Abstract:
An endoscope has a tubular shaft whose interior contains components, in particular lenses, spacers, diaphragms, prisms and filters of an optical system, said components being at least partially surrounded by a support piece made of shrunk material. It is proposed that the components be surrounded by a transparent and tube-sleeve-shaped shrunk material which has been shrunk before the components are introduced into the tubular shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of pending U.S. patent application Ser. No. 11/206,562 filed Aug. 18, 2005, which in turn is a continuation of international application PCT/EP 2004/000765 filed on Jan. 29, 2004 which designates the United States and which claims priority of German patent application No. 103 07 904.1 filed on Feb. 18, 2003. All prior applications are herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an endoscope, with a tubular shaft whose interior contains components, in particular lenses, spacers, diaphragms, prisms and filters of an optical system, said components being at least partially surrounded by a support piece made of shrunk material. 
         [0003]    The invention also relates to a method for assembling components, in particular lenses, spacers, diaphragms and filters of an optical system in the interior of a tubular shaft of an endoscope, said components being surrounded by a support piece made of shrunk material. 
         [0004]    Such an endoscope and such a method are known from document DE 197 32 991 C2. 
         [0005]    In the method disclosed in the latter document, the shrinkable material is used to fix the components of the optical system in the tubular shaft. To do this, the components are introduced into a support piece made of shrinkable material at least partially surrounding said components, and this unit is then pushed into the tubular shaft. The dimensions are such that a small gap remains between the outside face of the support piece and the inside face of the tubular shaft. As the material shrinks, it expands slightly in the radial direction and fills the gap, so that in this way the unit is fixed on the inside face of the tubular shaft. 
         [0006]    DE 39 12 720 C2 also discloses the use of a plastic shrinkable tube for positioning the elements of a relay lens system of an endoscope. The material is chosen such that it does not transmit light, i.e. is opaque. This is intended to ensure that light does not pass from the light guide into the area of the relay lens system or into the area of the objective lens and there cause reflections or glare. The lenses of the lens system can first be placed in a correct position. The shrinkable tube is then shrunk by application of heat so that it holds the lenses, without a lens fixture in the conventional sense being needed. 
         [0007]    This construction is intended to make it possible to produce endoscopes extremely inexpensively, and provision is therefore also made to produce the lenses from plastic. 
         [0008]    In the document DE 39 12 720 C2 mentioned earlier, the aim is to fix the expensive components of the optical system to the inside face of a metal tubular shaft by using the shrink properties of the material surrounding these components. 
         [0009]    It is an object of the present invention is to further optimize an endoscope and a method for assembling components in such a way that, by using shrinkable materials, it is possible to fix the optical components relative to one another in a way which can also be checked. 
       SUMMARY OF THE INVENTION 
       [0010]    According to the invention, the object in respect of an endoscope is achieved by the fact that the components are surrounded by a transparent and tube-shaped shrunk material which has been shrunk before the components are introduced into the tubular shaft. 
         [0011]    According to the invention, the object in respect of a method is achieved by the following steps, namely introducing the components into a transparent and tube-shaped shrinkable material to form a unit, shrinking the material to fix the position of the components relative to one another, checking the position of the components relative to one another through the transparent shrunk material, and introducing the unit composed of shrunk tube-shaped material, and the components contained therein, into the tubular shaft. 
         [0012]    The optical system of an endoscope is made up of a succession of different optical components. A particularly good image quality can be obtained using what are referred to as rod lenses. For this purpose, several rod lenses separated from one another by spacers are arranged in series, and other components such as diaphragms, filters or cover glasses or prisms can additionally be provided. 
         [0013]    For a good image quality, it is not only necessary for these parts to be precisely oriented relative to one another and fixed axially along an optical axis; it is also necessary for their relative rotation positions to be unchangeable. In the course of assembly, it is expedient to check the optical image qualities of such a lens system so that, if appropriate, systems with optical misalignments can be eliminated. 
         [0014]    The quality check of the optical system is normally made only after complete assembly of the endoscope. If optical errors are found, it is then very expensive to correct these, and in most cases the endoscope has to be completely dismantled. 
         [0015]    With the present invention, it is now possible to produce a unit composed of the optical components and the tube outside the endoscope and to check this unit visually. For this purpose, a transparent shrinkable material is used which in many respects affords advantages over the opaque materials known from the prior art. On the one hand, the position of the components relative to one another can be visually checked at the time the individual components are introduced into the material before it has been shrunk. In particular, it is possible to establish whether, for example, individual filter components or diaphragms have turned relative to one another, or whether, for example, a gap is or is not present between a spacer and a rod lens. 
         [0016]    It is also possible to check the correct arrangement of the lens components, lenses, spacers and, if appropriate, diaphragms, filters and/or prisms. 
         [0017]    After this unit has been shrunk, a check can once again be made, namely as to whether the shrinking has caused any relative changes to take place. During shrinkage, the material surrounding the optical elements moves. By provision of the transparent material, it is now possible for the first time to perform a visual check even after the shrinking process. Of course, checks are also already possible in the direction of the optical axis that is to say through the optical elements. Thus, such a preliminary check can be made even before the optical system is fitted in the shaft. After introduction of the shrunk unit and final positioning of this unit in the shaft, a final check can then also be made. 
         [0018]    In this way, the reliability of the assembly and the assembly as such, can also be simplified and improved. 
         [0019]    In a further embodiment of the invention, all the components are surrounded by a single tube of transparent and shrunk material. 
         [0020]    This measure has the advantage that all the components are introduced into a single tube-shaped body and this unit can be handled as such after shrinking, for example can be simply inserted as a unit into the tubular shaft of the endoscope. This unit can be introduced into the endoscope shaft in the appropriate position of rotation or can be brought to the correct position of rotation after introduction. If, for example, a front closure forms a prism with a lateral angle of view, the position, that is to say lateral angle of view, can be chosen to the left, to the right, upward or downward. 
         [0021]    In a further embodiment of the invention, the components are fixed to the inside face of the tubular shaft via the tube-shaped shrunk material. 
         [0022]    There are a great many ways of doing this, for example by adhesive fixation where the adhesive can be applied before introduction of the unit, or can be introduced for fixing after introduction through radial bores in the tubular shaft. 
         [0023]    In a further embodiment of the invention, the tube is fixed to the inside face of the tubular shaft by radial expansion of the shrunk material. 
         [0024]    This measure has the advantage that the effect, known from DE 197 32 991 C2, can now additionally be used to fix the already “pre-shrunk”unit to the inside face of the tubular shaft by a further shrinking process. This entails a further axial shrinkage with slight radial expansion. 
         [0025]    The extent of the shrinking process can be controlled by the nature and duration of the shrink treatment. In a first preliminary shrinking process, the shrink phenomenon is utilized so that the components introduced into the tube can be fixed relative to one another. After insertion of this unit into the tubular shaft, a further shrinking process is carried out, its sole purpose being to fill the gap between the outside face of the unit, composed of pre-shrunk shrinkable tube and the components contained therein, and the inside face of the tubular shaft into which this unit is inserted, in order thereby to fix this unit on this inside face of the tubular shaft as it experiences a slight expansion in the radial direction during this further shrinking. For this purpose, certain preliminary treatments of the shrinkable tube can be envisaged, for example one or more beads in the form of rings or partial rings lying within the cross section. These geometric departures from the otherwise cylindrical shape of the shrinkable tube entail radial expansion of the geometry of the shrinkable tube upon its axial shrinkage, without expansion of the material as such. 
         [0026]    In one embodiment of the method, the unit composed of components and of transparent shrinkable material is inserted, before shrinkage, into a retaining device in which the unit lies in an oriented position. 
         [0027]    This measure has the advantage that the retaining device can provide additional measures for keeping the unit correctly aligned. It is also possible, after insertion in the retaining device, to check the unit for correct fit before the shrink process is instigated. 
         [0028]    The unit inserted in the retaining device can be additionally fixed by a partial vacuum. 
         [0029]    In a further embodiment of the method, the unit is inserted into a groove of the retaining device. 
         [0030]    This is particularly advantageous if long endoscope shafts are to be fitted and in particular if there is a risk of the force of gravity causing bending or bulging. 
         [0031]    In a further embodiment, the unit inserted into the retaining device is weighed down by application of an object. 
         [0032]    This measure has the advantage that not only is a support provided in the direction of gravity by way of insertion, but bending in the sense of lifting up can be prevented by application of the object before shrinkage. 
         [0033]    In a further embodiment, the object is applied with a partial form fit onto the unit. 
         [0034]    This measure is of advantage if a great many small individual parts are assembled which have a tendency to change their position in the event of movements, for example during shrinkage. 
         [0035]    It will be appreciated that the features mentioned above and those still to be explained below can be used not only in the respectively cited combination, but also in other combinations or singly, without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]    The invention is described and explained in greater detail below on the basis of a number of selected illustrative embodiments and with reference to the attached drawings, in which: 
           [0037]      FIG. 1  shows a longitudinal section through a unit composed of a tube of transparent and shrinkable material and of optical components, namely rod lenses and spacers, before shrinkage, 
           [0038]      FIG. 2  shows a cross section of a retaining device in which the unit shown in  FIG. 1  is inserted, specifically upon shrinkage, 
           [0039]      FIG. 3  shows a longitudinal section through an endoscope during assembly, into which endoscope the unit shown in  FIG. 1 , after it has been shrunk in the retaining device  3  shown in  FIG. 2 , is inserted into the tubular shaft, and 
           [0040]      FIG. 4  shows, on a greatly enlarged scale, a partial longitudinal section through a shaft of an endoscope in whose tubular shaft a unit according to the invention is inserted, the left-hand half showing the unit fixed on the inside face of the tubular shaft by adhesive contacts, and the right-hand side showing it being fixed by means of further shrinkage. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    In  FIG. 1 , a unit, designated in its entirety by reference number  10 , comprises a tube  12  made of transparent and shrinkable material  14 . A plurality of components  16  of an optical system are introduced into the tube  12 , specifically, as viewed from left to right, a rod lens  18 , whose external diameter corresponds approximately to the clear internal diameter of the tube  12 , a tubular and stiff spacer  20 , a further rod lens  18 ′, a further spacer  21 , and a further rod lens  18 ″. 
         [0042]    This unit  10  is shown only by way of example, and other components such as filters, diaphragms or the like can of course also be included. It is also possible to provide closure windows at the ends or, in the case of an angled side view, suitable prisms. 
         [0043]    By virtue of the transparency of the material  14 , it is possible to check the desired correct fit of these components  16  relative to one another from the outside, for example to check whether the opposing end faces of the two rod lenses  18  and  18 ′ bear exactly on the spacer  20 . 
         [0044]    For the shrinking process, the unit  10  is inserted into a retaining device  30 , as is shown in  FIG. 2 . 
         [0045]    The retaining device  30  has an elongate body  32  whose length corresponds to least to the length of the unit  10 . 
         [0046]    Cut out on the top face of the body  32  there is a longitudinally extending groove  34  which is configured in such a way that the unit  10  can be inserted into this groove, the unit  10  protruding slightly above the upper edge of the retaining device. 
         [0047]    A roughly plate-shaped object  36  is placed onto this protruding area and bears with an at least partial form fit on the top face of the unit  10 , as it were pressing said unit  10  into the groove  34 . 
         [0048]    In this way, the unit  10  is inserted and fixed in the retaining device  30  in such a way that a uniform shrinking of the material  14  of the tube  12  is possible, but with the unit still being fixed in position. 
         [0049]    Alternatively or in addition, the position can be fixed by use of a partial vacuum. For this purpose, at least one opening  35  is provided in the bottom of the groove  34  and can be connected via an attachment piece  39  to a partial vacuum source (not shown here). 
         [0050]    As is known per se, in the actual shrinking process, energy is supplied from an energy source  38  and causes the material  14  of the tube  12  to shrink. 
         [0051]    One energy source is, for example, heat, if the material is designed such that it shrinks when heated. It is of course also possible to heat the retaining device  30  itself or to cause heated fluid to flow onto the retaining device. 
         [0052]    After the shrinkage, the object  36  is taken off and the now shrunk unit  10 ′ is removed from the retaining device  30 . 
         [0053]    By virtue of the transparency of the material  14  which is still present even after the shrinkage, it is possible once again to check, from the outside, the correct fit of the individual components  16  relative to one another. 
         [0054]    The shrunk unit  10 ′ is then inserted into a tubular shaft  42  of an endoscope  40 , as is shown in  FIG. 3 . 
         [0055]    The endoscope  40  shown in  FIG. 3  is represented highly schematically and, in addition to the tubular shaft  42  also referred to as inner tube, it also comprises an outer tube  44  of greater diameter which is mounted in a housing  50 . The tubular shaft  42  is received in the interior of the outer tube  44 . 
         [0056]    As is normally the case, a light guide  46  is arranged in an approximately crescent-shaped space between tubular shaft  42  and outer tube  44 , said light guide  46  leading to a laterally angled light guide attachment  48 . In the illustrative embodiment shown, the light guide  46  is composed of a bundle of light-conducting glass fibers. The state shown in  FIG. 3  is a state of partial assembly in which the eyepiece cup is still to be applied to the right-hand end, and, if appropriate, closure components or the like to the left-hand end. 
         [0057]      FIG. 4  shows a cross section, on a greatly enlarged scale, through the shaft of an endoscope  40 , and, for the sake of clarity of the drawing, a slightly shorter spacer  20 ′ is shown here separating the two rod lenses  18  and  18 ′ from one another. 
         [0058]    From the cross-sectional view in  FIG. 4  it will be evident that the unit  10 ′ is inserted after shrinkage into the tubular shaft  42  received in the outer tube  44 . The external diameter is chosen in such a way that a small gap  52  is present between the outside face of the shrunk tube  12  and the inside face  56  of the tubular shaft  42 . 
         [0059]    In  FIG. 4 , for the sake of clarity of the drawing, this gap  52  is shown much larger than it really is. 
         [0060]    The width of the gap is chosen such that the shrunk unit  10 ′ can be pushed into the tubular shaft  42  easily, or at any rate with minimal resistance. 
         [0061]      FIG. 4  shows, on the left-hand side, that the unit  10 ′ is fixed on the inside face  56  of the tubular shaft  42  via an adhesive  54 . The adhesive  54  can either be introduced through openings (not shown here) from the outside or can be applied to the shrunk unit  10 ′ before the latter is inserted into the tubular shaft  42 . 
         [0062]    The right-hand end of  FIG. 4  shows that the unit  10 ′ is fixed to the inside face  56  of the tubular shaft  52  by further shrinkage of the tube and associated radial expansion, in which case, as has already been mentioned, the shrinkable tube can be geometrically designed in such a way that, for example by provision of beads, incisions or other configurations which promote expansion at predetermined locations, this expansion takes place in a specific manner during the further shrinking process. 
         [0063]    This possibility is chosen when the material  14  of the tube  12  permits two shrinking processes, namely a first or preliminary shrinking process for fixing the components to one another, for example in the retaining device  30  shown in  FIG. 2 , and then, after insertion into the tubular shaft  42  as shown in  FIG. 4 , a further shrinking and radial expansion for filling the gap  52 .