Method for assembling components of an optical system

p0001The invention relates to a method for mounting components, in particular of lenses, spacers, diaphragms, filters of an optical system in the interior of a tube shaft of an endoscope, wherein the structural elements are surrounded by a support element made from a shrink material.

p0002Such an endoscope and such a method are known from the <patcit id="pcit0001" dnum="DE19732991C2"><text>DE 197 32 991 C2</text></patcit> known.

p0003In the process known therefrom, the shrinkable material serves to fix the components of the optical system in the tube shaft. For this purpose, the structural elements are placed in a partially surrounding supporting element made of shrinkable material, and this assembly is inserted into the tubular shaft. The dimensioning is such that a small gap remains between the outer side of the support element and the inner side of the tubular shaft. When the material shrinks, it expands somewhat radially, fills the gap, so that the assembly is fixed to the inner side of the tube shaft.

p0004From the <patcit id="pcit0002" dnum="DE3912720C2"><text>DE 39 12 720 C2</text></patcit> It is also known to use a plastic shrink tube for positioning the elements of a relay lens system of an endoscope. The material is selected in such a way that it is opaque, that is, opaque. This is to prevent light from the optical fiber from entering the region of the relay lens system or into the region of the objective lens and causing reflections or transitions there. First, the lenses of the relay lens system can be positioned in a proper position. Subsequently, the shrink tube is shrunk by applying heat so that it holds the lenses without requiring a lens mount in the conventional sense.

p0005With this construction, it should be possible to manufacture endoscopes at an extremely low cost, therefore, for example, it is also intended to produce the lenses from plastic material.

p0006In the above-mentioned <patcit id="pcit0003" dnum="DE3912720C2"><text>DE 39 12 720 C2</text></patcit> Is to fix the high-quality components of the optical system on the inside of a metallic tube by utilizing the shrinking properties of the material surrounding these components.

p0007It is an object of the present invention to further optimize a method for assembling components in that, using shrinkable materials, a positional fixing of the optical components among one another is made possible, which is also controllable.

p0008According to the invention, the object is achieved in a method by the following steps: introduction of the components into a transparent and tubular shrinkable material, forming an assembly, shrinking the material to fix the components together, checking the position of the components one below the other through the transparent shrunk material , And placing the assembly of shrunken tubular material with the structural elements contained therein into the tube shaft.

p0009The optical system of an endoscope is constructed by juxtaposing different optical components. A particularly good imaging quality can be achieved by so-called stablins. For this purpose, a plurality of stator lenses, which are separated from one another by spacers, are arranged side by side, further components such as diaphragms, filters or terminating coverslips or prisms being additionally provided.

p0010For a good imaging quality, it is not only necessary to align these parts axially relative to one another along an optical axis and to fix them, but their relative rotational positions must also be unchangeable. In the course of the assembly it is useful to control the optical imaging qualities of such a lens system in order to eliminate systems with optical errors if necessary.

p0011The quality inspection of the optical system is usually carried out only after the endoscope has been completely assembled. It is then very costly, if optical errors occur, to correct these, usually the endoscope has to be completely disassembled.

p0012With the present invention, it is now possible to manufacture the optical components outside the endoscope and visually control this assembly. For this purpose, a transparent, shrinkable material is used, which in several respects offers advantages over the opaque materials known from the prior art. On the one hand, the position of the structural elements can be checked visually with each other when the individual structural elements are introduced into the material which has not yet been shrunk. In particular, it can be recognized whether, for example, individual filter elements or diaphragms have rotated relatively, or whether, for example, a gap is present axially between a spacer and a rod lens or not.

p0013Furthermore, the correct arrangement of the lens components, lenses, spacers and possibly diaphragms, filters and / or prisms can be controlled.

p0014After the shrinking of this assembly, a check is again possible, namely, whether any changes in the relative position have occurred due to the shrinking process. When shrinking, the material surrounding the optical elements moves. By providing the transparent material, it is now possible for the first time to carry out a visual check once again after shrinking. Of course, controls are also possible in the direction of the optical axis, ie through the optical elements. Thus, before the optical system is mounted in the shaft, such a pre-control can be carried out. After the shrunken assembly and final positioning of this assembly in the shaft, a final inspection can then be performed again.

p0015This facilitates and improves the mounting safety as well as the assembly as such.

p0016In a further embodiment, all components are surrounded by a single tube of transparent and shrunk material.

p0017This measure has the advantage that all structural elements can be introduced into a single tubular body and this assembly can be handled as a unit after shrinking, for example as an assembly, can easily be inserted into the tube shaft of the endoscope. This assembly can be inserted into the corresponding rotational position in the endoscope shaft or brought into the correct rotational position after insertion. If, for example, a front end forms a prism with lateral angle of view, then the position, ie lateral angle of flashing to the left, to the right, upwards or downwards, can be correspondingly selected.

p0018In a further embodiment, the structural elements are fixed to the inner side of the tubular shaft via the tubular, shrunken material.

p0019There are now numerous possibilities, for example by means of adhesive fixation, whereby the adhesive can be applied before the assembly is installed, or after introduction by radial bores in the tube shaft can be introduced into the fixing.

p0020In a further embodiment, the structural elements are fixed by radially expanding the shrunk material to the inner side of the tubular shaft.

p0021This measure has the advantage that the effect, as it is from the <patcit id="pcit0004" dnum="DE19732991C2"><text>DE 197 32 991 C2</text></patcit> Is now additionally used in order to fix the already "pre-shrunk" assembly by a further shrinking process on the inner side of the tube shaft. In this case, essentially a further axial shrinkage with a small radial expansion takes place.

p0022The degree of shrinking can be controlled by the type and duration of the shrinking treatment. In a first pre-shrinking operation, the shrinkage phenomenon is utilized to fix the components embedded in the tube together. After insertion of this assembly into the tube, further shrinking is performed, which serves merely the purpose of filling the gap between the outer side of the assembly of pre-shrunk shrink tube and the structural elements contained therein and the inner side of the tube into which this assembly is inserted To thereby fix this assembly to this inner side of the tube shaft by causing a small expansion in the radial direction during this post-shrinkage in the axial direction. For this purpose, certain pretreatments of the shrink tube can be provided, for example one or more beads in the form of rings or partial rings lying in the cross-section. These geometrical deviations from the other cylindrical shape of the shrink tube imply radial expansion of the geometry of the shrink sleeve in its axial shrinkage, even without expansion of the material as such.

p0023In an embodiment of the method, the assembly of structural elements and transparent shrinkable material before shrinking is inserted into a holding device in which the assembly is aligned.

p0024This measure has the advantage that additional measures are provided by the holding device in order to keep the assembly aligned. It is also possible, after inserting the assembly in the holding device nochm to check as to correct fit before the shrinking process is initiated.

p0025The assembly inserted in the holding device can additionally be fixed by applying a vacuum.

p0026In a further embodiment of the method, the assembly is inserted into a channel of the holding device.

p0027This is particularly advantageous when long endoscope shafts are to be mounted and in particular if there is a risk that deflections or bulges may be caused by the gravity.

p0028In a further embodiment, the assembly inserted into the holding device is weighted by placing an object.

p0029This measure has the advantage that not only a support in the gravity direction is brought about by inserting but also bending in the sense of a build-up can be prevented by placing the object before the shrinking.

p0030In a further embodiment, it is provided that the object is placed partially positively on the assembly.

p0031This measure has an advantage when a large number of small individual parts are combined, which tend to change their position during movements, for example during shrinkage.

p0032It goes without saying that the above-mentioned and the measures which are still to be explained below can be used not only in the particular combination indicated but also in other combinations or in a single setting without departing from the scope of the present invention.

p0033BRIEF DESCRIPTION OF THE DRAWINGS The invention is described and explained in more detail below with reference to a few selected exemplary embodiments in conjunction with the appended drawings. Show it:<dl id="dl0001"><dt>FIG</dt><dd>A longitudinal section of an assembly of a tube of transparent and shrink-shaped material and optical components, namely, stator lenses and spacers, prior to shrinking,</dd><dt>FIG</dt><dd>3 a cross section of a holding device in which the <figref idrefs="f0001">FIG</figref> Illustrated during assembly, during the shrinkage,</dd><dt>FIG</dt><dd>A longitudinal section through an endoscope during assembly in the straight line of FIG <figref idrefs="f0001">FIG</figref> As shown in FIG <figref idrefs="f0001">FIG</figref> Has been shrunk into the tube shaft, and FIG</dd><dt>FIG</dt><dd>A partial longitudinal section through a shank of an endoscope is inserted into the tube of the tube, a assembly according to the invention being inserted on the left half, a fixation of the assembly on the inside of the tube shaft being shown by gluing and on the right side fixing by further shrinking.</dd></dl>

p0034In <figref idrefs="f0001">FIG</figref> Is shown an assembly, denoted in its entirety by the reference numeral 10, which has a tube 12 of transparent and shrinkable material 14. Several structural elements 16 of an optical system have been introduced into the tube 12, namely, from the left to the right, a rod lens 18 whose outer diameter corresponds approximately to the inner diameter of the tube 12, a tubular rigid spacer 20, a further rod lens 18 ' A further spacer 21 and a further rod lens 18 ".

p0035This assembly 10 is only exemplary; other components such as filters, diaphragms or the like can, of course, be interposed. It is also possible to provide end-closing windows or, in the case of an angled lateral view, corresponding prisms.

p0036Because of the transparency of the material 14, it is possible to control the desired correct seating of these structural elements 16 one below the other from the outer side, for example, whether the opposing end faces of the two stator lenses 18 and 18 'lie precisely against the spacer 20.

p0037For the shrinking operation, the assembly 10 is placed in a holding device 30 as shown in FIG <figref idrefs="f0001">FIG</figref> Is shown.

p0038The holding device 30 has an elongated body 32, the length of which corresponds at least to the length of the assembly 10.

p0039On the upper side of the body 32, a longitudinally extending groove 34 is formed which is designed such that the assembly 10 can be inserted into this channel, the assembly 10 slightly exceeding the upper edge of the holding device.

p0040An approximately plate-shaped object 36, which at least partially engages positively on the upper side of the assembly 10, thus virtually presses it into the channel 34, is placed on this protruding region.

p0041As a result, the assembly 10 is inserted and fixed in the holding device 30 in such a way that a uniform shrinkage of the material 14 of the hose 12 is possible, but the assembly is nevertheless held in a fixed position.

p0042Alternatively or additionally, a vacuum can be used for positional fixing. For this purpose, at least one opening 35 is provided in the bottom of the channel 34, which opening can be connected via a connection 39 to a vacuum source, which is not shown here.

p0043During the actual shrinking process, as is known per se, energy is supplied from a power source 38, which causes the material 14 of the tube 12 to shrink.

p0044An energy source is, for example, heat when the material is designed to shrink with heat. It is, of course, also possible to heat the holding device 30 itself or to inflow it by a heated fluid.

p0045After shrinking, the object 36 is removed and the now shrunken assembly 10 'is removed from the holding device 30.

p0046Due to the transparency of the material 14, which is also present after the shrinking, it is possible to check again the correct fit of the individual components 16 one after the other from the outside.

p0047Subsequently, the shrunken assembly 10 'is inserted into a tubular shaft 42 of an endoscope 40 as shown in FIG <figref idrefs="f0002">FIG</figref> Is shown.

p0048This in <figref idrefs="f0002">FIG</figref> Is shown very schematically and has, in addition to the tubular shaft 42, which is also referred to as an inner tube, a diameter-large outer tube 44, which is mounted in a housing 50. The tubular shaft 42 is accommodated in the interior of the outer tube 44.

p0049In an approximately crescent-shaped space between the tubular shaft 42 and the outer tube 44, as is also customary, an optical fiber 46 is arranged, which leads to a laterally angled optical connector 48. In the exemplary embodiment shown, the light guide 46 is formed from a bundle of light-conducting glass fibers. The<figref idrefs="f0002">FIG</figref> Is a partial mounting state, the ocular shell is attached to the right end, and terminating elements or the like to the left end.

p0050In <figref idrefs="f0003">FIG</figref> A section through the shank of an endoscope 40 is shown in the greatly enlarged state. For illustrative reasons, a somewhat shorter spacer 20 'is shown here, which separates the two stator lenses 18 and 18' from each other.

p0051From the sectional view of Fig <figref idrefs="f0003">FIG</figref> It can be seen that the assembly 10 'is inserted into the tubular shaft 42, which is accommodated in the outer tube 44, after the shrinkage. The outer diameter is selected such that a small gap 52 is present between the outer side of the shrunken hose 12 and the inner side 56 of the tubular shaft 42.

p0052In <figref idrefs="f0003">FIG</figref> This gap 52 is shown to be excessively large for illustrative reasons.

p0053The gap width is selected in such a way that the shrunk-on assembly 10 'can be inserted into the tubular shaft 42 simply or at most with a low resistance.

p0054In <figref idrefs="f0003">FIG</figref> It is shown on the left side that the assembly 10 'is fixed via an adhesive 54 to the inner side 56 of the tubular shaft 42. The adhesive agent 54 can be applied either through openings (not shown here), from the outside, or applied to the tube shaft 42 prior to insertion of the shrunk assembly 10 '.

p0055At the right end of <figref idrefs="f0003">FIG</figref> It is shown that the assembly 10 'is fixed by a further shrinking of the hose and an associated radial expansion on the inner side 56 of the tube 52, the shrink tube being, as already mentioned, geometrically designed, for example, by providing beads, incisions or Other arrangements which promote expansion at predetermined points, such expansion takes place in a targeted manner during the post-shrinking process.

p0056This possibility is selected when the material 14 of the hose 12 allows two shrinking operations, namely a first or "pre-shrinking" process to fix the components together, for example in the embodiment shown in FIG <figref idrefs="f0001">FIG</figref> And subsequently, after being inserted into the tube shaft 42, as in FIG <figref idrefs="f0003">FIG</figref> , By further shrinking and radially expanding to fill the gap 52.