JP3820189B2 - Image forming apparatus, image processing circuit, program, storage medium, and pulse width data selection method - Google Patents

Description

【００７８】
この表１は、パターン検出処理回路２からＬＵＴ回路３ａ，３ｂへ出力されるコードである幅コードｃの一例を示すものである。すなわち、この幅コードｃは前述のパルス幅（パルス幅Ｗ）を決定するコードである。表１においては、パターン検出マトリクスの副走査方向の左列３ｄｏｔを縦軸、右列３ｄｏｔを横軸にとって、左列、右列それぞれのｄｏｔのオン／オフのパターンを示している。縦軸の「左列」の各３ｄｏｔにおいて、ベタ黒で示しているのは当該ｄｏｔがオンであることを示し、白抜きで示しているのは当該ｄｏｔがオフであることを示している。横軸の「右列」も同様である。そして、「左列」の３ｄｏｔのオン、オフのパターンと「右列」の３ｄｏｔのオン、オフパターンとの交叉する位置に示すＬ，Ｒの値から、幅コードｃは下式▲１▼〜▲４▼により決定される。例えば、パターン検出マトリクスの「左列」の３ｄｏｔと「右列」の３ｄｏｔとが全てオンであるときは、表１よりＬ＝４，Ｒ＝４であるから、式▲１▼より、幅コードｃは“８”の値となる。
【００７９】
式▲２▼、▲３▼において、ｌ_ｉ，ｒ_ｉは、それぞれ、パターン検出マトリクスの左列および右列にあてはまる画像データのオン／オフ情報を表わす（オンが１、オフが０）。添え字ｉは、パターン検出マトリクス内での縦方向（副走査方向）の位置を示す（上から０，１，２）。
【００８０】
【数１】

【００８１】
幅コードｃの各値に対応するパルス幅Ｗは、ＬＵＴ３ａ，３ｂにテーブルデータとして予め設定しておく。また、書き込み周期内での前述のパルス開始位置（パルス開始位置Ｓ）は、式▲５▼により決定する。
【００８２】
式▲５▼において、Ｐは書き込み周期内の分解能の最大階級値（１／２５６分解能の場合には２５５）を示し、ｋは式▲６▼により決定する。
【００８３】
【数２】

【００８４】
いま、一例として、幅コードｃの各値に対応するパルス幅Ｗを表２のように設定すると、パルス開始位置Ｓは表３のようになる。
【００８５】
【表２】

【００８６】
【表３】

【００８７】
幅コードｃの各値に対応するパルス幅Ｗを求める手段について説明する。この手段では、所定の画像パターン（テストパターン）の画像を感光体５１上に実際に形成して、幅コードｃの各値に対応するパルス幅Ｗを求めるものである。この画像パターンの例については、図３〜図８に示す。図３〜図８の各（ａ）〜（ｄ）においては、各画像パターンと当該各画像パターンに対応する幅コードｃが示されている。すなわち、図３〜図８の各図がそれぞれ複数の画像パターンの１組を示していて、各組（各図）における（ａ）〜（ｂ），（ａ）〜（ｄ），（ａ）〜（ｃ）は、それぞれパターン検出マトリクスに対する相対位置が異なる画像パターンとなっている。そして、各画像パターンは、オン画素密度は同じだが、このようにパターン検出マトリクスとの相対位置が異なるために、パターン検出処理回路２が生成する幅コードｃが異なる（ように意図的に選択されている）。図３〜図８に示す画像パターンは、画像パターンの一部分だけを示していて、実際に出力する画像パターンのサイズは、例えば２０mm×２０mm程度の大きさである。
【００８８】
図９〜図１１は、パルス幅Ｗを求める手順を説明するフローチャートである。図９〜図１１の処理は、画像形成装置２０の製造工程において行ってもよいが、ＣＰＵ１４が所定のプログラムに基づいて自動で実行することも可能である。図中のＷの添え字０及び１は、それぞれＬＵＴ回路３ａ及びＬＵＴ回路３ｂに対応する。Ｗ［０］〜Ｗ［８］は、幅コードｃ＝０〜８に対応するパルス幅Ｗを表わしている。Ｗ［０］は、パターン検出マトリクス内の画素が全てオフの場合に相当するが、このときにＬＤ６ａ，６ｂから光パルスを出力すると、画像の白地に不要な画像が描かれる、いわゆる地汚れが発生することがあるため、Ｗ［０］＝０と固定とした。
【００８９】
まず、ＬＵＴ回路３ａ，３ｂについて、幅コードｃ＝０〜８に対応するパルス幅W0，Ｗ1を設定する（ステップＳ１）。このパルス幅Ｗ0（０）〜Ｗ0（８）、Ｗ1（０）〜Ｗ1（８）はデフォルト値となる。黒ベタ画像のパターンの画像を出力して（ステップＳ２）、その黒ベタ画像について、トナー濃度は適正か否か判断する（ステップＳ３）。
【００９０】
この判断は、図９〜図１１の処理を画像形成装置２０の製造工程で行なう場合は、転写紙などに形成された画像を目視にて評価するが、ＣＰＵ１４の制御により自動で行なう場合は、図１２に示すように、図２の構成に対して感光体５１上のトナー濃度を検出する濃度検出装置１７を追加して次のように行ってもよい。
【００９１】
すなわち、濃度検出装置１７は、反射型光センサからなる２つのトナー濃度センサ１８ａ，１８ｂとコンパレータ１９とから構成される。各トナー濃度センサ１８ａ，１８ｂは、感光体５１上の異なる位置に形成される２つの画像パターンのトナー濃度を、光反射率の検出により測定する。そして、反射型光センサ１８ａと１８ｂの検出値をコンパレータ１９で比較し、その比較の結果をＣＰＵ１４に出力する。
【００９２】
この濃度が適正でないときは（ステップＳ３のＮ）、パルス幅Ｗ0［８］，Ｗ1［８］の設定を変更し（ステップＳ４）、ステップＳ２に戻る。適正であるときは（ステップＳ３のＹ）、図３に示す２ｄｏｔ幅の垂直ライン（ａ）と（ｂ）を出力する（ステップＳ５）。そして、出力された図３の２ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ６）。このチェックで同じでないと判断したときには（ステップＳ６のＮ）、パルス幅Ｗ0［４］，Ｗ1［４］の設定を変更し（ステップＳ７）、ステップＳ５に戻る。
【００９３】
２ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じであったときには（ステップＳ６のＹ）、図４に示す１ｄｏｔ幅の水平ライン（ａ）と（ｂ）を出力する（ステップＳ８）。そして、出力された図４の１ｄｏｔ幅の水平ライン（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ９）。このチェックで濃度が同じでないと判断したときには（ステップＳ９のＮ）、パルス幅Ｗ0［２］，Ｗ1［２］の設定を変更し（ステップＳ１０）、ステップＳ８に戻る。
【００９４】
濃度が同じになったときには（ステップＳ９のＹ）、すでに設定したパルス幅Ｗ0［８］，Ｗ0［４］，Ｗ0［０］の値から周知の補間法によりＷ0［４］の仮値を設定し、同様に、幅Ｗ1［８］，Ｗ1［４］，Ｗ1［０］の値からＷ1［４］の仮値を設定する（ステップＳ１１）。
【００９５】
そして、図４に示す１ｄｏｔ幅の垂直ライン（ａ）と（ｂ）を出力する（ステップＳ１２）。そして、出力された図４の２ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ１３）。このチェックで同じでないと判断したときには（ステップＳ１３のＮ）、パルス幅Ｗ0［２］，Ｗ1［２］の設定を変更し（ステップＳ１４）、ステップＳ１２に戻る。
【００９６】
１ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じであったときには（ステップＳ１３のＹ）、図４に示す１ｄｏｔ幅の水平ライン（ｃ）と（ｄ）を出力する（ステップＳ１５）。そして、出力された図４の１ｄｏｔ幅の水平ライン（ｃ）と（ｄ）の濃度が同じかどうかチェックする（ステップＳ１６）。このチェックで濃度が同じでないと判断したときには（ステップＳ１６のＮ）、パルス幅Ｗ0［２］，Ｗ1［２］の設定を変更し（ステップＳ１７）、ステップＳ１５に戻る。
【００９７】
濃度が同じになったときには（ステップＳ１６のＹ）、すでに設定したパルス幅Ｗ0［８］，Ｗ0［４］，Ｗ0［２］，Ｗ0［０］の値から補間法によりＷ0［６］の仮値を設定し、同様に、幅Ｗ1［８］，Ｗ1［４］，Ｗ1［２］，Ｗ1［０］の値からＷ1［６］の仮値を設定する（ステップＳ１８）。
【００９８】
そして、図５に示す３ｄｏｔ幅の垂直ライン（ａ）と（ｂ）を出力する（ステップＳ１９）。そして、出力された図５の３ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ２０）。このチェックで同じでないと判断したときには（ステップＳ２０のＮ）、パルス幅Ｗ0［６］，Ｗ1［６］の設定を変更し（ステップＳ２１）、ステップＳ１９に戻る。
【００９９】
３ｄｏｔ幅の垂直ライン（ａ）と（ｂ）の濃度が同じであったときには（ステップＳ２０のＹ）、図５に示す３ｄｏｔ幅の水平ライン（ｃ）と（ｄ）を出力する（ステップＳ２２）。そして、出力された図５の３ｄｏｔ幅の水平ライン（ｃ）と（ｄ）の濃度が同じかどうかチェックする（ステップＳ２３）。このチェックで濃度が同じでないと判断したときには（ステップＳ２３のＮ）、パルス幅Ｗ0［６］，Ｗ1［６］の設定を変更し（ステップＳ２４）、ステップＳ２２に戻る。
【０１００】
濃度が同じになったときには（ステップＳ２３のＹ）、すでに設定したパルス幅Ｗ0［８］，Ｗ0［６］，Ｗ0［４］，Ｗ0［２］，Ｗ0［０］の値から補間法によりＷ0［７］，Ｗ0［５］，Ｗ0［３］，Ｗ0［１］の仮値を設定し、同様に、幅Ｗ1［８］，Ｗ1［６］，Ｗ1［４］，Ｗ1［２］，Ｗ1［０］の値からＷ1［７］，Ｗ1［５］，Ｗ1［３］，Ｗ1［１］の仮値を設定する（ステップＳ２５）。
【０１０１】
次に、図６に示す横２ｄｏｔ網点（ａ）と（ｂ）を出力する（ステップＳ２６）。そして、出力された図６の横２ｄｏｔ網点（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ２７）。このチェックで同じでないと判断したときには（ステップＳ２７のＮ）、パルス幅Ｗ0［１］，Ｗ1［１］の設定を変更し（ステップＳ２８）、ステップＳ２６に戻る。
【０１０２】
濃度が同じであったときは（ステップＳ２７のＹ）、図７に示す３ｄｏｔＬ型網点（ａ）と（ｂ）を出力する（ステップＳ２９）。そして、出力された図７の３ｄｏｔＬ型網点（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ３０）。このチェックで同じでないと判断したときには（ステップＳ３０のＮ）、パルス幅Ｗ0［５］の設定を変更し（ステップＳ３１）、ステップＳ２９に戻る。
【０１０３】
濃度が同じであったときは（ステップＳ３０のＹ）、図７に示す３ｄｏｔＬ型網点（ａ）と（ｃ）を出力する（ステップＳ３２）。そして、出力された図７の３ｄｏｔＬ型網点（ａ）と（ｃ）の濃度が同じかどうかチェックする（ステップＳ３３）。このチェックで同じでないと判断したときには（ステップＳ３３のＮ）、パルス幅Ｗ1［５］の設定を変更し（ステップＳ３４）、ステップＳ３２に戻る。
【０１０４】
濃度が同じであったときは（ステップＳ３３のＹ）、図７に示す３ｄｏｔＬ型網点（ａ）と（ｄ）を出力する（ステップＳ３５）。そして、出力された図７の３ｄｏｔＬ型網点（ａ）と（ｄ）の濃度が同じかどうかチェックする（ステップＳ３６）。このチェックで同じでないと判断したときには（ステップＳ３６のＮ）、パルス幅Ｗ0［３］の設定を変更し（ステップＳ３７）、ステップＳ３５に戻る。
【０１０５】
濃度が同じであったときは（ステップＳ３６のＹ）、図７に示す３ｄｏｔＬ型網点（ａ）と（ｅ）を出力する（ステップＳ３８）。そして、出力された図７の３ｄｏｔＬ型網点（ａ）と（ｅ）の濃度が同じかどうかチェックする（ステップＳ３９）。このチェックで同じでないと判断したときには（ステップＳ３９のＮ）、パルス幅Ｗ1［３］の設定を変更し（ステップＳ４０）、ステップＳ３８に戻る。
【０１０６】
濃度が同じであったときは（ステップＳ３９のＹ）、図８に示す５ｄｏｔＬ型網点（ａ）と（ｂ）を出力する（ステップＳ４１）。そして、出力された図８の５ｄｏｔＬ型網点（ａ）と（ｂ）の濃度が同じかどうかチェックする（ステップＳ４２）。このチェックで同じでないと判断したときには（ステップＳ４２のＮ）、パルス幅Ｗ0［７］の設定を変更し（ステップＳ４３）、ステップＳ４１に戻る。
【０１０７】
濃度が同じであったときは（ステップＳ４２のＹ）、図８に示す５ｄｏｔＬ型網点（ａ）と（ｃ）を出力する（ステップＳ４４）。そして、出力された図８の５ｄｏｔＬ型網点（ａ）と（ｃ）の濃度が同じかどうかチェックする（ステップＳ４５）。このチェックで同じでないと判断したときには（ステップＳ４５のＮ）、パルス幅Ｗ1［７］の設定を変更し（ステップＳ４６）、ステップＳ４４に戻って、一連の処理を終了する。
【０１０８】
図９〜図１１の処理をＣＰＵ１４がＲＯＭ１５のプログラムに基づいて行なうことにより、パルス幅データ選択手段、パルス幅データ選択処理を実現している。また、図９〜図１１の各工程を画像形成装置２０の製造工程で行なうことにより、画像形成工程、判定工程、選択工程を実現している。
【０１０９】
以上のようにして、ＬＵＴ回路３ａ，３ｂのそれぞれに用いる、例えば表２に例示されるようなパルス幅Ｗの値が求められる。そして、この値をＬＵＴ回路３ａ，３ｂのテーブルデータとして製造工程で予め設定しておくか、ＣＰＵ１４の動作により図９〜図１１の処理を行なったときは、ＣＰＵ１４がＬＵＴ回路３ａ，３ｂのテーブルデータとして設定する。この設定により、データ設定手段、データ設定処理を実現している。
【０１１０】
このようなテーブルデータをＬＵＴ回路３ａ，３ｂに設定した画像形成装置２０を用い、図３〜図８の画像パターン全てと、連続的にオン画素密度が変化する網点パターンからなるグレースケールとを含む画像を転写材上に形成し、目視によって評価すれば、適正な画像濃度が得られることがわかる。
【０１１１】
すなわち、黒ベタ部の濃度は適正となる。１ｄｏｔ幅水平ライン（ａ）〜（ｄ）の濃度は同じになる。グレースケールの濃度変化は連続的となる。２ｄｏｔ幅垂直ライン（ａ）と（ｂ）の濃度は同じになる。３ｄｏｔ幅水平ライン（ａ）〜（ｄ）の濃度は同じになる。横２ｄｏｔ網点（ａ）と（ｂ）の濃度は同じになる。３ｄｏｔＬ型網点（ａ）〜（ｅ）の濃度は同じになる。５ｄｏｔＬ型網点（ａ）〜（ｃ）の濃度は同じになる。
【０１１２】
ＬＵＴ回路３ａ，３ｂに設定するテーブルデータが適切でないと、同じ網点パターンで、パターン検出マトリクスとの相対位置が異なる画像を出力した場合に、濃度差が発生するが、本画像形成装置２０によれば、そのような濃度差の発生を防止することができる。
【０１１３】
なお、本実施の形態では、２つのＬＤ６ａ，６ｂを使用して２本の光ビーム７ａ，７ｂで同時並行的に感光体５１を露光する例について説明したが、さらなる高速化を目的として、使用するＬＤの個数を３つ以上として、３本以上の光ビームで同時並行的に露光を行なうようにしても、前記と同様の手順で各ＬＵＴ回路へのテーブルデータの設定が可能である。ただし、光ビーム数が多いほど、トナーの濃度比較に用いるテストパターンとしての画像パターンの種類が増える。例えば１ｄｏｔ幅水平ラインについていえば、
１光ビーム（ＬＤ６ａのみを使用し、ＬＤ６ｂを使用しない）の場合、
▲１▼ＬＤ６ａの光ビームのみで描く。
▲２▼ＬＤ６ａの光ビームと、次の走査のＬＤ６ａの光ビームとの重ね合せで描く。
【０１１４】
２光ビーム（前記のようにＬＤ６ａ、ＬＤ６ｂを使用）の場合、
▲１▼ＬＤ６ａの光ビームのみで描く。
▲２▼ＬＤ６ａの光ビームとＬＤ６ｂの光ビームの重ね合せで描く。
▲３▼ＬＤ６ｂの光ビームのみで描く。
▲４▼ＬＤ６ｂの光ビームと、次の走査のＬＤ６ａの光ビームとの重ね合せで描く。
【０１１５】
４光ビーム（ＬＤ６ａ、ＬＤ６ｂのほかに、ＬＤ６ｃ、ＬＤ６ｄも使用する）の場合、
▲１▼ＬＤ６ａの光ビームのみで描く。
▲２▼ＬＤ６ａの光ビームとＬＤ６ｂの光ビームの重ね合せで描く。
▲３▼ＬＤ６ｂの光ビームのみで描く。
▲４▼ＬＤ６ｂの光ビームとＬＤ６Ｃの光ビームの重ね合せで描く。
▲５▼ＬＤ６ｃの光ビームのみで描く。
▲６▼ＬＤ６ｃの光ビームとＬＤ６ｄの光ビームの重ね合せで描く。
▲７▼ＬＤ６ｄの光ビームのみで描く。
▲８▼ＬＤ６ｄの光ビームと、次の走査のＬＤ６ａの光ビームとの重ね合せで描く。
というように、（光ビーム数×２）種類の画像パターンが必要である。よって、光ビーム数が増えるほど、トナー濃度比較の回数は増えることになる。
【０１１６】
なお、一度ＬＵＴ回路３ａ，３ｂにパルス幅Ｗのテーブルデータを設定してから、そのままそのデータで画像形成装置２０を使用し続けた場合、副走査位置に形成される画像と、２つの副走査の中間位置に形成される画像とは、感光体５１の特性の経時変化や、ＬＤ６ａ，６ｂの経時劣化による光量低下などにより、トナーの濃度が異なってくる。
【０１１７】
そこで、画像形成装置２０が図９〜図１１を参照して説明した処理を実行してパルス幅Ｗのテーブルデータを算出する機能を有しているときは、図１３に示すように、画像形成装置２０の主電源がオンとなるたびに（ステップＳ５１のＹ）、所定のプロセス設定を行なった（ステップＳ５２）後に、パルス幅Ｗのテーブルデータを算出する処理を実行し（ステップＳ５３）、算出したテーブルデータをＬＵＴ回路３ａ，３ｂに設定して（ステップＳ５４）、スタンバイ状態とするようにすれば（ステップＳ５５）、経時劣化によるトナーの濃度の差異は生じない。
【０１１８】
ステップＳ５１により主電源投入検出手段を、ステップＳ５３，Ｓ５４によりパルス幅データ更新手段を実現している。
【０１１９】
以上説明した画像形成装置２０によれば、２台のＬＤ６ａ，６ｂで同時並行的に静電潜像の形成を行なうので、単一の光ビームで静電潜像を形成する場合に比べて、高速の画像形成が可能となる。
【０１２０】
この際に、ＬＵＴ回路３ａ，３ｂに設定されているテーブルデータは前述のとおりであるため、形成される画像全体にわたって、コードｃの違いによる濃度の違いを防止することができる。
【０１２１】
また、図９〜図１１の処理をＣＰＵ１４の制御で行なう場合は、コードｃの違いによる濃度の違いを防止できるようなパルス幅Ｗを画像形成装置２０が自動で選択して設定することができる。
【０１２２】
濃度検出装置１７は、２つのトナー濃度センサ１８ａ，１８ｂを備えているので、画像パターンを感光体５１上に２組同時に形成して、そのトナー濃度を同時に検出することができるので、迅速な処理が行なえる。
【０１２３】
図１３を参照して説明した処理を行なうので、画像形成装置２０の経時変化に対応して適切なパルス幅Ｗを選択して用いることができる。この場合に、主電源をオンにしたときに限らず、所定のタイミング、例えば所定の枚数の画像形成が行われるごとにステップＳ５３，Ｓ５４を実行するようにしてもよい。
【０１２４】
【発明の効果】
請求項１，９に記載の発明は、単一の光ビームで静電潜像を形成する場合に比べて、高速の画像形成を可能となり、かつ、形成される画像全体にわたって、コードの違いによる濃度の違いを防止することができる。
【０１２５】
請求項２，１０に記載の発明は、請求項１，９に記載の発明において、形成される画像全体にわたって、コードの違いによる濃度の違いを防止することができる。
【０１２６】
請求項３に記載の発明は、請求項１又は２に記載の発明において、コードの違いによる濃度の違いを防止できるようなパルス幅データを画像形成装置が自動で選択して設定することができる。
【０１２７】
請求項４に記載の発明は、請求項３に記載の発明において、コードの違いによる濃度の違いを防止できるようなパルス幅データを画像形成装置が自動で選択して設定することができる。
【０１２９】
請求項５に記載の発明は、請求項３又は４に記載の発明において、画像形成装置の経時変化に対応して適切なパルス幅データを選択して用いることができる。
【０１３０】
請求項６に記載の発明は、請求項５に記載の発明において、画像形成装置の経時変化に対応して適切なパルス幅データを選択して用いることができる。
【０１３１】
請求項７に記載の発明は、請求項３又は４に記載の発明において、単一の光ビームで静電潜像を形成する場合に比べて、２倍の高速で画像形成が可能となる。
【０１３２】
請求項８に記載の発明は、請求項１〜７の何れかの一に記載の発明において、原稿の画像を読取って高速で画像形成を行なうことができる。
【０１３３】
請求項１１に記載の発明は、請求項９又は１０に記載の発明において、画像形成装置の経時変化等に対応してパルス幅データの更新を行なうことができる。
【０１３４】
請求項１２に記載の発明は、請求項９〜１１の何れかの一に記載の発明において、各パターン検出処理回路及びパルス幅設定回路により、高速に画像形成を行なうことができる。
【０１３５】
請求項１３に記載の発明は、請求項１２に記載の発明において、各２台のパターン検出処理回路及びパルス幅設定回路により、高速に画像形成を行なうことができる。
【０１３６】
請求項１４に記載の発明は、コードの違いによる濃度の違いを防止できるようなパルス幅データを画像形成装置が自動で選択して設定することができる。
【０１３７】
請求項１５に記載の発明は、請求項１４に記載の発明において、コードの違いによる濃度の違いを防止できるようなパルス幅データを画像形成装置が自動で選択して設定することができる。
【０１３８】
請求項１６に記載の発明は、請求項１４又は１５に記載の発明において、単一の光ビームで静電潜像を形成する場合に比べて、２倍の高速で画像形成が可能となる。
【０１３９】
請求項１７に記載の発明は、記憶しているプログラムにより請求項１４〜１６の何れかの一に記載の発明と同様の効果を奏する。
【０１４０】
請求項１８に記載の発明は、コードの違いによる濃度の違いを防止できるようなパルス幅データを作成して、コードの違いによる濃度の違いを防止することができる。
【０１４１】
請求項１９に記載の発明は、請求項１８に記載の発明において、コードの違いによる濃度の違いを防止できるようなパルス幅データを作成して、コードの違いによる濃度の違いを防止することができる。
【０１４２】
請求項２０に記載の発明は、請求項１８又は１９に記載の発明において、単一の光ビームで静電潜像を形成する場合に比べて、２倍の高速で画像形成が可能となる。
【図面の簡単な説明】
【図１】本発明の一実施の形態である画像形成装置の全体構成の説明図である。
【図２】プリンタユニットにおける露光装置、感光体等の概念図である。
【図３】幅コードに対応するパルス幅を求めるために使用する２ｄｏｔ幅垂直ラインの画像パターンの説明図である。
【図４】幅コードに対応するパルス幅を求めるために使用する１ｄｏｔ幅水平ラインの画像パターンの説明図である。
【図５】幅コードに対応するパルス幅を求めるために使用する３ｄｏｔ幅水平ラインの画像パターンの説明図である。
【図６】幅コードに対応するパルス幅を求めるために使用する横２ｄｏｔ網点の画像パターンの説明図である。
【図７】幅コードに対応するパルス幅を求めるために使用する３ｄｏｔＬ型網点の画像パターンの説明図である。
【図８】幅コードに対応するパルス幅を求めるために使用する５ｄｏｔＬ型網点の画像パターンの説明図である。
【図９】幅コードに対応するパルス幅を求める手順を示すフローチャートである。
【図１０】同フローチャートである。
【図１１】同フローチャートである。
【図１２】濃度検出装置を備えた場合のプリンタユニットにおける露光装置、感光体等の概念図である。
【図１３】幅コードに対応するパルス幅を求めてＬＵＴ回路に設定する処理のフローチャートである。
【図１４】単一のＬＤで露光走査を行なう重複走査方式を用いた画像形成装置の構成例を説明するブロック図である。
【符号の説明】
２ パターン検出処理回路、パターン検出処理手段
３ａ，３ｂ パルス幅設定回路、パルス幅設定手段
５ａ，５ｂ ドライバ
６ａ，６ｂ 発光素子
１７ 濃度検出装置
１８ａ，１８ｂ 濃度センサ
１９ コンパレータ
２０ 画像形成装置
２２ 画像読取装置
４２ 露光装置
５１ 感光体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, an image processing circuit, a program, a storage medium, and a pulse width data selection method.
[0002]
[Prior art]
In an electrophotographic image forming apparatus, as a method of doubling the pixel density in the sub-scanning direction, the photosensitive member is exposed and scanned with a light beam having a beam diameter larger than the sub-scanning pitch, and a plurality of light beams for exposure overlap. A so-called overlap scanning method is also known in which an image is formed at a different position.
[0003]
For example, an IC manufactured by Oak Technology in the United States, PM-2060i has a function of converting a binary image data input of 1200 dpi into a multi-value PWM output of a 600 dpi writing cycle, and is optically applied to a 600 dpi printer engine. A print output equivalent to 1200 dpi is possible without any mechanical change.
[0004]
A so-called multi-beam scanning method in which a photosensitive member is exposed and scanned simultaneously with a plurality of light beams is widely used for the purpose of improving recording density and recording speed.
[0005]
[Problems to be solved by the invention]
An example of the operation of the write signal processing unit of the exposure apparatus in the image forming apparatus using the overlapping scanning method will be described with reference to FIG. Here, a case where an image forming apparatus having a recording density of 600 dpi in both the main scanning and sub-scanning directions is used to form an image having a recording density of 1200 dpi in both the main scanning and sub-scanning directions will be described.
[0006]
In FIG. 14, the line memory 101 holds 1200 dpi image data for three lines and sends image data corresponding to the position in the main scanning direction to be recorded to the pattern detection processing circuit 102.
[0007]
The pattern detection processing circuit 102 refers to on / off information for 6 dots of 2 dots that are continuous in the main scanning direction to be recorded and 4 dots above and below them in 1200 dpi image data. A matrix in which the main scanning direction and the sub-scanning direction to be referred to are referred to as a pattern detection matrix), and a code corresponding to the pattern is sent to the LUT (lookup table) circuit 103.
[0008]
The LUT circuit 103 sends a preset pulse width signal and pulse position signal to a PWM (pulse width modulation) circuit 104 corresponding to the code sent from the pattern detection processing circuit 102.
[0009]
The PWM circuit 104 sends a PWM signal to the LD driver 105 based on the received pulse width signal and pulse position signal. The PWM signal is output in synchronization with the video clock signal (frequency of 600 dpi).
[0010]
The LD driver 105 supplies a drive current to the LD 106 when receiving the “ON” signal, and supplies an offset current to the LD 106 when receiving the “OFF” signal.
[0011]
As a result, the LD 106 emits light, and the photosensitive drum (not shown) is exposed and scanned by the light beam. The sub-scanning pitch of this exposure scanning is such that the light intensity is 1 / e with respect to the light intensity at the center of the beam. ² By forming an electrostatic latent image at the position where the irradiation positions of adjacent light beams overlap on the photosensitive drum, it is smaller than the sub-scanning pitch of the exposure scan. In addition, image formation at a small pitch is possible. Thus, using an image forming apparatus having a recording density of 600 dpi, an image can be formed at 1200 dpi without changing the video clock frequency and the feed speed in the sub-scanning direction.
[0012]
An object of the present invention is to enable high-speed image formation in an overlap scanning type image forming apparatus as compared with the case where an electrostatic latent image is formed with a single light beam. In addition, it prevents density differences due to code differences over the entire formed image. It is to be.
[0013]
Another object of the invention is in this case to prevent density differences due to code differences over the entire formed image.
[0014]
Another object of the present invention is to enable an image forming apparatus to automatically select and set pulse width data that can prevent a difference in density due to a difference in code.
[0015]
Another object of the present invention is to enable the automatic selection process in this case to be performed quickly.
[0016]
Another object of the present invention is to make it possible to select and use appropriate pulse width data corresponding to a change with time of an image forming apparatus.
[0017]
[Means for Solving the Problems]
The invention according to claim 1 is a photoconductor and a light beam output from a plurality of light emitting elements. Said The photosensitive member is exposed and scanned, and each light emitting element emits light. Said An electrostatic latent image is formed simultaneously at a plurality of positions on the photoconductor with a light beam, Said The light beam sub-scanning pitch is 1 / e with respect to the light intensity at the center of the beam. ² By forming an image at a position where a plurality of the light beams overlap on the photoconductor, Said An exposure device capable of forming an image at a pitch half the sub-scanning pitch, and the exposure device comprises: Image formation Based on a pattern detection matrix including two pattern detection units in the main scanning direction including three pixels in the sub-scanning direction including pixels corresponding to the positions at which the light beams of the image data overlapped with each other. The product of a predetermined weight according to the position of each pixel included in the unit and on / off information is calculated, and for each of the two units included in the pattern detection matrix, the unit A width having a plurality of values representing a pulse width of the light beam by generating a code representing the sum of the products calculated for each of the pixels included in the pixel and adding the codes generated for each of the two units A pattern detection processing means for generating a code, and a pulse width for designating a preset pulse width value of the light beam corresponding to the width code Referring to over data is output from the pattern detection processing circuit Said From the pattern detection processing circuit, the pulse width of the light beam is set and the pulse start position data representing the start position of the pulse of the light beam set in advance corresponding to the pulse width data and the code is referred to. Output Said The image forming apparatus includes: a pulse width setting unit that sets a pulse start position of a light beam; and a driver that causes the light emitting elements to emit light at the set pulse width and pulse start position.
[0018]
Therefore, since an electrostatic latent image is formed in parallel with a plurality of light beams output from a plurality of light emitting elements and an overlapping scanning method is executed, when forming an electrostatic latent image with a single light beam, Compared to high-speed image formation In addition, density differences due to code differences can be prevented over the entire formed image. The
[0019]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the pulse width setting unit includes: Consisting of image patterns with the same on-pixel density For each set of a plurality of image patterns having different relative positions with respect to the pattern detection matrix, Image formation The pulse width data is set so that the density is uniform when
[0020]
Therefore, it is possible to prevent the density difference due to the code difference over the entire formed image.
[0021]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a toner density sensor that detects a toner density of a toner image of the image pattern formed on the photoreceptor; Consisting of image patterns with the same on-pixel density For each of a plurality of sets of image patterns having different relative positions with respect to the pattern detection matrix, each image pattern is formed on the photoconductor in each set, and the toner density sensor Said Image pattern Said For each set, the toner density is detected for each of the plurality of image patterns. Detected toner concentration The pulse width data selection means for selecting the value of the pulse width data so that is uniform, and the selected Said The pulse width data is referred to by the pulse width setting means. Said Data setting means for setting as pulse width data.
[0022]
Accordingly, the image forming apparatus can automatically select and set the pulse width data that can prevent the difference in density due to the difference in code.
[0023]
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the pulse width data selecting unit includes an image pattern having the same on-pixel density for at least three values of the width code. Said The plurality of image patterns having different relative positions to the pattern detection matrix Image formation Of the same on-pixel density formed Said Select the value of the pulse width data so that the density of the image pattern is the same, and correspond to the remaining values Said For pulse width data, a provisional value is determined by interpolating from the pulse width value with respect to the already determined value, and this provisional value is used as an initial value, which is composed of image patterns having the same on-pixel density and is positioned relative to the pattern detection matrix. Multiple image patterns with different Image formation Then, the test patterns having the same on-pixel density formed are selected to have the same density.
[0024]
Accordingly, the image forming apparatus can automatically select and set the pulse width data that can prevent the difference in density due to the difference in code.
[0027]
According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect of the present invention, the pulse width data selecting unit is configured at a predetermined timing. Said Selection of the pulse width data value and the data setting means Said Pulse width data updating means for setting pulse width data is provided.
[0028]
Accordingly, it is possible to select and use appropriate pulse width data corresponding to the temporal change of the image forming apparatus.
[0029]
According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, the image forming apparatus further comprises main power-on detecting means for detecting the main power-on of the image forming apparatus. When the power-on is detected, the pulse width data selection means Said Selection of the pulse width data value and the data setting means Said Set the pulse width data.
[0030]
Accordingly, it is possible to select and use appropriate pulse width data corresponding to the temporal change of the image forming apparatus.
[0031]
Claim 7 The invention described in claim 3 Or 4 In the image forming apparatus described above, the exposure apparatus includes two sets of the light emitting elements.
[0032]
Therefore, it is possible to form an image twice as fast as when forming an electrostatic latent image with a single light beam.
[0033]
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, an image of a document is read. Image formation An image reading device for outputting the image data as image data.
[0034]
Therefore, it is possible to form an image at a high speed by reading a document image.
[0035]
The invention according to claim 9 is: Multiple light emitting elements output Corresponds to the position where the light beams overlap Of image data Based on a pattern detection matrix including two pixels in the main scanning direction, the unit of pattern detection including three pixels in the sub-scanning direction including pixels is determined in advance according to the position of each pixel included in the unit within the unit. A product of the calculated weight and on / off information, and for each of the two units included in the pattern detection matrix, a code representing a sum of the products calculated for each of the pixels included in the unit A pattern detection processing circuit for generating a width code having a plurality of values representing the pulse width of the light beam by adding the codes generated for each of the two units, and corresponding to the width code Multiple presets Said Output from light emitting element Said Output from the pattern detection processing circuit with reference to pulse width data specifying the pulse width value of each light beam Said From the pattern detection processing circuit, the pulse width of the light beam is set and the pulse start position data representing the start position of the pulse of the light beam set in advance corresponding to the pulse width data and the code is referred to. Output Said A pulse width setting circuit for setting a pulse start position of the light beam, Said An exposure apparatus that exposes and scans the surface of the photosensitive member with a light beam is used to form an image by electrophotography, and each of the light emitting elements emits light Said The electrostatic latent image is simultaneously formed at a plurality of positions on the photoconductor with a light beam, Said The light beam sub-scanning pitch is 1 / e with respect to the light intensity at the center of the beam. ² An image forming apparatus that is smaller than the beam diameter defined by the value Exposure scan Do multiple Said By setting the pulse width for the light emitting element, and forming an image at a position where the plurality of light beams overlap on the photoconductor, Exposure scan of Said At half the sub-scanning pitch Image formation This is an image processing circuit that makes it possible.
[0036]
Therefore, when forming an electrostatic latent image with a plurality of light beams output from a plurality of light emitting elements simultaneously and executing an overlapping scanning method to form an electrostatic latent image with a single light beam. Compared to this, high-speed image formation is possible.
[0037]
According to a tenth aspect of the present invention, in the image processing circuit according to the ninth aspect, the pulse width setting circuit includes: Consisting of image patterns with the same on-pixel density For each set of a plurality of image patterns having different relative positions with respect to the pattern detection matrix, Image formation The pulse width data is set so that the density is uniform when
[0038]
Therefore, it is possible to prevent the density difference due to the code difference over the entire formed image.
[0039]
Claim 11 The invention described in claim 9 or 10 In the image processing circuit described in (1), the pulse width setting circuit can update the preset pulse width data.
[0040]
Therefore, it is possible to update the pulse width data in response to a change with time of the image forming apparatus.
[0041]
Claim 12 The invention described in claim 9-11 The image processing circuit according to any one of the above, wherein a plurality of the pattern detection processing circuits and the pulse width setting circuits are provided in accordance with the number of the light emitting elements.
[0042]
Therefore, each pattern detection processing circuit and pulse width setting circuit can form an image at high speed.
[0043]
Claim 13 The invention described in claim 12 The image processing circuit described in 1 is provided with two each of the pattern detection processing circuit and the pulse width setting circuit.
[0044]
Therefore, image formation can be performed at high speed by each of the two pattern detection processing circuits and the pulse width setting circuit.
[0045]
According to a fourteenth aspect of the present invention, an exposure apparatus that exposes and scans the surface of the photosensitive member with a light beam output from a plurality of light emitting elements is provided to perform image formation by an electrophotographic method, and each of the light emitting elements emits light. Said The electrostatic latent image is simultaneously formed at a plurality of positions on the photoconductor with a light beam, Said The light beam sub-scanning pitch is 1 / e with respect to the light intensity at the center of the beam. ² Which is smaller than the beam diameter defined by Exposure scan Do multiple Said About the light emitting element Light beam By setting a pulse width and forming an image at a position where a plurality of the light beams overlap on the photoconductor, Exposure scan of Said At half the sub-scanning pitch Image formation Enable Image formation Based on a pattern detection matrix including two pattern detection units in the main scanning direction including three pixels in the sub-scanning direction including pixels corresponding to the positions at which the light beams of the image data overlapped with each other. The product of a predetermined weight according to the position of each pixel included in the unit and on / off information is calculated, and for each of the two units included in the pattern detection matrix, the unit A width having a plurality of values representing a pulse width of the light beam by generating a code representing the sum of the products calculated for each of the pixels included in the pixel and adding the codes generated for each of the two units A pattern detection processing means for generating a code, and a pulse width for designating a preset pulse width value of the light beam corresponding to the width code Referring to over data is output from the pattern detection processing circuit Said From the pattern detection processing circuit, the pulse width of the light beam is set and the pulse start position data representing the start position of the pulse of the light beam set in advance corresponding to the pulse width data and the code is referred to. Output Said A pulse width setting means for setting a pulse start position of the light beam, a driver for causing each of the light emitting elements to emit light at the set pulse width and pulse start position, and formed on the photoconductor Image pattern A toner concentration sensor for detecting the toner concentration of the toner image of Image forming apparatus Control Consisting of image patterns with the same on-pixel density For each of a plurality of sets of image patterns having different relative positions with respect to the pattern detection matrix, each image pattern is formed on the photoconductor in each set, and the toner density sensor Said Image pattern Said For each set, the toner density is detected for each of the plurality of image patterns. Detected toner concentration A pulse width data selection process for selecting a value of the pulse width data so that is uniform, and this selected Said The pulse width data is referred to by the pulse width setting means. Said A computer-readable program for causing a computer to execute data setting processing to be set as pulse width data.
[0046]
Accordingly, the image forming apparatus can automatically select and set the pulse width data that can prevent the difference in density due to the difference in code.
[0047]
According to a fifteenth aspect of the present invention, in the program according to the fourteenth aspect, the pulse width data selection process includes image patterns having the same on-pixel density for at least three values of the width code. Said The plurality of image patterns having different relative positions to the pattern detection matrix Image formation Of the same on-pixel density formed Said Select the value of the pulse width data so that the density of the image pattern is the same, and correspond to the remaining values Said For pulse width data, a provisional value is determined by interpolating from the pulse width value with respect to the already determined value, and this provisional value is used as an initial value, which is composed of image patterns having the same on-pixel density and is positioned relative to the pattern detection matrix. Multiple image patterns with different Image formation Then, the test patterns having the same on-pixel density formed are selected to have the same density.
[0048]
Accordingly, the image forming apparatus can automatically select and set the pulse width data that can prevent the difference in density due to the difference in code.
[0049]
The invention according to claim 16 is the program according to claim 14 or 15, Said In the pulse width data selection process, the value of the pulse width data is selected when the exposure apparatus includes two light emitting elements.
[0050]
Therefore, it is possible to form an image twice as fast as when forming an electrostatic latent image with a single light beam.
[0051]
Claim 17 The invention described in claim 14-16 A storage medium storing the program according to any one of the above.
[0052]
Therefore, it is claimed by the stored program. 14-16 The same operations and effects as the invention described in any one of the above are obtained.
[0053]
According to an eighteenth aspect of the present invention, an exposure apparatus that exposes and scans the surface of the photosensitive member with a light beam output from a plurality of light emitting elements is provided to perform image formation by electrophotography, and each of the light emitting elements emits light. Said The electrostatic latent image is simultaneously formed at a plurality of positions on the photoconductor with a light beam, Said The light beam sub-scanning pitch is 1 / e with respect to the light intensity at the center of the beam. ² Which is smaller than the beam diameter defined by Exposure scan Do multiple Said About the light emitting element Light beam By setting a pulse width and forming an image at a position where a plurality of the light beams overlap on the photoconductor, Exposure scan of Said At half the sub-scanning pitch Image formation Enable Image formation Based on a pattern detection matrix including two pattern detection units in the main scanning direction including three pixels in the sub-scanning direction including pixels corresponding to the positions at which the light beams of the image data overlapped with each other. The product of a predetermined weight according to the position of each pixel included in the unit and on / off information is calculated, and for each of the two units included in the pattern detection matrix, the unit A width having a plurality of values representing a pulse width of the light beam by generating a code representing the sum of the products calculated for each of the pixels included in the pixel and adding the codes generated for each of the two units A pattern detection processing means for generating a code, and a pulse width for designating a preset pulse width value of the light beam corresponding to the width code Referring to over data is output from the pattern detection processing circuit Said From the pattern detection processing circuit, the pulse width of the light beam is set and the pulse start position data representing the start position of the pulse of the light beam set in advance corresponding to the pulse width data and the code is referred to. Output Said Pulse width setting means for setting a pulse start position of the light beam, and a driver for causing the light emitting elements to emit light at the set pulse width and pulse start position. Image forming apparatus For Consisting of image patterns with the same on-pixel density An image forming step of forming an image on each of the image patterns on the photoconductor for each of a plurality of sets of image patterns having different relative positions with respect to the pattern detection matrix; Said A determination step of determining a toner density of an image pattern, and for each of the plurality of image patterns for each of the sets The determined toner density Selecting a value of the pulse width data so as to be uniform, and a pulse width data selection method.
[0054]
Therefore, pulse width data that can prevent a difference in density due to a difference in code can be created, and a difference in density due to a difference in code can be prevented.
[0055]
According to a nineteenth aspect of the present invention, in the pulse width data selecting method according to the eighteenth aspect, at least three values of the width code are composed of image patterns having the same on-pixel density. Said The plurality of image patterns having different relative positions to the pattern detection matrix Image formation Of the same on-pixel density formed Said Select the value of the pulse width data so that the density of the image pattern is the same, and correspond to the remaining values Said For pulse width data, a provisional value is determined by interpolating from the pulse width value with respect to the already determined value, and this provisional value is used as an initial value, which is composed of image patterns having the same on-pixel density and is positioned relative to the pattern detection matrix. Multiple image patterns with different Image formation Then, the test patterns having the same on-pixel density formed are selected to have the same density.
[0056]
Therefore, pulse width data that can prevent a difference in density due to a difference in code can be created, and a difference in density due to a difference in code can be prevented.
[0057]
Claim 20 The invention described in claim 18 or 19 In the pulse width data selection method described in (1), the image forming step, the determination step, and the selection step are executed for the image forming apparatus including two light emitting elements.
[0058]
Therefore, it is possible to form an image twice as fast as when forming an electrostatic latent image with a single light beam.
[0059]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
[0060]
FIG. 1 is a diagram illustrating a schematic configuration of an electrophotographic image forming apparatus according to the first embodiment. The image forming apparatus 20 includes an image scanner 22 that is an image reading apparatus, a printer unit 23 that performs image formation on a sheet based on image data read by the image scanner 22, and an ADF (Automatic) provided on the image scanner 22. Document Feeder) 24.
[0061]
A contact glass 25 on which an original to be read is placed is provided on the upper surface of the image scanner 22. Below the contact glass 25, a first carriage 28 that includes the illumination lamp 26 and the mirror 27 and can travel along the contact glass 25, and a second carriage that includes the mirrors 29 and 30 and can travel along the contact glass 25. A scanning optical system 34 including a carriage 31, an imaging lens 32, and a CCD (Charge Coupled Device) 33 that is a photoelectric conversion element is provided. The first and second carriages 28 and 31 are driven by a carriage motor (not shown) such as a stepping motor, and travel from the home position (right side) shown in FIG. 1 to the left side at a speed ratio of 2: 1.
[0062]
In the printer unit 23, a paper transport path from a paper feed tray 35 for stacking paper to a paper discharge stacker unit 38 via a printer engine 36, a fixing device 37, etc. for forming an image on the paper by electrophotography. 39 is formed. The printer engine 36 exposes the photoconductor 51 based on the image data read by the image scanner 22, the charging device 52 that uniformly charges the surface of the photoconductor 51, and the image scanner 22, and forms an electrostatic latent image. The exposure device 42, the developing unit 53 that develops the electrostatic latent image formed on the surface of the photoconductor 51 with toner, and the toner image on the photoconductor 51 is transferred to the paper conveyed through the paper conveyance path 39. And a cleaning device 54 for cleaning the surface of the photoconductor 51 after the transfer.
[0063]
The ADF 24 includes a document table 45 on which a document to be fed to the contact glass 25 by the ADF 24 is placed, and a paper discharge unit 46 from which the document that has been read is discharged. Inside the ADF 24, a document conveyance path 47 that communicates from the document table 45 to the paper discharge unit 46 is formed. In the document conveyance path 47, conveyance mechanisms such as an endless belt 49 wound around a plurality of pairs of rollers 48 and a conveyance roller 50 are provided. This transport mechanism is driven by an ADF motor (not shown) such as a stepping motor, and transports the originals placed on the original table 45 one by one toward the contact glass 25. A main body operation panel 55 having a keyboard and a display is provided on the upper surface of the ADF 24.
[0064]
FIG. 2 is a conceptual diagram of the exposure device 42, the photoreceptor 51, and the like in the printer unit 23. Here, an example will be described in which an image having a recording density of 1200 dpi in both the main scanning and sub-scanning directions is formed using the printer unit 23 having a recording density of 600 dpi in both the main scanning and sub-scanning directions.
[0065]
The line memory 1 holds the image data for three lines of 1200 dpi binary image data read by the image scanner 22 and subjected to predetermined signal processing and image processing. Is output to the pattern detection processing circuit 2.
[0066]
The pattern detection processing circuit 2 implements pattern detection processing. Among 1200 dpi image data, 2 dots continuous in the main scanning direction to be recorded, 4 dots above and below them, and 6 dots on / off information. (The matrix to be referred to (for example, the main main scanning direction 2 dots × sub scanning direction 3 dots) is called a pattern detection matrix), and a 600 dpi code corresponding to the information pattern is converted into an LUT (look-up table) circuit 3a. , 3b, respectively.
[0067]
Each of the LUT circuits 3a and 3b implements a pulse width setting means, and a pulse width signal and a pulse position signal set in advance corresponding to the code sent from the pattern detection processing circuit 2 are respectively PWM (pulse (Width modulation) outputs to circuits 4a and 4b.
[0068]
Each PWM circuit 4a, 4b outputs a PWM signal to LD (laser diode) drivers 5a, 5b, respectively, based on the received pulse width signal and pulse position signal. The PWM signal is output in synchronization with a predetermined video clock signal (frequency of 600 dpi). The PWM circuits 4a and 4b can output a pulse signal in which the pulse width and the pulse start position are set with a resolution of 1/256 of the write cycle, for example, within a write cycle of 600 dpi.
[0069]
Each of the LD drivers 5a and 5b realizes a driver, and when receiving an “ON” signal, a driving current is received. When receiving an “OFF” signal, an offset current is set, and LDs (laser diodes) 6a and 6b, which are light emitting elements, respectively. To supply. This drive current is output at the pulse width and pulse position specified by the pulse width signal and pulse position signal. Thus, the photosensitive member 51 is simultaneously scanned with two light beams 7a and 7b (two for convenience in this example, but three or more LDs may be used) output from the LDs 6a and 6b. A so-called multi-light beam scanning method is realized.
[0070]
That is, the photosensitive member 51 is exposed and scanned by the light beams 7a and 7b output from the two LDs 6a and 6b, and electrostatic latent images are formed simultaneously at a plurality of positions on the photosensitive member 51. The sub-scanning pitches 7a and 7b have a light intensity of 1 / e with respect to the light intensity at the beam center. ² By forming an image at a position where the light beams 7a and 7b overlap on the photosensitive member 51, the beam diameter is smaller than the sub-scanning pitch of exposure scanning. Image formation is possible.
[0071]
The light beams 7 a and 7 b emitted from the LDs 6 a and 6 b are scanned in the main scanning direction by the polygon mirror 8 that rotates at a constant speed, and form an image on the surface of the photoreceptor 51 through the lens 9. The sub-scanning pitch of each light beam from the LD 6a and LD 6b on the surface of the photoreceptor 51 is 600 dpi.
[0072]
The synchronization detector 11 includes a photoelectric conversion element and a signal waveform shaping circuit, detects the light beams 7a and 7b of the LD 6a and LD 6b, and outputs the detection signals to the synchronization detection signal separation circuit 12.
[0073]
The synchronization detection signal separation circuit 12 separates the detection signal into the synchronization detection signals of the LD 6 a and LD 6 b and outputs them to the memory control circuit 13.
[0074]
The memory control circuit 13 controls the output of image data from the line memory 1 to the pattern detection processing circuit 2 based on this synchronization detection signal.
[0075]
The CPU 14 operates using the RAM 16 as a work area in accordance with a program stored in the ROM 15 which is a storage medium, and controls the overall operation of each circuit in FIG.
[0076]
Table 1 shows an example of codes generated by the pattern detection processing circuit 2 according to the on / off information of the image data.
[0077]
[Table 1]

[0078]
Table 1 shows an example of a width code c that is a code output from the pattern detection processing circuit 2 to the LUT circuits 3a and 3b. That is, the width code c is a code for determining the aforementioned pulse width (pulse width W). In Table 1, the left column 3dot in the sub-scanning direction of the pattern detection matrix is indicated by the vertical axis and the right column 3dot is indicated by the horizontal axis, and the dot on / off patterns in the left column and the right column are shown. In each 3 dots of the “left column” on the vertical axis, solid black indicates that the dot is on, and white indicates that the dot is off. The same applies to the “right column” on the horizontal axis. The width code c is calculated from the following formulas (1) to (3) from the values of L and R at the intersection of the “left column” 3 dot on / off pattern and the “right column” 3 dot on / off pattern. Determined by (4). For example, when 3 dots of the “left column” and 3 dots of the “right column” are all on in the pattern detection matrix, L = 4 and R = 4 from Table 1, and therefore, from the formula (1), the width code c has a value of “8”.
[0079]
In equations (2) and (3), l _i , R _i Represents on / off information of image data corresponding to the left column and the right column of the pattern detection matrix (on is 1 and off is 0), respectively. The subscript i indicates the position in the vertical direction (sub-scanning direction) in the pattern detection matrix (from the top 0, 1, 2).
[0080]
[Expression 1]

[0081]
The pulse width W corresponding to each value of the width code c is set in advance as table data in the LUTs 3a and 3b. Further, the aforementioned pulse start position (pulse start position S) within the write cycle is determined by the equation (5).
[0082]
In equation (5), P indicates the maximum class value of resolution within the writing period (255 in the case of 1/256 resolution), and k is determined by equation (6).
[0083]
[Expression 2]

[0084]
As an example, when the pulse width W corresponding to each value of the width code c is set as shown in Table 2, the pulse start position S is as shown in Table 3.
[0085]
[Table 2]

[0086]
[Table 3]

[0087]
A means for obtaining the pulse width W corresponding to each value of the width code c will be described. In this means, an image of a predetermined image pattern (test pattern) is actually formed on the photosensitive member 51, and the pulse width W corresponding to each value of the width code c is obtained. Examples of this image pattern are shown in FIGS. In each of FIGS. 3 to 8, (a) to (d), each image pattern and a width code c corresponding to each image pattern are shown. That is, each figure of FIGS. 3 to 8 shows one set of a plurality of image patterns, and (a) to (b), (a) to (d), (a) in each set (each figure). (C) are image patterns having different relative positions with respect to the pattern detection matrix. Each image pattern has the same on-pixel density, but has a different relative position to the pattern detection matrix in this way, and therefore the width code c generated by the pattern detection processing circuit 2 is different (as selected intentionally). ing). The image patterns shown in FIGS. 3 to 8 show only a part of the image pattern, and the size of the actually output image pattern is, for example, about 20 mm × 20 mm.
[0088]
9 to 11 are flowcharts illustrating a procedure for obtaining the pulse width W. The processing in FIGS. 9 to 11 may be performed in the manufacturing process of the image forming apparatus 20, but may be automatically executed by the CPU 14 based on a predetermined program. Subscripts 0 and 1 of W in the figure correspond to the LUT circuit 3a and the LUT circuit 3b, respectively. W [0] to W [8] represent pulse widths W corresponding to the width codes c = 0 to 8, respectively. W [0] corresponds to the case where all the pixels in the pattern detection matrix are off. However, if light pulses are output from the LDs 6a and 6b at this time, an unnecessary image is drawn on a white background of the image, so-called background smearing occurs. Since it may occur, W [0] = 0 was fixed.
[0089]
First, pulse widths W0 and W1 corresponding to the width code c = 0 to 8 are set for the LUT circuits 3a and 3b (step S1). The pulse widths W0 (0) to W0 (8) and W1 (0) to W1 (8) are default values. A black solid image pattern image is output (step S2), and it is determined whether or not the toner density is appropriate for the black solid image (step S3).
[0090]
This determination is made by visually evaluating the image formed on the transfer paper or the like when the processes of FIGS. 9 to 11 are performed in the manufacturing process of the image forming apparatus 20, but when the process is automatically performed under the control of the CPU 14, As shown in FIG. 12, a density detector 17 for detecting the toner density on the photoconductor 51 may be added to the configuration of FIG.
[0091]
That is, the density detection device 17 includes two toner density sensors 18 a and 18 b made of a reflection type photosensor and a comparator 19. Each of the toner density sensors 18a and 18b measures the toner density of two image patterns formed at different positions on the photoconductor 51 by detecting the light reflectance. Then, the detection values of the reflection type optical sensors 18 a and 18 b are compared by the comparator 19, and the comparison result is output to the CPU 14.
[0092]
If this density is not appropriate (N in Step S3), the settings of the pulse widths W0 [8] and W1 [8] are changed (Step S4), and the process returns to Step S2. If it is appropriate (Y in step S3), the 2-dot width vertical lines (a) and (b) shown in FIG. 3 are output (step S5). Then, it is checked whether or not the density of the output 2-dot width vertical lines (a) and (b) in FIG. 3 is the same (step S6). When it is determined that they are not the same in this check (N in step S6), the settings of the pulse widths W0 [4] and W1 [4] are changed (step S7), and the process returns to step S5.
[0093]
When the densities of the 2-dot width vertical lines (a) and (b) are the same (Y in step S6), the 1-dot width horizontal lines (a) and (b) shown in FIG. 4 are output (step S8). . Then, it is checked whether the density of the output 1-dot width horizontal lines (a) and (b) in FIG. 4 is the same (step S9). If it is determined in this check that the concentrations are not the same (N in step S9), the settings of the pulse widths W0 [2] and W1 [2] are changed (step S10), and the process returns to step S8.
[0094]
When the concentrations are the same (Y in step S9), a temporary value of W0 [4] is set by a known interpolation method from the values of the pulse widths W0 [8], W0 [4], and W0 [0] that have already been set. Similarly, a temporary value of W1 [4] is set from the values of widths W1 [8], W1 [4], W1 [0] (step S11).
[0095]
Then, the 1-dot width vertical lines (a) and (b) shown in FIG. 4 are output (step S12). Then, it is checked whether or not the density of the output 2-dot width vertical lines (a) and (b) in FIG. 4 is the same (step S13). When it is determined that they are not the same in this check (N in step S13), the settings of the pulse widths W0 [2] and W1 [2] are changed (step S14), and the process returns to step S12.
[0096]
When the densities of the 1-dot width vertical lines (a) and (b) are the same (Y in Step S13), the 1-dot width horizontal lines (c) and (d) shown in FIG. 4 are output (Step S15). . Then, it is checked whether the density of the output 1-dot width horizontal line (c) and (d) in FIG. 4 is the same (step S16). If it is determined in this check that the concentrations are not the same (N in step S16), the settings of the pulse widths W0 [2] and W1 [2] are changed (step S17), and the process returns to step S15.
[0097]
When the density becomes the same (Y in step S16), the temporary value of W0 [6] is interpolated from the values of the pulse widths W0 [8], W0 [4], W0 [2], and W0 [0] that have already been set. Similarly, a temporary value of W1 [6] is set from the values of the widths W1 [8], W1 [4], W1 [2], W1 [0] (step S18).
[0098]
Then, the 3-dot width vertical lines (a) and (b) shown in FIG. 5 are output (step S19). Then, it is checked whether or not the density of the output 3dot wide vertical lines (a) and (b) in FIG. 5 is the same (step S20). When it is determined that they are not the same in this check (N in step S20), the settings of the pulse widths W0 [6] and W1 [6] are changed (step S21), and the process returns to step S19.
[0099]
When the densities of the 3-dot width vertical lines (a) and (b) are the same (Y in step S20), the 3-dot width horizontal lines (c) and (d) shown in FIG. 5 are output (step S22). . Then, it is checked whether or not the density of the output 3dot wide horizontal line (c) and (d) in FIG. 5 is the same (step S23). If it is determined in this check that the concentrations are not the same (N in step S23), the settings of the pulse widths W0 [6] and W1 [6] are changed (step S24), and the process returns to step S22.
[0100]
When the concentrations are the same (Y in step S23), the values of the pulse widths W0 [8], W0 [6], W0 [4], W0 [2], W0 [0] that have already been set are interpolated by the interpolation method. Temporary values of [7], W0 [5], W0 [3], W0 [1] are set, and similarly, widths W1 [8], W1 [6], W1 [4], W1 [2], W1 Temporary values of W1 [7], W1 [5], W1 [3], W1 [1] are set from the value [0] (step S25).
[0101]
Next, horizontal 2 dot halftone dots (a) and (b) shown in FIG. 6 are output (step S26). Then, it is checked whether or not the density of the output 2 dot halftone dots (a) and (b) in FIG. 6 is the same (step S27). When it is determined that they are not the same in this check (N in step S27), the settings of the pulse widths W0 [1] and W1 [1] are changed (step S28), and the process returns to step S26.
[0102]
If the densities are the same (Y in step S27), 3dotL type halftone dots (a) and (b) shown in FIG. 7 are output (step S29). Then, it is checked whether the output 3dotL type halftone dots (a) and (b) in FIG. 7 have the same density (step S30). When it is determined that they are not the same in this check (N in step S30), the setting of the pulse width W0 [5] is changed (step S31), and the process returns to step S29.
[0103]
If the densities are the same (Y in step S30), 3dotL type halftone dots (a) and (c) shown in FIG. 7 are output (step S32). Then, it is checked whether or not the density of the output 3dotL type halftone dots (a) and (c) in FIG. 7 is the same (step S33). When it is determined that they are not the same in this check (N in step S33), the setting of the pulse width W1 [5] is changed (step S34), and the process returns to step S32.
[0104]
If the densities are the same (Y in step S33), 3dotL type halftone dots (a) and (d) shown in FIG. 7 are output (step S35). Then, it is checked whether or not the density of the output 3dotL type halftone dots (a) and (d) in FIG. 7 is the same (step S36). When it is determined that they are not the same in this check (N in step S36), the setting of the pulse width W0 [3] is changed (step S37), and the process returns to step S35.
[0105]
If the densities are the same (Y in step S36), the 3dotL halftone dots (a) and (e) shown in FIG. 7 are output (step S38). Then, it is checked whether or not the density of the output 3dotL type halftone dots (a) and (e) in FIG. 7 is the same (step S39). When it is determined that they are not the same in this check (N in step S39), the setting of the pulse width W1 [3] is changed (step S40), and the process returns to step S38.
[0106]
When the densities are the same (Y in step S39), 5 dot L type halftone dots (a) and (b) shown in FIG. 8 are output (step S41). Then, it is checked whether or not the density of the outputted 5 dot L type halftone dots (a) and (b) in FIG. 8 is the same (step S42). When it is determined that they are not the same in this check (N in step S42), the setting of the pulse width W0 [7] is changed (step S43), and the process returns to step S41.
[0107]
If the densities are the same (Y in step S42), 5 dot L type halftone dots (a) and (c) shown in FIG. 8 are output (step S44). Then, it is checked whether the density of the outputted 5 dot L type halftone dots (a) and (c) in FIG. 8 is the same (step S45). When it is determined that they are not the same in this check (N in step S45), the setting of the pulse width W1 [7] is changed (step S46), the process returns to step S44, and the series of processes is terminated.
[0108]
The CPU 14 performs the processing of FIGS. 9 to 11 based on the program of the ROM 15, thereby realizing pulse width data selection means and pulse width data selection processing. 9 to 11 are performed in the manufacturing process of the image forming apparatus 20, thereby realizing an image forming process, a determining process, and a selecting process.
[0109]
As described above, the value of the pulse width W as exemplified in Table 2 used for each of the LUT circuits 3a and 3b is obtained. Then, this value is set in advance in the manufacturing process as table data of the LUT circuits 3a and 3b, or when the processing of FIGS. 9 to 11 is performed by the operation of the CPU 14, the CPU 14 sets the table of the LUT circuits 3a and 3b. Set as data. By this setting, data setting means and data setting processing are realized.
[0110]
Using the image forming apparatus 20 in which such table data is set in the LUT circuits 3a and 3b, all of the image patterns in FIGS. 3 to 8 and a gray scale composed of a halftone dot pattern in which the on-pixel density continuously changes are obtained. It can be seen that an appropriate image density can be obtained by forming an image including the image on a transfer material and evaluating it visually.
[0111]
That is, the density of the black solid portion is appropriate. The densities of the 1 dot width horizontal lines (a) to (d) are the same. The gray scale density change is continuous. The densities of the 2-dot wide vertical lines (a) and (b) are the same. The densities of the 3 dot width horizontal lines (a) to (d) are the same. The density of the horizontal 2 dot halftone dots (a) and (b) is the same. The concentrations of the 3 dot L type halftone dots (a) to (e) are the same. The densities of the 5 dot L halftone dots (a) to (c) are the same.
[0112]
If the table data set in the LUT circuits 3a and 3b is not appropriate, a density difference occurs when images having the same halftone dot pattern and different relative positions to the pattern detection matrix are output. Accordingly, the occurrence of such a density difference can be prevented.
[0113]
In this embodiment, the example in which the two light beams 7a and 7b are used to expose the photoconductor 51 in parallel in parallel using the two LDs 6a and 6b has been described. Even if the number of LDs to be used is three or more and exposure is performed in parallel with three or more light beams, table data can be set in each LUT circuit in the same procedure as described above. However, as the number of light beams increases, the types of image patterns as test patterns used for toner density comparison increase. For example, for a 1-dot wide horizontal line,
In the case of one light beam (only LD6a is used and LD6b is not used)
(1) Draw only with the light beam of LD6a.
(2) Draw by superimposing the light beam of the LD 6a and the light beam of the LD 6a in the next scan.
[0114]
In the case of two light beams (using LD 6a and LD 6b as described above),
(1) Draw only with the light beam of LD6a.
(2) Draw by superimposing the light beam of LD6a and the light beam of LD6b.
(3) Draw only with the light beam of LD6b.
(4) Draw by superimposing the light beam of the LD 6b and the light beam of the LD 6a in the next scan.
[0115]
In the case of four light beams (LD6c and LD6d are also used in addition to LD6a and LD6b),
(1) Draw only with the light beam of LD6a.
(2) Draw by superimposing the light beam of LD6a and the light beam of LD6b.
(3) Draw only with the light beam of LD6b.
(4) Draw by superimposing the light beam of LD6b and the light beam of LD6C.
(5) Draw only with the light beam of LD6c.
(6) Draw by superimposing the light beam of LD6c and the light beam of LD6d.
(7) Draw only with the light beam of LD6d.
(8) Draw by superimposing the light beam of the LD 6d and the light beam of the LD 6a in the next scan.
Thus, (number of light beams × 2) types of image patterns are required. Therefore, as the number of light beams increases, the number of toner density comparisons increases.
[0116]
Note that if table data having a pulse width W is once set in the LUT circuits 3a and 3b and then the image forming apparatus 20 is continuously used with the data, the image formed at the sub-scanning position and the two sub-scans are displayed. The toner density differs from the image formed at the intermediate position due to the change in the characteristics of the photoconductor 51 with time and the decrease in the amount of light due to the deterioration of the LDs 6a and 6b with time.
[0117]
Therefore, when the image forming apparatus 20 has a function of calculating the table data of the pulse width W by executing the processing described with reference to FIGS. 9 to 11, as shown in FIG. Each time the main power supply of the apparatus 20 is turned on (Y in step S51), a predetermined process setting is performed (step S52), and then processing for calculating table data of the pulse width W is executed (step S53). If the table data thus set is set in the LUT circuits 3a and 3b (step S54) and is set in the standby state (step S55), the difference in toner density due to deterioration with time does not occur.
[0118]
Step S51 realizes main power-on detection means, and Steps S53 and S54 realize pulse width data update means.
[0119]
According to the image forming apparatus 20 described above, the electrostatic latent image is formed in parallel by the two LDs 6a and 6b, so that compared to the case where the electrostatic latent image is formed by a single light beam. High-speed image formation is possible.
[0120]
At this time, since the table data set in the LUT circuits 3a and 3b is as described above, it is possible to prevent a difference in density due to a difference in the code c over the entire formed image.
[0121]
Further, when the processing of FIGS. 9 to 11 is performed by the control of the CPU 14, the image forming apparatus 20 can automatically select and set a pulse width W that can prevent a difference in density due to a difference in the code c. .
[0122]
Since the density detection device 17 includes two toner density sensors 18a and 18b, two sets of image patterns can be simultaneously formed on the photoconductor 51, and the toner density can be detected simultaneously. Can be done.
[0123]
Since the processing described with reference to FIG. 13 is performed, it is possible to select and use an appropriate pulse width W corresponding to the temporal change of the image forming apparatus 20. In this case, not only when the main power supply is turned on, steps S53 and S54 may be executed at a predetermined timing, for example, every time a predetermined number of images are formed.
[0124]
【The invention's effect】
Claim 1, 9 The invention described in (1) enables high-speed image formation as compared with the case where an electrostatic latent image is formed with a single light beam. In addition, it is possible to prevent differences in density due to code differences over the entire formed image. The
[0125]
Claim 2, 10 The invention described in claim 1, 9 In the invention described in 1), it is possible to prevent a difference in density due to a difference in code over the entire formed image.
[0126]
According to a third aspect of the invention, in the invention of the first or second aspect, the image forming apparatus can automatically select and set pulse width data that can prevent a difference in density due to a difference in code. .
[0127]
According to a fourth aspect of the invention, in the invention of the third aspect, the image forming apparatus can automatically select and set pulse width data that can prevent a difference in density due to a difference in code.
[0129]
Claim 5 The invention described in claim 3 Or 4 In the described invention, it is possible to select and use appropriate pulse width data corresponding to the temporal change of the image forming apparatus.
[0130]
Claim 6 The invention described in claim 5 In the invention described in the above, it is possible to select and use appropriate pulse width data corresponding to a change with time of the image forming apparatus.
[0131]
Claim 7 The invention described in claim 3 Or 4 In the described invention, it is possible to form an image at twice as fast as when forming an electrostatic latent image with a single light beam.
[0132]
Claim 8 The invention described in claim 1 7 In the invention according to any one of the above, an image of a document can be read and image formation can be performed at high speed.
[0133]
Claim 11 The invention described in claim 9 or 10 In the invention described in the above, the pulse width data can be updated in accordance with a change with time of the image forming apparatus.
[0134]
Claim 12 The invention described in claim 9-11 In the invention described in any one of the above, image formation can be performed at high speed by each pattern detection processing circuit and the pulse width setting circuit.
[0135]
Claim 13 The invention described in claim 12 In the invention described in (1), image formation can be performed at high speed by each of the two pattern detection processing circuits and the pulse width setting circuit.
[0136]
Claim 14 The image forming apparatus can automatically select and set pulse width data that can prevent a difference in density due to a difference in code.
[0137]
Claim 15 The invention described in claim 14 In the invention described in the above, the image forming apparatus can automatically select and set the pulse width data that can prevent the density difference due to the code difference.
[0138]
Claim 16 The invention described in claim 14 or 15 In the invention described in (1), it is possible to form an image at twice as fast as in the case of forming an electrostatic latent image with a single light beam.
[0139]
Claim 17 The invention described in claim is based on a stored program. 14-16 There exists an effect similar to the invention as described in any one of these.
[0140]
Claim 18 In the invention described in (1), pulse width data that can prevent a difference in density due to a difference in code can be created, and a difference in density due to a difference in code can be prevented.
[0141]
Claim 19 The invention described in claim 18 In the invention described in 1), pulse width data that can prevent a difference in density due to a difference in code can be created, and a difference in density due to a difference in code can be prevented.
[0142]
Claim 20 The invention described in claim 18 or 19 In the invention described in (1), it is possible to form an image at twice as fast as in the case of forming an electrostatic latent image with a single light beam.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of an exposure device, a photoreceptor, and the like in a printer unit.
FIG. 3 is an explanatory diagram of an image pattern of a 2 dot width vertical line used for obtaining a pulse width corresponding to a width code.
FIG. 4 is an explanatory diagram of an image pattern of a 1-dot width horizontal line used for obtaining a pulse width corresponding to a width code.
FIG. 5 is an explanatory diagram of an image pattern of a 3 dot width horizontal line used for obtaining a pulse width corresponding to a width code.
FIG. 6 is an explanatory diagram of an image pattern of horizontal 2 dot halftone dots used for obtaining a pulse width corresponding to a width code.
FIG. 7 is an explanatory diagram of an image pattern of a 3 dot L type halftone dot used for obtaining a pulse width corresponding to a width code.
FIG. 8 is an explanatory diagram of an image pattern of 5 dot L type halftone dots used for obtaining a pulse width corresponding to a width code.
FIG. 9 is a flowchart showing a procedure for obtaining a pulse width corresponding to a width code.
FIG. 10 is a flowchart of the same.
FIG. 11 is a flowchart of the same.
FIG. 12 is a conceptual diagram of an exposure device, a photoconductor and the like in a printer unit provided with a density detection device.
FIG. 13 is a flowchart of processing for obtaining a pulse width corresponding to a width code and setting the pulse width in an LUT circuit.
FIG. 14 is a block diagram illustrating a configuration example of an image forming apparatus using an overlapping scanning method in which exposure scanning is performed with a single LD.
[Explanation of symbols]
2. Pattern detection processing circuit, pattern detection processing means
3a, 3b Pulse width setting circuit, pulse width setting means
5a, 5b driver
6a, 6b Light emitting element
17 Concentration detector
18a, 18b Concentration sensor
19 Comparator
20 Image forming apparatus
22 Image reader
42 Exposure equipment
51 photoconductor

Claims (20)

A photoreceptor,
Exposing and scanning on the photosensitive member with a light beam in which a plurality of light emitting elements outputs, the concurrent formation of an electrostatic latent image at a plurality of locations on the photoreceptor by the light beams each of light emitting elements is emitted to perform sub-scanning pitch of the plurality of the light beam is intended light intensity relative to the light intensity of the beam center is smaller than the beam diameter defined by the value that is a 1 / e ^2, the plurality over the photosensitive member by forming an image on the light beam are overlapped position, and imageable exposure apparatus at half the pitch of the sub-scanning pitch,
With
The exposure apparatus includes:
Based on a pattern detection matrix including two pattern detection units in the main scanning direction including three pixels in the sub-scanning direction including pixels corresponding to the positions where the light beams of the image data for image formation overlap. A product of a weight determined in advance according to the position of each pixel included in the unit and on / off information is calculated, and for each of the two units included in the pattern detection matrix, A code representing the sum of the products calculated for each of the pixels included in the unit is generated, and a plurality of values representing the pulse width of the light beam are obtained by adding the codes generated for each of the two units. Pattern detection processing means for generating a width code having;
Referring to pulse width data for designating the value of the pulse width of the light beam that has been set in advance corresponding to the width code, to set the pulse width of the light beam output from the pattern detection processing circuit, wherein Referring to pulse start position data indicating the pulse start position of the light beam that has been set in advance in correspondence with the said code pulse width data, the pulse starting position of the light beam output from the pattern detection processing circuit Pulse width setting means for setting,
A driver for causing each light emitting element to emit light at the set pulse width and pulse start position;
An image forming apparatus. The pulse width setting means has a uniform density when each image pattern is formed in each set of a plurality of sets of a plurality of image patterns having a same on-pixel density and different relative positions with respect to the pattern detection matrix. The pulse width data is set so that
The image forming apparatus according to claim 1. A toner density sensor for detecting a toner density of a toner image of the image pattern formed on the photoreceptor;
For each of a plurality of sets of a plurality of image patterns that are composed of image patterns having the same on-pixel density and have different relative positions with respect to the pattern detection matrix, each image pattern is formed on the photoconductor in each set, and the toner density sensor by detecting the toner density of the image pattern on the photosensitive member, wherein said pulse width data selection plurality of the toner concentration detected per image patterns to select the value of the pulse width data to be a uniform for each set Means,
A data setting means for setting the selected the pulse width data as the pulse width data to be referenced by the pulse width setting means,
The image forming apparatus according to claim 1, further comprising: The pulse width data selection means, for at least three values of the width code, said plurality of image patterns relative positions are different with respect to the pattern detection matrix and an image pattern of the same on the pixel density and the image formation, is formed concentration of the image pattern of the same on the pixel density is selected the value of the pulse width data to be the same, for the pulse width data corresponding to the remaining values, interpolated from the value of the pulse width to a value previously determined The provisional value is determined, and the provisional value is used as an initial value to form an image of a plurality of image patterns having the same on-pixel density and different relative positions with respect to the pattern detection matrix. The image forming apparatus according to claim 3, wherein the density is selected so that the density of the test patterns is the same. At a predetermined timing, said by pulse width data selecting means selects the pulse width data value, and, a pulse width data updating means for setting the pulse width data by the data setting means,
The image forming apparatus according to claim 3 or 4. A main power-on detection means for detecting the main power-on of the image forming apparatus;
The pulse width data updating means, the selection of the value of the pulse width data according to the pulse width data selecting unit upon detecting the insertion of the main power supply, and performs setting of the pulse width data by the data setting means,
The image forming apparatus according to claim 5. The exposure apparatus includes two sets of the light emitting elements.
The image forming apparatus according to claim 3 or 4. An image reading device that reads an image of a document and outputs it as image data for image formation ;
The image forming apparatus according to claim 1. Based on a pattern detection matrix including two units of pattern detection consisting of three pixels in the sub-scanning direction including pixels of image data corresponding to positions where light beams output from a plurality of light emitting elements overlap, A product of a weight determined in advance according to the position of each pixel included in the unit and on / off information is calculated, and for each of the two units included in the pattern detection matrix, A code representing the sum of the products calculated for each of the pixels included in the unit is generated, and a plurality of values representing the pulse width of the light beam are obtained by adding the codes generated for each of the two units. A pattern detection processing circuit for generating a width code having,
Referring to pulse width data for specifying the value of the pulse width of the light beams output from a plurality of the light emitting element that is set in advance corresponding to the width code, the light output from the pattern detection processing circuit Set the pulse width of the beam, and output from the pattern detection processing circuit with reference to the pulse start position data representing the pulse start position of the light beam set in advance corresponding to the pulse width data and the code and a pulse width setting circuit for setting a pulse start position of the light beam,
Performs image formation by an electrophotographic system provided with an exposure apparatus that exposes and scans the photosensitive member by the light beam, the electrostatic latent image at a plurality of locations on the photoreceptor by the light beams each of light emitting elements is emitted by performing the formation concurrently, the sub-scanning pitch of the plurality of the light beam is intended light intensity relative to the light intensity of the beam center is smaller than the beam diameter defined by the value that is a 1 / e ² in the image forming apparatus, a plurality of the light emitting element which performs exposure scanning can make settings of the pulse width, the a position overlapped plurality of the light beam on the photosensitive member by forming an image, said exposure scanning It enables image formation at half the sub-scanning pitch.
Image processing circuit. The pulse width setting circuit has a uniform density when each image pattern is formed in each set of a plurality of sets of a plurality of image patterns having a same on-pixel density and different relative positions with respect to the pattern detection matrix. The pulse width data is set so that
The image processing circuit according to claim 9. The pulse width setting circuit can update the preset pulse width data.
The image processing circuit according to claim 9 or 10. A plurality of the pattern detection processing circuits and the pulse width setting circuits are provided according to the number of the light emitting elements, respectively.
The image processing circuit according to claim 9. Two each of the pattern detection processing circuit and the pulse width setting circuit are provided,
The image processing circuit according to claim 12. An exposure apparatus that exposes and scans the surface of the photosensitive member with a light beam output from a plurality of light emitting elements is used to form an image by an electrophotographic method, and a plurality of light beams emitted from each of the light emitting elements are used to form a plurality of light on the photosensitive member. perform the formation of an electrostatic latent image concurrently at the position, the sub-scanning pitch of the plurality of the light beam is defined by the value of light intensity relative to the light intensity of the beam center is 1 / e ² beam are those smaller than the diameter, for a plurality of said light emitting element which performs exposure scanning can make settings of the pulse width of the light beam, in a position overlapping a plurality of said light beam on said photosensitive member by forming an image , to allow the image formation in half the pitch of the sub scanning pitch of the exposure scanning, consisting of the sub-scanning direction of the three pixels including the pixels corresponding to the light beam are overlapped position of the image data for image formation Based on a pattern detection matrix including two units of turn detection in the main scanning direction, a weight determined in advance according to a position in each unit of each pixel included in the unit, and on / off information A product is calculated, and for each of the two units included in the pattern detection matrix, a code representing the sum of the products calculated for each of the pixels included in the unit is generated, and generated for each of the two units. Pattern detection processing means for generating a width code having a plurality of values representing the pulse width of the light beam by adding the generated codes, and a pulse width of the light beam set in advance corresponding to the width code values with reference to the pulse width data for designating a, sets the pulse width of the light beam output from the pattern detection processing circuit, the pulse width data Referring to pulse start position data indicating the start position of the pulse of the light beam that has been set in advance corresponding to the data and the code, setting the pulse start position of the light beam output from the pattern detection processing circuit A pulse width setting means for driving, a driver for causing each of the light emitting elements to emit light at the set pulse width and pulse start position, and a toner density sensor for detecting a toner density of a toner image of an image pattern formed on the photosensitive member If, controls the image forming apparatus includes a, each of said image patterns in each set for a plurality of sets of a plurality of image patterns relative positions are different with respect to the pattern detection matrix and an image pattern of the same on pixel density the image formed on the photosensitive member, to detect the toner density of the image pattern on the photosensitive member by the toner density sensor And the pulse width data selection processing for selecting the value of the pulse width data as the toner concentration detected per the plurality of image patterns for each set is uniform,
And data setting processing for setting the selected the pulse width data as the pulse width data to be referenced by the pulse width setting means,
A computer-readable program that causes a computer to execute. The pulse width data selecting process, for at least three values of the width code the plurality of image patterns relative positions are different with respect to the pattern detection matrix and an image pattern of the same on the pixel density and image formation was formed concentration of the image pattern of the same on the pixel density is selected the value of the pulse width data to be the same, for the pulse width data corresponding to the remaining values, interpolated from the value of the pulse width to a value previously determined The provisional value is determined, and the provisional value is used as an initial value to form an image of a plurality of image patterns having the same on-pixel density and different relative positions with respect to the pattern detection matrix. Select so that the density of the density test pattern is the same,
The program according to claim 14. In the pulse width data selection process, the value of the pulse width data is selected when the exposure apparatus includes two light emitting elements.
The program according to claim 14 or 15. A program according to any one of claims 14 to 16 is stored.
Storage medium. An exposure apparatus that exposes and scans the surface of the photosensitive member with a light beam output from a plurality of light emitting elements is used to form an image by an electrophotographic method, and a plurality of light beams emitted from each of the light emitting elements are used to form a plurality of light on the photosensitive member. perform the formation of an electrostatic latent image concurrently at the position, the sub-scanning pitch of the plurality of the light beam is defined by the value of light intensity relative to the light intensity of the beam center is 1 / e ² beam are those smaller than the diameter, for a plurality of said light emitting element which performs exposure scanning can make settings of the pulse width of the light beam, in a position overlapping a plurality of said light beam on said photosensitive member by forming an image , to allow the image formation in half the pitch of the sub scanning pitch of the exposure scanning, consisting of the sub-scanning direction of the three pixels including the pixels corresponding to the light beam are overlapped position of the image data for image formation Based on a pattern detection matrix including two units of turn detection in the main scanning direction, a weight determined in advance according to a position in each unit of each pixel included in the unit, and on / off information A product is calculated, and for each of the two units included in the pattern detection matrix, a code representing the sum of the products calculated for each of the pixels included in the unit is generated, and generated for each of the two units. Pattern detection processing means for generating a width code having a plurality of values representing the pulse width of the light beam by adding the generated codes, and a pulse width of the light beam set in advance corresponding to the width code values with reference to the pulse width data for designating a, sets the pulse width of the light beam output from the pattern detection processing circuit, the pulse width data Referring to pulse start position data indicating the start position of the pulse of the light beam that has been set in advance corresponding to the data and the code, setting the pulse start position of the light beam output from the pattern detection processing circuit And an image pattern having the same on-pixel density for an image forming apparatus comprising: a pulse width setting unit configured to perform a driver for causing the light emitting elements to emit light at the set pulse width and pulse start position. An image forming step of forming an image on each of the image patterns on the photoconductor with respect to a plurality of sets of image patterns having different relative positions with respect to the detection matrix;
A determination step of determining toner concentration of the image pattern image forming,
A selection step of selecting the value of the pulse width data so that the toner density determined for the plurality of image patterns for each set is uniform;
A pulse width data selection method comprising: The image pattern of at least three for values, the plurality of image patterns relative positions are different with respect to the pattern detection matrix and an image pattern of the same on the pixel density and the image formation, the same on-pixel density formed in the width code concentrations selecting the value of the pulse width data to be the same, for the pulse width data corresponding to the remaining values, such values of the temporary interpolated from the values of the pulse width to a value previously determined, Using this temporary value as an initial value, a plurality of image patterns consisting of image patterns having the same on-pixel density and different relative positions to the pattern detection matrix are imaged, and the densities of the formed test patterns having the same on-pixel density are the same. Choose to be,
The pulse width data selection method according to claim 18. For the image forming apparatus including the two light emitting elements, the image forming step, the determining step, and the selecting step are executed.
The pulse width data selection method according to claim 18 or 19.

Images