Abstract:
An endoscope having a viewing direction aligned obliquely with respect to a longitudinal axis, the endoscope including: a shaft with a cladding tube and a fiber tube arranged therein; an object lens arranged in the shaft; and a prism module arranged in the shaft for deflecting the beam path, wherein the prism module is arranged eccentrically with respect to the object lens.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based upon and claims the benefit of priority from PCT/EP2016/000142 filed on Jan. 28, 2016, which claims benefit to DE 10 2015 101 624.9 filed on Feb. 4, 2015, the entire contents of each of which are incorporated herein by reference. 
     
    
     BACKGROUND 
     Field 
       [0002]    The present disclosure generally relates to endoscopes, and more particularly to an endoscope having an oblique viewing direction with a prism module arranged concentrically with respect to an object lens. 
       Prior Art 
       [0003]    Endoscopes facilitate observation of the inside of bodily cavities, which are usually only accessible through small access openings. This involves insertion of a shaft of the endoscope into the hollow space through the opening. 
         [0004]    The optical components are typically located at the distal, inserted end of the shaft. They are usually arranged inside a fiber tube, which is surrounded by a casing tube or outer tube. A transport lens system brings the image function to the eyepiece. The image data of a video endoscope can then be transported to an external display device and displayed accordingly. 
         [0005]    In endoscopes in which the viewing direction is not parallel but oblique to the longitudinal axis of the shaft, a prism module is provided for deflecting the beam path. 
         [0006]    A disadvantage of the known endoscopes is that the size and space requirement of the prism module in the transverse direction relative to the shaft is relatively large. This results from the prism module in the prior art exhibiting a large cross-section in order to enable an adequate image quality. 
         [0007]    The illustration of  FIG. 1  shows a longitudinal sectional view of a video endoscope  10  known from the prior art. 
         [0008]    In this case, however, only one fiber tube  11 , which contains the essential optical components, is illustrated. This fiber tube  11  is provided for insertion into an outer tube or cladding tube  12 , which is shown here only in phantom. The region between the cladding tube  12  and the fiber tube  11  serves, for example, for receiving optical fibers (not shown here) for illuminating the observation region or field of view. 
         [0009]    Cladding tube  12  and fiber tube  11  with the optical components arranged in the interior of the fiber tube  11  form the shaft  13 . This is used for insertion into an opening to a bodily cavity that is to be observed, such as, for the area of endoscopic surgery. 
         [0010]    Inside the fiber tube  11  of the video endoscope  10 , a prism module  14 , a lens  15  and an image acquisition unit  16  are arranged as optical components. The object lens  15  is used here to image the area or field of view to be observed on the image acquisition unit  16 . An image sensor or video sensor, for example a CCD sensor or a CMOS sensor, can be used as the image acquisition unit  16 . The object lens  15  provides a corresponding optical image on a light-sensitive region of the image acquisition unit  16 . Evaluation electronics (not shown here) are generally arranged outside the endoscope  10  and connected to the video endoscope  10  by means of a cable connection (likewise not shown). 
         [0011]    The video endoscope  10  illustrated in  FIG. 1  is a so-called “oblique-looking video endoscope.” This means that the observation direction is not aligned in the direction of the longitudinal axis of the video endoscope  10 , but rather obliquely to the longitudinal extent of the video endoscope  10  or its shaft  13 . The object lens  15  and the image acquisition unit  16  are already parallel to the longitudinal axis of the video endoscope  10  or of the shaft  13  with the fiber tube  11  or the cladding tube  12  for reasons of space. This in principle ensures a compact, linear structure so as to simultaneously minimize the cross-sectional dimensions of the video endoscope  10 . 
         [0012]    However, the region to be observed does not lie in the direction of the longitudinal axis, but obliquely thereto and away from the axis. Accordingly, in order to allow for a deflection of the beam path from the region to be monitored onto the object lens  15  or the image acquisition unit  16 , the prism module  14  is required. 
         [0013]    The prism module  14  typically comprises two interconnected individual prisms  17  and  18 . The two prisms  17  and  18  are connected to one another at a connection point  19 , generally by means of adhesion. The adhesive site is realized by means of an optical adhesive for adjustment of the refractive indices at the connection point  19 . Thus, sufficient reflection at the connecting point of the prisms  17  and  18  is made possible. This leads to a sketched beam path  20  with a reflection on the upper side edge of the prism  18  and on the connecting plane  19 . 
         [0014]    The video endoscope  10  of  FIG. 1  shows that the lower region of the prism module  14  makes a virtually insignificant contribution to the optical image on the image acquisition unit  16 . That&#39;s because the beam path  20  essentially runs in the upper region of the prism module  14  in the illustration. Thus, the lower region of the prism module  14  is in practice not decisive for the optical quality of the image. 
         [0015]    In  FIG. 4 , a known video endoscope  10  is shown, in which the prism module  14  is aligned centrally with the fiber tube  11 . Here, the prism module  14  extends over the entire inner cross-section  24  of the fiber tube  11 . The optical path  20  consequently runs primarily centrally with the fiber tube  11 . This allows for a corresponding image to be produced by the object lens  15  on the image acquisition unit  16 , which essentially corresponds to the cross-section of the prism module  14 . 
       SUMMARY 
       [0016]    The endoscopes described herein can either be of the type of lens endoscopes or video endoscopes. Lens endoscopes contain an eyepiece in the lens system for transport and display on an eyepiece. In the case of a video endoscope, an image sensor of the shaft provides an image taken behind an object lens to produce video camera pictures. 
         [0017]    It is an object to provide an endoscope, which allows for smaller later dimensions or cross-sections of the prism module. 
         [0018]    Such object can be achieved by an endoscope in which the prism module is arranged eccentrically with respect to the object lens, thus, not central or centered. In conventional endoscopes, however, the prism module is aligned centrally with the object lens. However, due to the radiation course, this is not necessary. Instead, a structural shape of the prism module with a comparably reduced cross-section is used. This therefore has smaller cross-sectional dimensions. By means of an eccentric arrangement with respect to the object lens, the overall cross-section of the prism module can be reduced. 
         [0019]    The prism module can be arranged eccentrically with respect to the cross-section of the shaft or the fiber tube. At the same time, the cross-section of the prism module can be reduced in comparison with the prior art. The cross-section of the fiber tube can be simultaneously maintained or also reduced. In this way, free space is created in the region between the prism module and the shaft or fiber tube, or the cross-sectional dimensions of the fiber tube are also reduced. 
         [0020]    The object lens and/or possibly the image acquisition unit can be arranged eccentrically with respect to the cross-section of the shaft or of the fiber tube. Accordingly, free space may result between the lens or the image acquisition unit and the fiber tube or the shaft. The distance between fiber tube and prism module can be only present on one side or can be larger on one side than on the opposite side. This creates space in the area between the prism module and the fiber tube or shaft in the respective interior space. 
         [0021]    The outer cross-section of the prism module can be smaller than the inner cross-section of the shaft or of the fiber tube. Due to the fact that the prism module does not occupy the complete cross-section of the shaft or fiber tube, free space is created in the intermediate region. An eccentric arrangement of the optical components, such as the prism module of the image acquisition unit or the lens, is thereby made possible. The cross-section of the prism module, perpendicular to the longitudinal direction of the endoscope, can be smaller than the internal cross-section of the fiber tube or the shaft. In this way, the reduction takes place in the part of the prism module that is practically irrelevant for the image transmission. A hollow space can be provided in the shaft, such as, in the region between the prism module and the inner wall of the fiber tube. This can be a crescent-shaped hollow space. As a result, an at least substantially arcuate or round external shape of the prism module does not fill the entire internal cross-section of the fiber tube or of the shaft. Depending on the outer shape of the prism module and the inner cross-section of the fiber tube or the shaft, however, other forms of the resulting free space or hollow space can also result. 
         [0022]    At least one component can be arranged between the prism module and the inner wall of the shaft or of the fiber tube, in particular in the hollow space. Such component can be an electrical and/or electronic component. At this point, various elements can be provided, for example active and/or passive components. Such components can be measuring devices, measuring sensors or the like. Such components can also be mechanical components. 
         [0023]    At least one heating element can be arranged between the prism module and the inner wall of the shaft or of the fiber tube, such as in the hollow space. Alternatively, a cooling element can be similarly arranged. A heating foil and/or at least one heating wire can be used as the heating element. If desired, a Peltier element or the like can also be provided. Heating elements can serve to prevent fogging of the optical components by condensing water. A suitable temperature control, such as by means of heating, can be required for this purpose. 
         [0024]    At least one temperature sensor can be arranged between the prism module and the inner wall of the shaft or of the fiber tube, such as in the hollow space. The temperature sensor can be a thermistor. This allows for temperature measurement in the region of the prism module. A temperature sensor can be used to determine the current temperature. The temperature sensor can serve to carry out temperature measurements and/or temperature control and/or prevent overheating, for example in the case of heating, by means of a heating element. 
         [0025]    The prism module can comprise a plurality of prisms, such as at least two prisms assembled to make up the prism module. Such a configuration facilitates a deflection of the beam path. The prism module can be configured for rotating and/or tilting or for generally deflecting the beam path. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Exemplary embodiments are described in more detail below with reference to the drawings, which: 
           [0027]      FIG. 1  illustrates a longitudinal section of a shaft of a video endoscope according to the prior art, 
           [0028]      FIG. 2  illustrates a longitudinal section of a shaft of a video endoscope in accordance with a first exemplary embodiment, 
           [0029]      FIG. 3  illustrates a longitudinal section of a shaft of a video endoscope in accordance with a second exemplary embodiment, 
           [0030]      FIG. 4  illustrates a schematic representation of the beam path in a video endoscope according to the prior art of  FIG. 1 , 
           [0031]      FIG. 5  illustrates a schematic representation of a beam path of a video endoscope in accordance with the exemplary embodiment of  FIG. 2 , and 
           [0032]      FIG. 6  illustrates a schematic representation of a beam path of a video endoscope in accordance with the exemplary embodiment of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    The video endoscope  10  of  FIG. 2 , unlike the known video endoscope  10  of  FIG. 1 , includes a prism module  14  which is reduced in diameter or cross-section and is configured to be axially offset (note that the outer tube or cladding tube  12  is not shown in  FIG. 2 ). The lower wall of the fiber tube  11  is correspondingly spaced from the lower edge of the prism assembly  14 . For this purpose, the transverse dimensioning of the prism module  14  in the vertical direction of the drawing plane was compared with the diameter D 0  of the fiber tube  11 . 
         [0034]    Thus, a hollow space  22  is formed in the region between the lower edge  21  of the prism module  14  and the wall of the fiber tube  11 . This hollow space  22  can remain free, or different components can be arranged therein. For example, a heating element (not shown here) or another component or part can be provided. For example, a measuring device such as a thermistor or the like can be used. 
         [0035]    The prism module  14  is consequently oriented eccentrically to the fiber tube  11  in this case. Since the beam path continues to pass centrically to the fiber tube  11 , the object lens  15  with the image acquisition unit  16  and the surrounding object lens tube is aligned centrally with the fiber tube  11  as in the prior art. 
         [0036]    Accordingly, the beam path  20  essentially extends centrally to the fiber tube  11 . Only the prism module  14  is thus arranged eccentrically or decentrically, i.e. with the optical axis corresponding to the beam path, but with its cross-section decentered thereto. 
         [0037]    In the second exemplary embodiment of the invention according to  FIG. 3 , a prism module  14  reduced in diameter or cross-section can be used. 
         [0038]    However, in this case, the cross-section of the fiber tube  11  has also been reduced. Thus, the outer diameter D 1  of the fiber tube  11  has been reduced in comparison to the known solution of  FIG. 1 . In this case, an additional hollow space  22  is not produced at all or only to a small extent. 
         [0039]    In the exemplary embodiment of  FIG. 3 , the prism module  14  is aligned centrally with respect to the fiber tube  11 . The object lens  15  with the image acquisition unit  16  is aligned with the surrounding system tube  23  decentrally to the fiber tube  11 . This ensures that the beam path can enter the object lens  15  and the image acquisition unit  16  centrally. As a result, however, the prism module  14  and the object lens  15  are aligned eccentrically with respect to one another. 
         [0040]    In  FIGS. 5 and 6 , corresponding beam paths  20  with sketched cross-sections  24  of the respective prism module  14  are shown in a front view according to  FIGS. 2 and 3 . 
         [0041]    In  FIG. 5 , which corresponds with the exemplary embodiment of  FIG. 2 , a prism module  14 , which is reduced in cross-section  24 , is provided. The prism module  14  has a cross-section that is smaller than the cross-section of the fiber tube  24  represented here by dashed lines. In this case, the prism module  14  is arranged in the upper region of the fiber tube  11 . Consequently, a hollow space  22  for installing additional structural elements  22   a  is formed in the lower region. Such structural elements can include electrical and/or electronic components, measuring devices, measuring sensors, and heating or cooling elements. 
         [0042]    The illustration of  FIG. 6  corresponds to the second exemplary embodiment of  FIG. 3 . Due to the reduction, also of the cross section  24  of the fiber tube  11 , the prism module  14  on the other hand occupies the entire cross-section of the fiber tube  11 . The corresponding gain in space is achieved by a reduction of the outer cross-section of the fiber tube  11  and possibly also of the entire shaft  13  with the envelope tube  12 . 
         [0043]    While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
         
           
               10  Video endoscope 
               11  Fiber tube 
               12  Cladding tube 
               13  Shaft 
               14  Prism module 
               15  Object lens 
               16  Image acquisition unit 
               17  Prism 
               18  Prism 
               18  Connection level 
               20  Beam path 
               21  Lower edge 
               22  Hollow space 
               22   a  Structural elements 
               23  Lens tube/system pipe 
               24  Cross-section