NOISE DETECTION IN MULTI-TOUCH SENSORS
First Claim
1. A method of detecting noise in one of at least three touch images, each touch image comprising a plurality of touch sample values obtained by stimulating a touch sensor at a unique frequency, the method comprising:
- determining a mismatch of sample values obtained at each pair of frequencies;
comparing the mismatches to identify one or more noisy frequencies; and
if one or more noisy frequencies are identified, computing a touch value as a function of sample values obtained at frequencies other than the identified noisy frequencies.
3 Assignments
0 Petitions
Accused Products
Abstract
Multi-touch touch-sensing devices and methods are described herein. The touch sensing devices can include multiple sense points, each of which can be stimulated with a plurality of periodic waveforms having different frequencies to measure a touch value at the sense point. Noise at one or more of the frequencies can interfere with this measurement. Therefore, various noise detection (and rejection) techniques are described. The noise detection techniques include two-clean-frequency noise detection, one-clean-frequency noise rejection, and combined two-clean-frequency/one-clean-frequency noise detection. Each of the noise detection techniques can include statistical analyses of the sample values obtained. The touch sensing methods and devices can be incorporated into interfaces for a variety of electronic devices such as a desktop, tablet, notebook, and handheld computers, personal digital assistants, media players, and mobile telephones.
-
Citations
70 Claims
-
1. A method of detecting noise in one of at least three touch images, each touch image comprising a plurality of touch sample values obtained by stimulating a touch sensor at a unique frequency, the method comprising:
-
determining a mismatch of sample values obtained at each pair of frequencies; comparing the mismatches to identify one or more noisy frequencies; and if one or more noisy frequencies are identified, computing a touch value as a function of sample values obtained at frequencies other than the identified noisy frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 56, 65)
-
-
10. A touch sensing device comprising:
-
a touch sensitive surface having a plurality of touch sensors; drive circuitry configured to apply drive signals to the touch sensors wherein the drive signals comprise at least three periodic waveforms each having a unique frequency; sense circuitry configured to derive a touch image for each frequency, each touch image comprising a plurality of touch sample values obtained at each frequency; and additional circuitry configured to detect noise in one of the touch images by; determining a mismatch of sample values obtained at each pair of frequencies; comparing the determined mismatches to identify a noisy frequency; and if a noisy frequency is identified, computing a touch value as a function of sample values obtained at frequencies other than the identified noisy frequency. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
-
-
26. A method of detecting noise in one or more of at least two touch images, each touch image comprising a plurality of touch sample values obtained by stimulating a touch sensor at a unique frequency, the method comprising:
-
computing a smoothed image corresponding to each frequency from each of the at least two touch images; computing a high pass image corresponding to each frequency from the touch image at each frequency and the smoothed image at each frequency; computing a spatial variance for each frequency from the high pass image for each frequency, the spatial variance being representative of noise energy in each of the high pass images; computing a temporal variance representative of noise energy for each frequency as a function of time, wherein the temporal variance is a function of the computed spatial variance for each frequency and one or more prior spatial variances for each frequency; and comparing the computed temporal variances for each frequency to identify a noisy frequency. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 57, 66)
-
-
36. A touch sensing device comprising:
-
a touch sensitive surface having a plurality of touch sensors; drive circuitry configured to apply drive signals to the touch sensors wherein the drive signals comprise at least three periodic waveforms each having a unique frequency; sense circuitry configured to derive a touch image for each frequency, each touch image comprising a plurality of touch sample values obtained at each frequency; and additional circuitry configured to detect noise in one of the touch images by; computing a smoothed image corresponding to each frequency from each of the at least two touch images; computing a high pass image corresponding to each frequency from the touch image at each frequency and the smoothed image at each frequency; computing a spatial variance for each frequency from the high pass image for each frequency, the spatial variance being representative of noise energy in each of the high pass images; computing a temporal variance representative of noise energy for each frequency as a function of time, wherein the temporal variance is a function of the computed spatial variance for each frequency and one or more prior spatial variances for each frequency; and comparing the computed temporal variances for each frequency to identify a noisy frequency. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
-
-
55. A method of detecting noise in one or more of at least three touch images, each touch image comprising a plurality of touch sample values obtained by stimulating a touch sensor at a unique frequency, the method comprising:
-
determining whether noise in any of the at least three touch images exceeds a background noise level; if noise in any of the touch images exceeds a background noise level performing a one-clean-frequency noise detection method; and if noise in all of the touch images does not exceed a background level or if the one-clean-frequency noise detection method finds noise in any one of the touch images, performing a two-clean-frequency noise detection method. - View Dependent Claims (58)
-
-
59. A touch sensing device comprising:
-
a touch sensitive surface having a plurality of touch sensors; drive circuitry configured to apply drive signals to the touch sensors wherein the drive signals comprise at least three periodic waveforms each having a unique frequency; sense circuitry configured to derive a touch image for each frequency, each touch image comprising a plurality of touch sample values obtained at each frequency; and additional circuitry configured to detect noise in one of the touch images by; determining whether noise in any of the at least three touch images exceeds a background noise level; if noise in any of the at least three touch images does not exceed a background noise level performing a two-clean-frequency noise detection method; and if noise in any of the at least three touch images exceeds a background noise level performing a one-clean-frequency noise detection method. - View Dependent Claims (60, 61, 62, 63, 64, 67, 68, 69, 70)
-
Specification