| 摘要 |
PROBLEM TO BE SOLVED: To read and write information by controlling effect of double refraction through an information recording medium. SOLUTION: The pickup device is constituted of a light source 1, a beam splitter 3, a variable optical element 4 and an objective lens 5. The variable optical element 4 is formed with liquid crystal elements and is provided with a phase shift area that imparts at least two or more phase differences to light, each phase quantity for light in each phase area by an applied voltage Vi in is adjusted accordance with the double refraction of the information recording medium 9. The light emitted from the light source 1 is made incident on the variable optical element 4 through the beam splitter 3, polarized in accordance with the phase shift quantity of the variable optical element 4, converged by the objective lens 5 and radiated to the medium 9. The reflected light, which is polarized by the effect of the double refraction of the medium 9, is again polarized by the phase shift quantity of the variable optical element, and is turned to reflected light in a polarization direction reflectible by the beam splitter 3; then, the light reflected by the beam splitter 3 is photodetected by a condensing lens 6 and a photodetector 7. |
