OPTICAL PICKUP DEVICE READABLE IRRESPECTIVE OF KIND OF DISK

摘要

PROBLEM TO BE SOLVED: To allow the optical pickup to read a disk irrespective of the type of disk by providing a numerical aperture regulating means for regulating an effective numerical aperture of an objective lens to conduct focusing suitable for the form of a loaded disk. SOLUTION: A beam form a light source 21 is made incident on an objective lens 25 via a diffraction grating 24 and a beam splitter 23. Then a numerical aperture regulation means 30 regulates the diameter of the transmitted beam between the objective lens 25 and a beam splitter 23 and makes the regulated beam incident on the objective lens 25 so as to change the valid numerical aperture. The beam passing through the numerical aperture regulation means 30 passes through the objective lens 25 and focused onto a disk 10. Furthermore, the path of an optical signal modulated by a signal on a disk information recording side is changed by the beam splitter 23 and reaches a photodetector 28 via a sensing lens 27.