DETECTING THE LOCATIONS OF A PLURALITY OF OBJECTS ON A TOUCH SURFACE

• US 20110074735A1
• Filed: 06/22/2009
• Published: 03/31/2011
• Est. Priority Date: 06/23/2008
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Wassvik, Ola, Christiansson, Tomas
• Granted Patent: US 9,134,854 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• 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 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: G06F 3/0423 using sweeping light beams, e.g. using rotating or vibrating mirror

Abstract

An apparatus is controlled to detect locations of a plurality of objects on a touch surface of a panel. An input scanner arrangement introduces at least three beams of radiation into the panel for propagation by internal reflection, and sweeps the beams inside the panel across a sensing area, preferably in at least two different principal directions. At least one radiation detector is arranged to receive the beams from the input scanner arrangement while they are swept across the sensing area. A data processor is connected to the radiation detector(s) and operated to identify the locations based on an attenuation of the beams caused by the objects touching the touch surface within the sensing area, the attenuation being identifiable from an output signal of the radiation detector(s). Each output signal may be further processed to generate a transmission signal, by dividing the output signal by a background signal which represents the output signal without any object on the touch surface.

Claims

1. An apparatus for detecting locations of a plurality of objects on a touch surface, said apparatus comprising:

a panel defining the touch surface and an opposite surface;

an input scanner arrangement adapted to introduce at least three beams of radiation into the panel, such that each beam propagates by internal reflection between the touch surface and the opposite surface in a respective main direction, and to sweep each beam along the surface across a sensing area of the panel;

at least one radiation detector configured to receive the beams from the input scanner arrangement while they are swept across the sensing area; and

a data processor connected to said at least one radiation detector and configured to identify said locations based on an attenuation of said beams caused by the objects touching the touch surface within said sensing area, said attenuation being identifiable from an output signal of the radiation detector.

2. The apparatus of claim 1, wherein at least part of the sensing area is swept by a first set of mutually acute first beams, wherein the first beams have a maximum mutual acute angle of ≦

30°

, and preferably ≦

20°

.

3. The apparatus of claim 2, wherein the first beams are swept in a first principal direction across the panel.

4. The apparatus of claim 3, wherein at least one second beam is swept in a second principal direction across the panel.

5. The apparatus of claim 4, wherein the second principal direction is orthogonal to the first principal direction.

6. The apparatus of claim 4, wherein the panel is rectangular, and the first and second principal directions are parallel to a respective side of the panel.

7. The apparatus of claim 1, wherein said at least one second beam is included in a second set of mutually acute second beams, wherein the second beams are swept in the second principal direction and have a maximum mutual acute angle of ≦

30°

, and preferably ≦

20°

.

8. The apparatus of claim 7, wherein the first set comprises three first beams and/or the second set comprises three second beams.

9. The apparatus of claim 7, wherein the main direction of one of the first beams in the first set is orthogonal to the first principal direction and/or one of the second beams in the second set is orthogonal to the second principal direction.

10. The apparatus of claim 7, wherein each pair of second beams has a unique mutual acute angle within the second set.

11. The apparatus of claim 7, wherein the main direction of one of the second beams is orthogonal to the second principal direction.

12. The apparatus of claim 2, wherein each pair of first beams has a unique mutual acute angle within the first set.

13. The apparatus of claim 2, wherein the main direction of one of the first beams is orthogonal to the first principal direction.

14. The apparatus of claim 1, wherein the main directions of said at least three beams are mutually acute, in at least part of the sensing area, wherein each pair of said beams define a unique mutual acute angle.

15. The apparatus of claim 1, wherein the main directions of said at least three beams are equiangular in at least part of the sensing area.

16. The apparatus of claim 1, wherein the input scanner arrangement is configured to sweep the beams by translating each beam across the sensing area.

17. The apparatus of claim 1, wherein the input scanner arrangement is configured to sweep the beams across the sensing area with essentially constant mutual angles between the main directions of the beams.

18. The apparatus of claim 17, wherein each beam has an essentially invariant main direction while being swept across the sensing area.

19. The apparatus of claim 1, wherein said panel is defined by linear periphery portions, and each beam is translated in a respective principal direction which is essentially parallel to one of said linear periphery portions.

20. The apparatus of claim 1, further comprising an output scanner arrangement which is synchronized with the input scanner arrangement so as to receive the beams from the input scanner arrangement while they are swept across the sensing area and to direct the beams onto said at least one radiation detector.

21. The apparatus of claim 20, wherein the input and output scanner arrangements are configured to introduce and receive each beam on opposite sides of the sensing area.

22. The apparatus of claim 20, further comprising a reflector arranged along at least part of the periphery of the panel, wherein the reflector is configured to receive the beams from the panel and reflect them back into the panel, and wherein the input and output scanner arrangements are configured to introduce and receive each beam from the same side of the sensing area.

23. The apparatus of claim 22, wherein the reflector is a retro-reflecting device.

24. The apparatus of claim 1, wherein said at least one radiation detector comprises a plurality of radiation-sensing elements that are arranged along at least part of the periphery of the panel.

25. The apparatus of claim 1, wherein said data processor is further configured to:

obtain at least two output signals from said at least one radiation detector;

generate at least two transmission signals by dividing said at least two output signals by a background signal; and

identify said attenuation as peaks in said at least two transmission signals.

26. (canceled)

27. A method of detecting locations of a plurality of objects on a touch surface, said method comprising:

introducing at least three beams of radiation into a panel that defines the touch surface and an opposite surface, said beams propagating by internal reflection between the touch surface and the opposite surface;

sweeping the beams along the touch surface across a sensing area of the panel;

receiving the beams on at least one radiation detector while they are swept across the sensing area; and

identifying said locations based on an attenuation of said beams caused by the objects touching the touch surface within said sensing area, said attenuation being identifiable from an output signal of the radiation detector.

28. A method of operating an apparatus for detecting locations of a plurality of objects on a touch surface, said touch surface being part of a panel that defines the touch surface and an opposite surface, said method comprising:

operating an input scanner arrangement to introduce at least three beams of radiation into the panel, such that each beam propagates by internal reflection between the touch surface and the opposite surface in a respective main direction, and to sweep each beam along the surface across a sensing area of the panel;

operating at least one radiation detector to receive the beams from the input scanner arrangement while they are swept across the sensing area; and

identifying said locations based on an attenuation of said beams caused by the objects touching the touch surface within said sensing area, said attenuation being identifiable from an output signal of the radiation detector.

29. A computer program product comprising computer code which, when executed on a data-processing system, is adapted to carry out the method of claim 28.

30. A method for detecting a location of at least one object on a touch surface on a radiation transmissive panel, said method comprising the steps of:

obtaining at least two output signals from a detection arrangement which is optically coupled to one or more elongate outcoupling sites on said panel, said at least two output signals representing a respective spatial distribution of radiation along said one or more outcoupling sites;

generating at least two transmission signals, wherein said step of generating comprises dividing said at least two output signals by a background signal; and

identifying said location based on peaks in said at least two transmission signals.

31. The method of claim 30, wherein said step of identifying comprises identifying a radiation path for each peak in said at least two transmission signals, and identifying intersection points for the thus-identified radiation paths.

32. The method of claim 31, wherein said step of identifying further comprises calculating the integrated area under each peak in said at least two transmission signals, and solving an equation system that relates each integrated area to at least one of said intersection points.

33. The method of claim 30, wherein said step of generating further comprises operating a logarithmic function on the result said dividing.

34. The method of claim 30, wherein the background signal represents the spatial distribution of radiation along said one or more outcoupling sites without said at least one object on the touch surface.

35. The method of claim 30, wherein the background signal is pre-set, derived during a separate calibration step, or derived from one or more preceding output signals.

36. The method of claim 30, wherein each spatial distribution originates from a respective beam of radiation, which is introduced into the panel to propagate by internal reflection between the touch surface and an opposite surface of the panel in a respective main direction, such that each beam is received at said one or more outcoupling sites.

37. A computer program product comprising computer code which, when executed on a data-processing system, is adapted to carry out the method of claim 30.

38. A device for detecting a location of at least one object on a touch surface on a radiation transmissive panel, said device comprising:

means for obtaining at least two output signals from a detection arrangement which is optically coupled to one or more elongate outcoupling sites on said panel, said at least two output signals representing a respective spatial distribution of radiation along said one or more outcoupling sites;

means for generating at least two transmission signals, wherein said generating comprises dividing said at least two output signals by a background signal; and

means for identifying said locations based on peaks in said at least two transmission signals.