JPH0675034U - Cordless digitizer - Google Patents

Abstract

(57) [Abstract] [Purpose] Not only xy coordinate detection but also z direction position (height)
We provide a cordless digitizer that can detect position. [Structure] The frequency of the output signal is changed in accordance with the height change of the position indicator, and the height of the position indicator is detected based on the frequency of the output signal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cordless digitizer that does not have a connecting cable between a tablet and a pointing device.

[0002]

[Prior art]

 There are various conventional techniques for this type of cordless digitizer. Here, the configuration and operation of the example will be described with reference to FIGS. Although FIG. 1 also shows an apparatus according to an embodiment of the present invention, only the prior art will be described here. As shown in FIG. 1, on the tablet, a transmitter coil group 2 composed of X side loop coil groups X1, X2, X3, ... Arranged sequentially in the X direction, and a sequential arrangement in the Y direction. A receiving coil group 1 including Y-side loop coil groups Y1, Y2, Y3, ... Is provided. Each X side loop coil group of the transmitting coil group 2 is connected to the X direction selection circuit 32 of the drive circuit 3 controlled by the control circuit 5, and each Y side loop coil group of the receiving coil group 1 is controlled by the control circuit 5. Each of them is connected to the Y direction selection circuit 42 of the sense circuit 4 to be controlled. The X-direction selection circuit 32 selects one of the X-side loop coils at each measurement timing based on an X-address signal (not shown) from the control circuit 15 and connects it to the transmission circuit 31. A signal whose frequency changes with a predetermined repetition period is generated from the transmission circuit 31, and a signal whose frequency changes at a predetermined time interval is sequentially supplied to each X-side loop coil. . In this state, if the position indicator 6 is placed close to the transmitter coil of the tablet to which the above-mentioned signal is supplied, the position indicator 6 is magnetically coupled with the transmitter coil, and A magnetic field matching the frequency of the above signal is generated from the coil 61 of the position indicator 6. Since this magnetic field is generated toward the tablet, it causes the reception coil group 1 to generate a predetermined signal. In the sense circuit 4, the Y-direction selection circuit 42 switches and connects the receiving coil groups 1 one after another to take out the signal, and the receiving circuit 41 measures the signal.

The position indicator 6 includes a coil 61 and a reference capacitor c0, a first capacitor c1 and a first switch s1, a second capacitor c2 and a second switch s2, a third capacitor c3 and a third capacitor c3. It is composed of a switch s3, a fourth capacitor c4 and a fourth switch s4. In the following, each pair of these capacitors and switches will be simply referred to as a switch pair in this specification. The reference capacitor c0 is a capacitor that forms an LC resonance circuit with the coil 61. The first switch pair (the first capacitor c1 and the switch s1) to the fourth switch pair are respectively connected in parallel to the LC resonance circuit and are used to identify the on / off operation of each switch. It

As shown in FIG. 2, in this device, the X-direction selection circuit 32 sequentially connects the X-side loop coils x1, x2, x3, ... A signal whose frequency changes in a repetition cycle of is supplied. When the X-direction selection circuit 32 selects any X-side loop coil, the Y-direction selection circuit 42 operates to sequentially receive the Y-side loop coils y1, y2, y3, ... Connect to the input side of. In this device, one timing when the Y-direction selection circuit 42 selects each Y-side loop coil is one measurement timing.

Then, at each measurement timing, the control circuit 15 fetches the output of the sense circuit 41 and performs the processing shown in FIG. FIG. 3 is a schematic diagram showing one method for determining the pointing position of the position pointing device 2 on the tablet, which is one of the processes of the control circuit 15. As shown in FIG. 2, when the X-direction selection circuit 32 selects the loop coil x1 and the Y-direction selection circuit 42 selects each Y-side loop coil, each output level of the reception circuit 41 (FIG. 3), Each output level of the receiving circuit 41 when the X-direction selection circuit 32 selects the loop coil x2 and the Y-direction selection circuit 42 selects each Y-side loop coil (FIG. 3), the X-direction selection circuit 32 loops. The output level of the receiving circuit 41 when the coil x3 is selected and the Y-direction selecting circuit 42 selects each Y-side loop coil (FIG. 3), ... The control circuit 15 determines the pointing position of the position pointing device 2 on the tablet by using the output level of the above as data. The data taken into the control circuit 15 has a frequency component corresponding to the on / off state of the switch of the position indicator 6. That is, the load of the position indicator 6 is changed when any switch of the position indicator 6 is turned on or not turned on. Therefore, of the signals of which the frequency with respect to the oscillation coil 2 is changed by the drive circuit 3, the position indicator 6 acts only on the frequency signal that matches its own resonance frequency to selectively generate a magnetic field. Therefore, the signal measured by the sense circuit 4 has a frequency indicating the switch operating state of the position indicator 6.

[0006]

[Problems to be solved by the device]

 By the way, in the above-mentioned device, it was possible to detect the xy coordinate position on the tablet plate surface, but it was difficult to detect the upper height position of the position indicator 6 on the tablet plate surface, that is, the z position. . This is because when the height of the position indicator 6 is detected in this type of cordless digitizer, the detection is generally performed at the level of the output signal. Since the receiving coil group 1 of the tablet of the above device and the coil 61 of the position indicator 6 are magnetically coupled, the distance becomes significantly smaller as the distance (height of the position indicator) increases. Therefore, the signal level in that case also becomes extremely small. Therefore, in such level detection, the height that can be detected is extremely small. The present invention has been made to improve this point, and provides a cordless digitizer capable of detecting a wide range of the z-direction position in addition to the xy coordinate position with respect to the tablet of the position indicator 6. is there.

[0007]

[Means for Solving the Problems]

 Therefore, in this invention, an electric field or a magnetic field is generated from the pointing device toward the conductor provided on the tablet, and the pointing position on the tablet of the pointing device is based on the signal generated in the conductor of the tablet by electromagnetic coupling. In a cordless digitizer configured to detect coordinates, etc., an electromagnetic shielding plate is provided below the conductor of the tablet, and the frequency of the output signal generated in the conductor of the tablet by the electric field or magnetic field generated by the position indicator is detected. A frequency detecting means for detecting is provided, and the height variation of the position indicator with respect to the electromagnetic shielding plate is configured to appear as a frequency variation of the output signal, and the position indicator of the position indicator is output based on the output of the frequency detecting means. It is configured to detect the height with respect to the electromagnetic shielding plate.

[0008]

[Action]

 By providing the electromagnetic shielding plate, it is possible to reduce the attenuation of the output signal with respect to the distance (height) of the position indicator 6 from the tablet. Further, the height fluctuation of the coil 61 of the position indicator 6 with respect to the electromagnetic shield plate appears as a frequency change of the reception signal of the sense circuit 4. It is considered that this is because the stray capacitance between the coil 61 and the electromagnetic shield changes. Since the frequency can be detected even when the signal is relatively small, the height detection region can be expanded also by this.

[0009]

【Example】

 The device of the embodiment of the present invention will be described below. FIG. 4 is a schematic diagram of a cordless digitizer according to the present invention. The receiving coil 1 and the transmitting coil 2 of the tablet are controlled by the control circuit 5. These receiving coil 1 and transmitting coil 2 are arranged close to an electromagnetic shield plate 7 made of a silicon steel plate or the like. When the coil 61 of the position indicator 6 and the transmitting coil of the tablet are magnetically coupled, a predetermined magnetic field is generated from the coil 61 of the position indicator 6. It is considered that when the position indicator 6 moves up and down with respect to the electromagnetic shield plate 7, the stray capacitance between the coil 61 of the position indicator 6 and the electromagnetic shield plate 7 changes. The frequency of the magnetic field generated by the coil 61 also changes depending on its height. As described above, according to the present invention, the height of the position indicator 6 is detected by the frequency of the signal, so that there is an advantage that the height can be measured even when the signal level is relatively small.

FIG. 1 shows an overall electrical configuration of an apparatus according to an embodiment of the present invention. The difference from the above-mentioned conventional device is that the height calculating means of the position indicator 6 is provided in the control circuit 15. The height calculating means is composed of a waveform converter 412, a reference signal generator 413, an AND circuit 414 and a counter 415. The signal generated in the receiving coil 1 selected by the Y-direction selection circuit 42 is input to both the A / D converter 411 and the waveform converter 412. The A / D converter 411 is one component of the XY coordinate detecting means. As shown in FIG. 5, the waveform converter 412 converts the input signal into a rectangular wave with a threshold value of "0" (detection signal in FIG. 5). Then, the AND circuit 414 creates a combined signal with the reference signal. This synthesized signal becomes a signal corresponding to the cycle of this oscillation system. The combined signal is counted by the counter 415 and the counting result is sent to the control circuit 5. The control circuit 5 detects the frequency from this count value. Then, referring to a “frequency-height table” stored in advance in a memory (not shown), the height corresponding to the detected frequency is output. FIG. 6 is an explanatory diagram showing the frequency-height relationship in the device of this embodiment. The frequency f0 to f1 is a state in which all the switches of the position indicator 6 shown in FIG. 1 are turned off, the frequency f1 to f2 is a state in which the first switch s1 is turned on, and the frequency f2 to f3 is a second switch. s2, the frequencies f3 to f4 turn on the third switch s3, and the frequencies f4 to f5 turn on the fourth switch s4. By detecting the frequency of the output signal of the sense circuit 4, it is possible to detect which switch is pressed and the height of the position indicator 6. The drive circuit 3 of FIG. 1 sequentially supplies signals having the boundary frequencies f0, f1, f2, f3, f4 or f5 shown in FIG. 6 to the selected oscillation coil at a predetermined repetition period. is doing.

In the above description, the position indicator generates a predetermined magnetic field by supplying a signal of a predetermined frequency to the transmitting coil, and this magnetic field causes a predetermined signal to be generated in the receiving coil of the tablet. The cordless digitizer of the above is mentioned, but the invention is not limited to this. For example, even if the position indicator itself can generate magnetic fields of a plurality of predetermined frequencies by the power of a battery or the like, its frequency fluctuates according to the height of the position indicator due to the action with the electromagnetic shield plate. As long as it is one, it can be implemented.

[0012]

[Effect of device]

 As described above, according to the present invention, the electromagnetic shield plate is provided close to the loop coil group of the tablet, and the height of the position indicator is detected by the frequency of the output signal of the loop coil group. The advantage is that the height detection area can be expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the measurement timing of FIG. 1 and the conventional device.

FIG. 3 is an explanatory diagram schematically showing the coordinate determination operation of FIG. 1 and the conventional device.

FIG. 4 is a schematic diagram showing a configuration of a main part of the present invention.

FIG. 5 is a timing chart for explaining the operation of the frequency detecting means according to the present invention.

FIG. 6 is a frequency chart of an apparatus according to an embodiment of the present invention.
It is explanatory drawing which shows a height relationship.

[Explanation of symbols]

 1: Tablet 2: Position indicator

Claims (1)

[Scope of utility model registration request] 1. An electric field or a magnetic field is generated from a pointing device toward a conductor provided on a tablet, and based on a signal generated in a conductor of the tablet by electromagnetic coupling, coordinates of a pointing position on the tablet of the pointing device are calculated. In a cordless digitizer configured to detect, a frequency detecting means is provided below the conductor of the tablet, and a frequency detecting means for detecting the frequency of an output signal generated in the conductor of the tablet by the electric field or magnetic field generated by the position indicator. And the height variation of the position indicator with respect to the electromagnetic shield is expressed as a frequency variation of the output signal, and the height of the position indicator with respect to the electromagnetic shield is based on the output of the frequency detecting means. A cordless digitizer characterized by being configured to detect.