| 摘要 |
PURPOSE:To reduce the eclipse of light flux, by composing the titled lens system of the 1st - 4th lens groups having positive, negative, negative, and positive refractive power successively from an object side, and moving the 3rd lens group in one direction longer than the movement of the 2nd lens group to attain zooming. CONSTITUTION:The titled lens group consists of the 1st lens group I having a refractive system and a reflective system successively in the light advancing direction, the 2nd lens group II having a negative refractive index and located between the refractive and reflective systems of the 1st lens group I to be moved for zooming, the 3rd lens group III having a negative refractive index and located between the 2nd lens group and an image surface to be moved for zooming, and the 4th lens group having a positive refractive index and fixed during zooming. The 3rd lens group III is moved in one direction longer than the movement of the 2nd lens group to attain zooming. |
