System and method for preventing detection of touch screen input data

• US 6,630,896 B1
• Filed: 05/16/2000
• Issued: 10/07/2003
• Est. Priority Date: 05/16/2000
• Status: Expired due to Term

• Current Assignee: NCR Voyix Corporation
• Original Assignee: NCR Corporation
• Inventors: Nathan, Robert H.
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): DANG, HUNG Q
• Application Number:
  US09/573,428
• Time in Patent Office: 1,239 Days
• Field of Search: 341/34, 341/33, 341/26, 341/5, 178/18.01, 178/19.04, 178/18.06, 178/18.05, 345/173, 345/174, 345/179, 340/5.21
• US Class Current: 341/34
• CPC Class Codes: G06F 21/83 input devices, e.g. keyboards, mice or controllers thereof
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A system and method obfuscates a reference voltage being applied to a touch screen to reduce the likelihood that location coordinates may be obtained from electrically coupling to the touch screen. The method is performed by applying a varying reference voltage to a first plane of a touch screen with a time of application duration being substantially less than a touch period and by measuring a voltage present on a second plane during a portion of the application duration of the voltage to the first plane. A system may include a controller for randomly varying the reference voltage level and coupling a reference source that generates the reference voltage to a first plane of a touch screen for an application period that is significantly less than the touch period.

Claims

1. A method for preventing detection of a location coordinate generated by a touch screen comprising:

applying a varying reference voltage to a first plane of a touch screen with a time of application duration being substantially less than a touch period; and

measuring a voltage present on a second plane during a portion of the application duration of the voltage to the first plane.

2. The method of claim 1 further comprising:

de-coupling a voltage source from said first plane upon expiration of a timer timing a period corresponding to said application duration time so that application of said reference voltage to said first plane is terminated.

3. The method of claim 2 wherein said reference voltage level is randomly selected before applying a next reference voltage to said first plane.

4. The method of claim 1 further comprising:

applying a varying reference voltage to said first plane of said touch screen in an orthogonal direction with a time of application duration being substantially less than a touch period; and

measuring a voltage present on said second plane during a portion of the application duration of the voltage to the first plane.

5. The method of claim 1 further comprising:

applying a varying reference voltage to said second plane of said touch screen with a time of application duration being substantially less than a touch period; and

measuring a voltage present on said first plane during a portion of the application duration of the voltage to the second plane.

6. A system for preventing detection of location coordinates corresponding to a touch location on a touch screen comprising:

means for applying a varying reference voltage to a first plane of a touch screen with a time of application duration being substantially less than a touch period; and

means for measuring a voltage present on a second plane during a portion of the application duration of the voltage to the first plane.

7. The system of claim 6 further comprising:

means for de-coupling a voltage source from said first plane upon expiration of a timer timing a period corresponding to said application duration time so that application of said reference voltage to said first plane is terminated.

8. The system of claim 6 further comprising:

means for randomly selecting a reference voltage level before applying a next reference voltage to said first plane.

9. A system for preventing detection of location coordinates of a touch applied to a touch screen comprising:

a controller for generating a reference voltage level and for applying the generated voltage level to a first plane of a touch screen for a time that is substantially less than a touch period; and

a voltage measurement device for measuring a voltage on a second plane of the touch screen during the time the generated voltage level is applied to the first plane.

10. The system of claim 9 wherein said controller randomly generates said reference voltage level.

11. The system of claim 9 wherein the controller couples and de-couples a voltage source to the first plane to apply the generated voltage level for a time that is substantially less than a touch period.

12. The system of claim 11 wherein said controller changes a direction of a voltage potential being applied to said first plane from said voltage source in response to a voltage being measured on said second plane.

13. The system of claim 11 wherein said controller de-couples said voltage source from said first plane and couples said voltage source to said second plane so that a second location coordinate may be determined.