JP2005115211A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner which has a simple structure and forms a wide scanning region with high accuracy by scanning with a plurality of light beams at high accuracy, and to provide and an image forming apparatus furnished with the device. <P>SOLUTION: The optical scanner is so composed that a scanned plane formed by scanning with each of two light beams L1 and L2 emitted form a first and a second deflection mirror faces 651a and 651b, respectively, intersect on a main scanning plane which is substantially orthogonal to a first axes AX1a and AX1B. Thus, the intersected beams L1 and L2 are focused on a plane to be scanned 2a with substantially the same part of a scanning lens 66, and the plane to be scanned 2a is scanned with a substantially the same imaging characteristic and scanning characteristic. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical scanning device that scans a light beam using a plurality of deflection mirror surfaces, and an image forming apparatus equipped with the optical scanning device.

  Conventionally, in an optical scanning device used in an image forming apparatus such as a laser beam printer, a copying machine, or a facsimile machine, a transmission optical system is used to increase the deflection angle of a light beam, and the deflection mirror surface of two deflection elements. A configuration for deflecting a light beam is known. In such a configuration, the light beam deflected by the first deflection mirror surface is guided to the second deflection mirror surface by the transmission optical system, and the light beam from the first deflection mirror surface is further deflected by the second deflection mirror surface. The deflection angle of the light beam is increased. Then, the light beam emitted from the second deflection mirror surface is guided onto the surface to be scanned through the scanning lens. Thus, by combining the first and second deflection mirror surfaces and the transmission optical system, the deflection angle of the light beam is increased.

  However, in such a configuration, the arrangement of the transmission optical system causes an increase in the size of the optical scanning device that increases the deflection angle by using two deflection mirror surfaces. As a means for avoiding such an increase in the size of the apparatus, a plurality of scanning pieces are formed on the surface to be scanned with a plurality of scanning light beams, and these scanning pieces are connected in the main scanning direction to form one scanning region. The structure which forms is known (for example, patent document 1).

JP 2003-98459 A (FIG. 3)

  In the above-described conventional apparatus, a scanning optical system that includes a light source that emits a light beam, a deflecting mirror surface that deflects the light beam, and a scanning lens that forms an image of the light beam deflected by the deflecting mirror surface on the surface to be scanned. Are arranged side by side in the main scanning direction. Each scanning optical system scans the surface to be scanned with the scanning light beam, so that three scanning pieces are formed on the surface to be scanned, and these three scanning pieces are joined in the main scanning direction. Thus, one scanning region is formed. In this way, three scanning lenses are prepared to form three scanning light beams by forming images of the three scanning light beams on the surface to be scanned, and each scanning light beam is scanned through the corresponding scanning lens. The image is formed on the surface. For this reason, the following problems occur. That is, since the manufacturing error of each scanning lens cannot be removed, the imaging characteristics and scanning characteristics of the scanning light beam by each scanning lens on the surface to be scanned may not match. For this reason, an error occurs in each scanning position on the surface to be scanned of each scanning light beam, and one scanning region cannot be formed with high accuracy by connecting the scanning pieces by each scanning light beam. . Further, the spot diameter of each scanning light beam formed on the surface to be scanned is different for each scanning piece. Furthermore, since a scanning lens is required corresponding to each deflection mirror surface, the number of parts increases.

  The present invention has been made in view of the above-described problems, and includes an optical scanning device that can scan a plurality of light beams with high accuracy to form a wide scanning region with high accuracy, and the device. Another object of the present invention is to provide an image forming apparatus.

  In order to achieve the above object, the optical scanning device according to the present invention has a one-to-one correspondence with a light source that emits N (where N ≧ 2 is a natural number) light beams and N light beams from the light sources. And at least one connection with deflection means having N deflection mirror surfaces each of which swings around a main scanning deflection axis and deflects and scans the light beam from the light source. A main scan having an image element and forming an image of each of the N scanning light beams emitted from the deflecting means on the surface to be scanned through all of the imaging elements and substantially orthogonal to the main scanning deflection axis An image forming means for forming N scanning pieces extending in the direction, and one scanning region is formed by connecting the N scanning pieces in the main scanning direction on the surface to be scanned. It is characterized by that.

  In the invention configured as described above, the N light beams are deflected by the N deflection mirror surfaces corresponding to the respective light beams on a one-to-one basis, and then the surface to be scanned using the common imaging element. By forming an image on the scanning surface, N scanning pieces forming one scanning region when formed in the main scanning direction are formed on the surface to be scanned. Therefore, there is no difference due to manufacturing errors of the imaging elements in the imaging characteristics and scanning characteristics of the scanning light beams deflected toward the scanning surface by the respective deflection mirror surfaces. An error does not occur in each scanning position on the surface to be scanned, and each scanning piece by each scanning light beam can be formed on the surface to be scanned with high accuracy. Therefore, by connecting these scanning pieces in the main scanning direction, a wide scanning region can be formed with high accuracy on the surface to be scanned. That is, optical scanning on the surface to be scanned can be performed with high accuracy. Further, the spot diameters of the scanning light beams formed by the respective scanning light beams on the surface to be scanned can be made uniform. In addition, the number of parts can be reduced as compared with a conventional apparatus in which an imaging element is individually provided on each deflection mirror surface and the scanning light beam is imaged on the surface to be scanned.

  Further, the deflection mirror surface may be arranged side by side in a direction parallel to the main scanning direction. With such a configuration, it is not necessary to make the light beam enter and exit the deflecting mirror surface at an angle with respect to the main scanning plane. That is, the optical components of the optical scanning device can be arranged in the same main scanning plane. As a result, it is possible to reduce the apparatus size in the sub-scanning direction substantially orthogonal to the main scanning direction, that is, to reduce the apparatus thickness.

  Further, the imaging means may be composed of a single scanning lens. With this configuration, an optical scanning device that is simpler and has a smaller number of parts can be configured, and the optical scanning device can be further downsized.

  Further, sweep surfaces formed by sweeping at least two scanning light beams out of N scanning light beams emitted from the deflecting means intersect in a main scanning plane substantially orthogonal to the main scanning deflection axis. You may comprise as follows. With this configuration, the intersecting scanning light beams are imaged on the surface to be scanned by substantially the same part of the imaging element. Therefore, the surface to be scanned can be scanned with substantially the same imaging characteristics and scanning characteristics. Therefore, each scanning piece can be formed with high accuracy.

  Further, two light beams are emitted from the light source, the two light beams are deflected and scanned by the deflecting means, and the two scanning light beams are imaged by the imaging means and An optical scanning device for forming a scanning region, wherein a sweep surface formed by sweeping each of the two scanning light beams intersects in a main scanning plane substantially orthogonal to the main scanning deflection axis. May be. With such a configuration, the two scanning light beams deflected by the two deflecting mirror surfaces are imaged on the surface to be scanned by the same portion at substantially the center of the imaging element. Therefore, since the two scanning light beams deflected by both deflection mirror surfaces can be scanned on the scanning surface with substantially the same imaging characteristics and scanning characteristics, the two scanning light beams are scanned by the two scanning light beams. Two scanning pieces can be accurately formed on the surface. Therefore, one scanning region can be formed with higher accuracy by connecting the two scanning pieces. Further, the spot diameters of the two scanning light beams formed by the two scanning light beams on the surface to be scanned can be made uniform. In addition, since the area of the entire sweep surface formed by sweeping each of the two scanning light beams can be reduced, the imaging means can be made smaller.

  Each of the deflection mirror surfaces may be configured to be substantially conjugate with the surface to be scanned in a sub-scanning plane that is substantially orthogonal to the main scanning direction. By adopting such a configuration, it is possible to prevent the influence of the swing in the sub-scanning direction of the deflection mirror surface having a conjugate relationship with the surface to be scanned. Further, the size of the deflecting mirror surface in the sub-scanning direction can be reduced to reduce the size and weight of the deflecting means. As a result, the driving speed of the deflection mirror surface can be further improved to further increase the deflection speed of the light beam.

  Further, as the deflecting means, one having two deflecting elements having a single deflecting mirror surface (for example, a galvanometer mirror) arranged in parallel can be used, but the deflecting means configured as follows may be used. Good. That is, the deflection means includes a first movable member having the first deflection mirror surface, a second movable member having the second deflection mirror surface, and the first and second movable members substantially in the main scanning direction. A support member that is swingably supported around the main scanning deflection axis extending in an orthogonal direction, and a mirror driving unit that swings the first and second deflection mirror surfaces around the main scanning deflection axis to deflect a light beam. The two deflection mirror surfaces are constituted by the first and second deflection mirror surfaces. Here, for the first movable member, the second movable member, and the support member, the first movable member, the second movable member, and the support member are integrally formed by processing one substrate. Also good. By integrally forming in this way, the characteristics of the first and second deflection mirror surfaces can be made uniform, and the light beam can be stably deflected. The deflecting unit is configured to be movable around a main scanning deflection axis extending in a direction substantially perpendicular to the main scanning direction, and a movable member having a deflecting mirror surface for deflecting a light beam on one surface. It consists of two deflection elements each having a supporting member to be supported and a mirror driving unit, and the deflection mirror surface of the one of the two deflection elements is the first deflection mirror surface, and the deflection mirror surface of the other deflection element. Is the second deflection mirror surface, and the two deflection mirror surfaces can be formed of the first and second deflection mirror surfaces. Note that a micromachining technique can be applied to the substrate processing method. By using the processing technique, a deflecting unit can be created with high accuracy, which is advantageous in stabilizing the deflection angle of the light beam.

  Moreover, a silicon single crystal can be used as the substrate, the movable member, and the support member. For example, a movable member can be formed by using a silicon single crystal substrate as a support member and applying a micromachining technique to the substrate. When the movable member and the support member of the deflection element are configured using the silicon single crystal in this way, the first and second deflection mirror surfaces can be manufactured with high accuracy. Further, the movable member can be supported in a swingable manner with the same spring characteristics as stainless steel, and the first and second deflection mirror surfaces can be swung stably and at high speed.

  Further, the first and second deflection mirror surfaces may be driven to swing around the main scanning deflection axis in a resonance mode by a mirror driving unit. With this configuration, the first and second deflection mirror surfaces can be driven to swing around the main scanning deflection axis with less energy. In addition, the main scanning period of the light beam can be stabilized.

  Further, as a driving force for swinging and driving the first and second deflecting mirror surfaces, an electrostatic adsorption force, an electromagnetic force, or the like can be used, and each has the following characteristics. When the electrostatic attraction force is used, it is not necessary to form a coil pattern, the deflection element can be miniaturized, and the deflection operation of the light beam can be further accelerated. On the other hand, when the electromagnetic force is used, the first and second deflection mirror surfaces can be driven to oscillate with a lower driving voltage than when the electrostatic attraction force is generated, and the voltage control is facilitated. Can improve the position system. Thus, since it has a mutually different characteristic, what is necessary is just to employ | adopt the driving force according to the intended purpose.

<First Embodiment>
FIG. 1 is a view showing an image forming apparatus equipped with an exposure unit according to a first embodiment of an optical scanning 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 four-cycle color printer. 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, the engine controller 10 responds to the print command from the CPU 111 of the main controller 11. The engine unit EG is controlled to form an image corresponding to the print command on a sheet such as copy paper, transfer paper, paper, and OHP transparent sheet.

  In this engine unit EG, a photosensitive member 2 (corresponding to a “latent image carrier” of the present invention) is provided so as to be rotatable in the arrow direction (sub-scanning direction) in FIG. Further, a charging unit 3, a rotary developing unit 4, and a cleaning unit (not shown) are arranged around the photoconductor 2 along the rotation direction. A charging controller 103 is electrically connected to the charging unit 3 and applies a predetermined charging bias. By applying this bias, the outer peripheral surface of the photoreceptor 2 is uniformly charged to a predetermined surface potential. Further, the photosensitive member 2, the charging unit 3, and the cleaning unit integrally constitute a photosensitive member cartridge, and the photosensitive member cartridge is integrally detachable from the apparatus main body 5.

  Then, light beams L 1 and L 2 are irradiated from the exposure unit 6 corresponding to the optical scanning device of the present invention toward the outer peripheral surface of the photosensitive member 2 charged by the charging unit 3. The exposure unit 6 exposes light beams L1 and L2 on the surface of the photoreceptor 2 (corresponding to the “scanned surface” of the present invention) in accordance with an image signal given from an external device, and corresponds to the image signal. An electrostatic latent image is formed. The configuration and operation of the exposure unit 6 will be described in detail later.

  The electrostatic latent image thus formed is developed with toner by the developing unit 4 (corresponding to the “developing means” of the present invention). That is, in this embodiment, the developing unit 4 is configured as a support frame 40 that is rotatably provided around the axis, and a cartridge that is detachable with respect to the support frame 40, and for yellow that contains toner of each color. A developing unit 4Y, a magenta developing unit 4M, a cyan developing unit 4C, and a black developing unit 4K are provided. Then, based on a control command from the developing device controller 104 of the engine controller 10, the developing unit 4 is rotationally driven and these developing devices 4Y, 4M, 4C, 4K are selectively brought into contact with the photosensitive member 2. Alternatively, when positioned at a predetermined developing position facing each other with a predetermined gap, toner is applied to the surface of the photoreceptor 2 from a developing roller provided in the developing unit and carrying toner of a selected color. As a result, the electrostatic latent image on the photoreceptor 2 is visualized with the selected toner color.

  The toner image developed by the developing unit 4 as described above is primarily transferred onto the intermediate transfer belt 71 of the transfer unit 7 in the primary transfer region TR1. The transfer unit 7 includes an intermediate transfer belt 71 that is stretched over a plurality of rollers 72, 73, and the like, and a drive unit (not shown) that rotates the intermediate transfer belt 71 in a predetermined rotation direction by rotationally driving the roller 73. It has.

  In the vicinity of the roller 72, a transfer belt cleaner (not shown), a density sensor 76 (FIG. 2), and a vertical synchronization sensor 77 (FIG. 2) are arranged. Among these, the density sensor 76 is provided facing 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. 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.

  When transferring a color image to a sheet, each color toner image formed on the photoreceptor 2 is superimposed on the intermediate transfer belt 71 to form a color image and taken out from the cassette 8 one by one. The color image is secondarily transferred onto the sheet conveyed along the conveyance path F to the secondary transfer region TR2.

  At this time, in order to correctly transfer the image on the intermediate transfer belt 71 to a predetermined position on the sheet, the timing of feeding the sheet to the secondary transfer region TR2 is managed. Specifically, a gate roller 81 is provided on the transport path F on the front side of the secondary transfer region TR2, and the gate roller 81 rotates in accordance with the timing of the circumferential movement of the intermediate transfer belt 71. Are sent to the secondary transfer region TR2 at a predetermined timing.

  Further, the sheet on which the color image is formed in this way is conveyed to the discharge tray portion 51 provided on the upper surface portion of the apparatus main body 5 via the fixing unit 9 and the discharge roller 82. When images are formed on both sides of the sheet, the sheet on which the image is formed on one side as described above is switched back by the discharge roller 82. As a result, the sheet is conveyed along the reverse conveyance path FR. Then, it is put again on the transport path F before the gate roller 81. At this time, the image is transferred to the surface of the sheet that is in contact with the intermediate transfer belt 71 and transfers the image in the secondary transfer region TR2. The surface is the opposite of the surface. In this way, images can be formed on both sides of the sheet.

  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.

  3 is a main scanning sectional view showing a configuration of an exposure unit (optical scanning device) provided in the image forming apparatus of FIG. 1, and FIGS. 4 and 5 show a deflecting element (deflecting means) as one component of the exposure unit. FIG. 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 multi-laser light source 62 is fixed to the exposure housing 61 so that light beams L 1 and L 2 can be emitted from the multi-laser light source 62. The multi-laser light source 62 is electrically connected to a light source driving unit (not shown) of the exposure control unit 102. For this reason, the light source driving unit controls ON / OFF of the multi-laser light source 62 in accordance with the image data, and the multi-laser light source 62 emits light beams L1 and L2 modulated corresponding to the image data.

  Further, in this exposure housing 61, in order to scan and expose the light beams L1 and L2 from the multi-laser light source 62 onto the surface 2a of the photosensitive member 2, a collimator lens 631, a cylindrical lens 632, and “deflection” of the present invention. A deflection element 65 corresponding to “means”, a scanning lens 66 corresponding to “imaging means” of the present invention, and a folding mirror 68 are provided. That is, the light beams L 1 and L 2 from the multi-laser light source 62 are shaped into collimated light of an appropriate size by the collimator lens 631 and then incident on the cylindrical lens 632 having power only in the sub-scanning direction Y. Further, the light beam L1 that has passed through the cylindrical lens 632 is folded back by the folding mirror 641, and then further folded by the folding mirror 642 as shown in FIG. 3, and is incident on the deflection mirror surface 651a of the deflection element 65. Then, by adjusting the cylindrical lens 632, the collimated light is imaged in the vicinity of the deflection mirror surface 651a of the deflection element 65 in the sub-scanning direction Y. In addition, the light beam L 2 that has passed through the cylindrical lens 632 is folded back by the folding mirror 643 and then incident on the deflection mirror surface 651 b of the deflection element 65. Then, by adjusting the cylindrical lens 632, the collimated light is imaged near the deflection mirror surface 651b of the deflection element 65 in the sub-scanning direction Y. Thus, in this embodiment, the collimator lens 631 and the cylindrical lens 632 function as the beam shaping system 63 that shapes the light beam from the multi-laser light source 62.

  The deflecting 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 beam reflected by the deflecting mirror surfaces 651a and 651b is in the main scanning direction. The light beam can be deflected to X. More specifically, the deflection element 65 is configured as follows.

  In this deflecting element 65, as shown in FIG. 4, 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 further processed. Thus, two movable plates (corresponding to “first and second movable members” of the present invention) 656a and 656b are provided in the main scanning direction X with a predetermined distance therebetween. The movable plate 656a is formed in a flat plate shape, is elastically supported on the silicon substrate 652 by a torsion spring 657, and can swing around a first axis AX1a extending substantially parallel to the sub-scanning direction Y. In addition, an aluminum film or the like is formed as a first deflection mirror surface 651a at the center of the upper surface of the movable plate 656a. The movable plate 656b is configured in the same manner as the movable plate 656a. That is, the movable plate 656b formed in a flat plate shape is provided to be swingable with respect to the silicon substrate 652 around the first axis AX1b, and an aluminum film or the like is provided at the center of the upper surface of the movable plate 656a as the second deflection mirror. A film is formed as the surface 651b.

  In addition, electrodes 658a and 658b are respectively fixed to the movable plates 656a and 656b on the inner bottom surface of the recess 652a of the silicon substrate 652 at positions facing both ends of the movable plate. These two electrodes 658a and 658b function as electrodes for swinging and driving the movable plates 656a and 656b around the first axes AX1a and AX1b. That is, these electrodes 658a and 658b are electrically connected to a drive unit (not shown) of the exposure control unit 102, and electrostatic application is performed between the electrodes and the deflecting mirror surfaces 651a and 651b by applying a voltage to the electrodes. The attraction force acts to draw one end of the deflecting mirror surfaces 651a and 651b toward the electrode. Therefore, when a predetermined voltage is alternately applied to the electrodes 658a and 658b from the drive unit, the deflection mirror surfaces 651a and 651b can be reciprocally oscillated using the torsion spring 657 as the first axes AX1a and AX1b. When the driving frequency of the reciprocating vibration is set to the resonance frequency of the deflecting mirror surfaces 651a and 651b, the deflection width of the deflecting mirror surfaces 651a and 651b is increased, and the vibration maintenance can be further stabilized. In this embodiment, the electrodes 658a and 658b are arranged symmetrically with the deflecting mirror surfaces 651a and 651b so as to swing in the opposite phase, but are configured to swing in the same phase. Needless to say.

  Thus, in the deflecting element (deflecting means) 65, the drive unit of the exposure control unit 102 functions as the “mirror drive unit” of the present invention, and the deflection mirror surfaces 651a and 651b are moved to the first axis by controlling the drive unit. The light beam is scanned in the main scanning direction by swinging around AX1a and AX1b. That is, the first axes AX1a and AX1b are caused to function as main scanning deflection axes.

  The light beam thus deflected by the deflecting element 65 is irradiated onto the surface (scanned surface) 2 a of the photosensitive member 2 through the scanning lens 66 and the folding mirror 68. That is, the light beam L1 is deflected by the first deflecting mirror surface 651a to scan the scanned surface 2a1 in the main scanning direction X, and the light beam L2 is deflected by the second deflecting mirror surface 651b to scan the scanned surface 2a2. Scanning in the direction X is performed. As a result, a line-shaped latent image extending in the main scanning direction X is formed on the surface 2 a of the photoreceptor 2 by scanning the light beam in parallel with the main scanning direction X.

  Thus, in this embodiment, a latent image is formed on the surface 2a of the photoreceptor 2 without using a transmission optical system configured using a transmission lens. Therefore, the influence of chromatic aberration can be eliminated, and the light beam can be scanned with excellent stability.

  In this embodiment, as shown in FIG. 3, the start or end of the scanning light beam from the deflection element 65 is guided to the synchronization sensor 60 by the folding mirrors 69a to 69c. 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.

  As described above, according to this embodiment, the two light beams L1 and L2 emitted from the multi-laser light source 62 are arranged so as to correspond to the light beams L1 and L2 on a one-to-one basis, and the first axis After being deflected by the first and second deflection mirror surfaces 651a and 651b swinging around AX1a and AX1b (main scanning deflection axis), the scanning lens 66 forms an image on the scanned surfaces 2a1 and 2a2. To do. Then, by connecting these two scanning pieces in the main scanning direction X, one line-like latent image (“scanning region” in the present invention) is formed. Accordingly, since the scanning light beams L1 and L2 deflected by the deflecting mirror surfaces 651a and 651b using the common scanning lens 66 are imaged on the scanned surface, the deflected mirror surfaces 651a and 651b scan the scanned surface. There is no difference in the imaging characteristics and scanning characteristics of the scanning light beams L1 and L2 deflected toward 2a on the surface to be scanned 2a due to manufacturing errors of the scanning lens. Therefore, no error occurs in each scanning position of the scanning light beams L1 and L2 on the scanned surface 2a, and each scanning piece by the scanning light beams L1 and L2 can be formed on the scanned surface 2a with high accuracy. Therefore, by connecting these scanning pieces in the main scanning direction X, a single line-like latent image can be formed on the scanned surface 2a with high accuracy. That is, the optical scanning of the surface to be scanned 2a can be performed in a wide scanning region and with high accuracy. Further, the spot diameters of the light beams L1 and L2 formed on the scanned surface 2a by the light beams L1 and L2 can be made uniform. Further, the number of parts can be reduced as compared with the conventional apparatus in which each deflecting mirror surface is individually provided with a scanning lens and a light beam is imaged on the surface to be scanned.

  In this embodiment, the deflection mirror surfaces 651a and 651b are arranged side by side in a direction parallel to the main scanning direction X. Therefore, it is not necessary to make the light beam enter and exit the deflecting mirror surfaces 651a and 651b at an angle with respect to the main scanning plane. That is, the optical components of the exposure unit 6 can be arranged in the same main scanning plane. As a result, the apparatus size can be reduced in the sub-scanning direction Y substantially orthogonal to the main scanning direction X, that is, the apparatus can be thinned.

  In this embodiment, the imaging means is constituted by a single scanning lens 66. Therefore, it is possible to configure the exposure unit 6 that is simpler and has a smaller number of parts, and it is possible to further reduce the size of the exposure unit 6.

  Further, the main scanning in which the sweep surfaces formed by the sweeps of the two scanning light beams L1 and L2 emitted from the first and second deflection mirror surfaces 651a and 651b are substantially orthogonal to the first axes AX1a and AX1b. It is comprised so that it may cross | intersect in a plane. Accordingly, the intersecting light beams L 1 and L 2 are imaged on the scanned surface 2 a by substantially the same portion of the scanning lens 66. Therefore, since the surface to be scanned 2a can be scanned with substantially the same imaging characteristics and scanning characteristics, each scanning piece by the light beams L1 and L2 can be formed with high accuracy. Further, as shown in FIG. 3, the entire area of the sweep surface formed by sweeping each of the two light beams L1 and L2 before entering the scanning lens 66 can be reduced. Therefore, the folding mirrors 641, 642, 643 can be arranged so that the width in the main scanning direction X is narrow, and can be arranged on the same plane as the deflection mirror surfaces 651a, 651b. Therefore, the exposure unit 6 can be further downsized.

  Further, in this embodiment, two light beams L1 and L2 are emitted from the multi-laser light source 62, and the two light beams L1 and L2 are deflected by the first and second deflecting mirror surfaces 651a and 651b for scanning. At the same time, the two light beams L1 and L2 are imaged by the scanning lens 66, thereby forming one line-like latent image on the surface to be scanned 2a. The sweep plane formed by sweeping each of the two scanning light beams L1 and L2 is configured to intersect in the main scanning plane substantially orthogonal to the first axes AX1a and AX1b. Accordingly, the two scanning light beams L1 and L2 deflected by the two deflecting mirror surfaces 651a and 651b are imaged on the scanned surface 2a by the same portion at the substantially center of the scanning lens 66. Therefore, the two light beams L1 and L2 deflected by the deflecting mirror surfaces 651a and 651b can be scanned on the scanning surface 2a with substantially the same imaging characteristics and scanning characteristics. With L1 and L2, two scanning pieces can be accurately formed on the surface to be scanned 2a. Therefore, by connecting these two scanning pieces, one line-like latent image can be formed with higher accuracy. Further, the spot diameters of the scanning light beams L1 and L2 formed by the scanning light beams L1 and L2 on the surface to be scanned 2a can be made uniform. Further, as shown in FIG. 3, the area of the entire sweep surface formed by sweeping each of the two scanning light beams L1 and L2 incident on the scanning lens 66 can be reduced. Therefore, the scanning lens 66 can be configured to have a narrow width in the main scanning direction X.

  In this embodiment, both the first and second deflecting mirror surfaces 651a and 651b are substantially conjugate with the surface (scanned surface) 2a of the photosensitive member 2 in the sub-scanning plane that is substantially orthogonal to the main scanning direction X. It is configured. By adopting such a configuration, it is possible to prevent the influence of the swinging of both deflection mirror surfaces 651a and 651b in the sub-scanning direction Y. Further, the size of the deflection mirror surfaces 651a and 651b in the sub-scanning direction Y can be reduced to reduce the size and weight of the deflection element (deflecting means). As a result, the driving speed of the deflection mirror surfaces 651a and 651b can be further improved to further increase the scanning speed of the light beam.

  In this embodiment, the first and second deflection mirror surfaces 651a and 651b are driven to swing around the first axes AX1a and AX1b (main scanning deflection axes) in the resonance mode by the mirror driving unit. Therefore, the first and second deflection mirror surfaces 651a and 651b can be driven to swing around the first axes AX1a and AX1b with a small amount of energy. In addition, the main scanning period of the light beam can be stabilized.

  Furthermore, in this embodiment, since the first deflection mirror surfaces 651a and 651b and the support member are integrally formed on one silicon substrate 652 using a micromachining technique, a deflection element (deflection means) is highly accurately formed. 65 can be created, and the characteristics of the first and second deflecting mirror surfaces 651a and 651b can be made uniform, which is advantageous in improving the scanning performance of the light beam. In addition, the movable plates 656a and 656b can be swingably supported with the same spring characteristics as stainless steel, and the first and second deflection mirror surfaces 651a and 651b can be swung stably and at high speed. Can do.

Second Embodiment
6 and 7 are diagrams showing a second embodiment of the optical scanning device according to the present invention, and are diagrams showing a deflecting element as one component of the exposure unit. This embodiment is greatly different from the first embodiment in that the configuration of the deflecting means 85 is different. The deflecting unit 85 is configured by arranging two deflecting elements shown in FIG. 6 in parallel. Hereinafter, the configuration of the deflecting means 85 will be described in detail with a focus on the differences from the first embodiment with reference to these drawings.

  The deflecting means 85 includes two deflecting elements having the same structure as the deflecting element 85a shown in FIG. Since each deflector has the same structure, the configuration of one deflection element 85a having the first deflection mirror surface 851a will be described here, and the description of the configuration of the other deflection element having the second deflection mirror surface will be omitted. To do. The deflection element 85a 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 deflects the light beam reflected by the deflection mirror surface 851a in the main scanning direction X. It is possible. More specifically, the deflection element 85a is configured as follows.

  In this deflecting element 85a, as shown in FIG. 6, the silicon substrate 852a functions as a “supporting member” of the present invention, and a part of the silicon substrate 852a is further processed to move the movable plate 856a (“movable in the present invention” Member ") is provided. The movable plate 856a is formed in a flat plate shape, is elastically supported on the silicon substrate 852a by a torsion spring 857a, and is swingable about a first axis BX1a extending substantially parallel to the sub-scanning direction Y. In addition, an aluminum film or the like is formed as a first deflection mirror surface 851a at the center of the upper surface of the movable plate 856a.

  Further, as shown in FIG. 7, a concave portion 8521a is provided at a substantially central portion of the silicon substrate 852a so that the movable plate 856a can swing around the first axis BX1a. Electrodes 8581a and 8582a are fixed to positions on the inner bottom surface of the recess 8521a that face both ends of the movable plate 856a. These two electrodes 8581a and 8582a function as electrodes for swinging and driving the movable plate 856a around the first axis BX1a. That is, these electrodes 8581a and 8582a are electrically connected to a drive unit (not shown) of the exposure control unit 102, and electrostatic application between the electrodes and the first deflection mirror surface 851a is caused by applying a voltage to the electrodes. The attracting force acts to draw one end portion of the first deflection mirror surface 851a toward the electrode side. Therefore, when a predetermined voltage is alternately applied to the electrodes 8581a and 8582a from the drive unit, the first deflection mirror surface 851a can be reciprocally oscillated using the torsion spring 857a as the first axis BX1a. When the driving frequency of this reciprocating vibration is set to the resonance frequency of the deflecting mirror surface 851a, the deflection width of the deflecting mirror surface 851a is increased, and vibration maintenance can be further stabilized.

  As described above, in the deflecting unit 85, the driving unit of the exposure control unit 102 functions as the “mirror driving unit” of the present invention, and the deflection mirror surface 851a is swung around the first axis BX1a by controlling the driving unit. Thus, the light beam is deflected and scanned in the main scanning direction X. That is, the first axis BX1a is caused to function as the main scanning deflection axis.

  The first and second deflection mirror surfaces are configured by arranging two deflection elements configured as described above in parallel in the main scanning direction. Other configurations are all the same as those in the first embodiment, and have the same effects as those in the first embodiment.

  In the first and second embodiments, the deflection mirror surface is oscillated using electrostatic force, but may be oscillated using other driving force. Here, for example, an electromagnetic force can be used as another driving force.

<Third Embodiment>
8 and 9 are views showing a third embodiment of the optical scanning device according to the present invention. The third embodiment is greatly different from the second embodiment in that the deflection mirror surface 851a is driven to swing using electromagnetic force, and other configurations are the same as those of the second embodiment. is there. Also in the deflection element 65 of the first embodiment, the deflection mirror surfaces 651a and 651b can be driven to swing using electromagnetic force by adopting the same configuration as that of the present embodiment. Here, the deflection element 85a shown in FIGS. 8 and 9 will be described as an example. Further, the same reference numerals are used for parts having the same configuration as in the second embodiment.

  In the deflection element 85a, as shown in FIG. 8, a movable plate 856a is provided by processing a part of the silicon substrate 852a. The movable plate 856a is formed in a flat plate shape, is elastically supported on the silicon substrate 852a by a torsion spring 857a, and is swingable about a first axis BX1a extending substantially parallel to the sub-scanning direction Y. Further, on the upper surface of the movable plate 856a, a planar coil 855a electrically connected to a pair of outer electrode terminals (not shown) formed on the upper surface of the silicon substrate 852a via a torsion spring 857a is coated with an insulating layer. ing. In addition, an aluminum film or the like is formed as a deflection mirror surface 851a at the center of the upper surface of the movable plate 856a.

  Further, as shown in FIG. 9, a concave portion 8521a is provided at a substantially central portion of the silicon substrate 852a so that the movable plate 856a can swing around the first axis BX1a. Then, permanent magnets 8591a and 8592a are fixed to the inner bottom surface of the recess 8521a at the outer positions of both ends of the movable plate 856a in different orientations. The planar coil 855a is electrically connected to a drive unit (not shown) of the exposure control unit 102, and the direction of the current flowing through the planar coil 855a by energization of the coil 855a and the magnetic flux generated by the permanent magnets 8591a and 8592a. Lorentz force acts depending on the direction, and a moment for rotating the movable plate 856a is generated. As a result, the movable plate 856a (deflection mirror surface 851a) swings with the torsion spring 857a as the first axis BX1a. Here, if the current flowing through the planar coil 855a is an alternating current and is continuously repeated, the deflection mirror surface 851a can be reciprocally oscillated with the torsion spring 857a serving as the first axis BX1a. When the driving frequency of this reciprocating vibration is set to the resonance frequency of the deflecting mirror surface 851a, the deflection width of the deflecting mirror surface 851a is increased, and vibration maintenance can be further stabilized.

  In order to swing the first deflection mirror surface 851a in this way, an electromagnetic force, an electrostatic force, or the like is used, but it goes without saying that any of them may be used. However, since each driving method has the following characteristics, it is desirable to adopt them appropriately in consideration of them. That is, when an electromagnetic force is used as a driving force for swinging and driving the first deflection mirror surface 851a, the first deflection mirror surface 851a is driven to swing at a lower driving voltage than when an electrostatic attraction force is generated. Thus, voltage control is facilitated, and the positional accuracy of the scanning light beam can be increased. On the other hand, when the electrostatic attraction force is used as the driving force, it is not necessary to form a coil pattern, the deflection element 85a can be further miniaturized, and the deflection scanning can be further speeded up. Further, the first deflection mirror surface 851a may be configured to swing around the main scanning deflection axis in the resonance mode. With this configuration, the first deflection mirror surface 851a can be driven to swing around the main scanning deflection axis with less energy. In addition, the main scanning period of the scanning light beam can be stabilized.

<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 spirit of the present invention. For example, in the above-described embodiment, the surface to be scanned is scanned with two light beams, but a plurality of light beams of two or more are scanned by a plurality of deflection mirror surfaces corresponding one-to-one with the plurality of light beams. The scanning area may be formed by forming a plurality of scanning pieces on the surface to be scanned by deflection. Even such a configuration has the same effects as the above-described embodiment.

  Further, in this case, it is desirable that a sweep surface formed by sweeping each of at least two scanning light beams among the plurality of scanning light beams intersects in the main scanning plane. With this configuration, the intersecting scanning light beams are imaged on the scanned surface 2a by substantially the same portion of the scanning lens. Therefore, it is possible to scan the scanned surface 2a with substantially the same imaging characteristics and scanning characteristics. Therefore, each scanning piece can be formed with high accuracy.

  In the above-described embodiment, the imaging unit is configured by the single scanning lens 66, but the imaging unit may be configured by a plurality of scanning lenses (imaging elements). Even in such a configuration, each of the scanning light beams is imaged on the surface to be scanned through all of the plurality of scanning lenses, so that the same effect as the above-described embodiment can be obtained.

  Further, as the deflection mirror surface, a conventionally known deflection element such as a galvanometer mirror can be used instead of the above-described deflection element. Also in this case, the plurality of scanning light beams deflected by the plurality of deflection mirror surfaces are imaged on the surface to be scanned 2a via the common scanning lens. Therefore, it has the same effect as the above-described embodiment.

  In the above embodiment, the optical scanning device according to the present invention is used as the exposure unit of the color image forming apparatus, but the application target of the present invention is not limited to this. That is, as an exposure unit of an image forming apparatus that scans a light beam on a latent image carrier such as a photoconductor to form an electrostatic latent image and develops the electrostatic latent image with toner to form a toner image. Can be used. Of course, the application target of the optical scanning device is not limited to the exposure means provided in the image forming apparatus, but can be applied to all optical scanning devices that scan the surface to be scanned with the light beam.

1 is a diagram illustrating an image forming apparatus equipped with an exposure unit according to a first embodiment of an optical scanning device according to the present invention. FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus in FIG. 1. FIG. 2 is a main scanning sectional view showing a configuration of an exposure unit (optical scanning device) equipped in the image forming apparatus of FIG. 1. It is a figure which shows the deflection | deviation element which is one component of an exposure unit. It is a figure which shows the deflection | deviation element which is one component of an exposure unit. It is a figure which shows the deflection | deviation element of the exposure unit which is 2nd Embodiment of the optical scanning device concerning this invention. It is a figure which shows the deflection | deviation element of the exposure unit which is 2nd Embodiment of the optical scanning device concerning this invention. It is a figure which shows the deflection | deviation element of the exposure unit which is 3rd Embodiment of the optical scanning device concerning this invention. It is a figure which shows the deflection | deviation element of the exposure unit which is 3rd Embodiment of the optical scanning device concerning this invention.

Explanation of symbols

2 ... photosensitive body (latent image carrier), 2a, 2a1, 2a2 ... scanned surface, 4 ... developing unit (developing means), 6 ... exposure unit (optical scanning device), 62 ... light source, 65 ... deflection element (deflection) Means), 85a ... deflection element, 66 ... scanning lens (imaging means), 651a, 651b, 851a ... deflection mirror surface, 652, 852a ... silicon substrate (support member), 656a, 656b, 856a ... movable plate (movable member) ), L1, L2 ... light beam, AX1a, AX1b, BX1a ... main scanning deflection axis, X ... main scanning direction, Y ... sub-scanning direction

Claims (14)

A light source that emits N (where N ≧ 2 natural numbers) light beams;
The N light beams from the light source are arranged so as to have a one-to-one correspondence with each other, and each of them swings around a main scanning deflection axis to deflect and scan the light beams from the light source. Deflection means having a deflection mirror surface;
The main scanning deflection shaft has at least one imaging element and forms an image of each of the N scanning light beams emitted from the deflecting means on the surface to be scanned through all of the imaging elements. Imaging means for forming N scanning pieces extending in the main scanning direction substantially perpendicular to the main scanning direction,
An optical scanning device characterized in that one scanning region is formed by joining the N scanning pieces on the surface to be scanned in the main scanning direction.   2. The optical scanning device according to claim 1, wherein the N deflection mirror surfaces are arranged side by side in a direction parallel to the main scanning direction.   3. The optical scanning device according to claim 1, wherein the image forming unit includes a single scanning lens as the image forming element.   Sweep surfaces formed by sweeping at least two scanning light beams out of N scanning light beams emitted from the deflecting means intersect in a main scanning plane substantially orthogonal to the main scanning deflection axis. The optical scanning device according to claim 1. Two light beams are emitted from the light source, the two light beams are deflected and scanned by the deflecting means, and the two scanning light beams are imaged by the imaging means to form the scanning region. The optical scanning device according to any one of claims 1 to 3, wherein
An optical scanning device in which sweep surfaces formed by sweeping each of the two scanning light beams intersect in a main scanning plane substantially orthogonal to the main scanning deflection axis.   6. The optical scanning device according to claim 4, wherein each of the deflection mirror surfaces is substantially conjugate with the surface to be scanned in a sub-scanning plane substantially orthogonal to the main scanning direction. The deflection means includes
A first movable member having the first deflection mirror surface;
A second movable member having the second deflection mirror surface;
A support member that swingably supports the first and second movable members about the main scanning deflection axis extending in a direction substantially orthogonal to the main scanning direction;
A mirror drive unit that swings the first and second deflection mirror surfaces around the main scanning deflection axis to deflect the light beam;
6. The optical scanning device according to claim 5, wherein the two deflection mirror surfaces are constituted by the first and second deflection mirror surfaces. The deflecting means supports a movable member having a deflecting mirror surface for deflecting a light beam on one surface, and the movable member swingably around the main scanning deflection axis extending in a direction substantially perpendicular to the main scanning direction. Consists of two deflecting elements including a support member and a mirror drive unit,
The deflection mirror surface of the one of the two deflection elements is a first deflection mirror surface, and the deflection mirror surface of the other deflection element is a second deflection mirror surface,
6. The optical scanning device according to claim 5, wherein the two deflection mirror surfaces are constituted by the first and second deflection mirror surfaces.   9. The optical scanning device according to claim 7, wherein the movable member and the support member are integrally formed by processing one substrate.   The optical scanning device according to claim 9, wherein the substrate, the movable member, and the support member are made of silicon single crystal.   11. The optical scanning device according to claim 7, wherein the mirror driving unit swings and drives the first and second deflection mirror surfaces around the main scanning deflection axis in a resonance mode.   12. The optical scanning device according to claim 7, wherein the mirror driving unit swings and drives the first and second deflection mirror surfaces around the main scanning deflection axis by electrostatic attraction force.   12. The optical scanning device according to claim 7, wherein the mirror driving unit swings and drives the first and second deflection mirror surfaces around the main scanning deflection axis by electromagnetic force. A latent image carrier;
An exposure having the same configuration as the optical scanning device according to any one of claims 1 to 13, wherein the surface of the latent image carrier is scanned with a light beam to form an electrostatic latent image on the latent image carrier. Means,
An image forming apparatus comprising: developing means for developing the electrostatic latent image with toner to form a toner image.

Images