JP2005070205A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an optical scanner in which a deflection angle is increased by guiding a light beam deflected on a first deflection mirror face to a second deflection mirror face with a transmission optical system and further deflecting the light beam on the second deflection mirror face, and to miniaturize an image forming apparatus which is furnished with the optical scanner. <P>SOLUTION: A first and a second deflection mirror faces 651a and 651b are arranged facing the side of the reflection face 671a of a concave face mirror 671, a light beam deflected with a first deflection mirror face 651a is reflected on the concave mirror face 671a and guided to a second deflection mirror face 651b. The structure is such that the light beam is folded back with the concave face mirror 671 of the transmission optical system 67, thus, the device is more miniaturized than a conventional device in which the first deflection mirror face, the transmission optical system and the second deflection mirror face are arranged in line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical scanning device used in an image forming apparatus such as a laser beam printer, and more particularly, to an optical scanning device that increases the deflection angle by sequentially making a light beam incident on two deflecting mirror surfaces and an image forming apparatus equipped with the optical scanning device. It relates to the device.

  Conventionally, an optical scanning device used in an image forming apparatus such as a laser beam printer, a copying machine, or a facsimile machine has employed a configuration using two deflection mirror surfaces in order to increase the deflection angle (for example, Patent Document 1). In the optical scanning device described in Patent Document 1, 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 from the first deflection mirror surface is guided by the second deflection mirror surface. The deflection angle of the light beam is increased by further deflecting the beam. 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 scanning speed of the light beam is improved.

JP-A-53-97447 (2nd page, Fig. 1)

  In the conventional apparatus described above, a transmission optical system is provided to guide the light beam deflected by the first deflection mirror surface to the second deflection mirror surface, and the transmission optical system is constituted by two transmission lenses. . That is, the first deflection mirror surface and the second deflection mirror surface are arranged apart from each other by a distance (2f1 + 2f2). Here, reference numerals f1 and f2 respectively denote focal lengths of two transfer lenses, that is, the first and second transfer lenses. A first transfer lens is disposed between the first and second deflection mirror surfaces at a distance f1 from the first deflection mirror surface to the second deflection mirror surface side. Further, the second transfer lens is disposed at a distance (f1 + f2). By adopting such a lens arrangement, the transmission optical system is a so-called afocal optical system.

  Thus, since the first deflection mirror surface, the transmission optical system, and the second deflection mirror surface are arranged in a predetermined direction and in a straight line, the apparatus becomes longer in the predetermined direction, and two deflection mirror surfaces are used. As a result, the size of the optical scanning device that increases the deflection angle is increased. Further, when a plurality of transfer lenses are used as described above, the following problems occur. That is, the transmission optical system is complicated and the number of optical components increases. Further, when the ambient environment of the apparatus, particularly the environmental temperature, changes, the wavelength of the light beam changes, and the apparatus provided with a plurality of transfer lenses is greatly affected by the chromatic aberration of the lens. In other words, the optical characteristics of the transmission optical system change greatly with changes in the surrounding environment of the apparatus. As a result, the scanning characteristics of the light beam become unstable, and the quality of the image formed on the scanned surface may deteriorate.

  The present invention has been made in view of the above problems, and guides the light beam deflected by the first deflection mirror surface to the second deflection mirror surface by the transmission optical system, and further deflects the light beam by the second deflection mirror surface. Accordingly, a first object of the present invention is to reduce the size of an optical scanning device and an image forming apparatus equipped with the optical scanning device that increase the deflection angle.

  A second object of the present invention is to scan a light beam stably with a simple configuration.

  In order to achieve the first object, the optical scanning device according to the present invention reflects the light beam while deflecting around the predetermined main scanning deflection axis to deflect the light beam. At least one scanning optical system having a deflecting means having two deflecting mirror surfaces and an imaging means for forming an image of the light beam on the surface to be scanned, and scanning the light beam on the surface to be scanned in the main scanning direction A transmission optical system that includes the above-described reflection element and guides the light beam deflected by the first deflection mirror surface to the second deflection mirror surface by the reflection surface of the reflection element, and the first and second deflection mirror surfaces reflect The deflection angle of the light beam arranged toward the reflection surface side of the element and deflected by the second deflection mirror surface and emitted toward the scanned surface is made larger than the deflection angle of the light beam by the first deflection mirror surface. It is characterized by.

  In the invention configured as described above, the first and second deflecting mirror surfaces are arranged facing the reflecting surface side of the reflecting element, and the light beam deflected by the first deflecting mirror surface is reflected by the reflecting surface of the reflecting element. It is reflected and guided to the second deflection mirror surface. Since the light beam is configured to be folded by the reflection element in this way, the device is downsized compared to the conventional device in which the first deflection mirror surface, the transmission optical system, and the second deflection mirror surface are arranged in a straight line. can do.

  Here, the number of reflection elements provided in the transmission optical system is not particularly limited, but the oscillation drive phases of the first and second deflection mirror surfaces are set according to whether the number is an odd number or an even number. Is desirable. That is, when the transmission optical system has an odd number of reflection elements, the first and second deflection mirror surfaces are driven to swing in opposite phases, whereas when the transmission optical system has an even number of reflection elements, It is desirable that the second deflection mirror surfaces are driven to swing in the same phase.

  Further, as one aspect of configuring the transmission optical system with an odd number of reflecting elements, for example, the transmission optical system is configured with a concave mirror arranged so that the reflecting surface thereof faces the first and second deflection mirror surfaces. Can be considered. In this transmission optical system, the light beam deflected by the first deflection mirror surface is reflected by the concave mirror surface and guided to the second deflection mirror surface. Thus, by using a concave mirror as a reflective element, a transmission optical system can be configured with a single reflective element, and a plurality of optical components (two transmission lenses) are indispensable for configuring the transmission optical system. Compared with the conventional apparatus, the transmission optical system can be simple and configured with a small number of optical components. Further, since the transmission lens is not required, the influence of chromatic aberration can be eliminated, and the light beam can be scanned with excellent stability.

  Alternatively, the light beam from the light source may be shaped into a parallel light beam by a collimator lens, and the parallel light beam may be focused by a focusing lens, and the focused light beam may be incident on the first deflection mirror surface. Good. In the optical scanning device configured as described above, since the focused light beam is incident on the first deflection mirror surface, the numerical aperture of the collimator lens can be set large, and as a result, the light use efficiency can be increased. .

  In addition, any shape can be adopted as the shape of the concave mirror surface. In particular, an ellipse having a focal point at approximately the center position of the first deflection mirror surface and approximately the center position of the second deflection mirror surface is 2 When an ellipsoid formed by rotating an imaginary straight line passing through two central positions as a rotation axis is used as the above-described surface mirror surface, the following operational effects can be obtained. That is, since the first and second deflection mirror surfaces are located at the two focal points of the elliptical surface, the principal ray of the light beam deflected by the first deflection mirror surface is reflected by the concave mirror surface (elliptical reflection surface). Thereafter, the light enters the second deflection mirror surface. Therefore, the light beam deflected by the first deflection mirror surface can be reliably guided to the second deflection mirror surface, and the light beam can be scanned stably.

  The transmission optical system is preferably disposed outside the scanning region of the light beam scanned by the scanning optical system. By adopting such a configuration, it is possible to prevent interference between the light beam and the transmission optical system. In addition, the light beam can be easily incident on and emitted from the transmission optical system, and the apparatus can be thinned.

  Further, the arrangement relationship between the first and second deflection mirror surfaces is arbitrary, but a specific operational effect can be obtained by satisfying the following arrangement relationship. For example, if the first and second deflecting mirror surfaces are arranged side by side in a direction parallel to the main scanning direction, it is necessary to make the light beam enter and exit the first and second deflecting mirror surfaces at an angle with respect to the main scanning plane. Disappear. 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, if the first and second deflection mirror surfaces are arranged side by side in the sub-scanning direction substantially orthogonal to the main scanning direction, the area occupied by the deflection unit in the main scanning plane is minimized, and the apparatus size in the main scanning plane is reduced. Therefore, the apparatus can be downsized.

  Further, at least one of the first and second deflection mirror surfaces may be configured to be substantially conjugate with the surface to be scanned in the 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 deflecting mirror surface can be further improved to further increase the scanning 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 extends the first movable member having the first deflection mirror surface, the second movable member having the second deflection mirror surface, and the first and second movable members in a direction substantially orthogonal to the main scanning direction. A support member that swingably supports a main scanning deflection axis; and a mirror driving unit that swings and drives the first and second movable members about the main scanning deflection axis. The first and second deflection mirror surfaces are swung around to scan the light beam in the main scanning direction. Here, the first movable member, the second movable member, and the support member may be integrally formed by processing one substrate. By integrally forming in this way, the characteristics of the first and second deflection mirrors can be made uniform, and the light beam can be scanned stably. Note that a micromachining technique can be applied to the substrate processing method, and by using the processing technique, a deflecting unit can be created with high accuracy, which is advantageous in improving the scanning performance of the light beam.

  A silicon single crystal substrate can be used as the substrate. For example, the first and second movable members can be formed by using a silicon single crystal substrate as a support member and applying a micromachining technique to the substrate. Thus, if the movable member and support member of a deflection | deviation element are comprised using a silicon single crystal, the 1st and 2nd movable member can be manufactured with high precision. In addition, the movable member can be swingably supported with the same spring characteristics as stainless steel, and the deflection mirror surface can be swung stably and at high speed.

  Further, the first and second deflecting mirror surfaces may be driven to swing around the main scanning deflection axis in the resonance mode by the 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 means can be miniaturized, and the deflection scanning can be further speeded up. On the other hand, when an electromagnetic force is used, the deflection mirror surface can be driven to swing with a lower drive voltage than when an electrostatic attraction force is generated, voltage control is facilitated, and the positional accuracy of the deflection mirror surface is increased. be able to. 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 the engine unit EG, the photosensitive member 2 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.

  The light beam L is 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 a light beam L on the surface of the photosensitive member 2 (corresponding to the “scanned surface” of the present invention) in accordance with an image signal given from an external device, and outputs electrostatic light corresponding to the image signal. A 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. 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 driven to rotate, and the developing devices 4Y, 4C, 4M, and 4K are selectively brought into contact with the photoreceptor 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 and 4 are main scanning sectional views showing the structure of an exposure unit (optical scanning device) provided in the image forming apparatus of FIG. FIG. 5 is a sub-scan sectional view showing a configuration of an exposure unit (optical scanning device) provided in the image forming apparatus of FIG. 6 and 7 are diagrams showing a deflecting element (deflecting means) which is one component of the exposure 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 so that a light beam can be emitted from the laser light source 62. The 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 laser light source 62 according to the image data, and a light beam modulated in accordance with the image data is emitted from the laser light source 62.

  In the exposure housing 61, a collimator lens 631, a cylindrical lens 632, a folding mirror 641, a focusing lens 64, a deflecting element are provided in order to scan and expose a light beam from the laser light source 62 onto the surface of the photoreceptor 2. 65, a scanning lens 66, a transmission optical system 67, and a folding mirror 68 corresponding to the “imaging means” of the present invention 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 631, and then incident on the cylindrical lens 632 having power only in the sub-scanning direction Y as shown in FIG. The Further, the light beam that has passed through the cylindrical lens 632 is folded back by the folding mirror 641 and then incident on the focusing lens 64 having power only in the main scanning direction X as shown in FIG. 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. 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 laser light source 62. On the other hand, the focal length of the focusing lens 64 is longer than the distance between the lens 64 and the first deflection mirror surface 651a. Therefore, a line image extending in the main scanning direction X is formed in the vicinity of the deflection mirror surface 651a of the deflection element 65.

  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. 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 further processed. Thus, the two movable plates 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 increases, and the deflecting mirror surfaces 651a and 651b reach positions close to the electrodes 658a and 658b. Can be displaced. Further, when the end portions of the deflecting mirror surfaces 651a and 651b reach resonance with the electrodes 658a and 658b by resonance, the electrodes 658a and 658b also contribute to driving the deflecting mirror surfaces 651a and 651b, and both the end portion and the flat portion are driven. Vibration maintenance can be further stabilized by the electrodes. In this embodiment, since the number of reflection elements included in the transmission optical system 67 described below is “1”, the electrodes 658 a and 658 b are arranged symmetrically with respect to the deflection mirror surfaces 651 a and 651 b and are opposite to each other. It is configured to oscillate in phase.

  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 deflected and swung in the main scanning direction X by swinging around AX1a and AX1b in opposite phases. That is, the first axes AX1a and AX1b are caused to function as main scanning deflection axes.

  The light beam reflected by the first deflection mirror surface 651a of the deflecting element 65 configured as described above is incident on the transmission optical system 67, and then is transmitted by the transmission optical system 67 to the second deflection mirror surface 651b of the deflection element 65. Returned to Therefore, for example, the light beam deflected to the first deflection angle by the deflection element 65 is emitted toward the scanning lens 66 at a second deflection angle larger than the first deflection angle. In this embodiment, the transmission optical system 67 is configured as follows.

  As shown in FIG. 4, the transmission optical system 67 includes a single concave mirror (reflective element) 671. The reflective surface 671a of the concave mirror 671 and the first and second deflecting mirror surfaces 651a and 651b. Are arranged so as to face each other. The light beam deflected by the first deflecting mirror surface 651a is reflected by the reflecting surface 671a of the concave mirror 671 and guided to the second deflecting mirror surface 651b. In this embodiment, an ellipsoidal mirror in which the reflecting surface 671a is formed into an ellipsoid is used as the concave mirror 671. More specifically, an ellipse having a focus at approximately the center position P1a of the first deflection mirror surface 651a and approximately the center position P1b of the second deflection mirror surface 651b is represented by an imaginary straight line VL passing through the two center positions P1a and P1b. A part of an ellipsoid formed by rotating as a rotation axis is used as the reflection surface 671a. Therefore, the following effects can be obtained. That is, since the first and second deflection mirror surfaces 651b are positioned at two focal points, the principal ray of the light beam deflected by the first deflection mirror surface 651a is reflected by the concave mirror surface (elliptical reflection surface) 671a. Thereafter, the light enters the second deflection mirror surface 651b. Therefore, the light beam deflected by the first deflection mirror surface 651a can be reliably guided to the second deflection mirror surface 651b. The light beam is reflected by the second deflection mirror surface 651b, and the light beam is emitted toward the scanning lens 66 at a second deflection angle larger than the first deflection angle. As a result, the light beam can be scanned stably.

  The light beam deflected by the deflecting element 65 in this manner is applied to the surface (scanned surface) of the photosensitive member 2 through the scanning lens 66 and the folding mirror 68. As a result, a light beam is scanned in parallel with the main scanning direction X, and a line-like latent image extending in the main scanning direction X is formed on the surface of the photoreceptor 2.

  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 first and second deflection mirror surfaces 651a and 651b are arranged facing the reflection surface 671a side of the concave mirror 671, and are deflected by the first deflection mirror surface 651a. The light beam is reflected by the concave mirror surface 671a and guided to the second deflection mirror surface 651b. Since the light beam is thus folded back by the concave mirror 671 of the transmission optical system 67, the conventional apparatus in which the first deflection mirror surface, the transmission optical system, and the second deflection mirror surface are linearly arranged is used. In comparison, the apparatus can be miniaturized.

  In addition, since the transmission optical system 67 is configured by a single reflection element by using the concave mirror 671 as the reflection element of the present invention, a plurality of optical components (two transmission lenses) are included in the configuration of the transmission optical system. Compared with the conventional apparatus that required the above, the transmission optical system can be simplified and can be configured with a small number of optical components. Further, since the transmission lens is not required, the influence of chromatic aberration can be eliminated, and the light beam can be scanned with excellent stability.

  Further, since the converging lens 64 is provided so that the converging light beam is incident on the first deflecting mirror surface 651a, the numerical aperture of the collimator lens can be set large, and as a result, the light utilization efficiency can be improved. Can be increased.

  Further, in this embodiment, as shown in FIG. 4, the transmission optical system 67 is disposed outside the scanning region of the light beam scanned by the scanning optical system (deflection element 65 and scanning lens 66). For this reason, interference between the light beam and the transmission optical system 67 can be prevented. In addition, the light beam can be easily incident on and emitted from the transmission optical system 67, and the apparatus can be thinned. From the viewpoint of reducing the thickness of the apparatus, the arrangement of the first and second deflection mirror surfaces 651a and 651b arranged in a direction parallel to the main scanning direction X greatly contributes to the reduction of the apparatus thickness. That is, when such an arrangement is adopted, it is not necessary to make the light beam incident on and emerge from the first and second deflecting mirror surfaces 651a and 651b 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, the apparatus size in the sub-scanning direction Y can be reduced, that is, the apparatus can be thinned.

  In this embodiment, both the first and second deflection mirror surfaces 651a and 651b are substantially conjugate with the surface (scanned surface) of the photoreceptor 2 in the sub-scanning plane that is substantially orthogonal to the main scanning direction X. It may be 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.

  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, 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
8 and 9 are main scanning sectional views showing a second embodiment of the optical scanning device according to the present invention. FIG. 10 is a sub-scan sectional view of the optical scanning device of FIG. The difference between the exposure unit 6 as the optical scanning device according to the second embodiment and the first embodiment is the configuration of the deflection element 65. That is, the second embodiment is that the first and second deflection mirror surfaces 651a and 651b are arranged in the sub-scanning direction Y as shown in FIG. In the exposure unit 6 configured in this way, the light beam from the laser light source 62 is shaped into collimated light of an appropriate size by the collimator lens 631, and then only in the sub-scanning direction Y as shown in FIG. The light enters a cylindrical lens 632 having power. Further, the light beam that has passed through the cylindrical lens 632 is folded back by the folding mirror 641 and then incident on the focusing lens 64 having power only in the main scanning direction X as shown in FIG. Then, by adjusting the cylindrical lens 632, the collimated light is imaged near the deflection mirror surface 651a at the lower position in the sub-scanning direction Y. The light beam deflected by the deflecting mirror surface 651a is reflected by the concave mirror surface 671a of the transmission optical system 67 and guided to the deflecting mirror surface 651b at the upper position, and directed toward the scanning lens 66 by the deflecting mirror surface 651b. Is deflected.

  Also in the second embodiment, since the light beam is configured to be folded back by the concave mirror 671 of the transmission optical system 67, the same effects as the first embodiment can be obtained. Further, since the first and second deflection mirror surfaces 651a and 651b are arranged side by side in the sub-scanning direction Y, the area occupied by the deflection element (deflecting means) 65 in the main scanning plane as shown in FIGS. This minimizes the size of the apparatus in the main scanning plane, and enables downsizing of the apparatus.

<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 embodiment, the transmission optical system 67 is configured by one concave mirror 671, but the configuration of the transmission optical system 67 is not limited to this. That is, the apparatus is made compact by using a transmission optical system that has at least one reflecting element and guides the light beam deflected by the first deflecting mirror surface to the second deflecting mirror surface by the reflecting surface of the reflecting element. Can be achieved. For example, as shown in FIG. 11, one plane mirror 673 is provided as a “reflecting element” of the present invention, and the first and second deflection mirror surfaces 651a and 651b are arranged so as to face the reflecting surface 673a side of the plane mirror 673. You may do (3rd Embodiment). Transmission lenses 672 and 674 are disposed between the deflection mirror surfaces 651a and 651b and the plane mirror 673, respectively. For this reason, the light beam deflected by the first deflecting mirror surface 651 a is incident on the reflecting surface 673 a of the plane mirror 673 via the transfer lens 672. Then, the light beam folded back by the reflection surface 673a is guided to the second deflection mirror surface 651b through the transmission lens 674. The light beam is deflected by the second deflecting mirror surface 651b and emitted toward the surface to be scanned. In the third embodiment, the first and second deflection mirror surfaces 651a and 651b are driven to oscillate in opposite phases, so that the deflection angle of the light beam deflected by the second deflection mirror surface 651b is the first deflection. It is larger than the deflection angle of the light beam by the mirror surface 651a.

  The number of reflecting elements is not limited to “1”. For example, as shown in FIG. 12, two plane mirrors 676 and 677 are provided as “reflecting elements” of the present invention, and the first deflecting mirror surface 651a. May be arranged so as to face the reflecting surface 676a side of the plane mirror 676, and the second deflection mirror surface 651b may face the reflecting surface 677a side of the plane mirror 677 (fourth embodiment). Transmission lenses 675 and 678 are arranged between the deflection mirror surfaces 651a and 651b and the plane mirrors 676 and 677, respectively. For this reason, the light beam deflected by the first deflecting mirror surface 651 a is incident on the reflecting surface 676 a of the plane mirror 676 via the transfer lens 675. Then, the light beam folded back by the reflecting surface 673a is folded by the reflecting surface 677a of the plane mirror 677 and then guided to the second deflection mirror surface 651b through the transfer lens 678. The light beam is deflected by the second deflecting mirror surface 651b and emitted toward the surface to be scanned. In the fourth embodiment, the first and second deflection mirror surfaces 651a and 651b are driven to swing in the same phase, so that the deflection angle of the light beam deflected by the second deflection mirror surface 651b is the first deflection. It is larger than the deflection angle of the light beam by the mirror surface 651a.

  Further, the number of reflection elements included in the transmission optical system 67 may be set to “3” or more. However, when the transmission optical system 67 has an odd number of reflection elements, the first and second deflection mirror surfaces 651a and 651b. The first and second deflection mirror surfaces 651a and 651b are preferably driven to swing in the same phase when the transmission optical system 67 has an even number of reflecting elements.

  In the above embodiment, both the first and second deflection mirror surfaces 651a and 651b are substantially conjugate with the surface of the photosensitive member 2 (scanned surface) in the sub-scanning plane. Only one of the mirror surfaces 651a and 651b may be substantially conjugate with the surface (scanned surface) of the photosensitive member 2, and by adopting such a configuration, sub-scanning of the deflection mirror surface having a conjugate relationship with the scanned surface is possible. The influence of swinging in the direction can be prevented.

  Further, in the above embodiment, the deflection mirror surfaces 651a and 651b are swung using the electrostatic attraction force, but may be swung using another driving force. Here, for example, an electromagnetic force can be used as another driving force. In addition, about the point using an electromagnetic force, it describes in Unexamined-Japanese-Patent No. 2002-48998, for example. Thus, it goes without saying that either electromagnetic force or electrostatic force may be used to swing the deflecting mirror surfaces 651a and 651b. 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 driving the deflection mirror surface 651 to swing, the deflection mirror surface 651 can be driven to swing with 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 65 can be further miniaturized, and the deflection scanning can be further speeded up. . Further, when the deflection mirror surface 651 is driven to swing, the deflection mirror surface 651 may be driven to swing around the main scanning deflection axis in the resonance mode. With this configuration, the deflection mirror surface 651 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.

  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. 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. FIG. 2 is a sub-scan sectional view showing a configuration of an exposure unit (optical scanning device) provided 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 main scanning sectional view showing a second embodiment of the optical scanning device according to the present invention. It is a main scanning sectional view showing a second embodiment of the optical scanning device according to the present invention. FIG. 9 is a sub-scan sectional view of the optical scanning device of FIG. 8. It is a main scanning sectional view showing a third embodiment of the optical scanning device according to the present invention. It is a main scanning sectional view showing a 4th embodiment of an optical scanning device concerning the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Photosensitive body (latent image carrier), 4 ... Developing unit (developing means), 6 ... Exposure unit (optical scanning device), 65 ... Deflection element (deflecting means), 66 ... Scanning lens (imaging means), 67 ... Transmission optical system, 651a, 651b ... Deflection mirror surface, 652 ... Silicon substrate (support member), 656a, 656b ... Movable plate, 671 ... Concave mirror (reflection element), 671a ... Concave mirror surface (reflection surface), 672 674, 675, 678 ... transfer lens, 673, 676, 677 ... flat mirror (reflective element), 673a, 676a, 677a ... reflective surface, L ... light beam, P1a, P1b ... reflection position, X ... main scanning direction, Y ... Sub-scanning direction

Claims (17)

Deflection means having first and second deflection mirror surfaces, each deflecting the light beam while swinging around a predetermined main scanning deflection axis, and imaging the light beam on the surface to be scanned A scanning optical system that scans a light beam in the main scanning direction on the surface to be scanned;
A transmission optical system having at least one reflection element, and guiding the light beam deflected by the first deflection mirror surface to the second deflection mirror surface by the reflection surface of the reflection element;
The first and second deflecting mirror surfaces are arranged facing the reflecting surface of the reflecting element, and the deflection angle of the light beam deflected by the second deflecting mirror surface and emitted toward the scanned surface is An optical scanning device characterized in that it is larger than the deflection angle of the light beam by the first deflection mirror surface.   2. The optical scanning device according to claim 1, wherein when the transmission optical system has an odd number of reflecting elements, the first and second deflecting mirror surfaces are driven to swing in opposite phases.   The transmission optical system includes, as the reflection element, a concave mirror disposed so that a reflection surface thereof faces the first and second deflection mirror surfaces, and the concave mirror surface is deflected by the first deflection mirror surface. 3. The optical scanning device according to claim 2, wherein the reflected light beam is reflected by the second deflection mirror surface. A light source that generates a light beam;
A collimator lens for shaping the light beam from the light source into a parallel light beam;
The optical scanning device according to claim 3, further comprising: a focusing lens that focuses the parallel light beam emitted from the collimator lens and guides the focused light beam to the first deflection mirror surface.   The concave mirror surface is an ellipse having a focal point at approximately the center position of the first deflection mirror surface and approximately the center position of the second deflection mirror surface, and a virtual straight line passing through the two center positions as a rotation axis. The optical scanning device according to claim 3, wherein the optical scanning device is an ellipsoid formed by rotation.   2. The optical scanning device according to claim 1, wherein when the transmission optical system has an even number of reflecting elements, the first and second deflecting mirror surfaces are driven to swing in the same phase.   The optical scanning device according to claim 1, wherein the transmission optical system is disposed outside a scanning region of a light beam scanned by the scanning optical system.   8. The optical scanning device according to claim 1, wherein the first and second deflection mirror surfaces are arranged side by side in a direction parallel to the main scanning direction.   8. The optical scanning device according to claim 1, wherein the first and second deflecting mirror surfaces are arranged side by side in a sub-scanning direction substantially orthogonal to the main scanning direction.   10. The optical scanning device according to claim 1, wherein at least one of the first and second 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 a main scanning deflection axis extending in a direction substantially orthogonal to the main scanning direction;
A mirror drive unit that swings and drives the first and second movable members around the main scanning deflection axis;
11. The optical scanning according to claim 1, wherein the mirror driving unit swings the first and second deflection mirror surfaces around the main scanning deflection axis to scan the light beam in the main scanning direction. apparatus.   The optical scanning device according to claim 11, wherein the first movable member, the second movable member, and the support member are integrally formed by processing one substrate.   The optical scanning device according to claim 12, wherein the substrate is a silicon single crystal substrate.   The optical scanning device according to claim 11, 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.   The optical scanning device according to claim 11, wherein the mirror driving unit swings and drives the deflection mirror surface about the main scanning deflection axis by electromagnetic force.   The optical scanning device according to claim 11, wherein the mirror driving unit swings and drives the deflection mirror surface about the main scanning deflection axis by an electrostatic attraction force. A latent image carrier;
17. The optical scanning device according to claim 1, wherein the surface of the latent image carrier is the surface to be scanned and a light beam is scanned to form an electrostatic latent image on the latent image carrier. Exposure means for forming an image;
An image forming apparatus comprising: developing means for developing the electrostatic latent image with toner to form a toner image.

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