Abstract:
A support apparatus is configured to ease the series of work operations for adjusting the height of laser scan unit. The support apparatus support laser scan unit which is utilized within an image forming apparatus. The support apparatus comprises mounting plate which has laser scan unit mounted thereon. Laser scan unit cooperates with a photo conductor when laser scan unit is mounted on mounting plate. The support apparatus comprises support wall which supports mounting plate within cabinet. Support wall extends vertically within the image forming apparatus. Adjustment mechanism is positioned along the vertical extent of the support wall and adjusts a height of an end of mounting plate.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a support apparatus for supporting a laser scan unit that irradiates the surface of an image support body with a light beam, said support apparatus supporting the laser scan unit through support members, within an image forming apparatus, facing the image support member, and further relates to the image forming apparatus comprising the image support body, the laser scan unit, and support members therein.  
       DESCRIPTION OF RELATED ART  
       [0002]     A conventional image forming apparatus (printers, image transmission devices, photocopiers and the like) is equipped with a laser scan unit that creates an undeveloped electrostatic image on the surface of a light-sensitive body by exposing the surface with a light beam. This type of laser scan unit is supported by a support apparatus that can finely adjust the scanning direction so that the light bean scans a specific point on the light-sensitive body. After the laser scan unit is positioned at the appropriate point, the laser scan unit is tightened at the appropriate point by screws (see reference documents 1 and 2).  
         [0000]     [Reference Document 1] 
         [0003]     Japanese Laid Kokai (laid open) Patent Publication H10-153744 ( FIG. 1 ).  
         [0000]     [Reference Document 2] 
         [0004]     Japanese Kokai (laid open) Patent Publication 2002-162590 ( FIG. 2 )  
         [0005]     Because a conventional support apparatus supports the laser scan unit through a frame that must be secured from the top by screws, it becomes necessary to adjust the position of the laser scan unit and to tighten the laser scan unit by the screws from the region above the laser scan unit. This type of apparatus presents less of a problem if the laser scan unit is mounted within the upper region of the image forming apparatus. However, various problems can occur if the laser scan unit is structured so as to be mounted in the center or at the bottom of the image forming apparatus.  
         [0006]     To explain further, mounting the laser scan unit at the center or bottom of the image forming apparatus requires that the technician assemble the image forming apparatus, by continuing to peer down into the image forming apparatus from an opening at the top, before the laser scan unit can be adjusted. This reduces the productivity of the adjustment operation. Also, the adjustment cannot be conducted after the device in which the laser scan unit is installed has been completely assembled because components that are located in the image forming apparatus over the laser scan unit must be removed in order to provide access to the laser scan unit for the adjustment. Moreover, when printing a test image, the laser scan unit must be covered by the components located above the laser scan unit in order to prevent outside-light from irradiating the light-sensitive element. This makes the adjustment of the laser scan unit, which must be conducted while checking the results of test prints, an extremely troublesome job.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention puts forth a support apparatus and an image forming apparatus to eliminate the aforesaid problems in the current art. The main purpose of the support apparatus and the image forming apparatus is to allow the technician to do the aforesaid series of operations with a comfortable position, to allow adjustment of the laser scan unit even after the device into which the laser scan unit is installed has been completely assembled, and to allow the technician to conveniently produce test images while conducting the adjustment operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention is further described in the detailed description which follows, with reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:  
         [0009]      FIG. 1  is a diagrammatic cross section of an image forming apparatus of the type to which the present invention can be appropriately applied.  
         [0010]      FIG. 2  is a diagrammatic cross section of the laser scan unit shown in  FIG. 1 .  
         [0011]      FIG. 3  is a perspective view of the photo conductor and laser scan unit shown in  FIG. 1 .  
         [0012]      FIG. 4  is a top view of the structure that supports the laser scan unit shown in  FIG. 1 .  
         [0013]      FIG. 5  is a side view of the structure supporting the laser scan unit shown in  FIG. 1 .  
         [0014]      FIG. 6  is a detail frontal view of the adjustment structure of  FIG. 5 .  
         [0015]      FIG. 7  is a frontal view of the  FIG. 1  image forming apparatus with covers removed.  
         [0016]      FIG. 8  is a is a cross section of the third mounting flange of the laser scan unit shown in  FIG. 2 .  
         [0017]      FIG. 9  is a side view of the laser scan unit support structure shown in  FIG. 1 .  
         [0018]      FIG. 10  is a perspective view on an additional embodiment of the laser scan unit support structure.  
         [0019]      FIG. 11  is a top view of the laser scan unit support structure shown in  FIG. 10 .  
         [0020]      FIG. 12  is a rear view of the laser scan unit support structure as shown in  FIG. 10 .  
         [0021]      FIG. 13  is a side view of the laser scan unit support structure as shown in  FIG. 10 .  
         [0022]      FIG. 14  is a partial perspective view of the laser scan unit support structure shown in  FIG. 10 .  
         [0023]      FIG. 15  is a partial side view of the laser scan unit support structure shown in  FIG. 10 .  
         [0024]     FIGS.  16 (A) and  16 (B) are scanning line adjustment diagrams relating to the laser scan unit support structure shown in  FIG. 10 .  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]     The embodiments of the present invention are explained in the following, in reference to the above-described drawings.  
       First Embodiment  
       [0026]      FIG. 1  is a diagrammatic cross section of an image forming apparatus of the type to which the present invention can be appropriately applied. The image forming apparatus includes photo conductor (image support body)  1 . In the vicinity of photo conductor  1 , electrostatic roller  2  is arranged. Electrostatic roller  2  applies a uniform electrostatic charge to the surface of photo conductor  1 . Laser scan unit  3  forms a undeveloped electrostatic image on the surface of photo conductor  1  by exposing the surface with a light beam. Developer unit  5  includes imaging roller  4  that applies toner to develop the undeveloped electrostatic image on photo conductor  1 . Transfer roller  6  transfers the toner image on photo conductor  1  to recording paper. Cleaning unit  7  cleans the surface of photo conductor  1 . After passing between photo conductor  1  and transfer roller  6 , recording paper from paper storage  8  exits through delivery chute  10  via fusing unit  9 . In addition, scanner  11  is installed above the image forming apparatus in order to scan an original document for copying or sending as a facsimile transmission.  
         [0027]     printing apparatus  13 , which includes photo conductor  1  (on which the image is generated), laser scan unit  3 , and other components, is located beneath delivery chute  10  in the relatively lower region of cabinet  12 . Laser scan unit  3  is oriented in the approximate horizontal direction facing photo conductor  1 , and the axis of light is oriented in the approximate horizontal direction. The light beam emitted by laser scan unit  3  travels through the passage between developer unit  5  and electrostatic roller  2  to irradiate photo conductor  1 .  
         [0028]      FIG. 2  is a diagrammatic cross section of the laser scan unit shown in  FIG. 1 . Laser scan unit  3 , which can also be referred to as an LSU, includes semiconductor laser (light source)  21 . Semiconductor laser  21  emits a laser beam. Cylindrical lens (first optical system)  22  focuses the light beam emitted from semiconductor laser  21 . Polygon mirror  23  deflects the focused light beam in order to scan it across the surface of photo conductor  1 . Lens (second optical system)  24  forms the deflected and scanned light beam from polygon mirror  23  onto the surface of photo conductor  1 . Synchronizing sensor  25  monitors the timing of the laser beam, and housing  26  serves as a cover.  
         [0029]     First and second mounting flanges  27  and  28  are attached to opposing edges of laser scan unit  3  in the scanning direction. Also, third mounting flange  29  is provided at the approximate center and oriented in the scanning direction on the side of laser scan unit  3  opposite to photo conductor  1 .  
         [0030]      FIG. 3  is a perspective view of the photo conductor and laser scan unit shown in  FIG. 1 . Laser scan unit  3 , by means of the deflector installed therein, scans the surface of photo conductor  1  while a secondary scanning action is executed by the rotation of photo conductor  1 , which is circular in cross section, around its axial centerline  31 .  
         [0031]      FIG. 4  is a top view of the support structure of the laser scan unit shown in  FIG. 1 . First support sidewall  42  is provided on one sidewall of cabinet  12  (within which the image forming apparatus is installed), and second support sidewall  43  is provided on the opposing sidewall. First and second mounting plates  44  and  45  are suspended between first and second support sidewalls  42  and  43  on the approximate horizontal plane along the scanning axis of laser scan unit  3 .  
         [0032]     Laser scan unit  3  is supported by first and second mounting plates  44  and  45 , and attached to first mounting plate  44  by means of screws  46  and  47  which fasten first and second mounting flanges  27  and  28  so as to form a one-piece structure with first mounting plate  44 . Moreover, laser scan unit  3  is attached to second mounting plate  45  by means of fastening fixture  48  that secures mounting flange  29  thereto, mounting flange  29  being located on laser scan unit  3  on the side opposite photo conductor  1 .  
         [0033]      FIG. 5  is a side view of the support structure of the laser scan unit shown in  FIG. 1 . End part  44   a,  which is one extremity of first mounting plate  44 , is fixed to first support sidewall  42  through L-bracket  50  which is “L” shaped in cross section. L-bracket  50  and first mounting plate  44  form frame member  51 , to which laser scan unit  3  is fixedly attached, as a single movable structure. One end of L-bracket  50  is connected to first mounting plate  44  through screw  52 , and the other end of L-bracket  50 , which passes through orifice  54  in plate part  53  of first support sidewall  42  and also extends through outer surface  42 a of first support structure  42 , is attached to first support sidewall  42  by screws  55 .  
         [0034]     Adjustment mechanism  56 , which provides means of adjusting the scanning position of laser scan unit  3 , is provided at outer surface  42 a of first support sidewall  42 , and is oriented at an approximate right angle to the scanning plane of laser scan unit  3 ; that is, adjustment mechanism  56  is located so as to displace end part  44   a  of first mounting plate  44  in the vertical direction.  
         [0035]     End part  44   b,  which is the other extremity of first mounting plate  44 , is fixedly attached to second support sidewall  43  through screw  59  that secures end part  44   b  to support flange  58 . Support flange  58  protrudes from the inner surface of second support sidewall  43  as a result of being bent inward along an approximately horizontally oriented bend line. When adjustment is executed through adjustment mechanism  56 , the vertical bending movement of support flange  58  on second support sidewall  43  allows the positional displacement of end part  44   a  of first mounting plate  44 .  
         [0036]     As shown in  FIG. 3 , the position of laser scan unit  3  can be set by adjustment mechanism  56  through the adjustment of one end of laser scan unit  3  along the scanning axis, that is, an adjustment that vertically displaces end part  44   a  of first mounting plate  44  at an approximate right angle to the scanning direction. The attitude of laser scan unit  3  is supported at the other end of the scanning direction, that is, through the support provided by end part  44   b  at the other end of mounting plate  44 . Therefore, the scanning position, particularly corrections to the inclination angle of the scanning direction, can be set in relation to axial centerline  31  of photo conductor  1  which serves as the reference line. The correction of the scanning direction can also be effective as means of compensating for paper inclination generated by the paper transport mechanism.  
         [0037]      FIG. 6  is a detailed frontal view of the adjustment mechanism shown in  FIG. 5 . Adjustment mechanism  56  includes adjuster lever  61  which is able to displace first mounting plate  44  in relation to first support sidewall  42  through one edge of adjuster lever  61 . The one edge of adjuster lever  61  contacts L-bracket  50  which is attached to first mounting plate  44 . Adjuster lever  61  is pivotally attached to support sidewall  42  through stub shaft  62 , incorporates cam  64  which extends upward from bearing  63  of stub shaft  62  to ride against L-bracket  50 , indexing arm  65  that extends horizontally from bearing  63 , and grip flange  66  which is formed on the leading edge of indexing arm  65 .  
         [0038]     Cam  64  is formed as a curved external surface with a continually changing radius in relation to stub shaft  62 , and can move L-bracket  50  in an upward or downward direction corresponding to the rotational angle of adjuster lever  61 . In other words, manually grasping grip flange  66  of adjuster lever  61  and moving it downward rotates adjuster lever  61  counter-clockwise (as viewed in  FIG. 6 ) with the result that cam  64  pushes L-bracket  50  in an upward direction. Conversely, moving grip flange  66  upward rotates adjuster lever  61  in a clockwise direction (as viewed in  FIG. 6 ) which has the effect of allowing L-bracket  50  to move downward as a result of the weight applied by laser scan unit  3  which is attached thereto.  
         [0039]     Vertically oriented slotted holes  67  are formed in L-bracket  50  to allow the vertically adjustable fixed attachment of L-bracket  50  to first support sidewall  42  through screws  55 , and thereby allowing the height of L-bracket  50  to be adjusted by loosening screws  55 . T-shaped plate  68  is placed between L-bracket  50  and the heads of screws  55  to allow screws  55  to be tightened to a higher torque value.  
         [0040]     Guide slots  70  are formed in L-bracket  50 , and guide pins  69  protrude from first support sidewall  42 . The insertion of guide pins  69  into guide slots  70  restricts the lateral movement of L-bracket  50  while allowing the vertical positioning adjustment.  
         [0041]     Indicator line  73 , which is scribed on the end portion of indexing arm  65  opposite to index scale  72 , and index scale  72 , which is scribed on first support sidewall  42 , form a mechanical display that shows the amount of adjustment applied to laser scan unit  3 , said adjustment being indicated through the relative angle of adjuster lever  61  in respect to first support sidewall  42 . This indicator mechanism makes the adjustment operation easier because the technician is able to execute the adjustment while checking the extent that laser scan unit  3  has been moved. This is especially convenient in cases where laser scan unit  3  is to be replaced because the position of laser scan unit  3  can be verified before replacement, and the adjustment applied to the newly installed laser scan unit  3  can begin at the position of the previous laser scan unit  3 , thus it is possible to shorten the time for the adjustment.  
         [0042]     The radial length of indexing arm  65  of adjuster lever  61  is established to provide an enlarged visual indication, through indictor line  73 , of the extent of adjustment applied to laser scan unit  3 . In other words, stub shaft  62  of adjuster lever  61  is located nearer to cam  64  than to indicator line  73 . This allows indicator line  73  to move through a wider indication range in respect to the amount of vertical displacement of L-bracket  50 , which is in contact with cam  64 , and in respect to the corresponding extent of adjustment of laser scan unit  3 . For example, 0.1 mm of movement of L-bracket  50  may be indicated by a 1 mm movement of indicator line  73 . Moreover, the locations of the indexed scale and indicator line may be reversed, that is, the indexed scale may be provided on the adjuster lever and indicator line on the support sidewall.  
         [0043]     Indexed scale  72 , which is scribed into first support sidewall  42 , includes index reference line  75  which is longer than the other indexing lines as means of denoting a reference position for laser scan unit  3 . The adjustment operation starts by aligning indicator line  73  with index reference line  75 . A test print is run, and then the scanning position is determined based on the test print. Adjustments are made in the necessary direction while noting the position of indicator line  72 .  
         [0044]     Position securing screw  76  and looseness suppression screw  77  are attached to adjuster lever  61 .  
         [0045]      FIG. 7  is a frontal view of the image forming apparatus shown in  FIG. 1  but with the covers removed. As explained previously, adjuster lever  61  is attached to the external surface of first support sidewall  42 . The grip part of adjuster lever  61  can be easily grasped, and the lever conveniently operated, when adjuster lever  61  is exposed during assembly when covers  78  and  79  (which comprise part of cabinet  12 ) are removed, and during maintenance when covers  78  and  79  are open. Furthermore, it becomes possible to use the indicator line on adjuster lever  61  and the indexing scale to read the amount of adjustment applied to laser scan unit  3 .  
         [0046]     While the adjustment operation requires that the screws be loosened and tightened, screws  55 , which secure L-bracket  50  to first support sidewall  42  as shown in  FIG. 5  and  6 , can be easily installed, tightened, and loosened because their shank parts are oriented horizontally and their head parts lie against the external surface of first support sidewall  42 .  
         [0047]      FIG. 8  is a cross section illustrating the third mounting flange of the laser scan unit shown in  FIG. 2 . As-noted previously, laser scan unit  3  is attached to second mounting plate  45  through spring-loaded fastening fixture  48  that allows attitude changes in laser scan unit  3  made through the adjustment mechanism. Spring-loaded fastening fixture  48  includes guide part  81  which allows the movement of third mounting flange  29  only in the vertical direction at a right angle to the light emission axis of laser scan unit  3 , and spring  82  that pressurizes third mounting flange  29  against second mounting plate  45  at the initial position.  
         [0048]     Guide part  81  fixedly attaches to threaded hole  83  formed in second mounting plate  45 , and thru-hole  84  is provided in third mounting flange  29  of laser scan unit  3  in order to allow the vertical displacement of third mounting flange  29  of guide part  81 . Spring  82  is installed, in a compressed state, between third mounting flange  29  and stop washer  85  which is located opposite and above second mounting plate  45 , in order to clamp third mounting flange  29  of scanning gun  3  in a downward direction against second mounting plate  45 .  
         [0049]     Thus structured, spring-loaded fastening fixture  48  allows the vertical movement of third mounting flange  29  of laser scan unit  3  while restricting its horizontal movement, therefore regulating the distance between laser scan unit  3  and photo conductor  1 . Spring-loaded fastening fixture  48  secures laser scan unit  3  in a manner that allows its adjustment to a desired position, therefore maintaining precision focus of the light beam emitted from laser scan unit  3  on the imaging surface of the image support body (photo conductor  1 ) regardless of the operation of the adjustment mechanism.  
         [0050]      FIG. 9  is a side view of the laser scan unit support structure shown in  FIG. 1 . The upward displacement of end part  44   a  of first mounting plate  44 , brought about through the operation of adjustment mechanism  56 , has the effect of upward moving of third mounting flange  29  of laser scan unit  3  and thus compressing spring  82 . The downward displacement of end part  44   a  of first mounting plate  44 , brought about through the operation of adjustment mechanism  56 , has the effect of lowering third mounting flange  29  and thus decompressing spring  82 . Adjustment mechanism  56  displaces first mounting plate  44  through a curved path, and allows precision altitude changes of laser scan unit  3 .  
       Second Embodiment  
       [0051]      FIG. 10  is a perspective drawing of a second embodiment of the support mechanism of the laser scan unit as prescribed by the invention.  FIG. 11  is a top view,  FIG. 12  is a rear view, and  FIG. 13  is a side view of the support mechanism of the laser scan unit shown in  FIG. 10 .  
         [0052]     In a similar structure to that described for the previous embodiment, laser scan unit  3  is supported by forward and rearwardly positioned first and second mounting plates (first and second support members)  103  and  104 , said members  103  and  104  extending approximately horizontally along the scanning direction of laser scan unit  3 , between first support sidewall  101  which is located on one side of the image forming apparatus cabinet, and second support sidewall  102  which is located on the other side of said cabinet.  
         [0053]     As shown in  FIG. 11 , similar to the first mounting plate  44  structure of the previous embodiment, the forward portion of laser scan unit  3 , located in opposition to photo conductor  1 , is fixed on first mounting plate by first and second mounting flanges  111  and  112  and screws  113  and  114 . As shown in  FIG. 10 , L-bracket  121 , which is similar in structure to previously noted L-bracket  50 , is provided on end part  103   a  which forms one end of first mounting plate  103 .  
         [0054]     As shown in  FIGS. 12 and 13 , laser scan unit  3  also attaches to second mounting plate  104  through screws  118  and third mounting flange  117 , which is located on the rear side of laser scan unit  3 , opposite to photo conductor  1 . The rear part of laser scan unit  3  is supported by second mounting plate  104 . Note that this structure differs that of the previously embodiment in that third mounting flange  117  attaches directly and fixedly to second mounting plate  104  through screws  118 .  
         [0055]      FIG. 14  is a perspective view of a part of the laser scan unit support structure shown in  FIG. 10 . First adjustment mechanism  122 , which is essentially similar to adjustment mechanism  56  of the previous embodiment, is provided on external surface  101   a  of fist support sidewall  101 . As shown in  FIG. 10 , the operation of adjuster lever  123  displaces end part  103  a of first mounting plate  103  in the vertical direction at an approximate right angle to the scanning axis, pivots laser scan unit  3  on end part  103   b  on the other end of first mounting plate  103 , and thus forms a mechanism able to adjust the attitude of laser scan unit  3 .  
         [0056]     As shown in  FIG. 14 , flange  131 , which is a bend-formed L-shaped extremity of end part  104   a  of second mounting plate  104 , attaches to the inner surface of first support sidewall  101  through screws  132 . Second adjustment mechanism  141 , which is provided at external surface  101   a  of first support sidewall  101 , is able to adjust the scanning position of laser scan unit  3  through the vertical displacement of end part  104   a  of second mounting plate  104 .  
         [0057]     As shown in  FIG. 10 , flange  133 , which is formed as an L-shaped part of end part  104   b  at the other end of second mounting plate  104 , attaches to the inner surface of second support sidewall  102  through screws  134 . As end part  104   b  of second mounting plate  104  rigidly connects with and second support sidewall  102 , raising or lowering end part  104   a  of second mounting plate  104 , as a result of the operation of second adjustment mechanism  141 , has the effect of having second mounting plate  104  vertically bent and the effect of having second mounting plate  104  slightly twisted around its centerline. Furthermore, end part  104 b, which forms the other end of second mounting plate  104 , may be structured to pivot around screw  134 .  
         [0058]     As can be seen in  FIG. 14 , tab  144 , which is formed as an extension of end part  104   a  of second mounting plate  104 , protrudes through window  143 , which is formed in first support sidewall  101 , and pasts the outer surface of sidewall  101 . Window  143  allows the vertical movement of tab  144  within a predetermined range. Loosening screw  132  allows flange  131  to pivot on screw  132  which has the effect of displacing end part  104   a  of second mounting plate  104  in the vertical direction.  
         [0059]     Second adjustment mechanism  141  incorporates adjuster wheel  146  that displaces second mounting plate  104 , through contacting with tab  144 , in relation to first support sidewall  101 . Adjuster wheel  146  pivots on the axial center of center screw  147  (i.e. support shaft) which is attached to first support sidewall  101 , said pivoting movement being enabled by hand or through the use of an appropriate tool.  
         [0060]      FIG. 15  is a side view of the relevant part of the laser scan unit support mechanism shown in  FIG. 10 . Adjuster wheel  146  has a varying radius whereby different points on the periphery of adjuster wheel  146  have different radial distances to center screw  147 . This structure differs from first adjustment mechanism  122  in that adjuster wheel  146  incorporates multiple flat circumferential contact surfaces  151 , each contact surface  151  having a longer radial dimension, in respect to center screw  147 , than the preceding one so as to form a stepped circumference on adjuster wheel  146 . As any contact surface  151  may be brought into contact with the lower surface of tab  144 , tab  144  can be secured at various incremental positions in respect to center screw  147 .  
         [0061]     Adjuster wheel  146  has a total of nine contact surfaces  151  that provide nine adjustment positions. Turning adjuster wheel  146  in a clockwise direction, as viewed in  FIG. 16 , will move tab  144  to incrementally higher positions, while turning adjuster wheel  146  in a counter-clockwise direction will move tab  144  to incrementally lower positions.  
         [0062]     Moreover, adjuster wheel  146  is provided with thru-holes  154  through which screw  153  may be inserted as means of securing adjuster wheel  146  at a specific adjustment position. Each thru-hole  154  corresponds to a specific contact surface  151 . The insertion of screw  153  through thru-hole  154  and its secure attachment to threaded bore  155 , which is provided in first support sidewall  101 , forms a mechanism able to lock adjuster wheel  146  to the desired position.  
         [0063]     The operation of second adjustment mechanism  141  is executed with screw  132  loosened, said screw  132  being used to secure flange  131  of second mounting plate  104 . The rotational movement of adjuster wheel  146  has the effect of vertically displacing tab  144  while pivoting flange  131  on the shaft of screw  132 . As shown in  FIG. 10 , second mounting plate  104 , of which one end is secured through end part  104   b,  is able to incline a small amount vertically and to twist, thus making it possible to vertically displace third mounting flange  117 . Laser scan unit  3  is secured at one point on second mounting plate  104  through screw  118 , and second mounting plate  104  is less solid than first mounting plate  103 . Therefore, the inclination of second mounting plate  104  has little effect on the set position of laser scan unit  3 , thereby providing a mechanism through which the only effect applied to laser scan unit  3  by the inclination of second mounting plate  104  is the vertical displacement of the rear portion of laser scan unit  3 .  
         [0064]     While the rear portion of laser scan unit  3  can be vertically displaced through the effect of second adjustment mechanism  141  on second mounting plate  104 , the adjustable inclination of laser scan unit  3  is centered along the support axis of first mounting plate  103 . In other words, the set position of laser scan unit  3  can be adjusted through establishing its inclination in respect to the axial center line of photo conductor  1  in the horizontal direction.  
         [0065]      FIG. 16  is a diagram illustrating the adjustment that can be applied to the scanning position in regard to the laser scan unit support mechanism shown in  FIG. 10 .  FIG. 16A  shows the effect of first adjustment mechanism  122  which is able to adjust the inclination angle of the scanning line. Adjustment range W, which shows the angle within which the scanning line can be inclined through first adjustment mechanism  122 , may cover an adjustment range within which the scanning line can, for example, be moved up 2.38 mm or down 2.28 mm from the center of the surface on photo conductor  1 .  FIG. 16B  shows the effect of second adjustment mechanism  141  through which the position of scanning line center C (beam spot along the primary scanning direction) can be adjusted vertically (the secondary scanning direction) at an approximately right angle to the scanning direction. Adjustment range W, within which second adjustment mechanism  141  is able to adjust the scanning position, may be established, for example, to provide 1.51 mm of adjustment above the mid-point of the surface of photo conductor  1 , and 1.51 mm of adjustment below. The actual scanning line adjustment is executed by initially adjusting the scanning line inclination angle with first adjustment mechanism  122 , and then adjusting the center point of the scanning line with second adjustment mechanism  141 . The result is an easy and accurate scanning line adjustment operation.  
         [0066]     It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.  
         [0067]     The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.  
         [0068]     This application is based on the Japanese Patent Application No. 2003-67763 filed on Mar. 13, 2003 and the Japanese Patent Application No. 2004-025311 filed on Feb. 2, 2004, entire content of which is expressly incorporated by reference herein.