Method for identifying touch object

• US 8,970,521 B2
• Filed: 03/27/2012
• Issued: 03/03/2015
• Est. Priority Date: 09/22/2011
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Chiu, Ching-Ting
• Primary Examiner(s): ABDIN, SHAHEDA A
• Application Number:
  US13/431,144
• Publication Number:
  US 20130076700A1
• Time in Patent Office: 1,071 Days
• Field of Search: 345/173, 345/156, 345/174, 345/204, 178/18.1, 178/18.9, 178/18.01, 178/18.09
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A method for identifying touch object on a touch panel has steps of (A) reading m capacitance variations on a first direction, wherein the m capacitance variations respectively correspond to m sensed units of the touch panel; (B) determining whether a difference between the capacitance variation of a k^th sensed unit and that of another sensed unit exceeds a preset noise ripple, wherein k is equal to or smaller than m, m is a positive integer; (C) determining whether the capacitance variation of the k^th sensed unit exceeds those of the adjacent sensed units; and (D) determining a touch stylus touched on the touch panel when the difference exceeds the preset noise ripple and the capacitance variation of the k^th sensed unit exceeds those of the adjacent sensed units. Accordingly, the method can correctly identify a range touched by a stylus from the sensed signals combined with LCM noise signals.

Claims

1. A method for identifying touch object on to a touch panel, the method comprising:

(A) reading m capacitance variation values on a first direction, wherein the m capacitance variation values respectively correspond to m sensed units of the touch panel;

(B) determining whether a difference value between the capacitance variation value of a k^th sensed unit and that of another sensed unit is larger than a preset noise ripple value, wherein k is equal to or smaller than m and m is a positive integer;

(C) determining whether the capacitance variation value of the k^th sensed unit is larger than those of the adjacent sensed units; and

(D) determining a touch stylus touched on the touch panel when the difference value is larger than the preset noise ripple value and the capacitance variation value of the k^th sensed unit is larger than those of the adjacent sensed units.

2. The method as claimed in claim 1, wherein the method is applied to a self-sensing sensing frame, and the sensed unit is a sensed line.

3. The method as claimed in claim 1, wherein the method is applied to a full mutual-scanning sensing frame and the sensed unit is a sensed point.

4. The method as claimed in claim 3, wherein in the step (B), when the difference value is smaller than the preset noise ripple value the, the step (B) further comprising:

comparing the capacitance variation value of the k^th sensed unit with a capacitance variation threshold for finger, and if the capacitance variation of the k^th sensed unit is greater than the capacitance variation threshold for finger, determining that the capacitance variation of the k^th sensed unit is not a liquid crystal module noise.

5. The method as claimed in claim 1, wherein the capacitance variation value of each sensed unit is equal to a value subtracting a capacitance value of a corresponding true sensed signal from a base value.

6. The method as claimed in claim 5, further comprising a step of updating the base value performed when no touch stylus touched on the touch panel is determined, wherein the step of updating the base value comprises:

(a1) obtaining the capacitance variation values of the m sensed units, and a minimum of the capacitance variation values of the m sensed units;

(a2) subtracting the base value from the minimum of the capacitance variation values;

(a3) determining if the difference value of the step (a2) is greater than zero; and

(a4) if positive, updating the base value by adding the difference value of the step (a2) to the base value of each sensed unit.

7. The method as claimed in claim 1, wherein

in the step (B), taking each three adjacent sensed units as a group, wherein the three adjacent sensed units of each group comprise a previous, a present and a next sensed unit in a position sequence, the step (B) comprises:

(a) respectively subtracting the capacitance variation values of the previous sensed unit and the next sensed unit from the present sensed unit to obtain two difference values;

determining if the two difference values of the step (a) are both less than the noise ripple value;

if positive, storing zeros in the buffer of the present sensed unit;

(b) if negative in the step (a), determining if the capacitance variation value of the present sensed unit

(c) if negative in the step (b), respectively subtracting the capacitance variation values of the previous sensed unit and the next sensed unit from the capacitance variation values of the present sensed unit to obtain two different values;

selecting the smaller one of the two difference values of the step (c) to compare with zero;

if the smaller difference value is greater than zero, storing the smaller difference value in the present sensed unit;

if the smaller difference value is less than zero, storing zero in the buffer of the present sensed unit.

8. The method as claimed in claim 7, further comprising:

presetting an upper threshold and a lower threshold of capacitance variation for stylus; and

if the value stored in the buffer of the sensed unit is greater than the lower threshold of capacitance variation for stylus, and is less than the upper threshold of capacitance variation for stylus, determining the sensed unit touched by the stylus.

9. A method for identifying touch object on a touch panel, the method comprising:

(A) reading m capacitance variation values on a first direction, wherein the m capacitance variation values respectively correspond to m sensed units of the touch panel;

(B) determining whether a difference value between the capacitance variation value of a k^th sensed unit and that of another sensed unit is larger than a preset noise ripple value, wherein k is equal to or smaller than m and m is a positive integer; and

(C) determining that the capacitance variation value of the k^th sensed unit is not a liquid crystal module noise when the difference value is larger than the preset noise ripple value.

10. The method as claimed in claim 9, wherein the method is applied to a self-sensing sensing frame, and the sensed unit is a sensed line.

11. The method as claimed in claim 9, wherein the method is applied to a full mutual-scanning sensing frame and the sensed unit is a sensed point.

12. The method as claimed in claim 9, wherein in the step (B), when the difference value is smaller than the preset noise ripple value, the step (B) further comprising:

comparing the capacitance variation value of the k^th sensed unit with a capacitance variation threshold for finger, and if the capacitance variation of the k^th sensed unit is greater than the capacitance variation threshold for finger, determining that the capacitance variation value of the k^th sensed unit is not the liquid crystal module noise.

13. The method as claimed in claim 9, wherein the capacitance variation value of each sensed unit is equal to a value subtracting a capacitance value of a corresponding true sensed signal from a base value.

14. The method as claimed in claim 9, further comprising a step of updating the base value performed when the capacitance variation value of each sensed unit is not determined to be not the liquid crystal module noise, wherein the step of updating the base value has steps of:

(a1) obtaining the capacitance variation values of the m sensed units, and a minimum of the capacitance variation values of the m sensed units;

(a2) subtracting the base value from the minimum of the capacitance variation values;

(a3) determining if the difference value of the step (a2) is greater than zero; and

(a4) if positive, updating the base value by adding the difference value of the step

(a2) to the base value of each sensed unit.

15. The method as claimed in claim 9, wherein

in the step (B), taking each three adjacent sensed units as a group, wherein the three adjacent sensed units of each group comprise a previous, a present and a next sensed unit in a position sequence, the step (B) comprising:

respectively subtracting the capacitance variation values of the previous sensed unit and the next sensed unit from the present sensed unit to two difference values;

determining if the two difference values of the step (a) are both less than the noise ripple value;

if positive, storing zeros in the buffer of the present sensed unit;

(b) if negative in the step (a), determining if the capacitance variation value of the present sensed unit is greater than the capacitance variation threshold for finger;

if positive, storing the current capacitance variation value in the buffer of the present sensed unit

(c) if negative in the step (b), respectively subtracting the capacitance variation values of the previous sensed unit and the next sensed unit from the capacitance variation values of the present sensed unit to obtain two difference values;

selecting the smaller one of the two difference values of the step (c) to compare with

if the smaller difference value is greater than zero, storing the smaller difference value in the buffer of the present sensed unit;

if the smaller difference value is less than zero, storing zero in the buffer of the present sensed unit.

16. The method as claimed in claim 15, further comprising:

presetting an upper threshold and a lower threshold of capacitance variation for stylus; and

if the value stored in the buffer of the sensed unit is greater than the lower threshold of capacitance variation for stylus, and is less than the upper threshold of capacitance variation for stylus, determining the sensed unit is touched by the stylus.