JPH0441387Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a coordinate input device, and more specifically, to improve the number of coordinate calculations when moving the coordinate indicating means in a capacitively coupled coordinate input device, and to reduce the size of the device itself. Concerning becoming.

"Prior Art" In a capacitive coupling type coordinate input device, electrode wires are arranged at a predetermined interval in two orthogonal directions on a coordinate input board, and electrode wires are placed at a desired position on the coordinate input board. A detection electrode is provided on a coordinate indicating means such as an input pen or a cursor that is brought into contact to input coordinates. Then, scanning pulses are sequentially applied to the electrode wires, and at this time, the induced pulses generated on the detection electrodes by electrostatic induction are impedance-converted, and are further guided to the device main body, amplified and digitally converted within the device main body, and then sent to the microcomputer. The calculation means calculates the contact position of the coordinate indicating means at that time based on the magnitude of the induced pulse at that time. (For the calculation procedure, see
-19380, patent application No. 59-37679, etc. ) ``Problem that the invention attempts to solve'' Incidentally, in recent years, the development of various systems and programs related to graphic processing has progressed, and in connection with this, for example, the trajectory of the coordinate indicating means when inputting handwriting or signature input is becoming more detailed. Regarding coordinate input devices, the number of times coordinate detection can be performed per second when moving (sliding) the coordinate indicating means on the coordinate input panel has become an issue. (Hereinafter, this ability will be referred to as "dynamic point detection ability.") Regarding this dynamic point detection ability, the applicant company evaluated its own capacitively coupled coordinate input device and found that, for example, coordinate input When the means was slid, a noise voltage of several hundred to several kilohertz was superimposed on the normal induction pulses due to vibrations on the detection electrode, and as a result, the dynamic point detection ability was reduced. This is because when the arithmetic processing unit performs a data check, that is, when detecting signals at the same position multiple times and calculating coordinate data for each, and confirming that they are the same, the data that should originally match is detected. This is because the coordinate data of each time did not match due to noise and was treated as an error.

Another problem is that electronic devices have become smaller in recent years.
There is a trend toward lower prices, and the applicant company is also demanding smaller and lower costs for the entire device.In particular, it is necessary to reduce the size and cost of the entire device. If you try to amplify a small signal on the main unit via a cable, external noise such as noise from the commercial power supply, etc.
Special shielding measures are required on the main body side to reduce the effects of electromagnetic waves, switching noise, etc., making it difficult to downsize and lower the price.

``Means for Solving the Problems'' Therefore, in this invention, based on the above analysis results, we have developed a tablet consisting of a plurality of electrode wires arranged in the direction of the coordinate axes, a control unit that applies pulse signals to the tablet, and a control unit that applies pulse signals to the tablet. In a coordinate input device, the coordinate input device includes a coordinate indicating means that detects a signal by capacitively coupling with a pulse signal detected by the coordinate indicating means, and a calculation section that calculates position coordinates from the signal detected by the coordinate indicating means. This invention proposes an indicating means for a coordinate input device that incorporates a removal filter and a signal amplification circuit.

"Function" In the present invention, a low-frequency removal filter for removing noise voltage having a frequency component and an amplifier circuit for amplifying induced pulses are inserted inside the coordinate indicating means which is equipped with shielding measures. As a result, the noise voltage generated due to the sliding of the coordinate indicating means is removed, and even if the signal is detected multiple times at the same position and the coordinates are detected for each, the phenomenon of mismatching of coordinate data due to sliding will not occur. .

``Example'' The details of the present invention will be explained below based on the illustrated example. FIG. 1 shows the block configuration. FIG. 2 is a schematic diagram of the input pen with the shield portion omitted. In the figure, reference numeral 1 denotes a coordinate input board, on which electrode wires are arranged at predetermined intervals in two orthogonal directions (X direction, Y direction) (not shown). 2 is the decoder driver,
Address signal supplied from central processing unit 3
Scanning pulses are sequentially applied to the aforementioned electrode lines according to AD. The central processing unit is hereinafter referred to as "CPU".
In addition, in the following description, when an abbreviation is shown in parentheses after the name of other parts, the abbreviation will be used thereafter.

Reference numeral 4 represents an input pen serving as a coordinate indicating means, and reference numeral 5 represents a detection electrode slidably held at the tip of the input pen. Reference numeral 6 denotes a switch, which opens and closes in accordance with the sliding movement of the detection electrode 5. Reference numeral 7 denotes an impedance converter, which receives a signal at high impedance and sends out a signal at low impedance in order to induce an electrostatic induction pulse in the detection electrode. Reference numeral 8 denotes a low frequency removal filter which in this embodiment removes frequency components below 10kHz. 9 is a signal amplification circuit which has a low impedance output. 10 is a sample hold circuit, which is connected to the CPU 3 via the input/output port 12.
In response to the timing pulse TP supplied from
The input voltage (electrostatic induction pulse voltage) at that point is held for a while. Reference numeral 11 denotes an analog-to-digital converter (AD converter) which digitally converts the output voltage of the sample and hold circuit 10 in response to the same timing pulse TP. The sample and hold circuit 10 is used to hold the electrostatic induction pulse voltage while the AD converter 11 performs digital conversion.

The CPU 3 is a so-called microcomputer that is an integrated circuit, and according to a program stored in a read-only memory (ROM) 13,
Predetermined processing is executed using random access memory (RAM) 14.

Thus, when the user brings the input pen 4 into contact with the coordinate input panel 1 to input handwriting, for example, the detection electrode 5 slides into the input pen 4 at the time of contact.
The switch 6 is "closed" and the signal is transmitted to the CPU 3 via the input/output port 12.

In response to this, the CPU 3 sends an address signal AD to the decoder driver 2 as described above to apply a scanning pulse to a predetermined electrode line of the coordinate input panel 1, and at the same time sends a timing pulse TP to the sample hold circuit 10 and AD converter 11. is supplied, and the digital value of the induced pulse at this time is recorded in the RAM 14. After this operation is performed for all electrode lines or for a predetermined range of electrode lines, the first coordinate data is calculated based on the magnitude of these pulses.

Next, the same operation is performed multiple times, and the coincidence or mismatch of the coordinate data each time is checked. Note that calculation of these coordinate data requires a predetermined time, and the detection electrode is moving during this time, so theoretically, the coordinate data calculated each time should be different. However, in actual equipment, the calculation of coordinate data is performed in microseconds, and quantization makes the coordinates the same for the amount of movement within a predetermined range, so if there is no influence of noise etc., the above The coordinate data related to multiple coordinate detections will be the same.

With conventional devices, when detecting coordinates multiple times, the noise voltage caused by the vertical movement of the detection tip was superimposed, causing the coordinate data to not match and resulting in an error. In the present invention, as a result of this noise voltage being cut off by the low-frequency removal filter 8, the data of the plurality of coordinate detections coincide, and the coordinate data is sent to a computer body (not shown) each time of detection.

"Effects of the invention" As explained above, according to the invention, the noise voltage generated due to the movement of the coordinate input means can be canceled out, reducing the occurrence of errors and improving the dynamic point detection ability. This makes it possible to downsize and lower the cost of the entire device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a schematic diagram of the input pen. 1...Coordinate input panel, 4...Input pen, 8...Low frequency removal filter, 9...Signal amplification circuit.

Claims (1)

[Scope of utility model registration request] A tablet consisting of a plurality of electrode wires arranged in the coordinate axis direction, a control unit that applies a pulse signal to the tablet, a coordinate indicating means that performs signal detection by capacitively coupling with the pulse signal applied to the tablet, and the coordinate system. A coordinate input device comprising a calculation section for calculating position coordinates from a signal detected by an indicating means, characterized in that a low frequency removal filter and a signal amplification circuit are built into the coordinate indicating means. means of instruction.