U.S. patent application number 09/767693 was filed with the patent office on 2001-07-26 for device for adjusting the eccentricity of a lens in a frame.
This patent application is currently assigned to ASAHI KOGAKU KOGYO KABUSHIKI KAISHA. Invention is credited to Hamasaki, Takuji, Iikawa, Makoto.
Application Number | 20010009071 09/767693 |
Document ID | / |
Family ID | 18543873 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009071 |
Kind Code |
A1 |
Iikawa, Makoto ; et
al. |
July 26, 2001 |
Device for adjusting the eccentricity of a lens in a frame
Abstract
A lens eccentricity adjusting device includes a circular opening
formed on a lens frame, a lens being fitted into the circular
opening; at least three flat countersunk head screws each screwed
into the lens frame, the flat countersunk head screws including a
male thread portion that is screwed into the lens frame and a head
portion having a tapered surface; and at least one elastic member
positioned between the flat countersunk head screws and the rim of
the lens. The eccentricity is adjusted by deforming at least one
elastic member via pressure of the tapered surface of a
corresponding flat countersunk head screw on the rim of the lens,
in accordance with an amount the corresponding flat countersunk
head screw is screwed into the lens frame, so that the lens is
moved in the circular opening in a radial direction.
Inventors: |
Iikawa, Makoto; (Saitama,
JP) ; Hamasaki, Takuji; (Saitama, JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN
1941 ROLAND CLARKE PLACE
RESTON
VA
20191
|
Assignee: |
ASAHI KOGAKU KOGYO KABUSHIKI
KAISHA
|
Family ID: |
18543873 |
Appl. No.: |
09/767693 |
Filed: |
January 24, 2001 |
Current U.S.
Class: |
33/645 |
Current CPC
Class: |
G02B 7/023 20130101;
G02B 27/62 20130101 |
Class at
Publication: |
33/645 |
International
Class: |
G01D 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2000 |
JP |
2000-16787(P) |
Claims
What is claimed is:
1. A lens eccentricity adjusting device for adjusting an
eccentricity of a lens having a circular rim which is held by a
lens frame, said adjusting device comprising: a circular opening
formed on said lens frame, said lens being fitted into said
circular opening; at least three flat countersunk head screws, each
being screwed into said lens frame, said at least three flat
countersunk head screws being positioned at substantially regular
intervals along a circumference of said lens, each of said at least
three flat countersunk head screws comprising a male thread portion
that is screwed into said lens frame and a head portion having a
tapered surface which tapers down to said male thread portion; and
at least one elastic member positioned between each of said at
least three flat countersunk head screws and said rim of said lens;
wherein said eccentricity is adjusted by deforming said at least
one elastic member so as to apply pressure on said rim of said lens
via said tapered surface of corresponding one of said at least
three flat countersunk head screws, in accordance with the amount
of which said corresponding one of said at least three flat
countersunk head screws is screwed into said lens frame, so that
said lens is moved in said circular opening in a radial
direction.
2. The lens eccentricity adjusting device according to claim 1,
wherein said at least one elastic member comprises a ring member
which is fixed to said lens frame via said at least three flat
countersunk head screws to hold said lens between said lens frame
and said ring member, so that an axial center of said ring member
is substantially coincident with the center axis of said circular
opening, wherein said ring member is fixed to said lens frame so
that an inner peripheral surface of said ring member is in contact
with said rim of said lens.
3. The lens eccentricity adjusting device according to claim 2,
wherein said ring member comprises at least three through holes
into which said at least three flat countersunk head screws are
respectively inserted to be screwed into said lens frame.
4. The lens eccentricity adjusting device according to claim 1,
wherein said at least one elastic member comprises at least three
ring members into which said at least three flat countersunk head
screws are respectively inserted to be screwed into said lens
frame, so as to hold said lens between said lens frame and said at
least three ring members, wherein each of said at least three ring
members is fixed to said lens frame so that an outer peripheral
surface of said each ring member is in contact with said rim of
said lens.
5. The lens eccentricity adjusting device according to claim 1,
wherein said at least one elastic member comprises at least three
deformable portions formed integrally with said lens frame to
correspond to said at least three flat countersunk head screws,
each of said at least three deformable portions being in contact
with said rim of said lens.
6. The lens eccentricity adjusting device according to claim 1,
wherein said at least one elastic member is formed from a type of
engineering plastics.
7. The lens eccentricity adjusting device according to claim 1,
wherein an amount of said eccentricity, that is adjusted according
to a variation of the amount of which each of said at least one
flat countersunk head screw is screwed into said lens frame, is of
the order of several micrometers.
8. The lens eccentricity adjusting device according to claim 1,
wherein said lens frame holds another lens, said lens eccentricity
adjusting device being operated to adjust said eccentricity of said
lens with respect to said another lens.
9. The lens eccentricity adjusting device according to claim 1,
wherein said at least three flat countersunk head screws comprise
three flat countersunk head screws which are positioned at
substantially 120.degree. intervals along said circumference of
said lens.
10. The lens eccentricity adjusting device according to claim 3,
wherein said ring member comprises a tapered surface formed around
one end of each of said at least three through holes, wherein each
of said at least three flat countersunk head screws is screwed into
said lens frame with said tapered surface of each of said at least
three flat countersunk head screws being in intimate contact with
corresponding said tapered surface of each of said at least three
through holes.
11. The lens eccentricity adjusting device according to claim 4,
wherein each of said at least three ring members comprises a
tapered surface formed around one end of a through hole of each of
said at least three ring members; wherein each of said at least
three flat countersunk head screws is screwed into said lens frame
with said tapered surface of each of said at least three flat
countersunk head screws being in intimate contact with
corresponding said tapered surface of each of said at least three
ring members.
12. The lens eccentricity adjusting device according to claim 5,
wherein said lens frame comprises: at least three threaded holes
into which said at least three flat countersunk head screws are
respectively screwed; and a tapered surface formed around an outer
end of each of said at least three threaded holes; wherein each of
said at least three flat countersunk head screws is screwed into
corresponding one of said three threaded holes with said tapered
surface of each of said at least three flat countersunk head screws
being in intimate contact with corresponding said tapered surface
of said each of said at least three threaded holes.
13. The lens eccentricity adjusting device according to claim 2,
wherein said lens frame is made of a macroscopically undeformable
material.
14. The lens eccentricity adjusting device according to claim 4,
wherein said lens frame is made of a macroscopically undeformable
material.
15. The lens eccentricity adjusting device according to claim 5,
wherein said lens frame is made of an elastic material.
16. A method for adjusting an eccentricity of a lens having a
circular rim which is held by a lens frame, comprising: fitting
said lens into a circular opening formed on said lens frame;
screw-engaging at least three flat countersunk head screws into
said lens frame at an equi-angular distance outside around said
circular opening; positioning at least one elastic member between
each of said at least three flat countersunk head screws and said
rim of said lens; and adjusting the position of the lens in the
circular opening by adjusting screwing position of at least one of
said at least three flat countersunk head screws which is screwed
into said lens frame so that said lens is moved in said circular
opening in a radial direction, wherein said at least one elastic
member is depressed by the pressure of said three flat countersunk
head screws on said rim of said lens.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a device for adjusting the
eccentricity of a lens in a frame (holder).
[0003] 2. Description of the Related Art
[0004] Various devices for adjusting the eccentricity of a lens
that is held by a lens frame are known in the art. For instance, in
one known device, the eccentricity is adjusted by directly pressing
the rim of the lens in a radial direction by an adjustment screw.
In another known device, the eccentricity is adjusted by providing
an adjustment frame between the lens and the lens frame. In another
known device, the eccentricity is adjusted by injecting an adhesive
between the rim of the lens and the lens frame. However, these
known devices have the following problems. In the above-mentioned
first device, pressure on the rim of the lens by the adjustment
screw may cause the lens to be distorted. In the above-mentioned
second device, the cost of production increases since it is
necessary to provide an adjustment frame between the lens and the
lens frame. In the above-mentioned third device, the cost of
production increases since the lens frame needs to be provided with
one or more injection groove or hole through which an adhesive is
injected; and it is extremely difficult or almost impossible to
remove the lens from the lens frame once lens is cemented to the
lens frame.
SUMMARY OF THE INVENTION
[0005] The primary object of the present invention is to provide a
device for adjusting the eccentricity of a lens, wherein the
eccentricity can be adjusted using the adjusting device with a high
degree of precision even though the structure of the device is
simple.
[0006] To achieve the object mentioned above, according to an
aspect of the present invention, a lens eccentricity adjusting
device is provided for adjusting an eccentricity of a lens having a
circular rim which is held by a lens frame, the adjusting device
including a circular opening formed on the lens frame, the lens
being fitted into the circular opening; at least three flat
countersunk head screws, each being screwed into the lens frame,
the flat countersunk head screws being positioned at substantially
regular intervals along a circumference of the lens, each of the
flat countersunk head screws including a male thread portion that
is screwed into the lens frame and a head portion having a tapered
surface which tapers down to the male thread portion; and at least
one elastic member positioned between each of the flat countersunk
head screws and the rim of the lens. The eccentricity is adjusted
by deforming the at least one elastic member so as to apply
pressure on the rim of the lens via the tapered surface of a
corresponding flat countersunk head screw, in accordance with the
amount of which the corresponding flat countersunk head screw is
screwed into the lens frame, so that the lens is moved in the
circular opening in a radial direction.
[0007] In an embodiment, the at least one elastic member is a ring
member which is fixed to the lens frame via the flat countersunk
head screws to hold the lens between the lens frame and the ring
member, so that an axial center of the ring member is substantially
coincident with the center axis of the circular opening, wherein
the ring member is fixed to the lens frame so that an inner
peripheral surface of the ring member is in contact with the rim of
the lens. Preferably, the lens frame is made of a macroscopically
undeformable material.
[0008] Preferably, the ring member includes a tapered surface
formed around one end of each of the at least three through holes,
wherein each flat countersunk head screw is screwed into the lens
frame with the tapered surface of each flat countersunk head screw
being in intimate contact with a corresponding tapered surface of
each through hole therefor.
[0009] Preferably, the ring member includes at least three through
holes into which the at least three flat countersunk head screws
are respectively inserted to be screwed into the lens frame.
[0010] In another embodiment, the at least one elastic member
includes at least three ring members into which the at least three
flat countersunk head screws are respectively inserted to be
screwed into the lens frame, so as to hold the lens between the
lens frame and the at least three ring members, wherein each of the
at least three ring members is fixed to the lens frame so that an
outer peripheral surface of the each ring member is in contact with
the rim of the lens. Preferably, the lens frame is made of a
macroscopically undeformable material.
[0011] Preferably, each of the at least three ring members includes
a tapered surface formed around one end of a through hole of each
of the at least three ring members. Each of the at least three flat
countersunk head screws is screwed into the lens frame with the
tapered surface of each of the at least three flat countersunk head
screws being in intimate contact with corresponding the tapered
surface of each of the at least three ring members.
[0012] In another embodiment, the at least one elastic member
includes at least three deformable portions formed integrally with
the lens frame to correspond to the at least three flat countersunk
head screws, each of the at least three deformable portions being
in contact with the rim of the lens. Preferably, the lens frame is
made of an elastic material.
[0013] Preferably, the lens frame includes at least three threaded
holes into which the at least three flat countersunk head screws
are respectively screwed; and a tapered surface formed around an
outer end of each of the at least three threaded holes. Each of the
at least three flat countersunk head screws is screwed into
corresponding one of the three threaded holes with the tapered
surface of each flat countersunk head screw being in intimate
contact with a corresponding tapered surface of each threaded hole
therefor.
[0014] Preferably, the at least one elastic member is formed from a
type of engineering plastics.
[0015] Preferably, an amount of the eccentricity, that is adjusted
according to a variation of the amount of which each of the at
least one flat countersunk head screw is screwed into the lens
frame, is of the order of several micrometers.
[0016] The lens frame can hold another lens, the lens eccentricity
adjusting device being operated to adjust the eccentricity of the
lens with respect to the another lens.
[0017] In an embodiment, the three flat countersunk head screws are
positioned at substantially 1200 intervals along the circumference
of the lens. According to another aspect of the present invention,
a method for adjusting an eccentricity of a lens having a circular
rim which is held by a lens frame is provided, including fitting
the lens into a circular opening formed on the lens frame;
screw-engaging at least three flat countersunk head screws into the
lens frame at an equi-angular distance outside and around the
circular opening; positioning at least one elastic member between
each of the at least three flat countersunk head screws and the rim
of the lens; and adjusting the position of the lens in the circular
opening by adjusting the screwing position of at least one of the
at least three flat countersunk head screws which is screwed into
the lens frame so that the lens is moved in the circular opening in
a radial direction, wherein the at least one elastic member is
depressed by the pressure of the three flat countersunk head screws
on the rim of the lens.
[0018] The present disclosure relates to subject matter contained
in Japanese Patent Application No.2000-016787 (filed on Jan. 26,
2000) which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The present invention will be described below in detail with
reference to the accompanying drawings in which:
[0020] FIG. 1 is a cross sectional view of the first embodiment of
a lens barrel having a lens eccentricity adjusting device according
to the present invention, taken along I-I line in FIG. 2, looking
in the direction of the appended arrows;
[0021] FIG. 2 is a front view of the first embodiment of the lens
barrel shown in FIG. 1;
[0022] FIG. 3 is a view similar to that of FIG. 1 and illustrates
the second embodiment of the lens barrel having a lens eccentricity
adjusting device according to the present invention;
[0023] FIG. 4 is a fragmentary front view of the second embodiment
of the lens barrel shown in FIG. 3, showing a fundamental portion
thereof;
[0024] FIG. 5 is a view similar to that of FIG. 1 and illustrates
the third embodiment of the lens barrel having a lens eccentricity
adjusting device according to the present invention; and
[0025] FIG. 6 is a fragmentary front view of the third embodiment
of the lens barrel shown in FIG. 5, showing a fundamental portion
thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] FIGS. 1 and 2 show the first embodiment of a lens barrel
having a lens eccentricity adjusting device according to the
present invention. The lens barrel 10 is provided with a lens group
L including a front lens element L1 and a rear lens element L2, and
a cylindrical lens frame 12 which encloses the lens group L1 to
hold the same. The lens frame 12 is made of an undeformable
material in a macroscopic view (e.g., a hard engineering plastic).
The front lens element L1 is fixed to the lens frame 12 with a
known device (e.g., the inner edge of the front end of the lens
frame 12 is deformed inwardly by heat) after having been fitted in
the lens frame 12 from the front side thereof (the left side as
viewed in FIG. 1). The fixing structure of the front lens element
L1 to the lens frame 12 does not relate to the present invention,
therefore, details on the fixing structure of the front lens
element L1 are not herein described. The lens frame 12 is provided
at the rear end thereof with a circular opening 12a in which the
circular rear lens element L2 is fitted. The lens frame 12 is
provided on the rear face thereof (the right face as viewed in FIG.
1) with three threaded holes 12c at substantially 120.degree.
intervals along the circumference of the rear lens element L2. The
lens barrel 10 is further provided with a holding ring (annular
member) 13 that is fixed to the rear face of the lens frame 12 via
three flat countersunk head screws 14 which are respectively
screwed into the three threaded holes 12c, so that the axial center
of the holding ring 13 is coincident with the axis of the circular
opening 12a of the lens frame 12. The rear lens element L2 is held
between the lens frame 12 and the holding ring 13. The holding ring
13 is made of an elastic material; specifically, in the illustrated
embodiment, a polycarbonate resin which is a type of engineering
plastics is used. The lens frame 12 is provided, at the outer edge
of the rear end of the lens frame 12, with an annular projection
12b which extends rearward (toward the right as viewed in FIG. 1).
The holding ring 13 is fixed to the lens frame 12 with an outer
peripheral surface of the holding ring 13 being in contact with the
inner peripheral surface of the annular projection 12b. As shown in
FIG. 2, the three flat countersunk head screws 14, by which the
holding ring 13 is fixed to the lens frame 12, are positioned at
substantially regular intervals around the circumference of the
rear lens element L2. Each of the three flat countersunk head
screws 14 is provided with a male thread portion 14a that is
screwed into one of the threaded holes 12c of the lens frame 12,
and a head portion 14b from which the males thread portion 14a
extends. The head portion 14b is provided with a tapered surface
14c which tapers down to the male thread portion 14a (toward the
left as viewed in FIG. 1). The holding ring 13 is provided with
three through holes 13a into which the three flat countersunk head
screws 14 are inserted to be screwed into the three threaded holes
12c of the lens frame 12, respectively. The holding ring 13 is
provided, around the rear end of each of the three through holes
13a, with a tapered surface 13b which tapers toward the front end
(the left end as viewed in FIG. 1) of the corresponding through
hole 13a. As can be seen in FIG. 1, each flat countersunk head
screw 14 is fixed to the lens frame 12 with the tapered surface 14c
of the flat countersunk head screw 14 being in intimate contact
with the corresponding tapered surface 13b. The holding ring 13 is
provided, at the inner edge of the rear end of the holding ring 13,
with an annular tapered portion 13c which tapers rearward in the
direction of the optical axis O of the lens group L1 (i.e., toward
the right side as viewed in FIG. 1). The annular tapered portion
13c extends along and contacts with an annular beveled surface L2a
formed at the rear end of the rim of the rear lens element L2. The
rear lens element L2 is fixed to the lens frame 12 in the circular
opening 12a via the holding ring 13 and the flat countersunk head
screws 14 with the annular tapered portion 13c being in pressing
contact with the annular beveled surface L2a of the rear lens
element L2.
[0027] In the lens barrel 10 having the structure described above,
if one of the three flat countersunk head screws 14 is further
screwed into the corresponding threaded hole 12c in a state shown
in FIG. 1, the tapered surface 14c of the flat countersunk head
screw 14 digs into the through hole 13a along the tapered surface
13b. This causes part of the holding ring 13 around the flat
countersunk head screw 14 to deform to expand in a radial direction
of the holding ring 13, so that the corresponding part of the
annular tapered portion 13c presses the annular beveled surface L2a
of the rear lens element L2 inwardly. By utilizing this pressing
force, the eccentricity of the rear lens element L2 with respect to
the front lens element L1 in the lens frame 12 can be adjusted.
Namely, the amount of eccentricity of the rear lens element L2 with
respect to the front lens element L1 varies by a variation of the
amount of screwing of each flat countersunk head screw 14 into the
corresponding threaded hole 12c. In the illustrated embodiment, the
eccentricity of the rear lens element L2 with respect to the front
lens element L1 can be adjusted by moving the rear lens element L2
in a direction perpendicular to the optical axis O within a
tolerance of the inner diameter of the lens frame 12 (for example,
approximately 10 micrometers). The holding ring 13 and the three
flat countersunk head screws 14 are fundamental elements of the
lens eccentricity adjusting device that is incorporated in the
first embodiment of the lens barrel 10.
[0028] In the first embodiment of the lens barrel 10, since the
rear lens element L2 is pressed indirectly by the flat countersunk
head screws 14 via the holding ring 13, which is made of an elastic
material, the amount of deformation of the rear lens element L2 is
minimal as compared with a case where the rear lens element L2 is
pressed directly by screws. Moreover, deformation of the holding
ring 13 due to a tightening operation of any one of the flat
countersunk head screws 14 reliably presses the corresponding part
of the annular beveled surface L2a of the rear lens element L2
inwardly, since the outer peripheral surface of the holding ring 13
is in contact with the inner peripheral surface of the annular
projection 12b, which is made of a macroscopically undeformable
material. An arrow F1 shown in FIG. 1 indicates the direction in
which the annular tapered portion 13c of the holding ring 13
presses the annular beveled surface L2a of the rear lens element L2
by the deformation of the holding ring 13.
[0029] FIGS. 3 and 4 show the second embodiment of the lens barrel
having a lens eccentricity adjusting device according to the
present invention. In a lens barrel 100 of the second embodiment, a
lens frame 120, which corresponds to the lens frame 12 of the first
embodiment, is provided with a circular opening 120a, which
corresponds to the circular opening 12a of the first embodiment, so
that the rear lens element L2 is fixed into the circular opening
120a. The lens frame 120 is provided on the rear end face thereof
with three circular recesses 120b positioned at substantially
regular intervals along a circumference of the rear lens element
L2. The lens barrel 100 is provided with three elastic rings 130
which are made of an elastic material that is similar to the
material of the holding ring 13 of the first embodiment. The three
elastic rings 130 are respectively fitted in the three circular
recesses 120b. Three flat countersunk head screws 14 are inserted
into the three elastic rings 130 to be screwed into three threaded
holes 120c of the lens frame 120 which correspond to the three
threaded holes 12c of the first embodiment, respectively. Each
elastic ring 130 is provided with a through hole 130a into which
one of the three flat countersunk head screws 14 is inserted. Each
elastic ring 130 is further provided, around the rear end of the
through hole 130a, with a tapered surface 130b which tapers toward
the front end (the left end as viewed in FIG. 3) of the through
hole 130a. As can be seen in FIG. 3, each flat countersunk head
screw 14 is fixed to the lens frame 120 with the tapered surface
14c of the flat countersunk head screw 14 being in intimate contact
with the tapered surface 130b of the corresponding elastic ring
130.
[0030] Each elastic ring 130 is provided at the rear end thereof
with a large diameter portion 130c which contacts the annular
beveled surface L2a of the rear lens element L2. The rear lens
element L2 is fixed to the lens frame 120 in the circular opening
120a via the elastic rings 130 and the flat countersunk head screws
14 with the large diameter portion 130c of each elastic ring 130
being in pressing contact with the annular beveled surface L2a of
the rear lens element L2. In the lens barrel 100 having the
structure described above, if one of the three flat countersunk
head screws 14 is further screwed into the corresponding threaded
hole 120c from the position shown in FIG. 3, the tapered surface
14c of the flat countersunk head screw 14 digs into the through
hole 130a of the corresponding elastic ring 130 around the tapered
surface 130b thereof. This causes the elastic ring 130 to deform
and expand radially, so that the large diameter portion 130c of the
elastic ring 130 presses the annular beveled surface L2a of the
rear lens element L2 inwardly. By utilizing this pressing force,
the eccentricity of the rear lens element L2 can be adjusted with
respect to the front lens element L1. An arrow F2 shown in FIG. 3
indicates the direction in which the large diameter portion 130c of
the elastic ring 130 shown in FIG. 3 presses the annular beveled
surface L2a of the rear lens element L2 by deformation of the
elastic ring 130. In the second embodiment, similar to the first
embodiment, the eccentricity of the rear lens element L2 with
respect to the front lens element L1 can be adjusted by moving the
rear lens element L2 in a direction perpendicular to the optical
axis O within a tolerance of the inner diameter of the lens frame
120 (approximately 10 micrometers). The three elastic rings 130 and
the three flat countersunk head screws 14 are fundamental elements
of the lens eccentricity adjusting device that is incorporated in
the second embodiment of the lens barrel 100.
[0031] FIGS. 5 and 6 show the third embodiment of the lens barrel
having a lens eccentricity adjusting device according to the
present invention. In a lens barrel 200 of the second embodiment, a
lens frame 220, which corresponds to the lens frame 12 of the first
embodiment, is provided with a circular opening 220a, which
corresponds to the circular opening 12a of the first embodiment, so
that the rear lens element L2 is fixed into the circular opening
220a. In the third embodiment, intermediate members which
correspond to the holding ring 13 of the first embodiment or the
elastic rings 130 of the second embodiment are not used, rather,
the lens frame 220 itself is made of an elastic material such as a
polycarbonate resin, so that a pressing force by each flat
countersunk head screw 14 is transmitted to the rear lens element
L2 via corresponding part of the elastic lens frame 220. This
structure is peculiar to the third embodiment of the lens barrel
having a lens eccentricity adjusting device according to the
present invention.
[0032] The lens frame 220 is provided on the rear end face thereof
with a circumferential groove 220g which is a circular groove about
the optical axis O. As shown by a two-dot chain line in FIG. 5, the
depth of the circumferential groove 220g in the direction parallel
to the optical axis O is smaller than the length of the male
threaded portion 14a of each flat countersunk head screw 14, while
the width of the circumferential groove 220g is smaller than the
diameter of the male threaded portion 14a of each flat countersunk
head screw 14. The lens frame 220 is provided on the rear end face
thereof with three threaded holes 220b positioned at substantially
regular intervals on and along the circumferential groove 220g.
Three flat countersunk head screws 14 are respectively screwed into
the three threaded holes 220b of the lens frame 120 directly. The
lens frame 220 is provided, around the rear end of each of the
three through holes 220b, with a tapered surface 220c which tapers
toward the front end (the left end as viewed in FIG. 5) of the
corresponding through holes 220b. As can be seen in FIG. 5, each
flat countersunk head screw 14 is fixed to the lens frame 220 with
the tapered surface 14c of the flat countersunk head screw 14 being
in intimate contact with the corresponding tapered surface
220c.
[0033] The lens frame 220 is provided, at the inner edge of the
rear end of the lens frame 220, with six inward protrusions 220d
(only two are shown in FIG. 6) so that two of the inward
protrusions 220d are positioned on the opposite sides of each flat
countersunk head screw 14 along a circumference of the rear lens
element L2. Each of the six inward protrusions 220d extends along
and contacts the annular beveled surface L2a of the rear lens
element L2. The rear lens element L2 is fixed to the lens frame 220
in the circular opening 220a via the flat countersunk head screws
14 with the six inward protrusions 220d being in press-contact with
the annular beveled surface L2a of the rear lens element L2. In a
state shown in FIG. 5 where the rear lens element L2 is properly
fixed to the lens frame 220, each inward protrusion 220d is
elastically deformed slightly outward in a radial direction of the
lens frame 220. Each inward protrusion 220d, which is connected to
the circumferential groove 220g, can be easily deformed outward in
a radial direction of the lens frame 220.
[0034] The lens frame 220 is further provided on the rear end face
thereof with six radial grooves 220e (two of them are shown in FIG.
6) so that two radial grooves 220e are positioned on the opposite
sides of each flat countersunk head screw 14 along a circumference
of the rear lens element L2. Each radial groove 220e extends from
the circumferential groove 220g to the circular opening 220a
inwardly in a radial direction of the lens frame 220. The depth of
each radial groove 220e is identical to that of the circumferential
groove 220g. By providing the lens frame 220 with not only the
circumferential groove 220g but also two radial grooves 220e on the
opposite sides of each flat countersunk head screw 14 along a
circumference of the rear lens element L2, the inner portion
(deformable portion) 220f of the lens frame 220 which is positioned
between each flat countersunk head screw 14 and the rear lens
element L2 can be easily deformed toward the rim of the rear lens
element L2.
[0035] In the lens barrel 200 having the structure described above,
if one of the three flat countersunk head screws 14 is further
screwed into the corresponding threaded hole 220b in a state shown
in FIG. 5, the tapered surface 14c of the flat countersunk head
screw 14 digs into the through hole 220b along the tapered surface
220c. This causes the corresponding inner portion 220f of the lens
frame 220 to deform toward the rim of the rear lens element L2 to
thereby press the inner portion 220f inwardly. By utilizing this
pressing force, the eccentricity of the rear lens element L2 can be
adjusted with respect to the front lens element L1. An arrow F3
shown in FIG. 5 indicates the direction in which the inner portion
220f shown in FIG. 5 presses the rear lens element L2. Although the
lens frame 220 is made of an elastic material, portions of the lens
frame 220 other than the inner portions 220f and the inward
protrusions 220d possess high stiffness, and hence, are not
substantially deformed by a tightening operation of any flat
countersunk head screw 14. In the third embodiment, similar to the
first embodiment, the eccentricity of the rear lens element L2 with
respect to the front lens element L1 can be adjusted by moving the
rear lens element L2 in a direction perpendicular to the optical
axis O within a tolerance of the inner diameter of the lens frame
220 (approximately 10 micrometers). The inner portions 220f of the
lens frame 220 and the three flat countersunk head screws 14 are
fundamental elements of the lens eccentricity adjusting device that
is incorporated in the third embodiment of the lens barrel 200.
[0036] In each of the above illustrated embodiments, although the
three flat countersunk head screws 14 are positioned at
substantially regular intervals along a circumference of the rear
lens element L2, the present invention is not limited solely to
this particular structure. Namely, more than three flat countersunk
head screws 14 can be positioned at substantially regular intervals
along a circumference of the rear lens element L2.
[0037] Although the holding ring 13, each of the three elastic
rings 130 and the lens frame 220 are made of an elastic material in
the first, second and third embodiments respectively, the elastic
material is not limited solely to polycarbonate resin, but can be
any other elastic material. The configuration of the lens group
fixed to the lens frame and the shape of each lens fixed to the
lens frame are not limited solely to each of the above illustrated
particular embodiments.
[0038] As can be understood from the foregoing, according to a lens
eccentricity adjusting device to which the present invention is
applied, since at least one elastic member, which is deformed by
pressure of the tapered surface of a corresponding flat countersunk
head screw to press the rim of the lens in accordance with the
amount the corresponding flat countersunk head screw is screwed
into the lens frame, is disposed between each of the flat
countersunk head screws and the rim of said lens, the eccentricity
of the lens can be adjusted using the adjusting device with a high
degree of precision though the structure of the device is
simple.
[0039] Obvious changes may be made in the specific embodiments 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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