ADAPTIVE DIGITAL FILTERING METHOD AND APPARATUS IN TOUCH SENSING SYSTEM

• US 20110285654A1
• Filed: 05/09/2011
• Published: 11/24/2011
• Est. Priority Date: 05/20/2010
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: PARK, Jong-kang, AHN, Hae-yong, CHOI, Yoon-kyung
• Granted Patent: US 9,134,857 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• 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

An adaptive digital filtering method and apparatus for touch data in a touch system is described. Adaptive digital filtering involves estimating a signal-to-noise ratio (SNR) for stored touch data, and reducing a digital filter order if the SNR is high and increasing the digital filter order if the SNR is small.

Claims

1. An adaptive digital filtering method for touch data acquired in a touch display device including a plurality of sense channels, the method comprising:

storing the touch data in a buffer;

estimating a signal-to-noise ratio (SNR) for the stored touch data;

selecting a digital filter tap for a digital filter having plurality of filter taps based on the estimated SNR; and

filtering on the touch data using the digital filter after selecting the digital filter tap.

2. The method of claim 1, further comprising:

after estimating of the SNR, determining a noise level reference value based on the estimated SNR; and

performing noise nulling on stored touch data having a value less than the noise level reference value.

3. The method of claim 2, wherein the determining of the noise level reference value comprises determining the noise level reference value such that the estimated SNR satisfies a condition for a preset standard jitter.

4. The method of claim 1, wherein among the stored touch data, only touch data in accordance with a preset effective distribution is selected and used to estimate the SNR.

5. The method of claim 1, further comprising:

determining a noise level value for a preset sampling length using touch data continuously stored during a period of the preset sampling length, wherein the SNR is estimated in accordance with the determined noise level value.

6. The method of claim 5, further comprising:

before determining the noise level value, performing noise nulling on the touch data having a value less than a noise level reference.

7. The method of claim 6, further comprising:

defining estimation conditions for estimating of the SNR, such that a touch state during which a touch input is applied to the touch display device is maintained during the period of the preset sampling length during which the touch data is stored, and a state transition between the touch state and a non-touch state during which the touch input is not applied to the touch display device does not occur during the period of the preset sampling length.

8. The method of claim 7, wherein defining the estimation conditions for estimating the SNR further comprises:

defining that a maximum jitter from an average value for coordinates defined on the touch display device and associated with the touch data as collected during the period of the preset sampling length is to be less than a reference value.

9. The method of claim 7, wherein upon determining that the estimation conditions for estimating the SNR are not satisfied, estimating the SNR by reinitializing the buffer storing the touch data and restoring touch data in the buffer.

10. The method of claim 1, wherein the selecting the digital filter tap based on the estimated SNR comprises;

estimating the SNR and comparing the estimated SNR with entries into a pre-characterized lookup table.

11. A digital filtering touch controller device comprising:

a touch data collection unit that stores touch data obtained from a sense channel of a touch display device; and

a signal-to-noise ratio (SNR) estimation unit that estimates a SNR using the stored touch data and selects a digital filter tap of a digital filtering unit based on the estimated SNR, wherein the digital filtering unit performing digital filtering on the touch data.

12. The digital filtering touch controller device of claim 11, further comprising:

a noise nulling unit that determines a noise level reference value based on the estimated SNR and performs noise nulling on stored touch data having a value less than the noise level reference value.

13. The digital filtering touch controller device of claim 12, wherein the noise nulling unit determines the noise level reference value such that the estimated SNR satisfies a condition for a preset standard jitter.

14. The digital filtering touch controller device of claim 11, wherein the touch data collection unit stores only touch data in accordance with a preset effective distribution.

15. The digital filtering touch controller device of claim 11, wherein the SNR estimation unit determines a noise level value in a preset sampling length using touch data continuously stored during a period of the preset sampling length, and calculates the SNR from the determined noise level value.

16. The adaptive digital filtering touch controller device of claim 15, further comprising an SNR estimation condition check unit that determines whether a touch state during which a touch input is applied to the touch display device is maintained during the period of the preset sampling length during which the touch data is stored, and whether a state transition between the touch state and a non-touch state during which the touch input is not applied to the touch display device has occurred during the period of the preset sampling length.

17. The adaptive digital filtering touch controller device of claim 16, wherein the SNR estimation condition check unit further determines whether a maximum jitter from an average value for coordinates on the touch display device and associated with the touch data during the period of the preset sampling length is less than a reference value.

18. The adaptive digital filtering touch controller device of claim 16, further comprising a control unit that reinitializes a buffer in the touch data collection unit storing the touch data if the estimation conditions for estimating the SNR are not satisfied.

19. The adaptive digital filtering touch controller device of claim 11, wherein the SNR estimation unit determines the digital filter tap by estimating the SNR and comparing the estimated SNR with values in a pre-characterized lookup table.

20. An adaptive digital filtering touch display system comprising:

a touch display that comprises a plurality of sensing channels for performing a touch sensing operation and is designed to sense changes in a plurality of sensing units disposed on the sensing channels and output a plurality of sensed touch signals;

a touch controller that receives the plurality of sensed touch signals, wherein the touch controller estimates an SNR based on the plurality of sensed touch signals to adaptively adjust a digital filter order and to obtain an adaptively digital-filtered touch signal; and

a display that displays the adaptively digital-filtered touch signal.