Touch Surface With A Compensated Signal Profile

• US 20120162144A1
• Filed: 09/01/2010
• Published: 06/28/2012
• Est. Priority Date: 09/02/2009
• Status: Active Grant

• Current Assignee: FlatFrog Laboratories AB
• Original Assignee: FlatFrog Laboratories AB
• Inventors: Fåhraeus, Christer, Christiansson, Tomas, Wall, Henrik, Wassvik, Ola
• Granted Patent: US 8,692,807 B2
• Time in Patent Office: Days
• US Class Current: 345/178
• 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 3/0418 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

Abstract

An apparatus, method and computer-readable medium for determining a location of at least one object on a touch surface of a light transmissive panel. The method comprises the steps of: introducing light into the panel for propagation by internal reflection between the touch surface and an opposite surface; receiving the light propagating in the panel; and iteratively i) determining a current signal profile of light received by the light detection arrangement, ii) updating, when a condition is met, a background signal profile of light received by the light detection arrangement, iii) calculating a current compensated signal profile as a function of the background signal profile and the current signal profile and iv) determining, when the object touches the touch surface and thereby attenuates the light propagating in the panel, the location as a function of the compensated signal profile.

Claims

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

a light transmissive panel defining the touch surface and an opposite surface,

an illumination arrangement configured to introduce light into the panel for propagation by internal reflection between the touch surface and the opposite surface,

a light detection arrangement configured to receive the light propagating in the panel, and

a processor unit configured to iteratively

determine a current signal profile of light received by the light detection arrangement,

update, when a condition is met, a background signal profile of light received by the light detection arrangement,

calculate a current compensated signal profile as a function of the background signal profile and the current signal profile, and

determine, when the object touches the touch surface and thereby attenuates the light propagating in the panel, the location as a function of the compensated signal profile.

2. An apparatus according to claim 1, wherein the processor unit is configured to calculate the compensated signal profile by dividing the current signal profile with the background signal profile.

3. An apparatus according to claim 1, wherein the processor unit is configured to calculate the compensated signal profile by subtracting the logarithm of the background signal profile from the logarithm of the current signal profile.

4. An apparatus according to claim 1, wherein the processor unit is configured to calculate the compensated signal profile by subtracting the background signal profile from the current signal profile.

5. An apparatus according to claims 1-4, wherein the processor unit is configured to determine the location by subtracting a previously determined compensated signal profile from the compensated signal profile.

6. An apparatus according to claim 1, wherein each of the signal profiles comprises a respective signal profile of a first main direction of the panel and a respective signal profile of a second main direction of the panel.

7. An apparatus according to claim 1, wherein the illumination arrangement comprises a set of light emitters for introducing the light and wherein the light detection arrangement comprises a set of light detectors for receiving the light, the light for forming the background signal profile and the light for forming the current signal profile introduced and received at a respective time by the same sets of light emitters and light detectors.

8. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile independent of a presence of the object on the touch surface.

9. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile when the object touches the touch surface and thereby attenuates the light propagating in the panel.

10. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile when the apparatus is initiated.

11. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile at predetermined time intervals.

12. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile when the processor unit determines that the object does not touch the touch surface.

13. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile as a function of a currently measured signal profile and a previously updated background signal profile.

14. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile by weighting a currently measured signal profile relatively lower than a previously updated background signal profile.

15. An apparatus according to claim 1, wherein the processor unit is configured to update a first section of the background signal profile different from a second section of the background signal profile.

16. An apparatus according to claim 1, wherein the processor unit is configured to update a first section of the background signal profile indicative of the location of the object different from a second section of the background signal profile not indicative of the location of the object.

17. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile by determining the background signal profile as a function of the location of the object.

18. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile by determining the background signal profile as a function of time passed since the location of the object was determined.

19. An apparatus according to claim 1, wherein the processor unit is configured to, when the object is removed from the touch surface, update a first section of the background signal profile associated with the location of the object faster than a second section of the background signal profile not associated with the location of the object.

20. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile as a function of a time-distributed variation of light received by the light detection arrangement.

21. An apparatus according to claim 1, wherein the processor unit is configured to update the background signal profile as a function of the location of the object determined over a specific time interval.

22. An apparatus according to claim 1, comprising a memory unit configured to store data indicative of the presence of at least one object on the touch surface, wherein the processor unit is configured to update the background signal profile as a function of the presence of the at least one object.

23. An apparatus according to claim 1, wherein the processor unit is further configured to determine the location of the object as a function of a previously determined compensated signal profile.

24. An apparatus according to claim 1, comprising an interface device providing a graphical user interface aligned with the light transmissive panel wherein the processor unit is configured to update the background signal profile as a function of the graphical user interface.

25. (canceled)

26. A method for determining a location of at least one object on a touch surface of a light transmissive panel defining the touch surface and an opposite surface, the method comprising the steps of iteratively:

determining a current signal profile of light received by a light detection arrangement after propagation in the light transmissive panel by internal reflection between the touch surface and the opposite surface,

updating, when a condition is met, a background signal profile of light received by the light detection arrangement,

calculating a current compensated signal profile as a function of the background signal profile and the current signal profile, and

determining, when the object touches the touch surface and thereby attenuates the light propagating in the panel, the location as a function of the compensated signal profile.

27. A computer-readable medium storing processing instructions that, when executed by a processing unit, performs the method according to claim 26.