Abstract:
The objective of the present invention is to provide a single endoscope that provides a field of view substantially greater than a hemisphere comprising a forward field of view and a panoramic field of view that are integrated on a single image plane. The invention is described with respect to a rigid endoscope, but the technology can be implemented on a flexible endoscope as well. The advantage of such an endoscope is that it would provide substantially more information to the physician than any single existing endoscope, and it can be used in place of multiple endoscopes with varying directions of view that are swapped throughout a procedure to provide different views. The invention can also be used in non-medical applications for inspection in closed or generally inaccessible spaces such as for example the interior of jet engines.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. provisional application No. 60,462,951, filed Apr. 15, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to the field of endoscopic imaging, and particularly to the imaging and illumination design of an endoscope that integrates on a single image plane a forward field of view (FFOV) and a panoramic field of view (PFOV), thereby providing the user a total field of view comprising the FFOV and the PFOV simultaneously.  
         BACKGROUND OF THE INVENTION  
         [0003]    Current art in endoscope design typically provides a 35° total viewing angle that may be rotated elevationally by angles up to 70° using prisms and mirrors. Further the view may be rotated axially by means of sheaths containing additional prisms/mirrors. Wide-angle views up to 120° are known but such designs suffer from high distortion and difficult component fabrication due to the need for aspherical or highly curved elements. For many medical procedures, such as nasal sinoscopy, the restricted viewing provided by current art endoscopes require that several endoscopes or different viewing angles be used at different points in the procedure. The act of withdrawing and inserting the endoscope, especially since the process may be somewhat blind, can be the cause of additional trauma to the patient. Panoramic imaging systems are known in the art but either do not have forward viewing or accomplish forward viewing in a different way than the current invention. U.S. Pat. No. 6,028,719 assigned to InterScience, Inc. discloses a general technique of integrating a forward view and a panoramic view utilizing a single reflector for the panoramic field of view.  
           [0004]    There are many existing patents for optical systems that provide omnidirectional imaging. We believe we have some unique characteristics that are not covered in any existing patent and that provide a unique new capability to imaging systems and omnidirectional optical components in general. Jeffrey Charles has several U.S. patents on the subject including U.S. Pat. No. 6,333,826 and U.S. Pat. No. 6,449,103, BeHere Corporation has several US patents including U.S. Pat. No. 6,392,687, U.S. Pat. No. 6,424,377 and U.S. Pat. No. 6,480,229, and Remote Reality has U.S. Pat. No. 6,611,282.  
           [0005]    The patents by Jeffrey Charles focus solely on the panoramic field of view, and efforts to maximize that field of view for near field applications. The Charles&#39; patents include a frontal exclusion zone of about 60 degrees that can be tapered approaching the far field by the use of a torroidal-shaped reflector. Although this exclusion zone eventually disappears as a point where the boundaries of the panoramic field meet, there is no account in the patent for the overlapping area past the point of convergence in the processing or interpretation of the image. The minor disclosure of including forward optics to image the frontal exclusion zone makes no mention of details of how to match the magnification or the relative F/# of the integrated images as well as a means of interpreting or processing the overlapping images. The mere inclusion of forward viewing lenses does not automatically lend itself to an easily interpretable image. The focus of the optical system is near field prior to the overlap. Although there is provision to include the forward viewing optics to image the frontal exclusion zone, there will only be one point (or one radial distance) in which the frontal zone and the panoramic zone exist with either no gap or no overlap.  
           [0006]    The BeHere technology also concentrates on the panoramic field of view and only makes provisions to extend the panoramic view as far forward as possible by changing the shape of the reflector. By placing a dimple in the apex of the parabolic reflector, imaging beyond the secondary reflector is achieved in the far field. These inventions provide no means for forward imaging in the near field.  
           [0007]    The Remote Reality invention is a super wide-angle panoramic imaging apparatus that claims up to a 260° vertical field of view using a two reflector configuration. The invention includes an undefined blind spot along the optical axis. The invention claims a single view point while also having a substantially flat and stigmatic image plane.  
           [0008]    None of these omnidirectional viewing systems provide a means of incorporating the optical system in an endoscope or borescope.  
         OBJECTS OF THE INVENTION  
         [0009]    It is an object of the present invention to provide a means of integrating panoramic imaging capabilities with a forward viewing endoscope design.  
           [0010]    It is an object of the present invention to provide a means of integrating panoramic imaging capabilities with a forward viewing endoscope design utilizing a two reflector panoramic imaging component.  
           [0011]    It is an object of the present invention to provide an endoscope design capable of presenting a forward field of view and a panoramic field of view integrally on a single image plane.  
           [0012]    It is an object of the present invention to provide a total field of view that is upright and unreversed without need for extensive computer processing to accomplish said upright and unreversed field of view.  
           [0013]    It is an object of the present invention to provide an endoscope design in which the boundaries of the forward field of view and panoramic field of view can be customized to fit to specific application needs.  
           [0014]    It is an object of the present invention to provide illumination means for a forward field of view and a panoramic field of view of an endoscope.  
           [0015]    It is an object of the present invention to provide an endoscope capable of an integrated panoramic and forward view that can approach or exceed a solid angle of 2π steradians.  
           [0016]    It is an object of the present invention to provide the total field of view with low distortion, chromatic aberration, and viewpoint error. Such qualities are necessary to support diagnostic assessments during intended medical procedures.  
         SUMMARY OF THE INVENTION  
         [0017]    The objective of the present invention is to provide a single endoscope that provides a total field of view substantially greater than a hemisphere comprising a forward field of view and a panoramic field of view that are integrated on a single image plane. The invention is described with respect to a rigid endoscope, but the technology can be implemented on a flexible endoscope as well. The advantage of such an endoscope is that it would provide substantially more information to the physician than any single existing endoscope, and it can be used in place of multiple endoscopes with varying directions of view that are swapped throughout a procedure to provide different views. The invention can also be used in non-medical applications for inspection in closed or generally inaccessible spaces, such as the interior of jet engines.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    The present invention, and the objects and advantages thereof, may best be understood by reference to the following detailed description and accompanying drawings in which:  
         [0019]    [0019]FIG. 1 is an overall view of the entire panoramic/forward view endoscope.  
         [0020]    [0020]FIG. 2 is a longitudinal cross-section of the panoramic/forward view element and the endoscope objective.  
         [0021]    [0021]FIG. 3 is an axial cross section of the distal tip of the panoramic/forward view endoscope.  
         [0022]    [0022]FIG. 4 is an axial cross section of the relay and objective area of the panoramic/forward view endoscope.  
         [0023]    [0023]FIG. 5 is a first embodiment of the illumination distribution.  
         [0024]    [0024]FIG. 6 is a second embodiment of the illumination distribution.  
         [0025]    [0025]FIG. 7 is a third embodiment of the illumination distribution.  
         [0026]    [0026]FIG. 8 is a fourth embodiment of the illumination distribution.  
         [0027]    [0027]FIG. 9 is a fifth embodiment of the illumination distribution.  
         [0028]    [0028]FIG. 10 is a sixth embodiment of the illumination distribution.  
         [0029]    [0029]FIG. 11 is a seventh embodiment of the illumination distribution. 
     
    
     DETAILED DESCRIPTION  
       [0030]    The present invention provides an endoscope design that provides a total field of view substantially greater than a hemisphere comprising a forward field of view and a panoramic field of view that are continuous and integrated on a single image plane. The integrated fields of view are matched in magnification and brightness and there is a relatively seamless boundary between them with no blindspots or overlapping of the fields. The invention comprises panoramic and forward view imaging technology as well as panoramic and forward illumination technology. The invention is demonstrated on a rigid endoscope but the technology can be implemented on a flexible endoscope as well.  
         [0031]    The present invention is initially described with respect to FIG. 1. FIG. 1 shows the panoramic/forward view endoscope  100 ; which comprises a rigid endoscope eyepiece  110 , housing of a rigid endoscope relay system  112 , an illumination light guide port  114 , housing of a endoscope objective  116 , and housing of an integrated panoramic/forward viewing optical element  118 .  
         [0032]    The present invention utilizes a endoscope eyepiece  110 , an endoscope relay system  112 , and an illumination light guide port  114  as known in the art. The improvements of the present invention to existing endoscope design are substantially provided in the endoscope objective  116  and the panoramic/forward viewing optical element  118 . It is these elements that contribute to the unique 2π+ steradian (solid angle) viewing capabilities of the present invention. The layout of the modified endoscope objective  116  and the panoramic/forward viewing optical element  118  is shown in detail in FIG. 2.  
         [0033]    As shown in FIG. 2, the endoscope objective  116  is adjacent to the endoscope relay system  112 . The endoscope objective  116  essentially comprises at least one focusing element. The figure depicts an embodiment comprising a first focusing element  120  and a second focusing element  122 . The endoscope objective  116  serves to transform the converging ray bundles collected by the panoramic/forward view element  118  into telecentric input for the endoscope relay system  112 .  
         [0034]    As shown in FIG. 2, the endoscope objective  116  is adjacent to and receives optical input from the panoramic/forward viewing optical element  118 . The panoramic/forward viewing optical element  118  essentially comprises a Panoramic Field of View (PFOV) optical element group  127 , a Forward Field of View (FFOV) optical element group  136 , and a focusing optical element group  139 . The PFOV optical element group  127  essentially comprises two reflectors each having one mirror surface and each having a central aperture. A first reflector  124  is essentially a solid convex surface with the mirrored surface facing the distal end of the endoscope  100  and a central aperture. The first reflector  124  is symmetric about its central axis and central aperture and is aligned along the optical axis  111 . A cross-section of the first reflector  124 , as depicted in FIG. 2, would show the reflective surface to be a portion of a mathematical conic section, such as but not limited to a sphere or a parabola. A second reflector  126  with mirror surface facing the first reflector  124  can be planar, concave or convex. The surface geometry of both the first reflector  124  and the second reflector  126  can be optimized to obtain the desired PFOV  128  for a specific application.  
         [0035]    The Forward Field of View (FFOV) optical element group  136  is comprised of a first lens group  132 , a second lens group  134 , and a third lens group  135  that images portions of the object substantially distal to the endoscope, i.e. the FFOV  130 . The first lens group  132  gathers rays from a wide angle centered on the optical axis  111 . The second and third lens groups  134 ,  135  focus and reduce the size of the gathered ray bundle so that it may pass through the apertures of the first and second reflectors  124  and  126 .  
         [0036]    The focusing optical element group  139  is centered along the optical axis  111  and is placed in line in the optical path between the PFOV optical element group  127  and the endoscope objective  116 . It comprises at least two focusing optical elements, a first focusing optical element  137  and a second focusing optical element  138 . The focusing optical element group  139  collects the panoramic field of view  128  from the secondary reflector  126  and the forward field of view  130  from the FFOV optical element group  136 . It is the function of the focusing optical element group  139  to focus the two independent optical paths from the panoramic field of view  128  and the forward field of view  130  as a coplanar image and to control the image aberrations on this coplanar image.  
         [0037]    As shown in FIG. 2, image information from the PFOV is collected by the first reflector  124  and is then reflected onto the second reflector  126 . The second reflector  126  then reflects the image information through the central aperture of the first reflector  124  to the focusing optical element group  139  and the endoscope objective  116 . The forward field of view optical element group  136  passes the image information of the forward field of view  130  through the central aperture of the second reflector  126  and the first reflector  124  to the focusing optical element group  139  and the endoscope objective  116 . The geometries of the first and second reflectors  124  and  126  are designed to accept rays from the PFOV  128  and converge them with the FFOV  130  for coplanar focusing by the focusing optical element group  139  and the endoscope objective  116 . The image information from the FFOV  130  and the PFOV  128  provide an overall field of view of approximately 240 degrees. The image information from the FFOV  130  and the PFOV  128  are matched substantially seamlessly on the image plane with virtually no overlap and no gap between them. The magnification and relative F# (or brightness) of the FFOV  130  and the PFOV  128  are matched as well.  
         [0038]    As shown in FIGS. 2 and 3, disposed circumferentially about a substantial portion of the panoramic/forward viewing optical element  118  is a transparent cylindrical tube  141  that provides structural support and sealing for the system as well as a means for rays from the PFOV  128  to enter the system. It is known in the art that panoramic imaging systems comprised of spherical reflectors suffer from so-called non-single viewpoint. Images from such non-single viewpoint systems cannot be processed to produce geometrically correct perspective views. For spherical reflector systems, each object point is viewed from a different viewpoint. Such variability of the viewpoint causes uncorrectable parallax in perspective views generated from such imagery. A further advantage of the transparent cylindrical tube  141  is to significantly reduce the size of the so-called viewpoint caustic and therefore parallax errors in the acquired perspective views. The viewpoint error can be brought to a minimum through the specification of the refractive index and thickness of the cylindrical tube  141 .  
         [0039]    Shown in FIGS. 2 and 4, as the panoramic/forward viewing element  118  is encircled by the transparent cylindrical tube  147 , the endoscope relay  112  and modified endoscope objective  116  are circumferentially encased by endoscope lumenal housing  140 . The circumference of the endoscope lumenal housing  140  is lined by endoscope illumination means  142 . This illumination is distributed to the PFOV  128  and the FFOV  130 . FIGS. 5, 6,  7 ,  8 ,  9 ,  10 , and  11  show several options for distributing the illumination to the PFOV  128  and the FFOV  130 .  
         [0040]    Shown in FIG. 5 is a first embodiment of the illumination distribution in the panoramic/forward view endoscope  100 . In this embodiment the transparent cylindrical tube  141  comprises at least two sections, a distal section  150  and a proximal section  152  joined by an angled seam  154 . In this embodiment a semi-transparent/semi-reflective coating could be introduced on the seam  154  so as to promote the proper distribution of the illumination between the periphery of the endoscope  100  and the distal end of the endoscope  100 . An adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive. This embodiment could benefit from the optional addition of a rigid and opaque internal support  156  for added structural support and as a means of preventing internal light leakage.  
         [0041]    Shown in FIG. 6 is a second embodiment of the illumination distribution in the panoramic/forward view endoscope  100 . In this embodiment, a diffuse ring  158  of width R is on the outer circumference of the solid transparent cylindrical tube  141 . The diffuse ring  158  is located distal to the PFOV  128  so as not to interfere with the imaging in the PFOV  128 . In this embodiment an adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive. This embodiment could benefit from the optional addition of a rigid and opaque internal support  156  for added structural support and as a means of preventing internal light leakage.  
         [0042]    Shown in FIG. 7 is a third embodiment of the illumination means. In this embodiment, a diffuse ring  158  of width R is on the inner circumference of the solid transparent cylindrical tube  141 . The diffuse ring  158  is located distal to the PFOV  128  so as not to interfere with the imaging in the PFOV  128 . The diffuse ring  158  would radially scatter some of the light to illuminate the PFOV  128  that is propagating through the tube  141  to illuminate the FFOV  130 . As in the first embodiment an adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive. This embodiment could benefit from the optional addition of a rigid and opaque internal support  156  for added structural support and as a means of preventing internal light leakage.  
         [0043]    Shown in FIG. 8 is a fourth embodiment of the illumination distribution in the panoramic/forward view endoscope  100 . In this embodiment, a curved notch  160  is on the outer circumference of the solid transparent cylindrical tube  141 . The curved notch  160  is located distal to the PFOV  128  so as not to interfere with the imaging in the PFOV  128 . The notch  160  is included to interrupt and divert the transmission of a portion of the illumination along the transparent cylindrical tube  141  and therefore allowing illumination to be distributed to the PFOV  128 . As in the first embodiment an adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive. This embodiment could benefit from the optional addition of a rigid and opaque internal support  156  for added structural support and as a means of preventing internal light leakage. Alternatively the notch may be an angled notch  162  as shown in the fifth embodiment in FIG. 9.  
         [0044]    [0044]FIG. 10 shows a sixth alternative embodiment of the illumination means. In this embodiment a portion of the illumination fibers continue along the inner circumference of the transparent tube to illuminate the forward field of view. The remainder of the illumination fibers end at the proximal end of the transparent tube to distribute light to the panoramic field of view. The transparent cylindrical tube  141  comprises at least two sections, a distal section  150  and a proximal section  152  joined by an angled seam  154 . In this embodiment a reflective coating is introduced on the seam  154  so as to promote the proper distribution of the illumination to the periphery of the endoscope  100 . An adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive.  
         [0045]    [0045]FIG. 11 shows a seventh alternative embodiment of the illumination means. In this embodiment a portion of the illumination fibers continue along the inner circumference of the transparent tube to illuminate the forward field of view. The remainder of the illumination fibers end at the proximal end of the transparent tube to distribute light to the panoramic field of view. The transparent cylindrical tube  141  comprises at least two sections, a distal section  150  and a proximal section  152  joined by a seam  154 . In this embodiment a reflective coating is introduced on the seam  154  and the proximal section  152  is made entirely of diffuse glass with a light blocking barrier  156  on its inner diameter so as to promote the proper distribution of the illumination to the periphery of the endoscope  100 . An adequate interface is established between the endoscope illumination means  142  and the transparent cylindrical tube  141 , such as but not limited to optically transparent adhesive.  
         [0046]    While only certain preferred features of the invention have been illustrated and described, many modifications, changes and substitutions will occur to those skilled in the art. It is, therefore, to be understood that this disclosure and its associated claims are intended to cover all such modifications and changes as fall within the true spirit of the invention