NOISE REDUCTION IN DIGITIZER SYSTEM

• US 20130027361A1
• Filed: 10/04/2012
• Published: 01/31/2013
• 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 8,648,830 B2
• Time in Patent Office: Days
• US Class Current: 345/178
• 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 at least two detecting elements from the plurality of detecting elements substantially simultaneously to obtain output from each of the at least two detecting elements;

selecting as a candidate carrier of mere noise, at least one detecting element from the at least two detecting elements providing output above a defined threshold in at least one frequency used for finger touch detection;

selecting at least one other detecting element of the at least two detecting elements as a candidate carrier of a stylus signal providing output in a known frequency of emission of a stylus; and

reducing the output sampled on the at least one other detecting element selected as the candidate carrier of the stylus signal in accordance with output sampled on the at least one detecting element selected as the candidate carrier of mere noise.

2. The method of claim 1, wherein the at least one frequency used to select the candidate carrier of mere noise is a frequency used for finger touch detection that provided a highest output level in the output sampled.

3. The method of claim 1, comprising:

selecting a frequency for estimating a noise level at the known frequency of emission of the stylus; and

determining an output level provided by each of the at least two detecting elements in the at least one frequency used to select the candidate carrier of mere noise and in the known frequency of emission of a stylus.

4. The method of claim 3, comprising:

determining a ratio between output in the frequency selected at said candidate carrier of mere noise and said candidate carrier of the stylus signal,

from the ratio and the output in the known frequency of emission of the stylus at the candidate carrier of the stylus signal, determining a noise level at the known frequency of emission of the stylus at said candidate carrier of the stylus signal, and

reducing output at the known frequency of emission of the stylus at said candidate carrier of a stylus signal in accordance with the noise level determined at the known frequency of emission of the stylus.

5. The method of claim 4, wherein said ratio is a complex proportion to compensate for at least one of phase and magnitude differences between respective detecting elements during said reducing.

6. The method of claim 4, comprising detecting output in a plurality of frequencies, and calculating an average ratio in accordance with said output of said plurality of frequencies to reduce the output of the known frequency of emission of the stylus at the candidate carrier of the stylus signal.

7. The method of claim 4, further comprising deliberately generating noise at the frequency selected for estimating the noise level at the known frequency of emission of the stylus.

8. The method of claim 3, wherein the known frequency of stylus emission is changed to a new frequency during use, the method comprising changing said frequency selected.

9. The method of claim 1, wherein said candidate carrier of mere noise is selected as a detecting element exhibiting a strongest noise signal as long as it is beyond a determined distance from the location of the candidate carrier of the stylus signal.

10. The method of claim 1, wherein said candidate carrier of mere noise is selected as the detecting element from the detecting elements identified that is furthest away from the location of the candidate carrier of the stylus signal.

11. The method of claim 1, wherein:

said candidate carrier of mere noise is selected,

noise reduction is carried out over a group of detecting elements from the plurality of detection elements on the basis of said selection being correct,

a resulting signal pattern over said group of elements is analyzed, and

said selection is allowed if said resulting signal pattern is indicative of a correct selection, otherwise a new selection of candidate carrier of mere noise is made.

12. The method of claim 1, comprising sampling a group of detecting elements from the plurality of the detecting elements, selecting at least one detecting element which is least affected by the stylus and reducing respective outputs of other detecting elements from the plurality of the detecting elements in accordance with the output of the at least one detecting element selected.

13. The method of claim 1, wherein the plurality of detecting elements is conductive detectors arranged in an array associated with said digitizer.

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

15. The method of claim 1, wherein said detecting elements are transparent conductors.

16. The method of claim 1, wherein one of the plurality of detecting elements is selected as a candidate carrier of a gaming piece signal.

17. The method of claim 1, wherein said stylus comprises an active oscillator and an energy pick up circuit.

18. The method of claim 1, wherein said stylus comprises a resonance circuit.

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

20. The method of claim 1, wherein said detecting elements are loop elements.