JPH0248724A - Codeless tablet - Google Patents

Abstract

PURPOSE:To make the title codeless tablet to be comparatively simple and easy to be handled by varying the tuning frequency of a position indicator in accordance with the input state of data of the position indicator and varying the frequency of the driving current of a driving line at a prescribed time interval. CONSTITUTION:An AC current which is impressed on a driving line group 1 and whose frequency changes at the prescribed time interval is converted into an AC magnetic field having the frequency which changes at the prescribed time interval, and the AC magnetic field is given to a sense line group 4. With the AC magnetic field given to the sense line group 4, the AC voltage whose frequency changes at the prescribed time interval is induced and the induced voltage comes to be a large amplitude when the frequency coincides with the tuning frequency. The induced voltage of the large amplitude is detected and the device recognizes the frequency. Thus, the tablet is easy to be used without enlarging the mounting density of the conductor group.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tablet for determining position coordinates on a surface. More specifically, the present invention relates to a cordless tablet in which a position indicator indicating a position on the tablet surface does not have a cable connected to the tablet body.

[Conventional technology]

Tablets that determine positional coordinates on a surface are widely used as input devices for inputting figures and the like to computers. This type of tablet has a table on which a coordinate reading mechanism is formed and a position indicator that can be positioned arbitrarily on the table. Furthermore, in order to improve its usability, consideration has been given to the ability to attach meaning to the input data when inputting the indicated position. This meaning is, for example, to define the input timing of input data, or to define the attributes (color designation) of a figure or the like created by a series of input data. In this specification, these meanings are simply expressed as input states (
Attributes) settings. Conventional devices of this type are
The coordinate reading mechanism constituting the tablet generally has a plurality of groups of conducting wires arranged in a grid pattern. The position indicator had a magnetism generating mechanism to generate a predetermined induced voltage in the group of conducting wires. Usually, this magnetism generating mechanism is composed of a coil and an alternating current source that applies an alternating current to the coil.

In the configuration of such a conventional device, in order to make the magnetic generation mechanism and the coordinate reading mechanism cordless without a connecting cable, it is necessary to set the magnetic generation mechanism and the coordinate reading start timing or the manual state of the indicated position in the position indicator. It is necessary to provide a mechanism for making the tablet device recognize the (attribute), such as an ultrasonic transmitter, and the configuration of the position indicator becomes complicated. In this case, the magnetism generating mechanism is generally equipped with a battery, but this is inconvenient in terms of battery life.

For this reason, magnetic generators using permanent magnets have been developed (for example, Japanese Patent Publication No. 59-53569).
. This device uses a drive line and a sense line as a pair because a permanent magnet used as a magnetic generator generates a steady magnetic field. That is, the position coordinates of the position indicator can be determined by arranging the drive line and the sense line in close proximity and changing the magnetic field generated by the alternating current applied to the drive line by the steady magnetic field of the permanent magnet. This is a detection method.

Further, as a wireless state recognition mechanism for position data, there are devices described in, for example, Japanese Patent Laid-Open No. 63-29829 and Japanese Patent Laid-Open No. 63-56716.

This device is equipped with an antenna coil around the reading area of the tablet, and a tuning circuit that includes a coil, a capacitor, and a resistor in the position indicator, and has a switch that changes the values of these capacitors and resistors. ing. Intermittent alternating current is applied to the antenna coil, and the phase shift of the alternating voltage reflected on the antenna coil is detected by the magnetic field generated by the tuning circuit due to the alternating current applied to the antenna coil, and the switch is activated. Detects on/off and recognizes the state of the input data.

[Problems to be Solved by the Invention] As described above, conventional cordless tablets that combine the above-described magnetism generation mechanism and state recognition mechanism have been put into practical use. Although this method is an excellent method that is easy to use and does not require the use of batteries, it has the following problems.

In other words, since a permanent magnet is used in the magnetic generation mechanism,
The number of drive lines and sense lines increases. X-Y
A tablet that determines the coordinate position requires an XIm drive line group, an X-axis sense line group, a Y-axis drive line group, and a Y-axis sense line group, and the mounting density of the conducting wire groups arranged in a grid pattern is It was large and difficult to manufacture.

Furthermore, since the above-mentioned antenna coil is used as the state recognition mechanism, it is necessary to provide the antenna coil in addition to the above-mentioned group of conducting wires, which increases the difficulty and complicates the circuit configuration accordingly.

[Means for solving problems]

Therefore, the present invention includes: a plurality of drive line groups provided along a first direction; a drive circuit that applies an alternating current whose frequency changes at predetermined time intervals to the drive line group; A tuning circuit that tunes to the alternating current applied to the drive line group, the position indicator having a switch that changes the tuning frequency and generating a magnetic field, and a position indicator that generates a magnetic field along a second direction that intersects with the first direction. a plurality of sense wire groups provided in the position indicator, and in which AC voltages having a frequency matching the tuning frequency are induced in accordance with the magnetic field of the position indicator; and a sense line for selectively extracting the AC voltage induced in the sense line groups. control circuit, the drive circuit, and the sense circuit, calculate the data obtained by the sense circuit, determine the position of the position indicator, and recognize the state of the instruction data according to its frequency. It has a control circuit.

[Effect]

The alternating current, which is applied to the drive line group and whose frequency changes at predetermined time intervals, is converted by the position indicator into an alternating current magnetic field whose frequency changes at predetermined time intervals. This alternating magnetic field is applied to the sense line group.

An alternating current magnetic field applied to the sense line group induces an alternating voltage in the sense line group whose frequency changes at predetermined time intervals. This induced voltage has a large amplitude when its frequency matches the tuning frequency. The device detects this large amplitude induced voltage and recognizes its frequency.

[Example] First, the overall configuration of the apparatus will be explained with reference to FIG.

In FIG. 1, 1 is a group of multiple drive lines (10 are shown as X1 to X10 in FIG. 1) arranged in the X-axis direction, and 2 is a group of these multiple drive lines. A drive circuit that selectively applies an alternating current signal, and 3 a position indicator having a tuning circuit consisting of a coil 31 and a capacitor 32, and a switch 33 that changes the capacitance of the capacitor of this tuning circuit and sets the input state of the indicated position. , 4 is a plurality of sense line groups orthogonal to the drive line group 1, 5 is a sense circuit that selectively detects the AC voltage induced in the sense line group 4, and 6 is a sense line group that connects the drive circuit 2 and the sense circuit 5. This is a control circuit that controls the

Although the position indicator 3 is shown in FIG. 1 in a simplified manner to avoid complication, the actual position indicator 3 has the configuration shown in FIG. 2. That is, the coil 31 and the capacitor 1c
. A reference capacitor 320 with a capacitance (iCl), a second capacitor 322 with a capacitance C2, a third capacitor 323 with a capacitance C8, and a fourth capacitor 324 with a capacitance C4 are connected by switching the respective capacitors. switches 331.332.333 and 3
It has 34. When all of these four switches are off, a tuned circuit is formed in which the reference capacitor 320 of capacitance C0 acts. When the first switch 331 is turned on, the first capacitor 321 with a capacitance CI and the capacitor C0
A tuning circuit having a composite capacitance with the reference capacitor 320 is formed. Similarly, when the second switch 332 is on, the second capacitor 322 and the reference capacitor 32
0 is formed, and the third switch 3
33 is on, the third capacitor 323 and the reference capacitor 320 act on a tuning circuit, and when the fourth switch 334 is on, the fourth capacitor 324 and the reference capacitor 320 act on the tuning circuit. is formed. By turning these switches on and off, the tuning frequency of the alternating current magnetic field generated by the tuning circuit can be changed.

As shown in FIG. 3, the drive circuit 2 includes a scanner unit 21 and a variable frequency alternating current source 22, which are selectively connected to specific drive lines of the plurality of drive line groups 2.

The scanner section 21 is controlled by a processor 61 of the control circuit 6 via a boat 63. The variable frequency alternating current source 22 generates an alternating current whose frequency changes at predetermined time intervals under the control of the processor 61 of the control circuit 6 using a PLL circuit (not shown). The sense circuit 5 also includes a scanner unit 51 that switches and connects to a specific sense line among a plurality of sense line groups in which AC voltage is induced, and an amplifier 52 that amplifies the AC voltage extracted from the scanner unit 51 to a predetermined value. and an A/D converter 53 that converts the AC voltage into a digital value. This digital value is transferred to the memory 6 in the control wholesale circuit 6 via the port 65.
2, and a predetermined calculation is performed by the processor 61 to determine the position coordinates. Note that this sense circuit 5 is connected to ftdJ? by the pro sensor 61 of the control circuit 6 via the boat 65. It is sold wholesale.

Next, the coordinate reading operation of this embodiment device will be explained using FIG. 4, FIG. 5, and FIG. 6.

The position indicator 3 is now located at the position shown in FIG. 1, that is, near the intersection of the drive line X4 and the sense line Y5,
Consider the case where the position coordinates of the center position of the coil 31 are read. In this case, the drive circuit 2 selectively drives the plurality of drive lines X1 to XIO in a predetermined order as shown in FIG. 5 under the control of the control circuit 6. Furthermore, in the drive during each period shown in FIG. 5, under the control of the processor 61 of the control circuit 6, the variable frequency AC current source 22 of the drive circuit 2 is used for a predetermined period of time as shown in FIG. 4(a). An alternating current whose frequency changes at intervals is applied to each drive line.

Now, when all the switches 33 of the position indicator 3 are off, the tuning circuit of the position indicator 3 is set to the tuning frequency determined by the reference capacitor 320. Now, an alternating current whose frequency changes at predetermined time intervals as shown in FIG. is being applied.

Referring to FIG. 5, time t. Between L1, the scanner section 21 of the drive circuit 2 is connected to the drive line X1, and as shown in FIG.
The alternating current shown in a) is applied to the drive line Xl. Between the next time points t+f and z, the drive line
) is applied, and the devices operate in the same manner one after another until time t1°.

Now, time t. During t4, the drive line
During the period when the alternating current shown in a) is applied, the control circuit 6
operates the scanner section 51 of the sense circuit 5 to scan all the sense lines and detect the AC voltage induced by the AC magnetic field generated by the coil 31 of the position indicator 3.

Since the drive line X1 is sufficiently far away from the coil 31 of the position indicator 3, no induced AC voltage exceeding a predetermined level is detected from any of the sense lines Y1 to Y10.

In this way, the drive circuit 2 scans the drive lines one after another in a predetermined order, and the drive line X3 (
When the alternating current shown in FIG. 4(a) is applied to the drive line
5. Obtain an induced AC voltage of a predetermined level or higher at Y6. In this case, the alternating current magnetic field generated by the coil 31 of the position indicator 3 has a frequency that matches the tuned frequency of the above-mentioned tuned circuit among the alternating current shown in FIG. 4(a) above, due to its tuned circuit. Generates a large level of alternating magnetic field in response to alternating current. Therefore, the induced voltages in the sense lines Y4, Y5, and Y6 have a large amplitude with respect to the frequency tuned to the tuning circuit of the position indicator 3, as shown in FIG. 4(b).

Similarly, when the drive circuit 2 performs scanning between time points tQtlo, that is, up to the final scanning, a sensing result as shown in the lower diagram of FIG. 5 is obtained.

In addition, in order to avoid complexity, the diagram shown in Figure 5 is
The alternating current applied by the drive circuit 2 and the sense circuit 5
Although the detected output voltage is shown in a simplified manner, the actual applied current and output voltage are shown in FIGS. 4(a) and 4(b), respectively. moreover,
The detected output voltage of the sense circuit 5 shown in the lower diagram of FIG. 5 expresses the change in amplitude of each detected voltage having the tuning frequency shown in FIG. 4(b).

That is, when the scanning operations of the drive circuit 2 and the sense circuit 5 are combined, when the alternating current shown in FIG. 4(a) is applied to the drive lines X3, X4, and X5, the sense lines Y4, Y5, and Y6 of the sense circuit 5 At this time, an AC voltage shown in FIG. 4(b) is generated, and the amplitude of this induced AC voltage is varied depending on the distance of each sense line from the coil 31 of the position indicator 3. Also, drive lines X3, X4, and
The amplitude also varies depending on the distance between the coil 31 and the coil 31. This means that the coil 31 of the position indicator 3 is near the drive lines X3, X4, and X5, and the sense lines Y4, Y
5 and Y6. Arrangement interval of drive line group 1 arranged in the X-axis direction and arrangement interval of sense line group 4 arranged in the Y-axis direction (Dx, Dy in Fig. 1)
is already known, and the origin of the XY coordinates can be set in advance as shown at point P in Figure 1. Therefore, the order of any of the drive lines X3, X4, and X5 obtained through this scanning operation and the sense lines Y4, Y5, and Y6
The memory of the control circuit 6 (RA
M), the approximate position of the position indicator 3 can be recognized.

In this case, instead of scanning all of the drive line groups 1, as shown in the embodiment described above, the scan may be thinned out at appropriate intervals, or alternatively, the AC voltage induced in the sense lines may be It is also possible to configure so that the subsequent scan is stopped at the stage when it is detected by the sense circuit 5. In these cases, the drive line at the moment when an AC voltage is induced in the sense line group is identified, and multiple adjacent drive lines including this identified drive line are subjected to the next operation described below. Therefore, configure it to select.

Next, a detailed position determination operation for the center position of the coil 31 whose approximate position has been recognized will be described.

The drive circuit 2 drives the drive lines X3, X4, and X5 in a predetermined order, and the sense circuit 5 drives the sense lines Y4, Y
5 and Y6 are controlled by the control circuit 6. FIG. 6 depicts the results of this scanning operation. When a predetermined alternating current is applied to the drive line X3 between periods T and T1, the sense circuit obtains an alternating current voltage shown in the lower part of FIG. 3. The same applies to drive lines X4 and X5. It should be noted that the waveforms shown in FIG. 6 are only shown for large amplitudes that match the tuning frequency, in order to avoid complication of the drawing. Only this large amplitude AC voltage is used for position determination.

In the sense circuit 5, the AC voltages induced on the sense lines Y4, Y5 and Y6 are converted into digital values by an A/D converter 53 shown in FIG. 3 at appropriate intervals.

These data are stored in the memory (RAM) of the control circuit 6 at a stable stage in each period between ToTI, TIT2, and T2T.

The apparatus of this embodiment is configured such that the data shown in the lower diagram of FIG. 3, which are the largest data values that are most easily used, are stored in the RAM, respectively. The control circuit 6 calculates the position of the coil 31 of the position indicator 3 in the drive lines X3, X4, and X5 in the X-axis direction using the data A1, data C, and data E among these data. Similarly, the position of the coil 31 in the Y-axis direction is calculated using data B, data C, and data D.

These calculated positions in the X-axis direction and Y-axis direction of the coil 31 are based on the drive line X3 and the sense line Y4, respectively. By adding and subtracting the respective positions, the coordinates of the center of the coil 31 of the position indicator 3 can be precisely determined.

At this time, the processor 61 of the control circuit 6 constantly monitors the frequency of the detected output voltage of the sense circuit 5, and also sets the human power state in advance according to the frequency of the output voltage. Defined by software. In this embodiment, when all the switches 33 of the position indicator 3 are off, the manually entered position coordinates are always displayed, for example, on the CRT screen of the host computer, so that the user of the device can see the position status. It is configured to perform an operation to recognize the Therefore, when the frequency of the detected output voltage of the sense circuit 5 matches the frequency between the periods τ and τ1 of the alternating current for the drive line shown in FIG. 4(a), all the switches of the position indicator 3 are turned off. Therefore, the device performs the operations described above. When the frequency of the output voltage of the sense circuit 5 matches the frequency of the alternating current during the period τ112 in FIG. 4(a), this indicates that the first switch 331 of the position indicator 3 is turned on. The device is the first
becomes the input state. Similarly, when the frequency of the output voltage of the sense circuit 5 matches the frequency of the alternating current during the period 1211 in FIG. When the frequency matches the frequency of the alternating current signal during the period τ3τ4, the third switch 333 is turned on, which is the third input state, and when the frequency matches the frequency of the alternating current during the period τ4τ5, the fourth switch 334 is turned on. The fourth input state is reached.

In this case, as described above, instead of momentarily changing the frequency of the drive current applied to the drive line in the position determination operation of the position indicator, first a series of position determination operations are performed using a drive current of the same frequency. The frequency of the alternating current applied to the drive line group may be changed for each position measurement operation, such as performing the next position determination operation at the same frequency different from this frequency.

In this case, the frequency of the detection voltage of the sense circuit 5 may be constantly monitored as described above, but since the frequency of the drive current of the drive circuit 2 in each measurement operation is known, In each measurement operation, the processor 61 of the control circuit 6 is set to the manual state for each measurement operation, so that the sense circuit 5 detects an induced voltage exceeding a predetermined level in each measurement operation, and the control circuit 6, the data may be treated as a predetermined input state.

When using the device, the user arbitrarily moves the position indicator 3 to position it at the coordinate position to be input, and also selects a desired input state from among a plurality of input states. Turn off all the switches, or turn on one of the switches.

Assume that the first switch 331 is now turned on. The tuning circuit of the position indicator 3 has a tuning frequency determined by the combined capacitance of the reference capacitor 320 and the first capacitor 321. This tuning frequency is set in advance so as to exactly match the frequency of the drive current during the periods τ and τ2 shown in FIG. 4(a). Therefore, the detected output voltage of the sense circuit 5 has a large amplitude when it matches this frequency (FIG. 4(C)). This output voltage is the third
After being converted into a digital value by the A/D converter 53 shown in the figure, it is input into the control circuit 6, its frequency is recognized by the processor 61, and this input data becomes the first input state.

When the second switch 332 is on, the output of the sense circuit 5 matches the frequency of the alternating current during the period 1213, as shown in FIG. Set to input state. Similarly, when the third switch is turned on or the fourth switch is turned on, the output voltage of the sense circuit 5 is changed as shown in FIG.
Since the periods τ3 and τ4 shown in a) match the frequencies of the drive currents shown in the periods τ and τ2 (see FIGS. 4(e) and 4(F)), the third input state and the fourth input state, respectively. is set to

〔Effect of the invention〕

As explained above, according to the present invention, the tuning frequency of the tuning circuit of the position indicator 3 is made variable according to the data input state of the position indicator, and the drive current for driving the drive line is controlled for a predetermined period of time. Since the frequency is configured to be variable at intervals, it is possible to provide a cordless tablet that is relatively simple and easy to use.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an apparatus according to one embodiment of the present invention, and FIG.
3 is a block diagram showing an example of the circuit configuration of the present invention, FIG. 4 is a timing diagram showing the relationship between drive current and detection voltage, and FIGS. 6th
The figure is a timing chart showing an example of a position determination operation of the device according to the embodiment of the present invention. 1: Drive line group 2: Drive circuit 3: Position indicator 4: Sense line group 5: Sense circuit 6: Control circuit Figure 2

Claims (2)

[Claims] (1) a plurality of drive line groups provided along a first direction; a drive circuit that selectively applies an alternating current whose frequency changes at predetermined time intervals to the drive line group; a position indicator that generates a magnetic field and has a tuning circuit that tunes to AC signals having respective frequencies of the AC current applied to the wire group; and a position indicator that is provided along a second direction that intersects with the first direction. ,
a plurality of sense line groups in which AC voltages whose frequency changes at predetermined time intervals according to the magnetic field of the position indicator are induced; a sense circuit that selectively extracts the AC voltage induced in the sense line groups; In addition to controlling the drive circuit and the sense circuit, the AC voltage value obtained by the sense circuit is calculated to determine the coordinate value of the position indicator, and the frequency of the AC voltage obtained by the sense circuit is determined. A cordless tablet that identifies the state or attribute of the position data of the position indicator. (2) The cordless tablet according to claim (1), wherein the drive circuit selectively applies an alternating current of a different frequency to the drive line group for each measurement period.