| 摘要 |
PURPOSE:To attain compact constitution and to simplify optical adjustment by constituting an optical pickup of a means for dividing a luminous flux into two and leading them to difference components of a photodetector and a means for detecting differentially an information signal from output of each component of the photodetector. CONSTITUTION:The luminous flux irradiated from an LD 15 is collimated by a collimator lens 16, reflected in the 1st beam splitter 17 and focused on a recording medium 19 as a minute spot by an objective lens 18. The reflected luminous flux from the recording medium 19 passes again through the objective lens 18, the direction of polarized plane is rotated by 45 deg. through the 1st beam splitter 17 and a 1/4 wavelength plate 23 and the result is made incident on the 2nd beam splitter 20 and separated into two optical fluxes. The 1st split luminous flux 21 is condensed toward a light sensor 24 by a condenser lens 25. The 2nd split luminous flux 26 is reflected in the reflecting section 27 at the bottom of the beam splitter 20 and condensed on the light sensor 24 by the condenser lens 25. Thus, the optical pickup is constituted compactly and the S/N of the signal detection is improved by differential detection. |
