Object position detector

• US 5,841,078 A
• Filed: 10/30/1996
• Issued: 11/24/1998
• Est. Priority Date: 06/08/1992
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Miller, Robert J., Bisset, Stephen J.
• Primary Examiner(s): Shankar, Vijay
• Application Number:
  US08/739,607
• Time in Patent Office: 755 Days
• Field of Search: 345/173, 345/174, 341/33, 178/18.01, 178/18.03, 178/18.06, 178/19.03
• US Class Current: 178/18.06
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 2203/04101 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface and also measures the distance of the input means within a short range in the Z direction, possibly with a separate measurement setup
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• 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

Abstract

A proximity sensor system includes a sensor matrix array having a characteristic capacitance between 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 analog 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. The profile of position may also be integrated to provide Z-axis (pressure) information.

Claims

1. A method for providing an electrical signal representative of the position of an object in a two dimensional plane, including the steps of:

providing a capacitive sensing plane including a matrix of conductive lines arranged as a plurality of spaced apart row conductive lines and column conductive lines, said capacitive sensing plane having a touch surface, said capacitive sensing plane characterized by an inherent mutual capacitance between the various ones of said row conductive lines and said column conductive lines, said row conductive lines and column conductive lines electrically insulated from said touch surface, said mutual capacitance measurably varying with the proximity of an object to said row conductive lines and said column conductive lines;

selecting individual ones of said row conductive lines one at a time and simultaneously sensing a measurable variance in said mutual capacitance between the selected one of said row conductive lines and each of said plurality of column conductive lines in response to the proximity of an object; and

producing a set of object-sensed electrical signals related to the measurable variance in said mutual capacitance.

2. The method of claim 1, further including the steps of:

sensing a no-object-present mutual capacitance between each individual one of said row conductive lines and each of said column conductive lines, and producing a set of no-object-present electrical signals related thereto; and

subtracting said set of no-object-present electrical signals from said set of object-sensed electrical signals.

3. An object proximity sensor, including:

a plurality of row conductive lines disposed on a substrate;

a plurality of column conductive lines disposed on said substrate and insulated from said row conductive lines;

said plurality of row and column conductive lines forming a capacitive sensing plane, said capacitive sensing plane having a touch surface electrically insulated from said plurality of row and column conductive lines, said capacitive sensing plane characterized by an inherent mutual capacitance between the various ones of said row and column conductive lines, said mutual capacitance measurably varying with the proximity of an object to said row and column conductive lines; and

means for selecting individual ones of said row conductive lines one at a time and for simultaneously sensing a measurable variance in said mutual capacitance between the selected one of said row conductive lines and each of said plurality of column conductive lines in response to the proximity of an object and for producing a set of object-sensed electrical signals related thereto.

4. The object proximity sensor of claim 3 wherein said row conductive lines are disposed on said first face of said substrate and said column conductive lines are disposed on a second face of said substrate opposite said first face.

5. The object proximity sensor of claim 3, further including:

means for sensing a no-object-present mutual capacitance between each individual one of said row conductive lines and each of said column conductive lines, for producing a set of no-object-present electrical signals related thereto; and

means for subtracting said set of no-object-present electrical signals from said set of object-sensed electrical signals.

6. The object proximity sensor of claim 5 wherein said means for producing a set of no-object-present electrical signals related to said no-object-present mutual capacitance of each of said row conductive lines and said no-object-present mutual capacitance of each of said column conductive lines comprises means for computing weighted minima of said object-sensed electrical signals thereof.