| 摘要 |
PURPOSE: To finely record additional information on an optical recording medium in a continuous manner so as to distinguish an individual medium and to easily discriminate whether the medium is an illegally copied one or not so as to prevent the occurrence of an illegal copying. CONSTITUTION: An ultraviolet laser beam emitted from a UV laser light source 1 is intensity-modulated by an optical modulator 2 and split into three beams by a phase diffraction grating 5 through lenses 3 and 4. These beams are reflected by a mirror 14 through a semi-transparent mirror 11, image-formed by a condensing lens 6 and made incident on an optical disk 8 to record additional information. Moreover, the reflected beam from the disk 8 is reflected by the mirror 14 through the lens 6, made incident on an optical detector 13 from the mirror 11 through a cylindrical lens 12 and the light quantity is detected. |
