Erase mark detecting circuit for detecting an erase mark superimposed on data recorded on a sector of an optical recording medium

An erase mark recording and detecting circuit for use in an optical information recording/reproducing apparatus, in which an erase mark, which is selectively superimposed on information data recorded in selected ones of unit information record areas of an optical information recording medium comprising a plurality of unit information record areas, is detected with the aid of a reproduction signal read out of said optical information recording medium, comprising:

• an erase mark recording means for selectively recording an erase mark on a unit information record area of the optical information recording medium by employing a recording signal formed solely of a DC component for recording optical information on the optical information recording medium;
• a level detecting means for detecting a mean level of said reproduction signal reproduced from said unit information record area of the optical information recording medium;
• an information data detecting means for processing the reproduction signal to detect a presence of information data recorded in the unit information record area;
• and
• an erase mark detecting means for providing a signal indicating detection of an erase mark superimposed on said unit information record area in accordance with a detection by said level detection means that the mean level of the reproduction signal detected is above a reference value and a detection by said information data detecting means of a said presence of information data in said selected unit information record area.

An optical information recording/reproducing apparatus, comprising:

• an optical head comprising (a) a light source for producing a light beam for recording/reproducing optical information on an optical information recording medium including a plurality of unit information record areas and (b) a photodetector by which a reflection light beam reflected by the optical information recording medium is detected to produce an information data reproducing signal, wherein an erase mark is selectively superimposed on information data recorded in selected ones of said unit information record areas of said recording medium;
• a power determining means for controlling a power of the light beam emanated from the light source;
• an erase mark detecting circuit comprising a level detecting means for detecting a mean level of said information data reproducing signal;
• an information data detecting means for detecting that information data is recorded on one of the unit information record areas of the information recording medium;
• and an erase mark detection means for providing a signal indicating detection of an erase mark superimposed on said one of the information data recording areas in accordance with an output of said level detecting means indicating that the mean level of the reproduction signal is above a reference value and an output of said information data detecting means indicating a presence of information data in said one of said unit information recording areas.