Full scale calibration measurement for multi-touch surfaces

• US 8,125,464 B2
• Filed: 10/15/2010
• Issued: 02/28/2012
• Est. Priority Date: 01/03/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Land, Brian Richards, Hotelling, Steve Porter, Lim, Richard Wei Kwang
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US12/905,878
• Publication Number:
  US 20110037735A1
• Time in Patent Office: 501 Days
• Field of Search: 345173-179, 178 1801- 1809
• 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 output values obtained from sensors in one or more regions in an 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 each of the output values obtained from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the region associated with each output value; 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 region associated with each output value.

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 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 output values,

determining a second range as number representative of a difference between the full-event and the no-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 output values for one or more sensors in that region, and

computing a difference between the averaged no-event output value for each region and the baseline output value.

4. The method of claim 1, wherein 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 comprises:

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

5. The method of claim 1, wherein applying offset adjustment values to output values obtained from sensors in the sensor panel to generate offset compensated output values comprises:

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

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

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

8. An apparatus for normalizing output values obtained from sensors in one or more regions in an 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 each of the output values obtained from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the region associated with each output value, 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 region associated with each output value.

9. The apparatus of claim 8, further comprising:

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

10. The apparatus of claim 8, 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.

11. The apparatus of claim 8, the panel processor further programmed for applying offset adjustment values to output values obtained 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.

12. The apparatus of claim 8, the event sensor panel comprising a multi-touch sensor panel.

13. The apparatus of claim 8, the event sensor panel comprising a multi-hover sensor panel.

14. The apparatus of claim 8, further comprising a computing system that incorporates the apparatus, the computing system comprising:

an event sensor panel coupled to the panel processor and the one or more event detection and demodulation circuits;

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.

15. The apparatus of claim 14, further comprising a mobile telephone that incorporates the computing system.

16. The apparatus of claim 14, further comprising a digital audio player that incorporates the computing system.

17. An apparatus for normalizing output values obtained from sensors in one or more regions in an 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 each of the output values obtained from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the region associated with each output value; 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 region associated with each output value.

18. A computer-readable storage medium comprising program code for normalizing output values obtained from sensors in one or more regions in an 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 each of the output values obtained from sensors in the sensor panel to generate offset compensated output values, the applied offset adjustment values selected in accordance with the region associated with each output value; 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 region associated with each output value.