JPS63225818A - Display device - Google Patents

Abstract

PURPOSE:To obtain a display device where the coordinate detection precision is high even if the display screen is enlarged, by providing an amplitude detecting means and a gate circuit in the output part of the phase change detecting means of a magnetic flux detecting means and preventing the operation of the device if the input signal level to the phase change detecting means is low. CONSTITUTION:Amplitude detecting means 1001-1003 which detect the amplitude of the signal generated in a magnetic flux detecting means 40, the gate circuit which is opened when the amplitude reaches a prescribed threshold, and a means 1000 which closes the gate circuit by the output of the gate circuit are provided. The occurrence of an erroneous coincidence pulse is prevented by the gate circuit, and the coincidence pulse indicating phase inversion after the time when the amplitude level of the magnetic flux detecting means 40 exceeds a certain value is processed as a true coincidence pulse. Thus, the display device is obtained where coordinates are accurately detected with a high precision even if the display screen is enlarged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a display device, and relates to a display device that has a function as a coordinate input surface on a flat display panel surface, for example, as a means of interaction between a computer and its operator. The present invention relates to a display device with an input function.

[Prior Art] Conventionally, a display device with an input function in which a coordinate input function is provided on the surface of a flat display panel is disclosed in Japanese Patent Application No. 1986 by the present applicant.
The one shown in the specification of No.-226767 has been proposed.

FIG. 4 is a block diagram showing the configuration of a display device with an input function. In the figure, (1) is a flat display panel, for example, a TN mode display liquid crystal cell, with an XY matrix electrode configuration. For example, it has a plurality of X transparent electrodes αD and Y transparent electrodes (12), each of which is perpendicular to each other.
Both ends of each transparent electrode αD (12 are structured so that a signal can be applied from the outside. (2), the broom is
The driver for C311,■ is the driver for A pattern to be displayed on the cell (1) is written. (6) is a liquid crystal display controller that constitutes display signal application means, and a pattern in the X direction corresponding to the selected X transparent electrode (2) of the liquid crystal cell (1) is written. Read the data from the memory (5), drive the X driver (company),
Perform display control such as forwarding to.

(7) is a position detection circuit which generates a detection signal from the signal from the input pen (4). (8) is a position detection scanning circuit, (9)
is the input/output mode controller, and in the display mode, the display data and control signals from the liquid crystal display controller (6) are
Driver for Y (2) - Y driver I3υ, (2
), and in one position detection mode, various signals from the position detection scanning circuit (8) are supplied to the X driver +211.
It plays the role of a changeover switch for adding to (1), X driver +311, and (2), respectively. A part of the position detection circuit (7) and the position detection scanning circuit (8) constitute a position detection means. 0■ is the CPU, and the display pattern is stored in the memory (5
) and control the entire device.

FIG. 5 is a circuit diagram showing in detail the configuration related to the position detection mode in FIG. 4. In the figure, (800) is a clock generator, and its output terminal is connected via the input/output mode controller (9) to the X driver 31), the clock input terminal CK of (802) is connected to the clock input terminal CK. The output terminal of the frequency divider (801) is connected to the data input terminal of the X driver C311-■ via the input/output mode controller (9) and the start terminal 5 (5) of the counter (802).
connected to.

A latch (803) latches the output of the counter (802) with a latch pulse (1).

(804) is a sine wave generator that generates a sine wave of one frequency fO. (805) is a common emitter transistor, which 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 fO. (701) is a phase comparator constituting the phase comparison means, and output terminal P
Output from O. (702) is a differential amplifier. (7
03) is a comparator, which outputs a coincidence pulse when the output of the phase comparator (701) reaches a certain level.

(2), (support) is the same X driver as shown in Figure 4, but it actually has an n-stage shift register inside, and data from the data input terminal is processed by clock pulses from the clock input terminal GK. Shift sequentially. In addition, the driver output terminal (Oi)<i=1 to n) is connected to the data in the shift register (Di)<i=t to n) and the alternating current terminal (DF
), one of the voltages applied to voltage application terminals 1, 2, v3, and V4 is output. The truth table of the output voltage is shown in Table 1.

Also, constant DC voltages El-E2 and E3 are applied to the voltage application terminals 1 and v2-v3, and DC voltage E4 is applied to the terminal V4 during the display mode via the input/output mode controller (9). In the detection mode, two sine wave voltages with 1800 different phases in Table 1 are applied, and as shown in Figure 5, the internal switch group of the input/output mode controller (9) is set to the position shown by the broken line in the display mode. In detection mode, they are connected as shown by solid lines.

Figure 5 also shows the X driver (9), the country, and the X transparent electrode (
121) to (12n)L Although not shown in the figure, in reality, an X driver and an X transparent electrode are provided at positions perpendicular to these, and in the position detection mode, they operate in the same way as the X driver and X transparent electrode. do.

Next, the operation will be explained.

The present applicant proposed a display device with an input function.

The display mode and position detection mode are repeated in a time-sharing manner at regular intervals. In other words, if the horizontal direction is the passage of time as shown in Figure 6, one frame period is divided into (n+2) periods,
From period TI to Tn, display mode, period Tn++,
Tn+t operates as a position detection mode.

First, in the display mode, the internal switches of the input/output mode controller (9) are connected as shown by the broken lines in Figure 5, and the liquid crystal display controller (6) sequentially receives the data of the pattern to be displayed from the memory (5). Reading is performed and display is performed using a conventionally well-known voltage averaging driving method. In other words, the DC voltages (El-E2, E3, E4) are set to bias voltages suitable for the voltage averaging drive method, and the 5-period T+, Tt, .
..., Y transparent electrode (121), (122) for each Tn
, (...12n), and is applied to the selected X transparent electrode O11 in each period. At this time, the driver outputs at both ends of each X transparent electrode (Ill) and Y transparent electrode O2 output the same voltage.

Next, the single position detection mode will be explained using FIG. 7. FIG. 7 is a waveform diagram showing temporal changes in signals output from each section shown in FIG. During period T n + 1, the internal switch group of the input/output mode controller (9) switches to the fifth
It is connected as shown by the solid line in the figure, and detects the Y coordinate of the position of the input pen (4).

In the position detection mode, a sine wave generator (8) is connected to the ■4 terminal of the Y driver (9) and the v4 terminal of the Y driver (support).
A sine wave voltage Vmsm (2πfOt) generated in step 04) and a sine wave voltage of 1Vmain (2πfot) whose phase is shifted by 180° by a transistor (805) are applied. Furthermore, Y driver c111. Since the DF terminal of ■ is grounded, it becomes 1L", and the Y driver C31
1, @ output Of (i=1~n) +c C, as shown in Table 1, when the data in the internal shift register is 1L", the DC voltage Ex is applied to the V4 terminal, and when it is 1H", it is applied to the V4 terminal. Sine wave voltage Vmsin (2πfot) or -Vm+j
+s (27f Ot ) is output.

The basic clock C (signal C in Figure 7) generated by the clock generator (8oo'') is converted to (n
+2) The start pulse sp (signal SP in Figure 7) which is frequency-divided and output is sent to the counter (802) (signal CN in Figure S7).
T) to start counting, and at the same time, the Y driver G11. It is supplied to the data input terminal of the @ shift register. After that, the output value of the counter (802) increases by 1" every time one basic clock pulse C is generated. In synchronization with this, the data in the internal shift register of the Y driver (9) -■ shifts one by one. Therefore, the Y transparent electrode (17J) to which a voltage of ±Vmth(2πfO
), (122), and (12m) in order (2Vm/R
A sinusoidal current of o)・ain(2Zfo t) flows.

At this time, the pickup coil (4α) of the input pen (4) placed at the position An electromotive force is generated by a component perpendicular to .This electromotive force has the same frequency as the sinusoidal current flowing through the Y transparent electrode U, but has a phase difference of 90 degrees, and its level is at point X.
A sinusoidal wave is inversely proportional to the distance from the Y transparent electrode (12
m), the distance is the shortest, but since the magnetic flux of the component perpendicular to one surface of the liquid crystal cell is almost zero, the output of the pickup coil +4G is also almost zero. The output signal of this pickup coil f4ol is amplified by a head amplifier 1411, and passes through a bandpass filter (700) with a center frequency fO in order to increase the SIN ratio. As mentioned above, the output waveform of the band pass filter (700) when the current is passed through the Y transparent electrodes (2) one by one is shown in the seventh figure.
The signal is shown in the figure.

In addition, the two input terminals of the differential amplifier (702) are applied with the Y driver 13υ and the respective sine wave generators Vmsin (2πfot) applied to the country's four terminals, so one output i is Y transparent. A sine wave proportional to the current flowing through the electrode uz is output (see signal r in FIG. 7).

As can be seen from Fig. 7, the bandpass filter (700
) is the phase of the output signal from the Y transparent electrode (121) to (1
The period during which current is flowing through the X transparent electrode (12 (m
+1)) to (12rl) is 180 degrees different from the period in which the current is flowing. Therefore, when the output signal r of the differential amplifier (702) and the output signal S of the bandpass filter (700) are input to the phase comparator (701), the waveform of the output signal P becomes like the signal P in FIG. 7. and a comparator (70
When the reference potential terminal B of 3) is set to the potential of VR, when the level of the output signal P of the phase comparator (701) reaches VR, the comparator (703) outputs a coincidence pulse j, and the latch (803) Latch the counter (802) output.

In other words, an alternating current is sequentially applied to the X transparent electrode 0 to scan, and the m-th Y transparent type i (12
When m) is scanned, the comparator (703) generates a coincidence pulse and latches the output value m of the counter (802). By reading the output value of this latch (803), the CPUQQ detects the X coordinate of the position of the input pen (4)°.

The above-mentioned operation is performed during the period Tm-z in FIG. 6, and the same operation is performed during the period Tm+x with the X driver CD,
The X coordinate of the position of the input pen (4) is detected by using the transparent electrode (ill).

[Problem that the invention seeks to solve]

Conventional display devices are configured as described above, so when the display screen is enlarged, the output waveform diagram of the signals of the main parts shown in Figure 7 actually becomes the output waveform diagram as shown in Figure 8. becomes.

When there is a pickup coil (4) above the m-th electrode, when the output value of the counter (802) is around the value of m, the output signal of the band-pass filter (700) has a constant level. Therefore, the phase comparator (701) operates normally, but when the output value of the counter (802) is a value that has a large difference from m, the position of the pickup coil decoy and the position of the electrode through which the AC component current flows As the distance between P and P of the phase comparator (701) increases, the level of the output signal of the band pass filter (700) decreases and the S/N ratio of the phase information deteriorates. The shaded area at P) becomes unstable.

Therefore, the comparator (703) outputs an erroneous coincidence pulse signal 11. This erroneous coincidence pulse signal lf
There was a problem in that the detected coordinates were incorrect because the latch (803) latched the value of the counter (800).

This invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a display device that can prevent the generation of erroneous coincidence pulses even when the display screen is enlarged, and can perform accurate coordinate detection with high precision. With the goal.

[Means for solving problems]

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

[Effect]

The display device according to the present invention uses a gate circuit to prevent the generation of erroneous coincidence pulses, and processes coincidence pulses that indicate phase reversal after the amplitude level of the magnetic flux detection means exceeds a certain value as true coincidence pulses.

〔Example〕

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

FIG. 1 is a block diagram showing the configuration of a display device according to an embodiment of the present invention. In Figure 1, (1000)
is a gate control circuit equipped with an amplitude detection means, a gate circuit, and a means for closing the gate circuit; the other components are the same as those shown in FIG. - or make an equivalent action.

! Figure i82 is a circuit diagram showing details of the input pen (4), position detection circuit (7), position detection scanning circuit (8), and gate control circuit (1000) shown in Figure 1.

In Figure 2, the input pen (4), the position detection circuit (7)
- Each component of the position detection set meal circuit (8) is the same as that in the conventional example shown in FIG.
Or make a corresponding action.

In the figure, (1001) is a diode, (1002)
is a resistor, (1003) is a capacitor, these constitute an envelope detection circuit, and a bandpass filter (700)
This is an amplitude detection means for extracting amplitude information from an output signal containing an AC component. (1004) is a comparator which compares the potentials of input terminals A and B and outputs a low level from the C terminal when A)B. (1005) is a variable resistor, which determines the comparison potential of the B input terminal of the comparator (1004), that is, a predetermined threshold value. (1006)
is the inverter gate - (1007) is the resistor, (1
008) is an OR gate that constitutes a differentiating circuit, detects the fall of the output of the comparator (1004), and generates a pulse. (1009) is or gate, (1010), (
1011) is a set/resettable type flip-flop, (1012) is an OR gate, (1013)
is an inverter gate.

Moreover, FIG. 3 is an output waveform diagram showing changes in signals over time in the main parts of FIG.
The signal is the output of the bandpass filter (700) and its amplitude envelope, the signal CA is the output of the comparator (1004), the signal s1 is the output of the comparator (1004), and the signal S2 is the output of the OR gate ( 1
The output of the flip-flop (101
0) Q output-signal S4 is a flip-flop (1011
), the signal l is the output of the comparator (703),
The signal 7t is the waveform of the output of the OR gate (1012).

Next, the operation will be explained.

The display device according to the embodiment of the present invention operates in the same manner as the conventional example, repeating the display mode and the position detection mode in a time-sharing manner as shown in FIG.
3 and 3 will be explained.

In Figure 2, the pickup coil (
Although not shown, 4I is placed, for example, on the m-th Y transparent electrode (12m) of the liquid crystal cell (1).

When an alternating current component current is sequentially passed through each Y transparent electrode port, the output signal of the bandpass filter (700) has a waveform like the signal shown in Fig. 3, and the phase change point of this signal is P. coordinates are detected based on the point). Comparator (7
The output signal l of 03) generates a pulse at one phase change point as shown in signal l in Fig. 3, but in addition to the true phase change point, an erroneous pulse signal lf may also be generated at a low level of the signal. Output.

On the other hand, the output signal of the bandpass filter (700) is processed by envelope line detection circuits (1001), (1002), (1003).
), the signal input to the A terminal of the comparator (1004) has the waveform shown in signal CA in FIG. Therefore, when the output waveform of the comparator (1004) reaches a predetermined threshold, the gate circuit will be opened.
Signal s1 and null in FIG. That is, a bandpass filter (
700) becomes low level only when the amplitude of the output becomes larger than a predetermined level. Therefore, the flip-flop (1
The signal S4 of the Q output of 011) is the signal 54Ic in FIG.
As shown, one of the pulses (signal S2 in FIG. 3) indicating the falling edge of one comparator (1004).

Q output of flip-flop (1010) (signal S3)
Apply the gate and use the resulting pulse to low level? ,
(Li, OR '7'-) The low level pulse of (1012) causes the signal to become high level again and close the gate circuit.

Therefore, among the output pulses of the comparator (703) (signal l in FIG. 3), the Q of the flip-flop (1011) is
A pulse signal that shows a true phase change by applying a gate with an OR gate (1012) to remove only the period when the output (signal 54) is at a low level! (You can extract

〔Effect of the invention〕

As described above, according to the present invention, the output section of the phase change detection means of the magnetic flux detection means includes an amplitude detection means for detecting the output level of the magnetic flux detection means, and a gate circuit that opens when this output level exceeds a predetermined value. Since the system is configured such that it does not operate when the input signal level to the phase change detection means is low, even if one display screen is enlarged, a cylindrical display device with coordinate detection accuracy can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a display device according to an embodiment of the present invention; FIG. 2 is a circuit diagram showing details of the position detection scanning circuit, position detection circuit, gate control circuit, and input pen in FIG. 1; Fig. 3 is an output waveform diagram showing changes over time in the signals of the main parts in Fig. 2, Fig. 4 is a block diagram showing the configuration of a conventional display device, and Fig. 5 is a position detection operation of a conventional display device. FIG. 6 is an explanatory diagram illustrating time-sharing operation between display mode and position detection mode,
FIG. 7 is an output waveform diagram showing the changes over time of the main signals of each part in FIG. 5, and FIG. 8 is a waveform diagram showing the changes over time of the signals of the conventional display device. (1)...Flat display panel, (4)...Input pen, (6)...Display signal application means, [7) + +8
)... Position detection means, uto...
000)...Gate circuit and means for closing the gate circuit, (1001), (1002), (1003)...Amplitude detection means. Note that the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] A flat display panel having an X-Y matrix electrode configuration, a display signal applying means for applying a display signal to the X-Y matrix electrodes, and at least one electrode of the X-Y matrix electrodes. AC component current applying means for sequentially applying a current having an AC component to the group one by one; an input pen equipped with a magnetic flux detection means; and a signal generated in the phase of the AC component current applied to the matrix electrode and the magnetic flux detection means. and 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 signal generated in the magnetic flux detection means is The present invention is characterized by comprising: amplitude detection means for detecting amplitude; a gate circuit that opens when the output of the amplitude detection means reaches a threshold; and means for closing the gate circuit using an output pulse of the gate circuit. Display device.