| 摘要 |
PURPOSE: To extract the periodic signals of a bit to be read from background noise even when the background noise is left as it is by adjusting the position of a read beam around the bit to be read in a horizontal direction or a vertical direction relating to the recording hierarchy. CONSTITUTION: In the case of reading recorded bits in an individual layer inside an optical disk volume, signals accompanied with the background noise(BGN) from all close bits illuminated by the read beam are supplied. In order to eliminate the BGN, the bit 6 to be read positioned in the original hierarchy 0 of the read beam 70 +80 is searched by a waist 50 whose diameter is 2ω0 and refraction is maximum. That is, the position of the read beam is adjusted around the bit to be read in the horizontal direction or the vertical direction relating to the recording hierarchy. Thus, the cyclic signals of the bit to be read is extracted from the BGN. |
