JPH0744143Y2 - Color signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a color signal processing circuit.

(B) Conventional technology For example, in Japanese Unexamined Patent Publication No. 62-34488 (H04N1 / 40), by controlling the amplitude of the carrier color signal according to a correction signal of a differential waveform based on the envelope of the carrier color signal, A configuration is disclosed in which an edge portion of a carrier color signal is emphasized to prevent color blurring, blurring, and the like.

(C) Problems to be Solved by the Invention However, the above configuration can deal with the change in the amplitude, but cannot deal with the change in the phase of the carrier color signal.

Therefore, the present invention provides a color signal processing circuit capable of controlling the amplitude of a carrier color signal in response to changes in the amplitude and phase of the carrier color signal.

(D) Means for Solving the Problems The present invention provides a delay circuit having a delay time n times (n is a natural number) the carrier color signal period, and a subtraction circuit for deriving the difference between the output of the delay circuit and the delayed signal. And a variable gain amplifier that controls the amplitude of the non-delayed carrier color signal based on the output of the subtraction circuit.

(E) Action The frequency of the carrier color signal reproduced by a video tape recorder or the like has a predetermined value, and therefore its cycle is also constant. Therefore, if the difference between the carrier color signal that has passed through the delay circuit having a delay time n times the carrier color signal cycle and the non-delayed carrier color signal is calculated, the amplitude of the carrier color signal corresponding to the change in the color signal and A change in phase can be extracted as a change in amplitude, and the amplitude of the carrier color signal is controlled according to the extraction result.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the embodiment, FIG. 2 is a waveform diagram showing waveforms, and FIG. 3 is a circuit diagram showing a concrete circuit.

In the figure, 1 is an input terminal of a carrier color signal, 2 is a delay circuit, 3 is a subtraction circuit, 4 is a waveform shaping circuit, 5 is a variable gain amplifier (amplifier whose gain can be switched), 6
Is an output terminal for the processed carrier color signal.

The delay time of the delay circuit 2 is set to n times the cycle of the input carrier color signal, for example, n = 1. Subtraction circuit 3
Derives the difference between this delay circuit output and the original carrier color signal (non-delayed signal). The waveform shaping circuit 4 rectifies the output signal waveform of the subtraction circuit 3 to obtain a DC control signal. Then, the gain of the variable gain amplifier 5 for amplifying the non-delayed carrier color signal is controlled by the output of the waveform shaping circuit 4.

Next, the operation of the embodiment will be described with reference to the waveform chart of FIG. 2A is an input carrier color signal, B is a delayed carrier color signal delayed by one cycle of the carrier color signal, and C is a subtraction circuit 3.
The output, d is the output of the waveform shaping circuit 4 after rectification, and e is the output of the processing circuit.

The input carrier color signal is, for example, a reproduction signal from a video tape recorder, and an output from a reproduction color signal processing circuit (not shown) is input. The reproduction color signal processing circuit is
As is well known, the color signal recorded by low-pass conversion is frequency-converted into the original frequency band, and the time-axis fluctuation is corrected.
It is supplied to the processing circuit shown in the figure.

The input carrier color signal is delayed by the delay circuit 2 for a predetermined time (here, one carrier color signal period), and becomes as shown in (b). Then, the delayed carrier color signal is subtracted from the original non-delayed carrier color signal to derive the difference between the two. The signal corresponding to this difference is the Ha signal. The difference signal C has an amplitude of zero when there is no change in the color signal, and an amplitude related to the change appears when there is a change in the amplitude or phase of the carrier color signal.

The difference signal is supplied to the waveform shaping circuit 4 and is rectified to have a waveform like D. In other words, a signal representing the case where the amplitude of the difference signal is zero and the case where there is amplitude is obtained as a DC level (L
No change at level. There is a change at H level). The gain of the variable gain amplifier 5 is changed based on the output of the waveform shaping circuit 4. That is, when the output of the waveform shaping circuit 4 is at the H level, the gain is increased so that the amplitude of the carrier color signal becomes larger, and when the output is at the L level, the gain remains unchanged. That is, 2
Gain is controlled in stages.

As a result, the output signal looks like E and the color signal is emphasized in the part where the color signal changes.

FIG. 3 shows a specific configuration of FIG. The same items are denoted by the same reference numerals. The delay circuit 2 uses a circuit that is often used. The output of this delay circuit is inverted by the buffer 6 and combined with the original carrier color signal. The waveform shaping circuit 4 is a rectifying circuit including a diode 7, a resistor 8 and a capacitor 9. The waveform shaping circuit 4 outputs an H level when the input carrier color signal changes in amplitude or phase, and outputs an L level when there is no change. Is output.

Then, according to the output of the waveform shaping circuit, the FET 10 of the variable gain amplifier 5 is controlled to the on / off state, and the gain is changed. In other words, when H level output, FET
Turns on and the gain increases. This emphasizes the change in the color signal.

(G) Effect of the Invention As described above, according to the present invention, it is possible to emphasize the changed portion of the color signal and obtain a reproduced image with good color separation, which is effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the embodiment, FIG. 2 is a waveform diagram, and FIG. 3 is a circuit diagram showing a specific configuration. 2 ... Delay circuit 3 ... Subtraction circuit 4 ... Waveform shaping circuit 5 ... Variable gain amplifier

Claims (1)

[Scope of utility model registration request] 1. A delay circuit having a delay time n times the period of a carrier color signal, a subtraction circuit for deriving a difference between a non-delayed carrier color signal and the output of the delay circuit, and the subtraction circuit based on the output of the subtraction circuit. And a variable gain amplifier for controlling the amplitude of a non-delayed carrier color signal.