JPS6362946B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an image and character display device that enables clear character display.

[Conventional technology]

When displaying characters on the picture tube screen of a television receiver, the usual method is to blank the video signal in the area where the characters are to be displayed and insert the character signal during the blanking period. used. The conventional video and character display device 1 shown in FIG.
Supply green and blue primary color drive signals from the collector 3
Video output transistors Q _r , Q _g , Q _b are connected, and these video output transistors Q _r , Q _g ,
Q _b and character output transistor Q _c constitute a video output circuit 3. Each video output transistor Q _r ,
Q _g and Q _b are color difference signals R-Y, G-Y,
B-Y is applied, and a luminance signal Y is applied via a blanking circuit 4 commonly connected to the emitters.

In this example, the insulated signal cathode of the picture tube 2 is connected in parallel with the video output transistor Q _g .
A character output transistor Q _c is connected, and a character signal is applied to the base of this character output transistor Q _c via a blanking circuit 4 .

The blanking circuit 4 is connected to a luminance signal input terminal 5 and a character signal generation circuit 6, and one of the input luminance signal and character signal is selectively taken out. 7 is a switch circuit, which includes a transistor _Qy for luminance signal input and a transistor for character signal input.
Q _d is connected to a common emitter resistor R _e to form a differential pair, and its emitter output is connected to each video output transistor Q _r , Q _g , Q _b via a buffer transistor Q _e . It is supplied to the emitsuta of.

The character signal input transistor Q _d is supplied with a character signal from the collector of a transistor Q _{2 which level-shifts the collector output of the transistor Q 1 to} which the character signal output from the character signal generation circuit 6 is applied. Further, the collector of the transistor _Q2 is connected to the base of the character output transistor _Qc .

Therefore, when a character signal is now output from the character signal generating circuit 6, the transistor _Qd for inputting the character signal of the switch circuit 7 is saturated, and the transistor _Qy for inputting the luminance signal is cut off. the result,
Since the buffer transistor Q _e is also cut off and the brightness signal output of the blanking circuit 4 is at its maximum, the video output transistors Q _r , Q _g , and Q _b are all cut off and blanking is applied.

On the other hand, since a high-level character signal is applied to the base of the character output transistor Q _c via the blanking circuit 4, the character output transistor
Green characters are displayed on the screen of the picture tube 2 due to the conduction of Q _c .

[Problem that the invention seeks to solve]

In the conventional video and character display device 1 described above, the blanking signal formed in the blanking circuit 4 has a phase delay with respect to the character signal, and the timing of the blanking signal and the character signal in the video output circuit 3 is There were problems such as not being able to match accurately and not being able to display clear characters.

[Means for solving problems]

This invention solves the above problem, and the blanking signal for erasing the video signal to be output is input with a phase delay with respect to the character signal input separately in place of the video signal. and a correction means for adding an edge detection signal obtained by time-differentiating the character signal to the blanking signal and correcting the waveform roundness and phase lag of the blanking signal itself. This is a summary of what was done.

[Effect]

In this invention, when inserting a character signal into the blanking period of a video signal, an edge detection signal obtained by time-differentiating the character signal is added to the blanking signal, and the waveform of the blanking signal itself is rounded and the phase lag is detected. This enables clear character display without blurring.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. 1 and 2 are a main circuit diagram and a signal waveform diagram of each part of the circuit, respectively, showing an embodiment of the video and character display device of the present invention. In FIG. 1, the same components as in FIG. 3 are given the same reference numerals.

In FIG. 1, a video and character display device 11 has a configuration in which the emitter of a character output transistor quantity Q _c and the base of a video output transistor Q _g are connected via a differential capacitor C for correction. For this reason,
The differential signal of the emitter output of the character output transistor Q _c is applied as an edge detection signal to the base of the video output transistor Q _g during blanking.

The character output transistor Q _c is made conductive by the character signal, and the differential signal of its emitter output is shown in Figure D.
As shown in the figure, the character signal becomes a single-peak pulse with different polarities at the rising and falling edges. Therefore, when the blanking signal _{shown in FIG} . conduction occurs at an accelerated rate, and at the terminal edge, the state is forcibly switched to the cut-off state.

That is, FIGS. 2B, C, and _D show the collector outputs ( _cathode Input) waveforms are hypothetical and shown with dashed lines. These virtual waveforms do not actually exist independently, but they are shown in Figure 2 B, C, and D.
The collector outputs of the video output transistor Q _g and the character output transistor Q _c due to the simultaneous input of the signals shown by solid lines in FIG.

Therefore, the rounding of the waveform at the starting edge of the blanking signal is corrected, and the phase lag with respect to the character signal at the ending edge is also removed. That is,
The character signal output seen from the collectors of the video output transistor Q _g and the character output transistor Q _c is the second
As shown in Figure E, it has a sharp leading edge and trailing edge, which is the cause of the waveform rounding of the rising edge and shadows of characters seen in the conventional character signal output shown by the dotted line in the middle of Figure E. There is no hump-like waveform at the trailing edge, which makes it possible to display clear characters without blur.

In this way, the video and character display device 1 has the following features:
When inserting a character signal into the blanking period of a video signal, the edge detection signal obtained by time-differentiating the character signal using a differentiating capacitor C is added to the blanking signal, and the waveform roundness and phase delay of the blanking signal itself are detected. Since the structure is configured to correct for this, it is possible to suppress the occurrence of faint shadows that occur on the right edge of the outline of the characters projected on the screen of the picture tube 2, prevent blurring of the characters, and enable clear character display. , the channel characters displayed on the screen of the picture tube 2,
The ease of viewing text information etc. from a personal computer etc. can be doubled.

〔Effect of the invention〕

As explained above, according to the present invention, when inserting a character signal into the blanking period of a video signal, an edge detection signal obtained by time-differentiating the character signal is added to the blanking signal, and the blanking signal is The structure corrects the roundness and phase lag of the waveform of the image tube, which suppresses the appearance of faint shadows on the right edge of the outline of the characters projected on the picture tube screen, prevents blurring of the characters, and makes them clearer. It has excellent effects such as doubling the visibility of channel characters displayed on the picture tube screen and character information from a personal computer or the like.

[Brief explanation of drawings]

1 and 2 are main circuit diagrams and signal waveform diagrams of various parts of the circuit, respectively, showing an embodiment of the video and character display device of the present invention, and FIG. 3 is an example of a conventional video and character display device. It is a main part circuit diagram. DESCRIPTION OF SYMBOLS 11... Video and character display device, 2... Picture tube, 3... Video output circuit, 4... Blanking circuit, 6... Character signal generation circuit, C... Differential capacitor.

Claims (1)

[Claims] 1. A video output circuit in which a blanking signal for erasing a video signal to be output is inputted with a phase delay with respect to a character signal input separately in place of the video signal, and a video output circuit that time-differentiates the character signal. A video and character display device comprising a correction means for adding an edge detection signal obtained by the blanking signal to the blanking signal and correcting the waveform roundness and phase delay of the blanking signal itself.