value is less than zero (0) and greater than the previous slope value, wherein

when yes then begin the step of validating the node, and

when no then continue to next step;

determining if there is another mutual value, wherein

when yes then return to the step of determining if at least one of the mutual values is greater than the mutual touch threshold, and

when no then continue to the next step; and

determining if there is another self-value, wherein

when yes then examine another self-value and return to the step of determining if at least one of the self-values is greater than a self-touch threshold, and

when no then end the touch detection frame as completed.

6. The method according to claim 5, wherein the nodes are arranged in a matrix extending from east to west on a X-axis and from north to south on a Y-axis and wherein the step of validating the node comprises the steps of:

identifying the node having a local maximum mutual value as a current node;

determining if there is a valid node north of the current node, wherein

when no then continue to the step of determining if there is a valid node south of the current node, and

when yes then perform a mutual measurement on the north node and continue to the next step;

determining if the north node is greater than the current node,

when yes then make the north node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node south of the current node, wherein

when no then continue to the step of determining if there is a valid node east of the current node, and

when yes then perform a mutual measurement on the south node and continue to the next step;

determining if the south node is greater than the current node, wherein

when yes then make the south node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node east of the current node, wherein

when no then continue to the step of determining if there is a valid node west of the current node, and

when yes then perform a mutual measurement on the east node and continue to the next step;

determining if the east node is greater than the current node,

when yes then make the east node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node west of the current node, wherein

when no then continue to the step of determining if there is a valid node left of the current node, and

when yes then perform a mutual measurement on the west node and continue to the next step;

determining if the west node is greater than the current node,

when yes then make the west node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node left of the current node, wherein

when no then define a left mutual value as a center mutual value minus a right mutual value and continue to the step of determining a fine position for the node, and

when yes then perform a mutual measurement on the left node and continue to the next step;

determining if there is a valid node right of the current node, wherein

when no then define the mutual value as the center mutual value minus the left mutual value and continue to the step of determining the fine position for the node, and

when if yes then perform a mutual measurement on the right node and continue to the next step;

defining a fine position of the node by subtracting the left value from the right value, dividing this difference by the center value and multiplying the result thereof by 64 and continue to the next step; and

determining whether interpolation was performed for each axis, wherein

when yes, then add another touch point to a list of all detected touch points and return to the step of determining if there are additional mutual values, and

when no, then interpolate another axis by using left and right nodes of the other axis for starting again at the step of determining if there is a valid node left of the current node.

7. A system for determining gesturing motions and forces thereof on a touch sensing surface having a visual display, said system comprising:

a first plurality of electrodes arranged in a parallel orientation having a first axis, wherein each of the first plurality of electrodes comprises a self-capacitance;

a second plurality of electrodes arranged in a parallel orientation having a second axis substantially perpendicular to the first axis, the first plurality of electrodes are located over the second plurality of electrodes and form a plurality of nodes comprising overlapping intersections of the first and second plurality of electrodes, wherein each of the plurality of nodes comprises a mutual capacitance;

a flexible electrically conductive cover over the first plurality of electrodes, wherein a face of the flexible electrically conductive cover forms the touch sensing surface;

a plurality of deformable spacers between the flexible electrically conductive cover and the first plurality of electrodes, wherein the plurality of deformable spacers maintains a distance between the flexible electrically conductive cover and the first plurality of electrodes;

a digital processor and memory, wherein digital outputs of the digital processor are coupled to the first and second plurality of electrodes;

an analog front end coupled to the first and second plurality of electrodes;

an analog-to-digital converter (ADC) having at least one digital output coupled to the digital processor;

wherein

values of the self-capacitances are measured for each of the first plurality of electrodes by the analog front end,

the values of the measured self-capacitances are stored in the memory,

the digital processor is configured to determine for each measured self-capacitance value of each of the first plurality of electrodes left and right slope values for the at least one self-value, wherein;

the left slope value is equal to the at least one self-value minus a self-value of a electrode to the left, and

the right slope value is equal to the at least one self-value minus a self-value of a electrode to the right;

the digital processor is further configured;

to determine from the measured self-capacitance values local maximum self-capacitance values when the left slope value is greater than zero (0) and the right slope value is less than zero (0),

or a ration between a positive left slope value and a positive right slope value is greater than a predefined threshold or when a ratio between a negative left slope value and a negative right slope value is less than a predefined threshold;

to control the analog front end to measure values of the mutual capacitances of the nodes of at least one of the first electrodes having at least one local maximum self-capacitance values of the largest values,

to store the values of the measured mutual capacitances in the memory; and

the digital processor uses the stored self and mutual capacitance values for determining a gesturing motion and at least one force associated therewith applied to the touch sensing surface.

8. The system according to claim 7, wherein the digital processor, memory, analog front end and ADC are provided by a digital device.

9. The system according to claim 8, wherein the digital device comprises a microcontroller.

10. The system according to claim 7, wherein the flexible electrically conductive cover comprises a flexible metal substrate.

11. The system according to claim 7, wherein the flexible electrically conductive cover comprises a flexible non-metal substrate and an electrically conductive coating on a surface thereof.

12. The system according to claim 7, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Indium Tin Oxide (ITO) on a surface of the flexible substrate.

13. The system according to claim 7, wherein the flexible electrically conductive cover comprises a substantially light transmissive flexible substrate and a coating of Antimony Tin Oxide (ATO) on a surface of the flexible substrate.

14. A system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein the system is configured to select an object shown in the visual display when the object is touched with a first force.

15. The system according to claim 14, wherein the system is configured to lock the object in place when the object is touched with a second force.

16. The system according to claim 15, wherein the system is configured to release the lock on the object when the object is touched with a third force and the touch is moved in a direction across the touch sensing surface.

17. The system according to claim 15, wherein the system is configured to release the lock on the object when the touch at a first force to the object is removed and thereafter the object is touched again at a second force.

18. The system according to claim 17, wherein the second force is greater than the first force.

19. A system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein

when a right portion of an object shown in the visual display is touched with a first force;

and a left portion of the object is touched with a second force;

and when the first force is greater than the second force the system is configured to rotate the object in a first direction, and when the second force is greater than the first force to rotate the object in a second direction.

20. The system according to claim 19, wherein the first direction is clockwise and the second direction is counter-clockwise.

21. The system according to claim 19, wherein when the touch at the left portion of the object moves toward the right portion of the object, the system is configured to rotate the object in a third direction, and when the touch at the right portion of the object moves toward the left portion of the object, the system is configured to rotate the object in a fourth direction.

22. The system according to claim 21, wherein the first and second directions are substantially perpendicular to the third and fourth directions.

23. A system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein the system is configured to change a size of an object shown in the visual display when a portion of the object is touched with a force, wherein the greater the force the large the size of the object becomes.

24. The system according to claim 23, wherein the size of the object is fixed when the touch and the force are moved off of the object.

25. The system according to claim 23, wherein the size of the object varies in proportion to the amount of force applied to the object.

26. A system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein the system is configured to handle pages of a document shown in the visual display when a portion of the document is touched with a force sufficient to flip through the pages.

27. The system according to claim 26, wherein the system is configured to remove a currently visible page when the touch at the currently visible page is moved in a first direction parallel with the touch sensing surface.

28. The system according to claim 27, wherein the system is configured to insert the removed page into a new document when the removed page is touched with the force near the new document.

29. A method system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein the system is configured to values of an alpha-numeric character shown in the visual display when the alpha-numeric character is touched with different forces, wherein a first force will cause the alpha-numeric character to increment and a second force will cause the alpha-numeric character to decrement.

30. The system according to claim 29, wherein the value of the alphanumeric character is locked when the touch is moved off of the alpha-numeric character and parallel to the touch sensing surface.

31. A system according to claim 7 for determining the gesturing motion and the at least one force associated therewith, wherein the system is configured to increment a value of an alpha-numeric character shown in the visual display when an upper portion of the alpha-numeric character is touched with a force;

and

to decrement the value of the alpha-numeric character by touching when a lower portion of the alpha-numeric character is touched with the force.

32. The system according to claim 31, wherein the value of the alphanumeric character is locked when the touch is moved off of the alpha-numeric character and parallel to the touch sensing surface.

33. The system according to claim 31, wherein a speed of incrementing or decrementing the value of the alpha-numeric character is proportional to a magnitude of the force applied to upper portion or lower portion, respectively, of the alpha-numeric character.

34. The system according to claim 29, wherein the alpha-numeric character is a number.

35. The system according to claim 29, wherein the alpha-numeric character is a letter of an alphabet.

36. A method for decoding multiple touches and forces thereof on a touch sensing surface comprising electrodes arranged in a matrix extending from east to west on an X-axis and from north to south on a Y-axis, said method comprising the steps of:

scanning a plurality of channels aligned on the X-axis for determining self-capacitance values of each of the plurality of channels;

comparing the self-capacitance values to determine which one of the channels has a local maximum self-capacitance value, wherein a self-capacitance value is only compared when the self-capacitance value is greater than a self-touch threshold,

scanning a plurality of nodes of each channel for which a local maximum self-capacitance value has been determined for determining mutual values of the nodes comparing the mutual values to determine which one of the nodes has the largest mutual capacitance value, wherein the node having the largest mutual capacitance value on a local maximum self-capacitance value channel is a potential touch location, wherein for each channel only mutual values that are greater than a mutual touch threshold are considered, wherein the nodes are formed by electrodes of the X-axis and electrodes of the Y-axis;

wherein for each considered mutual value of a channel a next slope value and a previous slope value are determined, wherein the next slope value is equal to a current mutual value minus a next mutual value of a next node, and wherein the previous slope value is equal to the current mutual value minus a previous mutual value of a previous node;

determining if the next slope value is less than zero (0) and the previous slope value is greater than zero (0), wherein

when yes then begin a step of validating the node, and

when no then continue to the next step;

determining if the next slope value is greater than zero (0) and less than a percentage of the previous slope value, wherein

when yes then begin the step of validating the node, and

when no then continue to the next step;

determining if the next slope value is less than zero (0) and greater than the previous slope value, wherein

when yes then begin the step of validating the node, and

when no then continue to the next step;

determining if there is another mutual value, wherein

when yes then return to the step of determining if at least one of the mutual values is greater than the mutual touch threshold, and

when no then continue scanning and comparing for a next channel

until a touch detection frame is completed;

wherein the step of validating a node comprises the steps of;

identifying the node having a local maximum mutual value as a current node;

determining if there is a valid node north of the current node, wherein

when no then continue to the step of determining if there is a valid node south of the current node, and

when yes then perform a mutual measurement on the north node and continue to the next step;

determining if the north node is greater than the current node,

when yes then make the north node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step determining if there is a valid node south of the current node, wherein

when no then continue to the step of determining if there is a valid node east of the current node, and

when yes then perform a mutual measurement on the south node and continue to the next step;

determining if the south node is greater than the current node, wherein

when yes then make the south node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node east of the current node, wherein

when no then continue to the step of determining if there is a valid node west of the current node, and

when yes then perform a mutual measurement on the east node and continue to the next step;

determining if the east node is greater than the current node,

when yes then make the east node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node west of the current node, wherein

when no then continue to the step of determining if there is a valid node left of the current node, and

when yes then perform a mutual measurement on the west node and continue to the next step;

determining if the west node is greater than the current node,

when yes then make the west node the current node and continue to the step of determining whether a touch point already exists at this node, and

when no then continue to the next step;

determining if there is a valid node left of the current node, wherein

when no then define a left mutual value as a center mutual value minus a right mutual value and continue to the step of determining a fine position for the node, and

when yes then perform a mutual measurement on the left node and continue to the next step;

determining if there is a valid node right of the current node, wherein

when no then define the mutual value as the center mutual value minus the left mutual value and continue to the step of determining the fine position for the node, and

when yes then perform a mutual measurement on the right node and continue to the next step;

defining a fine position of the node by subtracting the left value from the right value, dividing this difference by the center value and multiplying the result thereof by 64 and continue to the next step; and

determining whether interpolation was performed for each axis, wherein

when yes, then add another touch point to a list of all detected touch points and return to the step of determining if there are additional mutual values, and

when no, then interpolate another axis by using left and right nodes of the other axis for starting again at the step of determining if there is a valid node left of the current node; and

determining a force at the potential touch location from a change in the mutual capacitance values of the node at the potential touch location during no touch and during a touch thereto.