Detecting Multitouch Events in an Optical Touch-Sensitive Device Using Touch Event Templates

• US 20120218229A1
• Filed: 04/30/2012
• Published: 08/30/2012
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: Beechrock Limited
• Original Assignee: Rapt Ip Limited
• Inventors: Drumm, Owen
• Granted Patent: US 9,092,092 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 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

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. Touch events disturb the optical beams. Touch event templates are used to determine the actual touch events based on which optical beams have been disturbed.

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:

determining, a priori, a set of touch event templates for a group of expected touch events, each touch event template for an expected touch event defined by at least two beams that would be disturbed by the expected touch event;

receiving information indicating which beams have been disturbed by actual touch events; and

comparing the received information to the touch event templates, to determine the actual touch events.

2. The method of claim 1 wherein the group of expected touch events includes a class of touch events that can be parameterized, and the set of touch event templates spans the class of touch events as a function of the parameters.

3. The method of claim 1 wherein the group of expected touch events includes a class of oval-shaped touch events, the set of touch event templates spans the class of oval-shaped touch events as a function of at least one of length of major axis, length of minor axis, orientation of major axis, x location within the active area and y location within the surface.

4. The method of claim 3 wherein the set of touch event templates spans the class of oval-shaped touch events over a range of at least 5 mm to 10 mm for length of major axis.

5. The method of claim 3 wherein the set of touch event templates includes a class of round touch events, the set of touch event templates spans the class of round touch events as a function of a diameter of the touch event.

6. The method of claim 1 wherein the set of touch event templates includes a series of touch event templates for an expected touch event, the touch event templates in the series defining different numbers of beams that would be disturbed by the expected touch event.

7. The method of claim 6 wherein the series of touch event templates is defined by N beams and an n-beam template in the series is defined by the first n of the N beams.

8. The method of claim 6 wherein the series of touch event templates is defined by N beams and an n-beam template in the series is defined by a subset of n of the N beams.

9. The method of claim 1 wherein the set of touch event templates includes a template model that defines multiple touch event templates in the set.

10. The method of claim 8 wherein the template model is a function of a variable, and the step of comparing the received information to the touch event templates comprises comparing the received information to the template model and, if there is a match, also determining a value for the variable based on the received information.

11. The method of claim 1 wherein the touch event templates are defined by at least two beams that would have reduced transmission due to the expected touch event.

12. The method of claim 11 wherein at least one touch event template is further defined by at least one beam that would have enhanced transmission due to the expected touch event.

13. The method of claim 1 wherein the received information is a set of transmission coefficients indicative that a transmission of a beam between an emitter and a detector has been disturbed.

14. The method of claim 1 wherein the beams within a touch event template are not all equally weighted.

15. The method of claim 14 wherein, within a touch event template, a beam closer to a center of the expected touch event is weighted more heavily than a beam that is farther way from the center of the expected touch event.

16. The method of claim 14 wherein, within a touch event template, angular diverse beams are weighted more heavily than beams that are more parallel to each other.

17. The method of claim 1 wherein, within a touch event template, two beams are weighted less if the two beams are from the same emitter or to the same detector.

18. The method of claim 1 wherein, within a touch event template, no two beams are parallel.

19. The method of claim 1 wherein, within a touch event template, no two beams are from the same emitter or to the same detector.

20. The method of claim 1 wherein a data record for the touch event template includes information about the expected touch event beyond the beams that would be disturbed by the expected touch event.

21. The method of claim 1 wherein the number of touch event templates in the set of touch event templates is reduced due to symmetry.

22. The method of claim 1 wherein the step of comparing the received information to the touch event templates is ordered to increase the computational efficiency of the comparison.

23. The method of claim 1 wherein the received information includes numerical measures of the disturbances to the beams, and the step of comparing the received information to the touch event templates comprises combining the numerical measures for the beams defining the touch event template.

24. The method of claim 23 wherein combining the numerical measures for the beams defining the touch event template comprises averaging the numerical measures.

25. The method of claim 23 wherein combining the numerical measures for the beams defining the touch event template comprises taking a weighted average of the numerical measures.

26. The method of claim 23 wherein combining the numerical measures for the beams defining the touch event template comprises taking a median value of the numerical measures.

27. The method of claim 23 wherein combining the numerical measures for the beams defining the touch event template comprises taking a certain percentile value of the numerical measures.

28. The method of claim 23 wherein combining the numerical measures for the beams defining the touch event template comprises estimating a confidence of the combined numerical measure.

29. 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 information indicating which beams have been disturbed by actual touch events and comparing the received information to a set of touch event templates to determine the actual touch events, wherein the set of touch event templates for a group of expected touch events is determined a priori, each touch event template for an expected touch event is defined by at least two beams that would be disturbed by the expected touch event.