Canon Kabushiki Kaisha

Yasuhiro Izumi

Chiaki Terasawa

Shigeru Oshima

Yasuyuki Tomita

Jun Hosoya

Yoshiharu Nakamura

Takashi Kamai

Tateki Nakamura

Hiroshi Fujike

For a camera of the kind permitting change-over of the aspect ratio of its image pickup area from one aspect ratio to another, an optical system and an apparatus using the optical system are arranged to be capable of preventing the angle of view of a zoom lens from being changed by the change-over of the aspect ratio.

Zoom lens

A zoom lens is disclosed comprising, from front to rear, a first lens unit of positive refractive power, a second lens unit of negative refractive power, a flare cut stop for cutting a lower marginal ray of an off-axial bundle of rays for a maximum image height, a third lens unit of positive refractive power and a fourth lens unit of positive refractive power, wherein the second and third lens units move axially to effect zooming, while either varying the aperture diameter of the flare cut stop or axially moving the flare cut stop to thereby cut the harmful rays for good optical performance.

Disclosed is a device that comprises a cylindrical member, a viscous member which is applied to the cylindrical face of the cylindrical member to provide a viscous layer, a contact member, which contacts the cylindrical face, and a contact area varying member which varies the contact area, wherein the contact area is variable to change braking force for revolutions.

Device for varying braking force

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Kanagawa-ken, Japan

Yasuhiro Izumi