IMAGING UNIT

Abstract

An imaging unit includes a housing having an opening; a positioning portion provided in the housing; an imaging optical system including a bending optical system having two reflecting surfaces which bend an optical path of the imaging optical system, an incident surface of the bending optical system being exposed outwardly from the housing; an image sensor installed in the housing and includes an imaging surface which receives light reflected by one of the reflecting surfaces positioned on an exit side of the imaging optical system; a circuit board which closes at least part of the opening and to which the image sensor is fixedly connected; and a cover fixedly fitted to the housing so as to close the opening and press the circuit board toward the image sensor so that the image sensor or the circuit board comes in contact with the positioning portion.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging unit having an imaging optical system and an image sensor that captures light emanating from a photographic object which is passed through the imaging optical system. The imaging optical system and the image sensor are accommodated in a housing of the imaging unit.

2. Description of the Related Art

In recent years, mobile electronic devices which are designed mainly for taking still/moving photographic images, such as digital cameras (still-video cameras) and digital camcorders (motion-video cameras), and other mobile electronic devices which are designed to have the capability of taking such photographic images as a subsidiary function, such as mobile phones equipped with a camera and personal digital assistants (PDAs) equipped with a camera, have become widespread. In these types of mobile electronic devices, it is common to provide the mobile electronic device therein with an imaging unit which is structured such that an image sensor and a photographing optical system for leading light emanating from a photographic object (object to be photographed) to the image sensor are accommodated in a hollow housing of the imaging unit. Additionally, in recent years, the downsizing (slimming down) of the mobile electronic devices has further progressed, so that the demand to also slim down the imaging unit has become stronger.

Japanese Unexamined Patent Publication No. 2008-242446 discloses an example of a conventional imaging unit. This imaging unit is provided with a box-shaped housing, an imaging optical system (including an incident-side prism, an exit-side prism and lens groups positioned between the incident-side prism and the exit-side prism), an image sensor (image pickup device) and a substrate (circuit board). The housing has an opening on a surface on one of the opposite sides thereof in the direction of the thickness of the housing. The imaging optical system and the image sensor are housed in the housing, and the substrate is fixed to the housing so as to close the opening of the housing, and the image sensor is fixedly connected to an inner surface of the substrate. The traveling direction of light emanating from a photographic object which is incident on the incident-side prism (which serves as an incident portion of the imaging optical system) changes (i.e., is reflected) at an angle of 90 degrees by the incident-side prism, and thereafter passes through the aforementioned lens groups to be incident on the exit-side prism. Thereupon, the traveling direction of the light incident on the exit-side prism again changes (i.e., is reflected) at an angle of 90 degrees by the exit-side prism to be received (captured) by the imaging surface (photosensitive surface) of the image sensor.

This imaging unit uses the aforementioned substrate, which supports the image sensor, as a cover for closing the aforementioned opening of the housing, thus making it possible to reduce the thickness of the entire imaging unit as compared with the case where the substrate is included inside a housing the entire surface thereof being closed.

If the thickness of the substrate in the aforementioned Japanese Unexamined Patent Publication No. 2008-242446 is reduced, the mechanical strength of the substrate deteriorates, which causes the substrate to bend to thereby displace the position of the imaging surface from the original position thereof if an external force is exerted thereon or vibrations occur in a mobile electronic device which incorporates the imaging unit. Therefore, the substrate needs to be thick, to a certain extent, in the imaging unit disclosed in the aforementioned Japanese Unexamined Patent Publication No. 2008-242446; however, an increase in thickness of the substrate causes an increase in thickness of the imaging unit.

SUMMARY OF THE INVENTION

The present invention provides an imaging unit having a structure so as to be capable of securely positioning the image sensor while achieving a reduction in thickness of the entire imaging unit without incurring an increase in the number of components of the imaging unit.

According to an aspect of the present invention, an imaging unit is provided, including a housing having an opening; a positioning portion provided in the housing; an imaging optical system including first and second reflecting surfaces, provided on an incident side and an exit side of the imaging optical system, respectively, the first and second reflecting surfaces bending an optical path of the imaging optical system, wherein an incident surface of the imaging optical system is exposed outwardly from the housing; an image sensor which is installed in the housing and includes an imaging surface which receives light reflected by the second reflecting surface; a circuit board which closes at least part of the opening and to which the image sensor is fixedly connected; and a cover, made of metal, which is fixedly fitted to the housing so as to close the opening and press the circuit board toward the image sensor so that one of the image sensor and the circuit board comes in contact with the positioning portion.

It is desirable for a traveling direction of light which travels from the incident surface toward the first reflecting surface to be opposite to a traveling direction of light reflected by the second reflecting surface.

It is desirable for the cover to include at least one pressure leaf which is resiliently deformable and presses the circuit board toward the image sensor.

It is desirable for the opening to be formed on one of opposite sides of the housing in the direction of thickness of the housing, for the image sensor to include a flat cover glass which covers the imaging surface, and for the positioning portion to include at least one flat positioning surface which is orthogonal to a direction of thickness of the housing and with which the cover glass is in surface contact.

It is desirable for the positioning portion to include a prism mounting recess which is open to the opening side; and at least one positioning projection formed around the prism mounting recess, wherein the positioning projection projects toward the opening and includes the flat positioning surface at an end surface of the positioning projection. The imaging optical system includes a prism which is installed in the prism mounting recess and reflects incident light toward the imaging surface, and the imaging unit further includes a packing made of an elastic material which includes an exposing hole through which the imaging surface is exposed toward the prism side and a through-hole through which the positioning projection passes, the packing being held between the positioning portion and the image sensor.

It is desirable for the housing to include at least two engaging projections formed on two side surfaces positioned on opposite sides of the housing. The cover includes corresponding at least two resilient engaging lugs having engaging holes in which the at least two engaging projections are disengageably engageable.

It is desirable for the imaging optical system to include a lens group that is movable along an optical path that is bent by the first reflecting surface. The opening is formed entirely in the one surface of the housing. The movable lens group and the image sensor are installed in an internal space of the housing.

It is desirable for the positioning portion to be formed integral with the housing.

According to the present invention, the image sensor can be correctly positioned with respect to the housing via the positioning portion of the housing and the cover since the circuit board is pressed toward the image sensor by the cover so that the image sensor or the circuit board comes in contact with the positioning portion that is formed inside the housing if the opening of the housing is closed by the cover.

The cover is made of metal, thus showing an appropriate mechanical strength though even if the thickness of the cover is reduced. Therefore, even if an external force is exerted on the imaging unit or vibrations occur in the imaging unit when the thickness of the entire imaging unit is reduced by reducing the thickness of the circuit board and the cover, the image sensor (the imaging surface thereof) can be held at a predetermined position.

Moreover, the positioning of the image sensor with respect to the housing does not cause an increase in the number of components because such positioning is carried out using the cover.

The present disclosure relates to subject matter contained in Japanese Patent Applications Nos. 2010-219530 (filed on Sep. 29, 2010), 2010-230839 (filed on Oct. 13, 2010), 2010-232558 (filed on Oct. 15, 2010) and 2011-021974 (filed on Feb. 3, 2011) which are expressly incorporated herein by reference in their entireties.

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 perspective view of an embodiment of an imaging unit according to the present invention, viewed obliquely from above;

FIG. 2 is a front exploded perspective view of the imaging unit, viewed obliquely from above;

FIG. 3 is a front elevational view of the imaging unit;

FIG. 4 is a front elevational view of the imaging unit with a cover and a circuit board removed when an imaging optical system is set at the telephoto extremity;

FIG. 5 is a cross sectional view taken along the line V-V shown in FIG. 1 when the imaging optical system is set at the telephoto extremity;

FIG. 6 is a view similar to that of FIG. 4, showing the imaging unit with the cover and the circuit board removed when the imaging optical system is set at the wide-angle extremity;

FIG. 7 is a perspective view of a second lens group frame, a first light shield frame and peripheral parts;

FIG. 8 is a perspective view of a third lens group frame, a second light shield frame and peripheral parts;

FIG. 9 is a perspective view of the cover in a modified embodiment of the imaging unit;

FIG. 10 is an exploded perspective view of another modified embodiment of the imaging unit; and

FIG. 11 is a view similar to that of FIG. 5, showing yet another modified embodiment of the imaging unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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.

As shown in FIGS. 1 and 2, the imaging unit 10 is provided with a body module 15, a board module 65 and a cover 76 constitute the major components of the imaging unit 10.

The body module 15 is provided with a housing (casing) 16 made of synthetic resin. The housing 16 is provided at the front left end thereof with a mounting recess 17 formed into the shape of a letter D in cross section. In addition, the housing 16 is provided, on the front thereof except this front left end (on the substantially entire front part of the housing 16), with a substantially rectangular accommodating recess (opening) 18. The housing 16 is provided between the mounting recess 17 and the accommodating recess 18 with a partition wall 19. The housing 16 is provided at a center of the partition wall 19 with a communication hole (through-hole) 20 (see FIGS. 4 through 6) via which the mounting recess 17 and the accommodating recess 18 are communicatively connected with each other. The housing 16 is provided, in the accommodating recess 18 at the right end thereof, with a positioning portion 22 having a substantially rectangular shape, in a front view, which projects forward from the base of the accommodating recess 18 (i.e., from a front surface of the base surface in the accommodating recess 18). The positioning portion 22 is provided with three positioning projections 23 (spacers) which project forward, and the front end surfaces of the three positioning projections 23 are formed as flat positioning surfaces 24 which lie in a common plane orthogonal to the forward/rearward direction (i.e., the direction of the thickness of the housing 16). In addition, the housing 16 is provided in the positioning portion 22 with a prism mounting recess 25 which is open at the front and left sides. The positioning portion 22 is provided on the left side thereof with a pair of (upper and lower) limit projections (light shield frame position limit portions) 26 which project leftward (see FIG. 6), and the left end surface of the pair of limit projections 26 are formed as light shield frame position limit surfaces 26a which are flat surfaces lying in a common plane orthogonal to the leftward/rightward direction (i.e., in a common plane orthogonal to the longitudinal direction of the housing 16). The housing 16 is provided, around the front edge of the inner peripheral surface of the accommodating recess 18, with a board support surface 27 which is positioned behind the frontmost end of the housing 16 and lies in a plane orthogonal to the forward/rearward direction, and is further provided on the board support surface 27 with two lock projections 28 which project forward from the board support surface 27. The housing 16 is provided, at the front end of the center of the upper surface of the housing 16, with a first engaging recess 30 which is recessed downward from the upper surface (periphery) of the housing 16. The housing 16 is also provided, at the front end of the upper surface of the housing 16 on the left-hand side of the first engaging recess 30, with a second engaging recess 31 which is recessed downward from the upper surface (periphery) of the housing 16 by the same amount as the first engaging recess 30 and is wider than the first engaging recess 30. The housing 16 is provided in the second engaging recess 31 with an engaging projection 32. The housing 16 is also provided on the lower surface thereof with a first engaging recess 30, a second engaging recess 31 and an engaging projection 32 which have the same configurations as those provided on the upper surface of the housing 16. The positional relationship between the first engaging recess 30, the second engaging recess 31 and the engaging projection 32 which are formed on the lower surface of housing 16 is identical to the positional relationship between the first engaging recess 30, the second engaging recess 31 and the engaging projection 32 which are formed on the upper surface of housing 16; however, the positions of the first engaging recess 30, the second engaging recess 31 and the engaging projection 32 which are formed on the lower surface of the housing 16 in the leftward/rightward direction are all shifted to the right with respect to those formed on the upper surface of the housing 16. Additionally, the housing 16 is provided on the right side thereof with a pair of (upper and lower) engaging projections 34.

As shown in FIGS. 4 through 6, the body module 15 is provided in the mounting recess 17 with a first prism (incident-side prism/ incident-side reflecting surface) LP1 that is fit-engaged in the mounting recess 17 and fixed thereto. The first prism LP1 is provided with an incident surface LP1-a which is orthogonal to the forward/rearward direction and an exit surface LP1-b which is orthogonal to the leftward/rightward direction. The body module 15 is provided with a lens (lens element) L1 which is fitted into the front end of the mounting recess 17 and fixed thereto. The lens L1 is substantially the same in cross sectional shape as the mounting recess 17, and the optical axis of the lens L1 extends in the forward/rearward direction. The front surface of the lens L1 is exposed to the front of the imaging unit 10, and the rear surface of the lens L1 and the incident surface LP1-a face each other in the forward/rearward direction. As shown in FIGS. 2 and 5, the body module 15 is provided with two lenses (lens elements) L2 and L3 which are fixedly fitted into the communication hole 20 to face the exit surface LP1-b of the first prism LP1 in the leftward/rightward direction. The lens L1, the first prism LP1, the lens L2 and the lens L3 are optical elements of a first lens group LG1 provided in the body module 15.

The body module 15 is provided in the prism mounting recess 25 with a second prism (exit-side prism/exit-side reflecting surface) LP2 that is fit-engaged in the prism mounting recess 25 and fixed thereto. The second prism LP2 has an incident surface LP2-a which is orthogonal to the leftward/rightward direction and an exit surface LP2-b which is orthogonal to the forward/rearward direction. The incident surface LP2-a faces the exit surface LP1-b in the leftward/rightward direction.

The body module 15 is provided with a first rod (cylindrical rod) 36 and a second rod (cylindrical rod) 37 which are made of metal and extend linearly in the leftward/rightward direction. The first rod 36 and the second rod 37 are each fixed at both ends thereof to an inner surface of the right side wall of the housing 16 and the partition wall 19 so that the left ends of the first rod 36 and the second rod 37 are aligned in the upward/downward direction and so that the right ends of the first rod 36 and the second rod 37 are aligned in the upward/downward direction.

The body module 15 is provided with a second lens group frame 39 made of synthetic resin. An insertion hole 40 in which the first rod 36 is inserted is formed through the upper part of the second lens group frame 39, and a rotation prevention groove 41 in which the second rod 37 is engaged is formed in the lower end of the second lens group frame 39. The second lens group frame 39 is prevented from rotating about the first rod 36 by the engagement of the rotation prevention groove 41 with the second rod 37, and accordingly, the second lens group frame 39 can slide on and along the first rod 36 and the second rod 37 in the leftward/rightward direction. The body module 15 is provided with a second lens group (movable lens group/first movable lens group) LG2 configured of two lenses (lens elements) L4 and L5 which face the exit surface LP1-b of the first prism LP1 and the incident surface LP2-a of the second prism LP2 in the leftward/rightward direction, respectively. The second lens group LG2 is fixedly fitted into a lens holding hole which is formed through the second lens group frame 39 in the leftward/rightward direction. A light shielding sheet 43 which is provided at a center thereof with a light-bundle limiting aperture 43a is fixed to the right side surface of the second lens group frame 39 so that the center of the light-bundle limiting aperture 43a is positioned coaxially with the optical axis of the lenses L4 and L5. In addition, a nut holding hole 42, both ends of which in the leftward/rightward direction are formed as open ends, is formed at the upper end of the second lens group frame 39, and a driven nut (upper driven nut) 44 through which a female screw hole with the axis thereof extending in the leftward/rightward direction is formed is fixedly fitted into the nut holding hole 42 (the end of the nut holding hole 42 at the first rod 36 constitutes a rotation stop for the upper driven nut 44). The body module 15 is provided with a first motor M1 configured of a stepping motor which is fixed to the housing 16 in the upper part of the accommodating recess 18. The first motor M1 is provided with a rotary drive shaft M1a which extends linearly leftwards, and a male screw thread formed on the rotary drive shaft M1a in the vicinity of the end (left end with respect to FIG. 4) thereof is screw-engaged with the aforementioned female screw hole of the upper driven nut 44. Accordingly, forward and reverse rotations of the rotary drive shaft M1a that are caused by forward and reverse rotations of the first motor M1 cause the second lens group frame 39 (the lenses L4 and L5) to move linearly between the telephoto extremity position (shown in FIGS. 4 and 5) and the wide-angle extremity position (shown in FIG. 6) in the leftward/rightward direction along the first rod 36 and the second rod 37.

In addition, the body module 15 is provided with a third lens group frame (second movable lens frame) 47 made of synthetic resin. An insertion hole 48 in which the second rod 37 is inserted is formed through the lower part of the third lens group frame 47, and a rotation prevention groove 49 in which the first rod 36 is engaged is formed in the upper end of the third lens group frame 47. Accordingly, the third lens group frame 47 can slide on and along the first rod 36 and the second rod 37 in the leftward/rightward direction (while being prevented from rotating about the second rod 37). The body module 15 is provided with a third lens group (movable lens group/second movable lens group) LG3 configured of a lens (lens element) L6 and the optical axis thereof is coaxial with the optical axis of the second lens group LG2. The third lens group LG3 is fixedly fitted into a lens holding hole which is formed through the third lens group frame 47 in the leftward/rightward direction. A nut holding hole 50, both ends of which in the leftward/rightward direction are formed as open ends, is formed at the lower end of the third lens group frame 47, and a driven nut (lower driven nut) 44, through which a female screw hole with the axis thereof extending in the leftward/rightward direction is formed, is fixedly fitted into the nut holding hole 50 (the end of the nut holding hole 50 at the second rod 37 constitutes a rotation stop for the lower driven nut 44). The body module 15 is provided with a second motor M2 which is identical in specifications to the first motor M1 and fixed to the housing 16 in the lower part of the accommodating recess 18. The second motor M2 is provided with a rotary drive shaft M2a (identical in specifications to the rotary drive shaft M1a), and a male screw thread formed on the rotary drive shaft M2a in the vicinity of the end (left end with respect to FIG. 4) is screw-engaged with the aforementioned female screw hole of the lower driven nut 44. Therefore, forward and reverse rotations of the rotary drive shaft M2a that are caused by forward and reverse rotations of the second motor M2 cause the third lens group frame 47 (the third lens group L3) to move linearly between the telephoto extremity position (shown in FIGS. 4 and 5) and the wide-angle extremity position (shown in FIG. 6) in the leftward/rightward direction along the first rod 36 and the second rod 37.

The first lens group LG1 (L1, LP1, L2 and L3), the second lens group LG2 (L4 and L5), the third lens group LG3 (L6) and the second prism LP2 that have been described above are optical elements of an imaging optical system (bending optical system). A zooming operation is performed by moving the second lens group LG2 (the lenses L4 and L5) and the third lens group LG3 (the lens L6) along the first rod 36 and the second rod 37, and a focusing operation is performed by moving only the third lens group LG3 along the first rod 36 and the second rod 37.

It should be noted that the housing 16, the first rod 36, the second rod 37, the imaging optical system, the first motor M1 and the second motor M2 are components of the body module 15.

The body module 15 is provided, in the vicinity of the first rod 36 in the accommodating recess 18, with a columnar guide bar (upper guide bar) 52 made of metal which extends parallel to the first rod 36, the second rod 37 and an optical axis A of the lenses L2 through L6. The left end of the guide bar 52 is fixed to the second lens group frame 39 in the vicinity of the upper end thereof. A metal slidable cylinder (upper slidable cylinder) 53 is fitted on the guide bar 52 to be freely slidable thereon. The guide bar 52 is integrally provided at the right end thereof with a stopper 52a that is disk-shaped, the diameter of which is greater than the inner diameter of the slidable cylinder 53. A compression coil spring (biaser) S1 is installed around the first rod 36 and positioned between the second lens group frame 39 and the slidable cylinder 53. The left end and the right end of the compression coil spring S1 are fixed to the second lens group frame 39 and the slidable cylinder 53, respectively. When no external force is applied to the slidable cylinder 53 (when the slidable cylinder 53 is at the telephoto extremity position thereof), the compression coil spring S1 is in a free state in which the slidable cylinder 53 is positioned between the right end of the compression coil spring S1 and the stopper 52a (a space is provided between the slidable cylinder 53 and the stopper 52a).

The body module 15 is provided with a first light shield frame 54 made of a lightproof material, the upper end of which is fixed to the slidable cylinder 53. The first light shield frame 54 is a planar member orthogonal to the axis of the guide bar 52. The first light shield frame 54 is provided at a center thereof with a light-bundle limiting aperture 54a in the shape of a rectangle. The first light shield frame 54 is provided at the upper end thereof with a fixing hole 54b which is fixedly engaged with the slidable cylinder 53, and the first light shield frame 54 is provided at the lower end thereof with a rotation prevention groove 54c in which the second rod 37 is engaged. Movement of the slidable cylinder 53 together with the guide bar 52 and the second lens group frame 39 in the leftward/rightward direction causes the first light shield frame 54 to slide on and along the second rod 37 in the leftward/rightward direction.

The body module 15 is provided, in the vicinity of the second rod 37 in the accommodating recess 18, with a columnar guide bar (lower guide bar) 58 (see FIGS. 1 and 8) which is identical in specifications to the upper guide bar 52 and extends parallel to the guide bar 52. The left end of the guide bar 58 is fixed to the third lens group frame 47 in the vicinity of the lower end thereof. A metal slidable cylinder (lower slidable cylinder) 53 (identical in specifications to the upper slidable cylinder 53) is fitted on the guide bar 58 to be freely slidable thereon. The guide bar 58 is integrally provided at the right end thereof with a stopper 58a that is disk-shaped, the diameter of which is greater than the inner diameter of the lower slidable cylinder 53. A compression coil spring (biaser) S2 is installed on the second rod 37 and positioned between the third lens group frame 47 and the lower slidable cylinder 53 in a compressed state (resiliently deformed state). The compression coil spring S2 provides a biasing force so that the lower slidable cylinder 53 is biased to move rightward, and accordingly, the lower slidable cylinder 53 abuts the stopper 58a when no leftward external force is applied to the lower slidable cylinder 53.

The body module 15 is provided with a second light shield frame 59 which is positioned between the first light shield frame 54 and the second prism LP2 and the lower end of which is fixed to the lower slidable cylinder 53 that is supported by the guide bar 58. The second light shield frame 59 is made of a lightproof material and configured from a planar member orthogonal to the axis of the guide bar 58. The second light shield frame 59 is provided at a center thereof with a light-bundle limiting aperture 59a in the shape of a rectangle. The second light shield frame 59 is provided at the lower end thereof with a fixing hole 59b which is fixedly engaged with the lower slidable cylinder 53, and the second light shield frame 59 is provided at the upper end thereof with a rotation prevention groove 59c in which the first rod 36 is engaged. Movement of the lower slidable cylinder 53, which is supported by the guide bar 58, together with the guide bar 58 and the third lens group frame 47 in the leftward/rightward direction causes the second light shield frame 59 to slide on and along the first rod 36 in the leftward/rightward direction.

Among the above described components, the pair of limit projections 26, the second rod 37, the second lens group frame 39, the guide bar 52, the upper slidable cylinder 53 and the compression coil spring S1 are components of a light-shield-frame position adjustment mechanism for the first light shield frame 54. In addition, the pair of limit projections 26, the first rod 36, the third lens group frame 47, the lower slidable cylinder 53, the guide bar 58 and the compression coil spring S2 are components of a light-shield-frame position adjustment mechanism for the second light shield frame 59.

The board module 65 is provided with a circuit board 66. The circuit board 66 has substantially the same front shape as that shape of the accommodating recess 18 and is configured from a flat plate orthogonal to the forward/rearward direction. The circuit board 66 is provided on the rear surface thereof with a printed circuit (not shown), and two circular holes 67 are formed through two diagonally opposite corners of the circuit board 66, respectively.

The board module 65 is provided with an image sensor (image pickup device) 69 (see FIGS. 1 and 5) which is fixed at the right end of the rear surface of the circuit board 66. A plurality of terminals (not shown) of the image sensor 69 are fixedly connected to the aforementioned printed circuit by soldering. The image sensor 69 is provided on the rear thereof with an imaging surface (not shown) orthogonal to the forward/rearward direction. In addition, the image sensor 69 is provided, on the incident surface (the rear surface in the drawings), with a cover glass 70 which is made of a flat glass plate and fixedly installed so as to cover the entire imaging surface of the image sensor 69.

A rear surface (rear end) of the image sensor 69 is covered with a packing (fixer) 72 made of an elastic material such as rubber which is open at the front and left sides. The packing 72 is provided with an exposing hole (through-hole) 73 through which the entire imaging surface of the image sensor 69 is rearwardly exposed, and is further provided on the right-hand side of the exposing hole 73, with a through-hole 74.

The circuit board 66, the image sensor 69 and the packing 72 that have been described above are components of the board module 65.

The cover (casing) 76 is a press-molded sheet metal product and is integrally provided with a base 77, two (upper and lower) short engaging lugs 78, two (upper and lower) long engaging lugs (resilient engaging lug) 79 and a pair of (upper and lower) side engaging lugs (resilient engaging lugs) 81. The base 77 is formed as a planar member orthogonal to the forward/rearward direction. The upper short engaging lug 78 and the upper long engaging lug 79 extend rearward from the upper edge of the base 77, and the lower short engaging lug 78 and the lower long engaging lug 79 extend rearward from the lower edge of the base 77. The pair of side engaging lugs 81 extend rearward from the right edge of the base 77. Each side engaging lug 81 is in shape of a letter T as viewed from a side thereof. The base 77 is slightly greater in size (dimensions) than the circuit board 66 and has a substantially rectangular shape with a size capable of closing the front opening (defined by the accommodating recess 18) of the housing 16 (this size is substantially the same as or greater than the front opening of the housing 16). The base 77 is provided with three pressure leaves 84, 85 and 86 each of which is resiliently deformable in the forward/rearward direction.

The pressure leaves 84, 85 and 86 are provided with pressure projections 84a, 85a and 86a, respectively, which project rearwardly (portions of the front surfaces of the pressure leaves 84, 85 and 86 which respectively correspond to the pressure projections 84a, 85a and 86a are dent (recessed) rearward). The pressure leaves 84, 85 and 86 in a free state lie in a plane in which the other part of the base 77 lies.

An engaging hole 80 and an engaging hole 82 are formed through each long engaging lug 79 and each side engaging lug 81, respectively.

To install the board module 65 and the cover 76 to the body module 15, firstly the front opening of the accommodating recess 18 is closed by the circuit board 66 so that the outer edge of the rear surface of the circuit board 66 comes into surface contact with the board support surface 27 while the two circular holes 67 of the circuit board 66 are brought into engagement with the two lock projections 28 (thereupon, the front surface of the circuit board 66 and the front surface of the housing 16 substantially lie in a common plane). Thereupon, as shown in FIG. 5, the three positioning projections 23 of the housing 16 forwardly pass through the exposing hole 73 and the through-hole 74 of the packing 72 so that the flat positioning surfaces 24 of the three positioning projections 23 come in surface contact with a flat rear surface of the cover glass 70 (at the outer periphery of a rear surface portion immediately behind the imaging surface of the image sensor 69). In addition, the imaging surface of the image sensor 69 faces the exit surface LP2-b of the second prism LP2 in the forward/rearward direction through the exposing hole 73. Additionally, a rear surface of the packing 72 comes in contact with the front surface of the positioning portion 22.

Subsequently, the base 77 fully covers, from the front, a portion of the front of the housing 16 from the partition wall 19 rightward to fix the cover 76 to the housing 16 by respectively engaging the upper and lower short engaging lugs 78 with the first engaging recesses 30, respectively engaging the upper and lower engaging holes 80 of the upper and lower long engaging lugs 79 with the upper and lower engaging projections 32, and respectively engaging the engaging holes 82 of the upper and lower side engaging lugs 81 with the upper and lower engaging projections 34.

Upon the imaging unit 10 being assembled in the above described manner, the circuit board 66 and the image sensor 69 are pressed rearward due to the pressure projections 84a, 85a and 86a of the pressure leaves 84, 85 and 86 coming in contact with a right-hand side portion of the front surface of the circuit board 66 so that a pressing force (biasing force) in the rearward direction acts on the front side of the circuit board 66 from the pressure leaves 84, 85 and 86 (via the pressure projections 84a, 85a and 86a) that are slightly resiliently deformed forwardly. Thereupon, an integral combination of the circuit board 66 and the image sensor 69 is held from the front and the rear sides thereof between the flat positioning surfaces 24 of the three positioning projections 23 and the pressure projections 84a, 85a and 86a of the cover 76, and accordingly, the circuit board 66 and the image sensor 69 are precisely positioned with respect to the housing 16 and the second prism LP2 in the forward/rearward direction by the three positioning projections 23 of the housing 16 and the pressure projections 84a, 85a and 86a of the cover 76.

Since the cover 76 is made of metal, each of the base 77 and the pressure leaves 84, 85 and 86 exhibits an appropriate mechanical strength even if the thickness of the cover 76 is small. Therefore, even if an external force is exerted on the imaging unit 10 or vibrations occur in the imaging unit 10 when it is attempted to reduce the thickness of the entire imaging unit 10 by reducing the thickness the circuit board 66 and the cover 76, the position of the image sensor 69 (the imaging surface thereof) in the forward/rearward direction is held at a predetermined design position.

Moreover, the positioning of the image sensor 69 with respect to the housing 16 and the second prism LP2 does not cause an increase in the number of components because such positioning is carried out using the cover 76.

If the imaging unit 10 is directed toward an object located in front of the imaging unit 10, light reflected by the object (light emanating from a photographic object) enters the first prism LP1 through the incident surface LP1-a after passing through the lens L1 and is reflected at an angle of 90 degrees by an inner surface of the first prism LP1 to travel toward the exit surface LP-1b. Subsequently, the reflected light that emerges from the exit surface LP1-b enters the second prism LP2 from the incident surface LP2-a after passing through the lenses L2 through L6, the light-bundle limiting aperture 54a of the first light shield frame 54 and the light-bundle limiting aperture 59a of the second light shield frame 59, and is reflected at an angle of 90 degrees by an inner surface of the second prism LP2 to travel toward the exit surface LP-2b. Subsequently, the reflected light that emerges from the exit surface LP2-b is captured (received) by the aforementioned imaging surface of the image sensor 69 after passing through the exposing hole 73 and the cover glass 70.

Even if an external force is exerted on the imaging unit 10 or vibrations occur in the imaging unit 10 as described above, the position of the image sensor 69 (the imaging surface thereof) in the forward/rearward direction is held at a predetermined design position with precision, and accordingly, a sharp object image with no blur can be captured by the image sensor 69 even if an external force is exerted on the imaging unit 10 or vibrations occur in the imaging unit 10 as described above.

Additionally, if the above described imaging optical system is driven to perform a zooming operation and a focusing operation by moving the second lens group LG2 (the lenses L4 and L5) and the third lens group LG3 (the lens L6) along the first rod 36 and the second rod 37 with the first motor M1 and the second motor M2, an image capturing operation in a state where the imaging optical system is zoomed and focused on a photographic object image becomes possible.

Although the present invention has been described based on the above illustrated embodiment, making various modifications to the above illustrated embodiment is possible.

For instance, the pressure leaves 84, 85 and 86 can be made to be inclined rearwardly with respect to the base 77 when the pressure leaves 84, 85 and 86 are in free state so that the free ends thereof are positioned behind the peripheral portions that surround the pressure leaves 84, 85 and 86, respectively, on the front surface of the base 77. This structure makes it possible to increase the aforementioned pressing force that is applied to the circuit board 66 from the pressure leaves 84, 85 and 86 (the pressure projections 84a, 85a and 86a) when the cover 76 is fixed to the housing 16.

In the case where the pressure leaves 84, 85 and 86 are made to be inclined rearwardly, the pressure projections 84a, 85a and 86a can be omitted.

The number of the pressure leaves (84, 85 and 86) of the cover 76 can be one or two, or more than three.

Furthermore, the shapes of the pressure leaves 84, 85 and 86 can be modified, e.g., as those formed on a cover 76′ shown in FIG. 9.

Alternatively, the pressure leaves 84, 85 and 86 can be omitted from the base 77 by forming projections corresponding to the pressure projections 84a, 85a and 86a on the back of the base 77.

Additionally, a rear surface of the circuit board 66 can be made to contact the three positioning projections 23 (the flat positioning surfaces 24 thereof) instead of a rear surface of the image sensor 69.

It is possible to make the image sensor 69 or the circuit board 66 abut a front surface (positioning surface) of the positioning portion 22 with the three positioning projections 23 omitted from the positioning portion 22.

It is possible to mold the positioning portion 22 (the three positioning projections 23) as a separate member from the housing 16 and to fix the positioning portion 22 to the housing 16 after molding the positioning portion 22.

Additionally, the dimensions of the circuit board 66 can be determined so as only to close part of the front opening of the accommodating recess 18.

Additionally, as shown in FIG. 10, it is possible for the body module 15 to be configured of a first lens group unit 1 and a body unit 2 that are independent of each other and for the housing (which corresponds to the housing 16) of the body module 15 be configured of two components (a holder 3 and a main housing 7).

The first lens group unit 1 is provided with a holder 3 formed as a synthetic-resin molded product. The holder 3 is provided at the left end thereof with a pair of (upper and lower) lugs 4, each of which has a through-hole 5. A prism accommodating space which is open at the front and right sides is formed in the holder 3. The holder 3 is provided at the front opening of the prism accommodating space with a front lens holding hole 6 which is open at the front and at a left portion thereof, and is provided at the right opening of the prism accommodating space with a right lens holding hole. The first prism LP1 is fitted into the prism accommodating hole to be fixed therein, and the lens L1 is fitted into the front lens holding hole 6 to be fixed therein. In addition, the lenses L2 and L3 are fitted into the right lens holding hole to be fixed therein.

The main housing 7 of the body unit 2 is identical in structure to the housing 16 from which a left end portion thereof (which corresponds to the holder 3) is removed, and is provided at the left end of the main housing 7 with an installation recess 8. In addition, the same components as those installed in the accommodating recess 18 of the housing 16 are installed in the accommodating recess 18 of the main housing 7, and the front of the main housing 7 is covered with the cover 76.

The first lens group unit 1 and the body unit 2 are fixed together as one unit by inserting from the left side a pair of set screws B into the upper and lower through-holes 5 of the holder 3 and screwing the male thread portions of the pair of set screws B into a pair of female screw holes (not shown) formed in upper and lower left end surfaces of the main housing 7 with a portion of the holder 3 which is positioned on the right-hand side of the pair of lugs 4 being fitted into the installation recess 8 and with a pair of (upper and lower) spacers S held between the upper and lower lugs 4 of the holder 3 and the upper and lower left end surfaces of the main housing 7 (that are the left end surfaces of a pair of projections of the main housing 7 which are formed on the vertically opposite sides of the installation recess 8).

Upon the first lens group unit 1 and the body unit 2 being fixed together as one unit, the right end of the holder 3 (in which the right lens holding hole is formed) is fitted into the communication hole 20 (not shown in FIG. 10) of the partition wall 19 of the main housing 7, and the optical axis A of the lenses L2 and L3 coincides with the optical axis of the second lens group LG2 and the third lens group LG3.

In addition, the technical principle of “the formation of an opening in an entire surface of the housing” claimed in the claims of the present invention does not limit the size of the opening of the housing to that disclosed in the above illustrated embodiment; namely, such a technical principle is a concept including the formation of the opening, the size of which relative to the housing is slightly smaller or greater than that disclosed in the above illustrated embodiment.

Additionally, the direction of the optical path passing through the imaging optical system (the first lens group LG1, the second lens group LG2, the third lens group LG3 and the second prism LP2) can be changed by making the lens L1 exposed toward the opposite side of the imaging unit 10 from the cover 76 side in the forward/rearward direction by modifying the shape of a housing 16′ as shown in FIG. 11 (a modification in which a portion of the housing which corresponds to the holder 3 shown in the modified embodiment in FIG. 10 is inverted in the forward/rearward direction.

Additionally, each of the first prism LP1 and the second prism LP2 can be replaced by a mirror.

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.

Claims

1. An imaging unit comprising: a housing having an opening;a positioning portion provided in said housing;an imaging optical system including first and second reflecting surfaces, provided on an incident side and an exit side of said imaging optical system, respectively, said first and second reflecting surfaces bending an optical path of said imaging optical system, wherein an incident surface of said imaging optical system is exposed outwardly from said housing;an image sensor which is installed in said housing and includes an imaging surface which receives light reflected by said second reflecting surface;a circuit board which closes at least part of said opening and to which said image sensor is fixedly connected; anda cover, made of metal, which is fixedly fitted to said housing so as to close said opening and press said circuit board toward said image sensor so that one of said image sensor and said circuit board comes in contact with said positioning portion.

2. The imaging unit according to claim 1, wherein a traveling direction of light which travels from said incident surface toward said first reflecting surface is opposite to a traveling direction of light reflected by said second reflecting surface.

3. The imaging unit according to claim 1, wherein said cover comprises at least one pressure leaf which is resiliently deformable and presses said circuit board toward said image sensor.

4. The imaging unit according to claim 1, wherein said opening is formed on one of opposite sides of said housing in the direction of thickness of said housing, wherein said image sensor comprises a flat cover glass which covers said imaging surface, andwherein said positioning portion comprises at least one flat positioning surface which is orthogonal to said direction of thickness of said housing and with which said cover glass is in surface contact.

5. The imaging unit according to claim 4, wherein said positioning portion comprises: a prism mounting recess which is open to said opening side; andat least one positioning projection formed around said prism mounting recess, wherein said positioning projection projects toward said opening and includes said flat positioning surface at an end surface of said positioning projection,wherein said imaging optical system comprises a prism which is installed in said prism mounting recess and reflects incident light toward said imaging surface, andwherein said imaging unit further comprises a packing made of an elastic material which includes an exposing hole through which said imaging surface is exposed toward said prism side and a through-hole through which said positioning projection passes, said packing being held between said positioning portion and said image sensor.

6. The imaging unit according to claim 1, wherein said housing comprises at least two engaging projections formed on two side surfaces positioned on opposite sides of said housing, and wherein said cover comprises corresponding at least two resilient engaging lugs having engaging holes in which said at least two engaging projections are disengageably engageable.

7. The imaging unit according to claim 1, wherein said imaging optical system comprises a lens group that is movable along an optical path that is bent by said first reflecting surface, wherein said opening is formed entirely in one surface of said housing, andwherein said movable lens group and said image sensor are installed in an internal space of said housing.

8. The imaging unit according to claim 1, wherein said positioning portion is formed integral with said housing.