KR970000825B1 - Lcd device and signal processing apparatus using the same - Google Patents

Abstract

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Description

LCD display device and video signal processing device using same

1 is a circuit diagram showing the principle of an example of a conventional liquid crystal display device.

2 is a timing diagram illustrating the operation of the apparatus of FIG.

3 is a block diagram showing a configuration of one embodiment of a liquid crystal display device of the present invention.

4 is a timing diagram illustrating the operation of the apparatus of FIG.

5 is a block diagram showing the configuration of one embodiment applied to a video signal recording and reproducing apparatus of the present invention.

6 is a timing diagram illustrating the operation of the apparatus of FIG.

* Explanation of symbols for main parts of the drawings

1: gate driving circuit 2, 12: gate bus

3: source driving circuit 4, 14: source bus

5: TFT 6: Capacitor

7 display device 11 gate driver

13: source driver 15: TFT active matrix LCD

18: still image control circuit 19: LCD circuit

20 system control circuit 31 imaging lens

36: magnetic head 37: magnetic disk

38: spindle motor 39: operation switch

[Industrial use]

The present invention relates to a liquid crystal display device represented by a TFT (thin film transistor) active matrix LCD and a video signal processing device such as an electronic still camera using the same for the monitor.

[Prior art]

In recent years, liquid crystal display devices having advantages of miniaturization and relatively low power consumption have been used as monitors of various video signal recording and reproducing apparatuses.

Among them, since a simple matrix type device is difficult to display with high density, an active matrix type device having a display element and a switching element at each display position has become mainstream.

1 is a circuit diagram showing an example of a conventional TFT active matrix LCD.

In the figure, 1 is a gate driving circuit (as a main circuit), and a switching pulse (scan pulse) is provided to a predetermined number of gate buses 2.

3 is a source driving circuit (holder circuit), and provides a video signal corresponding to a predetermined number of source buses 4.

At each display position, a thin film transistor (TFT) 5 as a switching element, a signal accumulation capacitor 6 connected to the drain thereof, and a display element 7 having a transparent electrode and a liquid crystal layer are arranged.

Next, the operation will be described with reference to the timing diagram of FIG.

The gate driving circuit 1 provides a switching pulse to the corresponding gate bus 2 in synchronization with the horizontal synchronization signal included in the video signal.

For example, as shown in FIG. 2A, if a switching pulse is provided to the gate bus 2 of the i-th row at the timing of a predetermined horizontal synchronization signal, in the case of interaced scanning for each field, At the timing of the horizontal synchronizing signal approximately one field later, the switching pulse is provided to the gate bus 2 of the (i + 1) th row as shown in the diagram (b).

However, in the case of line sequential scanning, the interval between switching pulses coincides with the period of horizontal scanning. As a result, the TFT 5 connected to the gate bus 2 provided with this switching pulse is turned ON.

On the other hand, the source driving circuit 3 divides a plurality of received video signals in a direction of a horizontal scan line which is synchronized with a horizontal synchronization signal included in the video signal.

As a result, these video signals are accumulated in the capacitor 6 through the source drain of the TFT 5 and are transferred to the display element 7 for display.

The signal accumulated in the capacitor 6 is then held until the switching pulse is applied again after a time corresponding to the period of one frame elapses. Of course, the capacitor 6 can be omitted if the resistance ratio Roff / Ron of the liquid crystal capacitor and the TFT 5 is sufficiently large (where Roff is the internal resistance of the TFT 5 in the OFF state, and Ron is the internal resistance in the ON state). to be).

For example, when a video signal as shown in FIG. 2 (c) is applied to the source bus 4 of the j-th column, when a switching pulse is provided to the gate bus 2 of the i-th row, the source bus of the j-th column In the capacitor 6, which is connected to (4) and the gate bus 2 of the i < th > row, the video signal is sampled as shown in the diagram (d).

If the potential shown in FIG. 2E has been supplied to the counter electrode, a voltage as shown in FIG. 7F is applied to the display element 7.

The charge output by the capacitor 6 in accordance with the preceding input video signal applied to each display element affects the display when a subsequent video signal is applied to each display element 7, so that the subsequent video signal is reversed. Is applied to each display element with the same polarity.

In this way, a video signal corresponding to each pixel is supplied to display the entire image.

For example, in an electronic still camera or the like, the liquid crystal display device can check an image, photograph the subject at a predetermined timing, and record the video signal of the subject on a magnetic disk.

In addition, the liquid crystal display can be used to monitor the playback image by reproducing the video signal from the magnetic disk.

[Problems that the invention tries to solve]

As described above, the conventional liquid crystal display device has only a function of sequentially supplying a video signal supplied every frame to a display element and displaying it as a dynamic screen. For this reason, to display still images (still image means the same as still images), one frame (or one field) of video signal is stored in the frame memory (or field memory) once and the stored video signal is stored. A signal repeatedly read or recorded on a magnetic disk is repeatedly reproduced to be provided to a liquid crystal display device for display.

As a result, an expensive memory is required for reproducing still images, and the cost is high.

In addition, there is a drawback that the consumption of the battery, the magnetic head, the magnetic disk, or the like becomes large when the still image is obtained by playing on the magnetic disk.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation and provides a liquid crystal display device which can reproduce still images with a simple configuration and inexpensively.

In addition, the present invention provides an example applied to a video signal recording and reproducing apparatus capable of confirming a recording screen soon after recording with low power consumption.

[Means for solving the problem]

A liquid crystal display device according to an aspect of the present invention comprises an active matrix LCD having a display element and a switching element at each display position, a first driver for supplying a display video signal to the display element via a switching element, and a switching pulse. And a second driver that generates and turns the switching element on and off, and a control circuit to prevent the switching pulse from being supplied to the switching element for at least a period in which a still image can be recognized.

According to another aspect of the present invention, an embodiment applied to a video signal processing apparatus for photographing a subject and converting an image of the subject into a video signal including a video signal, a horizontal sync signal, and a vertical sync signal is provided. And an active matrix LCD having a switching element; A device, recording means for recording a video signal provided from the imaging device on a recording medium, operation means operated when recording the video signal provided from the imaging device on the recording medium, and a video signal provided from the imaging device when the operation means is operated. Is written to the recording medium and simultaneously For a predetermined period of time by the still image video signals it stops, and a control means for displaying on the liquid crystal display means.

[Action]

In the liquid crystal display device of the present invention, a video signal is supplied to the active matrix LCD by a first driver such as a source driver through a switching element, and a switching element of each pixel is driven by a second driver such as a gate driver.

When still image reproduction is commanded, the control circuit controls the second driver, for example, to stop the generation of the switching pulse for several seconds.

As a result, the signal of each pixel is maintained as it is in the active matrix LCD, and still images can be reproduced without using a frame memory or the like.

In the video signal recording and reproducing apparatus of the present invention, when an operation means such as a release switch is operated, a video signal provided from an imaging device such as a CCD is recorded on a recording medium such as a magnetic disk.

At this time, the supply of the switching pulse to the liquid crystal display means such as a TFT active matrix LCD is stopped, and the monitored video signal is displayed as it is for a predetermined period (for example, several seconds).

Therefore, the captured image can be confirmed as a still image soon after shooting.

As a result, the power consumed is minimized, and the consumption of the magnetic head and the magnetic disk is prevented.

EXAMPLE

3 is a block diagram showing the configuration of an embodiment of a liquid crystal display device of the present invention.

11 is a gate driver and provides a switching pulse to a predetermined number of gate buses 12. 13 is a source driver and provides a video signal to a predetermined number of source buses 14. 15 is a TFT active matrix LCD and is driven by the gate driver 11 and the source driver 13.

The above configuration for the TFT active matrix LCD 15 is similar to that in FIG.

16 is a source drive signal generation circuit, generates a source drive signal when receiving a video signal, and provides the signal to the source driver 13. 17 is a gate drive signal generation circuit, which generates a gate drive signal when received as a video signal.

18 is a still image control circuit, and the gate driving signal is intermittently provided from the gate driving signal generating circuit 17 to the gate driver 11.

The LCD circuit 19 is comprised by the above.

20 is a system control circuit and controls the operation of the LCD circuit 19.

Next, the operation will be described with reference to the timing diagram of FIG.

The source drive signal generation circuit 16 generates a source drive signal as soon as it receives an input video signal and provides it to the source driver 13. The source driver 13 applies the source driving signal (including the video signal) to the source of the TFT 5 of the TFT active matrix LCD 15 via the corresponding source bus 14.

On the other hand, the gate drive signal generation circuit 17 generates a gate drive signal in synchronization with the horizontal synchronization signal included in the input video signal. This gate driving signal is applied to the gate driver 11 through the still image control circuit 18. The gate driver 11 provides a switching pulse to each gate bus 12 in response to this gate driving signal.

This switching pulse is input to the gate of the TFT 5 to switch the TFT 5 ON and OFF.

In this way, an image corresponding to the video signal is displayed on the TFT active matrix LCD 15.

Next, when the still image control signal is inputted by the system control circuit 20, the still image control circuit 18 stops the provision of the gate drive signal from the gate drive signal generation circuit 17 to the gate driver 11. Let's do it.

For example, as shown in FIGS. 4A and 4B, the gates of the i th row and the (i + 2) row (in the case of line sequential scanning, the (i) and (i + 1) rows) The switching pulse supplied to the bus 12 is not provided after generating the still image control signal.

Thus, for example, when a video signal as shown in Fig. 4C has been applied to the source bus 14 in column j, it is connected to the gate bus 12 in row i and the source bus 14 in row j. The voltage that is sampled and held by the capacitor 6 and the TFT 5 is held thereafter as it is shown in FIG. 4 (d).

Therefore, when the counter electrode of the capacitor 6 is provided with the voltage as shown in FIG. 4 (e), the voltage as shown in FIG. 4 (f) is applied to the corresponding display element 7. . Since no switching pulse is applied to the gate bus 12, its voltage remains approximately constant.

As a result, a still image is displayed on the TFT active matrix LCD 15.

The provision of the switching pulse from the gate drive signal generation circuit 17 to the gate driver 11 is inhibited for a sufficient time period (e.g., several seconds) to confirm the still image.

In practice, charging to the capacitor 6 is naturally discharged through the OFF resistor of the TFT 5 while also maintaining an image on the display element 7.

As a result of the experiment, a still image can be obtained for about 10 seconds by the supply stop of the switching pulse.

FIG. 5 is a block diagram showing the configuration of one embodiment in the case where such a liquid crystal display device is applied to an electronic still camera, and the same reference numerals are given to the parts corresponding to those in FIG.

In FIG. 5, when a subject (not shown) is photographed, the imaging lens 31 causes light from the subject to enter the CCD 32. As shown in FIG. 33 is a CCD driver, which electrically drives the CCD 32.

34 is a processing circuit, which processes the provision of the CCD 32 to provide the processed video signal to the LCD circuit 19 and the recording / generating circuit 35. In this case, the switching circuit 40 is switched so that the processing circuit 34 and the LCD circuit 19 are electrically connected based on the selection signal from the system control circuit 20.

Reference numeral 36 denotes a magnetic head, which records and reproduces a video signal on the magnetic disk 37 as a recording medium rotated by the spindle motor 38. 39 is the same operation switch as the release switch, and is operated when shooting a subject.

On the other hand, when the video signal is reproduced from the magnetic disk 37, the system control circuit outputs the switching signal to the selection signal so that the output of the recording / reproducing circuit 35 is provided to the LCD circuit 19.

In this case, the magnetic head 36 generates a video signal from the magnetic disk 37, and the recording / reproducing circuit 35 reproduces the reproduced data based on the recording / reproducing signal from the system control circuit 20. The video signal is transmitted to the LCD circuit 35.

Next, the operation will be described with reference to FIG.

While the imaging lens 31 causes the image of the subject to be imaged on the CCD 32, as the CCD driver 33 receives the CCD drive signal by the system control circuit 20, the CCD 32 receives the CCD driver ( Driven by 33 to provide a photoelectric conversion signal to the processing circuit 34.

The processing circuit 34 processes the received signal and converts it into a video signal of any format such as, for example, the National Television System Commitee (NTSC) scheme. This video signal is applied to the LCD circuit 19 and displayed as described above.

If the operation switch 39 is operated at a predetermined timing while the image is monitored by the LCD circuit 19, the system control circuit 20 applies a recording / reproduction control signal to the recording / reproduction circuit 35.

At this time, the recording / reproducing circuit 35 generates the recording gate pulse shown in Fig. 6A during one field period, and FM-modulates the video signal input from the processing circuit 34 between the magnetic heads 36. ) To provide. As a result, a video signal for one field (one coma) is recorded on one track of the magnetic disk 37 which is rotated by the spindle motor 38 at a speed of 3600 rpm.

On the other hand, the system control circuit 20 provides the LCD circuit 19 with the still image control signal shown in Fig. 6B in synchronization with the recording control signal.

During the period in which the still image control signal is input in the LCD circuit 19, the generation of the switching pulse as shown in Fig. 6C is stopped as described above.

As a result, the video signal input to the source bus 14 of the j-th column as shown in FIG. 6D, for example, immediately after the operation switch 39 is operated as shown in FIG. Sampling is bound to the field.

Figure f shows the potential of the counter electrode.

This hold state continues until the still image control signal is released.

Therefore, the image captured by the LCD circuit 19 is displayed as a still image.

The user can thereby check the captured image without a separate operation.

In addition, the present invention can be applied not only to the case of interlace scanning but also to the case of line sequential scanning.

[Effects of the Invention]

As described above, according to the present invention, by stopping the supply of the switching pulse to the active matrix LCD for a predetermined time, a still image can be obtained simply and inexpensively without using a field memory, a frame memory, or the like.

Further, according to the present invention, when the recording operation is performed, the still image is displayed on the liquid crystal display means by stopping the supply of the switching pulse for a predetermined time, so that the user can check the actually recorded image without any further operation. .

In addition, the wear of the magnetic disk or the magnetic head can be reduced, and the power consumption can be extremely low, which is particularly advantageous for a portable video signal recording and reproducing apparatus using a battery.

Claims (12)

A liquid crystal display device for video display such as for receiving a video signal, comprising: an active matrix LCD member having a plurality of display elements and a plurality of switching elements; Drive signal supply means for supplying a drive signal to the display element through each of the switching elements based on the video signal; And control means for holding the switching element in the off state for a predetermined time such that the supply of the drive signal to the display element is stopped; And a still image displayed for the predetermined time without applying a separate video signal to the LCD member. 2. The apparatus of claim 1, wherein the video signal comprises a video signal, a horizontal sync signal, and a vertical sync signal; The drive signal supply means; First driving means for supplying the driving signal to the display element through each of the switching elements in accordance with the video signal and the vertical synchronization signal included in the video signal; A second driving means for supplying a switching signal to each corresponding one of the switching elements in accordance with the horizontal synchronization signal included in the video signal; And said control means includes means for prohibiting said second driving means from supplying said switching signal, and said control means drives said prohibition means for said predetermined period. The LCD device of claim 1, wherein the LCD member includes a plurality of capacitors connected to respective ones of the display elements for holding charge applied to each corresponding one of the display elements during the predetermined period. Liquid crystal display device characterized in that. 2. A liquid crystal display device as claimed in claim 1, wherein said display element is capable of holding a charge to hold said image displayed for at least said predetermined period. Means for photographing a subject and converting an image of the subject into a video signal including an image signal, a horizontal synchronization signal, and a vertical synchronization signal; An active matrix LCD member having a plurality of display elements and a plurality of switching elements; Drive signal supply means for supplying a drive signal to the display element based on each of the switching elements based on the video signal; And control means for holding the switching element in the off state for a predetermined time such that the supply of the drive signal to the display element is stopped; And a still image is displayed for the predetermined time without applying a separate video signal to the LCD member. The method of claim 5, wherein the drive signal supply means; First driving means for supplying the driving signal to the display element through each of the switching elements in accordance with the video signal and the vertical synchronization signal included in the video signal; A second driving means for supplying a switching signal to each of the switching elements in accordance with the horizontal synchronization signal included in the video signal; And said control means includes means for prohibiting said second driving means from supplying said switching signal, said control means driving said prohibition means for said predetermined period. The video signal processing apparatus according to claim 6, further comprising recording means for recording the video signal on a recording medium. 8. The video signal processing apparatus according to claim 7, further comprising reproducing means for reproducing the video signal recorded on the recording medium. 8. The recording apparatus according to claim 7, wherein said recording means includes switch means for initiating recording of said video signal; And said control means drives said prohibition means when said switch means is activated. 6. The LCD device according to claim 5, wherein the LCD member includes a plurality of capacitor means connected to each corresponding one of the display elements to hold charge applied to each corresponding one of the LCD members during the predetermined period. A video signal processing device. 11. A video signal processing apparatus according to claim 10, wherein said capacitor means is capable of holding electric charge for holding an image displayed on said LCD member for at least said predetermined period. 6. The video signal processing apparatus according to claim 5, wherein the LCD member is capable of holding electric charges to maintain an image displayed on the LCD member for at least the predetermined period.