JPS63257823A - Status identification system for position indicator - Google Patents

Abstract

PURPOSE:To improve the operability of a position indicator and to identify status by allowing an antenna coil to radiate a radio wave, allowing it to receive a reflected radio wave from a tuning circuit of the position indicator when the radio wave radiation is stopped and detecting the loss from the attenuation. CONSTITUTION:An antenna coil 13 fitted to a main body 12 of a tablet 1 receives an AC signal of a prescribed frequency and radiates a radio wave. The radio wave is received by a tuning circuit 22 of an input pen 2 and the circuit 22 generates the induced voltage of nearly the same frequency as that of the signal fed to the oil 13. The voltage is attenuated gradually from the loss in the circuit 22 when the radio wave radiation is stopped from the coil 13, but the reflected ratio wave is radiated from the coil in the circuit 22 based on the current flowing to the circuit 22 in this case. The reflected radio wave is received by the coil 13 stopping the radiation of the radio wave and the induced voltage generated in the coil 13 shown the same attenuation as that of that of the induced voltage in the circuit 22. Thus, the loss in the tuning circuit is detected and the status of the position indicator is identified.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is suitable for identifying the state of a position indicator in a coordinate input device, particularly the state of a position indicator that has specified a coordinate position to be input. It is related to the method.

(Prior Art) Conventionally, in a coordinate input device, as a method for identifying the state of a position indicator that specifies the coordinate position to be input on a tablet (hereinafter referred to as a pen-down state), a switch means is attached to the position indicator. The switch means is turned on (or turned off) only when the pen is down, and the switch means is turned on (or turned off) only when the pen is down.
or off) based on the timing signal through the code,
Alternatively, some were configured to use ultrasonic waves or infrared rays to send to a position detection circuit.

(Problems to be Solved by the Invention) However, in the case where a timing signal is sent from a position indicator using a code, the code impairs the operability of the position indicator. In the case of a position indicator that transmits signals, it is necessary to install these transmitters, signal generation circuits, batteries, etc. in the position indicator itself, making the configuration complicated, large and heavy, and the battery must be replaced and charged frequently. However, there was a problem in that these deteriorated the operability of the position indicator.

An object of the present invention is to provide a method that can identify the state of a position indicator without reducing its operability.

(Means for Solving the Problem) In order to solve the above problem, the present invention includes a tablet constituting a coordinate input section, a position indicator such as a stylus pen, and a coordinate input device that drives the tablet and uses the position indicator. In a coordinate input device equipped with a position detection circuit that detects a position, an antenna coil is provided around the coordinate input range of the tablet, the position indicator includes a coil and a capacitor, a predetermined frequency is set as a tuning frequency, and an internal a tuning circuit capable of changing the loss of the antenna is provided, and an alternating current signal of a predetermined frequency is applied to the antenna coil to transmit radio waves;
When the transmission of the radio waves is stopped, the radio waves reflected from the tuning circuit of the position indicator are received by an antenna coil, the loss in the tuning circuit is detected from the attenuation of the reflected signal, and the state of the position indicator is detected. I tried to identify it.

(Function) According to the present invention, the radio waves emitted from the antenna coil are received by the tuning circuit of the position indicator, and at this time, the tuning circuit of the position indicator has a signal approximately equal to the signal applied to the antenna coil. An induced voltage of the same frequency is generated. When the transmission of radio waves from the antenna coil stops, the induced voltage gradually attenuates due to internal loss in the tuned circuit, but at this time, reflected radio waves are transmitted from the coil in the tuned circuit based on the current flowing in the tuned circuit. Ru. The reflected radio wave is received by the antenna coil that has stopped transmitting the radio wave, but at this time, the induced voltage generated on the antenna coil side exhibits the same attenuation as the induced voltage in the tuned circuit, and from this, the induced voltage in the tuned circuit shows the same attenuation as the induced voltage in the tuned circuit. A loss is detected and the position indicator condition is identified.

(Example) Fig. 1 shows an outline of a coordinate input device implementing the method of the present invention, in which 1 is a tablet, 2 is a position indicator (hereinafter referred to as an input pen), and 3 is a position detection device. The circuit 4 is a timing control circuit.

The tablet 1 has a tablet main body 12 and an antenna coil 13 attached to a non-magnetic metal casing 11.
The tablet main body 12 is connected to the position detection circuit 3, and the antenna coil 13 is connected to the timing control circuit 4.

The tablet main body 12 is driven by the position detection circuit 3 and constitutes a detection section that detects the position specified by the input pen 2. The tablet main body 12 is housed approximately in the center of the housing 11. In addition, the top panel ll of the housing 11
A frame 14 drawn in a indicates the coordinate input range.

The tablet main body 12 and the position detection circuit 3 are disclosed in, for example, Japanese Patent Application No. 59-32244 filed by the present applicant.
``Position detection device'' in Japanese Patent Application No. 176133/1980 (see Japanese Patent Application Laid-open No. 1987-176133) or ``Coordinate Position Detection Device'' in Japanese Patent Application No. 58-238532 (see Japanese Patent Application Laid-Open No. 80-129616) can be used. .

The antenna coil 13 is formed by disposing an insulated conductor on the coordinate input range of the tablet body 12, that is, on the surface of the top panel lla of the housing 11 around the frame 14. Although the coil is shown as one turn in the drawing, it actually consists of several turns.

The input pen 2 has a built-in magnetic generator for specifying a position, for example, a bar magnet 21 and a tuning circuit 22.

FIG. 2 shows the detailed structure of the input pen 2, in which a core 24 of a ballpoint pen or the like is slid into the interior of a pen shaft 23 made of a non-metallic material such as synthetic resin from near the tip. A bar magnet 21 with a through hole that can be accommodated in a movable manner, a coil spring 25, and a switch 221. Coil with core 222.
Tuning circuit 22 consisting of a capacitor 223 and a resistor 224
are integrally combined and built-in, and a cap 26 is attached to the rear end.

FIG. 3 shows the detailed configuration of the tuning circuit 22 and timing control circuit 4 of the input vent 2.

As shown in FIG. 3, the tuning circuit 22 has a capacitor 223 connected in series to one end of a coil 222, and two selection terminals of a switch 221 connected directly and via a resistor 224 to the other end of the capacitor 223. Furthermore, the other end of the coil 222 is connected to the selection contact of the switch 221.

The switch 221 is in an unoperated state (non-operating state)
In this case, the other end of the coil 222 and the other end of the capacitor 223 are directly connected as shown by the solid line, and the pen shaft 23 is held by hand, etc., and the tip of the core body 24 is pressed against the tablet surface, etc. When it is pushed into the pen barrel 23 by the rear end, it is pressed through the coil spring 25 and becomes operational, and the other end of the coil 222 and the other end of the capacitor 223 are connected through the resistor 224 as shown by the broken line. It's like that. In addition, the coil 222 and the capacitor 22
The numerical value 3 is set to a value constituting a well-known resonant circuit that resonates at a predetermined frequency fO.

Further, in FIG. 3, 401 is a control circuit, 402 is a timing circuit, 403 is a drive circuit, 404 is a transmission/reception switching circuit, 405 is an amplifier, 406 is a reception timing switching circuit, 407 is a bandpass filter (B P F), 408 is a wave detector, and 409 is a low pass filter (LPF).

4(a) and 4(b) are signal waveform diagrams at each part of FIG. 3. The operation will be explained in detail below.

The control circuit 401 is composed of a well-known microprocessor, etc., and controls the timing circuit 4D2 and converts the output value from the low-pass filter 409 into an analog/digital (A
/D) Convert, perform the calculation processing described below, and input Ben 2
, and sends it to the position detection circuit 3.

A timing circuit 402 generates a rectangular wave signal A1 with a predetermined frequency fO, a transmission/reception switching signal B with a predetermined frequency fk, and reception timing signals C1, C2, and C3. The rectangular wave signal A is converted into a sine wave signal by a low-pass filter (not shown) and sent to the drive circuit 403, and the transmission/reception switching signal B
are sent to the transmission/reception switching circuit 404, and furthermore, based on the control of the control circuit 401, the reception timing signals C1,
One of C2 and C3 is sent to the reception timing switching circuit 406.

The sine wave signal sent to the drive circuit 403 is converted into a balanced signal and further sent to the transmission/reception switching circuit 404, which selects either the driving circuit 403 or the amplifier 405 based on the transmission/reception switching signal B. In order to alternately connect one side to the antenna coil 13, the antenna coil 1
3 is input with a signal that outputs or does not output a sine wave signal of frequency fO every time T (-1/2fk), and the signal is transmitted from the antenna coil 13 as a radio wave.

At this time, within the coordinate input range 14 of the tablet 1,
When the input vent 2 is held in a substantially upright state, that is, in use, the radio wave excites the coil 222 of the input vent 2,
The tuned circuit 22 generates an induced voltage E synchronized with the signal.

After that, the antenna coil 13 is switched by the transmission/reception switching circuit 404.
When the signal is switched to the amplifier 405 side, that is, when the reception period begins, the radio wave from the antenna coil 13 immediately disappears, but the induced voltage E gradually attenuates in accordance with the loss within the tuning circuit 22.

On the other hand, the current flowing through the tuned circuit 22 based on the induced voltage E causes the coil 222 to emit radio waves. Since the radio waves reversely excite the antenna coil 13, an induced voltage is generated in the antenna coil 13 due to the radio waves from the coil 222. The induced voltage is sent from the transmission/reception switching circuit 404 to the amplifier 405 only during the reception period, is amplified, becomes a reception signal F, and is further sent to the reception timing switching circuit 406.

The reception timing switching circuit 406 is for controlling which part of the reception signal F is output to the following bandpass filter 407, and during the period when the reception timing signal C1, C2, or C3 is at a high (H) level, the reception timing signal is F, and nothing is output during the low (L) level period.

The reception timing signal C1 is for extracting a signal corresponding to the entire period of the reception signal F, and is substantially an inverted signal of the transmission/reception switching signal B. Further, the reception timing signal C2 is a predetermined period at the beginning of the reception signal F, for example, t (-
The received signal C3 is used to extract a signal corresponding to the last predetermined period t of the received signal F.

Here, when the reception timing signal C1 is input manually to the reception timing switching circuit 406, the signal G1 is obtained as an output.

The signal G1 is sent to a bandpass filter 407, which is a filter having a pass band centered at the frequency fO, and the frequency fO in the signal G1.
A signal H1 (
Strictly speaking, several signals G1 are input to the bandpass filter 407 and output in a converged state).

The signal H1 is inputted to a detector 408, detected and rectified, and used as a signal generator 1. The signal H1 is then passed through a low-pass filter 409 with a sufficiently low cutoff frequency to obtain a voltage value corresponding to approximately 1/2 of 11 for the amplitude. It is converted into a DC signal Jl having C1 and sent to the control circuit 401.

Further, when the reception timing signal C2 is input to the reception timing switching circuit 406, the signal G2 is obtained at its output, and at this time, the output of the bandpass filter 407 is a signal H2 (strictly speaking, the number ) is obtained when the signals G2 are input to the bandpass filter 407 and converged. Furthermore, when the reception timing signal C3 is input to the reception timing switching circuit 406, the signal G3 is obtained at its output, and at this time, the signal H3 (strictly speaking, several signals G3
is input to the bandpass filter 407 and in a converged state) is obtained.

These signals H2, H3 are detected and rectified by the detector 408 as described above, and the signals I2. I3, the low-pass filter 409 converts the amplitude h2. Voltage values V G2.corresponding to approximately 1/2 of h3, respectively. DC signal J with V G3
2. J3 and sent to the control circuit 401.

The received signal F gradually attenuates as described above, but the voltage value Vc2 is proportional to the energy within the first predetermined period of the received signal F, and the voltage value Vc3 is proportional to the energy within the last predetermined period of the received signal F. Since it is proportional to the energy within, the ratio between the voltage values Ve2 and Vc3 represents the degree of attenuation of the received signal F.

Therefore, in the control circuit 401, the voltage value Vc2 obtained when the reception timing signal C2 is inputted to the reception timing switching circuit 406 and the voltage value Vc3 obtained when the signal C3 is inputted to the circuit 40B are converted into digital values, By calculating these ratios, the degree of attenuation of the received signal F can be obtained.

Here, in the input pen 2, the loss in the tuning circuit 22 differs by the amount of the resistor 224 between the non-operating state and the operating state of the switch 221, so the degree of attenuation of the received signal F is lower in the operating state than in the non-operating state. is larger, and the degree of attenuation will hardly change unless the ambient temperature etc. change significantly.

Therefore, in the control circuit 401, the attenuation degree of the received signal F corresponding to each of the non-operating state and the operating state of the switch 221 of the input pen 2 is stored in advance, and the calculation of the attenuation degree is repeated while the device is in use. By executing and comparing these, it is determined whether the switch 221 of the input pen 2 is in an inactive state or an active state.

Further, in the control circuit 401, the non-operating state of the switch 221 is defined as a coordinate value detection period, the operating state is defined as a pen-down state, and these pieces of information are transmitted to the position detection circuit 3.
If the input pen 2 is held in an upright position over the coordinate input range 14 of the tablet 1, the tablet 1 and the position detection circuit 3 can detect the position. The position can be input simply by pressing the tip of the input pen 2 against the tablet 1 at the desired position and activating the switch 221.

In the tuning circuit 22, instead of the switch 221 and the resistor 224, for example, by connecting in series with the coil 222 and the capacitor 223 something whose resistance value changes based on the operation of the input pen 2, It is also possible to change the loss continuously, and it is also possible to transmit continuous information, such as the thickness of lines when manually drawing characters or figures.

(Effects of the Invention) As explained above, according to the present invention, the position indicator is provided with a tuning circuit having a predetermined tuning frequency and whose internal loss can be changed, and arranged around the coordinate input range. A radio wave of the tuned frequency is transmitted and received from the antenna coil provided, and the degree of attenuation of the signal reflected from the tuned circuit is detected to identify the state of the tuned circuit, that is, the position indicator, close to the antenna coil. Therefore, not only is there no need for a cord between the position indicator and other circuits, but only a tuning circuit including a coil and a capacitor is required, eliminating the need for complex signal generation circuits, batteries, etc. This has advantages such as being unnecessary, providing a position indicator with extremely good operability, and being able to accurately identify its state.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an outline of a coordinate input device to which the method of the present invention is applied, FIG. 2 is a sectional view of a human-powered pen, FIG. 3 is a detailed configuration diagram of a tuning circuit and a timing control circuit, and FIG. a
) (b) is a signal waveform diagram of each part in FIG. 3. DESCRIPTION OF SYMBOLS 1... Tablet, 2... Input pen, 3... Position detection circuit, 4... Timing control circuit, 13... Antenna coil, 14... Coordinate input range, 22... Tuning circuit .

Claims (1)

[Scope of Claims] A coordinate input device comprising a tablet constituting a coordinate input section, a position indicator such as a stylus pen, and a position detection circuit that drives the tablet and detects a coordinate input position by the position indicator. , an antenna coil is provided around the coordinate input range of the tablet, and a tuning circuit is provided in the position indicator that includes a coil and a capacitor, has a predetermined frequency as a tuning frequency, and is capable of changing internal loss; An alternating current signal of a predetermined frequency is applied to the coil to transmit a radio wave, and when the transmission of the radio wave is stopped, the antenna coil receives the radio wave reflected from the tuning circuit of the position indicator, and the attenuation of the reflected signal is A method for identifying the state of a position pointing device, characterized in that the state of the position pointing device is identified by detecting a loss in the tuning circuit.