Single layer touch sensor with improved sensitivity and accuracy

• US 9,007,310 B1
• Filed: 02/29/2008
• Issued: 04/14/2015
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Wistron Corporation
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Olson, Dana
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): LAM, NELSON C
• Application Number:
  US12/072,935
• Time in Patent Office: 2,601 Days
• Field of Search: 345173-179, 178 1805- 1806
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality

Abstract

Touch sensor methods, devices and systems are disclosed. One embodiment of the present invention pertains to a touch sensing system comprising a sensing device for sensing one or more touches on a sensor surface made of multiple conductive strips in one direction and a dual processing device for determining a horizontal position and a vertical position of each touch by processing currents generated in response to the touch, where the currents charge and discharge a capacitor formed between the touch and the sensor surface.

Claims

1. A touch sensing system, comprising:

a sensing device to sense at least one touch on a single layer sensor surface comprising a plurality of conductive strips disposed along one direction; and

a processing device coupled to the sensing device to determine a horizontal position and a vertical position of the at least one touch by processing currents generated in response to the at least one touch, the currents simultaneously flowing in opposite directions away from the at least one touch through at least one of the plurality of conductive strips, wherein the processing device is configured to measure a first current through a first end of the at least one of the plurality of conductive strips and measure a second current through a second end of the at least one of the plurality of conductive strips, wherein the currents discharge a capacitor formed between the each one of the at least one touch and the single layer sensor surface.

2. The system of claim 1, wherein the one direction is one of a horizontal direction and a vertical direction.

3. The system of claim 2, wherein the horizontal position of the touch is obtained based on a difference between the currents provided the one direction that is the horizontal direction.

4. The system of claim 3, wherein the vertical position of the touch is obtained based on a sum of the currents.

5. The system of claim 4, wherein the touch is detected when the sum of the currents is greater than a threshold value.

6. The system of claim 1, wherein the processing of the currents is performed simultaneously for all of the currents.

7. The system of claim 1, wherein each of the plurality of conductive strips comprise two electrodes connected at both ends to current measurement circuits.

8. The system of claim 7, wherein the each of the plurality of conductive strips is less than a size of a finger in width and separated in distance such that the touch crosses several adjacent ones of the plurality of the conductive strips.

9. The system of claim 8, wherein the each of the plurality of conductive strips is three to five millimeters in width.

10. The system of claim 1, wherein the plurality of conductive strips is one of straight and wavy.

11. The system of claim 1, wherein the plurality of conductive strips is based on an indium tin oxide (ITO) or a polyethylene dioxythiophene (pdot).

12. A touch sensing device, comprising:

a single layer sensor surface to sense at least one touch applied on the single layer sensor surface, wherein the single layer sensor surface comprises a plurality of conductive strips disposed along one direction;

wherein the at least one touch forms a respective number of capacitors between the at least one touch and the single layer sensor surface; and

a processor coupled to the single layer sensor surface to locate the at least one touch by processing currents discharged by the respective number of capacitors, the currents simultaneously flowing in opposite directions away from the at least one touch through at least one of the plurality of conductive strips, wherein the processor is configured to measure a first current through a first end of the at least one of the plurality of conductive strips and measure a second current through a second end of the at least one of the plurality of conductive strips.

13. The device of claim 12, wherein the processor comprises a programmable system on chip (PSOC).

14. The device of claim 12, wherein the processor comprises current measurement circuitry coupled to both ends of each conductive strip.

15. A method for detecting a touch on a sensor, comprising:

charging and discharging a capacitor formed between the touch and a sensor surface of the sensor, wherein the sensor comprises a plurality of conductive strips disposed along one direction;

measuring currents generated in response to the touch, the currents simultaneously flowing in opposite directions away from the touch through at least one of the plurality of conductive strips, wherein the measuring of the currents includes measuring a first current through a first end of the at least one of the plurality of conductive strips and measuring a second current through a second end of the at least one of the plurality of conductive strips;

determining a first coordinate of the touch based on a difference of the currents; and

determining a second coordinate of the touch based on a sum of the currents.

16. The method of claim 15, wherein the charging is performed using a voltage source and the measuring is performed using a current measuring device.

17. The method of claim 15, wherein the charging and the measuring are performed using two voltage sources and two current measuring devices each coupled to a respective one of the plurality of conductive strips.

18. The method of claim 15, wherein the measuring the currents further comprises converting the currents into unitless current coefficients.

19. The method of claim 15, wherein the touch involved at least two adjacent ones of the plurality conductive strips.

20. The method of claim 19, wherein the determining the second coordinate of the touch comprises interpolating respective sums of currents measured for the at least two adjacent ones of the plurality of conductive strips.