Abstract:
An image capturing unit for an electronic endoscope, including a solid-state image capturing element, a metallic housing member, which hermetically encloses a circumference of an insulated base and is arranged to cover a front-end portion of the insulated base, at least one connection land, which is connected to at least one signal conductor at a position in vicinity to a rear-end portion of the insulated base outside the housing member, and a conductive cylindrical shield, which surrounds the at least one connection land and the at least one signal conductor and is spaced from the at least one connection land and the at least one signal conductor in a radial direction, is provided. An outer periphery of the rear-end portion of the insulated base is formed to be smaller than the circumference of the insulated base enclosed by the housing member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an image capturing unit, which is adapted to be built in a tip portion of an electronic endoscope.  
         [0002]     Generally, an image capturing unit of an electronic endoscope includes a solid-state image capturing element, an electrically insulated base to support the image capturing element, and a metallic housing to airtightly enclose the image capturing element and the insulated base therein. The image capturing unit further includes a plurality of connection lands that are arranged in vicinity to a rear end of the insulated base outside the housing and are connected to signal conductors thereat. Examples of such an image capturing unit are disclosed in Japanese Patent Provisional Publications Nos. 2003-100920 and HEI 10-74865.  
         [0003]     As an inserted portion of a tip of the endoscope is adapted to be inserted into live bodies, the image capturing unit of the endoscope is required to be downsized by tenths of a millimeter to a minimum extent,  
         [0004]     However, in the image capturing units disclosed in the above-referenced publications, in order to inhibit noises to signals from intruding from connecting points of the connection lands and the conductors, the rear-end portion of the image capturing unit is required to be shielded by a conductive cylinder, which is arranged to be spaced in a radial direction from the connection lands and the signal conductors.  
         [0005]     Therefore, as shown in  FIG. 10 , a diameter of a cylindrical shield  92 , which extends from a circumference of an insulated base  91 , tends to be greater than a diameter of a housing  94  that surrounds a solid-state image capturing element  93 , and the like. In such a configuration, as an entire image capturing unit becomes greater, it becomes difficult to use the image capturing unit in an endoscope with a considerably smaller diameter In exchange, other components of the image capturing unit, such as a light guide for illumination and channel tubes, are required to be downsized in diameters thereof. Therefore, functionalities of the endoscope may have been limited by the configuration.  
       SUMMARY OF THE INVENTION  
       [0006]     In view of the foregoing drawbacks, the present invention is advantageous in that an image capturing unit for an electronic endoscope, in which a cylindrical shield to surround contact points of connection lands and signal conductors is configured to be smaller, is provided, whilst functionalities of the endoscope may be substantially achieved,  
         [0007]     According to an aspect of the present invention, there is provided an image capturing unit for an electronic endoscope, including a solid-state image capturing element, which is adapted to capture an image of an object, a metallic housing member, which is adapted to airtightly or hermetically enclose a circumference of an insulated base holding the image capturing element and is arranged to cover a front-end portion of the insulated base, at least one connection land, which is connected to at least one signal conductor at a position in vicinity to a rear-end portion of the insulated base outside the housing member, and a conductive cylindrical shield, which is arranged to surround the position where the at least one connection land and the at least one signal conductor are connected and is spaced from the at least one connection land and the at least one signal conductor in a radial direction. An outer periphery of the rear-end portion of the insulated base is formed to be smaller than the circumference of the insulated base enclosed by the housing member, so that an outer periphery of the cylindrical shield is smaller than an outer periphery of the housing member.  
         [0008]     Optionally, the cylindrical shield and the housing member may be electrically connected with each other.  
         [0009]     Optionally, the insulated base may be formed to include a shield receiving portion, to which a front-end portion of the cylindrical shield is fitted. The cylindrical shield may be correctly positioned when the front-end portion of the cylindrical shield is fitted to receiving portion.  
         [0010]     Optionally, a shield receiving member, to which the front-end portion of the cylindrical shield is fitted, may be fixed to a rear-end portion of the housing member, so that the cylindrical shield is correctly positioned when the front-end portion of the cylindrical shield is fitted to the shield receiving member.  
         [0011]     Optionally, a portion of the housing member may be bent toward an axis thereof to form the rear-end portion, and the shield receiving member may be fixed to a rear surface of the rear-end portion.  
         [0012]     Optionally, the shield receiving member may be adhesively fixed to the housing member.  
         [0013]     Optionally, the shield receiving member may be brazed to the housing member.  
         [0014]     Optionally, the shield receiving member may have a form of a frame, of which cross-sectional shape is an approximate rectangle.  
         [0015]     Optionally, the shield receiving member may be made of an electrically insulated material.  
         [0016]     Optionally, an outer peripheral surface of the shield receiving member may be metalized. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a cross-sectional side view of an image capturing unit for an electronic endoscope according to a first embodiment of the invention.  
         [0018]      FIG. 2  is a plane view of the image capturing unit taken along a line II-II in  FIG. 1  according to the first embodiment of the invention.  
         [0019]      FIG. 3  is a cross-sectional side view of an image capturing unit for an electronic endoscope according to a second embodiment of the invention.  
         [0020]      FIG. 4  is a cross-sectional side view of an image capturing unit for an electronic endoscope according to a third embodiment of the invention.  
         [0021]      FIG. 5  is a plane view of the image capturing unit taken along a line V-V in  FIG. 4  according to the third embodiment of the invention.  
         [0022]      FIG. 6  is a perspective view of a shield receiving member of the image capturing unit according to the third embodiment of the invention.  
         [0023]      FIG. 7  is a perspective view of a variation of the shield receiving member of the image capturing unit according to the third embodiment of the invention.  
         [0024]      FIG. 8  is a cross-sectional side view of the image capturing unit before the cylindrical shield is installed according to the third embodiment of the invention.  
         [0025]      FIG. 9  is a cross-sectional side view of the image capturing unit before the cylindrical shield is installed according to the third embodiment of the invention.  
         [0026]      FIG. 10  is a cross-sectional side view of a conventional image capturing unit.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0027]     Hereinafter, referring to the accompanying drawings, an image capturing unit of an electronic endoscope according to illustrative embodiments of the invention will be described.  
       First Embodiment  
       [0028]      FIG. 1  is a cross-sectional side view of an image capturing unit  100  for an electronic endoscope according to a first embodiment of the invention. The image capturing unit  100  is provided at a tip of an inserted portion (not shown) of the endoscope, and includes a solid-state image capturing element  1 , of which a front surface is formed to be an approximate rectangle. Further, an image capturing area  2 , which is formed to be an approximate rectangle and substantially smaller than the image capturing element, is provided in a central portion of the image capturing element  1 .  
         [0029]     The image capturing element  1  is supported by an insulated block  3 , which is made of an insulated material, such as ceramic. The insulated block  3  is formed to include a recessed portion at a front thereof, so that the image capturing element  1  is adhesively fixed therein.  
         [0030]     On an outer surface of a rear portion of the insulated block  3 , a plurality of connection lands  5  that are connected to signal conductors  4  are provided. The signal conductors  4  are arranged inside the inserted portion of the endoscope. Each of the connection lands  5  is connected to a rear end of one of conductors  5 , which are buried in the insulated block  3  and extended in parallel with an axial direction of the inserted portion.  
         [0031]     Further, in the image capturing unit  1 , a plurality of bonding wires  7 , which connect a circuit (not shown) of the image capturing element  1  with the conductors  6 , are provided. The bonding wires  7  are arranged along two opposed edges of the image capturing element  1  to extend outwardly, so that each of the bonding wires  7  is connected to a front end of each of the conductors  6  that are exposed from two opposed edges of a front end of the insulated block  3 . Each of the bonding wires  7  is curved toward a front of the image capturing element  1  as the bonding wire  6  extends from the front surface of the image capturing element  1 .  
         [0032]     The image capturing unit  100  further includes a housing  8 , which contains the image capturing element therein. The housing  8  is made of one of metals, and has a shape of a rectangular cylinder that encircles by a front portion of the image capturing unit  100 , so that vapor and the like should not enter the image capturing unit  100  during high-pressure and high-temperature steam sterilization.  
         [0033]     The image capturing unit  100  includes an approximate rectangular rear frame  9 , which is made of one of metals, and is arranged on an inner periphery at a rear portion of the housing  8 , so that space between the housing  8  and the insulated block  3  is maintained. The rear frame  9  is airtight or hermetically sealed at an entire welding surface A to the housing  8 , so that the rear frame  9  is assembled to be integral with the housing  8 . Further, the rear frame  9  is airtight or hermetically sealed at an entire seal surface B to the insulated block  3  with a fixing method such as by welding, with an inorganic adhesive agent, for example.  
         [0034]     The image capturing unit  100  includes an approximate rectangular front frame  9 , which is made of one of metals, and is arranged on the inner periphery at a front portion of the housing  8 . The front frame  11  is airtight or hermetically sealed at an entire welding surface C to the housing  8 , whilst a rear end of the front frame  11  is in contact with the front end of the insulated block  3 , so that the housing  8  is stabilized to the insulated block  3  through the front frame  11 . Further, a transparent cover glass  10  to seal the front surface of the image capturing element  1  from exterior environment is provided. The cover glass  10  is airtight or hermetically sealed to a seal surface D of a front-most portion of the front frame  11 .  
         [0035]     The image capturing unit  100  further includes a cylindrical shield  12  to surround connecting portions of the signal conductors  4  and the connection lands  5 , so that noises to signals through the signal conductors  4  and the connection lands  5  are inhibited from intruding. A front end of the cylindrical shield  12  is electrically connected to a rear end of the housing  8  (i.e., a soldered portion E is formed) by soldering.  
         [0036]      FIG. 2  is a plane view of the image capturing unit  100  taken along a line II-II in FIG. I according to the first embodiment of the invention. The cylindrical shield  12  is arranged to surround the connection lands  5  and the signal conductors  4  that are connected to the connection lands  5 . As the cylindrical shield  12  is arranged, the cylindrical shield  12  is spaced from the connection lands  5  and the signal conductors  4  that are connected to the connection lands  5  in a radial direction, and a void space between the connection lands  5  and the signal conductors  4  and the cylindrical shield  14  is filled with a potting agent  13  such as an epoxy-based adhesive agent.  
         [0037]     With the cylindrical shield  12  attached to the housing  8  by soldering, a diameter of the cylindrical shield  12  of the image capturing unit  100 , is configured to be smaller than a diameter of a portion surrounded by the housing  8 .  
         [0038]     Therefore, a diameter of a portion of the image capturing unit  100 , which extends from a connected portion between the cylindrical shield  12  and the housing  8 , can be configured to be smaller, so that other components of the image capturing unit, such as a light guide for illumination and channel tubes, can be configured to have substantially larger diameters to provide substantially greater functionalities of the endoscope. Further, the image capturing unit  100  configured as above can be used in an endoscope with a small diameter.  
       Second Embodiment  
       [0039]      FIG. 3  is a cross-sectional side view of an image capturing unit  200  for an electronic endoscope according to a second embodiment of the invention. In the present and following embodiments, configurations corresponding to the configuration of the first embodiment is referred to by the identical reference numerals, and description of those is omitted.  
         [0040]     In the present embodiment, the insulated block  3  is formed to have a shield receiving portion  3   a  on a circumference of the insulated block  3 . The shield receiving portion  3   a  is formed to have a cross-sectional shape of an approximate rectangle, which is engaged with a front end of the cylindrical shield  12 . With this configuration, the cylindrical shield  12  can be positioned easily and correctly in a radial direction and in a circumferential direction, as the image capturing unit  200  is assembled.  
       Third Embodiment  
       [0041]      FIG. 4  is a cross-sectional side view of an image capturing unit  300  for an electronic endoscope according to a third embodiment of the invention.  FIG. 5  is a plane view of the image capturing unit taken along a line V-V in  FIG. 4  according to the third embodiment of the invention.  FIG. 6  is a perspective view of a shield receiving member  14  of the image capturing unit  300  according to the third embodiment of the invention.  FIG. 7  is a perspective view of a variation of the shield receiving member  14   a  of the image capturing unit  300  according to the third embodiment of the invention.  
         [0042]     In the present embodiment, the image capturing unit  300  is provided with the shield receiving member  14 , which is fixed to a rear surface of the housing  8 , and the cylindrical shield  12  is fixedly fitted to outer peripheral surfaces of the shield receiving member  14 ,  
         [0043]     The shield receiving member  14  is formed to be an approximate rectangular frame, which is substantially smaller than a diameter of the housing  8 . The shield receiving member  14  is made with an insulated material, such as ceramic, so that the shield receiving member  14  can withstand voltage from the connection lands  5 , which are arranged in vicinity to the shield receiving member  14 , Outer peripheral surfaces (metalized surfaces  15 ) of the shield receiving member  14  is metalized, so that the metalized surfaces  15  can be easily soldered as the cylindrical shield  12  is attached to the shield receiving member  14 . It should be noted that edges of the shield receiving member  14  may be beveled as shown in  FIG. 7 .  
         [0044]     As the image capturing unit  300  is configured, the cylindrical shield  12  is required to be in an exactly correct position with respect to outer peripheral surfaces of the housing  8 , so that outer peripheral surfaces of the cylindrical shield  12  do not protrude from the outer peripheral surfaces of the housing  8 .  
         [0045]      FIG. 8  is a cross-sectional side view of the image capturing unit  300  before the cylindrical shield  12  is installed according to the third embodiment of the invention. The rear end portion of the housing  8  is bent toward an axis of the housing  8 . The shield receiving member  14  is fixed to a rear surface (i.e., an adhered surface F) of the housing  8  in a correct position with respect to the housing  8  with heat-resistant adhesive agent, such as silicone-based adhesive agent and epoxy-based adhesive agent. The shield receiving member  14  may not necessarily be airtight or hermetically sealed to the adhered surface F.  
         [0046]     In the present embodiment, it is preferred that the adhesive agent is resistant to heat ranging approximately from 300 to 350 degrees C., so that the adhesive agent should not be deteriorated by heat generated during a soldering work, that takes place in vicinity to the adhered surface F. As the shield receiving member  14  is adhered to the adhered surface F of the housing  8 , positions of the outer peripheral surfaces of the shield receiving member  14  are accurately adjusted with respect to the outer peripheral surfaces of the housing  8  by using a tool (not shown) and the like.  
         [0047]      FIG. 9  is a cross-sectional side view of the image capturing unit  300  before the cylindrical shield  12  is installed according to the third embodiment of the invention. After the signal conductors  4  are soldered to the connection lands  5 , as shown in  FIG. 9 , inner peripheral surfaces of a front end portion of the cylindrical shield  12  are closely fitted to the outer peripheral surfaces of the shield receiving member  14  (see  FIG. 4 ). Thereafter, the front end portion of the cylindrical shield  12  along with the metalized surfaces  15  of the shield receiving member  14  is soldered to a soldered portion E of the housing  8 . It should be noted that the soldering may be replaced with brazing with other conductive material.  
         [0048]     With the above configuration, the cylindrical shield  12  can be attached to the housing  8  in the correct position with respect to the outer peripheral surfaces of the housing, whilst the outer peripheral surfaces of the cylindrical shield  12  do not protrude from the outer peripheral surfaces of the housing  8 .  
         [0049]     The present disclosure relates to the subject matter contained in Japanese Patent Applications Nos. P2005-193227, filed on Jul. 1, 2005 and P2005-197037, filed on Jul. 6, 2005, which are expressly incorporated herein by reference in their entireties.