MULTIPOINT SENSING METHOD FOR CAPACITIVE TOUCH PANEL

• US 20100117981A1
• Filed: 12/29/2008
• Published: 05/13/2010
• Est. Priority Date: 11/07/2008
• Status: Active Grant

• Current Assignee: National Chiao Tung University (Government of The Republic of China)
• Original Assignee: National Chiao Tung University (Government of The Republic of China)
• Inventors: Chao, Paul C.P., Chen, Jian Ting, Ruan, Jyun-Yao
• Granted Patent: US 8,144,132 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• 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

A multi-point sensing method used in a capacitive touch panel is disclosed to detect the voltage variation of every electrode patterned on two parallel electrode layers by means of a capacitive sensing circuit, and measure the vertical capacitance at the intersection crossed by the electrodes of the two electrode layers where the voltage variation is detected, and then compare the vertical capacitance thus measured with the initial vertical capacitance at the same intersection before touch, as a result, the intersection corresponding to the measured vertical capacitance can be determined as the touch point when the comparison result shows different.

Claims

1. A multipoint sensing method used in a capacitive touch panel comprising a first electrode layer and a second electrode layer being electrically insulated and stacked with said first electrode layer, and adapted to sense multiple touch points when touch event occurs on one of the first electrode layer and the second electrode layer, the multipoint sensing method comprising the steps of:

a). inputting AC signals to multiple first electrodes of the first electrode layer and multiple second electrodes of the second electrode layer before touch event so as to detect a first capacitance between each two adjacent first electrodes, a second capacitance between each two adjacent second electrodes and a vertical capacitance intersected between one of the first electrode and one of the second electrode;

b). using the AC signal to detect variation of each of the first capacitance and each of the second capacitance, and recording to positions of the respective first electrodes and second electrodes which corresponding to the first capacitance and the second capacitance that are changed; and

c). using the AC signal to measure the vertical capacitance at each of the positions intersected by the respective first electrode and second electrode recorded in step b), and comparing the vertical capacitance thus obtained with the initial vertical capacitance measured in step a), and determining the intersected positions to be the touch points when the respective comparison result shows a difference.

2. The multipoint sensing method as claimed in claim 1, further comprising a capacitive sensing procedure for measuring one of the first capacitance, the second capacitance and the vertical capacitance, the capacitance sensing procedure is to provide a negative feedback amplifier having one of the first capacitance, the second capacitance and the vertical capacitance to be a feedback loop for respectively measuring one of the first capacitance, the second capacitance and the vertical capacitance.

3. The multipoint sensing method as claimed in claim 2, wherein the amplifier comprises a high input end electrically grounded, a low input end adapted to receive the AC signal, and an output end for feeding output signal back to the low input end.

4. The multipoint sensing method as claimed in claim 3, wherein the low input end and the output end of the amplifier are respectively electrically connected to two adjacent first electrodes of the first electrode layer during sensing each of the first capacitance.

5. The multipoint sensing method as claimed in claim 3, wherein the low input end and the output end of the amplifier are respectively electrically connected to two adjacent second electrodes of the second electrode layer during sensing each of the second capacitance.

6. The multipoint sensing method as claimed in claim 3, wherein the low input end and the output end of the amplifier are respectively electrically connected to one of the first electrode and one of the second electrode during sensing each of the vertical capacitance.

7. The multipoint sensing method as claimed in claim 2, further comprising a step of providing an input resistor electrically connected with the feedback loop of the amplifier for constructing an integrating amplifier with one of the first capacitance, the second capacitance and vertical capacitance.

8. The multipoint sensing method as claimed in claim 1, wherein the step of detecting variation of the first capacitance is to input the AC signal to one of the two adjacent first electrodes and then to detect the voltage variation of the other one of the two adjacent first electrodes.

9. The multipoint sensing method as claimed in claim 8, further comprising the step of estimating the variation of the equivalent resistance and equivalent capacitance of the two adjacent first electrodes according to the detected voltage variation for evaluating the region on the first electrodes adjacent to the touch point.

10. The multipoint sensing method as claimed in claim 8, wherein the method of detecting the variation of the second capacitance during step b) is to input the AC signal to one of the two adjacent second electrodes and then to detect the voltage variation of the other one of the two adjacent second electrodes.

11. The multipoint sensing method as claimed in claim 10, further comprising the step of estimating the variation of the equivalent resistance and equivalent capacitance of the two adjacent second electrodes according to the detected voltage variation for evaluating the region on the second electrodes adjacent to the touch point.

12. A multipoint sensing method used in a capacitive touch panel comprising a plurality of first electrodes arranged on a first plane in a first direction and a plurality of second electrodes arranged on a second plane in a second direction, and adapted to sense multiple touch points when touch event occurs on the touch panel, the multipoint sensing method comprising the steps of:

a) calculating and storing an initial vertical capacitance at every intersection crossed by each of the first electrodes and each of the second electrodes;

b) monitoring the voltage variation of the first electrodes and the second electrodes and recording the position where causing the voltage variation; and

c) detecting each vertical capacitance intersected by the first electrodes and the second electrodes which crossing the recorded position, and comparing the detected vertical capacitance with the initial vertical capacitance stored in step a) respective to the recorded position, and then determining the intersection corresponding to the detected vertical capacitance to be the touch point when the comparison result shows different.

13. The multipoint sensing method as claimed in claim 12, wherein the method of detecting the voltage variation of the first electrodes is to input an AC signal to one of two adjacent first electrodes and then to read the output voltage from the other one of the two adjacent first electrodes.

14. The multipoint sensing method as claimed in claim 13, further comprising the step of providing a negative feedback amplifier for having the two adjacent first electrodes to be a feedback loop of the negative feedback amplifier.

15. The multipoint sensing method as claimed in claim 14, wherein the amplifier comprises a high input end electrically grounded, a low input end for receiving AC signal, and an output end for feeding output signal back to the low input end.

16. The multipoint sensing method as claimed in claim 12, wherein the method of detecting the voltage variation of the second electrodes is to input an AC signal to one of two adjacent second electrodes and then to read the output voltage from the other one of the two adjacent second electrodes.

17. The multipoint sensing method as claimed in claim 16, further comprising the step of providing a negative feedback amplifier for having the two adjacent second electrodes to be a feedback loop of the negative feedback amplifier.