JPS60229488A - Title brightness switching circuit of home video camera - Google Patents

Abstract

PURPOSE:To offer a title brightness switching circuit suitable for miniaturization of a home video camera by constituting a signal selecting a white character and a color character with a binary signal of high and low levels and using the signal as a title brightness switching signal. CONSTITUTION:Input signals at input terminals 7, 8 are inputted to an AND gate 5 at the same time and (1) level is outputted to the selection of white color and (0) level is outputted to the selection of red/green/blue color from the AND gate 5. This signal is inputted to a luminance signal setting circuit 6 to control it in correspondence to (1) and (0) and the brightness signal level of the white level and the red/green/blue level lower than the white level in the brightness is set. Then a title signal is synthesized by superimposing a chrominance carrier on a DC potential at a title signal synthesis circuit 2, and the title signal is added to the video signal by a color title adder circuit 3. Thus, the bright signal level for the white character and the color character is switched easily in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a home video camera with a color title addition function, and particularly to an electric circuit suitable for title brightness switching.

[Background of the invention]

An example of this conventional rice cultivation will be explained using FIG. 1.

In Fig. 1, 1 is a manual switch for selecting the color carrier wave and luminance signal level corresponding to various color characters;
5 is a title signal synthesis circuit that superimposes color carrier waves corresponding to various color characters on a DC potential; 5 is a title signal synthesis circuit that switches between the video signal and the title signal synthesized by the title signal synthesis circuit 2 using character pulses to add a color title to the video signal; The color title addition circuits for addition are shown.

In the case of the title adding circuit shown in FIG. 1, as an example, the title can be switched between white, red, green, and blue. Each terminal of manual switch 1 has terminal 1
A is white with no signal, terminals 2A, 5A, and 4A are red, respectively.
Color carrier waves corresponding to green and blue are input, and a desired color can be selected by switching a switch. Also, in conjunction with this, (IA-1B, 2A-2B, 3A-
3B, 4A-4E correspond. ) Switch the brightness signal level of each color. However, in the example shown in the figure, the luminance signal level is not switched between red, green, and blue. The title signal synthesis circuit 2 synthesizes the selected bright white, red, green, and blue color signals and luminance signals in this manner, and the title addition circuit 3 adds the title signal to the video signal.

However, switching between white text and color text using this method requires large parts such as a manual switch with an Fi2 circuit, and when adding a color title addition function to a camera, it is difficult for households to request a smaller size. This is very disadvantageous for video cameras.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a title brightness switching circuit that eliminates the drawbacks of the prior art described above and is suitable for downsizing home video cameras.

[Summary of the invention]

The present invention provides a high (H) signal for selecting white characters and color characters.
IGE), low (LOW) binary signals, and only when the characters are white, all signals are set to ``no'' (or ``low'').
By using the AND or NAND output (OR or NOR) of these signals as the title brightness switching signal, it is possible to easily switch the title brightness suitable for control by a microcomputer. becomes possible.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG. In Figure 2, the first
The same reference numerals as in the figures indicate components having the same functions. Also, 4 is a color carrier switching circuit, and 5 is an AND(A)/I)
) gate, 6 is a luminance signal setting circuit, 7.8 is a title switching signal input terminal, and 9 to 12 are color carrier wave input terminals. As in the case of Figure 1, the letters are white, red, green, ! The case of switching to is explained below. The binary signals inputted from the input terminals 7.8 are respectively white-(1,1), red-(1°0), and green-(
o, 1), blue - (0, 0), in the color carrier switching circuit 4, each color carrier supplied to terminals 9 to 12 is selected in response to the input signal of each input terminal 7.8. be done. However, there is no signal for white. At the same time, the input signals of the input terminals 7 and 8 are input to the AND gate 5, and the AND gate 5 outputs "1" for the selection of white, and "0" for the selection of red, green, and blue. This signal is input to the brightness signal setting circuit 6Vc and controlled in correspondence with rl and roJ, thereby setting brightness signal levels for white and for red, green, and blue, which have lower brightness. Thereafter, as in the case of FIG. 1, a title signal synthesis circuit 2 superimposes a color carrier wave on the DC potential to synthesize a title signal, and a color title addition circuit 3 adds the title signal to the video signal. In this way, the luminance signal level of white characters and color characters can be easily switched.

In the embodiment shown in FIG. 2, an AND gate is used, but of course it is also possible to change the settings of the luminance signal setting circuit 6 and use a NAND (AIAND) gate. Also,
When selecting white, a signal of (1, 1) is applied, but if (O, a) is set to white, the AND gate 5 needs to be an OR or NOR gate.

〔Effect of the invention〕

According to the present invention, a title brightness switching circuit suitable for miniaturization and control by a microcomputer can be constructed without using large parts such as a manual switch with two circuits.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional color title adding circuit, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1...Manual switch 2...Title signal synthesis circuit 3...Color title addition circuit 4...Color carrier switching circuit 5...AND gate 6...Brightness signal setting circuit 7, 8 .9.10.11.12 ... Input terminal Figure 1 Exposure 2 Figure □~9 □~101 □~// □~/2 Torca O Shoulder Vitego 1 Fit 2 White) 4> Green) Plaster) Nishishita

Claims (1)

[Claims] In a title adding device that adds a selectable title signal to a video signal, in which title color and brightness level can be selected, the color operates by a combination of binary signals applied to a plurality of input terminals in order to select the color of the title signal. It has a carrier wave switching means, a gate circuit that performs a logical operation on the signals applied to the plurality of input terminals, and a luminance signal level setting means that switches the luminance level based on the output of the gate circuit, and the color of the title is set to white. A title brightness switching circuit for a home video camera, characterized in that the binary signals applied to the plurality of input terminals are all set to the same combination of signals in order to achieve this.