Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2001-02-23
2003-04-29
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S694000, C359S703000
Reexamination Certificate
active
06556359
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lens unit, and in particular, to a technology for operating smoothly a movable lens frame provided in the lens unit.
In recent years, a movable lens frame having therein a movable lens that moves in the direction of an optical axis is provided in a lens unit employed in a video camera, a still camera and a digital still camera, and the movable lens frame has been required to move more smoothly. As a lens unit like this, there is known a lens unit which has two movable lens frames, for example, and slides on two guide shafts.
On the other hand, as a structure of the lens unit, there have been known a type wherein a lens and others are incorporated in the direction that is in parallel with an optical axis of a lens and a type of a box body wherein a lens and others are mainly incorporated in the direction perpendicular to an optical axis of a lens, which is different from a conventional type.
Now, referring to the drawings, there will be explained an example of a conventional way for a type to incorporate mainly in the direction perpendicular to an optical axis of a lens, for a lens unit that has two movable lens frames and slides on two guide shafts, which differs from a conventional type.
FIG. 13
is a side sectional view of the state of telephoto end showing a structure of a lens unit in a conventional example, and FIG.
14
(
a
) shows sectional view taken on line A—A in
FIG. 13
, FIG.
14
(
b
) shows sectional view taken on line B—B in FIG.
13
and FIG.
14
(
c
) shows sectional view taken on line D—D in FIG.
13
.
Structures of a lens unit in FIG.
13
and
FIG. 14
will be explained. The numeral
19
is a box-shaped box body, and box body
19
has an opening section on its top in FIG.
14
(
a
). Further, front fixed lens frame
51
described later is fixed on the side of the box body
19
closer to a subject on an optical axis of a lens. Further, inside the box body
19
, there are provided positioning grooves
19
a
and
19
b
, groove
19
a
positioning both ends of the first guide shaft
31
and groove
19
b
positioning both ends of the second guide shaft
32
.
The numeral
31
is a first guide shaft provided inside the box body
19
to extend to be in parallel with an optical axis, and both ends of the first guide shaft
31
are positioned by the positioning groove
19
a
. The numeral
32
is a second guide shaft provided inside the box body to extend to be in parallel with an optical axis, and both ends of the second guide shaft
32
are positioned by the positioning groove
19
b.
The numeral
51
is a front fixed lens frame having lens L
1
, and it is fixed on the box body
19
directly. The numeral
69
is a first movable lens frame having lens L
2
, and the first movable lens frame
69
moves to be in parallel with an optical axis. Further, on the first movable lens frame
69
, there are formed guide bush
69
a
and rotation-stopper section
69
d
. On the guide bush section
69
a
, there are provided hole
69
b
and hole
69
c
through which the first guide shaft
31
slides. On rotation-stopper section
69
d
, there is provided an elongated hole through which the second guide shaft
32
slides.
The numeral
79
is a fixed lens frame that is arranged to be in parallel with an optical axis between the first movable lens frame
69
and second movable lens frame
89
, and has lens L
3
. The fixed lens frame
79
has therein hole
79
a
, elongated hole
79
b
, protruded portion
79
c
and protruded portion
79
d
. The hole
79
a
engages with the first guide shaft
31
, and the elongated hole
79
b
is engaged with the second guide shaft
32
. Positioning in the direction perpendicular to an optical axis is conducted by the first guide shaft
31
and the second guide shaft
32
. Protruded portion
79
c
and protruded portion
79
d
engage respectively with grooves provided on box body
19
to conduct positioning in the optical axis direction. Incidentally, the fixed lens frame
79
may also be positioned directly on the box body
19
to be held thereon.
The numeral
89
represents a second movable lens frame having lens L
4
, and the second movable lens frame
89
moves to be in parallel with an optical axis. Further, the second movable lens frame
81
has guide bush section
89
a
and rotation-stopper section
89
d
. On the guide bush section
89
a
, there are provided hole
89
b
and hole
89
c
through which the second guide shaft
32
slides. On rotation-stopper section
69
d
, there is provided an elongated hole through which the first guide shaft
31
slides.
The symbol
49
A is a guide shaft holding member, and guide shaft holding member
49
A has claw section
49
A
a
, claw section
49
A
b
, holding section
49
A
d
and holding section
49
A
e
, as shown in FIG.
14
(
a
). Each of the holding section
49
A
d
and holding section
49
A
e
holds one end of each of the first guide shaft
31
positioned by positioning groove
49
a
on the box body
11
and the second guide shaft
32
positioned by positioning groove
49
b
. Further, claw section
49
A
a
and claw section
49
A
b
engage with grooves on the box body
11
to fix the guide shaft holding member
49
A on the box body
11
.
The symbol
49
B is a guide shaft holding member, and guide shaft holding member
49
B is the same as the guide shaft holding member
49
A stated above in terms of function, thereby explanation of the guide shaft holding member
49
B will be omitted. Further, filter
21
and CCD
22
are fixed on the rear side of the box body
11
.
Motor
25
that drives the first movable lens frame
69
is fixed on the box body
19
at the position opposite to the opening on the box body, and the first movable lens frame
69
is connected with the motor
25
by a connecting member mounted on the first movable lens frame
69
. The foregoing is the same for the second movable lens frame
89
, and an unillustrated motor is fixed on the box body
19
at the position opposite to the opening on the box body
19
, and the second movable lens frame
89
is connected with the unillustrated motor by an unillutrated connecting member mounted on the second movable lens frame
89
. Sensor
24
for the initial position of the first movable lens frame
69
is fixed on the same side of the box body as for the motor
25
, as shown in FIG.
14
(
b
), and an unillustrated sensor for the initial position of the second movable lens frame
89
is fixed in the same manner. An opening section of the box body
19
is covered by an unillustrated cover so that the inside of the box body is in the state of a dark box.
Now, a movement from a wide-angle end to a telephoto end will be explained. When the motor
25
drives, guide bush section
69
a
of the first movable lens frame
69
slides on the first guide shaft
31
. Incidentally, rotation-stopper section
69
d
of the first movable lens frame
69
slides on the second guide shaft
32
.
The longer, length X in the optical axis direction between hole
69
b
and hole
69
c
on guide bush section
69
a
of the first movable lens frame
69
sliding on the first guide shaft
31
is, the more stable, the operation in the course of movement of the first movable lens frame
69
is. It is therefore preferable to design the aforesaid length X of the guide bush section
69
a
to be long as far as possible.
However, guide bush length X of guide bush section
69
a
in the optical axis direction of the first movable lens frame
69
cannot be long to interfere, for example, the rotation-stopper section
89
d
of the second movable lens frame
89
and the protruded portion
79
d
of fixed lens
78
. When guide bush length X of the guide bush section
69
a
is short, sliding friction between the first guide shaft
31
and the guide bush section
69
a
deteriorates smoothness of sliding. Further, when the first movable lens frame is used for variable power of a zoom lens, for example, if sliding is not stable, there is easily caused a problem of the so-called camera shake.
SUMMARY OF THE INVENTION
The invention has been attaine
Emura Tetsuji
Numaguchi Takayuki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Konica Corporation
Schwartz Jordan M.
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