OPTICAL PICK-UP OF OPTICAL DISK DRIVE

摘要

PROBLEM TO BE SOLVED: To reduce the number of components and simplify structure by using a holographic lens with a pattern for converting only a first laser beam to parallel light when reproducing two types of optical disks while utilizing laser beams with different wavelengths in an objective lens and a photodiode. SOLUTION: When a low-density optical disk 110 is to be reproduced, laser beam with a first wavelength through a prism 115 is converted into parallel light by an incident holographic lens 117. By forming a number of steps on the inner surface of the projection of a pattern being formed at the holographic lens 117, conversion efficiency to parallel light can be increased. The beam spot size of the first laser beam being formed on the surface of a photodiode 119 that is condensed by a light reception lens 118 is allowed to have nearly the same size as the light spot of the second laser beam. The second laser beam is transmitted through the holographic lens 117 as it is.