JPH08280041A - Image pickup device - Google Patents

Abstract

PURPOSE: To automatically perform suitable white balance control when photographing an object including blue sky. CONSTITUTION: The image photographed by an imaging device 3 is divided by a dividing processing part 40 and when the existence of blue sky in the object is decided by its divided luminance signals and divided color difference signals, the white extraction range of a white extraction part 38 is changed to be widened toward the amber side corresponding to a white extraction range control signal 39. Thus, the output of a correct signal arithmetic part 10 for white balance is corrected and white balance can be performed without being affected by blue sky.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and more particularly to a white balance thereof.

[0002]

2. Description of the Related Art Conventionally, a method of automatically performing white balance control in an image pickup device such as a video camera has been devised. A conventional example will be described below with reference to the drawings.

FIG. 4 is a block diagram of an image pickup apparatus for explaining a conventional automatic white balance control means. FIG.
, 1 is an imaging lens for the subject, 2 is an iris,
3 is an image sensor for photoelectrically converting incident light, 4 is an AGC amplifier for amplifying a signal from the image sensor 3 to a proper level by a feedback loop, and 5 is a signal generated by the image sensor 3 for conversion into luminance and chromaticity signals. Luminance / chromaticity signal generation circuit, 6 a gain control circuit for a red signal R, 7 a gain control circuit for a blue signal B, 8 a color difference signal generation circuit, 9
Is an encoder circuit for converting into a standard television signal.

Reference numeral 40 denotes a luminance signal YH and a color difference signal (R-
Y) and (B-Y) are divided into a plurality of parts in the image, and 30 is a color difference signal for white balance control (BY), which is a divided color difference signal divided by the division processing part 40.
1 is a color difference signal for white balance control (RY) which is a divided color difference signal, 32 is a luminance signal for white balance control YH which is a divided luminance signal, 38 is a color difference signal (RY),
A white extraction unit that extracts only the color corresponding to the (BY) achromatic portion, 39 is a white extraction range control unit that controls the white extraction range of the white extraction unit 38, and 10 is a correction that calculates a white balance correction signal. A signal calculation unit, 33 is a B gain correction output from the correction signal calculation unit 10, 34 is an R gain correction output from the correction signal calculation unit 10, 23 is a synchronization signal for obtaining a timing necessary for calculation processing, and 24 is a calculation Reference value of processing (Rr
ef, Bref).

Reference numeral 20 is an iris position detector, and 21 is an AGC.
A gain detector, 22 is an image sensor driving unit, 35 is an iris position signal generated by the iris position detector 20,
Reference numeral 36 is a drive signal for controlling the image sensor drive unit 22, and 37 is an AGC gain signal generated by the AGC gain detector 21.

In the above structure, the optical signal incident on the image pickup device 3 is photoelectrically converted here, amplified by the AGC amplifier 4 to an appropriate level, and then output to the luminance signal / chromaticity signal generation circuit 5. In the luminance signal / chromaticity signal generation circuit 5,
High frequency component YH of luminance signal, low frequency component YL of luminance signal
A red signal R and a blue signal B are generated, and the R and B signals are input to the gain control circuits 6 and 7, respectively, where the white balance control signals 34 and 3 from the correction signal calculation unit 10 are generated.
After being amplified by 3 respectively, each color signal R
′, B ′, and is input to the color difference signal generation circuit 8 together with the luminance signal YL, and color difference signals (RY),
(BY) is generated. This color difference signal (RY),
(BY) is input to the encoder 9 together with the luminance signal YH to generate and output a standard television signal. Here, the luminance signal YH, the color difference signals (RY), (B-
Y) is divided into a plurality of places in the image by the division processing unit 40, and only the color corresponding to the achromatic portion of the subject is extracted by the white extraction unit 38 and input to the correction signal calculation unit 10.

The calculation contents of the correction signal calculation unit 10 are for basic control of the white balance, and the control method is as follows: the color difference signal (RY) 31 and the color difference signal 31 input to the correction signal calculation unit 10. White balance correction data is calculated by using the color difference signal (BY) 30 and comparing it with Rref and Bref of the reference value 24 corresponding to white. The correction data is calculated inside the correction signal calculation unit 10, and is output as an R gain correction output 34 and a B gain correction output 33 so that white balance control can be performed.

The iris position detector 20 is composed of a Hall element or the like, and as shown in FIG.
A voltage that becomes lower as it closes is output, and AG
The C gain detector 21 detects the gain control feedback voltage of the AGC amplifier 4 and outputs the gain control state.
The control portion of the image pickup device drive unit 22 is included in the correction signal calculation unit 10, and the exposure is controlled by a so-called electronic shutter by changing the charge storage time of the image pickup device 3. That is, the control amount is known in the correction signal calculation unit 10, and the states of the iris, AGC, and electronic shutter described above are known, so that the illuminance of the subject can be specified.

By the way, generally, the illuminance of a subject shows a relatively high numerical value and the color temperature thereof is relatively high under outdoor sunlight. On the contrary, in artificial lighting indoors, the illuminance of the subject is low and the color temperature is relatively low in many cases. From this, the color temperature of the subject can be specified to some extent according to the illuminance of the subject. The white extraction range control unit 39 stores a plurality of patterns of white extraction ranges as shown in FIG. 6, and when the information about the illuminance of the subject is received from the correction signal calculation unit 10, when the subject is relatively bright, As shown in FIG. 6 (a), the blue color is determined to be an achromatic portion, and when the subject is relatively dark, the amber color is determined to be an achromatic portion as shown in FIG. 6 (b). , If the subject has normal brightness,
The white extraction unit 38 is controlled so that the portion shown in FIG. 6C is determined to be an achromatic portion.

[0010]

However, in the white extraction of the conventional example described above, when the weather is outdoor, the amber colors are not considered to be achromatic, but the blue colors are judged to be achromatic. In a subject including the sky, a malfunction may occur so that the white balance is properly adjusted with respect to the sky, and as a result, the actual achromatic portion may shift to amber.

The present invention has been made in order to solve such a problem, and provides an image pickup apparatus capable of automatically performing an appropriate white balance control when photographing a subject including the sky during fine weather outdoors. It is intended to be provided.

[0012]

In order to achieve the above-mentioned object, in the present invention, an image pickup device is constructed as in the following (1) to (4).

(1) White balance control means for determining the color temperature of a light source for illuminating an object based on the output of the image pickup device or the output of an external light sensor, and based on the output of the white balance control means for performing white balance control. And a determining unit that determines whether or not the subject includes a clear sky, and the white balance control unit corrects the control state when the determining unit determines that the clear sky is included. The imaging device that is the one.

(2) The white balance control means includes a storage means for storing a white balance condition when the subject includes a clear sky, and when the determining means determines that the clear sky is included, The image pickup apparatus according to (1), wherein the white balance condition is read from the storage unit, and white balance control is performed based on the read white balance condition.

(3) The judging means comprises a dividing means for dividing the image photographed by the image pickup device into a plurality of areas, and the subject is a clear sky based on the divided luminance signal and the divided color signals obtained by the dividing means. The image pickup apparatus according to (1) above, which is for determining whether or not

(4) The white balance control means includes white extraction means for extracting the color of the achromatic portion of the subject, and when the determination means determines that the sky is clear, the white extraction means extracts the white balance. The image pickup apparatus according to (1) or (3), which changes a color range.

[0017]

With the configurations (1) to (4), the control state of the white balance control means is corrected when the determination means determines that the subject includes a clear sky. In the configuration of (2), the data stored in the storage unit is used when the control state is corrected.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples.

(Embodiment 1) FIG. 1 is a block diagram showing the arrangement of an "imaging device" according to the first embodiment. In the figure, 1 to 40 are the same or equivalent parts as the parts having the same reference numerals in FIG. 4 showing the above-mentioned conventional example, and the description thereof is omitted here.

Reference numeral 50 denotes an image recognition unit for determining whether or not the subject being imaged contains a blue sky, and 52 denotes the image recognition unit 5.
A determination signal from 0, and 51 is a reference value generation unit that defines three types of threshold levels of a luminance signal and a color difference signal used in the image recognition unit 50. The basic signal processing of the image pickup apparatus is the same as that of the above-mentioned conventional example.

The image recognition section 50 is provided with a luminance signal YH 32, color difference signals (RY) 31, (B) via the division processing section 40.
-Y) 30 is input, and each of the divided luminance signal and the divided color difference signal is compared with the corresponding threshold level of the reference value generation unit 51. Each of these threshold levels is a level corresponding to the blue sky in fine weather, and from the above comparison, it is determined that the blue part located at the top of the image and having high brightness is the blue sky, and that the subject contains the blue sky. judge.

FIG. 2 is a conceptual diagram for explaining the detection of blue sky in the image recognition section 50. This is an example in which an image being photographed is divided into 16 by the division processing unit 40, and is an image of photographing in bright outdoors, and the portion A in the figure corresponds to the blue sky.

As described in the conventional example, in a bright outdoor environment as shown in FIG. 2, the white extraction range is controlled so that blue is relatively emphasized as shown in FIG. 6 (a). At this time, in addition to the achromatic portion of the subject, the blue of the blue sky is also determined to be an achromatic portion, and the white balance is controlled to amber.

Here, when the image recognition unit 50 determines that the image contains blue sky, the determination signal 52 is output to the white extraction control unit 39, and the white extraction range control unit 39 operates as shown in FIG.
A white extraction range as shown in (c) is selected. According to the selected white extraction range, the range determined as the achromatic part by the white extraction unit 38 expands to the amber side, and the average value of the color difference signals including the blue sky part of the white extraction result is actually It is close to white. Therefore, the correction signal calculation unit 10 determines the white balance control signal 3 based on the color temperature at this time.
By outputting 3, 34, white balance can be achieved without being affected by the blue sky.

In addition, even when a subject including a blue sky is photographed in an illumination state in which the color temperature is low, such as near dusk, the white balance does not become extremely amber system and is appropriate. White balance control is performed.

The division processing section 40, the image recognition section 50,
The reference value generation unit 51 portion corresponds to the determination means in the claims.

Although the number of divisions of the division processing part is 16 divisions, it is not limited to 16 if the number of divisions is plural, and needless to say, the more the number of divisions, the higher the accuracy of image recognition.

(Second Embodiment) FIG. 3 is a block diagram showing the arrangement of an "imaging device" according to the second embodiment. 1 to 51 in the figure
1 is the same as or equivalent to the same reference numeral in FIG. 1 showing the above-described first embodiment, and description thereof will be omitted here.
Reference numeral 54 is a control signal storage unit that stores a white balance control signal suitable for the outdoor sun color temperature. The determination signal 53 from the image recognition unit 50 is output to the correction signal calculation unit 10. The basic signal processing of the image pickup apparatus is the same as that of the above-mentioned conventional example.

Whether or not the blue sky is present in the image recognition unit 50 is determined in the same manner as in the first embodiment, and the determination result is output to the correction signal calculation unit 10 as a determination signal 53.

As described in the first embodiment, in the bright outdoors, the white extraction range is controlled so that blue is relatively emphasized as shown in FIG. 6 (a). At this time, in addition to the achromatic portion of the subject, the blue of the blue sky is also determined to be the achromatic portion, and the white balance is controlled to the amber level.

When the image recognition section 50 determines that the image contains blue sky, the determination signal 53 is output to the correction signal calculation section 10, and the correction signal calculation section 10 is stored in the control signal storage section 54. It outputs a white balance control signal suitable for the stored outdoor sun color temperature. Therefore,
When the subject being photographed contains a blue sky, the white balance can be accurately adjusted to the color temperature of the sun without being affected by the chromatic color portion of the subject.

It should be noted that instead of storing the white balance control signal itself in the storage section, the white balance conditions other than the white balance control signal are stored, and when the subject includes blue sky, the white balance condition is read out and stored. On the basis of the above, the correction signal calculation unit 10 can also be implemented by forming a required white balance control signal.

Further, the data stored in the storage unit may be data obtained when the image pickup apparatus has previously taken a picture in fine weather.

(Modification) Each of the above embodiments relates to a so-called internal photometric white balance control in which the white balance control is performed by using the color difference signal generated from the output of the image pickup device as the color temperature information. The present invention is not limited to this, and the white balance control may be performed in the same manner as the white balance control of the so-called external photometry method, in which the white balance control is performed using the output of the external light sensor as color temperature information.

Further, although each of the embodiments is an example of a device for shooting a moving image, the present invention is not limited to this and can be similarly implemented in a device for shooting a still image.

[0036]

As described above, according to the present invention,
Appropriate white balance control is automatically performed when a subject including the sky is photographed during fine weather outdoors.
In addition, appropriate white balance control is performed even when a subject including a blue sky is photographed in an illumination state in which the color temperature is low such that it is close to dusk.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment.

FIG. 2 is a conceptual diagram illustrating image recognition.

FIG. 3 is a diagram showing a configuration of a second embodiment.

FIG. 4 is a diagram showing a configuration of a conventional example.

FIG. 5 is a diagram showing output characteristics of an iris position detector.

FIG. 6 is an explanatory diagram of a white extraction range.

[Explanation of symbols]

 3 image sensor 6 gain control circuit 7 gain control circuit 10 correction signal calculation unit 38 white extraction unit 39 white extraction range control unit 40 division processing unit 50 image recognition unit 51 reference value generation unit

Claims (4)

[Claims] 1. A white balance control means for determining a color temperature of a light source for illuminating a subject based on an output of an image pickup device or an output of an external light sensor, and white balance control means for performing white balance control, and an output of the image pickup device. A determination unit that determines whether or not the subject includes a clear sky, and the white balance control unit corrects the control state when the determination unit determines that the clear sky is included. An image pickup apparatus characterized by the following. 2. The white balance control means comprises a storage means for storing a white balance condition when the subject includes a clear sky, and when the determining means determines that the clear sky is included, 2. The image pickup apparatus according to claim 1, wherein the white balance condition is read out from a storage unit and white balance control is performed based on the read white balance condition. 3. The determining means includes a dividing means for dividing an image photographed by the image pickup device into a plurality of areas, and the subject is a clear sky based on the divided luminance signal and the divided color signals obtained by the dividing means. The image pickup apparatus according to claim 1, wherein it is determined whether or not the image is included. 4. The white balance control means includes white extraction means for extracting the color of the achromatic portion of the subject, and when the determination means determines that the sky is clear, the color extracted by the white extraction means. The image pickup apparatus according to claim 1 or 3, wherein the range is changed.