| 摘要 |
PURPOSE:To improve the recording density of an optical disk by providing a level difference between adjacent recording steps, using the optical disk having a slope between the recording steps and detecting a tracking error by the use of a four-division photodetector. CONSTITUTION:In the optical disk 7, the recording steps 8 and 9 are spirally formed so that they have the level difference in an up-and-down direction by interposing the slope 10. The level difference between the recording steps 8 and 9 is formed to be <=1/10 of the wavelength lambda of a laser light beam used. The width of the recording steps 8 and 9 is set 0.8 times as long as the spot diameter d0 of the laser beam used. The tilt angle theta of the slope 10 is formed at 42 deg.. By using the four-division photodetector arranged in parallel so that it may coincide with the groove direction of the recording step 8, the tracking error is detected. Thus, a dedicated track servo groove is not necessitated and the recording density is improved. |
