DEVICE AND METHOD FOR DETECTING TOUCH SCREEN

• US 20130038573A1
• Filed: 10/12/2012
• Published: 02/14/2013
• Est. Priority Date: 03/19/2008
• Status: Active Grant

• Current Assignee: eGalax_eMPIA Technology Inc.
• Original Assignee: eGalax_eMPIA Technology Inc.
• Inventors: Tang, Chi-Hao, Chang, Chin-Fu
• Granted Patent: US 8,952,928 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• 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 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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

Abstract

The invention discloses a full screen driven detection. A driving signal is simultaneously provided to all first conductive strips arranged in parallel in a first direction in a touch screen, and mutual capacitive signals are detected from all second conductive strips arranged in parallel in a second direction. The mutual capacitive signals can be used for determining whether an external conductive object coupled to the ground is touching or approaching the touch screen or not even if water or other conductive object not coupled to ground is on the touch screen. Thus, the baseline of the mutual capacitive signals can be updated if the touch screen is not touched or approached by any external conductive object coupled to ground over a predetermined period of time.

Claims

1. A method for detecting a touch screen comprising:

providing the touch screen including a plurality of first conductive strips and a plurality of second conductive strips;

performing a full screen driven detection including;

simultaneously providing a driving signal to all of the first conductive strips;

when all of the first conductive strips are provided with the driving signal, detecting mutual capacitive signals of all of the second conductive strips to generate a one-dimensional (1D) sensing information based on the signals of all of the second conductive strips; and

determining whether at least one external conductive object coupled to ground is touching or approaching the touch screen based on the 1D sensing information; and

when determining the touch screen is not touched or approached by any external conductive object over a predetermined period of time based on the 1D sensing information, performing a 2D mutual capacitive detection to obtain a 2D sensing information, and updating reference values based on the 2D sensing information, wherein the 2D mutual capacitive detection includes;

sequentially providing a driving signal to one or more different conductive strips in the first conductive strips;

each time one or more different conductive strips in the first conductive strips being provided with the driving signal, detecting the signals of all of the second conductive strips to obtain a 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal generated based on the mutual capacitive signals of all of the second conductive strips; and

combining each 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal to generate a 2D sensing information.

2. The method of claim 1, wherein when determining the touch screen is not touched or approached by any external conductive object for the predetermined period of time based on the 1D sensing information, a 2D mutual capacitive detection is performed to obtain a 2D sensing information, and a location of each external conductive object coupled to ground is determined based on the 2D sensing information.

3. The method of claim 1, wherein a location of each external conductive object coupled to ground is determined from the amount of change between mutual capacitive signals of the 2D sensing information and the reference values.

4. The method of claim 1, wherein updating the reference values based on the 2D sensing information includes using the 2D sensing information as the new reference values or using an average of the 2D sensing information and the original reference values as the new reference values.

5. The method of claim 1, wherein the driving signal is provided to all of the first conductive strips at a first frequency, and when the touch screen is not touched or approached by any external conductive object coupled to ground for a predetermined period of time or a predetermined number of times since providing the driving signal to all of the first conductive strips at the first frequency, the driving signal is provided to all of the first conductive strips at a second frequency instead, wherein the first frequency is faster than the second frequency.

6. The method of claim 5, wherein when an approach or a touch of an external conductive object coupled to ground on the touch screen is determined while all of the first conductive strips are provided with the driving signal at the second frequency, the driving signal is provided to all of the first conductive strips at the first frequency again.

7. The method of claim 1, wherein the touch screen includes an insulating surface layer, a first sensing layer including the first conductive strips, an insulating layer, and a second sensing layer including the second conductive strips.

8. The method of claim 1, wherein the touch screen is a rectangle including two opposite long sides and two opposite short sides, wherein the first conductive strips are arranged in parallel with the two opposite short sides, and the second conductive strips are arranged in parallel with the two opposite long sides.

9. A device for detecting a touch screen in accordance with the present invention includes:

the touch screen including a plurality of first conductive strips and a plurality of second conductive strips; and

a controller for performing a full screen driven detection, including;

simultaneously providing a driving signal to all of the first conductive strips;

when all of the first conductive strips are provided with the driving signal, detecting mutual capacitive signals of all of the second conductive strips to generate a one-dimensional (1D) sensing information based on the signals of all of the second conductive strips; and

determining whether at least one external conductive object coupled to ground is touching or approaching the touch screen based on the 1D sensing information; and

when the controller determining the touch screen is not touched or approached by any external conductive object over a predetermined period of time based on the 1D sensing information, performing a 2D mutual capacitive detection to obtain a 2D sensing information to update reference values based on the 2D sensing information, wherein the 2D mutual capacitive detection includes;

sequentially providing a driving signal to one or more different conductive strips in the first conductive strips, and providing a DC potential to all of the guarding conductive strips;

each time one or more different conductive strips in the first conductive strips being provided with the driving signal, detecting the signals of all of the second conductive strips to obtain a 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal generated based on the mutual capacitive signals of all of the second conductive strips; and

combining each 1D sensing information corresponding to the one or more first conductive strips being provided with the driving signal to generate a 2D sensing information.

10. The device of claim 9, wherein when determining the touch screen is not touched or approached by any external conductive object for the predetermined period of time based on the 1D sensing information, a 2D mutual capacitive detection is performed to obtain a 2D sensing information, and a location of each external conductive object coupled to ground is determined based on the 2D sensing information.

11. The device of claim 9, wherein a location of each external conductive object coupled to ground is determined from the amount of change between mutual capacitive signals of the 2D sensing information and the reference values.

12. The device of claim 9, wherein updating the reference values based on the 2D sensing information includes using the 2D sensing information as the new reference values or using an average of the 2D sensing information and the original reference values as the new reference values.

13. The device of claim 9, wherein the driving signal is provided to all of the first conductive strips at a first frequency, and when the touch screen is not touched or approached by any external conductive object coupled to ground for a predetermined period of time or a predetermined number of times since providing the driving signal to all of the first conductive strips at the first frequency, the driving signal is provided to all of the first conductive strips at a second frequency instead, wherein the first frequency is faster than the second frequency.

14. The device of claim 13, wherein when an approach or a touch of an external conductive object coupled to ground on the touch screen is determined while all of the first conductive strips are provided with the driving signal at the second frequency, the driving signal is provided to all of the first conductive strips at the first frequency again.

15. The device of claim 9, wherein the touch screen includes an insulating surface layer, a first sensing layer including the first conductive strips, an insulating layer, and a second sensing layer including the second conductive strips.

16. The device of claim 9, wherein the touch screen is a rectangle including two opposite long sides and two opposite short sides, wherein the first conductive strips are arranged in parallel with the two opposite short sides, and the second conductive strips are arranged in parallel with the two opposite long sides.