| 摘要 |
PURPOSE:To increase the curvature radius of a using lens and at the same time to prevent the generation of a ghost, by tilting a lens to the incident laser beam and setting the effective focal length shorter than the para-focal length. CONSTITUTION:The effective focal length fe of an incident beam which is distant away from an optical axis by (h) is set shorter than the focal length (f) to the luminous flux on a para-axis. So is with a lens. That is, the equation is satisfied as an effective focal length, where the incident angle and the refraction angle to the 1st surface of curvature radius R1 are i1.i1' along with i2.i2' set to the 2nd surface of curvature radius R2 respectively, the refractive index is (n), and the geometric-optical path length is A in a lens. In such a way, the incident angle i1.i1' and the optical path length A are varied in accordance with the incident position although the inclination delta is constant between the incident beam and the optical axis. Then the distance fe varies. |
