COMBINED HOLOGRAM OPTICAL ELEMENT, COMPATIBLE OPTICAL PICKUP AND OPTICAL INFORMATION STORAGE MEDIUM SYSTEM EMPLOYING THE SAME

摘要

A hologram optical element, usable in a compatible optical pickup including the hologram optical element and an optical information storage medium system including the compatible optical pickup, is used in combination with an objective lens for a compatible optical pickup used for first and second low-density information storage media using lights having a second wavelength and a third wavelength and at least one kind of high-density information storage medium using light having a first wavelength. The hologram optical element includes a combined hologram on one side to allow lights having the second wavelength and the third wavelength to travel at different angles for focusing the light onto the first and second low-density information storage media, respectively.