Position detecting device and position detecting method

• US 8,148,652 B2
• Filed: 01/29/2009
• Issued: 04/03/2012
• Est. Priority Date: 02/13/2008
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Matsubara, Masaki
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): HARRIS, DOROTHY H
• Application Number:
  US12/362,438
• Publication Number:
  US 20100033437A1
• Time in Patent Office: 1,160 Days
• Field of Search: 345/173
• US Class Current: 178/18.06
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• 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 position detecting device includes: X-axis electrodes and Y-axis electrodes; a driving section for supplying an AC signal to the X-axis electrodes; a synchronous clock generating section for generating synchronous clock signals at the timing when the AC signal passes through zero-cross points; a first switch for selectively supplying the AC signal outputted from the driving section to one of the X-axis electrodes at the timing of the synchronous clock signal; a second switch for selecting one of the Y-axis electrodes at the timing of the synchronous clock signal; a synchronous detector for synchronous-detecting a signal outputted by the Y-axis electrodes through the second switch; and a position calculating section for calculating a position indicated by an indicator based on the signal outputted from the synchronous detector, wherein the position corresponds to one or more intersections of the X-axis electrodes and Y-axis electrodes.

Claims

1. A position detecting device comprising:

X-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other;

Y-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other and that extend perpendicularly to the X-axis electrodes;

a driving section configured to supply an AC signal to the X-axis electrodes;

a synchronous clock generating section configured to generate a synchronous clock signal at the timing when the AC signal passes through a zero-cross point;

a first change-over switch configured to selectively supply the AC signal to a determined electrode among the X-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal passing through a zero-cross point;

a second change-over switch configured to select a determined electrode among the Y-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal passing through a zero-cross point;

a synchronous detector configured to detect a signal outputted by the Y-axis electrodes through the second change-over switch, and outputting the detected signal; and

a position calculating section configured to calculate a position indicated by an indicator on the position detecting device, based on the signal outputted from the synchronous detector, the position corresponding to one or more intersections of the X-axis electrodes and Y-axis electrodes.

2. The position detecting device according to claim 1, further comprising a filtering section configured to filter a determined frequency component from the signal outputted from the synchronous detector, and outputting the filtered signal.

3. The position detecting device according to claim 2, wherein the filtering section is selected from a group consisting of a low pass filter, a band elimination filter, and a band pass filter.

4. The position detecting device according to claim 2, wherein the filtering section is configured to remove the main frequency component of the AC signal.

5. The position detecting device according to claim 1, wherein the AC signal is a sine wave.

6. The position detecting device according to claim 1, wherein the AC signal supplied by the driving section is a rectangular wave.

7. A position detecting method for calculating a position indicated by an indicator, the position corresponding to one or more intersections of X-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other and Y-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other and that extend perpendicularly to the X-axis electrodes, the method comprising:

generating a synchronous clock signal at the timing when an AC signal to be supplied to the X-axis electrodes passes through a zero-cross point;

selectively supplying the AC signal to the X-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal passing through a zero-cross point;

selecting one of the Y-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal passing through a zero-cross point;

detecting a signal outputted by the selected one of the Y-axis electrodes; and

calculating the position indicated by the indicator based on the detected signal.

8. The method according to claim 7, further comprising filtering out a determined frequency component from the detected signal, prior to calculating the position indicated by the indicator.

9. A position detecting device comprising:

X-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other;

Y-axis electrodes formed by a plurality of conductors that are arranged substantially parallel to each other and that extend perpendicularly to the X-axis electrodes;

a driving section configured to supply an AC signal to the X-axis electrodes;

a synchronous clock generating section configured to generate a synchronous clock signal at the timing when the AC signal is zero;

a first change-over switch configured to selectively supply the AC signal to a determined electrode among the X-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal being zero;

a second change-over switch configured to select a determined electrode among the Y-axis electrodes at the timing of the synchronous clock signal, which is generated at the timing of the AC signal being zero;

a synchronous detector configured to detect a signal outputted by the Y-axis electrodes through the second change-over switch, and outputting the detected signal; and

a position calculating section configured to calculate a position indicated by an indicator on the position detecting device, based on the signal outputted from the synchronous detector, the position corresponding to one or more intersections of the X-axis electrodes and Y-axis electrodes.

10. The position detecting device according to claim 9, further comprising a filtering section configured to filter a determined frequency component from the signal outputted from the synchronous detector, and outputting the filtered signal.