Movement detection method for multiple objects on a capacitive touchpad

• US 20070132741A1
• Filed: 09/13/2006
• Published: 06/14/2007
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Chiu, Yen-Chang, Yang, Tso-Chieh, Chung, Hsuang-Lung
• Granted Patent: US 8,040,324 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• 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 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

In a movement detection method for multiple objects on a capacitive touchpad, the waveform of sensed values on the touchpad is monitored for its variation to determine respective movements of the objects on the touchpad, and various operational gestures are further determined exactly.

Claims

1. A movement detection method for multiple objects on a capacitive touchpad, the method comprising the steps of:

detecting sensed values on the touchpad for obtaining a waveform of the sensed values when the touchpad is touched;

identifying the waveform for determining a first peak and a second peak thereof;

determining a first object and a second object on the touchpad if both of the first peak and the second peak are greater than a first threshold value;

dividing the waveform for defining a first region and a second region corresponding to the first object and the second object, respectively;

monitoring a first variation in the sensed values within the first region and a second variation in the sensed values within the second region;

determining the first object moving on the touchpad if the first variation is greater than a second threshold value; and

determining the second object moving on the touchpad if the second variation is greater than a third threshold value.

2. The method of claim 1, wherein the step of identifying the waveform comprises the step of determining a valley between the first peak and the second peak.

3. The method of claim 2, wherein the step of dividing the waveform comprises the steps of:

defining two regions in the waveform at two opposite sides of the valley which have the sensed values greater than a fourth threshold value as the first region and the second region, respectively, if the valley is lower than or equal to the fourth threshold value; and

dividing a region in the waveform which has the sensed values greater than the fourth threshold value into the first region and the second region with the valley as a boundary if the valley is greater than the fourth threshold value.

4. The method of claim 1, wherein the step of monitoring a first variation and a second variation comprises the step of detecting the sensed values on the touchpad twice with a reference time interval and calculating a difference in the sensed values therebetween.

5. The method of claim 1, wherein the step of determining the first object moving on the touchpad comprises the step of determining the first object having a displacement in a first direction if the sensed values in the first region have a trend of increasing in the first direction and decreasing in a second direction opposite to the first direction.

6. The method of claim 1, wherein the step of determining the second object moving on the touchpad comprises the step of determining the second object having a displacement in a first direction if the sensed values in the first region have a trend of increasing in the first direction and decreasing in a second direction opposite to the first direction.

7. The method of claim 1, wherein the step of monitoring a first variation and a second variation comprises the step of monitoring a first displacement of the first peak and a second displacement of the second peak.

8. The method of claim 1, wherein the step of monitoring a first variation and a second variation comprises the step of monitoring a first displacement of a first center of mass of the first region and a second displacement of a second center of mass of the second region.

9. A movement detection method for multiple objects on a capacitive touchpad, the method comprising the steps of:

detecting whether or not the touchpad is touched;

detecting whether or not one or more objects move on the touchpad if there are at least two objects detected in the previous detecting step; and

producing a respective digital signal corresponding to a respective object which is detected moving on the touchpad in the previous detecting step.

10. The method of claim 9, wherein the respective digital signal comprises a displacement of the respective object during a reference time interval.

11. The method of claim 9, wherein the respective digital signal comprises an absolute coordinate or a relative coordinate of the respective object.

12. The method of claim 9, wherein the step of detecting whether or not one or more objects move on the touchpad comprises the steps of:

detecting sensed values on the touchpad for obtaining a waveform of the sensed values when the touchpad is touched;

identifying the waveform for determining a first peak and a second peak thereof;

determining a first object and a second object on the touchpad if both of the first peak and the second peak are greater than a first threshold value;

dividing the waveform for defining a first region and a second region corresponding to the first object and the second object, respectively;

monitoring a first variation in the sensed values within the first region and a second variation in the sensed values within the second region;

determining the first object moving on the touchpad if the first variation is greater than a second threshold value; and

determining the second object moving on the touchpad if the second variation is greater than a third threshold value.

13. The method of claim 12, wherein the step of identifying the waveform comprises the step of determining a valley between the first peak and the second peak.

14. The method of claim 13, wherein the step of dividing the waveform comprises the steps of:

defining two regions in the waveform at two opposite sides of the valley which have the sensed values greater than a fourth threshold value as the first region and the second region, respectively, if the valley is lower than or equal to the fourth threshold value; and

dividing a region in the waveform which has the sensed values greater than the fourth threshold value into the first region and the second region with the valley as a boundary if the valley is greater than the fourth threshold value.

15. The method of claim 12, wherein the step of monitoring a first variation and a second variation comprises the step of detecting the sensed values on the touchpad twice with a reference time interval and calculating a difference in the sensed values therebetween.

16. The method of claim 12, wherein the step of determining the first object moving on the touchpad comprises the step of determining the first object having a displacement in a first direction if the sensed values in the first region have a trend of increasing in the first direction and decreasing in a second direction opposite to the first direction.

17. The method of claim 12, wherein the step of determining the second object moving on the touchpad comprises the step of determining the second object having a displacement in a first direction if the sensed values in the first region have a trend of increasing in the first direction and decreasing in a second direction opposite to the first direction.

18. The method of claim 12, wherein the step of monitoring a first variation and a second variation comprises the step of monitoring a first displacement of the first peak and a second displacement of the second peak.

19. The method of claim 12, wherein the step of monitoring a first variation and a second variation comprises the step of monitoring a first displacement of a first center of mass of the first region and a second displacement of a second center of mass of the second region.