Automatic touch screen calibration method

Claim 2

An automatic calibration method for a touch screen which is used in conjunction with and which overlays a CRT display during interactive sessions, said calibration being done by each individual before an interactive session of the touch screen/CRT use, whereby to calibrate any coordinates put out by the touch screen with the coordinates of points on said CRT display, said method comprising the steps of: (a) displaying, prior to each of the interactive sessions, a first point on the display; (b) obtaining first coordinates of a first touch on the touch screen at approximately the first point; and (c) generating terms in a translation matrix for translating coordinates of the first touch into display coordinates.

Claim 3

A method as recited in claim 1, further comprising prompting the first touch at the first point prior to step (b).

Claim 4

A method as recited in claim 1, wherein the first point has X and Y display coordinates and the first coordinates of the first touch are X and Y touch coordinates, and wherein said step (c) comprises the steps of: (ci) generating an X coefficient equal to the X display coordinate divided by the X touch coordinate; and (cii) generating a Y coefficient equal to the Y display coordinate divided by the Y touch coordinate.

Claim 5

A method as recited in claim 1, further comprising the steps of: (d) displaying a second point on the display; and (e) obtaining second coordinates of a second touch at approximately the second point, and wherein step (c) comprises generating the translation matrix in dependence upon the first and second coordinates.

Claim 6

A method as recited in claim 4, wherein the first point has X and Y display coordinates, the second point has origin display coordinates equal to (0, 0), the first coordinates of the first touch are X1 and Yl touch coordinates and XO and YO touch coordinates, and wherein step (c) comprises the following steps to generate four of the terms: (ci) generating an X coefficient equal to the X display coordinate divided by the Xl touch coordinate; (cii) generating an X intercept equal to the XO touch coordinate; (ciii) generating a Y coefficient equal to the Y display coordinate divided by the Y1 touch coordinate; and (civ) generating a Y intercept equal to the YO touch coordinate, so that any subsequent touch, having X and Y touch coordinates, on the touch screen during the interactive session can be translated into display coordinates by multiplying the X touch coordinate by the X coefficient and adding the X intercept and by multiplying the Y touch coordinate by the Y coefficient and adding the Y intercept.

Claim 7

A method as recited in claim 1, further comprising the steps of: (d) displaying a second point on the display; (e) obtaining second coordinates of a second touch at approximately the second point; (f) displaying a third point on the display; (g), obtaining third coordinates of a third touch at approximately the third point, and wherein step (c) comprises generating the translation matrix in dependence upon the first, second and third coordinates.

Claim 8

A method as recited in claim 6, further comprising the steps of: (h) prompting the second touch at the second point prior to step (e); and (i) prompting the third touch at the third point prior to step (g).

Claim 9

A method as recited in claim 6, further comprising the step of (6) indicating an error if at least one of said first, second and third coordinates has a value which is outside of a predetermined range of values.

Claim 10

A method as recited in claim 6, wherein the first and second points define a first line and the second and third points define a second line substantially perpendicular to the first line, and wherein said method further comprises the steps of: (h) calculating an angle formed by a third line defined by the first and second coordinates and a fourth line defined by the second and third coordinates; and (i) indicating an error if the angle is smaller than 90° by a first predetermined value and if the angle is greater than 90° by a second predetermined value.

Claim 11

A method as recited in claim 9, wherein the first coordinates are X1, Y1, the second coordinates are X0, YO and the third coordinates are X2, Y2, and wherein step (c) comprises the steps of: (ci) calculating a first distance Dl between the first and second touches as follows: (cii) calculating a second distance D2 between the second and third touches as follows: (ciii) defining an angle θ 1 as follows: ; and (civ) generating six terms of the coordinate translation matrix as follows: so that any subsequent touch, having touch screen coordinates of X ts and Y ts , can be translated into normalized coordinates of X N and Y N as follows:

Claim 12

A method as recited in claim 10, wherein a third distance D3 is defined between the second and first points in terms of display coordinates, a fourth distance D4 is defined between the second and third points in terms of display coordinates and the second point has display coordinates of XD, YD, and wherein step (c) further comprises the step of (cv) generating four additional terms of the coordinate translation matrix as follows: so that the normalized coordinates can be translated into graphic display coordinates X gd and Y gd , as follows: