Surgery – Endoscope – Having imaging and illumination means
Reexamination Certificate
2002-06-07
2004-02-24
Leubecker, John P. (Department: 3739)
Surgery
Endoscope
Having imaging and illumination means
C600S169000, C359S513000
Reexamination Certificate
active
06695775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Art
This invention relates to a lens assembly which is particularly suitable for use as an optical objective lens system on an endoscopic insertion instrument.
2. Prior Art
For insertion into a body cavity, endoscopes generally have an insertion instrument which is extended out on the front side of a manipulating head assembly. An illumination means and an endoscopic observation means are incorporated into a distal end portion of the insertion instrument for endoscopic observation and examination of intracavitary sites of interest. The illumination means includes a light guide which is constituted by a bundle of fiber optics to transmit illumination light to a distal end of the insertion instrument from a light source to which an endoscope is disconnectibly connected. A light emitting end of the light guide is disposed in an illumination window which is provided on a rigid tip end section of the insertion instrument. An illumination lens is fitted in the illumination window to disperse illumination light from the light guide in a forward direction. The endoscopic observation means is provided for picking up information of an intracavitary site which is under illumination by the illumination window, and for this purpose includes an optical objective lens system. Optical images of an intracavitary site obtained through the optical objective lens system are either optically or electronically transferred to a viewing device. That is, in the case of an optical endoscope, optical images of an intracavitary site are transferred through an image guide to an eyepiece which is connected to the manipulating head assembly to permit an operator to view the optical images therethrough. In the case of an electronic endoscope, images of an intracavitary site are converted into electric signals by the use of an image sensor device and transferred to a video processor and thereby processed into video signals for display on a viewing screen.
No matter whether an endoscope is an optical type or an electronic type, its optical objective lens system of the endoscopic observation means is composed of a plural number of lens elements. A light incident end or face of a light guide is located at the focus of the optical objective lens system in the case of the optical endoscope, and an image sensor device is located at the focus of the optical objective lens system in the case of the electronic endoscope. The plural number of lens elements of the objective lens system are fitted in a lens tube or tubes of a lens assembly block to be fitted in the observation window. In aligning optical axes of the objective lens system and the light receiving face of the image guide or the image sensor device with each other, it is the general practice to fixe the light receiving face in a retainer tube to be fitted and assembled with the lens tube.
In this connection, a first lens element of an objective lens system, which is located in a foremost position within a lens tube, that is, in a foremost position on the side of a subject, is usually constituted by a planoconcave lens element, with a concave side facing inward of the lens tube. Since the first lens is fitted in an exposed state on a rigid tip end section of an endoscopic insertion instrument, its exposed outer surface is often contaminated by deposition of body fluids or other contaminants which degrade observing picture images to a considerable degree. Therefore, usually a lens surface cleaner is provided on the endoscopic insertion instrument thereby to wash away contaminants from the lens surface. The lens cleaner includes a fluid nozzle which is arranged to spurt a wash fluid toward an exposed outer surface of a first lens element. A wash liquid or cleaning liquid, which is normally water, is spurted toward the outer surface of the first lens, and then compressed air is blasted on the lens surface to remove residues of the wash liquid.
In a body cavity, the first lens element which is located at the distal end of an endoscopic insertion instrument is heated almost to the same level as the body temperature of the patient, and, in the case of an electronic endoscope, heated to a higher level due to existence of a heat generating device such as solid-state image sensor device or the like. On the other hand, a lens cleaning liquid is supplied without heating, that is, a cleaning liquid of approximately ambient temperature is supplied through the lens cleaner. Therefore, the first lens element is cooled off quickly upon sprinkling a cleaning liquid on its outer surface. When the first lens element is cooled off, the inner side of the lens can be fogged by condensation of water vapor in case moisture exists within the lens tube. Besides, since the concave surface on the inner side of the first lens element is of a large curvature, the temperature drop and condensation of moisture occur conspicuously in a center portion of the lens which is far thinner than peripheral portions. Fogging even in a slight degree of a center portion of the first lens element causes considerable degradations to picture images and makes the endoscopic observation difficult because light fluxes necessary for forming images are concentrated in the center portion. A distal end portion of an endoscopic insertion instrument can be cooled off quickly due to other reasons, resulting in fogging of and condensation of moisture on the first lens element of the objective lens system.
Therefore, an optical objective lens system to be incorporated into an endoscopic insertion instrument needs to have an anti-fogging function thereby to prevent fogging or condensation of moisture on lens elements in a lens tube, particularly on a first or foremost lens element of the objective lens system. For this purpose, dry air or nitrogen gas or other moisture-free gas is sealed in the internal space of a lens tube. In addition, in order to maintain a dry state and to prevent intrusion of moisture from outside, it is necessary to seal up fitting portions of a first lens. In forming a seal of this sort, it has been known in the art to fill silicon or other adhesive in a gap space between inner periphery of the lens tube and circumferential surface of the first lens element, for example, as shown in Laid-Open Japanese Patent Application H9-234183. However, considering the severe conditions in which endoscopes are used, that is, considering repeated washing, disinfection and heated sterilization of endoscopes in use, it appears almost impossible for an adhesive or seal material to prevent moisture from creeping into a lens tube of an objective lens system over a long period of time.
In this regard, proposed in Laid-Open Japanese Patent Application 2000-193892 is An air-tight structure which is formed by soldering together a lens tube and a first lens element of an optical objective lens system. In this case, as compared with an adhesive or seal material, the use of metal solder makes it possible to form an extremely sturdy air-tight structure. In addition, because of freedom from drops in air-tightness over a long period of time, it can securely prevent moisture from creeping into the lens tube from outside through the fitting mount portion of the first lens. In this connection, since the lens tube is formed of a metal, solder can be easily applied thereto. However, on the part of the lens element of glass, solder can be easily detached from the lens element if applied directly on a glass surface. Therefore, in order to prevent this, a soldering lens surfaces need to be metalized before applying solder thereto.
The air-tight structure by soldering is advantageous because it can maintain air-tightness stably over a long period of time. However, due to a difference in thermal expansion rate between metal and glass, detachment of solder or damages to lens elements may occur, for example, when the endoscopic insertion instrument is heated in an autoclave for sterilization. For this reason, it is undesirable to solder a circumferential surface of a lens element to an inner
Kobayashi Tadasu
Kuboya Hiroshi
Miura Nobuyuki
Sakamoto Kazuhiro
Watanabe Joji
Fuji Photo Optical Co., Ltd.
Leubecker John P.
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