| 摘要 |
PURPOSE:To increase the photographic view angle of a negative-refracting-power zoom lens in which a lens group for focusing precedes at its wide angle end to a wide angle side easily and efficiently by mounting an attachment lens which has specific relation and negative refracting power on the zoom lens. CONSTITUTION:The 1st lens group 1 is moved to the object side and the 2nd lens group 2 is moved to the image plane side to vary the power; and the 1st lens group 1 is moved for focusing. The 4th lens group 4 with negative refracting power and said attachment lens are mounted in front of the 1st lens group 1 at the wide-angle end zoom position and extended together with the 1st lens group 1 to increase the photographic view angle to the wide-angle side more. In this case, the zoom lens may be such a type that the 3rd lens group 3 is not provided. When the whole system is increased in view angle, an inequality holds, where fA and f1 are the focal lengths of the attachment lens 4 and the 1st lens group 1.
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