Abstract:
A camera module includes a lens barrel holding a lens, and a main body holding the lens barrel, the lens barrel being capable of moving relative to the main body in the direction of the optical axis of the lens. The lens barrel has a protuberance on the underside thereof throughout the circumferential direction. The main body has a recess at a position corresponding to the protuberance of the lens barrel throughout the circumferential direction, the recess accommodating the protuberance. The protuberance is formed so as to have a height such that the protuberance is disposed in the recess both before and after the movement of the lens barrel relative to the main body in the direction of the optical axis of the lens.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a camera module in which a lens barrel holding a lens is vertically movable relative to a main body, and more specifically, it relates to a camera module configured so that its optical system is not affected by foreign matter generated by the rubbing of the lens barrel against the main body when the lens barrel moves vertically.  
         [0003]     2. Description of the Related Art  
         [0004]     Hitherto, a camera module switchable between a normal photographing mode and a macro photographing mode has been known. In such a camera module, in order to perform focus adjustment according to mode switching, a lens barrel holding a lens is held in a fixed main body. The lens barrel is moved relative to the main body in the direction of the optical axis of the lens, thereby changing the distance between the lens and an image sensor disposed in the main body. Thus, switching between a normal photographing position and a macro photographing position can be performed. Such a camera module is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2003-337279.  
         [0005]     The lens barrel slides with the outer peripheral surface in contact with the inner peripheral surface of the main body so as to prevent foreign matter from entering an optical system held in the lens barrel. However, if the lens barrel is repeatedly moved relative to the main body, foreign matter can be generated by abrasion of the outer peripheral surface of the lens barrel and the inner peripheral surface of the main body. If such foreign matter generated between the main body and the lens barrel enter the optical system, the foreign matter can affect the image obtained in the image sensor.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is made in consideration of the above problem. It is an object of the present invention to provide a camera module not allowing foreign matter generated by the sliding of the lens barrel relative to the main body to enter the optical system.  
         [0007]     To solve the above problem, in an aspect of the present invention, a camera module includes a lens barrel holding a lens, and a main body holding the lens barrel, the lens barrel being capable of moving relative to the main body in the direction of the optical axis of the lens. The lens barrel has a protuberance on the underside thereof throughout the circumferential direction. The main body has a recess at a position corresponding to the protuberance of the lens barrel throughout the circumferential direction, the recess accommodating the protuberance. The protuberance is formed so as to have a height such that the protuberance is disposed in the recess both before and after the movement of the lens barrel relative to the main body in the direction of the optical axis of the lens. Therefore, foreign matter generated by movement of the lens barrel relative to the main body can be prevented from entering the inner peripheral side where an optical system is disposed.  
         [0008]     In another aspect of the present invention, a camera module includes a lens barrel holding a lens, and a main body holding the lens barrel, the lens barrel being capable of moving relative to the main body in the direction of the optical axis of the lens. The lens barrel has a recess in the underside thereof throughout the circumferential direction. The main body has a protuberance at a position corresponding to the recess of the lens barrel throughout the circumferential direction, the protuberance being accommodated by the recess. The protuberance is formed so as to have a height such that the protuberance is disposed in the recess both before and after the movement of the lens barrel relative to the main body in the direction of the optical axis of the lens. Therefore, foreign matter generated by movement of the lens barrel relative to the main body can be prevented from entering the inner peripheral side where an optical system is disposed.  
         [0009]     The protuberance and the recess may face each other with a slight gap between their sides. In this case, friction does not occur between the protuberance and the recess, and generation of foreign matter can be prevented. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an exploded perspective view of a camera module in an embodiment;  
         [0011]      FIG. 2  is a perspective view showing a main body with a lens barrel attached thereto; and  
         [0012]      FIG. 3  is a sectional view of the camera module. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     A first embodiment of the present invention will now be described with reference to the drawings in detail.  FIG. 1  is an exploded perspective view of a camera module in this embodiment. As shown, the camera module in this embodiment includes a flat substrate  1  and a hollow main body  2  disposed thereon. The main body  2  rotatably holds a lens barrel  7  therein. The lens barrel  7  includes a cam member  3 , a lens barrel main body  4 , and a lever member  5 . On the top of the main body  2 , an elastic plate  6  is provided.  
         [0014]     On the top of the substrate  1 , an image sensor  12  is disposed. The image sensor  12  includes a two-dimensional array of photoelectric transducers. The image sensor  12  receives light from a photographic subject through an optical system of the camera module and outputs image data. On the underside of the main body  2 , a filter  11  is disposed. The filter  11  is a so-called IR filter and is provided for removing infrared light from the light from the optical system.  
         [0015]     The outer periphery on the bottom of the main body  2  has a raised outer peripheral rail surface  20  formed along the circumferential direction. Protrusions  30  formed on the underside of the lens barrel  7  are in contact with the outer peripheral rail surface  20 . Outer peripheral walls of the main body  2  have openings  24  formed therein. Through one of the openings  24 , a switching lever  50  provided in the lens barrel  7  protrudes outward. The openings  24  are horizontally long so that the switching lever  50  can be operated horizontally.  
         [0016]     The cam member  3 , which constitutes the lens barrel  7 , is hollow cylindrical and, as mentioned above, has protrusions  30  on the underside. The lower ends of the protrusions  30  are in contact with the outer peripheral rail surface  20  of the main body  2  and move along the outer peripheral rail surface  20  when the lens barrel  7  rotates relative to the main body  2 . The cam member  3  has four cutout-like engaged portions  31  formed in the top thereof in the circumferential direction. The engaged portions  31  engage with engaging portions  52  of the lever member  5 .  
         [0017]     The lens barrel main body  4  holds lenses  10  and is fitted into and fixed to the cam member  3 . The lever member  5  is generally ring-shaped and has the switching lever  50  outwardly protruding from the peripheral surface. In addition, the lever member  5  has a plurality of lens-barrel different-in-level portions  51  formed in the top thereof. Moreover, as mentioned above, the lever member  5  has engaging portions  52  formed on the underside thereof. The engaging portions  52  engage with the engaged portions  31  formed in the top of the cam member  3 , and thereby the lever member  5  is fixed to the cam member  3 .  
         [0018]     The elastic plate  6  is formed of metal and has a circular cutout in the center. Around the circular cutout, four concentric circular-arc-shaped cutouts are formed along the circumferential direction, and thereby elastic narrow spring portions  60  are formed. Every spring portion  60  is bent downward and is lowest at the middle, which forms a pressing portion  61 . The pressing portion  61  presses the top of the lever member  5 , which constitutes the lens barrel  7 , so as to urge the lens barrel  7  downward. The elastic plate  6  has fixing holes  62  formed in four corners thereof. The main body  2  has elastic-plate fixing portions  25  formed on the top thereof. The elastic-plate fixing portions  25  are fitted in the fixing holes  62 , and thereby the elastic plate  6  is fixed to the main body  2 .  
         [0019]      FIG. 2  is a perspective view showing the main body  2  with the lens barrel  7  attached thereto. In this figure, the walls of the main body  2  are omitted. As described above, the main body  2  has an outer peripheral rail surface  20  formed on the bottom thereof along the circumferential direction. The outer peripheral rail surface  20  includes main-body different-in-level portions  21 , each including an upper level, a lower level, and a sloping surface  21 a therebetween.  
         [0020]     The protrusions  30  of the lens barrel  7  in contact with the outer peripheral rail surface  20  move between the upper level and the lower level along the main-body different-in-level portions  21  with the rotation of the lens barrel  7  by operating the switching lever  50 . The lens barrel  7  thereby moves vertically and changes the distance between the lens  10  held in the lens barrel main body  4  and the image sensor  12  disposed in the main body  2 , thereby switching between the normal photographing mode and the macro photographing mode.  
         [0021]     As described above, the lens barrel  7  is urged by the pressing portions  61  of the elastic plate  6 , at a plurality of places on the top thereof, and has lens-barrel different-in-level portions  51 . The lens-barrel different-in-level portions  51  are disposed so as to be urged by the pressing portions  61  when the protrusions  30  are in contact with the upper levels of the main-body different-in-level portions  21 . Each lens-barrel different-in-level portion  51  includes a lower level between upper levels, and sloping surfaces  51 a between the lower level and the upper levels.  
         [0022]     In  FIG. 2 , the protrusions  30  of the lens barrel  7  are disposed on the upper levels of the outer peripheral rail surface  20 . In this state, the pressing portions  61  of the spring portions  60  press the lower levels in the top of the lens barrel  7  as shown by arrows in the figure. When the lens barrel  7  is rotated by operating the switching lever  50 , the protrusions  30  move onto the lower levels of the outer peripheral rail surface  20  via the sloping surfaces  21 a of the main-body different-in-level portions  21 . Accordingly, the lens barrel  7  moves downward. At the same time, the pressing portions  61  move onto the upper levels via the sloping surfaces  51 a of the lens-barrel different-in-level portions  51 . When, from this state, the lens barrel  7  is rotated in the reverse direction by operating the switching lever  50 , the same operation is performed in the reverse direction. That is to say, the lens barrel  7  moves upward, and the pressing portions  61  move onto the lower levels.  
         [0023]     As described above, the pressing portions  61  of the spring portions  60  move between the upper levels and the lower levels of the lens-barrel different-in-level portions  51  with the vertical movement of the lens barrel  7 . Since the position of the pressing portions  61  in the vertical direction is fixed and therefore the vertical movement of the lens barrel  7  does not cause displacement of the spring portions  60 , it is possible to prevent deterioration of the spring portions  60  and to extend the life of the spring portions  60 .  
         [0024]      FIG. 3  is a sectional view of the camera module. As shown, the lens barrel main body  4 , which constitutes the lens barrel  7 , holds a lens  10  therein. The lens  10  includes three lens elements. The main body  2  has an inward protruding mount portion  23  formed around the inner periphery thereof below the lens barrel  7 . On this mount portion  23 , the periphery of the filter  11  is disposed.  
         [0025]     The cam member  3 , which constitutes the lens barrel  7 , has a downward protruding protuberance  32  formed at the lower end thereof throughout the circumferential direction. On the other hand, the mount portion  23  of the main body  2  has a recess  22  formed in the outer periphery thereof throughout the circumferential direction. In the recess  22 , the protuberance  32  of the lens barrel  7  is inserted. The width of the recess  22  is slightly larger than the width of the protuberance  32 , and the sides of the recess  22  and the protuberance  32  face each other with a slight gap therebetween.  
         [0026]     The length by which the protuberance  32  is inserted in the recess  22  is larger than the stroke of the vertical movement of the lens barrel  7 . In  FIG. 3 , the lens barrel  7  is at the lower position, and the lower end of the protuberance  32  is close to the bottom of the recess  22 . When the lens barrel  7  is at the upper position, the lower end of the protuberance  32  remains in the recess  22 .  
         [0027]     As described above, a protuberance  32  is provided on the inner periphery of the lower end of the lens barrel  7 , a recess  22  to accommodate the protuberance  32  is provided in the main body  2 , and the protuberance  32  is disposed in the recess  22  both before and after the vertical movement of the lens barrel  7 . Therefore, if foreign matter such as abrasion dust is generated by the sliding of the lens barrel  7  relative to the main body  2 , it is hard for the foreign matter to enter the area where the filter  11  and the image sensor  12  are disposed. Therefore, the image obtained in the image sensor  12  is not affected. In addition, the recess  22  and the protuberance  32  are formed so that the sides of the recess  22  and the protuberance  32  face each other with a slight gap therebetween. Therefore, it is harder for the foreign matter generated on the outer periphery side of the lens barrel  7  to enter the inside.  
         [0028]     In this embodiment, a protuberance  32  is provided on the underside of the lens barrel  7 , and a recess  22  is provided in the main body  2 . Alternatively, it is possible to provide a protuberance in the main body  2  and to provide a recess in the underside of the lens barrel  7 . Also in this case, whether the lens barrel  7  is at the upper or lower position, the protuberance is in the recess. Therefore, although the lens barrel  7  moves vertically, it is harder for the foreign matter generated on the outer periphery side of the lens barrel  7  to enter the inside.  
         [0029]     Although embodiments of the present invention have been described above, it is to be understood that the present invention is not intended to be limited to these embodiments, and various changes may be made therein without departing from the scope of the technical idea of the present invention.