JP2572625B2 - Tablet input device - Google Patents

Description

The present invention relates to a tablet input device used for a tablet for directly inputting characters, symbols, figures, characters, and the like, a digitizer for inputting coordinate signals, and the like.

[Prior art] Conventional capacitive coupling type tablet input devices include JP-B-43-7649, JP-B-52-4414, and JP-B-58.
No. -6966 is known.

[Problem to be Solved by the Invention] In the tablet used in the above-mentioned conventional capacitively-coupled tablet input device, since a plurality of electrodes are arranged long in the coordinate axis direction, the scanning pulse vibrates and harmonic components are reduced. It became larger and generated noise outside. When used on a tablet input device placed on a steel desk, etc., the signal detection pen detects scanning pulses and noise from the desk and performs S / N
In some cases, the ratio was deteriorated and erroneous detection was performed.

Means for Solving the Problems The present invention has been made to solve the above problems, and has a tablet including a plurality of electrodes arranged in a coordinate axis direction, and each electrode of the tablet. A control circuit for sequentially applying a signal to the input terminal; a signal detection pen for capacitively coupling to the electrode to which the signal is applied; and a tablet input device that receives a detection signal of the signal detection pen as an input signal so that the entire tablet is placed. And a tablet input device in which a conductor having the same potential as the reference potential of the control circuit is disposed.

[Operation] In the present invention, the conductor on which the tablet and the entire control circuit (integrated on the substrate) are integrally mounted is set to the reference potential and the conductive potential of the control circuit, thereby enabling the tablet and the entire control circuit to be integrated. Capacitance coupling between the grounds reduced harmonic components and reduced noise detection.

Examples The present invention will be described with reference to the accompanying drawings. Scan pulses are sequentially applied from the one-chip CPU 2 on the substrate 1 on which the control circuit and the like are mounted to the electrode lines 4 and 5 arranged in the coordinate axis direction of the tablet 3. The main part of the control circuit mounted on the substrate shown in FIG. The ground electrode 6 is electrically connected to an aluminum plate 7 disposed so as to cover the entire board 1 and tablet 3. The tip of the signal detection pen 8 is brought into contact with the tablet 3, and the scanning pulse applied from the one-chip CPU of the control circuit (not shown) is capacitively coupled to one of the electrode lines 4 and 5,
By applying the detected signal to the control circuit, the coordinate position signal of the tablet 3 with which the signal detection pen 8 is in contact is specified. When the circuit is configured in this manner, the substrate 1 equivalently forms a ground plane because the ground of the substrate 1 and the aluminum plate 7 have the same potential. As a result, the impedance of the power supply and the ground line is reduced, and the output pulse wave generated in the control circuit of the substrate 1 has reduced harmonic components. The tablet drive pulses applied to the electrode wires 4 and 5 of the tablet 3 also have reduced harmonic components, and reduce radiation noise generated outside the device.

Further, since the aluminum plate 7 has a shielding effect of blocking external noise from a desk, a mounting table or the like from entering the tablet 3 and the substrate 1, noise does not enter the signal detection pen 8. As described above, the tablet drive pulse is detected from the tablet 3 by the signal detection pen 8, and the waveform of the signal amplified by the amplifier 9 has an improved S / N ratio.

As a result, as a means for applying the scanning pulse to the electrode lines 4 and 5 of the conventional tablet 3 shown in FIG.
What has been performed through the resistor pulled up to the V drive voltage can be operated with only the 5V power supply without the decoder as shown in FIG.

[Effects of the Invention] Since the present invention is configured as described above, noise radiated from the device to the outside is reduced, and cost can be reduced.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is a schematic diagram of the entire structure, FIG. 2 is a scanning pulse application portion, and FIG. 3 is a conventional scanning pulse application portion. DESCRIPTION OF SYMBOLS 1 ... board, 2 ... 1 chip CPU 3 ... tablet, 4,5 ... electrode wire 6 ... earth electrode, 7 ... aluminum plate 8 ... signal detection pen, 9 ... amplifier

Claims (1)

(57) [Claims] 1. A tablet comprising a plurality of electrodes arranged in a coordinate axis direction, a control circuit for sequentially applying a signal to each electrode of the tablet, and a signal detection for capacitively coupling with the electrode to which the signal is applied. In a pen and a tablet input device using a detection signal of the signal detection pen as an input signal, a conductor having the same potential as a reference potential of the control circuit is arranged so as to mount the entire tablet input device. Tablet input device.