Optical: systems and elements – Lens – Reverse telephoto
Reexamination Certificate
1999-09-07
2001-07-03
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
Reverse telephoto
C359S770000, C359S781000, C359S737000, C359S726000
Reexamination Certificate
active
06256155
ABSTRACT:
BACKGROUND OF THE INVENTION
In recent years, image pick-up elements such as CCD devices have achieved high resolution and become compact as a result of advances in fine pattern technology which have enabled the pick-up element pixel size to be reduced. As a result of these advances, highly efficient and much smaller-sized objective optical systems have been in demand in optical systems which employ such image pick-up elements as, for example, endoscope systems. Especially in the case where an optical system employs, for example, a beam-folding prism or mirror which serves as a visual beam conversion element to provide a side or perspective view, there is the tendency for the entire optical system to become large as compared with an optical system that provides only a direct view. Thus, a size-reduction in such an optical system is desired. Moreover, while small size and high performance of an optical system are desired, nevertheless, an inexpensive objective optical system with three or fewer lens elements is also desired.
As a prior art example of an objective optical system that uses a visual field conversion optical element, the optical system described in Japanese Laid Open Patent Application No. H2-69710 is known. This prior art optical system combines a negative lens element, a visual field conversion optical element, a positive lens element and a positive lens element. However, since the refractive power of the negative lens element is weak, the correction of field curvature is insufficient. Moreover, since the Abbe number of a positive lens element is small, the amount of chromatic aberration is large.
Another prior art example of an objective optical system that uses a visual field conversion optical element is disclosed in Japanese Laid Open Patent Application No. H5-307139. This optical system consists of a negative lens element, a visual field conversion optical element, a positive lens element, and a positive lens element. However, the refractive index of the negative lens element is small and the generation of lateral color is large.
Another prior art example of a visual field conversion optical element is disclosed in Japanese Laid Open Patent Application No. 37-9530.
BRIEF SUMMARY OF THE INVENTION
This invention is an objective optical system for use with, for example, an endoscope. A first object of the invention is to provide an objective optical system that includes a visual field conversion optical element which folds the rays at least once. Such an optical element enables a side or perspective view in an optical system which is reduced in size as compared with prior art systems employing a visual field conversion optical element. A second object of the invention is to provide a visual field conversion optical element within an objective optical system that yields a high-quality image at low cost by employing in the objective optical system, at most, three lens elements that can be made of inexpensive materials.
REFERENCES:
patent: 3901220 (1975-08-01), Koyasu et al.
patent: 4042295 (1977-08-01), Yamasita et al.
patent: 4059344 (1977-11-01), Yamasita
patent: 4138192 (1979-02-01), Yamasita
patent: 4598980 (1986-07-01), Doi et al.
patent: 4684224 (1987-08-01), Yamashita et al.
patent: 4735491 (1988-04-01), Takahashi
patent: 4746203 (1988-05-01), Nishioka et al.
patent: 3214544 A1 (1982-11-01), None
patent: 37-9530 (1963-07-01), None
patent: 2-69710 (1990-03-01), None
patent: 5-307139 (1993-11-01), None
Arnold Bruce Y.
Arnold International
Epps Georgia
Olympus Optical Co,. Ltd.
Spector David N.
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