Method and apparatus for laplace constrained touchscreen calibration
First Claim
1. A method for calibrating a touch system, comprising:
- defining a set of calibration targets that have associated display coordinates (Xi, Yi) that are in a display coordinate system;
accepting touchscreen coordinates (xi, yi) that have noise, the touchscreen coordinates (xi, yi) each being associated with one of the calibration targets, the touchscreen coordinates being in a touchscreen coordinate system; and
computing non-linear correction parameters for a given polynomial expansion up to an order N (N≧
3) that includes a set of polynomial terms based on the touchscreen coordinates (xi, yi) in terms of the display coordinates (Xi, Yi), the non-linear correction parameters defining a one-to-one correspondence between display coordinates (X,Y) and touchscreen coordinates (x,y) that is non-linear, the computing comprising producing the one-to-one correspondence by using a linear combination of the polynomial terms to provide polynomial terms within the set that satisfy Laplace'"'"'s equation and dropping at least some or all correction parameters corresponding to some polynomial terms violating Laplace'"'"'s equation such that an average magnitude of a Laplacian of at least one of x and y touchscreen coordinates with respect to the display coordinates is smaller than an average magnitude of a Laplacian of a one-to-one correspondence computed with a conventional general fit in the presence of the noise of the touchscreen coordinates (xi, yi), the Laplacians of the x and y touchscreen coordinates being based on ∂
2x/∂
X2+∂
2x/∂
Y2 and ∂
2y/∂
X2+∂
2y/∂
Y2, respectively.
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0 Petitions
Accused Products
Abstract
A computer readable medium has instructions to calibrate a touch system by detecting touch points on a touchscreen that are each associated with touchscreen coordinates in a touchscreen coordinate system. The instructions associated each of the touch points with known calibration targets, and each of the calibration targets has display coordinates in a display coordinate system that is associated with at least one of a display screen and an operating system. The instructions fit the display coordinates and the touchscreen coordinates non-linearly with respect to each other based on a generalized Laplace-constrained fit that is used to identify correction parameters used to map a user generated run-time touch point on the touchscreen to a display coordinate location on a display screen. The correction parameters represent non-linear corrections.
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Citations
19 Claims
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1. A method for calibrating a touch system, comprising:
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defining a set of calibration targets that have associated display coordinates (Xi, Yi) that are in a display coordinate system; accepting touchscreen coordinates (xi, yi) that have noise, the touchscreen coordinates (xi, yi) each being associated with one of the calibration targets, the touchscreen coordinates being in a touchscreen coordinate system; and computing non-linear correction parameters for a given polynomial expansion up to an order N (N≧
3) that includes a set of polynomial terms based on the touchscreen coordinates (xi, yi) in terms of the display coordinates (Xi, Yi), the non-linear correction parameters defining a one-to-one correspondence between display coordinates (X,Y) and touchscreen coordinates (x,y) that is non-linear, the computing comprising producing the one-to-one correspondence by using a linear combination of the polynomial terms to provide polynomial terms within the set that satisfy Laplace'"'"'s equation and dropping at least some or all correction parameters corresponding to some polynomial terms violating Laplace'"'"'s equation such that an average magnitude of a Laplacian of at least one of x and y touchscreen coordinates with respect to the display coordinates is smaller than an average magnitude of a Laplacian of a one-to-one correspondence computed with a conventional general fit in the presence of the noise of the touchscreen coordinates (xi, yi), the Laplacians of the x and y touchscreen coordinates being based on ∂
2x/∂
X2+∂
2x/∂
Y2 and ∂
2y/∂
X2+∂
2y/∂
Y2, respectively. - View Dependent Claims (2, 3)
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4. A computer readable non-transitory medium for calibrating a touch system, comprising:
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instructions to detect touch points on a touchscreen, the touch points each being associated with touchscreen coordinates in a touchscreen coordinate system; instructions to associate each of the touch points with known calibration targets, each of the calibration targets having display coordinates in a display coordinate system, the display coordinate system being associated with at least one of a display screen and an operating system; and instructions to fit the touchscreen coordinates non-linearly in terms of the display coordinates based on a generalized Laplace-constrained fit, the generalized Laplace-constrained fit being used to identify correction parameters used to map a user generated run-time touch point on the touchscreen to a display coordinate location on a display screen, the correction parameters representing non-linear corrections. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A computer readable non-transitory medium for calibrating a touch system, comprising:
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instructions to detect calibration touch points on a touchscreen, the touch points each being associated with touchscreen coordinates in a touchscreen coordinate system; instructions to associate each of the touch points with known calibration targets, each of the calibration targets having display coordinates in a display coordinate system that is associated with a display screen, the calibration targets forming an outline in the display coordinate system; and instructions to fit the touchscreen coordinates non-linearly in terms of the display coordinates, the fit being used to identify correction parameters used to map touch points on the touchscreen to display coordinate locations on the display screen; the instructions to fit further comprising; instructions to generate generalized Laplace-constrained expansions to fit the touchscreen coordinates in terms of the display coordinates; and instructions to invert the generalized Laplace-constrained expansions of the display coordinates in terms of the touchscreen coordinates based on one of a virtual calibration grid and an analytic conversion. - View Dependent Claims (17, 18, 19)
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Specification