Abstract:
A shock mounting system for a 3-chip video camera. The system comprises a prism mounting bracket with a pair of laterally spaced support legs. A standard 3 chip color camera is received between the support legs and a plurality of elastomeric plugs are molded to fit between the camera assembly and the housing within which it is situated. The elastomeric plugs are formed from flowable elastomeric material injected into molding chambers formed during the assembly process.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to shock mounting electronic devices. In particular, the invention relates to shock mounting an imaging device used in an endoscopic video camera.  
         [0003]     2. Description of the Prior Art  
         [0004]     Charged coupled device (CCD) video cameras have come into extensive use in industrial and medical fields. In medical applications these cameras attach to an eyepiece of an optical instrument called an endoscope so that one or more physicians observe on a television monitor what one formerly viewed directly by eye at the endoscope eyepiece. With a diameter of generally less than 10 mm, endoscopes are passed into body cavities through small holes to observe structures and perform procedures previously requiring large surgical openings. Two of the most common types of CCD cameras that are in use in medical surgery today are the single CCD camera and the 3-CCD camera, the latter sometimes called a 3-chip camera. In the case of the 3-CCD camera, light entering the camera from a lens system is separated by a multi-part glass prism assembly, whose optical faces are coated with high and low pass dichroic coatings, such that red light wavelengths of the incoming light image are reflected to one CCD, the blue wavelengths from the image are reflected to a second CCD, and the green wavelengths pass through to a third CCD. The three primary color images from the three CCD&#39;s are then recombined to form one color image. The recombined color image has greater line resolution than a comparable single CCD medical camera, and superior color reproduction. The high resolution, superior color video image produced by the 3-CCD camera is favored by some surgeons for use in medical procedures. The negative side of the 3-CCD camera is that it is larger, heavier, more expensive than a single CCD camera, and the adhesively assembled glass prism and CCD assembly is relatively easily damaged by rough handling. Further, the recombination of the three primary color images must be done with extreme accuracy to obtain the improved image resolution. Any displacement or breakage of components in the assembly due to shock or thermal distortion severely reduces image resolution or eliminates it entirely, and is virtually unrepairable.  
         [0005]     Prior U.S. patent application Ser. No. 09/252,330, filed Feb. 18, 1999 and entitled Shock Mounting System for CCD Camera, assigned to the assignee hereof and incorporated by reference herein, shows one way of shock mounting a CCD camera. The disclosure in that application involved securing support plates to the prism assembly (to join the components together) and then enclosing the support plates in an elastomeric preformed boot structure interposed between the support plates and the camera housing. It has been found that the invention disclosed herein is an improvement over the devices and methods disclosed in this prior application.  
         [0006]     It is accordingly an object of this invention to produce a system to reinforce and mount a camera assembly to enable it to withstand inadvertent shock loads.  
         [0007]     It is another object of this invention to produce a system and method to shock mount a 3-CCD camera assembly to enable it to withstand shock loads such as a drop from a surgical table to a hard floor that would normally destroy an unmodified 3-CCD camera.  
         [0008]     It is a further object of this invention to produce a system for converting a 3-CCD camera from non-ruggedized form to a ruggedized form.  
         [0009]     It is another object of this invention to produce a shock mounting system for a 3-CCD camera that is relatively easy to manufacture and repair.  
       SUMMARY OF THE INVENTION  
       [0010]     These and other objects are accomplished by the preferred embodiment disclosed herein which is a shock mounting system for a 3-chip CCD camera. The system is embodied in a camera head comprising a camera assembly having at least one CCD imaging device and an inlet window for receiving an image to be presented to the CCD imaging device. The camera head comprises a housing for containing the camera assembly. A camera mount is interposed between the camera assembly and the housing, the camera mount being immovably secured to the camera assembly. Elastomeric plugs are formed from flowable elastomeric material that is interposed between the camera mount and the housing.  
         [0011]     In another aspect the invention comprises a method of producing a shock mounted camera. The method comprises the steps of producing a camera comprising: providing a housing; providing a camera assembly to be received within the housing; providing a plurality of support members to be immovably secured to the housing, adjacent the camera assembly, while providing a predetermined gap between the camera assembly and the support members; placing the camera assembly adjacent the support members; providing access to the gap; injecting a flowable elastomeric material into the gap; and allowing the flowable elastomeric material in the gap to cure, thereby creating a resilient buffer between the camera assembly and the support members. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is an expanded front perspective view of a 3-CCD camera head constructed in accordance with the principles of this invention.  
         [0013]      FIG. 2  is a side elevation view of a portion of  FIG. 1  in an assembled configuration.  
         [0014]      FIG. 3  is a cross-sectional view of  FIG. 2  taken along the line  3 - 3 .  
         [0015]      FIG. 4  is a left side view of  FIG. 2 .  
         [0016]      FIG. 5  is a cross-sectional view of  FIG. 4  taken along the line  5 - 5 .  
         [0017]      FIG. 6  is a cross-sectional view of  FIG. 4  taken along the line  6 - 6   
         [0018]      FIG. 7  is a cross-sectional view of  FIG. 2  taken along the line  7 - 7 .  
         [0019]      FIG. 8  is a perspective view of  FIG. 2  showing a step in the method of making the invention  
         [0020]      FIG. 9  is a perspective view of  FIG. 8  showing another step in the method of making the invention.  
         [0021]      FIG. 10  is a perspective view of  FIG. 9  showing another step in the method of making the invention.  
         [0022]      FIG. 11  is a perspective view of  FIG. 10  showing another step in the method of making the invention.  
         [0023]      FIG. 12  is a perspective view of  FIG. 11  showing another step in the method of making the invention.  
         [0024]      FIG. 13  is a perspective view of  FIG. 12  showing another step in the method of making the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]     A representative 3-chip camera  100  constructed in accordance with the principles of this invention is shown in the drawings. As shown in  FIG. 1 , camera  100  comprises a 3-CCD/prism camera assembly  102  which fits in housing  104  and is operated by an associated electronics assembly (not shown) which operates the camera assembly in a conventional manner (the electronics assembly forms no part of this invention). The camera assembly  102  includes a CCD/prism subassembly  106  which is shown in  FIG. 1  as it is received from the manufacturer thereof. Subassembly  106  is a major part of a non-ruggedized 3-chip camera produced in a conventional manner. The invention converts this existing subassembly  106  to a ruggedized version (as embodied by camera  100 ) capable of withstanding shocks and vibrations. When fully assembled, camera  100  will include housing  104  which will encase all of the components of 3-CCD/prism camera assembly  102  in a hermetically sealed enclosure in a conventional manner. As will be understood below, a predetermined number of individual elastomeric shock mount corner plugs  118  are interposed between the prism subassembly  106  and the housing  104  in order to minimize the transmission of any damaging shocks and vibrations between the housing and the prism subassembly.  
         [0026]     The front or distal face  105  of housing  104  comprises a light transparent aperture (not shown) which receives a C-mount or other connection for threadably or otherwise connecting camera  100  to an optical device for forming an image, such as an associated endoscope or, in particular, a laparoscope or arthroscope (not shown). An optical coupler or similar device may be interposed between the camera and endoscope.  
         [0027]     Camera assembly  102  comprises components designed to be interposed between CCD/prism subassembly  106  and housing  104 . Such additional components are, in general, a frame or prism mount  108 , mounting blocks  110  and  112 , stop plates  114 ,  116  and elastomeric corner plugs  118 . The exact nature and number of additional components needed to properly isolate prism subassembly  106  to produce the ability to adequately protect it from shocks and vibrations depends upon the structure of the prism subassembly received from its manufacturer. In the embodiment shown in the drawings, prism subassembly  106  is provided by its manufacturer in the form of a 3-CCD prism body  120  having a front inlet window  122  for receiving an image to be conveyed to CCD&#39;s  124   a,    124   b  and  124   c.  Prism body  120  is also provided with a metal mounting bracket  126  bonded to the body on one side and a glass plate  128  bonded to the body on the other side (best seen in  FIG. 3 ).  
         [0028]     Mounting bracket  126  is provided with two non-threaded longitudinal- and lateral-position-fixing apertures  140  and  142 , used for longitudinal- and lateral-positioning of the prism subassembly  106  within prism mount  108 , and a threaded transverse-position-fixing aperture  144  used to secure the prism body transversely relative to prism mount  108 . As will be understood below, when all three apertures  140 ,  142  and  144  are properly engaged, the prism subassembly  106  will be fixed in three dimensions relative to prism mount  108 . In the conventional use for which prism subassembly  106  was originally designed by the manufacturer, the outer surface  146  of mounting bracket  126  would simply be abutted against a retaining surface (not shown) by a screw passing through the retaining surface and received in aperture  144 . As will be understood below, the structure and method disclosed herein modifies the normal use of mounting bracket  126  to achieve the benefits of the invention.  
         [0029]     Prism mount  108  serves as an intermediate structure adapted to receive prism subassembly  106  and adapted to itself be received in and secured to housing  104 . Prism mount  108  has a front plate  150  with a light transmitting aperture  152  to be aligned with prism inlet window  122  and additional peripheral apertures  154  to enable it to be secured to housing  104 . Integrally formed with front plate  150  and extending proximally therefrom are laterally spaced support members in the form of plates or legs  156  and  158 . It will be understood that support legs  156  and  158  need not be part of front plate  150  and could be independent members separately formed and/or directly attached to or formed as part of housing  104 . As best seen in  FIG. 7 , the support legs  156  and  158  are each spaced apart by a distance D 1  greater than the width D 2  of the modified prism subassembly  106 . Additionally, the cross-section of each support leg  156  and  158  is generally 3-sided to partially enclose the mounting brackets attached to each side of the prism body.  
         [0030]     Mounting blocks  110  and  112  are provided to serve as extension elements so the width of the prism body (as modified by the mounting brackets), from the laterally outermost surface  146  of mounting bracket  126  to the laterally outermost surface  160 , is symmetrical about the inlet window  122  of the prism subassembly. In the preferred embodiment, mounting blocks  110  and  112  are made of made of a steel alloy known as kovar because of its thermal characteristics which allow thermal expansion/contraction (imposed on the system by sterilization processes) without destroying the integrity of the assembly. Kovar is a material which has a dimensional stability (coefficient of thermal expansion) very close to that of the glass in the prism and the CCD chips. The blocks are preferably bead-blasted to improve adhesion to the assembly and sized to be a comparable thermal mass to that of block  126 . It will be understood that glass plate  128  and mounting blocks  110  and  112  could be replaced by another element like mounting bracket  126 . As will be understood, the structure of the components (plate  128 , blocks  110  and  112 ) on the side of prism subassembly  106  opposite mounting bracket  126  is just to ensure symmetry of the prism subassembly within prism mount  108 . These components are, therefore, also referred to as “mounting blocks”.  
         [0031]     As shown in the drawings, after the placement of mounting blocks on both side of prism subassembly  106 , the subassembly has a front side  130  and two lateral sides  132  and  134 . The sides  132  and  134  are adapted to fit between support legs  156  and  158  of the prism mount  108 . Mounting bracket  126  is adapted to fit within the inside 3-sided structure of support leg  158 , as best seen in  FIG. 7 . While the preferred embodiment of the prism mount is shown as having a front plate  150  and two laterally spaced and longitudinally extending legs  156  and  158 , it will be understood that the front plate could be omitted and the legs could be secured directly to the camera housing.  
         [0032]     If a mounting block (or blocks) on each side of the prism assembly is missing or of insufficient size, the predetermined number of mounting blocks  110  and  112  could be additionally bonded to the side of the prism as best shown in  FIGS. 3 and 5  in order to assure that the mounting block assembly extends laterally a sufficient distance from the sides of the prism to adequately fill the space defined between the prism mount support legs  156  and  158  so that only small gaps  136 ,  138  are created (in three dimensions) adjacent each side of the prism.  
         [0033]     Support leg  158  is provided with a plurality of apertures which are used to accurately position the modified prism subassembly  106  within the prism mount  108  and to facilitate formation of an elastomeric interface. These apertures are intended to cooperate with the apertures preformed in the mounting block  126  attached to the prism body by the manufacturer of subassembly  106 .  
         [0034]     Referring now to  FIGS. 8 through 13  the method of producing camera  102  will be described. As already mentioned, mounting block  126  has a central threaded aperture  144  and two longitudinal- and lateral-position-fixing apertures  140  and  142  on either side thereof. Support leg  158  is provided with a central non-threaded aperture  170  adapted to be aligned with threaded aperture  144 , and two alignment apertures  172  and  174  adapted to be aligned with apertures  140  and  142 , respectively. As shown in  FIG. 8 , after the modified prism subassembly is placed between support legs  156  and  158 , pins  176 ,  177  are inserted through holes  172  and  174  in support leg  158  to position the prism subassembly  106  relative to the prism mount  108  in the X and Y directions.  
         [0035]     Then, as shown in  FIG. 9 , additional screws are used to position the components in the Z direction. To do this, support leg  158  is provided with four threaded apertures  180 ,  182 ,  184  and  186  which are symmetrically situated around central aperture  170 . As seen in  FIG. 10 , the apertures are intended to receive threaded transverse-position-setting screws  181 ,  183 ,  185  and  187 . These screws each have a predetermined length and their distal ends are intended to provide transverse stop surfaces which define the gap  136  between the inside surface  137  of support leg  158  and the outside surface  132  of mounting bracket  126 . It will be understood that when transverse-position-fixing screw  188  ( FIG. 10 ) is received in aperture  170  and threaded into aperture  144  in mounting block  126 , the mounting block will be pulled transversely toward support leg  158  until its outer surface  132  abuts the ends of transverse-position-setting screws  181 ,  183 ,  185  and  187 , thereby forming a chamber  190 . Stop plate  116 , best seen in  FIG. 11 , is attached by screw  191 b to the proximal end of support leg  158  to define the back wall of chamber  190 . (Similarly, stop plate  114  is attached by screw  191   a  to support leg  156 .)  
         [0036]     Support leg  158  is also provided with injection apertures  192 ,  193 ,  194  and  195 , as shown in  FIG. 12  to provide access to chamber  190 . Flowable elastomeric material (e.g. liquid silicone) may be injected into these apertures and into chamber  190  in the direction of arrows  196  and allowed to cure into one or more resilient plugs. (Injection apertures could alternatively be provided in other structures, e.g. front plate  150 , to provide access to chamber  190 .) Depending upon the quantity of injected elastomeric material, the interior of chamber  190  may be entirely or only partially filled with elastomeric material. In the preferred embodiment only a small amount of flowable elastomeric material is injected into each aperture  192 ,  193 ,  194  and  195  so that the material when cured will be in the form of four elastomeric plugs  118  situated at each corner of mounting block  126  as best seen in FIGS.  6  and  7 . Each plug  118  will cure into a resilient shock absorbing corner structure having three sides, each side interposing a resilient buffer between the laterally, proximally and distally facing surfaces of each corner of mounting block  126  and the associated facing surfaces of support leg  158  (and stop plate  116 ). A small amount of material may remain in the injection apertures.  
         [0037]     It will be understood that the mounting plate could be cylindrical rather than rectangular. In any event it would still have laterally, longitudinally and transversely facing surfaces and, although the elastomeric plugs would conform to such surfaces, they would be curved structures rather than corner structures.  
         [0038]     The opposite side of the prism subassembly  106 , modified by glass block  128  and mounting blocks  110  and  112  is similarly provided with elastomeric corner plugs  118 . While support leg  156  is provided with all the same apertures as support leg  158  in order to preserve thermal stability of the camera, the longitudinal/lateral locating pins, transverse-position-fixing screws and transverse-position-setting screws need not be used in support leg  156 . After elastomeric plugs  118  have been formed and sufficiently cured adjacent support legs  156  and  158 , the pins  176 ,  177 , screws  181 ,  183 ,  185 ,  187  and  188  may all be removed ( FIG. 13 ). The resulting assembly may now be secured within housing  104 .  
         [0039]     It will be understood that the elastomeric plugs also provide a thermal barrier between adjacent components. Therefore, the temperatures to which housing  104  is subjected during autoclaving are not immediately experienced by the prism subassembly, thereby minimizing thermal stresses on camera  102 .  
         [0040]     While mounting brackets have been shown as being separate components attached/boned to the sides of the prism subassembly, it will be understood that the functions of the mounting brackets may be achieved by appropriately shaping or modifying the prism itself.  
         [0041]     While the invention has been disclosed in the form of an apparatus and method for use with a 3-CCD camera, it will be understood that the principles of this invention could be applied to other camera assemblies.  
         [0042]     It will be understood by those skilled in the art that numerous improvements and modifications may be made to the preferred embodiment of the invention disclosed herein without departing from the spirit and scope thereof.