U.S. patent application number 11/371005 was filed with the patent office on 2006-09-21 for lens barrel.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Hidenori Miyamoto.
Application Number | 20060209437 11/371005 |
Document ID | / |
Family ID | 37002531 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060209437 |
Kind Code |
A1 |
Miyamoto; Hidenori |
September 21, 2006 |
Lens barrel
Abstract
A lens barrel includes a first optical element that is allowed
to move along an optical axis, a first driven member connected to
the first optical element, a second optical element disposed in the
optical axis of the first optical element, which is allowed to move
along the optical axis, a second driven member connected to the
second optical element, a first drive shaft disposed substantially
parallel to the optical axis to drive the first driven member along
the optical axis, a second drive shaft disposed substantially
parallel to the optical axis to drive the second driven member
along the optical axis, a first drive unit connected to an end of
the first drive shaft to drive the first drive shaft, and a second
drive unit connected to an end of the second drive shaft to drive
the second drive shaft and disposed at a position that partially
overlaps a position of the first drive unit when viewed from the
direction of the optical axis.
Inventors: |
Miyamoto; Hidenori;
(Urayasu-shi, JP) |
Correspondence
Address: |
STAAS & HALSEY LLP
SUITE 700
1201 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
37002531 |
Appl. No.: |
11/371005 |
Filed: |
March 9, 2006 |
Current U.S.
Class: |
359/824 ;
348/E5.028 |
Current CPC
Class: |
G03B 17/17 20130101;
G02B 7/021 20130101; H04N 5/2254 20130101 |
Class at
Publication: |
359/824 |
International
Class: |
G02B 7/02 20060101
G02B007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2005 |
JP |
JP 2005-072320 |
Claims
1. A lens barrel comprising: a first optical element that is
allowed to move along an optical axis; a first driven member
connected to the first optical element; a second optical element
disposed in the optical axis of the first optical element, which is
allowed to move along the optical axis; a second driven member
connected to the second optical element; a first drive shaft
disposed substantially parallel to the optical axis to drive the
first driven member along the optical axis; a second drive shaft
disposed substantially parallel to the optical axis to drive the
second driven member along the optical axis; a first drive unit
connected to an end of the first drive shaft to drive the first
drive shaft; and a second drive unit connected to an end of the
second drive shaft to drive the second drive shaft and disposed at
a position that partially overlaps a position of the first drive
unit when viewed from the direction of the optical axis.
2. A lens barrel according to claim 1, further comprising: a barrel
body in which the first optical element and the second optical
element are housed; and a support member detachably mounted at the
barrel body, which supports the first drive shaft, the second drive
shaft, the first drive unit and the second drive unit.
3. A lens barrel according to claim 1, wherein: the first drive
unit is connected to an end of the first drive shaft toward a
subject side along the optical axis; and the second drive unit is
connected to an end of the second drive shaft toward an image side
along the optical axis.
4. A lens barrel according to claim 3, further comprising: a barrel
body in which the first optical element and the second optical
element are housed; and a support member detachably mounted at the
barrel body, which supports the first drive shaft, the second drive
shaft, the first drive unit and the second drive unit.
5. A lens barrel according to claim 4, further comprising: a light
quantity adjustment unit disposed toward the image side along the
optical axis relative to the first optical element and the second
optical element; and a light quantity adjustment drive unit
disposed on a side opposite from the second drive unit with the
optical axis present in between, to drive the light quantity
adjustment unit.
6. A lens barrel according to claim 3, further comprising: a guide
unit that guides movement of the first optical element and the
second optical element along the optical axis and is disposed on a
side where the first drive shaft and the second drive shaft are
disposed relative to the optical axis.
7. A lens barrel according to claim 6, wherein: a first range over
which the guide unit guides the first optical element and a second
range over which the guide unit guides the second optical element
partially overlap along the optical axis.
8. A lens barrel according to claim 7, further comprising: a light
quantity adjustment unit disposed toward the image side along the
optical axis relative to the first optical element and the second
optical element; and a light quantity adjustment drive unit
disposed on a side opposite from the second drive unit with the
optical axis present in between, to drive the light quantity
adjustment unit.
9. A lens barrel according to claim 2, further comprising: a guide
unit that guides movement of the first optical element and the
second optical element along the optical axis and is disposed on a
side where the first drive shaft and the second drive shaft are
disposed relative to the optical axis.
10. A lens barrel according to claim 9, wherein: a first range over
which the guide unit guides the first optical element and a second
range over which the guide unit guides the second optical element
partially overlap along the optical axis.
11. A lens barrel according to claim 10, further comprising: a
light quantity adjustment unit disposed toward the image side along
the optical axis relative to the first optical element and the
second optical element; and a light quantity adjustment drive unit
disposed on a side opposite from the second drive unit with the
optical axis present in between, to drive the light quantity
adjustment unit.
12. A lens barrel according to claim 3, further comprising: a light
quantity adjustment unit disposed toward the image side along the
optical axis relative to the first optical element and the second
optical element; and a light quantity adjustment drive unit
disposed on a side opposite from the second drive unit with the
optical axis present in between, to drive the light quantity
adjustment unit.
13. A lens barrel comprising: a first optical element that is
allowed to move along an optical axis; a first driven member
connected to the first optical element; a second optical element
disposed in the optical axis of the first optical element, which is
allowed to move along the optical axis; a second driven member
connected to the second optical element; a first drive shaft
disposed substantially parallel to the optical axis to drive the
first driven member along the optical axis; a second drive shaft
disposed substantially parallel to the optical axis to drive the
second driven member along the optical axis; a first drive unit
connected to an end of the first drive shaft to drive the first
drive shaft; a second drive unit connected to an end of the second
drive shaft to drive the second drive shaft; a barrel body in which
the first optical element and the second optical element are
housed; and a support member detachably mounted at the barrel body,
which supports the first drive shaft, the second drive shaft, the
first drive unit and the second drive unit.
14. An imaging apparatus, comprising: a first optical element that
is allowed to move along an optical axis; a first driven member
connected to the first optical element; a second optical element
disposed in the optical axis of the first optical element, which is
allowed to move along the optical axis; a second driven member
connected to the second optical element; a first drive shaft
disposed substantially parallel to the optical axis to drive the
first driven member along the optical axis; a second drive shaft
disposed substantially parallel to the optical axis to drive the
second driven member along the optical axis; a first drive unit
connected to an end of the first drive shaft to drive the first
drive shaft; a second drive unit connected to an end of the second
drive shaft to drive the second drive shaft and disposed at a
position that partially overlaps a position of the first drive unit
when viewed from the direction of the optical axis; and an
image-capturing element that captures a subject image via the first
optical element and the second optical element.
15. An imaging apparatus according to claim 14, wherein: the first
drive unit is connected to an end of the first drive shaft toward a
subject to be imaged along the optical axis; and the second drive
unit is connected as an end of the second drive shaft toward the
image-capturing element along the optical axis.
16. An imaging apparatus according to claim 15, further comprising:
an objective lens disposed at a position closest to the subject
along the optical axis; and a deflecting member disposed between
the objective lens and the first optical element to deflect light
from the subject.
17. An imaging apparatus according to claim 15, wherein: the
deflecting member is a prism.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of the following priority application is
herein incorporated by reference: Japanese Patent Application No.
2005-072320 filed Mar. 15, 2005
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a lens barrel that includes
a plurality of optical elements driven independently of one another
along the direction of the optical axis thereof.
[0004] 2. Description of Related Art
[0005] The lens barrel of a camera that houses the photographic
optical system of the camera, known in the related art may include
a plurality of movable lens units that move independently of one
another along the direction of the optical axis thereof.
[0006] At a lens barrel that includes an optical system adopting
such a multiple unit structure, lead screws extending parallel to
the optical axis and transmission mechanisms that are connected to
the movable lens units and each include a threaded portion to
engage with the lead screw are disposed so as to drive the movable
lens units along the optical axis by rotationally driving the lead
screws. One lead screw is disposed in conjunction with each movable
lens unit.
[0007] Japanese Laid Open Patent Publication No. 2003-241056
discloses a lens barrel that includes two movable lens units. In
this lens barrel, two lead screws are disposed adjacent to the
optical system, with motors for rotationally driving the individual
lead screws disposed side-by-side at the ends of the lead screws on
one side.
[0008] In the structure described above in which the plurality of
lead screws each disposed parallel to the optical axis are driven
by motors disposed side-by-side, the distance between the axes of
the lead screws is likely to be significant due to the restrictions
imposed by the motor size, which makes it difficult to provide a
lens barrel as a compact unit, specifically with regard to its
measurement along the direction perpendicular to the optical axis
of the lens barrel (the direction along which the lead screws are
disposed).
SUMMARY OF THE INVENTION
[0009] A lens barrel according to a first aspect of the present
invention includes a first optical element that is allowed to move
along an optical axis, a first driven member connected to the first
optical element, a second optical element disposed in the optical
axis of the first optical element, which is allowed to move along
the optical axis, a second driven member connected to the second
optical element, a first drive shaft disposed substantially
parallel to the optical axis to drive the first driven member along
the optical axis, a second drive shaft disposed substantially
parallel to the optical axis to drive the second driven member
along the optical axis, a first drive unit connected to an end of
the first drive shaft to drive the first drive shaft, and a second
drive unit connected to an end of the second drive shaft to drive
the second drive shaft and disposed at a position that partially
overlaps a position of the first drive unit when viewed from the
direction of the optical axis.
[0010] The lens barrel according to the first aspect may further
include a barrel body in which the first optical element and the
second optical element are housed, and a support member detachably
mounted at the barrel body, which supports the first drive shaft,
the second drive shaft, the first drive unit and the second drive
unit. It is preferable that the first drive unit is connected to an
end of the first drive shaft toward a subject side along the
optical axis, and the second drive unit is connected to an end of
the second drive shaft toward an image side along the optical
axis.
[0011] The lens barrel according to the first aspect may further
include a light quantity adjustment unit disposed toward the image
side along the optical axis relative to the first optical element
and the second optical element, and a light quantity adjustment
drive unit disposed on a side opposite from the second drive unit
with the optical axis present in between, to drive the light
quantity adjustment unit.
[0012] The lens barrel according to the first aspect may further
include a guide unit that guides movement of the first optical
element and the second optical element along the optical axis and
is disposed on a side where the first drive shaft and the second
drive shaft are disposed relative to the optical axis. It is
preferable that a first range over which the guide unit guides the
first optical element and a second range over which the guide unit
guides the second optical element partially overlap along the
optical axis.
[0013] A lens barrel according to a second aspect of the present
invention includes a first optical element that is allowed to move
along an optical axis, a first driven member connected to the first
optical element, a second optical element disposed in the optical
axis of the first optical element, which is allowed to move along
the optical axis, a second driven member connected to the second
optical element, a first drive shaft disposed substantially
parallel to the optical axis to drive the first driven member along
the optical axis, a second drive shaft disposed substantially
parallel to the optical axis to drive the second driven member
along the optical axis, a first drive unit connected to an end of
the first drive shaft to drive the first drive shaft, a second
drive unit connected to an end of the second drive shaft to drive
the second drive shaft, a barrel body in which the first optical
element and the second optical element are housed, and a support
member detachably mounted at the barrel body, which supports the
first drive shaft, the second drive shaft, the first drive unit and
the second drive unit.
[0014] An imaging apparatus according to a third aspect of the
present invention includes a first optical element that is allowed
to move along an optical axis, a first driven member connected to
the first optical element, a second optical element disposed in the
optical axis of the first optical element, which is allowed to move
along the optical axis, a second driven member connected to the
second optical element, a first drive shaft disposed substantially
parallel to the optical axis to drive the first driven member along
the optical axis, a second drive shaft disposed substantially
parallel to the optical axis to drive the second driven member
along the optical axis, a first drive unit connected to an end of
the first drive shaft to drive the first drive shaft, a second
drive unit connected to an end of the second drive shaft to drive
the second drive shaft and disposed at a position that partially
overlaps a position of the first drive unit when viewed from the
direction of the optical axis, and an image-capturing element that
captures a subject image via the first optical element and the
second optical element.
[0015] In the third aspect, it is preferable that the first drive
unit is connected to an end of the first drive shaft toward a
subject to be imaged along the optical axis, and the second drive
unit is connected as an end of the second drive shaft toward the
image-capturing element along the optical axis. The imaging
apparatus according to the third aspect may further include an
objective lens disposed at a position closest to the subject along
the optical axis, and a deflecting member disposed between the
objective lens and the first optical element to deflect light from
the subject. The deflecting member may be a prism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an external view of a lens barrel achieved in an
embodiment of the present invention, taken from the side of a
subject to be photographed;
[0017] FIG. 2 is a sectional view taken along line II-II in FIG.
1;
[0018] FIG. 3 is a sectional view taken along line III-III in FIG.
2;
[0019] FIG. 4 is a sectional view taken along line IV-IV in FIG.
3;
[0020] FIG. 5 is a sectional view taken along line V-V in FIG.
3;
[0021] FIGS. 6A.about.6C show the structures adopted at the
objective lens and a first lens unit in the lens barrel shown in
FIG. 1;
[0022] FIG. 7 presents an external perspective of the lens barrel
in FIG. 1, taken from the side on which a CCD is disposed;
[0023] FIGS. 8A and 8B schematically illustrate the method adopted
when assembling the lens barrel in FIG. 1;
[0024] FIG. 9 schematically illustrates the positions at which lead
screws and motors are disposed in a lens barrel representing a
comparison example to be compared with the present invention;
[0025] FIG. 10 schematically illustrates the positions at which
lead screws and motors are disposed in the lens barrel shown in
FIG. 1; and
[0026] FIG. 11 schematically shows the structure adopted in an
image-capturing device that includes the lens barrel achieved in
the embodiment.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] In a lens barrel achieved in an embodiment of the present
invention, which includes a plurality of movable optical element
units driven independently of one another, lead screws that drive
two lens units are disposed adjacent to each other and motors which
drive the individual lead screws are disposed on opposite sides,
one on the side of the corresponding lead screw toward an objective
lens along an optical axis and the other on the side of the
corresponding lead screw toward the image along the optical axis.
This configuration reduces the external dimensions of the lens
barrel.
[0028] The following is a detailed explanation of the embodiment of
the present invention, given in reference to drawings. FIG. 1 is an
external view of the lens barrel achieved in the embodiment of the
present invention, taken from the side of a subject to be
photographed, FIG. 2 is a sectional view taken along line II-II in
FIG. 1, FIG. 3 is a sectional view taken along line III-III in FIG.
2, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3 and
FIG. 5 is a sectional view taken along line V-V in FIG. 3.
[0029] A lens barrel 1 achieved in the embodiment includes an
optical path bending optical system which alters the direction of
the optical axis and may be used as, for instance, a photographic
lens barrel in a digital still camera. The lens barrel 1 includes a
barrel body 2, a motor holder unit 3, a guide shaft 4 and a
rotation-preventing shaft 5 (see FIG. 3 for details of the guide
shaft 4 and the rotation-preventing shaft 5).
[0030] The barrel body (lens barrel main body) 2, formed so as to
assume a substantially rectangular parallelopiped box shape houses
therein the bending optical system to be detailed later. The motor
holder unit 3 is detachably mounted at a side of the barrel body 2
to support lead screws 110 and 120 and motors 130 and 140 to be
detailed later. The motor holder unit 3 is formed in a box shape,
and includes an opening at which it is joined to the barrel body 2.
In addition, an opening is formed at the barrel body 2 at a
position toward the motor holder unit 3, and thus, as the barrel
body 2 and the motor holder unit 3 are joined by setting their
openings to face opposite each other, a continuous space is formed
inside.
[0031] It is to be noted that the barrel body 2 and the motor
holder unit 3 are each formed through injection molding of a resin
material.
[0032] The guide shaft 4, disposed inside the barrel body 2, is a
member formed as a round rod extending parallel to an optical axis
I2 (see FIG. 2). The guide shaft 4 guides a second lens unit 40 and
a third lens unit 50 to be detailed later along the direction of
the optical axis. The rotation-preventing shaft 5 is disposed
inside the barrel body 2 over an area on the side opposite from the
guide shaft 4 with the second lens unit 40 and the third lens unit
50 present between them. The rotation-preventing shaft 5, a member
formed as a round rod extending parallel to the optical axis I2,
prevents rotation of the second lens unit 40 and the third lens
unit 50 around the guide shaft 4.
[0033] Inside the barrel body 2, an optical system that includes an
objective lens 10, a prism 20, a first lens unit 30, the second
lens unit 40, the third lens unit 50, a shutter unit 60, a fourth
lens unit 70, a low pass filter (LPS) 80 and an image-capturing
element 90, is housed. The objective lens 10 as referred to in this
context is the lens that is is posed closest to the subject among
the components of the optical system housed inside the barrel body
2. The first lens unit 30, the second lens unit 40, the third lens
unit 50 and the fourth lens unit 70 each include one or more
lenses. The image-capturing element 90, which may be a CCD or a
CMOS, captures a subject image having passed through the objective
lens 10, the prism 20, the first lens unit 30 and the like. The
image-capturing element 90 in the embodiment is constituted with a
CCD.
[0034] The objective lens 10 is fixed on the surface of the barrel
body 2 located toward the subject, adjacent to an opening formed
near the top end of the lens barrel 1 mounted in a camera being
held sideways, i.e., during a regular photographing operation. The
prism 20 is fixed at the barrel body 2 over an area on the exit
side of the objective lens 10 and is used as a bending optical unit
that changes the direction of the image light having exited the
objective lens 10 by, for instance, 90.degree..
[0035] The first lens unit 30 is fixed at the barrel body 2 over an
area on the exit side of the prism 20 (the side set facing downward
during the regular photographing operation). In addition, the
optical axis I2 of the optical system extending from the first lens
unit 30 through the components disposed at subsequent stages is set
perpendicular to an optical axis I1 of the objective lens 10.
During the regular photographing operation, the optical axis I2 is
set along a substantially vertical direction.
[0036] The first Lens unit 30 is constituted by pasting together
lenses 31 and 32 sequentially disposed along the optical axis I2
starting on the light entry side with the lens 31 having a greater
external diameter than the external diameter of the lens 32. The
first lens unit 30 is positioned by locking the portion of the
external circumferential edge, of the lens 31 projecting beyond the
lens 32 at a recessed portion formed at the barrel body 2.
[0037] FIGS. 6A through 6C show the structures adopted in the
objective lens 10 and the first lens unit 30. In FIG. 6A, the first
lens unit 30 is viewed from a direction running perpendicular to
the optical axes I1 and I2, whereas FIGS. 6B and 6C respectively
present views taken along line b-b and c-c in FIG. 6A. The
objective lens 10 adopts a D-cut shape achieved by cutting off the
portion of its external circumferential edge, which would be set
adjacent to the first lens unit 30. An end surface 10a along which
the portion is taken off is a flat surface to face down during a
regular photographing operation. The lenses 31 and 32 in the first
lens unit 30, too, each adopt a D-cut shape achieved by cutting off
part of the external circumferential edge of the respective lens,
which would be set adjacent to the objective lens 10. End surfaces
31a and 32a of the lenses 31 and 32 where those parts are cut off
are flat surfaces facing toward the object or photographic subject
along the optical axis I1, i.e., facing toward the objective lens
10. The first lens unit 30 is disposed by setting the end surface
31a of the lens 31 so as to face opposite the rear surface (located
on the opposite side from the subject) of the objective lens 10
over a very small distance.
[0038] The second lens unit 40, which is disposed inside the space
in the barrel body 2 on the exit side of the first lens unit 30, is
a movable optical element supported at the barrel body 2 so as to
be allowed to move along the optical axis I2. A lens holder 41,
which is a frame disposed around the second lens unit 40, is
provided in conjunction with the second lens unit 40, and as the
movable lens holder 41 slides along the longitudinal direction of
the guide shaft 4 and the rotation-preventing shaft 5, it moves
along the optical axis I2. As shown in FIG. 3, the guide shaft 4
and the rotation-preventing shaft 5, disposed over areas on the two
opposing sides with the optical axis I2 of the lens holder 41
present between them, each extend parallel to the optical axis
I2.
[0039] As shown in FIG. 5, the lens holder 41 includes an opening
41a and a groove portion 41b. The diameter of the opening 41a at
which the guide shaft 4 is inserted is set larger than the diameter
of the guide groove 4 by an extent which will create the necessary
clearance.
[0040] The groove portion 41b, at which the rotation-preventing
shaft 5 is inserted, is formed by recessing or notching the outer
edge of the lens holder 41. The groove width at the groove portion
41b is set greater than the diameter of the rotation-preventing
shaft 5 by an extent which will create the necessary clearance. It
is to be noted that the rotation-preventing shaft 5 does not
restrain the lens holder 41 along the direction in which the groove
portion 41b extends, i.e., along a substantially horizontal
direction in FIG. 5, so as to absorb any dimensional inconsistency
that may manifest between the opening 41a and the groove portion
41b.
[0041] In addition, the lens holder 41 includes a lens holder nut
42. The lens holder nut 42 is a driven member having a female
threaded portion to engage with the lead screw 110 to be detailed
later formed an inner surface at one side of a groove at which the
lead screw 110 is inserted. The lens holder nut 42 is formed in a
two-pronged shape with the two prongs enclosing the groove portion.
The lens holder nut 42 is supported so as to be allowed to rotate
around a shaft portion 41c disposed at the external circumferential
edge of the lens holder 41 to range parallel to the optical axis
I2, and a force is applied to the lens holder nut 42 by a spring
42a (see FIGS. 8A and 8B) along a given rotating direction so as to
press the female threaded portion against the surface of the lead
screw.
[0042] The third lens unit 50 is disposed on the exit side of the
second lens unit 40 and is housed inside the space in the barrel
body 2 where the second lens unit 40 is also housed. The third lens
unit 50 is a movable optical element supported at the barrel body 2
so as to be allowed to move along the optical axis I2.
[0043] A lens holder 51, which is a frame disposed around the third
lens unit 50, is provided in conjunction with the third lens unit
50. As is the movable lens holder 41 described earlier, the movable
lens holder 51 is supported by the guide shaft 4 and the
rotation-preventing shaft 5 so as to be allowed to move along the
optical axis I2. In addition, the lens holder 51 includes a lens
holder nut 52 adopting a structure similar to the lens holder nut
42 at the lens holder 41, which engages with the lead screw 120 to
be detailed later. A force is applied to the lens holder unit 52 by
a spring 52a (see FIGS. 8A and 8B).
[0044] It is to be noted that the range of movement of the second
lens unit 40 and the range of movement of the third lens unit 50
are set so that they partially overlap.
[0045] The shutter unit 60 includes a shutter portion which
includes a shutter curtain for blocking the image light having
exited the third lens unit 50 to enter the fourth lens unit 70 and
an aperture portion (light quantity adjustment portion) which is
disposed on the subject side of the shutter portion and includes an
ND filter for reducing the quantity of image light. At the aperture
portion, a specific ND filter is driven into/out of the optical
path in response to an insert instruction signal or a retreat
signal output by a control unit (not shown).
[0046] The shutter unit 60 further includes a shutter drive portion
61 and an ND filter drive portion 62 that respectively drive the
shutter portion and the ND filter. The shutter drive portion 61 and
the ND filter drive portion 62 are disposed on the two sides of the
optical path. The shutter drive portion 61 is disposed next to the
image side of the motor 140 along the opticalaxis I2, whereas the
position of the ND filter drive portion 62 is offset toward the
subject side relative to the shutter drive portion 61 along the
optical axis I2.
[0047] The fourth lens unit 70 is fixed at the barrel body 2 over
an area on the exit side of the shutter unit 60.
[0048] The LPF 80 is an optical low pass filter fixed at the barrel
body 2 over an area on the exit side of the fourth lens unit
70.
[0049] The CCD 90 is an image-capturing element at which an image
is formed with the image light having exited the LPF 80 and the
image is captured as an electrical signal. The electrical signal
output from the CCD 90 is first input to an image processing device
200, as shown in FIG. 11, and is then saved as an image file. An
imaging apparatus 210 is constituted with the lens barrel 1 and the
image processing device 200. The imaging apparatus 210 may further
include a liquid crystal monitor 220 and, in such a case, an image
having been saved can be displayed at the liquid crystal monitor
220 or the like at the imaging apparatus 210.
[0050] FIG. 7 is an external perspective of the lens barrel 1 taken
from the side where the CCD 90 is disposed.
[0051] The CCD 90 is supported on a circuit board 91 fixed onto its
rear surface. As shown in FIG. 3, the circuit board 91 is mounted
via an elastic member (spring) 92 present between the circuit board
9 and an end surface 2a of the barrel body 2 facing opposite the
circuit board 91.
[0052] A pin 2b is formed so as to project out of the end surface
2a and, as the pin 2b is inserted at an opening 91a formed at the
circuit board 91, the circuit board 91 is positioned along a
direction perpendicular to the optical axis I2.
[0053] The circuit board 91 is locked by screwing, for instance,
three screws 93 disposed over intervals at its peripheral edge into
the end surface 2a of the barrel body 2 and then tightening the
screws. While the elastic member 92 mentioned earlier is pressed
and becomes elastically deformed as the screws 93 are screwed in,
the extent to which the elastic member 92 becomes deformed depends
upon the extent to which the screws 93 are tightened. Accordingly,
by tightening or loosening some of the three screws 93, the circuit
board 91 can be tilted along any direction relative to the optical
axis I2. An angle adjustment is achieved by tilting the circuit
board 91 as described above so as to adjust the image-capturing
surface of the CCD 90 in correspondence to the inclination of the
image plane attributable to the optical system.
[0054] As shown in FIG. 4, the motor holder unit 3 includes the
lead screws 110 and 120 and the motors 130 and 140.
[0055] The lead screws 110 and 120 are both disposed so as to
extend parallel to the optical axis I2 and each constitute a drive
shaft with a threaded portion formed at the external
circumferential surface thereof. The lead screws 110 and 120, set
side-by-side along the optical axis I1, are disposed so that the
lead screw 120 is positioned further toward the subject side than
the lead screw 110 along the optical axis I1.
[0056] The lead screws 110 and 120 are each supported at the motor
holder unit 3 so as to be allowed to rotate around the respective
central axis. The lead screw 110 engages with the lens holder nut
42 connected to the lens holder 41 at the first lens unit 40 and
drives the first lens unit 40 along the optical axis I2. The lead
screw 120 engages with the lens holder nut 52 connected to the lens
holder 51 at the second lens unit 50 and drives the second lens
unit 50 along the optical axis I2.
[0057] The motor 130 rotationally drives the lead screw 110 and is
connected to an end of the lead screw 110 toward the subject side
along the optical axis I2 (toward the upper side in FIG. 4). The
motor 130 includes a housing formed in a cylindrical shape
substantially coaxial with the lead screw 110, and is fixed by
fastening a flange portion 131, which projects out toward the
external circumference from the end surface of the housing located
on the side toward the lead screw 110, onto the motor holder unit 3
with a screw 132 (see FIG. 10 for details of the flange portion 131
and the screw 132).
[0058] The motor 140, which rotationally drives the lead screw 120,
is connected to an end of the lead screw 120 toward the image side
along the optical axis I2 (toward the bottom side in FIG. 4). The
motor 140 is positioned over an area that partially overlaps the
area where the motor 130 is mounted, when viewed from the direction
of the optical axis I2.
[0059] The motor 140 includes a housing formed in a cylindrical
shape substantially coaxial with the lead screw 120, and is fixed
by fastening a flange portion 141, which projects out toward the
external circumference from the end surface of the housing located
on the side toward the lead screw 120, onto the motor holder unit 3
with a screw 142 (see FIG. 10 for details of the flange portion 141
and the screw 142).
[0060] While the motors 130 and 140 are disposed so that one of
them is positioned on the subject side and the other is positioned
on the image side in the example presented in FIG. 4, the two
motors 130 and 140 may instead be disposed on the same side. It is
to be noted that the subject side indicates a direction toward a
subject to be imaged or photographed by a camera at which the lens
barrel 1 is mounted and the image side indicates a direction toward
an image of the subject generated or captured by the
image-capturing element 90. In the latter case, the lead screw 110
and the lead screw 120 should have lengths different from each
other, and the motors 130 and 140 should be disposed at positions
different from one another along the longitudinal direction of the
lead screws 110 and 120 so that the motors 130 and 140 overlap when
viewed from the direction of the optical axis I2, instead of
setting the motors 130 and 140 side-by-side along the lateral
direction (along the optical axis I1).
[0061] It is to be noted that end portions 110a and 120a of the
lead screws 110 and 120 on the side opposite from the side where
the lead screws are connected with the motors 130 and 140 are
respectively inserted at recessed portions 3a and 3b formed at the
motor holder unit 3. The recessed portions 3a and 3b may be formed
by using a material with a smaller coefficient of friction than
that of the material used to constitute the motor holder unit 3.
The lead screws 110 and 120 are thus each supported on two sides,
which helps reduce the extent of vibration when they rotate.
[0062] In addition, position detectors 150 that detect the
positions of the movable lens units, i.e., the second lens unit 40
and the third lens unit 50, are disposed at the lens barrel 1, as
shown in FIG. 5.
[0063] While not shown in FIGS. 1 through 4, a pair of position
detectors 150 may be provided in conjunction with each of the lens
units 40 and 50. The position detectors 150 provided in conjunction
with each lens unit are disposed near the two ends of the range of
movement of the detection target lens unit.
[0064] The position detectors 150 each include a photointerrupter
disposed at the inner wall surface of the barrel body 2 facing
opposite the corresponding lens holder 41 or 51 to detect the
passage of a projection 151 projecting out of the external
circumferential edge of the lens holder 41 (51). The
photointerrupter includes an LED and an SPD disposed so as to face
opposite each other over a distance large enough for the projection
151 to pass through and detects the passage of the projection 151
based upon whether or not the light emitted from the LED is blocked
by the projection 151.
[0065] The control unit (not shown) in the lens barrel 1 drives the
second lens unit 40 and the third lens unit 50 over their
respective ranges of movement by driving the motors 130 and 140. In
addition, the control unit determines the positions of the
individual lens units 40 and 50 in correspondence to the timing
with which the projections 151 at the lens units 40 and 50 pass
through the corresponding position detectors 150.
[0066] Next, the method adopted when assembling the lens barrel 1
achieved in the embodiment is explained.
[0067] In the embodiment, a module assembled in advance by mounting
the lead screws 110 and 120 and the motors 130 and 140 at the motor
holder unit 3 is then mounted at the barrel body 2.
[0068] FIGS. 8A and 8B schematically illustrate the method adopted
when mounting the motor holder unit 3 at the barrel body 2, with
FIG. 8A showing the state before the motor holder unit 3 is mounted
and FIG. 8B showing the state after the motor holder unit 3 is
mounted. It is to be noted that in order to simplify the
illustration, the structures of the individual members are not
shown in detail in FIGS. 8A and 8B.
[0069] As shown in FIG. 8A, the motor holder unit 3 is mounted at
the barrel body 2 along a direction running perpendicular to the
optical axes I1 and I2 (along the up/down direction in FIG. 8A).
The lens holder nuts 42 and 52 each include a groove portion
extending along the mounting direction with the end thereof located
toward the motor holder unit 3, which is formed as an open end, and
the female threaded portion formed at one side surface inside the
groove portion. Thus, as the motor holder unit 3 is mounted at the
barrel body 2, the lead screws 110 and 120 are inserted at the
groove portions of the corresponding lens holder nuts 42 and 52, as
explained earlier.
[0070] The motor holder unit 3 is then locked onto the barrel body
2 by fitting elastic tabs 2c, formed at the end of the barrel body
2 on the side toward the motor holder unit 3, into openings 3c
formed at the corresponding positions at the motor holder unit 3
and holding the inserted tabs 2c inside the openings 3c.
[0071] It is to be noted that elastic members 6 constituted of a
material with elasticity such as rubber are disposed in the space
over which the barrel body 2 and the motor holder unit 3 to be
joined with each other face opposite each other. As tension is
applied to the tabs 2c by repulsion of the elastic members 6, the
positional relationship between the barrel body 2 and the motor
holder unit 3 is stabilized, which makes it possible to maintain a
substantially constant positional relationship between the lead
screws 110 and 120 and the lens holder nuts 42 and 52.
[0072] Next, an explanation is given on the operational effects
achieved in the embodiment of the present invention by comparing
the embodiment with a comparison example provided for reference. It
is to be noted that structural features of the comparison example
similar to those of the embodiment are not explained and the
following explanation focuses on the differences between the
embodiment and the comparison example.
[0073] FIG. 9 shows the positions at which the lead screws and the
motors are disposed in a lens barrel in the comparison example.
[0074] A motor holder unit 200 in the comparison example includes
lead screws 210 and 220 and the motors 230 and 240. As the lead
screws 110 and 120 in the embodiment, the lead screws 210 and 220
are disposed parallel to the optical axis I2 to drive the lens
holder nuts 42 and 52 respectively. The optical axis I2 is assumed
to run along a vertical direction in FIG. 9. The motors 230 and 240
are disposed so as to lie side-by-side at the ends of the lead
screws 210 and 220 on the side toward the subject along the optical
axis I2, i.e., so as not to overlap when viewed from the direction
of the optical axis I2.
[0075] The structure adopted in this comparison example does not
allow the distance D2 between the axes of the lead screws 210 and
220 to be any less than (C+D)/2 with C and D respectively
representing the housing diameters at the motors 230 and 240. This
means that the thickness of the lens barrel along the optical axis
of the objective lens is bound to be large, assuming that the lens
barrel in the comparison example includes a bending optical system
similar to that of the embodiment.
[0076] FIG. 10 shows the positional arrangement adopted with regard
to the lead screws 110 and 120 and the motors 130 and 140 in the
lens barrel 1 in the embodiment.
[0077] In the embodiment, the motors 130 and 140 are disposed at
the ends of the lead screws 110 and 120 on the sides opposite from
each other, and thus, the distance D1 between the axes of the lead
screws 110 and 120 can be set smaller than (A+B)/2 with A and B
respectively representing the housing diameters at the motors 130
and 140. As a result, the thickness of the lens barrel 1 along the
optical axis I1 of the objective lens 10 can be reduced.
[0078] The following operational effects can be achieved in the
embodiment structured as described above. [0079] (1) As the motors
130 and 140 are disposed over areas overlapping each other when
viewed from the direction of the optical axis I2 so that a distance
E along the optical axis I1 between the outer ends of the motors
130 and 140 is set smaller than (A+B) as shown in FIG. 10, the lens
barrel 1 can be provided as a more compact unit. [0080] (2) The
lead screws 110 and 120 and the motors 130 and 140, supported at
the motor holder unit 3, can be provided as a module. The module
can then be detachably mounted at the barrel body 2. As a result,
the assembly process through which the lens barrel 1 is assembled
is simplified. More specifically, the two lead screws 110 and 120
and the two motors 130 and 140 can be mounted at the barrel body 2
through a single mounting operation. [0081] (3) Since the motors
130 and 140 are mounted on the sides of the lead screws 110 and 120
opposite from each other, i.e., at the end toward the subject side
and the end toward the image side, the distance D1 between the axes
of the lead screws 110 and 120 can be reduced by an extent matching
the extent to which the areas where the motors 130 and 140 are
disposed partially overlap each other when viewed from the
direction of the optical axis I2. As a result, the dimension of the
lens barrel 1 taken along the direction in which the lead screws
110 and 120 are disposed can be reduced. [0082] (4) The guide shaft
4 used to guide the second lens unit 40 and the third lens unit 50
is disposed adjacent to the lead screws 110 and 120. This means
that the second lens unit 40 and the third lens unit 50 are not
caused to rotate around the connecting portions where they connect
with the guide shaft 4 by the drive force and thus, they do not
become tilted. Consequently, the friction is reduced and, at the
same time, the level of drive accuracy is improved. [0083] (5)
Since the common guide shaft 4 guides the second lens unit 40 and
the third lens unit 50, they do not become decentered relative to
each other and the ranges of movement of the individual lens units
are allowed to partially overlap each other. [0084] (6) Since the
ND filter drive portion 62 is disposed on the side opposite from
the motor 140 with the optical axis I2 present between them, the ND
filter drive portion 62 can be set further toward the subject side
along the optical axis I2, which makes it possible to reduce the
external dimensions of the lens barrel 1. [0085] (7) Since the
external edges of the objective lens 10 and the first lens unit 30,
which would be set adjacent to each other, are cut off, the
objective lens 10 and the first lens unit 30 can be disposed close
to each other while preventing interference. As a result, the
external dimensions of the lens barrel 1 can be reduced. In
addition, the structure assumed at each lens unit 10 or 30, i.e.,
only one side of each lens is cut off, can be achieved by a
machining a round lens through a small number of machining
steps.
EXAMPLE OF VARIATIONS
[0086] The present invention is not limited to the embodiment
described above and allows for numerous variations and
modifications which will be equally included in the scope of the
present invention. [0087] (1) While the lens barrel in the
embodiment described above includes a bending optical system, the
present invention may also be adopted in conjunction with an
optical system that does not include a bending portion.
[0088] In addition, the lens barrel may be adopted in another type
of apparatus, as well as in a digital still camera, as in the
embodiment. [0089] (2) While the structure in the embodiment
includes two drive shafts, the present invention may be adopted in
a structure having three or more drive shafts, to provide a lens
barrel as a more compact unit by disposing the drive units
connected to at least two drive shafts on different sides. [0090]
(3) The assembly process can be simplified by using an integrated
module that is prepared in advance by mounting the drive shafts and
the drive units at a support member in conjunction with the
plurality of drive units disposed parallel to each other on one
side, as well as in conjunction with the drive units disposed on
different sides of the corresponding drive shafts, as in the
embodiment. [0091] (4) As shown in FIG. 11, the imaging apparatus
210 may be provided as a compact unit by connecting the lens barrel
1 explained above to the image processing device 200. As an imaging
apparatus 210, a digital camera or film camera may be used.
[0092] The above described embodiments are examples and various
modifications can be made without departing from the scope of the
invention.
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