JPH0346633Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a back color generating circuit used in a television studio transmission system.

[Conventional technology]

Conventionally, this type of back color generation circuit inputs subcarriers having a phase difference of 90 degrees to subcarrier input terminals 17 and 18 for composite signals, as shown in the block diagram of FIG. 3, and inputs color difference signals. Terminals 2 and 3 are supplied with DC voltages having a relationship between sine and cosine, and multiplier circuits 19 and 20 multiply these signals to output a multiplied voltage.
The outputs of 20 are mixed by a mixing circuit 21, and a gain control circuit 22 is further controlled from a color difference signal control input terminal 11 to output a subcarrier containing color difference signal information. This output and the DC voltage supplied from the luminance signal input terminal 1 are input to the gain control circuit 23,
This circuit 23 performs a blanking gate using the signal from the blanking input terminal 10 and outputs a one-to-one mixed signal. This output and the black burst signal from the input terminal 12 are mixed in the mixing circuit 7 and outputted from the output terminal 24 as a back color signal of a composite signal.

[Problem that the invention attempts to solve]

This conventional back color generating circuit has the disadvantage that since it is used for composite signals, the circuit is somewhat complicated and adjustment is troublesome.

It is an object of the present invention to provide a back color generating circuit which eliminates such drawbacks, simplifies the circuit, and facilitates adjustment thereof.

[Means for solving problems]

The configuration of the back color generation circuit of the present invention includes a first gain control circuit that inputs a DC voltage brightness signal, applies a blanking gate, and outputs a back color brightness signal, and a black burst output to the output of the first gain control circuit. a first mixing circuit that adds a signal;
Second and third gain control circuits each input a color difference signal of a DC signal having a phase relationship between sine and cosine, gate the blanking period, perform gain control during the video period, and adjust the back color saturation, respectively. and second and third mixing circuits that add burst signals to the respective outputs of the second and third gain control circuits.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. Luminance signal input terminal 1 and color difference signal input terminal 2,
Input signals from 3 are supplied to gain control circuits 4, 5, and 6. The control signals for each of these gain control circuits are
The gain control circuit 4 has a luminance signal input terminal 10,
The gain control circuits 5 and 6 have a color difference signal control input terminal 1.
Supplied from 1.

The output of the gain control circuit 4 and the signal from the black burst input terminal 12 are mixed in the mixing circuit 7, and similarly the output of the gain control circuits 5 and 6 and the signal 13 from each burst input terminal are mixed in the mixing circuits 8 and 9. A luminance signal and a color difference signal are taken out from each output terminal of these mixing circuits 7 to 9.

Next, the operation of this embodiment will be explained. A DC luminance signal is supplied to the luminance signal input terminal 1, a blanking gate is applied by the gain control circuit 4, and a black burst from the input terminal 12 is added, so that the output of the mixing circuit 7 is a back-color luminance signal. It is output from the terminal 14 as . Also,
As the color difference signal input terminals 2 and 3, it is necessary to supply DC signals having a sine and cosine relationship with a 90° phase shift, and the two color difference signals having such a relationship are sent to separate gain control circuits. Enter 5 and 6.

Here, as the control signal, as shown in FIG. 2, a DC voltage is used that can simultaneously control the gain of the blanking signal during the blanking period and the two color difference signals during the video period to adjust the degree of color saturation. The outputs of these gain control circuits 5 and 6 and the burst signal from the input terminal 13 are mixed by mixers 8 and 9, and two back color color difference signals having information on hue and color saturation are output.

[Effect of idea]

As explained above, in the present invention, when configuring a component signal back color generation circuit, the circuits that process the luminance signal and two color difference signals can be made completely the same, so that the phase and characteristics of these three signals can be changed. In addition, since the blanking gate and the color saturation are adjusted by one gain control circuit, the circuit can be simplified.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention;
This figure is a waveform diagram of the color difference signal control voltage shown in FIG. 1, and FIG. 3 is a block diagram of an example of a conventional back color generator. In the figure, 1... Luminance signal input terminal, 2, 3... Color difference signal input terminal, 4, 5, 6, 22, 23... Gain control circuit, 7, 8, 9, 21... Mixing circuit, 10...
Luminance signal control input terminal, 11... Color difference signal control input terminal, 12... Black burst input terminal, 1
3... Burst input terminal, 14, 24... Back color output terminal, 17, 18... Subcarrier input terminal, 19, 20... Multiplication circuit.

Claims (1)

[Scope of utility model registration request] The first input inputs a DC voltage brightness signal, applies a blanking gate, and outputs a back color brightness signal.
a gain control circuit, a first mixing circuit that adds a black burst signal to the output of the first gain control circuit, and a color difference signal of a DC signal having a phase relationship between sine and cosine, and inputs the color difference signal during the blanking period. The second and third stages adjust the back color saturation by applying a gate and controlling the gain during the video period, respectively.
1. A back color generation circuit comprising: a gain control circuit; and second and third mixing circuits that add burst signals to respective outputs of the second and third gain control circuits.