| 摘要 |
PURPOSE:To reduce the size of the optical pickup device for the optical disk by making surfaces aspherical on both the light source side and the optical disk side and eliminating deterioration in wave front aberration. CONSTITUTION:In a used state, the figure shows a light source, i.e., an object point 1, an objective lens 2 for the optical disk, the pit surface of the optical disk, i.e., an image surface 3, the protective layer 4 of the optical disk, an optical medium 5, a photodetecting element 6, the distance L between object images, the operation distance P of the lens 2, the center thickness (d) of the lens 2, the thickness (t) of the optical disk protective layer, and the total angle at half maximum theta of luminous flux of the light source 1. Then the surfaces are made aspherical on both the sides of the light source 1 and optical disk and a1.P+b1<=log(-1/beta)<=a2.P+b2 holds, where L is the distance L between the object images, P is the operation distance, and beta is the lateral magnification. In this case, a1=0.0028L-0.327, b1=0.028L+0.343, a2=0.0068L-0.348, and b2=0.026L+0.610. |
