Digital Camera Patent Abstract
The present digital camera system includes a camera body and an
interchangeable lens barrel. The camera body contains an image pickup
device with an imaging range Ri, and the interchangeable lens barrel
is removably attached to the camera body. The mount opening portions
of the interchangeable lens barrel and camera body includes openings
equal to or larger than a square opening range Rm formed by connecting
ends of segments Sd tilted outwardly from the four corners of an
imaging range Ri diagonally to the outside by 12 degrees to 14 degrees
and extended to a flange back FB position. The circumscribed circle
diameter Dm of the mount opening portion is 1.8 times or larger
of the circumscribed circle diameter Di of the imaging range Ri.
The digital camera system can provide an interchangeable lens and
digital camera body reducible in size without deterioration in amount
of peripheral light. Digital Camera Patent Claims
What is claimed is:
1. A digital camera system having a predetermined image circle,
the system comprising: a camera body: and an interchangeable lens
having a lens side mount portion for attaching the interchangeable
lens to said camera body and a lens side opening portion having
an opening provided in the lens mount portion through which luminous
flux can pass for forming an image in the image circle and allowing
the forming of an image in the image circle; said camera body having
an image pickup device having an imaging range with an aspect ratio
of 4:3 on an imaging surface within the image circle, a body side
mount portion located at a position spaced from the imaging surface
by a predetermined distance and a body side opening portion having
an opening provided in the body side mount portion for allowing
luminous flux from the interchangeable lens to pass through, the
image circle being set larger than the imaging range to include
the imaging range therein, wherein the size of the opening of the
body side opening portion is equal to or larger than a square formed
by connecting ends of segments tilted by an angle .theta. with respect
to an optical axis diagonally from four corners of the imaging range
and extended to the opening of the body side opening portion, and
the angle .theta. satisfies:
2. A digital camera system according to claim 1, wherein the angle
.theta. further satisfies:
3. A digital camera system according to claim 1, wherein:
where Di is a diameter of the image circle.
4. A digital camera system according to claim 3, wherein the diameter
Di of the image circle further satisfies:
5. A digital camera system according to claim 1, wherein:
where Dm is a diameter of a circumscribed circle of a square formed
by connecting ends of segments extended to the body side opening
portion and Di is a diameter of the image circle.
6. A camera body of a digital camera to which an interchangeable
lens having a predetermined image circle is removably mounted, the
camera body comprising: an image pickup device having an imaging
surface of an imaging range with a predetermined aspect ratio, the
image circle being set larger than the imaging range to include
the imaging range therein; and a mount portion to which the interchangeable
lens is mounted, the mount portion having an opening portion having
an opening for allowing luminous flux from the interchangeable lens
to pass through, being located at a position spaced from the imaging
surface by a predetermined distance, wherein the size of the opening
of the opening portion is equal to or larger than a square formed
by connecting ends of segments tilted by an angle .theta. with respect
to an optical axis diagonally from four corners of the imaging range
and extended to the opening of the opening portion, and the angle
.theta. satisfies:
7. A camera body according to claim 6, wherein the angle .theta.
further satisfies:
8. A camera body according to claim 6, further comprising a connecting
terminal provided in an area outside of a square formed by connecting
ends of the segments and within a circumscribed circle of the square.
9. A camera body according to claim 8, wherein the connecting terminal
is electrically connected to a terminal provided in the interchangeable
lens when the interchangeable lens is mounted to the camera body.
10. A camera body according to claim 8, wherein the connecting
terminals communicates with the interchangeable lens when the interchangeable
lens is mounted to the camera body.
11. A camera body according to claim 8, wherein the connecting
terminal supplies power to the interchangeable lens when the interchangeable
lens is mounted to the camera body.
12. A camera body according to claim 8, wherein the connecting
terminal is provided for detecting mounting of the interchangeable
lens to the camera body.
13. A camera body according to claim 6, further comprising a connecting
terminal provided in an area outside of a plane tilted by 10 degrees
in a direction spaced from a long side of the imaging surface with
respected to an optical axis and extended to the opening portion
and within a circumscribed circle of the square.
14. A camera body according to claim 6, further comprising a connecting
terminal provided in an area outside of a plane tilted by 8 degrees
in a direction spaced from the short side of the imaging surface
with respected to an optical axis and extended to the opening portion
and within a circumscribed circle of the square.
15. A camera body according to claim 6, further comprising: a mirror
movable between a position entering into a photographic optical
path and an exiting position; and a mirror box holding the mirror,
wherein the mirror box has an interior of a size which permits passage
of luminous flux through an area surrounded by segments tilted by
10 degrees in a direction along the short side and by 8 degrees
in a direction along the long side in a direction spaced from four
corners of the imaging range with respect to an optical axis and
extended to the mount portion.
16. A camera body according to claim 6, wherein a diameter Di of
an image circle circumscribing the imaging range of the image surface
satisfies:
17. A camera body according to claim 6, wherein:
where a diameter of a circumscribed circle of the mount portion
opening portion is Dm, and a diameter of an image circle circumscribing
the imaging range of the image surface is Di.
18. A digital camera system having a predetermined image circle,
the system comprising: a camera body; and an interchangeable lens,
for forming an image within the image circle, the lens having a
lens side mount portion for mounting the interchangeable lens to
said camera body and a lens side opening portion having an opening
provided in the lens mount portion through which luminous flux can
pass for forming an image in the image circle and allowing the forming
of an image in the image circle; said camera body having an image
pickup device having an imaging range with an aspect ratio of 4:3
on an imaging surface within the image circle, a body side mount
portion located at a position spaced from the imaging surface by
a predetermined distance, and a body side opening portion having
an opening provided in the body side mount portion, through which
luminous flux from the interchangeable lens can pass the image circle
being set larger than the imaging range to include the imaging range
therein. wherein the opening of the body side opening portion has
a size equal to or larger than a size of a square formed by connecting
ends of segments tilted by an angle .theta. with respect to an optical
axis diagonally from four corners of the imaging range and extended
to the opening of the opening portion and satisfies:
19. A digital camera system according to claim 18, the angle .theta.
satisfies:
20. A digital camera system having a predetermined image circle,
the system comprising: a camera body; and an interchangeable lens,
having a lens side mount portion for mounting the interchangeable
lens to the camera body and a lens side opening portion having an
opening provided in the lens side mount portion through which luminous
flux can pass for forming an image in the image circle, the interchangeable
lens forming an image in accordance with the image circle; said
camera body having an image pickup device having an imaging range,
a body side mount portion provided at a position spaced from the
imaging surface by a predetermined distance, and a body side opening
portion having an opening provided in the body side mount portion,
through which luminous flux from the interchangeable lens pass,
the image circle being set larger than the imaging range to include
the imaging range therein, wherein the opening of the body side
opening portion satisfies:
21. A digital camera body to which an interchangeable lens having
a predetermined image circle can be removably mounted, the digital
camera body comprising: an image pickup device having an imaging
surface of an imaging range with a predetermined aspect ratio, the
image circle being set larger than the imaging range to include
the imaging range therein; a mount portion to which the interchangeable
lens is mounted, the mount portion being located at a position spaced
from the imaging surface by a predetermined distance; and an opening
portion having an opening provided in the mount portion, through
which luminous flux from the interchangeable lens can pass, wherein
a size of the opening of the opening portion is equal to or larger
than a circumscribed circle of a square formed by connecting ends
of segments tilted outwardly by a predetermined angle with respect
to an optical axis diagonally from four corners of the imaging range
and extended to the opening of the opening portion and satisfies:
22. A digital camera body to which an interchangeable lens having
a predetermined image circle is removably mounted, the digital camera
body comprising: an image pickup device having an imaging surface
of an imaging range with a predetermined aspect ratio, the image
circle being set larger than the imaging range to include the imaging
range therein; a mount portion to which the interchangeable lens
is mounted, the mount portion being located at a position spaced
from the imaging surface by a predetermined distance; and an opening
portion having an opening provided in the mount portion, through
which luminous flux from the interchangeable lens can pass, wherein
a size of the opening of the opening portion is equal to or larger
than a circumscribed circle of a square formed by connecting ends
of segments tilted outwardly by a predetermined angle with respect
to an optical axis diagonally from four corners of the imaging range
and extended to the opening of the mount portion and satisfies:
23. A digital camera body according to claim 22, wherein the aspect
ratio of the imaging range is 4:3.
24. An interchangeable lens removably mounted to a digital camera
body, the interchangeable lens comprising: an optical system for
forming an image in accordance with an imaging range of the digital
camera body; a mount portion for mounting to the digital camera
body; and an opening portion having an opening provided in the mount
portion, through which luminous flux can pass for forming an an
image in accordance with an imaging range of the digital camera
body, wherein
25. An interchangeable lens according to claim 24, wherein the
circumscribed circle diameter Dc of the imaging range of the digital
camera body satisfies:
26. An interchangeable lens according to claim 25, wherein the
circumscribed circle diameter Dc of the imaging range of the digital
camera body satisfies:
27. An interchangeable lens according to claim 24, wherein the
opening portion has a size equal to or larger than a size of a circumscribed
circle of a square formed by connecting ends of segments tilted
outwardly by a predetermined angle .theta. in a direction spaced
from four corners of the imaging range with respect to an optical
axis and extended to the opening portion.
28. An interchangeable lens according to claim 27, wherein the
segments tilt in a diagonal direction of the imaging range, and
the angle .theta. satisfies:
29. An interchangeable lens according to claim 28, the angle .theta.
further satisfies:
30. An interchangeable lens according to claim 27, further comprising
a connecting terminal arranged in a region between the square and
the opening portion.
31. An interchangeable lens according to claim 30, wherein the
lens connecting terminal is electrically connected to a connecting
terminal provided in the digital camera body when the interchangeable
lens is mounted on the digital camera body.
32. An interchangeable lens according to claim 30, wherein the
lens connecting terminal communicates with the digital camera body
when the interchangeable lens is mounted on the digital camera body.
33. An interchangeable lens according to claim 30, wherein power
is supplied from the digital camera body to the interchangeable
lens through the lens connecting terminal when the interchangeable
lens is mounted on the digital camera body.
34. An interchangeable lens removably mounted to a digital camera
body, for forming an image within a predetermined image circle,
the interchangeable lens comprising: an optical system for forming
an image in the image circle, the image circle being set in accordance
with an imaging range of an image pickup device of the digital camera
body, the optical system forming an image in the image circle set
larger than the imaging range to include the imaging range therein,
a mount portion for mounting to the digital camera body; and an
opening portion having an opening provided in the mount portion,
for allowing luminous flux to pass through, wherein
is satisfied where a diameter of the image circle is Di and a minimum
circle diameter including the opening portion is Dm1.
35. A digital camera system having a predetermined image circle,
the system comprising: a camera body; and interchangeable lenses,
for forming an image within the image circle when selectively mounted
to the camera body, each of the lenses having a lens side mount
portion for attaching the asscociated interchangeable lens to the
camera body, and a lens side opening portion having an opening provided
in the lens side mount portion through which luminous flux can pass
for forming an image within the image circle and allowing the forming
of an image in the image circle; said camera body having an image
pickup device having an imaging range with an aspect ratio of 4:3
on an imaging surface within the image circle, a body side mount
portion provided at a position spaced from the imaging surface by
a predetermined distance and a body side opening portion having
an opening provided in the body side mount portion through which
luminous flux from the interchangeable lens pass, the image circle
being set larger than the imaging range to include the imaging range
therein, wherein the opening of the lens side opening portion of
an interchangeable lens having a widest outermost light beam of
an exit luminous flux among the interchangeable lenses has a size
equal to or larger than a size of a square formed by connecting
ends of a first plane formed by tilting a long side of the imaging
range by a predetermined angle .theta.1 with respect to an optical
axis and extending the long side to the opening of the lens side
opening portion and a second plane formed by tilting a short side
of the imaging range by a predetermined angle .theta.2 with respect
to the optical axis and extending the short side to the opening
of the lens side opening portion, wherein the angles .theta.1 and
.theta.2 satisfy:
36. A digital camera system according to claim 35, wherein the
square lies within a circumscribed circle of a square formed by
connecting ends of segments tilted by a predetermined angle .theta.3
in a direction away from four corners of the imaging range with
respect to the optical axis and extended to the opening portion,
and the angle .theta.3 satisfies:
37. A digital camera system having a predetermined image circle,
said system comprising: a camera body: and an interchangeable lens,
for forming an image within the image circle, the lens having a
lens side mount portion for attaching the interchangeable lens to
the camera body, and a lens side opening portion having an opening
provided in the lens side mount portion through which luminous flux
can pass for forming an image in the image circle and allowing the
forming of an image in the image circle; said camera body having
an image pickup device having an imaging range with an aspect ratio
of 4:3 on the imaging surface within the image circle, a body side
mount portion provided at a position spaced from the imaging surface
by a predetermined distance and a body side opening portion having
an opening provided in the mount portion through which luminous
flux from the interchangeable lens can pass, the image circle being
set larger than the imaging range to include the imaging range therein,
wherein the body side opening portion has a size equal to or larger
than a size of a square formed by connecting ends of a first plane
formed by tilting a long side of the imaging range by a predetermined
angle with respect to an optical axis and extending a long side
to the opening of the body side opening portion and a second plane
formed by tilting a short side of the imaging range by a predetermined
angle with respect to the optical axis and extending the short side
to the opening of the body side opening portion, wherein, when a
luminous flux of a main light beam parallel to the optical axis
is at a periphery of the imaging range, luminous flux equal to F
No. 3 can be guided.
38. A digital camera system having a predetermined image circle
the camera system comprising: a camera body; and an interchangeable
lens having a lens side mount portion for attaching an interchangeable
lens to the camera body and a lens side opening portion having an
opening provided in the lens mount portion through which luminous
flux can pass for forming an image in the image circle and allowing
the forming of an image in the image circle, the camera body having
an image pickup device having an imaging surface of an imaging range
with a predetermined aspect ratio, a body side mount portion located
at a position spaced from the imaging surface by a predetermined
distance and a body side opening portion having an opening provided
in the body side mount portion for allowing luminous flux from the
interchangeable lens to pass through, the image circle being set
larger than the imaging range to include the imaging range therein,
wherein a size of the body side opening of the opening portion is
equal to or larger than a square formed by connecting ends of segments
tilted by an angle .theta. with respect to an optical axis diagonally
from four corners of the imaging range and extended to the opening
of the opening portion, and the angle .theta. satisfies:
39. A digital camera system according to claim 38, wherein the
angle .theta. further satisfies:
40. A digital camera system according to claim 38, further comprising:
a mirror movable between a position entering a photographic optical
path and an exiting position; and a mirror box holding the mirror;
wherein the mirror box has an interior of a size which permits passage
of luminous flux through an area surrounded by segments tilted by
10 degrees in a direction along a short side and by 8 in a direction
along a long side in a direction spaced from four corners of the
imaging range with respect to an optical axis and extended to the
mount portion.
41. A digital camera system according to claim 38, wherein a diameter
Di of the image circle satisfies:
42. A digital camera system according to claim 38, wherein
where a diameter of a circumscribed circle of the square is Dm,
and a diameter of the image circle is Di.
43. An interchangeable lens which can be mounted to the camera
body set forth in claim 6, the interchangeable lens comprising:
a lens side mount portion for attaching the interchangeable lens
to the camera body; and a lens side opening portion provided in
the lens side mount portion and having an opening through which
luminous flux can pass for forming an image in the image circle;
wherein the interchangeable lens allows the forming of an image
in the image circle.
Digital Camera Patent Description
This application claims benefits of Japanese Application No. 2003-168383
filed in Japan on Jun. 12, 2003, the contents of which are incorporated
by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital camera system having
an interchangeable lens and a camera body to which the interchangeable
lens can be attached.
2. Related Art Statement
An image pickup device in a recent digital camera has a narrow
dynamic range. Furthermore, it is difficult to receive and performs
photoelectric conversion on light emitted diagonally at a predetermined
angle or larger. Therefore, the influence of the decrease in amount
of peripheral light is more significant than a silver halide camera.
In order to solve the problem, Japanese Unexamined Patent Application
Publication No. 6-37289 discloses a technology for increasing an
opening diameter of a micro-lens on the periphery of an image pickup
device. According to the disclosed technology, the opening diameter
of a micro-lens of an image pickup device is increased continuously
toward the periphery.
In order to reduce the influence of the decrease in amount of peripheral
light, Japanese Unexamined Patent Application Publication No. 5-130469
discloses a technology for forming a light path of an image pickup
device such that the vignetting of a light beam can be prevented
in a light path from a photographic lens to the image pickup device.
A video camera disclosed in the patent document has a larger opening
in an image frame plate so as to prevent vignetting, and the strength
of the image frame plate in a diagonal direction of the opening
is reinforced by a projection.
On the other hand, a lens interchangeable, single-lens reflex type
digital camera system has been disclosed. For example, an electronic
camera disclosed in Japanese Unexamined Patent Application Publication
No. 11-88783 relates to a single-lens reflex type electronic camera
having a solid-state imaging device such as a CCD in a film opening
by using the body of a conventional silver halide camera.
SUMMARY OF THE INVENTION
A digital camera system according to the present invention has
a predetermined image circle. The digital camera system includes
an interchangeable lens having a lens side mount portion for attaching
the interchangeable lens to a camera body and a lens side opening
portion provided in the lens mount portion through which luminous
flux can pass for forming an image in the image circle and allowing
the forming of an image in the image circle, and a camera body having
an image pickup device having an imaging range with the aspect ratio
of 4:3 on an imaging surface within the image circle, a body side
mount portion located at a position apart from the imaging surface
by a predetermined distance and a body side opening portion provided
in the body side mount portion for allowing luminous flux from the
interchangeable lens to pass through. In this case, the size of
the body side opening portion is equal to or larger than the square
formed by connecting ends of segments tilted by an angle .theta.
with respect to an optical axis diagonally from four corners of
the imaging range and extended to the body side opening portion,
and the angle .theta. satisfies:
A camera body according to the present invention of a digital camera
to which an interchangeable lens is removably mounted, includes
an image pickup device having an imaging surface of an imaging range
with a predetermined aspect ratio, and a mount portion to which
the interchangeable lens is mounted, the mount portion having an
opening portion for allowing luminous flux from the interchangeable
lens to pass through, being located at a position apart from the
imaging surface by a predetermined distance. In this case, the size
of the opening portion is equal to or larger than the square formed
by connecting ends of segments tilted by an angle .theta. with respect
to an optical axis diagonally from four corners of the imaging range
and extended to the opening portion, and the angle .theta. satisfies:
Another digital camera system according to the present invention
has a predetermined image circle. The digital camera system includes
an interchangeable lens, which can form an image within the image
circle, the lens having a lens side mount portion for mounting the
interchangeable lens to a camera body and a lens side opening portion
provided in the lens side mount portion for allowing luminous flux
for forming an image in the image circle to pass through, and a
camera body having an image pickup device having an imaging surface,
a body side mount portion provided at a position apart from the
imaging surface by a predetermined distance, and a body side opening
portion provided in the body side mount portion, for allowing luminous
flux from the interchangeable lens to pass through. In this case,
the body side opening portion satisfies:
A digital camera body according to the invention to which an interchangeable
lens having a predetermined image circle can be removably mounted,
the digital camera body including an image pickup device having
an imaging surface of an imaging range with a predetermined aspect
ratio, a mount portion to which the interchangeable lens is mounted,
the mount portion being located at a position apart from the imaging
surface by a predetermined distance, and an opening portion provided
in the mount portion, for allowing luminous flux from the interchangeable
lens to pass through. In this case, the size of the opening portion
is equal to or larger than the circumscribed circle of the square
formed by connecting ends of segments tilted by a predetermined
angle with respect to an optical axis diagonally from four corners
of the imaging range and extended to the opening portion and satisfies:
where the minimum circle diameter including the opening portion
is Dm and the diameter of the image circle is Di.
An interchangeable lens according to the present invention is removably
mounted to a digital camera body. The interchangeable lens includes
a mount portion for mounting to the digital camera body, and an
opening portion provided in the mount portion, for allowing luminous
flux to pass through. In this case,
is satisfied where the diameter of the circumscribed diameter of
the imaging range of the digital camera body is Dc and the minimum
circle diameter including the opening portion is Dm1.
Another digital camera system according to the present invention
has a predetermined image circle. The digital camera system includes
interchangeable lenses, which can form an image within the image
circle, each of the lenses having a lens side mount portion for
mounting the interchangeable lens to a camera body, and a lens side
opening portion provided in the lens side mount portion for allowing
luminous flux for forming an image within the image circle to pass
through, and a camera body having an image pickup device having
an imaging range with the aspect ratio of 4:3 on an imaging surface
within the image circle, a body side mount portion provided at a
position apart from the imaging surface by a predetermined distance
and a body side opening portion provided in the mount portion for
allowing luminous flux from the interchangeable lens to pass through.
In this case, the lens side opening portion of an interchangeable
lens having the widest outermost light beam of an exit luminous
flux among the interchangeable lenses has a size equal to or larger
than the size of the square formed by connecting ends of a first
plane formed by tilting the long side of the imaging range by a
predetermined angle .theta.1 apart with respect to an optical axis
and extending the long side to the lens side opening portion and
a second plane formed by tilting the short side of the imaging range
by a predetermined angle .theta.2 apart with respect to the optical
axis and extending the short side to the lens side opening portion.
In this case, the angles .theta.1 and .theta.2 satisfy:
Another digital camera system according to the present invention
has a predetermined image circle. The digital camera system includes
an interchangeable lens, which can form an image within the image
circle, the lens having a lens side mount portion for mounting the
interchangeable lens to the camera body, and a lens side opening
portion provided in the lens side mount portion for allowing luminous
flux for forming an image in the image circle to pass through, and
a camera body having an image pickup device having an imaging range
with the aspect ratio of 4:3 on the imaging surface within the image
circle, a body side mount portion provided at a position apart from
the imaging surface by a predetermined distance and a body side
opening portion provided in the mount portion for allowing luminous
flux from the interchangeable lens to pass through. In this case,
the body side opening portion has a size equal to or larger than
the size of the square formed by connecting ends of a first plane
formed by tilting the long side of the imaging range by a predetermined
angle apart with respect to an optical axis and extending the long
side to the body side opening portion and a second plane formed
by tilting the short side of the imaging range by a predetermined
angle apart with respect to the optical axis and extending the short
side to the body side opening portion, wherein, when luminous flux
of a main light beam parallel to the optical axis enters to the
periphery of the imaging range, the luminous flux equal to F No.
3 can be guided.
The other features and advantages of the present invention will
be apparent from descriptions below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective diagram (including a partial section view)
of a lens replaceable single-lens reflex type digital camera in
a digital camera system according to a first embodiment of the invention;
FIG. 2 is a perspective diagram of a digital camera body of the
digital camera in FIG. 1;
FIG. 3 is a vertical section diagram of a mount portion, mirror
box portion and imaging unit where an interchangeable lens is attached
to the camera body of the digital camera in FIG. 1;
FIG. 4 is an exploded perspective diagram around the mount portion
of the camera body in FIG. 1;
FIG. 5 is a light beam diagram showing the emission of an object
luminous flux captured from an interchangeable lens barrel to an
image pickup device in the digital camera in FIG. 1;
FIG. 6 is a graph showing a relationship of a luminous flux angle
.theta. incident on a photoelectric conversion surface of an image
pickup device and F number of an interchangeable lens in the digital
camera in FIG. 1;
FIG. 7 is a graph showing mount diameters Dn for F numbers of an
interchangeable lens in the digital camera in FIG. 1 by using FBs
as parameters;
FIG. 8A is a diagram showing a longitudinal section (section in
X-direction) of a photoelectric conversion surface where a center
luminous flux and peripheral luminous flux through a wide angle
interchangeable lens barrel attached to the digital camera in FIG.
1 are emitted to the photoelectric conversion surface (image forming
surface);
FIG. 8B shows a latitudinal section (section in Y-direction) of
a photoelectric conversion surface where a center luminous flux
and peripheral luminous flux through a wide angle interchangeable
lens barrel attached to the digital camera in FIG. 1 are emitted
to the photoelectric conversion surface (image forming surface);
FIG. 9A is a diagram showing a longitudinal section (section in
XZ-direction) of a photoelectric conversion surface where a center
luminous flux and peripheral luminous flux through a replacement
telephoto lens barrel attached to the digital camera in FIG. 1 are
emitted to the photoelectric conversion surface (image forming surface);
FIG. 9B is a diagram showing a latitudinal section (section in
YZ-direction) of a photoelectric conversion surface where a center
luminous flux and peripheral luminous flux through a replacement
telephoto lens barrel attached to the digital camera in FIG. 1 are
emitted to the photoelectric conversion surface (image forming surface);
FIG. 10 is a diagram showing an effective screen range (effective
imaging range) and recording screen range (imaging and recording
screen) of a photoelectric conversion surface of an image pickup
device in the digital camera in FIG. 1 and image circles corresponding
to the ranges;
FIG. 11 is a light beam diagram showing a relationship of a mount
opening and the circumscribed circle with respect to an imaging
range inscribing a reference image circle of the image pickup device
in the digital camera in FIG. 1;
FIG. 12 is a light beam diagram showing a relationship between
an image circle circumscribing an imaging range of an image pickup
device applied in a digital camera according to a second embodiment
of the invention and a circumscribed circle of a mount opening;
FIG. 13A shows a light beam diagram of a section along a ZX surface
(horizontal surface) between a photoelectric conversion surface
of the image pickup device and the mount opening portion in the
digital camera in FIG. 12;
FIG. 13B shows a light beam diagram of a section along a ZY surface
(vertical surface) between a photoelectric conversion surface of
the image pickup device and the mount opening portion in the digital
camera in FIG. 12; and
FIG. 14 is a diagram showing an imaging range of a 4/3 type image
pickup device and the image circle on an imaging range of a square
type image pickup device applied in a digital camera according to
a third embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the invention will be described with reference to
drawings.
FIG. 1 is a perspective diagram (including a partial section view)
of a lens replaceable single-lens reflex type digital camera in
a digital camera system according to a first embodiment of the invention.
FIG. 2 is a perspective diagram of a digital camera body of the
digital camera. FIG. 3 is a vertical section diagram of a mount
portion, mirror box portion and imaging unit where an interchangeable
lens is attached to the camera body of the digital camera. FIG.
4 is an exploded perspective diagram around the mount portion of
the camera body.
A digital camera 1 of a digital camera system according to this
embodiment includes a digital camera body and multiple kinds of
interchangeable lens, which can be attached to the camera body and
has unique opening shapes of a mount portion and mirror box portion
corresponding to a contained image pickup device. Before the description
of the opening shape, internal constructions of a digital camera
body (called camera body hereinafter) 11 and interchangeable lens
barrel 12 as an interchangeable lens will be described with reference
to FIGS. 1 to 4.
The interchangeable lens barrel 12 is a lens barrel containing
multiple kinds of photographic optical system 12a having various
kinds of focal distances as shown in FIGS. 5 and 6, which will be
described later. The interchangeable lens barrel 12 has a lens side
mount portion 37, which can be attached to the body side mount portion
47, which will be described later, of the camera body 11.
The camera body 11 is a so-called single-lens reflex type camera
body including various components provided inside the camera body
portion 11a and having a body side mount portion in the front of
the surface such that the lens barrel 12 for holding a photographic
optical system 12a can be removably attached. In other words, the
substantial center portion of the front side of the camera body
portion 11a has an exposure opening of a predetermined size, which
can guide object luminous flux into the camera body portion 11a.
A body side mount portion 47 is provided on the periphery of the
exposure opening.
A more detailed construction of the camera body 11 will be described.
First of all, various operation members for operating the camera
body portion 11a, such as a release button 17 for generating instruction
signals for starting a photographic operation, are provided at a
predetermined position of the upper surface portion or back surface
portion of the camera body 11a.
The camera body portion 11a has, at predetermined positions, a
front plate 41, a body side mount portion 47, a mirror box 42, a
finder 13, a shutter portion 14, an imaging unit 15 and multiple
circuit substrates including a main circuit substrate 16. The front
plane 41 has a body side opening portion 41a in the front of the
surface side of the camera body portion 11a. The body side mount
portion 47 is located on the front surface portion 41b of the front
plane 41. The mirror box 42 is fixed behind the mount portion of
the front plane 41. The finder 13 is provided for forming a desired
object image, which is formed by the photographic optical system
12a, at a predetermined position different from the position on
the photoelectric conversion surface 27a, which is an imaging surface
of the image pickup device 27. The finder 13 is a so-called observation
optical system. The shutter portion 14 is supported by a projection
42f behind the mirror box 42 and includes a shutter mechanism for
controlling the time for irradiating object luminous flux to a photoelectric
conversion surface of the image pickup device 27. The imaging unit
15 is a unit fixed and held behind the shutter portion 14 by the
projection 41f of the front plane 41. The imaging unit 15 includes
the image pickup device 27 for obtaining object imaging signals
from object light through the imaging optical system 12a. Various
electric members of electric circuits such as an image signal processing
circuit for performing various kinds of signal processing on the
image signals obtained by the image pickup device 27 are implemented
on the multiple circuit substrates such as main circuit substrate
16. A dust-preventive filter 21 is provided in the front of the
surface of the imaging unit 15. The dust-preventive filter 21 prevents
adherence of dust to the photoelectric conversion surface of the
image pickup device.
The mirror box 42 has a mirror box opening portion 42a and a space
behind the mirror box opening portion 42a. The mirror box opening
portion 42a pivotally supports a reflector 13b and allows the passage
of object luminous flux from the photographic optical system 12a
without vignetting of the luminous flux for forming an image on
the photoelectric conversion surface 27a of the image pickup device
27.
The reflector 13b lies in the space behind opening portion 42a
and can pivotably move between a reflecting (dotted-line) position
for reflecting incident luminous flux to the finder 13 side and
a turnout (solid-line) position turning out from the reflecting
position.
The finder 13 has the reflector 13b, a pentaprism 13a and an eyepiece
13c. The reflector 13b is arranged to guide am object luminous flux
through the photographic optical system 12a by bending the optical
axis of the object luminous flux to the observation optical system
side. The pentaprism 13a receives luminous flux emitted from the
reflector 13b and forms an erect image. The eyepiece 13c forms an
image best suitable for enlarging and observing an image formed
by the pentaprism 13a.
The reflector 13b, as set forth above, moves between the turnout
position away from an optical axis O of the photographic optical
system 12a and a predetermined position on the optical axis. Normally,
the reflector 13b is located at a predetermined angle, such as 45
degrees, with respect to the halo on the optical axis of the photographic
optical system 12a. Thus, when the camera 1 is at the normal state,
the optical axis of the object luminous flux having passed through
the photographic optical system 12a is bent by the reflector 13b
and is reflected to the pentaprism 13a side above the reflector
13b.
On the other hand, while the camera is performing a photographic
operation and during the actual exposure operation, the reflector
13b moves from the optical path of the photographic optical system
12a to the aforesaid predetermined turnout position. Thus, the object
luminous flux is guided to the image pickup device side and forms
an image on the photoelectric conversion surface.
The shutter portion 14 is similar to those generally used in a
conventional camera, such as a focal plane type shutter mechanism
and a driving circuit for controlling operations of the shutter
mechanism.
The imaging unit 15 includes the image pickup device 27, an image
pickup device fixing plate 28, an optical low-pass filter (called
LPF hereinafter) 25, a low-pass filter receiving member 26, an image
pickup device storage case member 24 (called CCD case 24 hereinafter),
a dust-preventive filter receiving member 23, the dust-preventive
filter 21, a piezoelectric element 22 and a press member 20. The
image pickup device 27 constituted by a CCD for obtaining image
signals corresponding to the light irradiated onto the photoelectric
conversion surface of the image pickup device 27 through the photographic
optical system 12a as shown in FIG. 3 and so on. The image pickup
device fixing plate 28 is constituted by a: thin-plate like member
for fixing and supporting the image pickup device 27. The optical
LPF 25 is an optical element on the photoelectric conversion surface
of the image pickup device 27, for removing high frequency components
from an object luminous flux irradiated through the photographic
optical system 12a. The low-pass filter receiving member 26 is constituted
by an elastic member substantially in a frame shape and is provided
on the periphery between the optical LPF 25 and the image pickup
device 27. The CCD case 24 stores, fixes and holds the image pickup
device 27 and supports the optical LPF 25 by closely abutting to
the periphery and the vicinity. A predetermined position of the
CCD case 24 is closely in close contact with the dust-preventive
filter receiving member 23. The dust-preventive filter receiving
member 23 is provided in the front of the surface side of the CCD
case 24 and is in close contact with the periphery or the vicinity.
The dust-preventive filter 21 is a dust-preventive member supported
by the dust-preventive filter receiving member 23 and faces toward
the optical LPF 25 at a position spaced apart from the optical LPF
25 by a predetermined distance in the front of the surface side
of the optical LPF 25 on the photoelectric conversion surface side
of the image pickup device 27. The piezoelectric element 22 is provided
on the periphery of the dust-preventive filter 21 and removes dust
by giving a predetermined amount of vibration to the dust-preventive
filter 21. The press member 20 is constituted by an elastic body
for connecting, fixing and holding the dust-preventive filter 21
to the dust-preventive filter receiving member 23 in an air-tight
manner.
The image pickup device 27 performs photoelectric conversion processing
on object luminous flux received by the photoelectric conversion
surface 27a of the image pickup device 27 through the photographic
optical system 12a. Thus, the image pickup device 27 can obtain
image signals corresponding to the object image on the photoelectric
conversion surface. The image pickup device 27 may be a 4/3 type
charge-coupled device or the like. In this case, the term "4/3
type" refers to the size of the image pickup device, and a
4/3 type image pickup device has an image circle with the diameter
of about 21.2 to 25 mm.
The image pickup device 27 is implemented at a predetermined position
on the main circuit substrate 16 through the image pickup device
fixing plate 28. An image signal processing circuit and work memory,
not shown, are implemented together on the main circuit substrate
16. Thus, output signals from the image pickup device 27, that is,
image signals obtained through optoelectric processing are transmitted
to the image signal processing circuit. A protection glass (not
shown for simplicity) is attached in front of the photoelectric
conversion surface of the image pickup device 27.
The signal processing performed in the image signal processing
circuit includes various kinds of signal processing such as processing
for converting image signals obtained from the image pickup device
27 to signals suitable for recording. In this case, the image signals
correspond to the image formed on the optoelectric surface of the
image pickup device 27 by the photographic optical system 12a held
within the lens barrel 12 attached to the body side mount portion
47. These kinds of signal processing are the same as processing
normally performed in a general digital camera for handling electronic
image signals.
The optical LPF 25 is provided in the front of the surface side
of the image pickup device 27 through the low-pass filter receiving
member 26. The optical LPF 25 is constituted by crystal, which is
an optical element having a double refraction characteristic. The
optical LPF 25 further contains an infrared absorbing glass.
The CCD case 24 covers the optical LPF 25. The CCD case 24 has
a rectangular opening substantially at the center. The optical LPF
25 and image pickup device 27 are provided in the opening from the
back. A step 24a having a substantial L-shaped section is provided
on the internal periphery on the back side of the opening.
As described above, the low-pass filter receiving member 26 constituted
by an elastic member is provided between the optical LPF 25 and
the image pickup device 27. The low-pass filter receiving member
26 is provided at a position avoiding an effective range of the
photoelectric conversion surface on the periphery of the front surface
side of the image pickup device 27. Furthermore, the low-pass filter
receiving member 26 is abutted to the vicinity of the periphery
of the back side of the optical LPF 25. The optical LPF 25 and the
image pickup device 27 are in constant contact with each other substantially
in an air-tight manner. Thus, elastic force toward the optical axis
by the low-pass filter receiving member 26 acts on the optical LPF
25.
Then, the periphery of the front surface side of the optical LPF
25 is located so as to be in contact with the step 24a of the CCD
case 24 substantially in an air-tight manner. Thus, the position
in the optical axis direction of the optical LPF 25 is controlled
against the elastic force by the low-pass filter receiving member
26 for attempting to move the optical LPF 25 toward the optical
axis.
In other words, the optical LPF 25 laid within the opening of the
CCD case 24 from the back surface side is positionally controlled
by the step 24a in the optical axis direction. Thus, the optical
LPF 25 is prevented from coming out from the inside of the CCD case
24 toward the front surface side.
In this way, after the optical LPF 25 is inserted from the back
surface side into the opening of the CCD case 24, the image pickup
device 27 is located on the back surface side of the optical LPF
25. In this case, the low-pass filter receiving member 26 is held
at its periphery between the optical LPF 25 and the image pickup
device 27.
As described above, the image pickup device 27 is implemented on
the main circuit substrate 16 through the image pickup device fixing
plate 28. The image pickup device fixing plate 28 is fixed through
a spacer 28a with a screw into a screw hole from the back surface
side of the CCD case 24. The main circuit substrate 16 is fixed
to the image pickup device fixing plate 28 with a screw through
a spacer 16a.
The dust-preventive filter receiving member 23 is fixed to the
screw hole of the CCD case 24 in the front of the surface side of
the CCD case 24 with a screw. A peripheral slot in a substantial
ring shape is provided at a predetermined position in the front
of the surface side on the periphery side of the CCD case 24. On
the other hand, a ring-shape projection to fit to the peripheral
slot of the CCD case 24 is provided in a substantial-ring form at
a predetermined position on the back surface side of the periphery
side of the dust-preventive filter receiving member 23. Therefore,
when the ring-shape projection fits into the peripheral slot, the
CCD case 24 and the dust-preventive filter receiving member 23 fit
into each other substantially in an air-tight manner in a ring-shaped
area, that is, in an area having the peripheral slot and the ring-shaped
projection.
The dust-preventive filter 21 contains glass and has a circular
or polygonal plate as a whole. An area extending at least from the
center of the dust-preventive filter 21 to the edge is transparent.
The transparent area faces toward the front surface side of the
optical LPF 25 through a predetermined space. The dust-preventive
filter 21 is fixed and is held by a press member such that the dust-preventive
filter 21 can be associated with the dust-preventive filter receiving
member 23 in an air-tight manner. The press member is constituted
by an elastic body such as a flat spring.
The dust-preventive filter receiving member 23 has a circular or
polygonal opening in the vicinity of the substantial center of the
dust-preventive filter receiving member 23. The opening is designed
to be large enough for object luminous flux through the photographic
optical system 12a to illuminate the photoelectric conversion surface
of the image pickup device 27 at the back.
The body side mount portion 47 has a square body side mount opening
portion 41a, a body side mount plate 45, a mount spring 46, a contact
spring holder 51, a contact spring 53, a mount contact frame 52,
and a mount contact pin 54. The body side mount opening portion
41a is provided within the front surface portion 41b of the front
plate 41, as shown in FIGS. 3 and 4. The body side mount plate 45
and the mount spring 46 are fixed to the front surface portion 41b.
A mount flexible substrate (called FPC hereinafter) 55 is attached
to the contact spring 53. The mount contact spring 54 is a camera
body side connecting terminal. The end of the mount FPC 55 is connected
to a lens drive control portion and/or a power supply portion within
the camera body 11.
The body side mount plate 45 has a bayonet 45a on the internal
periphery of the opening. The mount spring 46 has a spring portion
46d. The body side mount plate 45 is fixed to the front plate 41
with the mount spring 46 being inserted on the back of the body
side mount plate 45, by screwing a screw 61 through a screw inserting
hole 45c into an opening portion screw portion 41c. A mount lock
pin 44 is provided on the periphery of the front surface portion
41b of the front plate 41.
Nine mount contact pins 54 are inserted to pin holes 52c of the
mount contact frame 52. The contact spring holder 51 is fixed to
and is supported by the mount contact frame 52 by screwing the screw
62 into the screw hole 52b through a screw inserting hole 51a. The
fixed and supported mount contact pins 54 are forced, extended and
held toward the front of the mount contact frame 52 by nine contact
springs 53 attached to the contact spring holder 51.
The mount contact frame 52 having the contact spring holder 51
is fixed outward under the square body side opening portion 41a
by screwing screw 63 to the screw hole 41d through the screw inserting
hole 52a. Thus, the bottom part of the body side mount opening portion
41a can be obtained. When the mount contact frame 52 is attached,
the mount contact pins 54 are provided in the form of a circular
arc inside of the opening portion 45a of the body side mount plate
45 and under the body side opening portion 41a.
On the other hand, as shown in FIG. 3, the lens side mount portion
37 of the interchangeable lens barrel 12 has a lens side mount opening
portion 31a and a bayonet nails 31b, which can associate with the
bayonet 45a of the body side mount plate 45. Furthermore, nine mount
contacts 33 are provided in the form of a circular arc at the bottom
of the lens side mount opening portion 31a. The nine mount contacts
33 are lens side connecting terminals held by the terminal holder
32. The mount contacts 33 are connected to the lens side FPC 34.
The lens side FPC 34 has a power supply line and/or an electric
drive control line and is connected to a focus driving portion,
for example, within the interchangeable lens barrel 12.
In order to attach the interchangeable lens barrel 12 to the camera
body 11 having the above-described construction, the lens side mount
portion 37 of the interchangeable lens barrel 12 is rotationally
fitted into the mount plate 45 of the body side mount portion 47.
Then, the bayonet nails 31b are associated therewith such that the
lens can be attached. Under the lens-attached condition, the interchangeable
lens barrel 12 is electrically connected to the drive control portion
of the camera body 11 through the connecting terminal portion so
as to allow the control for focus, zoom and iris driving. An object
luminous flux enters to the finder 13 or the image pickup device
27 through the lens side mount opening portion 31a and the body
side mount opening portion 41a, and the object can be observed or
be shot.
Here, the form of the mount opening of the lens mount portion 37
and/or the body side mount portion 47 for passing luminous flux
and the form of luminous flux passing portion of the mirror box
42 will be described.
In the description below and the drawings, the direction along
the optical axis O is the Z-direction. The object side (lens side)
of the Z-direction is the front while the image pickup device side
(image-forming side) is the back. The direction orthogonal to the
optical axis O and along the longer side in the imaging range (photoelectric
conversion surface) of the image pickup device is an X-direction
(horizontal direction). The left and right are determined from the
object viewpoint. The direction orthogonal to the optical axis O
and along the shorter side of the imaging range (photoelectric conversion
surface) of the image pickup device is a Y-direction (vertical direction).
In a digital camera system according to this embodiment, in order
for object luminous flux captured by the interchangeable lens barrel
12 to enter to the periphery of the imaging range of the image pickup
device 27, the mount portion and the member, such as a mirror box,
between the image pickup device and the lens must have openings.
In other words, in order to guide light uniformly to the center
and periphery of the image pickup device, the openings must have
a form allowing the same luminous flux angle as the luminous flux
angle of the luminous flux from the end to the center of the imaging
range. In this case, as the degrees of the tilt of the main light
beam of a luminous flux incident on the periphery to the optical
axis increases, the size of the openings can be reduced.
FIG. 5 is a light beam diagram showing an entering state of an
object luminous flux captured from the interchangeable lens barrel
12 to the image pickup device 27.
As shown in FIG. 5, the object luminous flux entering from the
exit pupil diameter D0 of the interchangeable lens barrel 12 and
the center and peripheral luminous flux entering to the center and
periphery of the optical axis O of the photoelectric conversion
surface 27a on the imaging range of the image pickup device 27 have
a luminous flux angle .theta. about the respective main light beams,
where the luminous flux angle .theta. refers to an angle of one
side of a luminous flux (that is, half angle).
In order to prevent a shortage in light amount of the periphery
in the imaging range, the vignetting of the peripheral luminous
flux must be prevented at the lens side mount opening portion 31a
(having at least an opening range Rm mentioned later), the body
side mount opening portion 41a (opening having the opening range
equal to the opening range Rm mentioned later for preventing the
vignetting of luminous flux passing therethrough) and a light passing
portion of the mirror box 42. At the limit of the longer focal distance
side (Tele side), the photographic optical system 12a requires a
shown lens side opening portion 31a because the main light beam
of the peripheral luminous flux is parallel to the optical axis
O. On the other hand, on the short focal distance side (Wide side)
shorter than the long focal distance, the photographic optical system
12a requires an opening 31a' narrower than the lens side opening
portion 31a because the main light beam of the peripheral luminous
flux is a light beam tilting toward the optical axis O.
In the photographic optical system 12a, when an object distance
is at infinity, the exit pupil position 12a0 of the exit pupil diameter
D0 is spaced from the photoelectric conversion surface 27a, which
is at an image-forming position), by a focal distance f. The luminous
flux angle .theta. is expressed by:
The relationship of the exit pupil diameter D0, the focal distance
f and F No. (the F-number) is:
Based on EQ1, the relationship between the luminous flux angle
.theta. and the F-number is:
FIG. 6 is a graph showing a relationship between the luminous flux
angle .theta. and the F-number (or Av value). In FIG. 6, when the
slope of the main light beam is 5 degrees or 10 degrees, the luminous
flux angle .theta. is an angle of the outer light beam of a peripheral
luminous flux with respect to the optical axis O. The angle of the
slope of the main light beam is plus in the counterclockwise direction
in FIG. 5.
The mount diameter Dm (FIG. 11) of the mount portion (such as lens
side opening portion 31a or the body side opening portion 41a) required
at the position spaced from the imaging surface by a predetermined
distance (flange back) FB with respect to an image circle (having
a diameter Di, see FIG. 11) including the imaging range of the photoelectric
conversion surface 27a is expressed by:
As described above, the image pickup device 27 is a 4/3 type CCD
and has an imaging range of the photoelectric conversion surface
27a of 17.8 mm (long side).times.13.4 mm (short side) with an aspect
ratio of about 4:3 (where the imaging range corresponds to an effective
pixel range L-w2.times.L-h2 mentioned later, see FIG. 10). The diameter
Di2 of the image circle I-ce circumscribing the square imaging range
is 22.28 mm.
FIG. 7 is a graph indicating mount diameters for F-numbers by using
FBs as parameters when the value of the diameter Di2 is applied
to the diameter Di of the image circle of the image pickup device
27 based on EQ4.
The luminous flux angle .theta. required for capturing an object
bundle from an interchangeable lens depends on the intensity of
the used lens in principle. In other words, as the intensity of
the used lens increases (that is, as the F number decreases), the
luminous flux angle .theta. must be increased. For example, in order
to guide a luminous flux having the F No. 2.8 to the end of the
image circle, the luminous flux angle .theta. is about 10 degrees.
In order to guide a luminous flux having F No. 1.4, the luminous
flux angle .theta. is about 20 degrees (FIG. 6). In this way, by
increasing the luminous flux angle .theta., the lens having larger
intensity can be used. However, as shown in the graph, the relationship
of the applicable F-numbers and luminous flux angles .theta. is
not linear. Then, when a lens having a small F No. is used, the
luminous flux angle .theta. must be rapidly increased.
Generally, the F No. of a wide angle lens is smaller while the
F No. of a telephoto lens is larger. Generally, when a focal distance
is about 50 mm, the F No. is about 1.4. When the focal distance
is about 300 mm, the F No. is about 2 to 2.8. This is because, a
telephoto lens is no longer practical when the F No. is small.
As described above, the main light beam of a peripheral luminous
flux is not always parallel to the optical axis. Especially, when
a wide-angle lens is used, the amount of the slope is increased.
For example, FIGS. 8 and 9 show a light beam diagrams of a wide-angle
lens and a telephoto lens, respectively.
FIGS. 8A, 8B and 9A, 9B are diagrams showing states where the center
luminous flux and peripheral luminous flux enter to the photoelectric
conversion surface (Image-forming surface) 27a of an image pickup
device. FIGS. 8A, 8B is show a case where a wide angle interchangeable
lens barrel (with f 12.55 mm and F No. 1.4) is attached. FIGS. 9A,
9B show a case where a telephoto interchangeable lens barrel (with
f 300 mm and F No. 2.8). FIGS. 8A and 9A show sections in a longer
side direction (XY section) of the photoelectric conversion surface
27a. FIGS. 8B and 9B show sections in a shorter side direction (YZ
section) of the photoelectric conversion surface 27a.
The angles .alpha.-w1 and .alpha.-w2 of inclination of the main
light beam of a peripheral luminous flux by a wide-angle photographic
optical system 12aW shown in FIGS. 8A and 8B are about 5 degrees.
The angles .alpha.-t1 and .alpha.-t2 of the main light beam of the
peripheral luminous flux by a telephoto photographic optical system
12aT shown in FIGS. 9A and 9B are smaller than the angles of inclination
of the main light beam of the wide-angle photographic optical system
12aW.
Based on this fact, no problems occur if the luminous flux angle
.theta. is set to be compliant with the lens having an F No. 3 to
4 or below when the amount of inclination of the main light beam
is zero. More preferably, the luminous flux angle .theta. is set
to be compliant with the lens having the F No. 2 to 2.8 or below.
In order to satisfy the optical characteristic, the proper size
of the camera body must be practically obtained while in consideration
of the proper F-number. Therefore, the compliant F-number is applied
from the viewpoint of the size of the camera body as described below.
In other words, the height of a camera body of a lens replaceable
silver halide camera system is about 90 to 120 mm. The thickness
is about 60 to 80 mm. That is, a size which is extremely larger
than the height and the thickness is not practical. In order to
obtain a height of about 90 to 100 mm, the mount opening diameter
must be about 50 mm or below and preferably smaller than 45 mm.
The diameter is desirably about 40 mm. In order to achieve the thickness
of about 60 to 80 mm as described above, the flange back FB must
be about 35 to 50 mm.
Apparently from the relationship between the mount opening diameter
and the F number of the image pickup device 27 shown in FIG. 7,
which is a 4/3 type CCD, when the size of the opening diameter is
limited, the luminous flux angle .theta. must be set so as to have
the compliant F number larger than F numbers 1.4 to 1.8 and more
preferably F numbers 1.6 to 2.2.
In order to achieve the optical limitation and a practical body
size, the luminous flux angle .theta. is preferably set to be compliant
with the lens having F-numbers 1.4 to 4. More preferably, the luminous
flux angle .theta. is set to be compliant with the lens having F-numbers
1.6 to 2.8.
Therefore, when the circle of the reference opening is a circle
obtained by extending a predetermined image circle to the opening
portion in a direction away from the optical axis O by a predetermined
angle in accordance with the compliant F number as described above,
the desired compliant F number can be obtained.
Since the real imaging range of the image pickup device 27 is rectangular,
the required shape of the opening does not have to be circular.
At least a square inscribing the reference opening is only required.
Therefore, an opening is required having a size larger than the
square formed by connecting ends of a segment extending to the opening
portion in a direction away from the optical axis by a predetermined
angle in accordance with the proper F number diagonally from the
square of the imaging range.
According to this embodiment, the diameter Di of the image circle
corresponding to the recording screen range is 21 to 23 mm or 21.6
to 22.7. The diagonal length of the recording range inscribing the
image circle is about half (21.6 mm) of the diagonal line of a 135-format
screen. In other words, when a lens having the focal distance of
50 mm is used in a digital camera according to this embodiment,
the angle of view can be the same as the angle obtained when a lens
having the focal distance of about 100 mm is used in a 135-format
camera. Therefore, the correlation of the angle of view with respect
to the 135-format camera can be realized only by doubling the focal
distance of the lens.
The imaging range on the photoelectric conversion surface 27a of
the image pickup device 27 is a screen with the aspect ratio of
4:3 inscribing the image circle. No practical problems occur when
luminous flux from the lens can reach onto the recording screen
range within the imaging range. However, an image circle larger
than the image circle corresponding to the recording screen range
to some extent is desirably set in consideration of errors occurring
in pa manufacture and in assembly.
FIG. 10 is a diagram showing a valid screen range (valid imaging
range) and recording screen range (imaging and recording range)
in the photoelectric conversion surface 27a of the image pickup
device 27 (see FIG. 3) and image circles corresponding to the ranges.
In the image pickup device 27, as shown in FIG. 10, a recording
screen range L-w1.times.L-h1 must be smaller than a valid screen
range L-w2.times.L-h2. The recording screen range L-w1.times.L-h1
is a range to be actually converted to electric signals as image
information during image processing and to be captured. The valid
screen range L-w2.times.L-h2 is an entirely shootable range of the
image pickup device 27. This is because the outer area around a
required recording pixel (called peripheral pixel area hereinafter)
is required for creating the recording pixel by the image pickup
device 27. Furthermore, due to the precision limits in dimension
of the image pickup device 27 itself and positional errors in assembly
of the image pickup device 27 to the camera body 11 through the
image pickup device fixing plate 28 and the front plate 41, the
position of the optical axis O is displaced from the center of the
valid screen range L-w2.times.L-h2 of the image pickup device 27.
In order to absorb the displaced amount, the valid screen range
L-w2.times.L-h2 is taken larger than the recording screen range
L-w1.times.L-h1 as described above.
The form of the opening must be determined so as to prevent vignetting
of the object luminous flux in a range entering to the valid screen
range L-w2.times.L-h2 as the imaging range, which is passing through
the interchangeable lens barrel 12 and the camera body 11. The decrease
in light amount of peripheral light in the valid screen range L-w2.times.L-h2
must be prevented.
The circumscribed circle of the recording screen range L-w1.times.L-h1
is the recording screen image circle I-cr, and the diameter is Di1.
The circumscribed circle of the valid screen range (imaging range)
L-w2.times.L-h2 including the peripheral pixel area is a valid screen
image circle (imaging range image circle) I-ce of the valid screen
range (imaging range), and the diameter is Di2. In the real design,
the valid screen image circle I-ce is slightly larger. The increased
amount .DELTA.d is added to the diameter Di2 of the valid screen
image circle I-ce, and the valid screen image circle I-ce is added
to the recording screen image circle I-cr. Then, an image circle
I-c0 having a diameter Di3 can be obtained. By applying the imaging
range of the image circle I-c0, the form of the openings can be
set. More specifically, the image circle I-co having the increased
amount .DELTA.d of about 1 mm is handled as a reference image circle
corresponding to the recording screen range. However, in the description
below, the form of openings are set by using the valid screen image
circle I-ce as an imaging range image circle (which is a reference
image circle I-c having the diameter Di mentioned below) and by
using the valid screen range L-w2.times.L-h2 as an imaging range
(imaging range Ri mentioned below). The size of the valid screen
range (imaging range) L-w2.times.L-h2 is 17.8 mm.times.13.4 mm according
to this embodiment.
The diameter Dm of the circumscribed circle Im for the square mount
opening range Rm, which is a reference opening guided by a luminous
flux angle .theta. of a predetermined half angle diagonally from
the end of the imaging range Ri inscribing the reference image circle
I-c is determined as follows.
In this case, the mount opening range Rm minimizes the size of
the form of the lens side mount opening portion 31a. In other words,
the lens side mount opening portion 31a of the interchangeable lens
having the maximum mount opening portion among interchangeable lenses
of the camera system is set to be sufficient to cover at least the
square of the mount opening range Rm (where the minimum mount opening
range of the lens side mount opening portion 31a is Rm). The body
side mount opening 41a is also set to at least the size of the square
opening range Rm. Thus, the form of the opening prevents the vignetting
of object luminous flux passing through the mount opening range
Rm.
In order to guide a desired luminous flux to the periphery of the
image pickup device, nothing should block the luminous flux from
the exit pupil position of the optical system to the image pickup
device. Therefore, the members provided between the exit pupil position
to and the image pickup device also needs need openings. In other
words, members, such as a mirror box, a body side mount, a lens
side mount and a flare iris, provided between the exit pupil position
and the image pickup device must have the opening range Rm in order
to prevent the vignetting of object luminous flux. Since the camera
system is lens-interchangeableable, the range of the opening on
the camera body side must be set so as to handle the attachment
of an interchangeable lens (called the maximum light beam interchangeable
lens hereinafter) having the outermost light beam in exit light
beams is the farthest from the optical axis among interchangeable
lenses of the camera system. On the other hand, the opening range
of the interchangeable lens side can be set in accordance with the
outermost light beam of the exit light beams of each lens. In other
words, the opening range can be smaller with an interchangeable
lens having a narrower outermost light beam than that of the maximum
light beam interchangeable lens. In this case, in the lens side
mount portion, the forms of fitting portions of the mount, such
as bayonet nails, relating to the mount to the camera body are common
in all interchangeable lenses.
FIG. 11 is a light beam diagram showing a relationship between
the mount opening range Rm and the circumscribed circle Im and the
imaging range Ri inscribed in the reference image circle Ic.
As shown in FIG. 11, the mount opening range Rm giving the minimum
opening of the lens side mount opening portion 31a is a square range
obtained by connecting ends of four segments Sd extending to the
position of the mount opening portion tilting outward and being
spaced by a flange back FB with respect to the optical axis O diagonally
from the square of the imaging range Ri. The predetermined luminous
flux angle .theta.d may be 12 to 14 degrees in order to satisfy
the flange back FB and/or F number.
The body side opening 41a also has at least the size of the mount
opening range Rm. Furthermore, in shooting, those elements blocking
the object luminous flux (such as the reflector 13b and the shutter
opening frame) are not positioned in the space enclosed by four
planes of the four segments within the mirror box 42.
In the camera body shown in FIG. 2, as shown in the section diagram
in FIG. 3, the mirror box 42, the front plate 41 and the body side
mount portion 47 are located between the image pickup device 27
and the interchangeable lens 12. Therefore, the opening portion
of these members is formed so as to satisfy the mount opening range
Rm at the position in the optical axis direction where the opening
is located.
By setting the mount opening range Rm as described above, the interchangeable
lens with the AV value of 2.5 to 2 becomes compliant even when the
luminous flux having a main light beam parallel to the optical axis
enters the end of the imaging surface. In other words, even when
F No. 1.4 (AV value: 1) is used, the difference in light amount
for the AV value of 1.5 to 1 only occurs between the center and
the periphery.
As described above, the lens having a small F No. as described
above is a wider angle lens. Therefore, the main light beam of peripheral
luminous flux tilts by some degrees with respect to the optical
axis. Therefore, the above-described difference in light amount
does not actually occur. Like the lens shown in FIGS. 8A, 8B, when
the main light beam of the peripheral luminous flux tilts by about
5 degrees, the luminous flux of 1.4 to 1 in AV value can be guided
to the periphery. In other words, with the interchangeable lens
having F No. 1.4 only causes 0.4 or below in AV value between the
center and the periphery, which is not a significant problem. On
the other hand, even a brighter telephoto lens causing the main
light beam of the peripheral luminous flux to be substantially parallel
to the optical axis has F No. 2 to 2.8 (2 to 3 in AV value), which
is not a practical problem.
The diameter Dm of the circumscribed circle Im having the mount
opening range Rm, which is a reference opening here depends on the
distance from the imaging surface to the opening. The diameter Di
of the image circle Ic in view of the placement of the mirror box
42 having the reflector 13b between the image pickup device and
the body mount desirably satisfies:
Thus, the turnout reflector 13b can be located outside of the inclined
plane formed by facing segments Sd (FIG. 11) connecting the imaging
range between the body mount and the image pickup device and the
mount opening. Furthermore, the inserted reflector 13b, shutter
14 and various filters may be located between the body mount and
the image pickup device.
Furthermore, as described above, a body side mount contact pin
54 and lens side mount contact 33, which are terminals for connecting
the power supply line and the drive control signal line are provided
in the body side mount portion 47 of the camera body 11 and the
lens mount portion 37 of the interchangeable lens barrel 12. The
area for locating the connection terminal portions can be reduced
in size by locating the connection terminal portions in a comb-shaped
space area Tm (FIG. 11) established between the square-shaped mount
opening range Rm and the circumscribed circle Im.
The area for locating the connection terminal portions is not limited
to the comb-shaped space area Tm shown in FIG. 11 but may be an
upper or left or right side horizontal comb space area.
As an example of a real typical value of the imaging portion and
mount portion in the digital camera 1 according to the first embodiment,
the image circle diameter Di in the range of 21.6 to 22.6 mm. The
flange back (distance from the photoelectric conversion surface
to the mount opening portion) FB is 40.2 mm. The imaging range (which
is a valid pixel range with an aspect ration of about 4:3 on the
photoelectric conversion surface) Lw.times.Lh (=the above-described
Lw2.times.Lh2) is 17.8 mm.times.13.4 mm.
Next, a digital camera system according to a second embodiment
of the invention will be described with reference to FIGS. 12 and
13A and 13B.
FIG. 12 is a light beam diagram showing a relationship between
an image circle circumscribing an imaging range of an image pickup
device of a camera body applied in this embodiment and a circumscribed
circle of a mount opening. FIGS. 13A and 13B are light beam diagrams
between the photoelectric conversion surface of the image pickup
device according to this embodiment and a mount opening portion.
FIG. 13A shows a light beam diagram of a section along a ZX surface
(horizontal surface). FIG. 13B is a light beam diagram of a section
along a ZY surface (vertical surface).
An interchangeable lens type digital camera according to this embodiment
is a digital camera having compliant F No. of a short side and long
side of an imaging range different from those of the digital camera
1 according to the first embodiment. In the digital camera, a compliant
F No. is set at the ends in the short and long side directions of
the imaging range. The opening having a size equal to or larger
than the size of the square is obtained by extending the ends in
the short and long side directions from the short and long sides
of the imaging range to the mount opening portion position in a
direction away from the optical axis by a predetermined angle corresponding
to the compliant F No.
The other constructions are similar to that of the digital camera
1 according to the first embodiment, and the same reference numerals
are given to the same components hereinafter.
In the digital camera according to this embodiment, for setting
a form of the mount opening, four segments extended to the opening
portion position spaced by the flange back FB so as to be away from
the optical axis O by the angle .theta.h of inclination of about
10 degrees in a direction (Y-direction) along the short side and
the angle .theta.w of inclination of about 8 degrees in a direction
(X-direction) along the long side from four corners of the imaging
range Ri of the photoelectric conversion surface 27a of the image
pickup device inscribing an image circle Ic as shown in FIGS. 12,
13A and 13B, that is, a an upper left segment, a an upper right
segment, a lower left segment and a lower right segment are Sd1,
Sd2, Sd3 and Sd4, respectively. A square obtained by connecting
the lens side front ends of the segments is a minimum mount opening
range Rm'.
The mount opening of the camera body side may be set so as to satisfy
the minimum mount opening range Rm'. The minimum mount opening range
Rm' is set in accordance with the maximum light beam interchangeable
lens having the widest outmost light beam of an exit luminous flux
among interchangeable lenses of the camera system.
On the other hand, the minimum mount opening range of the interchangeable
lens side may be set in order not to block the outermost light beam
of the exit luminous flux of each interchangeable lens. However,
the mount must have a predetermined form to be mounted to the camera
body in order to be compliant as a camera system. The lens side
mount opening portion will be described with reference to the maximum
light beam interchangeable lens, for example.
In other words, a first plane obtained by tilting the long side
of the imaging range Ri by 10 degrees in a direction (Y-direction)
away from the optical axis O and extending the long side to the
position of the opening portion is called plane H1. A second plane
obtained by tilting the short side of the imaging range Ri by 8
degrees in a direction (X-direction) away from the optical axis
O and extending the short side to the position of the opening portion
is called plane H2. The plane H1 is a plane (boundary plane shown
in FIG. 13B) provided between the segment Sd1 and the segment Sd2
or between the segment Sd3 and the segment Sd4. The plane H2 is
a plane (boundary plane shown in FIG. 13A) provided between the
segment Sd1 and the segment Sd3 or between the segment Sd2 and the
segment Sd4. The square established by the lens-side front four
sides of the planes H1 and H2 is called minimum mount opening range
Rm'.
The square Rm.sup.1 is within a circumscribed circle of the square
formed by connecting ends of the segments tilted by a predetermined
angle .theta.3 (see FIG. 12) in direction away from the four corners
of the imaging range Ri with respect to the optical axis and extended
to the opening portion. Thus, the imaging range Ri is within the
valid pixel range with the aspect ratio of 4:3. Therefore, the angle
.theta.3 can be equal to the tilting angle .theta. according to
the first embodiment and can be set so as to satisfy the condition
below:
The circumscribed circle of the mount opening range Rm' is Im',
and the lens side mount opening portion 31a of the maximum light
beam interchangeable lens can have the minimum opening portion.
The body side mount opening portion 41a has a size equal to the
size of the mount opening range Rm' or larger. The space within
the mirror box 42 and surrounded by the four planes H1 and H2 formed
by four segments Sd1, Sd2, Sd3 and Sd4 contains nothing (reflector
13b and shutter frames) to block object luminous flux in shooting.
A main light beam of a peripheral light beam parallel to the optical
axis can be adapted up to AV 3.6 (equal to adaptive F No. 3.5) at
the end of the mount opening range Rm' in the long side direction
and up to AV 3 (equal to adaptive F No. 2.8) at the end in the short
side direction. Therefore, when a lens with F No. 1.4 is used as
an interchangeable lens barrel, the amount of light falls by 2.6
levels at the end in the long side direction and by 2 levels at
the end in the short side direction. However, as described above,
the lens barrel with F No. 1.4 may be a wide angle lens barrel,
and the main light beam of a peripheral ray beam tilts with respect
to the optical axis O. When the above illustrated lens barrel is
used, the amount of light falls by about 1.2 levels at the end in
the long side direction and by about 0.8 levels at the end in the
short side direction, which are practically not a problem. On the
other hand, when a telephoto lens barrel causing a peripheral luminous
flux with a main light beam substantially parallel to the optical
axis is used, the F No. is 2 to 2.8 (equal to AV 2 to 3). Therefore,
the telephoto lens barrel can be used with no problems.
When a digital camera according to this embodiment is used, the
reference mount diameter Dm of the circumscribed circle Im of the
minimum mount opening range Rm' depends on the distance (flange
back FB) from the imaging surface to the opening portion. However,
in consideration of the existence of the mirror box 42 between the
image pickup device 27 and the body side mount portion 47, the relationship
between the reference opening diameter Dm and the image circle Di
is desirably set so as to satisfy:
In a digital camera according to this embodiment, a connecting
terminal for electric connection between the camera body and the
interchangeable lens barrel may be provided outside of the square
of the mount opening range Rm' and is desirably provided outside
of the square and inside of the circumscribed circle Im' of the
square.
The mirror box 42, the front panel 41, and the body side mount
portion 47 and so on are provided between the image pickup device
27 and the interchangeable lens 12, as shown in the section diagram
in FIG. 3, in the camera body shown in FIG. 2. Therefore, in order
to apply this embodiment to the camera body shown in FIG. 2, the
opening portions of these members must satisfy the mount opening
range Rm' in the positions in the optical axis direction where the
openings are provided.
Next, a digital camera system according to a third embodiment of
the invention will be described with reference to FIG. 14 and so
on.
FIG. 14 is a diagram showing an imaging range of a 4/3 type image
pickup device and the image circle on the imaging range of a square
image pickup device applied to this embodiment.
In an interchangeable lens type digital camera according to this
embodiment, a square image pickup device having an imaging range
with the aspect ratio of 1:1 is applied. The mount opening portion
of the camera adopts the same shape as the mount opening shape adopted
to the digital camera according to the second embodiment.
The other construction is similar to that of the digital camera
according to the first or second embodiment, and the same reference
numerals are given to the same components in the description below.
An image pickup device applied to the camera body of the digital
camera according to this embodiment is a square image pickup device
as described above. The image circle Ic, which is a circumscribed
circle of the imaging range Ri' (an area Lw'.times.Lh': valid screen
range) of the photoelectric conversion surface has the same diameter
as that of the image circle corresponding to the imaging range Ri
of the image pickup device 27 with the aspect ratio 4:3 applied
to the digital camera according to the second embodiment. Therefore,
the mount opening of the camera according to this embodiment is
the same as the mount opening range Rm' (FIG. 12) set based on the
imaging range Ri of the image pickup device 27, like the camera
according to the second embodiment.
In other words, as shown in FIGS. 12, 13A and 13B, the minimum
mount opening of the mount opening range Rm' (the circumscribed
circle Im') is a square formed by connecting lens side ends of four
segments Sd1 extended by a flange back FB dimension from four corners
of the imaging range Ri of the photoelectric conversion surface
27a of an image pickup device inscribing the image circle Ic in
a direction apart from an optical axis by the tilting angle .theta.w
of about 10 degrees in a direction (Y-direction) along the short
side and by the tilting angle .theta.w of about 8 degrees in a direction
(X-direction) along the long side.
The 4/3 type image pickup device (image pickup device) 27 is replaced
by a square type image pickup device, and the square type image
pickup device is mounted to the camera body having the opening portion
of the mount opening range Rm' to which the interchangeable lens
barrel 12 according to the second embodiment designed for the 4/3
type image pickup device. Then, differences in amount of enter light
by the outputs of the image pickup devices were measured. Table
1 below shows results of the measurement of amounts of reduction
in EV value of the amounts of peripheral light with respect to the
amount of center light between the 4/3 type image pickup device
and the square type image pickup device at peripheral positions
(on the short side, long side and diagonal line).
TABLE 1 4:3 SQUARE ZOOMING IMAGE PICKUP IMAGE PICKUP STATE DEVICE
DEVICE DIFFERENCE SHORT SIDE WIDE -0.203 -0.293 -0.09 STANDARD -0.133
-0.179 -0.046 TELE -0.148 -0.174 -0.026 LONG SIDE WIDE -0.396 -0.278
-0.118 STANDARD -0.216 -0.179 -0.037 TELE -0.249 -0.174 -0.075 DIAGONAL
WIDE -0.963 -0.963 0 STANDARD -0.883 -0.883 0 TELE -1.003 -1.003
0
As shown in Table 1, the difference in amount of reduction in EV
value of the amount of peripheral light with respect to the amount
of center light between the 4/3 type image pickup device and the
square image pickup device is about .+-.0.1 EV, which is practically
not a problem. Therefore, only by attaching the square type image
pickup device to the camera body according to the second embodiment
instead, the digital camera body according to this embodiment can
be a digital camera body having the aspect ratio of 1:1 compliant
with the interchangeable lens barrel having the F number applied
in the second embodiment.
Cameras having various specifications may be applied in an interchangeable
lens type digital camera system. Therefore, cameras can have imaging
ranges with different aspect ratios even having the same image circle.
Especially, even when an image pickup device with the aspect ratio
of 1:1 is mounted to the camera system according to this embodiment,
the length-to-width concept of the camera no longer exists. In this
case, when a screen with an arbitrary aspect ratio is trimmed and
is read from the imaging range, the direction for holding a camera
does not have to be changed for vertically long pictures and horizontally
long pictures. Thus, the usability can be improved.
A connecting terminal for electric connection between the camera
body and the interchangeable lens barrel in the digital camera according
to this embodiment may be provided outside of the square of the
mount opening range Rm' and is desirably provided outside of the
square and inside of the circumscribed circle Im' of the square.
The present invention is not limited to the above-described embodiments,
but various changes can be practically implemented without departing
from the principle. Furthermore, the above-described embodiments
includes various steps of the invention, and various inventions
can be extracted by combining disclosed multiple constructional
requirements as necessary.
For example, even when several constructional requirements are
removed from the entire constructional requirements according to
the embodiments, so long as the problems described in the section,
Problems to be Solved by the Invention, can be solved, and the advantages
described in the section, Advantages of the Invention, can be obtained,
the construction the constructional requirement of which is removed
can be extracted as the invention. |