Lens barrel

Details Lens barrel Lens barrel

2002-12-06

2004-08-31

Mack, Ricky (Department: 2873)

Optical: systems and elements

Lens

With variable magnification

C359S694000, C359S699000

Reexamination Certificate

active

06785059

ABSTRACT:

This application claims benefit of Japanese Application No. 2001-377613 filed Dec. 11, 2001, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens barrel, and more particularly, to a lens barrel in which a plurality of optical elements are fixed and held with a high accuracy and which has a high optical performance.
2. Related Background Art
Conventionally, a lens barrel for holding a photographing optical system used in a photographing apparatus (camera) and the like is ordinarily formed of plastic parts and the like molded by injection molding and so on.
Here, the lens barrel is arranged such that a plurality of optical elements such as lenses and the like constituting the photographing optical system are held by frame members, support members, and the like (hereinafter, simply referred to as frame members and the like) corresponding to the respective optical elements, and these frame members and the like are relatively moved in a direction along an optical axis.
In this case, the optical axes of the plurality of optical elements constituting the photographing optical system must be in agreement with each other.
For example, when the respective optical axes of a plurality of optical elements held by a single frame member and the like or the respective optical axes of a plurality of optical elements held by a plurality of frame members and the like are not in agreement with each other, an optical performance cannot be maintained and an excellent subject image cannot be formed.
Accordingly, when the lens barrel is manufactured, it is a very important problem to secure the accuracy of parts such as the respective frame members and the like constituting the lens barrel. Specifically, surfaces for prescribing the positions of the respective optical elements held by, for example, the frame members, that is, lens position prescribing surfaces in the radial direction and the optical axis direction of the optical elements (hereinafter, simply referred to as position prescribing surfaces) must be accurately prescribed.
For this purpose, an arrangement shown in, for example,
FIG. 11
is used in a conventional lens barrel.
FIG. 11
is an enlarged main portion sectional view showing only an upper half portion of the optical elements about the optical axis thereof by taking out a frame member constituting a part of the conventional lens barrel and the optical elements held by the frame member. Further,
FIG. 12
is a sectional view showing a part of molds for injection molding the frame member shown in
FIG. 11
, the sectional view showing a region corresponding to FIG.
11
.
As shown in
FIG. 11
, the frame member
116
constituting a part of the conventional lens barrel is composed of a frame portion
116
a
for fixing and holding the plurality of optical elements and a support portion
116
b
for holding the frame portion
116
a.
The frame portion
116
a
is formed to hold a front lens group
156
a
as a first lens and a rear lens group
156
b
as a second lens, respectively.
In this case, the position of the front lens group
156
a
in a direction along an optical axis O is prescribed by a position prescribing surface, which is denoted by a reference numeral
116
c
, of the frame portion
116
a
. Further, the position of the front lens group
156
a
in a diameter direction is prescribed by a position prescribing surface, which is denoted by a reference numeral
116
d, of the frame portion
116
a.
In contrast, the position of the rear lens group
156
b
in the direction along the optical axis O is prescribed by a position prescribing surface, which is denoted by a reference numeral
116
e
, of the frame portion
116
a
. Further, the position of the rear lens group
156
b
in the diameter direction is prescribed by a position prescribing surface, which is denoted by a reference numeral
116
f
, of the frame portion
116
a.
To mold the frame portion
116
a
arranged as described above, the injection molding mold as shown in
FIG. 12
, that is, a first mold member
120
and a second mold member
121
are used.
Note that a line denoted by a symbol X in
FIG. 12
shows a dividing position of the mold members
120
and
121
.
In this case, the position prescribing surface
116
c
(the optical axis direction) in the frame portion
116
a
is formed by a surface, which is denoted by a reference numeral
121
c
, of the second mold member
121
. Further, the position prescribing surface
116
d
(the diameter direction) in the frame portion
116
a
is formed by a surface denoted by a reference numeral
121
d
of the second mold member
121
.
In contrast, the position prescribing surface
116
e
(the optical axis direction) of the frame portion
116
a
is formed by a surface, which is denoted by a reference numeral
121
e
, of the second mold member
121
. Further, the position prescribing surface
116
f
(the diameter direction) of the frame portion
116
a
is formed by a surface, which is denoted by a reference numeral surface
121
f
, of the second mold member
121
.
The plurality of optical elements (
156
a
,
156
b
) are sequentially inserted into frame portion
116
a
arranged as described above from the same direction, that is, from the side of a rear opening
116
g
and assembled.
Accordingly, in the molds (
120
,
121
) used when the frame portion
116
a
in the lens barrel is molded, all the position prescribing surfaces (
116
c
,
116
d
,
116
e
,
116
f
) of the plurality of optical elements (
156
a
,
156
b
) are molded by the single mold member
121
. In contrast, in manufacture, the dimensional accuracy of parts can be easily increased by molding them in the same molding member. From the above arrangement, in this example, the frame portion
116
a
, which can prescribe the positions of the respective optical elements (
156
a
,
156
b
) easily with a high accuracy, can be realized.
As described above, the frame member (
116
) of the lens barrel, which is to be molded from the molds (
120
,
121
) of a mode shown in
FIG. 12
, is assembled by sequentially inserting the plurality of optical elements from the same direction with respect to the frame member, that is, from the rear opening
116
g
into the inside of the frame portion
116
a.
Therefore, as shown in
FIG. 12
, the diameter Rb of the surface
121
f
of the second mold member
121
corresponding to the position prescribing surface
116
f
of the other rear lens group
156
b
in the diameter direction must be definitely set larger than the diameter Ra of the surface
121
d
of the second mold member
121
corresponding to the position prescribing surface
116
d
of the one front lens group
156
a
in the diameter direction (Ra<Rb).
As a result, a step denoted by a reference numeral d
0
(=(Rb·Ra)/2) is arisen between the position prescribing surfaces
116
d
and
116
f
in the diameter direction, as shown in FIG.
11
.
Further, in the example shown in
FIG. 11
, since the lens group
156
a
must be fixed to the frame member
116
, the front lens group
156
a
is fixed to the frame member
116
on, for example, the outer peripheral portion of the lens group
156
a
through an adhesive
200
. Thus, in this case, a bonding portion where the lens group
156
a
is fixed must be interposed between the lens groups
156
a
and
156
b.
That is, the step shown by the reference numeral dO must be formed so as to secure an adhesive reservoir for applying the adhesive
200
, thereby the diameter of the frame portion
116
a
is increased.
Note that, in the case shown in
FIG. 11
, the lens group
156
b
is also fixed to the frame member
116
on the outer peripheral portion thereof through an adhesive
201
.
From the above arrangement, in the lens barrel of the mode described above, the dimension in the diameter direction of the frame portion
116
a
is increased from the necessity for securing the position prescribing surfaces of the respective optical elements, from which a problem is arisen in that the frame portion
116
a
a

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