JP4472237B2 - Image forming apparatus and copying machine - Google Patents

Description

【０１００】
Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７は、画像記憶部５４に記憶された画像データに基づいて、以下に説明するノイズ除去処理を行う。Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７の構造およびＹ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７で実行する各ノイズ除去処理については後述するが、該ノイズ除去処理には演算パラメータが必要であり、本実施の形態では、Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７に接続されたパラメータ記憶部５８に保存されている演算パラメータを用いる。パラメータ記憶部５８に保存される演算パラメータとしては、各画素の光学情報の閾値や、後述する各種ノイズ除去処理での平均値の算出に関わる画素数ｉ等がある。
【０１０１】
処理後画像記憶部５９は、図２に示す露光量管理ファイル４０と同様のファイル構造を有しており、Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７においてＸ方向ノイズおよびＹ方向ノイズを除去した画像データを記憶する。処理後画像記憶部５９は、ノイズを除去した後の画像データを構成する各画素の光学情報を、感光体９上での画素位置を特定する座標情報に対応付けて記憶する。本実施の形態では、ノイズを除去した画像データの光学情報として、電界強度が記憶されている。
【０１０２】
次に、Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７の構成、および、Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７で実行するノイズ除去処理について図４ないし図１０を参照して説明する。
【０１０３】
電子写真方式を用いた画像形成に際して、例えば、Ｘ方向(主走査方向)に方向性を有するノイズ(Ｘ方向ノイズ)や、Ｙ方向(副走査方向)に方向性を有するノイズ(Ｙ方向ノイズ)のように、方向性を有する直線状のノイズが静電潜像中に発生すると、この方向性を有するノイズの発生によって、上述したように、プリンタ１によって形成される画像中には、感光体９の感度ムラＳに起因しない横スジＮｘや縦スジＮｙ等の異常画像が重畳されてしまう(図４，図８参照)。Ｙ方向ノイズ除去部５６およびＸ方向ノイズ除去部５７は、以下に説明するノイズ除去処理を行うことにより、このような横スジＮｘや縦スジＮｙを除去する。
【０１０４】
なお、本実施の形態のノイズ除去処理は、方向性を有するノイズの発生方向が既知である場合に有効となる。このため、ノイズ除去処理に先立って、ノイズの発生方向を解析するノイズ方向解析処理を行う。ここに、ノイズ方向判定ステップとしての機能が実現されている。なお、ノイズ方向の解析については、公知の画像解析技術を用いて容易に実現することが可能であるため、ここでは説明を省略し、ノイズ方向解析処理が終了し、ノイズの発生方向が既知であるものとして説明する。
【０１０５】
まず、図４に示すように、感光体９を搭載するプリンタ１で形成した画像６０中に、感光体９の感度ムラに起因する画像Ｓに加えてＹ方向に方向性を持ったノイズに起因する縦スジＮｙが重畳している場合に、Ｙ方向ノイズ除去部５６によって、画像６０から縦スジＮｙを除去するノイズ除去処理について説明する。
【０１０６】
ここで、図５はＹ方向ノイズ除去部５６の機能的構成を示すブロック図であり、図６はＹ方向ノイズ除去部５６が実行するノイズ除去処理について概略的に説明するフローチャートである。Ｙ方向ノイズ除去部５６が実行するノイズ除去処理では、まず、画像記憶部５４に記憶されている画像データを、ノイズ除去用の補正前画像データ記憶部５６ａに記憶する(ステップＳ１)。
【０１０７】
補正前画像データ記憶部５６ａに記憶された画像データに基づいて、画像平均値算出部５６ｂで、全画素の光学情報の平均値Ｐaveを取得する(Ｓ２)。本実施の形態の画像平均値算出部５６ｂは、平均値算出部５５で算出された全画素の光学情報の平均値Ｐaveを読み出し、この値を全画素の光学情報の平均値Ｐaveとして取得する。
【０１０８】
次に、補正前画像データ記憶部５６ａに記憶された画像データから、注目画素決定部５６ｃにより、図７中Ｐ(ｘ，ｙ)(ただし、ｘ＝１〜Ｎ，ｙ＝１〜Ｍ、(Ｎ，Ｍは正の整数))で示す任意の画素を注目画素Ｐ(ｘ，ｙ)として決定する(Ｓ３)。本実施の形態では、ステップＳ４で、注目画素Ｐ(ｘ，ｙ)のｘ、ｙをそれぞれｘ＝１，ｙ＝１に設定する。なお、注目画素Ｐ(ｘ，ｙ)は、感光体の画像形成域全面を１００ｍｍ^２以下の小領域に分割した各小領域に少なくとも一点設定されるように決定する。この小領域の面積は、５０ｍｍ^２以下が好ましく、２５ｍｍ^２が好ましい。
【０１０９】
この小領域の面積は、理想的には、書き込み画素の大きさが最も好ましい。しかし、実際上、この方法では、微細な不規則なノイズを拾い易く、その微細で不規則なノイズを除去することは非常に困難であり、ノイズ除去の計算のための負担も大きいため、小領域の面積の下限を０．０１ｍｍ^２好ましくは０．０４ｍｍ^２以下とすることが実際的で好ましい。
【０１１０】
そして、周辺画素平均値算出部５６ｄによって以下に示す(２)式の演算を行うことにより、この注目画素Ｐ(ｘ，ｙ)を含みＹ方向に沿って２ｎ＋１画素の光学情報の平均値Ｐave(ｘ，ｙ)を算出する(Ｓ５)。ここに、平均値取得ステップとしての機能が実現される。このとき、平均値Ｐave(ｘ，ｙ)を算出するための画素数２ｎ＋１の“ｎ”は、パラメータ記憶部５８に記憶されている平均値の算出に関わる画素数ｉより取得する。
【０１１１】
【数２】

【０１１２】
続いて、注目画素補正部５６ｅにおいて、ステップＳ５で算出した平均値Ｐave(ｘ，ｙ)および平均値算出部５５で算出した画像全体の画素の光学情報の平均値Ｐaveを閾値として用いて、注目画素Ｐ(ｘ，ｙ)の光学情報に対し、以下に示す(３)式の演算を施してＰ'(ｘ，ｙ)を取得する(Ｓ５)。ここに、ノイズ除去ステップとしての機能が実現されている。
【０１１３】
【数３】

【０１１４】
これにより、注目画素Ｐ(ｘ，ｙ)の光学情報から、注目画素Ｐ(ｘ，ｙ)を中心としてＹ方向に±ｎ画素の範囲における光学情報の平均値Ｐave(ｘ，ｙ)が減算され、感光体の感度ムラに起因しない縦スジＮｙを除去した画像データの光学情報を有する画素Ｐ'(ｘ，ｙ)を取得することができる。
【０１１５】
なお、本実施の形態では、注目画素Ｐ(ｘ，ｙ)を中心としてＹ方向に±ｎ画素の範囲における画素の光学情報の平均値Ｐave(ｘ，ｙ)を算出しているが、これに限るものではなく、注目画素Ｐ(ｘ，ｙ)を通るｙ方向のｋ個の画素(ｋは整数)の光学情報平均値を算出すればよい。このとき、注目画素Ｐ(ｘ，ｙ)は、Ｙ方向において平均を算出する範囲内の中心にある必要はない。
【０１１６】
しかしながら、Ｙ方向ノイズＮｙの除去精度を確保するためには、注目画素Ｐ(ｘ，ｙ)が平均を算出する範囲内の中心にあることが好ましい。
【０１１７】
また、本実施の形態では、処理後の画像の平均濃度を処理前の画像とほぼ等しくするために、(３)式に示すように、画像全体の画素の光学情報の平均値Ｐaveを加算するようにしたが、これに限るものではなく、ノイズ除去後の画像データの濃淡変動のみが必要な場合には、必ずしもＰaveを加算する必要はなく、Ｐaveの代わりに任意の値を加算するようにしてもよい。このような場合にも、Ｐaveの代わりとなる任意の値をパラメータ記憶部５８に記憶しておくことで、処理を効率的に行うことができる。
【０１１８】
また、本実施の形態では、平均化を行う注目画素Ｐ(ｘ，ｙ)を含みＹ方向に沿った画素数ｋの大きさを限定するものではないが、画素数ｋは小さすぎても大きすぎても十分なノイズ除去は行えないため、画素数ｋは、注目画素Ｐ(ｘ，ｙ)に対して高い相関が得られる範囲に設定する必要がある。
【０１１９】
そして、得られたＰ'(ｘ，ｙ)の光学情報をこの画素の座標に対応付けて補正後画像データ記憶部５６ｆに記憶するとともに(Ｓ７)、注目画素Ｐ(ｘ，ｙ)におけるｘに１を加算し(Ｓ８)、処理終了判断部５６ｇによって、ｘ＋１で示されるｘがＮより大きくなったと判断されるまで、ステップＳ５からＳ８の処理を繰り返す(Ｓ９のＮ)。
【０１２０】
処理終了判断部５６ｇが、ｘ＋１で示されるｘがＮより大きくなったと判断した場合には(Ｓ９のＹ)、ｙに１を加算し(Ｓ１０)、処理終了判断部５６ｇによって、ｙ＋１で示されるｙがＭより大きくなったと判断される(Ｓ１１のＹ)まで、ステップＳ５からＳ１０の処理を繰り返す(Ｓ１１のＮ)。
【０１２１】
なお、本発明は両端における処理を規定するものではないため、Ｐave(ｘ，ｙ)の演算において、ｙ＜０またはｙ＞Ｍとなる場合、Ｐave(ｘ，ｙ)＝０としても良いし、Ｐave(ｘ，ｙ)＝Ｐave(ｘ，０)またはＰave(ｘ，Ｍ)としてもよい。この場合のパラメータＭも、パラメータ記憶部５８に記憶されている。
【０１２２】
これにより、処理を行う対象画像中の任意の注目画素Ｐ(ｘ，ｙ)を、対象画像の全画素に対して設定し、対象画像中の全画素の光学情報からＹ方向ノイズに起因する縦スジＮｙを除去することで、ノイズ除去処理を行うことによって、縦スジ部分の画素の光学情報とそれ以外の部分の画素の光学情報との間に格差が生じることを抑制することができる。
【０１２３】
また、本実施の形態では、注目画素Ｐ(ｘ，ｙ)を感光体の画像形成域全面を１００ｍｍ^２以下の小領域に分割した各小領域に少なくとも一点設定されるように決定するため、高解像度のプリンタ１に搭載する感光体９の感度分布を良好に測定することができる。
【０１２４】
次に、図８に示すように、感光体９を搭載するプリンタ１用いて形成した画像６０に、Ｘ方向ノイズに起因する横スジＮｘおよびＹ方向ノイズに起因する縦スジＮｙが重畳している場合に、この画像から横スジＮｘおよび縦スジＮｙを除去するノイズ除去処理について図９および図１０を参照して説明する。
【０１２５】
本実施の形態の画像処理装置５３は、図８に示すように、画像６０中に、Ｙ方向ノイズＮｙのみならずＸ方向にもノイズＮｘが発生している場合には、上述したように縦スジＮｙの除去を行った画像データ中の任意の注目画素Ｐ'(ｘ，ｙ)に対して、Ｘ方向ノイズ除去部５７によって、Ｘ方向ノイズ除去処理を実行する。
【０１２６】
ここで、図９はＸ方向ノイズ除去部５７の機能的構成を示すブロック図であり、図１０はＸ方向ノイズ除去部５７が実行するノイズ除去処理について概略的に説明するフローチャートである。Ｘ方向ノイズ除去部５７が実行するノイズ除去処理では、まず、Ｙ方向ノイズ除去部５６の補正後データ記憶部５６ｆに記憶されている画像データを、補正前画像データ記憶部５７ａにコピーする(ステップＳ２０)。
【０１２７】
補正前画像データ記憶部５７ａにコピーされた画像データに基づいて、画像平均値算出部５７ｂで、全画素の光学情報の平均値Ｐaveを取得する(Ｓ２１)。本実施の形態の画像平均値算出部５７ｂは、画像平均値算出部５６ｂと同様に、平均値算出部５５で算出された全画素の光学情報の平均値Ｐaveを読み出し、この値を全画素の光学情報の平均値Ｐaveとして取得する。
【０１２８】
次に、補正前画像データ記憶部５７ａに記憶された画像データから、注目画素決定部５７ｃにより、Ｐ'(ｘ，ｙ)(ただし、ｘ＝１〜Ｎ，ｙ＝１〜Ｍ、(Ｎ，Ｍは正の整数))で示す任意の画素を注目画素Ｐ'(ｘ，ｙ)として決定する(Ｓ２２)。本実施の形態では、ステップＳ２３で、注目画素Ｐ'(ｘ，ｙ)のｘ、ｙをそれぞれｘ＝１，ｙ＝１に設定する。
【０１２９】
そして、周辺画素平均値算出部５７ｄによって以下に示す(４)式の演算を行うことにより、この注目画素Ｐ'(ｘ，ｙ)を含みＸ方向に沿って２ｎ＋１画素の光学情報の平均値Ｐ'ave(ｘ，ｙ)を算出する(Ｓ２４)。Ｘ方向とＹ方向とは直交しているため、この平均値Ｐ'ave(ｘ，ｙ)が直交平均値であり、ここに、直交平均値取得ステップとしての機能が実現される。このとき、平均値Ｐ'ave(ｘ，ｙ)を算出するための画素数２ｎ＋１の“ｎ”も、図６の処理と同様に、パラメータ記憶部５８に記憶されている平均値の算出に関わる画素数ｉより取得する。
【０１３０】
【数４】

【０１３１】
続いて、注目画素補正部５７ｅにおいて、ステップＳ２４で算出した平均値Ｐ'ave(ｘ，ｙ)および平均値算出部５５で算出した画像全体の画素の光学情報の平均値Ｐaveを用いて、注目画素Ｐ'(ｘ，ｙ)の光学情報に対して、以下に示す(５)式の演算を施すことによりＰ''(ｘ，ｙ)を取得する(Ｓ２５)。ノイズ方向がＸ方向とＹ方向との２方向である場合、ここに、ノイズ除去ステップとしての機能が実現される。
【０１３２】
【数５】

【０１３３】
これにより、注目画素Ｐ'(ｘ，ｙ)の光学情報から、注目画素Ｐ'(ｘ，ｙ)を中心としてＹ方向に±ｎ画素の範囲における光学情報の平均値Ｐ'ave(ｘ，ｙ)が減算され、感光体９の感度ムラに起因せずＹ方向ノイズに起因する縦スジＮｙに加えて、感光体９の感度ムラに起因せずＸ方向ノイズに起因する横スジＮｘを除去した光学情報を有する画素Ｐ''(ｘ，ｙ)を取得することができる。
【０１３４】
そして、得られたＰ''(ｘ，ｙ)の光学情報をこの画素の座標に対応付けて補正後画像データ記憶部５７ｆに記憶するとともに(Ｓ２６)、注目画素Ｐ'(ｘ，ｙ)におけるｘに１を加算し(Ｓ２７)、処理終了判断部５７ｇによって、ｘ＋１で示されるｘがＮより大きくなったと判断されるまで、ステップＳ２４からＳ２７の処理を繰り返す(Ｓ２８のＮ)。
【０１３５】
処理終了判断部５７ｇが、ｘ＋１で示されるｘがＮより大きくなったと判断した場合には(Ｓ２８のＹ)、ｙに１を加算し(Ｓ２９)、処理終了判断部５７ｇによって、ｙ＋１で示されるｙがＭより大きくなったと判断される(Ｓ３０のＹ)まで、ステップＳ２４からＳ２９の処理を繰り返す(Ｓ３０のＮ)。
【０１３６】
なお、本発明は両端における処理を規定するものではないため、Ｐave(ｘ，ｙ)の演算において、ｘ＜０またはｙ＞Ｎとなる場合、Ｐave(ｘ，ｙ)＝０としても良いし、Ｐave(ｘ，ｙ)＝Ｐave(０，ｙ)またはＰave(Ｎ，ｙ)としてもよい。この場合のパラメータも、パラメータ記憶部５８に記憶されている。
【０１３７】
これにより、ノイズの発生方向が、Ｙ方向とこれに直交するＸ方向の２方向である場合にも、感光体９の表面状態に起因せず方向性を有するノイズＮｘ，Ｎｙを各連続方向において効果的に除去することができる。
【０１３８】
なお、処理後画像記憶部５９に記憶されて電界強度と露光量との間には線形関係がないため、複数段階に調整した各露光量で露光することで中間調付近の画像を複数形成し、上述したノイズ除去処理を各画像に対して行う。
【０１３９】
本実施の形態では、Ｘ方向およびＹ方向のノイズに起因する横スジＮｘ，縦スジＮｙを除去するノイズ除去処理について説明を行ったが、これに限定されるものではなく、直線状に方向性を有するノイズであれば斜め方向のノイズに起因する異常画像も同様に除去することが可能である。斜め方向に方向性を有する異常画像が発生している場合、画像データに対して回転処理を施して、発生しているノイズの方向性がＸ方向またはＹ方向となるように調整することにより、いずれの方向性を有するノイズであっても該ノイズが方向性を有しているならば除去することができる。なお、画像データに対する回転処理については公知の画像処理技術を用いて容易に実現することが可能であり、ここでは説明を省略する。
【０１４０】
なお、本実施の形態では、表面感度の測定対象となる感光体を用いて用紙上に形成した画像を光学的に読み取る入力装置５２を用いた場合について説明したが、感光体上に形成されて用紙に転写する以前のトナー像を光学的に読み取ることで画像データを取得するようにした場合、用紙上に形成した画像から画像データを取得する場合と比較して、転写工程や定着工程を含まない分、転写工程や定着工程に際して発生するノイズを含まない画像データを得ることが可能になるので、感光体の感度分布をより高精度に測定することができる。
【０１４１】
プリンタ１の記憶装置における露光量管理ファイル４０には、処理後画像記憶部５９に記憶されたデータが書き込まれている。すなわち、プリンタ１で形成した画像に基づいて、感光体感度測定装置５０で取得した感度情報４０ｂが、画素位置情報４０ａ毎に対応付けられて記憶されている。ここに、感度取得ステップが実現される。
【０１４２】
このような構成において、マイクロコンピュータは、画像形成に際して、外部接続された図示しないＰＣ等から送信された画像データに基づいて、光源のＯＮ／ＯＦＦを駆動制御する。また、マイクロコンピュータは、光源のＯＮ／ＯＦＦ駆動と同時に、露光走査装置１１のポリゴンミラー２０を回転させるモータ２１を駆動制御する。これにより、露光走査装置１１から出射された露光光が、感光体９表面において主走査方向(Ｘ方向)へ１次元走査される。加えて、マイクロコンピュータは、図示しない感光体モータを駆動制御して感光体９を軸心回りに回転させる。これにより、１次元走査される露光位置に対して感光体９表面の顕像化領域が副走査方向(Ｙ方向)に機械的に移動して、感光体９表面に２次元の静電潜像が形成される。
【０１４３】
続いて、マイクロコンピュータは、現像ユニット１２を駆動制御して、感光体９表面に形成された静電潜像にトナーを付着させることでトナー像を形成し、転写チャージャ１４を駆動制御することでトナー像を用紙上に転写させる。用紙上に転写されたトナー像は、定着ユニット７によって定着される。
【０１４４】
静電潜像の形成に際して、マイクロコンピュータは、感光体９の回転数と、画像データとに基づいて、露光走査装置１１によって露光走査する画素位置を特定し、露光量管理ファイル４０を参照して、特定した画素位置情報４０ａに対応する感度情報４０ｂに基づいて、露光量を制御する。ここに、露光位置特定手段および露光量補正手段としての機能が実現される。これにより、感光体９に対する露光量が画素位置毎に調整される。
【０１４５】
ここで、感度情報４０ｂは、各画素位置情報４０ａに対応する露光量と画像情報(あるいは、画像情報から算出される静電電位情報)との関係を示している。感度分布の測定を、画像形成領域における全ての画素について行わない場合、測定された場所(測定点)の感度情報を各画素に割り振る必要がある。測定点の感度情報４０ｂを各画素に割り振る方法としては、ある測定点と隣りの測定点との中間の画素までは測定点の感度情報とする方法、各測定点からの距離に応じて１次元あるいは多次元の方程式から算出する方法等を例示することができる。測定点の感度情報４０ｂを、どの方法を用いて各画素に割り振るかは、測定の密度、ＣＰＵの性能等により適宜選択される。
【０１４６】
露光量の制御に際しては、求められた感度情報４０ｂを、図１１に示すように、基準感度情報４０ｃと対比させ、基準感度情報４０ｃに対する感度情報４０ｂの値に応じて露光量を補正し、決定する。基準感度情報４０ｃは、不偏の基準として予め設定しておいてもよいが、公知の技術であるＰセンサ等による算出、あるいは、全画素位置情報４０ａの感度情報４０ｂの平均等を例示することができる。要求される潜像電位を得るために、通常は、基準感度情報４０ｃにしたがって露光量が決定されるが、本実施の形態では感度情報４０ｂに基づいて露光量を補正し、決定する。
【０１４７】
このように、静電潜像の形成に際して、露光量管理ファイル４０を参照して露光量を補正することにより、感光体９に対する露光量を画素位置毎の感度に応じて適切に調整することができるので、場所毎に感度にムラが生じている感光体９を用いて画像を形成する場合にも、感光体９の感度ムラに起因して、顕像化した画像中に濃淡ムラが発生することを顕像化領域全体に亘って防止することができ、感光体９の感度分布状態に依存することなく、画像の濃淡ムラのない高精細で高画質の画像を形成することができる。
【０１４８】
なお、本実施の形態では、図１に示すプリンタ１への適用例を示したが、これに限るものではなく、プリンタエンジン６に代えて、例えば、図１２に示すようなプリンタエンジン６３を備えるプリンタに適用してもよい。図１２に示すプリンタエンジン６３は、感光体９、この感光体９の外周面に接触配置された帯電ブレード６４ａを有する帯電装置６４、露光部(図示せず)、感光体９にトナーを供給する現像ユニット６５、感光体９の表面に残存するトナーを回収するクリーナーユニット６６等が一体的に組み合わされたプロセスカートリッジ６７と、転写チャージャ６８および分離チャージャ６９とによって構成されている。プロセスカートリッジ６７は、本体ハウジング２に対して着脱自在に装着されている。
【０１４９】
このようなプリンタによれば、第一の実施の形態と同様に、感度ムラを有する感光体を用いて画像形成を行った場合にも濃淡ムラのない高精細な画像を形成することができるとともに、プロセスカートリッジ６７を用いることにより、組み立て作業の容易化を図ることができる。また、プロセスカートリッジ６７が本体ハウジング２に対して着脱自在に設けられているため、感光体９、帯電装置６４、現像ユニット６５、クリーナーユニット６６等のプロセスカートリッジ６７を構成する部材の交換に際しては、プロセスカートリッジ６７単位で交換することができるので、長寿命の部品を継続使用するとともに、消耗品の交換作業の容易化を図ることができる。
【０１５０】
また、本実施の形態では、図１に示すプリンタ１への適用例を示したが、これに限るものではなく、プリンタエンジン６に代えて、例えば、図１３に示すように、３つの駆動ローラ７０ａ，７０ｂ，７０ｃに巻回された感光ベルト７１と、感光ベルト７１の外周面に対向配置された帯電チャージャ７２、露光部(図示せず)、現像ユニット１２、転写チャージャ７３、クリーニングブラシ７４、除電光源７５等によって構成されるプリンタエンジン７６を備えるプリンタに適用してもよい。このプリンタエンジン７６には、感光ベルト７１の内周側に設けられたクリーニング前露光部７７が設けられている。このクリーニング前露光部７７は、感光ベルト７１の内周側に設けられていてもよいし、外周側に設けられていてもよい。
【０１５１】
さらに、本実施の形態では、モノクロ画像を形成するプリンタへの適用例を示したが、これに限るものではなく、例えば、Ｙ，Ｍ，Ｃ，Ｋの４色の画像を形成するカラープリンタへ適用してもよい。これによって、カラー画像を形成するプリンタにおいても、感光体９の感度ムラに起因する濃淡ムラを抑制した画像を形成することができる。
【０１５２】
次に、本発明の第二の実施の形態について図１４を参照して説明する。本実施の形態は、複写機への適用例を示す。
【０１５３】
図１４は、本実施の形態の複写機を示す縦断側面図である。複写機８０は、原稿の画像を読み取る画像読取装置としてのスキャナ８１と、スキャナ８１が読み取った画像を用紙に形成するプリンタ１と、を備えている。
【０１５４】
スキャナ８１は、図示しない原稿が載置されるコンタクトガラス８２を備えている。原稿は、原稿面をコンタクトガラス８２に対向させて載置される。コンタクトガラス８２の上側には、コンタクトガラス８２上に載置された原稿を押さえる原稿圧板８３が設けられている。
【０１５５】
コンタクトガラス８２の下方には、光を発光する光源８４およびミラー８５を搭載する第一走行体８６と、二枚のミラー８７，８８を搭載する第二走行体８９と、ミラー８５，８７，８８によって導かれる光を結像レンズ９０を介して受光するＣＣＤ(Charge Coupled Device)イメージセンサ９１等によって構成される読取光学系９２が設けられている。ＣＣＤイメージセンサ９１は、ＣＣＤイメージセンサ９１上に結像される原稿からの反射光を光電変換した光電変換データを生成する光電変換素子として機能する。ＣＣＤイメージセンサ９１で光電変換された光電変換データは、図示しない画像処理系によってデータ処理されてデジタル画像データとされる。第一、第二走行体８６，８９は、コンタクトガラス８２に沿って往復動自在に設けられており、図示しないモータ等の移動装置によって２：１の速度比で走行する。
【０１５６】
プリンタ１は、ＣＣＤイメージセンサ９１で光電変換されて図示しない画像処理系によってデータ処理されたデジタル画像データに基づいてプリンタエンジン６を駆動制御することで、デジタル画像データに基づく画像を記録媒体に形成する。
【０１５７】
このとき、露光走査装置１１は、露光量管理ファイル４０に記憶された感度情報４０ｂに基づいて、露光する画素位置に応じて露光量を制御する。
【０１５８】
これによって、感光体９の感度ムラに起因して、プリンタ１によって形成される画像中に濃淡ムラが発生することを防止して、スキャナ８１で読み取った原稿の画像を再現性良く記録媒体に複写することができる。
【０１５９】
なお、本実施の形態では、第一の実施の形態で説明したプリンタ１を備える複写機としたが、これに限るものではなく、プリンタ１に代えて、例えば、図１２や図１３に示すプリンタエンジンを備えるプリンタを用いてもよい。
【０１６０】
【実施例】
次に、本発明の実施例について以下に説明する。実施例では、以下に説明するようにして複数の感光体を実際に作製し、作製した感光体に対して上述したノイズ除去処理を施すことによりによって得られたデータに基づいて、作製した感光体の品質を比較した。
【０１６１】
まず、下記組成の混合物をボールミルポットに取り、φ１０ｍｍアルミナボールを使用して７２時間ボールミリングした。
酸化チタン(ＣＲー６０：石原産業製)：５０.０重量部
アルキッド樹脂(ベッコライトＭ６４０１−５０：大日本インキ化学工業製)：１５.０重量部
メラミン樹脂(スーパーベッカミンＬ−１２１−６０：大日本インキ化学工業製)１０.０重量部
メチルエチルケトン(関東化学製)：３１.７重量部
【０１６２】
このミリング液に対して、シクロヘキサノン(関東化学製)：１０５.０重量部を加え、さらに２時間ボールミリングして下引き層用塗布液を作製した。
【０１６３】
この下引き層用塗布液中に周長２９０.３ｍｍ、厚さ３０μｍのニッケルシームレスベルト(ビッカース硬度４８０〜５１０、純度９９.２％以上)を浸漬させ、ニッケルシームレスベルトに対して下引き層用塗布液を浸漬塗工し、１３５℃で２５分間乾燥して、膜厚６.５μｍの下引き層を形成した。
【０１６４】
続いて、下記組成の混合物をボールミルポットに取り、φ１０ｍｍ瑪瑙ボールを使用し時間ボールミリングした。
以下に(化１)で示す化学式構造を有する電荷発生物質(リコー製)：１.５重量部
【化１】

以下に(化２)で示す化学式構造を有する電荷発生物質(リコー製)：１.５重量部
【化２】

ポリビニルブチラール樹脂(エスレックＢＬＳ：積水化学製)：１.０部
シクロヘキサノン(関東化学製)：８０.０重量部
【０１６５】
このミリング液に対して、さらにシクロヘキサノン７８.４部とメチルエチルケトン２３７.６重量部とを加えて調整した電荷発生層塗布液を作製した。この電荷発生層塗布液に対して、上述の下引層を積層したニッケルシームレスベルトを浸漬させ、下引層を積層したニッケルシームレスベルトに対して電荷発生層塗布液を浸漬塗工し、１３０℃で２０分間乾燥し、厚さ０.１２μｍの電荷発生層を形成した。
【０１６６】
次に、下記組成の電荷輸送層塗工液を調整した。
以下に(化３)で示す化学式構造を有する電荷輸送物質(リコー製)：７重量部
【化３】

ポリカーボネート樹脂(Ｃ−１４００：帝人化成製)：１０重量部
シリコーンオイル(ＫＦ−５０：信越化学製)：０.００２重量部
テトラヒドロフラン(関東化学製)：８４１.５重量部
シクロヘキサノン(関東化学製)：８４１.５重量部
３−ｔ−ブチル−４−ヒドロキシアニソール(東京化成製)：０.０４重量部
【０１６７】
上述した電荷輸送層塗工液を、下引層、電荷発生層を積層したニッケルシームレスベルトを回転させながらスプレー塗工した後、１４０℃で３０分間乾燥して、厚さ約２５μｍの電荷輸送層を形成して感光体を作製した。
【０１６８】
上述のような作製方法により作製される感光体のスプレー塗工条件を５種類に変化させて作製した５本の感光体をそれぞれ幅３６７ｍｍに切断し、切断した感光体の任意の位置２０点の膜厚を、触針式の膜厚計で測定した。この測定結果に基づいて、(膜厚の最大値−膜厚の最小値)によって取得される値を膜厚のムラとして求めたところ、作製した各感光体の膜厚ムラはそれぞれ、０.９μｍ、１.２μｍ、１.８μｍ、２.５μｍ、３．０μｍであった。
【０１６９】
続いて、厚さ０．８ｍｍ、ゴム硬度７０のウレタンゴム上に厚さ約４０μｍのアクリル系粘着剤を積層し、さらに剥離紙を積層した。これを幅４ｍｍ、長さ２８５ｍｍの長さにトムソン刃で打ち抜き寄り止めガイドとした。
【０１７０】
感光体基体の端部から５ｍｍの両側縁内面に、上記の寄り止ガイドを剥離紙を剥しながら貼り付け固定し感光体を作製した。
【０１７１】
このように作製した感光体をＩＰＳｉＯ Ｃｏｌｏｒ ５０００改造機(リコー製)に搭載し画像形成装置を作製した。パソコンで全面グレーの画像を作成し、帯電電圧−８００Ｖ、露光量０．３μＪ／ｃｍ^２で白黒モード、１２００ｄｐｉ、２×２ドットで画像形成を行った。
【０１７２】
このとき用いたＩＰＳｉＯ Ｃｏｌｏｒ ５０００改造機は完成品ではなかったため、感光体に起因しない多くの横スジ、縦スジが存在した。
【０１７３】
画像形成した画像を明度リニアな入力特性を持つスキャナにより１００ｄｐｉの解像度でパソコンに電子情報として取り込んだ。取り込んだ画像情報から感光体の周方向の長さ２９０．３ｍｍ部分のみをトリミングした。
【０１７４】
この画像データに対して上述した第一の実施の形態と同様にＸ方向およびＹ方向のノイズＮｘ，Ｎｙを除去し、ノイズ除去後の画像を１０×１０画素のフィルタサイズで平滑化を行いノイズ除去画像を得た。その結果、ノイズ除去処理前の画像には図２または図６に示すように直線状のノイズが発生していたのに対し、ノイズ除去処理後の画像６０’は図１５に示すように感光体９の感度ムラに起因する画像Ｓのみ、すなわち、感度分布のみを反映していることが判る。なお、ここでは、膜厚ムラが２．５μｍの感光体を用いて形成した画像について説明する。
【０１７５】
ところで、露光量０．３μＪ／ｃｍ^２では、画像濃度(ＩＤ)と感光体の電界強度(Ｅ：Ｖ／μｍ)との間には、以下に(６)式で示す関係が存在する。
Ｅ＝−２０．１×(１．１９−ＩＤ) …(６)
【０１７６】
画像データは、画像の各座標(感光体表面の各座標)毎に光学情報を有しているため、(６)式によれば、露光量０．３μＪ／ｃｍ^２での、各座標毎の感光体の電界強度を求めることができる。
【０１７７】
ここで、画像形成域中での電界強度のバラツキの許容範囲を決定付ける規定範囲を０．３５Ｖ／μｍに設定したところ、感光体の膜厚ムラが０．９μｍ、１．２μｍのものは合格で、その他の感光体は不合格と判定することができた。
【０１７８】
なお、実施例においては、顕像化された画像における画素と、この画素の感光体上での位置との整合を完全には取らなかったが、例えば、感光体の書き込み位置を特定する手段を設けることで、感光体の感度ムラが生じた原因解析に用いることができる。
【０１７９】
続いて、電界強度のバラツキが規定範囲内となる膜厚ムラ１．２μｍとなる製造条件で感光体を量産し、製造５０本毎に前述の感度分布の測定を行った。これによれば、感光体製造１２００本目に感度分布の閾値を超えてしまったため、量産を中止したが、その後、スプレーガンの清掃を行い製造を再開したところ、感光体製造を２８００本行っても感度分布の閾値を超える感光体は製造されなかった。
【０１８０】
【発明の効果】
本願発明によれば、感光体の感度ムラに起因して、顕像化した画像に濃淡ムラが発生することを顕像化領域全体に亘って防止することができる画像形成装置及び複写機を提供することができる。
【図面の簡単な説明】
【図１】本発明の第一の実施の形態のプリンタを示す断面図である。
【図２】露光量管理ファイルを示す説明図である。
【図３】感光体感度測定装置を示すブロック図である。
【図４】電子写真方式を用いて形成した画像中に発生するノイズを示す説明図である。
【図５】Ｙ方向ノイズ除去部の機能的構成を示すブロック図である。
【図６】Ｙ方向ノイズ除去部が実行するノイズ除去処理について概略的に説明するフローチャートである。
【図７】光学情報を平均化する画素を示す説明図である。
【図８】電子写真方式を用いて形成した画像中に発生するノイズを示す説明図である。
【図９】Ｘ方向ノイズ除去部の機能的構成を示すブロック図である。
【図１０】Ｘ方向ノイズ除去部が実行するノイズ除去処理について概略的に説明するフローチャートである。
【図１１】感光体表面電位と露光量との関係を示すグラフである。
【図１２】別の実施の形態のプリンタエンジンを示す断面図である。
【図１３】また別の実施の形態のプリンタエンジンを示す断面図である。
【図１４】本発明の第二の実施の形態の複写機を示す断面図である。
【図１５】実施例においてノイズ除去処理後の画像を示す説明図である。
【符号の説明】
９ 感光体
１０ 帯電装置
１１ 露光走査装置
８０ 複写機
８１ 画像読取装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, a sensitivity information acquisition method, and a copying machine.
[0002]
[Prior art]
In recent years, there has been a demand for an image forming apparatus that can form an image with high resolution, high definition, and faithful to an original image. In particular, recently, there is an increasing demand for an image forming apparatus capable of forming a halftone image such as a photograph. In such image formation using a lot of halftones, the sensitivity unevenness inherent to the photoreceptor itself cannot be ignored when the resolution of the image is 1000 dpi or more, and the surface potential of the photoreceptor in the halftone range is 10 to 20V. In many cases, unevenness occurs in the formed image, resulting in a problem.
[0003]
In general, a photoreceptor is composed of a cylindrical base and a photosensitive layer laminated on the outer peripheral surface of the base. The photosensitive layer is configured by sequentially laminating a charge generation layer, a charge transport layer, a protective layer, and the like on the surface of the substrate. Sensitivity unevenness of a photoreceptor having such a photosensitive layer is caused by uneven surface condition of the substrate, coating unevenness of each layer laminated on the substrate surface, and the like.
[0004]
In particular, in an image forming apparatus using coherent light such as laser light or LED light, density unevenness may occur in a visualized image due to film thickness unevenness of the photoconductor. It is necessary to detect the unevenness of sensitivity early. The density unevenness of the image due to the film thickness unevenness of the photoconductor tends to become more prominent when the resolution of the image written on the photoconductor becomes higher. Therefore, the more the photoconductor is applied to a high-resolution image forming apparatus. Therefore, it is necessary to detect the sensitivity unevenness of the photoconductor early and reliably.
[0005]
By the way, as a method for measuring the sensitivity of the photosensitive member, generally, after charging the photosensitive member, the potential of the photosensitive member when exposed to a certain amount of light is measured, or the photosensitive member is There is a method of measuring the amount of writing light irradiated until reaching a certain amount of potential. Since many photoconductors have a cylindrical shape, when using the measurement method as described above, the surface potential of the photoconductor charged and exposed while rotating around the axis is measured using a surface potentiometer or the like. A method of measuring along the circumference of the heart is common.
[0006]
At this time, if the distance between the photoconductor and the surface electrometer is not always constant, the measurement accuracy of the surface potential deteriorates. Therefore, when measuring the sensitivity of the photoconductor, the photoconductor can be rotated around the axis at a fixed position. The distance between the surface of the photoconductor and the surface electrometer is kept constant by holding the position of the surface electrometer relative to the surface of the photoconductor.
[0007]
However, if the position of the surface electrometer is fixed with respect to the surface of the photoconductor that is rotatably held around the axis at a fixed position, only a part of the sensitivity in the axial direction of the photoconductor can be measured. Since the sensitivity of the photoreceptor varies depending on the surface condition of the substrate and the lamination state of each layer of the photosensitive layer laminated on the substrate surface, it is desirable to measure over the entire visualization region related to image formation on the photoreceptor.
[0008]
In order to measure the sensitivity of the photoconductor over the entire visualization area, for example, a plurality of surface electrometers are arranged and fixed along the axial direction of the photoconductor that is rotatably held around the axis at a fixed position. A way to do this is conceivable. According to such a method, it is possible to measure the surface potential of the photoreceptor over a wide range. However, in actuality, if surface electrometers are placed close to each other, the surface electrometers interfere with each other and cannot accurately measure the surface potential of the photoreceptor. There are physical limitations. For high image quality, the entire visible area is 100 mm.²Although it is necessary to divide into the following regions and measure the sensitivity of the photosensitive member in each region, for the reasons described above, the sensitivity distribution of the photosensitive member can be obtained only with a very rough matrix.
[0009]
In addition, in order to measure the sensitivity of the photoconductor over the entire visualized region, there is also a method of measuring the surface potential while finely changing the position of the surface electrometer relative to the photoconductor along the axial direction of the photoconductor. Conceivable. However, this method requires a great deal of labor for sensitivity measurement. In addition, since charging and exposure are performed each time the sensitivity of a photoconductor is measured, the position of the surface potentiometer with respect to the photoconductor is changed along the axial direction of the photoconductor while changing the entire imaging area. In order to measure the surface potential, charging and exposure are repeated many times. However, when charging and exposure are repeated, the first measurement result and measurement are repeated despite the measurement of the sensitivity in the same region. In many cases, the electrostatic characteristics of the photosensitive member are different from the measurement results after the measurement. For this reason, it is often difficult to determine whether the photosensitive member has inherent sensitivity unevenness or sensitivity unevenness caused by repeated measurement.
[0010]
Further, there is a method of measuring the film thickness of each layer forming the photosensitive layer in order to measure the sensitivity of the photosensitive member over the entire visualization region. When measuring the film thickness of each layer forming the photosensitive layer, the film thickness is generally measured by a physical film thickness meter or an eddy current film thickness meter. However, in the method of measuring the film thickness over the entire image forming area of the photoconductor, a great deal of labor is required and the surface of the photoconductor is likely to be damaged by the measurement. For this reason, the current situation is that the measured photoconductor must be discarded.
[0011]
For this reason, there is a need for a simple method for measuring the sensitivity of the photoconductor over the entire visualization region.
[0012]
Here, the surface state of the substrate of the photosensitive member may change uniformly over the entire surface of the substrate, but hardly changes in a partial manner unless it is intentionally manufactured. Further, since the charge generation layer has absorption in the visible region, the film thickness can be determined relatively easily by visual observation. For this reason, it is relatively easy to manage the surface state of the substrate and the film thickness of the charge generation layer.
[0013]
On the other hand, since the charge transport layer and the protective layer, which are not preferable when absorbing the writing light, are generally formed of a transparent material, it is impossible to visually measure the film thickness. Assuming that the surface state of the film and the film thickness of the charge generation layer are constant, a uniformly charged photoconductor is uniformly exposed and developed, transferred, and fixed. It is considered that shading unevenness caused by the film thickness unevenness of the layer is generated, and the film thickness distribution of the photoreceptor is reflected. That is, it is considered that the sensitivity unevenness of the photoreceptor can be obtained from the density unevenness of the visualized image.
[0014]
By the way, in image formation using an electrophotographic method, generally, a one-dimensional optical writing is performed in the main scanning direction by a laser, an LED, or the like, and the photosensitive member is moved in the sub-scanning direction to the optical writing position. The two-dimensional electrostatic latent image is formed. For this reason, when the adjustment of the writing device is incomplete or the rotation control of the photoreceptor is incomplete, the two-dimensional electrostatic latent image has a linear shape along the main scanning direction or the sub-scanning direction. It becomes easy to generate noise. Such linear noise has a characteristic that it tends to become noticeable when an image having a uniform density region or a gentle gradation region is formed.
[0015]
When noise occurs in the electrostatic latent image, an abnormal image such as a horizontal stripe or a vertical stripe that is not caused by a photoconductor such as so-called banding is superimposed on an image obtained by visualizing the electrostatic latent image. There are many cases. Horizontal stripes and vertical stripes not caused by this photoconductor occur irregularly, and the image density unevenness due to noise not caused by this photoconductor often becomes equal to or higher than the image density unevenness due to the film thickness distribution of the photoconductor. It may end up. In particular, in a photoconductor intended for use in a high-resolution image forming apparatus, it is caused by noise that is not caused by the photoconductor, rather than slight density unevenness in the image caused by the photoconductor such as the film thickness distribution of the photoconductive layer. In most cases, the density unevenness is much larger. For this reason, for example, even if the image density of each part of the image is measured by a Macbeth densitometer or the like, it is extremely difficult to measure the image density difference due to the film thickness unevenness of the photoreceptor.
[0016]
Ideally, such a problem caused by noise is to take measures such as sufficient maintenance of the image forming apparatus to eliminate noise in the electrostatic latent image and form an image free from density unevenness due to noise. Although it can be eliminated if possible, in reality, it is difficult to completely suppress the generation of noise. In particular, the situation in which the measurement of the film thickness distribution of the photoconductor is required is that the image forming apparatus itself is often incomplete, such as during the development of an image forming apparatus on which the photoconductor is mounted. It is difficult to avoid noise superimposition.
[0017]
For this reason, in order to determine the sensitivity unevenness of the photoconductor from the density unevenness of the visualized image, it is essential to remove the density unevenness that does not originate from the photoconductor from the formed image.
[0018]
For example, as disclosed in Japanese Patent Application Laid-Open No. 2000-2621, as a conventional technique for detecting density unevenness of an image, an image region is divided into two or more regions for the purpose of inspection of a color filter or the like. There is an “image shading unevenness detection method” in which the unevenness area is specified by comparing the difference between the density average of the area and the overall average and a threshold value set separately.
[0019]
Further, as disclosed in Japanese Patent Laid-Open No. 2001-243473, the difference between the average luminance value of the target image area and the average luminance value of the donut-shaped area set so as to surround the area is calculated and set separately. There is an “image density unevenness detection method” that detects an uneven area in comparison with a threshold value. According to the technique disclosed in the publication, it is possible to improve the detection sensitivity of point-like unevenness for the purpose of detecting unevenness of a color filter.
[0020]
In addition, a method for making noise in an image inconspicuous using a smoothing filter is well known.
[0021]
[Problems to be solved by the invention]
However, the techniques disclosed in Japanese Patent Laid-Open Nos. 2000-2621 and 2001-243473 cannot detect slight shading unevenness from an image on which noise is superimposed. It was not possible to sufficiently extract an image due to uneven thickness.
[0022]
In addition, the method of making the noise in the image less noticeable using the smoothing filter does not remove the noise but only diffuses the noise in the image to make it less noticeable. Therefore, it is difficult to obtain a detailed film thickness distribution of the photoconductor over the image forming area of the photoconductor from the image information of the image formed.
[0023]
Further, since there is no linear correlation between the charge amount or electric field intensity on the photoconductor and the exposure amount, it is impossible to measure useful sensitivity simply by measuring the density of one image.
[0024]
If the sensitivity distribution of the photosensitive member is known even if the photosensitive member has uneven sensitivity, the density of the formed image is corrected by correcting the exposure amount at the time of image formation, such as shaving correction. It is possible to suppress the occurrence of unevenness. Further, as disclosed in Japanese Patent Laid-Open No. 2001-305838, an image having a uniform density can be obtained by offsetting the sensitivity deviation of the photosensitive member and the deviation of the writing light quantity.
[0025]
However, these methods have a sensitivity deviation of the photosensitive member and a deviation of the writing light amount in the main scanning direction of the writing light, but ignore the sensitivity deviation of the photosensitive member in the sub-scanning direction of the writing light. There is no deviation in the amount of writing light in the direction.
[0026]
Japanese Patent Laid-Open No. 2002-67387 discloses an image forming apparatus using an a-Si photosensitive member in which the surface of the a-Si photosensitive member is divided into a plurality of blocks in the main scanning direction and the sub-scanning direction of the writing light. An image forming apparatus is disclosed that obtains a uniform image by dividing and correcting the amount of light to be written from the light attenuation curve in each block.
[0027]
However, as described above, although it is most difficult to measure the sensitivity distribution of the photosensitive member at high density over the entire visualized region, Japanese Patent Application Laid-Open No. 2002-67387 discloses the photosensitive member. There is no disclosure of a method for measuring the sensitivity distribution.
[0028]
In addition, as described above, the sensitivity distribution of the photoconductor often occurs due to the film thickness deviation of the photosensitive layer, but if the film thickness deviation of the photosensitive layer is too large, uneven development and uneven transfer occur. Even if the amount of light to be written is corrected, the shading unevenness of the image cannot be sufficiently suppressed. In particular, the tendency is strong in the case of a high-resolution image forming apparatus in which the resolution of a written image is 100 dpi or more.
[0029]
An object of the present invention is to prevent the occurrence of density unevenness in a visualized image due to the sensitivity unevenness of the photoreceptor over the entire visualized area.
[0030]
[Means for Solving the Problems]
In the image forming apparatus according to the first aspect, the film thickness difference in the image forming area is 0.2 to3.0a photoreceptor having a photosensitive layer of μm;
A charging device for charging the surface of the photoreceptor;
An exposure scanning device that exposes and scans the surface of the photoreceptor charged by the charging device;
A visualization device that visualizes an electrostatic latent image formed on the surface of the photoreceptor by exposure scanning by the exposure scanning device;
A sensitivity storage device that stores sensitivity information of the photoconductor with respect to exposure light from the exposure scanning device in a storage area in association with each exposure position on the surface of the photoconductor;
Exposure amount correction means for correcting the exposure amount by the exposure scanning device for each exposure position with reference to the storage area of the sensitivity storage device;
An image forming apparatus comprisingThere,
In order for the image forming apparatus to obtain sensitivity information of the photoreceptor,
Means for visualizing an electrostatic latent image formed by uniformly exposing and scanning a uniformly charged photoconductor surface, and obtaining image data including optical information of each pixel constituting the visualized image Means to do
Noise direction determining means for determining a continuous direction of noise data in which pixels having the optical information in the acquired image data are linearly continuous;
Average value acquisition means for averaging the optical information of a plurality of pixels including any target pixel in the image data along the continuous direction of the noise data determined by the noise direction determination means, and acquiring an average value;
The noise removing unit sets all pixels in the image data as the target pixel, and sets the average value acquired by the average value acquisition unit from the optical information of each target pixel as a threshold value. Noise removing means for subtracting the threshold value from the optical information of the noise data continuous in a shape;
The sensitivity acquisition unit acquires the optical information of all the pixels after the noise removal unit subtracts the threshold as the sensitivity of the photosensitive member.
An image forming apparatus characterized by comprising:
Therefore, during exposure scanning by the exposure scanning device, the exposure area by the exposure scanning device is corrected for each exposure position with reference to the storage area of the sensitivity storage device, thereby causing a visible image due to the sensitivity unevenness of the photoconductor. It is possible to prevent the occurrence of uneven density in the image to be visualized over the entire visualized area.
Further, in the image data obtained by visualizing the electrostatic latent image obtained by uniformly exposing and scanning the surface of the uniformly charged photoconductor, the optical characteristics of noise data in which pixels having optical information exceeding the threshold value are linearly continued. By acquiring the optical information of all the pixels after subtracting the threshold value as the sensitivity of the photoconductor, it is possible to avoid troublesome work or damage to the photoconductor by directly measuring the sensitivity of the photoconductor by film thickness measurement or potential measurement. It is possible to easily measure the sensitivity distribution of the photoreceptor over the entire visualized region without incurring.
Furthermore, the threshold value suitable for the image data is set by obtaining an average value obtained by averaging the optical information of a plurality of pixels including any target pixel in the image data along the continuous direction of the noise data as a threshold value. By subtracting this threshold value from the optical information of all the pixels, it is possible to suppress the generation of a difference between the noise data and the other image data by performing noise removal.
The image forming apparatus according to claim 2, wherein the average value of a plurality of pixels including an arbitrary pixel of interest in the image data along a direction orthogonal to a continuous direction of the noise data from which the average value is acquired is obtained. An orthogonal average value acquisition means for averaging the optical information after subtraction and acquiring the orthogonal average value is provided,
In the noise removing unit, a noise removing unit that subtracts the orthogonal average value as the threshold value from the optical information of each pixel of interest after subtracting the average value using all the pixels in the image data as the pixel of interest. The image forming apparatus according to claim 1, further comprising:
Therefore, even when there are a plurality of continuous directions of noise data, the average value obtained by averaging the optical information of a plurality of pixels including any target pixel in the image data along each continuous direction is obtained as a threshold value. Setting a suitable threshold value for image data and subtracting this threshold value from the optical information of all pixels suppresses the generation of a gap between noise data and other image data by removing noise. can do.
According to a third aspect of the present invention, there is provided an image forming apparatus comprising: a developing device that attaches toner to the surface of the photoconductor; and a transfer device that transfers the toner attached to the surface of the photoconductor to a recording medium. The image forming apparatus further comprises means for visualizing the electrostatic latent image by transferring the toner attached to the electrostatic latent image on the surface of the photosensitive member by the converting device onto the recording medium by the transfer device. Item 3. The image forming apparatus according to Item 1 or 2.
Therefore, by obtaining image data from the toner image formed on the recording medium, the sensitivity of the photoconductor is not affected by structural limitations such as providing a mechanism for obtaining the image data around the photoconductor. Can be easily determined.
According to a fourth aspect of the present invention, there is provided an image forming apparatus that attaches toner to the surface of the photosensitive member, and causes the toner to adhere to the electrostatic latent image on the surface of the photosensitive member by the developing device. 3. The image forming apparatus according to claim 1, further comprising means for visualizing the electrostatic latent image.
Therefore, since the image data can be acquired from the toner image formed on the photosensitive member and the image data is not acquired from the toner image formed on the recording medium, the transfer process is not included. Image data that is not affected by noise generated in subsequent steps can be acquired.
In the image forming apparatus according to the fifth aspect of the present invention, a visible area of the surface of the photosensitive member by the visualizing device is 100 mm. ² The image forming apparatus according to claim 1, wherein the sensitivity information is stored for each unit divided by the following units.
Therefore, the correction of the exposure amount by the exposure scanning device can be subdivided.
An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein exposure scanning is performed at a writing resolution of 1000 dpi or more. Therefore, a high-resolution and high-quality image can be formed.
The image forming apparatus according to claim 7 comprises an exposure position specifying means for specifying an exposure position by the exposure scanning device,
The image forming apparatus according to claim 1, wherein the exposure amount correcting unit corrects an exposure amount by the exposure scanning device according to an exposure position specified by the exposure position specifying unit. Therefore, by correcting the exposure amount by the exposure scanning device in accordance with the specified exposure position, it is possible to reliably prevent the occurrence of density unevenness due to the sensitivity unevenness of the photoreceptor over the entire visible area. .
An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, wherein the photosensitive member has a photosensitive layer in which a plurality of layers, at least one layer of which is formed using a spray coating method, are laminated on a substrate surface. An image forming apparatus. Therefore, even the photosensitive member having the photosensitive layer formed by a method in which unevenness of the film thickness that causes the sensitivity unevenness of the photosensitive member is likely to occur can obtain the operation of the invention described above.
The image forming apparatus according to claim 9 is an image forming apparatus according to any one of claims 1 to 7, wherein the photosensitive member has a photosensitive layer that is laminated on a surface of a substrate and an outermost layer is formed by using a spray coating method. is there. Accordingly, even the photosensitive member having the outermost layer of the photosensitive layer formed by a method in which unevenness of the film thickness that causes the sensitivity unevenness of the photosensitive member is easily generated can be obtained.
According to a tenth aspect of the present invention, there is provided an image reading apparatus that reads an image of a document;
The image forming apparatus according to any one of claims 1 to 3, wherein an image based on image data read by the image reading apparatus is formed on a recording medium;
A copying machine comprising:
Therefore, it is possible to obtain a copying machine having the operation of the invention according to any one of claims 1 to 4.
[0056]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. This embodiment shows an application example to a printer as an image forming apparatus.
[0057]
FIG. 1 is a longitudinal sectional side view schematically showing a printer according to a first embodiment of the present invention. A main body housing 2 having a housing shape of the printer 1 is provided with a manual feed tray 3 on which sheets to be manually fed are stacked, and a paper discharge tray 4 on which paper after image formation is discharged.
[0058]
In the main body housing 2, a paper feed tray 5 that holds a plurality of sheets stacked is provided. In the main body housing 2, a paper path 8 that communicates from the paper feed tray 5 or the manual feed tray 3 to the paper discharge tray 4 via the printer engine 6 and the fixing unit 7 is provided.
[0059]
In the present embodiment, the recording medium is realized by sheets stacked on the manual feed tray 3 and the paper feed tray 5.
[0060]
The printer engine 6 includes a photosensitive member 9 provided at the center of the printer engine 6, a charging roller 10 as a charging device disposed around the photosensitive member 9, an exposure scanning device 11, a developing unit 12, and a pre-transfer charger 13. The transfer charger 14, the separation charger 15, the separation claw 16, the pre-cleaning charger 17, the cleaning unit 18, the static elimination lamp 19, and the like.
[0061]
In the present embodiment, a developing device 12, a transfer charger 14, a fixing unit 7, etc. realize a visualization device.
[0062]
Although not described because it is a known technique, the exposure scanning device 11 includes a light source (not shown) that emits light, a polygon mirror 20 that scans the light emitted from the light source, a motor 21 that rotates the polygon mirror 20, In addition, a mirror 23 that reflects the light scanned by the polygon mirror 20 toward the photosensitive member 9 through the lens 22 is provided.
[0063]
Here, the photoconductor 9 will be described. Although not shown in detail because it is a known technique, the photoconductor 9 includes a cylindrical or columnar conductive support 9a and a photosensitive layer 9b provided on the outer peripheral surface of the conductive support 9a. ing.
[0064]
First, the conductive support 9a will be described. The conductive support 9a has a volume resistance of 10^-10A material having conductivity of Ω · cm or less is used. Examples of the conductive material include metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, and platinum, and metal oxides such as tin oxide and indium oxide. As the conductive support 9a, a film-like plastic, a cylindrical plastic, paper or the like coated with a material showing these conductivity by vapor deposition or sputtering, or aluminum, aluminum alloy, nickel, stainless steel, etc. After the raw material is made into a raw pipe by a method such as extrusion or drawing, a pipe whose surface is treated by cutting, superfinishing, polishing, or the like is used.
[0065]
Further, an endless nickel belt or an endless stainless steel belt disclosed in Japanese Patent Application Laid-Open No. 52-36016 can be used as the conductive support 9a.
[0066]
Further, a conductive support 9a may be used in which a conductive powder dispersed in a suitable binder resin is coated on a cylindrical or columnar support and a conductive layer is provided. In this case, as the conductive powder, metal powder such as carbon black, acetylene black, aluminum, nickel, iron, nichrome, copper, zinc, silver, or metal oxide powder such as conductive tin oxide, ITO, etc. Is mentioned. Examples of the binder resin for dispersing the conductive powder include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-acetic acid. Vinyl copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin , Epoxy resins, melamine resins, urethane resins, phenol resins, alkyd resins, and other thermoplastic resins, thermosetting resins, and photocurable resins.
[0067]
The conductive layer can be provided by dispersing and applying the above-described conductive powder and binder resin in a suitable solvent as necessary. Examples of the solvent used for generating the conductive layer include tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene, and the like. Furthermore, a heat-shrinkable tube containing the above-mentioned conductive powder in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, or polytetrafluoroethylene is placed on a suitable cylindrical substrate. By providing, a conductive support provided with a conductive layer can also be used favorably.
[0068]
Next, the photosensitive layer 9b will be described. The photosensitive layer 9b has a single layer type in which a charge generation material and a charge transport material are mixed, a forward layer type in which a charge transport layer is provided on the charge generation layer, and a charge generation layer provided on the charge transport layer. There is a reverse layer type.
[0069]
Regardless of the single layer type or the reverse layer type configuration, the difference in film thickness of the photosensitive layer 9b in the image forming region of the photosensitive member 9 of the present embodiment is 0.2 to 3.0 μm, preferably 0. The thickness is set to 3 to 2.8 μm, more preferably 0.4 to 2.6 μm. If the difference in film thickness of the photosensitive layer 9b in the image forming area is 0.2 μm or less, there is almost no unevenness in density due to the photoconductor 9, so that it is not necessary to correct the amount of light to be written, and the film of the photosensitive layer 9b in the image forming area. When the thickness difference is 3.0 μm or more, uneven development or transfer unevenness occurs, and even if the amount of writing light is corrected, unevenness in density of the image cannot be sufficiently suppressed. However, the photosensitive layer 9b in the image forming area of the photoreceptor 9 can be suppressed. By setting the film thickness difference to 0.2 to 3.0 μm, it is possible to suppress the occurrence of development unevenness and transfer unevenness, and sufficiently suppress the density unevenness of the image. The difference in film thickness of the photosensitive layer 9b in the present embodiment is that the photosensitive layer 9b is measured over the entire image forming area by physical, optical, electrical, and electrochemical techniques, and the maximum and minimum values are measured. It is obtained by calculating the difference from the value.
[0070]
A charge generation material is contained in the single layer type photosensitive layer and the charge generation layer used for the forward layer type and the reverse layer type. Various materials can be used as the charge generation material. Representative examples include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squalic acid dyes, various phthalocyanine pigments, naphthalocyanine pigments, and azurenium salts. And dyes.
[0071]
The charge generation layer is formed by dispersing the above-described charge generation material together with a binder resin in an appropriate solvent, if necessary, applying this onto a conductive support, and drying. The film thickness of the charge generation layer is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm. In dispersing the charge generating material and the binder resin in the solvent, various dispersing methods such as a ball mill, an attritor, a sand mill, and an ultrasonic wave can be used. Various dispersion methods such as a ball mill, an attritor, a sand mill, and an ultrasonic wave are well-known techniques, and thus description thereof is omitted.
[0072]
The binder resin used in the charge generation layer as necessary includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, and poly-N-vinyl. Examples include carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, and the like. . Among these, polyvinyl acetal typified by polyvinyl butyral is used favorably. The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material.
[0073]
Solvents used in the formation of the charge generation layer include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. Can be mentioned. In particular, a ketone solvent, an ester solvent, and an ether solvent can be favorably used as the solvent used in forming the charge generation layer.
[0074]
Next, the charge transport layer will be described. The charge transport layer can be formed by applying a coating solution formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent on the above-described charge generation layer and drying. The film thickness of the charge transport layer is preferably about 5 to 100 μm, and in particular, high resolution image formation is possible by setting the thickness to 5 to 15 μm. Various additives such as a plasticizer, a leveling agent, and an antioxidant can be added to the charge transport layer as necessary.
[0075]
Charge transport materials include hole transport materials and electron transport materials. Among these, examples of the charge transport material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3, Examples thereof include electron-accepting substances such as 7-trinitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.
[0076]
Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bisstilbene derivatives, enamine derivatives, etc. Other known materials. These charge transport materials may be used alone or in combination of two or more.
[0077]
Examples of the binder resin used for forming the charge transport layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate. Copolymer, polyvinyl acetate, polyvinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin And thermoplastic or thermosetting resins such as melamine resin, urethane resin, phenol resin, and alkyd resin.
[0078]
The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight with respect to 100 parts by weight of the binder resin.
[0079]
Examples of the solvent used for forming the charge transport layer include tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, and acetone.
[0080]
In the photoreceptor 9 of the present embodiment, a plasticizer or a leveling agent may be added to the charge transport layer. As a plasticizer added to the charge transport layer, a plasticizer used as a plasticizer for general resins such as dibutyl phthalate and dioctyl phthalate can be used as it is. The amount of the plasticizer used is suitably about 0 to 30% by weight with respect to the binder resin. As a leveling agent added to the charge transport layer, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers having a perfluoroalkyl group in the side chain, or oligomers can be used. The amount of the leveling agent used is suitably 0 to 1% by weight based on the binder resin.
[0081]
By the way, since the surface state of each layer of the photosensitive layer 9b and the film thickness of each layer are non-uniform, it causes the sensitivity unevenness of the photoreceptor 9, and therefore the surface state of each layer of the photosensitive layer 9b and the film thickness of each layer. In order to make uniform, an undercoat layer (not shown) may be provided between the conductive support 9a and the photosensitive layer 9b, or a protective layer (not shown) may be laminated on the photosensitive layer 9b.
[0082]
The undercoat layer provided between the conductive support 9a and the photosensitive layer 9b is suitably and preferably set to a thickness of 0 to 5 μm. The undercoat layer generally contains a resin as a main component, but these resins are resins having a high solvent resistance with respect to a general organic solvent in consideration of coating a photosensitive layer thereon with a solvent. It is desirable. As described above, resins having high solvent resistance to general organic solvents include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, and polyurethane. Curable resins that form a three-dimensional network structure, such as melamine resin, phenol resin, alkyd-melamine resin, and epoxy resin.
[0083]
Further, a fine powder pigment of a metal oxide that can be exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide, etc. may be added to the undercoat layer in order to prevent moire and reduce residual potential. .
[0084]
Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer in this embodiment. In addition, the undercoat layer of the present embodiment has Al₂O₃Anodic oxidation, organic matter such as polyparaxylylene (parylene), SiO₂, SnO₂TiO₂, ITO, CeO₂A material provided with an inorganic material such as a vacuum thin film can also be used favorably. In addition, known ones can be used.
[0085]
Similar to the formation of the photosensitive layer 9b, the undercoat layer can be formed by applying various materials for forming the undercoat layer dispersed in an appropriate solvent using the various coating methods described above.
[0086]
Materials used for the protective layer laminated on the photosensitive layer 9b include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide. , Polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene Resins such as polymers, polyurethane, polyvinyl chloride, polyvinylidene chloride, and epoxy resins can be used.
[0087]
The protective layer contains wear-resistant particles for the purpose of improving wear resistance. Abrasion-resistant particles include fluorine resins such as polytetrafluoroethylene, silicone resins or metal oxides such as titanium oxide, tin oxide, aluminum oxide, silicon oxide, zirconium oxide, and inorganic materials such as potassium titanate. Etc. can be added. In particular, from the viewpoint of wear resistance, metal oxides are preferable as the wear-resistant particles. The particle size of the wear-resistant particles is preferably 0.2 to 0.8 μm, and more preferably 0.3 to 0.7 μm. In particular, since the occurrence of scratches with a size of 5 to 50 μm related to abnormal images due to white streaks and filming is extremely reduced, it is very difficult to use a metal oxide with a particle size of 0.3 to 0.6 μm. preferable. Among metal oxides, aluminum oxide is preferable because it does not cause a reduction in image quality due to reaction and accumulation with various impurities generated during image formation. Further, among aluminum oxides, those produced by a vacuum process are very preferable because the particle diameter is almost constant and the purity is high.
[0088]
Further, in order to give the protective layer charge mobility, the protective layer usually contains a charge transport material contained in the charge transport layer. Thereby, the residual potential can be lowered, which is preferable. The thickness of the protective layer is suitably about 0.11 to 10 μm.
[0089]
In addition, in the photoreceptor 9 of the present embodiment, an intermediate layer (not shown) can be provided between the photosensitive layer 9b and the protective layer. In the intermediate layer, a binder resin is generally used as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, various coating methods as described above can be employed. In addition, about 0.05-2 micrometers is suitable for the thickness of an intermediate | middle layer.
[0090]
As a method of laminating each layer for forming the photosensitive layer 9b, dip coating method, ring coating method, spray coating method, roll coating method, blade coating method, beat coating method (beat coating), nozzle coating method (nozzle coating), spinner Although any coating method such as a coating method (spinner coating) can be used, the photoreceptor 9 of the present embodiment has at least one of a plurality of layers constituting the photosensitive layer 9b formed by a spray coating method. Yes. Further, the outermost layer of the photoreceptor 9 of the present embodiment is formed by using a spray coating method. Various coating methods such as dip coating, ring coating, spray coating, roll coating, blade coating, beat coating (beat coating), nozzle coating (nozzle coating), and spinner coating (spinner coating). Since the construction method is a known technique, description thereof is omitted.
[0091]
Although not particularly illustrated, the printer 1 includes a control system that drives and controls each unit included in the printer 1. The control system is realized by a microcomputer configured by connecting a CPU for instructing driving to each unit included in the printer 1 and a storage device such as a ROM and RAM for storing a control program and data necessary for executing the program. Has been.
[0092]
A storage device (not shown) of the microcomputer stores an exposure amount management file 40 (see FIG. 2) that stores sensitivity information of the photosensitive member 9 with respect to exposure light emitted from the exposure scanning device 11 for each location. In the exposure amount management file 40, pixel position information 40a for specifying a pixel position where the exposure light of the exposure scanning device 11 performs exposure scanning is associated with sensitivity information 40b at the pixel position specified by the pixel position information 40a. Is remembered. Here, a sensitivity storage device is realized by the storage device. Sensitivity information 40b in the exposure management file 40 is acquired by the method described below using the photoconductor sensitivity measuring apparatus shown in FIG. Note that the storage device can be formed of a memory such as a semiconductor element and can be detachably attached to the printer main body.
[0093]
Hereinafter, acquisition of sensitivity information 40b for each pixel position stored in the exposure management file 40 will be described with reference to FIGS. In the present embodiment, sensitivity information 40b for each pixel position is acquired using the photoconductor sensitivity measuring device 50 shown in FIG. As shown in FIG. 3, the photoconductor sensitivity measuring device 50 includes an input device 52 that inputs image data of an image formed using a photoconductor that is a sensitivity measurement target, and various types of image data input by the input device 52. And an image processing device 53 that performs processing.
[0094]
The input device 52 optically reads an unillustrated reading unit that optically reads an image formed on a recording medium such as paper using the printer 1 on which the photoconductor 9 to be measured for surface sensitivity is mounted. A photoelectric conversion unit (not shown) that photoelectrically converts the optical information of the image to acquire image data including the optical information of each pixel constituting the image. Examples of the optical information include information representing brightness, reflectance, density, brightness, chromaticity, and the like. Description of the reading unit and the photoelectric conversion unit is omitted because it is a known technique, but the input device 52 is realized by, for example, a scanner, a digital camera (electronic still camera, video camera), a microdensitometer, or the like. Is possible. It is assumed that the input device 52 of the present embodiment optically reads an image formed on a recording medium using a photoconductor that is a surface sensitivity measurement target.
[0095]
Note that the input device 52 of the present embodiment optically reads an image formed on a recording medium. However, the present invention is not limited to this. For example, the input device 52 is formed on the photoreceptor 9 and is recorded on the recording medium. The toner image before transfer may be optically read. In this case, a developing device 12 realizes a visualization device.
[0096]
In addition, the input device 52 according to the present embodiment acquires image data by photoelectrically converting an optically read image, but the present invention is not limited to this, and image data read in advance is stored in a storage medium. The input device 52 may be realized by a medium reading device that stores the image data and acquires the image data by reading the image data stored in the storage medium. As the storage medium, various known storage media such as a magnetic recording medium such as a flexible disk and an optical storage medium such as a CD-R / RW can be used.
[0097]
Next, the image processing device 53 will be described. The image processing device 53 includes an image storage unit 54 that temporarily stores image data photoelectrically converted by the photoelectric conversion unit of the input device 52. Although not particularly illustrated, the image storage unit 54 includes a storage medium such as a RAM and a hard disk, and a writing device that stores optical information in the storage medium. The image data stored in the image storage unit 54 is read by the average value calculation unit 55 and used for the calculation of the following equation (1). Further, the image data stored in the image storage unit 54 is subjected to an X direction noise removal process and a Y direction noise removal process executed by the Y direction noise removal unit 56 and the X direction noise removal unit 57.
[0098]
The average value calculation unit 55 calculates an overall average value obtained by averaging the optical information of each pixel over the entire image by performing the calculation of the expression (1) based on the image data stored in the image storage unit 54. To do.
[0099]
[Expression 1]

[0100]
The Y-direction noise removal unit 56 and the X-direction noise removal unit 57 perform noise removal processing described below based on the image data stored in the image storage unit 54. The structure of the Y direction noise removing unit 56 and the X direction noise removing unit 57 and each noise removing process executed by the Y direction noise removing unit 56 and the X direction noise removing unit 57 will be described later. In this embodiment, calculation parameters stored in the parameter storage unit 58 connected to the Y direction noise removing unit 56 and the X direction noise removing unit 57 are used. The calculation parameters stored in the parameter storage unit 58 include a threshold value of optical information of each pixel, the number i of pixels related to calculation of an average value in various noise removal processes described later.
[0101]
The post-processing image storage unit 59 has the same file structure as the exposure amount management file 40 shown in FIG. 2, and the Y direction noise removal unit 56 and the X direction noise removal unit 57 reduce the X direction noise and the Y direction noise. The removed image data is stored. The post-processing image storage unit 59 stores the optical information of each pixel constituting the image data after removing the noise in association with the coordinate information specifying the pixel position on the photoconductor 9. In the present embodiment, electric field strength is stored as optical information of image data from which noise has been removed.
[0102]
Next, the configurations of the Y direction noise removing unit 56 and the X direction noise removing unit 57 and the noise removing process executed by the Y direction noise removing unit 56 and the X direction noise removing unit 57 will be described with reference to FIGS. explain.
[0103]
When forming an image using an electrophotographic system, for example, noise having directionality in the X direction (main scanning direction) (X direction noise) and noise having directionality in the Y direction (sub-scanning direction) (Y direction noise) As described above, when linear noise having directionality is generated in the electrostatic latent image, the photosensitive member is included in the image formed by the printer 1 as described above due to the generation of noise having directionality. Abnormal images such as horizontal streak Nx and vertical streak Ny that are not caused by the sensitivity unevenness S of 9 are superimposed (see FIGS. 4 and 8). The Y direction noise removal unit 56 and the X direction noise removal unit 57 remove such horizontal stripes Nx and vertical stripes Ny by performing a noise removal process described below.
[0104]
Note that the noise removal processing according to the present embodiment is effective when the direction of occurrence of noise having directionality is known. For this reason, prior to the noise removal process, a noise direction analysis process for analyzing the noise generation direction is performed. Here, a function as a noise direction determination step is realized. The analysis of the noise direction can be easily realized by using a known image analysis technique. Therefore, the description is omitted here, the noise direction analysis process is completed, and the noise generation direction is known. It will be explained as being.
[0105]
First, as shown in FIG. 4, in the image 60 formed by the printer 1 on which the photoconductor 9 is mounted, in addition to the image S caused by the sensitivity unevenness of the photoconductor 9, it is caused by noise having directionality in the Y direction. A description will be given of noise removal processing for removing the vertical stripe Ny from the image 60 by the Y-direction noise removal unit 56 when the vertical stripe Ny is superimposed.
[0106]
Here, FIG. 5 is a block diagram showing a functional configuration of the Y direction noise removing unit 56, and FIG. 6 is a flowchart for schematically explaining the noise removing process executed by the Y direction noise removing unit 56. In the noise removal process executed by the Y-direction noise removal unit 56, first, the image data stored in the image storage unit 54 is stored in the pre-correction image data storage unit 56a for noise removal (step S1).
[0107]
Based on the image data stored in the pre-correction image data storage unit 56a, the image average value calculation unit 56b acquires the average value Pave of the optical information of all the pixels (S2). The image average value calculation unit 56b of the present embodiment reads the average value Pave of the optical information of all the pixels calculated by the average value calculation unit 55, and acquires this value as the average value Pave of the optical information of all the pixels.
[0108]
Next, from the image data stored in the pre-correction image data storage unit 56a, the target pixel determination unit 56c performs P (x, y) (where x = 1 to N, y = 1 to M, ( An arbitrary pixel indicated by N and M is a positive integer)) is determined as a target pixel P (x, y) (S3). In the present embodiment, in step S4, x and y of the target pixel P (x, y) are set to x = 1 and y = 1, respectively. Note that the target pixel P (x, y) is 100 mm over the entire image forming area of the photosensitive member.²It is determined that at least one point is set in each of the small areas divided into the following small areas. The area of this small area is 50mm²The following is preferred, 25 mm²Is preferred.
[0109]
Ideally, the area of this small region is most preferably the size of the writing pixel. However, in practice, this method is easy to pick up fine irregular noise, and it is very difficult to remove the fine irregular noise, and the burden for the calculation of noise removal is large. The lower limit of the area of the area is 0.01 mm²Preferably 0.04mm²The following is practical and preferable.
[0110]
Then, by calculating the following equation (2) by the peripheral pixel average value calculation unit 56d, the average value Pave (2) of the optical information of 2n + 1 pixels including the target pixel P (x, y) along the Y direction is obtained. x, y) is calculated (S5). Here, a function as an average value acquisition step is realized. At this time, “n” of the pixel number 2n + 1 for calculating the average value Pave (x, y) is acquired from the pixel number i related to the calculation of the average value stored in the parameter storage unit 58.
[0111]
[Expression 2]

[0112]
Subsequently, in the target pixel correction unit 56e, the average value Pave (x, y) calculated in step S5 and the average value Pave of the optical information of the pixels of the entire image calculated in the average value calculation unit 55 are used as threshold values. The optical information of the pixel P (x, y) is calculated by the following expression (3) to obtain P ′ (x, y) (S5). Here, a function as a noise removing step is realized.
[0113]
[Equation 3]

[0114]
Thereby, the average value Pave (x, y) of the optical information in the range of ± n pixels in the Y direction around the target pixel P (x, y) is subtracted from the optical information of the target pixel P (x, y). In addition, it is possible to obtain the pixel P ′ (x, y) having the optical information of the image data from which the vertical streak Ny that is not caused by the sensitivity unevenness of the photoconductor is removed.
[0115]
In this embodiment, the average value Pave (x, y) of the optical information of the pixels in the range of ± n pixels in the Y direction around the target pixel P (x, y) is calculated. The optical information average value of k pixels (k is an integer) in the y direction passing through the target pixel P (x, y) may be calculated. At this time, the target pixel P (x, y) does not have to be at the center in the range in which the average is calculated in the Y direction.
[0116]
However, in order to ensure the removal accuracy of the Y-direction noise Ny, it is preferable that the target pixel P (x, y) is at the center within the range for calculating the average.
[0117]
Further, in this embodiment, in order to make the average density of the processed image substantially equal to that of the image before processing, the average value Pave of the optical information of the pixels of the entire image is added as shown in equation (3). However, the present invention is not limited to this. When only the density fluctuation of the image data after noise removal is necessary, it is not always necessary to add Pave, and an arbitrary value is added instead of Pave. May be. Even in such a case, the process can be efficiently performed by storing an arbitrary value instead of Pave in the parameter storage unit 58.
[0118]
Further, in the present embodiment, the size of the number k of pixels including the target pixel P (x, y) to be averaged and extending in the Y direction is not limited. Even if it is too much, sufficient noise removal cannot be performed, so the number of pixels k needs to be set in a range in which a high correlation is obtained with respect to the target pixel P (x, y).
[0119]
The obtained optical information of P ′ (x, y) is stored in the corrected image data storage unit 56f in association with the coordinates of this pixel (S7), and is set to x in the target pixel P (x, y). 1 is added (S8), and the processing from step S5 to S8 is repeated until it is determined by the processing end determination unit 56g that x indicated by x + 1 is larger than N (N in S9).
[0120]
When the process end determining unit 56g determines that x indicated by x + 1 is greater than N (Y in S9), 1 is added to y (S10), and the process end determining unit 56g indicates y + 1. Until it is determined that y is larger than M (Y in S11), the processes from Steps S5 to S10 are repeated (N in S11).
[0121]
Since the present invention does not prescribe the processing at both ends, if y <0 or y> M in the calculation of Pave (x, y), Pave (x, y) = 0 may be set. Pave (x, y) = Pave (x, 0) or Pave (x, M) may be set. The parameter M in this case is also stored in the parameter storage unit 58.
[0122]
As a result, any target pixel P (x, y) in the target image to be processed is set for all the pixels in the target image, and vertical information caused by noise in the Y direction is obtained from the optical information of all pixels in the target image. By removing the streak Ny, it is possible to suppress the occurrence of a difference between the optical information of the pixels in the vertical streak portion and the optical information of the pixels in the other portions by performing the noise removal process.
[0123]
In this embodiment, the pixel of interest P (x, y) is 100 mm over the entire image forming area of the photoreceptor.²Since at least one point is determined for each small area divided into the following small areas, the sensitivity distribution of the photoconductor 9 mounted on the high-resolution printer 1 can be measured well.
[0124]
Next, as shown in FIG. 8, the horizontal stripe Nx caused by the X direction noise and the vertical stripe Ny caused by the Y direction noise are superimposed on the image 60 formed by using the printer 1 on which the photoconductor 9 is mounted. In this case, a noise removal process for removing the horizontal streak Nx and the vertical streak Ny from this image will be described with reference to FIGS.
[0125]
As shown in FIG. 8, the image processing apparatus 53 according to the present embodiment, when noise Nx is generated not only in the Y direction noise Ny but also in the X direction in the image 60, as described above, The X-direction noise removal unit 57 performs an X-direction noise removal process on an arbitrary pixel of interest P ′ (x, y) in the image data from which the streak Ny has been removed.
[0126]
Here, FIG. 9 is a block diagram showing a functional configuration of the X-direction noise removing unit 57, and FIG. 10 is a flowchart schematically illustrating the noise removing process executed by the X-direction noise removing unit 57. In the noise removal processing executed by the X-direction noise removal unit 57, first, the image data stored in the post-correction data storage unit 56f of the Y-direction noise removal unit 56 is copied to the pre-correction image data storage unit 57a (step S1). S20).
[0127]
Based on the image data copied to the pre-correction image data storage unit 57a, the image average value calculation unit 57b acquires the average value Pave of the optical information of all the pixels (S21). Similar to the image average value calculation unit 56b, the image average value calculation unit 57b of the present embodiment reads the average value Pave of the optical information of all the pixels calculated by the average value calculation unit 55, and uses this value for all the pixels. Obtained as the average value Pave of the optical information.
[0128]
Next, from the image data stored in the pre-correction image data storage unit 57a, the target pixel determination unit 57c performs P ′ (x, y) (where x = 1 to N, y = 1 to M, (N, An arbitrary pixel indicated by M is a positive integer)) is determined as the target pixel P ′ (x, y) (S22). In this embodiment, in step S23, x and y of the target pixel P ′ (x, y) are set to x = 1 and y = 1, respectively.
[0129]
Then, by calculating the following expression (4) by the peripheral pixel average value calculation unit 57d, the average value P of the optical information of 2n + 1 pixels including the target pixel P ′ (x, y) along the X direction is obtained. 'ave (x, y) is calculated (S24). Since the X direction and the Y direction are orthogonal to each other, the average value P′ave (x, y) is an orthogonal average value, and a function as an orthogonal average value acquisition step is realized here. At this time, “n” of the number of pixels 2n + 1 for calculating the average value P′ave (x, y) is also related to the calculation of the average value stored in the parameter storage unit 58, as in the process of FIG. Obtained from the number of pixels i.
[0130]
[Expression 4]

[0131]
Subsequently, in the target pixel correction unit 57e, the average value P′ave (x, y) calculated in step S24 and the average value Pave of the optical information of the pixels of the entire image calculated in the average value calculation unit 55 are used. P ″ (x, y) is acquired by performing the following equation (5) on the optical information of the pixel P ′ (x, y) (S25). When the noise direction is two directions of the X direction and the Y direction, a function as a noise removal step is realized here.
[0132]
[Equation 5]

[0133]
Thus, from the optical information of the target pixel P ′ (x, y), the average value P′ave (x, y) of the optical information in the range of ± n pixels in the Y direction with the target pixel P ′ (x, y) as the center. ) Is subtracted, and in addition to the vertical streak Ny caused by the Y direction noise and not caused by the sensitivity unevenness of the photoconductor 9, the horizontal streak Nx caused by the X direction noise not caused by the sensitivity unevenness of the photoconductor 9 is removed. A pixel P ″ (x, y) having optical information can be acquired.
[0134]
The obtained optical information of P ″ (x, y) is stored in the corrected image data storage unit 57f in association with the coordinates of this pixel (S26), and at the target pixel P ′ (x, y). 1 is added to x (S27), and the processing from step S24 to S27 is repeated (N in S28) until the processing end determination unit 57g determines that x indicated by x + 1 is greater than N.
[0135]
When the process end determination unit 57g determines that x indicated by x + 1 is greater than N (Y in S28), 1 is added to y (S29), and the process end determination unit 57g indicates y + 1. Until it is determined that y is greater than M (Y in S30), the processing from step S24 to S29 is repeated (N in S30).
[0136]
Since the present invention does not prescribe the processing at both ends, in the calculation of Pave (x, y), when x <0 or y> N, Pave (x, y) = 0 may be set. Pave (x, y) = Pave (0, y) or Pave (N, y) may be set. The parameters in this case are also stored in the parameter storage unit 58.
[0137]
As a result, even when the noise generation direction is two directions, ie, the Y direction and the X direction perpendicular to the Y direction, noise Nx and Ny having directionality regardless of the surface state of the photoconductor 9 are obtained in each continuous direction. It can be effectively removed.
[0138]
Since there is no linear relationship between the electric field intensity and the exposure amount stored in the post-processing image storage unit 59, a plurality of images near the halftone are formed by exposing with each exposure amount adjusted in a plurality of stages. The noise removal process described above is performed on each image.
[0139]
In the present embodiment, the noise removal processing for removing the horizontal streak Nx and the vertical streak Ny caused by noise in the X direction and the Y direction has been described. However, the present invention is not limited to this, and the directivity is linear. In the case of noise having a noise, it is also possible to remove abnormal images caused by oblique noise. When an abnormal image having directionality in an oblique direction has occurred, by performing rotation processing on the image data and adjusting the direction of the generated noise to be in the X direction or the Y direction, Any noise having any directionality can be removed if the noise has directionality. Note that the rotation processing for image data can be easily realized by using a known image processing technique, and the description thereof is omitted here.
[0140]
In this embodiment, the case of using the input device 52 that optically reads an image formed on a sheet using a photoconductor to be measured for surface sensitivity has been described. However, the photosensor is formed on the photoconductor. When the image data is acquired by optically reading the toner image before being transferred to the paper, the transfer process and the fixing process are included compared to the case where the image data is acquired from the image formed on the paper. Therefore, it is possible to obtain image data that does not include noise generated during the transfer process and the fixing process, and therefore, the sensitivity distribution of the photoconductor can be measured with higher accuracy.
[0141]
Data stored in the post-processing image storage unit 59 is written in the exposure amount management file 40 in the storage device of the printer 1. That is, the sensitivity information 40b acquired by the photoconductor sensitivity measuring device 50 based on the image formed by the printer 1 is stored in association with each pixel position information 40a. Here, the sensitivity acquisition step is realized.
[0142]
In such a configuration, the microcomputer drives and controls the light source ON / OFF based on image data transmitted from an externally connected PC (not shown) or the like during image formation. Further, the microcomputer drives and controls a motor 21 that rotates the polygon mirror 20 of the exposure scanning device 11 simultaneously with ON / OFF driving of the light source. Thereby, the exposure light emitted from the exposure scanning device 11 is one-dimensionally scanned in the main scanning direction (X direction) on the surface of the photoreceptor 9. In addition, the microcomputer drives and controls a photoconductor motor (not shown) to rotate the photoconductor 9 about the axis. As a result, the visualization region on the surface of the photoconductor 9 is mechanically moved in the sub-scanning direction (Y direction) with respect to the exposure position to be one-dimensionally scanned, and a two-dimensional electrostatic latent image is formed on the surface of the photoconductor 9. Is formed.
[0143]
Subsequently, the microcomputer drives and controls the developing unit 12 to form a toner image by attaching toner to the electrostatic latent image formed on the surface of the photoconductor 9, and drives and controls the transfer charger 14. Transfer the toner image onto the paper. The toner image transferred onto the paper is fixed by the fixing unit 7.
[0144]
When forming the electrostatic latent image, the microcomputer specifies a pixel position to be exposed and scanned by the exposure scanning device 11 based on the rotation number of the photosensitive member 9 and the image data, and refers to the exposure amount management file 40. The exposure amount is controlled based on the sensitivity information 40b corresponding to the specified pixel position information 40a. Here, functions as exposure position specifying means and exposure amount correction means are realized. Thereby, the exposure amount with respect to the photoreceptor 9 is adjusted for each pixel position.
[0145]
Here, the sensitivity information 40b indicates the relationship between the exposure amount corresponding to each pixel position information 40a and the image information (or electrostatic potential information calculated from the image information). When the sensitivity distribution is not measured for all the pixels in the image forming area, it is necessary to assign sensitivity information of the measured location (measurement point) to each pixel. As a method of assigning the sensitivity information 40b of the measurement point to each pixel, a method of using the sensitivity information of the measurement point up to an intermediate pixel between a certain measurement point and the adjacent measurement point, one-dimensional depending on the distance from each measurement point Or the method etc. which are calculated from a multidimensional equation can be illustrated. Which method is used to allocate the sensitivity information 40b of the measurement point to each pixel is appropriately selected depending on the measurement density, CPU performance, and the like.
[0146]
In controlling the exposure amount, the obtained sensitivity information 40b is compared with the reference sensitivity information 40c as shown in FIG. 11, and the exposure amount is corrected and determined according to the value of the sensitivity information 40b with respect to the reference sensitivity information 40c. To do. The reference sensitivity information 40c may be set in advance as an unbiased reference, but may be calculated by a known technique such as a P sensor or the average of sensitivity information 40b of all pixel position information 40a. it can. In order to obtain the required latent image potential, the exposure amount is usually determined according to the reference sensitivity information 40c. In the present embodiment, the exposure amount is corrected and determined based on the sensitivity information 40b.
[0147]
As described above, when the electrostatic latent image is formed, the exposure amount is corrected with reference to the exposure amount management file 40, so that the exposure amount on the photoconductor 9 can be appropriately adjusted according to the sensitivity for each pixel position. Therefore, even when an image is formed using the photosensitive member 9 in which the sensitivity is uneven for each location, unevenness in density occurs in the visualized image due to the sensitivity unevenness of the photosensitive member 9. This can be prevented over the entire visualization region, and a high-definition and high-quality image without unevenness of the image can be formed without depending on the sensitivity distribution state of the photoconductor 9.
[0148]
In the present embodiment, the application example to the printer 1 shown in FIG. 1 is shown, but the present invention is not limited to this. For example, a printer engine 63 as shown in FIG. You may apply to a printer. A printer engine 63 shown in FIG. 12 supplies toner to the photosensitive member 9, a charging device 64 having a charging blade 64 a disposed in contact with the outer peripheral surface of the photosensitive member 9, an exposure unit (not shown), and the photosensitive member 9. A developing unit 65, a process cartridge 67 and a transfer charger 68 and a separation charger 69, which are integrally combined with a cleaner unit 66 for collecting toner remaining on the surface of the photosensitive member 9, and the like. The process cartridge 67 is detachably attached to the main body housing 2.
[0149]
According to such a printer, as in the first embodiment, a high-definition image having no shading unevenness can be formed even when image formation is performed using a photoconductor having sensitivity unevenness. By using the process cartridge 67, the assembly work can be facilitated. In addition, since the process cartridge 67 is detachably attached to the main body housing 2, when replacing members constituting the process cartridge 67 such as the photosensitive member 9, the charging device 64, the developing unit 65, and the cleaner unit 66, Since replacement is possible in units of process cartridges 67, it is possible to continue using long-life parts and facilitate replacement of consumables.
[0150]
In the present embodiment, the application example to the printer 1 shown in FIG. 1 has been described. However, the present invention is not limited to this, and instead of the printer engine 6, for example, as shown in FIG. A photosensitive belt 71 wound around 70a, 70b, and 70c, a charging charger 72 disposed opposite to the outer peripheral surface of the photosensitive belt 71, an exposure unit (not shown), a developing unit 12, a transfer charger 73, a cleaning brush 74, You may apply to the printer provided with the printer engine 76 comprised by the static elimination light source 75 grade | etc.,. The printer engine 76 is provided with a pre-cleaning exposure unit 77 provided on the inner peripheral side of the photosensitive belt 71. The pre-cleaning exposure unit 77 may be provided on the inner peripheral side of the photosensitive belt 71 or may be provided on the outer peripheral side.
[0151]
Furthermore, in this embodiment, an example of application to a printer that forms a monochrome image has been shown. However, the present invention is not limited to this, and for example, to a color printer that forms images of four colors Y, M, C, and K. You may apply. As a result, even in a printer that forms a color image, it is possible to form an image in which shading unevenness caused by sensitivity unevenness of the photoconductor 9 is suppressed.
[0152]
Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment shows an application example to a copying machine.
[0153]
FIG. 14 is a longitudinal sectional side view showing the copying machine of the present embodiment. The copying machine 80 includes a scanner 81 as an image reading device that reads an image of a document, and a printer 1 that forms an image read by the scanner 81 on a sheet.
[0154]
The scanner 81 includes a contact glass 82 on which a document (not shown) is placed. The document is placed with the document surface facing the contact glass 82. On the upper side of the contact glass 82, a document pressure plate 83 for pressing a document placed on the contact glass 82 is provided.
[0155]
Below the contact glass 82, a first traveling body 86 on which a light source 84 for emitting light and a mirror 85 are mounted, a second traveling body 89 on which two mirrors 87 and 88 are mounted, and mirrors 85, 87 and 88. There is provided a reading optical system 92 constituted by a CCD (Charge Coupled Device) image sensor 91 or the like for receiving the light guided by the light through the imaging lens 90. The CCD image sensor 91 functions as a photoelectric conversion element that generates photoelectric conversion data obtained by photoelectrically converting reflected light from a document imaged on the CCD image sensor 91. The photoelectric conversion data photoelectrically converted by the CCD image sensor 91 is processed by an image processing system (not shown) into digital image data. The first and second traveling bodies 86 and 89 are provided so as to reciprocate along the contact glass 82 and travel at a speed ratio of 2: 1 by a moving device such as a motor (not shown).
[0156]
The printer 1 forms an image based on the digital image data on a recording medium by driving and controlling the printer engine 6 based on the digital image data photoelectrically converted by the CCD image sensor 91 and processed by an image processing system (not shown). To do.
[0157]
At this time, the exposure scanning device 11 controls the exposure amount according to the pixel position to be exposed based on the sensitivity information 40b stored in the exposure amount management file 40.
[0158]
As a result, unevenness in density in the image formed by the printer 1 due to uneven sensitivity of the photosensitive member 9 is prevented, and the original image read by the scanner 81 is copied to a recording medium with high reproducibility. can do.
[0159]
In this embodiment, the copying machine including the printer 1 described in the first embodiment is used. However, the present invention is not limited to this. For example, the printer shown in FIGS. You may use the printer provided with an engine.
[0160]
【Example】
Next, examples of the present invention will be described below. In the examples, a plurality of photoconductors were actually produced as described below, and the photoconductors produced were based on data obtained by subjecting the produced photoconductors to the noise removal process described above. Compared the quality.
[0161]
First, a mixture having the following composition was placed in a ball mill pot and ball milled for 72 hours using φ10 mm alumina balls.
Titanium oxide (CR-60: Ishihara Sangyo): 50.0 parts by weight
Alkyd resin (Beckolite M6401-50: manufactured by Dainippon Ink and Chemicals): 15.0 parts by weight
Melamine resin (Super Becamine L-121-60: manufactured by Dainippon Ink and Chemicals) 10.0 parts by weight
Methyl ethyl ketone (manufactured by Kanto Chemical): 31.7 parts by weight
[0162]
To this milling solution, 105.0 parts by weight of cyclohexanone (manufactured by Kanto Chemical Co., Inc.) was added, and ball milling was further performed for 2 hours to prepare an undercoat layer coating solution.
[0163]
A nickel seamless belt (Vickers hardness of 480 to 510, purity of 99.2% or more) having a circumference of 290.3 mm and a thickness of 30 μm is immersed in the coating solution for the undercoat layer, and used for the undercoat layer with respect to the nickel seamless belt. The coating solution was dip coated and dried at 135 ° C. for 25 minutes to form an undercoat layer having a film thickness of 6.5 μm.
[0164]
Subsequently, a mixture having the following composition was placed in a ball mill pot and ball milled for a time using a φ10 mm bowl.
A charge generating material having the chemical structure shown below (Chemical Formula 1) (manufactured by Ricoh): 1.5 parts by weight
[Chemical 1]

The charge generating material having the chemical structure shown below in (Chemical Formula 2) (manufactured by Ricoh): 1.5 parts by weight
[Chemical 2]

Polyvinyl butyral resin (ESREC BLS: Sekisui Chemical Co., Ltd.): 1.0 part
Cyclohexanone (manufactured by Kanto Chemical): 80.0 parts by weight
[0165]
A charge generation layer coating solution prepared by adding 78.4 parts of cyclohexanone and 237.6 parts by weight of methyl ethyl ketone to the milling solution was prepared. In this charge generation layer coating solution, the nickel seamless belt laminated with the above undercoat layer was dipped, and the charge generation layer coating solution was dip coated on the nickel seamless belt laminated with the undercoat layer. And dried for 20 minutes to form a charge generation layer having a thickness of 0.12 μm.
[0166]
Next, a charge transport layer coating solution having the following composition was prepared.
Charge transport material having the chemical formula structure shown below (Chemical Formula 3) (Ricoh): 7 parts by weight
[Chemical Formula 3]

Polycarbonate resin (C-1400: manufactured by Teijin Chemicals): 10 parts by weight
Silicone oil (KF-50: manufactured by Shin-Etsu Chemical): 0.002 parts by weight
Tetrahydrofuran (manufactured by Kanto Chemical): 841.5 parts by weight
Cyclohexanone (manufactured by Kanto Chemical): 841.5 parts by weight
3-t-butyl-4-hydroxyanisole (manufactured by Tokyo Chemical Industry): 0.04 parts by weight
[0167]
The above-mentioned charge transport layer coating solution is spray-coated while rotating a nickel seamless belt on which an undercoat layer and a charge generation layer are laminated, and then dried at 140 ° C. for 30 minutes, so that the charge transport layer has a thickness of about 25 μm. To form a photoreceptor.
[0168]
Five photoconductors produced by changing the spray coating conditions of the photoconductor produced by the above-described production method into 5 types are each cut to a width of 367 mm, and at 20 arbitrary positions on the cut photoconductor. The film thickness was measured with a stylus type film thickness meter. Based on this measurement result, a value obtained by (maximum film thickness-minimum film thickness) was obtained as film thickness unevenness. As a result, the film thickness unevenness of each photoconductor produced was 0.9 μm. They were 1.2 μm, 1.8 μm, 2.5 μm, and 3.0 μm.
[0169]
Subsequently, an acrylic adhesive having a thickness of about 40 μm was laminated on a urethane rubber having a thickness of 0.8 mm and a rubber hardness of 70, and a release paper was further laminated. This was punched with a Thomson blade to a length of 4 mm in width and 285 mm in length to make a detent guide.
[0170]
The above detent guides were affixed to the inner surfaces of both side edges of 5 mm from the end of the photoreceptor substrate while peeling the release paper to prepare a photoreceptor.
[0171]
The photoreceptor thus prepared was mounted on a modified IPSiO Color 5000 (manufactured by Ricoh) to prepare an image forming apparatus. Create a full gray image on a personal computer, charge voltage -800V, exposure 0.3μJ / cm²In black and white mode, an image was formed with 1200 dpi and 2 × 2 dots.
[0172]
Since the IPSiO Color 5000 remodeled machine used at this time was not a finished product, there were many horizontal and vertical stripes not attributable to the photoreceptor.
[0173]
The formed image was captured as electronic information in a personal computer at a resolution of 100 dpi by a scanner having lightness linear input characteristics. Only the portion with a length of 290.3 mm in the circumferential direction of the photoreceptor was trimmed from the captured image information.
[0174]
Similar to the first embodiment described above, noises Nx and Ny in the X direction and Y direction are removed from the image data, and the image after noise removal is smoothed with a filter size of 10 × 10 pixels. A removed image was obtained. As a result, linear noise has occurred in the image before the noise removal processing as shown in FIG. 2 or FIG. 6, whereas the image 60 ′ after the noise removal processing has a photosensitive member as shown in FIG. It can be seen that only the image S caused by the 9 sensitivity unevenness, that is, only the sensitivity distribution is reflected. Here, an image formed using a photoconductor having a film thickness unevenness of 2.5 μm will be described.
[0175]
By the way, the exposure amount 0.3 μJ / cm²Then, there is a relationship represented by the following equation (6) between the image density (ID) and the electric field strength (E: V / μm) of the photosensitive member.
E = −20.1 × (1.19−ID) (6)
[0176]
Since the image data has optical information for each coordinate of the image (each coordinate on the surface of the photoreceptor), the exposure amount is 0.3 μJ / cm according to the equation (6).²Thus, the electric field strength of the photoreceptor for each coordinate can be obtained.
[0177]
Here, when the specified range that determines the allowable range of variation in electric field intensity in the image forming area is set to 0.35 V / μm, the film thickness unevenness of the photoconductor is 0.9 μm and 1.2 μm is acceptable. Thus, the other photoconductors could be judged as rejected.
[0178]
In the embodiment, the pixel in the visualized image and the position of the pixel on the photoconductor are not completely matched. For example, a means for specifying the writing position of the photoconductor is provided. By providing it, it can be used for the cause analysis of the sensitivity unevenness of the photoreceptor.
[0179]
Subsequently, the photoconductor was mass-produced under manufacturing conditions where the variation in electric field intensity was within a specified range and the film thickness unevenness was 1.2 μm, and the above-described sensitivity distribution was measured for every 50 manufactured products. According to this, since the threshold of the sensitivity distribution was exceeded at the 1200th photoconductor production, the mass production was stopped. After that, the spray gun was cleaned and the production was resumed. No photoreceptor was manufactured that exceeded the sensitivity distribution threshold.
[0180]
【The invention's effect】
According to the present invention, there is provided an image forming apparatus and a copying machine capable of preventing the occurrence of uneven density in a visualized image due to uneven sensitivity of a photoreceptor over the entire visualized area. can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a printer according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing an exposure amount management file.
FIG. 3 is a block diagram showing a photoconductor sensitivity measuring apparatus.
FIG. 4 is an explanatory diagram showing noise generated in an image formed by using an electrophotographic method.
FIG. 5 is a block diagram illustrating a functional configuration of a Y-direction noise removing unit.
FIG. 6 is a flowchart schematically illustrating noise removal processing executed by a Y-direction noise removal unit.
FIG. 7 is an explanatory diagram showing pixels that average optical information.
FIG. 8 is an explanatory diagram showing noise generated in an image formed by using an electrophotographic method.
FIG. 9 is a block diagram illustrating a functional configuration of an X-direction noise removing unit.
FIG. 10 is a flowchart schematically illustrating noise removal processing executed by an X-direction noise removal unit.
FIG. 11 is a graph showing the relationship between the photoreceptor surface potential and the exposure amount.
FIG. 12 is a cross-sectional view showing a printer engine according to another embodiment.
FIG. 13 is a cross-sectional view showing a printer engine according to another embodiment.
FIG. 14 is a sectional view showing a copying machine according to a second embodiment of the present invention.
FIG. 15 is an explanatory diagram illustrating an image after noise removal processing in the embodiment.
[Explanation of symbols]
9 Photoconductor
10 Charging device
11 Exposure scanning device
80 copier
81 Image reader

Claims (10)

A photoreceptor having a photosensitive layer having a film thickness difference of 0.2 to 3.0 μm in an image forming region;
A charging device for charging the surface of the photoreceptor;
An exposure scanning device that exposes and scans the surface of the photoreceptor charged by the charging device;
A visualization device that visualizes an electrostatic latent image formed on the surface of the photoconductor by exposure scanning by the exposure scanning device;
A sensitivity storage device that stores sensitivity information of the photoconductor with respect to exposure light from the exposure scanning device in a storage area in association with each exposure position on the surface of the photoconductor;
Exposure amount correction means for correcting the exposure amount by the exposure scanning device for each exposure position with reference to the storage area of the sensitivity storage device;
An image forming apparatus comprising:
In order for the image forming apparatus to obtain sensitivity information of the photoreceptor,
Means for visualizing an electrostatic latent image formed by uniformly exposing and scanning a uniformly charged photoconductor surface, and obtaining image data including optical information of each pixel constituting the visualized image And the pixels having the optical information in the acquired image data are continuously generated in a straight line having directivity in the sub-scanning direction and / or the main scanning direction, which is generated without causing the sensitivity unevenness of the photosensitive member. In order to remove the noise data when it has noise data,
A noise direction determining means for determining a continuous direction of the noise data; a means for acquiring an average value Pave of optical information of all pixels based on the acquired image data; and an arbitrary value based on the acquired image data A pixel is determined as a pixel of interest P (x, y) (where x = 1 to N, y = 1 to M ),
It said noise direction determining means determines the arbitrary of the target pixel P (x, y) by averaging the optical information of a plurality of pixels including the average value Pave of the said in the image data along the continuing direction of the noise data ( average value acquisition means for acquiring x, y);
All the pixels in the image data are set as the target pixel P (x, y), and the average value acquired by the average value acquisition unit from the optical information of each target pixel is used as a threshold value. y) = P (x, y) -Pave (x, y) + Pave
The noise removal means for subtracting the threshold value from the optical information of the noise data in which pixels having optical information are linearly continuous, and the optical information of all the pixels after the noise removal means subtracts the threshold value as the sensitivity of the photoconductor An image forming apparatus comprising: a sensitivity acquisition unit that acquires the image. The optical information after subtracting the average value of a plurality of pixels including any pixel of interest in the image data along the direction orthogonal to the continuous direction of the noise data from which the average value was acquired is averaged to obtain an orthogonal average Comprising an orthogonal mean value acquisition means for acquiring a value;
In the noise removing unit, a noise removing unit that subtracts the orthogonal average value as the threshold value from the optical information of each pixel of interest after subtracting the average value using all the pixels in the image data as the pixel of interest. The image forming apparatus according to claim 1, further comprising:   An electrostatic latent image formed on the surface of the photosensitive member by the developing device using a developing device that attaches toner to the surface of the photosensitive member and a transfer device that transfers the toner attached to the surface of the photosensitive member to a recording medium. 3. The image forming apparatus according to claim 1, further comprising: a unit that visualizes the electrostatic latent image by transferring the toner adhered to the recording medium to the recording medium by the transfer device.   Means for visualizing the electrostatic latent image by attaching a toner to the electrostatic latent image on the surface of the photosensitive member by the visualizing device using a visualizing device for attaching the toner to the surface of the photosensitive member. The image forming apparatus according to claim 1, further comprising: The said sensitivity memory | storage device memorize | stores the said sensitivity information for every unit which divided | segmented the visualization area | region by the said imaging device of the said photoreceptor surface into a unit of 100 mm < ² > or less. Image forming apparatus. The image forming apparatus according to claim 1, wherein the exposure scanning device performs exposure scanning at a writing resolution of 1000 dpi or more. Comprising exposure position specifying means for specifying an exposure position by the exposure scanning device;
The image forming apparatus according to claim 1, wherein the exposure amount correcting unit corrects an exposure amount by the exposure scanning device in accordance with an exposure position specified by the exposure position specifying unit.   The image forming apparatus according to claim 1, wherein the photosensitive member has a photosensitive layer in which a plurality of layers, at least one layer of which is formed using a spray coating method, are laminated on a substrate surface.   The image forming apparatus according to claim 1, wherein the photosensitive member has a photosensitive layer that is laminated on a substrate surface and has an outermost layer formed by a spray coating method. An image reading device for reading an image of a document;
A copier comprising: an image forming apparatus according to claim 1, wherein an image based on image data read by the image reading apparatus is formed on a recording medium.

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