Abstract:
An optical scanner includes a polygonal mirror; a mirror for reflecting the beam from the polygonal mirror; an optical box having a cap and containing the mirror; a first mirror regulating portion in a direction of a normal line of the mirror, the first regulating portion being provided opposed to such a surface of the reflecting surface and a back surface as is closer to the cap; and a second mirror regulating portion in a beam sub-scanning direction, the second regulating portion being provided opposed to such a surface of the mirror as is closer to the cap; wherein the mirror has a plurality of apex lines, and the first regulating portion and the second regulating portion are disposed at positions which are remoter from the cap than the apex line that is closest to the cap, with respect to a direction perpendicular to a main scan direction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of co-pending U.S. patent application Ser. No. 14/167,633 filed Jan. 29, 2014, the contents of which are incorporated by reference herein as if set forth in full; and also claims the benefit of priority under 35 U.S.C. §119 based on Japanese Patent Application No. 2013-015921 filed Jan. 30, 2013, which is incorporated by reference herein as if set forth in full. 
     
    
     FIELD OF THE INVENTION AND RELATED ART 
       [0002]    The present invention relates to an optical scanning device for optically writing an image with the use of a beam of laser light. It relates to also an image forming apparatus, such as a laser beam printer (LBP), a digital copying machine, a digital facsimile machine (FAX), etc., which is equipped with the optical scanning device. 
         [0003]    An optical scanning device employed by an image forming apparatus such as a laser beam printer, a digital copying machine, etc., is equipped with a light source unit, and a deflecting device, such as a polygon mirror, which changes a beam of light in direction. It emits a beam of laser light from its light source unit while modulating the beam of laser light with image formation signals, and periodically changes the beam of laser light in direction. It is also equipped with an optical element having the so-called f-θ characteristic. It forms an electrostatic latent image on an object such as a photosensitive drum, by causing the laser beam from its deflecting device, to converge in the form of a spot, on the object. The abovementioned characteristic of an optical element, which is referred to as “f-θ” characteristic, is such a characteristic of an optical element that as a scanning beam of light enters an optical element at an angle θ, the optical element focuses the beam of light in such a manner that the beam of light forms an image, the size of which equals the product of the focal length of the optical element (lens) and the angle θ (f×θ). The light beam deflecting device and optical focusing element are supported by an optical casing (box), the opening of which remains covered with its lid. 
         [0004]    Some optical scanning devices have a mirror for deflecting a beam of laser light so that the beam of laser light hits the object, such as a photosensitive drum, to be scanned by the beam of laser light, at a preset angle. 
         [0005]    In particular, the mirror which directs the beam of laser light deflected by the optical deflecting device, toward the object to be scanned, is in the form of a rectangular parallelepiped, which is very large in the ratio of its long edge to its short edge. A mirror such as this one is likely to be supported by its lengthwise ends. The optical box has a mirror seating primary surface, by which the mirror is supported by its reflective surface, and a mirror seating secondary surface, by which the mirror is supported by its surface which is perpendicular to its reflective surface. Further, the mirror is stationarily held to the mirror seating primary and secondary surfaces by a regulating member such as a leaf spring. 
         [0006]    There is disclosed a regulating member as a means for stationarily holding the mirror, in Japanese Laid-open Patent Application H10-246862. According to this patent application, the mirror is square in cross-section, and its closest edge to the lid of the optical box is kept pressed by the regulating member to keep the mirror pressed upon the mirror seating primary and secondary surfaces of the optical box, which are on the opposite side of optical box from the regulating member. 
         [0007]    However, the regulating member disclosed in Japanese Laid-open Patent Application H10-246862 presses on the edge of the mirror, which is on the lid side of the optical box. Therefore, the optical box has to be structured so that the distance between its lid and the mirror is large enough to prevent the lid and regulating member from interfering with each other. Thus, this patent application is likely to increase an optical scanning device in size. 
       SUMMARY OF THE INVENTION 
       [0008]    Thus, the primary object of the present invention is to reduce an optical scanning device in size. 
         [0000]    Another object of the present invention is to provide the following optical scanning device, or image forming apparatus characterized in that: 
         [0009]    According to an aspect of the present invention, there is provided an optical scanning apparatus comprising a light source; a rotatable polygonal mirror for deflecting a beam from said light source; a mirror for reflecting the beam deflected by said rotatable polygonal mirror toward a predetermined surface; an optical box and a closing member mounted to said optical box, wherein said mirror is accommodated in a space defined by said optical box and said closing member; a first regulating portion for regulating a movement of said mirror in a direction of a normal line of a reflecting surface of said mirror, said first regulating portion being provided opposed to such a surface of the reflecting surface of said mirror and a back surface of said mirror as is closer to said closing member; and a second regulating portion for regulating a movement of said mirror in a beam sub-scanning direction of said mirror, said second regulating portion being provided opposed to such a surface of surfaces of said mirror perpendicular to the sub-scanning direction as is closer to said closing member; wherein said mirror has a plurality of apex line, and said first regulating portion and said second regulating portion are disposed at positions which are remoter from said closing member than the apex line that is closest to said closing member, with respect to a direction perpendicular to a main scan direction. 
         [0010]    According to another aspect of the present invention, there is provided an optical scanning apparatus comprising a light source; a rotatable polygonal mirror for deflecting a beam from said light source; a mirror for reflecting the beam deflected by said rotatable polygonal mirror toward a predetermined surface; an optical box and a closing member mounted to said optical box, wherein said mirror is accommodated in a space defined by said optical box and said closing member; a first regulating portion for regulating a movement of said mirror in a direction of a normal line of a reflecting surface of said mirror, said first regulating portion being provided opposed to such a surface of the reflecting surface of said mirror and a back surface of said mirror as is closer to said closing member; and a reference portion for positioning said mirror in a beam sub-scan direction of said mirror, said reference portion being provided opposed to such a surface of the reflecting surface of said mirror and a back surface of said mirror as is closer to said closing member; wherein said mirror has a plurality of apex line, and said first regulating portion and said reference portion are disposed at positions which are remoter from said closing member than the apex line that is closest to said closing member, with respect to a direction perpendicular to a main scan direction. 
         [0011]    According to a further aspect of the present invention, there is provided an image forming apparatus comprising a light source; a rotatable polygonal mirror, having apex lines for deflecting a beam from said light source; a mirror for reflecting the beam deflected by said rotatable polygonal mirror toward a predetermined surface; an optical box and a closing member mounted to said optical box, wherein said mirror is accommodated in a space defined by said optical box and said closing member; a first regulating portion for regulating a movement of said mirror in a direction of a normal line of a reflecting surface of said mirror, said first regulating portion being provided opposed to such a surface of said mirror closer to said closing member; and a second regulating portion for regulating a movement of said mirror in a beam sub-scanning direction of said mirror, said second regulating portion being provided opposed to such a surface of surfaces of said mirror perpendicular to the sub-scanning direction as is closer to said closing member; wherein said first regulating portion and said second regulating portion are disposed at positions which are remoter from said closing member than the closest apex line said closing member. 
         [0012]    According to a further aspect of the present invention, there is provided an image forming apparatus comprising a light source; a rotatable polygonal mirror for deflecting a beam from said light source; a mirror for reflecting the beam deflected by said rotatable polygonal mirror toward a predetermined surface; an optical box and a closing member mounted to said optical box, wherein said mirror is accommodated in a space defined by said optical box and said closing member; a first regulating portion for regulating a movement of said mirror in a direction of a normal line of a reflecting surface of said mirror, said first regulating portion being provided opposed to such a surface of the reflecting surface of said mirror and a back surface of said mirror as is closer to said closing member; and a reference portion for positioning said mirror in a beam sub-scan direction of said mirror, said reference portion being provided opposed to such a surface of the reflecting surface of said mirror and a back surface of said mirror as is closer to said closing member; wherein said mirror has a plurality of apex line, and said first regulating portion and said reference portion are disposed at positions which are remoter from said closing member than the apex line that is closest to said closing member, with respect to a direction perpendicular to a main scan direction, wherein said mirror has a plurality of apex line, and said first regulating portion and said reference portion are disposed at positions which are remoter from said closing member than the apex line that is closest to said closing member, with respect to a direction perpendicular to a main scan direction. 
         [0013]    Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a sectional view of an image forming apparatus equipped with an optical scanning device in accordance with the present invention, and shows the structure of the apparatus. 
           [0015]      FIG. 2  is a perspective view of the optical scanning device in the first embodiment of the present invention, and shows the structure of the device. 
           [0016]      FIG. 3  is a sectional view of the optical scanning device in the first embodiment, and shows the structure of the mirror, and its adjacencies, of the device. 
           [0017]      FIG. 4  also is a sectional view of the optical scanning device in the first embodiment, and shows the structure of the mirror, and its adjacencies, of the device. 
           [0018]      FIG. 5  is a perspective view of the optical scanning device in the second embodiment of the present invention, and shows the structure of the device. 
           [0019]      FIG. 6  is a perspective view of the optical scanning device in the second embodiment, and shows the structure of the device, in particular, the structure of the primary and secondary regulating members positioned at the lengthwise ends of the mirror, one for one. 
           [0020]      FIG. 7  is a perspective view of the optical scanning device in the second embodiment, and shows the structure of the device, in particular, the structure of the mirror and its adjacencies. 
           [0021]      FIG. 8  is a sectional view of the optical scanning device in the third embodiment of the present invention, and shows the structure of the device. 
           [0022]      FIG. 9  is a perspective view of the primary and secondary regulating members of the optical scanning device in the fourth embodiment, which are disposed at the lengthwise ends, one for one, of the mirror of the device, and shows the structure of the primary and secondary regulating members. 
           [0023]      FIG. 10  is a sectional view of the mirror, and its adjacencies, of the optical scanning device in the fourth embodiment, and shows the structure of the mirror and its adjacencies. 
           [0024]      FIG. 11  is a perspective view of the primary and secondary regulating members of the optical scanning device in the fifth embodiment of the present invention, which are disposed at the lengthwise ends, one for one, of the mirror of the device, and shows the structure of the primary and secondary regulating members. 
           [0025]      FIG. 12  is a sectional view of the optical scanning device in the fifth embodiment of the present invention, and shows the structure of the device, in particular, the structure of the mirror, and its adjacencies, of the device. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Hereinafter, the present invention is concretely described with reference to some of the image forming apparatuses equipped with an optical scanning device which is in accordance with the present invention. 
       Embodiment 1 
       [0027]    To begin with, referring to  FIGS. 1-4 , the image forming apparatus in the first embodiment of the present invention, which is equipped with an optical scanning device which is in accordance with the present invention is described about its structure.  FIG. 1  is a drawing which shows the structure of the image forming apparatus  1  in this embodiment of the present invention. Referring to  FIG. 1 , an optical scanning device  2  is on a holder  3 , which is a part of the casing of the image forming apparatus  1 . 
         [0028]    The image forming apparatus  1  has: a sheet feeding/conveying portion  4 , in which multiple sheets P of recording medium are storable; a sheet feeder roller  5 ; a transfer roller as a transferring means; and a fixing device  7  as a fixing means. Further, the image forming apparatus  1  is provided with a process cartridge bay, in which a process cartridge  8  (as image forming means) is disposed so that it opposes the transfer roller  6 , with the presence of the recording medium conveyance passage between the cartridge  8  and transfer roller  6 . 
         [0029]    The process cartridge  8  has a photosensitive drum  9  (as image bearing member). The sheets P of recording medium in the sheet feeding/conveying portion  4  are fed one by one into the main assembly of the image forming apparatus  1 , while being separated from the rest of the sheets P in the sheet feeding/conveying portion  4  by the combination of the sheet feeder roller  5  and an unshown separating means. Then, each sheet P of recording medium is conveyed by a pair of registration rollers  21  to the nip between the photosensitive drum  9  and transfer roller  6 , with such a timing that the arrival of each sheet P at the nip synchronizes with the arrival of the toner image on the peripheral surface of the photosensitive drum  9  at the nip. Then, the toner image on the peripheral surface of the photosensitive drum  9  is transferred onto the sheet P by the transfer roller  6 . 
         [0030]    After the transfer of the toner image onto the sheet P of recording medium, the sheet P is conveyed to the fixing device  7 , in which the toner image on the sheet P is fixed to the sheet P by heat and pressure. Then, the sheet P, which has the fixed toner image, is discharged from the image forming apparatus  1  by a pair of discharge rollers  10 . 
         [0031]      FIG. 2  is a partially exploded perspective view of the optical scanning device  2  in this embodiment. It shows the structure of the device  2 . Referring to  FIG. 2 , the beam L 1  of laser light emitted from the light source unit  11  (as light source) is made to converge by the cylindrical lens  15  only in the secondary scanning direction. Then, the converged beam L 1  of laser light is limited in diameter to a preset value by the optical iris with which the optical box  13  formed of black resin is provided. Then, the beam L 1  of laser light is made to linearly converge on the reflective surface  17  of the rotational polygon mirror  22  for deflecting the beam of light which comes from the light source unit  11 . 
         [0032]    The secondary scan direction of the beam of light means such direction that corresponds to the rotational direction of the photosensitive drum  9  (direction in which sheet P is conveyed). The primary scan direction of the beam of light is such direction that corresponds to the direction of the axial line of the photosensitive drum  9  (direction perpendicular to direction in which sheet P is conveyed). 
         [0033]    The rotational polygon mirror  22  is rotationally driven by a driving means such as a motor with which the light deflecting device  18  is provided. That is, the rotational polygon mirror  22  is rotated with the driving means such as a motor with which the light deflecting device  18  is provided. The rotational polygon mirror  22  deflects the beam L 1  of laser light as the beam L 1  emitted from the light source unit  11  is projected upon the rotational polygon mirror  22  through the cylindrical lens  15  and optical iris  14 . The light deflecting device  18  deflects the beam L 1  in such a manner that as the beam L 1  is deflected by the rotational polygon mirror  22 , the beam L 1  scans the peripheral surface of the photosensitive drum  9 . 
         [0034]    The beam L 2  of laser light, which is the beam L 1  of laser light deflected by the rotational polygon mirror  22  rotated by the deflecting device  18 , passes through the f-θ lens, which functions as the focusing lens for making the beam of laser light converge. The f-θ lens is characterized in that as the beam L 2  of laser light enters the f-θ lens at an angle θ, the beam L 2  is focused into an image, the size of which is equal to the value of the product between the focal distance f of the f-θ lens and the angle θ. Referring to  FIG. 3 , as the beam L 2  of laser light passes through the f-θ lens, it is reflected by the reflective surface  90  of the long and narrow mirror  20 , which is for reflecting the beam of laser light deflected by the rotational polygon mirror  22 , toward the preset surface. Then, the beam L 2  of laser light is made to converge on the peripheral surface of the photosensitive drum  9 , while being moved in a manner of scanning the peripheral surface of photosensitive drum  9 , as shown in  FIG. 1 , forming thereby an electrostatic latent image on the peripheral surface of the photosensitive drum  9 . The light source unit  11 , cylindrical lens  15 , optical iris  14 , rotational polygon mirror  22 , light deflecting device  18 , f-θ lens  19 , and mirror  22  are disposed within the optical box  13 , and are supported by the box  13 . The top opening of the optical box  13  is covered with a lid  12  made of resin or metallic plate. That is, the interior of the optical box  13 , in which the various optical members (light source unit  11 , cylindrical lens  15 , optical iris  14 , rotational polygon mirror  22 , light directing device  18 , f-θ lens  19 , and mirror  22 ) are disposed, is covered by the lid  12  attached to the optical box  13 . That is, the optical box  13  and its lid  12  are equivalent to the first and second members which make up the housing in which the various optical members are disposed. 
         [0035]      FIG. 3  is a sectional view of the mirror  20 , and its adjacencies (to which mirror  20  is fixed), of the optical scanning device  2  in this embodiment, as seen from the lengthwise end of the mirror  20 , in the direction indicated by an arrow mark A in  FIG. 2 . It shows the structure of the mirror  20  and its adjacencies (to which mirror  20  is fixed). 
         [0036]    The optical box  13  has the mirror seating primary surface  27  (which is parallel to the reflective surface  90  of the mirror  20 ) and mirror seating secondary surface  23  (which hereafter may be referred to simply as primary and secondary seating surfaces  27  and  23 , respectively). The primary seating surface  27  is an integral part of the internal surface of the optical box  13 . The secondary seating surface  23  is perpendicular to the primary seating surface  27 . It also is an integral part of the internal surface of the optical box  13 . 
         [0037]    The reflective surface  90  of the mirror  20  is in contact with the primary seating surface  27 . The bottom surface  91  of the mirror  20 , which is perpendicular to the reflective surface  90 , is in contact with the secondary seating surface  23 . The leaf spring  16  which is the primary regulating means (first regulating means) for regulating the mirror  20  in the normal direction (opposite direction from direction indicated by arrow mark F 1  in  FIG. 4 ) of the reflective surface  90  is provided with a pressing portion  40 , which applies a force F 1  to the mirror  20  to keep the mirror  20  pressed upon the primary seating surface  27 . The optical scanning device  2  is structured so that the pressing portion  40  of the leaf spring  16  faces the opposite surface  28  of the mirror  20  from the reflective surface  90  of the mirror  20 , and also, is placed in contact with the surface  28 . This is the structural arrangement of the optical scanning device  2 , by which the mirror  20  is supported by the optical box  13 . 
         [0038]    The leaf spring  16  is provided with a hole  92 , into which the spring anchoring portion  25  (protrusive portion) of the optical box  13  is fitted to keep the leaf spring  16  fixed to the optical box  13 . In terms of the direction parallel to the axis Z (upward direction) in  FIG. 3 , the edge  41  of the lengthwise end of the leaf spring  16 , which is closer to the lid  12 , is not protrusive upward beyond the edge  93  of the mirror  20 , which is the closest portion of the mirror  20  to the lid  12 . The direction parallel to the axis Z is such direction that is parallel to the rotational axis of the rotational polygon mirror  22 . 
         [0039]    The stopper  24  is an integral part of the internal surface of the optical box  13 , and functions as the secondary regulating member (second regulating member) which regulates the mirror  20  in the movement in terms of the secondary scan direction (indicated by arrow mark V in  FIG. 3 ) of the beam of the laser light. The optical box  13  is structured so that the stopper  24  faces the top surface  94  of the mirror  20 , which is closer to the lid  12  in terms of the secondary scan direction (indicated by arrow mark V in  FIG. 3 ) than the bottom surface of the mirror  91 . Thus, the edge  95  of the mirror  20  remains in contact with the area of contact  24   a  of the stopper  24 , preventing thereby the mirror  20  from shifting in the direction parallel to the axis Z (upward direction in  FIG. 4 ) as shown in  FIG. 4 . 
         [0040]    In terms of the direction indicated by the arrow mark V, the stopper  24  is between the lid  12  and mirror  20 . In terms of the direction perpendicular to the reflective surface  90  (direction perpendicular to direction indicated by arrow mark V in  FIG. 4 ), the stopper  24  overlaps with the mirror  20  at least partially. 
         [0041]    In terms of the direction parallel to the axis Z, the top surface  42  of the stopper  24  is positioned farther from the inward surface  43  of the lid  12  than the edge  93  of the mirror  20 , which is the closest of the four edges of the mirror  20  which extend in the primary scan direction (parallel to axis Y), to the lid  12 . 
         [0042]    Also in terms of the direction parallel to the axis Z, the edge  41  of the leaf spring  16  (primary regulating member), which is closest to the lid  12 , of the edges of the leaf spring  16 , is positioned farther from the inward surface  43  of the lid  12 , than the edge  93  of the mirror  20 . 
         [0043]    Therefore, in terms of the direction parallel to the axis Z (upward in  FIG. 3 ), neither the edge  41  of the lengthwise top end of the leaf spring  16  (as primary regulating member), nor the top surface  42  of the stopper  24 , are above the edge  93  of the mirror  20 , which is the closest portion of the mirror  20  to the lid  12 . 
         [0044]    Referring to  FIG. 3 , in terms of the secondary scan direction (indicated by arrow mark V in  FIG. 3 ) of the beam of laser light, there is provided a gap δ between the top surface  94  of the mirror  20 , which is the closest of the surfaces of the mirror  20 , to the lid  12 , and the stopper  24  (as secondary regulating member). 
         [0045]    Referring also to  FIG. 3 , a letter W stands for the length of the reflective surface  90  of the mirror  20 , in terms of the secondary scan direction (indicated by arrow mark V in  FIG. 3 ) of the bean of laser light, and a letter E stands for the effective reflective range of the reflective surface  90 , in terms of the secondary scan direction. Further, a letter D stands for the diameter of the beam L 2  of the laser beam at the reflective surface  90  of the mirror  20 , in terms of the secondary scan direction of the beam of the laser light. In this embodiment, the optical scanning device  2  is structured so that the distance  5  of the above described gap is set so that the following mathematical formula is satisfied: 
         [0000]      δ&lt;( E−D )/2  (1).
 
         [0046]      FIG. 4  shows the state of the optical scanning device  2 , in which the mirror  20  which was in the position shown in  FIG. 3  has moved in the secondary scan direction of the beam of laser light indicated by the arrow mark V in  FIG. 4 , and the edge  95  of the mirror  20  has come into contact with the stopper  24 . In the normal usage, the mirror  20  is prevented by the friction between the reflective surface  90  of the mirror  20  and the primary seating surface  27  which is a part of the internal surface of the optical box  13 , from moving in the secondary scan direction of the beam of laser light indicated by the arrow mark V in  FIG. 4 . 
         [0047]    However, the top surface  94  of the mirror  20  is not under the pressure generated by the pressure applying means such as a spring. Therefore, if the optical scanning device  2  is subjected to an excessive amount of impact, it is possible that the mirror  20  will moves in the direction indicated by the arrow mark V in  FIG. 4 . 
         [0048]    In this embodiment, even if the mirror  20  moves in the direction indicated by the arrow mark V in  FIG. 4 , the maximum distance by which the mirror  20  is allowed to move is the distance δ of the gap. Therefore, as long as the distance δ of the gap satisfies the mathematical equation (1), it does not occur that the beam L 2  misses the effective reflective range E of the reflective surface  90  of the mirror  20 . Further, even if the mirror  20  moves in the direction indicated by the arrow mark V in  FIG. 4 , the angle θ of reflection of the laser beam L 2  at the reflective surface  90  of the mirror  20  does not change. Therefore, it does not occur that the beam L 2  misses the preset point on the peripheral surface of the photosensitive drum  9  in terms of the secondary scan direction. 
         [0049]    Also referring to  FIG. 4 , when the edge  95  of the mirror  20  is in contact with the stopper  24 , there is the gap G, which is roughly several millimeters wide, between the closest edge  93  of the mirror  20  to the lid  12  and the inward surface  43  of the lid  12 . Therefore, it does not occur that the mirror  20  comes into contact with the lid  12 . 
         [0050]    Further, the optical scanning device  2  is structured so that, in terms of the direction parallel to the axis Z, the top surface  42  of the stopper  24  is positioned farther from the inward surface  43  of the lid  12  than the edge  93  of the mirror  20 , which is the closest to the lid  12 , of the four edges of the mirror  20  which extend in the primary scan direction (parallel to axis Y). Further, the optical scanning device  2  is structured so that, in terms of the direction parallel to the axis Z, the closest edge  41  of the leaf spring  16  (as primary regulating member) to the lid  12  is positioned farther from inward surface  43  of the lid  12  than the edge  93  of the mirror  20 . 
         [0051]    Therefore, it is possible to position the inward surface of the lid  12  infinitesimally close to the edge  93  of the mirror  20 , which is the closest portion of the mirror  20  to the lid  12  in terms of the direction parallel to the axis Z, as shown in  FIG. 4 . 
         [0052]    In other words, it is possible to reduce the optical scanning device  2  in its dimension in terms of the direction parallel to the axis Z (upward direction in  FIG. 4 ) which is parallel to the rotational axis of the rotational polygon mirror  22  shown in  FIG. 4 , and therefore, it is possible to reduce the image forming apparatus  1  in size and thickness. Further, the leaf spring  16  (as primary regulating member) presses the mirror  20  only in the direction (indicated by arrow mark F 1  in  FIG. 4 ) which is perpendicular to the mirror seating primary surface  27 , to regulate the mirror  20  in movement. As for the regulation of the movement of the mirror  20  in the direction (opposite from direction indicated by arrow mark V in  FIG. 4 ) perpendicular to the mirror seating secondary surface  23 , the stopper  24  with which the optical box  13  is provided functions as the regulating portion. 
         [0053]    Therefore, this embodiment allows the leaf spring  16  to reduce in size, and therefore, can reduce the leaf spring  16  in cost. In addition, the leaf spring  16  is not required to press the mirror  20  upon both the mirror sealing primary surface  27  and mirror sealing secondary surface  23 . Therefore, the leaf spring  16  may be very simply in shape and structure. Thus, this embodiment can improve an optical scanning device ( 2 ) in quality. 
         [0054]    In this embodiment, the optical scanning device  2  is structured so that the distance between the lid  12  and edge  93  is minimized in terms of the direction parallel to the axis Z. However, this embodiment is not intended to limit the present invention in terms of the structure of the optical scanning device  2 . That is, all that is required of an optical scanning device by the present invention is that, in terms of the primary scan direction (parallel to axis Y), the stopper  24  is positioned farther from the inward surface  43  of the lid  12 , than the edge  93  of the mirror  20 , that is, the closest of the four edges of the mirror  20  (which extend in the primary scan direction) to the lid  12 , and also, that the closest edge portion  41  of the leaf spring  16  (as primary regulating member) to the inward surface  42  of the lid  12  is positioned farther from the edge  93  of the mirror  20  in terms of the preset direction. 
         [0055]    As described above, in this embodiment, the optical scanning device  2  is structured so that in terms of the preset direction which is perpendicular to the primary scan direction (parallel to axis Y), the edge  92  of the mirror  20  is positioned closest to the lid  12 . Thus, this embodiment can reduce an optical scanning device ( 2 ), and an image forming apparatus (a), in dimension in terms of a preset direction which is perpendicular to the primary scan direction (parallel to axis Y) of the optical scanning device ( 2 ). 
       Embodiment 2 
       [0056]    Next, referring to  FIGS. 5-7 , the optical scanning device  2  in the second embodiment of the present invention is described about its structure, with reference to the image forming apparatus equipped with the optical scanning device. The components of the optical scanning device  2  and the components of the image forming apparatus, which are similar in structure to the counterparts in the first embodiment are given the same referential codes, one for one, and are not described. Further, even if a given component of the optical scanning device  2  or image forming apparatus is given a referential code which is different from the one given to the counterpart in the first embodiment, it is not described here as long as it is similar in structure to the counterpart. 
         [0057]      FIG. 5  is a perspective view of the optical scanning device  2  in this embodiment, minus its lid.  FIG. 6  is a perspective view of the mirror  50 , and its adjacencies, of the optical scanning device  2 . It shows the structure of the mirror  50  and its adjacencies, in particular, the portion of the device  2 , to which the mirror  20  of the device  2  is attached.  FIG. 7  is a partial sectional view of the mirror  50 , and its adjacencies, of the optical scanning device  2 . It shows the mirror  50  and its adjacencies, in particular, the portion of the device  2 , to which the mirror  50  is attached. 
         [0058]    The mirror  50  which deflects the beam of laser light deflected by the rotational polygon mirror  22 , toward the preset surface, is fixed to the optical box  53  with the use of a leaf spring  51  having a pair of elastic portions  55  and  56 . More specifically, the leaf spring  51  has the elastic portion  55  (as primary regulating portion) for regulating the mirror  50  in the movement in the direction (indicated by arrow mark F 2  in  FIG. 2 ) perpendicular to the reflective surface  90  of the mirror  50 . Further, the leaf spring  51  has the elastic portion  56  (as secondary regulating portion) for regulating the mirror  50  in the movement in the secondary scan direction (indicated by arrow mark V in  FIG. 7 ) of the beam of laser light. 
         [0059]    Also in this embodiment, the elastic portion  55  (as primary regulating portion) is positioned so that it faces the surface  28  of the mirror  50 , which is the opposite surface of the mirror  50  from the reflective surface  90  of the mirror  50  and is closer to the lid  62  of the optical box  64 . As for the elastic portion  56  (as secondary regulating portion), it is in contact with the top surface  94  of the mirror  50 , which is closer to the lid  62  in terms of the secondary scan direction (indicated by arrow mark V in  FIG. 7 ) of the beam of laser light, than the opposite surface of the mirror  50  from the surface  94 . 
         [0060]    Also in this embodiment, the optical scanning device  2  is structured so that the elastic portion  55  (as primary regulating portion) is positioned farther from the inward surface of the lid  62 , than the edge  61  of the mirror  50 , which is closest to the lid  62 , of the four edges of the mirror  50  which extend in the secondary scan direction (indicated by arrow mark V in  FIG. 7 ). Further, the elastic portion  56  (as secondary regulating portion) also is disposed farther from the inward surface  63  of the lid  62  than the edge  61 . 
         [0061]    Each of the elastic portions  55  and  56  (as primary and secondary regulating portions, respectively) is a piece of long and narrow plate formed of an elastic substance. They extend from the outward side of the lengthwise end of the mirror  50  toward the lengthwise center of the mirror  50  as shown in  FIG. 6 . 
         [0062]    Referring to  FIG. 6 , the leaf spring  51  having the elastic portions  55  and  56  is fixed to the optical box  53  with the use of a small screw  52 . The optical scanning device  2  is structured so that after the fixation of the leaf spring  51  to the optical box  53 , the base portion of the leaf spring  51 , by which the leaf spring  51  is fixed to the optical box  53 , will be on the outward side of the mirror  50  in terms of the lengthwise direction of the mirror  50 . The portion of the bottom wall of the optical box  53 , to which the square base portion  51   a  of the leaf spring  51  is fixed, is provided with a roughly U-shaped edge  54  (in top view), which surrounds the square base portion  51   a  of the leaf spring  51  as the leaf spring  51  is fixed to the bottom wall of the optical box  53 . That is, the square base portion  51   a  of the leaf spring  51  is fitted into the area surrounded by the U-shaped protrusion  54 , and then, is fixed to the bottom wall of the optical box with the use of the small screw  51 . The U-shaped protrusion  54  prevents the problem that as the small screw  52  is rotated to be tightened to fix the leaf spring  51  to the optical box  53 , the leaf spring  51  is rotated by the rotation of the small screw  52 . 
         [0063]    Also referring to  FIG. 6 , the leaf spring  51  is bifurcate. That is, it has two elastic portions  55  and  56 . The surface  28  of the elastic portion  55 , which faces the mirror  50 , is provided with a mirror pressing portion  57 , which was formed by embossing. Next, referring to  FIG. 7 , the pressing portion  57  applies a force F 2  to the mirror  50  to keep the mirror  50  pressed upon the primary seating surface  68 , which is an integral part of the internal surface of one of the walls of the optical box  53 . 
         [0064]    A pressing portion  58 , which is one of the edges of the elastic portion  56 , applies a force F 3  to the mirror  50  to keep the mirror  50  pressed upon the secondary seating surface  69 , which is an integral part of the inward surfaces of the optical box  53 . Referring to  FIG. 7 , the edge  59  of the elastic portion  55 , which is the closest portion of the elastic portion  55 , to the lid  62 , in terms of the direction (upward direction in  FIG. 7 ) parallel to the axis Z, and the edge  60  of the elastic portion  56 , which is the closest portion of the elastic portion  56 , to the lid  62 , in terms of the direction (upward direction in  FIG. 7 ) parallel to the axis Z, do not protrude beyond the edge  61  of the mirror  50 , which is the closest portion of the mirror  50  to the lid  62 . 
         [0065]    Thus, like the first embodiment, this embodiment also makes it possible to position the lid  62  infinitesimally close to the edge  61  of the mirror  50 , which is the closest portion of the mirror  50  to the lid  62 . Further, in this embodiment, the mirror  50  remains pressed upon the secondary seating surface  69  by the pressing portion  58 . Therefore, it does not occur that the mirror  50  is moved in the direction indicated by the arrow mark V in  FIG. 7 , by impact. Thus, this embodiment can further reduce an optical scanning device in the gap G between the inward surface  63  of the lid  62 , and the edge  61  of the mirror  50 , which is closest portion of the mirror  50  to the lid  62 , than the first embodiment. 
         [0066]    Further, referring to  FIG. 5 , the optical scanning device  2  is provided with the pair of leaf springs  51 , which are disposed at both lengthwise ends of the mirror  50 , one for one. Further, referring to  FIGS. 6 and 7 , the elastic portion  55  (as primary regulating portion) extends in parallel to the lengthwise direction (parallel to axis Y in  FIG. 7 ) which is parallel to the primary scan direction. 
         [0067]    Therefore, this embodiment makes it possible to position the inward surface  64   a  of the external wall  64  of the optical box  13 , infinitesimally close to the edge  65  of the mirror  50 , which is the closest portion of the mirror  50  to the external wall  64 , in terms of the direction parallel to the axis X. Thus, this embodiment makes it possible to reduce an optical scanning device ( 2 ) in dimension in terms of the direction parallel to the axis X in  FIG. 7  (left-right direction in  FIG. 7 ). Otherwise, the optical scanning device  2  in this embodiment is the same in structure as the one in the first embodiment. Further, this embodiment can provide the same effects as the first embodiment. 
       Embodiment 3 
       [0068]    Next, referring to  FIG. 8 , the optical scanning device in the third embodiment of the present invention is described about its structure. The components of the optical scanning device in this embodiment, which are the same in structure as the counterparts in the preceding embodiments are given the same referential codes as those given to the counterparts, one for one, and are not described. Further, even if a given component of the optical scanning device in this embodiment is given a referential code which is different from the one given to the counterpart in the first embodiment, it is not described as long the given component is same in structure as the counterpart in the preceding embodiments. 
         [0069]    This embodiment is a modification of the second embodiment. In the case of the optical scanning device in the second embodiment, which is shown in  FIG. 7 , the beam L 2  of laser light (beam of light) is reflected by the mirror  50  toward the bottom surface of the optical box  53 , which is on the opposite side of the optical box  50  from the lid  62  of the box  50 . Further, the photosensitive drum  9 , on the peripheral surface of which an electrostatic image is formed, is below the optical scanning device  2 . 
         [0070]    Referring to  FIG. 8 , in this embodiment, the beam L 2  of laser light (beam of light) is reflected by the reflective surface  90  of the mirror  102  toward the lid  115 , passes through the window  100 , with which the lid  115  is provided. Then, it forms an electrostatic latent image on the peripheral surface of the photosensitive drum  9  disposed above the optical scanning device  2 . 
         [0071]    Referring again to  FIG. 8 , the lid  115  in this embodiment is provided with a dust cover  101 , which is formed of transparent glass and covers the window  100 . 
         [0072]    The mirror  102 , which reflects the beam of laser light deflected by the rotational polygon mirror  22 , is fixed to the optical box  104  with the use of a leaf spring  103  having a pair of elastic portions  106  and  107 . More specifically, the leaf spring  103  has the elastic portion  106  (as primary regulating portion) which regulates the mirror  120  in the movement in the primary scan direction (opposite direction from direction indicated by arrow mark F 8  in  FIG. 8 ) which is perpendicular to the reflective surface  90  of the mirror  102 . The leaf spring  103  has also the elastic portion  106  (as secondary regulating portion) which regulates the mirror  102  in the movement in the secondary scan direction (indicated by arrow mark V in  FIG. 8 ). 
         [0073]    In this embodiment, the optical scanning device  2  is structured so that the elastic portion  106  (as primary regulating member) faces the reflective surface  90  of the mirror  102 , which is closer to the lid  115  than the opposite surface  28  of the mirror  102  from the reflective surface  90 , and also, so that the elastic portion  107  (as secondary regulating portion) is placed in contact with the top surface  94  of the mirror  102 , which is closer to the lid  115  in terms of the primary scan direction (indicated by arrow mark V in  FIG. 8 ) than the opposite surface of the mirror  102  from the top surface  94 . 
         [0074]    The elastic portion  106  (as primary regulating portion) is positioned farther from the inside wall  43  of the lid  115  than the edge  114  of the mirror  102 , which is closest to the lid  115 , of the four lengthwise edges of the mirror  102 , which extend in the secondary scan direction (indicated by arrow mark V in  FIG. 8 ) of the beam of light. Further, the elastic portion  107  (as secondary regulating member) is positioned farther from the inward surface  43  of the lid  115  than the edge  114 . 
         [0075]    Also in this embodiment, the elastic portion  106  (as primary regulating portion), and the elastic portion  107  (as secondary regulating portion), are long and narrow. Referring to  FIG. 8 , the elastic portions  106  and  107  extend from the outward side of the mirror  102  toward the center of the mirror  102 , in terms of the lengthwise direction of the mirror  102 . 
         [0076]    The leaf spring  103  having the elastic portions  106  and  107  which are integral parts of the leaf spring  103  is fixed to the optical box  104  with the use of the small screw  52  shown in  FIG. 6 , like the leaf spring  51  in the above described second embodiment. That is, the portion of the leaf spring  103 , by which the leaf spring  103  is fixed to the optical box  104  with the use of the small screw  52 , is on the outward side of the mirror  102  in terms of the lengthwise direction of the mirror  102 . The inward surface of the bottom wall of the optical box  104  is provided with a protrusive portion  54 , which is roughly U-shaped (in top view). The square base portion  51   a  of the leaf spring  103 , by which the leaf spring  103  is fixed to the optical box  104 , is placed on the bottom surface of the optical box  104  in such a manner that it fits into the area surrounded by the protrusive portion  54 , whereby it is prevented that when the small screw  52  is rotated to be tightened, the leaf spring  103  is rotationally moved by the rotation of the small screw  52 . 
         [0077]    Referring to  FIG. 8 , the leaf spring  103  also is bifurcated, having two prongs, that is, the elastic portions  106  and  107 . The elastic portion  106  is provided with a mirror pressing portion  108  which is on the surface of the elastic portion  106 , which faces the reflective surface  90  of the mirror  102 . The pressing portion  108  is formed by embossing. The pressing portion  108  applies a force F 8  to the mirror  102  to keep the mirror  102  pressed upon the primary seating surface  109 , which is an integral part of the inward surface of the optical box  104 . 
         [0078]    A mirror pressing portion  110 , which is one of the edges of the elastic portion  107 , applies a force F 9  to the mirror  102  to keep the mirror  102  pressed upon the secondary seating surface  111 , which is an integral part of the internal surface of the optical box  104 . Referring to  FIG. 8 , the edge  112  of the elastic portion  106 , which is the closest portion of the elastic portion  106  to the lid  115 , and the edge  113  of the elastic portion  107 , which is the closest portion of the elastic portion  107  to the lid  115 , are not protrusive upward beyond the edge  114  of the mirror  102 , which is the closest portion of the mirror  102  to the lid  115 , in terms of the direction parallel to axis Z (upward in  FIG. 8 ). Otherwise, the optical scanning device  2  in this embodiment is the same in structure as the optical scanning device  2  in the preceding embodiments, and the effects of this embodiment are the same as those of the preceding embodiments. 
       Embodiment 4 
       [0079]    Next, referring to  FIGS. 9 and 10 , the optical scanning device in the fourth embodiment of the present invention is described about its structure. The components of the optical scanning device in this embodiment, which are the same in structure as the counterparts in the preceding embodiments, are given the same referential codes and those given to the counterparts, one for one. Further, even if a given components of the optical scanning device in this embodiment is given a different referential code from the one given to the counterparts in the preceding embodiments, it is not described as long as it has the same name as the counterpart. 
         [0080]    This embodiment is another modification of the second embodiment described above. In the second embodiment, the leaf spring  51  is bifurcated, having the elastic portions  55  and  56  (as primary and secondary regulating portions, respectively). 
         [0081]    Referring to  FIGS. 9 and 10 , in this embodiment, the optical scanning device is provided with a leaf spring  96  (as primary regulating member) and a leaf spring  97  (as secondary regulating member), which are independent from each other. Referring to  FIG. 9 , the portion  96   a  of the leaf spring  96 , by which the leaf spring  96  is fixed to the optical box  53 , is provided with a square hole  96   b , through which the protrusion  53   a , with which the optical box  53  is provided, is put to fix the leaf spring  96  to the optical box  53 . 
         [0082]    Referring to  FIG. 10 , the leaf spring  96  fixed to the optical box  53  keeps the mirror  50  pressed on the primary seating surface  98 , which is a part of the internal surface of the optical box  53 , by applying a force F 4  to the mirror  50 . Further, the leaf spring  97  fixed to the optical box  53  by the small screw  52  keeps the mirror  50  pressed upon the secondary seating surface  99 , which is a part of the internal surface of the optical box  53 , by applying a force F 5  to the mirror  50 . 
         [0083]    Also in this embodiment, the mirror  50  for reflecting the beam of laser light deflected by the rotational polygon mirror  22 , is fixed to the optical box  53  by the leaf springs  96  and  97 . The leaf spring  96  (as primary regulating member) which is an elastic member regulates the mirror  50  in the movement in the direction (opposite from direction indicated by arrow mark F 4  in  FIG. 10 ) perpendicular to the reflective surface  90  of the mirror  50 . The leaf spring  97  (as secondary regulating member) which is an elastic member regulates the mirror in the movement in the secondary scan direction (opposite from direction indicated by arrow mark F 5  in  FIG. 10 ). 
         [0084]    Further, the optical scanning device is structured so that the leaf spring  96  (as primary regulating member) opposes the surface  28  of the mirror  50 , which is the opposite surface of the mirror  50  from the reflective surface  90  of the mirror  50  and is closer to the lid  62  than the reflective surface  90 , and also, so that the leaf spring  97  (as secondary regulating member) is placed in contact with the top surface  94  of the mirror  50 , which is closer to the lid  62  in terms of the secondary scan direction (indicated by arrow mark F 5  in  FIG. 10 ) of the beam of light than the opposite surface of the mirror  50  from the top surface  94 . 
         [0085]    Further, the leaf spring  96  (as primary regulating member) is positioned farther from the inward surface  63  of the lid  62  than the edge  61  of the mirror  50 , which is closest to the lid  62 , of the four long edges of the mirror  50 , which correspond in position to the four corners of the cross-sectional view of the mirror  50  and extend in the direction parallel to the secondary scan direction (opposite from direction indicated by arrow mark F 5  in  FIG. 10 ) of the scanning beam of light. Further, the leaf spring  97  (as secondary regulating member), and the top surface  52   a  of the small screw  52 , are positioned farther from the inward surface of the lid  62  than the edge  61  of the mirror  50 . 
         [0086]    The leaf spring  96  (as primary regulating member) is made of an elastic substance, and is in the form of a long and narrow piece of plate, and so is the leaf spring  97  (as secondary regulating member). Referring to  FIG. 9 , the leaf spring  96  extends in the lengthwise direction of the mirror  50 , from the outward side of the lengthwise end of the mirror  50  toward the center of the mirror  50 . 
         [0087]    Also referring to  FIG. 9 , the leaf spring  97  is fixed to the optical box  53  with the use of the small screw  52 . More concretely, the area of the optical box  53 , to which the leaf spring  97  is fixed by its square base portion  97   a , is surrounded by a protrusive portion  54 , which is roughly U-shaped (in top view). The base portion  97   a  of the leaf spring  97  is fitted into the area surrounded by the protrusive portion  54  to prevent the problem that as the small screw  52  is rotated to be tightened, the leaf spring  97  is rotationally moved by the rotation of the small screw  52 . 
         [0088]    Next, referring to  FIG. 10 , the surface of the leaf spring  96 , which is to face the surface  28  of the mirror  50 , is provided with a mirror pressing portion  57 , which is formed by embossing. It is by this pressing portion  57  that a force F 4  is applied to the mirror  50  to keep the mirror  50  pressed upon the primary seating surface  98 , which is an integral part of the internal surface of the optical box  53 . 
         [0089]    A mirror pressing portion  58 , which is one of the edges of the leaf spring  97 , applies a force F 5  to the mirror  50  to keep the mirror  50  pressed upon the secondary seating surface  99 , which is an integral part of the internal surface of the optical box  53 . Also referring to  FIG. 10 , the edge  59  of the leaf spring  96 , which is the closest portion of the leaf spring  96  to the lid  62 , and the edge  60  of the leaf spring  97 , which is the closest portion of the leaf spring  97  to the lid  62 , and the top surface of the head portion of the small screw  52 , are not protrusive upward beyond the edge  61  of the mirror  50 , which is the closet portion of the mirror  50  to the lid  62  in terms of the direction parallel to the axis Z (upward direction in  FIG. 10 ). 
         [0090]    Thus, this embodiment allows the lid  62  to be placed infinitesimally close to the edge  61  of the mirror  50 , which is the closest portion of the mirror  50  to the lid  62 , in terms of the direction parallel to the axis Z, as does any of the preceding embodiments. Further, in this embodiment, the mirror  50  remains pressed upon the mirror seating secondary surface  99  by the leaf spring  97 , and therefore, it does not occur that the mirror  50  is moved in the opposite direction from the direction indicated by the arrow mark F 5  in  FIG. 10 , by impact. Therefore, this embodiment can further reduce the gap G between the edge  61  of the mirror  50  and the lid  61 . 
         [0091]    Referring to  FIG. 9 , the combination of the leaf springs  96  and  97  is positioned at each of the lengthwise ends of the mirror  50 . The leaf spring  96  (as primary regulating member) extends in the direction parallel to the lengthwise direction (parallel to axis Y) of the mirror  50 . 
         [0092]    Referring to  FIG. 10 , this embodiment allows the surface  64   a , which is the inward surface of a part of the external wall  64  of the optical box  53 , to be placed infinitesimally close to the edge  65  of the mirror  50 , which is the closest portion of the mirror  50  to the surface  64   a . Thus, it allows an optical scanning device to be reduced in dimension in terms of the direction parallel to the axis X (left-right direction) in  FIG. 10 . Otherwise, the optical scanning device  2  in this embodiment is the same in structure as those in the preceding embodiments. That is, this embodiment can provide the same effects as those obtainable by the preceding embodiments. 
       Embodiment 5 
       [0093]    Next, referring to  FIGS. 11 and 12 , the optical scanning device in the fifth embodiment of the present invention is described about its structure. The components of this device, which are the same in structure as the counterparts in the preceding embodiments are given the same referential codes as those given to the counterparts, one for one, and are not described here. Further, as long as a given component of the optical scanning device in this embodiment is the same in structure as the counterpart in the preceding embodiments, it is not described even if it has a different referential code from the one given to the counterpart. 
         [0094]      FIG. 11  is a perspective view of the portion of the optical scanning device  2  in this embodiment, to which the mirror  70  is fixed, and the adjacencies of the portion, and shows the structure of this portion and its adjacencies.  FIG. 12  is a partially sectional view of the portion of the optical scanning device  2  in this embodiment, to which the mirror  70  is fixed, and the adjacencies of the portion, and shows the structure of this portion and its adjacencies. 
         [0095]    The mirror  70  which reflects the beam of laser light deflected by the rotational polygon mirror  22  is fixed to the optical box  72  with the use of the leaf spring  71  having a pair of elastic portions  55  and  56 . The elastic portion  55 , which is the primary regulating portion, is formed of an elastic substance, and regulates the mirror  70  in the movement in the direction (opposite to direction indicated by arrow mark F 6  in  FIG. 12 ) perpendicular to the reflective surface  90  of the mirror  70 . The elastic portion  56  which is the second regulatory portion, regulates the mirror  70  in the movement in the secondary scan direction (indicated by arrow mark F 7  in  FIG. 12 ). 
         [0096]    The base portion  71   a  of the leaf spring  71  is provided with a hole  75 . The optical box  72  is provided with a leaf spring anchoring portion  76 , which is in the form of a protrusion. Thus, the leaf spring  71  is fixed to the optical box  72  by fitting the leaf spring anchoring portion  76  of the optical box  72  into the hole  75  of the base portion  71  of the leaf spring  71 . 
         [0097]    The leaf spring  71  is provided with a pair of elastic portions  55  and  56 , which have mirror pressing portions  73  and  74 , respectively. The pressing portion  73  applies a force F 6  to the mirror  70  to keep the mirror  70  pressed upon the mirror seating primary surface  82 , which is an integral part of the internal surface of the external wall of the optical box  72 . The pressing portion  74  is for applying a force F 7  to the mirror  70  to keep the mirror  70  pressed upon the mirror seating secondary surface  83 , which is an integral part of the inward surface of the external wall of the optical box  72 . The mirror seating secondary surface  82  is the referential surface for positioning the mirror  70  in terms of the secondary scan direction (indicated by arrow mark F in  FIG. 12 ) of the beam of laser light. 
         [0098]    Also in this embodiment, the optical scanning device is structured so that the elastic portion  55  which is the primary regulating portion faces the surface  28  of the mirror  50 , which is the opposite surface of the mirror  50  from the reflective surface  90  of the mirror  50  and is closer to the inward surface of the lid  81  than the reflective surface  90 . As for the secondary seating surface  83  which serves as the referential surface, it is an integral part of the top surface  94  and is positioned so that it faces the top surface  94  of the mirror  50 , which is closer to the inward surface  43  of the lid  81 , in terms of the secondary scan direction (indicated by arrow mark F 7  in  FIG. 12 ), than the bottom surface  91  of the mirror  50 . Further, the elastic portion  56  which is the secondary regulating portion in this embodiment is placed in contact with the bottom surface  91  of the mirror  50 , which is the surface of the mirror  50 , which faces the optical box  72 , on the opposite side of the mirror  50  from the inward surface  43  of the lid  83 , in terms of the secondary scan direction (indicated by arrow mark F 7  in  FIG. 7 ). 
         [0099]    Further, the edge  77  of the elastic portion  55  (as primary regulating portion), which is the closest portion of the elastic portion  55  to, to the inward surface  43  of the lid  81 , is positioned farther from the edge  80  of the mirror  50 , which is closest portion of the mirror  50  to the inward surface  43  of the lid  81 , in terms of the secondary scan direction (indicated by arrow mark F 7  in  FIG. 12 ), of the four edges of the mirror  50 , which extend in the primary scan direction (parallel to axis Y) and correspond in position to the four corners of the mirror  50  (which is rectangular in sectional view). Further, the topmost surface  79  of the mirror anchorage portion  78  having the secondary seating surface  83  which is the referential surface, is positioned farther from the inward surface of the lid  81  than the edge  80  of the mirror  50 . 
         [0100]    The elastic portion  55  which is the primary regulating portion, and the elastic portion  56  which is the secondary regulating portion, are in the form of a long and narrow piece of plate made of an elastic substance. The elastic portion  56  which functions as the secondary regulating portion may be an integral part of the optical box  72 . 
         [0101]    Referring to  FIG. 11 , the leaf spring  71  is bifurcated, having the two elastic portions  55  and  56 . The elastic portions  55  and  56  are provided with mirror pressing portions  73  and  74 , respectively, which oppose the surface  28  of the mirror  50 , which is the opposite surface of the mirror  50  from the reflective surface  90  of the mirror  50 , and the bottom surface  90  of the mirror  50 . Both elastic portions  55  and  56  are formed by embossing. 
         [0102]    Referring to  12 , the mirror pressing portion  73  of the elastic portion  55  applies a force F 6  to the mirror  70  to keep the mirror  70  pressed upon the primary seating surface  82 , which is an integral part of the inward surface of the optical box  72 . The elastic portion  56  applies a force F 7  to the mirror  70  to keep the mirror  70  pressed upon the secondary seating surface  83 , which is an integral part of the inward surface of the optical box  70 . 
         [0103]    Also referring to  FIG. 12 , the edge  77  of the lengthwise end of the elastic portion  55 , which is the closest portion of the elastic portion  55  to the inward surface  43  of the lid  81 , and the topmost surface  79  of the mirror anchorage portion  78  having the secondary seating surface  83 , are not protrusive upward beyond the edge  80  of the mirror  70 , in terms of the direction parallel to the axis Z (upward direction in  FIG. 12 ). That is, in terms of the direction parallel to the axis Z, the edge  80  of the mirror  70  is closest to the inward surface  43  of the lid  81 . Also in terms of the direction parallel to the axis Z, the edge  77  of the elastic portion  55 , and the topmost surface of the mirror anchorage portion  78 , are positioned farther from the lid  80  than the edge  80 . 
         [0104]    Therefore, this embodiment also allows the lid  81  to be positioned infinitesimally close to the edge  80  which is the closest portion of the mirror  70  to the inward surface  43  of the lid  81 . Thus, it allows an optical scanning device to be reduced in size. 
         [0105]    In this embodiment, the optical scanning device  2  was structured so that the lid  81  and edge  80  can be positioned as close as possible to each other, in terms of the direction parallel to the axis Z. However, this embodiment is not intended to limit the present invention in terms of the structure of an optical scanning device. For example, an optical scanning device may be structured so that the edge  80  which is the closest portion of the mirror  70  to the lid  81  is positioned as close as possible to the lid  81  in terms of a preset direction which is perpendicular to the primary scan direction (which is parallel to axis Y). This structural arrangement can also reduce an optical scanning device, and an image forming apparatus employing an optical scanning device, in dimension in terms of a preset direction which is perpendicular to the primary scan direction (direction of axis Y). 
         [0106]    Also in this embodiment, it is by the elastic portion  56  that the mirror  70  is kept pressed upon the secondary seating surface  83 . Therefore, it does not occur that the mirror  70  is moved in the opposite direction from the direction indicated by the arrow mark F 7  in  FIG. 12  by impact. Therefore, this embodiment can further reduce the gap G between the inward surface  43  of the lid  81 , and the edge  80  of the mirror  70 , which is the closest portion of the mirror  70  to the inward surface of the lid  81 , than the first embodiment. 
         [0107]    Further, this embodiment is the same as the second embodiment in that both the mirror pressing portion ( 73 ) for pressing the mirror ( 70 ) toward the primary seating surface ( 82 ), and the mirror pressing portion ( 74 ) for pressing the mirror ( 70 ) toward the secondary seating surface ( 83 ), are integral parts of the leaf spring ( 71 ). In this embodiment, the directions indicated by arrow marks B and C, which are the directions in which the elastic portions  55  and  56  having the two mirror pressing portions  73  and  74 , respectively, bend, are parallel to the planes X and Z which coincide with the axes X and Z, respectively. Therefore, it does not occur that the leaf spring  71  becomes twisted. Therefore, it is ensured that the preset amount of pressure which is applied to the mirror  70  by the leaf spring  71  to keep the mirror  70  pressed upon the mirror sealing surface remains stable. Otherwise, this embodiment is the same as the preceding embodiments, in the structure of the components, such as the mirror regulating secondary member (portion), of the optical scanning device. The effects of this embodiment are the same as those obtainable by the preceding embodiments. 
         [0108]    The preceding embodiments of the present invention are not intended to limit the present invention in scope. The present invention encompasses various modifications of the preceding embodiments, within the gist of the present invention. For example, the regulating member such as the mirror regulating secondary member does not need to be a leaf spring; it may be an integral part of the optical box. Further, the means for fixing the leaf spring to the optical box may be different in structure from those in the preceding embodiments. 
         [0109]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
         [0110]    This application claims priority from Japanese Patent Application No. 015921/2013 filed Jan. 30, 2013 which is hereby incorporated by reference.