| 摘要 |
PROBLEM TO BE SOLVED: To efficiently utilize light to either disk, in an optical pickup device which can be used commonly to different disks. SOLUTION: The holographic optical element is formed by closely sticking an isotropic medium 72 to birefringence mediums 73 formed in a saw-toothed shape. The refractive index of any one birefringence medium 73 with respect to light having a specific wavelength is specified to be equal to the refractive index of the isotropic medium 72 with respect to light having the same wavelength. Therefore, an optical path of a transmitted light beam is selected by the wavelength and the polarization direction of an incident light beam. |
