JP3247595B2 - LCD display video signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display video signal generation device, and more particularly to a device for generating a video signal superimposed on a main video signal and input to a liquid crystal display means. It is.

[0002]

2. Description of the Related Art FIG. 4 is a diagram exemplifying a conventional apparatus for generating an input video signal in which characters and the like are superimposed and displayed on a main image. In FIG. 4, the OS
The D data synthesizing circuit 9 receives the RG from the field memory 4.
This is a superimposing circuit comprising 24 2-channel multiplexers for switching between 24-bit main image data of B and RGB superimposed data. The data to be imposed are R, G, B and blanking (BLK) signals (superimposed characters by RGB signals and a video signal of the background) by a program of a character generator (CG) built in the microcomputer (microcomputer) 1. And a signal for switching between the two. The display position and timing of the character to be imposed are determined by the input HSYNC and VSYNC, and the pattern is determined by the R, G, B, and BLK signals described above. Will be displayed.

For this reason, the RGB signal and the BLK signal generated by the microcomputer 1 are input to the OSD data synthesizing circuit 9 via the latch circuit, and the synthesized data is converted into 24-bit data of the liquid crystal panel 8. Before being used for display driving, gamma (γ) correction is performed in the ROM II 10. In ROMII10,
A gamma correction table having a look-up table configuration is prepared, and the gamma correction table can be selected according to which display mode, RGB or video, is selected. ROMII1
The output of “0” is input to the liquid crystal panel 8 via the latch circuit 7. The clock (25 MHz) from the basic clock transmitter 11 is input as a timing clock to the latch circuits 5 and 7 and the liquid crystal panel 8, via the 周 frequency dividing circuit 2, and to the microcomputer 1 and the latch circuit 3.

As shown in the above example, conventionally, in a liquid crystal display device for displaying a video signal or an RGB signal from a personal computer, when superimposing information such as character characters is superimposed on a main image and displayed by a microcomputer or the like, After superimposing data from the character signal generator is synthesized with the main image, gamma correction is performed, or after the main image is gamma corrected, superimposition data is synthesized and displayed on the liquid crystal panel. However, circuit means such as an OSP data synthesizing circuit for synthesizing image data is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has been conventionally provided as an independent component in a conventional apparatus for generating a superimposed liquid crystal display video signal. It is an object of the present invention to provide a circuit device for synthesizing image data, which has been performed, and a gamma correction unit, and to provide a space-saving and low-cost apparatus for generating an input video signal for liquid crystal video display.

[0006]

According to the first aspect of the present invention, there is provided an input means for inputting a superimposed signal from a pattern generating means such as a main video signal and a character as a digital signal, respectively, and a memory having a built-in lookup table. A liquid crystal display video signal generation device comprising processing means for performing digital gamma correction using the look-up table for a video signal from the input means, wherein the memory has a built-in superimpose table in addition to the gamma correction table. A function of outputting an imposed composite display video signal by using either a gamma correction table or a superimpose table in correspondence with an input signal from the input means in the processing means. Extends look-up tables that previously existed for gamma correction Te and makes it possible to output a combined image of the two signals by selectively in response to a main video signal and superimpose the signal.

According to a second aspect of the present invention, in the first aspect of the present invention, only the superimpose signal is used without performing gamma correction of the main video signal at the pixel position where the superimpose signal is active. To have a function to process and output as a video signal,
It is intended to provide means for realizing a process of generating a composite video.

According to a third aspect of the present invention, in the first or second aspect, a correction table for a superimpose signal is included as the superimpose table, and for example, an RGB signal is used as the superimpose signal. Even if given in binary, the display video signal imposed by the table processing matches the main video (video) signal.

[0009]

Next, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an outline of a configuration of a liquid crystal display device including a gamma correction circuit including a superimpose function according to the present invention. In addition,
In this embodiment, there are components similar to those of the prior art shown in FIG. 2, and these components are given the same numbers so that the above description of the prior art can be referred to. In FIG. 1, a character pattern generator 1 composed of a microcomputer or the like receives a clock obtained by dividing the output of a basic clock oscillator 11 by a 1/2 frequency divider 2, and uses this as a reference clock to generate superimposed data. Generate certain RGB and BLK signals. These signals are input to the ROMI 6 through the latch circuit 3.

On the other hand, a video signal (RGB24BIT signal)
Is once written to the field memory 4. This memory is a high-speed FIFO capable of high-speed aperiodic read / write operation.
It is a serial access memory that performs an O (First in First out) operation. After the writing, the data is read out at a timing synchronized with the clock of the reference clock
Is input to ROMI6. At this time, the latch circuit 3
R, which is the superimposed data input from
If the GB and BLK (blanking) signals are all “0”, the video signal (RGB
24 BIT signal) passes through a gamma (γ) table in the ROMI 6 and is input to the liquid crystal panel 8 via the latch circuit 7.

Here, the ROMI 6 incorporates not only a gamma correction table but also a superimpose table so that the table can be selected according to whether the input signal is a video signal or a superimpose signal. It has become. The gamma correction table is switched according to whether the video display signal is a video signal or an RGB signal to a microcomputer. And the latch circuit 3
R, which is the superimposed data input from
Either GB or BLK signal is "1" (active)
, The video signal (RGB) from the field memory 4
24 BIT signal) does not pass through the γ correction table in the ROMI 6, and the RGB signal (binary) which is the superimposed data input from the latch circuit 3 is the ROMI6 signal.
And input to the liquid crystal panel 8 via the latch circuit 7.

The above operation will be described more specifically with reference to the drawings. FIG. 2 illustrates a ROMI data map. FIG. 3 shows a flowchart of the operation using the data map of FIG. In this example, ROM data having a gray screen is shown. However, this is not limited to a display screen when there is no signal (blue screen) or a display screen (gray screen) instead of a lens cap. In the application screen of FIG. 7, a signal corresponding to the screen generation is added.

Here, as shown in the flowchart of FIG. 3, first, the BK screen is processed (step S1). If the BK screen signal is obtained, the video signal for forming the gray screen display screen as described above is obtained. Is selected (step S2). For a signal that does not require BK screen processing, it is detected whether or not the signal has a BLK signal (step S3).
/ Video display mode (step S
A gamma correction operation is performed according to (4) (step S5), and output as a video signal.

On the other hand, if the BLK signal is detected in step S3, it is next detected whether or not there is a superimpose signal (step S6). If so, the R, G, and B are prepared. If there is no table processing operation (step S7), the video signal is output with R, G, and B set to 0 by the "black" operation.

[0015]

The method according to the prior art requires circuit means for synthesizing superimposed data from a character pattern generator such as a microcomputer with a main image such as a main video such as a video. Although the device was complicated and large in size because of the configuration in which the image signal passed through the correction circuit, the cost was high.However, a digital gamma correction circuit using a memory such as a ROM in the present invention as a lookup table was provided. A simple, compact, and low-cost LCD image display device that gamma-corrects normal video signals and personal computer signals and has a circuit function for superimposing character signals at the same time. Will be able to do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a liquid crystal display video signal generation device of the present invention.

FIG. 2 is a diagram illustrating a ROMI data map which is an element of the present invention.

FIG. 3 is a flowchart showing an example of an operation using a ROMI table of the present invention.

FIG. 4 is a block diagram illustrating a conventional apparatus for generating a superimposed video signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microcomputer, 2 1/2 frequency divider circuit, 3, 5, 7 ... Latch circuit, 4 ... Field memory, 6 ... ROMI, 8 ... Liquid crystal panel, 9 ... OSD data synthesis circuit, 10 ... ROMI
I, 11: Basic clock oscillator, S1 to S8: Operation steps.

Claims (3)

(57) [Claims] 1. An input means for inputting a superimposed signal from a pattern generating means such as a main video signal and a character as a digital signal, a memory having a built-in look-up table, and the look-up table from the input means. In a liquid crystal display video signal generation device comprising processing means for performing digital gamma correction using the video signal of the above, a superimpose table is built in the memory in addition to the gamma correction table, and the processing means receives an input from the input means. Liquid crystal display video signal generation characterized by adding a function of outputting an imposed composite display video signal by using either a gamma correction or a superimpose table corresponding to a signal. apparatus. 2. The function of the processing means has a function of processing only the superimpose signal and outputting it as a video signal without performing gamma correction of the main video signal at a pixel position where the superimpose signal is active. 2. The liquid crystal display video signal generation device according to claim 1, wherein the liquid crystal display video signal generation device is configured to perform the following. 3. The liquid crystal display video signal generation device according to claim 1, wherein a correction table for a superimpose signal is included as the superimpose table.