JP2730050B2 - Liquid crystal display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display device for displaying television images using a liquid crystal display. More specifically, the present invention relates to a liquid crystal display device that can support different broadcasting systems such as NTSC, Pal, Secum, etc.

[Prior Art] A liquid crystal display device has a scanning line number of 220 to 240 for the NTSC system.
For book, pal or secum systems, the number is 260-280. The number of scanning lines depends on the size of the display, but the number of CRT scanning lines including non-interlace (525 for NTSC,
This is about one-half of 625 for the Pal or Secum system), which is the number that is the easiest for technical support in driving the liquid crystal display. Although the number of scanning lines differs depending on the broadcasting system used, the aspect ratio of the display screen is the same.

[Problems to be solved by the invention]

Here, in an image receiving apparatus using a liquid crystal display,
Since the number of scanning lines is fixed, it is common to display video signals of the PAL (Pal) / SECAM (Secam) system on an NTSC image receiving apparatus by thinning out the scanning lines.

However, in this case, if the scanning lines are simply thinned out, one scanning line out of six scanning lines, that is, two scanning lines adjacent to each other every twelve scanning lines will be thinned out. In this case, the pitch of the screen becomes coarse, and the image is deteriorated. Further, if the pixel is simply thinned out, a difference in the selection period occurs between the scanning electrodes, resulting in uneven contrast.

[Means for solving the problem]

The liquid crystal display device of the present invention is a liquid crystal display device that displays a video signal of a Pal system or a Secum system. It is characterized by including a control circuit for controlling so as not to be adjacent in an even field.

A counting means for repeatedly counting a predetermined number of scanning lines for each field; and a first counting value of the counting means or the counting means for each field. And a select circuit for alternately outputting the second count value, wherein the scan electrode drive circuit inhibits the selection of the scan electrodes when the select circuit outputs.

[Action]

By shifting the thinned scanning lines so that they are not adjacent to each other in the odd field and the even field, the loss of the collected information is eliminated.

Further, the selection period for selecting the scanning electrodes can be made non-selected at the timing of thinning out the scanning lines, thereby preventing a specific scanning electrode from being selected for a long time.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is an explanatory view of the scanning method of the present invention. The left side shows the normal scanning method in the Pal-Secum method, and the right side shows the scanning method corresponding to the NTSC method. The numbers of the scanning lines are given for the sake of convenience, the solid line is a section for each scanning electrode, and the broken line is a section for each field. Even numbers indicate scanning in even fields, and odd numbers indicate scanning in odd fields. That is,
No. 1 and No. 2 are written to the same scan electrode, and No. 3 scan is thinned out. Next, Nos. 4 and 5 and Nos. 6 and 7 are written to the same scan electrode, respectively, and the No. 8 scan is skipped. In the following, thinning-out of non-adjacent even-numbered fields and odd-numbered fields, such as Nos. 15, 20, 27, 32, etc., is performed. As can be seen from the figure, it is natural because the positions to be thinned are separated.

FIG. 1 shows an embodiment of a part of the control circuit of the present invention. This circuit comprises a clock signal Y _CLK defining the selection timing of the scanning electrode driving signals, and forms the inhibit signal Y _INH defining a decimation selection.

The signal H _SYNC corresponds to a horizontal synchronizing signal and the signal V _SYNC corresponds to a vertical synchronizing signal. Here, they are handled as appropriately shaped signal systems.

The clock signal of the hexadecimal binary counter 11 is a signal
H _SYNC , the reset input is the signal V _SYNC and Q ₁ , Q ₂ , Q ₃ are binary outputs. The gate circuit 12 goes high at count 2 and the gate circuit 13 goes high at count 4.

The field discriminating circuit 14 uses the signal _VSYNC as a clock signal and changes its output Q to high or low to discriminate an even number of fields. The timing of thinning out each even and odd field is separately controlled. When Q is high, the output of the select circuit 15 becomes high when the count is 2, and when Q is low, the output of the select circuit 15 is high.
Is set to be high when the count is 4. Therefore, the output of the select circuit 15 can be made high in response to the scan numbers 3, 8, 15, 20, 27, 32,... In the frame.

The output of the select circuit 15 is the signal Y _INH . A signal obtained by _{ANDing the} inverted signal and the signal obtained by delaying the signal _HSYNC is a signal _YCLK, which is a clock signal for driving the scan electrodes. Delay circuit 16 is to match slightly delays the signal H _SYNC timing signals Y _INH.

FIG. 4 shows a shift register circuit for determining the selection timing of the scan electrode drive signal of the present invention, and FIG. 3 shows a conventional shift register circuit as a comparative example.
Q is the output.

In a conventional shift register as shown in FIG.
The signal Y _CLK as a clock signal, if you enter a signal V _SYNC as a data signal, to pause the clock at the timing of thinning, the selection period in the output QYj 'corresponding to the timing becomes doubled.

However, in the shift register circuit of this embodiment, the signal
Since the H _SYNC and the inverted signal of the signal Y _INH are output through the AND gate, the selection period at the thinning timing changes to the non-selection period, and QYj has an appropriate waveform.

By incorporating the control circuit shown in FIG. 1 and the shift register circuit shown in FIG. 4 into the scan electrode drive circuit, it is possible to appropriately reduce scanning. Thus, the liquid crystal display for the NTSC system can be applied to the Pal-Secum system.

〔The invention's effect〕

The liquid crystal display device of the present invention is a liquid crystal display device that displays a video signal of a Pal system or a Secum system. By having a control circuit that controls not to be adjacent in even fields,
Even if the specific scanning is thinned out, the pixel pitch does not become coarse, so that it is possible to reduce the deterioration of the image quality of the video of different types of broadcasting.

Also, in a liquid crystal display device provided with a scan electrode drive circuit for selecting a scan electrode of a liquid crystal display, a counting means for repeatedly counting a predetermined number of scanning lines for each field, and a first count value of the counting means for each field Or a select circuit for alternately outputting the second count value of the counting means, wherein the scan electrode drive circuit inhibits selection of the scan electrode when the select circuit outputs, thereby providing a liquid crystal display. Since the scan electrode driving circuit can be configured so that the selection period for selecting each scan electrode does not continue to be selected at the time of thinning, unevenness in contrast due to thinning of the scanning lines can be suppressed.

The present invention is most suitable for a simple liquid crystal display type image receiving apparatus, and is very effective when applied to a system which places importance on portability and is used worldwide.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a part of a control circuit of the present invention. FIG. 2 is an explanatory diagram of a scanning method according to the present invention. FIG. 3 is a diagram showing a conventional shift register circuit. FIG. 4 is a diagram showing a shift register circuit according to an embodiment of the present invention. 11 hexadecimal binary counter 12 gate circuit 13 gate circuit 14 field discriminating circuit 15 select circuit 16 delay circuit

Claims (2)

(57) [Claims] In a liquid crystal display device for displaying a video signal of a pal system or a secum system, scanning lines are thinned out at a fixed rate for each video signal of each field, and the thinned scanning lines are odd fields and even fields. A liquid crystal display device comprising a control circuit for controlling the liquid crystal display so as not to be adjacent to each other. 2. A liquid crystal display device comprising a scanning electrode driving circuit for selecting a scanning electrode of a liquid crystal display, a counting means for repeatedly counting a predetermined number of scanning lines for each field, and a counting means of the counting means for each field. A select circuit for alternately outputting the count value of 1 or the second count value of the counting means, wherein the scan electrode driving circuit inhibits selection of the scan electrode when the select circuit outputs. Characteristic liquid crystal display device.