Force sensor baseline calibration

• US 9,164,605 B1
• Filed: 02/03/2010
• Issued: 10/20/2015
• Est. Priority Date: 02/03/2010
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Pirogov, Oleksandr, Karpin, Oleksandr, Hutnyk, Volodymyr
• Primary Examiner(s): Okebato, Sahlu
• Application Number:
  US12/699,741
• Time in Patent Office: 2,085 Days
• Field of Search: 345/173, 345/156
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04144 using an array of force sensing means position sensing using the local deformation of sensor cells G06F3/0447
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

An apparatus may include processing logic coupled with a force sensor input and a touch sensor input. The processing logic is configured to determine a relative force magnitude based on a force signal received at the force sensor input and a baseline measurement of the force sensor. The processing logic updates the baseline measurement in response to detecting that the touch signal indicates the absence of the one or more touches from the sensing surface.

Claims

1. An apparatus, comprising:

one or more inputs configured to receive a force signal from a force sensor and a touch signal from a touch sensor, wherein the force signal indicates a magnitude of a force applied at a sensing surface, and wherein the touch sensor includes a capacitance sensor; and

processing logic coupled with the one or more inputs, wherein the processing logic is configured to

determine a relative force magnitude based on the force signal and a baseline measurement of the force sensor, and

update the baseline measurement of the force sensor in response to the touch signal received from the capacitance sensor that indicates a removal of one or more touches from the sensing surface, the force signal being received after a detecting of the removal of the one or more touches from the sensing surface, the force signal being a raw force signal,

wherein the update of the baseline measurement of the force sensor comprises setting the baseline measurement equal to a signal level of the force signal, wherein the signal level corresponds to a time during which the touch signal indicates that the one or more touches are removed from the sensing surface.

2. The apparatus of claim 1, wherein the touch signal indicates an absence of the one or more touches from the sensing surface by indicating the removal of the one or more touches from the sensing surface.

3. The apparatus of claim 1, wherein the removal of the one or more touches from the sensing surface corresponds to a falling edge of the touch signal.

4. The apparatus of claim 1, wherein the touch sensor includes an array of capacitive sensor elements.

5. The apparatus of claim 1, wherein the touch signal indicates a location for each of the one or more touches at the sensing surface.

6. The apparatus of claim 1, wherein the force sensor comprises a plurality of force sensitive elements, and wherein the force signal is generated from a plurality of force signals each generated by one of the plurality of force sensitive elements.

7. The apparatus of claim 1, wherein the processing logic is configured to calculate, using the force signal, a magnitude of a component force applied by each of the one or more touches at the sensing surface.

18. The apparatus of claim 1, wherein the processing logic is configured to update the baseline measurement of the force sensor in response to detecting a falling edge of the touch signal.

8. A method, comprising:

receiving from a force sensor a force signal indicating a magnitude of a force applied at a sensing surface;

receiving a touch signal from a touch sensor, wherein the touch sensor includes a capacitance sensor;

determining a relative force magnitude based on the force signal and a baseline measurement of the force sensor; and

updating the baseline measurement of the force sensor in response to the touch signal received from the capacitance sensor that indicates a removal of one or more touches from the sensing surface, the force signal being received after a detecting of the removal of the one or more touches from the sensing surface, the force signal being a raw force signal,

wherein the updating of the baseline measurement of the force sensor comprises setting the baseline measurement equal to a signal level of the force signal, wherein the signal level corresponds to a time during which the touch signal indicates that the one or more touches are removed from the sensing surface.

9. The method of claim 8, wherein detecting the removal of the one or more touches from the sensing surface comprises detecting a falling edge of the touch signal.

10. The method of claim 8, further comprising determining, from the touch signal, a location for each of the one or more touches at the sensing surface.

11. The method of claim 8, further comprising generating the force signal from a plurality of force signals, wherein each of the plurality of force signals is generated by one of a plurality of force sensing resistors.

12. The method of claim 8, further comprising calculating, using the force signal, a magnitude of a component force applied by each of the one or more touches at the sensing surface.

13. The method of claim 8, wherein updating the baseline of the force sensor comprises setting the baseline equal to a measurement of a signal generated by the force sensor while the one or more touches are absent from the sensing surface.

19. The method of claim 8, wherein the updating of the baseline measurement of the force sensor is responsive to detecting a falling edge of the touch signal.

14. An apparatus, comprising:

a force sensor input configured to receive, from a force sensor, a force signal indicating a magnitude of one or more forces applied at a sensing surface;

a touch sensor input configured to receive, from a touch sensor, a touch signal indicating a location of each of one or more touches at the sensing surface, wherein the touch sensor includes a capacitance sensor; and

processing logic coupled with the force sensor input and the touch sensor input, wherein the processing logic is configured to determine, based on the force signal and the locations of each of the one or more touches, a magnitude of a force applied by each of the one or more touches at the sensing surface, and wherein the processing logic is further configured to update a baseline measurement of the force sensor in response to the touch signal received from the capacitance sensor that indicates a removal of the one or more touches from the sensing surface, the force signal being received after a detecting of the removal of the one or more touches from the sensing surface, the force signal being a raw force signal,

wherein the update of the baseline measurement of the force sensor comprises setting the baseline measurement equal to a signal level of the force signal, wherein the signal level corresponds to a time during which the touch signal indicates that the one or more touches are removed from the sensing surface.

15. The apparatus of claim 14, wherein the processing logic is further configured to determine a relative force magnitude based on the force signal and the baseline measurement of the force sensor.

20. The apparatus of claim 14, wherein the removal of the one or more touches from the sensing surface corresponds to a falling edge of the touch signal.

21. The apparatus of claim 14, wherein the touch sensor includes an array of capacitive sensor elements.

22. The apparatus of claim 14, wherein the force sensor comprises a plurality of force sensitive elements, and wherein the force signal is generated from a plurality of force signals each generated by one of the plurality of force sensitive elements.

16. A method, comprising:

receiving from a force sensor a force signal indicating a magnitude for each of one or more forces measured by one or more force sensing elements at a sensing surface;

receiving from a touch sensor a touch signal indicating a location of each of one or more touches at the sensing surface, wherein the touch sensor includes a capacitance sensor;

determining, based on the magnitude for each of the one or more forces and the location of each of the one or more touches, a magnitude of a component force for each of the one or more touches at the sensing surface; and

updating a baseline measurement of the force sensor in response the touch signal received from the capacitance sensor that indicates a removal of the one or more touches from the sensing surface, the force signal being received after a detecting of the removal of the one or more touches from the sensing surface, the force signal being a raw force signal,

wherein the update of the baseline measurement of the force sensor comprises setting the baseline measurement equal to a signal level of the force signal, wherein the signal level corresponds to a time during which the touch signal indicates that the one or more touches are removed from the sensing surface.

17. The method of claim 16, further comprising:

determining the relative force magnitude based on the force signal and the baseline measurement of the force sensor.

23. The method of claim 16, wherein detecting the removal of the one or more touches from the sensing surface comprises detecting a falling edge of the touch signal.

24. The method of claim 16, further comprising generating the force signal from a plurality of force signals, wherein each of the plurality of force signals is generated by one of a plurality of force sensing resistors.