JPS6374274A - Character signal inserting device - Google Patents

Abstract

PURPOSE:To clearly recognize a white character even if the white character is inserted onto a white screen by providing an integration circuit generating a trapezoidal wave signal in response to an inputted character signal pulse and a comparator circuit comparing the trapezoidal wave signal and a reference voltage so as to output a switching pulse. CONSTITUTION:The integration circuit 7 generates the trapezoidal signal based on the inputted character signal pulse and gives the trapezoidal wave signal to a comparator circuit 5 using a voltage VC1 as a comparison reference voltage and a comparator circuit 3 using a voltage VC2 as a comparison reference voltage. In this case, the reference voltages are the voltages VC1, VC2. The comparator circuit 5 compares the inputted trapezoidal signal with the comparison reference voltage VC1, generates a switching pulse and gives it to a signal level switching circuit 4. Moreover, the comparator circuit 3 compares the trapezoidal signal with the comparison reference voltage VC2 (>VC1), generates a narrow switching pulse and gives it to a signal level switching circuit 2. The signal switching circuit 4 switches the signal level of a composite video signal into a 100% white level VS2 during the narrow switching pulse and outputs a signal being the inserted character signal to the composite video signal to an output terminal 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a character signal that is displayed on a television screen by inserting an externally input character signal into a video signal in, for example, a television camera or a video tape recorder. The present invention relates to an insertion device.

2. Description of the Related Art An example of a conventional character signal insertion device will be described below with reference to the drawings.

FIG. 3 shows a block diagram of a typical conventional character signal insertion device. In FIG. 3, 11 is a signal input terminal, 12 is a signal level switching circuit, 13 is a signal output terminal,
14 is a comparison circuit, and 16 is a character signal input terminal.

The operation of the conventional character signal insertion device configured as described above will be described below.

A composite video signal is input from the signal input terminal 11 and supplied to the signal level switching circuit 12 . On the other hand, a character signal is inputted from the character signal input terminal 13 and supplied to the comparison circuit 14 . The comparison circuit 14 compares the character signal input from the input terminal 15 with a certain reference value VC3 to detect a character insertion period and outputs it to the signal level switching circuit 12. The signal level switching circuit 12 switches the level of the composite video signal input from the signal input terminal 11 to the DC level of vs5 during the character signal insertion period based on the signal output from the comparison circuit 14, and converts the output signal to the DC level of vs5. The decoded video signal into which is inserted is outputted to the signal output terminal 13.

Problems to be Solved by the Invention However, in the above configuration, for example, white 1oO
% level screen has a problem in that even if a character signal of 100% white level is inserted, the inserted character signal becomes invisible. In addition, to improve this point, there is a method of setting the inserted character signal level to 100% white or higher, but in this case, when this video signal passes through the peak person GO circuit, its output brightness level will change. There was a problem in that it changed depending on the presence or absence of a character signal. There is also a method of adding the character signal to the video signal by a certain level.
In this case as well, there is a problem in that the brightness level of the character signal changes or the brightness level of the video signal changes.

In view of the above problems, the present invention provides a character signal insertion device that allows characters to be clearly recognized even when, for example, white characters are inserted into a white screen.

Means for Solving the Problems In order to solve the above-mentioned problems, the character signal insertion device of the present invention includes a first method that creates a trapezoidal wave signal corresponding to the input character signal by integrating the input character signal. means, second means for comparing the trapezoidal wave signal obtained by said first means with a first potential to create a first switching pulse, and a trapezoidal wave signal obtained by said first means. 2nd signal
third means for creating a second switching pulse narrower in width than said first switching pulse as compared to the potential of said second switching pulse;
fourth means for switching the input composite video signal with the first DC signal by the first switching pulse obtained by the means; The present invention includes a sixth means for switching the composite video signal obtained by the means described above with a second DC signal.

Operation According to the above-described configuration, the present invention integrates a character signal to create a trapezoidal wave signal, and compares it with two different reference values to create two switching pulses. Then, the wider one of the two switching pulses converts the level of the input decoded video signal to the black level, and the narrower switching pulse converts the level of the decoded video signal to the white 100% level. By converting to , the signal level becomes black for a short period before and after a white character, so that even if a white character is inserted into a white screen, for example, the white character can be clearly recognized.

Embodiment Hereinafter, a character signal insertion device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the invention. In FIG. 1, 1 is an input terminal into which a decoded video signal is input, 2 is a signal level switching circuit, 3 is a comparison circuit, 4 is a signal level switching circuit, 5 is a comparison circuit, and 6 is an input terminal for character signal pulses. A character signal input terminal, 7 is an integrating circuit, and 8 is an output terminal for outputting a signal in which a character signal is inserted into a decoded video signal. Moreover, FIG. 2 shows signal waveforms at each point of (a) to ((a) in FIG. 1) on the ship.

The operation of the character signal insertion device of this embodiment configured as described above will be described below with reference to FIGS. 1 and 2.

First, a decoded video signal as shown in (Δ) in FIG. 2 is input from the input terminal 1 and supplied to the signal level switching circuit 4. Further, character signal pulses as shown in ('b) in FIG. 2 are inputted from the character signal input terminals and supplied to the integrating circuit 7. The integrating circuit 7 generates a trapezoidal wave signal as shown in FIG. 2 (C) based on the input character signal pulse,
This trapezoidal wave signal is supplied to a comparison circuit 6 which uses VCl as a comparison reference voltage and a comparison circuit 3 which uses VCL as a comparison reference voltage. At this time, vcl<vcl. The comparison circuit 5 compares the input trapezoidal wave signal with the comparison reference voltage vc1, generates a switching pulse as shown in FIG. 2(d), and supplies it to the signal level switching circuit 4. The signal level switching circuit 4 switches the signal level of the decoded video signal inputted from the input terminal 1 to the black level (pedestal level) Vst during the switching pulse, and outputs a signal as shown in (0) in FIG. .

Further, in the comparator circuit 3, the trapezoidal wave signal and the comparison reference voltage v
02 (> Val), a narrow switching pulse as shown in (0) in FIG. 2 is generated and supplied to the signal level switching circuit 2. The signal level switching circuit 2 is supplied with a signal from the signal level switching circuit 4.

The signal level of the decoded video signal as shown in (f') of FIG. 2 is switched to the white 100% level VSZ during the period of the narrow switching pulse, and the decoded video signal as shown in (g) of FIG. A signal obtained by inserting a character signal into a video signal is output to an output terminal 8.

Effects of the Invention As described above, according to the present invention, an integrating circuit generates a trapezoidal wave signal corresponding to an input character signal pulse, compares the trapezoidal wave signal with the reference voltage Vl, and outputs a switching pulse. A comparator circuit 5, a comparator circuit that compares the trapezoidal wave signal with the reference voltage VC2 and outputs a switching pulse with a narrow width (in this case, Vc+<VO2), and a comparator circuit that compares the trapezoidal wave signal with the reference voltage VC2 and outputs a switching pulse with a narrow width (in this case, Vc+<VO2); A signal level switching circuit that switches the signal level of the gray signal to the black level, and a signal level switching circuit that switches the signal level of the decoded video signal level to the white 100% level using a narrow switching pulse output from the comparison circuit. By doing this, it is possible to obtain a signal in which the signal level of the leading edge and trailing edge of a white character is the black level. As a result, for example, even when inserting white text on a white screen, the text can be clearly recognized, and the brightness level of the video signal does not change due to the text insertion. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a character signal insertion device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram at each part of FIG. 1, and FIG. 3 is a block diagram of a conventional character signal insertion device. 1... Input terminal, 2... Signal level switching circuit, 3... Comparison circuit, 4... Signal level switching circuit, 5...・Comparison circuit, 6...
...Character signal input terminal, 7...Integrator circuit, 8.
...Output terminal. Name of agent: Patent attorney Toshio Nakao and one other person? ,
4-A 8g level cut T5J road 3.5- Comparison circuit Fig. 1 Fig. 2 Fig. 3 f

Claims (2)

[Claims] (1) A character signal insertion device that displays a character signal on a television screen by inserting a character signal into a composite video signal, and which integrates the input character signal to display a character signal corresponding to the character signal. first means for creating a trapezoidal wave signal; second means for comparing the trapezoidal wave signal obtained by said first means with a first potential to create a first switching pulse; third means for comparing the trapezoidal wave signal obtained by the means with a second potential to create a second switching pulse narrower than the first switching pulse; fourth means for switching the input composite video signal with the first DC signal by the first switching pulse obtained; and by the fourth means, by the second switching pulse obtained by the third means. A character signal insertion device comprising: fifth means for switching the obtained composite video signal with a second DC signal. (2) The first DC signal is substantially the same as the pedestal level of the input composite video signal, and the second DC signal is substantially the same as the white 100% level of the composite video signal. A character signal insertion device according to claim 1.