JPH01194018A - Coordinate input device - Google Patents

Abstract

PURPOSE:To cancel generated noise voltage, to reduce the generation of an error and to improve the detecting capacity of a dynamic point by inserting a low band interrupting filter for interrupting a noise voltage having a frequency component into a route for transmitting an induction pulse from an input pen detecting electrode into a coordinate calculating means. CONSTITUTION:Electrode lines are arranged in a coordinate input board 1 in two orthogonal directions (X and Y directions) with prescribed intervals. A decoder driver 2 impresses scanning pulses successively to the electrode lines in accordance with an address signal AD supplied from a CPU 3. A detecting electrode 5 is held on the tip of an input pen 4 so as to be slided and a switch 6 is opened/closed in accordance with the sliding of the electrode 5. A preamplifier 7 amplifies an electrostatic induction pulse generated on the electrode 5. The low band interrupting filter 8 interrupts <=10kHz frequency component. Consequently, a phenomenon generating the discrepancy of coordinate data due to the sliding of the input pen is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device, and more particularly, to an improvement in the number of coordinate calculations when moving a coordinate indicating means in a capacitively coupled coordinate input device.

"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 amplified, digitally converted, and supplied to calculation means consisting of a microcomputer, which calculates the Based on the magnitude of the induced pulse, the contact position of the coordinate indicating means at that time is calculated.

(For the calculation procedure, see Japanese Patent Publication No. 53-19380,
See patent application No. 59-37679, etc. ) ``Problem to be solved by the invention'' By the way, in recent years, various systems and programs related to graphic processing have been developed, and in connection with this, for example, the trajectory of the coordinate indicating means when inputting handwriting or signature is 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 capacitive coupling type coordinate input device and found that, for example, the coordinate indicating means ( When the input pen (hereinafter referred to as "input pen" is a representative example) is stationary at an appropriate position on the coordinate input board, the number of detections per second was 88, but the number of detections per second was 1.75 m/s. It was found that when the input pen was moved in a circular motion, the number of detections decreased to 2.1 times per second. As a result of various studies on the cause of this, it was discovered that when the input pen slides, a noise voltage of about several hundred to several kilohertz is superimposed on the induced pulse generated in the input pen detection electrode.

Therefore, when checking data, that is, when detecting signals at the same position multiple times, calculating coordinate data based on each signal, and confirming that the coordinate data is the same,
It has been found that the coordinate data of each time, which should originally match, is not converted to -M and is treated as an error, resulting in a decrease in the dynamic point detection ability.

It is not clear why the noise voltage increases when the input pen is slid, but the main causes are (1) There are slight irregularities on the input panel, and the detection electrodes of the input pen vibrate up and down when sliding. . As a result, the capacitance between the detection electrode and the electrode wire of the coordinate input panel changes instantaneously, and at this time, the impedance of the circuit is high and the charge stored in the electrode wire and detection electrode does not fluctuate. (2) As the detection electrode moves up and down, the springs that bias it expand and contract, generating a voltage due to the piezoelectric phenomenon. An example of this is being able to do something.

"Means for Solving the Problem" Therefore, in the present invention, based on the above analysis results, a low-frequency noise voltage cut-off having the above-mentioned frequency component is added to the path for transmitting the induced pulse from the detection electrode of the input pen to the coordinate calculation means. I decided to insert a cutoff filter.

"Function" By doing this, the noise voltage generated due to the movement of the input pen is blocked, and as a result, even if the signal is detected multiple times at the same position and the coordinates are calculated for each,
Regardless of the influence of other external noises, etc., the phenomenon of mismatching of coordinate data due to sliding of the input pen no longer occurs.

``Example'' The details of the present invention will be explained below based on the illustrated example. 1st
The figure shows the block configuration. 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). A decoder driver 2 sequentially applies scanning pulses to the aforementioned electrode lines in accordance with an address signal AD supplied from the central processing unit 3.

The central processing unit will be hereinafter referred to as rcPUJ, and in the following description, when an abbreviation is given 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 according to the sliding movement of the detection electrode 5. A preamplifier 7 amplifies the electrostatic induction pulse generated at the detection electrode.

Reference numeral 8 denotes a low-pass cutoff filter, which in this embodiment cuts off frequency components of 10 KHz or less. Reference numeral 9 denotes a sample and hold circuit, which responds to the timing pulse TP supplied from the CPU 3 through the input/output port 10 and holds the input voltage (electrostatic induction pulse ζ pressure) at that time for a while. 11 is an analog-to-digital converter (AD converter);
In response to the same timing pulse TP, the output voltage of the sample hold circuit 9 is digitally converted. The sample and hold circuit 9 is used to hold the electrostatically induced 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) 12, a random access memory (RA) is used.
M) Execute predetermined processing while using 13.

When the user brings the input pen 4 into contact with the coordinate input panel 1 to perform handwriting input, for example, the detection electrode 5 slides into the input pen 4 at the moment of contact, and the switch 6 is turned on. Closed”, and the signal is sent to the CPU 3 via the input/output port 10.
can be conveyed to.

In response to this, the CPU 3 sends the 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 9 and AD converter 11.
The digital value of the induced pulse at this time is stored in RAM.
Record on 13. After this operation is performed for all electrode lines or 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, noise voltage caused by the vertical movement of the detection tip was superimposed.
The coordinate data at this time did not match and was considered an error, but in the present invention, this noise voltage is cut off by the low-pass cutoff filter 8, and as a result, the data of the plurality of coordinate detections match, and the coordinate data is sent to a computer (not shown) each time it is detected.

"Effects of the Invention" As explained above, according to the present invention, it is possible to cancel the noise voltage generated due to the movement of the coordinate input means, reduce the occurrence of errors, and improve the dynamic point detection ability. Can be done.

Actual measurements at the applicant company revealed that the same product as above had a circle i1 at a speed of 1.75 m/s! 69 per second during operation
．． This increased to 44 times.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1...Coordinate input board, 3, 12.13...Coordinate calculation means, 8...
Low cut filter. Patent applicant Pentel Co., Ltd.

Claims (1)

[Claims] A coordinate input board with electrode wires arranged in two orthogonal directions,
a coordinate indicating means provided with a detection electrode and brought into contact with a desired position on the input panel; A coordinate input device comprising: a coordinate calculation means for calculating the coordinates of the abutting position, the guidance pulse being supplied to the coordinate calculation means via a low-pass filter.