| 摘要 |
PURPOSE:To obtain a low-cost wide-angle lens having a large numerical aperture, by arranging four positive and meniscus lenses so that respective centers of curvatures of all lens faces are on the object side of these lens faces. CONSTITUTION:All of lenses 1-4 are positive and meniscus lenses and are so arranged that centers of curvatures of all lens faces are on the object side of lens faces. When a focal length (f) as the whole of the lens system is denoted as 100, conditions of expressions are satisfied. A focal length f3 of the lens 3 and a focal length f4 of the lens 4 are set to satisfy 5.98f<=f3 <=6.6f and 6.73f<=f4<=7.43f, thereby realizing a wide-angle lens which collimates the light from a minute luminous body and has a large numerical aperture and is low-cost. |
