Photography – With object illumination for exposure – Variable illumination angle
Reexamination Certificate
2003-06-26
2004-05-04
Perkey, W. B. (Department: 2851)
Photography
With object illumination for exposure
Variable illumination angle
C396S200000, C362S018000
Reexamination Certificate
active
06731870
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flash device which can adjust the flash coverage or luminous intensity distribution characteristic in accordance with, e.g., the focal length of a zoom lens in use.
2. Description of the Related Art
FIGS. 8A and 8B
show a typical (conventional) zoom flash device
100
. The zoom flash device
100
has a flash tube
50
, a lens
52
and a reflector
54
. One of the lens
52
and the reflector
54
is moved relative to the other along an optical axis of the zoom flash device
100
to change the space between the lens
52
and the reflector
54
to adjust the flash coverage (luminous intensity distribution) in accordance with the focal length (angle of view) of a zoom lens (not shown).
The structure of such a conventional zoom flash device is unfavorable with respect to the recent tendency of miniaturization of cameras because a sufficient space allowing one of the lens
52
and the reflector
54
to move relative to the other needs to be provided between lens
52
and the reflector
54
.
In addition, if such a space between the lens
52
and the reflector
54
is large, vignetting occurs. Namely, a portion of the flash light reflected by the reflector
54
is obstructed by the edge of the aperture of the lens
52
, thus not exiting out of an exit surface (front surface) of the lens
52
. This problem of vignetting is noticeable, especially with the marginal rays of flash light that pass through the perimeter of the lens
52
, thus causing a reduction in luminous intensity of the marginal rays of flash light.
SUMMARY OF THE INVENTION
The present invention provides a flash device which can adjust the flash coverage without changing the space between the lens and the reflector with a minimum reduction in luminous intensity of the marginal rays of flash light. Other aspects and advantages of the present invention will become apparent to one skilled in the art by reading the following disclosure and the appended claims.
According to an aspect of the present invention, a flash device is provided, including a flash tube; a reflector having a first reflector portion and a second reflector portion which are arranged symmetrically with respect to a plane including an axis of the flash tube, a space between the first reflector portion and the second reflector portion increasing in a direction toward a front end aperture of the reflector; and a lens positioned so as to be opposed to the front end aperture of the reflector. At least a part of the first reflector portion on a side of said front end aperture and at least a part of the second reflector portion on a side of said front end aperture are interlocked with each other to be movable in opposite directions along a direction perpendicular to the plane.
It is desirable for the part of the first reflector portion and the part of the second reflector portion to parallel-translate in the opposite directions.
It is desirable for the first reflector portion to include a first rear stationary reflector and a first front movable reflector. The second reflector portion includes a second rear stationary reflector and a second front movable reflector. The first front movable reflector and the second front movable reflector are interlocked with each other to be movable in the opposite directions along the direction perpendicular to the plane. The first and second front movable reflectors parallel-translate in the opposite directions.
The reflector can include two end reflector plate portions positioned at opposite ends of the flash tube, respective front ends of the two end reflector plate portions, the first reflector portion and the second reflector portion forming a substantially rectangular front end aperture of the reflector.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2002-189156 (filed on Jun. 28, 2002) which is expressly incorporated herein by reference in its entirety.
REFERENCES:
patent: 4821053 (1989-04-01), Dowe et al.
patent: 5160192 (1992-11-01), Sugawara
patent: 5584572 (1996-12-01), Ishikawa
patent: 5734934 (1998-03-01), Horinishi et al.
patent: 6598986 (2003-07-01), Yano
patent: 1236504 (1989-09-01), None
patent: 1239540 (1989-09-01), None
patent: 1239541 (1989-09-01), None
patent: 3220537 (1991-09-01), None
English Language Translation of JP Appln. No. 1-236504.
English Language Translation of JP Appln. No. 1-239540.
English Language Translation of JP Appln. No. 1-239541.
English Language Translation of JP Appln. No. 3-220537.
Greenblum & Bernstein P.L.C.
PENTAX Corporation
Perkey W. B.
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