| 摘要 |
PROBLEM TO BE SOLVED: To provide a double wavelength holography laser module generating two different wavelength laser light so as to read all kinds of optical disk products of a DVD system, a CD system, and a CD-R system. SOLUTION: A double wavelength holography laser module 200 is provided with a holography optical element 220, a multi-element photo-detector 230, and, for example, a laser light source 210 generating laser light of two or more desired wavelengths. A laser beam emitted from a laser light source of desired wavelengths passes through an HOE and an object lens device 250. This object lens device is used for focusing the laser light on the optical disks of a DVD system 260a, a CD system 260b or a CD-R system according to a selected wavelength. The object lens device has a dual lens system which is switched so as to put a numerical aperture(NA) variable single lens or put a single lens in an optical path at a time. Although the laser beam has two different wavelengths, there is only one optical path provided for the laser beam. |
