Patent Publication Number: US-2016238919-A1

Title: Imaging apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an imaging apparatus, and in particular relates to an imaging apparatus equipped with a light shield structure which prevents unwanted light from being incident on an imaging surface. 
     2. Description of the Related Art 
     Imaging apparatuses are typically provided with a light shield structure, as needed, for preventing or reducing internal reflection of unwanted light (that does not contribute to image formation on the imaging surface) in an optical path from traveling toward an imaging surface in order to prevent deterioration in the quality of photographing images (e.g., to prevent flare and ghost from occurring). As an example of such a light shield structure, a light shield structure in which saw-tooth light-shield grooves (light-shield lines) are formed on the inner wall surface of a (round, rectangular or square) tubular portion constituting part of a lens barrel is disclosed in Japanese Unexamined Patent Publication No. 2012-226317 (Patent Literature 1). In Japanese Unexamined Patent Publication No. 2007-163637 (Patent Literature 2), a light shield structure is disclosed in which a stray-light reflecting surface having a curved shape, which reflects unwanted light rays among the light rays incident from a diaphragm aperture (opening) back toward the diaphragm aperture to prevent these unwanted light rays from traveling toward the imaging surface, is formed on the inner periphery of a tubular portion of a lens barrel. 
     To form light-shield grooves such as disclosed in Patent Literature 1 or a stray light reflecting surface such as disclosed in Patent Literature 2, the thickness of the aforementioned tubular portion, which constitutes part of a lens barrel, must be great. However, imaging apparatuses of recent years which are incorporated in cellular phones or smartphones have been miniaturized to a remarkable degree, and the components of these apparatuses are extremely small in size compared with those of conventional imaging apparatuses, (i.e., imaging apparatuses having a camera as its main function) and accordingly, there has been a problem with it being difficult for the tubular portion, which constitutes part of a lens barrel, to secure a sufficient thickness to allow the tubular portion to be provided thereon with known light-shield grooves or with a known stray-light reflecting surface. 
     SUMMARY OF THE INVENTION 
     The present invention has been devised in view of the above described problem, and the present invention provides an imaging apparatus capable of reducing internal reflection of light in an optical path with a space-saving structure. 
     According to an aspect of the present invention, an imaging apparatus is provided, including an optical path forming member which includes at least one exterior wall surrounding an imaging optical system and defines an optical path inside the exterior wall; a through-portion which extends through the exterior wall of the optical path forming member; a lid member which covers the through-portion from the outside of the optical path forming member; and a plurality of light shield walls provided on one of the optical path forming member and the lid member, wherein the plurality of light shield walls are intermittently arranged in a direction along an optical axis of the imaging optical system so that the through-portion includes a plurality of internal spaces which are respectively positioned between the light shield walls. 
     It is desirable for the plurality of internal spaces to be a plurality of slits provided in the exterior wall of the optical path forming member, and for the plurality of light shield walls to be portions of the exterior wall, the plurality of light shield walls being alternately positioned between the plurality of slits in the direction along the optical axis of the imaging optical system. 
     It is desirable for the lid member to include a protrusion which is inserted into the through-portion, and for the plurality of light shield walls to be provided on the protrusion of the lid member. 
     It is desirable for the imaging optical system to include at least one movable lens group which is movable along the optical axis. A range of formation of the through-portion and the plurality of light shield walls in the direction along the optical axis includes at least a part of a moving range of the movable lens group, the part of the moving range ranging from a center of the moving range to a limit of travel of the movable lens group on the image side of the moving range. 
     It is desirable for the through-portion and the plurality of light shield walls to be provided on at least a portion of the exterior wall, a distance from the optical axis to the portion of the exterior wall being the shortest compared to distances, in a plane orthogonal to the optical axis, from the optical axis to a remaining portion of the exterior wall. 
     It is desirable for the optical path forming member to be formed from a combination of a box-shaped body and a cover, wherein one side of sides of the box-shaped body that surround the optical path is open, the cover closes the opening of the box-shaped body, and the through-portion is provided in the cover. 
     It is desirable for the lid member to include a thin sheet which is smaller in thickness than the exterior wall of the optical path forming member. 
     It is desirable for the imaging optical system to include a bending optical system, including a reflector element which reflects light rays traveling from an object toward the image plane, and for the through-portion and the plurality of light shield walls to be provided at positions which are closer to the image side than the reflector element and surround the optical path. 
     In an embodiment, an imaging apparatus is provided, including an optical path forming member which includes at least one exterior wall surrounding an imaging optical system and defines an optical path inside the exterior wall; a plurality of slits which extend through the exterior wall of the optical path forming member and a plurality of light shield walls which are formed as portions of the exterior wall, the plurality of slits and the plurality of light shield walls being provided in the optical path forming member and alternately arranged in a direction along an optical axis of the imaging optical system; and a cover sheet which is mounted onto an outer surface of the exterior wall of the optical path forming member to cover the plurality of slits. 
     It is desirable for the optical path forming member to be formed from a combination of a box-shaped body and a cover, wherein one side of sides of the box-shaped body that surround the optical path is open, the cover closes the opening of the box-shaped body, and the plurality of slits are provided in the cover. 
     In an embodiment, an imaging apparatus is provided, including an optical path forming member which includes at least one exterior wall surrounding an imaging optical system and defines an optical path inside the exterior wall; a through-hole which extends through the exterior wall of the optical path forming member; a cover sheet which is mounted onto an outer surface of the exterior wall of the optical path forming member to cover the through-hole, the cover sheet including a protrusion which is inserted into the through-hole; and a plurality of grooves and a plurality of light shield walls which are provided in the protrusion of the cover sheet and alternately arranged in a direction along an optical axis of the imaging optical system. 
     It is desirable for the optical path forming member to be formed from a combination of a box-shaped body and a cover, wherein one side of sides of the box-shaped body that surround the optical path is open, the cover closes the opening of the box-shaped body, and the through-hole is provided in the cover. 
     According to the imaging apparatus of the present invention, internal reflection of light in an optical path can be reduced with a space-saving structure with no increase in wall thickness of the optical path forming member. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2015-25452 (filed on Feb. 12, 2015) which is expressly incorporated herein by reference in its entirety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described below in detail with reference to the accompanying drawings in which: 
         FIG. 1  is a front external perspective view of an embodiment of an imaging apparatus according to the present invention, viewed from the object side; 
         FIG. 2  is a rear external perspective view of the imaging apparatus, viewed from the opposite side thereof from the side shown in  FIG. 1 ; 
         FIG. 3  is a rear external perspective view of the imaging apparatus with the cover sheet shown in  FIG. 2  removed; 
         FIG. 4  is an exploded perspective view of the imaging apparatus, viewed from the opposite side thereof from the object side; 
         FIG. 5  is a perspective view of an internal structure of the imaging apparatus and a cover member thereof in a state where the second lens group and the third lens group are positioned at their respective positions when the imaging optical system is set at the telephoto extremity, viewed from the object side; 
         FIG. 6  is a perspective view of an internal structure of the imaging apparatus in a state where the second lens group and the third lens group are positioned at their respective positions when the imaging optical system is set at the wide-angle extremity, viewed from the opposite side of the imaging apparatus from the side shown in  FIG. 5 ; 
         FIG. 7  is a sectional view of the imaging apparatus, taken along a plane lying on the first, second and third optical axes; 
         FIG. 8  is a sectional view of part of the imaging apparatus, illustrating a state where internal reflection of light is reduced by a plurality of light shield walls and a light shield frame; 
         FIG. 9  is a sectional view of part of the imaging apparatus, illustrating a state where internal reflection of light is reduced only by the plurality of light shielding walls; 
         FIG. 10  is a rear external perspective view of a second embodiment of the imaging apparatus with the cover sheet removed, viewed from the opposite side of the imaging apparatus from the object side; 
         FIG. 11  is an exploded perspective view of the second embodiment of the imaging apparatus, viewed from the opposite side thereof from the object side; 
         FIG. 12  is a perspective view of the cover sheet shown in  FIG. 11  that constitutes an element of the second embodiment of the imaging apparatus, viewed from the object side; and 
         FIG. 13  is a sectional view of the cover sheet shown in  FIGS. 11 and 12 , taken along the line XIII-XIII shown in  FIG. 12 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of an imaging apparatus (imaging unit)  10  according to the present invention will be discussed below with reference to  FIGS. 1 through 9 . In the following descriptions, forward and rearward directions, leftward and rightward directions, and upward and downward directions are determined with reference to the directions of the double-headed arrows shown in the drawings. The imaging apparatus  10  has an elongated shape which is thin in the forward and rearward directions and long in the leftward and rightward directions as shown in  FIGS. 1 and 2 , each showing the external appearance and shape of the imaging apparatus  10 . The imaging apparatus  10  can be incorporated in various mobile apparatuses such as a cellular phone, a smart phone and tablet computer. 
     The imaging apparatus  10  is provided with an imaging optical system shown in  FIG. 7 . As shown in  FIG. 7 , this imaging optical system is provided with a first lens group G 1 , a second lens group G 2 , a third lens group (movable lens group) G 3  and a fourth lens group G 4 , in that order from the object side. The first lens group G 1  is provided with a first prism (reflector element) L 11 , and the imaging apparatus  10  is further provided, on the image plane side of the fourth lens group G 4 , with a second prism L 12 . The imaging optical system of the imaging apparatus  10  is configured as a bending optical system which reflects (bends) light rays at substantially right angles at each of the first prism L 11  and the second prism L 12 . The first lens group G 1  is configured of a first lens element L 1 , the first prism L 11  and a second lens element L 2 . The first lens element L 1  is positioned in front of (on the object side of) an incident surface L 11 - a  of the first prism L 11 , while the second lens element L 2  is positioned on the right-hand side (image side) of an exit surface L 11 - b  of the first prism L 11 . Each of the second lens group G 2 , the third lens group G 3  and the fourth lens group G 4  is a lens group including no reflector element (prism). The second prism L 12  is provided with an incident surface L 12 - a  and an exit surface L 12 - b , and the incident surface L 12 - a  is positioned on the right-hand side of the fourth lens group G 4 . The imaging apparatus  10  is provided with an image sensor (image pickup device)  13  in front (on the image side) of the exit surface L 12 - b  of the second prism L 12 . The image sensor  13  is arranged so that the imaging surface thereof faces the exit surface L 12 - b  of the second prism L 12 . Although the first lens element L 1 , the second lens element L 2 , the second lens group G 2 , the third lens group G 3  and the fourth lens group G 4  are each shown as a single lens element in  FIG. 7 , each of these four optical elements can be composed of a plurality of lens elements. 
     In the imaging optical system of the imaging apparatus  10 , the optical axis before being bent by a reflecting surface L 11 - c  of the first prism L 11  (i.e., the optical axis of the first lens element L 1 ) will be hereinafter referred to as the first optical axis O 1 , the optical axis after being bent by the first prism L 11  and extending to a reflecting surface L 12 - c  of the second prism L 12  will be hereinafter referred to as the second optical axis O 2  (which is coincident with the optical axes of the second lens element L 2 , the second lens group G 2 , the third lens group G 3  and the fourth lens group G 4 ), and the optical axis after being bent by the reflecting surface L 12 - c  of the second prism L 12  will be hereinafter referred to as the third optical axis O 3 . The first optical axis O 1 , the second optical axis O 2  and the third optical axis O 3  define a plane that lies on the sheet of  FIG. 7 . 
     Object-emanating light rays that are incident on the first lens element L 1 , along the first optical axis O 1 , enter the first prism L 11  through the incident surface L 11 - a  and are reflected by the reflection surface L 11 - c  of the first prism L 11  in a direction along the second optical axis O 2  to exit from the exit surface L 11 - b  of the first prism L 11 . 
     Subsequently, the light rays emanating from the exit surface L 11 - b  of the first lens element L 11  pass through the second lens element L 2  of the first lens group G 1  and the second through fourth lens groups G 2 , G 3  and G 4 , which lie on the second optical axis O 2 , and are incident on the second prism L 12  via the incident surface L 12 - a  thereof. Subsequently, the light rays which are passed through the incident surface L 12 - a  are reflected by the reflection surface L 12 - c  of the second prism L 12  in a direction along a third optical axis O 3  (extending forwardly) and are incident on the imaging surface of the image sensor  13  to form an object image thereon. 
     As shown in  FIG. 4 , the imaging apparatus  10  is provided with a housing (part of an optical path forming member/box-shaped body)  15 , a first lens-group unit  16 , a motor unit  30 , a cover member (part of the optical path forming member/cover)  40  and a cover sheet (lid member/sheet)  41 . The housing  15  is a box-shaped body which is elongated in the leftward and rightward directions along the second optical axis O 2  and which is small in thickness in the forward and rearward directions along the optical axes O 1  and O 3 . Furthermore, this box-shaped housing  15  is hollow, and a major part of the rear of the hollow body thereof is open. The first lens group G 1  and a support mechanism therefor are unitized to be provided as the first lens-group unit  16 . The first lens-group unit  16  is mounted to one end (specifically the left end) of the housing  15 , with respect to the lengthwise direction thereof.  FIG. 4  that shows an exploded perspective view of the imaging apparatus  10  shows a state where the housing  15  and the first lens-group unit  16  are combined. The fourth lens group G 4 , the second prism L 2  and the image sensor  13  (see  FIG. 7 ) are fixedly held by the housing  15  in the vicinity of the other end (specifically the right end) thereof in the lengthwise direction of the housing  15 . The image sensor  13  is connected to a drive control circuit, which is provided in a mobile apparatus in which the imaging apparatus  10  is incorporated, via a flexible printed wiring board  19  (see  FIG. 7 ). 
     As shown in  FIGS. 4 and 7 , the housing  15  is provided therein with an optical path space  15   a  in which the second lens group G 2  and the third lens group G 3  are accommodated. The housing  15  is provided on the right-hand side of the optical path space  15   a  with a holding frame  15   b  which fixedly holds the fourth lens group G 4  and the second prim L 12 . The housing  15  is provided on both sides of the holding frame  15   b  in the upward and downward directions with two motor holding recesses  15   c  (see  FIGS. 1 through 4 ). The optical path space  15   a  and each motor holding recess  15   c  of the housing  15  are open at the back of the housing  15 , and the holding frame  15   b  of the housing  15  is closed at the back of the housing  15 . The housing  15  is further provided, on the rear side thereof in a left part of the optical path space  15   a , with an upper and lower pair of bracket support portions  15   d  (see  FIG. 4 ) and is provided, on the rear of the housing  15  on the right side of the holding frame  15   b , with a cover support projection  15   e  (see  FIGS. 2 through 4 ). In addition, the housing  15  is provided, on each side of the optical path space  15   a  with respect to the upward and downward directions, with a cover engaging projection  15   f  and a cover engaging recess  15   g , respectively (see  FIGS. 1 through 4 ). The housing  15  is also provided on the right end thereof with a cover engaging projection  15   h  (see  FIG. 4 ). The housing  15  is provided on the front side thereof with a guide groove  15   i  which is formed as an elongated groove that is elongated in the leftward and rightward directions (see  FIG. 1 ). 
     As shown in  FIGS. 4 through 6 , the imaging apparatus  10  is provided in the optical path space  15   a  of the housing  15  with an upper and lower pair of guide rods  22  and  23  which extend along both the upper and lower sides of the housing  15 . Each guide rod  22  and  23  extends parallel to the second optical axis O 2 . Both ends (the left and right ends) of each guide rod  22  and  23  are fixed in the housing  15 . The second lens group G 2  and the third lens group G 3  are held by a second lens group frame  20  and a third lens group frame  21 , respectively. The second lens group frame  20  is provided with an upper and lower pair of through-holes  20   a  (see  FIG. 6 ) which are slidably fitted on the pair of guide rods  22  and  23 , respectively, and the third lens group frame  21  is provided with an upper and lower pair of through-holes  21   a  (see  FIG. 5 ) which are slidably fitted on the pair of guide rods  22  and  23 , respectively, so that the second lens group frame  20  and the third lens group frame  21  are guided along the second optical axis O 2  by the pair of guide rods  22  and  23  to be movable along the second optical axis O 2 . 
     As shown in  FIGS. 4 through 7 , each of the second lens group G 2  and the third lens group G 4  is non-circular in outer peripheral shape. Specifically, portions of the rim (edge) of each of the second lens group G 2  and the third lens group G 3  which face the front and the rear of the imaging apparatus  10  are cut off into flat surfaces. The outer peripheral shapes of the second lens element L 2  of the first lens group G 1  and the lens element which constitutes the fourth lens group G 4  are also formed to be non-circular in outer peripheral shape, being similar to those of the second lens group G 2  and the third lens group G 3 . As can be seen from  FIG. 7 , the formation of each of these lens elements or lens groups (L 2 , G 2 , G 3  and G 4 ) that are arranged on the second optical axis O 2  and have a non-circular shape, so as to reduce the diameter thereof in the forward and rearward directions, makes it possible to reduce the thickness of the imaging apparatus  10  in the forward and rearward directions. Additionally, as shown in  FIG. 7 , the second lens group G 2  is formed so that the distance D 2  from the second optical axis O 2  to the rear edge (rear flat-cut portion) of the second lens group G 2  is smaller than the distance D 1  from the second optical axis O 2  to the front edge (front flat-cut portion) of the second lens group G 2  (i.e., D 1 &gt;D 2 ); likewise, the third lens group G 3  is formed so that the distance D 4  from the second optical axis O 2  to the rear edge (rear flat-cut portion) of the third lens group G 3  is smaller than the distance D 3  from the second optical axis O 2  to the front edge (front flat-cut portion) of the third lens group G 3  (i.e., D 3 &gt;D 4 ), and accordingly, each of the second lens group G 2  and the third lens group G 3  is shaped to be asymmetrical about the second optical axis O 2  with respect to the forward and rearward directions (with respect to the thickness direction of the imaging apparatus  10 ). The lens holding portions of the second lens group frame  20  and the third lens group frame  21  are non-circular in shape to correspond to the outer peripheral shapes of the second lens group G 2  and the third lens group G 3 . 
     As shown in  FIGS. 4 through 7 , the imaging apparatus  10  is provided between the third lens group G 3  (the third lens group frame  21 ) and the fourth lens group G 4  with a light shield frame  24 . A central through-hole  24   a , having a substantially rectangular shape, is formed at a center of the light shield frame  24 , and a front and rear pair of rod insertion holes  24   b  (see  FIG. 5 ) are formed in the light shield frame  24  at positions above and below the central through-hole  24   a . The light shield frame  24  is supported and guided by the upper and lower pair of guide rods  22  and  23  to be slidable thereon along the second optical axis O 2  with the front and rear pair of rod insertion holes  24   b  fitted on the upper and lower pair of guide rods  22  and  23 , respectively. The imaging apparatus  10  is provided between the light shield frame  24  and the third lens group frame  21  with an extension spring  25  (conceptually shown by two-dot chain lines in  FIG. 7 ), the axis of which extends in the leftward and rightward directions and one and the other ends of which are hooked onto the light shield frame  24  and the third lens group frame  21 , respectively. When no force other than the biasing force of the extension spring  25  is exerted on the light shield frame  24  and the third lens group frame  21 , the light shield frame  24  and the third lens group frame  21  are positioned close to each other as shown in  FIG. 6 . As shown in  FIGS. 1 and 5 , the light shield frame  24  is further provided with a stopper  24   c  which projects forwardly to be slidably engaged in a guide slot  15   i  formed in the housing  15 . 
     As shown in  FIGS. 4 through 6 , the motor unit  30  is provided with a second-lens-group drive motor  31 , a second-lens-group drive motor support bracket  32 , a nut  33 , a third-lens-group drive motor  34 , a third-lens-group drive motor support bracket  35  and a nut  36 . The second-lens-group drive motor  31  is configured of a motor body  31   a  and a lead screw  31   b  and the third-lens-group drive motor  34  is configured of a motor body  34   a  and a lead screw  34   b . The lead screw  31   b  projects leftward from the motor body  31   a  and is rotatable about the axis thereof that is parallel to the second optical axis O 2 . Likewise, the lead screw  34   b  projects leftward from the motor body  34   a  and is rotatable about the axis thereof that is parallel to the second optical axis O 2 .  FIG. 4  shows a state where the lead screw  31   b  and the lead screw  34   b  are separated from the second-lens-group drive motor  31  and the third-lens-group drive motor  34 , respectively, and positioned in the housing  15  for the purpose of illustration. The female screw hole formed through the nut  33  (see  FIG. 6 ) is screw-engaged with the lead screw  31   b  of the second-lens-group drive motor  31 , and the female screw hole formed through the nut  36  (see  FIG. 5 ) is screw-engaged with the lead screw  34   b  of the third-lens-group drive motor  34 . Each of the nuts  33  and  36  is prevented from rotating about the axis of the associated lead screw  31   b  or  34   b  by engagement with a rotation prevention portion (not shown) formed in the housing  15 . 
     As shown in  FIGS. 4 through 6 , each of the second-lens-group drive motor support bracket  32  and the third-lens-group drive motor support bracket  35  is generally in the shape of a plate extending in the leftward and rightward directions. The second-lens-group drive motor support bracket  32  is provided with a motor-body support lug  32   a , a screw support lug  32   b  and an engaging hole  32   c . The motor-body support lug  32   a  is formed at one end (the right end) of the second-lens-group drive motor support bracket  32  to support the motor body  31   a  of the second-lens-group drive motor  31 , and the screw support lug  32   b  is formed in the vicinity of the other end (the left end) of the second-lens-group drive motor support bracket  32  to support the end of the lead screw  31   b . The engaging hole  32   c  is formed in the vicinity of the screw support lug  32   b  to extend through the second-lens-group drive motor support bracket  32  in the forward and rearward directions. Similar to the second-lens-group drive motor support bracket  32 , the third-lens-group drive motor support bracket  35  is provided with a motor-body support lug  35   a , a screw support lug  35   b  and an engaging hole  35   c . The motor-body support lug  35   a  is formed at one end (the right end) of the third-lens-group drive motor support bracket  35  to support the motor body  34   a  of the third-lens-group drive motor  34 , and the screw support lug  35   b  is formed in the vicinity of the other end (the left end) of the third-lens-group drive motor support bracket  35  to support the end of the lead screw  34   b . The engaging hole  35   c  is formed in the vicinity of the screw support lug  35   b  to extend through the third-lens-group drive motor support bracket  35  in the forward and rearward directions. 
     The motor unit  30  is installed in the housing  15  with the motor body  31   a  of the second-lens-group drive motor  31  and the motor body  34   a  of the third-lens-group drive motor  34  housed in the two (upper and lower) motor holding recesses  15   c , respectively, and while portions of the second-lens-group drive motor support bracket  32  and the third-lens-group drive motor support bracket  35 , in the vicinity of the ends (the left ends) thereof, are fitted to the upper and lower pair of bracket support portions  15   d  to be supported thereby, respectively. Thereupon, the positions of the second-lens-group drive motor support bracket  32  and the third-lens-group drive motor support bracket  35  with respect to the housing  15  are fixed by engaging the engaging holes  32   c  and  35   c  with protrusions which protrude from the upper and lower pair of bracket support portions  15   d , respectively. The nut  33  is screw-engaged with the lead screw  31   b  of the second-lens-group drive motor  31  and is also engaged in a nut-engaging recess formed in the second lens group frame  20  (see  FIG. 6 ). The nut  36  is screw-engaged with the lead screw  34   b  of the third-lens-group drive motor  34  and is also engaged in a nut-engaging recess formed in the third lens group frame  21  (see  FIG. 5 ). Therefore, a combination of the nut  33  and the second lens group frame  20  can integrally move in a direction along the second optical axis O 2 , and a combination of the nut  36  and the third lens group frame  21  can integrally move in a direction along the second optical axis O 2 . 
     The cover member  40  is a press-molded product made of a metal plate and is provided with a planar main body portion (exterior wall)  40   a , an upper and lower pair of first engaging lugs  40   b , an upper and lower pair of second engaging lugs  40   c , and a third engaging lug  40   d , as shown in  FIGS. 1 through 5 . The planar main body portion  40   a  covers a rear surface of the imaging apparatus  10 . The first engaging lugs  40   b , the second engaging lugs  40   c  and the third engaging lug  40   d  project forward from a peripheral edge of the planar main body portion  40   a . The planar main body portion  40   a  is elongated in a direction of the second optical axis O 2 . One of the first engaging lugs  40   b  and one of the second engaging lugs  40   c  are provided on an upper long edge of the planar main body portion  40   a  at different positions in the lengthwise direction thereof, and the other first engaging lug  40   b  and the other second engaging lug  40   c  are provided on a lower long edge of the planar main body portion  40   a  at different positions in the lengthwise direction thereof. The third engaging lug  40   d  is provided on the planar main body portion  40   a  at one end (the right end) thereof in the lengthwise direction of the planar main body portion  40   a . The pair of first engaging lugs  40   b  are each provided with a rectangular engaging hole  40   e , and the third engaging lug  40   d  is provided with a rectangular engaging hole  40   f . The planar main body portion  40   a  is further provided in the vicinity of the left end thereof with a first lens-group unit exposing hole  40   g , through which the first lens-group unit  16  is rearwardly exposed. The planar main body portion  40   a  is provided in the vicinity of the right end thereof with a circular engaging hole  40   h.    
     The cover member  40  is mounted onto the housing  15 , to which all the built-in components such as the motor unit  30  have been fixed and which has been connected to the first lens-group unit  16 . More specifically, the cover member  40  is fixedly mounted onto the housing  15  by placing the planar main body portion  40   a  on the rear of the optical path space  15   a , engaging the engaging holes  40   e  of the upper and lower first engaging lugs  40   b  with the upper and lower cover engaging projections  15   f , engaging the upper and lower second engaging lugs  40   c  with the upper and lower cover engaging recesses  15   g , engaging the engaging hole  40   f  of the third engaging lug  40   d  with the cover locking cover  15   h , and engaging the circular engaging hole  40   h  with the cover support projection  15   e . Upon the cover member  40  being mounted onto the housing  15 , the second-lens-group drive motor support bracket  32  and the third-lens-group drive motor support bracket  35  are pressed by the planar main body portion  40   a  of the cover member  40 , so that the motor unit  30  is stably held inside the housing  15 . Some of the components of the first lens-group unit  16  can be installed in and removed from the housing  15  through the first lens-group unit exposing hole  40   g  with the cover member  40  mounted to the housing  15 . 
     Drive control for the second-lens-group drive motor  31  and the third-lens-group drive motor  34  becomes possible by connecting a flexible printed wiring board  37  (see  FIG. 4 ) which extends from the motor unit  30  to the aforementioned drive control circuit of the mobile apparatus in which the imaging apparatus  10  is incorporated. Driving the second-lens-group drive motor  31  to rotate the lead screw  31   b  thereof causes the nut  33  to move in the axial direction of the lead screw  31   b , thus causing the driving force of the second-lens-group drive motor  31  to be transmitted to the second lens group frame  20  via the nut  33 , so that the second lens group frame  20 , which is guided by the pair of guide rods  22  and  23 , moves along the second optical axis O 2 . Likewise, driving the third-lens-group drive motor  34  to rotate the lead screw  34   b  thereof causes the nut  36  to move in the axial direction of the lead screw  34   b , thus causing the driving force of the third-lens-group drive motor  34  to be transmitted to the third lens group frame  21  via the nut  33 , so that the third lens group frame  21 , which is guided by the pair of guide rods  22  and  23 , moves along the second optical axis O 2 . 
     A power-varying operation (zooming operation) to vary the focal length of the imaging optical system and a focusing operation to bring an object into focus are performed by changing the positions of the second lens group G 2  and/or the third lens group G 3  in the direction of the second optical axis O 2  by moving the second lens group frame  20  and the third lens group frame  21 . The third lens group G 3  solely moves in the focusing operation, while the second lens group G 2  and the third lens group G 3  move relative to each other in a predetermined moving manner in the zooming operation.  FIGS. 4, 5 and 7  show the positions of the second lens group G 2  (the second lens group frame  20 ) and the third lens group G 3  (the third lens group frame  21 ) when the focal length of the imaging optical system is at a maximum in the zoom range, i.e., when the imaging optical system is set at the telephoto extremity, and  FIG. 6  shows the positions of the second lens group G 2  (the second lens group frame  20 ) and the third lens group G 3  (the third lens group frame  21 ) when the focal length of the imaging optical system is at a minimum in the zoom range, i.e., when the imaging optical system is set at the wide-angle extremity. 
     When the imaging optical system is at the wide-angle extremity as shown in  FIG. 6 , the third lens group G 3  (the third lens group frame  21 ) is positioned close to the fourth lens group G 4 , and the second lens group G 2  (the second lens group frame  20 ) is positioned close to the third lens group G 3  (the third lens group frame  21 ) while being positioned at a relatively large distance from the first lens group G 1  (from the second lens element L 2 ). In this state, the light shield frame  24  is positioned close to the third lens group frame  21  due to the biasing force of the extension spring  25 , while the stopper  24   c  that is shown in  FIG. 1  is positioned in the guide hole  15   i  at, or in the close vicinity of, the right end thereof. 
     When the imaging optical system is at the telephoto extremity as shown in  FIGS. 4, 5 and 7 , the second lens group G 2  (the second lens group frame  20 ) is positioned close to the first lens group G 1  (to the second lens element L 2 ), while the third lens group G 3  (the third lens group frame  21 ) is positioned close to the second lens group G 2  (the second lens group frame  20 ) while being positioned at a relatively large distance from the fourth lens group G 4 . In this state, the light shield frame  24  is in contact with the left end of the guide hole  15   i , thus being prevented from further moving leftward, and is positioned in between the third lens group G 3  and the fourth lens group G 4  in a direction along the second optical axis O 2  as shown in  FIG. 7 . The position of the light shield frame  24  when the imaging optical system is at the telephoto extremity is maintained by the biasing force of the extension spring  25 . 
     If the imaging apparatus  10  having the above described structure is directed at an object located in front thereof, object-emanating light rays that travel through the first lens group G 1 , the second lens group G 2 , the third lens group G 3 , the central through-hole  24   a  of the light shield frame  24  and the fourth lens group G 4  are captured (received) by the imaging surface of the image sensor  13 . 
       FIG. 7  shows the operating range (moving range) M 1  of the third lens group G 3  in the zoom range from the wide-angle extremity to the telephoto extremity. The moving range of the third lens group G 3  when a focusing operation is performed is also included within the operating range M 1  shown in  FIG. 7 . The operating range M 1  in  FIG. 7  is shown with the position of the surface of the third lens group G 3  (the right surface of the third lens group G 3  with respect to  FIG. 7 ) which is the closest to the image side as a reference; the position of this surface of the third lens group G 3  when the imaging optical system is at the wide-angle extremity is shown by “W” and the position of the same when the imaging optical system is at the telephoto extremity is shown by “T”. When the imaging optical system is at the wide-angle extremity, the distance between the third lens group G 3  and the fourth lens group G 4  is small, while the light shield frame  24  is positioned close to the third lens group G 3 , so that the possibility of object-emanating light rays passing through the third lens group G 3  (after passing through the first lens group G 1  and the second lens group G 2 ) becoming harmful stray light that travels toward the fourth lens group G 4 , as a result of being reflected by an inner surface of the housing  15  or an inner surface of the cover member  40 , is low. 
     On the other hand, when the imaging optical system is at the telephoto extremity, the distance between the third lens group G 3  and the fourth lens group G 4  is great, so that the object-emanating light rays are susceptible to being internally reflected by an inner surface of the housing  15  or by an inner surface of the cover member  40  between the third lens group G 3  and the fourth lens group G 4 . The light shield frame  24 , which is installed between the third lens group G 3  and the fourth lens group G 4 , has a light shielding function; specifically, the light shield frame  24  can prevent light that is internally reflected in the light path space  15   a  from traveling toward the fourth lens group G 4 . However, the imaging apparatus  10  is originally flat in shape and small in thickness in the forward and rearward directions; moreover, the planar main body portion  40   a  of the cover member  40  is positioned close to the second optical axis O 2 , according to the above described arrangement in which each of the second lens group G 2  and the third lens group G 3  is shaped to be asymmetrical about the second optical axis O 2  with respect to the forward and rearward directions (D 1 &gt;D 2  and D 3 &gt;D 4  (see  FIG. 7 )). In other words, the imaging apparatus  10  has four exterior walls (a front wall, an upper wall and a lower wall formed by the housing  15 ; and a rear wall formed by the planar main body portion  40   a  of the cover member  40 ) which surround the second optical axis O 2 , and the rear wall (the planar main body portion  40   a ) is closest to the second optical axis O 2  among the four exterior walls in a plane orthogonal to the second optical axis O 2 . Hence, this arrangement of the imaging apparatus  10  makes it susceptible to internal reflection of object-emanating light rays at the cover member  40  (i.e., rear wall). In addition, since the light shield frame  24  is movable along the pair of guide rods  22  and  23 , it is required to secure a clearance between the light shield frame  24  and the inner surface of the housing  15  or the cover member  40  to prevent the light shield frame  24  from interfering with the housing  15  or the cover member  40 ; however, such a clearance forms an unwanted light path through which light travels toward an inner surface of the housing  15  or the cover member  40  after traveling past the outer periphery of the light shield frame  24 . Accordingly, to obtain a higher light shielding capability in the imaging apparatus  10  under such conditions, a light shield structure which reduces the internal reflection (namely, a light shield structure which restricts the traveling of the internally reflected light in a direction toward the fourth lens group G 4 ) is provided on the cover member  40  itself, which is a part of the exterior walls forming an optical path of the imaging apparatus  10 . This light shield structure will be hereinafter discussed. 
     As shown in  FIGS. 3 through 5 and 7 through 9 , the planar main body portion  40   a  of the cover member  40  is provided with a plurality of slits (through-portions/internal spaces)  40   i , via which the optical path space  15   a  is communicatively connected with the outside of the imaging apparatus  10 . The plurality of slits  40   i  are elongated through-holes which are parallel to one another, are mutually separated by a predetermined interval (distance), and extend in the vertical direction (the upward and downward directions) of the imaging apparatus  10  (i.e., in a direction substantially orthogonal to the direction of the second optical axis O 2 ). The planar main body portion  40   a  of the cover member  40  is also provided with a plurality of light shield walls  40   j , which are respectively defined between the plurality of slits  40   i , so that the plurality of slits  40   i  and the plurality of light shield walls  40   j  are alternately arranged. The intervals between the plurality of slits  40   i  and the intervals between the plurality of light shield walls  40   j  are substantially identical with respect to a direction along the second optical axis O 2 , and each slit  40   i  and each light shield wall  40   j  are substantially identical in width. As shown in  FIG. 7 , in a direction along the second optical axis O 2 , the range of formation of the plurality of slits  40   i  and the plurality of light shield walls  40   j  occupies a major part of the operating range M 1  of the third lens group G 3 . In other words, in a direction along the second optical axis O 2 , the range of formation of the plurality of slits  40   i  and the plurality of light shield walls  40   j  is set to correspond to the distance between the third lens group G 3  and the fourth lens group G 4  when the distance therebetween becomes maximum (i.e., when the imaging optical system is set to the telephoto extremity). 
     As shown in  FIGS. 2, 4 and 7 through 9 , the cover sheet (lid member/sheet)  41  is fixed to a rear surface of the planar main body portion  40   a  of the cover member  40  and externally covers the plurality of slits  40   i . The cover sheet  41  is smaller in thickness than the cover member  40 . The sheet  41  can be fixed to the cover member  40  by an arbitrary means, for instance, by an adhesive layer formed on one side (front side) of the cover sheet  41  to allow the sheet  41  to be fixed to the cover member  40  via this adhesive layer. In this case, it is desirable for the adhesive layer to provide adhesion to the peripheral area of the sheet  41  that is not directly overlaid on the slits  40   i  without providing adhesion to a plurality of areas of the cover sheet  41  that are respectively overlaid on the plurality of slits  40   i . This makes it possible to reduce the amount of dirt and dust on the cover sheet  41  in the aforementioned plurality of areas that are respectively overlaid on the plurality of slits  40   i.    
     Accordingly, the imaging apparatus  10  incorporates the light shield structure in which a plurality of groove-shaped spaces (the internal spaces of the plurality of through-portions that extend through the planar main body portion  40   a ), which are formed by the plurality of slits  40   i  and the cover sheet  41 , and the plurality of light shield walls  40   j , which are formed as portions of the cover member  40 , are alternately arranged.  FIGS. 8 and 9  show the function of the light shield structure of the imaging apparatus  10 .  FIG. 8  shows the case where the light shield structure, which is composed of the cover member  40  and the cover sheet  41 , and the light shield frame  24  are both used.  FIG. 9  shows the case where only the light shield structure, which is composed of the cover member  40  and the cover sheet  41 , is used with the light shield frame  24  removed. As shown in  FIGS. 8 and 9 , if part of the light rays emanating from the object and passing through the third lens group G 3  (after passing through the first lens group G 1  and the second lens group G 2 ) travels toward the cover member  40 , the light rays which reach the cover sheet  41  and are reflected thereby are prevented from traveling toward the fourth lens group G 4  by the sides of the plurality of light shield walls  40   j  (i.e., by inner side walls of the plurality of slits  40   i ) at the areas where the plurality of slits  40   i  are formed. In addition, part of the light traveling toward the cover member  40  directly reaches sides of the plurality of light shield walls  40   j  before being reflected by the cover sheet  41 , thus being prevented from traveling toward the fourth lens group G 4 . 
     Namely, the plurality of slits  40   i  covered by the cover sheet  41  and the plurality of light shield walls  40   j  that are respectively adjacent to the plurality of slits  40   i  form a toothed structure having alternate projections and depressions (light-shield grooves) which reduces internal reflection of light caused by the cover member  40 . Although there is a possibility of reflection of light which travels toward the fourth lens group G 4  occurring at the front surface of each light shield wall  40   j  that faces toward the second optical axis O 2 , the total area of the front surfaces of the plurality of light shield walls  40   j  which are exposed in the optical path space  15   a  has been reduced by an amount corresponding to the area of formation of the plurality of slits  40   i , which makes it possible to minimize the occurrence of harmful stray light. As can be seen from a comparison between  FIG. 8  and  FIG. 9 , a superior light shield effect can be achieved by using the light shield structure, which is composed of the cover member  40  and the cover sheet  41 , together with the light shield frame  24  (see  FIG. 8 ); however, a certain degree of light shield effect can be achieved by using only the light shield structure, which is composed of the cover member  40  and the cover sheet  41  (see  FIG. 9 ). Accordingly, the structure of the imaging apparatus  10  from which the light shield frame  24  is omitted is also possible. 
     The above described light shield structure is configured so that the plurality of slits  40   i  and the plurality of light shield walls  40   j  are formed only within the thickness of the planar main body portion  40   a  in the cover member  40  and not so that a light shield projection is projected inside the optical path space  15   a  from the cover member  40  or bottomed grooves (serrated teeth, etc.) are formed on the inner surface of the cover member  40 ; hence, it is possible to minimize the thickness of the cover member  40  (to prevent variations in thickness of the cover member  40 ). A certain degree of effect can also be achieved by forming only the plurality of slits  40   i  in the cover member  40  (i.e., without providing the cover sheet  41 ) in the case where attention is directed only toward suppression of internal reflection; however, when the imaging apparatus  10  is actually constructed, it is required to prevent foreign particles (e.g., dust) from entering the optical path space  15   a  through the plurality of slits  40   i  from outside and also to prevent harmful light from entering the optical path space  15   a  from outside through the plurality of slits  40   i . Such harmful external effects can be prevented by providing the cover sheet  41  that covers the plurality of slits  40   i . The cover member  40  is a relatively large member which forms an optical path of the imaging apparatus  10  in cooperation with the housing  15 , and additionally, the cover member  40  also holds the motor unit  30 . Therefore, the cover member  40  is required to have a certain amount of thickness to secure a sufficient strength. Whereas, the cover sheet  41 , which is specialized for the purpose of covering the plurality of slits  40   i , can be made extremely thin, and accordingly, the additional (minimal) thickness of the cover sheet  41  to the thickness of the cover member  40  hardly exerts an influence on the size of the imaging apparatus  10  in the forward and rearward directions (i.e., the thickness of the imaging apparatus  10 ), which makes it possible to achieve a superior light shield structure without loss of compactness of the imaging apparatus  10 . In a mobile apparatus incorporating the imaging apparatus  10 , the plurality of slits  40   i  need to be covered at least in a state where the imaging apparatus  10  is workable as a component of camera. Accordingly, a wall surface of the mobile apparatus incorporating the imaging apparatus  10  can also be used as a lid member for covering the plurality of slits  40   i  instead of the cover sheet  41 . 
     The light shield structure of the imaging apparatus  10  is superior also in productivity. Namely, it is difficult to form complicated tooth-shaped light-shield grooves or a light-shielding curved surface on the metal cover member  40  at low production cost, whereas the light shield structure of the imaging apparatus  10  can be achieved simply and at low cost by a simple punch press operation, or the like, because the plurality of slits  40   i  are simple through-holes formed through the cover member  40 . Additionally, the light shield structure is completed simply by mounting the cover sheet  41  to the rear surface of the cover member  40  that includes the plurality of slits  40   i  and the plurality of light shield walls  40   j , which contributes to a reduction in number of man-hours at the time of manufacturing. 
     The cover sheet  41  can be made of various materials. For instance, the cover sheet  41  can be made of a synthetic resin and formed into a thin film. In addition, to reduce internal reflection, the cover sheet  41  itself can be made low in optical reflectance. Specifically, the optical reflectance can be minimized by, e.g., a technique for making the color of the cover sheet  41  dark (black) or a technique for making the front surface of the cover sheet  41  which faces the plurality of slits  40   i  a coarse surface or a non-glossy matt surface. 
     As described above, in the imaging apparatus  10 , the plurality of slits  40   i  and the plurality of light shield walls  40   j  are formed to correspond to a major portion of the operating range M 1  of the third lens group G 3  in a direction along the second optical axis O 2  (see  FIG. 7 ). With this structure, the effect of reducing internal reflection almost over the entire range between the third lens group G 3  and the fourth lens group G 4  is obtained; however, it is possible to change the range of formation of the plurality of slits  40   i  and the plurality of light shield walls  40   j . In this case, as a condition for the range of formation of the plurality of slits  40   i  and the plurality of light shield walls  40   j , it is desirable that this range covers at least a rear half range M 2  (see  FIG. 7 ) which ranges from the center of the operating range M 1  to the limit of travel of the third lens group G 3  on the image plane side in the operating range M 1  (i.e., to the position of the third lens group G 3  when the imaging apparatus is set at the wide-angle extremity). 
     Subsequently, the second embodiment of the imaging apparatus, which is designated by the reference numeral  110 , will be hereinafter discussed with reference to  FIGS. 10 through 13 . In the drawings from  FIG. 10  onward, elements and portions of the imaging apparatus  110  which are the same as those of the previous embodiment of the imaging apparatus  10  are designated by the same reference numerals. Specifically, in the imaging apparatus  110 , the housing  15  (which contains internal parts such as the second lens group frame  20  and the third lens group frame  21 ), the first lens-group unit  16  and the motor unit  30  are the same as those of the previous embodiment of the imaging apparatus  10 , whereas a cover member (an element of the optical-path forming member/cover)  140  and a cover sheet (lid member/sheet)  141  which are elements of the imaging apparatus  110  and respectively correspond to the cover member  40  and the cover sheet  41  have structures unique to the second embodiment of the imaging apparatus  110 . 
     As shown in  FIGS. 10 and 11 , the planar main body portion  40   a  of the cover member  140  is provided with a single rectangular through-hole (through-portion)  140   i  that is formed through the planar main body portion  40   a . The size of the rectangular through-hole  140   i  on the planar main body portion  40   a  is substantially the same as the total area of the plurality of slits  40   i  and the plurality of light shield walls  40   j , and also the position of formation of the through-hole  140   i  corresponds to the total area of the plurality of slits  40   i  and the plurality of light shield walls  40   j.    
     As shown in  FIG. 11 through 13 , the cover sheet  141  is provided with a sheet body  141   a  which has a sufficient area for covering the through-hole  140   i  of the cover member  140  and is further provided on the front side of the sheet body  141   a  with a protrusion  141   b . In  FIG. 11 , the protrusion  141   b , which is provided on the back of the sheet body  141   a , is shown by broken lines. In the making of the cover sheet  141 , the sheet body  141   a  and the protrusion  141   b  can be formed integral with each other, or the protrusion  141   b  can be fixed onto the sheet body  141   a  with an adhesive, etc., after the sheet body  141   a  and the protrusion  141   b  are formed separately from each other. The cover sheet  141  is provided on the protrusion  141   b  with a plurality of elongated bottomed grooves (internal spaces)  141   c  and a plurality of light shield walls  141   d  which are alternately arranged. The intervals between the plurality of elongated bottomed grooves  141   c  and the intervals between the plurality of light shield walls  140   d  are substantially identical, and each elongated bottomed groove  141   c  and each light shield wall  140   d  are substantially identical in width. 
     The cover sheet  141  can be mounted to the cover member  140  by inserting the protrusion  141   b  into the through-hole  140   i  and affixing the sheet body  141   a  to the back of the planar main body portion  40   a . The outward appearance of the imaging apparatus  110  with the cover sheet  141  affixed to the planar main body portion  40   a  is substantially the same as that of the previous embodiment of the imaging apparatus  10  that is shown in  FIG. 2 , and the through-hole  140   i  of the cover member  140  is covered by the cover sheet  141 . Accordingly, the cover sheet  141  prevents foreign particles from entering the imaging apparatus  110  through the through-hole  140   i  and prevents harmful light from entering the imaging apparatus  110  from outside through the through-hole  140   i.    
     In a state where the cover sheet  141  is mounted to the cover member  140 , both the lengthwise direction of each elongated bottomed grooves  141   c  and the lengthwise direction of each light shield wall  141   d  are coincident with the upward/downward direction of the imaging apparatus  110  (i.e., a direction substantially orthogonal to the direction of the second optical axis O 2  that is shown in  FIG. 7 ), and the plurality of elongated bottomed grooves  141   c  and the plurality of light shield walls  141   d  are alternately arranged in a direction along the second optical axis O 2 . The protruding amount of the protrusion  141   b  of the cover sheet  141  from the sheet body  141   a  (i.e., the thickness of the protrusion  141   b ) is set to be substantially the same as the thickness of the planar main body portion  40   a  of the cover member  140 . Therefore, in a completed state of the imaging apparatus  110 , the plurality of elongated bottomed grooves  141   c  and the plurality of light shield walls  141   d  correspond in configuration to the plurality of slits  40   i  (which includes the bottoms thereof that are defined by portions of the front surface of the cover sheet  41 ) and the plurality of light shield walls  40   j  of the previous embodiment of the imaging apparatus  10 , which makes it possible to obtain the effect of reducing internal reflection caused by the cover member  140  while maintaining compactness of the imaging apparatus  110  in the forward and rearward directions with no increase in thickness of the cover member  140 . In addition, the light shield structure of the imaging apparatus  110  has a simple structure that includes the cover member  140 , in which the through-hole  140   i  is formed, and the cover sheet  141  that is mounted to the cover member  140 , thus being superior in productivity and production cost. 
     Although the present invention has been described based on the above illustrated embodiments, the present invention is not limited solely thereto; various modifications to the above illustrated embodiment are possible without departing from the scope of the invention. For instance, although the imaging optical system of each of the above described embodiments of the imaging apparatuses  10  and  110  is provided with a bending optical system including reflector elements such as the first prism L 11  and the second prism L 12 , the present invention can also be applied to an imaging apparatus having an imaging optical system that is not provided with a bending optical system. 
     Although a combination of the housing  15  and the cover member  40  or  140  forms an optical path forming member in each of the above illustrated embodiments of the imaging apparatuses  10  and  110 , the present invention can also be applied to an imaging apparatus which includes an optical path forming member, wherein a portion of this optical path forming member which corresponds to the cover member  40  or  140  is integrally formed with the housing  15 . 
     The present invention is especially suitable for the case where the optical path forming member, in which at least one through-hole (such as the plurality of slits  40   i  or the through-hole  140   i ) is formed, is made of metal such as the cover member  40  or  140 ; however, the material of the optical path forming member is not limited to metal and can be a synthetic resin or the like. 
     Although the plurality of slits  40   i  or the through-hole  140   i  are formed in the cover member  40  or  140  which is positioned on the rear side of the imaging apparatus  10  or  110  (the rear side being closest to the second optical axis O 2  among the exterior walls of the optical path forming member) in each of the above illustrated embodiments, an alternative position can be selected for forming of the through-portion(s) such as the plurality of slits  40   i  or the through-hole  140   i  with respect to the circumferential direction about the optical axis of the imaging optical system. For instance, in each of the imaging apparatuses  10  and  110 , the distance from the second optical axis O 2  to the front wall of the housing  15  is small (compared with the distance of either the upper wall or the lower wall of the housing  15  from the second optical axis O 2 ), though not so small as that from the second optical axis O 2  to the cover member  40  or  140  that is positioned on the rear side of the imaging apparatus  10  or  110 , and accordingly, it is also effective to provide a light shield structure, similar to the cover member  40  or  140  that is positioned on the rear side of the imaging apparatus  10  or  110 , on the front side of the housing  15 . Additionally, unlike each of the above illustrated embodiments of the imaging apparatuses  10  and  110 , in a type of imaging apparatus in which the position of the second optical axis O 2  is set to be a little closer to the front (i.e., to the front wall of the housing  15 ) than the planar main body portion  40   a  of the cover member  40  or  140 , it is also possible to provide a light shield structure, which includes at least one through-hole such as the plurality of slits  40   i  or the through-hole  140   i , only on the front wall of the housing  15  without providing a light shield structure (composed of the plurality of slits  40   i  and the plurality of light shield walls  40   j , or the through-hole  140   i , the plurality of elongated bottomed grooves  141   c  and the plurality of light shield walls  141   d ) which includes at least one through-hole on the cover member  40  or  140  on the rear wall of the housing. 
     The plurality of slits  40   i , which are formed in the first embodiment of the imaging apparatus  10 , are mutually identical in width and arranged at substantially regular intervals, the plurality of light shield walls  40   j , which are formed in the first embodiment of the imaging apparatus  10 , are mutually identical in width and arranged at substantially regular intervals, the plurality of elongated bottomed grooves  141   c , which are formed in the second embodiment of the imaging apparatus  110 , are mutually identical in width and arranged at substantially regular intervals, and the plurality of light shield walls  141   d , which are formed in the second embodiment of the imaging apparatus  110 , are mutually identical in width and arranged at substantially regular intervals in the above illustrated embodiments; however, it is possible for the slits  40   i , the walls  40   j , the elongated bottomed grooves  141   c  and the plurality of light shield walls  141   d  to be formed mutually different in width and/or arranged at irregular intervals. 
     Although the plurality of slits  40   i  and the plurality of light shield walls  40   j , which are formed in the imaging apparatus  10 , and the plurality of elongated bottomed grooves  141   c  and the plurality of light shield walls  141   d , which are formed on in the imaging apparatus  110 , all extend in a direction substantially orthogonal to an optical axis (the second optical axis O 2 ) (i.e., in the vertical direction) in the above illustrated embodiments, a certain degree of light shield effect on reduction of internal reflection can be achieved even if the extending directions of all the slits, walls and grooves are made to be inclined to some degree (even if these extending directions are given a component of tilt in the leftward and rightward directions of the imaging apparatus  10  or  110 ), and the present invention does not exclude such a modified embodiment. 
     Obvious changes may be made in the specific embodiments of the present invention described herein, such modifications being within the spirit and scope of the invention claimed. It is indicated that all matter contained herein is illustrative and does not limit the scope of the present invention.