Full scale calibration measurement for multi-touch surfaces

• US 20080158176A1
• Filed: 01/03/2007
• Published: 07/03/2008
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Hotelling, Steven Porter, Lim, Richard Wei Kwang, Land, Brian Richards
• Granted Patent: US 8,125,455 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

Normalization of regions of a sensor panel capable of detecting multi-touch events, or a sensor panel capable of detecting multi-hover events, is disclosed to enable each sensor in the sensor panel to trigger a virtual button in a similar manner, given the same amount of touch or hover. Each sensor produces an output value proportional to the level or amount of touch or hover. However, due to processing, manufacturing and physical design differences, the sensor output values can vary from region to region or panel to panel for a given amount of touch or hover. To normalize the sensor output values across regions, gain and offset information can be obtained in advance, stored in nonvolatile memory, and later used to normalize the sensor output values so that all regions in the sensor panel can trigger virtual buttons similarly, providing a uniform “response function” at any location on the sensor panel.

Claims

1. A method for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, comprising:

storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values, the applied offset adjustment values and gain multiplication factors selected in accordance with the regions within which the sensors are located; and

determining whether virtual buttons associated with the sensors have been triggered by comparing the normalized output values for the sensors with a fixed threshold.

2. The method of claim 1, further comprising:

obtaining the gain multiplication factor for a particular region by

recording and averaging no-event and full-event raw output values for one or more sensors in that region,

computing a first range as a difference between the averaged full-event and no-event raw output values,

determining a second range as number representative of a difference between the full-event and non-event, and

dividing the first range by the second range.

3. The method of claim 1, further comprising:

obtaining the offset adjustment value for a particular region by

recording and averaging no-event raw output values for one or more sensors in that region,

selecting a baseline output value applicable to all regions, and

computing a difference between the averaged non-event raw output value for each region and the baseline output value.

4. The method of claim 1, the step of applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values comprising:

performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment values and gain multiplication factors for the regions within which the sensors are located.

5. The method of claim 1, the multi-event sensor panel comprising a multi-touch sensor panel.

6. The method of claim 1, the multi-event sensor panel comprising a multi-hover sensor panel.

7. A method for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, comprising:

storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region;

applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the regions within which the sensors are located; and

determining whether virtual buttons associated with the sensors have been triggered by comparing the offset compensated output values for the sensors with a particular threshold selected in accordance with the regions within which the sensors are located.

8. The method of claim 7, further comprising:

obtaining the gain multiplication factor for a particular region by

recording and averaging no-event and full-event raw output values for one or more sensors in that region,

computing a first range as a difference between the averaged full-event and no-event raw output values,

determining a second range as number representative of a difference between the full-event and non-event, and

dividing the first range by the second range.

9. The method of claim 7, further comprising:

obtaining the offset adjustment value for a particular region by

recording and averaging no-event raw output values for one or more sensors in that region, and

computing a difference between the averaged non-event raw output value for each region and the baseline output value.

10. The method of claim 7, the step of computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region comprising:

adding the baseline output value to an offset compensated output value component of a slope representative of the gain multiplication factor.

11. The method of claim 7, the step of applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values comprising:

performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment values for the regions within which the sensors are located.

12. The method of claim 7, the multi-event sensor panel comprising a multi-touch sensor panel.

13. The method of claim 7, the multi-event sensor panel comprising a multi-hover sensor panel.

14. An apparatus for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, comprising:

non-volatile memory storing an offset adjustment value and a gain multiplication factor for each of the one or more regions; and

a panel processor coupled to the non-volatile memory and programmed for

applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values, the applied offset adjustment values and gain multiplication factors selected in accordance with the regions within which the sensors are located, and

determining whether virtual buttons associated with the sensors have been triggered by comparing the normalized output values for the sensors with a fixed threshold.

15. The apparatus of claim 14, further comprising:

a multi-event sensor panel;

one or more event detection and demodulation circuits coupled to the multi-event sensor panel and the panel processor for generating the raw output values.

16. The apparatus of claim 14, the panel processor further programmed for applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values by performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment values and gain multiplication factors for the regions within which the sensors are located.

17. The apparatus of claim 14, the multi-event sensor panel comprising a multi-touch sensor panel.

18. The apparatus of claim 14, the multi-event sensor panel comprising a multi-hover sensor panel.

19. The apparatus of claim 15, further comprising a computing system that incorporates the apparatus, the computing system comprising:

a panel subsystem coupled to the panel processor and including the one or more event detection and demodulation circuits; and

a host processor coupled to the panel processor.

20. The apparatus of claim 19, further comprising a mobile telephone that incorporates the computing system.

21. The apparatus of claim 19, further comprising a digital audio player that incorporates the computing system.

22. An apparatus for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, comprising:

means for storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

means for applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values, the applied offset adjustment values and gain multiplication factors selected in accordance with the regions within which the sensors are located; and

means for determining whether virtual buttons associated with the sensors have been triggered by comparing the normalized output values for the sensors with a fixed threshold.

23. An apparatus for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, comprising:

non-volatile memory storing an offset adjustment value and a gain multiplication factor for each of the one or more regions; and

a panel processor coupled to the non-volatile memory and programmed for

computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region,

applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the regions within which the sensors are located, and

determining whether virtual buttons associated with the sensors have been triggered by comparing the offset compensated output values for the sensors with a particular threshold selected in accordance with the regions within which the sensors are located.

24. The apparatus of claim 23, further comprising:

a multi-event sensor panel;

one or more event detection and demodulation circuits coupled to the multi-event sensor panel and the panel processor for generating the raw output values based on events occurring at the panel.

25. The apparatus of claim 23, the panel processor further programmed for computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region by adding the baseline output value to an offset compensated output value component of a slope representative of the gain multiplication factor.

26. The apparatus of claim 23, the panel processor further programmed for applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values by performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment values for the regions within which the sensors are located.

27. The apparatus of claim 23, the multi-event sensor panel comprising a multi-touch sensor panel.

28. The apparatus of claim 23, the multi-event sensor panel comprising a multi-hover sensor panel.

29. The apparatus of claim 23, further comprising a computing system that incorporates the apparatus, the computing system comprising:

a panel subsystem coupled to the panel processor and including the one or more event detection and demodulation circuits; and

a host processor coupled to the panel processor.

30. The apparatus of claim 29, further comprising a mobile telephone that incorporates the computing system.

31. The apparatus of claim 29, further comprising a digital audio player that incorporates the computing system.

32. An apparatus for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch-or hover, comprising:

means for storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

means for computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region;

means for applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the regions within which the sensors are located; and

means for determining whether virtual buttons associated with the sensors have been triggered by comparing the offset compensated output values for the sensors with a particular threshold selected in accordance with the regions within which the sensors are located.

33. A computer-readable medium comprising program code for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, the program code for causing performance of a method comprising:

storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

applying offset adjustment values and gain multiplication factors to raw output values received from sensors in the sensor panel to generate normalized output values, the applied offset adjustment values and gain multiplication factors selected in accordance with the regions within which the sensors are located; and

determining whether virtual buttons associated with the sensors have been triggered by comparing the normalized output values for the sensors with a fixed threshold.

34. A computer-readable medium comprising program code for normalizing raw output values received from sensors in one or more regions in a multi-event sensor panel to enable the sensors in any region to trigger virtual buttons given a similar amount of touch or hover, the program code for causing performance of a method comprising:

storing an offset adjustment value and a gain multiplication factor for each of the one or more regions;

computing a threshold for each of the one or more regions using a baseline output value and the stored gain multiplication factor for that region;

applying offset adjustment values to raw output values received from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the regions within which the sensors are located; and

determining whether virtual buttons associated with the sensors have been triggered by comparing the offset compensated output values for the sensors with a particular threshold selected in accordance with the regions within which the sensors are located.