Optical: systems and elements – Lens – Telephoto
Reexamination Certificate
2002-01-31
2002-09-03
Lester, Evelyn A (Department: 2873)
Optical: systems and elements
Lens
Telephoto
Reexamination Certificate
active
06445511
ABSTRACT:
BACKGROUND OF THE INVENTION
Generally speaking, focusing with a camera which uses photographic film is performed by moving either the entire camera lens or by moving only one part of the camera lens. It is difficult mechanically to rapidly perform focus adjustment by moving the entire camera lens, as the entire camera lens becomes too massive for cameras that use large film sizes.
Even for 6 mm×8 mm size film (i.e., mid-size film), it is desirable to adapt an inner-focus technique wherein only a part of the lens is moved for focusing. Further, it is desirable that the moving distance of the lens group that is moved for focusing be as short as possible.
Various developments of inner-focus-type lenses have been made for mid-size film lenses. See, for example, Japanese Laid Open Patent Application S61-051117, and Japanese Laid Open Patent Application H10-206729. However, there remains a demand for improved inner-focus-type lenses where focusing is accomplished even faster.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a high performance, inner-focus-type lens having a faster focusing response rate than was previously available in lenses of cameras for use with mid-size (6 mm×8 mm) film. More specifically, the object of the present invention is to provide an inner-focus-type lens with a focal length of about 300 mm and an F number of about 4.0 which has a rapid focus response and that is especially suited for use as a lens of a camera that utilizes mid-size film.
REFERENCES:
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patent: 4609263 (1986-09-01), Imaizumi
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patent: 4812026 (1989-03-01), Iima
patent: 4852984 (1989-08-01), Takahashi et al.
patent: 5490014 (1996-02-01), Suzuki
patent: 5610769 (1997-03-01), Shoji
patent: 6381079 (2002-04-01), Ogawa
patent: 6384975 (2002-05-01), Hayakawa
patent: 61-51117 (1986-03-01), None
patent: 10-206729 (1998-08-01), None
Arnold Bruce Y.
Arnold International
Fuji Photo Optical Co., Ltd.
Lester Evelyn A
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