Touch screen for stylus emitting wireless signals

• US 9,454,272 B2
• Filed: 05/22/2014
• Issued: 09/27/2016
• Est. Priority Date: 05/22/2014
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Ningrat, Kusuma Adi, Noviello, Giuseppe
• Primary Examiner(s): Bibbins, Latanya
• Application Number:
  US14/284,650
• Publication Number:
  US 20150338950A1
• Time in Patent Office: 859 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• 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 3/0442 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

A touch screen device is configured with rows of conductors capable of receiving wireless signals from a stylus. When the stylus touches the touch screen, the stylus emits multiple wireless signals in different directions. The conductors receiving the emitted wireless signals provide the signals to circuitry that filters, amplifies, and digitizes the wireless signals, as received at each conductor. The magnitude of each conductor'"'"'s received wireless signal is computed, and the computed magnitudes are used to determine the location of the stylus on the touch screen surface. The stylus is assumed to be closer to conductors receiving stronger signals than those receiving weaker signals.

Claims

1. A touch screen device, comprising:

a touch screen with a plurality of conductors configured to receive wireless signals from a stylus touching the touch screen, said wireless signals comprising a plurality of signals having different frequencies that digitally encode stylus information;

a circuit coupled to the plurality of conductors and configured to generate amplified and digitized representations of the received wireless signals; and

a processor configured to convert the digitized representations of the wireless signals from the time domain to the frequency domain and use magnitudes in the frequency domain to decode the stylus information and determine a location of the stylus on the touch screen.

2. The touch screen device of claim 1, further comprising memory storing instructions that enable the processor to perform an algorithmic transform from the time domain to the frequency domain.

3. The touch screen device of claim 2, wherein the algorithmic transform comprises a fast Fourier transform.

4. The touch screen device of claim 1, wherein the processor determines the location of the stylus by calculating a relative strength value based on the magnitudes in the frequency domain.

5. The touch screen device of claim 1, wherein the processor decodes the stylus information in the wireless signals by setting significance of bits associated with each of the different transmission frequencies of the wireless signals.

6. The touch screen device of claim 5, wherein the stylus information comprises an indication of at least one member of a group comprising a stylus identifier, stylus touch pressure on the touch screen, and stylus inclination relative to the touch screen.

7. The touch screen device of claim 1, wherein the plurality of conductors comprise a first group of conductors spanning one direction of the touch screen and a second group of conductors spanning a perpendicular direction of the touch screen.

8. The touch screen device of claim 7, wherein the first group of conductors are configured to receive the wireless signals, and the second group of conductors are configured to detect changes in capacitance caused by stylus or finger touches of the touch screen.

9. The touch screen device of claim 7, wherein the first and second groups of conductors are configured to receive the wireless signals from the stylus.

10. A touch screen device, comprising:

a touch screen with a plurality of conductors configured to receive a plurality of wireless signals from a stylus touching the touch screen, said plurality of wireless signals comprising a first plurality of signals having first different frequencies and a second plurality of signals having second different frequencies;

a circuit coupled to the plurality of conductors and configured to generate amplified and digitized representations of the received first and second pluralities of wireless signals; and

a processor configured to convert the digitized representations of the received first and second pluralities of wireless signals from the time domain to the frequency domain, determine whether one or more frequency domain signals are corrupted by noise, discard the noise corrupted frequency domain signals and use magnitudes in the frequency domain of non-discarded frequency domain signals to determine a location of the stylus on the touch screen.

11. The touch screen device of claim 10, wherein said plurality of wireless signals further comprises a third plurality of signals having third different frequencies, and wherein said processor operates to identify as the noise corrupted frequency domain signals those frequency domain signals corresponding to one of the first through third pluralities of wireless signals having magnitudes in the frequency domain which differ from the magnitudes of the others of the first through third pluralities of wireless signals.

12. The touch screen device of claim 10, wherein different frequencies in each of the first through third pluralities of wireless signals digitally encode stylus information.

13. The touch screen device of claim 12, wherein the processor is further configured to use the magnitudes in the frequency domain corresponding to the first and second pluralities of wireless signals to decode the stylus information.

14. The touch screen device of claim 13, wherein the processor decodes the stylus information in the wireless signals by setting significance of bits associated with each of the different frequencies in the first and second pluralities of wireless signals.

15. The touch screen device of claim 14, wherein the stylus information comprises an indication of at least one member of a group comprising a stylus identifier, stylus touch pressure on the touch screen, and stylus inclination relative to the touch screen.

16. The touch screen device of claim 10, further comprising memory storing instructions that enable the processor to perform an algorithmic transform from the time domain to the frequency domain.

17. The touch screen device of claim 16, wherein the algorithmic transform comprises a fast Fourier transform.

18. The touch screen device of claim 10, wherein the plurality of conductors comprise a first group of conductors spanning one direction of the touch screen and a second group of conductors spanning a perpendicular direction of the touch screen.