Focusing endoscope

Abstract: An endoscope (10) includes a focusing mechanism (17) having a focus control element (80) at a proximal end (19) of the endoscope and a mechanical coupling connecting the focus control element (80) to an image transmitting device (e.g., an electro-optical sensor (24) or one or more optical fibres (26)) mounted at a distal end (14) of an elongated insertion section (12) of the endoscope (10). Rotation of the focus control element (80) moves the image transmitting device (24) with respect to a lens assembly (22) of the endoscope (10) to focus the image received by the lens assembly (22).

Description: This invention relates to endoscopes and more particularly to electronic endoscopes. Generally, endoscopes are instruments for visualising the interior of an object, such as the human body (e.g., an internal organ or anatomical body passage). A typical endoscope includes an elongated flexible or rigid outer tube within which a lens system is disposed at a distal end. The image of the object being viewed by the optical system is transmitted through an optical system from the distal end to a proximal end of the tube for viewing by the user or for reception by a camera. Some endoscopes also carry fiber optic cables for illuminating the area of observation with light supplied by an external source. In some endoscopes, the optical system includes a bundle of fibre optic cables positioned immediately proximally of a stationary objective lens assembly located at the distal end of the tube. The lens assembly focuses the image into the end of the fibre bundle, which in turn transmits the image proximally. An electronic endoscope typically includes an electro-optic image sensor (such as a charge coupled device or CCD) in place of the fibre optic bundle. The CCD is positioned closely adjacent the objective lens assembly and generates a video signal of the object being observed. The video signal is transmitted by an electrical cable to the proximal end of the endoscope and is processed for viewing on a display such as a CRT monitor. US 4,846,155 discloses an endoscope which has a distal end in which is located an objective lens and a solid state imaging sensor such that the sensor relays the image from the objective lens to a monitor. The endsocope provides automatic focussing by mounting the sensor on a piezo-electric element. Signal processing means are used processes the signals from the sensor to provide a feed-back signal to the piezo-electric element to correctly position the sensor with respect to the objective lens. This invention provides an endoscope with a focusing mechanism having a focus control element at a proximal end of the endoscope and a mechanical coupling connecting the focus control element to an image transmitting device mounted at the distal end of an elonged insertion section of the endoscope for causing the image transmitting device to move along at least part of the length of the insertion section in response to activation of the focus control element. According the present invention, there is provided an endoscope apparatus for internal inspection of an object, comprising an elonged insertion section having a distal end to be inserted into said object and a proximal end to be manipulated by a user, said distal end enclosing a chamber, an image transmitting device mounted in said chamber of said distal end, said device being movable along at least part of the length of said insertion section and a focusing mechanism have a focus element comprising a rotatable manipulator accessible to said user at said proximal end and a mechanical coupling connecting said focus control element to said device for causing said device to move along said at least part of the length of said insertion section for focusing in response to activation of the focus control element, characterisied in that said rotatable manipulator comprises an outer sleeve which surrounds an inner sleeve, wherein said inner sleeve and said outer sleeve are connected by a coupling which may be selectively engaged and disengaged by relative motion of said inner and outer sleeves along the length of the insertion section. As a result of the coupling between the inner and outer sleeve, the focusing mechanism can be made easy to assemble and disassemble. The mechanical coupling may be a rigid actuator coupled between the manipulator and the device, with the actuator moving along at least part of the length of the insertion section in response to rotation of the manipulator. This arrangement allows an image viewed by the endoscope to be easily focused while in use without removal from the surgical site. The mechanical coupling may include a helical surface disposed on an inner sleeve which surrounds and is rotatable around the insertion section. The rigid actuator can then include a follower configured to engage the helical surface and to move along the helical surface in response to rotation of said rotatable manipulator. The outer sleeve of the rotatable manipulator rotates smoothly with little physical effort and preferably can be operated easily with one hand. The mechanical coupling can include a slot provided along and in parallel with a portion of the length of the insertion section, with the follower riding within said slot. The slot permits the rotatable manipulator to focus the image while maintaining a non-rotating image on an external display. The manipulator can include an element that is ferromagnetically coupled to the rigid actuator through an external wall of the insertion section. This avoids passing a mechanical element (such as the follower discussed above) through the external wall, thereby allowing the interior of the insertion section to be more completely sealed to reduce the risk of foreign material coming into contact with the electrical and optical components of the device. The electronic endoscope can be disposable, and the insertion can be sterilised and packaged in a sterile container together with a sterilised conduit that is used to connect the insertion section to a control unit; the conduit may carry an optical fibre for transmitting light from the control unit to the insertion section, and an electrical cable for carrying electrical signals from the sensor to the control unit. The endoscope and integral cable for providing both electrical and illumination requirements to the endoscope may have a single connector for connection to a video processor (camera control unit). The endoscope with integral cable may be provided in a sterile container so that the endoscope is disposable after use in a surgical procedure. The image transmitting device may include an electo-optical sensor. The present invention will now be disclosed by way of example only with reference to the accompanying drawings, whereas:- Fig. 1 is a cross-sectional side view of a distal region of an endoscope according to the invention. Fig. 2 is a cross-sectional side view of a proximal rear end portion of the endoscope of Fig. 1. Fig. 2a is an enlarged view of the region enclosed by 2a-2a of Fig. 2. Fig. 3 is a diagrammatic view of a lens assembly of the endoscope of Fig. 1. Fig. 4 is a top view of a main housing of the endoscope of Fig. 2. Fig. 5 is a side view of a focus sleeve of the endoscope of Fig. 2. Fig. 6 is a diagrammatic view of the endoscope of Fig 1 in use. As shown in Figs. 1 and 2, an electronic endoscope 10 includes an elongated insertion section 12 for insertion into a body cavity or narrow body passage 103 (see Fig. 6) to observe an object therein. Elongated insertion section 12 extends along a longitudinal axis 13 of endoscope 10 from a distal end 14 to a handle 16 at the proximal end 19 of endoscope 10. Handle 16 permits the user to position elongated insertion section 12 of endoscope 10 appropriately and also houses a focus control mechanism 17 for endoscope 10, which is described in detail below. A cable 18 extends from proximal end 19 for connection to a power source and camera control unti 106 (Fig. 6). Images observed at distal end 14 of endoscope 10 are processed by the video processor for viewing on a display unit, such as a colour CRT 108. Elongated insertion section 12 includes an outer tube 20 for housing an objective lens assembly 22, an image transmitting device (which in this embodiment includes an electro-optic module 23, having an electro-optical sensor 24 (e.g. a charge-coupled device (CCD) for converting optical images of the received light into electrical image signals), and light guiding fiber optic elements 26 for illuminating the area being observed. Outer tube 20 extends from distal end 14 of endoscope 10 to a first end of a main housing 30 at handle 16 where tube 20 is soldered within a counterbore of main housing 30. Outer tube 20, fabricated from anodised aluminium, has a length of about 13 inches (33.02cm), an outer diameter of .379 inches (.963cm) and a wall thickness of approximately 0.010 (0.025cm) inches. Elongated insertion section 12 further includes an inner cylindrical tube 31 and a CCD tube 32, each coaxially disposed within outer tube 20. Inner cylindrical tube 31 extends proximally approximately 2.4 inches (6.09cm) from the distal end 14 of the outer tube 20 to an enlarged proximal end 31a that receives the distal end of CCD tube 32. Tube 31 is radially spaced from outer tube 20 to provide a cylindrical passage within which fiber optic elements 26 pass to distal end 14. CCD tube 32 is shown having a first cylindrical member 33 extending from a region directly behind lens assembly 22 to a region partially within main housing 30 and a second extension member 34 soldered to first cylindrical member 33 which extends to focus control mechanism 17. The distal end 33a of CCD tube 32 has a pair of enlarged diameter regions 29a, 29b as shown to receive electro-optic module 23 and a crimped end of cable 18, respectively. Electro-optic module 23 is secured into region 29a of CCD tube 32 with epoxy. Cable 18 has a woven ground conductor surrounded by a band 21 which is crimped to prove a snug fit within region 29b. Referring also to Fig. 3, an optical image from the area being observed is provided to a front face 25 of CCD 24 by lens assembly 22 through a series of four lenses. Images incident on lens assembly 22 pass through a negative lens 35, a doublet lens 36, a meniscus lens 38, an aperture stop 40, and a second doublet 42, and are incident on face 25 of CCD 24. Negative lens 35 has a flat distal surface 37. Distal surface 37 being flat provides the advantage of being easily cleaned and maintained. Doublets 36 and 42 are fabricated from a pair of lens elements of glass materials having different optical characteristics (e.g. refractive index) that are joined with a thin layer of epoxy. Lens elements 35-42 are spaced from each other by air and are encased within a lens housing 41. Meniscus lens 38, aperture stop 40, and second doublet 42 are supported by a spacer 43 (Fig. 1) to assure their concentricity within lens housing 41. The four-lens objective lens assembly 22 supported within lens housing 41 has a physical length of about 16 mm, a focal length of 4 mm, and an f number of 5. Lens assembly 22 provides a field of view of approximately 75 degrees. Lens assembly 22 fits snugly within tube 31 and is recessed from the tip of outer tube 20 to protect exposed distal surface 37 of lens element 35. Lens assembly 22 and inner cylindrical tube 31 are rigidly attached with epoxy. Electro-optic module 23 is the solid-state image sensor portion of a commercially available electronic camera (lens objective removed) which is manufactured by Panasonic Communications and Systems Company, Secaucus, N.J., model No. GP-KS202. Electro-optic module 23 has a diameter of about 0.5 inches (1.27cm) and is sized to fit within distal end 33b of CCD tube 32, and includes a CCD 24 with its associated preamplifier/driver circuitry (not shown). Images generated by CCD 24 are transferred via the preamplifier/driver circuit (not shown) to individual wires 27 of cable 18. Cable 18 is inserted within CCD tube 32 and supplies power to electro-optic module 23 and receives electrical image signals to be provided to video processor 106 or camera control unit external to endoscope 10 via wires 27. Fiber optic elements 26 are disposed in a cylindrical region between outer surfaces of both inner cylindrical tube 31 and CCD tube 32 and the inner surface of outer tube 20 along the length of insertion section 12 extending from distal end 14 to main housing 30 such that in operation, a ring of light is provided around the area viewed by lens assembly 22. During assembly, fiber optic elements 26 are fed in an evenly spaced manner within the region between tubes 20 and 31 (before inner cylindrical tube 31 is glued in place). The loose ends of fiber optic elements 26 are allowed to extend beyond the distal end 14. Fiber optic elements 26 are potted in place with an epoxy and portions extending beyond distal end 14 are then cut and polished to ensure a clear epoxy-free glass surface at the ends of each fiber optic element. Fiber optic elements 26 are fabricated using a highly transmissive glass-like material, manufactured by Cuda Products Corp., Jacksonville, FL, such that light provided from an external light source 110 (See Fig. 6) to the proximal end of fiber optic elements 26 is provided to distal end 14 with minimal loss. Referring again to Fig. 2, focus control mechanism 17 allows a user to focus endoscope 10 by adjusting the distance between objective lens assembly 22 and CCD 24 by ± 1 mm. As mentioned above, objective lens assembly 22 and CCD 24 are rigidly secured to outer tube 20 and CCD tube 32, respectively. The spacing between CCD 24 and lens assembly 22 is varied by moving CCD tube 32 axially along longitudinal axis 13 of endoscope 10. As will be discussed below, front face 25 of CCD 24 is moved by focus control mechanism 17 in response to rotation of focus ring 80 by the user. Main housing 30 has a through hole 46 extending its length to receive CCD tube 32 and to allow cable 18 to pass through endoscope 10 (Fig. 4). A pair of oblong slots 48, 50 are disposed through opposite sidewalls of an end portion 65 of main housing 30 for respectively receiving a pair of cam screws 76, 78. Oblong slots 48, 50 have a length of about .35 inches (0.889 cm) to provide the extent of forward and rearward motion of CCD tube 32 and are parallel to axis 13 for purposes to be described. A cylindrical actuator 62 is interposed between main housing 30 and CCD tube 32 and is threaded to receive the proximal end of CCD tube 32. A pair of threaded holes 66, 67 orthogonal to axis 13 are disposed through the walls of actuator 62 and are aligned with oblong slots 48, 50 of main housing 30. A lock nut 63 secures actuator 62 to the proximal end of CCD tube 32. Along an outer surface of main housing 30 is a cylindrical focus sleeve 68 having a pair of diametrically opposed helical grooves 70, 71 each of which is aligned with a corresponding one of threaded holes 66, 67 of actuator 62 and a corresponding one of oblong slots 48, 50 (See Fig. 5). Each one of a pair of cam bearings 72, 74 having through holes 75, 77 engages a corresponding one of helical grooves 70, 71 and contacts actuator 62 along diametrically opposite helical surfaces of slots 70, 71. Each helical groove 70, 71 travels approximately 135° around focus sleeve 68 and has a width slightly larger than the diameter of cam bearings 72, 74. Cam bearings 72, 74 are made from a polymer plastic such as Delrin ™ , a product of Dupont Co., Wilmington, DE. Cam screws 76, 78 are placed within cam bearings 72, 74 and are screwed into threaded holes 66, 67 and are screwed into threaded holes 66, 67 of actuator 62. A focus ring 80 surrounds main housing 30 and is secured to focus sleeve 68 using a horizontally disposed pin 82 that engages a hole 86 of focus sleeve 68 (Fig. 2A). An o-ring seal 98 is placed between main housing 30 and focus ring 80. Main housing 30 has a band 86 disposed on its outer surface that is proximal to the edge of slots 48, 50 nearest insertion section 12. Band 86 provides a support surface 88 for a thrust plate washer 90 placed between focus sleeve 68 and main housing 30. A rear housing 102 is threaded onto a rear portion of main housing 30 with strain relief retainer 104. Retainer 104 holds strain relief 105 of cable 18. A second seal 100 (a Quad Ring, Gallagher No. AS568-014-559N) is positioned between main housing 30 and rear housing 102. Seals 98, 100 protect the inner workings of focusing mechanism 45 from the environment during surgical use and during sterilisation. Main housing 30 has an opening 92 along a side portion for receiving a light post 94. Light post 94 is a coupling member having a threaded end disposed in opening 92 with its opposite end having a fitting 96 for receiving a cable having fiber optic elements 26. The cable 18 is connected to a light source 110 (Fig. 6). The mechanical configuration described provides a focus control mechanism 17 that is easily assembled and disassembled. For example, to disassemble focus control mechanism 17, rear housing 102 is unscrewed from the rear portion of main housing 30 and with retainer 104 is drawn along cable 18. Focus ring 80 axially separated from focus sleeve 68 by applying a sufficient force proximally along the length of hand 16 sufficient to separate pin 82 from hole 86 of focus sleeve 68. With focus ring 80 removed, cam screws 76, 78 are exposed and can be unscrewed from actuator 62 allowing cam bearings 72, 74 to be removed from through holes 75, 77 of focus sleeve 68. With cam bearings 72, 74 removed, focus sleeve 68 can be slid off of the end of main housing 30. Referring to Fig. 6, endoscope 10, operating as a laparoscope, is shown inserted into a patient's abdomen 103 with a visual image 104 of the surgical site being transmitted to a video processor (i.e. camera control unit) 106 for viewing on a CRT display 108. A user focuses endoscope 10 by turning focus ring 80 in a circumferential clockwise or counterclockwise direction. With pin 82 firmly engaged within hole 86, focus sleeve 68 is mechanically bound to focus ring 80 such that any rotation of ring 80 is transferred to focus sleeve 68. Likewise, the transferred motion of the focus sleeve is conveyed to CCD tube 32 through cam screws 76, 78 and cam bearings 72, 74 causing CCD tube 32 to move linearly along axis 13 to change the spacing between lens assembly 22 and front face 25 of CCD 24, thereby focusing image 104. The helical path provided by grooves 70, 71 would normally cause CCD tube 32 and attached CCD 24 to rotate about axis 13, thus causing the image 104 being viewed on CRT 108 to also rotate. However, cam bearings 72, 74 are also captured within oblong slots 48, 50 of main housing 30 which are parallel with axis 13 so that CCD tube 32 is precluded form rotating and maintains an upright image on CRT 108 a CCD tube 32 is moved with respect to lens assembly 22. In another embodiment, first cylindrical member 33 and second extensions member 34 (Figs. 1 and 2) of CCD tube 32 can be formed as a single continuous tube. In another alternative embodiment, focus ring 80 is coupled to CCD tube 32 magnetically rather than mechanically. One example of such a magnetic coupling technique is described in U.S. Patent No. 5,056,902, entitled "Magnetically Coupled Actuator", assigned to the present assignee. According to this technique, focus ring 80 includes an element (such as a magnet) that is ferromagnetically coupled to actuator 62 through the external wall of housing 30. (Alternatively, the magnet can be disposed on actuator 62.)

Claims: An endoscope apparatus (10) for internal inspection of an object, comprising: an elongated insertion section (12) having a distal end (14) to be inserted into said object and a proximal end (19) to be manipulated by a user, said distal end (14) enclosing a chamber, an image transmitting device (24) mounted in said chamber of said distal end (14), said device (24) being movable along at least part of the length of said insertion section (12), a focusing mechanism (17) having a focus control mechanism element comprising a rotatable manupulator accessible to said user at said proximal end (19) and a mechanical coupling (68, 72, 74, 76,78) connecting said focus control element (80) to said device (24) for causing said device (24) to move along said at least part of the length of said insertion section (12) for focusing in response to activation of the focus control element (80), characterized in that said rotatable manipulator comprises an outer sleeve (80) which surrounds an inner sleeve (68), wherein said inner sleeve (68) and said outer sleeve (80) are connected by a coupling which may be selectively engaged and disengaged by relative motion of said inner and outer sleeves (68, 80) along the length of the insertion section (12). The apparatus of Claim 1, characterized in that said mechanical coupling comprises a rigid actuator (62) coupled between said manipulator and said device (24), said actuator moving along the length of the insertion section in response to rotation of the manipulator. The apparatus of Claim 2, characterised in that said mechanical coupling further comprises a helical surface (70, 71), and said rigid actuator (62) includes a follower (72, 74) configured to engage said helical surface (70, 71) and to move along said helical surface (70, 71) in response to rotation of said rotatable manipulator. The apparatus of Claim 3, characterised in that said helical surface is connected to said rotatable manipulator. The apparatus of Claim 3 or Claim 4, characterised in that said helical surface (70, 71) is disposed on the inner sleeve (68). The apparatus according to any one of the preceding claims characterised in that the coupling connecting said inner sleeve (68) and said outer sleeve (80) includes a pin (82) for joining said inner (68) and outer (80) sleeves, said pin (82) being oriented generally along the length of the insertion section. The apparatus according to Claims 3 to 5, characterised in that said follower (72, 74) comprises a projection on said rigid actuator (62), said helical surface (70, 71) comprises a groove on said rotatable manipulator, said follower (72, 74) riding within said groove (79, 71) and said mechanical coupling (68, 72,74,76, 78) further comprises a slot (48, 50) provided along a portion of the length of the insertion section (12), said follower (72, 74) riding within said slot. The apparatus of Claim 7, characterised in that said slot (48, 50) is disposed parallel to said length, engagement of said follower (72, 74) and said slot avoiding rotation of said image transmitting device (24) during said focusing. The apparatus according to any one of the preceding claims characterised in that the outer sleeve (80) is rotatable around an external wall of said insertion section (12). The apparatus according to any one of the preceding claims characterised in that said rotatable manipulator (80) is ferromagnetically coupled to said rigid actuator (62) through an external wall of said insertion section (12). The apparatus according to any one of the preceding claims characterised in that a rear housing (102) is releasably threaded onto a rear portion of the insertion section (12) to prevent axial separation of the focus ring (80) and the focus sleeve (68). The apparatus according to any one of the preceding claims characterised in that the image transmitting device comprises an electro-optic sensor.

Inventors: KAZAKEVICH YURY E, KENNEDY JOHN E, LUCEY PAUL V, MIHALCA GHEORGHE, KAZAKEVICH, YURY E., KENNEDY, JOHN E., LUCEY, PAUL V., MIHALCA, GHEORGHE
Applicants: SMITH & NEPHEW INC, SMITH & NEPHEW, INC.
Application year: 1993
Main classification: A61B1
IPC codes: A61B1, G02B23