Paintbrush stylus for capacitive touch sensor pad

• US 5,488,204 A
• Filed: 10/17/1994
• Issued: 01/30/1996
• Est. Priority Date: 06/08/1992
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Wolf, Ralph, Allen, Timothy P., Mead, Carver A.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): LOOMIS, PAUL A
• Application Number:
  US08/324,438
• Time in Patent Office: 470 Days
• Field of Search: 178/12, 178/19, 178/20, 178/87, 345/173, 345/174, 345/175, 345/179, 345/180, 345/181, 341/5, 382/3, 382/13, 355/27, 355/266, 395/117, 395/118, 395/122
• US Class Current: 178/18.06
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/04855 Interaction with scrollbars
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text
• CPC Class Codes: G06F 3/04892 Arrangements for controlling cursor position based on codes indicative of cursor displacements from one discrete location to another, e.g. using cursor control keys associated to different directions or using the tab key arrangements for controlling cursor position based on coordinate signals G06F3/038
• CPC Class Codes: G06V 40/20 Movements or behaviour, e.g. gesture recognition recognition of facial expressions G06V40/16

Abstract

A proximity sensor system includes a touch-sensor pad with a sensor matrix array having a characteristic capacitance on horizontal and vertical conductors connected to sensor pads. The capacitance changes as a function of the proximity of an object or objects to the sensor matrix. The change in capacitance of each node in both the X and Y directions of the matrix due to the approach of an object is converted to a set of voltages in the X and Y directions. These voltages are processed by circuitry to develop electrical signals representative of the centroid of the profile of the object, i.e, its position in the X and Y dimensions. Noise reduction and background level setting techniques inherently available in the architecture are employed. A conductive paintbrush-type stylus is used to produce paint-like strokes on a display associated with the touch-sensor pad.

Claims

1. A conductive paintbrush stylus for use with a capacitive touch sensor pad comprising:

an electrically conductive handle;

a plurality of electrically conductive bristles affixed to said handle;

wherein the total resistance of said handle and said bristles is no more than the skin resistance of a human finger.

2. The conductive paintbrush stylus of claim 1 wherein said total resistance is less than about 10M ohms.

3. The conductive paintbrush stylus of claim 1 wherein said plurality of electrically conductive bristles are formed from carbon fibers.

4. The conductive paintbrush stylus of claim 1 wherein said plurality of electrically conductive bristles are formed from fine wire.

5. The conductive paintbrush stylus of claim 4 wherein said plurality of electrically conductive bristles are formed from phosphor bronze wire.

6. A conductive paintbrush stylus for use with a touch sensor pad having a characteristic capacitance, said paintbrush comprising:

an electrically conductive handle;

a plurality of electrically conductive bristles affixed to said handle;

wherein the time constant of an RC circuit comprising the total resistance of said handle and said bristles and said characteristic capacitance is less than a sampling period used to sense the presence of a conductive object on said touch sensor pad.

7. The conductive paintbrush stylus of claim 6 wherein said plurality of electrically conductive bristles are formed from carbon fibers.

8. The conductive paintbrush stylus of claim 6 wherein said plurality of electrically conductive bristles are formed from fine wire.

9. The conductive paintbrush stylus of claim 8 wherein said plurality of electrically conductive bristles are formed from phosphor bronze wire.

10. The conductive paintbrush stylus of claim 6 wherein said plurality of electrically conductive bristles are affixed to said handle with a conductive adhesive.

11. A conductive paintbrush stylus for use with a touch sensor pad having a characteristic capacitance, said paintbrush comprising:

a bundle of carbon fibers having a length extending substantially the length of said paintbrush stylus, a first portion of said length of said bundle impregnated with a thin insulating material to form a rigid handle, and a second portion of said length of said bundle remaining exposed to form conductive bristles;

wherein the time constant of an RC circuit comprising the total resistance of said handle and said bristles and said characteristic capacitance is less than a sampling period used to sense the presence of a conductive object on said touch sensor pad.