JP2976227B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device such as a video camera, and more particularly to white balance correction.

[Conventional technology]

A white balance correction method for an imaging device 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).
The signal gain control unit 4 is a gain control unit for a B (blue) signal.
Is a color difference signal generation unit, 6 is an encoder, 7 and 8 are gate units, 9 and 10 are clip units, 11 is an RB 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, and 15b is an automatic white balance correction signal generator.

In FIG. 4, the image formed on the image sensor 1 is converted into an electric signal, and the luminance and chromaticity generating unit 2 outputs a luminance signal Y _H having a luminance signal band, a luminance signal Y _L having a color signal band, and a color signal. An R signal and a B signal, which are signals, are generated. The R signal and the B signal are input to gain controllers 3 and 4, respectively, are subjected to level control by a control signal from the tracking corrector 14, and are 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, these color difference signals (R
−Y _L ) and (B−Y _L ) are input to the encoder 6 together with the luminance signal Y _H , and a standard television signal is obtained as an output.

The color difference signals (R-Y _L ) and (B-Y _L ) are
Automatic white balance correction signal generator 1 via M and N
It is also distributed to 5b and input to the gate units 7, 8. 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 output to the
And a signal having a color difference signal in a practical color temperature range and exceeding the proper range and having excessive saturation is amplitude-limited.

The color difference signals (R-Y _L ) and (B-Y _L ) undergo various processes to become (R-Y _L ) ′ and (B-Y _L ) ′, respectively, and are input to the RB detection unit 11. In this circuit diagram, (R-
The difference between (Y _L ) ′ and (B−Y _L ) ′ gives the (RB) signal. 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 _refl (voltage corresponding to _RB = 0) in the comparison amplification unit 13
Are compared, and the judgment signal of the magnitude is compared with the tracking correction unit.
Entered in 14.

The tracking correction unit 14 generates a gain control signal to the gain control units 3 and 4 based on the determination signal from the comparison amplification unit 13, and operates in a direction in which 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, and the color difference signal subjected to white balance correction is supplied to the encoder 6, and Obtain a standard television signal at the output.

[Problems to be solved by the invention]

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 when 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 control units 3 and 4 in FIG. 4 are respectively one, points on the white and yellow vector diagrams are W and Ye, respectively. Since the negative feedback loop operates so that the (RB) signal becomes zero, the white balance correction direction is parallel to the (RB) axis of the vector diagram. Therefore, the point on the vector diagram where this negative feedback operation is stable is Ye
−Ye ′ = Ye′−a = ab = W−W ′ (where the line Ye−b is parallel to the RB axis and the 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, white means changing to blue,
Normal white balance correction has not been performed.

As described above, in the conventional white balance correction device, when the color temperature distribution of the subject is nonuniform 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.

The present invention has been made in view of such a problem,
It is an object of the present invention to provide an image pickup apparatus capable of reducing a white balance correction error due to a subject having a nonuniform color temperature distribution and having a bias, and obtaining a normal white balance correction effect.

[Means for solving the problem]

In order to achieve the above object, in the present invention, the imaging apparatus is configured as in the following (1).

(1) Imaging means, color correction means for correcting the color signal of the yellow part of the output screen of the imaging means to green, and the entire screen after the yellow part in the screen has been corrected to green by the color correction means A white balance control signal forming means for forming a white balance control signal using the color signals of the above, and a gain for controlling the balance of the gains of a plurality of color signals output from the imaging means based on the output of the white balance control signal forming means. An imaging device having a control unit.

[Action]

According to the configuration (1), when the color of the subject is a color that causes erroneous correction, gain control for reducing the erroneous correction is performed.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

FIG. 1 is a block diagram of an “imaging device” according to an embodiment of the present invention. 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 is R
A division unit that divides the -Y _L and B-Y _L signals by operating an analog switch or the like by a division pulse from a terminal P 'to perform division. Averaging unit for averaging the divided R-Y _L signal 19,
20 is a 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 Convert to A /
The D converter 23 determines the color of the divided part based on the values from the A / D converters 21 and 22, and uses the information to determine the level adjustment unit.
A color discriminating unit that controls 24, 25, 24 is a level adjusting unit that adjusts a value from the A / D converter 21 by a signal from the color discriminating unit 23,
25 level adjusting section for adjusting the signal from the color discrimination unit 23 the value from the A / D converter 22, 26 is output from the level adjusting section _{24,25 (R-Y L) '} , (B-Y L ) ′, A correction signal control unit 27 that controls the white balance correction output, and a D / D that 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.cont. A
A (digital-analog) converter 28 is also a D / A converter that outputs R.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 subject.

Next, the operation of dividing the drawing will be described. When the screen is divided into 20 blocks as shown in FIG. 2, it is divided within one field in the order of the figure numbers. The averaging units 19 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, reset pulses are output to the averaging units 19 and 20 by the divided signal generation unit 16 and the contents are reset.

The above operation is performed for each field, and the data of each divided screen is output to the microcomputer 29. The microcomputer 29 performs a white balance correction operation based on the divided data.

Next, the operation of the color determination unit 23 will be described. Color discriminator 23
Data A / D-converted R-Y _L and B-Y _L is inputted to. The input data is within the color determination section 23 is pre-set R-Y _L, the reference value R indicating the white level of B-Y _L
ref and _Bref are compared with each other to determine what color exists in each of the divided blocks. For simplicity, R _ref = 0,
B _ref = 0, and R-Y _L , B-
Let the data of Y _L be r1 and −b1, respectively. Where r1 <b1,
If 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 other words, a part of the screen signal is sequentially supplied to the color determination unit 23,
R-Y _L = r1 and B-Y _L = b1 respectively compared Rref, and Bref, it is determined to be white if r1 = Rref, b1 = Bref.

Here, as described above, for simplicity, Rref = 0, Bref
If = 0, white is determined when r1 = 0 and b1 = 0, but the hue can be determined by comparing these three levels r1, b1, 0 with each other.

That is, for example, if r1> 0 and b1 <0, it is determined that the color is in the upper left quadrant of FIG. 3, and if r1 <b1, the hue of the area below the RB straight line in FIG. It is determined that the color is a hue, and if r1> 0, it is determined that the color is above the BY-Y straight line in FIG. 3, so that r1 <b1 and r1> 0 is a yellow hue. Is determined to be in the region of.

Next, when the hue of the input signal is determined to be yellow by the color determination unit 23, (BY) * X is applied to BY and RY of the signal. = −b2 (RY) * Y = A region corresponding to the hue of yellow by multiplying the coefficients X and Y that satisfies −r2 (that is, B−Y below RB in FIG. 3) Can be rotated counterclockwise by a predetermined angle, so that the yellow hue can be shifted to the green, that is, the hue near the lower left side on the RB straight line in FIG. 3 or in the vicinity thereof. By performing the above operation, the signal at the point Ye in the vector diagram of FIG. 3 is actually converted as a signal at the point G and input to the correction signal control unit 26.

The correction signal control unit 26 generates a gain control signal based on the input signal and the white level reference values R _ref , B _ref and sends it to the gain control units 3 and 4 via the D / A converters 27 and 28. Output and perform white balance correction operation. Therefore, for example, when the color distribution of the object is 50% white and 50% yellow, the negative feedback loop is (R−
B) The signal operates so that the signal becomes zero.
Since the (RB) signal of the point Ye is input to the point 26 as the point G obtained by converting the (RB) signal to 0, good white balance correction can be obtained without causing a correction error as in the related art. In this embodiment, signal generation means 24 to 28 generate signals for gain control of the gain control means. 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 ″ =
W becomes G′G ″ = WW ″, so that warm white balance correction can be performed.

In the above embodiment, the two gain control units 3 and 4 are provided, but the present invention is not limited to this.
It can also be implemented in individual form.

〔The invention's effect〕

As described above, according to the present invention, even when there is a subject having a color that causes erroneous correction in white balance correction, the color signal is converted into a color signal that does not cause erroneous correction, and white balance correction is performed. And good white balance correction can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a screen division diagram of a color detecting means of the embodiment, FIG. 3 is a vector diagram for explaining the operation of the embodiment, FIG. FIG. 5 is a vector diagram of the conventional example, and FIG. 5 is a vector diagram for explaining the operation of the conventional example. 3,4 Gain control unit 23 Color discriminating unit 24,25 Level adjustment unit 26 Correction signal control unit

Claims (1)

(57) [Claims] 1. An image pickup means, a color correction means for correcting a color signal of a yellow portion of an output screen of the image pickup means to green, and a color correction means for correcting a yellow portion in the screen to green by the color correction means. White balance control signal forming means for forming a white balance control signal using color signals of the entire screen; and controlling the balance of the gains of the plurality of color signals output from the imaging means based on the output of the white balance control signal forming means. An image pickup apparatus comprising: