| 摘要 |
A light beam emitted from a laser source is divided into a first light beam and a second light beam. An optical divider is further provided to separate a combined light beam of the first and second light beams into a first light bundle near the optical axis and a second light bundle in the edge portion and to diverge the first and second light bundles so that the first and second light bundles are individually detected by plural detectors. The first light beam is signal light focused on an optical information recording medium by an objective lens and reflected off the medium, and the second light beam is reference light not focused on the optical information recording medium. A focus error signal is then detected for the first light bundle for compensating focus error. |
