JPH10257517A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the nonuniformity or imbalance of color temperature in a screen and enable white balance control with less error by detecting color information for each of plural areas provided by dividing an output screen. SOLUTION: R-YL and B-YL signals of color difference signals divided by dividing parts 17 and 18 are averaged by averaging parts 19 and 20. The averaged signals are inputted from terminals P and Q to a microcomputer 29. Then, the average B-YL and R-YL signals are converted to digital values by A/D converters 21 and 22 and based on these values, a color discrimination part 23 discriminates the colors of divided sections. Based on that information, level adjusting parts 24 and 25 are controlled. Namely, the color information of area discriminated as 1st color information is converted to 2nd color information and afterwards, white balance is controlled while using the color information of area, which is not the 1st color information, and the 2nd color information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus such as a video camera, and more particularly to white balance correction.

[0002]

2. Description of the Related Art A white balance correction method for an image pickup apparatus such as a video camera is roughly classified into a method using a color temperature sensor and a method using a video signal.

FIG. 4 is a conventional circuit block diagram in an automatic white balance correction method using a video signal. In the figure, 1 is an image sensor, 2 is a luminance and chromaticity generator, and 3 is R
(Red) signal gain control section, 4 is a B (blue) signal gain control section, 5 is a color difference signal generation section, 6 is an encoder, 7 and 8 are gate sections, 9 and 10 are clip sections, and 11 is R- B signal detection unit, 12 is an averaging unit, 13 is a comparison amplification unit, 14 is a tracking correction unit that generates a tracking correction signal, 1
5b is an automatic white balance correction signal generator.

In FIG. 4, an image formed on an image sensor 1 is converted into an electric signal.
Luminance signal Y _H, R signal is a luminance signal Y _L and the chrominance signal having a color signal band having a luminance signal bandwidth, B signals are generated. The R signal and the B signal are input to gain controllers 3 and 4, respectively, subjected to level control by a control signal from the tracking corrector 14, and output as R 'and B' signals, respectively. The R 'signal and B' signal are input to the color difference signal generation unit 5 together with the luminance signal Y _L. Color difference signals from the three signals (R-Y _L) and (B-Y _L) is generated. Further, the color difference signals (R-Y _L ) and (B-Y
_L) is input to the encoder 6 with the luminance signal Y _H,
A standard television signal is obtained as this output.

The color difference signals (R-Y _L ) and (B-Y _L )
Are also distributed to the automatic white balance correction signal generator 15b via the terminals M and N, respectively.
8 is input. With this circuit, unnecessary signals during a blanking period and abnormal signals due to level saturation at the time of shooting a high-luminance object are removed.

The signals from the gates 7 and 8 are input to clipping units 9 and 10, respectively, and the amplitude of a color difference signal in a practical color temperature range that exceeds a proper range and has excessive saturation is limited.

The color difference signals (R-Y _L ) and (B-Y _L ) are subjected to various processes, and are subjected to (R-Y _L ) ', (B-Y
_L ) ', which is input to the RB detection unit 11. In this circuit diagram, the difference between the (R-Y _L) 'and (B-Y _L)', is obtained (R-B) signals. The (RB) signal is further input to the averaging unit 12, and the average (RB) signal value over the entire screen is output as a DC value. The signal from the averaging unit 12 and the reference voltage V
_ref1 (the voltage corresponding to RB = 0) is compared, and the magnitude determination signal is input to the tracking correction unit 14.

[0008] The tracking correction unit 14 is a comparator
A gain control signal for the gain control units 3 and 4 is generated based on the determination signal from the control unit 3 and the operation is performed in a direction in which the white balance is corrected. As described above, the gain controllers 3 and 4, the color difference generator 5, and the automatic white balance correction signal generator 15b form a negative feedback loop. Obtain a standard television signal at the output.

[0009]

However, in the above-described conventional white balance correction device, an error may occur in white balance correction. A typical example in which a correction error occurs is a case where the color distribution of the subject is 50% white and 50% yellow. This case will be described with reference to the vector diagram of FIG. 5 and the block diagram of FIG.

When the gains of the gain controllers 3 and 4 in FIG. 4 are respectively one, points on the white and yellow vector diagrams are W and Ye, respectively. Negative feedback loop is (RB)
Since the operation is performed so that the signal becomes zero, the correction direction of the white balance is a direction parallel to the (RB) axis of the vector diagram. Therefore, the point on the vector diagram where this negative feedback operation is stable is as follows: Ye−Ye ′ = Ye′−a = ab = WW−W ′
Ye ′ and W ′ (where the line portion Ye−
b is parallel to the RB axis, and point a is a point on a line segment passing through the origin (W) and perpendicular to the RB axis).

That is, Ye and W after the correction are coordinate positions of Ye 'and W', respectively. That is, in this case,
Yellow means changing to green, and white means changing to blue, and normal white balance correction is not performed.

As described above, in the conventional white balance correction apparatus, when the color temperature distribution of the subject is uneven and the distribution is uneven, an error occurs in the white balance correction, and it is difficult to obtain a correct correction effect. There was a problem that is.

The present invention has been made in view of such a problem, and even if there is unevenness or deviation in the color temperature in the screen, the adverse effect caused by the unevenness or deviation can be suppressed, and white balance control with less error can be realized. It is an object of the present invention to provide an imaging device that can be used.

[0014]

In order to achieve the above object, according to the present invention, an image pickup apparatus is provided with the following (1), (2),
The configuration is as shown in (3).

(1) imaging means, dividing means for dividing the output screen of the imaging means into a plurality of areas, averaging means for averaging the color difference signals for each area divided by the dividing means, Determining means for detecting color information for each of the plurality of areas based on an output of the averaging means, and determining that the color information of each area is predetermined first color information;
After converting the color information of the area determined to be the first color information into the second color information by the determination means, the color information of the area that is not the first color information and the second color information And a white balance control unit that controls the white balance by using the above.

(2) The imaging device according to (1), wherein the first color information is yellow.

(3) The imaging device according to (1), wherein the second color information is green.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples of an image pickup apparatus.

[0019]

FIG. 1 is a block diagram of an "imaging device" according to an embodiment. In the figure, reference numeral 16 denotes a division signal generator for dividing a color difference signal, and outputs a pulse for switching for extracting a part of the color difference signal from the screen from a terminal P 'every 1 V (vertical scanning period). At the end of each V, a reset pulse is output from the terminal Q '. 17, 18
Dividing sections for dividing the R-Y _L and B-Y _L signals, respectively.
An analog switch or the like is operated by the divided pulse from the terminal P 'to perform division. 19 averaging unit for averaging the divided R-Y _L signal, 20 is an averaging unit for averaging the divided B-Y _L signal. The averaged signal is input to a microcomputer (hereinafter referred to as a microcomputer) 29 from terminals P and Q. 21 A / D converting the B-Y _L signal averaged from terminal P to a digital value (analog - digital) converter, 22 a digital value R-Y _L signal averaged from terminal Q A / D converter for converting to
Reference numeral 23 denotes a color discriminating unit which discriminates the color of the divided part based on the values from the A / D converters 21 and 22 and controls the level adjusting units 24 and 25 based on the information. A level adjuster for adjusting the value from the converter 21 by a signal from the color discriminator 23; 25, a level adjuster for adjusting the value from the A / D converter 22 by a signal from the color discriminator 23;
The output from the level adjusting unit 24, 25 (R-Y _L) ',
A correction signal control unit 27 for controlling the white balance correction output based on (B−Y _L ) ′ converts the value from the correction signal control unit 26 from a digital value to an analog value, and outputs a white balance correction signal B. D / A (Digital-Analog) converter for outputting a signal from the R.cont. This is a D / A converter that outputs cont. The same or corresponding parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, 16 to 23 are color detecting means for detecting the color of the object.

Next, the operation of dividing the screen will be described. When the screen is divided into 20 blocks as shown in FIG.
It is divided within one field in the order of the numbers in FIG. Averaging unit 1
9 and 20 average and amplify the divided color difference signals and output data to the microcomputer 29. When the A / D converters 21 and 22 of the microcomputer take in the data, the averaging units 19 and 2
A reset pulse is output to 0 by the divided signal generator 16 and the content is reset.

The above operation is performed for each field, and the data of each divided screen is output to the microcomputer 29. Microcomputer 2
In step 9, a white balance correction operation is performed based on these divided data.

Next, the operation of the color determining section 23 will be described. The A / D converted R-Y _L and B-
Y _L data is input. The input data is R-Y _L and B which are set in advance in the color discrimination unit 23.
-Y _L reference value R _ref indicating the white level, is compared with the B _ref, it is determined what colors are present in each of the divided blocks. For simplicity, the _{R ref = 0, B ref =} 0, is input, of a block _{R-Y L, B-Y} L data respectively r1, and -b1. Here, r1 <
If b1, r1> o, the color of this block is considered to be at the position of the point Ye in FIG. 3 in a vector diagram.
In this case, the B-Y _L to X times to -b2, the R-Y _L y
A signal that is multiplied to −r2 is applied to the level adjusters 24 and 2.
5 respectively. By performing the above operations,
Actually, the signal at the point Ye in the vector diagram of FIG. 3 is converted as a signal at the point G and input to the correction signal control unit 26.

The correction signal control section 26 generates a gain control signal based on the input signal and the white level reference values R _ref and B _ref, and outputs the gain control signal via the D / A converters 27 and 28. , 4 to perform a white balance correction operation.
Therefore, for example, the color distribution of the subject is 50% white and 50% yellow.
%, The negative feedback loop operates so that the (RB) signal becomes zero, but the correction signal control unit 26 informs the correction signal control unit 26 of (R) of the point Ye.
-B) Since the signal is input as the point G converted to 0, good white balance correction can be obtained without causing a correction error as in the related art. In this embodiment, 24 to
Reference numeral 28 denotes a signal generation unit that generates a signal for gain control of the gain control unit. Note that the method does not necessarily need to be converted to the point G, and may be any point as long as no erroneous correction occurs. For example, if the point Ye is converted to a point G ′, W after white balance correction is GG ″ = G ′
G "= WW", which is W ", so that warm white balance correction can be performed.

In the above embodiment, the gain control unit is
Although four and two are provided, the present invention is not limited to this, and may be implemented, for example, with one gain control unit.

[0026]

As described above, according to the configuration of the present invention, even if the color temperature in the screen is nonuniform or uneven, the adverse effect due to the nonuniformity or offset can be suppressed, and white balance control with less error can be achieved. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a screen division diagram of a color detection unit according to the embodiment.

FIG. 3 is a vector diagram for explaining the operation of the embodiment.

FIG. 4 is a vector diagram of a conventional example.

FIG. 5 is a vector diagram for explaining the operation of the conventional example.

[Explanation of symbols]

 3, 4 gain control unit 23 color discrimination unit 24, 25 level adjustment unit 26 correction signal control unit

Claims (3)

[Claims] An imaging unit; a dividing unit that divides an output screen of the imaging unit into a plurality of regions; an averaging unit that averages a color difference signal of each region divided by the dividing unit; Based on the output of the averaging means, detecting the color information for each of the plurality of areas, and determining that the color information of each area is predetermined first color information; and After converting the color information of the area determined to be the first color information into the second color information, white balance is performed using the color information of the area that is not the first color information and the second color information. An image pickup apparatus comprising: a white balance control unit configured to control the operation of the imaging device. 2. The imaging device according to claim 1, wherein the first color information is yellow. 3. The imaging apparatus according to claim 1, wherein the second color information is green.