Variable-length information recording with reference marks for time reference during information reading

A device for recording/reading information along tracks of a moveable medium being driven at a uniform speed, said device comprising:

• means for detecting length-reference alterations in a sensitive layer of said movable medium and information representing alterations in said layer representing recorded information, and for converting said length-reference alterations and said information alterations into electrical signals;
• means for converting the length of said detected length-reference alterations and said information alterations into numbers proportional to said length;
• means for storing in memory at least said numbers corresponding to the detection of said length-reference alterations;
• and
• calculating means for determining a number of increments associated with each said information alteration detected and converted into one of said electrical signals, on the basis of said numbers and of a maximum number of increments (N).

A method for recording and reading information on a movable media having a reference surface and being driven at a uniform speed, said method comprising the steps of:

• recording said information during a writing phase including a first step of forming first variable-length deviations from said reference surface by converting variable duration pulsed information signals wherein transitions from said deviations to flat surface areas between said deviations represent said information and wherein said writing phase further includes a second step of forming a series of sequences of length-reference second deviations from said reference surface, each of said second deviations being of different length and each sequence of said series of sequences including at least two deviations and wherein each sequence of said series of second deviations is associated with predetermined area in which said first variable-length deviations are formed and wherein each of said sequences of deviations are formed and wherein each of said sequences of deviations of said series forms a length reference for said predetermined area;
• reading said information in a read phase including a first step of reading said length-reference second deviations and converting said length-reference second deviations into duration-reference pulsed signals, for a respective associated said predetermined area and said read phase further includes a second step of reading said first variable-length deviations representing information formed in said associated predetermined area and converting said first variable-length deviations into pulsed signals and a third step of reproducing said recording information by comparison with said duration-reference pulsed signals.