JP2005189791A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct bending and inclination of a scanning line with a simple adjustment mechanism, to adjust the bending and inclination of the scanning line independently between each station, and to improve the alignment accuracy of the scanning line, thereby preventing color unevenness and color deviation. Reduce.
In an optical scanning device in which an optical element group that forms an image on beams corresponding to beams emitted from a plurality of laser light sources is disposed in an optical housing for each beam, an optical element constituting the optical element group is provided. Among the elements, correction means for adjusting and holding the postures of a plurality of optical elements is provided, the correction means can be adjusted independently, and the optical elements are held in a non-contact manner with respect to the optical housing.
[Selection] Figure 1

Description

  The present invention relates to an optical scanning device and an image forming apparatus using the same.

  Conventionally, a light beam from a light source is deflected by a light deflecting means of a rotary polygon mirror, and the deflected light beam is condensed toward a scanned surface by using a scanning imaging optical system such as an fθ lens. 2. Description of the Related Art An optical scanning apparatus that forms a light spot on a surface and scans a surface to be scanned with the light spot is widely known in connection with image forming apparatuses such as an optical printer, an optical plotter, and a digital copying machine.

  In an image forming apparatus using an optical scanning device, an image writing step of writing an image by optical scanning is adopted as one step in the image forming process. The quality of an image formed by the image process is determined by optical scanning. It is influenced by the quality of The quality of optical scanning depends on the scanning characteristics of the optical scanning device in the main scanning direction and the sub-scanning direction.

  One of the scanning characteristics in the main scanning direction is the constant speed of optical scanning. For example, when a rotating polygon mirror is used as the light deflecting means, the light beam is deflected at a constant angular velocity, so that a scanning imaging optical system having an fθ characteristic is used in order to realize a constant speed of optical scanning. .

  However, it is not easy to realize perfect fθ characteristics due to the relationship with other performance required for the scanning imaging optical system. For this reason, in the actual optical scanning, the optical scanning is not performed at a uniform speed, and the constant speed as the scanning characteristic is accompanied by a deviation from the ideal constant speed scanning.

  The scanning characteristics in the sub-scanning direction include scanning line bending and scanning line inclination. The scanning line is the movement locus of the light spot on the surface to be scanned and is ideally a straight line, and the optical scanning device is designed so that the scanning line is a straight line. In general, a scanning line is bent due to a part processing error or an assembly error.

  In addition, if an imaging mirror is used as the scanning imaging optical system and an angle is set in the sub-scanning direction of the deflected beam between the direction of incidence of the deflected beam and the direction of reflection on the imaging mirror, the principle Therefore, even when the scanning line is bent and the scanning imaging optical system is configured as a lens system, the scanning line is scanned in the multi-beam scanning method in which the scanning surface is optically scanned with a plurality of light spots separated in the sub-scanning direction. Bending is inevitable.

  The inclination of the scanning line is a phenomenon in which the scanning line is not correctly orthogonal to the sub-scanning direction, and is a kind of bending of the scanning line. Therefore, in the following description, unless otherwise specified, the inclination of the scanning line is included in the expression “bending of the scanning line”.

  If the constant speed of optical scanning is not perfect, distortion in the main scanning direction occurs in the formed image, and scanning line bending causes distortion in the sub-scanning direction in the formed image. When an image is so-called monochrome and written by a single optical scanning device, it can be formed if scanning line bending or incompleteness of constant velocity (deviation from ideal constant velocity scanning) is suppressed to some extent. Although there is no “visual distortion” in the resulting image, it is never less than that.

  Separately from a monochrome image, three colors of magenta, cyan, and yellow, or four colors with black added thereto, are formed as color component images, and these color component images are superimposed to form a color image synthetically. Forming is conventionally performed by a color copying machine or the like.

  As one method for forming such a color image, an image for each color component is formed on a photoconductor that can form an image for each color component by using an optical scanning device provided for each color component. There is an image forming method called a tandem type. In the case of such an image forming method, if the scanning line bends and inclinations are different between the optical scanning devices, even if the scanning line bending for each optical scanning device is corrected, An abnormal image called “color shift” appears and degrades the image quality of the color image.

  Further, as a way of causing the color misregistration phenomenon, there is a phenomenon that the color tone in the color image does not become a desired one.

Conventionally, in order to prevent the occurrence of the above-described problems such as color misregistration, an adjustment screw that is movable in the optical axis direction of the long lens is attached to one support portion that sandwiches the optical axis of the long lens in the sub-scanning direction. A configuration has been proposed in which a scanning line is corrected by rotating and adjusting a long lens within a cross section orthogonal to the deflection scanning direction by adjusting the adjustment screw as the adjustment unit used (see, for example, Patent Document 1). .
JP 2002-131694 A

  However, in the configuration disclosed in Patent Document 1, scanning line bending correction may still not be possible for environmental fluctuations that are affected by the material of the lens used in the imaging optical system. The reason is as follows.

  In recent years, in order to improve scanning characteristics, it has become common to adopt special surfaces typified by aspherical surfaces in the imaging optical system of optical scanning devices, and such special surfaces can be easily formed. An imaging optical system made of a resin material that can be manufactured at a low cost is often used.

  An imaging optical system made of a resin material is susceptible to changes in temperature and humidity due to changes in temperature and humidity, and such changes in optical characteristics also change the degree of scanning line bending and the constant velocity. For this reason, for example, when several tens of color images are continuously formed, the temperature inside the apparatus rises due to continuous operation of the image forming apparatus, and the optical characteristics of the imaging optical system change. The scanning line curvature and constant velocity of the writing line gradually change, and the color shift between the color image obtained in the initial stage and the color image obtained in the final stage may be completely different due to the phenomenon of color misregistration.

  A scanning imaging lens such as an fθ lens that is representative of a scanning optical system is generally formed as a strip-shaped lens that is long in the main scanning direction by cutting a lens unnecessary portion (portion where no deflected light beam is incident) in the sub-scanning direction. In the case where the scanning imaging lens is composed of a plurality of lenses, the lens length in the main scanning direction increases as the arrangement position moves away from the light deflecting unit, and the length has a length of more than 10 cm to 20 cm. A scale lens is required. Such a long lens is generally formed by resin molding using a resin material. However, if the temperature distribution in the lens becomes non-uniform due to a change in the external temperature, the lens is warped and the lens becomes a bow shape in the sub-scanning direction. It becomes.

  Such warpage of the long lens causes the scanning line bending described above, but when the warping is significant, the scanning line bending occurs extremely. Such a phenomenon occurs even when the initial adjustment is performed using the configuration shown in Patent Document 1. In addition, in the configuration of Patent Document 1, no countermeasure is taken against the inclination of the scanning line that causes problems such as color misregistration other than scanning line bending. Further, the configuration disclosed in Patent Document 1 has a problem in that it is difficult to ensure positioning accuracy because positioning in the optical axis direction changes depending on how the screws are fastened.

  The present invention has been made in view of the above circumstances, and corrects the bending and inclination of the scanning line with a simple adjustment mechanism, and independently adjusts the bending and inclination of the scanning line between the stations. The object is to improve color matching accuracy and reduce color unevenness and color misregistration.

  In the present invention, the scanning line bending adjustment is performed by a rotation mechanism around the center of the lens in the sub-scanning section and the subsequent β tilt adjustment, and the scanning line tilt adjustment is rotated within a vertical plane passing through the optical axis. The purpose is to achieve high accuracy by performing adjustment with a center and thereafter performing γ tilt adjustment, and independently performing feedback adjustment.

  It is another object of the present invention to obtain an optical scanning device with reduced color shift corresponding to tandem.

  Another object of the present invention is to obtain a color image forming apparatus with reduced color misregistration corresponding to tandem.

  In order to achieve such an object, the invention described in claim 1 is directed to a light in which an optical element group that forms an image on beams corresponding to beams emitted from a plurality of laser light sources is arranged in an optical housing for each beam. The scanning device includes a correction unit that adjusts and holds the postures of a plurality of optical elements among the optical elements constituting the optical element group. The correction unit can be independently adjusted. And is held in a non-contact manner.

  According to a second aspect of the present invention, in the first aspect of the invention, the first rotation centering on the vicinity of the center of the lens in the cross section in the sub-scanning direction including the substantially optical axis of the scanning lens constituting a part of the optical element group. An adjustment mechanism, and a second adjustment mechanism having a rotation center in a vertical plane substantially including the optical axis, wherein the first adjustment mechanism and the second adjustment mechanism are integrated with the optical element and the correction unit. It is characterized by.

  According to a third aspect of the present invention, in the first aspect of the invention, the correction means includes a motor and a speed reduction mechanism as a drive unit, and the motor and the speed reduction mechanism are integrated with the correction means. To do.

  The invention according to claim 4 is the invention according to claim 2, characterized in that optical element support members are provided on both sides or one side of the scanning lens in the sub-scanning direction.

  The invention according to claim 5 is the invention according to claim 1, wherein the scanning lens constituting a part of the optical element group includes at least the scanning lens L1 and the scanning lens L2, and the scanning lens L1 is equidistant from the deflector. The scanning lens L1 has a two-stage stacked structure with a predetermined interval in the sub-scanning direction, and a support member is provided on one side of the end surface in the sub-scanning direction of the scanning lens L1, and the support members have different lengths in the main scanning direction. The holding member and the gap holding member provided at both ends are sandwiched and held integrally with the support member and the opposite surface in the sub-scanning direction.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the scanning lens constituting a part of the optical element group includes at least the scanning lens L1 and the scanning lens L2. The lens L2 has an attitude adjustment mechanism, and the scanning lens L1 adjustment resolution and the scanning lens L2 adjustment resolution differ according to the required accuracy.

  According to a seventh aspect of the present invention, in the sixth aspect of the invention, the adjustment action points of the plurality of scanning lenses L1 are arranged opposite to the optical axis, the adjustment resolution is equal, and the adjustment of the plurality of scanning lenses L2 is performed. The resolution is the same, and a differential screw mechanism using a stepping motor and a gear train as an actuator is used, and feedback control is performed based on information of the color misregistration detection means.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein a plurality of scanned surfaces are provided.

  According to a ninth aspect of the present invention, in the first aspect of the present invention, the optical element is not in contact with the optical housing and is held by a correction means.

  A tenth aspect of the invention is characterized by using the optical scanning device according to any one of the first to ninth aspects.

  According to the present invention, the bending and inclination of the scanning line are corrected with a simple adjustment mechanism, the scanning line is bent and the inclination is independently adjusted between each station, and the scanning line alignment accuracy is improved to improve color unevenness, It is possible to reduce color misregistration.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing an outline of a tandem type writing optical system. Either a scanning lens system or a scanning mirror system can be used. Here, a schematic diagram in the case of two stations will be described, but the four stations may be left-right symmetrical, which is exactly the same as in the case of two stations.

  Two LD units 21 and 22 are arranged at a predetermined distance in the sub-scanning direction, and the beam emitted from the lower LD unit 22 is in the same direction as the beam from the upper LD unit 1 by a folding mirror 23 on the way. The light beams are bent and incident on the cylinder lenses 24 and 25, respectively, and are converged linearly in the vicinity of the reflecting surfaces of the two upper and lower polygon mirrors 26 and 27 separated by a predetermined distance in the sub-scanning direction. The beam deflected by the polygon mirror is subjected to beam shaping by scanning lenses L18 and 9 separated by a predetermined distance in the sub-scanning direction, and further shaped to an fθ characteristic and a predetermined beam spot diameter by the scanning lens L2, and scanned on the surface of the photoreceptor.

  After the scanning lens L1, the beams are guided to the two photoconductors by different paths. The upper beam is raised 90 ° upward by the folding mirror 30, further bent 90 ° by the folding mirror 31, and incident on the long plastic lens 33 (scanning lens L 2), and then bent in the vertical direction by the folding mirror 32. Then, the photoconductor 1A is scanned.

  Further, the lower beam does not enter the folding mirror halfway and enters the lower long plastic lens 15 (scanning lens L2), and then the optical path is bent by the two folding mirrors 16 and 17, and a predetermined drum is formed. The photosensitive member 2A is scanned at a pitch.

  Here, it is indispensable to adopt a plastic lens for the scanning optical system because of a demand for cost reduction. In particular, in a tandem type writing unit, since one set of optical elements is used for each station and the number of parts is four times, the cost reduction effect due to plasticization is very large.

  However, even a single long plastic optical element is likely to warp in the longitudinal direction, particularly in the direction perpendicular to the scanning plane, due to molding conditions, residual stress, and the like. The amount of warpage is several tens of microns, and the amount and direction may vary depending on the type. Therefore, it is very difficult to accurately curve and tilt the scanning line between stations. Furthermore, if the internal temperature rises, even if the initial adjustment is performed with high accuracy, the temperature distribution difference between the main scanning direction and the sub-scanning direction of the plastic optical element is generated and the warpage changes, so that the scanning line bending inclination changes. A problem occurs.

  FIG. 2 is an external configuration diagram showing an embodiment of the scanning line bending and tilt adjusting mechanism of the present invention. Here, the configuration operation in one station will be described. The scanning lens L1 is positioned on a flat plate (sheet metal) and fixed by adhesion or the like. Rotating fulcrums 34 are provided at both ends of the flat plate, the fulcrum positions are arranged at substantially the center of the scanning lens sub-scanning section, and β tilt is possible by fitting with the bearing portion of the optical housing 42. The direction and amount of scanning line bending is uniquely determined by the direction and amount of β tilt of the scanning lens. For example, when the scanning line is bent upward, the scanning line L is tilted β in the − direction (bowing direction) in the figure, so that the scanning line is corrected, and the scanning line is bent downward. In such a case, the scan line bending can be corrected by β tilting in the + direction (upward direction) in the figure.

  Further, according to the present embodiment, correction can be made by tilting β in a direction that cancels out bending due to deviation in flatness of the folding mirror.

  The actual operation of β tilt will be described with reference to FIGS. FIG. 3 is a front view seen from the point A shown in FIG. The compression spring 36 and the stepping motor 44 are disposed on the left and right of the fulcrum of the flat plate, and the compression spring 36 is disposed on the lower side of the flat plate in a direction rotating in the negative direction in FIG. The stepping motor 44 is screwed to the upper surface of a flat plate, a screw having a predetermined pitch is cut on the motor shaft, and a nut 47 having an oval cross section in the axial direction is arranged to be engaged with the motor shaft. By being regulated, axial movement is possible. The β tilt adjustment resolution is an amount that is uniquely determined by the step angle, screw pitch, and distance from the fulcrum.

  In this embodiment, the distance between the polygon scanner and the scanning lens L1 is short because of the tandem optical system. In addition, since the folding mirrors cannot be separated, the scanning lenses L1 are inevitably arranged in two steps so as to be close to each other in the sub-scanning direction. Therefore, the space for driving the scanning lens independently is very small. In this embodiment, a flat plate is arranged on the opposite side of the scanning lens L1 opposite to each other, and the hinge is shifted in the longitudinal direction (main scanning direction), so that the upper and lower scanning lenses L1 are arranged in a small space. Β tilt can be performed independently of each other (see FIG. 5).

  Further, as shown in FIG. 6, the positions (adjustment action points) of the stepping motors 53 and 56 are opposed to each other with the optical axis of the scanning lens L1 interposed therebetween, and are arranged at an equal distance L with respect to the rotation fulcrum. Equivalent adjustment resolution can be obtained. In addition, since the stepping motor can be arranged at the same position as the scanning lens L1 in the direction orthogonal to the optical axis (Z direction), there is an advantage that space can be used efficiently.

Next, the scanning line inclination adjusting mechanism and the scanning lens correction mechanism provided in the scanning lens L2 will be described with reference to FIG.
The scanning lens L2 is sandwiched and held integrally by two upper and lower flat plates in the sub-scanning direction. Here, the upper sheet metal 40 is a sheet metal obtained by channel bending and box bending at both ends, and the height in the sub-scanning direction of the both ends bent is set to be the same as or slightly lower than the height of the scanning lens L2. The lower sheet metal 41 is reinforced by bending the channel, and the scanning lens L2 is positioned by a positioning portion such as an emboss 38, and both ends are clamped and held together. The leaf springs 37 and 43 are disposed at the end of the upper sheet metal and are always pressed downward. A stepping motor 45 is screwed to the upper sheet metal 40 at the opposite end.

  As shown in FIG. 4, the stepping motor shaft is threaded at a predetermined pitch, and is provided with a nut portion 51 that engages with the screw portion 50 to form a spur gear on the outside, and is integrated with the motor shaft. A differential screw portion 50 is formed by meshing a spur gear 48 configured as described above and a two-stage gear 49 and further meshing with a nut portion 51 having a spur gear formed on the outside. By providing the bearings of the gear train on the upper and lower sheet metals, the differential screw mechanism can be integrated with the holding member. FIG. 4 is a front view seen from the point B shown in FIG.

  The differential screw mechanism is configured such that the motor shaft and the nut are rotated in the same direction by the gear train, and by providing a difference in the number of teeth of the gear train, a rotational phase difference between the motor shaft and the nut portion is generated. A minute movement in the thrust direction is possible and the resolution can be increased. In addition, an adjustment resolution of one digit or more can be obtained as compared with a conventional adjustment resolution composed only of screws and nuts.

  In this embodiment, a high resolution method using a differential screw mechanism is adopted in the scanning line inclination γ tilt adjustment, and the scanning line bending adjustment mechanism is a mechanism using conventional screws and nuts. Depending on the required accuracy required, the method can be freely changed and selected.

  Further, in this embodiment, a leaf spring having a stronger pressing force than the opposite leaf spring is disposed at the end portion on the stepping motor side, and the spherical tip of the nut portion hits the housing by pressing, so that the scanning line is inclined. Adjustment is carried out at the bottom of the lower metal plate, here a cylindrical projection formed on the housing, is positioned at two points with the tip of the nut, and is held by the pressing force of the leaf spring. Then, the tilt of the scanning line can be corrected by γ-tilting the fulcrum provided in a substantially optical axis shape by the movement of the nut as the rotation center.

  In this embodiment, the stepping motor is feedback-controlled according to the amount of color misregistration pattern written on the intermediate transfer belt, etc., so that the scanning line curve and inclination, which have changed due to temperature rise in the machine, are corrected with high accuracy. It becomes possible to do.

  Therefore, according to the present embodiment, since the scanning lenses L1 and L2 are both mounted and held on the flat plate, there is no direct contact with the housing. As a result, the temperature of the housing rises due to heat generated by the high-speed rotation of the polygon scanner, and heat does not propagate directly to the optical element due to heat conduction. Therefore, characteristics such as the beam spot diameter deteriorate due to the difference in refractive index distribution due to the temperature difference. Few. Further, deformation due to the difference in temperature distribution of the optical element can be prevented.

  Further, according to the present embodiment, the distance between the polygon scanner and the scanning lens L1 is short because of the tandem optical system. In addition, since the folding mirrors cannot be separated, the scanning lenses L1 are inevitably arranged in two steps so as to be close to each other in the sub-scanning direction. Therefore, the space for driving the scanning lens independently is very small.

  Further, according to the present embodiment, as shown in FIG. 5, a flat plate is disposed on the opposite side to the mutually facing surfaces of the scanning lens L1, and the hinges are further displaced in the longitudinal direction (main scanning direction). In a small space, the two upper and lower scanning lenses L1 can be β-tilted independently of each other.

  FIG. 6 shows an image forming apparatus to which the optical scanning device according to the embodiment of the present invention is applied. The image forming apparatus shown in FIG. 6 uses a copier or a printer capable of forming a full-color image. In addition to this, there is a facsimile apparatus capable of performing the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image.

  The image forming apparatus 1 shown in FIG. 6 has a tandem structure in which a plurality of photosensitive drums 1A, 2A, 3A, and 4A capable of forming an image corresponding to a color-separated color (yellow, cyan, magenta, and black) are juxtaposed. The visible image formed on each photoconductive drum is used so as to be superimposed and transferred onto a transfer sheet S that is a recording medium conveyed by a transfer belt 5 that is movable while facing the photoconductive drum. It has become.

  Now, the configuration related to the image forming process will be described as a representative of one photosensitive drum 1A as follows. Since the other photosensitive drums 2A to 4A have the same configuration, for convenience, reference numerals assigned to the photosensitive drum 1A are attached to the part numbers of the photosensitive drums.

  Around the photosensitive drum 1A, a charging device 1B using a configuration such as a corotron or a scoroton for executing an image forming process along the rotation direction indicated by an arrow (in FIG. 6, a configuration using a roller is shown). 1) and the subsequent drawings, the optical scanning device 20, the developing device 1D, and the cleaning device 1E that use laser light from the laser light source are respectively disposed.

  In the image forming apparatus 1 shown in FIG. 6, the document reading unit 6 is disposed above the image forming unit in which the devices that perform these image forming processes are disposed, and the document placed on the document placing table 6 </ b> A. The image information read by the reading device 7 is output to an image processing control unit (not shown), and the writing information for the optical scanning device 20 described above can be obtained. The charging device 1B is not limited to a contact type using a roller, but can also use a corona discharge type using a discharge wire.

  In this embodiment, the developing devices are arranged in the order in which yellow, cyan, magenta and black toners can be supplied from the right side of the extended portion of the transfer belt 5 in FIG. The reading device 7 forms an image on a light source 7A for scanning a document placed on the document placing table 6A and a reflected light from the document on a CCD 7B provided for each color separation. A plurality of reflecting mirrors 7C and an imaging lens 7D are provided, and image information corresponding to the light intensity for each color separation is output from each CCD 7B to the image processing control unit.

  The transfer belt 5 is a member made of a dielectric material such as a polyester film wound around a plurality of rollers, and one of the stretched parts faces each of the photosensitive drums 1A to 4A, and faces each of the photosensitive drums. Inside the position, transfer devices 8A, 8B, 8C and 8D are arranged. To the transfer belt 5, the recording medium S fed from the inside of the paper feeding cassette 9 </ b> A of the paper feeding device 10 is fed via the registration rollers 9, and the recording medium S is transferred from the transfer device 8 </ b> A to the transfer belt 5. Is electrostatically adsorbed by the corona discharge and conveyed.

  The separation device 11 of the recording medium S is located at the position where the recording medium S after the image transfer from each of the photosensitive drums 1A to 4A has moved, and the neutralizing device facing the other portion of the stretched portion with a belt interposed therebetween. 12 is arranged. Note that reference numeral 13 in FIG. 6 denotes a cleaning device that removes the toner remaining on the transfer belt 5.

  The transfer devices 8 </ b> A to 8 </ b> D have a characteristic of electrostatically attracting the images carried on the photosensitive drums 1 </ b> A to 4 </ b> A toward the recording medium S using positive corona discharge. The separation device 11 performs negative AC corona discharge from the upper surface of the recording medium S to neutralize the electric charge accumulated in the recording medium S and release the electrostatic adsorption state. Separation using curvature is made possible and toner dust is prevented from being generated due to peeling discharge during separation. Further, the static eliminator 12 neutralizes the accumulated charge of the transfer belt 5 by performing negative AC corona discharge having a polarity opposite to the charging characteristics of the transfer devices 8A to 8D from both the front and back surfaces of the transfer belt 5. Initialization is to be performed.

  In each of the photosensitive drums 1A to 4A, the surfaces of the photosensitive drums 1A to 4A are uniformly charged by the charging devices 1B to 4B, and based on image information for each color separation color read by the reading device 7 in the document reading unit 6. An electrostatic latent image is formed on the photosensitive drum using the writing devices 1C to 4C, and the electrostatic latent image can be formed by toner of a color having a complementary color relationship corresponding to the color separation color supplied from the developing devices 1D to 4D. After the visual image processing, the image is electrostatically transferred to the recording medium S carried by the transfer belt 5 via the transfer devices 8A to 8D.

  The recording medium S to which the image for each color separation carried on each of the photosensitive drums 1A to 4A is transferred is discharged by the charge removing device 11 and then is separated by using the curvature of the transfer belt 5, and then the fixing device. 14, the toner in the unfixed image is fixed and discharged.

  In a quadruple tandem machine, it is difficult to obtain a resist so that there is no color misregistration of the four colors by simply increasing the component accuracy and assembly accuracy, resulting in higher costs. In the present invention, self-printing is performed in the apparatus, and after the amount of color misregistration in the sub-scanning direction is recognized, the scanning lens L1 is β-tilted to control the position of the scanning line on the photoconductor according to the amount. Thus, the scanning line bending is corrected, and the scanning lens L2 is γ tilted to perform the scanning line inclination correction (skew correction).

  In practice, a patch pattern for recognizing color misregistration is created on a transfer belt (explained here as an intermediate transfer medium), and this is detected by a P sensor. After forming a line-shaped four-color pattern and recognizing how much the other Y, M, and C colors have shifted in the forward or backward direction with respect to the black line as a reference, color misregistration correction in writing of each color is performed. carry out.

  The detection and correction are performed when the entire process control is performed when the power is turned on, when an in-machine temperature difference of 5 ° C. occurs, when several hundreds of jobs progress, when the photosensitive member, the developing unit, and the belt unit are replaced. When the correction process is completed, these patterns are cleaned by the cleaning bias roller and removed from the transfer belt.

  As mentioned above, although the Example of this invention was described, it is not limited to the said Example, A various deformation | transformation is possible in the range which does not deviate from the summary.

1 is an external perspective view showing a tandem type writing optical system. It is an external appearance perspective view of the scanning line inclination adjustment mechanism and scanning lens correction mechanism which concern on the Example of this invention. It is a sectional side view which shows the structure of the scanning line inclination adjustment mechanism based on the Example of this invention. It is a sectional side view which shows the structure of the scanning lens correction mechanism which concerns on the Example of this invention. It is front sectional drawing which shows the arrangement structure of the scanning lens which concerns on the Example of this invention. 1 is a side sectional view showing a configuration of an image forming apparatus that is an embodiment of the present invention. It is a top view which shows the arrangement structure of the stepping motor based on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A, 2A, 3A, 4A Photosensitive drum 1B, 2B, 3B, 4B Charging device 1C, 2C, 3C, 4C Writing device 1D, 2D, 3D, 4D Developing device 1E, 2E, 3E, 4E Cleaning device 5 Transfer Belt 6 Document Reading Unit 6A Document Placement Table 7 Reading Device 7A Light Source 7B CCD
7C Reflector 7D Imaging lens 8A, 8B, 8C, 8D Transfer device 9 Registration roller 9A Paper feed cassette 10 Paper feed device 11 Separating device 12 Charger 13 Cleaning device 14 Fixing device 15 Long plastic lens bottom (scanning lens L2)
20 Optical scanning device 21, 22 LD unit 16, 17, 23, 30, 31, 32 Folding mirror 24, 25 Cylinder lens 26 Above polygon mirror 27 Below polygon mirror 28 Above scanning lens L1 29 Below scanning lens L1 33 Long plastic lens Top (scanning lens L2)
34 Rotating fulcrum 35, 52 Sheet metal 36 Compression spring 37 Plate spring 38 Emboss 39 Cylinder fulcrum 40 Upper sheet metal 41 Lower sheet metal 42 Optical housing 43 Plate spring 44, 45, 53, 56 Stepping motor 46 Lead screw 47 Nut 48 First gear 49 Second stage Gear 50 Screw part 51 Nut part 54 Upper L1 support sheet metal 55 Lower L1 support sheet metal

Claims (10)

In an optical scanning device in which an optical element group for forming images of beams emitted from a plurality of laser light sources on corresponding photosensitive members is disposed in an optical housing for each beam,
Among the optical elements constituting the optical element group, the optical element group includes a correction unit that adjusts and holds the postures of a plurality of optical elements,
The optical scanning device characterized in that the correction means can be adjusted independently, and the optical element is held in a non-contact manner with respect to the optical housing. A first adjustment mechanism having a rotation center in the vicinity of the center of the lens in the cross section in the sub-scanning direction, which includes the substantially optical axis of the scanning lens constituting a part of the optical element group;
A second adjustment mechanism having a rotation center in a vertical plane including the substantially optical axis,
2. The optical scanning device according to claim 1, wherein the first adjustment mechanism and the second adjustment mechanism are integrated with the optical element and the correction unit.   The optical scanning apparatus according to claim 1, wherein the correction unit includes a motor and a speed reduction mechanism as a drive unit, and the motor and the speed reduction mechanism are configured integrally with the correction unit.   The optical scanning device according to claim 2, wherein an optical element supporting member is provided on both sides or one side of the scanning lens in the sub-scanning direction. A scanning lens constituting a part of the optical element group includes at least a scanning lens L1 and a scanning lens L2.
The scanning lens L1 is a two-stage stacked structure equidistant from the deflector and provided with a predetermined interval in the sub-scanning direction, and a support member is provided on one side of the end surface of the scanning lens L1 in the sub-scanning direction. The length of the direction is different,
2. The optical scanning device according to claim 1, wherein the scanning lens L2 is configured to sandwich and hold a supporting member, a clamping member provided on the opposite surface in the sub-scanning direction, and a spacing member provided at both ends. . A scanning lens constituting a part of the optical element group includes at least a scanning lens L1 and a scanning lens L2.
A scanning lens L1 posture adjustment mechanism and a scanning lens L2 posture adjustment mechanism;
2. The optical scanning device according to claim 1, wherein the scanning lens L1 adjustment resolution and the scanning lens L2 adjustment resolution are different from each other according to the required accuracy.   The adjustment action points of the plurality of scanning lenses L1 are arranged opposite to the optical axis, the adjustment resolution is equivalent, the adjustment resolutions of the plurality of scanning lenses L2 are equivalent, and a stepping motor and a gear train are used as actuators. 7. The optical scanning device according to claim 6, wherein the optical scanning device is constituted by a differential screw mechanism and is feedback-controlled based on information of a color misregistration detection means.   The optical scanning device according to claim 1, wherein a plurality of the scanned surfaces are provided.   The optical scanning device according to claim 1, wherein the optical element is not in contact with the optical housing and is held by the correction unit.   An image forming apparatus using the optical scanning device according to claim 1.

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