JPS6147472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a back color signal generator for color television.

Conventional back color signal generation devices are capable of adjusting the saturation level, brightness level, and hue level individually, so if the saturation signal, that is, the color subcarrier, falls below a specified potential, for example, exceeds the synchronization signal level, or On the other hand, there were cases where the voltage was higher than the white level. Back color signals with levels other than those specified may adversely affect the synchronization separation function of subsequent equipment, and excessive levels in the white direction will cause waveform distortion when passed through the white clipper, which is also prohibited under the Radio Law. This was also a major problem from a practical standpoint.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a back color signal generating device which eliminates the drawbacks of the prior art.

According to the present invention, the conventional drawbacks are solved by controlling the saturation signal according to the brightness level, and the brightness,
A back color signal generation circuit can be obtained which can always obtain an output signal complying with radio regulations even if the hue and saturation are arbitrarily adjusted.

The present invention will be described in detail below with reference to the drawings of one embodiment of the present invention. FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, a subcarrier supplied from a subcarrier input terminal 101 is phase-controlled in a phase adjustment circuit 10 according to a phase control voltage from a terminal 20. The phase adjustment circuit 10 can change the phase of the subcarrier between 0° and 360°, thereby changing the hue of the back color.

The output of the phase adjustment circuit 10 enters the saturation adjustment circuit 11, where the amplitude of the subcarrier is controlled according to the control voltage from the saturation control voltage correction circuit 13, and the saturation is adjusted. In the saturation adjustment circuit 11, it is undesirable for the subcarrier level to exceed the synchronization signal level, black level, and white level, so in the correction circuit 13, the saturation control voltage from the terminal 21 is adjusted according to the brightness control voltage from the terminal 22. be corrected. At the same time, the blanking signal from the terminal 102 enters the correction circuit 13, and the level of the subcarrier is set to zero during the blanking period. Correction circuit 13
This will be explained in detail later.

The subcarrier adjusted to a predetermined amplitude by the saturation adjustment circuit 11 is sent to the brightness signal adjustment circuit 1 by the addition circuit 12.
The luminance signal level of the predetermined level from 4 is added. The brightness signal adjustment circuit 14 is supplied with the brightness control voltage from the terminal 22 and the blanking signal from the terminal 102, and a brightness signal level corresponding to the control voltage is created and the blanking period is set to zero level.

The adder circuit 12 outputs a back color signal in which a subcarrier having a predetermined level of amplitude and phase is superimposed on a luminance signal of a predetermined level, and this output is added to the black burst signal from the terminal 103 in an adder circuit 15. It is then output to the outside as a final back color signal. The black burst signal is a signal containing a synchronization signal and a color burst carried on the back porch of the synchronization signal, and the output of the adder circuit 15 becomes a back color signal according to the regulations.

Next, the saturation control voltage correction circuit 13 will be explained. In the correction circuit 13, the brightness level determined by the brightness control voltage from the terminal 22 is compared with the white level and black level defined by the Radio Law, and modifies the saturation control voltage from the terminal 21 as follows. That is, when the brightness level determined by the brightness control voltage reaches the white level and the black level, the saturation control voltage is set to the minimum, and when the brightness level is intermediate, the saturation control voltage is set to the maximum. By doing this, the level of the subcarrier carried on the luminance signal will never be higher than the white level or lower than the black level. The characteristics of the correction circuit 13 are shown in FIG. In FIG. 2, the horizontal axis represents the brightness control voltage, and the vertical axis represents the maximum saturation control voltage output from the correction circuit 13. As is clear from FIG. 2, as the luminance level approaches the black level or white level, the permissible subcarrier amplitude decreases, and the possible subcarrier amplitude reaches its maximum when the luminance level is in the middle. As mentioned above, the blanking signal is supplied to the correction circuit 13, and the blanking signal is non-additively mixed (NAM) with the corrected saturation control voltage, so that the level of the subcarrier becomes zero during the blanking period. be made to be.

FIG. 3 is a block diagram of the correction circuit 13, which includes a V-shape forming circuit 16, a signal inversion/offset adjustment circuit 17
and NAM circuit 18. Positive and negative polarities are created from the saturation control signal from the terminal 21 by a circuit consisting of two transistors, and after positive polarity non-addition mixing (P-NAM), a positive polarity signal is taken out. This signal passes through the signal inversion/offset adjustment circuit 17, and the brightness control voltage from the terminal 22 and the blanking signal from the terminal 102 are NAM-added.

As explained above, in the present invention, the range of saturation control is controlled by the level of the brightness signal, so that no matter what value the brightness signal level takes, the level of the subcarrier in the back color signal is It will not be outside the specified range.

[Brief explanation of the drawing]

1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the saturation control voltage correction circuit 13 in FIG. 1, and FIG. 3 is a configuration of the correction circuit in FIG. 1. Diagram showing. In the figure, 10... phase adjustment circuit, 11...
Saturation adjustment circuit, 12... Addition circuit, 13... Circuit that compares the luminance level with white and black levels and corrects the saturation control voltage, 14... Luminance signal adjustment circuit gated with a blanking signal, 15... ...addition circuit, 2
0... Phase control terminal, 21... Saturation control circuit, 2
2...Brightness control terminal, 101...Subcarrier input terminal, 102...Blanking signal input terminal,
103...Black burst input terminal, 104...
...Back color output terminal.

Claims (1)

[Claims] 1 A phase adjustment circuit that changes the phase of the input subcarrier using an external hue control voltage, and receives external saturation control voltages and brightness control voltages to suppress the saturation level and adjust the brightness level when the brightness level is at the white level or black level. a saturation adjustment circuit that controls the amplitude of the subcarrier from the phase adjustment circuit so that the saturation level becomes large when has an intermediate value; and a brightness signal adjustment circuit that generates a brightness signal level according to the brightness control voltage. A back color signal generating device comprising: a circuit; and an adding circuit for adding the output of the luminance signal adjusting circuit and the output of the saturation adjusting circuit, and the output of the adding circuit is used as a back color signal.