Capacitive Position Sensor

• US 20100045632A1
• Filed: 04/10/2009
• Published: 02/25/2010
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited), QRG Limited
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Sleeman, Peter, Yilmaz, Esat, Trend, Matthew, Philipp, Harald, Brunet, Samuel
• Granted Patent: US 8,830,180 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G01B 2210/58 Wireless transmission of information between a sensor or probe and a control or evaluation unit
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: G06F 1/16 Constructional details or arrangements
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• CPC Class Codes: G06F 2203/04112 Electrode mesh in capacitive digitiser: electrode for touch sensing is formed of a mesh of very fine, normally metallic, interconnected lines that are almost invisible to see. This provides a quite large but transparent electrode surface, without need for ITO or similar transparent conductive material
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/041661 using detection at multiple resolutions, e.g. coarse and fine scanning; using detection within a limited area, e.g. object tracking window
• 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
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H05K 1/0296 Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18

Abstract

A capacitive position sensor has a two-layer electrode structure. Drive electrodes extending in a first direction on a first plane on one side of a substrate. Sense electrodes extend in a second direction on a second plane on the other side of the substrate so that the sense electrodes cross the drive electrodes at a plurality of intersections which collectively form a position sensing array. The sense electrodes are provided with branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced. Providing sense electrode branches allow a sensor to be made which has a greater extent in the first direction for a given number of sense channels, since the co-extending portions provide an interpolating effect. The number of sense electrode branches per drive electrode can be increased which allows a sensor to be made which has ever greater extent in the first direction without having to increase the number of sense channels.

Claims

1. A capacitive position sensor comprising:

a plurality of drive electrodes extending in a first direction on a first plane;

a plurality of sense electrodes extending in a second direction on a second plane offset from the first plane so that the sense electrodes cross the drive electrodes at a plurality of intersections which collectively form a position sensing array;

wherein the sense electrodes have branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced.

2. The sensor of claim 1, wherein for each drive electrode there is one set of sense electrode branches providing co-extending portions that occupy a region in between adjacent sense electrodes in the first direction.

3. The sensor of claim 1, wherein for each drive electrode there are multiple sets of sense electrode branches that are offset from each other in the second direction, the multiple sets providing respective co-extending portions extending over different respective regions in the first direction.

4. The sensor of claim 3, wherein the sense electrodes are separated from each other in the first direction by a distance P_sense and the drive electrodes are separated from each other in the second direction by a distance P_drive, wherein:

P_sense/P_drive=2m±

1

where ‘

m’

is the number of sets of sense electrode branches per drive electrode.

5. The sensor of claim 4, wherein P_drive is of comparable dimension to the touch size of the touching object for which the sensor is designed.

6. The sensor of claim 1, wherein in plan view each drive electrode covers an area that fully encloses its associated sense electrode branches.

7. The sensor of claim 1, wherein the gaps between individual ones of the drive electrodes are small.

8. The capacitive touch sensor of claim 7, wherein the gaps are dimensioned to be sufficiently small to be invisible or almost invisible.

9. The capacitive touch sensor of claim 7, wherein the gaps are less than around 100 micrometers.

10. The capacitive touch sensor of claim 1, further comprising a display module arranged below the drive electrodes.

11. The capacitive touch sensor of claim 10, wherein the display module is an LCD.

12. The capacitive touch sensor of claim 1, wherein each drive and/or sense electrode is made of a continuous sheet of electrically conductive material.

13. The capacitive touch sensor of claim 1, wherein each drive and/or sense electrode is made of a mesh or filigree pattern of interconnected lines of highly conductive material which collectively define each electrode.

14. The capacitive touch sensor of claim 13, wherein the interconnected lines have a sufficiently small width so as to be invisible or almost invisible.

15. The capacitive touch sensor of claim 1, wherein the drive electrodes extend in a first linear direction and the sense electrodes extend in a second linear direction transverse to the first linear direction so that the plurality of intersections form a grid pattern.

16. The capacitive touch sensor of claim 1, wherein the drive electrodes extend arcuately and the sense electrodes extend radially so that the plurality of intersections lie on one or more arcuate paths.

18. A method of sensing position of an actuation on a two-dimensional position sensor according to claim 1, the method comprising:

applying drive signals to each of the plurality of drive electrodes;

measuring sense signals received from each of the plurality of sense electrodes representing a degree of capacitive coupling of the drive signals between the drive electrodes and each group of the sense electrodes;

determining the position in the first direction by an interpolation between sense signals obtained from each of the plurality of sense electrodes; and

determining the position in the second direction by an interpolation between sense signals obtained by sequentially driving each of the plurality of drive electrodes with respective drive signals.

17. A touch sensitive panel for a capacitive touch sensor, the touch sensitive panel having a plurality of drive electrodes arranged on one side of a substrate in a first layer and a plurality of sense electrodes arranged on the other side of the substrate in a second layer so that the sense electrodes cross the drive electrodes at a plurality of intersections offset from each other by the thickness of the substrate, wherein the sense electrodes have branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced.