Multi-touch input discrimination

• US 8,243,041 B2
• Filed: 01/18/2012
• Issued: 08/14/2012
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Westerman, Wayne Carl
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): MARINELLI, PATRICK
• Application Number:
  US13/353,273
• Publication Number:
  US 20120113041A1
• Time in Patent Office: 209 Days
• Field of Search: 345156-173, 178 1801- 2004, 382/172, 382/312, 382/191, 382/181, 382/203, 382/210
• US Class Current: 345/173
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• 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 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• 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 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• 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: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06V 40/107 Static hand or arm
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

Techniques for identifying and discriminating between different types of contacts to a multi-touch touch-screen device are described. Illustrative contact types include fingertips, thumbs, palms and cheeks. By way of example, thumb contacts may be distinguished from fingertip contacts using a patch eccentricity parameter. In addition, by non-linearly deemphasizing pixels in a touch-surface image, a reliable means of distinguishing between large objects (e.g., palms) from smaller objects (e.g., fingertips, thumbs and a stylus) is described.

Claims

1. A method to discriminate input sources to a touch-surface device, comprising:

obtaining a proximity image;

segmenting the proximity image to identify a plurality of patches;

dampening the value of peripheral patch pixels to obtain damped peripheral patch pixel values;

reducing the value of each pixel, including the damped peripheral patch pixel values, in a non-linear fashion to obtain reduced patch pixel values;

determining an eccentricity value for each of the reduced patch pixel values of the plurality of patches;

determining a minor radius value for each of the reduced patch pixel values of the plurality of patches;

ignoring each patch having a minor radius value greater than a first threshold;

identifying a first patch as a thumb contact if the eccentricity value of the first patch is greater than a second threshold; and

using the identified patch to control an operation of a touch-surface device.

2. The method of claim 1, further comprising identifying a second patch as a fingertip contact if the eccentricity value of the second patch is less than the second threshold.

3. The method of claim 2, further comprising identifying the first and second patches as contacts from a right hand if the second patch is detected to the right of the first patch.

4. The method of claim 2, further comprising identifying the first and second patches as contacts from a left hand if the second patch is detected to the left of the first patch.

5. The method of claim 1, wherein the eccentricity value of a patch is determined by taking a ratio of a major radius value of the patch and a minor radius value of the patch.

6. The method of claim 1, wherein the second threshold comprises a constant value.

7. The method of claim 1, wherein the act of ignoring is performed before the acts of identifying.

8. The method of claim 7, wherein the first threshold comprises a constant value.

9. The method of claim 7, wherein the first threshold comprises a linear function.

10. The method of claim 1, wherein the act of using comprises changing an operational mode of the touch-surface device.

11. A method of reducing noise in a multi-touch touch-surface device operations, comprising:

obtaining a proximity image from a multi-touch touch-surface, the proximity image having a plurality of pixels, each pixel having a value;

segmenting the proximity image to identify one or more patches, each patch comprising a plurality of patch pixels;

reducing the value of peripheral patch pixels to obtain damped peripheral patch pixel values;

further reducing the value of each pixel, including the damped peripheral patch pixel values, in a non-linear fashion; and

using the further reduced pixel values to parameterize the patch.

12. The method of claim 11 further comprising:

determining a minor radius value for the one or more patches;

identifying a first patch as a palm contact if the minor radius of the first patch is greater than a specified threshold; and

using the identified patch to control an operation of a touch-surface device.

13. The method of claim 12, wherein the specified threshold comprises a constant value.

14. The method of claim 11, wherein the act of further reducing comprises reducing the value of a pixel to the square-root of the value of the pixel.

15. The method of claim 11, further comprising determining a centroid value for one or more patches, wherein the act of determining the centroid value uses pixel values that have not been further reduced in a non-linear fashion.

16. The method of claim 12, wherein the act of using comprises changing an operational mode of the touch-surface device.

17. A method of reducing noise in a multi-touch surface device operation comprising:

obtaining a proximity image from a multi-touch touch-surface, the proximity image having a plurality of pixels, each pixel having a value;

smoothing the values of the plurality of pixels to obtain smoothed pixel values;

segmenting the proximity image using the smoothed pixel values to obtain one or more patches, each patch comprising a plurality of patch pixels;

dampening the plurality of patch pixels of the one or more patches for pixels around a periphery of the one or more patches to provide damped periphery patch pixel values;

reducing the value of each pixel, including the damped peripheral patch pixel values, in a non-linear fashion;

using the reduced pixel values to parameterize the one or more patches.

18. The method of claim 17 further comprising:

determining a minor radius value for the one or more patches;

identifying a first patch as a palm contact if the minor radius of the first patch is greater than a specified threshold; and

using the identified patch to control an operation of a touch-surface device.

19. The method of claim 18, wherein the specified threshold comprises a constant value.

20. The method of claim 17, wherein the act of reducing comprises reducing the value of a pixel to the square-root of the value of the pixel.

21. The method of claim 17, further comprising determining a centroid value for one or more patches, wherein the act of determining the centroid value uses pixel values that have not been reduced in a non-linear fashion.

22. The method of claim 18, wherein the act of using comprises changing an operational mode of the touch-surface device.

23. The method of claim 17 further comprising:

constraining the values of the plurality of pixels to remove background noise and provide constrained pixel values; and

the act of segmenting comprises using the smoothed pixel values and the constrained pixel values to obtain the one or more patches.

24. The method of claim 23 wherein the act of dampening the plurality of pixels around the periphery of the one or more patches comprises at least reducing the value of each peripheral pixel using the smoothed pixel values and the constrained pixel values.