JP2004021173A - Optical scanner and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical scanner capable of reducing color slurring caused by the tilt of the rotary shaft of a light deflector and making plotting timing on a surface to be scanned coincident, and an image forming apparatus using the optical scanner. <P>SOLUTION: In the optical scanner, a plurality of light beams emitted from even-numbered light sources are reflected and deflected by the different deflection surfaces of the same light deflector having a plurality of deflection surfaces so as to form an image on the surface to be scanned through a corresponding scanning lens system for each. The light deflector has the even-numbered deflection surfaces, and the even-numbered light sources are arranged on opposite sides to each other with respect to the optical axis of the scanning lens system, and the even-numbered light sources and the scanning lens system are arranged to be point-symmetrical each other with respect to the rotary shaft of the light deflector. <P>COPYRIGHT: (C)2004,JPO

Description

【００６４】
このように本実施形態では２個の光源を走査レンズ系の光軸に対して互いに反対側に配置し、かつ上記の式（１），（２）を満たすように２個の光源を適切に配置することにより、前述の実施形態１と同様な効果を得ている。
【００６５】
尚、光偏向器５の偏向面の面数が５面に限らず奇数面であれば、本発明は前述の実施形態３と同様に適用することができる。
【００６６】
［カラー画像形成装置］
図８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。
【００６７】
本実施形態は、像担持体である複数の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８において、６０はカラー画像形成装置、（１１，１２），（１３，１４）は実施形態１又は３に記載したような、同一ポリゴンミラーの異なる面で２本のビームを走査する光走査装置、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８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。
【００６８】
図８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。
【００６９】
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２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。
【００７０】
本実施態様におけるカラー画像形成装置は上述の如く２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。
【００７１】
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。
【００７２】
尚、本発明ではカラー画像形成装置に実施形態１又は３の光走査装置を適用したが、もちろんモノクロ画像形成装置に適用しても良い。
【００７３】
【発明の効果】
本発明によれば前述の如く偶数個の光源を走査レンズ系の光軸に対して互いに反対側に配置することにより、光偏向器の回転軸の倒れによる走査線の湾曲方向を同じにすることができ、特にカラー画像形成装置においては、色ずれを低減させることができ、また光偏向器の面数が偶数の場合、奇数の場合において、該偶数個の光源を最適に配置することにより、描画タイミング（走査開始位置のタイミング）を揃えることができる簡易な構成の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。
【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１の光走査装置の副走査断面図
【図３】光偏向器の回転軸がＸ方向に倒れた場合の走査線湾曲を表すグラフ
【図４】光偏向器の回転軸がＹ方向に倒れた場合の走査線湾曲を表すグラフ
【図５】光偏向器の偏向面が偶数の場合の入射方向と同期検知タイミングとを説明する図
【図６】本発明の実施形態２の光走査装置の副走査断面図
【図７】本発明の実施形態３の光偏向器の偏向面が奇数の場合の入射方向を説明する図
【図８】本発明の光走査装置を用いたカラー画像形成装置の副走査断面図
【図９】従来の光走査装置の主走査断面図
【図１０】従来の光走査装置の副走査断面図
【図１１】従来の光走査装置における光偏向器の回転軸がＸ方向に倒れた場合の走査線湾曲を表すグラフ
【図１２】従来の光走査装置における光偏向器の回転軸がＹ方向に倒れた場合の走査線湾曲を表すグラフ
【符号の説明】
１ａ、１ｂ‥‥光源
２ａ、２ｂ‥‥コリメーターレンズ
３ａ、３ｂ‥‥シリンドリカルレンズ
４ａ、４ｂ‥‥絞り
５，５５，６５，７５‥‥光偏向器（ポリゴンミラー）
６ａ、６ｂ‥‥走査レンズ系
７ａ、７ｂ‥‥折り返しミラー
８ａ、８ｂ‥‥被走査面（感光体ドラム面）
９ａ、９ｂ‥‥入射光学手段
６４ａ、６４ｂ‥‥ＢＤ光学系
１１，１２，１３，１４‥‥光走査装置
２１，２２，２３，２４‥‥感光体ドラム
３１，３２，３３，３４‥‥現像器
４１，４２，４３，４４‥‥光ビーム
５１‥‥搬送ベルト
５２‥‥外部機器
５３‥‥プリントコントローラ
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 in particular, scans a plurality of light beams emitted from an even number of light sources on a corresponding surface to be scanned via one optical deflector (polygon mirror). The present invention is suitable for an image forming apparatus such as a laser beam printer (LBP) having an electrophotographic process, a digital copying machine, and a multi-function printer (multi-function printer) for forming an image.
[0002]
[Prior art]
Conventionally, an optical scanning device used for an image forming apparatus such as a laser beam printer, a digital copying machine, a multifunction printer, etc., guides a light beam, which is light-modulated and emitted from a light source, to an optical deflector by an incident optical system. The light beam reflected and deflected by the optical deflector is spot-formed on the surface of the photosensitive drum, which is the surface to be scanned, by a scanning lens system having fθ characteristics, and the light beam is optically scanned on the surface of the photosensitive drum to obtain image information. We are recording. Further, the optical scanning device guides a plurality of light fluxes, which are light-modulated from a plurality of light sources, to a plurality of photosensitive drum surfaces through one optical deflector, and performs deflection scanning (reflection) on two or more different deflection surfaces. (Deflection) to record image information.
[0003]
FIG. 9 is a sectional view (main scanning sectional view) of a main part of a conventional optical scanning device having a plurality of light sources in the main scanning direction.
[0004]
In the figure, a divergent light beam emitted from one light source 91a is converted into a substantially parallel light beam by a collimator lens 92a, and after entering a cylindrical lens 93a having a predetermined refractive power only in the sub-scanning direction, the light beam is restricted by a stop 94a. . Of the substantially parallel light beam incident on the cylindrical lens 93a, the light beam is emitted as it is in the main scanning section. In the sub-scan section, the light is converged and formed as a substantially linear image on the deflection surface (reflection surface) 95a of the optical deflector 95 formed of a polygon mirror.
[0005]
The light flux reflected and deflected by the deflecting surface 95a of the optical deflector 95 is guided through a scanning lens system (fθ lens system) 96a having fθ characteristics onto a photosensitive drum surface 98a as a surface to be scanned. By rotating the container 95 in the direction of arrow A, the photosensitive drum surface 98a is optically scanned in the direction of arrow B (main scanning direction) to record image information.
[0006]
Similarly to the divergent light beam emitted from the light source 91a, the divergent light beam emitted from the other light source 91b rotates the optical deflector 95 in the arrow A direction, thereby causing the light deflector 95 to rotate on the photosensitive drum surface 98b in the arrow C direction (main scanning direction). Direction) to record image information.
[0007]
In the optical scanning device shown in the figure, a first scanner S1 and a second scanner S2 are arranged symmetrically with respect to an optical deflector 95.
[0008]
FIG. 10 is a sectional view (sub-scan sectional view) of a main part in the sub-scan direction of FIG. In the figure, the optical path is bent downward by 90 ° in the drawing by the return mirrors 97a and 97b, and the light flux reflected and deflected by the optical deflector 95 is guided onto the surfaces of the photosensitive drums 98a and 98b.
[0009]
By deflecting and scanning a plurality of light beams by one light deflector in this way, it is possible to omit the light deflector which was conventionally required for one light beam, thereby simplifying the entire apparatus and reducing the power consumption. We are trying to reduce costs.
[0010]
[Problems to be solved by the invention]
In such an optical scanning device, as shown in FIG. 10, an optical deflector 95 is generally provided on the photosensitive drum surfaces 98a and 98b by using an equal number of folding mirrors 97a and 97b for a plurality of scanning lens systems 96a and 96b. The light fluxes reflected and deflected by are imaged.
[0011]
Here, for example, when the rotation axis 95c of the optical deflector 95 is inclined, the scanning line for scanning on the photosensitive drum surfaces 98a and 98b is curved. In particular, in the optical scanning device as shown in FIG. 9, when the rotation axis 95c of the optical deflector 95 is inclined in the X-axis direction due to the symmetry of the arrangement of the respective optical systems, two scannings are performed as shown in FIG. The curving directions of the lines are the same on the photosensitive drum surfaces 98a and 98b, but when the rotation axis 95c of the optical deflector 95 is inclined in the Y-axis direction, the curving directions of the two scanning lines are as shown in FIG. It is reversed on the photosensitive drum surfaces 98a and 98b.
[0012]
Such an optical scanning device is generally used for a color image forming apparatus, and if the scanning lines have the same bending direction, the color shift is inconspicuous, but if the scanning line has the opposite bending direction, There is a problem that it is recognized as a color shift.
[0013]
As another problem, when the drawing timing of the light beam reflected and deflected by one deflecting surface of the optical deflector (timing of the scanning start position) and the drawing timing of the light beam reflected and deflected by another deflecting surface deviate simultaneously. A buffer (storage unit) for temporarily storing the transmitted image signal is required, and as a result, there is a problem that the entire apparatus becomes complicated and the cost increases.
[0014]
An object of the present invention is to provide an optical scanning device capable of reducing a color shift due to a tilt of a rotation axis of an optical deflector and matching drawing timing on a surface to be scanned, and an image forming apparatus using the same. And
[0015]
[Means for Solving the Problems]
The optical scanning device of the invention according to claim 1 is
A plurality of light beams emitted from an even number of light sources are reflected and deflected by different deflecting surfaces of the same light deflector having a plurality of deflecting surfaces, and are respectively scanned on the surface to be scanned via the corresponding scanning lens systems. In an optical scanning device that forms an image on
The optical deflector has an even number of deflecting surfaces, the even number of light sources are arranged on opposite sides of an optical axis of the scanning lens system, and connects the even number of light sources and the scanning lens system to each other. It is characterized in that they are arranged so as to be point-symmetric with respect to the rotation axis of the optical deflector.
[0016]
The invention of claim 2 is the invention according to claim 1,
For the even number of light sources, an even number of folding mirrors are arranged in each optical path from the light sources to the surface to be scanned.
[0017]
The optical scanning device according to claim 3 is:
A plurality of light beams emitted from an even number of light sources are reflected and deflected by different deflecting surfaces of the same light deflector having a plurality of deflecting surfaces, and are respectively scanned on the surface to be scanned via the corresponding scanning lens systems. In an optical scanning device that forms an image on
The light deflector has an odd number of deflecting surfaces, the even number of light sources are arranged on opposite sides with respect to an optical axis of the scanning lens system, and an incident light beam from one light source and a scanning lens system. The angle between the optical axis and the optical axis of the scanning lens system is d (degree), the angle between the incident light beam from the other light source and the number of deflection surfaces of the optical deflector is n (number). When
a <{360 (degrees) × (n-1) / n} -270 (degrees)
d = (360 (degrees) / n) + a
It is characterized in that the even number of light sources are arranged so as to satisfy the following expression.
[0018]
An image forming apparatus according to a fourth aspect of the present invention,
An optical scanning device according to claim 1, a photosensitive member disposed on a surface to be scanned, and an electrostatic latent image formed on the photosensitive member by a light beam scanned by the optical scanning device. A developing device for developing the toner image as a toner image, a transfer device for transferring the developed toner image to a transfer material, a fixing device for fixing the transferred toner image to the transfer material, and code data input from an external device And a printer controller for converting the image signal into an image signal and outputting the image signal to the optical scanning device.
[0019]
The laser beam printer of the invention according to claim 5 is
A light beam is guided to a photosensitive drum provided on the surface to be scanned by using the optical scanning device according to any one of claims 1 to 3.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[Embodiment 1]
FIG. 1 is a cross-sectional view of a main part in the main scanning direction (main scanning cross-sectional view) according to the first embodiment of the present invention, and FIG. is there.
[0021]
In this specification, the plane formed by the optical axis of the scanning lens system and the light beam deflected by the optical deflector is a main scanning section, and the plane including the optical axis of the scanning lens system and orthogonal to the main scanning section is sub-scanning. Defined as a cross section.
[0022]
In the figure, S1 and S2 are first and second scanners, respectively. The first and second scanners S1 and S2 each include a collimator lens (2a, 2b) for converting a state of a light beam from the light source (1a, 1b) into a light beam in another state, and a line image long in the main scanning direction. A cylindrical lens (3a, 3b) for forming an image, an aperture stop (4a, 4b) for regulating a light beam, a light deflector 5 as a deflecting means, and a light beam from the light deflector 5 for scanning the surface (8a , 8b) having a scanning lens system (6a, 6b) having fθ characteristics and a writing position detecting means (64a, 64b) for determining a drawing timing (timing of a scanning start position). ing.
[0023]
In this embodiment, the light sources 1a and 1b are arranged on opposite sides of the optical axes La and Lb of the scanning lens systems 6a and 6b, respectively, and the light sources 1a and 1b and the scanning lens systems 6a and 6b are connected to an optical deflector. 5 are arranged so as to be point-symmetric with respect to the rotation axis 5c. That is, the first scanner S1 and the second scanner S2 are arranged point-symmetrically about the rotation axis 5c of the optical deflector 5.
[0024]
In the present embodiment, the first and second scanners S1 and S2 use the same optical deflector 5 in combination, and the first and second scanners S1 and S2 use different optical deflectors 5 from each other. Light beams reflected and deflected by the deflection surfaces 5a and 5b are used.
[0025]
Further, in the present embodiment, the drawing timing of the first and second scanners S1 and S2 on the photosensitive drum surfaces (8a and 8b) as the surfaces to be scanned is determined from different deflection surfaces 5a and 5b of the optical deflector 5, respectively. Is detected by the writing start position detecting means (BD optical system) (64a, 64b), and is determined using the signal from the writing start position detecting means (64a, 64b).
[0026]
In the first and second scanners S1 and S2, each of the light sources 1a and 1b is composed of a semiconductor laser (light source) and has a single or a plurality of light emitting points. The collimator lenses 2a and 2b convert the divergent light beams emitted from the light sources 1a and 1b into substantially parallel light beams or convergent light beams. Each of the cylindrical lenses 3a and 3b has a predetermined refractive power only in the sub-scanning direction. The aperture stops 4a and 4b shape the light beams emitted from the cylindrical lenses 3a and 3b into a desired optimum beam shape.
[0027]
Each element such as the light source (1a, 1b), the collimator lens (2a, 2b), the cylindrical lens (3a, 3b), and the aperture stop (4a, 4b) is one element of the incident optical means (9a, 9b). Make up.
[0028]
The optical deflector 5 is composed of a polygon mirror having four deflecting surfaces, and is rotated at a constant speed in a direction indicated by an arrow A in the figure by driving means (not shown) such as a motor. In the present embodiment, as described above, the first and second scanners S1 and S2 use the optical deflector 5 in combination, and the first and second scanners S1 and S2 use different optical deflectors 5 from each other. The light flux reflected and deflected by the deflecting surfaces 5a and 5b is used.
[0029]
Each of the scanning lens systems 6a and 6b has first and second two scanning lenses 6a1, 6a2, 6b1 and 6b2, and the light flux reflected and deflected by the optical deflector 5 is spotted on the scanning surfaces 8a and 8b. By forming a conjugate relationship between the vicinity of the deflecting surface of the optical deflector 5 and the vicinity of the scanned surfaces 8a and 8b in the sub-scan section, a tilt correction function is provided.
[0030]
Reference numerals 7a and 7b denote folding mirrors, respectively, which are provided in the optical path between the first and second scanning lenses 6a1, 6a2, 6b1, and 6b2. In the present embodiment, for the light sources 1a and 1b, the same number of folding mirrors are provided in the optical path from the light sources 1a and 1b to the scanned surfaces 8a and 8b (one in this embodiment, but may be two or more). Are placed.
[0031]
Reference numerals 64a and 64b denote writing position detection means (BD optical system), respectively, a synchronization detection lens (hereinafter, referred to as "BD lens") 61a, 61b for detecting synchronization, and a slit (hereinafter, referred to as "BD slit"). .) 62a, 62b and synchronization detecting elements (hereinafter, referred to as "BD sensors") 63a, 63b, and determine the writing timing of each of the scanners S1, S2 on the scanned surfaces 8a, 8b. .
[0032]
The BD lenses 61a and 61b are anamorphic lenses having different curvatures in the main scanning direction and the sub-scanning direction, and form BD light fluxes on the BD slits 62a and 62b in both the main scanning direction and the sub-scanning direction. In the scanning section, scanning is performed on the BD slits 62a and 62b, and in the sub-scanning section, the deflecting surface and the BD slits 62a and 62b are substantially conjugate with each other.
[0033]
The BD slits 62a and 62b determine an image writing position. The ends of the BD slits 62a and 62b have a knife edge shape, and determine the position where the spot substantially formed by the BD lenses 61a and 61b scanned in the main scanning direction enters the surfaces of the BD sensors 63a and 63b. Thus, the BD detection accuracy is higher when the light is emitted by the knife edges of the BD slits 62a and 62b than when the BD light flux is emitted at the light receiving surface ends of the BD sensors 63a and 63b.
[0034]
Although the BD lenses 61a and 61b may be provided individually as in this embodiment, a part of the first scanning lenses 6a1 and 6b1 of the first and second scanners S1 and S2 may be used. When a part of the first scanning lenses 6a1 and 6b1 is used, the BD slits 62a and 62b are usually arranged at positions optically equivalent to the photosensitive drum surfaces 8a and 8b.
[0035]
In the present embodiment, first, in the first scanner S1, a divergent light beam that is light-modulated from the light source 1a according to image information and emitted is converted into a substantially parallel light beam or a convergent light beam by the collimator lens 2a, and is incident on the cylindrical lens 3a. I do. The light beam incident on the cylindrical lens 3a is emitted as it is in the main scanning section and passes through the aperture stop 4a (partially shielded). Further, in the sub-scan section, the light converges and passes through the aperture stop 4a (partially shielded) and is formed as an almost linear image (a linear image elongated in the main scanning direction) on the deflection surface 5a of the optical deflector 5. Here, the light beam from the light source 1a enters the deflection surface 5a of the optical deflector 5 at an angle of 90 ° with respect to the optical axis La of the scanning lens system 6a.
[0036]
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 8a via the first scanning lens 6a1, the folding mirror 7a, and the second scanning lens 6a2. By rotating the optical deflector 5 in the direction of arrow A, the photosensitive drum surface 8a is optically scanned in the direction of arrow B (main scanning direction) at a constant speed. As a result, an image is recorded on the photosensitive drum surface 8a as a recording medium.
At this time, in order to adjust the drawing timing (timing of the scanning start position) on the photosensitive drum surface 8a before optically scanning the photosensitive drum surface 8a, the light flux reflected and deflected by the deflection surface 5a of the optical deflector 5 is adjusted. After a part (BD light flux) is condensed on the surface of the BD slit 62a by the BD lens 61a, the light is guided to the BD sensor 63a. The writing timing of image recording on the photosensitive drum surface 8a is adjusted using a writing position detection signal (BD signal) obtained by detecting an output signal from the BD sensor 63a.
[0037]
In the second scanner S2, a divergent light beam emitted from the light source 1b is incident on the deflecting surface 5b of the optical deflector 5 in a direction opposite to the incident direction of the first scanner S1, and is reflected and deflected by the deflecting surface 5b. Are formed as spots on the photosensitive drum surface 8b via the first scanning lens 6b1, the return mirror 7b, and the second scanning lens 6b2, and are optically scanned.
[0038]
At this time, in order to adjust the drawing timing on the photosensitive drum surface 8b before the optical scanning on the photosensitive drum surface 8b, a part of the light beam (BD light beam) reflected and deflected by the deflection surface 5b of the optical deflector 5 is adjusted. After being condensed on the surface of the BD slit 62b by the BD lens 61b, the light is guided to the BD sensor 63b. The writing timing of image recording on the photosensitive drum surface 8b is adjusted using the writing position detection signal (BD signal) obtained by detecting the output signal from the BD sensor 63b.
[0039]
Incidentally, also in the second scanner S2, the light beam from the light source 1b is incident on the deflection surface 5b of the optical deflector 5 at an angle of 90 ° with respect to the optical axis Lb of the scanning lens system 6b.
[0040]
In this embodiment, as described above, the light sources 1a and 1b are arranged on opposite sides of the optical axes La and Lb of the scanning lens systems 6a and 6b, and the light sources 1a and 1b and the scanning lens systems 6a and 6b are connected to the optical deflector. 5 are arranged so as to be point-symmetric with respect to the rotation axis 5c. That is, the first scanner S1 and the second scanner S2 are arranged point-symmetrically about the rotation axis 5c of the optical deflector 5.
[0041]
Further, in the present embodiment, as shown in FIG. 2, folding mirrors 7a and 7b are arranged in an optical path between the first scanning lenses 6a1 and 6b1 and the second scanning lenses 6a2 and 6b2, and the optical path is in the sub-scanning section. In the drawing, each light beam is guided to the surfaces of the photosensitive drums 8a and 8b after being bent downward by 90 degrees.
[0042]
By irradiating the light beams from the opposite sides with respect to the optical axes La and Lb of the scanning lens systems 6a and 6b in this manner, the photosensitive drum surfaces 8a and 8b can be rotated no matter how the rotating shaft 5c of the optical deflector 5 is tilted. The scanning lines scanned above can be aligned in the same direction. Note that, instead of using one folding mirror for each scanner as in the present embodiment, for example, even if the scanner S1 is configured with one folding mirror and the scanner S2 is configured with three folding mirrors, scanning is not performed. The bending directions of the lines can be aligned in the same direction. That is, by aligning the even mirrors of the turning mirrors of the scanner arranged with the optical deflector interposed therebetween, the bending direction of the scanning line due to the tilt of the rotation axis of the optical deflector can be made the same.
[0043]
FIG. 3 is a graph in which the trajectory of the scanning line when the rotation axis 5c of the optical deflector 5 is tilted 7 minutes in the X direction is plotted for each image height. FIG. 4 is a graph in which the trajectory of the scanning line when the rotation axis 5c of the optical deflector 5 is tilted 7 minutes in the Y direction is plotted for each image height.
[0044]
As shown in FIGS. 3 and 4, even if the rotation axis 5c of the optical deflector 5 is tilted and the scanning line is curved, the color misregistration (difference between two scanning line curvatures) occurs because the directions are aligned. Can be reduced.
[0045]
When the light deflector 5 has four deflecting surfaces, the first scanner S1 and the second scanner S2 are arranged point-symmetrically about the rotation axis 5c of the light deflector 5 as in the present embodiment. The drawing timing can be made the same, thereby eliminating the need for a buffer (storage device) conventionally required, thereby simplifying the entire apparatus and reducing the cost.
[0046]
If the number of deflecting surfaces of the optical deflector 5 is not limited to four but is an even surface, the first scanner S1 and the second scanner S2 are arranged point-symmetrically about the rotation axis 5c. The drawing timing can be adjusted.
[0047]
FIGS. 5A and 5B are schematic diagrams when a light beam is incident at an angle of, for example, 60 ° with respect to the optical axis of the scanning lens system by the optical deflector 55 having six surfaces. As shown in FIGS. 3A and 3B, when the first scanner S1 is scanning on the optical axis of the scanning lens, the second scanner S2 also scans on the optical axis of the scanning lens, and It can be understood that when the scanner S1 of the second scanner S2 detects synchronization, the second scanner S2 also performs synchronization detection. As a result, the drawing timings on the surface to be scanned can be matched.
[0048]
The first scanning lenses 61a and 61b may be formed so that the radius of curvature in the sub-scanning cross section is asymmetric with respect to the optical axis. Thereby, it is possible to satisfactorily correct the curvature of field in the sub-scanning direction. In the case where the first scanning lens 61a is used for both the first scanner S1 and the second scanner S2, conventionally, the reference of the mounting seat surface has to be provided both above and below the lens. In the case of a scanning lens arranged point-symmetrically with respect to the rotation axis 5c of the optical deflector 5 as described above, the reference for the mounting seat surface may be held at one of the upper and lower positions.
[0049]
In the present embodiment, the luminous flux from the light source (1a, 1b) is directly transmitted through the aperture stop (4a, 4b) without using the collimator lens (2a, 2b) and the cylindrical lens (3a, 3b). The light may be guided to the deflector 5. In this embodiment, the scanning lens system (6a, 6b) is composed of two lenses, but is not limited to this, and may be composed of, for example, a single lens or three or more lenses.
[0050]
[Embodiment 2]
FIG. 6 is a sectional view (sub-scan sectional view) of a main part of the second embodiment of the present invention in the sub-scan direction. In the figure, the same elements as those shown in FIG. 2 are denoted by the same reference numerals. The main scanning section is the same as that in FIG.
[0051]
The present embodiment is different from the above-described first embodiment in that an optical deflector 65 having a deflecting surface having two stages in a sub-scanning cross section is used, and the present apparatus is divided into four first, second, third, and fourth sections. The scanner (hereinafter, also referred to as “station”) S1 to S4. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0052]
That is, in the figure, S1 and S2 are first and second scanners, respectively. In the first and second scanners S1 and S2, one folding mirror 71a and 71b is disposed between the first scanning lens 16a and 16b and the second scanning lens 17a and 17b, respectively.
[0053]
S3 and S4 are third and fourth scanners, respectively. The third and fourth scanners S3 and S4 respectively include three folding mirrors 71c, 71d, 71e, 71f, 71g and 71h between the first scanning lenses 16c and 16d and the second scanning lenses 17c and 17d. Is placed.
[0054]
Each of the scanners S1 to S4 in the present embodiment uses the same optical deflector 65 together, and each of the scanners S1 to S4 reflects a total of four light beams reflected and deflected on different deflection surfaces of the optical deflector 65. A color image is formed by performing deflection scanning using the same polygon motor.
[0055]
In this embodiment, what is particularly noticed is the number of folding mirrors arranged in each of the scanners S1 to S4. The light flux reflected and deflected by the upper deflecting surface 65a has its optical path bent by a total of three folding mirrors 71c, 71d, 71e, 71f, 71g, and 71h, and then the corresponding photosensitive drums 18c. 18d. The light flux reflected and deflected by the lower deflecting surface 65b is incident on the corresponding photosensitive drums 18a and 18b after the light path is bent by one folding mirror 71a and 71b.
[0056]
As described above, in the present embodiment, the same number of folding mirrors are used for the light flux incident on the scanning lens system from the side opposite to the optical axis (in FIG. 6, the light fluxes on the left and right sides of the optical deflector 65). Is bent, the directions of the scanning line curvatures can be made uniform, thereby reducing the color shift (difference between the two scanning line curvatures).
[0057]
When the upper light beam reflected by the deflection surface 65a is reflected by an odd number of turning mirrors as in the present embodiment, the lower light beam reflected by the deflection surface 65b is also reflected by the odd number of turning mirrors. For example, the scanning line curvature can be aligned in the upper and lower stages. Similarly, when the upper stage is an even number of folding mirrors, if the lower stage is also an even number of folding mirrors, the scanning lines can be curved in the same direction in the upper stage and the lower stage.
[0058]
[Embodiment 3]
FIG. 7 is a diagram showing a case where the number of deflecting surfaces of the optical deflector according to the third embodiment of the present invention is an odd number, and shows the relationship between the optical deflector and the incident directions of the two light beams A1 and B1. In the figure, the same elements as those shown in FIG. 5 are denoted by the same reference numerals.
[0059]
This embodiment is different from the first embodiment in that, when the number of deflecting surfaces of the light deflector 75 is an odd number (five), the light deflector 75 and the first and second scanners S1 and S2 are used. Are defined in relation to the incident directions of the two light beams A1 and B1, and the drawing timings are matched. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0060]
Matching the drawing timing (timing of the scanning start position) means that two light beams incident on different deflecting surfaces of the optical deflector go to the optical axis direction of the scanning lens system at the same time.
[0061]
In this embodiment, the angle between the incident light beam A1 from one light source (first scanner S1) and the optical axis of the scanning lens system is a (degree), and the incident light beam from the other light source (second scanner S2). When the angle between B1 and the optical axis of the scanning lens system is d (degree), and the number of deflecting surfaces of the optical deflector is n (number),
b = (360 / nk) -a / 2, a> 0, k = (n-1) / 2
It becomes. Here, if the condition that the light beam B1 of the second scanner S2 enters the optical deflector at an acute angle is added,
c = 180− {2 · (180−b)}> 90
That is, in this embodiment,
a <{360 (degrees) × (n-1) / n} -270 (degrees) ‥‥ (1)
d = (360 (degrees) / n) + a (2)
By arranging the two light sources so as to satisfy the following expression, the drawing timing is matched.
[0062]
Table 1 shows the incident angle of the light beam A1 at each number of deflection surfaces when the angle d = 90 (degrees).
[0063]
[Table 1]

[0064]
As described above, in the present embodiment, two light sources are arranged on the opposite sides with respect to the optical axis of the scanning lens system, and the two light sources are appropriately set so as to satisfy the above equations (1) and (2). By arranging, the same effect as in the first embodiment is obtained.
[0065]
Note that the present invention can be applied in the same manner as in the above-described third embodiment as long as the number of deflecting surfaces of the optical deflector 5 is not limited to five but is an odd number.
[0066]
[Color image forming apparatus]
FIG. 8 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention.
[0067]
The present embodiment is a tandem type color image forming apparatus that records image information on a plurality of photosensitive drum surfaces as image carriers. In FIG. 8, reference numeral 60 denotes a color image forming apparatus, and (11, 12) and (13, 14) denote optical scanning for scanning two beams on different surfaces of the same polygon mirror as described in the first or third embodiment. The devices 21, 22, 23, and 24 are photosensitive drums as image carriers, 31, 32, 33, and 34 are developing units, and 51 is a transport belt. In FIG. 8, 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.
[0068]
In FIG. 8, 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) and (13, 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 the photosensitive surfaces of the photosensitive drums 21, 22, 23, and 24 are irradiated with these light beams. Scanning is performed in the main scanning direction.
[0069]
In the color image forming apparatus according to the present embodiment, two optical scanning devices (11, 12) and (13, 14) are arranged, each of which is C (cyan), M (magenta), Y (yellow), and B (black). An image signal (image information) is recorded on the surfaces of the photosensitive drums 21, 22, 23, 24 in parallel with each color, and a color image is printed at high speed.
[0070]
As described above, the color image forming apparatus according to the present embodiment uses the two light scanning devices (11, 12) and (13, 14) to convert the latent images of the respective colors into the corresponding photosensitive images by using the light beams based on the respective image data. They are formed on the surfaces of the drums 21, 22, 23, and 24. Thereafter, multiple transfer to a recording material is performed to form one full color image.
[0071]
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.
[0072]
In the present invention, the optical scanning device according to the first or third embodiment is applied to a color image forming apparatus, but may be applied to a monochrome image forming apparatus.
[0073]
【The invention's effect】
According to the present invention, by arranging the even number of light sources on the opposite sides to the optical axis of the scanning lens system as described above, the curvature directions of the scanning lines due to the tilt of the rotation axis of the optical deflector are made the same. In particular, in a color image forming apparatus, it is possible to reduce the color shift, and when the number of surfaces of the optical deflector is an even number, in the case of an odd number, by optimally arranging the even number of light sources, It is possible to achieve an optical scanning device having a simple configuration capable of aligning drawing timing (timing of a scanning start position) 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 sub-scan sectional view of the optical scanning device according to the first embodiment of the present invention.
FIG. 3 is a graph showing scanning line curvature when the rotation axis of the optical deflector is tilted in the X direction.
FIG. 4 is a graph showing a scanning line curve when the rotation axis of the optical deflector is tilted in the Y direction.
FIG. 5 is a diagram for explaining the incident direction and the synchronization detection timing when the number of deflecting surfaces of the optical deflector is even.
FIG. 6 is a sub-scan sectional view of an optical scanning device according to a second embodiment of the present invention.
FIG. 7 is a diagram illustrating an incident direction when an optical deflector according to a third embodiment of the present invention has an odd number of deflecting surfaces.
FIG. 8 is a sub-scan sectional view of a color image forming apparatus using the optical scanning device of the present invention.
FIG. 9 is a main scanning sectional view of a conventional optical scanning device.
FIG. 10 is a sub-scan sectional view of a conventional optical scanning device.
FIG. 11 is a graph showing a scanning line curve when the rotation axis of the optical deflector in the conventional optical scanning device is tilted in the X direction.
FIG. 12 is a graph showing a scanning line curve when the rotation axis of the optical deflector in the conventional optical scanning device is tilted in the Y direction.
[Explanation of symbols]
1a, 1b light source
2a, 2b @ collimator lens
3a, 3b cylindrical lens
4a, 4b aperture
5,55,65,75 ° optical deflector (polygon mirror)
6a, 6b scanning lens system
7a, 7b folding mirror
8a, 8b ‥‥ scanned surface (photosensitive drum surface)
9a, 9b: Incident optical means
64a, 64b ‥‥ BD optical system
11,12,13,14 optical scanning device
21, 22, 23, 24 ° photoreceptor drum
31, 32, 33, 34 ° developing unit
41, 42, 43, 44 ° light beam
51 ‥‥ conveyor belt
52 ‥‥ external equipment
53 ‥‥ print controller
60 ° color image forming apparatus

Claims (5)

A plurality of light beams emitted from an even number of light sources are reflected and deflected by different deflecting surfaces of the same light deflector having a plurality of deflecting surfaces, and are respectively scanned on the surface to be scanned via the corresponding scanning lens systems. In an optical scanning device that forms an image on
The optical deflector has an even number of deflecting surfaces, the even number of light sources are arranged on opposite sides of an optical axis of the scanning lens system, and connects the even number of light sources and the scanning lens system to each other. An optical scanning device, wherein the optical scanning device is arranged so as to be point-symmetric with respect to a rotation axis of an optical deflector. 2. The optical scanning device according to claim 1, wherein, for each of the even number of light sources, an even number of folding mirrors are arranged in each optical path from the light sources to the surface to be scanned. A plurality of light beams emitted from an even number of light sources are reflected and deflected by different deflecting surfaces of the same light deflector having a plurality of deflecting surfaces, and are respectively scanned on the surface to be scanned via the corresponding scanning lens systems. In an optical scanning device that forms an image on
The light deflector has an odd number of deflecting surfaces, the even number of light sources are arranged on opposite sides with respect to an optical axis of the scanning lens system, and an incident light beam from one light source and a scanning lens system. The angle between the optical axis and the optical axis of the scanning lens system is d (degree), the angle between the incident light beam from the other light source and the number of deflection surfaces of the optical deflector is n (number). When
a <{360 (degrees) × (n-1) / n} -270 (degrees)
d = (360 (degrees) / n) + a
An optical scanning device, wherein the even number of light sources are arranged so as to satisfy the following expression. An optical scanning device according to claim 1, a photoconductor disposed on a surface to be scanned, and an electrostatic latent image formed on the photoconductor by a light beam scanned by the optical scanning device. A developing device for developing the toner image as a toner image, a transferring device for transferring the developed toner image to a material to be transferred, a fixing device for fixing the transferred toner image to the material to be transferred, and code data input from an external device A printer controller for converting the image data into an image signal and outputting the image signal to the optical scanning device. A laser beam printer using the optical scanning device according to claim 1 to guide a light beam to a photosensitive drum provided on the surface to be scanned.

Images