JPS6331139Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an electromagnetic induction type coordinate reading device that eliminates the calculation of coordinates outside the effective range.

A conventional electromagnetic induction type coordinate reading device is shown in FIG. In the figure, 1 is a tablet on which a plurality of sense lines are laid, 2a and 2b are scanning circuits that sequentially scan the X-axis sense line and the Y-axis sense line, respectively. The minute induced voltage generated in the preamplifier section 4 is amplified, and the quantization circuit 5 further amplifies, detects, and filters the voltage, and converts it into a digital quantity. Then, the arithmetic control circuit 6 calculates coordinate values based on the digitized induced voltage values sent from the quantization circuit 5, and transfers the coordinate values to an external device via the interface circuit 7. Also, the arithmetic control circuit 6
also sends a scanning address to the scanning circuit 2.

The circuit section including the tablet 1, the scanning circuit 2, and the preamplifier section 4 is called the sense circuit 8.
The figure shows a detailed diagram considering the mounting position of the conventional sense circuit 8.

x ₁ , x ₂ ... x _o is the X-axis sense line, y ₁ , y ₂ ...
yn is a Y-axis sense line, and 8 is a terminal resistor of the sense line loop. The scanning circuit 2 decodes the scanning address sent from the arithmetic control circuit and sequentially turns on the switches Sx ₁ , Sx ₂ . . _. Sx _o and Sy ₁ , Sy ₂ . When the coordinate indicator is located at point A (x mark), the X axis is
When the switch Sx ₃ of the axis scanning circuit 2a is turned on, that is, when the sense line x ₃ is selected, a maximum induced voltage is generated in the terminating resistor 8 through the common line and the common ground. Similarly, regarding the Y-axis, the maximum induced voltage occurs when sense line _y3 is selected. This minute induced voltage is amplified by a preamplifier section 4, passes through a quantization circuit, and then a coordinate value is calculated by an arithmetic control circuit. The coordinate calculation is performed by comparing not only the maximum induced voltage but also voltages induced in other sense lines, but since the calculation method is also described in other documents, it will not be described here.

However, in FIG. 2, when the coordinate indicator is located at point B between the common ground and the common line, when the switch Sx _o-2 of the scanning circuit is turned on,
Sense line Sx _o and common ground, terminating resistor 8
A loop is formed between the common line and the switch Sx o-1, and although the coordinate indicator does not actually exist within the effective range of the sense line x _o-2, it exists between the common ground and the common line, so that an induced voltage is generated in the termination resistor _{8 .}
The same is true when the switch of the Y-axis scanning circuit is turned on or when any switch of the Y-axis scanning circuit is turned on. Therefore, the arithmetic and control circuit 6 may detect the induced voltage on each of the X-axis and Y-axis and calculate the wrong coordinate value. Therefore, in reality, there is a drawback in that it is necessary to shield the alternating magnetic field from the coordinate indicator in the area surrounded by the dotted line.

The present invention was made to promptly eliminate the above-mentioned drawbacks, and by locating the terminal resistor 8 between the X-axis scanning circuit and the Y-axis scanning circuit, it is possible to prevent incorrect coordinates from being detected outside the effective range of the coordinate reading device. The purpose is to prevent calculations without requiring special processing such as shielding.

This embodiment will be described in detail below with reference to FIG. The components are the same as the conventional model (Fig. 2), but the shield has been removed. Terminal resistor 8
It is located at the center of the axis scanning circuit 2a and the Y-axis scanning circuit 2b. In other words, when the coordinate indicator is located at point C, when switch Sx ₁ of the X-axis scanning circuit 2a is turned on, the induced voltage is generated even though there is no coordinate indicator within the sense line as explained in Fig. 2. occurs. However, at this time, even if any switch S ₁ ...S _o of the Y-axis scanning circuit 2b is turned on, no induced voltage is generated in the termination resistor 8. Therefore, the arithmetic control circuit does not obtain induced voltages on the X-axis and Y-axis sense lines at the same time, determines that the coordinate indicator is outside the effective range, and does not calculate erroneous coordinate values. When the coordinate indicator is at point D, contrary to the above, the Y-axis scanning circuit 2
When the switch b is turned on, an induced voltage may be generated, but no matter which switch of the X-axis scanning circuit 2a is turned on, no induced voltage is generated in the terminating resistor 8, so coordinates are not calculated.

Further, the same effect as that of the present invention can be obtained by overlapping the common ground and the common line in FIG. 2 so that no induced voltage is generated. However, it is difficult to implement, and although it would be easier to implement it using a multilayer board, it would significantly increase costs.

As described above, according to the present invention, the conventional shield is removed by locating the termination resistor of the sense line in the center of the X-axis scanning circuit and the Y-axis scanning circuit without making any changes to the conventional circuit. This makes it possible to provide significant effects such as improving the reliability of the device itself and reducing costs by reducing the number of parts.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional electromagnetic induction type coordinate reading device, Fig. 2 is a conventional sense circuit diagram, and Fig. 3 is a block diagram of a conventional electromagnetic induction type coordinate reading device.
The figure is a sense circuit diagram according to the present invention. 1...Tablet, 2a...X-axis scanning circuit, 2
b...Y-axis scanning circuit, 3...Coordinate indicator, 4...
Preamplifier section, 5...Quantization circuit, 6...Arithmetic control circuit, 7...Interface circuit, 8...Terminal resistor, _Sx1 ~ _Sxo , _Sy1 ~ _Syo ...Switch, _x1 ~
x _o , y ₁ ~ _{y o} ... sense line.

Claims (1)

[Scope of utility model registration request] a tablet having a large number of sense lines laid out at a constant pitch in the X-axis and X-axis directions; an X-axis and Y-axis scanning circuit that sequentially scans the sense lines; a coordinate indicator positioned on the tablet; an amplifier circuit that detects a voltage induced in the sense line by coupling with an alternating magnetic field generated by a coordinate indicator; a quantization circuit that receives an output signal of the amplifier circuit and converts it into a digital quantity; and the pair of scanning circuits. an arithmetic control circuit that gives a scanning address to the quantizer and receives the output signal of the quantization circuit and calculates the coordinate values of the coordinate indicator; and an interface circuit that receives the coordinate values output from the arithmetic control circuit and outputs them to the outside. an electromagnetic induction type coordinate reading device, located between the common ground of the sense line and the common line, and connected to the X-axis scanning circuit and the Y-axis scanning circuit;
An electromagnetic induction type coordinate reading device, characterized in that a terminating resistor is provided at a position between the axis scanning circuit and coordinate calculation outside the effective range of the coordinate reading device.