| 摘要 |
PROBLEM TO BE SOLVED: To reduce the cost of an optical head by providing a composite prism with both functions of a polarized beam splitter and a Wollaston prism. SOLUTION: A semiconductor laser unit 11 has a built-in semiconductor laser 15 and a built-in servo error signal receiving element 16 and is provided with a hologram optical element 17 and a composite prism 12 consists of a joined and integrated body of a 1st prism 19 and a 2nd prism 20 via a polarization film 18. A divergent laser beam radiated from the laser 15 is reflected by the polarization film 18 and converged on a recording medium 21 by an objective lens 13. Return light reflected from the medium 21 is separated into a servo error signal and an information signal by the film 18. The servo error signal is reflected by the film 18, diffracted by the element 17 and received by the element 16. The information signal is transmitted through the film 18 and separated into a normal light component α and an abnormal light component β with the second prism 20, which are respectively received by respective pin photodiodes 22, 23. |
