| 摘要 |
PROBLEM TO BE SOLVED: To improve recording density by constituting an optical means detecting positional information recorded on a recording layer so as to use the interaction between an evanescent wave and recording layer. SOLUTION: A radiation beam from a semiconductor laser 21 is made incident on an evanescent wave generator 10, and a reflected beam is led to a photodiode 26. Four kinds of pits d0-d4 with different depth are formed on respective recording tracks, and the information to be recorded is modulated to the time series data using four values from 0 to 3. That is, the data 0-3 are made to correspond to pit depth d0 (that is, original medium surface)-d4, and a master disk is formed by laser cutting. By this process, original information is recorded/preserved on a recording medium as a modulated pit string having four values in the depth direction. Since displacement in the outside of surface direction of the recording layer 1b is used as the information also, an information amount recorded in one pit is increased at least twice. |
