| 摘要 |
PURPOSE:To make the focal length at the short focal length end longer than the focal length of a standard lens and make a zoom lens system compact by the constitution in which a main lens system consisting of a combined positive lens of biconvex and biconcave, a biconvex single lens and a negative meniscus lens convex on the image side is disposed in succession to the variable magnification system of 3-group constitution. CONSTITUTION:A combined positive lens of biconvex and biconcave, biconvex single lens, and a negative meniscus lens convex to the image side are disposed as the main lens system in succession to the variable magnification system consisting of the positive 1st lens group F for focusing, the negative 2nd lens group V for variable magnification, and the positive 3rd lens group C for correction of image point movement, successively from the object side, and the main lens system is so constituted as to satisfy condition equations I-IV. With such constitution, the zoom lens system is obtained which is longer in the focal length of the short focal length end of the zoom lens system than the focal length of a standard length, is about 2- 2.5 times zoom ratios, and is compact and inexpensive. |
