Multi-Touch Tracking

• US 20100097342A1
• Filed: 10/21/2008
• Published: 04/22/2010
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Simmons, Martin, Pickett, David
• Granted Patent: US 8,866,790 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• 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 2203/04808 Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• 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
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

A method of tracking multiple touches over time on a touch sensor, for example a capacitive touch screen. The method analyses first and second touch data sets from adjacent first and second time frames. First, the touch data sets are analyzed to determine the closest touch in the second time frame to each of the touches in the first time frame, and calculating the separation between each such pair of touches. Then, starting with the pair of touches having the smallest separation, each pair is validated until a pairing is attempted between touches for which the touch in the second time frame has already been paired. At this point, the as-yet unpaired touches from the first and second touch data sets are re-processed by re-applying the computations but only including the as-yet unpaired touches. This re-processing is iterated until no further pairings need to be made. The method avoids complex algebra and floating point operations, and has little memory requirement. As such it is ideally suited to implementation on a microcontroller.

Claims

1. A method of tracking multiple touches over time, wherein a touch data set is provided for each time frame, each touch data set in general comprising a plurality of touch coordinates, and each touch coordinate defining a touch, the method comprising:

a) providing first and second touch data sets for first and second time frames;

b) determining the closest touch in the second time frame to each of the touches in the first time frame, and calculating the separation between each such pair of touches;

c) starting with the pair of touches having the smallest separation, validating each pair until a pairing is attempted between touches for which the touch in the second time frame has already been paired;

d) whereupon the as-yet unpaired touches from the first and second touch data sets are re-processed by re-applying steps b) and c) if necessary a plurality of times.

2. The method of claim 1, wherein pairings are not validated if the distance between provisionally paired touches exceeds a threshold distance.

3. The method of claim 2, wherein, if the pair of touches having the smallest separation are separated by more than the threshold distance, then no more pairings are sought between touches in the first and second touch data sets.

4. A device for processing touch data to track multiple touches over time between successive time frames, wherein the device is configured to perform the method of claim 1.

5. The device of claim 4, wherein the device comprises a microcontroller.

6. The device of claim 4, wherein the device comprises memory and the method of claim 1 is embodied in a computer program stored in the memory of the device.

7. The device of claim 4, further comprising an output port, wherein the device is configured to output data to the output port, wherein the data comprises touch co-ordinates ordered in, or tagged by, tracked touches obtained by the method of claim 1.