| 摘要 |
PROBLEM TO BE SOLVED: To shorten an overall optical path and to miniaturize the device and also to enhance durability by providing a hologram element having a larger expanded divergent angle of a light beam from a light source than the conventional practice. SOLUTION: A transparent flat plate member 12 is equipped with the 1st hologram element 8 on a surface opposite to a semiconductor laser 7 of the light source and the 2nd hologram element 9 on a surface opposite to an optical disk 10. The 1st hologram element 8 has a diffraction function for further expanding the divergent angle of the light beam diverged from the semiconductor laser 7. The 2nd hologram element 9 is operated to function as an objective lens for diffracting an incident light beam expanded by the 1st hologram element 8 to be converged on the optical disk 10. In addition, the 1st hologram element 8 has also a splitting function for diffracting and separating reflected light from the disk 10. Consequently, the overall optical path can remarkably be shortened, and the device can superlatively be miniaturized in size and reduced in weight. |
