Touch systems and methods including rejection of unintentional touch signals
A touch sensor can be used with a finger and/or a pen configured to provide a touch input to the touch sensor. Some implementations involve touch capacitive touch sensing, although many implementations are also applicable to other touch and pen technologies, such as resistive, surface acoustic wave, bending wave, touch force, electromagnetic (E-M). Discrimination between intentional touches and unintentional touches on the touch surface can be performed using first criteria. For each touch identified as an intentional touch, discrimination between a finger touch and a pen touch can be performed using second criteria.
1. A method of determining a touch location on a touch surface of a touch panel comprising a matrix of intersecting electrodes with nodes at intersections of the electrodes, the method comprising:
discriminating between one or more intentional touches and one or more unintentional touches on the touch surface using first criteria; and
for each touch identified as an intentional touch, discriminating between a finger touch and a pen touch using second criteria, wherein discriminating between the finger touch and the pen test comprises identifying the touch as a pen touch if a distance between a touch and a profile of a previously identified intentional or unintentional touch is greater than a distance threshold.
2. The method of claim 1 , wherein the intentional touches comprise multiple temporally overlapping touches.
3. The method of claim 1 , wherein discriminating between the intentional and unintentional touches using the first criteria comprises identifying a touch as an unintentional touch based on at least one of:
a size of a profile of the touch on the touch surface;
a number of peaks within the profile; and
a distance between a peak of the profile and nodes of the profile.
4. The method of claim 1 , wherein discriminating between the pen touch and the finger touch using the second criteria comprises:
determining a slope of a profile of a touch on the touch surface;
identifying the touch as a finger touch if the slope is greater than a slope threshold; and
identifying the touch as a potential pen touch if the slope is less than the slope threshold.
5. The method of claim 1 , wherein discriminating between the finger touch and the pen touch comprises identifying the touch as a pen touch if nodes within the predetermined radius of a profile of the touch have signal values less than an ambient threshold.
6. A method of determining a touch location on a touch surface of a touch panel comprising a matric of intersecting electrodes with nodes at intersections of the electrodes, the method comprising:
discriminating between one or more intentional touches and one or more unintentional touches on the touch surface using first criteria;
for each touch identified as an intentional touch, discriminating between a finger touch and a pen touch using second criteria; and
re-identifying the pen touch as a finger touch if the pen touch was previously identified as a finger touch.
7. The method of claim 1 , wherein discriminating between the intentional and the unintentional touch comprises:
determining a profile of a touch on the touch surface; and
identifying the touch as an unintentional touch based on one or more of:
a size of the profile;
a number of peaks within the profile; and
a distance between a peak of the profile and nodes of the profile.
8. A touch sensor, comprising:
a touch panel having a touch surface and a matrix of electrodes with nodes at intersections of the electrodes; and
a touch controller configured to
discriminate between one or more intentional touches and one or more unintentional touches on the touch surface using first criteria; and
for each touch identified as an intentional touch, discriminate between a finger touch and a pen touch using second criteria, wherein the controller is configured to re-identify the pen touch as a finger touch if the pen touch was previously identified as a finger touch.
9. The touch sensor of claim 8 , wherein the intentional touches comprise multiple temporally overlapping touches.
10. The touch sensor of claim 8 , wherein the controller discriminates between the intentional and unintentional touches using the first criteria by identifying a touch as an unintentional touch based on at least one of:
a size of a profile of the touch on the touch surface;
a number of peaks within the profile; and
a distance between a peak of the profile and nodes of the profile.
11. The touch sensor of claim 8 , wherein the controller discriminates between the pen touch and the finger touch using the second criteria by:
determining a slope of a profile of a touch on the touch surface;
identifying the touch as a finger touch if the slope is greater than a slope threshold; and
identifying the touch as a potential pen touch if the slope is less than the slope threshold.
12. A touch sensor comprising:
a touch panel having a touch surface and a matrix of electrodes with nodes at intersections of the electrodes; and
a touch controller configured to:
discriminate between one or more intentional touches and one or more unintentional touches on the touch surface using first criteria; and
for each touch identified as an intentional touch, discriminate between a finger touch and a pen touch using second criteria, wherein the controller discriminates between the finger touch and the pen touch by identifying the touch as a pen touch if a distance between a touch and a profile of a previously identified intentional or unintentional touch is greater than a distance threshold.
13. The touch sensor of claim 8 , wherein controller is configured to discriminate between the finger touch and the pen touch by identifying the touch as a pen touch if nodes within the predetermined radius of a profile of the touch have signal values less than an ambient threshold.
14. The touch sensor of claim 8 , wherein the controller is configured to discriminate between the intentional and the unintentional touch by:
determining a profile of a touch on the touch surface; and
identifying the touch as an unintentional touch based on one or more of:
a size of the profile;
a number of peaks within the profile; and
a distance between a peak of the profile and nodes of the profile.