Method and Apparatus For Detecting A Multitouch Event In An Optical Touch-Sensitive Device

• US 20110157096A1
• Filed: 08/07/2009
• Published: 06/30/2011
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: Beechrock Limited
• Original Assignee: Rapt Ip Limited
• Inventors: Drumm, Owen
• Granted Patent: US 8,350,831 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 2203/04108 Touchless 2D- 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 without distance measurement in the Z direction
• 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 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

A touch sensitive optical control device comprising a set of light emitters 14, 22 and light detectors 18, 24 arranged relative to a touchable surface 30 such that light transmitted by the emitters is received by the detectors along multiple intersecting beams which pass transversely of the surface and touching the surface at a beam interrupts the light transmitted along the beam. Candidate touch points T1, T2, F1, F2 are defined at the intersections of interrupted beams and are confirmed or not as actual touch points by examining test beams 40, 42, 54, 56 near to or coincident with the candidate touch point.

Claims

1. A method for determining a touch point in a touch-sensitive optical device comprising a plurality of optical emitters and a plurality of optical detectors, the optical emitters and the optical detectors defining therebetween a plurality of optical beam paths forming an optical beam intersection pattern extending over an area, the method comprising the steps of:

detecting a modulation of energy transmitted along each of a pair of optical beam paths;

assigning a candidate touch point at the intersection of said pair of modulated beams;

analyzing predetermined other beams near to or coincident with said candidate touch point; and

responsive to said analysis, determining whether the candidate touch point is an actual touch point.

2. The method of claim 1, wherein said step of assigning is based on a function of the degree of modulation of the predetermined other beams.

3. The method of claim 2, wherein the contributions of the predetermined other beams are weighted in said function dependent on the degree of modulation.

4. The method as claimed in claim 3, wherein the weighting for each predetermined other beam depends upon one or more of:

the proximity of the predetermined other beam to the candidate touch point;

the angle of the predetermined other beam to the angle of the beams defining the candidate touch point; and

the number of predetermined other beams.

5. The method as claimed in claim 1, wherein the step of analyzing is based on predetermined other beam intersection points near to or coincident with said candidate touch point.

6. The method as claimed in claim 1, further comprising the step of retrieving stored data from a database defining the predetermined other beams or predetermined other beam intersections for each beam intersection point, said step of analyzing based at least in part on said stored data.

7. The method as claimed in claim 6, wherein the stored data includes respective weighting and/or proximity values relating to the predetermined other beams or predetermined other beam intersections.

8. The method as claimed in claim 6, wherein the beam intersection pattern is symmetrical about at least one axis of the area of optical beam paths, wherein said step of retrieving comprises retrieving stored data regarding beams on one side of said at least one axis, the method further comprising the step of extrapolating the beam data for the beams on the symmetrically opposite side of said at least one axis based on said stored data.

9. The method as claimed in claim 1, further comprising the step of designating said modulation as an interruption of the beam if said modulation exceeds a threshold level, and wherein in said step of assigning, said candidate touch point is assigned at the intersection of a pair of interrupted beams.

10. The method as claimed in claim 9, wherein said threshold level is an adaptive threshold level.

11. The method as claimed in claim 9, wherein said step of designating comprises comparing the detected modulation with a predefined modulation level for that touch point region.

12. The method as claimed in claim 11, wherein the method comprises the step of retrieving data indicative of a typical modulation level for an actual touch point for that touch point region.

13. The method as claimed in claim 12, wherein said data comprises one or more of the following:

the number of beams passing through the touch point region;

the number of intersections of beams falling within the touch point region;

or maximum modulation to be expected in the touch point region.

14. The method as claimed in claim 1, further comprising the step of grouping actual touch points into clusters based on a search radius distance from a cluster member to at least one other member of the same cluster.

15. The method as claimed in claim 14, wherein said beam intersection pattern is non-uniform and said search radius distance varies according to the position of the cluster member in the beam intersection pattern.

16. The method as claimed in claim 14, further comprising the step of estimating the centre of a cluster as the average position of all of the cluster members.

17. The method as claimed in claim 14, further comprising the step of estimating the centre of a cluster as the centre of a bounding rectangle around the cluster.

18. The method as claimed in claim 14, further comprising the step of estimating the centre of a cluster as the average position of outlying cluster members.

19. The method as claimed in claim 16, wherein said estimation step is based on a weighted average, the weights depending on the degree of modulation of the beams at each point contributing to the average.

20. The method as claimed in claim 1, further comprising the step of determining the orientation of a non-circular touch contact area.

21. The method as claimed in claim 20, wherein in said determining step, the orientation is determined by mathematically rotating at least two confirmed touch points lying on or near the perimeter of the contact area around the estimated centre of the contact area and determining the minimum or maximum average absolute value of the distance between each touch point and a fixed axis.

22. The method as claimed in claim 1, comprising the steps of:

initialising a point validity value for said candidate touch point;

(ii) selecting a predetermined other beam near to or coincident with said candidate touch point;

(iii) measuring the strength of said predetermined other beam;

(iv) calculating an attenuation margin for said predetermined other beam based on said measured beam strength;

(v) multiplying said attenuation margin by a weighting value;

(vi) adding the weighted attenuation margin to said point validity value;

(vii) repeating steps (ii)-(vi) for a plurality of predetermined other beams near to or coincident with said candidate touch point;

(viii) normalizing said point validity value; and

(ix) if said point validity value exceeds a threshold value, designating said candidate touch point as an actual touch point.

23. The method as claimed in claim 22, wherein said point validity value is initialised to 0.

24. The method as claimed in claim 22, wherein step (iv) comprises subtracting a threshold value from said measured beam strength.

25. The method as claimed in claim 22, wherein step (viii) comprises dividing said point validity value by the number of predetermined other beams.

26. The method as claimed in claim 1, further comprising the step of storing an indication of said actual touch point in a validated point list.

27. The method as claimed in claim 1, further comprising the step of determining if a candidate touch point is near the boundary of a touch event, and wherein said steps of analyzing and determining whether the candidate touch point is an actual touch point are carried out only in respect of those candidate touch point near the boundary of a touch event.

28. A touch-sensitive optical device comprising a plurality of optical emitters and a plurality of optical detectors, the optical emitters and the optical detectors arranged relative to a touchable surface such that energy transmitted by the emitters is received by the detectors along multiple intersecting beams which pass adjacent the surface, and wherein touching the surface at a beam causes a detectable modulation of the energy transmitted along the beam, the device further comprising a processing means operable to perform the following steps:

(i) detect a modulation of energy transmitted along an optical beam path;

(ii) assign a candidate touch point at the intersection of a pair of modulated beams;

(iii) analyze predetermined other beams near to or coincident with said candidate touch point; and

(iv) responsive to said analysis, determine whether the candidate touch point is an actual touch point.