| 摘要 |
PURPOSE:To facilitate manufacture and reduce cost by condensing light from a light source with two or more single lenses. CONSTITUTION:A finite magnification unit uses as a composite lens two single lenses, a collimator lens G1 and an objective lens G2. Emitted light from a semiconductor laser LD of a point light source passes through a cover glass Gt, then is incident to a collimator lens G1 and becomes nearly parallel light, thereafter, is condensed by an objective lens G2 and is focused on a information recording surface of a disk Gd. In this case, a light pick-up is used especially as an integrated movable body of the light source and the lenses, while the semiconductor laser LD, cover glass Gt, collimator lens G1 and objective lens G2 are installed in a suitable case, and focusing control and tracking control to the disk Gd are performed by moving the case. |
