Abstract:
A variable direction-of-view endoscope ( 74 ) with a spherical viewing window ( 34 ) symmetric about a symmetry plane ( 52 ) sealed to a distal end portion ( 18 ). The endoscope optical system can be adjusted to vary the direction of a view vector ( 22 ) through an unlimited range ( 50 ) about a pivot axis ( 23 ). The spherical viewing window ( 34 ) enables a process that switches the device between an initial configuration ( 54 ) and a final configuration ( 56 ), both having the same viewing direction ( 55 ). In addition to providing the user with an alternative to a possibly unfavorable viewpoint, this redundancy enables a stereo imaging process which captures ( 66 ) and displays ( 72 ) a stereo image pair ( 70 ) affording the user three-dimensional viewing.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to endoscopes (including devices such as borescopes, fiberscopes, etc.) and specifically to variable direction-of-view and stereo viewing endoscopic devices.  
         BACKGROUND OF THE INVENTION  
         [0002]    Endoscopes are elongated devices used to visualize the inside of cavities. They are commonly utilized for medical and industrial applications. There has been a long felt need for endoscopes capable of varying their direction-of-view.  
           [0003]    Most rigid endoscopes capable of varying their direction of view have a window that limits their scanning range. U.S. Pat. No. 4,697,577 to Forkner (1987) discloses a swing prism type of endoscope with a direction-of-view variable between 30 and 70 degrees from forward. WIPO publication WO 01/22865 by Ramsbottom (2001) discloses a similar device for varying the direction of view between 0 and 120 degrees. These two examples demonstrate an additional shortcoming of existing swing prism endoscopes: they only view on one side of the shaft axis. Other types of variable direction-of-view endoscopes, such as that disclosed in U.S. Pat. No. 5,762,603 to Thompson, have similar limitations.  
           [0004]    An apparatus intended to solve these problems was disclosed in WIPO publication WO 99/42028 by Hoeg et al. (1999). This endoscope features a retractable rotatable housing that can protrude beyond the outer diameter of the endoscope shaft. The housing has a window that moves with the viewing direction. This design is unnecessarily complex and has potential sealing, electrical, and mechanical problems. Consequently this design has never been implemented, and therefore all the variable direction-of-view endoscopes heretofore known suffer from a number of disadvantages, including:  
           [0005]    a) A generally limited direction-of-view range, which restricts viewing freedom and does not allow the user to look directly backwards, a feature that would be useful in many situations.  
           [0006]    b) A limited view of the region directly in front of the endoscope, making it difficult to investigate the targeted area due to the user being unable view alternate sides of the shaft axis without rotating the endoscope.  
           [0007]    c) Only one unique viewpoint for each particular view due to the fact that there are no redundant viewing configurations, resulting in the user having no alternative to an unfavorable viewpoint.  
           [0008]    d) Difficult interpretation of depth in the view, as existing variable direction-of-view endoscopes do not provide a way to accomplish three-dimensional viewing.  
           [0009]    From the discussion above, it should become apparent that there is a need for a variable direction-of-view endoscope that will provide an increased or unlimited scanning range which gives the user increased viewing freedom and backwards viewing capability; provide a swing-through-center capability by centering the direction of view range on the forward direction; provide redundant viewing capability such that each particular view direction can be obtained from multiple unique viewpoints; and provide the user with three-dimensional imaging to ease the interpretation of depth in the view.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    In accordance with the present invention, a variable direction-of-view endoscope comprises an adjustable imaging system and a symmetric viewing window. The imaging system includes a pivotable optical component. The device features redundant viewing configurations that can be switched between using a simple flipping process. Additional steps to provide the user with three-dimensional viewing are also disclosed. The term “endoscope” as used herein is defined as an endoscope used for medical procedures, a borescope, a fiberscope, etc.  
           [0011]    What is claimed is an apparatus for use as an endoscope, comprising a generally tubular member having a distal end portion, a proximal end portion, and a longitudinal axis; a viewing system, comprising a pivotable view vector originating from said distal end portion, wherein said pivotable view vector has a pivot axis that is not parallel to either said pivotable view vector or said longitudinal axis; a viewing window attached to said distal end portion, wherein said viewing window comprises a transparent viewing area about a symmetry plane, wherein said symmetry plane is generally parallel to both said pivot axis and said longitudinal axis near said distal end portion, and wherein said pivotable view vector passes through said transparent viewing area; a means for controllably rotating said distal end portion about said longitudinal axis; and a means for controllably rotating said pivotable view vector about said pivot axis.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIGS. 1A, 1B, and  1 C show examples of the prior art.  
         [0013]    [0013]FIG. 2A is a perspective view of the distal end of an endoscope according to the preferred embodiment of the invention.  
         [0014]    [0014]FIG. 2B is a side view of the distal end depicted in FIG. 2A according to the preferred embodiment of the invention.  
         [0015]    [0015]FIG. 2C is a top view of the distal end depicted in FIG. 2A according to the preferred embodiment of the invention.  
         [0016]    [0016]FIG. 3 is a flow chart illustrating a redundant configuration flipping process according to the preferred embodiment of the invention.  
         [0017]    [0017]FIGS. 4A and 4B show initial and final configurations of the redundant configuration flipping process illustrated in FIG. 3.  
         [0018]    [0018]FIG. 5 is a flow chart illustrating a stereo imaging process according to the preferred embodiment of the invention.  
         [0019]    [0019]FIG. 6 is a schematic of a complete system according to the preferred embodiment of the invention.  
         [0020]    [0020]FIGS. 7A, 7B, and  7 C are sectional top views of viewing windows according to alternative embodiments of the invention.  
         [0021]    [0021]FIG. 8 is a side view of the distal end of an endoscope according to an alternative embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The following detailed description illustrates the invention by way of example, not by way of limitation of the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what we presently believe is the best mode of carrying out the invention.  
       Prior Art Devices  
       [0023]    Referring now to the drawings, in which like reference numbers represent similar or identical structures throughout, FIGS. 1A and 1B are schematic sectional views of the distal end of traditional variable direction-of-view swing prism endoscopes. A pivotable reflector  10 , usually a prism, reflects light received through a viewing window  12  to a fixed reflector  14 , also a prism, which further reflects the light into an optical train  16  for transmission to the viewer (not shown). These optical elements are mounted in the distal end portion  18  of a tubular member  20 . The view vector  22  is adjusted by rotating the pivotable reflector  10  about the pivot axis  23 . Each of these designs has a limited range  24  over which the view vector  22  can be varied.  
         [0024]    In another example of prior art shown in FIG. 1C, a pivotable reflector  10  is mounted in a rotatable housing  26 . The light enters through a viewing window  12 , is reflected to a fixed reflector  14  and then into an optical train  16 . The housing  26  is pivoted about the pivot axis  23  using a pair of gears  28  and a drive shaft  30 . The interface  32  between the rotatable housing  26  and the distal end portion  18  of the tubular member  20  is difficult to seal and poses significant threats of leakage and contamination.  
       Preferred Embodiment  
       [0025]    A preferred embodiment of the distal end of an endoscope according to the present invention is shown in FIG. 2A. A rigid metal distal end portion  18  is disposed at the distal end of a tubular member  20 . It should be appreciated that the tubular member  20  may be constructed as either rigid or flexible to suit the particular application. A generally spherical viewing window  34  is sealed to the distal end portion  18 . The window  34  comprises a transparent layer of rigid material, such as glass, that seals the endoscope against fluids and other debris. Of course, alternate materials for window  34  that accomplish the same sealing and viewing goals are also possible. The overall size of the distal end portion  18  is reduced near the window  34  to permit rearward viewing. Illumination is delivered through illumination ports  36  on the front and sides of the distal end portion  18  using standard light guides or optical fibers (not shown).  
         [0026]    [0026]FIG. 2B shows a partial section side view of the preferred embodiment of the present invention. A pivotable reflector  10  is positioned inside the spherical viewing window  34  and a fixed reflector  14  is positioned adjacent to the pivotable reflector  10  in the reduced distal end portion  18 . An optical train  16  formed by a series of lenses is disposed inside the tubular member  20  between the fixed reflector  14  and a viewer (not shown), such as a camera. A pair of metal gears  28  is used to control the rotation of the pivotable reflector  10  about the pivot axis  23 . Alternative actuation means such as pull-wires or push-rods may also be acceptable depending on the particular application.  
         [0027]    In the preferred embodiment, the pivotable reflector  10  and fixed reflector  14  are both glass prisms. However, it should be appreciated that the pivotable reflector  10  and fixed reflector could be made of other materials, such as plastic, or may be a mirrored surface based on any rigid material. It should also be appreciated that the reflectors  10 ,  14  do not have to be the same and could be any combination of reflector types, such as the ones mentioned above.  
         [0028]    The pivotable reflector  10  and the fixed reflector  14  are positioned in the distal end portion  18  so as to define an optical path comprising three segments  38 ,  40 ,  42 . This path passes from a viewed scene outside the endoscope (not shown), through the spherical viewing window  34 , to the pivotal reflector  10 , to the fixed reflector  14 , and then along the optical train  16  to the viewer (not shown). The first optical path segment  38  passes from the viewed scene (not shown) through the spherical viewing window  34  to the pivotable reflector  10 . The second optical path segment  40  passes from the pivotable reflector  10  to the fixed reflector  14 , coincident with the pivot axis  23 . The third optical path segment  42  passes from the fixed reflector  14  along the optical train  16  to the viewer (not shown). Additional lenses such as a negative objective  46  are positioned along the optical path to facilitate image transmission and improve optical performance. It should be noted that the first optical path segment  38  is offset from the longitudinal axis  48  of the endoscope. A view vector  22  exists in coincidence with the first optical path segment  38 .  
         [0029]    By rotating the pivotable reflector  10 , the first optical path segment  38  and view vector  22  may be swept through an unlimited range  50 , as shown in FIG. 2C. This unlimited range  50  includes portions on either side of a symmetry plane  52 , which is parallel to the longitudinal axis  48  and the pivot axis  23 . The pair of gears  28  allows this unlimited rotation to be controlled from the proximal end of the endoscope (not shown). The view vector  22  may be swept about the longitudinal axis  48  by pivoting the distal end portion  18  about the longitudinal axis  48  through rotation of the shaft  20 .  
         [0030]    [0030]FIGS. 3, 4A and  4 B illustrate a process of operating the endoscope of the preferred embodiment of the present invention to view in the same direction from two separate view points. This process adjusts the endoscope without causing a net change in the direction of the view vector  22 . At the outset, the endoscope has an initial configuration  54 , having a certain viewing direction  55 . The two reflectors  10 ,  14  and the three optical path segments  38 ,  40 ,  42  shown in FIG. 4A represent this initial endoscope configuration  54 . The initial endoscope configuration  54  can be any arbitrary configuration comprising an initial distal end orientation  56  and an initial pivotable reflector orientation  58 .  
         [0031]    The process of adjusting the endoscope involves primarily two steps. In the first step  59 , the distal end portion is rotated by approximately 180 degrees about the longitudinal axis  48  from the initial distal end orientation  56  to a final distal end orientation  60 . This causes the pivotable reflector  10  and the fixed reflector  14  to be rotated about the longitudinal axis  48  by 180 degrees. In the second step  61  the pivotable reflector  10  is adjusted to a final pivotable reflector orientation  62  that is symmetric across the symmetry plane  52  from the initial pivotable reflector orientation  58 . These two steps can be executed in any order or simultaneously. A final endoscope configuration  64  comprising a final distal end orientation  60  and a final pivotable reflector orientation  62  is thus achieved. The two reflectors  10 ,  14  and the three optical path segments  38 ,  40 ,  42  shown in FIG. 4B represent this final endoscope configuration  64 .  
         [0032]    The final endoscope configuration  64  has the same viewing direction  55  as the initial endoscope configuration  54  but is mirrored, or flipped, across the longitudinal axis  48 . It should be noted that the view vector  22  in the final configuration shown in FIG. 4B is offset from the view vector  22  in the initial configuration shown in FIG. 4A. Consequently, this redundant configuration flipping process can be used to view in the same direction from two different configurations of the endoscope.  
         [0033]    The redundant configuration flipping process is a part of a four-step process used to provide three-dimensional viewing with the endoscope of the preferred embodiment. FIG. 5 illustrates this stereo imaging process. In the first step  66   a,  a first image is captured from an initial endoscope configuration  54 , having a viewing direction  55 . In the second step  68 , the view vector is offset by changing the endoscope configuration to a final endoscope configuration  64  with the same viewing direction  55 . When using the endoscope of the present embodiment, this second step  68  is accomplished by the redundant configuration flipping process described above. Other endoscopes may require a different process to reach the final configuration  64 . In the third step  66   b,  a second image is captured from the final endoscope configuration  64 . The two captured images constitute a stereo pair of images  70 . In the fourth step  72 , the stereo pair  70  is displayed using a stereo image display device. This could be any standard stereo image display device such as a stereo viewing headset or a monitor with alternately displayed frames coupled with synchronized LCD shutter glasses.  
         [0034]    [0034]FIG. 6 illustrates a complete system according to a preferred embodiment of the present invention. An endoscope  74  according to the present invention is positioned with its distal end portion  18  in a cavity  76 . Illumination is delivered to the endoscope  74  from a light source  78 . The operator controls the system through a keypad  80  or other appropriate input device. This input is received by a central control unit  82 , which in turn directs a motor control unit  84 . The motor control unit  84  controls the configuration of the endoscope  74  through actuators in the endoscope  74 . An image processing unit  86  receives image signals from the endoscope  74  and adjusts the signals as needed. The central control unit  84  receives the adjusted signals from the image processing unit  86  and relays the signals to a video display device  88  and a stereo image display device  90 . The central control unit  82 , the motor control unit  84 , and the image processing unit  86  may be implemented as a personal computer running an appropriate control program. They may alternatively be constructed as dedicated hardware devices.  
         [0035]    This complete system is set up to accomplish the stereo imaging process described above. As part of this system the motor control unit  84  and the endoscope  74  are together configured to effect the redundant configuration flipping process described above.  
         [0036]    For various reasons, such as ease of manufacture, it may be desirable to replace the spherical viewing window  34  in the preferred embodiment shown in FIGS. 2A, 2B and  2 C with an alternative viewing window. A key element of the viewing window is that it is symmetric about the symmetry plane  52 . For example, an alternative viewing window that would also afford swing-through-center viewing could be a faceted window comprising one or more flat segments  92  symmetric about the symmetry plane  52 , as shown in the top view FIG. 7A. There could be any number of facets combining to form a complete or partial symmetric enclosure sealed to the distal end portion of the endoscope. Alternatively, the viewing window could be a continuous smooth surface  94 , as shown in the top view FIG. 7B. Yet another possible viewing window is one that is also radially symmetric about the pivot axis  23 , as shown in the top view cross section FIG. 7C. Such a window could be cylindrical, conical, or spherical. It could be continuous or made up of several curved segments  96 . It should be appreciated, however, that although the above viewing windows are potential embodiments of the present invention, the spherical viewing window  34 , as shown and described, appears to exhibit superior optical characteristics.  
         [0037]    [0037]FIG. 8 shows a partial section side view of an alternate embodiment of the present invention. This embodiment is very similar to the preferred embodiment shown in FIGS. 2A, 2B, and  2 C. It features a rigid metal distal end portion  18  disposed at the distal end of a tubular member  20 . A generally spherical viewing window  34  is sealed to the distal end portion  18 . Differently in this embodiment, however, a pivotable camera  98  having a view vector  22  is positioned inside the spherical viewing window  34 . This embodiment may be operated in a substantially equivalent manner to the preferred embodiment described above. The distal end portion  18  is pivoted about the longitudinal axis  48  by rotating the shaft  20 . A pair of metal gears  28  is used to control the rotation of the camera  98  about the pivot axis  23 . Total camera rotation may be limited to 180 degrees from forward to limit twist of the camera cable  99 , but it will be appreciated by one of skill in the art that conventional slip rings may be used to remove this limitation. Other actuation means such as pull-wires or push-rods may also be acceptable depending on the particular application.  
         [0038]    Accordingly, the present invention provides an increased or unlimited scanning range that gives the user increased viewing freedom and backwards viewing capability, a swing-through-center capability by centering the direction of view range on the forward direction, redundant viewing capability such that each particular view can be obtained from two unique viewpoints and three-dimensional viewing. Furthermore, the present invention has secondary advantages, such as redundant viewing window surfaces that give the user an alternative view port should the initial port become blocked by debris. The invention also provides for symmetric left or right-handed use.  
         [0039]    The present invention has been described above in terms of a presently preferred embodiment so that an understanding of the present invention can be conveyed. However, there are many configurations for a variable direction-of-view endoscope and method for viewing not specifically described herein but with which the present invention is applicable. Many structural and material variations are possible, as are variations in application. For example, while the examples were given with respect to an endoscope for use in surgical procedures, the present invention would be equally applicable with respect to a borescope for use within various mechanical structures. The scope of the present invention should therefore not be limited by the embodiments illustrated, but rather it should be understood that the present invention has wide applicability with respect to viewing instruments and procedures generally. All modifications, variations, or equivalent elements and implementations that are within the scope of the appended claims should therefore be considered within the scope of the invention.