JP2005055471A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost optical scanner by locating optical elements so as not to make images projected on a plane (a scanning plane) vertical to the planes of deflection of respective scanning lenses interfere with other optical components and members of an optical housing, and so as to access to the scanning lenses from the upper face side of an optical box for the purpose of simplifying initial adjustment of the optical scanner and adjusting the scanning lenses from the upper face side of the optical box so as to shorten the adjustment cycle time, in the optical scanning device which guides a plurality of luminous fluxes to various surfaces to be scanned with a common deflector. <P>SOLUTION: An image forming apparatus is characterized by being provided with a printer controller which converts code data inputted from an external device to an image signal and inputs it to the optical scanner. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２７】
走査終了側
【外２】

【００２８】
Ｒは曲率半径、Ｋ、Ｂ４、Ｂ６、Ｂ８、Ｂ１０は非球面係数である。
【００２９】
本実施例では、主走査方向の形状を光軸に対し、対称に構成している、即ち、走査開始側と走査終了側の非球面係数を一致させている。
【００３０】
また、副走査方向は、光軸に対して走査開始側と走査終了側で、ｆθレンズ９６のうち少なくとも１面の副走査面（光軸を含み主走査面と直交する面）内の曲率を、該レンズの有効部内において連続的に変化させており、主走査方向形状を光軸に対して対称に構成している。
【００３１】
副走査方向の形状は、光軸に対して走査開始側と走査終了側で、光軸をＸ軸、主走査面内において光軸と直交する方向をＹ軸、副走査面内で光軸と直交する方向をｚ軸とし、
以下の連続関数で表せる。
走査開始側
【外３】

【００３２】
走査終了側
【外４】

【００３３】
（ｒ’は副走査方向曲率半径、Ｄ_２、Ｄ_４、Ｄ_６、Ｄ_８ Ｄ_１０は係数）
係数のサフィックスｓは走査開始側、ｅは走査終了側を表している。
【００３４】
副走査方向曲率半径とは、主走査方向の形状（母線）に直交する断面内における曲率半径である。
【００３５】
本実施例では、副走査方向のピント補正（像面湾曲補正）とｆθレンズにおける副走査方向の倍率の一様性（スポット径の像高による変動）を補正するために、最も被走査側のレンズ９６ｂ（Ｇ２）の被走査面側の面（ｒ４面）の副走査曲率半径を連続的に変化させている。通常、副走査曲率半径を少なくとも２面変化させて、両者を補正しているが、本実施形態では、主走査方向の形状で倍率の一様性が補正されるように構成しているため、一面のみ変化させることで像面湾曲を補正している。
【００３６】
次に本発明の目的を達成するための手段と効果について説明する。
【００３７】
本実施例のｆθレンズ９６は、プラスチックレンズで作製されており、成形上有利なように主走査方向の形状が、走査開始側と終了側で対象に構成されている。
更に、副走査方向の曲率半径は少なくとも１面が連続的に変化しており、像面湾曲、波面収差、スポット径の変動を補正している。さらに、本実施形態では、副走査方向に斜入射で光束が偏向面へ 入射しているために発生する走査線湾曲と、波面収差の劣化をＧ２レンズの偏芯（ｚ方向に１．４５６ｍｍシフト）により補正している。
【００３８】
本発明の光走査走査装置は、異なる２方向から同一角度で偏向面の略同一位置に入射した２つの光束を、レンズの光軸を挟み対称な位置を光束が通過するように最も偏向器側のレンズ９６ａ（Ｇ１）を配置している。複数の入射光束は、偏向面の副走査方向の略同一位置で偏向されるため、偏向面を低く構成できる。また、Ｇ１レンズ９６ａは、副走査方向の曲率半径が略平面であり、副走査方向のパワーをほとんど有していないため、光束が副走査方向の軸外を通過することによる光学性能の劣化を防止している。
【００３９】
図１において下方から斜め上方に偏向面へ入射した光束は、Ｇ１レンズ９６ａを通過したあと、第一の折り返しミラー９９ａで反射され、最も被走査面側のレンズ９６ｂ（Ｇ２）を通過し、第二の折り返しミラー９９ｂで反射し、平板で構成された防塵ガラス９８を通過した後被走査面としての感光ドラム面上を走査する。また、図１において上方から斜め下方に入射した光束は、Ｇ１レンズ９６ａを通過したあと、Ｇ２レンズ９６ｂを通過し、第３の折り返しミラー１００ａで反射され、被走査面としてのドラム面９７を走査する。
【００４０】
本実施形態のｆθレンズ９６は、成形上有利になるように主走査方向の形状を被走査面９７の垂直二等分線に対して対称に構成し、最も偏向器側のレンズは、副走査方向の曲率半径が略平面であり、副走査方向のパワーをほとんど有していない。副走査方向の結像性能は、最も被走査面側のレンズの最も被走査側の面のみで補正している。
【００４１】
次に、本光走査装置の光学系による調整について説明する。本実施形態における光走査装置は、以下の調整を出荷時に行うことにより、良好な光学特性を得ている。
【００４２】
主走査方向倍率誤差の非対称性補正（画像伸縮の非対称性補正）
走査線高さ補正（副走査方向スポット高さ補正）
走査線傾き補正 （副走査方向傾き補正）
走査線湾曲補正 （副走査方向曲がり補正）
上記、１〜３は、図１に示す最も被走査面側のレンズ９６ｂ（Ｇ２レンズ）で行い、４は、最も被走査面側の折り返しミラー９９ｂ、１００ａで行っている。１はＧ２レンズをＹ方向に、２はＺ方向に偏芯（シフト）させ、３はＸ軸周りに回転（チルト）させることにより補正している。
【００４３】
又、４は、図６に示すように折り返しミラーの母線を反射面の法線方向に撓ませることにより補正している。
【００４４】
１〜３の調整はＧ２レンズをＹ−Ｚ面内でシフト又はチルトさせているため、レンズをＸ方向に突き当てながら調整できるため、レンズの姿勢が安定し、調整精度を高くできるメリットを有する。尚、レンズ調整完了後は、紫外線硬化樹脂により光学箱に接着している。
【００４５】
上記全ての調整は、被走査面相当位置でのスポット位置を図５の受光素子５１ａ、５１ｂ、５１ｃ５１ｄにより測定する測定手段５０と、測定手段５０の測定値に基づいて不図示の調整手段により光学箱上面から調整を行っている。測定手段５０の受光素子５１ａ、５１ｂ、５１ｃ、５１ｄは、２次元のエリアＣＣＤを用いており、演算手段により演算された出力結果は、スポット位置を１０^−６ｍ以下のオーダーで得ることができる。又、不図示の調整手段は、光学箱上面（モータ座面の上方）よりｆθレンズ近傍まで下降するアームを有しており、Ｇ２レンズを自動でハンドリングし所望の方向へ所望量移動させるメカ機構と、図 ６に示すように、折り返しミラーの反射面法線と平行にビスで押圧し、撓ませるためのメカ部材を有している。
【００４６】
上述の調整を短時間で効率よく行うために、
複数の被走査面位置でのスポット位置を同時に測定し、調整する
光学部品に一方向からアクセスする
ことが、必要であり、上記を達成するために本実施例では４色に対応する被走査面９７全てを同時に測定、調整すると共に、図４に示すように光学部品の上面（図１の上側に対応）への正射影像が、下式を満足するようにレンズ及びミラーを配置している。
【００４７】
０≦Ｓ／Ｖ＜０．２
Ｓ：他の光学部材と干渉している領域の面積
Ｖ：他の光学部材と干渉していない領域の面積
上式を満足しない場合は、光学部品同士の重なりが大きくなり、上面又は下面の一方向から調整することが困難になる。
【００４８】
また、本実施形態では、ｆθレンズ９６は二枚で構成されているが、ｆθレンズは、一枚又は三枚以上であってもよく、さらに、回折素子等の光学素子を用いても全く同様の効果を得ることができる。さらに、光源９１にシングルビームレーザーを用いているが、２以上の複数の発光点を有するマルチビームレーザーを用いても同様の効果が得られる。又、測定手段の受光素子として、２次元ＣＣＤを用いたが、１次元のラインＣＣＤ等を用いてもよく、スポット位置を精度よく測定可能な構成であればこの限りではない。さらに、調整手段もレンズをハンドリングすることにより調整を行ったが、レンズの姿勢を変えることが可能な構成であればその他の方法を用いても良いことは自明である。
【００４９】
以上のように、複数の光束を共通の偏向器で異なる被走査面へ導光する光走査装置において、光走査装置の出荷時初期調整を簡素化し、調整時間を短縮するために、各走査レンズの偏向面に垂直な面（走査面）への光学部材の投影像が、他の光学部材及び光学ハウジングの部材に干渉しないように配置することにより、走査レンズを光学箱上面又は下面の一方向から調整し、高精度な調整と調整タクトが短縮可能となる。又、調整時に複数の被走査面の光学特性を同時且つ独立に測定し、調整することにより低価格な光走査装置を提供できる。
【００５０】
（実施例２）
本実施形態の実施形態１と異なる点は、測定手段及び、調整手段の構成であり、その他の構成及び効果は、実施形態１と同様である。
【００５１】
本実施形態の測定手段の構成を図７に示す。測定手段７０は、被走査面相当位置でのスポット位置を受光素子７１ａ、７１ｂにより測定する測定手段と、測定手段７０の測定値に基づいて不図示の調整手段により光学箱上面から調整を行っている。測定手段の受光素子７１ａ、７１ｂは、２次元のエリアＣＣＤを用いており、２つの被走査面を同時に測定可能である。これは、被走査面の間隔（ピッチ）が狭い場合に有利な構成となっている。測定データは、不図示の演算手段により演算され、出力結果はスポット位置の座標を１０^−６ｍ以下のオーダーで得ることができる。又、不図示の調整手段は、光学箱上面（モータ座面の上方）よりＧ２レンズ９６ｂ近傍まで下降するアームを有しており、Ｇ２レンズ９６ｂを自動でハンドリングし所望の方向へ所望量移動させるメカ機構を有している。アームは、測定手段の受光素子７１ａ、７１ｂと同数（２つ）有している。本実施形態では、４つの被走査面を有するため、調整手段を図中左右方向に移動させて調整を行っている。調整手段及び測定手段は、被走査面ごとに独立に動作するため、測定及び、調整時間を短縮できると共に、被走査面の間隔が狭い走査装置の調整を行うことができる。
【００５２】
以上のように、本実施形態では、測定及び調整を２つの被走査面で同時、且つ独立に行い、走査レンズを光学箱上面から調整することにより、被走査面の間隔が狭い光走査装置の調整において、測定、及び調整時間を短縮することが可能となり、低価格な光走査装置を提供できる。
【００５３】
（実施例３）
本実施形態の実施形態１と異なる点は、調整手段の構成であり、その他の構成及び効果は、実施形態１と同様である。
【００５４】
本実施形態の測定手段は、被走査面相当位置でのスポット位置を図５の受光素子５１ａ、５１ｂ、５１ｃ、５１ｄにより測定する測定手段５０と、測定手段の測定値に基づいて不図示の調整手段により光学箱上面から調整を行っている。測定手段の受光素子５１ａ、５１ｂ、５１ｃ、５１ｄは、２次元のエリアＣＣＤを用いており、４つの被走査面を同時に測定している。測定データは、不図示の演算手段により演算され、出力結果はスポット位置の座標を１０^−６ｍ以下のオーダーで得ることができる。
【００５５】
不図示の調整手段は光学箱下面（測定手段の対向面）側から図中上方に移動可能なアームを有しており、調整時はＧ２レンズ９６ｂ近傍にアームが移動し、レンズをハンドリングして調整を行う。アームは測定手段の受光素子５１ａ、５１ｂ、５１ｃ、５１ｄと同数（４つ）有しており、本実施形態では、４つのアームで調整を行っている。調整時は、演算手段の出力データを元に、Ｇ２レンズ９６ｂをＹ−Ｚ面内でシフト又は／且つチルトさせ、良好な光学特性を得た後に、光学箱と接着する。本実施形態では測定手段と、調整手段を対向させて配置することにより測定手段と調整手段のメカ的干渉を防止することが出来る。
【００５６】
調整手段及び測定手段は、被走査面ごとに独立に動作するため、測定及び、調整時間を大幅に短縮できる。
【００５７】
以上のように本実施形態では、測定及び調整を４つの被走査面で同時且つ独立に行い、測定を上面から行い、調整を下面のみから行うことにより、測定装置と調整装置の干渉を防止し、測定及び調整時間を大幅に短縮することが可能となり、低価格な光走査装置を提供できる。
【００５８】
（画像形成装置）
図９は、本発明の画像形成装置の実施形態を示す副走査方向の要部断面図である。図９において、図９において、６０はカラー画像形成装置、１１は各々実施形態１〜３に示したいずれかの構成を有する走査光学装置、２１，２２，２３，２４は各々像担持体としての感光ドラム、３１，３２，３３，３４は各々現像器、５１は搬送ベルトである。
【００５９】
図において、カラー画像形成装置６０には、パーソナルコンピュータ等の外部機器５２からＲ（レッド）、Ｇ（グリーン）、Ｂ（ブルー）の各色信号が入力する。これらの色信号は、装置内のプリンタコントローラ５３によって、Ｃ（シアン），Ｍ（マゼンタ），Ｙ（イエロー）、Ｂ（ブラック）の各画像データ（ドットデータ）に変換される。これらの画像データは、それぞれ走査光学装置１１に入力される。そして、これらの走査光学装置からは、各画像データに応じて変調された光ビーム４１，４２，４３，４４が出射され、これらの光ビームによって感光ドラム２１，２２，２３，２４の感光面が主走査方向に走査される。
【００６０】
本実施態様におけるカラー画像形成装置は１つの走査光学装置（１１）から、各Ｃ（シアン），Ｍ（マゼンタ），Ｙ（イエロー）、Ｂ（ブラック）の各色に対応した光線を射出し、感光ドラム２１，２２，２３，２４面上に画像信号（画像情報）を記録し、カラー画像を高速に印字するものである。
【００６１】
本実施態様におけるカラー画像形成装置は上述の如く１つの走査光学装置１１により各々の画像データに基づいた光ビームを用いて各色の潜像を各々対応する感光ドラム２１，２２，２３，２４面上に形成している。その後、記録材に多重転写して１枚のフルカラー画像を形成している。
【００６２】
前記外部機器５２としては、例えばＣＣＤセンサを備えたカラー画像読取装置が用いられても良い。この場合には、このカラー画像読取装置と、カラー画像形成装置６０とで、カラーデジタル複写機が構成される。
【００６３】
【発明の効果】
本発明によれば前述の如く、複数の光束を共通の偏向器で異なる被走査面へ導光する光走査装置において、光走査装置の出荷時初期調整を簡素化し、調整時間を短縮するために、各走査レンズの偏向面に垂直な面（走査面）への光学部材の投影像が、他の光学部材及び光学ハウジングの部材に干渉しないように配置することにより、走査レンズを光学箱上面又は下面の一方向から調整し、高精度な調整と調整タクトが短縮可能となる。又、調整時に複数の被走査面の光学特性を同時且つ独立に測定し、調整することにより低価格な光走査装置を提供できる。
【図面の簡単な説明】
【図１】本実施例１の光走査装置における副走査断面図。
【図２】本実施例１の光走査装置における斜視図。
【図３】本実施例１の光走査装置における上面への正射影像。
【図４】本実施例１の測定手段を示す図。
【図５】被走査面相当位置でのスポット位置を示す図。
【図６】本実施例１の折り返しミラーの調整手段を示す図。
【図７】本実施例２の測定手段を示す図。
【図８】従来の光走査装置。
【図９】本発明の画像形成装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device used in an image forming apparatus such as a laser printer or a digital copying machine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an optical scanning device used in an image forming apparatus such as a laser beam printer or a digital copying machine guides a light beam emitted from a light source to a deflecting element by incident optical means, and the light beam deflected by the deflecting element. Are imaged in a spot shape on the surface of the photosensitive drum, which is the surface to be scanned, by the scanning optical means, and the photosensitive drum surface is optically scanned with the luminous flux.
[0003]
In such an optical scanning device, the light beam emitted from the light source is converted into substantially parallel light by a collimator lens or the like, and the light beam converted into substantially parallel light for performing tilt correction is lined near the deflection surface by a cylindrical lens. An image is formed. The light beam deflected by the deflecting surface of the deflector scans the surface of the photosensitive drum with a scanning lens at a substantially constant speed to form a spot.
[0004]
In FIG. 8, reference numerals 1a, 1b, 1c, and 1d denote light source means, for example, semiconductor lasers. Reference numerals 2a, 2b, 2c and 2d denote cylindrical lenses which have a predetermined refractive power only in the sub-scanning direction. Each element such as the light source means 1 and the cylindrical lens 2 constitutes one element of the incident optical means 51.
[0005]
Reference numeral 3 denotes an optical deflector as a deflecting element, which is composed of, for example, a rotating polygon mirror, and is rotated at a constant speed in the direction of arrow A in the figure by driving means (not shown) such as a motor. Reference numerals 11a and 11b denote three fθ lenses having fθ characteristics, in the sub-scan section, in the vicinity of the deflection surfaces 3a and 3b of the optical deflector 3, and in the vicinity of the photosensitive drum surfaces 100a, 100b, 100c and 100d as the scanned surfaces. It has a tilt correction function by making a conjugate relationship between them (see JP-A-11-125784).
[0006]
Further, in order to form a color image of two or more colors, a plurality of light beams are incident on a single deflector, and the plurality of light beams deflected by the deflector are respectively guided to different scanned surfaces, thereby deflecting. The number of vessels is not increased.
[0007]
[Problems to be solved by the invention]
In the assembly of the above conventional optical scanning device, there is a problem that adjustment time becomes long because highly accurate adjustment is required. For example, in the conventional optical scanning device shown in FIG. 8, a CCD camera (not shown) is arranged at a position corresponding to the surface to be scanned corresponding to each color in order to adjust the spot position on the surface to be scanned by a single scanning unit. Adjustment is performed by adjusting the angle of the side folding mirror. After the adjustment at one drum surface equivalent position is completed, the CCD camera is moved to the next drum surface equivalent position, and the same adjustment is repeated to obtain desired optical characteristics. Since this spot position is usually adjusted with a relative difference of several tens of μm, a mechanical mechanism for precisely adjusting the angle of the folding mirror is required, and the adjustment time becomes long, resulting in a cost increase. . When these adjustments are made at the time of shipment, since the orthogonal projection images are superimposed on the upper surface or the lower surface (left or right in the figure) of the optical element, adjustment means for accessing the folding mirror is not available. Because it interferes with the folding mirror, which is an optical member, it cannot be accessed by the adjusting means from the top surface (left side in the figure), and it must be accessed from the side (front of the paper), resulting in a large adjustment tool. In addition, since the adjustment work becomes complicated, there are problems that adjustment accuracy is deteriorated and adjustment time is lengthened. Although an example of adjusting the folding mirror is shown here, these adjustments are the same when adjusting not only the folding mirror but also other optical members such as the fθ lens.
[0008]
The present invention provides an optical scanning apparatus that guides a plurality of light beams to different scanning surfaces with a common deflector, in order to simplify the initial adjustment of the optical scanning apparatus at the time of shipment and to shorten the adjustment time. By disposing the projection image of the optical member on the surface perpendicular to the deflection surface (scanning surface) so as not to interfere with other optical members and members of the optical housing, the scanning lens can be viewed from one direction of the upper surface or the lower surface of the optical box. Adjustment is possible, and high-precision adjustment and adjustment tact can be shortened. In addition, a low-cost optical scanning device can be provided by simultaneously measuring and adjusting the optical characteristics of a plurality of scanned surfaces during adjustment.
[0009]
[Means for Solving the Problems]
(1-1)
A plurality of optical elements for deflecting light beams from a plurality of light sources with the same deflector and scanning different scanned surfaces at substantially constant speed,
The optical element is held in the same optical housing, and the optical element is arranged so that an orthogonal projection image of the optical element on the upper or lower surface of the optical housing does not interfere with other optical members. Ya (1-2)
When the region S where the orthographic projection interferes with other optical members and the region where the orthogonal projection does not interfere with V satisfy S / V <0.2,
(1-3)
The optical element on the most deflector side is characterized in that light beams directed to two or more different scanned surfaces pass in common,
(1-4)
The optical element is made of plastic, and
(1-5)
The light source means is constituted by a monolithic multi-beam laser.
[0010]
(1-6)
The scanning optical device according to any one of (1-1) to (1-5), a photosensitive member disposed on the surface to be scanned, and a light beam scanned by the scanning optical device on the photosensitive member. A developing device that develops the electrostatic latent image formed on the toner as a toner image, a transfer device that transfers the developed toner image to a transfer material, and a fixing device that fixes the transferred toner image to the transfer material; Providing
(1-7)
The scanning optical device according to any one of (1-1) to (1-5), and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical device. It is characterized by that.
[0011]
(2-1)
A plurality of scanning lenses for deflecting light beams from a plurality of light sources with the same deflector and scanning different scanned surfaces at substantially constant speed,
In the optical scanning device in which the plurality of optical elements are held in the same optical housing,
In order to obtain desired optical characteristics, a plurality of optical elements are adjusted simultaneously and independently from one direction,
(2-2)
A measuring unit that simultaneously measures optical characteristics on a plurality of scanned surfaces, and an adjusting unit that simultaneously adjusts the plurality of optical elements,
(2-3)
The measuring means is characterized by measuring the irradiation position, lateral magnification, optical characteristics of the straightness of the scanning line,
(2-4)
Adjusting the optical element in one plane, or
(2-5)
The scanning optical device adjusted according to any one of (2-1) to (2-4), the photoconductor disposed on the surface to be scanned, and the light beam scanned by the scanning optical device. A developing device that develops the electrostatic latent image formed on the photoreceptor as a toner image, a transfer device that transfers the developed toner image to a transfer material, and the transferred toner image is fixed to the transfer material. Equipped with a fuser,
(2-6)
The scanning optical device adjusted according to any one of (2-1) to (2-4), and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical device It is characterized by comprising.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
FIG. 1 is a sub-scan sectional view of the optical system of the present invention. FIG. 2 is an exploded view of the optical system main scanning section in the optical apparatus of the present invention.
[0013]
91 is a light source such as a semiconductor laser, and 92 is a collimator lens that converts divergent light from the light source into a substantially parallel light beam.
[0014]
Reference numeral 93 denotes an aperture stop that adjusts the diameter of the passing light beam.
[0015]
Reference numeral 94 denotes a cylindrical lens as a second optical system, which has a predetermined refractive power only in the sub-scanning direction. After passing through the stop 93, a linear image is formed on the deflecting surface of the deflector within the sub-scanning section. As an image.
[0016]
Reference numeral 95 denotes a polygon mirror as a deflector, which rotates at a constant speed in the direction of an arrow.
[0017]
Reference numeral 96 denotes an fθ lens as a third optical system, and both 96a and 96b are constituted by an aspherical anamorphic lens in the main scanning plane, and the light beam deflected by the deflector 95 is used as a scanning surface. An image is formed on the drum surface, and the surface tilt of the deflector is corrected.
[0018]
The dust-proof glass 98 is attached to the lid of the optical box in order to prevent dust such as toner from entering the optical scanning device (optical box).
[0019]
FIG. 3 is a perspective view of the optical system in the optical apparatus of the present invention.
[0020]
91 is a light source such as a semiconductor laser, and 92 is a collimator lens that converts divergent light from the light source into a substantially parallel light beam.
[0021]
Reference numeral 93 denotes an aperture stop that adjusts the diameter of the passing light beam.
[0022]
A cylindrical lens 94 as a second optical system has a predetermined refractive power only in the sub-scanning direction. After passing through the cylindrical lens 94, the cylindrical lens 94 is substantially lined with the deflection surface of the deflector in the sub-scanning section. It is formed as an image. Light beams from a plurality of light sources are incident on the deflection surface at an angle of 2.2 deg in the sub-scan section in order to scan different scanning surfaces. The optical axes of the collimator lens, aperture stop, and cylindrical lens are all arranged so as to be orthogonal to the principal ray. In other words, 2.2 deg. Tilted.
[0023]
The light beam deflected by the deflector 95 is imaged on the surface of the photosensitive drum as the surface to be scanned by the fθ lenses 96a and 96b as the third optical system.
[0024]
The Fθ lenses 96a and 96b of the present embodiment are configured by using a plurality of optical systems shown in FIG. 2 as shown in FIGS. 1 and 3, but all have the same optical characteristics.
[0025]
The fθ lens 96 in this embodiment is expressed using a function of the following formula.
[0026]
The origin is the intersection of the fθ lens and the optical axis,
As shown in FIG. 2, on the scanning start side and the scanning end side with respect to the optical axis, the optical axis is the X axis, the direction perpendicular to the optical axis in the main scanning plane is the Y axis, and the optical axis is orthogonal to the sub scanning plane. The direction to do is the z-axis,
It can be expressed by the following continuous function.
Scan start side [Outside 1]

[0027]
End of scanning [Outside 2]

[0028]
R is a radius of curvature, and K, B4, B6, B8, and B10 are aspherical coefficients.
[0029]
In this embodiment, the shape in the main scanning direction is configured symmetrically with respect to the optical axis, that is, the aspheric coefficients on the scanning start side and the scanning end side are made to coincide.
[0030]
The sub-scanning direction is a scanning start side and a scanning end side with respect to the optical axis, and the curvature in at least one sub-scanning surface (a surface including the optical axis and perpendicular to the main scanning surface) of the fθ lens 96 is set. The lens is continuously changed in the effective portion of the lens, and the shape in the main scanning direction is configured symmetrically with respect to the optical axis.
[0031]
The shape in the sub-scanning direction is the X axis on the scanning start side and the scanning end side with respect to the optical axis, the Y axis in the direction perpendicular to the optical axis in the main scanning plane, and the optical axis in the sub scanning plane. Let the orthogonal direction be the z-axis,
It can be expressed by the following continuous function.
Scan start side [Outside 3]

[0032]
End of scanning [Outside 4]

[0033]
(Where r ′ is the radius of curvature in the sub-scanning direction, and D ₂ , D ₄ , D ₆ , and D ₈ D ₁₀ are coefficients)
The coefficient suffix s represents the scanning start side, and e represents the scanning end side.
[0034]
The sub-scanning direction radius of curvature is a radius of curvature in a cross section perpendicular to the shape (bus line) in the main scanning direction.
[0035]
In this embodiment, in order to correct focus correction (field curvature correction) in the sub-scanning direction and uniformity of magnification in the sub-scanning direction (fluctuation of spot diameter due to image height) in the fθ lens, the most scanning side is used. The sub-scanning curvature radius of the surface (r4 surface) on the surface to be scanned of the lens 96b (G2) is continuously changed. Usually, the sub-scanning curvature radius is changed by changing at least two planes, and both are corrected. However, in the present embodiment, since the uniformity of the magnification is corrected by the shape in the main scanning direction, The curvature of field is corrected by changing only one surface.
[0036]
Next, means and effects for achieving the object of the present invention will be described.
[0037]
The fθ lens 96 of the present embodiment is made of a plastic lens, and the shape in the main scanning direction is configured on the scanning start side and the end side so as to be advantageous in molding.
Further, at least one surface has a continuously changing radius of curvature in the sub-scanning direction to correct field curvature, wavefront aberration, and spot diameter fluctuation. Furthermore, in the present embodiment, the G2 lens is decentered (shifted by 1.456 mm in the z direction) and the scan line curvature caused by the incident light beam incident on the deflecting surface at an oblique incidence in the sub-scanning direction. ).
[0038]
The optical scanning / scanning apparatus of the present invention is the most deflector side so that two light beams incident on substantially the same position of the deflection surface at the same angle from two different directions pass through a symmetrical position across the optical axis of the lens. Lens 96a (G1) is disposed. Since the plurality of incident light beams are deflected at substantially the same position in the sub-scanning direction of the deflection surface, the deflection surface can be configured to be low. Further, since the G1 lens 96a has a substantially flat curvature radius in the sub-scanning direction and has almost no power in the sub-scanning direction, the optical performance is deteriorated due to the light beam passing off the axis in the sub-scanning direction. It is preventing.
[0039]
In FIG. 1, the light beam incident on the deflection surface obliquely upward from below passes through the G1 lens 96a, is reflected by the first folding mirror 99a, passes through the lens 96b (G2) closest to the surface to be scanned, After being reflected by the second folding mirror 99b and passing through a dust-proof glass 98 constituted by a flat plate, the surface of the photosensitive drum as the surface to be scanned is scanned. In FIG. 1, a light beam incident obliquely downward from above passes through the G1 lens 96a, then passes through the G2 lens 96b, is reflected by the third folding mirror 100a, and scans the drum surface 97 as the surface to be scanned. To do.
[0040]
The fθ lens 96 of this embodiment is configured so that the shape in the main scanning direction is symmetrical with respect to the perpendicular bisector of the surface to be scanned 97 so as to be advantageous in molding, and the lens on the most deflector side is sub-scanning. The radius of curvature in the direction is substantially flat and has almost no power in the sub-scanning direction. The imaging performance in the sub-scanning direction is corrected only on the most scanned surface of the lens on the most scanned surface side.
[0041]
Next, adjustment by the optical system of the optical scanning device will be described. The optical scanning device according to the present embodiment obtains good optical characteristics by performing the following adjustment at the time of shipment.
[0042]
Asymmetry correction of magnification error in main scanning direction (asymmetry correction of image expansion / contraction)
Scan line height correction (sub-scan direction spot height correction)
Scan line tilt correction (Sub-scan direction tilt correction)
Scan line curvature correction (sub-scan direction bending correction)
1 to 3 are performed by the lens 96b (G2 lens) closest to the scanning surface shown in FIG. 1, and 4 is performed by the folding mirrors 99b and 100a closest to the scanning surface. 1 is corrected by decentering (shifting) the G2 lens in the Y direction, 2 is rotating in the Z direction, and 3 is rotating (tilting) around the X axis.
[0043]
In addition, as shown in FIG. 6, correction is performed by bending the busbar of the folding mirror in the normal direction of the reflecting surface as shown in FIG.
[0044]
Since the G2 lens is shifted or tilted in the Y-Z plane in the adjustments 1 to 3, the lens can be adjusted while being abutted in the X direction. Therefore, there is an advantage that the lens posture is stable and the adjustment accuracy can be increased. . After the lens adjustment is completed, the lens is bonded to the optical box with an ultraviolet curable resin.
[0045]
All the above adjustments are performed by measuring means 50 for measuring the spot position at the position corresponding to the surface to be scanned by the light receiving elements 51a, 51b, 51c51d in FIG. 5 and by adjusting means (not shown) based on the measurement values of the measuring means 50. Adjustments are made from the top of the box. The light receiving elements 51a, 51b, 51c and 51d of the measuring means 50 use a two-dimensional area CCD, and the output result calculated by the calculating means can obtain the spot position on the order of 10 ⁻⁶ m or less. . Further, the adjusting means (not shown) has an arm that descends from the upper surface of the optical box (above the motor seat surface) to the vicinity of the fθ lens, and a mechanical mechanism that automatically handles the G2 lens and moves it in a desired direction. As shown in FIG. 6, it has a mechanical member for pressing and bending with a screw parallel to the normal surface of the reflecting mirror.
[0046]
In order to perform the above adjustment in a short time and efficiently,
It is necessary to simultaneously measure and adjust the spot positions at a plurality of scanned surface positions from one direction, and in order to achieve the above, the scanned surface corresponding to four colors in this embodiment. All 97 are measured and adjusted simultaneously, and the lens and mirror are arranged so that the orthogonal projection image on the upper surface of the optical component (corresponding to the upper side in FIG. 1) satisfies the following formula as shown in FIG. .
[0047]
0 ≦ S / V <0.2
S: Area of a region interfering with another optical member V: Area of a region not interfering with another optical member When the above formula is not satisfied, the overlap between optical components increases, and the upper surface or the lower surface It becomes difficult to adjust from the direction.
[0048]
In the present embodiment, the fθ lens 96 is composed of two lenses. However, the fθ lens may be one lens or three or more lenses, and even if an optical element such as a diffractive element is used, it is exactly the same. The effect of can be obtained. Further, although a single beam laser is used as the light source 91, the same effect can be obtained even when a multi-beam laser having a plurality of light emitting points of two or more is used. Further, although a two-dimensional CCD is used as the light receiving element of the measuring means, a one-dimensional line CCD or the like may be used, and this is not limited as long as the spot position can be measured with high accuracy. Further, although the adjusting means is also adjusted by handling the lens, it is obvious that other methods may be used as long as the posture of the lens can be changed.
[0049]
As described above, in an optical scanning device that guides a plurality of light beams to different scanning surfaces with a common deflector, each scanning lens is simplified in order to simplify initial adjustment at the time of shipment of the optical scanning device and shorten adjustment time. The scanning lens is arranged in one direction on the upper surface or the lower surface of the optical box by arranging the projection image of the optical member on the surface (scanning surface) perpendicular to the deflection surface of the optical box so as not to interfere with other optical members and members of the optical housing. It is possible to shorten the high-precision adjustment and adjustment tact. In addition, a low-cost optical scanning device can be provided by simultaneously and independently measuring and adjusting the optical characteristics of a plurality of scanned surfaces during adjustment.
[0050]
(Example 2)
The difference of the present embodiment from the first embodiment is the configuration of the measurement unit and the adjustment unit, and the other configurations and effects are the same as those of the first embodiment.
[0051]
The configuration of the measuring means of this embodiment is shown in FIG. The measuring means 70 adjusts from the upper surface of the optical box by a measuring means for measuring the spot position at the position corresponding to the scanned surface by the light receiving elements 71a and 71b, and an adjusting means (not shown) based on the measurement value of the measuring means 70. Yes. The light receiving elements 71a and 71b of the measuring means use a two-dimensional area CCD and can measure two scanned surfaces simultaneously. This is an advantageous configuration when the distance (pitch) between the scanned surfaces is narrow. The measurement data is calculated by a calculation means (not shown), and the output result can be obtained with the coordinates of the spot position on the order of 10 ⁻⁶ m or less. The adjusting means (not shown) has an arm that descends from the upper surface of the optical box (above the motor seat surface) to the vicinity of the G2 lens 96b. The G2 lens 96b is automatically handled and moved in a desired direction by a desired amount. It has a mechanical mechanism. The arm has the same number (two) as the light receiving elements 71a and 71b of the measuring means. In the present embodiment, since there are four surfaces to be scanned, the adjustment is performed by moving the adjusting means in the horizontal direction in the figure. Since the adjusting means and the measuring means operate independently for each surface to be scanned, it is possible to shorten the measurement and adjustment time, and it is possible to adjust the scanning device having a narrow interval between the surfaces to be scanned.
[0052]
As described above, in this embodiment, measurement and adjustment are performed simultaneously and independently on the two scanned surfaces, and the scanning lens is adjusted from the upper surface of the optical box, so that the distance between the scanned surfaces is narrow. In the adjustment, the measurement and adjustment time can be shortened, and an inexpensive optical scanning device can be provided.
[0053]
(Example 3)
The difference of the present embodiment from the first embodiment is the configuration of the adjusting means, and other configurations and effects are the same as those of the first embodiment.
[0054]
The measuring means of the present embodiment includes a measuring means 50 for measuring the spot position at the position corresponding to the surface to be scanned by the light receiving elements 51a, 51b, 51c, 51d in FIG. 5, and an adjustment (not shown) based on the measurement value of the measuring means. Adjustment is performed from the upper surface of the optical box by means. The light receiving elements 51a, 51b, 51c and 51d of the measuring means use a two-dimensional area CCD and measure four scanned surfaces simultaneously. The measurement data is calculated by a calculation means (not shown), and the output result can be obtained with the coordinates of the spot position on the order of 10 ⁻⁶ m or less.
[0055]
The adjusting means (not shown) has an arm that can move upward in the figure from the lower surface of the optical box (opposite surface of the measuring means). During adjustment, the arm moves in the vicinity of the G2 lens 96b and handles the lens. Make adjustments. The arms have the same number (four) as the light receiving elements 51a, 51b, 51c, 51d of the measuring means, and in this embodiment, adjustment is performed with four arms. At the time of adjustment, the G2 lens 96b is shifted or / and tilted in the YZ plane based on the output data of the calculation means, and after obtaining good optical characteristics, it is bonded to the optical box. In the present embodiment, mechanical interference between the measuring means and the adjusting means can be prevented by arranging the measuring means and the adjusting means to face each other.
[0056]
Since the adjustment unit and the measurement unit operate independently for each surface to be scanned, the measurement and adjustment time can be greatly shortened.
[0057]
As described above, in this embodiment, measurement and adjustment are performed simultaneously and independently on the four scanned surfaces, measurement is performed from the upper surface, and adjustment is performed from the lower surface only, thereby preventing interference between the measurement device and the adjustment device. The measurement and adjustment time can be greatly shortened, and an inexpensive optical scanning device can be provided.
[0058]
(Image forming device)
FIG. 9 is a cross-sectional view of the main part in the sub-scanning direction showing the embodiment of the image forming apparatus of the present invention. In FIG. 9, in FIG. 9, reference numeral 60 denotes a color image forming apparatus, 11 denotes a scanning optical device having any one of the configurations shown in the first to third embodiments, and 21, 22, 23, and 24 denote image carriers. The photosensitive drums 31, 32, 33 and 34 are developing units, and 51 is a conveyor belt.
[0059]
In the figure, R (red), G (green), and B (blue) color signals are input to the color image forming apparatus 60 from an external device 52 such as a personal computer. These color signals are converted into C (cyan), M (magenta), Y (yellow), and B (black) image data (dot data) by a printer controller 53 in the apparatus. These image data are respectively input to the scanning optical device 11. From these scanning optical devices, light beams 41, 42, 43, and 44 modulated according to each image data are emitted, and the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are caused by these light beams. Scanned in the main scanning direction.
[0060]
The color image forming apparatus in this embodiment emits light corresponding to each color of C (cyan), M (magenta), Y (yellow), and B (black) from one scanning optical device (11). Image signals (image information) are recorded on the drums 21, 22, 23, and 24, and color images are printed at high speed.
[0061]
In the color image forming apparatus according to the present embodiment, as described above, one scanning optical device 11 uses the light beam based on each image data to convert the latent images of the respective colors onto the corresponding photosensitive drums 21, 22, 23, and 24. Is formed. Thereafter, a single full color image is formed by multiple transfer onto a recording material.
[0062]
As the external device 52, for example, a color image reading device including a CCD sensor may be used. In this case, the color image reading apparatus and the color image forming apparatus 60 constitute a color digital copying machine.
[0063]
【The invention's effect】
According to the present invention, as described above, in an optical scanning device that guides a plurality of light beams to different scanned surfaces by a common deflector, in order to simplify the initial adjustment of the optical scanning device at the time of shipment and shorten the adjustment time. The scanning lens is arranged so that the projection image of the optical member on the surface (scanning surface) perpendicular to the deflection surface (scanning surface) of each scanning lens does not interfere with other optical members and members of the optical housing. Adjusting from one direction on the lower surface enables high-precision adjustment and adjustment tact time to be shortened. In addition, a low-cost optical scanning device can be provided by simultaneously and independently measuring and adjusting the optical characteristics of a plurality of scanned surfaces during adjustment.
[Brief description of the drawings]
FIG. 1 is a sub-scan sectional view of an optical scanning device according to a first embodiment.
FIG. 2 is a perspective view of the optical scanning apparatus according to the first embodiment.
FIG. 3 is an orthogonal projection image on the upper surface of the optical scanning device according to the first embodiment.
FIG. 4 is a diagram illustrating a measuring unit according to the first embodiment.
FIG. 5 is a diagram showing spot positions at positions corresponding to the surface to be scanned.
FIG. 6 is a diagram illustrating a folding mirror adjusting unit according to the first embodiment.
FIG. 7 is a view showing a measuring means of the second embodiment.
FIG. 8 shows a conventional optical scanning device.
FIG. 9 is an image forming apparatus according to the present invention.

Claims (13)

A plurality of optical elements for deflecting light beams from a plurality of light sources with the same deflector and scanning different scanned surfaces at substantially constant speed,
The optical element is held in the same optical housing, and the optical element is disposed so that an orthogonal projection image of the optical element on the upper or lower surface of the optical housing does not interfere with other optical members. Scanning device. 2. The optical scanning device according to claim 1, wherein S / V <0.2 is satisfied, where V is a region S in which the orthogonal projection interferes with another optical member, and V is a non-interfering region. 2. The optical scanning device according to claim 1, wherein the optical element closest to the deflector passes in common the light beams directed to two or more different scanned surfaces. The optical scanning device according to claim 1, wherein the optical element is made of plastic. 2. The optical scanning device according to claim 1, wherein the light source means is constituted by a monolithic multi-beam laser. The scanning optical device according to any one of claims 1 to 5, a photosensitive member disposed on the surface to be scanned, and a light beam scanned by the scanning optical device, formed on the photosensitive member. An image including a developing device that develops an electrostatic latent image as a toner image, a transfer device that transfers the developed toner image onto a transfer material, and a fixing device that fixes the transferred toner image onto the transfer material. Forming equipment. 6. An image forming apparatus comprising: the scanning optical apparatus according to claim 1; and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical apparatus. . A plurality of scanning lenses for deflecting light beams from a plurality of light sources with the same deflector and scanning different scanned surfaces at substantially constant speed,
In the optical scanning device in which the plurality of optical elements are held in the same optical housing,
A method of adjusting an optical scanning device, wherein a plurality of optical elements are adjusted simultaneously and independently from one direction in order to obtain desired optical characteristics. 9. The adjusting method according to claim 8, further comprising measuring means for simultaneously measuring optical characteristics on a plurality of scanned surfaces and adjusting means for simultaneously adjusting the plurality of optical elements. 10. The adjustment method according to claim 8, wherein the measuring unit measures an irradiation position, a lateral magnification, and a straight line optical characteristic of the scanning line. The adjustment method according to claim 8, wherein the adjustment of the optical element is performed within one plane. A scanning optical device adjusted according to any one of claims 8 to 11, a photosensitive member disposed on the surface to be scanned, and a light beam scanned by the scanning optical device on the photosensitive member. A developing device that develops the formed electrostatic latent image as a toner image, a transfer device that transfers the developed toner image to a transfer material, and a fixing device that fixes the transferred toner image to the transfer material. An image forming apparatus provided. 12. A scanning optical device adjusted according to claim 8, and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical device. Image forming apparatus.

Images