| 摘要 |
PROBLEM TO BE SOLVED: To provide a device for deciding the front side and the rear side of an optical disk, with which the front and the rear sides of a medium are surely decided at a low cost without giving any process on the medium. SOLUTION: The device is composed of such a point light emission source 5 such as an LED or a laser diode, a half mirror 4 which passes the light beam emitted from the point light emission source 5 and divides the light beam from a reflected light reflected on the reflective face of the optical disk 1, a lens 2 which condenses the light beam emitted from the point light emission source 5 on the reflective face of the optical disk 1, a light shielding plate 3 which blocks the light beam divided by the half mirror 4 asymmetrically from the light beam axis, and a divided light receiving element 6 which has optoelectronic transduction function, and the decision is made by on which side of the divided light receiving element the light beam is received. |
