Method for detecting an arbitrary number of touches from a multi-touch device

• US 9,092,089 B2
• Filed: 09/15/2010
• Issued: 07/28/2015
• Est. Priority Date: 09/15/2010
• Status: Active Grant

• Current Assignee: Advanced Silicon SA
• Original Assignee: Advanced Silicon SA
• Inventors: Vuadens, Francois, Chappatte, Norman, Weishaupt, Andreas
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): BIBBEE, CHAYCE R
• Application Number:
  US12/882,715
• Publication Number:
  US 20120062474A1
• Time in Patent Office: 1,777 Days
• Field of Search: 345/173
• 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 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 3/04166 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

A method for detecting an arbitrary number of touches from an input image of a multi-touch device comprising the following steps:

• • processing said input image and obtaining a processed image;
  • segmentation by thresholding of said processed image (8000) and obtaining a segmented image;
  • identifying regions of the segmented image;
  • finding local maxima, each local maximum being of size one pixel on a sub-region inside each region;
  • determining at least one touch position based on said local maxima.

Claims

1. A method for detecting an arbitrary number of touches from an input image delivered by a multi-touch device, said method comprising the following steps:

processing at a processing device said input image and obtaining a processed image;

segmentation at the processing device by thresholding of said processed image and obtaining a segmented image;

identifying at the processing device regions of the segmented image;

finding local maxima at the processing device, each local maximum being of size one pixel and belonging to a sub-region of size N×

N pixels, wherein N is an odd integer number;

wherein said finding comprises a plurality of iterations where at each iteration;

a said sub-region is defined, said sub-region being centered on one pixel of a region, said pixel being changed at each iteration;

verifying whether the pixels inside said sub-region, other than the pixel in the center of said sub-region, have a value lower than the value of said pixel in the center of said sub-region;

if the previous step is verified, identifying said pixel in the center of said sub-region as a local maximum of size one pixel;

discarding at the processing device some regions according to predetermined conditions;

determining at the processing device at least one touch position based on said local maxima by computing a geometric center of each region that remains after said discarding, wherein said computing takes into account all the pixels of a region if said region contains one local maximum of size one pixel, and wherein said computing further takes into account only the pixels inside the sub-regions centered in each local maximum of a region if said region contains more than one local maxima of size one pixel.

2. The method claim 1, wherein N is equal to three.

3. The method of claim 1, wherein said region is a group of connected pixels.

4. The method of claim 1, wherein said processing comprises filtering said input image.

5. The method of claim 1, wherein said predetermined conditions are based on the area, the square shapedness factor of said regions and/or the number of the local maxima of size one pixel found in each region.

6. The method of claim 1, comprising a calibration step for obtaining a baseline image.

7. The method of claim 6, comprising subtracting said input image with said baseline image, obtaining a signed image and finding false touches.

8. The method of claim 4, wherein said filtering comprises a first gray level image filtering.

9. The method of claim 8, wherein said first gray level image filtering comprises a smoother.

10. The method of claim 4, wherein said filtering further comprising a time-domain filtering of said input image.

11. The method of claim 4, wherein said filtering further comprising a first gray level image filtering.

12. The method of claim 4, wherein said filtering further comprising a binary image filtering.

13. The method of claim 12, wherein said binary image filtering comprises a binary morphological filter.

14. The method of claim 1, wherein said identifying regions comprising region labelling and the analysis of said regions.

15. The method of claim 1 further comprising the following steps:

creating trajectories based on said touches positions;

for each trajectory, assigning a status bit identifying each trajectory as assigned or not assigned;

solving a linear assignment problem of each labeled trajectory;

solving a linear assignment problem of each unlabeled trajectory and updating the labeled trajectories; and

filtering said updated labeled trajectories.

16. The method of claim 15, wherein creating a trajectory for each of said touches positions comprising computing a distance matrix.

17. The method of claim 16, wherein creating a trajectory for each of said touches positions comprising computing a likelihood matrix, taking into account the followings parameters:

position, velocity module, change in direction, and change in intensity.

18. The method of claim 17, comprising updating said parameters based on said filtering.

19. The method of claim 1, further comprising:

a preliminary analysis for detecting a gesture or a simple gesture;

outputting the coordinates of a relative motion vector if there is not detection of a gesture;

outputting a simple gesture signal if there is detection of a simple gesture; and

performing comparison against reference gestures if there is a gesture and there is not a simple gesture.

20. A non-transitory, tangible computer readable medium having instructions executable by a processor for performing the method of claim 1 when said instructions are executed.

21. A multi-touch equipment for a multi-touch device comprising:

processing means for processing an input image output by a multi-touch device, and for obtaining a processed image;

segmentation means for thresholding of said processed image and obtaining a segmented image;

identifying means for identifying regions of the segmented image;

computation means for finding local maxima, each local maximum being of size one pixel and belonging to a sub-region;

wherein said finding comprises a plurality of iterations where at each iteration;

a said sub-region is defined, said sub-region being centered on one pixel of a region, said pixel being changed at each iteration;

verifying whether the pixels inside said sub-region, other than the pixel in the center of said sub-region, have a value lower than the value of said pixel in the center of said sub-region;

if the previous step is verified, identifying said pixel in the center of said sub-region as a local maximum of size one pixel;

said computation means discarding some regions according to predetermined conditions;

determination means for determining one or a plurality of touch positions based on said local maxima by computing a geometric center of each region that remains after said discarding, wherein said computing takes into account all the pixels of a region if said region contains one local maximum of size one pixel, and wherein said computing further takes into account only the pixels inside the sub-regions centered in each local maximum of a region if said region contains more than one local maxima of size one pixel.