| 摘要 |
PURPOSE:To obtain a recording and reproducing objective lens whose operating distance is long and chromatic aberration is excellently corrected by constituting the objective lens of the 1st- and 2nd-group lenses and causing the lenses to satisfy specific conditions. CONSTITUTION:This objective lens is constituted from the light source side of the 1st-group lens which is a joined positive lens of three lenses, the 1st double-convex lens, 2nd double-concave lens, and 3rd double-convex lens, and the 2nd-group lens composed of the 4th meniscus lens with its convex surface on the light source side and the lenses are caused to satisfy the conditions of Formula I. The r2 and r3 of the Formula I respectively represent the radii of curvature of the joining surfaces of the 1st and 2nd lenses and 2nd and 3rd lenses. The n1 and n2 respectively represent the refractive indexes of the 1st and 2nd lenses. The f1 and f2 respectively represent the focal distances of the 1st and 3rd lenses. Therefore, the chromatic aberration of this objective lens can be corrected excellently. |
