JPH03123289A - False chrominance signal attenuation circuit - Google Patents

Abstract

PURPOSE:To attenuate a false chrominance signal generated when photographing a high luminance object by responding to the acute change in a luminance signal level, and controlling the amplifying gain of a color difference signal. CONSTITUTION:A detection circuit 60 detects the acute level change of a luminance signal Y, and that output signal S6 controls the gain of amplifiers 10, 20. The amplifiers 10, 20 receive and amplify the color difference signal. Also, the circuit 60 possesses a delay circuit 61 which delays the luminance signal Y for a prescribed amount and a differentiation circuit which differentiates signals S1, S2 before and after the delay, and outputs signals S3, S6 from circuits 62, 63. And, a signal S4 is subtracted from the signal S3 at a subtraction circuit, that output is supplied to a detection circuit 64, and is outputted as the above signal S6. Here, adding circuits 11, 21 adds the signal S6 to a preliminarily set gain control voltage at resistors 12, 22. The signal S6 responds to the acute change in the level of the signal Y and controls the amplifying gain, so the false chrominance signal generated when photographing the high luminance object can be attenuated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a false color signal attenuation circuit, and in particular, to a false color signal attenuation circuit capable of reducing false color signals generated when a high-brightness object is imaged by an imaging device. The present invention relates to a color signal attenuation circuit.

[Prior Art] FIG. 4 is a circuit block diagram showing part of a conventional encoder circuit provided in a video camera (or video movie). Referring to FIG. 4, this encoder circuit receives color difference signals R-Y from the previous stage color signal processing circuit.
and B-Y; modulators 1 and 2 connected to the outputs of amplifiers 10 and 20; and an adder 9 for adding the output signals of modulators 1 and 2; It includes a suppression circuit 3 that suppresses the color signal output from the adder 9, and a bandpass filter 5 connected to the output of the suppression circuit 3. A color signal is outputted via the filter 5. The gain of each amplifier 10 and 20 is preset by resistors 12 and 22, respectively. This encoder circuit further includes a brightness processing section 6 connected to receive the brightness signal Y, a blanking circuit 7 connected to the output of the brightness signal processing section 6, and a blanking circuit 7 connected to the output of the blanking circuit 7. synchronous signal mixing circuit 8.

In operation, the color difference signals R-Y and B-Y amplified by amplifiers 10 and 20, respectively, are modulated by subcarriers in modulators 1 and 2, respectively, and then combined by adder 9. The chroma signal output from the adder 9 is given to the high brightness discoloration suppression circuit 3. The suppression circuit 3 suppresses the chroma signal in response to the level of the luminance signal Y applied via the clamp circuit 4.

That is, when the level of the luminance signal is high, by improving the balance between the luminance signal and the chroma signal, it is possible to improve the appearance of unnaturally dark colors on the screen. The suppressed chroma signal is output via a bandpass filter 5.

On the other hand, the luminance signal Y given to the luminance signal processing section 6 is γ
After correction, KNEE compression, contour compensation, etc. are performed, the signal is applied to the blanking circuit 7. After blanking processing is performed in circuit 7, a synchronizing signal is mixed in circuit 8. A desired luminance signal is output from the circuit 8.

To control the high brightness discoloration suppression circuit 3, a clamp circuit 4 clamps the luminance signal from the luminance signal processing section 6, and the amount of suppression of the chroma signal in the suppression circuit 3 is controlled by the clamped signal. Note that the brightness signal used for controlling the suppression circuit 3 may be used by extracting only the high brightness portion. Furthermore, there are cases where both the luminance signal before and after the γ processing are used, but the purpose is the same.

[Problems to be Solved by the Invention] In the conventional circuit shown in FIG. 4, the high-brightness discoloration suppression circuit 3 responds to the level of the brightness signal Y to prevent unnatural colors from appearing on a high-brightness screen. However, it is not possible to suppress false color signals that appear at the edges of the subject on the screen when a high-brightness subject is imaged. That is, colors that are not included in the original high-brightness object appear at the edges of the object on the screen.

This invention was made in order to solve the above-mentioned problems, and an object of the present invention is to obtain a false color signal attenuation circuit that can attenuate false color signals that occur when imaging a high-brightness subject. do.

[Means for Solving the Problems] A false color signal attenuation circuit according to the present invention includes: a gain controllable amplification means for amplifying a color difference signal; a detection means for detecting a steep change in a luminance signal level; control means for controlling the gain of the amplification means in response to the detection means.

[Operation] In the false color signal attenuation circuit according to the present invention, the control means controls the gain of the amplification means in response to a steep change in the luminance signal level detected by the detection means. Therefore, even when a high-brightness subject is imaged, the detection means detects a sharp change in the brightness signal level, and the gain of the color difference signal at the corresponding timing is reduced. As a result, false color signals that may occur around high-brightness objects on the screen are attenuated or eliminated.

[Embodiment of the Invention] FIG. 1 is a circuit block diagram showing a part of an encoder circuit showing an embodiment of the invention. Referring to Figure 1,
The difference from the conventional circuit shown in FIG. The gain is controlled by S6. That is, the circuit 60 is connected to receive the brightness signal Y, and outputs the signal S6 in response to the brightness signal Y. The detection circuit 60 includes a delay circuit 61 for delaying the luminance signal Y by a predetermined amount, a differentiation circuit 62 for differentiating the signal Sl before delay (that is, corresponding to the luminance signal Y), and a differentiation circuit 62 for differentiating the signal S2 after the delay. circuit 63, a subtraction circuit 65 that subtracts signals S3 and S4 output from differentiating circuits 62 and 63, respectively, and a detection circuit 64 connected to the output of subtraction circuit 65.
including. A signal S6 for controlling amplifiers 10 and 20 is output from detection circuit 64.

Adding circuits 11 and 21 are connected to amplifiers 10 and 20, respectively. The adder circuit 11 superimposes a signal S6 applied from the detection circuit 60 via the capacitor 13 on a gain control voltage set in advance by the resistor 12. That is, the signal S6 is superimposed on the control voltage for controlling the gain of the amplifier 10 through capacitive coupling by the capacitor 13. Similarly, signal S6 is superimposed on the gain control voltage for amplifier 20 in summing circuit 21 by capacitive coupling by capacitor 23.

FIG. 2 is a characteristic diagram showing the amplification characteristics of the amplifiers 10 and 20 shown in FIG. 1 with respect to the gain side i31] voltage.

As can be seen from FIG. 2, the gains of amplifiers 10 and 20 are controlled in proportion to the gain control voltages output from adder circuits 1 and 21.

FIG. 3 is a timing diagram of each signal for explaining the operation of the circuit shown in FIG. 1. In Figure 3 - as an example,
The brightness level of the brightness signal Y (Sl) is IH for one horizontal scanning period
A high case is shown in two parts. The operation will now be described with reference to FIGS. 1 and 3.

As shown in FIG. 3, a signal S1 is applied to a delay circuit 61, and a delayed signal S2 is output.

Differentiating circuit 62 differentiates signal S1 to obtain signal S3.
Output. Similarly, the differentiating circuit 63 outputs a signal S4 by differentiating the signal S2. The subtraction circuit 65 receives the signal S
3 and S4 are performed, and an output signal S5 is provided to the detection circuit 64. The detection circuit 64 responds to the signal S5 by detecting the width T.
outputs a signal S6 having o. As can be seen from FIG. 2, the signal S6 indicates the timing of the leading edge and the trailing edge of the high-brightness portion of the brightness signal Y, that is, the timing of the edge of the image of the high-brightness object on the screen.

Therefore, the control voltages of the amplifiers 10 and 20 are reduced at the timing when a false color signal appearing at the edge of an image of a high-brightness object is superimposed.

As a result, the gains of amplifiers 10 and 20 are reduced at the timing when the false color signal occurs.

That is, for example, the color difference signal RY contains a signal component that will become a false color signal in the future, as indicated by the arrow P in FIG. By applying this color difference signal RY to the aforementioned amplifier 10 as a signal s11, an output signal S12 is obtained in which the signal component that becomes a false color signal is attenuated or removed, as indicated by arrow Q. Similarly, signal components that become false color signals are removed from the color difference signal B-Y.

Note that in the circuit shown in FIG.
1 and 21 to the amplifiers 1o and 20, but depending on the circuit configuration, this signal S
6 can also be applied to amplifiers 1o and 2°.

[Effects of the Invention] As described above, according to the present invention, since the control means for controlling the amplification gain of the color difference signal in response to a sharp change in the luminance signal level is provided, it is possible to A false color signal attenuation circuit capable of attenuating or removing generated false color signals was obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a part of an encoder circuit showing an embodiment of the present invention. FIG. 2 is a characteristic diagram showing the amplification characteristics of the amplifier shown in FIG. FIG. 3 is a timing diagram of each signal for explaining the operation of the circuit shown in FIG. 1. FIG. 4 is a circuit block diagram showing part of a conventional encoder circuit. In the figure, 1 and 2 are modulators, 3 is a high brightness discoloration suppression circuit,
4 is a clamp circuit, 5 is a bandpass filter, 6 is a luminance signal processing section, 7 is a blanking circuit, 8 is a synchronization signal mixing circuit, 10.20 is an amplifier, 11.21 is an addition circuit, 6
0 is a detection circuit, 61 is a delay circuit, 62, 63 is a differentiation circuit, and 64 is a detection circuit. Fig. 3 Fig. 2

Claims (1)

[Scope of Claims] A gain controllable amplification means connected to receive a color difference signal and for amplifying the color difference signal; and a detector connected to receive a luminance signal and detecting a sudden change in the luminance signal level. and control means for controlling the gain of the amplification means in response to the detection means.