| 摘要 |
PURPOSE:To obtain a bright optical system by constituting it with the first biconvex lens, the second biconcave lens, the third biconcave lens, the fourth biconvex lens, and the fifth positive meniscus lens, and constituting it so that its focal distance, lens thickness, refractive index, Abbe number, and radius of curvature satisfy specified conditions. CONSTITUTION:In an optical system constituted of four groups and five pieces as a whole, which consists of the first lens of a biconvex lens, the second lens of a biconcave lens, the third lens of a biconcave lens, the fourth lens of a biconvex lens, and the fifth lens of a positive meniscus lens, in order from an object side with joining the third lens and the fourth lens, various conditions of inequalities (1)-(4) are satisfied. The inequality (1), the inequality (2), the inequality (3) and the inequality (4) are related to holding a front-element diameter so as to be small enough, a correction of a comatic aberration of an out-of- axis beam, a condition for correcting a chromatic aberration, and a radius of curvature of a surface of an image side of the fifth lens, respectively. In this way, an optical system which is small in size, light in weight, bright, and also has a good performance can be obtained.
|
