Patent Description:
Endoscopes are well known devices for visually inspecting inaccessible places such as human body cavities. Typically, as inter alia disclosed in <CIT>, the endoscope comprises an elongated insertion cord with a handle at the proximal end as seen from the operator and visual inspections means, such as a built-in camera, i.e. an optical assembly adapted to focus incident light onto an image sensor, at the distal end of the elongated insertion cord. Electrical wiring for the image sensor and other electronics such as LED lighting run along the inside of the elongated insertion cord from the handle to the tip at the distal end. In modern endoscopes the image sensor is typically an electronic image sensor allowing the captured images to be processed and displayed on a display unit to which the endoscope is, in use, connected.

<CIT> discloses an optical assembly for a disposable endoscope. It deals, however, almost exclusively with the details of the optical assembly. The optical assembly is accommodated in an image sensor insert which also accommodates the image sensor. Details of the image sensor and how it is accommodated are not given. The lenses and spacers are arranged in a single lens barrel and may be secured there by means of subsequent deformation of the lens barrel which may potentially induce misalignment. Moreover, being separate from the imaging sensor it necessitates further elements such as the image sensor insert, where further misalignment could be introduced.

<CIT> discloses a lens barrel adapted for stability and durability in severe conditions, such as high and low climatic temperatures and rapid temperature changes, thermal shock. It is therefore made of ceramic in combination with glass lenses. Only the barrel itself is dealt with. Details of the apparatus where it may be implemented and how, e.g. relation to an image sensor, are not given.

Based on this background it is the object of the present disclosure to provide an endoscope with a new and improved optical assembly that renders itself for simple manufacturing and facilitates the easy assembly of the endoscope, and so keeps the costs down to allow the use as a disposable endoscope.

According to the present invention as defined in claim <NUM>, this object is achieved by an endoscope comprising a handle at the proximal end, an insertion cord connected to the handle, and a tip part at the distal end of the insertion cord, said tip part comprising an optical assembly accommodating a lens stack, said lens stack comprising a number of lenses and a number of spacers in fixed relationship with each other inner through passage with an inwardly extending ledge adapted to engage said lens stack and being surrounded by a first circumferential wall part having a circumference adapted to receive and support said lens stack and having a first predetermined height above said inwardly extending ledge in said axial direction, and said second lens barrel part comprising a inner through passage adapted to engage said lens stack and being surrounded by an second circumferential wall part having a circumference adapted to receive said first circumferential wall part and having a second predetermined height above said inwardly extending ledge in said axial direction, wherein said distance is longer than said predetermined height of said first circumferential wall part so that each of said inwardly extending ledges abut one of either first or second abutment surfaces, and wherein an image sensor is accommodated at least partially in said second lens barrel part.

By providing a two-part lens barrel in this way it becomes possible to easily align, assemble, and secure the lenses and the interposed spacers in a desired mutual relation ensuring good imaging properties of the optical assembly. In particular, having the inner surface of the second lens barrel part adapted to receive and accommodate at least partially said outer circumferential surface of said first lens barrel part allow these two parts to mutually align, and hence the ledge of the second lens barrel part to press equally on the lens stack on the element thereof that it abuts, thus also ensuring alignment of the lenses and spacers of the lens stack. A lens stack with an aligned image sensor may thus be provided, thereby obviating the need of subsequent alignment of the two parts during the assembly of the endoscope. Furthermore the overall alignment is facilitated as it allows the second lens barrel part, already aligned with the first lens barrel part and the lens stack to also be aligned with the image sensor.

According to an embodiment said first and second parts are secured in mutual engagement, in particular by means of an adhesive. Because the adhesive may be applied from the exterior of the optical assembly to the outer surface of the first lens barrel part where it meets the second lens barrel part, the adhesive is kept far away from the lenses of the lens stack with no risk of contaminating the surfaces thereof and deteriorating the optical properties of the optical assembly. Even if by capillary effect or the like the glue enters into any gap between the first and the second lens barrel parts, this is far away from the lenses and involves no risk of contaminating them.

According to an embodiment said first circumferential wall part comprises a smooth external surface matching a smooth internal surface of said second circumferential wall part. Matching smooth inner and outer surfaces allows easy insertion of the first lens barrel part into the second lens barrel part during assembly, while keeping the manufacturing of the parts by e.g. injection moulding simple.

According to an embodiment the first lens barrel part is made from a plastic material. Plastic materials are low cost and thus suitable for disposable endoscopes. Moreover, manufacturing of parts in plastic by e.g. injection moulding is as also cost efficient and contributes to keeping the costs down.

According to an embodiment the first lens barrel part is made from an opaque material. Using an opaque material will allow blocking and/or absorption of undesired light, e.g. stray light that could reach the image sensor and disturb the captured image.

According to an embodiment the second lens barrel part is made of a plastic material. Plastic materials are low cost and thus suitable for disposable endoscopes. Moreover, manufacturing of parts in plastic by e.g. injection moulding is as also cost efficient and contributes to keeping the costs down.

According to an embodiment one more or all of the lenses are made from a plastic material. Along the lines of the above plastic is also suitable for as many lenses as possible, but it can be envisaged that certain lenses may require material with optical properties not fulfilled by available plastic materials.

According to an embodiment the lens is integral with the first lens barrel part. This ensures the correct alignment of in particular the optical axis of the first lens element of the stack.

Furthermore, this is advantageous in the manufacturing because it allows for the further preferred embodiment, where the lens and the first lens barrel part are integrally formed in a two-stage two-component injection moulding process.

According to an embodiment the object is achieved by a system comprising a display unit and an endoscope according to claim <NUM>.

The disclosure will now be made in greater detail based non-limiting exemplary embodiments and with reference to the drawings, on which.

Turning first to <FIG>, a system according to the the present invention is shown. The system comprises a display unit <NUM>, such as a monitor with a screen, and an endoscope <NUM> connectable thereto via a wireless connection or a cable <NUM>, as shown. The endoscope <NUM> is preferably a forward looking, disposable, i.e. single use, endoscope that is to be discarded after use in a patient, rather than cleaned, sterilized and reused. The endoscope <NUM> comprises a handle <NUM> at the proximal end adapted to be gripped by the hand of an operator, and a bendable insertion cord <NUM> extending towards the distal end of the endoscope <NUM> and adapted to be inserted into a patient. At the distal end of the insertion cord the endoscope comprises a tip part connected to the remainder of the insertion cord, i.e. a main tube part, via an articulated bending section <NUM>. The articulated bending section <NUM> is highly bendable as compared to the main tube part. The bending motion of the bending section is controlled by the user using an operating member <NUM> such as knob or a lever via control cables (not visible) connected to the tip part or the distal end of the bending section <NUM>. The bending section <NUM> comprises a thin covering sheath, and the inner details are thus not visible in <FIG>.

The tip part comprises illumination means such as LEDs (not visible) in order to provide light for an optical image capturing system. The optical image capturing system comprises an optical assembly <NUM> as illustrated in cross-section in <FIG> and <FIG>. <FIG> shows the assembled state of a first embodiment and <FIG> is an exploded view of the first embodiment for better identification of the various parts.

The optical assembly <NUM> comprises a lens stack <NUM>. The lens stack <NUM> in the illustrated embodiment comprises three lenses arranged in an axial direction along a common central axis A, viz. a first lens <NUM>, a second lens <NUM> and a third lens <NUM>, separated by a first spacer <NUM> and a second spacer <NUM>. One, more or preferably all of these lenses <NUM>, <NUM>, <NUM> are made of a plastic material, with suitable transparency, refractive index and other optical properties. Preferably the same transparent material would be used for all lenses <NUM>, <NUM>, <NUM>. Other embodiments of the optical assembly <NUM> may have other numbers of lenses and consequently other numbers of spacers, in particular further lenses and more spacers, but evidently one less of each would also be possible. Such further lenses could preferably also be made of a plastic material, e.g. the same transparent material could be used those for lenses too. Lens <NUM> is the most distal lens of the optical assembly <NUM> when mounted in the tip of the forward-looking endoscope <NUM>. As can be seen lens <NUM> comprises a plano concave lens part surrounded by an integral flange <NUM>, which is preferably annular, i.e. surrounds the plano concave lens part entirely. In the first embodiment of the optical assembly <NUM>, the plane surface <NUM> of the plano concave lens part faces exterior of the optical assembly <NUM>. The surrounding flange <NUM> comprises an abutment surface <NUM> adapted to engage an inwardly extending ledge part <NUM> of the interior end surface of a first lens barrel part <NUM>. The first lens barrel part <NUM> is essentially tubular and comprises a central passage <NUM> allowing light to pass the length thereof. The first lens barrel part <NUM> is preferably made of an opaque material blocking and/or absorbing undesired stray light. The opaque material may, in particular, be an opaque plastic material, allowing the first lens barrel part <NUM> to be manufactured by injection moulding. Preferably, in the assembled state the abutment surface <NUM> integral flange <NUM> of the lens <NUM> is pressed into contact with the ledge part <NUM> provided by the interior end surface of the first lens barrel part <NUM> in a sealing manner. However, it can be envisaged that the lens <NUM> is instead provided integrally with the first lens barrel part <NUM>, e.g. by moulding both integrally in a two-stage two-component injection moulding process. This would further ensure alignment, as the lens <NUM> would then not be able to be inserted incorrectly, dislodge, or to be displaced with respect to the first lens barrel part <NUM> during assembly of the optical assembly <NUM>. Also sealing of the essentially tubular first lens barrel part <NUM> at the distal end would be guaranteed. As can be seen the central lens part of the plano concave lens <NUM> is accommodated in an aperture <NUM> in the first lens barrel part <NUM>. The aperture <NUM> is preferably circular and matches the diameter of the preferably also circular plano concave central lens part of the lens <NUM>. The dimensions are preferably so that the plane surface <NUM> lies flush with the external end surface <NUM> of the first lens barrel part <NUM>. This allows the plano concave lens <NUM> to provide a front window of the endoscope imaging system which, when in direct contact with the environment, is not prone to pick up contaminants, that might block or interfere with the vision. Evidently, other lens types for this lens as well as the other lenses to be described could be chosen, depending on the optical imaging properties desired.

Below the plano concave lens <NUM>, in the stack in the orientation of the stack <NUM> illustrated in <FIG>, or in other words more proximal to the handle <NUM> of the endoscope <NUM>, is a first spacer <NUM>. The first spacer <NUM> is preferably an annular member with an outer diameter corresponding to the inner dimension of the first lens barrel part <NUM>. A circumferential wall part <NUM> extends at a predetermined height h<NUM> from the ledge <NUM> (downwardly in the orientation shown in the figures). The circumferential wall part <NUM> of the first lens barrel <NUM> part is preferably cylindrical, at least over a majority of the length of the interior thereof, so as to form an outer circumferential surface adapted to guide and align the lens stack <NUM> once inserted during manufacture. The circumferential wall part <NUM>, or at least the inner surface thereof is adapted in circumference to the lenses and spacers of the lens stack <NUM> so that they are surrounded in a manner supporting them. Accordingly, the inner dimension of the first lens barrel part <NUM> is a diameter and the first spacer <NUM> has a circular circumference. The central aperture of the first spacer <NUM> can have any suitable shape and dimension. The preferred shape, however, is circular, with a diameter suitable to fulfil the needs for depth of focus and amount of light captured. The first spacer <NUM> as illustrated has plane upper and lower surfaces ensuring a good abutment with the first lens <NUM> and a second lens <NUM> accommodated below it and spaced apart from the first lens by the first spacer <NUM>. The distance between the two surfaces evidently also allows room for convexities of the lenses. The cross-section of the annular body of the first spacer <NUM> is preferably rectangular as illustrated, but suitable other shapes such as trapezes or ovals could be used instead.

The second lens <NUM> is in the illustrated embodiment plano convex, but could have any suitable shape giving the optical properties desired. Like the first lens <NUM> it comprises a central optically active part <NUM>, i.e. refractive, and a circumferential flange part <NUM> for abutting the first spacer <NUM> and a second spacer <NUM>. The second spacer <NUM> is preferably also an annular member with an outer circumference corresponding to the inner diameter of the cylindrical inner circumferential wall part <NUM> of the lens barrel <NUM>. The central aperture of the second spacer <NUM> can have any suitable shape and dimension. Preferred however it is also circular, with a diameter suitable to fulfil the needs for depth of focus and amount of light captured. The second spacer as illustrated has also plane upper and lower surfaces ensuring a good abutment with the second lens <NUM> and a third lens <NUM> accommodated below it and spaced apart from the second lens <NUM> by the second spacer <NUM>. The cross-section of the annular body of the second spacer <NUM> is preferably the shape of an asymmetric trapeze as illustrated, but suitable other shapes such as squares, rectangles or ovals could be used instead.

The third lens <NUM> comprises the lowermost lens in the lens stack in the illustrated orientation, or with respect to the endoscope <NUM> the most proximal to the handle <NUM>. The third lens <NUM> is in the illustrated embodiment also plano convex, but could have any suitable shape giving the optical properties desired. Like the first and second lenses <NUM>, <NUM>, the third lens <NUM> comprises a central optically active part <NUM>, i.e. refractive, and a circumferential flange part <NUM> for abutting the second spacer <NUM> and with an abutment surface <NUM> on the other side adapted for engaging a ledge part <NUM> a second lens barrel part <NUM>.

As can be seen the second lens barrel part <NUM> also comprises a tubular member with an inner surface <NUM> defining a central passage <NUM> allowing light to pass the length thereof. Similar to the first lens barrel part <NUM>, the second lends barrel part <NUM> may be made of an opaque material blocking and/or absorbing any undesired stray light. The opaque material is preferably an opaque plastic material, allowing also the second lens barrel part <NUM> to be manufactured by injection moulding.

The upper part of the second lens barrel part <NUM> comprises a second circumferential wall part <NUM> with an inner surface <NUM> as illustrated comprises a cylindrical bore section <NUM> adapted to the external dimensions of the outer surface <NUM> of the first lens barrel part <NUM>, so that during assembly the first lens barrel part <NUM> may, at least partially, be inserted into the cylindrical bore section <NUM> towards the ledge part <NUM> extending inwardly into the central passage <NUM>. The ledge part <NUM> may be an inwardly projecting circumferential rib, as shown, or may be a number of circumferentially spaced protrusions. The second circumferential wall part <NUM> has a height h<NUM> above the ledge <NUM>. The dimensions are so selected that when the stack of lenses <NUM>, <NUM>, <NUM> and the spacers <NUM>, <NUM> are pressed together between the first lens barrel part <NUM> and the second lends barrel part <NUM>, the end face <NUM> of the first lens barrel part <NUM> does not abut the ledge part <NUM>. Instead a gap <NUM> is left end face <NUM> and the ledge <NUM> to take up manufacturing tolerances and ensure that the lenses <NUM>, <NUM>, <NUM> and the spacers <NUM>, <NUM> are properly aligned axially. By suitable selection of dimensions of the outer surface <NUM> and the inner surface <NUM>, the inserted first lens barrel part <NUM> may be held firmly in place in the cylindrical bore section <NUM> of the second lens barrel part <NUM> by friction and the elastic forces between the two parts. Being both preferably made of plastic materials, this is much easier to achieve as compared to the ceramic materials used in <CIT> which in comparison to plastic materials are rigid, brittle and abrasive. Alternatively or additionally, an adhesive may be poured or migrate by capillary action into any gap between the outer surface <NUM> and the inner surface <NUM> to mutually secure them. Since this can be done from the exterior of the assembled parts, no risk of contaminating the lenses <NUM>, <NUM>, <NUM> by the adhesive and deteriorating the optical properties. To facilitate the insertion the outer rim <NUM> of at the end face <NUM> of the first lens barrel part <NUM> and/or the inner rim <NUM> of the second lens barrel part <NUM> may be chamfered. Apart from that their respective surfaces are preferably smooth in order to allow easy sliding insertion one into the other during assembly. This from a manufacturing perspective is much simpler than e.g. providing the surfaces of the parts with matching threads and screwing them together.

By proper selection of dimensions and materials, the elements of the lens stack <NUM> may be held in firm engagement with each other clamped between the interior end surface of the first lens barrel part <NUM> and the ledge part <NUM> of the second lens barrel part, thus ensuring their fixation in proper alignment along the axis A, both mutually and with the lens barrels parts <NUM>, <NUM>, providing the two-part housing of the optical assembly <NUM>. That is to say, the axial length d between the abutment surface <NUM> at the distal end of the lens stack <NUM> and the abutment surface <NUM> at the proximal end is longer than the height h<NUM> of the circumferential wall part <NUM> above the respective ledge <NUM>. It is also to say that the outer circumference of the lenses <NUM>, <NUM>, <NUM> and spacers <NUM>, <NUM> match the inner circumference of the first lens barrel part <NUM>.

Below the ledge <NUM> in the orientation of the optical assembly as illustrated in <FIG>, i.e. end most proximal to the handle of the forward-looking endoscope of <FIG>, the central passage <NUM> may be adapted to accommodate an image sensor <NUM>. This may be using a, preferably cylindrical, bore section <NUM> ensuring the alignment. Though not shown, such a bore section may comprise shoulders protrusions or ledges for the image sensor <NUM> to abut and rest on. The image sensor <NUM> may be held in place by means of adhesive og locking means may be incorporated in the bore section <NUM> of the inner surface <NUM>. To facilitate the insertion into the bore section <NUM> the inner rim <NUM> may be chamfered.

Turning now to <FIG> a cross-section of an alternative embodiment of the optical assembly <NUM> is shown where the internal lens barrel part, i.e. the first lens barrel part <NUM> is proximal rather than distal and the second lens barrel part <NUM> is distal. Apart from this reversal, the clamping principle according to the disclosure remains the same. It will be understood that in this embodiment, the first lens barrel part <NUM> is adapted to receive the image sensor <NUM>, and may in that respect exhibit the same features as the second lens barrel part <NUM> of the first embodiment.

In both embodiments the two lens barrel parts <NUM>, <NUM> may be assembled by sliding the first lens barrel part <NUM> into the second lens barrel part <NUM>, thereby clamping the lens stack <NUM> in the desired position and alignment. In this pressed-together state the whole optical assembly <NUM> may be held together by friction or, preferably, by an adhesive inserted remotely from the lenses <NUM>, <NUM>, <NUM>, which are largely protected within the central bore of the first lens barrel part <NUM>.

Once assembled and preferably tested, the optical assembly <NUM> may be mounted in the tip of the endoscope <NUM>. In this respect, it should be noted that even though the above description has referred to a forward-looking endoscope <NUM>, it is not excluded that endoscope in which the optical assembly is mounted is a sideways looking endoscope, e.g. a duodenoscope.

Claim 1:
An endoscope comprising a handle at the proximal end, an insertion cord connected to the handle, and a tip part at the distal end of the insertion cord, said tip part comprising an optical assembly accommodating a lens stack, said lens stack comprising a number of lenses and a number of spacers arranged in fixed relationship with each other in an axial direction to transmit incident light onto an image sensor, said lens stack comprising a first abutment surface and a second abutment surface arranged at a distance from said first abutment surface in said axial direction,
wherein said optical assembly comprises a two-part lens barrel, said two-part lens barrel comprising first lens barrel part and a second lens barrel part,
said first lens barrel part comprising an essentially tubular body having an inner through passage with an inwardly extending ledge adapted to engage said lens stack and being surrounded by a first circumferential wall part having a circumference adapted to receive and support said lens stack and having a first predetermined height above said inwardly extending ledge in said axial direction, and
said second lens barrel part comprising an inner through passage adapted to engage said lens stack and being surrounded by a second circumferential wall part having a circumference adapted to receive said first circumferential wall part and having a second predetermined height above said inwardly extending ledge in said axial direction,
wherein said distance is longer than said predetermined height of said first circumferential wall part so that each of said inwardly extending ledges abut one of either first or second abutment surfaces, and
wherein the image sensor is accommodated at least partially in said second lens barrel part.