JP3195176B2 - Coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate input device suitable for handwriting input using an input pen, and more particularly to a coordinate input device called a capacitance type.

[0002]

2. Description of the Related Art Various types of electrostatic capacitance type coordinate input devices have been proposed.
By arranging a plurality of X electrodes and Y electrodes on the tablet at equal intervals in a matrix and using the capacitance existing between the input pen pressed on the tablet and each electrode, each electrode is Are known which determine a coordinate of an input pen by detecting a pulse voltage sequentially applied to the input pen.

In this type, the voltage applied to each electrode changes according to the distance (capacitance) to the input pen. Therefore, by detecting the voltage applied to each electrode, the pointing position of the input pen is detected. However, it is impossible to improve the resolution beyond the pitch between the electrodes simply by detecting the voltage applied to each electrode. Therefore, measures have been taken to make the minimum resolution smaller than the pitch between the electrodes. For example, a change function of the contact coordinates of the input pen and a change function of the magnitude of the induced pulse are measured or calculated in advance and stored. Conventionally, a method has been proposed in which the magnitude of an induced pulse generated in accordance with the contact of an input pen is compared with a change function table to estimate the position of the input pen.

[0004]

However, in the above-mentioned prior art, complicated processing such as collation between a change in the contact coordinates of the input pen and a change function table of the magnitude of the induced pulse is performed. Since it is indispensable, there is a problem that a general-purpose CPU or the like has a limitation in processing capacity and cannot cope with high speed. In addition, the change function table of the magnitude of the induced pulse is obtained by actual measurement or calculation under predetermined conditions. However, in an actual use form, the case where the input pen is directly pressed on the tablet and the case where the input pen is pressed through a sheet such as drafting paper are used. In some cases, it is necessary to correct the change function according to the thickness of the sheet, and from this point, there is a problem that it is not possible to cope with high speed. Furthermore, since the capacitance between the input pen and the tablet also changes depending on the material of the sheet interposed between them, even if the change function is corrected according to the thickness of the sheet, the detection accuracy of the coordinates of the input pen will be improved. However, there was a problem that was reduced.

[0005] The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide a coordinate input device having a simple configuration and high detection accuracy.

[0006]

In order to achieve the above-mentioned object, the present invention provides a plurality of Xs arranged at equal pitches P.
A tablet in which electrodes and Y electrodes are laminated in a matrix via an insulating layer; an input pen that oscillates a voltage at a predetermined frequency; and a voltage applied to each electrode based on a change in capacitance between the input pen and each electrode. Voltage detection means for detecting a voltage
Of the voltage values detected by the voltage detection means, when the voltage value from the electrode with the largest applied voltage is V ₁ , and the voltage values from the electrodes on both sides of the electrode are V ₂ and V ₃ , respectively, the bias amount L of the electrode arrangement direction between the electrode closest to the input pen and the input _{pen, L = P (V 1 V} 2 -V 1 V 3) / 2 (V 1 V 3 + V 1 V 2 -2V
₂ V ₃ ).

[0007]

The voltage oscillating from the input pen is applied to each electrode of the tablet arranged in a matrix through the capacitance, and the applied voltage is determined according to the capacitance (distance) between the input pen and each electrode. Therefore, a voltage corresponding to the distance from each electrode to the input pen is output. Here, when the pitch between the electrodes is P, the voltage value from the electrode with the largest applied voltage is V ₁ , and the voltage values from the electrodes on both sides of the electrode are V ₂ and V ₃ , respectively, The deviation amount L between the electrodes closest to the input pen in the electrode array direction is represented by L = P (V ₁ V ₂ −V ₁ V ₃ ) / 2 (V ₁ V ₃ + V ₁ V ₂ −2 V
₂ V ₃ ). This operation expression is based on a known P and three voltage values V
₁ , V ₂ , and V _3, and because it is a linear function, the load on the CPU is light. Further, since it is irrelevant to the distance between the input pen and the tablet, regardless of the use form of the input pen, The coordinates of the input pen can always be detected with high accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a coordinate input device according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a tablet provided in the coordinate input device of FIG. 1, FIG. 1 is a configuration diagram of an input pen used in the coordinate input device of FIG. 1, and FIG. 5 is a circuit diagram of the input pen.

In FIG. 1, reference numeral 1 denotes a tablet, reference numeral 2 denotes an input pen, reference numeral 3 denotes an operator's finger,
The tablet 1 is installed on the front of a liquid crystal display device 30 or a CRT (not shown) so that coordinates can be input using the input pen 2 and the finger 3. As shown in FIGS. 2 and 3,
The tablet 1, a plurality of X electrodes 4 made of ITO material perpendicular to each other (X _1, X _2, ......, X _n) and Y electrodes _{5 (Y 1, Y 2,} ......, Y n) having The protective film comprises a laminate of a transparent glass substrate 6, a transparent protective film 7 attached to the upper surface of the glass substrate 6, and a transparent shield film 8 attached to the lower surface of the glass substrate 6. Reference numeral 7 has a function of protecting the X electrode 4 and a function of enhancing the writing quality when the input pen 2 is run to perform handwriting input. The shield film 8 has a function of blocking noise to the liquid crystal display device 30. Having. X electrode 4 and Y electrode 5
Are made of a transparent conductive material such as ITO, the X electrodes 4 are arranged on the upper surface of the glass
Are arranged on the lower surface of the glass substrate 6 at the same pitch P, and the X electrodes 4 and the Y electrodes 5 are arranged in a matrix via the insulating glass substrate 6.

Returning to FIG. 1, one end of each of the X electrodes 4 has an X
The X-side multiplexer 9 is connected to an analog switch 10.
This analog switch 10 has first and second contacts 10.
a, 10b, and an oscillation circuit 11 is connected to the first contact 10a.
Is connected. Also, the second switch of the analog switch 10
An A / D converter 14 is connected to the contact 10b of the A / D converter via an amplifier circuit 12 and a filter circuit 13.
Converter 14 is connected to CPU 15. This C
The PU 15 is a voltage detection unit that determines an electrode closest to the input pen 2 or the finger 3 based on data output from the A / D converter 14, and a PU 15 that is closest to the input pen 2 based on an arithmetic expression described later. A built-in operation means for calculating the amount of deflection of the input pen 2 between the electrode and the electrode adjacent thereto, and a built-in switching means for switching the analog switch 10 to one of the first and second contacts 10a and 10b. The coordinates of the input pen 2 or the finger 3 calculated by the CPU 15 are output to the host computer 16. On the other hand, one end of each of the Y electrodes 5 is connected to a Y-side multiplexer 17.
The A / D converter 14 is connected to the Y-side multiplexer 17 via an amplifier circuit 18 and a filter circuit 19. These circuit components are mounted on the periphery of the glass substrate 6 so as not to interfere with the electrodes 4 and 5, and are connected to the host computer 16 via a cable (not shown).

As shown in FIG. 4, the input pen 2 is formed in a cylindrical shape suitable for being manually operated by an operator by hand, and has a built-in button battery 20 and a printed circuit board 21. A conductive pen tip 22 is held at the tip of the input pen 2 by a spring 23 so as to be able to enter and exit, and the periphery of the pen tip 22 is covered with an insulating cap 24. Circuit components of the oscillation circuit 25 shown in FIG. 5 are mounted on the printed board 21, and the periphery of the printed board 21 is covered with a metal shield member 26. The oscillation circuit 25 is simply composed of a coil, a low power consumption transistor, and the like, and is driven by the button battery 20. A switch 27 is interposed between the oscillation circuit 25 and the button battery 20, and both fixed contacts 27a and 27 of the switch 27 are provided.
b is fixed to the printed circuit board 21, and the movable contact 27c of the switch 27 is fixed to the pen tip 22. Therefore, when the input pen 2 is not in use, the pen tip 22 is urged by the spring 23 and the movable contact 27c is separated from the fixed contacts 27a and 27b. Circuit 25 does not operate. On the other hand, in a use state in which the input pen 2 is pressed against the tablet 1, the pen tip 22 retreats a little inward against the spring force of the pulling 23, and the movable contact 27c becomes the fixed contact 27a. , 27b, the switch 27 is turned on, the oscillation circuit 25 operates, and a voltage of a predetermined frequency is output from the tip of the pen tip 22.

Next, the operation of the coordinate input device configured as described above will be described. First, the case of inputting coordinates using the input pen 2 will be described. In this case, the operator holds the input pen 2 with his hand and the pen tip 2 of the input pen 2
2 is pressed directly to an arbitrary position on the tablet 1 or via a sheet (not shown), and an oscillation circuit 25 built in the input pen 2 is operated to output a voltage of a predetermined frequency from the tip of the pen tip 22. . On the other hand, on the tablet 1 side, the analog switch 10 has been switched to the second contact 10b side by a signal from a switching means built in the CPU 15 (this switching operation will be described later). Side multiplexer 9
Works and are sequentially turned on X-side multiplexer 9 to SW ₁ to SW _n. Then, as shown in FIG.
A voltage oscillating from the input pen 2 is applied to (X ₁ , X ₂ ,..., X _n ) through the capacitance, and the applied voltage is applied between the pen tip 22 of the input pen 2 and each X electrode 4. Since the capacitance changes in accordance with the distance between the pen tip 22 and each X electrode 4, a voltage corresponding to the distance from each X electrode 4 to the pen tip 22 is output. After the voltage output from each X electrode 4 is amplified by the amplifier circuit 12, the noise component is removed by the filter circuit 13 and converted into DC. Further, the DC converted signal is digitally converted by the A / D converter 14. After the conversion, the data is read into the CPU 15.
The voltage detecting means built in the CPU 15 detects the input pen 2 based on the data output from the A / D converter 14.
Is determined, and the voltage values applied to the X electrode 4 and the X electrodes 4 located on both sides of the X electrode 4 are sent to the calculating means. Then, the amount of deviation of the input pen 2 between the X electrode 4 closest to the input pen 2 and the X electrode 4 adjacent thereto is calculated.

That is, for three consecutive X electrodes 4 (hereinafter referred to as A electrode, B electrode and C electrode),
When the pen tip 22 of the input pen 2 is in the positional relationship as shown in FIG. 7, the magnitude of the voltage value output from each of the electrodes A, B, and C is V ₁ which is the maximum for the B electrode, and V ₂ becomes smaller in the order of V ₃ of the C electrode. Here, based on the theory that the voltage values output from the respective electrodes A, B, and C are inversely proportional to the square of the distance to the pen tip 22, the respective theoretical values are obtained. _{= V 2 = K / r 1} 2 = K / ^{[H 2 + (P-L)} 2 ] ............ B voltage value of the electrode _{= V 1 = K / r 2} 2 = K / (H 2 + L 2 ) ........................ C becomes the electrode voltage value _{= V 3 = K / r 3} 2 = K / in ^{[H 2 + (P + L)} 2 ] ............ (however, r ₁ is the a electrodes distance from to the pen tip 22, r ₂ is the length of a perpendicular line beat from B electrode distance to the pen tip 22, r ₃ is the distance from the C electrode to the pen tip 22, H is the electrode formation surface of the pen tip 22 , L are B on the electrode forming surface
The amount of deviation from the electrode to the pen tip 22, P is the pitch between each X electrode 4, and K is a constant). By solving the simultaneous equations of these equations, L = P (V ₁ V ₂ −V ₁ V ₃ ) / 2 (V ₁ V ₃ + V ₁ V ₂ -2V ₂ V ₃ ) Become. As is apparent from this equation, L is irrelevant to the size of H, so that the input pen 2 is directly pressed onto the protective film 7 of the tablet 1 to perform handwriting input.
Regardless of whether the input pen 2 is pressed against a sheet of drafting paper or the like placed on the tablet 1 to perform handwriting input, the known P and the voltage value V ₁ output from the three electrodes A, B, and C are used. , V ₂ , and V ₃ .

When the theoretical value of the above equation is compared with the actually measured value of the output voltage, it can be seen that both curves almost coincide with each other as shown in FIG. Here, the vertical axis in FIG. 9 indicates the output value, and the horizontal axis indicates the distance X from the point O when the input pen contacts the point O on the tablet. From this, the deviation L can be accurately detected by the above-mentioned formula, and since the formula is a linear function, the calculation is simple and the load on the CPU 15 is reduced.

The detection of the coordinates of the input pen 2 in the Y-axis direction is the same as described above. In this case, the CPU 15 operates the Y-side multiplexer 17 and switches the Y-side multiplexer 17 to SW.
They are sequentially turned on in ₁ to SW _n. Then, as shown in FIG. 6, the pen tip 2 is attached to each Y electrode 5 (Y ₁ , Y ₂ ,..., Y _n ).
Voltages corresponding to the distances up to 2 are output. These voltages are amplified by the amplifier circuit 18, then digitized by the A / D converter 14 via the filter circuit 19, and the data is read by the CPU 15. Then, the CPU 15 determines the Y electrode 5 closest to the input pen 2 and performs the same calculation as the above equation to detect the coordinates of the input pen 2 in the Y-axis direction. After the coordinates of the input pen 2 in the X and Y axis directions are determined in this manner, the CPU 1
5 sends this position information to the host computer 16,
A diagram or the like corresponding to the movement of the input pen 2 is displayed on the screen of the liquid crystal display device 30.

Next, the case where coordinates are input by the operator's finger 3 will be described. In this case, the analog switch 10 is switched to the first contact 10a side by a signal from a switching means built in the CPU 15, and X The oscillation circuit 11 is connected to the side multiplexer 9. In this state, the CPU 15 operates the X-side multiplexer 9 and the Y-side multiplexer 17, and the SW of the X-side multiplexer 9
₁ is turned on, and then SW ₁ -S of the Y-side multiplexer 17.
W _n are sequentially turned on.
Similarly, after turning on each of W _{2 to} SW _n ,
SW ₁ to SW _n of the side multiplexer 17 are sequentially turned on. Then, an oscillating waveform is inputted from the oscillating circuit 11 to each of the X electrodes 4 (X ₁ , X ₂ ,..., X _n ). A part of the line is pulled out by the finger 3, and the X electrode 4 and the Y electrode 5
Since the capacitance formed therebetween decreases, a voltage corresponding to the change in capacitance is output from each Y electrode 5. The voltage output from each of the Y electrodes 5 is input to the A / D converter 14 via the amplifier circuit 18 and the filter circuit 13 in the same manner as when the coordinate of the input pen 2 in the Y-axis direction is detected. After being digitized by the / D converter 14, the data is read by the CPU 15. Voltage detecting means built in the CPU 15 determines the Y electrode 5 having the smallest voltage value and the X electrode 4 corresponding to the Y electrode 5 based on the data output from the A / D converter 14, and 3 are detected in the X and Y axis directions. Further, after determining the coordinates of the finger 3 in the X and Y axis directions in this manner,
The CPU 15 sends the position information to the host computer 16 and selects, for example, a menu corresponding to the contact position of the finger 3 from the menu displayed on the liquid crystal display device 30.

The switching means of the analog switch 10 is, for example, time-division driving in which the first contact 10a and the second contact 10b of the analog switch 10 are automatically switched at predetermined time intervals. The CPU 15 may switch between the detecting means of the input pen 2 and the detecting means of the finger 3. In this case, switching of the analog switch 10 is performed in several milliseconds, and the X and Y side multiplexers 9 and
If the scanning of 17 is performed in a few μms, the coordinate detection of the input pen 2 or the finger 3 can be accurately performed even when the analog switch 10 is switched in a time-sharing manner to transmit data to the host computer 16 in a unit of several milliseconds. It can be carried out.

The present invention is not limited to the above embodiment,
For example, it is possible to omit the oscillation circuit 11 on the tablet 1 side and to input coordinates only with the input pen 2. Also,
The configuration of the tablet 1 is not limited to the above embodiment. For example, instead of forming each X electrode 4 on the upper surface of the glass substrate 6, the tablet 1 may be formed on the lower surface of the protective film 7. , 5 and the protective film 7 and the shield film 8 can all be formed on the glass substrate 6 by using a film forming technique such as printing or CVD.

[0019]

As described above, according to the present invention,
The position information when the input pen is pressed on the tablet is
Irrespective of the distance between the input pen and the tablet, the voltage is output from the three electrodes and the pitch between the electrodes, which is a known value, is calculated with a highly accurate linear function formula. It is possible to provide a coordinate input device that has a small burden on the input device and a high detection accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a coordinate input device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a tablet provided in the coordinate input device of FIG.

FIG. 3 is a sectional view of the tablet.

FIG. 4 is a configuration diagram of an input pen used in the coordinate input device of FIG. 1;

FIG. 5 is a circuit diagram of the input pen.

FIG. 6 is an explanatory diagram showing a detection operation of the input pen.

FIG. 7 is an explanatory diagram showing a positional relationship between the input pen and three electrodes.

FIG. 8 is an explanatory diagram showing a positional relationship between an output voltage and three electrodes.

FIG. 9 is a comparison diagram between an actually measured value and a theoretical value of the output voltage.

[Explanation of symbols]

 1 tablet 2 input pen 3 finger 4 X electrode 5 Y electrode 6 glass substrate 9 X side multiplexer 15 CPU 17 Y side multiplexer 22 pen tip 24 cap 25 oscillation circuit 27 switch

──────────────────────────────────────────────────続 き Continued on the front page (72) Kinya Inoue, Inventor Kinya 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Yoshihisa Endo 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Al (72) Inventor Tadashi Mame 1-7 Yukitani Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (56) References JP-A-8-137607 (JP, A) JP-A-7 JP-13681 (JP, A) JP-A-5-313811 (JP, A) JP-A-5-165560 (JP, A) JP-A-4-192018 (JP, A) JP-A-61-110225 (JP, A) JP-A-60-181816 (JP, A) JP-A-60-178527 (JP, A) JP-A-61-115240 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 3/03 G06F 3/033-3/037

Claims (2)

(57) [Claims] 1. A plurality of Xs arranged at an equal pitch P interval
A tablet in which electrodes and Y electrodes are laminated in a matrix via an insulating layer; an input pen that oscillates a voltage at a predetermined frequency; and a voltage applied to each electrode based on a change in capacitance between the input pen and each electrode. Voltage detection means for detecting a voltage
Of the voltage values detected by the voltage detection means, when the voltage value from the electrode with the largest applied voltage is V ₁ , and the voltage values from the electrodes on both sides of the electrode are V ₂ and V ₃ , respectively, the bias amount L of the electrode arrangement direction between the electrode closest to the input pen and the input _{pen, L = P (V 1 V} 2 -V 1 V 3) / 2 (V 1 V 3 + V 1 V 2 -2V
₂ V ₃ ). 2. The coordinate input device according to claim 1, wherein said tablet has an insulating layer as a glass substrate, X electrodes and Y electrodes are formed of a transparent material, and said tablet is laminated on a liquid crystal display device via a transparent shield film. .