JP4109329B2 - Print proof creation system - Google Patents

Description

このように、７８４（２８×２８）ドット毎の数え上げ処理（ステップＳ８）と加重平均処理（ステップＳ９）を４４８００ＤＰＩのビットマップデータｂｉの全範囲で行うことにより、１６００ＤＰＩの測色的データｑが得られる。
【００６５】
次に、得られた１６００ＤＰＩの測色的データｑに図９に示すアンチエリアジングフィルタＡＦを使用したアンチエリアジングフィルタ処理を行い、アンチエリアジングフィルタ処理後の出力装置１６の解像度に等しい４００ＤＰＩの測色的データβを作成する（ステップＳ１０）。
ステップＳ１０のアンチエリアジングフィルタ処理過程は、出力装置１６の解像度（この実施形態では、４００ＤＰＩ）でカラー印刷プルーフ画像を作成しようとするとき、この出力装置１６の解像度を原因とするエリアジング雑音（折り返し雑音）の発生を予め回避するために挿入した過程である。アンチエリアジングフィルタ処理を有効に行うためには、アンチエリアジングフィルタＡＦがかけられる原信号である画像データ（この場合、測色的データｑ）の解像度が出力装置１６の解像度（４００ＤＰＩ）より高い解像度になっていることが必要である。この実施形態では、その解像度が１６００ＤＰＩに選択されている。
【００６６】
図９に示したアンチエリアジングフィルタＡＦのマトリクス（ここでは、要素数がｎ×ｎの正方マトリクス）の構成について考える。
【００６７】
解像度１６００ＤＰＩの画像データである測色的データｑを解像度４００ＤＰＩの画像データである測色的データβに変換するためには、４００ＤＰＩの１ドットが１６００ＤＰＩの１６ドットに対応することからアンチエリアジングの効果を考えない場合のフィルタの最小限の要素数は４×４である。
【００６８】
そして、エリアジング雑音をできるだけ小さくするためには、アンチエリアジングフィルタＡＦの要素数は大きければ大きいほど望ましいが、演算速度、ハードウェア等との関係で制限される。
【００６９】
一方、色情報はノイゲバウア方程式によって再現できることからも類推できるように、直流成分を含む比較的低周波の成分を通過させる必要があることから、直流成分の近傍ではできるだけ挿入損失が発生しないような周波数特性にする必要がある。したがって、マトリクスの中心の応答が０ｄＢになることが理想である。
【００７０】
また、モアレ等の干渉縞成分｛網周波数（スクリーン線数）成分以下の成分｝はアンチエリアジングフィルタ処理（ステップＳ１４）を行ってもすべて残すようにしたい。
【００７１】
さらに、アンチエリアジングフィルタＡＦの減衰特性が急峻であると、このアンチエリアジングフィルタ処理を行うことによる新たな偽模様が現れてしまうことも考慮しなければならない。
【００７２】
図９は、このような観点を総合して作成された要素数が９×９のアンチエリアジングフィルタＡＦの構成例を示している。なお、各要素をｄｉｊで表すとき、各要素ｄｉｊの値（フィルタ係数ともいう）は全部加えて１．０にする必要性があることから、各要素ｄｉｊの実際の値は各要素ｄｉｊの総和（Σｄｉｊ）で割っておく。
【００７３】
このように構成したアンチエリアジングフィルタＡＦのフィルタ係数の配置は、図９から分かるように、中央部分から外方に向かうにしたがってほぼ釣り鐘状に単調減少的に減衰する周波数特性になっている。
【００７４】
図１０Ａ、図１０Ｂは、このアンチエリアジングフィルタ処理の説明に供される線図である。図１０Ａに示すように、１６００ＤＰＩの測色的データｑの左上の９×９ドット分に対して図９に示した要素がｄｉｊで表される９×９のアンチエリアジングフィルタＡＦを対応させ、対応する各要素を掛け算して、それらの総和を求めてアンチエリアジングフィルタ処理を行う。すなわち、測色的データｑの各要素をｅｉｊと表すとき、Σ（ｄｉｊ×ｅｉｊ）（９×９要素分）を求め、これを解像度４００ＤＰＩの測色的データβとする。なお、上述したように、アンチエリアジングフィルタＡＦの総和はΣｄｉｊ＝１に規格化しているが、小数を含む掛け算は時間がかかるので、アンチエリアジングフィルタＡＦの各要素の値は図９に示した値をそのまま用いて、ｄ’ｉｊとするとき、Σ（ｄ’ｉｊ×ｅｉｊ）／Σｄ’ｉｊとしてアンチエリアジングフィルタ処理後の値を求めてもよい。
【００７５】
この場合、アンチエリアジングフィルタ処理では、解像度１６００ＤＰＩの測色的データｑを解像度４００ＤＰＩの測色的データβに変換するのであるから、測色的データｑに対する２回目のアンチエリアジングフィルタ処理は、図１０Ｂに示すように、アンチエリアジングフィルタＡＦを測色的データｑの４ドット分、例えば、右側にずらして行えばよい。以下、同様にして４ドット分ずつずらしてアンチエリアジングフィルタ処理を行い、アンチエリアジングフィルタＡＦの右端が測色的データｑの右端に等しい位置でアンチエリアジングフィルタ処理を行った後には、図１０Ｂに示す、上から５番面の要素ｅ₅₁にアンチエリアジングフィルタＡＦの要素ｄ₁₁を対応させて行い、以下同様にして、要素ｅ_16001600と要素ｄ₉₉とが対応するまで４ドットずつずらしてアンチエリアジングフィルタ処理を行うことで、１６００ＤＰＩの測色的データｑの解像度を低下させて４００ＤＰＩの測色的データβを得ることができる。アンチエリアジングフィルタ処理は、カラー印刷物の印刷網に特有の空間周波数応答を保存したまま、出力装置１６に固有の空間周波数応答を遮断するフィルタ処理であるともいえる。
【００７６】
以上のようにして、所望の印刷条件に対応して色変換処理されたカラー印刷プルーフデータであるＲＧＢデータは、ラスタイメージ処理装置１４に供給されることで、走査イメージの画像データに変換され、出力装置１６に供給される。
【００７７】
出力装置１６では、感材マガジン３６から取り出された感光材料２８が図４に示す主走査方向ｘに回転する露光ドラム３８に巻装される。一方、露光ヘッド２６を構成する光源ユニット４２Ｒ、４２Ｇ、４２Ｂの各レーザダイオードＬＤから出力されたレーザビームは、拡がりを持っており、それぞれが重畳されてリニアライトモジュレータ４６Ｒ、４６Ｇ、４６Ｂを構成する光変調素子４４に導かれる。前記各光変調素子４４は、夫々が露光部制御回路４０からのＲ、Ｇ、Ｂの各画像データによって変調されるため、前記レーザビームが前記光変調素子４４によってパルス幅変調、パルス強度変調、あるいはこれらの組み合わせによって変調されて感光材料２８に導かれる。
【００７８】
この場合、前記光変調素子４４に導入されるレーザビームは、複数のレーザダイオードＬＤから出力される発散光が重畳されているため、各レーザダイオードＬＤの各光変調素子４４の個体差に起因するむらが平滑化されて感光材料２８に導かれる。また、複数のレーザダイオードＬＤを用いることにより、光量を稼ぎ高速での画像記録を行うことができる。なお、光源としては、レーザダイオードＬＤの代わりにＬＥＤを用いてもよい。また、同一チップ上に複数の発光素子を配置したマルチチャネルＬＤ、ＬＥＤ等を用いることもできる。
【００７９】
前記感光材料２８には、図１１に示すように、第１走査によってリニアライトモジュレータ４６Ｒ、４６Ｇ、４６Ｂの長さ分の画像がＲ、Ｇ、Ｂ毎に記録され、次いで、前記リニアライトモジュレータ４６Ｒ、４６Ｇ、４６Ｂが副走査方向ｙに所定量変位された後、第２走査が行われる。Ｒ、Ｇ、Ｂの各画像は、主走査方向ｘに対して重ね合わされることにより所望の色となる。この処理を繰り返すことにより、感光材料２８に２次元的な潜像からなるカラー印刷プルーフ画像が形成される。
【００８０】
なお、感光材料２８は、隣接する画素に照射されるレーザビームの影響を受け、所望の発色とならない場合があるため、隣接する走査部分に関しては、所定の記録時間間隔を持たせて処理することが望ましい。例えば、隣り合ったラインの記録は、１周期をおいてから記録する、いわゆるインターリーブ方式で行う。また、図１２に示すように、露光ドラム３８に形成される画素の倍率を調整して、１回目の走査でａ１、ａ２、…の画素を形成し、２回目の走査で前記画素間のｂ１、ｂ２、…の画素を形成することで、隣接する画素による影響を少なくすることができる。
【００８１】
カラー印刷プルーフ画像の潜像が形成された感光材料２８は、露光ドラム３８から剥離された後、転写部３４に搬送される。前記転写部３４に搬送された感光材料２８は、バッファ４８においてその搬送速度が調整される。次いで、前記感光材料２８は、水塗布部５０において湿し水が塗布された後、加熱ドラム５６に巻装される。一方、前記加熱ドラム５６には、受材マガジン５４から供給される受像材料３２が巻装されている。従って、前記感光材料２８は、前記受像材料３２に重畳された状態で加熱ドラム５６に巻装される。
【００８２】
ヒータ５８によって所定温度に加熱された加熱ドラム５６は、重畳された前記感光材料２８および前記受像材料３２を加熱し、前記感光材料２８に記録された潜像が顕像となって前記受像材料３２に転写される。カラー印刷プルーフ画像が転写された受像材料３２は、感光材料２８から剥離された後、ドライヤ６２によって乾燥されて受材トレイ６８に排出される。一方、前記感光材料２８は、感材トレイ６６に排出される。
【００８３】
ここで、出力装置１６は、キャリブレーション処理部２２を有しており、このキャリブレーション処理部２２において、当該出力装置１６の固有の特性、感光材料２８の特性等に対応した画像データのキャリブレーションが行われる。
【００８４】
すなわち、供給された同一の画像データによる出力画像が常に同じになるように、各波長毎に画像データと記録光量制御信号データとを対応させる変換テーブルを作成しておき、前記変換テーブルを用いて、画像データを感光材料２８の感度の相違、階調特性の相違に応じて補正し、記録光量制御信号データを得ることにより、常に定められたグレーカーブを再現させるようにする。このとき、画像データを供給された画像データよりもビット数の多い記録光量制御信号データに変換することで、滑らかな階調再現が可能となり、記録時の階調飛びを防ぐことができる。
【００８５】
また、図１３Ａに示すように、ｉ−１番目およびｉ番目の隣接する光変調素子４４からのレーザビームにより感光材料２８に記録される画素の濃度は、直前に記録された画素の光の影響を受けて所望の濃度よりも高くなってしまう（図１３Ｂの斜線部分参照）。そこで、画素間データ補正部２４において、ｉ番目の光変調素子４４に供給する駆動信号Ｐｉをｉ−１番目の光変調素子４４に供給する駆動信号Ｐ（ｉ−１）の所定の関数ｆを用いて、
Ｐｉ’＝Ｐｉ−ｆ｛Ｐ（ｉ−１）｝ …（４）
として補正することにより、図１３Ｃに示すように、隣接する画素の影響のない画像を形成することができる。
【００８６】
また、図１４Ａに示すように、第１走査時における一方の端部（ｊ番目）の光変調素子４４と第２走査時における他方の端部（１番目）の光変調素子４４とが記録に際して隣接するため、この部分での濃度に図１４Ｂの斜線部分に示すような影響が生じ、これを原因として、得られる画像上に筋状のむらが発生する。そこで、前記と同様に、１番目の光変調素子４４に供給する駆動信号Ｐ１をｊ番目の光変調素子４４に供給する駆動信号Ｐｊの所定の関数ｇを用いて、
Ｐ１’＝Ｐ１−ｇ（Ｐｊ） …（５）
として補正することにより、図１４Ｃに示すように、隣接する画素の影響のない画像を形成することができる。なお、この場合の影響は、走査の時間間隔が比較的大きいため、１つの光変調素子４４内で隣接する前記の画素間の影響よりも小さい。
【００８７】
画素間データ補正部２４では、さらに、光変調素子４４間の光透過率の相違、スイッチング特性の相違を吸収するため、各光変調素子４４毎に補正カーブを持たせ、補正を行うようにすることもできる。このようにして、隣接画素間の全ての濃度変動の影響を補正することができる。
【００８８】
また、出力装置１６を構成する転写部３４では、ヒータ５８を用いて感光材料２８および受像材料３２を加熱し、画像の転写現像記録を行うようにしている。この場合、温度センサ６０により加熱ドラム５６の温度を測定し、その温度を所定の一定温度に制御することにより、安定した転写現像記録を行うことができる。また、測定された温度に基づき露光部３０における露光ヘッド２６に供給される制御信号を補正して記録状態を安定させるようにすることも可能である。さらに、加熱ドラム５６は、前記感光材料２８および前記受像材料３２が巻装されている場合と巻装されていない場合とで温度に変動が生じる。そこで、露光部３０における感光材料２８の処理量に応じて温度を制御するようにしてもよい。さらにまた、処理対象となる前記感光材料２８および前記受像材料３２のサイズによって加熱ドラム５６に接触する面積が異なるため、前記加熱ドラム５６の表面の温度分布にむらの生じる場合がある。そこで、例えば、ヒータ５８を加熱ドラム５６の軸線方向に分割して設けるとともに、前記加熱ドラム５６の複数の領域を複数の温度センサ６０で測定し、前記各ヒータ５８を個々に制御することにより、温度むらをなくすことが可能である。
【００８９】
さらに、出力装置１６を構成する転写部３４には、測色計６４（検出器）が設けられており、この測色計６４により画像の色を測定し、当該出力装置１６や感光材料２８、受像材料３２等の特性の経時的変化を補正することもできる。例えば、感光材料２８に所望のカラー印刷プルーフ画像を形成するとともに、前記感光材料２８の側部にテストデータに基づくテストパターンを形成する。そして、そのテストパターンの色を測色計６４を用いて測色し、その測色値が所定の値となるように補正を行えばよい。この場合、前記テストパターンとしてグレー色のパターンと単色のパターンとを作成し、前記グレー色のパターンによって画像のグレーバランスを補正し、前記単色のパターンによって個々の色補正を行うようにすることができる。感光材料の側部に設けた前記テストパターンは、画像出力のたびに出力して計測し補正することができる。この場合、補正データは、キャリブレーション処理部２２（信号データ変換部）に供給され、記録光量制御信号データが補正されることにより、再現性のある出力を実現することができる。
【００９０】
また、側部に設けられたテストパターンの中、同一の画像データにより出力されたテストパターンの測色データから、熱現像処理のむらを検知することもできる。さらに、このむらの情報を加熱ドラム５６のヒータ５８を制御する転写部制御回路７０、あるいは、露光部制御回路４０にフィードバックすることで、現像むらを抑制することができる。
【００９１】
なお、前記テストパターンは、べた画像であっても、あるいは、網点画像であってもよい。また、このテストパターンを繰り返しパターンまたは一様パターンとすることにより、光変調素子４４の個体差を検出して一層高精度な色補正を行うことができる。
【００９２】
以上のように形成されたカラー印刷プルーフ画像に基づき、カラー印刷画像を予測し、必要に応じてレイアウトデータＬ／Ｏの修正を行うことにより、所望のカラー印刷画像を効率的に得ることができる。
【００９３】
ところで、前述したＬＵＴや補正方法を用いることにより、印刷物とカラー印刷プルーフ画像との色を測色的に一致させることは可能であるが、観察光源の相違等、測色計では制御することのできないレベルのグレーバランスの相違により、色に不一致の生じるおそれがある。このような不一致は、以下のような目視補正機能を組み込むことにより、高精度に補正し、さらに精度のよいプルーフを作成することができる。
【００９４】
目視による調整方法としては、階調カーブの調整によるものとグレーバランスの調整によるものとが可能であるが、一方のみあるいは両方を組み合わせて行うこともできる。図１５は、この両方の目視補正機能をＲ、Ｇ、Ｂ毎に設定した一次元ＬＵＴである目視補正ＬＵＴ１００（第２色ずれ補正手段）を用いて実現する場合を示したものである。
【００９５】
目視補正をグレーバランスの調整により実現する場合、先ず、合わせる対象となる印刷物のグレー色の目標チャートを用意する。目標チャートには、Ｃ、Ｍ、Ｙ、Ｋの各色の網％値が定まり、予め決められた印刷条件で印刷された印刷物あるいはそれと測色的に等価な色パッチが選択される。また、観察条件の相違を補正する必要があるため、この目標チャートの分光吸収特性が印刷物に一致していることが望ましい。
【００９６】
一方、出力装置１６により、前記目標チャートの色を測色的に再現させ得るプルーフ画像を中心とし、その周囲にＲＧＢデータをわずかずつ変えたプルーフ画像を配置したテストチャートを出力する。例えば、図１６に示すように、Ｒ＝Ｇ＝Ｂ＝０のＲＧＢデータにより生成されるパッチを中心とし、その周囲にＲ、Ｇ、Ｂの各データを増加させたパッチを六角形状に配置したテストチャートを作成する。なお、このテストチャートは、明るさを一定にし、グレー色の色味方向へのずれが出力されるようにすることが望ましい。また、このテストチャートの中心のパッチは、出力装置１６、感光材料２８、観察条件等の全てが設定した条件を満足しているときに目標チャートと同じ測色値となるように設定される。
【００９７】
そこで、上記のようにして出力されたテストチャートと目標チャートとを目視により比較し、同じ色に見えるパッチを選択する。そして、選択された前記パッチのＲＧＢデータが中心のパッチのＲＧＢデータとなるように、目視補正ＬＵＴ１００を設定する。
【００９８】
目視補正を階調カーブの調整により実現する場合には、図１６に示すテストチャートの代わりに、前記目標チャートに対応するパッチを中心としてグレー色の明るさが段階的に変わるパッチを周囲に配置したテストチャートを作成する。そして、このテストチャートを実際に使用する観察条件下で目標チャートと比較し、同じ色に見えるパッチを選択することで目視補正ＬＵＴ１００を設定する。なお、目標チャートはグレー色に限らず、例えば、Ｒ、Ｇ、Ｂの各単色とし、単色に対する階調カーブの調整を行うようにしてもよいことは勿論である。
【００９９】
以上のようにして設定された目視補正ＬＵＴ１００を用いて、グレーバランスの調整および階調の調整を行うことにより、補正されたプルーフデータであるＲＧＢ’データを得ることができる。なお、これらの調整作業は、どちらを先に行ってもよく、また、目標チャートとテストチャートの中心とが完全に一致するまで両者を順次繰り返し行うようにしてもよい。
【０１００】
前記の補正されたＲＧＢ’データは、出力装置１６におけるキャリブレーション処理部２２に供給され、キャリブレーションＬＵＴにより修正されることにより、記録光量制御信号データであるＲＧＢ”データが生成される。このようにして得られたＲＧＢ”データに従って、高精度に色を予測することのできるプルーフ画像を作成することができる。
【０１０１】
【発明の効果】
以上のように、本発明では、廉価な構成からなる出力装置を用いて、カラー印刷物に使用される用紙、インキ等を含む種々の印刷条件や網掛け処理の条件を考慮したカラー印刷プルーフ画像を得ることができ、この画像に基づいて印刷画像を容易且つ高精度に予測することができる。
【図面の簡単な説明】
【図１】本実施形態の印刷プルーフ作成システムの概略構成ブロック図である。
【図２】レイアウトデータの説明図である。
【図３】図１に示す印刷プルーフ作成システムを構成する出力装置の構成説明図である。
【図４】図３に示す出力装置を構成する露光ヘッドの構成説明図である。
【図５】図１に示す印刷プルーフ作成装置を構成する色変換処理部の説明図である。
【図６】図１に示す印刷プルーフ作成装置を構成する網点シミュレーション処理部の説明図である。
【図７】図６に示す像構造シミュレーション処理の説明図である。
【図８】図８Ａおよび図８Ｂは、図７に示す像構造シミュレーション処理におけるビットマップデータの説明図である。
【図９】図７に示す像構造シミュレーション処理におけるアンチエリアジングフィルタの説明図である。
【図１０】図１０Ａおよび図１０Ｂは、図９に示すアンチエリアジングフィルタを用いた処理の説明図である。
【図１１】図４に示す露光ヘッドによる露光記録方法の説明図である。
【図１２】図４に示す露光ヘッドによる露光記録方法の説明図である。
【図１３】図１３Ａ〜図１３Ｃは、図４に示す露光ヘッドにより隣接画素を記録する際の補正の説明図である。
【図１４】図１４Ａ〜図１４Ｃは、図４に示す露光ヘッドにより第１走査および第２走査を行う際の隣接画素の補正の説明図である。
【図１５】目視による色調整を行う場合の工程の説明図である。
【図１６】目視による色調整を行う場合におけるテストチャートの説明図である。
【図１７】従来のカラー印刷プルーフ画像を作成する処理の説明図である。
【符号の説明】
１０…インタープリタ １２…印刷プルーフ作成装置
１４…ラスタイメージ処理装置 １６…出力装置
１８…色変換処理部 ２０…網点シミュレーション処理部
２２…キャリブレーション処理部 ２４…画素間データ補正部
２６…露光ヘッド ２８…感光材料
３０…露光部 ３２…受像材料
３４…転写部 ３８…露光ドラム
４０…露光部制御回路 ５６…加熱ドラム
６０…温度センサ ６４…測色計
７０…転写部制御回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printing proof creation system for creating a color printing proof image (also referred to as a color printing proof) for proofreading before creating a color printed matter including a halftone dot image by a color printing machine using a rotary press or the like. About.
[0002]
[Prior art]
Conventionally, a color printing proof image for proofreading a color or the like has been created by a color printer before creating a color print using a halftone dot image as a product by a color printer.
[0003]
A color printer is used to create a color printing proof image because the color printer has a relatively simple configuration and is inexpensive, and, as is well known, the plate making for a color printing machine is known. This is because there is no need to create a film, a printing plate (PS plate), etc., and it is possible to easily create a hard copy with an image formed on a sheet a plurality of times in a short time.
[0004]
FIG. 17 shows a flow of a method for creating a color print proof image according to the prior art.
[0005]
First, an image on the image original 2 is read by an image reading device such as a color scanner having a CCD area sensor or the like, and gradation image data Ia for each color of R (red), G (green), and B (blue) is obtained. It is created (step S1).
[0006]
Next, the RGB gradation image data Ia is converted into four halftone dot area ratio data (halftone%) for each color of C (cyan), M (magenta), Y (yellow), and K (black) by color conversion processing. It is converted to aj (j = 0-3) (also referred to as data) (step S2). This conversion can be carried out in various ways depending on the relationship with the color printer, and is usually the know-how of each printing company corresponding to the color printer.
[0007]
The image on the color print produced by this color printing machine is a halftone dot image. Therefore, when actually producing a color print, the dot area ratio data aj after color conversion processing is developed into bitmap data. On the basis of this, a plate making film or the like is created. However, an automatic developing machine (automatic machine) or the like is required, and the steps after the plate making film creating process are considerably complicated.
[0008]
For this reason, the color digital printer DP is used for the reason described above in order to easily create a color print proof image. DP uses a density gradation method, for example, to digitally control the emission intensity and time of an LED (light emitting diode) or LD (laser diode) corresponding to the three primary colors for each pixel to form an image on the donor film, This is transferred to an image receiving sheet, and an image is formed on the sheet. The PS plate is produced from the printing plate, and is considerably cheaper than a color printing machine for printing using this. Small volume and light weight.
[0009]
Therefore, in order to use DP, the halftone dot area ratio data aj of CMYK four plates created in step S2 are temporarily converted into image data (common color space) independent of so-called devices (printing, CRT, photograph, LED, etc.). For example, it is necessary to convert the data into tristimulus value data X, Y, and Z.
[0010]
Therefore, image data processing for converting the dot area ratio data aj of the CMYK4 version into tristimulus value data X, Y, Z is performed (step S3). Conventionally, processing using the Neugebauer equation has been adopted as this image data processing.
[0011]
In this case, the colorimetric value data Xi, Yi, Zi for each color is previously measured by a colorimeter (i is 2 in the case of the 4th edition of CMYK).^FourColor = 16 colors) is measured. In this measurement, first, each color of 16 colors is printed in advance on a printing paper when a color printed material is created by a color printer (usually referred to as solid printing). The 16 colors specifically correspond to the presence / absence of each of the C color, M color, Y color, and K color, and 2 in total.^FourColor = 16 colors.
[0012]
That is, the W (white) color, which is the background color of the printing paper when nothing is printed, the primary colors C, M, Y only, the K color, and the mixed colors C + M, C + Y, C + K, M + Y, M + K , Y + K, C + M + Y, C + M + K, C + Y + K, M + Y + K, and C + M + Y + K. These reflected colors formed on the printing paper are measured with a colorimeter, for example, a spectrometer, to obtain colorimetric value data Xi, Yi, Zi.
[0013]
In the processing using the Neugebauer equation, as shown in the following equation (1), the halftone dot area ratio data hi are multiplied as the coefficients of the colorimetric value data Xi, Yi, and Zi, and the tristimulus after image data processing is performed. Value data X, Y, and Z are created (step S3).
[0014]
X = Σhi · Xi
Y = Σhi ・ Yi
Z = Σhi · Zi (1)
However, i = 0-15
h0 = (1-c). (1-m). (1-y). (1-k)
h1 = c. (1-m). (1-y). (1-k)
h2 = (1-c) .m. (1-y). (1-k)
h3 = c.m. (1-y). (1-k)
h4 = (1-c). (1-m) .y. (1-k)
h5 = c. (1-m) .y. (1-k)
h6 = (1-c) .m.y. (1-k)
h7 = c.m.y. (1-k)
h8 = (1-c). (1-m). (1-y) .k
h9 = c. (1-m). (1-y). k
h10 = (1-c) · m · (1-y) · k
h11 = c · m · (1-y) · k
h12 = (1-c). (1-m) .y.k
h13 = c · (1−m) · y · k
h14 = (1-c) · m · y · k
h15 = c · m · y · k
C, m, y, and k represent halftone dot area ratio data aj for each color of C, M, Y, and K.
[0015]
Tristimulus value data X, Y, and Z after image data processing created in this way are supplied to the DP, and the DP uses the tristimulus value data X, Y, and Z based on a lookup table (LUT). Creates a color-printed proof image CPa, which is a hard copy in which an image is formed on a sheet, after conversion into data for each of the three primary colors related to LEDs, etc. (so-called device-dependent image data, also called intrinsic color space data) To do.
[0016]
By the way, as described above, when the tristimulus value data X, Y, and Z for DP are created using the Neugebauer equation, the color of the image formed on the color printed matter created by the color printer Since the colorimetric values measured with a colorimeter are used, the color of the color printed matter can be faithfully reproduced in the image on the hard copy, but interference fringes such as moire and rosette appearing on the color printed matter. In other words, there is a problem that interference unevenness caused by the periodic structure of halftone dots, which is a characteristic peculiar to printing, cannot be reproduced in the image on the hard copy.
[0017]
If these false patterns actually appear on the color printed material, it is based on a request to faithfully reproduce the false patterns on the color printed proof image CPa, and is based on the conventional technology in which the false patterns do not appear. In this regard, the color print proof image CPa is generally not an accurate (faithful) proof image for color prints with respect to image structure.
[0018]
The reason why false patterns do not appear in DP hard copy images is that the Neugebauer equation is interpreted as an expression based on a kind of probability theory, and the microscopic (micro) image structure (network structure) related to false patterns. Is considered to be caused by the inability to reproduce.
[0019]
In order to reproduce the image structure, it is necessary to have a mechanism (threshold matrix, bitmap data, etc.) having exactly the same structure as the printed material to be approximated on the image output device that outputs the hard copy. Therefore, it is difficult to cope with all the various printing conditions, and the apparatus becomes quite expensive.
[0020]
In addition, it is not sufficient to reproduce the above-described image structure in order to create an accurate proof image for a color printed matter. For example, there are various types of paper and ink used for printing depending on the purpose of the printed matter and the user. In this case, there are color printers that can use materials that are the same as or very similar to the printed matter, but their application range is considerably limited. Furthermore, it is also necessary to create a proof image in consideration of the environment for comparing and examining the printed matter and the proof image. For example, when the light source to be observed is different, the color of the printed matter or the proof image is different.
[0021]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and uses a relatively inexpensive and relatively low-resolution image output device such as a color printer to accurately produce printed matter produced by a color printer. It is an object of the present invention to provide a print proof creation system capable of obtaining a color print proof image that matches the above.
[0022]
[Means for Solving the Problems]
  The present inventionFrom the layout data of a color printed matter including gradation image data that is subjected to shading processing and non-gradation image data that is character data or line drawing data that is not subjected to shading processing, an output device is used to output the color printed matter.A system for creating a color print proof image,
  Paper used for the color printed matterOrinkPertaining toAccording to the first printing conditionThe layoutConvert the data,The color having a color according to the first printing conditionFirst conversion means for generating image data of a common color space independent of the output device;
  The color printed matterFor generatingAccording to the second printing condition for shadingThe layoutDataThen, after converting into bitmap data having a resolution higher than the resolution of the layout data, calorimetric data having a resolution of the output device lower than the resolution of the bitmap data is obtained from the bitmap data, and the measurement is performed. The color data has an image structure corresponding to the second printing condition.Image data of the common color spaceAsSecond converting means to generate;
  Color misregistration correction means for correcting color misregistration of the image data due to the image structure generated by the conversion processing of the second conversion means;
  SaidThe layoutdataIs the gradation image dataThe first conversion means,Said second converting meansAnd the color misregistration correction meanschooseIf the layout data is the non-gradation image data, only the first conversion means is selected.Selection means to
  Selected by the selection meansThe first conversion means or the second conversion meansAnd each means including at least the first conversion means among the color misregistration correction meansGenerated byeachimage dataIs subjected to the addition / subtraction calculation processing or multiplication / division calculation processing, so that the color corresponding to the first printing condition and the second printing condition are satisfied.Has an image structureOf the common color spaceGet the image data, and this image dataRecordConversion processing according to output conditions specific to the output device, and image data in a specific color space depending on the output deviceLivingThird conversion means formed;
  The color printing proof image is created based on the image data obtained by the third converting means.SaidAn output device;
  It is characterized by providing.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of a print proof creation system according to the present embodiment. This system, for example, interprets layout data L / O (see FIG. 2) in which character data DC, line drawing data DL, and gradation image data DI are laid out as a print image, and separates each data according to its type. Interpreter 10, print proof creating device 12 for creating color print proof data for calibrating a color print from the layout data L / O, and converting the color proof print data into raster image data for scanning out. It is basically composed of a raster image processing device 14 and an output device 16 for creating a color print proof image based on the raster image data.
[0025]
In the print proof creation device 12, the color conversion processing unit 18 (image data conversion unit) uses the printing conditions of the color printed matter created by the color printer and the output device 16 for the character data DC and the line drawing data DL. Color conversion processing is performed based on the output conditions of the color printing proof image to be created. In addition, the halftone dot simulation processing unit 20 (image data conversion unit) performs processing for reproducing the image structure of an image caused by the halftone processing when creating a color print on the gradation image data DI. Is done.
[0026]
In the output device 16, the calibration processing unit 22 performs a process of calibrating a change in output characteristics of the output device 16 over time, a change in characteristics of the recording material, and the like. Further, the inter-pixel data correction unit 24 performs a process of correcting the influence of interference generated between recorded pixels due to the recording material scanning method by the exposure head 26.
[0027]
Here, the configuration of the output device 16 will be described more specifically with reference to FIG.
[0028]
The output device 16 heats the color printing proof image by exposing the photosensitive material 28 to a latent image of a color printing proof image and heating the image receiving material 32 on the photosensitive material 28. And a transfer part 34 for transferring and forming the visible image on the image receiving material 32.
[0029]
The exposure unit 30 includes a photosensitive material magazine 36 holding the photosensitive material 28 wound in a roll shape, an exposure drum 38 around which the photosensitive material 28 taken out from the photosensitive material magazine 36 is wound, and the exposure drum 38. An exposure head 26 that forms a latent image of a color printing proof image by scanning a beam modulated on the basis of the color printing proof data with respect to the photosensitive material 28 wound around the exposure material 30, and an exposure unit 30 and an exposure head 26. And an exposure unit control circuit 40 that performs the operation control. The exposure head 26 forms a two-dimensional image on the photosensitive material 28 by moving along the rotation axis of the rotating exposure drum 38.
[0030]
As shown in FIG. 4, the exposure head 26 is configured to move in the sub-scanning direction y along the rotation axis of the exposure drum 38 that rotates in the main scanning direction x. The exposure head 26 includes light source units 42R, 42G, and 42B in which slits 41R, 41G, and 41B parallel to the sub-scanning direction y are formed, and a plurality of laser diodes LD are arranged therein. 42G and 42B, linear light modulators (LLM) 46R, 46G, and 46B having a plurality of light modulation elements 44 arranged in the sub-scanning direction y, and a condenser lens 47. The Beams from the plurality of laser diodes LD enter each light modulation element 44.
[0031]
The light modulation elements 44 constituting the LLMs 46R, 46G, and 46B transmit the transmitted light beams from the light source units 42R, 42G, and 42B according to the color printing proof data of R (red), G (green), and B (blue). For example, PZT (PbZrO) which is a piezoelectric material is modulated._Three, PbTiO_Three), A PLZT element that is a metal compound ceramic with La added thereto, a liquid crystal switching element, and the like can be used. The beams output from the laser diodes LD of the light source units 42R, 42G, and 42B are made of light having different wavelengths, and R, G, and B latent images are formed on the photosensitive material 28 according to the wavelengths. To do.
[0032]
The laser wavelength of the beam output from the laser diode LD needs to correspond to the photosensitive wavelength of each layer that develops colors R, G, and B of the photosensitive material 28, but the photosensitive wavelengths are not necessarily R, G, and B. There is no need, and for example, a laser diode LD that outputs a stable red and infrared beam can be used.
[0033]
In FIG. 4, the light modulation elements 44 are arranged in a straight line parallel to the rotation axis of the exposure drum 38, but the arrangement is not limited to this. For example, the light modulation elements 44 can be recorded on the photosensitive material 2 at a pitch different from the pitch between the light modulation elements 44 by arranging the light modulation elements 44 obliquely with respect to the rotation axis of the exposure drum 38. Thereby, high-resolution recording can be performed or the resolution can be easily changed. Furthermore, it is also possible to arrange the light modulation elements 44 in a staggered manner and perform recording at intervals smaller than the pitch.
[0034]
The transfer unit 34 adjusts the conveyance speed of the photosensitive material 28 supplied from the exposure unit 30 to avoid loosening of the photosensitive material 28 and generation of excessive tension, and the photosensitive material 28 that has passed through the buffer 48. A water application unit 50 for applying dampening water to the film, a receiving material magazine 54 for holding the image receiving material 32 wound in a roll shape, and the photosensitive material 28 and the image receiving material 32 are wound in a superimposed state. A color printing proof image is formed from a heating drum 56 that heats the heating drum 56, a heater 58 such as a halogen lamp that heats the heating drum 56 to a predetermined temperature, a temperature sensor 60 that detects the temperature of the heating drum 56, and the photosensitive material 28. A dryer 62 for drying the transferred image receiving material 32, a colorimeter 64 for measuring the color of the image recorded on the image receiving material 32, and a photosensitive material containing the photosensitive material 28. It includes a ray 66, a receiving material tray 68 for accommodating the image-receiving material 32, and a transfer unit control circuit 70 for controlling the operation of the transfer unit 34.
[0035]
As the photosensitive material 28 used in the exposure unit 30, a latent image obtained by imagewise exposure is thermally developed and transferred to an image receiving material 32 in the presence of an image forming solvent to obtain a visible image. A so-called photothermographic material is exemplified. The photothermographic material basically has a photosensitive silver halide, a reducing agent, a binder, and a dye-donating compound (which may also serve as a reducing agent) on a support, and further if necessary. And an organic metal oxidizing agent or the like can be contained.
[0036]
The photothermographic material may provide a negative image or a positive image upon exposure. There are two methods for giving positive images: a method using a direct positive emulsion as a silver halide emulsion (a method using a nucleating agent and a light covering method), and a positive diffusible dye image is emitted. Any of the methods using the dye-donating compound to be used can be employed.
[0037]
Examples of photothermographic materials that give positive images include those described in JP-A-6-161070, JP-A-6-289555, etc., and photothermographic methods that give negative images. As the photosensitive material, for example, those described in JP-A-5-181246, JP-A-6-242546, JP-A-7-127386, JP-A-7-195709 and the like can be used.
[0038]
The printing proof creation system according to the present embodiment is basically configured as described above. Next, processing in this system will be described in detail.
[0039]
First, as shown in FIG. 2, layout data L / O in which character data DC, line drawing data DL, and gradation image data DI are laid out as a print image is supplied to the interpreter 10.
[0040]
In this case, in the normal printing process, each color plate of C color, M color, Y color, and K color is created from the layout data L / O, and after making the plate from each color plate, each plate is Used to form a color print image with a desired ink on a desired printing paper. Note that when creating each version of CMYK, for example, in the gradation image data DI subjected to the shading process, the gradation image data DI composed of the CMYK halftone data includes the desired type of mesh, the screen angle, and the screen. By comparison with threshold data having the number of lines (second printing condition), the data is converted into bitmap data composed of binary data of value “1” or value “0”. Then, a laser or the like is driven on the basis of the bitmap data, and CMYK color plates are formed on the photosensitive material. In this case, an image structure that is an interference fringe such as moire or rosette generated due to the shading process appears in a color print image created using the color plate. In addition, the color print image has characteristics depending on the printing paper and ink to be used, and a different color tone appears depending on the light source for observing the color print image.
[0041]
In view of this, in the print proof creation system of the present embodiment, a color print proof image equivalent to the color print image has a simple configuration in consideration of the print conditions and the output conditions of the output device 16 with respect to the layout data L / O. Can be easily obtained.
[0042]
That is, the interpreter 10 interprets the supplied layout data L / O, separates it into character data DC, line drawing data DL, and gradation image data DI, and supplies them to the print proof creation device 12. The print proof creation device 12 supplies the character data DC and the line drawing data DL to the color conversion processing unit 18 and supplies the gradation image data DI to the halftone dot simulation processing unit 20. Note that, when the shading process is performed on the line drawing data DL, the line drawing data DL is also supplied to the halftone dot simulation processing unit 20.
[0043]
The color conversion processing unit 18 performs color conversion processing as shown in FIG. First, the character data DC or line drawing data DL composed of the dot area ratio data of CMYK4 version is output using the color reproduction prediction look-up table (LUT) 80 set corresponding to the first printing condition. Is converted into colorimetric data that does not depend on, for example, tristimulus value data X, Y, and Z.
[0044]
In this case, the printing conditions include the type of printing paper (coated paper, matte coated paper, non-coated paper, etc.) for forming the color print image that is finally obtained, the type of ink used for printing, and the like. The color reproduction prediction LUT 80 is obtained by creating a test pattern of a printed material for these printing conditions and measuring the tristimulus value data X, Y, and Z of the color by colorimetry. Note that the relationship between colors not included in the test pattern can be obtained by interpolation processing.
[0045]
In addition, the color of the color print varies depending on the observation light source. Accordingly, a color reproduction prediction LUT 80 is prepared in consideration of an observation light source such as observation under daylight or fluorescent light as the first printing condition, and the color reproduction prediction LUT 80 is prepared according to the observation conditions. Keep selectable. In this case, some printing paper contains a fluorescent brightening agent. This fluorescent whitening agent has different light emission states depending on the proportion of ultraviolet rays contained in the observation light source. Therefore, if the observation light source is different, the color is also different. Therefore, for example, the coefficient ε representing the dependence of the observation light source and the coefficients ΔX, ΔY, ΔZ representing the dependence of the fluorescent brightening agent can be selected according to the observation light source and the printing paper, and the standard Tristimulus value data X of the color reproduction prediction LUT80 for the observation light source₀, Y₀, Z₀The
X = X₀+ ΕΔX
Y = Y₀+ ΕΔY
Z = Z₀+ ΕΔZ (2)
And converted to new tristimulus value data X, Y, and Z.
[0046]
Specifically, for example, the amount of ultraviolet rays is different from that of a standard observation light source. In the visible region, tristimulus values are obtained with a light source having the same spectral intensity, and the difference from the tristimulus values obtained with a standard observation light source is used. A certain coefficient is assumed to be ΔX, ΔY, ΔZ. Then, by substituting into the equation (2) the coefficient ε, which is the internal ratio of the amount of ultraviolet light of the observation light source to be found between these two light sources, and the coefficients ΔX, ΔY, ΔZ in the desired observation light source Stimulus value data X, Y, Z can be obtained.
[0047]
In this way, by selecting the color reproduction prediction LUT 80 according to the first printing condition, and performing the color conversion processing by performing the correction corresponding to the observation condition and the fluorescent whitening agent of the printing paper to be used as necessary, Tristimulus value data X, Y, and Z in consideration of the first printing condition can be obtained.
[0048]
Next, the tristimulus value data X, Y, Z are obtained by using a proof output condition look-up table (LUT) 82 (third conversion means) set corresponding to the output condition of the output device 16 to be used. Color printing proof data corresponding to the output device 16, for example, RGB data is converted.
[0049]
Proof output conditions include the type of photosensitive material 28 used in the output device 16 and the type of image receiving material 32 (matte paper, gloss paper, etc.). The proof output condition LUT 82 sets the photosensitive material 28 and the image receiving material 32 corresponding to these proof output conditions, creates a test pattern from the output device 16, and measures tristimulus value data X, Y, and Z of the color. It can be obtained by color. Note that the relationship between colors not included in the test pattern can be obtained by interpolation processing.
[0050]
By selecting the one corresponding to the desired proof output condition from the proof output condition LUT 82 set in this way, and converting the tristimulus value data X, Y, Z into RGB data, the photosensitive device used in the output device 16 is used. RGB data considering the material 28 and the image receiving material 32 can be obtained. The color reproduction prediction LUT 80 and the proof output condition LUT 82 can be combined into one LUT, and color printing proof data can be created directly from the dot area ratio data aj.
[0051]
On the other hand, the halftone dot simulation processing unit 20 performs color conversion processing on halftone dot area rate data that requires halftone processing as shown in FIG. That is, the halftone dot simulation processing unit 20 can accurately reproduce the image structure of the color printed matter by performing an image structure simulation process (second conversion means, step S5) described in detail later. However, in this process, the color reproduced by the image structure is shifted, and it is necessary to correct it.
[0052]
Therefore, an image structure color correction look-up table (LUT) 84 (first color misregistration correction means) for generating correction data for correcting the color misregistration is created in advance corresponding to the printing conditions. The image structure color correction LUT 84 can be obtained, for example, as a colorimetric value of a test image output from the output device 16 based on data obtained by performing an image structure simulation process using test pattern data.
[0053]
Accordingly, in the halftone dot simulation processing unit 20, first, the gradation image data DI or line drawing data DL composed of the CMYK4 version halftone dot area ratio data aj is the same as in the case of the color conversion processing unit 18. Using the color reproduction prediction LUT 80 (first conversion means) set in accordance with the printing conditions, color measurement data independent of the output device, for example, tristimulus value data X, Y, Z (colorimetric data α and To be converted). Further, the halftone dot area ratio data aj is subjected to an image structure simulation process to be converted into colorimetric data β having an image structure corresponding to the halftone process. The colorimetric data β has a color shift. Further, the dot area ratio data aj is converted into color correction data X ′, Y ′, Z ′ (referred to as calorimetric data γ) by the image structure color correction LUT 84. The colorimetric data α, β, and γ are corrected for color misregistration by a simple arithmetic processing such as α + (β−γ) or α · β / γ, and a desired image structure is given. The common color space data is generated. As in the case of the color conversion processing unit 18, the common color space data is used for the color printing proof corresponding to the output device 16 using the proof output condition LUT 82 set in accordance with the output condition of the output device 16 to be used. Data, for example, RGB data is converted.
[0054]
Here, the image structure simulation processing in step S5 will be described with reference to FIG.
[0055]
In the image structure simulation process, first, a bitmap development process specific to the image structure simulation process is performed (step S6). In this case, a threshold matrix 92 having a higher resolution than that at the time of actual printing is selected in accordance with the mesh type, screen line number, and mesh angle under the same conditions (second printing conditions) as the printing supplied from the input end 90. . This is for increasing the resolution of the bitmap data bi. The type of screen, the number of screen lines, and the screen angle related to the threshold matrix 92 are indispensable for reproducing the same moire and the like that the same type of screen, the number of screen lines, and the screen angle as in the case of printing.
[0056]
In order to increase the resolution, for example, a threshold value matrix 92 having 256 × 256 = 65536 elements is used as the threshold value matrix 92 for creating halftone dots. For example, values 0, 1, 2,..., 255 are taken as threshold values in each element. The threshold value matrix 92 and the halftone dot area ratio data ai are compared to create bitmap data bi (step S7).
[0057]
The resolution of the bitmap data bi for the CMYK 4 version created in this way is 44800 (256 × 175) DPI when the number of screen lines is 175. This resolution needs to be 2000 DPI or more. Here, as a desirable example corresponding to various conditions as described above, the case of 44800 DPI will be described.
[0058]
Next, the bitmap data bi having 44800 DPI is converted into data having a resolution of 1600 DPI. For this purpose, a counting process for counting 28 × 28 (784) dots of the bitmap data bi and converting it to 1 dot of the counting data p may be performed (step S8).
[0059]
In order to explain the counting process in step S8 in an easy-to-understand manner, an example of 28 × 28 dots of the C version bitmap data bi is shown in FIG. 8A, and an example of 28 × 28 dots of the M version bitmap data bi is shown. Shown in FIG. 8B. In FIG. 8A and FIG. 8B, the values of elements not shown are all “0”. Further, it is assumed that the remaining elements of the Y version and K version bitmap data bi are all the value “0”.
[0060]
Therefore, with respect to 28 × 28 dots, the CMYK 4th version bitmap data bi (here, it is needless to say that the 2nd version bitmap data bi of the C version and the M version may be used) and the color Every (2 because the version number is 4)^FourA process of counting the area ratio ci for each color) is performed.
[0061]
In the pixel in the example of FIGS. 8A and 8B (corresponding to 28 × 28 dots), the area ratio ci for each color is calculated as follows.
[0062]
C color; ci = c_C= 3/784
(Area ratio c_CRepresents a portion where only the C color exists when the C plate and the M plate are viewed transparently, and the overlapping portion of the C color and the M color is the area ratio c of C + M = B color_{C + M}And)
C + M color; c_{C + M}= 2/784
W color; c_W= 779/784
(When the C and M plates are overlapped and seen transparently, the portion where neither the C color nor the M color exists)
The area ratio ci for the remaining colors (13 colors such as Y color and K color) is zero. By creating the area ratio ci for each 28 × 28 dots in this way, 1600 DPI counting data p (each element value is represented by the area ratio ci) is created.
[0063]
Next, the 16 solid colors printed on the color printed matter are measured by a colorimeter, and the colorimetric value data Xi, Yi, Zi for each color that has been measured in advance (i is the 4th version of CMYK). In the case of 2^FourThe colorimetric data q (tristimulus value data X, Y, Z) is obtained as shown in the equation (3) using the area ratio ci for each color counted in step S8 for color = 16 colors) as a weighting factor ( Step S9). In other words, the colorimetric value data Xi, Yi, Zi are weighted and averaged by the area ratio ci for each color to obtain tristimulus value data X, Y, Z (colorimetric data q).
[0064]

In this way, by performing the counting process (step S8) and the weighted average process (step S9) for each of 784 (28 × 28) dots over the entire range of the 44800 DPI bitmap data bi, the 1600 DPI colorimetric data q is obtained. can get.
[0065]
Next, anti-aliasing filter processing using the anti-aliasing filter AF shown in FIG. 9 is performed on the obtained 1600 DPI colorimetric data q, and 400 DPI equal to the resolution of the output device 16 after the anti-aliasing filter processing is performed. Colorimetric data β is created (step S10).
The anti-aliasing filter process in step S10 includes aliasing noise (caused by the resolution of the output device 16 when trying to create a color proof image at the resolution of the output device 16 (in this embodiment, 400 DPI)). This is a process inserted to avoid the occurrence of aliasing noise in advance. In order to effectively perform the anti-aliasing filter processing, the resolution of the image data (in this case, the colorimetric data q) that is the original signal to which the anti-aliasing filter AF is applied is higher than the resolution (400 DPI) of the output device 16. It must be in resolution. In this embodiment, the resolution is selected to 1600 DPI.
[0066]
Consider the configuration of the matrix of the anti-aliasing filter AF shown in FIG. 9 (here, a square matrix having n × n elements).
[0067]
In order to convert calorimetric data q, which is image data with a resolution of 1600 DPI, into calorimetric data β, which is image data with a resolution of 400 DPI, since one dot of 400 DPI corresponds to 16 dots of 1600 DPI, anti-aliasing When the effect is not considered, the minimum number of elements of the filter is 4 × 4.
[0068]
In order to minimize aliasing noise as much as possible, the larger the number of elements of the anti-aliasing filter AF, the better. However, the number of elements is limited in relation to the calculation speed and hardware.
[0069]
On the other hand, color information can be reproduced by the Neugebauer equation, and it is necessary to pass a relatively low-frequency component including a DC component, so that it can be inferred that the frequency at which insertion loss does not occur as close as possible to the DC component. It needs to be a characteristic. Therefore, it is ideal that the response at the center of the matrix is 0 dB.
[0070]
Further, it is desired that all interference fringe components such as moire {components below the network frequency (number of screen lines) component} remain even after the anti-aliasing filter processing (step S14).
[0071]
Further, it must be taken into account that if the attenuation characteristic of the anti-aliasing filter AF is steep, a new false pattern appears due to this anti-aliasing filter processing.
[0072]
FIG. 9 shows a configuration example of the anti-aliasing filter AF having 9 × 9 elements created by combining these viewpoints. When each element is represented by dij, it is necessary to add all the values of each element dij (also referred to as filter coefficients) to 1.0, so the actual value of each element dij is the sum of the elements dij. Divide by (Σdij).
[0073]
As can be seen from FIG. 9, the arrangement of the filter coefficients of the anti-aliasing filter AF configured as described above has a frequency characteristic that attenuates in a monotonically decreasing manner in a substantially bell shape as it goes outward from the central portion.
[0074]
10A and 10B are diagrams used for explaining the anti-aliasing filter processing. As shown in FIG. 10A, a 9 × 9 antialiasing filter AF in which the element shown in FIG. 9 is represented by dij corresponds to 9 × 9 dots in the upper left of the 1600 DPI colorimetric data q, The corresponding elements are multiplied to obtain the sum of them, and anti-aliasing filter processing is performed. That is, when each element of the colorimetric data q is represented as eij, Σ (di × eij) (9 × 9 elements) is obtained, and this is used as the calorimetric data β with a resolution of 400 DPI. As described above, the total sum of the anti-aliasing filter AF is standardized to Σdij = 1, but multiplication including decimals takes time, so the values of each element of the anti-aliasing filter AF are shown in FIG. The value after the anti-aliasing filter processing may be obtained as Σ (d′ ij × eij) / Σd′ij when d′ ij is used as it is.
[0075]
In this case, in the anti-aliasing filter process, the calorimetric data q with a resolution of 1600 DPI is converted into the calorimetric data β with a resolution of 400 DPI. Therefore, the second anti-aliasing filter process for the calorimetric data q is As shown in FIG. 10B, the anti-aliasing filter AF may be shifted by 4 dots of the colorimetric data q, for example, to the right. Thereafter, after anti-aliasing filter processing is performed by shifting by four dots in the same manner, and after anti-aliasing filter processing is performed at a position where the right end of the anti-aliasing filter AF is equal to the right end of the colorimetric data q, Element 5 on top from the top shown in 10B₅₁Element d of anti-aliasing filter AF₁₁To the element e, and so on._16001600And element d₉₉By performing anti-aliasing filter processing by shifting by 4 dots until and correspond to each other, the resolution of 1600 DPI colorimetric data q can be reduced to obtain 400 DPI colorimetric data β. It can be said that the anti-aliasing filter process is a filter process that cuts off the spatial frequency response unique to the output device 16 while preserving the spatial frequency response unique to the print network of the color print.
[0076]
As described above, the RGB data, which is the color print proof data subjected to the color conversion processing corresponding to the desired printing conditions, is supplied to the raster image processing device 14 to be converted into the image data of the scanning image, It is supplied to the output device 16.
[0077]
In the output device 16, the photosensitive material 28 taken out from the photosensitive material magazine 36 is wound around an exposure drum 38 that rotates in the main scanning direction x shown in FIG. On the other hand, the laser beams output from the laser diodes LD of the light source units 42R, 42G, and 42B constituting the exposure head 26 have a spread, and are superimposed on each other to form linear light modulators 46R, 46G, and 46B. It is guided to the light modulation element 44. Each of the light modulation elements 44 is modulated by R, G, B image data from the exposure unit control circuit 40, so that the laser beam is modulated by the light modulation element 44 by pulse width modulation, pulse intensity modulation, Alternatively, the light is modulated by a combination thereof and guided to the photosensitive material 28.
[0078]
In this case, the laser beam introduced into the light modulation element 44 is caused by individual differences of the light modulation elements 44 of the laser diodes LD because the divergent light output from the plurality of laser diodes LD is superimposed. Unevenness is smoothed and guided to the photosensitive material 28. Also, by using a plurality of laser diodes LD, it is possible to increase the amount of light and perform image recording at high speed. As the light source, an LED may be used instead of the laser diode LD. A multichannel LD, LED, or the like in which a plurality of light emitting elements are arranged on the same chip can also be used.
[0079]
As shown in FIG. 11, on the photosensitive material 28, images corresponding to the lengths of the linear light modulators 46R, 46G, and 46B are recorded for each of R, G, and B by the first scanning, and then the linear light modulator 46R. , 46G, 46B are displaced by a predetermined amount in the sub-scanning direction y, and then the second scan is performed. Each of the R, G, and B images has a desired color by being superimposed with respect to the main scanning direction x. By repeating this process, a color proof image composed of a two-dimensional latent image is formed on the photosensitive material 28.
[0080]
Note that the photosensitive material 28 may be affected by the laser beam applied to adjacent pixels and may not produce a desired color, so that the adjacent scanning portion is processed with a predetermined recording time interval. Is desirable. For example, recording of adjacent lines is performed by a so-called interleave method in which recording is performed after one cycle. 12, the magnification of the pixels formed on the exposure drum 38 is adjusted to form pixels a1, a2,... In the first scan, and b1 between the pixels in the second scan. , B2,... Can reduce the influence of adjacent pixels.
[0081]
The photosensitive material 28 on which the latent image of the color print proof image is formed is peeled off from the exposure drum 38 and then conveyed to the transfer unit 34. The photosensitive material 28 conveyed to the transfer unit 34 is adjusted in its conveyance speed in the buffer 48. Next, the photosensitive material 28 is wound around the heating drum 56 after dampening water is applied in the water application unit 50. On the other hand, the image receiving material 32 supplied from the receiving material magazine 54 is wound around the heating drum 56. Accordingly, the photosensitive material 28 is wound around the heating drum 56 in a state of being superimposed on the image receiving material 32.
[0082]
The heating drum 56 heated to a predetermined temperature by the heater 58 heats the superimposed photosensitive material 28 and the image receiving material 32, so that the latent image recorded on the photosensitive material 28 becomes a visible image and the image receiving material 32. Is transferred to. The image receiving material 32 to which the color printing proof image has been transferred is peeled off from the photosensitive material 28, dried by the dryer 62, and discharged to the receiving material tray 68. On the other hand, the photosensitive material 28 is discharged to the photosensitive material tray 66.
[0083]
Here, the output device 16 has a calibration processing unit 22, and in this calibration processing unit 22, calibration of image data corresponding to the characteristic of the output device 16, the characteristic of the photosensitive material 28, and the like. Is done.
[0084]
That is, a conversion table that associates the image data with the recording light amount control signal data for each wavelength is created so that the output images of the same supplied image data are always the same, and the conversion table is used. The image data is corrected according to the difference in sensitivity and the difference in gradation characteristics of the photosensitive material 28, and the recording light quantity control signal data is obtained, so that a predetermined gray curve is always reproduced. At this time, by converting the image data into recording light amount control signal data having a larger number of bits than the supplied image data, smooth gradation reproduction is possible, and gradation skipping during recording can be prevented.
[0085]
Further, as shown in FIG. 13A, the density of the pixel recorded on the photosensitive material 28 by the laser beam from the (i−1) -th and i-th adjacent light modulation elements 44 is influenced by the light of the pixel recorded immediately before. As a result, it becomes higher than the desired density (see the shaded area in FIG. 13B). Therefore, in the inter-pixel data correction unit 24, a predetermined function f of the drive signal P (i−1) supplied to the i−1th light modulation element 44 from the drive signal Pi supplied to the ith light modulation element 44 is obtained. make use of,
Pi '= Pi-f {P (i-1)} (4)
As shown in FIG. 13C, it is possible to form an image without the influence of adjacent pixels.
[0086]
Further, as shown in FIG. 14A, one end (jth) light modulation element 44 during the first scan and the other end (first) light modulation element 44 during the second scan are recorded. Since they are adjacent to each other, the density shown in FIG. 14B has an influence on the density at this portion, and this causes streaky irregularities on the obtained image. Therefore, similarly to the above, using a predetermined function g of the drive signal Pj supplied to the jth light modulation element 44, the drive signal P1 supplied to the first light modulation element 44,
P1 '= P1-g (Pj) (5)
As shown in FIG. 14C, it is possible to form an image without the influence of adjacent pixels. Note that the influence in this case is smaller than the influence between adjacent pixels in one light modulation element 44 because the scanning time interval is relatively large.
[0087]
The inter-pixel data correction unit 24 further performs correction by providing a correction curve for each light modulation element 44 in order to absorb differences in light transmittance and switching characteristics between the light modulation elements 44. You can also. In this way, the influence of all density fluctuations between adjacent pixels can be corrected.
[0088]
Further, in the transfer unit 34 constituting the output device 16, the photosensitive material 28 and the image receiving material 32 are heated using a heater 58 to perform image transfer development recording. In this case, stable temperature development and recording can be performed by measuring the temperature of the heating drum 56 by the temperature sensor 60 and controlling the temperature to a predetermined constant temperature. It is also possible to stabilize the recording state by correcting the control signal supplied to the exposure head 26 in the exposure unit 30 based on the measured temperature. Further, the temperature of the heating drum 56 varies depending on whether the photosensitive material 28 and the image receiving material 32 are wound or not. Therefore, the temperature may be controlled according to the processing amount of the photosensitive material 28 in the exposure unit 30. Furthermore, since the area in contact with the heating drum 56 differs depending on the size of the photosensitive material 28 and the image receiving material 32 to be processed, the temperature distribution on the surface of the heating drum 56 may be uneven. Therefore, for example, the heater 58 is divided and provided in the axial direction of the heating drum 56, a plurality of regions of the heating drum 56 are measured by a plurality of temperature sensors 60, and the heaters 58 are individually controlled. It is possible to eliminate temperature unevenness.
[0089]
Further, the transfer unit 34 constituting the output device 16 is provided with a colorimeter 64 (detector). The colorimeter 64 measures the color of the image, and the output device 16, the photosensitive material 28, It is also possible to correct a change in characteristics of the image receiving material 32 and the like with time. For example, a desired color printing proof image is formed on the photosensitive material 28 and a test pattern based on test data is formed on the side of the photosensitive material 28. Then, the color of the test pattern is measured using the colorimeter 64, and correction is performed so that the colorimetric value becomes a predetermined value. In this case, a gray color pattern and a single color pattern are created as the test pattern, the gray balance of the image is corrected by the gray color pattern, and individual color correction is performed by the single color pattern. it can. The test pattern provided on the side of the photosensitive material can be output and measured and corrected every time an image is output. In this case, the correction data is supplied to the calibration processing unit 22 (signal data conversion unit), and the recording light quantity control signal data is corrected, whereby a reproducible output can be realized.
[0090]
In addition, it is possible to detect unevenness of the thermal development processing from the colorimetric data of the test patterns output from the same image data among the test patterns provided on the side portions. Further, the uneven development can be suppressed by feeding back this unevenness information to the transfer portion control circuit 70 that controls the heater 58 of the heating drum 56 or the exposure portion control circuit 40.
[0091]
The test pattern may be a solid image or a halftone dot image. In addition, by making this test pattern a repetitive pattern or a uniform pattern, it is possible to detect individual differences of the light modulation elements 44 and perform more accurate color correction.
[0092]
A desired color print image can be efficiently obtained by predicting a color print image based on the color print proof image formed as described above and correcting the layout data L / O as necessary. .
[0093]
By the way, by using the above-described LUT and correction method, it is possible to make the color of the printed product and the color printing proof image colorimetrically coincide with each other. There is a risk of color mismatch due to an unacceptable level of gray balance. Such discrepancy can be corrected with high accuracy by incorporating the following visual correction function, and a proof with higher accuracy can be created.
[0094]
As a visual adjustment method, a gray scale curve adjustment and a gray balance adjustment are possible, but only one or a combination of both can be performed. FIG. 15 shows a case where both of these visual correction functions are realized using a visual correction LUT 100 (second color misregistration correction means) which is a one-dimensional LUT set for each of R, G, and B.
[0095]
When the visual correction is realized by adjusting the gray balance, first, a gray target chart of a printed material to be matched is prepared. In the target chart, halftone values of each color of C, M, Y, and K are determined, and a printed matter printed under predetermined printing conditions or a color patch that is colorimetrically equivalent thereto is selected. Further, since it is necessary to correct the difference in observation conditions, it is desirable that the spectral absorption characteristics of the target chart match the printed matter.
[0096]
On the other hand, the output device 16 outputs a test chart in which a proof image in which the RGB data is slightly changed is arranged around the proof image that can reproduce the color of the target chart colorimetrically. For example, as shown in FIG. 16, a patch generated from RGB data of R = G = B = 0 is arranged at the center, and patches in which R, G, and B data are increased are arranged in a hexagonal shape around the patch. Create a test chart. In this test chart, it is desirable to keep the brightness constant and to output a shift of the gray color direction. The central patch of the test chart is set so that the colorimetric value is the same as that of the target chart when all of the output device 16, the photosensitive material 28, the observation conditions, and the like satisfy the set conditions.
[0097]
Therefore, the test chart output as described above and the target chart are compared visually to select a patch that looks the same color. Then, the visual correction LUT 100 is set so that the RGB data of the selected patch becomes the RGB data of the center patch.
[0098]
When the visual correction is realized by adjusting the gradation curve, instead of the test chart shown in FIG. 16, a patch whose gray color brightness changes stepwise around the patch corresponding to the target chart is arranged around Create a test chart. Then, the visual correction LUT 100 is set by comparing the test chart with a target chart under observation conditions in which the test chart is actually used, and selecting a patch that looks the same color. Note that the target chart is not limited to the gray color, but, for example, each of the R, G, and B colors may be used, and the gradation curve for the single color may be adjusted.
[0099]
Using the visual correction LUT 100 set as described above, the gray balance adjustment and the gradation adjustment are performed, whereby RGB ′ data that is corrected proof data can be obtained. Either of these adjustment operations may be performed first, or both may be sequentially repeated until the center of the target chart and the center of the test chart completely coincide.
[0100]
The corrected RGB ′ data is supplied to the calibration processing unit 22 in the output device 16 and is corrected by the calibration LUT to generate RGB ”data that is recording light quantity control signal data. According to the RGB "data obtained as described above, a proof image capable of predicting a color with high accuracy can be created.
[0101]
【The invention's effect】
As described above, in the present invention, by using an output device having an inexpensive configuration, a color printing proof image in consideration of various printing conditions including paper, ink, etc. used for color printed matter and shading processing conditions can be obtained. The print image can be predicted easily and with high accuracy based on this image.
[Brief description of the drawings]
FIG. 1 is a schematic configuration block diagram of a printing proof creation system according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of layout data.
FIG. 3 is an explanatory diagram of a configuration of an output device constituting the print proof creation system shown in FIG. 1;
4 is an explanatory diagram of the configuration of an exposure head that constitutes the output device shown in FIG. 3; FIG.
FIG. 5 is an explanatory diagram of a color conversion processing unit constituting the print proof creation apparatus shown in FIG. 1;
6 is an explanatory diagram of a halftone dot simulation processing unit constituting the printing proof creation apparatus shown in FIG. 1. FIG.
7 is an explanatory diagram of the image structure simulation process shown in FIG. 6. FIG.
8A and 8B are explanatory diagrams of bitmap data in the image structure simulation process shown in FIG.
9 is an explanatory diagram of an anti-aliasing filter in the image structure simulation process shown in FIG.
10A and 10B are explanatory diagrams of processing using the anti-aliasing filter shown in FIG. 9;
11 is an explanatory diagram of an exposure recording method by the exposure head shown in FIG.
12 is an explanatory diagram of an exposure recording method by the exposure head shown in FIG. 4. FIG.
13A to 13C are explanatory views of correction when recording adjacent pixels by the exposure head shown in FIG.
14A to 14C are explanatory diagrams of correction of adjacent pixels when the first scan and the second scan are performed by the exposure head shown in FIG.
FIG. 15 is an explanatory diagram of a process in the case of performing color adjustment by visual observation.
FIG. 16 is an explanatory diagram of a test chart when color adjustment is performed visually.
FIG. 17 is an explanatory diagram of processing for creating a conventional color printing proof image.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Interpreter 12 ... Printing proof production apparatus
14 ... Raster image processing device 16 ... Output device
18 ... color conversion processing unit 20 ... halftone dot simulation processing unit
22 ... Calibration processing unit 24 ... Inter-pixel data correction unit
26 ... Exposure head 28 ... Photosensitive material
30 ... Exposure section 32 ... Image receiving material
34 ... transfer section 38 ... exposure drum
40: Exposure unit control circuit 56 ... Heating drum
60 ... temperature sensor 64 ... colorimeter
70: Transfer section control circuit

Claims (9)

Color printing of the color printed matter using an output device from layout data of color printed matter including gradation image data to be shaded and non-gradation image data that is character data or line drawing data not to be shaded A system for creating a proof image,
The layout data is converted according to a first printing condition relating to paper or ink used for the color printed matter, and image data in a common color space independent of the output device having a color according to the first printing condition is generated. First conversion means;
Follow the second printing condition according to the screening process for generating the color print, the layout data, after converting into bitmap data consisting of higher resolution than the resolution of the layout data, from the bit map data Obtaining colorimetric data having a resolution of the output device lower than the resolution of the bitmap data, and generating the colorimetric data as image data of the common color space having an image structure corresponding to the second printing condition Second conversion means for
Color misregistration correction means for correcting color misregistration of the image data due to the image structure generated by the conversion processing of the second conversion means;
When the layout data is the gradation image data, the first conversion unit , the second conversion unit, and the color misregistration correction unit are selected, and the layout data is the non-gradation image data. Selecting means for selecting only the first conversion means ;
Of the first conversion means or the second conversion means and the color misregistration correction means selected by the selection means , each image data generated by each means including at least the first conversion means is subjected to addition / subtraction calculation processing or multiplication / division. by processing to obtain the image data of said common color space having the image structure in accordance with the corresponding color and the second printing condition in said first printing condition, the image data, before Kide force device-specific and conversion processing in accordance with the output conditions, the image data of the specific color space dependent on the output device and the third conversion means that generates,
Based on the image data obtained by said third converting means, and said output device to create the color printing proof image,
A printing proof creation system comprising: The system of claim 1, wherein
The first proof condition includes a condition of an observation light source when comparing a color print and a color proof image. The system of claim 1, wherein
The print proof creation system, wherein the second printing condition includes a condition of a mesh type, a mesh angle, and a screen line number. The system of claim 1, wherein
The output device includes an exposure unit that forms a color print proof image composed of a latent image on a photosensitive material with a beam that is modulated and output according to image data from an exposure head;
A transfer portion that heats the photosensitive material in a state where the image receiving material is superposed on the photosensitive material, and transfers a color print proof image composed of a visible image to the image receiving material;
A printing proof creation system comprising: The system of claim 4 , wherein
The exposure head is arranged in a scanning direction, and a plurality of light modulation elements that modulate light transmittance according to image data; and the illumination light that is arranged in the scanning direction and that is composed of divergent light is irradiated to the light modulation elements. And a light source to
The exposure unit includes an exposure unit control circuit that drives and controls the light modulation element. The system of claim 5 , wherein
The exposure unit control circuit includes a pixel-to-pixel data correction unit that corrects the mutual influence of pixels formed adjacently on a photosensitive material. The system of claim 5 , wherein
The exposure unit control circuit performs a process for setting the heating drum to a predetermined temperature based on a signal from a temperature sensor that detects the temperature of the heating drum constituting the transfer unit. The system of claim 5 , wherein
The exposure unit control circuit performs a process of correcting the drive control signal of the light modulation element based on a signal from a colorimeter that measures the color of a color print proof image formed of a visible image formed in the transfer unit. A featured print proof creation system. The system of claim 1, wherein
The system according to the correction data set to visually match the color of the test chart created by the output device using the image data obtained by the third conversion means and the color of the target chart made of a color print , A print proof creation system comprising second color misregistration correction means for processing the image data.

Images