| 摘要 |
PURPOSE:To constitute a compact pickup by allowing an optical system which consists of the lens elements, i.e. a positive and a positive lens successively from an optical source side to an optical disk side to meet specific requirements. CONSTITUTION:This lens is used with projection magnification beta between -1/2 and -1/8 and consists of two positive lenses L1 and L2 successively from the light source side to the side of an optical disk 10, and the surface of the 1st lens L1 on the light source side is made aspherical. Various requirements shown by inequalities are met. In the inequalities, f1 and f2 are the focal lengths of the 1st and the 2nd lenses L1 and L2, and r1 and r2 are the radius of paraxial curvature of the surface of the 1st lens L1 on the light source side and the radius of curvature of the surface of the 1st lens L1 on the optical disk side; and d1 is the on-axis thickness of the 1st lens L1 and (f) is the focal length of the whole system. |
