| 摘要 |
PURPOSE:To obtain a zoom lens which is bright, is short in the overall length of the lens and is corrected of aberrations satisfactorily in a lens system of 4-group constitution having positive, negative, negative and positive refracting powers successively from an object side by satisfying prescribed conditions. CONSTITUTION:In a lens system of 4-group constitution having positive, negative, negative and positive refracting powers successively from an object side, the 4th group consists of a front group and a rear group, which front group is of the 4- element constitution of a biconvex lens having strong refracting power on an image plane side, a positive lens having strong refracting power on an object side, a negative lens directing its concave surface to the object side and a positive lens having strong refracting power on the object side, and which rear group is of the 3-element constitution of a positive lens, a positive lens having strong refracting power on the object side and a negative meniscus lens directing its concave surface to the object side, whereby the conditions of the equations (1)-(8) are satisfied. Here, RIVi and DIVi are the thickness and air space of the i-th lens of the 4th group, and fw is the focal length in the zoom position at the wide angle end. Thus, the zoom lens which is bright, is short in the overall length of the lens and is corrected of aberrations satisfactorily is obtained. |
