Optical instrument, in particular an endoscope, having an interchangeable head

An optical instrument, in particular an endoscope, has a shaft and an inter-changeable head. The interchangeable head is detachably connected to the distal end of the shaft at a coupling point. The instrument also has a first transmission system for distal transmission of illuminating power, and a second transmission system for proximal transmission of image information, the first transmission system and the second transmission system passing through the coupling point. The interchangeable head and/or the coupling point are/is designed in such a way that upon loosening of the interchangeable head image information of perceptively modified quality is transmitted by the second transmission system.

BACKGROUND OF THE INVENTION

The invention relates to an optical instrument and in particular to an endoscope.

The invention more specifically relates to an optical instrument, having a shaft and having an interchangeable head that is detachably connected to the distal end of the shaft at the coupling point, and having, furthermore, a first transmission system for transmission of illuminating power in distal direction and having a second transmission system for transmission of image information in proximal direction, the first transmission system and the second transmission system passing through the coupling point.

Such an optical instrument, in particular an endoscope, is generally known through its use, the interchangeable heads being interchangeable objectives or supplementary lenses in the case of known instruments without the invention being limited thereto.

Although the present invention is described using the example of an endoscope, the invention is not limited to an endoscope, but rather can be used generally in optical instruments or devices.

Endoscopes are used for medical purposes, on the one hand, and for technical purposes, on the other hand. In medicine, endoscopes are used in minimally invasive surgery for visual control of operations. In the technical field, endoscopes are used to investigate cavities that are difficult to access, in particular to investigate operating cycles in engines, turbines and in reaction chambers, including during their operation.

Furthermore, known endoscopes include those with a rigid shaft and those with a flexible shaft, it being possible for endoscopes with a flexible shaft to be introduced to the place of use through winding paths, and also various viewing directions being made possible by means of a deflecting mechanism.

Endoscopes are usually fitted with a first transmission system for transmission of illuminating power in distal direction, and with a second transmission system for transmission of image information in proximal direction. It is normally incoherent fiber bundles, that is to say optical waveguides that are used as the first transmission system for transmitting illuminating power. However, within the meaning of the present invention, illuminating power is also understood as electric power used to feed a light source on or in the endoscope. In the case of endoscopes, the transmission system for transmitting image information comprises either lenses, coherent bundles of optical fibers, that is to say so-called image waveguides, electric lines that conduct in the proximal direction electric signals generated by a distally arranged image pick-up, lightwave data lines, or teletransmissions by means of temporally modulated radio waves or temporally modulated light.

With known endoscopes, there is usually also present at the distal end of the shaft of the endoscope an imaging optics that images the space to be observed onto the start of the transmission link, for example onto a fiber bundle.

The imaging optics used, which is not exchangeable, fixes the direction of view and the field of view. In order to configure an existing endoscope in a more versatile fashion with regard to direction of view, field of view and working distance, endoscopes are currently being offered with interchangeable heads in the form of interchangeable objectives, it being possible to vary the direction of view, the field of view and the working distance by selecting an appropriate interchangeable objective. The possibilities of use of the endoscope, which is not infrequently very expensive, can be widened in this way by keeping various interchangeable objectives at the ready.

The interchangeable objectives of the known endoscopes, in particular in accordance with U.S. Pat. No. 4,706,653, are not independent optics, but are designed only as supplementary lenses of telephoto or wide-angled nature such as are known from photography. The interchangeable objectives of the known endoscopes also include, for example, deflecting optics in order to be able to switch over from a straight ahead direction of view without interchangeable objective to a lateral direction of view with an interchangeable objective coupled on. In the case of interchangeable objectives of the known endoscopes, there are also included, if appropriate, in addition to the imaging optics optical waveguides and optical elements for illumination that adapt the illuminating light to the field of view.

In order to avoid the leakage of illuminating light into the observing optics at the coupling point, in the case of the known endoscopes a staircase-like spatial graduation at the coupling point has mostly been provided between the light transmission system and image transmission system.

A substantial problem with endoscopes that are fitted with interchangeable objectives is the risk of an overlooked loss of the interchangeable objective when the latter becomes undesirably loosened from the distal end of the shaft of the endoscope. In the case both of endoscopes for medical purposes and of endoscopes for technical purposes, an overlooked loss of the interchangeable objective in the area of observation, that is to say in the case of medical endoscopes in human or animal bodies, and in the case of technical endoscopes, for example, when the endoscope is used in aircraft maintenance during engine inspection, is associated with devastating consequences in some circumstances.

Various antiloss safeguards such as bayonet closures, subdivided threads, subdivided left/right threads and thread/bayonet combinations have been developed to solve this problem in the case of known endoscopes.

Apart from the fact that such antiloss safeguards render it difficult to mount the interchangeable objectives on the shaft of the endoscope because of the small dimensions of the interchangeable objectives in the case of endoscopes, such antiloss safeguards do not completely solve the problem of the overlooked loss, since in the event of failure of the antiloss safeguards it is possible nevertheless for the interchangeable objective to come loose from the shaft of the endoscope without this being noticed.

As already mentioned previously, optical instruments, in particular endoscopes, are also known in the case of which the transmission system has for the purpose of proximal transmission of image information at least one electronic image pick-up that is arranged in the region of the distal end of the shaft such as is known, for example, from U.S. Pat. No. 5,379,756. In this known endoscope, an imaging optics is connected upstream of the image pick-up, which is not exchangeable, at the distal end of the shaft. This endoscope has no interchangeable head. Document U.S. Pat. No. 6,184,923 discloses a comparable optical instrument in the form of an endoscope having an electronic image pick-up, this endoscope containing at the distal end an interchangeable head that has an imaging optics for imaging the area of observation onto the image pick-up. Thus, in this instrument only the imaging optics is exchangeable, but not the image pick-up. However, the production costs of the shaft with permanently integrated image pick-up or a camera are increased thereby.

SUMMARY OF THE INVENTION

In accordance with one aspect, the invention is based on the object of developing an optical instrument, in particular an endoscope, to the effect that the risk of an overlooked loss of the interchangeable head is avoided.

Irrespective of the aim of indicating to the user of the optical instrument a loosening of the interchangeable head by a loss of image quality, according to a further aspect it is an object of the present invention to develop an optical instrument, in particular an endoscope, to the effect that the instrument can be produced with lower costs, at least with regard to the shaft.

According to a first aspect of the present invention, an optical instrument is provided, comprising a shaft having a distal end, an interchangeable head detachably connected to said distal end of said shaft at a coupling point, a first transmission system for transmission of illuminating power in distal direction, said first transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, a second transmission system for transmission of image information in proximal direction, said second transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, at least one of said interchangeable head and said coupling point being designed in such a way that upon loosening of said interchangeable head image information of perceptively modified quality is transmitted by said second transmission system.

According to another aspect of the present invention, an optical instrument is provided, comprising a shaft having a distal end, an interchangeable head detachably connected to said distal end of said shaft at a coupling point, a first transmission system for transmission of illuminating power in distal direction, said first transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, a second transmission system for transmission of image information in proximal direction, said second transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, wherein said second transmission system has an imaging optics, said imaging optics being arranged partially in said interchangeable head and partially in said shaft, at least one of said interchangeable head and said coupling point being designed in such a way that upon loosening of said interchangeable head image information of perceptively modified quality is transmitted by said second transmission system.

According to another aspect of the invention, an optical instrument is provided, comprising a shaft having a distal end, an interchangeable head detachably connected to said distal end of said shaft at a coupling point, a first transmission system for transmission of illuminating power in distal direction, said first transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, a second transmission system for transmission of image information in proximal direction, said second transmission system being arranged partially in said shaft and partially in said interchangeable head and passing through said coupling point, wherein said second transmission system has at least one image pick-up that is arranged in said interchangeable head, and an electric signal line that leads from said image pick-up through said coupling point in proximal direction.

The solution according to the invention is based on the principle of indicating to the user a loosening of the interchangeable head that can lead to complete detachment from the shaft of the endoscope simply by virtue of the fact that the observed image is modified in a qualitatively perceptible fashion upon loosening of the interchangeable head. Such a modification of the observed image can be expressed by virtue of the fact that the image becomes brighter and of weaker contrast, darker, worse and/or more blurred, or even disappears. The way in which the transmitted image information changes upon loosening of the interchangeable head depends on the principle on which the transmission of the illuminating power and/or the transmission of the image information are/is based, as emerges from the following description of preferred refinements of the invention. The solutions according to the invention therefore depart from the concept of providing only an antiloss safeguard at the coupling point between the interchangeable head and the shaft of the endoscope. In the case of the known endoscopes, a loosening of the interchangeable head from the shaft of the endoscope can, by contrast, not be noticed on the basis of the transmitted image information, since the interchangeable heads of the known endoscopes are designed merely as supplementary lenses. This is because in the known endoscopes the image sharpness and the contrast are maintained given an interchangeable objective that is coming loose or has fallen off, and the field of view is changed only slightly, something which is scarcely perceptible if attention is not exclusively focused thereon. In the event of unexpected loosening, the change in the field of view remains overlooked, since the operation is not influenced.

In a preferred refinement, the second transmission system has an imaging optics, the imaging optics being arranged partially in the interchangeable head and partially in the shaft, the part of the imaging optics arranged in the shaft being exchangeable.

In the case of this refinement, as well, in which the second transmission system constitutes an optical system, a loosening of the interchangeable head is indicated to the user by a worsening of the image, that is to say by a blurry image. The image can then disappear again entirely in the event of a loss of the interchangeable head. The advantage of the partial distribution of the imaging optics over the interchangeable head and over the shaft has the advantage that the interchangeable head can be implemented in a simplified way and at lower cost, and this leads overall to a reduction in the cost of the optical instrument, since a part of the imaging optics need be provided only once, specifically in the shaft of the instrument.

The exchangeability of the part of the imaging optics arranged in the shaft has the advantage that the endoscope can be readapted if necessary to a new future range of interchangeable heads.

As is provided in a further preferred refinement, the invention can advantageously be used even when the second transmission system has an image pick-up that is arranged in the interchangeable head, and an electric signal line from the video image sensor in the proximal direction, the coupling point then being designed such that upon loosening of the interchangeable head the signal line is interrupted in the proximal direction.

In the case of such a refinement, the image information is transmitted starting from the electronic image pick-up by electric signals into which the optical signals received by the image pick-up have previously been converted. The coupling point can be designed, for example, with one or more contacts in such a way that upon loosening of the interchangeable head at least one contact is opened and thereby the transmitted image information is modified, for example a segment of the image or the entire image disappears.

Whereas in the case of the endoscopes known in the prior art the image pick-up, for example in the form of a CCD chip, is integrated in the shaft, and the imaging optics connected upstream of the image pick-up can be exchanged, if necessary, the inventive refinement mentioned above has the advantage that, because of the integration of the at least one image pick-up in the interchangeable head, it is also possible to design the interchangeable head as a part subject to wear when the optical instrument is used under harsh conditions. Moreover, the shaft of the instrument can be produced in a particularly cost-effective fashion, since it need not contain optical components of any sort, not even the image pick-up itself.

Preference is given here to the signal line being designed as a plug-in contact in the region of the coupling point.

In this way, the image pick-up can then be connected to the shaft of the instrument in a way that is easy to handle in a signal-conducting fashion.

In a further preferred refinement, the at least one image pick-up is a miniaturized camera.

The development of complete, autonomous camera units is heading toward miniaturized designs that are particularly suitable for use in an interchangeable head of an endoscope, since endoscopes always have to be of the slimmest possible design. Using such miniaturized camera modules is therefore advantageous particularly in the case of endoscopes.

In a preferred refinement, the first transmission system comprises an optical waveguide that extends through the shaft and through the interchangeable head, and is interrupted at the coupling point, and the distal end of the shaft and the interchangeable head each have a flat, preferably polished surface at the coupling point.

In the case of this preferred refinement, the loosening of the interchangeable head becomes noticeable by a brightening and attendant turbidity (contrast weakening) of the transmitted image information when the basis of the second transmission system for transmitting the image information is an image waveguide system based on fibers or lenses. Whereas in the case of existing interchangeable heads in the form of interchangeable objectives the light transmission and image transmission systems situated close to one another are delimited in staircase fashion for the purpose of mutual separation, it has been found that through diffraction and absorption flat polished boundary surfaces permit a certain small slit width (other than zero) below a critical slit width without the occurrence of image degradation. The manufacturing tolerances permit the slit width to be kept below this critical slit width in conjunction with a tightened connection between the interchangeable head and the distal end of the shaft. This effect of image impairment does not occur until loosening of the interchangeable head occurs, that is to say given an increasing slit spacing when the critical slit width is exceeded. If the interchangeable head is then loosened, illuminating light is reflected into the image transmission system owing to this measure because of the enlargement of the slit between the interchangeable head and shaft, as a result of which the user experiences a loosening of the interchangeable head through the image turbidity and is warned. A further advantage of this measure consists in that the interior is additionally sealed against the ingress of liquids and dusts owing to the matching seating of the interchangeable head and the shaft. Moreover, the flat locating surface between the interchangeable head and shaft can be produced more easily than the staircase-like stepped seating, provided with conventional endoscopes, between the interchangeable head and the shaft.

In a further preferred refinement, the second transmission system has an imaging optics, the imaging optics being arranged entirely in the interchangeable head.

This measure has the advantage that even a slight loosening of the interchangeable head, for example a slight distancing or tilting, has the effect that the image can clearly be detected as degraded by defocusing. In the event of a complete loss of the interchangeable head, it is even the case that no further image is transmitted. What is important, however, is that in the event of a loosening of the interchangeable head the degradation of the image already warns the user about the possibility of losing the interchangeable head, and so he can withdraw the endoscope in good time from the observation space before the interchangeable head is lost. In this inventive refinement, there are thus no optically imaging elements in the shaft of the endoscope, and so the endoscope cannot be used without an interchangeable head.

The previously mentioned refinements, in which the second transmission system has an imaging optics, can also preferably be used in those optical instruments in which the second transmission system has an electronic image pick-up that is arranged in the shaft of the instrument. Upon loosening of the interchangeable head, the imaging of an object onto the image pick-up is disturbed such that a degraded image is noticed in this case, as well, as soon as the interchangeable head is loosened. Also, in the case of such a refinement the imaging optics can be arranged, in turn, partially in the interchangeable head and partially in the shaft upstream of the image pick-up.

In a further preferred refinement, the first transmission system has a light source and an electric power line from the proximal end to the light source, the light source being arranged in the interchangeable head, and the coupling point is designed such that upon loosening of the interchangeable head the signal line is interrupted in the distal direction.

In a way resembling the previously mentioned refinement, in this refinement the first transmission system is likewise based on a transmission of electric power, the light source then being arranged in the interchangeable head, for example in the form of an LED. Upon loosening of the interchangeable head, the electric power line can be interrupted, for example by providing appropriate contacts between the interchangeable head and the distal end of the shaft in the region of the coupling point.

In a further preferred refinement, the interchangeable head is connected to the distal end of the shaft at the coupling point by means of at least one positioning pin that engages in a corresponding bore.

It is advantageous in this case that the interchangeable heads can be positioned exactly when being coupled to the shaft so that image sharpness and image alignment are correct. An out-of-round positioning pin with a correspondingly complementary bore can suffice to fulfill this purpose. However, at least two positioning pins are preferred, the result being that the interchangeable head can be centered even more accurately and, moreover, secured exactly in terms of rotation. Moreover, the positioning pins open up the additional possibility of being used for transmission of electric signals and power. In the known endoscopes, securing the interchangeable objective in terms of rotation is achieved by means of an index groove on the circumference of the shaft or of the interchangeable objective, the centering being achieved by accurate fitting of the diameters. The positioning of the interchangeable objective in the case of the known endoscopes thus requires two independent elements that each need to be recessed with the required precision. However, this is expensive in terms of production, since complicated machines and operating cycles are required.

In a further preferred refinement, the at least one positioning pin is exchangeable.

It is advantageous in this case that in the event of damage to or bending of the positioning pin it is necessary to exchange only the latter without the interchangeable head as a whole becoming unusable. By contrast, in the case of the known endoscopes, in which the interchangeable objectives are secured in terms of rotation by means of cams and index grooves, there is the risk of the cams breaking off during alignment, and of the interchangeable objective as a whole becoming unusable.

In a further preferred refinement, the at least one positioning pin serves the purpose of transmitting electric signals or electric power.

This measure is advantageous, in particular, in the case of a refinement of the image transmission system of the inventive endoscope with an optoelectronic image pick-up (video image sensor) in the interchangeable head, since the at least one positioning pin can be used to perform transmission of electric signal s and power that can, moreover, easily be severed and restored.

Consequently, when the interchangeable head has an optoelectronic image pick-up (video image sensor or complete camera), it is preferred in accordance with a further refinement for the transmission of electric signals through the coupling point to be performed by the at least one positioning pin.

The connection of the interchangeable head to the shaft of the endoscope via the at least one positioning pin and the bore can advantageously be designed in such a way that upon loosening of the interchangeable head transmission of electric signals through the coupling point is interrupted.

In the case of one refinement of the interchangeable head having an optoelectronic image pick-up, this measure constitutes an advantageously simple measure for interrupting the image transmission upon loosening of the interchangeable head so that upon loosening of the interchangeable head the user is immediately informed of this circumstance before the interchangeable head is completely detached from the shaft of the endoscope. However, a comparable effect is also achieved when the positioning pins serve the purpose not of signal transmission, but the latter is performed via contacts at the coupling point, as was described previously.

In conjunction with the inventive refinement that the user is warned of a loosening of the interchangeable head by a degradation of the transmitted image, the previously mentioned positioning pins have the further advantage that the positioning pins can still maintain the connection between the interchangeable head and the shaft while the user is already being warned of the loosening of the interchangeable head. In other words, the user is already warned of a loosening of the interchangeable head, and of the risk of its falling off, while the interchangeable head is still held connected to the shaft of the endoscope via the positioning pins.

In a further preferred refinement, there is arranged between the interchangeable head and the distal end of the shaft at least one elastic element that upon loosening of the interchangeable head distances the latter from the distal end of the shaft.

Such an elastic element between the shaft and interchangeable head, for example a spring or an elastomer, has the effect that an enlarged spacing and thus the image impairment to be produced always result as the interchangeable head loosens. It is thereby possible advantageously to prevent possible loosening of the union nut between the interchangeable head and the distal end of the shaft, and to prevent the possibility that this cannot, however, be noticed through the possibly still close-fitting contact between the interchangeable head and the distal end of the shaft.

It is further preferred in this case when the distancing is limited to less than the length of the at least one positioning pin.

Owing to this measure, it is advantageously possible in conjunction with the antiloss safeguard to prevent the elastic element from knocking the interchangeable head completely off the distal end of the shaft in the event of loosening of the interchangeable objective, and the subsequent loss of the interchangeable head. The limitation can be implemented, for example, by a stop or by virtue of the fact that in the unstressed state the elastic element has a longitudinal extension that is smaller with reference to the distal end of the shaft than the length of the at least one positioning pin, such that the interchangeable head is still held on the shaft by the positioning pin.

In a further preferred refinement, at least one operating element is arranged in the interchangeable head.

With this refinement, in addition to the function of transmission of images and light, the interchangeable head can be assigned additional functions, for example the at least one operating element can acquire auxiliary functions for imaging, such as focusing, zoom, changing the direction of view, image rotation, active and passive sensor functions, for example for spacing, pressure, temperature, vibrations, surface hardness, ultrasound reflection, layer thickness, dielectric constant, magnetic permeability, refractive index, induced eddy currents, electromagnetic fields, radar, lidar, ionizing radiation, thermal capacity, electric and thermal conductivities, pH values, chemical substance concentrations, moisture content, fluorescence, deep optical backscattering, etc., as well as processing functions such as gripping, removing, grinding, drilling, sawing, water jet processing, sandblasting, blasting with gases, heating, cooling, laser processing, etc. “Operating element” is to be understood entirely generally in this sense.

It is preferred in this case when the at least one operating element can be connected to the distal end of the shaft by means of a plug.

This refinement is advantageous, in particular for operating elements that are dependent on an electric power supply, since then the power supply for the at least one operating element can also be disconnected and easily restored at the coupling point via the plug.

Further advantages emerge from the following description and the attached drawing.

It goes without saying that the abovementioned features, and those still to be explained below, can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1illustrates an optical instrument provided with the general reference numeral10. In the exemplary embodiment shown, the optical instrument10is an endoscope12, but the invention is not limited to such an instrument.

The endoscope12has an elongated shaft14. In the exemplary embodiment shown here, the shaft14is flexible in such a way that, apart from a straight course, the shaft14can also adopt a curved course, as is illustrated inFIG. 1by way of example.

The endoscope12is used as a technical endoscope in the inspection of machines, for example aircraft engines. The endoscope12can also be used for operating purposes in the field of minimally invasive surgery.

The endoscope12has an operating part16at the proximal end of the shaft14. Arranged at the proximal end of the operating part16is an eyepiece18that constitutes part of a transmission system, described in yet more detail later, of the endoscope12for the purpose of transmitting image information. Direct observation with the eye is possible through the eyepiece18, or a camera (not illustrated) can be connected to the eyepiece18, the camera then being connected to an image reproduction unit, for example a monitor, on which the area observed with the endoscope12is visually represented.

As in the case of flexible endoscopes, the endoscope12is usually fitted with a deflecting mechanism for deflecting a distal end19of the shaft14. The deflecting mechanism comprises a mechanism (not illustrated in more detail) that can be actuated via a first positioning wheel20and a second positioning wheel22on the operating part16.

The deflecting mechanism works in two independent deflecting directions, the first positioning wheel20and the second positioning wheel22each being assigned to one deflecting direction.

Furthermore, there is connected to the endoscope housing16a fiber-optics cable24that is connected to an external light source (not illustrated) for feeding illuminating light into the endoscope12.

An interchangeable head26is detachably connected at a coupling point30to the distal end19of the shaft14.

Details of the interchangeable head26and the coupling point30are illustrated inFIGS. 2 to 6.

The endoscope12further has a transmission system32for transmitting illuminating power, which is formed here from two fiber bundles34that extend in parallel from the distal end19of the shaft14through the shaft14and the fiber-optics cable24as far as the connector (not illustrated) for connecting the fiber-optics cable24to a light source (not illustrated). The transmission system32for transmitting illuminating power is therefore completely based in the present exemplary embodiment on the transmission of light waves.

The transmission system32likewise has two fiber bundles36that extend continuously through the interchangeable head26and, in the state of the interchangeable head26connected to the distal end19of the shaft14, cooperate with the fiber bundles34, that is to say pass through the coupling point30.

The endoscope12further has a transmission system38for transmitting image information that consists, here, of an ordered fiber bundle40that extends through the shaft14from the distal end19up to the proximal end of the endoscope housing16, that is to say up to the eyepiece18. In the present exemplary embodiment, the transmission system38is likewise based completely on the transmission of light waves.

The transmission system38further has an imaging optics42that is arranged in the interchangeable head26and, in the coupled state of the interchangeable head26, launches the image information into the ordered fiber bundle40of the shaft14.

The imaging optics42of the interchangeable head26consists of a series connection of various lenses that are illustrated inFIGS. 6a) and6b) by appropriately curved surfaces.

The ordered fiber bundle40of the shaft14is protected at its distal end with the aid of a plane-parallel cover glass44. The cover glass44does not have an optically imaging effect. The entire imaging optics42of the endoscope12is arranged in the interchangeable head26such that no image information is transmitted through the endoscope12with the interchangeable head26completely removed, as inFIGS. 2a) andb) andFIGS. 3 and 4.

However, in an alternative design that is not illustrated here, the imaging optics42can also be arranged partially in the interchangeable head26and partially in the shaft14, the part of the imaging optics42arranged in the shaft14then preferably being exchangeable.

Furthermore, the ordered fiber bundle40is coated with a protective sheath46.

Because of the complete arrangement of the imaging optics42in the interchangeable head26, whereas the shaft14does not have an optical imaging system of such type, the quality of the image information transmitted by the transmission system38is degraded as soon as the interchangeable head26is slightly loosened from the distal end19of the shaft14. This state is illustrated inFIG. 6a). In the case of an excessive slit formation, such as occurs inFIG. 6a), as a consequence of loosening of the interchangeable head26, the image sharpness that can be observed through the eyepiece18is greatly reduced, as a result of which the user of the endoscope12is made aware of a loosening of the interchangeable head26.

At the coupling point30, the interchangeable head26and the distal end19of the shaft14further have flat and preferably polished surfaces48(interchangeable head26) and50(distal end19of the shaft14).

As is illustrated inFIG. 6a), upon loosening of the interchangeable head26illuminating light35enters the ordered fiber bundle40of the transmission system38from the fiber bundles34by reflections at the surface48of the interchangeable head26, such that the user perceives a clearly brighter image given such a loosening of the interchangeable head26.

By contrast, given an interchangeable head26that is completely connected to the distal end19of the shaft14in a proper way, as is illustrated inFIG. 6b), no illuminating light leaks from the transmission system32into the transmission system38. A reduction in contrast of the image observed through the eyepiece18occurs, however, given an enlargement of the slit between the interchangeable head36and the distal end19as soon as the slit is enlarged beyond a critical minimum, and so the user is also warned by the turbidity or brightening of the image about a loosening of the interchangeable head26.

As already mentioned, the surfaces48and50are preferably polished flat.

Furthermore, the interchangeable head26is connected at the coupling point30to the distal end19of the shaft14via two positioning pins52and54that are fastened on the interchangeable head26, corresponding bores56and58being recessed in the distal end19of the shaft14.

In cooperation with the bores56and58, the positioning pins52and54serve, on the one hand, to position the interchangeable head26exactly relative to the distal end19of the shaft14so that the imaging optics42of the interchangeable head26cooperates exactly with the ordered fiber bundle40. This ensures an exact image alignment and image sharpness.

On the other hand, in cooperation with the bores56and58, the positioning pins52and54have the effect of securing the interchangeable head26on the shaft14in terms of rotation.

Even when loosening has already occurred, as illustrated inFIG. 6a), the positioning pins52and54still maintain a connection to the distal end19of the shaft14. As previously described, when the user is already warned about the loosening of the interchangeable head26by a degradation of the image quality, that is to say an occurrence of blurring and/or by turbidity or brightening of the image, although it is loose the interchangeable head26is still connected to the shaft14, and so the endoscope can still be withdrawn, together with the interchangeable head26, in good time from the observation area before the interchangeable head26becomes completely detached.

Finally, the interchangeable head26can be screwed (compareFIG. 6b) to the distal end19of the shaft14by means of a union nut60that is captively secured on the interchangeable head26and can be displaced on the interchangeable head26in the non-coupled state of the interchangeable head26(compareFIG. 2a) in which the union unit60can be displaced completely in the distal direction). In the screwed state of the interchangeable head26, moreover, the effect of the surfaces48and50lying flat on one another is to avoid ingress of dust and liquids and other contaminants into the coupling point30between the interchangeable head26and the shaft14.

Furthermore, there is arranged between the interchangeable head26and the distal end19of the shaft14an elastic element68that, upon loosening of the interchangeable head26, distances the latter from the distal end19of the shaft14. In the exemplary embodiment shown, the elastic element68is designed in the form of a small compression spring that is embedded, for example, in the distal end19of the shaft14. Upon loosening of the interchangeable head26, the elastic element68presses the interchangeable head26away from the distal end19of the shaft14as early as when the union nut60is loosened, the result of this being, in the event of loosening of the union nut60, to prevent the interchangeable head26from remaining in close contact with the distal end19of the shaft14, and to prevent the user from thereby not being able to establish any change in the image information. However, in order to prevent the elastic element68from undesirably completely repelling the interchangeable head26when the union nut60is completely detached, the spacing of the interchangeable head26by the elastic element68is limited to a length that is less than the length of the positioning pin52or54, such that even with the elastic element68completely unstressed a connection still exists between the interchangeable head26and the shaft14via the positioning pins52and54, with the result that it is possible at least to prevent the interchangeable head26from falling off.

In refinements that are not illustrated, the previously mentioned positioning pins52and54can also be used to transmit electric signal s or power, for example whenever the interchangeable head has an optoelectronic image pick-up (video image sensor) (compare also the subsequent exemplary embodiment in accordance withFIG. 7), it then being possible for the electric signal s to be transmitted correspondingly through the coupling point via at least one of the pins. In such a refinement, the electrically conducting connection between at least one of the positioning pins52or54and the corresponding bore56or58can be designed such that the transmission of signals is interrupted as early as during a loosening of the interchangeable head from the distal end of the shaft, as a result of which the image disappears and the user is thereby warned about the loosening.

Also illustrated inFIGS. 2a) andb) are two marks62and64that permit a coarse preliminary orientation of the interchangeable head26upon mounting of the latter on the shaft14, in order to facilitate the insertion of the positioning pins52and54into the bores56and58.

Furthermore, the positioning pins52and54can be removed from the interchangeable head26, and so they can easily be exchanged in the case of bending or some other form of damage.

Instead of the fiber bundle40in the shaft14, it is also possible to arrange behind the cover glass44in the region of the distal end19of the shaft14an electronic image pick-up (not illustrated) that is connected to a video monitor unit via a signal line leading in the proximal direction. In the case of such a variant, the imaging optics42is again arranged completely in the interchangeable head26or partially in the interchangeable head26and partially in the shaft14. Upon loosening of the interchangeable head26, the image pick-up is then no longer situated exactly in the image plane of the imaging optics42, as a result of which perceptibly modified image information is transmitted in the proximal direction.

Illustrated inFIG. 7as a further exemplary embodiment is an optical instrument, denoted by the general reference numeral70, in the region of a distal end72of its shaft74.

The optical instrument70is an endoscope, for example, the shaft74being rigid, for example.

This optical instrument70has a transmission system76for transmitting image information from distal to proximal ends, which has an optoeletronic image pick-up (video image sensor)78whose image information is conducted in the proximal direction in the form of electric signal s via electric signal lines80and82.

The optoelectronic image pick-up78, upstream of which an imaging optics83is connected, is not arranged in the shaft74of the instrument70, however, but in an interchangeable head84that can be removed from the shaft74. In the state of the interchangeable head84connected to the shaft74, the electric signal lines80and82pass through a coupling point86, the coupling point86being appropriately fitted with a plurality of contacts88on the interchangeable head side and shaft side.

The image pick-up78and the imaging optics83can also be designed as a complete camera unit.

Upon loosening of the interchangeable head84, the contacts88are correspondingly opened and the conduction of signals by the electric signal lines80and82is correspondingly interrupted as a result, and so no further image information can be transmitted in the proximal direction from the image pick-up78, and thus the image disappears for the observer.

The instrument70further has a transmission system90for transmitting illuminating power from proximal end to distal end, which is formed, in turn, by an optical waveguide92in the form of a fiber bundle that passes through the coupling point86in the state of the interchangeable head84connected to the shaft74.

Instead of an optically conducting transmission system for transmitting illuminating power, such a system can, however, also be based on an electric power line93that is interrupted in the region of the coupling point86in the case of a loosening of the interchangeable head84, there then being arranged in the interchangeable head84a light source94, for example in the form of an LED, which is correspondingly extinguished upon loosening of the interchangeable head84, the result being the occurrence of a perceptible darkening of the transmitted image.

Furthermore, provided, in turn, in the exemplary embodiment illustrated inFIG. 7are positioning pins96and98that engage in corresponding bores100and102in the interchangeable head84in order to ensure exact positioning of the interchangeable head84with reference to the distal end72of the shaft74, and thus ensure exact closure of the contacts88between the shaft74and the interchangeable head84.

Also provided, in turn, is an elastic element104that, upon loosening of the fastening element108in the anchorage110, distances the interchangeable head84such that the image information is noticeably modified by opening of at least one contact. The fastening element108is captively secured by a ring112.

The orientation of the surfaces of the coupling point86was selected arbitrarily in this exemplary embodiment.

A further optical instrument, in particular an endoscope, provided with the general reference numeral120is illustrated by a detail in the region of its distal end inFIG. 8. This exemplary embodiment can be implemented, in particular, in the case of the endoscope12inFIG. 1.

The instrument120has a shaft122, which is illustrated inFIG. 8only in the region of its distal end124.

The instrument120further has an interchangeable head126, which can be fastened through screwing by means of a union nut128on the distal end124of the shaft122. A coupling point between the interchangeable head126and the distal end124of the shaft122is denoted by129.

The instrument120has a first transmission system130for transmitting illuminating power in the distal direction, which system has an optical waveguide134arranged in the shaft and an optical waveguide136arranged in the interchangeable head.

The instrument120also has a second transmission system138, for transmitting image information in the proximal direction, which, like the first transmission system130, likewise passes through the coupling point129when the interchangeable head126is fastened on the shaft122. The transmission system138for transmitting image information has an image pick-up140, arranged in the interchangeable head126, in the form of a complete camera, in particular a miniaturized camera. The transmission system138also has an electric signal line141that leads in the proximal direction from the image pick-up140through the coupling point129when the interchangeable head126is fastened on the shaft122.

A total of three signal lines141are illustrated inFIG. 8, these being designed as a plug-in contact. For this purpose, the signal lines141have contact fingers142integrated in the interchangeable head126, and arranged at the distal end124of the shaft122are contact plugs144, of which there are a corresponding number and in which the contact fingers142engage upon connecting the interchangeable head126to the distal end124of the shaft122.

The instrument120further has a channel148through which, for example, a gas or a liquid can be conducted from the proximal to the distal ends. The interchangeable head126has an operating element150that is designed as a nozzle152that is arranged at the distal end of a channel154constructed in the interchangeable head126. In this arrangement, the channel154is aligned with the channel148when the interchangeable head126is connected to the shaft122. The nozzle152can serve the purpose, for example, of directing the fluid, fed through the channel148and further through the channel154, onto the end of the image pick-up140on the light entry side, in order, for example, to keep this end free from contaminants. Furthermore, there is provided on the interchangeable head126an elastic element156that can serve, for example, as in the previous exemplary embodiment to distance the interchangeable head126from the distal end124of the shaft122when the union nut128is loosened or becomes loose.

Illustrated inFIG. 9is a further exemplary embodiment of an optical instrument160, which is described below only with reference to the differences from the instrument120.

An interchangeable head162of the instrument160has an operating element164that is, for example, a processing tool166with a motor168. The processing tool166is, for example, a drill, milling cutter, grinder or the like. Provided at a coupling point170between the interchangeable head162and a distal end172of a shaft174of the instrument160for the purpose of supplying electric power to the operating element164are plug-in contacts that have contact fingers176, arranged on the interchangeable head162, and contact plugs178that are arranged at the distal end172of the shaft174and in which the contact fingers176engage upon fastening the interchangeable head162on the shaft174.

In this exemplary embodiment, the interchangeable head162therefore takes over not only the function of image transmission and illumination, but also the function of a processing instrument, which is fully integrated in the interchangeable head162.

Illustrated inFIG. 10is an exemplary embodiment, modified slightly by comparison withFIG. 9, of an instrument160′, which does not differ from the instrument160with regard to the shaft174, but merely with regard to an interchangeable head180which, instead of the processing tool166with motor168, has as operating element182a light source184, for example a UV light-emitting diode, for carrying out inspections with fluorescent light. As emerges fromFIG. 10, for the purpose of supplying electric power, the operating element182has contact fingers186that are advantageously compatible with the contact plugs178of the shaft174such that the interchangeable head180can be fastened on the same shaft174as the interchangeable head162.

A further interchangeable head188, compatible with the shaft174, is illustrated inFIG. 11, and together these correspondingly form an instrument160″.

As operating element190, the interchangeable head188has a sensor192that is, for example, capable of detecting physical or chemical states. It is also illustrated inFIG. 11how the plug-in contacts are joined in the state when the interchangeable head188is fastened on the shaft174.

Illustrated inFIG. 12is a further instrument, which is provided with the general reference numeral200and has a shaft202and an interchangeable head204that differs from the preceding exemplary embodiments in that a transmission system206for transmitting image information in the proximal direction has two image pick-ups208and210, which are both arranged in the interchangeable head204. Both image pick-ups208and210are, in turn, preferably designed as complete miniaturized cameras.

Whereas, in the case of the exemplary embodiment illustrated inFIG. 12, both image pick-ups208and210are arranged in the interchangeable head204in parallel alignment relative to one another in a configuration for looking straight ahead, inFIG. 13the image pick-up210′ is not aligned parallel to the other image pick-up208′, but looking at it in an inclined fashion, in an exemplary embodiment200′ modified slightly by comparison with the instrument200.

The signal lines for the image pick-ups208,210or208′ and210′ are correspondingly designed as plug-in contacts that permit the interchangeable heads204and204′ to be handled easily when being exchanged.

In the case of the exemplary embodiments illustrated inFIGS. 12 and 13, as well, there is the advantageous possibility of providing only one and the same shaft202, while the interchangeable heads204and204′ can be fastened on the shaft202such that they can be exchanged for one another, because the plug-in contacts for connecting the corresponding signal line are of universal configuration.

In the case of the exemplary embodiments illustrated inFIGS. 8 to 13, it is possible, if appropriate, to notice a loosening of the respective interchangeable head by a degradation of the image quality, as with the previous exemplary embodiment.