Method and apparatus for electronic touch mapping

• US 4,623,757 A
• Filed: 11/29/1984
• Issued: 11/18/1986
• Est. Priority Date: 11/29/1984
• Status: Expired due to Term

• Current Assignee: Interaction Systems Incorporated (Computer Library Systems, Inc.)
• Original Assignee: Interaction Systems Incorporated (Computer Library Systems, Inc.)
• Inventors: Marino, Michael J.
• Primary Examiner(s): Schreyer, Stafford D.
• Application Number:
  US06/676,185
• Time in Patent Office: 719 Days
• Field of Search: 178/18, 178/19, 178/20, 340/712, 340/706
• US Class Current: 178/18.03
• CPC Class Codes: G06F 2203/04113 Peripheral electrode pattern in resistive digitisers, i.e. electrodes at the periphery of the resistive sheet are shaped in patterns enhancing linearity of induced field
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Touch mapping method and apparatus locate a touch to an unpatterned and continuous layer of selected electrical conductivity in response to the incremental electrical charge which the conductive layer draws at one or more known positions, in response to electrical excitation, and relative to the charge which layer draws in the absence of the touch condition. The measurement of electrical charge provides touch location for a variety of touch impedances and other impedences coupled with the selectively conductive layer.

Claims

1. In a method for mapping a touch to an unpatterned and selectively electrically conductive layer having a known conductivity property, wherein the mapping is relative to at least a first coordinate axis, the improvement comprising the steps of

A. measuring an electrical charge which said layer draws over a selected time duration from an electrical signal source in response to the touch,

B. applying at least one of a means for effecting said measurement and said source to said conductive layer at a first position relative to said coordinate, and

C. determining said mapping of the touch relative to said first position in response to said charge measurement.

2. In a method according to claim 1, the further improvement comprising the steps of

A. measuring at a second position relative to said coordinate axis electrical charge which said layer draws from said electrical signal source in response to the touch, where said first and second positions are selected so that the touch is between said first and second positions, and

B. determining the mapping of the touch in response to an arithmetic ratio function of the measured electrical charges drawn at said first and second positions respectively.

3. In a method according to claim 1 the further improvement comprising the steps of

A. coupling said electrical signal source to said conductive layer at the touch, and

B. providing said first position at the periphery of said layer.

4. In a method according to claim 1 the further improvement comprising the step of

A. coupling said electrical signal source to said conductive layer at the periphery of said layer.

5. In a method according to claim 1 the further improvement comprising the steps of

A. coupling said electrical signal source to said conductive layer at said first position, and

B. providing said first position at the periphery of said layer.

6. In a method according to claim 1 the further improvement wherein said measuring step includes measuring an incremental charge which said layer draws in the presence of said touch relative to a charge drawn in the absence of said touch.

7. In a method according to claim 1 the further improvement comprising the steps of

A. clamping an electrical potential of the conductive layer to a known level at periodic intervals, and

B. continuing said measurement of charge over plural ones of said periodic intervals.

8. In a method for mapping a touch to an unpatterned and selectively electrically conductive layer having a known conductivity per dimension, wherein the mapping is relative to at least a first coordinate axis, and including applying an electrical measuring signal to said layer, the improvement comprising the steps of

A. measuring an incremental electrical charge which said layer draws over a selected time duration from said measuring signal in the presence of said touch, relative to a charge drawn over said time duration in the absence of said touch,

B. applying at least one of said measuring signal and a means for effecting said charge measurement to said layer at a first position relative to said first coordinate, and

C. determining said mapping of the touch relative to said first position in response to said charge measurement.

9. In a method according to claim 8 the further improvement comprising the steps of

A. applying a first electrical measuring signal to said layer at said first position,

B. applying concurrently a second electrical measuring signal to said layer at a second position relative to said first coordinate and spaced from said first position so that the touch being located is between said first and second positions relative to said first coordinate, and

C. selecting said first and second measuring signals to attain a minimal charge drawn by said layer at said first position in the absence of said touch.

10. In a method according to claim 9 the further improvement wherein said first and second measuring signals are substantially identical.

11. In a method according to claim 8 the further improvement comprising the step of applying said measuring signal with a known periodic voltage wave-form.

12. In a method according to claim 9 the further improvement comprising the steps of

A. measuring an incremental charge which said layer draws, at said second position from said source signal, in the presence of said touch relative to a charge drawn in the absence of said touch, and

B. determining the location of the touch in response to an arithmetic ratio function of said incremental charges measured at said first and said second positions.

13. A method for locating a touch to an unpatterned and selectively electrically conductive layer having a known conductivity per dimension wherein the location is along a first axis, said method comprising the steps of

A. applying to said conductive layer at a first location along said first axis a first measuring signal having a selected voltage,

B. applying a second measuring signal having a selected voltage to said conductive layer at a second location spaced along said first axis from said first location so that the touch is between said first and second locations,

C. measuring at each of said first and second locations an incremental electrical charge which the layer draws over a selected time duration from said first and second measuring signals in the presence of said touch, relative to the charge drawn over said time duration in the absence of said touch, and

D. determining the relative location of the touch in response to a ratio function of said measures of incremental charge at said first and second locations.

14. A method according to claim 13 comprising the further steps of

A. applying said first and second measuring signals concurrently,

B. selecting said measuring signals to attain minimal electrical charge drawn at each of said first and second positions in the absence of a touch to said conductive layer.

15. A method according to claim 14 comprising the further step of

A. selecting said first and second measuring signals to have identical time-varying periodic voltages having at least a first clamped value.

16. In apparatus for locating a touch to a touch panel having an unpatterned and selectively electrically conductive layer thereon with a known conductivity per dimension property and wherein the location is with reference to at least a first coordinate axis, said apparatus having the improvement comprising

A. electrical source means for applying a known electrical source signal to said conductive layer,

B. means for measuring an incremental charge which said layer draws over a selected time duration from said source means in the presence of the touch at at least a first position known with reference to said first coordinate and relative to which the touch is to be located, relative to a charge which the layer draws over a selected time duration from said source means at said first location in the absence of said touch, and

C. means for determining the relative location of the touch in response to the measurement of incremental charge at at least said first position.

17. In apparatus according to claim 16 the further improvement comprising electrical current mirror circuitry connected with said source means and with said conductive layer and with said measuring means for applying said source signal to said conductive layer and for applying to said measuring means a current signal responsive to the current signal said conductive layer draws from said source means.