JP2010204494A - Exposure apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the flexibility of arranging a scanning lens and a folding member regardless of the incident method of a luminous flux to a deflection and reflection face of an optical deflector, so as to deal with the miniaturization of a body. <P>SOLUTION: The exposure apparatus incudes: a polygon mirror 71 which deflects and scans a plurality of luminous fluxes L1 to L4 emitted from a plurality of light sources on a plane including a rotary axis into two opposite directions; mirrors 74, 75, 76 which are provided between the polygon mirror 71 and respective photoreceptors 2Y, M, C, K and performs a k-guide of the deflected luminous fluxes onto the photoreceptors 2Y, M, C, K; a first lens 73a having fθ characteristics which are provided on the respective optical paths and condenses the luminous fluxes L1 to L4 onto the photoreceptors 2Y, M, C, K, wherein the first lens 73a has four optical faces A, B, C, D on a subscanning cross section and two luminous fluxes L2, L3 out of the luminous fluxes L1 to L4 pass the optical faces. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an image forming apparatus, and more particularly to an exposure apparatus that deflects and scans a light beam from a light source and focuses the light on an exposure surface, and an image forming apparatus including the exposure apparatus.

  An optical scanning apparatus widely known in connection with an electrophotographic image forming apparatus such as a digital copying machine or a laser printer generally deflects a light beam emitted from a light source device by an optical deflector and uses an fθ lens or the like. Condensing toward the surface to be scanned by the scanning imaging optical system and the folding mirror to form a light spot on the surface to be scanned, and the surface to be scanned is optically scanned (main scanning) with this light spot. Yes.

  Here, when the optical scanning device is used as an exposure device, a photosensitive surface of a photosensitive medium such as a photoconductive photosensitive member is disposed on a surface to be scanned of the optical scanning device. As an example of a full-color image forming apparatus, four photoconductors are arranged in the conveyance direction of the recording paper, and light beams emitted from a plurality of light source devices corresponding to the photoconductors are deflected and scanned by one deflecting unit. A developing device that uses a plurality of optical scanning optical systems corresponding to the photosensitive member to simultaneously expose each photosensitive member to form a latent image, and uses these latent images with developers of different colors such as yellow, magenta, cyan, and black. In some cases, after the visible images are formed by the above, these visible images are sequentially superimposed on the same recording paper, transferred, and fixed to obtain a color image.

  As described above, an image forming apparatus that obtains a two-color image, a multi-color image, a color image, or the like by using two or more combinations of an exposure apparatus and a photoreceptor is known as a so-called tandem type image forming apparatus. Here, in the tandem-type image forming apparatus, if an optical deflector is individually provided for each light flux, the cost becomes high and the apparatus becomes larger, so an exposure apparatus in which each light flux shares a single optical deflector is used. Conventionally proposed. In recent years, many digital copying machines, laser printers, and the like that are placed on a desk have become widespread, and further downsizing is required in order to reduce the installation area as much as possible. Therefore, as the main body is miniaturized, the exposure apparatus must also cope with the miniaturization.

  In response to a request for downsizing an exposure apparatus, Patent Document 1 discloses a plurality of light sources that emit light beams, an optical deflector that deflects and scans each light beam, and a scanning optical system that includes at least one scanning lens; A plurality of scanned surfaces, and each light beam is deflected by the same deflecting / reflecting surface of the optical deflector and then condensed by the scanning optical system onto each different scanned surface. Has an angle in the sub-scanning direction with respect to the normal of the deflecting reflecting surface of the optical deflector, and at least the scanning lens closest to the optical deflector of the scanning optical system is shared by all the light beams and deflected by the optical deflector After that, the light beam closest to the scanned surface in the sub-scanning direction is separated toward the corresponding scanned surface at the position closest to the optical deflector in the direction approaching the corresponding scanned surface. An exposure apparatus is described. This exposure apparatus is a so-called oblique incidence optical system, and the size of the exposure apparatus is reduced by sharing the deflection reflection surface of the optical deflector.

  In Patent Document 2, in the one-side scanning oblique incidence optical system similar to Patent Document 1, light beams deflected by the same deflecting reflection surface of the optical deflector out of light beams from a plurality of light sources are deflected and reflected. Light from the deflecting / reflecting surface to the corresponding scanned surface is incident on one side in the sub-scanning direction with respect to the normal of the surface and incident on one side in the sub-scanning direction with respect to the normal of the deflecting / reflecting surface. An even number of folding mirrors in the sub-scanning direction are arranged on the road, and a beam to be scanned corresponding to the deflecting / reflecting surface of the light beam incident and deflected and reflected from the opposite side of the sub-scanning direction with respect to the normal line of the deflecting / reflecting surface. The exposure apparatus is characterized in that an odd number of folding mirrors in the sub-scanning direction are arranged on the optical path to the surface. In this exposure apparatus, the number of folding mirrors is set so that the scanning line bends in the same direction, and color misregistration in a full-color image can be reduced, and a small exposure apparatus is realized.

  Patent Document 3 discloses a plurality of light sources that emit light beams, an optical deflector that deflects the first to fourth light beams emitted from the plurality of light sources, and first to third beams deflected by the optical deflector. At least one folding member provided for each optical path so as to guide the fourth light flux to the first to fourth scanned members, and each light flux provided in each optical path for the first to fourth light beams. The first lens and the second lens having the fθ characteristic for condensing on the scanned member, and the first and second light fluxes and the third and fourth light fluxes include the rotation axis of the optical deflector. The positions of the second and third scanned members that are deflected on both sides of the plane and are incident on the second and third light beams are the first and fourth scanned members on which the first and fourth light beams are incident. The second and third light beams are closer to the optical deflector than The optical path to the member is an image forming apparatus formed on the side closer to the member to be scanned than the optical path until the first and fourth light fluxes reach the folding member in the sub-scanning section. The light flux is separated from the second and third scanned members by the first folding member and folded in a direction approaching the optical deflector, and then the second and third scanned members are reflected by the second folding member. By being guided to the scanning member, respectively, the second and third optical paths are formed. In the first and fourth optical paths, the first lens is disposed upstream of the folding member, and the second lens is the folding member. Arranged on the downstream side, and in the second and third optical paths, the first lens is arranged on the upstream side of the first folding member, the second lens is on the downstream side of the second folding member, and Arranged close to one lens An image forming apparatus characterized in that the image forming apparatus is installed is described. In this image forming apparatus, the exposure apparatus is reduced in size by bringing the second and third optical paths closer to the vicinity of the first lens.

  However, in the case of the conventional technology as described above, the following problems occur. First, since the thing of patent document 1 and patent document 2 injects a several light beam in a subscanning direction with a different angle with respect to the same deflection | deviation reflective surface, a light source must also be arranged in a subscanning direction, Alternatively, the arrangement of the light source becomes complicated because the light beam must be folded and guided to the deflecting / reflecting surface by a folding mirror or the like. Furthermore, since a plurality of light beams are close to each other, it is necessary to take a sufficient distance to separate the plurality of light beams after passing through the scanning lens without being broken by the folding mirror. (Width in the sub-scanning direction) becomes large.

  Moreover, in the thing of patent document 3, since the optical path of a light beam will fluctuate | variate in a subscanning direction by component precision or a temperature rise, the light beam which passes the 1st lens vicinity may be scattered with a 1st lens. . Further, as a method for reducing the size of the main body, for example, a method of narrowing the interval between a plurality of members to be scanned and reducing the depth direction or the width direction of the apparatus can be cited. It is necessary to reduce the distance of one lens. When the first lens is brought close to the optical deflector, the component accuracy becomes strict in order to stabilize the optical performance of the first lens, which makes it difficult to manufacture or increases the cost of the lens. End up.

  The present invention has been made in view of the above background, and the object of the present invention is to improve the degree of freedom of arrangement of the scanning lens and the folding member without depending on the incident method of the light beam on the deflecting reflection surface of the optical deflector. An object of the present invention is to provide an exposure apparatus that can cope with downsizing of the main body.

  According to the first aspect of the present invention, there is provided an optical deflector that deflects and scans a plurality of light beams emitted from a plurality of light sources in two directions opposed to a plane including a rotation axis, the optical deflector, and respective scanned surfaces. And at least one folding member for guiding the light beam deflected by the optical deflector to the scanned member, and the light beam deflected by the optical deflector provided on each optical path on the scanned member. An exposure apparatus comprising: at least one optical imaging means for focusing light on the optical scanning means, wherein the optical imaging means comprises at least two optical surface pairs each consisting of an entrance surface and an exit surface in the sub-scan section. An exposure apparatus characterized in that at least two of the plurality of light beams pass through different optical surface pairs of the optical imaging means.

  According to a second aspect of the present invention, in the exposure apparatus according to the first aspect, at least one of the optical imaging means includes the two pairs of optical surfaces.

  According to a third aspect of the present invention, in the exposure apparatus according to the first or second aspect, the optical imaging means is a lens having an fθ characteristic.

  According to a fourth aspect of the present invention, in the exposure apparatus according to any one of the first to third aspects, the light beam deflected by the optical deflector is guided to the scanned member on the side close to the rotation axis of the optical deflector. The emitted light beam is once folded by the folding member in a direction away from the member to be scanned and then guided to the member to be scanned.

  According to a fifth aspect of the present invention, in the exposure apparatus according to any one of the first to fourth aspects, the optical deflector has a plurality of deflecting reflecting surfaces, and the plurality of light beams are arranged on the deflecting reflecting surface of the optical deflector in a sub-scan section. The incident light is parallel to the normal line.

According to a sixth aspect of the present invention, in the exposure apparatus according to any of the first to fifth aspects, the plurality of light beams are deflected by different deflection reflecting surfaces of the optical deflector.
According to a seventh aspect of the present invention, in the exposure apparatus according to the first to fifth aspects, at least two of the plurality of light beams are deflected by the same deflecting reflection surface of the optical deflector. It is.

  According to an eighth aspect of the present invention, in the exposure apparatus according to any one of the first to fourth aspects, the plurality of light beams are incident at an angle with respect to the normal line of the deflecting reflection surface of the optical deflector in the sub-scan section. To do.

According to a ninth aspect of the present invention, in the exposure apparatus according to the eighth aspect, the optical imaging means is composed of two lenses provided in respective optical paths.
The invention according to claim 10 is the exposure apparatus according to claim 8, wherein the optical imaging means provided on the optical path to the member to be scanned on the side closer to the rotation axis of the optical deflector among the plurality of light beams. Is composed of one lens, and the optical imaging means provided on the optical path to the member to be scanned far from the rotation axis of the optical deflector is composed of two lenses. It is.

  According to an eleventh aspect of the present invention, there is provided an image forming apparatus for forming an image on the image carrier by performing an electrophotographic process of charging, exposure and development on the image carrier, and exposure of the electrophotographic process. A means for executing the process includes the exposure apparatus according to any one of claims 1 to 10, wherein the image carrier that is a surface to be scanned is exposed.

  According to the present invention, in the opposed scanning optical system that has a plurality of light sources and is scanned in two directions opposed to a plane including the rotation axis of the optical deflector, the optical imaging means is At least two pairs of optical surfaces composed of a pair of incident surface and exit surface are provided, and at least two of the plurality of light beams pass through the two pairs of optical surfaces of the optical imaging means, and thus are folded by the folding member. The optical path thus formed is not displaced by the optical imaging means, the degree of freedom of the arrangement of the folding members is increased, and a smaller exposure apparatus and an image forming apparatus including the same can be provided.

1 is a schematic configuration diagram illustrating a printer according to an embodiment. FIG. 2 is an enlarged configuration diagram illustrating a process unit for K of the printer illustrated in FIG. 1. It is a schematic block diagram which shows the optical writing unit which concerns on a 1st Example. It is a schematic block diagram which shows the optical writing unit based on a 2nd Example. It is a schematic block diagram which shows the optical writing unit based on a 3rd Example.

  An exposure apparatus according to the present invention includes: an optical deflector that deflects and scans a plurality of light beams emitted from a plurality of light sources in two directions opposite to a plane including a rotation axis; and the optical deflector and each scanned surface And at least one folding member for guiding the light beam deflected by the optical deflector to the scanned member, and the light beam deflected by the optical deflector provided on each optical path. An exposure apparatus comprising: at least one optical imaging means for condensing the optical imaging means; wherein the optical imaging means includes at least two optical surface pairs each consisting of an entrance surface and an exit surface in the sub-scan section. And at least two of the plurality of light beams pass through different optical surface pairs of the optical imaging means.

  The optical imaging means of the exposure apparatus is a lens having fθ characteristics, and at least one of the optical imaging means includes the two sets of optical surface pairs. In the exposure apparatus, the light beam guided to the scanned member closer to the rotation axis of the optical deflector out of the plurality of light beams deflected by the optical deflector is once emitted from the scanned member by the folding member. The light is guided back to the member to be scanned after being folded back.

  In addition, the optical deflector of the exposure apparatus has a plurality of deflecting and reflecting surfaces, and the plurality of light beams can be incident in parallel to the normal line of the deflecting and reflecting surface of the optical deflector in the sub-scan section. The plurality of light beams can be deflected by different deflection reflecting surfaces of the optical deflector.

  The image forming apparatus according to the embodiment will be described below. Hereinafter, an electrophotographic printer (hereinafter simply referred to as a printer) will be described as an image forming apparatus according to an embodiment of the present invention. First, the basic configuration of the printer will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram showing a printer according to the embodiment, and FIG. 2 is an enlarged configuration diagram showing a process unit for K of the printer shown in FIG. FIG. 1 shows the printer from the side, and the right side in the figure is the front side of the printer and the left side is the rear side.

  The printer includes four process units 1Y, M, C, and K for forming toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached.

  The process unit will be described taking the process unit 1K for forming a K toner image as an example. As shown in FIG. 2, the process unit 1K includes a drum-shaped photosensitive member 2K as a latent image carrier, a drum cleaning device 3K, a charge eliminating device (not shown), a charging device 4K, and a developing device 5K as developing means. Etc. The process unit 1K, which is an image forming unit, can be attached to and detached from the printer body, so that consumable parts can be replaced at a time.

  The charging device 4K uniformly charges the surface of the photoreceptor 2K that is driven to rotate clockwise in the drawing by a driving unit (not shown). The surface of the uniformly charged photoconductor 2K is exposed and scanned by the laser beam L to carry an electrostatic latent image for K. The electrostatic latent image for K is developed into a K toner image by a developing device 5K using K toner (not shown). Then, intermediate transfer is performed on an intermediate transfer belt 16 described later.

  The drum cleaning device 3K removes the transfer residual toner adhering to the surface of the photoreceptor 2K after the intermediate transfer process. The static eliminator neutralizes residual charges on the photoreceptor 2K after cleaning. By this charge removal, the surface of the photoconductor 2K is initialized, and the photoconductor 2K is ready for the next image formation. Similarly, in the process units (1Y, M, C) of other colors, (Y, M, C) toner images are formed on the photoconductors (2Y, M, C), and on the intermediate transfer belt 16 described later. Intermediate transfer.

  The developing device 5K includes a vertically long hopper 6K that stores K toner (not shown) and a developing unit 7K. In the hopper 6K, an agitator 8K that is rotationally driven by a driving means (not shown), an agitation paddle 9K that is rotationally driven by a driving means (not shown) vertically below, and a rotational drive that is driven by a driving means (not shown) in the vertical direction thereof. A toner supply roller 10K to be used is disposed.

  The K toner in the hopper 6K moves toward the toner supply roller 10K by its own weight while being stirred by the rotational drive of the agitator 8K and the stirring paddle 9K. The toner supply roller 10K has a metal cored bar and a roller portion made of foamed resin or the like coated on the surface of the metal core roller 10K, while adhering K toner in the hopper portion 6K to the surface of the roller portion. Rotate. In the developing unit 7K of the developing device 5K, a developing roller 11K that rotates while contacting the photoreceptor 2K and the toner supply roller 10K, and a thinning blade 12K that contacts the tip of the developing roller 11K are disposed. Yes.

  The K toner adhered to the toner supply roller 10K in the hopper 6K is supplied to the surface of the development roller 11K at the contact portion between the development roller 11K and the toner supply roller 10K. When the supplied K toner passes through the contact position between the roller and the thinning blade 12K as the developing roller 11K rotates, the layer thickness on the roller surface is regulated.

  Then, the K toner after the layer thickness regulation adheres to the electrostatic latent image for K on the surface of the photosensitive member 2K in the developing region which is a contact portion between the developing roller 11K and the photosensitive member 2K. By this adhesion, the electrostatic latent image for K is developed into a K toner image. Although the process unit for K has been described with reference to FIG. 2, the process units 1Y, M, and C for Y, M, and C also perform Y, M, and C on the surfaces of the photoreceptors 2Y, M, and C by a similar process. A C toner image is formed.

  In FIG. 1 described above, an optical writing unit 70 is disposed above the process units 1Y, M, C, and K in the vertical direction. An optical writing unit 70 serving as an exposure apparatus optically scans the photoreceptors 2Y, M, C, and K in the process units 1Y, M, C, and K with a laser beam L emitted from a semiconductor laser based on image information. By this optical scanning, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 2Y, M, C, and K. The optical writing unit 70 irradiates the photosensitive member through a plurality of optical lenses and mirrors while polarizing the laser beam L emitted from the light source in the main scanning direction with a polygon mirror rotated by a polygon motor. It is.

  Below the process units 1Y, 1M, 1C, and 1K, there is disposed a transfer unit 15 that moves the endless intermediate transfer belt 16 endlessly in the counterclockwise direction while stretching. In addition to the intermediate transfer belt 16, the transfer unit 15 serving as transfer means includes a driving roller 17, a driven roller 18, four primary transfer rollers 19Y, 19M, 19C, 19K, a secondary transfer roller 20, a belt cleaning device 21, A cleaning backup roller 22 and the like are provided.

  The intermediate transfer belt 16 is stretched by a driving roller 17, a driven roller 18, a cleaning backup roller 22 and four primary transfer rollers 19Y, 19M, 19C, and 19K disposed inside the loop. Then, it is moved endlessly in the same direction by the rotational force of the driving roller 17 that is driven to rotate counterclockwise in the figure by a driving means (not shown).

  The four primary transfer rollers 19Y, 19M, 19C, and 19K sandwich the intermediate transfer belt 16 thus moved endlessly between the photoreceptors 2Y, 2M, 2C, and 2K. By this sandwiching, primary transfer nips for Y, M, C, and K where the front surface of the intermediate transfer belt 16 and the photoreceptors 2Y, M, C, and K abut are formed. A primary transfer bias is applied to each of the primary transfer rollers 19Y, 19M, 19C, and 19K by a transfer bias power source (not shown), whereby the electrostatic latent images on the photoreceptors 2Y, 2M, 2C, and 2K, A transfer electric field is formed between the primary transfer rollers 19Y, 19M, 19C, and 19K. Instead of the primary transfer rollers 19Y, 19M, 19C, and 19K, a transfer charger, a transfer brush, or the like may be employed.

  When Y toner formed on the surface of the photoreceptor 2Y of the Y process unit 1Y enters the above-described primary transfer nip for Y as the photoreceptor 2Y rotates, the photosensitive member 2Y is exposed to light by the action of the transfer electric field and nip pressure. Primary transfer is performed on the intermediate transfer belt 16 from the body 2Y. The intermediate transfer belt 16 on which the Y toner image is primarily transferred in this way passes through the primary transfer nips for M, C, and K along with the endless movement thereof, and the photoreceptors 2M, C, and K. The upper M, C, and K toner images are sequentially superimposed on the Y toner image and primarily transferred.

A four-color toner image is formed on the intermediate transfer belt 16 by the primary transfer of superposition. The secondary transfer roller 20 of the transfer unit 15 is disposed outside the loop of the intermediate transfer belt 16, and the intermediate transfer belt 16 is sandwiched between the driven roller 18 inside the loop.
By this sandwiching, a secondary transfer nip where the front surface of the intermediate transfer belt 16 and the secondary transfer roller 20 abut is formed.

  A secondary transfer bias is applied to the secondary transfer roller 20 by a transfer bias power source (not shown). By this application, a secondary transfer electric field is formed between the secondary transfer roller 20 and the driven roller connected to the ground. Below the transfer unit 15, a paper feed cassette 30 that stores a plurality of recording sheets P in a bundle of sheets is slidably attached to the printer housing.

  In the paper feed cassette 30, a paper feed roller 30a is brought into contact with the top recording paper P of the paper bundle, and the recording paper is rotated by rotating it in a counterclockwise direction in the drawing at a predetermined timing. P is sent out toward the paper feed path 31. A registration roller pair 32 is disposed near the end of the paper feed path 31. The registration roller pair 32 stops the rotation of both rollers as soon as the recording paper P delivered from the paper feed cassette 30 is sandwiched between the rollers. Then, rotation driving is resumed at a timing at which the sandwiched recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 16 in the above-described secondary transfer nip, and the recording paper P is directed to the secondary transfer nip. Send it out. The four-color toner image on the intermediate transfer belt 16 brought into close contact with the recording paper P at the secondary transfer nip is secondarily transferred onto the recording paper P under the influence of the secondary transfer electric field and the nip pressure. Combined with the white color of P, a full color toner image is obtained.

  The recording paper P having the full-color toner image formed on the surface in this manner is separated from the secondary transfer roller 20 and the intermediate transfer belt 16 by the curvature when passing through the secondary transfer nip. Then, the toner is fed into a fixing device 34 described later via a post-transfer conveyance path 33. The transfer residual toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 16 after passing through the secondary transfer nip. The residual toner is cleaned from the belt surface by a belt cleaning device 21 that is in contact with the front surface of the intermediate transfer belt 16.

  The cleaning backup roller 22 disposed inside the loop of the intermediate transfer belt 16 backs up the cleaning of the belt by the belt cleaning device 21 from the inside of the loop.

  The fixing device 34 forms a fixing nip by a fixing roller 34a containing a heat source such as a halogen lamp (not shown) and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure. The recording paper P fed into the fixing device 34 is sandwiched between the fixing nips such that the unfixed toner image carrying surface is brought into close contact with the fixing roller 34a. Then, the toner in the toner image is softened by the influence of heating and pressurization, and the full color image is fixed.

  The recording paper P discharged from the fixing device 34 passes through the post-fixing conveyance path 35 and then reaches the branch point between the paper discharge path 36 and the pre-reversal conveyance path 41. On the side of the post-fixing conveyance path 35, a switching claw 42 that is rotationally driven around a rotation shaft 42a is disposed. By the rotation, the vicinity of the end of the post-fixing conveyance path 35 is closed. Or open it. At the timing when the recording paper P is sent out from the fixing device 34, the switching claw 42 stops at the rotational position indicated by the solid line in the drawing, and the vicinity of the end of the post-fixing conveyance path 35 is opened. Therefore, the recording paper P enters the paper discharge path 36 from the conveyance path 35 after fixing, and is sandwiched between the rollers of the paper discharge roller pair 37.

  When the single-sided print mode is set by an input operation to an operation unit including a numeric keypad (not shown) or a control signal sent from a personal computer (not shown), the recording sandwiched between the paper discharge roller pair 37 is performed. The paper P is discharged out of the machine as it is.

  Then, it is stacked on the stack portion that is the upper surface of the upper cover 50 of the housing. On the other hand, when the duplex printing mode is set, the trailing edge of the recording paper P conveyed through the paper discharge path 36 while the front end is sandwiched between the paper discharge roller pair 37 passes through the post-fixing conveyance path 35. The switching claw 42 is rotated to the position of the one-dot chain line in the drawing, and the vicinity of the end of the post-fixing conveyance path 35 is closed. At substantially the same time, the paper discharge roller pair 37 starts to rotate in the reverse direction.

  Then, the recording paper P is conveyed while the rear end side is directed to the top, and enters the pre-reversal conveyance path 41. The front portion of the printer is a reversing unit 40 that can be opened and closed with respect to the housing body by rotating about a rotating shaft 40a. When the paper discharge roller pair 37 rotates in the reverse direction, the recording paper P enters the pre-reversal conveyance path 41 of the reversing unit 40 and is conveyed from the upper side to the lower side in the vertical direction.

  Then, after passing between the rollers of the pair of reverse conveying rollers 43, it enters the reverse conveying path 44 that is curved in a semicircular shape. In addition, the upper and lower surfaces are reversed as they are conveyed along the curved shape, and the traveling direction from the upper side in the vertical direction to the lower side is also reversed and conveyed from the lower side in the vertical direction toward the upper side. The

  Thereafter, the toner enters the secondary transfer nip again through the above-described paper feed path 31. Then, after the full color image is collectively transferred to the other surface, the post-transfer conveyance path 33, the fixing device 34, the post-fixation conveyance path 35, the paper discharge path 36, and the paper discharge roller pair 37 are sequentially passed. And discharged outside the machine.

Next, an exposure apparatus according to the embodiment will be described. FIG. 3 is a schematic configuration diagram of the optical writing unit according to the first embodiment of the present invention. Four laser beams L emitted from light sources such as four semiconductor lasers (not shown) are linearly formed on the reflection surface of the polygon mirror 71 by an incident optical system such as a collimator lens, an aperture stop, and a cylindrical lens (not shown). Image. The polygon mirror 71 is rotated by a polygon motor 72 at a constant angular velocity. The fθ lens 73 as an optical imaging means has an fθ characteristic, and forms a spot on the photosensitive member 2 as a scanned member that is imaged and scanned on the surface by a light beam reflected and deflected by the polygon mirror 71. In addition, the spot moving speed in the main scanning direction on the photosensitive member 2 is designed to be constant.
In this example, the fθ lens 73 has a first optical surface pair consisting of an optical surface A, which is an incident surface, and an optical surface B, which is an exit surface, with its optical axis in a substantially horizontal direction and an optical surface C that is an incident surface. A second optical surface pair consisting of the optical surface D which is the exit surface is provided with its optical axis in the vertical direction.

  In FIG. 3, the laser beam L is L1 for the laser beam L scanned on the photoconductor 2K, L2 for the laser beam L scanned on the photoconductor 2C, and the photoconductor 2M. The laser beam L scanned at L is L3, and the laser beam L scanned at the photoreceptor 2Y is L4.

  Since the laser beams L1 and L2 and the laser beams L3 and L4 are substantially symmetrical on both sides of the plane including the rotation axis of the polygon mirror 71, the laser beams L1 and L2 will be described. The laser beam L1 is reflected and deflected by the polygon mirror 71, passes through the optical surface A and the optical surface B, which are the first optical surface pair of the fθ lens 73, and is guided to the photoreceptor 2K by the folding mirror 74. . After the laser beam L2 is reflected and deflected by the polygon mirror 71, the laser beam L2 is once folded back in the direction away from the photosensitive member 2C by the folding mirror 75, and then folded again in the direction of the photosensitive member 2C by the folding mirror 76, and then the fθ lens. The light passes through the optical surface C and the optical surface D, which are the second optical surface projections 73, and is guided to the photoreceptor 2C.

  In this embodiment, the distance (optical path length) from the polygon mirror 71 to the photosensitive member 2 is different between the laser beam L1 and the laser beam L2, but the optical path lengths of the laser beam L1 and the laser beam L2 are different depending on the layout of the main body. Even in the case where they can be equalized, it is possible to cope with this by designing the optical surfaces A to D of the fθ lens 73 optimally. Further, although the polygon mirror is shown in a two-stage shape, two identical mirrors may be arranged on the same axis, or the two-stage mirror may be formed as a single component. Alternatively, the same effect can be obtained with a thick one-stage mirror shape.

  According to the present embodiment, it is possible to provide an optical writing unit that has a high degree of freedom in the arrangement of the fθ lens 73 and the folding mirror and can cope with downsizing.

  FIG. 4 is a schematic configuration diagram of an optical writing unit in the second embodiment of the present invention. As in the first embodiment, four laser beams L emitted from light sources such as four semiconductor lasers (not shown) are transmitted from the polygon mirror 71 by an incident optical system such as a collimator lens, an aperture stop, and a cylindrical lens (not shown). A linear image is formed on the reflecting surface. The relationship between the laser beams L1 to L4 and the photosensitive member is the same as in the first embodiment, and the laser beams L1 and L2 and the laser beams L3 and L4 are substantially symmetrical on both sides of the plane including the rotation axis of the polygon mirror 71. Therefore, the laser beams L1 and L2 will be described. The laser beams L1 and L2 incident on the polygon mirror 71 are so-called oblique incident optical systems that are incident at an oblique angle with respect to the normal line of the reflecting surface of the polygon mirror 71. The fθ lens 73 having fθ characteristics is composed of two lenses, a first lens 73a and a second lens 73b.

  In this example, the first lens 73a has an optical surface C, which is an incident surface surface, with a first optical surface pair consisting of an optical surface A, which is an incident surface, and an optical surface B, which is an exit surface, in the substantially horizontal direction. The second optical surface pair consisting of the optical surface D which is the exit surface is provided with its optical axis in the vertical direction.

  The laser beam L1 reflected and deflected by the polygon mirror 71 passes through the first optical surface pair of the first lens 73a, that is, the optical surface A and the optical surface B, is folded by the folding mirror 74, and passes through the second lens 73b. After passing, the light is guided to the photoreceptor 2K. The laser beam L2 is once folded back in the direction away from the photosensitive member 2C by the folding mirror 75, and is folded again in the direction of the photosensitive member 2C by the folding mirror 76, and then the second optical surface pair of the first lens 73a. The light passes through a certain optical surface C and optical surface D, and then passes through the second lens 73b and is guided to the photoreceptor 2C. In this embodiment, the distance (optical path length) from the polygon mirror 71 to the photosensitive member 2 is different between the laser beam L1 and the laser beam L2, but the optical path lengths of the laser beam L1 and the laser beam L2 are different depending on the layout of the main body. Even in the case where they can be equalized, it is possible to cope with this by designing the optical surfaces A to D of the fθ lens 73 optimally. The second lens 73b uses a lens having the same shape in each optical path, but different lenses may be used.

  In the present embodiment, it is possible to provide an optical writing unit that has a high degree of freedom in arrangement of the first lens 73a and the folding mirror even in the oblique incidence optical system and can cope with downsizing.

  FIG. 5 is a schematic block diagram of an optical writing unit in the third embodiment of the present invention. As in the first embodiment, four laser beams L emitted from light sources such as four semiconductor lasers (not shown) are transmitted from the polygon mirror 71 by an incident optical system such as a collimator lens, an aperture stop, and a cylindrical lens (not shown). A linear image is formed on the reflecting surface. The relationship between the laser beams L1 to L4 and the photosensitive member is the same as in the first embodiment, and the laser beams L1 and L2 and the laser beams L3 and L4 are substantially symmetrical on both sides of the plane including the rotation axis of the polygon mirror 71. Therefore, the laser beams L1 and L2 will be described. The laser beams L1 and L2 incident on the polygon mirror 71 are so-called oblique incident optical systems that are incident at an oblique angle with respect to the normal line of the reflecting surface of the polygon mirror 71.

  In this example, the fθ lens having the fθ characteristic includes a first lens 73a and a second lens 73b having two different configurations, and the laser beam L1 is a pair of lenses of the first lens 73a and the second lens 73b. And the laser beam L2 passes only through the first lens 73a.

  Here, as in the first embodiment, the first lens 73a has an optical surface A that is a first optical surface pair, an optical surface B, an optical surface C that is a second optical surface pair, and an optical surface D. I have. The second lens 73b has a characteristic of forming an image of the light beam that has passed through 73a on the photosensitive member 2.

  The laser beam L1 reflected and deflected by the polygon mirror 71 passes through the optical surface A and the optical surface B, which are the first optical surface pair of the first lens 73a, is folded by the folding mirror 74, and passes through the second lens 73b. After passing, the light is guided to the photoreceptor 2K. The laser beam L2 is reflected and deflected by the polygon mirror 71, then passes through the optical surface A and the optical surface B, which are the first optical surface pair of the first lens 73a, and is temporarily separated from the photoreceptor 2C by the folding mirror 75. After being folded back in the direction away from the photoconductor 2C by the folding mirror 76, it passes through the optical surface C and the optical surface D, which are the second optical surface pair of the first lens 73a, and passes through the photoconductor 2C. Is guided to.

  In this embodiment, the distance (optical path length) from the polygon mirror 71 to the photosensitive member 2 is different between the laser beam L1 and the laser beam L2, but the optical path lengths of the laser beam L1 and the laser beam L2 are different depending on the layout of the main body. Even in the case where they can be equalized, it is possible to cope with this by designing the optical surfaces A to D of the fθ lens 73 optimally.

  In the present embodiment, it is possible to provide an optical writing unit that has a high degree of freedom in arrangement of the first lens 73a and the folding mirror even in the oblique incidence optical system and can cope with downsizing. Further, by using the optical surfaces C and D of the first lens 73a for the laser beam L2, the same effect as that of the second lens 73b for the laser beam L1 can be obtained, and therefore on the optical path of the laser beam L2 (L3). In addition, the second lens 73b is unnecessary, and an optical writing unit that can reduce the number of lenses can be provided.

1Y, M, C, K: Process unit 2Y, M, C, K: Photoconductor (scanned member)
3K: drum cleaning device 4K: charging device 5K: developing device 6K: hopper unit 7K: developing unit 8K: agitator 9K: stirring paddle 10K: toner supply roller 11K: developing roller 12K: thinning blade 15: transfer unit 16: intermediate Transfer belt 17: Drive roller 18: Driven roller 19Y, M, C, K: Primary transfer roller 20: Secondary transfer roller 21: Belt cleaning device 22: Cleaning backup roller 30: Paper feed cassette 30a: Paper feed roller 31: Paper feed path 32: Registration roller pair 33: Post-transfer conveyance path 34: Fixing device 34a: Fixing roller 34b: Pressure roller 35: Post-fixation conveyance path 36: Paper discharge path 37: Paper discharge roller pair 40: Reversing unit 40a: Rotating shaft 41: Pre-reversing transport path 42: Switching claw 42a: Rotating shaft 43: Reverse transport roller pair 44: Reverse transport path 0: upper cover 70: writing unit (exposure device)
71: Polygon mirror 72: Polygon motor (deflection reflection surface)
73: fθ lens (optical imaging means)
73a: first lens (fθ lens: optical imaging means)
73b: second lens (fθ lens: optical imaging means)
74: Folding mirror (folding member)
75: Folding mirror (folding member)
76: Folding mirror (folding member)
A, B, C, D: Optical surface

JP 2007-316207 A JP 2007-010797 A Japanese Patent No. 4181765

Claims (11)

An optical deflector that deflects and scans a plurality of light beams emitted from a plurality of light sources in two directions facing a plane including a rotation axis;
At least one folding member that is provided between the optical deflector and each scanned surface and guides the light beam deflected by the optical deflector to the scanned member;
In an exposure apparatus comprising: at least one optical imaging unit that collects a light beam provided on each optical path and deflected by the optical deflector on a scanned member;
The optical imaging means includes at least two optical surface pairs each consisting of an entrance surface and an exit surface in a sub-scan section, and at least two of the plurality of light beams have different optical surfaces of the optical imaging means. An exposure apparatus characterized by passing through a pair.   2. The exposure apparatus according to claim 1, wherein at least one of the optical imaging means includes the two pairs of optical surfaces.   3. The exposure apparatus according to claim 1, wherein the optical image forming means is a lens having an f [theta] characteristic.   4. The exposure apparatus according to claim 1, wherein a light beam guided to a scanned member closer to a rotation axis of the optical deflector among the plurality of light beams deflected by the optical deflector is An exposure apparatus characterized in that the light is guided back to the scanned member after being folded back in a direction away from the scanned member by the folding member.   5. The exposure apparatus according to claim 1, wherein the optical deflector has a plurality of deflection reflection surfaces, and the plurality of light beams are in a normal line of the deflection reflection surface of the optical deflector in a sub-scanning section. An exposure apparatus characterized in that the light is incident in parallel.   6. The exposure apparatus according to claim 1, wherein the plurality of light beams are deflected by different deflection reflection surfaces of the optical deflector.   6. The exposure apparatus according to claim 1, wherein at least two of the plurality of light beams are deflected by the same deflection reflection surface of the optical deflector.   5. The exposure apparatus according to claim 1, wherein the plurality of light beams are incident at an angle with respect to the normal line of the deflecting reflection surface of the optical deflector in the sub-scan section.   9. The exposure apparatus according to claim 8, wherein the optical imaging means is composed of two lenses provided in respective optical paths.   9. The exposure apparatus according to claim 8, wherein the optical imaging means provided on the optical path to the scanned member on the side close to the rotation axis of the optical deflector among the plurality of light beams is constituted by one lens, An exposure apparatus characterized in that the optical imaging means provided on the optical path to the member to be scanned far from the rotation axis of the optical deflector is composed of two lenses.   In an image forming apparatus that forms an image on the image carrier by performing an electrophotographic process of charging, exposure, and development on the image carrier, as means for executing the exposure process of the electrophotographic process, An image forming apparatus comprising the exposure apparatus according to claim 1, wherein the image carrier that is a surface to be scanned is exposed.