Method and apparatus for classifying touch events on a touch sensitive surface

1. An apparatus for classifying touch events, the apparatus comprising:

a touch sensitive surface configured to generate a touch event when an object or finger touches the touch sensitive surface, wherein the touch event entails a mechanical vibration generated upon contact with the surface;

a sampler configured to continuously sample and store mechanical vibration data spanning a period of time from before a touch event to after the touch event;

a touch event detector configured to detect the onset of the touch event; and

a touch event classifier configured to classify the touch event to identify the object used for the touch event based on sample mechanical vibration data captured during an entirety of the touch event including a frequency domain center of mass associated with the touch event.

2. The apparatus of claim 1 , wherein the touch event classifier comprises:

a conversion unit configured to convert a mechanical vibration signal into an electrical signal;

an extraction unit configured to derive a series of features representative of the touch event from the electrical signal; and

a classification unit configured to classify the touch input using the features to identify the object used for the touch event.

3. The apparatus of claim 2 , wherein the acoustic signal is created through the use of a passive tool impacting the touch sensitive surface.

4. The apparatus of claim 1 , wherein the mechanical vibration comprises an acoustic signal.

5. The apparatus of claim 1 , wherein the touch event detector is embedded in the apparatus to detect the touch event.

6. The apparatus of claim 1 , wherein the touch event detector is attached to the touch sensitive surface to detect the touch event.

7. The apparatus of claim 1 , wherein the mechanical vibration is created via any one of finger parts including a tip, a pad, a fingernail, and a knuckle.

8. The apparatus of claim 7 , wherein each of the finger parts is used to provide a touch based interface.

9. The apparatus of claim 7 , wherein each of the finger parts are bound to different user interface actions.

10. The apparatus of claim 1 , wherein the sampler comprises a sliding window sampler that stores mechanical vibration data associated with a particular length of time that overwrites old data after the particular length of time with new mechanical vibration data.

11. The apparatus of claim 1 , wherein the touch event classifier classifies the touch event based on an average absolute amplitude, a total absolute amplitude, and a standard deviation of absolute amplitude of the touch event.

12. The apparatus of claim 1 , wherein the touch event classifier classifies the touch event as a knuckle touch event.

13. The apparatus of claim 1 , wherein a user interface is commanded to display a right click menu when the touch event classifier classifies the touch event as a first type of touch event, and wherein an item displayed on the user interface is selected when the touch event classifier classifies the touch event as a second type of touch event.

14. A method for classifying touch events, the method comprising:

continuously sampling and storing acoustic signal data spanning a period of time from before a touch event to after a touch event in a sampler;

detecting the touch event, wherein the touch event is made by an object touching or striking a touch sensitive surface and entails an acoustic signal due to impacting the touch sensitive surface;

deriving a set of features representative of the touch event from the acoustic signal data stored in the sampler captured during an entirety of the touch event, the features including a frequency domain center of mass associated with the touch event; and

classifying the touch event using the features to identify the object used for the touch event.

15. The method of claim 14 , wherein said detecting the touch event comprises capturing a mechanical vibration signal.

16. The method of claim 15 , wherein said classification of the touch event comprises:

converting the mechanical vibration signal into an electrical signal;

extracting a series of features representative of the touch event from the electrical signal; and

classifying the touch event using the features to identify the object used for the touch event.

17. The method of claim 14 , wherein the mechanical vibration is created via any one of finger parts including a tip, a pad, a fingernail, and a knuckle.

18. The method of claim 17 , wherein each of the finger parts is used to provide input to a touch based interface.

19. The method of claim 17 , wherein each of the finger parts is used to input different user interface actions.

20. The apparatus of claim 14 , wherein the mechanical vibration is created through the use of a passive tool impacting the touch sensitive surface.