JP4018894B2 - Optical scanning device - Google Patents

Description

（ただしφが小さいとき。以下、数式２という。）となる。従って数式２より角度φを設定することにより、被走査面５でのビ-ムスポット位置、すなわち複数ビ-ムの場合にはビ-ムピッチを設定することが可能となる。
【００２５】
図４（Ａ）〜（Ｃ）は、光源モジュ-ル１２（１２ａ、１２ｂ）の構成例を示す。図中１３はレンズホルダ、１４は接着剤、１５はレンズセル、１６はレンズホルダ、１７はベース部材、１８は押さえ板である。
【００２６】
図４（Ａ）は、光源モジュ-ル１２の機能を単純に示した図であるが、光ビ-ムを出射する機能を有するモジュ-ルであればどのような形態のものでも構わない。図４（Ｂ）においては、半導体レ-ザ６はレンズホルダ１３に圧入等の工法により固定し、カップリングレンズ７は接着剤１４等により固定する。半導体レ-ザ６とカップリングレンズ７の位置合わせは、以降の光学系の特性に応じ、その出射ビ-ム１１の光軸方向及びコリメ-ト性が所定値になるようにカップリングレンズ７の位置を調整する。図４（Ｃ）においては、半導体レ-ザ６はベース部材１７に押さえ板１８に固定し、カップリングレンズ７は雄ねじ部を有するレンズセル１５に接着等により固定する。これらベース部材１７及びレンズセル１５は共通のレンズホルダ１６に、半導体レ-ザ６とカップリングレンズ７の相対位置関係が所定値になるように固定する。半導体レ-ザ６を固定したベース部材１７は、図の紙面上下方向及び図の紙面に垂直な方向に移動し、カップリングレンズ７を固定したレンズセル１５は、図の紙面の左右方向に移動する。このことで、半導体レ-ザ６とカップリングレンズ７との相対位置関係を調整できる。
【００２７】
なお上述の半導体レ-ザ６、６ａ、６ｂは、シングルビ-ムを出射するシングルビ-ム半導体レ-ザでも構わないし、複数のレ-ザ光を出射するマルチビ-ム半導体レ-ザであっても構わない。
【００２８】
ところで、組立工場等における上述のような光走査装置２０の組み立て時には、被走査面５における複数ビ-ム間のビ-ムピッチを所定値に初期調整する必要がある。ところが、
（１）光源モジュ-ル１２の組み立て調整誤差（半導体レ-ザ６とカップリングレンズ７の位置合わせ誤差）
（２）保持部材に対する光源モジュ-ル１２の組み付け誤差
（３）ビ-ム合成プリズム９における光軸ぶれ
等の影響により、合成された２本の光ビ-ム１１ａ、１１ｂ間の角度φが所定値（設定値）より大きくずれてしまうことがあり、被走査面５におけるビ-ムピッチを所定値に初期調整することが不可能な場合がある。このような場合には、光路中に配設された出射方向変更手段８ａ、８ｂを用いて、角度φを調整することにより、ビ-ムピッチを所定値に調整する。
【００２９】
一方、工場出荷後、ユ-ザ等の使用中に環境（温度）変化又は経時的な影響等により、ビ-ムピッチの初期調整値が変動してしまうことがあり得る。このような場合にも、出射方向変更手段８ａ、８ｂを用いることにより、変動したビ-ムピッチを補正することができる。
【００３０】
しかしながら、
（Ａ）初期調整時に必要な調整量と、
（Ｂ）ユ-ザ等の使用中に環境変動等により発生するビ-ムピッチ変動を補正するのに必要な調整量、
とは、調整量（必要な調整ストロ-ク及び分解能）が大きく異なる場合が多く、単一の出射方向変更手段、または同じ構成の（複数の）出射方向変更手段では、調整量（Ａ）、（Ｂ）を同時に達成することが困難である場合が多かった。
【００３１】
この問題を、カップリングレンズ７の焦点距離ｆｃｏｌ＝１５［ｍｍ］、走査光学系全系の副走査横倍率ｍＺ＝５．３倍の光走査装置を例に説明する。
調整量（Ａ）：上記（１）〜（３）による角度φの設定値からのずれ量ΔφＡは、経験的に（最大で）、ΔφＡは２０［’］＝５．８［ｍｒａｄ］程度である。なお、これをビ-ムピッチ変動量Δｚに換算すると、上記数式２により、

である。
調整量（Ｂ）：環境変動等によるビ-ムピッチ変動Δｚは、経験的に（最大で）、

程度であり、これを出射光軸のずれ量ΔφＢに換算すると、上記数式２により、

である。
【００３２】
従って、上記調整量（Ａ）、（Ｂ）より、両者の調整量の比（ΔφＡ／ΔφＢ）＝４６であり、両方の調整を、単一の出射方向変更手段、または同じ構成の複数の出射方向変更手段で行うことは困難であることが理解できる。
【００３３】
ここで、ビ-ムピッチの初期調整とフィ-ドバック調整について説明する。図５（Ａ）〜（Ｃ）は、被走査面５におけるビ-ムスポットＢｓの配列の一例（２ビ-ム走査装置の場合：１２００ｄｐｉ）を示す図である。
【００３４】
ビ-ム合成後の２光ビ-ムのなす角度φの誤差（半導体レ-ザとカップリングレンズの位置合わせ誤差、保持部材に対する光源モジュ-ルの組付誤差、ビ-ム合成プリズムにおける光軸ぶれ等に起因する光軸ずれ）により、光書込装置の組立時（初期調整前）には、被走査面５上のビ-ムピッチは、およそ１００〜５００μｍ程度になる（図５（Ａ）参照）。ビ-ムピッチを所定値（例えば走査密度が１２００ｄｐｉの場合には２１．２μｍ：図５（Ｂ）参照）に初期調整（粗調整）するには、感度の高い出射方向変更手段を用いればよい。温度変化／経時的要因等によりビ-ムピッチが変動した場合（変動量Δｐ＝１０〜２０μｍ程度：図５（Ｃ）参照）には、この変動量を検出し、感度の低い出射方向変更手段を用いてフィ-ドバック調整を行えばよい。また、感度の高い出射方向変更手段では分解能が不足し、所定値に初期調整できない場合には、感度の低い出射方向変更手段を初期調整に補助的に用いても構わない。
【００３５】
既述のように、出射方向変更手段の調整量（変動量）に対する被走査面でのビ-ムスポット位置の移動量、すなわち「感度」に関し、一方の出射方向変更手段８ａの感度と他方の出射方向変更手段８ｂの感度とを異ならせることにより、上記（Ａ）、（Ｂ）のような互いに異なる感度を必要とする２つの調整を容易に行うことが可能となる。すなわち、調整感度の高い側をビ-ムピッチの初期調整（Ａ）に用い、調整感度の低い側をビ-ムピッチ変動の補正（Ｂ）に用いればよいからである。
【００３６】
図示の実施形態の場合、図２において示した２つの出射方向変更手段８ａ、８ｂを異なる光ビ-ム１１ａ、１１ｂの光路に配設しているが、２の出射方向変更手段８ａ、８ｂをどちらか一方の光路に配設しても構わない。
【００３７】
なお、被走査面５におけるビ-ムスポット配列（ビ-ムピッチ）を検出する手段を光走査装置２０に設けておくことにより、ユ-ザ等による使用中のビ-ムピッチ変動を検出することができる。検出手段としては、フォトダイオ-ド等を用いて電気的に検出しても構わないし、本実施形態の光走査装置２０を画像形成装置の光書込装置として使用した場合には、その出力画像を利用して検出しても構わない。フォトダイオ-ド等を用いて電気的にビ-ムピッチ（変動量）を検出する構成の場合には、その検出信号に基づき、目標値との比較演算をすることにより、出射方向変更手段８ａ、８ｂを駆動するための入力信号を得ることができる。少なくとも感度の低い側の出射方向変更手段にこのような構成を付加することにより、自動的にビ-ムピッチ変動を補正（フィ-ドバック調整）することが可能となる。また出力画像を利用して検出した場合には、ユ-ザ又はサ-ビスマン等が、画像出力装置に設けられた走査パネル等から入力して補正することができる。感度の高い側の出射方向変更手段にこのようなフィ-ドバック調整機構を設ければ、工場での光走査装置の組立時のビ-ムピッチの初期調整も自動化可能となる。
【００３８】
次に出射方向変更手段の構成について説明する。
図６は、出射方向変更手段として光路内に配設された透過型光学素子を偏心させる構成の例を示す図である。図中２１は三角プリズムである。小さい頂角θ１を有する三角プリズム（内部屈折率：ｎ）２１を通過した光ビ-ムは、その出射角度を角度β１を、
β１＝（ｎ−１）×θ１
だけ変更される。従って三角プリズム２１を、光ビ-ムの光軸を回転軸として角度γ１だけ回転させることにより、出射ビ-ムの副走査方向成分φ１は、

だけ変化させることができる。そして、三角プリズム２１の配置角度の調整量γ１に対する、被走査面５でのビ-ムスポットの変位量（副走査方向）Δｚは、上記数式２より、

（以下、数式３という）となる。
【００３９】
例えば、ｍＺ＝５．３倍、ｆｃｏｌ＝１５［ｍｍ］、ｎ＝１．５、θ１＝１．５［°］＝０．０２６１８［ｒａｄ］の場合には、上記数式３は、
Δｚ＝１．０４×ｓｉｎ（γ１）［ｍｍ］
（以下、数式３−１という）となり、三角プリズム２１の角度γ１を-９０°から＋９０°まで回転させることにより、ビ-ムスポットの位置Δｚを±１［ｍｍ］程度の範囲で調整することができる。
【００４０】
三角プリズム２１の回転には、例えば図９に示すウォ-ム＆ホイ-ルを利用した減速機構を用いることができ、それにより、調整ストロ-クが広く、かつ調整分解能の小さい、すなわちダイナミックレンジの広い調整機構を実現することができる。この機構は、全周に歯車（ホイ-ル３２）が形成されたプリズムホルダ３１に三角プリズム２１を保持し、ステッピングモ-タ３４等により駆動されるウォ-ム３３により、三角プリズム２１を回転させる。
【００４１】
ステッピングモ-タ３４の基準ステップ角度ｓ＝１８［°］、ウォ-ムのピッチｗ＝０．５［ｍｍ］、ホイ-ルの半径ｒ＝２０［ｍｍ］の場合（図９（Ｂ））、１ステップ当たりの三角プリズム２１の回転角度Δγ１とすると、
ｓｉｎ（Δγ１）＝［（ｓ／３６０゜）×ｗ］／ｒ
＝［（１８゜／３６０゜）×０．５］／２０
＝０．０２５／２０＝０．００１２５
より、
Δγ１＝０．０７１６［°］＝４．３［’］
となる。上記数式３−１にてγ１＝Δγ１とすると、
Δｚ＝０．００１３［ｍｍ］＝１．３［μｍ］
であり、分解能Δｚ＝１．３［μｍ］にて調整することができる。
【００４２】
なお図示の構成では、ウォ-ム＆ホイ-ルを利用しているため、三角プリズム２１は３６０°回転可能であり、そのため調整範囲は上述のように数式３−１より、±１．０４［ｍｍ］となる。
【００４３】
図６に示すように、単一の三角プリズム２１のみで出射方向変更手段を構成する場合には、出射ビ-ムの副走査方向成分だけではなく、主走査方向成分も変化してしまう。これを回避するためには、図７に示すように２つの三角プリズム２１を直列に並べ、それらを互いに反対向きに回転させることで、光ビ-ムの出射角度を特定の平面内にて変化させることが可能となる。
【００４４】
図８の光路内に配設された反射型光学素子を偏心させる構成である出射方向変更手段の例を説明する。本例は、図２における出射方向変更手段８ａ、８ｂを、それぞれ三角プリズム２１（透過型光学素子）及びガルバノミラ-（反射型光学素子）２２とした構成である。出射方向変更手段８ａ（三角プリズム２１）側では、上述した出射方向変更手段の構成（１）での検討が適用できる。一方、出射方向変更手段８ｂ（ガルバノミラ-２２）側では、ガルバノミラ-２２の配置角度の調整量をβ２とすると、光ビ-ム１１ｂの反射後の出射方向は、φ２＝２×β２だけ変化させることができる。従って、ガルバノミラ-２２の配置角度の調整量β２に対する、被走査面上５のビ-ムスポットの変位量Δｚ（副走査方向）は、上記数式２より、

（以下、数式４という）となる。
【００４５】
いま図９の出射方向変更手段８ｂ（ガルバノミラ-２２）側において、ステッピングモ-タ３４の基準ステップ角度ｓ＝３．６［°］、ウォ-ム３３のピッチｗ＝０．３［ｍｍ］、ホイ-ル３２の半径ｒ＝１５［ｍｍ］の場合（ｍＺ＝５．３倍、ｆｃｏｌ＝１５［ｍｍ］）、１ステップ当たりのガルバノミラ-２２の回転角度Δβ２とすると、

より、

となる。上記数式４にてβ２＝Δβ２とすると、

であり、分解能Δｚ＝３１．８［μｍ］にて調整することができる。
【００４６】
そこで、工場での組立時のビ-ムピッチの初期調整を感度の高い出射方向変更手段８ｂ（ガルバノミラ-２２）側で行い、ユ-ザ使用時のビ-ムピッチ変動の補正（望ましくは、ビ-ムピッチ変動の検出結果に基づきフィ-ドバック補正する）には、感度の低い出射方向変更手段８ａ（三角プリズム２１）側で行えばよい。初期調整（ガルバノミラ-２２側）の分解能（３１．８μｍ）では不十分の場合には、補助的に、三角プリズム２１側の調整を付加すればよい。
【００４７】
出射方向変更手段のさらに他の構成を図１０に示す。光ビ-ムの出射方向を可変する他の手段として、光源モジュ-ルの取り付け姿勢を変化させる構成を採用したもので、図示のように、光源モジュ-ル１２を副走査断面内（または副走査断面の成分を有する平面内）にて傾ければよいものである。
【００４８】
あるいは図１１に示すように、出射ビ-ム１１とはわずかに偏心した回転軸ｒ回りに光源モジュ-ル１２を回転させることにより、出射ビ-ム１１の副走査方向成分を可変することができる。いま光源モジュ-ル１２の回転軸ｒと出射ビ-ム１１のなす角度をθ２、光源モジュ-ル１２の回転角度をγ２とすると、出射ビ-ムの副走査方向成分φ３は、
φ３＝ｔａｎ（θ２）×ｓｉｎ（γ２）
にて表される。従って、光源モジュ-ル１２の回転角度γ２に対する、被走査面５でのビ-ムスポットの変位量（副走査方向）Δｚは、上記数式２より、

（以下、数式５という。）となる。
【００４９】
出射方向変更手段としては、光源モジュ-ル１２が、少なくとも半導体レ-ザとカップリングレンズから構成されている場合には、半導体レ-ザとカップリングレンズの（副走査方向の）相対位置を可変する構成を採用することができる。この構成では、相対位置の変位量（副走査方向成分）Δδに対する、被走査面５でのビ-ムスポットの変位量（副走査方向）Δｚは、Δｚ＝ｍＹ×Δδとなる。
【００５０】
また出射方向変更手段としては、光源モジュ-ル１２が、少なくとも半導体レ-ザ６とカップリングレンズ７から構成されている場合には、半導体レ-ザとカップリングレンズの間に平行平板（平行平板ガラス）を配設し、この平行平板を少なくとも副走査断面の成分を有する平面内にて傾ける構成を採用することができる。
【００５１】
すなわち図１２に示すように、半導体レ-ザ６とカップリングレンズ７の間に配設される平行平板２３の厚さをｔ、内部屈折率をｎ、副走査断面内の傾き角度をβ３とすると、平行平板２３による光ビ-ム１１のシフト量Δδ１は、
Δδ１＝ｔ×β３×［１−（１／ｎ）］
にて表される。従って、平行平板２３の傾き角度β３に対する、被走査面５でのビ-ムスポットの変位量（副走査方向）Δｚは、上記数式１より、

（以下、数式６という。）となる。
【００５２】
図１３は、本発明に係る光走査装置の第２実施形態に用いる光源装置のを示す図であり、図中４０は（４ビ-ム）光源装置、４１は第１の光源モジュ-ル、４２は第２の光源モジュ-ル、４３はベース部材、４４はビ-ム合成プリズム、４５はテ-パ付きねじ、４６は鋼球、４７は第１の出射方向変更手段、４８は第２の出射方向変更手段、４９は第３の出射方向変更手段、５０は第４の出射方向変更手段、５１はホルダ部材、５２ａ、５２ｂ、５２ｃはステッピングモ-タである。
【００５３】
図１３（Ａ）に示す光源装置４０の分解斜視図において、２対の半導体レ-ザ６とカップリングレンズ７がベース部材４３に固定され、第１の光源モジュ-ル４１を構成している。第１の光源モジュ-ル４１は、それと同構成の第２の光源モジュ-ル４２とともに、ホルダ部材５１に回動可能に固定する。第１の光源モジュ-ル４１から出射した２本の光ビ-ムと第２の光源モジュ-ル４２から出射した２本の光ビ-ムは、ビ-ム合成プリズム４４により、互いに近接して合成される。ビ-ム合成プリズム４４による合成は、ハ-フミラ-を用いる方法でも良いし、レ-ザ光のもつ偏向特性を利用したものでも構わない。合成した４本の光ビ-ムは、図示しないアパ-チャにより整形する。
【００５４】
第１、第２の光源モジュ-ル４１、４２、ビ-ム合成プリズム４４、ホルダ部材５１等で光源装置４０を構成する。光源装置４０は、一体化したユニット構成とすることが可能であり、そうすれば半導体レ-ザの劣化等により、光源装置４０を交換する必要が生じた場合でも容易に対応できる。また光源装置４０には、図１３（Ｂ）に示すように、テ-パ付きねじ４５と鋼球４６からなる第１の出射方向変更手段４７が設けてある。
【００５５】
図１４は、この実施形態におけるビ-ムスポットの位置を示す図で、走査密度１２００ｄｐｉ時の、被走査面におけるビ-ムスポットＢＳ１〜ＢＳ４の配置を示したものである。図中ＢＳ１及びＢＳ４は、第１の光源モジュ-ル４１から出射される２本の光ビ-ムに対応するビ-ムスポット、ＢＳ２及びＢＳ３は、第２の光源モジュ-ル４２から出射される２本の光ビ-ムに対応するビ-ムスポット、Ｃ１はＢＳ１とＢＳ４の中央位置、Ｃ２はＢＳ２とＢＳ３の中央位置である。またｑ１はＢＳ１とＢＳ４の間隔（ビ-ムピッチ）で、目標値は、３×ｑｒ＝３×２１．２＝６３．５［μｍ］、ｑ２はＢＳ２とＢＳ３の間隔（ビ-ムピッチ）で、目標値は、ｑｒ＝２１．２［μｍ］、ｑ３はＣ１とＣ２の間隔で目標値は、０［μｍ］、ｑｒは１２００ｄｉｐでの走査線間隔（２１．２μｍ）である。
【００５６】
光走査装置に光源装置４０を組み付けた状態（仮組立時；初期調整前）においては、図１４（Ｂ）に示すように各ビ-ムスポットＢＳ１〜ＢＳ４は無秩序に配列している。この状態から、図１４（Ａ）に示す各ビ-ムスポット間隔（ビ-ムピッチ）が等しくなるように調整するためには、まず第１の出射方向変更手段４７によりｑ３を粗調整した後、第２から第４の出射方向変更手段４８〜５０によりｑ１〜ｑ３を各目標値になるように微調整する。初期調整時には、ビ-ムピッチを検出した後、手動にて各出射方向変更手段を駆動してもよいし、光源装置が備えるステッピングモ-タにより駆動しても構わない。温度変化や経時的要因の影響によりビ-ムピッチが変動した場合には、ビ-ムピッチ（変動）を検出し、その検出結果に基づき第２〜第４の出射方向変更手段４８〜５０をフィ-ドバック制御すればよい。従って初期調整時（組立時）に利用する第１の出射方向変更手段４７はフィ-ドバック機構を有する必要はなく、例えばスクリュ-ドライバ等により手動にて駆動する構成であっても構わない。
【００５７】
また共通のベース部材４３に２対の半導体レ-ザとカップリングレンズを固定した構成の光源モジュ-ルの場合、半導体レ-ザとカップリングレンズの相対位置合わせ調整（いわゆる光軸・コリメ-ト調整）を、使用するビ-ム合成プリズム４４を付加した調整機にて行うことにより、初期調整を困難にする原因である、既述の光源モジュ-ルの組立調整誤差、保持部材に対する光源モジュ-ルの組み付け誤差、ビ-ム合成プリズムにおける光軸ぶれのうち、組立調整誤差と組み付け誤差の影響を効果的に除去することが可能となる。そのため、同一の光源モジュ-ル内のビ-ムスポット間隔（ｑ１、ｑ２）は、仮組立状態でも比較的所定値に近く、感度の高い出射方向変更手段は必要としない。
【００５８】
以下、具体的に説明する。
第１の出射方向変更手段４７は、被走査面でのビ-ムスポットＢＳ２、ＢＳ３の中央位置Ｃ２を移動させて、「ビ-ムスポットＢＳ１、ＢＳ４の中央位置Ｃ１」と「中央位置Ｃ２」との相対位置合わせを行う。すなわち図１４（Ｂ）のｑ３を可変させる。テ-パ付きねじ４５を押し込みまたは引き抜くことにより、鋼球４６を介して第２の光源モジュ-ル４２を図に示すβ方向に姿勢を変化させることができる。これにより第２の光源モジュ-ル４２から出射する２本の光ビ-ムの出射角度、すなわちＣ１の位置を調整できる。
【００５９】
第２の光源モジュ-ル４２を出射する２本の光ビ-ムの出射角度を調整する第１の出射角度調整手段４７の動作について、図１３（Ｃ）を用いて説明する。テ-パ付きねじ４５のテ-パ角度（２×θ３）を２０°、ねじのピッチｐを０．３［ｍｍ］、第２の光源モジュ-ル４２の（副走査断面内の）回転軸（支点）から鋼球（力点）までの距離をｒ３＝２０［ｍｍ］とし、テ-パ付きねじ４５を基本ステップ角ｓ＝７．５°の図示しないステッピングモ-タにより駆動するものとすると、ステッピングモ-タの１ステップに対するテ-パ付きねじ４５の押し込み量（引き抜き量）ｕは

なので、このときの鋼球４６の移動量（左右方向）ｖは、

となる。このときの第２の光源モジュ-ル４２のβ偏心量をβ３とすると、ｔａｎ（β３）＝ｖ／ｒ３＝０．００１８／２０であり、被走査面上のビ-ムスポットＢＳ２、ＢＳ３の移動量Δｚは、（式２）より、

となる。すなわち７．３［μｍ］の分解能で２つのビ-ムスポットＢＳ２、ＢＳ３を同時に副走査方向に移動調整することができる。
【００６０】
また光源装置４０は、第１の光源モジュ-ル４１から出射される２本の光ビ-ムの被走査面上のビ-ムスポットＢＳ１、ＢＳ４の間隔ｑ１を調整するために、第２の出射方向変更手段４８を備える。この第２の出射方向変更手段４８は、図１３（Ｄ）に示すように、第１の光源モジュ-ル４１が出射する２本の光ビ-ムの二等分線に平行な軸γ４を回転軸として回転可能な構成となっている。すなわち図１１に示す出射方向変更手段を適用したものとなっている。図１３（Ｄ）においては、ビ-ム合成プリズム４４にて折り返される光ビ-ムを展開して示す。
【００６１】
すなわち、ビ-ム間の光学特性の偏差が発生することを抑制するため、４本の光ビ-ムはポリゴンミラ-３の偏向反射面付近にて交差する構成としてある。具体的には、第１の光源モジュ-ル４１から出射する２本の光ビ-ムのなす角度を２×α１、第２の光源モジュ-ル４２から出射する２本の光ビ-ムのなす角度を２×α２、各光源モジュ-ル４１、４２から出射する２本の光ビ-ムの二等分線のなす角度を２×α３とし、
２×α１＝２×α２＝３［°］
２×α３＝５［°］
に設定してある。
【００６２】
いま、ねじピッチｐ＝０．５［ｍｍ］のねじと組み合わせたステッピングモ-タ５２ａ（基本ステップ角ｓ＝７．５°）により、回転軸からｒ４＝２０［ｍｍ］の力点にて、第１の光源モジュ-ル４１を作動させることで、第１の光源モジュ-ル４１の回転駆動を行う構成である場合を考えると、ステッピングモ-タ５２ａの１ステップに対する力点の作動量ｕは、

なので、このときの第１の光源モジュ-ル４１のγ回転量をγ４とすると、

であり、被走査面上の２つのビ-ムスポットＢＳ１、ＢＳ４の間隔の変動量Δｑ１は、上記数式５により、θ２＝α１として、

（以下、数式７という。）となり、数値的には、

となる。
【００６３】
なお、図１３（Ａ）、（Ｂ）に示す構成によれば、第１の光源モジュ-ル４１の回転中心は、２つのカップリングレンズ７、７の光学軸の中間部（図１３（Ｂ）のγで表される回転軸に相当する）に位置することになるが、ビ-ム合成プリズム４４にて合成された後の２本の光ビ-ムの二等分線（図１３（Ｄ）のγ４で示される回転軸）回りに回転する構成とすることが望ましい。
【００６４】
また光源装置４０には、第２の光源モジュ-ル４２から出射する２本光ビ-ムの被走査面上のビ-ムスポットＢＳ２、ＢＳ３の間隔ｑ３を調整するために、第３の出射方向変更手段４９を備えている。この第３の出射方向変更手段４９の構成及び作用（調整メカニズム）は、上述の第２の出射方向変更手段４８と同一である。
【００６５】
さらに、光源装置４０が備える第４の出射方向変更手段５０により、第１の出射方向変更手段４７と同様に、被走査面におけるビ-ムスポットの中央位置Ｃ１、Ｃ２の相対位置合わせ（ｑ３の調整）を行うことができる。第４の出射方向変更手段５０の構成及び作用（調整メカニズム）は、第２、第３の出射方向変更手段４８、４９と同じであり、第１の出射方向変更手段４７とは異なる。
【００６６】
すなわち、第４の出射方向変更手段５０おいて、ステッピングモ-タ５２ｃの基本ステップ角ｓ、回転軸から力点までの距離ｒが第２の出射方向変更手段４８と同じ構成である場合には、上記数式７のα１をα３に置き換えれば、ステッピングモ-タ５２ｃの１ステップに対する、被走査面におけるビ-ムスポットの中央位置Ｃ１とＣ２の間隔の変動量Δｑ３を求めることができる。すなわち、

となる。
【００６７】
上述のように光源装置４０には、被走査面のビ-ムスポット（間隔）を調整するために４つの調整手段（出射方向変更手段４７〜５０）を備えているが、各々の機能をまとめると、下記のようになる。すなわち、
第１の出射方向変更手段４７：第２の光源モジュ-ル４２を副走査断面内にて可動し、ビ-ムスポットの中央位置Ｃ１、Ｃ２の間隔（ｑ３）調整を行う。
第２の出射方向変更手段４８：第１の光源モジュ-ル４１を出射ビ-ムに略平行な回転軸回りに可動し、ビ-ムスポットＢＳ１、ＢＳ４の間隔（ｑ１）調整を行う。
第３の出射方向変更手段４９：第２の光源モジュ-ル４２を出射ビ-ムに略平行な回転軸回りに可動し、ビ-ムスポットＢＳ２、ＢＳ３の間隔（ｑ２）調整を行う。
第４の出射方向変更手段５０：光源装置４０を出射ビ-ムに略平行な回転軸回りに可動し、ビ-ムスポットの中央位置Ｃ１、Ｃ２の間隔（ｑ３）調整を行う。
【００６８】
そして、「感度」の低い調整手段である第２から第４の出射方向変更手段４８〜５０に対しフィ-ドバック調整機構を設け、ビ-ムピッチの検出結果に基づき、それらをステッピングモ-タ（圧電素子等、他の駆動手段でも構わない）で駆動することで、自動的にビ-ムピッチ補正が可能となる。一方、比較的「感度」の高い調整手段である第１の出射方向変更手段４７は、光源装置組立時の初期調整に用いればよい。従って第１の出射方向変更手段４７の駆動（テ-パ付きねじ４５を回す）は、上記の説明ではステッピングモ-タ５２ａによるものとしたが、ステッピングモ-タ５２ａを備えず手動にて（スクリュ-ドライバ等を利用して）行う方法でも構わない。
【００６９】
なお、第２、第３の出射方向変更手段４８、４９は、第４の出射方向変更手段５０と独立ではない。そのため第４の出射方向変更手段５０の駆動により、第１の光源モジュ-ル４１のビ-ムスポットＢＳ１、ＢＳ４の間隔及び第２の光源モジュ-ル４２のビ-ムスポットＢＳ２、ＢＳ３間隔は変動してしまう。従って、この挙動を考慮した調整フロ-を組み立てる必要がある。
【００７０】
図１５の調整フロ-は、まず光源装置及び光走査装置を仮組立し（ステップ１）、４つのビ-ムスポット位置（走査位置）を検出し（ステップ２）、２つの中央位置Ｃ１、Ｃ２の間隔ｑ３を算出し、第１の出射方向変更手段４７によりｑ３を粗調整し（ステップ３）、ｑ３の誤差が目標値（第２〜第４の出射方向変更手段４８〜５０にて、調整（微調整）可能な値）以内であるかどうかを判断する。目標値以内でなければステップ２へ戻ってやり直し、目標値以内であればステップ５へ進む。以上がビ-ムピッチの初期調整（工場での仮組立時の粗調整）である。
【００７１】
ついで、４つのビ-ムスポット位置（走査位置）を検出し（ステップ５）、ビ-ムスポットＢＳ１、ＢＳ４の間隔（ｑ１）、ビ-ムスポットＢＳ２、ＢＳ３の間隔（ｑ２）及び中央位置Ｃ１、Ｃ２の間隔（ｑ３）を算出し（ステップ６）、ビ-ムピッチ誤差が仕様値以内であるかどうかを判断し（ステップ７）、仕様値以内であればステップ１１へ進み、仕様値以内でなければステップ８へ進む。
【００７２】
そして、第４の出射方向変更手段５０により、２つの中央位置Ｃ１、Ｃ２の間隔（ｑ３）を調整し（ステップ８）、第２の出射方向変更手段４８により、ビ-ムスポットＢＳ１、ＢＳ４の間隔（ｑ１）を調整し、（ステップ９）、第３の出射方向変更手段４９により、ビ-ムスポットＢＳ２、ＢＳ３の間隔（ｑ２）を調整し（ステップ１０）、再びステップ５へ戻り、それ以降を繰り返す。
【００７３】
ステップ１１では、温度変化、経時的要因によりビ-ムピッチ変動が発生しているかどうかを判断し、発生していればステップ５へ戻る。
【００７４】
これらステップ５〜ステップ１１がビ-ムピッチの初期調整（工場での仮組立時の粗調整）、及びユ-ザ先での使用中における温度変化／経時的要因によるビ-ムピッチ変動のフィ-ドバック補正である。
【００７５】
なお本実施形態においては、出射方向変更手段として光源モジュ-ルの姿勢変化を利用したものを採用したが、光学的またはメカ的レイアウトにより、種々の出射方向変更手段を適宜組み合わせて構成しても構わない。
【００７６】
上述した本発明に係る光走査装置を電子写真プロセスを用いた画像形成装置の光走査装置として使用すれば、複数の光ビ-ムを同時に走査することが可能となるため、プリント速度の高速化、高密度化が可能となる。またシングルビ-ム光源装置と同じプリント速度／走査密度を達成するには、ポリゴンスキャナの回転数を低減することが可能となるため、消費電力が小さくなり、熱発生も低減する。また騒音も小さくなる。
【００７７】
またデジタルカラ-複写機、カラ-プリンタ等の画像出力装置においては、各色（例えば、ブラック：Ｋ、シアン：Ｃ、マゼンタ：Ｍ、イエロ-：Ｙ）に対応する感光手段（例えば感光体ドラム）を、画像記録媒体（例えば紙）の搬送方向に直列に配列したタンデム方式が採用されることが多いが、図１６（Ａ）に示すように、各色に対応する光走査装置を別体（１０Ｋ、１０Ｃ、１０Ｍ、１０Ｙ）としても良いし、図１６（Ｂ）に示すように共通体（１０Ａ）としても構わない。あるいは図１６（Ｃ）、（Ｄ）に示すように光走査装置を二体化した構成としても削ない。このような構成により、１感光体ドラム型の画像出力装置の場合（４色に対応して４回の書込が必要）と比較して、４倍の出力画像を得ることが可能となる。なお光走査装置を１０Ｋ、１０Ｃ、１０Ｍ、１０Ｙの符号に付したＫ、Ｃ、Ｍ、Ｙはもちろん上述したトナ-の色に対応している。
【００７８】
ここで、すべての光走査装置１０Ｋ、１０Ｃ、１０Ｍ、１０Ｙから出射されるビ-ムの本数が各々１本の場合には、これらの光走査装置を適用した画像出力装置によりフルカラ-（４色）画像を得ることができる。それに対し、４つの光走査装置１０Ｋ、１０Ｃ、１０Ｍ、１０Ｙの少なくとも一つ（例えばブラックに対応する光走査装置１０Ｋ）を本発明の構成の４ビ-ム光走査装置とし、この光走査装置のみで光走査を行うことにより、フルカラ-画像時と比較して４倍の高密度化が可能となる。あるいは記録媒体の搬送速度（及びプロセス速度）を４倍に変更すれば、画像出力枚数を４倍に増加することが可能となる。またフルカラ-画像時においても、文字画像についてはブラックにて書き込むことが多く高解像度も要求されることが多いため、上記の４ビ-ム光走査装置１０Ｋに付加して、他の光走査装置１０Ｃ、１０Ｍ、１０Ｙ：１ビ-ム）も同時に書き込むことにより、文字／写真／線画イメ-ジ等が混在した画像においてもより高品位な出力画像を得ることが可能となる。
【００７９】
【発明の効果】
請求項１に係る光走査装置は、以上説明してきたように、調整感度の異なる出射方向変更手段を２つ以上備える光走査装置であるため、光走査装置の初期調整（組立時のビームピッチの初期調整時）、及びビームピッチ変動を補正するためのフィードバック調整を容易に行うことが可能となるという効果があり、また、ユーザ先にて環境変動等によりビームピッチが変動した場合でも、オペレータ（ユーザ又はサービスマン等）による手動の調整が必要なく、自動的にビームピッチを調整（補正）することができるという効果がある。
【００８０】
請求項２〜６に係る光走査装置は、上記共通の効果に加え、光源装置の光学的またはメカ的レイアウトの自由度を拡大することができるという効果がある。
【００８２】
請求項７に係る光走査装置は、上記共通の効果に加え、光源装置を小型、軽量化して交換が容易なものとすることができるという効果がある。
【００８３】
請求項８に係る画像形成装置は、請求項１ないし８のいずれかの光走査装置を使用し、複数の光ビームを同時に走査することが可能となるため、プリント速度の高速化／高密度化を図ることが可能となり、またシングルビーム光源装置と同じプリント速度／走査密度を達成するには、ポリゴンスキャナの回転数を低減することが可能となるため、消費電力の低減や熱発生の低減に繋がり、環境に対する負荷を低減することが可能となり、さらには騒音発生を抑制することができるという効果がある。
【図面の簡単な説明】
【図１】本発明に係る光走査装置の第１実施形態の光学的配置を示す斜視図である。
【図２】図１の光走査装置が備える光源装置の光学的配置（副走査断面）を示す平面図である。
【図３】図１の光走査装置の走査光学系の副走査断面を展開して示した図である。
【図４】光源モジュ-ルの構成例を示す図である。
【図５】被走査面におけるビ-ムスポットの配列の一例を示す図である。
【図６】出射方向変更手段として光路内に配設された透過型光学素子を偏心させる構成の例を示す図である。
【図７】三角プリズムの回転の減速機構の例を示す図である。
【図８】２つの三角プリズムで、光ビ-ムの出射角度を変化させる例を示す図である。
【図９】三角プリズムで出射方向を変更する機構の例を示す図である。
【図１０】出射方向の変更例を示す図である。
【図１１】他の出射方向の変更例を示す図である。
【図１２】平行平板を用いた出射方向変更手段の例を示す図である。
【図１３】本発明に係る光走査装置の第２実施形態に用いる光源装置のを示す図である。
【図１４】図１３の実施形態におけるビ-ムスポットの位置を示す図である。
【図１５】出射方向変更手段を用いた調整フロ-図である。
【図１６】本発明に係る光走査装置を電子写真プロセスを用いた画像形成装置の構成例を示す図である。
【符号の説明】
１ 光源装置
２ シリンドリカルレンズ
３ 偏向器（ポリゴンミラ-）
４ 走査結像光学系（走査レンズ）
５ 被走査面（感光体ドラム）
６、６ａ、６ｂ 半導体レ-ザ
７、７ａ、７ｂ カップリングレンズ
８、８ａ、８ｂ 出射方向変更手段
９ ビ-ム合成手段（ビ-ム合成プリズム）
１０ アパ-チャ
１１、１１ａ、１１ｂ 光ビ-ム
１２ａ、１２ｂ 光源モジュ-ル
１３ レンズホルダ
１４ 接着剤
１５ レンズセル
１６ レンズホルダ
１７ ベース部材
１８ 押さえ板
２０ 光走査装置
２１ 三角プリズム
２２ ガルバノミラ-（反射型光学素子）
２３ 平行平板
３１ プリズムホルダ
３２ ホイ-ル
３３ ウォ-ム
３４ ステッピングモ-タ
４０ （４ビ-ム）光源装置
４１、４２ 光源モジュ-ル
４３ ベース部材
４４ ビ-ム合成プリズム
４５ テ-パ付きねじ
４６ 鋼球
４７ 第１の出射方向変更手段
４８ 第２の出射方向変更手段
４９ 第３の出射方向変更手段
５０ 第４の出射方向変更手段
５１ ホルダ部材
５２ａ、５２ｂ、５２ｃ ステッピングモ-タ
ＢＳ１〜ＢＳ４ ビ-ムスポット
Ｃ１、Ｃ２ ビ-ムスポットの中央位置
Δｚ ビ-ムスポット位置ずれ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device used as an optical writing unit of a laser writing optical system in an image forming apparatus such as a laser printer, a digital copying machine, or a laser facsimile.
[0002]
[Prior art and problems to be solved by the invention]
In the optical scanning device used in the laser writing optical system of the image forming apparatus, as a means for improving the recording speed, there is a method for increasing the rotational speed of the polygon mirror which is a deflecting means. However, this method has problems such as durability of the polygon motor, noise, vibration, laser modulation speed, and the like, and there is a limit in improving the recording speed. Therefore, a proposal has been made to improve the recording speed by scanning a plurality of optical beams at a time and simultaneously recording a plurality of lines.
[0003]
As a multi-beam light source device that emits a plurality of laser beams, for example, there is a system that uses a semiconductor laser array having a plurality of light emitting points (light emitting channels) in one package. However, with this method, it is difficult to increase the number of channels in the manufacturing process, it is difficult to eliminate the influence of thermal or electrical crosstalk, it is difficult to shorten the wavelength, and it is currently expensive. It is a light source means.
[0004]
On the other hand, single-beam semiconductor lasers are still relatively easy to shorten the wavelength, can be manufactured at low cost, and are widely used in various industrial fields.
[0005]
A light source device and a multi-beam scanning device for synthesizing a plurality of laser beams by using such a single beam semiconductor laser or a multi-beam semiconductor laser as a light source and using a beam combining means. Many proposals have been made.
[0006]
However, compared to the method of using a semiconductor laser array as a light source means, the method of synthesizing a plurality of laser beams using a beam synthesizing means is influenced by environmental fluctuations or factors over time. The problem that the beam spot arrangement (beam pitch: scanning line interval) on the surface to be scanned fluctuates easily.
[0007]
In order to solve this problem, the following proposals have been made.
(1) A multi-beam scanning optical device disclosed in Japanese Patent Application Laid-Open No. 2000-227563 is a scanning device that combines light beams emitted from a plurality of light sources using a beam combining prism. -Beam spot position on the surface to be scanned by adjusting the beam exit direction by shifting the beam combining prism along the optical path and adjusting the tilt in the main scanning section or sub-scanning section Adjust.
(2) An optical beam scanning device disclosed in Japanese Patent Application Laid-Open No. 10-215351 is a scanning device that combines optical beams emitted from a plurality of light sources using a beam synthesis prism, and is a polygon. The beam spot position on the surface to be scanned is adjusted by shifting the cylindrical lens for forming a line image on the mirror reflection surface in the sub-scanning direction and adjusting the light beam emission direction. adjust.
(3) A multi-beam scanning method and multi-beam scanning device disclosed in Japanese Patent Application Laid-Open No. 9-189873 is a scanning device that synthesizes light beams emitted from a plurality of light sources using a half mirror. The beam spot position on the surface to be scanned is adjusted by adjusting the emission direction of the light beam by adjusting the inclination of the galvano mirror provided in the optical path and adjusting the inclination of the light source device.
[0008]
The conventional techniques (1) to (3) above all detect the variation of the beam spot array on the surface to be scanned due to temperature variation or temporal factors, and adjust the feedback based on the detection result. However, in the method of combining the output beams from a plurality of light sources using the beam combining means, a light source device (or an error due to component processing error, assembly error, adjustment error, etc.) When assembling an optical scanning device), it is often difficult to initially adjust (set) the beam spot array on the surface to be scanned to a predetermined value, and this initial adjustment and feedback adjustment are easy. Proposals related to the optical scanning device that can be made have not been made by the inventors of the present application.
[0009]
Accordingly, an object of the present invention is to facilitate initial adjustment of the beam spot arrangement (beam pitch) on the surface to be scanned, and to compensate for environmental fluctuations or beam spot arrangement fluctuations over time (feedback adjustment). It is to propose a multi-beam optical scanning device capable of
[0010]
[Means for Solving the Problems]
  In order to achieve the above object, an optical scanning device according to claim 1 of the present invention is provided.
  Generate a light beamTwo sets of two pairs of semiconductor lasers and coupling lensesA light beam is emitted from a light source device composed of a light source module and scanned as a beam spot on the surface to be scannedAnd
A holding member for arranging and holding the two sets of light source modules in the main scanning direction; and a combining means for combining the two light beams emitted from the two sets of light source modules close to each other,
  BS1 and BS4 are beam spots on the scanned surface of the two light beams emitted from one of the light source modules,
  BS2 and BS3 are beam spots on the scanned surface of the two light beams emitted from the other light source module,
  When the center position of the beam spots BS1 and BS4 is C1, and the center position of the beam spots BS2 and BS3 is C2, the distance between the beam spots BS1 and BS4 in the main scanning direction and the main positions of the beam spots BS2 and BS3 are set. The interval in the scanning direction was set to be narrower than the interval between the central positions C1 and C2 in the main scanning direction.In an optical scanning device,
  The light source device includes two or more emission direction changing means for changing the sub-scanning direction component of the emission direction of the light beam,
  The one outDirection change meansIs one that changes the sub-scanning direction component of the light beam emission direction by tilting one of the two sets of light source modules substantially in the sub-scan section, and has higher sensitivity than the other changing means,
  Other exit direction changing meansIs to change the sub-scanning direction component of the light beam in the emission direction by rotating the light source device about the optical axis of the emission beam, and has a lower sensitivity than the one changing means,
  furtherDetection means for detecting a beam spot position on the surface to be scannedAnd a correction means for feedback adjusting the fluctuation of the beam spot interval on the scanned surface from the target value.,
  The correction means includesBased on the detection result of the beam spot position by the detection means, the high sensitivityOneThe beam spot interval on the scanned surface is changed by the emitting direction changing means.GoalAdjust to the value above, low sensitivityotherBy the emission direction changing means, the beam spot interval on the scanned surface is changed.GoalFeedback adjustment of fluctuation from value,
It is characterized by that. In this specification, “sensitivity” means the amount of movement (resolution) of the beam spot position on the surface to be scanned with respect to the adjustment amount (variation amount) of the emission direction changing means.
[0011]
According to the second aspect of the present invention, in order to achieve the above object, in the optical scanning device according to the first aspect, the one emission direction changing means having a different sensitivity from the other has a transmission optical element in the optical path. It is characterized by being eccentric.
[0012]
According to the third aspect of the present invention, in order to achieve the above object, in the optical scanning device according to the first aspect, the one emission direction changing means having a different sensitivity from the other has a reflective optical element in the optical path. It is characterized by being eccentric.
[0013]
According to the fourth aspect of the present invention, in order to achieve the above object, in the optical scanning device according to the first aspect, the one emission direction changing means having a different sensitivity from the others is the mounting posture of the light source module. It has the means to change this.
[0014]
According to the fifth aspect of the present invention, in order to achieve the above object, in the optical scanning device of the first aspect, at least one of the light source modules is composed of a semiconductor laser and a coupling lens, and the sensitivity is changed. The one emitting direction changing means different from the above is characterized in that the relative position between the semiconductor laser and the coupling lens is changed.
[0015]
In order to achieve the above object, according to the sixth aspect of the present invention, in the optical scanning device according to the first aspect, at least one of the light source modules is composed of a semiconductor laser and a coupling lens. The one emitting direction changing means different from the above is characterized in that a parallel plate is tiltably disposed in an optical path between the semiconductor laser and the coupling lens.
[0016]
  According to the seventh aspect of the present invention, in the optical scanning device of the first aspect,,UpBased on the detection result by the detection means, according to the following adjustment flow (step (1) to step (5)),By the one emitting direction changing means,
(1) By tilting one of the two sets of light source modules in a substantially sub-scan section, the distance between the two central positions C1 and C2 is increased.Goal aboveAdjust to the value,
  By the other emission direction changing means,
(2) By rotating the light source device about the optical axis of the outgoing beam, the interval between the two central positions C1 and C2 is feedback adjusted,
(3) Feedback adjustment of the distance between the two beam spots BS1 and BS4 by rotating one of the two light source modules around the optical axis of the emitted beam,
(4) Feedback adjustment of the two beam spot intervals BS2 and BS3 is performed by rotating the other of the two sets of light source modules about the optical axis of the outgoing beam,
(5) The interval in the sub-scanning direction of the four beam spots BS1 to BS4 isspecificationIf the value is less than or equal to the value, the adjustment flow ends andSpecifications aboveIf it exceeds the value, return to step (2),
the aboveThe beam spot interval in the sub-scanning direction on the surface to be scanned can be adjusted.
[0017]
  According to claim 8Image forming apparatusIn order to achieve the above object, the claims1Thru / or 7 optical scanning deviceA photosensitive unit that forms an electrostatic image by toner, a developing unit that visualizes the electrostatic image with toner, and a transfer unit that transfers the toner image visualized by the developing unit to a recording sheet.It is characterized by that.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing an optical arrangement of a first embodiment of an optical scanning device according to the present invention. In the figure, reference numeral 20 denotes an optical scanning device. In this specification, an optical scanning device refers to a device that scans a light beam emitted from a light source device as a beam spot on a surface to be scanned. In addition, the “main scanning direction” and “sub-scanning direction” usually mean the direction in which the beam spot is scanned on the surface to be scanned and the direction orthogonal thereto, but in this specification, at each location of the optical path, The directions corresponding to the main scanning direction and the sub-scanning direction of the surface to be scanned are referred to as “main scanning direction” and “sub-scanning direction”, respectively, in a broad sense. In each figure, X is a direction along the optical path (optical axis), Y is a main scanning (corresponding) direction, and Z is a sub-scanning (corresponding) direction.
[0020]
In the figure, 1 is a light source device, 2 is a cylindrical lens, 3 is a deflector (polygon mirror), 4 is a scanning imaging optical system (scanning lens), and 5 is a surface to be scanned (photosensitive drum). A plurality of light beams 11 emitted from the light source device 1 are formed on the deflection reflection surface of the polygon mirror 3 as a deflector by the action of the cylindrical lens 2 (imaged in the sub-scanning direction and long in the main scanning direction). After being formed as a line image, the scanning imaging optical system (scanning lens) 4 scans the surface to be scanned (photosensitive drum) 5 as a beam spot. A plurality of beam spots on the scanned surface 5 are required to maintain a predetermined interval (a beam pitch) according to the scanning density. In order to set the beam pitch, the angle φ formed by the two optical beams 11a and 11b shown in FIG. 2 may be set.
[0021]
FIG. 2 is a plan view showing an optical arrangement (sub-scanning section) of the light source device 1. In the present specification, an apparatus that includes at least two light source modules and emits an optical beam is referred to as a light source apparatus. In the figure, 6a and 6b are semiconductor lasers, 7a and 7b are coupling lenses, 8a and 8b are emission direction changing means, 9 is a beam synthesis means (a beam synthesis prism), 10 is an aperture, and 11a. , 11b is an optical beam.
[0022]
In FIG. 2, a light beam 11a emitted from a light source module 12a (consisting of a semiconductor laser 6a and a coupling lens 7a corresponding thereto), and a light source module 12b (semiconductor laser 6b). The light beam 11b emitted from the corresponding coupling lens 7b passes through the emission direction changing means 8a and 8b, and then is synthesized by the beam synthesis means (beam synthesis prism) 9. Then, the aperture 10 is shaped according to the characteristics of the subsequent optical system. The angle formed by the two optical beams 11a and 11b is set to φ.
[0023]
The light source device 1 of the present embodiment includes a beam combining prism 9, an aperture 10 and two emission direction changing means 8a and 8b in addition to the two light source modules 12a and 12b. The light source device may have a unit configuration that can be separated from the optical scanning device, or may have a configuration that cannot be separated from the optical scanning device. The light source modules 12a and 12b, the beam synthesizing prism 9, the aperture 10, and the emission direction changing means 8a and 8b are integrally fixed to a holding member (not shown) to constitute the light source device 1. However, the holding member may be configured to be separable from the optical scanning device, or may be a part of a housing member or the like constituting the optical scanning device.
[0024]
FIG. 3 is a developed view of the sub-scan section of the scanning optical system. When the semiconductor laser (light emitting point) 6 is shifted from the optical axis of the coupling lens 7 by a distance δ in the sub-scanning direction, a beam spot position shift of Δz occurs on the surface to be scanned 5. If the sub-scanning lateral magnification of the scanning optical system is mZ, the beam spot position shift (distance in the sub-scanning direction between the center line and the laser beam on the surface to be scanned) Δz is
Δz = mZ × δ
(Hereinafter referred to as Equation 1). On the other hand, if the focal length of the coupling lens 7 is fcol and the inclination of the exit beam 11 in the sub-scan section is φ,
δ = fcol × tanφ
Therefore, the above formula 1 is

(However, when φ is small. Hereinafter, it is referred to as Expression 2). Therefore, by setting the angle φ from the equation 2, it is possible to set the beam spot position on the scanned surface 5, that is, the beam pitch in the case of a plurality of beams.
[0025]
4A to 4C show configuration examples of the light source module 12 (12a, 12b). In the figure, 13 is a lens holder, 14 is an adhesive, 15 is a lens cell, 16 is a lens holder, 17 is a base member, and 18 is a pressing plate.
[0026]
FIG. 4A is a diagram simply showing the function of the light source module 12, but it may be of any form as long as it has a function of emitting an optical beam. In FIG. 4B, the semiconductor laser 6 is fixed to the lens holder 13 by a method such as press fitting, and the coupling lens 7 is fixed by an adhesive 14 or the like. The alignment of the semiconductor laser 6 and the coupling lens 7 is performed so that the direction of the optical axis and the collimating property of the emission beam 11 become predetermined values according to the characteristics of the optical system thereafter. Adjust the position. In FIG. 4C, the semiconductor laser 6 is fixed to the base member 17 to the holding plate 18, and the coupling lens 7 is fixed to the lens cell 15 having the male screw portion by bonding or the like. The base member 17 and the lens cell 15 are fixed to a common lens holder 16 so that the relative positional relationship between the semiconductor laser 6 and the coupling lens 7 becomes a predetermined value. The base member 17 to which the semiconductor laser 6 is fixed moves in the vertical direction of the drawing and the direction perpendicular to the drawing, and the lens cell 15 to which the coupling lens 7 is fixed moves in the horizontal direction of the drawing. To do. Thus, the relative positional relationship between the semiconductor laser 6 and the coupling lens 7 can be adjusted.
[0027]
The semiconductor lasers 6, 6a, 6b described above may be single beam semiconductor lasers that emit a single beam, or multi-beam semiconductor lasers that emit a plurality of laser beams. It does not matter.
[0028]
By the way, when assembling the optical scanning device 20 as described above in an assembly factory or the like, it is necessary to initially adjust the beam pitch between a plurality of beams on the scanned surface 5 to a predetermined value. However,
(1) Assembly adjustment error of light source module 12 (positioning error of semiconductor laser 6 and coupling lens 7)
(2) Assembly error of the light source module 12 to the holding member
(3) Optical axis shake in the beam synthesis prism 9
As a result, the angle φ between the two combined optical beams 11a and 11b may deviate more than a predetermined value (set value), and the beam pitch on the scanned surface 5 is set to a predetermined value. It may not be possible to make initial adjustments. In such a case, the beam pitch is adjusted to a predetermined value by adjusting the angle φ by using the emission direction changing means 8a and 8b disposed in the optical path.
[0029]
On the other hand, after the factory shipment, the initial adjustment value of the beam pitch may fluctuate due to environmental (temperature) change or influence over time during use of the user or the like. Even in such a case, the changed beam pitch can be corrected by using the emission direction changing means 8a and 8b.
[0030]
However,
(A) Adjustment amount required at the time of initial adjustment,
(B) Adjustment amount necessary to correct beam pitch fluctuations caused by environmental fluctuations during use of the user, etc.
And the adjustment amount (necessary adjustment stroke and resolution) are often greatly different. With a single emission direction changing means or a plurality of emission direction changing means having the same configuration, the adjustment amount (A), It was often difficult to achieve (B) at the same time.
[0031]
This problem will be described by taking as an example an optical scanning device having a focal length fcol = 15 [mm] of the coupling lens 7 and a sub-scanning lateral magnification mZ = 5.3 times in the entire scanning optical system.
Adjustment amount (A): The deviation amount ΔφA from the set value of the angle φ according to the above (1) to (3) is empirically (maximum), and ΔφA is about 20 [′] = 5.8 [mrad]. is there. In addition, when this is converted into the beam pitch fluctuation amount Δz,

It is.
Adjustment amount (B): Beam pitch variation Δz due to environmental variation is empirically (maximum)

When this is converted into the amount of deviation ΔφB of the outgoing optical axis,

It is.
[0032]
Therefore, from the adjustment amounts (A) and (B), the ratio of the two adjustment amounts (ΔφA / ΔφB) = 46, and both adjustments can be performed by a single exit direction changing means or a plurality of exits having the same configuration. It can be understood that it is difficult to perform with the direction changing means.
[0033]
Here, the initial adjustment of the beam pitch and the feedback adjustment will be described. 5A to 5C are diagrams showing an example of the arrangement of beam spots Bs on the surface to be scanned 5 (in the case of a two-beam scanning device: 1200 dpi).
[0034]
  Error of angle φ formed by two light beams after beam composition (positioning error of semiconductor laser and coupling lens, error of assembly of light source module to holding member, light in beam composition prism) When the optical writing apparatus is assembled (before initial adjustment), the beam pitch on the surface to be scanned 5 is about 100 to 500 μm due to the optical axis deviation due to axial fluctuation or the like (see FIG.5(See (A)). The beam pitch is a predetermined value (for example, 21.2 μm when the scanning density is 1200 dpi: FIG.5For the initial adjustment (coarse adjustment) in (B), a highly sensitive exit direction changing means may be used. When the beam pitch fluctuates due to temperature change / temporal factors, etc. (fluctuation amount Δp = about 10 to 20 μm: FIG.5(See (C)), this variation amount may be detected and feedback adjustment may be performed using the emitting direction changing means with low sensitivity. In addition, when the exit direction changing means with high sensitivity is insufficient in resolution and cannot be initially adjusted to a predetermined value, the exit direction changing means with low sensitivity may be used as an auxiliary for initial adjustment.
[0035]
As described above, with respect to the movement amount of the beam spot position on the surface to be scanned with respect to the adjustment amount (variation amount) of the emission direction changing means, that is, “sensitivity”, the sensitivity of one emission direction changing means 8a and the other By making the sensitivity of the emission direction changing means 8b different, two adjustments requiring different sensitivities such as (A) and (B) can be easily performed. That is, the higher adjustment sensitivity may be used for the initial adjustment of the beam pitch (A), and the lower adjustment sensitivity may be used for the correction of the beam pitch fluctuation (B).
[0036]
In the case of the illustrated embodiment, the two emission direction changing means 8a and 8b shown in FIG. 2 are arranged in the optical paths of the different light beams 11a and 11b, but the two emission direction changing means 8a and 8b are provided. You may arrange | position in either one optical path.
[0037]
Incidentally, by providing means for detecting the beam spot arrangement (beam pitch) on the surface to be scanned 5 in the optical scanning device 20, it is possible to detect the beam pitch fluctuation in use by the user or the like. it can. The detection means may be electrically detected using a photodiode or the like, and when the optical scanning device 20 of the present embodiment is used as an optical writing device of an image forming apparatus, an output image thereof You may detect using. In the case of a configuration in which the beam pitch (variation amount) is detected electrically using a photodiode or the like, the emission direction changing means 8a, An input signal for driving 8b can be obtained. By adding such a configuration to the exit direction changing means on at least the low sensitivity side, it becomes possible to automatically correct beam pitch variation (feedback adjustment). When detection is performed using an output image, a user or a serviceman can input and correct from a scanning panel or the like provided in the image output apparatus. If such a feedback adjustment mechanism is provided in the exit direction changing means on the high sensitivity side, the initial adjustment of the beam pitch at the time of assembling the optical scanning device at the factory can be automated.
[0038]
Next, the configuration of the emission direction changing means will be described.
FIG. 6 is a diagram showing an example of a configuration in which a transmissive optical element disposed in the optical path as an emission direction changing unit is decentered. In the figure, reference numeral 21 denotes a triangular prism. The light beam that has passed through a triangular prism (internal refractive index: n) 21 having a small apex angle θ1 has an exit angle of β1,
β1 = (n−1) × θ1
Only changed. Accordingly, by rotating the triangular prism 21 by the angle γ1 with the optical axis of the optical beam as the rotation axis, the sub-scanning direction component φ1 of the outgoing beam is

Can only be changed. The displacement amount (sub-scanning direction) Δz of the beam spot on the surface to be scanned 5 with respect to the adjustment angle γ1 of the arrangement angle of the triangular prism 21 is expressed by the above equation 2.

(Hereinafter referred to as Equation 3).
[0039]
For example, when mZ = 5.3 times, fcol = 15 [mm], n = 1.5, θ1 = 1.5 [°] = 0.02618 [rad], Equation 3 is
Δz = 1.04 × sin (γ1) [mm]
(Hereinafter referred to as Equation 3-1), and by adjusting the angle γ1 of the triangular prism 21 from −90 ° to + 90 °, the beam spot position Δz is adjusted within a range of about ± 1 [mm]. Can do.
[0040]
  For the rotation of the triangular prism 21, for example, FIG.9The speed reduction mechanism using the worm and wheel shown in FIG. 5 can be used, and thereby, an adjustment mechanism having a wide adjustment stroke and a small adjustment resolution, that is, a wide dynamic range can be realized. In this mechanism, the triangular prism 21 is held by a prism holder 31 having a gear (wheel 32) formed on the entire circumference, and the triangular prism 21 is rotated by a worm 33 driven by a stepping motor 34 or the like. .
[0041]
  When the reference step angle s of the stepping motor 34 is 18 [°], the pitch of the worm is w = 0.5 [mm], and the radius of the wheel is r = 20 [mm] (FIG.9(B)) Assuming the rotation angle Δγ1 of the triangular prism 21 per step,
sin (Δγ1) = [(s / 360 °) × w] / r
                = [(18 ° / 360 °) × 0.5] / 20
                = 0.025 / 20 = 0.00125
Than,
Δγ1 = 0.0716 [°] = 4.3 [′]
It becomes. If γ1 = Δγ1 in the above equation 3-1,
Δz = 0.0013 [mm] = 1.3 [μm]
And can be adjusted with a resolution Δz = 1.3 [μm].
[0042]
In the configuration shown in the figure, since the worm & wheel is used, the triangular prism 21 can be rotated by 360 °. Therefore, the adjustment range is ± 1.04 [ mm].
[0043]
  As shown in FIG. 6, when the exit direction changing means is composed of only a single triangular prism 21, not only the sub-scan direction component but also the main scan direction component of the exit beam changes. To avoid this, figure7As shown in FIG. 5, the two triangular prisms 21 are arranged in series and rotated in opposite directions, whereby the emission angle of the light beam can be changed in a specific plane.
[0044]
A description will be given of an example of the emitting direction changing means that is configured to decenter the reflection type optical element disposed in the optical path of FIG. In this example, the emission direction changing means 8a and 8b in FIG. 2 are configured as a triangular prism 21 (transmission type optical element) and a galvano mirror (reflection type optical element) 22, respectively. On the emission direction changing means 8a (triangular prism 21) side, the above-described examination of the configuration (1) of the emission direction changing means can be applied. On the other hand, on the emission direction changing means 8b (galvano mirror-22) side, if the adjustment amount of the arrangement angle of the galvano mirror 22 is β2, the emission direction after reflection of the light beam 11b is changed by φ2 = 2 × β2. be able to. Accordingly, the displacement amount Δz (sub-scanning direction) of the beam spot 5 on the surface to be scanned with respect to the adjustment angle β2 of the arrangement angle of the galvano mirror 22 is expressed by the following equation 2.

(Hereinafter referred to as Equation 4).
[0045]
Now, on the exit direction changing means 8b (galvano mirror 22) side of FIG. 9, the reference step angle s = 3.6 [°] of the stepping motor 34, the pitch w of the worm 33 = 0.3 [mm], the wheel -When the radius r of the ru 32 is 15 [mm] (mZ = 5.3 times, fcol = 15 [mm]), and when the rotation angle Δβ2 of the galvano mirror-22 per step is

Than,

It becomes. If β2 = Δβ2 in the above equation 4,

And can be adjusted with a resolution Δz = 31.8 [μm].
[0046]
Therefore, initial adjustment of the beam pitch at the time of assembly at the factory is performed on the side of the emitting direction changing means 8b (galvano mirror 22) having high sensitivity, and correction of beam pitch fluctuation when the user is used (preferably, the beam pitch). (Feedback correction is performed based on the detection result of the pitch variation) may be performed on the side of the emission direction changing means 8a (triangular prism 21) having low sensitivity. If the resolution (31.8 μm) of the initial adjustment (galvano mirror-22 side) is insufficient, the adjustment on the triangular prism 21 side may be supplementarily added.
[0047]
FIG. 10 shows still another configuration of the emission direction changing means. As another means for changing the emitting direction of the light beam, a configuration in which the mounting posture of the light source module is changed is adopted. As shown in the figure, the light source module 12 is placed in the sub-scan section (or the sub-scanning section). It may be tilted in a plane having a component of the scanning section.
[0048]
Alternatively, as shown in FIG. 11, by rotating the light source module 12 about the rotation axis r slightly deviated from the emission beam 11, the sub-scanning direction component of the emission beam 11 can be varied. it can. If the angle between the rotation axis r of the light source module 12 and the exit beam 11 is θ2, and the rotation angle of the light source module 12 is γ2, the sub-scanning direction component φ3 of the exit beam is
φ3 = tan (θ2) × sin (γ2)
It is represented by Therefore, the displacement amount (sub-scanning direction) Δz of the beam spot on the surface to be scanned 5 with respect to the rotation angle γ2 of the light source module 12 is given by

(Hereinafter referred to as Equation 5).
[0049]
As the emission direction changing means, when the light source module 12 is composed of at least a semiconductor laser and a coupling lens, the relative position (in the sub-scanning direction) of the semiconductor laser and the coupling lens is determined. A variable configuration can be employed. In this configuration, the displacement amount (sub-scanning direction) Δz of the beam spot on the surface to be scanned 5 with respect to the displacement amount (sub-scanning direction component) Δδ of the relative position is Δz = mY × Δδ.
[0050]
As the emitting direction changing means, when the light source module 12 is composed of at least the semiconductor laser 6 and the coupling lens 7, a parallel plate (parallel) is provided between the semiconductor laser and the coupling lens. (Flat glass) may be provided, and the parallel plate may be inclined in a plane having at least a component of the sub-scanning section.
[0051]
That is, as shown in FIG. 12, the thickness of the parallel plate 23 disposed between the semiconductor laser 6 and the coupling lens 7 is t, the internal refractive index is n, and the inclination angle in the sub-scan section is β3. Then, the shift amount Δδ1 of the optical beam 11 by the parallel plate 23 is
Δδ1 = t × β3 × [1- (1 / n)]
It is represented by Accordingly, the displacement amount (sub-scanning direction) Δz of the beam spot on the surface to be scanned 5 with respect to the inclination angle β3 of the parallel plate 23 is expressed by the following equation 1.

(Hereinafter referred to as Equation 6).
[0052]
FIG. 13 is a diagram showing a light source device used in the second embodiment of the optical scanning device according to the present invention, in which 40 is a (4 beam) light source device, 41 is a first light source module, 42 is a second light source module, 43 is a base member, 44 is a beam combining prism, 45 is a taper screw, 46 is a steel ball, 47 is a first emitting direction changing means, and 48 is a second member. , 49 is a third emission direction changing means, 50 is a fourth emission direction changing means, 51 is a holder member, and 52a, 52b and 52c are stepping motors.
[0053]
In the exploded perspective view of the light source device 40 shown in FIG. 13A, two pairs of semiconductor lasers 6 and a coupling lens 7 are fixed to a base member 43 to constitute a first light source module 41. . The first light source module 41 is rotatably fixed to the holder member 51 together with the second light source module 42 having the same configuration. The two light beams emitted from the first light source module 41 and the two light beams emitted from the second light source module 42 are brought close to each other by the beam combining prism 44. Are synthesized. The beam combining prism 44 may be combined using a half mirror or a method using a deflection characteristic of laser light. The combined four optical beams are shaped by an aperture (not shown).
[0054]
The first and second light source modules 41 and 42, the beam combining prism 44, the holder member 51 and the like constitute the light source device 40. The light source device 40 can have an integrated unit configuration, and can easily cope with a case where the light source device 40 needs to be replaced due to deterioration of the semiconductor laser or the like. Further, as shown in FIG. 13B, the light source device 40 is provided with first emission direction changing means 47 including a taper screw 45 and a steel ball 46.
[0055]
FIG. 14 is a diagram showing the positions of the beam spots in this embodiment, and shows the arrangement of the beam spots BS1 to BS4 on the surface to be scanned when the scanning density is 1200 dpi. In the figure, BS1 and BS4 are beam spots corresponding to two light beams emitted from the first light source module 41, and BS2 and BS3 are emitted from the second light source module 42. A beam spot corresponding to two optical beams, C1 is a central position of BS1 and BS4, and C2 is a central position of BS2 and BS3. Q1 is the distance between BS1 and BS4 (beam pitch), the target value is 3 × qr = 3 × 21.2 = 63.5 [μm], q2 is the distance between BS2 and BS3 (beam pitch), The target value is qr = 21.2 [μm], q3 is the interval between C1 and C2, the target value is 0 [μm], and qr is the scanning line interval (21.2 μm) at 1200 dip.
[0056]
In a state where the light source device 40 is assembled to the optical scanning device (at the time of temporary assembly; before initial adjustment), the beam spots BS1 to BS4 are arranged randomly as shown in FIG. 14B. From this state, in order to adjust the beam spot intervals (beam pitches) shown in FIG. 14A to be equal, first, after q3 is roughly adjusted by the first emission direction changing means 47, Fine adjustment is made so that q1 to q3 become the respective target values by the second to fourth emission direction changing means 48 to 50. At the time of initial adjustment, after the beam pitch is detected, each emission direction changing means may be driven manually, or may be driven by a stepping motor provided in the light source device. When the beam pitch fluctuates due to the influence of temperature change or temporal factors, the beam pitch (fluctuation) is detected, and the second to fourth emission direction changing means 48 to 50 are set based on the detection result. What is necessary is just to control back. Therefore, the first emission direction changing means 47 used at the time of initial adjustment (during assembly) does not need to have a feedback mechanism, and may be configured to be manually driven by, for example, a screw driver.
[0057]
In the case of a light source module in which two pairs of semiconductor lasers and a coupling lens are fixed to a common base member 43, relative alignment adjustment between the semiconductor laser and the coupling lens (so-called optical axis / collimator) Adjustment of the light source module described above, which causes the initial adjustment to be difficult by performing adjustment with a beam combining prism 44 to be used, and the light source for the holding member. It is possible to effectively remove the effects of assembly adjustment errors and assembly errors out of module assembly errors and optical axis fluctuations in the beam combining prism. Therefore, the beam spot interval (q1, q2) in the same light source module is relatively close to a predetermined value even in the temporarily assembled state, and a highly sensitive exit direction changing means is not required.
[0058]
This will be specifically described below.
The first emission direction changing means 47 moves the center position C2 of the beam spots BS2 and BS3 on the surface to be scanned, so that “the center position C1 of the beam spots BS1 and BS4” and “the center position C2”. Relative alignment. That is, q3 in FIG. 14B is varied. By pushing or pulling out the taper screw 45, the posture of the second light source module 42 can be changed in the β direction shown in the drawing via the steel ball 46. Thus, the emission angle of the two light beams emitted from the second light source module 42, that is, the position of C1 can be adjusted.
[0059]
The operation of the first emission angle adjusting means 47 for adjusting the emission angles of the two light beams emitted from the second light source module 42 will be described with reference to FIG. The taper angle (2 × θ3) of the taper screw 45 is 20 °, the screw pitch p is 0.3 [mm], and the rotation axis (in the sub-scan section) of the second light source module 42 If the distance from the (fulcrum) to the steel ball (force point) is r3 = 20 [mm] and the taper screw 45 is driven by a stepping motor (not shown) having a basic step angle s = 7.5 °, The pushing amount (pulling amount) u of the taper screw 45 for one step of the stepping motor is

Therefore, the moving amount (left-right direction) v of the steel ball 46 at this time is

It becomes. Assuming that the β eccentricity of the second light source module 42 at this time is β3, tan (β3) = v / r3 = 0.018 / 20, and the beam spots BS2 and BS3 on the scanned surface The movement amount Δz is calculated from (Equation 2)

It becomes. That is, the two beam spots BS2 and BS3 can be simultaneously moved and adjusted in the sub-scanning direction with a resolution of 7.3 [μm].
[0060]
The light source device 40 also adjusts the distance q1 between the beam spots BS1 and BS4 on the surface to be scanned of the two light beams emitted from the first light source module 41. An emission direction changing means 48 is provided. As shown in FIG. 13D, the second emission direction changing means 48 sets an axis γ4 parallel to the bisector of the two light beams emitted from the first light source module 41. It is configured to be rotatable as a rotating shaft. That is, the emission direction changing means shown in FIG. 11 is applied. In FIG. 13 (D), the optical beam folded back by the beam combining prism 44 is shown expanded.
[0061]
That is, in order to suppress the occurrence of optical characteristic deviations between the beams, the four light beams intersect with each other in the vicinity of the deflecting reflection surface of the polygon mirror 3. Specifically, the angle formed by the two light beams emitted from the first light source module 41 is 2 × α1, and the two light beams emitted from the second light source module 42 are The angle formed by 2 × α2 and the angle formed by the bisectors of the two light beams emitted from the light source modules 41 and 42 are 2 × α3.
2 × α1 = 2 × α2 = 3 [°]
2 × α3 = 5 [°]
It is set to.
[0062]
Now, with a stepping motor 52a (basic step angle s = 7.5 °) combined with a screw having a screw pitch p = 0.5 [mm], the first point is r4 = 20 [mm] from the rotation axis. Considering the case where the first light source module 41 is rotationally driven by operating the light source module 41, the operation amount u of the power point for one step of the stepping motor 52a is:

So, if the γ rotation amount of the first light source module 41 at this time is γ4,

The variation amount Δq1 of the distance between the two beam spots BS1 and BS4 on the surface to be scanned is expressed by the following equation 5 as θ2 = α1.

(Hereinafter referred to as Equation 7).

It becomes.
[0063]
13A and 13B, the rotation center of the first light source module 41 is an intermediate portion between the optical axes of the two coupling lenses 7 and 7 (FIG. 13B ) (Corresponding to the rotation axis represented by γ) of the two optical beams after being synthesized by the beam synthesis prism 44 (FIG. 13 (FIG. 13)). It is desirable to have a configuration that rotates about a rotation axis) indicated by γ4 in D).
[0064]
Further, the light source device 40 has a third emission in order to adjust the distance q3 between the beam spots BS2 and BS3 on the scanned surface of the two light beams emitted from the second light source module 42. Direction changing means 49 is provided. The configuration and operation (adjustment mechanism) of the third emission direction changing means 49 are the same as those of the second emission direction changing means 48 described above.
[0065]
Further, by the fourth emission direction changing means 50 provided in the light source device 40, as in the case of the first emission direction changing means 47, relative alignment of the center positions C1 and C2 of the beam spots on the surface to be scanned (q3 Adjustment). The configuration and operation (adjustment mechanism) of the fourth emission direction changing unit 50 are the same as those of the second and third emission direction changing units 48 and 49, and are different from the first emission direction changing unit 47.
[0066]
That is, in the fourth emission direction changing means 50, when the basic step angle s of the stepping motor 52c and the distance r from the rotation axis to the force point are the same as those of the second emission direction changing means 48, If α1 in Equation 7 is replaced with α3, the variation Δq3 of the distance between the center positions C1 and C2 of the beam spot on the surface to be scanned for one step of the stepping motor 52c can be obtained. That is,

It becomes.
[0067]
As described above, the light source device 40 is provided with four adjusting means (emission direction changing means 47 to 50) for adjusting the beam spot (interval) on the surface to be scanned. And the following. That is,
First emission direction changing means 47: The second light source module 42 is moved in the sub-scan section, and the distance (q3) between the center positions C1 and C2 of the beam spot is adjusted.
Second exit direction changing means 48: The first light source module 41 is moved around a rotation axis substantially parallel to the exit beam to adjust the distance (q1) between the beam spots BS1 and BS4.
Third exit direction changing means 49: The second light source module 42 is moved around a rotation axis substantially parallel to the exit beam to adjust the distance (q2) between the beam spots BS2 and BS3.
Fourth exit direction changing means 50: The light source device 40 is moved around a rotation axis substantially parallel to the exit beam, and the distance (q3) between the center positions C1 and C2 of the beam spot is adjusted.
[0068]
Then, a feedback adjustment mechanism is provided for the second to fourth emission direction changing means 48 to 50 which are adjustment means having a low “sensitivity”, and these are adjusted to a stepping motor (piezoelectric) based on the detection result of the beam pitch. Beam pitch correction can be automatically performed by driving with other driving means such as an element. On the other hand, the first emission direction changing means 47, which is an adjustment means having relatively high “sensitivity”, may be used for initial adjustment when the light source device is assembled. Accordingly, in the above description, the driving of the first emitting direction changing means 47 (turning the taper screw 45) is performed by the stepping motor 52a. However, the stepping motor 52a is not provided and is manually operated (screw). It may be performed using a driver).
[0069]
The second and third emission direction changing means 48 and 49 are not independent of the fourth emission direction changing means 50. Therefore, by driving the fourth emission direction changing means 50, the distance between the beam spots BS1 and BS4 of the first light source module 41 and the distance between the beam spots BS2 and BS3 of the second light source module 42 are as follows. It will fluctuate. Therefore, it is necessary to assemble an adjustment flow considering this behavior.
[0070]
In the adjustment flow of FIG. 15, first, the light source device and the optical scanning device are temporarily assembled (step 1), the four beam spot positions (scanning positions) are detected (step 2), and the two central positions C1 and C2 are detected. , Q3 is roughly adjusted by the first emission direction changing means 47 (step 3), and the error of q3 is adjusted by the target value (second to fourth emission direction changing means 48-50). (Fine adjustment) is possible value). If it is not within the target value, the process returns to Step 2 and starts again, and if it is within the target value, the process proceeds to Step 5. The above is the initial adjustment of the beam pitch (rough adjustment during temporary assembly at the factory).
[0071]
Next, four beam spot positions (scanning positions) are detected (step 5), the distance between the beam spots BS1 and BS4 (q1), the distance between the beam spots BS2 and BS3 (q2), and the center position C1. , C2 interval (q3) is calculated (step 6), and it is determined whether or not the beam pitch error is within the specification value (step 7). If not, go to Step 8.
[0072]
Then, the distance (q3) between the two central positions C1 and C2 is adjusted by the fourth emission direction changing means 50 (step 8), and the beam spots BS1 and BS4 are adjusted by the second emission direction changing means 48. The interval (q1) is adjusted (step 9), the third exit direction changing means 49 adjusts the interval (q2) between the beam spots BS2 and BS3 (step 10), and the process returns to step 5 again. Repeat thereafter.
[0073]
In step 11, it is determined whether beam pitch fluctuation has occurred due to temperature change and temporal factors. If so, the process returns to step 5.
[0074]
These steps 5 to 11 are the initial adjustment of the beam pitch (coarse adjustment at the time of temporary assembly at the factory), and feedback of beam pitch fluctuation due to temperature change / time-dependent factors during use at the user's tip It is a correction.
[0075]
In the present embodiment, the light source module using the posture change of the light source module is adopted as the light emission direction changing means, but various light emission direction changing means may be appropriately combined depending on the optical or mechanical layout. I do not care.
[0076]
If the above-described optical scanning device according to the present invention is used as an optical scanning device of an image forming apparatus using an electrophotographic process, a plurality of optical beams can be scanned simultaneously, so that the printing speed is increased. High density is possible. In order to achieve the same print speed / scanning density as that of the single beam light source device, it is possible to reduce the number of rotations of the polygon scanner, thereby reducing power consumption and heat generation. Noise is also reduced.
[0077]
In an image output device such as a digital color copying machine or a color printer, photosensitive means (for example, a photosensitive drum) corresponding to each color (for example, black: K, cyan: C, magenta: M, yellow: Y). Are often arranged in series in the conveying direction of the image recording medium (for example, paper). However, as shown in FIG. 16A, the optical scanning device corresponding to each color is separated (10K). 10C, 10M, 10Y) or a common body (10A) as shown in FIG. Alternatively, as shown in FIGS. 16C and 16D, the optical scanning device is not cut into two structures. With such a configuration, it is possible to obtain four times as many output images as in the case of a single photosensitive drum type image output device (requires four writings corresponding to four colors). In addition, K, C, M, and Y attached to the reference numerals 10K, 10C, 10M, and 10Y correspond to the above-described toner colors.
[0078]
Here, when the number of beams emitted from all the optical scanning devices 10K, 10C, 10M, and 10Y is one each, a full color (four colors) is obtained by an image output device to which these optical scanning devices are applied. ) Images can be obtained. On the other hand, at least one of the four optical scanning devices 10K, 10C, 10M, and 10Y (for example, the optical scanning device 10K corresponding to black) is a four-beam optical scanning device having the configuration of the present invention, and only this optical scanning device is used. By performing the optical scanning with, it is possible to increase the density four times as compared with a full color image. Alternatively, if the conveyance speed (and process speed) of the recording medium is changed to four times, the number of image output sheets can be increased four times. Further, even in the case of a full color image, since a character image is often written in black and a high resolution is often required, it is added to the above-described 4-beam optical scanning device 10K and other optical scanning devices. 10C, 10M, 10Y: 1 beam) at the same time, it becomes possible to obtain a higher quality output image even in an image in which characters / photos / line drawing images are mixed.
[0079]
【The invention's effect】
  As described above, since the optical scanning device according to the first aspect is an optical scanning device including two or more emission direction changing means having different adjustment sensitivities, initial adjustment of the optical scanning device (the beam pitch at the time of assembly) Initial adjustment) and feedback adjustment to correct beam pitch fluctuations can be easily performed.In addition, even when the beam pitch fluctuates due to environmental fluctuations or the like at the user's site, it is possible to automatically adjust (correct) the beam pitch without the need for manual adjustment by an operator (user or serviceman) Has the effectThe
[0080]
The optical scanning device according to the second to sixth aspects has an effect that the degree of freedom of optical or mechanical layout of the light source device can be expanded in addition to the common effect.
[0082]
  Claim7In addition to the above-mentioned common effects, the optical scanning device according to the invention has an effect that the light source device can be reduced in size and weight and can be easily replaced.
[0083]
  Claim8Since the image forming apparatus according to the present invention uses the optical scanning device according to any one of claims 1 to 8 and can simultaneously scan a plurality of light beams, the printing speed can be increased / densified. In order to achieve the same print speed / scanning density as a single beam light source device, it is possible to reduce the number of revolutions of the polygon scanner, which leads to a reduction in power consumption and heat generation. It is possible to reduce the load on the noise, and further, it is possible to suppress the generation of noise.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical arrangement of a first embodiment of an optical scanning device according to the present invention.
2 is a plan view showing an optical arrangement (sub-scanning cross section) of a light source device provided in the optical scanning device of FIG. 1. FIG.
3 is a developed view of a sub-scanning section of a scanning optical system of the optical scanning device of FIG. 1. FIG.
FIG. 4 is a diagram illustrating a configuration example of a light source module.
FIG. 5 is a diagram illustrating an example of an array of beam spots on a surface to be scanned.
FIG. 6 is a diagram illustrating an example of a configuration in which a transmission optical element disposed in an optical path as an emission direction changing unit is decentered.
FIG. 7 is a diagram illustrating an example of a rotation speed reduction mechanism of a triangular prism.
FIG. 8 is a diagram illustrating an example in which an emission angle of an optical beam is changed by two triangular prisms.
FIG. 9 is a diagram illustrating an example of a mechanism for changing an emission direction using a triangular prism.
FIG. 10 is a diagram illustrating an example of changing the emission direction.
FIG. 11 is a diagram showing another example of changing the emission direction.
FIG. 12 is a diagram illustrating an example of an emission direction changing unit using a parallel plate.
FIG. 13 is a diagram showing a light source device used in a second embodiment of the optical scanning device according to the present invention.
14 is a diagram showing the position of a beam spot in the embodiment of FIG.
FIG. 15 is an adjustment flowchart using the emission direction changing means.
FIG. 16 is a diagram showing a configuration example of an image forming apparatus using an electrophotographic process for the optical scanning device according to the present invention.
[Explanation of symbols]
1 Light source device
2 Cylindrical lens
3 Deflector (polygon mirror)
4 Scanning imaging optical system (scanning lens)
5 Scanned surface (photosensitive drum)
6, 6a, 6b Semiconductor laser
7, 7a, 7b coupling lens
8, 8a, 8b Output direction changing means
9 Beam synthesis means (beam synthesis prism)
10 Aperture
11, 11a, 11b Optical beam
12a, 12b Light source module
13 Lens holder
14 Adhesive
15 Lens cell
16 Lens holder
17 Base member
18 Presser plate
20 Optical scanning device
21 Triangular prism
22 Galvano mirror (reflective optical element)
23 Parallel plate
31 Prism holder
32 wheels
33 Worms
34 Stepping motor
40 (4 beam) light source device
41, 42 Light source module
43 Base member
44 beam synthesis prism
45 Tapered screw
46 steel balls
47 First emission direction changing means
48 Second emission direction changing means
49 Third exit direction changing means
50 Fourth emission direction changing means
51 Holder member
52a, 52b, 52c Stepping motor
BS1 to BS4 beam spots
C1, C2 Beam spot center position
Δz Beam spot position deviation

Claims (8)

A light beam is emitted from a light source device composed of two sets of light source modules consisting of two pairs of semiconductor lasers that generate a light beam and a coupling lens, and is scanned as a beam spot on the surface to be scanned .
A holding member for arranging and holding the two sets of light source modules in the main scanning direction; and a combining means for combining the two light beams emitted from the two sets of light source modules close to each other,
BS1 and BS4 are beam spots on the scanned surface of the two light beams emitted from one of the light source modules,
BS2 and BS3 are beam spots on the scanned surface of the two light beams emitted from the other light source module,
When the center position of the beam spots BS1 and BS4 is C1, and the center position of the beam spots BS2 and BS3 is C2, the distance between the beam spots BS1 and BS4 in the main scanning direction and the main positions of the beam spots BS2 and BS3 are set. In the optical scanning device in which the interval in the scanning direction is set to be narrower than the interval in the main scanning direction between the central positions C1 and C2 ,
The light source device includes two or more emission direction changing means for changing the sub-scanning direction component of the emission direction of the light beam,
Out morphism direction change means of the scratch, one of the two sets of light source modules, by tilting in a substantially sub-scan section, which varies a sub scanning direction component of the emission direction of the light beam, the other More sensitive than changing means,
The other emission direction changing means changes the sub-scanning direction component of the emission direction of the light beam by rotating the light source device about the optical axis of the emission beam, and more than the one changing means. Low sensitivity,
And detecting means for detecting a beam spot position on the surface to be scanned, and correction means for feedback adjusting a variation from the target value of the beam spot interval on the surface to be scanned ,
The correcting means adjusts the beam spot interval on the scanned surface to a target value by the one emitting direction changing means having high sensitivity based on the detection result of the beam spot position by the detecting means , and the other having low sensitivity. The emission direction changing means feedback adjusts the fluctuation of the beam spot interval on the scanned surface from the target value ,
An optical scanning device. 2. The optical scanning device according to claim 1, wherein said one emitting direction changing means having a different sensitivity is provided with a transmissive optical element decentered in the optical path. 2. The optical scanning device according to claim 1, wherein said one emitting direction changing means having a different sensitivity is provided with a reflective optical element decentered in the optical path. 2. The optical scanning device according to claim 1, wherein said one emission direction changing means having different sensitivity from the other has means for changing the mounting posture of said light source module. 2. The optical scanning device according to claim 1, wherein at least one of the light source modules is composed of a semiconductor laser and a coupling lens, and the one emission direction changing means having different sensitivity from the others is the semiconductor laser and the coupling lens. An optical scanning device characterized by changing the relative position of the optical scanning device. 2. The optical scanning device according to claim 1, wherein at least one of the light source modules is composed of a semiconductor laser and a coupling lens, and the one emission direction changing means having different sensitivity from the others is the semiconductor laser and the coupling lens. An optical scanning device characterized in that a parallel plate is tiltably disposed in an optical path between the two. The optical scanning apparatus according to claim 1, based on the detection result by the above Symbol detection means, according to the following adjustment flow (step (1) through Step (5)),
By the one emitting direction changing means,
(1) By adjusting one of the two sets of light source modules substantially within the sub-scan section, the interval between the two central positions C1 and C2 is adjusted to the target value,
By the other emission direction changing means,
(2) By rotating the light source device about the optical axis of the outgoing beam, the interval between the two central positions C1 and C2 is feedback adjusted,
(3) Feedback adjustment of the distance between the two beam spots BS1 and BS4 by rotating one of the two light source modules around the optical axis of the emitted beam,
(4) Feedback adjustment of the two beam spot intervals BS2 and BS3 is performed by rotating the other of the two sets of light source modules about the optical axis of the outgoing beam,
(5) If the sub-scanning direction between the four beam spots BS1~BS4 is below specification value terminates the adjustment flow, if it exceeds the specification value returns to step (2),
Optical scanning apparatus, wherein the adjustable sub-scanning direction of the beam spot interval in the surface to be scanned. A photosensitive means for forming an electrostatic image by the optical scanning device according to any one of claims 1 to 7, a developing means for visualizing the electrostatic image with toner, and a toner image visualized by the developing means. An image forming apparatus comprising: a transfer unit that transfers to a recording sheet.

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