JPH02100491A - Character and pattern display device on television screen - Google Patents

Abstract

PURPOSE:To prevent the missing of a chrominance signal by providing a chrominance signal bypassing circuit to extract the chrominance signal from an input video signal and mix the extracted chrominance signal in the output video signal of a superimposing circuit. CONSTITUTION:An input video signal (a) is simultaneously inputted to a superimposing circuit 2 and a chrominance signal bypassing circuit 3, and for the video signal (a) inputted to the superimposing circuit 2, a character or pattern signal is inserted into the signal (a), and the signal is outputted. In this output video signal (b), one part of the chrominance signal equivalent to character or pattern signal inserted part is missing. On the other hand, for the video signal (a) inputted to the chrominance signal bypassing circuit 3, only its chrominance signal is extracted, outputted, and mixed with the output video signal (b) of the superimposing circuit 2. Thus, the missing part of the chrominance signal of the output video signal of the superimposing circuit 2 can be supplemented.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a character/pattern display device that inserts a character or pattern signal into a video signal in a video circuit such as a VTR and displays the character or pattern on a television screen. In particular, it is suitable for inserting character or pattern signals into SECAM video signals.

[Prior Art] Conventionally, a display device shown in FIG. 3 is known as a display device that inserts a character or pattern signal into a video signal in a video circuit such as a VTR and displays the character or pattern on a television screen. In the figure, numeral 1 is a video signal input terminal, 2 is a superimpose circuit, 4 is a buffer amplifier, and 5 is a video signal output terminal. A video signal input from the video signal input terminal 1 is input to a superimpose circuit 2 to insert a character or pattern signal, and this video signal is outputted from a video signal output terminal 5 via a buffer amplifier 4. . This output video signal is sent to a CRT, as is well known, to display characters or patterns on a television screen.

Details of the superimpose circuit described above are shown in FIG. 4 or 6.
It is as shown in the figure. Figure 4 shows PAL and NTS
This is a case where the above-mentioned characters, etc. are inserted into a video signal of the C system, and FIG. 6 is a case where characters, etc. are inserted into a video signal of the SECAM system.

In FIG. 4, numeral 6 is a character/pattern generation circuit;
8 is a black level voltage generation circuit, 8 is a white level voltage generation circuit,
9 is a black level insertion circuit, and 10 is a white level insertion circuit. The black or white level signal insertion timing pulse of the character or pattern generated from the character/pattern generation circuit 6 is input to the black level voltage generation circuit 7 and the white level voltage generation circuit 8, and is inputted from these circuits 7 and 8. Different black level voltages or white level voltages are generated according to the characters or patterns according to the timing of the timing pulse. These black level voltages or white level voltages are supplied to the black level insertion circuit 9 or the white level insertion circuit 10 described above.
is input. On the other hand, the black level insertion circuit 9 receives a video signal from the video signal input terminal 1 explained in FIG. This video signal is formed by a luminance signal 101, a color signal 102 superimposed on the luminance signal, and a synchronization signal 103, as its waveform is shown in FIG. 6a. As shown in FIG. 6, the level of the video signal input to the black level insertion circuit 9 becomes a black level (indicated by reference numeral 104) in accordance with the input black level voltage. The video signal in which the black level has been partially inserted in accordance with the above-mentioned characters etc. is processed by the above-mentioned white level insertion circuit 1.
0, and as shown in FIG.
). In this way, the white level and the above-mentioned black level are inserted in accordance with the above-mentioned characters or patterns (the inserted portion is indicated by reference numeral 106).The video signal is sent from the video signal output terminal 15 to the buffer amplifier 4 described in FIG. 3 above. is input.

By the way, as described above, the color signal is missing in the portion where the white level or black level of the video signal is inserted.

This loss of color signals is not a problem when using PAL or NTSC video signals, but in the case of SECAM video signals where the color signal is an FM modulated wave, the loss of color signals causes the colors to appear on the TV screen. Noise occurs. For this reason, in the case of SECAM video signals, it is necessary to prevent the above-mentioned color signal loss.

As described above, FIG. 6 shows a superimpose circuit that processes SECAM video signals.

In FIG. 6, the same reference numerals as those in FIG. 4 indicate the same components, so detailed explanation thereof will be omitted. Code 11.12
is a band rejection filter whose rejection band is set to the frequency of the color signal, and is connected between the black level voltage generation circuit 7 and the black level insertion circuit 9 similar to those described above, and between the white level voltage generation circuit 8 and the white It is connected so as to be interposed between the level insertion circuit 10 and the level insertion circuit 10 . By connecting these band rejection filters 11 and 12 as described above, the signals input from the black level voltage generation circuit 7 or the white level voltage generation circuit 8 to the black level insertion circuit 9 or the white level insertion circuit 10, respectively, can be controlled. Among them, a signal with a frequency corresponding to the frequency of the color signal is blocked, thereby preventing omission of the color signal in the video signal output from the black level insertion circuit 9 and the white level insertion circuit 10.

FIG. 7 shows a video signal of each part in FIG. 6, and the same reference numerals as in FIG. 5 indicate the same parts.

7a shows the video signal input to the black level insertion circuit 9, FIG. 7 shows the video signal output from the black level insertion circuit 9 and is manually input to the white level insertion circuit lO, and FIG. 7C shows the white level The figures respectively show the video signals output from the insertion circuit 10, and it can be seen that the color signals in the portions where characters and patterns have been inserted are not missing.

[Problem to be solved by the invention] Since the circuit for displaying characters and patterns on a television screen is relatively large in scale, - ICs with most of them built into one chip are used for boat fishing. There is. This kind of I
Since most of C is configured in the same manner as described in FIG. 4, the color signal in the input video signal is partially lost. For this reason, when processing video signals of the SECAM format, it has been necessary to take some countermeasures.

The following two measures can be considered as countermeasures.

Countermeasure example 1> Figure 8 shows a circuit in which countermeasure example 1 is implemented, and the third
The same reference numerals as in the figure, FIG. 4 or FIG. 6 indicate the same thing.

Of the character/pattern display circuits configured by ICs, the character/pattern signal generation circuit 6 of the superimpose circuit 2 has the same functions as the black level voltage generation circuit 7 and the white level voltage generation circuit 8 described above. An external black level voltage generation circuit 7a and a white level voltage generation circuit 8a are connected. 9a, 10a, IIa, and 12a are a black level insertion circuit, a white level insertion circuit, and a band rejection filter similar to the black level insertion circuit 9, white level insertion circuit 10, and band rejection filter 11.12 described above, respectively; It is connected in the same way as it was.

The circuit shown in FIG. 8 operates in the same manner as the circuit shown in FIG. The insertion circuit 9 and the white level insertion circuit 10 are not used.

<Countermeasure Example 2> FIG. 9 is a circuit showing Countermeasure Example 2. i in the diagram, No. 1, No. 2
is the above-mentioned superimposed circuit and is formed in the IC 16. 13 is a separation circuit that separates the luminance signal and color signal of the video signal, and 14° is a mixing circuit. A video signal input from the video signal terminal 1 is input to a separation circuit 13 and separated into a luminance signal and a color signal. The luminance signal is input to a superimpose circuit 2, into which character and pattern signals are inserted. The video signal into which this signal has been inserted is outputted and input to the mixing circuit 14, where it is mixed with the color signal from the separation circuit 13, which was manually input. This mixed video signal is input to the buffer amplifier 4 explained in FIG. 3 via the video signal output terminal 15.

Although countermeasure examples 1 and 2 described above can prevent the loss of color signals, they both require a large number of parts, which increases costs and reduces the reliability of the device. be. Particularly in the case of Countermeasure Example 1, an IC must be used that can take out the output of the character/pattern signal generation circuit 2 to the outside of the IC.

This invention reduces the number of parts, improves the reliability of the device, and reduces costs in a character/pattern display device on a television screen that prevents color signal loss and is compatible with SECAM video signals. The purpose is to achieve this goal.

[Means for Solving the Problem] In a character/pattern display device on a television screen that is equipped with a superimpose circuit that inserts a character or pattern signal into an input video signal, the input/output of the superimpose circuit is A color signal bypass circuit that passes the frequency components of the color signal is connected in parallel to the color signal, and the color signal that has passed through the color signal bypass circuit can compensate for the missing portion of the color signal that occurs in the superimpose circuit. I can,
Even if a SECAM video signal is input as the video signal described above, the continuity of the color signal can be ensured, and therefore the generation of color noise on the television screen can be prevented.

Furthermore, by making the color signal bypass circuit a circuit block independent of the superimposed circuit, it can be connected without changing the superimposed circuit, and the superimposed circuit can be configured inside the IC. Even if the IC is external, it can be easily connected as a circuit.

[Operation] A human video signal is simultaneously input to the superimpose circuit and the color signal bypass circuit, and a character or pattern signal is inserted into the video signal input to the superimpose circuit and output. This output video signal lacks the color signal in the inserted portion of the character or pattern signal. On the other hand, from the video signal input to the color signal bypass circuit, only the color signal is extracted and output, and mixed with the output video signal of the superimpose circuit. This mixing error compensates for the missing portion of the color signal in the output video signal of the superimpose circuit.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a circuit configuration diagram showing one embodiment, and FIG. 2 is a diagram showing signal waveforms at various parts in FIG. 1.

In FIG. 1, the same reference numerals as those in FIG. 3 indicate the same elements, so a detailed explanation thereof will be omitted.

Reference numeral 3 denotes a color signal bypass circuit, whose input side and output side are connected to the input end and output side of the superimpose circuit 20, respectively. This color signal bypass circuit is constituted by a band-pass filter or a high-pass filter whose transmission characteristics are set so as to pass the frequency component of the color signal and block the frequency component of the luminance signal.

Next, the operation shown in FIG. 1 will be explained using FIG. 2 as well. In FIG. 2, the same reference numerals as in FIG. 5 indicate the same components. The input video signal shown in FIG. 2a from the video signal input terminal 1 is input to a superimpose circuit 2 and a color signal bypass circuit 3. As described above, the character or pattern signal is inserted into the video signal input to the superimpose circuit 2, and as shown in Figure 2, the color signal in the part where the character or pattern signal was inserted is missing. Output as a video signal. From the video signal input to the color signal bypass circuit 3, only the color signal thereof is extracted and output, as shown in FIG. 2C.

The output video signal of the superimpose circuit 2 and the output color signal of the color signal bypass circuit 3 are mixed, and as shown in FIG. The signal is color signal bypass circuit 3
This is supplemented by the output color signal of , resulting in a signal with no missing color signals. This signal passes through the buffer amplifier 4 and is output to the video signal output terminal 5.

[Effects of the Invention] As described above, the present invention provides a character/pattern display device on a television screen equipped with a superimpose circuit 2 that inserts a character or pattern signal into an input video signal. (SECAM) system video signal is input, and since a color signal bypass circuit 3 is provided which extracts a color signal from the input video signal and mixes it with the output video signal of the superimpose circuit 2, the output video signal As a character/pattern display device on a TV screen that does not cause color signal loss, it can be configured with a small number of parts, improving device reliability,
It is possible to obtain something that can reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram showing signals of each part in FIG. 1, FIGS. 3 to 7 show conventional examples, and FIG. Figures 4 and 6 are block diagrams, Figure 5 is a signal waveform diagram showing the signals of each part in Figure 4, Figure 7 is a signal waveform diagram showing the signals of each part in Figure 6, and Figure 8. and FIG. 9 are block diagrams for explaining the present invention. 1: Video signal input terminal 2 Varnish-bar inbose circuit 3: Color signal bypass circuit. 4: Buffer amplifier 5: Video signal output terminal

Claims (3)

[Claims] (1) A character/pattern display device on a television screen that is equipped with a superimpose circuit that inserts a character or pattern signal into an input video signal, in which a SECAM video signal is input as the video signal. A character/pattern display device on a television screen, comprising a color signal bypass circuit that extracts a color signal from the input video signal and mixes it with the output video signal of the superimpose circuit. (2) The character/pattern display device on a television screen according to claim 1, wherein the color signal bypass circuit is constituted by a band pass filter. (3) The character/pattern display device on a television screen according to claim 1, wherein the color signal bypass circuit is constituted by a high-pass filter.