JPH01186092A - White balance correction circuit - Google Patents

Abstract

PURPOSE:To obtain a circuit suppressing the reduction in the saturation of a chrominance signal by obtaining a mean value of R-Y, B-Y color difference signals, comparing it with a prescribed value, adding them at a prescribed ratio to generate R-Y, B-Y color difference signals thereby applying white balance correction. CONSTITUTION:An R-Y mean value detection circuit 1 obtains a mean value of the R-Y color difference signals, and an R-Y mean value comparator circuit 2 compares the R-Y mean value with a prescribed value. A B-Y mean value detection circuit 6 obtains the mean value of B-Y color difference signals and a B-Y mean value comparison circuit 7 compares the B-Y mean value with a prescribed value. R-Y, B-Y adder circuits 3, 8 add output signals of the circuits 2, 7. A gain control circuit 4 uses the output of the circuit 3 to apply gain control of the 1st color signal 16 and a gain control circuit 9 uses the output of the circuit 8 to apply gain control of the 2nd color signal 19. R-Y, B-Y color difference circuits 5, 10 generate R-Y, B-Y color difference signals from the output signals of the circuits 4, 9 to constitute a white balance correction circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a simple white balance correction circuit for a video camera.

Conventional technology In recent years, as the demand for camera-integrated videos has expanded, low-cost, high-performance camera-integrated videos have become required, and full-auto white balance, which is an element of product value, has become more important. There is a growing demand for low-cost, high-performance white balance correction circuits. A conventional white balance correction circuit will be described below with reference to the drawings.

FIG. 3 shows a block diagram of this white balance correction circuit, where 1 indicates the color difference average value 12 of the R-Y color difference signal 11.
2 is an R-Y average value comparison circuit that compares the color difference average value 12 with a white balance reference value 13 and outputs a white balance correction value 14. 4
5 is a gain control circuit that controls the gain of the first color signal 16 based on the white balance correction value 14, and 5 is a gain control circuit that controls the gain of the first color signal 16 based on the white balance correction value 14;
This is an RY color difference circuit that creates 1.

The same signal processing is performed on the B-Y color difference signal 21, and 6 is a B-Y average value detection circuit that detects the color difference average value 22 of the BY color difference signal 21, and 7 is a color difference average value detection circuit. 2
2 and a white balance reference value 23, and outputs a white balance correction value 24. 9 is a gain control circuit that controls the gain of the second color signal 19 using the white balance correction value 24, and 10 is a gain control circuit that controls the gain of the second color signal 19 using the white balance correction value 24;
This is a BY color difference circuit that creates

The white balance correction operation of the conventional white balance correction circuit configured as described above will be explained.

Now, the white balance of the RY color difference signal 11 at the reference color temperature is performed by setting the white balance reference value 13. Similarly, the white balance of the BY color difference signal 21 is determined by setting the white balance reference value 23.

In case the color temperature changes from this state, R-Y color difference signal 1
1 changes, and at the same time, the color difference average value 12 changes. Therefore, the white balance correction value 14 changes.

Gain control of the color signal 16 is performed so that the change in the white balance correction value 14 suppresses the change in the color difference average value 12. B-Y
Similarly, the gain control of the color signal 19 is performed for the color difference signal so that the change in the white balance correction value 24 suppresses the change in the color difference average value 22. As mentioned above, R-
White balance correction has been performed by a series of circuit operations that suppress changes in the Y color difference signal 11 and the B-Yfi difference signal 22.

Problems to be Solved by the Invention However, in the above configuration, when the color signal 16 and the color signal 19 include a color component, this color component is suppressed, resulting in a decrease in saturation and an accompanying color reproduction problem. It had the problem of deterioration.

The present invention takes advantage of these points and aims to provide a white balance correction circuit that alleviates the suppression of color components and improves the deterioration of color remarking.

Means for Solving the Problems The present invention provides an R-Y average value detection circuit that calculates the average value of the R-Y color difference signal, and an R-Y average value detection circuit that compares the R-Y average value with a predetermined value.
Average value comparison circuit and calculating the average value of the B-Y color difference signal B
-Y average value detection circuit, B-Y average value comparison circuit that compares the B-Y average value with a predetermined value, output signal of the R-Y average value comparison circuit, and output signal of the B-Y average value comparison circuit. R to add
- A gain control circuit that controls the gain of the first color signal using the outputs of the Y adder circuit, the B-Y adder circuit, and the R-Y adder circuit; and the gain control circuit that controls the gain of the first color signal using the output of the B-Y adder circuit; Gain control circuit to control and these two gains: t;1)
From the output signals of the 8 circuits, Fl-Y color difference signal and B-Y
This is a white balance correction circuit equipped with a color difference circuit that creates color difference signals.

Effect of the present invention With the above-described configuration, the white balance correction when the color temperature changes is set by the related R-Y white balance correction value and B-Y white balance correction value, so that the white balance correction value when the color temperature changes is set. At the time of signal input, white balance correction is not performed, and the correction can be stabilized at the equilibrium point of the white balance correction value, reducing suppression of saturation of the input color signal and improving color reproduction.

Embodiment Hereinafter, a white balance correction circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a white balance correction circuit according to an embodiment of the present invention, and the same constituent blocks as those in the conventional example shown in FIG. 3 are given the same reference numerals. The difference between FIG. 1 and FIG. 3 is that an addition circuit 3 and an addition circuit 8 are provided for adding the white balance correction value 14 and the white balance correction value 24.

Regarding the white balance correction circuit configured as above,
The operation will be explained with reference to FIG.

Figure 2 shows R-Y when the color temperature changes from the standard color temperature.
White balance correction value 15, B-Y white balance correction value 25f
: In the diagram shown, at a color temperature of B, the B-Y color difference signal is E.
This indicates that the white balance correction is performed using the H correction value and the R-Y color difference signal. Addition circuits 3 and 8 perform white balance correction at color temperature B using E and H correction values, at color temperature A using F and H correction values, and at color temperature C using G and J correction values. As shown, the addition constant is set so that linearity is established between the white balance correction value and the color temperature. In this state, if a color signal that is not a change in color temperature is input, B-Y white balance correction attempts to perform the same correction as in the input state of color temperature B, and R-Y white balance correction attempts to perform the same correction as in the input state of color temperature C. Since the camera attempts to perform the same correction as in the on state, the white balance correction is stable at the equilibrium point between color temperature B and color temperature C, and the white balance correction is not performed with the color signal.
Suppression of saturation of color signals is reduced.

As described above, by associating the R-Y white balance correction value and the B-Y white balance correction value, white balance correction is performed when the color temperature changes, suppression of saturation is reduced during color input, and color reproduction is performed. It is possible to perform white balance correction with improved white balance.

Effects of the Invention As described above, according to the present invention, there is provided an RY average value detection circuit for calculating the average value of the RY color difference signal, and an RY average value and a predetermined value of the RY average value detection circuit output. and a B-Y average value comparison circuit that compares the B-Y color difference signals.
a B-Y average value detection circuit, a B-Y average value comparison circuit that compares the B-Y average value of the output of the B-Y average value detection circuit with a predetermined value, and an output signal of the R-Y average value comparison circuit and the above-mentioned B-Y average value comparison circuit; B-Y
A R-Y addition circuit and a B-Y addition circuit that add the output signals of the average value comparison circuit at a predetermined ratio, and a first gain control circuit that performs gain control on a first color signal using the output of the R-Y addition circuit. a second gain control circuit that performs gain control on a second color signal using the output of the B-Y addition circuit; and a R-Y color difference from the third color signal and the output signal of the first gain control circuit. a white balance correction circuit comprising an R-Y color difference circuit that creates a signal, and a B-Y color difference circuit that creates a B-Y color difference signal from the third color signal and the output signal of the second gain control circuit; Accordingly, it is possible to realize a white balance correction circuit that suppresses a decrease in saturation of color signals and improves color reproduction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a white balance correction circuit according to an embodiment of the present invention, FIG. 2 is a white balance correction characteristic diagram of the same embodiment, and FIG. 3 is a block diagram of a conventional white balance correction circuit. 1...R-Y average value detection circuit, 2...
R-Y average value comparison circuit, 3.8...addition circuit,
4, 9...Gain control circuit, 6...R-
Y color difference circuit, 6...B-Y average value detection circuit, 7...B-Y average value comparison circuit, 10...
...B-Y color difference circuit. Name of agent: Patent attorney Toshio Nakao and one other person? s
2 figure 131!1

Claims (1)

[Claims] an RY average value detection circuit that calculates the average value of the RY color difference signal; an RY average value comparison circuit that compares the RY average value output from the RY average value detection circuit with a predetermined value; - a B-Y average value detection circuit for calculating the average value of the Y color difference signal;
A B-Y average value comparison circuit that compares the B-Y average value output from the Y average value detection circuit with a predetermined value, and an output signal of the R-Y average value comparison circuit and an output signal of the B-Y average value comparison circuit. an R-Y addition circuit and a B-Y addition circuit that add at a predetermined ratio;
a first gain control circuit that performs gain control on the first color signal based on the output of the R-Y addition circuit; and a second gain control circuit that gain-controls the second color signal based on the output of the B-Y addition circuit. a control circuit; an RY color difference circuit that creates an RY color difference signal from a third color signal and an output signal of the first gain control circuit; and a control circuit that controls the third color signal and the second gain control circuit. A white balance correction circuit including a BY color difference circuit that creates a BY color difference signal from an output signal of the circuit.