Optical: systems and elements – Lens – With support
Reexamination Certificate
2000-08-15
2002-05-21
Ben, Loha (Department: 2873)
Optical: systems and elements
Lens
With support
C359S826000, C359S694000, C359S696000, C310S323170, C310S323210, C310S328000, C396S079000, C356S147000
Reexamination Certificate
active
06392827
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an apparatus, such as an optical apparatus including binoculars, a camera including a digital camera and a video camera, and the like, and particularly relates to a drive mechanism, for example, for driving a lens and to a guide mechanism, for example, for guiding the lens, with which the apparatus is provided.
Description of the Related Arts
In the field of digital cameras, a more downsized (i.e. miniaturized) and compact camera is desired in contrast with a conventional common camera. Meanwhile, as a drive mechanism for driving a lens used in the digital camera, there has been employed a cam mechanism as has been conventionally used in a common camera. That is, the digital camera has a construction in which a pin is fixed to a lens frame (or a movable frame), and in which a plurality of cam slots, engaging the same pin, are formed in a plurality of cylindrical members that engage and overlap one over the other. With the construction, a lens supported by the lens frame is driven in its optical axis.
However, even if one tries to downsize or miniaturize the cylindrical member having the cam slot and/or to downsize the pin engaging the cam slot, etc., there is a limitation to downsizing those components from a point of view of processing and/or assembling it. In other words, there arises a problem that the miniaturization of the cam mechanism can not catch up with the miniaturization of an optical system used therein.
Also, the cam mechanism is equipped with a tilt prevention mechanism for preventing a tilt of each lens advancing and retreating in its optical axis. With this arrangement, the movable frame for holding the lens advances and retreats while turning about the optical axis. Therefore, in case that one tries to miniaturize it while realizing a prevention of mutual interference of the plurality of movable frames, it is difficult to let a span of the tilt prevention mechanism be longer. As a result, a prevention of the tilt of the lens becomes difficult.
Furthermore, in the conventional cam mechanism, each lens is accommodated inside the cylindrical member. Therefore, it is difficult to perform the alignment of the optical system after assemblage thereof.
On the other hand, conventionally, a camera, video camera, digital camera, or the like, has had a guide mechanism for guiding a lens in a direction of an optical axis thereof at a time of moving the lens for zooming, focussing, etc. upon photographing. In the construction, there has been conventionally provided, for example, an MR (magnetic resistance) sensor for detecting a position of the lens that is driven in the optical direction, in order to control the position thereof. This MR sensor is a magnetic sensor, which is a magneto-resistive sensor having a characteristic that its resistance varies in a magnetic field when the intensity of the magnetic field varies. That is, the MR sensor moves in a longitudinal direction nearby a magnetized plate in which there are arranged a plurality of N- and S-poles alternately, with which arrangement the position of an object connected to the MR sensor is detected by reading the state of the magnetic field.
In this construction, in order to enhance an ability of the detection, it is necessary to ensure an accuracy of mutual location and mutual structures between the MR sensor and its counterpart magnetized plate. In this construction, a gap between a sensor surface of the MR sensor and the magnetized plate opposing the sensor surface thereof must be most strictly taken care of in order to ensure the accuracy thereof. However, the MR sensor and the magnetized plate are mounted on separated members moving relative to each other. Therefore, generally speaking, it is difficult to ensure the accuracy of the gap therebetween, only by the accuracy of components employed in the structure and/or by the accuracy of assemblage thereof.
In order to solve this technical problem, it has been practiced that, for example, a spacer or the like having a thickness corresponding to a required gap therebetween is inserted between the MR sensor and the magnetized plate, and that one of the MR sensor and the magnetized plate is brought into a press contact with the other thereof by means of a plate spring, or the like, by which the accuracy of the gap is ensured.
Meanwhile, in a type where the lens frame is hung down by a guide shaft, the lens frame is driven along the guide shaft in the direction of the optical axis. In this arrangement, however, it is necessary to restrict or prevent the turning of the lens frame around the guide shaft. In order to prevent the turning thereof, it has been practiced that an additional guide shaft is provided parallel to the foregoing guide shaft in which the additional guide shaft is fitted to a groove, or the like, that is additionally provided on the lens frame.
In this construction, in case that the optical performance thereof is considerably degraded due to swinging of the center of the optical axis of the lens frame, it is necessary to further suppress the play or looseness between the groove of the lens frame and the additional guide shaft, and the lens frame is biased on one side relative to the additional guide shaft by means of a spring, etc.
However, in the above construction, there are installed the detector for detecting the position of the lens and the mechanism for restricting or preventing the turning of the lens separately, in the guide mechanism for guiding the lens. This leads to an increment of the number of component parts and the number of assembling steps, which in turn incurs a large-sized apparatus and/or a high cost of production.
On the other hand, there has been conventionally provided, for example, a drive mechanism employing a piezoelectric element. The drive mechanism has a plurality of driving parts for linearly driving a plurality of lenses, for instance. With reference to
FIG. 25
illustrating a drive mechanism for driving a lens in a camera, it is explained about the drive mechanism.
FIG. 25
is a perspective view of the drive mechanism for driving the lens. The lens drive mechanism has a lens frame
321
a
for holding a lens
300
L
1
; a shaft bearing part
333
a
connected to the lens frame
321
a
; a guide shaft
328
a
, extending in a direction of the optical axis, slidably engaging the shaft bearing part
333
a
for guiding the lens frame
321
a
in the direction thereof; a lens frame
321
b
for holding a lens
300
L
2
; a shaft bearing part
333
b
connected to the lens frame
321
b
; a guide shaft
328
b
, extending in the direction of the optical axis, slidably engaging the shaft bearing part
333
b
for guiding the lens frame
321
b
in the direction thereof.
The guide shaft
328
a
is held near a front end portion and a rear end portion of the guide shaft
328
a
by a hole portion
330
a
formed on a front wall
330
f
of a stationary frame
330
and by a hole portion
330
a
′ formed on a middle wall
330
m
of the stationary member
330
, so that the front end portion and the rear end portion of the guide shaft
328
a
slidably engage the stationary frame
330
.
In the same way, the guide shaft
328
b
is held near a front end portion and a rear end portion of the guide shaft
328
b
hole portion
330
b
formed on the front wall
330
f
of the stationary frame
330
and by a hole portion
330
b
′ (unshown in the figure) formed on the middle wall
330
m
of the stationary member
330
, so that the front end portion and the rear end portion of the guide shaft
328
b
slidably engage the stationary frame
330
.
Each of the shaft bearing parts
333
a
,
333
b
is equipped with a plate-spring-like holding plate
331
a
,
331
b
which is mounted thereto respectively with a screw (the holding plate
331
b
is hidden in the figure). The holding plates
331
a
,
331
b
make press connect with the guide shafts
328
a
,
328
b
, respectively. Therefore, when the lens frames
321
a
,
321
b
move on the guide shafts
328
a
,
328
b
, the
Kuwana Minoru
Mizumoto Kenji
Ueyama Masayuki
Ben Loha
Minolta Co. , Ltd.
Sidley Austin Brown & Wood LLP
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