| 摘要 |
PURPOSE:To obtain a zoom lens keeping always stable high performance over the whole power modification range by specifying the constitution of lenses in a lens group having negative refractive power which is arranged on the object side. CONSTITUTION:The zoom lens is formed by a lens group G1 having negative refractive power, a lens group having positive refractive power, a lens group G3 having negative refractive power, and a lens group having positive refractive power which are arranged successively from the object side and power modifica tion is executed by changing the interval between respective lens groups. When it is defined that the radius of curvature of the joint surface of a lens L3 to be an adhered negative lens in the lens group G1 is R6, the refractive indexes of the negative and positive lenses on the object side which constitute the lens L3 are n3 and n4 and the Abbe values of a lens L1 to be a positive lens and a lens L4 to be a positive meniscus lens are nu1, nu4, R6>0, n3/n4>0.99 and nu1>nu4. Consequently, spherical aberration and a difference based upon the color of a curved image surface are reduced and the chromatic aberration of power in the shortest focal distance can be compensated. |
