| 摘要 |
PROBLEM TO BE SOLVED: To impart an astigmatism lens function by utilizing a surface where no grating of any diffraction grating is formed. SOLUTION: A diffraction grating 2 is constituted of synthetic resins, while the astigmatic lens function is imparted by utilizing its surface formed with no grating of the diffraction grating 2 to compenstae an astigmatic difference of a semiconductor laser 1. Consequently, a sub-beam for tracking control can be formed in keeping independency of both surfaces, and also the astigmatic difference of the semiconductor laser 1 is easily compensated. |
