JPH0619609A - Coordinate reading device - Google Patents

Abstract

PURPOSE:To prevent the erroneous detection of a switch caused by the phase change due to the environmental temperature variation and also to stably detect many switch states with a coordinate reading device which detects the switch states based on the phase information. CONSTITUTION:A coordinate reading device consists of a coordinate pointer 4 which includes a resonance circuit 5 consisting of a coil and a capacitor and an operation circuit 6 connected to each other and changes the resonance frequency with operation of the circuit 6, a sense line plate which generates an AC magnetic field and is connected to the pointer 4 via the AC magnetic field to detect an induction signal, a phase comparator 9 which detects the phase signal of the induction signal on the basis of the phase of the AC magnetic field, a temperature detection circuit 10 which measures the atmospheric temperature of the coordinate reading device, and an operating state detection circuit 13 which corrects the phase signal or the threshold value based on the temperature data measured by the circuit 10 and then compares the phase signal with the threshold value to detect the state of the circuit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate reading device, and more particularly to a technique for detecting the state of an operation circuit such as a switch provided in a coordinate indicator.

[0002]

2. Description of the Related Art As a method for detecting the switch state of a coordinate indicator in a conventional coordinate reading apparatus, an excitation line 62 and a sense line 63 are laid on a sense line plate 61 as shown in FIG. The induction signal generated in the sense line 63 is detected by electromagnetically coupling the resonance circuit 65 including the coil and the capacitor provided in the coordinate indicator 64, and the phase of the induction signal is compared with the threshold value. The method is known. One or a plurality of operating circuits 66 each composed of a switch and a capacitor are connected to the resonance circuit 65 of the coordinate indicator 64, and the operating circuit 66 is operated so that the resonance frequency is changed. deep.

FIG. 4 shows a phase signal when each switch is operated when three switches are provided as the operation circuit 66 in such a coordinate reading device. P1, P
2, P3 are phase signals at the time of operating each switch, and H1, H
2 and H3 are threshold values for determining the switch state. If the detected phase signal is Pn, Pn is P0,
The value is close to any of P1, P2, and P3. The phase signal Pn is compared with the threshold value H1, and if Pn <H1, it is determined that the switch is off, and if Pn ≧ H1, it is compared with H2.
If Pn <H2, it is determined that the switch state is that the switch 1 is on. If Pn ≧ H2, then it is compared with H3. If Pn <H3, it is determined that the switch state is that the switch 2 is ON. The phase signal Pn thus detected is successively compared with the respective threshold values to detect the state of the switch. For example, Pn shown in FIG. 4 is determined to have operated the switch 2.

[0004]

However, in the conventional configuration in which the switch state is detected by the phase signal, the phase signal changes due to the temperature, so that the switch state is erroneously detected due to the temperature change. was there.

FIG. 2 shows the relationship between the phase change due to temperature and the threshold value for judging the switch state.
S1Tn, S2Tn, S3Tn, S1Tm, S2Tm,
S3Tm is a phase signal at temperatures Tn and Tm, respectively, and changes so as to be below or above each threshold value, indicating that the switch state may be erroneously detected. In order to avoid this, it is necessary to set a large amount of phase between the switches, and it is difficult to detect a large number of switch states.

Therefore, an object of the present invention is to provide a coordinate reading device capable of stably detecting a large number of switch states even if a temperature change occurs.

[0007]

In order to solve the above problems, according to the present invention, a resonance circuit composed of a coil and a capacitor and an operating circuit are not connected, and the operating circuit changes the resonance frequency. A coordinate indicator configured to, and a sense line plate that generates an alternating magnetic field and is coupled to the coordinate indicator by the alternating magnetic field to detect an induced signal; and a phase of the induced signal based on the phase of the alternating magnetic field. A phase comparison circuit that detects a signal, a temperature detection circuit that measures the temperature of the atmosphere of the device, and the phase signal after correcting the phase signal or the threshold value based on the temperature data measured by the temperature detection circuit. The coordinate reading device is configured by an operation state detection circuit that detects the state of the operation circuit by comparing

[0008]

In the coordinate reading device thus constructed, the temperature of the atmosphere of the device is detected, the phase signal or the threshold value for judging each switch state is corrected according to the temperature change, and then the phase reading is performed. Since the switch state is detected by comparing the signal with the threshold value, it is possible to stably detect a large number of switch states regardless of the temperature.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the coordinate reading device according to the present invention will be described below with reference to the drawings. First, the configuration will be described. FIG. 1 is a block diagram of a coordinate reading device according to the present invention. In the figure, 1 is an oscillation circuit,
The basic signal is given to the excitation circuit 2. The exciting circuit 2 produces an exciting signal and supplies it to the exciting line 3 laid on the sense line plate.

A coordinate indicator 4 has a resonance circuit 5 and an operation circuit 6. The resonance circuit 5 is a parallel resonance circuit composed of a coil and a capacitor, and resonates with the excitation signal from the excitation line 3. The operation circuit 6 is a series circuit of a switch and a capacitor in this embodiment. In addition to the configuration using a switch, for example, a configuration in which a pressure sensitive resistance element is used to continuously change the operating state is also conceivable. The resonance circuit 5 is set so that the resonance frequency is slightly changed by the operation of the operation circuit 6.

Reference numeral 7 denotes a sense line, which is laid orthogonal to the exciting line 3 and receives a signal generated from the resonance circuit 5. The amplifier circuit 8 amplifies the signal received on the sense line 7 and supplies it to the phase comparison circuit 9. The phase comparison circuit 9 compares the phase of the signal from the amplifier circuit 8 with the phase of the excitation signal from the excitation circuit 2 to obtain the amount of deviation of the phase signal. A temperature detection circuit 10 reads the temperature of the atmosphere of the device. The change in phase due to temperature is greatly affected in the phase comparison circuit 9. For this reason, in the present embodiment, the temperature detection circuit 10 is mounted in the vicinity of the phase comparison circuit 9 for the purpose of correcting the phase fluctuation in the phase comparison circuit 9.

Reference numeral 13 denotes an operation state detection circuit, which is composed of a threshold value correction circuit 11 and a switch detection circuit 12. The threshold value correction circuit 11 corrects the threshold value for detecting the operating state based on the temperature data detected by the temperature detection circuit 10. The switch detection circuit 12 is
The switch state is detected from the threshold value corrected by the threshold value correction circuit 11 and the phase signal obtained by the phase comparison circuit 9.

Next, the operation of the threshold correction circuit 11 will be described. FIG. 3 shows the relationship between the phase change due to temperature and the threshold value corrected according to temperature. Experiments have shown that the phase changes almost linearly with temperature. Therefore, two threshold values H1Tn, H1Tm, H2Tn, H2Tm, and H3T at temperatures Tn and Tm are set in advance.
n, H3Tm are obtained in advance, and the threshold value H1 at the temperature Tx is obtained.
Tx, H2Tx, and H3Tx are calculated by the following linear expression (Expression 1).

H1Tx = (H1Tm−H1Tn) / (Tm−Tn) × (Tx−Tn) + H1Tn (Equation 1) In order to determine each switch state by the above calculation formula from the temperature data read by the temperature detection circuit 10. Each threshold H1
Tx, H2Tx, H3Tx are calculated, and the switch detection circuit 1
It is transferred to 2 together with the phase signal obtained by the phase comparison circuit 9.
As a matter of course, in the case of performing fine correction, the threshold values at a plurality of temperatures may be obtained and the correction may be performed by the linear equation between the temperatures. Further, the correction may be performed by an appropriate function.

Next, the operation of the switch detection circuit 12 will be described with reference to FIG. When the temperature is Tx, the threshold correction circuit 11 corrects the threshold as H1Tx, H2Tx, and H3Tx. The phase signal obtained by the phase comparison circuit 9 is set to P4.
Then, the switch detection circuit 12 first detects the phase signal P
4 is compared with the threshold value H1Tx, and if P4 <H1Tx, it is determined that the switch state is off. If P4 ≧ H1Tx, it is compared with H2Tx. If P4 <H2Tx, it is determined that the switch state is that the switch 1 is on. P4
If ≧ H2Tx, then compare with H3Tx, P4 <H3
If it is Tx, it is determined that the switch state is that the switch 2 is on. If P4 ≧ H3Tx, it is determined that the switch 3 is on. In this way, the state of the switch is detected by sequentially comparing the phase data P4 obtained by the phase comparison circuit 9 and each threshold value. The phase signal P shown in FIG.
In No. 4, it is determined that the switch 2 has been operated.

In this way, the operating environment temperature is sequentially detected, and the threshold value for judging the switch state is corrected by this. Therefore, even if the temperature changes, the switch state is not erroneously detected. Further, it becomes possible to reduce the interval between the threshold values, and it becomes possible to detect a large number of switches.

Next, a second embodiment will be described. In this embodiment, instead of the threshold value correction circuit 11 of the first embodiment, a phase correction circuit for correcting the phase signal obtained by the phase comparison circuit 9 is provided. The operation other than this phase correction circuit is the same as that of the first embodiment.

The operation of the phase correction circuit will be described with reference to FIG. As described in the first embodiment, assuming that the phase changes substantially linearly with temperature and the rate of change does not change depending on each switch state, the phase can be corrected by a linear expression with respect to temperature. it can. The phase signals Sn and Sm at the temperatures Tn and Tm shown in FIG. 5 may be previously obtained by an experiment, and the phase signal P5a obtained by the phase comparison circuit may be corrected by the following (Equation 2).

P5b = P5a − ((Sm−Sn) / (Tm−Tn) × (Tx−Tn)) (Equation 2) The switch detection circuit 13 uses a preset threshold value and this phase correction circuit. A switch state is detected by comparing the corrected phase signal P5b.

As described above, also in this embodiment, by sequentially detecting the operating environment temperature and correcting the change in the phase signal due to the temperature, it is possible to prevent the switch state from being erroneously detected even if the temperature changes. it can. The first and second embodiments have been described as being corrected by a linear expression in order to correct the threshold value or the phase signal. However, this is because in the present embodiment, the relationship between the temperature and the detected phase signal is represented by a substantially linear expression, and the relationship between the two may change if the circuit design conditions or the like change. .

In such a case, it suffices to finely correct each range by a linear expression as described above, or to perform arithmetical correction by approximating with an appropriate function. It is also possible to store the correction amount in the table and perform the correction by pulling the table. Further, in the first and second embodiments, the excitation line and the sense line are laid orthogonally, and the state of the coordinate indicator is detected by the induction signal induced by the electromagnetic coupling between the excitation line and the sense line. It was However, in the present invention, the coupling principle is not an essential technique, and other coupling principles can be implemented. For example, a method has been proposed in which excitation and detection are performed in a time-sharing manner using the same coupling line. However, even in such a principle, if the method of detecting the state of the coordinate indicator by changing the phase of the induction signal is performed similarly It is possible.

[0022]

As described above, according to the present invention, since the temperature detecting circuit for measuring the temperature of the operating environment and the means for correcting the phase information according to the detected temperature are provided, even if the operating environment temperature changes. The phase signal for detecting the switch state or the threshold value for determining each switch state can be corrected in accordance with the detected temperature, and a large number of stable switches can be obtained without erroneously detecting the switch state due to temperature changes. The switch status could be detected.

[Brief description of drawings]

FIG. 1 is a block diagram of a coordinate reading device according to the present invention.

FIG. 2 is a relationship diagram between a phase change due to temperature and a threshold value for determining a switch state.

FIG. 3 is a relationship diagram of a phase change due to temperature and a threshold value corrected according to temperature.

FIG. 4 is a diagram showing a phase amount when each switch is operated.

FIG. 5 is a diagram showing a correction function corresponding to each switch and a threshold value for selecting the function.

FIG. 6 is a block diagram of a conventional coordinate reading device.

[Explanation of symbols]

 1 Oscillation Circuit 2 Excitation Circuit 3 Excitation Line 4 Coordinate Indicator 5 Resonance Circuit 6 Operation Circuit 7 Sense Line 8 Amplifier Circuit 9 Phase Comparison Circuit 10 Temperature Detection Circuit 11 Threshold Correction Circuit 12 Switch Detection Circuit 13 Operation State Detection Circuit

Claims (1)

[Claims] 1. A coordinate indicator configured to connect a resonance circuit composed of a coil and a capacitor to an operating circuit, the resonance indicator being configured to change the resonance frequency by operating the operating circuit, and an alternating magnetic field. A sense line plate that is coupled to the coordinate indicator by the AC magnetic field to detect an induction signal, a phase comparison circuit that detects the phase signal of the induction signal based on the phase of the AC magnetic field, and the threshold signal. The operation state detection circuit detects the state of the operation circuit by comparing it with a value, and the temperature detection circuit measures the temperature of the atmosphere of the apparatus. The operation state detection circuit is measured by the temperature detection circuit. A coordinate reading device characterized in that the state of the operating circuit is detected after correcting the phase signal or the threshold value based on temperature data.