JP3545249B2 - White balance adjustment circuit and digital camera using the same - Google Patents

Description

【００１３】
Ｒデータはアンプ２２でα倍され、Ｂ信号はアンプ２４でβ倍される。つまり、Ｒデータに利得αが与えられ、Ｂデータに利得βが与えられる。一方、Ｂデータには利得は与えられない。アンプ２２および２４からそれぞれ出力されたＲ′データおよびＢ′データならびに信号処理回路２０からのＧデータは、マトリクス回路２６でマトリクス演算を施され、これによって輝度データＹと色差データＲ′−Ｙ およびＢ′−Ｙとが生成される。
【００１４】
Ｒ′データ，ＧデータおよびＢ′データはまた、積分回路２８に入力される。画面は、図６に示すように水平方向および垂直方向に８分割され、６４個の分割エリアが画面に形成されている。このため、積分回路２８は、Ｒ′データ，ＧデータおよびＢ′データを各色成分毎にかつ分割エリアごとに積分する。これによって、１フレーム期間に６４個のｉ_Ｒ’データ，６４個のｉ_Ｇデータおよび６４個のｉ_Ｂ’データが生成される。
【００１５】
ＣＰＵ３０は、積分回路２８から出力されたｉ_Ｒ’データ，ｉ_Ｂデータおよびｉ_Ｂ’データに基づいて現フレームの被写体の色を評価し、色評価値に基づいてアンプ２２および２４の利得αおよびβを制御する。具体的には、図４および図５に示すフロー図を処理する。
【００１６】
ＣＰＵ３０はまずステップＳ１で利得αおよびβを“１”に設定し、ステップＳ３で変数ｘを所定値Ｘに設定する。次に、ステップＳ５で１フレーム期間が経過したかどうかを判断し、“ＹＥＳ”であれば、ステップＳ７で現フレームのＲ′データ，ＧデータおよびＢ′データの積分値ｉ_Ｒ’，ｉ_Ｇ およびｉ_Ｂ’を積分回路２８から取り込み、ステップＳ９でこれらの積分値に基づいて色判定を行う。つまり、図６に示す被写体像に着目した場合、斜線で示す１４領域は同一色の青空であるため、ＣＰＵ３０はこの１４領域の積算値を無効にし、残りの５０領域の積算値を有効にする。
【００１７】
ステップＳ１１では、有効な積算値のみを色成分毎に個別に加算し、トータルの積算値Ｉ_Ｒ’，Ｉ_Ｇ，Ｉ_Ｂ’を算出する。これによってＲ′データ，ＧデータおよびＢ′データに関連する積算値は得られるが、Ｒ′データおよびＢ′データには利得αおよびβが与えられており、積算値Ｉ_Ｒ’およびＩ_Ｂ’は現フレームで撮影された被写体像を正確に反映しているわけではない。このため、ＣＰＵ３０は、ステップＳ１３で積算値Ｉ_Ｒ’を現利得αで割算して積算値Ｉ_Ｒを求め、ステップＳ１５で積算値Ｉ_Ｂ’を現利得βで割算して積算値Ｉ_Ｂを求める。算出された積算値Ｉ_ＲおよびＩ_Ｂは、信号処理回路２０から出力されたＲ信号およびＢ信号を図６に示す有効エリアについて積算した積算値と等価となり、現フレームで撮影された被写体像を正確に反映することになる。
【００１８】
ＣＰＵ３０はその後、ステップＳ１７で積算値Ｉ_Ｒ，Ｉ_ＢおよびＩ_Ｇに基づいて積算値Ｉ_Ｒ−Ｙ およびＩ_Ｂ−Ｙ を算出する。この２つの積算値もまた、Ｒデータ，ＧデータおよびＢデータに関連する色差データＲ−ＹおよびＢ−Ｙを図６の有効エリアについて積算した値と等価となる。このようにして得られた積算値Ｉ_Ｒ−ＹおよびＩ_Ｂ−Ｙが、現フレームで撮影された被写体の色評価値となる。
【００１９】
このように、利得αが与えられたＲ′データの積算値Ｉ_Ｒ’から利得αを取り除き、利得βが付与されたＢ′データの積算値Ｉ_Ｂ’から利得βを取り除き、これによって得られた積算値Ｉ_ＲおよびＩ_Ｂと積算値Ｉ_Ｇとに基づいて色評価値を算出するようにしたため、評価された色と被写体の実際の色との間にずれが生じることはない。つまり、被写体の色を正確に評価することができる。
【００２０】
テーブル３０ａには、図３（Ａ）に示すように複数の重み付け係数が格納されており、各重み付け係数は図３（Ｂ）に示すそれぞれのグラフ上の複数の領域に割り当てられている。つまり、Ｉ_Ｒ−Ｙ軸が１７分割され、それぞれに“０”，“７”または“８”が割り当てられる。Ｉ_Ｂ−Ｙ軸もまた１７分割され、それぞれに“０”または“８”が割り当てられる。また、Ｉ_Ｒ−Ｙ軸およびＩ_Ｂ−Ｙ軸によって仕切られた４つの象限のそれぞれが６４分割され、各領域に“０”，“６”“７”または“８”が割り当てられる。“８”が割り当てられた第１領域がテーブルのほぼ中央に形成され、“０”が割り当てられた第２領域が第１領域の周辺に形成され、そして、“６”および“７”が割り当てられた第３領域が第１領域と第２領域との間に形成される。なお、第１領域および第３領域は白バランス調整を施す引き込み範囲を示す。
【００２１】
ステップＳ１９では、ステップＳ１７で算出された色評価値に対応する重み付け係数をこのようなテーブル３０ａから検出する。そして、ステップＳ２１で、数２に従って重み付け量γを算出し、ステップＳ２３で、数３に従って最適利得α_Ｔおよびβ_Ｔを算出する。
【００２２】
【数２】

【００２３】
【数３】

【００２４】
数２では、検出された重み付け係数ｍが重み付け係数の最大値“８”の何パーセントであるかが求められる。検出された重み付け量ｍが“８”であれば、重み付け量γは“１００”となり、検出される重み付け係数が“０”であれば、重み付け量γは“０”となる。また、検出された重み付け係数が“７”であれば、重み付け量γは“８７．５”となり、検出された重み付け係数ｍが“６”であれば、重み付け量γは“７５”となる。
【００２５】
数３では、被写体のＲ成分とＧ成分との間での白バランスのずれ量（Ｉ_Ｇ／Ｉ_Ｒ）と利得αの初期値（＝１）のそれぞれに重み付け量γに応じた重み付けが施される。被写体のＢ成分とＧ成分との間での白バランスのずれ量（Ｉ_Ｇ／Ｉ_Ｂ）と利得βの初期値（＝１）のそれぞれにもまた、重み付け量γに応じた重み付けが施される。γ＝１００であれば、最適利得α_ＴはＩ_Ｇ／Ｉ_Ｒとなり、最適利得β_ＴはＩ_Ｇ／Ｉ_Ｂとなる。γ＝０であれば、最適利得α_Ｔ＝β_Ｔ＝１となる。また、γ＝８７．５であれば、最適利得α_Ｔは０．８７５×（Ｉ_Ｇ／Ｉ_Ｒ）＋０．１２５となり、最適利得β_Ｔは０．８７５×（Ｉ_Ｇ／Ｉ_Ｂ）＋０．１２５となる。γ＝６であれば、最適利得α_Ｔは０．７５×（Ｉ_Ｇ／Ｉ_Ｒ）＋０．２５となり、最適利得β_Ｔは０．７５×（Ｉ_Ｇ／Ｉ_Ｂ）＋０．２５となる。
【００２６】
このように、被写体の色評価値が第１領域内にあれば、γ＝１００となり、Ｒ＝Ｇ＝Ｂとなるように最適利得α_Ｔおよびβ_Ｔが求められる。また、被写体の色評価値が第２領域内にあれば、γ＝０となり、最適利得α_Ｔおよびβ_Ｔはいずれも初期値（＝１）になる。このため、第２領域では白バランス調整が中止される。一方、被写体の色評価値が第３領域にあれば、初期値（＝１）を考慮して最適利得α_Ｔおよびβ_Ｔが補正される。
【００２７】
つまり、被写体の色評価値が第１領域内にあれば、Ｒデータ，ＧデータおよびＢデータが完全に一致する値が最適利得α_Ｔおよびβ_Ｔとなるが、被写体の色評価値が第３領域にあれば、Ｒデータ，ＧデータおよびＢデータの間にわずかなずれが生じる値が最適値α_Ｔおよびβ_Ｔとなる。これによって、たとえば光源が赤色で被写体が赤みを帯びていれば、生成される画像も赤みを帯びる。また、光源が青色で被写体が青みを帯びていれば、生成される画像も青みを帯びる。
【００２８】
ステップＳ２５では、ＣＰＵ３０は現利得α＝最適利得α_Ｔであるかどうか判断し、“ＮＯ”であればステップＳ２７で最適利得α_Ｔ＞現利得αであるかどうか判断する。そして、“ＹＥＳ”であればステップＳ２９で現利得αに所定値Ｘを加算し、“ＮＯ”であればステップＳ３１で現利得αから係数Ｘを減算する。つまり、利得αと最適利得α_Ｔとの差が徐々に縮まるように、利得αが更新される。ＣＰＵ３０は、その後ステップＳ３３〜Ｓ４１で、現利得βを上述と同じ要領で更新する。そして、ステップＳ５に戻り、次フレームで撮影された被写体像に同じ処理を施す。このようにして、利得αおよびβが数フレーム期間かけて最適利得α_Ｔおよびβ_Ｔに収束していく。なお、ステップＳ２９，Ｓ３１，Ｓ３９および４１で、アンプ２２および２４の利得が実際に変更される。
【００２９】
以上のように、Ｒ′データ，ＧデータおよびＢ′データと現利得αおよびβとに基づいて被写体の色を正確に評価するようにしたため、被写体が突然切り換えられた時でも、切り換え後の被写体に適切に白バランス調整を施すことができる。つまり、たとえば被写体の光源が赤色から白色に突然切り換えられた場合、アンプ２２および２４から出力されたＲ′データおよびＢ′データは信号処理回路２０から出力されたＲデータおよびＢデータと大きく異なるが、この実施例では実質的に、利得αおよびβが付与されていないＲデータおよびＢデータとＧデータとに基づいて色評価が行われる。このため、被写体の実際の色が引き込み範囲内にあるのに引き込み範囲外と判別されたり、被写体の実際の色が引き込み範囲外にあるのに引き込み範囲内と判別されるようなことはなく、適切に白バランス調整をかけることがある。
【００３０】
また、被写体の色評価値が引き込み範囲の周辺部分つまり第３領域にあるときは、最適利得α_Ｔおよびβ_Ｔに初期値（＝１）を加味した補正が施されるため、生成される画像に被写体の色に応じた色付けを施すことができる。つまり、被写体が赤みを帯びていれば生成される画像も赤みを帯び、被写体が青みを帯びていれば生成される画像も青みを帯びる。
【００３１】
なお、この実施例ではアンプ２２および２４を設け、それぞれの利得αおよびβを制御するようにしたが、ＲＧＢ変換のマトリクス演算式に利得αおよびβを付加し、この利得αおよびβを制御するようにしてもよい。つまり、アンプ２２および２４を省略するとともに、信号処理回路２０で数４に従ってマトリクス演算を施し、被写体に応じてマトリクス係数を変更するようにしてもよい。
【００３２】
【数４】

【図面の簡単な説明】
【図１】この発明の一実施例を示ブロック図である。
【図２】補色フィルタを示す図解図である。
【図３】（Ａ）は重み付け係数および引込範囲を示す図解図であり、（Ｂ）は色評価値の分布を示すグラフである。
【図４】ＣＰＵの動作の一部を示すフロー図である。
【図５】ＣＰＵの動作の他の一部を示すフロー図である。
【図６】被写体像および画面に形成された分割エリアを示す図解図である。
【図７】従来技術を示すブロック図である。
【図８】図７に示す従来技術の動作の一部を示す図解図である。
【符号の説明】
２０…信号処理回路
２２，２４…アンプ
２６…マトリクス回路
２８…積分回路
３０…ＣＰＵ[0001]
[Industrial applications]
The present invention relates to a white balance adjustment circuit, and more particularly to a white balance adjustment circuit that is applied to, for example, a digital camera and adjusts a white balance based on a color information signal of a photographed subject.
[0002]
[Prior art]
Referring to FIGS. 7 and 8, in this type of conventional white balance adjustment circuit 1, matrix circuit 4 performs color difference signals R'-Y and B 'based on R' signal, B 'signal and G signal. -Y is generated, and the CPU 5 controls the gains α and β of the amplifiers 2 and 3 according to the color difference signals R′-Y and B′-Y. That is, the CPU 5 calculates the color evaluation value of the subject based on the color difference signals R'-Y and B'-Y, and the color evaluation value converges to the intersection of the RY axis and the BY axis shown in FIG. Thus, the gains of the amplifiers 2 and 3 are changed little by little. When the calculated color evaluation value is out of the range (retraction range) indicated by oblique lines in FIG. 8, the CPU 5 sets the gains α and β to “1” because it is not appropriate to perform white balance adjustment. Was.
[0003]
[Problems to be solved by the invention]
However, in such a conventional technique, since the gain of the next frame is determined based on the R 'signal and the B' signal of the current frame, when the subject is suddenly switched, the white balance of the switched subject is properly adjusted. There was a possibility that adjustment was not possible. That is, for example, when the light source is suddenly switched to white during shooting under a red light source, the R ′ signal and B ′ signal output from the amplifiers 2 and 3 in the first frame after the switching are changed to the input R signal and This is significantly different from the B signal, and as a result, the color of the subject after switching is incorrectly evaluated. Then, the white balance adjustment is executed while the actual color of the subject is out of the pull-in range shown in FIG. 8, or the white balance adjustment is stopped even though the actual color of the subject is in the pull-in range. Will occur. Thus, the white balance could not be properly adjusted depending on the situation of the subject.
[0004]
Therefore, a main object of the present invention is to provide a white balance adjustment circuit that can appropriately adjust the white balance regardless of the situation of a subject.
[0005]
[Means for Solving the Problems]
The present invention relates to an integrating means for integrating a second color information signal in a white balance adjustment circuit for generating a second color information signal having an adjusted white balance by multiplying an input first color information signal of a subject by a gain. Dividing means for dividing the integral value by the integrating means by the gain, color evaluation value calculating means for calculating a color evaluation value based on the division value by the dividing means, and control means for controlling the gain according to the color evaluation value. And a white balance adjustment circuit.
[0006]
[Action]
The input R signal and B signal are multiplied by α and β by the corresponding amplifiers, and the R ′ signal and B ′ signal output from each amplifier are integrated by the integration circuit and the CPU. On the other hand, no gain is given to the G signal, and the G signal is integrated as it is. As a result, the integral values IR _' , IB _', and _IG are obtained. The CPU, the integrated value I _{R 'and} I _B' divided by the current gain α, and beta, calculates an integrated value I _R and I _B of the input R signal and B signal. CPU further converts such integrated value _I R of primary color components, the _{I G} and _{I B} to the integral value _{I R-Y} and _{I B-Y} chrominance components. The converted integral values I _RY and IB _Y become the color evaluation values.
[0007]
The CPU calculates the optimum gain α _T and the optimum gain β _T based on the calculated color evaluation value. That is, the weighting coefficient corresponding to the calculated color evaluation value is read from the table in which the weighting coefficient is assigned to the color evaluation value, and the initial gain amount and the shift amount of the white balance are weighted in accordance with the weighting coefficient. Initial gain amount is α = β = 1, the amount of deviation of white balance is _I G / _{I R} and _I G / _{I B.} The calculated optimal gain α _T and optimal gain β _T are compared with the current gains α and β, and the gains α and β are updated so that the difference between them is reduced.
[0008]
【The invention's effect】
According to the present invention, since the color of the subject is evaluated based on the current gain and the second color information signal, the white balance can be appropriately adjusted even when the color of the subject suddenly changes.
[0009]
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0010]
【Example】
Referring to FIG. 1, a digital camera 10 of this embodiment includes a lens 12, and a light image incident from the lens 12 is applied to a CCD imager 16 via a complementary color filter 14. As shown in FIG. 2, the complementary color filter 14 has a filter element of Ye, Cy, Gr or Mg corresponding to each pixel. Therefore, each pixel signal output from the CCD imager 16 has only one complementary color component of Ye, Cy, Gr, and Mg.
[0011]
Such a pixel signal is converted into a digital signal, that is, pixel data by the A / D converter 18, and the pixel data is input to the signal processing circuit 20. The signal processing circuit 20 performs color interpolation and RGB conversion on the input pixel data. That is, first, pixel data having only one complementary color component is interpolated with the other three complementary color components, and then a matrix operation is performed in accordance with Equation 1. As a result, R data, G data, and B data of each pixel are generated.
[0012]
(Equation 1)

[0013]
The R data is multiplied by α by the amplifier 22, and the B signal is multiplied by β by the amplifier 24. That is, the gain α is given to the R data, and the gain β is given to the B data. On the other hand, no gain is given to the B data. The R 'data and B' data respectively output from the amplifiers 22 and 24 and the G data from the signal processing circuit 20 are subjected to a matrix operation in a matrix circuit 26, whereby luminance data Y and color difference data R'-Y and B′−Y are generated.
[0014]
The R 'data, G data and B' data are also input to the integration circuit 28. The screen is divided into eight in the horizontal and vertical directions as shown in FIG. 6, and 64 divided areas are formed on the screen. Therefore, the integration circuit 28 integrates the R 'data, the G data, and the B' data for each color component and for each divided area. Thus, 64 i _{R 'data,} 64 _{i G} data and 64 i _B' in one frame period data is generated.
[0015]
CPU30 is, i _{R 'data,} i _B data and i _B' output from the integrating circuit 28 based on the data to evaluate the color of the subject of the current frame, the gain of the amplifier 22 and 24 based on the color evaluation values α and Control β. Specifically, the flowcharts shown in FIGS. 4 and 5 are processed.
[0016]
The CPU 30 first sets the gains α and β to “1” in step S1, and sets a variable x to a predetermined value X in step S3. Next, it is determined whether the one frame period has elapsed in step S5, "YES" if, R of the current frame in step S7 'data, G data and B' integrated value i _R data _{', i G} And iB _' are fetched from the integration circuit 28, and a color judgment is made in step S9 based on these integrated values. That is, when focusing on the subject image shown in FIG. 6, since the 14 regions indicated by oblique lines are blue sky of the same color, the CPU 30 invalidates the integrated values of the 14 regions and validates the integrated values of the remaining 50 regions. .
[0017]
In step S11, only the effective integrated values are individually added for each color component to calculate total integrated values IR _' , _IG , and IB _' . As a result, integrated values relating to R 'data, G data and B' data are obtained, but gains α and β are given to R 'data and B' data, and integrated values IR _' and IB _{' are provided.} Does not accurately reflect the subject image captured in the current frame. Therefore, CPU 30 may _'determine the the current gain accumulated value divided by the alpha _{I R,} integrated value I _B at step _S15' integrated value I _R in step S13 the integrated value I by dividing by the current gain β of _{Find B.} Calculated integrated value I _R and I _B becomes the integrated value equivalent obtained by integrating the effective area indicating the R and B signals output from the signal processing circuit 20 in FIG. 6, the subject image photographed in the current frame It will reflect accurately.
[0018]
CPU30 then calculates the integrated value _{I R-Y} and _{I B-Y} based on the integrated value _I R, _{I B} and _{I G} in step S17. These two integrated values are also equivalent to the values obtained by integrating the color difference data RY and BY related to the R data, G data and B data for the effective area in FIG. Thus the integrated value obtained by I _R-Y and I _B-Y becomes the color evaluation values of an object photographed in the current frame.
[0019]
Thus, removing the gain α from the gain α is given R 'integrated value I _{R data',} removes the gain β from the gain β is given B 'integrated value I _{B data'} obtained by this because it has to calculate the integrated value I _R and I _B and the integrated value I color evaluation values based on the _G, it does not occur misalignment between the actual color of the evaluated color and subject. That is, the color of the subject can be accurately evaluated.
[0020]
As shown in FIG. 3A, a plurality of weighting factors are stored in the table 30a, and each weighting factor is assigned to a plurality of regions on each graph shown in FIG. 3B. That is, the I- _R-Y axis is divided into 17, and "0", "7", or "8" is assigned to each. The IB _-Y axis is also divided into 17, and "0" or "8" is assigned to each. _Further, each of the four quadrants partitioned by _{I R-Y} axis and _{I B-Y} axis is 64 divided, "0" in each area, "6""7" or "8" is assigned. A first area assigned “8” is formed substantially at the center of the table, a second area assigned “0” is formed around the first area, and “6” and “7” are assigned. The third region is formed between the first region and the second region. The first region and the third region indicate a pull-in range in which white balance adjustment is performed.
[0021]
In step S19, a weighting coefficient corresponding to the color evaluation value calculated in step S17 is detected from such a table 30a. Then, in step S21, the weighting amount γ is calculated according to equation 2, and in step S23, the optimum gains α _T and β _T are calculated according to equation 3.
[0022]
(Equation 2)

[0023]
[Equation 3]

[0024]
In Expression 2, it is determined what percentage of the maximum value “8” of the detected weighting coefficient m is. If the detected weight m is “8”, the weight γ is “100”, and if the detected weight coefficient is “0”, the weight γ is “0”. If the detected weighting coefficient is “7”, the weighting amount γ is “87.5”, and if the detected weighting coefficient m is “6”, the weighting amount γ is “75”.
[0025]
In Equation 3, the white balance shift amount (I _G / I _R ) between the R component and the G component of the subject and the initial value (= 1) of the gain α are weighted in accordance with the weight amount γ. Is done. Each of the white balance shift amount (I _G / I _B ) between the B component and the G component of the subject and the initial value (= 1) of the gain β is also weighted in accordance with the weight amount γ. You. If gamma = 100, the optimum gain alpha _T is _I G / _{I R,} and the optimum gain beta _T becomes _I G / _{I B.} If γ = 0, the optimal gain α _T = β _T = 1. Also, if gamma = 87.5, optimum gain alpha _T is _{0.875 × (I G / I R} ) +0.125 , and the optimum gain beta _T is _{0.875 × (I G / I B} ) +0. 125. If gamma = 6, the optimal gain alpha _T is _{0.75 × (I G / I R} ) +0.25 , and the optimum gain beta _T becomes _{0.75 × (I G / I B} ) +0.25.
[0026]
As described above, if the color evaluation value of the subject is within the first area, γ = 100, and the optimal gains α _T and β _T are obtained so that R = G = B. If the color evaluation value of the subject is within the second area, γ = 0, and both of the optimal gains α _T and β _T become initial values (= 1). Therefore, the white balance adjustment is stopped in the second area. On the other hand, if the color evaluation value of the subject is in the third area, the optimal gains α _T and β _T are corrected in consideration of the initial value (= 1).
[0027]
That is, if the color evaluation value of the subject is within the first area, the values where the R data, G data, and B data completely match are the optimum gains α _T and β _T , but the color evaluation value of the subject is the third gain. if the area, R data, the value a slight deviation occurs between the G data and B data the optimum value alpha _T and beta _T. Thus, for example, if the light source is red and the subject is reddish, the generated image is also reddish. If the light source is blue and the subject is bluish, the generated image is also bluish.
[0028]
In step S25, the CPU 30 determines whether or not the current gain α = optimal gain α _T. If “NO”, the CPU 30 determines in step S27 whether or not the optimal gain α _T > current gain α. If “YES”, the predetermined value X is added to the current gain α in step S29, and if “NO”, the coefficient X is subtracted from the current gain α in step S31. That is, the gain α is updated so that the difference between the gain α and the optimal gain α _T gradually decreases. The CPU 30 thereafter updates the current gain β in the same manner as described above in steps S33 to S41. Then, returning to step S5, the same processing is performed on the subject image captured in the next frame. Thus, the gains α and β converge to the optimal gains α _T and β _T over several frame periods. In steps S29, S31, S39 and S41, the gains of the amplifiers 22 and 24 are actually changed.
[0029]
As described above, the color of the subject is accurately evaluated based on the R ′ data, G data, and B ′ data and the current gains α and β. Therefore, even when the subject is suddenly switched, The white balance can be adjusted appropriately. That is, for example, when the light source of the subject is suddenly switched from red to white, the R 'data and B' data output from the amplifiers 22 and 24 are significantly different from the R data and B data output from the signal processing circuit 20. In this embodiment, the color evaluation is substantially performed based on the R data, the B data, and the G data to which the gains α and β are not applied. Therefore, it is not determined that the actual color of the subject is outside the pull-in range even though the actual color is within the pull-in range, or that the actual color of the subject is outside the pull-in range even though the actual color of the subject is outside the pull-in range. The white balance may be adjusted appropriately.
[0030]
Further, when the color evaluation value of the subject is in the peripheral part of the pull-in range, that is, in the third area, the correction is performed in consideration of the initial values (= 1) to the optimum gains α _T and β _T , and thus the generated image is generated. Can be colored according to the color of the subject. In other words, if the subject is reddish, the generated image is also reddish, and if the subject is bluish, the generated image is also bluish.
[0031]
In this embodiment, the amplifiers 22 and 24 are provided to control the gains α and β. However, the gains α and β are added to the matrix calculation formula of RGB conversion to control the gains α and β. You may do so. In other words, the amplifiers 22 and 24 may be omitted, and the signal processing circuit 20 may perform a matrix operation according to Equation 4 and change the matrix coefficient according to the subject.
[0032]
(Equation 4)

[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of the present invention.
FIG. 2 is an illustrative view showing a complementary color filter;
FIG. 3A is an illustrative view showing a weighting coefficient and a pull-in range, and FIG. 3B is a graph showing a distribution of color evaluation values.
FIG. 4 is a flowchart showing a part of the operation of the CPU;
FIG. 5 is a flowchart showing another portion of the operation of the CPU;
FIG. 6 is an illustrative view showing a subject image and a divided area formed on a screen;
FIG. 7 is a block diagram showing a conventional technique.
FIG. 8 is an illustrative view showing one portion of an operation of the conventional technique shown in FIG. 7;
[Explanation of symbols]
20 signal processing circuits 22, 24 amplifier 26 matrix circuit 28 integration circuit 30 CPU

Claims (7)

In a white balance adjustment circuit for generating a second color information signal in which a white balance is adjusted by multiplying an input first color information signal of a subject by a gain,
Integrating means for integrating the second color information signal;
Division means for dividing the integral value by the integration means by the gain;
A white balance adjusting circuit, comprising: a color evaluation value calculation unit that calculates a color evaluation value based on a division value by the division unit; and a control unit that controls the gain according to the color evaluation value. The control means, a table having a plurality of weighting coefficients respectively assigned to a plurality of color evaluation values, a weighting coefficient detection means for detecting a weighting coefficient corresponding to the color evaluation value generated by the evaluation means from the table, and 2. The white balance adjustment circuit according to claim 1, further comprising gain control means for controlling the gain based on the detected weighting coefficient. A first predetermined number is allocated to a first predetermined area of the table, a second predetermined number smaller than the first predetermined number is allocated to a second predetermined area located around the first predetermined area, and The white balance according to claim 2, wherein a third predetermined number smaller than the first predetermined number and larger than the second predetermined number is assigned to a third predetermined area between the first predetermined area and the second predetermined area. Adjustment circuit. 4. The gain control unit according to claim 2, wherein the gain control unit includes an optimum gain calculation unit that calculates an optimum gain using the detected weighting coefficient, and an update unit that updates the gain based on the optimum gain and the current gain. White balance adjustment circuit. The optimum gain calculating means calculates a shift amount of the white balance based on the division value, and weights each of the calculated shift amount and the initial gain amount corresponding to the weighting coefficient. 5. The white balance adjustment circuit according to claim 4, further comprising a weighting means for calculating said optimum gain. A comparing unit that compares the optimal gain and the current gain; and a gain updating unit that updates the gain so as to reduce a difference between the optimal gain and the current gain according to a comparison result of the comparing unit. The white balance adjustment circuit according to claim 4 or 5, further comprising means. A digital camera comprising the white balance adjustment circuit according to claim 1.

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