JPS6214787Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a color bar generation circuit, which reduces shocks that occur when switching between a color bar signal and a camera video signal, does not disturb the output signal during switching, and has a simplified color bar generation circuit. The purpose is to provide circuits.

Conventionally, in a video camera, a video signal and
An example of a circuit for switching between a color bar signal and a color bar signal for checking the reference hues of the three primary colors of red, green, and blue is the circuit shown in FIG. When the changeover switch 1 is connected to the a side contact, the three primary color reference signals from the color bar output circuit 2 are supplied to the encoder 4, and it is checked whether the output from the encoder 4 indicates the correct reference color. Ru. When the changeover switch 1 is connected to the b-side contact, the three primary color video signals from the video signal processing circuit 3 are supplied to the encoder 4, which outputs them as NTSC signals.

In such a conventional circuit, the reference level of the video signal output from the video signal processing circuit 3 is 3.5V as shown in FIG. 2A, so the three primary color output signals from the color bar output circuit 2 are also The reference level must be set to 3.5V as shown in Figure 2 C to E. For this purpose, timing pulses for the three primary colors are supplied to the color bar output circuit 2 by the oscillator 5 and the counter 6, and the color bar output circuit 2 newly sets a reference voltage of 3.5 V and a peak level voltage of 4.5 V as shown in C to E in the figure. V rectangular waves must be generated for each of the three primary colors, making the circuit configuration complicated, and the reference level being obtained independently of the video signal processing circuit 3, requiring unnecessary circuit configurations, etc. There were some shortcomings.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to FIG.

The oscillator 5 and the counter 6 constitute a color bar generator 7. Oscillator 5 generates a 126 KHz clock pulse as shown in FIG. 2B and supplies it to counter 6. The counter 6 divides the frequency of this clock pulse, for example, a 63KHz timing pulse as shown in Figure C for the blue signal, a 15.75KHz timing pulse as shown in Figure D for the green signal, and a 15.75KHz timing pulse for the red signal. generates a 31.5 KHz timing pulse as shown in the figure E, and is supplied to the encoder 4 via the switch 1.

On the other hand, red, green, and blue three-color image pickup tubes 8-1 to 8-3
The video signal from is supplied to the video signal processing circuit 3. The video signal processing circuit 3 generates a video signal of a level corresponding to the saturation of each color, with the black level within the blanking period as a reference voltage of 3.5V, as shown in FIG. 2A, and switches the switch 1. is supplied to the encoder 4 via.

A switch 1 switches between a color bar signal and a video signal. That is, when the switch 1 is switched to the a side by the control signal, the color bar signal is supplied to the encoder 4, and the switch 1 is switched to the b side.
When switched to the side, the video signal is supplied to the encoder 4.

When the switch 1 is switched to the a side and the color bar signal is supplied to the encoder 4, the encoder 4
outputs a color bar composite signal in accordance with the timing of the timing pulse, and these outputs are observed with a vector scope or the like. The encoder 4 is configured so that the level and vector of the specified standard color bar composite signal are obtained based on the level of the color bar composite signal observed by the vector scope.
adjustments will be made.

As described above, the power supply voltage Vd is supplied to the video signal processing circuit 3 so that the black level during the blanking period is 3.5 V. This reference voltage Vd is also supplied to the ground side of the oscillator 5 and the counter 6. Therefore, the output clock pulse of the oscillator 5 and the three pulses from the counter 6 are
As shown in Figures B to E, the reference voltage is 3.5 V, and the peak voltage becomes a square wave of 4.5 V due to resistor division. This square wave is directly supplied to the encoder 4 via the switch 1.

In this way, the reference voltages for the color bar signal and the video signal are applied to switch 1 at the same level, so when switch 1 switches from the color bar signal to the video signal, the output signal is not disturbed by the switching. Switching can be performed smoothly without any occurrence.

As mentioned above, the color bar generation circuit according to the present invention includes a circuit that generates a reference frequency signal and a circuit that outputs timing pulses of the three primary color bars of red, green, and blue using the reference frequency signal. , the ground side voltages of the two circuits are set equal to the reference level of the video signal processing circuit used by switching the output video signal with the color bar signal, so that the color bar signal and the video signal from the image pickup tube are This reduces the shock that occurs when switching between the two, does not disturb the output signal during switching, and does not require a circuit to match the reference level of the color bar signal to the black level within the blanking period of the video signal. , the circuit can be simplified, and the pulse period and level of the color bar signal can be adjusted extremely easily.

[Brief explanation of the drawing]

Fig. 1 is an example of a circuit having a conventional color bar generation circuit, Fig. 2 is a timing diagram of a color bar signal and a video signal, and Fig. 3 is an example of a circuit having a color bar generation circuit of the present invention. It is a figure of an Example. 1... Selector switch, 2... Color bar output circuit, 3... Video signal processing circuit, 4... Encoder, 5... Oscillator, 6... Counter, 7... Color bar generation circuit.

Claims (1)

[Scope of utility model registration request] In a color bar generation circuit consisting of a circuit that generates a reference frequency signal and a circuit that outputs timing pulses of three primary color bars of red, green, and blue using the reference frequency signal, the ground side voltages of the two circuits are connected to the output video. A color bar generation circuit configured to set the signal equal to the reference level of a video signal processing circuit used by switching the signal with the color bar signal.