POSITION DETECTING DEVICE AND POSITION DETECTING METHOD

• US 20100289758A1
• Filed: 07/31/2009
• Published: 11/18/2010
• Est. Priority Date: 08/06/2008
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Matsubara, Masaki
• Granted Patent: US 8,581,857 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

An electrostatic capacity type position detecting device having increased scanning speed is provided. The device includes a signal supplying electrode including a plurality of electrodes arranged in parallel with each other in a first direction, and a receiving electrode also including a plurality of electrodes arranged in parallel with each other in a second direction perpendicular to the first direction. A one-shot pulse having a predetermined time width is applied sequentially to the plurality of electrodes of the signal supplying electrode at a frequency equal to an integral multiple of 200 kHz. In other words, the sequential application of the one-shot pulse occurs with a time difference that is shorter than (e.g., 1/N of) the predetermined time width. A current change caused at rising and falling edges of the one-shot pulse is detected through the receiving electrode, to thereby indicate a position on the position detecting device.

Claims

1. A position detecting device comprising:

a signal supplying electrode in which a plurality of electrodes are arranged in parallel with each other in a first direction;

a receiving electrode in which a plurality of electrodes are arranged in parallel with each other in a second direction substantially perpendicular to the first direction;

a signal supplying circuit adapted to supply a signal having a predetermined time width to each of a first electrode and a second electrode of the signal supplying electrode with a time difference therebetween that is shorter than the predetermined time width; and

a position calculating section adapted to detect a change in a signal outputted from the receiving electrode and calculate a position on the position detecting device indicated by an indicator based on the detected change.

2. The position detecting device according to claim 1, wherein the time difference is set to 1/n of the predetermined time width of the signal and n is an integer.

3. The position detecting device according to claim 2, wherein the signal supplying circuit supplies the signal in a manner in which a phase of the signal is controlled so that the time difference is constant.

4. The position detecting device according to claim 3, wherein the signal supplied to each of the electrodes of the signal supplying electrode by the signal supplying circuit has substantially the same amount of change in the signal level at a rising edge and a falling edge.

5. The position detecting device according to claim 4, wherein the signal supplied to each of the electrodes of the signal supplying electrode by the signal supplying circuit is formed in a manner in which a pulse signal is repeatedly supplied at a predetermined time interval.

6. The position detecting device according to claim 5, further comprising:

a selection circuit adapted to selectively supply the signal to the electrodes of the signal supplying electrode, the selection circuit switching the electrodes connected to the signal supplying circuit.

7. The position detecting device according to claim 6, further comprising:

a differential amplifying circuit adapted to differentially amplify the signal outputted from the receiving electrode.

8. The position detecting device according to claim 1, wherein the plurality of electrodes in the signal supplying electrode and the plurality of electrodes in the receiving electrode form a plurality of intersections, respectively, each forming a capacitor.

9. A position detecting method to be applied on a signal supplying electrode formed with a plurality of electrodes arranged in parallel with each other in a first direction and a receiving electrode formed with a plurality of electrodes arranged in parallel with each other in a second direction substantially perpendicular to the first direction, wherein a change in a signal outputted from the receiving electrode is detected and used to determine a position on the signal supplying electrode and the receiving electrode, the method comprising the steps of:

supplying a first signal having a predetermined time width to a first electrode of the signal supplying electrode; and

supplying a second signal having the predetermined time width to a second electrode of the signal supplying electrode, with a time difference measured from the supplying of the first signal, which is shorter than the predetermined time width.

10. The position detecting method according to claim 9, further comprising the step of:

controlling a phase of each signal so that the time difference is constant.

11. The position detecting method according to claim 9, wherein the time difference is 1/n of the predetermined time width and n is an integer.