Patent Publication Number: US-2011075023-A1

Title: Substrate holding apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2009-221361, filed on Sep. 25, 2009, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     This disclosure relates to a substrate holding apparatus for accommodating and holding a substrate in a case. 
     BACKGROUND DISCUSSION 
     A known substrate holding apparatus is disclosed in JP1997-74291A (hereinafter referred to as Reference 1) includes a case formed by a case cover and a case body, and a substrate fixed in the case. Supporting portions (fitting slits) support both sides of the substrate are arranged at both sides of an inner portion of the case body in a direction where the substrate is slid from an opening to the inner portion of the case body so as to be accommodated therewithin (the direction will be hereinafter referred to as a substrate inserting direction). Pressing portions extending in the substrate inserting direction are provided at a bottom surface of the case body and at the case cover, respectively. The substrate is pressed and deformed by the pressing portions in a condition where the case cover is fitted to the case body. Accordingly, the substrate is pressed to the supporting portions, therefore being fixed to the case. 
     A known substrate holding apparatus disclosed in JP2000-49475A (hereinafter referred to as Reference 2) includes a case formed by a case cover and a case body, and a substrate positioned and fixed in the case. The case body includes substrate guiding grooves. The case cover is fixed to the case body. 
     According to the substrate holding apparatus described in Reference 1, for example, in the case where a plurality of substrates is accommodated in the case, the substrates are electrically connected to one another before being accommodated within the case. Such procedures may be inappropriate for the substrates, therefore causing difficulty in accommodating the substrates in the case. Further, an electronic component mounted on each of the substrates generally protrudes from a surface of the substrate. Consequently, when the substrate is slid into the case in a direction along the surface of the substrate (in the substrate inserting direction) and accommodated in the case, the case requires a sufficient space over a whole range of a movement of the electronic component for preventing the electronic component protruding from the surface of the substrate, from interfering with an inner portion of the case. As a result, the size of the case is increased, therefore increasing the size of the substrate holding apparatus. 
     Meanwhile, according to the substrate holding apparatus described in Reference 2, when a plurality of substrates is positioned and fixed within the case, distances between the substrates are determined by distances between substrate guiding grooves for the substrates, respectively. Accordingly, a reduction of the distances between the substrates is restricted by a condition of a mold used for molding the case (the condition is the strength of the mold and the like). Further, the case requires a sufficient space for moving the substrates in a direction along a surface of each of the substrates into the case and for accommodating the substrates in the case. 
     A need thus exists for a substrate holding apparatus, which is not susceptible to the drawback mentioned above. 
     SUMMARY 
     According to an aspect of this disclosure, a substrate holding apparatus includes a case including a case body formed in a tubular shape that has a bottom surface and a case cover covering an end of an opening of the case body, a plurality of substrates at which electric circuits are mounted, the plurality of substrates being accommodated and held in the case in an overlapping manner with one another in a thickness direction of the plurality of substrates along a direction of the opening of the case body, and a plurality of support portions formed at an inner wall surface of the case body in a projecting manner in a column shape and extending in the thickness direction of the plurality of substrates, the plurality of support portions constituting a plurality of support portion groups, the plurality of support portions including end surfaces of which heights from the bottom surface of the case body in the thickness direction are the same as one another in each of the plurality of support portion groups, the heights of the end surfaces of the support portions in one of the plurality of support portion groups being different from the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, one of the plurality of substrates including a peripheral edge portion formed by guide grooves into which the support portions in one of the plurality of support portion groups are inserted in the thickness direction, the heights of the end surfaces of the support portions in the one of the plurality of support portion groups being greater than the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, the one of the plurality of substrates being supported by the end surfaces of the support portions in the other of the plurality of support portion groups, the heights of the end surfaces of the support portions in the other of the plurality of support portion groups being smaller than the heights of the end surfaces of the support portions in the one of the plurality of support portion groups. 
     According to another aspect of the disclosure, a substrate holding apparatus includes a case having a case body formed in a tubular shape that has a bottom surface and a case cover covering an end of an opening of the case body, a plurality of substrates at which electric circuits are mounted, the plurality of substrates being accommodated and held in the case in an overlapping manner with one another in a thickness direction of the plurality of substrates along a direction of the opening of the case body, and a plurality of support portions formed at an inner wall surface of the case body in a projecting manner in a column shape and extending in the thickness direction of the plurality of substrates, the plurality of support portions constituting a plurality of support portion groups, the plurality of support portions including end surfaces of which heights in the thickness direction from the bottom surface of the case body are the same as one another in each of the plurality of support portion groups, the heights of the end surfaces of the support portions in one of the plurality of support portion groups being different from the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, one of the plurality of substrates including a peripheral edge portion formed by guide grooves into which the support portions in one of the plurality of support portion groups are inserted in the thickness direction, the heights of the end surfaces of the support portions in the one of the plurality of support portion groups being greater than the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, the one of the plurality of substrates being supported by the end surfaces of the support portions in the other of the plurality of support portion groups, the heights of the end surfaces of the support portions in the other of the plurality of support portion groups being smaller than the heights of the end surfaces of the support portions in the one of the plurality of support portion groups, the substrates adjacent to each other in the thickness direction including respective facing surfaces at which connector portions are formed to project, the connector portions being fitted to each other in a case where one of the substrates is arranged in an overlapping manner relative to the other of the substrates in the thickness direction so that the substrates are electrically connected to each other. 
     According to a further aspect of the disclosure, a substrate holding apparatus includes a case having a case including a case body formed in a tubular shape that has a bottom surface and a case cover covering an end of an opening of the case body, a plurality of substrates at which electric circuits are mounted, the plurality of substrates being accommodated and held in the case in an overlapping manner with one another in a thickness direction of the plurality of substrates along a direction of the opening of the case body, and a plurality of support portions formed at an inner wall surface of the case body in a projecting manner in a column shape and extending in the thickness direction of the plurality of substrates, the plurality of support portions constituting a plurality of support portion groups, the plurality of support portions including end surfaces of which heights in the thickness direction from the bottom surface of the case body are the same as one another in each of the plurality of support portion groups, the heights of the end surfaces of the support portions in one of the plurality of support portion groups being different from the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, one of the plurality of substrates including a peripheral edge portion formed by guide grooves into which the support portions in one of the plurality of support portion groups are inserted in the thickness direction, the heights of the end surfaces of the support portions in the one of the plurality of support portion groups being greater than the heights of the end surfaces of the support portions in the other of the plurality of support portion groups, the one of the plurality of substrates being supported by the end surfaces of the support portions in the other of the plurality of support portion groups, the heights of the end surfaces of the support portions in the other of the plurality of support portion groups being smaller than the heights of the end surfaces of the support portions in the one of the plurality of support portion groups, the substrates adjacent to each other in the thickness direction including respective facing surfaces at which connector portions are formed to project, the connector portions being fitted to each other in a case where one of the substrates is arranged in an overlapping manner relative to the other of the substrates in the thickness direction so that the substrates are electrically connected to each other, one of the plurality of substrates that faces the case cover including a peripheral edge portion that is supported and positioned between the end surfaces of the support portions in one of the plurality of support portion groups and a facing surface of the case cover, the heights of the end surfaces of the support portions in the one of the plurality of support portion groups being greatest among the plurality of support portion groups, the case being a case for a camera in which the plurality of substrates are accommodated and held in the case body and at least a lens is mounted at the case cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein: 
         FIG. 1  is an exploded perspective view illustrating a substrate holding apparatus; and 
         FIG. 2  is an exploded planar view illustrating the substrate holding apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of a substrate holding apparatus will be described hereinafter with reference to the attached drawings.  FIGS. 1 and 2  are exploded perspective and planar views, respectively, illustrating a vehicle camera (camera) on which the substrate holding apparatus according to the embodiment is mounted. As shown in  FIG. 1 , the vehicle camera includes a case  10  formed by a case body  11  and a case cover  12 , and first, second, and third substrates  13 ,  14 , and  15 . Electric circuits (electronic components) are mounted on the first, second, and third substrates  13 ,  14 , and  15 , respectively. 
     The case body  11  is formed into an approximately square-shaped tube having a bottom surface. The case body  11  includes four connecting walls  11   a  arranged at corners of an inner wall of the case body  11 . The connecting walls  11   a  are integrally formed with the case body  11  in a projecting manner while extending in the direction of an opening of the case body  11  (the direction of the opening of the case body  11  corresponds to a vertical direction seen in  FIG. 1  and thickness directions of the first, second, and third substrates  13 ,  14 , and  15 ). Each of the connecting walls  11   a  has an approximate half-cylindrical shape. A bolt insertion hole  11   b  is formed in the center of the connecting wall  11   a  along a direction where the connecting wall  11   a  extends. The case body  11  is formed by a resin or aluminum material. 
     The case body  11  includes a plurality of first support portions  21 , a plurality of second support portions  22 , and a plurality of third support portions  23 . Each of the first, second, and third support portions  21 ,  22 , and  23  serves as a support portion integrally formed with the case body  11 . The support portion is formed in an approximate square-shaped (column-shaped) pole and in a projecting manner while extending along the direction of the opening of the case body  11 . Upper end surfaces  21   a ,  22   a , and  23   a  of the first, second, and third support portions  21 ,  22 , and  23  facing toward the direction of the opening of the case body  11  and serving as end surfaces have predetermined heights from the bottom surface of the case body  11 . The first, second, and third support portions  21 ,  22 , and  23  are stepped while having different heights from one another. That is, the heights of the upper end surfaces  21   a ,  22   a , and  23   a  from the bottom surface of the case body  11  are designed to gradually increase in the aforementioned order. In addition, the third support portion  23  protrudes slightly outward from an end of the opening of the case body  11  in the vertical direction seen in  FIG. 1 . 
     As illustrated in  FIG. 2 , two first support portions  21  are arranged at both end portions of each of long sides of a rectangle of the case body  11  and one first support portion  21  is arranged at an intermediate portion of each of short sides of the rectangle of the case body  11 . That is, a total of six first support portions  21  as a group is provided at the case body  11  so as to form a first support portion group (support portion group). Two second support portions  22  are arranged at an intermediate portion of each of the long sides of the rectangle of the case body  11  so as to be positioned at an approximate central portion between the first support portions  21   a  arranged at the both end portions of the long side of the rectangle. Further, two second support portions  22  are arranged at both end portions of each of the short sides of the rectangle of the case body  11 . That is, a total of eight second support portions  22  as a group is provided at the case body  11  so as to form a second support portion group (support portion group). In addition, three third support portions  23  are arranged at each of the long sides of the rectangle of the case body  11 . Two of the aforementioned three third support portions  23  are positioned in the approximate central portions, respectively, between the first and second support portions  21  and  22  that are located adjacent to each other at the long side of the rectangle of the case body  11 . Further, the rest of the aforementioned three third support portions  23  is positioned at an approximate central portion between the second support portions  22  that are arranged at the intermediate portion of the long side of the rectangle of the case body  11 . Further, two third support portions  23  are arranged at each of the short sides of the rectangle of the case body  11 . The aforementioned two third support portions  23  are positioned approximately at approximate central portions, respectively, between the first and second support portions  21  and  22  that are adjacent to each other at the short side of the rectangle of the case body  11 . That is, a total of ten third support portions  23  as a group is provided at the case body  11  so as to form a third support portion group (support portion group). As described above, the number of the first, second, and third support portions  21 ,  22 , and  23  is set to increase in the described order as the heights of the upper end surfaces  21   a ,  22   a , and  23   a  from the bottom surface of the case body  11  increase in the described order. In addition, a body-side connector portion  31  is provided at one side (right side in  FIG. 2 ) of the bottom surface of the case body  11  in a longitudinal direction of the case body  11 . A cable led from the body-side connector portion  31  to an outer side of the case  10  is electrically connected to a peripheral device (for example, a monitor and the like) or to a power source (battery). Further, the body-side connector portion  31  is directly attached to the first substrate  13  so as to be electrically connected thereto. 
     The first substrate  13  is formed into an approximate rectangular plate as seen in a plan view so as to conform to an outer shape of the inner wall of the case body  11 , which is seen in a plan view. Four notched portions  13   a  notched into curved shapes are formed at corners of the rectangular plate of the first substrate  13  so as to prevent from interfering with the connecting walls  11   a . A plurality of guide grooves (eight guide grooves)  13   b  having approximate square shapes is formed at a peripheral edge portion of the first substrate  13 . All of the second support portions  22  (second support portion group) is inserted in the guide grooves  13   b  along a longitudinal direction of the second support portion group (along the thickness direction of the first substrate  13 ). A plurality of guide grooves (ten guide grooves)  13   c  having approximate square shapes is formed at the peripheral edge portion of the first substrate  13 . All of the third support portions  23  (third support portion group) is inserted in the guide grooves  13   c  along a longitudinal direction of the third support portion group (along the thickness direction of the first substrate  13 ). Thus, when the first substrate  13  is accommodated within the case body  11  along the direction of the opening of the case body  11  while the second and third support portions  22  and  23  are inserted in the respective guide grooves  13   b  and  13   c , the peripheral edge portion of the first substrate  13  is in contact only with the upper end surfaces  21   a  of the first support portions  21  so as to be supported thereby. That is, the first substrate  13  is accommodated in the case body  11  while being positioned at the lowest height from the bottom surface of the case body  11 . 
     As shown in  FIG. 2 , a back-surface connector portion  32  is provided at an end portion (right side in  FIG. 2 ) in a longitudinal direction of the first substrate  13 . The back-surface connector portion  32  protrudes from the back surface of the first substrate  13  so as to face the body-side connector portion  31 . When the first substrate  13  is accommodated within the case body  11  along the direction of the opening of the case body  11 , the back-surface connector portion  32  is fitted to the body-side connector portion  31 ; thereby, the first substrate  13  is fixed to the case body  11  and positioned on the first support portions  21  (upper end surfaces  21   a ) at the same time as being electrically connected to the peripheral device. A power supply circuit supplying an electric power to the second and third substrates  14  and  15  is mounted on the first substrate  13 . In addition, an upper-surface connector portion  33  directly and electrically connected to the second substrate  14  is arranged at an end surface of the first substrate  13 , which faces toward the direction of the opening of the case body  11  (the end surface is an upper surface of the first substrate  13 ). The upper-surface connector portion  33  is positioned at one of the corners on the upper surface of the first substrate  13  (at an upper right side on the upper surface seen in  FIG. 2 ) so as not to overlap the back-surface connector portion  32  and the body-side connector portion  31  in the thickness direction. 
     The second substrate  14  is formed in an approximate rectangular plate as seen in a plan view so as to conform to the outer shape of the inner wall of the case body  11  seen in a plan view. Four notched portions  14   a  notched into curved shapes are formed at corners of the rectangular plate of the second substrate  14  so as to prevent from interfering with the connecting walls  11   a . A plurality of guide grooves (ten guide grooves)  14   b  having approximate square shapes is formed at a peripheral edge portion of the second substrate  14 . All of the third support portions  23  (third support portion group) is inserted in the guide grooves  14   b  along the longitudinal direction of the third support portion group (along the thickness direction of the second substrate  14 ). Thus, when the second substrate  14  is accommodated within the case body  11  along the direction of the opening of the case body  11  while the third support portions  23  are inserted in the guide grooves  14   b , the peripheral edge portion of the second substrate  14  is in contact only with the upper end surfaces  22   a  of the second support portions  22  (second support portion group) so as to be supported thereby. That is, the second substrate  14  is accommodated in the case body  11  while being positioned at an intermediate height from the bottom surface of the case body  11 . A distance between the first and second substrates  13  and  14  in the thickness direction is determined by a difference between the heights of the upper surfaces  21   a  and  22   a  of the first and second support portions  21  and  22 . 
     As shown in  FIG. 2 , a back-surface connector portion  34  is provided at one of the corners on a back surface of the second substrate  14  (at a lower right side on the back surface as seen in  FIG. 2 ). The back-surface connector portion  34  protrudes from the back surface of the second substrate  14  so as to face the upper-surface connector portion  33 . When the second substrate  14  is accommodated within the case body  11  along the direction of the opening of the case body  11 , the back-surface connector portion  34  is fitted to the upper-surface connector portion  33 ; thereby, the second substrate  14  is fixed to the first substrate  13  on the second support portions  22  (upper end surfaces  22   a ) at the same time as being electrically connected to the first substrate  13 . An image processing circuit processing an image signal (for example, an NTSC signal) output from the third substrate  15  is mounted on the second substrate  14 . In addition, an upper-surface connector portion  35  directly and electrically connected to the third substrate  15  is arranged at an end surface of the second substrate  14 , which faces toward the direction of the opening of the case body  11  (the end surface is an upper surface of the second substrate  14 ). The upper-surface connector portion  35  is positioned at one of the corners on the upper surface of the second substrate  14  (at an upper left side on the upper surface seen in  FIG. 2 ) so as not to overlap the back-surface connector portion  32 , the upper-surface connector portion  33 , the back-surface connector portion  34 , and the body-side connector portion  31  in the thickness direction. 
     The third substrate  15  is formed in an approximate rectangular plate as seen in a plan view so as to conform to the outer shape of the inner wall of the case body  11  seen in a plan view. Four notched portions  15   a , each notched into a curved shape, are formed at corners of the rectangular plate of the third substrate  15  so as to prevent from interfering with the connecting walls  11   a . The third substrate  15  is fixed to the case cover  12 ; therefore, for example, when the end of the opening of the case body  11  is closed by the case cover  12 , a peripheral edge portion of the third substrate  15  is in contact with the upper end surfaces  23   a  of the third support portions  23  (third support portion group) so as to be supported thereby. 
     In particular, the case cover  12  includes a recessed portion  12   a  formed in an approximate square shape as seen from the bottom surface of the case body  11 . The recessed portion  12   a  has an outer shape that is approximately the same size as the outer shape of the inner wall of the case body  11  seen in a plan view. The case cover  12  further includes a plurality of pressing portions  12   b . The pressing portions  12   b  are formed on a surface (inner wall surface) of an inner wall of the case cover  12  so as to horizontally protrude toward an inner side of the case cover  12  as seen in  FIG. 2 . The pressing portions  12   b  formed in approximate square-shaped poles face the third support portions  23  (third support portion group) in a direction where the case cover  12  is attached to the case body  11 . When the case cover  12  is attached to the case body  11 , the peripheral edge portion of the third substrate  15  is positioned and supported between facing surfaces of the pressing portions  12   b , which face the peripheral edge portion, and the upper end surfaces  23   a  of the third support portions  23  facing the peripheral edge portion. As a result, the third substrate  15  is further firmly fixed to the case body  11  (case  10 ). Further, the third substrate  15  is accommodated within the case  10  (case cover  12 ) so as to be positioned at the highest level in the vertical direction in  FIG. 1  while protruding slightly outward from the end of the opening of the case body  11  in the vertical direction. A distance between the second and third substrates  14  and  15  in the thickness direction is determined by a difference between the heights of the upper surfaces  22   a  and  23   a  of the second and third support portions  22  and  23 . Thread portions of bolts inserted into the bolt insertion holes  11   b  are fastened to nut portions embedded or pierced in the case cover  12 ; thereby, the case cover  12  is fixed to the case body  11 . 
     As shown in  FIG. 2 , a back-surface connector portion  36  is provided at one of the corners on a back surface of the third substrate  15  (at a lower left side on the back surface as seen in  FIG. 2 ). The back-surface connector portion  36  protrudes from the back surface of the third substrate  15  so as to face the upper-surface connector portion  35 . When the case cover  12  is attached to the case body  11 , the back-surface connector portion  36  is fitted to the upper-surface connector portion  35 ; thereby the third substrate  15  is further firmly fixed to the case body  11  on the third support portions  23  (upper end surfaces  23   a ) at the same time as being electrically connected to the second substrate  14 . An image pickup device is mounted on the third substrate  15 . The image pickup device is formed, for example, by CMOS or CCD. Light irradiated through a lens L attached to the case cover  12  (see  FIG. 1 ) is converted to an image signal by the image pickup device mounted on the third substrate  15 . Then, the image signal is output from the third substrate  15  to the second substrate  14 . 
     In addition, the electric circuits arranged on facing walls of the first and second substrates  13  and  14 , respectively, and between facing walls of the second and third substrates  14  and  15 , respectively, are dislocated from one another so as not to overlap one another in the thickness direction in a condition where the first, second, and third substrates  13 ,  14 , and  15  are provided adjacent to one another in the vertical direction (thickness direction). Such arrangement of the electric circuits is intended to secure distances required for arranging the electric circuits between the first and second substrates  13  and  14  and between the second and third substrates  14  and  15  in the thickness direction and to prevent increase of the distances in the thickness direction. 
     Assembling steps of the substrate holding apparatus according to the embodiment will be briefly explained as follows. First, while the second and third support portions  22  and  23  are being inserted in the respective guide grooves  13   b  and  13   c  of the first substrate  13 , the first substrate  13  is accommodated in the case body  11  along the direction of the opening of the case body  11  until the peripheral edge portion of the first substrate  13  is supported by the upper end surfaces  21   a  of the first support portions  21  in contact therewith. At this time, the back-surface connector portion  32  is fitted to the body-side connector portion  31 ; thereby, the first substrate  13  is fixed to the case body  11  and positioned on the first support portions  21  (upper end surfaces  21   a ) in the thickness direction at the same time as electrically connected to the peripheral device. In addition, the position of the first substrate  13  is determined in such a way that the second and third support portions  22  and  23  are respectively inserted in the guide grooves  13   b  and  13   c.    
     Next, while the third support portions  23  are inserted in the guide grooves  14   b  of the second substrate  14 , the second substrate  14  is accommodated in the case body  11  along the direction of the opening of the case body  11  until the peripheral edge portion of the second substrate  14  is supported by the upper end surfaces  22   a  of the second support portions  22  in contact therewith. At this time, the back-surface connector portion  34  is fitted to the upper-surface connector portion  33 ; thereby, the second substrate  14  is fixed to the first substrate  13  and positioned on the second support portions  22  (upper end surfaces  22   a ) in the thickness direction at the same time as being electrically connected to the first substrate  13 . In addition, the position of the second substrate  14  is determined in such a way that the third support portions  23  are inserted in the guide grooves  14   b.    
     Then, the case cover  12  is fixed to the case body  11  in such a way that the end of the opening of the case body  11  is closed by the case cover  12  to which the third substrate  15  is fixed. At this time, the peripheral edge portion of the third substrate  15  that is in contact with the upper end surfaces  23   a  in the thickness direction is positioned between the facing surfaces of the pressing portions  12   b  facing the peripheral edge portion, and the upper end surfaces  23   a  of the third support portions  23  facing the peripheral edge portion. As a result, the third substrate  15  is firmly fixed to the case body  11 . Further, the back-surface connector portion  36  is fitted to the upper-surface connector portion  35 ; thereby, the third substrate  15  is further firmly fixed to the second substrate  14  on the third support portions  23  (upper end surfaces  23   a ) in the thickness direction at the same time as being electrically connected the second substrate  14 . 
     As described above, the first, second, and third substrates  13 ,  14 , and  15  are overlapped in the thickness direction while being arranged at intervals of the distances corresponding to the difference between the heights of the first and second substrates  13  and  14  and to the difference between the heights of the second and third substrates  14  and  15 . Thus, the first, second, and third substrates  13 ,  14 , and  15  are accommodated within the case  10  (case body  11 ). According to such configuration, the light irradiated through the lens L attached to the case cover  12  is converted to the image signal by the third substrate  15  (image pickup device). Then, the image signal converted by the image pickup device is output from the third substrate  15  to the second substrate  14 . The image signal outputted from the third substrate  15  is processed by the image processing circuit mounted on the second substrate  14  and thereafter is outputted from the second substrate  14  via the first substrate  13  to the peripheral device. At this time, the electric power is applied to the second and third substrates  14  and  15  by the first substrate  13  (power supply circuit). 
     In addition, the aforementioned embodiment may be modified as follows. The height of the upper end surfaces  23   a  of the third support portions  23  may be set so that the third support portions  23  are accommodated within the case body  11  without protruding outward from the end of the opening of the case body  11  in the vertical direction. In this case, an area of an opening of the recessed portion  12   a  may be reduced; thereby, the peripheral edge portion of the third substrate  15  is positioned and supported between an end of an opening of the case cover  12  and the upper end surfaces  23   a  of the third support portions  23  to therefore fix the third substrate  15  to the case body  11 . 
     The first, second, and third support portions  21 ,  22 , and  23  may have circular cylindrical shapes or other shapes as long as being formed in column shapes. Moreover, the thickness direction of the first, second, and third substrates  13 ,  14 , and  15 , where the first, second, and third support portions  21 ,  22 , and  23  extend, (the direction of the opening of the case body  11 ) does not need to be completely perpendicular to the first, second, and third substrates  13 ,  14 , and  15 . 
     The case body  11  may have a circular cylindrical shape or other shapes as long as being formed into a tubular member having a bottom surface. That is, the case body  11  may be modified as long as including column-shaped supporting portions that are arranged at the inner wall and that support the first, second, and third substrates  13 ,  14 , and  15 . In this case, outer shapes of the first, second, and third substrates are not necessarily formed so as to conform to the outer shape of the inner wall of the case body  11  seen in a plan view. In addition, when a plurality of support portions including upper end surfaces having the same height are arranged at the inner wall of the case body  11 , each of the support portions is necessarily formed in a projecting manner from the inner wall of the case body  11  so as to support the first, second, and third substrates  13 ,  14 , and  15 . 
     In the embodiment, spacers may be appropriately provided to be supported between the first and second substrates  13  and  14  arranged adjacent to each other in the thickness direction and between the second and third substrates  14  and  15  arranged adjacent to each other in the thickness direction. Moreover, the number of substrates to be accommodated within the case  10  may be two, four or more than four substrates. 
     In addition, the substrate holding apparatus according to the embodiment may be applied to electric equipments other than the vehicle camera. Moreover, the substrate holding apparatus according to the embodiment may be modified as follows. The substrate holding apparatus may be formed by the first substrate  13  on which the image pickup device is mounted, the second substrate  14  on which the image processing circuit is mounted, and the third substrate  15  on which the power supply circuit is mounted. The image signal output from the image pickup device mounted on the first substrate  13  is processed by the image processing circuit mounted on the second substrate  14 . The power supply circuit mounted on the third substrate  15  supplies the electric power to the first and second substrates  13  and  14 . According to the configuration of the substrate holding apparatus, various electric circuits required for the vehicle camera may be integrally accommodated within the case  10 . In particular, the image signal is processed within the case  10  (by the image processing circuit mounted on the second substrate  14 ); thereby, the image signal may be output directly to a monitor and the like while not being out put to an additional processing circuit. 
     As described above, according to the embodiment, the first, second, and third substrates  13 ,  14 , and  15  are accommodated within the case  10  while being positioned at the predetermined intervals of the distances corresponding to the difference between the heights of the first and second support portions  21  and  22  and to the difference between the heights of the second and third support portions  22  and  23 . Further, when being accommodated within the case  10  as described above, the first, second, and third substrates  13 ,  14 , and  15  are overlapped with one another in the thickness direction corresponding to the direction of the opening of the case body  11 . Furthermore, the electric circuits (and the body-side connector  31  directly connected to the first substrate  13  and the upper-surface substrates  33  and  35  directly connected to the second and third substrates, respectively) mounted on the first, second, and third substrates  13 ,  14 , and  15 , respectively, are dislocated from one another thereon in the thickness direction so as to be prevented from interfering with one another (overlapping one another) between the first and second substrates  13  and  14  and between the second and third substrates  15 . Accordingly, the first, second, and third substrates  13 ,  14 , and  15  may be accommodated within the case  10  while not being affected by a movement of the electric circuits (electronic components) when the substrates are slid in the case  10  along the thickness direction; therefore, the size of the case  10  (case body  11 ) is prevented from being increased. Moreover, the first, second, and third support portions  21 ,  22 , and  23  (first, second, and third support portion groups) are configured to extend in the thickness direction of the first, second, and third substrates  13 ,  14 , and  15  and to support the peripheral edge portions of the first, second, and third substrates  13 ,  14 , and  15  on the upper end surfaces  21   a ,  22   a , and  23   a . Accordingly, the distance between the first and second substrates  13  and  14  is determined by the difference between the heights of the first and second support portions  21  and  22  (first and second support portion groups) while the distance between the second and third substrates  14  and  15  is determined by the difference between the heights of the second and third support portions  22  and  23  (second and third support portion groups). Further, the distance between the first and second substrates  13  and  14  is not determined by the sizes of areas of the upper end surfaces  21   a ,  22   a , and  23   a  of the first, second, and third support portions  21 ,  22 , and  23 . Consequently, the distance between the first and second substrates  13  and  14  and the distance between the second and third substrates  14  and  15  may be reduced while not being restricted by the mold for molding the first, second, and third support portions  21 ,  22 , and  23 . 
     According to the aforementioned embodiment, the upper-surface connector portions  33 ,  35  and the back-surface connector portions  34 ,  36  are formed to project at the respective facing surfaces of the first, second, and third substrates  13 ,  14 , and  15  arranged adjacent to one another in the thickness direction. The upper-surface connector portions  33 ,  35  and the back-surface connector portions  34 ,  36  are fitted to each other in a case where one of the first, second, and third substrates  13 ,  14 , and  15  is arranged in an overlapping manner relative to the other of the first, second, and third substrates  13 ,  14 , and  15  in the thickness direction so that the first, second, and third substrates  13 ,  14 , and  15  are electrically connected to each other. 
     In addition, the upper-surface connector portion  33  is fitted to the back-surface connector portion  34  and the upper-surface connector portion  35  is fitted to the back-surface connector portion  36 . Thus, the first, second, and third substrates  13 ,  14 , and  15  supported by the upper end surfaces  21   a ,  22   a , and  23   a  of the first, second, and third support portions  21 ,  22 , and  23  (first, second, and third support portion groups) and arranged adjacent to one another in the thickness direction are fixed to one another. 
     According to the aforementioned embodiment, the third substrate  15  facing the case cover  12  includes the peripheral edge portion that is supported and positioned between the upper end surfaces  23   a  of the third support portions  23  in the third support portion group and the facing surface of the case cover  12 . The height of the upper end surfaces  23   a  of the third support portions  23  in the third support portion group is greatest among the first, second, and third support portion groups. 
     Accordingly, the third substrate  15  is firmly fixed to the case body  11 . 
     According to the aforementioned embodiment, the case  10  is a case for the vehicle camera in which the first, second, and third substrates  13 ,  14 , and  15  are accommodated and held in the case body  11 . At least the lens L is mounted at the case cover  12 . 
     Accordingly, the vehicle camera in which the size of the case  10  is further reduced may be provided without restriction due to a condition of the mold for molding the case  10  and by the movement of the electric circuits (electronic components) when the first, second, and third substrates  13 ,  14 , and  15  are slid in the case  10  along the thickness direction. 
     The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.