Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
1999-01-15
2001-03-27
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
Having imaging and illumination means
C600S129000, C600S130000, C385S117000
Reexamination Certificate
active
06206825
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to an objective optical system for endoscopes, and more specifically to an objective optical system for endoscopes which is configured to allow a plurality of adapter optical systems to be attached and detached thereto and therefrom for changing a direction toward a visual field, a field angle and an observation distance.
b) Description of the Prior Art
Conventionally, medical endoscopes which permit inserting elongated insert sections into living bodies for observing organs in the living bodies and passing forceps through forceps channels for sampling tissues of living bodies for detailedly diagnosing diseased parts in detail are widely used. Industrial endoscopes which permit observation and inspections of interiors of boilers, turbines, chemical plants and so on are widely known in industrial fields.
Attached to an industrial endoscope, in particular, is a direct view type adapter for observing a diseased part which is located in the longitudinal direction before the insert section or a side-view type adapter for observing an inside wall which is located sideways in a direction perpendicular to the inserting direction. In practice, one simultaneously selects an adapter which has a field angle that is optimum for a location to be observed and another adapter which has an optimum observation distance (or a depth of field) and so on.
It is effective from an economical viewpoint to configure such an expensive endoscope as a tip adapter type endoscope which can be equipped with adapters having a direction of a visual field, a field angle and an observation distance matched with a location to be observed.
Also widely used in the industrial fields are electronic endoscopes which provide images of qualities remarkably improved owing to progress made in solid-state image pickup devices (CCD's).
A conventionally known example of such electronic endoscopes is an electronic endoscope disclosed by Japanese Patent Kokai Publication No. Hei 2-74,912 which has a composition shown in FIG.
1
. This conventional electronic endoscope has no mechanism of the tip adapter type described above and is not versatile in the industrial fields. When an attempt is made to configure this electronic endoscope as the tip adapter type by dividing a lens system thereof into a subsystem which is located before an aperture'stop S and replaceable with an adapter, and another subsystem located after the aperture stop S, for example, it is necessary to dispose a light guide to be used in an illumination system at a location of a lens unit L. A reason to select this disposition is that it is optimum to dispose a light guide G so that it turns below a side-viewing prism P as shown in
FIG. 2
for attaching a side-viewing adapter.
When the light guide is disposed at the location of the lens unit L in the electronic endoscope disclosed by Japanese Patent Kokai Publication No. Hei 2-74,912, an objective optical system of this electronic endoscope has a large outside diameter at its tip. For disposing the light guide without enlarging its outside diameter, it is necessary to reduce an outside diameter of the lens unit L or a number of optical fibers which are to be used for composing a light guide. As a result, rays are eclipsed by the lens unit L or illuminating rays are reduced, thereby making brightness insufficient.
On the other hand, there is known an objective optical system for tip adapter type electronic endoscopes which has a composition shown in FIG.
3
. This objective optical system for tip adapter type endoscopes is configured to concentrate all light guides at the location of the lens unit L for correcting the defect of the electronic endoscope disclosed by Japanese Patent Kokai publication No. Hei 2-74,912.
In the recent years where images of having higher qualities and full-screen sizes are strongly demanded, it is expected that electronic endoscopes which can provide images suited for display on high definition televisions (HDTV's) will be adopted in the near future.
For obtaining images of such high qualities, however, it is necessary to configure picture elements so as to have a smaller size, or lower illuminance per picture element on an image surface, thereby making it difficult to maintain the conventional image brightness. Further, it is known that depths of field are reduced by reducing sizes of picture elements.
For correcting the defects described above, it is necessary to reserve a required depth of field by enlarging an F number of an objective lens system and compensate for brightness by increasing the number of optical fibers that are used for making the light guide.
In the field of the endoscopes which should desirably have smaller diameters, however, it is undesirable to increase the number of optical fibers that are used for making the light guide since such increase results in enlarging the outside diameters of the endoscopes. In the case of the objective optical system for the tip adapter type of electronic endoscopes illustrated in
FIG. 3
, the objective optical system has an outside diameter which is enlarged by increasing the number of optical fibers. When the objective optical system for tip adapter type endoscopes is configured to provide a full-size screen, it may not accept an increase the heights of rays caused by enlarging an image side and allow a visual field to be eclipsed. In
FIG. 3
, the reference symbol AD represents an adapter lens system and the reference symbol M designates a master lens system.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide an objective optical system for endoscopes which permits using lens elements having relatively small outside diameters and reducing outside diameters of tips of endoscopes without reducing numbers of optical fibers to be used for composing light guides, and more specifically an objective optical system for tip adapter type endoscopes.
The objective optical system according to the present invention is characterized in that it is disposed, in an object side tip of an endoscope, in parallel with an illumination optical system which is inserted in a longitudinal direction and tied up in a bundle, and that it comprises lens elements which are disposed in the object side tip of the endoscope and have an outside diameter smaller than that of lens elements located in the vicinity of an image pickup device disposed on the object side in the endoscope.
The objective optical system for endoscopes according to the present invention which has the object side tip having a small outside diameter permits reducing outside diameters of tips of endoscopes without reducing numbers of optical fibers which are to be used for composing light guides.
Further, the objective optical system for endoscopes according to the present invention is characterized in that it is configured as an adapter type objective optical system for endoscopes having a tip to and from which an adaptor comprising an aperture stop for the objective optical system can freely be attached and detached.
The objective optical system for endoscopes according to the present invention consists, as exemplified in
FIG. 4
, of a lens unit A which is disposed as a tip on the object side and a lens unit B which is disposed on a side of an image pickup device; the lens unit A having an outside diameter smaller than that of the lens unit B.
A tip adapter lens system AD having a small outside diameter is freely attachable and detachable, as shown in
FIG. 5
, to and from the object side of an objective optical system (master lens system) M which is composed of the lens unit A and the lens unit B shown in FIG.
4
.
An image of an object to be observed is allowed by the adapter lens system AD to pass through an aperture stop S
1
and fall nearly perpendicularly onto an image receiving surface of an image pickup device disposed in the objective optical system (master lens system) M. In other words, a nearly telecentric optical system is composed of the adapter le
Leubecker John P.
Olympus Optical Co,. Ltd.
Pillsbury Madison & Sutro LLP
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