Object position and proximity detector

• US 5,495,077 A
• Filed: 06/02/1994
• Issued: 02/27/1996
• Est. Priority Date: 06/08/1992
• Status: Expired due to Term

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Bisset, Stephen, Allen, Timothy P., Miller, Robert J., Steinbach, Gunter
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kim, Kevin
• Application Number:
  US08/252,969
• Time in Patent Office: 635 Days
• Field of Search: 178/18, 345/173-178, 341/33, 341/34
• 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 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 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. An object proximity sensor, including:

a touch-sensitive transducer disposed on a substrate, said touch sensitive transducer including a matrix of row conductive lines disposed in a first direction and column conductive lines disposed in a second direction generally perpendicular to said first direction, said row conductive lines and said column conductive lines insulated from one another, and an insulating layer disposed over said row conductive lines and said column conductive lines, said insulating layer forming a touch surface, said insulating layer having a thickness selected to promote capacitive coupling between a finger placed proximate to the touch surface of said insulating layer and said row conductive lines and said column conductive lines;

means for simultaneously injecting electrical charge onto each of said row conductive lines, and for sensing a row-sense voltage created on each of said row conductive lines by said electrical charge onto each of said row conductive lines;

means for simultaneously injecting electrical charge onto each of said column conductive lines, and for sensing a column-sense voltage created on each of said column conductive lines by said electrical charge onto each of said column conductive lines; and

means for producing a set of object-sensed electrical signals related to said row-sense voltage and said column-sense voltage; and

means for processing said set of row electrical signals and said set of column electrical signals to create a proximity electrical signal proportional to the proximity of said object to said touch surface.

2. The object proximity sensor of claim 1 wherein said row conductive lines are disposed on a first face of said substrate and said column conductive lines are disposed on a second face of said substrate opposite said first face, said touch sensitive transducer further including a plurality of spaced-apart conductive sensor pads disposed in a row and column matrix pattern on said substrate, each of said sensor pads connected to a corresponding one of said row conductive lines or column conductive lines.

3. The object proximity sensor of claim 1, further including:

means for sensing a minimum no-object proximate capacitance from among said row conductive lines, for sensing a minimum no-object proximate capacitance from among said column conductive lines, for producing a set of minimum background electrical signals related thereto; and

means for subtracting said set of minimum background electrical signals from said set of object-sensed electrical signals.

4. The object proximity sensor of claim 1, further including:

means for producing a set of average no-object-proximate electrical signals related to an average no-object-proximate capacitance from among said row conductive lines and an average no-object-proximate capacitance from among said column conductive lines; and

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

5. The object proximity sensor of claim 1 wherein the ones of said sensor pads associated with odd numbered ones of said row conductive lines are disposed along a first set of column positions and the ones of said sensor pads associated with even numbered ones of said row conductive lines are disposed at a second set of column positions offset from said first set of column positions wherein said sensor pads form a closely packed repetitive pattern wherein each pad is not in contact with adjoining pads.

6. A method for providing an electrical signal representative of the position of an object in a two dimensional sensing plane and of the proximity of the object to the two dimensional sensing plane, including the steps of:

providing a sensing plane including a matrix of conductors arranged as a plurality of rows and columns of spaced apart row conductive lines and column conductive lines, said sensing plane having an inherent capacitance on the various ones of said row conductive lines and column conductive lines, said capacitance varying with the proximity of an object to said row and column conductors;

simultaneously generating from among said row conductive lines a first electrical signal proportional to a no-object-proximate value of said capacitance when no object is proximate to said sensing plane from among said row conductive lines;

simultaneously generating from among said row conductive lines a corresponding second electrical signal proportional to the value of said capacitance when an object is located proximate to but not necessarily in contact with said sensing plane;

subtracting each of said corresponding first electrical signals from said second electrical signals to produce a set of row electrical signals;

simultaneously generating from among said column conductive lines a third electrical signal proportional to the no-object-proximate value of said capacitance when no object is proximate to said sensing plane from among said column conductive lines;

simultaneously generating for each conductor in the column dimensions a corresponding fourth electrical signal proportional to the value of said capacitance when an object is located proximate to but not necessarily in contact with said sensing plane;

subtracting each of said corresponding third electrical signals from said fourth electrical signals to produce a set of column electrical signals;

encoding said set of row electrical signals and said set of column electrical signals into electrical signals indicating the position of said object in said row dimension and said column dimension; and

processing said set of row electrical signals and said set of column electrical signals to create proximity electrical signal proportional to proximity of said object to said sensing plane.

7. The method of claim 6 wherein the step of encoding said set of row electrical signals and said set of column electrical signals into electrical signals indicating the position of said object in said row dimension and said column dimension comprises separately encoding said set of row electrical signals into a first digital signal and encoding said set of column electrical signals into a second digital signal.

8. The method of claim 6 wherein the step of encoding said set of row electrical signals and said set of column electrical signals into electrical signals indicating the position of said object in said row dimension and said column dimension comprises separately encoding said set of row electrical signals into a first digital signal and encoding said set of column electrical signals into a second digital signal, and further including the step of encoding said proximity electrical signal into a third digital signal.

9. The method of claim 6 further including the step of providing a signal when said row electrical signal for any of said row or column electrical signal exceeds a threshold value.

10. The method of claim 6, wherein said first and third electrical signals are proportional to the minimum no-object-proximate value of said capacitance from among said row conductive lines and column conductive lines.

11. The method of claim 6, wherein said first and third electrical signals are proportional to the average no-object-proximate value of said capacitance from among said row conductive lines and column conductive lines.