Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
1997-11-19
2001-09-18
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S696000
Reexamination Certificate
active
06292308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lens barrel having optical members including a zooming lens, a focusing lens and a diagram.
2. Description of the Related Art
For the lens barrel of the kind arranged to move some of various lens groups with a stepping motor which is employed as a drive source by transmitting its driving force through the meshing engagement of a feeding screw and a rack screw, the stepping motor has been arranged to be approximately in a cylindrical shape for the purpose of imparting universal applicability to the stepping motor.
Further, a motor unit which is approximately cylindrical in appearance has been arranged as an actuator at a diaphragm driving part in cases where a linear movement is necessary, like in the case of the diaphragm driving part of a video camera.
However, the conventional arrangement mentioned above has presented various problems as described below.
An effort to minimize the size of a lens barrel without lowering its optical performance results in an approximately cylindrical shape of the lens barrel.
However, in order to arrange a driving part for each of a zooming lens, a focusing lens and a diaphragm to have a sufficient torque, the outside diameter of the lens barrel increases with a driving load. The increase in the driving load makes the driving part hardly containable within the shape of the minimum size of the lens barrel.
In the case of the conventional lens barrel which is shown in
FIG. 6
, an actuator unit
59
for driving a magnifying power varying system or a focusing system is formed with a U-shaped sheet metal member
59
a
arranged to support a motor
59
b
which is provided with a screw shaft
59
c
. The U-shaped sheet metal member
59
a
is screwed to the lens barrel
51
. The lens barrel
51
has a cutout part
51
a
which is provided for mounting the actuator unit
59
thereon and extends over the whole moving range of the power varying system or the focusing system.
However, the structure of making the U-shaped sheet metal member
59
a
support the actuator unit
59
and of screwing the U-shaped sheet metal
59
a
to the lens barrel
51
necessitates the cutout part
51
a
of the lens barrel
51
to be large. The large cutout part
51
a
lowers the strength of the lens barrel
51
and also makes it difficult to attain a required degree of precision. The provision of the U-shaped sheet metal member
59
a
brings forth another problem which lies in that the meshing engagement of rack teeth (not shown) and the screw shaft
59
c
cannot be ascertained in their assembled state.
Further, for the lens barrel of this kind, use is generally made of a diaphragm unit including, in one unified body, a plurality of diaphragm blades, a diaphragm base plate and a blade retaining member which are arranged to sandwich the diaphragm blades therebetween, and a diaphragm driving part. The diaphragm unit which is arranged in this manner is disposed and fixed in position within the lens barrel in a state of being completely independent of the lens barrel.
However, the unitizing arrangement of the diaphragm device inevitably causes an increase in number of parts of the diaphragm device. The increased number of parts causes not only an increase in cost but also an increase in space required, and thus has resulted in a larger size of the lens barrel.
Further, depending on the mounting precision, the diaphragm unit tends to cause a discrepancy between an optical axis and the center of the diaphragm and thus has caused one of four corners of an image plane to become dark or, in the worst case, to be eclipsed.
SUMMARY OF THE INVENTION
One aspect of this invention resides in the provision of a lens barrel which is arranged to permit reduction in size by making driving parts for a zooming system, a focusing system and a diaphragm respectively to be in an arc form i.e., circumferentially of the lens barrel optical axis with arcuate outer surfaces which may not extend radially outwardly of an outer circumference of a lens barrel part, and disposing the driving parts externally of the lens barrel which has approximately a cylindrical shape.
Another aspect of this invention resides in the provision of a lens barrel of the kind arranged to move an optical member in the direction of an optical axis by rotating a screw shaft with a motor and by axially moving a meshing member which meshes with the screw shaft, wherein an aperture part is provided in an approximately tubular member so as to cause the meshing member to mesh with the screw shaft in a position of the aperture part.
A further aspect of this invention resides in the provision of a lens barrel, wherein a diaphragm member is set in position in a state of being sandwiched in the direction of an optical axis with one of the sandwiched sides thereof supported by a lens holding member.
These and other aspects and features of this invention will become apparent from the following detailed description of embodiments thereof taken in connection with the accompanying drawings.
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Azusawa Katsumi
Matsuda Kazuya
Tsuzuki Masahiko
Watanabe Takashi
Canon Kabushiki Kaisha
Epps Georgia
Mack Ricky
Robin,Blecker & Daley
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