| 摘要 |
PROBLEM TO BE SOLVED: To permit discriminating of kinds on a reproducing device side, to prevent forgery work, and improve additional value by superimposing a record information having comparatively high density on record information having a comparatively low density and recording them on a flat plane. SOLUTION: A low density pit P1 is formed on a surface of a disk 1, further, a high density pit P0 is formed on the low density pit P1. When a density ratio of the high density pit P0 to a low density pit P1 is preferably 20:1, separation at the time of reading is made good. Also, a shape of the low density pit P1 may be not only a square but also an elliptical shape and a groove shape of a track. Further, arrangement of the low density pit P1 may be performed in a circular form being same as the high density pit P0, but also the information can be recorded by arranging the pit in the radius directions of a disk and varying groove width. The low density pit P1 is not required to arrange on a whole disk surface, may be arranged independently at a place other than an arrangement place of the high density pit P0. |
