Equalized capacitive touchpad and touch positioning mehtod

• US 20090244029A1
• Filed: 03/24/2009
• Published: 10/01/2009
• Est. Priority Date: 03/25/2008
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Lin, Tse-Chi, Lin, Chun-Yu, Huang, Chun-Chung, Wang, Tsun-Min
• Granted Patent: US 8,525,801 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• 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

An equalized capacitive touchpad and a touch positioning method for a capacitive touchpad use an equalizer to correct a sensed value detected from a sensing line of the capacitive touchpad, to thereby offset the attenuation of the sensed value due to the impedance of the sensing line. Thus, the sensed values generated from different positions along a sensing line are equalized, and the touch positioning accuracy of the capacitive touchpad is improved.

Claims

1. An equalized capacitive touchpad, comprising:

a touch sensor having a plurality of sensing lines in a first direction and a plurality of sensing lines in a second direction to generate, in response to a touch, a capacitance variation in the first direction and a capacitance variation in the second direction respectively;

a front-end circuit coupled to the sensing lines, detecting the capacitance variations so as to generate a sensed value in the first direction and a sensed value in the second direction, wherein the sensed value in the second direction is used to determine a position information in the second direction; and

an equalizer coupled to the front-end circuit, determining an equalization value according to the position information in the second direction, so as to correct the sensed value in the first direction.

2. The equalized capacitive touchpad of claim 1, wherein the equalizer comprises:

a memory storing an equalize function; and

an arithmetic logic unit coupled to the memory, determining the equalization value according to the equalize function.

3. The equalized capacitive touchpad of claim 1, wherein the sensing lines in the second direction have a balanced resistance/capacitance distribution.

4. The equalized capacitive touchpad of claim 3, wherein the sensing lines in the second direction are interleaving arranged.

5. The equalized capacitive touchpad of claim 3, wherein the sensing lines in the second direction are arranged in a same direction and each of them has a U shape.

6. The equalized capacitive touchpad of claim 3, wherein the sensing lines in the second direction are interleaving arranged each of them has a U shape.

7. The equalized capacitive touchpad of claim 1, wherein the sensing lines are transparent.

8. The equalized capacitive touchpad of claim 1, wherein the sensing lines are made of an indium tin oxide, indium zinc oxide, carbon paste or silver ink.

9. The equalized capacitive touchpad of claim 1, wherein the sensing lines in the first direction intersect the sensing lines in the second direction.

10. The equalized capacitive touchpad of claim 1, wherein the sensing lines in the first direction intersect the sensing lines in the second direction orthogonally.

11. A touch positioning method for a capacitive touchpad, comprising the steps of:

in response to a touch, generating a capacitance variation in a first direction and a capacitance variation in a second direction;

detecting the capacitance variations so as to generate a sensed value in the first direction and a sensed value in the second direction;

determining a position information in the second direction according to the sensed value in the second direction;

determining an equalization value according to the position information in the second direction;

correcting the sensed value in the first direction with the equalization value; and

determining a position information in the first direction according to the corrected sensed value in the first direction.

12. The touch positioning method of claim 11, wherein the step of determining an equalization value according to the position information in the second direction comprises the steps of:

storing an equalize function; and

determining the equalization value according to the equalize function.

13. The touch positioning method of claim 11, wherein the sensed values in the second direction are substantially equalized.