Movable filter device

Details Movable filter device Movable filter device

2000-02-18

2001-05-01

Gray, David M. (Department: 2851)

Photography

Having variable focal length of camera objective

Lens moves in or out of light path

C396S355000, C396S544000

Reexamination Certificate

active

06226460

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a movable optical filter device in a video camera or the like.
CONVENTIONAL ART
FIG. 5
shows a conventional movable filter device. A rotary disk
102
holds a plurality of optical filters
101
a
to
101
d
. As the optical filters
101
a
to
101
d
, generally, ND filters (neutral density filters) and color temperature conversion filters are used. A roller
107
a
held by an elastic arm
107
b
is always pressing the rotary disk
102
. By turning a rotary knob
106
, rotation is transmitted to the rotary disk
102
through gears
105
a
to
105
c
. As the rotary disk
102
rotates, when the roller
107
a
gets into a dent
102
e
of the rotary disk
102
, the rotary disk
102
is held in that position by the pressure from the roller
107
a
. In this state, the optical axis z of the camera and the center of the optical filter
101
a
a coincide. By thus turning the rotary knob
106
, a desired filter can be set on the optical axis z of the camera. In such conventional movable filter device, if the rotary knob
106
was turned too much, the roller
107
a
surpassed the dent
102
e
, thereby causing overshoot. To prevent overshoot, on the other hand, if the dent
102
e
was too deep, the rotary load increased, and the operation was not smooth. In spite of the advantage that a plurality of optical filters can be selected, the device is large in size, many in the number of parts, and hence expensive. The invention is devised to solve these problems, and it is hence an object thereof to present a movable filter device capable of preventing the optical filter from stopping at other than a specified position, and which is small in size, low in cost, and smooth in operation.
SUMMARY OF THE INVENTION
In the movable filter device of the invention, one rotary member holds one optical filter. In order to use a plurality of optical filters alone or in combination, if necessary, a plurality of rotary members are overlaid so as to move them individually. The rotary member is rotatably supported at point (P) on a holding member. Two stopper pins limit the rotation of the rotary member between a first position and a second position. The optical filter is set on the optical axis of the camera when the rotary member is at the first position. One end of an elastic member is rotatably coupled to point (
2
c
) in the rotary member, and the other end of the elastic member is rotatably coupled to a point (
3
c
) in the holding member. The position ofpoint (
3
c
) is preferably at a remote position over the rotary member as seen from point (P). The position of point (
2
c
) is preferably so that the line linking point (P) and point (
3
c
) may intersect with the track of point (
2
c
), within the limitations of the rotation, and that the distance between point (
3
c
) and point (
2
c
) may be smaller than the distance between point (P) and point (
2
c
). The elastic member generates force in a direction of extending the distance between point (
2
c
) and point (
3
c
), and the rotary member is thrust toward the first position or the second position by the force generated by the elastic member, which is because the distance between point (
2
c
) and point (
3
c
) is extended to its longest when the rotary member is located at the first position or the second position. The thrusting force by the elastic member prevents the optical filter from stopping at other than the first position or the second position, and also improves the feel of manipulation of the variable filter device. In the movable filter device of the invention, when the rotary member abuts against the stopper pin, the low rigidity portion provided in the rotary member is elastically deformed, and absorbs the impact. As a result, the sound in manipulation is suppressed, and the feel of manipulation is improved.


REFERENCES:
patent: 4681418 (1987-07-01), Kodaira
patent: 5079576 (1992-01-01), Kodaira

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