Endoscope with relative rotation and axial motion between an optical element and an imaging device

An apparatus for viewing a region comprises a hollow member elongated between a proximal end and a distal end configured to be inserted into the region, an optical element disposed in the distal end, and an image detector disposed adjacent to the optical element. The optical element and the image detector are arranged for relative rotation. The apparatus is particularly well-suited for use in an endoscope, and in particular with an endoscope having an off-axis field of view.

BACKGROUND 
This invention relates to imaging devices, and in particular to endoscopes. 
Endoscopes are widely used to inspect regions of the body (e.g., joint 
spaces) through a small puncture wound during surgery (such as 
arthroscopic surgery). Typically, the endoscope includes an elongated 
insertion tube equipped with a set of optical fibers which extend 
continuously 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 fibers, and the 
viewing end, where the light is emitted to illuminate the region under 
inspection. 
Received light representing an optical image of the joint space is 
collected by an optical element (such as one or more lenses of a lens 
assembly) mounted in the distal viewing tip and is passed to, e.g., a 
solid-state image detector (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.degree. 
or at 70.degree. ). 
SUMMARY OF THE INVENTION 
This invention features an imaging device in which the image detector and 
the optical element are arranged for relative rotation. The invention is 
particularly, but by no means exclusively, useful in an endoscope that has 
an off-axis direction of view, because it allows the user to control the 
orientation of the displayed image when the endoscope is rotated to change 
the field of view. As a result, the user can maintain the displayed image 
in any orientation that he or she selects, regardless of the rotational 
position of the endoscope. 
In one aspect of the invention, the optical element and the image detector 
are disposed adjacent to each other and arranged for relative rotation in 
the distal end of an elongated, hollow member. 
Preferred embodiments include the following features. 
An actuator is arranged to provide the relative rotation between the 
optical element and the image detector. preferably, the actuator is 
rotatably disposed with respect to the proximal end of the hollow member 
and is coupled to the image detector so that rotation of the actuator 
causes the image detector to rotate with respect to the optical element 
(which is stationary with respect to the hollow member). 
The image detector (e.g., a solid state pickup device) is supported at the 
distal end of an elongated inner member disposed within the hollow member. 
The actuator engages the proximal end of the inner member. This engagement 
is configured to permit the inner member to be moved axially with respect 
to the hollow member to change the spacing between the image detector and 
the optical element. This feature allows the image to be focussed on the 
image detector without interference from the linkage to the actuator. 
In one embodiment, the engagement between the actuator and the proximal end 
of the inner member is provided by a key on the actuator that is disposed 
in a slot in the proximal end of the inner member. The slot has a 
longitudinal length sufficient to allow the inner member to move axially 
with respect to the hollow member. A second actuator is linked to the 
proximal end of the inner member for moving the inner member axially 
(e.g., during the focussing operation). 
The optical element is configured to provide an off-axis direction of 
view--that is, a direction of view that is at a nonzero angle with respect 
to the axis of the hollow member. preferably, the optical element includes 
at least one lens. 
Another aspect of the invention features a method of viewing a region of 
the body using an endoscope that implements structural features of the 
invention. The endoscope is inserted into the body and placed in a first 
rotational position so that an image of the body region detected by the 
image detector is displayed in a first orientation on a display device; 
then, the endoscope is rotated to a second, different rotational position 
and the actuator is manipulated so that the image of the body region is 
displayed in the first orientation. 
Preferred embodiments include the following features. 
The overall result --displaying the image in the first rotational position 
despite rotating the endoscope--can be achieved in multiple ways. For 
example, the endoscope may first be rotated to the second rotational 
position so that the image is displayed in a second, different orientation 
on the display device; the actuator is then rotated to cause the displayed 
image to return to the first orientation. Alternatively, the endoscope is 
rotated to the second rotational position while holding the actuator 
stationary so that the image remains in the first displayed orientation as 
the endoscope is rotated. 
The invention allows the user to rotate the endoscope at will (e.g., to 
change the direction of view as necessary during surgery) without 
necessarily rotating the displayed image. The orientation of the displayed 
image can be maintained in any selected orientation independently of the 
rotational position of the endoscope. As a result, even when the endoscope 
is rotated by, e.g., 180 degrees, the user need not view the image "upside 
down." 
Moreover, rotating the image detector with respect to the optical element 
enables an external fiber optic cable, which receives light from an 
external light source, to be connected in-line at the proximal end of the 
handle (rather than at a side-facing light post on the handle). Connecting 
the fiber optic cable to the handle in this way reduces the tendency of 
the fiber optic cable to become twisted or wrapped around the handle when 
the endoscope is rotated. This enhances the maneuverability of the 
endoscope, and substantially reduces the risk of damaging the fiber optic 
cable (and its associated connectors). 
Other features and advantages of the invention will become apparent from 
the following detailed description, and from the claims.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to FIG. 1, endoscope 10, suitable for viewing inside of a remote 
area, such as, for example, viewing into a body cavity, joint space, or 
passageway during arthroscopic surgery, includes elongated insertion tube 
12 attached to handle 14. Lens assembly 16 (shown schematically) is 
mounted within the distal end of insertion tube 12. CCD tube 20 supports a 
charge-coupled device (CCD) or other suitable image detector 22 proximally 
adjacent to lens assembly 16. CCD tube 20 and CCD are rotatably mounted 
with respect to lens assembly 16, about longitudinal axis 18, within 
insertion tube 12 and handle 14. Actuator 30 is linked to the proximal end 
of CCD tube 20 and is rotatably mounted to handle 14. As described in more 
detail below, actuator 30 is manipulated by a user to produce relative 
rotation between CCD tube 20 (and thus CCD 22) and insertion tube 12 about 
longitudinal axis 18. 
Endoscope 10 has a direction of view (shown by vector 26 in FIG. 1) that is 
off-axis, i.e., arranged at a nonzero angle to longitudinal axis 18. The 
direction of view is determined by the orientation of window lens 24 of 
lens assembly 16 (i.e., the angle formed between longitudinal axis 18 and 
vector 26, vector 26 being perpendicular to window lens 24 at distal 
viewing tip 19) and is typically 30.degree., 45.degree., or 70.degree.. 
The field of view, angle .THETA., 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 26. 
Endoscope 10, as shown, views area A. To illuminate area A, endoscope 10 
includes a set 28 of optical fibers 29 that extend through handle 14 and 
insertion tube 12 to distal viewing tip 19. Light from external light 
source 1 is transmitted through light cable 2 to a light coupler 4 at the 
back of handle 14, which is in turn connected to one end of optical fiber 
set 28. The arrangement of optical fibers 29 at distal viewing tip 19 is 
described briefly below and in more detail in U.S. patent application Ser. 
No. 08/475,900 "Rotatable Fiber Optic Joint," filed concurrently with this 
patent application, assigned to the present assignee, and incorporated 
herein by reference. 
In use, light from external light source 1 is coupled through cable 2 and 
optical fiber set 28, and exits distal viewing tip 19 to illuminate area 
A. Light from objects within area A is collected by lens assembly 16 and 
passed to CCD 22, which converts the light into electrical signals 
representing the objects. The electrical signals are transmitted (by 
circuitry not shown) to a camera control unit 6 for processing in the 
usual manner. The resultant image is displayed on display screen 8. 
The user rotates handle 14 and insertion tube 12 together about 
longitudinal axis 18 to change the orientation of the field of view and 
observe areas adjacent to area A. All other things being equal, rotating 
handle 14 causes the image projected onto display screen 8 to be rotated, 
as well, because CCD tube 20 and CCD 22 are rotated with insertion tube 
12. But with the invention, the user can readjust the orientation of the 
image on display screen 8 and reorient the displayed image in its original 
orientation simply by rotating actuator 30. As a result, the user can 
continue to view the image in the original orientation, despite having 
rotated endoscope 10. 
Referring as well to FIG. 2, insertion tube 12 includes inner tube 42, 
which houses CCD tube 20, and outer tube 44. Inner tube 42 and outer tube 
44 extend along different, parallel axes--longitudinal axis 18 and 
longitudinal axis 48, respectively. The offset between longitudinal axis 
18 and longitudinal axis 48, which is preferably about 0.013 inches, 
creates a channel 50 between tubes 42, 44. Channel 50 houses optical fiber 
set 28 in insertion tube 12. 
At distal viewing tip 19, lens assembly 16 is aligned along longitudinal 
axis 18. Window lens 24 of lens assembly 16 is angled with respect to the 
longitudinal axis 18 to determine the direction of view of endoscope 10, 
and could be recessed from the distal end of outer tube 44 to protect the 
exposed exterior surface of window lens 24. Wedge 52, at distal viewing 
tip 19, deflects optical fibers 28 such that light is directed along the 
direction of view in accordance with the orientation of window lens 24, 
e.g., at 30.degree. with respect to axis 18. Individual optical fibers 29 
of optical fiber set 28 are arranged in a crescent shape within wedge 52, 
corresponding to the shape of channel 50, to evenly disperse the light 
across the width of insertion tube 12. Lens assembly 16, wedge 52, optical 
fibers 28, and outer tube 44 are all bonded together by, for example, an 
epoxy. Lens assembly 16 is also attached to inner tube 42 by, for example, 
an epoxy. The construction of distal viewing tip 19 is also described in 
the above-identified patent application. 
CCD 22 is positioned proximally of lens assembly 16 and is aligned along 
longitudinal axis 18. CCD tube 20 is rotatably mounted within inner tube 
42 of insertion member 12 and handle 16 in a manner described in detail 
below. Additionally, CCD tube 20 is axially movable along longitudinal 
axis 18 within inner tube 42 and handle 14 to adjust the focus of the 
image detected by CCD 22. CCD 22, including its associated electrical and 
optical systems, are of the type described in detail in copending U.S. 
patent application Ser. No. 07/958,688, filed Oct. 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 20 and CCD 22 are moved axially 
along longitudinal axis 18 with respect to lens assembly 16. This motion 
changes the spacing between lens assembly 16 and CCD 22, thereby adjusting 
the focus of the image. The focussing mechanism of endoscope 10 differs in 
some respects from that described in the '668 application, as described 
below. 
Referring to FIGS. 3 and 4, the proximal end of CCD tube 20 is engaged by 
actuator 30. More specifically, actuator 30 is coupled by pin 62 to 
bushing 60, which in turn is linked to CCD tube 20 by key 64. In 
particular, pin 62 is inserted through bore 66 in actuator 30, into a 
first longitudinal slot 68 in bushing 60. Key 64 is disposed within a 
second longitudinal slot 70 in bushing 60, so that a rounded portion 65 of 
key 64 extends into a slot 72 in CCD tube 20. Key 64 is biased into slot 
72 by spring 74, which urges key 64 away from an interior surface of the 
body of actuator 30. Rotation of actuator 30 about longitudinal axis 18 is 
translated through pin 62, bushing 60, and the engagement of key 64 in 
slot 72 to cause CCD tube 20 (and thus CCD 22) to rotate about axis 18. 
Notably, during the assembly or disassembly of CCD tube 20 from endoscope 
10, rounded portion 65 of key 64 functions as a cam against the exterior 
surface of CCD tube 20 (including slot 72 and slot edges 73, 75). For 
example, as CCD tube 20 is axially removed from endoscope 10, rounded 
portion 65 engages slot edge 75 to push key 64 against spring 74 such that 
key 64 is removed from slot 72. 
The body of actuator 30 includes a raised ridge 33 aligned with the 
vertical dimension of the imaging surface of CCD 22. Ridge 33 gives the 
user a frame of reference to determine the rotational position of CCD 22 
with respect to handle 14 (and thus insertion tube 12). Ridge 33 also 
provides the user with a convenient way of holding CCD 22 rotationally 
stationary, if desired, when handle 14 and insertion tube 12 are rotated. 
FIG. 3 shows the mechanism used to move CCD 22 axially with respect to lens 
assembly 16 for adjusting focus. The proximal end of focus sleeve 80 
includes threads 82 that engage threads on focus knob 84. When focus knob 
84 is rotated, focus sleeve 80 is prevented from rotating by the 
engagement of pins 86 within elongated slots in a stationary alignment 
ring 88. Alignment ring 88 is retained in handle by retaining ring 90. 
Thus, rotational motion of focus knob 84 is translated into axial movement 
of focus sleeve 80, which is attached to CCD tube 20 (by lock nut 98 and 
washer 99 being tightened against focus adjustment nut 92), thereby 
causing CCD tube 20 to also move axially. Slot 72 in CCD tube 20 and the 
slots in alignment ring 88 are of sufficient length to permit the axial 
movement of CCD tube 20 for focusing. 
The initial focus position of endoscope 10 is preset during manufacture as 
follows. The proximal end of CCD tube 20 includes threads 94 which are 
engaged by the threads of a focus adjustment nut 92. When focus adjustment 
nut 92 is rotated, wave spring 95 pushes focus adjustment nut 92 
proximally into retainer ring 96 to translate rotation of focus adjustment 
nut 92 to axial movement of CCD tube 20. When infinity (i.e., the initial 
"in focus" position) is located, focus adjustment nut 92 is locked into 
position by tightening lock nut 98 and washer 99 against focus adjustment 
nut 92. This arrangement of focus adjustment nut 92, lock nut 98 and 
washer 99 also secures the proximal end of CCD tube 20 within handle 14. 
The distal end of CCD tube 20 is mounted in inner tube 42, and aligned 
about longitudinal axis 18, by the close tolerance between CCD tube 20 and 
inner tube 42. 
FIG. 3 also shows the connection between external fiber optic cable (FIG. 
1) and optical fiber set 28 at the proximal end 32 of handle 14. The 
individual fibers 29 of set 28 (each of which is approximately 2.0 mils in 
diameter) are epoxied into threaded bushing 34, and the proximal ends 36 
of each optical fiber 29 are uniformly polished for efficiently receiving 
light from light coupler 4. A sheath 40 covers and bundles individual 
optical fibers 29 through a substantial portion of handle 14. 
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 (5 1/4 mm) where cable enters coupler 4, 
and is reduced substantially (to a diameter, 4b, of 3 1/2 mm) at the 
junction between cable 2 and optical fiber set 28. The ratio between 
diameters 4a and 4b multiplied by the numerical aperture of cable 2 (0.54) 
provides the desired numerical aperture (0.81) of optical fiber set 28. 
In use, insertion tube 12 of endoscope 10 is inserted into a body cavity, 
joint space, or passageway during surgery. Distal viewing tip 19 is 
oriented by a user such that the desired area within the body cavity is 
within the field of view of endoscope 10 and displayed on display screen 
8. To view a different part of the body cavity, the user rotates handle 
14, e.g., clockwise, which causes insertion tube 12, CCD tube 20, and CCD 
22, to rotate in the same direction about longitudinal axis 18. Thus, not 
only is the direction of view changed, so too is the orientation of the 
image on display screen 8. To reorient the image on in its initial 
orientation on display screen 8, the user rotates actuator 30 in a 
direction opposite from the rotation of handle 14 (e.g., counterclockwise) 
until the image is properly oriented on display screen 8. 
The user can avoid this two step procedure and maintain the orientation of 
the displayed image fixed by holding actuator 30 stationary (ridge 33 
provides a convenient grasping point) while rotating handle 14. This 
causes CCD tube 20 (and hence CCD 22) to remain stationary while insertion 
tube 12 rotates about CCD tube 20. 
Other embodiments are within the scope of the following claims. 
For example, inner tube 42 and outer tube 44 may be coaxial so that the 
channel created for optical fibers 29 is an annular ring formed between 
the inner and outer tubes. Likewise, other arrangements of individual 
optical fibers 29 at distal viewing tip 19 can be used. For example, 
optical fibers 29 can be arranged in an annular ring about the perimeter 
of window lens 24. 
The endoscope can include any of the features of the above identified 
patent applications. For example, as described in the "Rotatable Fiber 
Optic Joint" application, the endoscope may allow the insertion tube to be 
rotated with respect to the handle, and include a rotatable joint between 
discrete sets of optical fibers in the handle and in the insertion tube, 
respectively.