JPH0294871A - Display device - Google Patents

Abstract

PURPOSE:To prevent the difference of the deterioration between the middle part and the peripheral part of a display screen by arranging a polarized plate and a liquid crystal panel on a display screen and providing an effective pattern control means to be masked in matching with the aspect ratio of a displayed video signal. CONSTITUTION:In the case of displaying a high definition TV signal, changeover switches 103, 113, 123 are thrown respectively to the position of the high definition TV and a changeover switch 244 is opened. In this case, the entire screen of a CRT 130 is scanned. Moreover, since no voltage is applied to the liquid crystal, the light is transmitted through in the entire screen. In the case of displaying an NTSC video signal, the changeover switches 103, 113, 123 are thrown respectively to the position of the NTSC and the changeover switch 244 is closed. In this case, the entire screen of the CRT 130 is scanned but the video image is displayed on the middle part. A halftone picture is displayed at both edges of the CRT 130 and since an AC voltage is applied to the liquid crystal at both edges, no light is transmitted through. Plural video signals with different aspect ratio are displayed without causing the difference of the deterioration between the middle part and the peripheral part of the display pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a display device such as a television receiver.

(Prior Art) The conventional television (hereinafter referred to as TV) system has 525 scanning lines and Aspect!・NTSC system with ratio (ratio of screen width to height) of 4:3, number of scanning lines 625
A PAL system with an aspect ratio of 4:3 is known.

In contrast to these conventional methods, in recent years the number of scanning lines has been increased to 1125.
Currently, a high-definition TV system with an aspect ratio of 16:9 is being considered. This high definition TV system requires a dedicated display device with a screen aspect ratio of 16:9. Here, the display device is a CRT (Catho
de-ROy Tube) may be used.

By the way, since it is inconvenient to have a conventional display device and a high-definition TV display device separately, there is a need to display these two signals on one display device. The conventional method to achieve this is to use a CRT with a large aspect ratio.

For example, a high-quality TV with an aspect ratio of 16:9
When displaying a video signal with a small aspect ratio, such as an NTSC signal with an aspect ratio of 4:3 (12:9), on an RT, first, 1050 scanning lines are generated by interpolation from 525 scanning lines, and then the CRT There is a method in which the deflection width of the scanning line is set to 12/16 in the horizontal direction and displayed. According to this method, the image is displayed only in the central part 12/16 of the screen in the horizontal direction, and the 4/16 parts at both ends are not scanned and therefore not displayed.

This situation is shown in FIG. Here, (a) shows a high-definition TV.
This figure shows how a signal is displayed as an image, and FIG. 7(b) shows an image of an NTSC signal.

FIG. 4 shows the configuration of a conventional display device that displays images of two signals, a high-definition TV signal and an NTSC signal.
First, the first horizontal deflection circuit 101 manually generates a high-definition TV horizontal synchronization signal to generate a high-definition TV signal water'lZ deflection signal, and the second horizontal deflection circuit 102 manually generates an NTSC horizontal synchronization signal to generate an NTSC Generate a horizontal deflection signal for the signal.

One of the horizontal deflection signals outputted from the first and second horizontal deflection circuits 101 and 102 is selected by a changeover switch 103 and sent to a horizontal deflection coil 104.

Here, the frequency Fhd of the high-definition TV horizontal deflection signal is Fh'd -30X1125=33.75 [KIIz
l, and the frequency Fn of the horizontal signal for NTSC signals is F
n-30X525X2=31.5 [KIIzl. Also, the amplitude level of the horizontal deflection signal for NTSC signals is 12/
16 - smaller by 0.75. This amplitude relationship is shown in FIG. In FIG. 5, (a) shows a high-definition TV horizontal deflection signal, and (b) shows an NTSC signal horizontal deflection signal.

Next, the first vertical deflection circuit 111 inputs the high-definition TV vertical synchronization signal to generate a vertical deflection signal for the high-definition TV signal, and the second vertical deflection circuit 112 manually inputs the NTSC vertical synchronization signal and generates a vertical deflection signal for the high-definition TV signal. Generate a vertical deflection signal for the signal. 1st
And one of the vertical deflection signals outputted from the second vertical deflection circuit Ill, 112 is selected by the changeover switch 113 and sent to the vertical deflection coil 114.

Here, the ratio of the scanning period to the scanning period of the vertical deflection signal for high-definition TV signals (hereinafter referred to as vertical scanning period ratio) is 0.92, and the vertical scanning period ratio for NTSC signals is 0.
．． It is 83. This ratio relationship is shown in FIG. In Figure 6, (a) is a high-definition TV vertical deflection signal, (b)
The figure shows a vertical deflection signal for an NTSC signal.

Furthermore, the first video signal processing circuit! A second video signal processing circuit 122 inputs the NTSC video signal and generates an RGB video signal for the NTSC signal. One of the ROB video signals output from the first and second video signal processing circuits 121 and 122 is selected by a changeover switch 123 and sent to the cathode electrode 124 of the CRT 130.

In the above configuration, when displaying a high-definition TV signal as an image, the changeover switches 103, 113 and 123 are respectively set to the high-definition TV side. At this time, the CRT 130 scans the entire display screen. When displaying an image of an NTSC signal,
Changeover switches 103, 113 and 123 are set to N respectively.
Set it to the TSC side. At this time, the CRT 130 scans only the central portion of the display screen in the horizontal direction.

However, in the conventional display device as described above, when displaying an image of an NTSC signal with a small aspect ratio, only the center of the display screen is scanned, so there is a difference in the degree of phosphor deterioration between the center and both ends. It will happen. That is,
The phosphor deteriorates quickly in the central part, which is constantly scanned, and hardly deteriorates in the opposite ends, which are not scanned. Therefore, when a high-quality TV signal with a large aspect ratio is displayed as an image on this display device, the image quality differs between the center and both ends of the display screen. Of course, it is undesirable for such deterioration of a portion of the screen to occur when displaying an image of a high-definition TV signal.

(Problems to be Solved by the Invention) As described above, in conventional display devices, when a video signal with a small aspect ratio is displayed as an image on a display device with a large aspect ratio, deterioration progresses only in the center of the display screen, and the aspect ratio When displaying an image from a video signal with a large amount of noise, a serious deterioration in image quality occurs.

Therefore, the present invention was made to solve the above problems, and provides a display device that can display a plurality of video signals with different aspect ratios without causing a difference in the degree of deterioration between the central part and the peripheral part of the display screen. The purpose is to provide

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, a display device according to the present invention has the following features:
In a display device that switches and displays a plurality of image signals having different aspect ratios, a deflection width control means for controlling the deflection width of a scanning line for a video signal to be displayed according to the aspect ratio of a display screen, and a control width of this means a time axis control means for compressing or expanding a video signal to be displayed on a time axis according to the time axis, and an IQ light plate and a liquid crystal panel arranged on a display screen, and applying voltage to the liquid crystal panel according to display switching of the video signal. The device is configured to include effective screen control means for switching and controlling the voltage and masking the display screen according to the aspect ratio of the video signal to be displayed.

(Function) According to the above configuration, for example, when displaying a video signal with a small aspect ratio on a display device with a large aspect ratio, the deflection width of the scanning line is matched to the display screen and the video signal is time-axis compressed. , it is possible to display the image signal at the aspect ratio while scanning the scanning line to both ends of the screen, which eliminates the difference in deterioration of the phosphor between the center and both ends of the screen, and reduces the aspect ratio. Even when a large video signal is displayed as an image, serious deterioration in image quality does not occur. Furthermore, when displaying an image of a video signal with a small aspect ratio, unnecessary parts of the display screen are masked by a liquid crystal panel, so no light passes through those parts even if they are being scanned, making it much easier to see.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. However, in FIG. 1, the same parts as in FIG. 4 are denoted by the same reference numerals, and different parts will be described here.

FIG. 1 shows its configuration. The circuit configuration of this display device is such that a time axis compression circuit 225 is inserted between the second video processing circuit 122 and the changeover switch 123, and the second water ≦
1 and the time constant of the deflection circuit 102 is changed, and the other configuration is the same as that shown in FIG.

Here, the time constant of the second horizontal deflection circuit +02 is NTS
The frequency F n of the horizontal deflection signal for the C signal is F+1-30.
x525x2-31.5 As Elzl, Figure 5 (b
) The amplitude level is adjusted to be the same as the amplitude level of the horizontally biased signal for high-definition TV, while keeping it the same as the conventional horizontally deflected signal.

At this time, the high-definition TV horizontal bias signal is shown in FIG. 2(a), and the NTSC horizontal deflection signal is shown in FIG. 2(b). As a result, even when an NTSC video signal is displayed, the scanning lines are deflected over the entire display screen.

On the other hand, the time axis compression circuit 225 is connected to the video signal processing circuit 222.
The time axis of the NTSC video signal outputted from the NTSC video signal is compressed to 16=12, and the parts other than the video signal are outputted with halftone color signals added thereto. As a result, the NTSC video signal is displayed in the center of the horizontal scanning period with an aspect ratio of 4=3.
The peripheral areas are displayed in halftones.

A liquid crystal panel device is arranged on the display screen of the CRT 130. This liquid crystal panel device has a first polarizing plate 250, a liquid crystal panel 240, and a second polarizing plate 260 arranged in this order. The polarization direction of the polarizing plate 250 and the polarizing plate 260 is 90
The degree is off.

°The liquid crystal panel 240 consists of a first glass plate 246 whose surface is covered with a transparent electrode 24 and a transparent electrode 2 whose surface is covered only at both ends.
It has a structure in which the liquid crystal 242 is sandwiched between a second glass plate 247 covered with a transparent electrode 241 and a transparent electrode 2.
43, an AC voltage 24 is connected via a switch 244.
5 is applied. First and second gala plates 240, 2
47, which is in contact with the liquid crystal 242, is subjected to alignment treatment, and when no alternating current voltage is applied, the incident light is rotated by 90 degrees due to a twisting effect. Therefore, in this state, the light transmitted through the first polarizing plate 250 is rotated by 90 degrees due to the twisting effect of the liquid crystal panel 240, so that the light transmitted through the first polarizing plate 250 is rotated by 90 degrees.
Transparent.

On the other hand, since the twisting effect disappears when an AC voltage is applied, the light that has passed through the first polarizing plate 250 does not pass through the second (-front plate 2 [io).

In the above configuration, the operation thereof will be explained below.

When displaying a high-definition TV signal as an image, use the selector switch 10.
3, 113, and 123 to the high-definition TV side, and open the selector switch 244. At this time, CR
T 130 scans the entire screen. Also, since no voltage is applied to the liquid crystal, light is transmitted throughout the screen.

When displaying an NTSC video signal, press the selector switch l port 3.
, 113, and 123 are set to the NTSC side, and the changeover switch 244 is closed. At this time, the CRT
130 scans the entire screen as described above, but
The elephant appears only in the center. Halftones are displayed at both ends of the CRT 130, but since alternating current voltage is applied to the liquid crystals at both ends, no light passes through them.

Therefore, according to the above configuration, an NTSC video signal with a small aspect ratio is transmitted to a high B1iTV with a large aspect ratio.
When displaying an image on a display device, the deflection width of the scanning line is matched to the display screen, and the NTSC video signal is time-axis compressed. A single image can be displayed.

For this reason, there is no difference in the deterioration of the phosphor between the center and both ends of the screen, so no serious deterioration in image quality occurs even when displaying a video signal with a large aspect ratio. When displaying an image from a video signal with a small value, unnecessary parts of the display screen are masked by a liquid crystal panel device, so that even if the part is being scanned, no light passes through it, making it very easy to see.

As another embodiment, a configuration may be considered in which the NTSC vertical polarization circuit 112 and the changeover switch 3 are omitted. In this case, the vertical deflection coil 114 always includes the vertical deflection circuit 112.
A vertical deflection signal with a vertical scanning period ratio of 0.92 is supplied. The time axis compression circuit 225 is N
It is necessary to time-base compress the TSCJiJ RG B video signal to 12X0.8310.92:1B-10,8321G.

With this configuration, when displaying an NTSC video signal in one image, the upper and lower J(0,83
/0.92=0.90 times the screen size will be displayed, but there is an advantage that the circuit scale can be reduced.

Although the case where a video signal with a small aspect ratio is displayed on a display device for a video signal with a large aspect ratio has been described above, the present invention is not limited to the above embodiments, and various modifications can be made. For example, a high quality TV video signal with a large aspect ratio is converted into a high quality TV video signal with a small aspect ratio.
When displaying an image on a TSC display device, the 1-same width of the horizontal deflection signal is left unchanged, the deflection width of the vertical deflection signal is narrowed to fit the screen, the image signal is expanded in the vertical direction on the time axis, and the width of the screen is This can be achieved by masking the top and bottom with a liquid crystal panel device.

[Effects of the Invention] As described above, according to the present invention, there is provided a display device that can display video signals with different aspect ratios without causing a difference in the degree of deterioration between the central part and the peripheral part of the display screen. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a display device according to the present invention, and FIG. 2 is a diagram showing the waveform of a horizontal deflection signal of the embodiment.
FIG. 3 is a diagram for explaining the operation of a conventional display device, FIG. 4 is a block diagram showing the configuration of a conventional display device, and FIG. 5 is a waveform of a horizontal deflection signal of the display device shown in FIG. 4. A diagram showing
FIG. 6 is a diagram showing the waveform of the vertical deflection signal of the display device shown in FIG. 4. 101, 102...horizontal deflection circuit, 111, 11
2... Vertical deflection circuit, 103, 113, 12
3...Selector switch,...Horizontal deflection coil, 114
...Vertical deflection coil, ...CRT cathode electrode, 1
30...CRT. ...Time axis compression circuit, 240...Liquid crystal panel, 241
... Electrode, 242 ... Liquid crystal, 244 ... Changeover switch, ... AC power supply, 246, 247 ... Glass plate, 250° ... Deflection plate.

Claims (1)

[Claims] In a display device that switches and displays images of a plurality of video signals having different aspect ratios, a deflection width control means for controlling the deflection width of a scanning line for a video signal to be displayed in accordance with the aspect ratio of a display screen, and a control width of this means A time axis control means that compresses or expands the video signal to be displayed according to the time axis, and a polarizing plate and a liquid crystal panel are arranged on the display screen,
The display is characterized by comprising effective screen control means that switches and controls the voltage applied to the liquid crystal panel in accordance with the display switching of the video signal, and masks the display screen according to the aspect ratio of the video signal being displayed. Device.