CONTACT IDENTIFICATION AND TRACKING ON A CAPACITANCE SENSING ARRAY

• US 20130169582A1
• Filed: 01/01/2012
• Published: 07/04/2013
• Est. Priority Date: 01/01/2012
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Ryshtun, Andriy
• Granted Patent: US 8,982,090 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/03545 Pens or stylus
• 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 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• 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

Abstract

Active stylus operation when there is no physical connection between the stylus and the touch array requires communication and synchronization. It is possible to use the touchscreen stack-up itself to communicate synchronization signals or other information optically by outfitting the active stylus with an optical receiver and transmitting signals either with additional diodes or by modulating the display clock itself.

Claims

1. A user input device comprising:

a display;

a capacitance sensor array disposed intermediate to a user and the display;

a capacitance sensing circuit coupled to the capacitance sensing array; and

an optical transmit (TX) circuit coupled to the capacitance sensing circuit, wherein the optical TX circuit is configured to receive a signal from the capacitance sensing array and to transmit the signal to an optical receiver.

2. The user input device of claim 1, wherein the capacitance sensor array and the capacitance sensing circuit are configured to measure mutual capacitance.

3. The user input device of claim 1, wherein the capacitance sensor array comprises a plurality of row and column electrodes and wherein the plurality of row and column electrodes are constructed from a transparent conductive material.

4. The user input device of claim 1, wherein the optical TX circuit comprises a IR LED coupled to an optical transmitter.

5. The user input device of claim 4 wherein the capacitance sensor comprises:

a clock;

a clock divider coupled to the clock; and

a panel scan engine coupled to the clock divider,

wherein the clock is configured to supply a synchronization signal to the optical TX circuit and wherein the panel scan engine is configured to measure capacitance on the capacitance sensor array.

6. The user input device of claim 4, wherein the IR LED is disposed proximate to a display backlight diffuser and configured to transmit an optical signal into the display backlight diffuser and to a stylus.

7. The user input device of claim 1, wherein the optical transmit circuit is configured to receive a plurality of signals from the capacitance sensing circuit and to transmit the plurality of signals optically to the optical receiver.

8. A stylus comprising:

an optical receive (RX) circuit,

a tip driver, and

a conductive tip;

wherein the stylus is configured to receive an optical signal and generate a transmit signal for receipt by the capacitance sensing circuit through the capacitance sensor array.

9. The stylus of claim 8, wherein the optical RX circuit comprises a light tube, a photodiode, and an optical receiver.

10. The stylus of claim 8 wherein the optical RX circuit further comprises a clock divider coupled between the optical receiver and the tip driver, wherein the clock divider is configured to divide down the optical signal to match a clock signal for a capacitance sensing circuit.

11. The stylus of claim 8, wherein the optical RX circuit further comprises:

a frequency modifier; and

a phase locked loop (PLL), wherein the frequency modifier and the PLL are coupled between the receiver and the stylus tip driver and configured to match the transmit signal to a desired signal.

12. The stylus of claim 8 wherein the frequency modifier is a subsection of the PLL and wherein the PLL is coupled to the receiver and the stylus tip driver.

13. A method comprising

receiving a optical signal on a stylus, the stylus comprising a stylus tip driver;

configuring the stylus tip driver to transmit a transmit signal based on the received optical signal; and

transmitting a transmit signal from the stylus tip driver.

14. The method of claim 13 wherein the transmitting the optical signal comprises:

generating the optical signal;

passing the optical signal to an optical transmitter; and

driving the synchronization signal from a IR LED, the IR LED disposed proximate to a backlight diffuser of a display.

15. The method of claim 13 wherein the optical signal is a clock signal.

16. The method of claim 15, wherein the clock signal is generated by a capacitance sensor configured to measure capacitance between the stylus and a plurality of receive electrodes.

17. A method comprising:

transmitting an optical signal to a stylus;

receiving a transmit signal from the stylus, wherein the transmit signal is in response to from the optical signal;

demodulating the transmit signal; and

calculating a position of the stylus from the demodulated transmit signal.

18. The method of claim 17 wherein demodulating the transmit signal yields a mutual capacitance for a mutual capacitance between the stylus and a plurality of receive electrodes.

19. The method of claim 17 wherein the optical signal provides synchronization between the stylus and a circuit configured to demodulate the transmit signal.

20. The method of claim 17 wherein the optical signal provides information on a sensing circuit to the stylus.