JPS6182582A - Character display method to television picture - Google Patents

Abstract

PURPOSE:To give a border to the character by a simple processing by differentiating a front end and rear end of the character display signal, obtaining the pulse, setting the pulse to the reverse polarity against the polarity of the character display signal and overlapping and displaying to a video signal for displaying a picture together with the character display signal. CONSTITUTION:When a character is displayed a character signal W is inputted into a mixer 15. When an input terminal Tin2 character signal W is inputted in the mixer 15, by the first differential circuit composed of a capacitor 29 and a resistance 35 and the second differential circuit composed of a capacitor 32 and a resistance 21, the front end and rear end of the signal are respectively differentiated. Since a color demodulating signal C inputted to an input terminal Tin2 is inputted to the base of a transistor 26 and a luminance demodulating signal Y inputted to an input terminal Tin3 is inputted to a collector of the transistor 26, a collector of the transistor 26, namely, from the output terminal Tout, a composite video signal Sv, in which they are synthesized, is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a character display method applied when displaying m-sized characters on a television image.

[Prior Art] Displaying text superimposed on a television image is done, for example, at broadcasting stations and expensive television receivers. High-class waveform 11 with a little blackening! There are 6 types of embedding. For example, when displaying the character "24" in an image as shown in Figure 5, the area around it (the shaded area in the diagram)
If it is made 75% white, the character "24" can be read without any problem.

At that time, the video signal waveform of the line x-x'' in the figure is shown as a solid line in Figure 6.However, if such waveform processing is not performed, the periphery of the character will be 10
In the 0% white state, the video signal waveform becomes as shown by the dotted line in FIG. 6, causing a problem that characters cannot be distinguished. For this reason, set the character signal to a white level higher than the 100% white level of the normal video signal, so that the surrounding area is 100% white of the video signal.
There is also a method that allows characters to be clearly legible even with 0% white.

[Problems to be Solved by the Invention] Incidentally, magnetic disk playback devices in electronic still cameras often display numbers such as track numbers superimposed on images, but such devices can be connected to any receiver. Since the playback device is often used as If a signal of white or higher is input, AGC
There is a risk that the circuit will work and cause a decrease in image brightness or synchronization problems.

This invention was made to solve these problems, and it is a television that can give outlines to characters through simple processing, making it easy to read characters even when the surrounding area is 100% white. The purpose is to provide a method for displaying characters on images.

[Means for Solving the Problems] When displaying characters superimposed on a television image, the present invention differentiates the leading edge and trailing edge of a character display signal to obtain a pulse 19; In this method, the polarity of the character display signal is reversed to that of the character display signal, and the signal is superimposed on the image signal for image display together with the character display signal.

[Operation] In the present invention of such a method, the signal levels of the leading edge and trailing edge of the character display signal are lowered by a differential pulse,
This gives the outline of the characters.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the present invention will be described as applied to a magnetic disk reproducing device.

In Figure 1, 11 is 1/2 interest operation method.
This head stores a composite video signal for displaying a frame image as a repeated reproduction signal of one field, one field per rotation, and reads the reproduction signal from a magnetic disk (not shown) storing a plurality of the signals. The head 1
The reproduction signal read in step 1 is supplied to a luminance demodulation circuit 13 and a color demodulation circuit 14 via a reproduction amplifier 12, respectively. The luminance demodulated signal Y from the luminance demodulation circuit 13 is supplied to the mixer 15, and the color demodulated signal C from the color demodulation circuit 14 is supplied to the mixer 15 via the NTSC encoder 16.

The mixer 15 is further supplied with a character signal W. The mixer 15 mixes the luminance demodulated signal Y, the color demodulated signal C, and the character signal W, and outputs a composite video signal Sv for television video. This composite video signal Sv
is sent to the television via the output amplifier 17.

The mixer 15 is constructed as shown in FIG.

That is, a resistive voltage divider circuit of resistors 21 and 22, a resistive voltage divider circuit of resistors 23 and 24, and a series circuit of resistor 25, PNPN upper type transistor 26, and resistor 27 are connected between the power supply terminal and the ground, respectively. are doing. The input terminal Tin1, which inputs the character signal W, is grounded through a variable resistor 28, and is connected to the connection point between the resistors 25 and 26 through a capacitor 29, a diode 30 in the opposite direction, and a resistor 31 in series. and capacitor 32, forward diode 3
3 and a resistor 34 are connected in series to the connection point between the resistors 23 and 24. The connection point between the two capacitors and the cathode of the diode 30 is connected to the first power supply terminal via the resistor 35, and the resistor 35 and the capacitor 29 connect the first
The resistor 21 and capacitor 32 constitute a second differential circuit. Note that a resistor 36 is connected in parallel to the diode 33.

The input terminal Tin2 for inputting the color demodulated signal C is connected to the resistor 23 through a capacitor 37 and a resistor 38 in series.
and 24, and the connection point is connected to the base of the transistor 26. The collector of the transistor 26 is connected to the output terminal TOut.

An input terminal Tin3 into which the luminance demodulated signal Y is input is connected to the collector of the transistor 26 and the emitter of an NPN type transistor 39.

The transistor 39 has its collector connected to the power supply terminal and its base connected to the movable terminal of the variable resistor 28.

In the apparatus according to the embodiment of the present invention having such a configuration, the reproduction signal read from the magnetic disk by the head 11 is supplied to the luminance demodulation circuit 13 and the color demodulation circuit 14 via the reproduction amplifier 12, respectively. And brightness demodulation circuit 1
The luminance (U modulation signal Y and the color demodulated one word C outputted from the color demodulation circuit 14 via the NTSC encoder) from 3 are respectively input to the mixer 15. When displaying characters, a character signal W is input.In this mixer 15, an input terminal T inl
When a character signal W as shown in FIG. The leading edge and trailing edge of are respectively differentiated as shown in FIG. 3(b). Then, from the pulse generated by being differentiated by the first differentiating circuit, a diode 30
Only the negative pulse shown in (d> in FIG. Only positive pulses as shown in FIG. 3(C) are taken out and supplied to the base of the transistor 26.

As a result, a mixed pulse consisting of the negative pulse supplied to the emitter of the transistor 26 and a negative pulse obtained by inverting the positive pulse supplied to the base of the transistor 26 is outputted to the collector of the transistor 26. Further, since the color demodulated signal C input to the input terminal Tir+z is input to the base of the transistor 26, and the luminance demodulated signal Y input to the input terminal Tin3 is input to the collector of the transistor 26, the collector of the transistor 26, That is, the output terminal T
A composite video signal Sv as shown in FIG. 3(e) in which these signals are combined is outputted from out.

This composite video signal Sv becomes a signal in which when the character signal W is at a 100% white level, the front and trailing edges of the signal are lowered in level by a negative differential pulse. That is,
The signal looks like a letter with a black border. However, in this case, the inner side of the character signal except for the leading and trailing edges is not lowered in level, so that, for example, when the character "24" is displayed, it is displayed in the form shown in FIG. 4.

However, even with such bordering, the characters can be read sufficiently.

In this way, it is possible to give an outline to a character by simple processing using a simple circuit using only a differential circuit and an inversion circuit using transistors.
Characters can be easily read even if they are 0% white. Note that in this case, the level reduction by the differential pulse does not have to be such that complete black is obtained, but may be such that the outline appears clearly to some extent.

Note that the circuit groove configuration of the mixer is not limited to that of the embodiment described above, and may be modified in various ways without departing from the gist of the present invention.

[Effect of the invention 1 As detailed above, according to the present invention, it is possible to give an outline to a character by simple processing, and even if the surrounding area is 10
It is possible to provide a method for displaying characters on a television image that allows characters to be easily read even when the characters are 0% white.

[Brief explanation of drawings]

Figures 1 to 4 show embodiments of this invention.
The figure is a block diagram, Figure 2 is a specific circuit diagram of the mixer in Figure 1, Figure 3 is a waveform diagram to explain the processing of each part of the circuit in Figure 2, and Figure 4 is an example of character display. FIG. 5 is a diagram showing a conventional display state in which characters are superimposed on an image, and FIG. 6 is a diagram showing a video signal between line XX- in FIG. 15...Mixer, 21.35...Resistor, 2, 32
...Capacitor, 26...PNPN upper type resistor. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure V Figure 3 Figure 4

Claims (1)

[Claims] When displaying characters superimposed on a television image, a pulse is obtained by differentiating the leading and trailing edges of a character display signal, and the pulse is made to have a polarity opposite to that of the character display signal. A method for displaying characters on a television image, characterized in that characters are displayed in a superimposed manner on a video signal for image display together with a character display signal.