Patent ID: 7649823

Claim:
A method for reproducing digital codes at irregular intervals from pieces of data information and pieces of meaningless information stored in an information storage medium, comprising the steps of: a) producing an analog data signal continuously varying a physical quantity from said pieces of data information and said pieces of meaningless information stored in said information storage medium; b) converting said analog data signal to a data stream containing said digital codes expressing discrete values of said physical quantity and synchronous data codes expressing a discrete value representative of said pieces of meaningless information through a demodulation technique corresponding to a modulation technique assigning values of said digital data codes to values of physical quantity that is periodically varied; said step b) includes the sub-steps of b-1) producing first signals representative of a series of coordinates in a quadrature coordinate system from said analog data signal, b-2) converting said series of coordinates in said quadrature coordinate system to a series of coordinates in a polar coordinate system so as to produce second signals from said first signal, and b-3) reversely mapping said series of coordinates in said polar coordinate system to said digital data codes and said synchronous data codes for producing said data stream; and c) eliminating said synchronous data codes from said data stream so as to leave said digital data codes representative of said pieces of data information at said irregular intervals.