| 摘要 |
PURPOSE:To arrange the front-side principal point of an objective lens sufficiently in front and to maintain the performance of the objective lens by allowing an optical system consisting of six positive, negative, positive, positive, negative, and positive elements in six groups to meet specific requirements. CONSTITUTION:The optical system consisting of six elements in six groups meets various requirements shown by inequalities I -IV. In the inequalities, F1,2,3 is the composite focal length of the 1st-the 3rd lens groups and F4,5,6 is the composite focal length of the 4th-the 5th lens groups; and F is the composite focal length of the whole lens system, r3 is the radius of curvature of the 2nd lens group on the light source side, and r10 is the radius of curvature of the 5th lens group at the disk side. The negative meniscus lens in the 2nd group has the concave surface on the light source side and the positive meniscus lens in the 3rd group has the convex surface on the light source side; and the positive meniscus lens in the 4th group has the concave surface on the light source side, and the negative meniscus lens in the 5th group has the convex surface on the light source side. |
