Lens hood for zoom lenses

Claim 1

A lens hood device for a zoom lens system, comprising: a fixed lens barrel for supporting an image forming lens component; an operating ring rotatably mounted about the periphery of said fixed lens barrel, and further mounted for movement along the optical axis of said image forming lens component; a lens hood comprising a lens hood ring detachably secured to a forward end of said operating ring; a zoom operating ring threadedly engaged with said operating ring by a first helicoid portion for movement together with said operating ring along the optical axis, and being disposed against rotation relative to said fixed lens barrel; a cam ring mounted for rotation at a fixed position about the optical axis relative to said fixed lens barrel and being capable of rotation together with the movement of said zoom operating ring along the optical axis relative to said fixed lens barrel, said cam ring having a cam slot for effecting movement of a zoom lens component which is disposed against rotation relative to said fixed lens barrel along the optical axis, and said cam slot of said cam ring being so disposed as to move said zooming lens component along the optical axis relative to said image forming component so that said zooming lens system may be zoomed to the Tele side when said operating ring is moved forwardly along the optical axis relative to said fixed lens barrel; said lens hood ring being so disposed as to be capable of preventing light rays from any point outside the field angle in the zooming lens system during a zooming operation from coming into said focusing lens component when said operating ring is moved along the optical axis relative to said fixed lens barrel; and a focusing operating ring in threaded engagement with said fixed lens barrel by a second helicoid portion, said focusing operating ring being mounted for rotation together with said operating ring and a focusing lens component being supported by said focusing operating ring, whereby together with the rotation of said operating ring relative to said fixed barrel said first helicoid portion effects movement of said operating ring along the optical axis relative to said fixed lens barrel and concurrently said operating ring moves said focusing operating ring along the optical axis via the second helicoid portion, the pitch of said first and second helicoid portions being substantially equal whereby said focusing operating ring moves said focusing lens component along the optical axis relative to said fixed lens barrel and said operating ring moves said lens hood ring in the same direction along the optical axis by substantially the same amount as the amount said focusing lens component is moved.