Full scale calibration measurement for multi-touch surfaces

• US 9,223,436 B2
• Filed: 02/24/2012
• Issued: 12/29/2015
• 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): NGUYEN, JENNIFER T
• Application Number:
  US13/405,218
• Publication Number:
  US 20120154339A1
• Time in Patent Office: 1,404 Days
• Field of Search: 345173-178, 178 1801- 1806
• US Class Current: 1/1
• 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 sensor output values in a sensor panel, comprising:

performing a scan of the sensor panel to generate a plurality of sensor output values;

determining one or more spatial regions of the sensor panel associated with each of the plurality of sensor output values, each region associated with a plurality of sensors, an offset adjustment value, and a gain multiplication factor;

obtaining the offset adjustment value for each region by

recording and averaging no-event 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 no-event output value for the region and the baseline output value; and

applying the offset adjustment value and the gain multiplication factor to each previously generated sensor output value located in a region to generate normalized sensor output values for the region.

2. The method of claim 1, further comprising determining whether a virtual input has been triggered by comparing a function of one or more normalized sensor output values with a threshold.

3. The method of claim 1, further comprising:

obtaining the gain multiplication factor for each 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.

4. The method of claim 1, the applying of the offset adjustment value and the gain multiplication factor to each sensor output value to generate normalized output values comprising:

performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment value and the gain multiplication factor for the region within which each sensor is located.

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

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

7. An apparatus for normalizing sensor output values in a sensor panel, comprising:

a panel processor programmed for

performing a scan of the sensor panel to generate a plurality of sensor output values;

determining one or more spatial regions of the sensor panel associated with each of the plurality of sensor output values, each region associated with a plurality of sensors, an offset adjustment value, and a gain multiplication factor;

obtaining the offset adjustment value for each region by

recording and averaging no-event 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 no-event output value for the region and the baseline output value; and

applying the offset adjustment value and the gain multiplication factor to each previously generated sensor output value located in a region to generate normalized sensor output values for the region.

8. The apparatus of claim 7, the processor further programmed for determining whether a virtual input has been triggered by comparing a function of one or more normalized sensor output values with a threshold.

9. The apparatus of claim 7, further comprising one or more event detection and demodulation circuits coupled to the panel processor for generating the output values.

10. The apparatus of claim 9, further comprising a computing system that incorporates the apparatus, the computing system comprising:

the sensor panel, the 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.

11. The apparatus of claim 10, further comprising a mobile telephone that incorporates the computing system.

12. The apparatus of claim 10, further comprising a digital audio player that incorporates the computing system.

13. The apparatus of claim 7, the panel processor further programmed for applying the offset adjustment value and gain multiplication factor to each sensor output value to generate normalized output values by performing mathematical operations in accordance with an error compensation algorithm using the offset adjustment value and the gain multiplication factor for the region within which each sensor is located.

14. The apparatus of claim 7, the sensor panel comprising a touch sensor panel.

15. The apparatus of claim 7, the sensor panel comprising a hover sensor panel.

16. An apparatus for normalizing sensor output values in a sensor panel, comprising:

means for performing a scan of the sensor panel to generate a plurality of sensor output values;

means for determining one or more spatial regions of the sensor panel associated with each of the plurality of sensor output values, each region associated with a plurality of sensors, an offset value, and a gain multiplication factor;

means for obtaining the offset adjustment value for each region by

recording and averaging no-event 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 no-event output value for the region and the baseline output value; and

means for applying the offset adjustment value and the gain multiplication factor to each previously generated sensor output value located in the region to generate normalized output values for the region.

17. The apparatus of claim 16, further comprising means for determining whether a virtual input has been triggered by comparing a function of one or more normalized sensor output values with a threshold.

18. A non-transitory computer-readable storage medium comprising program code for normalizing sensor output values in a sensor panel, the program code for causing performance of a method comprising:

performing a scan of the sensor panel to generate a plurality of sensor output values;

determining one or more spatial regions of the sensor panel associated with each of the plurality of sensor output values, each region associated with a plurality of sensors, an offset adjustment value, and a gain multiplication factor;

obtaining the offset adjustment value for each region by

recording and averaging no-event 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 no-event output value for the region and the baseline output value; and

applying the offset adjustment value and the gain multiplication factor to each previously generated sensor output value located in the region to generate normalized sensor output values for the region.

19. The non-transitory computer-readable storage medium of claim 18, the method further comprising determining whether a virtual input has been triggered by comparing a function of one or more normalized sensor output values with a threshold.