| 摘要 |
PURPOSE:To obtain long back focus by symmetrically arranging an intermediate group of the 4th relay lens system in the a positive lens, a both-concave negative lens and a positive lens. CONSTITUTION:Since the intermediate group of the 4th group GIV which is a relay lens system is arranged in the order of the positive lens L10, the biconcave negative lens L11 and the positive lens L12, the back focus can be sufficiently extended without increasing the negative refractive power of the biconcave negative lens L11 or a lens L7 of the 3rd group GII of a compensator. In this case, the refractive power itself of the whole intermediate group of the 4th group GIV which is the relay lens system is extremely small and the intermediate group has mainly an aberration compensating function. Conditions to fulfill the duties are expressed by inequalities 1-4. provided that phi42 is the refractive power of the intermediate group of the 4th group GIV which is the relay lens system, fs is the synergistic means value between the shortest focal distance and the longest focal distance of the zoom lens system, SF421, SF422, SF423 are the shape factors of an object side positive lens L10, the intermediate biconvex negative lens L11 and an image side positive lens L12 of the intermediate group of the 4th group GIV. |
