Method for calibrating touch panel displays

• US 5,751,276 A
• Filed: 05/23/1996
• Issued: 05/12/1998
• Est. Priority Date: 05/23/1996
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Shih, Yung-Ho
• Primary Examiner(s): Powell, Mark R.
• Assistant Examiner(s): Kovalick, Vincent E.
• Application Number:
  US08/652,899
• Time in Patent Office: 719 Days
• Field of Search: 345/156, 345/173, 345/174, 345/178
• US Class Current: 345/178
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment

Abstract

A method for calibrating a touch panel display includes generating contact coordinates (x_i, y_i,i=1, . . . , N) indicative of N touch points of contact on the touch panel display, where N>3. The touch points can be selected at random on the touch panel, and are not constrained to specific, predefined locations. The contact coordinates (x_i, y_i) are related into screen coordinates (x_i, y_i,) according to the following mapping transformation: ##EQU1## This mapping transformation accounts for all possible two-dimensional transformations including transposition, rotation, and shearing. After N sets of digitizer and screen coordinates are found, values for the parameters a₁, b₁, c₁, a₂, b₂, and c₂ are derived. Preferably, the parameters are determined using an optimizing algorithm, such as a least square fitting algorithm. The parameters a₁, b₁, c₁, a₂, b₂, and c₂ are stored and thereafter used for all mapping transformations.

Claims

1. A method for calibrating a touch panel display, comprising the following steps:

generating N contact coordinates (x_i, y_i, i=1, . . . ,N) in response to contact at N touch points on the touch panel display, where N>

3;

mapping the contact coordinates (x_i, y_i) into screen coordinates (x_i, y_i) according to the following mapping transformation;

##EQU9##

2. A method as recited in claim 1 and further comprising the step of deriving parameters a₁, b₁, c₁, a₂, b₂ and c₂ using the contact and screen coordinates.

3. A method as recited in claim 1 and further comprising the step of deriving parameters a₁, b₁, c₁, a₂, b₂, and c₂ using an optimizing algorithm.

4. A method as recited in claim 1 and further comprising the step of deriving parameters a₁, b₁, c₁, a₂, b₂, and c₂ using a least squares fitting algorithm.

5. A method for calibrating a touch panel display, comprising the following steps:

displaying N touch points on the touch panel display using N screen coordinates (x_i, y_i, i=1, . . . ,N), where N>

3;

generating N contact coordinates (x_i, y_i, i=1, . . . ,N) in response to contact at the N touch points on the touch panel display;

relating the contact coordinates (x_i, y_i) to the screen coordinates (x_i, y_i) according to the following mapping transformation;

##EQU10## deriving parameters a₁, b₁, c₁, a₂, b₂, and c₂ using the contact and screen coordinates and the mapping transformation; and

storing the parameters a₁, b₁, c₁, a₂, b₂, and c₂.

6. A method as recited in claim 5 wherein the deriving step comprises computing the parameters a₁, b₁, c₁, a₂, b₂ , and c₂ using an optimizing algorithm.

7. A method as recited in claim 5 wherein the deriving step comprises computing the parameters a₁, b₁, c₁, a₂, b₂ and c₂ using a least squares fitting algorithm.

8. A method as recited in claim 5 and further comprising the step of subsequently mapping the contact coordinates (X_i, y_i) into screen coordinates (x_i, y_i) using the stored parameters a₁, b₁, c₁, a₂, b₂, and c₂.

9. A method for calibrating a touch panel display, comprising the following steps:

(a) displaying a touch point on the touch panel display according to a screen coordinate (x_i, y_i);

(b) contacting the touch panel display at the touch point;

(c) generating contact coordinates (x₁, y_i) indicative of the touch point;

(d) storing the contact coordinates (x_i, y_i);

(e) repeating steps (a)-(d) for N touch points;

(f) formulating a mapping relationship that maps the N stored contact coordinates (x_i, y_i) into the N screen coordinates (x_i, y_i) according to the following mapping transformation;

##EQU11## (f) deriving parameters a₁, b₁, c₁, a₂, b₂, and c₂ using the contact and screen coordinates and the mapping transformation; and

(g) storing the parameters a₁, b₁, c₁, a₂ , b₂, and c₂.

10. A touch panel display device comprising:

a touch panel and a screen;

a digitizer to detect points of contact on the touch panel and to generate digitizer coordinates (x_i, y_i) indicative of the contact points;

a processor programmed to map the digitizer coordinates (X_i, y_i) from the digitizer onto screen coordinates (x_i,y_i) for depiction on the screen using the following mapping transformation;

##EQU12##

11. A touch panel display device as recited in claim 10 wherein the processor is firther programmed to derive parameters a₁, b₁, c₁, a₂, b₂, and c₂ using the digitizer and screen coordinates and the mapping transformation.

12. A touch panel display device as recited in claim 11, further comprising a memory to store the parameters a₁, b₁, c₁, a₂ , b₂, and c₂.

13. A touch panel display that is calibrated by mapping contact coordinates (x_i, y_i) indicative of N touch points, where n≧

3, into screen coordinates (x_i, y_i) according to the following mapping transformation;

##EQU13##