Touchscreen panel signal processing
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 S 1 ). The method also includes generating, based on the partial frame, a new frame which comprises estimates of the un-sampled parts (step S 2 ). The method also includes determining whether at least one touch event is present in the new frame (step S 3 ), 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 S 4 ). The method also includes outputting touch information based on one or more sub-frames (step S 7 ).
1. A method of processing output signals from a touch panel having a full resolution, the method comprising:
obtaining a partial frame having a resolution less than a full resolution of the touch panel;
reconstructing, based on the partial frame, a new frame having the full resolution;
and for each of one or more touch events detected in the new frame;
determining a first location based on the new frame;
determining a second location based on a sub-frame obtained at and around the first location; and,
outputting one or more second locations.
2. The method according to claim 1 , wherein the touch panel comprises an array of sensor areas and the partial frame is obtained by sampling a sampling fraction of the sensor areas selected at random.
3. The 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. The method according to claim 2 , wherein the size of each sub-frame is dependent on the sampling fraction.
5. The method according to claim 1 , wherein the touch panel composes an array of sensor areas and the partial frame is obtained by sampling a sampling fraction of the sensor areas corresponding to a predetermined pattern.
6. The method according to claim 5 , wherein the size of each sub-frame is dependent on the sampling fraction.
7. The method according to claim 1 , further comprising, for each touch event, in response to a difference between the first location and the second location exceeds a threshold amount, refining or confirming the second location based on the second location and a third location determined based on an additional sub-frame obtained at and around the second location.
8. The method according to claim 1 , wherein determining the second location is based on an average of the sub-frame and one or more additional sub-frames, each additional sub-frame obtained at and around the first location.
9. The method according to claim 1 , further comprising:
generating a corrected partial frame by subtracting a reference partial frame from the partial frame, wherein the new frame is reconstructed using the corrected partial frame;
and in response to detecting no touch events in the new frame;
generating a new reference partial frame based on exponential smoothing of the reference partial frame and the partial frame; and
storing the new reference partial frame.
10. The method according to claim 1 , wherein the new frame is reconstructed by:
generating, using a zero-insertion process based on the partial frame, an intermediate frame having the full resolution;
generating the new frame by filtering the intermediate frame using a spatial low-pass filter having a bandwidth.
11. The method according to claim 10 , wherein the bandwidth of the spatial low-pass filter depends on the sampling fraction.
12. The method according to claim 1 , wherein the new frame is reconstructed by applying a compressive sensing algorithm to the partial frame.
13. The method according to claim 12 , further comprising filtering the new frame using a spatial low-pass filter having a bandwidth before detecting one or more touch events in the new frame.
14. The method according to claim 1 , wherein the touch panel comprises an array of sensor areas and each sensor area measures capacitance.
15. The method according to claim 1 , wherein the touch panel comprises an array of sensor areas and each sensor area measures force applied proximate to that sensor area.
16. The method according to claim 1 , wherein the touch panel comprises an array of sensor areas and each sensor measures capacitance and force applied proximate to that sensor area.
17. An apparatus comprising:
a touch panel having a full resolution, the touch panel comprising 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 having a resolution less than a full resolution of the touch panel;
a signal reconstruction module configured to reconstruct, based on the partial frame, a new frame having the full resolution;
a touch decision module configured, for each of one or more touch events detected in the new frame, to determine a first location based on the new frame;
a sub-frame acquisition module configured to, for each touch event detected by the touch decision module, determine a second location based on a sub-frame obtained at and around the first location; and,
a communications module configured to output one or second locations.