JP3258773B2 - Multi-mode liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dot matrix liquid crystal panel having a scanning line number suitable for image reproduction of a video signal of the NTSC system.
The present invention relates to a multi-mode liquid crystal display device capable of reproducing an image of an ECAM video signal.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device such as a liquid crystal projector has a dot matrix liquid crystal panel instead of a CRT.

In this liquid crystal panel, a display thin film transistor is provided for each pixel of each horizontal scanning line (hereinafter, referred to as a line), and image data of a video signal is supplied in units of lines to reproduce an image. In the case of color reproduction in which three primary color signals are supplied as video signals, the liquid crystal panel is formed in, for example, a triple matrix structure for each primary color.

The required number of lines of a liquid crystal panel is determined by the number of lines in a screen effective period of a television system of a video signal, and when scan conversion described later is not performed, the NTSC system (525 lines, field frequency) 59.94 (≒ 60) Hz, horizontal frequency 15.734
In KHz, 2 to 1 interlaced scanning), the number becomes almost 240, and the PAL / SECAM method (625 lines,
Field frequency 50Hz, horizontal frequency 15.625K
Hz, 2: 1 interlaced scanning), the number is almost 270 lines.

In order to improve the image quality, the line driving frequency is doubled to the normal speed, and the interlaced scanning video signal is converted to non-interlaced scanning at double speed and supplied to the display device. The required number of lines on the panel is 480 (= 240 × 2) (NTSC), twice the normal number,
Or 540 (= 270 × 2) (PAL / SECA)
M).

A conventional liquid crystal display of this type is:
It is formed so as to receive only the video signal of the optimal television system according to the use area and reproduce the screen. For example, in the case of domestic use, 240 lines suitable for the screen reproduction of the video signal of the NTSC system, or It is formed using a display device having a structure of 480 liquid crystal panels.

In the case of a liquid crystal television receiver adapted to the conventional NTSC system video signal screen reproduction, the video signal is supplied to the display device as the number of lines. , PAL system, and S
There is a problem that a normal screen reproduction cannot be performed with respect to an ECAM video signal.

That is, if the video signals of the PAL system and the SECAM system are supplied as they are to the display device, the number of lines of the display device becomes insufficient compared with the video signal to be reproduced on the screen, and the reproduced screen is lacking in the upper and lower parts. Becomes

By the way, in order to prevent the above-mentioned loss, it is conceivable to correct the image signal by correcting the aspect ratio to reduce the upper and lower sides. In this case, the left and right sides are simultaneously reduced, and the left and right sides of the reproduced image are lost. I do.

The applicant of the present application has already filed Japanese Patent Application Laid-Open No. 4-274684 in order to solve the above-mentioned problem.

According to this application, when a video signal of the PAL / SECAM system is reproduced on a screen, the number of lines of the video signal is set to NT.
By performing scan conversion to the number of lines of the SC system, the NTS
A multi-method compatible liquid crystal display device that can normally reproduce not only NTSC video signals but also PAL / SECAM video signals on a dot matrix liquid crystal panel with the number of lines suitable for screen reproduction of C video signals. It is shown.

However, in the above-described technique, when performing double scanning on 480 liquid crystal panels, a transversal filter including a plurality of line memories, a multiplier, an adder, and the like is required.

When a reproduced video signal is input from a VCR or the like, the image is displayed from the first line of the video signal, so that the image may be bent at the upper portion of the screen of the liquid crystal panel due to skew distortion.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and the number of lines is 48 times the normal number.
Even if 0 liquid crystal panels are used, not only a video signal of the NTSC system but also a PAL system and a SECAM
It is an object of the present invention to provide a multi-method compatible liquid crystal display device that can normally reproduce a video signal of a system on a liquid crystal panel.

It is another object of the present invention to provide a multi-mode liquid crystal display device which eliminates image bending generated at the upper portion of a liquid crystal panel due to skew distortion when a reproduced video signal from a VCR is displayed on a dot matrix liquid crystal panel. Aim.

[0016]

SUMMARY OF THE INVENTION The present invention relates to a dot matrix liquid crystal panel of scanning lines suitable for screen reproduction of an NTSC video signal and a scanning line for each field of PAL and SECAM video signals. A scanning line number conversion unit for converting the number of scanning lines into 12/7 based on the ratio of the field frequency to the scanning method;
-12, and a time correcting means for correcting each field to the original time length and supplying the same to the display device.

Further, according to the present invention, a scanning line dot matrix liquid crystal panel adapted to screen reproduction of an NTSC video signal and a scanning line of each field of a PAL and SECAM video signal are set to N (where N is Is an integer of 2 or more), and a first scanning line number converting unit, and the scanning lines from the first scanning line number converting unit are converted into M-1 / M (where M is an integer of 7 or more). A second scanning line number conversion unit, and a time period for adjusting the time axis of each converted scanning line number to M / N (M-1), correcting each field to the original time length, and supplying the same to the display device. A multi-mode liquid crystal display device comprising a correction unit.

Further, the present invention includes a timing controller for switching a drive signal of a dot matrix liquid crystal panel according to a field frequency of each system in accordance with a discrimination signal of an NTSC system, a PAL system, and a SECAM system of a video signal to be reproduced on a screen. This is a multi-method compatible liquid crystal display device.

[0019]

In the case of the liquid crystal display device of the present invention configured as described above, the number of lines of the liquid crystal panel is 480.

The PAL / SECAM video signal is converted into 6 lines per field by means of converting the number of scanning lines.
25/2 lines are converted to 12/7 536 lines,
The number of lines in the retrace period at this time is $ 25 x (12/7)
Since the number of lines is $ 43, the number of lines in the screen valid period for each field is (536-43 =) 493.

Next, each field is corrected to the original 50 Hz by the time axis correcting means and supplied to the liquid crystal panel.

For this reason, the PAL and NTSC video signals are converted at the same field frequency as before conversion, and the number of lines in the screen effective period of each field is converted, so that not only the NTSC video signals but also the PAL / SECAM video signals Can also be displayed on a liquid crystal panel compatible with the NTSC system.

Furthermore, by changing the combination of the same video signal for each field and displaying, the vertical resolution is improved.

Further, by providing the timing controller, the driving signal of the liquid crystal panel is switched according to the field frequency of the video signal supplied to the liquid crystal panel.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-mode liquid crystal display device according to the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of a multi-method compatible liquid crystal display device. The multi-method compatible liquid crystal display device includes a dot matrix liquid crystal panel having 480 lines driven by primary colors, a color subcarrier of 3.58 MHz, The system has a four-system configuration capable of reproducing a total of four types of video signals, that is, two types of video signals of the NTSC system at 4.43 MHz and video signals of the PAL system and the SECAM system.

First, a video signal (video signal) to be reproduced on a screen is supplied from an input terminal 1 to a signal processing circuit 2 and a discrimination circuit 3.

Then, in the signal processing circuit 2, the input video signal is converted into three primary color signals of R, G and B, and the three primary color signals are supplied to the scanning line number conversion unit 4.

The A / D converter 4a converts the input analog R, G, B primary color signals into digital signals, and the number of scanning lines from the A / D converter 4a. And the number of scanning lines from the first scanning line number conversion circuit 4b is PAL / SECA.
It comprises a second scanning line number conversion circuit 4c for converting to 7/12 in the M system, and a D / A converter 4d for converting a digital output signal from the second scanning line number conversion circuit 4c into an analog signal. ing.

The discrimination circuit 3 discriminates the television system of the input video signal by a known discrimination method,
The discrimination signal D between the NTSC system and the PAL system / SECAM system is supplied to the timing controller 5.

In this timing controller 5, the first
, An oscillator 5a, a second oscillator 5b, a frequency divider 5c, a switch 5d, and a counter 5e.
Oscillator 5a generates a first reference clock K1 phase-locked to the horizontal synchronization signal of the video signal from the input terminal 1, and the second oscillator 5b generates a first reference clock K1 for the horizontal synchronization signal of the video signal from the input terminal 1. Phase locked and clock K
A second reference clock K2 having a frequency 6/7 times 1 is generated, and the reference clocks K1 and K2 are supplied to the counter 5e.

The counter 5e receives the reference clocks K1 and K2 from the first oscillator 5a and the second oscillator 5b as inputs, and outputs a color signal driver circuit, an X driver circuit, and a Y driver.
A drive signal for the driver circuit is created and supplied to the liquid crystal drive unit 6.

Further, the switch 5d is connected to the discrimination signal D
When the video signal of the NTSC system is input, the signal is switched to the side a, and PAL / SECA
When an M-type video signal is input, the mode is switched to the b side.

On the other hand, R, G, B from the scanning line number conversion unit 4
The signal is input to the liquid crystal driving unit 6.

The liquid crystal driver 6 includes a color signal driver 6a for controlling white balance, contrast, brightness and the like.
And an X driver 6b having a color signal driver 6a as an input
And a Y driver 6c controlled by a signal from the timing controller 5, and a liquid crystal panel 6d controlled by the X driver 6a and the Y driver 6b.

Next, the conversion operation of the number of scanning lines will be described in detail with reference to FIGS.

FIG. 2 is a block diagram of the scanning line number converter 4. FIG. 3 is a timing chart of an input signal when a PAL / SECAM video signal is input and an output signal after the scanning line number conversion. FIG. 4 is a timing chart showing a start pulse and a reset pulse of the counter 5e, and FIG. 5 is a timing chart of an input signal when an NTSC video signal is input and an output signal after the number of scanning lines is converted. It is.

In FIG. 2, the number-of-scanning-lines conversion section 4 has an A /
It comprises a D converter 4a, a line memory A as a first scan conversion circuit 4b, a line memory B as a second scan conversion circuit 4c, and a D / A converter 4d.

First, a case where a video signal of the PAL / SECAM system is input will be described with reference to FIG.

The R, G, and B primary color signals of each field output from the signal processing circuit 2 are input to the A / D converter 4a.

Here, the reference clock K1 from the first oscillator 5a is supplied to the A / D converter 4a by the frequency dividing circuit 5c.
A divided clock (1 / 2K1) is supplied,
The signal is converted into a digital signal by the 1 / 2K1 clock.

This digital signal is similarly written by the line memory A at a clock of 1 / 2K1.

On the other hand, on the read side of the line memory A,
The reference clock K1 from the first oscillator 4a is supplied as it is, and is read by this clock K1.

The reset at this time is performed on the writing side.
fH (horizontal frequency), 2 fH on the read side.

As a result, since the video signal of one horizontal cycle is read at 2fH and the same video signal is read again at the next 2fH, the number of scanning lines of the video signal can be doubled.

Next, in the line memory B, the video signal is written with the reference clock K1, and is read with the reference clock K2 because the switch 5d is switched to the b side.

The reset at this time is read at 2 fH on the writing side and at 12/7 fH (horizontal frequency of 12/7 times) on the reading side.

As a result, in the line memory 2, as shown in FIG. 3, since the data is read at 12/7 fH, the time axis of one horizontal cycle is 12/7, and the number of lines in each field is 53.
The number of scanning lines is converted by thinning out to six lines.

Here, of the 536 scanning line number converted signals, the number of lines in the retrace period is ｛25 × (12
/ 7) Since there are $ 43 lines, the number of lines in the effective display period is 493 lines.

The signal whose number of scanning lines has been converted is converted into an analog value by the reference clock K2, and the number of lines is 536.
This is a signal for non-interlace scanning of a book.

Next, the display timing on the liquid crystal panel by the counter 5e will be described with reference to FIG. 4A.

FIG. 4A is a timing chart showing a start pulse and a reset pulse of the counter 5e when a PAL / SECAM video signal is input.

The effective display period in FIG. 4A is from data 44 to data 536.

The counter 5e generates a start pulse as shown in FIG. 4A. The start pulse activates the color signal driver 6a, the X driver 6b, and the Y driver 6c from the data 51, and generates a reset pulse. Each of the above drivers is stopped by data 1 by a reset pulse.

For this reason, of the data of the effective display period,
Seven data (four lines) between data 44 and data 50 and six data between final data 531 and data 536 are not supplied to each driver, and occur when a video signal such as a VCR is reproduced. Is not displayed on the liquid crystal panel.

Next, a case where an NTSC video signal is input will be described with reference to FIG.

The R, G, and B primary color signals of each field output from the signal processing circuit 2 are input to the A / D converter 4a.

Here, the reference clock K1 from the first oscillator 5a is supplied to the A / D converter 4a by the frequency dividing circuit 5c.
A divided clock (1 / 2K1) is supplied,
The signal is converted into a digital signal by the 1 / 2K1 clock.

This digital signal is similarly written by the line memory A at a 1 / 2K1 clock.

On the other hand, on the read side of the line memory A,
The reference clock K1 from the first oscillator 4a is supplied as it is, and is read by this clock K1.

Incidentally, the reset at this time is performed on the writing side.
fH (horizontal frequency), 2 fH on the read side.

As a result, since the video signal of one horizontal cycle is read at 2fH and the same video signal is read again at the next 2fH, the number of scanning lines of the video signal can be doubled.

Next, the write clock and the read clock of the line memory B are performed by the reference clock K1 because the switch 4d is switched to the a side, and the reset of the write side and the read side is performed at 2fH, respectively. Therefore, the double-speed converted signal input to the line memory B is output from the line memory B after being delayed by 水平 horizontal cycle.

The double-speed converted signal is converted into an analog value by the reference clock K1, and becomes a non-interlace scanning signal having 525 lines.

Next, the display timing on the liquid crystal panel by the counter 5e will be described with reference to FIG. 4B.

FIG. 4B is a timing chart showing a start pulse and a reset pulse of the counter 5e when an NTSC video signal is input.

The effective display period in FIG. 4 is from data 41 to data 525.

The counter 5e generates a start pulse as shown in FIG. 4B. The start pulse activates the color signal driver 6a, the X driver 6b and the Y driver 6c from the data 46, and generates a reset pulse. Each of the above drivers is stopped by data 1 by a reset pulse.

For this reason, of the data of the effective display period,
Five data (two lines) between the data 41 and the data 45 are not supplied to each driver, and the skew distortion generated when a video signal such as a VCR is reproduced is not displayed on the liquid crystal panel.

FIG. 6 shows a state in which a signal obtained by converting the number of scanning lines of a video signal according to the PAL system is displayed on the liquid crystal panel 6d.

As is clear from FIG. 6, in this embodiment,
The video signal (an-1) converted into the number of scanning lines is sequentially scanned from the first line of the liquid crystal panel 6d in odd fields, and sequentially scanned from the second line of the liquid crystal panel 6d in even fields. Has been done.

Therefore, the vertical resolution is improved by changing the combination of the same video signal for each field.

Similarly, in the case of the NTSC system, the scanning line converted video signal (an-1) is sequentially scanned from the video signal of the first line of the liquid crystal panel 6d in odd fields, and the liquid crystal panel 6d in even fields. The variable pair drive is sequentially performed from the video signal of the second line.

[0074]

Since the present invention is configured as described above, it is possible to convert PAL and SECAM video signals with a simple configuration having first and second scan conversion means and time axis correction means. By simply thinning out, the number of scanning lines in each field can be converted, and not only an NTSC video signal but also a PAL video signal can be displayed on a dot matrix liquid crystal panel suitable for an NTSC video signal.

Further, according to the present invention, when a reproduced video signal from a VCR is displayed on a dot matrix liquid crystal panel, it is possible to eliminate image bending generated at the upper portion of the liquid crystal panel due to skew distortion.

Further, the video signal which has been subjected to the scanning line conversion is sequentially scanned from the first line of the liquid crystal panel in odd fields, and is sequentially scanned from the second line of the liquid crystal panel in even fields, thereby improving the vertical resolution. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a multi-mode liquid crystal display device according to the present invention.

FIG. 2 is a block diagram of a scanning line number conversion unit of the multi-mode liquid crystal display device of the present invention.

FIG. 3 is a timing chart when a PAL video signal is input.

FIG. 4 is a timing chart showing a start pulse and a reset pulse of a counter 5e.

FIG. 5 is a timing chart when an NTSC video signal is input.

FIG. 6 is a diagram showing a state in which a PAL video signal is displayed on a liquid crystal panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Signal processing circuit 3 Discrimination circuit 4 Number of scanning lines conversion part 4a A / D converter 4b First number of scanning lines conversion circuit 4c Second number of scanning lines conversion circuit 4d D / A converter 5 Timing controller 5a First oscillator 5b Second oscillator 5c Divider 5d Switch 5e Counter 6 Liquid crystal driver 6a Color signal driver 6b X driver 6c Y driver 6d Liquid crystal panel

Claims (1)

(57) [Claims] 1. A dot-matrix liquid crystal panel of scanning lines adapted to screen reproduction of an NTSC video signal, a predetermined first clock signal, a second clock signal having a frequency 6/7 times the first clock signal, and Clock signal generating means for generating a third clock signal having a frequency which is half the frequency of the first clock signal; and a first memory, wherein an input video signal is written to the first memory by the third clock signal. ,
A first scanning line number conversion means for reading from the first memory in response to the first clock signal; and a second memory having an output from the first scanning line number conversion means in accordance with the first clock signal. Write to memory and read from the second memory with the first clock signal if the input video signal is NTSC, or the second clock signal if the input video signal is PAL or SECAM. Second
A multi-mode liquid crystal display device comprising: a scanning line number conversion unit.