Abstract:
A solid state imaging device includes a package substrate and a solid state imaging element on the package substrate. The package substrate has a mounting plane on which the solid state imaging element is mounted. The package substrate has two reference planes having the same height as the mounting plane, the reference planes projecting in two opposite directions from the mounting plane. The reference planes respectively have at least one pair of positioning reference holes formed therein, such that the centers of the respective pairs of holes are away from the center of an imaging plane of the solid state imaging element by the same distance. The imaging device is produced by fixing the imaging element on the mounting plane of the package substrate such that the center of the imaging element is aligned with the center of a phantom line diagonally connecting the center of one of the positioning reference holes in one of the reference planes with the center of one of the reference holes in the other of the reference planes. A solid state imaging unit utilizing the imaging device includes a lens mirror cylinder unit having pin members engaging diagonally opposed ones of each of the at least one pair of positioning reference holes, a reference plane corresponding to the reference planes of the package substrate and an optical lens having an optical axis that passes through the center of a phantom line connecting the centers of the pin members and the center of the imaging element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a solid state imaging device including a solid state imaging element mounted on a packaging substrate, a method for producing the same, a solid state imaging unit including a lens mirror cylinder unit attached to the solid state imaging device, a method for producing the same, and an imaging apparatus using the same. 
     2. Description of the Related Art 
     Conventionally, a solid state imaging element including CCDs is used in various types of imaging apparatuses such as digital cameras and video cameras. When used in these imaging apparatuses, the solid state imaging element is combined with a lens mirror cylinder unit including an optical lens for focusing light, representing an image, on the solid state imaging element. 
       FIG. 4  shows a manner of combining a solid state imaging element  100 B and a lens mirror cylinder unit. An optical axis L of an optical lens  100 A of the lens mirror cylinder unit, and an imaging plane center C of the solid state element  100 B, need to be positionally aligned with each other. The positional alignment is performed by adjustment of the angle of view based on X, Y and θ axes. In addition, a plane perpendicular to the optical axis L of the optical lens  100 A needs to be parallel to an imaging plane of the solid state imaging element  100 B. This is performed by focusing adjustment based on Z axis and tilt adjustment based on a and b axes. The tilt adjustment is performed for preventing partial defocusing. (The adjustment for preventing partial defocusing will be referred to simply as the “partial defocusing adjustment.) The positional adjustment based on the above-mentioned six axes is precisely performed in the micrometer (μm) order. 
     Conventionally, the positional alignment and adjustment based on these axes is performed over a long period of time using an expensive positional adjustment apparatus. For example, the positional alignment of the optical lens  100 A and the solid state imaging element  100 B is performed as follows. 
     As shown in  FIG. 5 , a package  101  having the solid state imaging element  100 B mounted thereon is fixed to a metal plate  102  formed of, for example, aluminum, with an adhesive or the like. 
     Then, a lens mirror cylinder unit  103  having the optical lens  100 A built therein is placed at a fixed position. With respect to the lens mirror cylinder unit  103 , the solid state imaging element  100 B is moved along and about the axes together with the package  101  provided on the metal plate  102 , in units of very fine distance and very fine angle. By such movement, the optical lens  100 A and the solid state imaging element  100 B are positioned to have an optimal positional relationship, by which an output signal from the solid state imaging element  100 B is optimal. In this position, the lens mirror cylinder unit  103  and the metal plate  102  hold the solid state imaging element  100 B on the package  101 . Thus, the solid state imaging element  100 B and the lens mirror cylinder unit  103  are integrally fixed with each other by tightening members, such as screws  104  or the like. 
     In order to simplify the above-described step of positional alignment of the lens mirror cylinder unit  103  and the solid state imaging element  100 B, the following proposals have been conventionally made. 
     Japanese Laid-Open Utility Mode Publication No. 5-46046 directed to a “Solid State Imaging Device” proposes the following technique. A solid state imaging element is mounted on apart of a flat plate having a surface polished so as to have a smoothness (surface roughness) of a maximum of about 5 μm. A package for covering this solid state imaging element is fixed such that the flat plate is partially exposed. The exposed part of the flat plate acts as a reference plane, i.e., a plane to which the lens mirror cylinder unit is to be attached. 
     According to Japanese Laid-Open Publication No. 2000-125212 directed to an “Imaging Module”, a flat part of a ceramic plate is used both as a reference plane of a semiconductor chip and a reference plane of a lens mirror cylinder unit. 
     Japanese Laid-Open Publication No. 10-326886 directed to “Solid State Imaging Device and Method for Mounting Solid State Imaging Device” and Japanese Laid-Open Publication No. 2000-307092 directed to “Solid State Imaging Device, Camera Using the Same, and Method for Producing the Same” propose the following technique. A pilot portion which is opened outward is provided on a side surface of a package, and a guide portion which is opened outward is provided on a side surface facing the side surface provided with the pilot portion. Using the pilot portion and the guide portion, a solid state imaging element, a lens mirror cylinder unit and a wiring board are positioned with respect to each other by a jig having pins projecting therefrom. 
     The above-described conventional techniques have the following problems. 
     According to the techniques described in Japanese Laid-Open Utility Mode Publication No. 5-46046 and Japanese Laid-Open Publication No. 2000-125212, the plane vertical to the optical axis of the optical lens and the imaging plane of the solid state imaging element can be adjusted to be parallel to each other with high precision, for the following reason. Since the plane on which the solid state imaging element is mounted and the plane on which the lens mirror cylinder unit is mounted are coplanar, the adjustment based on Z axis ( FIG. 5 ) (which is provided for focusing adjustment) and based on a and b axes (which are provided for tilt adjustment for partial defocusing adjustment) is performed with high precision. However, the optical axis of the lens mirror cylinder unit and the imaging plane center of the solid state imaging element cannot be aligned with high precision. The reason for this is because there is no reference position or plane for X, Y and θ axes, which are parallel to the plane on which the solid state imaging element is mounted. 
     According to the technique described in Japanese Laid-Open Publication No. 10-326886 and Japanese Laid-Open Publication No. 2000-307092, the positional alignment of the optical axis of the lens mirror cylinder unit and the imaging plane center of the solid state imaging element, i.e., the adjustment based on X, Y and θ axes, can be performed with high precision, by use of the pilot portion, the guide portion and the jig having pins projecting therefrom. However, the plane vertical to the optical axis of the optical lens and the imaging plane of the solid state imaging element cannot be adjusted to be parallel to each other with high precision. The reason for this is because there is no reference position or plane for Z axis (parallel to the pilot portion and the guide portion) provided for focusing adjustment and a and b axes provided for tilt adjustment for partial defocusing adjustment. Even for the positional adjustment based on X, Y and θ axes, this technique has inconveniences of requiring a positional adjustment jig having pins projecting therefrom and also requiring an additional step of alignment using the positional adjustment jig. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a solid state imaging device includes a package substrate; and a solid state imaging element mounted on the package substrate. The package substrate has a mounting plane on which the solid state imaging element is mounted. The package substrate has two reference planes having the same height as the mounting plane, the reference planes projecting in two opposite directions from the mounting plane. The reference planes respectively have at least one pair of positioning reference holes therein, such that the centers of the pair of holes are away from the center of an imaging plane of the solid state imaging element by the same distance. 
     In one embodiment of the invention, the at least one pair of positioning reference holes formed in the reference plane are tapered so as to expand toward the side of the imaging plane of the solid state imaging element. 
     In one embodiment of the invention, the package substrate has a recessed portion having the mounting plane in a bottom portion thereof. The solid state imaging element is mounted on the mounting plane. Internal leads accommodated in the recessed portion are connected to electrodes of the solid state imaging element via thin metal lines, and are also connected to external leads. A transparent cap member is mounted so as to cover the recessed portion. 
     According to another aspect of the invention, in a method for producing the above-described solid state imaging device is provided. For mounting the solid state imaging element on the mounting plane of the package substrate, the center of the imaging plane is matched to the center of a phantom line connecting the centers of the at least one pair of reference holes, and thus solid state imaging element is fixed on the mounting plane. 
     According to still another aspect of the invention, a solid state imaging unit includes the above-described solid state imaging device, and a lens mirror cylinder unit. The lens mirror cylinder unit includes pin members respectively engageable with the at least one pair of positioning reference holes, a positioning reference plane corresponding to the reference planes of the solid state imaging device, and an optical lens provided such that an optical axis thereof passes through the center of a phantom line connecting the centers of the pin members. The pin members are put into engagement with the positioning reference holes so as to position the solid state imaging element and the optical lens with respect to each other, thus to attach the lens mirror cylinder unit to the package substrate. 
     In one embodiment of the invention, the pin members are tapered so as to be reduced in diameter toward tips thereof. The tapered pin members and the tapered positioning reference holes are engaged with each other, such that the positioning reference plane of the lens mirror cylinder unit is parallel to the reference planes of the solid state imaging device. 
     In one embodiment of the invention, the reference planes of the solid state imaging device each have two positional reference holes, thus forming a phantom rectangle. The package substrate is held and attached between the lens mirror cylinder unit and a wiring board, via two positioning reference holes provided on one of two phantom diagonal lines of the phantom rectangle. 
     According to still another aspect of the invention, a method for producing the above-described solid state imaging unit is provided. The pin members are respectively put into engagement with the positioning reference holes so as to position the solid state imaging element and the optical lens and also to attach the lens mirror cylinder unit to the package substrate. 
     In one embodiment of the invention, the wiring board has four insertion holes in positional correspondence with the four positioning reference holes. The lens mirror cylinder unit has two securing tapping holes for securing screws in addition to the pair of tapered pin members, the securing tapping holes and the tapered pin members positionally corresponding to the four positioning reference holes. The pair of tapered pin members are sequentially put into engagement with two of the positional reference holes and two of the insertion holes of the wiring board. Screws are sequentially put into engagement with the remaining two insertion holes, the remaining two positional reference holes, and then the securing tapping holes, thereby tightening the wiring board, the solid state imaging device and the lens mirror cylinder unit. 
     According to still another aspect of the invention, an imaging apparatus using the above-described solid state imaging device or the above-described solid state imaging unit is provided. 
     The function of the present invention will be described. 
     Conventionally, a solid state imaging element and an optical lens are produced in separate steps with prescribed precision. The two components need to be positioned with respect to each other with high precision. In the case of a solid state imaging device having a conventional structure, after the imaging element chip is mounted, the optical lens is positioned to the imaging element chip. In this step, a total of six axes are necessary, including axes for adjustment of the angle of view, and axes for tilt adjustment, in order to provide absolute precision of positioning the optical lens and the imaging element chip. 
     In the case of a package of a solid state imaging element having a conventional structure, the package is mounted on a substrate acting as a reference and then a lens mirror cylinder unit is mounted to the reference. Therefore, the dispersion factors are accumulated. In addition, as described above, a total of six axes are necessary for positioning the solid state imaging element and the optical lens (regarding optical axis center, horizontal and vertical planes, tilt, rotation, etc.). 
     According to the present invention, the package substrate itself of the solid state imaging device has reference holes for positioning the solid state imaging element to the mounting plane. The reference holes are also used for positioning the solid state imaging element and the lens mirror cylinder unit as follows. By inserting the pin members into the reference holes of the solid state imaging device, the solid state imaging element and optical lens can be positioned to each other and also the lens mirror cylinder unit can be attached to the package substrate. Thus, (i) positional alignment of the optical axis of the optical lens and the imaging plane center of the solid state imaging element, and (ii) adjustment of the plane vertical to the optical axis of the optical lens to be parallel to the imaging plane of the solid state imaging element, can both be performed with high precision and with a smaller number of steps. 
     Thus, the invention described herein makes possible the advantages of providing a solid state imaging device for realizing positional alignment of the optical axis of an optical lens and the imaging plane center of a solid state imaging element, and also realizing a plane vertical to the optical axis of the optical lens to be parallel to the imaging plane of the solid state imaging element, both with high precision and with a smaller number of steps, without using a positional adjustment jig, and a method for producing the same; a solid state imaging unit including the solid state imaging device, and a method for producing the same; and an imaging apparatus using the same. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded isometric view illustrating assembly of a solid state imaging unit according to an example of the present invention; 
         FIG. 2A  is a plan view of a solid state imaging device according to an example of the present invention; 
         FIG. 2B  is a cross-sectional view taken along line A-A′ in  FIG. 2A ; 
         FIG. 3A  illustrates a manner of positioning the solid state imaging device and a lens mirror cylinder unit according to the present invention, when the distance between two pin members is shorter than the distance between two positioning reference holes; 
         FIG. 3B  illustrates a manner of positioning the solid state imaging device and a lens mirror cylinder unit according to the present invention, when the distance between two pin members is longer than the distance between two positioning reference holes; 
         FIG. 4  schematically shows a principle of positioning a solid state imaging element and an optical lens; and 
         FIG. 5  is an exploded isometric view of conventional positional adjustment and assembly of a solid state imaging element and a lens mirror cylinder unit. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a solid state imaging unit according to the present invention will be described by way of illustrative examples with reference to the attached drawings. 
       FIG. 1  is an exploded isometric view illustrating assembly of a solid state imaging unit  1  according to an example of the present invention. 
     As shown in  FIG. 1 , the solid state imaging unit  1  includes a solid state imaging device  2  including a solid state imaging element  21  mounted therein (described below with reference to FIG.  2 ), a lens mirror cylinder unit  3  including a lens  31  so as to focus light, representing a taken image, on the solid state imaging element  21 , and a wiring board  4  for transferring an output signal from the solid state imaging element  21  to an external device. These elements are arranged and assembled to have an optimal positional relationship to each other. 
     As shown in  FIGS. 2A and 2B , the solid state imaging device  2  includes the solid state imaging element  21 , a dual in-line package (DIP; hereinafter, referred to as the “package”)  22  acting as a packaging substrate on which the solid state imaging element  21  is to be mounted, a transparent cap  23  for covering the solid state imaging element  21 , and a plurality of external leads  24  for transferring an output signal for imaging from the solid state imaging element  21  to an external device. 
     The solid state imaging element  21  includes a plurality of CCDs arranged in a matrix. Each CCD converts light representing an image into an electric signal on a pixel-by-pixel basis. 
     The package  22  has a recessed portion  221  in a portion of a top surface thereof. The recessed portion  221  is generally square when seen from the top. A bottom portion of the recessed portion  221  includes a flat mounting plane  222  on which the solid state imaging element  21  is mounted. From two opposite sides of the recessed portion  221 , brim-like edges project outward. On the brim-like edges, reference planes  223   a  and  223   b  (projecting areas) are provided, respectively. The reference planes  223   a  and  223   b  are flat and at the same height as the mounting plane  222 . Positioning reference holes  22   a  and  22   b  are formed so as to pass through the brim-like edge from the reference plane  223   a , and positioning reference holes  22   c  and  22   d  are formed so as to pass through the brim-like edge from the reference plane  223   b . The solid state imaging device  2  is generally rectangular when seen from the top, and the four positioning reference holes  22   a  through  22   d  are located so as to form a phantom rectangle, the reference holes  22   a  through  22   d  being at the four corners of the phantom rectangle. The positioning reference holes  22   a  through  22   d  are used for positioning the solid state imaging element  21  and the lens mirror cylinder unit  3 . 
     Among the four positioning reference holes  22   a  through  22   d , two holes provided on a phantom diagonal line, e.g., the positioning reference holes  22   a  and  22   c , are tapered such that the cross-sectional area thereof near the upper end (on the side of the solid state imaging element  21 ) is larger than the cross-sectional area thereof near the lower end. 
     The solid state imaging element  21  is positioned on the mounting plane  222  on the package  22  as follows. A phantom straight line connecting the centers of two circular positioning reference holes provided on a phantom diagonal line (e.g., the positioning reference holes  22   a  and  22   c ) is drawn. The center of the solid state imaging element  21  (imaging plane center) is aligned to the center of the phantom straight line. In this state, the solid state imaging element  21  is fixed on the mounting plane  222  with an adhesive or the like. The center of the solid state imaging element  21  is aligned to the center of the phantom straight line as follows. The positions in the package  22  acting as references (centers of the circular positioning reference holes) are optically recognized by an optical device, and the solid state imaging element  21  is fixed at a prescribed position in a prescribed direction from the reference positions (i.e., the center of the phantom diagonal line connecting the centers of the two positioning reference holes). This technique is generally used. The positioning reference holes  22   b  and  22   d  are usable instead of the positioning reference holes  22   a  and  22   c.    
     The transparent cap  23  is a rectangular plate and is bonded so as to cover the inside of the recessed portion  221 . Thus, the inside of the recessed portion  221  is sealed with the space above the solid state imaging element  21  being hollow. 
     The plurality of external leads  24  hang downward from two opposite sides of the rectangle of the solid state imaging device  2 . Whereas the brim-like edges project from the shorter sides of the rectangle, the external leads  24  hang from a central portion of each longer side of the rectangle. Internal leads (not shown) provided in the recessed portion  221  on the package  22  are connected to electrodes (not shown) in the solid state imaging element  21  via thin metal lines (not shown) formed of aluminum or other metal. The internal leads are respectively connected to the external leads  24 . Thus, the electrodes of the solid state imaging element  21  are respectively conducted to the external leads  24 . The package  22  is not limited to be a pin insertion type package such as, for example, the dual in-line package, and may be a planar mounting type package in which the external leads  24  extend laterally or another planar mounting type package with no external leads. 
     Returning to  FIG. 1 , the lens mirror cylinder unit  3  includes a rectangular plate and a lens holder  32  provided on a central area of a top surface of the rectangular plate. The lens holder  32  accommodates a lens  31  embedded in the lens holder  32 . The lens  31  is embedded while being rotated. The lens mirror cylinder unit  3  also includes positioning pins  33   a  and  33   c  (pin members) projecting downward from a bottom surface of the rectangular plate. The positioning pins  33   a  and  33   c  positionally correspond to the positioning reference holes  22   a  and  22   c , respectively, provided on a phantom diagonal line, and are engageable with the positioning reference holes  22   a  and  22   c . The rectangular plate of the lens mirror cylinder unit  3  also has tapping holes (not shown) for screws in the bottom surface thereof, in positional correspondence with the positioning reference holes  22   b  and  22   d  of the package  22 . The bottom surface of the rectangular plate of the lens mirror cylinder unit  3  acts as a positioning reference plane which faces the reference planes  223   a  and  223   b.    
     The positioning pins  33   a  and  33   c  are tapered such so as to be reduced in diameter toward tips thereof. The positioning pins  33   a  and  33   c  are tapered at an equal angle to the positioning reference holes  22   a  and  22   c , such that the positioning reference holes  22   a  and  22   c  are respectively engaged with the positioning pins  33   a  and  33   c . In this manner, the lens mirror cylinder unit  3  is positioned and attached to the package  22  having the solid state imaging element  21  mounted therein. 
     As can be appreciated, the positioning reference holes  22   a  and  22   c , which are used for positioning the solid state imaging element  21  with respect to the package  22 , are also used for positioning the solid state imaging device  2  to the lens mirror cylinder unit  3 . The positioning pins  33   a  and  33   c , which are provided so as to positionally correspond to the positioning reference holes  22   a  and  22   c , are simply put into engagement with the positioning reference holes  22   a  and  22   c . Such a simple operation realizes the adjustment shown in  FIG. 4 ; i.e., both (i) positional alignment of the optical axis L of the lens ( FIG. 4 ) and the imaging plane center C of the solid state imaging element; and also (ii) adjustment of a plane, vertical to the optical axis L of the lens, to be parallel to the imaging plane of the solid state imaging element. Namely, such a simple operation realizes positional adjustments based on six axes, including focusing adjustment based on Z axis, adjustment of the angle of view based on X, Y and θ axes, and tilt adjustment for partial defocusing adjustment based on a and b axes. 
     The wiring board  4  is a rectangular plate. The wiring board  4  has four circular holes  41   a  through  41   d  in positional correspondence with the positioning reference holes  22   a  through  22   d  of the package  22 , respectively. The wiring board  4  also has a plurality of circular holes  42  in positional correspondence with the external leads  24  hanging from the package  22 . The circular holes  41   a  and  41   c , acting as positioning holes, respectively receive the positioning pins  33   a  and  33   c  inserted from above. The circular holes  41   b  and  41   d , acting as attaching holes, respectively receive securing screws  43  inserted from below. The securing screws  43  are inserted through the circular holes  41   b  and  41   d  and the positioning reference holes  22   b  and  22   d , and are tapped into the tapping holes formed in the bottom surface of the rectangular plate of the lens mirror cylinder unit  3 . The wiring board  4  may be a glass epoxy board or a flexible board. The positioning holes  41   a  and  41   c  and the attaching holes  41   b  and  41   d  are not required to be very precise in size and may be formed with some tolerance. 
     With reference to  FIGS. 3A and 3B , an exemplary manner of attaching the solid state imaging device  2  to the lens mirror cylinder unit  3  will be described. 
       FIGS. 3A and 3B  schematically illustrate how to realize the adjustment shown in  FIG. 4 ; i.e., (i) positional alignment of the optical axis L of the lens and the imaging plane center C of the solid state imaging element; and (ii) adjustment of a plane, vertical to the optical axis of the lens, to be parallel to the imaging plane of the solid state imaging element. Namely,  FIGS. 3A and 3B  schematically illustrate how to realize positional adjustments based on six axes, including focusing adjustment based on Z axis, adjustment of the angle of view based on X, Y and θ axes, and tilt adjustment for partial defocusing adjustment based on a and b axes. 
     First, the positioning pins  33   a  and  33   c  of the lens mirror cylinder unit  3  are inserted into the positioning reference holes  22   a  and  22   c  of the solid state imaging device  2 . The positioning pins  33   a  and  33   c  are longer than the thickness of the reference planes  223   a  and  223   b  having the positioning reference holes  22   a  and  22   c  formed therein, and thus are inserted to the positioning holes  41   a  and  41   c  of the wiring board  4  through the positioning reference holes  22   a  and  22   c . Thus, the lens mirror cylinder unit  3 , the solid state imaging device  2  and the wiring board  4  can be positioned with respect to each other. 
     Next, the securing screws  43  are inserted into the attaching holes  41   b  and  41   d  from below the wiring board  4 . The securing screws  43  reach the rectangular plate of the lens mirror cylinder unit  3  via the attaching holes  41   b  and  41   d , the positioning reference holes  22   b  and  22   d , and the tapping holes (not shown) formed in the rectangular plate. The securing screws  43  are tightened to the rectangular plate of the lens mirror cylinder unit  3  with the same torque. Thus, the lens mirror cylinder unit  3 , the solid state imaging device  2  and the wiring board  4  are secured with respect to each other. 
     With reference to  FIGS. 3A and 3B , high precision positioning of the solid state imaging device  2  and the lens mirror cylinder unit  3  will be described. 
       FIGS. 3A and 3B  are each a cross-sectional view of the assembly of solid state imaging device  2  and the lens mirror cylinder unit  3 , taken along the phantom diagonal line connecting the centers of the positioning reference holes  22   a  and  22   c . In  FIGS. 3A and 3B , Dpc represents the center of the phantom diagonal line, which matches the imaging plane center C of the solid state imaging element  21 . Dp 1  is the length between the center Dpc and the center of the positioning reference hole  22   a , and Dp 2  is the length between the center Dpc and the center of the positioning reference hole  22   c . Dhc is the center of the rectangular plate of the lens mirror cylinder unit  3  which matches the center Dpc. Dh 1  is the length between the center Dhc and the center of the positioning pin  33   a , and Dh 2  is the length between the center Dhc and the center of the positioning pin  33   c.    
     In  FIG. 3A , (Dh 1 +Dh 2 ) is shorter than (Dp 1 +Dp 2 ). In this case, the solid state imaging device  2  and the lens mirror cylinder unit  3  are positioned with respect to each other along the inner portion of the tapered wall of each of the positioning reference holes  22   a  and  22   c.    
     In  FIG. 3B , (Dh 1 +Dh 2 ) is longer than (Dp 1 +Dp 2 ). In this case, the solid state imaging device  2  and the lens mirror cylinder unit  3  are positioned with respect to each other along the outer portion of the tapered wall of each of the positioning reference holes  22   a  and  22   c.    
     In either case, the center Dpc and the center Dhc match each other. In this example, the diagonal line connecting the centers of the positioning reference holes  22   a  and  22   c  is used for positioning, but the present invention is not limited to this. 
     In this manner, the solid state imaging element  21  and the optical lens  31  are positionally aligned in terms of the centers thereof, and are also adjusted to be parallel to each other, with high precision. Namely, positional adjustments based on five axes, including adjustment of the angle of view based on X, Y and θ axes, and tilt adjustment for partial defocusing adjustment based on a and b axes are realized with high precision. 
     The positioning pins  33   a  and  33   c  are guided along the tapered walls of the positioning reference holes  22   a  and  22   c , respectively, so that the positioning pins  33   a  and  33   c  are inserted into the positioning reference holes  22   a  and  22   c  to the same level as each other. This will be described more specifically. In  FIGS. 3A and 3B , reference numeral  34  represents a reference plane  34  (bottom surface of the rectangular plate of the lens mirror cylinder unit  3 ) having the positioning pins  33   a  and  33   c  formed thereon. As described above, the positioning reference hole  22   a  extends from the reference plane  223   a , and the positioning reference hole  22   c  extends from the reference plane  223   b . A gap CL between the reference plane  223   a  and the reference plane  34  is equal to a gap CR between the reference plane  223   b  and the reference plane  34 . In  FIG. 3A , CL 1 =CR 1 . In  FIG. 3B , CL 2 =CR 2 . As a result, the reference planes  223   a  and  223   b  are parallel to the reference plane  34 . Thus, focusing adjustment based on Z axis is performed. 
     Instead of positioning reference holes  22   a  and  22   c , the positioning reference holes  22   b  and  22   d  may be used. In this case, the positioning reference holes  22   b  and  22   d  are also used for positioning the solid state imaging element  21  in the recessed portion  221  of the package  22 . The lens mirror cylinder unit  3  has positioning pins in positional correspondence with the positioning reference holes  22   b  and  22   d , instead of the positioning pins  33   a  and  33   c . The tapping holes (not shown) in the bottom surface of the rectangular plate of the lens mirror cylinder unit  3  are also formed in positional correspondence with the positioning reference holes  22   a  and  22   c , instead of the positioning reference holes  22   b  and  22   d.    
     In this state, however, the focusing adjustment based on Z axis does not have high precision. After the above-described step of assembly is completed, the optical lens  31  is rotated in the lens holder  32  so as to obtain an optimal output signal. Thus, the focusing adjustment based on Z axis obtains high precision. 
     As described above, the solid state imaging device  2  and the lens mirror cylinder unit  3  can be positioned with respect to each other with high precision while being assembled together, by the principle illustrated in  FIGS. 3A and 3B . 
     With the state of the art, the chip of the solid state imaging element  21  and the package  22  are positioned with respect to each other with sufficiently high precision, and the lens mirror cylinder unit  3  having the tapered pin members  33   a  and  33   c  and the optical lens  31  are also positioned with respect to each other with sufficiently high precision. 
     In summary, the present invention solves the above-described problems as follows. 
     The solid state imaging element  21  is fixed on the mounting plane  222  in the recessed portion  221  provided on the top surface of the package  22  with an adhesive or the like. The internal leads (not shown) in the recessed portion  221  of the package  22  and the electrodes (terminals) of the solid state imaging element  21  are respectively connected by thin metal lines formed of aluminum or other metal, and the internal leads are conducted to the external leads  24 . The transparent cap  23  is bonded to the package  22 , so that the recessed portion  221  is sealed while accommodating the solid state imaging element  21 . The space in the recessed portion  221  above the solid state imaging element  21  is hollow. 
     The brim-like edges are projected from two opposite sides of the package  22 . The brim-like edges respectively have the reference planes  223   a  and  223   b  (projecting areas), which are at the same height as the mounting plane  222  on which the solid state imaging element  21  is mounted. The four positioning reference holes  22   a  through  22   d  are formed on the brim-like edges. For example, the positioning reference holes  22   a  and  22   b  extend downward from the reference plane  223   a , and the positioning reference holes  22   c  and  22   d  extend downward from the reference plane  223   b . The positioning reference holes  22   a  through  22   d  are tapered so as to be used for positioning the solid state imaging device  2  and the lens mirror cylinder unit  3 . 
     Among the four positioning reference holes  22   a  through  22   d , the two positioning reference holes provided on a phantom diagonal line (e.g.,  22   a  and  22   c ) are used as a reference for mounting the solid state imaging element  21 . 
     The pair of tapered pins  33   a  and  33   c  of the lens mirror cylinder unit  3  are put into engagement with the reference positioning holes  22   a  and  22   c . Thus, the solid state imaging device  2  and the lens mirror cylinder unit  3  are positioned with respect to each other. Then, the securing screws  43  are put into engagement with the attaching holes  41   b  and  41   d  corresponding to the tapping holes of the lens mirror cylinder unit  3 . The securing screws  43  are then inserted through the positioning reference holes  22   b  and  22   d  and then the tapping holes. Thus, the wiring board  4 , the package  22  and the lens mirror cylinder unit  3  are tightened together. 
     As described above, according to the present invention, the package having the solid state imaging element mounted therein is provided with projecting areas (reference planes  223   a  and  223   b ) at the same height as the mounting plane  222  on which the solid state imaging element is mounted. The projecting areas extend in two opposite directions from the mounting plane. In addition, the positioning reference holes  22   a  through  22   d  are formed so as to extend downward from the reference planes  223   a  and  223   b , respectively. Owing to such a structure, the package  22  having the solid state imaging element  21  mounted therein and the lens mirror cylinder unit  3  are positioned to each other with high precision without any special adjustment step. This positioning corresponds to both (i) positional alignment of the optical axis L of the lens and the imaging plane center C of the solid state imaging element, and (ii) adjustment of a plane vertical to the optical axis of the lens to be parallel to the imaging plane of the solid state imaging element. In other words, positional adjustments based on six axes, including focusing adjustment based on Z axis, adjustment based on X, Y and θ axes, and tilt adjustment for partial defocusing adjustment based on a and b axes, are performed in a short time, easily, and with high precision. Therefore, the special positional adjustment device, jig and the like, which are conventionally used, are not necessary. The positional adjustment operation is significantly simplified. 
     In the above-described example, the positioning pins  33   a  and  33   c  are not stepped. Alternatively, the positioning pins  33   a  and  33   c  may have a stepped structure. In this case, the stepped portions (brim-like portions) act as stoppers for the reference planes  223   a  and  223   b . Thus, it is guaranteed that the positioning pins  33   a  and  33   c  are adjusted to be inserted to the same depth in the positioning reference holes  22   a  and  22   c.    
     As has been described so far, according to the present invention, after the solid state imaging element is positioned with respect to the mounting plane, the optical axis of the lens mirror cylinder unit and the imaging plane center of the solid state imaging element are positioned with respect to each other, using the reference planes at the same height as the mounting plane of the solid state imaging element and also using the tapered positioning reference holes provided in the reference planes. In other words, (i) positional alignment of the optical axis of the lens and the imaging plane center of the solid state imaging element (i.e., adjustment based on X, Y and θ axes), and (ii) adjustment of a plane vertical to the optical axis of the lens to be parallel to the imaging plane of the solid state imaging element (i.e., focusing adjustment based on Z axis, and tilt adjustment for partial defocusing adjustment based on a and b axes), are performed. Such adjustments based on the six axes are performed in the micrometer (μm) order, in a short time, easily and with high precision, without using any special positional adjustment device, jig and the like, as conventionally required. 
     Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.