JPH02174480A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the reduction in the vertical resolution by thinning out a horizontal scanning line placed for each horizontal scanning line of a video signal, applying arithmetic mean to a signal of the thinned horizontal scanning line and a signal of the succeeding horizontal scanning line and using the resulting signal for the succeeding horizontal scanning line. CONSTITUTION:Since a signal on a scanning line LP 103 is displayed as it is on a color liquid crystal display device 9 but a pulse FP is unchanged for 2 horizontal periods, a signal of the succeeding scanning line LP 104 is not displayed but thinned. When a signal of a scanning line LP 105 just after the scanning line LP 104 is supplied, terminals 4c, 4b of a switch 4 are connected. In this case, a luminance signal Y0 being the result of arithmetic mean between a signal of the LP 105 and a signal of the LP 104 from a 1H delay circuit 5 is formed. The signal Y0 is fed to a color decoder 8 and fed to the device 9 together with a color signal C and displayed as the scanning line LT 4. Thus, a defect of a lateral grating picture in the scanning direction is prevented by the thinning processing and the arithmetic mean processing in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a liquid crystal display device, particularly a liquid crystal panel made for NTSC video signals, which is suitable for displaying PAL video signals, for example. [Summary of the Invention] The present invention provides a liquid crystal display device in which one horizontal scanning line located for each of a plurality of horizontal scanning lines of a video signal of a second television system is thinned out, and the thinned out horizontal scanning line; By using the signal obtained by adding and averaging the horizontal scanning line and the next horizontal scanning line as the signal for the horizontal scanning line following the horizontal scanning line to be thinned out, image deterioration and loss due to horizontal scanning line thinning are prevented. This makes it possible to improve image quality.

[Conventional technology]

As a type of liquid crystal display device, the number of horizontal scanning lines (hereinafter simply referred to as scanning lines) is 240 and the number of pixels in the horizontal direction is 3, corresponding to the effective image area of one field of the NTSC system.
A device having 84 liquid crystal display panels is known. The effective video area of this liquid crystal display panel has only the number of scanning lines equivalent to approximately one field in an NTSC television signal, so the pixels of the first field and the second field are located on the same scanning line, Interlace is displayed. In addition, since this liquid crystal display panel has a number of scanning lines compatible with NTSC television signals,
In order to display a PAL television signal, a thinning operation is required.

Conventional scanning line thinning operations include the following types. In this specification, the scanning line in the PAL television signal STV is referred to as L PI in the first field.
OI to L Pill, LP201 in the second field
It is represented by LP211. In addition, the scanning lines of the liquid crystal display panel compatible with the NTSC system are expressed as LTI to LT9.
And, P PIOI to PPIII (white circles) are the first
Represents the pixels forming the diagonal line in the field, P
P2O1 to PP211 (black circles) represent pixels forming the diagonal line in the second field.

■Thinning in place: This is a predetermined number, for example 7 or 8
One scanning line is thinned out for each scanning line of a book. That is, as shown in FIG. 4, in the PAL television signal STV, the scanning line L P1O4 of the first field
and scanning line L P1O8 and scanning line L of the second field
P2O4 and scanning line L P2O3 are thinned out.

■Thinning by changing the position for each odd and even field:
This distinguishes between odd and even fields and changes the thinning position for each odd and even field. For example,
As shown in FIG. 5, the scanning line LP1O2 of the first field (odd field) and the scanning line LP204 of the second field (even field) are thinned out.

■Thinning that is performed by constantly displaying the averaged signal: Although not shown in the figure, this method uses an IH delay circuit and an addition circuit to always take the average of the signals of two adjacent scanning lines. The signal is input to a liquid crystal display device and displayed on a normal thinned-out liquid crystal panel.

[Problem B to be Solved by the Invention] However, each of the above-mentioned thinning methods has the following problems.

Regarding ■: Scanning line LT3 and scanning line L in Figure 4B
During T4, as between scanning line LT6 and scanning line LT7,
A step occurs in the diagonal lines 20, and the diagonal lines 20 do not connect smoothly. In addition, the scanning lines LP104 and LP104 to be thinned out
If there is a horizontal grid image in 2O4, the image will be lost.

Regarding ■: Discriminating between odd and even fields cannot guarantee sufficient performance when the electric field strength of the received signal is weak and an image containing noise is displayed, or during VTR variable speed playback. Even-numbered fields may be misjudged. If this judgment is mistaken, for example, as shown in FIG.
The scanning lines L P2O2 of the field are thinned out, and as a result, the horizontal shake of the image becomes large in the scanning lines LT2 and LT3, as is clear from the arrangement of the pixels P P1O3 and P P2O3 surrounded by the dashed line. Furthermore, even if there is no mistake in determining whether the fields are even or odd, the scanning lines L P1O3 and L P2O3 of the first and second fields of the PAL television signal STV are different from the scanning lines LT2 and LT3.
For example, in the case of a horizontal grid image,
- Pixels PP103 and PP2O3 surrounded by dotted chain lines
As is clear from the arrangement of the images, duplication occurs in the images.

Regarding (2): Similar to (2) above, a step may occur in the diagonal direction of the image, and the images in the diagonal direction may not be connected smoothly. Also, to display the average value of the upper and lower scanning lines,
Vertical resolution is reduced.

Therefore, an object of the present invention is to provide a liquid crystal display device that can prevent deterioration in image quality due to scan line thinning.

[Means to solve the problem]

The liquid crystal display device according to the present invention uses a liquid crystal panel that displays a video signal of a first television system to display a video signal of a second television system that has more horizontal scanning lines than the first television system. In a liquid crystal display device configured to display a video signal of a second television system, one horizontal scanning line located for each of a plurality of horizontal scanning lines is thinned out, and the horizontal scanning line to be thinned out and the horizontal scanning line are The signal obtained by adding and averaging the horizontal scanning line next to the line is used as the signal for the horizontal scanning line next to the horizontal scanning line to be thinned out.

[Effect]

For television signals that have been thinned out at fixed positions,
The signal of the thinned out scanning line and the signal of the next scanning line after the thinned out scanning line are averaged and used as the signal of the next scanning line after the thinned out scanning line.

Therefore, the images in the diagonal direction are smoothly connected, and there is no difference in level between the images in the diagonal direction. Furthermore, no image loss occurs in the horizontal grid image in the scanning line direction. And odd numbers
Since there is no need to discriminate between even fields, there are no discrimination errors and no horizontal shake of the image occurs.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the configuration shown in FIG. 1, the second
For a PAL type television as shown in Figure A (No. K STv is supplied to a low-pass filter 2 and a bypass filter 3, respectively. From this television signal STV, a luminance signal Y is separated by a low-pass filter 2, and a color signal Y is separated by a bypass filter 3. Signal C is separated.

On the one hand, the above-mentioned luminance signal Y is supplied as is to the terminal 4a of the switch 4. On the other hand, the signal is supplied to the terminal 4b of the switch 4 via the IH delay circuit 5, adder circuit 6, and VH2. The IH delay circuit 5 and the adder circuit 6 add the luminance signals Y of the two adjacent scanning lines, and the VH2 divides the luminance signal Y by, for example, (1/2), so that the average signal of the two adjacent scanning lines is sent to the terminal 4b. A luminance signal Yo is obtained.

The switch 4 is switched by a control signal to be described later, and either the luminance signal Y supplied to the terminal 4a or the luminance signal Yo supplied to the terminal 4b is supplied to the PAL color decoder 8.

The above-mentioned color signal C is supplied to the color decoder 8, and the color signal C is supplied to the color decoder 8, and the color signal C is supplied to the color decoder 8, and the color signal C is supplied to the color decoder 8.
It is decomposed into three primary color signals, G and B.

The three primary color signals and the luminance signals Y and Yo are supplied to a color liquid crystal display device 9 compatible with the NTSC system, which includes a drive circuit and a liquid crystal display panel (not shown), and are displayed on the color liquid crystal display device 9.

A pulse HP of one horizontal period output from the color liquid crystal display device 9 and a pulse FP shown in FIG. 2B are supplied to the flip-flop 10. Pulse HP is supplied to a clock terminal of flip-flop 10, and pulse FP is supplied to a data input terminal of flip-flop 10 and one terminal of exclusive NOR gate (EXNOR) 11. In the color liquid crystal display device 9, this panel FP is for outputting the signal of the l scanning line to the signal line of the liquid crystal panel. Output terminal of flip-flop lO [Q
] The output signal SQ from the flip-flop 10 is delayed by one horizontal period from the pulse FP described above and is supplied to the other terminal of the exclusive NOR gate 11. The switch 4 is controlled by supplying the control signal Sc output from the exclusive NOR gate 11 to the switch 4 described above.

Next, the thinning operation will be explained using the timing chart of FIG. 2 and the route map of FIG. 3. In this example, as mentioned above, the PAL television signal STV is
In order to display non-interlace on a liquid crystal panel for displaying television signals in the TSC system, scanning lines at fixed positions in the television signal STV in the PAL system, that is, scanning lines L P1O4, LP204, scanning lines L P1O8, L
Assume that P2O3 is thinned out.

In the color liquid crystal display device 9, each signal STV■ to STV for each IH of the television signal STV shown in FIG.
The image is displayed with a delay of one horizontal period from the timing when (2) is supplied. The color liquid crystal display device 9 outputs pulses HP and FP and supplies them to the flip-flop lO, and the pulse FP is also supplied to the exclusive NOR gate 11.

In the flip-flop 10 described above, the pulse HP of one horizontal period outputted from the color liquid crystal display device 9 is used as a clock, and the level of the pulse FP shown in FIG. 2B is sampled.

As shown in FIG. 2C, the output signal SQ representing the sampled level is delayed by one horizontal period and is supplied from the output terminal (Q) to the other terminal of the exclusive NOR gate 11.

The exclusive NOR gate 11 outputs a control signal SC shown in FIG. 2C. The control signal SC is the signal STV of the scanning line LPI05 of the television signal STV.
It is supplied to the switch 4 in accordance with the timing at which the signal (2) is supplied.

As shown in FIG. 3A, in the first field of the PAL television signal STV, the scanning line LP10
The signals up to the signal STV (3) are displayed as they are on the color liquid crystal display device 9. However, since the pulse FP does not change for two horizontal periods, the signal STV■ of the next scanning line LP2O3 is not displayed on the color liquid crystal display device 9 but is thinned out.

Next, when the signal STV■ of the scanning line LP105 immediately after the thinned out scanning line L P2O3 is supplied, the above-mentioned control signal SC becomes high level as shown in FIG. 2C, and the switch 4 is switched. and the terminal 4C14b is connected.

On the other hand, at this time, the L P2O3 signal STV■
and the signal S of the scanning line L P2O3 from the IH delay circuit 5.
From TV■, add average ((STV■+STV■)/2
] A luminance signal YO is formed. The averaged luminance signal Yo is supplied to the color decoder 8 via the switch 4, and then, together with the color signal C, to the color liquid crystal display device 9 via the color decoder 8.

As a result, the scanning line LT4 is displayed as shown in FIG. 3B.

Scanning line L in PAL television signal STV
When the signal processing of P2O3 is completed, the control signal SC becomes low level, so that the terminals 4a and 4C of the switch 4 are connected again.

Scanning lines LP106, LP2O3 signals STV■, ST
V■ is displayed as is on the color liquid crystal display device 9, similar to the signal STV■ of the scanning line LP103.

As shown in FIG. 3, in the first field of the PAL television signal STV, the scanning line L P2O
The signals up to the signal STV (3) are displayed as they are on the color liquid crystal display device 9. However, since the pulse FP does not change for two horizontal periods, the signal STV■ of the next scanning line LP108 is not displayed on the color liquid crystal display device 9 but is thinned out.

Next, when the signal STV■ of the scanning line LP109 is supplied, the switch 4 is switched by the above-mentioned control signal SC, and the terminal 4C14b is connected.

On the other hand, at this time, the signal S of the scanning line L P2O3 has already been
From TV■ and the signal STV■ of the scanning line LP108 from the IH delay circuit 5, the addition average ((STV■+STV■)
/2] luminance signal YO is formed.

The averaged luminance signal Yo is supplied to the color decoder 8 via the switch 4, and then, together with the color signal C, to the color liquid crystal display device 9 via the color decoder 8. As a result, as shown in FIG. 3B, the scanning line LT
Displayed as 7. PAL television signal S
When the signal processing of the scanning line LP109 in the TV is completed, the control signal SC becomes low level, so the switch 4 is turned on again.
The terminal 4as4c of is connected.

The thinning operation in the second field of the PAL television signal STV is the same as the thinning operation in the first field described above, so a redundant explanation will be omitted.

Through such thinning operation and averaging processing, the third
The diagonal line 12B corresponding to the diagonal line 12A in Figure A is shown in Figure 3B.
It can be obtained with As can be seen from the example of the diagonal line 12B in FIG. It is possible to prevent image loss in horizontal grid images in different directions. Further, since it is not necessary to discriminate between odd and even fields, there is no discrimination error and horizontal shake of the image can be prevented. Further, since the averaged scanning line signal is used only for the scanning line immediately after the thinned out scanning line, a decrease in vertical resolution can be prevented. Furthermore, since the image quality is improved, it can be commonly used for both PAL and NTSC television signals.

Although this embodiment describes television signals of the PAL system and the NTSC system, it is not limited thereto (it goes without saying that the invention can be similarly applied to television signals of other systems as well). be.

〔Effect of the invention〕

According to the liquid crystal display device according to the present invention, even when thinning is performed at a fixed position, images in diagonal directions can be smoothly connected, steps can be prevented from occurring in the diagonal direction of the image, and horizontal in the scanning line direction can be prevented. This has the effect of preventing image defects in grid images and improving image quality. In addition, there is no need to discriminate between odd and even fields, there is no error in discrimination between odd and even fields, it is possible to prevent horizontal shake of the image, and the quality of the image can be improved. Furthermore, since the averaged horizontal scanning line signal is used only for the scanning line immediately after the thinned out scanning line, it is possible to prevent a decrease in vertical resolution.

According to the embodiment, since the image quality is improved, P
It has the advantage that it can be used commonly for both AL and NTSC television signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a timing chart showing the circuit operation, FIG. 3 is a route diagram showing the horizontal scanning line thinning situation, and FIGS. 4 and 5 are FIG. 7 is a route map showing how horizontal scanning lines are thinned out in each conventional example. Explanation of main symbols in the drawings STV: television signal, 5: IH delay circuit, 6: addition circuit, 7: vRo

Claims (1)

[Claims] Using a liquid crystal panel that displays a video signal of a first television system, a video signal of a second television system that has more horizontal scanning lines than the first television system is displayed. In the liquid crystal display device, one horizontal scanning line located in each of the plurality of horizontal scanning lines of the video signal of the second television system is thinned out, and the thinned out horizontal scanning line and the horizontal scanning line are 1. A liquid crystal display device characterized in that a signal obtained by adding and averaging a line and a next horizontal scanning line is used as a signal for a horizontal scanning line following a horizontal scanning line to be thinned out.