Photography – Having variable focal length of camera objective – Automatic change of focal length
Reexamination Certificate
2000-08-14
2001-10-09
Perkey, W. B. (Department: 2851)
Photography
Having variable focal length of camera objective
Automatic change of focal length
C359S698000, C348S352000
Reexamination Certificate
active
06301439
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens driving control apparatus for a zoom lens used in a TV broadcasting camera.
2. Description of Related Art
Operability and mobility are considered important for a color TV camera for TV broadcasting. To meet these requirements, image pickup devices for cameras of this kind have recently become smaller in size. A small CCD (solid-state image sensor) measuring, for example, only ⅔ or ½ inch has come to be most popularly used for reduction in size and weight of a camera as a whole. In view of this trend, zoom lenses for broadcasting color TV cameras also have come to be arranged smaller in size and lighter in weight and to have advanced specifications.
Thus, for specifications and attaining effects of images, it has become one of most important factors for a broadcasting TV camera, in particular, to shorten the so-called M.O.D. (minimum object distance), i.e., the nearest distance at which a zoom lens can take a picture of an object located in front of the zoom lens.
However, the efforts to shorten the M.O.D. encounter a problem that the angle of view (a photo-taking angle of view) is caused to vary by focusing. In a case where the zoom lens is arranged to make focus adjustment with a first lens group disposed foremost on the side of object among other lens groups, i.e., a front lens group, this problem particularly becomes manifest. An art for solving this problem has been known, for example, from a disclosure made in U.S. Pat. No. 4,083,057.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a zoom lens which is arranged to eliminate the possibility of having a change of photo-taking angle of view caused by focusing, without necessitating any changes or modifications of the optical and mechanical arrangements of the zoom lens.
To attain this object, in accordance with an aspect of the invention, there is provided a lens driving control apparatus having a zooming operation member (unit) for operating a zoom part of the zoom lens and a focusing operation member (unit) for operating a focusing lens part of the zoom lens and arranged to drive the zoom part and the focusing lens part on the basis of operation command signals from the zooming and focusing operation members, in which information about driving of the zoom part for correcting a change of angle of view resulting from driving of the focusing lens part is computed on the basis of the operation command signal of the zooming operation member and the operation command signal of the focusing operation member or a position signal of the focusing lens part and a position signal of the zoom part, and the computed information is used as a zooming command signal for the zoom part.
Further, in particular, the lens driving control apparatus is provided with storage means for storing data necessary in computing a lens moving amount of the zoom part for correcting a change of angle of view resulting from driving of the focusing lens part. The lens moving amount computing operation can be speedily carried out by using the stored data. More specifically, the data stored by the storage means includes a group of coefficients of a proximate plane passing at least three of four dividing points obtained with a zooming range of the zoom part and a focus shifting range of the focusing lens part respectively divided into parts at dividing points and with positions of the zoom part and the focusing lens part at the dividing points and an angle of view determined by the two positions used as parameters.
The above and other objects and features of the invention will become apparent from the following detailed description of a preferred embodiment thereof taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4083057 (1978-04-01), Quinn
patent: 4156933 (1979-05-01), Pandres, Jr.
patent: 5204710 (1993-04-01), Tsukamoto et la.
patent: 5434621 (1995-07-01), Yu
patent: 5515204 (1996-05-01), Usui et al.
Canon Kabushiki Kaisha
Perkey W. B.
Robin Blecker & Daley
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