JP3796450B2 - Image reading apparatus and control method thereof - Google Patents

Description

【００７３】
光量／濃度変換部（ＬＯＧ変換部） １０７はルックアップテーブルROMにより構成される。これによりR4，G4，B4の輝度信号がCO，MO，YOの濃度信号に変換される。ライン遅延メモリ108は、後述する黒文字判定部113で、R4，G4，B4信号から生成されるUCR， ＦＩＬＴＥＲ， SEN等の判定信号までのライン遅延分だけ、CO，MO，YOの画像信号を遅延させる。
【００７４】
その結果、同一画素に対するC1，M1，Y1の画像信号と黒文字判定信号はマスキングUCR回路１０９に同時に入力される。
【００７５】
マスキング及びUCR回路１０９は、入力されたY1，M1，C1の３原色信号により黒信号（Bk）を抽出する。さらに、マスキング及びUCR回路１０９は、プリンタ２１２での記録色材の色濁りを補正する演算を施して、Y2，M2，C2，Bk2の信号を各読み取り動作の度に順次、所定のビット幅（８Ｂｉｔ）で出力する。
【００７６】
主走査変倍回路１１０は、公知の補間演算により画像信号及び黒文字判定信号の主走査方向の拡大縮小処理を行なう。また、空間フィルタ処理部（出力フィルタ） １１１は、後述するように、LUT１１７からの２ＢｉｔのＦＩＬＴＥＲ信号に基づいて、エッジ強調，スムージング処理の切り換えを行なう。
【００７７】
このように処理されたM4，C4，Y4，Bk4の面順次の画像信号と、２００線／４００線の切り換え信号であるSEN信号は、上記のレーザドライバ２１２に送られる。そして、プリンタ部２００でＰＷＭによる濃度記録が行なわれる。
【００７８】
図７は、図６に示す画像信号処理部２０９における各制御信号のタイミングを示す図である。
【００７９】
図７において、ＶＳＹＮＣ信号は、副走査方向の画像有効区問信号である。これにより、論理“１”の区間において、画像読み取り（スキャン）を行なって、順次、（C）、（M）、（Y）、（Bk）の出力信号を形成する。また、VE信号は、主走査方向の画像有効区間信号である。これにより、論理“１”の区間において主走査開始位置のタイミングをとる。これは、主にライン遅延のライン計数制御に用いられる。そして、ＣＬＯＣＫ信号は画素同期信号である。これにより、“０”→“１”の立ち上がリタイミングで画像データを転送し、上記のＡ／Ｄコンバータ１０２，黒文字判定部１１３の各信号処理部に供給する。それとともに、ＣＬＯＣＫ信号はレーザドライバ２１２に画像信号、２００線／４００線の切り換え信号を伝送するのに用いられる。
【００８０】
つづいて、レンズの特性について説明する。
【００８１】
主走査方向の各位置において発光光量の均一な照明を用意して、それをＣＣＤラインイメージセンサに結像させた場合、ＣＣＤ面上での照度の分布は、中央部は明るく、端部は暗くなる。この特性はコサイン四乗則として知られている。この対策を以下のようにして行なう。
【００８２】
白色ＬＥＤを使用して以下のように構成する。なお、白色ＬＥＤは、次のようにして白色光を実現する。すなわち、ＬＥＤから発光された青色または紫外の光を蛍光体にあて波長を変換する。そして、他の光を足しあわせることで、波長４００ｎｍから７００ｎｍを含む可視光領域の波長の光を発光する。
【００８３】
図８は、ＣＣＤ結像面上の光量分布を説明する図である。
【００８４】
上述のようにレンズのコサイン四乗則対策で、発光量が主走査方向の中央に比して端部の光量を大にすることで、ＣＣＤ結像面上の入射光量分布が平坦になっていることを説明する図である。
【００８５】
本実施の形態では、後述するように、端部の光量を中央部に比して大にするため、ＰＷＭ制御を使用した。これに限るものではなく、ＬＥＤへの電流供給量を増やす等してＬＥＤへの供給電力量を増やしても構わない。
【００８６】
蛍光燈もＰＷＭ制御されているが、その制御周期は、３００μＳ程度と、主走査の走査周期と同程度である。ここで、白色ＬＥＤは、蛍光燈より木目細かい制御が可能である。半導体素子であり、１０ｎＳオーダーかそれ以上高速のオンオフ制御が可能だからである。
【００８７】
次に上述の図９は、本実施の形態のイメージスキャナ部２０１のブロック図である。８０１は画像形成装置等の操作パネルやパーソナルコンピュータ等の操作画面に相当する。本装置の各々の機能を制御するコントローラ８０２は、操作パネル８０１やパーソナルコンピュータ２２８との通信によって、装置の起動、停止、動作モードの設定をコントロールしている。ＰＷＭ制御回路１０３１は、後述する光源としての白色ＬＥＤアレイ２０５全体のオン、オフを制御する。また、ＬＥＤオン時の光量調整の制御も行なう。モータ制御部８０７は、白色ＬＥＤアレイ２０５を含んだミラー台ユニットの副走査方向の駆動を制御する。信号処理部２０９は、上述のとおりである。
【００８８】
図１０は、白色ＬＥＤアレイ２０５の構成を説明する模式図である。
【００８９】
白色ＬＥＤアレイ２０５は、それぞれＬＥＤモジュール▲１▼〜▲６▼として分割されており、それぞれのＬＥＤモジュール▲１▼〜▲６▼にはＰＷＭ制御回路１０３１により点灯、及び光量制御される。
【００９０】
図１１は、上述のＬＥＤアレイ２０５のハード的な構成を説明する図である。
【００９１】
複数のＬＥＤは、電流制限抵抗を介して、ＰＷＭ制御回路１０３１につながっており、ＰＷＭ制御回路１０３１では、図示しないコントローラ８０２等の制御手段で、各ＬＥＤのデユーティを設定される。
【００９２】
このようなハード構成をとることで、任意の配光分布が可能となる。この構成を使用して、本実施の形態では中央部に比して端部において光量を大とする。
【００９３】
図１２は、ＰＷＭ制御による配光制御の様子を説明する図である。
【００９４】
本実施の形態ではＰＷＭ制御の周期を１０μＳとして、光量が多く必要な端部では、輝度を上げる、そのため、端部に供給する電流のデューティ比を大にする。一方、光量が相対的に小でよい、中央部では輝度を下げる。そのため中央部に供給するデユーティ比を小とする。
【００９５】
この制御は、相対的な制御で足りる。すなわち、端部が中央部に対して相対的に光量が大きくなるように制御しても構わない。あるいは、端部が中央部に対して相対的に光量が小さくなるように制御しても構わない。
【００９６】
図１３は、本実施の形態における白色ＬＥＤの構造図である。
【００９７】
青または紫外の発光を、光源ＬＥＤ１０５１にて発光させ、それを、蛍光体１０５２にて、黄色などほかの波長の光に変換する。複数の波長の光を足しあわせることで白色に発光させている。
【００９８】
図１４は、本実施の形態における白色ＬＥＤの分光特性を示す図である。
【００９９】
短波長側、青のピークが光源ＬＥＤ１０５１によるものであり、右側の緑から赤のブロードの部分が蛍光体１０５２により青から変換された光である。
【０１００】
蛍光体の発光効率は、蛍光体による発光量は変化してしまう。蛍光体による変換をする前の光の波長によって変動するため、微妙に、光源波長が異なるからである。そのため、色調が白色ＬＥＤごとにばらついたものができてしまうことになる。具体的には、純白、黄色がかった白、青色がかった白などである。この差は目視で了解し得るため無視できないことは上述したとおりである。
【０１０１】
そこで、下記のように、ＬＥＤについて（同一品種の白色ＬＥＤでも）、いくつかの段階に色調のランクごとに分けるようにする。
【０１０２】
図１５は、CIE（ＸＹＺ系色度座標）である。
【０１０３】
この図では、色度図上で３つのランクａ，ｂ，ｃにわかれている。ここで、上述の色調のばらつきはまったくランダムにばらつくわけではなく、ＸＹＺ系色度座標上で、右上がりの直線を引くとそれの上におよそ乗るような形で分散する。
【０１０４】
しかし、この白色ＬＥＤの色調ばらつきをまったく勘案しないでカラー画像読み取りを行った場合、▲１▼主走査方向に、色調ばらつきが発生する。また、▲２▼ＬＥＤ照明モジュールごとにも色調ばらつきが発生するため、カラー読み取り品質が劣化ししまう問題を発生する。
【０１０５】
本発明の実施の形態では、次のように構成することでかかる問題を解決する。
【０１０６】
前記ＬＥＤ光源モジュール２０５は、ＬＥＤの同一の色調ランクのＬＥＤから構成されるようにする。本実施の形態では、測色計で色度XYZ値を測り、ＸＹＺ系色度座標１０４にしたがって、ＬＥＤをランク分けする。ここで本実施の形態では、３つのランクに分けている。なお、より高精度には、このランク数を増やすことで対応が可能である。
【０１０７】
＜同一のランクのＬＥＤのみで、光源モジュール形成＞
ここで、たとえば、上述のようにランク分けし、同一のランクのＬＥＤのみで、光源モジュールを形成するとする。
【０１０８】
同一のランクのＬＥＤのみで、ひとつの光源モジュールを作成するメリットは、読み取った画像の色調のばらつきを抑制することである。より詳しくは、主走査方向に、さまざまな色調のＬＥＤがばらばらに配置された状態で読み取った場合、主走査方向に読み取った画像の色調がかなり違ってきてしまうという問題を回避することができる。すなわち、同一ランクのＬＥＤでのみ、光源モジュールが作成されており、主走査方向の色調のばらつきは回避できる。
【０１０９】
この場合、白色ＬＥＤ２０５を構成する複数の光源モジュール間で比較すると、モジュール間で色調が異なってしまうため、白色ＬＥＤアレイ２０５全体で色調のばらつきが発生する。上述のように、ほかの色調ランクのＬＥＤを使用しないという選択もあるが、それでは、歩留まりも悪く、高価になってしまう。
【０１１０】
＜ランクにより色演算手段のパラメータを換える＞
そこで、本実施の形態では、いろいろな色調ランクのＬＥＤを使用したうえで、次のように構成する。
【０１１１】
使用する白色ＬＥＤ光源モジュールの色調ランクの設定手段、前記色調ランクにしたがって、前記マトリックス色演算手段のパラメータを切り換える制御手段とを持つのである。
【０１１２】
図１６は、本実施の形態におけるランク分けを説明するフローチャートである。以下の処理は、コントローラ８０２による制御のもとの動作である。
【０１１３】
まず、使用する光源モジュールの色調ランクとして、操作パネル８０１等からの色調ランク信号を受信する（ステップＳ１０１）。なお、本実施の形態では、オペレータによる設定としたが、光源モジュールに、ランク情報を磁気的、電気的、光学的にもたせて、セッティング時、自動的に設定する手段をもつことにより、オペレータの煩雑な作業を回避することができる。
【０１１４】
次にこの色調ランクの設定情報にもとづいて、色演算手段でその差異を除去する。まず、受信した色調ランクの設定情報にもとづいて、対応する入力マスキング部１０６の係数を選択する（ステップＳ１０２）。選択された係数を入力マスキング係数として切り換える（ステップｓ１０３）。本実施の形態では、入カマスキング部１０６の係数をそれぞれに応じて、ランク分けに対応する適切なものに切り換える。このマスキング係数を使用して、上述したような演算処理を行なう（ステップＳ１０４）。
【０１１５】
本実施の形態では、ＬＥＤ光源モジュールの色調ランクがどれであっても、ＮＴＳＣ （National Television Standards Committee）の標準色空間に変換できるように、３×３のマスキング係数を設計する。上述した次式のようなマトリックス演算を行なう。
【０１１６】
【外２】

【０１１７】
なお、本実施の形態では、３×３の一次の項までのマトリクス演算であるが、より次数をあげ、例えば、二次の項まで含めたマトリクスとすればより精度が上げられる。
【０１１８】
また、３次元ルックアップテーブルによる、色空間のダイレクトマッピングを使用すれば、より良い。
【０１１９】
ここで、NTSC色空間でRGBを出力するのは、本実施の形態の、プリンタへのRGB−CMYK変換手段の入力フォーマットがNTSC相当の色空間を想定しているためである。
【０１２０】
以上説明したような本実施形態により、カラー画像読取装置の光源に白色ＬＥＤ照明モジュールを使用するとき、ＬＥＤの色調ばらつきによる、読み取り画像の品質劣化を抑制する。また、同一色調ランクのＬＥＤを使用することで、同一モジュールでの主走査方向の色調ばらつきが抑制できる。さらに、複数の色調ランクのＬＥＤ照明モジュールを使用する場合でも、その色調ランクを設定することにより、色演算手段でその差異を吸収することができ、複数のどの照明モジュールでも、同じ色調にカラー原稿画像を読み取ることができる。
【０１２１】
＜主走査位置によってマスキング係数を変える＞
同一ランクの白色ＬＥＤを使用した場合であっても、歩留まりの関係でランクの分別規格を緩めた場合など、若干の白レベル色調ばらつきが発生する場合がある。その場合でも、以下の構成をとることで、よりよいカラー読取を行なうことができる。
【０１２２】
また、別のランクの白色ＬＥＤを混在させた場合でも、ＬＥＤの色調ばらつきによる品質劣化を抑制する効果を狙うこともできる。この場合はランクわけをしなくてもすむこともできるため、コストダウンも狙えるだろう。
【０１２３】
図１７は、主走査位置によってマスキング係数を変えることのできる構成を説明する図である。
【０１２４】
あらかじめ、ターゲットの白色ＬＥＤアレイ２０５を使用して、管理された標準白色板２１１を読み取ることにより、主走査の位置による色の変化を測定する。これによって主走査方向の位置による光源の色調特性の変化を画素単位で測定することができる。こうして得られた、光源の主走査位置による画素単位の色調変化に対して、主走査位置に応じた画素単位の適切なマスキング係数を求める。
【０１２５】
次に上述の求めたマスキング係数を、白色ＬＥＤアレイ２０５のユニークなデータとして、この白色ＬＥＤアレイ２０５を搭載した画像読取装置に与える。すなわち、上述のこの与えられた１ラインの中の主走査位置に応じたマスキング係数は、図１７のマスキング係数記憶部１０６３に記憶される。
【０１２６】
主走査位置判別部１０６４には、主走査同期信号ＨＳＹＮＣと、画素クロックＣＬＫが入力され、画像読み取りの際に、現在どの主走査位置の情報が処理されているかを示す主走査位置情報がふくまれる情報が出力される。
【０１２７】
マスキング係数を選択するロード部１０６２では、前記主走査位置情報に応じて、マスキング係数記憶部１０６３から、現在処理する主走査位置に応じた画素単位のマスキング係数を読み出し、マスキング演算部1061に入力する。マスキング演算部では、先に説明してある、３×３のマトリクス演算を画素単位で行なう。
【０１２８】
ここで、上記説明では画素単位でマスキング係数を演算する構成を説明した。一方、主走査位置に応じたマスキング係数は、全画素分用意する構成ではなくてもよいことは、＜ランクにより色演算手段のパラメータを換える＞で説明した。すなわち、例えば、図１０で説明したＬＥＤモジュール▲１▼〜▲６▼単位で主走査位置に６箇所の代表点の値だけを記憶させる構成も有効である。これは、代表点と代表点の間の点は図示しないマスキング係数演算部による演算にて補間して求める方法をとることも可能であることを意味する。この場合、ＬＥＤモジュール▲１▼〜▲６▼単位で、相当のランク分けを行ない、ＬＥＤモジュール▲１▼〜▲６▼のそれぞれに対応したマスキング係数を取得するよう標準白色板２１１を読み取ることにより構成を簡単にできる。
【０１２９】
以上の本実施例の構成手順にて、白色ＬＥＤアレイ２０５に実装された白色ＬＥＤチップそれぞれの色調が完全には一致しない場合においても精密なカラー品質で画像を読み取ることができる。また、主走査位置に応じてマスキング係数を変える処理を行なうことにより、ＬＥＤ光源の色調ばらつきによる画像品質劣化を好適に抑制することができる効果がある。
【０１３０】
＜他の実施の形態＞
なお、上記第１乃至第３の実施形態では、外部ＰＣ８０９とはＳＣＳＩにより接続しているが、本発明はこれに限るものではなく、他の公知の規格のものを用いてもよいことは言うまでもない。
【０１３１】
また、本発明は、複数の機器（例えばホストコンピュータ、インターフェイス機器、スキャナなど）から構成されるシステムに適用しても、一つの機器からなる装置（例えば、複写機、ファクシミリ装置など）に適用してもよい。
【０１３２】
また、本発明の目的は、前述した実施形態の機能を実現するソフトウェアのプログラムコードを記録した記憶媒体（または記録媒体）を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読み出し実行することによっても、達成されることは言うまでもない。この場合、記憶媒体から読み出されたプログラムコード自体が前述した実施形態の機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているオペレーティングシステム（ＯＳ）などが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。ここでプログラムコードを記憶する記憶媒体としては、例えば、フロッピーディスク、ハードディスク、ＲＯＭ、ＲＡＭ、磁気テープ、不揮発性のメモリカード、ＣＤ−ＲＯＭ、ＣＤ−Ｒ、ＤＶＤ、光ディスク、光磁気ディスク、ＭＯなどが考えられる。
【０１３３】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるャｃ鰍ノ書込まれた後、そのプログラムコードの指示に基づき、その機能拡張カードや機能拡張ユニットに備わるＣＰＵなどが実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【０１３４】
本発明を上記記憶媒体に適用する場合、その記憶媒体には、先に説明した図１６に示すフローチャートに対応するプログラムコードが格納されることになる。
【０１３５】
【発明の効果】
以上説明したように、本発明の好適な実施例によれば、照明手段に色調ばらつきが発生する画像読み取りを行った場合においても、読み取り品質の劣化を軽減することができるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施例に係る画像形成装置の断面構成を示す図である。
【図２】ＣＣＤの外観構成を示す図である。
【図３】フォトセンサの断面図である。
【図４】フォトセンサの拡大図である。
【図５】プリンタ部での濃度再現の制御動作のタイミングチャートを示すである。
【図６】イメージスキャナ部の信号処理部における画像信号の流れを示すブロック図である。
【図７】信号処理部における各制御信号のタイミングを示す図である。
【図８】白色ＬＥＤ照明モジュールの主走査位置における発光量と、ＣＣＤ面上における照度を説明する図である。
【図９】イメージスキャナ部の構成を示すブロック図である。
【図１０】白色ＬＥＤの構成を示す図である。
【図１１】ＬＥＤ列を形成した白色ＬＥＤ照明モジュールを説明する図である。
【図１２】ＬＥＤのＰＷＭ制御を説明する図である。
【図１３】ＬＥＤの構造を説明する図である。
【図１４】白色ＬＥＤの分光特性を説明する図である。
【図１５】白色ＬＥＤの色調ランクを色度図上で説明する図である。
【図１６】ランクわけに関するフローチャートである。
【図１７】入力マスキング部の詳細を説明する図である。
【符号の説明】
２００ プリンタ部
２０１ イメージスキャナ部
２０２ 原稿圧板
２０３ 原稿台ガラス（プラテン）
２０４ 原稿
２０５ 白色ＬＥＤアレイ
２０６、２０７ ミラー
２０８ レンズ
２１０３ ラインセンサ
２１１ 標準白色板
２１０１，２１０２，２１０３ Ｒ，Ｇ，Ｂセンサ
２１２ レーザドライバ
２１３ 半導体レーザ
２１４ ポリゴンミラー
２１５ ｆ−θレンズ
２１６ ミラー
２１７ 感光ドラム
２１９ マゼンダ現像器
２２０ シアン現像器
２２１ イエロー現像器
２２２ ブラック現像器
２２３ 転写ドラム
２２４，２２５ 用紙カセット
２２６ 定着ユニット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus having a plurality of light sources having different color tones.
[0002]
[Prior art]
White light as a light source in the image reading apparatus is realized by adding a plurality of lights. Specifically, among a plurality of LEDs, blue or ultraviolet electromagnetic waves (hereinafter referred to as light) from a predetermined LED light source are converted into light of other wavelengths such as yellow by passing through a phosphor. White light is realized by adding together with the light. Here, since the light emission efficiency of the phosphor varies depending on the wavelength of the light source, if the light source wavelength is slightly different, the amount of light emitted by the phosphor varies accordingly. It also varies depending on the amount of phosphor. For this reason, the color tone varies for each white LED. As used herein, the color tone refers to the color composition, tone, intensity, etc. Specifically, pure white, yellowish white, blueish white and the like. This difference cannot be ignored because it can be understood visually.
[0003]
[Problems to be solved by the invention]
Therefore, when image reading is performed without taking into account the color tone variation of the light source, color tone variation occurs, and color tone variation also occurs for each light source module as an illuminating unit.
[0004]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems, and the image reading apparatus according to claim 1 has a plurality of white light sources having different color tone characteristics of irradiation light arranged in the main scanning direction of the photoelectric conversion means. Irradiation means, photoelectric conversion means for reading a subject image irradiated by the irradiation means and outputting an image signal, color space conversion means for converting a color space of the image signal based on a matrix coefficient, and the color space conversion means Comprises coefficient setting means for setting a matrix coefficient used for conversion of the color space of the image signal in accordance with a main scanning position based on a color tone characteristic of the white light source.
[0010]
According to a fourth aspect of the present invention, there is provided a control method comprising: irradiating means in which a plurality of white light sources having different tone characteristics of irradiated light are arranged in the main scanning direction of the photoelectric conversion means; A method for controlling an image reading apparatus having a photoelectric conversion means for outputting, a coefficient setting step for setting a matrix coefficient according to a main scanning position based on a color tone characteristic of the plurality of white light sources, and a setting in the coefficient setting step And a color space conversion step of converting the color space of the image signal based on the matrix coefficient.
[0017]
The image reading apparatus according to claim 7, an irradiation unit in which a plurality of white light sources having different color tone characteristics of irradiation light are arranged, a photoelectric conversion unit that reads a subject image irradiated by the irradiation unit and outputs an image signal; Corresponding to the color space conversion means for converting the color space of the image signal, the setting means for setting the color tone characteristics of the white light source according to the input operation by the operator, and the color tone characteristics of the white light source set by the setting means Control means for controlling the color space conversion means to convert the color space of the image signal based on the matrix coefficient.
[0021]
The control method according to claim 10 is an image having irradiation means in which a plurality of white light sources having different color characteristics of irradiation light are arranged, and photoelectric conversion means for reading a subject image irradiated by the irradiation means and outputting an image signal. A method for controlling a reading apparatus, wherein a setting step of setting a color tone characteristic of the white light source according to an input operation by an operator, and a matrix coefficient corresponding to the color tone characteristic of the white light source set in the setting step And a color space conversion step for converting the color space of the image signal.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the entire color copying machine as an image forming apparatus as an image reading apparatus used in the present embodiment will be described.
[0028]
FIG. 1 is a diagram illustrating a cross-sectional configuration of an image forming apparatus according to an embodiment of the present invention.
[0029]
In FIG. 1, reference numeral 201 denotes an image scanner unit, which reads a document and performs digital signal processing. Reference numeral 200 denotes a printer unit, which prints out an image corresponding to an original image read by the image scanner unit 201 in full color on a sheet.
[0030]
In the image scanner unit 201, a document 204 placed on a document table glass (platen) 203 is irradiated with light from the LED module 205 by a document pressure plate 202. The reflected light from the original 204 is guided to mirrors 206 and 207, and an image is formed on a three-line sensor (hereinafter referred to as CCD) 210 by a lens 208. The lens 208 is provided with an infrared cut filter 281.
[0031]
The CCD 210 color-separates the light information from the original 204 and, after reading the red (R), green (G), and blue (B) components of the full color information, sends them to the signal processing unit 209. Each color component reading resensor array of the CCD 210 is composed of 5000 pixels. As a result, the shortest direction 297 mm of the A3 size document, which is the maximum size among the documents placed on the platen glass 203, is read at a resolution of 400 dpi.
[0032]
The white LED array 205 and the mirror 206 are at a speed V, and the mirror 207 is at a speed of (1/2) V and perpendicular to the electrical scanning direction of the line sensor 210 (hereinafter referred to as the main scanning direction). The entire surface of the original 204 is scanned by mechanically moving in a direction (hereinafter referred to as a sub-scanning direction). The required light sources are firstly high luminous efficiency and low power consumption, secondly, the amount of light emission can be changed depending on the position in the main scanning direction, and thirdly, a white light source. A white LED array can be considered as the light source. That is, a plurality of white LEDs are arranged in the main scanning direction to illuminate the entire main scanning area. At this time, in order to make the end portion brighter than the center portion, for example, (1) the density of the light-emitting elements is made denser than the center. (2) The current flowing through the light emitting element is made larger at the peripheral part than at the center. (3) The duty of the peripheral part is made larger than the center by PWM control. Such a method can be considered.
[0033]
The reason why the LED is used as the light source in this embodiment is as follows.
[0034]
In some cases, a halogen lamp, a fluorescent lamp, a xenon lamp, or the like is used as a reading light source for a copying machine, a fax machine, or the like that uses a CCD linear image sensor for reading.
[0035]
A reduction optical system is assembled with a lens. For example, an original of A4 length and main scanning of 297 mm is formed with a lens on a CCD surface having a pixel size of 10 microns, 5000 elements, that is, a 50 mm long CCD surface. Here, due to the characteristics of the lens such as the cosine fourth law, there is a characteristic that the central portion of the main scanning is bright and has a large amount of light, and the dark portion of the main scanning end is dark and has a small amount of light. This directly degrades the S / N of the main scanning end signal of the CCD output signal.
[0036]
In the case of a halogen lamp, the number and position of the light emitting filaments and the number of filament windings can be made relatively free. Therefore, as the end portion is approached, the number of windings of the filament is increased so as to emit light brightly, thereby addressing the above-described problem.
[0037]
From the viewpoint of power consumption, fluorescent lamps and xenon lamps are more advantageous than halogen lamps. Fluorescent lamps and xenon lamps have relatively high luminous efficiency and can be said to be desirable light sources from the viewpoint of environmental considerations. However, the amount of light emission cannot be changed depending on the location in the main scanning direction by adjusting the number of windings of the filament as in the case of a halogen lamp.
[0038]
When performing color reading of an image reading apparatus with a copying machine, a color 3-line CCD image sensor may be used as a reading element. For example, three photodiode element arrays having an interval four times the main scanning pixel pitch are formed in parallel, and RGB color filters are formed in each element array.
[0039]
In this case, the light source for illuminating the document must be a so-called white light source including light having a plurality of wavelengths of 400 to 700 nm.
[0040]
Here, the merit of using the white LED, whose luminous efficiency and luminous luminance are remarkably improved, becomes clear.
[0041]
The standard white plate 211 is a white plate as a reference member for correcting non-uniformity in image reading by the three-line sensor 210 and the lens 208 as the photoelectric conversion means. By reading an image of the standard white plate 211 illuminated by the LED module 205, correction data of read data by the R, G, B sensors 2101, 2102 and 2103 is generated. The standard white plate 211 exhibits a substantially uniform reflection characteristic with visible light, and has a white color when visible. Here, the output data from the R, G, B sensors 2101, 2102, 2103 is corrected using the standard white plate 211.
[0042]
The signal processing unit 209 electrically processes the read signal and decomposes it into magenta (M), cyan (C), yellow (Y), and black (Bk) components, which are then converted into a printer unit. Send to 200. In addition, one component of M, C, Y, and Bk is sent to the printer unit 200 for one document scan (scan) in the image scanner unit 201, and one sheet is printed by a total of four document scans. Out is completed.
[0043]
In the printer unit 200, the M, C, Y, and Bk image signals from the image scanner unit 201 are sent to the laser driver 212. The laser driver 212 modulates and drives the semiconductor laser 213 according to the image signal. Then, the laser beam scans on the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216.
[0044]
The developing unit includes a magenta developing unit 219, a cyan developing unit 220, a yellow developing unit 221, and a black developing unit 222. These four developing units are alternately in contact with the photosensitive drum 217 and formed on the photosensitive drum 217. Develop the electrostatic latent image of M, C, Y, Bk with the corresponding toner. The transfer drum 223 winds the paper fed from the paper cassette 224 or the paper cassette 225 around the transfer drum 223, and transfers the toner image developed on the photosensitive drum 217 onto the paper.
[0045]
In this manner, after the toner images for the four colors M, C, Y, and Bk are sequentially transferred, the sheet passes through the fixing unit 226 and is discharged.
[0046]
Next, the image scanner unit 201 according to the present embodiment will be described in detail.
[0047]
FIG. 2 is a diagram showing an external configuration of the CCD 210.
[0048]
In FIG. 2, 2101 is a light receiving element array (photosensor) for reading red light (R), and 2102 and 2103 are for reading the wavelength components of green light (G) and blue light (B) in this order. This is a light receiving element array.
[0049]
Each of the R, G, and B sensors 2101, 1022, and 2103 has an opening of 10 μm in the main scanning direction and the sub-scanning direction.
[0050]
The three light receiving element arrays having different optical characteristics have a monolithic structure on the same silicon chip as follows. That is, the R, G, and B sensors are arranged in parallel to each other so as to read the same line of the document.
[0051]
By using the CCD 210 having such a configuration, an optical system such as the lens 208 in each color separation reading is made common. This makes it possible to simplify optical adjustment for each of R, G, and B colors.
[0052]
FIG. 3 is a cross-sectional view of the photosensor.
[0053]
As shown in FIG. 3, a photosensor 2101 for reading R color and photosensors 2102 and 2103 for reading visible information of G and B are arranged on a silicon substrate 2105.
[0054]
On the R-color photosensor 2101, an R filter 2107 that transmits an R-color wavelength component of visible light is disposed. Similarly, a G filter 2108 is disposed on the G color photosensor 2102, and a B filter 2109 is disposed on the B color photosensor 2103. Reference numeral 2106 denotes a planarization layer made of a transparent organic film.
[0055]
FIG. 4 is an enlarged view of the photosensors 2101, 2102 and 2103 indicated by the symbol B in FIG.
[0056]
As shown in FIG. 4, each of the sensors has a length of 10 μm per pixel in the main scanning direction. Each sensor has 5000 pixels in the main scanning direction. This is to make it possible to read in the lateral direction (length 297 mm) of an A3 size document with a resolution of 400 dpi as described above. The distance between the lines of the R, G, B sensors is 80 μm. Therefore, each line is separated by 8 lines with respect to the resolution in the sub-scanning direction of 400 dpi.
[0057]
Next, a density reproduction method in the printer unit of the image processing apparatus according to the present embodiment will be described.
[0058]
In this embodiment, in order to reproduce the density of the printer, the lighting time of the semiconductor laser 213 is controlled according to the image density signal by a PWM (Pulse Width Modulation) method. As a result, an electrostatic latent image having a potential corresponding to the laser lighting time is formed on the photosensitive drum 217. Then, the developing devices 219 to 222 develop the latent image with toner in an amount corresponding to the potential of the electrostatic latent image, thereby reproducing the density.
[0059]
FIG. 5 is a timing chart showing the density reproduction control operation in the printer unit according to this embodiment.
[0060]
Signal 10201 is the printer pixel clock. This corresponds to a resolution of 400 dpi. This clock is generated by the laser driver 212. In addition, a 400-line triangular wave 10202 is generated in synchronization with the printer pixel clock 10201. Note that the period of the 400-line triangular wave 10202 is the same as the period of the pixel clock 10201.
[0061]
Image data processing unit 209 transmits M, C, Y, Bk image data of 256 gradations (8 bits) at a resolution of 400 dpi and a 200/400 line switching signal in synchronization with the printer pixel clock signal 10201 described above. The The laser driver 212 synchronizes with the printer pixel clock 10201 by a FIFO memory (not shown). This 8-bit digital image data is converted into an analog image signal 10203 by a D / A converter (not shown). Then, it is compared with the above-described 400-line triangular wave 10202 in an analog manner, and as a result, a 400-line PWM output 10204 is generated.
[0062]
The 8-bit digital pixel data changes from 00H (H indicates a hexadecimal number) to FFH, and the 400-line PWM output 10204 has a pulse width corresponding to these values. One cycle of the 400-line PWM output is 63.5 μm on the photosensitive drum.
[0063]
In addition to the 400-line triangular wave, the laser driver 212 also generates a 200-line triangular wave 10205 having a period twice that of the 400-line triangular wave in synchronization with the printer pixel clock 10201. Then, the 200-line PWM output signal 10206 is generated by comparing the 200-line triangular wave 10205 and the 400 dpi analog image signal 10203. As shown in FIG. 5, the 200-line PWM output signal 10206 forms a latent image on the photosensitive drum with a period of 127 μm.
[0064]
In the density reproduction with 200 lines and the density reproduction with 400 lines, the gradation reproduction with 200 lines is better. This is because the minimum unit for density reproduction is 127 μm, which is twice the 400 lines. However, in terms of resolution, 400 lines that reproduce the density in units of 63.5 μm are suitable for high-resolution image recording. Thus, the 200-line PWM recording is excellent in gradation reproduction, while the 400-line PWM recording is excellent in terms of resolution. Therefore, switching between 200-line PWM and 400-line PWM is performed according to the nature of the image.
[0065]
A signal for performing the above switching is a 200-line / 400-line switching signal 10207 shown in FIG. From the image signal processing unit 209, the image signal is input to the laser driver 212 in units of pixels in synchronization with the 400 dpi image signal. When the 200-line / 400-line switching signal is logic low (hereinafter referred to as L level), the 400-line PWM output is selected. On the other hand, in the case of logic high (hereinafter referred to as H level), the 200-line PWM output is selected.
[0066]
Next, the image signal processing unit 209 will be described.
[0067]
FIG. 6 is a block diagram illustrating the flow of image signals in the image signal processing unit 209 of the image scanner unit 201 according to the present embodiment.
[0068]
As shown in FIG. 6, the image signal output from the CCD 210 is input to the analog signal processing circuit 101. Therefore, gain adjustment and offset adjustment are performed. The A / D converter 102 converts each color signal into 8-bit digital image signals R1, G1, and B1. Thereafter, the data is input to the shading correction unit 103. Therefore, a known shading correction using the read signal of the standard white plate 211 is performed for each color.
[0069]
The clock generator 121 generates a clock for each pixel. The main scanning address counter 122 counts the clocks from the clock generator 121 and generates a one-line pixel address output. Then, the decoder 123 decodes the main scanning address from the main scanning address counter 122. As a result, a line-unit CCD drive signal such as a shift pulse and a reset pulse, a VE signal representing a valid area in one line read signal from the CCD, and a line synchronization signal HSYNC * are generated. The main scanning address counter 122 is cleared by the HSYNC * signal and starts counting the main scanning address of the next line.
[0070]
As shown in FIG. 2, the light receiving sections 2101, 2102 and 2103 of the CCD 210 correct the spatial deviation in the sub-scanning direction in the line delay circuits 104 and 105 of FIG. This is because the light receiving units 2101, 1022, and 210 are arranged at a predetermined distance from each other. Specifically, the R and G signals are line-delayed in the sub-scanning direction in the sub-scanning direction with respect to the B signal, and are adjusted to the B signal.
[0071]
The input masking unit 106 is a part that converts the read color space determined by the spectral characteristics of the R, G, and B filters 2107, 2108, and 2109 of the CCD 210 into the NTSC standard color space. This performs a matrix operation as shown in the following equation.
[0072]
[Outside 1]

[0073]
The light quantity / density conversion unit (LOG conversion unit) 107 is configured by a lookup table ROM. As a result, the luminance signals of R4, G4, and B4 are converted into density signals of CO, MO, and YO. The line delay memory 108 delays the image signals of CO, MO, and YO by a black character determination unit 113 (to be described later) by the line delay until the determination signals such as UCR, FILTER, and SEN generated from the R4, G4, and B4 signals. Let
[0074]
As a result, the C1, M1, and Y1 image signals and the black character determination signal for the same pixel are simultaneously input to the masking UCR circuit 109.
[0075]
The masking and UCR circuit 109 extracts a black signal (Bk) from the input three primary color signals Y1, M1, and C1. Further, the masking and UCR circuit 109 performs an operation for correcting the color turbidity of the recording color material in the printer 212, and sequentially converts the signals Y2, M2, C2, and Bk2 to a predetermined bit width ( 8bit).
[0076]
The main scanning scaling circuit 110 performs enlargement / reduction processing of the image signal and the black character determination signal in the main scanning direction by a known interpolation calculation. Further, the spatial filter processing unit (output filter) 111 performs switching between edge enhancement and smoothing processing based on a 2-bit FILTER signal from the LUT 117, as will be described later.
[0077]
The M4, C4, Y4, and Bk4 frame sequential image signals processed in this way and the SEN signal that is a switching signal for 200 lines / 400 lines are sent to the laser driver 212 described above. The printer unit 200 performs density recording by PWM.
[0078]
FIG. 7 is a diagram showing the timing of each control signal in the image signal processing unit 209 shown in FIG.
[0079]
In FIG. 7, a VSYNC signal is an image effective interval signal in the sub-scanning direction. As a result, image reading (scanning) is performed in the logical “1” section, and output signals (C), (M), (Y), and (Bk) are sequentially formed. The VE signal is an image effective section signal in the main scanning direction. Thus, the timing of the main scanning start position is taken in the logical “1” section. This is mainly used for line count control of line delay. The CLOCK signal is a pixel synchronization signal. As a result, the image data is transferred at re-timing when “0” → “1” rises, and is supplied to the signal processing units of the A / D converter 102 and the black character determination unit 113. At the same time, the CLOCK signal is used to transmit an image signal and a 200-line / 400-line switching signal to the laser driver 212.
[0080]
Next, lens characteristics will be described.
[0081]
When illumination with a uniform amount of emitted light is prepared at each position in the main scanning direction and imaged on a CCD line image sensor, the distribution of illuminance on the CCD surface is bright at the center and dark at the edges. Become. This property is known as the cosine fourth law. This countermeasure is performed as follows.
[0082]
The white LED is used as follows. In addition, white LED implement | achieves white light as follows. That is, the wavelength is converted by applying blue or ultraviolet light emitted from the LED to the phosphor. Then, by adding other lights, light having a wavelength in the visible light region including wavelengths from 400 nm to 700 nm is emitted.
[0083]
FIG. 8 is a diagram for explaining the light amount distribution on the CCD image plane.
[0084]
As described above, as a countermeasure against the cosine fourth law of the lens, the light intensity at the end is larger than that at the center in the main scanning direction, so that the distribution of the incident light quantity on the CCD imaging surface becomes flat. FIG.
[0085]
In this embodiment, as will be described later, PWM control is used in order to increase the amount of light at the end compared to the center. The present invention is not limited to this, and the amount of power supplied to the LED may be increased by increasing the amount of current supplied to the LED.
[0086]
Although the fluorescent lamp is also PWM-controlled, its control cycle is about 300 μS, which is about the same as the scanning cycle of main scanning. Here, the white LED can be controlled more finely than the fluorescent lamp. This is because it is a semiconductor element and can be turned on and off at a high speed on the order of 10 nS or more.
[0087]
Next, FIG. 9 described above is a block diagram of the image scanner unit 201 of the present embodiment. Reference numeral 801 corresponds to an operation panel such as an image forming apparatus or an operation screen such as a personal computer. A controller 802 that controls each function of the apparatus controls the start, stop, and operation mode setting of the apparatus through communication with the operation panel 801 and the personal computer 228. The PWM control circuit 1031 controls on and off of the entire white LED array 205 as a light source to be described later. It also controls light amount adjustment when the LED is on. The motor control unit 807 controls driving of the mirror base unit including the white LED array 205 in the sub-scanning direction. The signal processing unit 209 is as described above.
[0088]
FIG. 10 is a schematic diagram illustrating the configuration of the white LED array 205.
[0089]
The white LED array 205 is divided into LED modules {circle around (1)} to {circle around (6)}, and each of the LED modules {circle around (1)} to {circle around (6)} is turned on and the amount of light is controlled by the PWM control circuit 1031.
[0090]
FIG. 11 is a diagram illustrating a hardware configuration of the LED array 205 described above.
[0091]
The plurality of LEDs are connected to the PWM control circuit 1031 via a current limiting resistor. In the PWM control circuit 1031, the duty of each LED is set by control means such as a controller 802 (not shown).
[0092]
By adopting such a hardware configuration, an arbitrary light distribution can be achieved. By using this configuration, the amount of light at the end portion is larger than that at the center portion in this embodiment.
[0093]
FIG. 12 is a diagram for explaining a state of light distribution control by PWM control.
[0094]
In this embodiment, the PWM control cycle is set to 10 μS, and the luminance is increased at the end portion where a large amount of light is required. Therefore, the duty ratio of the current supplied to the end portion is increased. On the other hand, the luminance is lowered at the central portion where the amount of light may be relatively small. For this reason, the duty ratio supplied to the central portion is made small.
[0095]
For this control, relative control is sufficient. That is, the end portion may be controlled so that the amount of light is relatively large with respect to the central portion. Or you may control so that an edge part may become relatively small with respect to a center part.
[0096]
FIG. 13 is a structural diagram of the white LED in the present embodiment.
[0097]
Blue or ultraviolet light is emitted by the light source LED 1051 and converted into light of other wavelengths such as yellow by the phosphor 1052. It emits white light by adding light of multiple wavelengths.
[0098]
FIG. 14 is a diagram showing the spectral characteristics of the white LED in the present embodiment.
[0099]
On the short wavelength side, the blue peak is due to the light source LED 1051, and the green to red broad portion on the right side is light converted from blue by the phosphor 1052.
[0100]
As for the luminous efficiency of the phosphor, the amount of light emitted by the phosphor changes. This is because the light source wavelength is subtly different because it varies depending on the wavelength of light before conversion by the phosphor. Therefore, the color tone is different for each white LED. Specifically, pure white, yellowish white, blueish white and the like. As described above, this difference cannot be ignored because it can be understood visually.
[0101]
Therefore, as described below, the LEDs (even white LEDs of the same type) are divided into several stages according to the rank of the color tone.
[0102]
FIG. 15 shows CIE (XYZ chromaticity coordinates).
[0103]
In this figure, there are three ranks a, b, and c on the chromaticity diagram. Here, the above-described variation in color tone does not vary at random, but is distributed in such a way that when a straight line rising to the right is drawn on the XYZ chromaticity coordinates, the straight line rides on it.
[0104]
However, when a color image is read without considering the color tone variation of the white LED, (1) color tone variation occurs in the main scanning direction. In addition, (2) color tone variation also occurs for each LED lighting module, which causes a problem that the color reading quality deteriorates.
[0105]
In the embodiment of the present invention, this problem is solved by configuring as follows.
[0106]
The LED light source module 205 is composed of LEDs having the same color tone rank. In this embodiment, the chromaticity XYZ values are measured with a colorimeter, and the LEDs are ranked according to the XYZ system chromaticity coordinates 104. Here, in this embodiment, it is divided into three ranks. It should be noted that higher accuracy can be handled by increasing the number of ranks.
[0107]
<Light source module formation using only LEDs of the same rank>
Here, for example, it is assumed that a light source module is formed by ranks as described above and only LEDs having the same rank.
[0108]
An advantage of creating one light source module with only LEDs of the same rank is to suppress variations in color tone of the read image. More specifically, when reading is performed in a state in which LEDs of various color tones are arranged in the main scanning direction, the problem that the color tone of the image read in the main scanning direction is considerably different can be avoided. That is, a light source module is created only with LEDs of the same rank, and variations in color tone in the main scanning direction can be avoided.
[0109]
In this case, when a plurality of light source modules constituting the white LED 205 are compared, the color tone is different between the modules, and thus the color tone variation occurs in the entire white LED array 205. As described above, there is a choice not to use LEDs of other color tone ranks, but this results in poor yield and high price.
[0110]
<Change the parameters of the color calculation means according to the rank>
Therefore, in this embodiment, after using LEDs of various tone ranks, the following configuration is provided.
[0111]
It has a color tone rank setting means for the white LED light source module to be used, and a control means for switching the parameters of the matrix color calculation means in accordance with the color tone rank.
[0112]
FIG. 16 is a flowchart for explaining ranking in the present embodiment. The following processing is an operation under the control of the controller 802.
[0113]
First, a color tone rank signal from the operation panel 801 or the like is received as the color tone rank of the light source module to be used (step S101). In the present embodiment, the setting is made by the operator. However, the light source module is provided with rank information magnetically, electrically, and optically, and has a means for automatically setting at the time of setting. Troublesome work can be avoided.
[0114]
Next, the difference is removed by the color calculation means based on the setting information of the tone rank. First, the coefficient of the corresponding input masking unit 106 is selected based on the received color tone rank setting information (step S102). The selected coefficient is switched as an input masking coefficient (step s103). In the present embodiment, the coefficient of the input masking unit 106 is switched to an appropriate one corresponding to the ranking according to each. Using this masking coefficient, the arithmetic processing as described above is performed (step S104).
[0115]
In the present embodiment, a masking coefficient of 3 × 3 is designed so that any color tone rank of the LED light source module can be converted into a standard color space of NTSC (National Television Standards Committee). A matrix operation as shown in the following equation is performed.
[0116]
[Outside 2]

[0117]
In the present embodiment, the matrix calculation is performed up to a 3 × 3 primary term. However, the accuracy is further improved if the order is increased, for example, a matrix including a secondary term.
[0118]
It is better to use direct mapping of the color space using a three-dimensional lookup table.
[0119]
Here, the reason why RGB is output in the NTSC color space is that the input format of the RGB-CMYK conversion means to the printer of the present embodiment assumes a color space equivalent to NTSC.
[0120]
According to the present embodiment as described above, when the white LED illumination module is used as the light source of the color image reading apparatus, the quality deterioration of the read image due to the color tone variation of the LED is suppressed. Further, by using LEDs of the same color tone rank, it is possible to suppress color tone variations in the main scanning direction in the same module. Furthermore, even when using LED lighting modules having a plurality of color tone ranks, the color calculation means can absorb the difference by setting the color tone rank, and a color document with the same color tone can be obtained by any of the plurality of illumination modules. The image can be read.
[0121]
<Change the masking coefficient depending on the main scanning position>
Even when white LEDs of the same rank are used, some white level color tone variations may occur, for example, when the rank classification standard is loosened due to yield. Even in this case, better color reading can be performed by adopting the following configuration.
[0122]
In addition, even when white LEDs of different ranks are mixed, an effect of suppressing quality deterioration due to LED color tone variation can be aimed at. In this case, it is possible to reduce the cost because it is not necessary to rank.
[0123]
FIG. 17 is a diagram illustrating a configuration in which the masking coefficient can be changed depending on the main scanning position.
[0124]
By using the target white LED array 205 in advance, the managed standard white plate 211 is read, and the change in color due to the main scanning position is measured. As a result, a change in the color tone characteristic of the light source due to the position in the main scanning direction can be measured in units of pixels. An appropriate masking coefficient in pixel units corresponding to the main scanning position is obtained for the color tone change in pixel units depending on the main scanning position of the light source.
[0125]
Next, the obtained masking coefficient is given to the image reading apparatus equipped with the white LED array 205 as unique data of the white LED array 205. That is, the masking coefficient corresponding to the main scanning position in the given one line is stored in the masking coefficient storage unit 1063 in FIG.
[0126]
The main scanning position determination unit 1064 receives the main scanning synchronization signal HSYNC and the pixel clock CLK, and includes main scanning position information indicating which main scanning position information is currently processed at the time of image reading. Information is output.
[0127]
The load unit 1062 for selecting a masking coefficient reads out the masking coefficient in pixel units corresponding to the main scanning position to be processed from the masking coefficient storage unit 1063 according to the main scanning position information, and inputs it to the masking calculation unit 1061. . The masking operation unit performs the 3 × 3 matrix operation described above in units of pixels.
[0128]
Here, in the above description, the configuration in which the masking coefficient is calculated for each pixel has been described. On the other hand, the fact that the masking coefficient corresponding to the main scanning position does not have to be prepared for all the pixels has been described in <Changing the parameters of the color calculation means according to the rank>. That is, for example, a configuration in which only the values of the six representative points are stored in the main scanning position in units of LED modules {circle around (1)} to {circle around (6)} described with reference to FIG. This means that it is also possible to take a method in which the points between the representative points are obtained by interpolation by calculation by a masking coefficient calculation unit (not shown). In this case, by performing a considerable ranking in units of LED modules (1) to (6), and reading the standard white plate 211 so as to obtain masking coefficients corresponding to the LED modules (1) to (6). The configuration can be simplified.
[0129]
With the above-described configuration procedure of the present embodiment, an image can be read with a precise color quality even when the color tones of the white LED chips mounted on the white LED array 205 do not completely match. Further, by performing the process of changing the masking coefficient according to the main scanning position, there is an effect that image quality deterioration due to the color tone variation of the LED light source can be suitably suppressed.
[0130]
<Other embodiments>
In the first to third embodiments, the external PC 809 is connected by the SCSI, but the present invention is not limited to this, and other known standards may be used. Yes.
[0131]
Further, the present invention can be applied to a system (for example, a copier, a facsimile machine, etc.) consisting of a single device, even if it is applied to a system composed of a plurality of devices (eg, host computer, interface device, scanner, etc.). May be.
[0132]
Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included. Examples of the storage medium for storing the program code include a floppy disk, hard disk, ROM, RAM, magnetic tape, nonvolatile memory card, CD-ROM, CD-R, DVD, optical disk, magneto-optical disk, MO, etc. Can be considered.
[0133]
Furthermore, after the program code read from the storage medium is written into the function expansion card inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU of the function expansion card or function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0134]
When the present invention is applied to the above-described storage medium, the program code corresponding to the flowchart shown in FIG. 16 described above is stored in the storage medium.
[0135]
【The invention's effect】
As described above, according to a preferred embodiment of the present invention, there is an effect that deterioration in reading quality can be reduced even when an image reading in which a color tone variation occurs in the illumination unit is performed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a cross-sectional configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing an external configuration of a CCD.
FIG. 3 is a cross-sectional view of a photosensor.
FIG. 4 is an enlarged view of a photosensor.
FIG. 5 is a timing chart of the density reproduction control operation in the printer unit.
FIG. 6 is a block diagram illustrating a flow of an image signal in a signal processing unit of the image scanner unit.
FIG. 7 is a diagram illustrating the timing of each control signal in the signal processing unit.
FIG. 8 is a diagram for explaining the light emission amount at the main scanning position of the white LED illumination module and the illuminance on the CCD surface.
FIG. 9 is a block diagram illustrating a configuration of an image scanner unit.
FIG. 10 is a diagram showing a configuration of a white LED.
FIG. 11 is a diagram illustrating a white LED illumination module in which an LED array is formed.
FIG. 12 is a diagram illustrating LED PWM control.
FIG. 13 is a diagram illustrating the structure of an LED.
FIG. 14 is a diagram for explaining spectral characteristics of a white LED.
FIG. 15 is a diagram for explaining a tone rank of a white LED on a chromaticity diagram.
FIG. 16 is a flowchart related to rank reasoning.
FIG. 17 is a diagram illustrating details of an input masking unit.
[Explanation of symbols]
200 Printer section
201 Image scanner
202 Document pressure plate
203 Platen glass (platen)
204 Manuscript
205 White LED array
206, 207 Mirror
208 lenses
2103 Line sensor
211 Standard white plate
2101, 2102, 2103 R, G, B sensors
212 Laser driver
213 Semiconductor laser
214 polygon mirror
215 f-θ lens
216 mirror
217 Photosensitive drum
219 Magenta developer
220 Cyan developer
221 Yellow developer
222 Black developer
223 Transfer drum
224,225 Paper cassette
226 Fixing unit

Claims (12)

Irradiating means is formed by arranging plural color characteristic of the illumination light is different white light source in a main scanning direction of said photoelectric conversion means,
Photoelectric conversion means for reading the subject image irradiated by the irradiation means and outputting an image signal;
Color space conversion means for converting the color space of the image signal based on a matrix coefficient ;
Characterized by having a <br/> and coefficient setting means for setting in accordance with the basis of the main scanning position of the matrix coefficients in the color tone characteristics of the white light source used by the color space conversion means for converting the color space of the image signal Image reading device. The image reading apparatus according to claim 1 , wherein the coefficient setting unit sets the matrix coefficient in units of pixels of the photoelectric conversion unit . Said illumination means, a plurality have a group constituted by a plurality of white light sources in the main scanning direction, the coefficient setting means, according to claim 1, characterized in that sets the matrix coefficients for each of groups The image reading apparatus described in 1. Image reading comprising: irradiation means in which a plurality of white light sources having different color tone characteristics of irradiation light are arranged in the main scanning direction of the photoelectric conversion means; and photoelectric conversion means for reading a subject image irradiated by the irradiation means and outputting an image signal An apparatus control method comprising:
A coefficient setting step for setting a matrix coefficient in accordance with the main scanning position based on the color tone characteristics of the plurality of white light sources;
Control method characterized by chromatic the color space conversion step of converting the color space of the image signal based on the matrix coefficients set in the coefficient setting step. 5. The control method according to claim 4 , wherein, in the coefficient setting step, the matrix coefficient is set for each pixel of the photoelectric conversion means . Said illumination means, a plurality have a group constituted by a plurality of white light sources in the main scanning direction, in the coefficient setting step, according to claim 4, characterized in that said matrix coefficient set for each of the group The control method described in 1. Irradiation means in which a plurality of white light sources having different color characteristics of irradiation light are arranged;
Photoelectric conversion means for reading the subject image irradiated by the irradiation means and outputting an image signal;
Color space conversion means for converting the color space of the image signal;
Setting means for setting the color tone characteristics of the white light source according to an input operation by an operator ;
Control means for controlling the color space conversion means to convert the color space of the image signal based on a matrix coefficient corresponding to the color tone characteristic of the white light source set by the setting means. Image reading device. The image reading apparatus according to claim 7 , wherein the color tone characteristic is determined based on an XYZ colorimetric chromaticity diagram. The image reading apparatus according to claim 7 or 8 , wherein the irradiation unit includes a plurality of white light sources having different color tone characteristics of the irradiation light arranged in the main scanning direction. A method for controlling an image reading apparatus , comprising: irradiation means in which a plurality of white light sources having different color tone characteristics of irradiation light are arranged; and photoelectric conversion means for reading a subject image irradiated by the irradiation means and outputting an image signal ,
A setting step of setting in accordance with an input operation by the operator to the color tone characteristics of the white light source,
And a color space conversion step of converting a color space of the image signal based on a matrix coefficient corresponding to a color tone characteristic of the white light source set in the setting step . The control method according to claim 10 , wherein the color tone characteristic is determined based on an XYZ colorimetric chromaticity diagram. The control method according to claim 10 or 11 , wherein the irradiation unit includes a plurality of white light sources having different color tone characteristics of the irradiation light arranged in the main scanning direction.

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