JP4596942B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device used as a writing device such as a digital copying machine and a laser printer, and to an image forming apparatus such as a digital copying machine and a laser printer using the optical scanning device. The image forming apparatus is suitable for a multicolor image forming apparatus capable of forming a color image by superimposing images.

  By deflecting the light beam from the light source by the light deflecting means of a polygon mirror (rotating polygon mirror) and condensing the deflected light beam toward the surface to be scanned using a scanning imaging optical system such as an fθ lens, There is known an optical scanning device that forms a light spot on a surface to be scanned and scans the surface to be scanned with the light spot. An optical scanning apparatus is widely known as an apparatus for writing an image in an image forming apparatus such as an optical printer, an optical plotter, or a digital copying machine.

  In an image forming apparatus using an optical scanning device, an electrophotographic process including charging, exposure, development, transfer, fixing, and cleaning processes is used as an image forming process. In the exposure process, which is one process in the electrophotographic process, an image writing process is performed in which an image is written by optical scanning. The quality of an image formed through the above process is affected by the quality of optical scanning. 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 polygon mirror is used as the light deflecting means, the light beam is deflected at a constant angular velocity, whereas the constant speed of the optical scanning is required on the surface to be scanned, and the constant speed of the optical scanning is realized. Therefore, a scanning imaging optical system having an fθ characteristic is used. However, due to the relationship with other performances required for the scanning imaging optical system, it is not easy to realize complete fθ characteristics. For this reason, in the actual optical scanning, the optical scanning is not performed at a completely constant 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 a 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. However, in practice, the scanning line is usually bent due to a processing error or an assembly error of the optical element or the mechanical part.

  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, the scanning line is bent. Even when the scanning imaging optical system is configured as a lens system, the scanning line is inevitably bent 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.

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 is formed by writing with a single optical scanning device, scanning line bending and isokinetic incompleteness (deviation from ideal isokinetic scanning) are suppressed to some extent. If this is the case, the “distortion that can be visually recognized” does not occur in the formed image. However, the distortion of the image is never small.

  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. One of the methods for forming such a color image is an image forming apparatus called a tandem type that forms an image for each color component on a photoconductor for each color component. The tandem type image forming apparatus includes a plurality of image forming stations including a photoconductor and an apparatus or unit for executing an electrophotographic process corresponding to the photoconductor. Therefore, if the optical scanning devices that execute the exposure process have different scanning line position variations with respect to the photosensitive member, or the scanning line is bent or tilted, the color formed by superimposing the images corresponding to the respective colors formed at each station. An abnormal image called “color shift” appears in the image, degrading the image quality of the color image.

  Conventionally, as an optical scanning device, in order to reduce the bending and inclination of a scanning line, a long lens constituting a scanning imaging optical system is curved with a plurality of supporting points as support points or tilted in the sub-scanning direction. A configuration for correcting the scanning line bending and the scanning line inclination has been proposed (see, for example, Patent Document 1).

  Further, in an image forming apparatus using an electrophotographic process called a Carlson process, a latent image is formed by exposure, developed with toner, and transferred to a transfer body of a toner image according to rotation of a photosensitive drum as an image carrier. Done. Therefore, in a multicolor image forming apparatus in which a plurality of photosensitive drums are arranged along the transfer direction of the transfer body and the toner images formed at the image forming stations of the respective colors are overlaid, the latent images due to the eccentricity of the photosensitive drums and the variation in the diameters. Due to registration error in the sub-scanning direction of each toner image due to the time difference from image formation to transfer, the difference between the photosensitive drums of each color, the speed fluctuation or meandering of the transfer body, for example, the transfer belt or the conveyance belt for conveying the recording paper. The image quality deteriorates due to color shift or color change.

  Conventionally, this registration deviation is regularly detected at the start-up of the apparatus or between jobs by the registration deviation detection pattern recorded on the transfer body, regardless of whether it is due to the optical scanning apparatus or other than the optical scanning apparatus, In the sub-scanning direction, the position of the leading line is corrected by matching the timing of writing every other deflection reflection surface of the polygon mirror, and in the main scanning direction, the light emission start timing of the light source is adjusted by the synchronization detection signal. Thus, the writing position is corrected (see, for example, Patent Document 2, Patent Document 3, and Patent Document 4). In addition to this correction, the scanning time from the scanning start end to the scanning end is detected, and by taking measures such as adjusting the frequency of the pixel clock to the detected scanning time, the full width magnification between each color is adjusted (for example, (See Patent Document 5).

  On the other hand, in such a multicolor image forming apparatus, speeding up and density increase are progressing year by year. As a countermeasure, there is a method to increase the rotation speed of the polygon motor. However, since the bearing life is limited and heat and vibration cannot be suppressed, it is possible to scan multiple beams simultaneously at a lower rotation speed. A method using a multi-beam light source capable of realizing high speed and high density has been proposed. However, since the multi-beam light source has a difference in pitch and wavelength between the light sources, as disclosed in Patent Document 4, the misregistration between the light sources is detected by individually detecting the registration deviation as a set of a plurality of lines. Examples to avoid have been proposed. Furthermore, examples using a liquid crystal deflection element as means for correcting the scanning position in the sub-scanning direction have been proposed (see, for example, Patent Document 6 and Patent Document 7).

  In recent years, it has become common to employ an optical element having a special surface typified by an aspherical surface for an imaging optical system of an optical scanning device with the aim of improving scanning characteristics. There is a resin material as a material that can easily form an optical element having such a special surface. Since a special surface can be formed by integrally molding the resin material, the cost is low. Therefore, an optical element made of the resin material is frequently used in the imaging optical system.

  An optical element made of a resin material is susceptible to changes in temperature and humidity due to changes in temperature and humidity. When such an optical element is used in a scanning imaging optical system of an optical scanning device, due to changes in temperature and humidity, The curve of the scanning line and the constant velocity also change. For this reason, for example, when several tens of color images are continuously formed, the in-machine temperature rises due to the continuous operation of the image forming apparatus, and the optical characteristics of the imaging optical system change. The curve and the constant velocity of the scanning line for writing the image gradually change, and due to the phenomenon of color misregistration, the color image obtained in the initial stage may be completely different from the color image obtained in the final stage. . Also, as the temperature inside the optical scanning device rises, the housing of the optical scanning device expands, the position of the receiving surface of the optical element changes, the beam position relative to the optical element changes, or a folding mirror is installed. There arises a problem that the scanning position with respect to the photosensitive member is shifted with time, such as an angle change.

  A scanning imaging lens such as an fθ lens, which is a typical optical element constituting the scanning imaging optical system, generally cuts a non-lens-use portion (a portion where no deflected light beam is incident) in the sub-scanning direction, and is a long strip in the main scanning direction. Formed as a shaped lens. In the case where the scanning imaging optical system is composed of a plurality of lenses, the lens length in the main scanning direction increases as the arrangement position of the lens is further away from the light deflecting unit, and is about 100 mm to 200 mm or longer. A long lens with 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 is bowed in the sub-scanning direction. It becomes. Such warping of the long lens causes the above-described scanning line bending, but when the warping is significant, the scanning line bending also occurs extremely.

  As an example of an optical scanning device corresponding to a multi-color image forming apparatus, a light beam from a light source corresponding to each color is scanned collectively with a single polygon mirror, and each light beam is scanned with a corresponding scanning optical system or photosensitive. There are known a configuration in which a plurality of mirrors for guiding to a body drum are integrally supported by a common housing, and a configuration in which an optical scanning device is individually provided for each photosensitive drum (for example, Patent Document 8). reference). According to such a configuration described in Patent Document 8, since the components are arranged so that the light beams directed toward the photosensitive drum pass through different paths, each irradiation is performed depending on the environmental temperature or the like where the multicolor image forming apparatus is installed. The position can easily vary.

  The deviation of the irradiation position can be corrected, for example, by periodically detecting a registration deviation detection pattern recorded on a transfer member such as an intermediate transfer belt at the time of starting up the apparatus or between jobs. it can. However, since the irradiation position further varies due to heat from the fixing device and the polygon motor accompanying the printing operation, there is a problem that color misregistration and color change gradually occur when the number of prints for one job is large. In particular, as in the invention described in Patent Document 8, when the optical system is arranged so as to face each other with a polygon mirror interposed therebetween, the scanning direction is opposite in the opposite optical system, so that the writing position is changed due to fluctuations in the main scanning magnification. In addition, the displacement of the scanning position between the colors increases due to the distortion of the housing.

  As a countermeasure, it is conceivable that the temperature is constantly observed to reach a predetermined temperature change range, or when the predetermined number of prints is exceeded, the printing operation is stopped halfway and the deviation of the irradiation position is corrected again. . However, considering the flow of creating a resist deviation detection pattern, detecting and correcting it, creating a detection pattern again, detecting it, and correcting it, it takes several minutes to complete the correction. As a result, productivity is lowered and toner is wasted in forming the detection pattern. Therefore, it is desirable to minimize the frequency of light beam irradiation position correction.

JP 2002-258189 A Japanese Patent Publication No.7-19084 JP 2001-253113 A, JP 2003-154703 A Japanese Patent Laid-Open No. 9-58053 JP 2003-233094 A JP 2003-215484 A JP 2002-148551 A

  In view of the technical problems in the conventional optical scanning apparatus and image forming apparatus, the present invention reduces scanning line bending caused by warping of a resin imaging element included in a scanning imaging optical system, and temperature. An object of the present invention is to provide an optical scanning device having a configuration capable of effectively reducing fluctuations in scanning position caused by a change, and an image forming apparatus using the same.

According to the present invention, the light source, the first imaging optical system that condenses and couples the divergent light beam from the light source, and the light beam from the light source are deflected toward the scanning medium. And a second imaging optical system that is disposed between the deflector and the light source and forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector, and a light beam from the deflector on the scanned medium In an optical scanning device having a third imaging optical system that scans at a constant speed as a light spot, press and hold at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction. And the pressure expansion coefficient of the pressing member is smaller in the central part than the peripheral part in the deflection direction of the optical element when the pressing member presses the optical element from the support member side. The pressing member presses the optical element from the opposite side of the support member The most important feature that towards the center portion from the deflection direction the peripheral portion of the optical element is large when.

The thickness of the pressing member is such that when the pressing member presses the optical element from the support member side, the central part is thinner than the peripheral part in the deflection direction of the optical element, and when pressing from the opposite side of the support member, the optical element It is preferable that the central portion is thicker than the peripheral portion in the deflection direction.
When the pressing member presses the optical element from the support member side, the contact area of the pressing member with respect to the optical element is smaller in the central part than the peripheral part in the deflection direction of the optical element and presses from the opposite side of the support member. It is preferable that the central portion is larger than the peripheral portion in the deflection direction of the optical element .

It is preferable that the optical element be adjustable in rotation about a direction substantially parallel to the optical axis as a rotation axis.
The posture of the optical element is preferably controlled by a posture control mechanism that can be rotated and adjusted with a direction substantially orthogonal to the optical axis and parallel to the deflection scanning surface as a rotation axis.
The optical element is adjusted by an attitude control mechanism, and an actuator for operating the attitude control mechanism may be a differential gear composed of a stepping motor, a screw, and a gear.

An image forming apparatus according to the present invention is an image forming apparatus based on an electrophotographic process, and includes the optical scanning device according to the present invention as an apparatus for performing an exposure process in an electrophotographic process. It is.
The image forming apparatus has a plurality of image bearing members, by an electrostatic latent image formed on the image bearing member is developed with each color toner, a configuration for superimposing the respective color toner images on the transfer member, a color image Ru can be formed.
The image forming apparatus capable of forming the color image is preferably provided with color misregistration detection means, and the posture of the optical element is controlled based on the detection result to perform color misregistration correction.
The color misregistration detecting means may detect a resist misregistration by forming a toner image of each color on the transfer body.
The image forming apparatus may have a network communication function.

The optical scanning device according to the present invention can be mounted on the image forming apparatus to reduce the number of corrections of irradiation position deviation that is performed as a countermeasure against color misregistration or color change that occurs during a job. As a result, productivity can be improved and the number of detection pattern formations can be reduced, so that the number of pattern formations for deviation correction can be reduced, and the amount of toner consumed by pattern formation can be reduced. Therefore, power consumption can be reduced and consumption of consumables can be suppressed.
The effect of each invention described in each claim is as follows.

According to the first to fifth aspects of the present invention, it is possible to reduce the occurrence of bending of the scanning line due to deformation of the scanning optical element due to temperature change by a simple method.
According to the sixth and seventh aspects of the invention, by adjusting the scanning optical element, it is possible to obtain an image with little bending or inclination of the scanning line.

According to the eighth aspect of the present invention, a high-quality image can be formed by applying the optical scanning device capable of obtaining the above-described effect to the image forming apparatus.
According to the ninth to eleventh aspects, it is possible to form a color image with little color misregistration.
According to the twelfth aspect of the present invention, it is possible to construct an information processing system capable of processing outputs from a plurality of devices by having a network communication function.

Embodiments of an optical scanning device and an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 shows an embodiment of an optical scanning apparatus corresponding to a tandem type image forming apparatus that scans four stations. The optical scanning device consisting of 4 stations is divided into two stations on the left and right, and one polygon mirror as a deflector is arranged for two stations and is shared by the two stations. Each station individually constitutes an optical scanning unit, and has a system in which the optical scanning directions on the surface to be scanned are aligned and juxtaposed. The four photosensitive drums 101, 102, 103, and 104 corresponding to each station are arranged at equal intervals along the moving direction of the transfer body 105, and sequentially form toner images of different colors. The toner images of the respective colors formed on the respective photosensitive drums are transferred to the transfer body 150 and overlapped to form a color image.

  An optical scanning device that scans each photosensitive drum is integrally formed by a housing (not shown), and scans a light beam by a polygon mirror 106. Since the rotation direction of the polygon mirror 106 is the same, the image is written so that the respective writing start positions coincide. In the illustrated embodiment, a pair of semiconductor lasers are provided for each photosensitive drum, and scanning is performed by shifting one line pitch in the sub-scanning direction in accordance with the recording density so that two lines are scanned simultaneously. ing. Since the configuration of each optical scanning unit is the same, one side of the optical scanning unit centered on the polygon mirror 106 will be described here. The laser beams 201 and 202 from the respective light source units 107 and 108 have portions whose emission positions differ in the sub-scanning direction for each light source unit, in the embodiment, the emission positions of the light source units 107 and 108 have a predetermined height, in the embodiment. It is deployed so as to be different by 6 mm. The beam from the light source unit 108 is bent by the incident mirror 111 and is incident on the polygon mirror 106 with the main scanning direction approaching the beam from the light source unit 107 directly directed to the polygon mirror 106. Each of the light source units 107 and 108 has a coupling lens that collects the divergent light emitted from the semiconductor laser as the respective light source and couples it to the subsequent optical system as a substantially parallel light beam. In the present invention, the coupling lens is referred to as a first imaging optical system.

  Cylindrical lenses 113 and 114 are disposed between the light source units 107 and 108 and the polygon mirror 106. The cylindrical lenses 113 and 114 are arranged so that one side is a plane and the other side is a convex cylindrical surface having a common curvature in the sub-scanning direction, and the optical path lengths to the deflection points of the polygon mirror 106 are equal. is there. Each light beam is converged only in the sub-scanning direction so that a long line image is formed in the main scanning direction in the vicinity of the deflection reflection surface of the polygon mirror 106. Cylindrical lenses 113 and 114 constitute a second imaging optical system, and are arranged so that the deflection point and the surface of the photosensitive drum are in a conjugate relationship in the sub-scanning direction in combination with a scanning imaging optical system described later. Thus, a surface tilt correction optical system is formed.

A non-parallel plate 117 is disposed between the light source unit 107 and the cylindrical lens 113. The non-parallel plate 117 is a glass substrate in which any one surface is slightly inclined in the main or sub-scanning direction, and is controlled to rotate around the optical axis so that the relative scanning position with respect to the beam from the light source unit 107 serving as a reference. Adjust.
The polygon mirror 106 has six deflecting reflecting surfaces, and is configured in two stages in the embodiment. A groove is provided so that an intermediate portion not used for deflection is slightly smaller in diameter than the inscribed circle of the polygon mirror 106. It has a shape with reduced windage. The thickness of one layer of the polygon mirror 106 is about 2 mm. The phases of the upper and lower polygon mirrors are the same.

  The polygon mirror 106 is rotationally driven at a constant speed by a motor (not shown), and deflects and reflects the laser beam from the light source unit by each deflection reflection surface. A scanning imaging optical system as a third imaging optical system is disposed on the path of the deflected laser beam. The scanning imaging optical system has an imaging lens 120 as a first scanning lens. The imaging lens 120 is also integrally formed or joined in two layers, and each imaging lens 120 has power so that the beam moves at a constant speed on the surface of the photosensitive member in accordance with the rotation of the polygon mirror 106 in the main scanning direction. It has a non-arc surface shape. On the beam path after passing through the imaging lens 120, anamorphic lenses 122 and 123 as second scanning lenses are provided for each beam. The imaging lens 120 and the anamorphic lenses 122 and 123 constitute a scanning imaging optical system, and each beam is condensed on the surface of the photosensitive drums 101 and 102 to form a light spot, and the light spot is scanned. As a result, latent images are formed on the surfaces of the photosensitive drums 101 and 102 to record the images.

  In the embodiment shown in FIG. 1, the two stations described above are taken as a set, another set of stations are juxtaposed, and a total of four stations are arranged at equal intervals. The four stations are yellow, magenta, cyan, and black color stations, respectively. Each color station is composed of a plurality of mirrors so that the optical path lengths from the polygon mirror to the photoconductor surface coincide with each other, and the incident positions and incident angles with respect to the photoconductor drums arranged at equal intervals are equal. The optical path is bent. In the illustrated embodiment, three mirrors are arranged per station.

Explaining the optical path for each color station, the beam 201 from the light source unit 107 is deflected by the upper stage of the polygon mirror 106 via the cylindrical lens 113, passes through the upper layer of the imaging lens 120, and is reflected by the mirror 126. Then, the light passes through the anamorphic lens 122, is reflected by the mirrors 127 and 128, is guided to the photosensitive drum 102, and forms a magenta image as the second station.
The beam 202 from the light source unit 108 is reflected by the incident mirror 111 through the non-parallel plate 117 and the cylindrical lens 114, is deflected at the lower stage of the polygon mirror 106, passes through the lower layer of the imaging lens 120, and is reflected by the mirror 129. , Passes through the anamorphic lens 123, is reflected by the mirrors 130 and 131, is guided to the photosensitive drum 101, and forms a yellow image as a first station.
The remaining set of optical scanning units has the same configuration and will not be described in detail, but the beam from the light source unit 109 is guided to the photosensitive drum 104 to form a black image as a fourth station. The beam from the unit 110 is guided to the photosensitive drum 103 to form a cyan image as a third station.

  FIG. 2 shows an example of a light source unit. All the light source units have the same configuration as that shown in FIG. In FIG. 2, semiconductor lasers 301 and 302 and coupling lenses 303 and 304 are arranged symmetrically in the main scanning direction with respect to the emission axis in the scanning means corresponding to each color. In the semiconductor laser, the outer periphery of the package is press-fitted into the fitting holes of the base members 305 and 306 from the back side, the base members 305 and 306 are brought into contact with the back surface of the holder 307, and the screws penetrating from the front side of the holder 307 The base members 305 and 306 are fixed to the holder 307 by being screwed to the respective three points of the members 305 and 306. Coupling lenses 303 and 304 are in a state in which the outer periphery is abutted against V-grooves 308 and 309 formed to open in a direction opposite to holder 307 and pressed against the inside of V-grooves 308 and 309 by leaf springs 310 and 311. Thus, the leaf springs 310 and 311 are fixed to the holder 307 by screws, and the coupling lenses 303 and 304 are fixed.

  Arrangement of the base members 305 and 306 on the contact surface with the holder 307 (surface perpendicular to the optical axis) so that the light emitting points of the semiconductor lasers 301 and 302 are on the optical axes of the coupling lenses 303 and 304, respectively. Is adjusted and fixed. Further, the position on the V groove (in the optical axis direction) is adjusted and fixed so that the light emitted from the coupling lenses 303 and 304 becomes a parallel light flux. The optical axes of the respective emitted lights are inclined so as to intersect with each other with respect to the emission axis C. In the illustrated embodiment, the inclination of the support members of the semiconductor lasers 301 and 302, that is, the base members 305 and 306, is set so that this intersection position is in the vicinity of the deflecting and reflecting surface of the polygon mirror.

The printed circuit board 312 on which the drive circuits of the semiconductor lasers 301 and 302 are formed is fixed to a pedestal erected on the holder 307 with screws, and the lead terminals of the respective semiconductor lasers are inserted into the through holes of the printed circuit board 312 and soldered. Thus, the light source unit 300 is integrally formed.
The light source unit inserts and positions the cylindrical portions 313 of the holders 307 in engagement holes formed at different heights on the wall surface of the housing in which the optical scanning device is incorporated, and the contact surface 314 is formed on the housing. It is abutted against the wall and screwed. When the light source unit is mounted, the amount of tilt γ is adjusted with reference to the cylindrical portion 313, so that the beam spot interval on the surface to be scanned by the beams from the two semiconductor lasers 301 and 302 depends on the recording density. It can be adjusted to the scanning line pitch P.

As in this embodiment, a light source unit is configured using a plurality of semiconductor lasers, and a plurality of light source units are combined to increase the number of light beams scanned on the photosensitive drums 101, 102, 103, and 104. Can do. As a result, the output speed of the image forming apparatus equipped with the present optical scanning device can be increased. Conversely, if the output speed is not increased , the rotation speed of the polygon motor can be reduced to reduce power consumption and heat generation. Can be configured.

  Next, as a means for improving the output speed, a method other than the method of increasing the light sources and the light source units will be described. With respect to the light source, the semiconductor laser is used in the above-described embodiments. However, the same effect can be obtained by using a semiconductor laser array (laser diode array: LDA) in which a plurality of light emitting points are arranged in a monolithic array as the light source. Can do. A light source unit may be configured by coupling divergent light beams emitted from a plurality of light emitting points with a common coupling lens and combining a plurality of combinations of the semiconductor laser array and the coupling lens. As another light source, the light source may be configured using a surface emitting laser array in which a plurality of light emitting points are two-dimensionally arrayed.

  FIG. 3 shows a configuration example of a support housing of an anamorphic lens that is one of the scanning lenses constituting the scanning imaging optical system. In FIG. 3, the anamorphic lens 405 is made of resin, and a rib portion 406 is formed so as to surround the lens portion, and a positioning projection 407 is formed on one side edge of the central portion in the length direction. The anamorphic lens 405 is supported by a support plate 401. The support plate 401 is formed into a channel shape by bending both side edges in the width direction of the elongated sheet metal, and the projection 407 of the anamorphic lens 405 is engaged with a notch formed in the bent portion of the support plate 401. . The anamorphic lens 405 is positioned in the longitudinal direction by the lower surface of the rib portion 406 being abutted against a cut and raised portion 410 formed at a position near one end in the longitudinal direction of the support plate 401. The positioned anamorphic lens 405 and the support plate 401 are sandwiched by being biased from above and below by a pair of leaf springs 403 near both ends in the length direction, and the support plate 401 holds the anamorphic lens 405. The leaf spring 403 is fitted from the outside in a state where the anamorphic lens 405 is superimposed on the support plate 401, and one end portion is brought out from the opening 413 formed in the bottom portion of the support plate 401 to the inside of the support plate 401. It is inserted and fixed in the opening 414 formed in the base of the part.

  A screw hole 412 is formed at the center in the length direction of the support plate 401, and an adjustment screw 408 is screwed into the screw hole 412 from the bottom surface side of the support plate 401. A plate spring 402 is arranged at the position of the adjustment screw 408 so as to span the width direction of the support plate 401 so as to hold the support plate 401 from the bottom surface side, and bent portions at both ends of the plate spring 402 are below the anamorphic lens 405. It hangs around the upper surface of the rib. The adjustment screw 408 passes through the hole 419 of the leaf spring 402 and is screwed into the screw hole 412 of the support plate 401 to which the leaf spring 402 is attached. The lower surface of the rib of the anamorphic lens 405 is brought into contact with the tip of the adjustment screw 408, and the leaf spring 402 biases the anamorphic lens 405 so as to press it toward the support plate 401, so that the anamorphic lens 405 is pressed against the tip of the adjustment screw 408. It is comprised so that the lower surface of a rib may contact | abut reliably. In the illustrated embodiment, not only the central portion in the longitudinal direction of the anamorphic lens 405 but also the vicinity of both end portions, therefore, adjustment screws 408 are provided at a total of three locations.

  Like the anamorphic lens 405, a long plastic optical element is likely to warp in the longitudinal direction, particularly in the direction orthogonal to the scanning plane, due to molding conditions, residual stress, and the like. The amount of warpage varies depending on the type, but may be several tens of microns, and the direction of warpage also varies depending on the type. Also, since the anamorphic lens 405 is long and has low rigidity, it is likely to be deformed (warped) only by applying a slight stress. Will also deform. For this reason, it has been very difficult to accurately correct the bending and inclination of the scanning line between the stations.

  In the above embodiment of the present invention, the anamorphic lens 405 is placed along the support plate 401 to keep the shape stable, and the anamorphic lens 405 is deformed even when a local stress is applied during tilt adjustment described later. In other words, the straightness of the bus is maintained. The support plate 401 mounted with the anamorphic lens 405 is positioned by fitting a projection 418 formed at one end in the length direction into a recess 427 provided on the housing side. Further, the tip of the leaf spring 426 whose base is fixed to the housing side is interposed between the bottom surface of the anamorphic lens 405 and the mounting surface of the housing, and biases one end of the anamorphic lens 405 upward in FIG. Yes.

  A stepping motor 415 is fixed to the housing or the like on the other end side (right side in FIGS. 3 and 4) of the support plate 401, and is movable and fixed to the support plate 401 through a fitting hole formed in the support plate 401. A feed screw formed at the tip of the shaft of the stepping motor 415 is screwed into the screw hole of the tube 416. The rotation of the stepping motor 415 allows the other end of the support plate 401 to be displaced in the sub-scanning direction (anamorphic lens height direction) by the screw hole of the movable cylinder 416 and the lead of the feed screw of the motor 415. Thus, the other end side of the support plate 401 follows the forward / reverse rotation of the stepping motor 415 together with the other end side of the anamorphic lens 405, and the projection 418 on one end side of the support plate 401 is within the plane orthogonal to the optical axis. The rotation can be adjusted using the engaging portion as a fulcrum. This rotation direction is represented by γ. Along with this, the bus line of the anamorphic lens 405 in the sub-scanning direction is tilted, and the scanning line as the imaging position of the anamorphic lens 405 is tilted.

  In the embodiment shown in FIG. 1, the rotation fulcrum end direction is aligned with the anamorphic lenses of the first, second, and third stations in order from the right side, and the scanning line of the fourth station at the left end as a reference is arranged. Then, the tilt adjustment is performed for each unit so that the other scanning lines are parallel.

  FIG. 4 is a view of the mounting state of the anamorphic lens 405 as seen from the optical axis direction. The anamorphic lens 405 is supported at both ends in the length direction by the upper end of the upright bending portion 410 formed on the support plate 401, and a total of three positions, the center in the length direction and the position close to the upright bending portion 410, are provided on the adjustment screw 408. Supported at the tip. When the protruding amount of the adjusting screw 408 is not enough for the height of the upright bending portion 410, the anamorphic lens 405 bus 412 is warped downward by the attractive force of the elastic force of the leaf spring 402. On the contrary, when the protruding amount of the adjusting screw 408 exceeds the height of the upright bending portion 410, the anamorphic lens 405 is pushed by the adjusting screw 408 and warps upward. Therefore, by adjusting these adjustment screws 408, the focal line of the anamorphic lens 405 can be curved in the sub-scanning direction, and the bending of the scanning line can be corrected. In general, the bending of the scanning line is caused by an arrangement error of optical elements constituting the optical system, a warp during molding, or the like. Linearity can be corrected by bending the anamorphic lens 405 in a direction that cancels the bending of the scanning line. Alternatively, the direction and amount of bending between the scanning lines can be made uniform.

  The adjustment screw 408 may be provided at a plurality of locations along the main scanning direction. As shown in FIGS. 3 and 4, by arranging the adjusting screws 408 at a total of three positions between the central portion in the longitudinal direction of the anamorphic lens 405 and the vertical bent portions 410 at both ends, the M-type or W-type It is possible to correct the bending of the mold. In the embodiment, an adjustment screw 408 is provided for all anamorphic lenses and is adjusted so that the scanning line of each station is straight when assembled.

  When the internal temperature of the image forming apparatus rises, even if the initial adjustment is performed with high accuracy, the temperature difference between the main scanning direction and the sub-scanning direction is generated in the plastic optical element and the member holding it, and the optical element is warped. As a result of this, or a change in warpage, there arises a problem that the scanning line bend and the scanning line inclination amount on the surface to be scanned change.

  In view of this, the present invention proposes a method for reducing changes in scanning line bending and scanning line inclination when a temperature distribution difference occurs in the optical element and the member holding the optical element due to temperature changes. As one of the methods, the adjustment screw that corrects and adjusts the optical element, that is, the material of the adjustment screw 408 in FIGS. 3 and 4 is made different depending on the arrangement location. When the materials of the adjusting screws 408 are different, the linear expansion coefficients of the adjusting screws are different, and a difference occurs in the amount of elongation due to a temperature rise. As a result, the amount by which the optical element is pushed in varies depending on the location, and the change when a temperature distribution difference occurs can be reduced.

As shown in FIG. 4, when the anamorphic lens 405 is pushed toward the support plate 401 from above by the leaf spring 403, it is common due to the influence of the frictional force acting between the upright bent portion 410 and the anamorphic lens 405. The vicinity of the center of the lens warps upward. Therefore, the material of each adjusting screw 408 is made different so that a force to counteract this works. That is, if the linear expansion coefficient of the adjusting screw in the peripheral portion of the anamorphic lens 405 is increased and the linear expansion coefficient of the adjusting screw in the vicinity of the central portion is decreased, the amount of change in the peripheral portion becomes larger than that in the central portion, and the anamorphic lens 405 The force that generates the warp can be countered.

  In the case of this embodiment, it is pressed by the adjusting screw from the support plate 401 side supporting the anamorphic lens 405, but when it is pressed by the adjusting screw from the opposite side of the support plate 401, the above is reversed. The curvature of the anamorphic lens 405 can be canceled by decreasing the linear expansion coefficient of the adjustment screw in the peripheral portion and increasing the linear expansion coefficient of the adjustment screw in the vicinity of the central portion. That is, when the anamorphic lens 405 is pressed from the support plate 301 side, the linear expansion coefficient of the adjustment screw 408 is larger at the periphery of the anamorphic lens 405, and when the adjustment screw 408 is pressed from the opposite side of the support plate 401, The linear expansion coefficient is made smaller at the periphery of the anamorphic lens 405. By doing so, the warp of the anamorphic lens 405 can be canceled.

  Another example of the anamorphic lens support portion will be described with reference to FIG. In the example shown in FIG. 5, the anamorphic lens 405 is held between the upper sheet metal 526 and the lower sheet metal 523 from both sides of the anamorphic lens 405 in the sub-scanning direction. An adjustment mechanism for pressing the anamorphic lens 405 is provided at three positions in the longitudinal direction of the upper metal plate 526 and at a position offset from the vertical bending portion of the lower metal plate 523 (corresponding to the vertical bending portion 410 in FIGS. 3 and 4). Yes.

  Also in this example, generally the vicinity of the center portion of the anamorphic lens 405 is warped upward due to the influence of the frictional force acting on the anamorphic lens 405 by the leaf spring and the lens support portion. Further, when the metal plate 526, 523 is supported from above and below, the adjusting screw is deformed by being sandwiched between the metal plates 526, 523. In such a case, in order to cancel the warp of the anamorphic lens 405, when pressing from the support plate side of the anamorphic lens 405, it is possible to make it difficult to deform the adjustment screw in the periphery of the lens relative to the adjustment screw in the vicinity of the center. In the case of pressing from the opposite side of the support plate, this can be dealt with by making the adjustment screw near the center of the lens difficult to deform with respect to the adjustment screw at the periphery. That is, it is possible to cope with the warp of the lens by making it difficult to deform the adjusting screw.

  As a method therefor, there is a method in which the thickness of the adjusting screw and the contact area between the adjusting screw and the anamorphic lens 405 are varied depending on the location of the adjusting screw. That is, when the adjustment screw is pressed from the support plate side of the anamorphic lens 405, the thickness of the adjustment screw on the peripheral side of the anamorphic lens 405 is increased, and when it is pressed from the opposite side of the support plate, the center of the anamorphic lens 405 is set. Increase the thickness of the adjusting screw near the section. By doing so, the warp of the anamorphic lens 405 can be canceled. In other words, when the anamorphic lens 405 is pressed from the support plate side, the contact area of the adjusting screw with the anamorphic lens 405 is increased, and when the anamorphic lens 405 is pressed from the opposite side, the adjustment area is adjusted. This is the same as increasing the screw contact area near the center. By doing so, it is possible to counter the occurrence of warpage against the stress generated by the deformation of the anamorphic lens 405.

Next, an example of a pressure adjusting mechanism by a method different from the adjusting screw will be described with reference to FIGS. Reference numeral 519 indicates this pressing adjustment mechanism. The pressing adjustment mechanism 519 includes a bracket 527 fixed on the upper sheet metal 526, a taper pin 528, and a roller 526. The bottom and top metal plate 526 of the bracket 527 is bent in a U shape, square hole of the same shape is opened, the roller 529 is dropped into this square hole. The taper pin 528 is supported by the hole and screw hole of the bracket 527 from the direction orthogonal to the axis of the roller 529, and the taper portion of the taper pin 528 contacts the roller 529. By adjusting the rotational position of the taper pin 528, the taper pin 528 is led in the screw hole of the bracket 527 and moves in the axial direction, and linearly moves in the direction in which the roller 529 is tightened and loosened depending on the direction of rotation. By tightening the roller 529 with the taper pin 528, the anamorphic lens 405 is pressed and bent in the sub-scanning direction, whereby the scanning line bending can be corrected.

Next, an example of the scanning line bending adjustment mechanism will be described with reference to FIG. The scanning line inclination adjusting mechanism is mainly configured by a stepping motor 535 attached to the other end portion of the upper sheet metal 526. The shaft 536 of the stepping motor 535 is threaded with a predetermined pitch, and the threaded portion 550 is screwed into the nut portion 551. A spur gear 552 is formed on the outer side of the nut portion 551. A spur gear 548 is integrally formed on the motor shaft 536, and the spur gear 548 meshes with another spur gear 549A. The spur gear 549A constitutes a two-stage gear together with the spur gear 549B substantially integral with the spur gear 549A, and the lower spur gear 549B meshes with the spur gear 552. The gears 548 and 552 have substantially the same diameter, and the gears 549A and 549B have substantially the same diameter, but there is a slight rotational difference between the gear 548 integrated with the motor shaft 536 and the gear 552 integrated with the nut portion 551. Thus, the number of teeth is made different so that the differential screw mechanism 555 is configured. Therefore, when the stepping motor 535 is rotated forward and backward, a rotation difference is generated between the screw portion 550 and the nut portion 551, and the nut portion 551 moves up and down little by little together with the gear 552. A bearing portion of the gear train is provided between the upper and lower sheet metals 526 and 523, and the differential screw mechanism 555 is integrally formed with the holding member of the anamorphic lens 405. The rotation center portion of the gear 552 extends through the lower sheet metal 523 and contacts the support plate 532. The support plate 532 corresponds to the support plate 401 in the embodiment shown in FIGS.

  The differential screw mechanism 555 is configured such that the motor shaft 536 and the nut portion 551 are rotated in the same direction by a gear train, and when the motor 53 is driven by providing a gear number difference in the gear train, A rotational phase difference is generated between the shaft 536 and the nut portion 551, and the nut portion 551 moves slightly in the thrust direction. By moving the nut portion 551, the support plate 532 and the anamorphic lens 405 are tilted by a minute angle with one end portion in the length direction as a fulcrum, so that the resolution of scanning line tilt adjustment can be enhanced. Compared with a conventional adjustment resolution composed only of screws and nuts, an adjustment resolution of one digit or more can be obtained.

  The anamorphic lens 405 sandwiched and integrated by the upper and lower sheet metals 526 and 523 is positioned on a support plate 532 as a lens holder, or the integrated fulcrum is in contact with the bottom surface of the lower sheet metal 523 and rotates around the fulcrum. be able to. Therefore, when the stepping motor 535 is driven, it swings like a seesaw with the direction substantially parallel to the lens optical axis as the rotation axis (this swing is called “γ tilt”), and the scanning line tilt is adjusted. Both end portions of the upper and lower sheet metals 526 and 523 are pressed in the sub-scanning direction by plate springs fastened to the lens holder 532, and hold the state after adjustment. Although the lens holder 532 is illustrated as a separate member, it may be formed integrally with the optical housing.

  Next, the scanning line position correcting mechanism 800 will be described with reference to FIG. A protrusion projecting in the optical axis direction is provided in the vicinity of the optical axis of the lower metal plate 523, and the shaft of the nut portion 804 constituting the differential gear is rotatably fitted in a hole provided at the tip thereof. Thrust direction is prevented by a ring or the like. A stepping motor 801 having shafts 802 and 806 extending in both directions is attached to an appropriate support portion such as an optical housing, and a screw portion 803 formed on the shaft 802 is screwed into the nut portion 804. A spur gear 807 is integrally attached to the other shaft 806 of the motor 801, and the gear 807 meshes with the spur gear 808. The gear 808 is substantially integrated with the spur gear 809 to form a two-stage gear, and the gear 809 meshes with a spur gear 805 formed on the outer peripheral side of the nut portion 804. In the gear train described above, the nut portion 804 is slightly moved in the direction orthogonal to the optical axis by the forward and reverse rotation of the motor 801 on the same principle as the operating screw mechanism described with reference to FIG. As described above, since the protruding portion projecting in the optical axis direction is fitted in the vicinity of the optical axis of the lower metal plate 523, the nut portion 804 is anamorphic with the fulcrum as the center of rotation by the minute movement of the nut portion 804. The lens 405 can be β tilted. “Β tilt” means that the scanning line position can be corrected by rotating the anamorphic lens 405 with a direction substantially orthogonal to the optical axis and parallel to the deflection scanning surface as a rotation axis.

  In the differential gear mechanism 800, the stepping motor 801 is a double-shaft type, a screw is attached to one side, a spur gear is attached to the other side, and a two-stage gear bearing that provides a phase difference between the screw and the nut is integrated with the optical housing. This can save space. Further, as the distance (arm length) from the fulcrum to the nut fitting hole of the lower sheet metal is increased, the adjustment resolution in the β tilt direction can be improved. In the optical simulation, if the scanning lens is tilted by β, the scanning line position and the scanning line curve change simultaneously, but the scanning line curve changes less than 1/10 with respect to the scanning line position change, for example, the scanning line position changes by 50 μm. Even if it is made, the change of the scanning line curve is 5 μm or less, and there is no practical problem.

  The anamorphic lens has been described as a resin-molded lens. However, the anamorphic lens can be handled by a glass lens and can be adjusted in the same manner as the resin-molded lens.

In FIG. 1, on the scanning start side and the scanning end side of the image recording area, when two optical scanning stations sharing one polygon mirror are taken as one unit, substrates 138, 139 on which a photosensor is mounted for each unit, and 148 and 149 are provided to detect the scanning beam at each station. In the embodiment, the substrates 138 and 148 form a synchronization detection sensor and are commonly used to measure the timing of starting writing on the photosensitive drum based on the detection signal. On the other hand, the substrates 139 and 149 serve as end detection sensors, detect a change in scanning speed by measuring a time difference between detection signals with the synchronous detection sensor, and detect a change in scanning speed as a light source. By resetting the reference frequency of the pixel clock for modulating each semiconductor laser by inversely proportional multiplication, the full width magnification on the transfer belt 105 of the image recorded by each station can be stably maintained.

Further, as shown in FIG. 9, a time difference Δt from the photodiode 152 to the photodiode 153 is measured by configuring one of the sensors with a photodiode 152 perpendicular to the main scanning direction and a non-parallel photodiode 153. Thus, the sub-scanning position shift Δy of the light beam can be detected. The shift Δy in the sub-scanning position is calculated by using the inclination angle γ of the photodiode 153 and the scanning speed V of the light beam. Δy = (V / tan γ) · Δt
It is represented by In this embodiment, the irradiation position can be maintained so that the sub-scanning resist of each color image does not shift by controlling the rotational phase of the optical axis deflecting means (described later) or the polygon mirrors so that Δt is always constant. it can. Further, if the sensor is arranged on both the scanning start side and the scanning end side, the difference in sub-scanning position deviation between the ends, that is, the inclination of the scanning line can be detected.

  In the embodiment described above, the scanning position of the other station is aligned with the reference station in each unit, and the degree of image overlap between the reference stations of each unit is detected between the units. The writing timing and pixel clock cycle are uniformly corrected. The degree of image overlap is determined by reading the detection pattern of the toner image formed on the transfer belt 105 at the reference station of each unit and detecting the magnification in the main scanning direction, the sub-scanning resist, and the inclination of the scanning line as relative deviations. Periodic correction control is performed.

  With respect to the main scanning direction, correction control is performed by resetting the modulation pixel clock based on the detection result. With respect to the sub-scanning direction, as shown in FIGS. 7 and 8, correction control is performed by controlling the posture of the anamorphic lens with a stepping motor. After the correction process, these patterns are cleaned by a cleaning bias roller and removed from the transfer belt 105.

  Correction control is performed, for example, at the time of starting up the apparatus or between jobs. When the number of prints for one job increases, correction is performed by interrupting in the middle in order to suppress deviation due to temperature changes during that time. Is applied.

  As shown in FIG. 1, the detection means includes an LED element 154 for illumination, a photosensor 155 that receives reflected light, and a pair of condenser lenses 156. In the embodiment shown in FIG. 1, detection means are provided at a total of three locations, the center of the image and the left and right ends. A line pattern inclined by about 45 ° from the main scanning line is formed on the transfer bell 105 by the toner image of black and magenta serving as a reference in each unit, and the detection time difference is read according to the movement of the transfer belt 105. . FIG. 10 shows an example of reading the toner image on the detection line according to the movement of the transfer body, that is, the transfer belt 105. The vertical direction of the paper corresponds to the main scanning direction, and the sub-scanning resist of each color is obtained from the difference between the detection time difference tmk and the theoretical value t0, and the deviation of the main scanning resist of each color is obtained from the difference between the detection time differences tk and tm.

Here, since this pattern is formed by a plurality of light sources, in the embodiment, two beams, as shown in FIG. 11, unevenness is generated by d in the main scanning direction due to the wavelength difference between the light sources, and in the sub scanning direction. The line width differs depending on the combination as indicated by D1 and D2 due to pitch error. In the case of two beams, when the line interval scanned on one surface of the polygon mirror is reduced, the interval between the next line scanned on the adjacent surface is increased.
Therefore, in this embodiment, all light sources are used, and a line width that extends over at least three lines along the detection position so that the beam from one of the light sources is scanned on two or more adjacent surfaces of the polygon mirror. A line pattern is formed by setting, and both edges of the line are detected along the detection position to obtain an intermediate point. This makes it possible to detect deviations that are averaged in a form that includes all pitch errors, and has the same effect as detecting the average value for each light source separately, and variations in pitch and main scanning magnification. Not affected.
By the way, since the line width may change at each detection depending on the light source from which the line pattern starts to be written, it is necessary to always form the first line of the line pattern with a specific light source.

  On the other hand, in the unit, as shown in FIG. 9, it is possible to always monitor the scanning position deviation between stations using the photodiodes 152 and 153. In the embodiment, the photodiodes 152 and 153 are arranged at both ends of the scanning region in the main scanning direction so that the inclination of the scanning line can be detected, and the registration position and the inclination are mechanically corrected by feedback correction, Control is performed so as to match the scanning position of the reference station. As for the main scanning magnification, as described above, based on the detection time of the synchronization detection signal and the end detection signal, the magnification change between stations is always monitored, and each semiconductor laser is adjusted to match the magnification of the reference station. The reference frequency of the pixel clock to be modulated is corrected. Therefore, the color misregistration of all the stations can be corrected as long as the overlapping state of the images at the reference station between the units is matched. As described above, in this embodiment, the periodic correction by toner image detection is minimized, so that the overlay accuracy of each color image can be maintained without taking time to interrupt the printing operation.

  In addition, as shown in FIG. 1, the four stations are divided into two stations, and the scanning direction of each station is aligned by scanning with a polygon mirror that rotates in the same direction. While making it difficult for deviations to occur, consideration is given to shortening the time required for correction by enabling correction between units only by electrical correction.

  FIG. 12 shows an example of an image forming apparatus having a tandem configuration on which the optical scanning device is mounted. An image forming station is constituted by four photosensitive drums and process units arranged around them. Since the configuration of each station is the same, the leftmost photosensitive drum 901 and the surrounding process units will be described as representatives. Around the photosensitive drum 901, a charging charger 902 that charges the photosensitive drum 901 to a high voltage, a developing roller 903 that attaches a charged toner to an electrostatic latent image recorded by the optical scanning device 900, and develops it, developing A toner cartridge 904 for supplying toner to the roller 903 and a cleaning case 905 for scraping and storing toner remaining on the photosensitive drum 901 are disposed. As described above, image recording is simultaneously performed on the photosensitive drum 901 by using a plurality of lines by scanning each deflection reflection surface of the polygon mirror. The above-described image forming stations are arranged in parallel in the moving direction of the transfer belt 906, and yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 906 at appropriate timing, and are superimposed to form a color image. Each image forming station has basically the same configuration except that the toner color is different.

On the other hand, the transfer paper is pulled out one by one from the paper feed tray 907 by the paper feed roller 908 and sent out by the registration roller pair 909 in accordance with the recording start timing in the sub-scanning direction, and the color image on the transfer belt 906 is transferred. It is transferred to paper. Next, the color image is fixed on the transfer paper by the fixing roller 910 and is discharged to the paper discharge tray 911 by the paper discharge roller 912.
In the present invention, a single polygon mirror is used, 4 stations are divided into 2 stations, and the stations are symmetrically opposed with the single polygon mirror as the center, and laser beams are incident from both sides. Thus, a counter scanning method in which deflection and scanning are performed in opposite directions may be used.

  Further, the image forming apparatus according to the present invention may be connected to an electronic arithmetic device (such as a computer) and an image information communication system (such as a facsimile) via a network so that they can communicate with each other. By doing so, it is possible to form an information processing system capable of processing output from a plurality of devices with a single image forming apparatus. In addition, if a plurality of image forming apparatuses are connected to the network, it is possible to know the status of each image forming apparatus from each output request, for example, whether the job is busy, whether the power is on, or whether it is malfunctioning. it can. Then, by knowing the state of each image forming apparatus, it is possible to select and output the image output apparatus having the best state (best suited to the user's desire).

It is a perspective view which shows the Example of the optical scanning device concerning this invention. It is a disassembled perspective view which shows the example of the light source part applicable to this invention. It is a disassembled perspective view which shows the example of the optical element holding structure applicable to this invention. (A) is a partial cross-sectional front view, (b) is a side cross-sectional view of the optical element holding structure. It is a perspective view which shows another example of the optical element holding structure applicable to this invention. It is front sectional drawing which shows the example of the optical element press adjustment mechanism applicable to this invention. It is front sectional drawing which shows the example of the attitude | position control mechanism of the optical element applicable to this invention. It is front sectional drawing which shows another example of the attitude | position control mechanism of the optical element applicable to this invention. It is a front view which shows the example of the detection pattern of the scanning beam detection sensor applicable to this invention. It is a front view which shows another example of the detection pattern of the scanning beam detection sensor applicable to this invention. It is a model figure which shows the example of the position and width | variety of the scanning line in a to-be-scanned surface. 1 is a front view showing an embodiment of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Photosensitive drum 102 Photosensitive drum 103 Photosensitive drum 104 Photosensitive drum 105 Transfer belt 106 Polygon mirror as a deflector 107 Light source unit 108 Light source unit 113 Cylindrical lens 114 as a 2nd imaging optical system 114 2nd imaging optical system Cylindrical lens as 120 Imaging lens as third imaging optical system 122 Anamorphic lens as third imaging optical system 123 Anamorphic lens as third imaging optical system 301 Semiconductor laser as light source 302 Semiconductor laser as light source 303 Coupling lens as the first imaging optical system 304 Coupling lens as the first imaging optical system 405 Anamorphic lens

Claims (12)

A light source, a first imaging optical system that condenses and couples the divergent light beam from the light source, a deflector that deflects the light beam from the light source toward the scanned medium, and the deflector and the light source. A second imaging optical system that forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector; a third imaging optical system that scans the light beam from the deflector at a constant speed as a light spot on the scanned medium; In an optical scanning device having
Having a pressing member that presses and holds at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction and controls the posture;
When the pressing member presses the optical element from the support member side, the center of the pressing member is smaller than the peripheral part in the deflection direction of the optical element, and the pressing member places the optical element on the opposite side of the support member. An optical scanning device characterized in that the central portion is larger than the peripheral portion in the deflection direction of the optical element when pressed from the center . A light source, a first imaging optical system that condenses and couples the divergent light beam from the light source, a deflector that deflects the light beam from the light source toward the scanned medium, and the deflector and the light source. A second imaging optical system that forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector; a third imaging optical system that scans the light beam from the deflector at a constant speed as a light spot on the scanned medium; In an optical scanning device having
Having a pressing member that presses and holds at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction and controls the posture;
The thickness of the pressing member is such that when the pressing member presses the optical element from the support member side, the central part is thinner than the peripheral part in the deflection direction of the optical element, and when pressing from the opposite side of the support member, the optical element An optical scanning device characterized in that the central portion is thicker than the peripheral portion in the deflection direction . A light source, a first imaging optical system that condenses and couples the divergent light beam from the light source, a deflector that deflects the light beam from the light source toward the scanned medium, and the deflector and the light source. A second imaging optical system that forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector; a third imaging optical system that scans the light beam from the deflector at a constant speed as a light spot on the scanned medium; In an optical scanning device having
Having a pressing member that presses and holds at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction and controls the posture;
When the pressing member presses the optical element from the support member side, the contact area of the pressing member with respect to the optical element is smaller in the central part than the peripheral part in the deflection direction of the optical element and presses from the opposite side of the support member. Is an optical scanning device characterized in that the central portion is larger than the peripheral portion in the deflection direction of the optical element . A light source, a first imaging optical system that condenses and couples the divergent light beam from the light source, a deflector that deflects the light beam from the light source toward the scanned medium, and the deflector and the light source. A second imaging optical system that forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector; a third imaging optical system that scans the light beam from the deflector at a constant speed as a light spot on the scanned medium; In an optical scanning device having
Having a pressing member that presses and holds at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction and controls the posture;
The thickness of the pressing member is such that when the pressing member presses the optical element from the support member side, the central part is thinner than the peripheral part in the deflection direction of the optical element, and when pressing from the opposite side of the support member, the optical element The central part is thicker than the peripheral part in the deflection direction.
When the pressing member presses the optical element from the support member side, the center of the pressing member is smaller than the peripheral part in the deflection direction of the optical element, and the pressing member places the optical element on the opposite side of the support member. An optical scanning device characterized in that the central portion is larger than the peripheral portion in the deflection direction of the optical element when pressed from the center . A light source, a first imaging optical system that condenses and couples the divergent light beam from the light source, a deflector that deflects the light beam from the light source toward the scanned medium, and the deflector and the light source. A second imaging optical system that forms a line image that is long in the deflection direction in the vicinity of the deflecting reflection surface of the deflector; a third imaging optical system that scans the light beam from the deflector at a constant speed as a light spot on the scanned medium; In an optical scanning device having
Having a pressing member that presses and holds at least one of the optical elements constituting the third imaging optical system in a direction orthogonal to the deflection direction and controls the posture;
When the pressing member presses the optical element from the support member side, the contact area of the pressing member with respect to the optical element is smaller in the central part than the peripheral part in the deflection direction of the optical element and presses from the opposite side of the support member. Is larger in the center than in the periphery of the deflection direction of the optical element,
When the pressing member presses the optical element from the support member side, the center of the pressing member is smaller than the peripheral part in the deflection direction of the optical element, and the pressing member places the optical element on the opposite side of the support member. An optical scanning device characterized in that the central portion is larger than the peripheral portion in the deflection direction of the optical element when pressed from the center . 6. The optical scanning device according to claim 1, wherein the attitude of the optical element is controlled by an attitude control mechanism that can be rotationally adjusted about a direction substantially orthogonal to the optical axis and parallel to the deflection scanning surface. An optical scanning device. 7. The optical scanning device according to claim 6, wherein the actuator for operating the attitude control mechanism is a differential gear composed of a stepping motor, a screw and a gear . 8. An image forming apparatus using an electrophotographic process, wherein the optical scanning apparatus according to claim 1 is mounted as an apparatus for performing an exposure process in the electrophotographic process . 9. The image forming apparatus according to claim 8 , comprising a plurality of image carriers, developing the electrostatic latent image formed on the image carrier with each color toner, and superimposing the color toner images on the transfer body to form a color image. An image forming apparatus capable of forming a color image by forming . The image forming apparatus according to claim 9 , further comprising a color misregistration detection unit, and controlling the attitude of the optical element based on the detection result to perform color misregistration correction . 11. The image forming apparatus according to claim 10, wherein the color misregistration detecting means forms a toner image of each color on the transfer member and detects a resist misregistration . 12. The image forming apparatus according to claim 8, wherein the image forming apparatus has a network communication function .

Images