Photography – Camera detail – Diaphragm shutter unit
Reexamination Certificate
1998-07-28
2001-01-23
Gray, David M. (Department: 2851)
Photography
Camera detail
Diaphragm shutter unit
C396S460000, C396S497000
Reexamination Certificate
active
06176627
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a camera exposure controlling method camera and a diaphragm driving device for controlling the camera exposure and, more particularly, to a diaphragm driving device that prevents an overrun defect, employing the aperture-priority method.
(b) Description of the Related Art
Generally, in order to determine the amount of camera exposure, a method of controlling F-numbers, which indicate the relative size of the lens aperture opening (for example, 1.4, 2.8, 4, 5.6, 8, 11, 16, 22, etc.), or a method of controlling the shutter speed (which typically has values of B, 1, 2, 4, {fraction (1/30)}, {fraction (1/60)}, {fraction (1/125)}, {fraction (1/250)}, {fraction (1/500)}, {fraction (1/1000)}, etc.), can be used.
Among the methods, the former is called “aperture priority method” while the latter called the “shutter speed priority method”.
When a camera has a diaphragm and a shutter, as a separate item, either the aperture priority method or the shutter priority method can be implemented without any difficulty depending on the situation. However, when a diaphragm is used for a shutter as well as for controlling the aperture, the aperture and the shutter speed are controlled at the same time. In the latter case, the sector may be formed as a single type or a double type.
In the single type sector, as shown in
FIG. 7
, a diaphragm ring
200
for controlling the aperture has a cam
202
contacting a sector opening and closing device
204
. Because this cam
202
has a smooth surface to enable continuous movement, the single type sector tends to have overexposure problems, shown as R in FIG.
6
. Although the rotating diaphragm ring
200
stops at a predetermined position on the cam
202
, inertia may force the diaphragm ring to overrun after the diaphragm ring stops at the right position with a diminishing oscillation. Because of this overrun exposure, the total amount of light reaching the film plane cannot be uniformly controlled.
Therefore, an aperture priority method cannot be employed in such a single type sector.
A double type sector has a first set of sectors that is used to control the aperture and a second set of sectors that is used to control the shutter speed. Therefore, while a double type sector may prevent the overrun exposure problem, it requires a complicated mechanism and an expensive complex structure.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of controlling a camera exposure with a diaphragm driving device capable of preventing overrun exposure problems as well as implementing the aperture priority method even with a single type sector.
This and other objects may be achieved by a diaphragm driving device including a shutter base, a driver installed on the base, and a diaphragm ring rotatably placed on the shutter base with the same center and connected to the driver to receive rotational force therefrom. The diaphragm ring has a cam along its circumference composed of a plurality of circular arc portions, that are spaced apart from each other by a respective radius corresponding to each aperture, and connecting portions interconnecting the adjoining circular arc portions. The connecting portions may be formed with rectilinear portions or curved portions. A rotatable sector opening and closing device is fixed on the shutter base. The head of the sector opening and closing device contacts the cam side of the diaphragm ring. This sector opening and closing device rotates along the cam side to open and close the sector.
In the camera exposure controlling method, a desired aperture is set by stopping rotation of the diaphragm ring when the sector opening and closing device reaches the circular arc portion corresponding to the correct aperture. Thereafter, the opening time of the shutter is determined.
REFERENCES:
patent: 4426145 (1984-01-01), Hashimoto
Gray David M.
Howrey Simon Arnold & White , LLP
Samsung Aerospace Industries Ltd.
LandOfFree
Method of controlling exposure of camera and diaphragm... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of controlling exposure of camera and diaphragm..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of controlling exposure of camera and diaphragm... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552327