Capacitive touch sensor and capacitive pen

• US 9,030,439 B2
• Filed: 12/17/2012
• Issued: 05/12/2015
• Est. Priority Date: 12/19/2011
• Status: Active Grant

• Current Assignee: eGalax_eMPIA Technology Inc.
• Original Assignee: eGalax_eMPIA Technology Inc.
• Inventors: Chang, Chin-Fu, Yeh, Shang-Tai, Chiu, Shih-Hao
• Primary Examiner(s): Johnson, Gerald
• Assistant Examiner(s): STERNBANE, LAURENCE J
• Application Number:
  US13/716,404
• Publication Number:
  US 20130155013A1
• Time in Patent Office: 876 Days
• Field of Search: 345156-184
• US Class Current: 345/174
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• 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 3/044 by capacitive means
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• CPC Class Codes: G06F 3/0488 using a touch-screen or digitiser, e.g. input of commands through traced gestures

Abstract

When a touch sensor is approached or touched by a capacitive pen in a small area, the corresponding approach or touch signal might be slightly less than the threshold originally used for normal detection. By comparing the sum of the corresponding approach or touch signal and some adjacent signals with the threshold, the approach or touch of a small-area object that otherwise would not be detected by the original method can be determined. The capacitive pen can be made of bonded conductive fibers.

Claims

1. A capacitive writing device, comprising:

a capacitive pen including a conductive pen body and a conductive pen head in contact with the conductive pen body, and the conductive pen head including a contact portion and a non-contact portion, wherein the material of the contact portion is softer than the material of the non-contact portion, and the conductive pen head is made of bonded conductive fibers, some or all of which extend from the non-contact portion to the contact portion;

a touch sensor including a plurality of driven conductive strips provided with a driving signal and a plurality of sensed conductive strips providing changes in capacitive coupling, each time the driving signal being provided, one or more intersections between one or more of the driven conductive strips being simultaneously provided with the driving signal and each sensed conductive strip generating capacitive coupling; and

a control circuit for determining the location of the capacitive pen on the touch sensor based on the changes in capacitive coupling produced at the intersections when the capacitive pen is held on the touch sensor by an external conductive object.

2. The capacitive writing device of claim 1, wherein the control circuit further executes the following operations:

obtaining an image of change in capacitive coupling from the touch sensor, wherein each value in the image of change in capacitive coupling is the change in capacitive coupling for one of the intersections;

detecting one or more intersections with a value greater than a first threshold from the image of change in capacitive coupling; and

determining a single intersection approached or touched by the capacitive pen when at least one intersection with the value greater than the first threshold is detected, wherein all intersections adjacent to the single intersection approached or touched by the capacitive pen have values smaller than the first threshold.

3. The capacitive writing device of claim 1, wherein the control circuit further executes the following operations:

obtaining an image of change in capacitive coupling from the touch sensor, wherein each value in the image of change in capacitive coupling is the change in capacitive coupling for one of the intersections;

detecting one or more detected intersections from the image of change in capacitive coupling, wherein the value of the detected intersection is smaller than a first threshold and larger than a second threshold;

detecting one or more first regions, wherein each first region includes one of the detected intersections and an intersection adjacent to the detected intersection, and the sum of values of the intersections in each first region is greater than the first threshold; and

determining a first region approached or touched by the capacitive pen when at least one first region is detected, wherein the values of all intersections adjacent to the first region approached or touched by the capacitive pen are all smaller than a third threshold.

4. The capacitive writing device of claim 3, wherein the control circuit further executes the following operations:

detecting one or more second regions if no first region is detected, wherein each second region includes four adjacent intersections including one of the detected intersections, and the sum of values of the intersections in each second region is greater than the first threshold; and

determining a second region approached or touched by the capacitive pen when at least one second region is detected, wherein the values of all intersections adjacent to the second region approached or touched by the capacitive pen are all smaller than a third threshold.

5. The capacitive writing device of claim 3, wherein the first threshold>

the second threshold>

the third threshold.

6. The capacitive writing device of claim 3, wherein the second threshold is ½

of the first threshold, and the third threshold is ¼

of the first threshold.

7. The capacitive writing device of claim 3, wherein the maximum width on the touch sensor by the capacitive pen is less than the distance between the centers of two conductive strips arranged adjacent and in parallel with each other, the two conductive strips arranged adjacent and in parallel with each other are the driven conductive strips or the sensed conductive strips.

8. The capacitive writing device of claim 4, wherein each first region or second region determined to be approached or touched by the capacitive pen is a first region or a second region approached or touched by a pen, wherein the maximum width on the touch sensor touched by the pen is less than or equal to 3 mm.