| 摘要 |
Position of secondary focal point (Fsi) on secondary focal point line (LFS) is such that lateral distance (Li) between each secondary focal point and vertical axial plane (Pv) is increasing then decreasing at least once. Also, position of secondary focal point on secondary focal point line is such that axial distance (Xi) between each secondary focal point and focal plane (PF) of lens (18) is increasing then decreasing at least once. |
