JPH0730916A - Color reproduction correction circuit for color image pickup device - Google Patents

Abstract

PURPOSE:To obtain color reproducibility excellent at all times even when the lighting condition is changed by varying a correction coefficient of linear matrix processing according to white balance correction variable. CONSTITUTION:A microcomputer 4 inputs a GRB signal converted into a digital signal to calculate white balance correction data wb, wr. Furthermore, the microcomputer 4 uses the data wb, wr to select a most suitable lighting condition (b). The calculated data wb, wr are used for correction data corresponding to each color signal through a parallel serial conversion circuit 5 and D/A converters 6-8 and then white balance is executed. The selected lighting condition (k) is inputted to a control section 10 through the circuit 5 and a D/A converter 9. A linear matrix circuit 11 controlled by the control section 10 uses the lighting condition (k) to make arithmetic operation processing and outputted signals Go, Bo, Ro are added respectively to image pickup signals Gi, Bi, Ri and then color reproduction correction is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image pickup device,
Particularly, the present invention relates to a color reproduction correction circuit for faithfully reproducing the color of a subject.

[0002]

2. Description of the Related Art Generally, a color image pickup apparatus such as a color video camera is provided with a color reproduction correction circuit, and white balance correction and linear matrix processing are performed to improve the color reproduction of an object.

FIG. 3 is a block diagram showing an example of a conventional color reproduction correction circuit in a color video camera.

A color video camera is a CCD (Charge C
gain control of the GBR image pickup signal from the image pickup device such as
Further, the color reproduction error is corrected by linear matrix processing.

A white balance correction circuit 10 shown in FIG.
Reference numeral 1 inputs the GBR video signals when an achromatic subject is imaged, and generates correction data (gain control signal) for making these signals the same level.
According to these correction data, the gain control of each of the RGB image pickup signals is performed to perform white balance correction.

Further, the gain-controlled image pickup signals Gi, Bi, Ri are input to the linear matrix circuit 1
02 performs the arithmetic processing shown by the following equation, and outputs the resulting signals MGo, MBo, MRo as the image pickup signals Gi, Bi, R
i is added to i to correct the color reproduction error (Japanese Patent Laid-Open No. 2-11).
7293).

MGo = a (Gi-Ri) + b (Gi-Bi) MBo = c (Bi-Gi) + d (Bi-Ri) MRo = e (Ri-Gi) + f (Ri-Bi) where a to f is a correction coefficient, which is fixed according to the standard. Also, the matrix ON / OFF switch 10
Linear matrix processing can be selected by 3.

[0008]

However, in the above-mentioned conventional color reproduction correction circuit, the linear matrix circuit 10 corrects the color separation characteristic on the basis of a specific illumination condition (color temperature).
However, it is difficult to obtain good color reproducibility when shooting outdoors, where the lighting conditions change drastically.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color reproduction correction circuit that automatically copes with changes in illumination conditions and always obtains good color reproducibility.

[0010]

A color reproduction correction circuit according to the present invention includes a white balance correction means for generating a white balance correction amount for equalizing the levels of respective color signal components for an achromatic subject, and the white balance correction means. Linear matrix processing means for performing linear matrix processing using a correction coefficient according to the amount.

[0011]

The correction coefficient of the linear matrix processing is controlled according to the white balance correction amount, and the color reproduction automatically corresponding to the change of the illumination condition is performed.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a color reproduction correction circuit according to the present invention, and FIG. 2 is a block diagram of a three-plate CCD color image pickup device using this embodiment. In FIG. 2, since the signal systems of the GBR have the same block configuration, only the G signal system is denoted by the reference numeral, and the reference numerals of B and R are omitted.

First, in FIG. 2, three CCD image pickup devices 21 are provided corresponding to each color signal of GBR, each image pickup signal is amplified by a preamplifier 22, and a white balance correction is performed by a gain controller 23.

The output signal Gi of the gain controller 23,
Bi and Ri are input to the mixer 24, and are added to the linear matrix processed signals Go, Bo, and Ro according to the present embodiment, and the color reproduction is corrected.

The GBR signal thus corrected for white balance and color reproduction is input to the driver 27 through the processing circuit 25 and the amplifier 26, and is output as the camera signal output GBR.

The color reproduction correction circuit 20 of the present embodiment inputs the GBR signal which is the output of the amplifier 26 and outputs correction data for white balance to the gain controller 2.
Output to 3 respectively.

Further, the color reproduction correction circuit 20 according to the present embodiment.
Are output signals Gi, Bi, and
And Ri, the linear matrix processing according to the present embodiment is performed, and the outputs Go, Bo, and Ro are mixed in the mixer 24.
Output to each.

Next, the color reproduction correction circuit 20 of this embodiment will be described.

In FIG. 1, each GBR signal from the amplifier 26 is input to each of the A / D converters 1, 2 and 3 and is converted into a digital signal to be inputted to the microcomputer 4
To enter.

ROM (Rand in the microcomputer 4
om Access Memory) stores a table of weighted numerical values k (hereinafter, referred to as illumination conditions) corresponding to the color temperature of the illumination light source. As will be described later, this illumination condition k is used for weighting the correction coefficient of the linear matrix calculation, and acts so as to cancel the change in the illumination condition at the time of shooting.

The microcomputer 4 calculates the white balance correction data Wb and Wr and determines the illumination condition k by referring to the table. Then, through the parallel-serial conversion circuit 5, correction data corresponding to each color signal is output to the D / A converters 6, 7, and 8, and the illumination condition k is output to the D / A converter 9. The correction data converted into analog signals are output to the gain control 23, respectively, and the illumination condition k also converted into analog signals is output to the control unit 10 of the linear matrix circuit.

The linear matrix circuit 11 includes a controller 10
In accordance with the above, linear matrix processing is performed on the input image pickup signal GiBiRi, and the output signal GoBoRo is mixed by the mixer 24.
Output to.

A control signal is input from the microcomputer 4 to the control unit 10, and the linear matrix processing O is performed.
N / OFF and selection of preset data are performed.

Next, the operation of this embodiment will be specifically described.

First, the microcomputer 4 inputs the GBR signal converted into a digital signal and calculates the white balance correction data Wb and Wr by the following equation.

Wb = G / B Wr = G / R.

Further, the microcomputer 4 refers to the table stored in the ROM using the correction data Wb and Wr and selects the most suitable illumination condition k.

The calculated correction data Wb and Wr are input to the control terminal of the gain controller 23 as correction data corresponding to each color signal through the parallel / serial conversion circuit 5 and the D / A converters 6 to 8 and the image pickup of each color is performed. White balance correction is performed by controlling the gain of the signal.

The selected illumination condition k is input to the control unit 10 through the parallel / serial conversion circuit 5 and the D / A converter 9.

The linear matrix circuit 11 controlled by the control unit 10 performs the arithmetic processing shown by the following equation using the illumination condition k.

Go = ka (Gi-Ri) + kb (Gi-Bi) Bo = kc (Bi-Gi) + kd (Bi-Ri) Ro = ke (Ri-Gi) + kf (Ri-Bi).

The signals GoBoRo output in this way are input to the mixer 24, respectively added to the image pickup signals GiBiRi, and color reproduction correction is performed.

Since the signal GoBoRo output from the linear matrix circuit 11 is a correction signal in consideration of the illumination conditions, it automatically responds to changes in the illumination conditions and always obtains good color reproducibility.

Since the illumination condition k is generated by the microcomputer 4, it becomes easy to add a learning function and the like, and it has expandability.

In the present embodiment, only the illumination condition k is generated by the microcomputer 4, but of course the correction coefficient a
It is also possible to calculate ~ f and k by the microcomputer 4 and use the result as a correction coefficient for the linear matrix processing.

[0037]

As described in detail above, the color reproduction correction circuit according to the present invention changes the correction coefficient of the linear matrix processing according to the white balance correction amount, so that even if the illumination condition changes, a good color can be obtained. Reproducibility can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a color reproduction correction circuit according to the present invention.

FIG. 2 is a block diagram of a three-plate CCD color image pickup device using this embodiment.

FIG. 3 is a block diagram showing an example of a conventional color reproduction correction circuit in a color video camera.

[Description of Reference Signs] 1 A / D converter 2 A / D converter 3 A / D converter 4 Microcomputer 5 Parallel / serial conversion circuit 6 D / A converter 7 D / A converter 8 D / A converter 9 D / A converter 10 control unit 11 linear matrix circuit

Claims (3)

[Claims] 1. A color reproduction correction circuit for faithfully reproducing the color of a subject imaged by a color image pickup device, which generates a white balance correction amount for equalizing the levels of respective color signal components for an achromatic subject. A color reproduction correction circuit, comprising: white balance correction means; and linear matrix processing means for performing linear matrix processing using a correction coefficient according to the white balance correction amount. 2. The linear matrix processing means determines an illumination condition correction coefficient based on the white balance correction amount, and a linear matrix correction coefficient based on the illumination condition correction coefficient, and performs linear matrix processing. The color reproduction correction circuit according to claim 1, further comprising an arithmetic processing unit. 3. The lighting condition determining means stores a table that defines a lighting condition correction coefficient corresponding to each of the white balance correction amounts, and inputs the white balance correction amount to input the corresponding lighting condition. The color reproduction correction circuit according to claim 2, further comprising: a search unit that searches for the condition correction coefficient.