Method and apparatus for operating a touch panel

• US 8,314,779 B2
• Filed: 02/23/2009
• Issued: 11/20/2012
• Est. Priority Date: 02/23/2009
• Status: Active Grant

• Current Assignee: Solomon Systech Limited
• Original Assignee: Solomon Systech Limited
• Inventors: Chan, Wing Chi Stephen, Ng, Wai Hon, Choi, Wai Pak, Cheng, Wai Kin, Chu, Kwok Wah, Lui, Siu Hong, Lu, Yao
• Primary Examiner(s): HALEY, JOSEPH R
• Application Number:
  US12/390,637
• Publication Number:
  US 20100214232A1
• Time in Patent Office: 1,366 Days
• Field of Search: None
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04808 Several contacts: gestures triggering a specific function, e.g. scrolling, zooming, right-click, when the user establishes several contacts with the surface simultaneously; e.g. using several fingers or a combination of fingers and pen
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

A controller for detection of touches by a single finger or multiple fingers on a touch panel, the touch panel including a first group of electrodes arranged in a first direction and a second group of electrodes arranged in a second direction, thereby forming a plurality of crossover points. The controller includes: a plurality of signal drivers coupled to the first group of electrodes and configured to excite the first group of electrodes sequentially using a spread spectrum signal; a plurality of signal sensors coupled to the second group of electrodes and configured to detect peaks and troughs of capacitive coupled signals at the second group of electrodes, the detecting being performed simultaneously for the crossover points along a current one of the first group of electrodes that is being excited; and a signal processing device configured to detect the touches on the touch panel and to determine touch positions and touch movements, based on the detected peaks and troughs of the capacitive coupled signals.

Claims

1. A controller for detection of touches by a single finger or multiple fingers on a touch panel, the touch panel including a first group of electrodes arranged in a first direction and a second group of electrodes arranged in a second direction, thereby forming a plurality of crossover points, the controller comprising:

a plurality of signal drivers coupled to the first group of electrodes and configured to excite the first group of electrodes sequentially using a spread spectrum driving signal provided by an analog waveform generator using no code division multiplexing;

a plurality of signal sensors coupled to the second group of electrodes and configured to detect peaks and troughs of capacitive coupled signals at the second group of electrodes, the detecting being performed simultaneously for the crossover points along a current one of the first group of electrodes that is being excited; and

a signal processing device comprising an analog to digital converter (ADC) to convert analog signals from the signal sensors into digital data and a digital signal processing (DSP) unit configured to compensate the digital data, and to detect the touches, calculate touch positions, and generate touch images based on the compensated digital data, wherein the DSP unit comprises;

an image segmentation component configured to divide into groups ones of the plurality of crossover points at which the capacitive coupled signals have variations, each of the groups corresponding to an approximated finger touch image, thereby to generate a plurality of approximated finger touch images;

a finger windowing component configured to reshape the approximated finger touch images to generate reshaped finger touch images; and

a center of mass calculation component configured to determine the touch positions by determining a center of mass for each of the reshaped finger touch images.

2. The controller of claim 1, wherein the signal processing device further comprises:

a frame scan controller configured to control frame scans of the touch panel by scheduling an exciting sequence for the first group of electrodes and a sampling sequence for the second group of electrodes;

a finger touch tracking unit configured to track touch movements based on the calculated touch positions;

a finger event detector configured to determine predefined touch events for the touches according to characteristics of the touch movements, to generate touch information; and

a communication interface configured to output the generated touch information.

3. The controller of claim 1, wherein the waveform generator is further configured to generate a direct current (DC) free waveform as the spread spectrum driving signal.

4. The controller of claim 1, wherein the plurality of signal drivers are each configured to convert the spread spectrum driving signal from a low voltage waveform signal to a high voltage driving signal, the high voltage level being programmable.

5. The controller of claim 1, wherein each of the plurality of signal sensors further comprises:

peak detect and hold circuitry to detect the peaks of the capacitive coupled signals; and

trough detect and hold circuitry to detect the troughs of the capacitive coupled signals.

6. The controller of claim 2, wherein the ADC is a 5-bit or 6-bit flash ADC.

7. The controller of claim 2, wherein the ADC is configured to accumulate a plurality of samples of the analog signals at different times, to increase a resolution for the ADC and to average out background noise signals.

8. The controller of claim 2, wherein the frame scan controller is further configured to control the plurality of signal drivers and the plurality of signal sensors to be powered on only during each of the frame scans.

9. The controller of claim 2, wherein the frame scan controller further comprises:

a data arrangement component configured to organize transfer of the digital data away from the ADC; and

a scan speed regulation component configured to control the frame scans dynamically and adaptively based on the characteristics of the touch movements.

10. The controller of claim 2, wherein the DSP unit is further configured to obtain reference mutual capacitance data of the crossover points for compensation of the digital data, and calibrate the reference mutual capacitance data during initialization and at various times during operation when no touch is being detected.

11. The controller of claim 10, wherein the DSP unit is further configured to:

subtract the digital data from the reference mutual capacitance data to generate the compensated digital data, if the touch panel is a glass touch panel; and

subtract the reference mutual capacitance data from the digital data to generate the compensated digital data, if the touch panel is a plastic touch panel.

12. The controller of claim 2, further configured to determine a plurality of manipulation operations based on the characteristics of the touch movements, wherein the manipulation operations may be applied to a two dimensional (2D) or three dimensional (3D) graphic object.

13. The controller of claim 12, further configured to provide a visual indicator for indicating information regarding the manipulation operations.

14. The controller of claim 1, further configured to be integrated with a graphics or display controller to form an integrated controller.

15. A method for detection of touches by a single finger or multiple fingers on a touch panel, the touch panel including a first group of electrodes arranged in a first direction and a second group of electrodes arranged in a second direction, thereby forming a plurality of crossover points, the method comprising:

exciting the first group of electrodes sequentially using a spread spectrum driving signal provided by an analog waveform generator using no code division multiplexing;

detecting, as analog signals, peaks and troughs of capacitive coupled signals at the second group of electrodes, the detecting being performed simultaneously for the crossover points along a current one of the first group of electrodes being excited; and

converting the analog signals into digital data for digital signal processing, to detect the touches on the touch panel and to determine touch positions and to generate touch images based on compensated digital data, wherein generating the touch images comprises;

dividing into groups ones of the plurality of crossover points at which the capacitive coupled signals have variations, each of the groups corresponding to an approximated finger touch image, thereby to generate a plurality of approximated finger touch images;

reshaping the approximated finger touch images to generate reshaped finger touch images; and

determining the touch positions by determining a center of mass for each of the reshaped finger touch images.

16. The method of claim 15, wherein the digital signal processing further comprises:

averaging the digital data;

compensating the averaged digital data for offsets, to determine the touch positions;

tracking the touch positions to determine characteristics of touch movements;

determining predefined touch events for the touches according to the characteristics of the touch movements, thereby to generate touch information; and

outputting the generated touch information,

wherein the offsets result from inherent variations of mutual capacitance between the first and second groups of electrodes and background noise.

17. The method of claim 15, further comprising generating a direct current (DC) free waveform as the spread spectrum driving signal.

18. The method of claim 16, further comprising:

controlling an exciting sequence for the first group of electrodes; and

controlling a sampling sequence for the second group of electrodes.

19. The method of claim 16, further comprising controlling

the exciting dynamically and adaptively based on the characteristics of the touch movements.

20. The method of claim 16, further comprising:

detecting a finger enter incident if a finger is placed on the touch panel;

detecting a finger hold incident if a finger is held on the touch panel with or without movement;

detecting a finger leave incident if a finger is withdrawn from the touch panel;

detecting a single click event if a finger enter incident and a finger leave incident are detected for a single finger;

detecting a double click event if two single click events are detected for a single finger;

detecting a directional enter event if at least two finger enter incidents are detected for first and second fingers and the touch positions indicate one of four directions;

detecting a directional click event if at least two click events are detected for first and second fingers and the touch positions indicate one of the four directions;

detecting a drag event if a finger enter incident and a consecutive number of finger hold incidents following that finger enter incident are detected for a single finger; and

detecting a directional drag event if at least one drag event is detected for first and second fingers and the touch positions indicate one of the four directions;

wherein the four directions include a horizontal direction, a vertical direction, an upward diagonal direction, and a downward diagonal direction.

21. The method of claim 20, further comprising:

determining a selecting operation for a single click event;

determining a moving operation for a directional drag event;

determining a rotating operation for a directional enter event and a directional drag event following that directional enter event, if a movement of the two fingers is perpendicular to one of the four directions; and

determining a scaling operation for a directional enter event and a directional drag event following that directional enter event, if a distance between the two fingers is changed or an average position of the two fingers is changed,

wherein the selecting, moving, rotating, and scaling operations may be applied to a two dimensional (2D) or three dimensional (3D) graphic object.

22. The method of claim 20, wherein the single click event and the double click event are further assigned as input functions for object selection and direction selection, respectively.

23. The method of claim 16, further comprising the determining of predefined touch events, wherein the predefined touch events are user-definable and user-programmable.