| 摘要 |
PROBLEM TO BE SOLVED: To generate a stable focus error signal by various detection methods, by inexpensive constitution by providing a polarizing beam splitter reflecting luminous flux and irradiating it on a recording surface of a record medium and an optical element of an infinite focal distance made incident with converged light reflected from the recording surface and passing through the polarizing beam splitter and changeable its converged point. SOLUTION: Divergent luminous flux outgoing from a semiconductor laser 1 is reflected by the polarizing beam splitter 3 tilted by 20 deg. to an optical axis to be converged on a track 8 of an optical disk through a condenser lens 4, a rise mirror 5 and an objective lens 6. Reflected light follows an opposite path, and transmits through the polarizing beam splitter 3 according to its polarization characteristic. The transmitted luminous flux is removed in its coma aberration by a Wollaston prism 9 arranged tilted to the optical axis to be separated to three components of a P polarization component, an S polarization component and a PS mixture component. The stable focus error signal is generated from three components by a spot size detection method or an anisotropic method. |
