Lens guide mechanism of a lens shutter type of camera

A zoom lens which includes front and rear lens groups, said zoom lens being provided with a rear lens group drive mechanism for driving said rear lens group to move along an optical axis relative to said front lens group, said zoom lens comprising:

• a shutter mounting stage which supports a lens shutter consisting of a plurality of shutter blades;
• a lens supporting member which supports said rear lens group, said lens supporting member being movable along said optical axis relative to said shutter mounting stage without rotating about said optical axis;
• a first guide shaft extending from a first member to a second member in a direction of said optical axis, a rear end of said first guide shaft being secured to said second member, wherein said first guide shaft is supported on said first member such that said first guide shaft is movable in said direction of said optical axis relative to said first member and immovable in a circumferential direction of said first member;
• a second guide shaft extending in said direction of said optical axis, said second guide shaft being supported on said shutter mounting stage to be guided in said direction of said optical axis, a rear end of said second guide shaft being secured to said lens supporting member;
• a gear rotatably supported on said shutter mounting stage, said gear being immovable in said direction of said optical axis relative to said shutter mounting stage, said gear having a hole formed at an axial center, and a female thread being formed on an inner periphery of said hole;
• a screw shaft on which a male thread is formed, said screw shaft extending in said direction of said optical axis, a rear end of said screw shaft being secured to said lens supporting member, said gear being rotatable fitted on said screw shaft and said female thread meshing with said male thread;
• a first encoder provided on said shutter mounting stage for detecting a size of a diaphragm formed by said lens shutter, said first encoder comprising a first photosensor and a first rotating disk associated with said first photosensor;
• and
• a second encoder provided on said shutter mounting stage for detecting an axial position of said rear lens group, said second encoder comprising a second photosensor and a second rotating disk associated with said second photosensor,
• wherein said first and second guide shafts are positioned substantially opposite to each other with respect to said optical axis,
• and wherein said first and second rotating disks are positioned adjacent to said first guide shaft, and said first guide shaft being positioned between said first and second rotating disks.