NOISE REDUCTION IN DIGITIZER SYSTEM

• US 20140152620A1
• Filed: 02/10/2014
• Published: 06/05/2014
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: N-Trig Ltd (Microsoft Corporation)
• Inventors: PERSKI, Haim, Rimon, Ori
• Granted Patent: US 9,164,618 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• 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 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• 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 3/046 by electromagnetic means

Abstract

A method for noise reduction in a digitizer includes determining a location of a stylus with a known frequency of emission over a first sampling period, sampling output from a plurality of detecting elements over a second sampling period, identifying detecting elements with sampled output in the second sampling period above a defined threshold in a selected frequency, the selected frequency being close to but different than the known frequency of the stylus, selecting as a candidate carrier of mere noise a detecting element from the detecting elements identified that is spaced away from the determined location of the stylus, and reducing values of output sampled over the second sampling period from at least one other detecting element, in accordance with the output sampled over the second sampling period from the detecting element selected as the candidate carrier of mere noise.

Claims

1. A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements spread over a sensing surface for detecting an electromagnetic signal and finger touch, the method comprising:

sampling outputs from a plurality of detecting elements substantially simultaneously to detect input originating from a stylus;

identifying based on the outputs, at least one detecting element of the plurality of detecting elements that received input originating from a user touching the sensing surface;

determining a first level of output from the at least one detecting element in a frequency associated with emission from the stylus; and

adjusting levels of the outputs from at least a portion of the plurality of detecting elements in the frequency associated with emission from the stylus based on the first level of output.

2. The method of claim 1, wherein adjusting levels of the outputs provides for reducing noise due to the presence of any one of:

a finger, hand or palm.

3. The method according to claim 1, wherein adjusting the levels of the outputs from at least the portion of the plurality of detecting elements in the frequency associated with emission from the stylus includes reducing the levels of outputs based on the first level of output.

4. The method of claim 1 comprising:

selecting from the at least one detecting element, a detecting element that is least affected by the stylus; and

determining the first level of output from the detecting element that is least affected by the stylus.

5. The method of claim 1, comprising:

selecting from the at least one detecting element, a detecting element that provided a highest level of output in a frequency used for finger touch detection; and

determining the first level of output from the detecting element that provided the highest level of output in the frequency used for finger touch detection.

6. The method of claim 1, comprising:

selecting from the at least one detecting element, a detecting element that provided output in a frequency used for finger touch detection that is also relatively close the frequency associated with emission from the stylus; and

determining the first level of output from the detecting element that provided the output in the frequency used for finger touch detection that is also relatively close the frequency associated with emission from the stylus.

7. The method of claim 1, comprising:

identifying based on the outputs, at least one other detecting element from the plurality of detecting elements, as a candidate carrier of a stylus signal;

selecting from the at least one detecting element, a detecting element that is beyond a determined distance from the location of at least one other detecting element; and

determining the first level of output from the detecting element that is beyond a determined distance from the location of at least one other detecting element.

8. The method of claim 1, comprising:

identifying based on the outputs, at least one other detecting element from the plurality of detecting elements as a candidate carrier of a stylus signal;

selecting from the at least one detecting element, a detecting element that is furthest away from the location of the at least one other detecting element; and

determining the first level of output from the detecting element that is least affected by the stylus.

9. The method of claim 1, comprising:

identifying based on the outputs, at least one other detecting element from the plurality of detecting elements as a candidate carrier of a stylus signal;

determining a second and third level of output in a frequency used for finger touch detection from the at least one detecting element and the candidate carrier of a stylus signal respectively;

determining a ratio between the second level of output and the third level of output;

from the ratio and the first level of output, determining a noise level at the frequency associated with emission from the stylus at the candidate carrier of the stylus signal;

determining a forth level of output from in the frequency associated with emission from the stylus from candidate carrier of a stylus signal; and

reducing the forth level of output in accordance with the noise level determined.

10. The method of claim 9, comprising:

determining the second and third level of output in a plurality of different frequencies used for finger touch detection from the at least one detecting element and the candidate carrier of a stylus signal respectively; and

calculating an average ratio in accordance the plurality of different frequencies from which the second and third level of output is determined.

11. The method of claim 1, wherein a frequency of emission of the stylus changes in response to pressure applied on the stylus by a user and wherein the frequency associated with emission from the stylus is updated responsive to the change.

12. The method of claim 1, comprising determining a position of the stylus based on the levels of the outputs as adjusted.

13. The method of claim 1, wherein said digitizer comprises a detection surface for carrying said detecting elements, said detecting surface further being touch sensitive.

14. The method of claim 1, wherein said detecting elements are transparent conductors arranged in a grid array.

15. An apparatus for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting electromagnetic signals emitted by a stylus, the apparatus comprising:

a sampler for sampling outputs from a plurality of detecting elements substantially simultaneously to detect input originating from a stylus, and

a noise reduction unit for reducing noise on the outputs signals from at least a portion of the plurality of detecting elements, the noise reduction unit;

identifying based on the outputs, at least one detecting element of the plurality of detecting elements that received input originating from a user touching a detection surface of the digitizer;

determining a first level of output from the at least one detecting element in a frequency associated with emission from the stylus; and

adjusting levels of the outputs from at least a portion of the plurality of detecting elements in the frequency associated with emission from the stylus based on the first level of output.

16. The apparatus according to claim 15, comprising a detector detecting levels of the outputs in the frequency associated with emission from the stylus and in one or more frequencies used for finger touch detection.

17. The apparatus of claim 16, wherein the detector detects position of the stylus on a detecting surface of the digitizer.

18. The apparatus of claim 15, wherein a frequency of emission of the stylus changes in response to pressure applied on the stylus by a user and wherein the digitizer updates the frequency associated with emission from the stylus responsive to the change.

19. The apparatus of claim 15, wherein said digitizer comprises a detection surface for carrying said detecting elements, said detecting surface further being finger touch sensitive.

20. The apparatus of claim 15, wherein said detecting elements are transparent conductors arranged in a grid array.

21. The apparatus of claim 15, wherein the noise reduction unit reduces noise due to the presence of any one of:

a finger, hand or palm.