| 摘要 |
PURPOSE:To improve a signal reproducing CN ratio by controlling an optical pickup so that the projection angles of the optical axes of two divided beams from the interfaces of a beam splitter are approximately equal and the optical refractive indexes of the beam splitter at the projecting parts of the two beams are approximately equal. CONSTITUTION:The projection angles of the optical axes of two beams divided by two dividing faces 24a, 24b of the beam splitter 24 from the interfaces S1, S2 are made approximately equal and the refractive indexes of prism parts having the interfaces S1, S2 against air are approximately equal. Even when the incident angles are changed due to defocusing, no difference is generated between both the beams, so that focus offset is not superposed to a focus error signal, a track error signal and an information reproducing signal. Consequently, the focus error signal, track error signal and information reproducing signal obtained by using the outputs of the two photodetecting elements 28, 30 are made accurate. |
