| 摘要 |
An optical head includes a blue color laser beam sources, a red color laser beam sources, a dichroic prism, a collimator lens, a beam splitter, an objective lens, a photo detector element, a detection lens, and a hologram element having a first hologram and a second hologram and the first hologram changes a phase of a +1st order diffraction light of a blue color laser beam so that its condensing point falls on a second photo detecting portion and the second hologram changes a phase of a -1st order diffraction light of a red color laser beam so that its condensing point falls on a third photo detecting portion.
|
