Multi-touch touch screen with single-layer ITO bars arranged in parallel

• US 8,248,383 B2
• Filed: 04/21/2009
• Issued: 08/21/2012
• Est. Priority Date: 04/24/2008
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Dews, Christopher William, Seaborg, Charles Henry Jr.
• Primary Examiner(s): Abdulselam, Abbas
• Application Number:
  US12/427,460
• Publication Number:
  US 20090267914A1
• Time in Patent Office: 1,218 Days
• Field of Search: 345/156, 345/173, 345174-177, 178/18.01, 178 1802- 1809
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• 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
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A touch screen includes a plurality of single-layer ITO bars having a substantially rectangular shape and arranged in parallel to each other in order to detect touches on the touch screen. The location of a touch on the touch screen in the direction along an ITO bar is determined by applying a signal on one end of the ITO bar and measuring the change in the amplitude and the delay of the signal on the opposite end of the ITO bar. Such application and measurement of the signal can be repeated with the application of the signal occurring on the opposite end of the ITO bar and the measurement of the signal occurring on said one end of the ITO bar, in order to enhance the accuracy of the measurement.

Claims

1. A touch screen, comprising:

a plurality of conductive bars arranged in parallel to each other, each of the conductive bars including a single conductive layer with a substantially rectangular shape; and

a touch screen controller coupled to the conductive bars, the controller configured to;

apply a first excitation signal to a first end of one of the conductive bars and measure a first response signal corresponding to the first excitation signal at a second end of said one of the conductive bars, the touch screen controller configured to determine a position of a touch on said one of the conductive bars in a first direction along said one of the conductive bars based on a first difference between the first response signal and the first excitation signal;

apply a second excitation signal to the second end of said one of the conductive bars and measure a second response signal at the first end of said one of the conductive bars, the touch screen controller configured to determine the position of the touch on said one of the conductive bars in the first direction along said one of the conductive bars based on the first difference between the first response signal and the first excitation signal and a second difference between the second response signal and the second excitation signal; and

determine the positions of multiple touches on the touch screen that occur substantially simultaneously on different ones of the conductive bars.

2. The touch screen of claim 1, wherein the first difference is a first voltage difference V1 between the peak voltages of the first excitation signal and the first response signal, the second difference is a second voltage difference V2 between the peak voltages of the second excitation signal and the second response signal, and the position of the touch in percentage from the first end on said one of the conductive bars is given by 100×

V1/(V1+V2).

3. The touch screen of claim 2, further comprising:

signal generation circuitry for generating the first excitation signal and the second excitation signal;

first multiplexing circuitry for selecting and coupling said one of the conductive bars to the signal generation circuitry to apply the first excitation signal and the second excitation signal to said one of the conductive bars;

voltage measurement circuitry for measuring voltages of the first response signal and the second response signal; and

second multiplexing circuitry for selecting and coupling said one of the conductive bars to the voltage measurement circuitry to determine the first voltage difference and the second voltage difference.

4. The touch screen of claim 1, wherein the first difference and the second difference are measured multiple times and averaged.

5. The touch screen of claim 1, wherein the touch screen controller is further configured to determine the position of the touch in a second direction across the conductive bars by interpolation of positions in the second direction of two of the conductive bars with a deepest touch and a second deepest touch.

6. The touch screen of claim 1, wherein the single conductive layer is a single layer of indium tin oxide (ITO).

7. A touch screen, comprising:

a plurality of conductive bars arranged in parallel to each other, each of the conductive bars including a single conductive layer with a substantially rectangular shape; and

a touch screen controller coupled to the conductive bars, the controller configured to apply a first excitation signal including digital pulses to a first end of one of the conductive bars and measure a first response signal corresponding to the first excitation signal at a second end of said one of the conductive bars both with and without a touch on said one of the conductive bars, and the touch screen controller further configured to apply a second excitation signal including the digital pulses to the second end of said one of the conductive bars and measure a second response signal corresponding to the second excitation signal at the second end of said one of the conductive bars both with and without a touch on said one of the conductive bars,

the touch screen controller configured to measure a first difference value (N1−

n1) between a first number n1 of the digital pulses and a second number N1 of the digital pulses needed for the first response signal to move from a first predetermined threshold to a second predetermined threshold with and without the touch, respectively,

the touch screen controller configured to measure a second difference value (N2−

n2) between a third number n2 of the digital pulses and a fourth number N2 of the digital pulses needed for the second response signal to move from the first predetermined threshold to the second predetermined threshold with and without the touch, respectively, and

the touch screen controller determining a position of the touch on said one of the conductive bars in a direction along said one of the conductive bars based on the first difference value (N1−

n1) and the second difference value (N2−

n2).

8. The touch screen of claim 7, wherein the position of the touch in percentage from the first end on said one of the conductive bars is given by 100×

(N1−

n1)/[(N1−

n1)+(N2−

n2)].

9. The touch screen of claim 7, wherein the single conductive layer is a single layer of indium tin oxide (ITO).

10. In a touch screen including a plurality of conductive bars arranged in parallel to each other, each of the conductive bars including a single conductive layer with a substantially rectangular shape, a method of determining a position of a touch on the touch screen, the method comprising:

applying a first excitation signal to a first end of one of the conductive bars;

measuring a first response signal corresponding to the first excitation signal at a second end of said one of the conductive bars;

determining the position of a touch on said one of the conductive bars in a first direction along said one of the conductive bars based on a first difference between the first response signal and the first excitation signal;

applying a second excitation signal to the second end of said one of the conductive bars;

measuring a second response signal at the first end of said one of the conductive bars;

determining the position of the touch on said one of the conductive bars in the first direction along said one of the conductive bars based on the first difference between the first response signal and the first excitation signal and a second difference between the second response signal and the second excitation signal; and

determining the positions of multiple touches on the touch screen that occur substantially simultaneously on different ones of the conductive bars.

11. The method of claim 10, wherein the first difference is a first voltage difference V1 between the peak voltages of the first excitation signal and the first response signal, the second difference is a second voltage difference V2 between the peak voltages of the second excitation signal and the second response signal, and the position of the touch in percentage from the first end on said one of the conductive bars is given by 100×

V1/(V1+V2).

12. The method of claim 10, wherein the first difference and the second difference are measured multiple times and averaged.

13. The method of claim 10, further comprising determining the position of the touch in a second direction across the conductive bars by interpolation of positions in the second direction of two of the conductive bars with a deepest touch and a second deepest touch.

14. The method of claim 10, wherein the single conductive layer is a single layer of indium tin oxide (ITO).

15. In a touch screen including a plurality of conductive bars arranged in parallel to each other, each of the conductive bars including a single conductive layer with a substantially rectangular shape, a method of determining a position of a touch on the touch screen, the method comprising:

applying a first excitation signal including digital pulses to a first end of one of the conductive bars both with and without a touch on said one of the conductive bars;

measuring a first response signal corresponding to the first excitation signal at a second end of said one of the conductive bars both with and without the touch on said one of the conductive bars;

applying a second excitation signal including the digital pulses to the second end of one of the conductive bars both with and without the touch on said one of the conductive bars;

measuring a second response signal corresponding to the second excitation signal at the second end of said one of the conductive bars both with and without the touch on said one of the conductive bars;

determining a first difference value (N1−

n1) between a first number n1 of the digital pulses and a second number N1 of the digital pulses needed for the first response signal to move from a first predetermined threshold to a second predetermined threshold with and without the touch, respectively,

determining a second difference value (N2−

n2) between a third number n2 of the digital pulses and a fourth number N2 of the digital pulses needed for the second response signal to move from the first predetermined threshold to the second predetermined threshold with and without the touch, respectively, and

determining the position of the touch on said one of the conductive bars in a direction along said one of the conductive bars based on the first difference value (N1−

n1) and the second difference value (N2−

n2).

16. The method of claim 15, wherein the position of the touch in percentage from the first end on said one of the conductive bars is given by 100×

(N1−

n1)/[(N1−

n1)+(N2−

n2)].

17. The method of claim 15, wherein the single conductive layer is a single layer of indium tin oxide (ITO).