JP3564042B2 - Image forming apparatus and color misregistration detection processing method of image forming apparatus - Google Patents

Description

【００９２】
一方、主走査方向に関して、左右各々の各色の位置ずれ量δｅｍｆ、δｅｍｒは、
ｄｍｆＢｋ＝ｖ＊（ｔｍｆｌ−ｔｓｆｌ）……（４）
ｄｍｆＹ ＝ｖ＊（ｔｍｆ２−ｔｓｆ２）……（５）
ｄｍｆＭ ＝ｖ＊（ｔｍｆ３−ｔｓｆ３）……（６）
ｄｍｆＣ ＝ｖ＊（ｔｍｆ４−ｔｓｆ４）……（７）
ｄｍｒＢｋ＝ｖ＊（ｔｍｒｌ−ｔｓｒｌ）……（８）
ｄｍｒＹ ＝ｖ＊（ｔｍｒ２−ｔｓｒ２）……（９）
ｄｍｒＭ ＝ｖ＊（ｔｍｒ３−ｔｓｒ３）……（１０）
ｄｍｒＣ ＝ｖ＊（ｔｍｒ４−ｔｓｒ４）……（１１）から、
δｅｍｆＹ＝ｄｍｆＹ−ｄｍｆＢｋ ……（１２）
δｅｍｆＭ＝ｄｍｆＭ−ｄｍｆＢｋ ……（１３）
δｅｍｆＣ＝ｄｍｆＣ−ｄｍｆＢｋ ……（１４）と、
δｅｍｒＹ＝ｄｍｒＹ−ｄｍｒＢｋ ……（１５）
δｅｍｒＭ＝ｄｍｒＭ−ｄｍｒＢｋ ……（１６）
δｅｍｒＣ＝ｄｍｒＣ−ｄｍｒＢｋ ……（１７）となり、計算結果の正負からずれ方向が判断出来、上記δｅｍｆから書出し位置を、δｅｍｒ−δｅｍｆから主走査幅を補正する。
【００９３】
なお、主走査幅に誤差がある場合は、書出し位置はδｅｍｆのみでなく、主走査幅補正に伴い変化した画像周波数の変化量を加味して算出する。
【００９４】
〔第２実施形態〕
図７は、本発明の第２実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図４と同一のものには同一の符号を付してある。なお、センサの光学系は、図２に示したは第１実施形態と同じである。以下、第１実施形態と異なる点のみ説明する。
【００９５】
図７において、１０５はピークホールド回路で、Ｉ／Ｖ変換回路１０１から出力されるパターン検知波形のピーク値を一定時間保持する。
【００９６】
搬送ベルト３に形成された色ずれ検知パターンが読み取られて、Ｉ／Ｖ変換回路１０１でパターン検知に基づく電流が電圧信号に変換されると、ピークホールド回路１０５の働きでパターン検知波形のピーク値を一定時間保持する。その結果、振幅値がパターン検知波形のピーク値と等しいパルス波形が生成される。この波形を増幅して振幅値が電源電圧に等しいパルス波形に変換する。
【００９７】
図８は、図７に示したＩ／Ｖ変換回路１０１から出力されるパターン検知波形の一例を示す特性図であり、図５と同一のものには同一の符号を付してある。
【００９８】
図８において、（ａ），（ｂ）は第１実施形態と同様である。（ｃ）は出力波形（ｂ）の波形を反転して生成した出力波形である。この出力波形（ｃ）はそれぞれの波形のピーク時に色ずれ検出パターンを検知していることになる。
【００９９】
（ｄ）は出力波形（ｃ）に対して、図６に示したピークホールド回路１０５の信号処理により生成されるパルス信号である。なお、ピークホールド回路１０５はピーク時の電圧を一定時間保つ働きがあり、出力波形（ｃ）の波形がピーク時を迎えたときに、パルス信号（ｄ）が出力波形（ｃ）のピーク時の電圧まで立ち上がる。
【０１００】
その後、一定時間を経過するとＧＮＤレベルに戻る。その結果、パルス信号（ｄ）の立ち上がりのタイミングが色ずれ検出パターンの検知タイミングとなって、図７に示すＣＰＵ１０４に入力される。ＣＰＵ１０４は４色分のパルスの立ち上がリタイミングの時間差をそれぞれ求めて、求めた時間差と予め設定してある時間差の値の差から色ずれ量を算出する。以後の処理は、第１実施形態と同様である。
【０１０１】
〔第３実施形態〕
図９は、本発明の第３実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図７と同一のものには同一の符号を付してある。センサの光学系は、第１実施形態と同じであるため、以下、第１実施形態と異なる構成および動作について説明する。
【０１０２】
図において、１０６はＡ／Ｄ変換器で、Ｉ／Ｖ変換回路１０１が当該受光光量に比例する電流を電圧信号に変換する。１０７はＲＡＭで、Ａ／Ｄ変換器１０６によりＡ／Ｄ変換されたデジタル化された受光光量データを記憶する。
【０１０３】
この様に構成されたカラー画像形成装置において、受光部（ＰＤ）１００で正反射光を検知して光量を電流に変換すると、Ｉ／Ｖ変換回路１０１が当該受光光量に比例する電流を電圧信号に変換する。次に、Ａ／Ｄ変換器１０６を用いてデジタル化する。そして、デジタル化された受光光量データをＣＰＵ１０４で読み取りＲＡＭ１０７に格納する。そして、ＲＡＭ１０７に保存されたデータから波形のピークを検出して、色ずれ検出パターンの位置を検出する。
【０１０４】
図１０は、図９に示したＩ／Ｖ変換回路１０１から出力されるパターン検知波形の一例を示す特性図であり、図８と同一のものには同一の符号を付してある。
【０１０５】
図１０において、（ａ），（ｂ）は第１実施形態と同様である。（ｃ）は出力波形（ｂ）をデジタル化したものであり、図中の点と点の間隔はサンプリング周期によって決定される。この間隔が小さいほど測定精度が向上する。
【０１０６】
ここでは説明の簡略化を図るため点と点の間隔を大きく取ってある。この点はＣＰＵ１０４によってＲＡＭ１０７に順次格納される。このとき、データのアドレスは連続しているものとする。このデータを大まかに４個に区切り、それぞれの中から、最小値のデータが格納されているアドレスを検出する。
【０１０７】
これが、色ずれ検出パターンの位置情報となる。さらに、それぞれのアドレスの差分を求めてサンプリング周期を掛け合わせると、各色ずれ検出パターンの検知時間差を検出でき、該求めた時間差とあらかじめ設定してある時間差の値との差から各色の色ずれ量を算出する。以後の処理は、第１実施形態と同様である。
【０１０８】
〔第４実施形態〕
図１１は、本発明の第４実施形態を示すカラー画像形成装置における色ずれパターン検知機構の一例を説明する図であり、図２と同一のものには同一の符号を付してある。なお、パターン読み取り系が正反射光学系で構成されている場合に対応する。
【０１０９】
図において、５１は発光素子で、例えばＬＥＤで構成されている。５２ａ，５２ｂは受光素子で、例えばフォトセンサである。３は搬送ベルトで、９、１０、１１、１２は色ずれ検出パターンである。
【０１１０】
５３は前記発光素子５１からの発光光で、５４ｂは受光光で、搬送ベルト３又は、色ずれ検出パターン９、１０、１１、１２からの反射光の内、受光素子５２にて受光される。
【０１１１】
図１２は、本発明の第４実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図４と同一のものには同一の符号を付してある。
【０１１２】
図１２において、受光素子５２ａがＰＤｌ００に、受光素子５２ｂがＰＤ２００に対応する。ＰＤｌ００、２００で検出した色ずれ検出パターンは、Ｉ／Ｖ変換回路１０１、２０１により各々電流から電圧に変換される。２つの受光素子５２ａ，５２ｂの受光感度の差はＩ／Ｖ変換回路１０１、２０１の変換率を調整することにより、Ｉ／Ｖ変換後は同じになる。
【０１１３】
比較部１０２では、受光素子５２ａ，５２ｂに対応した信号レベルが互いに比較され、受光素子５２ｂに対応する信号レベルの方が受光素子５２ａに対応する信号レベルより低い期間、正パルスが後述する図１３にに示すタイミングで出力される。
【０１１４】
図１３は、図１２に示したＩ／Ｖ変換回路１０１，２０１から出力されるパターン検知波形の一例を示す特性図である。
【０１１５】
図１３において、（ａ）は受光素子５２ａ，５２ｂの搬送ベルト３の搬送方向のパターン幅を時間ｔで示した状態である。（ｂ）は受光素子５２ａの出力をＩ／Ｖ変換回路１０１によるＩ／Ｖ変換後の出力波形である。（ｃ）は受光素子５２ｂの出力をＩ／Ｖ変換回路２０１によるＩ／Ｖ変換後、さらに図示しないクリップ回路にて高レベルがクリップされた後の出力波形である。
【０１１６】
なお、上記第４実施形態においては、図１２に示す出力波形（ｃ）（ｂ）には各々４つの谷が存在する。第１番目がイエローの色ずれ検出パターンで、第２番目がマゼンタ、第３番目がシアン、第４番目がブラックの色ずれ検出パターンに相当する。
【０１１７】
図１３に示す例では、受光素子５２ａ，５２ｂは搬送ベルト３の搬送方向に沿って隣接して配置されているので、色ずれ検出パターン９、１０、１１、１２が、搬送ベルト３の搬送により、受光素子５２ａ，５２ｂを通過すると、受光素子５２ａでの出力波形の信号レベルが立上がる時、同時に、受光素子５２ｂでの出力波形の信号レベルが立下がる。
【０１１８】
一方、図１３のＩ／Ｖ変換回路１０１，２０１で、２つの受光素子５２ａ，５２ｂの受光感度の差が調整されているので、受光素子５２ａ，５２ｂに対応する信号の振幅の中間レベルで立上がりと立下がりが交差する。そして、Ｉ／Ｖ変換回路１０１，２０１によるＩ／Ｖ変換後の各信号レベルは、下地レベルが同じなので、このままでは、コンパレータ等の比較部１０２に入力すると、出力にチャタリングが発生してしまう。
【０１１９】
そこで、受光素子５２ｂに対応した信号の高レベル（下地レベル）をクリップし、各信号の下地レベルを異なる値とする。つまり、正パルス（ｄ）の立ち上がりは、色ずれ検出パターン９、１０、１１、１２の中心が受光素子５２ａ，５２ｂの中心部を通過したタイミングを示す。このタイミングは、色ずれ検出パターン９、１０、１１、１２の線幅の変動や、発光部５１の光量変動の影響を受けない。
【０１２０】
そこで、図１３に示すように、各色パルス波形（正パルス（ｄ））の立上りの時間差をＣＰＵ１０４が求め、該求めた時間差とあらかじめ設定してある時間差の値との差から各色の色ずれ量を算出する。以後の処理は、第１実施形態と同様である。
【０１２１】
〔第５実施形態〕
図１４は、本発明の第５実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図４と同一のものには同一の符号を付してある。本実施形態は、本発明に係るピークホールド回路の詳細例に対応する。以下、構成および動作について説明する。
【０１２２】
図１４において、受光素子５２、すなわち、ＰＤｌ００からの検出電流は、Ｉ／Ｖ変換回路１０１によって電圧に変換される。上側ピークホールド回路３０１と下側ピークホールド回路３０３により最大値、最小値がそれぞれ検出されて、抵抗器３０２，抵抗器３０４で分圧される。Ｉ／Ｖ変換回路１０１の出力波形と抵抗器３０２，抵抗器３０４で分圧された電圧値を比較回路３０５で大小関係を判断して、後述する図１４に示す出力波形（ｂ）に対応するパルス信号を生成する。
【０１２３】
ここで、上側ピークホールド回路３０１と下側ピークホールド回路３０３が最大値・最小値をそれぞれ取得するためには、予めラインを１つ読み込んでおく必要がある。ここで取得した最大値，最小値から、パルス変換基準電圧を作成する。つまり、本実施形態では、図６でしたレジマークの直前に、最大値，最小値取得用のレジマークを作成する必要がある。具体的には、図１５に示すように、レジマークの直前にピーク決定用のマーク１３ａ，１４ａを化正する。
【０１２４】
図１６は、図１４に示した色ずれセンサ回路によるパターン検知波形の一例を示す特性図であり、図５と同一のものには同一の符号を付してある。
【０１２５】
図１６において、（ａ）は受光素子５２の搬送ベルト３の搬送方向の幅を時間ｔで表しし、Ｉ／Ｖ変換回路の出力波形（ｂ）の推移と受光素子５２の位置関係を示す。搬送ベルト３はグロスが高く、発光光５３の大部分が正反射光５４ｂとなり、受光素子５２にて受光される。
【０１２６】
トナー像である色ずれ検出パターンはグロスが低く、発光光５３の大部分が散乱され、図２に示すような受光素子５２にて受光される正反射光５４ｂは僅かである。出力波形（ｂ）は、搬送ベルト３を検出している時高く、色ずれ検出パターンを検出している時低くなる。なお、閾値（ｃ）の値は抵抗器３０２，３０４の分圧比によって決定される。この関係は、Ａ：Ｂ＝抵抗器３０２：抵抗器３０４の式で表現される。
【０１２７】
搬送ベルト３に色ずれ検出パターンイエロー９、マゼンタ１０、シアン１１、ブラック１２を形成し、光センサ６ａ，６ｂにて検出する。受光素子５２からは、図１６に示すように４つのピークをもつ出力波形（ｂ）が出力される。第１番目がイエローの色ずれ検出パターンで、第２番目がマゼンタ、第３番目がシアン、第４番目がブラックの色ずれ検出パターンに相当する。このとき、４色のパターンを検知する波形は同様の形状を示す。第１〜４番目の谷は、閾値（ｃ）より低くなり、図１６に示すパルス信号（ｄ）が比較回路３０５から出力される。そして、図３に示した演算部５３で、図１６に示す第１〜４番目の各々のパルス信号（ｄ）の中心位置を求め、さらに、各中心位置の時間差を求める。求めた時間差と予め設定してある時間差の値の差から、色ずれ量を算出する。以後の処理は、第１実施形態と同様である。
【０１２８】
〔第６実施形態〕
なお、上述した様な反射型光学系においては受光部の検知光量を大きくできる正反射光学系が使われることが多いが、反面、正反射光学系はグロス値の大小に反応するため、像担持体上に出来たキズによって生じるグロス値の減少に対しても敏感に検知してしまう。このため、使用を重ねてキズが多くなった像担持体では、キズをレジマークと誤検知するケースが生じてくる。そこで、ピーク値の検出レベルを調整することにより、多少のキズが搬送ベルト上に生じても、色ずれ検知パターン画像を正常に読み取れるように構成してもよい。以下、その実施形態について説明する。
【０１２９】
図１７は、本発明の第６実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図１４と同一のものには同一の符号を付してある。本実施形態は、本発明に係るピークホールド回路の他の詳細例（第５実施形態の変形例）に対応する。以下、構成および動作について説明する。
【０１３０】
図１７において、４０２はアナログスイッチで、ＣＰＵ３１からの信号で任意の抵抗値（抵抗器４０１−１〜４０１−Ｎ）を選択できるようになっている。
【０１３１】
図１８は、図１７に示した色ずれセンサ回路によるパターン検知波形の一例を示す特性図であり、図１６と同一のものには同一の符号を付してある。
【０１３２】
図１８に示すように、画像形成に伴う経時変化等の要因により像担持体（搬送体として構成される場合）上にキズ等が生じた場合、出力波形（ｂ）の中央部分には像担持体上に形成されたキズによる波形が発生している。この場合、閾値（ｃ）の基準電圧値が初期設定値状態のＡレベルでは、誤検知パルスＥＰ１，ＥＰ２が発生してしまい制御エラーとなる。
【０１３３】
そこで、ＣＰＵ３１は、図１５に示すアナログスイッチ４０２を操作指示して、その抵抗値を切り替えて基準電圧値生成条件を設定制御する。そして、基準電圧値がＢレベル（Ａレベルを越える）となれば誤検知パルスは発生しなくなり、正常に制御を完了することが可能な状態となる。
【０１３４】
〔第７実施形態〕
図１９は、本発明の第７実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図であり、図１４と同一のものには同一の符号を付してある。本実施形態は、本発明に係るピークホールド回路の他の詳細例（第５実施形態の変形例）に対応する。
【０１３５】
なお、第５実施形態と異なる特徴点は、上側ピークホールド回路３０１と下側ピークホールド回路３０３のそれぞれに記憶したピーク値をクリアするためのリセット信号入力端子が上側ピークホールド回路３０１と下側ピークホールド回路３０３に付加されている点である。以下、構成および動作について説明する。
【０１３６】
上述したように像担持体がベルト状の場合は、取り付け部の構成にもよるが、測定対象物と色ずれ検出センサ間の距離が変動しやすく、それに伴い出力電圧値も変動してしまう事が多い。そのようなケースでは、ピークホールド回路３０１，３０３が取得した最大値，最小値が必ずしも最適なものでは無い可能性が生じることになる。
【０１３７】
そこで、本実施形態では、ある周期でピークホールド回路３０１，３０３が取得したピーク値を、例えばＣＰＵ３１からのリセット信号をクリアして新たなピーク値を取得しなおすことでより正確なレジマーク検出が可能となる。
【０１３８】
なお、図６に示したレジマークを１つの単位として、複数のレジマーク郡を測定して複数の色ずれ値を取得して読み取り精度を向上させる処理を行う場合には、レジマーク群を検知する直前のタイミングでＣＰＵ３１からリセット信号を受け取り、再度ピーク値取得用マークから新たなピーク値を取得して測定精度の向上を図ることが可能である。
【０１３９】
〔第８実施形態〕
なお、上記第１〜第７実施形態では、レジスト補正用の色ずれ画像検出処理を全て正反射光学系により検出する場合について説明したが、従来系の乱反射光学系に、ピークホールド手段と、リセット手段を組み込んで、黒色と他の色の色ずれ検知処理を切り換えて色ずれ量検知処理を行えるように構成してもよい。
【０１４０】
図２０は、本発明の第８実施形態を示すカラー画像形成装置における色ずれセンサ回路によるパターン検知波形の一例を示す特性図であり、横軸は時間を示す。
【０１４１】
図２０において、（ａ）は受光素子５２の搬送ベルト３の搬送方向のパターン幅を時間ｔで示した状態である。（ｃ）はＩ／Ｖ変換回路１０１により出力されるパターン読み取り出力波形で、（ｂ）は基準電圧１０３である。（ｄ）は搬送ベルト３上に形成された色ずれ検出パターンの検出パターン読み取り時に出力されるパルス信号である。
【０１４２】
図２０に示す例では、光学系に乱反射光学系を用いているために、Ｉ／Ｖ変換回路の出力波形（ｂ）は反射特性をもつＹＭＣ色レジマークを検知した場合には出力が増大して、Ｂｋ色レジマークを検知した際には出力が減少する。
【０１４３】
従って、測定光学系が乱反射光学系の場合には、ＹＭＣ色レジマークとＢｋ色レジマークで出力波形の振る舞いが異なるため、それぞれのレジマークの間にリセット信号をＣＰＵ３１等より挿入して、既にホールドされているピーク値をクリアする処理を行う。
【０１４４】
これにより、ＹＭＣ色レジマークとＢｋ色レジマークの読み取りに基づくパルス信号をＣＰＵ３１が得ることができる。
【０１４５】
図２１は、本発明に係る画像形成装置における画像処理手順の一例を示すフローチャートである。なお、（１）〜（１４）は各ステップを示す。
【０１４６】
先ず、ＣＰＵ３１は、各画像形成ステーションのレジスト補正タイミングかどうかを判定し（１）、レジスト補正タイミングでないと判定した場合には、ステップ（１２）へ進み、出力すべき画像データを受信するのを待機し、画像データを受信したら、ＣＰＵ３１内の不揮発性メモリに記憶されている現在の補正タイミングで、各画像形成ステーションでの画像書き出しを制御しながら、画像を形成する（１３）。そして、画像形成終了と判定されるまで画像形成を繰り返し（１４）、画像形成が終了したら、処理を終了する。なお、画像形成により形成された画像形成数は、上記不揮発性メモリに記憶され、次のレジスト補正タイミング時に参照される。
【０１４７】
なお、ステップ（１）におけるレジスト補正タイミングの判定は、一定の画像形成枚数毎、あるいは、図示しない操作パネルや外部ホストからのレジスト補正指示や、前回のレジスト補正実行時からの経過時間，プリント枚数等を基準としてレジスト補正タイミングを判定するものとする。
【０１４８】
一方、ステップ（１）で、レジスト補正タイミングであると判定された場合には、ＣＰＵ３１は、位置ずれ補正モードを設定して、位置ずれ検知パターンデータをＲＯＭ等から読み出して（２）、各画像形成ステーションで各色に対応する位置ずれ検知パターン（図６参照）を形成する（３）。
【０１４９】
次に、各画像形成ステーションで形成された位置ずれ検知パターンを搬送ベルト３に転写したら（４）、位置ずれパターン画像を正反射光学系、例えば図２に示した読み取りトナー像検出センサを構成する受光素子５２により位置ずれ検知パターンを検出し（５）、検出したパターン画像に基づく電流値をＩ／Ｖ変換回路１０１によりＩ／Ｖ変換した後、ピークホールド回路１０５によりピークホールドする（６）。
【０１５０】
次に、ピークホールド回路１０５によりピークホールドした値と基準電圧値とを比較して基準電圧値をピークホールドした値が越えるかどうかを判定して（７）、越えたと判定した場合には、各色毎のパターン検出パルス信号を生成し（８）、搬送ベルト３上に転写された位置ずれ検知パターンの読み取りがＮ回終了するのを待機し（９）、読み取りが終了したら、該各色毎のパターン検出パルス信号に演算処理を加えて、ＣＰＵ３１が基準色である黒色線パターンと他の色の線パターンとの位置ずれ量を算定する（１０）。
【０１５１】
次に、算定された位置ずれ量に基づき、各画像形成ステーションの画像書き出しタイミングを決定して、例えば不揮発性メモリに記憶される前回の補正タイミングデータを今回算定された補正タイミングデータに書き換えて（１１）、処理を終了する。
【０１５２】
上記実施形態によれば、正反射光学系を用いた色ずれ検出手段で反射光量を大きく確保できるため、光源の発光量を押さえることが出来る。さらに、ＹＭＣＫ４色のトナーを同様に検知できるので、光源の発光周波数を自由に選択することが可能となる。さらに、色ずれ検出手段からの出力信号の１点が色ずれ検出パターンの位置情報を示すので、少ない演算量で色ずれ量を算出可能である。
【０１５３】
また、レジマーク測定波形自身からパルス変換に用いる基準電圧値をリアルタイムに生成することでＬＥＤの光量個体差ばらつきや経時劣化による光量低下、また像担持体の表面反射率劣化に起因する出力変動に関して調整機構を設ける必要が無くなり、コストダウンを図ることができる。
【０１５４】
また、基準電圧値の補正機構を設けることで、像担持体上のキズによるレジマーク誤検知を防止できる。
【０１５５】
以下、図２２に示すメモリマップを参照して本発明に係る画像形成装置を適用可能な画像処理システムで読み出し可能なデータ処理プログラムの構成について説明する。
【０１５６】
図２２は、本発明に係る画像形成装置を適用可能な画像処理システムで読み出し可能な各種データ処理プログラムを格納する記憶媒体のメモリマップを説明する図である。
【０１５７】
なお、特に図示しないが、記憶媒体に記憶されるプログラム群を管理する情報、例えばバージョン情報，作成者等も記憶され、かつ、プログラム読み出し側のＯＳ等に依存する情報、例えばプログラムを識別表示するアイコン等も記憶される場合もある。
【０１５８】
さらに、各種プログラムに従属するデータも上記ディレクトリに管理されている。また、各種プログラムをコンピュータにインストールするためのプログラムや、インストールするプログラムが圧縮されている場合に、解凍するプログラム等も記憶される場合もある。
【０１５９】
本実施形態における図２１に示す機能が外部からインストールされるプログラムによって、ホストコンピュータにより遂行されていてもよい。そして、その場合、ＣＤ−ＲＯＭやフラッシュメモリやＦＤ等の記憶媒体により、あるいはネットワークを介して外部の記憶媒体から、プログラムを含む情報群を出力装置に供給される場合でも本発明は適用されるものである。
【０１６０】
以上のように、前述した実施形態の機能を実現するソフトウエアのプログラムコードを記録した記憶媒体を、システムあるいは装置に供給し、そのシステムあるいは装置のコンピュータ（またはＣＰＵやＭＰＵ）が記憶媒体に格納されたプログラムコードを読出し実行することによっても、本発明の目的が達成されることは言うまでもない。
【０１６１】
この場合、記憶媒体から読み出されたプログラムコード自体が本発明の新規な機能を実現することになり、そのプログラムコードを記憶した記憶媒体は本発明を構成することになる。
【０１６２】
プログラムコードを供給するための記憶媒体としては、例えば、フロッピーディスク，ハードディスク，光ディスク，光磁気ディスク，ＣＤ−ＲＯＭ，ＣＤ−Ｒ，磁気テープ，不揮発性のメモリカード，ＲＯＭ，ＥＥＰＲＯＭ等を用いることができる。
【０１６３】
また、コンピュータが読み出したプログラムコードを実行することにより、前述した実施形態の機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているＯＳ（オペレーティングシステム）等が実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【０１６４】
さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張ボードやコンピュータに接続された機能拡張ユニットに備わるメモリに書き込まれた後、そのプログラムコードの指示に基づき、その機能拡張ボードや機能拡張ユニットに備わるＣＰＵ等が実際の処理の一部または全部を行い、その処理によって前述した実施形態の機能が実現される場合も含まれることは言うまでもない。
【０１６５】
【発明の効果】
以上説明したように、本発明によれば、搬送体の表面状態に左右されることなく、かつ、搬送体の転写面色に左右されることなく、僅かな光量で搬送体に転写される各色ズレパターンと搬送体自体との反射率の差異を検知して、簡単、かつ安価な構成で色ずれ量を精度よく算定して各画像形成ステーションで形成される色画像を精度良く重ねて色ずれのないカラー画像を形成させることができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示すカラー画像形成装置の一例を説明する概略斜視図である。
【図２】図１に示したセンサの詳細構成を説明する概略説明図である。
【図３】本発明に係るカラー画像形成装置における色ずれ処理機構を説明するためのブロック図である。
【図４】図２に示した受光素子を含む受光処理回路の一例を示すブロック図である。
【図５】図４に示した比較部から出力されるパルス信号の特性を説明する図である。
【図６】図１に示された搬送ベルトに形成される色ずれ検出パターン例を示す図である。
【図７】本発明の第２実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図８】図７に示したＩ／Ｖ変換回路から出力されるパターン検知波形の一例を示す特性図である。
【図９】本発明の第３実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図１０】図９に示したＩ／Ｖ変換回路から出力されるパターン検知波形の一例を示す特性図である。
【図１１】本発明の第４実施形態を示すカラー画像形成装置における色ずれパターン検知機構の一例を説明する図である。
【図１２】本発明の第４実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図１３】図１２に示したＩ／Ｖ変換回路から出力されるパターン検知波形の一例を示す特性図である。
【図１４】本発明の第５実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図１５】図１に示された搬送ベルトに形成される他の色ずれ検出パターン例を示す図である。
【図１６】図１４に示した色ずれセンサ回路によるパターン検知波形の一例を示す特性図である。
【図１７】本発明の第６実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図１８】図１７に示した色ずれセンサ回路によるパターン検知波形の一例を示す特性図である。
【図１９】本発明の第７実施形態を示すカラー画像形成装置における色ずれ検出処理回路の一例を示すブロック図である。
【図２０】本発明の第８実施形態を示すカラー画像形成装置における色ずれセンサ回路によるパターン検知波形の一例を示す特性図である。
【図２１】本発明に係る画像形成装置における画像処理手順の一例を示すフローチャートである。
【図２２】本発明に係る画像形成装置を適用可能な画像処理システムで読み出し可能な各種データ処理プログラムを格納する記憶媒体のメモリマップを説明する図である。
【図２３】この種のカラー画像形成装置における色ずれ状態を説明する図である。
【図２４】この種のカラー画像形成装置の搬送ベルトに形成される色ずれパターンの検出機構を説明する図である。
【符号の説明】
１ 感光ドラム
２ レーザスキャナ
３ 搬送ベルト
６ 光センサ
９〜１２ 色じれ検出パターン
５１ 発光素子
５２ 受光素子
ＣＯＮＴ コントロールユニット[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus capable of forming a color image by arranging a plurality of image forming stations side by side and sequentially superimposing and transferring an image formed in each image forming station onto a recording sheet conveyed by a conveying body, and an image forming apparatus. The present invention relates to a color misregistration detection processing method of an apparatus.
[0002]
[Prior art]
In an electrophotographic color image forming apparatus, various methods have been proposed which have a plurality of image forming units for speeding up and sequentially transfer images of different colors onto a recording material held on a transport belt. I have.
[0003]
By the way, problems of an apparatus having a plurality of image forming units include uneven movement of a plurality of photosensitive drums and a conveying belt due to mechanical accuracy and the like, and a problem of transporting the photosensitive drum at the transfer position of each image forming unit to the outer peripheral surface of the photosensitive drum. The relationship between the amount of movement of the belt and the like may be different for each color, may not match when the images are superimposed, and may cause a color shift.
[0004]
In particular, in a color image forming apparatus having a plurality of image forming units (image forming stations) each having a laser scanner and a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum in each image forming unit. If they differ from one another in the forming section, the scanning width of the laser on the photosensitive drum will differ, resulting in a color shift.
[0005]
FIG. 23 is a diagram illustrating a color misregistration state in this type of color image forming apparatus.
[0006]
In FIG. 23, reference numeral 7 denotes an original image position, and reference numeral 8a denotes an image position when a color shift occurs. In FIG. 23, (a), (b), and (c) show cases where there is a color shift in the main scanning direction, but two lines are drawn apart in the transport direction for the sake of explanation.
[0007]
In particular, (a) shows the inclination shift of the main scanning line, which occurs when there is an inclination between the optical unit and the photosensitive drum. For example, the position is corrected in the direction of the arrow by adjusting the position of the optical unit, the photosensitive drum, and the position of the lens.
[0008]
2B shows a color shift due to a variation in the width of the main scanning line, which is caused by a difference in the distance between the optical unit and the photosensitive drum. This is likely to occur when the optical unit is a laser scanner. For example, the image frequency is finely adjusted (if the scanning width is long, the frequency is increased. Then, the image is corrected in the direction of the arrow by changing the length of the scanning line.
[0009]
(C) shows the writing position error in the main scanning direction. For example, if the optical unit is a laser scanner, the correction is made in the direction of the arrow by adjusting the writing start timing from the beam detection position.
[0010]
(D) shows the writing position error in the paper transport direction. For example, the correction is made in the direction of the arrow by adjusting the writing start timing of each color from the detection of the leading edge of the sheet.
[0011]
To correct these color shifts, a pattern for color shift detection is formed on the conveyor belt for each color, and detected by a pair of optical sensors provided on both sides of the downstream side of the conveyor belt, and the detected shift is detected. In accordance with the amount, a controller (not shown) performs the above-described various adjustments electrically or mechanically to perform color misregistration correction control.
[0012]
FIG. 24 is a diagram illustrating a mechanism for detecting a color misregistration pattern formed on a transport belt of this type of color image forming apparatus. FIG. 24 shows a case where the light emitting element 51 and the light receiving element 52 are configured by a diffuse reflection optical system using the transport belt 3 as a reflection surface.
[0013]
In the figure, reference numeral 51 denotes a light emitting element, which is constituted by an LED, for example. 52 is a light receiving element, for example, a photo sensor. Reference numeral 3 denotes a conveyor belt, and 9a to 9d, 10a to 10d, 11a to 11d, and 12a to 12d are patterns for detecting color misregistration. Although the patterns 9, 10, 11, and 12 are shown as a single pattern, they correspond to a state in which they pass immediately below the light receiving element 52, and are originally formed on the transfer belt at predetermined intervals. Shall be.
[0014]
Reference numeral 53 denotes light emitted from the light emitting element 51, and reference numeral 54 denotes light received by the light receiving element 52 among light reflected from the transport belt or the patterns 9, 10, 11, and 12 for detecting color misregistration. .
[0015]
[Problems to be solved by the invention]
Since the color misregistration detection mechanism in the conventional color image forming apparatus is configured as described above, in the case of the configuration using the irregular reflection optical system, the light amount received by the light receiving unit is small compared to the irradiation light amount of the light emitting unit. For this reason, it is difficult to obtain a sufficient amount of light for detection. As a countermeasure, for example, it is necessary to arrange a plurality of light emitting elements 51 around the light receiving element 52 or to use a light source having a large amount of emitted light. However, there is a problem that both measures cause a cost increase.
[0016]
In addition, since it is affected by the spectral sensitivity of the conveyor belt 3 and the color shift detection patterns 9, 10, 11, and 12, there are various restrictions on the wavelength of the light emitting element 51, the color of the conveyor belt 3, and the method of forming the color shift detection pattern. Occurs. For example, for the wavelength of the light emitting element 51, it is common to use an infrared region that exhibits reflection characteristics for all three colors of YMC. In this case, Bk has absorption characteristics.
[0017]
Therefore, the polarity of the detection waveform of the light receiving element at the time of Bk measurement is opposite to that at the time of detecting another color, and the detection level needs to be different from that of the other colors. In general, the transport belt is generally black (Bk), but this makes it impossible to detect a color shift detection pattern of Bk formed on the transport belt.
[0018]
As a countermeasure, it is necessary to improve the reflectance of the base by coloring the surface of the conveyor belt gray or forming a solid pattern (patch image pattern) of any of YMC under the color shift detection pattern of Bk. However, the former countermeasure causes a cost increase, and the latter countermeasure has a problem that the amount of waste toner is increased.
[0019]
In addition, when a registration mark is detected via the irregular reflection optical system, a method of generating a pulse waveform by comparing a predetermined reference voltage value with a measurement waveform for a pattern and using the pulse waveform as registration mark position information is described below. Such a problem exists.
[0020]
For example, an LED is often used as a light source of a sensor for detecting a registration mark. However, since the LED has a large variation in light emission amount, a mechanism for adjusting the light emission amount or a mechanism for adjusting the sensitivity of the I / V conversion circuit, Alternatively, a mechanism for adjusting the reference voltage value according to the light emission amount is required.
[0021]
Then, although a method of performing adjustment in production by providing a volume, etc. on the circuit is commonly, a problem that costs absolutely since it takes labor increases occur in the regulation work.
[0022]
In addition, when the light source decreases the light amount due to the deterioration over time or when the gloss value of the measurement object decreases due to the deterioration over time, there is a problem that the balance between the measured waveform and the reference voltage value is lost.
[0023]
As a solution to the above problem, there is a method in which a sensor detection waveform is read into an CPU through an A / D input port and the amount of light emitted from an LED or a reference voltage value is adjusted in accordance with the output.
[0024]
However, it is not practical because the A / D port of the CPU, which tends to be short, is used, and the response speed cannot cope with small fluctuations in the output waveform.
[0025]
Further, as described in the above conventional example, a specular reflection optical system that can increase the amount of light detected by the light receiving unit is often used in such a reflection type optical system. Therefore, the detection is sensitive to a decrease in the gloss value caused by a flaw formed on the image carrier. For this reason, in the case of an image carrier having been repeatedly used and having increased scratches, there may be cases where the scratches are erroneously detected as registration marks.
[0026]
The present invention has been made to solve the above problems, and a first object of the present invention is to convert a light detection current generated by a light receiving unit that receives light reflected by a light emitting unit into a voltage, The maximum value and the minimum value of the generated voltage are stored, a reference signal is generated according to the stored maximum value and the minimum value, and a light receiving output of the reflected light of each pattern image by the light receiving unit is generated. By comparing the magnitude of the reference signal to generate a pulse signal and calculating the amount of positional deviation between the images based on the comparison output, the transfer of the carrier is not affected by the surface condition of the carrier. Detects the difference in reflectance between each color misregistration pattern transferred to the carrier with a small amount of light and the carrier itself without being affected by the surface color, and accurately calculates the amount of color misregistration with a simple and inexpensive configuration Formed at each image forming station To provide a color shift detection processing method of an image forming apparatus and an image forming apparatus capable of forming a color image without color shift colors image superimposed accurately.
A second object is to read each of the pattern images formed on the carrier, determine a threshold based on the maximum value and the minimum value of the read output, and determine the read output of each pattern image and the threshold. Detecting the amount of misalignment between the images formed by the plurality of image forming stations based on the plurality of image forming stations, and correcting the positions of the images formed by the respective image forming stations based on the detected amount of misalignment. The difference between the reflectivity of each color misregistration pattern transferred to the carrier with a small amount of light and the carrier itself without being influenced by the surface condition of the carrier and without being influenced by the transfer surface color of the carrier. Color misregistration amount is accurately calculated with a simple and inexpensive configuration, and color images formed in each image forming station are accurately overlapped to form a color image without color misregistration. To provide a color shift detection processing method of an image forming apparatus and an image forming apparatus capable.
[0027]
[Means for Solving the Problems]
According to a first aspect of the present invention, a plurality of image forming stations are arranged, and an image formed in each image forming station can be sequentially overlapped and transferred onto a recording sheet conveyed by a conveying body to form a color image. An image forming apparatus, wherein each of the plurality of image stations forms a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station on the carrier. Pattern forming means for controlling image formation of a station; a light emitting unit; a light receiving unit for receiving light reflected by the light emitting unit; a voltage converting unit for converting a light detection current generated by the light receiving unit into a voltage; A voltage storage unit for storing a maximum value and a minimum value of the voltage generated by the conversion unit; and a reference according to the maximum value and the minimum value stored in the voltage storage unit. A first signal generating unit for generating a signal, and a light receiving output of the reflected light of each of the pattern images by the light receiving unit is compared with a reference signal generated by the first signal generating unit to generate a pulse signal. A pattern detection unit including a second signal generation unit for performing the operation, and a calculation unit for calculating a positional shift amount between the respective images based on an output of the pattern detection unit.
[0028]
A second invention according to the present invention is characterized in that the light emitting section and the light receiving section of the pattern detecting means are constituted by a regular reflection optical system.
[0029]
A third invention according to the present invention is characterized in that the voltage value storage section has a reset section that clears a stored value in response to an external signal.
[0030]
A fourth invention according to the present invention is characterized in that the first signal generator can variably set the generation condition.
[0031]
A fifth invention according to the present invention is characterized in that the voltage value storage unit acquires a maximum value and a minimum value from a dedicated registration mark.
[0032]
In a sixth aspect according to the present invention, the maximum value and the minimum value of the light receiving section correspond to the surface reflected light amount and the toner reflected light amount of the carrier, or the toner reflected light amount and the surface reflected light amount of the carrier, respectively. It is characterized by the following.
[0033]
According to a seventh aspect of the present invention, it is possible to form a color image by arranging a plurality of image forming stations side by side and sequentially superimposing and transferring the images formed in the respective image forming stations onto recording paper conveyed by a conveying body. A color misregistration detection processing method of an image forming apparatus, wherein a reference color line pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station among the plurality of image forming stations are formed on the carrier. A pattern forming step of controlling image formation of each image forming station so as to form a current, a voltage converting step of converting a current detected by a light receiving unit that receives light reflected by the light emitting unit into a voltage, and a voltage converting step generated by the voltage converting step. A voltage value storing step of storing a maximum value and a minimum value of the obtained voltage value, and the maximum value and the minimum value stored in the voltage value storing step. A first signal generating step of generating a reference signal in accordance with the following, and comparing a light receiving output of the reflected light of the pattern image by the light receiving section with a reference signal generated by the first signal generating step, to generate a pulse. A pattern detection step including a second signal generation step of generating a signal, a calculation step of calculating a displacement amount between the respective color images based on an output of the pattern detection step, and a displacement amount calculated by the calculation step A control step of correcting and controlling the position of the image by each image forming station other than the reference color based on the reference color.
[0034]
An eighth invention according to the present invention is characterized in that the light emitting section and the light receiving section are constituted by a regular reflection optical system.
[0035]
A ninth invention according to the present invention is a ninth invention according to the present invention, wherein a plurality of image forming stations are juxtaposed, and the images formed at the respective image forming stations are sequentially recorded on a record conveyed by a conveying body. An apparatus for forming an image by superimposing and transferring, wherein pattern forming means for controlling image formation of each of the image forming stations so as to form a pattern image for detecting a positional shift on the carrier, respectively, A reading unit that reads each of the pattern images formed in, a threshold value is determined based on the maximum value and the minimum value of the reading output by the reading unit, and the reading output of each of the pattern images by the reading unit and the threshold value are determined. Displacement detection means for detecting a displacement between respective images formed by the plurality of image forming stations based on the displacement, and detecting the displacement Characterized in that it comprises a correcting means for correcting the position of the image formed by the respective image forming stations based on the positional deviation amount detected by the stage.
[0036]
A tenth invention according to the present invention is characterized in that the displacement detecting means has a storage unit for storing the threshold value.
[0037]
An eleventh invention according to the present invention is characterized in that the storage section has a reset section that clears a stored threshold value in response to an external reset signal.
[0038]
A twelfth invention according to the present invention is characterized in that the displacement detection means is capable of changing a condition for determining the threshold.
[0039]
According to a thirteenth aspect of the present invention, the reading means includes: a light emitting unit; a sensor that detects light reflected from the carrier by the light emitting unit and outputs a current corresponding to the amount of reflected light; Converting means for converting a current into a voltage, wherein the displacement detecting means determines the threshold value by dividing a maximum value and a minimum value of the output voltage from the converting means by a resistance means. .
[0040]
A fourteenth invention according to the present invention is characterized in that the displacement detection means can change the threshold value by changing a resistance value of the resistance means.
[0041]
According to a fifteenth aspect of the present invention, the position shift detecting means has a comparing means for comparing a read output of each of the patterns by the reading means with the threshold, and generating a pulse according to the comparison result, The displacement amount is detected according to the output timing of the pulse.
[0060]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
FIG. 1 is a schematic perspective view illustrating an example of a color image forming apparatus according to the first embodiment of the present invention. For example, image forming means (images of four colors, ie, yellow Y, magenta M, cyan C, and black K) (Forming station).
[0061]
In the figure, reference numerals 1a, 1b, 1c, and 1d denote photosensitive drums for forming an electrostatic latent image (a, b, c, and d indicate K, C, M, and Y, respectively), 2a, 2b, 2c, and 2d A laser scanner 3 that performs exposure according to an image signal to form an electrostatic latent image on the photosensitive drum 1, and 3 is an endless conveyance belt that also serves as a transfer belt that sequentially conveys paper to an image forming unit for each color, is not shown. It is rotationally driven by a driving roller 4 driven by a belt motor.
[0062]
The drive roller 4 is connected to a drive unit including a motor and gears (not shown), and drives the transport belt 3 at a predetermined speed. Reference numeral 5 denotes a driven roller which rotates in accordance with the movement of the conveyor belt 3 and applies a constant tension to the conveyor belt 3. Reference numerals 6a and 6b denote a pair of optical sensors, which are provided on the belt end side so as to be orthogonal to the transport direction of the transport belt 3 for detecting a misregistration detection pattern formed on the transport belt 3. A control unit CONT includes a CPU, a RAM, and a ROM (not shown), and executes a control program stored in the ROM to process a sensor signal, image data, and the like input through an input port (not shown). , And controls the driving of the engine unit, the driving of the laser scanner 2, and the like.
[0063]
Data to be printed is sent from a personal computer (PC) constituted by a host computer (not shown) to the printer, and when image formation in accordance with the printer engine is completed and the printer is ready for printing, paper is supplied from a paper cassette (not shown). Then, the paper reaches the transport belt 3, and the paper is sequentially transported by the transport belt 3 to the image forming units of each color.
[0064]
The image signals of the respective colors are sent to the respective laser scanners 2 in synchronization with the sheet conveyance by the conveyance belt 3 to form an electrostatic latent image on the photosensitive drum 1, and the toner is developed by a developing unit (not shown). The image is transferred onto a sheet by a transfer unit (not shown).
[0065]
In FIG. 1, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the sheet is separated from the transport belt, the toner image is fixed on the sheet by heat in a fixing device (not shown), and is discharged to the outside. Hereinafter, the operation of the present embodiment will be described.
[0066]
In order to reduce color misregistration, a color misregistration detection pattern as shown in FIG. 6 is formed at each image forming station on the transport belt 3 as described above, and is provided on both sides of the transport belt 3. The image data is read by the pair of optical sensors 6a and 6b, and the amount of color shift between the colors is detected.
[0067]
FIG. 2 is a schematic explanatory view for explaining the detailed configuration of the optical sensors 6a and 6b shown in FIG. 1, and corresponds to a case where the pattern reading system is constituted by a regular reflection optical system.
[0068]
In the figure, reference numeral 51 denotes a light emitting element, which is constituted by, for example, an LED. 52 is a light receiving element, for example, a photo sensor. Reference numeral 3 denotes a transport belt, and reference numerals 9, 10, 11, and 12 denote color misregistration detection patterns.
[0069]
Reference numeral 53 denotes light emitted from the light emitting element 51, and reference numeral 54b denotes received light, which is received by the light receiving element 52 of the reflected light from the conveyor belt 3 or the color misregistration detection patterns 9, 10, 11, and 12.
[0070]
In the present embodiment, the light emitting unit and the light receiving unit are configured by a regular reflection optical system using the transport belt 3 as a reflection surface, and the difference between the reflectance of the transport belt 3 and the regular reflection light of the color misregistration detection pattern, that is, , The position of the color misregistration detection pattern is accurately detected based on the difference in gloss. Therefore, even if the black toner is on the conveyor belt 3, the pattern can be detected from the difference in gloss, and the background image (patch image) can be detected using another developing color toner for black as in the related art. Need not be formed, and the amount of toner to be collected during color misregistration correction can be significantly reduced.
[0071]
In addition, when an object having a high gloss value is irradiated with light, very large regular reflection light can be obtained. For example, by applying mirror finishing to the surface of the conveyor belt 3, the gloss value can be increased. Then, when a toner image is formed on the transport belt 3, the specularity of the portion is lost and the gloss value is reduced. The variation of the gloss value may be detected by the optical sensors 6a and 6b using the regular reflection optical system to detect the color misregistration detection pattern.
[0072]
FIG. 3 is a block diagram for explaining a color misregistration processing mechanism in the color image forming apparatus according to the present invention.
[0073]
As shown in FIG. 3, a calculation unit 34 that performs arithmetic processing on detection data detected by a pattern detection unit 32 including an LED light emitting unit and a photosensor light receiving unit, and calculates a color shift amount and a correction value. An image output unit 55 for performing formation, a timer 33 and a CPU 31 for performing timing adjustment and various settings of each unit, a RAM (not shown), and a ROM (not shown) are provided. It is assumed that the timer 33, the CPU 31, the calculation unit 34, the image output unit 55, and the pattern detection unit 32 are provided in the control unit CONT shown in FIG.
[0074]
FIG. 4 is a block diagram showing an example of a light receiving processing circuit including the light receiving element 52 shown in FIG.
[0075]
In FIG. 4, reference numeral 100 denotes a photodetector, which detects the light received by the light receiving element 52 from among the reflected light from the transport belt or the color misregistration detection patterns 9, 10, 11, and 12. An I / V conversion circuit 101 converts a current value proportional to the received light into a voltage signal. A comparison unit 102 compares the voltage signal output from the I / V conversion circuit 101 with the reference voltage 103, and outputs a result signal to the CPU 104.
[0076]
In the image forming apparatus configured as described above, the color misregistration detection pattern detected by the light receiving element 52 illustrated in FIG. 2 is converted from current to voltage by the I / V conversion circuit 101 (I / V) as illustrated in FIG. V conversion), the comparison unit 102 compares the signal with the reference voltage 103, and outputs a positive pulse signal as shown in FIG. 5 while the signal level is lower than the reference voltage.
[0077]
FIG. 5 is a diagram for explaining the characteristics of the pulse signal output from the comparison unit 102 shown in FIG. 4, and is output when the detection pattern of the color misregistration detection pattern formed on the conveyor belt 3 shown in FIG. Corresponding to the pulse signal to be performed. In FIG. 5, the horizontal axis indicates time.
[0078]
5A shows a state in which the pattern width of the light receiving element 52 in the transport direction of the transport belt 3 is indicated by time t. (B) is a pattern reading output waveform output by the I / V conversion circuit 101, and (c) is a reference voltage 103.
[0079]
As shown in this figure, from the transition of the output waveform (b) and the positional relationship of the light receiving element 52, the transport belt 3 has a high gloss, and most of the emitted light 53 shown in FIG. The light is received by the light receiving element 52.
[0080]
On the other hand, the color misregistration detection toner image formed on the transport belt 3 has low gloss, most of the emitted light 53 is scattered, and the specularly reflected light 54b received by the light receiving element 52 is slight.
[0081]
As a result, the output waveform (b) has a characteristic that it is high when the conveyor belt 3 is detected and becomes low when the color misregistration detection pattern is detected.
[0082]
Therefore, by utilizing the above characteristics, the color misregistration detection patterns yellow 9, magenta 10, cyan 11, and black 12 are formed on the conveyor belt 3 at each image forming station at a predetermined timing, and a pair of light for color misregistration detection is formed. Upon detection by the sensors 6a and 6b, the light receiving element 52 outputs four waveforms corresponding to the output waveform (b) shown in FIG.
[0083]
In FIG. 5, the first is an output waveform corresponding to the yellow color misregistration detection pattern, the second is an output waveform corresponding to magenta, the third is an output waveform corresponding to cyan, and the fourth is a black waveform. Output waveform corresponding to the color misregistration detection pattern.
[0084]
At this time, the waveforms for detecting the patterns of the four colors have the same shape. The first to fourth valleys are lower than the threshold (c), and as a result, a pulse corresponding to (d) in FIG. 5 is output from the comparing unit 102 shown in FIG.
[0085]
In response to this, the calculation unit 34 shown in FIG. 3 calculates the center position of each of the first to fourth pulse signals shown in FIG. 5D, and further calculates the time difference between the respective center positions. Then, the color shift amount is calculated from the difference between the obtained time difference and the value of the preset time difference. Thereafter, the CPU 31 individually controls the image forming timing and the like so as to correct the color shift of each image forming station in accordance with the color shift amount calculated by the calculation unit 34.
[0086]
According to this embodiment, since the regular reflection optical system is used, when the position of the color misregistration detection pattern is detected by the difference between the regular reflectance of the transport belt 3 and the color misregistration detection pattern, that is, the difference in gloss, The transport belt 3 has a high gloss, and most of the emitted light 53 becomes the regular reflected light 54 b and is received by the light receiving element 52. At this time, the color misregistration detection pattern, which is a toner image, has low gloss, most of the emitted light 53 is scattered, and the specular reflected light 54b received by the light receiving element 52 is slight. That is, the output of the light receiving element 52 is high when the conveyance belt 3 is detected, and is low when the color misregistration detection pattern is detected. The regular reflection light from the conveyor belt 3 has a sufficient amount of light, and the light receiving element 52 obtains an output waveform (b) having a sufficient amplitude for detection.
[0087]
Therefore, one light emitting element 51 is sufficient. Since the amount of specularly reflected light is much larger than that of diffusely reflected light, it is possible to use a light emitting element with a small amount of emitted light.
[0088]
In addition, by using the regular reflection optical system, the amount of regular reflection light is related only to the gloss value of the object to be measured, and the influence of the spectral sensitivity of the transport belt 3 and the color misregistration detection patterns 9, 10, 11, and 12 is affected. Since it is no longer received, it is possible to similarly detect toners of four colors of YMCK, and it is possible to freely set the emission wavelength of the light emitting element.
[0089]
FIG. 6 is a diagram showing an example of a color misregistration detection pattern formed on the transport belt shown in FIG. Hereinafter, the color misregistration correction calculation processing by the calculation unit 34 shown in FIG.
[0090]
In FIG. 6, 9a to 9d and 10a to 10d are patterns for detecting the amount of color misregistration in the paper transport direction, and 11a to 11d and 12a to 12d represent the amount of color misregistration in the main scanning direction orthogonal to the paper transport direction. This is a pattern for detection. In this example, the inclination is 45 degrees. Note that a to d indicate black (hereinafter, Bk), yellow (hereinafter, Y), magenta (hereinafter, M), and cyan (hereinafter, C), respectively.
[0091]
tsfl to tsf4, tmfl to tmf4, tsrl to tsr4, tmrl to tmr4 indicate the detection timing of each pattern, and the arrows indicate the moving direction of the transport belt 3. The transport speed of the transport belt 3 is Vmm / s, Bk is the reference color, and the theoretical distance between each color of the paper transport direction pattern and the Bk pattern is dsYmm, dsMmm, dsCmm, the paper transport direction pattern of each color and the main scanning direction. The actually measured distance between the patterns is dmfBkmm, dmfYmm, dmfMmm, dmfCmm, dmrBkmm, dmrYmm, dmrMmm, and dmrCmm, respectively. ) To (17),

[0092]
On the other hand, with respect to the main scanning direction, the positional shift amounts δemf and δemr of the respective left and right colors are:
dmfBk = v * (tmfl-tsfl) (4)
dmfY = v * (tmf2-tsf2) (5)
dmfM = v * (tmf3-tsf3) (6)
dmfC = v * (tmf4-tsf4) (7)
dmrBk = v * (tmrl-tsrl) (8)
dmrY = v * (tmr2-tsr2) (9)
dmrM = v * (tmr3-tsr3) (10)
dmrC = v * (tmr4−tsr4) (11)
δemfY = dmfY−dmfBk (12)
δemfM = dmfM−dmfBk (13)
δemfC = dmfC−dmfBk (14)
δemrY = dmrY−dmrBk (15)
δemrM = dmrM−dmrBk (16)
δemrC = dmrC−dmrBk (17), and the direction of deviation can be determined from the positive or negative of the calculation result, and the writing position is corrected from δemf and the main scanning width is corrected from δemr−δemf.
[0093]
If there is an error in the main scanning width, the writing position is calculated not only by δemf but also by taking into account the amount of change in the image frequency that has changed due to the main scanning width correction.
[0094]
[Second embodiment]
FIG. 7 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the second embodiment of the present invention, and the same components as those in FIG. 4 are denoted by the same reference numerals. The optical system of the sensor is the same as that shown in FIG. 2 in the first embodiment. Hereinafter, only different points from the first embodiment will be described.
[0095]
In FIG. 7, reference numeral 105 denotes a peak hold circuit which holds the peak value of the pattern detection waveform output from the I / V conversion circuit 101 for a certain period of time.
[0096]
When the color misregistration detection pattern formed on the conveyor belt 3 is read and the current based on the pattern detection is converted into a voltage signal by the I / V conversion circuit 101, the peak value of the pattern detection waveform is obtained by the operation of the peak hold circuit 105. Is held for a certain period of time. As a result, a pulse waveform having an amplitude value equal to the peak value of the pattern detection waveform is generated. This waveform is amplified and converted into a pulse waveform whose amplitude value is equal to the power supply voltage.
[0097]
FIG. 8 is a characteristic diagram showing an example of a pattern detection waveform output from the I / V conversion circuit 101 shown in FIG. 7, and the same components as those in FIG. 5 are denoted by the same reference numerals.
[0098]
8A and 8B are the same as in the first embodiment. (C) is an output waveform generated by inverting the waveform of the output waveform (b). In the output waveform (c), the color misregistration detection pattern is detected at the peak of each waveform.
[0099]
(D) is a pulse signal generated by the signal processing of the peak hold circuit 105 shown in FIG. 6 for the output waveform (c). Note that the peak hold circuit 105 has a function of maintaining the voltage at the peak time for a certain period of time, and when the waveform of the output waveform (c) reaches the peak time, the pulse signal (d) generates the pulse signal at the peak of the output waveform (c). Start up to voltage.
[0100]
Thereafter, after a certain period of time, the level returns to the GND level. As a result, the rising timing of the pulse signal (d) becomes the detection timing of the color misregistration detection pattern and is input to the CPU 104 shown in FIG. The CPU 104 obtains the time difference of the retiming at the rise of the pulse for four colors, and calculates the amount of color shift from the difference between the obtained time difference and a preset time difference value. Subsequent processing is the same as in the first embodiment.
[0101]
[Third embodiment]
FIG. 9 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the third embodiment of the present invention, wherein the same components as those in FIG. 7 are denoted by the same reference numerals. Since the optical system of the sensor is the same as that of the first embodiment, the configuration and operation different from those of the first embodiment will be described below.
[0102]
In the figure, reference numeral 106 denotes an A / D converter, and the I / V conversion circuit 101 converts a current proportional to the amount of received light into a voltage signal. Reference numeral 107 denotes a RAM which stores digitized received light amount data A / D converted by the A / D converter 106.
[0103]
In the color image forming apparatus configured as described above, when the light receiving unit (PD) 100 detects regular reflection light and converts the light amount into a current, the I / V conversion circuit 101 outputs a current proportional to the received light amount to a voltage signal. Convert to Next, digitization is performed using the A / D converter 106. Then, the digitized received light amount data is read by the CPU 104 and stored in the RAM 107. Then, the peak of the waveform is detected from the data stored in the RAM 107 to detect the position of the color misregistration detection pattern.
[0104]
FIG. 10 is a characteristic diagram showing an example of a pattern detection waveform output from the I / V conversion circuit 101 shown in FIG. 9, and the same components as those in FIG. 8 are denoted by the same reference numerals.
[0105]
In FIG. 10, (a) and (b) are the same as in the first embodiment. (C) is a digitized version of the output waveform (b), and the interval between points in the figure is determined by the sampling period. The smaller the interval, the better the measurement accuracy.
[0106]
Here, the intervals between the points are set large to simplify the description. This point is sequentially stored in the RAM 107 by the CPU 104. At this time, it is assumed that data addresses are continuous. This data is roughly divided into four pieces, and an address at which the data of the minimum value is stored is detected.
[0107]
This is the position information of the color misregistration detection pattern. Further, when the difference between the respective addresses is obtained and multiplied by the sampling period, the detection time difference of each color misregistration detection pattern can be detected. Is calculated. Subsequent processing is the same as in the first embodiment.
[0108]
[Fourth embodiment]
FIG. 11 is a view for explaining an example of a color misregistration pattern detecting mechanism in a color image forming apparatus according to the fourth embodiment of the present invention, and the same components as those in FIG. 2 are denoted by the same reference numerals. Note that this corresponds to a case where the pattern reading system is configured by a regular reflection optical system.
[0109]
In the figure, reference numeral 51 denotes a light emitting element, which is constituted by, for example, an LED. 52a and 52b are light receiving elements, for example, photo sensors. Reference numeral 3 denotes a transport belt, and reference numerals 9, 10, 11, and 12 denote color misregistration detection patterns.
[0110]
Reference numeral 53 denotes light emitted from the light emitting element 51, and reference numeral 54b denotes received light, which is received by the light receiving element 52 out of reflected light from the conveyor belt 3 or the color misregistration detection patterns 9, 10, 11, and 12.
[0111]
FIG. 12 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the fourth embodiment of the present invention, and the same components as those in FIG. 4 are denoted by the same reference numerals.
[0112]
12, the light receiving element 52a corresponds to PD100, and the light receiving element 52b corresponds to PD200. The color misregistration detection patterns detected by the PDs 100 and 200 are converted from current to voltage by the I / V conversion circuits 101 and 201, respectively. The difference between the light receiving sensitivities of the two light receiving elements 52a and 52b becomes the same after the I / V conversion by adjusting the conversion rates of the I / V conversion circuits 101 and 201.
[0113]
In the comparing unit 102, the signal levels corresponding to the light receiving elements 52a and 52b are compared with each other, and during a period in which the signal level corresponding to the light receiving element 52b is lower than the signal level corresponding to the light receiving element 52a, the positive pulse is generated as shown in FIG. Are output at the timing shown in FIG.
[0114]
FIG. 13 is a characteristic diagram showing an example of a pattern detection waveform output from the I / V conversion circuits 101 and 201 shown in FIG.
[0115]
13A shows a state in which the pattern width of the light receiving elements 52a and 52b in the transport direction of the transport belt 3 is indicated by time t. (B) is an output waveform after I / V conversion of the output of the light receiving element 52a by the I / V conversion circuit 101. (C) is an output waveform after I / V conversion of the output of the light receiving element 52b by the I / V conversion circuit 201, and after the high level is clipped by a clip circuit (not shown).
[0116]
In the fourth embodiment, each of the output waveforms (c) and (b) shown in FIG. 12 has four valleys. The first corresponds to a yellow color misregistration detection pattern, the second corresponds to a magenta color, the third corresponds to a cyan color misregistration pattern, and the fourth corresponds to a black color misregistration detection pattern.
[0117]
In the example shown in FIG. 13, since the light receiving elements 52 a and 52 b are arranged adjacent to each other along the transport direction of the transport belt 3, the color misregistration detection patterns 9, 10, 11 and 12 are caused by the transport of the transport belt 3. When the light passes through the light receiving elements 52a and 52b, the signal level of the output waveform at the light receiving element 52a rises, and at the same time, the signal level of the output waveform at the light receiving element 52b falls.
[0118]
On the other hand, since the difference between the light receiving sensitivities of the two light receiving elements 52a and 52b is adjusted by the I / V conversion circuits 101 and 201 in FIG. 13, the signal rises at an intermediate level of the amplitude of the signal corresponding to the light receiving elements 52a and 52b. And falling intersect. Since the signal levels after the I / V conversion by the I / V conversion circuits 101 and 201 have the same background level, chattering occurs in the output when input to the comparator 102 such as a comparator.
[0119]
Therefore, the high level (background level) of the signal corresponding to the light receiving element 52b is clipped, and the background level of each signal is set to a different value. In other words, the rising of the positive pulse (d) indicates the timing when the centers of the color misregistration detection patterns 9, 10, 11, and 12 pass through the center of the light receiving elements 52a and 52b. This timing is not affected by variations in the line width of the color misregistration detection patterns 9, 10, 11, and 12 and variations in the light amount of the light emitting unit 51.
[0120]
Therefore, as shown in FIG. 13, the CPU 104 calculates the rising time difference of each color pulse waveform (positive pulse (d)). Is calculated. Subsequent processing is the same as in the first embodiment.
[0121]
[Fifth Embodiment]
FIG. 14 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the fifth embodiment of the present invention, in which the same components as those in FIG. This embodiment corresponds to a detailed example of the peak hold circuit according to the present invention. Hereinafter, the configuration and operation will be described.
[0122]
14, the detection current from the light receiving element 52, that is, the detection current from the PD100 is converted into a voltage by the I / V conversion circuit 101. The maximum value and the minimum value are detected by the upper peak hold circuit 301 and the lower peak hold circuit 303, respectively, and are divided by the resistors 302 and 304. A comparison circuit 305 determines the magnitude relationship between the output waveform of the I / V conversion circuit 101 and the voltage values divided by the resistors 302 and 304, and corresponds to an output waveform (b) shown in FIG. Generate a pulse signal.
[0123]
Here, in order for the upper peak hold circuit 301 and the lower peak hold circuit 303 to obtain the maximum value and the minimum value, it is necessary to read one line in advance. A pulse conversion reference voltage is created from the maximum value and the minimum value acquired here. That is, in the present embodiment, it is necessary to create a registration mark for acquiring the maximum value and the minimum value immediately before the registration mark shown in FIG. Specifically, as shown in FIG. 15, the marks 13a and 14a for peak determination are corrected immediately before the registration mark.
[0124]
FIG. 16 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration sensor circuit shown in FIG. 14, and the same components as those in FIG. 5 are denoted by the same reference numerals.
[0125]
In FIG. 16, (a) represents the width of the light receiving element 52 in the transport direction of the transport belt 3 by time t, and shows the transition of the output waveform (b) of the I / V conversion circuit and the positional relationship of the light receiving element 52. The transport belt 3 has a high gloss, and most of the emitted light 53 becomes the regular reflected light 54 b and is received by the light receiving element 52.
[0126]
The color misregistration detection pattern, which is a toner image, has low gloss, most of the emitted light 53 is scattered, and the specular reflected light 54b received by the light receiving element 52 as shown in FIG. 2 is slight. The output waveform (b) is high when the conveyance belt 3 is detected, and low when the color misregistration detection pattern is detected. Note that the value of the threshold (c) is determined by the voltage division ratio of the resistors 302 and 304. This relationship is expressed by the equation of A: B = resistor 302: resistor 304.
[0127]
The color shift detection patterns yellow 9, magenta 10, cyan 11, and black 12 are formed on the conveyor belt 3, and are detected by the optical sensors 6a and 6b. The light receiving element 52 outputs an output waveform (b) having four peaks as shown in FIG. The first corresponds to a yellow color misregistration detection pattern, the second corresponds to a magenta color, the third corresponds to a cyan color misregistration pattern, and the fourth corresponds to a black color misregistration detection pattern. At this time, the waveforms for detecting the patterns of the four colors have the same shape. The first to fourth valleys become lower than the threshold (c), and the pulse signal (d) shown in FIG. Then, the arithmetic unit 53 shown in FIG. 3 obtains the center position of each of the first to fourth pulse signals (d) shown in FIG. 16, and further obtains the time difference between the respective center positions. A color shift amount is calculated from a difference between the obtained time difference and a preset time difference value. Subsequent processing is the same as in the first embodiment.
[0128]
[Sixth embodiment]
In the above-mentioned reflection type optical system, a regular reflection optical system which can increase the amount of light detected by the light receiving unit is often used. On the other hand, since the regular reflection optical system responds to the magnitude of the gloss value, the image carrying It is also sensitive to the decrease in gloss value caused by scratches on the body. For this reason, in the case of an image carrier having been repeatedly used and having increased scratches, there may be cases where the scratches are erroneously detected as registration marks. Therefore, by adjusting the detection level of the peak value, the color misregistration detection pattern image may be normally read even if some scratches occur on the transport belt. Hereinafter, the embodiment will be described.
[0129]
FIG. 17 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the sixth embodiment of the present invention. The same components as those in FIG. 14 are denoted by the same reference numerals. This embodiment corresponds to another detailed example (a modification of the fifth embodiment) of the peak hold circuit according to the present invention. Hereinafter, the configuration and operation will be described.
[0130]
In FIG. 17, reference numeral 402 denotes an analog switch which can select an arbitrary resistance value (resistors 401-1 to 401-N) by a signal from the CPU 31.
[0131]
FIG. 18 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration sensor circuit shown in FIG. 17, and the same components as those in FIG. 16 are denoted by the same reference numerals.
[0132]
As shown in FIG. 18, when a flaw or the like occurs on the image carrier (when it is configured as a carrier) due to a change over time due to image formation or the like, the image carrier is displayed at the center of the output waveform (b). A waveform is generated due to a flaw formed on the body. In this case, when the reference voltage value of the threshold value (c) is at the A level in the initial set value state, erroneous detection pulses EP1 and EP2 are generated, resulting in a control error.
[0133]
Therefore, the CPU 31 instructs the operation of the analog switch 402 shown in FIG. 15, switches the resistance value, and sets and controls the reference voltage value generation condition. When the reference voltage value reaches the B level (exceeds the A level), no erroneous detection pulse is generated, and the control can be normally completed.
[0134]
[Seventh embodiment]
FIG. 19 is a block diagram showing an example of a color misregistration detection processing circuit in a color image forming apparatus according to the seventh embodiment of the present invention, and the same components as those in FIG. 14 are denoted by the same reference numerals. This embodiment corresponds to another detailed example (a modification of the fifth embodiment) of the peak hold circuit according to the present invention.
[0135]
The fifth embodiment is different from the fifth embodiment in that the reset signal input terminals for clearing the peak values stored in the upper peak hold circuit 301 and the lower peak hold circuit 303 are different from the upper peak hold circuit 301 and the lower peak hold circuit 301. This is the point added to the hold circuit 303. Hereinafter, the configuration and operation will be described.
[0136]
When the image carrier is in the form of a belt as described above, the distance between the object to be measured and the color misregistration detection sensor tends to fluctuate, depending on the configuration of the mounting portion, and the output voltage value fluctuates accordingly. There are many. In such a case, the maximum and minimum values obtained by the peak hold circuits 301 and 303 may not always be optimal.
[0137]
Therefore, in the present embodiment, more accurate registration mark detection can be performed by clearing a reset value from the CPU 31 and reacquiring a new peak value for the peak value acquired by the peak hold circuits 301 and 303 in a certain cycle. It becomes possible.
[0138]
In the case where the registration marks shown in FIG. 6 are used as one unit and a plurality of registration mark groups are measured to obtain a plurality of color misregistration values and a process for improving reading accuracy is performed, the registration mark group is detected. It is possible to receive a reset signal from the CPU 31 at a timing immediately before the acquisition and obtain a new peak value from the peak value acquisition mark again to improve the measurement accuracy.
[0139]
[Eighth Embodiment]
In the first to seventh embodiments, the case has been described in which all the color misregistration image detection processing for registration correction is detected by the regular reflection optical system. Means may be incorporated to switch the color misregistration detection processing between black and another color to perform the color misregistration amount detection processing.
[0140]
FIG. 20 is a characteristic diagram illustrating an example of a pattern detection waveform by the color misregistration sensor circuit in the color image forming apparatus according to the eighth embodiment of the present invention, and the horizontal axis indicates time.
[0141]
FIG. 20A shows a state in which the pattern width of the light receiving element 52 in the transport direction of the transport belt 3 is indicated by time t. (C) is a pattern reading output waveform output by the I / V conversion circuit 101, and (b) is a reference voltage 103. (D) is a pulse signal output when the detection pattern of the color misregistration detection pattern formed on the transport belt 3 is read.
[0142]
In the example shown in FIG. 20, since an irregular reflection optical system is used as the optical system, the output waveform (b) of the I / V conversion circuit increases when a YMC color registration mark having reflection characteristics is detected. Therefore, when the Bk color registration mark is detected, the output decreases.
[0143]
Accordingly, when the measurement optical system is a diffuse reflection optical system, the behavior of the output waveform is different between the YMC color registration mark and the Bk color registration mark. A process for clearing the held peak value is performed.
[0144]
Thereby, the CPU 31 can obtain a pulse signal based on reading of the YMC color registration mark and the Bk color registration mark.
[0145]
FIG. 21 is a flowchart illustrating an example of an image processing procedure in the image forming apparatus according to the present invention. Note that (1) to (14) indicate each step.
[0146]
First, the CPU 31 determines whether or not it is the registration correction timing of each image forming station (1). If it is determined that the registration correction timing has not been reached, the process proceeds to step (12), where the CPU 31 determines that image data to be output is received. After waiting and receiving the image data, an image is formed at the current correction timing stored in the nonvolatile memory in the CPU 31 while controlling the image writing in each image forming station (13). The image formation is repeated until it is determined that the image formation is completed (14), and when the image formation is completed, the processing is completed. The number of images formed by image formation is stored in the non-volatile memory, and is referred to at the next registration correction timing.
[0147]
The determination of the registration correction timing in step (1) is performed at every fixed image formation number, or at a registration correction instruction from an operation panel or an external host (not shown), the elapsed time since the last registration correction execution, and the number of prints. It is assumed that the registration correction timing is determined on the basis of the above.
[0148]
On the other hand, if it is determined in step (1) that it is the registration correction timing, the CPU 31 sets the position shift correction mode, reads the position shift detection pattern data from the ROM or the like (2), and A misregistration detection pattern (see FIG. 6) corresponding to each color is formed in the forming station (3).
[0149]
Next, when the misregistration detection pattern formed in each image forming station is transferred to the transport belt 3 (4), the misregistration pattern image is configured into a regular reflection optical system, for example, a read toner image detection sensor shown in FIG. A position shift detection pattern is detected by the light receiving element 52 (5), a current value based on the detected pattern image is subjected to I / V conversion by the I / V conversion circuit 101, and then peak-held by the peak hold circuit 105 (6).
[0150]
Next, the peak hold circuit 105 compares the peak-held value with the reference voltage value to determine whether or not the value obtained by peak-holding the reference voltage value is exceeded (7). A pattern detection pulse signal is generated for each color (8), and the reading of the misregistration detection pattern transferred onto the conveyor belt 3 is waited for N times to be completed (9). The CPU 31 calculates the positional deviation between the black line pattern as the reference color and the line pattern of another color by adding arithmetic processing to the detected pulse signal (10).
[0151]
Next, the image writing timing of each image forming station is determined based on the calculated positional deviation amount, and the previous correction timing data stored in, for example, the non-volatile memory is rewritten with the correction timing data calculated this time ( 11), end the process.
[0152]
According to the above-described embodiment, a large amount of reflected light can be secured by the color misregistration detection unit using the regular reflection optical system, so that the amount of light emitted from the light source can be suppressed. Further, since the Y, M, C, and K toners can be similarly detected, the light emission frequency of the light source can be freely selected. Further, since one point of the output signal from the color misregistration detecting means indicates the position information of the color misregistration detection pattern, the color misregistration amount can be calculated with a small amount of calculation.
[0153]
In addition, the reference voltage value used for pulse conversion is generated in real time from the registration mark measurement waveform, thereby reducing the light amount due to individual differences in the light amount of the LED and deterioration with time, and the output fluctuation due to the surface reflectance deterioration of the image carrier. There is no need to provide an adjustment mechanism, and costs can be reduced.
[0154]
In addition, by providing the reference voltage value correcting mechanism, it is possible to prevent registration mark erroneous detection due to a scratch on the image carrier.
[0155]
Hereinafter, the configuration of a data processing program readable by an image processing system to which the image forming apparatus according to the present invention can be applied will be described with reference to a memory map shown in FIG.
[0156]
FIG. 22 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by an image processing system to which the image forming apparatus according to the present invention can be applied.
[0157]
Although not shown, information for managing a group of programs stored in the storage medium, for example, version information, a creator, and the like are also stored, and information dependent on the OS or the like on the program reading side, for example, a program is identified and displayed. Icons and the like may also be stored.
[0158]
Further, data dependent on various programs is also managed in the directory. In addition, a program for installing various programs on a computer or a program for decompressing a program to be installed when the program to be installed is compressed may be stored.
[0159]
The functions shown in FIG. 21 in this embodiment may be performed by a host computer by a program installed from the outside. In this case, the present invention is applied even when a group of information including a program is supplied to the output device from a storage medium such as a CD-ROM, a flash memory, or an FD, or from an external storage medium via a network. Things.
[0160]
As described above, the storage medium storing the program codes of the software for realizing the functions of the above-described embodiments is supplied to the system or the apparatus, and the computer (or CPU or MPU) of the system or the apparatus stores the storage medium in the storage medium. It goes without saying that the object of the present invention is also achieved by reading and executing the program code thus obtained.
[0161]
In this case, the program code itself read from the storage medium implements the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.
[0162]
As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, EEPROM, or the like can be used. it can.
[0163]
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.
[0164]
Further, after the program code read from the storage medium is written into a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that a CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.
[0165]
【The invention's effect】
As described above, according to the present invention, each color shift transferred to the transporting body with a small amount of light is not affected by the surface condition of the transporting body and is not affected by the transfer surface color of the transporting body. By detecting the difference in reflectance between the pattern and the carrier itself, the amount of color misregistration is accurately calculated with a simple and inexpensive configuration, and the color images formed in each image forming station are superimposed with high accuracy to reduce the color misregistration. No color image can be formed.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view illustrating an example of a color image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic explanatory diagram illustrating a detailed configuration of a sensor illustrated in FIG. 1;
FIG. 3 is a block diagram for explaining a color misregistration processing mechanism in the color image forming apparatus according to the present invention.
FIG. 4 is a block diagram illustrating an example of a light receiving processing circuit including the light receiving element illustrated in FIG. 2;
FIG. 5 is a diagram illustrating characteristics of a pulse signal output from a comparison unit illustrated in FIG. 4;
6 is a diagram illustrating an example of a color misregistration detection pattern formed on the transport belt illustrated in FIG. 1;
FIG. 7 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a second exemplary embodiment of the present invention.
8 is a characteristic diagram showing an example of a pattern detection waveform output from the I / V conversion circuit shown in FIG.
FIG. 9 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a third embodiment of the present invention.
10 is a characteristic diagram showing an example of a pattern detection waveform output from the I / V conversion circuit shown in FIG.
FIG. 11 is a diagram illustrating an example of a color misregistration pattern detection mechanism in a color image forming apparatus according to a fourth embodiment of the present invention.
FIG. 12 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a fourth embodiment of the present invention.
13 is a characteristic diagram illustrating an example of a pattern detection waveform output from the I / V conversion circuit illustrated in FIG.
FIG. 14 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a fifth embodiment of the present invention.
FIG. 15 is a diagram illustrating another example of a color misregistration detection pattern formed on the transport belt illustrated in FIG. 1;
16 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration sensor circuit shown in FIG.
FIG. 17 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a sixth embodiment of the present invention.
18 is a characteristic diagram showing an example of a pattern detection waveform by the color misregistration sensor circuit shown in FIG.
FIG. 19 is a block diagram illustrating an example of a color misregistration detection processing circuit in a color image forming apparatus according to a seventh embodiment of the present invention.
FIG. 20 is a characteristic diagram showing an example of a pattern detection waveform by a color misregistration sensor circuit in the color image forming apparatus according to the eighth embodiment of the present invention.
FIG. 21 is a flowchart illustrating an example of an image processing procedure in the image forming apparatus according to the present invention.
FIG. 22 is a diagram illustrating a memory map of a storage medium that stores various data processing programs that can be read by an image processing system to which the image forming apparatus according to the present invention can be applied.
FIG. 23 is a diagram illustrating a color misregistration state in this type of color image forming apparatus.
FIG. 24 is a diagram illustrating a mechanism for detecting a color misregistration pattern formed on a transport belt of a color image forming apparatus of this type.
[Explanation of symbols]
1 Photosensitive drum
2 Laser scanner
3 Conveyor belt
6 Optical sensor
9-12 Color blur detection pattern
51 Light-emitting element
52 light receiving element
CONT control unit

Claims (15)

An image forming apparatus capable of forming a color image by arranging a plurality of image forming stations and sequentially superimposing and transferring an image formed at each image forming station onto recording paper conveyed by a conveying body,
Among the plurality of image stations, image forming of each image forming station is controlled so that a reference color pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station are formed on the carrier. Pattern forming means;
A light emitting unit,
A light receiving unit that receives light reflected by the light emitting unit,
A voltage conversion unit that converts a light detection current generated by the light receiving unit into a voltage,
A voltage storage unit that stores a maximum value and a minimum value of the voltage generated by the voltage conversion unit,
A first signal generation unit that generates a reference signal according to the maximum value and the minimum value stored in the voltage storage unit;
A pattern detection unit including a second signal generation unit configured to compare the magnitude of a reference signal generated by the first signal generation unit with a light reception output of reflected light of each pattern image by the light reception unit and generate a pulse signal; When,
An image forming apparatus comprising: a calculating unit that calculates a positional shift amount between the respective images based on an output of the pattern detecting unit. 2. The image forming apparatus according to claim 1, wherein the light emitting unit and the light receiving unit of the pattern detecting unit are configured by a regular reflection optical system. The image forming apparatus according to claim 1, wherein the voltage value storage unit includes a reset unit that clears a stored value according to an external signal. The image forming apparatus according to claim 1, wherein the first signal generation unit can variably set a generation condition. The image forming apparatus according to claim 1, wherein the voltage value storage unit acquires a maximum value and a minimum value from a dedicated registration mark. 2. The light receiving unit according to claim 1, wherein the maximum value and the minimum value of the light receiving unit correspond to a surface reflected light amount of the conveyance body and a toner reflection light amount, or a toner reflection light amount and a surface reflection light amount of the conveyance body, respectively. Image forming device. A color misregistration detection method of an image forming apparatus capable of forming a color image by arranging a plurality of image forming stations in parallel and sequentially superimposing and transferring the images formed in the respective image forming stations onto recording paper conveyed by a conveying body. So,
Of the plurality of image forming stations, the image forming of each image forming station is performed such that a reference color line pattern image by a predetermined image forming station and a color misregistration detection pattern image by another image forming station are formed on the carrier. A pattern forming process to be controlled;
A voltage conversion step of converting a current detected by a light receiving unit that receives light reflected by the light emitting unit into a voltage,
A voltage value storage step of storing a maximum value and a minimum value of the voltage value generated by the voltage conversion step,
A first signal generation step of generating a reference signal according to the maximum value and the minimum value stored in the voltage value storage step;
A pattern detection step including a second signal generation step of generating a pulse signal by comparing the light reception output of the reflected light of the pattern image by the light receiving section with the reference signal generated by the first signal generation step; ,
A calculating step of calculating a displacement amount between the respective color images based on an output of the pattern detecting step;
A control step of correcting and controlling the position of the image by each image forming station other than the reference color, based on the displacement amount calculated in the calculation step,
A color misregistration detection processing method for an image forming apparatus, comprising: 8. The color misregistration detection processing method for an image forming apparatus according to claim 7, wherein the light emitting unit and the light receiving unit are configured by a regular reflection optical system. A device for juxtaposing a plurality of image forming stations and forming an image by sequentially superimposing and transferring an image formed at each image forming station onto a record conveyed by a conveying body,
Pattern forming means for controlling image formation of each of the image forming stations to form a pattern image for position shift detection on the transport body,
Reading means for reading each of the pattern images formed on the carrier,
A threshold value is determined based on a maximum value and a minimum value of the read output by the reading unit, and each image formed by the plurality of image forming stations is determined based on the read output of each pattern image by the reading unit and the threshold value. Displacement detection means for detecting the displacement between the two,
Correction means for correcting the position of an image formed by each of the image forming stations based on the amount of displacement detected by the displacement detection means;
An image forming apparatus comprising: The image forming apparatus according to claim 9, wherein the displacement detection unit includes a storage unit that stores the threshold value. The image forming apparatus according to claim 9, wherein the storage unit includes a reset unit that clears a stored threshold value in response to an external reset signal. The image forming apparatus according to claim 9, wherein the displacement detecting unit is configured to change a condition for determining the threshold. The reading unit includes a light emitting unit, a sensor that detects reflected light of the carrier by the light emitting unit, and outputs a current corresponding to a reflected light amount, and a conversion unit that converts a current output from the sensor into a voltage. Have
10. The image forming apparatus according to claim 9, wherein the displacement detecting unit determines the threshold value by dividing a maximum value and a minimum value of the output voltage from the conversion unit by a resistance unit. The image forming apparatus according to claim 9, wherein the displacement detection unit is configured to change the threshold value by changing a resistance value of the resistance unit. The position shift detecting means includes a comparing means for comparing a read output of each of the patterns by the reading means with the threshold value and generating a pulse in accordance with a comparison result, and the position detecting means detects the position in accordance with an output timing of the pulse. The image forming apparatus according to claim 9, wherein the shift amount is detected.

Images