INTEGRATED TOUCH-SENSING DISPLAY APPARATUS AND METHOD OF OPERATING THE SAME

• US 20110216042A1
• Filed: 11/12/2009
• Published: 09/08/2011
• Est. Priority Date: 11/12/2008
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Wassvik, Ola, Christiansson, Thomas
• Granted Patent: US 8,860,696 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G02B 6/429 by surface irregularities on the light guide, e.g. by mechanical modification of the surface of the light guide on its exterior
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• 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 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means
• 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 integrated touch-sensing display is operated to detect the location of one or more objects on a touch surface. The integrated touch-sensing display defines a display area. A light guide (14) is arranged over the display area to define the touch surface (16). The light guide (14) is illuminated internally such that an object (20) contacting the touch surface (16) causes part of the illuminating light to be scattered towards the display area. An array of light sensors (6) is integrated within the display area to detect the scattered light. Based on output signals from the light sensors (6), a processing element obtains image data that represents the light that impinges on the display area excluding ambient light, and determines the location of the object (20) on the touch surface (16). Ambient light may be suppressed by a spectral passband filter in front of each light sensor (6), and/or by electronic filtering of the output signals from the sensors (6). The light guide (14) may be illuminated by invisible light, and may be arranged to cause an illuminating beam to be internally reflected at a peripheral edge surface of the light guide (14), so as to increase the intensity of illuminating light inside the light guide (14).

Claims

1. An integrated touch-sensing display apparatus, comprising:

an array of picture elements that defines a display area;

an array of light-sensing elements integrated within the display area;

a light guide located in front of the display area to define a touch surface;

a light source arrangement for providing illuminating light inside the light guide, such that an object contacting the touch surface causes part of the illuminating light to be scattered towards the display area; and

a processing element configured to obtain, based on output signals from the light-sensing elements, image data that represents the light that impinges on the display area excluding ambient light, and to determine, based on the image data, the location of the object on the touch surface.

2. The integrated touch-sensing display apparatus of claim 1, further comprising a filter arrangement for suppressing said ambient light.

3. The integrated touch-sensing display apparatus of claim 2, wherein the light source arrangement is configured to modulate the illuminating light at a predetermined modulation frequency, and wherein the filter arrangement comprises a circuit for lock-in detection at the modulation frequency, which circuit operates on the output signals from the light-sensing elements.

4. The integrated touch-sensing display apparatus of claim 2, wherein the light source arrangement is configured to modulate the illuminating light at a predetermined modulation frequency, and wherein the filter arrangement means-comprises at least one bandpass filter operating on the output signals from the light-sensing elements to remove frequencies outside a passband around the modulation frequency.

5. The integrated touch-sensing display apparatus of claim 4, wherein the at least one bandpass filter comprises an analog filter circuit.

6. The integrated touch-sensing display apparatus of claim 4, wherein the array of light-sensing elements and the at least one bandpass filter are integrated on a common substrate.

7. The integrated touch-sensing display apparatus of claim 3, wherein the modulation frequency is at least about 0.5 kHz.

8. The integrated touch-sensing display apparatus of claim 2, wherein the light source arrangement is configured to provide the illuminating light in a confined wavelength region, and wherein the filter arrangement comprises at least one spectral passband filter which is arranged in front of the light-sensing elements so as to suppress the ambient light in relation to the illuminating light.

9. The integrated touch-sensing display apparatus of claim 1, wherein the illuminating light is invisible to the human eye.

10. The integrated touch-sensing display apparatus of claim 9, wherein the illuminating light is in a wavelength region above 700 nm.

11. The integrated touch-sensing display apparatus of claim 1, wherein at least a subset of the light-sensing elements is provided with a respective lens device that defines the field of view of the light-sensing element.

12. The integrated touch-sensing display apparatus of claim 11, wherein the lens device is arranged to focus an area of the touch surface onto the light-sensing element.

13. The integrated touch-sensing display apparatus of claim 1, wherein the light guide is made of solid material that defines the touch surface, a parallel opposite surface, and a peripheral edge surface which is orthogonal to the touch surface and connects the touch surface to the opposite surface, wherein the combination of light source arrangement and light guide is arranged to propagate the illuminating light by total internal reflection between the touch surface and the opposite surface such that the propagating light is internally reflected at least once against the peripheral edge surface.

14. The integrated touch-sensing display apparatus of claim 13, wherein the light source arrangement is arranged to inject at least one beam of light into the light guide such that the beam, in a plane parallel to the touch surface, hits the peripheral edge surface at an angle α

to the normal of the peripheral edge surface;

0<

α

<

90°

.

15. The integrated touch-sensing display apparatus of claim 14, wherein the angle is selected to cause multiple reflections of the beam against the peripheral edge surface.

16. The integrated touch-sensing display apparatus of claim 13, wherein the peripheral edge surface is at least partly provided with a reflective material.

17. The integrated touch-sensing display apparatus of claim 16, wherein the light source arrangement is configured to inject the beam through an injection port comprising an opening in the reflective material.

18. The integrated touch-sensing display apparatus of claim 17, further comprising a light transmissive index-matched wedge which is arranged on said opening such that a beam-receiving surface of the wedge is orthogonal to a main direction of the beam.

19. The integrated touch-sensing display apparatus of claim 17, comprising a set of injection ports, each comprising an opening in the reflective material, the total surface area of the openings being less than 10%, and preferably less than 2%, of the total surface area of the peripheral edge surface.

20. The integrated touch-sensing display apparatus of claim 1, further comprising an angle-control element intermediate the light source arrangement and the light guide, said angle-control element being configured to prevent the illuminating light from propagating through the light guide without being reflected in the touch surface.

21. The integrated touch-sensing display apparatus of claim 20, wherein the angle-control element is configured to receive at least part of light emitted by the light source and redirect the thus-received light for reflection in the touch surface.

22. The integrated touch-sensing display apparatus of claim 1, wherein the array of light-sensing elements is located behind the array of picture elements, as seen from the touch surface.

23. The integrated touch-sensing display apparatus of claim 22, wherein each light-sensing element is arranged to at least partially overlap a respective picture element.

24. The integrated touch-sensing display apparatus of claim 1, wherein the processing element is configured to determine the location of the object by identifying a high-intensity region in the image data.

25. A method of operating an integrated touch-sensing display apparatus, which apparatus comprises an array of picture elements that defines a display area;

an array of light-sensing elements integrated to sense light within the display area;

a light guide located in front of the display area to define a touch surface; and

a light source arrangement, said method comprising;

controlling said at least one light source arrangement to provide illuminating light inside the light guide, such that an object contacting the touch surface causes part of the illuminating light to be scattered towards the display area;

obtaining, based on output signals from the light-sensing elements, image data that represents the light that impinges on the display area excluding ambient light, and

determining, based on the image data, the location of the object on the touch surface.

26. The method of claim 25, further comprising controlling the light source arrangement to modulate the illuminating light at a predetermined modulation frequency, and operating a circuit for lock-in detection at the modulation frequency on the output signals from the light-sensing elements.

27. The method of claim 25, further comprising controlling the light source arrangement to modulate the illuminating light at a predetermined modulation frequency, and obtaining the image data from at least one bandpass filter which operates on the output signals from the light-sensing elements to remove frequencies outside a passband around the modulation frequency.

28. The method of claim 25, further comprising operating the light source arrangement to provide the illuminating light in a confined wavelength region, wherein at least one wavelength filter is arranged in front of the light-sensing elements so as to suppress the ambient light in relation to the illuminating light.

29. The method of claim 28, wherein the illuminating light is in a wavelength region above 700 nm.

30. The method of claim 25, wherein the light guide is made of solid material that defines the touch surface, a parallel opposite surface, and a peripheral edge surface which is orthogonal to the touch surface and connects the touch surface to the opposite surface, said method further comprising operating the light source arrangement to propagate the illuminating light by total internal reflection between the touch surface and the opposite surface such that the propagating light is internally reflected at least once against the peripheral edge surface.

31. The method of claim 30, wherein the light source arrangement is operated to cause multiple reflections of the beam against the peripheral edge surface.

32. The method of claim 25, wherein determining the location comprises identifying a high-intensity region in the image data.

33. A computer-readable medium comprising program instructions which, when executed by a processor, cause the processor to perform the method of claim 25.