JPH06119100A - Cordless digitizer - Google Patents

Abstract

PURPOSE:To enlarge an effective coordinate reading area by effectively detecting coordinate also by a sense wire in the vicinity of the tip part of a driving wire by making counter electromotive current in the direction of cancelling a magnetic field to flow through a nearby closed loop wiring by the magnetic field generated at the longitudinal tip part of the driving line. CONSTITUTION:The closed loop wiring 7 is adjacently arranged outside of the short side (longitudinal tip part) le2 (deriving line element 1e2) of the driving wire 23. Current ie in the direction of cancelling rotary magnetic field generated by AC current (i) flowing through the short side le2 is made to flow through the closed loop wiring 7. As the result, rotary magnetic field phi generated by the short side le2 is decreased by rotary magnetic field generated by the closed loop wiring 7. Output voltage V0 when the position of a sense wire 43 is at the central part of the driving wire 23 and when the position is approaching the short side le2 are almost the same. Thus, a coordinate can effectively be detected also by the sense wire 43 in the vicinity of the tip part of the driving wire 23 and the effective coordinate reading area by a position instruction device 3 can be enlarged with extremely simple and inexpensive constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordless digitizer for detecting position coordinates on a flat plate indicated by a cordless position indicator.

[0002]

2. Description of the Related Art As a conventional technique of a cordless digitizer, the one disclosed in Japanese Patent Laid-Open No. 2-45819 is known. This is a drive in which a plurality of loop-shaped drive lines (drive line group) provided along the first direction on the plane plate and an alternating current is selectively supplied to each drive line of the drive line group. A circuit, a cordless position indicator having a magnetic material that converges a rotating magnetic field generated by an alternating current supplied to each drive line, and a second direction on the plane plate intersecting the first direction. A plurality of loop-shaped sense lines (sense line group) in which an alternating current is induced according to the magnetic field converged by the position indicator, and the alternating current induced in the sense lines of the sense line group. And a sense circuit selectively taken out. The principle of such coordinate detection according to the conventional technique will be briefly described with reference to FIGS. FIG. 3 is a schematic circuit diagram related to coordinate detection in the X-axis direction (horizontal direction in the figure). One of a plurality of drive lines (drive line group 2) in which the drive circuit 1 is formed in a loop shape (here Is one of a plurality of sense lines (sense line group 4) each selectively connected to the drive line 2 ₃ ) and formed in a loop shape.
One (here, the sense line 4 ₃ ) is selected by the analog selector 5 and connected to the input end of the amplifier 8. In FIG. 3, reference numeral 3 is a cordless position indicator having a magnetic material that converges a rotating magnetic field generated by an alternating current supplied to each drive line. This position indicator 3
When moving in the X-axis direction in the vicinity A point, the output voltage V ₀ which amplifier 8 shows the variation characteristics shown in FIG. 4 (a), the by determining in conjunction with the output voltage V ₀ which adjacent sense lines The X coordinate where the position indicator 3 is placed can be detected (see Japanese Patent Laid-Open No. 2-45819).

[0003]

Problems of the 0007] Conventional 3 technology, the output voltage V according to the position of the sense line 4 ₁ to 4 _n
The amplitude of ₀ is different. That is, the sense lines 4 ₁ to
When 4 _n is near the center of the drive lines 2 _{1 to} 2 _n (here, in the case of the sense line 4 ₃ ), the change of the output voltage V ₀ is as shown in FIG.
Identical to the waveform shown in, but its maximum value V _A is approximately constant (for sense line 4 ₅ here in accordance sense line 4 ₁ to 4 _n approaches the end portion of the driving line 2 ₁ to 2 _n ) The maximum value of the output voltage becomes large as shown by V _B in FIG.
Thus, sense line 4 ₅ is not used in the coordinate detection, there is a problem that the effective coordinate reading area in the digitizer surface is reduced. An object of the present invention is to provide a cordless digitizer capable of effectively detecting a coordinate even by a sense line near the end of the drive line and increasing the effective coordinate reading area in the digitizer plane.

[0004]

The above object is to provide a plurality of loop-shaped drive lines (drive line groups) provided along a first direction on a flat plate and each drive line of the drive line group. A drive circuit for selectively supplying an alternating current, a cordless position indicator having a magnetic material for converging a rotating magnetic field generated by the alternating current supplied to the drive lines, and the first plate on the flat plate. A plurality of loop-shaped sense lines (sense line group), which are provided along a second direction intersecting with the direction of, and in which an alternating current is induced according to the magnetic field converged by the position indicator.
And a sense circuit that selectively takes out the alternating current induced in the sense lines of this sense line group, in a cordless digitizer, by providing a closed loop wiring in the vicinity of the longitudinal ends of the drive lines. To be achieved.

[0005]

The magnetic field l ₂ generated at the longitudinal end portion (driving line element l _e2 ) of the drive line causes the counter electromotive current ie in the direction of canceling the magnetic field l ₂ to flow in the closed loop wiring, so that the length of the drive line increases. The magnetic field generated at the end of the direction (driving line element l _e2 ) is greatly reduced. As a result, the output voltage characteristic of the drive line at the end becomes almost the same as the others, and effective coordinate detection becomes possible. This enlarges the effective coordinate reading area in the digitizer plane.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. Prior to describing a specific embodiment of the present invention, FIG.
The principle of coordinate detection will be described with reference to. Note that FIG.
3, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. Now, assuming that the current i in the direction shown in FIG. 2 is flowing through the drive line 2 _X having the drive circuit 1, the magnetic field generated by the drive line 2 _X is from the front side of the drawing surface in the loop of the drive line 2 _X. It becomes the direction to penetrate to the back side. At this time, a certain sense line 4 _Y
The magnetic field detected by the drive line elements l _e1 and l _e3 when the sense line 4 _Y is located near the center of the drive line 2 _X.
The output voltage V ₀ is small because there is only a magnetic field generated by.
However, as the position of the sense line 4 _Y approaches the end of the drive line 2 _X , the magnetic field generated by the drive line element l _e2 is added and the output voltage V ₀ increases (see FIG. 4).

Therefore, in the present invention, in order to cancel the influence of the magnetic field due to the drive line element l _e2 , the drive lines 2 ₁ to 2 _{n are}
A closed loop wiring 7 was provided near the end (driving line element l _e2 ). 1 is a circuit diagram showing an embodiment of a cordless digitizer according to the present invention, and the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. Reference numeral 6 denotes a sense circuit including the analog selector 5 and the amplifier 8 shown in FIG. That is, in FIG. 1, the drive circuit 1 selects one (here, the drive line 2 ₃ ) of the plurality of drive lines 2 ₁ to 2 _n (drive line group 2) formed in a loop shape and selects an alternating current. Supply current i. In FIG. 1, only one drive line 2 ₃ is shown for simplification. The drive line 2 ₃ generates a rotating magnetic field φ by the alternating current i, and the rotating magnetic field φ is converged by the position indicator 3 containing a magnetic material. In addition, a plurality of sense lines 4 ₁ to 4 _n (sense line group 4: only one sense line 4 ₃ is shown in FIG. 1 for simplification) formed in loops are provided with positions. An alternating current is induced according to the magnetic field converged by the indicator 3, and the sense circuit 6
The alternating current induced in one sense line (here, the sense line 4 ₃ ) selected by is amplified, converted into a voltage, and output as an output voltage V ₀ . A closed loop wiring 7 is arranged adjacent to the outside of the short side (end of the drive line in the longitudinal direction) l _e2 (drive line element l _e2 ) of the drive line 2 ₃ . Then, in the closed loop wiring 7, the current ie in the direction of canceling the rotating magnetic field generated by the alternating current i flowing through the short side l _e2 flows. As a result, the rotating magnetic field φ generated by the short side l _e2 is closed loop wiring 7
Is canceled by the rotating magnetic field generated by the sense line 4 ₁
To 4 _n output voltage V ₀ which when the position is approaching to the short side l _e2 when the center portion of the driving line 2 ₁ to 2 _n of approximately the same. Incidentally, a closed loop wiring Figure 1, one drive line 1: was made to correspond to 1, the entire drive line 2 ₁ to 2 _n may be provided a single closed loop wiring.

[0008]

As described above, according to the present invention, the sense line near the end of the drive line is formed with a very simple and inexpensive structure in which the closed-loop wiring is provided near the end of the drive line in the longitudinal direction. Can also detect coordinates effectively,
The effect is that the effective coordinate reading area on the digitizer surface can be increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the device of the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a circuit diagram of a conventional device.

FIG. 4 is a coordinate detection characteristic diagram of the same.

[Explanation of symbols]

1: Drive circuit 2: Drive line group 2 ₁ to 2 _n , 2 _X : Drive line 3: Position indicator 4: Sense line group 4 ₁ to 4 _n , 4 _Y : Sense line 5: Analog selector 6: Sense circuit 7 : Closed loop wiring 8: Amplifier

Claims (1)

[Claims] 1. A plurality of loop-shaped drive lines (drive line groups) provided along a first direction on a plane plate, and an alternating current is selectively supplied to each drive line of the drive line group. Drive circuit, a cordless position indicator having a magnetic material that converges a rotating magnetic field generated by an alternating current supplied to each drive line, and a second direction intersecting the first direction on the plane plate. A plurality of loop-shaped sense lines (sense line group), which are provided along the position indicator and in which an alternating current is induced according to the magnetic field converged by the position indicator, and the alternating current induced in the sense lines of the sense line group. A cordless digitizer comprising a sense circuit for selectively extracting an electric current, wherein a closed loop wiring is provided in the vicinity of the longitudinal end of the drive line.