JPH0122931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the position of the excitation coil by comparing and calculating the induced signals induced in the sense line on the tablet by the alternating magnetic field generated from the excitation coil. This invention relates to an electromagnetic induction type coordinate reading device.

First, regarding this type of conventional coordinate reading device,
This will be explained with reference to the figures.

FIG. 1 is a block diagram of a conventional coordinate reading device. In the figure, 1 is a tablet, and both sides of the tablet have sense lines Xn,
Many Ym have been installed. These sense lines are connected to an X scanning circuit 2a and a Y scanning circuit 2b, and are sequentially selected one by one by these scanning circuits and connected to an amplified wave circuit 3. A scanning address 5 is given from the control circuit 4 to the scanning circuits 2a and 2b. 6 is an excitation coil that generates an alternating magnetic field. This alternating magnetic field induces an induction signal in the sense line near the excitation coil, but each sense line plate is connected to the scanning circuits 2a and 2.
Since the sense lines are selected one by one by b and connected to the amplified wave circuit 3, the induced signals of each sense line are sequentially input to this amplified wave circuit as scanning is performed. This induced signal is amplified by an amplification wave circuit, and then inputted to the control circuit 4, where it is compared and calculated to detect the position of the excitation coil.

Figure 2 is an explanatory diagram showing the state of the induced signal input to the amplified wave circuit when the excitation coil is placed on the tablet in a conventional coordinate reading device. The level of the induced signal, Xn, indicates the X-axis sense line. The control circuit is configured such that the amplitude level of the guidance signal is
If it exceeds Vrqf, it is recognized that the excitation coil is within the reading range, and its position is detected. In the figure, it is detected that the excitation coil is located near the sense line Xμ that induced the maximum amplitude Vμ.

However, in the above conventional coordinate reading device, when the excitation coil 6 is brought close to the scanning circuits 2a, 2b and the amplified wave circuit 3, the alternating magnetic field from the excitation coil is coupled to these circuits themselves, and the As a result, there was a drawback that the wrong position of the excitation coil was detected even though the excitation coil was not on the sense line of the tablet.

FIG. 3 is an explanatory diagram showing the state of the induction signal input to the amplified wave circuit when an excitation coil is placed near the X scanning circuit in a conventional coordinate reading device. The explanation of the symbols is the same as in Fig. 2, so it will be omitted. An induced signal of uniform amplitude is added to the amplified wave circuit, and since this signal is not a signal induced in the sense line, the position information of the excitation coil is not included. It will be obvious that the wrong position will be detected instead of the one that contains it.

The present invention has been made to solve the above-mentioned drawbacks, and includes arranging a sense line for detecting outside the reading range around the scanning circuit and the amplified wave circuit,
The purpose of this is to prohibit detection of the position of the excitation coil by detecting the induction signal induced to the sense line, and to prevent the detection of an erroneous position.

Examples of the coordinate reading device according to the present invention will be described below.
This will be explained with reference to the figures.

FIG. 4 is a block diagram of a coordinate reading device according to the present invention, in which 11 is a tablet, 12a, 12b
13 represents a scanning circuit, 13 represents an amplified wave circuit, and 14 represents a control circuit. The operation of the circuit described above is the same as that of the conventional coordinate reading device, so a description thereof will be omitted. 16
a, 16b, 16c, 17 and 18 are circuits added according to the present invention, and 16a, 16b, 1
6c is a sense line for detecting a reading range, 17 is a detection circuit that detects a signal induced to this sense line, and 18 is a scanning circuit 12 using the detected signal.
This is a switch circuit that opens and closes the signal line input from a and 12b to the amplified wave circuit 13. In the coordinate reading device having the above configuration, the scanning circuit 12a,
12b or near the amplified wave circuit 13, that is, sense lines 16a, 16b, 1 for detecting outside the reading range
When an excitation coil exists near 6c, the signal induced to the out-of-reading range detection sense line is detected by the detection circuit 17, and the switch circuit 18 opens the signal line from the amplified wave circuit 13 to the control circuit 14. Therefore, even if an erroneous induction signal is directly induced in the scanning circuits 12a, 12b or the amplified wave circuit 13, this signal will not be input to the control circuit, and the control circuit will not detect the erroneous position of the excitation coil.

In the embodiment shown in FIG. 3, a switch circuit 18 is provided to open and close the signal line from the amplified wave circuit 13 to the control circuit 14, but if the control circuit 14 is configured to detect the position with a microcomputer or the like, It is also possible to directly input the detection signal from the detection circuit 17 to the control circuit and prohibit the operation of detecting the position of the erroneous excitation coil by means of software.

As described above, the present invention includes a sense line for detecting outside the reading range near the scanning circuit and the amplified wave circuit,
Since a circuit for detecting the induced voltage induced in the sense line and a switch circuit for opening and closing the signal line from the amplified wave circuit to the control circuit according to the output signal of the detection circuit are provided, the scanning circuit or the amplified wave circuit Even if an erroneous guidance signal is induced, the signal is not transmitted to the control circuit, and the control circuit can be prevented from detecting an erroneous position.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional coordinate reading device, Fig. 2 is an explanatory diagram explaining that the conventional coordinate reading device detects the position of an excitation coil on a sense line, and Fig. 3 is a block diagram showing a conventional coordinate reading device. FIG. 4 is a block diagram showing the coordinate reading device according to the present invention. 11... Tablet, 12a, 12b... Scanning circuit, 13... Amplified wave circuit, 14... Control circuit, 16a, 16b, 16c... Sense line for detecting outside the reading range, 17... Detection circuit, 18... switch circuit.

Claims (1)

[Claims] 1 Consists of a tablet with a large number of sense lines laid out on a flat plate, a scanning circuit that sequentially selects the sense lines, an amplification wave circuit that amplifies the signal on the sense lines, and an excitation coil that generates an alternating magnetic field. In a coordinate reading device that detects the position of the excitation coil by amplifying the induced signal induced in the sense line by the alternating magnetic field and then performing a comparison operation, an out-of-reading range detection signal is detected around the scanning circuit and the amplification wave circuit. A detection circuit for detecting an induced signal on this sense line by the excitation coil, and a switch circuit for prohibiting detection of the position of the excitation coil by the output of this detection circuit are provided. A coordinate reading device characterized by: