| 摘要 |
PURPOSE:To obtain an objective lens of a small size and a light weight for optomagnetic discs which has NA as large as 0.8-0.9 and a working distance as long as 1-1.5mm. and permits sufficient control. CONSTITUTION:One of two lenses L1, L2 which constitute the 1st group is a positive meniscus lens and the other is a negative meniscus lens. Two pieces of 4 lenses L3-L6 constituting the 2nd group constitute a combined convex lens which is convex on an object side, and the other two pieces are positive meniscus lenses. When the focal length of the 1st group is defined as f1, the focal length of the 2nd group as f2, the focal length of the entire system as (f), the radii of curvature of the 5th, 6th and 10th lense faces from the object side are defined as r5, r6, r10, and the refractive indices of the 3rd, 4th lenses from the object side to light of 8,200Angstrom wavelength as n3, n4, the objective lens satisfies the inequalities (I)-(IV). |
