| 摘要 |
PURPOSE:To make excellent compensation for aberrations by composing a collimator lens of three different kinds of lenses and making the lenses meet specific requirements. CONSTITUTION:An optical system for optical disks consists of the collimator lens and an objective. Light information from a light source enters the collimator lens, passes through the 3rd positive lens, the 2nd biconvex lens, and the 1st biconvex lens in it, and then enters the objective. The three lenses constituting the collimator lenses meet the requirements shown by inequalities. The inequality I is for preventing the spherical aberration and chromatic aberration from being compensated too much or too less and realizing such an Abbe number that material supply is easy. The inequality II is for flattening an image. When the inequalities hold, proper compensation is carried out and the chromatic aberration is compensated excellently even when the system is combined with a single objective. |
