| 摘要 |
PROBLEM TO BE SOLVED: To realize a satisfactory tracking characteristic with a simple constitution without making a guide groove deeper by forming the protruding part made to be more lifted than edge parts of the bottom surface at the central part of the bottom surface of the guide groove for performing a tracking. SOLUTION: A tracking is performed by detecting the difference between light quantities to be returned to two photodiodes as the difference signal of the tracking. At the time of the tracking, since an optical interference in a groove 13 and difference in level parts of the land part other than the groove is generated and, moreover, the interference is in a form in which edge parts 13a are emphasized, it becomes the interference in which light scatterins or diffractions at the edge parts 13a are large and the difference in reflectances of the guide groove 13 and the land part can be made large. Thus, since light scatterings and effects of diffraction can be made large with a simple constitution in which only the protruding part 13b made to be more lifted than the edge parts 13a are formed at the central part of the bottom surface of the guide groove 13 in an optical disk 10, the satisfactory tracking characteristic is obtained without making the depth of the guide groove larger. |
