JPS63268027A - Coordinate input device with liquid crystal display - Google Patents

Abstract

PURPOSE:To eliminate the noises which are produced when a liquid crystal element is driven and to ensure the normal detection of coordinates, by detecting the tablet coordinates after a fixed period from the rise and fall time points of a liquid crystal drive waveform AC transforming signal. CONSTITUTION:The liquid crystal drive waveform AC transforming signal delivered from a display control circuit 4 is supplied to a delay circuit 12 and an EX-OR circuit 13. The circuit 12 delays said transforming signal by a time set previously. An exclusive OR is secured between the delayed signal (a) and an undelayed signal and supplied to a tablet control circuit 11. Then an X can circuit 7, a Y scan circuit 8 and a coordinate detecting circuit 9 are controlled via the circuit 11 synchronously with an exclusive OR signal, i.e., a signal (b). The tablet coordinates can be detected by the circuit 9 when a coordinate 6 indicates a tablet 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coordinate input device with a liquid crystal display in which a tablet and a liquid crystal display element are integrated into a laminated structure.

[Summary of the invention]

The present invention provides a coordinate input device with a liquid crystal display in which a tablet and a liquid crystal display element are integrated in a laminated structure. After a preset time has elapsed from the falling point, tablet scanning is started and coordinates are detected.
This prevents the tablet's coordinate detection accuracy from deteriorating due to the influence of noise that occurs in synchronization with the falling edge, and enables normal coordinate detection.

[Conventional technology]

An explanation of a conventional coordinate input device with a liquid crystal display is shown in Figures 3 and 4.
Do it in a detailed manner using diagrams.

FIG. 3 shows a block diagram of a conventional coordinate input device with a liquid crystal display, and FIG. 4 shows a timing diagram related to FIG.

In FIG. 3, 1 is a liquid crystal panel, 2 is a segment drive circuit that drives the segment lines of the liquid crystal panel 1, 3 is a common drive circuit that also drives the common line of the liquid crystal panel 1, and 4 is display data.

It shows a display control circuit that outputs signals such as a drive control signal and a liquid crystal drive waveform alternating signal.

Further, the tablet 6 on which a group of parallel conductors is laid is a coordinate indicator that generates an alternating magnetic field, and 7 is the X of the tablet 5.
X scanning circuit for scanning a group of parallel conductors laid in the direction, 8
9 is an X scanning circuit that scans a group of parallel conductors laid in the Y direction of the tablet 5, and 9 is an X scanning circuit that scans a group of parallel conductors laid in the Y direction of the tablet 5; A coordinate detection circuit that detects coordinate values.

lO is the X scanning circuit 7. X scanning circuit 8. Coordinate detection circuit 9
Each shows the tablet control circuit that controls the
In the conventional coordinate input device with a liquid crystal display, the display control circuit 4 and the tablet control circuit 10 are not synchronized and operate independently.

[Problems to be Solved by the Invention] In the conventional technology, since the display control circuit 4 and the tablet left control circuit 10 are not synchronized, the segment drive circuit 2 and the common drive circuit are not synchronized, as shown in the timing diagram of FIG. 3
The rise of the liquid crystal drive waveform alternating signal for inverting the liquid crystal drive waveform applied to the liquid crystal panel l at a constant cycle,
Noise that occurs synchronously at the falling edge, that is, noise that occurs every time the liquid crystal drive waveform applied to the liquid crystal panel is reversed, is added to the induced signal output from the tablet by indicating with the coordinate indicator 6, There was a problem that the coordinate detection accuracy of the tablet deteriorated and normal coordinate detection could not be performed.

[Means for solving problems]

In order to solve the conventional problems, the present invention includes a delay circuit that delays the liquid crystal drive waveform alternating signal, and an exclusive configuration between the liquid crystal drive waveform alternating signal before the delay and the liquid crystal drive waveform alternating signal after the delay. The configuration includes an EX-OR circuit that calculates a logical sum, and by inputting the output signal of the EX-OR circuit to the tablet control circuit, the rise of the liquid crystal drive waveform AC conversion No. 13 is achieved.

The coordinates of the tablet are detected after a certain period of time after the fall.

[Effect]

In the coordinate input device with a liquid crystal display configured as described above, the coordinates of the tablet are detected after a preset time from the rising and falling points of the liquid crystal drive waveform alternating signal.

Therefore, coordinate detection is performed while avoiding the noise that occurs synchronously with the rise and fall of the LCD drive waveform AC signal, that is, the noise that occurs every time the LCD drive waveform applied to the LCD panel is reversed, so that the output from the tablet is avoided. This prevents the tablet's coordinate detection accuracy from deteriorating and allows normal coordinate detection without adding noise to the induced signal.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment according to the present invention, and the same components as those of the conventional coordinate input device with a liquid crystal display shown in FIG. 3 are given the same numbers.

In FIG. 1, 1 is a liquid crystal panel, 2 is a segment drive circuit, 3 is a common drive circuit, and 4 is a display control circuit. The display-side i''in circuit 4 outputs signals such as display data, drive control signals, and liquid crystal drive waveform alternating signals, which are connected to the segment drive circuit 2 and the common drive circuit 3.
are entered respectively. Further, the liquid crystal drive waveform alternating signal is connected to the delay circuit 12 and EX-OR which is an exclusive OR.
The signal is also input to the circuit 13, and the delay circuit 12 delays the liquid crystal drive waveform alternating signal by a preset time.

The EX-OR circuit 13 performs exclusive OR of the liquid crystal drive waveform alternating signal from the display control circuit 4 and the liquid crystal drive waveform alternating signal delayed by the delay circuit 12 (hereinafter referred to as No. 3 a). The output signal (hereinafter referred to as signal) is input to the tablet+tjl1ff11 circuit 11.

In synchronization with the signal, from the tablet control circuit 11,
X scanning circuit 7. X scanning circuit 8. A signal for controlling the coordinate detection circuit 9 is output, and in response to the control signal, the X scanning circuit 7 and the X scanning circuit 8 output a scanning signal for scanning the group of parallel conductors laid on the tablet 5. A group of conductors is scanned. At this time, the coordinate indicator 6 that generates an alternating magnetic field indicates an arbitrary position on the tablet 5, so that an induced signal is output from the tablet 5, and the coordinates are detected by the coordinate detection circuit 9.

FIG. 2 is a timing diagram related to the block diagram of FIG. 1, and only the parts related to the present invention are described.

In FIG. 2, when the liquid crystal drive waveform AC conversion signal output from the display control circuit 4, the signal a output from the delay circuit 12, and the signal output from the EX-OR circuit 13, the liquid crystal drive waveform AC conversion signal is output from the display control circuit 4. rising of the signal.

The noise generated in synchronization with the falling edge and the induced signal output from the tablet 5 are shown, respectively, and after a preset time (1) in the delay circuit 12 with respect to the liquid crystal drive waveform alternating signal, that is, Since coordinate detection is performed in synchronization with the falling edge of the signal, it is possible to perform coordinate detection while avoiding noise that occurs in synchronization with the rising and falling edges of the liquid crystal drive waveform alternating current signal.

〔Effect of the invention〕

As described above, according to the present invention, coordinates can be detected while avoiding noise generated when driving a liquid crystal display element, so that deterioration in coordinate detection accuracy can be prevented. As a result, it is possible to provide an input device with a high resolution and high +17 degree liquid crystal display required for handwritten character recognition, graphic recognition, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a coordinate input device with a liquid crystal display according to the present invention, FIG. 2 is a timing diagram of this embodiment, FIG. 3 is a block diagram of a conventional coordinate input device with a liquid crystal display, and FIG. 4 is a block diagram of a conventional coordinate input device with a liquid crystal display. FIG. 3 is a timing diagram of the device. l...? fLi product panel 2...Segment drive circuit 3...Common drive circuit 4...Display control circuit 5...Tablet 6...Coordinate indicator 7...X scanning circuit 8 ...Y scanning circuit 9...Coordinate detection circuit to, 11...Tablet system? :I11 circuit 12・
...Delay circuit 13...EX-OR circuit and above Applicant: Seiko Electronics Co., Ltd.

Claims (1)

[Claims] A coordinate input device with a liquid crystal display in which a tablet and a liquid crystal display element are laminated and integrated, includes a delay circuit that delays a liquid crystal drive waveform alternating signal for inverting the liquid crystal drive waveform at a constant cycle, and the liquid crystal drive waveform alternating signal. and the delayed signal which is the output signal of the delay circuit EX-
A liquid crystal display comprising an OR circuit, inputting the output signal of the EX-OR circuit to a tablet control circuit, and detecting coordinates after a certain period of time from the rise and fall of the liquid crystal drive waveform alternating signal. Coordinate input device.