| 摘要 |
PROBLEM TO BE SOLVED: To effectively emit an irregular reflection beam of a beam in the inside of an optical disk to the outside by forming so that an outer edge part surface of a disk becomes a non-square surface for an upper/lower surface. SOLUTION: The optical disk is a CD 1 that the outer edge part surface 2 is cut at an angle of 45 deg. for the upper/lower surface of the disk. A laser beam emitted into the inside of the optical disk is irregularly reflected in the inside of the disk to be diffused toward a central direction and an outer peripheral direction. At this time, the reflection beam 3 irregularly reflected in the inside of the disk, repeating internal reflection in the outer peripheral direction of the disk and diffusing shows the route of the reflection beam in the case of reflecting at the angle (30 deg.) of the critical angle or below of the CD. In such a case, since a reflection angle is within the critical angle, the majority of the reflection beam are emitted to the outside as a refractive beam 4 on the disk upper/lower surface. Since the emission of the refractive beam 4 in such a case is the refraction in the outer peripheral direction, it hardly affect an optical pickup. Further, it is emitted to the outside as the refraction beam 5 also on the outer edge part surface 2. |
