| 摘要 |
PROBLEM TO BE SOLVED: To record an information signal on the recording surface of the optical recording medium by a hologram which is hardly forged. SOLUTION: The hologram representing an additional information signal is recorded in a two-dimensional area on the recording surface of the optical recording medium which has a spiral track or concentric tracks. The resolution in the direction crossing the tracks of the hologram is 1/n (n: integer between 1 and 10) as large as the track pitch and the resolution in the direction of tracing the tracks of the hologram is equal to the length of channel bits. When the error correcting capability of the optical recording medium is E in terms of the length, the length in the direction of tracing the tracks of the hologram is 0.1 mm to less than E/3. |
