Optical: systems and elements – Stereoscopic – With right and left channel discriminator
Reexamination Certificate
2001-02-16
2003-09-02
Chang, Audrey (Department: 2872)
Optical: systems and elements
Stereoscopic
With right and left channel discriminator
C359S462000, C359S376000, C359S377000, C359S378000, C600S111000, C600S166000, C348S045000
Reexamination Certificate
active
06614595
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical system for a stereo endoscope.
BACKGROUND OF THE INVENTION
Conventionally, optical systems for stereo endoscope are known, as described in U.S. Pat. Nos. 4,924,853 and 5,527,263.
In endoscopic surgery, both a wide angle image and a magnified image are required. The wide angle image is used for finding an organ, a disease, or a treatment tool and the magnified image is used for treatment.
A conventional rigid endoscope usually has only one observation optical system. When a wide angle objective lens is arranged in the optical system, the above-mentioned needs are carried out by using one of following methods: (a) changing the distance to an object; and (b) using an optical zoom function on a TV camera system to connect.
On the other hand, an endoscopic robot surgery system has been recently developed. In this system, surgical treatment tools and an endoscope are operated remotely by a surgeon. Since the robot enables precise surgical treatment, surgeons require the endoscope to have better image capabilities with higher magnification and higher resolution at the time of treatment.
When the above methods (a) or (b) are used in endoscopic robot surgery in order to get a magnified image of a object, the following problems arise.
For method (a), if a rigid endoscope is brought close to a target object, interference between the endoscope and treatment tools will cause a problem. Therefore, the field angle of view should be narrow at the time of treatment to get both high magnification and long working distance (WD). However, if an objective lens has a narrow angle, the wide angle image needed for finding an organ, a disease or a treatment tool will not be obtained.
For method (b), a combination of a wide angle rigid endoscope and a camera system with an optical zoom function enables both a wide image as well as a high magnification image. But the high magnification image quality is worse than the wide image because the point spread property of the rigid endoscope is fixed and the final point spread property at the imaging surface in the camera system is magnified according to the optical zoom state in the camera system. A longer focal length of the zoom optics makes the final point spread property worse. This deterioration of the image quality at a high magnification state is not suitable for precise treatment.
Moreover, in the endoscopic robot surgery system, a stereo endoscope system is preferred in order to obtain a depth perception. In this case, however, the following additional problem arise.
First, it is more difficult to get a good image quality than in the case of a two-dimensional image (2D). In the stereo endoscope, it is necessary to transmit the right and left images within the space of the limited insertion part. In this case, image quality of the stereo endoscope will be degraded more than in the case of 2D.
Second, it is difficult to add a zoom function in the stereo endoscope system while keeping the right and left optical conditions satisfied.
SUMMARY OF THE INVENTION
In view of the foregoing disadvantages inherent in the known types of prior art, the present invention solves the above-mentioned problems. Thus, it is an object of the present invention to provide a stereo endoscope which gives both a wide angle image for finding an organ or treatment tools and high magnification stereoscopic images used for a precise treatment.
A stereo endoscope of the present invention which attains the above objective comprises, a right optical system which forms a right image for stereoscopic observation and which comprises a right objective optical system and a right relay optical system, a left optical system which forms a left image for stereoscopic observation and which comprises a left objective optical system and a left relay optical system, a third optical system which forms a third image for finding an organ or treatment tools and which comprises a third objective optical system and a third relay optical system, wherein the axes of the right, left and third relay optical systems are arranged in parallel, respectively.
The three optical systems according to this invention satisfy the following conditions.
(1) FAw/FAlr>1.3
(2) 0.3<LDw/LDlr<0.8
FAw represents a field an angle of view of the third optical system; FAlr represents a field angle of view of the right or left optical system; LDw represents a maximum lens diameter of the third relay optical system; and LDlr represents a maximum lens diameter of the left or right relay optical system.
Such constitution can obtain both a wide angle image used for finding an organ, a disease or a treatment tool and narrow angle stereoscopic images with high resolution used for precise treatment.
The first condition (1) means that the field angle of view of the third optical system is significantly larger than that of right and left optical systems. The constant 1.3 in the first condition (1) is selected in order to obtain a significant difference in a visual field area. The constant 1.3 is the square root of 1.7 and the value 1.7 means the difference in the visual field area. The 1.7 times difference seems to be a minimum for a practical stereo endoscope design. Moreover, it is desirable that the ratio of FAw/FAlr is larger than 1.3 in order to obtain a larger difference in the field of view between the stereo images and the third image. For example, in the case that FAlr is 40 degrees for cardiac surgery, FAw should be more than 52 degrees. In another case, if FAlr is 60 degrees for general abdominal surgery, FAw should be more than 78 degrees.
If the first condition (1) is not satisfied, the third optical system bears no significance to finding an organ or treatment tools because the difference in the field of view between the stereo Images and the third image is too small. Therefore, it is desirable that the first condition (1) be satisfied.
The second condition (2) means that the maximum lens diameter of the right and left relay optical systems are significantly larger than that of the third relay optical system. The upper limit constant 0.8 in the second condition (2) is selected in order to obtain a significant difference in the effective aperture size of the relay optical systems. In general, a maximum lens diameter of a relay optical system relates to the optical numerical aperture (NA) of the relay optical system.
The stereo endoscope in this invention has an insertion tube. Right, left and third relay optical systems must be supported in the insertion tube of the stereo endoscope. Therefore, it is very important to optimize the maximum lens diameter of the relay optical systems. Furthermore, since the maximum lens diameter of an objective optical system is the same as or smaller than that of a relay optical system, in general, it is enough for this invention to compare the maximum lens diameter of the relay optical systems.
Since the maximum lens diameter of the right relay optical system should be the same as that of the left relay optical system, the ratio of the maximum lens diameter of the third relay optical system to that of the right and the left optical systems is one of the most important parameters. Since the right and the left optical systems must be designed with high resolution for precise treatment, it is necessary for the right and the left optical system to have a large NA in order to get a high resolution according to diffraction theory. Enlarging the lens diameter is one of the effective methods to get a large NA because in general NA of a relay optical system is proportional to the maximum lens diameter of the relay optical system. Since the third relay optical system is used for finding, image quality of the third optical system is permissible even if it is somewhat bad. Therefore, NA of the third relay optical system may be smaller than that of the right and the left relay optical systems. However, too small a NA of the third relay system causes brightness problem of the third image. The lower limit constant 0.3 in the second conditio
Armstrong Westerman & Hattori, LLP
Chang Audrey
Olympus Optical Co,. Ltd.
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