JPS62125788A - White balance circuit - Google Patents

Abstract

PURPOSE:To lighten a request for a holding characteristic of a peak holding circuit and to obtain a correct white balance by providing a latch circuit between a comparison circuit and a controller and controlling this latch circuit by a gate pulse impressed to a gate circuit for the peak holding circuit. CONSTITUTION:Between the comparison circuits 13, 14 and the controller 17, the latch circuits 21, 22 are respectively disposed and these latch circuits 21, 22 are controlled by the gate pulse from a terminal 12. According to this constitution, the request for the holding characteristic of the peak holding circuits 9-11 may be performed only during a period when the gate circuits 6-8 open a gate and the holding characteristic (leak characteristic) to the peak holding circuits 9-11 is quite softened. Thereby, the freedom for the selection of a design or an element is increased and the correct white balance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance circuit suitable for use in, for example, a video camera.

[Summary of the invention]

The present invention provides a white balance circuit that peak-holds the respective levels of two primary color signals, compares the outputs, and controls the gain of at least one of the two primary color signals via a controller. By providing a launch circuit between the circuits, the requirements for the hold characteristics (leak characteristics) of the peak hold circuit are relaxed.

[Conventional technology]

To obtain white balance for a video camera, set the gain of the white balance amplifier for each channel of the primary color signals R, G, and B so that the color difference signal becomes zero when shooting a white subject, and store the values in digital memory. There is a way to do this, and Figure 2 is one example.

That is, in FIG. 2, (1) is a video camera, and the primary color signal R3G from this video camera (1),
B is supplied to the signal processing circuit (2) and subjected to signal processing,
From this, a luminance signal Y and color difference signals R-Y and B-Y are obtained, and by passing these through an encoder (not shown), a standard television signal is extracted.

In addition, each primary color signal from the video camera (1) is supplied to white balance amplifiers (3) to (5), amplified, and then passed through gate circuits (6) to (8) to peak hold circuits (9), respectively. ) to (11). Gate circuit (
6) to (8) use a peak old circuit (9
) to (11), and the terminal (
The gate 1- is opened by the gate pulse generated corresponding to the center part of the screen from 12).

Each output of the peak hold circuit (91, (10)) is compared by a comparison circuit (13), and the peak hold circuit (10)
.

(11) are compared in a comparison circuit (14), and the output level of the peak hold circuit (10) is compared with the peak hold circuit +91. (11) Depending on whether the output level is large or small, each output side is set to “1” or “0”.
An output signal of ° is obtained. These output signals are supplied to a controller (17) via switches (15) and (16). The switches (15) and (16) are controlled by the controller (17) and are closed during vertical blanking to send the respective outputs of the comparator circuits (13) and (14) to the controller (17).
17). The digital signal taken into the controller (17) is converted into an analog signal by the D/A converter (1B), (1), and the gain of the amplifier (31, (5)) is adjusted by the converted analog signal. controlled.

In other words, the levels of the red and blue primary color signals are controlled to be the same as the level of the green primary color signal. and a D/A converter (18) from the controller (17).

The final operation information for (19) is stored in memory (20).

[Problem that the invention seeks to solve]

By the way, the white balance circuit is unnatural if the white balance gain changes between the two sides, so the controller (
Control of the gain of amplifier (31, (1), etc. by 17) is generally performed during vertical blanking. Therefore, peak hold circuits (9) to (11) block data near the middle of the screen. It is necessary to accurately old up to the time of ranking, and there are strict requirements against leaks.

However, in the case of the conventional circuit shown in Figure 2, it is difficult for the peak hold circuits (9) to (11) to accurately hold data near the middle of the screen until blanking, and the held level gradually changes. However, there were disadvantages such as the hold characteristics deteriorated and accurate white balance could not be achieved.

The present invention has been made in view of the above, and provides a white balance circuit that can achieve a white balance of [U:, 6Tt] by relaxing the demands on the hold characteristics (leak characteristics) of the peak hold circuit. It is something.

[Means for solving problems]

The white balance circuit according to the present invention has two primary color signals R
, G or each level of G, B is connected to a gate circuit (6).
The peak hold circuits (9) and (10) or (10) and (11) pass through (7) or (1) and (8) to hold the peak, and the outputs of these peak hold circuits are connected to the comparison circuit (13). or (14), the gain of at least one of the two primary color signals is controlled via the controller (17), and a launch circuit (21) or (22) is provided between the controller and the upper δd comparison circuit. It is configured to provide

[Effect]

White balance booster (3) and (4) or (4)
The two primary color signals R, G or G, B from and (5) are passed through gate circuits (6) and (7) or (7) and (8) to beak hawked circuits (9) and (10) or (10) and ( 1
1) Hold the peak. Then, each output of the peak hold circuit is compared by a comparison circuit (13) or (14), and the comparison output is sent to a launch circuit (21) or (22) controlled by a gate pulse supplied to a gate circuit.
After that, the amplifier (
3) or (5), and the gain of each primary color signal is controlled so that the level of each primary color signal becomes the same. As a result,
The intervention of the latch circuit eases the demands on the hold characteristics (leak characteristics) of the peak hold circuit, increasing the degree of freedom in design and selection of elements.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained based on FIG.
<Explain. In the figure, the same reference numerals are given to the FJ8 portions corresponding to those in FIG. 2, and detailed explanation thereof will be omitted.

In this embodiment, launch circuits (21>, (
22), and these latch circuits (21), (
22) is controlled by a gate pulse from terminal (12). In other words, the launch circuits (21) and (22) operate when the gate pulse is on, that is, the gate circuits (6) to
When no signal is supplied from (8) to the peak hold circuits (9) to (11), the comparison circuits (13), (1,
The output of 4) is sent as is to the controller (17), and when the pulse to day 1 is off, that is, the gate circuits (6) to (8)
When no signal is supplied to the peak hold circuits (9) to (11), a latch operation is performed to hold the data immediately before the gate pulse is turned off.

With such a configuration, peak hold circuits (9) to (11)
The requirement for the hold characteristics is only the time during which the gate circuits (6) to (8) open the gates, and from the time when the gate circuits (6) to (8) in Fig. 2 open the gates to the blanking time. It can be seen that the hold characteristics (leak characteristics) for the peak hold circuits (9) to (11) are considerably relaxed compared to the hold characteristics required for the peak hold circuits (9) to (11). This makes circuit design easier and increases the degree of freedom in design and selection of elements.For example, the values of the capacitors used in peak hold circuits (9) to (11) can be made smaller, which improves the rise characteristics of the peak hold circuit. Become.

〔Effect of the invention〕

As described above, according to the present invention, a latch circuit is provided between the comparison circuit and the controller, and this latch circuit is controlled by the gate pulse applied to the gate circuit for the peak hold circuit in front of the comparison circuit. Therefore, the requirements for the hold characteristics of the peak hold circuit are only limited to the time that the gate circuit is on, and the requirements for the hold characteristics (leak characteristics) of the peak hold circuit are relaxed, making it easier to design and select elements. This increases the degree of freedom and allows for accurate white balance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional circuit. (1) is a video camera, (3) to (5) are white balance enhancers, (6) to (8) are gate circuits, (9) to
(11) is a peak hold circuit, (13), (1
4) is a comparison circuit, (17) is a controller, (18),
(19) is a D/A converter, and (20) is a memory. Procedural amendment January 9, 1986 Michibu Uga, Director General of the Patent Office], Indication of the case 1985 Patent I! No. 265427 3,
? Relationship with the case of a person who engages in ili tE Patent applicant address: 6-7-35, Kitashinyo, Tokyo Parts Store Name (2
18) Sony Corporation Representative Director Norio Ohga 4, Agent 6, Number of inventions to be increased due to amendment The primary color signals are corrected to ``and the primary color signals R, G, and B from this video camera (1) are''. (2) Same, page 3, 2 lines, 1 is supplied. ” and then add the following. [Also, primary color signals R, G from amplifiers (3) to (5). B is supplied to the signal processing circuit (2) and processed, from which a luminance signal Y, color difference signals R-Y, B-Y are obtained,
A standard television signal is extracted by passing this through an encoder (not shown). (3) Correct ``1-old'' on page 3, line 4 and page 4, line 15 to ``hold'' by d1. (4) In the drawings, Figures 1 and 2 have been revised as shown in the attached sheet.
Snake. that's all

Claims (1)

[Claims] The respective levels of the two primary color signals are passed through a gate circuit and peak held in a peak hold circuit, the outputs of the peak hold circuit are compared in a comparison circuit, and at least one of the two primary color signals is transmitted through a controller. What is claimed is: 1. A white balance circuit for controlling the gain of a white balance circuit, and further comprising a latch circuit provided between the controller and the comparison circuit.