Touch detection in a capacitive sensor system
A system has a two-dimensional (2D) touch detection system operable to be activated and de-activated and an additional sensor operable in communication with the 2D touch detection system. The additional sensor is capable to determine whether a touch event has occurred or is about to occur and to activate the 2D touch detection system if a touch event has occurred or is about to occur.
1. A system comprising:
a two-dimensional (2D) touch detection system comprising a plurality of capacitive touch sensors coupled with a 2D touch detection controller and being operable to be activated and de-activated;
an additional three-dimensional (3D) gesture detection system comprising a 3D gesture detection controller and additional capacitive sensors arranged around the plurality of capacitive touch sensors and further comprising a touch detection electrode covering a touch sensor area of the 2D touch detection system being further configured to detect a touch on a touch sensor area of the 2D touch detection system, wherein the 3D gesture detection controller is communicatively coupled with the 2D touch detection controller, and the 3D gesture detection system being operable to be activated and de-activated;
wherein the 3D gesture detection system is configured to determine a gesture performed by an object in a 3D sensing space defined by said additional capacitive sensors and touch events with said touch detection electrode and to activate the 2D touch detection system and de-activate the 3D gesture detection system if a touch event has detected by the 3D gesture detection system.
2. The system according to claim 1 , wherein a difference signal of subsequent samples from the touch detection electrode is generated and evaluated over time.
3. The system according to claim 2 , wherein the difference signal is fed to an Unscented Kalman Filter.
4. The system according to claim 3 , wherein an output signal of the Unscented Kalman Filter is subtracted from the difference signal and fed to a threshold comparison unit which is configured to output a touch event signal.
5. The system according to claim 2 , wherein the system determines whether a touch occurred by evaluating whether a characteristic bent in a course of a negative slope of the difference signal is present.
6. The system according to claim 5 , wherein the system is further configured to evaluate the negative slope of the difference signal to determine a time to of a zero crossing of a line projected from a portion of the difference signal having said negative slope and wherein the system is configured to determine a touch when a value of the difference signal at time t 0 is positive.
7. The system according to claim 1 , wherein for determination of a touch event, the 3D gesture detection system uses a stochastic filter for noise suppression.
8. The system according to claim 7 , wherein the stochastic filter is an Unscented Kalman filter.
9. The system according to claim 7 , wherein the stochastic filter suppresses sinusoidal noise.
10. The system according to claim 1 , wherein the 3D gesture detection system comprises a plurality of receiving electrodes configured to determine a gesture and shares at least one electrode from the touch detection system as a touch detection electrode.
11. The system according to claim 10 , further comprising a multiplexer switch configured to share the at least one electrode between the 3D gesture detection system and the 2D touch detection system.
12. The system according to claim 1 , wherein the 3D gesture detection system comprises four receiving electrodes forming a frame around said touch detection electrode and is configured to determine a gesture.
13. The system according to claim 1 , wherein the 3D gesture detection system comprises a plurality of receiving electrodes configured to determine a gesture and a multiplexer configured to share at least one electrode from the touch detection system to operate as a transmission electrode for the 3D gesture detection system.
14. The system according to claim 1 , wherein the 3D gesture detection system comprises a transmission electrode arranged below said additional capacitive sensors.
15. The system according to claim 1 , wherein the capacitive touch detection system comprises a projected capacitive touch controller.
16. A method for operating an input device, comprising:
providing a two-dimensional (2D) touch detection system comprising a plurality of capacitive touch sensors coupled with a 2D touch detection controller and being operable to be activated and de-activated;
providing an additional three-dimensional (3D) gesture detection system comprising a 3D gesture detection controller and additional capacitive sensors arranged around the plurality of capacitive touch sensors and further comprising a touch detection electrode covering a touch sensor area of the 2D touch detection system, further being configured to detect a touch on a touch sensor area of the 2D touch detection system, and the 3D gesture detection system being operable to be activated and de-activated;
coupling the 3D gesture detection controller communicatively with the 2D touch detection controller;
activating the 3D gesture detection controller and de-activating the 2D touch detection controller by the 3D gesture detection controller;
determining by the 3D gesture detection system gestures performed by an object in a 3D sensing space defined by said additional capacitive sensors and detecting through said touch detection electrode whether a touch event has occurred; and
activating the 2D touch detection system and de-activating the 3D gesture detection system if the touch event has occurred.
17. The method according to claim 16 , wherein a difference signal of subsequent samples from the touch detection electrode is generated and evaluated over time.
18. The method according to claim 17 , comprising filtering the difference signal by an Unscented Kalman Filter.
19. The method according to claim 18 , comprising subtracting the filtered signal from the difference signal and feeding the subtracted signal to a threshold comparison unit which outputs a touch event signal.
20. The method according to claim 17 , comprising determining whether a touch occurred by evaluating whether a characteristic bent in a course of a negative slope of the difference signal is present.
21. The method according to claim 20 , wherein the negative slope of the difference signal is evaluated to define a time to of a zero crossing of a line projected from a portion of the difference signal having said negative slope and wherein a touch is determined when a value of the difference signal at time t 0 is positive.
22. The method according to claim 16 , wherein for determination of a touch event, the 3D gesture detection system uses a stochastic filter for noise suppression.
23. The method according to claim 22 , wherein the stochastic filter is an Unscented Kalman filter.
24. The method according to claim 22 , wherein the stochastic filter suppresses sinusoidal noise.
25. The method according to claim 16 , wherein the 3D gesture detection system comprises a plurality of receiving electrodes configured to determine a gesture and the method comprises the step of sharing at least one electrode from the touch detection system as a touch detection electrode.
26. The method according to claim 25 , wherein sharing is performed by controlling a multiplexer switch configured to share the at least one electrode between the 3D gesture detection system and the 2D touch detection system.
27. The method according to claim 16 , wherein the 3D gesture detection system comprises four receiving electrodes forming a frame around said touch detection electrode and is configured to determine a gesture.
28. The method according to claim 16 , wherein the 3D gesture detection system comprises a plurality of receiving electrodes configured to determine a gesture and the method comprises the step of sharing at least one electrode from the touch detection system to operate as a transmission electrode for the 3D gesture detection system.
29. The method according to claim 16 , wherein the 3D gesture detection system comprises a transmission electrode arranged below said additional capacitive sensors.
30. The method according to claim 16 , wherein the capacitive touch detection system comprises a projected capacitive touch controller.
31. A system comprising:
a two-dimensional (2D) touch detection system comprising a plurality of capacitive touch sensors coupled with a 2D touch detection controller and being operable to be activated and de-activated;
an additional three-dimensional (3D) gesture detection system comprising a 3D gesture detection controller and additional capacitive sensors arranged around the plurality of capacitive touch sensors and further comprising a touch detection electrode covering a touch sensor area of the 2D touch detection system, wherein the 3D gesture detection controller is communicatively coupled with the 2D touch detection controller, and the 3D gesture detection system being operable to be activated and de-activated;
wherein the 3D gesture detection system is configured to determine a gesture performed by an object in a 3D sensing space defined by said additional capacitive sensors and touch events with said touch detection electrode, to activate the 2D touch detection system and de-activate the 3D gesture detection system if a touch event has detected by the 3D gesture detection system.