JP2004126192A - Optical scanner and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact optical scanner which is tolerant of ambient temperature variation and wavelength variation of a semiconductor laser and suitable for high-definition printing, and an image forming apparatus using the same. <P>SOLUTION: The optical scanner has a light source means 1, an optical means 2 which guides luminous flux from the light source means to an optical deflecting means 5, and an imaging optical system 6 which guides luminous flux from the deflecting means to a surface 7 to be scanned and optically scans the surface to be scanned through the rotating operation of the deflecting means; and the optical means has a diffraction part on one or more surfaces and satisfys respective conditional expressions. <P>COPYRIGHT: (C)2004,JPO

Description

【００１６】
とするとき、
【００１７】
【外６】

【００１８】
なる条件を満足することを特徴としている。
【００１９】
更に、
前記光学手段は、プラスチック材より成ることを特徴としている。
【００２０】
本発明の光走査装置は、、
光源手段と、該光源手段からの光束を光偏向手段に導光する光学手段と、該光偏向手段からの光束を被走査面に導光する結像光学系と、を有し、該光偏向手段の回動動作に基いて該被走査面を光走査する光走査装置において、
該光学手段は１以上の面に回折部を有しており、
【００２１】
【外７】

【００２２】
とするとき、
【００２３】
【外８】

【００２４】
なる条件を満足することを特徴としている。
【００２５】
更に、
前記光学手段は、プラスチック材より成ることを特徴としている。
【００２６】
本発明の光走査装置は、
光源手段と、該光源手段からの光束を光偏向手段に導光する光学手段と、
該光源手段と該光学手段とを一体的に保持する保持手段と、
該光偏向手段からの光束を被走査面に導光する結像光学系と、を有し、該光偏向手段の回動動作に基いて該被走査面を光走査する光走査装置において、
該光学手段は１以上の面に回折部を有しており、
【００２７】
【外９】

【００２８】
とするとき、
【００２９】
【外１０】

【００３０】
なる条件を満足することを特徴としている。
【００３１】
更に、
前記光学手段は、プラスチック材より成ることを特徴としている。
【００３２】
本発明の光走査装置は、
光源手段と、該光源手段からの光束を光偏向手段に導光する光学手段と、
該光源手段と該光学手段とを一体的に保持する保持手段と、
該光偏向手段からの光束を被走査面に導光する結像光学系と、を有し、該光偏向手段の回動動作に基いて該被走査面を光走査する光走査装置において、
該光学手段は１以上の面に回折部を有しており、
【００３３】
【外１１】

【００３４】
とするとき、
【００３５】
【外１２】

【００３６】
なる条件を満足することを特徴としている。
【００３７】
更に、
前記光学手段は、プラスチック材より成ることを特徴としている。
【００３８】
本発明の画像形成装置は、
上記の光走査装置と、前記被走査面に配置された感光体と、前記光走査装置で走査された光ビームによって前記感光体上に形成された静電潜像をトナー像として現像する現像器と、現像されたトナー像を被転写材に転写する転写器と、転写されたトナー像を被転写材に定着させる定着器とを有することを特徴としている。
【００３９】
本発明の画像形成装置は、
上記の光走査装置と、外部機器から入力したコードデータを画像信号に変換して前記光走査装置に入力せしめるプリンタコントローラとを有していることを特徴としている。
【００４０】
本発明のカラー画像形成装置は、
各々が上記の光走査装置から成る複数の光走査装置と、各々の光走査装置の被走査面に配置され、互いに異なった色の画像を形成する複数の像担持体とを有することを特徴としている。
【００４１】
更に、本発明のカラー画像形成装置は、
外部機器から入力した色信号を異なった色の画像データに変換して各々の光走査装置に入力せしめるプリンタコントローラを有していることを特徴としている。
【００４２】
【発明の実施の形態】
［実施形態１］
図１は本発明の実施形態１の光走査装置の主走査方向の要部断面図（主走査断面図）である。
【００４３】
ここで、主走査方向とは光偏向手段の回転軸及び結像光学系の光軸に垂直な方向（光偏向手段で光束が反射偏向（偏向走査）される方向）を示し、副走査方向とは光偏向手段の回転軸と平行な方向を示す。また主走査断面とは主走査方向に平行で結像光学系の光軸を含む平面を示す。また副走査断面とは主走査断面と垂直な断面を示す。
【００４４】
同図において１は光源手段であり、例えば半導体レーザー等より成っている。２は光学手段としてのコリメータレンズ（集光レンズ）であり、半導体レーザー１から放射された光束を略平行光束（もしくは略発散光束もしくは略収束光束）に変換している。コリメータレンズ２の材料は、プラスチック材料で構成されており、半導体レーザー１側の面に回折光学素子２ａが付加されており、被走査面７側の面は通常の屈折レンズ面から構成されている。
【００４５】
３は開口絞りであり、通過光束を制限してビーム形状を整形している。４はシリンドリカルレンズ（レンズ系）であり、副走査方向にのみ所定のパワー（屈折力）を有しており、開口絞り３を通過した光束を副走査断面内で後述する光偏向器５の偏向面（反射面）５ａにほぼ線像として結像させている。
【００４６】
５は光偏向手段としての光偏向器であり、例えば６面構成のポリゴンミラー（回転多面鏡）より成っており、モーター等の駆動手段（不図示）により図中矢印Ａ方向に一定速度で回転している。
【００４７】
６は集光機能とｆθ特性とを有する結像光学系としてのｆθレンズ系であり、第１、第２の２枚のｆθレンズ６ａ，６ｂを有し、光偏向器５によって反射偏向された画像情報に基づく光束を被走査面としての感光ドラム面７上に結像させ、かつ副走査断面内において光偏向器５の偏向面５ａと感光ドラム面７との間を共役関係にすることにより、倒れ補正機能を有している。
【００４８】
７は被走査面としての感光ドラム面である。
【００４９】
本実施形態１において半導体レーザー１から出射した光束はコリメータレンズ２により略平行光束に変換され、開口絞り３によって該光束（光量）が制限され、シリンドリカルレンズ４に入射している。シリンドリカルレンズ４に入射した略平行光束のうち主走査断面においてはそのままの状態で射出する。また副走査断面内においては収束して光偏向器５の偏向面５ａにほぼ線像（主走査方向に長手の線像）として結像している。そして光偏向器５の偏向面５ａで反射偏向された光束は第１、第２のｆθレンズ６ａ，６ｂを介して感光ドラム面７上にスポット状に結像され、該光偏向器５を矢印Ａ方向に回転させることによって、該感光ドラム面７上を矢印Ｂ方向（主走査方向）に等速度で光走査している。これにより記録媒体としての感光ドラム面７上に画像記録を行なっている。
【００５０】
本実施形態１の光走査装置におけるコリメータレンズ２は、半導体レーザー１側の面に付加された回折光学素子２ａによって、プラスチック材料の屈折率の波長依存特性によって発生するコリメータレンズ２の屈折部のパワー変化と屈折率の温度依存特性によって発生するコリメータレンズ２の屈折部のパワー変化とを同時に両立して補正するように、コリメータレンズ２の回折光学素子部（回折部）と屈折部の合成としてのトータルの焦点距離と、回折光学素子部のパワーと屈折部のパワーの比率、結像光学系であるｆθレンズ系６の焦点距離、等が適切な関係になるように定められている。
【００５１】
以下、その詳細を説明する。
【００５２】
【外１３】

【００５３】
【外１４】

【００５４】
【外１５】

【００５５】
【外１６】

【００５６】
【外１７】

【００５７】
【外１８】

【００５８】
【外１９】

【００５９】
【外２０】

【００６０】
【外２１】

【００６１】
【外２２】

【００６２】
【外２３】

【００６３】
【外２４】

【００６４】
【外２５】

【００６５】
【外２６】

【００６６】
【外２７】

【００６７】
【外２８】

【００６８】
【外２９】

【００６９】
【外３０】

【００７０】
【外３１】

【００７１】
【外３２】

【００７２】
【外３３】

【００７３】
【外３４】

【００７４】
【外３５】

【００７５】
【外３６】

【００７６】
【外３７】

【００７７】
【外３８】

【００７８】
【外３９】

【００７９】
【外４０】

【００８０】
【外４１】

【００８１】
尚、以上は単位を「ｍｍ」で表したが、他の単位、例えば「インチ（ｉｎｃｈ）」であっても同様の式が導き出せる。
【００８２】
［画像形成装置］
図３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。図において、符号１０４は画像形成装置を示す。この画像形成装置１０４には、パーソナルコンピュータ等の外部機器１１７からコードデータＤｃが入力する。このコードデータＤｃは、装置内のプリンタコントローラ１１１によって、画像データ（ドットデータ）Ｄｉに変換される。この画像データＤｉは、実施形態１〜４に示したいずれかの構成を有する光走査ユニット１００に入力される。そして、この光走査ユニット１００からは、画像データＤｉに応じて変調された光ビーム１０３が出射され、この光ビーム１０３によって感光ドラム１０１の感光面が主走査方向に走査される。
【００８３】
静電潜像担持体（感光体）たる感光ドラム１０１は、モータ１１５によって時計廻りに回転させられる。そして、この回転に伴って、感光ドラム１０１の感光面が光ビーム１０３に対して、主走査方向と直交する副走査方向に移動する。感光ドラム１０１の上方には、感光ドラム１０１の表面を一様に帯電せしめる帯電ローラ１０２が表面に当接するように設けられている。そして、帯電ローラ１０２によって帯電された感光ドラム１０１の表面に、前記光走査ユニット１００によって走査される光ビーム１０３が照射されるようになっている。
【００８４】
先に説明したように、光ビーム１０３は、画像データＤｉに基づいて変調されており、この光ビーム１０３を照射することによって感光ドラム１０１の表面に静電潜像を形成せしめる。この静電潜像は、上記光ビーム１０３の照射位置よりもさらに感光ドラム１０１の回転方向の下流側で感光ドラム１０１に当接するように配設された現像器１０７によってトナー像として現像される。
【００８５】
現像器１０７によって現像されたトナー像は、感光ドラム１０１の下方で、感光ドラム１０１に対向するように配設された転写ローラ１０８によって被転写材たる用紙１１２上に転写される。用紙１１２は感光ドラム１０１の前方（図３において右側）の用紙カセット１０９内に収納されているが、手差しでも給紙が可能である。用紙カセット１０９端部には、給紙ローラ１１０が配設されており、用紙カセット１０９内の用紙１１２を搬送路へ送り込む。
【００８６】
以上のようにして、未定着トナー像を転写された用紙１１２はさらに感光ドラム１０１後方（図３において左側）の定着器へと搬送される。定着器は内部に定着ヒータ（図示せず）を有する定着ローラ１１３とこの定着ローラ１１３に圧接するように配設された加圧ローラ１１４とで構成されており、転写部から搬送されてきた用紙１１２を定着ローラ１１３と加圧ローラ１１４の圧接部にて加圧しながら加熱することにより用紙１１２上の未定着トナー像を定着せしめる。更に定着ローラ１１３の後方には排紙ローラ１１６が配設されており、定着された用紙１１２を画像形成装置の外に排出せしめる。
【００８７】
図３においては図示していないが、プリントコントローラ１１１は、先に説明したデータの変換だけでなく、モータ１１５を始め画像形成装置内の各部や、後述する光走査ユニット内のポリゴンモータなどの制御を行う。
【００８８】
［カラー画像形成装置］
図４は本発明の実施態様のカラー画像形成装置の要部概略図である。本実施形態は、光走査装置（光走査光学系）を４個並べ各々並行して像担持体である感光ドラム面上に画像情報を記録するタンデムタイプのカラー画像形成装置である。図４において、６０はカラー画像形成装置、１１，１２，１３，１４は各々実施形態１〜４に示したいずれかの構成を有する光走査装置、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。尚、図４においては現像器で現像されたトナー像を被転写材に転写する転写器（不図示）と、転写されたトナー像を被転写材に定着させる定着器（不図示）とを有している。
【００８９】
図４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、それぞれ光走査装置１１，１２，１３，１４に入力される。そして、これらの光走査装置からは、各画像データに応じて変調された光ビーム４１，４２，４３，４４が射出され、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。
【００９０】
本実施態様におけるカラー画像形成装置は光走査装置（１１，１２，１３，１４）を４個並べ、各々が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、各々平行して感光ドラム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。
【００９１】
本実施態様におけるカラー画像形成装置は上述の如く４つの光走査装置１１，１２，１３，１４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。
【００９２】
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。
【００９３】
【発明の効果】
本発明によれば前述の如く屈折部を含む光学手段（例えば、コリメータレンズ）に回折光学素子を付加し、屈折部と回折部のパワー比率を最適に設定することによって屈折部の材料（例えば、プラスチック材料）の屈折率の温度依存特性によるパワー変化を補正し、かつ半導体レーザーのモードホッピングによって発生する屈折率の波長依存特性に起因する被走査面上でのピントずれを出力画像に劣化の認められない程度に小さく抑えることができる光走査装置及びそれを用いた画像形成装置を達成することができる。
【００９４】
さらに本発明によれば光源手段（例えば、半導体レーザー）と屈折部を含む光学手段（例えば、コリメータレンズ）を線膨張係数ρの材質で一体的に保持することにより、保持部材の膨張によっても屈折部の材料の屈折率の温度依存特性によるパワー変化を補正する構成とし、それによって光源手段（例えば、半導体レーザー）のモードホッピングによって発生する屈折率の波長依存特性に起因する被走査面上でのピントずれをより一層効果的に補正することができる。
【００９５】
特に、コリメータレンズとしてプラスチックレンズを使用した場合、環境変動に強く、高精細印字に適したコンパクトな光走査装置及びそれを用いた画像形成装置で顕著な効果を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施形態１の光走査装置の主走査断面図
【図２】本発明の実施形態３の光走査装置の主走査断面図
【図３】本発明の画像形成装置の実施形態を示す副走査断面図
【図４】本発明のカラー画像形成装置の実施形態を示す副走査断面図
【図５】従来の光走査装置の主走査断面図
【符号の説明】
１　光源（半導体レーザー）
２　コリメータレンズ
３　開口絞り
４　シリンドリカルレンズ
５　光偏向手段（ポリゴンミラー）
６　ｆθレンズ
７　被走査面（感光ドラム）
１１、１２、１３、１４‥‥光走査装置
２１、２２、２３、２４‥‥像担持体（感光ドラム）
３１、３２、３３、３４‥‥現像器
４１，４２，４３，４４‥‥光ビーム
５１‥‥搬送ベルト４１
５２‥‥外部機器
５３‥‥プリンタコントローラ
６０‥‥カラー画像形成装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical scanning device and an image forming apparatus using the same, and particularly to a semiconductor laser as a light source and high-definition printing excellent in environmental resistance characteristics, despite forming a collimator lens with an inexpensive material. It is suitable for an image forming apparatus such as a laser beam printer having an electrophotographic process, a digital copying machine, and a multifunction printer (multifunction printer).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an optical scanning device used for a laser beam printer, a digital copying machine, or the like, a light beam emitted from a light source means after being modulated in accordance with an image signal is periodically emitted by an optical deflector comprising a rotating polygon mirror. The light is converged in the form of a spot on a photosensitive recording medium (photosensitive drum) surface by an fθ lens system having fθ characteristics, and image recording is performed by optical scanning on the recording medium surface.
[0003]
FIG. 5 is a schematic view of a main part of a conventional optical scanning device.
[0004]
In the figure, a light beam emitted from a light source means 91 composed of a semiconductor laser is converted into a substantially parallel light beam by a collimator lens 92. The light beam (light amount) is shaped by an aperture stop 93, and a cylindrical lens 94 having a refractive power only in the sub-scanning direction. Incident on Of the substantially parallel light beam incident on the cylindrical lens 94, it is emitted as it is in the main scanning section, converges in the sub-scanning section, and is deflected by the deflecting surface 95a of an optical deflector 95 composed of a rotating polygon mirror. An image is formed substantially as a line image in the vicinity.
[0005]
The light flux reflected and deflected by the deflecting surface 95a of the optical deflector 95 is guided to the surface of the photosensitive drum as the surface to be scanned 97 via an fθ lens system (scanning optical means) 96 having fθ characteristics. By rotating the unit 95 in the direction of arrow A, the photosensitive drum surface 97 is optically scanned in the direction of arrow B (main scanning direction) to record image information.
[0006]
In such optical scanning devices and image forming apparatuses, in recent years, demands for high-definition printing as well as cost reduction and size reduction have been increasing.
[0007]
In order to satisfy these requirements, for example, there is an example in which chromatic aberration (power change) generated in a collimator lens due to mode hopping of a semiconductor laser as a light source is offset by a diffractive optical element (for example, see Patent Document 1).
[0008]
In Document 1, different from the dispersion characteristics of ordinary optical materials, a chromatic aberration (power change) generated by a collimator lens is diffracted by using a diffractive optical element having an abnormal dispersion characteristic showing a negative dispersion value. Canceled by optical element. This makes it possible to satisfactorily correct the chromatic aberration (power change) caused by the wavelength change due to the mode hopping of the semiconductor laser on the final scanned surface, that is, the defocus.
[Patent Document 1]
JP 2000-171741 A
[Problems to be solved by the invention]
However, in Reference 1, since only the chromatic aberration (power change) caused by the dispersion value of the collimator lens is considered, the chromatic aberration (power change) caused by the temperature dependence of the refractive index is compared with the chromatic aberration (power change) caused by the dispersion value. It is more difficult to use a much larger plastic lens as the collimator lens in (2).
[0010]
In an optical scanning optical system used in an optical scanning device, a point in which a focus shift caused by a change in power of a collimator lens is magnified many times on a surface to be scanned, and an auto focus performed by a pickup lens or the like. The mechanism also uses plastic that is inferior to environmental resistance characteristics because of the fact that the focus shift of the collimator lens and the focus shift on the surface to be scanned are greatly different, and the autofocus accuracy is deteriorated and feedback is complicated. It has not reached practical use as a material.
[0011]
When optical glass is used as the optical material, the temperature dependence of the refractive index is relatively small due to its characteristics. Therefore, it is usually sufficient to correct only the power change due to dispersion.
[0012]
However, when an inexpensive plastic lens is used as the material of the collimator lens, it is necessary to correct both because the temperature-dependent coefficient of the refractive index is larger than the dispersion. It is difficult to correct at the same time.
[0013]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact optical scanning device resistant to environmental temperature fluctuations and wavelength fluctuations of a semiconductor laser and suitable for high-definition printing, and an image forming apparatus using the same.
[0014]
[Means for Solving the Problems]
The optical scanning device of the present invention includes:
A light source unit; an optical unit that guides a light beam from the light source unit to a light deflecting unit; and an imaging optical system that guides the light beam from the light deflecting unit to a surface to be scanned. An optical scanning device that optically scans the surface to be scanned based on a rotating operation of the means;
The optical means has a diffractive portion on one or more surfaces,
[0015]
[Outside 5]

[0016]
When
[0017]
[Outside 6]

[0018]
It is characterized by satisfying certain conditions.
[0019]
Furthermore,
The optical means is made of a plastic material.
[0020]
The optical scanning device of the present invention includes:
A light source unit; an optical unit that guides a light beam from the light source unit to a light deflecting unit; and an imaging optical system that guides the light beam from the light deflecting unit to a surface to be scanned. An optical scanning device that optically scans the surface to be scanned based on a rotating operation of the means;
The optical means has a diffractive portion on one or more surfaces,
[0021]
[Outside 7]

[0022]
When
[0023]
[Outside 8]

[0024]
It is characterized by satisfying certain conditions.
[0025]
Furthermore,
The optical means is made of a plastic material.
[0026]
The optical scanning device of the present invention includes:
Light source means, and optical means for guiding the light flux from the light source means to the light deflecting means,
Holding means for integrally holding the light source means and the optical means,
An imaging optical system that guides the light beam from the light deflecting means to the surface to be scanned, and an optical scanning device that optically scans the surface to be scanned based on a rotation operation of the light deflecting means;
The optical means has a diffractive portion on one or more surfaces,
[0027]
[Outside 9]

[0028]
When
[0029]
[Outside 10]

[0030]
It is characterized by satisfying certain conditions.
[0031]
Furthermore,
The optical means is made of a plastic material.
[0032]
The optical scanning device of the present invention includes:
Light source means, and optical means for guiding the light flux from the light source means to the light deflecting means,
Holding means for integrally holding the light source means and the optical means,
An imaging optical system that guides the light beam from the light deflecting means to the surface to be scanned, and an optical scanning device that optically scans the surface to be scanned based on a rotation operation of the light deflecting means;
The optical means has a diffractive portion on one or more surfaces,
[0033]
[Outside 11]

[0034]
When
[0035]
[Outside 12]

[0036]
It is characterized by satisfying certain conditions.
[0037]
Furthermore,
The optical means is made of a plastic material.
[0038]
The image forming apparatus of the present invention includes:
The above-described optical scanning device, a photoconductor arranged on the surface to be scanned, and a developing device that develops, as a toner image, an electrostatic latent image formed on the photoconductor by a light beam scanned by the optical scanning device. And a transfer device for transferring the developed toner image to the transfer material, and a fixing device for fixing the transferred toner image to the transfer material.
[0039]
The image forming apparatus of the present invention includes:
It is characterized by including the optical scanning device described above and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the optical scanning device.
[0040]
The color image forming apparatus of the present invention includes:
A plurality of optical scanning devices each comprising the above-described optical scanning device, and a plurality of image carriers that are arranged on a surface to be scanned of each optical scanning device and form images of different colors from each other. I have.
[0041]
Furthermore, the color image forming apparatus of the present invention
It is characterized by having a printer controller that converts color signals input from an external device into image data of different colors and inputs the image data to each optical scanning device.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
FIG. 1 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction of the optical scanning device according to the first embodiment of the present invention.
[0043]
Here, the main scanning direction indicates a direction perpendicular to the rotation axis of the light deflecting means and the optical axis of the imaging optical system (the direction in which the light beam is reflected and deflected (deflection scanning) by the light deflecting means). Indicates a direction parallel to the rotation axis of the light deflecting means. The main scanning section indicates a plane parallel to the main scanning direction and including the optical axis of the imaging optical system. The sub-scanning section indicates a section perpendicular to the main scanning section.
[0044]
In FIG. 1, reference numeral 1 denotes a light source means, which is composed of, for example, a semiconductor laser or the like. Reference numeral 2 denotes a collimator lens (condensing lens) as an optical unit, which converts a light beam emitted from the semiconductor laser 1 into a substantially parallel light beam (or a substantially divergent light beam or a substantially convergent light beam). The material of the collimator lens 2 is made of a plastic material, a diffractive optical element 2a is added to the surface on the side of the semiconductor laser 1, and the surface on the surface to be scanned 7 is formed of a normal refractive lens surface. .
[0045]
Reference numeral 3 denotes an aperture stop, which shapes a beam shape by limiting a passing light beam. Reference numeral 4 denotes a cylindrical lens (lens system) having a predetermined power (refractive power) only in the sub-scanning direction, and deflects a light beam passing through the aperture stop 3 by an optical deflector 5 described later in the sub-scan section. An image is formed as a substantially linear image on the surface (reflection surface) 5a.
[0046]
Reference numeral 5 denotes an optical deflector as an optical deflecting means, which is composed of, for example, a polygon mirror (rotating polygon mirror) having a six-plane configuration, and is rotated at a constant speed in a direction indicated by an arrow A in the figure by a driving means (not shown) such as a motor. are doing.
[0047]
Reference numeral 6 denotes an fθ lens system as an imaging optical system having a light condensing function and fθ characteristics, which has first and second two fθ lenses 6a and 6b, and is reflected and deflected by the optical deflector 5. By forming a light beam based on image information on the photosensitive drum surface 7 as a surface to be scanned, and making the deflecting surface 5a of the optical deflector 5 and the photosensitive drum surface 7 conjugate in the sub-scanning section , And has a tilt correction function.
[0048]
Reference numeral 7 denotes a photosensitive drum surface as a surface to be scanned.
[0049]
In the first embodiment, a light beam emitted from the semiconductor laser 1 is converted into a substantially parallel light beam by a collimator lens 2, the light beam (light amount) is restricted by an aperture stop 3, and is incident on a cylindrical lens 4. Of the substantially parallel light beam incident on the cylindrical lens 4, the light beam is emitted as it is in the main scanning section. Further, in the sub-scan section, the light converges and forms an almost linear image (a linear image elongated in the main scanning direction) on the deflection surface 5a of the optical deflector 5. The light beam reflected and deflected by the deflecting surface 5a of the optical deflector 5 forms a spot image on the photosensitive drum surface 7 via the first and second fθ lenses 6a and 6b. By rotating in the direction A, the photosensitive drum surface 7 is optically scanned at a constant speed in the direction of arrow B (main scanning direction). Thus, an image is recorded on the photosensitive drum surface 7 as a recording medium.
[0050]
The collimator lens 2 in the optical scanning device of the first embodiment has a power of a refraction portion of the collimator lens 2 generated by the wavelength-dependent characteristic of the refractive index of the plastic material by the diffractive optical element 2a added to the surface on the semiconductor laser 1 side. The combination of the diffractive optical element unit (diffraction unit) and the refraction unit of the collimator lens 2 is corrected so that the change and the power change of the refraction unit of the collimator lens 2 caused by the temperature-dependent characteristic of the refractive index are simultaneously compatible. The total focal length, the ratio of the power of the diffractive optical element unit to the power of the refracting unit, the focal length of the fθ lens system 6 that is the imaging optical system, and the like are determined so as to have an appropriate relationship.
[0051]
Hereinafter, the details will be described.
[0052]
[Outside 13]

[0053]
[Outside 14]

[0054]
[Outside 15]

[0055]
[Outside 16]

[0056]
[Outside 17]

[0057]
[Outside 18]

[0058]
[Outside 19]

[0059]
[Outside 20]

[0060]
[Outside 21]

[0061]
[Outside 22]

[0062]
[Outside 23]

[0063]
[Outside 24]

[0064]
[Outside 25]

[0065]
[Outside 26]

[0066]
[Outside 27]

[0067]
[Outside 28]

[0068]
[Outside 29]

[0069]
[Outside 30]

[0070]
[Outside 31]

[0071]
[Outside 32]

[0072]
[Outside 33]

[0073]
[Outside 34]

[0074]
[Outside 35]

[0075]
[Outside 36]

[0076]
[Outside 37]

[0077]
[Outside 38]

[0078]
[Outside 39]

[0079]
[Outside 40]

[0080]
[Outside 41]

[0081]
In the above, the unit is represented by “mm”, but the same formula can be derived even with another unit, for example, “inch”.
[0082]
[Image forming apparatus]
FIG. 3 is a cross-sectional view of a main part in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In the figure, reference numeral 104 denotes an image forming apparatus. Code data Dc is input to the image forming apparatus 104 from an external device 117 such as a personal computer. The code data Dc is converted into image data (dot data) Di by the printer controller 111 in the apparatus. This image data Di is input to the optical scanning unit 100 having any of the configurations shown in the first to fourth embodiments. The optical scanning unit 100 emits a light beam 103 modulated according to the image data Di, and the light beam 103 scans the photosensitive surface of the photosensitive drum 101 in the main scanning direction.
[0083]
The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with a light beam 103 scanned by the optical scanning unit 100.
[0084]
As described above, the light beam 103 is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. This electrostatic latent image is developed as a toner image by a developing device 107 disposed so as to contact the photosensitive drum 101 on the downstream side in the rotation direction of the photosensitive drum 101 from the irradiation position of the light beam 103.
[0085]
The toner image developed by the developing device 107 is transferred onto a sheet 112 as a transfer material by a transfer roller 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The paper 112 is stored in a paper cassette 109 in front of the photosensitive drum 101 (right side in FIG. 3), but can be fed manually. A paper feed roller 110 is provided at an end of the paper cassette 109, and feeds the paper 112 in the paper cassette 109 to a transport path.
[0086]
As described above, the sheet 112 onto which the unfixed toner image has been transferred is further conveyed to the fixing device behind the photosensitive drum 101 (left side in FIG. 3). The fixing device includes a fixing roller 113 having a fixing heater (not shown) therein and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and the paper conveyed from the transfer unit. The unfixed toner image on the sheet 112 is fixed by heating the sheet 112 while pressing it at a pressure contact portion between the fixing roller 113 and the pressure roller 114. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and discharges the fixed paper 112 to the outside of the image forming apparatus.
[0087]
Although not shown in FIG. 3, the print controller 111 controls not only the above-described data conversion but also control of the motor 115 and other components in the image forming apparatus, a polygon motor in an optical scanning unit described later, and the like. I do.
[0088]
[Color image forming apparatus]
FIG. 4 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. This embodiment is a tandem-type color image forming apparatus in which four optical scanning devices (optical scanning optical systems) are arranged and image information is recorded in parallel on a photosensitive drum surface as an image carrier. In FIG. 4, reference numeral 60 denotes a color image forming apparatus; 11, 12, 13, and 14 each an optical scanning device having any of the configurations shown in the first to fourth embodiments; 21, 22, 23, and 24 each represent an image carrier; , Photosensitive drums 31, 32, 33, and 34 are developing devices, and 51 is a transport belt. In FIG. 4, a transfer device (not shown) for transferring the toner image developed by the developing device to the transfer material, and a fixing device (not shown) for fixing the transferred toner image to the transfer material are provided. are doing.
[0089]
In FIG. 4, 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 respective image data (dot data) of C (cyan), M (magenta), Y (yellow), and B (black) by a printer controller 53 in the apparatus. These image data are input to the optical scanning devices 11, 12, 13, and 14, respectively. From these optical scanning devices, light beams 41, 42, 43, and 44 modulated in accordance with the respective image data are emitted, and these light beams cause the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 to be exposed. Scanning is performed in the main scanning direction.
[0090]
The color image forming apparatus according to the present embodiment includes four optical scanning devices (11, 12, 13, 14), each of which has a color of C (cyan), M (magenta), Y (yellow), and B (black). Correspondingly, an image signal (image information) is recorded on the photosensitive drums 21, 22, 23, and 24 in parallel, and a color image is printed at a high speed.
[0091]
As described above, the color image forming apparatus in this embodiment converts the latent images of each color into the corresponding photosensitive drums 21 and 22 by using the light beams based on the respective image data by the four optical scanning devices 11, 12, 13 and 14. , 23 and 24. Thereafter, multiple transfer to a recording material is performed to form one full color image.
[0092]
As the external device 52, for example, a color image reading device having 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.
[0093]
【The invention's effect】
According to the present invention, as described above, a diffractive optical element is added to an optical unit (for example, a collimator lens) including a refraction unit, and a material of the refraction unit (for example, Correction of power change due to temperature dependence of refractive index of plastic material), and deterioration of output image due to defocus on scan surface due to wavelength dependence of refractive index caused by mode hopping of semiconductor laser It is possible to achieve an optical scanning device and an image forming apparatus using the optical scanning device, which can be reduced to an unacceptably small size.
[0094]
Further, according to the present invention, the light source means (for example, a semiconductor laser) and the optical means (for example, a collimator lens) including a refraction unit are integrally held by a material having a linear expansion coefficient ρ, so that the light is refracted by the expansion of the holding member. A power change due to the temperature-dependent characteristic of the refractive index of the material of the portion is corrected, whereby the light-receiving means (for example, a semiconductor laser) on the surface to be scanned due to the wavelength-dependent characteristic of the refractive index generated by mode hopping. Defocus can be corrected even more effectively.
[0095]
In particular, when a plastic lens is used as the collimator lens, a remarkable effect can be obtained in a compact optical scanning device that is resistant to environmental fluctuations and is suitable for high-definition printing and an image forming apparatus using the same.
[Brief description of the drawings]
FIG. 1 is a main scanning cross-sectional view of an optical scanning device according to a first embodiment of the present invention. FIG. 2 is a main scanning cross-sectional view of an optical scanning device according to a third embodiment of the present invention. FIG. 4 is a sub-scan sectional view showing an embodiment of the color image forming apparatus of the present invention. FIG. 5 is a main scan sectional view of a conventional optical scanning device.
1 light source (semiconductor laser)
2 Collimator lens 3 Aperture stop 4 Cylindrical lens 5 Light deflecting means (polygon mirror)
6 fθ lens 7 Scanned surface (photosensitive drum)
11, 12, 13, 14 {optical scanning device 21, 22, 23, 24} image carrier (photosensitive drum)
31, 32, 33, 34 {developers 41, 42, 43, 44} light beam 51} transport belt 41
52 {external equipment 53} printer controller 60} color image forming apparatus

Claims (3)

A light source unit; an optical unit for guiding a light beam from the light source unit to a light deflecting unit; and an imaging optical system for guiding the light beam from the light deflecting unit to a surface to be scanned. An optical scanning device that optically scans the surface to be scanned based on a rotating operation of the means;
The optical means has a diffractive portion on one or more surfaces,
[Outside 1]

When
[Outside 2]

An optical scanning device characterized by satisfying the following conditions. Light source means, and optical means for guiding the light flux from the light source means to the light deflecting means,
Holding means for integrally holding the light source means and the optical means,
An imaging optical system that guides the light beam from the light deflecting means to the surface to be scanned, and an optical scanning device that optically scans the surface to be scanned based on a rotation operation of the light deflecting means
The optical means has a diffractive portion on one or more surfaces,
[Outside 3]

When
[Outside 4]

An optical scanning device characterized by satisfying the following conditions. 3. An image, comprising: the optical scanning device according to claim 1 or 2; and a printer controller configured to convert code data input from an external device into an image signal and input the image signal to the optical scanning device. Forming equipment.

Images