Detecting Multitouch Events in an Optical Touch-Sensitive Device by Combining Beam Information

• US 20120212458A1
• Filed: 04/30/2012
• Published: 08/23/2012
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: Beechrock Limited
• Original Assignee: Rapt Ip Limited
• Inventors: Drumm, Owen
• Granted Patent: US 8,531,435 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• 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 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• 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 3/042 by opto-electronic means
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421

Abstract

An optical touch-sensitive device is able to determine the locations of multiple simultaneous touch events. The optical touch-sensitive device includes multiple emitters and detectors. Each emitter produces optical beams which are received by the detectors. The optical beams preferably are multiplexed in a manner so that many optical beams can be received by a detector simultaneously. Touch events disturb the optical beams. To determine whether a candidate touch point is an actual touch event, multiple beams that would be affected are considered together.

Claims

1. A method for determining simultaneous touch events on a surface, the surface having emitters and detectors arranged around its periphery, the emitters producing optical beams received by the detectors, the touch events disturbing the optical beam, the method comprising:

receiving numerical metrics indicating which beams have been disturbed by touch events;

for a candidate touch point, combining the numerical metrics for at least two beams that would be disturbed by the candidate touch point; and

determining the touch events based on the combined metrics.

2. The method of claim 1 wherein combining the numerical metrics results in a higher SNR compared to the uncombined numerical metrics.

3. The method of claim 1 wherein combining the numerical metrics results in a higher confidence decision whether a candidate touch point is a location of a touch event, compared to the uncombined numerical metrics.

4. The method of claim 1 wherein combining the numerical metrics comprises summing the numerical metrics.

5. The method of claim 1 wherein combining the numerical metrics comprises averaging the numerical metrics.

6. The method of claim 1 wherein combining the numerical metrics comprises selecting a median of the numerical metrics.

7. The method of claim 1 wherein combining the numerical metrics comprises selecting a certain percentile value of the numerical metrics.

8. The method of claim 1 wherein combining the numerical metrics comprises taking a root mean square of the numerical metrics.

9. The method of claim 1 wherein the step of combining the numerical metrics comprises:

determining a combined metric for K beams, where K is an integer greater than or equal to 2; and

subsequently determining a combined metric for more than K beams.

10. The method of claim 9 wherein the beams for a candidate touch point are ordered;

the combined metric for K beams is based on the first K beams in the order; and

the combined metric for more than K beams is based on the first (more than K) beams in the order.

11. The method of claim 9 wherein the step of subsequently determining a combined metric for more than K beams occurs if the combined metric for K beams has too low confidence.

12. The method of claim 9 wherein the step of subsequently determining a combined metric for more than K beams occurs if the combined metric for K beams has too low SNR.

13. The method of claim 9 wherein the step of subsequently determining a combined metric for more than K beams occurs in response to ambiguity in determining the touch events.

14. The method of claim 1 wherein the numerical metrics are analog.

15. The method of claim 14 wherein beams from emitters to detectors are wide enough to be partially disturbed by a touch event, and the numerical metrics are a function of such partial disturbances.

16. The method of claim 1 wherein the numerical metrics indicate transmissions of beams from emitters to detectors, and the at least two beams include at least two beams that would have transmission reduced by the candidate touch point.

17. The method of claim 1 wherein the numerical metrics are transmission coefficients for beams between emitters and detectors.

18. The method of claim 1 wherein the numerical metrics measure a change in polarization for beams between emitters and detectors.

19. The method of claim 1 wherein the numerical metrics measure a change in angle of propagation for beams between emitters and detectors.

20. The method of claim 1 wherein combining the numerical metrics comprises taking a weighted average of the numerical metrics.

21. The method of claim 20 wherein a beam closer to a center of a candidate touch point is weighted more heavily than a beam that is farther way from the center of the candidate touch point.

22. The method of claim 20 wherein angular diverse beams are weighted more heavily than beams that are more parallel to each other.

23. The method of claim 1 wherein two beams are weighted less if the two beams are from the same emitter or to the same detector.

24. The method of claim 1 wherein all of the at least two beams overlap a contact area of the candidate touch point.

25. The method of claim 1 wherein all of the at least two beams overlap a contact area of the candidate touch point by at least 50%.

26. An optical touch-sensitive device comprising:

a surface for which touch events are to be detected;

emitters and detectors arranged around a periphery of the surface, the emitters producing optical beams received by the detectors, the touch events disturbing the optical beam; and

a touch event processor coupled, directly or indirectly, to the emitters and detectors, the touch event processor receiving numerical metrics indicating which beams have been disturbed by touch events;

for a candidate touch point, combining the numerical metrics for at least two beams that would be disturbed by the candidate touch point; and

determining the touch events based on the combined metrics.