| 摘要 |
PROBLEM TO BE SOLVED: To read information even on an optical recording medium having a birefringent property. SOLUTION: A diffraction element 23 has an optical material forming a diffraction grating 21 with a rugged cross section and another optical material 22 charged between the projecting parts of the diffraction grating 21 at least. In this case, between two kinds of these optical materials 21 and 22, at least one optical material 21 shows the birefringent property and the other optical material 22 has a refraction factor different from both the normal light refraction factor and the abnormal light refraction factor of one optical material 21 showing the birefringent property. |
