JP3619066B2 - Automatic white balance adjustment device and automatic white balance adjustment method - Google Patents

Description

上式の１／Σ_Ｒはフレーム毎に変化する値であるが、除算をなくすためにはこの値を定数とする必要がある。
【００５３】
そこで上式５のΣ_Ｒをフレーム平均Σ_{Ｒ（ａｖｒ）}とみなし、１／Σ_{Ｒ（ａｖｒ）}を用いて利得値を概算する。ここで１／Σ_{Ｒ（ａｖｒ）}を定数Ｃ_Ｒとする。
ｒ_Ｒ（Ｎ）≒１−Ｃ_Ｒ・ｄ_Ｒ（Ｎ） （式５）
このように（式５）を用いれば除算器を用いずに利得の収束値を概算することができる。また、（式５）の右辺にある乗算もビットシフト演算をもちいれば、さらに小さな回路規模で利得の収束値を概算することができる。
【００５４】
同様にＢ信号の利得収束値は、
ｒ_Ｂ（Ｎ）＝１−Ｃ_Ｂ・ｄ_Ｂ（Ｎ） （式６）
で概算でき、これらの演算はｄ_Ｒ、ｄ_Ｂが入力されるマイクロコンピュータ２７で行う。
【００５５】
本実施の形態では（式５）、（式６）で得られる利得の収束値を用いて実施の形態２と同様に、重み係数α_Ｒ、β_Ｒ（あるいはα_Ｒ、β_Ｒ）を前フレームの利得値と利得の収束概算値との差分値によって変化させれば、ホワイトバランスの収束時間や収束動作を調整することができる。
【００５６】
上述のように、減算回路を用いて利得の収束値を概算し、利得の算出式に用いる重み係数を前フレームの利得値と利得の収束概算値との差分値により変化させれば、ホワイトバランスの収束時間や収束条件を調整可能な装置の演算回路規模の縮小化が可能となる。
【００５７】
実施の形態５．
以上、これまでの実施の形態では、Ｒ、Ｂ信号の利得制御回路に入力する利得値の収束動作に関して説明した。本実施の形態では利得値の収束条件として上限値、下限値などの制限域を設定することにより撮影画像に過度なホワイトバランス処理が施されることを防止する。
図６に本実施の形態で規定する利得値の制限域を示す。
【００５８】
本実施の形態では、Ｒ、Ｂ信号の利得制御回路に入力する利得値の上限、下限値について説明する。通常、自然画などの被写体を撮影する場合、各色信号の積分値に極端な差はないと考えられる。しかし、例えば赤い服を着た人物などを撮影する場合や極端に赤味を帯びた特殊な光源下で画像を撮影する場合、Ｒ信号成分が他の色信号に比べ極端に多くなることがある。このような撮影条件下で利得値の制限なしにホワイトバランス処理を行うと、Ｒ信号が抑制され過ぎ、見た目と撮影画像の色が極端に異なる不自然な画像が撮影される。そこで前述の実施の形態１乃至４の計算法によって求められる各信号の利得値に上限値、下限値を設け、ホワイトバランス処理が過度に行われることを防止する。
【００５９】
図６は利得値の制限域を示した図であり、Ｒ、Ｂ信号の利得値が図中の実線で囲まれた領域内に収まるようにする。本実施の形態では利得の収束値が制限領域外にある場合には、利得値の計算結果が制限域を越えるまで利得値を更新し、超えた場合には利得値をあらかじめ設定した上限値あるいは下限値をマイクロコンピュータから出力する。マイクロコンピュータにはあらかじめ利得値の制限領域を入力しておき、常に制限域内の利得値を出力するよう設定する。このような法によってホワイトバランス処理がかかり過ぎることを防止する。
【００６０】
上述のように、Ｒ、Ｂ信号の利得制御回路に入力する利得値に上限値、下限値などの制限域を設定することによって、過度にホワイトバランス処理され画像が不自然な色になることを防止し、見た目と同様の画像を撮影できるようにする。
【００６１】
実施の形態６
前述した実施の形態では、ホワイトバランス処理に必要な各色信号の利得値の計算をマイクロコンピュータによって行う方法について説明した。本実施の形態では、各色信号の利得値を計算する際に必要な重み係数を、ルックアップテーブルとしてＲＯＭなどのメモリに保存、読み出しを行うことで全ての処理をハードウェア化し処理の高速化を図る。
【００６２】
図７は本実施の形態の構成を示す図であり、３２、３３は除算（あるいは減算）を行う演算回路、３４、３５は利得値の計算に必要な乗算および加算を行う演算回路、３６、３７は前フレームの利得値と利得の収束値（あるいは収束概算値）との差分値、重み係数との関係を示すＬＵＴ（ルックアップテーブル）、３８、３９はそれぞれＲ、Ｂ信号の利得値の制限値と３４、３５の出力結果を比較する比較回路である。
その他の構成は図５と同様である。
【００６３】
本実施の形態の動作について説明する。これまでの実施の形態では、利得の計算に必要なパラメータはハードウェア化した演算回路を用いて算出していたが主な演算はマイクロコンピュータで行う例について述べた。本実施の形態では、これまでの実施の形態で述べたものと同様の利得算出式を用い、マイクロコンピュータで行っていた重み係数の算出や利得の算出などの全ての計算をハードウェア化した演算回路で行う。
【００６４】
ホワイトバランスの収束時間などの条件が決めれば、前フレームの利得値と利得の収束値（あるいは収束概算値）との差分値に対する重み係数値をあらかじめＬＵＴ化することができる。図７の３６は、前フレームの利得値と、利得の収束値（あるいは収束概算値）との差分値に対する重み係数をＬＵＴとしたものである。ＬＵＴにはホワイトバランスの収束条件に合わせてあらかじめ計算した重み係数値をＲＯＭなどのメモリ装置に記憶しておき、必要に応じて記憶データを読み出せるようにする。図７のＬＵＴ３６では、入力信号ｒ_Ｒ（Ｎ＋１）（あるいはｄ_Ｒ（Ｎ＋１））と前フレームの利得値ｋ_Ｒ（Ｎ）に応じた必要な重み係数をα_Ｒ、β_Ｒを読み出し、演算回路３４に入力する構成となっている。さらに演算回路３４では、入力信号はｒ_Ｒ（Ｎ＋１）（あるいはｄ_Ｒ（Ｎ＋１））、ｋ_Ｒ（Ｎ）、重み係数α_Ｒ、β_Ｒを用いて（式１）（あるいは、（式３））の計算を行い、この回路で得た利得値ｋ_Ｒ（Ｎ＋１）を出力する。比較回路３８では、演算回路３４の出力信号ｋ_Ｒ（Ｎ＋１）と利得値の上・下限値との比較を行う。ｋ_Ｒ（Ｎ＋１）が利得値の制限域内であれば入力信号をそのままＤ／Ａ変換回路２８に送信し、入力信号が利得値の制限域外であれば、上限値（あるいは下限値）をＤ／Ａ変換回路２８に送る。Ｒ信号の利得値は２８でデジタル値からアナログ値に変換され、利得制御回路１９に送られる。そして利得制御回路１９で信号レベル調整された出力値がエンコーダ２１に送られる。Ｒ信号と同様にＢ信号においても、利得制御回路２０に入力する利得値を求める際に必要な計算をハードウェア回路で行い、撮影画像のホワイトバランス処理を行う。
【００６５】
上述のように、ホワイトバランス処理に伴う演算回路を全てハードウェア化し、前フレームの利得値と利得の収束値との差分に対する重み係数値をあらかじめ計算した結果をＲＯＭなどのメモリに記憶しＬＵＴとして用いることで、ホワイトバランス処理に伴う演算を高速化することができる。また、本発明を用いればＬＵＴに記憶する重み係数を変更することによって、ホワイトバランス処理かかる収束時間や収束動作を制御することができる。
【００６６】
【発明の効果】
この発明に係る自動ホワイトバランス調整装置は、複数の色フィルタを備え連続した複数の画像を撮像するカラー撮像装置の自動ホワイトバランス調整装置であって、Ｎ番目の現画像フレームにおける各色信号を利得値ｋ(N)によりレベル調整する利得制御回路と、各色信号の出力値を積分する積分回路と、各々２色の色信号の積分値の比ｒ(N)を出力する除算回路と、（Ｎ＋１）番目のフレーム画像を撮像する際に必要な利得値ｋ (N+1) を算出し記憶する算出記憶手段とを有し、算出記憶手段は、任意の重み係数αと現フレームの利得値ｋ (N)の積に任意の重み係数βと積分値の比ｒ(N)の積を加えたものに基づいて、利得値ｋ (N+1)を算出する。各信号の利得値を現フレームの利得値と利得の収束値のそれぞれに任意の重み係数を乗じた計算式によって求め、重み係数の設定値を調整することでホワイトバランスの収束過程を制御することができる。そのため、例えば、画像観察者に色の変化の違和感を覚えさせないようにすることが可能である。
【００６７】
また、算出記憶手段は、重み係数α、βを、利得値の収束値と前フレームの利得値の差分値に基づいて求める。重み係数を前フレームの利得値と利得の収束値との差分値によって変化させることにより収束時間や収束動作の調整を行うことが可能となり、また重み係数を視覚特性に合わせて設定することによりホワイトバランス処理を迅速に自然に収束させることができる。
【００６８】
また、算出記憶手段は、重み係数α、βを、視覚特性に基づいて求める。そのため、ひとの視覚特性を利用し、例えば色変化に対して反応が鈍い色相にあるときには、重み係数の設定値を大きくして、利得値の変化を大きくすることにより観察者に違和感を与えずに利得収束時間の高速化を図ることができる。
【００６９】
また、複数の色フィルタを備え連続した複数の画像を撮像するカラー撮像装置の自動ホワイトバランス調整装置であって、Ｎ番目の現画像フレームにおける各色信号を利得値ｋ(N)によりレベル調整する利得制御回路と、各色信号の出力値を積分する積分回路と、各々２色の色信号の積分値の差分値ｄ(N)を出力する減算回路と、（Ｎ＋１）番目のフレーム画像を撮像する際に必要な利得値ｋ (N+1) を算出し記憶する算出記憶手段とを有し、算出記憶手段は、任意の重み係数αと現フレームの利得値ｋ (N)の積に任意の重み係数βと積分値の差分値ｄ(N)の積を加えたものに基づいて、利得値ｋ (N+1)を算出する。そのため、装置の回路規模を小さくすることができる。
【００７０】
また、算出記憶手段は、重み係数α、βを、積分値の差分値と前フレームの利得値に基づいて求める。そのため、装置の演算回路規模の縮小化が可能となる。
【００７１】
また、利得値の制限域を設け、算出記憶手段は、利得値が制限域を越えないように制限する。そのため、過度にホワイトバランス処理され画像が不自然な色になることを防止し、見た目と同様の画像を撮像することが可能となる。
【００７２】
また、重み係数α、βをルックアップテーブルとして記憶する記憶手段をさらに有し、算出記憶手段は、重み係数α、βを記憶手段から読み出す。そのため、装置の全ての演算回路のハードウェア化を図ることができ、ホワイトバランス処理に伴う演算の高速化をすることができる。
【００７３】
また、他の発明に係る自動ホワイトバランス調整方法は、複数の色フィルタを備え連続した複数の画像を撮像するカラー撮像装置の自動ホワイトバランス調整方法であって、Ｎ番目の現画像フレームにおける各色信号を利得値ｋ(N)によりレベル調整する利得制御工程と、各色信号の出力値を積分する積分工程と、各々２色の色信号の積分値の比ｒ(N)を出力する除算工程と、（Ｎ＋１）番目のフレーム画像を撮像する際に必要な利得値ｋ (N+1) を算出し記憶する算出記憶工程とを有し、算出記憶工程は、任意の重み係数αと現フレームの利得値ｋ (N)の積に任意の重み係数βと積分値の比ｒ(N)の積を加えたものに基づいて、利得値ｋ (N+1)を算出する。各信号の利得値を現フレームの利得値と利得の収束値のそれぞれに任意の重み係数を乗じた計算式によって求め、重み係数の設定値を調整することでホワイトバランスの収束過程を制御することができる。そのため、例えば、画像観察者に色の変化の違和感を覚えさせないようにすることが可能である。
【００７４】
また、算出記憶工程は、重み係数α、βを、利得値の収束値と前フレームの利得値の差分値に基づいて求める。重み係数を前フレームの利得値と利得の収束値との差分値によって変化させることにより収束時間や収束動作の調整を行うことが可能となり、また重み係数を視覚特性に合わせて設定することによりホワイトバランス処理を迅速に自然に収束させることができる。
【００７５】
また、算出記憶工程は、重み係数α、βを、視覚特性に基づいて求める。そのため、ひとの視覚特性を利用し、例えば色変化に対して反応が鈍い色相にあるときには、重み係数の設定値を大きくして、利得値の変化を大きくすることにより観察者に違和感を与えずに利得収束時間の高速化を図ることができる。
【００７６】
また、複数の色フィルタを備え連続した複数の画像を撮像するカラー撮像装置の自動ホワイトバランス調整方法であって、Ｎ番目の現画像フレームにおける各色信号を利得値ｋ(N)によりレベル調整する利得制御工程と、各色信号の出力値を積分する積分工程と、各々２色の色信号の積分値の差分値ｄ(N)を出力する減算工程と、（Ｎ＋１）番目のフレーム画像を撮像する際に必要な利得値ｋ (N+1) を算出し記憶する算出記憶工程とを有し、算出記憶工程は、任意の重み係数αと現フレームの利得値ｋ (N)の積に任意の重み係数βと積分値の差分値ｄ(N)の積を加えたものに基づいて、利得値ｋ (N+1)を算出する。そのため、装置の回路規模を小さくすることができる。
【００７７】
また、算出記憶工程は、重み係数α、βを、積分値の差分値と前フレームの利得値に基づいて求める。そのため、装置の演算回路規模の縮小化が可能となる。
【００７８】
また、利得値の制限域を設け、算出記憶工程は、利得値が制限域を越えないように制限する。そのため、過度にホワイトバランス処理され画像が不自然な色になることを防止し、見た目と同様の画像を撮像することが可能となる。
【００７９】
さらに、重み係数α、βをルックアップテーブルとして記憶する記憶手段をさらに有し、算出記憶工程は、重み係数α、βを記憶手段から読み出す。そのため、装置の全ての演算回路のハードウェア化を図ることができ、ホワイトバランス処理に伴う演算の高速化をすることができる。
【図面の簡単な説明】
【図１】この発明による自動ホワイトバランス調整装置の構成図である。
【図２】利得値ｋ_Ｂ、ｋ_Ｒをそれぞれ横軸、縦軸にとり、Ｒ、Ｂ信号の利得値をプロットしたグラフである。
【図３】利得値の収束値と前フレームの利得値の差分値に対する重み係数α_Ｒ、β_Ｒの例を示したものである。
【図４】利得値の収束値と前フレームの利得値の差分値に対する重み係数α_Ｒ、β_Ｒのさらに異なる例を示したものである。
【図５】この発明による自動ホワイトバランス調整装置の他の例を示す構成図である。
【図６】利得値の制限域を示した図である。
【図７】この発明による自動ホワイトバランス調整装置の他の例を示す構成図である。
【図８】従来のホワイトバランス調整装置の構成図である。
【図９】マイクロコンピュータ（算出記憶手段）の動作を示すフローチャートである。
【符号の説明】
１９，２０ 利得制御回路（利得制御工程）、２２，２３，２４ 積分回路（積分工程）、２５，２６ 除算回路（除算工程）、２７ マイクロコンピュータ（算出記憶手段，算出記憶工程）、３０，３１ 減算回路（減算工程）、３６，３７ ルックアップテーブル（記憶手段）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color imaging apparatus such as a digital still camera, and more particularly to an automatic white balance adjustment apparatus and an automatic white balance adjustment method for adjusting white balance of an imaging apparatus.
[0002]
[Prior art]
Normally, in a color image capturing device such as a digital still camera, the signal level obtained by the red (R), green (G), and blue (B) signal systems so that a white image is captured when a white screen is captured. Adjust so that is equal. Such signal level adjustment is called white balance and has been used in various color imaging devices so far.
[0003]
For example, FIG. 8 shows a conventional white balance adjusting device disclosed in Japanese Patent Laid-Open No. 56-80988. In FIG. 8, a light image incident from a lens 1 is converted into an electric signal by an image pickup device 2 and color separation is performed. Input to the circuit 3. The color separation circuit 3 separates the image into three color signals of R, G, and B. The R and B outputs of the color separation circuit 3 are supplied directly to the process circuit 6 via the red (Rch) gain control circuit 4 and the blue (Bch) gain circuit 5. The process circuit 6 generates Y, RY, and BY color signals and supplies them to the encoder circuit 7.
[0004]
Next, the operation will be described.
In this path, the RY color signal output from the process circuit 6 is integrated by the integration circuit 8 and guided to the comparison circuit 10. The BY color signal is integrated by the integration circuit 9 and guided to the comparison circuit 11. In the comparison circuits 10 and 11, the integration value supplied from the integration circuits 8 and 9 is compared with the reference value from the reference voltage generation circuit 15. The outputs of the comparison circuits 10 and 11 are input to the microcomputer 12 and used for reversible counting synchronized with the pulse.
[0005]
As a result of this reversible counting, two types of reversible calculated values of Rch and Bch (hereinafter referred to as RchUDC and BchUDC) are obtained, and these are input to the gain control circuit 4 or 5 via the digital-analog exchanger 13 or 14. Is done.
In this way, by inputting the reversible calculation results RchUDC and BchUDC to the gain control circuits 4 and 5, gain control of each color is executed.
[0006]
Here, when the polarity of both comparison circuits 10 and 11, the direction of increase / decrease of the reversible counting function, and the control characteristics of both gain control circuits 4 and 5, when an achromatic color is imaged, an RY color signal and a BY color signal If the negative feedback loop is configured so that each becomes zero, the white balance is automatically adjusted even if the light source that irradiates the subject changes.
[0007]
Next, the operation of the microcomputer 12 will be described based on the flowchart of FIG. When the microcomputer 12 is started, as shown in FIG. 9, first, in step S1, an initial value of the reversible calculation value (RchUDC) and an initial value of the reversible calculation value (BchUDC) are set. The value is output to the gain control circuit 4 and the gain control circuit 5 via the digital-analog converters 13 and 14 (step S2).
[0008]
In this state, if the output of the comparison circuit for red 10 is larger than the reference value in step S3 (H), RchUDC is decreased by 1 in step S4, whereas if it is smaller (L), only 1 in step S5. Is added.
[0009]
Similarly, in step S6, if the output of the blue comparison circuit 11 is larger than the reference value (H), BchUDC is incremented by 1 in step S7, and if smaller (L), it is decremented by 1 in step S8. . These outputs are output after pulse synchronization in step S9, and white balance adjustment is performed by the gain control circuit 4 and the control circuit 5.
[0010]
[Problems to be solved by the invention]
As described above, in the prior art shown in FIG. 8, the color difference signals RY and BY signals obtained when a subject having an achromatic color average voltage for one screen of the color difference signals RY and BY is photographed. Since the gain value of the gain control circuit is incremented and decremented until it becomes equal to the average voltage, white balance can be adjusted without bothering photographing a white object or the like.
[0011]
However, since the increase / decrease width of the gain value of the gain control circuit is constant, when the screen changes extremely, for example, when the screen suddenly changes from a reddish screen to a bluish screen, R There is a problem in that it takes time to be equal to the average voltage of the -Y and BY signals.
[0012]
The present invention has been made to solve the above-described problems. By making it possible to adjust the gain value for each color signal in accordance with the screen change, the convergence including the time required for the white balance to converge is achieved. An object of the present invention is to obtain an automatic white balance adjusting device and an automatic white balance adjusting method capable of adjusting and controlling the operation.
[0013]
[Means for Solving the Problems]
An automatic white balance adjustment device according to the present invention is an automatic white balance adjustment device of a color imaging device that includes a plurality of color filters and captures a plurality of continuous images, and each color signal in an Nth current image frame is represented by a gain value. a gain control circuit that adjusts the level by k (N), an integration circuit that integrates the output value of each color signal, and a division circuit that outputs a ratio r (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheCalculation storage means for calculating and storing, and the calculation storage means includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral ratio r (N)k (N + 1)CalculateThen, the weighting coefficients α and β are obtained based on the difference value between the gain value convergence value and the gain value of the previous frame.
[0015]
The calculation storage means sets the weighting coefficients α and β asExpressed by the visual response speed to the color change for each hue or the visual discrimination sensitivity for each hueDetermine based on visual characteristics.
[0016]
An automatic white balance adjustment device for a color image pickup device that includes a plurality of color filters and picks up a plurality of continuous images, wherein each color signal in the Nth current image frame is gain-adjusted by a gain value k (N). A control circuit, an integration circuit for integrating the output values of the respective color signals, a subtraction circuit for outputting a difference value d (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheCalculation storage means for calculating and storing, and the calculation storage means includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral difference value d (N)k (N + 1)CalculateThen, the weighting coefficients α and β are obtained based on the difference value of the integral value and the gain value of the previous frame.
[0018]
In addition, a gain value limit area is provided, and the calculation storage means limits the gain value so as not to exceed the limit area.
[0019]
In addition, the storage unit stores the weighting factors α and β as a lookup table, and the calculation storage unit reads the weighting factors α and β from the storage unit.
[0020]
An automatic white balance adjustment method according to another aspect of the invention is an automatic white balance adjustment method for a color imaging apparatus that captures a plurality of continuous images with a plurality of color filters, and each color signal in an Nth current image frame. A gain control step of adjusting the level of the color signal by the gain value k (N), an integration step of integrating the output values of the respective color signals,
A division step for outputting a ratio r (N) of integral values of two color signals each;Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheA calculation storage step for calculating and storing, and the calculation storage step includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral ratio r (N)k (N + 1)CalculateThen, the weighting coefficients α and β are obtained based on the difference value between the gain value convergence value and the gain value of the previous frame.
[0022]
In the calculation storage step, the weight coefficients α and β are set as follows.Expressed by the visual response speed to the color change for each hue or the visual discrimination sensitivity for each hueDetermine based on visual characteristics.
[0023]
An automatic white balance adjustment method for a color image pickup apparatus that includes a plurality of color filters and picks up a plurality of continuous images, wherein each color signal in an Nth current image frame is gain-adjusted by a gain value k (N). A control step, an integration step of integrating the output values of the respective color signals, a subtraction step of outputting a difference value d (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheA calculation storage step for calculating and storing, and the calculation storage step includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral difference value d (N)k (N + 1)CalculateThen, the weighting coefficients α and β are obtained based on the difference value of the integral value and the gain value of the previous frame.
[0025]
Further, a gain value limit area is provided, and the calculation storage step limits the gain value so as not to exceed the limit area.
[0026]
Furthermore, it has a memory | storage means which memorize | stores weighting coefficient (alpha) and (beta) as a look-up table, and a calculation memory | storage process reads weighting coefficient (alpha) and (beta) from a memory | storage means.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram of an automatic white balance adjusting apparatus according to the present invention. In FIG. 1, 16 is a lens for imaging a subject on an image sensor, 17 is an R, G, and B color filter, 18 is an image sensor that photoelectrically converts light from the lens, and 19 and 20 are R and B signals, respectively. A gain control circuit (gain control step) 42 that performs the gain control of the gain control unit 42 calculates a gain value input to the gain control circuit 19.
[0028]
In the gain value calculator 42, 22, 23, and 24 are integrated values Σ of the R, G, and B signals, respectively._R, Σ_G, Σ_BIs an integration circuit (integration process), 25 is Σ_GΣ for_RIs a division circuit (division process) that outputs the ratio of_GΣ for_B27 is a microcomputer as calculation storage means (calculation storage step) for calculating and storing the gain value, and 28 and 29 are D for converting the gain value from digital to analog. / A conversion circuit. The gain value calculator 42 includes these components, that is, the integration circuits 22, 23, 24, the division circuits 25, 26, the microcomputer 27, and the D / A conversion circuits 28, 29.
[0029]
Next, the operation will be described.
When an image is taken with a color image photographing device, a subject is imaged with a lens, and the imaging light transmitted through the color filter is photoelectrically converted with an image sensor. In the apparatus of FIG. 1, the light imaged by the lens 16 passes through the R, G, and B color filters 17 and is photoelectrically converted by the image sensor 18. The R, G, and B color signals output from the image sensor 18 are integrated by integrating circuits 22 to 24, respectively. Each output signal Σ of the integrating circuits 22-24_R, Σ_G, Σ_BIs input to division circuits 25 and 26, and Σ_GΣ for signal_R, Σ_BIs converted to the ratio of Then, the microcomputer 27 outputs an output signal r from the dividing circuits 25 and 26._R(= Σ_G/ Σ_R), R_B(= Σ_G/ Σ_B), The gain value k input to the gain control circuit_R, K_BCalculate
[0030]
Specifically, the microcomputer 27 uses (Equation 1) and (Equation 2) to obtain the gain value k necessary for shooting the (N + 1) th frame image._R(N + 1), k_B(N + 1) is calculated. The gain values of the R and B signals output from the microcomputer 27 are converted from digital values to analog values by the D / A circuits 28 and 19 and sent to the gain control circuits 19 and 20. The gain control circuits 19 and 20 adjust the levels of the R and B signals according to the gain value converted into the analog value.
k_R(N + 1) = α_R・ K_R(N) + β_R・ R_R(N) (Formula 1)
k_B(N + 1) = α_B・ K_B(N) + β_B・ R_B(N) (Formula 2)
However, in the above formula,
Σ_R(N), Σ_G(N), Σ_B(N): Integration value of each signal in the Nth frame
r_R(N): Σ_G(N) / Σ_R(N))
r_B(N): Σ_G(N) / Σ_B(N)
k_R(N), k_B(N): R and B signal gain values in the Nth frame
α_R, Β_R, Α_B, Β_B: Weight coefficient
It is.
[0031]
Next, the process by which the white balance adjustment converges according to the present invention will be described with reference to FIG. 2 shows k._B, K_RAre plotted on the horizontal axis and the vertical axis, respectively, and the gain values of the R and B signals are plotted.
[0032]
The gain value of each color signal is changed so that the average signal level of the R, G, and B signals in the captured image is equal to the signal level obtained when an achromatic image is captured. Therefore, when the image to be photographed is largely switched, the gain value of each signal converges in stages as shown in FIG. 2 (convergence from A to B in FIG. 2).
[0033]
When the conventional method is used, the gain value of each signal changes along a path as indicated by a dotted line in FIG. In the case of the conventional method, since the amount of increase / decrease in the gain value is always constant, the time for the white balance to converge becomes longer as the difference between the gain value before the image change and the convergence value after the change is larger. That is, the convergence time of white balance differs depending on the change in the image.
[0034]
On the other hand, when the method according to the present invention is used, the gain value changes, for example, as shown by the solid line arrow in FIG. 2 (in the coordinates of FIG. Will move to the inner dividing point).
[0035]
Thus, in the present invention, unlike the conventional method, the convergence process of the gain value is the weighting factor α._R, Β_R(Or α_B, Β_BThe white balance convergence operation can be controlled by adjusting these values.
[0036]
As described above, in the present invention, the gain control of the R and B signals is performed so that the average signal level of the R, G, and B signals of the captured image is equal to the signal level obtained when the achromatic image is captured. This relates to a white balance adjustment device. The gain value of each signal is obtained by a formula obtained by multiplying the gain value of the previous frame and the convergence value of the gain by an arbitrary weighting factor, and the white balance is adjusted by adjusting the setting value of the weighting factor. The balance convergence process can be controlled.
[0037]
By controlling the process of convergence of white balance, for example, it is possible to prevent the image observer from feeling uncomfortable with the color change. In other words, when the human visual characteristics are used, for example, when the hue is slow in response to the color change, the setting value of the weighting factor is increased to increase the change of the gain value, so that the observer does not feel uncomfortable. In addition, the gain convergence time can be increased.
[0038]
Embodiment 2. FIG.
In the first embodiment described above, the gain value k_R(N + 1), and k_BWeighting coefficient (α used in the formula of (N + 1)_R, Β_R, And α_B, Β_B) Is an arbitrary constant, but in the following embodiment, the weighting factor used in the gain value calculation formula is a function using the difference between the gain value convergence value and the gain value of the previous frame as a parameter.
[0039]
3 and 4 show the weighting coefficient α for the difference between the convergence value of the gain value and the gain value of the previous frame._R, Β_R(Alternatively, the weighting factor α for the B signal_B, Β_B).
[0040]
This embodiment will be described with an example in which the time until the white balance adjustment converges is given. When the convergence time is constant, when the change in the captured image is large, that is, when the difference between the gain value in the current frame and the gain convergence value after the image change is large, β in (Expression 1)_RIncrease α_RNeeds to be reduced (in the case of (Equation 2), β_BTo increase α_B). On the other hand, if the change in the captured image is small, β in (Equation 1)_RReduce α_RNeeds to be increased (in the case of (Equation 2), β_B, Α_BIncrease). Β_R, Α_RIf the function is as shown in FIG. 3, the convergence time can be kept substantially constant regardless of the image change.
[0041]
Further, when the weight coefficient shown in FIG. 4 is used, when the color of the entire image changes greatly, the gain value changes gradually at first, gradually changes, then changes gradually and converges again. If the weighting factor is defined as a function of the difference value between the convergence value of the gain value and the gain value of the previous frame in this way, the convergence time and convergence operation of white balance can be adjusted.
[0042]
Also, the weighting factor can be controlled in consideration of human visual characteristics. For example, the gain value of the previous frame and the convergence value of the gain are used as parameters, and the convergence of white balance is accelerated for images with poor color identification sensitivity, and the convergence is delayed for other images. By performing the control, the observer can quickly converge the white balance process without feeling unnaturalness.
[0043]
As described above, in the present embodiment, when the gain value of each signal is obtained by a calculation formula obtained by multiplying the gain value of the previous frame and the convergence value of the gain by an arbitrary weighting factor, the weighting factor is used as the gain value of the previous frame. It is possible to adjust the convergence time and convergence behavior by changing the difference between the value and the convergence value of the gain, and quickly and naturally converge the white balance processing by setting the weighting factor according to the visual characteristics. Can be made.
[0044]
Embodiment 3 FIG.
In the first and second embodiments described above, the ratio r of the integral values of the R, G, and B signals._R, R_BIs used to calculate the gain values of the R and B signals. r_R, R_BSince the calculation requires a division circuit, the scale of the arithmetic circuit becomes large and the calculation takes time. Therefore, in this embodiment, r_R, R_BInstead of the difference d between the integral value of R and the integral value of G_R(= Σ_R−Σ_G), The difference d between the integral value of B and the integral value of G_B(= Σ_B−Σ_G) Is used to approximate the convergence of the gain, and the circuit scale of the entire white balance adjusting device is reduced by replacing the divider circuit with the subtractor circuit.
[0045]
FIG. 5 is a diagram showing the configuration of the automatic white balance adjusting apparatus according to the present embodiment. 5 in FIG. 5 is an integral value Σ of R_RAnd Σ_GIs a subtracting circuit (subtracting step) for outputting a difference value of B, 31 is an integral value Σ of B_BAnd Σ_GIt is a subtraction circuit (subtraction process) which outputs the difference value.
Other configurations are the same as those of the first embodiment.
[0046]
A calculation formula for obtaining the respective gain values of the R and B signals using the difference between the integral values of the respective color signals will be described.
Rewriting (Equation 1)
k_R(N + 1) = α_R・ K_R(N) + β_R・ (Σ_R-D_R(N)) / Σ_R
k_R(N + 1) -β_R= Α_R・ K_R(N) -β_R/ Σ_R・ D_R(N) (Formula 1-2)
It can be rewritten as
[0047]
Σ in (Equation 1-2)_RIs a value that changes from frame to frame, but in order to eliminate division, this value must be a constant. Therefore, Σ in (Equation 1-2)_RThe frame average Σ_{R (avr)}And gain value is estimated. β_R/ Σ_{R (avr)}The constant β_R’And k_R(N + 1) -β_RK_RWhen replaced with '(N + 1)', (Equation 1-2) becomes the following equation.
k_R′ (N + 1) = α_R・ K_R(N) -β_R′ ・ D_R(N) (Formula 3)
Similarly, the formula for calculating the gain value of the B signal is
k_B′ (N + 1) = α_B・ K_B(N) -β_B′ ・ D_B(N) (Formula 4)
It becomes.
[0048]
If the gain is calculated using (Expression 3) and (Expression 4), a subtracting circuit can be used instead of the dividing circuit. In general, since the circuit scale of the subtraction circuit is smaller than that of the division circuit, the circuit scale of the entire white balance adjustment device can be reduced by using this embodiment.
[0049]
As described above, the gain value input to the gain control circuit for the R and B signals is approximated by the calculation formula obtained by multiplying the gain value of the previous frame and the difference value of each color signal by an arbitrary weighting factor, thereby obtaining white. The circuit scale of the white balance adjusting device capable of controlling the balance convergence process can be reduced.
[0050]
Embodiment 4 FIG.
In the above-described third embodiment, the gain value k_R'(N + 1), and k_BThe weighting coefficient (α used in the calculation formula of ′ (N + 1)_R, Β_R′ And α_B, Β_B′) Is an arbitrary constant, but in the following embodiment, the weight coefficient used in the gain value calculation formula is set to the difference value d of the integral value._RLet (N) be a function of the gain value of the previous frame.
Other configurations are the same as those of the third embodiment.
[0051]
In the present embodiment, as in the second embodiment, the weighting coefficient is changed according to the gain value of the previous frame or the convergence value of the gain to adjust the convergence operation of the white balance, and the circuit of the arithmetic circuit necessary for obtaining the gain value The purpose is to reduce the scale.
[0052]
In the second embodiment described above, the weighting coefficient is changed according to the difference value between the gain value of the previous frame and the convergence value of the gain, and the convergence value is obtained using a division circuit having a large circuit scale. In this embodiment, the approximate value of the convergence value is obtained by eliminating the division circuit in order to reduce the circuit scale necessary for calculating the gain value and using a subtraction circuit instead. Then, the convergence time and the convergence operation of the white balance processing are adjusted by changing the weighting coefficient according to the approximate gain value.
An approximate expression for the gain convergence value of the R signal is shown below.

1 / Σ of the above formula_RIs a value that changes from frame to frame, but in order to eliminate division, this value must be a constant.
[0053]
Therefore, Σ in the above formula 5_RThe frame average Σ_{R (avr)}1 / Σ_{R (avr)}Is used to approximate the gain value. Where 1 / Σ_{R (avr)}Is a constant C_RAnd
r_R(N) ≈1-C_R・ D_R(N) (Formula 5)
Thus, using (Equation 5), the convergence value of the gain can be estimated without using a divider. Further, if the multiplication on the right side of (Equation 5) is also performed using a bit shift operation, the convergence value of the gain can be estimated with a smaller circuit scale.
[0054]
Similarly, the gain convergence value of the B signal is
r_B(N) = 1-C_B・ D_B(N) (Formula 6)
These operations can be approximated by d_R, D_BIs performed by the microcomputer 27.
[0055]
In the present embodiment, the weighting factor α is used in the same manner as in the second embodiment using the convergence value of the gain obtained by (Equation 5) and (Equation 6)._R, Β_R(Or α_R, Β_R) Is changed by the difference value between the gain value of the previous frame and the approximate convergence value of the gain, the white balance convergence time and convergence operation can be adjusted.
[0056]
As described above, if the gain convergence value is approximated using a subtraction circuit, and the weighting factor used in the gain calculation formula is changed according to the difference value between the gain value of the previous frame and the approximate convergence value of the gain, white balance can be obtained. It is possible to reduce the scale of the arithmetic circuit of a device that can adjust the convergence time and convergence condition.
[0057]
Embodiment 5. FIG.
In the foregoing embodiments, the convergence operation of the gain value input to the gain control circuit for the R and B signals has been described. In the present embodiment, an excessive white balance process is prevented from being performed on the photographed image by setting a limit area such as an upper limit value and a lower limit value as a convergence condition of the gain value.
FIG. 6 shows a limit range of the gain value defined in the present embodiment.
[0058]
In the present embodiment, an upper limit and a lower limit of the gain value input to the gain control circuit for the R and B signals will be described. Usually, when photographing a subject such as a natural image, it is considered that there is no extreme difference in the integrated value of each color signal. However, for example, when shooting a person wearing red clothes, or when shooting an image under a special light source that is extremely reddish, the R signal component may be extremely large compared to other color signals. . When white balance processing is performed without limiting the gain value under such shooting conditions, the R signal is excessively suppressed, and an unnatural image in which the appearance and the color of the shot image are extremely different is shot. Therefore, an upper limit value and a lower limit value are provided for the gain values of the respective signals obtained by the calculation methods of the first to fourth embodiments described above to prevent excessive white balance processing.
[0059]
FIG. 6 is a diagram showing a gain value limit area, and the gain values of the R and B signals are set within the area surrounded by the solid line in the figure. In the present embodiment, when the gain convergence value is outside the limit region, the gain value is updated until the calculation result of the gain value exceeds the limit region, and if it exceeds, the gain value is set to a preset upper limit value or The lower limit value is output from the microcomputer. The microcomputer is set in advance so that a gain value limit region is input in advance and a gain value within the limit region is always output. Such a method prevents excessive white balance processing.
[0060]
As described above, by setting a limit range such as an upper limit value or a lower limit value for the gain values input to the gain control circuit for the R and B signals, it is possible to cause an excessively white balance process and an unnatural color in the image. To prevent the image from appearing as it looks.
[0061]
Embodiment 6
In the above-described embodiment, the method for calculating the gain value of each color signal necessary for the white balance processing by the microcomputer has been described. In this embodiment, the weighting factors necessary for calculating the gain value of each color signal are stored in a memory such as a ROM as a lookup table and read out to make all processing hardware and increase the processing speed. Plan.
[0062]
FIG. 7 is a diagram showing a configuration of the present embodiment, 32 and 33 are arithmetic circuits for performing division (or subtraction), 34 and 35 are arithmetic circuits for performing multiplication and addition necessary for calculating gain values, 37 is a difference value between the gain value of the previous frame and the convergence value (or approximate convergence value) of the gain, and a LUT (Look Up Table) indicating the relationship between the weighting factors, and 38 and 39 are the gain values of the R and B signals, respectively. It is a comparison circuit that compares the limit value and the output results of 34 and 35.
Other configurations are the same as those in FIG.
[0063]
The operation of this embodiment will be described. In the embodiments described so far, the parameters necessary for the calculation of the gain have been calculated using a hardware arithmetic circuit, but an example in which the main arithmetic is performed by a microcomputer has been described. In this embodiment, the same gain calculation formula as described in the previous embodiments is used, and all calculations such as weight coefficient calculation and gain calculation performed by the microcomputer are implemented as hardware. Do in the circuit.
[0064]
If conditions such as the convergence time of white balance are determined, the weight coefficient value for the difference value between the gain value of the previous frame and the convergence value of the gain (or the approximate convergence value) can be converted into an LUT in advance. Reference numeral 36 in FIG. 7 denotes a weighting coefficient for the difference value between the gain value of the previous frame and the gain convergence value (or approximate convergence value) as an LUT. In the LUT, weight coefficient values calculated in advance according to the convergence condition of the white balance are stored in a memory device such as a ROM so that stored data can be read out as necessary. In the LUT 36 of FIG._R(N + 1) (or d_R(N + 1)) and the gain value k of the previous frame_RThe necessary weighting coefficient corresponding to (N) is expressed as α_R, Β_RIs read out and input to the arithmetic circuit 34. Further, in the arithmetic circuit 34, the input signal is r._R(N + 1) (or d_R(N + 1)), k_R(N), weighting factor α_R, Β_RIs used to calculate (Equation 1) (or (Equation 3)), and the gain value k obtained by this circuit is calculated._R(N + 1) is output. In the comparison circuit 38, the output signal k of the arithmetic circuit 34_RA comparison is made between (N + 1) and the upper and lower limit values of the gain value. k_RIf (N + 1) is within the gain value limit range, the input signal is directly transmitted to the D / A conversion circuit 28. If the input signal is outside the gain value limit range, the upper limit value (or lower limit value) is D / A converted. Send to circuit 28. The gain value of the R signal is converted from a digital value to an analog value at 28 and sent to the gain control circuit 19. The output value whose signal level is adjusted by the gain control circuit 19 is sent to the encoder 21. Similarly to the R signal, for the B signal, a calculation necessary for obtaining the gain value input to the gain control circuit 20 is performed by the hardware circuit, and the white balance processing of the captured image is performed.
[0065]
As described above, all the arithmetic circuits associated with the white balance processing are implemented as hardware, and the weight coefficient value for the difference between the gain value of the previous frame and the convergence value of the gain is calculated in advance and stored in a memory such as a ROM as an LUT. By using it, it is possible to speed up the calculation associated with the white balance processing. Further, by using the present invention, it is possible to control the convergence time and convergence operation for white balance processing by changing the weighting factor stored in the LUT.
[0066]
【The invention's effect】
An automatic white balance adjustment device according to the present invention is an automatic white balance adjustment device of a color imaging device that includes a plurality of color filters and captures a plurality of continuous images, and each color signal in an Nth current image frame is represented by a gain value. a gain control circuit that adjusts the level by k (N), an integration circuit that integrates the output value of each color signal, and a division circuit that outputs a ratio r (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheCalculation storage means for calculating and storing, and the calculation storage means includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral ratio r (N)k (N + 1)Is calculated. The gain value of each signalPresentThe convergence process of white balance can be controlled by calculating the gain value of the frame and the convergence value of the gain by an arbitrary weighting factor and adjusting the setting value of the weighting factor. Therefore, for example, it is possible to prevent the image observer from feeling uncomfortable with the color change.
[0067]
The calculation storage means obtains the weighting factors α and β based on the difference value between the gain value convergence value and the gain value of the previous frame. By changing the weighting factor according to the difference value between the gain value of the previous frame and the convergence value of the gain, it is possible to adjust the convergence time and convergence operation, and by setting the weighting factor according to the visual characteristics, white Balance processing can be quickly and naturally converged.
[0068]
Further, the calculation storage means obtains the weighting factors α and β based on the visual characteristics. For this reason, when the human visual characteristics are used, for example, when the hue is slow in response to the color change, the weighting factor setting value is increased to increase the gain value change so that the observer does not feel uncomfortable. In addition, the gain convergence time can be increased.
[0069]
An automatic white balance adjustment device for a color image pickup device that includes a plurality of color filters and picks up a plurality of continuous images, wherein each color signal in the Nth current image frame is gain-adjusted by a gain value k (N). A control circuit, an integration circuit for integrating the output values of the respective color signals, a subtraction circuit for outputting a difference value d (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheCalculation storage means for calculating and storing, and the calculation storage means includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral difference value d (N)k (N + 1)Is calculated. Therefore, the circuit scale of the device can be reduced.
[0070]
Further, the calculation storage means obtains the weighting coefficients α and β based on the difference value of the integral value and the gain value of the previous frame. Therefore, the scale of the arithmetic circuit of the device can be reduced.
[0071]
In addition, a gain value limit area is provided, and the calculation storage means limits the gain value so as not to exceed the limit area. Therefore, it is possible to prevent the image from becoming an unnatural color due to excessive white balance processing and to capture an image similar to the appearance.
[0072]
In addition, the storage unit stores the weighting factors α and β as a lookup table, and the calculation storage unit reads the weighting factors α and β from the storage unit. For this reason, all the arithmetic circuits of the apparatus can be implemented as hardware, and the arithmetic operation associated with the white balance processing can be accelerated.
[0073]
An automatic white balance adjustment method according to another invention is an automatic white balance adjustment method for a color imaging apparatus that captures a plurality of continuous images with a plurality of color filters, and each color signal in an Nth current image frame. A gain control step of adjusting the level of the color signal by the gain value k (N), an integration step of integrating the output values of the respective color signals, and a division step of outputting a ratio r (N) of the integrated values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheA calculation storage step for calculating and storing, and the calculation storage step includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral ratio r (N)k (N + 1)Is calculated. The gain value of each signalPresentIt is possible to control the white balance convergence process by calculating the gain value of the frame and the convergence value of the gain by an arbitrary weighting factor and adjusting the setting value of the weighting factor. Therefore, for example, it is possible to prevent the image observer from feeling uncomfortable with the color change.
[0074]
In the calculation storage step, the weighting coefficients α and β are obtained based on the difference value between the convergence value of the gain value and the gain value of the previous frame. By changing the weighting factor according to the difference value between the gain value of the previous frame and the convergence value of the gain, it is possible to adjust the convergence time and convergence operation, and by setting the weighting factor according to the visual characteristics, white Balance processing can be quickly and naturally converged.
[0075]
In the calculation storage step, the weight coefficients α and β are obtained based on the visual characteristics. For this reason, when the human visual characteristics are used, for example, when the hue is slow in response to the color change, the weighting factor setting value is increased to increase the gain value change so that the observer does not feel uncomfortable. In addition, the gain convergence time can be increased.
[0076]
An automatic white balance adjustment method for a color image pickup apparatus that includes a plurality of color filters and picks up a plurality of continuous images, wherein each color signal in an Nth current image frame is gain-adjusted by a gain value k (N). A control step, an integration step of integrating the output values of the respective color signals, a subtraction step of outputting a difference value d (N) of the integration values of the two color signals,Gain value k required for capturing the (N + 1) -th frame image (N + 1) TheA calculation storage step for calculating and storing, and the calculation storage step includes an arbitrary weighting factor α andPresentFrame gain valuek (N)Gain value based on the product of an arbitrary weighting factor β and the integral difference value d (N)k (N + 1)Is calculated. Therefore, the circuit scale of the device can be reduced.
[0077]
In the calculation storage step, the weighting coefficients α and β are obtained based on the difference value of the integral value and the gain value of the previous frame. Therefore, the scale of the arithmetic circuit of the device can be reduced.
[0078]
Further, a gain value limit area is provided, and the calculation storage step limits the gain value so as not to exceed the limit area. Therefore, it is possible to prevent the image from becoming an unnatural color due to excessive white balance processing and to capture an image similar to the appearance.
[0079]
Furthermore, it has a memory | storage means which memorize | stores weighting coefficient (alpha) and (beta) as a look-up table, and a calculation memory | storage process reads weighting coefficient (alpha) and (beta) from a memory | storage means. For this reason, all the arithmetic circuits of the apparatus can be implemented as hardware, and the arithmetic operation associated with the white balance processing can be accelerated.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an automatic white balance adjusting device according to the present invention.
FIG. 2 Gain value k_B, K_RAre plotted on the horizontal axis and the vertical axis, respectively, and the gain values of the R and B signals are plotted.
FIG. 3 is a weighting factor α for the difference value between the gain convergence value and the gain value of the previous frame._R, Β_RThis is an example.
FIG. 4 is a weighting factor α for the difference between the gain value convergence value and the gain value of the previous frame._R, Β_RA further different example is shown.
FIG. 5 is a block diagram showing another example of an automatic white balance adjusting device according to the present invention.
FIG. 6 is a diagram showing a limit range of a gain value.
FIG. 7 is a block diagram showing another example of an automatic white balance adjusting device according to the present invention.
FIG. 8 is a configuration diagram of a conventional white balance adjustment device.
FIG. 9 is a flowchart showing the operation of the microcomputer (calculation storage means).
[Explanation of symbols]
19, 20 Gain control circuit (gain control step), 22, 23, 24 Integration circuit (integration step), 25, 26 Division circuit (division step), 27 Microcomputer (calculation storage means, calculation storage step), 30, 31 Subtraction circuit (subtraction process), 36, 37 Look-up table (storage means).

Claims (10)

An automatic white balance adjustment device for a color imaging device that captures a plurality of continuous images with a plurality of color filters,
A gain control circuit for adjusting the level of each color signal in the Nth current image frame by a gain value k (N);
An integration circuit for integrating the output value of each color signal;
A division circuit that outputs a ratio r (N) of integral values of two color signals,
Calculation storage means for calculating and storing a gain value k (N + 1) necessary for capturing the (N + 1) -th frame image ;
The calculation storage means is based on a product of an arbitrary weighting factor α and the gain value k (N) of the current frame plus a product of the arbitrary weighting factor β and the ratio r (N) of the integration value. A gain value k (N + 1) is calculated, and the weighting factors α and β are obtained based on the difference value between the convergence value of the gain value and the gain value of the previous frame.
An automatic white balance adjustment device characterized by that. The calculation storage means obtains the weighting factors α and β based on a visual characteristic expressed by a visual reaction speed with respect to a color change for each hue or a visual identification sensitivity for each hue.
  2. The automatic white balance adjusting apparatus according to claim 1, wherein An automatic white balance adjustment device for a color imaging device that captures a plurality of continuous images with a plurality of color filters,
  Each color signal in the Nth current image frame is represented by a gain value k. (N) A gain control circuit for adjusting the level by
  An integration circuit for integrating the output value of each color signal;
  Difference value d of integral values of two color signals for each (N) A subtraction circuit that outputs
  Gain value k required for capturing the (N + 1) -th frame image (N + 1) Calculation storage means for calculating and storing
  The calculation storage means includes an arbitrary weighting factor α and a gain value k of the current frame. (N) The difference value d between an arbitrary weighting factor β and the above integral value in the product of (N) Based on the product of (N + 1) And calculate the weighting factors α and β based on the difference value of the integral value and the gain value of the previous frame.
  An automatic white balance adjustment device characterized by that. A limit area for the gain value is provided, and the calculation storage means limits the gain value so as not to exceed the limit area.
  4. The automatic white balance adjusting device according to claim 1, wherein Storage means for storing the weighting factors α and β as a lookup table is further included, and the calculation storage device reads the weighting factors α and β from the storage device.
  5. The automatic white balance adjusting device according to claim 1, wherein An automatic white balance adjustment method for a color imaging apparatus that captures a plurality of continuous images with a plurality of color filters,
  Each color signal in the Nth current image frame is represented by a gain value k. (N) A gain control step of adjusting the level by
  An integration step of integrating the output value of each color signal;
  Ratio r of integral values of two color signals for each (N) A division process that outputs
  Gain value k required for capturing the (N + 1) -th frame image (N + 1) A calculation storage step for calculating and storing
  The calculation storage step includes an arbitrary weighting factor α and a gain value k of the current frame. (N) The ratio r between the arbitrary weighting factor β and the above integral value in the product of (N) Based on the product of (N + 1) And calculating the weighting factors α and β based on the difference between the convergence value of the gain value and the gain value of the previous frame.
  An automatic white balance adjustment method characterized by this. In the calculation storage step, the weighting factors α and β are used for the color change for each hue. Calculated based on visual characteristics expressed by visual reaction speed or visual discrimination sensitivity for each hue
  The automatic white balance adjustment method according to claim 6. An automatic white balance adjustment method for a color imaging apparatus that captures a plurality of continuous images with a plurality of color filters,
  Each color signal in the Nth current image frame is represented by a gain value k. (N) A gain control step of adjusting the level by
  An integration step of integrating the output value of each color signal;
  Difference value d of integral values of two color signals for each (N) A subtraction step for outputting
  Gain value k required for capturing the (N + 1) -th frame image (N + 1) A calculation storage step for calculating and storing
  The calculation storage step includes an arbitrary weighting factor α and a gain value k of the current frame. (N) Is a difference value d between an arbitrary weighting factor β and the above integral value. (N) Based on the product of (N + 1) And calculate the weighting factors α and β based on the difference value of the integral value and the gain value of the previous frame.
  An automatic white balance adjustment method characterized by this. A limit area for the gain value is provided, and the calculation storage step limits the gain value so as not to exceed the limit area.
  9. The automatic white balance adjusting method according to claim 6, wherein the automatic white balance is adjusted. Storage means for storing the weighting factors α and β as a lookup table is further included, and the calculation storage step reads the weighting factors α and β from the storage means.
  10. The automatic white balance adjusting method according to claim 6, wherein the automatic white balance is adjusted.

Images