| 摘要 |
An optical pick-up unit is suitable for scanning a first type of record carrier having a first information density and at least a second type of record carrier, the second type of record carrier having a second information density different from the first information density. The optical pick-up unit comprises a first radiation source (16, 86) for emitting a first diverging radiation beam (24) for scanning the first type of record carrier, and at least a second radiation source (48, 96) for emitting a second radiation beam (50) for scanning the second type of record carrier. The optical pick-up unit also comprises a first beam splitter (58, 93, 104) for combining the first radiation beam and the second radiation beam on a common optical path. The first beam splitter is a plane-parallel plate-type beam splitter. A correcting element (20, 22, 72) for astigmatism and coma correction is arranged between the first radiation source and the first beam splitter. |
