SCANNING ENDOSCOPE FOR SURGICAL APPLICATIONS

Abstract: Adjustment of the field-of-view angle in a surgical endoscope from the outside of the patient's body is made possible by including in the objective op­ tical system an assembly of mutually movable prisms (30, 32). The prisms can be moved by a wire running alongside the optical fibers (70, 72) which convey illumination through the tube. In one embodiment, a movable prism pivots with respect to a fixed prism about an axis coincident with the axis of the image as it is transmitted between the prisms; in another embodiment, a partially silvered prism is slidable between two fixed prisms so as to pick up the image from one of them in one position, and the image from the other in the other position. Apparatus in the eyepiece is also disclosed to compensate for the rotation of the image when the pivoting embodiment is used.

Description: This invention relates to surgical microtelescopes, and more particularly to a device of that type in which the scanning angle can be varied while the device is in place. Scanning microtelescopes such as arthrascopes and cystoscopes are frequently used to examine the interior of the body by threading an optical observation head through a narrow passage in the body. In order to minimize the discomfort to the patient and permit access to a maximum number of body areas the optical observation head must be extremely small, with a diameter of as little as 3mm. It is obviously very difficult to place any movable objective lens system in such a small enclosure, and even more difficult to actuate it through the long flexible catheter which connects the head to the eyepiece on the outside of the body. Because of the size constraints and the need for the entire microtelescope to be sterilizable, known expedients such as movable mirrors cannot be used in surgical microtelescopes. Consequently, it has previously been necessary to provide separate instruments for each offset angle (i.e. the angle between the axis of the head and the axis of the field of vision being examined. Thus, if a surgeon wished to observe a body cavity at a 30° viewing angle and then at a 70° viewing angle, the first instrument had to be withdrawn and a second instrument inserted, thereby increasing patient discomfort and the risk of injury. US-A 3,880,148 corresponds to the preamble of Claim 1. The present invention makes it possible to examine a body cavity at several set-off angles, while the instrument is in place, by providing the objective lens system with a split prism whose parts can be moved with respect to one another. This invention provides an objective lens system for surgical microtelescopes which has a variable offset angle. The invention provides the foregoing improvement by means of an optical system including a split prism whose parts are relatively movable. According to the invention there is provided, a surgical microtelescope comprising: an elongated sterilizable observation head having mounted therein an optical system including a first prism and a second prism being movable with respect to said first prism and a lens so that in a first position of said movable prism, an image with a first angle of view is transmitted through said first prism and said second movable prism to said lens; an elongated optical conduit adjacent said lens; an eyepiece receiving from said elongated optical conduit the image obtained from said head; actuating means connected to said movable prism and extending between said head and the eyepiece end of said conduit for imparting relative movement to said movable prism from said eyepiece end of said conduit, said relative movement of said movable prism being such as to vary the angle between the axis of the field of view of said optical system and axis of said head characterised in that, a third prism is provided and in that said second movable prism has a partially mirrored surface so disposed that in a second position of said second movable prism an image with a second angle of view different from the first angle of view is transmitted through said third prism and said second movable prism to said lens. In an embodiment of the invention, a partially mirrored prism can be translated between two fixed prisms so as to interact with one of the feed prisms in one position, and with the other in another position. This arrangement allows the field of view to be switched between two fixed angles, and it dispenses with the requirement of a stiff actuator. The use of the split prisms makes it possible to confine the motion of the parts within the objective lens system to a very small space without loss of field width or image quality. One particular preferred embodiment of the present invention will now be described by way of example only, and with reference to the accompanying drawings in which: Fig. 1a is a general side elevation of a prior art device; Fig. 1b is a partial longitudinal section of the head of the prior art device of Fig. 1a; Fig. 2 is a vertical longitudinal section of the head of the device of the invention; and Fig. 3 is a horizontal section along line III-III of Fig. 2. As illustrated in Figs. 1a and 1b, scanning microtelescopes such as cystoscope conventionally consist of a head 11 attached to a tube 12 terminating in an eyepiece 14. In use, the head 11 and tube 12 are inserted into the body of the patient, with the eyepiece 14 remaining outside the body of the patient for observation by the physician. A light source 16 is conventially mounted in the eyepiece 14, and its light is transmitted through optical fibers 18 to the head 11. Typically, the objective assembly of the head 11 consists of a negative lens 20, a prism 22, and a positive lens 24. The positive lens 24 transmits the image seen by the negative lens 20 to an optical conduit located within the tube 12. The image may be transmitted to the eyepiece 14 through this optical conduit by lens relays, fiber optics, a gradient index relay rod, or any other suitable conventional optical apparatus. In Fig. 1b, the angle ∝ between the axis 26 of the head 11 and the axis 28 of the field of view of the lens 20 is on the order of 70°. Typically, cystoscopes are manufactured with a view angle of 70° or 30° for the most common purposes. It should be noted that the typical diameter of the head 11 for surgical microtelescopes is on the order of 3mm, and that its walls must be thick enough to be sturdy and to be easily sterilizable. Consequently, the components of the objective system must be extremely small and precisely aligned. Also, the field of view of the lens 20 must have a rather wide angle in order to afford the physician a useful view. For these reasons, conventional means such as tiltable mirrors cannot be used to vary the angle ∝ in any given cystoscope, and the instant has to be removed and another reinserted if the physician desires different view angles --- a procedure which is not only cumbersome for the physician, but also uncomfortable for the patient and a potential source of injury. The present invention makes practical a surgical microtelescope in which the field-of-view angle ∝ can be changed by the physician, between two fixed settings, without removing the instrument. As shown in Figs. 2 and 3, the objective system of this invention is similar to that of the prior art except that the prism 22 of Fig. 1b is replaced by a split prism assembly. The split prism assembly interposed between the positive lens 120 and the negative lenses 122, 124 (which look, respectively, through transparent windows 126, 128) consists of three prisms 130, 132, 134, of which only two are active at any given tine. The negative lenses 122, 124 may be omitted in certain applications without departing from the invention. Because of the difference in the angle of the two fields of view, it is necessary to provide two illumination fiber bundles 70 and 72. The bundle 70 is attached at such an angle to illuminate the field of view when ∝ is 70°, while the bundle 72 is attached at such an angle as to illuminate the field of view at ∝ =30°. As best shown in Fig. 3, the central prism 130 is transversely reciprocable by alternately pulling the flexible wires 136, 138. The minor face 140 of prism 130 is silvered on half of its area (142) and clear on the other half (144). In the position of prism 130 shown in Fig. 3, the image seen by lens 124 through window 128 (at an ∝ min angle of 30°) is transmitted through prisms 134 and 130, as shown in dotted lines, to lens 120. If the prism 130 is moved downward in Fig. 3, the mirrored surface 142 blocks the image from window 128 and instead reflects the image from window 126 (at the ∝ max angle of 70°) through lens 122 and prism 132 into lens 120. It will be noted that in the present invention, the two images are neither rotated nor inverted with respect to one another, so that no eyepiece compensation is needed.

Claims: A surgical microtelescope comprising: (a) an elongated sterilizable observation head (11) having mounted therein an optical system including a first prism (134) and a second prism (130) being movable with respect to said first prism (134) and a lens (120) so that in a first position of said movable prism (130), an image with a first angle of view is transmitted through said first prism and said second movable prism (134) to said lens (120); (b) an elongated optical conduit adjacent said lens (120); (c) an eyepiece (14) receiving from said elongated optical conduit the image obtained from said head (11); (d) actuating means (136,138) connected to said movable prism (130) and extending between said head (11) and the eyepiece end of said conduit for imparting relative movement to said movable prism (130) from said eyepiece end of said conduit, said relative movement of said movable prism (130) being such as to vary the angle between the axis of the field of view of said optical system and the axis of said head; characterised in that, a third prism (130) is provided and in that said second movable prism has a partially mirrored surface so disposed that in a second position of said second movable prism (130) an image with a second angle of view different from the first angle of view is transmitted through said third prism (132) and said second movable prism (130) to said lens (120). A microtelescope according to claim 1, in which said second movable prism (130) slidably movable between said first and second prism (132, 134)

Inventors: FORKNER, JOHN F.
Applicants: BAXTER INTERNATIONAL INC. (A DELAWARE CORPORATION)
Application year: 1987
Main classification: G02B23
IPC codes: G02B23, A61B1