| 摘要 |
PURPOSE:To constitute a compact lens system with a high performance of F number 4.5-5.6 and half field angle 16-20 deg., by arranging five groups consisting of five lenses bisymmetrically and satisfying prescribed conditional expression. CONSTITUTION:A bisymmetrical lens system consists of the first positive lens, the second negative meniscus lens with the convex facing to the object, the third lens with both faces concaved, the fourth negative meniscus lens with the convex facing to the image, and the fifth positive lens which are arranged in order from the object side, and they satisfy the conditions of conditional expressions. In expressions, (f) and fi are focal lengths of the whole of the system and the first lens, respectively, and d3 and d7 are thickness on the axis of the second and the fourth lenses, respectively. |
