| 摘要 |
PURPOSE:To form a zoom lens which has a variable focal distance range of 35- 135mm., is a fast lens of an F3.5 class at a wide angle side, and also has a very compact constitution. CONSTITUTION:A titled lens has the first group of a positive refractive power as a focusing part, the second group of a negative refractive power as a variator part, the third group of a positive refractive power as a compensator part, and the fourth group of a positive refractive power as a master part, in order from an object side, and a variable power is executed by a relation movement of the first, the third and the fourth groups. Also, the second group is constituted of a negative lens G4 having a stronger curvature in an image side, a joint lens formed by joining positive and negative elements G5, G6, a negative lens G7 having a stronger curvature in an object side, and a positive lens G8, in order from the object side, and conditions in the expressions are satisfied. In the expressions, fII, fW, RIIi and NIIi denote a focal distance of the second group, the shortest focal distance of the whole system of the zoom lens, a radius of curvature of the i-th lens surface of the second group, and a refractive power of the first nitric material (d) line of the second group, respectively. |
