Abstract:
The invention pertains to an objective with two viewing directions for an endoscope, with a first distal objective part aligned with its axis in the first viewing direction, a second objective part aligned with its axis in the second viewing direction, and with a proximal objective part directed with its axis on an image sensor or an image guide, as well as a switching device having a prism for switchably deflecting the light path from the first or second distal objective part into the proximal objective part, wherein the switching device includes a ray switching device that can be brought mechanically into the light path.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based upon and claims the benefit of priority from PCT/EP2010/002717 filed on May 4, 2010, which claims benefit to DE 10 2009 020 262.5 filed on May 7, 2009 and DE 10 2009 059 004.8 filed on Dec. 17, 2009, the entire contents of each of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention generally relates to an objective with two viewing directions for an endoscope, and particularly to an objective of the type described in claim  1 . 
         [0004]    2. Prior Art 
         [0005]    An objective of the same class in accordance with the invention is known from EP 0 363 118 B1. This shows an endoscope objective with two distal objective parts for two different viewing directions and with a common proximal objective part. Electrically controllable polarization filters are provided as switching devices. The brightness of this design is inadequate. 
         [0006]    EP 0 347 140 B1 shows an objective with two viewing directions, wherein it is possible to switch between these mechanically by turning the image guide relative to the objective. As is apparent, the manufacturing cost of this design is enormous. 
         [0007]    The goal of the present invention consists of, in an objective of the class indicated, to make it possible to switch the viewing direction in a simple manner and with good image brightness. 
       SUMMARY 
       [0008]    According to the invention, a ray switching device can be mechanically introduced into the light path for switching. In this way the drawbacks of the two designs mentioned initially can be avoided. It is only necessary to move one optical component, and the optical drawbacks of polarization filters are avoided. 
         [0009]    Preferably according to claim  2  the optical path length through the objective is the same in both directions. As a result, the optical conditions are simplified. 
         [0010]    In objectives of the type in question here, a strongly negatively refracting lens is located at the distal end of each of the two distal objective parts; this creates large imaging errors. These are corrected in the proximal part of the objective, which must therefore be adapted to the distal objective part for correction. The features of claim  3  are advantageously provided for this. In the case of light paths in the two distal objective parts that are identical except for possible reflections, it is guaranteed that both of the distal objective parts are correctly compensated in terms of imaging errors by the corrective measures in the proximal objective part. 
         [0011]    Advantageously, according to claim  4 , the boundary surface of a prism is switched to be alternately reflecting or transparent. For this purpose a mirror arranged in parallel to the boundary surface is used, which can be moved into or out of the light path and thus either accomplishes the desired reflection or, in its absence, allows the light path to pass through the boundary surface. This results in a very simply designed solution with good image brightness. 
         [0012]    The features of claim  5  are advantageously provided. These make it possible to ensure that only the switchable mirror determines whether or not reflection takes place at the boundary surface. 
         [0013]    The surfaces of the first gap are generally oblique to the objective axis. As a result, a slight parallel shift of the light path takes place, leading to a slight change in the viewing direction. 
         [0014]    Therefore the features of claim  6  are advantageously provided. A second gap with the opposite direction of inclination compensates for the parallel shift of the first gap, so that the resulting viewing direction of the objective, as desired, is straight ahead. 
         [0015]    The features of claim  7  are advantageously provided. This results in a design of the prism in which the exit surface toward the proximal objective part is transparent in the area in which the light path is to emerge toward the proximal objective part, but beside that area is made to be internally reflective so that the deflection of the light path for a second viewing direction can take place there. 
         [0016]    The reflective design according to claim  7  can be achieved, for example, by a reflective coating of the exit surface in this area or advantageously, according to claim  8 , in that the reflecting area is designed to be totally reflective. For this purpose the refractive index of the prism and the reflection angle must be selected correspondingly. 
         [0017]    The mirror should be as close to the boundary surface as possible so that nothing that would cause problems can get between them. Then, however, there is a risk of interferences. The gap between the mirror and the boundary surface therefore must not be too narrow. Advantageously according to claim  9  it should amount to more than 1 μm and especially advantageously according to claim  10 , greater than 5 μm. 
         [0018]    The mirror used for switching between the viewing directions according to claim  1  is advantageously designed in a structural unit with a nearby diaphragm, so that when the mirror is moved out of the light path, the diaphragm is brought into the light path. Then with this diaphragm the light path travelling in the first, straight-ahead viewing direction is limited, which leads to a distinct simplification of the design. 
         [0019]    The ray deflection device can also be made in a completely different way, e.g., as a mirror or as an additional prism, and is advantageously designed according to claim  12 . In this case the prism has two areas that can be alternately brought into the light path and give different deflections, adapted to the two distal objective parts. For switching it is only necessary to move the prism to the extent that it enters the light path with its first or second area. In a preferred exemplified embodiment the prism can be designed as a flat plate in one area and allows the light path to pass straight through, while it is designed as an actual prism in the other area. 
         [0020]    Claim  13  shows an advantageous design for an objective in which the first objective part is designed for viewing straight ahead in the direction of the axis of the proximal objective part. Here the first area of the prism is designed with parallel face surfaces as a flat plate which allows the light path of the first distal objective part to pass through without affecting it. 
         [0021]    The mechanical movement of the prism can take place in various ways, for example by rotation of the light, but is advantageously designed according to claim  14 , and specifically as a shift transverse to the axis of the proximal objective part. 
         [0022]    According to claim  15  one or both of the distal objective parts can be connected to the prism to be moved jointly. In this way for example the design can be improved in terms of optical adjustment, and different design possibilities arise, also regarding the space requirement in the constricted interior space of the endoscope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The invention is illustrated by way of an example and represented schematically in the drawings, in which: 
           [0024]      FIG. 1  illustrates a side view of an objective according to the invention in a first design in the switching position of the oblique viewing direction, 
           [0025]      FIG. 2  illustrates a front view according to  FIG. 1  in the switching position of the straight-ahead viewing direction. 
           [0026]      FIG. 3  illustrates a top view of the mirror visible in  FIGS. 1 and 2  in a variant embodiment with adjacent diaphragm, 
           [0027]      FIG. 4  illustrates a highly schematic representation of an objective according to the invention in a second embodiment in a first switching position, and 
           [0028]      FIG. 5  illustrates the objective of  FIG. 4  in its second switching position. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  shows an objective  1  according to the invention in a first embodiment that consists of three objective parts. 
         [0030]    A proximal objective part  2  is arranged with its axis  3  in the axis of the shaft (not shown) of an endoscope, in the distal end area of which the objective  1  is disposed. The proximal objective part  2  consists of several lenses and, together with one of two distal objective parts, generates an image through a glass plate  5  in an image plane  4 , which for example may have an electronic image sensor. The image plane  4  may also be an intermediate image plane, from which a customary image guide, for example an image guide with a relay lens arrangement, transfers the image to an eyepiece positioned proximally on the endoscope. 
         [0031]    In the distal area of the objective  1 , a first distal objective part  6  is disposed, which looks straight ahead through a window  7  of the endoscope, otherwise not shown, with its axis  8  parallel to the axis  3  of the proximal objective part, thus in the direction of the axis of the endoscope. Furthermore, a second distal objective part  9  is provided, which looks with its axis  10  in a second, oblique viewing direction through a window  11 . 
         [0032]    The second distal objective part  9  on its distal end has a negative refracting lens  12 , which sits on an entry surface  13  of a prism  14 . The light path shown in  FIG. 1 , falling from the inclined viewing direction of the axis  10 , is reflected on an exit surface  15  of the prism  14  located perpendicular to the axis  3  of the proximal objective part and is cast onto a boundary surface  16  of the prism  14 , from which after a further reflection, the light path is brought into the direction of the axis  3  of the proximal objective part  2 , to emerge through the exit surface  15  of the prism  14  into the proximal objective part  2 , where its image is formed in the image plane  4  with the light path shown. 
         [0033]    The light path shown in  FIG. 1 , entering in the direction of the axis  10  in the oblique viewing direction, is thus internally reflected twice within the prism  14 , once at the exit surface  15  and then at the boundary surface  16 . Since no reflection occurs in the first distal objective part  6  and reflection occurs twice in the distal objective part  9 , the same image orientation results in both distal objective parts, e.g., in both cases an upright image or in both cases an upside-down image. 
         [0034]    In the reflecting area of the exit surface  15  in which the internal reflection must take place, the exit surface  15  may be, for example, mirror-coated from the outside. This mirror coating, however, then must not be extended into the area in which the light path is to pass through after reflection at the boundary surface  16  in the direction toward the proximal objective part  2 . An elegant solution to this problem, as shown in  FIG. 1 , consists of not mirror-coating the exit surface  15 , but instead selecting the refractive index of the prism  14  and the reflection angle at the exit surface  15  such that total reflection occurs. 
         [0035]    As  FIG. 1  shows, the reflection angle for the second reflection, which takes place at the boundary surface  16 , is selected to be very acute, so that total reflection cannot occur here. The light rays striking the boundary surface  16  from the inside thus pass through this. The reflection of the light rays at the boundary surface  16 , shown in  FIG. 1 , therefore must be accomplished by other means. 
         [0036]    For this purpose, as shown in  FIGS. 1 and 2 , a mirror  17  adjacent to the boundary surface  16  is provided, which has a mirror coating surface in the direction of the boundary surface  16 .  FIGS. 1 and 2  show two switching positions of the mirror  17 . In the position in  FIG. 1 , the mirror sits in the light path and brings about the back-reflection of the rays shown in  FIG. 1 , 
         [0037]      FIG. 2  shows the unchanged design of  FIG. 1  in the same view, wherein only the switching position of the mirror  17  is altered. 
         [0038]    In the position according to  FIG. 2 , the mirror  17  is shifted to the side. The light path entering obliquely in the direction of the axis  10  through the second distal objective part  9  is no longer reflected internally at the boundary surface  16  in the direction of the proximal objective part  2 , but emerges through the boundary surface  16  and escapes into space. The light path shown in  FIG. 2 , entering through the first distal objective part  6 , looking straight ahead in the direction of its axis  8 , which is captured in mirror position  17  according to  FIG. 1  by the back part of said mirror, can now, the mirror having been pushed aside in the switching position according to  FIG. 2 , enter the prism through the boundary surface  16  and proceed straight ahead in the direction of the axis  8  through the exit surface  15  to the proximal objective part  2 , as is shown in  FIG. 2 . 
         [0039]    If the mirror  17  is moved from the position according to  FIG. 2  back into the light path to the position according to  FIG. 1 , once again the blocking of the light path entering through the first distal objective part  6  occurs and once again the course of the ray shown in  FIG. 1  takes place. Since total reflection does not occur at the boundary surface  16 , the reflection at this point is determined solely by the switching position of the mirror  17  and thus can be controlled systematically. 
         [0040]    In the embodiment of  FIGS. 1 and 2  the mirror  17  is designed as a simple, flat mirror, which is movable, sliding on the boundary surface  16  of the prism  14  between the two switching positions of  FIGS. 1 and 2 , specifically with a movement direction in the plane of the drawing. 
         [0041]    However, the mirror  17  could also be moved in the direction perpendicular to the plane of the drawing. Then, as shown in  FIG. 3 , it could be disposed in a sliding plate  18  in a structural unit with a diaphragm  19 . By moving the sliding plate  18  in the direction of the arrow  20 , therefore, optionally either the mirror  17  or the diaphragm  19 , formed as a hole in the sliding plate  18 , can be moved into the light path. 
         [0042]    When the sliding plate  18  of  FIG. 3  is used, the light path shown in  FIG. 1  can be generated if the sliding plate  18  is moved such that the mirror  17  is located in the light path, thus in the position according to  FIG. 1 . After sliding the slide plate  18  until the diaphragm  19  is in the light path, the result is the light path according to  FIG. 2 , which is now limited by the diaphragm  19  in the desired manner. 
         [0043]    The mirror  17 , either as a single component or as a structural unit according to  FIG. 3 , is arranged in the direction of the boundary surface  16 , movable on this. In this case the mirror is located in a gap between the boundary surface  16  and the exit surface  21  of a glass rod  22  arranged in parallel to this, which as shown in  FIG. 1  carries an additional, negatively refracting lens  12  on its proximal entry surface  23 . 
         [0044]    The first gap, formed between the boundary surface  16  and the exit surface  21  of the glass rod  22 , like any gap between parallel surfaces, upon passage of light results in a parallel displacement of the light path. This leads to a slight shift in the viewing direction, thus a slight tipping of the straight-ahead viewing direction. 
         [0045]    To avoid this, a second gap  24  is shown with broken lines in  FIG. 1 , produced at this point by separating and pulling apart two parts of the glass rod  22 . The second gap  24  is arranged at an angle to the axis  8  which amounts to 180°0 minus the angle of the first gap. Like the first gap, the second gap  24  causes a parallel shift of the light path, but in the opposite direction from the first gap, so that the two shifts cancel one another. 
         [0046]    At least when it is located in the switching position of  FIG. 1  and is placed in the light path, the mirror  17  should be close to the boundary surface  16  so that little air or even dust can enter between these surfaces in an interfering way. Then, however, the risk of interferences between the two closely adjacent opposing surfaces exists. The gap between the mirror  17  and the boundary surface  16  thus must not be too narrow. In any case it must be greater than 1 μm and preferably greater than 5 μm. 
         [0047]    As a comparison of  FIGS. 1 and 2  shows, the light paths in the two distal objective parts  6  and  9  are formed identically except for the fact that a double reflection takes place in the second distal objective part  9 , as a result of which the light path is formed in the manner shown in  FIG. 1 . As a result, the same image orientation occurs in both cases. If the image formed in image plane  4  is upright in the case of the image formation in  FIG. 1 , it is upright in the case of the image formation in  FIG. 2 . 
         [0048]      FIGS. 4 and 5  show an objective  1 ′ in a second embodiment. The objective  1 ′ provided for installation in the distal end region of an endoscope shaft, not shown, is illustrated in a highly schematic representation of its essential components. 
         [0049]    A proximal objective part  2 ′ is aligned with its axis  3 ′ on an image plane  4 ′ which in the illustrated exemplified embodiment is the light-sensitive plane of an electronic image sensor  30 . This is connected in a manner not shown, over electrical lines, to the image processing devices. Instead of the image plane  4 ′ of the image sensor  30 , the distal end surface of an image guide fiber bundle may be provided, with which the image is transported over the length of the endoscope. 
         [0050]    The objective has two distal objective parts for different viewing directions. A first distal objective part  6 ′ in the highly schematized illustrated exemplified embodiment consists of a lens part  31  and a planar plate  32 , which is passed through by the axis  8 ′ of the first distal objective part  6 ′ perpendicular to the plane-parallel faces. 
         [0051]    As is apparent from  FIG. 4 , the axis  8 ′ of the first distal object part  6 ′ coincides with axis  3 ′ of the proximal objective part  2 ′. In the conventional construction mode, this axis is located parallel to the longitudinal axis of the endoscope shaft, so that this first distal objective part  6 ′ looks straight ahead. 
         [0052]    Between the proximal objective part  2 ′ and the first distal objective part  6 ′ in the direction of the optical axis is an interval in which a prism  14 ′ is disposed. Transverse to the axis  3 ′ of the proximal objective part  2 ′, the prism  14 ′ can be moved in the direction of the double arrow  33 . For this purpose, for example, a sled, not shown, is provided, which is disposed in the housing, not shown, or the holder of the objective  1 ′. The propulsion for moving this can take place by manual actuation or for example with an electric motor. 
         [0053]    Falling one behind another in the direction of the double arrow  33 , the prism  14 ′ has two areas, specifically a first area  34  and a second area  35 . 
         [0054]    The first area  34  of the prism  14 ′ is designed as a planar plate. A distal planar surface  36  and a proximal planar surface  37  are located perpendicular to the axis  3 ′ of the proximal objective  2 ′. 
         [0055]    In the representation of  FIG. 4  the prism  14 ′ is located in a sliding position in which the light path coming from the first distal objective part  6 ′ travels through the plane-parallel first region  34  of the prism  14  on its path to the proximal objective part  2 ′. 
         [0056]    The second region  35  of the prism  14 ′ has the same proximal planar surface  37  passing through it as the first region  34 . Distally, however, it has oblique surfaces, specifically a reflection surface  38  for internal reflection and an exit surface  39  in front of which a distal objective portion  9 ′ is arranged. 
         [0057]      FIG. 5  shows the objective  1 ′ in a position in which the prism  14 ′ is switched into another position, specifically such that the second area  35  of the prism  14 ′ is located distally in front of a proximal objective part  2 ′. The ray axis shown in  FIG. 5  travels from the axis  10 ′ of the second distal objective part  9 ′ after reflection at  40  on the proximal planar surface  37  of the prism  14 ′, and after reflection at  41  on the distal oblique surface  38 , into the axis  3 ′ of the proximal objective part  2 ′. The internal reflection points at  40  and  41  can both be made totally reflecting in the exemplified embodiments. 
         [0058]    In the position of  FIG. 5 , the image sensor  30  thus looks through the second distal objective part  9 ′ at an oblique angle while in the position of  FIG. 4  it looks straight ahead through the first distal objective part  6 ′. 
         [0059]    As comparison of  FIGS. 4 and 5  shows, the second proximal objective part  9 ′ is connected to the prism  14 ′ for joint movement. The connection means for this are not shown in the drawing. The other component groups  6 ′,  2 ′ and  30  are once again fastened together, as comparison of  FIGS. 4 and 5  shows. 
         [0060]    In a modified embodiment, not shown, for example the second distal objective part  9 ′ may stand permanently in the position of  FIG. 5  and be permanently connected to the components  6 ′,  12 ′ and  30 , while the prism  14 ′ can be moved in the direction of the double arrow  33  independently of all other components. In an alternative design, both distal objective parts  6 ′ and  9 ′ can be connected to the prism  14 ′ for joint movement. In this way, design variation possibilities exist, each of which has its own advantages, for example for construction reasons or for reasons of space. 
         [0061]    As can be seen from the comparison of  FIGS. 4 and 5 , in the objective  1 ′ shown, care is taken that the optical path length, also called “optical distance” or “light path,” is the same in both viewing directions. Comparison of  FIGS. 4 and 5  specifically shows that the optical path length through the prism area  35  of the prism  14 ′ is substantially longer than that through the planar plate area  34 . However, this is compensated by the light path through the planar plate  32  shown in  FIG. 4 , which can be of dimensions such that the optical path length is actually the same in both ray paths of  FIGS. 4 and 5 . 
         [0062]    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.