WO1996041225A1

WO1996041225A1 - Rotatable fibre optic joint

Info

Publication number: WO1996041225A1
Application number: PCT/US1996/008821
Authority: WO
Inventors: Paul V. Lucey; Roger D. Greeley
Original assignee: Smith & Nephew, Inc.
Priority date: 1995-06-07
Filing date: 1996-06-05
Publication date: 1996-12-19
Also published as: AU6151596A; US5621830A

Abstract

An endoscope (10) includes an insertion member (12) rotatably mounted to a handle (14). A first set of optical fibers (20) carried by the handle meets a second set of optical fibers (40) disposed within the insertion member at a joint (30) constructed to allow relative rotation between the sets of optical fibers (20, 40) about the longitudinal axis of the insertion member.

Description

ROTATABLE FIBRE OPTIC JOINT

This invention relates to endoscopes which use optical fibres to provide iliumination.

Endoscopes are widely used to inspect regions of the body (e.g., joint spaces) through a small puncture wound. Typically, the endoscope includes an elongated insertion tube equipped with a set of optical fibres which extend from a proximal handle, through the insertion tube to the distal viewing tip of the endoscope. A cable that rigidly attaches to the handle (e.g., at a post on the side of the handle) carries light from an external light source to the proximal end of the optical fibres, and the light is transmitted through the optical fibres to the distal viewing end, where the light is emitted to illuminate the region under inspection.

Received light representing an optical image of the body region is collected by a lens assembly mounted in the distal viewing end and is passed to, e.g., a solid-state image pickup device (such as a charge-coupled-device, or CCD). The CCD converts the received optical image to electrical signals that are processed for viewing on a display.

Some endoscopes have a direction of view (i.e., the direction along which the endoscope emits and receives light) along the longitudinal axis of the insertion tube. The distal viewing ends of other endoscopes are constructed to provide an off-axis direction of view (e.g., at 30* or at 70"). The insertion tube of the latter type of endoscope is often rotatable with respect to the handle to allow the user to view different areas without requiring that the entire endoscope be rotated. However, although the insertion tube may be rotatable with respect to the handle, the optical fibres, by virtue of extending from the handle through the insertion tube to the distal viewing tip, are not. Rotating the insertion tube can cause the optical fibres to become twisted or wrapped around the handle, decreasing the maneuverability of the endoscope and risking damage to the optical fibres. It is an object of the present invention to overcome the problem outlined above.

Accordingly, there is provided an apparatus comprising: a first set of optical fibres having at least a portion extending along a longitudinal axis; a second set of optical fibres having at least a portion extending along said longitudinal axis; and a joint between said portions of said first set of optical fibres and said second set of optical fibres constructed to allow relative rotation between said portion about said longitudinal axis.

This invention features a rotatable joint between sets of optical fibres. The invention is particularly, but by no means exclusively, useful in an endoscope having an insertion tube rotatably mounted to the endoscope handle. In this case, one set of optical fibres may be carried by the insertion tube, with another set of optical fibres being disposed in the handle.

The rotatable joint between the sets of optical fibres allows the insertion tube to be rotated (e.g., to change the viewing angle of the endoscope) without also rotating either the optical fibres in the handle or an external fibre optic cable that connects the handle to a light source. The fibre optic cable thus remains stationary and does not become twisted or wrapped around the handle when the insertion tube is rotated. The maneuverability of he endoscope is enhanced and the risk of damaging the fibre optic cable (and its associated connectors) is reduced substantially.

In one aspect of the invention, a portion of each of the first and second sets of optical fibres extends along a longitudinal axis, and the joint is constructed to allow relative rotation between the sets of optical fibres about the longitudinal axis.

Preferred embodiments comprise the foiiowing features.

The ends of the first and second sets of optical fibres may be spring-biased together. This improves light transmission efficiency by reducing the spacing between the ends as much as possible.

Light transfer efficiency at the joint may be further enhanced by a light transmitting substance, such as an immersion oil, placed between the ends of the respective sets of fibres. Preferably, the substance has an index of refraction substantially equal to that of at least one of sets of optical fibres. The substance also lubricates the joint. The joint is sealed to avoid leakage of the substance.

Another aspect of the invention features an endoscope, equipped with the rotatable joint.

Preferred embodiments comprise the following features. The endoscope comprises an insertion member rotatably mounted to a handle. The handle and insertion member cany the first and second set of optical fibres, respectively. Individual fibres of the first and second sets of optical fibres are arranged in first and second annular rings, respectively. These annular rings are adjacent to one another, are centered about the longitudinal axis, and are spring- biased together. The width ofthe first annular ring is greater than the width of the second annular ring, thereby maintaining efficient light transfer even if the rings become misaligned.

The endoscope also comprises an optical element and an image detector mounted in the distal end of the insertion tube. Preferably, the optical element (which includes at least one lens) is configured to provide a direction of view at a nonzero angle with respect to the longitudinal axis. The image detector is a solid-state image pickup device, such as a CCD.

Other features and advantages ofthe invention will become apparent from the following detailed description, and from the claims.

Fig. 1 is a diagrammatic view of an endoscope equipped with a rotatable joint between sets of optical fibres in the handle and in the insertion tube of the endoscope.

Fig. 2 is a cross-sectional view ofthe endoscope of Fig. 1.

Fig. 3 shows one ofthe components ofthe rotatable joint in detail.

Fig. 4 is a cross-section of a portion of the component of Fig. 3, taken along line 4-4. Fig. 5 is an enlarged cross-sectional view of he rotatable joint.

Fig. 6 is an enlarged cross-sectional view ofthe insertion tube of the endoscope of Fig. 1 and of another component of the rotatable joint.

Fig. 7 is a cross-section of a portion ofthe component of Fig.

6, taken along line 7-7.

Fig. 8 is a cross-section, taken along line 8-8 of Fig, 6, showing the distal viewing tip ofthe endoscope. Fig. 9 illustrates the actuator of the rotatable joint.

Referring to Fig. 1 , endoscope 10, suitable for viewing into a body cavity, joint space, or passageway during arthroscopic surgery, includes an elongated insertion tube 12 rotatably mounted to handle 14. Actuator 16, which is also rotatably mounted to handle 14, is manipulated by a user to rotate insertion tube 12 about a longitudinal axis 18 to rotatably orient insertion tube 12 with respect to an area to be viewed, e.g., area A or area B.

External light source 1 provides the light used to illuminate areas A and B via a light cable connected to a proximal surface 5 of handle 14 at coupler 4. A first set 20 of optical fibres, extending through handle 14 from light coupler 4 to joint 30 (shown schematically), transmits light received from source 1 to a second set 40 of optical fibres, which meet optical fibre set 20 at joint 30. The optical fibres in set 40 extend from joint 30 through insertion tube 12 to distal viewing tip 41, to transmit light out distal viewing tip 41 to area A or area B. The construction and operation of joint 30 are described in detail below. Suffice it here to say that joint 30 enables relative rotation between optical fibre sets 20. 40 about axis 18 when insertion member 12 is rotated with respect to handle 14 by actuator 16, while also providing efficient light transmission between them.

Endoscope 10 has an off-axis direction of view, i.e., a direction of view oriented at a nonzero angle with respect to longitudinal axis 18. The direction of view is determined by the orientation of a lens assembly 50 (Fig. 2) at distal viewing tip 41 (i.e., the angle formed between longitudinal axis 18 and a vector 21 that is perpendicular to the lens at distal viewing tip 41) and is typically 30°, 45", or 70". The field of view, angle Q, is an angle within which the endoscope receives light from external objects, i.e., the angle over which the endoscope "sees," and is equidistant on either side of vector 21.

Endoscope 10 illuminates (and views, as described below) area A when insertion tube is oriented as shown in Fig. 1. To illuminate and view another area, e.g., area B. a user rotates actuator 16, which rotates insertion tube 12 with respect to handle 14 about longitudinal axis 18, to orient distal viewing tip 41 to view area B along vector 21' (shown in dashed lines). Rotatable joint 30 allows set 20 of optical fibres and external cable 2 to remain stationary when insertion tube 12 is rotated. As a result, cable 2 does not become twisted or wound about handle 14 when insertion tube is rotated. This makes endoscope 10 easier to use and manipulate in the body. Moreover, the stresses imposed on optical fibre set 20 and cable 2 are significantly reduced, particularly at light coupler 4, which increases reliability and operating lifetime.

Referring to Fig. 2, light from objects illuminated by endoscope 10 is collected by lens assembly 50 mounted in distal viewing tip and passed to a charge-coupled-device (CCD) 52 or other suitable image detector supported proximal ly to lens assembly 50 at the distal end of a CCD tube 54. CCD 52 converts the light into electrical signals representing an image of the objects. The electrical signals are transmitted (by wiring which extends through CCD tube 54 and through handle 14) to a camera control unit 6 for processing in the usual manner. The resultant image is displayed on display screen 8 (Fig. 1).

CCD 52, including its associated electrical and optical systems, are of the type described in detail in copending U.S. patent application serial number 07/958,688. filed October 9, 1992, incorporated herein by reference. In particular, as described in the '668 application, upon manipulation of a focusing mechanism by a user, CCD tube 54 and CCD 52 are moved axially along longitudinal axis 18 with respect to lens assembly 50. This motion changes the spacing between lens assembly 50 and CCD 52, thereby adjusting the focus of the image.

Referring also to Figs. 3-6, rotatable joint 30 will be described in detail. At joint 30, the individual optical fibres of sets 20, 40 are arranged in a pair of annular fibre rings 26, 46, each of which surrounds CCD tube 54, is centered about longitudinal axis 18. and extends for a short distance along longitudinal axis 18. Annular fibre rings 26, 46 abut each other at joint 30 for efficient light transmission therebetween, and are mounted within handle 14 for relative rotation, as will be described.

Figs. 3 and 4 show the construction of set 20 of optical fibres and a stationary annulus 22 that defines annular fibre ring 26. Sheath 56 carries optical fibre set 20 from light coupler 4 to joint 30. At joint 30, the distal ends of individual glass fibres 19 of set 20 are removed from sheath 56 and are arranged evenly around the exterior surface of an inner ring 23. A slightly larger, outer ring 24 surrounds inner ring 23 and captures fibres 9 therebetween. Inner and outer rings 23, 24 each extend along longitudinal axis 18 and are sized such that individual optical fibres 19 are densely arranged between inner ring 23 and outer ring 24. Fibres 19 are epoxied in place between rings 23, 24 and are cut off at the face 28 of rings 23, 24. The ends of optical fibres 19 are polished flat to form annular fibre ring 26.

Refemng as well to Figs. 6-7, annular fibre ring 46 likewise is formed by securing the proximal ends of individual optical fibres 39 of set 40 between an elongated inner ring 43 and an elongated outer ring 44, which together form a rotatable annulus 42. Optical fibres 39 are arranged evenly around the exterior of ring 43, and are surrounded by outer ring 44 to form annular ring 46 of optical fibres at a face 48 of rings 43, 44. Inner and outer rings 43, 44 are sized such that individual optical fibres 39 are densely arranged therebetween for maximum light transfer. Individual optical fibres 39 of optical fibres 40 are secured between inner and outer rings 43, 44 by, for example, an epoxy, and are also arranged such that at ring face 48, the individual optical fibres are parallel to longitudinal axis

18 and are polished flat at the ends, for efficient light transmission.

Individual fibres 39 extend from the distal end of rotating annulus 42 and are gathered within a channel 58 in insertion tube 12. Channel 58 carries optical fibres 39 from joint 30 to distal viewing tip 41.

Referring in particular to Figs. 4 and 7, annular fibre rings 26, 46 are each centered about longitudinal axis 18 and are in radial alignment. The radial thickness 27 of annular fibre ring 26 is, however, greater than the radial thickness 47 of annular fibre ring 46. For example, radial thickness 27 is 0.3 mm, while radial thickness 47 is 0.2 mm (and as a result, fibre ring 26 extends 0.05 mm radially inwardly and outwardly of fibre ring 46). (The individual optical fibres 19, 39 are each about 2.0 mil in diameter.)

Referring to Fig. 5, annuli 22, 42 are each disposed over a sleeve 60 within handle 14 (CCD tube 54 passes through sleeve 60) so that faces 28, 48 (and hence fibre rings 26, 46) abut each other. Sleeve 60 is bonded to rotating annulus inner ring 43 by a retaining compound, such as, for example, Loctite 620. Sleeve 60 centers annular fibre rings 26, 46 with respect to longitudinal axis, The radial overlap between fibre rings 26, 46 discussed above helps ensure efficient light transfer between fibres 19, 39, even if annular fibre rings 26, 46 are slightly radially misaligned.

Outer ring 44 of rotating annulus 42 is secured to actuator 16 in a manner described in detail below. When actuator 16 is rotated, it causes annulus 42 and sleeve 60 to rotate with respect to annulus 22 (which is held stationary within handle 14 by the engagement of anti-rotation tabs 112 (Fig. 3) on ring 24 within a corresponding throat 113 in handle 14). To enhance light transmission between the abutting fibre rings 26, 46, a light transmissive fluid 62 (such as immersion oil, e.g., type A manufactured by Cargille Labs) is disposed between faces 28. 48 over sleeve 60. Fluid 62 has index of refraction substantially equal to that of one, or preferably both, sets 20, 40 of optical fibres 20, 40. In addition, fluid 62 lubricates joint 30 for ease of use.

A seal 64, preferably made from rubber, retains fiuid 62 within joint 30 between faces 28, 48. Seal 64 is sized to securely fit over the abutting portions of outer rings 24, 44. The proximal and distal ends of seal 64 are enlarged and snugly disposed in corresponding grooves 66, 68 machined in outer rings 24, 44, respectively. O-riπg 70 provides a seal between stationary annulus inner ring 23 and sleeve 60 to prevent fiuid 62 from leaking from the proximal end of joint 30 into handle 14.

Stationary annulus 22 is biased toward rotating annulus 42 by coil^'spriπg 72, which exerts approximately a one pound force, to urge stationary ring face 28 against rotating ring face 48. This further improves light transfer by reducing the gap between fibre rings 26, 46 to as small as possible. One end of spring 72 abuts an inner wall 80 of handle 14. The other end of spring 72 engages one end of a cylindrical spring retainer 78. The opposite (proximal) end of spring retainer engages a retaining ring 74 secured within a groove 76 machined in outer ring 24. Thus, retaining ring 74 acts as a flange surface for spring retainer 78. (A discrete retaining ring 74 is used instead of an integral flange because during manufacturing it is necessary to grip stationary annulus 22 to polish the ends ofthe individual optical fibres 19 at ring face 28; an integral flange would make this manufacturing step more difficult.)

Cylindrical spring retainer 78 surrounds seal 64 and the abutting faces 28, 48 of anπuli 22, 42. The force of spring 72 urges spring retainer 78 distally away from wall 80, thereby biasing stationary annulus 22 (via retaining ring 74) against rotating annulus 42.

Referring to Figs. 2, 6, and 8, insertion tube 12 includes inner tube 90 and outer tube 92 (CCD tube 54 is disposed within inner tube 90). Inner tube 90 and outer tube 92 are aligned along different axes — longitudinal axis 18 and longitudinal axis 88, respectively. The offset between longitudinal axis 18 and longitudinal axis 88, which is preferably about 0.013 inches, creates the above-described channel 58 between inner tube 92 and outer tube 90 for optical fibres 40. CCD tube 54, CCD 52, and lens assembly 50 are aligned along longitudinal axis 18.

At distal viewing tip 41 , window lens 94 of lens assembly 50 is oriented with respect to longitudinal axis 18 to determine the direction of view of endoscope 10 and could be recessed from the distal end of outer tube 92 to protect its exposed distal surface. Wedge 96, at distal viewing tip 41 , deflects optical fibres 40 such that light is directed along the direction of view in accordance with the orientation of window lens 94, e.g., at 30° with respect to axis 18. As shown in Fig. 8, individual optical fibres 39 of optical fibres 40 are arranged in a crescent shape, corresponding to the shape of channel 58 formed between inner tube 90 and outer tube 92, to disperse the light across the width of insertion tube 12.

Lens assembly 50, wedge 96, and optical fibres 40 are all bonded within the distal end of outer tube 92 by, for example, an epoxy. Lens assembly 50 is also epoxied to the distal end of inner tube 90. CCD tube 54 is axially movable within inner tube 90 for focusing, as discussed above.

The proximarend of outer tube 92 is inserted into an eccentric bore 98, aligned about longitudinal axis 88, within the distal end of rotating annulus outer ring 44. Outer tube 92 is attached to the distal end of outer ring 44 by, for example, weld 86. Inner tube 90 is attached to inner wail 99 of rotating annulus inner ring 43, by, for example, an epoxy. Actuator 16 is inserted onto the distal end of handle 14 over tubes 90, 92. Thrust washer 100, wave spring 101 , threaded retainer 102, and thrust washer 104 are radially mounted over the proximal end of actuator 16. Thrust washers 100, 104 provide radial bearings and are preferably made from a plastic having exceptional bearing characteristics, such as, for example, Torlon 4301.

Retainer 106, threaded into rotating annulus outer ring 44, holds tubes 90. 92 (and the components of joint 30) and actuator 16, respectively, within handle 14. Seal 105, preferably a quad ring, seals the interface between actuator 16 and handle 14. Seals 107 avoid contaminants from entering handle 14 at the interface between actuator 16 and ring 43.

Referring as well to Fig. 9, the proximal end of actuator 16 includes tabs 108 (only one of which is shown) which engage corresponding slots 110 (Fig. 7) formed in rotating annulus outer ring 44. Accordingly, when actuator 16 is rotated, tabs 108 engage slots 110 to rotate annulus outer ring 44, thereby also rotating inner ring 43, optical fibres 40, and tubes 90, 92 (which are attached to inner and outer rings 43. 44, respectively) about longitudinal axis 18. Anti-rotation tabs 112 (see Fig. 3) on stationary annulus outer ring 24 engage throat 113 in handle 1 to prevent the frictioπal forces between stationary annulus 22 and rotating annulus 44 to cause stationary annulus 22 to rotate. CCD tube 54, which is coupled to handle 14 at the focusing mechanism (not shown), including CCD 52 and its associated electrical and optical systems, also remains stationary.

Fig. 2 shows the connection between external fibre optic cable 2 (Fig. 1 ) and optical fibre set 20 at the proximal end 5 of handle 14. The individual fibres 19 of set 20 are epoxied into threaded bushing 34, and the proximal ends 36 of optical fibres 29 are uniformly polished for efficiently receiving light from light coupler 4. Light coupler 4 is designed to change the numerical aperture of light cable 2, which has a relatively low value (e.g., 0.54) for efficient light transfer, to a higher value (e.g., 0.81), which is desirable for adequately illuminating area A (Fig. 1). This is done by providing light coupler 4 with different inside diameters 4a, 4b at its ends. That is, diameter 4a is relatively large (SV* mm) where cable enters coupler 4, and is reduced substantially (to a diameter, 4b, of 3 mm) at the junction between cable 2 and optical fibre set 28. The ratio between diameters 4a and 4b multiplied by the numerical aperture of cable 2 (0.54) provides the desired numerical aperture (0.8 ) of optical fibre set 28.

In use, insertion tube 12 of endoscope 10 is inserted into a body cavity, joint space, or passageway during arthroscopic surgery. Distal viewing tip 41 is oriented such that the desired area (e.g., area A, Fig. 1) within the body cavity is within the field of view of endoscope 10 and is illuminated by light emitted from optical fibres 39 at distal viewing tip 41. Light from objects in field of view is collected by lens assembly 50 and passed to CCD 52. CCD 52 converts the received optical image to electrical signals, which are processed by CCU 6 to display an image of the objects on display screen 8.

To view a different area (such as area B), the user rotates actuator 16 while holding handle 14 stationary. As diseussed, the rotation of actuator 16 causes tubes 90, 92, and hence also lens assembly 50, to rotate about longitudinal axis. In addition, actuator 16 rotates annulus 42 - and hence annular fibre ring 46 - with respect to annulus 22 and annular fibre ring 26. The rotation is not conveyed to either set 20 of optical fibres or external light cable 2.

Other embodiments are within the scope of the following claims.

For example, inner tube 90 and outer tube 92 may be coaxial so that the channel created for optical fibres 39 is annular. 15 Likewise, other arrangements of individual optical fibres 39 at distal viewing tip 41 can be used. For example, optical fibres 99 can be arranged In an annular ring about the perimeter of window lens 94.

Other features may be added to the endoscope. For example, focusing capability may be provided, as described in the aforementioned '668 patent application.

Claims

.CLAIMS

1. An apparatus comprising: a first set of optical fibres having at least a portion extending along a longitudinal axis; a second set of optical fibres having at least a portion extending along said longitudinal axis; and a joint between said portions of said first set of optical fibres and said second set of optical fibres constructed to allow relative rotation between said portions about said longitudinal axis.

2. The apparatus of claim 1 wherein said joint is constructed to maintain ends of said portions of said first set of optical fibres and said second set of optical fibres adjacent to one another for light transmission therebetween.

3. The apparatus of claim 2 further comprising a spring mounted to bias said ends of said portions together.

4. The apparatus of claim 3 further comprising a light- transmitting substance disposed ^"between said ends of said portions of said first set of optical fibres and said second set of optical fibres.

5. The apparatus of claim 4 wherein said substance has an index of refraction substantially equal to an index of refraction of at least one of said first and said second sets of optical fibres.

6. The apparatus of claim 4 wherein said substance is immersion oil.

17 7. The apparatus of claim 5 wherein said substance is a liquid and said joint is constructed to contain said liquid between said ends of said portions of said first and said second sets of optical fibres.

5 8. An assembly for delivering light from a source to a region remote from the source comprising: a first set of optical fibres carried within a base and having a proximal end and a distal end, said proximal end being configured to receive light from the source;

10 a second set of optical fibres earned within an elongated insertion member disposed along a longitudinal axis and configured to be inserted into the remote region, said second set of optical fibres having a proximal end and a distal end, said distal end configured to transmit light from said insertion member into said

15 remote region; and said insertion member being rotatably mounted to said base at a joint between said distal end of said first set of optical fibres and said proximal end of said second set of optical fibres, said joint being constructed to allow relative rotation between said distal end

20 of said first set of optical fibres and said proximal end of said second set of optical fibres about the longitudinal axis.

9. The assembly of claim 8 wherein said distal end of said first set of optical fibres is configured so that individual fibres thereof are

25 arranged in a first annular ring, and said proximal end of said second set of optical fibres is configured so that individual fibres thereof are arranged in a second annular ring, said first and said second annular rings being adjacent to one another and centered about said longitudinal axis.

30

10. The assembly of claim 9 wherein said first annular ring is configured with a width greater than a width of said second annular ring.

11. The assembly of claim 9 further comprising a substance disposed between said first annular ring and said second annular ring, said joint being constructed to contain said substance between said first and said second annular rings.

12. The assembly of claim 9 wherein said joint includes a spring to bias said first annular ring and said second annular ring together.

13. The assembly of claim 8 wherein said assembly is an endoscope further comprising an optical element disposed at said distal end of said insertion member and an image detector disposed adjacent to said optical element.

14. The endoscope of claim 13 wherein said base is a handle.

15. The endoscope of claim 13 wherein said optical element is configured to provide a direction of view at a nonzero angle with respect to said longitudinal axis.

16. The endoscope of claim 13 wherein said optical element includes at least one lens.

17. The endoscope of claim 13 wherein said image detector is a solid-state image pickup device.