Optical stylus synchronization

• US 8,982,090 B2
• Filed: 01/01/2012
• Issued: 03/17/2015
• 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
• Primary Examiner(s): Patel, Kumar
• Assistant Examiner(s): ONYEKABA, AMY
• Application Number:
  US13/342,096
• Publication Number:
  US 20130169582A1
• Time in Patent Office: 1,171 Days
• Field of Search: 345156-179, 178 1801- 2004
• 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 in a stackup with the display;

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

an optical transmit (TX) circuit coupled to the capacitance sensor circuit, wherein the optical TX circuit is configured to receive a first signal from the capacitance sensor circuit and to transmit the first signal via light passing through the capacitance sensor array to an optical receiver included in a stylus, wherein the capacitance sensor circuit is configured to measure a capacitance using a second signal generated responsive to the first signal, and wherein the second signal is received by the capacitance sensor array.

2. The user input device of claim 1, wherein the capacitance sensor array and the capacitance sensor 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 an IR LED coupled to an optical transmitter to transmit the first signal.

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 the first signal as 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 the first signal as an optical signal into the display backlight diffuser and to the 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 sensor circuit and to transmit the plurality of signals optically to the optical receiver.

8. A stylus comprising:

an optical receive (RX) circuit configured to receive an optical signal transmitted through a capacitance sensor array,

a tip driver coupled with the optical RX circuit and configured to generate a transmit signal based on the received optical signal, and

a conductive tip, wherein the tip driver is further configured to apply the transmit signal to the conductive tip to transmit the transmit signal to a capacitance sensor 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 an optical receiver and the tip driver, wherein the clock divider is configured to divide down the optical signal to match a clock signal for the capacitance sensor 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 an optical receiver and the tip driver and are configured to match the transmit signal to a desired signal.

12. The stylus of claim 11, wherein the frequency modifier is a subsection of the PLL and wherein the PLL is coupled to the optical receiver and the tip driver.

13. A method comprising:

receiving at a stylus tip of a stylus an optical signal passing through a capacitance sensor array;

generating a transmit signal based on the received optical signal; and

transmitting the transmit signal from the stylus tip to a capacitance sensor via the capacitance sensor array to be used in a capacitance measurement.

14. The method of claim 13, wherein receiving the optical signal comprises receiving a synchronization signal from an IR LED, the IR LED disposed proximate to a backlight diffuser of a display associated with the capacitance sensor.

15. The method of claim 13, wherein the optical signal is generated based on a clock signal.

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

17. A method comprising:

transmitting an optical signal through a capacitance sensor array to a stylus, wherein the optical signal is configured to synchronize the stylus with a sensing device;

receiving at the capacitance sensor array a transmit signal from the stylus, wherein the transmit signal is modulated based on a modulation of the optical signal;

demodulating the transmit signal to measure a capacitance; and

calculating a position of the stylus based on the measured capacitance.

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 of the capacitance sensor array.

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 synchronization information on a sensing circuit to the stylus.