JP2004304686A - Adjustment method for image reading apparatus, adjustment chart, image reading apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adjustment method for an image reading apparatus and an adjustment chart which enable a focal position in both main and sub scanning directions to be simultaneously adjusted and to provide an image reading apparatus and an image forming apparatus having excellent performance in both main and sub scanning directions by adopting the adjustment method. <P>SOLUTION: In the adjustment method for the image reading apparatus having a lighting system for lighting an original; at least one folding mirror for leading a reflected image from an original to an image forming lens 4; the image forming lens 4 for reducing the reflected image from the original and forming the reduced image; and an original reading line sensor 5 for applying photoelectric conversion to the image of the original formed by the image forming lens 4, adjustment charts 1, 2 are placed on the original face in the main and sub scanning directions, images of the adjustment charts 1, 2 are formed on a line sensor 5 through the image forming lens 4 and the focal point is adjusted so that MTF values in the main and sub scanning directions satisfy a prescribed value at the same time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

＜非球面係数＞

図１７に構成図、図１８に収差図を示す。図１７において、レンズは、物体側から順に、正の第１レンズＬ１、正の第２レンズＬ２、負の第３レンズＬ３、負の第４レンズＬ４、正の第５レンズＬ５からなり、これらレンズ系の両側に平行平面板が配置されている。第２レンズＬ２と第３レンズＬ３は接合されている。第３レンズＬ３と第４レンズＬ４の間に絞りが配置されている。図１９、図２１、図２３に示す実施例も、各レンズの諸元が異なるだけで、基本的な上記の構成は同じである。
【００５８】
【実施例２】
ｆ＝８４．４３１、Ｆ＝５．０６、ｍ＝０．２３６２２、Ｙ＝１５２．４、ω＝１９．０゜

＜非球面係数＞

図１９に構成図、図２０に収差図を示す。
【００５９】
【実施例３】
ｆ＝８４．２８５、Ｆ＝４．９５、ｍ＝０．２３６２２、Ｙ＝１５２．４、ω＝１９．１゜

＜非球面係数＞

図２１に構成図、図２２に収差図を示す。
【００６０】
【実施例４】
ｆ＝９０．１６３、Ｆ＝４．６５、ｍ＝０．２３６２２、Ｙ＝１５２．４ 、ω＝１７．９゜

＜非球面係数＞

図２３に構成図、図２４に収差図を示す。
【００６１】
本発明にかかるの画像読取装置のピント調整方法のさらに別の実施形態は、これまで説明してきたいずれかの画像読取装置のピント調整方法において、反射ミラーおよび結像レンズの少なくとも１面が光軸に対し非共軸形状であることを特徴とする画像読取装置のピント調整方法である。近年、より高性能な結像レンズとして、主走査方向と副走査方向の像面位置を一致させる手段として、光軸に対して非共軸の、所謂アナモフィックな面をスキャナ光学系の反射ミラーや結像レンズに用いる方法がある。アナモフィックな面は、主走査方向と副走査方向を別々に収差補正可能であるため、設計中央値では、主走査と副走査の像面を精度良く一致させた非常に良好な結像レンズが得られる。しかし、加工ばらつきにより、主走査方向と副走査方向が個別に変動するため、非球面レンズと比較して、主走査方向と副走査方向のＭＴＦを知る必要性がさらに高くなる。本発明により、主走査方向と副走査方向のＭＴＦを見ながら、ピントの調整と、さらには、空気間隔による像面湾曲補正を行うことで、良好な性能を得ることができる。また、アナモフィックな面形状は、球面でも良いが、非球面とすることで、さらに高性能なレンズが得られる。
【００６２】
本発明にかかるの画像読取装置のピント調整方法のさらに別の実施形態は、これまで説明してきたいずれかの画像読取装置のピント調整方法において、ピント調整後に結像レンズを接着により固定することを特徴とする画像読取装置のピント調整方法である。従来、結像レンズを取り付け部材に固定する場合、レンズの外周部に例えばベルトなどを回し、ベルトの端部をビスで取り付け部材に固定していた。しかし、この方法では、ベルトを強く締め付けるとレンズが変形し、結像性能が変化することがあり、ビスの止め方によりレンズの姿勢が変わり、やはり結像性能が変化してしまう。そこで、図２５に示すように、例えばＶブロックのようなレンズを取り付け部材４０のＶ字形溝に結像レンズ４１の鏡筒の一部を嵌め、取り付け部材４０とレンズ鏡筒とを接着剤４２で固定するとよい。また、接着するにあたっては、図２５（ａ）のように、レンズ鏡筒周面の一部を上記Ｖ字形溝に嵌めた状態で、レンズ鏡筒と取り付け部材４０とを直接接着してもよい。また図２５（ｂ）のように、横断面Ｌ字形の中間部材４３をレンズ鏡筒と取り付け部材４０に沿わせ、上記中間部剤４３を介して接着によりレンズ鏡筒を固定してもよい。さらに、より高精度な光学系が必要となり、接着剤の固化時に発生する収縮による微少量のレンズの位置変化が問題となる場合は、治具によりレンズを保持したまま固化させるとよい。こうすることで、ピント調整した状態を保ったまま精度よく保持することができる。
【００６３】
さらに、前に説明した実施の形態のように、結像レンズを複数の保持部材で構成し、少なくとも一つのレンズを平行移動して、レンズ間の空気間隔調整を行うように構成したものにおいて、前述のようにネジを使用しない場合、保持部材としての鏡筒同士を接着により固定することができる。
【００６４】
次に、本発明にかかる画像読取装置の実施形態についた説明する。本発明にかかる画像読取装置の実施形態は、これまで説明してきたピント調整方法によりピント調整された画像読取装置であり、その一例を図２６に示す。図２６において、原稿５２は、コンタクトガラス５１の上に配置され、コンタクトガラス５１の下部に配置された照明光学系（図示せず）により、原稿５２が照明されるように構成されている。原稿５２からの反射光は、第１走行体５３の第１ミラー５３ａにより横方向に反射され、その後、第２走行体５４の第１ミラー５４ａと第２ミラー５４ｂで折り返され、縮小結像レンズ５５へ導かれ、結像レンズ５５によりＣＣＤからなるラインセンサ５６上に原稿５２面の画像が結像されるように構成されている。原稿５２の長手方向を読み取る場合は、第１走行体５３がＶの速度で、符号５３Ｂで示す位置までコンタクトガラス５１と平行に移動し、それと同時に第２走行体５４が、第１走行体５３の半分の速度１／２Ｖで、符号５４Ｂで示す位置まで移動し、原稿５２全体を読み取るように構成されている。この画像読取装置の上記結像レンズ５５は、前述の調整方法によってピント調整されている。
【００６５】
本発明にかかる画像読取装置の別の実施形態は、光学系の任意の光路中に色分解機能を持たせることによって、原稿情報をフルカラーで読み取ることを特徴とするカラー原稿読取装置である。色分解は、結像レンズ５５とＣＣＤからなるラインセンサ５６の間に色分解プリズムや、フィルタを選択的に挿入し、Ｒ、Ｇ、Ｂに色分解する方法であってもよいし、例えばＲ、Ｇ、Ｂ光源を順次点灯させて原稿を照明して、各光源の色ごとに原稿５２を読み取る方法であってもよい。または、Ｒ、Ｇ、Ｂのフィルタを持った受光素子が１チップに３列に配列されている、所謂３ラインＣＣＤを用い、この受光面にカラー画像を結像させることにより３原色に色分解する方法であってもよい。
【００６６】
本発明にかかる画像形成装置の実施形態は、上記の画像読取装置を具備した画像形成装置である。その一例を図２７に示す。図２７において、画像形成装置は、画像読取装置２００と画像形成部１００を具備する。画像形成部１００はレーザプリンターと同様の構成である。画像読取装置２００は、図２６について説明した装置の構成と同様の構成・動作により、原稿５２の画像情報をラインセンサ５６より電気信号として出力する。画像形成部１００は、潜像担持体１１１として「円筒状に形成された光導電性の感光体」を有している。潜像担持体１１１の周囲には、帯電手段としての帯電ローラ１１２、現像装置１１３、転写ローラ１１４、クリーニング装置１１５が配備されている。帯電手段としては「コロナチャージャ」を用いることもできる。さらに、ラインセンサ５６からの原稿情報を受けてレーザビームＬＢにより光走査を行う光走査装置１１７が設けられ、帯電ローラ１１２と現像装置１１３との間で「光書込による露光」を行うようになっている。
【００６７】
図２７において、符号１１６は定着装置、符号１１８はカセット、符号１１９はレジストローラ対、符号１２０は給紙コロ、符号１２１は搬送路、符号１２２は排紙ローラ対、符号１２３はトレイ、符号Ｐは記録媒体としての転写紙をそれぞれ示している。画像形成を行うときは、光導電性の感光体である像担持体１１１が時計回りに等速で回転駆動され、その表面が帯電ローラ１１２により均一帯電され、光走査装置１１７のレーザビームＬＢの光書込による露光を受けて静電潜像が形成される。形成された静電潜像は所謂「ネガ潜像」であって画像部が露光されている。この静電潜像は現像装置１１３により反転現像され、像担持体１１１上にトナー画像が形成される。
【００６８】
転写紙Ｐを収納したカセット１１８は、画像形成装置１００本体に脱着可能であり、図のごとく装着された状態において、収納された転写紙Ｐの最上位の１枚が給紙コロ１２０により給紙され、給紙された転写紙Ｐは、その先端部をレジストローラ対１１９に捕らえられる。レジストローラ対１１９は、像担持体１１１上のトナー画像が転写位置へ移動するのにタイミングを合わせて、転写紙Ｐを転写部へ送り込む。送り込まれた転写紙Ｐは、転写部においてトナー画像と重ね合わせられ転写ローラ１１４の作用によりトナー画像を静電転写される。トナー画像を転写された転写紙Ｐは定着装置１１６へ送られ、定着装置１１６においてトナー画像を定着され、搬送路１２１を通り、排紙ローラ対１２２によりトレイ１２３上に排出される。
【００６９】
トナー画像が転写された後の像担持体１１１の表面は、クリーニング装置１１５によりクリーニングされ、残留トナーや紙粉等が除去される。潜像担持体１１１は光導電性の感光体であり、その均一帯電と光走査とにより静電潜像が形成され、形成された静電潜像がトナー画像として可視化される。
【００７０】
【発明の効果】
請求項１記載の発明は、実際に使用する、折り返しミラー、結像レンズ、および光電変換するためのラインセンサを用いて、主走査と副走査のピント調整を同時に行うことができるため、結像レンズの最も性能の良好なピント位置に光学系を調整することができ、従来の画像読取装置と比べると、主走査方向、副走査方向共に高精度な出力が得られ、従来問題となっていた副走査方向の解像力不良などの問題を解決することができる。さらに、シェーディングのために、光学系内にシェーディング補正板が入った場合でも、その状態で主走査方向と副走査方向のピント調整を行うことができるなど、実使用状態で良好な結像性能を発揮させることが可能となる。
【００７１】
さらに、倍率調整も同時行うことで、光学系の調整工程の大幅な効率化を達成することができる。これにより調整工程に要する電力を大幅に削減することが出来るとともに、本調整により、レンズユニット単体でのＭＴＦ検査が不必要となり、レンズ検査機製作に関わる、原材料や加工に要するエネルギーを大幅に低減でき、地球環境保全に大きく貢献できる。
【００７２】
請求項２記載の発明は、カラー画像読取装置の調整をＲ、Ｇ、Ｂ各色の主走査と副走査の調整を同時に行うことができるため、全ての色に対して結像レンズの最も性能の良好なピント位置に光学系を調整することが可能となり、副走査方向の解像力不良などの問題を解決することができると共に、色再現性や色滲み等の発生しない、高精度なフルカラー読取装置を得ることができる。
【００７３】
請求項３記載の発明は、請求項２記載の発明において、さらに各色各像高の主走査方向と副走査方向の合成ＭＴＦを用いて調整を行うことで、煩雑なフルカラー読取装置のピント調整作業を非常に簡潔、かつ短時間で行うことができ、大幅な調整効率の向上を達成することができる。
【００７４】
請求項４記載の発明は、ラインセンサの長手方向に平行なパターンを移動させることで、読取装置の走行体を移動させることなしに、副走査方向のＭＴＦが得られるため、読取装置の走行体移動に伴う振動や、非等速性にともなうジターなどの影響がなく、精度の高い調整が可能となる。
【００７５】
請求項５記載の発明は、ラインセンサの長手方向に平行なパターンを等速で回転移動させることで、請求項４記載の発明の効果に加え、常に副走査方向のＭＴＦ出力を得ることが可能となり、調整効率の大幅な向上を図ることができる。
【００７６】
請求項６記載の発明は、副走査調整用チャートを平面上に配置し、それを往復運動させることで、副走査のＭＴＦが得られるため、特にフルカラー読取装置に使用した場合、検査装置の小型化や省電力化を図ることができる。
【００７７】
請求項７記載の発明は、副走査調整用チャートの移動速度を、読取装置の読取速度と同期させることで、どのような読取速度の読取装置に対しても、精度の高い調整が可能となる。
【００７８】
請求項８記載の発明は、ラインセンサの長手方向に平行なパターンを移動させることなく、また、読取装置の走行体を移動させることなく、副走査方向のＭＴＦが得られるため、調整装置の簡素化および省電力化を図ることができると共に、条件式の範囲にパターンの角度を設定することで、副走査のＭＴＦが高精度で得られるため、高いピント調整精度が確保出来ると共に、地球環境保全に大きく貢献できる。
【００７９】
請求項９記載の発明は、レンズの検査、調整時に、レンズの任意の空気間隔を変化させることによって像面湾曲を調整することが可能であるため、加工誤差などによるレンズの光軸近傍の結像位置と読み取り領域の周辺部の結像位置変動を調整することができ、読み取り領域全域にわたって、良好な読取画像品質を得ることができる。また、結像レンズ以外の構成要素である、折り返しミラーや光電変換するためのラインセンサに反りなどが生じ、光軸近傍と周辺画角のピント位置が変動した場合でも、空気間隔を調整し、像面湾曲を主走査方向と副走査方向のＭＴＦが最良となるように調整出来るため、結像レンズ以外の構成要素の変動も補正可能な、非常に高性能な画像読取用の光学系を得ることが出来る。
【００８０】
請求項１０記載の発明は、ピント調整時に結像レンズをγ回転させることで、結像レンズの組付け偏心による主走査方向および副走査方向の全ての像高に対する結像性能劣化を小さく抑えることが可能となり、像面全域に亘り良好な読取性能を得ることができる。
【００８１】
請求項１１記載の発明は、空気間隔調整を行うレンズ群毎に、個別の保持部材で保持し、その保持部材同士の空気間隔を調整することができるため、次のような効果を得ることができる。
（１）面倒なレンズのバラシや再組付けの工程をなくすことが可能となる
（２）レンズ自体には直接手を振れず調整することが可能となるため、レンズの再組付け時に発生が予想されるレンズ内部へのゴミの混入やレンズ面の汚れの発生を防止することができると共に、組付けに必要な特別な技術がなくても、像面湾曲調整が可能となる。
（３）組付け偏心が変化しないため、偏心の影響が最も少なくなるレンズの位置が、調整によって変化することがない。
上記効果により、像面湾曲補正のための空気間隔調整と、ピント調整の工程を大幅に低減することが可能となり、調整コストを大幅に下げることが出来る。
【００８２】
請求項１２記載の発明は、請求項１１記載の発明の効果に加え、移動するレンズを一つとすることで、ピント調整機の、調整のための機構が低減でき、調整機自体の構成の簡素化、低コスト化を達成できると共に、調整個所低減による調整効率向上と精度の向上を達成することができる。
【００８３】
請求項１３記載の発明は、分割された保持部材同士が互いに勘合するようインロー部を設けることで、ピント調整機に空気間隔調整のためにレンズを移動させるための駆動機構を高精度にする必要がなく、調整機の更なる簡素化と低コスト化、さらに調整時間の短縮が可能となる。
【００８４】
請求項１４記載の発明は、請求項１０記載の分割するセルを樹脂製とすることで、上記効果に加えて、鏡筒も低コストなスキャナ光学系が得られると共に、金属製のセル製作に関わる原材料や加工エネルギーを削減できるため、地球環境の保護に大きく貢献することができる。
【００８５】
請求項１５記載の発明は、保持部材を非円筒形状とすることで、薄型の画像読取装置を得ることが可能となる。
請求項１６記載の発明は、分割した保持部材を使用したときのレンズのγ回転を一つのレンズで行うため、ピント調整装置のγ回転機構を低減することが可能となり、調整機の簡素化と低コスト化が達成できると共に、ピント調整の高精度化を達成することができる。
【００８６】
請求項１７記載の発明は、光学系の高性能化のために非球面を導入した場合に、非球面の加工エラーにより、光軸に非対称な成分が発生し、主走査と副走査の像面位置が別々に変動した場合でも、主走査と副走査の最もバランスの良い像面位置にピント調整が可能であり、更に、空気間隔調整により像面湾曲を補正することで、主走査と副走査のバランスを最適に補正することができる。
【００８７】
請求項１８記載の発明は、請求項１７記載の発明の効果に加え、結像レンズに非球面を採用する場合、レンズの構成枚数を５枚構成とすることで、原稿情報を高速に読取必要のある、デジタル複写機用の画像読取装置に最適なレンズを、低コストで得ることができ、像面湾曲補正のための空気間隔調整を行っても良好な性能を有する結像レンズが得られると共に、レンズの枚数低減による、ガラス材料や加工エネルギーの削減と、全てのレンズ材質として、化学的に安定で鉛や砒素等の有害物質を含まない光学ガラスを使用しているため、材料のリサイクル化が可能で、加工時の廃液による水質汚染の無いことにより、地球環境保全に大きく貢献することができる。
【００８８】
請求項１９記載の発明は、光学系内に、主走査方向と副走査方向を個別に収差補正可能な光軸対し非共軸の所謂アナモフィック面を有することで、主走査方向と副走査方向の像面位置を一致させて非常な高性能な光学系を得ることが可能となり、アナモフィック面の加工誤差により主走査と副走査の像面位置の変動が発生しても、最もバランスのとれた位置に調整することができる。また、特にミラーにアナモフィック面を採用する場合、結像レンズのみや、ミラー単体の評価では、光学系としての最適ピント位置を知ることが出来ないが、本発明によりミラーおよび結像レンズを含めて最良なピント位置に調整が可能となるばかりでなく、空気間隔調整を行うことで、アナモフィックミラーの加工誤差を含め、主走査方向と副走査方向の像面位置を最適に補正することができる。
【００８９】
請求項２０記載の発明は、上記請求項１〜１３のいずれかに記載のピント調整方法で調整されたレンズを取り付け部材に固定するとき、固定手段として接着を用いることで、ベルトなどで締め付ける場合に発生するレンズの変形やレンズの移動が発生することなく、良好な性能を保ったままレンズを保持することが可能となる。
【００９０】
請求項２１ないし２４記載の発明によれば、請求項１ないし２０記載の調整方法を実施するのに適した画像読取装置の調整用チャートを提供することができるとともに、主走査方向と副走査方向のピントを同時に調整することが可能な画像読取装置の調整用チャートを提供することができる。
【００９１】
請求項２５の発明は、画像読取装置に、請求項１から１９のいずれかに記載の調整方法を取り入れることにより、良好な読み取り画像品質を有する画像読取装置を得ることができる。
【００９２】
請求項２６の発明は、画像形成装置の画像読取装置として、請求項２５記載の画像読取装置を具備する事により、良好な読み取り画像品質を基に画像を形成するため、画質の高い画像を形成することができる画像形成装置を得ることができる。
【図面の簡単な説明】
【図１】横軸にディフォーカスを、縦軸に解像力の指標となるＭＴＦをとり、軸上と、主走査方向と副走査方向それぞれにつき軸外でＭＴＦを測定した例を示す特性線図である。
【図２】本発明に用いることができる調整用チャートの例を測定光学系とともに示す正面図である。
【図３】本発明に用いることができる調整用チャートの別の例を示す正面図である。
【図４】ラインセンサを焦点深度方向に微小量移動させたときの各色、各像高のＭＴＦを測定し、ディフォーカス量を横軸に、ＭＴＦを縦軸にとって表した特性線図である。
【図５】本発明にかかる調整方法に使用可能な主走査方向調整用チャートの例を示す正面図である。
【図６】本発明にかかる調整方法に使用可能な副走査方向調整用チャートの例を示す正面図である。
【図７】本発明にかかる調整方法に使用可能な副走査方向調整用チャートの別の例を示す斜視図である。
【図８】本発明にかかる調整方法に使用可能な副走査方向調整用チャートのさらに別の例を示す斜視図である。
【図９】本発明にかかる調整方法に使用可能なチャートのさらに別の例を示すもので、（ａ）は主走査方向調整用チャートの正面図、（ｂ）は主走査方向調整用チャートと副走査方向調整用チャートを組み合わせた斜視図である。
【図１０】本発明にかかる調整方法に使用可能なチャートのさらに別の例を示す斜視図である。
【図１１】本発明にかかる調整方法に使用可能な副走査方向調整用チャートのさらに別の例を示す正面図である。
【図１２】本発明にかかる調整方法に使用可能なチャートのさらに別の例を示すもので、（ａ）は全体を、（ｂ）は副走査方向調整用チャートを拡大した正面図である。
【図１３】本発明に好適な結像レンズの例を示す断面図である。
【図１４】本発明に好適な結像レンズの別の例を示す斜視図である。
【図１５】本発明に好適な結像レンズのさらに別の例を示す断面図である。
【図１６】本発明に好適な結像レンズのさらに別の例を示す斜視図である。
【図１７】本発明に好適な結像レンズの実施例を示す光学配置図である。
【図１８】同上実施例の収差曲線図である。
【図１９】本発明に好適な結像レンズの別の実施例を示す光学配置図である。
【図２０】同上実施例の収差曲線図である。
【図２１】本発明に好適な結像レンズのさらに別の実施例を示す光学配置図である。
【図２２】同上実施例の収差曲線図である。
【図２３】本発明に好適な結像レンズのさらに別の実施例を示す光学配置図である。
【図２４】同上実施例の収差曲線図である。
【図２５】本発明に適用して好適な結像レンズの固定構造の例を示す側面図である。
【図２６】本発明にかかる画像読取装置の実施形態を模式的に示す光学配置図である。
【図２７】本発明にかかる画像形成装置の実施形態を模式的に示す光学配置図である。
【符号の説明】
１ 主走査方向調整用チャート
２ 副走査方向調整用チャート
４ 勝三レンズ
５ ラインセンサ
５２ 原稿
５３ａ 折り返しミラー
５４ａ 折り返しミラー
５４ｂ 折り返しミラー
５５ 結像レンズ
５６ ラインセンサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is applicable to a scanner, a copier, a facsimile, and the like, and relates to an adjustment method, an adjustment chart, an image reading apparatus, and an image forming apparatus for these image reading apparatuses.
[0002]
[Prior art]
2. Description of the Related Art As an optical system used in an image reading apparatus such as a scanner, a copying machine, and a facsimile, there is a reduced reading optical system that reduces reflected light of a document illuminated by an illumination system and forms an image on a line sensor by an imaging lens. The focus adjustment of the optical system is performed using a pattern arranged on the document surface. That is, the above-mentioned pattern is a pattern composed of normal black and white lines that are orthogonal to the longitudinal direction of the line sensor and arranged at equal intervals. The positions of the image lens and the line sensor are changed so that the reduction ratio and the output of the line sensor are adjusted to be good.
[0003]
However, in the conventional adjustment method, only the output in the main scanning direction orthogonal to the longitudinal direction of the line sensor is seen at the time of focus adjustment. Therefore, even if the focus in the main scanning direction is satisfactorily adjusted to achieve a predetermined resolution, the resolution in the sub-scanning direction may be less than a predetermined level. This will be described with reference to FIG. FIG. 1 shows an example in which the horizontal axis represents the defocus, and the vertical axis represents the MTF as an index of the resolving power, and measured off-axis on the axis and in each of the main scanning direction and the sub-scanning direction. If the MTF is equal to or higher than a predetermined threshold level, it is determined that the performance is satisfied. There is a possibility that the positions of the imaging lens and the line sensor are adjusted with the position indicated by A in FIG. On-axis indicated by a circled symbol 1 in FIG. 1 and off-axis indicated by a circled symbol 2: the resolution in the main scanning direction exceeds a threshold level for satisfying performance. However, the off-axis: resolution in the sub-scanning direction of the circled symbol 3 cannot satisfy the threshold level for satisfying the predetermined performance, which causes problems such as poor resolution in the sub-scanning direction. . When a resolution failure in the sub-scanning direction occurs as described above, it is necessary to perform focus adjustment again, which makes the focus adjustment operation extremely complicated.
[0004]
As a focus adjustment method for setting the resolving power to a high level, when the image forming position on the lens optical axis is used as a reference, at a position separated from the optical axis in the width direction of the document, the image forming position of the lens in the optical axis direction Is formed so as to maximize the displacement, and the lens is formed in a first direction parallel or orthogonal to the width direction in the image plane of the image at the position where the displacement of the image forming position in the optical axis direction is maximum. There is a method in which the peak of the resolution characteristic curve is positioned at an intermediate portion in the optical axis direction between the peak of the resolution characteristic curve at the optical axis position of the lens and the peak of the resolution characteristic curve in the second direction orthogonal to the first direction. For example, see Patent Document 1).
[0005]
However, in the invention described in Patent Document 1, it is necessary to know the performance of the imaging lens in advance without performing focus adjustment by looking at the MTF output in the sub-scanning direction. If the image forming performance varies within the tolerance, the focus cannot be adjusted to a position having a good resolution in both the main scanning direction and the sub-scanning direction.
[0006]
The following is a prior example of the present applicant's application for performing focus adjustment in the sub-scanning direction. First, on a document surface, first patterns arranged in a direction perpendicular to the longitudinal direction of the first document reading line sensor and arranged at regular intervals in the longitudinal direction of the first document reading line sensor; A second pattern arranged in a direction parallel to the longitudinal direction of the first original reading line sensor, and reading the first pattern with the first original reading line sensor. There is an image reading apparatus in which a pattern is read by a second document reading line sensor, output signals in the main scanning direction and the sub-scanning direction are adjusted favorably, and the focusing of the optical system can be adjusted ( Patent Document 2).
[0007]
When the focus adjustment in the main scanning direction is performed, a pattern arranged at equal intervals in the longitudinal direction of the line sensor for reading the original is read by the imaging lens, and when the focus adjustment in the sub-scanning direction is performed, the original is read. A reading member made of a light-transmissive material is movably inserted into an optical path connecting the surface and the imaging lens, and the reading member is appropriately moved so that the reading member is equally spaced in a direction orthogonal to the longitudinal direction of the line sensor. There is an adjustment method for an image reading apparatus that reads an arrayed pattern via an imaging lens (see Patent Document 3). Also, by moving the strip-shaped chart in parallel in the sub-scanning direction, a solid-state image sensor can read a reading surface in which a plurality of lines are formed at equal intervals in the sub-scanning direction, and adjust the focus in the sub-scanning direction. There is a focus adjustment assisting device and a focus adjustment method that can be performed (see Patent Document 4).
[0008]
Further, the present invention relates to a method for adjusting an image reading apparatus which scans an original in the sub-scanning direction while scanning an original on a one-dimensional image sensor via an imaging lens to read the entire front surface of the original. A second sub-scanning adjustment chart, in which one long dark strip in the main scanning direction is arranged on the background, is placed on the document surface and vibrated at a constant cycle in the sub-scanning direction, and the change in light and dark is concluded. There is also a configuration in which the focus of the imaging lens in the sub-scanning direction is detected and adjusted by detecting with a one-dimensional image sensor via an image lens (see Patent Document 5).
[0009]
[Patent Document 1]
JP-A-8-214112
[Patent Document 2]
JP-A-11-317839
[Patent Document 3]
JP 2001-144899 A
[Patent Document 4]
JP 2001-230896 A
[Patent Document 5]
JP-A-2002-16757
[0010]
[Problems to be solved by the invention]
However, the invention described in Patent Document 2 is unnecessary as a scanner optical system, and requires a line sensor used only for focus adjustment in the sub-scanning direction, which increases cost and increases the size of the scanner optical system. It will lead to conversion. In the inventions described in Patent Documents 3, 4, and 5, since it is necessary to separately switch and adjust the main scanning direction and the sub-scanning direction, when the focus in the main scanning direction is adjusted, The performance fluctuation in the sub-scanning direction cannot be known. Therefore, it is necessary to switch between the adjustment in the main scanning direction and the adjustment in the sub-scanning direction several times so that performance is gradually optimized so that it takes a very long time to perform the adjustment. Is complicated.
[0011]
Accordingly, the present invention provides an adjustment method for an image reading apparatus that can simultaneously adjust the focus position in the main scanning direction and the sub-scanning direction, an adjustment chart, and the adjustment method. It is an object of the present invention to provide an image reading apparatus and an image forming apparatus having good performance in both scanning directions.
Further, the present invention aims to achieve the following items in consideration of the global environment.
(1) Power saving by drastically reducing man-hours for adjusting the scanner optical system.
(2) Reduction of raw materials related to the production of the lens unit inspection apparatus and energy related to the processing by eliminating the need for the lens unit inspection.
(3) Reduction of energy related to metal raw materials and metal processing by converting the holding member to resin.
(4) Since the lens is made of optical glass which is chemically stable and does not contain harmful substances such as lead and arsenic, the material can be recycled, and there is no water pollution due to waste liquid during processing. In addition, the use of an aspherical surface reduces the number of lens components, thereby reducing energy related to glass materials and glass processing.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an image reading apparatus adjustment method, an adjustment chart, an image reading apparatus, and an image forming apparatus according to the present invention will be described with reference to the drawings.
[0013]
One embodiment of the image reading apparatus adjustment method according to the present invention includes an illumination system for illuminating a document, at least one folding mirror for guiding a reflected image from the document to an imaging lens, and In an adjustment method in an image reading apparatus having an image forming lens for reducing and forming a reflected image and a line sensor for reading a document for photoelectrically converting the document image formed by the image forming lens, a main scanning direction and a sub An adjustment chart in the scanning direction is arranged, and this adjustment chart is imaged on the line sensor by the imaging lens, and the focus can be adjusted so that the MTFs in the main scanning direction and the sub-scanning direction simultaneously satisfy a predetermined value. It is characterized by having.
[0014]
As the adjustment chart, for example, as shown in FIG. 2, five charts (1) -a, (1) -b, and (1)-in the main scanning direction are used to measure the main scanning and the sub-scanning at the same time. c, (1) -d, (1) -e and four charts (2) -a, (2) -b, (2) -c, (2) -d in the sub-scanning direction are main-scanned. The line sensors 5 arranged in a line in the longitudinal direction of the line sensor 5 are used. Each chart is obtained by arranging a plurality of straight lines in a stripe shape, the chart in the main scanning direction is a plurality of straight lines in the sub-scanning direction arranged in the main scanning direction, and the chart in the sub-scanning direction is a plurality of straight lines in the main scanning direction. Are arranged in the sub-scanning direction. On the optical axis 3 of the imaging lens 4 at the center in the main scanning direction, there is only the chart (1) -c in the main scanning direction, and no chart in the sub-scanning direction. Each chart is dispersedly arranged at a predetermined position in the main scanning direction.
[0015]
The chart as described above is arranged on the same surface as the document, for example, on a contact glass on which the document is placed in the case of a copying machine, and the chart is reduced on the light receiving surface of the line sensor 5 by the imaging lens 4. An image is formed. At least one folding mirror is arranged between the chart and the imaging lens 4, but is omitted in FIG. The detection output of the portion corresponding to each chart of the line sensor 5 fluctuates in accordance with the repetition of the stripe of each chart, and an MTF according to the sharpness of the image is obtained. By arranging the chart in the main scanning direction and the chart in the sub-scanning direction as described above, MTFs in the main scanning direction and the sub-scanning direction can be obtained at the same time. Can be adjusted. Explaining with reference to the example of FIG. 1, the adjustment is performed so that the position of the focus plane A exists in an area where the threshold level is equal to or higher than the threshold level in both the main scanning direction and the sub scanning direction. The position and number of charts in the main scanning direction and the sub-scanning direction can be arbitrarily changed depending on the performance of the imaging lens 4. In accordance with the MTF performance of the imaging lens 4 in the main scanning direction and the sub-scanning direction in the image height direction, by optimally arranging the focusing lens 4, the focus adjustment in the main scanning direction and the sub-scanning direction over the entire image height can be performed with high accuracy. It is possible to do. After the adjustment is completed, the chart is removed.
[0016]
As an actual adjustment method, either one of the imaging lens 4 and the line sensor 5 is moved or the imaging lens 4 and the line sensor 5 are moved for focusing. The interval between the sensors 5 is changed. It is common for an image reading apparatus to simultaneously adjust the imaging magnification at the time of focus adjustment. Therefore, a magnification adjustment pattern is also arranged on the focus adjustment chart, and in addition to the movement of the imaging lens 4 or the line sensor 5 by the focus adjustment, the imaging lens 4 and the line sensor 5 are integrally moved, or a folding mirror. It is preferable to change the distance from the document surface to the imaging lens 4 by moving the position.
[0017]
In order to perform the focus adjustment and the magnification adjustment, the distance from the document surface to the imaging lens 4 and the distance between the imaging lens 4 and the line sensor 5 may be changed. The mirror, the imaging lens, the line sensor, and the like provided in the image reading device may be arbitrarily combined and changed.
[0018]
According to another embodiment of the adjustment method of the image reading apparatus according to the present invention, in order to read a document image in color, in the above-described embodiment, a filter for color separation is arranged on the front surface of the sensor in the line sensor. A focus adjustment method for an image reading apparatus in which a plurality of line sensors are arranged in a sub-scanning direction, such that MTFs of the plurality of line sensors in a main scanning direction and a sub-scanning direction simultaneously satisfy a predetermined value. A focus adjustment method for an image reading apparatus, wherein focus adjustment is possible.
[0019]
As an example of the line sensor, as shown in FIG. 3, a three-line charge-coupled device (charge-coupled device) having three color separation filters of red (R), green (G), and blue (B) on its front surface There is a so-called three-line CCD in which a device (hereinafter referred to as “CCD”) is arranged in one package. When such a three-line CCD is used, as shown in FIG. 3, the width of the adjustment chart set on the original surface in the short direction, that is, the sub-scanning direction, is set wider than the line interval of the three-line CCD. Set. This makes it possible to adjust the MTFs of the three colors R, G, and B in the main scanning direction and the sub-scanning direction at one time over the entire image height. In the above example, the case where the number of line sensors is three has been described, but the number of line sensors may be any number as long as it is two or more.
[0020]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is a method of combining the MTFs at an arbitrary image height in the main scanning direction and the sub-scanning direction of the plurality of line sensors in the above-described embodiment. And a focus adjustment method for the image reading apparatus, wherein the focus adjustment is performed by the combined MTF.
[0021]
A specific adjustment method will be described by taking a case where a three-line CCD is used as an example. As shown in FIG. 4, for example, when the CCD is moved by a small amount in the optical axis direction of the lens, that is, in the depth of focus direction, the MTF of each color and each image height is measured. Next, the MTF is plotted on the vertical axis, and all measured MTFs are plotted. Based on this plotted FIG. 4, for example, by adjusting the position of the CCD to the defocus position where the total MTF becomes the maximum, that is, the MTF peak position in FIG. The focus can be adjusted to an optimum position.
[0022]
When it is sufficient to adjust each color to a value equal to or higher than the MTF of a certain threshold level as a specification of the scanner optical system, the position of the CCD should be adjusted to a certain area in FIG. 4, that is, an OK range shown in FIG. It becomes. There is also a method of not actually creating a diagram in which the MTF of each color is plotted as described above. Specifically, the MTF of each color is displayed in real time when the CCD is moved in the depth direction, and the position where the MTF of each color is maximized, and the CCD such that the MTF of each image height of each color satisfies the threshold level. May be adjusted.
According to a fourth aspect of the present invention, in the focus adjustment method of the image reading apparatus according to any one of the first to third aspects, the adjustment chart in the sub-scanning direction is arranged in the longitudinal direction of the line sensor. A focus adjustment method for an image reading apparatus, comprising moving patterns arranged in parallel and at equal intervals.
[0023]
The adjustment chart in the main scanning direction is, for example, as shown in FIG. 5, a plurality of straight lines perpendicular to the longitudinal direction of the line sensor, which are generally used in the related art, are equidistant and parallel in the main scanning direction. A so-called line chart arranged in the above manner can be used. On the other hand, as shown in FIG. 6, the adjustment chart in the sub-scanning direction is a chart in which a plurality of straight lines in the longitudinal direction of the line sensor, that is, in the main scanning direction are arranged at equal intervals in parallel with the sub-scanning direction. By moving the chart in the sub-scanning direction, the detection output of a specific sensor constituting the line sensor changes, so that the MTF in the sub-scanning direction can be read from the line sensor output.
[0024]
Note that the arrangement pitch of the charts for the main scanning direction and the sub-scanning direction can be set arbitrarily so that the frequency of the MTF to be measured is the same as the frequency required in the scanner optical system used. The frequency in the main scanning direction and the frequency in the sub-scanning direction may be the same or different.
[0025]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention relates to a method of moving the adjustment chart in the sub-scanning direction in the above adjustment method, wherein the plurality of adjustment charts in the sub-scanning direction are in the same direction. (Rotational movement) at a constant speed (in the sub-scanning direction).
[0026]
Specifically, as shown in FIG. 7, a stripe-shaped pattern is formed on the surface of the belt-shaped support 7 parallel to the longitudinal direction of the line sensor and arranged at equal intervals in the sub-scanning direction. Can be used as a sub-scanning direction adjustment chart held by two rollers 9, 10. Due to the rotation of the rollers 9, 10, the belt 7 rotates at a constant speed, and the stripe pattern moves in the sub-scanning direction. MTF can be measured by detecting this with a line sensor. As shown in FIG. 8, on the surface of the cylindrical rotator 11, a stripe pattern parallel to the longitudinal direction of the line sensor and arranged at regular intervals in the sub-scanning direction is formed, and the rotator 11 is rotated. Then, a method of detecting this with a line sensor is also conceivable. In the present invention, since the chart only needs to move in the same direction at a constant speed, for example, in the example of FIG. 7, two rollers are shown, but the number of rollers may be any number, The belt 7 can be moved by a gear other than the rollers, for example.
[0027]
In the present invention, since it is necessary to measure the main scanning direction and the sub-scanning direction at the same time, as an actually used chart, as shown in FIG. A mask 14 having a main scanning adjustment chart 15 and an opening 16 for sub-scanning measurement may be arranged. The sub-scanning measurement chart 12 is composed of a stripe pattern formed on the surface of a drum-shaped rotating body that is long in the direction of the rotation axis. The mask 14 is a plate-shaped member that is long in the direction of the rotation axis of the rotator. The main scanning adjustment charts 15 are formed at equal intervals at three positions in the longitudinal direction, and the openings 16 are arranged between these charts 15. ing. The MTF in the main scanning direction can be measured by the detection output of the main scanning adjustment chart 15 by the line sensor, and the detection output of the line sensor corresponding to the sub-scanning measurement chart 12 seen to move in the sub-scanning direction through the opening 16. Can measure the MTF in the sub-scanning direction.
[0028]
The sub-scanning chart may have a pattern only in the range to be measured. Accordingly, as shown in FIG. 10, the sub-scanning chart may be divided into a plurality. In the example of FIG. 10, a sub-scanning chart 20 is formed on the surfaces of two drums 18 and 18 that are driven to rotate, and the mask 14 and the mask 14 shown in FIG. The same mask 14 is arranged, and the sub-scanning chart 20 can be detected by a line sensor through the opening 16 of the mask 14. In this example, the sub-scanning chart is divided into two, but the number of divisions is arbitrary.
[0029]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is characterized in that, in the above-described adjustment method, the adjustment chart in the sub-scanning direction reciprocates in the sub-scanning direction. . It is desirable that the adjustment chart be kept flat on the original placement surface. However, when a cylindrical chart is used and a 3-line CCD is used, for example, if the outer diameter of the cylinder is small, the cylindrical chart has a curvature in the sub-scanning direction. Due to the difference between the reading positions of (G) and blue (B), the chart is in a state of being lifted from the document installation surface, and it is not possible to perform accurate adjustment. In order to prevent this, the outer diameter of the cylinder may be increased. However, in such a case, the size of the apparatus is increased, and accordingly, it is necessary to increase the drive source, which causes a problem such as an increase in power consumption. Therefore, in the invention according to claim 6, as shown in FIG. 11, a chart in the sub-scanning direction is made a flat surface, a stripe-like pattern is formed thereon, and the pattern is reciprocated in the sub-scanning direction.
[0030]
Still another embodiment of the adjustment method of the image reading device according to the present invention is the adjustment method of the image reading device, wherein the movement of the adjustment chart in the sub-scanning direction is synchronized with a reading cycle of the line sensor. Features. Generally, in a line sensor used in a scanner optical system, a signal output speed of document information is set in accordance with a reading speed of the scanner optical system. This adjustment method can be used irrespective of the reading speed of the scanner optical system. However, in order to accurately measure the MTF in the sub-scanning direction, it is necessary to synchronize with the signal output of the line sensor corresponding to the reading speed. , The moving speed of the chart can be changed.
[0031]
Still another embodiment of the method for adjusting an image reading apparatus according to the present invention is the method for adjusting an image reading apparatus according to any one of claims 1 to 3, wherein the adjustment chart in the sub-scanning direction is a length of the line sensor. Θ is an inclination angle (unit: degree) with respect to the direction parallel to the line sensor length of the sub-scanning adjustment chart, and MTF (H) is an arbitrary angle of view of the imaging lens. And the higher MTF value in the sagittal direction and the meridional direction at the defocus position, and the lower MTF value in the sagittal direction and the meridional direction at an arbitrary angle of view and the defocus position of the imaging lens. In this case, the minute angle satisfies the following condition.
θ <MTF (H) / MTF (L) × 45
[0032]
In the adjustment method according to the fourth to sixth aspects, the MTF in the sub-scanning direction is obtained by moving the adjustment chart in the sub-scanning direction in the sub-scanning direction. A drive source for moving the image sensor and a speed change mechanism for synchronizing with the reading speed are required. Therefore, as shown in FIG. 12, the MTF measurement in the sub-scanning may be performed by tilting the adjustment chart 22 in the sub-scanning direction by a small angle (θ) with respect to the longitudinal direction of the line sensor, that is, the main scanning direction. .
[0033]
In the optical system, for an image on the optical axis of the imaging lens, when the lens has no eccentricity, the point image distribution has a shape (circle) in which the main scanning direction and the sub-scanning direction are completely symmetrical, The MTFs in the main scanning direction and the sub scanning direction are exactly the same. In such a case, the MTF has the same value even when the adjustment chart is inclined by 45 degrees. On the other hand, when the imaging lens has an angle of view, the point image distribution is changed in the main scanning direction and the sub-scanning direction due to the influence of aberrations (astigmatism, coma aberration, etc.) of the imaging lens. It becomes asymmetric, and the MTFs in the main scanning direction and the sub-scanning direction have different values. In such a state, if the inclination angle θ of the adjustment chart is increased, the measurement accuracy of the MTF in the sub-scanning direction is significantly deteriorated. Therefore, the inclination angle of the pattern of the sub-scanning adjustment chart 22 is set in a range satisfying the above conditional expression. This makes it possible to accurately measure the MTF in the sub-scanning direction.
[0034]
Still another embodiment of the method for adjusting an image reading device according to the present invention is the method for adjusting an image reading device according to any one of claims 1 to 8, wherein an arbitrary air interval of the imaging lens is changed during focus adjustment. And correcting the field curvature by adjusting the focus of the image reading apparatus. In the imaging lens, the curvature of field fluctuates due to various parameters constituting the lens, such as a radius of curvature, a wall thickness, a surface interval, a refractive index of a glass material to be used, and a processing error of the lens. The imaging position changes between the vicinity of the axis and the periphery. However, when more accurate reading performance is required as a scanner optical system as in recent years, there is a case where a performance variation due to a variation in each of the above parameters cannot be allowed.
[0035]
Therefore, while adjusting the focus in the main scanning direction and the sub-scanning direction, the curvature of field of the imaging lens consisting of a plurality of lenses is changed by changing the air gap between the lenses, and the lens is formed over the entire reading area. It is preferable to perform the field curvature correction and the focus adjustment so that the imaging performance of the above becomes good. FIG. 13 shows an example of an imaging lens which makes this possible. In FIG. 13, a front lens group 27 including three lenses L1, L2, and L3 and a rear lens group 28 including three lenses L4, L5, and L6 are incorporated in a lens barrel 26. A spacer is interposed between the end surface receiving portion 26a of the lens L4 formed on the lens barrel 26 and the end surface of the lens L4, and the thickness of the spacer is changed to reduce the air gap 30 between the lenses L3 and L4. It can be changed. The curvature of field can be corrected by changing the air gap. The air interval to be changed for performing the field curvature correction may be one lens interval or a plurality of lens intervals, and can be arbitrarily selected by the imaging lens. By selecting a point where the curvature of field can be changed without changing the symmetry of the coma aberration as a point where the air gap is changed, the performance of the imaging lens can be further improved.
[0036]
According to still another embodiment of the adjustment method of the image reading device according to the present invention, in the focus adjustment method of the image reading device according to any one of claims 1 to 9, a lens is rotated in a circumferential direction. This is a focus adjustment method for an image reading apparatus. In an image reading apparatus using a line sensor, in order to form a document image on the line sensor as a line image in the main scanning longitudinal direction, as shown in FIG. (referred to as γ rotation) so that the influence of the eccentricity of the assembly of the lens 31 is reduced. Conventionally, when an imaging lens is inspected by, for example, an MTF inspection machine, the above-described γ rotation is performed, a mark is formed in a rotation direction in which the influence of eccentricity is reduced, and the image of the imaging lens is read using the mark as a mark. Attach it to the device. Alternatively, a method has been proposed in which an image forming lens is attached to an image reading apparatus, and γ rotation is performed while looking at only the MTF in the main scanning direction.
[0037]
However, when performing the γ rotation when inspecting the imaging lens with an MTF inspection machine or the like, when the imaging lens is attached to the inspection machine and the attachment to the image reading device are not the same condition, or the lens is held. Due to the processing tolerance of the roundness and coaxiality of the holding member, for example, the lens barrel, etc., and the inclination of the mounting part, select the γ rotation of the imaging lens to a position where the influence of eccentricity is small on the inspection machine. However, when attached to an image reading apparatus, there is a problem that the influence of eccentricity is large. Also, when looking for only the MTF in the main scanning direction on the image reading apparatus and searching for a position where the influence of the eccentricity is small, the influence of the main scanning direction and the sub-scanning direction on the eccentricity of assembling the lens is different. There is a problem in that even if the influence of the eccentricity is small in the direction, the influence is large in the sub-scanning direction.
[0038]
Therefore, by simultaneously viewing the MTFs in the main scanning direction and the sub-scanning direction and setting the image reading apparatus to a position where the influence of the eccentricity during assembly is small when adjusting the focus of the image reading apparatus, the above-described conventional problem can be solved. The position of the image lens in the circumferential direction can be a position where the influence of eccentricity is small in both the main scanning direction and the sub-scanning direction.
[0039]
According to still another embodiment of the method for adjusting the image reading apparatus according to the present invention, in the focus adjusting method for the image reading apparatus according to claim 9 or 10, the imaging lens is held by at least two lens holding members. A focus adjustment method for an image reading apparatus, wherein an arbitrary air gap between lenses held by a holding member is changed to correct curvature of field.
For example, in the lens barrel structure as shown in FIG. 13, when the air gap 30 of the lens is to be changed, the three lenses on the front side or the rear side of the air gap 30 are once removed from the lens barrel 26, for example, as described above. It is necessary to insert a simple spacer or the like between the lens and the receiving portion of the lens barrel that receives the lens, or change the thickness of the spacer and reassemble the three removed lenses. With such an adjustment step, a step of removing the lens and a step of reassembling the lens are necessary, and even if a direction in which the influence of the eccentricity of the lens assembly by the γ rotation is small in the first assembled state is found, the lens must be remounted. Since the direction of the eccentricity changes due to the assembly, it is necessary to search again for a direction in which the influence of the eccentricity is small, and it takes time to correct the curvature of field, which increases the cost.
[0040]
Japanese Patent Application Laid-Open No. H11-337799 discloses a prior example of a lens barrel according to the application of the present applicant, in which a lens holding member is divided into a plurality of parts and the air gap is adjusted. This is because, in the lens barrel that holds the lens, the lens barrel is divided into at least two parts and joined together, and the joint between the lens barrels is formed in a screw structure, and the lens barrels are rotated relative to each other. Thus, the distance between the lenses attached to each lens barrel is changed to obtain good imaging performance. In the present invention, since the divided holding members are fitted to each other by screws, the state of adjustment as described above fluctuates, and there is a problem that γ rotation must be performed again.
[0041]
Therefore, in the above-described embodiment, for example, as shown in FIG. 15, a lens barrel that holds the front group lens 27 and a lens barrel that holds the rear group lens 28, and adjusts the distance between these lens barrels to adjust the distance between the lenses. The air spacing was adjusted. In the example shown in FIG. 15A, as a holding member, a front group lens 27 and a rear group lens 28 each having three lenses are held by lens barrels 31 and 32 which are separate holding products. It is. At the time of focus adjustment, the jigs hold the front and rear lens barrels 31 and 32 and move the respective lens barrels in parallel so as not to rotate by γ to adjust the distance between the lenses of the front and rear groups.
[0042]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is a focus adjustment method of the image reading apparatus in which the air gap between the lenses is changed to correct the curvature of field as described above. It is characterized in that only the holding member is moved. In the example shown in FIG. 15A, in order to perform field curvature correction, when changing the air gap between the imaging lenses, one of the front and rear group lenses 27 and 28 is fixed, and the other is fixed. The curvature of field is corrected by moving only the lens group of.
[0043]
In the case where the curvature of field is corrected by changing the air gap between the lenses, in order to move the plurality of lenses in parallel so that the lenses do not rotate γ at the time of correction, the relative positional accuracy of the moving lenses must be adjusted. Need to secure. Therefore, the movement accuracy of both the front and rear groups must be increased, which causes a cost increase of the focus adjustment device. Therefore, in the example of the imaging lens as shown in FIG. 15, by using one moving lens group, it is possible to suppress the required accuracy of the focus adjustment device, and to provide a low-cost focus adjustment method and apparatus. can do.
[0044]
Further, as described above, in the adjustment process of the image reading apparatus, it is general to adjust the focus and the magnification together. Depending on the power arrangement of the lenses, it may be possible to set the moving lens group so that the correction of the curvature of field and the adjustment of the magnification can both be achieved by the movement of one lens group. In such a case, by moving only one lens group, it is possible to greatly reduce the number of adjustment and fixing operations.
[0045]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is a focus adjustment method of the image reading apparatus in which the air gap between the lenses is changed to correct the curvature of field. And a focus adjustment method for an image reading apparatus, wherein the image reading apparatus has a spigot portion. In order to perform the field curvature correction, the lens is moved in parallel, and the adjustment of the air gap between the lenses is further facilitated. As shown in FIG. 15B, the front lens group 27 and the rear lens group 28 are held by separate lens barrels 35 and 36, respectively. The space between the front and rear lens barrels 35 and 36 can be adjusted using the spigot portion 39 as a guide. The “slot part” refers to a part configured such that the concave part and the convex part are detachably fitted to each other. By having the spigot portion 39, the distance between the lens barrels 35 and 36 can be adjusted, and thereby the air gap 30 between the lenses L3 and L4 can be adjusted. Can be maintained with high precision, so that the precision of the lens can be maintained high even if the precision of the adjuster is further reduced.
[0046]
According to still another embodiment of the image reading apparatus adjustment method according to the present invention, in the focus adjustment method for an image reading apparatus according to any one of claims 1 to 13, the holding member is a resin lens barrel. This is a focus adjustment method for an image reading apparatus. The holding member corresponds to a lens barrel. As shown in FIG. 15, when the lens barrel is divided into front and rear lens barrels, if the material of the lens barrel is machined by a metal cutting process such as aluminum, the cost of the lens barrel itself increases, which causes a cost increase. . Therefore, in the invention according to claim 14, the lens barrel is made of resin. This makes it possible to improve the efficiency of the interval adjustment without increasing the cost of the lens barrel itself.
[0047]
In the description of the invention according to claims 9 to 13, in the imaging lens composed of a total of six lenses, an example has been shown in which the adjustment point is the air gap between the third lens and the fourth lens. It is not limited, and may be adjusted anywhere. Also, as a lens type, a so-called Gauss type having four elements in six groups has been described as an example, but the same effect can be obtained with any lens type.
[0048]
Still another embodiment of the adjustment method of the image reading device according to the present invention is that, in the focus adjustment method of the image reading device in which the holding member is a resin lens barrel, the outer shape of the holding member is non-cylindrical. This is a focus adjustment method for an image reading apparatus. The shape of the lens barrel as the holding member is generally a cylindrical shape, but in order to reduce the thickness of the image reading apparatus, for example, as shown in FIG. Or a D-shaped cross section in which only the upper or lower part is cut by a plane. By doing so, an unnecessary portion of the imaging lens is removed, and it is possible to cope with a reduction in the thickness of the image reading device.
[0049]
Still another embodiment of the image reading apparatus adjustment method according to the present invention is the image reading apparatus focus adjustment method according to any one of claims 10 to 14, wherein only one lens group held by the holding member is used. This is a focus adjustment method for an image reading device, which is rotated in a circumferential direction. As described with reference to the embodiment shown in FIGS. 14 and 15, the lens is rotated by γ so that the influence of the lens eccentricity is reduced. At this time, the influence of the eccentricity is concentrated on one group by the configuration of the lens, and only the group is rotated by γ, so that the influence of the eccentricity of the assembly of the entire imaging lens system can be suppressed small, and the adjusting device itself is used. Can be simplified, and the adjustment process can be simplified.
[0050]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is the focus adjustment method of the image reading apparatus described above, wherein at least one of the reflection mirror and the imaging lens has an aspheric surface. It is characterized by the following.
[0051]
In general, when an aspherical lens is used, a great effect can be obtained for a specific aberration correction depending on where the aspherical lens is used. On the other hand, in the aspherical surface processing, a glass aspherical lens, a plastic aspherical lens, and a so-called hybrid aspherical lens in which an aspherical surface is formed by a thin resin layer on a glass spherical lens are usually processed by molding. Aspherical surface formation by molding makes it more difficult for the surface shape to be symmetrical with respect to the optical axis than spherical lens processing. If the surface is highly effective in correcting aberrations, the MTF in only the main scanning direction or only in the sub-scanning direction is significantly deteriorated. Alternatively, the moving direction of the image plane may be opposite in the main scanning direction and the sub-scanning direction. Therefore, when an aspherical surface is adopted, by adjusting the focus while viewing the MTF in both the main scanning direction and the sub-scanning direction, it is possible to bring out the performance of the imaging lens by 100%. Further, by adjusting the distance between the lenses while observing the MTFs in the main scanning direction and the sub-scanning direction, it is possible to obtain an imaging lens having better imaging performance.
[0052]
Still another embodiment of the adjustment method of the image reading apparatus according to the present invention is the focus adjustment method of the image reading apparatus according to the above embodiment, wherein the imaging lens has three positive lenses and two negative lenses, for a total of five lenses. A focus adjusting method for an image reading apparatus, wherein at least one surface of the imaging lens has an aspherical surface. For example, an imaging lens used in an image reading device used in a digital copying machine or the like requires high contrast in a high spatial frequency region, and has an aperture efficiency close to 100% up to the peripheral portion of the angle of view. Further, it is necessary to keep distortion aberration small. Furthermore, in order to read a color original satisfactorily, it is necessary to match the image forming positions of the red, green, and blue colors on the light receiving surface in the optical axis direction, and the chromatic aberration of each color must be corrected extremely well. .
[0053]
As such an imaging lens, a so-called Gaussian type having a four-group, six-element configuration as shown in FIGS. 13 and 15 is widely used. 13 and 15, the front lens group 27 includes a positive lens L1, a positive lens L2, and a negative lens L3, and the lenses L2 and L3 are joined. The rear lens group 28 includes a negative lens L4, a positive lens L5, and a positive lens L6, and the lenses L5 and L6 are cemented. The front lens group 27 and the rear lens group 28 are symmetrical. The Gaussian type can satisfactorily correct the curvature of field up to a half angle of view of about 20 °, and can suppress the occurrence of coma flare even with a relatively large aperture. However, since the number of constituent lenses is as large as six, the outer diameter of the lens becomes large, and there is a limit to miniaturization and cost reduction of the lens and a device using the lens.
[0054]
Therefore, in still another embodiment of the adjustment method of the image reading apparatus according to the present invention, a positive lens, a cemented lens of a negative lens and a positive lens, a diaphragm, a negative lens, and a positive lens are configured from the object side. Has an aspherical surface. With such a configuration, it is possible to satisfactorily correct the distortion by setting the lens configuration such that the power arrangement of the lens is substantially symmetric about the stop. Further, since the curvature of field in the main scanning direction and the sub-scanning direction can be accurately matched, the asymmetry of the point image distribution can be reduced, and the focus adjustment method in the sub-scanning direction according to claim 8. Can be widened. Further, by adjusting the aperture interval, it is possible to perform the field curvature correction without changing the symmetry of the coma aberration, and the F / NO. Is as bright as about 4.65 to 5.0, the aperture efficiency is close to 100% up to the periphery, the aberration is well corrected, the contrast is high in the high spatial frequency range, and it can be used for full-color reading. In addition, it is possible to configure a small and low-cost imaging lens and an apparatus using the same.
[0055]
Hereinafter, examples of the imaging lens of the present invention will be described. The meanings of the symbols in the examples are as follows.
f: synthetic focal length of e-line of the whole system
FNo: F number
m: Shrinkage
ω: half angle of view (degree)
Y: Object height
ri (i = 1 to 10): radius of curvature of the i-th lens surface counted from the object side
di (i = 1 to 9): i-th surface interval counted from the object side
nj (j = 1 to 6): refractive index of the material of the j-th lens counted from the object side
vj (j = 1 to 6): Abbe number of the material of the j-th lens counted from the object side
rc1: radius of curvature of the contact glass on the object side
rc2: radius of curvature of the contact glass on the image side
rc3: radius of curvature of the object side of the CCD cover glass
rc4: radius of curvature of the image side of the CCD cover glass
dc1: Contact glass thickness
dc3: thickness of CCD cover glass
nc1: Refractive index of CCD cover glass
nc3: refractive index of contact glass
vc1: Abbe number of contact glass
vc3: Abbe number of CCD cover glass
nd: refractive index of d-line
ne: refractive index of e-line
The aspheric surface is represented by the following equation.
X = ((1 / R) × Y²) / (1 + SQRT (1- (1 + K) × (Y / R)²)) + A4 × Y⁴+ A6 × Y⁶+ A8 × Y⁸+ A10 × Y¹⁰
here,
X: distance from the tangent plane to the aspherical vertex of the aspheric surface at a height Y from the optical axis
Y: Height from optical axis
R: paraxial radius of curvature of the aspherical surface
K: Conical multiplier
A4, A6, A8, A10: Aspheric coefficient
SQRT: Meaning of square root
In the numerical examples, E-XY is 10^-XYIs the meaning of
[0056]
18, FIG. 20, FIG. 22, and FIG. 24 showing the aberration of each embodiment, the line with the symbol e is the e-line (546.07 nm), the line with the symbol g is the g line (436.83 nm), The line with the symbol c indicates the c-line (656.27 nm), and the line with the symbol F indicates the F-line (486.13 nm). In the diagram of spherical aberration, a broken line indicates a sine condition, and in a diagram of astigmatism, a solid line indicates a sagittal ray and a dotted line indicates a meridional ray.
[0057]
Embodiment 1
f = 84.532, F = 5.01, m = 0.36222, Y = 152.4, ω = 19.0 °

<Aspherical surface coefficient>

FIG. 17 shows a configuration diagram, and FIG. 18 shows an aberration diagram. In FIG. 17, the lens includes, in order from the object side, a positive first lens L1, a positive second lens L2, a negative third lens L3, a negative fourth lens L4, and a positive fifth lens L5. Parallel plane plates are arranged on both sides of the lens system. The second lens L2 and the third lens L3 are cemented. An aperture is arranged between the third lens L3 and the fourth lens L4. The embodiments shown in FIGS. 19, 21 and 23 have the same basic configuration as above except for the specifications of each lens.
[0058]
Embodiment 2
f = 84.431, F = 5.06, m = 0.36222, Y = 152.4, ω = 19.0 °

<Aspheric coefficient>

FIG. 19 is a configuration diagram, and FIG. 20 is an aberration diagram.
[0059]
Embodiment 3
f = 84.285, F = 4.95, m = 0.36222, Y = 152.4, ω = 19.1 ゜

<Aspheric coefficient>

FIG. 21 is a configuration diagram, and FIG. 22 is an aberration diagram.
[0060]
Embodiment 4
f = 90.163, F = 4.65, m = 0.36222, Y = 152.4, ω = 17.9 °

<Aspheric coefficient>

FIG. 23 shows a configuration diagram, and FIG. 24 shows an aberration diagram.
[0061]
Still another embodiment of the focus adjustment method for an image reading apparatus according to the present invention is the focus adjustment method for any one of the image reading apparatuses described above, wherein at least one surface of the reflection mirror and the imaging lens has an optical axis. A focus adjustment method for an image reading apparatus, wherein the focus adjustment method has a non-coaxial shape. In recent years, as a higher performance imaging lens, as a means for matching the image plane position in the main scanning direction and the sub-scanning direction, a so-called anamorphic surface that is non-coaxial to the optical axis, There is a method used for an imaging lens. Since the anamorphic surface can correct aberrations in the main scanning direction and the sub-scanning direction separately, a very good imaging lens that accurately matches the main scanning and sub-scanning image planes is obtained at the design median. Can be However, since the main scanning direction and the sub-scanning direction change individually due to processing variations, the necessity of knowing the MTF in the main scanning direction and the sub-scanning direction is further increased as compared with the aspherical lens. According to the present invention, good performance can be obtained by performing focus adjustment and further correcting the field curvature by the air gap while observing the MTFs in the main scanning direction and the sub-scanning direction. Further, the anamorphic surface shape may be a spherical surface, but by making it aspherical, a lens with higher performance can be obtained.
[0062]
Still another embodiment of the focus adjustment method for an image reading device according to the present invention is the focus adjustment method for any of the image reading devices described above, wherein the imaging lens is fixed by adhesion after the focus adjustment. This is a focus adjustment method for an image reading apparatus. Conventionally, when an imaging lens is fixed to a mounting member, for example, a belt or the like is turned around the lens, and an end of the belt is fixed to the mounting member with a screw. However, in this method, if the belt is strongly tightened, the lens may be deformed and the imaging performance may be changed. The posture of the lens changes depending on how the screws are stopped, and the imaging performance also changes. Then, as shown in FIG. 25, a lens such as a V-block is fitted into a V-shaped groove of the mounting member 40 with a part of the lens barrel of the imaging lens 41, and the mounting member 40 and the lens barrel are bonded with an adhesive 42. It is good to fix with. Further, in bonding, as shown in FIG. 25A, the lens barrel and the mounting member 40 may be directly bonded with a part of the peripheral surface of the lens barrel fitted in the V-shaped groove. . As shown in FIG. 25B, an intermediate member 43 having an L-shaped cross section may be arranged along the lens barrel and the mounting member 40, and the lens barrel may be fixed by bonding through the intermediate agent 43. Furthermore, when a more precise optical system is required and a small amount of lens position change due to shrinkage generated when the adhesive is solidified becomes a problem, it is preferable to solidify the lens while holding it with a jig. By doing so, it is possible to accurately maintain the focus adjusted state.
[0063]
Further, as in the embodiment described above, the imaging lens is configured by a plurality of holding members, and at least one lens is moved in parallel to adjust the air gap between the lenses. When the screws are not used as described above, the lens barrels as the holding members can be fixed by bonding.
[0064]
Next, an embodiment of an image reading apparatus according to the present invention will be described. The embodiment of the image reading apparatus according to the present invention is an image reading apparatus that has been adjusted in focus by the focus adjustment method described above, and an example thereof is shown in FIG. In FIG. 26, a document 52 is arranged on a contact glass 51, and the document 52 is configured to be illuminated by an illumination optical system (not shown) arranged below the contact glass 51. The reflected light from the original 52 is laterally reflected by the first mirror 53a of the first traveling body 53, and is then turned back by the first mirror 54a and the second mirror 54b of the second traveling body 54 to form a reduced imaging lens. The image of the document 52 is formed on a line sensor 56 composed of a CCD by an imaging lens 55. When reading the longitudinal direction of the document 52, the first traveling body 53 moves at a speed of V in parallel with the contact glass 51 to a position indicated by reference numeral 53B, and at the same time, the second traveling body 54 It is configured to move to the position indicated by the reference numeral 54B at half the speed of 1/2 V and read the entire document 52. The focus of the imaging lens 55 of this image reading apparatus is adjusted by the above-described adjustment method.
[0065]
Another embodiment of the image reading apparatus according to the present invention is a color document reading apparatus characterized in that document information is read in full color by providing a color separation function in an arbitrary optical path of an optical system. For the color separation, a method of selectively inserting a color separation prism or a filter between the imaging lens 55 and the line sensor 56 composed of a CCD and performing color separation into R, G, and B may be used. , G, and B light sources are sequentially turned on to illuminate the original, and the original 52 is read for each color of each light source. Alternatively, a so-called three-line CCD in which light receiving elements having R, G, and B filters are arranged in three rows on one chip is used, and a color image is formed on the light receiving surface to perform color separation into three primary colors. May be used.
[0066]
An embodiment of the image forming apparatus according to the present invention is an image forming apparatus including the above-described image reading device. An example is shown in FIG. 27, the image forming apparatus includes an image reading device 200 and an image forming unit 100. The image forming unit 100 has the same configuration as a laser printer. The image reading apparatus 200 outputs the image information of the document 52 as an electric signal from the line sensor 56 by the same configuration and operation as the configuration of the apparatus described with reference to FIG. The image forming section 100 has a “photoconductive photoconductor formed in a cylindrical shape” as the latent image carrier 111. Around the latent image carrier 111, a charging roller 112 as a charging unit, a developing device 113, a transfer roller 114, and a cleaning device 115 are provided. "Corona charger" can also be used as the charging means. Further, there is provided an optical scanning device 117 that receives the document information from the line sensor 56 and performs optical scanning with the laser beam LB, so that “exposure by optical writing” is performed between the charging roller 112 and the developing device 113. Has become.
[0067]
27, reference numeral 116 denotes a fixing device, reference numeral 118 denotes a cassette, reference numeral 119 denotes a pair of registration rollers, reference numeral 120 denotes a paper feed roller, reference numeral 121 denotes a conveyance path, reference numeral 122 denotes a pair of paper discharge rollers, reference numeral 123 denotes a tray, and reference numeral P Denotes transfer paper as a recording medium. When performing image formation, the image carrier 111, which is a photoconductive photoconductor, is rotated clockwise at a constant speed, the surface thereof is uniformly charged by the charging roller 112, and the laser beam LB of the optical scanning device 117 is An electrostatic latent image is formed upon exposure by optical writing. The formed electrostatic latent image is a so-called “negative latent image”, and the image portion is exposed. This electrostatic latent image is reversely developed by the developing device 113, and a toner image is formed on the image carrier 111.
[0068]
The cassette 118 containing the transfer paper P is detachable from the main body of the image forming apparatus 100. When the cassette 118 is attached as shown in the figure, the top one of the stored transfer paper P is fed by the feed roller 120. The leading end of the fed transfer paper P is captured by the pair of registration rollers 119. The registration roller pair 119 feeds the transfer paper P to the transfer section at the same timing as the toner image on the image carrier 111 moves to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer portion, and the toner image is electrostatically transferred by the operation of the transfer roller 114. The transfer paper P on which the toner image has been transferred is sent to the fixing device 116, where the toner image is fixed by the fixing device 116, passes through the transport path 121, and is discharged onto the tray 123 by the discharge roller pair 122.
[0069]
The surface of the image carrier 111 after the transfer of the toner image is cleaned by the cleaning device 115 to remove residual toner, paper dust, and the like. The latent image carrier 111 is a photoconductive photoreceptor, and an electrostatic latent image is formed by uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image.
[0070]
【The invention's effect】
According to the first aspect of the present invention, the focus adjustment in the main scanning and the sub-scanning can be performed simultaneously using the folding mirror, the imaging lens, and the line sensor for photoelectric conversion, which are actually used. The optical system can be adjusted to the focus position where the lens has the best performance. Compared with the conventional image reading device, high-precision output is obtained in both the main scanning direction and the sub-scanning direction, which has been a problem in the past. Problems such as poor resolution in the sub-scanning direction can be solved. Furthermore, even if a shading correction plate is inserted in the optical system for shading, it is possible to adjust the focus in the main scanning direction and the sub-scanning direction in that state, and to achieve good imaging performance in actual use conditions. It is possible to demonstrate.
[0071]
Furthermore, by performing the magnification adjustment at the same time, it is possible to achieve a significant increase in the efficiency of the optical system adjustment process. As a result, the power required for the adjustment process can be significantly reduced, and this adjustment eliminates the need for MTF inspection on the lens unit alone, and significantly reduces the energy required for raw materials and processing involved in the production of lens inspection machines. And greatly contribute to global environmental conservation.
[0072]
According to the second aspect of the present invention, since the main scanning and the sub-scanning adjustment of each of the R, G, and B colors can be performed simultaneously for the adjustment of the color image reading apparatus, the highest performance of the imaging lens can be obtained for all the colors. It is possible to adjust the optical system to a good focus position, solve problems such as poor resolution in the sub-scanning direction, and realize a high-precision full-color reading device that does not cause color reproducibility or color blur. Obtainable.
[0073]
According to a third aspect of the present invention, in the invention of the second aspect, the image height of each color is further adjusted by using a combined MTF in the main scanning direction and the sub-scanning direction, so that a complicated focus adjustment operation of a full-color reading apparatus is performed. Can be performed very simply and in a short time, and a large improvement in adjustment efficiency can be achieved.
[0074]
According to the fourth aspect of the present invention, by moving the pattern parallel to the longitudinal direction of the line sensor, the MTF in the sub-scanning direction can be obtained without moving the traveling body of the reading device. There is no influence of vibration due to movement or jitter due to non-uniformity, and highly accurate adjustment is possible.
[0075]
According to the fifth aspect of the invention, by rotating the pattern parallel to the longitudinal direction of the line sensor at a constant speed, the MTF output in the sub-scanning direction can be always obtained in addition to the effect of the fourth aspect of the invention. Thus, the adjustment efficiency can be greatly improved.
[0076]
According to the sixth aspect of the present invention, since the sub-scanning adjustment chart is arranged on a plane and reciprocated, the MTF for the sub-scanning can be obtained. And power saving can be achieved.
[0077]
According to the seventh aspect of the invention, by synchronizing the moving speed of the sub-scanning adjustment chart with the reading speed of the reading device, highly accurate adjustment can be performed for any reading speed of the reading device. .
[0078]
The MTF in the sub-scanning direction can be obtained without moving the pattern parallel to the longitudinal direction of the line sensor and without moving the traveling body of the reading device. By setting the angle of the pattern within the range of the conditional expression, the MTF for sub-scanning can be obtained with high accuracy, so that high focus adjustment accuracy can be ensured and global environmental conservation can be achieved. Can greatly contribute to
[0079]
According to the ninth aspect of the present invention, when inspecting and adjusting the lens, the curvature of field can be adjusted by changing an arbitrary air gap of the lens. Variations in the image position and the imaging position at the periphery of the reading area can be adjusted, and good read image quality can be obtained over the entire reading area. In addition, even if the components other than the imaging lens, such as a folding mirror and a line sensor for photoelectric conversion, are warped and the focus position near the optical axis and the peripheral angle of view fluctuates, the air gap is adjusted. Since the curvature of field can be adjusted so that the MTF in the main scanning direction and the sub-scanning direction is the best, a very high-performance image reading optical system capable of correcting fluctuations of components other than the imaging lens is obtained. I can do it.
[0080]
According to a tenth aspect of the present invention, the imaging lens is rotated by γ at the time of focus adjustment, so that deterioration of imaging performance with respect to all image heights in the main scanning direction and the sub-scanning direction due to assembly decentering of the imaging lens is suppressed. And good reading performance can be obtained over the entire image plane.
[0081]
According to the eleventh aspect of the present invention, since each lens group for adjusting the air gap can be held by a separate holding member and the air gap between the holding members can be adjusted, the following effects can be obtained. it can.
(1) It is possible to eliminate troublesome lens dispersion and reassembly steps.
(2) Since the lens itself can be adjusted without shaking hands, it is possible to prevent dust from being mixed into the lens and contamination of the lens surface, which are expected to occur when the lens is reassembled. And the field curvature can be adjusted without special techniques required for assembly.
(3) Since the assembly eccentricity does not change, the position of the lens where the influence of the eccentricity is minimized does not change by the adjustment.
According to the above effects, it is possible to greatly reduce the steps of adjusting the air gap for correcting the curvature of field and adjusting the focus, thereby greatly reducing the adjustment cost.
[0082]
According to the twelfth aspect of the present invention, in addition to the effects of the eleventh aspect of the present invention, the mechanism for adjusting the focus adjustment device can be reduced by using one moving lens, and the configuration of the adjustment device itself can be simplified. And cost reduction, as well as improved adjustment efficiency and improved accuracy by reducing the number of adjustment points.
[0083]
According to the invention of claim 13, the drive mechanism for moving the lens for adjusting the air gap in the focus adjustment device is required to have high precision by providing the spigot portion so that the divided holding members fit each other. Therefore, it is possible to further simplify the adjusting device, reduce the cost, and further reduce the adjusting time.
[0084]
According to a fourteenth aspect of the present invention, in addition to the above-mentioned effects, a low-cost scanner optical system can be obtained for the lens barrel, and the metal cell can be manufactured by forming the cell to be divided according to the tenth aspect from resin. Since the related raw materials and processing energy can be reduced, it can greatly contribute to the protection of the global environment.
[0085]
According to the fifteenth aspect of the present invention, a thin image reading device can be obtained by making the holding member non-cylindrical.
In the invention according to claim 16, since the γ rotation of the lens when the divided holding member is used is performed by one lens, the γ rotation mechanism of the focus adjustment device can be reduced, and the adjustment machine can be simplified and The cost can be reduced, and the focus adjustment can be performed with high accuracy.
[0086]
According to a seventeenth aspect of the present invention, when an aspherical surface is introduced to improve the performance of an optical system, an asymmetrical component is generated on the optical axis due to a processing error of the aspherical surface. Even when the positions vary independently, the focus can be adjusted to the image plane position having the best balance between the main scanning and the sub-scanning, and the main scanning and the sub-scanning can be performed by correcting the field curvature by adjusting the air gap. Can be optimally corrected.
[0087]
According to the eighteenth aspect of the present invention, in addition to the effect of the seventeenth aspect, when an aspherical surface is used for the imaging lens, it is necessary to read the document information at high speed by configuring the number of lenses to five. It is possible to obtain, at low cost, an optimal lens for an image reading device for a digital copying machine, and to obtain an imaging lens having good performance even if air spacing is adjusted for field curvature correction. At the same time, glass materials and processing energy are reduced by reducing the number of lenses, and optical glass that is chemically stable and does not contain harmful substances such as lead and arsenic is used for all lens materials. It can greatly contribute to global environmental conservation by eliminating water pollution due to wastewater during processing.
[0088]
According to a nineteenth aspect of the present invention, the optical system has a so-called anamorphic surface which is non-coaxial with respect to an optical axis capable of individually correcting aberrations in the main scanning direction and the sub-scanning direction. It is possible to obtain an extremely high-performance optical system by matching the image plane positions, and even if the main scanning and sub-scanning image plane positions fluctuate due to anamorphic processing errors, the most balanced position Can be adjusted. In particular, when an anamorphic surface is used for the mirror, it is impossible to know the optimum focus position as an optical system by evaluating only the imaging lens or the mirror alone, but the present invention includes the mirror and the imaging lens. In addition to being able to adjust to the best focus position, by adjusting the air gap, it is possible to optimally correct the image plane position in the main scanning direction and the sub-scanning direction, including the processing error of the anamorphic mirror.
[0089]
According to a twentieth aspect of the present invention, when the lens adjusted by the focus adjusting method according to any one of the first to thirteenth aspects is fixed to a mounting member, the lens is fastened with a belt or the like by using an adhesive as a fixing means. It is possible to hold the lens while maintaining good performance, without causing lens deformation or lens movement occurring at the same time.
[0090]
According to the twenty-first to twenty-fourth aspects of the present invention, it is possible to provide an adjustment chart for an image reading apparatus suitable for carrying out the adjustment method according to the first to twentieth aspects, and to provide a main scanning direction and a sub-scanning direction. It is possible to provide an adjustment chart of the image reading apparatus capable of simultaneously adjusting the focus of the image reading apparatus.
[0091]
According to a twenty-fifth aspect of the present invention, an image reading apparatus having good read image quality can be obtained by incorporating the adjustment method according to any one of the first to nineteenth aspects into the image reading apparatus.
[0092]
According to a twenty-sixth aspect of the present invention, by providing the image reading device of the twenty-fifth aspect as an image reading device of an image forming apparatus, an image is formed on the basis of good read image quality, thereby forming a high-quality image. An image forming apparatus capable of performing the above-described operations can be obtained.
[Brief description of the drawings]
FIG. 1 is a characteristic diagram showing an example in which a horizontal axis represents a defocus, and a vertical axis represents an MTF as an index of a resolving power, and an MTF is measured on the axis and off-axis in each of the main scanning direction and the sub-scanning direction. is there.
FIG. 2 is a front view showing an example of an adjustment chart that can be used in the present invention together with a measurement optical system.
FIG. 3 is a front view showing another example of the adjustment chart that can be used in the present invention.
FIG. 4 is a characteristic diagram in which the MTF of each color and each image height when the line sensor is moved by a small amount in the depth of focus direction is measured, and the defocus amount is plotted on the horizontal axis and the MTF is plotted on the vertical axis.
FIG. 5 is a front view showing an example of a main scanning direction adjustment chart that can be used in the adjustment method according to the present invention.
FIG. 6 is a front view showing an example of a sub-scanning direction adjustment chart that can be used in the adjustment method according to the present invention.
FIG. 7 is a perspective view showing another example of a sub-scanning direction adjustment chart that can be used in the adjustment method according to the present invention.
FIG. 8 is a perspective view showing still another example of a sub-scanning direction adjustment chart that can be used in the adjustment method according to the present invention.
9A and 9B show still another example of a chart that can be used in the adjustment method according to the present invention, wherein FIG. 9A is a front view of a main scanning direction adjustment chart, and FIG. FIG. 9 is a perspective view in which sub-scanning direction adjustment charts are combined.
FIG. 10 is a perspective view showing still another example of a chart that can be used in the adjustment method according to the present invention.
FIG. 11 is a front view showing still another example of a sub-scanning direction adjustment chart that can be used in the adjustment method according to the present invention.
FIGS. 12A and 12B show still another example of a chart that can be used in the adjustment method according to the present invention, wherein FIG. 12A is an enlarged front view of the entire chart and FIG.
FIG. 13 is a sectional view showing an example of an imaging lens suitable for the present invention.
FIG. 14 is a perspective view showing another example of the imaging lens suitable for the present invention.
FIG. 15 is a sectional view showing still another example of the imaging lens suitable for the present invention.
FIG. 16 is a perspective view showing still another example of the imaging lens suitable for the present invention.
FIG. 17 is an optical arrangement diagram showing an embodiment of an imaging lens suitable for the present invention.
FIG. 18 is an aberration curve diagram of the example.
FIG. 19 is an optical layout diagram showing another embodiment of the imaging lens suitable for the present invention.
FIG. 20 is an aberration curve diagram of the example.
FIG. 21 is an optical arrangement diagram showing still another embodiment of the imaging lens suitable for the present invention.
FIG. 22 is an aberration curve diagram of the example.
FIG. 23 is an optical arrangement diagram showing still another embodiment of the imaging lens suitable for the present invention.
FIG. 24 is an aberration curve diagram of the example.
FIG. 25 is a side view showing an example of an imaging lens fixing structure suitable for application to the present invention.
FIG. 26 is an optical layout diagram schematically showing an embodiment of the image reading apparatus according to the present invention.
FIG. 27 is an optical layout diagram schematically showing an embodiment of the image forming apparatus according to the present invention.
[Explanation of symbols]
1 Main scanning direction adjustment chart
2 Sub-scanning direction adjustment chart
4 Shozo Lens
5 Line sensor
52 manuscript
53a folding mirror
54a folding mirror
54b folding mirror
55 imaging lens
56 line sensor

Claims (26)

An illumination system for illuminating the original, at least one folding mirror for guiding a reflected image from the original to the imaging lens, an imaging lens for reducing and forming the reflected image from the original, and an imaging lens In an adjustment method in an image reading apparatus having a line sensor for reading a document that photoelectrically converts the copied document image,
An adjustment chart in the main scanning direction and the sub scanning direction is arranged on the document surface, and the adjustment chart is imaged on a line sensor by the imaging lens,
A method for adjusting an image reading apparatus, wherein focus adjustment is performed so that MTFs in a main scanning direction and a sub-scanning direction simultaneously satisfy a predetermined value. 2. The image reading apparatus according to claim 1, wherein the line sensor includes a plurality of sensors in which filters for color separation are arranged in front of the sensor, and the plurality of line sensors are arranged in the sub-scanning direction. And adjusting the focus so that the MTFs of the plurality of line sensors in the main scanning direction and the sub-scanning direction simultaneously satisfy a predetermined value. 3. The image reading apparatus according to claim 2, wherein MTFs of the image heights of the plurality of line sensors in all of the main scanning direction and the sub-scanning direction are combined, and the focus is adjusted by the combined MTF. Adjustment method. The adjustment method for an image reading device according to any one of claims 1 to 3, wherein the sub-scanning direction adjustment chart moves patterns arranged at regular intervals in parallel with the longitudinal direction of the line sensor. Adjustment method for image reading device. 5. The adjustment method for an image reading device according to claim 4, wherein the plurality of sub-scanning direction adjustment charts are rotated at a constant speed in the same direction. 5. The method according to claim 4, wherein the sub-scanning direction adjustment chart reciprocates in the sub-scanning direction. 7. The adjustment method for an image reading apparatus according to claim 5, wherein the movement of the sub-scanning direction adjustment chart is synchronized with a reading cycle of the line sensor. In the adjustment method of the image reading device according to any one of claims 1 to 3, the adjustment chart in the sub-scanning direction is arranged to be inclined at a small angle with respect to the longitudinal direction of the line sensor. A method for adjusting an image reading apparatus, wherein the following condition is satisfied.
θ <MTF (H) / MTF (L) × 45
Where θ is the inclination angle (unit: degree) of the sub-scanning adjustment chart with respect to the direction parallel to the line sensor length, and MTF (H) is the sagittal direction and meridional direction at an arbitrary angle of view and defocus position of the imaging lens. Higher MTF value, MTF (L): Lower MTF value in the sagittal direction and meridional direction at an arbitrary angle of view and defocus position of the imaging lens 9. The adjustment method for an image reading apparatus according to claim 1, wherein at the time of focus adjustment, an arbitrary air interval of the imaging lens is changed to correct a field curvature. Method. The method for adjusting an image reading device according to claim 1, wherein the lens is rotated in a circumferential direction during focus adjustment. 11. The image reading apparatus according to claim 9, wherein the image forming lens is held by at least two lens holding members, and an arbitrary air gap between the lenses held by the holding members is changed. A method for adjusting an image reading apparatus, comprising correcting a surface curvature. The method for adjusting an image reading device according to claim 11, wherein only one holding member is moved. The method for adjusting an image reading device according to claim 11, wherein the plurality of holding members have spigots. The method for adjusting an image reading device according to claim 1, wherein the holding member is a resin lens barrel. 15. The method according to claim 14, wherein the outer shape of the holding member is a non-cylindrical shape. The method for adjusting an image reading device according to claim 10, wherein only one lens group held by the holding member is rotated in a circumferential direction. The method for adjusting an image reading device according to claim 1, wherein at least one surface of the reflection mirror and the imaging lens is an aspheric surface. 18. The method for adjusting an image reading device according to claim 17, wherein the imaging lens has a total of five lenses including three positive lenses and two negative lenses, and at least one surface of the imaging lens is an aspheric surface. Adjustment method for image reading device. The method for adjusting an image reading device according to claim 1, wherein at least one surface of the reflection mirror and the imaging lens has a non-coaxial shape. 20. The method for adjusting an image reading device according to claim 1, wherein the imaging lens is fixed by adhesion after focus adjustment. It is composed of a main scanning direction adjustment chart and a sub-scanning direction adjustment chart in which a plurality of straight lines are arranged in a stripe shape, and the main scanning direction adjustment chart is one in which a plurality of straight lines in the sub-scanning direction are arranged in the main scanning direction. The chart in the sub-scanning direction is an adjustment chart of the image reading apparatus in which a plurality of straight lines in the main scanning direction are arranged in the sub-scanning direction. 22. The adjustment chart of the image reading apparatus according to claim 21, wherein there are a plurality of main scanning direction adjustment charts and a plurality of sub-scanning direction adjustment charts, and the plurality of charts are dispersedly arranged in the main scanning direction. 23. The adjustment chart of the image reading device according to claim 21, wherein the sub-scanning direction adjustment chart is provided so as to be movable in the sub-scanning direction. 23. The adjustment chart of the image reading device according to claim 21, wherein a plurality of straight lines constituting the sub-scanning direction adjustment chart are slightly inclined with respect to the main scanning direction. It has an illumination system for illuminating the original, an imaging lens for reducing and forming the reflected light of the original illuminated by the illumination system, and a line sensor for photoelectrically converting the original image formed by the imaging lens. An image reading apparatus, wherein the focus adjustment of the image reading apparatus is performed by the adjustment method according to any one of claims 1 to 20. An image forming apparatus for forming an image corresponding to an image information signal read by the image reading apparatus, comprising: the image reading apparatus according to claim 25 as the image reading apparatus.

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