Abstract:
A guide member provided between at least one light emitting element located at a predetermined position and a circuit board, the light emitting element is provided with a plurality of lead wires, the circuit board is provided with a plurality of insertion holes in which a plurality of the lead wires of the light emitting element are inserted, respectively, and the guide member is provided with a plurality of guide holes through which each lead wire of the light emitting element is guided into each corresponding insertion hole of the plurality of insertion holes of the circuit board. A mounting method for mounting the light emitting element is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a guide member for mounting a light emitting element to a circuit board and a mounting method thereof, in a scanning optical system.  
           [0003]    2. Description of the Related Art  
           [0004]    For example, in an optical scanner used in a monochromatic laser printer, laser light emitted from a semiconductor laser (laser diode [LD]) is irradiated onto a surface of a photosensitive drum through a collimator lens, a polygonal mirror and an fθ lens. In such an optical scanner, the LD is supported by a supporting frame whose position relative to a holder frame which holds the collimator lens is adjusted in an adjusting stage to align the emission center of the LD with the center axis of the collimator lens.  
           [0005]    In a multi-beam scanning optical system used in a color printer having four LDs (for yellow, cyan, magenta, black), each LD has a supporting frame, and therefore the adjusting operation must be carried out for each LD. After completion of the adjusting operations, each lead wire of the LDs is inserted in an insertion hole of a LD drive circuit board and is soldered to a circuit pattern formed on the LD drive circuit board. Thus, the LDs are mounted to the LD drive circuit board. However, as a result of the adjusting operations, there is a possibility that the position of the front ends of the lead wires of the LDs is deviated from a correct designed position due to irregularity of the supporting frames and/or the lens holder frame and irregularity of the emission centers of the LDs. Consequently, it is difficult to insert the lead wires of all the LDs into the insertion holes of the LD drive circuit board which are correctly formed in a design position. To solve this problem, in the prior art, the LDs are mounted to respective separate LD drive circuit boards or the LDs are connected to a common LD drive circuit board using a flexible circuit board.  
           [0006]    However, if each LD has an individual LD drive circuit board, the number of the LD drive circuit boards is increased, thus leading to an increase in the size of the apparatus. Moreover, if the LDs are connected to the LD drive circuit board via the flexible circuit board, the distance between the LDs and the LD drive circuit board is increased, and hence, the output property of the LDs is deteriorated.  
         SUMMARY OF THE INVENTION  
         [0007]    To eliminate the drawbacks of the prior art mentioned above, the present invention provides a guide member which can be used to mount a plurality of light emitting elements to a circuit board and a method for mounting a plurality of light emitting elements to a circuit board.  
           [0008]    For example, a guide member is provided between at least one light emitting element located at a predetermined position and a circuit board, the light emitting element is provided with a plurality of lead wires, the circuit board is provided with a plurality of insertion holes in which a plurality of said lead wires of the light emitting element are inserted, respectively, and the guide member is provided with a plurality of guide holes through which each lead wire of the light emitting element is guided into each corresponding insertion hole of the plurality of insertion holes of the circuit board.  
           [0009]    The guide holes can extend through the guide member from a first surface of the guide member adjacent to the light emitting element to a second surface of the guide member adjacent to the circuit board, the diameter of the guide hole at the second surface being smaller than the diameter of the guide hole at the first surface.  
           [0010]    It is desirable for the guide holes to be tapered so that the diameter thereof is decreased from the first surface of the guide member adjacent to the light emitting element toward the second surface of the guide member adjacent to the circuit board.  
           [0011]    It is desirable for the diameter of the guide hole at the second surface to be not greater than the diameter of the insertion holes.  
           [0012]    In another aspect of the present invention, a mounting method is provided for mounting at least one light emitting element to a circuit board by inserting a plurality of lead wires of the light emitting element in corresponding insertion holes formed in the circuit board, wherein a guide member is provided between the light emitting element and the circuit board, the guide member being provided with a plurality of tapered guide holes whose diameter is reduced from a first surface of the guide member opposed to the light emitting element toward a second surface thereof opposed to the circuit board, the mounting method including inserting each lead wire of the light emitting element into the corresponding guide hole of the guide member, and inserting the lead wires extending from the guide holes into the corresponding insertion holes of the circuit board.  
           [0013]    The light emitting element can be mounted to the guide member in advance by inserting the lead wires of the light emitting element into the corresponding guide holes of the guide member, and thereafter, the lead wires extending from the guide holes are inserted in the corresponding insertion holes.  
           [0014]    The guide member can be secured to the circuit board in advance so that the guide holes in the second surface of the guide member are registered with the corresponding insertion holes of the circuit board, and thereafter, the lead wires of the light emitting elements are inserted in the corresponding insertion holes by inserting the lead wires in the corresponding guide holes.  
           [0015]    The present disclosure relates to subject matter contained in Japanese Patent Application No.2001-369721 (filed on Dec. 4, 2001) which is expressly incorporated herein by reference in its entirety. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention will be discussed below with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is a plan view of a multi-beam scanning optical system which is mounted to a color printer, to which an embodiment of the present invention is applied;  
         [0018]    [0018]FIG. 2 is an enlarged plan view of a laser unit shown in FIG. 1;  
         [0019]    [0019]FIG. 3 is a schematic view showing a positional relationship between LDs and collimator lenses, provided in a laser unit shown in FIG. 2;  
         [0020]    [0020]FIG. 4 is a plan view of a laser unit (without an LD drive circuit board) shown in FIG. 2, as viewed from the LD side;  
         [0021]    [0021]FIG. 5 is a schematic sectional view showing a mounting operation of an LD to an LD drive circuit board, by way of example; and  
         [0022]    [0022]FIG. 6 is a schematic view of a guide member according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    [0023]FIG. 1 shows an embodiment of the invention, applied to a multi-beam scanning optical system  10  mounted to a color printer. The multi-beam scanning optical system  10  includes a laser unit  11 , a collimating mirror  12 , a polygonal mirror  13 , an fθ lens  14 , a mirror portion  15  and a synchronization detection portion  16 . The laser unit  11  is provided with four laser diodes (LDs/light emitting elements)  20  ( 20 A through  20 D) and emits four laser beams respectively. Each laser beam emitted from the laser unit  11  is reflected by the collimating mirror  12  and is made incident upon the polygonal mirror  13  which rotates at high speed, so that the laser beams scan in a lateral direction of the multi-beam scanning optical system  10 . The laser beams reflected by the polygonal mirror  13  are transmitted through the fθ lens  14  and are reflected by a mirror to scan four photosensitive drums (not shown) which are located on respective light paths of the reflected light beams. Note that the laser light reflected by the polygonal mirror  13  is partly received by the synchronization detection portion  16  through the mirror portion  15 . In the illustrated embodiment, the writing timing can be synchronized by the synchronization detection portion  16 .  
         [0024]    The laser unit  11  according to the present invention will be discussed below in detail.  
         [0025]    In FIG. 2 which shows an enlarged view of the laser unit  11 , the laser unit  11  includes the four LDs  20 A through  20 D, four collimator lenses  22  ( 22 A through  22 D), two prisms  24 A,  24 B, and a single LD drive circuit board  26 .  
         [0026]    The LDs  20 A through  20 D are supported by respective supporting frames  21  ( 21 A through  21 D). As shown in FIG. 3, the LDs  20 A and  20 D are arranged so that the emission surfaces thereof are spaced in parallel in the vertical direction (upward and downward direction in FIG. 3). The LDs  20 B and  20 C are arranged so that the emission surfaces are spaced in parallel in the vertical direction (upward and downward direction in FIG. 3) and are located on opposite sides of a straight line connecting the centers of the LD  20 A and the LD  20 D. The distance between the adjacent emission surfaces of the four LDs  20 A through  20 D in the vertical direction (upward and downward direction in FIG. 3) is substantially the same.  
         [0027]    The collimator lenses  22 A through  22 D are supported by the lens holder frame  23  and are located in front of the LDs  20 A through  20 D. The collimator lenses  22 A through  22 D collimate the laser light emitted from the LDs  20 A through  20 D, respectively. The prisms  24 A and  24 B are adapted to shift the optical axes of the collimator lenses  22 B and  22 C so as to be aligned in parallel, so that the optical axes of the collimator lenses  22 B and  22 C and the optical axes of the collimator lenses  22 A and  22 D are made parallel at the emission surfaces thereof. Namely, the four laser lights passing through the collimator lenses  22 A through  22 D are emitted from the laser unit  11  in parallel and at an equal distance in the vertical direction.  
         [0028]    The positions of the supporting frames  21 A through  21 D which support the LDs  20 A through  20 D relative to the lens holder frame  23  are adjusted in the directions X and Y in FIG. 4, so that the emission axes of the LDs  20 A through  20 D are aligned with the corresponding optical axes of the collimator lenses  22 A through  22 D. After adjustment, the supporting frames  21 A through  21 D are secured to the lens holder frame  23  by screws. FIG. 4 shows the laser unit  11  in which the supporting frames  21 A through  21 D are secured (before the LD drive circuit board  26  is mounted), as viewed from an arrow V shown in FIG. 2.  
         [0029]    Three lead wires  2  which can be connected to the LD drive circuit board  26  extend from the rear end of each LD  20  ( 20 A through  20 D). The LD drive circuit board  26  is provided thereon with circuit elements such as a drive circuit for driving the LDs  20 A through  20 D, and insertion holes  27  (shown in FIG. 5) in which the lead wires  2  of the LDs  20 A through  20 D are inserted. The LDs  20 A through  20 D and the LD drive circuit board  26  are connected to each other by inserting the lead wires  2  of the LDs  20 A through  20 D in the corresponding insertion holes  27  and soldering the lead wires to the circuit pattern of the LD drive circuit board  26 .  
         [0030]    However, since the connection is carried out after the LDs  20 A through  20 D and the collimator lenses  22 A through  22 D are assembled into an integral unit, the positions of the front ends of the lead wires  2  of the LDs  20 A through  20 D may be deviated from designed correct positions as a result of the positional adjustment of the LDs  20 A through  20 D relative to the collimator lenses  22 A through  22 D. Moreover, the lead wires  2  of the LDs  20 A through  20 D may bend during an assembling operation. If the positional deviation of the lead wires  2  at the front ends thereof occurs, it is difficult to insert all the lead wires  2  (3×4=12 wires in the illustrated embodiment) of the LDs  20 A through  20 D in the insertion holes  27  of the LD drive circuit board  26  because the relative position of the LDs  20 A through  20 D cannot be adjusted. It is possible to arrange the collimator lenses  22 A through  22 D after the LDs  20 A through  20 D are connected to the LD drive circuit board  26 . However, in this alternative, it is difficult to adjust the relative position of the LDs  20 A through  20 D and the collimator lenses  22 A through  22 D, and hence, it is difficult to align the optical axes of the collimator lenses  22 A through  22 D with the emission centers of the LDs  20 A through  20 D.  
         [0031]    In the illustrated embodiment, as can be seen in FIG. 5, a guide member  30  is provided between the LDs  20 A through  20 D and the LD drive circuit board  26 , so that the lead wires  2  of the LDs  20 A through  20 D can be easily inserted in the corresponding insertion holes  27  of the LD drive circuit board through the guide member  30 .  
         [0032]    [0032]FIG. 6 schematically shows the guide member  30 . The guide member  30  is provided with guide through holes  32  which are tapered to reduce the diameter from large openings  32   a , at a first surface of the guide member  30  opposed to the LDs  20 A through  20 D, toward small openings  32   b  at a second surface of the guide member  30  opposed to the LD drive circuit board  26 . The guide holes  32  are formed corresponding to the insertion holes  27  of the LD drive circuit board  26  as clearly shown in FIG. 5. Namely, the diameter of the small openings  32   b  of the guide holes  32  is the same or smaller than the diameter of the insertion holes  27 . When the guide member  30  is secured to the LD drive circuit board  26 , the guide holes  32  are connected to the corresponding insertion holes  27 . Since the guide member  30  have the tapered guide holes  32 , the front ends of the lead wires  2  can be easily inserted in the large openings  32   a  of the guide holes  32 , even if the front ends of the lead wires of the LDs  20 A through  20 D are deviated from the corresponding insertion holes  27 . Consequently, the lead wires  2  are guided along the inner peripheral surfaces of the guide holes  32  while adjusting the position of the front ends thereof, so that the lead wires  2  can be precisely inserted in the insertion holes  27  through the small openings  32   b  of the guide holes  32 . Note that the guide member  30  also provides a distance between the LDs  20 A through  20 D and the LD drive circuit board  26  to thereby reduce the stress of the lead wires  2  of the LDs  20 A through  20 D.  
         [0033]    In the above-described structure, the LDs  20 A through  20 D are connected to the LD drive circuit board  26  as follows.  
         [0034]    &lt;First Step&gt; 
         [0035]    The LDs  20 A through  20 D are inserted in and secured to the supporting frames  21 A through  21 D.  
         [0036]    &lt;Second Step&gt; 
         [0037]    The position of the supporting frames  21 A through  21 D relative to the lens holder frame  23  is adjusted so that the emission axes of the LDs  20 A through  20 D are made coincident with the optical axes of the corresponding collimator lenses  22 A through  22 D. Thereafter, the supporting frames  21 A through  21 D are secured to the lens holder frame  23  by screws.  
         [0038]    &lt;Third Step&gt; 
         [0039]    The lead wires  2  of the LDs  20 A through  20 D are inserted in the corresponding guide holes  32  of the guide member  30 . In this state, the lens holder frame  23  is integral with the guide member  30 .  
         [0040]    &lt;Fourth Step&gt; 
         [0041]    The lead wires  2  of the LDs  20 A through  20 D which extend from the guide holes  32  of the guide member  30  are inserted in the corresponding insertion holes  27  of the LD drive circuit board  26 .  
         [0042]    &lt;Fifth Step&gt; 
         [0043]    The lead wires  2  of the LDs  20 A through  20 D are connected to the circuit pattern of the LD drive circuit board  26  by soldering or the like.  
         [0044]    The assembling operation mentioned above is given by way of example and can be modified. In an alternative, for example, the third and fourth steps are replaced with the following modified third and fourth steps, respectively.  
         [0045]    &lt;Modified Third Step&gt; 
         [0046]    The guide member  30  is secured to the LD drive circuit board  26  while the small openings  32   b  of the guide holes  32  are registered with the corresponding insertion holes  27 .  
         [0047]    &lt;Modified Fourth Step&gt; 
         [0048]    The lead wires  2  of the LDs  20 A through  20 D are inserted in the corresponding guide holes  32  and in the insertion holes  27  of the LD drive circuit board  26 .  
         [0049]    As mentioned above, in the arrangement wherein the LDs  20 A through  20 D are connected to the LD drive circuit board  26  through the guide member  30 , it is not necessary to provide an LD drive circuit board for each LD unlike the prior art. Consequently, the apparatus thereof can be made small. Furthermore, unlike the prior art, since it is not necessary to connect the LDs to each LD drive circuit board using a flexible circuit board, deterioration of the output properties of the LDs does not occur.  
         [0050]    The shape of the guide holes  32  is not limited to that in the illustrated embodiment, as long as the diameter thereof at the second surface of the guide member opposed to the LD drive circuit board  26  is smaller than the diameter at the first surface of the guide member opposed to the LDs  20 A through  20 D. It is, however, desirable that the guide holes  32  be tapered so that no or little bending of the lead wires of the LDs  20 A through  20 D occurs in the tapered guide holes  32 .  
         [0051]    Although the above discussion has been addressed to an embodiment of a guide member and a circuit board mounting method, applied to a multi-beam scanning optical system  10  having a plurality of LDs  20 A through  20 D, the present invention is not limited thereto. For instance, the guide member and the circuit board mounting method can be applied to an optical scanner having a single LD. In an optical scanner having a single LD, the lead wires of the LD may be bent during assembling operation. This problem can be advantageously eliminated by the present invention.  
         [0052]    According to a guide member of the present invention, a plurality of light emitting elements can be mounted to a single drive circuit board. Consequently, not only can the apparatus be made small, but also a high performance of the light emitting elements can be maintained.  
         [0053]    Obvious changes may be made in the specific embodiments of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.