JPH07109574B2 - Position indicator status detection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for detecting the state of a position indicator in a coordinate input device.

(Prior Art) Conventionally, in a coordinate input device, a position indicator has been used as a method of detecting a use state (hereinafter, referred to as a pen-down state) of a position indicator that specifies only a coordinate position to be input on a tablet. A switch means is provided, the switch means is turned on (or off) only when the pen is down, and a timing signal based on the on (or off) of the switch means,
Some have been configured to send to a position detection circuit via a cord or using ultrasonic waves or infrared rays.

(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 deteriorates the operability of the position indicator, and the timing signal is generated using ultrasonic waves or infrared rays. However, in the case of a device that sends a position indicator, the position indicator itself must be provided with these transmitters, signal generation circuits, batteries, etc., which complicates the configuration and makes it large and heavy, which deteriorates the operability of the position indicator. There was a problem to do.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of detecting a usage state and a coordinate input position of a position pointing device without deteriorating its operability.

(Means for Solving Problems) In order to solve the above problems, the present invention detects a state of a position indicator that detects that the tip of a pen-type position indicator is pressed against a tablet of a coordinate input device. The pen-type position indicator includes a coil and a capacitor with a core whose inductance changes when the tip of the position indicator is pressed in the pen axis direction, A tuning circuit that emits a radio wave at almost the same frequency and with a change in phase is provided, and the radio wave generation means intermittently emits a radio wave of substantially the same frequency as the tuning frequency and stops the transmission of the radio wave. During a period of time during which the electric wave is detected, the electric wave is detected by the electric wave detecting means, and a change in the phase of the received electric wave with respect to the transmitted electric wave is detected. We propose a state detection method for a pointing device that detects the pressing of a target input device against a tablet.

(Operation) According to the present invention, when the tip of the position indicator is pressed against the tablet of the coordinate input device, the inductance of the coil having the core of the tuning circuit changes. The electric wave transmitted from the electric wave generating means and received by the tuning circuit changes its phase and is reflected. The reflected radio wave is received by the radio wave detecting means during the period when the transmission of the radio wave is stopped, thereby detecting that the tip of the position indicator is pressed against the tablet of the coordinate input device.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which 1 is a tablet, 2 is a position indicator (hereinafter referred to as an input pen), 3 is a position detection circuit, and 4 is timing. It is a control circuit.

The tablet 1 has a housing 11 made of synthetic resin and a tablet body.
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 body 12 constitutes a detection unit which is driven by the position detection circuit 3 to detect the coordinate input position designated by the input pen 2. The tablet body 12 is arranged in the substantially center of the housing 11. There is. The top panel 11 of the housing 11
A frame 14 drawn in a indicates the coordinate input range.

The tablet body 12 and the position detection circuit 3 are, for example, the "coordinate position detection device" of Japanese Patent Application No. 58-238532 filed by the applicant of the present application (see Japanese Patent Laid-Open No. 60-129616).
Alternatively, Japanese Patent Application No. 59-33083 discloses a "position detection device"
No. 0-176134) can be used. In the former case, a large number of magnetostrictive transmission media which are parallel to the surface of the tablet body 12 and orthogonal to each other are arranged, and magnetostrictive vibrations are propagated periodically from one end to the other end of the input pen 2. When is approached, the position detection circuit 3 detects the XY coordinates from the propagation time up to that location by utilizing the fact that the magnetostrictive vibration increases at that location by the bar magnet provided on this location. In the latter case, each magnetic substance arranged orthogonally is excited by an alternating current and the induced voltage is taken out by each detection coil, and when a similar input pen approaches, the magnetic permeability of the magnetic substance is locally changed and induced. XY coordinates are detected by utilizing the change in voltage.

The antenna coil 13 is configured by disposing a conductive wire coated with an insulating coating such as vinyl chloride around the coordinate input range of the tablet body 12, here, on the back surface of the top panel 11a of the casing 11 around the frame 14. It is a thing. It should be noted that the illustrated example has one turn, but it may have a plurality of turns if necessary.

The input pen 2 is a magnetic generator for specifying a position, for example, a bar magnet.
21 and a tuning circuit 22 including a coil, a capacitor, and a resistor.

FIG. 2 shows a detailed structure of the input pen 2. A core body 24 such as a ballpoint pen and the core body 24 are slidably housed inside a pen shaft 23 made of a non-metallic material such as synthetic resin. A tuning circuit 22 including a bar magnet 21 having a through hole, a coil spring 25, a coil 222 containing a core 221, such as a ferrite core, a capacitor 223, and a variable capacitor 224 for fine adjustment is integrally combined. Built in, with a cap 26 at the rear end
Is installed.

The core 221 pushes the core body 24 into the pen shaft 23, for example, by pressing the tip of the core body 24 against the tablet surface,
The rear end moves against the coil spring 25,
The electromagnetic coupling with 222 is changed, and as will be described later, the usage state of the input pen 2 is identified based on the change in the electromagnetic coupling. As shown in FIG. 3, the capacitor 223 and the variable capacitor 224 are connected in parallel with each other, and the ends of the coil 222 are connected to the ends thereof,
The parallel resonant circuit 22 is configured.

Note that the resonance circuit 22 resonates (tunes) to the frequency of the radio wave transmitted from the antenna coil 13, so that the variable capacitor 224
It is adjusted and set by. The resonance circuit 22 has a core 221.
Selectivity Q = R / (ω0L) due to changes in the electromagnetic coupling between the coil 222 and the coil 222 and changes in its inductance.
(However, ω0 is the resonance angular velocity, R is the resistance value of the resonance circuit, and L is the inductance), and a phase shift occurs. At the same time, the resonance frequency also changes, but resonance is possible.

FIG. 3 shows a detailed configuration of the timing control circuit 4, in which 401 is an oscillator (OSC), 402 is a frequency dividing counter, and 4
03,404 is a NAND gate, 405 is a transmission terminal, 406 is a reception terminal, 407,408 is a reception switch, 409,410,4111 is an amplifier, 412 is a filter, 413 is a phase detector (PSD), 414 is a low-pass filter (LPF) 415 is a comparator. , 416 are output terminals.

FIG. 4 is a signal waveform diagram in each part of FIG. The operation will be described in detail below.

A clock pulse of, for example, 910 KHz generated from the oscillator 401 is divided into 1/2 and 1/32 by the frequency division counter 402.
One input terminal of the NAND gate 403 receives the pulse signal A of 455KHz divided by 1/2, and the other input terminal of the pulse signal of 28.44KHz divided by 1/32 (pulse width 1
7.6 μs) is input and the output is further NAND gate 4
It is sent to 04 and, as shown in FIG. 4, 45 every 17.6 μs.
It becomes the signal B that outputs or does not output the 5 KHz pulse signal.

The signal B is transmitted to the antenna coil 13 via the transmission terminal 405 and further transmitted as a radio wave. The tuning circuit 22
Resonates with the incoming radio waves. Since the circuit continues to resonate while being attenuated while the transmission on the transmission side is stopped, a signal C as shown in FIG. 4 is generated, and the signal C is transmitted as a radio wave from the coil 222 and the antenna Received by the coil 13.

Since the reception changeover switches 407 and 408 are changed over every 17.6 μs by the 28.44 KHz pulse signal, the signal from the reception terminal 406 is taken in only during the transmission stop period, and the fourth
It becomes the signal D shown in the figure. The received signal D is sent to the amplifiers 409 and 41.
It is amplified by 0 and becomes the signal E, and the resonance frequency is 455.
A noise component is removed through the KHz mechanical filter 412, and is sent to the phase detector 413 through the amplifier 411. The amplifier 410 has an automatic level control function to make the signal E have a constant amplitude.

The pulse signal A of 455 KHz is input to the phase detector 413. At this time, if the phase of the received signal E and the phase of the pulse signal A match, as shown in FIG. , And outputs a signal F obtained by folding back the received signal E. However, the present invention deals with the phase change characteristics of the signal A and the signal E.

The signal F is converted into a flat signal by the low-pass filter 414 having a sufficiently low cutoff frequency and input to the comparator 415.

Here, as an input of the phase detector 413, the frequency division counter 402
If the signal obtained by dividing the frequency by 1/2 is eR, refer to FIG. 5 (A). Since this is a square wave with an amplitude of 1, assuming that its angular velocity is ωR, eR = (4 / π) {sinωRt + (1/3) sin3ωRt + (1/5) sin5ωRt + ...} (1) The signal from the amplifier 411 is defined as ei, which is the maximum value Es, the synchronous component eS of the angular velocity ωS, and the maximum value Es.
Assuming that N and the asynchronous component eN which is the noise of the angular velocity ωN, the angular velocity ωS = ωR, then ei = eS + eN = ESsinωRt + ENsinωNt (2).

In this embodiment, when the input pen 2 is pressed against the tablet surface, the signals eR and eS are in phase, and when the signals eR and eS are in phase, the output of the phase detector 413 is changed. Let eO (signal F in FIGS. 3 and 4) be eO = eR × ei = (4 / π) {ESsinωRt} {sinωRt + (1/3) sin3ωRt + ……} + (4 / π) {ENsinωNt} {sinωRt + (1/3) sin3ωRt + ......} = (4 / π) ES {sin 2 ωRt + (1/3) sinωRt · sin3ωRt + ......} + (4 / π) EN {sinωNt · sinωRt + (1 / 3) sinωNt ・ sin3ωRt ＋ ……} (3). Here, since the DC component is included only in sin ωRt of the first term of the equation (3) and the other components are AC components, attention is paid only to the DC component as the output of the low-pass filter 414 in the next stage. Is the DC output ▲ ▼, sin ² ωRt ＝ (1
From (/) {1-cos2ωRt}, ▲ ▼ = (2 / π) ES ...... (4) Expression (4) is the average value of the signal eO in FIG. 5 (A), and the signal eO is input to one input terminal of the comparator 415.

Next, by separating the input pen 2 from the tablet surface, the inductance of the coil 222 changes, and the signals eR and e
When a phase difference φ occurs between S and S, the first term of the equation (3) is changed to e'O.
Then, e′O = (4 / π) ES {sin (ωRt−φ) sinωRt} = (4 / π) ES (1/2) {cosφ−cos (2ωRt + φ)} (5) Since the second term of the equation (5) is the AC component, the DC output ▲ ▼ becomes ▲ ▼ = (2 / π) EScosφ …… (6), and assuming φ = 180 °, ▲ ▼ =-(2 / π) ES. The equation (6) is the average value of the signal eO in FIG. 5 (c), and the signal ▲ ▼ is input to one input terminal of the comparator 415. In this way, the signal ▲ ▼
Is a signal with reference to FIGS. 5 (A) (B) (C) (D).
The maximum is when the phase difference φ = 0 between eR and eS and the minimum is the case when φ = 180 °, and a value between them is taken according to the change of the phase difference φ.

In this embodiment, the phase difference φ is changed by about 180 ° due to the change in the inductance of the coil 222 by separating the input pen 2 from the tablet surface.
The comparator 415 surely discriminates between a state where the phase difference φ = 0 when the input pen 2 is pressed against the tablet surface and a state other than φ = 0 when the input pen 2 is released. A predetermined threshold voltage + VT is input in advance to the other input terminal of the comparator 415, and the low pass filter 4
The output of 14 is compared with the threshold voltage VT, and the signal G at the output terminal 416 of the comparator 415 becomes high (H) level when the phase difference φ = 0, and when the phase difference φ changes, for example, by several tens of degrees, it becomes low (L). ) It becomes a level.

In the case of the signal D ', both the signals E and F are at "0" level, and the signal G is also at low (L) level. Therefore, the use state of the input pen 2 is identified without contact.

When the signal G is at high level, it is in the pen-down state,
When it is defined that the pen is not in the pen-down state at the low level and the signal G is sent to the position detection circuit 3, the input pen 2 is operated on the tablet 1 and the position of the input pen 2 at the position where the coordinate input is desired. The coordinates can be input only by pressing the tip on the tablet 1.

In the present embodiment, the inductance of the coil 222 is changed by moving the core 221 in accordance with the movement of the core body 24. However, the core 221 remains fixed and the bar magnet 21 is set in the same manner. It may be moved and moved closer to or away from the core 221 to change it.

(Effect of the invention) As described above, according to the present invention, a code is not required between the position indicator and other circuits, and it is only necessary to provide a tuning circuit including a coil and a capacitor.
It eliminates the need for complicated signal generation circuits and batteries, etc. as in the past, and it can detect the pressing of the tip of the position indicator against the tablet of the coordinate input device without contact, so it is possible to detect the state with extremely good operability. You can do it.

[Brief description of drawings]

FIG. 1 is a perspective view of a position indicator showing an embodiment of the present invention, FIG. 2 is a sectional view of an input pen, FIG. 3 is a block diagram of a timing control circuit, and FIG. 4 is a waveform of each part of FIG. 5 and 5 are waveform charts for explaining the operation of the phase detector shown in FIG. 1 ... Tablet, 2 ... Input pen (position indicator), 3
...... Position detection circuit, 4 …… Timing control circuit, 13 ……
Antenna coil, 14 ... coordinate input range, 22 ... tuning circuit, 221 ... core, 222 ... coil.

Claims (3)

[Claims] 1. A position indicator state detection system for detecting that the tip of a pen-type position indicator is pressed against a tablet of a coordinate input device, wherein the position indicator is a pen-type position indicator. Includes a coil with a core and a capacitor whose inductance changes when the tip of the head is pressed in the pen axis direction, and a radio wave which responds to an external signal at substantially the same frequency and with a phase change due to the change in the inductance. A radio wave generating means intermittently emits a radio wave having substantially the same frequency as the tuning frequency, and the radio wave detecting means receives the radio wave during a period in which the transmission of the radio wave is stopped, It is characterized in that the change in the phase of the received radio wave with respect to the transmitted radio wave is detected, and the pressing of the tip of the position indicator to the tablet of the coordinate input device is detected from the detection result. Position indicator state detection method to be. 2. The state detecting method of the position pointing device according to claim 1, wherein the generation of the radio wave and the detection of the radio wave are alternately performed by the same coil. 3. An antenna coil provided around a coordinate input range of a tablet of a coordinate input device is used as a coil for generating and detecting a radio wave. State detection method of the position indicator of.