| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device, in which recording and playing back of optical disks having different substrate thickness can be performed by using laser beams of two kinds of wavelengths. SOLUTION: The optical pickup device is provided with a semiconductor laser 1 which selectively generates a laser beam at 635 nm wavelength and a laser beam at 780 wavelength and with an optical element 5, having a center region 5b where a hologram is formed and a peripheral region 5a, where a diffraction grating is formed. The center region 5b transmits the laser beam of 635 nm wavelength, as it is but diffracts the laser beam at 780 nm wavelength, to cause the diameter of the beam to increase. A though the peripheral region 5a transmits the laser beam of 635 nm wavelength, as it is, it substantially blocks the laser beam of 780 nm through diffraction. |
