Optical: systems and elements – Lens – With support
Reexamination Certificate
2002-03-20
2004-04-13
Dang, Hung Xuan (Department: 2873)
Optical: systems and elements
Lens
With support
C359S811000, C396S526000, C362S455000, C353S100000
Reexamination Certificate
active
06721111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens guide mechanism and in particular, relates to a lens guide mechanism having a lens group which is guided to move linearly.
2. Description of the Related Art
In a known camera, a lens drive mechanism for a movable lens, such as a focusing lens group, is provided in a camera body as a lens unit. The lens unit includes a support barrel which constitutes a main body of the lens unit and which is provided with a linear movement guide mechanism which guides a lens frame which supports the movable lens. However, the structure of the support barrel is complex because it supports a motor or a gear, for driving the movable lens and hence, there is little space for accommodating the lens guide mechanism. Furthermore, in a lens shutter camera, the lens unit is often formed in the form of a lens-shutter unit which contains an exposure control mechanism in addition to the lens drive mechanism. In this case, the lens unit is more complicated and makes it more difficult to arrange the lens guide mechanism in the support barrel of the lens unit. Moreover, there is a demand for further miniaturization of the lens unit and, accordingly, it is desirable that the lens guide mechanism be incorporated effectively in a small space of the lens unit.
SUMMARY OF THE INVENTION
The present invention provides a lens guide mechanism which contributes to further miniaturization of a lens unit.
For example, a lens guide mechanism is provided, including a lens frame which supports a photographing lens group, the lens frame including a plurality of guide holes extending in a direction parallel with an optical axis; a support barrel in which the lens frame is provided; a gear holding member which is provided at a front end of the support barrel; a lens-drive gear train which is held between the support barrel and the gear holding member, the lens-drive gear train constituting a drive mechanism for the lens frame; and a plurality of linear movement guide rods provided in the gear holding member, which extend through the guide holes of the lens frame and support the lens frame to move linearly in the optical axis direction relative to the support barrel.
It is desirable for the gear holding member to include a gear retainer ring which is detachably attached to the front end face of the support barrel to cover the front end face of the support barrel; rear rod support portions which are formed in the gear retainer ring so as to be located behind the guide holes of the lens frame in the optical axis direction; and a front cover which is detachably attached to the gear retainer ring, the front cover having front rod support portions which are located in front of the guide holes of the lens frame. The linear movement guide rods are supported at the front ends thereof by the front rod support portions of the front cover, and are supported at the rear ends thereof by the rear rod support portions of the gear retainer ring.
The front ends of the linear movement guide rods can be secured to the front rod support portion, and the rear ends of the linear movement guide rods can be engaged with the rear rod support portions by attaching the front cover to the gear retainer ring.
It is desirable for the gear retainer ring to be provided on the inner peripheral surface thereof with U-shaped recesses in which the linear movement guide rods are accommodated.
The lens guide mechanism can further include coil springs which are provided around the linear movement guide rods to bias the lens frame in the optical axis direction.
It is desirable for the gear holding member to include a gear retainer ring which is detachably attached to a front end face of the support barrel to cover the front end face of the support barrel; and a front cover which is detachably attached to the gear retainer ring, the front cover having front rod support portions which are located in front of the guide holes of the lens frame and support the front end of the linear movement guide rods. One end of the coil springs abut against spring receiving members provided around the guide holes of the lens frame, and the other end of the coil springs abut against the front cover.
The lens frame, which is linearly guided by the linear movement guide rods, can include a front lens frame which supports one of a pair of sub-lens groups which optically function at a mutually close position and a mutually distant position, the one of the pair of sub-lens groups being located on the object side. The support barrel can further support a rear lens frame which supports the other of the pair of sub-lens groups located on the image side.
The lens guide mechanism can further include a drive ring which is rotatably supported by the support barrel, behind the rear lens frame, and is immovable in the optical axis direction, so that the front and rear lens frames are moved relative to the support barrel in accordance with a rotation of the drive ring; and a gear provided on the drive ring, the center of the gear being located on a center axis of rotation of the drive ring, the gear being in mesh with a gear of the lens-drive gear train to transmit a drive force of a lens drive motor to the drive ring through the lens-drive gear train.
It is desirable for the rear lens frame to be rotatable within a predetermined angle range with respect to the support barrel, the rotation of the rear lens frame being restricted at each extremity of the predetermined angle range so as to linearly move in the optical axis direction. The rear lens frame rotates between the two extremities and linearly moves in the optical axis direction at each of the two extremities, via a contact portion between the drive ring and the rear lens frame, in accordance with the rotation of the drive ring. The front lens frame and the rear lens frame are moved between the mutually close position and the mutually distant position via a contact portion between the rear lens frame and the front lens frame in accordance with the rotation of the rear lens frame. The front lens frame is linearly moved together with the rear lens frame via the contact portion between the rear lens frame and the front lens frame in accordance with the linear movement of the rear lens frame.
It is desirable for the rear lens frame to be always in contact with the drive ring so that rearward movement of the rear lens frame is restricted, the front lens frame being always in contact with the rear lens frame so that rearward movement of the front lens frame is restricted. It is desirable for the lens guide mechanism to further include coil springs which are provided around the linear movement guide rods, the coil springs biasing the front lens frame in a direction to come into contact with the rear lens frame. The support barrel can support a light intercepting mechanism which opens and closes a photographing aperture in the support barrel.
A second gear train which constitutes a driving mechanism for driving the light intercepting mechanism can be provided at the front end of the support barrel, wherein the lens-drive gear train of the lens drive mechanism and the second gear train of the light intercepting mechanism are supported between the front end of the support barrel and the gear holding member.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-81609 (filed on Mar. 21, 2001) which is expressly incorporated herein by reference in its entirety.
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patent: 5037187
Ishizuka Kazunori
Nomura Hiroshi
Sasaki Takamitsu
Takashima Maiko
Dang Hung Xuan
Greenblum & Bernstein P.L.C.
Martinez Joseph
PENTAX Corporation
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