JP2854353B2 - Blue back circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue-back circuit for changing a screen to a single blue color when a video signal of a television receiver is lost or noise increases.

2. Description of the Related Art A conventional blue-back circuit generates a sine signal as shown in FIG. In the sine circuit 11, the AND circuit 12 outputs a blue-back switching signal a, a horizontal blanking signal b, a vertical blanking signal c, and a sine blanking signal d from the sine output IC 13 for instructing switching to the blue-back display. Then, a blue signal e from the sine circuit 11 is derived from an OR output of this signal and a blue signal of a sine signal obtained from the sine output IC 13 (hereinafter referred to as “sine signal (blue)”).

On the other hand, in the video circuit 14, the input of the video signal f to the video chroma IC 16 is muted by the mute switch 15 operated by the blue back switching signal a, and a primary color signal (blue) g is derived from the video chroma IC 16. An AND circuit 17 obtains an AND output h of the primary color signal (blue) g and the sine blanking signal d obtained from the sine output IC 13 of the sine circuit 11, and further outputs a blue signal from the sine circuit 11 by an OR circuit 18. After the sign is superimposed on the signal e, the primary color signal (blue) is derived, and after the sign is superimposed, the blue of the sign and the background is displayed at the same level by the primary color signal (blue).

Problems to be Solved by the Invention In the above-mentioned conventional device, even in the case of a blue screen displaying the entire screen in a single blue color, the brightness is maintained at the same high level as the blue level when displaying a sign, so that eyes are tired. This is not only unfavorable to the eyes of the viewer, but also has the problem of shortening the life of the CRT, such as burning of the fluorescent screen of the CRT.

Means for Solving the Problems In order to solve the above problems, the present invention enables a blue screen to be displayed at a luminance of a halftone level. In the blue-back circuit for detecting the increase in the blue-back switching signal and deriving the display screen monochromatic blue by the blue-back switching signal, a blue signal of a video signal is normally output to a blue signal output terminal. A color signal output circuit for outputting a blue-back blue signal when a blue-back switching signal is generated; a luminance reducing unit for reducing the luminance of the blue signal; and the luminance reducing unit only when the blue-back switching signal is generated. Switch means for operating; sign signal generating means for generating a signal for displaying a blue sign; A first logic circuit for passing the output signal of the color signal output circuit when no sine signal is generated from the sine signal generation means, and passing the output of the first logic circuit and the sine signal from the sine signal generation means. And a second logic circuit for causing a display other than the portion for performing the sign display at the time of blue-back to be a blue screen of halftone luminance.

When a blue-back switching signal is generated, the blue primary color signal is switched to a half-tone blue-back signal whose brightness has been adjusted, so the blue-back is displayed at half-tone luminance and the sine signal is displayed at a normal luminance level. Is done.

Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
Parts corresponding to the conventional example shown in the figure are denoted by the same reference numerals.

In FIG. 1, reference numeral 1 denotes a sine circuit. The sine circuit 1 includes a sine output IC 13 for deriving various sine signals including a sine signal (blue) S and a sine blanking signal d according to an external instruction, and a video signal. When the signal disappears or noise increases, this is detected and the blue-back signal k is output by AND output of the blue-back switching signal a, the horizontal blanking signal b, and the vertical blanking signal c for making the entire display screen a single color of blue. It comprises an AND circuit 2 for deriving. Reference numeral 3 denotes a video circuit comprising a mute switch 15, a video chroma IC 16, a blue-back changeover switch 4, an AND circuit 5, a blue-back luminance adjustment volume 6, and an OR circuit 7. The mute switch 15 is selectively opened and closed by the blue-back switching signal a to mute the video signal f to the video chroma IC 16. The blue-back luminance adjustment volume 6 is connected to the AND circuit 2 of the sine circuit 1. This is for adjusting the luminance level of the blue-back signal k derived therefrom. The blue back changeover switch 4, the primary color signals (blue) g is also the adjustment of the luminance level in the blue background brightness adjustment volume 6 to the other terminal t ₂ rows from the video chroma IC16 to one terminal t ₁ The switching signal is guided, and switching is controlled by the blue-back switching signal a. The AND circuit 5 and the signal obtained from the common terminal t ₃ of the blue back changeover switch 4,
The AND circuit 7 outputs an AND output of the sine blanking signal d obtained from the sine output IC 13.
Is the AND output of the AND circuit 5 and the sine output IC
The OR output with the sine signal (blue) s obtained from 13 is obtained.

Therefore, when the blue-back switch signal a is not generated, the movable terminals of the mute switch 15 and the blue-back switch 4 maintain the illustrated state, and the video signal f is guided to the video chroma IC 16 without being muted. The primary color signal (blue) g from the chroma IC 16 is superposed on the sign signal (blue) by the AND circuit 5 and the OR circuit 7 and output. Since the video signal and the blue signal of the sine signal have not been adjusted in luminance level, they are displayed with normal luminance. The mute switch 15 is opened to generate the blue-back switching signal a due to the disappearance of the video signal or the increase of the noise, and the video signal f to the video chroma IC 16 is muted.
The movable terminal t ₃ of switched to the terminal t ₂ side. On the other hand, a blue-back signal k is generated from the AND circuit 2 of the blue-back signal a, the horizontal blanking signal b, and the vertical blanking signal c,
The brightness level of the blue-back signal k is adjusted to a halftone by the blue-back brightness adjusting volume 6 and is guided to the terminal t ₂ of the blue-back switch 4.

Therefore, from the common terminal t ₃ of blueback changeover switch 4 is derived is blue back signal luminance level is adjusted halftone, sine signal This signal is an AND circuit 5 and the OR circuit 7 is not adjusted brightness level ( Blue). As a result, from the OR circuit 7, the sine signal is a blue signal of a normal luminance level whose luminance level is not adjusted, and the blue-back signal generated in a portion other than the sine signal is a blue signal whose luminance level is adjusted to a halftone. The signal is derived, and the blue signal of the sign display is displayed at the same luminance level as in the past, but it is possible to display a halftone blue image at the time of blue back. When the blue-back switching signal a is generated, the video signal f to the video chroma IC 16 is completely muted by the mute switch 15, so that even if the blue-back luminance adjusting volume 6 lowers the blue-back luminance, the video signal f Noise does not appear on the display screen.

Effect of the Invention Since the present invention is configured as described above, the blue-back luminance at the time of blue-back switching can be set to a halftone, protecting the eyes of the viewer and extending the life of the display device, In addition, the blue sign in the blue back state is easily identified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example. 1 ... Sign circuit, 2,5 ... And circuit, 4 ... Blue-back changeover switch, 6 ... Blue-back luminance adjustment volume, 7 ... OR circuit, 13 ... Sign output IC.

Claims (1)

(57) [Claims] 1. A blue-back circuit for detecting a disappearance of a video signal of a television or an increase in noise of the video signal, deriving a blue-back switching signal, and changing a display screen to a single blue color by the blue-back switching signal. A color signal output circuit that normally outputs a blue signal of a video signal to a blue signal output terminal and outputs a blue signal for blue back when the blue back switching signal is generated; and a luminance reduction circuit that reduces the luminance of the blue signal. Means, switch means for operating the luminance reducing means only when the blue-back switching signal is generated, sign signal generating means for generating a signal for displaying a blue sign, and a sign signal from the sign signal generating means. A first logic circuit that allows the output signal of the color signal output circuit to pass when no color is generated; A second logic circuit for passing an output of a logic circuit and a sine signal from the sine signal generating means, so that a display other than a portion for performing a sine display at the time of a blue-back is a blue screen of halftone luminance. A blue-back circuit characterized by: