Method for object detection on a capacitive touchpad

• US 8,102,376 B2
• Filed: 12/28/2005
• Issued: 01/24/2012
• Est. Priority Date: 06/08/2005
• Status: Expired due to Fees

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Lii, Jia-Yih, Tang, Kuan-Chun
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): PHAM, LONG D
• Application Number:
  US11/318,883
• Publication Number:
  US 20060279551A1
• Time in Patent Office: 2,218 Days
• Field of Search: 345173-178
• US Class Current: 345/173
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

In an object detection method for a capacitive touchpad, at least one reference time interval is used to distinguish whether a variation of the sensed value on the touchpad is resulted from an operation of an object on the touchpad, actions such as an object touch down to the touchpad, an object lift from the touchpad and an object movement on the touchpad are then determined, and operations corresponding to various gestures are correctly detected.

Claims

1. An object detection method for a capacitive touchpad, comprising the steps of:

monitoring a set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a first sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values; and

determining that the object has left the touchpad when the set of differential sensed capacitive values between the first and second time intervals is negative and the sets of first and second sensed capacitive values are below a predetermined threshold.

2. The method of claim 1, further comprising the step of verifying that the object has touched on the touchpad before the step of monitoring a sensed capacitive value on the touchpad.

3. The method of claim 1, further comprising the steps of:

counting a time duration after the object is determined to have left the touchpad; and

producing a lift signal if the time duration reaches a second reference time interval.

4. An object detection method for a capacitive touchpad, comprising the steps of:

monitoring a set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a first sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values; and

determining that the object moves in a first direction from a reference position when the set of differential sensed capacitive values between the first and second time intervals is positive at points on the touchpad offset from the reference position in the first direction and negative at points on the touchpad offset from the reference position in a second direction opposite the first direction.

5. The method of claim 4, further comprising the step of verifying that the object touches on the touchpad before the step of monitoring a sensed capacitive value on the touchpad.

6. An object detection method for a capacitive touchpad, comprising the steps of:

monitoring a set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a first sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values;

determining that the object moves in a first direction from a reference position when the set of differential sensed capacitive values between the first and second time intervals is positive at points on the touchpad offset from the reference position in the first direction and negative at points on the touchpad offset from the reference position in a second direction opposite to the first direction;

calculating a position information of the object and sending out the position information; and

repeating the previous step if the object is detected to move on the touchpad again before a time duration after the previous time the object is detected to move on the touchpad reaches the reference time interval.

7. The method of claim 6, further comprising the step of verifying that the object touches on the touchpad before the step of monitoring a sensed capacitive value on the touchpad.

8. An object detection method for a capacitive touchpad, comprising the steps of:

verifying that an object has touched on the touchpad responsive to continuous variation of a set of sensed capacitive values corresponding to multiple positional locations of the object during a reference time interval including the step of subtracting a currently sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values;

counting a first time duration that the object remains on the touchpad;

verifying that the object has left the touchpad if the object is detected to leave the touchpad before the first time duration reaches a first reference time interval;

counting a second time duration after the object has left the touchpad; and

producing a tap signal if the second time duration reaches a second reference time interval;

wherein the step of verifying that the object leaves the touchpad comprises the steps of;

monitoring the set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a currently sensed capacitive value at each positional location during a third time interval from a second sensed capacitive value at each positional location at a fourth time interval forming a set of differential sensed capacitive values; and

determining that the object has left the touchpad when the set of differential sensed capacitive values is below the threshold within a third reference time interval and the set of differential sensed capacitive values remains negative during the third reference time interval.

9. The method of claim 8, wherein the step of verifying that an object has touched down on the touchpad comprises the steps of:

monitoring the sensed capacitive value on the touchpad;

monitoring a variation of the sensed capacitive value when the sensed capacitive value is greater than a threshold; and

determining that the object has touched on the touchpad if the sensed capacitive value remains greater than the threshold within a third reference time interval and the differential sensed capacitive value remains positive during the third reference time interval.

10. The method of claim 8, further comprising the step of calculating a position information of the object and sending out the position information if the tap signal is produced.

11. An object detection method for a capacitive touchpad, comprising the steps of:

monitoring a set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a currently sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values;

determining that the object has touched on the touchpad when the set of sensed capacitive values between the first and second time intervals is positive and the sets of currently and second sensed capacitive values remains greater than the threshold;

counting a first time duration that the object remains on the touchpad;

verifying that the object has left the touchpad if the object is detected to leave the touchpad before the first time duration reaches a second reference time interval;

counting a second time duration after the object has left the touchpad;

verifying that the object has touched on the touchpad again if the touchpad is detected to be touched again before the second time duration reaches a third reference time interval;

counting a third time duration that the object remains on the touchpad in the second touch; and

producing a drag signal if the third time duration reaches a fourth reference time interval;

wherein the step of verifying that the object leaves the touchpad comprises the steps of;

monitoring the set of sensed capacitive values on the touchpad;

subtracting a currently sensed capacitive value at each positional location during a third time interval from a second sensed capacitive value at each positional location at a fourth time interval forming a set of differential sensed capacitive values; and

determining that the object has left the touchpad when the set of sensed capacitive values remains less than the threshold within a fifth reference time interval and the set of differential sensed capacitive values remains negative during the fifth reference time interval.

12. The method of claim 11, further comprising the step of calculating a position information of the object and sending out the position information if the drag signal is produced.

13. An object detection method for a capacitive touchpad, comprising the step of:

monitoring a set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a currently sensed capacitive value at each positional location during a first time interval from a second sensed capacitive value at each positional location at a second time interval forming a set of differential sensed capacitive values;

determining that the object has touched the touchpad when the set of differential sensed capacitive values is greater than the threshold within a first reference time interval and the set of differential sensed capacitive values is positive during the first reference time interval;

counting a first time duration that the object remains on the touchpad;

verifying that the object has left the touchpad if the object is detected to leave the touchpad before the first time duration reaches a second reference time interval;

counting a second time duration after the object leaves the touchpad;

verifying that the object has touched on the touchpad again if the touchpad is detected to be touched again before the second time duration reaches a third reference time interval;

counting a third time duration that the object remains on the touchpad in the second touch;

verifying that the object has left from the touchpad if the object is detected to leave the touchpad again before the third time duration reaches a fourth reference time interval; and

producing a double tap signal if the object is verified to leave the touchpad in the previous step;

wherein the step of verifying that the object leaves the touchpad comprises the steps of;

monitoring the set of sensed capacitive values corresponding to multiple positional locations of the object on the touchpad;

subtracting a currently sensed capacitive value at each positional location during a third time interval from a second sensed capacitive value at each positional location at a fourth time interval forming a set of differential sensed capacitive values; and

determining that the object has left the touchpad when the set of sensed capacitive values remains less than the threshold within a fifth reference time interval and the set of differential sensed capacitive values remains negative during the fifth reference time interval.

14. The method of claim 13, further comprising the step of calculating a position information of the object and sending out the position information if the double tap signal is produced.