Equalized capacitive touchpad and touch positioning method

• US 8,830,201 B2
• Filed: 07/22/2013
• Issued: 09/09/2014
• Est. Priority Date: 03/25/2008
• Status: Expired due to Fees

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Huang, Chun-Chung, Wang, Tsun-Min
• Primary Examiner(s): NGUYEN, JENNIFER T
• Application Number:
  US13/948,002
• Publication Number:
  US 20130307822A1
• Time in Patent Office: 414 Days
• Field of Search: 345173-178, 178 1801- 1806
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• 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 of a mutual capacitance between two sensing lines of the capacitive touchpad, to thereby offset the attenuation of the sensed value due to the impedance of the two sensing lines. 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 M first sensing lines in a first direction and N second sensing lines in a second direction with M×

N mutual capacitances therebetween, where M and N are integers larger than one;

a controller coupled to the N second sensing lines, the controller comprising a front-end circuit for detecting the M×

N mutual capacitances to generate M×

N sensed values; and

an equalizer coupled to the front-end circuit, having M×

N equalization values respectively corresponding to the M×

N mutual capacitances between the M first sensing lines and the N second sensing lines, for determining a corresponding equalization value according to position information of a detected mutual capacitance, and correcting the sensed value with the corresponding equalization value to obtain a corrected sensed value;

wherein the equalization values are for compensating for resistor-capacitance filtering effect, and the corresponding equalization value increases as the detected mutual capacitance is more distant from the controller; and

wherein the corrected sensed value is used to determine a touched position.

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 corresponding equalization value according to the equalize function and the position information of the detected mutual capacitance.

3. The equalized capacitive touchpad of claim 1, wherein the controller is coupled to two ends of each of the M first sensing lines.

4. The equalized capacitive touchpad of claim 3, wherein the controller is coupled to two ends of each of the N second sensing lines.

5. The equalized capacitive touchpad of claim 1, wherein each of the M first sensing lines comprises two sub-sensing lines connected in parallel and each of the two sub-sensing lines has a plurality of capacitive sensor pads.

6. The equalized capacitive touchpad of claim 1, wherein each of the N second sensing lines comprises two sub-sensing lines connected in parallel and each of the two sub-sensing lines has a plurality of capacitive sensor pads.

7. The equalized capacitive touchpad of claim 1, wherein the M first sensing lines and the N second sensing lines are transparent.

8. The equalized capacitive touchpad of claim 1, wherein the M first sensing lines and the N second 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 M first sensing lines and the N second sensing lines intersect with each other.

10. The equalized capacitive touchpad of claim 1, wherein the M first sensing lines and the N second sensing line intersect with each other orthogonally.

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

detecting a plurality of mutual capacitances respectively formed between a plurality of first sensing lines and a plurality of second sensing lines by a controller to generate a plurality of sensed values;

determining a corresponding equalization value according to position information of a detected mutual capacitance;

correcting the sensed value with the corresponding equalization value to obtain a corrected sensed value; and

identifying a touched position according to the corrected sensed value;

wherein the equalizations values associated with the mutual capacitances are for compensating for resistor-capacitance filtering effect, and the corresponding equalization value increases as the detected mutual capacitance is more distant from the controller.

12. The touch positioning method of claim 11, wherein the step of determining the corresponding equalization value:

storing an equalize function in advance; and

determining the equalization value according to the equalize function and the position information of the detected mutual capacitance.

13. The touch positioning method of claim 11, wherein the step of detecting the plurality of mutual capacitances comprises the steps of:

sequentially applying a first signal to each of the plurality of first sensing lines;

receiving a second signal from each of the plurality of second sensing lines; and

determining the plurality of sensed values from the second signal.