Device and method for detecting touch screen

• US 20100295816A1
• Filed: 07/13/2009
• Published: 11/25/2010
• Est. Priority Date: 05/20/2009
• Status: Abandoned Application

• Current Assignee: Vimicro Corporation
• Original Assignee: Vimicro Corporation
• Inventors: Zhang, Chen
• Application Number:
  US12/475,593
• Publication Number:
  US 20100295816A1
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

Techniques for detecting multiple touch points for touch screen are disclosed. A touch screen includes a first conductive layer and a second conductive layer, each conductive layer having a positive terminal and a negative terminal, an operation of detecting multiple points on a touch screen includes: coupling the positive terminal of the second conductive layer to a positive reference voltage, coupling the negative terminal of the second conductive layer to a negative reference voltage, sampling the positive terminal of the first conductive layer to obtain a series of first voltage samples V1(i), sampling the negative terminal of the first conductive layer to obtain a series of second voltage samples V2(i), wherein i is a sampling number; concluding that a motion tendency of two touch points on the touch screen is contraction when absolute values of the differences V1(i)−V2(i) between the first voltage samples and the second voltage samples tend to increase; and concluding that the motion tendency of two touch points on the touch screen is expansion when the absolute values of the differences V1(i)−V2(i) tend to decrease.

Claims

1. A method for detecting a touch screen, the touch screen including a first conductive layer and a second conductive layer, each conductive layer having a positive terminal and a negative terminal, the method comprising:

coupling the positive terminal of the second conductive layer to a positive reference voltage, coupling the negative terminal of the second conductive layer to a negative reference voltage, sampling the positive terminal of the first conductive layer to obtain a series of first voltage samples V1(i), sampling the negative terminal of the first conductive layer to obtain a series of second voltage samples V2(i), wherein i is a sampling number;

concluding that a motion tendency of two touch points on the touch screen is contraction when absolute values of the differences V1(i)−

V2(i) between the first voltage samples and the second voltage samples tend to increase; and

concluding that the motion tendency of two touch points on the touch screen is expansion when the absolute values of the differences V1(i)−

V2(i) tend to decrease.

2. The method according to claim 1, further comprising:

counting a number of the absolute values of the differences V1(i)−

V2(i) being larger than a first threshold; and

concluding that there are two touch points on the touch screen when the number is larger than a predefined number threshold.

3. The method according to claim 1, further comprising:

determining whether all or most of the differences V1(i)−

V2(i) are larger than a second threshold or less than a third threshold;

determining whether the absolute values of the differences V1(i)−

V2(i) tend to increase if yes;

concluding that the motion tendency of two touch points on the touch screen is rotation otherwise.

4. The method according to claim 3, wherein the determining whether the absolute values of the differences V1(i)−

V2(i) tend to increase comprises;

computing a first average value of the differences V1(i)−

V2(i) of the first half of samples, and a second average value of the differences V1(i)−

V2(i) of the second half of samples;

determining whether an absolute value of the first average value is larger than an absolute value of the second average value;

indicating that the absolute values of the differences V1(i)−

V2(i) tend to decrease if yes; and

indicating that the absolute values of the differences V1(i)−

V2(i) tend to increase otherwise.

5. The method according to claim 3, wherein the second threshold is less than or equal to zero, and the third threshold is larger than or equal to zero.

6. A method for detecting a touch screen, the touch screen including a first conductive layer and a second conductive layer, each conductive layer having a positive terminal and a negative terminal, the method comprising:

coupling the positive terminal of the second conductive layer to a positive reference voltage, coupling the negative terminal of the second conductive layer to a negative reference voltage, sampling the positive terminal of the first conductive layer to obtain a series of first voltage samples V1(i), sampling the negative terminal of the first conductive layer to obtain a series of second voltage samples V2(i), wherein i is a sampling sequence number;

calculating differences V1(i)−

V2(i) of the first voltage samples and the second voltage samples; and

determining a motion tendency of two touch points according to the differences V1(i)−

V2(i).

7. The method according to claim 6, wherein the determining a motion tendency of two touch points according to the differences V1(i)−

V2(i) comprising;

concluding that a motion tendency of two touch points on the touch screen is contraction when absolute values of the differences V1(i)−

V2(i) between the first voltage samples and the second voltage samples tend to increase; and

concluding that the motion tendency of two touch points on the touch screen is expansion when the absolute values of the differences V1(i)−

V2(i) tend to decrease.

8. The method according to claim 6, wherein the determining a motion tendency of two touch points according to the differences V1(i)−

V2(i) comprising;

determining whether the differences V1(i)−

V2(i) tend to increase when all or most of differences V1(i)−

V2(i) is larger than 0, concluding that the motion tendency of two touch points on the touch screen is expansion if yes, and concluding that the motion tendency of two touch points on the touch screen is contraction otherwise;

determining whether the differences V1(i)−

V2(i) tend to decrease when all or most of differences V1(i)−

V2(i) is less than 0, concluding that the motion tendency of the two touch points on the touch screen is expansion if yes, and concluding that motion tendency of the two touch points on the touch screen is contraction otherwise.

9. The method according to claim 6, further comprising:

counting a number of the absolute values of the differences V1(i)−

V2(i) being larger than a first threshold; and

concluding that there are two touch points on the touch screen when the number is larger than a predefined number threshold.

10. The method according to claim 6, wherein the determining a motion tendency of two touch points according to the differences V1(i)−

V2(i) comprising;

determining whether some differences V1(i)−

V2(i) being larger than 0 and some differences V1(i)−

V2(i) being less than 0;

concluding that the motion tendency of the two touch points on the touch screen is rotation if yes; and

concluding that the motion tendency of the two touch points on the touch screen is expansion or contraction otherwise.

11. The method according to claim 10, wherein

determining whether absolute values of the differences V1(i)−

V2(i) tend to increase when the motion tendency of the two touch points on the touch screen is expansion or contraction;

concluding that a motion tendency of two touch points on the touch screen is contraction when the absolute values of the differences V1(i)−

V2(i) tend to increase; and

concluding that the motion tendency of two touch points on the touch screen is expansion when the absolute values of the differences V1(i)−

V2(i) tend to decrease.

12. A device for detecting touch screen, comprising:

a touch screen comprising a first conductive layer and a second conductive layer, each conductive layer having a positive terminal and a negative terminal;

a selector configured to couple the positive terminal of the second conductive layer to a positive reference voltage, and couple the negative terminal of the second conductive layer to a negative reference voltage;

an analog-to-digital configured to sample the positive terminal of the first conductive layer to obtain a series of first voltage samples V1(i), and sample the negative terminal of the first conductive layer to obtain a series of second voltage samples V2(i), wherein i is a sampling sequence number;

a micro processor configured to conclude that a motion tendency of two touch points on the touch screen is contraction when absolute values |V1(i)−

V2(i)| tend to increase and conclude that the motion tendency of the two touch points on the touch screen is expansion when the absolute values |V1(i)−

V2(i)| tend to decrease.

13. The device according to claim 12, wherein the micro processor is configured for:

counting a number of the absolute values |V1(i)−

V2(i)| being larger than a first threshold; and

determining that there are two touch points on the touch screen when the number is larger than a predefined number threshold.