| 摘要 |
PURPOSE:To use plastic for element lenses in a master group and to decrease the number of the element lenses by composing the master group of glass lenses and at least two plastic lenses. CONSTITUTION:A front lens group 1, a variator group 2, a compensator group 3, and the master group 4 are arranged successively from an object side, and a crystal plate 5 is provided behind the master group 4. Element lenses of the master system are made of plastic and the number of the elements is decreased to perform temperature compensation and compensate various aberrations. A concave plastic lens and a convex plastic lens are used in combination and then the quantity of focus variations of those plastic lenses cancel each other. For the purpose, at least one concave plastic lens and at least one convex plastic lens are used to perform the temperature compensation of the lens system. Further, the chromatic aberration of this lens system is compensated by using a Gaussian lens as at least one element lens. |
