| 摘要 |
PURPOSE:To correct satisfactorily an aberration by constituting the first - the third lens groups of a refractive power of positive, negative and positive in order from an object side, of plural lenses of a single glass material, and satisfying a specified condition between focal distances of each leans group. CONSTITUTION:The first - the third lens groups I , II and III having a refractive power of positive, negative and positive in order from an object are constituted. Each lens group I -III is constituted of plural lenses by using a single glass material, for instance, a molten quartz. When focal distances of each lens group I -III are denoted as f1, f2 and f3, respectively, a condition of 0.8<=¦f1/ f2¦<=3.8, and 1.1<=¦f1/f3¦<=4 is satisfied. In this way, it becomes unnecessary to take a chromatic aberration into consideration, and a lens having a high performance is constituted against a narrow light emitting spectrum. |
