JPH01263814A - Coordinate input device - Google Patents

Abstract

PURPOSE:To facilitate the coordinate input by detecting the moving position of a position pointing device on a display for execution of the coordinate input and displaying the pointed position on the display in the same coordinates and with high brightness. CONSTITUTION:A coordinate input device consists of a tablet 1 for input of coordinates, a position pointing device (stylus pen) 2, a controller 3 and a power unit 4. The tablet 1 contains a transparent substrate, a sensor part 10 which detects the position coordinates of the X/Y directions pointed by the pen 2, a coordinate display panel 50 set on the surface of the part 10, a back light 60 containing a reflecting plate, a light conducting plate 70 and a case 80. Then a position is pointed over the display via the pen 2 for acquisition of the relevant coordinate value. Based on this coordinate value, the moving locus of the pen 2 is displayed with high brightness at the same part as the pointed position on the display. Thus the input mistakes, etc., can be avoided.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention detects a coordinate position specified by a position indicator,
The present invention relates to a coordinate input device with a display that displays the specified position on a display superimposed on a coordinate detection section (hereinafter referred to as a sense section).

(Prior Art) Conventionally, as this type of device, there have been devices in which a translucent sensing section is superimposed on a liquid crystal display, and devices in which a backlight and a liquid crystal display are superimposed on the sensing section.

(Problem to be solved by the invention) However, in the former device, in order to avoid the influence of noise generated from the liquid crystal display, it is necessary to maintain a distance of 5 mm or more between the input surface of the tablet and the liquid crystal display. Since the display image is separated from the display image, there is a problem in that there is a misalignment between the tip of the position indicator and its trajectory displayed on the liquid crystal display, causing a sense of discomfort in input operations.

In addition, in the latter device, it is necessary to place the sensing part and the position indicator close to each other in order to perform accurate coordinate manually, so the backlight and liquid crystal display must be designed to be extremely thin. Also, based on this,
Extremely thin backlights, such as those using electroluminescent elements (hereinafter referred to as EL elements), are used as backlights, but it is difficult to achieve a sufficiently bright display screen with EL elements. There was a problem.

The object of the present invention was made in view of the above-mentioned problems, and it is possible to display the same coordinates as the specified position by the position indicator without any discomfort and with sufficient brightness, and furthermore, it is possible to input coordinates with good operability and high precision. The object of the present invention is to provide a coordinate input device that can perform the following tasks.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a sense section having translucency, a position indicator for specifying a position, and a coordinate value of the specified position by the position indicator. A display for displaying the position data determined by the position detection control circuit at the same coordinates as the designated position is superimposed on the sense section, and a The tablet was constructed with a backlight that illuminates the display from below.

Further, the sensing section includes an X-direction loop coil group in which a large number of loop coils are arranged in parallel in the X direction, a Y-direction loop coil group in which a large number of loop coils are arranged in parallel in the Y direction, and each of the loops. The sensing unit includes a transparent substrate that holds the coil group at a predetermined position, and the position indicator is a position indicator including at least a coil and a capacitor, and includes a tuning circuit that has a predetermined frequency as a tuning frequency. , further causing the position detection control circuit to sequentially select one loop coil from a group of loop coils in the X direction of the sense section.
a direction selection means; a Y direction selection means for sequentially selecting one loop coil from a group of loop coils in the Y direction of the sense section; a signal generation means for generating an AC signal of the predetermined frequency; A signal detection means for detecting an AC signal of a frequency, and a connection in which the signal generation means and the signal detection means are sequentially connected to each loop coil in the X direction and Y direction selected by the selection means in the X direction and Y direction. a switching means; and a coordinate detecting means for determining coordinate values of specified positions in the X direction and Y direction by the position indicator based on AC signals detected by the signal detecting means from each of the loop coils in the X direction and Y direction. A display that displays the position data in the X direction and Y direction obtained by the position detection control circuit at the same coordinates as the specified position is superimposed on the sense part, and a display is placed on the bottom of the sense part. A tablet was constructed by disposing a backlight that illuminates the display from below.

Further, a cold cathode tube was used as the backlight.

(Operation) According to the present invention, by specifying a position on the display using a position indicator, the specified position is detected by the sensing section, and the coordinate values of the position specified by the position indicator are determined in the position detection control circuit. Furthermore, based on these coordinate values, the locus of movement of the position indicator is clearly and brightly displayed in the same area as the designated position on the display.

More specifically, by specifying the position using the position indicator on the display, one of the loop coils of the sensing section in the X direction and the Y direction and the tuned circuit of the position indicator can be connected. This is repeated for all of the many loop coils in the X and Y directions.Based on the induced voltage obtained at this time, the coordinate detection means calculates the coordinate value of the specified position by the position indicator. is determined, and based on these coordinate values, the locus of movement of the position indicator is clearly and brightly displayed in the same area as the designated position on the display.

Furthermore, by using cold cathode tubes for the backlight, the display can be displayed even brighter.

(Example) FIG. 1 shows an outline of the coordinate input device of the present invention. In the figure, 1 is a tablet for inputting coordinates, 2 is a position indicator for specifying a position, such as a stylus pen ( (hereinafter simply referred to as a pen), 3 is a control device, and 4 is a power supply device.

FIG. 2 is a sectional view showing the structure of the tablet 1. According to FIG. 2, the tablet 1 includes a sensing part 1o which has a transparent substrate which will be described in detail later and detects the specified position coordinates in the X direction and Y direction by the Ben 2, and a sensing part 1o which is placed on the sensing part 10. A flat display panel 50 for displaying coordinates, for example, a liquid crystal display panel having a hard core acrylic plate (not shown) disposed on the upper surface, and an upper liquid crystal display panel 50 disposed below the sense section 10 to emit light emitted from the display panel 50.
A backlight 60 equipped with a reflector (not shown) for reflecting light toward the LCD panel 50 is disposed between the backlight 60 and the sense section 1o so as to illuminate the entire liquid crystal display panel 50 with uniform brightness. The light guide plate 70 is made of, for example, a milky white acrylic plate, and an opening 81 is formed in the center of the upper surface, and the sense part 10, the liquid crystal display panel 50. It is composed of a non-metallic case 80 in which a backlight 60 and a light guide plate 70 are integrally housed.

The backlight 60 is for improving the contrast of the liquid crystal display panel 50 and displaying it brightly, and uses, for example, a cold cathode tube. By using cold cathode tubes as the backlight 60 in this manner, the liquid crystal display panel 50 can be illuminated from below with a brightness three times or more greater than when, for example, an EL element is used as the backlight.

FIG. 3(a) is a schematic diagram showing the transparent substrate 11 constituting the sensing portion 1° of the tablet 1, and FIG. 3(b) is a partially omitted enlarged sectional view of the transparent substrate 11.

In Figure 3, 12, 13, 14, and 15 are transparent films made of polyester, polyvinyl chloride, vinyl chloride, etc., and 16 is a large number of copper wires (for example, 96) arranged in parallel along the Y direction (actually, it is annealed copper wires). (Use tinned wire.), 17
．． These are 96 copper wires arranged in parallel along the LtX direction. These are first transparent film 12 and transparent film 1.
Copper wires 17 are arranged in parallel between 3 and bonded with a transparent polyethylene adhesive, for example. Similarly, the copper wire 16 is arranged in parallel between the transparent film 14 and the transparent film 15 and bonded with the transparent adhesive, and the transparent film 13 and the transparent film 14 are further connected by the copper wire 16 and the copper wire 17. A transparent substrate 1'1 is formed by adhering them so that they are perpendicular to each other. For example, when the backlight 60 is used to illuminate the transparent film 15 side from the transparent film 12 side, the transparent film 1
On the 5 side, a sufficient amount of light can be obtained to brightly illuminate the liquid crystal display panel 5o as described above.

Furthermore, in FIG. 3, the surface of the transparent substrate 11 is shown to have considerable irregularities, but in reality, the thickness of the transparent film and the diameter of the copper wire are adjusted in one direction (X direction or Y direction). However, it is less than 0.2■ and can be almost ignored.

Furthermore, in order to construct the sense section 10 using the transparent substrate 11, the transparent substrate 11 is arranged in the center of a frame-shaped substrate (not shown), and the copper wires 16 and 17 are connected to the pattern of the frame-shaped substrate by, for example, soldering. They are connected to form a large number of loop coils for detecting coordinate values in the X and Y directions. Note that the copper wires 16 and 17 exposed from the transparent substrate 11 may be covered with an insulator except for the soldered portions.

FIG. 4 shows details of the loop coil group 160 for detecting coordinate values in the X direction and the loop coil group 170 for detecting coordinate values in the Y direction. The loop coil group 160 in the X direction includes a large number of loop coils 160-1, 160-1, for example, 48 loop coils arranged parallel to each other along the Y direction.
60-2, . 1, 170-2.

...... Consisting of 170-48, Figure 3 (a)
As shown in , the loop coil group 160 in the X direction and the loop coil group 170 in the Y direction are closely overlapped with each other with the transparent film 13 and the transparent film 14 interposed therebetween (however, this is not shown in the drawing for easy understanding). (The two are drawn separated.) Although each loop coil is configured with one turn here, it may be configured with multiple turns as necessary.

FIG. 5 is a cross-sectional view showing the detailed structure of the pen 2, in which a core 22 of a ballpoint pen or the like is slid into the interior of a pen shaft 21 made of a non-metallic material such as synthetic resin from near its tip. A ferrite core 23 having a through hole that can be accommodated in a movable manner;
Coil spring 24 and switch 251. Ferrite core 2
Coil 252.3 wound around coil 252.3. capacitor 253
and a tuning circuit 25 consisting of 254 are integrally combined and built in, and a cap 26 is attached to the rear end.

The coil 252 and capacitor 253 are connected in series with each other to form a well-known resonant circuit, as shown in FIG. 7, which will be described in detail later. , the voltage and current phases are set to values that resonate (synchronize) in the same phase. Further, the capacitor 254 is connected in parallel to both ends of the capacitor 253 via the switch 251, and when the switch 251 is turned on, the phase of the current in the above-mentioned resonant circuit is delayed, and the phase of the received signal, which will be described later, is adjusted to a predetermined value. Performs the action of retarding the angle. Note that the switch 251 can be operated by holding the pen shaft 21 by hand or the like and pressing the tip of the core body 22 against the top surface of the tablet 1, for example.
When pushed in, the rear end presses through the coil spring 24 and turns on.

As shown in FIG. 6, the control device 3 is comprised of a position detection control circuit 300 that controls the sense unit 10, a display control circuit 500 that controls the liquid crystal display panel 50, and a computer 900 that centrally controls these. ing.

The power supply device 4 includes a well-known rectifier, transformer, DC-DC converter, etc., and supplies power to each circuit within the control device 3.

FIG. 7 shows a position detection control circuit 300 together with a tuning circuit 25.
This is a professional diagram showing the details. In the same figure, 30
1 is a control circuit, 302 is a signal generation means (circuit), 30
3X and 303y are X-direction and Y-direction selection means (circuits). Further, 304x and 304y are transmission/reception switching circuits, 305 is an XY switching circuit, and 306 is a reception timing switching circuit, which constitute connection switching means. Also,
307 is a bandpass filter (BP F), which constitutes a signal detection means. Further, 308 is a detector, 309
is a low-pass filter (LPF), which together with the processing in the control circuit 301 described later constitutes the coordinate detection means. Also, 310°311 is a phase detector (P
S D), 312, and 313 are low-pass filters (L P
F), which together with the processing in the control circuit 301 described later constitute a switch on/off identification means. Also, 314x and 314y are drive circuits, 315x
, 315y is an amplifier.

Next, the operation of the position detection control circuit 300 will be explained together with its configuration. First, the manner in which radio waves for position detection are transmitted and received between the sense unit 10 and the Ben 2, and the signals obtained at this time will be explained. This will be explained according to FIG.

The control circuit 301 is composed of a well-known microprocessor or the like, and controls the signal generation circuit 302 and also controls the switching of each loop coil of the sensing section 10 via the selection circuits 303x and 303y according to the flowchart shown in FIG. , also controls switching of the coordinate detection direction for the XY switching circuit 305 and the reception timing switching circuit 30B, and furthermore, low-pass filters 309 , 312 , 3
The output value from H is converted into analog/digital (A/D), and the arithmetic processing described later is executed to calculate the value of the position specified by Ben 2. Furthermore, the state of the switch is identified, and these are converted into the above-mentioned values. It is sent to electronic computer 900.

The selection circuit 303x selects the loop coil group 160 in the X direction.
The selection circuit 303y sequentially selects the first loop coil in the Y direction.
The loop coils 0 to 1 are sequentially selected, and each operates based on information from the control circuit 301.

The transmission/reception switching circuit 304x connects one of the selected loop coils in the X direction alternately to the drive circuit 314x and the amplifier 315x.
y alternately connects one of the selected loop coils in the Y direction to a drive circuit 314y and an amplifier 315y, which operate according to a transmission/reception switching signal to be described later.

The signal generation circuit 302 has a predetermined frequency fO1, for example, 500.
kHz rectangular wave signal A1 Signal A- (not shown) obtained by delaying the phase of the rectangular wave signal A by a predetermined angle, a predetermined frequency fk1
For example, a transmission/reception switching signal B and a reception timing signal C of 15.825 kHz are generated.

The rectangular wave signal A is sent to a phase detector 310 and is converted into a sine wave signal by a low-pass filter (not shown), and then sent to a drive circuit 314 via an XY switching circuit 305.
x or 5i4y, the rectangular wave signal A' is sent to the phase detector 311, the transmission/reception switching signal B is sent to the transmission/reception switching circuits 304x and 304y, and the reception timing signal C is sent to the reception timing switching circuit 306.

Now, assuming that information for selecting the X direction is input from the control circuit 301 to the XY switching circuit 305 and the reception timing switching circuit 30B, the sine wave signal is transmitted to the drive circuit 3i4.
x, is converted into a balanced signal, and is further sent to the transmission/reception switching circuit 304x. The transmission/reception switching circuit 304x, based on the transmission/reception switching signal B, switches the drive circuit 314X and the amplifier 3.
15x, the signal output from the transmission/reception switching circuit 304x to the selection circuit 303x is for a time T (-1/2fk), in which a 500kHz signal is output or not output every 32 μsec. It becomes

The signal is passed through a selection circuit 303x to one loop coil 160-i (i-1, 2,
...48), but the loop coil 1
60-i generates radio waves based on the signal.

At this time, when Ben 2 is held in a substantially upright position on the tablet, that is, in a state of use, the radio waves based on the signal excites the coil 252 of Ben 2, and its tuning circuit 25 is synchronized with the signal. An induced voltage E is generated.

Thereafter, as the signal enters a no-signal period, that is, a reception period, the loop coil IGO-i is connected to the amplifier 315.
When switched to the x side, the radio waves from the loop coil 160-i disappear immediately, but the induced voltage E gradually attenuates in accordance with the loss within the tuning circuit 25.

On the other hand, the current flowing through the tuning circuit 25 based on the induced voltage E causes the coil 252 to emit radio waves. The radio waves are loop coil connected to amplifier 315x) and l[io −
In order to reversely excite the loop coil 160-i, an induced voltage due to the radio waves from the coil 252 is generated in the loop coil 160-i.

The induced voltage is applied to the 7 transmission/reception switching circuit 304x during the reception period.
The received signal F is sent to the amplification 2V315x and amplified.
The signal is then sent to the reception timing switching circuit 30G.

The reception timing switching circuit 30G receives either the X-direction or the Y-direction selection information, here the X-direction selection information, and the reception timing signal C, which is essentially an inverted signal of the transmission/reception switching signal B. and the signal C is high (H)
Since the received signal F is output during the level period and nothing is output during the low (L) level period, the signal G (substantially the same as the received signal F) is obtained as the output.

The signal G is sent to a bandpass filter 307, which is a ceramic filter having a natural frequency of frequency fO, and a signal having an amplitude depending on the energy of the acid component at frequency fO in the signal G. H (strictly speaking, in the state where several signals G are input to the bandpass filter 307 and converged) to the detector 308 and the phase detector 31
0, 311.

The signal H input to the detector 308 is detected and rectified to become a signal I, and then passed through a low-pass filter 309 with a sufficiently low cutoff frequency to a voltage value corresponding to approximately 1/2 of the amplitude, for example, Vx. The DC signal J is converted into a DC signal J having

The voltage value Vx of the signal J is between the pen 2 and the loop coil IGO.
- a value that depends on the distance between i, where approximately the distance 4
The voltage value Vx obtained for each loop coil is converted into a digital value in the control circuit 30 (a), and is converted into a digital value as described below. By executing the arithmetic processing, the coordinate values of the specified position in the X direction by the pen 2 are calculated.

Note that the coordinate values of the designated position in the Y direction by the pen 2 are also calculated in the same manner.

On the other hand, the rectangular wave signal A is input to the phase detector 310 as a detection signal, and at this time, the switch 251
Suppose that is off and the phase of the signal H substantially matches the phase of the rectangular wave signal A, then a signal (substantially the same as the signal I) which is exactly the positive inversion of the signal H is output. This signal is converted by the same low-pass filter 312 to a DC signal (substantially the same as signal J) having a voltage value corresponding to approximately 1/2 of the amplitude, and sent to the control circuit 301.

Further, the rectangular wave signal A' is inputted to the phase detector 311 as a detection signal, but as described above, the switch 25
1 is off and the phase of the signal H leads the phase of the rectangular wave signal A' by a predetermined angle, a signal with H components on the positive side and the negative side is output. This signal is converted into a DC signal by a low-pass filter 313 similar to the one described above, and is converted into a DC signal by the control circuit 3.
01, but since the output signal of the phase detector 311 has components on the positive and negative sides, the low-pass filter 3
The voltage value of the output of the low-pass filter 312 is considerably smaller than the voltage value of the output of the low-pass filter 312.

Here, when the switch 251 of the pen 2 is turned on, the phase of the current flowing through the tuning circuit 25 is delayed with respect to the induced voltage E, and the phase of the received signal F is also delayed by a predetermined angle, that is, almost the phase of the rectangular wave signal A'. It will match. Therefore, the output H of the bandpass filter 307 at this time is converted into a signal having components on the positive side and the negative side by the phase detector 310, and the output of the low-pass filter 312 is converted into a signal having components on the positive side and the negative side. However, the output of the low-pass filter 313 has a predetermined voltage value corresponding to approximately 1/2 of the amplitude. It becomes a DC signal with

In this way, when the switch 251 is off, a predetermined voltage value is obtained at the output of the low-pass filter 312, and when the switch 251 is on, a predetermined voltage value is obtained at the output of the low-pass filter 313. In the control circuit 301, by monitoring the output values of the low-pass filters 312 and 313, it is possible to identify whether the switch 251 is off or on.

Note that the information indicating the on (or off) state of the switch 251 identified here is used as information for specifying the value to be actually input among the coordinate values of the position specified by the pen 2.

Next, according to FIGS. 9 to 12, the position detection control circuit 3
The coordinate detection operation at 00 and the state of the pen 2, here the details of the operation of the on/off state of the switch 251, as well as the operation of the entire apparatus will be explained.

First, when the entire device is powered on and enters the /Ip constant start state, the control circuit 301 transmits information for selecting the X direction.
The selection circuit sends information to the Y switching circuit 305 and reception timing switching circuit 306, and also selects the first loop coil 1 [io 1] among the loop coils 160-1 to 160-48 in the X direction of the sensing unit 11]. 303X
and the loop coil tea-i is sent to the transmission/reception switching circuit 30.
Connect to 4X.

The transmission/reception switching circuit 304X is as described in 1. above. Based on the transmission/reception switching signal B, the loop coil 160-1 is alternately controlled to be switched to the drive circuit 314X and the amplifier 315x. At this time, the drive circuit 314X performs the switching control as shown in FIG. 10(a) during the transmission period of 32 μscc. 16 sine wave signals of 500 kHz are sent to the loop coil 180-1.

The switching between transmission and reception is repeated seven times with one loop coil, here 160-1, as shown in FIG. 10(l). The h-return period for these seven transmissions and receptions is
This corresponds to the selection period (448 usec) of one loop coil.

At this time, an induced voltage is obtained at the output of the amplifier 315X for one loop coil every seven reception periods, or this induced voltage is generated by the reception timing switching circuit 30 as described above.
Via G: Sent to 12 band filter 307! The signals are equalized and sent to the control circuit 301 via a wave detector 308, phase detectors 310, 311, and low-pass filters 309, 312, 313.

The control circuit 301 converts the output value of the low-pass filter 309 into A
/ D conversion and input, Ben 2 and loop coil 1eo
- i is temporarily stored as a detected voltage depending on the distance to i, for example, VXI.

Next, the control circuit 301 sends information for selecting the loop coil 1.130-2 to the selection circuit 303x, connects the loop coil IGO-2 to the transmission/reception switching circuit 304x, and connects the loop coil IGO-2 to the transmission/reception switching circuit 304x.
Obtain a detection voltage Vx2 that depends on the distance between the loop coil 160-2 and the loop coil 160-2 and record it. Detection voltage Vxl-VX48 depending on the distance in the X direction from Ben 2 for each loop coil as shown in Figure 10 (c) (However, only a part of it is expressed in analog form in Figure 10 (C) ) is memorized.

As shown in FIG. 11, the actual detected voltage is obtained only in several loop coils around the position (xp) at which Ben 2 is placed, at 15 in the center.

The control circuit 301 checks whether the voltage value of the detection voltage described above is below a certain detection level [2, If it is below a certain detection level, selects each loop coil in the X direction again. The voltage detection is repeated I7, and if the constant detection is one novel or more, the process proceeds to the next process.

Next, the control circuit 301 sends selection information in the Y direction to the XY switching circuit 305 and the reception timing switching circuit 306,
Similarly to the above, 17 selects the selection circuit 303y and the transmission/reception switching circuit 3.
Low-pass filter 3 when transmitting and receiving radio waves by switching 04y
09 is A/D converted to temporarily store a detected voltage depending on the distance between Ben 2 and each of the loop coils 170-1 to 170-4Pt in the Y direction. After that, perform a level check in the same manner as above, and if it is below a certain detection level, return to selection of the loop coil in the X direction and voltage detection, and if it is above a certain detection level,
From the voltage values stored in the memory 17, the coordinate values of the designated positions of the Ben 2 in the X and Y directions are calculated as described later.

Next, the control circuit 301 controls the loop coil 16 in the X direction.
0-1 to 16 (1-48 (or Y direction loop coil 1
70-1 to 170-48), a selection circuit 303
(or 303y), and the transmission and reception of the radio waves is repeated multiple times, for example, 7 times, and at that time, the low-pass filter 312
The output values obtained from and 313 are A/D converted, and as described above, it is detected which of these values is less than a predetermined value -L, and whether the switch 251 is on or off is determined.

The result of identifying whether the switch 251 is on or off is transferred to the computer 900 together with the coordinate values of the designated position of Ben 2 in the X and Y directions.

When the first [1 coordinate detection operation and state identification operation are completed in this way, the control circuit 301 performs the second [-1 and subsequent coordinate detection operations by looping in the X direction as shown in FIG. Among the coils 160-1 to 11'1O-48, information is sent to the selection circuit 303x to select only a certain number of loop coils, for example, 10 loop coils before and after the loop coil with the maximum detected voltage i. Also,
Among the loop coils 170-1 to 170-48 in the Y direction, a selection circuit 303y generates information for selecting only a certain number of loop coils, 10 loop coils, around the loop coil from which the maximum detected voltage was obtained. The output values are obtained in the same manner as described above, and the X-direction and Y-direction coordinate detection operations for Ben 2 and the on/off status identification operations of the switch 251 are performed, and the obtained coordinate values and identification results are sent to an electronic computer. 900, and repeat these steps.

To explain the level check described above in detail, it checks whether the maximum value of the detected voltage has reached the detection level and which loop coil has the maximum detected voltage, and then checks the detection level. If the value has not been reached, subsequent coordinate calculations, etc. are stopped, and the center of the loop coil to be selected in the next coordinate detection operation and state identification operation is set.

As one calculation method for determining the coordinate value in the X direction or the Y direction, for example, the coordinate value xp, the detection voltages Vxl to V
There is a method of approximating the waveform near the maximum value of x48 by an appropriate function and finding the coordinates of the maximum value of that function.

For example, in FIG. 10(c), the maximum detected voltage Vx
3 and the detection voltages Vx2 and VX4 on both sides thereof can be approximated by a quadratic function, it can be calculated as follows (
However, the coordinate values of the center positions of the loop coils tea-t to 160-48 are set to x1 to x48, and the interval therebetween is set to ΔX. ). First, from each voltage and coordinate value, Vx2-a (x2-xp) 2+b −-1
1) Vx3=a (x3 - xp) +b
-------(2) Vx4=a (x4-xp
) +b −−−−−−<3). Here, a and b are constants (a<0).

Also, x3-x2-ΔX (4
)x4−x2 =2Δx −=;
(5) becomes. Substituting equations (4) and (5) into equations (2) and (3) and rearranging, xp = x2 + Δx/2 ((3Vx2-4Vx30Vx4) / (Vx2-2 Vx3+Vx4)
1...(6)

Therefore, from each of the detection voltages Vxl to Vx48, the maximum detection voltage obtained during the level check and the detection voltages before and after it are extracted, and these and the detection voltage of the loop coil from which the maximum detection voltage was obtained are extracted. The coordinate value xp of the specified position of the pen 2 can be calculated by performing an operation corresponding to the above-mentioned equation (6) from the coordinate value (known) of the previous loop coil.

Each coordinate value detected in this manner is displayed on the liquid crystal display panel 50 under the control of the display panel control circuit 500 each time it is detected.

FIG. 13 shows details of the display control circuit 500, and position data consisting of X direction data and Y direction data sequentially instructed by the sense unit 10 is sent to the electronic computer 9.
00, the position data is arranged and stored in a certain order in the display memory 501, and the position data is sequentially read out by timing pulses from the controller 502, which is a display processor, and then sent to the X-direction driver 503 and the Y-direction driver. 504
is output to.

Furthermore, scanning pulses generated by a scanning pulse generator 505 are input to these X-direction drivers 503 and Y-direction drivers 504 in synchronization with the timing pulses of the controller 502, and each driver 503.50
4 inputs the position data in the X and Y directions to the liquid crystal display panel 50, so that the position indicated by the pen 2 on the sensing section 10 is displayed at the same position on the liquid crystal display panel 50. Therefore, the handwriting of characters and figures written with Ben 2 on the liquid crystal display panel 50 stacked on the sense section 10 is the same handwriting on the liquid crystal display panel 50, and moreover, the cold cathode tube disposed at the bottom of the sense section 10 60 and the light guide plate 70, the display is bright.

As described above, according to this embodiment, the sense section 10 is formed using the transparent substrate 11 through which light can pass, and the backlight 60 for changing the contrast of the display panel 50 and displaying brightly is provided in the sense section 10. Since it is arranged at the bottom of the display panel 50, the distance between the sensing section 10 and the surface of the display panel 50 can be significantly reduced compared to conventional devices, and even if coordinates are input from a position far from the surface of the display panel 50, the input There is no risk of mistakes etc.
A coordinate input device capable of highly accurate coordinate input can be realized.

Furthermore, since a cold cathode tube is used for the backlight 60, a bright and easy-to-read display screen is realized17.

Note that the number of loop coils and the arrangement thereof in the example are merely examples, and it goes without saying that the present invention is not limited thereto. Also, of course, a cursor can be used instead of a stylus pen.

FIG. 14 is a sectional view showing another embodiment of the tablet 1. The difference between this example and the tab 1 knot shown in Figure 2 is:
On both sides of the light guide plate 70a are approximately U-shaped reflecting plates 61, which are made of cold cathode tubes and whose inner surfaces are coated with aluminum. A, 61b having backlights 60a and 61b are disposed, a printed pattern that scatters light is superimposed on a reflecting plate 71 as a light guide plate 70a, an acrylic resin is superimposed on the printed pattern, and an acrylic resin is further placed on the acrylic resin. It uses a structure made up of overlapping diffuser plates. According to FIG. 14, the tablet 1 can be made thinner, and the entire display panel 50 can be more uniformly irradiated by the effects of the printed pattern of the light guide plate 70a, the diffusion plate, etc.

FIG. 15 is a partially omitted enlarged sectional view showing another preferred embodiment of the transparent substrate 11 of the sense section 0. The difference from the transparent substrate 11 shown in FIG. 3 is that a large number of copper wires 16 are arranged in parallel in the Y direction through the transparent film 13 (or transparent film 14°) in FIG. A large number of transparent films 15 and 1 are arranged in parallel in the direction.
2, copper wires 16 and 17 are laminated. According to this, the transparent film 14 (
Alternatively, the transparent film (13°) is no longer necessary, making it possible to reduce the number of parts, making the tablet 1 thinner and lowering costs, as well as improving the light transmittance of the transparent substrate 1), making it possible to realize an even brighter display screen. can.

In this example, a sense part having a transparent substrate in which a copper wire is laminated with a light-transmitting transparent film is used, but the present invention is not limited to this. For example, the electrode may be made of a nonmetallic transparent indium oxide or It is also possible to use a sense section composed of a section H that exhibits optical properties, or it is also possible to use a sense section in which colored electrodes are arranged on a transparent film such as polyester by means such as printing.

(Effects of the Invention) As described in Explanation 17, according to the present invention, when the position indicator is moved on the display, the moved position is detected and the coordinates are input, and the position is also displayed on the display. Since the position designated by the indicator is brightly displayed with the same coordinates, the coordinates can be input while confirming the locus of movement of the position indicator using the L/L view. In addition, the sense part of the tablet is made of a translucent material, and a backlight is placed at the bottom of the sense part to improve the contrast of the display and provide a bright display. We have realized a coordinate input device that can significantly reduce the distance from the display surface and can input highly accurate coordinates without the risk of input errors even when inputting coordinates from a position far from the display surface. can.

Further, by using a cold cathode tube for the backlight, a bright and easy-to-read display screen can be realized.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an outline of the coordinate input device of the present invention, FIG. 2 is a sectional view of a tablet, FIG. 3(a) is a schematic diagram of a transparent substrate, and FIG. Fig. 4 is a detailed configuration diagram of the loop coil group in the X and Y directions of the turflet, Fig. 5 is a sectional view of the stylus pen, and Fig. 6 is a block diagram of the control device. Figure, 7th
The figure is a block diagram showing details of the stylus pen tuning circuit and position detection circuit, Figure 8 is a signal waveform diagram of each part of Figure 7, Figure 9 is a flowchart of processing in the control circuit of the position detection control circuit, and Figure 10 is a block diagram showing details of the stylus pen tuning circuit and position detection circuit. Figures (a), (b), and (c) are timing diagrams showing the basic position detection operation in the position detection control circuit, and Figure 11 shows the detection voltage obtained from each loop coil during the first position detection operation. The figure shown in Fig. 12 is the second
13 is a display control circuit diagram, FIG. 14 is a sectional view showing another embodiment of the tablet, and FIG. 15 is another example of the transparent substrate of the tablet. It is a partially omitted enlarged sectional view showing an example. In the figure, 1...tablet, 2...stylus pen,
3... Control device, 4... Power supply device, 10... Sense unit, 50... Display panel, 60... Backlight, 300... Position detection control circuit.

Claims (3)

[Claims] (1) A sensing section having translucency, a position indicator for specifying a position, and a position detection control circuit for determining the coordinate values of the position specified by the position indicator, and on the sensing section, Displays that display the position data obtained by the position detection control circuit at the same coordinates as the specified position are superimposed, and a backlight that illuminates the display from below is provided at the bottom of the sense section to display the tablet. A coordinate input device characterized by comprising: (2) An X-direction loop coil group made up of a large number of loop coils arranged in parallel in the X direction, a Y-direction loop coil group made of a large number of loop coils arranged in parallel in the Y direction, and each loop coil group a sensing section including a transparent substrate held in a predetermined position; a position indicator including a tuning circuit that includes at least a coil and a capacitor and has a predetermined frequency as a tuning frequency; and a loop coil in the X direction of the sensing section. X-direction selection means for sequentially selecting one loop coil from a group; Y-direction selection means for sequentially selecting one loop coil from a Y-direction loop coil group of the sense unit; and an AC signal of the predetermined frequency. signal generating means for detecting the alternating current signal of the predetermined frequency;
connection switching means for alternately connecting the signal generating means and the signal detecting means to each of the loop coils in the X direction and Y direction selected by the direction selection means; a position detection control circuit comprising a coordinate detection means for determining coordinate values of a specified position in the X direction and Y direction by the position indicator based on an AC signal detected by the detection means; X determined by the position detection control circuit
A tablet is constructed by superimposing displays that display positional data in the direction and Y direction at the same coordinates as the designated position, and disposing a backlight at the bottom of the sense section to illuminate the display from below. A coordinate input device characterized by: (3) The coordinate input device according to claim 1 or 2, wherein the backlight comprises a cold cathode tube.