Frontally shielded capacitive touch sensor system

• US 5,457,289 A
• Filed: 03/16/1994
• Issued: 10/10/1995
• Est. Priority Date: 03/16/1994
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: MicroTouch Systems, Inc. (3M Company)
• Inventors: Stein, Robert A., Huang, Hung-Chih
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): LOOMIS, PAUL A
• Application Number:
  US08/213,684
• Time in Patent Office: 573 Days
• Field of Search: 178/18, 178/19, 178/20, 345/173, 345/174
• US Class Current: 178/18.08
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0444 using a single conductive element covering the whole sensing surface, e.g. by sensing the electrical current flowing at the corners

Abstract

A frontally shielded capacitive touch sensor system includes a capacitive touch sensor having a touch sensitive surface; a front shield mounted in front of the touch sensor and extending peripherally about the surface surrounding an exposed accessible area of the touch sensitive surface; a device for providing a first voltage on the touch sensor and detecting a change in capacitance representative of a touch to the touch sensor and for providing a second voltage on the front shield for controlling the capacitance between the touch sensor and the front shield and shielding the system from stray capacitance occurring at the front shield.

Claims

1. A frontally shielded capacitive touch sensor system, comprising:

a capacitive touch sensor having a touch sensitive surface;

a front shield mounted in front of said touch sensor and extending peripherally about said surface surrounding an exposed accessible area of said touch sensitive surface;

means for providing a first voltage on said touch sensor and means for detecting a change in capacitance representative of a touch to said touch sensor and for providing a second voltage on said front shield for controlling the capacitance between said touch sensor and said front shield and shielding the system from stray capacitance occurring at said front shield.

2. The frontally shielded capacitive touch sensor system of claim 1 in which said second voltage is substantially equal to said first voltage and substantially eliminates the capacitance between said front shield and said surface and said stray capacitance occurring at said front shield.

3. The frontally shielded capacitive touch sensor system of claim 1 in which said second voltage is greater than said first voltage and substantially eliminates the capacitance between said front shield and said surface, said stray capacitance occurring at said front shield, and substantially compensates for stray capacitance between said exposed accessible area and the ambient atmosphere.

4. The frontally shielded capacitive touch sensor system of claim 1 in which said second voltage is less than said first voltage.

5. The frontally shielded capacitive touch sensor system of claim 1 in which said second voltage is ground voltage.

6. The frontally shielded capacitive touch sensor system of claim 1 in which said means for providing a first voltage includes a voltage distribution network disposed about the periphery of said touch sensitive surface and said front shield covers said distribution network.

7. The frontally shielded capacitive touch sensor system of claim 1 in which said front shield includes a front conductive layer and a back non-conductive layer.

8. The frontally shielded capacitive touch sensor of claim 1 in which said means for providing said first and second voltages includes conductor means for interconnecting with said touch sensor.

9. The frontally shielded capacitive touch sensor of claim 1 in which said conductor means are integral with said front shield.

10. frontally shielded capacitive touch sensor of claim 9 in which said touch sensor includes a plurality of sensing contacts and said conductor means includes a plurality of terminals for engaging said contacts.