JPH0132533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a coordinate detection device for detecting the position of an excitation device such as a cursor on a tablet.

[Background of the invention]

When placing a cursor on a tablet and detecting the coordinate position of this cursor on the tablet, the distance between the tablet and the cursor depends on various conditions such as the structure of the coordinate detection device and the value of the current supplied to the cursor. value. If the interval exceeds this value, coordinate detection becomes impossible. Therefore, coordinate detection must be performed within this value. Recently, however, there has been a desire to maintain the distance between the tablet and the cursor not only within the above-mentioned value, but also within a certain predetermined value below this value. That is, for example, although coordinate detection is possible if the distance between the tablet and the cursor is within 5 mm, it is desired to maintain this distance at 3 mm or less. For example, when outputting the coordinate data of one point and another point, when the cursor is moved between the two points, unnecessary data will be output unless the cursor is moved a certain height. On the other hand, if the cursor has to be lifted high, the operability deteriorates.

Conventional coordinate detection devices do not have a means for determining whether the distance between the tablet and the cursor, that is, the height of the tablet, is within a predetermined height (coordinate input effective height). It was not possible to satisfy the demands of Here, the following means are generally assumed as such a determination means. That is, as the cursor moves away from the tablet, the signal voltage generated in the tablet wiring becomes smaller, so for example, the peak value of the selector signal level generated in the selector detection conductor is detected, and the determination is made based on this peak value. It is a means of doing this. However, such means require converting the selector signal level into a digital value,
Since the circuit configuration becomes complicated, it cannot be adopted.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coordinate detection device that can easily determine whether or not an excitation device is within an effective coordinate input height using a simple circuit configuration, in response to the above-mentioned needs.

[Summary of the invention]

In order to achieve the above object, the present invention provides a comparison means with the output of a signal processing means that outputs a signal with a phase difference according to the position of the excitation device with respect to a sine wave voltage applied to the excitation device. Therefore, the digital value is compared with the first set value, and a digital value corresponding to the phase difference of the output with respect to the sine wave voltage is obtained by the converting means,
Similarly, the output of the signal processing means is compared with a second setting value by the comparison means, and a digital value corresponding to the phase difference of the output with respect to the sine wave voltage is obtained by the conversion means, and both The present invention is characterized in that the difference between the digital values is calculated and the effective coordinate input height is determined based on this difference.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a circuit diagram of a coordinate detection device according to an embodiment of the present invention. In the figure, 1 is the oscillator, 2 is the oscillator 1
3 is a filter that converts the square wave output of frequency divider 2 into a sine wave voltage, 4 is an amplifier that amplifies the output of filter 3, 5 is a cursor excited by the output of amplifier 4, This is an excitation device such as a stylus pen (hereinafter referred to as a stylus pen).

6 is a tablet on which conductor wires such as sine wires, cosine wires, selector wires, etc. are wired; 7 and 8 are amplifiers that amplify the signals from these conductors; 9 is an adder that adds the signals of amplifiers 7 and 8; and 10 is a tablet. An amplifier 11 amplifies the signals added and combined by the adder 9, and a counter 11. Reference numeral 12 denotes an arithmetic processing unit configured using a microcomputer, which performs necessary calculations and controls to calculate the coordinates of the stylus pen 5.

13 is a comparator connected between the amplifier 10 and the counter 11; 14 and 15 are voltage dividing resistors that divide the power supply voltage; and 16 is a switch connected to the connection point between the resistors 14 and 15. Comparator 13
One input terminal of the amplifier 10 is connected to the output terminal of the amplifier 10, and the other input terminal is connected to the connection point between the resistors 14 and 15.

Next, the operation of this embodiment will be explained with reference to the waveform diagrams shown in FIGS. 2a to 2e and 3. When the sinusoidal signal voltage Esinωt is applied to the stylus pen 5, the coil (not shown) of the stylus pen 5 is excited, and the sinusoidal voltage Esinωt wired to the tablet 6 is excited.
A signal voltage corresponding to the position of the stylus pen 5 is induced in the line, cos line, etc. In addition, in FIG. 2a, only the sin line S related to the X-axis of the coordinates of the tablet 6 is shown, and illustration of other conducting wires is omitted.

The signal voltages induced on the sine line S and the cosine line are amplified by amplifiers 7 and 8, respectively, and then added by an adder 9, and the signal synthesized by the addition is sent to the amplifier 1.
amplified by 0. FIG. 2b shows a waveform diagram of the output signal E ₁ sin (ωt+Θ ₀ ) of the amplifier 10. This output signal has a phase difference of an angle Θ ₀ compared to the signal Esinωt applied to the stylus pen 5. This phase difference Θ ₀ is proportional to the distance r of the stylus pen 5 from the reference line in one period of the sin line S. Note that since the above-mentioned means are known, detailed explanation will be omitted. Amplifier 1 mentioned above
The operation until a signal having a phase difference of 0 is output is the same even when the coordinate input effective height does not need to be determined.

Here, in the following description of the operation, first, the operation in the case where determination of the coordinate input effective height is not required, that is, in the normal case, will be explained. In this case, switch 16 remains closed. Therefore, the "+" side input of the comparator 13 becomes the ground potential (0V), and the second input to the "-" side
It is compared with the voltage shown in Figure b. The comparator 13 outputs a high level signal when the "-" side input voltage is lower than 0V, and outputs a low level signal when it is higher than 0V. The output of this comparator 13 is shown in FIG. 2c. That is, stylus pen 5
A falling signal is output from the comparator 13 with a phase delayed by an angle Θ ₀ with respect to the sine wave signal voltage applied to the sine wave signal voltage. The output signal of the comparator 13 shown in FIG. 2c is input to the counter 11.

The counter 11 receives the clock pulse of the oscillator 1, the output pulse signal of the frequency divider 2, and the output signal of the above-mentioned comparator 13, and is set at the rising edge of the output pulse signal of the frequency divider 2. The configuration is such that it is reset at the falling edge. Therefore, the counter 11 counts the input clock pulses of the oscillator 1 during the phase difference Θ ₀ mentioned above. This count value is a value proportional to the distance r shown in Fig. 2a,
In other words, position data within the period (hereinafter referred to as
It is called PD value. ). Figure 2e shows the waveform of this PD value. Let PD ₀ be the PD value counted by the counter 11 during the above phase difference Θ ₀ .
This value PD ₀ is input to the arithmetic processing unit 12, and the arithmetic processing unit 12 calculates the actual value of the distance r of the stylus pen 5 based on the input value PD ₀ .

The coordinate detection operation in the normal case that does not require determination of the effective coordinate input height has been described above, but next, the operation in the case where determination of the effective coordinate input height is required will be described. Prior to this explanation, the principle of determining the effective coordinate input height in this embodiment will be described. As mentioned above, the peak value of the voltage induced in the conductive wire wired to the tablet 6, and therefore the peak value _E1 of the output voltage of the amplifier 10 shown in FIG. The higher the height, the smaller it is, and the lower it is, the larger it is. Therefore, by setting a certain voltage based on a predetermined coordinate input effective height and determining whether the peak value of the output voltage of the amplifier 10 is greater than or equal to this set value, the coordinate input effective height can be determined. It is possible to judge the

Therefore, the set value V ₁ is determined as shown in FIG. 2b, and the angle Θ ₁ corresponding to the set value V ₁ of this voltage waveform is
If the peak value is _E1 , the following formula holds true.

E ₁ sin (Θ ₁ − Θ ₀ ) = V ₁ ...(1) Then, the peak value E ₁ of the voltage waveform is the set value
To determine that V ₁ or more (E ₁ ≧ V ₁ ),
It is sufficient that the phase difference (Θ ₁ −Θ ₀ ) in the above equation (1) falls within the range of the following equation.

0<(Θ ₁ −Θ ₀ )≦90° (2) This will be explained in more detail with reference to FIG.

FIG. 3 is a waveform diagram showing four types of voltages.
As shown in the figure, when the set voltage is _Vs , the phase angle of the voltage waveform A corresponding to this set voltage _{Vs is Θa} ,
The phase angle of voltage waveform B, which has a smaller peak value than voltage waveform A, is larger than the phase angle Θ _a , and the phase angle of voltage waveform C, which has a smaller peak value than voltage waveform B _, is larger than the phase angle Θ _b . _c . The peak value of the voltage waveform C matches the set voltage _Vs , and therefore the phase difference ( _Θc - _Θ0 ) is 90°. The peak value of the voltage waveform D is smaller than the set voltage _Vs , and there is no phase angle corresponding to this voltage _Vs. From the above, it is clear that whether the peak value of the voltage waveform is equal to or higher than the set voltage can be determined by checking whether the phase difference is 90° or less. After all, in the case of the voltage waveform shown in Figure 2b, it is possible to check whether the phase difference (Θ ₁ - Θ ₀ ) is less than 90° without comparing the peak value E ₁ and the set value V ₁ . By doing so, it is possible to determine whether the peak value of the output voltage of the amplifier 10 is less than or equal to the set value, and thereby it is possible to determine the coordinate input effective height.

Now, returning to FIG. 1, the operation when the coordinate input effective height needs to be determined will be described. Initially, the switch 16 is kept in the closed state, and the PD value PD ₀ corresponding to the phase angle Θ ₀ is determined by the same operation as described above.
This value PD ₀ is stored in the memory of the arithmetic processing unit 12. Next, switch 16 is opened. switch 1
6 is opened, the voltage divided by the resistors 14 and 15 is input to the "+" side input terminal of the comparator 13. This voltage is preset to a set value V ₁ shown in FIG. 2b by selecting the resistance values of the resistors 14 and 15. The output voltage of amplifier 10 is this setting value.
The comparator ₁₃ outputs a low level signal when the output voltage is equal to or higher than the set value _V1 . The output of the comparator 13 in this case is shown in FIG. 2d. The output of the comparator 13 falls at a phase angle θ ₁ corresponding to the set voltage V ₁ . Therefore, the counter 11 has a phase angle θ ₁
, and the arithmetic processing unit 12 has a phase angle of 0.
Number of clock pulse counts between ~θ ₁ (PD value)
PD ₁ is input. The arithmetic processing unit 12 performs an arithmetic operation to subtract the previously stored value PD ₀ from this value PD ₁ . The value obtained by subtraction (PD ₁ −
PD ₀ ) is a value corresponding to the phase difference (Θ ₁ −Θ ₀ ).
Furthermore, in the arithmetic processing unit 12, the value obtained by the subtraction (PD ₁ - PD ₀ ) and the value corresponding to the phase angle of 90° are calculated.
The PD value is compared, and as a result of the comparison, the value (PD ₁ −
When PD ₀ ) is less than the PD value corresponding to a phase angle of 90°, it is determined that the stylus pen 5 is at the effective height, the value PD ₀ is used as coordinate detection data, and the stylus pen 5 is set at an appropriate position on the tablet 6. The displayed indicator lamp or the like indicates that coordinate detection is being carried out effectively. Furthermore, when the value (PD ₁ − PD ₀ ) exceeds the PD value corresponding to a phase angle of 90°, it is determined that the stylus pen 5 is not at the effective height, and the stored PD is
The value PD ₀ is not used as coordinate detection data and is canceled.

As an example, let us consider the case where the PD value within one cycle is expressed in 8 bits, that is, the maximum value PDmax of the PD value shown in Fig. 2 e is set to 255.
In this case, the PD value corresponding to a phase angle of 90° is 255×
90/360≒63. Therefore, the PD value (PD ₁ −
If PD ₀ ) is within the range of 0<(PD ₁ −PD ₀ )≦63, it is determined that the stylus pen 5 is at the effective height.

Next, manual cutting to change the effective height will be described. Now, leaving the set value V _s in Fig. 3 unchanged, the phase difference judgment criterion is set to 90°, that is, the phase difference (Θ _c −
Assuming that the phase difference is changed from Θ ₀ ) to phase difference (Θ _b −Θ ₀ ), all voltage waveforms having a peak value lower than the peak value of voltage waveform B will be determined to be invalid. For example, regarding waveform C, if the phase difference criterion is 90 degrees, its peak value reaches the set voltage V _s and it is determined to be valid, but if the phase difference criterion is 90 degrees, the peak value reaches the set voltage V s and it is determined to be valid. _b - Θ ₀ ), the phase difference Θ _c - _{Θ 0} ) of waveform C is not within the reference phase difference (Θ _b - _{Θ 0} ), and waveform C is determined to be invalid. In this way, the set voltage V _s
Even if the voltage remains constant, reducing the phase difference that serves as a criterion produces the same effect as raising the set voltage. In other words, the effective height can be changed by changing the phase difference used as a criterion between 0° and 90°. The phase difference serving as this judgment criterion is stored in the arithmetic processing unit 12 as a PD value corresponding to this, and the PD value (PD ₁ −
PD ₀ ).

As described above, in this embodiment, the effective height of the stylus pen is determined using the position data (PD value) obtained in the normal coordinate detection operation.
Since the stylus pen is determined to be at the effective height when the difference between the PD values when the switch is open and closed is less than the PD value corresponding to a predetermined phase difference, the A/D converter etc. There is no need to use it, and the effective height can be easily determined with a simple circuit configuration. Furthermore, the criteria for determination can be easily changed.

Note that the opening and closing of the switch that determines the set voltage of the comparator is automatically performed by commands from a microcomputer in the arithmetic processing unit. or,
The effective height can also be changed by changing the input voltage of the comparator by using a variable resistance as the voltage dividing resistor.

〔Effect of the invention〕

As described above, in the present invention, the effective height of the excitation device is determined using position data (PD value) obtained in normal coordinate detection operation,
When the PD value corresponding to the difference in phase angle corresponding to the first and second set values in the output voltage of the signal processing means is less than or equal to a predetermined value, it is determined that the excitation device is at the effective height. Therefore, the effective height can be easily determined with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a coordinate detection device according to an embodiment of the present invention, and FIGS. 2 a, b, c, d, and e and FIG. 3 are waveform diagrams illustrating the operation of the device shown in FIG. 1. . 1... Oscillator, 2... Frequency divider, 3... Filter, 4, 7, 8, 10... Amplifier, 5... Stylus pen, 6... Tablet, 9... Adder, 1
1...Counter, 12...Arithmetic processing unit, 13...
...Comparator, 14, 15...Resistor, 16...
Switch.

Claims (1)

[Claims] 1. A tablet having conductive wires arranged in a meandering manner at a predetermined period, an excitation device to which a sine wave signal voltage is applied, and a phase difference proportional to the position of the excitation device within the period with respect to the sine wave signal voltage. A coordinate detection device comprising: a signal processing means for outputting a signal of In,
a first comparing means for comparing the output of the signal processing means with a first setting value and a second setting value; and each digital value obtained by the converting means for each output signal of the first comparing means. A coordinate detection device comprising: a subtraction means for determining a difference between values; and a second comparison means for comparing the value obtained by the subtraction means with a predetermined value.