WO2011058562A1 - Capacitive sensor for a digitizer system - Google Patents

Capacitive sensor for a digitizer system Download PDF

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Publication number
WO2011058562A1
WO2011058562A1 PCT/IL2010/000942 IL2010000942W WO2011058562A1 WO 2011058562 A1 WO2011058562 A1 WO 2011058562A1 IL 2010000942 W IL2010000942 W IL 2010000942W WO 2011058562 A1 WO2011058562 A1 WO 2011058562A1
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WIPO (PCT)
Prior art keywords
conductive
sensor
capacitive sensor
plurality
area
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PCT/IL2010/000942
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French (fr)
Inventor
Eytan Mann
Original Assignee
N-Trig Ltd.
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Publication date
Priority to US26138609P priority Critical
Priority to US61/261,386 priority
Application filed by N-Trig Ltd. filed Critical N-Trig Ltd.
Publication of WO2011058562A1 publication Critical patent/WO2011058562A1/en

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    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means

Abstract

A capacitive sensor includes a plurality of sensing electrodes patterned on at least one substrate and spread over sensing area of the sensor and at least one conductive area other than the plurality of sensing electrodes pattern on at least one substrate and spread on the sensing area of the sensor, wherein the at least one conductive area is capacitively coupled to at least one of the plurality of sensing electrodes and is electrically isolated from each of the plurality of sensing electrodes, and wherein only the plurality of sensing electrodes is adapted to be electrically connected to circuitry during operation of the sensor. A digitizer system comprises the capacitive sensor and circuitry electrically connected to the plurality of sensing electrodes, the circuitry adapted for detecting output from the plurality of sensing electrodes, wherein the at least one conductive area is electrically isolated from the circuitry.

Description

CAPACmVE SENSOR FOR A DIGITIZER SYSTEM

RELATED APPLICATION/S

The present application claims the benefit under 35 U.S.C. §119(e) of U.S.

Provisional Application No. 61/261,386 filed on November 16, 2009 which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention, in some embodiments thereof, relates to a digitizer system including a capacitive sensor and, more particularly, but not exclusively, to a digitizer system including a grid based capacitive sensor.

BACKGROUND OF THE INVENTION

Capacitive sensors are used for position and proximity detection in many Human

Interface Devices (HID) that include a digitizer system such as laptop trackpads, MP3 players, computer monitors, and cell phones. The capacitive sensor senses positioning and proximity of a conductive object such as a conductive stylus or finger touch used to interact with the HID. Typically, the capacitive sensor is sensitive both to the size and the proximity of the interacting object.

Capacitive sensors include electrodes that can be constructed from different media, such as copper, Indium Tin Oxide (ΓΓΌ) and printed ink. ΓΤΟ is typically used to achieve transparency. Some capacitive sensors are grid based and are operated to detect mutual capacitance between the electrodes at different points in the grid.

U.S. Patent No. 7,372,455 entitled "Touch Detection for a Digitizer" assigned to

N-Trig Ltd., the contents of which is incorporated by reference, describes a detector for detecting touches by fingers or like body parts on a capacitive sensitive sensor. Typically the detector includes a grid of sensing conductors, extending into the sensing surface, a source of electrical energy oscillating at a predetermined frequency, and detection circuitry for detecting a capacitive influence on sensing conductors when an oscillating electrical energy is applied. Touch sensing is described as being based on the capacitive influence as detected on the sensing conductors. SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a capacitive sensor structured to enhance capacitive coupling between electrodes of the capacitive sensor and conductive objects interacting with the sensor. According to an aspect of some embodiments of the present invention there is also provided a digitizer system that operates with such a capacitive sensor for providing enhanced sensitivity in detecting and tracking conductive objects (and/or capacitive objects).

According to an aspect of some embodiments of the present invention there is provided a capacitive sensor comprising a plurality of sensing electrodes patterned on at least one substrate and spread over sensing area of the sensor, and at least one conductive area other than the plurality of sensing electrodes pattern on at least one substrate and spread on the sensing area of the sensor, wherein the at least one conductive area is capacitively coupled to at least one of the plurality of sensing electrodes and is electrically isolated from each of the plurality of sensing electrodes, and wherein only the plurality of sensing electrodes is adapted to be electrically connected to circuitry during operation of the sensor.

Optionally, the plurality of sensing electrodes includes an array of column conductive lines and an array of row conductive lines patterned, the row and column conductive lines forming a grid.

Optionally, the at least one conductive area at least partially fills an area on the at least one substrate not occupied by one of the row and column conductive lines.

Optionally, the at least one conductive area includes a plurality of conductive areas distributed between conductive lines of at least one of the array of column conductive lines and the array of row conductive lines.

Optionally, one of the array of row or column conductive lines is patterned on a first surface together with the at least one conductive area and the other array is patterned on a second surface.

Optionally, the first and second surface are separated by insulating material. Optionally, the at least one conductive area overlaps with a conductive line on the second surface. Optionally, the at least one conductive area includes a plurality of conductive areas that at least partially surround junctions between row conductive lines and column conductive lines.

Optionally, the at least one conductive area has an edge that recedes from a conductive line at a junction between the conductive line and a crossing conductive line.

Optionally, the array of row and column conductive lines are patterned from a same material as the at least one conductive area.

Optionally, the at least one conductive area is patterned from indium tin oxide.

Optionally, the at least one conductive area is patterned from at least one of indium-doped zinc oxide, a conductive polymer, carbon nano-tube, metal nano-particles, and antimony tin oxide.

Optionally, the capacitive sensor is patterned on a laminated glass substrate.

According to an aspect of some embodiments of the present invention there is provided a digitizer system comprising the capacitive sensor as described hereinabove, and circuitry electrically connected to the plurality of sensing electrodes, the circuitry adapted for detecting output from the plurality of sensing electrodes, wherein the at least one conductive area is electrically isolated from the circuitry.

Optionally, the circuitry includes triggering circuitry adapted to transmit a patterned signal to at least one sensing electrode of the plurality of sensing electrodes.

Optionally, the circuitry is operative to detect output from at least one other sensing electrode from the plurality of sensing electrodes when triggering that at least one sensing electrode, wherein the at least one other sensing electrode is capacitively coupled with the at least one sensing electrode triggered.

Optionally, the digitizer further comprises an electronic display screen, wherein the capacitive sensor is adapted to be overlaid on the electronic display screen.

Optionally, the digitizer system is adapted for detecting fingertip touch.

Optionally, the digitizer system is adapted for detecting fingertip hovering over the capacitive sensor.

Optionally, the digitizer system is adapted for detecting an electromagnetic stylus.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIGs. 1A and IB are simplified schematic top and cross sectional views of a grid based capacitive sensor including auxiliary conductive areas patterned between sensor lines of a capacitive sensor in accordance with some embodiments of the present invention.

FIGs. 2A and 2B are simplified schematic top and cross sectional views of a single row and column sensor line and associated auxiliary conductive areas of a capacitive sensor and a representation of capacitive coupling formed between the sensor lines and auxiliary conductive areas in accordance with some embodiments of the present invention;

FIG. 3 is a simplified schematic top view of a portion of single row and column sensor line and associated auxiliary conductive areas of a capacitive sensor around a junction in accordance with some other embodiments of the present invention.

FIGs. 4A, 4B, 4C, 4D and 4E are simplified schematic drawings of a grid based capacitive sensor with different exemplary patterns of auxiliary conductive areas in accordance with some embodiments of the present invention;

FIG. 5 is a simplified schematic drawing of a grid based capacitive sensor patterned with auxiliary conductive areas that do not overlap with areas covered by sensor lines of the capacitive sensor in accordance with some embodiments of the present invention;

FIG. 6 is a simplified schematic drawing of a grid based capacitive sensor patterned with auxiliary conductive areas that are segmented in accordance with some embodiments of the present invention;

FIGs. 7 A, 7B and 7C are simplified schematic side views of substrates for constructing a capacitive sensor in accordance with some embodiments of the present invention;

FIG. 8 is a simplified schematic drawing showing a side view of a grid based capacitive sensor patterned on a laminated glass substrate in accordance with some embodiments of the present invention; and

FIG. 9 is a schematic block diagram of a digitizer sensor in accordance with some embodiments of the present invention. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

As used herein, the term conductive object includes various conductive objects for interacting with a digitizer system and can include body parts such as one or more finger tips. As used herein, the term digitizer system includes various types of digitizer systems including touch screens.

The present invention, in some embodiments thereof, relates to a digitizer system including a capacitive sensor and, more particularly, but not exclusively, to a digitizer system including a grid based capacitive sensor.

According to some embodiments of the present invention, there is provided a capacitive sensor that includes a plurality of sensing electrodes as well as a plurality of auxiliary conductive areas spread over a sensing surface. According to some embodiments of the present invention, the auxiliary conductive areas are electrically isolated from each of the plurality of sensing electrodes. The present inventor has found that the presence of the auxiliary conductive areas may increase the capacitive coupling between a conductive object interacting with the sensor and one or more sensing electrodes positioned in an area of interaction.

According to some embodiments of the present invention, the capacitive sensor is a mutual capacitance sensor including row and column conductive lines (sensing lines) arranged in a grid pattern and the auxiliary conductive areas are positioned around but spaced away from junctions and/or crossings of the grid pattern formed by the conductive lines (the sensor lines). Typically, the sensing lines may also function as triggering lines. As used herein the term junction refers to an area of overlap between crossing sensor lines. According to some embodiments of the present invention, the auxiliary conductive areas are electrically isolated from each of the row and column sensor lines and their outputs are not sampled. Typically, the auxiliary conductive areas are not electrically connected to any circuitry of the digitizer system. Optionally, the auxiliary conductive areas are not electrically connected to ground.

According to some embodiments of the present invention, the conductive areas are patterned on the sensor to occupy area or partially fill an area along the sensing surface that isn't occupied by the sensor lines forming in the grid pattern. The present inventor has also found that the effect that a conductive object has on the mutual capacitance between row and column sensor lines can be increased by adding auxiliary conductive areas near junction areas between the row and column sensor lines.

Optionally, the auxiliary conductive areas increase capacitive coupling between the conductive object and one or more of the sensor lines near the junction and thereby increase the effect that the conductive object has on mutual capacitance formed between the row and column sensor lines at points of interaction. By increasing the effect that the conductive object has on mutual capacitance formed between the row and column sensor lines in an area of interaction, the sensitivity of the capacitive sensor to a presence (touch or hover) of a conductive object over the sensing surface can be improved. Typically, the auxiliary conductive areas are not connected to circuitry and can improve the sensitivity of the sensor without requiring additional connections to circuitry (such as may be required when adding additional sensing sensor lines) and/or without adding additional circuitry.

In some exemplary embodiments, the auxiliary conductive areas are shaped and/or patterned around junctions although displaced from the junction itself. The present inventor has found that increasing the capacitive coupling between an auxiliary conductive area and a sensor line at a point displaced from a junction point provides for increasing the change in the capacitive coupling due to interaction of a conductive object, without increasing (or without significantly increasing) the steady-state or baseline capacitive coupling that exists in the absence of interaction with a conductive object.

According to some embodiments of the present invention, the sensor is formed with two layers of sensing elements superimposed on each other but electrically isolated from each other. Optionally, one layer is formed with the auxiliary conductive areas as well as an array of the row sensor lines or alternately an array of the column sensor lines, while the other layer is formed with an array of the other of the row or column sensor lines. Optionally, the auxiliary conductive areas are patterned on the layer closest to the sensing surface.

In some exemplary embodiments one of the layers is patterned with sensor lines that are wider than the sensor lines patterned in the other layer. In some exemplary embodiments, the auxiliary sensor lines are patterned on the layer with the narrower sensor lines. Optionally, the wider sensor lines are not homogenous in width throughout their lengths. In some exemplary embodiments, the row and/or column sensor lines are pinched and/or narrowed near junction points.

Optionally, auxiliary conductive areas are patterned on both layers of the sensor or alternatively on one or more additional layers separate from the layers on which the row and column sensor lines are patterned. In some exemplary embodiments, a portion of an auxiliary conductive area on one layer partially overlaps an area occupied by sensor lines on the other layer. Optionally, partially overlapping an auxiliary conductive area with one of the sensor lines strengthens the capacitive coupling between the auxiliary conductive area and the sensor line with which it overlaps.

In some exemplary embodiments, junction points are at least partially surrounded by two or more auxiliary conductive areas. Optionally, the auxiliary conductive areas are patterned proximal to each of the crossing sensor lines but displaced or distanced from the junction.

Optionally a plurality of segmented auxiliary conductive areas with gaps in between is patterned between pairs of row and/or column sensor lines. The present inventor has found that segmenting the auxiliary conductive areas into a plurality of sections can help localize and reduce damage that may be caused by a short between an auxiliary conductive area and one or more of the row and column sensor lines. The present inventor has also found that segmenting the auxiliary conductive areas does not significantly reduce the coupling effect that the auxiliary conductive areas provide.

According to some embodiments of the present invention the capacitive sensor and/or the auxiliary conductive areas are transparent, e.g. formed with materials such as ITO^Jndium-doped Zinc Oxide (IZO), a conductive polymer, Carbon nano-tube, metal nano-particles such as Ag or Cu, Antimony Tin Oxide (ATO), or other conductive transparent materials. In some exemplary embodiments, the capacitive sensor is patterned on a laminated glass substrate wherein the first and second layers are laminated with non-conducting transparent laminating material, such that the patterned surfaces face each other.

According to some embodiments of the present invention there is provided a digitizer system including a mutual capacitive sensor as described herein and associated triggering and detection circuitry electrically connected to the row and column sensor lines of the sensor for interrogating and detecting output from the capacitive sensor. According to some embodiments of the present invention, detection is provided by triggering one or more sensor lines of one axis, e.g. row or column axis with an oscillating signal or another patterned signal and detecting signals along a second axis that arise in response to mutual capacitance formed between crossing lines. Output detected along the second axis is associated with specific junctions formed by the crossing lines. Typically, each of the row and column sensor lines can be operated as a triggering and/or a detecting axis during operation of the digitizer system. Although, a certain amount of mutual capacitance is typically detected with the digitizer system at all junctions affected by the triggering, a presence of a conductive object over an area of the sensing surface typically drains current and reduces the signal amplitude detected at the junctions in the area when triggered. The present inventor has found that a digitizer sensor including a capacitive sensor as described herein may provide for greater change in the signal amplitude detected from a junction over which a conductive object is interacting, relatively to the change detected if no auxiliary elements are provided. In some exemplary embodiments, the digitizer system provides for detecting a reduction in signal amplitude of between 15% and 30% in an area of finger touch. Optionally, the digitizer provides for detecting increases in signal amplitude of between 15% and 30% in of interaction with a conductive object that is floating (not grounded). Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring now to the drawings, FIGS. 1A and IB illustrates a simplified schematic top and cross sectional view of a grid based capacitive sensor including auxiliary conductive areas patterned between sensor lines of a capacitive sensor in accordance with some embodiments of the present invention. Typically, a grid based capacitive sensor 100 includes a grid of row sensor lines 20 and column sensor lines 30 patterned on layers (or surfaces) that are separated by non-conductive material 70 to form a capacitive sensing surface 80. Typically, one layer 72 of sensor 100 is patterned with a first set of parallel sensor lines, e.g. column sensor lines 30 and another layer is patterned with a second set of parallel sensor lines orthogonal to the first set, e.g. row sensor lines 20. Superposition of layers 72 and 74 provides a grid based sensor with plurality of junctions 25 between row sensor lines 20 and column sensor lines 30.

According to some embodiments of the present invention, sensor 100 additionally includes a plurality of auxiliary conductive areas 50 spread over sensing surface 80 and electrically isolated from each of row sensor lines 20 and column sensor lines 30. In some exemplary embodiments, auxiliary conductive areas 50 are patterned on one of layers 72 and 74, e.g. layer 72. Typically, auxiliary conductive areas 50 are position on a layer that is more distanced from the sensing and/or touch surface 80. Optionally, auxiliary conductive areas 50 may be patterned on both layers and/or on a separate layer, e.g. a third layer (not shown).

Typically, parallel sensor lines have a width ranging between 0.5-3 mm, e.g. 1 mm and are spaced at a distance of approximately 2-7 mm, e.g. 4 mm apart (center to center), depending on the size of sensing surface 80 and the desired resolution. Typically, auxiliary conductive areas 50 are wider (occupy a larger area) than the row and/or column sensor lines and are spread between the parallel sensor lines, e.g. column sensor lines 30. Typically, auxiliary conductive areas have a width of between 1-5 mm.

According to some embodiments of the present invention, the dimensions of auxiliary conductive areas 50 may vary over sensing surface 80 and/or auxiliary conductive areas 50 may be distributed non-uniformly over sensing surface 80, e.g. auxiliary conductive areas 50 may be concentrated in specific areas of sensing surface 80.

In some exemplary embodiments, row sensor lines 20 and column sensor lines 30 differ in width and/or the widths of one or more of the row or column sensor lines may vary over sensing surface 80 and the dimensions of auxiliary conductive areas 50 vary accordingly. In some exemplary embodiments, row sensor lines 20 and column sensor lines 30 are spaced at different distances and/or the distances between parallel sensor lines are not uniform, e.g. the parallel sensor lines are spaced more densely at the center of sensing area 80 or at a specific area of the sensing surface requiring greater sensitivity and the distribution pattern of auxiliary conductive areas 50 are altered accordingly.

In some exemplary embodiments, each auxiliary conductive area 50 is patterned proximal to a column sensor line 30 at a distance of approximately 15-200 μιη from the column sensor line and in the vicinity of a junction 25. Optionally, an auxiliary conductive area 50 patterned on layer 72 overlaps a portion of a row sensor line 20 patterned on layer 74. In other exemplary embodiments of the present invention, when auxiliary conductive areas 50 are alternately or additionally patterned on layer 74, auxiliary conductive areas 50 may be patterned proximal to row sensor lines 20 at a distance of approximately 15-200 μπι from the row sensor line and in the vicinity of one junction 25. Optionally, in such a case the auxiliary conductive areas in layer 74 may overlap portions of column sensor lines 30.

Typically, row sensor lines 20 and column sensor lines 30 are connected to triggering and detection circuitry associated with sensor 100 while auxiliary conductive areas are not electrically connected to any circuitry associated with the sensor and may be considered as dummy areas. According to some embodiments of the present invention, auxiliary conductive areas 50 are operative to increase the capacitive coupling capability of capacitive sensor 100 with interacting conductive objects, by increasing the overall area on the sensor that can capacitively couple with interacting objects.

Reference is now made to FIGS. 2A and 2B showing simplified schematic top and cross sectional views of a portion of single row and column sensor line and associated auxiliary conductive areas of a capacitive sensor around a junction area with representation of capacitive coupling formed between the sensor lines and auxiliary conductive areas in accordance with some embodiments of the present invention. Typically, in a grid based capacitive sensors, a mutual capacitance represented by capacitive connection 84 exists at each junction 25 between row sensor line 20 and column sensor line 30, .e.g. base-line or steady-state capacitive coupling. This mutual capacitance exists even in the absence of interaction with a conductive object and the amount of coupling between the lines may depend on the size of the overlapping area at junction 25, the distance between the crossing electrodes as determined by the thickness of isolating layer 70 and the material used.

According to some embodiments of the present invention, additional capacitive coupling within the sensor exists between each auxiliary conductive area 50 and row sensor line 20 represented by capacitive connection 82, and between each auxiliary conductive area 50 and column sensor line 30 represented by capacitive connection 86. According to some embodiments of the present invention, the amount of coupling between auxiliary conductive area 50 and a sensor line, e.g. column conductive 30 is controlled by the distance between auxiliary conductive area 50 and the sensor line and/or by the length of an edge (or border) of auxiliary conductive area 50 closest to the sensor line. Typically, a distance between auxiliary conductive area 50 and the sensor line and/or the length of an edge (or border) of auxiliary conductive area 50 closest to the sensor line is designed to meet system requirements. Optionally, capacitive coupling between auxiliary conductive area 50 and a sensor line on an alternate layer is increased by patterning auxiliary conductive area 50 so that it overlaps with the sensor line of the alternate layer, e.g. overlaps row sensor lines 20.

In accordance with some embodiments of the present invention, due to capacitive connections 82 and 86 between auxiliary conductive area 50 and the row and sensor lines, respectively, any coupling between a conductive object interacting with the sensor and auxiliary conductive area 50 will also affect signals sampled on the sensor lines and the overall capacitive coupling between the object and the sensor lines. Since the area covered by auxiliary conductive area 50 around junction 25 is relatively large as compared to that of the sensor lines, the capacitive coupling between a conductive object and the auxiliary conductive area may be relatively stronger and may significantly affect the signal formed on the sampled sensor line. Reference is now made to FIG. 3 showing a simplified schematic top view of a portion of single row and column sensor line and associated auxiliary conductive areas of a capacitive sensor around a junction in accordance with some other embodiments of the present invention. According to some embodiments of the present invention, it is desired to reduce the mutual capacitance formed at junction 25 between row conductive 20 and column conductive 30 in the absence of capacitive coupling with a conductive object. In some exemplary embodiments, one or both of the sensor lines are narrowed in junction 25 to reduce the overlapping area between the sensor lines and thereby the mutual capacitance between them. Typically narrowing sensor lines to reduce the mutual capacitance at junction 25 has to be balanced with increase in resistance of the line due to the narrowing.

In some additional embodiments of the present invention, auxiliary conductive areas 50 are shaped to include an edge 52 that recedes from one of the sensor lines, e.g. column sensor line 30 at junction 25 and then approaches the sensor line outside of (or distanced from) junction 25. The present inventor has found that distancing the auxiliary conductive area 50 from junction 25 helps to minimize the mutual capacitance formed between the sensor lines detected in the absence of a conductive object.

Reference is now made to FIGS. 4A, 4B, 4C, 4D and 4E showing simplified schematic drawings of a grid based capacitive sensor with different exemplary patterns of auxiliary conductive areas in accordance with some embodiments of the present invention. According to some embodiments of the present invention, different patterns and/or shapes of auxiliary conductive areas 50 may be used and the amount of space on the sensing surface that they occupy may also vary depending on their size and shape. Optionally, the size and shape of the auxiliary conductive areas 50 are selected for specific dimensions and conductivity properties of objects that are to be used for interaction with the sensor. Optionally, the size and shape of the auxiliary conductive areas 50 are selected based on ease of manufacturing. In each of the exemplary sensors 101, 102, 103, 104 and 105 shown, a pair of auxiliary conductive areas surrounds each junction 25. Alternatively only one conductive area may be positioned between two parallel sensor lines.

According to some embodiments of the present invention, row sensor lines 20, column sensor lines 30 and auxiliary conductive areas 50 are all patterned from the same material. Optionally, all conductive areas on sensing surface 80 are patterned from ITO so that the sensing surface is transparent and may be overlaid on a display screen, e.g. a flat panel display. Optionally, the auxiliary conductive areas are formed from material that is different that the material used to form the sensor lines.

Reference is now made to FIG. 5 showing a simplified schematic drawing of a grid based capacitive sensor patterned with auxiliary conductive areas that do not overlap with areas covered by sensor lines of the capacitive sensor in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a sensor 106 includes a set of four auxiliary conductive areas 50 that are positioned proximal to each of the row and column sensor line surrounding each junction point 25 so that there is no overlapping between auxiliary conductive areas 50 and the sensor lines. Optionally, auxiliary conductive areas are positioned at a distance of approximately 15-200 μπι from each of column sensor line 20 and row sensor line 30. Auxiliary conductive areas 50 that do not overlap either of the sensor lines may be pattern on any of the layers and/or on both layers. Optionally, auxiliary conductive areas are patterned on each of the separate surfaces and overlap each other.

Reference is now made to FIG. 6 showing a simplified schematic drawing of a grid based capacitive sensor patterned with auxiliary conductive areas that are segmented in accordance with some embodiments of the present invention. According to some embodiments of the present invention, a sensor 107 is patterned with a plurality of auxiliary conductive areas surrounding junctions 25 that are divided into a plurality of segments 50A, 50B and 50C. The present inventor has found that potential damage to sensor 107 due to accidental short between an auxiliary conductive area 50 and one of the sensor lines, e.g. column sensor line 30 may be contained by dividing auxiliary conductive area 50 into a plurality of segments that are electrically isolated from each other. The present inventor has also found through analysis that the improved capacitive coupling offered by auxiliary conductive areas 50 is not significantly altered by the segmentation. It is noted that auxiliary conductive areas 50 are not limited to elements with large surface areas. Optionally, each auxiliary conductive area 50 may be composed of a pattern of small dots, squares or hexagons positioned around junctions 25 and/or spread over the sensing surface. Reference is now made to FIGS. 7 A, 7B and 7C showing simplified schematic side views of substrates for constructing a capacitive sensor in accordance with some embodiments of the present invention. According to some embodiments of the present invention, row sensor lines 20 are patterned over one substrate 84 and column sensor lines 30 along with auxiliary conductive areas 50 are patterned over a second substrate 82. Optionally, each of substrates 82 and 84 are PolyEthylene Terephthalate (PET) foils or can be layered on glass. Typically the substrates are connected by non-conductive adhesive layer. Optionally the thickness of the adhesive layer is between 40 μπι - 150 μπι. According to some embodiments of the present invention, the first and second substrates can be swapped as shown in FIG. 7B so that the layer with auxiliary conductive areas 50 is positioned closer to a sensing surface 80. According to some embodiments of the present invention, the row and column sensor lines are patterned on a same substrate 89 but on opposite surfaces of substrate 89as shown in FIG. 7C. Typically a non-conductive layer 77 is add on sensing surface 80 to prevent electrical and/or direct physical contact between the sensor lines and the interacting object.

Reference is now made to FIG. 8 showing a simplified schematic side view of a grid based capacitive sensor patterned on a laminated glass substrate in accordance with some embodiments of the present invention. According to some embodiments of the present invention row sensor lines 20 are patterned over a substrate 85, e.g. a glass substrate and column sensor lines 30 along with auxiliary conductive areas 50 are patterned over a substrate 83, e.g. a glass substrate. According to some embodiments of the present invention, substrates 83 and 85 are superimposed so that row sensor lines 20 face column sensor lines 30 with auxiliary conductive areas 50 and electrical isolation layer 78, e.g. non-conductive laminating material is provided between the sensor lines. Optionally the grid based capacitive sensor patterned on laminated glass may be similar to laminated digitizer sensor described in US Patent Publication No. US2009107736 published on April 30, 2009 which is hereby incorporated by reference.

Reference is now made to FIG. 9 showing a schematic block diagram of a digitizer sensor in accordance with some embodiments of the present invention. Typically, digitizer system 1000 comprises a sensor 112 including a patterned arrangement of sensor lines, which is optionally transparent, and which is typically overlaid on a FPD. Typically sensor 112 is a grid based sensor including an array of horizontal and/or row sensor lines 20 and an array of vertical and/or column sensor lines 30. According to some embodiments of the present invention, sensor 112 additionally includes a plurality of auxiliary conductive areas 50 partially covering an area between row and column sensor lines.

According to some embodiments of the present invention, sensor lines extend toward edges of sensor 112 and PCB(s) are mounted along a border of the sensing surface on conductive pads connected to one end of each conductive line on the digitizing surface. Optionally, the PCB(s) or other circuitry is directly connected to the ends of the sensor lines without the use of conductive pads. In some exemplary embodiments, PCB 130 is an 'L' shaped PCB. Typically, one or more ASICs 116 positioned on PCB(s) 130 comprise circuitry to sample and process the sensor's output as obtained from sensor lines 20 and/or sensor lines 30 into a digital representation. Typically, the digital output signal is forwarded to a digital unit 120, e.g. digital ASIC unit also on PCB 130, for further digital processing. Typically, digital unit 120 together with ASIC 116 serves as the controller of the digitizer system and/or has functionality of a controller and/or processor. Output from the digitizer sensor is forwarded to a host 122 via an interface 24 for processing by the operating system or any current application. Optionally, at least a portion of the circuitry for sampling and processing the sensor's output and/or for triggering the system is connected to sensor lines, e.g. sensor lines 20 and/or sensor lines 30 via flexible PCB so that the circuitry is displaced from a sensing area of sensor 112. Alternatively, a portion of the circuitry may be directly mounted on the substrate forming sensor 112.

Typically, sensor 112 comprises a grid of sensor lines made of conductive materials, optionally ITO, patterned on a glass substrate, foil and/or other substrate. The sensor lines and the substrate are optionally transparent or are thin enough so that they do not substantially interfere with viewing an electronic display behind the lines. Typically, the grid is made of two layers, which are electrically insulated from each other. Typically, one of the layers contains a first set of equally spaced parallel sensor lines and the other layer contains a second set of equally spaced parallel sensor lines orthogonal to the first set. According to some embodiments of the present invention, at least one of the layers contains auxiliary conductive areas 50 that are not electrically or physically connected to any of the row and/or column sensor lines. Typically, the parallel sensor lines are input to amplifiers included in ASIC 116 but auxiliary conductive areas 30 are not connected to ASIC 116.

Typically, the parallel sensor lines are spaced at a distance of approximately 2-7 mm, e.g. 4 mm, depending on the size of the FPD and a desired resolution. Optionally the region between the grid lines is filled with a non-conducting material having optical characteristics similar to that of the (transparent) sensor lines, to mask the presence of the sensor lines. Optionally, the ends of the lines remote from the amplifiers are not connected so that the lines do not form loops.

Typically, ASIC 116 is connected to outputs of the various sensor lines in the grid and functions to process the received signals at a first processing stage. As indicated above, ASIC 116 typically includes an array of amplifiers to amplify the sensor's signals. Additionally, ASIC 116 optionally includes one or more filters to remove frequencies that do not correspond to frequency ranges used for excitation and/or obtained from objects used for user interactions. The signal is then sampled by an A D, optionally filtered by a digital filter and forwarded to digital ASIC unit 120, for further digital processing.

Typically, digital unit 120 receives the sampled data from ASIC 116, reads the sampled data, processes it and determines and/or tracks the position of physical objects, such as a stylus 144, a token 145 and/or a finger 146, and/or an electronic tag touching the digitizer sensor from the received and processed signals. Optionally stylus 144 is a conductive stylus that is operative to capacitively couple with sensor 112. Alternatively or additionally an electromagnetic stylus may also interacts with 112. Typically, digital unit 120 determines the presence and/or absence of physical objects, such as stylus 144, token 145 and/or finger 146 over time. Optionally, hovering of an object, e.g. stylus 144, finger 146 and token 145 is also detected and processed by digital unit 120. Optionally, token 145 is a game piece that is not connected to ground. Calculated position and/or tracking information are sent to the host computer via interface 124.

According to some embodiments of the present invention, digitizer system 112 is operated for capacitive touch detection based on junction touch method. Typically for detection based on junction touch method, digital unit 210 and/or ASIC 116 produces and sends an interrogation signal such as a triggering pulse to at least one of the sensor lines. Typically, the interrogation pulses and/or signals are pulse sinusoidal signals. Optionally, the interrogation pulses and/or signals are pulse modulated sinusoidal signals.

In an exemplary embodiment, an AC signal is applied to one or more parallel sensor lines (triggered lines) and when a finger 146 (or other conductive object such as stylus 144 and token 145) touches the sensor at a certain position near the triggered line, the capacitance between the triggered line and the corresponding orthogonal sensor lines changes in an area of touch and a coupled signal formed on the corresponding orthogonal sensor lines also changes, e.g. the amplitude is reduced in reference to a base-line amplitude. Base-line amplitude is amplitude recorded while no user interaction is present. According to some embodiments of the present invention, the capacitance between the triggered line and the corresponding orthogonal sensor lines in an area of touch is further changed due to capacitive coupling between finger 146 and a near by auxiliary conductive area 50 and due to capacitive coupling between the near by auxiliary conductive area and one or more of the crossing lines. Typically, the presence of a finger decreases the amplitude of the coupled signal by 15-30%. Optionally, a finger hovering above the display, i.e. near touch, can be detected. Alternatively, a presence of a token (that is not connected to ground) may increase the amplitude of the coupled signal by 15-30%.

Using this junction touch method, more than one finger 46 touch and/or other capacitive object (e.g. token 45) can be detected at the same time (multi-touch). Typically, an interrogation signal is transmitted to each of the driving lines in a sequential manner. Optionally, all or parts of the sensor lines are interrogated concurrently. Output is simultaneously sampled from each of the passive lines in response to each transmission of an interrogation signal to a driving line.

Optionally an electromagnetic stylus including passive circuitry and digital unit

120 produces and controls the timing and sending of a triggering pulse to be provided to an excitation coil 126 that surrounds the sensor arrangement and the display screen. The excitation coil provides a trigger pulse in the form of an electric or electromagnetic field that excites passive circuitry in the electromagnetic stylus or other object used for user touch to produce a response from the stylus that can subsequently be detected. In some exemplary embodiments, an excitation coil is not included. Host 122 includes at least a memory unit and a processing unit to store and process information obtained from ASIC 116 and digital unit 120. Typically, an electronic display associated with the host computer displays images. Optionally, the images are displayed on a display screen situated below a surface on which the object is placed and below the sensors that sense the physical objects or fingers. Optionally, the surface functions as a game board and the object is a gaming piece, or a toy. Typically, digitizer sensor operates as a user input device to host 122. Typically, host 122 maps input from digitizer sensor 112 to one or more functions of an application running on host 122 and displayed on the electronic display.

It should be noted that the embodiments of FIG. 9 is presented as the best mode

"platform" for carrying out the invention. However, in its broadest form the invention is not limited to any particular platform and can be adapted to operate on any digitizer or touch or stylus sensitive display or screen.

Digitizer systems used to detect stylus and/or finger touch location may be, for example, similar to digitizer systems described in incorporated U.S. Patent No. 7,372,455. Optionally digitizer systems used to detect stylus and/or finger touch location may be, for example, similar to digitizer systems described in U.S. Patent No. 6,690,156 and/or U.S. Patent No. 7,292,229 which are both hereby incorporated by reference. The present invention may also be applicable to other digitized sensor and touch screens known in the art, depending on their construction.

It is noted that although most of the embodiments have been described with reference to auxiliary conductive areas pattern on a common layer with column sensor lines 30 superimposed on a layer include row sensor lines 20, the embodiments of the present invention can be similarly practiced with auxiliary conductive areas pattern on a common layer with row sensor lines 20 superimposed on a layer include column sensor lines 30.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Claims

WHAT IS CLAIMED IS:
1. A capacitive sensor comprising:
a plurality of sensing electrodes patterned on at least one substrate and spread over a sensing area of the sensor; and
at least one conductive area other than the plurality of sensing electrodes pattern on at least one substrate and spread on the sensing area of the sensor,
wherein the at least one conductive area is capacitively coupled to at least one of the plurality of sensing electrodes and is electrically isolated from each of the plurality of sensing electrodes, and
wherein only the plurality of sensing electrodes is adapted to be electrically connected to circuitry during operation of the sensor.
2. The capacitive sensor according to claim 1, wherein the plurality of sensing electrodes includes an array of column conductive lines and an array of row conductive lines patterned, the row and column conductive lines forming a grid.
3. The capacitive sensor according to claim 2, wherein the at least one conductive area at least partially fills an area on the at least one substrate not occupied by one of the row and column conductive lines.
4. The capacitive sensor according to claim 2 or 3, wherein the at least one conductive area includes a plurality of conductive areas distributed between conductive lines of at least one of the array of column conductive lines and the array of row conductive lines.
5. The capacitive sensor according to claim 4, wherein one of the array of row or column conductive lines is patterned on a first surface together with the at least one conductive area and the other array is patterned on a second surface.
6. The capacitive sensor according to claim 5, wherein the first and second surface are separated by insulating material.
7. The capacitive sensor according to any claim 5 or claim 6, wherein the at least one conductive area overlaps with a conductive line on the second surface.
8. The capacitive sensor according to any of claims 2-7, wherein the at least one conductive area includes a plurality of conductive areas that at least partially surround junctions between row conductive lines and column conductive lines.
9. The capacitive sensor according to any of claims 2-8, wherein the at least one conductive area has an edge that recedes from a conductive line at a junction between the conductive line and a crossing conductive line.
10. The capacitive sensor according to any of claims 2-9, wherein the array of row and column conductive lines are patterned from a same material as the at least one conductive area.
11. The capacitive sensor according to any of claims 1-10, wherein the at least one conductive area is patterned from indium tin oxide.
12. The capacitive sensor according to any of claims 1-11, where the at least one conductive area is patterned from at least one of indium-doped zinc oxide, a conductive polymer, carbon nano-tube, metal nano-particles, and antimony tin oxide.
13. The capacitive sensor according to any of claims 1-12, wherein the capacitive sensor is patterned on a laminated glass substrate.
14. A digitizer system comprising:
a capacitive sensor according to any of claims 1-13; and
circuitry electrically connected to the plurality of sensing electrodes, the circuitry adapted for detecting output from the plurality of sensing electrodes,
wherein the at least one conductive area is electrically isolated from the circuitry.
15. The digitizer system according to claim 14, wherein the circuitry includes triggering circuitry adapted to transmit a patterned signal to at least one sensing electrode of the plurality of sensing electrodes.
16. The digitizer system according to claim 15, where the circuitry is operative to detect output from at least one other sensing electrode from the plurality of sensing electrodes when triggering that at least one sensing electrode, wherein the at least one other sensing electrode is capacitively coupled with the at least one sensing electrode triggered.
17. The digitizer system according to any of claims 14-16, further comprising an electronic display screen, wherein the capacitive sensor is adapted to be overlaid on the electronic display screen.
18. The digitizer system according to any of claims 14-17 adapted for detecting fingertip touch.
19. The digitizer system according to any of claims 14-18 adapted for detecting fingertip hovering over the capacitive sensor.
20. The digitizer system according to any of claims 14-19, adapted for detecting an electromagnetic stylus.
PCT/IL2010/000942 2009-11-16 2010-11-16 Capacitive sensor for a digitizer system WO2011058562A1 (en)

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