Algorithmic compensation system and method therefor for a touch sensor panel

• US 6,506,983 B1
• Filed: 03/05/1999
• Issued: 01/14/2003
• Est. Priority Date: 03/15/1996
• Status: Expired due to Term

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touchsystems Incorporated (Elo Touch Solutions, Inc.)
• Inventors: Babb, Joe Henry, Wilson, Geoffrey D.
• Primary Examiner(s): Shankar, Vijay
• Application Number:
  US09/263,694
• Time in Patent Office: 1,411 Days
• Field of Search: 178/18.01, 178/18.02, 178/18.03, 178/18.04, 178/18.05, 178/18.06, 178/18.07, 345/173, 345/174, 345/177, 345/178, 345/179
• US Class Current: 178/18.01
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A general method is described for producing an inexpensive touchscreen system that provides accurate positional information and compensates for manufacturing variations without complicated sensor arrangements. Utilizing a set of sensed signals that are unique to each location on the touchscreen sensor, equations for X and Y are derived via curve fitting methods. The coefficients of the equations are stored with the sensor. During touchscreen operation the coefficients are used to calculate X and Y to the desired accuracy directly and independently.

Claims

1. A system for relating a plurality of input values, each being responsive to and varying smoothly over a range of positions of a condition, with coordinate positions of the condition over a surface of a medium, comprising:

(a) a plurality of inputs receiving a set of input values produced in response to a condition at a coordinate position on the surface of the medium; and

(b) a memory for storing information relating to a mapping relationship of the plurality of input values to a coordinate position of the condition, said stored information including information derived for said medium and set of inputs from empirical observation, to account for an actual configuration of said medium and set of inputs.

2. The system according to claim 1, wherein the mapping relationship comprises a plurality of terms, each term being a coefficient or a mathematical function of at least one coefficient and a value associated with at least one detector output, the mapping equation relating the detector outputs with a position of the applied physical effect.

3. The system according to claim 1, wherein the mapping relationship comprises a mapping function operating to directly map the detector outputs to corrected coordinate positions of physical effects substantially without an intermediate representation of an uncorrected coordinate position.

4. The system according to claim 1, wherein the mapping relationship operates to map a localized physical effect detected by at least three detectors to a coordinate position of said location of the physical effect, said stored information including information derived for said medium and detectors from empirical observation, to account for an actual configuration of said medium and detectors.

5. The system according to claim 1, further comprising a processor for processing the input values at a plurality of distinct coordinate positions to derive the mapping relationship.

6. The system according to claim 1, further comprising a processor for processing the set of input values to determine a coordinate position of a condition, based on the stored information relating to the mapping relationship.

7. The system according to claim 1, wherein said position is a Cartesian coordinate position, said memory storing coefficients of a pair of mapping equations corresponding to said pair of Cartesian coordinates.

8. The system according to claim 1, wherein the mapping relationship consists of a polynomial equation, comprising a sum of a plurality of selected product terms of coefficients and one or more detector outputs.

9. The system according to claim 1, wherein the mapping relationship comprises a polynomial equation, the polynomial equation comprising a sum of a plurality of selected product terms of coefficients and one or more detector outputs, the plurality of terms being selected such that a predetermined minimum accuracy is achieved with minimum computational complexity.

10. The system according to claim 1, wherein the mapping relationship comprises a polynomial equation, the polynomial equation comprising a sum of a plurality of selected product terms of coefficients and one or more detector outputs, the plurality of terms being selected such that a predetermined minimum accuracy is achieved with a minimum number of coefficients.

11. The system according to claim 1, wherein the mapping relationship consists essentially of a polynomial equation, comprising a sum of a plurality of product terms of coefficients and input values, each term being between order zero and order four in the input value space.

12. The system according to claim 1, further comprising the step of providing four detectors for receiving the set of input values, the mapping relationship being equations of the form:

13. The system according to claim 1, wherein the surface is provided on a medium having a characteristic plane, divided into quadrants, further comprising the steps of producing a set of quadrant mapping relationships for each quadrant, the quadrant mapping relationships being equations having sets of coefficients, further comprising the steps of estimating a quadrant of the condition-effecting element and then applying a mapping relationship based on the estimated quadrant, employing the corresponding set of mapping relationship coefficients.

14. The system according to claim 1, wherein said mapping relationship is a mapping equation having coefficients, said coefficients being determined based on a predetermined set of mapping equation terms, using a least mean square error fitting of said detector outputs to said determined positions of said physical effect applied to said medium.

15. The system according to claim 1, wherein the mapping relationship comprises an mapping equation having a set of coefficients, further comprising the steps of:

providing a memory for storing the coefficients, and a host processor for evaluating the mapping equation and executing application software, the processor comprising local storage;

transferring the coefficients stored in the memory to the local storage; and

evaluating the mapping equation with the processor.

16. The system according to claim 15, wherein each of said coefficients is derived based on contributions from a plurality of detector outputs at a plurality of determined positions.

17. The system according to claim 16, wherein the determined positions are of sufficient number and of such arrangement to measure a configuration and a manufacturing variation of the system, the mapping equation being of sufficient complexity to compensate for the measured configuration and manufacturing variation.

18. The system according to claim 1, wherein the mapping relationship is derived based on sets of inputs at a plurality of coordinate are provided in a regular spaced arrangement.

19. The system according to claim 1, wherein said memory comprises a rotating magnetic storage disk.

20. The system according to claim 1, further comprising a host processor for evaluating said mapping relationship and executing application software, said host processor comprising local storage, and means for transferring the information stored in said memory to said local storage.

21. The system according to claim 1, further comprising an integrated structure for said medium and said inputs;

a processor outside of said integrated structure for evaluating said relation; and

an output transmitting information representative of said detector outputs from said integrated structure to said processor.

22. The system according to claim 1, wherein said substrate has a curved non-planar surface.

23. The system according to claim 1, wherein the condition is represented nonlinearly in said set of input values with respect to a coordinate position thereof.

24. The system according to claim 1, wherein each input signal is measured at a detector, said input values being nonlinearly related to a distance from a coordinate position to a respective detector.

25. The system according to claim 1, wherein said medium comprises an electrically conductive medium, and condition comprises a perturbation of an electrical field in said medium.

26. The system according to claim 25, wherein said inputs comprise electrodes in electrical communication with said conductive medium.

27. The system according to claim 25, wherein each of the electrodes has an electrical path, each input value being a current passing through one of the electrical paths of the associated electrode to interface electronics, said detectors, medium, and interface electronics being contained in an integrated structure, further comprising the an output from said interface electronics, said output of said interface electronics being transmitted out of said integrated structure.

28. The system according to claim 25, further comprising an electrode having a repositionable point of contact with the electrically conductive medium, the set of input values varying based on a position of the point of contact.

29. The system according to claim 25, further comprising interface electronics for generating detector output values based on said set of input values.

30. The system according to claim 25, further comprising a current source for injecting an electrical current having a time-varying waveform with respect to an electrical reference into said medium to produce said electrical field;

and a conductive pathway to said electrical reference, having a dielectric barrier, said pathway and barrier being for effecting said electrical field at said coordinate position on said medium.

31. The system according to claim 25, wherein said conductive medium is formed by a method comprising depositing a conductive layer on a substrate, the deposited conductive layer being subject to manufacturing variations as localized differences in impedance.

32. The system according to claim 31, wherein said conductive medium comprises a glass sheet with a coating selected from the group consisting of indium-tin-oxide and antimony-tin-oxide.

33. The system according to claim 25, further comprising a conductive repositionable contact electrode;

and a current source for inducing an electrical current to flow in said inputs and said repositionable contact electrode.

34. The system according to claim 33, wherein said current flows through said contact electrode and said conductive medium in series and said inputs in parallel.

35. The system according to claim 25, said medium comprising an electrically conductive medium having a rectangular surface, said inputs comprising four electrodes in electrical communication with corners of said rectangular surface, said detectors comprising electrodes in electrical communication with said conductive medium, said memory storing coefficients of a mapping relationship algorithm comprising a multiple variable least mean square fit of data relating to said detector outputs to said determined positions, said plurality of positions being of sufficient number and of such arrangement to measure a configuration and a manufacturing variation of said system, said mapping equation being of sufficient complexity to compensate for said measured configuration and manufacturing variation within a predetermined minimum accuracy.

36. The system according to claim 25, wherein said repositionable electrode comprises a conductive sheet spaced from said surface, and being locally deformable to alter a local spacing from said surface.

37. The system according to claim 25, wherein said inputs comprise spaced electrodes, one of said plurality of spaced electrodes and said repositionable electrode injecting an electrical current into said medium, and a remainder of said spaced electrodes each sense a resulting electrical signal in said medium to produce said set of input values.

38. The system according to claim 25, wherein said medium further comprises an electromechanical system for compensating said detector output.

39. The system according to claim 38, wherein said electromechanical system comprises a conductive pattern on said surface.

40. The system according to claim 39, wherein said conductive pattern is formed on a periphery of said surface.

41. The system according to claim 1, wherein said physical effect is a force, said detectors comprising force detectors, and said medium being a force-transmissive medium.

42. The system according to claim 1, further comprising an integrated structure including said medium and inputs, and a digital communications channel for transmitting the set of input values from the integrated structure.

43. The system according to claim 1, wherein said memory comprises a semiconductor memory physically associated with said medium and detectors.

44. The system according to claim 1, wherein the coordinate position comprises a pair of coordinates corresponding to an absolute position of the medium.

45. A method for relating a set including a plurality of input values, each being responsive to and varying smoothly over a range of positions of a condition, with coordinate positions of the condition over a surface, comprising the steps of:

(a) providing sets of measured input values produced at a plurality of distinct determined coordinate positions; and

(b) processing the sets of measured input values in conjunction with the respective distinct coordinate positions thereof to derive a multidimensional mapping relation, the mapping relation relating a set of input values with an associated coordinate position.

46. The method according to claim 45, further comprising the steps of providing a set of input values relating to a condition at an unknown coordinate position, and processing the set of input values from an unknown coordinate position, based on the multidimensional mapping relation, to determine the coordinate position of the condition.

47. The method according to claim 45, wherein the mapping relation comprises an equation having a set of coefficients and a plurality of terms, each term being associated with at least one coefficient and optionally a mathematical function of at least one measured input value.

48. The method according to claim 45, wherein the mapping relation is derived from a set of empirical measurements, to account for an actual configuration of the surface and a configuration of a set of detectors through which the set of input values is detected.

49. The method according to claim 45, wherein the mapping relation directly maps the set of input values to corrected coordinate positions substantially without an intermediate representation of an uncorrected coordinate position.

50. The method according to claim 45, wherein the mapping relation comprises a polynomial equation, the polynomial equation comprising a sum of a plurality of selected product terms of coefficients and one or more detector outputs, the plurality of terms being selected such that a predetermined minimum accuracy is achieved with minimum computational complexity.

51. The method according to claim 45, wherein the mapping relation comprises a polynomial equation, the polynomial equation comprising a sum of a plurality of selected product terms of coefficients and one or more detector outputs, the plurality of terms being selected such that a predetermined minimum accuracy is achieved with a minimum number of coefficients.