| 摘要 |
PROBLEM TO BE SOLVED: To provide a hologram laser by which the size of an optical pickup device can be reduced and, further, the reliability of the device can be improved. SOLUTION: Diffraction lattices 3 and 4 are formed on the emission side of a hologram glass 32 which has a hologram device 7 for beam deflection on its incident side. The central part diffraction grating 3 has rectangular grooves and the circumferential part diffraction grating 4 has blade-shaped asymmetrical grooves. As a laser beam emitted from one of semiconductor lasers transmits the diffraction gratings 3 and 4, its beam diameter is large. As a laser beam emitted from the other semiconductor laser transmits the diffraction grating 3 only, its beam diameter is small. |
