JP4032655B2 - Image forming apparatus - Google Patents

Description

であるから、このズレ分を各色のラインシンク発生タイミング（ＬＳＴｘ）に反映させることで変動前に戻すことが可能となる。
【００７７】
上述の各補正処理によって、図１１に示すように、初期状態から変動することで、それぞれのＳＯＳ出力タイミングがずれた場合に、まず、Ｙ色とＭ色についてＭ色に合うように、また、Ｃ色とＫ色についてＣ色に合うように同方向の補正が行われ、次に異方向の補正がＣ色とＭ色に行われ、Ｙ色とＭ色に対して補正がかかる。これで、カラーレジの補正としては完了するが、基準のズレ量が把握出来ているので、その分を全ての色について行うことでもとのポジションに印字が可能となる。
【００７８】
以上により、本実施の形態に係る画像形成装置では、製造コストの安い、簡単な構成で、レーザビームの走査方向に依存せずに、画素書き出し位置の設定と制御が可能となり、多重画像形成時における色ズレを防止することができる。また、制御については、従来のようにテスト画像を形成することを必要としないため、常時モニタリングが可能であり、必要に応じて即補正制御ができる。さらに、コマンダでの入力により、書き出し位置を所望に設定可能なため、製品出荷後でも、随時色ズレ補正を行うことができる。
【００７９】
なお、図３に示した、本実施の形態に係るＳＯＳセンサ、ＥＯＳセンサ、及びピックアップミラーの構成の変形例として、図１２に示すように、走査方向が同方向であるレーザ光を共通のセンサ（４０ＣＫ、４１ＹＭ）で検出するようにしてもよい。この例は、図３（Ｂ）に示すホルダ３９を利用した一体タイプであるが、１つのセンサに２つの走査レーザビームが入射されるように、それぞれのピックアップミラー３８を、所定角度分の傾きを設けて設置するようになっている。このようにする事で、センサの数を減らすことができ、コストダウンを達成できる。なお、この変形例の場合においては、同時に走査レーザビームが入射されると、どちらの色のビームであるかが判断つかないことが生じることから、例えば、光学レイアウトの変更（レーザビームのポリゴンミラーへの入射角に多少のオフセットを設けて、センサに対しては時系列的に入射させることが必要となる。さらに、後段の処理に都合の良いように、センサ信号出力をそれぞれ分離する分離回路を設ける必要がある。この概略構成としては、図１３に示すように、図４に示すセンサ部を図の如く変更したものである。
【００８０】
【発明の効果】
以上説明したように、本発明によれば、第１及び第２の主走査方向へ走査する光ビームによる画像信号に対応する走査開始信号と第２の主走査方向へ走査する光ビームによる画像信号に対応する走査終了信号との相関関係に基づいて、各画像信号毎に対応する光ビームによる画像担持体上への原画像の書き出しを開始するまでの待機時間を、各原画像を最終的に同一の記録媒体上に多重転写する際に各原画像間で位置ズレが生じないように補正するので、多重画像形成時における画像形成位置のズレを防止し、高品質の画像を形成することができる画像形成装置を提供できる、という優れた効果を有する。
【図面の簡単な説明】
【図１】 本発明の実施の形態に係る画像形成装置の概略構成図である。
【図２】 本発明の実施の形態に係る走査露光装置の概略構成図である。
【図３】 （Ａ）は本発明の実施の形態に係るピックアップミラー、ＳＯＳセンサ、ＥＯＳセンサの配置構成の概略図であり、（Ｂ）は（Ａ）に示す配置構成の他の例の概略図である。
【図４】 本発明の実施の形態に係る画像形成装置の主要構成部のブロック図である。
【図５】 本発明の補正制御における初期処理の流れを示すフローチャートである。
【図６】 本発明の補正制御における同方向走査レーザ光間における補正処理の流れを示すフローチャートである。
【図７】 同方向走査レーザ光間の補正処理の様子を説明するためのタイミングチャートである。
【図８】 （Ａ）はピックアップミラー、ＳＯＳセンサ、及びＥＯＳセンサの設置位置変動の様子を説明するための図であり、（Ｂ）は（Ａ）の位置変動に伴うＳＯＳ信号の変動の様子を説明するためのタイミングチャートである。
【図９】 本発明の補正制御における異方向走査レーザ光間における補正処理の流れを示すフローチャートである。
【図１０】 異方向走査レーザ光間の補正処理の様子を説明するためのタイミングチャートである。
【図１１】 同方向と異方向との双方の走査レーザ光間の補正処理の様子を説明するためのタイミングチャートである。
【図１２】 ピックアップミラー、ＳＯＳセンサ、ＥＯＳセンサの配置構成の変形例を示す概略図である。
【図１３】 図１２に示す変形例における画像形成装置の主要構成部のブロック図である。
【図１４】 従来の画像形成装置の概略構成図である。
【図１５】 従来の他の画像形成装置における走査露光装置についての概略構成図である。
【図１６】 （Ａ）及び（Ｂ）は、図１５に示す走査露光装置におけるＳＯＳ信号のズレを説明するための図である。
【符号の説明】
１０ 画像形成装置
１１ 走査露光装置
１２ 感光体ドラム
１８ 転写器
１８Ａ 転写ベルト
２２ ポリゴンミラー
２６ 記録媒体
３０ レーザダイオード
３６ ｆθレンズ
３８ ピックアップミラー
３９ ホルダ
４０ ＳＯＳセンサ
４１ ＥＯＳセンサ[0001]
BACKGROUND OF THE INVENTION
The present invention includes a light source and a plurality of image carriers, and sequentially scans light beams modulated and emitted from the light sources based on a plurality of different image signals, thereby corresponding to the image signals. The present invention relates to an image forming apparatus in which different original images are formed on an image carrier, and each original image is multiplex-transferred onto the same recording medium to form an image.
[0002]
[Prior art]
Conventionally, as an image forming apparatus such as a laser printer, a laser copier, and the like, an image forming apparatus is known in which a photosensitive member provided as an image carrier is scanned and exposed with a laser beam. In many cases, these image forming apparatuses are digitized and colorized.
[0003]
In these image forming apparatuses, in particular, when forming a color image, an original image corresponding to each of the four colors of black (K), yellow (Y), magenta (M), and cyan (C) is used. Finally, these four original images are superimposed to form a single color image. Compared to a conventional image forming apparatus that forms a black and white image, production in an image forming operation is performed. In some cases, the performance deteriorated.
[0004]
For this reason, so-called tandem image forming apparatuses capable of simultaneously forming original images corresponding to the respective colors K, Y, M, and C have been known. This tandem-type image forming apparatus has a plurality of photoconductors, and after exposing the photoconductors corresponding to each color with a laser beam emitted from the exposure device based on the image data signal separated for each color, Development is performed to form an original image for each color, and finally, an original image for each color is superimposed on the same transfer medium to form one color image. In this way, the tandem image forming apparatus significantly improves the productivity in the image forming operation that has been a problem in the past.
[0005]
However, in such a tandem type image forming apparatus, positional deviations at the time of superimposing original images may occur due to variations in the optical characteristics of the laser beam corresponding to each color emitted from the exposure apparatus. In some cases, this reduces the quality of the formed image. Therefore, in order to solve this problem, it is necessary to perform appropriate alignment control between the original images of each color.
[0006]
In order to perform appropriate alignment between the original images in order to form a high-quality color image, a scanning line writing position in the main scanning direction (hereinafter referred to as a side register), and a scanning line writing position in the sub-scanning direction (hereinafter referred to as “side registration”). (Hereinafter referred to as “lead registration”), writing end position or print width (hereinafter referred to as magnification) of the scanning line in the main scanning direction, curvature of the scanning line itself (hereinafter referred to as scanning line bending), and inclination of the scanning line (hereinafter referred to as scanning line). It is necessary to appropriately set the inclination).
[0007]
By the way, the tandem type image forming apparatus is roughly classified into two forms depending on the configuration of the scanning exposure apparatus that emits a laser beam for scanning exposure of each photosensitive member.
[0008]
In the first embodiment, as shown in FIG. 14, the scanning exposure apparatuses 72K, 72Y, 72M and 72C for deflecting and emitting one laser beam from a laser light source (not shown) by a rotating polygon mirror 73 The image forming apparatus 70 is in a form (hereinafter referred to as a quadruple tandem system) in which the K, Y, M, and C4 colors are separately arranged and provided. In the quadruple tandem image forming apparatus 70, the scanning exposure apparatuses 72K, 72Y, 72M, and 72C each have a rotating polygon mirror 73 that is rotated by a motor (not shown). By performing deflection scanning of the laser beam at 73, exposure of a monochrome image for each of the K, Y, M, and C colors is performed on the corresponding photosensitive member 74. Further, the single color images exposed on the photoreceptors 74 corresponding to the respective colors are developed by the respective developing units 76 and then transferred to the transfer belt 78 which is a common transfer member among the respective colors by the respective transfer units 77. It is designed to be transcribed. A fixing device 80 is disposed on the rearmost end side of the transfer belt 78. Here, a single color image for each color is sequentially superimposed on the recording medium P to finally form one color image. It has become.
[0009]
At this time, when superimposing each single color image at the time of color image formation (that is, alignment of the scanning exposure position in the laser beam corresponding to each color), the above-described side registration, lead registration, magnification, scanning line curve, In addition to this, the quadruple tandem type image forming apparatus 70 rotates the rotating polygon mirror 73 in each of the scanning exposure apparatuses 72K, 72Y, 72M, and 72C. It is necessary to provide a special mechanism for controlling the rotational phase of each motor to be operated.
[0010]
On the other hand, the second mode is a laser beam modulated based on image signals corresponding to four colors, as in the technique described in JP-A-3-142424 (hereinafter referred to as Prior Art 1). Is provided with a scanning exposure apparatus that deflects each of the two colors in opposite directions around the rotating polygon mirror as a center and performs exposure scanning in the main scanning direction (hereinafter referred to as a scanning exposure apparatus). , Referred to as a bidirectional spray paint method). In this bidirectional spray paint type image forming apparatus, each photosensitive drum is exposed and scanned by deflecting a laser beam corresponding to each color by one rotating polygon mirror, so that the scanning exposure apparatus itself has a relatively compact configuration. be able to. In the bidirectional spray paint type image forming apparatus, the multi-transfer operation of the single color image of each color at the time of color image formation is the same as that of the above-described quadruple tandem type image forming apparatus. In the deflection scanning operation, it is not necessary to provide a special rotation phase control mechanism between a plurality of motors as in the above-described four-tandem image forming apparatus.
[0011]
Therefore, in the quadruple tandem type image forming apparatus, each motor is independent, and therefore, with the rotational phase control of each motor, it is possible to perform alignment control with a high degree of freedom between each monochrome image, and almost all colors are controlled. It is possible to perform alignment to the same position. On the other hand, in the bidirectional spray paint type image forming apparatus, the laser beam of each color is deflected by a common rotary polygon mirror. Therefore, in the alignment control between the monochromatic images, the alignment is performed in units of scanning lines. .
[0012]
Here, a description will be given of formation position alignment control between single color images in each tandem image forming apparatus.
[0013]
When forming positions between monochromatic images are adjusted, it is necessary to correct side registration, lead registration, magnification, scanning line curvature, scanning line inclination, and the like and set them to appropriate values as described above.
[0014]
For example, a technique described in Japanese Patent Laid-Open No. Hei 2-291573 (hereinafter referred to as Prior Art 2) is known as a technique for aligning each monochromatic image with respect to a side register. In this prior art 2, before printing an image, test toner images of each color are formed, transferred to a transfer belt, and each color test is performed by a reading sensor (here, a CCD sensor) provided on the transfer belt. The toner image is read, the positional deviation between the test toner images of each color is read, and the deviation amount is calculated. Thus, it is possible to detect how much color laser beam is misaligned when actually writing with each laser beam. Based on the detection result thus obtained, the side registration which is the writing start position in the main scanning direction is corrected.
[0015]
In the prior art 1 described above, the register mark is exposed on each photosensitive member with a laser beam of each color and developed, and then a register mark image is formed on the transfer medium, and the register mark is provided on the transfer medium. The positional deviation is detected by the reading sensor, and the side registration which is the writing start position in the main scanning direction is corrected based on the detection result.
[0016]
In addition to the above, a technique using a scanning laser beam (hereinafter referred to as Prior Art 3) is known as a side registration correction method. In this prior art 3, a writing start position detection sensor (hereinafter referred to as an SOS sensor) outside the image forming area is provided, and scanning position information in the main scanning direction is obtained by detecting a laser beam by the SOS sensor. That is, based on the output signal of the SOS sensor generated when the laser beam passes over the SOS sensor, the SOS sensor arranged on the scanning start side starts a counting operation with the basic clock signal in the counter, Image export has started when the set value is reached. Here, in order to prevent the occurrence of minute positional deviation of the image writing position due to the influence of the division angle error in the rotary polygon mirror, it is necessary to use a signal synchronized with the SOS sensor as the basic clock signal of the counter. There is. In the quadruple tandem type image forming apparatus, the SOS sensor is provided on the scanning start position side with respect to the laser beam corresponding to each color image signal. In the bidirectional spray paint type image forming apparatus, Since the scanning direction of the laser beam corresponding to each color image signal is opposite to each other about the rotary polygon mirror, the SOS sensor is provided on the scanning start side located at each diagonal. In this case, the SOS signal output from the SOS sensor (SOS signal) when the passage of the scanning laser beam corresponding to each color is detected, and the SOS signal generated by the reference scanning laser beam and the SOS signal generated by the other scanning laser beam. From the correlation, the pixel writing start position can be corrected and controlled.
[0017]
[Problems to be solved by the invention]
However, in the above-described prior art 2, a test image for color matching is formed on the transfer medium that is the same medium, and the positional relationship between the colors, that is, the relationship of the scanning laser beam is determined by a reading sensor typified by a CCD sensor. I was getting. In this case, the high-quality color image is an image having no color misregistration, but the alignment accuracy (resolution) by each scanning laser beam naturally depends on the resolution of the reading sensor. For example, when the image writing density is 600 DPI (Dots PerInch), at least a resolution of 42.3 microns or less is required as the accuracy required for alignment of each color, so an expensive CCD sensor or the like is used as the reading sensor. The manufacturing cost may be high. In addition, it is expected that the resolution of the image will be further increased in the future, and the resolution required for the reading sensor is further increased, which may increase the manufacturing cost accordingly.
[0018]
Further, the above-described prior art 1 requires a CCD sensor that reads a register mark transferred onto a transfer material conveyance belt, an optical system that accompanies the CCD sensor, and an actuator that adjusts the inclination of a mirror that folds a scanning line. The structure may be complicated and the manufacturing cost may increase. Further, it takes time for various arithmetic processes related to the operation control of the actuator, and as a result, the processing time of the entire image forming operation increases, which may reduce the productivity of the image forming operation.
[0019]
Further, in the above-described prior art 3, for example, in the bidirectional spray paint type image forming apparatus provided with the scanning exposure device 72A shown in FIG. In the scanning exposure apparatus 72A, an fθ lens 73B composed of a plano-convex lens and a plano-concave lens is arranged in each of the vertical directions in FIG. 15 around a rotating polygon mirror 73A that rotates at a constant speed in the direction of arrow (1) in FIG. Has been placed. In addition, a laser light source that emits a laser beam modulated based on each color signal constituting a color image signal sent from an image data input unit (not shown) is provided, and the laser light emitted from this laser light source is Then, the light passes through the fθ lens 73B and is deflected from the scanning start position P1 in the direction of arrow (2) in FIG. 15 and from the scanning start position P2 in the direction of arrow (3) in FIG. 15 (that is, directions opposite to each other). To be scanned. In addition, the SOS sensors 82C and 82M for synchronizing the scanning start timing of the laser beam are arranged in the vicinity of the scanning start positions P1 and P2, respectively. Here, the laser beam deflected and scanned from the scanning start position P1 in the direction of arrow (2) in FIG. 15 corresponds to the C color image signal, and is deflected from the scanning start position P2 in the direction of arrow (3) in FIG. The laser beam to be scanned corresponds to the M color image signal. In the side registration correction, the color (reference color) used as a reference for correction is set as C color, and the color (reference color) to be matched with the reference color is set as M.
[0020]
As shown in FIGS. 16A and 16B, in the initial state, each writing start time T is set so that there is no recording position shift on the recording medium PP._C0And T_M0(SOS signal (1) and SOS signal (2) in FIG. 16A).
[0021]
As shown in FIG. 16 (A), the phase of the SOS signal corresponding to the M color of the reference color is shifted due to the position variation of the SOS sensor 82M ((3)), and the SOS corresponding to the C color of the reference color is generated. When there is no deviation in the phase of the signal ((1)), since each writing start time described above remains fixed, the M recording position on the recording medium PP is shifted from the C recording position. . At this time, the phase difference between the two SOS signals is equal to the initial phase difference ΔT._CM0To ΔT_CM1To change. Therefore, the deviation ΔT of M color_MIs
ΔT_M= ΔT_CM1-ΔT_CM0
It is. Therefore, this deviation ΔT_MBy using this to correct the start time for writing out the M color, the deviation from the C color can be eliminated. Here, the phase difference ΔT in the initial state_CM0And phase difference after deviation_CM1The magnitude relationship with
ΔT_CM1-ΔT_CM0> 0
In case of, deviation ΔT_MTherefore, it is necessary to advance the start time of M color writing, and in this case, the corrected writing start time T_M1Is
T_M1= T_M0-ΔT_M
It becomes. on the other hand,
ΔT_CM1-ΔT_CM0<0
In case of, deviation ΔT_MTherefore, it is necessary to delay the start time of M color writing, and in this case, the corrected writing start time T_M1Is
T_M1= T_M0+ (− ΔT_M) = T_M0-ΔT_M
It becomes.
[0022]
Therefore, as a result, when the M color is misaligned, the M color post-correction writing start time T_M1Is
T_M1= T_M0-ΔT_M
The corrected writing start time T can be obtained as_M1Can be used to obtain the SOS signal (4) corresponding to the M color whose start time has been appropriately corrected.
[0023]
Next, as shown in FIG. 16B, the phase of the SOS signal corresponding to the C color of the reference color is shifted due to the positional variation of the SOS sensor 82C ((5)), and the M color of the reference color is changed. When there is no deviation in the phase of the corresponding SOS signal ((2)), the writing start time described above remains fixed, so the M color recording position on the recording medium PP is deviated from the C color recording position. It will be. At this time, the phase difference between the two SOS signals is equal to the initial phase difference ΔT._CM0To ΔT_CM1To change. Therefore, the deviation ΔT of M color_MIs
ΔT_M= ΔT_CM1-ΔT_CM0
It is. Therefore, this deviation ΔT_MBy using this to correct the start time for writing out the M color, the deviation from the C color can be eliminated. Here, the phase difference ΔT in the initial state_CM0And phase difference after deviation_CM1The magnitude relationship with
ΔT_CM1-ΔT_CM0> 0
In case of, deviation ΔT_MTherefore, it is necessary to delay the start time of M color writing, and in this case, the corrected writing start time T_M1Is
T_M1= T_M0+ ΔT_M
It becomes. on the other hand,
ΔT_CM1-ΔT_CM0<0
In case of, deviation ΔT_MTherefore, it is necessary to advance the start time for writing out the M color, and in this case, the export start time T after correction_M1Is
T_M1= T_M0-(-ΔT_M) = T_M0+ ΔT_M
It becomes.
[0024]
Therefore, as a result, when the M color is misaligned, the M color post-correction writing start time T_M1Is
T_M1= T_M0+ ΔT_M
The corrected writing start time T can be obtained as_M1Can be used to obtain the SOS signal (6) corresponding to the M color whose start time is appropriately corrected.
[0025]
From the above, the correction procedure differs depending on whether or not the color to be shifted is the reference color (the direction of correction is reversed), and in detecting only the relative phase information of the two color SOS signals, which color is shifted. It may not be possible to determine whether or not the phase shift cannot be corrected appropriately. As a result, the side registration may not be corrected properly.
[0026]
The present invention has been made to solve the above-described problems, and provides an image forming apparatus capable of preventing a shift in image forming position during multiple image formation and forming a high-quality image. Objective.
[0027]
[Means for Solving the Problems]
  According to the first aspect of the present invention, a plurality of light sources and a plurality of image carriers are provided, and light beams modulated based on a plurality of different image signals including one reference image signal and emitted from the light sources are transmitted in a predetermined direction. Are deflected by a rotating polygon mirror that rotates at a constant speed, and a light beam corresponding to a plurality of image signals including the reference image signal is applied to each of the image carriers corresponding to the image signals by a first main scanning. Scanning each direction, and sequentially performing bidirectional scanning in which a light beam corresponding to the remaining plurality of image signals is scanned in a second main scanning direction opposite to the first main scanning direction. In the image forming apparatus for forming different original images on the respective image carriers corresponding to signals, and finally transferring the original images onto the same recording medium to form an image, the rotating polygon mirror Deflected by Further, the reference light beam corresponding to the reference image signal and at least one light beam scanned in the second main scanning direction are reflected near the scanning start position of the reference light beam and the at least one light beam. First reference means provided in the vicinity of the scanning end position, reference reference start position detection means for outputting a reference scan start signal by detecting the reference light beam reflected by the first reflection means, Scan end position detecting means for outputting a scan end signal by detecting the at least one light beam reflected by the first reflecting means, and the reference image signal deflected by the rotary polygon mirror Except for the reference light beam, each light beam including the at least one light beam is reflected so as to be reflected near each scanning start position. A plurality of second reflecting means, a plurality of scanning start position detecting means for outputting a scanning start signal by detecting each of the light beams reflected by the second reflecting means, and the reference scanning Each image by each of the light beams output from each of the light sources and deflected by the rotary polygon mirror after a predetermined waiting time has elapsed from the time when each of the start signal and the scan start signal is output. Control means for controlling to start writing each original image on the carrier, and the scanning start signal of the at least one light beam.From the output of the issueScan end signalDifference between the time interval until the output of the signal and the time interval in the initial state of the image forming apparatusBased on this, when each original image is finally multiplex-transferred onto the same recording medium, there is a positional deviation between the original image corresponding to the reference light beam and the original image corresponding to the at least one light beam. Correction means for correcting the waiting time corresponding to the at least one light beam so as not to occur.
[0028]
  According to the first aspect of the present invention, the reference scanning start position detecting means includes the reference light beam corresponding to the reference image signal deflected by the rotary polygon mirror and at least one light beam scanning in the second main scanning direction. The reference scanning is performed by detecting the reference light beam reflected by the first reflecting means provided in the vicinity of the scanning start position of the reference light beam and in the vicinity of the scanning end position of the at least one light beam so as to reflect Output a start signal. The scanning end position detecting means outputs a scanning end signal by detecting the at least one light beam reflected by the first reflecting means. Further, the plurality of scanning start position detection means excludes the reference light beam deflected by the rotary polygon mirror and reflects each light beam including the at least one light beam so as to reflect each light beam. A scanning start signal is output by detecting each light beam reflected by a plurality of second reflecting means provided in the vicinity. The control means uses each of the light beams output from each light source and deflected by the rotating polygon mirror after a predetermined waiting time has elapsed from the time when each of the reference scanning start signal and the scanning start signal is output. Control is performed to start writing each original image on each image carrier. In addition, the correcting means may be the scanning start signal of the at least one light beam.From the output of the issueScan end signalDifference between the time interval until the output of the signal and the time interval in the initial state of the image forming apparatusAccordingly, when each original image is finally multiplex-transferred onto the same recording medium, no positional deviation occurs between the original image corresponding to the reference light beam and the original image corresponding to the at least one light beam. Thus, the waiting time corresponding to the at least one light beam is corrected. Thereby, the formation position of the original image corresponding to the at least one light beam can be adjusted appropriately, and the original image corresponding to the reference light beam can be transferred when each original image is multiple-transferred onto the same recording medium. And an original image corresponding to the at least one light beam can form a high-quality image without positional deviation.
[0029]
  The invention according to claim 2 is the invention according to claim 1, whereinThe first reflecting means is constituted by one reflecting member that reflects the reference light beam and the at least one light beam, or a reflecting member that reflects the reference light beam and the at least one light beam. The reflective member is held by one fixed member.It is characterized by.
[0030]
  According to invention of Claim 2,The first reflecting means may be composed of a reference light beam and one reflecting member that reflects the at least one light beam.As this reflection member, for example, a single reflection mirror can be employed. Thereby, for example, it is possible to easily grasp the correlation between the phase shift of the scanning start signal and the phase shift of the scanning end signal caused by the position variation of the reflecting mirror. AlsoThe reflecting member that reflects the reference light beam and the reflecting member that reflects the at least one light beam may be held by one fixing member. This placeEven thoseShooting memberIf there is only one fixing member to be held, similarly, for example, it is possible to easily grasp the correlation between the phase shift of the scanning start signal and the phase shift of the scanning end signal caused by the positional variation of the fixing member.
[0033]
  ClaimItem 3The described invention is claimed.1 or contractDemandIn item 2In the invention described above, the correction means includes the reference scanning start signal.From the output of the issueThe scanning start signal of each light beam excluding the reference light beam scanned in the first main scanning direction.Difference between the time interval until the output of the signal and the time interval in the initial state of the image forming apparatusBased on the above, the scanning in the first main scanning direction is performed so that no positional deviation occurs between the respective original images corresponding to the respective image signals corresponding to the respective light beams scanned in the first main scanning direction. Each of the waiting times corresponding to each light beam excluding the reference light beam is corrected.
  ClaimIn item 4The described invention is claimed.1 contractDemandItem 3In the invention described in any one of the above items, the correction means isBefore the output of the scanning start signal of the at least one light beam scanning in the second main scanning direction.Scan in the second main scanning directionEach excluding said at least one light beamLight beamThe difference between the time interval until the output of the image and the time interval in the initial state of the image forming apparatusBased on the above, the scanning in the second main scanning direction is performed so that no positional deviation occurs between the original images corresponding to the image signals corresponding to the light beams scanned in the second main scanning direction. Each of the waiting times corresponding to each light beam excluding at least one light beam is corrected.
  ClaimItem 5The described invention is claimed.1 contractDemandItem 4In the invention described in any one of the above items, the apparatus further includes a temperature detection unit that detects a temperature in the apparatus, and performs correction by the correction unit when the temperature value detected by the temperature detection unit is equal to or higher than a predetermined value. It is characterized by that.
[0034]
  ClaimItem 5According to the described invention, the temperature detecting means detects the temperature in the apparatus. When the temperature value detected by the temperature detection means becomes a predetermined value or more, correction by the correction means is performed. Since the phase shift in the scanning start signal and the scanning end signal basically occurs due to the position fluctuation of the reflecting member due to the temperature state in the apparatus, the scanning is started by monitoring the temperature in the apparatus by the temperature detecting means. It is possible to indirectly grasp the state of the apparatus (the state where the temperature value in the apparatus is equal to or higher than a predetermined value) that may cause a phase shift between the signal and the scanning end signal. This makes it possible to efficiently perform the correction operation by performing correction by the correction means when the above state is reached, and as a result, reducing the load on the control unit that controls the entire apparatus. Can do.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0036]
FIG. 1 schematically shows an image forming apparatus 10 to which the present invention is applied. This image forming apparatus 10 includes four developing units (yellow developing unit Y, magenta developing unit M, cyan developing unit C, and black developing unit K) corresponding to each color signal constituting a color image signal, and each developing unit is the same. Each of which includes a photosensitive drum 12 as an image carrier.
[0037]
Further, the image forming apparatus 10 includes a scanning exposure device 11 for irradiating the photosensitive drum 12 included in each developing unit with a laser beam.
[0038]
FIG. 2 shows an outline of the scanning exposure apparatus 11 viewed from the direction of arrow A in FIG. The scanning exposure apparatus 11 includes an fθ lens 36 composed of a plano-convex lens and a plano-concave lens with a rotating polygon mirror (polygon mirror) 22 rotating at a constant speed in the direction of arrow (1) in FIG. They are arranged in the vertical direction. The laser scanning device 11 also includes laser light corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black), which is modulated based on each color signal constituting the image data signal. Are provided with four laser diodes 30. The laser light emitted from each laser diode 30 is converted into parallel light by the corresponding collimator lens 34 and refracted in the optical path by the reflection mirror 29, and then transmitted through the fθ lens 36 to the polygon mirror 22. Each is incident.
[0039]
Each laser beam incident on the polygon mirror 22 is reflected by the reflecting surface of the polygon mirror 22, passes through the fθ lens 36 again, is refracted by the mirror 27 disposed on the optical path different from that at the time of incidence, and is incident on the cylindrical mirror 28. Each is guided (see FIG. 1). The laser light guided to the cylindrical mirror 28 is refracted by the cylindrical mirror 28 so as to irradiate the exposure scanning position 13 on the surface of the photosensitive drum 12 (hereinafter referred to as the drum surface) of each developing unit. It has become. Therefore, the laser beam is scanned on the drum surface at a constant speed by the action of the fθ lens 36. The optical paths of the laser beams of the respective colors are indicated by arrows 15Y, 15M, 15C and 15K, respectively.
[0040]
In each developing unit, the photosensitive drum 12 is rotated at a predetermined speed in the direction of arrow (1) in FIG. 1 by a motor (not shown). As a result, each laser beam emitted from the scanning exposure device 11 is repeatedly scanned along the axial direction (main scanning direction) of the photosensitive drum 12 on the drum surface.
[0041]
In each developing unit, a charger 14 is provided slightly upstream of the exposure scanning position 13 along the drum rotation direction indicated by the arrow (1) in FIG. 1, so that the drum surface is uniformly charged. ing. As a result, the surface of the drum uniformly charged by the charger 14 is exposed and scanned with laser light, thereby removing the charged charges other than the image portion and leaving the charge in the image portion. A latent image is formed.
[0042]
Further, a developing device 16 is provided slightly downstream of the exposure scanning position 13 along the drum rotation direction indicated by the arrow (1) in FIG. The developing device 16 is filled with toner charged to a polarity opposite to that of the electrostatic latent image, and the electrostatic latent image formed on the drum surface is colored in each color (Y, M, C, K). A visible image (toner image) is formed by electrostatically adhering toner as charged fine particles.
[0043]
Further, a transfer unit 18 is provided below the photosensitive drum 12 in FIG. 1, and a transfer belt 18 </ b> A for transferring the toner image is sandwiched between the transfer unit 18 and the photosensitive drum 12. The transfer belt 18A is conveyed in order by the driving roller in the direction of arrow (2) in FIG. 1 through the developing units Y, M, C, and K. Further, the transfer unit 18 in each developing unit applies charges to the transfer belt 18A, and sequentially transfers the toner images for each color to the transfer belt 18A by the electrostatic force.
[0044]
Further, a fixing device 24 is disposed on the downstream side of the transfer belt 18A to which the toner image for each color is transferred in the direction indicated by the arrow (2) in FIG. In this fixing device 24, the toner image transferred to the transfer belt 18A by applying heat or pressure while sandwiching the recording medium 26 for recording an image and transporting it in the direction of arrow (3) in FIG. It is supposed to be fused.
[0045]
A cleaner 20 for removing toner remaining on the photosensitive drum 12 after transfer is provided at the rearmost end of the rotation direction of the photosensitive drum 12 of each developing unit (the direction indicated by the arrow (1) in FIG. 1). ing.
[0046]
In addition, as shown in FIG. 2, in the scanning exposure apparatus 11, laser light is respectively present near the scanning start position in the main scanning direction (arrows C and K in FIG. 2) of the laser light corresponding to C color and K color. SOS sensors 40C and 40K for detecting laser light are arranged in order to synchronize the timing of start of scanning (Start Of Scan; SOS). Further, in the main scanning direction (arrows Y and M in FIG. 2) of the laser light corresponding to the Y color and the M color, the SOS sensors 40Y and 40M are arranged in the vicinity of the scanning start position, respectively, and the scanning end position In the vicinity, EOS sensors 41Y and 41M for detecting the laser beam are arranged in order to synchronize the timing of the end of main scanning (End Of Scan; EOS) by the laser beam.
[0047]
In this case, the layout is such that EOS sensors are assigned for Y color and M color. These assignments are the reference colors and need to be assigned to colors whose scanning directions are different from the reference colors. In the present embodiment, since the C color is used as the reference color, EOS sensors are provided for the Y color and the M color, which are scanning directions different from the C color scanning direction.
[0048]
Further, the SOS sensors 40K, SOS 40C and the EOS sensors 41M, 41Y detect the laser beams picked up by the corresponding pickup mirrors 38K, 38CM, 38Y, respectively, as shown in FIG. Yes. Here, one pickup mirror 38CM is provided in common for the SOS 40C and the EOS sensor 41M. As another embodiment, as shown in FIG. 3B, the pickup mirrors 38C and 38M may be held by a common holder 39 so as to function as a unit. In addition, the laser beams picked up by the common pickup mirror 38CM or the like may have different scanning directions, and one of them may be a reference color. As the pickup mirror is integrally displaced in this way, a shift amount equivalent to the shift amount of the reference color (C color) is developed on the reference color (M color), so that the reference color (C color) is developed. ) Can be easily determined based on whether or not there is a deviation.
[0049]
That is, as shown in FIG. 8A, which is a schematic view seen from the direction of arrow A in FIG. 3A, attention is paid to the scanning laser beams of C and M colors. The temporal change in the sensor output position is mainly due to the displacement of the pickup mirror. When the mirror drawn by the solid line is displaced like the mirror drawn by the dotted line, the pickup point is displaced. That is, in FIG. 8A, the pickup is picked up at a position changed by Δθ as the scanning angle. As a result, as shown in FIG. 8B, the output timing of the C color SOS sensor before the change is advanced by Δt, and at the same time, the output timing of the M color EOS sensor is delayed by the same amount of Δt. Moreover, since the moving direction of the output timing is the reverse direction, it is convenient for correction.
[0050]
As described above, since the scanning directions of the C color and the M color are opposite to each other, the positional deviation is further deteriorated by correcting the reference color having a different scanning direction depending on the presence or absence of the positional variation of the reference color as in the past. Can be prevented and appropriate correction can be performed.
[0051]
FIG. 4 shows an outline of a registration control unit (hereinafter referred to as a regicon unit) that is a main component of the image forming apparatus 10. This regicon unit is positioned for laser light (Y and M colors, and C and K colors) whose scanning directions are the same direction, and laser light (C color and M colors) whose scanning directions are different directions, respectively. The shift is corrected, and the position shift is corrected as a whole. Here, the time difference between the output signals of each SOS sensor and EOS sensor is measured. Here, the C and K color scanning directions are referred to as normal scanning, and the Y and M scanning directions are referred to as reverse scanning. First, normal scanning will be described. Since the reference color is the C color, in order to measure the time difference of the SOS signal from the K color that is the reference color, the selector selects the two signals and performs the measurement using the register control counter. The counted value is stored in the data register. Similarly, reverse scanning Y and M colors are selected by the selector, and the count value is stored in the data register. In this reverse scanning, a value based on the M color is held. Since the two pairs scan in the same direction, when the signal time difference fluctuates, the output timing of the line sync signal corresponding to the fluctuation is changed.
[0052]
Thereafter, the time difference between the C color in the forward scan and the M color in the reverse scan is measured by the register control counter, and the count value is stored in the data register. In this way, the final correction value is calculated by the computing unit based on each stored data and is input to each line sync counter to obtain a desired line sync signal. Print data generated by image processing of image data is sent to the laser drive circuit at the timing of this line sync signal, and the semiconductor laser is modulated to perform actual printing. The counter value to the line sync signal can be set directly by an external commander and at the same time stored in the main control. This value is related to the data register of the registration control circuit, and is used for adjustment at the time of initial shipment and readjustment after shipment.
[0053]
Next, the operation of the present embodiment will be described in detail.
[0054]
In the image forming apparatus 10 according to the present embodiment, a processing routine shown in FIG. 5 is executed as an initial process for performing a preparatory stage operation before image formation at the time of startup.
[0055]
First, in step 100, the initial line sync generation time (Y, M, C, K) of each color is loaded into the data register as an initial value.
[0056]
In the next step 102, the user inputs and sets a desired time value as the line sync generation time of each color by the commander (setting of the external input line sync generation time).
[0057]
In the next step 104, it is determined whether or not the input setting of the line sync generation time for all colors has been completed. If the determination is negative, the process returns to step 102. If the determination is affirmative, the process proceeds to the next step 106. .
[0058]
In the next step 106, from the set initial value, as initial information, the phase difference between the detection signals of the SOS sensor 40Y and the SOS sensor 40M, the position between the detection signals of the SOS sensor 40K and the SOS sensor 40C, and so on. The phase difference, the phase difference between the detection signals of the SOS sensor 40M and the EOS sensor 41M, and the phase difference between the detection signals of the SOS sensor 40C and the EOS sensor 41M are measured, stored in the data register, and this processing routine is completed. To do.
[0059]
With the above-described initial processing, each value in the initial state of the image forming apparatus 10 can be properly grasped.
[0060]
Next, in the image forming apparatus 10, in the positional deviation correction process between laser beams whose scanning directions are the same, steps 200 to 212 of the processing routine shown in FIG. 6 are executed, as shown in FIG. 7. Correction processing is performed.
[0061]
FIG. 7A shows an initial state, and line sync signals (L / S (K), L / S (C)) of each color are generated from the output timing of each SOS sensor. The generation timing of the line sync signal at this time is held as LSTK (Line Sync Timing of K) and LSTC (Line Sync Timing of C), respectively. Further, the time difference of each SOS is held as SDTKC (Same Direction Timing of K and C).
[0062]
Here, as shown in FIG. 7B, when the C color sensor output is shifted (Δ), the writing start position fluctuates, and if no correction is made, a color shift of Δ will occur. At this time, since the value of SDTKC is changing, Δ is calculated by an arithmetic unit before and after the fluctuation of SDTKC, and the color deviation is eliminated by correcting the count value of the K line sync counter. .
[0063]
That is, the initial value of SDTKC (K to C color SOS signal time interval) which is a monitor means is
SDTKC = OLD_SDTKC
And the initial time (LSTx) from the SOS signal to the generation of the line sync signal is
LSTK = OLD_LSTK
LSTC = OLD_LSTC
When the C color beam detection position is displaced with a delay (see the figure),
SDTKC = NEW_SDTKC = OLD_SDTKC + Δ
The time until the line sync signal for each color is generated
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK + Δ
By doing so, it is possible to align the image writing position.
[0064]
On the contrary, when the C color beam detection position is advanced and displaced (time interval decreases),
SDTKC = NEW_SDTKC = OLD_SDTKC−Δ
The time until the line sync signal for each color is generated
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK−Δ
By doing so, it is possible to align the image writing position in the same way.
[0065]
In FIG. 7C, even when the K color sensor is shifted (Δ), the color misregistration is eliminated by correcting the count value of the K line sync counter in the same manner.
[0066]
That is, when the K color beam detection position is advanced and displaced (see the figure),
SDTKC = NEW_SDTKC = OLD_SDTKC + Δ
The time until the line sync signal for each color is generated
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK + Δ
By doing so, it is possible to align the image writing position. In addition, when the K-color beam detection position is displaced with a delay (time interval is reduced),
SDTKC = NEW_SDTKC = OLD_SDTKC−Δ
The time until the line sync signal for each color is generated
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK−Δ
In actuality, as shown in FIG. 7D, there may be fluctuations at the same time. Even in this case, since the variation of SDTKC is monitored and the variation is the amount of color misregistration, the color misregistration is eliminated by changing the count value of the line sync counter of the reference color correspondingly.
[0067]
That is, from the above, when both colors, which is a general case, deviate,
If the K color beam detection position is displaced with a delay (time interval increases),
SDTKC = NEW_SDTKC = OLD_SDTKC + Δ
The time until the line sync signal for each color is generated
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK + Δ
As a result, the image writing position can be aligned.
[0068]
In addition, when the K color beam detection position is advanced and displaced (time interval decreases), the sign of the shift amount changes,
LSTC = OLD_LSTC
LSTK = NEW_LSTK = OLD_LSTK−Δ
As a result, the image writing position can be aligned.
[0069]
Similarly, for Y color and M color, the variation of SDTYM is monitored so as to match the M color, and since the variation is the amount of color misregistration, the Y line sync counter of the reference color for reverse scanning is used. The positional shift is eliminated by changing the count value correspondingly.
[0070]
As a result of the above correction processing, those having the same scanning direction are matched to the C color and the M color, respectively. By correcting the color misregistration between the C color and the M color, all the color matching is completed. To do. In this embodiment, the M color is matched with the C color which is the original reference color. Unless otherwise specified, the C color and the M color will be described below. The K color and the Y color correspond to the C color and the M color, respectively, and there is no positional deviation.
[0071]
Next, in the image forming apparatus 10, in the positional deviation correction process between laser beams whose scanning directions are different directions, steps 300 to 314 of the processing routine shown in FIG. 9 are executed, as shown in FIG. Correction processing is performed.
[0072]
Here, correction in the C color and the M color will be described. In addition, in FIG. 10, the printing image in each timing of a circled number is also shown.
[0073]
First, as an initial state, it is assumed that printing is performed at timings (1) and (2). At this time, the time interval from the SOS sensor to the EOS sensor in M color is defined as OLD_DDSETM (Different Direction Sos to Eos Time of M). Next, it is assumed that the common pickup mirrors for C and M colors fluctuate and the single pickup mirror for M color (SOS side) fluctuates. At that time, the states are changed to (3), (4) and (5) (C and M colors are misaligned in the writing direction). ΔC, which is the deviation of the reference color C, changes by the same amount as the deviation of the output point of the EOS sensor as shown in (3) due to the effect of the common structure described above. On the other hand, the M color SOS sensor varies independently of these, and changes by ΔM. At this time, because the sensor output advances for C color, the registration for ΔC shifts in the writing direction (left direction), and the writing direction shifts for M color, but because the scanning direction is opposite, ΔM right Shift in the direction. Therefore, in order to align the registration on the print image, it is necessary to correct the M color timing by ΔC + ΔM and shift it to the left.
[0074]
Here, the time interval (NEW_DDSETM) from the SOS sensor to the EOS sensor of the M color beam after the fluctuation includes a deviation (ΔM) of M's own SOS pickup mirror and a deviation (ΔC) of the common mirror on the EOS side. Therefore, the difference DDTM (Differential Direction Time of M) is DDTM = NEW_DDSETM−OLD_DDSETM = ΔM + ΔC, which corresponds to the amount of misalignment of M color to be corrected. Therefore, by correcting the difference result to M color, registration correction of C color and M color can be performed.
[0075]
If the C color does not change, the correction method by monitoring the time interval between the SOS sensors, which is the basis of the registration correction, may be applied to the C color and the M color. However, whether or not the C color has changed is corrected. It is necessary to monitor when performing the process, which makes the process extremely complicated. Even if this determination process is not performed, if the variation of DDSETM is monitored, it can be automatically corrected. That is, in the correction based on the SOS to EOS time of the M color, ΔC becomes zero if the C color does not change.
DDTM = NEW_DDSETM-OLD_DDSETM = ΔM
Thus, only ΔM is corrected. It is possible to automatically correct by ΔM without monitoring ΔC.
[0076]
Note that when the state is completely restored (before correction), it is necessary to correct the deviation of the C color as the reference color. Changes in the time interval (DDCSMET: Differential Direction C-Sos to M-Eos Time) between the SOS sensor for the reference color C and the EOS sensor for the M color are monitored only because the contribution of the common mirror is included. Thus, the deviation of the reference color itself can be obtained. That is, DDTC (Different Direction Time of C) is

Therefore, it is possible to return to the pre-fluctuation by reflecting this deviation in the line sync generation timing (LSTx) of each color.
[0077]
As shown in FIG. 11, when each SOS output timing is shifted by the above-described correction processing as shown in FIG. 11, first, the Y color and the M color are matched to the M color. The C direction and the K color are corrected in the same direction so as to match the C color, then the correction in the different direction is performed on the C color and the M color, and the correction is applied to the Y color and the M color. This completes the correction of the color registration, but since the reference shift amount can be grasped, it is possible to print at the original position by performing the correction for all the colors.
[0078]
As described above, in the image forming apparatus according to the present embodiment, it is possible to set and control the pixel writing position without depending on the scanning direction of the laser beam with a simple configuration at a low manufacturing cost, and at the time of multiple image formation. Color misregistration can be prevented. In addition, since it is not necessary to form a test image as in the prior art, monitoring can always be performed, and immediate correction control can be performed as necessary. Furthermore, since the writing position can be set as desired by input from the commander, color misregistration correction can be performed at any time even after product shipment.
[0079]
As a modification of the configuration of the SOS sensor, the EOS sensor, and the pickup mirror according to the present embodiment shown in FIG. 3, as shown in FIG. 12, laser light having the same scanning direction is used as a common sensor. (40CK, 41YM) may be detected. This example is an integral type using the holder 39 shown in FIG. 3B, but each pickup mirror 38 is inclined by a predetermined angle so that two scanning laser beams are incident on one sensor. It is designed to be installed. By doing in this way, the number of sensors can be reduced and cost reduction can be achieved. In the case of this modified example, if a scanning laser beam is incident at the same time, it may not be possible to determine which color beam is, so that, for example, a change in the optical layout (a polygon mirror of the laser beam) It is necessary to provide a slight offset to the angle of incidence on the sensor, and make it incident on the sensor in time series, and a separation circuit that separates the sensor signal outputs for convenience in subsequent processing. As a schematic configuration, as shown in Fig. 13, the sensor unit shown in Fig. 4 is modified as shown in the figure.
[0080]
【The invention's effect】
As described above, according to the present invention, the scanning start signal corresponding to the image signal based on the light beam scanned in the first and second main scanning directions and the image signal based on the light beam scanned in the second main scanning direction. Based on the correlation with the scanning end signal corresponding to each, the waiting time until the writing of the original image on the image carrier by the light beam corresponding to each image signal is started, and finally each original image is When multiple transfers are performed on the same recording medium, correction is performed so that positional deviation does not occur between the original images. Therefore, it is possible to prevent image formation position deviation during multiple image formation and form a high-quality image. The image forming apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic block diagram of a scanning exposure apparatus according to an embodiment of the present invention.
3A is a schematic diagram of an arrangement configuration of a pickup mirror, an SOS sensor, and an EOS sensor according to an embodiment of the present invention, and FIG. 3B is an outline of another example of the arrangement configuration shown in FIG. FIG.
FIG. 4 is a block diagram of main components of the image forming apparatus according to the embodiment of the present invention.
FIG. 5 is a flowchart showing a flow of initial processing in correction control of the present invention.
FIG. 6 is a flowchart showing a flow of correction processing between scanning laser beams in the same direction in correction control of the present invention.
FIG. 7 is a timing chart for explaining the state of correction processing between scanning laser beams in the same direction.
FIG. 8A is a diagram for explaining how the installation positions of the pickup mirror, the SOS sensor, and the EOS sensor vary, and FIG. 8B illustrates how the SOS signal varies with the position variation of FIG. It is a timing chart for demonstrating.
FIG. 9 is a flowchart showing a flow of a correction process between different direction scanning laser beams in the correction control of the present invention.
FIG. 10 is a timing chart for explaining a correction process between different-direction scanning laser beams.
FIG. 11 is a timing chart for explaining a correction process between scanning laser beams in the same direction and in different directions.
FIG. 12 is a schematic diagram showing a modification of the arrangement configuration of the pickup mirror, the SOS sensor, and the EOS sensor.
13 is a block diagram of main components of the image forming apparatus in the modification shown in FIG.
FIG. 14 is a schematic configuration diagram of a conventional image forming apparatus.
FIG. 15 is a schematic block diagram of a scanning exposure apparatus in another conventional image forming apparatus.
FIGS. 16A and 16B are diagrams for explaining the shift of the SOS signal in the scanning exposure apparatus shown in FIG.
[Explanation of symbols]
10 Image forming apparatus
11 Scanning exposure equipment
12 Photosensitive drum
18 Transfer device
18A transfer belt
22 Polygon mirror
26 Recording media
30 Laser diode
36 fθ lens
38 Pickup mirror
39 Holder
40 SOS sensor
41 EOS sensor

Claims (5)

Rotating polyhedron comprising a plurality of light sources and a plurality of image carriers, and rotating light beams emitted from the respective light sources, which are modulated based on a plurality of different image signals including one reference image signal, at a constant speed in a predetermined direction The light beams corresponding to the plurality of image signals including the reference image signal are scanned in the first main scanning direction with respect to each of the image carriers corresponding to the respective image signals by being deflected by a mirror, and the rest The respective images corresponding to the image signals are sequentially performed by performing bidirectional scanning in which the light beams corresponding to the plurality of image signals are scanned in the second main scanning direction opposite to the first main scanning direction. In an image forming apparatus that forms different original images on a carrier, and finally multiplex-transfers each original image onto the same recording medium to form an image.
In the vicinity of the scanning start position of the reference light beam so as to reflect the reference light beam corresponding to the reference image signal deflected by the rotary polygon mirror and at least one light beam scanned in the second main scanning direction. And the 1st reflection means provided in the scanning end position vicinity of the said at least 1 light beam,
Reference scanning start position detecting means for outputting a reference scanning start signal by detecting the reference light beam reflected by the first reflecting means;
A scanning end position detecting means for outputting a scanning end signal by detecting the at least one light beam reflected by the first reflecting means;
Excluding the reference light beam corresponding to the reference image signal deflected by the rotary polygon mirror and reflecting each light beam including the at least one light beam near each scanning start position of each light beam. A plurality of second reflecting means provided in each;
A plurality of scanning start position detecting means for outputting a scanning start signal by detecting each of the light beams reflected by the second reflecting means;
Each of the light beams output from the light sources and deflected by the rotary polygon mirror after a predetermined waiting time has elapsed from the time when each of the reference scanning start signal and the scanning start signal is output. Control means for controlling to start writing each original image on each image carrier;
Based on a difference between the time interval in an initial state of the at least one of said image forming apparatus and the time interval from the output of the scanning start signal of the light beam to the output of the previous SL scanning end signal, each original image So that a positional deviation does not occur between the original image corresponding to the reference light beam and the original image corresponding to the at least one light beam when multiple transfer is finally performed on the same recording medium. Correction means for correcting the waiting time corresponding to one light beam;
An image forming apparatus.   The first reflecting means is constituted by one reflecting member that reflects the reference light beam and the at least one light beam, or a reflecting member that reflects the reference light beam and the at least one light beam. The image forming apparatus according to claim 1, wherein the reflection member is held by one fixed member. It said correction means, the image forming and the time interval between the output of the scanning start signal for each light beam except for the reference optical beam scanning from the output of the reference scan start signal Previous Symbol first main scanning direction Based on the difference from the time interval in the initial state of the apparatus , a positional deviation does not occur between the original images corresponding to the image signals corresponding to the light beams scanned in the first main scanning direction. the image forming apparatus according to claim 1 or billed to claim 2 corrects each of the waiting time corresponding to each light beam except for the reference optical beam scanning to the first main scanning direction. It said correcting means, each except for the second of the at least one light beam at least one of the you scanned from the output of the scanning start signal to the pre-Symbol second main scanning direction of the light beam to scan in the main scanning direction based on a difference between the interval time between the initial state of the time interval between the image forming apparatus to the output of the light beam, corresponding to the respective image signals corresponding to the light beam scanning to the second main scanning direction The standby time corresponding to each of the light beams excluding the at least one light beam scanned in the second main scanning direction is corrected so that a positional deviation does not occur between the original images . The image forming apparatus according to claim 3 . Further comprising a temperature detecting means for detecting the temperature in the apparatus, when the temperature value detected by the temperature detecting means exceeds a predetermined value, according to claim 1請 which is characterized in that the correction by the correction means the image forming apparatus according to any one of determined section 4.

Images