| 摘要 |
PURPOSE:To obtain a bright and compact wide angle lens superior in capacity, by satisfying prescribed conditions in the lens system constituted with the first group consisting of positive, negative meniscus, negative meniscus, and positive meniscus lenses and the second group consisting of positive, positive, negative, negative, positive, and positive lenses which are arranged in order from the object side. CONSTITUTION:In the lens system constituted with the first group consisting of positive, negative meniscus, negative meniscus, and positive meniscus lenses and the second group consisting of positive, positive, negative, negative, positive, and positive lenses which are arranged in order form the object side, surfaces of the 9th lens and the 10th lens in the image side are formed to aspherical surfaces, and the sign of derivatives of second degree of coordinates (y) in the direction of the optical axis of these aspherical surfaces to coordinates in the (x)-axis direction is invariable in the effective diameter, and conditions of inequalities (1)-(6) are satisfied. In the inequalities, f123, (f), D6, fII, L, f1, and Np are the resultant focal length of the first- the third lenses, the focal length of the whole of the system, the air gap between third and fourth lenses, the focal length of the second group, the overall length of lenses, the focal length of the first lens, and an average value of refractive indexes of fifth and sixth lenses, respectively. Thus, a bright and compact wide angle lens superior in capacity is obtained. |
