POSITION DETECTING DEVICE

• US 20100327889A1
• Filed: 06/22/2010
• Published: 12/30/2010
• Est. Priority Date: 06/29/2009
• Status: Active Grant

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Matsubara, Masaki
• Granted Patent: US 8,334,852 B2
• Time in Patent Office: Days
• US Class Current: 324/705
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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 selector switch is provided which always connects a receiving side electrode to one of a positive electrode input terminal and a negative electrode input terminal of a differential amplifier section. This selector switch is controlled so as to form a positive electrode region in which a plurality of electrode elements connected to the positive electrode input terminal are arranged, a negative electrode region in which a plurality of electrode elements connected to the negative electrode input terminal are arranged, and an insensitive region in which electrode elements are alternately connected to the positive electrode input terminal and the negative electrode input terminal.

Claims

1. A position detecting device comprising:

a plurality of conductors arranged in parallel with each other in a first direction and supplied with a predetermined signal;

a plurality of conductors arranged in parallel with each other in a second direction orthogonal to the first direction;

a signal detecting circuit including a differential amplifier circuit having a first input terminal and a second input terminal and subjecting a signal input via the first input terminal and the second input terminal to differential amplification; and

a conductor selecting circuit for selectively connecting the plurality of conductors arranged in parallel with each other in said second direction to the first input terminal and the second input terminal of said differential amplifier circuit, whereby a position indicated by an indicating object is detected on a basis of an output signal from said signal detecting circuit;

wherein said selecting circuit further selects the plurality of conductors arranged in parallel with each other in said second direction with passage of time such that of the plurality of conductors arranged in parallel with each other in said second direction, M (M>

=2) conductors adjacent to each other are connected to said first input terminal of said differential amplifier circuit, N (N>

=2) conductors adjacent to each other, the N conductors being in proximity to said M conductors adjacent to each other, are connected to said second input terminal of said differential amplifier circuit, and 2P (P>

=1) conductors adjacent to each other among the conductors excluding said M conductors and said N conductors, the number P being set smaller than said N, are divided into first and second groups of conductors, each group including P conductor(s), and the first group of P conductor(s) are connected to said first input terminal of said differential amplifier circuit and the second group of P conductor(s) are connected to said second input terminal of said differential amplifier circuit.

2. The position detecting device according to claim 1,

wherein said selecting circuit connects each of a pair of conductors adjacent to each other among said 2P conductors to the first and second input terminals of said differential amplifier circuit, respectively.

3. The position detecting device according to claim 1,

wherein said selecting circuit connects a conductor adjacent to said 2P conductors among the conductors excluding said M conductors, said N conductors, and said 2P conductors, to one of said first and second input terminals of said differential amplifier circuit.

4. The position detecting device according to claim 1,

wherein the first group of conductors connected to the first input terminal and the second group of conductors connected to the second input terminal form a repetitive pattern.

5. The position detecting device according to claim 4, wherein the repetitive pattern is an alternating pattern.

6. The position detecting device according to claim 1, further comprising a signal supplying circuit for supplying said predetermined signal,

wherein the signal supplying circuit sequentially supplies said signal to the plurality of conductors arranged in parallel with each other in said first direction at certain time intervals.

7. The position detecting device according to claim 6,

wherein said signal is a pulse wave having a predetermined width, and

said signal supplying circuit performs control such that said certain time intervals are an integral multiple of the pulse width of said signal.

8. The position detecting device according to claim 7,

wherein said signal is supplied such that a level at a time of rising of said signal and a level at a time of falling of said signal are substantially the same.

9. A position detecting method of a position detecting device, said position detecting device including a plurality of conductors arranged in parallel with each other in a first direction and supplied with a predetermined signal, a plurality of conductors arranged in parallel with each other in a second direction orthogonal to the first direction, a signal detecting circuit including a differential amplifier circuit having a first input terminal and a second input terminal and subjecting a signal input via the first input terminal and the second input terminal to differential amplification, and a conductor selecting circuit for selectively connecting the plurality of conductors arranged in parallel with each other in said second direction to the first input terminal and the second input terminal of said differential amplifier circuit, whereby a position indicated by an indicating object is detected on a basis of an output signal from said signal detecting circuit, said position detecting method comprising the step of:

said selecting circuit selecting the plurality of conductors arranged in parallel with each other in said second direction with passage of time such that

of the plurality of conductors arranged in parallel with each other in said second direction, M (M>

=2) conductors adjacent to each other are connected to said first input terminal of said differential amplifier circuit,

N (N>

=2) conductors adjacent to each other, the N conductors being in proximity to said M conductors adjacent to each other, are connected to said second input terminal of said differential amplifier circuit, and

2P (P>

=1) conductors adjacent to each other among the conductors excluding said M conductors and said N conductors, the number P being set smaller than said N, are divided into first and second groups of conductors, each group including P conductor(s), and the first group of P conductor(s) are connected to said first input terminal of said differential amplifier circuit and the second group of P conductor(s) are connected to said second input terminal of said differential amplifier circuit.