JP2004320671A - White balance adjusting device, white balance adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method which facilitate the operation for white balance adjustment and improve its performance. <P>SOLUTION: To deal with imaging under a high color temperature, a blackbody radiation curve is considered as a straight line (color temperature change straight line) on coordinates represented with (R-B) axis and (R+B-2G) axis for example, and a present color temperature is estimated from numerical integration data of R, G, and B signals, and pull-in operation along the color temperature change straight line is performed. Besides under the high color temperature, the present color temperature is estimated so that beige may remain when an R component is more than the R/G/B integration data, and that green may remain when a G component is more, instead of necessarily converging to achromatic color being a convergent point of white balance control, and a control target value is calculated according to an object to perform convergence. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

となるような、Ｒ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインを求める。
このＲ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインが、現在の色温度を引き込むゲイン値となる。
【００２９】
現在の色温度を引き込むＲ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインより、
Ｒ信号収束点＝Ｒ信号×Ｒ”ゲイン÷現在のＲゲイン
Ｇ信号収束点＝Ｇ信号×Ｇ”ゲイン÷現在のＧゲイン
Ｂ信号収束点＝Ｂ信号×Ｂ”ゲイン÷現在のＢゲイン
が求まる。各信号の収束点は図５（ｂ）のポイントＰｃの位置として示される。
【００３０】
ここで、図５（ｂ）座標軸の原点は、Ｒ信号：Ｇ信号：Ｂ信号＝１：１：１となっている。
従来の制御方式では、図５（ｂ）に破線矢印で示すようにポイントＰｄから座標原点に向かう引込制御を行っていた。
一方、本例の制御方法では色温度を引き込むゲイン制御を行うことにより、実線矢印に示すように、ポイントＰｄからポイントＰｃに向かう引込制御が行われるものとなる。これは、座標原点に対して（Ｒ＋Ｂ−２Ｇ）軸の負の方向に制御目標値がくることになり、Ｇ方向の成分を引き込むことなく被写体の色のバランスが保たれる事となる。図で言えば矢印ｇの分だけ緑色が残るものとなる。
【００３１】
次に、図６（ａ）には、積分値変換データが座標上のポイントＰ３であった場合を示している。これは、図３に示した領域▲２▼、つまり第４象限での引込枠Ｗ１の範囲内で且つ図面上、色温度変化直線ＬＢより右側となる範囲に、積分値変換データがあった場合である。
この場合は、高色温度下で肌色が多い被写体が写っているものと認識する。
そして、図６（ａ）に矢印で示すように、積分値変換データ（Ｐ３）の（Ｒ−Ｂ）値と（Ｒ＋Ｂ−２Ｇ）値を、同じ量だけ負の方向へ移動させ、黒体放射カーブとみなす色温度変化直線ＬＢにぶつかるポイントＰ４を求める。そしてそのポイントＰ４を、現在の色温度とする。
【００３２】
このポイントＰ４に相当するＲ、Ｇ、Ｂ値をＲ”、Ｇ”、Ｂ”として、

となるような、Ｒ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインを求める。
このＲ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインが、現在の色温度を引き込むゲイン値となる。
【００３３】
現在の色温度を引き込むＲ”ゲイン、Ｇ”ゲイン、Ｂ”ゲインより、
Ｒ信号収束点＝Ｒ信号×Ｒ”ゲイン÷現在のＲゲイン
Ｇ信号収束点＝Ｇ信号×Ｇ”ゲイン÷現在のＧゲイン
Ｂ信号収束点＝Ｂ信号×Ｂ”ゲイン÷現在のＢゲイン
が求まる。各信号の収束点は図６（ｂ）のポイントＰｃの位置として示される。
【００３４】
ここで、上記図５（ｂ）と同様、図６（ｂ）座標軸の原点は、Ｒ信号：Ｇ信号：Ｂ信号＝１：１：１となっており、従来の制御方式では、図６（ｂ）に破線矢印で示すようにポイントＰｄから座標原点に向かう引込制御を行っていた。
一方、本例の制御方法では色温度を引き込むゲイン制御を行うことにより、実線矢印に示すように、ポイントＰｄからポイントＰｃに向かう引込制御が行われるものとなる。
これは、図６（ｂ）の座標原点に対して第一象限の４５度方向に制御目標値がくることになり、（Ｒ−Ｂ）値と（Ｒ＋Ｂ−２Ｇ）値を同じ量だけ負の方向へ移動させた点を色温度とするという事は、現在の色温度に対してＲ方向の成分が多いとみなせ、Ｒ方向の成分を引き込むことなく被写体の色のバランスが保たれる事となる。図で言えば矢印ｆの分だけ肌色が残るものとなる。
【００３５】
以上のような色温度の推測及び収束目標値の算出が図４のステップＦ１０６，Ｆ１０７で行われ、それに応じてステップＦ１１１で各各可変ゲインアンプ３Ｒ、３Ｇ、３Ｂのゲイン制御が行われる。
つまり本例のホワイトバランス調整処理は、まず基準の白色を調整する基準色温度から高色温度側への色温度の変化（黒体放射カーブ）を直線（色温度変化直線ＬＢ）とみなす。
そしてフィードバック制御によって自動的にホワイトバランスをとる処理を行う色信号処理方式であって、Ｒ信号、Ｇ信号、Ｂ信号の各々の原色信号のフィールド毎の積分値データＲｉ，Ｇｉ，Ｂｉを得、その積分値データＲｉ，Ｇｉ，Ｂｉを変換して得られる積分値変換データの（Ｒ−Ｂ）値、（Ｒ＋Ｂ−２Ｇ）値より、黒体放射カーブを直線とみなした色温度変化直線ＬＢ上から現在の色温度を推測する。
さらにこの場合、高色温度下で肌色、緑色を自然な色に見せるために、積分値変換データが、引込枠Ｗ１の範囲内で色温度変化直線ＬＢより図面上で左側（図３の領域▲１▼）にある場合、つまりＧ成分が大きいの場合はＧ成分を残す様な色温度を推測する。また、積分値変換データが、引込枠Ｗ１の範囲内で色温度変化直線ＬＢより図面上で右側（図３の領域▲２▼）にある場合、つまりＲ成分が大きい場合はＲ成分を残す様な色温度を推測する。
そして推測した色温度の変化分のみのゲイン制御を行う事により、高色温度側での肌色、緑色に特化したホワイトバランスを取るものである。
【００３６】
このような処理方式によれば、まず黒体放射カーブを直線とみなす事により、コントローラ６で容易な演算で色温度を推測できることになる。
また、高色温度下では、ホワイトバランス制御の収束点である無彩色へ必ずしも収束させるのではなく、積分値データＲｉ，Ｇｉ，ＢｉよりＲ成分が多い時は肌色が残るように、Ｇ成分が多い時は緑色が残るように現在の色温度を推測し、被写体に応じて制御目標値を計算させて収束させる事により、ユーザーが視覚的に好適に感じるホワイトバランス制御を実現できる。
【００３７】
以上実施の形態について説明してきたが、本発明は各種変形例が考えられる。
例えば、上記実施の形態では（Ｒ−Ｂ）軸、（Ｒ＋Ｂ−２Ｇ）軸を用いての処理例を示したが、（Ｒ−Ｂ）／Ｇ軸、（Ｒ＋Ｂ−２Ｇ）／Ｇ軸による座標を用いても同様の処理が可能である。これはつまり上記実施の形態の各軸をＧ信号で除算して正規化するものであり、この場合、（Ｒ−Ｂ）軸，（Ｒ＋Ｂ−２Ｇ）軸を用いる場合よりも、色によるバラつきの吸収も行うことができる。
【００３８】
【発明の効果】
以上の説明から理解されるように、本発明によれば、例えば高色温度下での撮像に対応しては黒体放射カーブを直線（色温度変化直線）とみなす。そしてＲ信号、Ｇ信号、Ｂ信号の積分データより現在の色温度を推測し、色温度変化直線に沿った引き込み動作を行う。これにより、色温度の推測及び調整ゲインの設定のための演算処理が簡易化されるという効果がある。
特にこの場合、（Ｒ−Ｂ）軸と（Ｒ＋Ｂ−２Ｇ）軸で表される座標、もしくは（Ｒ−Ｂ）／Ｇ軸と（Ｒ＋Ｂ−２Ｇ）／Ｇ軸で表される座標を用いることが、黒体放射カーブを直線とみなすことに好適であり、ホワイトバランス制御機能を低下させずに簡易な演算処理を実現する。
【００３９】
また、高色温度下では、ホワイトバランス制御の収束点である無彩色へ必ずしも収束させるのではなく、Ｒ／Ｇ／Ｂの積分データよりＲ成分が多い時は肌色が残るように、Ｇ成分が多い時は緑色が残るように現在の色温度を推測し、被写体に応じて制御目標値を計算させて収束させる事により、ユーザーが視覚的に適切に感じる映像を得ることができ、ホワイトバランス制御を有するカメラシステムについての性能向上に寄与できる。
【図面の簡単な説明】
【図１】本発明の実施の形態のホワイトバランス調整装置のブロック図である。
【図２】実施の形態の座標上の引込範囲及び色温度変化直線の説明図である。
【図３】実施の形態の色温度推測処理の概念の説明図である。
【図４】実施の形態のホワイトバランス調整のためのゲイン調整処理のフローチャートである。
【図５】実施の形態の色温度推測及び引込制御の説明図である。
【図６】実施の形態の色温度推測及び引込制御の説明図である。
【符号の説明】
２ 原色分離回路、３ ホワイトバランスアンプ、３Ｒ，３Ｇ，３Ｂ 可変ゲインアンプ、５ オプティカルディテクタ、６ コントローラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a white balance adjustment device and a white balance control method for performing white balance adjustment in an imaging device / imaging system such as a video camera and a digital camera.
[0002]
[Prior art]
White balance means, for example, in an imaging system using a solid-state imaging device, when the color temperature of a light source (subject) changes, white changes along a blackbody radiation curve (blackbody locus) according to the change in color temperature. Moving and matching a colored white (eg, reddish at low color temperatures and bluish at high color temperatures) to achromatic white. Here, the color temperature refers to the absolute temperature (° K) of a black body having the same chromaticity as the test light source.
[0003]
By the way, in a video camera or a digital still camera using a solid-state imaging device such as a CCD (Charge-Coupled Device) as an imaging device, in order to project the white as an achromatic white from an imaging result obtained by imaging the white of a subject, It has an automatic white balance processing function that adjusts white that looks colored to achromatic white by moving white along a blackbody radiation curve according to a change in the color temperature of the light source. In actuality, the signal intensity of the three primary colors (R, G, B) of an image captured by a CCD or the like is electronically amplified and attenuated to change the signal balance of each color, and the color temperature of the image is corrected to correct the white color. A method of adjusting the balance is employed.
In particular, as the white balance control by the feedback control method, it is determined from the integrated value of the color difference signal for each field how much the subject has an achromatic white color, and from the result, the subject has an achromatic color. By controlling the gain of the current white balance amplifier by a certain amount so as to approach white and repeating this procedure for each field, a control for finally obtaining a white balance was performed.
[0004]
For example, the following document is known as a technique relating to white balance adjustment.
[Patent Document 1] JP-A-2002-281512
[0005]
[Problems to be solved by the invention]
By the way, conventionally, when performing white balance adjustment, white balance control is realized by controlling only the direction in which the gain is increased or decreased without particularly considering the current color temperature. Specifically, the gain is adjusted so that the R signal, the G signal, and the B signal become 1: 1: 1.
In this case, a subject having a high flesh color at a high color temperature is offset by the color temperature color, and is viewed as lower than the current color temperature, resulting in an overall bluish image. Had become.
Similarly, a subject having a lot of green color at a high color temperature draws green color, so that there has been a problem that white color becomes magenta.
[0006]
Further, since the actual change in color temperature (black body radiation curve) is represented by a curve, and the change in the curve differs depending on the sensor, this cannot be uniquely expressed by a mathematical expression. Therefore, an adjustment gain for white balance is calculated in which white moves along a blackbody radiation curve in accordance with a change in the color temperature of the light source (subject), and the colored white is adjusted to achromatic white. It is difficult.
Further, even if the curve as the blackbody radiation curve can be represented by a mathematical formula, the difficulty of calculating the adjustment gain is not solved.
[0007]
[Means for Solving the Problems]
Therefore, the present invention makes it possible to easily calculate a white balance control target value by considering a black body radiation curve as a straight line, while improving the pull-in of skin color and green color, particularly under a high color temperature, so that a white balance control target value can be calculated. The purpose is to improve the functions.
[0008]
For this reason, the white balance adjusting device of the present invention comprises a white balance amplifier provided with a variable gain amplifier for each of the input R signal, G signal, and B signal, and an R output from the white balance amplifier. The white balance amplifier includes an integrating unit for obtaining an integrated value for each of the signal, the G signal, and the B signal, and a control unit for controlling a gain of each variable gain amplifier of the white balance amplifier. This control means converts the integral values of the R signal, G signal, and B signal output from the integrating means into values on predetermined coordinates, and converts the black body radiation curve on the coordinates into a straight line. The current color temperature is estimated from the color temperature change line considered as, and a white balance adjustment gain is obtained based on the estimated color temperature, and the gain of each variable gain amplifier of the white balance amplifier is controlled by the adjustment gain. I do.
Further, the control means estimates the color temperature so that the G component is left if the G component is large, and if the R component is large, the control unit estimates the R component based on the color temperature change line. The color temperature is estimated so as to remain, and the white balance adjustment gain is obtained as a gain corresponding to the estimated change in the color temperature.
The above-mentioned predetermined coordinates are expressed by (RB) axis, (R + B-2G) axis, or (RB) / G axis, and (R + B-2G) / G axis. Coordinates.
[0009]
According to the white balance control method of the present invention, each of the R signal, G signal, and B signal output from the white balance amplifier means provided with a variable gain amplifier for each of the input R signal, G signal, and B signal. An integration step of obtaining an integration value of the above, an integration value conversion data calculation step of obtaining integration value conversion data as a value on predetermined coordinates from each integration value of the R signal, the G signal, and the B signal obtained in the integration step. An estimation step of estimating a current color temperature from the integration value conversion data obtained in the integration value conversion data calculation step and a color temperature change line that considers a black body radiation curve as a straight line on the coordinates. Gain control for determining the white balance adjustment gain based on the color temperature and controlling the gain of each variable gain amplifier of the white balance amplifier means And a step.
In the estimating step, the integrated value conversion data estimates the color temperature based on the color temperature change straight line so as to leave the G component when the G component is large. The color temperature is estimated so that the components remain, and in the gain control step, the white balance adjustment gain is obtained as a gain corresponding to the estimated change in the color temperature.
[0010]
That is, in the present invention, in the automatic white balance control by the feedback control, for example, in response to imaging at a high color temperature, the blackbody radiation curve is regarded as a straight line (color temperature change line). The current color temperature is estimated from the integrated data of the R signal, the G signal, and the B signal, and a control method of performing a pull-in operation along a color temperature change line is adopted.
By regarding the blackbody radiation curve as a straight line, simplification of the arithmetic processing is realized. In this case, it is possible to use coordinates represented by (RB) axis and (R + B-2G) axis, or coordinates represented by (RB) / G axis and (R + B-2G) / G axis. It is suitable to regard the blackbody radiation curve as a straight line.
In addition, the color temperature is estimated to leave the G component when the G component is large, and to leave the R component when the R component is large, so that the pull-in of the skin color and the green color at the high color temperature is improved. You.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram of the white balance adjustment device according to the embodiment. The white balance adjustment device is built in, for example, an imaging device such as a video camera and performs white balance adjustment on a captured video signal.
This white balance adjustment device It comprises a primary color separation circuit 2, a white balance amplifier 3, an optical detector 5, and a controller 6.
The input terminal 1 is subjected to signal processing of an electric signal obtained by a solid-state image sensor, for example, a CMOS image sensor, and is supplied as a digital signal. This digital signal is input to the primary color separation circuit 2.
The primary color separation circuit 2 separates the input digital signal into R (red), G (green), and B (blue) primary color signals.
The separated signals (the R signal, the G signal, and the B signal) are input to the white balance amplifier 3. The white balance amplifier 3 is provided with variable gain amplifiers 3R, 3G, and 3B corresponding to the R, G, and B signals, respectively. Each of the variable gain amplifiers 3R, 3G, and 3B amplifies (or attenuates) the R signal, the G signal, and the B signal at a gain controlled by the controller 6, and outputs the result.
[0012]
The R signal, G signal, and B signal output from the white balance amplifier 3 are output from the terminals 4R, 4G, and 4B to the next-stage circuit system (not shown) so as to be used for synthesizing with the video signal.
The R, G, and B signals are also supplied to an optical detector 5 for use in white balance adjustment. The optical detector 5 has an integrating circuit for integrating the R signal, the G signal, and the B signal for each field (or for each frame). That is, the optical detector 5 supplies, for example, integrated value data Ri, Gi, Bi of the R signal, the G signal, and the B signal in field units to the controller 6.
[0013]
The controller 6 is formed of, for example, a microcomputer or a DSP, and performs a predetermined operation by software. Specifically, an arithmetic function for obtaining RB data and R + B-2G data based on the integrated value data Ri, Gi, Bi supplied from the optical detector 5, and an arithmetic function for obtaining RB, R + B-2G A function of calculating a gain setting for setting each gain of the R signal, the G signal, and the B signal based on each data is provided.
The gain setting values obtained by these functions (software calculations) are fed back to the variable gain amplifiers 3R, 3G, and 3B in the white balance amplifier 3 to control the gains of the R, G, and B signals. Will do.
[0014]
In this white balance adjustment device, to obtain (adjust) the white balance basically means that the variable gain amplifiers 3R, 3G of the white balance amplifier 3 are adjusted so that the ratios of the R signal, the G signal, and the B signal are equal. And 3B gain (R gain, G gain, B gain).
And when adjusting the white balance,
R signal × R gain = G signal × G gain = B signal × B gain
That is,
R signal × R gain−G signal × G gain = B signal × B gain−G signal × G gain = 0
The white balance amplifier 3 is controlled so that the following holds.
[0015]
The present embodiment is particularly characterized in white balance control under a high color temperature. Hereinafter, the white balance adjustment processing performed by the controller 6 will be described.
[0016]
For the white balance adjustment, the controller 6 uses a coordinate system as shown in FIG. 2, that is, coordinates on the (RB) axis and the (R + B-2G) axis.
As will be described later, the controller 6 converts the integrated value data Ri, Gi, Bi from the optical detector 5 to obtain a data value on the coordinates (integrated value conversion data) in the white balance adjustment processing.
On these coordinates, for example, as shown in the figure, a drop-in frame W1 on the high color temperature side and a drop-in frame W2 on the low color temperature side are set.
For this purpose, pre-white balance adjustment is performed in advance. The pre-white balance adjustment refers to an adjustment for determining a reference white under a reference color temperature. In the pre-white balance adjustment, the reference white color temperature is determined, and the drop-in frames W1 and W2 are set.
The controller 6 holds the drawing frames W1 and W2 on the coordinates as shown in FIG. 2 as parameter values.
The pull-in frames W1 and W2 indicate a range in which a gain setting (white balance pull-in) for white balance adjustment is performed.
The range of the drop-in frames W1 and W2 shown in FIG. 2 is an example, and is not always set in this way.
[0017]
Here, considering the coordinates of FIG. 2 by the (RB) axis and the (R + B-2G) axis, the black body radiation curve CB is a curve shown by a dotted line. However, the blackbody radiation curve CB in FIG. 2 is merely an example, because the blackbody radiation curve differs depending on the sensor.
[0018]
As described above, in the conventional white balance adjustment, the white balance control is performed by controlling only the direction in which the gain is increased or decreased without particularly considering the current color temperature.
In this example, when the integrated value conversion data falls within the drop-in frame W2 on the low color temperature side, the R signal, the G signal, and the B signal are 1: 1: Adjust the gain so that it becomes 1.
[0019]
On the other hand, if the integrated value conversion data is within the drop-in frame W1 on the high color temperature side, a process of estimating the current color temperature is performed. At this time, the black body radiation curve CB is regarded as a straight line without using the black body radiation curve CB. The color temperature change straight line LB is set, for example, as a straight line corresponding to the set drop-in frame W1 (for example, a straight line connecting the lower limit side vertex of the drop-in frame W1 and the coordinate origin as shown in FIG. 2).
Using such a color temperature change line LB, the current color temperature is estimated from the integrated value data Ri, Gi, Bi of the R signal, G signal, and B signal, and a pull-in operation is performed along the color temperature change line LB. .
In this case, the color temperature is estimated to leave the G component when the G component is large, and to leave the R component when the R component is large. It will improve.
[0020]
FIG. 3 schematically shows such estimation of the color temperature.
In FIG. 3, the area (1) on the coordinates is within the range of the drop-in frame W1 in the third quadrant and the range of the drop-in frame W1 in the fourth quadrant, and is on the left side of the color temperature change line LB in the drawing. Area.
When the integrated value converted data obtained by converting the integrated value data Ri, Gi, Bi into data values on the coordinates is in the area (1) as indicated by a circle, (R + B-2G) as indicated by an arrow. ) A point at which the color temperature change line LB is translated along the axis and reaches the color temperature change line LB is defined as the current color temperature.
On the other hand, the area (2) on the coordinates is an area within the range of the drop-in frame W1 in the fourth quadrant and on the right side of the color temperature change line LB in the drawing.
If the integrated value converted data obtained by converting the integrated value data Ri, Gi, Bi into data values on the coordinates is in the above-mentioned area {circle over (2)} as indicated by △, (R + B−2G ) And (RB) axes are moved in the negative direction by the same amount (moved to the lower left by 45 ° on the coordinates). Then, the point at which the color temperature change line LB is reached is set as the current color temperature.
[0021]
FIG. 4 shows the processing of the controller 6 (processing for adjusting the gain of the white balance amplifier 3) for realizing the white balance adjustment with such a processing method, and will be described specifically.
[0022]
The process of FIG. 4 is performed every time the integrated value data Ri, Gi, Bi are input from the optical detector 5 in, for example, a field unit of a video signal.
When the integrated value data Ri, Gi, Bi are input in step F101, the controller 6 determines a point (integrated value converted data) on the coordinates in FIG. 2 from the integrated value data Ri, Gi, Bi in step F102. calculate.
In this case, first,
R ′ signal = Ri × R gain at the time of pre-white balance adjustment / current R gain
G ′ signal = Gi × G gain at the time of pre-white balance adjustment / current G gain
B ′ signal = Bi × B gain at the time of pre-white balance adjustment / current B gain
As a result, an R ′ signal, a G ′ signal, and a B ′ signal are obtained.
Then, an (RB) value and an (R + B-2G) value are generated by using the obtained R ′ signal, G ′ signal, and B ′ signal.
The (RB) value and the (R + B-2G) value become integral value conversion data on coordinates by the (RB) axis and the (R + B-2G) axis.
[0023]
Subsequently, in step F103, it is determined whether to perform the processing on the high color temperature side or the processing on the low color temperature side. If the processing is on the low color temperature side, the process proceeds to step F108, and the integration value conversion data is Then, it is determined whether or not it is within the range of the drop-in frame W2 shown in FIG.
If it is not within the range of the drop-in frame W2, the current process is terminated from step F109, and the input of the integral value data Ri, Gi, Bi of the next field is waited.
[0024]
If it is within the range of the drop-in frame W2, the process proceeds from step F109 to F110 to calculate a convergence target value corresponding to the low color temperature side.
In other words, the convergence target value is calculated so that the R signal, the G signal, and the B signal are 1: 1: 1 without paying particular attention to the color temperature, and in step F111, each variable gain amplifier 3R, Gain control is performed on 3G and 3B.
[0025]
On the other hand, if it is determined in step F103 that the process is on the high color temperature side, the process proceeds to step F104, in which it is determined whether the integrated value conversion data is within the range of the drop-in frame W1 shown in FIG.
If it is not within the range of the drop-in frame W1, the current process is ended from step F105, and the input of the integrated value data Ri, Gi, Bi of the next field is waited.
[0026]
If it is within the range of the drop-in frame W1, the process proceeds from step F105 to F106, and first, a process of estimating the current color temperature is performed.
In step F107, a convergence target value corresponding to the high color temperature side is calculated, and in step F111, each of the variable gain amplifiers 3R, 3G, and 3B of the white balance amplifier 3 is set to a gain value corresponding to the convergence target value. Is performed.
The processing of steps F106 to F111 will be described with reference to FIGS.
Note that points on the coordinate axes in FIGS. 5A and 6A are R gain, G gain, and B gain obtained by adjusting the reference white to the R, G, and B signals in the previous stage of the white balance amplifier 3. This is the data multiplied by the gain.
On the other hand, points on the coordinate axes in FIGS. 5B and 6B correspond to the R signal, the G signal, and the B signal in the subsequent stage of the white balance amplifier 3.
[0027]
FIG. 5A shows a case where the integration value conversion data is a point P1 on the coordinates. This is within the region (1) shown in FIG. 3, that is, within the range of the drop-in frame W1 in the third quadrant, or within the range of the drop-in frame W1 in the fourth quadrant, and on the left side of the color temperature change line LB in the drawing. This is the case where the integrated value conversion data is in the range of.
In such a case, it is recognized that a subject with much green at a high color temperature is captured. Then, as shown by the broken line arrow in FIG. 5A, the (R + B-2G) value of the integrated value conversion data (P1) is moved horizontally with respect to the (R + B-2G) axis, and is regarded as a blackbody radiation curve. A point P2 that hits the color temperature change line LB is determined. Then, the point P2 is set as the current color temperature.
[0028]
The R, G, and B values corresponding to the point P2 on the color temperature change line LB are R ", G", and B ". That is, the R at which the (RB) value and the (R + B-2G) value are the point P2. , G, B values.
For each of the R ", G", and B "values of the color temperature at this point P2,

R "gain, G" gain, and B "gain are obtained such that
The R "gain, G" gain, and B "gain are gain values for drawing the current color temperature.
[0029]
From the R "gain, G" gain, and B "gain that draw in the current color temperature,
R signal convergence point = R signal × R "gain ÷ current R gain
G signal convergence point = G signal x G "gain / current G gain
B signal convergence point = B signal × B "gain / current B gain
Is found. The convergence point of each signal is shown as the position of point Pc in FIG.
[0030]
Here, the origin of the coordinate axis in FIG. 5B is R signal: G signal: B signal = 1: 1: 1.
In the conventional control method, the pull-in control from the point Pd to the coordinate origin is performed as shown by a broken line arrow in FIG.
On the other hand, in the control method of the present embodiment, by performing gain control for drawing in the color temperature, pull-in control from point Pd to point Pc is performed as shown by the solid line arrow. This means that the control target value comes in the negative direction of the (R + B-2G) axis with respect to the coordinate origin, and the color balance of the subject is maintained without drawing in the component in the G direction. In the figure, green remains as much as the arrow g.
[0031]
Next, FIG. 6A shows a case where the integration value conversion data is a point P3 on the coordinates. This is because the integrated value conversion data exists in the area {circle around (2)} shown in FIG. 3, that is, in the range of the drop-in frame W1 in the fourth quadrant and on the right side of the color temperature change line LB in the drawing. It is.
In this case, it is recognized that a subject with many flesh colors is photographed at a high color temperature.
Then, as shown by the arrow in FIG. 6A, the (RB) value and the (R + B-2G) value of the integrated value conversion data (P3) are moved in the negative direction by the same amount, and the blackbody radiation is performed. A point P4 that hits the color temperature change line LB regarded as a curve is determined. Then, the point P4 is set as the current color temperature.
[0032]
R, G, and B values corresponding to this point P4 are R ", G", and B ".

R "gain, G" gain, and B "gain are obtained such that
The R "gain, G" gain, and B "gain are gain values for drawing the current color temperature.
[0033]
From the R "gain, G" gain, and B "gain that draw in the current color temperature,
R signal convergence point = R signal × R "gain ÷ current R gain
G signal convergence point = G signal x G "gain / current G gain
B signal convergence point = B signal × B "gain / current B gain
Is found. The convergence point of each signal is shown as the position of point Pc in FIG.
[0034]
Here, as in FIG. 5B, the origin of the coordinate axes in FIG. 6B is R signal: G signal: B signal = 1: 1: 1. As shown by the dashed arrow in b), the pull-in control from the point Pd to the coordinate origin was performed.
On the other hand, in the control method of the present embodiment, by performing gain control for drawing in the color temperature, pull-in control from point Pd to point Pc is performed as shown by the solid line arrow.
This means that the control target value comes in the direction of 45 degrees in the first quadrant with respect to the coordinate origin in FIG. 6B, and the (RB) value and (R + B-2G) value are negative by the same amount. The fact that the point moved in the direction is set as the color temperature means that the component in the R direction is more than the current color temperature, and the color balance of the subject is maintained without drawing the component in the R direction. Become. In the figure, the flesh color remains as much as the arrow f.
[0035]
The estimation of the color temperature and the calculation of the convergence target value as described above are performed in steps F106 and F107 in FIG. 4, and accordingly, in step F111, the gain control of each of the variable gain amplifiers 3R, 3G, and 3B is performed.
That is, in the white balance adjustment processing of this example, first, the change in the color temperature (black body radiation curve) from the reference color temperature for adjusting the reference white color to the higher color temperature side is regarded as a straight line (color temperature change line LB).
This is a color signal processing method for automatically performing white balance processing by feedback control, and obtains integral value data Ri, Gi, Bi for each field of primary color signals of R signal, G signal, and B signal, From the (RB) value and (R + B-2G) value of the integrated value conversion data obtained by converting the integrated value data Ri, Gi, Bi, a color temperature change straight line LB where the blackbody radiation curve is regarded as a straight line From the current color temperature.
Further, in this case, in order to make the skin color and the green color look natural at a high color temperature, the integrated value conversion data is located on the left side of the color temperature change line LB in the drawing within the range of the drop-in frame W1 (the area ▲ in FIG. 3). In the case of (1)), that is, when the G component is large, a color temperature that leaves the G component is estimated. Also, if the integrated value conversion data is on the right side of the color temperature change straight line LB in the drawing (region (2) in FIG. 3) within the range of the drop-in frame W1, that is, if the R component is large, the R component is left. A good color temperature.
By performing gain control only for the estimated change in color temperature, white balance specialized for skin color and green on the high color temperature side is achieved.
[0036]
According to such a processing method, the color temperature can be estimated by the controller 6 by easy calculation by first considering the blackbody radiation curve as a straight line.
Further, at a high color temperature, the G component is not always converged to an achromatic color which is a convergence point of the white balance control. When the R component is larger than the integrated value data Ri, Gi, Bi, the G component is left so that the skin color remains. When the color temperature is large, the current color temperature is estimated so that the green color remains, and the control target value is calculated and converged according to the subject, so that the white balance control that the user visually feels suitable can be realized.
[0037]
Although the embodiments have been described above, various modifications of the present invention are conceivable.
For example, in the above embodiment, the processing example using the (RB) axis and the (R + B-2G) axis has been described, but the coordinates by the (RB) / G axis and the (R + B-2G) / G axis The same processing can be performed by using. This means that each axis in the above embodiment is divided by the G signal to normalize. In this case, the variation due to the color is smaller than when the (RB) axis and the (R + B-2G) axis are used. Absorption can also be performed.
[0038]
【The invention's effect】
As understood from the above description, according to the present invention, the blackbody radiation curve is regarded as a straight line (color temperature change line), for example, corresponding to imaging at a high color temperature. Then, the current color temperature is estimated from the integrated data of the R, G, and B signals, and a pull-in operation is performed along a color temperature change line. This has the effect of simplifying the calculation processing for estimating the color temperature and setting the adjustment gain.
In particular, in this case, it is preferable to use the coordinates represented by the (RB) axis and the (R + B-2G) axis, or the coordinates represented by the (RB) / G axis and the (R + B-2G) / G axis. It is preferable to regard the blackbody radiation curve as a straight line, and realize a simple calculation process without lowering the white balance control function.
[0039]
At a high color temperature, the G component is not always converged to the achromatic color, which is the convergence point of the white balance control. When the R component is larger than the integrated data of R / G / B, the G component is changed so that the skin color remains. When the color temperature is large, the current color temperature is estimated so that green remains, and the control target value is calculated and converged according to the subject. It can contribute to the improvement of the performance of the camera system having.
[Brief description of the drawings]
FIG. 1 is a block diagram of a white balance adjustment device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a pull-in range on a coordinate and a color temperature change straight line according to the embodiment;
FIG. 3 is an explanatory diagram of a concept of a color temperature estimation process according to the embodiment;
FIG. 4 is a flowchart of a gain adjustment process for white balance adjustment according to the embodiment.
FIG. 5 is an explanatory diagram of color temperature estimation and pull-in control according to the embodiment.
FIG. 6 is an explanatory diagram of color temperature estimation and pull-in control according to the embodiment.
[Explanation of symbols]
2 primary color separation circuit, 3 white balance amplifier, 3R, 3G, 3B variable gain amplifier, 5 optical detector, 6 controller

Claims (8)

White balance amplifier means provided with a variable gain amplifier for each of the input R signal, G signal, and B signal;
Integrating means for obtaining an integrated value for each of the R signal, G signal, and B signal output from the white balance amplifier means;
Integrated value conversion data obtained as a value on a predetermined coordinate from each integrated value of the R signal, the G signal, and the B signal output from the integrating means; Control means for estimating the current color temperature from the change straight line, obtaining a white balance adjustment gain based on the estimated color temperature, and controlling the gain of each variable gain amplifier of the white balance amplifier means;
A white balance adjustment device comprising: The white balance adjustment device according to claim 1, wherein the predetermined coordinates are coordinates represented by an (RB) axis and an (R + B-2G) axis. The white balance adjusting device according to claim 1, wherein the predetermined coordinates are coordinates represented by (RB) / G axis and (R + B-2G) / G axis. The control unit estimates the color temperature so that the G component is large when the integrated value conversion data is based on the color temperature change line, and leaves the R component when the R component is large. 2. The white balance adjustment device according to claim 1, wherein the color temperature is estimated as described above, and the white balance adjustment gain is obtained as a gain corresponding to a change in the estimated color temperature. An integration step of obtaining an integrated value for each of the R signal, G signal, and B signal output from the white balance amplifier means provided with a variable gain amplifier for each of the input R signal, G signal, and B signal; ,
An integrated value conversion data calculating step of obtaining integrated value conversion data as a value on predetermined coordinates from each integrated value of the R signal, the G signal, and the B signal obtained in the integration step;
An estimation step of estimating a current color temperature from the integration value conversion data obtained in the integration value conversion data calculation step and a color temperature change straight line that considers a black body radiation curve as a straight line on the coordinates;
A gain control step of obtaining a white balance adjustment gain based on the estimated color temperature and controlling the gain of each variable gain amplifier of the white balance amplifier means;
A white balance adjustment method comprising: The white balance adjustment method according to claim 5, wherein the predetermined coordinates are coordinates represented by an (RB) axis and an (R + B-2G) axis. The white balance adjustment method according to claim 5, wherein the predetermined coordinates are coordinates represented by (RB) / G axis and (R + B-2G) / G axis. In the estimating step, the integrated value conversion data estimates the color temperature based on the color temperature change line so that the G component is left if the G component is large, and the R component is estimated if the R component is large. Guess the color temperature to leave
6. The white balance adjustment method according to claim 5, wherein in the gain control step, the white balance adjustment gain is obtained as a gain corresponding to the estimated change in color temperature.

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