Television – Camera – system and detail – Optics
Reexamination Certificate
2001-07-12
2004-09-21
Christensen, Andrew (Department: 2615)
Television
Camera, system and detail
Optics
C348S374000, C396S443000, C396S456000
Reexamination Certificate
active
06795122
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a focal-plane shutter for digital still cameras which is designed to actuate a first blade and a second blade in turn in the same direction when photographing is performed and to expose an imaging surface through a slit provided by both blades.
2. Description of Related Art
In focal-plane shutters used in digital still cameras, some types of shutters are known in accordance with the specifications of cameras. One of them, like a focal-plane shutter used in a film camera, is equipped with a first blade and a second blade to actuate these blades in turn at predetermined timing so that an imaging surface is exposed continuously from its one side to the other through a slit provided by the blades.
Digital still cameras using shutters constructed as mentioned above are divided into two classes, those in which an optical finder is provided as in the film camera so that the imaging surface is covered by at least one of the first blade and the second blade, except for the case where photographing is performed, and those, having finders referred to as electronic view finders, in which the entire surface in an exposure aperture is exposed to light from an object so that an image of the object can be observed through a monitor, even when photographing is not performed. Thus, the latter camera is such that, in photography, the first blade is moved to the position where the imaging surface is covered, and then an exposure operation is performed.
In the film camera, the area of the imaging surface is usually larger than that of the digital still camera. The film camera always has the optical finder. Due to the arrangement of an optical system and the placement of a film, each of the first blade and the second blade is composed of a plurality of blade components to achieve compactness of a shutter unit. However, in the digital still camera, particularly provided with the electronic view finder, each of the first blade and the second blade need not necessarily be constructed with a plurality of blade components, and is also known to have a single blade component. An example of a shutter constructed from such a viewpoint is shown in
FIG. 1
(refer to Japanese Patent Preliminary Publication No. Hei 11-326992).
Since the focal-plane shutter for digital still cameras mentioned above, in contrast with that for film cameras, is not subjected to severe restriction of space, each of the first blade and the second blade, as described above, can be constructed with a single blade component. However, if the entire shutter unit is enlarged, the number of degrees of design freedom of a camera will be limited in inverse proportion to shutter size, and the possibility of using this shutter unit will diminish. Thus, apart from the number of blade components of each of the first blade and the second blade to be constructed, at least, compactness of the entire shutter unit is the maximum requirement, together with cost reduction thereof.
When the conventional example shown in
FIG. 1
is considered from such a standpoint, the shutter is constructed so that the vertical dimension of a base plate
101
must be essentially increased. Specifically, in
FIG. 1
, a second blade
105
is located at a higher position than a first blade
102
, and when the exposure operation is performed, the second blade
105
passes the place of the first blade
102
and then blocks an optical path AP. Thus, the conventional example, in contrast with an ordinary shutter, unnecessarily provides a space for the second blade
105
and must increase the vertical dimension of the base plate
101
accordingly.
In the conventional example mentioned above, even though each of the first blade
102
and the second blade
105
is constructed with a plurality of blade components, it is impossible to obtain further compactness of the shutter unit. Specifically, for example, if the first blade
102
and the second blade
105
are constructed with respective two blade components and are arranged as in
FIG. 1
in a state where the respective two blade components are completely superimposed, the dimension above the optical path AP will be approximately halved. In this case, however, the two blade components of the first blade, after blocking the optical path AP in a state where the amount of mutual superposition is minimized, are moved downward by the same amount as in this state, and thus the dimension below the optical path AP is required twice. As a result, the upper and lower dimensions of the base plate
101
unit cannot be reduced.
In particular, when the focal-plane shutter is used, it is necessary to actuate each of the shutter blades at a high speed in photography. Thus, it is common practice to use a spring as a driving source of the shutter blade. However, when the shutter blade is restored to a state before photography against the biasing force of the spring, it is common practice to use a motor as a driving source of the shutter blade. In most cases, the exposure aperture is opened and closed by moving the shutter blades vertically in an ordinary photographing posture in which a camera is held by hands on both sides thereof.
A conventional digital camera using such a focal-plane shutter has been initially designed to follow the appearance of the film camera. However, in recent years, the low cost and high image quality of a CCD have been achieved, and the digital camera has exceeded the film camera in sales. As such, the design of appearance of the digital camera itself has been developed and as a result, peculiar compactness or downsizing of the internal structure of the camera has become necessary. Techniques for such compactness are disclosed, for examples, in Japanese Patent Preliminary Publication Nos. Hei 11-261863 and Hei 11-218838.
Specifically, in Hei 11-261863, as shown in
FIGS. 1 and 2
of this publication, the internal area of the casing of the camera is partitioned by an image display circuit substrate
19
, a partition plate
20
, a first record compaction circuit substrate
21
, and a first imaging circuit substrate
16
, and is divided into a middle space
23
A, a first side space
23
B, and a second side space
23
C so that electrical parts are arranged efficiently with respect to the function and radiation in each space. In a grip
5
, parts of a record compaction circuit system are arranged. In particular, by this construction, a rise in temperature of an image sensor
8
caused by the convection of air can be prevented and at the same time, compactness of a casing
2
can be achieved.
In this case, compactness is also required for the shutter constituting the camera, and an example of this is set forth in Hei 11-218838. According to this example, in
FIGS. 1
,
2
, and
6
of this publication, an imaging unit
73
is placed so that its one end on the side of a photographing lens
45
projects into a second aperture
63
a
of a frame
63
on the imaging unit side. Since a shutter blade
67
a
is placed on the side of the photographing lens
45
, shutter blades
67
a
-
67
e
are deflected by a shock produced when a shutter screen
65
is closed, but the shutter is designed so that the shutter blades do not come in contact with the imaging unit
73
. A length along the optical path of the photographing lens can thus be reduced, and it is possible to achieve compactness of the camera.
As mentioned above, the camera of Hei 11-261863 is constructed so that the arrangements of parts of electric circuits are changed and thereby the size of the casing can be diminished. Even in this case, however, space surrounded by heavy dotted lines in
FIGS. 1 and 2
of the publication still leaves room for compactness. The shutter unit is to be placed in this space, but if the shutter unit of Hei 11-218838 is used, it is conceivably possible to place this shutter unit in the space. It is an unquestionable fact, as described above, that the focal-plane shutter for digital still cameras in the future is subjected to restrictions from viewpoints different fro
Christensen Andrew
Nidec Copal Corporation
Pillsbury & Winthrop LLP
Tran Nhan
LandOfFree
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