Abstract:
A variable-view arthroscope or like instrument (endoscope, etc.) includes an elongated housing tube extending from an outer control end to an inner image input end that is closed by an input lens or window. A lighting apparatus illuminates a surgical working area beyond the image end of the housing tube. A first mirror intercepts light reflected from the surgical working area to produce a working image that is reflected to a second mirror that in turn reflects the working image to impinge upon the input end of a relay lens assembly. The working image is transmitted to a receptor, which is located near the outer (control) end of the housing tube. The relay lens applies the image to an image device, such as a conventional CCD unit, that transmits the image to a location exterior to the scope. A control varies the position of one or both of the mirrors between first and second limits.

Description:
BACKGROUND OF THE INVENTION 
     Arthroscopes and other like optical instruments, such as endoscopes, have long been known in the field of surgery and in other fields. In this application, the invention is described in connection with an arthroscope or similar instrument employed for surgery, as in human surgery. 
     Over the last fifteen or more years the nature of surgery has changed substantially, with minimally invasive surgery becoming a mainstay. Within the orthopedic community, in particular, arthroscopy and similar techniques have become the most common surgical procedures. Surgery using such techniques is less painful for the patient and, in most instances, can be performed more quickly and safely than with techniques that require greater invasion of the patient&#39;s body; anesthesia is also less complicated, the surgery can often be handled on an outpatient basis, and the procedures are more cost effective. Patients return to normal life more quickly, and hospital stays may be reduced in length or even eliminated. However, all of these benefits are available only if the minimally invasive surgery allows for better diagnostic capabilities, improved surgical techniques, and reduced iatrogenic damage. Similar benefits are available with other, non-surgical, instruments. 
     One problem in these minimally invasive techniques derives from limitations in the arthroscopes, endoscopes and other principal optical instruments employed. In particular, the rather limited field of view afforded by even the best instruments previously commercially available has inhibited progress to at least some extent; available instruments and techniques have not changed dramatically since 1985. A substantial improvement in the field of view available to a person employing an arthroscope or like instrument for exploratory or repair procedures is much needed. 
     Several techniques for modification (widening) of the view offered by arthroscopic/endoscopic instruments have been proposed, but they have not been especially successful. Generally, such proposals have required packing a plurality of movable lenses or prisms into the input end of the instrument; the resulting problems of precision of construction, precision of relative movements, space requirements, optical distortions, and elimination of undesired “ambient” light have been substantial. This is not particularly surprising; interaction between the prisms and lenses involved, along with light loss, exacerbates the problem. 
     There is a need for an arthroscope that affords the user a broadened effective field of view and that does not require movement of the arthroscope to vary its scope of view. One such arthroscope is disclosed in copending U.S. application Ser. No. 09/243,845, entitled “Variable View Arthroscope” and filed Feb. 3, 1999, having a common inventor with the present application. In this specification and in the appended claims the term “arthroscope” means and should be interpreted to include an endoscope or any other like optical instrument, whether used for surgery or otherwise. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a variable view arthroscope comprising an elongated housing having an image input end spaced from an outer control end. Lighting is provided for illuminating a working image area beyond the image input end of the housing tube. An input lens, located in the input end of the housing tube, intercepts light reflected back from the working area. The input lens, preferably a diverging type lens, closes (and usually seals) the image input end of the housing tube, which is beveled at an angle of 30° to 60°. The reflected light constitutes a working image and the light image or object rays pass from the working area through the input lens and are directed to a movable mirror. The movable mirror may be rotatable or it may move linearly. There is a control, for example, an elongated control rod, for varying the position of the movable mirror to any position or to a series of fixed positions between a first limit position and a second limit position. A fixed mirror is positioned to intercept light reflected from the movable mirror, redirecting that light toward a relay lens assembly located near the fixed mirror position. The relay lens assembly directs the light image from the fixed mirror through the length of the relay lens assembly to impinge upon a focusing lens assembly. The focusing lens assembly includes a focusing and zoom lens and their controls, and is preferably located in the control portion of the arthroscope. 
     In an alternative preferred embodiment of the present invention, the input end of the arthroscope includes an input lens, a first mirror, a second mirror and a relay lens assembly. The first mirror is fixed in relation to the input lens but the two move as a unit to alter the view of the arthroscope. The second mirror is movable and directs the image into the relay lens assembly. The input lens and first mirror may rotate about the same axis as the second mirror. As object rays pass through the input lens to the first mirror, to the second mirror and into the relay lens assembly, the length of the axial ray remains the same as the angle of view of the arthroscope changes. The lengths of the rim rays may also remain the same as the angle of view of the arthroscope changes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a variable view arthroscope constructed in accordance with a preferred embodiment of the invention; 
     FIG. 2 is an elevation view of the instrument of FIG. 1; 
     FIG. 3 is a plan view, on an enlarged scale, of the control portion of the arthroscope of FIGS. 1 and 2; 
     FIG. 4 is an elevation view, on an enlarged scale, of the control portion of the instrument of FIGS. 1 and 2; 
     FIG. 5 is a detail view taken approximately as indicated by line  5 — 5  in FIG. 3; 
     FIG. 6A is a sectional, longitudinal elevation view, on an enlarged scale, of the image input end of the arthroscope of FIG. 1, adjusted for a maximum upward view; 
     FIG. 6B is a sectional elevation view, like FIG. 6A, of the image input end of the arthroscope of FIG. 1, adjusted for an intermediate view; 
     FIG. 6C is a sectional elevation view, like FIGS. 6A and 6B, of the image input end of the arthroscope of FIG. 1, adjusted for a maximum downward view; 
     FIG. 6D is a sectional view taken approximately along line  6 D— 6 D in FIG. 6A; 
     FIG. 7A is an elevation view, on an enlarged scale, of a slide member used in the arthroscope of FIG. 1; 
     FIG. 7B is a plan view of the slide of FIG. 7A; 
     FIG. 7C is an end view of the slide of FIGS. 7A and 7B; 
     FIG. 8A is a plan view, on an enlarged scale, of a cam/axle member used in the control end (FIG. 3) of the arthroscope of FIG. 1; 
     FIG. 8B is an end view of the cam/axle member of FIG. 8A; 
     FIG. 8C is an elevation view of the cam/axle member of FIG. 8A; 
     FIG. 9A is a plan view, on an enlarged scale, of two control knobs from the control end (FIG. 3) of the arthroscope of FIG. 1; 
     FIG. 9B is an end view of the control knobs of FIG. 9A; 
     FIG. 9C is a section view, taken approximately along line  9 C— 9 C in FIG. 9A, of the control knobs; 
     FIG. 10 is an elevation view, on an enlarged scale, of the lighting apparatus for the arthroscope of FIG. 1; 
     FIG. 11A is a longitudinal sectional elevation view, like FIG. 6A, of the input (viewing) end of an arthroscope comprising another embodiment of the invention, adjusted for a maximum upward view; 
     FIG. 11B is a sectional elevation view, like FIG. 11A, of the apparatus of FIG. 11A adjusted for an intermediate view; and 
     FIG. 11C is a sectional elevation view, like FIG. 11A, adjusted for a maximum downward view. 
     FIG. 12A is a sectional elevation view of the input end of a variable view arthroscope, adjusted for a middle view, in accordance with another embodiment of the present invention. 
     FIG. 12B is a sectional elevation view of the input end of a variable view arthroscope, adjusted for a maximum upward view, in accordance with an embodiment of the present invention. 
     FIG. 12C is a sectional elevation view of the input end of a variable view arthroscope, adjusted for a maximum downward view, in accordance with an embodiment of the present invention. 
     FIG. 13 is a sectional elevation view of the input end of a variable view arthroscope, adjusted for a middle view, showing the input lens assembly and associated mechanism, in accordance with an embodiment of the present invention. 
     FIG. 14A is a sectional elevation view of the input end of a variable view arthroscope, adjusted for a middle view, showing the second mirror and associated mechanism, in accordance with an embodiment of the present invention. 
     FIG. 14B is a sectional end view of the second mirror, second mirror housing, axle, and second mirror associated mechanism in accordance with an embodiment of the present invention. 
     FIG. 15A is a sectional elevation view of the input end of a variable view arthroscope, showing the orientation of object rays in a maximum upward view in accordance with an embodiment of the present invention. 
     FIG. 15B is a sectional elevation view of the input end of a variable view arthroscope, showing the orientation of object rays in a maximum downward view, in accordance with an embodiment of the present invention. 
     FIG. 16 is a sectional elevation view of the input end of a variable view arthroscope, showing the orientation of image rays in both a maximum upward view and a maximum downward view, in accordance with an embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One preferred embodiment of the invention is illustrated as an arthroscope  30 , shown in FIGS. 1-10. 
     As shown in FIGS. 1 and 2, arthroscope  30  includes an elongated housing tube  31 , which has an image input end  32  and a control end  33 . Housing tube  31 , and more specifically its control end  33 , may extend into the outer control portion  35  of arthroscope  30 , shown in greater detail in FIGS. 3-5. As shown in FIGS. 1-4, the control portion  35 , from which the control end  33  of the housing tube  31  of arthroscope  30  projects, ends with a CCD attachment  36 . The CCD attachment  36  is connected by appropriate means to an image screen (not shown) to be viewed by a person using arthroscope  30 . CD attachment  36  may be of conventional construction, does not constitute a part of the present invention, and is not shown in detail. 
     As best shown in FIG.  2  and in the enlarged views of FIGS. 6A-6C, the image input end  32  of housing tube  31  is beveled at its extreme end; the bevel is usually between 30° and 60°. The outer end of housing tube  31 , shown in enlargement in FIGS. 6A-6C, is closed by a diverging input lens  37  (plural lenses may be used). Input lens  37  has an outer concave surface  38  spaced from an inner concave surface  39 . Input lens  37  is preferably sealed into the tip of the input end  32  of housing tube  31 ; a suitable seal material to mount lens  37  in place in the end of housing tube  31  is any conventional sealing adhesive approved by the FDA for in vivo use. Input lens (or lenses)  37  may be formed of optical glass or any other suitable lens material. When a single input lens is used, input lens  37  preferably has a rim matched as closely as possible to the inside diameter of the housing tube  31  at its image input end  32  to assure a good seal between the housing tube and the input lens. Similar expedients should be employed if plural input lenses are utilized. 
     Arthroscope  30  includes, at the opposite end of tube  31 , an outer control portion  35  and a light source  41  that is connected to a lighting assembly  42 ; see FIGS. 2 and 4. The lighting assembly  42  includes one or more optic fiber bundles  43 ; the fiber optic bundle (or bundles) extend to the input end of the arthroscope; see FIGS. 4 and 6D. For clarity, the optic fiber bundles  43  have been omitted in FIGS. 6A-6C. The lighting assembly  42  illuminates a surgical working area (not indicated) beyond the image input end  32  of the housing tube; typically, illumination of the surgical working area is through the input lens  37 . 
     A control, shown in FIG. 4 as a control rod  45 , extends longitudinally through the housing tube  31  from outer control portion  35  to its input end  32 . Rod  45  is used to vary the position of a slidably movable mirror  47  (See arrows A in FIGS. 6A-6C) along the axis of rod  45 . Mirror surface  47  is shown as planar in the drawings, but the movable mirror may be concave or other shapes. The mirror surface  47  is aligned with but spaced from the inner surface  39  of input lens  37 . See FIGS. 6A-6C. The end of control rod  45  is affixed to the movable mirror  47  at its base  46 , as best shown in the enlarged views of FIGS. 6A-6C. A suitable commercially available adhesive may be used to join the end of rod  45  to the base  46  of the movable mirror  47 ; alternatively, soldering or brazing may be used if desired. The tip of control rod  45  may be polished and coated to afford a suitable movable mirror, eliminating the need for a separate part such as base  46 . 
     At the control end  35  of the arthroscope  30  the control rod  45  extends into and engages a slide  48 . Slide  48  is driven linearly by two control knobs  49  and  50 , as described hereinafter in connection with FIGS. 9A-9C. 
     In the arthroscope  30 , as shown in FIGS. 6A-6C, the base  46  of the movable mirror  47  slides linearly between a maximum upward view position (FIG.  6 A), through an intermediate position (FIG.  6 B), to a maximum downward view position (FIG.  6 C). The movement of the movable mirror base  46  may be reversed, moving from its maximum downward position (FIG. 6C) toward its maximum upward position (FIG.  6 A). The images that may be provided to a surgeon by the arthroscope  30  overlap. The maximum upward view of FIG. 6A, with movable mirror  47  advanced by control rod  45  to a position immediately adjacent input lens  37 , has an overlap of about fifty percent with the maximum downward view (FIG. 6C) afforded when the sliding mirror  47  is fully retracted. 
     At the top of the input end of arthroscope  30 , as seen in FIGS. 6A-6C, there is a fixed mirror  52  mounted on a base  51 . The fixed mirror  52  intercepts object rays from the movable mirror surface  47  and re-directs those rays to impinge upon the input end  53 A of a relay lens assembly  53 . Relay lens assembly  53 , FIGS. 6A-6C, may be of conventional construction having an outer stainless sleeve  54  for stability and directs the light toward a receptor, shown as a focusing lens assembly  55  (FIGS. 1,  2 ,  3  and  4 ). The focusing lens assembly  55  consists of focusing and zoom lenses and is of conventional design. The focusing lens assembly  55  directs the light image in the customary manner, into the CCD attachment  36 ; see FIGS. 1-4. A slide  48  is located in the control portion  35  of arthroscope  30 ; the slide, shown in FIGS. 7A-7C, comprises a main body  57  having an axial relay lens opening  58 ; the relay lens opening  58  also extends through an enlarged end  59  of the slide. A socket  61  also in slide  48 , formed to align and attach control rod  45  to slide  48 , is shown in FIG.  7 B. In the illustrated embodiment, the control rod socket  61  is located directly below the axial opening  58  for the relay lens. 
     The cam portion  65  of cam/axle member  62  is positioned in a central transverse opening  63  in slide  48 ; see FIGS. 7A-7C for opening  63 , FIGS. 8A-8C for cam/axle member  62 . Opening  63  is not quite circular in cross-section; it is enlarged or “stretched” slightly, as is most apparent in FIG.  7 B. The cam/axle member  62  includes a large control knob shaft attachment segment  64  of circular cross-section, cam segment  65  contains a relay lens assembly slot  66 , and a small control knob shaft attachment segment  67 . This preferred construction is shown in detail in FIGS. 8A-8C. Two control knobs, shown in FIGS. 9A-9C, are mounted on the outer ends  64  and  67  of cam/axle member  62  (FIGS.  8 A- 8 C). The control knobs include a right-hand control knob  49  that is fitted onto the large control wheel shaft attachment segment  64  of the cam/axle member  62 . The second or left-hand control knob  50  fits onto the smaller control knob shaft attachment segment  67  of cam/axle member  62 . See FIGS. 8A-8C and  9 A- 9 C. 
     The control knobs  49  and  50  and their shaft attachments  64  and  67 , respectively, may be connected to each other by conventional means. Either of the control knobs  49  and  50  can be used to rotate cam  65  within slide opening  63 , thus causing slide  48  and the attached control rod  45  to move linearly in relation to the rotational motion of cam/axle  62 . 
     The lighting assembly  42 , illustrated in FIG.  2  and shown in greater detail in FIG. 10, may include a condenser lens  71  to focus light from a suitable source  41  onto one end  72  of the light bundles  43  that extend to the input end of the arthroscope  30 . See FIG.  6 D. Two or more fiber optic light bundles  43  may be provided to supply light to the input end of arthroscope  30 . As previously noted, the lighting assembly shown is conventional in construction and has been described only generally. 
     Operation of the arthroscope  30  (FIGS. 1-10) can now be considered. At the outset, light from source  41  (FIG. 2) is focused upon the end  72  of one or more fiber optic bundles  43 . Light passes through the fibers  43  and illuminates a surgical working area just beyond the input end  32  of the arthroscope  30  (FIGS.  1  and  2 ). In arthroscope  30 , light passes into bundle(s)  43  and reflects, at least in part, from the fixed mirror  52  onto the reflective surface of the movable mirror  47 , and then passes through the input lens  37  into the area to he illuminated. 
     Light reflected from the surgical working area forms an image of object rays after passing through input lens  37  and impinges on the movable mirror  47 . The image is directed from the movable mirror  47  to impinge upon the fixed mirror  52 . From the fixed mirror  52  the light image is re-directed toward the input end  53 A of the relay lens assembly  53 ; see FIGS. 6A-6D. The relay lens system  53  supplies the image to the CCD attachment  36 , through focusing lens assembly  55 , to be viewed by the surgeon or other person using the arthroscope  30 . 
     If the person using arthroscope  30  is dissatisfied with the image available through the CCD attachment  36 , control knobs  49  and/or  50  may be used to provide an image of a different portion of the surgical region. As shown, the control knobs, through cam/axle member  62  (FIGS.  8 A- 8 C), slide  48  (FIGS.  7 A- 7 C), and rod  45  (FIGS. 6A-6C) can advance the movable mirror  47  toward the input lens  37  (see FIG.  6 A), or retract the movable mirror  47  from the input lens  37  (see arrow A in FIGS.  6 B and  6 C) to a “lower” position. In this way the image supplied to the surgeon or other person using the instrument  30  can be and is varied to a substantial extent with no change in the position of the instrument. In effect, the overall viewing range of the instrument  30  is enhanced by at least thirty degrees with no need to reposition the instrument axially. Further alteration or correction of the image can be afforded by appropriate software. 
     FIGS. 11A,  11 B and  11 C afford sectional elevation views of the input end  132  of a modified instrument and FIGS. 11A,  11 B and  11 C correspond to FIGS. 6A,  6 B and  6 C, respectively. In FIGS. 11A-11C, the reference numerals and illustrated elements correspond to those employed in FIGS. 6A-6C, except for those elements that have been modified. The instrument input end  132  of a housing tube  131  is bevelled, as previously described, and is closed by an input lens  37 . The input lens  37  may have two concave lens surfaces, an outer surface  38  and an inner surface  39  as shown; other input lens structures may be used. A fixed mirror  52  is mounted in the upper portion of housing tube  31 , immediately adjacent input lens  37 ; the fixed mirror  52  has a reflective coating, on a base  51 , that faces the input end  53 A of a relay lens assembly  53 . 
     In the modification shown in FIG. I IA, there is a pivotally movable mirror  147  on a base  146 . The mirror base  146  is pivotally mounted on a shaft  148  that extends transversely of the instrument between the two sides  170  (only one shown) of a generally U-shaped support member  171  positioned in the lower part of housing tube  131 . The movable mirror base  146  is connected to the end of a control rod  145 , as by a pin  172 ; rod  145  is similar to rod  45 . The control rod  145  can be moved linearly as indicated by arrow B in FIGS. 11A, B and C. 
     The views of FIG.  11 B and FIG. 11C are the same as FIG. 11A except that FIG. 11B shows the pivotally movable mirror  147  at an intermediate position, for an intermediate image, and FIG. 11C shows the pivotally movable mirror  147  positioned for a maximum “downward” view. For this description, FIGS. 11A-11C are assumed to be vertically oriented, but they could equally well be horizontally oriented, as could FIGS. 6A-6C, so that references to “upward” and “downward” could equally well be modified to “right” and “left”, or vice versa. 
     Several parts of instrument  30  can be modified from those illustrated without appreciable effect on overall operation of instrument  30 . For example, input lens  37 , the shape of the movable mirrors and bases  46 ,  47 ,  146 ,  147  and the illustrated relay lens assembly  53  can be changed, as can the lighting assembly  42 ,  43 . The control rod  45  (or rod  145 ) also may be modified; control rod  45  constitutes a preferred mechanism for operating the movable mirror  47  but any mechanism that will move the mirror  47 , whether linearly or along a pivotal or other required path, can be used. The angle of the level of the outer end of housing tube  31  may be varied as desired; a level of 30° to 60° is preferred, but may depend on the primary use for instrument  30 . It will be recognized that use of a CCD unit for a display is not essential. The “software” used for the display may vary appreciably. Any preferred technique to enable the instrument user to move the movable mirror over its operational range is acceptable. 
     An alternative embodiment of the input end of a variable view arthroscope  30 ′ in accordance with the present invention is shown in FIGS. 12A-16. For clarity, only input end  100  of arthroscope  30 ′ is illustrated in full. Although shown as an arthroscope providing up-down view variability, a similar configuration of arthroscope  30 ′ could be oriented so as to provide side-to-side view variability or view variability along any other axis. The input end of the variable view arthroscope  30 ′ in accordance with this embodiment of the present invention is indicated generally at  100 . The input end  100  generally captures a light image, formed of object rays, and sends the image to the control end. As discussed herein, the object rays include an axial ray at the optical center of the object image, and rim rays at the outer edges or rims of the object image. 
     As shown in FIG. 12A, the input end  100  of the arthroscope  30 ′ is contained within an elongated housing tube  31 ′ that extends along a central, longitudinal axis. The end of the housing tube  31 ′ is closed by a window  104  that is fixed in place, such as by adhesive, and also may be sealed to form a sealed closure for the end of the housing tube  31 ′. The window  104  forms part of the sealing system for the arthroscope  30 ′. The window  104  may be placed so that it forms any desired angle for the closure of the end of the housing tube  31 ′; for example, the window maybe be placed to bevel the closure of the housing tube  31 ′ by between about 30 and 60 degrees. Window  104  may be flat glass or other suitable material, or it may have curved surfaces; for example, window  104  may be a meniscus lens, placed to curved outward from the end of the housing tube  31 ′. Preferably, the end of the housing tube  31 ′ should be formed so that the edges of the housing tube  31 ′ are flush with the outer surface of the window  104  when the window  104  is placed at the desired angle. 
     The input end  100  of the variable view arthroscope  30 ′ includes an input lens  112 , a first mirror  114 , and a second mirror  116 . The input lens  112  is placed proximate to the window  104  and is preferably an image expanding negative lens. The input lens  112  and the first mirror  114  are fixed in relation to each other, i.e., their relative positions, including the distance and the angle between them, do not vary; and typically they are oblique with respect to each other. The input lens  112  and first mirror  114  are, however, movable and move as a unit if mounted together. In the embodiment shown in FIGS. 12A-C, the input lens  112  and the first mirror  114  are mounted on, and fixed to, a swing arm  124 . Preferably they are mounted so that the plane of the surface of the first mirror  114  is at an angle of about 30 degrees from the plane perpendicular to the optical axis of the input lens  112 . When swing arm  124  moves, the input lens  112  and the first mirror  114  move as a unit on the swing arm  124  and preferably rotate around an axle  122 . The input lens  112 , the first mirror  114  and the swing arm  124  form the input lens assembly  120 . The input lens assembly  120  captures object rays from the selected viewing positions. The movement of the input lens assembly  120  allows the viewing position of the arthroscope  30 ′, and thus the particular input image captured in the arthroscope  30 ′, to be variable. Although in the illustrated embodiment the mounting functions as the arm that allows movement of the input lens assembly  120 , these functions may also be provided separately; e.g., the input lens mounting may be separate from the first mirror mounting. 
     The second mirror  116  is rotatable, and preferably also rotates around the axle  122 . The second mirror  116  receives the objects rays of the image captured and reflected from the input lens assembly  120 , and reflects these rays to the lens relay system  118 , from where they are sent to the control end of the arthroscope  30 ′. The second mirror  116  preferably is a top or first-surface reflecting mirror. Referring to FIG. 14B, the second mirror  116  is supported by housing  117  and suspended by axle  122 . Preferably, the center of the axle  122  and the reflecting surface of the second mirror  116  are substantially coplanar. Preferably, axle  122 , second mirror housing  117 , and swing arm  126  operate as one unit that rotates around axle  122 . In a preferred embodiment, the second mirror housing  117  and the axle  122  are formed as one unit, with the housing  117  supported on the axle  122 . The middle section of the axle  122  may be machined to reduce the thickness of the axle and allow for proper positioning of the second mirror  116 . The distance from the portion of the housing  117  that will support the mirror to the center of the axle  122  is the thickness of the second mirror  116 . When the second mirror  116  is mounted, the reflecting surface of the second mirror  116  is at the center of the axle  122 . To maintain the structural integrity of the axle  122 , the axle  122  and housing  117  are preferably machined from a substantially cylindrical blank with a thicker center portion. A slot that forms the housing  117  for the second mirror is formed in the thicker center portion, leaving a sidewall for strength. 
     The rotation of the input lens assembly  120  provides variability in the view of the arthroscope  30 ′. The input lens assembly  120  rotates around an axis that is parallel to the axis around which the second mirror  116  rotates. In the illustrated embodiment, the input lens assembly  120  preferably rotates around the axle  122  that is located at the center of and extends along the plane of the surface of the second mirror  116 ; i.e., the first and second mirrors  114 ,  116  rotate around the same axis. Preferably, the input lens assembly  120  will rotate approximately 30 degrees between the most upward-facing view (“full-up”) and the most downward facing view (“full-down”) although a different range may be selected as desired. In a preferred embodiment, the arthroscope  30 ′ has a total viewing range of about or greater than 100 degrees. Preferably the middle view of the arthroscope  30 ′, i.e., the view in the middle off the range of the arthroscope  30 ′, is at an angle 45 degrees up from the longitudinal axis of the housing tube  31 ′ of the arthroscope  30 ′ (as shown in FIG.  12 A). 
     As the input lens assembly  120  rotates to different angles, it will capture object rays of different views of the object. Input object rays are to be sent from input end  100  to the control end of the arthroscope  30 ′, typically via lens relay system  118 . The object rays should be properly oriented with respect to the lens relay system  118  for improved transmission. The second mirror  116  directs the objects rays for relay to the control end of the arthroscope  30 ′. The view of the object that is reflected from the first mirror  114  up to the second mirror  116  should preferably then be reflected from the second mirror  116  so that the center line or axial ray of the reflected image is coaxial with the center line of the lens relay system  118 . Typically, the center line of the lens relay system  118  is parallel to the longitudinal axis of the housing tube  31 ′. At the middle view of the arthroscope  30 ′, at 45 degrees up from the longitudinal axis of the housing tube  31 ′ in accordance with a preferred embodiment of this invention, the plane of the surface of the second mirror  116  is at an angle of approximately 22.5 degrees from the plane of the surface of the first mirror  114  to provide the proper orientation of the object rays into the lens relay system  118  from the second mirror  116 . 
     As the input lens assembly  120  rotates, the position of the second mirror  116  must change to preserve the desired alignment. Due to the geometry of mirrors, the angle change in a reflected ray will be double the angle change in the mirror, such as when the mirror rotates from a first position to a second position. Specifically, the angle change in a ray reflected from first mirror  114  will be double the angle change in the mirror  114  and input lens assembly  120 . Because the input lens assembly  120  is fixed in relation to the axle  122 , the axial ray reflecting from the first mirror  114  always extends to a point on the second mirror  116  along the axle  122 . The axle  122  is a fixed distance from the first mirror  114  and so the distance between the centers of the two mirrors is preserved regardless of the view. In order for the axial ray to be reflected at the proper angle toward the center of the relay system  118 , however, the second mirror  116  must rotate one half the angular change of the input lens assembly  120 . Accordingly, as the input lens assembly  120  rotates, the second mirror  116  should preferably rotate, and preferably only half the angle that the input lens assembly  120  rotates. Referring to FIG. 16 for purposes of illustration, the first mirror has a first position mla corresponding to a first view of the arthroscope  30 ′ and a second position mlb (shown in broken lines) corresponding to a second view of the arthroscope. The second mirror has a first position m 2 a corresponding to a first view of the arthroscope and a second position m 2 b (shown in broken lines) corresponding to a second view of the arthroscope. For any two viewing positions, the angular difference between mla and mlb should be twice the angular difference between m 2 a and m 2 b. In a preferred embodiment, if the input lens assembly  120  has a rotational range of about 30 degrees from a full-up view to a full-down view, the second mirror  116  correspondingly has a rotational range of about 15 degrees. 
     In a preferred embodiment, the rotation of the input lens assembly  120  and of the second mirror  116  is controlled by a single push rod  128 . The push rod  128 , analogous to control rod  45  discussed hereinabove, is controlled from the outer control portion  35 , preferably by control knobs  49 , 50  in a manner and with a mechanism similar to that described in relation to other embodiments of the present invention. The push rod  128  effects different angles of rotation for the input lens assembly  120  and for the second mirror  116 . The push rod  128  moves the mirrors  114 ,  116  by moving the swing arms  124 ,  126 . For the angle change of the first mirror  114  to be twice the angle change of the second mirror  116 , the length of the swing arm  124  connecting the first mirror  114  to the push rod  128  should be half the length of the swing arm  126  connecting the second mirror  116  to the push rod  128 . As the two swing arms  124 ,  126  rotate about the axle  122  to sweep out equal arcs, the longer swing arm  126  will cover a smaller angle than the shorter swing arm  124 . In a preferred embodiment, when the input lens assembly  120  is positioned in the middle view, the swing arms  124 ,  126  are vertical, that is, at 90 degrees to the axial ray as it passes between the second mirror  116  and the lens relay system  118 , to establish the desired relationship between the position of the first mirror  114  and the second mirror  116 . The 90 degree angle is created by a line between the center of axle  122  and the rotational points on swing arms  124 ,  126  at the connection point of connecting rods  134 ,  136  and the axial ray as it passes between the second mirror  116  and the lens relay system. 
     In the illustrated embodiment, each swing arm  124 ,  126  is connected to the push rod  128  with a connecting rod  134 ,  136 . The connecting rods  134 , 136  allow the linear motion of the push rod  128  to be converted to the rotational motion of the swing arms  124 ,  126  and allow the swing arms  124 , 126  to rotate freely. The connecting rods  134 ,  136  move at both ends and are preferably attached to the push rod  128  and to the swing arms  124 ,  126  by pins or other fasteners, such as shoulder screws. It should be understood that any mechanical arrangement that preserves the desired geometries of the mirrors and input lens is suitable; for example, more than one push rod may be effective. 
     The object rays obtained through the input lens  112 , first mirror  114 , and second mirror  116  are preferably relayed to the outer control portion  35  of the arthroscope  30 ′. It is preferred that the rays be relayed so as to preserve the quality of the image and to minimize aberrations. A lens relay system  118  passes the object rays to the control end. In various embodiments, the lens relay system  118  is a lens or a series of lenses, one alternative of which is commonly referred to as a field and relay lens system. The lens relay system  118  is preferably coaxial with the point on the second mirror  116 , preferably on the center line of the axle  122 , where the axial object ray  150  is reflected. In alternative embodiments, the lens relay system  118  may be replaced by an optical fiber coherent bundle. In additional embodiments, the lens relay system  118  may be a graded index lens or other lens having a varying refractive index. Although lens relay system  118  is shown as being contained within the input end  100  of the housing tube  31 ′, the lens relay system  118  typically extends further towards the control end  33 . If lens relay system  118  is replaced with a coherent bundle of optical fibers or is replaced with a graded index lens system, each will typically extend substantially along the length of housing tube  31 ′ as does lens relay system  118 . 
     In preferred embodiments of the present invention, the input lens  112 , the first mirror  114  and the second mirror  116  are preferably arranged so as to preserve the various image ray path lengths when the view is altered, in order to preserve the focus of the image and minimize aberration. This feature can be better understood by reference to FIGS. 15 A-B and  16 . The length of the axial ray  150  remains the same whether the view of the arthroscope  30 ′ is at full-up (FIG. 15A) or full-down (FIG.  15 B). Similarly, the lengths of the rim rays  152 , typically the rays at the top and bottom of the image, are the same whether the view of the arthroscope  30 ′ is at full-up (FIG. 15A) or full-down (FIG.  15 B). The lengths of the rim rays  152  are also the same as each other. Once focused, all rays of the system stay in focus regardless of the view. In this system, the distortion created by a wide angle lens does not change regardless of view. This analysis is further illustrated in FIGS. 15A and 15B. FIG. 16 illustrates the image tracings for the full-up and full-down view superimposed in the same view. The path of the axial ray in the arthroscope  30 ′ can be better understood by reference to this figure. The axial ray  150  passes through the center of the input lens  112 , reflects from the center of the first mirror  114  and reflects at the center line of the axle  122  from second mirror  116  to the center of the first lens of the relay lens system  118 . The path length of the axial ray  150  is always the same, regardless of the view of the arthroscope  30 ′: the path length of the axial ray  150  is fixed (1) from the input lens  112  to the first mirror  114  because they are fixed with respect to each other; (2) from the first mirror  114  to the second mirror  116  because the center point of the surface of the second mirror  116  where the axial ray  150  will reflect is on the axle  122 , which is the point about which the first mirror  112  rotates and is a fixed distance from the first mirror  112 ; (3) from the center of the second mirror  116  to the optical center of the first lens of the relay lens system  118 , which is a constant distance from the center of the second mirror  118  fixed at the axle  122 . 
     The language used herein is used for purposes of reference and not limitation. While the invention has been particularly shown and described with reference to preferred embodiments, it will be apparent to those skilled in the art that various modifications and alterations can be made in the device of the present invention without departing from the spirit and scope of the invention.