JP2009205176A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate optical adjustment and achieve a low cost and miniaturization of an apparatus in a tandem type image forming apparatus having a plurality of latent image carriers. <P>SOLUTION: Two light beams are emitted from two light sources to be incident on a light scanning element 65. The light scanning element 65 includes a deflection mirror face 651 reflecting the two light beams by being swingably provided around a main scanning deflection axis and a switching axis, collectively scans the two light beams in a main scanning direction by swinging the deflection mirror face 651 in a resonant mode around the main scanning deflection axis, swings and positions the deflection face 651 in a non-resonant mode around the switching axis, and switches a photoreceptor irradiated with the scanning light beams in a plurality of the photoreceptors by guiding the two scanning light beams in a sub-scanning direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a so-called tandem image forming apparatus.

  As this type of image forming apparatus, there is conventionally known an apparatus in which a photoconductor, an exposure unit, and a development unit are provided for each of four different colors, for example, yellow, magenta, cyan, and black. (For example, refer to Patent Document 1). In this conventional apparatus, an image of each color component is formed on the photoreceptor as follows. That is, for each color component, the light source of the exposure unit is controlled based on the image data indicating the image of the color component, and the light beam from the light source is applied to the surface of the photosensitive member by the light scanning optical system of the exposure unit. To form a latent image corresponding to the image data of the color component on the photosensitive member.

  As another apparatus, there has been proposed an image forming apparatus in which four light sources are provided and a light beam emitted from each light source is deflected by a common polygon mirror and scanned in the main scanning direction (for example, a patent). Reference 2). In the image forming apparatus described in Patent Document 2, four scanning light beams from a polygon mirror are respectively guided to four photoconductors by a folding mirror group, thereby forming a latent image.

JP-A-8-62920 (page 3-4, FIG. 17) JP 2001-296492 A (page 3-4, FIG. 1 and FIG. 2)

  By the way, in the image forming apparatus described in Patent Document 1, it is necessary to provide an exposure unit for each color component, which causes an increase in apparatus cost and a major obstacle to downsizing the apparatus. On the other hand, in the apparatus described in Patent Document 2, since the polygon mirror is shared, the apparatus described in Patent Document 1 is advantageous in terms of apparatus cost and apparatus size. However, as with the apparatus described in Patent Document 1, it is necessary to provide the same number of light sources as the number of color components, and there is room for improvement in terms of downsizing the apparatus. In addition, in any of the conventional apparatuses, it is necessary to provide a dedicated light source corresponding to each photoconductor, which has been one of the causes of increasing the apparatus cost. Furthermore, there is a limitation on the number of light sources, which reduces the degree of design freedom.

  Further, in the image forming apparatus described in Patent Document 2, in order to make the monochrome printing speed higher than the color printing speed, the light beams emitted from the light sources are close to each other and in the sub-scanning direction (main scanning of the light beam). It is configured to be in a line in a direction substantially perpendicular to the direction. Further, an optical path switching unit is additionally provided between the light source and the polygon mirror, and the optical path of the light beam is switched between color printing and monochrome printing. That is, the optical path switching unit includes a first state in which each laser beam emitted from the light source unit provided with four light sources is separated into each of a plurality of spatial regions in a predetermined direction and guided, It is configured to be switchable to a second state in which light is concentrated in the space area and guided. When performing color printing, the laser beam emitted from the light source unit is scanned on the photoconductor corresponding to the laser beam by setting the first state. On the other hand, at the time of monochrome printing, the laser beam emitted from the light source unit in the second state is collected on a certain photoconductor to draw a plurality of lines simultaneously on the photoconductor. Therefore, in the apparatus of Patent Document 2, it is possible to change the printing speed between monochrome printing and color printing.

  However, providing the optical path switching unit increases the apparatus cost. Furthermore, since it is necessary to precisely adjust the four light sources, the optical path switching unit, and the polygon mirror, there is a serious problem in terms of adjustment workability.

  The present invention has been made in view of the above problems, and in a tandem image forming apparatus having a plurality of latent image carriers, optical adjustment can be easily performed, and the cost and size of the apparatus can be reduced. It aims to plan.

  According to a first aspect of the image forming apparatus of the present invention, in order to achieve the above object, a plurality of latent image carriers and a plurality of light beams on which a latent image is formed by a light beam scanned in the first direction. A light source means for emitting light, and an optical scanning means having a deflecting mirror surface that is provided so as to be swingable about a main scanning deflection axis and a switching axis and reflects a plurality of light beams emitted from the light source means, The optical scanning means swings the deflection mirror surface in the resonance mode around the main scanning deflection axis to scan a plurality of light beams in the first direction, and swings the deflection mirror surface in the non-resonance mode around the switching axis. The plurality of scanning light beams are positioned and guided in the second direction, and the latent image carrier irradiated with the plurality of scanning light beams is switched among the plurality of latent image carriers.

  In the invention configured as described above, a plurality of light beams are emitted from the light source means and enter the optical scanning means. The optical scanning unit deflects a plurality of light beams from the light source unit to form a plurality of scanning light beams that are scanned in the first direction, and the plurality of scanning light beams are formed on a plurality of latent image carriers. Guide it to one of them. Therefore, the surface of the one latent image carrier is irradiated with a plurality of scanning light beams, and a plurality of line latent images corresponding to the plurality of scanning light beams are collectively formed. Moreover, in the present invention, since the optical scanning unit selectively switches the latent image carrier to which the plurality of scanning light beams are irradiated, a plurality of line latent images are displayed on the latent image carrier according to the switching operation. It is formed in a lump. Thus, any of the plurality of light beams from the light source means becomes a scanning light beam for forming a line latent image on all the latent image carriers. Therefore, the apparatus can be reduced in size and cost as compared with the conventional apparatus in which a dedicated light source is arranged for each latent image carrier. In addition, since the optical adjustment is only the adjustment of the light source means and the optical scanning means, the adjustment workability can be simplified. Furthermore, the number of light beams can be set without being limited by the number of latent image carriers, and an excellent design freedom can be obtained.

  In addition, the deflection mirror surface is swung around the main scanning deflection axis and the switching axis. However, the deflection mirror surface is swung around the main scanning deflection axis, and the deflection mirror surface is swung around the switching axis. The action by is different from each other. Therefore, the optical scanning means swings the deflection mirror surface around the main scanning deflection axis and the switching axis in a mode corresponding to each action. In other words, since the deflection mirror surface is swung in the resonance mode around the main scanning deflection axis to scan the light beam in the first direction, the deflection mirror surface is swung around the main scanning deflection axis with a small amount of energy. Can do. In addition, by adopting the resonance mode, it is possible to stabilize the main scanning period of the scanning light beam between the plurality of latent image carriers. On the other hand, the deflecting mirror surface is oscillated and positioned around the switching axis in the non-resonant mode to switch the light guide destination of the scanning light beam. After switching, the swinging of the deflection mirror surface around the switching axis can be stopped with high accuracy, and the scanning light beam can be guided to a desired latent image carrier.

  According to a second aspect of the image forming apparatus of the present invention, in order to achieve the above object, a plurality of latent image carriers in which a latent image is formed by a light beam scanned in the first direction, and a plurality of latent image carriers. A light source unit that emits a light beam and a deflection mirror surface corresponding to each of the plurality of light beams emitted from the light source unit are provided, and the plurality of deflection mirror surfaces swing around the main scanning deflection axis and the switching axis. The optical scanning means is configured to oscillate a plurality of deflection mirror surfaces around the main scanning deflection axis in a resonance mode and reflect the plurality of light beams on the corresponding deflection mirror surfaces, respectively. And scanning the plurality of deflecting mirror surfaces in the non-resonant mode around the switching axis to guide the plurality of scanning light beams in the second direction to scan among the plurality of latent image carriers. Are irradiated with multiple scanning light beams. It is characterized by comprising a switch the image bearing member. Since there are a plurality of light beams to be deflected, the same number of deflecting mirror surfaces as the number of light beams are provided.

  In the invention configured as described above, as in the invention according to the first aspect, any of the plurality of light beams from the light source means forms line latent images on all the latent image carriers. Scanning light beam. Therefore, the apparatus can be reduced in size and cost as compared with the conventional apparatus in which a dedicated light source is arranged for each latent image carrier. In addition, since the optical adjustment is only the adjustment of the light source means and the optical scanning means, the adjustment workability can be simplified. Furthermore, the number of light beams can be set without being limited by the number of latent image carriers, and an excellent design freedom can be obtained.

  Further, the optical scanning means swings the plurality of deflection mirror surfaces around the main scanning deflection axis and the switching axis in a mode corresponding to each action. In other words, each deflecting mirror surface is swung in the resonance mode around the main scanning deflection axis to scan the light beam in the first direction, so that a plurality of deflecting mirror surfaces are swung around the main scanning deflection axis with less energy. Can be driven. In addition, by adopting the resonance mode, it is possible to stabilize the main scanning period of the scanning light beam between the plurality of latent image carriers. On the other hand, the plurality of deflecting mirror surfaces are oscillated and positioned around the switching axis in the non-resonant mode to switch the light guide destination of the scanning light beam. After switching the light destination, the swinging of each deflection mirror surface about the switching axis is stopped with high accuracy, and the scanning light beam can be guided to a desired latent image carrier.

  Here, the plurality of deflecting mirror surfaces are configured to be independently swingable about the switching axis, and the optical scanning means independently swings and positions the plurality of deflecting mirror surfaces about the switching axis. Thus, the image quality can be enhanced by adjusting the intervals of the plurality of scanning light beams.

  As a driving force for swinging the deflection mirror surface, an electrostatic attracting force, an electromagnetic force, or the like can be used. In particular, a static force is used to swing the deflection mirror surface around the main scanning deflection axis. It is desirable to use an electroadsorption force, and it is desirable to use an electromagnetic force to drive the deflection mirror surface to swing around the switching axis. The reason for the former is that it is not necessary to form a coil pattern, the optical scanning means can be miniaturized, and the deflection scanning can be further speeded up. On the other hand, the latter reason is that the deflection mirror surface can be oscillated and driven with a lower drive voltage than when electrostatic attraction force is generated, voltage control is facilitated, and the positional accuracy and switching accuracy of the scanning light beam are improved. This is because it can be increased.

1 is a diagram illustrating a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus in FIG. 1. FIG. 2 is a sub-scanning sectional view showing a configuration of an exposure unit equipped in the image forming apparatus of FIG. 1. FIG. 2 is a main scanning sectional view showing a configuration of an exposure unit equipped in the image forming apparatus of FIG. 1. FIG. 6 is a sub-scan sectional view in which the optical configuration of the exposure unit is developed. The perspective view which shows the optical scanning element which is one component of an exposure unit. Sectional drawing along the 1st axis | shaft of the optical scanning element of FIG. Sectional drawing along the 2nd axis | shaft of the optical scanning element of FIG. The block diagram which shows the structure of an exposure unit and an exposure control part. FIG. 2 is a diagram schematically illustrating image processing in the image forming apparatus in FIG. 1. FIG. 2 is a schematic diagram illustrating a color image forming operation of the image forming apparatus of FIG. 1. FIG. 2 is a schematic diagram illustrating an example of a monochrome image forming operation of the image forming apparatus in FIG. 1. FIG. 7 is a schematic diagram illustrating another example of a monochrome image forming operation of the image forming apparatus in FIG. 1. FIG. 6 is a schematic diagram illustrating another example of a monochrome image forming operation of the image forming apparatus in FIG. 1. FIG. 5 is a diagram illustrating a second embodiment of an image forming apparatus according to the present invention. FIG. 9 is a diagram illustrating a third embodiment of an image forming apparatus according to the invention. FIG. 10 is a diagram illustrating a fourth embodiment of an image forming apparatus according to the invention. The subscanning sectional view which developed the optical composition of the exposure unit in a 4th embodiment. FIG. 9 is a diagram illustrating an image forming apparatus according to a fifth embodiment of the invention. FIG. 10 is a diagram illustrating a sixth embodiment of an image forming apparatus according to the invention. FIG. 9 is a diagram illustrating an image forming apparatus according to a seventh embodiment of the invention. FIG. 10 is a diagram showing an eighth embodiment of an image forming apparatus according to the invention. FIG. 25 is a sub-scan sectional view of an exposure unit showing a ninth embodiment of the image forming apparatus according to the present invention. The block diagram which shows the electric constitution of 9th Embodiment of the image forming apparatus concerning this invention. FIG. 24 is a diagram schematically illustrating image processing in the image forming apparatus in FIG. 23. FIG. 24 is a diagram schematically illustrating image processing in the image forming apparatus in FIG. 23. FIG. 24 is a schematic diagram illustrating a color image forming operation of the image forming apparatus of FIG. FIG. 24 is a schematic diagram illustrating an example of a monochrome image forming operation of the image forming apparatus in FIG. 23. The perspective view which shows the optical scanning element of the exposure unit which shows 10th Embodiment of the image forming apparatus concerning this invention. FIG. 30 is a main scanning sectional view of the optical scanning element in FIG. 29. FIG. 30 is a sub-scan sectional view of the optical scanning element in FIG. 29. FIG. 20 is a block diagram showing an electrical configuration of a tenth embodiment of an image forming apparatus according to the present invention.

I. Single Beam Image Forming Apparatus <First Embodiment>
FIG. 1 is a diagram showing a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram showing an electrical configuration of the image forming apparatus of FIG. This image forming apparatus is a so-called tandem type color printer, and yellow (Y), magenta (M), cyan (C), and black (K) four-color photoconductors 2Y, 2M, and 2C as latent image carriers. 2K are arranged in the apparatus main body 5 side by side. The apparatus forms a full-color image by superimposing the toner images on the photoreceptors 2Y, 2M, 2C, and 2K, or forms a monochrome image using only the black (K) toner image. That is, in this image forming apparatus, when a print command is given to the main controller 11 from an external device such as a host computer in response to an image formation request from the user, an engine controller is responded to the print command from the CPU 111 of the main controller 11. 10 controls each part of the engine unit EG to form an image corresponding to a print command on a sheet S such as copy paper, transfer paper, paper, and an OHP transparent sheet.

  In the engine unit EG, a charging unit, a developing unit, and a cleaning unit are provided for each of the four photoconductors 2Y, 2M, 2C, and 2K. Since the structure of the charging unit, the developing unit, and the cleaning unit is the same for all color components, the structure related to yellow will be described here, and the other color components will be denoted by the same reference numerals and description thereof will be omitted. .

  The photoreceptor 2Y is rotatably provided in the direction of the arrow in FIG. A charging unit 3Y, a developing unit 4Y, and a cleaning unit (not shown) are arranged around the photoreceptor 2Y along the rotation direction. The charging unit 3Y is composed of, for example, a scorotron charger, and uniformly charges the outer peripheral surface of the photoreceptor 2Y to a predetermined surface potential by applying a charging bias from the charging control unit 103. Then, a scanning light beam Ly is emitted from the exposure unit 6 toward the outer peripheral surface of the photoreceptor 2Y charged by the charging unit 3Y. As a result, an electrostatic latent image corresponding to the yellow image data included in the print command is formed on the photoreceptor 2Y. The exposure unit 6 is not exclusively for yellow, but is provided in common for each color component, and operates in accordance with a control command from the exposure control unit 102. The configuration and operation of the exposure unit 6 will be described in detail later. Further, image processing for image data and latent image formation based on the image data will be described in detail later.

  The electrostatic latent image formed in this way is developed with toner by the developing unit 4Y. The developing unit 4Y contains yellow toner. When a developing bias is applied from the developing device controller 104 to the developing roller 41Y, the toner carried on the developing roller 41Y partially adheres to each surface portion of the photoreceptor 2Y according to the surface potential. As a result, the electrostatic latent image on the photoreceptor 2Y is visualized as a yellow toner image. As the developing bias applied to the developing roller 41Y, a DC voltage or a voltage obtained by superimposing an AC voltage on the DC voltage can be used. In particular, the photosensitive member 2Y and the developing roller 41Y are spaced apart from each other. In a non-contact development type image forming apparatus that develops toner by flying toner with a voltage waveform in which an alternating voltage such as a sine wave, a triangular wave, or a rectangular wave is superimposed on a direct current voltage in order to efficiently fly the toner It is preferable that

  The yellow toner image developed by the developing unit 4Y is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TRy1. The color components other than yellow are also configured in exactly the same way as yellow, and a magenta toner image, a cyan toner image, and a black toner image are formed on the photoreceptors 2M, 2C, and 2K, respectively, and a primary transfer region. Primary transfer is performed on the intermediate transfer belt 71 by TRm1, TRc1, and TRk1, respectively.

  The transfer unit 7 includes an intermediate transfer belt 71 stretched between two rollers 72 and 73, and a belt driving unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction R2 by driving the roller 72 to rotate. ). Further, a secondary transfer roller 74 is provided at a position facing the roller 73 with the intermediate transfer belt 71 interposed therebetween, and is configured to be able to contact and separate with respect to the surface of the belt 71 by an electromagnetic clutch (not shown). Yes. When transferring a color image to the sheet S, the primary transfer timing is controlled to superimpose the toner images to form a color image on the intermediate transfer belt 71, and the color image is taken out from the cassette 8 and transferred to the intermediate transfer belt 71. The color image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2 between the belt 71 and the secondary transfer roller 74. On the other hand, when a monochrome image is transferred to the sheet S, only the black toner image is formed on the photoreceptor 2K, and the monochrome image is secondarily transferred onto the sheet S conveyed to the secondary transfer region TR2. In addition, the sheet S that has received the secondary transfer of the image in this way is conveyed toward the discharge tray portion provided on the upper surface portion of the apparatus main body via the fixing unit 9.

  The surface potential of each of the photoreceptors 2Y, 2M, 2C, and 2K after the toner image is primarily transferred to the intermediate transfer belt 71 is reset by a neutralizing unit (not shown), and the toner remaining on the surface is cleaned. Then, the next charging is performed by the charging units 3Y, 3M, 3C, and 3K.

  In the vicinity of the roller 72, a transfer belt cleaner 75, a density sensor 76 (FIG. 2), and a vertical synchronization sensor 77 (FIG. 2) are arranged. Among these, the cleaner 75 can be moved toward and away from the roller 72 by an electromagnetic clutch (not shown). Then, the blade of the cleaner 75 abuts on the surface of the intermediate transfer belt 71 that is stretched over the roller 72 while moving to the roller 72 side, and the toner that remains on the outer peripheral surface of the intermediate transfer belt 71 after the secondary transfer. Remove. The density sensor 76 is provided to face the surface of the intermediate transfer belt 71 and measures the optical density of the patch image formed on the outer peripheral surface of the intermediate transfer belt 71. Further, the vertical synchronization sensor 77 is a sensor for detecting the reference position of the intermediate transfer belt 71, and is a synchronization signal output in association with the rotational drive of the intermediate transfer belt 71 in the sub-scanning direction, that is, a vertical synchronization signal. It functions as a vertical sync sensor for obtaining Vsync. In this apparatus, the operation of each part of the apparatus is controlled based on the vertical synchronization signal Vsync in order to align the operation timing of each part and to superimpose toner images of each color accurately.

  In FIG. 2, reference numeral 113 denotes an image memory provided in the main controller 11 for storing image data given from an external device such as a host computer via the interface 112, and reference numeral 106 is executed by the CPU 101. A ROM for storing calculation data, control data for controlling the engine unit EG, and the like, and a reference numeral 107 are RAMs for temporarily storing calculation results in the CPU 101 and other data.

  FIG. 3 is a sub-scan sectional view showing a configuration of an exposure unit provided in the image forming apparatus of FIG. FIG. 4 is a main scanning sectional view showing a configuration of an exposure unit provided in the image forming apparatus of FIG. FIG. 5 is a sub-scan sectional view in which the optical configuration of the exposure unit is developed. FIGS. 6 to 8 are views showing an optical scanning element as one component of the exposure unit. Further, FIG. 9 is a block diagram showing the configuration of the exposure unit and the exposure control unit. Hereinafter, the configuration and operation of the exposure unit will be described in detail with reference to these drawings.

  The exposure unit 6 has an exposure housing 61. A single laser light source 62 is fixed to the exposure housing 61, and a light beam can be emitted from the laser light source 62. As shown in FIG. 9, the laser light source 62 is electrically connected to the light source driving unit 102a of the exposure control unit 102. For this reason, the light source driving unit 102a controls the laser light source 62 on / off according to the image data, and the laser light source 62 emits a light beam modulated according to the image data. Thus, in this embodiment, the laser light source 62 corresponds to the “light source” of the present invention.

  In the exposure housing 61, a collimator lens 63, a cylindrical lens 64, and an optical scanning element 65 are used to scan and expose the light beam from the laser light source 62 onto the surfaces of the photoreceptors 2Y, 2M, 2C, and 2K. A first scanning lens 66, a folding mirror group 67, and a second scanning lens 68 (68Y, 68M, 68C, 68K) are provided. That is, the light beam from the laser light source 62 is shaped into collimated light of an appropriate size by the collimator lens 63 and then incident on the cylindrical lens 64 having power only in the sub-scanning direction as shown in FIG. . The collimated light is converged only in the sub-scanning direction and is linearly formed near the deflection mirror surface 651 of the optical scanning element 65. Thus, in this embodiment, the “first optical system” of the present invention is configured by the collimator lens 63 and the cylindrical lens 64.

  The optical scanning element 65 is formed by using a micromachining technique in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technique, and the light beams reflected by the deflecting mirror surface 651 are orthogonal to each other. The light beam can be deflected in the direction, that is, the main scanning direction and the sub-scanning direction. More specifically, the optical scanning element 65 is configured as follows.

  In this optical scanning element 65, as shown in FIG. 6, a silicon single crystal substrate (hereinafter referred to as “silicon substrate”) 652 functions as a “support member” of the present invention, and a part of the silicon substrate 652 is processed. Thus, the outer movable plate 653 is provided. The outer movable plate 653 is formed in a frame shape, is elastically supported on the silicon substrate 652 by a torsion spring 654, and can swing around a second axis AX2 extending substantially parallel to the main scanning direction X. Further, a planar coil 655 electrically connected to a pair of outer electrode terminals (not shown) formed on the upper surface of the silicon substrate 652 via a torsion spring 654 is provided on the upper surface of the outer movable plate 653 as a “second axis driving coil. "Is provided by being coated with an insulating layer.

  A flat inner movable plate 656 is pivotally supported inside the outer movable plate 653. That is, the inner movable plate 656 is elastically supported on the inner side of the outer movable plate 653 by a torsion spring 657 whose axial direction is orthogonal to the torsion spring 654, and swings about a first axis AX1 extending substantially parallel to the sub-scanning direction Y. It is free. An aluminum film or the like is formed as a deflection mirror surface 651 at the center of the inner movable plate 656.

  Further, as shown in FIGS. 7 and 8, the outer movable plate 653 and the inner movable plate 656 can swing around the second axis AX2 and the first axis AX1, respectively, in the substantially central portion of the silicon substrate 652. In addition, a recess 652a is provided. Electrodes 658a and 658b are fixed to positions on the inner bottom surface of the recess 652a that face both ends of the inner movable plate 656 (see FIG. 7). These two electrodes 658a and 658b function as “first axis electrodes” for swinging and driving the inner movable plate 656 around the first axis AX1. That is, these first-axis electrodes 658 a and 658 b are electrically connected to the first drive unit 102 b of the exposure control unit 102, and static electricity is applied between the electrodes and the deflection mirror surface 651 by applying a voltage to the electrodes. The electroadsorption force acts to pull one end of the deflecting mirror surface 651 toward the electrode. Therefore, when a predetermined voltage is alternately applied from the first drive unit 102b to the first axis electrodes 658a and 658b, the deflection mirror surface 651 can be reciprocally oscillated with the torsion spring 657 as the first axis AX1. When the driving frequency of this reciprocating vibration is set to the resonance frequency of the deflecting mirror surface 651, the deflection width of the deflecting mirror surface 651 increases, and the end of the deflecting mirror surface 651 is displaced to a position close to the electrodes 658a and 658b. be able to. Further, when the end portion of the deflecting mirror surface 651 reaches a position close to the electrodes 658a and 658b by resonance, the electrodes 658a and 658b also contribute to driving the deflecting mirror surface 651, and vibration is maintained by both the end portion and the planar portion electrodes. Can be made more stable.

  As shown in FIG. 8, permanent magnets 659a and 659b are fixed to both ends of the outer movable plate 653 at outer positions on the inner bottom surface of the recess 652a in different orientations. Further, the second axis driving coil 655 is electrically connected to the second driving unit 102c of the exposure control unit 102, and the direction of the current flowing through the second axis driving coil 655 by the energization of the coil 655 is permanent. Lorentz force acts depending on the direction of magnetic flux generated by the magnets 659a and 659b, and a moment for rotating the outer movable plate 653 is generated. At this time, the inner movable plate 656 (deflection mirror surface 651) also swings around the torsion spring 654 as the second axis AX2 integrally with the outer movable plate 653. Here, if the current flowing through the second axis driving coil 655 is an alternating current and is continuously repeated, the deflection mirror surface 651 can be reciprocally oscillated with the torsion spring 654 as the second axis AX2.

  Thus, in the optical scanning element 65, the deflection mirror surface 651 can be driven to swing around the first axis AX1 and the second axis AX2 orthogonal to each other. Therefore, in this embodiment, the light beam is generated by swinging the deflecting mirror surface 651 about the first axis AX1 by controlling the mirror driving unit including the first axis driving unit 102b and the second axis driving unit 102c. The beam is deflected and scanned in the main scanning direction X. On the other hand, by swinging the deflection mirror surface 651 about the second axis AX2, the light beam is guided to any one of the four photoconductors 2Y, 2M, 2C, and 2K to scan the light beam in the photoconductor. Are selectively switched. Thus, in the present embodiment, the first axis AX1 functions as the main scanning deflection axis, and the second axis AX2 functions as the switching axis. Of course, it is needless to say that the first axis AX1 may function as the main switching axis and the second axis AX2 may function as the main scanning deflection axis.

  Returning to FIGS. 3 and 4, the description of the exposure unit 6 will be continued. The scanning light beam scanned by the optical scanning element 65 as described above is emitted from the optical scanning element 65 toward the selected photoconductor, and the scanning light beam is emitted from the first scanning lens 66, the folding mirror group 67, and The selected photosensitive member is irradiated through a second optical system constituted by the second scanning lens 68. For example, when the optical scanning element 65 is switched to the yellow photoreceptor 2Y, the yellow scanning light beam Ly is photosensitized through the first scanning lens 66, the folding mirror group 67, and the second scanning lens 68Y. A line-shaped latent image is formed by irradiating the body 2Y. The other color components are exactly the same as yellow.

  In this embodiment, the start or end of the scanning light beam from the optical scanning element 65 is imaged on the synchronization sensor 60 by the horizontal synchronization imaging lens 69. That is, in this embodiment, the synchronization sensor 60 functions as a horizontal synchronization reading sensor for obtaining a synchronization signal in the main scanning direction X, that is, a horizontal synchronization signal HSYNC.

  FIG. 10 is a diagram schematically showing image processing in the image forming apparatus of FIG. FIG. 11 is a schematic diagram showing a color image forming operation of the image forming apparatus of FIG. Hereinafter, the color image forming operation of the image forming apparatus of FIG. 1 will be described with reference to these drawings. In this image forming apparatus, when a color print command is given from an external device such as a host computer, image data D included in the print command is stored in the image memory 113. The image data D includes a plurality of one-line color data DL as shown in FIG. Then, the main controller 11 performs color separation to obtain a one-line image data group for each color component. That is, a plurality of one-line image data DLy is obtained for yellow, a plurality of one-line image data DLm for magenta, a plurality of one-line image data DLc for cyan, and a plurality of one-line image data DLk for black. Stored in the image memory 113. Thus, in this embodiment, the image memory 113 functions as the “storage unit” of the present invention. In this specification, “one line image data” means line data corresponding to one scan of the scanning light beam of the color. Therefore, when the scanning light beam from the laser light source 62 is scanned on the photoconductor 2 corresponding to the color component of the one-line image data while the laser light source 62 is ON / OFF controlled based on the one-line image data, the color component is In addition, a line latent image indicated by one line image data is formed.

  When the main controller 11 completes the color separation for one page or a predetermined block of the image data D, the main controller 11 outputs one-line image data from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2. Read in order (see the dashed-dotted arrow in FIG. 10). In this embodiment, the photoconductors 2Y, 2M, 2C, and 2K are spaced apart from each other by a predetermined interval. Therefore, the order is Y → Y → Y → M → Y → M → Y → M → C →. It is read out serially. Then, laser modulation data (PWM data) for pulse width modulation of the laser light source 62 is created based on the serial data composed of the one-line image data DLy, DLm, DLc, and DLk read out in this way, and a video not shown in the figure. Output to the engine controller 10 via the IF. For example, when one line image data is read from the image memory 113 serially in the order of Y → M → C → K → Y..., PWM data corresponding to each one line image data is given to the engine controller 10.

  On the other hand, the engine controller 10 that has received the PWM data scans the scanning light beam only on the photoconductor corresponding to the PWM data at each timing while rotating the photoconductors 2Y, 2M, 2C, and 2K at a constant speed V. A line latent image is formed. That is, when the PWM data is given, first, at timing t1, a light beam is emitted from the laser light source 62 to the optical scanning element 65 while the laser light source 62 is ON / OFF controlled corresponding to the yellow one-line image data. The Further, at this timing t1, the deflection mirror surface 651 is rotated and positioned around the second axis AX2, which is the switching axis, by energizing the coil 655 from the second axis driving unit 102c, and the light beam is guided to the photoreceptor 2Y. Set to Then, after the oscillation around the second axis AX2 is stopped, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, thereby serving as the main scanning deflection axis. The deflecting mirror surface 651 is reciprocally oscillated around the first axis AX1 to deflect the light beam and scan it in the main scanning direction X. As a result, as shown in the column of “timing t1” in FIG. 11, the scanning light beam Ly is scanned only on the photoreceptor 2Y to form a line latent image Iy1 corresponding to the yellow one-line image data DLy. Note that a two-dot chain line in FIG. 11 (and FIGS. 12 to 14, 27, and 28 described later) indicates an exposure position on the surface of the photoreceptor.

  When the formation of the line latent image Iy1 is completed, a light beam is emitted from the laser light source 62 to the optical scanning element 65 while the laser light source 62 is ON / OFF controlled corresponding to the magenta one-line image data at the next timing t2. Is done. At this timing t2, the deflection mirror surface 651 is rotated and positioned around the second axis AX2 by energization of the coil 655 from the second axis driving unit 102c, and the light beam is set to be guided to the photosensitive member 2M. The Then, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, and the deflection mirror surface 651 is reciprocally oscillated around the first axis AX1, thereby deflecting the light beam. Thus, scanning is performed in the main scanning direction X. As a result, as shown in the column of “timing t2” in FIG. 11, the scanning light beam Lm is scanned only on the photosensitive member 2M to form a line latent image Im1 corresponding to the magenta one-line image data DLm.

  Further, in the same manner as described above, the cyan line latent image Ic1, the black line latent image Ik1, the yellow line latent image Iy2,... Are formed on the photoreceptor 2 having the corresponding color components at the respective timings t3, t4, t5,. It will be done. In this way, latent images corresponding to the image data D are formed on the respective photoreceptors 2Y, 2M, 2C, and 2K. These latent images are developed by the developing units 4Y, 4M, 4C, and 4K to form toner images of four colors. Also, by controlling the primary transfer timing, the toner images are superimposed on the intermediate transfer belt 71 to form a color image. Thereafter, the color image is secondarily transferred onto the sheet S and further fixed onto the sheet S.

  FIG. 12 is a schematic diagram showing an example of a monochrome image forming operation of the image forming apparatus of FIG. Hereinafter, a monochrome image forming operation of the image forming apparatus of FIG. 1 will be described with reference to this drawing. However, when a monochrome image is formed, it is basically the same as the case of forming a color image except that the color component to be handled is only black, and therefore the difference between the two will be mainly described.

  In this image forming apparatus, when a monochrome print command is given from an external device such as a host computer, the image data D included in the print command is stored in the image memory 113. The image data D includes a plurality of black one-line image data. When the main controller 11 stores one line image data for one page or a predetermined block of the image data D in the memory 113, each photoconductor 2. One line image data is sequentially read from the image memory 113 at a timing corresponding to the latent image writing timing. Then, laser modulation data (PWM data) for pulse width modulation of the laser light source 62 is created based on the one-line image data read out in this way, and is output to the engine controller 10 via a video IF (not shown).

  On the other hand, the engine controller 10 that has received the PWM data scans the black photoconductor 2K with the scanning light beam at each timing while rotating the photoconductors 2Y, 2M, 2C, and 2K at a constant speed V, thereby generating line latent lines. Form an image. That is, first, at timing t 1, a light beam is emitted from the laser light source 62 to the optical scanning element 65 while the laser light source 62 is ON / OFF controlled corresponding to black one-line image data. Further, at this timing t1, the deflection mirror surface 651 is rotated and positioned around the second axis AX2 which is the switching axis by energizing the coil 655 from the second axis driving unit 102c, and the light beam is guided to the photosensitive member 2K. Set to Then, after the oscillation around the second axis AX2 is stopped, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, thereby serving as the main scanning deflection axis. The deflecting mirror surface 651 is reciprocally oscillated around the first axis AX1 to deflect the light beam and scan it in the main scanning direction X. As a result, as shown in the column of “timing t1” in FIG. 12, the scanning light beam Lk is scanned only on the photosensitive member 2K, and a line latent image Ik1 corresponding to black one-line image data is formed.

  When the formation of the line latent image Ik1 is completed, a light beam is emitted from the laser light source 62 to the optical scanning element 65 while the laser light source 62 is ON / OFF controlled corresponding to the next one-line image data at the next timing t2. Is done. Also at this timing t2, the oscillation around the second axis AX2 is stopped, and the light beam is set to be guided to the photosensitive member 2K. Then, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, and the deflection mirror surface 651 is reciprocally oscillated around the first axis AX1, thereby deflecting the light beam. Thus, scanning is performed in the main scanning direction X. As a result, as shown in the column of “timing t2” in FIG. 12, the scanning light beam Lk is scanned onto the photosensitive member 2K to form a line latent image Ik2 corresponding to the next one-line image data.

  Further, in the same manner as described above, black line latent images Ik3, Ik4, Ik5,... Are formed on the photoreceptor 2K at the respective timings t3, t4, t5,. Thus, a latent image corresponding to the image data D is formed on the black photoconductor 2K. These latent images are developed by each developing unit 4K to form a black toner image. Further, the toner image is primarily transferred onto the intermediate transfer belt 71, then secondarily transferred onto the sheet S, and further fixed onto the sheet S.

  Here, when the color image formed as described above is compared with the monochrome image, the monochrome image has a larger number of line latent images per unit time and is a high-definition image. That is, in this embodiment, the resolution of an image can be changed between a color image and a monochrome image. Of course, when priority is given to the monochrome image printing speed, the rotational speed of the photosensitive member 2K may be increased. When performing monochrome printing, the yellow, cyan, and magenta photoreceptors 2Y, 2M, and 2C may be controlled to stop rotating.

  FIG. 13 is a schematic diagram showing another example of the monochrome image forming operation of the image forming apparatus of FIG. In this monochrome image forming operation, as shown in the figure, the rotational speed of the photoreceptor 2K is set to four times the normal speed. Therefore, the black line latent images Ik1, Ik2, Ik3, Ik4, Ik5,... At the respective timings t1, t2, t3, t4, t5,... While corresponding to the movement of the photosensitive member 2K at a constant speed (4 V). Are formed on the photoreceptor 2K.

FIG. 14 is a schematic diagram showing another example of the monochrome image forming operation of the image forming apparatus of FIG. In this monochrome image forming operation, as shown in the figure, the rotational speed of the photosensitive member 2K is set to double the normal speed, and the scanning interval of the scanning light beam Lk is set to double. Therefore, black line latent images Ik1, Ik2, Ik3,... Are formed on the photosensitive member 2K at the respective timings t1, t3, t5,... While the photosensitive member 2K moves at a constant speed (2 V). To go. Accordingly, the printing speed is twice that of high-definition printing (FIG. 11) and half that of high-speed monochrome printing (FIG. 13).
Here, the relationship between the rotational speed of the photosensitive member 2K and the scanning timing is not limited to the above-described high-speed monochrome printing (FIG. 13) and double-speed monochrome printing (FIG. 14), but is arbitrary. However, in high-speed monochrome printing (FIG. 13) and double-speed monochrome printing (FIG. 14), the printing speed can be increased while the deflection mirror surface 651 is driven to swing around the first axis AX1 in the resonance mode. Therefore, it is possible to switch between color printing and monochrome printing without changing the swinging motion of the deflection mirror surface 651, and stable image formation can be performed. Further, the printing speed can be accurately controlled while the deflection mirror surface 651 is swung in the resonance mode.

  As described above, according to this embodiment, the following operational effects can be obtained.

  (A) In the image forming apparatus configured as described above, one line image data is sequentially read from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2 to create PWM data. . The laser light source 62 is modulated in accordance with the PWM data, and the light beam from the laser light source 62 is deflected in the main scanning direction X to form a scanning light beam. Moreover, since the photosensitive member 2 irradiated with the scanning light beam from the deflection mirror surface 651 is selectively switched according to the reading order of the one-line image data, a line latent image is formed on the photosensitive member 2 according to the switching operation. It is formed. As described above, the scanning light beams Ly, Lm, Lc, and Lk are respectively scanned on the surfaces of the four photoconductors 2Y, 2M, 2C, and 2K in spite of having only one laser light source 62. Line latent images can be formed on the photoreceptors 2Y, 2M, 2C, and 2K. Therefore, the apparatus can be reduced in size and cost as compared with the conventional apparatus that requires four light sources. Moreover, optical adjustment workability can be simplified.

  (B) Since the optical scanning element 65 configured to swing the deflection mirror surface 651 about the two axes of the first axis AX1 and the second axis AX2, an optical scanning unit (polygon mirror + oscillation described later) is used. Compared to the case of using a mirror and two oscillating mirrors), the exposure unit 6 can be downsized, which is advantageous in terms of downsizing the apparatus.

  (C) Since the outer movable plate 653 and the inner movable plate 656 of the optical scanning element 65 are formed by applying the micromachining technique to the single crystal substrate 652 of silicon, the optical scanning element 65 It can be manufactured with high accuracy. Further, the inner movable plate 656 and the outer movable plate 653 can be swingably supported with the same spring characteristics as stainless steel, and the deflection mirror surface 651 can be swung stably and at high speed.

  (D) Further, when the deflection mirror surface 651 is driven to swing by the mirror drive unit including the drive units 102b and 102c, the deflection mirror surface 651 is swung around the first axis (main scanning deflection axis) AX1 in the resonance mode. Since it is configured to drive, the deflection mirror surface 651 can be driven to swing around the first axis AX1 with less energy. In addition, the main scanning period of the scanning light beam can be stabilized.

  (E) On the other hand, the deflection mirror surface 651 is oscillated and driven in the non-resonant mode in order to oscillate and position the deflection mirror surface 651 around the second axis (switching axis) AX2. There is. That is, the swing drive of the deflection mirror surface 651 about the second axis AX2 switches the light guide destination of the scanning light beam, and therefore the swing of the deflection mirror surface 651 about the second axis AX2 is performed after switching the light guide destination. Need to be stopped. Therefore, in order to perform the swing drive and swing stop with high accuracy, it is desirable to drive the swing in the non-resonant mode.

  (F) As a driving force for swinging and driving the deflection mirror surface 651, an electrostatic adsorption force, an electromagnetic force, or the like can be used. In particular, the deflection mirror surface 651 has a first axis (main scanning deflection axis). ) Since electrostatic attraction force is used to swing around AX1, there is no need to form a coil pattern on the inner movable plate 656, the optical scanning element 65 can be miniaturized, and deflection scanning can be performed at higher speed. Can be

  (G) Further, since electromagnetic force is used to drive the deflection mirror surface 651 to swing around the second axis (switching axis) AX2, deflection is performed with a lower driving voltage than when electrostatic attraction force is generated. The mirror surface 651 can be driven to swing, voltage control is facilitated, and the positional accuracy and switching accuracy of the scanning light beam can be increased.

Second Embodiment
FIG. 15 is a view showing a second embodiment of the image forming apparatus according to the present invention. The second embodiment is greatly different from the first embodiment in that an optical scanning system 600 in which a polygon mirror 601 and a switching oscillating mirror 602 are combined is used as the “optical scanning means” of the present invention. In other respects, the configuration is basically the same as that of the first embodiment. In the second embodiment, a polygon mirror 601 is fixed to the exposure casing 61, and the polygon mirror 601 is rotated around a rotation axis (main scanning deflection axis) AX3 orthogonal to the main scanning direction X, thereby deflecting the mirror surface. The light beam from the laser light source 62 is deflected by 601a and scanned in the main scanning direction X. Then, the scanning light beam from the deflecting mirror surface 601 a is incident on the switching reflecting surface 602 a of the oscillating mirror 602.

  The swing mirror 602 is swingable about a swing shaft (switching shaft) AX4 extending in parallel with the main scanning direction X, and is driven to swing by a swing positioning mechanism (not shown). For this reason, the scanning light beam is deflected by the oscillating mirror 602 and guided to one of the four photosensitive members 2Y, 2M, 2C, and 2K. That is, the photoconductor to be irradiated with the scanning light beam can be selectively switched among the photoconductors.

  As in the first embodiment, when a color print command is given from an external device such as a host computer, the image data D included in the print command is stored in the image memory 113. When the main controller 11 completes the color separation for one page or a predetermined block of the image data D, the main controller 11 outputs one-line image data from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2. The PWM data is created by reading sequentially. The laser light source 62 is modulated in accordance with the PWM data, and the light beam from the laser light source 62 is deflected in the main scanning direction X by the polygon mirror 601 to form a scanning light beam. In addition, since the light guide destination (photosensitive member 2) of the scanning light beam is selectively switched by the oscillating mirror 602 according to the reading order of the one-line image data, the line latent image is applied to the photosensitive member 2 corresponding to the switching operation. Is formed. Also, monochrome printing is performed in the same manner as in the first embodiment.

  As described above, the scanning light beams Ly, Lm, Lc, and Lk are respectively scanned on the surfaces of the four photoconductors 2Y, 2M, 2C, and 2K in spite of having only one laser light source 62. Line latent images can be formed on the photoreceptors 2Y, 2M, 2C, and 2K. Therefore, the apparatus can be reduced in size and cost as compared with the conventional apparatus that requires four light sources. Moreover, optical adjustment workability can be simplified.

  In the second embodiment, the former is arranged on the laser light source 62 side among the polygon mirror 601 and the oscillating mirror 602 constituting the optical scanning means, but the latter is arranged on the laser light source 62 side. Also good.

<Third Embodiment>
FIG. 16 is a diagram showing an image forming apparatus according to a third embodiment of the invention. The third embodiment differs greatly from the first embodiment in that an optical scanning system 600 in which two oscillating mirrors 603 and 602 are combined is used as the “optical scanning means” of the present invention. The configuration is basically the same as in the first embodiment. In the third embodiment, the oscillating mirror 603 functions as the “main scanning oscillating mirror” of the present invention. That is, the oscillating mirror 603 is provided so as to be oscillatable about an oscillating axis (main scanning deflection axis) AX5 orthogonal to the main scanning direction X, and the oscillating mirror 603 is reciprocated by an oscillating positioning mechanism (not shown). By oscillating, the light beam from the laser light source 62 is deflected by the deflecting mirror surface 603a and scanned in the main scanning direction X. Then, the scanning light beam from the deflecting mirror surface 603 a is incident on the switching reflecting surface 602 a of the oscillating mirror 602.

  This oscillating mirror 602 has exactly the same configuration as that of the second embodiment, and functions as the “switching oscillating mirror” of the present invention. That is, the scanning light beam is deflected by the oscillating mirror 602 and guided to one of the four photosensitive members 2Y, 2M, 2C, and 2K. That is, the photoconductor to be irradiated with the scanning light beam can be selectively switched among the photoconductors.

  As in the first embodiment, when a color print command is given from an external device such as a host computer, the image data D included in the print command is stored in the image memory 113. When the main controller 11 completes the color separation for one page or a predetermined block of the image data D, the main controller 11 outputs one-line image data from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2. The PWM data is created by reading sequentially. The laser light source 62 is modulated in accordance with the PWM data, and the light beam from the laser light source 62 is deflected in the main scanning direction X by the main scanning oscillating mirror 603 to form a scanning light beam. In addition, since the light guide destination (photosensitive member 2) of the scanning light beam is selectively switched by the switching oscillating mirror 602 in accordance with the reading order of the one-line image data, the line is applied to the photosensitive member 2 corresponding to the switching operation. A latent image is formed. Also, monochrome printing is performed in the same manner as in the first embodiment.

  As described above, the scanning light beams Ly, Lm, Lc, and Lk are respectively scanned on the surfaces of the four photoconductors 2Y, 2M, 2C, and 2K in spite of having only one laser light source 62. Line latent images can be formed on the photoreceptors 2Y, 2M, 2C, and 2K. Therefore, the apparatus can be reduced in size and cost as compared with the conventional apparatus that requires four light sources. Moreover, optical adjustment workability can be simplified.

  In the third embodiment, the former of the oscillating mirror 603 that deflects the light beam constituting the optical scanning means in the main scanning direction X and the oscillating mirror 602 that deflects the light beam in the sub-scanning direction Y is used as the laser light source. Although arranged on the 62 side, the latter may be arranged on the laser light source 62 side.

<Fourth embodiment>
FIG. 17 is a view showing a fourth embodiment of the image forming apparatus according to the present invention. FIG. 18 is a sub-scan sectional view in which the optical configuration of the exposure unit in the fourth embodiment is developed. The fourth embodiment is greatly different from the first embodiment in that the scanning light beam scanned in the main scanning direction X by the deflection mirror surface 651 is imaged on the photosensitive member 2. That is, in the first embodiment, the first scanning lens 66 and the second scanning lenses 68Y, 68M, 68C, and 68K constitute an imaging optical system (second optical system), and the scanning lenses 66 and 68Y scan light beam Ly. Is imaged on the photoconductor 2Y, the scanning light beam Lm is imaged on the photoconductor 2M by the scanning lenses 66 and 68M, and the scanning light beam Lc is imaged on the photoconductor 2C by the scanning lenses 66 and 68C. 68K, the scanning light beam Lk is imaged on the photosensitive member 2K. On the other hand, in the fourth embodiment, as shown in FIG. 17, the scanning light beams Ly, Lm, Lc, and Lk are focused on the photoreceptors 2Y, 2M, 2C, and 2K by the single aspherical lens 661, respectively.

  The single aspherical lens 661 has a distortion characteristic in which the scanning light beam deflected by the inherent oscillation characteristic of the deflecting mirror surface 651 moves at a constant speed on the surface of each photosensitive member 2, and each photosensitive element The shape of both surfaces in the meridian plane (main scanning plane) are different from each other so as to correct the field curvature aberration in the meridional direction (main scanning direction X) of the scanning light beam at an arbitrary position on the surface of the body 2. And a non-arc in the meridional plane of at least one of the two surfaces so as to correct the field curvature aberration in the sphere missing direction (corresponding to the rotation direction of the photoreceptor 2). The curvature in the sphere direction at a position along the curve is determined so as to change without correlation with the curvature in the meridian direction. Note that the configuration and operation of the single aspherical lens are described in detail in, for example, Japanese Patent Publication No. 7-60221, and the description thereof is omitted here.

  When an imaging optical system corresponding to the “third optical system” of the present invention is constituted by this single aspherical lens 661, even with a single lens, there is almost no aberration, and an extremely good imaging spot is obtained. A scanning lens having a wide optical deflection and a short optical axis length can be configured. Therefore, it is possible to effectively reduce the size and cost of the exposure unit 6, and thus to reduce the size and cost of the image forming apparatus.

  Also in the fourth embodiment, a so-called surface tilt correction optical system is configured. That is, as shown in FIG. 18, the light beam from the laser light source 62 is shaped into collimated light by the collimator lens 63 and then incident on the cylindrical lens 64 having power only in the sub-scanning direction. The collimated light is converged only in the sub-scanning direction and is linearly formed near the deflection mirror surface 651 of the optical scanning element 65. Further, the scanning light beam from the deflecting mirror surface 651 is imaged on the surface of each photoconductor 2 by the single aspherical lens 661. For this reason, the surface of each photoconductor 2 and the deflecting mirror surface 651 are optically conjugate, and even if there is some blurring on the first axis (main scanning deflection axis) AX1, it is optically corrected. Further, since the shape of the light beam on the deflection mirror surface 651 is linear, the deflection mirror surface 651 can be made small, which is advantageous in terms of high-speed scanning.

  In this way, in the image forming apparatus using the single aspherical lens 661 as described above, color printing and monochrome printing are performed in the same manner as in the above-described embodiment, so that the same effects as those in the first embodiment can be obtained. This is the same in the fifth to eighth embodiments described later.

<Fifth Embodiment>
FIG. 19 is a diagram showing an image forming apparatus according to a fifth embodiment of the invention. In the fourth embodiment, the surface of each photoconductor 2 and the deflection mirror surface 651 are configured to have an optically conjugate relationship, whereas in the fifth embodiment, the deflection mirror surface 651 is a photoconductor. It is deviated from the conjugate point CP on the surface, so that it becomes a so-called non-conjugated optical system. Therefore, in the fifth embodiment, there is a possibility that the surface tilt error Δy occurs.

  However, the deflecting mirror surface 651 can deflect the light beam not only in the main scanning direction X but also in the sub-scanning direction Y. Therefore, in the fifth embodiment, the deflection of the deflection mirror surface 651 is rotated around the second axis AX2 by energization of the coil 655 from the second axis driving unit 102c (FIG. 9) to correct the surface tilt. .

<Sixth Embodiment>
FIG. 20 is a view showing a sixth embodiment of the image forming apparatus according to the present invention. In the sixth embodiment, as shown in the figure, after the light beam from the laser light source 62 is shaped into collimated light by the collimator lens 63, the collimated light is directly applied to the deflecting mirror surface 651 of the optical scanning element 65. Incident. Then, the scanning light beam deflected by the deflecting mirror surface 651 is imaged on the surface of each photoconductor 2 by the single aspherical lens 661. As described above, the sixth embodiment is a non-conjugated optical system as in the fifth embodiment. Therefore, in the sixth embodiment, there is a possibility that the surface tilt error Δy occurs.

  However, the deflecting mirror surface 651 can deflect the light beam not only in the main scanning direction X but also in the sub-scanning direction Y. Therefore, also in the sixth embodiment, similarly to the fifth embodiment, the deflection mirror surface 651 is rotated around the second axis AX2 by energization of the coil 655 from the second axis drive unit 102c (FIG. 9). Positioning and surface tilt correction are performed.

<Seventh embodiment>
FIG. 21 is a diagram showing an image forming apparatus according to a seventh embodiment of the invention. In the seventh embodiment, an optical scanning system 600 in which a polygon mirror 601 and a swinging mirror 602 are combined is used as the “optical scanning means” of the present invention. In addition, the single light aspherical lens 661 focuses the scanning light beams Ly, Lm, Lc, and Lk on the photoreceptors 2Y, 2M, 2C, and 2K, respectively. Other configurations are basically the same as those in the first embodiment.

  In the seventh embodiment, a polygon mirror 601 is fixed to the exposure housing 61, and the polygon mirror 601 is rotated around a rotation axis (main scanning deflection axis) AX3 orthogonal to the main scanning direction X, thereby deflecting the mirror surface. The light beam from the laser light source 62 is deflected by 601a and scanned in the main scanning direction X. Then, the scanning light beam from the deflecting mirror surface 601a is incident on the switching reflecting surface 602a of the oscillating mirror 602 via the single aspherical lens 661 corresponding to the “third optical system” of the present invention.

  The swing mirror 602 is swingable about a swing shaft (switching shaft) AX4 extending in parallel with the main scanning direction X, and is driven to swing by a swing positioning mechanism (not shown). For this reason, the scanning light beam is deflected by the oscillating mirror 602 and guided to one of the four photoconductors 2Y, 2M, 2C, and 2K, and formed on the surface thereof. Then, color printing and monochrome printing are executed as in the first embodiment.

  In the seventh embodiment, the former is arranged on the laser light source 62 side among the polygon mirror 601 and the oscillating mirror 602 constituting the optical scanning means, but the latter is arranged on the laser light source 62 side. Also good. Further, the arrangement position of the single aspherical lens 661 is not limited to this embodiment, and may be arranged, for example, on the exit side of the oscillating mirror 602.

<Eighth Embodiment>
FIG. 22 is a view showing an eighth embodiment of the image forming apparatus according to the present invention. In the eighth embodiment, an optical scanning system 600 in which two oscillating mirrors 603 and 602 are combined is used as the “optical scanning means” of the present invention. In addition, the single light aspherical lens 661 focuses the scanning light beams Ly, Lm, Lc, and Lk on the photoreceptors 2Y, 2M, 2C, and 2K, respectively. Other configurations are basically the same as those in the first embodiment.

  In the eighth embodiment, the oscillating mirror 603 is provided so as to be oscillatable about an oscillating axis (main scanning deflection axis) AX5 orthogonal to the main scanning direction X, and the oscillating mirror 603 is not shown. The light beam from the laser light source 62 is deflected and scanned in the main scanning direction X by the deflection mirror surface 603a by reciprocatingly swinging by the dynamic positioning mechanism. Then, the scanning light beam from the deflecting mirror surface 603 a is incident on the switching reflecting surface 602 a of the switching oscillating mirror 602.

  Further, after the scanning light beam is deflected in the sub-scanning direction Y by the oscillating mirror 602, the four photoconductors 2Y and 2M are passed through the single aspherical lens 661 corresponding to the “third optical system” of the present invention. 2C, 2K, and imaged on the surface. Then, color printing and monochrome printing are executed as in the first embodiment.

  In the eighth embodiment, the main scanning oscillating mirror 603 that deflects the light beam constituting the optical scanning means in the main scanning direction X and the switching oscillating mirror 602 that deflects the light beam in the sub-scanning direction Y are provided. Of these, the former is arranged on the laser light source 62 side, but the latter may be arranged on the laser light source 62 side. Further, the arrangement position of the single aspherical lens 661 is not limited to this embodiment, and may be arranged, for example, between the oscillating mirrors 603 and 602.

II. By the way, in the above-described embodiment, there is one scanning light beam at each timing, but the number of light beams incident on the optical scanning means such as the optical scanning element 65 and the optical scanning system 600 is M. The number of lines is increased to the number of lines (where M ≧ 2 is a natural number), and M lines of latent images are simultaneously formed on the surface of each photoconductor 2 by scanning M light beams in the main scanning direction X. May be. Specifically, the M laser light sources 62 constitute a light source unit (corresponding to the “light source unit” of the present invention), and are emitted from the light source unit by an optical scanning unit such as the optical scanning element 65 or the optical scanning system 600. The M light beams are deflected and scanned in the main scanning direction X, and the M scanning light beams are guided in the sub-scanning direction Y different from the main scanning direction X, among the N latent image carriers. What is necessary is just to comprise so that the photoreceptor 2 to which M scanning light beams are irradiated may be selectively switched. The multi-beam image forming apparatus will be described in detail below with reference to the drawings.

<Ninth Embodiment>
FIG. 23 is a sub-scan sectional view of an exposure unit showing the ninth embodiment of the image forming apparatus according to the present invention. FIG. 24 is a block diagram showing an electrical configuration of the ninth embodiment of the image forming apparatus according to the present invention. The ninth embodiment is greatly different from the first embodiment (single-beam image forming apparatus) in that it has a light source unit composed of two laser light sources 621 and 622, and two light beams are emitted from this light source unit. This is a point emitted toward the deflection mirror surface 651 of the optical scanning element 65. That is, in this embodiment, as shown in FIG. 24, the exposure control unit 102 is provided with two light source driving units 102a1 and 102a2. Then, the light source driving unit 102a1 performs ON / OFF control of the laser light source 621 based on PWM data 1 to be described later, whereby a light beam modulated in accordance with the image data is emitted from the laser light source 621. Further, the light source driving unit 102a2 controls the laser light source 622 to be turned on / off based on PWM data 2 described later, whereby a light beam modulated in accordance with the image data is emitted from the laser light source 622. Thus, two light beams corresponding to the image data are emitted from the light source unit. In addition, since the other structure is the same as 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  25 and 26 are diagrams schematically showing image processing in the image forming apparatus of FIG. FIG. 27 is a schematic diagram showing a color image forming operation of the image forming apparatus of FIG. Hereinafter, the color image forming operation (color printing operation) of the image forming apparatus of FIG. 23 will be described with reference to these drawings. In this image forming apparatus, when a color print command is given from an external device such as a host computer, image data D included in the print command is stored in the image memory 113. The image data D includes a plurality of one-line color data DL as shown in FIG. Then, the main controller 11 performs color separation to obtain a one-line image data group for each color component. That is, a plurality of one-line image data DLy1, DLy2,... For yellow, a plurality of one-line image data DLm1, DLm2,... For magenta, a plurality of one-line image data DLc1, DLc2,. A plurality of one-line image data DLk1, DLk2,... Are obtained and stored in the image memory 113. Thus, in this embodiment, the image memory 113 functions as the “storage unit” of the present invention.

  In this specification, “one line image data” means line data corresponding to one scan of the scanning light beam of the color. Therefore, when the scanning light beam from the laser light source 62 is scanned on the photoconductor 2 corresponding to the color component of the one-line image data while controlling the laser light sources 621 and 622 based on the one-line image data, the color A component line latent image indicated by one-line image data is formed. Further, the “one-line image data group” means M pieces of one-line image data (M = 2 in this embodiment) that are sent simultaneously or in association with each other.

  When the main controller 11 completes the color separation for one page or a predetermined block of the image data D, the one-line image data group is read from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2. Are read in order (see the dashed line arrow in FIG. 26). In this embodiment, the photoconductors 2Y, 2M, 2C, and 2K are spaced apart from each other by a predetermined interval. Therefore, the order is Y → Y → Y → M → Y → M → Y → M → C →. M pieces are read serially. Then, the light source unit is controlled based on the serial data composed of the one-line image data group (data unit surrounded by a thick broken line in FIG. 26) read out in this way. More specifically, a video in which laser modulation data (PWM data 1) for pulse width modulation of the laser light source 621 is generated on the basis of serial data composed of one-line image data DLy1, DLm1, DLc1, and DLk1 is omitted. Output to the engine controller 10 via the IF. Similarly, PWM data 2 is created for the laser light source 622 side. That is, laser modulation data (PWM data 2) for pulse width modulation of the laser light source 622 is created based on serial data consisting of one-line image data DLy2, DLm2, DLc2, and DLk2, and the video IF is omitted from illustration. Output to the engine controller 10. For example, when a one-line image data group is read from the image memory 113 serially in the order of Y → M → C → K → Y..., PWM data 1 and 2 corresponding to each one-line image data group are simultaneously sent to the engine controller 10. Given.

  In this embodiment, PWM data 1 and 2 for driving and controlling the laser light sources 621 and 622 on the main controller 11 side based on the one-line image data group serially read from the image memory 113 in accordance with the latent image writing timing. However, the one line image data group may be serially applied to the engine controller 10 to generate the PWM data 1 and 2 on the engine controller 10 side.

  On the other hand, in the engine controller 10 that has received the PWM data 1 and 2, only the photoconductor corresponding to the PWM data 1 and 2 at each timing while rotating the photoconductors 2Y, 2M, 2C, and 2K at a constant speed V. A line latent image is formed by scanning a scanning light beam. That is, when the PWM data 1 and 2 are given, first, at timing t1, two light beams from the light source unit are controlled while the laser light sources 621 and 622 are respectively controlled to be ON / OFF corresponding to the yellow one-line image data group. The beam is emitted to the optical scanning element 65. Further, at this timing t1, the deflection mirror surface 651 is rotated and positioned around the second axis AX2 which is the switching axis by energizing the coil 655 from the second axis driving unit 102c, and the two light beams are guided to the photoreceptor 2Y. Set to shine. Then, after the oscillation around the second axis AX2 is stopped, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, thereby serving as the main scanning deflection axis. The deflecting mirror surface 651 is reciprocally oscillated around the first axis AX1 to deflect the light beam and scan it in the main scanning direction X. As a result, as shown in the column of “timing t1” in FIG. 27, the scanning light beams Ly1 and Ly2 are scanned only on the photosensitive member 2Y, and two lines corresponding to the yellow one-line image data group (DLy1 and DLy2). Line latent images Iy1 and Iy2 are formed simultaneously.

  When the formation of the line latent images Iy1 and Iy2 is completed, the laser light sources 621 and 622 are controlled ON / OFF corresponding to the magenta one-line image data group (DLm1, DLm2) at the next timing t2. Light beams are emitted from the optical scanning elements 65 through 621 and 622. Further, at this timing t2, the deflection mirror surface 651 is rotated and positioned around the second axis AX2 by energization of the coil 655 from the second axis driving unit 102c, and the two light beams are guided to the photosensitive member 2M. Set to Then, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, and the deflection mirror surface 651 is reciprocally oscillated around the first axis AX1, thereby deflecting the light beam. Thus, scanning is performed in the main scanning direction X. Accordingly, as shown in the column of “timing t2” in FIG. 27, the scanning light beams Lm1 and Lm2 are scanned only on the photosensitive member 2M, and two lines corresponding to the magenta one-line image data group (DLm1, DLm2). Line latent images Im1 and Im2 are formed simultaneously.

  Further, in the same manner as described above, the color components corresponding to the cyan line latent images Ic1, Ic2, the black line latent images Ik1, Ik2, the yellow line latent images Iy3, Iy4,... At the respective timings t3, t4, t5,. Are formed on the photosensitive member 2. In this way, latent images corresponding to the image data D are formed on the respective photoreceptors 2Y, 2M, 2C, and 2K. These latent images are developed by the developing units 4Y, 4M, 4C, and 4K to form toner images of four colors. Also, by controlling the primary transfer timing, the toner images are superimposed on the intermediate transfer belt 71 to form a color image. Thereafter, the color image is secondarily transferred onto the sheet S and further fixed onto the sheet S.

  FIG. 28 is a schematic diagram showing an example of a monochrome image forming operation of the image forming apparatus of FIG. Hereinafter, the monochrome image forming operation (monochrome printing operation) of the image forming apparatus of FIG. 23 will be described with reference to this drawing. However, when a monochrome image is formed, it is basically the same as the case of forming a color image except that the color component to be handled is only black, and therefore the difference between the two will be mainly described.

  In this image forming apparatus, when a monochrome print command is given from an external device such as a host computer, the image data D included in the print command is stored in the image memory 113. The image data D includes a plurality of black one-line image data. When the main controller 11 stores one line image data for one page or a predetermined block of the image data D in the memory 113, each photoconductor 2. A one-line image data group is sequentially read from the image memory 113 at a timing corresponding to the latent image writing timing. Based on the one-line image data group read out in this way, laser modulation data (PWM data 1 and 2) for pulse width modulation of the laser light sources 621 and 622 is created, and the engine is transmitted via a video IF (not shown). Output to the controller 10.

  On the other hand, the engine controller 10 that has received the PWM data scans the black photoconductor 2K with two scanning light beams at each timing while rotating the photoconductors 2Y, 2M, 2C, and 2K at a constant speed of 4V. Two line latent images are formed simultaneously. That is, first, at timing t 1, light beams are emitted from the laser light sources 621 and 622 to the optical scanning element 65 while ON / OFF control of the laser light sources 621 and 622 is performed corresponding to the black one-line image data group. Further, at this timing t1, the deflection mirror surface 651 is rotated and positioned around the second axis AX2 which is the switching axis by energizing the coil 655 from the second axis driving unit 102c, and the light beam is guided to the photosensitive member 2K. Set to Then, after the oscillation around the second axis AX2 is stopped, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, thereby serving as the main scanning deflection axis. The deflection mirror surface 651 is reciprocally oscillated around the first axis AX1 to deflect the two light beams and scan in the main scanning direction X. Accordingly, as shown in the column of “timing t1” in FIG. 28, the scanning light beams Lk1 and Lk2 are scanned only on the photosensitive member 2K, and two line latent images Ik1 corresponding to the black one-line image data group, Ik2 is formed simultaneously.

  When the formation of the line latent images Ik1 and Ik2 is completed, the light from the laser light sources 621 and 622 is controlled while the laser light sources 621 and 622 are ON / OFF controlled corresponding to the next one line image data group at the next timing t2. The beam is emitted to the optical scanning element 65. Also at this timing t2, the oscillation around the second axis AX2 is stopped, and the light beam is set to be guided to the photosensitive member 2K. Then, a predetermined voltage is alternately applied to the first axis electrodes 658a and 658b from the first driving unit 102b in the set state, and the deflection mirror surface 651 is reciprocally oscillated around the first axis AX1, thereby two lights. The beam is deflected and scanned in the main scanning direction X. As a result, as shown in the column of “timing t2” in FIG. 28, the scanning light beams Lk1 and Lk2 are scanned on the photosensitive member 2K to simultaneously form line latent images Ik3 and Ik4 corresponding to the next one-line image data group. Is done.

  Further, in the same manner as described above, black line latent images (Ik5, Ik6), (Ik7, Ik8), (Ik9, Ik10),... Are formed on the photoreceptor 2K at the respective timings t3, t4, t5,. Go. Thus, a latent image corresponding to the image data D is formed on the black photoconductor 2K. These latent images are developed by each developing unit 4K to form a black toner image. Further, the toner image is primarily transferred onto the intermediate transfer belt 71, then secondarily transferred onto the sheet S, and further fixed onto the sheet S.

  Here, when the color printing time formed as described above is compared with the monochrome printing time, the rotational speed of the photosensitive member in monochrome printing is four times that in color printing. Even though the resolution is high, a printing speed of 4 times can be obtained (high-speed monochrome printing). In addition, the rotational speed of the photosensitive member 2K may be set to double that of color printing, and the scanning interval of the scanning light beams Lk1 and Lk2 may be set to double (double speed monochrome printing). Furthermore, the relationship between the rotational speed of the photosensitive member 2K and the scanning timing is not limited to the above-described high-speed monochrome printing (FIG. 28) and double-speed monochrome printing, but is arbitrary. However, in high-speed monochrome printing (FIG. 28) and double-speed monochrome printing, the printing speed can be increased while the deflection mirror surface 651 is driven to swing around the first axis AX1 in the resonance mode. Therefore, it is possible to switch between color printing and monochrome printing without changing the swinging motion of the deflection mirror surface 651, and stable image formation can be performed. Further, the printing speed can be accurately controlled while the deflection mirror surface 651 is swung in the resonance mode.

  Further, in order to increase the resolution in monochrome printing, a black line latent image is formed on the photosensitive member 2K at the respective timings t1 to t5, as described above, while the rotational speed of the photosensitive member 2 is matched with that at the time of color printing. As a result, the number of line latent images per unit time of a monochrome image is larger than that of a color image, and a high-definition image can be obtained. That is, in this embodiment, the resolution of an image can be changed between a color image and a monochrome image.

  As described above, according to this embodiment, two scanning light beams are applied to one of the four photosensitive members 2 to form two line latent images at one time. Image forming apparatus (first to eighth embodiments), that is, a printing speed twice as high as that of the apparatus that forms a line latent image one by one by irradiating the surface of the photoreceptor 2 with a single scanning light beam. . If the printing speed is set to be the same as that of a single beam image forming apparatus, the main scanning frequency of the scanning light beam can be reduced and the modulation frequency of each laser light source can be lowered.

  In this embodiment, since the light scanning destinations of the two scanning light beams are switched by the optical scanning element 65, both of the two light beams from the light source unit are lined on all the photoconductors 2. It functions as a scanning light beam for forming a latent image. Therefore, the apparatus can be reduced in size and cost compared with the conventional apparatus in which a dedicated light source is arranged for each photoconductor. Moreover, optical adjustment workability can be simplified. Further, the number M of light beams from the light source unit can be arbitrarily set without being limited to the number N of the photosensitive members 2, and an excellent design freedom can be obtained.

  Furthermore, in this embodiment, the same effects (B) to (G) as obtained in the first embodiment are obtained.

<Tenth Embodiment>
FIG. 29 is a perspective view showing an optical scanning element of an exposure unit showing the tenth embodiment of the image forming apparatus according to the present invention. 30 and 31 are a main scanning sectional view and a sub-scanning sectional view of the optical scanning element of FIG. 29, respectively. FIG. 32 is a block diagram showing an electrical configuration of the tenth embodiment of the image forming apparatus according to the present invention. Here, the tenth embodiment is greatly different from the first embodiment in that it has a light source section composed of two laser light sources 621 and 622, and two light beams L1 and L2 are emitted from the light source section. And the points where the light beams L1 and L2 are deflected by the deflecting mirror surfaces 651a and 651b, respectively. In addition, since the other structure is the same as 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  In the tenth embodiment, an optical scanning element 650 having two deflection mirror surfaces 651a and 651b is provided as the “optical scanning means” of the present invention. These deflection mirror surfaces 651a and 651b are swingable integrally around the first axis AX1 which is the main scanning deflection axis, and are independently independent around the second axis AX2 and the third axis AX3 which are the switching axes. And can be swung freely.

  Similarly to the optical scanning element 65 of the first embodiment, the optical scanning element 650 is also formed by using a micromachining technique in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technique. In this optical scanning element 650, as shown in FIG. 29, the silicon substrate 652 functions as a “support member” of the present invention, and an outer movable plate 653 is provided by processing a part of the silicon substrate 652. Yes. The outer movable plate 653 is formed in a frame shape, is elastically supported on the silicon substrate 652 by a torsion spring 654, and can swing around a first axis AX1 extending substantially parallel to the sub-scanning direction Y.

  Inside the outer movable plate 653, two inner movable plates 656a and 656b are independently pivotally supported. That is, the inner movable plate 656a is elastically supported on the inner side of the outer movable plate 653 by a torsion spring 657a whose axial direction is orthogonal to the torsion spring 654, and swings about the second axis AX2 extending substantially parallel to the main scanning direction X. It is free. A planar coil 655a is provided as a “second axis driving coil” coated with an insulating layer on the peripheral edge of the upper surface of the inner movable plate 656a. In addition, an aluminum film or the like is formed as a deflection mirror surface 651a at the center of the upper surface of the inner movable plate 656a.

  One inner movable plate 656b is configured similarly to the inner movable plate 656a. That is, the inner movable plate 656b is elastically supported on the inner side of the outer movable plate 653 by the torsion spring 657b, and can swing around the third axis AX3 extending substantially parallel to the main scanning direction X. Further, on the upper surface of the inner movable plate 656b, a planar coil 655b as a “third axis driving coil” and a deflection mirror surface 651b are provided.

  Further, as shown in FIGS. 30 and 31, an outer movable plate 653 and inner movable plates 656a, 656b are respectively arranged around the first axis AX1, the second axis AX2, and the third axis AX3 at the substantially central portion of the silicon substrate 652. A recess 652a is provided so as to be swingable. Electrodes 658a and 658b are fixed to the inner bottom surface of the recess 652a at positions facing both ends of the outer movable plate 653 (see FIG. 30). These two electrodes 658a and 658b function as “first axis electrodes” for swinging and driving the outer movable plate 653 around the first axis AX1. That is, these first axis electrodes 658 a and 658 b are electrically connected to the first drive unit 102 b of the exposure control unit 102. The outer movable plate 653 vibrates around the first axis AX1 by alternately applying a predetermined voltage from the first driving unit 102b to the first axis electrodes 658a and 658b, thereby both the deflecting mirror surfaces 651a and 651b. Can be reciprocated. When the driving frequency of this reciprocating vibration is set to the resonance frequency of the outer movable plate, the swing width of the outer movable plate 653 increases, and the end of the outer movable plate 653 is displaced to a position close to the electrodes 658a and 658b. Can do.

  As shown in FIG. 31, permanent magnets 659a to 659c are fixed to the end portions of the inner movable plates 656a and 656b on the inner bottom surface of the concave portion 652a in different orientations. The second axis driving coils 655a and 655b are electrically connected to the second driving unit 102c and the third driving unit 102d of the exposure control unit 102, respectively. For this reason, when the coil 655a is energized, the inner movable plate 656a (deflection mirror surface 651a) swings with the torsion spring 657a serving as the second axis AX2. Further, when the coil 655b is energized, the inner movable plate 656b (deflection mirror surface 651b) swings about the torsion spring 657b as the third axis AX3. Here, if the current flowing through the second axis driving coil 655a and the third axis driving coil 655b is continuously changed to an alternating current, the torsion spring 657a is used as the second axis AX2, and the deflection mirror surface 651a is reciprocally oscillated. Further, the deflection mirror surface 651b can be reciprocally oscillated using the torsion spring 657b as the third axis AX3. Thus, in this embodiment, both the deflection mirror surfaces 651a and 651b can be controlled independently.

  As described above, in the optical scanning element 650, the deflection mirror surface 651a is rotated around the first axis AX1 and the second axis AX2 orthogonal to each other, and the deflection mirror surface 651b is rotated around the first axis AX1 and the third axis AX3 orthogonal to each other. In addition, they can be driven to swing independently. Therefore, in this embodiment, the deflection mirror surfaces 651a and 651b are swung around the first axis AX1 by controlling the mirror drive unit including the first axis drive unit 102b, the second axis drive unit 102c, and the third axis drive unit. By moving, the two light beams L1 and L2 are deflected and scanned in the main scanning direction X. On the other hand, the light beam L1 is swung by swinging the deflection mirror surface 651a about the second axis AX2, and the light beam L2 is swung by swinging the deflection mirror surface 651b about the third axis AX3. The photosensitive member to which the scanning light beam is irradiated is selectively switched among the photosensitive members by being guided to any one of 2M, 2C, and 2K. Thus, in the present embodiment, the first axis AX1 functions as the main scanning deflection axis, and the second axis AX2 and the third axis AX3 function as the switching axes. Moreover, in this embodiment, the distance between the two scanning light beams (beam pitch P) can be controlled by independently driving the inner movable members 656a and 656b to swing around the switching axes AX2 and AX3. Yes.

  As in the ninth embodiment, when a color print command is given from an external device such as a host computer, the image data D included in the print command is stored in the image memory 113. When the main controller 11 completes the color separation for one page or a predetermined block of the image data D, the one-line image data group is read from the image memory 113 at a timing corresponding to the latent image writing timing to each photoconductor 2. Are sequentially read out to create PWM data 1 and 2. Then, the laser light sources 621 and 621 are modulated according to the PWM data 1 and 2, respectively. Further, the light beams L1 and L2 from the laser light sources 621 and 622 are deflected in the main scanning direction X by the deflecting mirror surfaces 651a and 651b, respectively, to form two scanning light beams and to read out one line image data group. In order to selectively switch the light guide destination (photosensitive member 2) of the two scanning light beams according to the order, two line latent images are simultaneously formed on the photosensitive member 2 corresponding to the switching operation. Further, when performing monochrome printing, it is performed in the same manner as in the ninth embodiment.

  As described above, also in the tenth embodiment, the same effects as those in the ninth embodiment can be obtained. In addition, since the interval between the two scanning light beams can be controlled as described above, the image quality can be improved by adjusting the interval between the scanning light beams as necessary.

  In the tenth embodiment, the two deflecting mirror surfaces 651a and 651b are independently driven to swing around the switching axes AX2 and AX3. However, they are driven in cooperation with each other. It may be.

  In the ninth and tenth embodiments, the optical scanning elements 65 and 650 are used as the “optical scanning means” of the present invention, but other than this, the polygon mirror 601 is similar to the second and third embodiments. And an optical scanning system 600 combining the two oscillating mirrors 603 and 602 can be used.

  In the ninth and tenth embodiments, the first scanning lens 66 and the second scanning lenses 68Y, 68M, 68C, and 68K constitute an imaging optical system (second optical system). That is, the scanning light beams Ly1 and Ly2 are imaged on the photosensitive member 2Y by the scanning lenses 66 and 68Y, the scanning light beams Lm1 and Lm2 are imaged on the photosensitive member 2M by the scanning lenses 66 and 68M, and the scanning lenses 66 and 68C are used. The scanning light beams Lc1 and Lc2 are imaged on the photoreceptor 2C, and the scanning light beams Lk1 and Lk2 are imaged on the photoreceptor 2K by the scanning lenses 66 and 68K. However, this imaging optical system may be configured by only the single aspherical lens 661 as in the fourth to eighth embodiments, and this imaging optical system is the “third optical system” of the present invention. Function as. By using the single aspherical lens 661, the same effects as those of the fourth to eighth embodiments can be obtained.

  In the ninth and tenth embodiments, two light beams are emitted from the light source unit, and the two scanning light beams are switched and set by the optical scanning means (optical scanning elements 65, 600, and 650). The number M of light beams emitted from the light source unit (light source means) is not limited to “2”, but may be three or more. Further, when the photoconductor is switched by the optical scanning element 650, it is desirable to provide the same number of deflection mirror surfaces as the number M of light beams.

III. Others The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the gist thereof. For example, in the above embodiment, the present invention is applied to an image forming apparatus that forms toner images of four colors on the photoreceptors 2Y, 2M, 2C, and 2K, respectively. However, the present invention is applicable to all so-called tandem image forming apparatuses. can do. That is, an image forming apparatus in general having N (where N ≧ 2 is a natural number) latent image carriers on which the surface of a line-like latent image is formed by scanning a single light beam in the main scanning direction. The present invention can be applied to and the same effects as the above-described embodiment can be achieved.

  In the above embodiment, the description is given using a printer that prints an image included in the print command on a sheet S such as transfer paper or copy paper based on a print command given from an external device such as a host computer. The present invention is not limited to this, and can be applied to all tandem image forming apparatuses including a copying machine and a facsimile apparatus.

  2Y, 2M, 2C, 2K ... photosensitive body, 6 ... exposure unit, 10 ... engine controller (control means), 11 ... main controller (control means), 62 ... laser light source, 63 ... collimator lens (first optical system), 64: Cylindrical lens (first optical system), 65, 650: Optical scanning element (optical scanning means), 66, 68Y, 68M, 68C, 68K ... Scanning lens (second optical system), 102b: First axis drive unit (Mirror drive unit), 102c ... second axis drive unit (mirror drive unit), 102d ... third axis drive unit (mirror drive unit), 113 ... image memory (storage unit), 600 ... optical scanning system (optical scanning unit) , 601 ... Polygon mirror, 601a, 603a, 651, 651a, 651b ... Deflection mirror surface, 602 ... Swing mirror for switching, 602a ... For switching Reflecting surface, 603 ... swing mirror for main scanning, 652 ... silicon substrate, 653 ... outer movable plate, 656, 656a, 656b ... inner movable plate, 661 ... single aspherical lens (third optical system), AX1 ... first 1 axis (main scanning deflection axis), AX2 ... second axis (switching axis), AX3 ... rotation axis (main scanning deflection axis), AX4 ... oscillation axis (switching axis), AX5 ... oscillation axis (main scanning deflection axis) ), D: Image data, Iy1, Iy2, Im1, Ic1, Ik1 to Ik5: Line latent images, Ly1, Ly2, Lm1, Lm2, Lc1, Lc2, Lk1, Lk2: Scanning light beam, X: Main scanning direction, Y ... Sub-scanning direction

Claims (5)

A plurality of latent image carriers on which latent images are formed by a light beam scanned in a first direction;
Light source means for emitting a plurality of light beams;
An optical scanning means provided with a deflection mirror surface that is swingably provided around a main scanning deflection axis and a switching axis and reflects the plurality of light beams emitted from the light source means;
The optical scanning means swings the deflection mirror surface in a resonance mode around the main scanning deflection axis to scan the plurality of light beams in the first direction, and in a non-resonance mode around the switching axis. A latent image carrier to which the plurality of scanning light beams are irradiated among the plurality of latent image carriers by swinging and positioning the deflection mirror surface and guiding the plurality of scanning light beams in a second direction. An image forming apparatus characterized by switching. A plurality of latent image carriers on which latent images are formed by a light beam scanned in a first direction;
Light source means for emitting a plurality of light beams;
A deflection mirror surface is provided corresponding to each of the plurality of light beams emitted from the light source means, and the plurality of deflection mirror surfaces are swingable about a main scanning deflection axis and a switching axis. Optical scanning means,
The optical scanning means swings the plurality of deflection mirror surfaces in a resonance mode around the main scanning deflection axis, reflects the plurality of light beams on the corresponding deflection mirror surfaces, and scans in the first direction. And the plurality of deflection mirror surfaces are oscillated and positioned around the switching axis in a non-resonant mode to guide the plurality of scanning light beams in the second direction, and the plurality of the plurality of latent image carriers are arranged in the plurality of latent image carriers. An image forming apparatus comprising: switching a latent image carrier to which a scanning light beam is irradiated. The plurality of deflecting mirror surfaces are independently swingable about the switching axis,
The image forming apparatus according to claim 2, wherein the optical scanning unit swings and positions the plurality of deflection mirror surfaces independently around the switching axis to adjust an interval between the plurality of scanning light beams.   The image forming apparatus according to claim 1, wherein the optical scanning unit swings and drives the deflection mirror surface about the main scanning deflection axis by an electrostatic adsorption force.   5. The image forming apparatus according to claim 1, wherein the optical scanning unit swings and positions the deflection mirror surface around the switching shaft by electromagnetic force. 6.

Images