Position detecting device and position detecting method

• US 8,581,857 B2
• Filed: 07/31/2009
• Issued: 11/12/2013
• Est. Priority Date: 08/06/2008
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Matsubara, Masaki
• Primary Examiner(s): Leiby, Christopher E
• Application Number:
  US12/534,062
• Publication Number:
  US 20100289758A1
• Time in Patent Office: 1,565 Days
• Field of Search: 345173-178, 345/204, 345211-214
• 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 capacitive type position detecting device comprising:

(a) a plurality of first electrodes arranged in a first direction;

(b) a plurality of second electrodes arranged in a second direction that is substantially perpendicular to the first direction;

(c) a signal supplying circuit including a clock signal generator configured to generate a clock signal having a clock period of CLK, the signal supplying circuit being configured to supply signals having a waveform, which includes a determined time width (TIME_WIDTH) between a rising part and a falling part of the waveform, to the plurality of first electrodes arranged in the first direction when TIME_WIDTH is an integer (s≧

2) multiple of CLK, wherein the signal supplying circuit is further configured to sequentially supply said signals of TIME_WIDTH to the first electrode Yn through Y {n+s} that are adjacent to each other per every CLK such that (s+l) is a total number of the first electrodes to which the rising parts of said signals of TIME_WIDTH are sequentially supplied within TIME_WIDTH, and the signal supplying circuit is further configured such that the rising part of the waveform in said signal supplied to the first electrode Y {n+s} occurs at the same time as the falling part of the waveform in said signal supplied to the first electrode Yn and no rising and falling parts of two adjacent first electrodes coincide with each other;

wherein, in a selected one of the second electrodes with which said first electrodes Yn and Y {n+s} intersect to form two intersections, a first current is generated at a timing of the rising part of the waveform supplied to said first electrode Y {n+s} and a second current is generated at a timing of the falling part of the waveform supplied to said first electrode Yn, the first current and the second current being combined to form a combined current signal in the selected one of the second electrodes,

(d) a current-to-voltage converter configured to be directly coupled to only the selected one of the second electrodes to convert the combined current signal to an analog voltage signal;

(e) an A/D converter configured to convert the analog voltage signal to a digital voltage signal; and

(f) a position calculating section configured to detect a position indicated by a position indicator on the position detecting device based on said digital voltage signal originating in the selected one of the second electrodes and received via said current-to-voltage converter and said A/D converter,

wherein, in a case where the position indicator is not present near the two intersections, the first current and the second current generated at the timings of the rising and falling parts of the waveform substantially cancel each other in the selected one of the second electrodes, and in a case where the position indicator is present on or near one of the two intersections, the first current and the second current do not substantially cancel each other in the selected one of the second electrodes.

2. The position detecting device of claim 1, wherein the signals supplied to the plurality of first electrodes are signals having a rectangular waveform.

3. The position detecting device of claim 2, wherein the signal supplying circuit comprises a shift register having cells respectively corresponding to the plurality of first electrodes arranged in the first direction, and the signal supplying circuit is further configured to control input signals to the shift register to thereby generate said signals having a rectangular waveform, which includes the determined time width between a rising part and a falling part of the rectangular waveform, to be supplied to the plurality of first electrodes arranged in the first direction.

4. The position detecting device of claim 1, wherein the position calculating section is further configured to receive an input signal that indicates which one of the plurality of first electrodes is supplied with said signal having a waveform including the determined time width, and the position calculating section is further configured to detect the position indicated by the position indicator based on said input signal and signals received from the plurality of second electrodes.

5. The position detecting device of claim 4, further comprising a selection circuit configured to sequentially select the plurality of second electrodes arranged in the second direction,

wherein the selection circuit is configured to selectively couple a determined one of the plurality of second electrodes to the current-to-voltage converter based on said input signal that indicates which one of the plurality of first electrodes is supplied with said signal having a waveform including the determined time width.

6. The position detecting device of claim 1, wherein the position calculating section comprises an integrating circuit for integrating the digital voltage signal originating in said selected one of the second electrodes, and the position calculation section is further configured to detect the position indicated by the position indicator based on a peak value of the signal integrated by the integrating circuit.

7. The position detecting device of claim 5, wherein the current-to-voltage converter is configured to amplify the combined current signal in addition to converting the combined current signal to an analog voltage signal.

8. A method for position detection used with a capacitive type position detecting device including:

(a) a plurality of transmission electrodes arranged in a first direction; and

(b) a plurality of reception electrodes arranged in a second direction that is substantially perpendicular to the first direction, the method comprising;

sequentially supplying signals having a waveform, which includes a determined time width (TIME_WIDTH) between a rising part and a falling part of the waveform, to the plurality of transmission electrodes wherein TIME_WIDTH is an integer (s≧

2) multiple of a clock period CLK, such that said signals are sequentially supplied to the transmission electrodes Yn through Y{n+s} that are adjacent to each other per every CLK wherein (s+l) is a total number of the transmission electrodes to which the rising parts of said signals of TIME_WIDTH are sequentially supplied within TIME_WIDTH, and that the rising part of the waveform in said signal supplied to the transmission electrode Y {n+s} occurs at the same time as the falling part of the waveform in said signal supplied to the transmission electrode Yn and no rising and falling parts of two adjacent transmission electrodes coincide with each other;

selecting one of the reception electrodes with which said transmission electrodes Yn and Y {n+s} intersect to form two intersections, wherein in the selected one of the reception electrodes a first current is generated at a timing of the rising part of the waveform supplied to said transmission electrode Y {n+s} and a second current is generated at a timing of the falling part of the waveform supplied to said transmission electrode Yn, the first current and the second current being combined to form a combined current signal in the selected one of the reception electrodes,

receiving the combined current signal from only the selected one of the reception electrode;

converting the received combined current signal to an analog voltage signal;

converting the analog voltage signal to a digital voltage signal; and

detecting a position indicated by a position indicator on the position detecting device based on said digital voltage signal originating in the selected one of the reception electrodes,

wherein, in a case where the position indicator is not present near the two intersections, the first current and the second current generated at the timings of the rising and falling parts of the waveform substantially cancel each other in the selected one of the reception electrodes, and in a case where the position indicator is present on or near one of the two intersections, the first current and the second current do not substantially cancel each other in the selected one of the reception electrodes.

9. The method of claim 8, wherein the signals supplied to the plurality of transmission electrodes are signals having a rectangular waveform.

10. The method of claim 9, wherein the step of sequentially supplying signals includes controlling input signals to a shift register having cells respectively corresponding to the plurality of transmission electrodes.

11. The method of claim 8, wherein the step of detecting a position includes receiving an input signal that indicates which one of the plurality of transmission electrodes is supplied with said signal having a waveform including the determined time width, to detect the position based on said input signal and signals received from the plurality of reception electrodes.

12. The method of claim 11, wherein the step of selecting one of the reception electrodes includes sequentially selecting the plurality of reception electrodes based on said input signal that indicates which one of the plurality of transmission electrodes is supplied with said signal.

13. The method of claim 8, wherein the step of detecting a position includes integrating the digital voltage signal originating in said selected one of the reception electrodes, to detect the position based on a peak value of the integrated signal.

14. The method of claim 13, wherein the step of converting the received combined current signal to an analog voltage includes amplifying the received combined current signal.