Photography – Camera detail – Diaphragm
Reexamination Certificate
2003-11-12
2004-11-16
Perkey, W. B. (Department: 2851)
Photography
Camera detail
Diaphragm
C348S342000, C348S360000, C348S361000
Reexamination Certificate
active
06817788
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical diaphragm device in which an optical filter such as an infrared cutoff filter or the like is installed insertably into and retractably from a light path, and in particular, relates to a diaphragm device to be assembled to a photographic device such as a CCTV (monitor camera system) lens or the like.
BACKGROUND ART
A day and night monitor camera system which by day takes color photographs by focusing light in visible light region and at night takes monochrome photographs by focusing light in near-infrared light region in addition to that in the visible light region on an image picking device (CCD, CMOS or the like) of a camera body so that an monitored image is projected on a TV monitor has been known (for instance, refer to Patent Document 1).
In the daytime, this system photographs in color using light in the visible light region alone by placing an infrared cutoff filter in front of an image pickup device (inside a camera body or a lens tube), and photographs in monochrome using light in both the infrared and visible light regions by withdrawing the filter from the front of the image pickup device at night.
FIGS.
4
(
a
) and
4
(
b
) are views showing the structure of a conventional CCTV camera which provides an infrared cutoff filter inside its camera body.
The CCTV camera comprises a camera body
100
A and a lens tube
200
A fixed in front thereof An image pickup device
130
and an infrared cutoff filter
110
are provided inside the camera body
100
A. In addition, a diaphragm
210
is provided inside the lens tube
200
A.
The infrared cutoff filter
110
in the camera body
100
A is driven by a filter driving actuator
230
provided in the camera body
100
A such as a motor or the like so that the filter
110
is inserted into and retracted from a light path L in front of the image pickup device
130
. FIG.
4
(
a
) shows a state that the infrared cutoff filter
110
is inserted into the light path L, and FIG.
4
(
b
) shows a state that the infrared cutoff filter
110
is retracted from the light path L. Meanwhile, the diaphragm
210
in the lens tube
200
A is driven by a diaphragm-driving actuator
220
provided in the lens tube
200
A such as a galvanometer or the like to adjust the diameter of its diaphragm aperture.
In FIG.
4
(
a
), since the infrared cutoff filter
110
is inserted into the light path L, light incident into the lens tube
200
A enters into the camera body
100
A through the diaphragm
210
, passes through the infrared cutoff filter
110
, and reaches the image pickup device
130
to be projected as a subject image. On the other hand, in FIG.
4
(
b
), since the infrared cutoff filter
110
is retracted from the light path L, light incident into the lens tube
200
A enters into the camera body
100
A via the diaphragm
210
, and directly reaches the image pickup device
130
without passing through the infrared cutoff filter
110
to be projected as a subject image.
FIGS.
5
(
a
) and (
b
) are views showing the structure of another conventional CCTV camera which provides an infrared cutoff filter inside a lens tube.
The CCTV camera comprises a camera body
100
B and a lens tube
200
B fixed in the front thereof. Unlike the conventional example shown in
FIG. 4
, an infrared cutoff filter
110
and a filter-driving actuator
230
are provided inside a lens tube
200
B, not inside a camera body
100
B. The image pickup device
130
and the diaphragm
210
are the same as in the example shown in FIG.
4
.
In addition, in this CCTV camera, a dummy filter
111
is provided adjacent to the infrared cutoff filter
110
. The dummy filter
111
comprises a translucent parallel plane panel having nearly the same thickness as that of the infrared cutoff filter
110
and serves to prevent light from being incorrectly focused to the image pickup device
130
due to any difference in the length of the light path, occurring when the infrared cutoff filter
110
is placed in the light path and away from the light path, by compensating for such difference.
Consequently, the infrared cutoff filter
110
and the dummy filter
111
are installed on the same holder (not shown) so that either the infrared cutoff filter
110
or the dummy filter
111
can be placed in the light path L by driving the holder with the filter-driving actuator
230
.
Since the conventional infrared cutoff filter is relatively thick (0.5 mm or more in thickness), in a CCTV camera described in Patent Document 1, a diaphragm device in which an infrared cutoff filter is provided integrally is structured while avoiding the complication of diaphragm structure by disposing the infrared cutoff filter on one surface side of a diaphragm board (not shown) when a diaphragm blade is disposed on the other surface side of the diaphragm board.
Patent Document 1: Japanese Patent Laid-open 2002-189238
In the conventional CCTV camera shown in
FIG. 4
, the infrared cutoff filter
110
is disposed inside the camera body
100
A. However, since the camera body
100
A has become smaller in recent CCTV cameras, it has become difficult to provide the infrared cutoff filter
110
and its driving mechanism (actuator
230
) inside the camera body
100
A itself.
Consequently, provision of the diaphragm
230
together with the infrared cutoff filter
110
in the lens tube
200
B as shown in
FIG. 5
becomes a promising structure. Especially, as described in Patent Document 1, installation of an infrared cutoff filter and its driving mechanism integrally on a diaphragm device has become common.
However, since a relatively thick infrared cutoff filter is used in a diaphragm device with a conventional infrared cutoff filter installed integrally as is described in Patent Document 1, the infrared cutoff filter and diaphragm blades must be disposed on the top and bottom faces of a diaphragm board respectively when considering the workability of the diaphragm blade and the infrared cutoff filter. This limits the downsizing of the diaphragm device. Further, to compensate for focusing, a dummy filter, in addition to the infrared cutoff filter, needs to be used in order to mrake the length of the light path equal. This also makes it difficult to downsize the diaphragm. Moreover, since the dummy filter is used in addition to the thick infrared cutoff filter, the weight of the filter must also be increased, which leads to a larger filter driving system. Consequently, it becomes difficult to meet the demand of reduction in size and weight of the lens tube.
Considering the above-described situation, an object of the present invention is to provide a diaphragm device which integrally provides an optical filter that can be inserted into and retracted from a light path, and is possible to reduce in size and weight so that it can be simply fixed to a lens tube of, for instance, a CCTV camera.
DISCLOSURE OF THE INVENTION
A diaphragm device of a first invention comprises: a diaphragm board having an aperture forming a light path; a diaphragm blade disposed on one face of the diaphragm board, and adjusting the aperture of the diaphragm for the light path by sliding along the board face; a diaphragm driving device driving the diaphragm blade to adjust the aperture of the diaphragm for the light path; an optical filter having transmission characteristics in accordance with a wave length; and a filter driving device to insert the optical filter into and retract it from the light path, wherein the above-described optical filter is formed in a thin film, disposed on one face side of the diaphragm board, and provided slidably along the diaphragm blades.
In the diaphragm device of the present invention, since the optical filter is formed in a thin film, disposed together with the diaphragm blades on one face of the diaphragm board, and provided slidably along the diaphragm blades, the structure can be simpler than that of the conventional example in which the diaphragm blades and the optical filter are disposed on both the front and bottom faces of the diaphragm board respectively. Fur
Negishi Shigeto
Saitoh Shigeki
Tomaru Takashi
Nihon Seimitsu Sokki Co., Ltd.
Perkey W. B.
Venable LLP
Voorhees Catherine M.
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