U.S. patent application number 09/774671 was filed with the patent office on 2001-09-13 for zoom lens assembling mechanism.
This patent application is currently assigned to ASAHI KOGAKU KOGYO KABUSHIKI KAISHA. Invention is credited to Aoki, Nobuaki, Nakamura, Satoru, Nomura, Hiroshi, Yamazaki, Yoshihiro.
Application Number | 20010021310 09/774671 |
Document ID | / |
Family ID | 18552401 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021310 |
Kind Code |
A1 |
Nomura, Hiroshi ; et
al. |
September 13, 2001 |
Zoom lens assembling mechanism
Abstract
A zoom lens assembling mechanism includes a stationary barrel; a
movable barrel; a linear guide barrel; a linear guide mechanism for
linearly guiding the linear guide barrel; and at least one lens
group which is linearly guided by the linear guide barrel. When the
movable barrel is in an operating range, the linear guide barrel is
linearly guided via the linear guide mechanism, while the movable
barrel moves with the linear guide barrel while relatively
rotating, to move the lens group. If the movable barrel is moved
forward from a frontmost position of the operating range in order
to disassemble an assembly including the movable barrel and the
linear guide barrel from the stationary barrel, the linear guide
barrel is no longer guided by the linear guide mechanism, and the
linear guide barrel moves forward while rotating with the movable
barrel to thereby remove the assembly.
Inventors: |
Nomura, Hiroshi; (Saitama,
JP) ; Aoki, Nobuaki; (Tokyo, JP) ; Yamazaki,
Yoshihiro; (Saitama, JP) ; Nakamura, Satoru;
(Tokyo, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
ASAHI KOGAKU KOGYO KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
18552401 |
Appl. No.: |
09/774671 |
Filed: |
February 1, 2001 |
Current U.S.
Class: |
396/72 |
Current CPC
Class: |
G02B 7/10 20130101 |
Class at
Publication: |
396/72 |
International
Class: |
G03B 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2000 |
JP |
2000-26705 |
Claims
What is claimed is:
1. A zoom lens assembling mechanism comprising: a stationary barrel
having a female helicoid formed on an inner peripheral surface of
said stationary barrel; a linear guide groove formed on said inner
peripheral surface of said stationary barrel to cut across said
female helicoid to extend parallel to an optical axis of said zoom
lens; an inner inclined groove formed on said inner peripheral
surface of said stationary barrel in front of said linear guide
groove in an optical axis direction so that a major part of said
inner inclined groove extends parallel to the threads of said
female helicoid, so that one end of said inner inclined groove
opens at a front end of said stationary barrel, and so that the
other end of said inner inclined groove is connected with said
linear guide groove; a movable barrel having a male helicoid formed
on an outer peripheral surface of said movable barrel to mesh with
said female helicoid, said movable barrel being moved forward and
rearward in said optical axis direction while rotating about said
optical axis in accordance with an engagement of said male helicoid
with said female helicoid; a linear guide barrel guided to be
movable together with said movable barrel in said optical axis
direction and to be rotatable relative to said movable barrel about
said optical axis; a linear guide projection formed on said linear
guide barrel to be engaged in said linear guide groove, so that
said linear guide projection can also be engaged in said inner
inclined groove; and at least one lens group guided in said optical
axis direction without rotating about said optical axis by said
linear guide barrel to be moved in said optical axis direction in a
predetermined moving manner in accordance with rotation of said
movable barrel to change a focal length of said zoom lens; wherein
said linear guide barrel is guided in said optical axis direction
with said linear guide projection being engaged in said linear
guide groove when said movable barrel is positioned in an operating
range, including a zooming range of said movable barrel, relative
to said stationary barrel; wherein said male helicoid and said
female helicoid are engaged with each other by an amount of
engagement in said optical axis direction which corresponds to a
width in said optical axis direction of an area on said inner
peripheral surface of said stationary barrel in which said inner
inclined groove is formed when said movable barrel is positioned in
a frontmost position thereof in said operating range; and wherein,
in the case where said movable barrel is moved forward from said
frontmost position relative to said stationary barrel in order to
disassemble an assembly including said movable barrel and said
linear guide barrel from said stationary barrel, said linear guide
barrel moves forward in said optical axis direction, and at the
same time, rotates together with said movable barrel about said
optical axis while said linear guide projection slides along said
inner inclined groove to thereby disassemble said assembly from
said stationary barrel.
2. The zoom lens assembling mechanism according to claim 1, further
comprising: a rotational barrel positioned around said movable
barrel, said rotational barrel being rotationally driven; a
rotation transmission groove formed on said outer peripheral
surface of said movable barrel to cut across said male helicoid to
extend parallel to said optical axis; an outer inclined groove
formed on said outer peripheral surface of said movable barrel
behind said rotation transmission groove in said optical axis
direction so that a major part of said outer inclined groove
extends parallel to the threads of said male helicoid, so that one
end of said outer inclined groove opens at a rear end of said
movable barrel, and so that the other end of said outer inclined
groove is connected with said rotation transmission groove; and an
inward projection formed on said rotational barrel to be engaged in
said rotation transmission groove, so that said inward projection
can also be engaged in said outer inclined groove; wherein rotation
of said rotational barrel is transmitted to said movable barrel
with said inward projection being engaged in said rotation
transmission groove when said movable barrel is positioned in said
operating range relative to said stationary barrel; and wherein, in
the case where said movable barrel is moved forward from said
frontmost position relative to said stationary barrel in order to
disassemble said assembly from said stationary barrel, said linear
guide barrel moves forward in said optical axis direction, and at
the same time, rotates together with said movable barrel about said
optical axis while said inward projection slides along said outer
inclined groove to thereby disassemble said assembly from said
stationary barrel.
3. The zoom lens assembling mechanism according to claim 1, further
comprising: a cam groove formed on an inner peripheral surface of
said movable barrel so that a rear end of said cam groove opens at
a rear end of said movable barrel; a linear guide slot formed on
said linear guide barrel to extend parallel to said optical axis so
that a rear end of said linear guide slot opens at a rear end of
said linear guide barrel; a lens frame which holds said lens group;
a cam follower formed on said lens frame to be engaged in said cam
groove; and a linear guide projection formed on said lens frame to
be engaged in said linear guide slot; wherein said cam follower and
said linear guide projection are respectively engaged in said cam
groove and said linear guide slot, at rear ends thereof, when said
assembly is moved forward from said stationary barrel to
disassemble said assembly from said stationary barrel.
4. The zoom lens assembling mechanism according to claim 3, wherein
said cam follower is formed on said linear guide projection.
5. The zoom lens assembling mechanism according to claim 1, further
comprising: a hood barrel positioned at the front of said zoom lens
around said movable barrel, guided in said optical axis direction
without rotating about said optical axis; an inward pin fixed to
said hood barrel to project radially inwards; and a hood barrel
guide groove formed on an outer peripheral surface of said movable
barrel, said inward pin being engaged in said hood barrel guide
groove so that said hood barrel moves in said optical axis
direction via rotation of said movable barrel; wherein said hood
barrel guide groove comprises an assembling section and an
operating section connected to said assembling section so as to
extend substantially along a circumferential direction of said
movable barrel; wherein one end of said assembling section opens at
the front end of said movable barrel; wherein said operating
section comprises a zooming section in which rotation of said
movable barrel causes said hood barrel to move forward and rearward
in said optical axis direction; wherein said rotation of said
movable barrel causes said hood barrel to move forward and rearward
in said optical axis direction to change a distance between a
frontmost lens group of said lens group and the front end of said
hood barrel in said optical axis direction in accordance with a
variation of said focal length; wherein said hood barrel can be
disassembled from said front of said zoom lens by moving said
inward pin forward to pull out said inward pin from said hood
barrel guide groove when said inward pin is positioned in said one
end of said assembling section; and wherein said assembly can be
dismounted from said stationary barrel by being moved slightly
forward from said frontmost position of said movable barrel
relative to said stationary barrel when said movable barrel is
positioned to have a predetermined rotational position relative to
said stationary barrel so as to allow said hood barrel to be
disassembled from said front of said zoom lens.
6. The zoom lens assembling mechanism according to claim 5, further
comprising a barrier block fixed to said front end of said hood
barrel and having at least one barrier blade for opening and
closing a photographic aperture of said zoom lens.
7. The zoom lens assembling mechanism according to claim 1, wherein
said linear guide groove, said inner inclined groove, and said
linear guide projection respectively comprise a plurality of linear
guide grooves, a plurality of inner inclined grooves, and a
plurality of linear guide projections.
8. The zoom lens assembling mechanism according to claim 2, wherein
said rotational transmission groove, said outer inclined groove,
and said inward projection respectively comprise a plurality of
rotational transmission grooves, a plurality of outer inclined
grooves, and a plurality of inward projections.
9. The zoom lens assembling mechanism according to claim 1, wherein
said zoom lens is incorporated in a digital camera.
10. A zoom lens assembling mechanism comprising: a stationary
barrel; a movable barrel extending from the inside of said
stationary barrel, and driven to move forward and rearward in an
optical axis direction while rotating about said optical axis; a
linear guide barrel guided to be movable together with said movable
barrel in said optical axis direction and to be rotatable relative
to said movable barrel about said optical axis; a linear guide
mechanism, provided on said linear guide barrel and said stationary
barrel, for guiding said linear guide barrel in said optical axis
direction without rotating said linear guide barrel about said
optical axis; and at least one lens group guided in said optical
axis direction without rotating about said optical axis by said
linear guide barrel to be moved in said optical axis direction in a
predetermined moving manner in accordance with rotation of said
movable barrel to change a focal length of said zoom lens; wherein,
when said movable barrel is positioned in an operating range
thereof including a zooming range of said movable barrel relative
to said stationary barrel, said linear guide barrel is guided in
said optical axis direction via said linear guide mechanism while
said movable barrel moves together with said linear guide barrel in
said optical axis direction while rotating about said optical axis
relative to said linear guide barrel to move said at least one lens
group in a predetermined moving manner; and wherein, in the case
where said movable barrel is moved forward from a frontmost
position of said operating range relative to said stationary barrel
in order to disassemble an assembly including said movable barrel
and said linear guide barrel from said stationary barrel, said
linear guide barrel is no longer guided by said linear guide
mechanism, and said linear guide barrel moves forward by a
predetermined amount of movement in said optical axis direction
while rotating together with said movable barrel about said optical
axis to thereby disassemble said assembly from said stationary
barrel.
11. The zoom lens assembling mechanism according to claim 10,
further comprising: a rotational barrel positioned around said
movable barrel and driven to rotate; and a rotation transmission
mechanism for transmitting rotation of said rotational barrel to
said movable barrel, wherein said rotation of said rotational
barrel is transmitted to said movable barrel via said rotation
transmission mechanism when said movable barrel is positioned in
said operating range relative to said stationary barrel; and
wherein, in the case where said movable barrel is moved forward
from said frontmost position relative to said stationary barrel in
order to disassemble said assembly from said stationary barrel,
said rotation transmission mechanism is made inoperable between
said rotational barrel and said movable barrel to thereby allow
said assembly to be disassembled from said stationary barrel
without rotating said rotational barrel about said optical
axis.
12. The zoom lens assembling mechanism according to claim 10,
wherein said stationary barrel comprises a female helicoid formed
on an inner peripheral surface of said stationary barrel; wherein
said movable barrel comprises a male helicoid formed on an outer
peripheral surface of said movable barrel to mesh with said female
helicoid, said movable barrel being moved forward and rearward in
said optical axis direction while rotating about said optical axis
in accordance with an engagement of said male helicoid with said
female helicoid.
13. The zoom lens assembling mechanism according to claim 10,
further comprising: a cam groove formed on an inner peripheral
surface of said movable barrel so that a rear end of said cam
groove opens at a rear end of said movable barrel; a linear guide
slot formed on said linear guide barrel to extend parallel to said
optical axis so that a rear end of said linear guide slot opens at
a rear end of said linear guide barrel; a lens frame which holds
said lens group; a cam follower formed on said lens frame thereon
to be engaged in said cam groove; and a linear guide projection
formed on said lens frame to be engaged in said linear guide slot;
wherein said cam follower and said linear guide projection are
respectively engaged in said cam groove and said linear guide slot,
at rear ends, thereof when said assembly is moved forward from said
stationary barrel to disassemble said assembly from said stationary
barrel.
14. The zoom lens assembling mechanism according to claim 13,
wherein said cam follower is formed on said linear guide
projection.
15. The zoom lens assembling mechanism according to claim 10,
further comprising: a hood barrel positioned at the front of said
zoom lens around said movable barrel, guided in said optical axis
direction without rotating about said optical axis; an inward pin
fixed to said hood barrel to project radially inwards; and a hood
barrel guide groove formed on an outer peripheral surface of said
movable barrel, said inward pin being engaged in said hood barrel
guide groove so that said hood barrel moves in said optical axis
direction via rotation of said movable barrel; wherein said hood
barrel guide groove comprises an assembling section and an
operating section connected to said assembling section so as to
extend substantially along a circumferential direction of said
movable barrel; wherein one end of said assembling section opens at
the front end of said movable barrel; wherein said operating
section comprises a zooming section in which rotation of said
movable barrel causes said hood barrel to move forward and rearward
in said optical axis direction; wherein said rotation of said
movable barrel causes said hood barrel to move forward and rearward
in said optical axis direction to change a distance between a
frontmost lens group of said lens groups and the front end of said
hood barrel in said optical axis direction in accordance with a
variation of said focal length; wherein said hood barrel can be
disassembled from said front of said zoom lens by moving said
inward pin forward to pull out said inward pin from said hood
barrel guide groove when said inward pin is positioned in said one
end of said assembling section; and wherein said assembly can be
dismounted from said stationary barrel by being moved slightly
forward from said frontmost position of said movable barrel
relative to said stationary barrel when said movable barrel is
positioned to have a predetermined rotational position relative to
said stationary barrel so as to allow said hood barrel to be
disassembled from said front of said zoom lens.
16. The zoom lens assembling mechanism according to claim 15,
further comprising a barrier block fixed to said front end of said
hood barrel and having at least one barrier blade for opening and
closing a photographic aperture of said zoom lens.
17. The zoom lens assembling mechanism according to claim 10,
wherein said linear guide mechanism comprises: a linear guide
groove formed on an inner peripheral surface of said stationary
barrel to extend parallel to an optical axis of said zoom lens; and
a linear guide projection formed on said linear guide barrel to be
engaged in said linear guide groove of said stationary barrel,
wherein said stationary barrel further comprises an inner inclined
groove formed on said inner peripheral surface thereof in front of
said linear guide groove in an optical axis direction so that a
major part of said inner inclined groove is inclined with respect
to said linear guide groove, so that one end of said inner inclined
groove opens at a front end of said stationary barrel, and so that
the other end of said inner inclined groove is connected with said
linear guide groove, wherein, when said movable barrel is
positioned in said operating range thereof, said linear guide
projection is engaged in said linear guide groove, and wherein, in
the case where said movable barrel is moved forward from said
frontmost position of said operating range relative to said
stationary barrel, said inner guide projection is inserted in said
inner inclined groove, so that said linear guide barrel moves
forward in said optical axis direction while rotating together with
said movable barrel.
18. The zoom lens assembling mechanism according to claim 17,
wherein said stationary barrel comprises a female helicoid formed
on said inner peripheral surface thereof, the threads of said
female helicoid extending parallel to said inner inclined groove,
wherein said movable barrel comprises a male helicoid formed on an
outer peripheral surface thereof to mesh with said female helicoid,
and wherein, said movable barrel is moved forward and rearward in
said optical axis direction while rotating with respect to said
stationary barrel, in accordance with an engagement of said male
helicoid with said female helicoid.
19. The zoom lens assembling mechanism according to claim 18,
wherein said male helicoid and said female helicoid are engaged
with each other when said linear guide projection is inserted in
one of said linear guide groove and said inner inclined groove.
20. The zoom lens assembling mechanism according to claim 10,
wherein said zoom lens is incorporated in a digital camera.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a zoom lens, or a zoom lens
barrel, that can be used in digital cameras, and more specifically,
to a zoom lens assembling mechanism which makes it easy for the
zoom lens to be assembled and disassembled.
[0003] 2. Description of the Related Art
[0004] A zoom lens, or a zoom lens barrel, having a movable barrel
(e.g., a cam barrel) that is supported to be movable in the
direction of the optical axis of the zoom lens while rotating about
the optical axis relative to a stationary barrel of the zoom lens
is known in the art. Such a zoom lens having a mechanism with which
the movable barrel can be dismounted from the stationary barrel by
rotating the movable barrel up to a position (disassembling
position) toward the front of the operating range of the movable
barrel, which includes the zooming range of the movable barrel, is
also known in the art. The opposite ends of the zooming range of
the movable barrel correspond to the wide-angle position and the
telephoto position of the movable barrel, respectively. In a zoom
lens having such a mechanism, the amount of overlap between the
movable barrel and the stationary barrel in the optical axis
direction (i.e., the length of supporting part of the stationary
barrel for the movable barrel) becomes smaller as the movable
barrel moves toward the front of the operating range thereof.
Therefore, when the movable barrel is moved to the maximum extended
position in the operating range thereof, the strength between the
movable barrel and the stationary barrel for supporting the movable
barrel by the stationary barrel is low, so that there is a
possibility of the movable barrel being eccentric and/or tilting
with respect to the optical axis, and/or deviating in the optical
axis direction. For instance, in the case where the movable barrel
and the stationary barrel are engaged with each other via male and
female helicoids (helicoidal threads) respectively formed on the
movable barrel and the stationary barrel, a sufficient amount of
engagement between the male and female helicoids cannot be ensured
when the movable barrel is moved to the maximum extended position
in the operating range thereof, which reduces the strength between
the movable barrel and the stationary barrel for supporting the
movable barrel by the stationary barrel. If the movable barrel is
eccentric and/or tilts with respect to the optical axis, and/or
deviates in the optical axis direction, the lens group or groups
which are supported inside the movable barrel cannot stay at their
right positions, which deteriorates the optical performance of the
zoom lens.
[0005] Upon assembly, every lens element of a digital camera must
be optically centered, correctly spaced, and held firmly with a
relatively high precision, e.g., tens times greater than that
required in conventional cameras using light-sensitive film since
object images are formed on the sensitive surface of a small CCD
(CCD image sensor) which is much smaller than the picture plane of
conventional cameras using light sensitive film. For instance, if
the angle of view is constant, the focal length of a photographing
lens becomes shorter as the size of the picture plane reduces,
which in turn reduces the sizes of all the elements of the
photographing lens such as lens elements, lens frames and other
elements. Therefore, the influence that a tolerance (e.g., 10
.mu.m) has on a photographing lens system of a digital camera is
much larger than the influence that the same tolerance would have
on a photographing lens system of a conventional camera using
light-sensitive film. Accordingly, manufacturing error which falls
within tolerance of optical performance in the photographing
optical system of a conventional camera using light-sensitive film
can be outside the tolerance of optical performance in the
photographing optical system of a digital camera.
[0006] To prevent such a deterioration of the optical performance
from occurring, it is possible to increase the amount of overlap
between the movable barrel and the stationary barrel in the optical
axis direction (increasing the amount of engagement of male and
female helicoids if the movable barrel and the stationary barrel
are engaged with each other via male and female helicoids) when the
movable barrel is in the maximum extended position in the operating
range thereof to ensure a sufficient strength between the movable
barrel and the stationary barrel for supporting the movable barrel
by the stationary barrel. However, in this structure, the amount of
rotational movement of the movable barrel from the frontmost
position in the operating range to the disassembling position is
great, which may impair the ease of assembly and disassembly of the
zoom lens. In general, the movable barrel is coupled to a linear
guide barrel to be rotatable about the optical axis relative to the
linear guide barrel and to be movable in the optical axis direction
together with the linear barrel, while the linear guide barrel is
guided in the optical axis direction without rotating about the
optical axis via linear guide grooves formed on the stationary
barrel. Frictional resistance is generated between the linear guide
barrel and the movable barrel when a driving force given to the
movable barrel to rotate the same is converted into another driving
force for moving the linear guide barrel linearly. Due to this
fact, if the amount of rotational movement of the movable barrel
from the frontmost position in the operating range to the
disassembling position is great, the frictional resistance
continues to be generated between the linear guide barrel and the
movable barrel while the movable barrel is being moved all the way
to the disassembling position when the movable barrel is dismounted
from the stationary barrel. This reduces efficiency of assembly and
disassembly of the zoom lens. Furthermore, if the amount of
rotational movement of the movable barrel from the frontmost
position in the operating range to the disassembling position is
great, the movable barrel has to be rotated relative to the linear
guide barrel to some degree in a range outside of the zooming
range, which unnecessarily moves the lens group or groups supported
within the linear guide barrel and the movable barrel. This is not
preferable from the viewpoint of maintenance of the optical
performance of the zoom lens and simplification of the lens group
guiding structure of the zoom lens.
[0007] If the amount of overlap between the movable barrel and the
stationary barrel in the optical axis direction is small, in some
cases a light shield structure has to be provided between the
movable barrel and the stationary barrel, since unwanted light can
possibly enter into the zoom lens from a gap between the movable
barrel and the stationary barrel. Moreover, in the case where
linear guide slots for guiding the linear guide barrel in the
optical axis direction without rotating the linear guide barrel
about the optical axis are formed on the stationary barrel to
extend along the length thereof, unwanted light can easily enter
into the zoom lens from the linear guide slots.
SUMMARY OF THE INVENTION
[0008] The present invention has been devised in view of the
above-described problems, wherein an object of the present
invention is to provide a zoom lens assembling mechanism with which
the optical performance of the zoom lens can be maintained, which
prevents unwanted light from entering into the zoom lens from a gap
between two barrels of the zoom lens, and which makes it easy for
the zoom lens to be assembled and disassembled.
[0009] To achieve the object mentioned above, according to an
aspect of the present invention, a zoom lens assembling mechanism
is provided, including a stationary barrel having a female helicoid
formed on an inner peripheral surface of the stationary barrel; a
linear guide groove formed on the inner peripheral surface of the
stationary barrel to cut across the female helicoid to extend
parallel to an optical axis of the zoom lens; an inner inclined
groove formed on the inner peripheral surface of the stationary
barrel in front of the linear guide groove in an optical axis
direction so that a major part of the inner inclined groove extends
parallel to the threads of the female helicoid, so that one end of
the inner inclined groove opens at a front end of the stationary
barrel, and so that the other end of the inner inclined groove is
connected with the linear guide groove; a movable barrel having a
male helicoid formed on an outer peripheral surface of the movable
barrel to mesh with the female helicoid, the movable barrel being
moved forward and rearward in the optical axis direction while
rotating about the optical axis in accordance with an engagement of
the male helicoid with the female helicoid; a linear guide barrel
guided to be movable together with the movable barrel in the
optical axis direction and to be rotatable relative to the movable
barrel about the optical axis; a linear guide projection formed on
the linear guide barrel to be engaged in the linear guide groove,
so that the linear guide projection can also be engaged in the
inner inclined groove; and at least one lens group guided in the
optical axis direction without rotating about the optical axis by
the linear guide barrel to be moved in the optical axis direction
in a predetermined moving manner in accordance with rotation of the
movable barrel to change a focal length of the zoom lens. The
linear guide barrel is guided in the optical axis direction with
the linear guide projection being engaged in the linear guide
groove when the movable barrel is positioned in an operating range,
including a zooming range of the movable barrel, relative to the
stationary barrel. The male helicoid and the female helicoid are
engaged with each other by an amount of engagement in the optical
axis direction which corresponds to a width in the optical axis
direction of an area on the inner peripheral surface of the
stationary barrel in which the inner inclined groove is formed when
the movable barrel is positioned in a frontmost position thereof in
the operating range. If the movable barrel is moved forward from
the frontmost position relative to the stationary barrel in order
to disassemble an assembly including the movable barrel and the
linear guide barrel from the stationary barrel, the linear guide
barrel moves forward in the optical axis direction, and at the same
time, rotates together with the movable barrel about the optical
axis while the linear guide projection slides along the inner
inclined groove to thereby disassemble the assembly from the
stationary barrel.
[0010] Preferably, the zoom lens further includes a rotational
barrel positioned around the movable barrel, the rotational barrel
being rotationally driven; a rotation transmission groove formed on
the outer peripheral surface of the movable barrel to cut across
the male helicoid to extend parallel to the optical axis; an outer
inclined groove formed on the outer peripheral surface of the
movable barrel behind the rotation transmission groove in the
optical axis direction so that a major part of the outer inclined
groove extends parallel to the threads of the male helicoid, so
that one end of the outer inclined groove opens at a rear end of
the movable barrel, and so that the other end of the outer inclined
groove is connected with the rotation transmission groove; and an
inward projection formed on the rotational barrel to be engaged in
the rotation transmission groove, so that the inward projection can
also be engaged in the outer inclined groove. Rotation of the
rotational barrel is transmitted to the movable barrel with the
inward projection being engaged in the rotation transmission groove
when the movable barrel is positioned in the operating range
relative to the stationary barrel. If the movable barrel is moved
forward from the frontmost position relative to the stationary
barrel in order to disassemble the assembly from the stationary
barrel, the linear guide barrel moves forward in the optical axis
direction, and at the same time, rotates together with the movable
barrel about the optical axis while the inward projection slides
along the outer inclined groove to thereby disassemble the assembly
from the stationary barrel.
[0011] Preferably, the zoom lens assembling mechanism further
includes a cam groove formed on an inner peripheral surface of the
movable barrel so that a rear end of the cam groove opens at a rear
end of the movable barrel; a linear guide slot formed on the linear
guide barrel to extend parallel to the optical axis so that a rear
end of the linear guide slot opens at a rear end of the linear
guide barrel; a lens frame which holds the lens group; a cam
follower formed on the lens frame to be engaged in the cam groove;
and a linear guide projection formed on the lens frame to be
engaged in the linear guide slot. The cam follower and the linear
guide projection are respectively engaged in the cam groove and the
linear guide slot, at rear ends thereof, when the assembly is moved
forward from the stationary barrel to disassemble the assembly from
the stationary barrel.
[0012] Preferably, the cam follower is formed on the linear guide
projection.
[0013] In an embodiment, the zoom lens further includes a hood
barrel positioned at the front of the zoom lens around the movable
barrel, guided in the optical axis direction without rotating about
the optical axis; an inward pin fixed to the hood barrel to project
radially inwards; and a hood barrel guide groove formed on an outer
peripheral surface of the movable barrel, the inward pin being
engaged in the hood barrel guide groove so that the hood barrel
moves in the optical axis direction via rotation of the movable
barrel. The hood barrel guide groove includes an assembling section
and an operating section connected to the assembling section so as
to extend substantially along a circumferential direction of the
movable barrel, wherein one end of the assembling section opens at
the front end of the movable barrel. The operating section includes
a zooming section in which rotation of the movable barrel causes
the hood barrel to move forward and rearward in the optical axis
direction. The rotation of the movable barrel causes the hood
barrel to move forward and rearward in the optical axis direction
to change a distance between a frontmost lens group of the lens
group and the front end of the hood barrel in the optical axis
direction in accordance with a variation of the focal length. The
hood barrel can be disassembled from the front of the zoom lens by
moving the inward pin forward to pull out the inward pin from the
hood barrel guide groove when the inward pin is positioned in the
one end of the assembling section. The assembly can be dismounted
from the stationary barrel by being moved slightly forward from the
frontmost position of the movable barrel relative to the stationary
barrel when the movable barrel is positioned to have a
predetermined rotational position relative to the stationary barrel
so as to allow the hood barrel to be disassembled from the front of
the zoom lens.
[0014] In an embodiment, the zoom lens further includes a barrier
block fixed to the front end of the hood barrel and having at least
one barrier blade for opening and closing a photographic aperture
of the zoom lens.
[0015] In an embodiment, the linear guide groove, the inner
inclined groove, and the linear guide projection respectively
include a plurality of linear guide grooves, a plurality of inner
inclined grooves, and a plurality of linear guide projections.
[0016] In an embodiment, the rotational transmission groove, the
outer inclined groove, and the inward projection respectively
include a plurality of rotational transmission grooves, a plurality
of outer inclined grooves, and a plurality of inward
projections.
[0017] The zoom lens can be incorporated in a digital camera.
[0018] According to another aspect of the present invention a zoom
lens assembling mechanism is provided, including a stationary
barrel; a movable barrel extending from the inside of the
stationary barrel, and driven to move forward and rearward in an
optical axis direction while rotating about the optical axis; a
linear guide barrel guided to be movable together with the movable
barrel in the optical axis direction and to be rotatable relative
to the movable barrel about the optical axis; a linear guide
mechanism, provided on the linear guide barrel and the stationary
barrel, for guiding the linear guide barrel in the optical axis
direction without rotating the linear guide barrel about the
optical axis; and at least one lens group guided in the optical
axis direction without rotating about the optical axis by the
linear guide barrel to be moved in the optical axis direction in a
predetermined moving manner in accordance with rotation of the
movable barrel to change a focal length of the zoom lens. When the
movable barrel is positioned in an operating range thereof
including a zooming range of the movable barrel relative to the
stationary barrel, the linear guide barrel is guided in the optical
axis direction via the linear guide mechanism while the movable
barrel moves together with the linear guide barrel in the optical
axis direction while rotating about the optical axis relative to
the linear guide barrel to move the at least one lens group in a
predetermined moving manner. If the movable barrel is moved forward
from a frontmost position of the operating range relative to the
stationary barrel in order to disassemble an assembly including the
movable barrel and the linear guide barrel from the stationary
barrel, the linear guide barrel is no longer guided by the linear
guide mechanism, and the linear guide barrel moves forward by a
predetermined amount of movement in the optical axis direction
while rotating together with the movable barrel about the optical
axis to thereby disassemble the assembly from the stationary
barrel.
[0019] Preferably, the zoom lens further includes a rotational
barrel positioned around the movable barrel and driven to rotate;
and a rotation transmission mechanism for transmitting rotation of
the rotational barrel to the movable barrel. The rotation of the
rotational barrel is transmitted to the movable barrel via the
rotation transmission mechanism when the movable barrel is
positioned in the operating range relative to the stationary
barrel. If the movable barrel is moved forward from the frontmost
position relative to the stationary barrel in order to disassemble
the assembly from the stationary barrel, the rotation transmission
mechanism is made inoperable between the rotational barrel and the
movable barrel to thereby allow the assembly to be disassembled
from the stationary barrel without rotating the rotational barrel
about the optical axis.
[0020] Preferably, the stationary barrel includes a female helicoid
formed on an inner peripheral surface of the stationary barrel. The
movable barrel includes a male helicoid formed on an outer
peripheral surface of the movable barrel to mesh with the female
helicoid, the movable barrel being moved forward and rearward in
the optical axis direction while rotating about the optical axis in
accordance with an engagement of the male helicoid with the female
helicoid.
[0021] Preferably, the zoom lens assembling mechanism further
includes a cam groove formed on an inner peripheral surface of the
movable barrel so that a rear end of the cam groove opens at a rear
end of the movable barrel; a linear guide slot formed on the linear
guide barrel to extend parallel to the optical axis so that a rear
end of the linear guide slot opens at a rear end of the linear
guide barrel; a lens frame which holds the lens group; a cam
follower formed on the lens frame thereon to be engaged in the cam
groove; and a linear guide projection formed on the lens frame to
be engaged in the linear guide slot. The cam follower and the
linear guide projection are respectively engaged in the cam groove
and the linear guide slot, at rear ends, thereof when the assembly
is moved forward from the stationary barrel to disassemble the
assembly from the stationary barrel.
[0022] Preferably, the cam follower is formed on the linear guide
projection.
[0023] In an embodiment, the zoom lens further includes a hood
barrel positioned at the front of the zoom lens around the movable
barrel, guided in the optical axis direction without rotating about
the optical axis; an inward pin fixed to the hood barrel to project
radially inwards; and a hood barrel guide groove formed on an outer
peripheral surface of the movable barrel, the inward pin being
engaged in the hood barrel guide groove so that the hood barrel
moves in the optical axis direction via rotation of the movable
barrel. The hood barrel guide groove includes an assembling section
and an operating section connected to the assembling section so as
to extend substantially along a circumferential direction of the
movable barrel, wherein one end of the assembling section opens at
the front end of the movable barrel. The operating section includes
a zooming section in which rotation of the movable barrel causes
the hood barrel to move forward and rearward in the optical axis
direction. The rotation of the movable barrel causes the hood
barrel to move forward and rearward in the optical axis direction
to change a distance between a frontmost lens group of the lens
groups and the front end of the hood barrel in the optical axis
direction in accordance with a variation of the focal length. The
hood barrel can be disassembled from the front of the zoom lens by
moving the inward pin forward to pull out the inward pin from the
hood barrel guide groove when the inward pin is positioned in the
one end of the assembling section. The assembly can be dismounted
from the stationary barrel by being moved slightly forward from the
frontmost position of the movable barrel relative to the stationary
barrel when the movable barrel is positioned to have a
predetermined rotational position relative to the stationary barrel
so as to allow the hood barrel to be disassembled from the front of
the zoom lens.
[0024] In an embodiment, the zoom lens assembling mechanism further
includes a barrier block fixed to the front end of the hood barrel
and having at least one barrier blade for opening and closing a
photographic aperture of the zoom lens.
[0025] In an embodiment, the linear guide mechanism includes a
linear guide groove formed on an inner peripheral surface of the
stationary barrel to extend parallel to an optical axis of the zoom
lens; and a linear guide projection formed on the linear guide
barrel to be engaged in the linear guide groove of the stationary
barrel. The stationary barrel further includes an inner inclined
groove formed on the inner peripheral surface thereof in front of
the linear guide groove in an optical axis direction so that a
major part of the inner inclined groove is inclined with respect to
the linear guide groove, so that one end of the inner inclined
groove opens at a front end of the stationary barrel, and so that
the other end of the inner inclined groove is connected with the
linear guide groove. When the movable barrel is positioned in the
operating range thereof, the linear guide projection is engaged in
the linear guide groove. In the case where the movable barrel is
moved forward from the frontmost position of the operating range
relative to the stationary barrel, the inner guide projection is
inserted in the inner inclined groove, so that the linear guide
barrel moves forward in the optical axis direction while rotating
together with the movable barrel.
[0026] Preferably, the stationary barrel includes a female helicoid
formed on the inner peripheral surface thereof, the threads of the
female helicoid extending parallel to the inner inclined groove,
wherein the movable barrel includes a male helicoid formed on an
outer peripheral surface thereof to mesh with the female helicoid.
The movable barrel is moved forward and rearward in the optical
axis direction while rotating with respect to the stationary
barrel, in accordance with an engagement of the male helicoid with
the female helicoid.
[0027] The male helicoid and the female helicoid are engaged with
each other when the linear guide projection is inserted in either
the linear guide groove or the inner inclined groove.
[0028] The zoom lens can be incorporated in a digital camera.
[0029] The present disclosure relates to subject matter contained
in Japanese Patent Application No.2000-26705 (filed on Feb. 3,
2000) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The present invention will be described below in detail with
reference to the accompanying drawings in which:
[0031] FIG. 1 is an exploded perspective view of an embodiment of a
zoom lens according to the present invention, showing the overall
structure thereof;
[0032] FIG. 2 is an axial cross sectional view of the zoom lens
shown in FIG. 1, showing the zoom lens above the optical axis
thereof;
[0033] FIG. 3 is a developed view of the inner peripheral surface
of a first cam barrel, showing the contours of first and second cam
grooves formed on the inner peripheral surface of the first cam
barrel;
[0034] FIG. 4 is an exploded perspective view of the first cam
barrel shown in FIG. 3, a linear guide barrel, a first lens frame
and a second lens frame;
[0035] FIG. 5 is a fragmentary rear view of the linear guide barrel
and the first lens frame, showing the periphery of an insertion
groove of the linear guide barrel;
[0036] FIG. 6 is an exploded perspective view of the linear guide
barrel, a linear guide ring and a retainer ring;
[0037] FIG. 7 is a developed view of the linear guide barrel, the
linear guide ring and the retainer ring;
[0038] FIG. 8 is a developed view of a second cam barrel and a
barrier drive ring, showing the positional relationship
therebetween when the zoom lens is set at the telephoto extremity
thereof (when the zoom lens is in a ready-to-photograph state);
[0039] FIG. 9 is a developed view of the second cam barrel and the
barrier drive ring, showing the positional relationship
therebetween when the zoom lens is positioned in the accommodation
position (when the power of the zoom lens is turned OFF);
[0040] FIG. 10 is an axial cross sectional view of the zoom lens
show in FIG. 1, showing the zoom lens above the optical axis
thereof, showing the positional relationship between an external
barrel and the second cam barrel (a first lens group) when the zoom
lens is set at the wide-angle extremity thereof;
[0041] FIG. 11 is an axial cross sectional view of the zoom lens
show in FIG. 1, showing the zoom lens above the optical axis
thereof, and showing the positional relationship between the
external barrel and the second cam barrel (the first lens group)
when the zoom lens is set at the telephoto extremity thereof;
[0042] FIG. 12 is an explanatory view showing variations in axial
position of the sensitive surface (image plane) of a CCD, the first
lens group, a second lens group, and a barrier block when the zoom
lens is driven from the accommodation position to the telephoto
extremity and thereafter to the wide-angle extremity;
[0043] FIG. 13 is an exploded perspective view of the barrier
block, viewed from behind the barrier block;
[0044] FIG. 14 is a perspective view of the barrier block with an
annular pressure plate being removed from the barrier block, viewed
from behind the barrier block;
[0045] FIG. 15A is a schematic front view of the barrier block,
showing two pairs of barrier blades in a fully open position;
[0046] FIG. 15B is a schematic front view of the barrier block,
showing the two pairs of barrier blades in a half-closed
position;
[0047] FIG. 15C is a schematic front view of the barrier block,
showing the two pairs of barrier blades in a fully closed
position;
[0048] FIG. 16 is a perspective view of the second cam barrel and
the barrier drive ring, showing the positional relationship between
a driven lever which extends from the barrier drive ring and a
rotation transfer recess formed on the second cam barrel;
[0049] FIG. 17 is a front view of the external barrel that is
supported by the external barrel to be freely rotatable about the
optical axis, in a state where the barrier drive ring is rotated to
one rotational limit thereof to thereby fully close the two pairs
of barrier blades;
[0050] FIG. 18 is a front view of the external barrel shown in FIG.
17, in a state where the barrier drive ring is rotated to the other
rotational limit thereof to thereby fully open the two pairs of
barrier blades;
[0051] FIG. 19 is an axial cross sectional view of the zoom lens
shown in FIG. 1, showing the zoom lens above the optical axis
thereof, and showing a state where the external barrel together
with the barrier block is dismounted from the zoom lens;
[0052] FIG. 20 is an axial cross sectional view of the zoom lens
shown in FIG. 1, showing the zoom lens above the optical axis
thereof, and showing a state where an assembly, composed of the
first and second cam barrels and the linear guide barrel, is
dismounted from the zoom lens after the barrier block is dismounted
from the zoom lens;
[0053] FIG. 21A is a developed view of the stationary barrel of the
zoom lens and the first cam barrel, showing a state where the first
cam barrel is engaged with the stationary barrel of the zoom lens
via helicoidal threads;
[0054] FIG. 21B is a view similar to that of FIG. 21A and
illustrates a state where the first cam barrel is engaged with the
stationary barrel of the zoom lens via helicoidal threads by a
different amount of engagement;
[0055] FIG. 21C is a view similar to that of FIGS. 21A and 21B and
illustrates a state where the first cam barrel is engaged with the
stationary barrel of the zoom lens via helicoidal threads by a
different amount of engagement;
[0056] FIG. 21D is a developed view of the stationary barrel of the
zoom lens and the first cam barrel, showing a state where the first
cam barrel is dismounted from the stationary barrel of the zoom
lens; and
[0057] FIG. 22 is a fragmentary developed view of the second cam
barrel, showing an embodiment of the contour of each guide groove
formed on the second cam barrel.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0058] A preferred embodiment of a zoom lens (zoom lens barrel)
according to the present invention that is incorporated in a
digital camera will be hereinafter discussed. Firstly, the overall
structure of the zoom lens will be discussed with reference mainly
to FIGS. 1 and 2. In the drawings and the following descriptions,
symbols "(F)", "(L)" and "(RL)" which are each appended as a suffix
to the reference numeral of some elements of the zoom lens barrel
indicate that the element is stationary, the element is movable
linearly along an optical axis O of the zoom lens without rotating
about the optical axis O, and the element is movable along the
optical axis O while rotating about the optical axis O,
respectively.
[0059] The photographic optical system of the zoom lens includes
three lens groups; namely, a first lens group (front lens group) L1
(L), a second lens group (middle lens group) L2 (L) and a third
lens group (rear lens group) L3 (L), in this order from the object
side (the left side as viewed in FIG. 2). The zoom lens performs
zooming by moving the first and second lens groups L1 and L2 along
the optical axis O relative to the sensitive surface of a
stationary CCD 12a (see FIG. 2) and at the same time changing the
space between the first and second lens groups L1 and L2 in a
predetermined manner. The zoom lens performs a focusing operation
by moving the third lens group L3 along the optical axis O to bring
an object into focus. The third lens group L3 functions as a
focusing lens group which is driven along the optical axis O
independently of the axial position of each of the first and second
lens groups L1 and L2. Thus, the zoom lens is an internal-focusing
type zoom lens having a lens construction which allows the focus to
be altered by moving the rearmost lens group provided as a focusing
lens group internally within the lens barrel.
[0060] The zoom lens is provided with a housing 10(F) which is
fixed to a camera body of a digital camera (not shown). The housing
10 can be integral with the camera body to be provided as an
element thereof. The zoom lens is provided in the housing 10 with a
stationary barrel 11(F) that is fixed to the housing 10. The
stationary barrel 11 is provided on an outer peripheral surface
thereof with a fine male thread 11a. The stationary barrel 11 is
provided on an inner peripheral surface thereof with a female
helicoid (female helicoidal thread) 11b and three linear guide
grooves 11c (only one is shown in FIG. 1) extending parallel to the
optical axis O, i.e., extending in the optical axis direction. The
three linear guide grooves 11c are formed to cut across the female
helicoid 11b. The three linear guide grooves 11c are formed at
120.degree. intervals (i.e., at an equi-angular distance) about the
axis of the stationary barrel 11.
[0061] As shown in FIG. 2, the housing 10 is provided with a CCD
insertion opening 10a, a filter fixing portion 10b and a focusing
lens group guide portion 10c. The CCD 12a which is fixed to a
substrate 12 is positioned in the CCD insertion opening 10a. A
filter 10d such as a low-pass filter is fixed to the filter fixing
portion 10b. The third lens group L3 is guided by the focusing lens
group guide portion 10c to be movable in the optical axis
direction. The axial position of the third lens group L3 on the
optical axis O is determined by the direction of rotation of a feed
screw 10e and the angle of rotation (amount of rotation) thereof.
The feed screw 10e extends parallel to the optical axis O from the
camera body in the focusing lens group guide portion 10c. The feed
screw 10e is driven by a pulse motor (not shown) provided in the
camera body. The angle of rotation of the feed screw 10e is
controlled via an encoder (not shown) of the pulse motor.
[0062] The zoom lens is provided on the stationary barrel 11 with a
rotational barrel 13 (RL). The rotational barrel 13 is provided on
an inner peripheral surface thereof with a fine female thread 13a
which meshes with the fine male thread 11a of the stationary barrel
11. The rotational barrel 13 is provided on an outer peripheral
surface thereof with a circumferential gear 13b (see FIG. 1). The
rotational barrel 13 is driven to rotate about the optical axis O
by a drive pinion (not shown) which meshes with the circumferential
gear 13b. When the rotational barrel 13 is driven to rotate about
the optical axis O, the rotational barrel 13 moves in the optical
axis direction while rotating about the optical axis O in
accordance with the engagement of the fine female thread 13a with
the fine male thread 11a. The rotational barrel 13 is provided at
the front end of an inner peripheral surface thereof with three
inward projections 13c at 1200 intervals about the axis of the
rotational barrel 13. As shown in FIG. 1, a flexible coding plate
14 (RL) is fixed on an outer peripheral surface of the rotational
barrel 13 along a circumference thereof, while a brush 15 (F) that
is in contact with the coding plate 14 is fixed to the housing 10.
The brush 15 remains in sliding contact with the coding plate 14
regardless of a movement of the coding plate 14 relative to the
brush 15 when the coding plate 14 moves in the optical axis
direction in accordance with the engagement of the fine female
thread 13a with the fine male thread 11a, so as to sense the
rotational position of the rotational barrel 13 as digital and/or
analogue information. The fine female thread 13a, which is provided
on the rotational barrel 13, is provided as a device for supporting
the rotational barrel 13 on the stationary barrel 11 so that the
rotational barrel 13 can rotate freely about the optical axis O on
the stationary barrel 11. However, alternatively, the rotational
barrel 13 can be supported on the stationary barrel 11 so as to be
able to rotate freely about the optical axis O without moving in
the optical axis direction relative to the stationary barrel
11.
[0063] The zoom lens is further provided with a linear guide barrel
16 (L), a first cam barrel 17 (movable barrel) (RL) and a second
cam barrel 18 (movable barrel) (RL). The first cam barrel 17 is
fitted on the linear guide barrel 16 to be rotatable about the
optical axis O relative to the linear guide barrel 16 and to be
immovable in the optical axis direction relative to the linear
guide barrel 16. The second cam barrel 18 is fitted on the front
end of the first cam barrel 17 to be rotatable together with the
first cam barrel 17 about the optical axis O and also to be movable
in the optical axis direction relative to the first cam barrel 17.
The linear guide barrel 16, the first cam barrel 17 and the second
cam barrel 18 are assembled in advance as a unit, and the rear of
this barrel unit is positioned in the stationary barrel 11. The
linear guide barrel 16 is provided at the rear end thereof with an
outer flange 16a. A linear guide ring (flange ring) 19(L) is fixed
to the front end of the linear guide barrel 16 via a retainer ring
20(L). The first cam barrel 17 is held between the outer flange 16a
and the linear guide ring 19, and is rotatable about the optical
axis O relative to the linear guide barrel 16 and also movable
together with the linear guide barrel 16 in the optical axis
direction.
[0064] The second cam ring 18, which is fitted on the front end of
the first cam barrel 17, is provided at the rear end thereof with
three linear guide portions 18a (only two are shown in FIG. 1) at
120.degree. intervals about the axis of the second cam ring 18.
Each of the three linear guide portions 18a is provided with a
spring holding groove 18a1, and a pair of guide grooves 18a2
positioned on the opposite sides of the spring holding groove 18a1
in a circumferential direction of the second cam ring 18 (see FIGS.
8 and 9). Each of the three linear guide portions 18a is further
provided, in each spring holding groove 18a1 at the front end (the
left end as viewed in FIG. 8 or 9) of each spring holding groove
18a1, with an engaging projection 18a3. All of the spring holding
grooves 18a1 and the pairs of guide grooves 18a2 extend parallel to
the optical axis O. The first cam barrel 17 is provided on an outer
peripheral surface thereof with three stopper portions 17a (only
two are shown in FIG. 1) at 120.degree. intervals about the axis of
the first cam barrel 17. Each of the three stopper portions 17a is
provided with a stopper projection 17a1, and a pair of guide
projections 17a2 positioned on the opposite sides of the stopper
projection 17a1 in a circumferential direction of the first cam
barrel 17 (see FIG. 4). Each pair of guide projections 17a2 of the
first cam barrel 17 are respectively fitted in the corresponding
pair of guide grooves 18a2 of the second cam ring 18 to be slidable
in the optical axis direction relative to the second cam ring 18,
with a compression spring 21 being held between each engaging
projection 18a3 and the corresponding stopper projection 17a1. Due
to this structure, the second cam barrel 18 can slide on the first
cam barrel 17 in the optical axis direction without rotating about
the optical axis O relative to the first cam barrel 17. The
compression springs 21 constantly bias the second cam barrel 18
toward the front of the zoom lens, so that the front end of the
second cam barrel 18 is usually in press-contact with the linear
guide ring 19. The second cam barrel 18 can move rearward, toward
the rear of the zoom lens, against the spring force of the
compression springs 21 by an amount of movement corresponding to a
predetermined clearance in the optical axis direction between the
guide grooves 18a2 and the guide projections 17a2. The second cam
barrel 18 can also be slightly inclined with respect to the first
cam barrel 17 (i.e., with respect to the optical axis O) by an
amount of inclination corresponding to a predetermined clearance in
a radial direction between the inner peripheral surface of the
second cam barrel 18 and the corresponding outer peripheral surface
of the first cam barrel 17.
[0065] The first cam barrel 17 is provided on an outer peripheral
surface thereof with a male helicoid (male helicoidal thread) 17b
that is engaged with the female helicoid 11b of the stationary
barrel 11, and three rotation transmission grooves 17c that extend
parallel to the optical axis O. The three rotation transmission
grooves 17c are formed so as to cut across the male helicoid 17b.
The three rotation transmission grooves 17c are formed at
120.degree. intervals about the axis of the first cam barrel 17.
The three inward projections 13c of the rotational barrel 13 are
respectively engaged with the three rotation transmission grooves
17c to be relatively slidable to each other. The three rotation
transmission grooves 17c and the corresponding three inward
projection 13c constitute a rotation transmission mechanism. The
linear guide barrel 16 is provided on the outer flange 16a thereof
with three linear guide projections 16b at 1200 intervals about the
axis of the linear guide barrel 16. Each linear guide projection
16b extends radially outwards to be engaged with the corresponding
linear guide groove 11c of the stationary barrel 11. The three
linear guide projections 16b and the corresponding linear guide
grooves 11c constitute a linear guide mechanism. The linear guide
barrel 16 is further provided with three linear guide slots 16c at
1200 intervals about the axis of the linear guide barrel 16 so that
the circumferential positions of the three linear guide slots 16c
coincide with those of the three linear guide projections 16b. Each
of the three linear guide slots 16c penetrates the linear guide
barrel 16 radially and extends parallel to the optical axis O.
[0066] As can be seen in FIGS. 4, 5 and 6, each of the three linear
guide slots 16c opens at the rear end of the linear guide barrel
16, and the rear end of each linear guide slot 16c is covered by
the corresponding part of the outer flange 16a and the
corresponding linear guide projection 16b at the radially outer
side of the linear guide barrel 16. The outer flange 16a is
provided with three insertion grooves 16h which respectively extend
along a portion of each three linear guide slots 16c from the front
end of the outer flange 16a to each respective rear end of the
three linear guide slots 16c (i.e., the rear end of the outer
flange 16a), so that a follower pin (cam follower) 22d and a
follower pin (cam follower) 23d can be inserted into each linear
guide slot 16c from the corresponding insertion groove 16h.
[0067] When the barrel unit which includes the linear guide barrel
16, the first cam barrel 17 and the second cam barrel 18 is coupled
to the stationary barrel 11 and the rotational barrel 13, each of
the three linear guide projections 16b of the linear guide barrel
16 is inserted into the corresponding linear guide groove 11c of
the stationary barrel 11 via a corresponding introducing groove
(inner inclined groove) lid formed on an inner peripheral surface
of the stationary barrel 11, and each of the three inward
projections 13c of the rotational barrel 13 is inserted into the
corresponding rotation transmission groove 17c of the first cam
barrel 17 via a corresponding introducing groove (outer inclined
groove) 17d formed on an outer peripheral surface of the first cam
barrel 17. After each linear guide projection 16b and each inward
projection 13c are inserted into the corresponding linear guide
groove 11c and the corresponding rotation transmission groove 17c,
respectively, the female helicoid 11b of the stationary barrel 11
and the male helicoid 17b of the first cam barrel 17 mesh with each
other.
[0068] FIG. 2 shows a state where the barrel unit, which includes
the linear guide barrel 16, the first cam barrel 17 and the second
cam barrel 18, has been coupled to the stationary barrel 11 and the
rotational barrel 13. In this state, rotating the rotational barrel
13 about the optical axis O via the gear 13b causes the rotational
barrel 13 to move in the optical axis direction while rotating
about the optical axis O due to the engagement of the fine female
thread 13a with the fine male thread 11a. At the same time, the
rotation of the rotational barrel 13 is transmitted to the first
cam barrel 17 and the second cam barrel 18, which is fitted on the
first cam barrel 17, due to the engagement of the inward
projections 13c with the rotation transmission grooves 17c, so that
the first cam barrel 17 and the second cam barrel 18 rotate about
the optical axis O. At this time, the first cam barrel 17 and the
second cam barrel 18 also move in the optical axis direction O due
to the engagement of the male helicoid 17b with the female helicoid
11b. Furthermore, the linear guide barrel 16 moves in the optical
axis direction without rotating about the optical axis O due to the
engagement of the linear guide projections 16b with the linear
guide grooves 11c, and at the same time the first and second cam
barrels 17 and 18, which rotate about the optical axis O relative
to the linear guide barrel 16, move together with the linear guide
barrel 16 in the optical axis direction.
[0069] The first cam barrel 17 is provided on an inner peripheral
surface thereof with three first cam grooves 17C1 for driving the
first lens group L1, and three second cam grooves 17C2 for driving
the second lens group L2. FIG. 3 is a developed view of the inner
peripheral surface of the first cam barrel 17, showing the contours
of the first and second cam grooves 17C1 and 17C2. The three first
cam grooves 17C1 are formed on the inner peripheral surface of the
first cam barrel 17 at 120.degree. intervals about the axis of the
first cam barrel 17. Likewise, the three second cam grooves 17C2
are formed on the inner peripheral surface of the first cam barrel
17 at 120.degree. intervals about the axis of the first cam barrel
17. Each of the first and second cam grooves 17C1 and 17C2 has
three predetermined positions: an accommodation position, a
telephoto position and a wide-angle, in this order along the
direction of rotation of the first cam barrel 17 (the vertical
direction as viewed in FIG. 3). The telephoto position shown in
FIG. 3 of each cam groove 17C1 and 17C2 determines the telephoto
extremity of the corresponding lens groups L1 and L2, respectively;
the wide-angle position of each cam groove 17C1 and 17C2 determines
the wide-angle extremity of the corresponding lens groups L1 and
L2, respectively; and the accommodation position of each cam groove
17C1 and 17C2 determines the position of the corresponding lens
groups Ld1 and L2, respectively, when the power of the digital
camera is turned OFF. The angle of rotation from the accommodation
position to the wide-angle extremity position is shown by "A" in
FIG. 3.
[0070] The zoom lens is provided with a first lens frame 22(L) and
a second lens frame 23(L) which support the first lens group L1 and
the second lens group L2, respectively. The first lens frame 22 is
guided by the first cam grooves 17C1 and the linear guide slots 16c
to be movable in the optical axis direction without rotating about
the optical axis O. Likewise, the second lens frame 23 is guided by
the second cam grooves 17C2 and the linear guide slots 16c to be
movable in the optical axis direction without rotating about the
optical axis O. The first lens frame 22 is provided with three
resilient extending pieces 22b which extend rearward from a
cylindrical portion 22a of the first lens frame 22. The three
resilient extending pieces 22b are formed on the first lens frame
22 at 1200 intervals about the axis of the first lens frame 22.
Each resilient extending piece 22b is provided on a radially outer
surface thereof with a square projection 22c which extends radially
outwards to be fitted in the corresponding linear guide slot 16c in
a slidable manner in the optical axis direction. Each resilient
extending piece 22b is further provided on top of each square
projection 22c with a follower pin 22d, which is fixed to the
resilient extending piece 22b to extend radially outwards. Each
square projection 22c is formed so that the opposite faces thereof,
which are respectively in sliding contact with the side faces of
the corresponding linear guide slot 16c, extend parallel to each
other. The zoom lens is provided with a first lens holder 22e which
encloses the first lens group L1 to hold the same. The first lens
holder 22e is fixed to the cylindrical portion 22a of the first
lens frame 22 via male and female threads 22f which are formed on
an outer peripheral surface of the first lens holder 22e and an
inner peripheral surface of the cylindrical portion 22a,
respectively. The position of the first lens group L1 relative to
the first lens frame 22 in the optical axis direction can be
adjusted by varying the amount of engagement between the male and
female threads 22f. A wave washer 22h is held between the holder
22e and an inner flange 22g of the first lens frame 22 to remove
the play between the first lens holder 22e (or the first lens group
L1) and the first lens frame 22 (see FIG. 2).
[0071] The second lens frame 23 is provided with three resilient
extending pieces 23b which extend forward from an annular plate
portion 23a of the second lens frame 23. The three resilient
extending pieces 23b are formed on the second lens frame 23 at
120.degree. intervals about the axis of the second lens frame 23.
Each resilient extending piece 23b is provided on a radially outer
surface thereof with a square projection 23c which extends radially
outwards to be fitted in the corresponding linear guide slot 16c in
a slidable manner in the optical axis direction. Each resilient
extending piece 23b is further provided on top of each square
projection 23c with the aforementioned follower pin 23d, which is
fixed to the resilient extending piece 23b to extend radially
outwards. The square projections 23c and the follower pins 23d of
the second lens frame 23 are identical to the square projections
22c and the follower pins 22d of the first lens frame 22 except
that the resilient extending pieces 23b of the second lens frame 23
extend in the direction opposite to the resilient extending pieces
22b of the first lens frame 22 in the optical axis direction. The
zoom lens is provided with a second lens holder 23e which encloses
the second lens group L2 to hold the same. The second lens holder
23e is fixed to the annular plate portion 23a of the second lens
frame 23 via set screws 23f. A shutter block 24 is provided around
the second lens group L2. The shutter block 24 is fixed to the
annular plate portion 23a of the second lens frame 23 via the set
screws 23f that are screwed into the rear of the shutter block 24.
The shutter block 24 functions to interrupt light bundles which are
incident on the CCD 12a at a shutter release operation.
[0072] Each of the first and second lens frames 22 and 23 is guided
linearly in the optical axis direction without rotating about the
optical axis O by the engagement of each of the three square
projections 22c and corresponding each of the three square
projections 23c with each common corresponding linear guide slot of
the three linear guide slots 16c. Each follower pin 22d penetrates
the corresponding linear guide slot 16c of the linear guide barrel
16 to be engaged with the corresponding first cam groove 17C1 of
the first cam barrel 17, which is fitted on the linear guide barrel
16 to be rotatable about the optical axis relative to linear guide
barrel 16. Likewise, each follower pin 23d penetrates the
corresponding linear guide slot 16c of the linear guide barrel 16
to be engaged with the corresponding second cam groove 17C2 of the
first cam barrel 17. When the first and second lens frames 22 and
23 are placed in the linear guide barrel 16 and the first cam
barrel 17, firstly each of the three square projections 22c and
corresponding one of the three square projections 23c are inserted
into a corresponding linear guide slot of the three linear guide
slots 16c from the rear end face of the linear guide barrel 16. At
the same time, each of the three follower pins 22d and
corresponding one of the three follower pins 23d are inserted into
corresponding one of the three insertion grooves 16h to be fitted
in the corresponding first and second cam grooves 17C1 and 17C2,
respectively. It should be noted that the hatched areas of the
first and second cam grooves 17C1 and 17C2 in FIG. 3 are used
solely for the purpose of inserting each follower pin 22d or 23d
into the corresponding cam groove 17Cl or 17C2 during assembly, and
thus are not used when the zoom lens is in operation.
[0073] According to the above described guide structure, rotating
the rotational barrel 13 about the optical axis o causes the barrel
unit which includes the linear guide barrel 16, the first cam
barrel 17 and the second cam barrel 18 to move in the optical axis
direction. During this movement of the barrel unit, the first and
second cam barrels 17 and 18 rotate together about the optical axis
O, but the linear guide barrel 16 does not rotate about the optical
axis O. As a result, the first lens frame 22 (the first lens group
L1) and the second lens frame 23 (the second lens group L2)
linearly move in the optical axis direction while changing the
space therebetween in accordance with the contours of the first and
second cam grooves 17C1 and 17C2 to thereby carry out a zooming
operation.
[0074] The coupling structure of the linear guide ring 19 and the
retainer ring 20 to the front end of the linear guide barrel 16
will be hereinafter discussed with reference to FIGS. 6 and 7. The
linear guide barrel 16 is provided, at the front end thereof at
120.degree. intervals about the axis of the linear guide barrel 16,
with three engaging lugs 16d each of which extends radially
outwards. A receiving area 16e is formed between any two adjacent
engaging lugs 16d of the linear guide barrel 16 in order to receive
one of three radially inward projections 19a of the linear guide
ring 19. The linear guide barrel 16 is provided immediately behind
the three engaging lugs 16d with three grooves 16f, respectively.
The radius of the linear guide barrel 16 from the axis of the
linear guide barrel 16 to the bottom surface of each groove 16f is
identical to the radius from the axis of the linear guide barrel 16
to the surface of each receiving area 16e. The linear guide barrel
16 is provided behind the three engaging lugs 16d with three
recesses 16g, respectively, each of which is connected with the
corresponding groove 16f. Each recess 16g is recessed rearward
(toward the right as viewed in FIG. 7) in the direction parallel to
the optical axis O, i.e., in the optical axis direction.
[0075] On the other hand, the linear guide ring 19 is provided with
the aforementioned three inward projections 19a at 120.degree.
intervals about the axis of the linear guide ring 19. The three
inward projections 19a can be inserted into the three receiving
areas 16e, respectively. If the linear guide ring 19 is rotated
about the axis thereof clockwise as viewed in FIG. 6 relative to
the linear guide barrel 16 with the three inward projections 19a
being properly inserted into the three receiving areas 16e,
respectively, each inward projection 19a slides into the
corresponding groove 16f. The linear guide ring 19 is provided with
three radially outward projections 19b at 120.degree. intervals
about the axis of the linear guide ring 19. The circumferential
positions of the three outward projections 19b are precisely
determined with reference to the circumferential positions of the
three inward projections 19a.
[0076] The retainer ring 20 is provided with radially inward blades
20a at 120.degree. intervals about the axis of the retainer ring
20. The three inward blades 20a can be inserted into the three
receiving areas 16e of the linear guide barrel 16, respectively. If
the retainer ring 20 is rotated about the axis thereof clockwise as
viewed in FIG. 6 relative to the linear guide barrel 16 with the
three inward blades 20a being properly inserted into the three
receiving areas 16e, respectively, each inward blade 20a slides
into the corresponding groove 16f. The retainer ring 20 is provided
on the front end face thereof with a plurality of grooves 20b which
are recessed rearward, toward the linear guide barrel 16, so that a
pin face wrench (not shown) can be engaged with the recessed
portions 20b to rotate the retainer ring 20 relative to the linear
guide barrel 16.
[0077] When the linear guide ring 19 is fixed to the front end of
the linear guide barrel 16, firstly the three inward projections
19a are respectively inserted into the three receiving areas 16e,
and then the linear guide ring 19 is rotated about the axis thereof
clockwise as viewed in FIG. 6 relative to the linear guide barrel
16 so that each inward projection 19a slides into the corresponding
groove 16f. Subsequently, each inward projection 19a is made to be
fitted in the corresponding recess 16g. This engagement of each
inward projection 19a with the corresponding recess 16g determines
the fixed circumferential position of the linear guide ring 19
relative to the linear guide barrel 16. Subsequently, the inward
blades 20a of the retainer ring 20 are respectively inserted into
the three receiving areas 16e, and then the retainer ring 20 is
rotated about the axis thereof clockwise as viewed in FIG. 6
relative to the linear guide barrel 16 so that each inward blade
20a slides into the corresponding groove 16f and presses the
corresponding inward projection 19a into the corresponding recess
16g. This prevents the linear guide ring 19 from moving in the
optical axis direction relative to the linear guide barrel 16. In
this state, since each of the three inward blades 20a of the
retainer ring 20 is held in one of the three grooves 16f between
the corresponding engaging lug 16d and the corresponding inward
projection 19a, the inward blades 20a and the engaging lugs 16d
function to prevent the linear guide ring 19 from coming off the
front end of the linear guide barrel 16. Between the linear guide
barrel 16 and the retainer ring 20 is provided a click-stop device
which prevents the retainer ring 20 from rotating counterclockwise
as viewed in FIG. 6 so that the retainer ring 20 cannot come off
the front end of the linear guide barrel 16 after the retainer ring
20 is properly engaged with the linear guide barrel 16. Three
indentations 20a1 which are formed on the retainer ring 20 and
corresponding three detents 16j which are formed on the linear
guide barrel 16 to be respectively engaged with the three
indentations 20a1 constitute the elements of the click-stop device
(see FIGS. 6 and 7).
[0078] Accordingly, the outward projections 19b of the linear guide
ring 19 that is fixed to the front end of the linear guide barrel
16 in the above described manner are located at predetermined
specific positions (angular positions) relative to the linear guide
projections 16b. The zoom lens is provided at the front thereof
with an external barrel (a hood barrel) 25(L). The external barrel
25 is provided, on an inner peripheral surface thereof at
120.degree. intervals about the axis of the external barrel 25,
with three linear guide grooves 25a which extend parallel to the
optical axis O. The three outward projections 19b of the linear
guide ring 19 are respectively engaged with the three linear guide
grooves 25a to guide the external barrel 25 to move in the optical
axis direction without rotating about the optical axis O. The
external barrel 25 is provided at the rear end thereof with three
radially inward pins (inward projections) 25b which are
respectively engaged with three guide grooves (hood barrel guide
grooves) 18b formed on outer peripheral surface of the second cam
barrel 18 at 120.degree. intervals about the axis thereof.
[0079] As shown in FIG. 8, each of the three guide grooves 18b of
the second cam barrel 18 defines an assembling position (or a
disassembling position) X at which the three inward pins 25b of the
external barrel 25 are respectively inserted into or taken out of
the three guide grooves 18b of the second cam barrel 18. Each of
the three guide grooves 18b further defines an accommodation
position, a telephoto position and a wide-angle extremity, which
determine the accommodation position, the telephoto extremity and
the wide-angle extremity of the first cam barrel 17, respectively.
The three guide grooves 18b are formed to move the external barrel
25 in the optical axis direction in accordance with the rotational
position of the second cam barrel 18, which rotates together with
the first cam barrel 17. More specifically, the three guide grooves
18b are formed to make the external barrel 25 function as a movable
lens hood so that the external barrel 25 advances relative to the
second cam barrel 18 (i.e., the first lens group L1) when the zoom
lens is set at the telephoto extremity thereof having a narrow
angle of view while the external barrel 25 retreats relative to the
second cam barrel 18 when the zoom lens is set at the wide-angle
extremity thereof having a wide angle of view. The external barrel
25 is positioned in the wide-angle extremity thereof and the
telephoto extremity thereof in FIG. 10 and FIG. 11,
respectively.
[0080] If the external barrel 25 is pressed rearward (i.e., toward
the camera body) by an external force when the camera is in use,
the compression springs 21 function as shock absorbers which can
absorb at least part of such an external force since the
compression springs 21 are positioned between the first cam barrel
17, which guides the first and second lens groups L1 and L2 in the
optical axis direction, and the second cam barrel 18, which guides
the external barrel 25 in the optical axis direction. Such an
external force is transmitted partly to the first cam barrel 17
after having been absorbed to some extent by the compression
springs 21, which prevents large external forces from being applied
to the first cam barrel 17. Consequently, the precision of the
axial position of each of the first and second lens groups L1 and
L2 is influenced negligibly by external forces applied to the
external barrel 25. In FIG. 2, the reference numeral 29(F)
designates a stationary external barrel which is integral with the
camera body. The external barrel 25 advances and retreats with
respect to the stationary external barrel 29.
[0081] The external barrel 25 is provided, at the front thereof in
the radially inner side of the external barrel 25, with a barrier
drive ring 26, so that the barrier drive ring 26 can rotate about
the optical axis O. The barrier drive ring 26 functions to open and
close two pairs of barrier blades 27c and 27d (i.e. the front pair
of barrier blades 27c and the rear pair of barrier blades 27d) by
rotating about the optical axis O. The two pairs of barrier blades
27c and 27d together function as a lens protection cover for
protecting the front surface of the first lens group L1 from
getting scratched, etc., when the digital camera is not in use. The
barrier block 27 is provided with a panel 27b having a photographic
aperture 27a, the aforementioned two pairs of barrier blades 27c
and 27d supported by the panel 27b therebehind to open and close
the photographic aperture 27a, and two torsion springs 27e which
constantly bias the two pairs of barrier blades 27c and 27d in a
direction to close the photographic aperture 27a. The barrier block
27 is further provided with an annular pressure plate 27f which
holds the two pairs of barrier blades 27c and 27d and the torsion
springs 27e between the panel 27b and the pressure plate 27f. The
barrier block 27 having such elements is assembled in advance as a
unit. The panel 27b is provided on a rear face thereof with two
pivots 27g (see FIGS. 13 and 14) and two engaging pins 27n. The
upper front barrier blade 27c1 of the front pair of barrier blades
27c and the upper rear barrier blade 27d1 of the rear pair of
barrier blades 27d are pivoted at corresponding one of the two
pivots 27g (the right pivot 27g as viewed in FIG. 13), while the
lower front barrier blade 27c2 of the front pair of barrier blades
27c and the lower rear barrier blade 27d2 of the rear pair of
barrier blades 27d are pivoted at the other pivot 27g (the left
pivot 27g as viewed in FIG. 13). Each of the rear pair of barrier
blades 27d is constantly biased to rotate in a direction to close
the photographic aperture 27a of the panel 27b by the corresponding
torsion spring 27e whose coil portion is fitted on the
corresponding engaging pin 27n. Each of the rear pair of barrier
blades 27d is provided in the vicinity of the pivoted portion
thereof with a driven pin 27h that is driven to open the
corresponding rear barrier blade 27d against the spring force of
the corresponding torsion spring 27e. Each of the front pair of
barrier blades 27c is provided on an outer edge thereof with an
engaging projection 27i which extends rearward to be engaged with
the outer edge of the corresponding rear barrier blade 27d so that
the engaging projection 27i of each of the front pair of barrier
blades 27c comes into engagement with the outer edge of the
corresponding rear barrier blade 27d to rotate the corresponding
front barrier blade 27c in the direction to open the photographic
aperture 27a together with the corresponding rear barrier blade 27d
when the corresponding rear barrier blade 27d is driven to rotate
in the direction to open the photographic aperture 27a. The upper
front barrier blade 27c1 is provided on a rear surface thereof with
an engaging projection 27j, while the upper rear barrier blade 27d1
is provided on a front surface thereof with an engaging projection
27k (see FIGS. 15A, 15B and 15C). When the upper rear barrier blade
27d1 is driven to rotate in the direction to close the photographic
aperture 27a, the engaging projection 27k of the upper rear barrier
blade 27d1 is engaged with the engaging projection 27j of the upper
front barrier blade 27c1 to drive the upper front barrier blade
27c1 to rotate in the direction to close the photographic aperture
27a together with the upper rear barrier blade 27d1. Likewise, the
lower front barrier blade 27c2 is provided on a rear surface
thereof with an engaging projection 27j, while the lower rear
barrier blade 27d2 is provided on a front surface thereof with an
engaging projection 27k (see FIGS. 15A, 15B and 15C). When the
lower rear barrier blade 27d2 is driven to rotate in the direction
to close the photographic aperture 27a, the engaging projection 27k
of the lower rear barrier blade 27d2 is engaged with the engaging
projection 27j of the lower front barrier blade 27c2 to drive the
lower front barrier blade 27c2 to rotate in the direction to close
the photographic aperture 27a together with the lower rear barrier
blade 27d2.
[0082] The pressure plate 27f is provided with two slots 27m
through which the two drive pins 27h of the rear pair of barrier
blades 27d penetrate toward the barrier drive ring 26,
respectively.
[0083] The barrier drive ring 26 is provided on the front thereof
with two protrusions 26b, while the external barrel 25 is provided
in the vicinity of the front end thereof with corresponding two
protrusions 25c (see FIGS. 16, 17 and 18). Two helical extension
springs 28 are positioned between the external barrel 25 and the
barrier drive ring 26 so that one and the other ends of one helical
extension spring 28 are hooked on one of the two protrusions 26b
and corresponding one of the two protrusions 25c, respectively, and
one and the other ends of the other helical extension spring 28 are
hooked on the other protrusion 26b and the other protrusion 25c,
respectively. The spring force of each helical extension spring 28
is stronger than the spring force of each torsion spring 27e. The
barrier drive ring 26 is constantly biased by the two helical
extension springs 28 to rotate in the direction to open the two
pairs of barrier blades 27c and 27d. The barrier drive ring 26 is
provided on the front thereof with two protrusions 26c which can be
respectively engaged with the two drive pins 27h of the rear pair
of barrier blades 27d to open the two pairs of barrier blades 27c
and 27d. When the barrier drive ring 26 is rotated to the
rotational limit thereof by the spring force of the helical
extension springs 28, each of the two protrusions 26c is engaged
with the corresponding driven pin 27h to push the same in the
direction to open the corresponding rear barrier blade 27d against
the spring force of the corresponding torsion spring 27e, so that
the corresponding front barrier blade 27c also opens via the
engaging projection 27i thereof (see FIGS. 15A, 15B and 15C).
[0084] On the other hand, the barrier drive ring 26 is provided
with a driven lever 26a which extends from the rim of the barrier
drive ring 26 toward the second cam barrel 18 to be engaged with,
and disengaged from, a rotation transfer recess 18c formed on an
outer peripheral surface of the second cam barrel 18 (see FIGS. 8,
9 and 16). Since the barrier drive ring 26 is supported by the
external barrel 25 to be rotatable about the optical axis O
relative to the external barrel 25, but immovable in the optical
axis direction relative to the external barrel 25, the barrier
drive ring 26 moves toward and away from the rotating second cam
barrel 18 if the external barrel 25 linearly moves in the optical
axis direction due to the engagement of the inward pins 25b of the
external barrel 25 with the guide grooves 18b of the second cam
barrel 18 as can be seen in FIGS. 8 and 9. The driven lever 26a and
the rotation transfer recess 18c are apart from each other when
positioned within a photographing range (i.e., between the
telephoto extremity and the wide-angle extremity) as shown in FIG.
8. When the zoom barrel retreats from the telephoto extremity
thereof to the accommodation position thereof, the driven lever 26a
approaches the rotation transfer recess 18c and is then engaged
with the rotation transfer recess 18c to apply a force to the
barrier drive ring 26 to rotate the same in the direction to close
the two pairs of barrier blades 27c and 27d. When the barrier drive
ring 26 rotates to the rotational limit thereof against the spring
force of the helical extension springs 28, each of the protrusions
26c of the barrier drive ring 26 disengages from the drive pins 27h
of the corresponding rear barrier blade 27d. As a result, each of
the rear pair of barrier blades 27d closes by the spring force of
the corresponding torsion spring 27e, so that each of the front
pair of barrier blades 27c also closes via the corresponding
engaging projections 27j and 27k to thereby close the photographic
aperture 27a (see FIG. 14). Conversely, when the zoom barrel
advances from the accommodation position thereof to the telephoto
extremity thereof, the driven lever 26a moves forwards and then
disengages from the rotation transfer recess 18c to thereby allow
the barrier drive ring 26 to rotate in the direction to open the
two pairs of barrier blades 27c and 27d by the spring force of the
helical extension springs 28. As a result, each of the protrusions
26c of the barrier drive ring 26 is engaged with the drive pin 27h
of the corresponding rear barrier blade 27d to push the same in the
direction to open the corresponding front barrier blade 27c via the
corresponding engaging projection 27i to thereby open the two pairs
of barrier blades 27c and 27d. Accordingly, as can be understood by
the above description, the two pairs of barrier blades 27c and 27d
are driven to open and close by rotation of the barrier drive ring
26. It should be noted that the barrier drive ring 26 has only one
driven lever 26a, whereas the second cam barrel 18 has three
rotation transfer recesses 18c formed at 120.degree. intervals
about the axis of the second cam barrel 18. One rotation transfer
recess 18c which is actually used is freely selected from the three
rotation 15 transfer recesses 18c during assembly.
[0085] The external barrel 25 that is guided in the optical axis
direction moves forward and rearward in the optical axis direction
by rotation of the second cam barrel 18 in the above described
manner. On the other hand, the first and second lens groups L1 and
L2 move forward and rearward in the optical axis direction by
rotation of the first cam barrel 17. FIG. 12 shows the axial
position of the sensitive surface (image plane) of the CCD 12a on
which subject images are formed through the photographic optical
system, and the variations in the axial positions of the first lens
group L1 (the principal point of the first lens group L1), the
second lens group L2 (the principal point of the first lens group
L2), and the barrier block 27 fixed to the front end of the
external barrel 25 (more specifically, the photographic aperture
27a formed on the panel 27b of the barrier block 27), when the zoom
lens is driven from the accommodation position to the wide-angle
extremity via the telephoto extremity. The contours of the first
and second cam grooves 17C1 and 17C2 of the first cam barrel 17 and
the guide grooves 18b of the second cam barrel 18 are determined so
that the first lens group L1, the second lens group L2 and the
barrier block 27 move in the optical axis direction to have the
moving paths shown in FIG. 12. The photographic aperture 27a has a
generally rectangular shape as viewed from the front of the digital
camera. The angle of view in the diagonal direction of the
photographic aperture 27a is greater than the angle of view in the
lateral (horizontal) direction of the photographic aperture 27a,
while the angle of view in the lateral direction of the
photographic aperture 27a is greater than the angle of view in the
longitudinal (vertical) direction of the photographic aperture 27a.
In FIG. 10, an incident light ray S on the zoom lens along the
angle of view in the longitudinal direction of the photographic
aperture 27a, an incident light ray M on the zoom lens along the
angle of view in the lateral direction of the photographic aperture
27a, and an incident light ray L on the zoom lens along the angle
of view in the diagonal direction of the photographic aperture 27a
are shown by two-dot chain lines.
[0086] A light shield barrel 26d which extends from the inner edge
of the barrier drive ring 26 to the front end of the outer
peripheral surface of the first lens frame 22 is adhered to the
inner edge of the barrier drive ring 26 by an adhesive. The light
shield barrel 26d is rotationally symmetrical about the optical
axis O, so that the shielding characteristics of the light shield
barrel 26d do not vary even if the light shield barrel 26d rotates
forwardly and reversely together with the barrier drive ring 26
about the optical axis O.
[0087] Almost all the above mentioned elements of the zoom lens
except for each spring, the feed screw 10e, the set screws 23f, the
follower pins 22d, the follower pins 23d, the shutter block 24, the
radially inward pins 25b, the flexible coding plate 14 and the
brush 15 are made of synthetic resin. Although each lens element of
the first, second and third lens groups L1, L2 and L3 can be made
of a plastic, at least the frontmost lens element is preferably a
glass lens for the purpose of preventing the front surface of the
first lens group L1 from being scratched.
[0088] In the above illustrated embodiment, although the third lens
group L3 functions as focusing lens group, the zoom lens can be
modified so that the first lens group L1 or the second lens group
L2 functions as focusing lens group. In the case where the second
lens group L2 functions as focusing lens group, the shutter block
can be modified to have an auto-focusing function. Such a shutter
block is well-known in the art.
[0089] As has been described above, in the present embodiment of
the zoom lens, rotating the rotational barrel 13 about the optical
axis O via the gear 13b causes the rotational barrel 13 to move in
the optical axis direction while rotating about the optical axis O
due to the engagement of the fine female thread 13a with the fine
male thread 11a. At the same time, the rotation of the rotational
barrel 13 is transmitted to the first cam barrel 17 due to the
engagement of the inward projections 13c with the rotation
transmission grooves 17c, so that the first cam barrel 17 rotates
about the optical axis O. At this time, the first cam barrel 17
also moves in the optical axis direction O due to the engagement of
the male helicoid 17b with the female helicoid 11b. This movement
of the first cam barrel 17 causes the first and second lens frames
22 and 23, which hold the first and second lens groups L1 and L2,
to move in the optical axis direction in accordance with the first
and second cam grooves 17C1 and 17C2, respectively, to perform a
zooming operation.
[0090] In this zooming operation, rotation is transmitted to the
first cam barrel 17 from the rotational barrel 13 via the three
inward projections 13c of the rotational barrel 13, which are
respectively engaged with the three rotation transmission grooves
17c of the first cam barrel 17. When the first cam barrel 17 moves
forward and rearward in the optical axis direction while rotating
about the optical axis O, the position of engagement of each of the
three inward projections 13c with respect to the associated
rotation transmission groove 17c varies. More specifically, the
more the first cam barrel 17 is extended forward from the
stationary barrel 11 in the optical axis direction, the more the
inward projections 13c move toward the rear ends of the rotation
transmission grooves 17c so that each inward projection 13c is
engaged in the associated rotation transmission groove 17c at a
position closer to the rear end thereof. The linear guide barrel
16, which moves together with the first cam barrel 17 in the
optical axis direction, is guided linearly in the optical axis
direction by the engagement of the three linear guide projections
16b with the three linear guide grooves 11c, so that the position
of engagement of each of the three linear guide projections 16b
with respect to the associated linear guide groove 11c in the
optical axis direction varies when the linear guide barrel 16 moves
forward and rearward in the optical axis direction. More
specifically, the more the linear guide barrel 16 is extended
forward from the stationary barrel 11 in the optical axis
direction, the more the linear guide projections 16b move toward
the front end of the stationary barrel 11 so that each linear guide
projection 16b is engaged in the associated linear guide groove 11c
at a position closer to the front end thereof. Accordingly, the
linear guide grooves 11c of the stationary barrel 11, in which the
linear guide projections 16b are engaged when the zoom lens is in
use (e.g., during a zooming operation of the zoom lens), are formed
as linear grooves extending parallel to the optical axis O, as
shown in FIGS. 1 and 21A through 21D. Likewise, the rotation
transmission grooves 17c of the first cam barrel 17, in which the
inward projections 13c are engaged when the zoom lens is in use
(e.g., during a zooming operation of the zoom lens), are also
formed as linear grooves extending parallel to the optical axis O,
as shown in FIGS. 1 and 21A through 21D.
[0091] The introducing grooves 11d are formed on the inner
peripheral surface of the stationary barrel 11, in front of the
linear guide grooves 11c in the optical axis direction, so that a
major part of each introducing groove lid extends parallel to
threads of the female helicoid 11b, so that one end of each
introducing groove lid opens at the front end of the stationary
barrel 11, and so that the other end of each introducing groove 11d
is connected with the corresponding linear guide groove 11c.
Likewise, the introducing grooves 17d are formed on the outer
peripheral surface of the first cam barrel 17, behind the rotation
transmission grooves 17c in the optical axis direction, so that a
major part of each introducing groove 17d extends parallel to
threads of the male helicoid 17b, so that one end of each
introducing groove 17d opens at the rear end of the first cam
barrel 17, and so that the other end of each introducing groove 17d
is connected with the corresponding rotation transmission groove
17c. The frontmost part of each introducing groove lid which opens
at the front end of the stationary barrel 11 is formed as a groove
extending parallel to the optical axis O. Likewise, rearmost part
of each introducing groove 17d which opens at the rear end of the
first cam barrel 17 is formed as a groove extending parallel to the
optical axis O.
[0092] Due to such structures of the linear guide barrel 16 and the
first cam barrel 17, an assembly composed of the first cam barrel
17 and the linear guide barrel 16 is mounted to and dismounted from
the stationary barrel 11 and the rotational barrel 13 in a manner
which will be hereinafter discussed with reference to FIGS. 21A,
21B, 21C and 21D. At the same time, the states of the first and
second lens frames 22 and 23 (the first and second lens groups L1
and L2) supported inside the linear guide barrel 16 when the
assembly composed of the first cam barrel 17 and the linear guide
barrel 16 is mounted to and dismounted from the stationary barrel
11 and the rotational barrel 13 will be discussed with reference to
FIG. 3.
[0093] FIG. 21A shows a state of engagement of the first cam barrel
17 with the stationary barrel 11 when each inward projection 13c of
the rotational barrel 13 is engaged in the corresponding rotation
transmission groove 17c in the vicinity of the front end thereof
and at the same time each linear guide projection 16b of the linear
guide barrel 16 is engaged in the corresponding linear guide groove
11c in the vicinity of the rear end thereof. In other words, FIG.
21A shows a state of engagement of the first cam barrel 17 with the
stationary barrel 11 when the first cam barrel 17 is rotated
relative to the stationary barrel 11 by a rotational angle of
155.degree. from the accommodation position of the first cam barrel
17. In the state shown in FIG. 21A, the first cam barrel 17 is
positioned in the maximum extended position (a wide-angle position
or a frontmost position) in the operating range of the first cam
barrel 17. At this time, each follower pin 22d of the first lens
frame 22, which is supported inside the linear guide barrel 16 and
the first cam barrel 17, is engaged in the corresponding first cam
groove 17C1 at the wide-angle position (WIDE) thereof, while each
follower pin 23d of the second lens frame 23, which is supported
inside the linear guide barrel 16 and the first cam barrel 17, is
engaged in the corresponding second cam groove 17C2 at the
wide-angle position (WIDE) thereof.
[0094] Rotating the assembly composed of the first cam barrel 17
and the linear guide barrel 16 in an advancing direction (a
direction indicated by an arrow M1 shown in FIG. 21A) from the
wide-angle position (the maximum extended position) causes the
first cam barrel 17 to move forward in the optical axis direction
while rotating about the optical axis O in accordance with the
engagement of the male helicoid 17b with the female helicoid 11b.
Since the linear guide projections 16b are respectively engaged in
the linear guide grooves 11c to guide the linear guide barrel 16
linearly in the optical axis direction when the linear guide barrel
16 is in the wide-angle position, the linear guide barrel 16 moves
in the optical axis direction together with the first cam barrel 17
without rotating about the optical axis O if the first cam barrel
17 moves in the optical axis direction while rotating about the
optical axis O. As a result, each linear guide projection 16b of
the linear guide barrel 16 reaches the border between the
associated linear guide groove 11c and the associated introducing
groove 11d and at the same time each the inward projection 13c of
the rotational barrel 13 reaches the border between the associated
rotation transmission groove 17c and the associated introducing
groove 17d. The state of engagement of the first cam barrel 17 with
the stationary barrel 11 at this time is shown in FIG. 21B, wherein
the first cam barrel 17 is rotated relative to the stationary
barrel 11 by a rotational angle of 168.degree. from the
accommodation position of the first cam barrel 17 in the
illustrated embodiment. At this time, each follower pin 22d of the
first lens frame 22 has moved to a position in the vicinity of an
assembling position (or a disassembling position) Q (see FIG. 3) in
the associated first cam groove 17C1. Likewise, each follower pin
23d of the second lens frame 23 has moved to a position in the
vicinity of the disassembling position Q in the associated second
cam groove 17C2. The first cam barrel 17 can be moved from the
accommodation position thereof, wherein the amount of overlap
between the first cam barrel 17 and the stationary barrel 11 in the
optical axis direction is maximum, to the position shown in FIG.
21B slightly in front of the wide-angle position of the first cam
barrel 17, by rotating the rotational barrel 13 about the optical
axis O relative to the stationary barrel 11.
[0095] Further rotating the assembly composed of the first cam
barrel 17 and the linear guide barrel 16 in the advancing direction
from the position shown in FIG. 21B causes the first cam barrel 17
to further move forward in the optical axis direction while
rotating about the optical axis O in accordance with the engagement
of the male helicoid 17b with the female helicoid 11b. At this
time, since each inward projection 13c moves in the associated
introducing groove 17d, whose major part is formed to extend
parallel to the threads of the male helicoid 17b, the rotational
barrel 13 does not rotate together with the first cam barrel 17
about the optical axis O. On the other hand, the linear guide
barrel 16 is no longer guided in the optical axis direction by the
stationary barrel 11 since each linear guide projection 16b moves
in the associated introducing groove 11d, whose major part is
formed to extend parallel to threads of the female helicoid 11b, so
that the linear guide barrel 16 is moved forward in the optical
axis direction while rotating about the optical axis O together
with the first cam barrel 17. Namely, when the assembly composed of
the first cam barrel 17 and the linear guide barrel 16 is rotated
in the advancing direction from the position shown in FIG. 21B, no
rotation is transmitted between the first cam barrel 17 and the
rotational barrel 13, and at the same time the assembly composed of
the first cam barrel 17 and the linear guide barrel 16 moves
forward in the optical axis direction from the stationary barrel 11
while rotating about the optical axis O with no relative rotation
between the first cam barrel 17 and the linear guide barrel 16.
Since the first cam barrel 17 and the linear guide barrel 16 do not
rotate relative to each other at this time, neither the first lens
frame 22 nor the second lens frame 23 moves in the optical axis
direction in the first cam barrel 17.
[0096] If the assembly composed of the first cam barrel 17 and the
linear guide barrel 16 is further rotated relative to the
stationary barrel 11 in the advancing direction from the position
shown in FIG. 21B by a predetermined rotational angle (a rotational
angle of 44.degree. in the illustrated embodiment), the first cam
barrel 17 is engaged with the stationary barrel 11 in a state shown
in FIG. 21C. In this state, each inward projection 13c is engaged
in the associated introducing groove 17d at a position therein in
the vicinity of the rear end thereof which opens at the rear end of
the first cam barrel 17, and at the same time, each linear guide
projection 16b is engaged in the associated introducing groove lid
at a position in the vicinity of the front end thereof which opens
at the front end of the stationary barrel 11. Hence, the first cam
barrel 17 and the stationary barrel 11 do not substantially overlap
each other in the optical axis direction, so that the male helicoid
17b and the female helicoid 11b are no longer in mesh with each
other. Therefore, in the state shown in FIG. 21C, the assembly
composed of the first cam barrel 17 and the linear guide barrel 16
can be dismounted from the stationary barrel 11 and the rotational
barrel 13 by moving the assembly forward from the stationary barrel
11 and the rotational barrel 13. FIG. 21D shows a state where the
assembly composed of the first cam barrel 17 and the linear guide
barrel 16 is dismounted from the stationary barrel 11 and the
rotational barrel 13. FIG. 20 also shows this state in cross
section.
[0097] Although the first cam barrel 17 and the linear guide barrel
16 rotate together about the optical axis O with no relative
rotation therebetween when the assembly composed of the first cam
barrel 17 and the linear guide barrel 16 is rotated relative to the
stationary barrel 11 from the position shown in FIG. 21B to the
position shown in FIG. 21C, the first cam barrel 17 and the linear
guide barrel 16 slightly rotate relative to each other about the
optical axis O when the assembly composed of the first cam barrel
17 and the linear guide barrel 16 is rotated relative to the
stationary barrel 11 from the position shown in FIG. 21C to the
position shown in FIG. 21D since frontmost part of each introducing
groove lid and rearmost part of each introducing groove 17d are
each formed as a groove extending parallel to the optical axis o as
noted above. In the present embodiment of the zoom lens, at the
moment the assembly composed of the first cam barrel 17 and the
linear guide barrel 16 has been rotated relative to the stationary
barrel 11 from the position shown in FIG. 21B to the position shown
in FIG. 21C, each of the follower pins 22d and 23d stays in the
associated first or second cam groove 17C1 or 17C2 between the
wide-angle position thereof and the disassembling position Q
thereof. Subsequently, if the first cam barrel 17 and the linear
guide barrel 16 are again rotated relative to each other about the
optical axis O when the assembly composed of the first cam barrel
17 and the linear guide barrel 16 is in the position shown in FIG.
21C, each of the follower pins 22d and 23d is moved in the
associated first or second cam groove 17C1 or 17C2 to the
disassembling position Q thereof in accordance with rotation of the
first cam barrel 17 in the advancing direction thereof.
[0098] If the assembly composed of the first cam barrel 17 and the
linear guide barrel 16 is dismounted from the stationary barrel 11
in the above described manner, the first and second lens frames 22
and 23 can be removed from the rear of the assembly of the first
cam barrel 17 and the linear guide barrel 16. In a state of the
assembly composed of the first cam barrel 17 and the linear guide
barrel 16 at the time the assembly is dismounted from the
stationary barrel 11, the rear ends of the three second cam grooves
17C2 are respectively positioned at the same positions as the rear
ends of the linear guide slots 16c in a circumferential direction
about the optical axis O. on the other hand, the three square
projections 23c, which are respectively engaged in the three linear
guide slots 16c, and the follower pins 23d are formed at the same
positions in a circumferential direction about the optical axis O.
Therefore, each of the three follower pins 23d that respectively
penetrate through the three linear guide slots 16c is positioned in
the associated second cam groove 17C2 in the vicinity of the rear
end opening thereof (i.e., in the vicinity of the disassembling
position Q), while each of the three square projections 23c is
positioned in the associated linear guide slot 16c in the vicinity
of the rear end opening thereof. Accordingly, the second lens frame
23 can be dismounted from the assembly composed of the first cam
barrel 17 and the linear guide barrel 16 by simply pulling out the
second lens frame 23 from the rear of the assembly. Subsequently,
if the first cam barrel 17 and the linear guide barrel 16 are
rotated relative to each other so that each follower pin 22d
positioned in the associated first cam groove 17C1 at the rear end
thereof (at the disassembling position Q) moves to the rear end
opening of the associated first cam groove 17C1, the first lens
frame 22 can also be dismounted from the rear of the stationary
barrel 11.
[0099] Each second cam groove 17C2 is provided in the vicinity of
the rear end opening thereof with a stop section N which serves as
a stop for preventing the associated follower pin 23d from moving
toward the rear end opening of the second cam groove 17C2 beyond
the stop. The depth of the stop section N in a radial direction of
the first cam barrel 17 is smaller than that of the zooming section
of the second cam groove 17C2. When one follower pin 23d is fitted
in the associated second cam groove 17C2, at least in the zooming
section thereof, a constant force is exerted upon the follower pin
23d radially outwards so that the follower pin 23d is fitted in the
associated second cam groove 17C2 without play. Such a constant
force is exerted upon the follower pin 23d via a resilient
deformation of the associated resilient extending piece 23b inwards
in a radial direction when the follower pin 23d is fitted in the
associated second cam groove 17C2, at least in the zooming section
thereof. When the follower pin 23d passes the stop section N, whose
depth is smaller than that of the zooming section of the second cam
groove 17C2 in the radial direction of the first cam barrel 17, a
frictional resistance between the follower pin 23d and the second
cam groove 17C2 increases since the amount of the resilient
deformation of the associated resilient extending piece 23b
increases inwards in the radial direction. Therefore, when the
follower pin 23d is in the second cam groove 17C2 on the dead end
side thereof beyond the stop section N, the stop section N prevents
the follower pin 23d from moving rearward accidentally, toward the
rear end opening of the second cam groove 17C2 beyond the stop
section N. If the second lens frame 23 does not come off the linear
guide barrel 16 and the first cam barrel 17, the first lens frame
22, which is positioned in front of the second lens group 23 and
which uses the three linear guide grooves 16 together with the
second lens frame 23, does not come off the linear guide barrel 16
and the first cam barrel 17 either. When the second lens frame 23
is removed from the assembly of the first cam barrel 17 and the
linear guide barrel 16, each follower pin 23d only needs to be
moved to the rear end opening of the second cam groove 17C2 beyond
the stop section N while each resilient extending piece 23b is
deformed inwards in the radial direction a little further after
each follower pin 23d reaches the stop section N.
[0100] An operation of mounting the assembly composed of the first
cam barrel 17 and the linear guide barrel 16 to the stationary
barrel 11 and the rotational barrel 13 is the reverse of the above
described operation of dismounting the assembly composed of the
first cam barrel 17 and the linear guide barrel 16 from the
stationary barrel 11 and the rotational barrel 13. Therefore,
firstly, the assembly composed of first cam barrel 17 and the
linear guide barrel 16 is held to have a relative rotational
position therebetween so that the follower pins 22d and 23d of the
first and second lens frames 22 and 23 are respectively positioned
in the first and second cam grooves 17C1 and 17C2 at the
disassembling positions Q thereof, and subsequently, the assembly
composed of the first cam barrel 17 and the linear guide barrel 16
is moved rearward, toward the stationary barrel 11 and the
rotational barrel 13, in the optical axis direction with the linear
guide projections 16b and the inward projections 13c being aligned
with the openings of the introducing grooves 11d and 17d,
respectively. As a result, the state shown in FIG. 21C is obtained.
Subsequently, the assembly composed of the first cam barrel 17 and
the linear guide barrel 16 is rotated in a direction (retracting
direction) indicated by an arrow M2 shown in FIG. 21C so as to have
the state shown in FIG. 21B. When the assembly composed of the
first cam barrel 17 and the linear guide barrel 16 is rotated
relative to the stationary barrel 11 from the position shown in
FIG. 21C to the position shown in FIG. 21B, the first cam barrel 17
and the linear guide barrel 16 rotate together about the optical
axis O without rotating relative to each other about the optical
axis O, while the rotational barrel 13 does not rotate about the
optical axis O relative to the stationary barrel 11, as described
above. After the state shown in FIG. 21B is obtained, if the first
cam barrel 17 is further rotated in the retracting direction, the
first cam barrel 17 and the linear guide barrel 16 move rearward in
the optical axis direction while rotating relative to each other
about the optical axis O to obtain the wide-angle position shown in
FIG. 21A. The first cam barrel 17 in the state shown in FIG. 21B
can be rotated in the retracting direction by rotating the
rotational barrel 13.
[0101] In the present embodiment of the zoom lens having the above
described structure, a sufficient amount of engagement between the
male and female helicoids 17b and 11b in the optical axis direction
is ensured even when the first cam barrel 17 is in the wide-angle
position (i.e., the maximum extended position) in the operating
range as shown in FIG. 21A, without forming each of the rotation
transmission grooves 17c and the linear guide grooves 11c to extend
up to a position immediately before a position of disengagement of
the male and female helicoids 17b and 11b in the optical axis
direction. Namely, since the introducing grooves lid, which have no
influence on the guiding mechanism for guiding the first and second
lens groups L1 and L2 in the optical axis direction or the rotation
transmission mechanism for transmitting rotation to the first cam
barrel 17, are formed on the stationary barrel 11 in an area in
front of the front end of an operating area of the female helicoids
11b which is used during operation of the zoom lens after assembly;
and furthermore since the introducing grooves 17d, which also have
no influence on the aforementioned guiding mechanism or the
aforementioned rotation transmission mechanism, are formed on the
first cam barrel 17 in an area behind the rear end of an operating
area of the male helicoids 17b which is used during operation of
the zoom lens after assembly, at least the areas of the male and
female helicoids 17b and 11b on which the introducing grooves lid
and 17d are formed overlap each other in the optical axis
direction. Due to this structure, when the first cam barrel 17 is
in the operating range which includes the zooming range, sufficient
strength between the first cam barrel 17 and the stationary barrel
11 for supporting the first cam barrel 17 by the stationary barrel
11 is ensured at all times to thereby minimize a possibility of the
first and second lens groups L1 and L2, supported inside the first
cam barrel 17, being eccentric and/or tilting with respect to the
optical axis O, and/or deviating in the optical axis direction.
Although problems with deterioration of optical performance of the
zoom lens due to eccentricity or tilt of a lens group or groups
with respect to the optical axis often occur in digital cameras
such as utilized in the present embodiment, such a deterioration of
the optical performance does not easily occur according to the
present embodiment of the zoom lens.
[0102] Furthermore, if the amount of engagement between the male
and female helicoids 17b and 11b in the optical axis direction is
great, unwanted light cannot easily enter into the zoom lens from a
gap between the first cam barrel 17 and the stationary barrel 11 to
thereby prevent unwanted light from entering into the CCD 12a from
the outside of the photographic optical path. Therefore, a light
shield structure does not have to be provided between the first cam
barrel 17 and the stationary barrel 11. Moreover, each of the
linear guide grooves 11c is not formed so as to make the front and
rear ends of the stationary barrel 11 connect with each other in a
straight line in the optical axis direction via the linear guide
groove 11c since the introducing grooves 11d, which extend so as to
be inclined to the optical axis O, are formed continuously with the
linear guide grooves 11c. Likewise, each of the rotation
transmission grooves 17c is not formed so as to make the front and
rear ends of the first cam barrel 17 connect with each other in a
straight line in the optical axis direction via the rotation
transmission groove 17c since the introducing grooves 17d, which
extend inclined to the optical axis O, are formed continuously with
the rotation transmission grooves 17c. Accordingly, unwanted light
cannot easily enter the zoom lens between the stationary barrel 11
and the first cam barrel 17 in a direction toward the back of the
stationary barrel 11 via the linear guide grooves 11c or the
rotation transmission grooves 17c.
[0103] When the assembly composed of the first cam barrel 17 and
the linear guide barrel 16 is rotated to move forward from the
wide-angle position (the maximum extended position shown in FIG.
21A) in an assembled state of the zoom lens to dismount the
assembly from the stationary barrel 11 and the rotational barrel
13, the assembly composed of the first cam barrel 17 and the linear
guide barrel 16 can be dismounted from the stationary barrel 11 and
the rotational barrel 13 without rotating the first cam barrel 17
and the linear guide barrel 16 relative to each other since the
linear guide projections 16b of the linear guide barrel 16 move in
the introducing grooves lid that extend parallel to threads of the
female helicoid 11b. If the linear guide barrel 16 and the first
cam barrel 17 are rotated together when dismounted from the
stationary barrel 11 and the rotational barrel 13, the linear guide
barrel 16 and the first cam barrel 17 can move with less frictional
resistance as compared with the case where the linear guide barrel
16 is guided linearly in the optical axis direction without
rotating about the optical axis O. Therefore, the efficiency of
assembling and disassembling the zoom lens does not deteriorate
even if a large amount of engagement between the male and female
helicoids 17b and 11b in the optical axis direction is secured when
the zoom lens is in the maximum extended position (shown in FIG.
21A) to thus increase the amount of rotation of the first cam
barrel 17 from the maximum extended position thereof to the
disassembling position. Furthermore, if no unnecessary rotation
occurs between the first cam barrel 17 and the linear guide barrel
16 during operation of mounting and dismounting the assembly,
composed of the first cam barrel 17 and the linear guide barrel 16,
to and from the stationary barrel 11 and the rotational barrel 13,
neither the first lens frame 22 nor the second lens frame 23
unnecessarily move inside the assembly composed of the first cam
barrel 17 and the linear guide barrel 16, so that the lens group
guiding/supporting structure for each of the first and second lens
frames 22 and 23 can be simplified. Specifically, in the present
embodiment of the zoom lens, each of the first and second cam
grooves 17C1 and 17C2 can be prevented from being formed
excessively long or having a complicated shape between the
wide-angle position (WIDE) and the disassembling position Q. This
ensures sufficient strength of the first cam barrel 17.
[0104] Likewise, when the assembly composed of the first cam barrel
17 and the linear guide barrel 16 is dismounted from the stationary
barrel 11 and the rotational barrel 13, the rotational barrel 13
does not rotate while the assembly composed of the first cam barrel
17 and the linear guide barrel 16 is dismounted from the stationary
barrel 11 and the rotational barrel 13 since the inward projections
13c of the rotational barrel 13 move in the introducing grooves 17d
that extend parallel to threads of the male helicoid 17b. This
reduces the frictional resistance to the first cam barrel 17, so
that the efficiency of assembling and disassembling operations of
the zoom lens does not deteriorate.
[0105] Furthermore, the relative rotational position between the
first cam barrel 17 and the linear guide barrel 16, when the
assembly composed of the first cam barrel 17 and the linear guide
barrel 16 is dismounted from the stationary barrel 11 and the
rotational barrel 13, allows the second lens frame 23 to be
dismounted from the assembly composed of the first cam barrel 17
and the linear guide barrel 16 by simply pulling out the second
lens frame 23 from the rear of the assembly. Accordingly, the
present embodiment of the zoom lens excels assembly and disassembly
of the lens groups to and from the zoom lens.
[0106] The mechanism for mounting and dismounting the assembly
composed of the first cam barrel 17 and the linear guide barrel 16
to and from the stationary barrel 11 and the rotational barrel 13
has been described above. This mechanism is associated with the
mechanism for mounting and dismounting the external barrel 25
(which bears the barrier block 27 at the front end thereof) to and
from the front of the zoom lens. The zoom lens assembling mechanism
of the present embodiment of the zoom lens which makes it easy for
the zoom lens to be assembled and disassembled, together with the
mechanism for mounting and dismounting the external barrel 25, will
be hereinafter discussed.
[0107] Each of the first and second lens groups L1 and L2 is driven
forward and rearward in the optical axis direction by rotation of
the first cam barrel 17 to vary the focal length, while the
external barrel 25 together with the barrier block 27 is driven
forward and rearward in the optical axis direction by rotation of
the second cam barrel 18, which rotates together with the first cam
barrel 17. The contours (profiles) of the first and second cam
grooves 17C1 and 17C2 of the first cam barrel 17 and the guide
grooves 18b of the second cam barrel 18 are determined so that the
first lens group L1, the second lens group L2 and the barrier block
27 move in the optical axis direction to have the moving paths
shown in FIG. 12.
[0108] FIG. 22 is a fragmentary developed view of the second cam
barrel 18, showing an embodiment of the contour (profile) of each
guide groove 18b formed on the second cam barrel 18, which is
rotated together with the first cam barrel 17 about the optical
axis O. Each of the three guide grooves 18b is provided with an
assembling section AS which includes the aforementioned assembling
position X (at which the three inward pins 25b of the external
barrel 25 are respectively inserted into, or taken out of, the
three guide grooves 18b of the second cam barrel 18), and an
operating section U which includes a zooming section Z. One end of
the assembling section AS opens at the front end of the second cam
barrel 18 and the other end is connected with one end of the
operating section U or the zooming section Z. A minor part of the
assembling section AS which includes the aforementioned assembling
position X extends in the optical axis direction. The operating
section U extends substantially along the circumference of the
second cam barrel 18. The opposite ends of the zooming section Z
correspond to the wide-angle position W and the telephoto position
T, respectively. The wide-angle position W is closer to the
assembling position X than the telephoto position T. Each of the
three guide grooves 18b is further provided on the opposite end
thereof with respect to the assembling position X with an
accommodation position A. When the external barrel 25 is coupled to
the second cam barrel 18, firstly the second cam barrel 18 is
rotated relative to the external barrel 25 about the axis thereof,
and then the three radially inward pins 25b of the external barrel
25 are respectively aligned at the assembling positions X of the
three guide grooves 18b of the second cam barrel 18. At this stage,
the three outward projections 19b of the linear guide ring 19 are
respectively inserted into the three linear guide grooves 25a so as
to guide the external barrel 25 in the optical axis direction
without rotating about the optical axis O. After the external
barrel 25 has been coupled to the second cam barrel 18 in such a
manner, rotating the second cam barrel 18 in forward and reverse
directions about the optical axis within the operating section U
causes the external barrel 25 to move forward and rearward in the
optical axis direction in accordance with the contours of the guide
grooves 18b. Therefore, in the zooming section Z, rotation of the
first cam barrel 17 causes the focal length of the photographic
optical system to vary while rotation of the second cam barrel 18,
which rotates about the optical axis O together with the first cam
barrel 17, causes the external barrel 25 to move forward and
rearward in the optical axis direction to change the space between
the frontmost lens group (the first lens group L1) and the barrier
block 27 in the optical axis direction to thereby prevent unwanted
light from being incident on the frontmost lens surface of the zoom
lens. In a state where each of the radially inward pins 25b of the
external barrel 25 is positioned in the operating section U of the
corresponding guide groove 18b, the external barrel 25 cannot be
dismounted from the second cam barrel 18 by moving the external
barrel 25 forward from the second cam barrel 18.
[0109] It is possible to control whether the second cam barrel 18
is driven using mechanical stops or electrically driven to rotate
to the assembling position X via the assembling section AS or
within the operating section U. In either controlling manner, when
the first cam barrel 17 is driven to rotate between the
accommodation position thereof and the wide-angle position thereof,
each radially inward pin 25b slides within the operating section U
of the associated guide groove 18b of the second cam barrel 18,
which rotates together with the first cam barrel 17, so that each
radially inward pin 25b does not enter the assembling section AS of
the associated guide groove 18b. If the first cam barrel 17 is
moved to the position shown in FIG. 21B slightly in front of the
wide-angle position of the first cam barrel 17, each radially
inward pin 25b slides into the assembling section AS of the
associated guide groove 18b to be positioned at the assembling
position X, which allows the external barrel 25 together with the
barrier block 27 to be dismounted from the front of the zoom lens
by moving the external barrel 25 forward from the assembly composed
of the first cam barrel 17 and the linear guide barrel 16, as shown
in FIG. 19.
[0110] As described above, when the first cam barrel 17 has been
moved to the position shown in FIG. 21B, each linear guide
projection 16b of the linear guide barrel 16 is positioned at the
border between the corresponding linear guide groove 11c and the
corresponding introducing groove lid and at the same time each the
inward projection 13c of the rotational barrel 13 is positioned at
the border between the corresponding rotation transmission groove
17c and the corresponding introducing groove 17d. Further rotation
of the first cam barrel 17 to move the first cam barrel 17 forward
allows the assembly composed of the first cam barrel 17 and the
linear guide barrel 16 to be dismounted from the stationary barrel
11 and the rotational barrel 13 by moving the assembly composed of
the first cam barrel 17 and the linear guide barrel 16 forward from
the stationary barrel 11. During this stage of dismounting the
assembly composed of the first cam barrel 17 and the linear guide
barrel 16, the first cam barrel 17 and the linear guide barrel 16
do not rotate relative to each other, and at the same time, the
rotational barrel 13 does not interfere with the rotation of the
first cam barrel 17. Accordingly, the present embodiment of the
zoom lens excels in the efficiency of assembly and disassembly of
the lens groups.
[0111] Once the zoom lens is disassembled in a manner as shown in
FIG. 20, the second lens frame 23 can be taken out of the assembly
composed of the first cam barrel 17 and the linear guide barrel 16
from the rear thereof without changing the relative rotational
position between the first cam barrel 17 and the linear guide
barrel 16. Subsequently, the first lens frame 22 can be taken out
of the assembly composed of the first cam barrel 17 and the linear
guide barrel 16 from the rear thereof if the first cam barrel 17
and the linear guide barrel 16 are rotated relative to each other
so that each follower pin 22d moves to the rear end opening of the
associated first cam groove 17C1.
[0112] Accordingly, in the present embodiment of the zoom lens, if
the first cam barrel 17 is moved to the position shown in FIG. 21B
slightly in front of the wide-angle position of the first cam
barrel 17, firstly the external barrel 25 together with the barrier
block 27 can be dismounted from the front of the zoom lens,
secondly an assembly which includes the first cam barrel 17, the
second cam barrel 18, the linear guide barrel 16, the first lens
group L1, the second lens group L2 and other members can be
dismounted from the stationary barrel 11, and thirdly the second
lens frame 23 that holds the second lens group L2 can be taken out
of the assembly. After the second lens frame 23 is taken out of the
assembly, the first lens frame 22 can be taken out of the assembly
by changing the relative rotational position between the first cam
barrel 17 and the linear guide barrel 16. Accordingly, the present
embodiment of the zoom lens can be easily assembled and
disassembled, and maintenance of the zoom lens is facilitated.
[0113] The present invention is not limited solely to the above
illustrated embodiment. For instance, in the illustrated
embodiment, in order to transmit rotation of the rotational barrel
13 to the first cam barrel 17, the three rotation transmission
grooves 17c are formed on the first cam barrel 17 at an
equi-angular distance (120.degree. intervals in the illustrated
embodiment) about the axis of the first cam barrel 17, while the
three inward projections 13c of the rotational barrel 13, which are
respectively slidably engaged in the three rotation transmission
grooves 17c of the first cam barrel 17, are formed on an inner
peripheral surface of the rotational barrel 13. In a conventional
zoom lens, for instance, a circumferential gear which is in mesh
with a drive pinion (not shown) is formed on a cam barrel which
corresponds to the first cam barrel 17 to rotate the cam barrel by
rotation of the drive pinion. However, according to this
conventional structure, there is a possibility of the cam barrel
being slightly deformed since the drive pinion meshes with the
circumferential gear of the cam barrel at a position away from the
rotational axis of the cam barrel. Although the above illustrated
embodiment of the zoom lens according to the present invention is
superior to a zoom lens having such conventional structure in that
there is no possibility of the cam barrel (the first cam barrel 17)
being deformed due to such conventional structure, the above
described zoom lens assembling mechanism according to the present
invention can also be applied to a zoom lens wherein a drive pinion
is in mesh with a circumferential gear formed on a cam barrel which
corresponds to the first cam barrel 17 of the above illustrated
embodiment. In other words, if only the above illustrated
embodiment of the zoom lens is structured so that at least a
certain amount of engagement between the male and female helicoids
17b and 11b in the optical axis direction is ensured even when the
first cam barrel 17 is in the maximum extended position thereof in
the operating range as shown in FIG. 21A and so that the linear
guide barrel 16 rotates together with the first cam barrel 17 when
the first cam barrel 17 is moved forward from the maximum extended
position thereof, the optical performance of the zoom lens can be
maintained while an excellent ability for the zoom lens to be
assembled and disassembled can be ensured.
[0114] Moreover, although, in the illustrated embodiment, the
movable barrel (cam barrel) positioned between the stationary
barrel 11 and the linear guide barrel 16 in the radial direction
includes two barrels (i.e., the first cam barrel 17 and the second
cam barrel 18), an integrally formed barrel can be alternatively
applied to the movable barrel of the present invention.
[0115] As can be understood from the above description, according
the present invention, a zoom lens assembling mechanism with which
the optical performance of the zoom lens can be maintained, which
prevents unwanted light from entering into the zoom lens from a gap
between two barrels of the zoom lens, and which makes it easy for
the zoom lens to be assembled and disassembled, can be
obtained.
[0116] Obvious changes may be made in the specific embodiment of
the present invention described herein, such modifications being
within the spirit and scope of the invention claimed. It is
indicated that all matter contained herein is illustrative and does
not limit the scope of the present invention.
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