DETECTING THE LOCATION OF AN OBJECT ON A TOUCH SURFACE

• US 20110074734A1
• 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 8,890,843 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 3/0423 using sweeping light beams, e.g. using rotating or vibrating mirror

Abstract

An apparatus is operated to determine the location of at least one object on a touch surface of a light transmissive panel. In the apparatus, an illumination arrangement introduces radiation into the panel for propagation by internal reflection between the touch surface and the opposite surface, so as to generate a grid of intersecting radiation paths in a sensing area, and a detection arrangement measures the transmitted energy in the radiation paths. A data processor then determines, based on the transmitted energy, the location based on an attenuation of two or more radiation paths caused by the object touching the touch surface within the sensing area. In the apparatus, the illumination arrangement generates at least a subset of the radiation paths by sweeping at least one beam of radiation along the touch surface. The detection arrangement comprises a fixed re-directing device which receives and re-directs the beam onto a common detection point while the beam is swept along the touch surface, and a radiation detector which is located at the common detection point to measure the energy of the beam(s).

Claims

1. An apparatus for determining a location of at least one object on a touch surface, said apparatus comprising:

a panel defining the touch surface and an opposite surface;

an illumination arrangement adapted to introduce radiation into the panel for propagation by internal reflection between the touch surface and the opposite surface, so as to generate a grid of intersecting radiation paths in a sensing area;

a detection arrangement adapted to measure the transmitted energy in said radiation paths; and

a data processor connected to the detection arrangement and configured to determine, based on the measured energy, said location based on an attenuation of two or more radiation paths caused by the object touching the touch surface within the sensing area;

wherein said illumination arrangement is configured to generate at least a subset of the radiation paths by sweeping at least one beam of radiation along the touch surface;

wherein said detection arrangement comprises a fixed re-directing device configured to receive and re-direct said at least one beam onto a common detection point while said at least one beam is swept along the touch surface; and

wherein said detection arrangement further comprises a radiation detector which is located at said common detection point to measure the energy of said at least one beam.

2. The apparatus of claim 1, wherein the illumination arrangement is configured to sweep said at least one beam with an essentially invariant main direction within the sensing area.

3. The apparatus of claim 1, wherein the fixed re-directing device comprises an elongate optical element that defines an output focal plane, wherein the illumination arrangement is configured such that the beam, while being swept within the sensing area, is swept along the elongate optical element at an essentially invariant angle of incidence, and wherein the radiation detector is arranged in said output focal plane.

4. The apparatus of claim 3, wherein the illumination arrangement is adapted to sweep at least two separate beams of radiation within the sensing area, such that each beam is swept along the elongate optical element at a respective angle of incidence, and wherein the detection arrangement comprises at least two radiation detectors, which are arranged at separate locations to measure the energy of the respective beam.

5. The apparatus of claim 1, wherein the radiation detector comprises a light-sensing surface and device for increasing the effective light-sensing area of the radiation detector, said device being arranged intermediate the re-directing device and the light-sensing surface.

6. The apparatus of claim 5, wherein said device for increasing the effective light-sensing area comprises one of a diffusing element and a concentrator.

7. The apparatus of claim 1, wherein the re-directing device is arranged to extend along an edge portion of said panel.

8. The apparatus of claim 1, wherein the illumination arrangement is configured to inject beams that are collimated at least in the plane of the panel.

9. The apparatus of claim 1, wherein the illumination arrangement and the detection arrangement are configured to introduce and receive said at least one beam on opposite ends of the sensing area.

10. The apparatus of claim 1, wherein the illumination arrangement comprises a beam-scanning device configured to sweep an input beam around an axis of rotation, a fixed beam-directing device configured to receive the thus-swept input beam and generate at least one output beam which is translated in a principal direction while having an essentially invariant main direction, and a coupling element connected to the panel for receiving and injecting said at least one output beam into the panel, thereby forming said at least one beam that is swept along the touch surface within the sensing area.

11. The apparatus of claim 10, wherein the beam-directing device comprises an elongate optical element that defines an input focal plane, wherein said axis of scanning is located in said input focal plane.

12. The apparatus of claim 10, wherein the beam-scanning device is configured to sweep at least two separate input beams along the elongate optical element, each input beam being swept around a separate axis of rotation in said input focal plane, thereby causing the elongate optical element to generate output beams with separate main directions.

13. The apparatus of claim 10, wherein the beam-directing device further comprises an elongate grating structure which is arranged to generate said at least one output beam as a set of diffracted beams with a predetermined angular spacing.

14. The apparatus of claim 10, wherein the beam-directing device is arranged to extend along an edge portion of said panel.

15. The apparatus of claim 14, wherein said principal direction is essentially parallel to said edge portion of said panel.

16. The apparatus of claim 10, wherein the illumination arrangement comprises a plate-shaped radiation guide which is arranged underneath the panel, as seen from the touch surface, and a beam-folding system which is arranged to optically connect the radiation guide to the panel, wherein the radiation guide is configured to guide said at least one output beam by internal reflection from the beam-directing device to the beam-folding system.

17. The apparatus of claim 1, wherein the illumination arrangement is configured to sweep a first set of mutually acute beams in a first principal direction across the panel, wherein the beams in the first set have a maximum mutual acute angle of ≦

30°

, and preferably ≦

20°

.

18. The apparatus of claim 17, wherein the main direction of one of the beams in the first set is orthogonal to the first principal direction.

19. The apparatus of claim 17, wherein each pair of beams in the first set has a unique mutual acute angle.

20. The apparatus of claim 17, wherein the illumination arrangement is configured to sweep at least one second beam in a second principal direction across the panel.

21. The apparatus of claim 17, wherein the illumination arrangement is configured to sweep a second set of mutually acute beams in a second principal direction across the panel, wherein the beams in the second set have a maximum mutual acute angle of ≦

30°

, and preferably ≦

20°

.

22. The apparatus of claim 21, wherein the first set comprises three beams and/or the second set comprises three beams.

23. The apparatus of claim 21, wherein the main direction of one of the beams in the second set is orthogonal to the second principal direction.

24. The apparatus of claim 21, wherein each pair of beams in the second set has a unique mutual acute angle.

25. The apparatus of claim 20, wherein the first and second principal directions are mutually orthogonal.

26. The apparatus of claim 20, wherein the panel is rectangular, and the first and second principal directions are parallel to a respective edge portion of the panel.

27. (canceled)

28. A method of determining a location of at least one object on a touch surface, said touch surface being part of a panel that defines the touch surface and an opposite surface, said method comprising the steps of:

introducing radiation into the panel for propagation by internal reflection between the touch surface and the opposite surface, so as to generate a grid of intersecting radiation paths in a sensing area;

measuring the transmitted energy in said radiation paths;

identifying, based on the measured energy, at least two radiation paths that are attenuated by an object touching the touch surface; and

determining the location of the object based on the attenuated radiation paths;

wherein the step of introducing comprises sweeping at least one beam of radiation along the touch surface;

wherein the step of measuring comprises receiving said at least one beam, while it is swept along the touch surface, by a fixed re-directing device which re-directs said at least one beam onto a common detection point, and measuring the energy of said at least one beam at said common detection point.

29. A method of operating an apparatus for determining a location of at least one object on a touch surface, said touch surface being part of a panel that defines the touch surface and an opposite surface, said method comprising the steps of:

operating an illumination arrangement to introduce radiation into the panel for propagation by internal reflection between the touch surface and the opposite surface, so as to generate a grid of intersecting radiation paths in a sensing area;

operating a detection arrangement to measure the transmitted energy in said radiation paths; and

determining, based on the transmitted energy, said location based on an attenuation of two or more radiation paths caused by the object touching the touch surface within the sensing area;

wherein the step of operating the illumination arrangement comprises the step of sweeping at least one beam of radiation along the touch surface, such that said at least one beam, after passing the sensing area, is received by a fixed re-directing device which re-directs said at least one beam onto a common detection point; and

wherein the step of operating the detection arrangement comprises measuring the energy of said at least one beam by a radiation detector which is located at the common detection point.

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