Patent Publication Number: US-2011064403-A1

Title: Domed-shaped camera

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a dome-shaped camera. This invention particularly relates to a dome-shaped camera shock-resistant or impact-resistant and able to withstand even when being struck with a hammer or a bat. 
     2. Description of the Related Art 
     There is a dome-shaped camera used as a surveillance camera. The dome-shaped camera has a transparent dome-shaped cover and a camera unit placed therein. The cover is smoked to make the camera inconspicuous. 
     There is a possibility that a surveillance camera is struck with a hammer or a bat and is thereby broken. 
     An advanced dome-shaped camera is designed to be shock-resistant or impact-resistant and able to withstand even when being struck with a hammer or a bat. In such an advanced camera, a dome-shaped cover is made of impact-resistant polycarbonate (PC) resin while a casing supporting the cover is made of metal such as aluminum. 
     Japanese patent application publication number 2003-174572 discloses a surveillance camera having a dome-shaped cover and a camera unit placed therein. In the surveillance camera of Japanese application 2003-174572, the cover is made of PC resin, and the camera unit is connected with a bracket by shaft screws. The bracket has vertically elongated holes through which the shaft screws extend respectively. Coil springs urge the shaft screws so that they will be normally located at limit positions in the elongated holes. The shaft screws can move vertically from their normal positions along the elongated holes against the forces of the coil springs. As the camera unit moves vertically, the shaft screws move together with the camera unit. Thus, in the event that the cover is struck and the camera unit receives a corresponding impact force, the camera unit moves vertically while the shaft screws move vertically against the forces of the coil springs. Thereby, the impact force is absorbed by the coil springs, and the camera unit is prevented from being damaged. 
     It is desirable that a cover in a dome-shaped camera hardly deforms even when receiving an impact force. Furthermore, it is desirable that a camera unit in a dome-shaped camera is more reliably prevented from being damaged even when a cover in the camera is struck. In addition, it is desirable to make an impact-resistant dome-shaped camera more compact. 
     SUMMARY OF THE INVENTION 
     It is a first object of this invention to provide a dome-shaped camera in which a cover hardly deforms even when receiving an impact force, and a camera unit is more reliably prevented from being damaged even when the cover is struck. 
     It is a second object of this invention to provide a dome-shaped camera which is impact-resistant and more compact. 
     A first aspect of this invention provides a dome-shaped camera comprising a casing having an axis; a camera portion supported on the casing; a dome-shaped cover being at least partly transparent and covering the camera portion; a flange portion having a first contact portion and a second contact portion, the first contact portion being in contact with an end of the dome-shaped cover, the second contact portion being in contact with the casing, wherein a position of the first contact portion in a radial direction with respect to the axis of the casing differs from that of the second contact portion; and means for fixing the flange portion to the casing. 
     A second aspect of this invention is based on the first aspect thereof, and provides a dome-shaped camera further comprising an inner cover placed inward of the dome-shaped cover and covering the camera portion, the inner cover having an opening corresponding to an image taking range of the camera portion; and a third contact portion provided on the casing at a position radially inward of an outer circumference of the casing, the third contact portion being in contact with an end surface of the inner cover. 
     A third aspect of this invention is based on the first aspect thereof, and provides a dome-shaped camera wherein the camera portion is elastically movable toward the casing in a direction along the axis of the casing. 
     A fourth aspect of this invention is based on the second aspect thereof, and provides a dome-shaped camera wherein the camera portion is elastically movable toward the casing in a direction along the axis of the casing. 
     A fifth aspect of this invention provides a dome-shaped camera comprising a camera portion; an arm portion having one end connected with the camera portion; a gimbals base with which an other end of the arm portion is integrally connected; a casing having an axis and a support portion for elastically supporting the gimbals base; and a dome-shaped cover attached to the casing and covering the camera portion, the dome-shaped cover being at least partly transparent; wherein an image of the gimbals base projected onto a plane perpendicular to the axis of the casing is smaller in area than an image of the camera portion projected onto the plane. 
     A sixth aspect of this invention is based on the fifth aspect thereof, and provides a dome-shaped camera wherein the support portion comprises means for urging the gimbals base in a direction away from the casing and parallel to the axis of the casing, and means for limiting movement of the gimbals base in the direction away from the casing and parallel to the axis of the casing. 
     A seventh aspect of this invention is based on the fifth aspect thereof, and provides a dome-shaped camera further comprising an inner cover placed inward of the dome-shaped cover and covering the camera portion, the inner cover having an opening corresponding to an image taking range of the camera portion, the inner cover further having a guide portion in engagement with the arm portion for guiding the arm portion along the axis of the casing. 
     An eighth aspect of this invention is based on the fifth aspect thereof, and provides a dome-shaped camera further comprising at least one of a circuit board and electronic parts placed in the casing at a position radially outward of the support portion. 
     A ninth aspect of this invention is based on the sixth aspect thereof, and provides a dome-shaped camera further comprising an inner cover placed inward of the dome-shaped cover and covering the camera portion, the inner cover having an opening corresponding to an image taking range of the camera portion, the inner cover further having a guide portion in engagement with the arm portion for guiding the arm portion along the axis of the casing. 
     A tenth aspect of this invention is based on the sixth aspect thereof, and provides a dome-shaped camera further comprising at least one of a circuit board and electronic parts placed in the casing at a position radially outward of the support portion. 
     An eleventh aspect of this invention is based on the seventh aspect thereof, and provides a dome-shaped camera further comprising at least one of a circuit board and electronic parts placed in the casing at a position radially outward of the support portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a dome-shaped camera according to an embodiment of this invention. 
         FIG. 2  is an exploded perspective view of the dome-shaped camera in  FIG. 1 . 
         FIG. 3  is an exploded perspective view of a camera unit in the dome-shaped camera in  FIG. 1 . 
         FIG. 4  is a perspective view of a casing in the dome-shaped camera in  FIG. 1 . 
         FIG. 5  is an exploded perspective view of a cover in the dome-shaped camera in  FIG. 1 . 
         FIG. 6  is a sectional view of a portion of the cover as taken along the line S 1 -S 1  of  FIG. 5 . 
         FIG. 7  is a sectional view of a portion of the dome-shaped camera in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a dome-shaped camera  50  has a base portion fitting into a hole in a ceiling board  61  and fixed to the ceiling board  61 . The dome-shaped camera  50  includes a casing  1  and a cover  2  attached to the casing  1 . The cover  2  has a dome-shaped member  2   a . The dome-shaped camera  50  is placed relative to the ceiling board  61  in a manner such that the casing  1  and the cover  2  are exposed. 
     The casing  1  takes a cylindrical shape, and is made of resin. The casing  1  is formed by, for example, injection molding. Preferably, the resin for the casing  1  is impact-resistant (shock-resistant). Examples of the impact-resistant resin are polycarbonate (PC) resin and PC/ABS (acrylonitrile butadiene styrene) alloy resin. 
     The cover member  2   a  is transparent (pervious to light) and approximately hemispherical. The cover member  2   a  may be semitransparent (partly transparent). The cover member  2   a  is coaxial with the casing  1 . Preferably, the cover member  2   a  is made of PC resin which is at least partly transparent and impact-resistant. 
     The cover member  2   a  may be smoked or colored, for example, gray to make inconspicuous the interior of the dome-shaped camera  50 . The mean thickness of the cover member  2   a  is equal to, for example, 2 mm. 
     A camera unit  51  having a lens section  3  is placed in the interior of the cover member  2   a . The camera unit  51  is covered with the cover member  2   a . Furthermore, a part of the camera unit  51  is covered with an inner cover  5 . The inner cover  5  has a slit-like opening  5   a  at a position corresponding to the lens section  3 . The lens section  3  and the inner cover  5  can be seen from the exterior through the cover member  2   a.    
     Preferably, the inner cover  5  is made of opaque resin. The inner cover  5  is formed by, for example, injection molding. Examples of the resin for the inner cover  5  are ABS resin and PC resin. Preferably, the inner cover  5  is black. The mean thickness of the inner cover  5  is equal to, for example, 1.5 mm. 
     The inner cover  5  takes an approximately hemispherical shape. The inner cover  5  is coaxially or concentrically placed in the cover member  2   a . Preferably, there is a prescribed radial spacing or clearance A between the cover member  2   a  and the inner cover  5  (see  FIG. 7 ). 
       FIG. 2  shows the casing  1 , the cover  2 , and the inner cover  5  which are inverted with respect to those in  FIG. 1  for an easier understanding. With reference to  FIG. 2 , during the assembly of the dome-shaped camera  50 , the inner cover  5  and the cover  2  are moved toward the casing  1  along an axial direction D 1  before being attached to the casing  1 . The inner cover  5  and the cover  2  are coaxial with the casing  1 . The camera unit  51  is mounted on the casing  1 . 
     With reference to  FIGS. 3 and 4 , the casing  1  includes an outer cylindrical portion  1   a  and a ceiling portion  1   b . There is an axis (a center line) CL with respect to the casing  1 . The outer cylindrical portion  1   a  has an outer circumferential surface. The ceiling portion  1   b  closes at least part of one end of the outer cylindrical portion  1   a . The ceiling portion  1   b  has a step-like hole of a circular cross-section which varies stepwise along an axial direction. The depth of the step-like hole at a radial position increases as the radial position moves toward the axis (center line) CL of the casing  1 . 
     In more detail, the ceiling portion  1   b  has a ring-shaped reference plane portion  1   b   1 , a first tapered portion  1   b   2 , a second tapered portion  1   b   3 , an inner circumferential plane portion  1   b   4 , a third tapered portion  1   b   5 , and a bottom portion  1   b   6  which are arranged in that order. The reference plane portion  1   b   1  extends in an outermost part of the ceiling portion  1   b , and has a flat annular surface perpendicular to the casing axis CL. The first tapered portion  1   b   2  extends inward from the reference plane portion  1   b   1 , and has a tapered surface and an inside diameter which gradually decreases as viewed in the depth-wise direction. The second tapered portion  1   b   3  extends inward from the first tapered portion  1   b   2 , and has a tapered surface steeper than that of the first tapered portion  1   b   2  and an inside diameter which gradually decreases as viewed in the depth-wise direction. The inner circumferential plane portion  1   b   4  extends axially from an innermost part of the second tapered portion  1   b   3 , and has an inner circumferential surface parallel to the casing axis CL. The third tapered portion  1   b   5  extends inward from the inner circumferential plane portion  1   b   4 , and has a tapered surface and an inside diameter which gradually decreases as viewed in the depth-wise direction. The bottom portion  1   b   6  extends inward from the third tapered portion  1   b   5 , and has a flat annular surface perpendicular to the casing axis CL. The bottom portion  1   b   6  is formed with a circular opening  1   d  coaxial with the casing axis CL. 
     The ceiling portion  1   b  has a step le extending throughout the outer circumferential edge thereof and connecting with the outer cylindrical portion  1   a . The step  1   e  has a surface perpendicular to the casing axis CL. 
     The ceiling portion  1   b  has a circumferential wall portion  1   f  located radially inward of the step le and extending parallel to the casing axis CL. The circumferential wall portion  1   f  is formed with a pair of connecting portions  1   g  in which nuts  62  are embedded respectively. The connecting portions  1   g  are diametrically opposed to each other. In other words, the connecting portions  1   g  are circumferentially spaced at an angular interval of 180°. The nuts  62  are diametrically aligned so as to have a common axis which crosses the casing axis CL at right angles. 
     The ceiling portion  1   b  has four axial projections  1   h   1 ,  1   h   2 ,  1   h   3 , and  1   h   4  located radially inward of the circumferential wall portion  1   f  and circumferentially spaced at angular intervals of 90°. The projections  1   h   1  and  1   h   3  are diametrically opposed to each other. The projections  1   h   1  and  1   h   3  are formed with inwardly-facing hook-shaped claws  1   h   1   t  and  1   h   3   t , respectively. Thus, the projections  1   h   1  and  1   h   3  are called the claw-added projections also. The projections  1   h   2  and  1   h   4  are diametrically opposed to each other. Each of the projections  1   h   2  and  1   h   4  is in the form of a board piece without a claw. Thus, the projections  1   h   2  and  1   h   4  are called the claw-less projections also. 
     The ceiling portion  1   b  has contact ribs  1   j   1 ,  1   j   2 ,  1   j   3 , and  1   j   4  provided on and axially projecting from the reference plane portion  1   b   1 . As viewed in  FIGS. 3 and 4 , the contact ribs  1   j   1 ,  1   j   2 ,  1   j   3 , and  1   j   4  have top or upper surfaces  1   j   1   t ,  1   j   2   t ,  1   j   3   t , and  1   j   4   t  (see  FIG. 7 ) whose axial positions are the same. Thus, the heights (axial dimensions) of the contact ribs  1   j   1 ,  1   j   2 ,  1   j   3 , and  1   j   4  are equal. The contact ribs  1   j   1  extend from the projection  1   h   1  in opposite circumferential directions, respectively. The contact ribs  1   j   1  connect with the projection  1   h   1 . The contact ribs  1   j   2  extend from the projection  1   h   2  in opposite circumferential directions, respectively. The contact ribs  1   j   2  connect with the projection  1   h   2 . The contact ribs  1   j   3  extend from the projection  1   h   3  in opposite circumferential directions, respectively. The contact ribs  1   j   3  connect with the projection  1   h   3 . The contact ribs  1   j   4  extend from the projection  1   h   4  in opposite circumferential directions, respectively. The contact ribs  1   j   4  connect with the projection  1   h   4 . 
     The inner edge of the bottom portion  1   b   6  which defines the opening  1   d  has engagement projections  1   k  and wall projections  1   m  extending in directions parallel to the casing axis CL. There are three engagement projections  1   k  circumferentially spaced at angular intervals of 120°. Each of the engagement projections  1   k  is formed with a claw  1   k   1  projecting radially outward. There are six wall projections  1   m  which are circumferentially arranged. Two wall projections  1   m  are located at opposite sides of each engagement projection  1   k , respectively. 
     The ceiling portion  1   b  has three support arms  1   n  circumferentially spaced at angular intervals of 120°. There is a positional phase difference of 60° in the circumferential direction between the support arms  1   n  and the engagement projections  1   k . The support arms  1   n  are flexible and elastically deformable. 
     The distal end of each of the support arms  1   n  is formed with a contact portion  1   n   1  projecting in a direction parallel to the casing axis CL. The directions in which the contact portions  1   n   1  project are equal or similar to the directions of the engagement projections  1   k.    
     Each of the support arms  1   n  has a base forming a fulcrum  1   ns  located in the second tapered portion  1   b   3 . Each support arm  1   n  is formed by a part of the ceiling portion  1   b  which is sandwiched between a pair of slits extending from the second tapered portion  1   b   3  to the opening  1   d . Each support arm  1   n  is flexible and swingable about its fulcrum  1   ns . When each support arm  1   n  receives a force in a direction parallel to the casing axis CL (a downward direction as viewed in  FIG. 4 ), the support arm  1  elastically bends along a direction corresponding to the direction of the force. 
     The engagement projections  1   k  and the wall projections  1   m  have radially-outward-facing surfaces which are approximately inscribed in a circle centered at the casing axis CL and having a first prescribed diameter. The distal ends of the claws  1   k   1  of the engagement projections  1   k  are inscribed in a circle centered at the casing axis CL and having a second prescribed diameter greater than the first prescribed diameter. 
     As shown in  FIG. 3 , the camera unit  51  includes a camera body  52 , a ring bracket  53  in engagement with the camera body  52 , and a gimbals  54  supporting the ring bracket  53 . 
     The camera body  52  is placed in the inner cover  5 . Preferably, there is a prescribed spacing or clearance between the inner cover  5  and the camera body  52  (see  FIG. 7 ). 
     The camera body  52  includes a lens section  3 , an image sensor  66 , and a camera base  52   a . An image of a subject is focused onto the image sensor  66  through the lens section  3 . The image sensor  66  converts the image into an electric signal. The camera base  52   a  supports the lens section  3 , the image sensor  66 , and other members. The electric signal is transmitted from the image sensor  66  via a cable (not shown in  FIG. 3 ). 
     The camera base  52   a  has an outer circumferential surface  52   ag  provided with four engagement portions  52   a   1  which are circumferentially spaced at angular intervals of 90°. The engagement portions  52   a   1  are designed for connection with engagement claws  53   b  (mentioned later) on the ring bracket  53 . 
     The camera base  52   a  takes a cylindrical shape having a prescribed outside diameter φa. Preferably, the camera base  52   a  is made of resin such as PC resin. The camera base  52   a  is formed by, for example, injection molding. 
     The lens section  3  is provided with mechanisms (not shown) designed to allow focusing and zooming adjustments. 
     The ring bracket  53  has an annular base  53   k , two support tabs  53   a , and four engagement claws  53   b . The support tabs  53   a  are provided on the annular base  53   k , and are diametrically opposed to each other. Thus, the support tabs  53   a  are circumferentially spaced at an angular interval of 180°. The engagement claws  53   b  are provided on the annular base  53   k , and are circumferentially spaced at angular intervals of 90°. 
     Preferably, the ring bracket  53  is made of resin such as PC resin. The ring bracket  53  is formed by, for example, injection molding. 
     The support tabs  53   a  have inwardly-facing surfaces to which nuts  53   c  are fixed respectively by, for example, welding. The nuts  53   c  are diametrically aligned so as to have a common axis CL 53 R. As will be made clear later, the ring bracket  53  is rotatable about the axis CL 53 R. Accordingly, the axis CL 53 R is referred to as a rotation axis also. 
     Each of the support tabs  53   a  has a circular aperture  53   d  coaxial with and corresponding in diameter to the threaded hole in the related nut  53   c . For each of the support tabs  53   a , a bolt or screw  63  can extend through the aperture  53   d  and mesh with the nut  53   c.    
     The axis CL 53 R of the nuts  53   c  crosses the casing axis CL at right angles under the conditions where the dome-shaped camera  50  has been assembled. 
     The gimbals  54  has an annular base  54   k  and a pair of arms  54   a . The arms  54   a  extend upward and radially outward from the base  54   k  as viewed in  FIG. 3 . Preferably, the arms  54   a  are integral with the base  54   k . The base  54   k  takes a ring shape having an axis (a center line) CL 54  and a prescribed outside diameter φb smaller than the outside diameter φa of the camera base  52   a . The arms  54   a  on the base  54   k  are diametrically opposed to each other. In other words, the arms  54   a  are circumferentially spaced at an angular interval of 180°. In  FIG. 3 , the arms  54   a  project from the base  54   k  in directions intermediate between axially upward directions and radially outward directions. Thus, the diametrical distance between same-axial-position portions (same-height portions) of the arms  54   a  increases as the same-axial-position portions move away from the base  54   k.    
     Each of the arms  54   a  has a slant portion  54   b  extending from the base  54   k  and inclined with respect to the base axis CL 54 , and an engagement portion  54   c  extending from the slant portion  54   b  in a direction parallel to the base axis CL 54 . The engagement portion  54   c  occupies a distal end of the related arm  54   a.    
     The engagement portions  54   c  have circular apertures  54   d  for accommodating the screws  63 , respectively. The screws  63  have heads designed to abut against the engagement portions  54   c . The apertures  54   d  are diametrically aligned so as to have a common axis CL 54 R which crosses the base axis CL 54  at right angles. As will be made clear later, the gimbals  54  is rotatable about the axis CL 54 R. Accordingly, the axis CL 54 R is referred to as a rotation axis also. 
     The diametrical distance between the inwardly-facing surfaces of the engagement portions  54   c  is equal to or slightly greater than the diametrical distance between the outwardly-facing surfaces of the support tabs  53   a  on the ring bracket  53 . 
     Preferably, the gimbals  54  is made of resin such as PC resin. The gimbals  54  is formed by, for example, injection molding. 
     Each of the engagement portions  54   c  has ribs  54   e  at opposite sides thereof. The ribs  54   e  enhance the rigidity of the related engagement portion  54   c . The ribs  54   e  are designed for engagement with the inner cover  5  as will be explained later. 
     Preferably, the outside diameter φa of the camera base  52   a  is equal to 57.6 mm while the outside diameter φb of the gimbals base  54   k  is equal to 42.0 mm. In this case, the ratio of the area Sb of an axially-projected outer circle of the gimbals base  54   k  to the area Sa of an axially-projected outer circle of the camera base  52   a  is equal to 0.532. Preferably, the area Sb of the axially-projected outer circle of the gimbals base  54   k  is significantly smaller than the area Sa of the axially-projected outer circle of the camera base  52   a.    
     Accordingly, it is preferable that an image of the gimbals base  54   k  projected onto a plane perpendicular to the casing axis CL is smaller in area than an image of the camera base  52   a  projected on the plane. 
     The gimbals base  54   k  has a prescribed inside diameter φc. Preferably, the inside diameter φc is approximately equal to the diameter of the circle in which the engagement projections  1   k  and the wall projections  1   m  on the casing  1  are inscribed. 
     The gimbals base  54   k  is in engagement with the ceiling portion  1   b  of the casing  1  (the bottom portion  1   b  of the casing  1  as viewed in  FIG. 3 ) via a snap fit. The gimbals base  54   k  is supported on the ceiling portion  1   b  of the casing  1 . 
     Referring to  FIGS. 3 and 4 , the camera unit  51  is assembled with respect to the casing  1  as follows. First, the ring bracket  53  is moved toward the camera base  52   a  of the camera body  52  along a direction DR 1  in  FIG. 3  before being connected with the camera base  52   a . At the time of the connection of the ring bracket  53  with the camera base  52   a , the claws  53   b  on the ring bracket  53  are forced into engagement with the engagement portions  52   a   1  on the camera base  52   a.    
     Thereafter, the gimbals  54  is moved toward the camera body  52  with the ring bracket  53  along a direction DR 2  in  FIG. 3 , and the rotation axis CL 53 R of the ring bracket  53  and the rotation axis CL 54 R of the gimbals  54  are made to coincide with each other. 
     Under the conditions where the rotation axes CL 53 R and CL 54 R coincide with each other, the bolts  63  are passed through the apertures  54   d  of the gimbals  54  and the apertures  53   d  of the ring bracket  53  before being made to mesh with the nuts  53   c . Thus, the camera body  52 , the ring bracket  53 , and the gimbals  54  are combined together. 
     Thereby, the camera body  52  is rotatable about the rotation axis CL 54 R so that camera&#39;s tilting adjustment can be implemented. During the installation of the dome-shaped camera  50  after the assembly thereof, the camera body  52  is manually rotated and adjusted to a desired tilt angle and then the bolts  63  are sufficiently fastened to the nuts  53   c . Thus, the tilting adjustment is completed, and the camera body  52  is maintained at the desired tilt angle. 
     During the assembly of the camera unit  51 , under the conditions where the camera body  52  and the gimbals  54  are combined together, the gimbals base  54   k  is connected with the bottom portion  1   b   6  of the ceiling portion  1   b  of the casing  1 . 
     Specifically, the gimbals base  54   k  is pressed into the casing  1  along a direction DR 3  in  FIG. 3  and is passed over the claws  1   k   1  on the engagement projections  1   k  of the bottom portion  1   b   6  while the engagement projections  1   k  are bent inward. When the gimbals base  54   k  is passed over the claws  1   k   1 , the lower surface  54   kb  (see  FIG. 7 ) of the gimbals base  54   k  elastically meets the contact portions  1   n   1  of the support arms  1   n  on the ceiling portion  1   b.    
     The elastic contact between the gimbals base  54   k  and the contact portions  1   n   1  of the support arms  1   n  limits further movement of the gimbals base  54   k  in the direction DR 3  (the pressing direction). The outward-facing surfaces of the wall projections  1   m  engage the gimbals base  54 , thereby centering the gimbals base  54  at the casing axis CL. The claws  1   k   1  on the engagement projections  1   k  are in engagement with the gimbals base  54   k , and limit movement of the gimbals base  54   k  in a falling-off direction (a direction opposite to the direction DR 3 ). Accordingly, the gimbals base  54   k  is held with respect to the bottom portion  1   b   6 . 
     The gimbals base  54   k  can rotate about the casing axis CL while being held with respect to the bottom portion  1   b   6 . The gimbals base  54   k  is elastically urged by the support arms  1   n  while being in engagement with the claws  1   k   1  on the engagement projections  1   k . Thus, the gimbals base  54   k  slips on the contact portions  1   n   1  of the support arms  1   n  and the claws  1   k   1  of the engagement projections  1   k  and hence receives frictional forces therefrom when rotating about the casing axis CL. The frictional forces give a good feel concerning an adjustment of camera&#39;s panning position. 
     With reference to  FIGS. 5 and 6 , the cover  2  includes the dome-shaped member  2   a , an annular flange  2   b , and a fixing ring  2   c  coaxial with each other. The cover member  2   a  has an end surface  2   at  abutting against the flange  2   b . The cover member  2   a  is secured to the flange  2   b  by the fixing ring  2   c.    
     The cover member  2   a  takes an approximately hemispherical shape. A radially-outward projection forming a flange  2   a   1  is provided on an annular end of the cover member  2   a . The flange  2   a   1  extends throughout the circumference defined by the annular end of the cover member  2   a.    
     Preferably, the cover member  2   a  is made of at least partly transparent resin such as PC resin. Generally, PC resin is excellent in impact resistance. Thus, in the case where PC resin is used for the cover member  2   a , the resultant dome-shaped camera  50  is rugged. 
     The resin for the cover member  2   a  is colored or colorless. In the case where the camera body  52  within the cover member  2   a  is required to be inconspicuous when seen from the exterior, it is preferable that the resin for the cover member  2   a  has a gray-based color. 
     The flange  2   b  takes a ring shape having a central opening  2   bk  and an axis (a center line) CL 2 . Preferably, the flange  2   b  is made of resin in terms of cost performance. Alternatively, the flange  2   b  may be made of metal such as aluminum. 
     The flange  2   b  has a circumferential wall portion  2   b   1 , a ceiling portion  2   b   2 , and a circumferential rib  2   b   3 . The circumferential wall portion  2   b   1  has an outer circumferential surface  2   b   1   s . The ceiling portion  2   b   2  connects with the circumferential wall portion  2   b   1 . The ceiling portion  2   b   2  has a ceiling surface  2   b   2   t  which extends from the circumferential wall portion  2   b   1  toward the flange axis CL 2 . The circumferential rib  2   b   3  is provided on the inner edge of the ceiling portion  2   b   2  which surrounds and defines the central opening  2   bk . The circumferential rib  2   b   3  extends throughout the circumference of the central opening  2   bk . The circumferential rib  2   b   3  projects from the ceiling portion  2   b   2  along a direction parallel to the flange axis CL 2 . 
     Preferably, the ceiling surface  2   b   2   t  is perpendicular to the flange axis CL 2 . The ceiling surface  2   b   2  may be slightly inclined relative to a plane perpendicular to the flange axis CL 2 . 
     The circumferential wall portion  2   b   1  has an inner surface  2   b   1   n . The dimensions and shape of the inner surface  2   b   1   n  are chosen so that the inner surface  2   b   1  will contact or adjacently oppose a part of an outer circumferential surface of the circumferential wall portion  1   f  in the ceiling portion  1   b  of the casing  1 . 
     The circumferential wall portion  2   b   1  is formed with a hole  2   b   4  for accommodating a screw or bolt  64  used to fix the circumferential wall portion  2   b   1  to the casing  1 . There may be two diametrically-opposed holes  2   b   4 . 
     The circumferential rib  2   b   3  has an outer circumferential surface, the dimensions and shape of which are chosen so that the outer circumferential surface will contact or adjacently oppose an inner circumferential surface of the cover member  2   a  at or near its end. 
     The fixing ring  2   c  has an inner circumferential surface  2   c   1  and a recess  2   c   2  for accommodating the flange  2   a   1  of the cover member  2   a . The dimensions and shape of the inner circumferential surface  2   c   1  of the fixing ring  2   c  are chosen so that the inner circumferential surface  2   c   1  will contact or adjacently oppose an outer circumferential surface of the end of the cover member  2   a . Preferably, the fixing ring  2   c  is made of resin such as PC resin or HIPS (high impact polystyrene) resin. Alternatively, the fixing ring  2   c  may be made of metal such as aluminum. 
     During the assembly of the cover  2 , the cover member  2   a  is fitted to the flange  2   b  while the circumferential rib  2   b   3  on the flange  2   b  is moved into the cover member  2   a  and the end surface  2   at  of the cover member  2   a  contacts the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b . Thus, the ceiling surface  2   b   2   t  of the flange  2   b  provides a contact portion in touch with the end of the cover member  2   a.    
     Thereafter, the fixing ring  2   c  is fitted to the cover member  2   a  and the flange  2   b  from above as viewed in  FIG. 5  in a manner such that an end surface  2   ct  of the fixing ring  2   c  contacts the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b  and the flange  2   a   1  of the cover member  2   a  is accommodated in the recess  2   c   2  in the fixing ring  2   c . In this way, the cover member  2   a , the flange  2   b , and the fixing ring  2   c  are fitted to each other as shown in  FIG. 6 . Under the conditions where the cover member  2   a , the flange  2   b , and the fixing ring  2   c  are fitted to each other, they are bonded together to form a single body in one of ways indicated below. 
     The first way uses adhesive for bonding the cover member  2   a , the flange  2   b , and the fixing ring  2   c  together. The second way uses snap fits for firmly connecting the cover member  2   a , the flange  2   b , and the fixing ring  2   c  together. In this case, the cover member  2   a , the flange  2   b , and the fixing ring  2   c  are formed with engagement claws for implementing the snap fits. The third way uses threads of screws provided on opposing surfaces of the cover member  2   a , the flange  2   b , and the fixing ring  2   c . In this case, the cover member  2   a , the flange  2   b , and the fixing ring  2   c  are firmly connected together by the screws. The fourth way uses ultrasonic welding for bonding the cover member  2   a , the flange  2   b , and the fixing ring  2   c  together. The fourth way premises that the cover member  2   a , the flange  2   b , and the fixing ring  2   c  are made of resin. 
     With reference back to  FIG. 2 , the inner cover  5  has a crown portion  5   b , a cylindrical barrel portion  5   c , and a flange  5   d  arranged in that order. The crown portion  5   b  takes an approximately hemispherical shape. The barrel portion  5   c  coaxially connects with the crown portion  5   b . The crown portion  5   b  and the barrel portion  5   c  have a common axis (center line) CL 5 . The flange  5   d  projects radially outward from an end of the barrel portion  5   c . The flange  5   d  extends substantially throughout the circumference of the end of the barrel portion  5   c.    
     The inner cover  5  has a slit-like opening  5   a  extending in an area containing a zone at and near the top end (apex) of the crown portion  5   b . The opening  5   a  further extends into the barrel portion  5   c . The opening  5   a  is designed to allow the camera unit  51  to continuously take images of an external scene while the lens section  3  is tilted between a minimum degree and a maximum degree. Thus, the opening  5   a  corresponds to the image taking range of the camera unit  51 . 
     An inner surface of the barrel portion  5   c  is formed with two pairs of ribs  5   e   1  and  5   e   2  extending in parallel to the axis CL 5  of the barrel portion  5   c . The rib pairs are circumferentially spaced from the opening  5   a  at an angular interval of about 90°. There is a prescribed interval between the rib pairs. 
     The rib pairs correspond to the ribs  54   e  on the opposite sides of one engagement portion  54   c  in the gimbals  54 , respectively. In each of the rib pairs, the interval between the ribs  5   e   1  and  5   e   2  and the dimensions and shape of the ribs  5   e   1  and  5   e   2  are chosen so that the rib  54   e  on the engagement portion  54   c  can fit into a region between the ribs  5   e   1  and  5   e   2  in the corresponding rib pair. 
     Preferably, the inner cover  5  is made of light-shading or light-shielding resin such as PC resin. 
     During the assembly of the dome-shaped camera  50 , the cover  2  and the inner cover  5  are attached to the casing  1  as follows. 
     First, the inner cover  5  is moved toward the casing  1  along a direction DR 5  in  FIG. 2  before being attached to the casing  1 . The flange  5   d  of the inner cover  5  is brought into contact with the claw-added projections  1   h   1  and  1   h   3  on the casing  1  and is passed over the claws of the projections  1   h   1  and  1   h   3 . Then, the flange  5   d  meets the contact ribs  1   j   1 - 1   j   4  on the casing  1 , and the flange  5   d  is held between the claws of the projections  1   h   1  and  1   h   3  and the contact ribs  1   j   1 - 1   j   4  on the casing  1 . In this way, the inner cover  5  is attached to the casing  1 . 
     At this time, the end surface  5   t  of the inner cover  5  (that is, the lower surface of the flange  5   d  as viewed in  FIG. 2 ) abuts against the top surfaces  1   j   1   t - 1   j   4   t  of the contact ribs  1   j   1 - 1   j   4 . 
     During the movement of the inner cover  5  relative to the casing  1 , the outer circumferential surface of the flange  5   d  on the inner cover  5  is guided by the inwardly-facing surfaces of the claw-added projections  1   h   1  and  1   h   3  and the claw-less projections  1   h   2  and  1   h   4  on the casing  1  so that the inner cover  5  is reliably centered at the casing axis CL. When the inner cover  5  is normally attached to the casing  1 , each rib  54   e  on the gimbals  54  fits in the region between the ribs  5   e   1  and  5   e   2  in the corresponding rib pair on the inner cover  5 . 
     Thereby, the inner cover  5  is held on the casing  1  while the rotation of the inner cover  5  about the casing axis CL is limited. 
     Thereafter, the cover  2  is moved toward the casing  1 , to which the inner cover  5  has been attached, in the direction D 1  before being attached to the casing  1 . Specifically, the circumferential wall portion  2   b   1  of the flange  2   b  on the cover  2  is fitted around the circumferential wall portion if in the casing  1 . At this time, the end surface  2   bt  of the circumferential wall portion  2   b   1  of the flange  2   b  abuts against the step  1   e  on the casing  1  (see  FIG. 7 ). Thus, the end surface  2   bt  of the flange  2   b  provides a contact portion in touch with the casing  1 . In the flange  2   b , the contact portion in touch with the casing  1  is located radially outward of the contact portion in touch with the casing member  2   a.    
     Subsequently, the bolt  64  is passed through the hole  2   b   4  in the flange  2   b  on the cover  2 , and is then driven into mesh with the nut  62  on the circumferential wall portion  1   f  in the casing  1  so that the cover  2  and the casing  1  are firmly connected together. Two bolts  64  may be used to connect the cover  2  and the casing  1 . 
     In the dome-shaped camera  50 , the support arms  1   n  on the casing  1  serve as means for urging the gimbals base  54   k  in a direction away from the casing  1  and parallel to the casing axis CL. The claws  1   k   1  of the engagement projections  1   k  on the casing  1  serve as means for limiting movement of the gimbals base  54   k  in the direction away from the casing  1  and parallel to the casing axis CL. 
     With reference to  FIG. 7 , a top of the cover member  2   a  in the dome-shaped camera  50  is struck with a hammer or a bat, and hence receives an impact. Accordingly, an impact force F is applied to the top of the cover member  2   a . The impact force F travels to the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b  via the end surface  2   at  of the cover member  2   a  which abuts against the ceiling surface  2   b   2   t . The impact force F becomes a force f 1  applied from the end surface  2   at  to the ceiling surface  2   b   2   t.    
     Since the end surface  2   at  of the cover member  2   a  contacts the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b  throughout the circumference thereof, the force f 1  is scattered so that a concentrated stress is absent from the cover member  2   a . Therefore, impact-responsive deformations of the end of the cover member  2   a  and a portion of the cover member  2   a  near the end are suppressed or prevented. 
     Similarly, a concentrated stress is absent from the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b . As previously mentioned, the force f 1  is scattered. Therefore, the flange  2   b  hardly deforms in response to the impact on the cover member  2   a.    
     The radial position of the contact between the cover member  2   a  and the flange  2   b  differs from that of the contact between the flange  2   b  and the casing  1 . Thus, the flange  2   b  can elastically bend in a direction DR 21  in response to the force f 1  so that a portion of the force f 1  can be absorbed. 
     Therefore, a weaker force caused by the impact force F is transmitted from the flange  2   b  to the step  1   e  on the casing  1 . Consequently, the cover member  2   a , the flange  2   b , and the casing  1  are hardly deformed and damaged by the impact on the cover member  2   a.    
     The step  1   e  is located at a position corresponding to the outer cylindrical portion  1   a  of the casing  1  so that the casing  1  is hardly deformed by a force applied to the step  1   e  which originates from the impact force F. The force applied to the step  1   e  travels and escapes to the ceiling board  61  through the outer cylindrical portion  1   a  substantially without damping. 
     In the case where the impact force F is so strong that the cover member  2   a  is deformed and brought into contact with the inner cover  5 , the impact force F travels from the cover member  2   a  to the inner cover  5  as an impact force FA. 
     The impact force FA travels to the top surfaces  1   j   1   t - 1   j   4   t  of the contact ribs  1   j   1 - 1   j   4  on the casing  1  via the end surface  5   t  of the inner cover  5  which abuts against the top surfaces  1   j   1   t - 1   j   4   t . The impact force FA becomes a force fa 1  applied from the end surface  5   t  to the top surfaces  1   j   1   t - 1   j   4   t . Since there are four pairs of the contact ribs  1   j   1 - 1   j   4 , each of the contact ribs  1   j   1 - 1   j   4  receives one eighth of the force fa 1 . 
     In the casing  1 , the contact ribs  1   j   1 - 1   j   4  are provided on the reference plane portion  1   b   1  which extends radially inward of the outer cylindrical portion  1   a . Thus, the contact ribs  1   j   1 - 1   j   4  can be deformed downward along a direction DR 22  to a certain degree as viewed in  FIG. 7  when receiving a strong force. The force fa 1  coming from the inner cover  5  is distributed to the contact ribs  1   j   1 - 1   j   4  so that each of the contact ribs  1   j   1 - 1   j   4  is subjected to a weaker stress and deforms only slightly. 
     The reference plane portion  1   b   1  of the casing  1  can elastically deform to a certain degree. A portion of the impact force FA which travels to the reference plane portion  1   b   1  via the contact ribs  1   j   1 - 1   j   4  can be at least partially absorbed by the deformation of the reference plane portion  1   b   1 . 
     In the case where the impact force FA applied to the inner cover  5  is so strong that the inner cover  5  is deformed and brought into contact with the camera body  52 , the impact force FA travels from the inner cover  5  to the camera body  52  as an impact force FB. 
     The impact force FB is caused by a portion of the impact force FA applied to the inner cover FA. The impact force FB is applied to the camera body  52 . 
     The impact force FB travels from the camera body  52  to the gimbals  54  via the support tabs  53   a  on the ring bracket  53 . 
     The gimbals  54  supports the camera body  52  through the ring bracket  53 . The ribs  54   e  of the engagement portions  54   c  in the gimbals  54  are connected with and guided by the ribs  5   e   1  and  5   e   2  on the inner cover  5 . Thus, the gimbals  54  may be moved downward along a direction DR 23  as viewed in  FIG. 7  when receiving the impact force FB. 
     The lower surface  54   kb  of the gimbals base  54   k  touches the contact portions  1   n   1  of the support arms  1   n  on the casing  1 . Thus, as the gimbals  54  is moved along a direction D 23 , the support arms  1   n  are elastically deformed along the direction D 23  also. Accordingly, the support arms  1   n  softly support the gimbals  54 . The support arms  1   n  absorb kinetic energy given to the camera body  52  in accordance with the impact force FB. Therefore, damage to the camera body  52  due to the impact force FB is effectively suppressed. 
     In the dome-shaped camera  50 , an impact force applied to the cover member  2   a  can propagate therefrom to the casing  1  via three paths (first, second, and third paths). The first path has a sequence of the cover member  2   a , the flange  2   b , and the casing  1 . The second path has a sequence of the cover member  2   a , the inner cover  5 , and the casing  1 . The third path has a sequence of the cover member  2   a , the inner cover  5 , the camera body  52 , the gimbals  54 , and the casing  1 . 
     An impact force propagating along the first path is damped especially by a deformation of the flange  2   b . An impact force propagating along the second path is damped especially by a deformation of the reference plane portion  1   b   1  in the casing  1 . Regarding an impact force propagating along the third path, kinetic energy of the camera body  52  is absorbed especially by deformations of the gimbals  54  and the support arms  1   n  on the casing  1 . 
     In the dome-shaped camera  50 , an impact force applied to the cover member  2   a  is prevented from directly traveling to the camera body  52 . Generally, only a sufficiently-damped impact force reaches the camera body  52 . In the event that the camera body  52  is moved by a transmitted impact force, kinetic energy of the camera body  52  is effectively absorbed so that damage to the camera body  52  is suppressed or prevented. 
     In the dome-shaped camera  50 , the outside diameter φb of the base  54   k  of the gimbals  54  is smaller than the outside diameter φa of the camera base  52   a . Accordingly, the volume of the interior space S of the casing  1  is increased as compared with an assumed case where the outside diameter φb is equal to the outside diameter φa. 
     With reference to  FIG. 7 , the two-dot dash lines denote the outlines of the support arms  1   n  in the assumed case where the outside diameter φb is equal to the outside diameter φa. The above-mentioned increase in the volume of the interior space S of the casing  1  corresponds to the sectional zone SP surrounded by the two-dot dash lines and the solid lines. The volume increase is equal to an annular space Vp formed by one revolution of the zone SP about the casing center CL. 
     The ribs  5   e   1  and  5   e   2  on the inner cover  5  are in engagement with the ribs  54   e  on the gimbals  54 . This engagement is designed to provide a guide structure by which the camera body  52  can move only in directions parallel to the casing axis CL. Therefore, even when the outside diameter φb of the gimbals base  54   k  is relatively small, the camera body  52  supported on the gimbals base  54   k  is prevented from swinging about of fulcrums formed by support portions SJ on the casing  1 . 
     The increased interior space S of the casing  1  can accommodate more parts (electronic parts) and larger circuit boards, being advantageous in designing the dome-shaped camera  50  to have more multiple-functions. 
     The dome-shaped camera  50  can be more compact although the casing  1  contains parts and circuit boards similar to those in a conventional camera. 
     With reference to  FIG. 7 , in the assumed case where the outside diameter φb of the base  54   k  of the gimbals  54  is equal to the outside diameter φa of the camera base  52   a , a widest circuit board which can be accommodated in the casing  1  is denoted by the broken lines  65   j . On the other hand, in the dome-shaped camera  50 , a widest circuit board which can be accommodated in the casing  1  is denoted by the broken lines  65 . The circuit board  65  is larger than the circuit board  65   j . Thus, the dome-shaped camera  50  is advantageous in that the casing  1  can accommodate more parts (electronic parts) and larger circuit boards. 
     In the event that the cover member  2   a  in the dome-shaped camera  50  is struck with a hammer or a bat and hence receives an impact force, the end surface  2   at  of the cover member  2   a  contacts the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b  throughout the circumference thereof and the impact force is transmitted from the cover member  2   a  to the flange  2   b . Therefore, even in this case, a concentrated stress is absent from the cover member  2   a . Thus, the cover member  2   a  except the point of the application of the impact force is hardly deformed or damaged. 
     The ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b  contacts the end surface  2   at  of the cover member  2   a . The end surface  2   bt  of the circumferential wall portion  2   b   1  of the flange  2   b  surface-contacts the step  1   e  on the casing  1  substantially throughout the circumference thereof, and the impact force is transmitted from the flange  2   b  to the casing  1 . The step  1   e  is located at a position corresponding to the outer cylindrical portion  1   a  of the casing  1 . The flange  2   b  can elastically deform in a manner like shearing between its inner part and its outer part. This elastic deformation of the flange  2   b  absorbs a portion of the impact force transmitted from the cover member  2   a.    
     Preferably, an outer portion of the casing  1  which defines the step  1   e  is high in rigidity. As mentioned above, the flange  2   b  surface-contacts the step le on the casing  1  substantially throughout the circumference thereof. The casing  1  receives an impact force from the flange  2   b , and transmits the received force to the ceiling board  61  substantially as it is. A concentrated stress hardly occurs in the flange  2   b . Thus, it is possible to reliably prevent the flange  2   b  from being deformed or damaged by the impact force applied thereto. 
     In the case where the impact force is so strong that the cover member  2   a  is deformed and brought into contact with the inner cover  5 , the impact force travels from the cover member  2   a  to the inner cover  5 . In this case, the end surface  5   t  of the inner cover  5  contacts the top surfaces  1   j   1   t - 1   j   4   t  of the contact ribs  1   j   1 - 1   j   4  on the casing  1 . Thus, the impact force applied to the inner cover  5  is prevented from directly traveling to the camera body  52 . Accordingly, it is possible to prevent the camera body  52  from being damaged. 
     The impact force applied to the inner cover  5  travels to the casing  1  via the contact ribs  1   j   1 - 1   j   4 . In the casing  1 , the contact ribs  1   j   1 - 1   j   4  are provided on the reference plane portion  1   b   1  which extends radially inward of the outer cylindrical portion  1   a . Thus, the reference plane portion  1   b   1  of the casing  1  can be elastically deformed relative to the outer cylindrical portion  1   a  in a direction along the casing axis CL. A portion of the impact force which travels to the reference plane portion  1   b   1  via the contact ribs  1   j   1 - 1   j   4  can be at least partially absorbed by the deformation of the reference plane portion  1   b   1 . 
     In the case where the impact force applied to the inner cover  5  is so strong that the inner cover  5  is deformed and brought into contact with the camera body  52 , the impact force travels from the inner cover  5  to the camera body  52 . In the gimbals  54 , the pair of the arms  54   a , which support the camera body  52  and which extend axially and radially outward, are elastically deformed by the impact force exerted on the camera body  52 . A portion of the impact force is absorbed by the elastic deformation of the arms  54   a  so that the camera body  52  is prevented from being damaged. 
     The gimbals  54  is supported by the support arms  1   n  on the casing  1  while being movable along the casing axis CL. The support arms  1   n  are flexible. Thus, the support arms  1   n  are elastically deformed by the impact force transmitted from the camera body  52  to the gimbals  54 . A portion of the impact force is absorbed by the elastic deformation of the support arms  1   n . Accordingly, the camera body  52  is more reliably prevented from being damaged. 
     The gimbals  54  has the base  54   k  which is held at the bottom portion  1   b   6  in the ceiling portion  1   b  of the casing  1  via the snap fit. The gimbals base  54   k  is smaller in external shape or outside diameter than the camera body  52  so as to provide the increased interior space S of the casing  1 . Therefore, the larger circuit board  65  can be placed in the interior space S of the casing  1 . Furthermore, more parts or larger parts can be placed in the interior space S of the casing  1 . 
     In the cover  2 , the end of the cover member  2   a  fits around the circumferential rib  2   b   3  of the flange  2   b , and the end surface  2   at  of the cover member  2   a  abuts against the ceiling surface  2   b   2   t  of the ceiling portion  2   b   2  in the flange  2   b . The cover member  2   a  is secured to the flange  2   b  by the fixing ring  2   c  which fits around the end of the cover member  2   a . This structure of the cover  2  makes it possible to prevent a concentrated stress from occurring in a place of the contact between the cover member  2   a  and the flange  2   b  and a region near that place. 
     As previously mentioned, the fixing ring  2   c  secures the cover member  2   a  to the flange  2   b . The fixing ring  2   c  may be detachably connected with the flange  2   b  via, for example, a snap fit or a screw. In this case, it is possible to replace the cover member  2   a  after the installation of the dome-shaped camera  50 . Thus, the maintenance of the dome-shaped camera  50  can be easy. 
     In the dome-shaped camera  50 , the cover member  2   a  and the inner cover  5  are hardly deformed when an impact force is applied to the cover member  2   a . Accordingly, the clearance A between the cover member  2   a  and the inner cover  5 , and the clearance between the inner cover  5  and the camera body  52  can be relatively small. 
     The clearance A between the cover member  2   a  and the inner cover  5  is set to, for example, 1.5 mm. The 1.5-mm clearance A is equal to about four fifth of that in a conventional dome-shaped camera. Accordingly, the dome-shaped camera  50  can be smaller in size than the conventional one. 
     The nuts  62  embedded in the circumferential wall portion  1   f  of the casing  1  may be omitted. In this case, the bolt or bolts  64  are replaced by a self-tapping screw or screws driven into a small through hole or holes in the wall of the casing  1 .