JPH1023451A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically execute color correction control capable of attaining suitable color reproduction in any white balance control mode. SOLUTION: Since color correction control parts 20, 21 capable of outputting color difference gain correction values different in each mode in accordance with various modes for white balance control are prepared by the same number of modes and a color difference gain correcting circuit 9 obtains a correction signal to be used at the time of correcting the color of a white balance controlled chrominance signal by using either one of the control parts 20, 21 corresponding to a mode selected by a mode selecting switch 17, the color difference gain correction value can be suitably changed in each white balance control mode and optimum color balance can be obtained in any white balance control mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus, and more particularly to a video camera which performs predetermined color correction after white balance control.

[0002]

2. Description of the Related Art Hitherto, means for automatically controlling white balance in an image pickup apparatus such as a video camera has been proposed. Hereinafter, a conventional example regarding the automatic white balance control will be described with reference to the drawings.

FIG. 5 is a block diagram of a video camera for explaining conventional automatic white balance control means. In FIG. 5, reference numeral 1 denotes an imaging lens for a subject, 2 denotes an iris, 3 denotes an image sensor that photoelectrically converts incident light, 4
Is an AGC amplifier (automatic gain control circuit) that amplifies an image signal from the image sensor 3 to an appropriate level by a feedback loop.

[0005] Reference numeral 5 denotes a luminance / chromaticity signal generation circuit,
The image signal amplified by the amplifier 4 is converted into luminance signals YH and YL and chromaticity signals R and B. 6 is a gain control circuit for the red signal R, and 7 is a gain control circuit for the blue signal B. Reference numeral 8 denotes a color difference signal generation circuit which generates color difference signals RY 'and BY' from the chromaticity signals R 'and B' whose gains have been controlled by the gain control circuits 6 and 7, respectively.

A color difference gain correction circuit 9 controls the gain of the color difference signals RY ′ and BY ′ generated by the color difference signal generation circuit 8. Reference numeral 10 denotes an encoder circuit, which is a color difference signal RY, B whose gain is controlled by the color difference gain correction circuit 9.
-Convert Y to a standard television signal. Reference numeral 11 denotes a color signal detection unit for controlling white balance.

Reference numeral 12 denotes a first for calculating a correction signal from the detected color signal and automatically performing white balance correction.
A correction signal calculator 13 for controlling a white balance set; 14 a correction signal output unit for outputting a white balance correction signal to each of the gain control circuits 6 and 7; Is the first correction signal calculator 12
A first reference which gives a control reference value of
Is a second reference which gives a control reference value of the correction signal calculation unit 13 of FIG.

Reference numeral 17 denotes a mode selection switch, which is a first correction signal calculator 1 for performing an automatic white balance control calculation.
2 and the second correction signal calculator 13 for performing the white balance set calculation. Reference numeral 18 denotes a color correction control unit that outputs a color difference gain correction amount according to a correction value of white balance, 31 denotes an R gain correction signal output from the correction signal output unit 14, and 32 denotes a B gain output from the correction signal output unit 14. This is a correction signal.

The automatic white balance control is to determine the color temperature of a light source for illuminating a subject based on the output of the image sensor 3 or the output of an external light sensor (not shown), and automatically perform white balance control. It is.
In addition, the white balance set performs white balance control independently of the above automatic white balance control,
The control result is held, and the operation is performed so that the average value of the color components in the image becomes zero.

Hereinafter, the operation of the image pickup apparatus configured as described above will be described. The optical signal of the subject incident on the imaging device 3 via the lens 1 and the iris 2 is photoelectrically converted here, amplified to an appropriate level by the AGC amplifier 4, and then supplied to the luminance and chromaticity signal generation circuit 5. In the luminance and chromaticity signal generation circuit 5, the high frequency component YH and the low frequency component Y
L, and a red signal R and a blue signal B are generated.

The red signal R and the blue signal B generated by the luminance and chromaticity signal generation circuit 5 are supplied to gain control circuits 6 and 6, respectively.
7, where it is amplified by the white balance control signals (R gain correction signal 31, B gain correction signal 32) from the correction signal output unit 14, and output as chromaticity signals R 'and B', respectively. These chromaticity signals R 'and B' are input to the color difference signal generation circuit 8 together with the low frequency component YL of the luminance signal, where the color difference signal R-
Y 'and BY' are generated.

The color difference signals RY ', B-
Y ′ is amplified to an appropriate level by the color difference gain correction circuit 9 and becomes color difference signals RY and BY. The color difference signals RY and BY are input to the encoder circuit 10 together with the high frequency component YH of the luminance signal, where a standard television signal is generated and output. The color difference signals RY and BY are used for color signal detection.

The calculation contents of the first correction signal calculation unit 12 are as follows:
This is for basic control of automatic white balance. The control method is such that the color difference signals RY and BY input to the first correction signal calculation unit 12 via the color signal detection unit 11 and the mode selection switch 17 are converted into the first color corresponding to white.
The white balance correction data is calculated by comparing the white balance correction data with the reference value 15. The correction data is calculated inside the first correction signal calculation unit 12, and is output from the correction signal output unit 14 as an R gain correction signal 31 and a B gain correction signal 32 so that white balance control can be performed.

The calculation contents of the second correction signal calculation section 13 are for controlling the white balance set. The control method is such that the color difference signals RY and BY input to the second correction signal calculation unit 13 via the color signal detection unit 11 and the mode selection switch 17 are converted to the second color corresponding to white.
Then, the white balance correction data is calculated by comparing with the reference value 16.

The white balance set is performed at a higher speed than the correction by the first correction signal calculation unit 12. When the white balance set becomes equal to the second reference value 16, a fixed correction value is output and the operation is stopped. The correction data obtained at this time is output from the correction signal output unit 14 to the R gain correction signal 31, B gain
The gain correction signal 32 is output so that white balance control can be performed.

The mode selection switch 17 switches between the automatic white balance control using the first correction signal calculation section 12 and the white balance set using the second correction signal calculation section 13 according to the photographer's intention.

FIGS. 6 and 7 are vector diagrams showing reference values for white balance control. In the automatic white balance control, the control is not always performed based on perfect white, but may be controlled by intentionally shifting the reference value as shown in FIG. For example, under illumination such as an incandescent lamp having a low color temperature, an expression close to human color perception can be obtained by shifting to an amber-based color. In such a case, a method of setting a reference value (first reference value 15) by shifting the center of the vector, that is, white, to an amber system is used.

On the other hand, in the white balance set, FIG.
Therefore, it is required that the reference value is a perfect white, that is, the center of the vector, so that a reference value (second reference value 16) different from the automatic white balance control is adopted.

By the way, since illumination such as a white fluorescent lamp has a low color rendering property and a high spectral power of yellow in spectral characteristics, the gain of one color difference signal RY is high and the other color difference signal BY is high.
Needs to be set low. In addition, since illumination such as an incandescent lamp has a high red spectral power due to spectral characteristics, the gain of one color difference signal RY is low and the other color difference signal BY is low.
Needs to be set high.

Therefore, the color correction controller 18 controls the first correction signal calculator 12 or the second correction signal calculator 13 according to the color temperature of the subject and the color signal detected by the color signal detector 11. The chrominance gain correction circuit 9 corrects the chrominance gains of the chrominance signals RY ′ and BY ′ generated by the chrominance signal generation circuit 8 based on the chrominance correction information set in advance according to the calculation contents. Information on the amount of correction is given.

[0020]

However, in the above-described conventional color difference gain correction, since the same color difference gain correction information is used in the automatic white balance control operation and the white balance set operation, the white balance control reference value is used. In some cases, the difference in color reproducibility due to the difference in the white balance correction result resulting from the difference cannot be completely corrected.

The present invention has been made in view of such circumstances, and a purpose thereof is to automatically perform color correction control for realizing appropriate color reproduction in any white balance control mode. Is to be able to do that.

[0022]

According to the present invention, there is provided an image pickup apparatus wherein a predetermined color correction is applied to a color signal subjected to white balance control by a given color correction signal. In accordance with various modes, a mode switching means for switching between the various modes of the white balance control, and a correction amount different for each mode in accordance with the various modes of the white balance control. The same number of color correction control means as the number of modes for outputting the color correction signal; and the predetermined color correction signals output from the white balance control means based on the color correction signals output from the color correction control means. Color correction means for performing a color correction of the color correction mode corresponding to the mode switched by the mode switching means. It characterized in that to perform the predetermined color correction using the control means.

According to another feature of the present invention, the various modes of the white balance control include at least an automatic white balance control mode and a white balance set mode.

According to another feature of the present invention, the various modes of the white balance control include at least an automatic white balance control mode and a preset white balance mode.

Another feature of the present invention is that a color temperature of a light source for illuminating a subject is determined based on an output of an image sensor or an output of an external optical sensor, and a first white balance control is automatically performed. A mode in which the white balance control means and the first white balance control means perform white balance control independently, and the second white balance control means for holding the control result and the first white balance control means A mode switching unit for switching between at least two modes, a mode using the second white balance control unit, and a color signal after white balance control by the first white balance control unit or the second white balance control unit. Color correction means for performing a predetermined color correction on the
First color correction control means for determining the correction amount in the color correction means according to the white balance control by the white balance control means, and the color correction in accordance with the white balance control by the second white balance control means Second color correction control means for determining the correction amount by the means,
The correction amounts determined by the first color correction control means and the second color correction control means are different.

Another feature of the present invention is that a color temperature of a light source for illuminating a subject is determined based on an output of an image pickup device or an output of an external optical sensor, and white balance control is automatically performed. The white balance control means is independent of the first white balance control means,
A second white balance control unit that stores at least one specific white balance control signal and performs white balance control based on the specific white balance control signal; and a mode using the first white balance control unit. A mode switching unit for switching between at least two modes, a mode using the second white balance control unit, and a color signal after white balance control by the first white balance control unit or the second white balance control unit. A first color correction control means for determining a correction amount by the color correction means in accordance with white balance control by the first white balance control means; In response to white balance control by the second white balance control means. A second color correction control means for determining a correction amount by the color correction means, and determining that the correction amounts determined by the first color correction control means and the second color correction control means are different. Features.

Another feature of the present invention is that the predetermined color correction performed by the color correction means is a process for controlling the gain of a color difference signal.

According to another feature of the present invention, the predetermined color correction performed by the color correction means is a process for controlling the hue of a color difference signal.

According to the present invention configured as described above, the correction amount for the color signal after white balance control by the color correction control means according to the selected white balance control mode among the plurality of color correction control means. Is determined, and color correction is performed by the color correction means. That is, when the mode of the white balance control is switched by the mode switching unit, the color correction unit obtains the color correction amount corresponding to the mode from the corresponding color correction control unit, so that the correction amount used for the color correction is reduced. It is changed to the one suitable for the selection mode.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a diagram that best illustrates the features of the present invention.
2 is the same as that shown in FIG. 5 which is a conventional example.
Hereinafter, a description will be given focusing on portions different from FIG.

In FIG. 1, reference numeral 20 denotes a first color correction control unit, which outputs a color difference gain correction amount according to a white balance correction value in the automatic white balance control mode. A second color correction control unit 21 outputs a color difference gain correction amount according to a white balance correction value in the white balance set mode. Note that the basic signal processing of the imaging apparatus is the same as that of the above-described conventional example.

The mode selection switch 17 has an automatic white balance control mode using the first correction signal operation section 12 and a second correction signal operation section 13 as in the conventional example of FIG.
Is switched according to the photographer's intention. Here, the mode selection switch 1
7, when the automatic white balance control mode is selected, the color signal detection unit 11 and the mode selection switch 1
The first and second color difference signals RY and BY input to the first correction signal calculation unit 12 via the first reference value 15 correspond to the first reference value 15 corresponding to white.
Then, white balance correction data is calculated by comparing with.

The correction data is calculated inside the first correction signal calculation section 12, and each of the gain control circuits 6 is controlled by the correction signal output section 14 so that white balance control can be performed as an R gain correction signal 31 and a B gain correction signal 32. , 7 are output. Then, color difference correction information is output to the first color correction control unit 20 according to the color temperature of the subject and the color signal detected by the color signal detection unit 11, and the color difference gain is set so that a preset correction is added to the color difference gain. The gain control circuit 9 is controlled.

Here, the gain correction amount of the color difference signals RY and BY will be described by taking a white fluorescent lamp and an incandescent lamp as an example.
FIG. 2 shows a specific example of a correction amount of a color difference signal under illumination by a white fluorescent lamp.

As described in the conventional example, illumination such as a white fluorescent lamp has a low color rendering property and a high spectral power of yellow due to spectral characteristics, so that the gain of one color difference signal RY is high and the other color difference signal is high. The gain of BY is set low. In the automatic white balance control mode, the gain of one color difference signal RY is set to normal +1.6 dB and the gain of the other color difference signal BY is set to normal, taking into account that the reference value is shifted to the amber system. Set to -1.2 dB.

FIG. 3 shows a specific example of the correction amount of the color difference signal under illumination by an incandescent lamp. Lights such as incandescent lamps have high red spectral power due to their spectral characteristics.
The gain of one color difference signal RY is reduced, and the other color difference signal B is reduced.
Set the gain of -Y high. Again, considering that the reference value is shifted to an amber system, one of the color difference signals R-
The gain of Y is the normal -1.2 dB, and the other color difference signal BY
Is set to the normal +1.6 dB.

On the other hand, when the white balance set mode is selected by the mode selection switch 17, the color difference signal R− input to the second correction signal calculation unit 13 via the color signal detection unit 11 and the mode selection switch 17. Y,
The white balance correction data is calculated by comparing BY with a second reference value 16 corresponding to white.

The correction data is calculated inside the second correction signal calculation section 13, and each gain control circuit 6 is controlled so that white balance control can be performed from the correction signal output section 14 as an R gain correction signal 31 and a B gain correction signal 32. , 7 are output. The color difference correction information is output to the second color correction control unit 21 in accordance with the color temperature of the subject and the color signal detected by the color signal detection unit 11, and the color difference gain is set so that a preset correction is added to the color difference gain. The gain control circuit 9 is controlled. The second color correction control unit 21 differs from the first color correction control unit 20 in the setting of the correction amount, and performs the white balance control according to the second reference value 16 so that the color reproducibility is appropriate. Correction amount is given.

Taking the white fluorescent lamp and the incandescent lamp as examples, the color difference signals RY,
The correction amount of BY will be described. Considering that the reference value is set to be completely white in the white balance set mode, the output of the red color difference signal is particularly smaller than in the automatic white balance control mode. Therefore, to improve the color reproducibility in this state, one of the color difference signals RY
Needs to be set higher.

Under the illumination of a white fluorescent lamp, the gain of one color difference signal RY is set to a normal +2.0 dB and the gain of the other color difference signal BY is set as shown in FIG. Is set to normal -1.2 dB. Further, under illumination of an incandescent lamp, the gain of one color difference signal RY is -0.8 dB and the gain of the other color difference signal BY is normal, as shown in FIG. Set to +1.6 dB.

As described above, the gain of one color difference signal RY or the other color difference signal BY is changed between the normal shooting mode (automatic white balance control mode) and the white balance set mode. Accordingly, an optimal color balance can be obtained in any mode.

The numerical values shown in FIGS. 2 and 3 are merely examples, and the correction amounts are different when devices such as an image sensor and signal processing are different. In addition, although the number of white balance control modes has been described as two, it is needless to say that the number of modes may be more than that and the color difference gain correction amount may be set according to each mode.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
It is a block diagram showing an embodiment. Note that reference numerals 1 to 15, 20 to 21, and 31 to 32 shown in FIG. 4 are the same as those shown in FIG. 1 which is the above-described first embodiment.
In the following, description will be made focusing on portions different from FIG.

In FIG. 4, reference numeral 22 denotes a mode selection switch for switching a white balance control mode, reference numeral 23 denotes a third correction signal calculator for performing white balance correction in a preset white balance mode, and reference numeral 24 denotes a preset white balance control signal. It is a preset value output unit that outputs to the third correction signal calculation unit 23. Note that the basic signal processing of the imaging apparatus is the same as that of the above-described conventional example. The preset white balance mode is a mode in which a white balance control signal corresponding to an assumed color temperature is provided in advance, and the signal is output.

The mode selection switch 22 switches between an automatic white balance control mode using the first correction signal calculation section 12 and a preset white balance mode using the third correction signal calculation section 23 according to the photographer's intention. Here, when the automatic white balance control mode is selected by the mode selection switch 22, as in the first embodiment, the first correction signal calculation unit 12
The white balance correction data is calculated by comparing the color difference signals RY and BY input to the first reference value 15 corresponding to white.

The correction data is calculated inside the first correction signal calculation unit 12, and white balance control can be performed as the R gain correction signal 31 and the B gain correction signal 32 from the correction signal output unit 14 via the mode selection switch 22. Output to each of the gain control circuits 6 and 7. Then, color difference correction information is output to the first color correction control unit 20 according to the color temperature of the subject and the color signal detected by the color signal detection unit 11, and the color difference gain is set so that a preset correction is added to the color difference gain. The gain control circuit 9 is controlled.

On the other hand, when the preset white balance mode is selected by the mode selection switch 22,
The third correction signal calculation unit 23 includes a color difference gain correction circuit 9.
Irrespective of the color difference signals RY and BY output from
The pre-stored preset white balance signal output from the preset value output unit 24 is input.

The preset white balance signal is
A predetermined operation is performed inside the third correction signal operation unit 23, and the correction signal output unit 1 is output via the mode selection switch 22.
4 are output to the gain control circuits 6 and 7 so that white balance control can be performed as an R gain correction signal 31 and a B gain correction signal 32. The color difference correction information is output to the second color correction control unit 21 in accordance with the color temperature of the subject and the color signal detected by the color signal detection unit 11, and a preset correction different from the automatic white balance control mode is performed. Is added to the color difference gain to control the color difference gain correction circuit 9.

The color difference gain correction amount in the preset white balance mode is the same as the color difference gain correction amount in the white balance setting of the first embodiment described above, and is corrected so that the color balance becomes optimal in the preset state. You.

As described above, the gain of one color difference signal RY or the gain of the other color difference signal BY is changed between the normal photographing mode (automatic white balance control mode) and the preset white balance set mode. Accordingly, an optimal color balance can be obtained in any mode.

In the above-described embodiment, the color correction is performed by controlling the gains of the color difference signals RY and BY in the color difference gain correction circuit 9, but the color difference signals RY and B-
Color correction may be performed by controlling the hue of Y.

[0052]

As described above, according to the present invention, the same number of color correction control means as the number of modes are provided for outputting color correction signals having different correction amounts for each mode according to various modes of white balance control. The predetermined color correction is applied to the color signal after the white balance control using the color correction control means corresponding to the switched mode, so that the correction amount of the color signal can be appropriately changed for each white balance mode. Thus, appropriate color reproduction can be realized in any white balance mode.

For example, when the various modes of the white balance control include an automatic white balance control mode and a white balance set mode, the correction amount of the color signal is appropriately set between the automatic white balance control mode and the white balance set mode. To improve the color balance in the white balance set mode.

When the various modes of the white balance control include the automatic white balance control mode and the preset white balance mode, the correction amount of the color signal is appropriately set between the automatic white balance control mode and the preset white balance mode. Can be changed to
The color balance in the preset white balance mode can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an imaging device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a color difference gain correction amount under a white fluorescent lamp.

FIG. 3 is a diagram illustrating a color difference gain correction amount under an incandescent lamp.

FIG. 4 is a block diagram illustrating a configuration of an imaging device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration example of a conventional imaging apparatus.

FIG. 6 is a vector diagram showing reference values at the time of automatic white balance control.

FIG. 7 is a vector diagram showing a reference value at the time of white balance setting.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens 2 iris 3 image sensor 4 AGC amplifier (automatic gain control circuit) 5 luminance / chromaticity signal generation circuit 6 R signal gain control circuit 7 B signal gain control circuit 8 color difference signal generation circuit 9 color difference gain correction circuit 10 encoder circuit 11 color Signal detection unit 12 First correction signal calculation unit 13 Second correction signal calculation unit 14 Correction signal output unit 15 First reference value 16 Second reference value 17 Mode selection switch 20 First color correction control unit 21 2 color correction control unit 22 mode selection switch 23 third correction signal calculation unit 24 preset value output unit

Claims (7)

[Claims] 1. An image pickup apparatus in which a predetermined color correction is applied to a color signal subjected to white balance control by a given color correction signal, wherein the white balance control is performed according to various modes. Means, mode switching means for switching between the various modes of the white balance control, and the same number as the number of modes for outputting a color correction signal having a different correction amount for each mode according to the various modes of the white balance control Color correction control means, and color correction means for performing the predetermined color correction on the color signal output from the white balance control means based on the color correction signal output from the color correction control means. The predetermined color compensation is performed using the color correction control means corresponding to the mode switched by the mode switching means. Imaging apparatus being characterized in that to perform the. 2. The imaging apparatus according to claim 1, wherein the various modes of the white balance control include at least an automatic white balance control mode and a white balance set mode. 3. The imaging apparatus according to claim 1, wherein the various modes of the white balance control include at least an automatic white balance control mode and a preset white balance mode. 4. A color temperature of a light source for illuminating a subject is determined based on an output of an image sensor or an output of an external light sensor,
First white balance control means for automatically performing white balance control; second white balance control means for performing white balance control independently of the first white balance control means and holding the control result; A mode switching unit that switches at least two modes of a mode using the first white balance control unit and a mode using the second white balance control unit; and the first white balance control unit or the second white mode. A color correction unit for performing a predetermined color correction on the color signal after the white balance control by the balance control unit; and a correction amount by the color correction unit according to the white balance control by the first white balance control unit. A first color correction control means for performing the second white balance control A second color correction control means for determining a correction amount by the color correction means in accordance with the white balance control by the step; a determination made by the first color correction control means and the second color correction control means An imaging apparatus characterized in that different correction amounts are used. 5. A color temperature of a light source for illuminating a subject is determined based on an output of an image sensor or an output of an external light sensor,
First white balance control means for automatically performing white balance control; and independent of the first white balance control means, wherein at least one specific white balance control signal is stored, and the specific white balance control signal is stored. A second white balance control unit for performing white balance control based on a control signal; and at least two modes of a mode using the first white balance control unit and a mode using the second white balance control unit. Mode switching means; color correction means for performing a predetermined color correction on the color signal after white balance control by the first white balance control means or the second white balance control means; and the first white balance According to the white balance control by the control means, First color correction control means for determining a correction amount by the correction means; and second color correction control for determining a correction amount by the color correction means in accordance with white balance control by the second white balance control means. An imaging apparatus comprising: a first color correction control unit and a second color correction control unit, wherein the first color correction control unit and the second color correction control unit have different correction amounts. 6. The imaging apparatus according to claim 1, wherein the predetermined color correction performed by the color correction unit is a process for controlling a gain of a color difference signal. 7. The imaging apparatus according to claim 1, wherein the predetermined color correction performed by the color correction unit is a process for controlling a hue of a color difference signal.