JPH01206393A - On-screen display device - Google Patents

Abstract

PURPOSE:To prevent a dot shift and a dot omission by outputting a clock pulse of a character generator and a sampling clock for bringing an output of the character generator to sampling from the same clock generating circuit. CONSTITUTION:A clock pulse of a character generator 6 and a sampling clock for bringing an output of the character generator 6 to sampling are outputted from the same clock generating circuit 9, therefore, repeat frequencies of the clock pulse and the sampling clock coincide completely, and do not become a discrepancy. In such a way, a dot shift and a dot omission caused by the discrepancy of the repeat frequencies of the clock pulse and the sampling clock of the character generator 6 are not generated.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an on-screen display device that displays characters such as letters and figures superimposed on a video screen using a dot matrix panel. The present invention relates to an on-screen display device that can display images without deviation.

"Prior Art" Conventionally, this type of on-screen display device has been constructed as shown in FIG. That is, the video signal input from the input terminal (1) is passed through the chroma processing circuit (2) to the R
It is separated into OB signals and input to the mixing circuit (3). Also, the H signal (horizontal synchronization signal) and ■ signal (vertical synchronization signal) separated from the video signal by the synchronization separation circuit (4)
is input to the timing circuit (5) and character generator (6).

The character data output from the character generator (6) whose reference position is determined by the H and V signals and created by the clock pulse from the clock pulse generation circuit (7) is input to the mixing circuit (3) and converted into a video signal. Superimpose. In the display driver (8), the mixing circuit (
The video signal superimposed with character data output from 3) is sampled by the dot clock from the dot clock generation circuit (9), and is sent to a dot matrix panel (for example, a liquid crystal display panel) (10) as display data.
Output to.

Based on the (2) signal from the timing circuit (5), a scan signal is output from the scan driver (11) to the dot matrix panel (10). As a result, the dot matrix panel (10) displays an on-screen display in which characters are superimposed on the video screen.

Specifically, as shown in FIG.
D 6140) (60) and this IC (60)
It consists of an LC circuit (70) connected between the SCin and OS Cout connection terminals for determining the repetition frequency of clock pulses.

"Problem to be Solved by the Invention" However, in the conventional example shown in FIG. 4, the repetition frequency of the clock pulse of the clock pulse generation circuit (7) and the repetition frequency of the dot clock of the dot clock generation circuit (9) do not match. I have to.

There was a problem in that characters with missing dots or misaligned dots were displayed.

That is, it is assumed that character data CD as shown in FIG. 6(b) is outputted from the character generator (6) by the clock pulse CP of the lock pulse generation circuit (7) as shown in FIG. 6(a). , the repetition frequency of the dot clock CQ as the sampling clock output from the dot clock generation circuit (9) is shown in the figure (
As shown in (c), when the clock pulse CP becomes higher than that of the clock pulse CP, the character display data CDD sampled by the dot clock CQ becomes as shown in (d) of the same figure, and the repetition frequency of the dot clock CQ becomes ( As shown in e), when the clock pulse Cp becomes lower than that of the clock pulse Cp, the character display data CDD sampled by the dot clock CQ becomes as shown in FIG. Because it will be.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an on-screen display device that can display characters without dot misalignment or dot dropout.

"Means for Solving the Problems" The present invention obtains character display data (matrix driving data) by sampling the output of a character generator using a sampling clock, and displays characters corresponding to this character display data on a dot matrix panel. In an on-screen display device that displays data superimposed on a video screen, the clock pulses of the character generator and the sampling clock for sampling the output of the character generator (i.e., the dot clock of the dot matrix panel) are connected to the same clock generation circuit. It is characterized in that it is output from.

"Operation" The clock pulses of the character generator and the sampling clock that samples the output of the character generator are output from the same clock generation circuit, so the repetition frequencies of the clock pulses and the sampling clock completely match. There is no mismatch. Therefore, no dot shift or dot drop occurs due to mismatch in repetition frequency between the clock pulse of the character generator and the sampling clock.

Embodiment F" FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 4 are given the same reference numerals. In Figure 1, (1) is an input terminal for inputting a video signal such as a television signal.
This input terminal (1) is coupled to a chroma processing circuit (2) and a sync separation circuit (4).

The output side of said chroma processing circuit (2) is coupled to a mixing circuit (3). The output side of the synchronization separation circuit (4) is connected to a timing circuit (5) and a character generator (6).
) is combined with The character generator (6
) is coupled to the mixing circuit (3). (
9) is an inverter (
12) to the character generator (6),
Display driver (8) without going through the inverter (12)
This is a dot clock generation circuit that outputs each clock. The display driver (8) samples the video signal superimposed with character data output from the mixing circuit (3) using the dot clock (sampling clock) CQ from the dot clock generation circuit (9) to generate video display data and It is configured to output character display data to vertical dot lines of a dot matrix panel (for example, a 240 dot x 320 dot liquid crystal panel) (10). (11) is the timing circuit (
5) is a scan driver that outputs a scan signal to the horizontal dot line of the dot matrix panel (10) based on the timing signal from the dot matrix panel (10).

Specifically, the character generator (6)
As shown in the figure, character generator IC (60)
The conventional LC circuit (70) shown in FIG.
The output side of the dot clock generation circuit (9) is connected to this ○5Cin terminal via an inverter (12).

Next, the operation of the above embodiment will be explained with reference to FIG. 3.

A video signal input from an input terminal (1) is input to a mixing circuit (3) via a chroma processing circuit (2). Furthermore, the H signal (horizontal synchronization signal) and ■ signal (vertical synchronization signal) separated from the video signal by the synchronization separation circuit (4) are sent to the timing circuit (5) and the character generator (6).
). The dot clock generation circuit (9)
As shown in figure (C), H from the timing circuit (5)
Since the dot clock synchronized with the signal is output as the sampling clock CQ, the clock pulse CQ shown in FIG.
(b) from the character generator (6)
Character data CD as shown in is output to the mixing circuit (3) and superimposed on the video signal. Therefore, the 1 display driver (8) samples the video signal and the character data CD shown in (b) of the figure using the sampling clock CQ started with the sample start pulse from the timing circuit (5), Display the character display data CDD shown on the dot matrix panel (10
) is output to the vertical dot line.

On the other hand, the scan driver (11) outputs a scan signal based on the timing signal from the timing circuit (5) to the horizontal dot lines of the dot matrix panel (10), as in the conventional example. Therefore, the dot matrix panel (10) provides an on-screen display in which characters are superimposed on the video screen.

"Effects of the Invention" As described above, the on-screen display device according to the present invention outputs the clock pulse of the character generator and the sampling clock for sampling the output of the character generator from the same clock generation circuit. The repetition frequency of the pulse and sampling clock perfectly match. Therefore, in on-screen display, it is possible to prevent dot misalignment or dot drop caused by the mismatch in repetition frequency between the glock pulse of the character generator and the sampling clock as in the conventional art.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the on-screen display device according to the present invention, FIG. 2 is a block diagram showing a specific example of the character generator shown in FIG. 1, and FIG. 3 explains the operation of FIG. 1. Timing chart, FIG. 4 is a block diagram showing a conventional example, FIG. 5 is a block diagram showing a specific example of the character generator and clock pulse generation circuit shown in FIG. 4, and FIG. 6 is a timing chart explaining the operation of FIG. 4. It is a chart. (6)...Character generator, (9)...Dot clock generation circuit, (10)...Dot matrix panel, CQ...Character generator (6)
Clock pulse, CQ...Sampling clock that samples the output of the character generator (6). Applicant Fujitsu General Ltd.

Claims (1)

[Claims] (1) In an on-screen display device that displays a character corresponding to character display data from a character generator superimposed on a video screen of a dot matrix panel, the clock pulse of the character generator and the output of the character generator are sampled. 1. An on-screen display device characterized in that a sampling clock is outputted from the same clock generation circuit as a sampling clock.