JPH07120242B2 - Display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a display device, for example, a function as a coordinate input surface on a flat display panel surface as a means of interaction between an electronic computer and its operator. The present invention relates to a display device having an input function.

[Conventional technology]

Conventionally, as a display device with an input function in which a flat display panel surface is provided with a coordinate input function, Japanese Patent Application No. 61-
The one shown in the 226767 specification has been proposed.

FIG. 4 is a block diagram showing the configuration of a display device having the input function. In the figure, (1) is a flat panel display panel, for example, a TN mode display liquid crystal cell, and an XY matrix electrode configuration. And has, for example, a plurality of X transparent electrodes (11) and Y transparent electrodes (12) which are orthogonal to each other,
Both ends of each transparent electrode (11), (12) are structured so that a signal can be given from the outside. (21), (2
2) is for X driver, (31), (32) is for Y driver,
Reference numeral (4) is an input pen, which is composed of, for example, a pickup coil (40) in which a coil is wound around a ferrite and a head amplifier (41). (5) is a memory for writing a pattern to be displayed in the liquid crystal cell (1). (6) is a liquid crystal display controller which constitutes a display signal applying means, and reads out pattern data in the X direction corresponding to the selected Y transparent electrode (12) of the liquid crystal cell (1) from the memory (5) and Display control such as transfer to drivers (21) and (22) is performed.

A position detection circuit (7) generates a detection signal from a signal from the input pen (4). (8) is a position detection scanning circuit, (9)
Is an input / output mode controller, and displays data and control signals from the liquid crystal display controller (6) in the display mode.
Drivers (21), (22), Y drivers (31), (3
2) respectively, and in the position detection mode, various signals from the position detection scanning circuit (8) are supplied to the X driver (21),
(22), Y drivers (31), (32) play the role of a switching switch for adding to each. Position detection circuit (7)
The position detecting means is constituted by a part of the above and the position detecting scanning circuit (8). A CPU (10) writes a display pattern in the memory (5) and controls the entire device.

FIG. 5 is a circuit diagram showing in detail the configuration relating to the position detection mode in FIG. In the figure, (800) is a clock generator, the output end of which is connected via the input / output mode controller (9) to the Y driver (31), the clock input terminal CK of the (32), and the frequency divider (801). ) And the clock input terminal CK of the counter (802). The output terminal of the frequency divider (801) is the input / output mode controller (9).
Is connected to the data input terminal D of the Y drivers (31) and (32) and the start terminal (S) of the counter (802). Reference numeral (803) is a latch, and the output of the counter (802) is latched by the latch pulse (l).

(804) is a sine wave generator, which generates a sine wave of frequency f ₀ . (805) is a transistor whose emitter is grounded, and generates a sine wave whose phase is 180 ° different from the output sine wave of the sine wave generator (804).

Further, (700) is a bandpass filter whose center frequency is f ₀ . Reference numeral (701) is a phase comparator which constitutes a phase comparing means, and outputs the phase of each sine wave input to the _two input terminals P ₁ and P ₂ as a voltage level from the output end PO. (702) is a differential amplifier. (703) is a comparator, which outputs a constant pulse when the output of the phase comparator (701) reaches a constant level.

Although (31) and (32) are the same drivers for Y as shown in FIG. 4, in reality, they have an n-stage shift register, and the data of the data input terminal D is sequentially output by the clock pulse of the clock input terminal CK. shift. The output terminals (Oi) (i = 1 to n) of the driver are applied to the voltage application terminals V1, V2, V3 according to the data (Di) (i = 1 to n) in the shift register and the value of the alternating current terminal (DF). , One of the voltages applied to V4
Output one. Table 1 shows a truth table of the output voltage.

In addition, a constant DC voltage is applied to the voltage application terminals V1, V2, and V3.
E1, E2, E3 are applied, and the terminal V4 via the input / output mode controller (9) is DC voltage E4 in the display mode, and in the position detection mode. Two sinusoidal voltages 180 ° out of phase are applied.

Further, the internal switch group of the input / output mode controller (9) is connected as shown by a broken line in the display mode as shown in FIG. 5 and as shown by a solid line in the position detection mode.

Although FIG. 5 shows only the Y drivers (31), (32), and the Y transparent electrodes (121) to (12n), the X driver and the X transparent electrode are actually provided at positions orthogonal to these. Therefore, in the position detection mode, the same operations as the Y driver and the Y transparent electrode are performed.

Next, the operation will be described.

The display device with an input function proposed by the applicant of the present invention repeats the display mode and the position detection mode in a fixed cycle in a time-division manner.
In other words, as shown in FIG. 6, when the time passes in the horizontal direction,
One frame period is divided into (n + 2) periods, and the period T ₁ to T _n operates in the display mode, and the periods Tn + 1 and Tn + 2 operate in the position detection mode.

First, in the display mode, the internal switch group of the input / output mode controller (9) is connected as shown by the broken line in FIG. 5, and the liquid crystal display controller (6) sequentially outputs the data of the pattern to be displayed from the memory (5). Reading is performed and display is performed by a conventionally known voltage averaging driving method. That DC voltage _{(E 1, E 2, E} 3, E 4) is set to a bias voltage suitable for the voltage averaging driving method, the period _{T 1, T 2, ...,} Y transparent electrode each Tn (121), A selection voltage is sequentially applied to (122) and (... 12n), and the selected X transparent electrode (11) is selected for each period.
Applied to. At this time, the driver outputs at both ends of the X transparent electrode (11) and the Y transparent electrode (12) output the same voltage.

Next, the position detection mode will be described with reference to FIG. FIG. 7 is a waveform diagram showing changes with time of the signals output from the respective parts shown in FIG. During the period Tn + 1, the internal switch group of the input / output mode controller (9) is connected as shown by the solid line in FIG. 5, and the Y at the position where the input pen (4) is located.
Detect coordinates.

In the position detection mode, a sine wave generator (804) is connected to the V4 terminal of the Y driver (31) and the V4 terminal of the Y driver (32).
Generated sine wave voltage V _msin (2πf _0t ) and -V _msin (2πf _2t )
_A sinusoidal voltage of _0t ) is applied. Furthermore, since the DF terminals of the Y drivers (31) and (32) are grounded, they become "L", and the outputs Oi (i = 1 to 1) of the Y drivers (31) and (32) are
In n), as shown in Table 1, when the data of the internal shift register is “L”, the DC voltage E ₂ is applied, and when the data is “H”, the sine wave voltage V _msin (2πf _0t ) Or −V
_msin (2πf _0t ) is output.

Start pulse SP (signal SP in FIG. 7) that is output by dividing the basic clock C (signal C in FIG. 7) generated in the clock generator (800) by (n + 2) in the frequency divider (801).
Resets the counter (802) (signal CNT in FIG. 7) and starts counting, and Y drivers (31), (32)
Is supplied to the data input terminal D of the shift register. After that, each time one basic clock pulse C is generated, the output value of the counter (802) is incremented by "1", and in synchronization with it, one data is stored in the internal shift register of the Y drivers (31) and (32). Since it is shifted by ± V _msin (2
The Y transparent electrodes (12) to which a voltage of πf _0t ) is applied are shifted to the adjacent one by one. That is, assuming that the resistance value of the Y transparent electrode (12) is R ₀ , the Y transparent electrodes (121), (122), ... (12
A sinusoidal current of (2Vm / R ₀ ) ・_sin (2πf _0t ) flows sequentially in m).

At this time, the pick-up coil (40) of the input pen (4) placed at the X position on the Y transparent electrode (12m) has a liquid crystal cell of an AC magnetic flux generated by a sinusoidal current flowing through each transparent electrode (12). An electromotive force is generated by a component perpendicular to one surface. This electromotive force has the same frequency as the sinusoidal current flowing through the Y transparent electrode (12) but a phase difference of 90 °, and the magnitude of the level is point X.
And a sine wave that is inversely proportional to the distance between the Y transparent electrode (12) through which the sine wave current flows. However, Y transparent electrode (12
When the current flows in m), the distance is the shortest, but the magnetic flux of the component perpendicular to the surface of the liquid crystal cell is almost zero, so the output of the pick-up coil (40) is also almost zero. The output signal of the pickup coil (40) is amplified by the head amplifier (41) and passes through a bandpass filter (700) having a center frequency f ₀ in order to increase the S / N ratio. Y as mentioned above
Figure 7 shows the output waveform of the bandpass filter (700) when the current is passed through the transparent electrode (12) one by one.
Shown in.

Moreover, since the respective sine wave voltages ± V _msin (2πf _0t ) applied to the V4 terminals of the Y drivers (31) and (32) are applied to the two input terminals of the differential amplifier (702), the output A sinusoidal wave proportional to the current flowing through the Y transparent electrode (12) is output to (see signal r in FIG. 7).

Band pass filter (700)
The phase of the output signal b of is different by 180 degrees between the period in which a current is passed from the Y transparent electrode (121) to (12m) and the period in which a current is passed from the Y transparent electrode (12 (m + 1)) to (12n). .
Therefore, when the output signal r of the differential amplifier (702) and the output signal b of the band pass filter (700) are input to the phase comparator (701), the waveform of the output signal p becomes like the signal p of FIG.
When the reference potential terminal B of the comparator (703) is set to the potential of VR, the comparator (703) outputs the coincidence pulse 1 when the level of the output signal p of the phase comparator (701) becomes VR and the latch (803). Latches the counter (802) output at that time.

That is, an alternating current is sequentially passed through the Y transparent electrode (12) to perform scanning, and the m-th Y transparent electrode (12) at which the input pen (4) is located.
When scanning m), the comparator (703) generates a coincidence pulse and latches the output value m of the counter (802). The CPU (10) reads the output value of the latch (803) to detect the Y coordinate of the position of the input pen (4).

The above-described operation is performed in the period Tn + 1 of FIG. 6, and the same operation is performed in the period Tn + 2 as X drivers (21) and (22) X.
Do with respect to the transparent electrode (11), X at the position of the input pen (4)
Detect coordinates.

[Problems to be solved by the invention]

Since the conventional display device is configured as described above, when the display screen is enlarged, the output waveform diagram of the signal of each main part shown in FIG. 7 is actually the output waveform diagram shown in FIG. Becomes

When the pick-up coil (40) is on the m-th electrode and the output value of the counter (802) is around m, the output signal b of the bandpass filter (700) has a constant level. Therefore, the phase comparator (701) operates normally, but when the output value of the counter (802) has a large difference from m, the position where the pick-up coil (40) is located and the electrode where the AC component current flows. Since the distance of the position becomes large, the level of the output signal b of the bandpass filter (700) becomes small and the S / N ratio of the phase information becomes poor. Therefore, the output p of the phase comparator (701) (see FIG. 8). The shaded part in the signal p) becomes unstable.

Therefore, the comparator (703) outputs the erroneous coincidence pulse signal lf. The latch (803) latches the value of the counter (800) with this erroneous coincidence pulse signal lf, which causes a problem that the detected coordinates are erroneous.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to obtain a display device capable of preventing an incorrect coincidence pulse even when the display screen is enlarged and performing accurate coordinate detection. With the goal.

[Means for solving problems]

A display device according to the present invention includes an amplitude detection unit that detects the amplitude of a signal generated in a magnetic flux detection unit, a gate circuit that opens when the amplitude reaches a predetermined threshold value, and a gate circuit that uses an output pulse of the gate circuit. It is equipped with a means for closing.

[Action]

The display device according to the present invention prevents the generation of an erroneous coincidence pulse by the gate circuit, and processes the coincidence pulse indicating the phase inversion after the amplitude level of the magnetic flux detecting means exceeds a certain value as a true coincidence pulse.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of a display device according to an embodiment of the present invention. In FIG. 1, (1000) is a gate control circuit provided with an amplitude detecting means, a gate circuit and a means for closing the gate circuit, and the other respective constituent elements are:
This is the same as each component shown in FIG. 4 of the conventional example, and the same reference numerals perform the same or corresponding operations.

FIG. 2 is a circuit diagram showing details of the input pen (4), the position detection circuit (7), the position detection scanning circuit (8) and the gate control circuit (1000) shown in FIG.

In FIG. 2, the components of the input pen (4), the position detection circuit (7), and the position detection scanning circuit (8) are the same as those of the conventional example shown in FIG. Performs a considerable operation.

In the figure, (1001) is a diode, (1002) is a resistor, and (1003) is a capacitor, which form an envelope detection circuit. Amplitude information is output from the output signal containing the AC component of the bandpass filter (700). Is an amplitude detecting means for taking out. (1004) is a comparator, which has input terminals A and B
The potentials are compared, and when A> B, a low level is output from the C terminal. (1005) is a variable resistor and a comparator (10
04) The comparison potential of the B input terminal, that is, a predetermined threshold value is determined. (1006) is an inverter gate, (1007)
Is a resistor, and (1008) is an OR gate, which constitutes a differentiating circuit and detects the falling edge of the output of the comparator (1004) and generates a pulse. (1009) is the OR gate, (1010),
(1011) is a settable and resettable D type flip-flop, (1012) is an OR gate, and (1013) is an inverter gate.

Further, FIG. 3 is an output waveform diagram showing changes with time of the signal in each main part of FIG. 2, where the signal CNT is the output value of the counter (802) and the signal SP is the output of the frequency divider (801). Start pulse, signal b is bandpass filter (700)
Output and envelope of its amplitude, signal CA is A input of comparator (1004), signal S1 is output of comparator (1004), signal S2 is output of OR gate (1008), signal S3 is Q output of flip-flop (1010) , The signal S4 is the Q output of the flip-flop (1011), the signal l is the output of the comparator (703), and the signal lt is the output of the OR gate (1012).

Next, the operation will be described.

The display device according to the embodiment of the present invention operates in the same manner as the conventional example, and as shown in FIG. 6, the display mode and the position detection mode are repeated in a time division manner.
FIG. 3 and FIG. 3 will be described.

Although the pick-up coil (40) at the tip of the input pen (4) is not shown in FIG. 2, for example, m in the liquid crystal cell (1).
It is placed on the second Y transparent electrode (12 m). Then, when an AC component current is passed through the Y transparent electrodes (12) one by one, the output signal b of the band pass filter (700) is the third signal.
A waveform like the signal b in the figure is obtained, and coordinate detection is performed based on the phase change point (point P) of this signal. Comparator (70
The output signal l of 3) generates a pulse at the phase change point, as shown in the signal l of FIG. 3, but the erroneous pulse signal lf is generated at a low level of the signal b other than the true phase change point. Output.

On the other hand, after passing the output signal b of the band pass filter (700) through the envelope detection circuits (1001), (1002), (1003),
The signal input to the A terminal of the comparator (1004) is the third
It has the waveform shown in signal CA in the figure. Therefore, when the output waveform of the comparator (1004) reaches a predetermined threshold value, the gate circuit is opened and becomes the signal S1 in FIG.
That is, it becomes low level only when the amplitude of the output of the band pass filter (700) becomes larger than a predetermined level. Therefore, the signal S4 of the Q output of the flip-flop (1011) is the third
As shown by the signal S4 in the figure, of the pulse (signal S2 in FIG. 3) indicating the falling edge of the comparator (1004), the gate is obtained by the Q output (signal S3) of the flip-flop (1010). It goes low with a pulse and goes high again with a low-level pulse from the OR gate (1012), closing the gate circuit.

Therefore, of the output pulse (signal l in FIG. 3) of the comparator (703), the OR gate (1012) is used to remove only the Q output (signal S4) of the flip-flop (1011) in the low level period. By applying the gate, the pulse signal lt showing the true phase change can be taken out.

〔The invention's effect〕

As described above, according to the present invention, the amplitude detecting means for detecting the output level of the magnetic flux detecting means and the gate circuit opened when the output level exceeds a predetermined value are provided at the output part of the phase change detecting means of the magnetic flux detecting means. Is provided so that it does not operate when the input signal level to the phase change detecting means is low. Therefore, even if the display screen is enlarged, a display device with high coordinate detection accuracy can be obtained.

[Brief description of drawings]

1 is a block diagram showing the configuration of a display device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing in detail the position detection scanning circuit, position detection circuit, gate control circuit, and input pen shown in FIG. FIG. 3 is an output waveform diagram showing changes of signals of respective main parts of FIG. 2 with respect to time, FIG. 4 is a block diagram showing a configuration of a conventional display device, and FIG. 5 is a position detection operation of the conventional display device. FIG. 6 is an explanatory view for explaining the time division operation in the display mode and the position detection mode,
FIG. 7 is an output waveform diagram showing changes with time of main signals of the respective parts of FIG. 5, and FIG. 8 is a waveform diagram showing changes with time of signals of the conventional display device. (1) ... flat panel display panel, (4) ... input pen,
(6) ... Display signal applying means, (7), (8) ... position detecting means, (11) ... X electrode, (12) ... Y electrode,
(40) …… Magnetic flux detection means, (701) …… Phase comparison means,
(804) ... means for applying alternating current component, (1000) ... means for closing gate circuit and gate circuit, (1001), (100
2), (1003) ... Amplitude detection means. The same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Iwata 8-1-1 Tsukaguchihonmachi, Amagasaki-shi, Hyogo Sanryo Electric Co., Ltd. Applied Equipment Research Laboratory (56) Reference JP-A-60-79219 (JP, A) ) JP-A-58-84339 (JP, A)

Claims (1)

[Claims] 1. A flat panel display panel having an XY matrix electrode structure, display signal applying means for applying a display signal to the XY matrix electrodes, and at least one electrode group of the XY matrix electrodes. An alternating current component current applying means for sequentially applying a current having an alternating current component, an input pen having a magnetic flux detecting means, a phase of the alternating current component current applied to the matrix electrode, and a signal generated in the magnetic flux detecting means. In a display device including a phase comparison means for comparing the phase and a position detection means for detecting the position of the input pen on the display panel based on the output of the phase comparison means, the amplitude of the signal generated in the magnetic flux detection means. A gate circuit that opens when the output of the amplitude detection means reaches a threshold value; Display device, characterized in that and means for closing the road.