| 摘要 |
PURPOSE:To attain a high-capacity lens system having a sufficiently long eye relief by constituting the lens system with five lenses of three groups and moving the second and third groups in opposite directions to vary the power and satisfying a specific condition in the second lens groups. CONSTITUTION:The lens system consists of five lenses of the first lens group G1 having a positive refracting power, the second lens group G2 having a positive refracting power, and the third lens group G3 having a negative refracting power which are arranged in order from the side of an eye point EP, and the second and third lens groups G2 and G3 are moved in opposite directions with an object image I, which is formed between both lens groups, between them when the power is varied. The second lens group G1 satisfies a formula where ra is the radius of curvature of the EP-side lens face and rb is that of the object- side lens face. Thus, the zoom lens system is obtained which has a sufficiently long eye relief, a compart constitution, and a high capacity.
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