Touchscreen panel signal processing

• US 10,289,247 B2
• Filed: 02/01/2017
• Issued: 05/14/2019
• Est. Priority Date: 02/05/2016
• Status: Active Grant

• Current Assignee: Cambridge Touch Technologies, Ltd.
• Original Assignee: Cambridge Touch Technologies, Ltd.
• Inventors: Nathan, Arokia, Lai, Jackson, Gao, Shuo
• Primary Examiner(s): Balaoing, Ariel A
• Application Number:
  US15/421,648
• Publication Number:
  US 20170228096A1
• Time in Patent Office: 832 Days
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 3/041661 using detection at multiple resolutions, e.g. coarse and fine scanning; using detection within a limited area, e.g. object tracking window
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

A method for processing signals from a touchscreen panel includes obtaining a partial frame by sampling parts of a frame from a touch panel which comprises an array of sensor areas (step S1). The method also includes generating, based on the partial frame, a new frame which comprises estimates of the un-sampled parts (step S2). The method also includes determining whether at least one touch event is present in the new frame (step S3), and upon a positive determination, for each touch event, determining a location of the touch event in the new frame and obtaining a sub-frame by sampling a region of a subsequent frame from the touch panel frame at and around the location (step S4). The method also includes outputting touch information based on one or more sub-frames (step S7).

Claims

1. A method comprising:

obtaining a partial frame by sampling parts of a frame from a touch panel which comprises an array of sensor areas;

generating, based on the partial frame, a new frame which comprises estimates corresponding to parts of the frame from the touch panel which were not sampled in the partial frame;

determining whether at least one touch event is present in the new frame; and

upon a positive determination; and

,

for each touch event;

determining a location of the touch event in the new frame;

obtaining a sub-frame by sampling a region of a subsequent frame from the touch panel frame at and around the location; and

,

outputting touch information based on one or more sub-frames.

2. A method according to claim 1, wherein the partial frame is obtained by sampling some of the sensor areas which are selected at random based on a sampling fraction.

3. A method according to claim 2, wherein rows and columns of the array are selected at random based on the sampling fraction and wherein the sampled sensor areas correspond to intersections of the selected rows and columns.

4. A method according to claim 2, wherein the size of a region for obtaining each sub-frame is dependent on the sampling fraction.

5. A method according to claim 1, wherein the partial frame is obtained by sampling a predetermined pattern of sensor areas which is selected in dependence upon a sampling fraction.

6. A method according to claim 5, wherein the size of a region for obtaining each sub-frame is dependent on the sampling fraction.

7. A method according to claim 1, further comprising, for each touch event:

determining a second location based on the sub-frame;

determining if a difference between the location and the second location exceeds a threshold amount; and

,

upon a positive determination, obtaining an additional sub-frame by sampling a region of a subsequent frame from the touch panel frame at and around the second location;

wherein the touch information is based on one or more sub-frames and any additional sub-frames.

8. A method according to claim 1, further comprising, for each touch event:

obtaining one or more additional sub-frames by sampling a region of a subsequent frame from the touch panel frame at and around the location; and

,

generating an averaged sub-frame by averaging the sub-frame and the additional sub-frame(s);

wherein the touch information is based on one or more averaged sub-frames.

9. A method according to claim 1, further comprising:

generating a corrected partial frame by subtracting a reference partial frame from the partial frame; and

upon a negative determination of the presence of one or more touch events;

generating a new reference partial frame based on exponential smoothing of the reference partial frame and the partial frame using a weighting factor; and

storing the new reference partial frame;

wherein the new frame is generated using the corrected partial frame.

10. A method according to claim 1, wherein the new frame is generated by:

generating an intermediate frame and setting a value stored for each location of the intermediate frame according to;

in dependence upon the location is a sampled location, a corresponding value is inserted from the partial frame;

in dependence upon the location is a location which was not sampled in the partial frame, a corresponding value is set to zero; and

,

generating the new frame by filtering the intermediate frame using a spatial low-pass filter having a bandwidth.

11. A method according to claim 10, further comprising:

setting the bandwidth of the spatial low-pass filter in dependence upon the sampling fraction.

12. A method according to claim 1, wherein the new frame is generated by applying a compressive sensing algorithm to the partial frame.

13. A method according to claim 12, further comprising:

filtering the new frame using a spatial low-pass filter having a bandwidth before determining the presence of one or more touch events in dependence thereupon.

14. A method according to claim 1, wherein each sensor area of the touch panel measures capacitance.

15. A method according to claim 1, wherein each sensor area of the touch panel measures force applied proximate to that sensor area.

16. A method according to claim 1, wherein each sensor area of the touch panel measures capacitance and force applied proximate to that sensor area.

17. A method according to claim 1, further comprising sampling some sensor areas from a touch panel which comprises an array of sensor areas.

18. A computer program product stored on a non-transitory computer readable medium which, when executed by a data processing unit, causes the data processing unit to execute the operations of:

obtaining a partial frame by sampling parts of a frame from a touch panel which comprises an array of sensor areas;

generating, based on the partial frame, a new frame which comprises estimates corresponding to parts of the frame from the touch panel which were not sampled in the partial frame;

determining whether at least one touch event is present in the new frame; and

upon a positive determination; and

,

for each touch event;

determining a location of the touch event in the new frame;

obtaining a sub-frame by sampling a region of a subsequent frame from the touch panel frame at and around the location; and

,

outputting touch information based on one or more sub-frames.

19. Apparatus comprising:

a touch panel which comprises a plurality of sensor areas disposed in an array, each sensor area configured to provide an output signal which varies in response to a touch;

a frame acquisition module configured to obtain a partial frame by sampling parts of a frame from the touch panel;

a signal reconstruction module configured to generate, based on the partial frame, a new frame which comprises estimates corresponding to parts of the frame from the touch panel which were not sampled in the partial frame;

a touch decision module configured to determine whether at least one touch event is present in the new frame and to determine a location for each touch event so determined;

a sub-frame acquisition module configured to, for each touch event determined by the touch decision module, obtain a regional sub-frame by sampling a region of a subsequent frame from the touch panel frame at and around the location; and

,

a communications module configured to output touch information based on one or more regional sub-frames.